Clinical Focus


  • Neonatal-Perinatal Medicine
  • Neonatology

Administrative Appointments


  • Co-Leader, Stanford Clinical and Translational Unit (CTRU) (2008 - Present)
  • Leader, Spectrum Child Health (2008 - Present)
  • Co-Director, Stanford Center for Clinical and Translational Education and Research (2008 - Present)
  • Vice Dean, Stanford University School of Medicine (2006 - 2013)
  • Senior Associate Dean for Academic Affairs, Stanford University School of Medicine (2001 - 2013)
  • Director, Charles B. and Ann L. Johnson Center for Pregnancy and Newborn Services, Lucile Packard Children's Hospital at Stanford (1997 - Present)
  • Harold K. Faber Professor of Pediatrics, Stanford University School of Medicine (1992 - Present)
  • Chief, Division of Neonatal and Developmental Medicine, Stanford University School of Medicine (1989 - 2007)
  • Program Director, Training in Developmental and Neonatal Biology, Stanford University School of Medicine (1989 - Present)
  • Associate Program Director, General Clinical Research Center; Head, Pediatric Component, Stanford University School of Medicine (1993 - 2008)

Honors & Awards


  • Member, Institute of Medicine of the National Academies, National Academy of Sciences (2012)
  • Jonas Salk Award for Leadership in Prematurity Prevention, March of Dimes Foundation (2011)
  • Maureen Andrew Mentor Award, Society for Pediatric Research (2011)
  • Albion Walter Hewlett Award, Stanford University School of Medicine (2009)
  • Alwin C. Rambar-James B.D. Mark Award for Excellence in Patient Care, Stanford University School of Medicine (2009)
  • Joseph W. St. Geme, Jr. Education Award, Western Society for Pediatric Research (2009)
  • Virginia Apgar Award in Perinatal Pediatrics, American Academy of Pediatrics (2006)
  • MENTOR Award for Excellence in Research Training, The National Institute of Child Health and Human Development (2004)
  • The Neonatal Education Award in Perinatal Pediatrics, American Academy of Pediatrics (2004)
  • Advisor of Highest Distinction for Exemplary Contributions to Undergraduate Education, Stanford University (2004)
  • The Duane Alexander Award for Academic Leadership in Perinatal Medicine, The National Institute of Child Health and Human Development (2003)
  • American Academy of Pediatrics Award for Excellence in Pediatric Research, American Academy of Pediatrics (1991)
  • Ross Young Investigator Award, Western Society for Pediatric Research (1990)
  • Kaiser Award for Outstanding and Innovative Contributions to Medical Education, The Henry J. Kaiser Family Foundation (1983)

Boards, Advisory Committees, Professional Organizations


  • Chair, Maureen Andrew Mentor Award Selection Committee, Society for Pediatric Research (2013 - Present)

Professional Education


  • Board Certification: Pediatrics, American Board of Pediatrics (1979)
  • Residency:University of Washington School of Medicine (1977) WA
  • Internship:University of Washington School of Medicine (1976) WA
  • Medical Education:University of Washington School of Medicine (1975) WA
  • Board Certification: Neonatal-Perinatal Medicine, American Board of Pediatrics (1979)
  • Fellowship:Stanford University Medical Center (1979) CA
  • B.A., Stanford University, Philosophy (1971)
  • M.D., University of Washington School of Medicine, Medicine (1975)

Current Research and Scholarly Interests


Our research is focused on the study of the ontogeny and control of heme catabolism and bilirubin production in the developing neonate. A better understanding of the role of increased bilirubin production in neonatal jaundice and the prevention of hemolytic jaundice has remained an overall objective of our program. To this end, we are actively investigating a more targeted, preventive approach to the diagnosis and treatment of newborns, who are high producers of the pigment and/or unable to efficiently eliminate bilirubin, thus leading to an accumulation of the pigment in circulation and tissues, which may lead to irreversible neurologic injury. Control of bilirubin production is a logical strategy, but has unexplored consequences for the immature mammal. Thus, we are studying the pivotal role of heme oxygenase (HO), the rate-limiting enzyme in the production of bilirubin, under a variety of commonly encountered pathological conditions, such as infection and hypoxia-ischemia, as well as in anti-oxidant defense, immune response and the regulation of hematopoiesis. In support of the above interests, studies are in progress, which are designed to screen a variety of metalloporphyrins and other compounds for maximum in vitro and in vivo efficacy with minimal side effects; to determine the ontogeny of the HO enzyme system in various murine tissues, focusing on perturbations resulting from treatment with HO inhibitors; and further to develop and test new technologies for noninvasive or minimally-invasive measurements of in vivo metabolism that could be used for diagnostic and monitoring purposes.

Clinical Trials


  • Early Blood Pressure Management in Extremely Premature Infants Not Recruiting

    This trial tests the feasibility of enrolling 60 extremely preterm infants in a randomized, double-blinded study of blood pressure management within 12 months. Eligible infants will receive an infusion drug (dopamine or a dextrose placebo) and a syringe drug (hydrocortisone or a normal saline placebo). Enrolled infants will be randomized to receive one of the following drug pairs: - dopamine and hydrocortisone - dopamine and normal saline - dextrose and hydrocortisone - dextrose and normal saline. In addition to the intervention above, the NRN is conducting a 6-month time-limited prospective observational study of all infants born at an NRN center between 23 and 26 weeks gestational age. All clinical decisions made for these babies will be at the discretion of the attending neonatologist/infant care team according to standard practice at each institution. Data on blood pressure management in the first 24 postnatal hours collected for each infant.

    Stanford is currently not accepting patients for this trial. For more information, please contact M Bethany Ball, (650) 725 - 8342.

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  • Laparotomy vs. Drainage for Infants With Necrotizing Enterocolitis Recruiting

    This trial will compare the effectiveness of two surgical procedures -laparotomy versus drainage - commonly used to treat necrotizing enterocolitis (NEC) or isolated intestinal perforations (IP) in extremely low birth weight infants (≤1,000 g). Infants diagnosed with NEC or IP requiring surgical intervention, will be recruited. Subjects will be randomized to receive either a laparotomy or peritoneal drainage. Primary outcome is impairment-free survival at 18-22 months corrected age.

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  • Late Hypothermia for Hypoxic-Ischemic Encephalopathy Recruiting

    This study is a randomized, placebo-controlled, clinical trial to evaluate whether induced whole-body hypothermia initiated between 6-24 hours of age and continued for 96 hours in infants ≥ 36 weeks gestational age with hypoxic-ischemic encephalopathy will reduce the incidence of death or disability at 18-24 months of age. The study will enroll 168 infants with signs of hypoxic-ischemic encephalopathy at 16 NICHD Neonatal Research Network sites, and randomly assign them to either receive hypothermia or participate in a non-cooled control group.

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  • Optimizing (Longer, Deeper) Cooling for Neonatal Hypoxic-Ischemic Encephalopathy(HIE) Not Recruiting

    The Optimizing Cooling trial will compare four whole-body cooling treatments for infants born at 36 weeks gestational age or later with hypoxic-ischemic encephalopathy: (1) cooling for 72 hours to 33.5°C; (2) cooling for 120 hours to 33.5°C; (3) cooling for 72 hours to 32.0°C; and (4) cooling for 120 hours to 32.0°C. The objective of this study is to evaluate whether whole-body cooling initiated at less than 6 hours of age and continued for 120 hours and/or a depth at 32.0°C in will reduce death and disability at 18-22 months corrected age.

    Stanford is currently not accepting patients for this trial. For more information, please contact M Bethany Ball, (650) 725 - 8342.

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  • Vitamin E for Extremely Preterm Infants Recruiting

    The purpose of this pilot trial is to test the safety and efficacy of administering one dose of vitamin E, via a tube into the stomach, to extremely preterm infants (less than 27 weeks gestation and less than 1000 grams birth weight). This pilot will examine whether a single dose of vitamin E will be absorbed into the infants' bloodstreams with resulting serum α-tocopherol level in the target range of 1-3 mg/dl.

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  • Inhaled PGE1 in Neonatal Hypoxemic Respiratory Failure Not Recruiting

    This pilot study was a randomized, placebo-controlled, clinical trial to test the safety of using the intravenous form of Prostaglandin E1 (PGE1) in an inhaled form for treatment of hypoxemic respiratory failure in term newborns. The study planned to enroll 50 infants diagnosed with hypoxemic respiratory failure at nine NICHD Neonatal Research Network sites, and randomly assign them to receive one dose over a 72-hour period of either high concentration PGE1 (300 ng/kg/min), low concentration PGE1 (150 ng/kg/min), or placebo (normal saline, the diluent for the drug). In addition to determining the safety, optimal dose, and duration of the therapy, this pilot trial planned to evaluate the feasibility of conducting a larger, multi-center randomized, blinded placebo-controlled trial.

    Stanford is currently not accepting patients for this trial. For more information, please contact Bethany Ball, (650) 725 - 8342.

    View full details

2013-14 Courses


Postdoctoral Advisees


Journal Articles


  • Transdisciplinary translational science and the case of preterm birth JOURNAL OF PERINATOLOGY Stevenson, D. K., Shaw, G. M., Wise, P. H., Norton, M. E., Druzin, M. L., Valantine, H. A., McFarland, D. A. 2013; 33 (4): 251-258

    Abstract

    Medical researchers have called for new forms of translational science that can solve complex medical problems. Mainstream science has made complementary calls for heterogeneous teams of collaborators who conduct transdisciplinary research so as to solve complex social problems. Is transdisciplinary translational science what the medical community needs? What challenges must the medical community overcome to successfully implement this new form of translational science? This article makes several contributions. First, it clarifies the concept of transdisciplinary research and distinguishes it from other forms of collaboration. Second, it presents an example of a complex medical problem and a concrete effort to solve it through transdisciplinary collaboration: for example, the problem of preterm birth and the March of Dimes effort to form a transdisciplinary research center that synthesizes knowledge on it. The presentation of this example grounds discussion on new medical research models and reveals potential means by which they can be judged and evaluated. Third, this article identifies the challenges to forming transdisciplines and the practices that overcome them. Departments, universities and disciplines tend to form intellectual silos and adopt reductionist approaches. Forming a more integrated (or 'constructionist'), problem-based science reflective of transdisciplinary research requires the adoption of novel practices to overcome these obstacles.

    View details for DOI 10.1038/jp.2012.133

    View details for Web of Science ID 000316833300001

    View details for PubMedID 23079774

  • Effect of light exposure on metalloporphyrin-treated newborn mice PEDIATRIC RESEARCH Schulz, S., Wong, R. J., Kalish, F. S., Zhao, H., Jang, K. Y., Vreman, H. J., Stevenson, D. K. 2012; 72 (2): 161-168

    Abstract

    Neonatal hyperbilirubinemia arises from increased bilirubin production and decreased bilirubin elimination. Although phototherapy safely and effectively reduces bilirubin levels, recent evidence shows that it has adverse effects. Therefore, alternative treatments are warranted. Metalloporphyrins, competitive inhibitors of heme oxygenase (HO), the rate-limiting enzyme in bilirubin production, effectively reduce bilirubin formation; however, many are photoreactive. Here, we investigated possible photosensitizing effects of chromium mesoporphyrin (CrMP) and zinc deuteroporphyrin bis-glycol (ZnBG).Administration of CrMP or ZnBG to 3-d-old mouse pups (3.75-30.0 ?mol/kg intraperitoneally) and exposure to cool white (F20T12CW) and blue (TL20W/52) fluorescent lights (+L) for 3 h, resulted in a dose-dependent mortality (50% lethal dose (LD50) = 21.5 and 19.5 ?mol/kg, respectively). In contrast to ZnBG, there was no significant difference in survival between the CrMP+L and CrMP groups. Following 30 ?mol/kg ZnBG+L, we found significant weight loss, decreased liver antioxidant capacities, and increased aspartate aminotransaminase levels. At 6-d post-light exposure, ZnBG+L-treated pups showed gross and histologic skin changes at doses >7.5 ?mol/kg. No lethality was observed following treatment with 30 ?mol ZnBG/kg plus exposure to blue light-emitting diodes. Phototoxicity of ZnBG was dependent on light source, emission spectrum, and irradiance.Low doses of ZnBG (<3.75 ?mol/kg) retained maximal HO inhibitory potency without photosensitizing effects, and therefore are potentially useful in treating neonatal hyperbilirubinemia.

    View details for DOI 10.1038/pr.2012.62

    View details for Web of Science ID 000306862000007

    View details for PubMedID 22580722

  • A deficiency in haem oxygenase-1 induces foetal growth restriction by placental vasculature defects ACTA PAEDIATRICA Wong, R. J., Zhao, H., Stevenson, D. K. 2012; 101 (8): 827-834

    Abstract

    Haem oxygenase-1 (HO-1), the rate-limiting enzyme in haem degradation, plays a role in angiogenesis and vasculogenesis and is highly expressed in the placenta. Deficiencies in HO-1 are associated with several pregnancy disorders, such as recurrent miscarriages and pre-eclampsia. The unique combination of tissue protective, smooth muscle relaxing and angiogenesis regulatory properties makes HO-1 a key player in the maintenance of a healthy pregnancy through a direct effect on placental structural and vascular development, thus affecting foetal development. Conclusion:? Therefore, we conclude that HO-1 plays an important role in placental vasculature development and a deficiency in HO-1 may contribute to pregnancy complications, such as pre-eclampsia, spontaneous abortions and premature births.

    View details for DOI 10.1111/j.1651-2227.2012.02729.x

    View details for Web of Science ID 000306398200025

    View details for PubMedID 22594519

  • Metalloporphyrins - an update. Frontiers in pharmacology Schulz, S., Wong, R. J., Vreman, H. J., Stevenson, D. K. 2012; 3: 68-?

    Abstract

    Metalloporphyrins are structural analogs of heme and their potential use in the management of neonatal hyperbilirubinemia has been the subject of considerable research for more than three decades. The pharmacological basis for using this class of compounds to control bilirubin levels is the targeted blockade of bilirubin production through the competitive inhibition of heme oxygenase (HO), the rate-limiting enzyme in the bilirubin production pathway. Ongoing research continues in the pursuit of identifying ideal metalloporphyrins, which are safe and effective, by defining therapeutic windows and targeted interventions for the treatment of excessive neonatal hyperbilirubinemia.

    View details for DOI 10.3389/fphar.2012.00068

    View details for PubMedID 22557967

  • Maternal Heme Oxygenase 1 Regulates Placental Vasculature Development via Angiogenic Factors in Mice BIOLOGY OF REPRODUCTION Zhao, H., Azuma, J., Kalish, F., Wong, R. J., Stevenson, D. K. 2011; 85 (5): 1005-1012

    Abstract

    The placental vasculature is critical for nutrient, gas, and waste exchange between the maternal and fetal systems. Its development depends on the proper expression and interaction of angiogenesis and associated growth factors. Heme oxygenase (HMOX), the enzyme for heme degradation, plays a role in angiogenesis and is highly expressed in the placenta. To evaluate the role of maternal HMOX1, the inducible HMOX isozyme, on placental vasculature formation, mice with a partial deficiency in Hmox1 (Hmox1(+/-)) were used. Three-dimensional images of placental vasculatures as well as spiral arteries from Hmox1(+/+) or Hmox1(+/-) placentas were created by vascular corrosion casting technique and imaged by micro-computerized tomography (microCT). The structures and morphologies of fetomaternal interfaces were observed by histological staining and the ultrastructure of uterine natural killer (uNK) cells, a major regulator in spiral artery remodeling, was analyzed by transmission electron microscopy. A group of growth factors and angiogenic factors from the decidua/mesometrial lymphoid aggregate of pregnancy (MLAp) as well as labyrinth regions were quantified using an angiogenesis PCR array kit and compared between Hmox1(+/+) or Hmox1(+/-) placentas. In conclusion, a partial deficiency of maternal Hmox1 resulted in the malformation of fetomaternal interface, insufficiency of spiral artery remodeling, and alteration of uNK cell differentiation and maturation. These changes were independent of the fetal genotype, but relied on the maternal HMOX1 level, which determined the balance of expression levels of pro- and antiangiogenic factors in the decidua/MLAp region. These results implied that Hmox1 polymorphisms among the human population might contribute to some unexplained cases of pregnancy disorders, such as fetal growth retardation and preeclampsia.

    View details for DOI 10.1095/biolreprod.111.093039

    View details for Web of Science ID 000296580000014

    View details for PubMedID 21778140

  • Effects of Zinc Deuteroporphyrin Bis Glycol on Newborn Mice After Heme Loading PEDIATRIC RESEARCH He, C. X., Campbell, C. M., Zhao, H., Kalish, F. S., Schulz, S., Vreman, H. J., Wong, R. J., Stevenson, D. K. 2011; 70 (5): 467-472

    Abstract

    Infants with hemolytic diseases frequently develop hyperbilirubinemia and are treated with phototherapy, which only eliminates bilirubin after its production. A better strategy might be to directly inhibit heme oxygenase (HO), the rate-limiting enzyme in bilirubin production. Metalloporphyrins (Mps) are heme analogs that competitively inhibit HO activity in vitro and in vivo and suppress plasma bilirubin levels in vivo. A promising Mp, zinc deuteroporphyrin bis glycol (ZnBG), is orally absorbed and effectively inhibits HO activity at relatively low doses. We determined the I(50) (the dose needed to inhibit HO activity by 50%) of orally administered ZnBG in vivo and then evaluated ZnBG's effects on in vivo bilirubin production, HO activity, HO protein levels, and HO-1 gene expression in newborn mice after heme loading, a model analogous to a hemolytic infant. The I(50) of ZnBG was found to be 4.0 ?mol/kg body weight (BW). At a dose of 15 ?mol/kg BW, ZnBG reduced in vivo bilirubin production, inhibited heme-induced liver HO activity and spleen HO activity to and below baseline, respectively, transiently induced liver and spleen HO-1 gene transcription, and induced liver and spleen HO-1 protein levels. We conclude that ZnBG may be an attractive compound for treating severe neonatal hyperbilirubinemia caused by hemolytic disease.

    View details for Web of Science ID 000296121100005

    View details for PubMedID 21785387

  • Is phototherapy exposure associated with better or worse outcomes in 501-to 1000-g-birth-weight infants? ACTA PAEDIATRICA Hintz, S. R., Stevenson, D. K., Yao, Q., Wong, R. J., Das, A., Van Meurs, K. P., Morris, B. H., Tyson, J. E., Oh, W., Poole, W. K., Phelps, D. L., McDavid, G. E., Grisby, C., Higgins, R. D. 2011; 100 (7): 960-965

    Abstract

    ?To compare risk-adjusted outcomes at 18- to 22-month-corrected age for extremely low birth weight (ELBW) infants who never received phototherapy (NoPTx) to those who received any phototherapy (PTx) in the NICHD Neonatal Research Network randomized trial of Aggressive vs. Conservative Phototherapy.Outcomes at 18 to 22-month-corrected age included death, neurodevelopmental impairment (NDI) and Bayley Scales Mental Developmental Index (MDI). Regression models evaluated the independent association of PTx with adverse outcomes controlling for centre and other potentially confounding variables.Of 1972 infants, 216 were NoPTx and 1756 were PTx. For the entire 501- to 1000-g-BW cohort, PTx was not independently associated with death or NDI (OR 0.85, 95% CI: 0.60-1.20), death or adverse neurodevelopmental endpoints. However, among infants 501-750 g BW, the rate of significant developmental impairment with MDI?

    View details for DOI 10.1111/j.1651-2227.2011.02175.x

    View details for Web of Science ID 000291224200021

    View details for PubMedID 21272067

  • Bilirubin Production and the Risk of Bilirubin Neurotoxicity SEMINARS IN PERINATOLOGY Stevenson, D. K., Vreman, H. J., Wong, R. J. 2011; 35 (3): 121-126

    Abstract

    Neonatal jaundice usually occurs in the transitional period after birth, presenting as an elevation of circulating bilirubin. Bilirubin neurotoxicity can occur if the levels of bilirubin become excessive (hyperbilirubinemia). This pathologic phenotype of newborn jaundice can develop because of excessive bilirubin production or impaired conjugation, with the risk for developing bilirubin-induced neurologic dysfunction, depending on the degree of the resultant bilirubin load. The plasma bilirubin level thus can be used to assess an infant's risk for developing bilirubin neurotoxicity relative to an infant's age in hours. Because all infants have an impaired conjugation ability, infants at greatest risk are those who have increased bilirubin production rates, because of hemolysis, for example. Therefore, developing potential preventive strategies as well as noninvasive technologies to treat and to identify infants with increased bilirubin production rates, respectively, are tantamount to reducing the incidence of bilirubin-induced neurologic dysfunction.

    View details for DOI 10.1053/j.semperi.2011.02.005

    View details for Web of Science ID 000292057900004

    View details for PubMedID 21641484

  • Panhematin provides a therapeutic benefit in experimental pancreatitis GUT Habtezion, A., Kwan, R., Akhtar, E., Wanaski, S. P., Collins, S. D., Wong, R. J., Stevenson, D. K., Butcher, E. C., Omary, M. B. 2011; 60 (5): 671-679

    Abstract

    Acute pancreatitis (AP) can result in pancreatic necrosis and inflammation, with subsequent multi-organ failure. AP is associated with increased neutrophil recruitment and a rise in pro-inflammatory cytokines such as TNF?. Pretreatment with haemin, results in recruitment of haem-oxygenase-1 (HO-1)(+) macrophages and protects against experimental pancreatitis. It is not clear whether modulation of HO-1 after onset of disease has a protective role. In this study, we tested the utility of Panhematin, a water-soluble haemin formulation, in activating and inducing pancreatic HO-1, and as a therapeutic agent in treating mouse acute pancreatitis.We defined the distribution of radiolabelled haemin, then used in vivo HO-1-luciferase bioluminescence imaging and the CO-release assay to test Panhematin-induced upregulation of HO-1 transcription and activity, respectively. Using two well-defined AP murine models, we tested the therapeutic benefit of Panhematin, and quantified cytokine release using a luminex assay.Intravenously administered Panhematin induces rapid recruitment of HO-1(+) cells to the pancreas within 2 h and de novo splenic HO-1 transcription by 12 h. Despite high baseline spleen HO-1 activity, the pancreas is particularly responsive to Panhematin-mediated HO-1 induction. Panhematin-treated mice, at various time points after AP induction had significant reduction in mortality, pancreatic injury, together with upregulation of HO-1 and downregulation of pro-inflammatory cytokines and CXCL1, a potent neutrophil chemoattractant.Despite AP-associated mortality and morbidity, no effective treatment other than supportive care exists. We demonstrate that Panhematin leads to: (i) rapid induction and activation of pancreatic HO-1 with recruitment of HO-1(+) cells to the pancreas, (ii) amelioration of AP even when given late during the course of disease, and (iii) a decrease in leucocyte infiltration and pro-inflammatory cytokines including CXCL1. The utility of Panhematin at modest doses as a therapeutic in experimental pancreatitis, coupled with its current use and safety in humans, raises the potential of its applicability to human pancreatitis.

    View details for DOI 10.1136/gut.2010.217208

    View details for Web of Science ID 000289076700015

    View details for PubMedID 21159893

  • In vitro inhibition of heme oxygenase isoenzymes by metalloporphyrins JOURNAL OF PERINATOLOGY Wong, R. J., Vreman, H. J., Schulz, S., Kalish, F. S., Pierce, N. W., Stevenson, D. K. 2011; 31: S35-S41

    Abstract

    Neonatal jaundice results from an increased bilirubin production and decreased hepatic bilirubin conjugation and excretion. Severe hyperbilirubinemia is currently treated with phototherapy or exchange transfusion; however, its prevention by inhibiting bilirubin formation is a more logical strategy. Heme oxygenase (HO), with inducible (HO-1) and constitutive (HO-2) isoenzymes, is the rate-limiting enzyme in heme catabolism, producing equimolar amounts of bilirubin and carbon monoxide (CO). Metalloporphyrins (Mps) are heme derivatives that competitively inhibit HO and thereby suppress hyperbilirubinemia. No systematic studies have been reported evaluating whether the HO isoenzymes are inhibited differentially by various Mps. Identification of Mps that selectively inhibit the inducible HO-1 without affecting the 'housekeeping' HO-2 isoenzyme might be desirable in the clinical setting of hemolytic disease, in which the Hmox1 gene is greatly induced. Although bilirubin production is due to the activity of both HO-1 and HO-2, the inhibition of HO-1 with a relative sparing of HO-2 activity might provide the most selective approach for the treatment of hemolytic disease.We determined for the deutero-, proto-, meso- and bis-glycol porphyrins with zinc, tin and chromium as central atoms, respectively, the concentration needed for 50% inhibition (I(50)) of HO-1 and HO-2 activities in rat spleen and brain tissue.For a given Mp, HO-1 activity was less inhibited than that of HO-2. The order of inhibitor potency of each Mp was nearly identical for both isoenzymes. Tin mesoporphyrin was the most potent inhibitor for both isoenzymes. HO-2 selectivity was greatest for tin protoporphyrin. Conversely, the Zn compounds were least inhibitory toward HO-2. No Mp preferentially inhibited HO-1.Mps that produce a less inhibitory effect on HO-2, while limiting the response of the inducible HO-1, such as ZnPP, may be a useful clinical tool.

    View details for DOI 10.1038/jp.2010.173

    View details for Web of Science ID 000289236900006

    View details for PubMedID 21448202

  • Phil Sunshine: Apgar Award recipient. Journal of perinatology Stevenson, D. K. 2011; 31: S2-5

    View details for DOI 10.1038/jp.2010.171

    View details for PubMedID 21448198

  • Metalloporphyrins in the management of neonatal hyperbilirubinemia SEMINARS IN FETAL & NEONATAL MEDICINE Stevenson, D. K., Wong, R. J. 2010; 15 (3): 164-168

    Abstract

    Neonatal jaundice in the first week of life is a common problem in newborns. It is due to an imbalance of bilirubin production and its elimination, which can lead to significantly elevated levels of circulating bilirubin or hyperbilirubinemia. Use of phototherapy and/or exchange transfusion are the current modes for treating neonatal hyperbilirubinemia and preventing any neurologic damage. These strategies, however, only remove bilirubin that has already been formed. Preventing the production of excess bilirubin may be a more logical approach. Synthetic heme analogs, metalloporphyrins, are competitive inhibitors of heme oxygenase, the rate-limiting enzyme in bilirubin production, and their use has been proposed as an attractive alternative strategy for preventing or treating severe hyperbilirubinemia.

    View details for DOI 10.1016/j.siny.2009.11.004

    View details for Web of Science ID 000278039100008

    View details for PubMedID 20006567

  • Understanding Neonatal Jaundice: A Perspective on Causation PEDIATRICS AND NEONATOLOGY Cohen, R. S., Wong, R. J., Stevenson, D. K. 2010; 51 (3): 143-148

    Abstract

    Neonatal jaundice can be best understood as a balance between the production and elimination of bilirubin, with a multitude of factors and conditions affecting each of these processes. When an imbalance results because of an increase in circulating bilirubin (or the bilirubin load) to significantly high levels (severe hyperbilirubinemia), it may cause permanent neurologic sequelae (kernicterus). In most infants, an increase in bilirubin production (e.g., due to hemolysis) is the primary cause of severe hyperbilirubinemia, and thus reducing bilirubin production is a rational approach for its management. The situation can become critical in infants with an associated impaired bilirubin elimination mechanism as a result of a genetic deficiency and/or polymorphism. Combining information about bilirubin production and genetic information about bilirubin elimination with the tracking of bilirubin levels means that a relative assessment of jaundice risk might be feasible. Information on the level of bilirubin production and its rate of elimination may help to guide the clinical management of neonatal jaundice.

    View details for Web of Science ID 000278799200002

    View details for PubMedID 20675237

  • Effect of Heme Oxygenase-1 Deficiency on Placental Development PLACENTA Zhao, H., Wong, R. J., Kalish, F. S., Nayak, N. R., Stevenson, D. K. 2009; 30 (10): 861-868

    Abstract

    Heme oxygenase (HO) is the rate-limiting enzyme in the heme catabolic pathway and highly expressed in the placenta. Deficiencies in HO-1, the inducible isoform, have been associated with pregnancy disorders, such as recurrent miscarriages, intrauterine growth retardation, and pre-eclampsia. The aim of this study was to identify if a deficiency in HO-1 affects placental development using a mouse model. When HO-1 heterozygote (Het, HO-1(+/-)) mice were cross-bred, an extremely low birth rate in homozygote (Mut, HO-1(-/-)) offspring (2.4%) and small litter sizes were observed. Placentas and fetuses from Het cross-breedings were relatively smaller and weighed less than those from wild-type (WT) cross-breedings at E12.5 and E15.5. Furthermore, Het placentas had significantly less HO-1 mRNA and protein levels than WT placentas, but no significant differences in placental HO activity. Interestingly, HO-2, the constituitive HO isoform, as well as iNOS and eNOS expression were significantly upregulated in Het placentas. Histological examination showed that the junctional zone (JZ) of Het placentas were markedly thinner than those of WT placentas and appeared to be due to an increase in apoptosis. Immunohistochemistry revealed that HO-1-expressing cells were located primarily in the JZ of Het placentas, specifically in the spongiotrophoblast layer. In addition, diastolic blood pressures and plasma soluble VEGFR-1 (sFlt-1) levels were significantly elevated in pregnant Het mice. We conclude that a partial deficiency in HO-1 is associated with morphological changes in the placenta and elevations in maternal diastolic blood pressure and plasma sFlt-1 levels, despite a compensatory increase in HO-2 expression.

    View details for DOI 10.1016/j.placenta.2009.07.012

    View details for Web of Science ID 000270706300006

    View details for PubMedID 19699520

  • Dermal Carbon Monoxide Excretion in Neonatal Rats During Light Exposure PEDIATRIC RESEARCH Vreman, H. J., Knauer, Y., Wong, R. J., Chan, M., Stevenson, D. K. 2009; 66 (1): 66-69

    Abstract

    Total body, head, and trunk carbon monoxide (CO) excretion rates were measured separately by gas chromatography in 1- to 7-d-old Wistar rat pups exposed to the dark and to mixed blue (one Special Blue-F20T12/BB) and white (two Cool White-F20T12/CW) fluorescent light or blue light emitting diode (LED) sources. During 48-min cycled exposures to the dark and to either light source, total body CO excretion rapidly increased 1.9- and 1.4-fold, respectively, over dark control levels. When CO excretion rates from the head and trunk were measured separately during exposure to either light source, CO excretion from the head did not change significantly; however, a large mean 4.4-fold increase in CO excretion from the trunk was observed. When light intensity delivered by the blue LED source was varied, we found that trunk CO excretion increased with increasing light intensities. In the presence of riboflavin (10 micromol/kg), total body CO excretion increased 2.8- and 2.1-fold during exposure to the mixed fluorescent light and blue LED sources, respectively. We conclude that light-induced elevations in total body CO excretion may be caused by transdermally excreted CO, which is most likely produced through endogenous photosensitizer-mediated photooxidation of dermal biomolecules.

    View details for Web of Science ID 000267249300013

    View details for PubMedID 19342986

  • Gastric protection by lansoprazole and the impact of heme oxygenase-1 and ferritin. World J Gastroenterol Schulz-Geske S, Erdmann K, Wong RJ, Stevenson DK, Schröder H, Grosser N. 2009; 15: 4392-401
  • Photoisomers ? Obfuscating factors in clinical peroxidase measurements of unbound bilirubin? Pediatrics McDonagh AF, Vreman HJ, Wong RJ, Stevenson DK 2009; 123: 67-76
  • Heme oxygenase-1 deficiency leads to disrupted response to acute stress in stem cells and progenitors BLOOD Cao, Y., Wagers, A. J., Karsunky, H., Zhao, H., Reeves, R., Wong, R. J., Stevenson, D. K., Weissman, I. L., Contag, C. H. 2008; 112 (12): 4494-4502

    Abstract

    An effective response to extreme hematopoietic stress requires an extreme elevation in hematopoiesis and preservation of hematopoietic stem cells (HSCs). These diametrically opposed processes are likely to be regulated by genes that mediate cellular adaptation to physiologic stress. Herein, we show that heme oxygenase-1 (HO-1), the inducible isozyme of heme degradation, is a key regulator of these processes. Mice lacking one allele of HO-1 (HO-1(+/-)) showed accelerated hematopoietic recovery from myelotoxic injury, and HO-1(+/-) HSCs repopulated lethally irradiated recipients with more rapid kinetics. However, HO-1(+/-) HSCs were ineffective in radioprotection and serial repopulation of myeloablated recipients. Perturbations in key stem cell regulators were observed in HO-1(+/-) HSCs and hematopoietic progenitors (HPCs), which may explain the disrupted response of HO-1(+/-) HPCs and HPCs to acute stress. Control of stem cell stress response by HO-1 presents opportunities for metabolic manipulation of stem cell-based therapies.

    View details for DOI 10.1182/blood-2007-12-127621

    View details for Web of Science ID 000261217000024

    View details for PubMedID 18509090

  • Aggressive vs. conservative phototherapy for infants with extremely low birth weight NEW ENGLAND JOURNAL OF MEDICINE Morris, B. H., Oh, W., Tyson, J. E., Stevenson, D. K., Phelps, D. L., O'Shea, T. M., McDavid, G. E., Perritt, R. L., Van Meurs, K. P., Vohr, B. R., Grisby, C., Yao, Q., Pedroza, C., Das, A., Poole, W. K., Carlo, W. A., Duara, S., Laptook, A. R., Salhab, W. A., Shankaran, S., Poindexter, B. B., Fanaroff, A. A., Walsh, M. C., Rasmussen, M. R., Stoll, B. J., Cotten, C. M., Donovan, E. F., Ehrenkranz, R. A., Guillet, R., Higgins, R. D. 2008; 359 (18): 1885-1896

    Abstract

    It is unclear whether aggressive phototherapy to prevent neurotoxic effects of bilirubin benefits or harms infants with extremely low birth weight (1000 g or less).We randomly assigned 1974 infants with extremely low birth weight at 12 to 36 hours of age to undergo either aggressive or conservative phototherapy. The primary outcome was a composite of death or neurodevelopmental impairment determined for 91% of the infants by investigators who were unaware of the treatment assignments.Aggressive phototherapy, as compared with conservative phototherapy, significantly reduced the mean peak serum bilirubin level (7.0 vs. 9.8 mg per deciliter [120 vs. 168 micromol per liter], P<0.01) but not the rate of the primary outcome (52% vs. 55%; relative risk, 0.94; 95% confidence interval [CI], 0.87 to 1.02; P=0.15). Aggressive phototherapy did reduce rates of neurodevelopmental impairment (26%, vs. 30% for conservative phototherapy; relative risk, 0.86; 95% CI, 0.74 to 0.99). Rates of death in the aggressive-phototherapy and conservative-phototherapy groups were 24% and 23%, respectively (relative risk, 1.05; 95% CI, 0.90 to 1.22). In preplanned subgroup analyses, the rates of death were 13% with aggressive phototherapy and 14% with conservative phototherapy for infants with a birth weight of 751 to 1000 g and 39% and 34%, respectively (relative risk, 1.13; 95% CI, 0.96 to 1.34), for infants with a birth weight of 501 to 750 g.Aggressive phototherapy did not significantly reduce the rate of death or neurodevelopmental impairment. The rate of neurodevelopmental impairment alone was significantly reduced with aggressive phototherapy. This reduction may be offset by an increase in mortality among infants weighing 501 to 750 g at birth. (ClinicalTrials.gov number, NCT00114543.)

    View details for Web of Science ID 000260454500005

    View details for PubMedID 18971491

  • Inhibition of heme oxygenase activity in newborn mice by azalanstat CANADIAN JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY Morisawa, T., Wong, R. J., Bhutani, V. K., Vreman, H. J., Stevenson, D. K. 2008; 86 (10): 651-659

    Abstract

    Inhibition of heme oxygenase (HO), the rate-limiting enzyme in heme catabolism, may be an ideal strategy for preventing neonatal jaundice. Although natural and synthetic heme analogs, called metalloporphyrins (Mps), have been extensively investigated for this purpose, some Mps are phototoxic, affect the activity of other enzymes, or induce HO-1 transcription-properties that may limit their clinical use. Another class of compounds, imidazole-dioxolanes, has been shown to selectively inhibit the inducible isozyme HO-1. Therefore, we investigated the efficacy of azalanstat (AZA), an imidazole-dioxolane, towards inhibiting HO activity in 7-day-old mice. We found that a single dose of AZA at 500 micromol.kg(-1) body mass (BM) administered i.p. significantly inhibited HO activity and reduced in vivo bilirubin production. In the spleen, HO inhibition (>50%) was observed within 0.25-3 h after administration. After 24 h, however, spleen HO activity, HO-1 protein, and HO-1 mRNA levels significantly increased 1.2-, 2.4-, and 4.0-fold, respectively. We conclude that AZA effectively inhibits in vivo HO activity only at a high dose and that it also induces spleen HO-1 gene transcription. Therefore, other imidazole-dioxolanes should be evaluated to determine whether they are more potent than AZA for use in treating neonatal jaundice.

    View details for DOI 10.1139/Y08-069

    View details for Web of Science ID 000260168100001

    View details for PubMedID 18841169

  • Regulation of maternal and fetal hemodynamics by heme oxygenase in mice BIOLOGY OF REPRODUCTION Zhao, H., Wong, R. J., Doyle, T. C., Nayak, N., Vreman, H. J., Contag, C. H., Stevenson, D. K. 2008; 78 (4): 744-751

    Abstract

    Heme oxygenase (HMOX) regulates vascular tone and blood pressure through the production of carbon monoxide (CO), a vasodilator derived from the heme degradation pathway. During pregnancy, the maternal circulation undergoes significant adaptations to accommodate the hemodynamic demands of the developing fetus. Our objective was to investigate the role of HMOX on maternal and fetal hemodynamics during pregnancy in a mouse model. We measured and compared maternal tissue and placental HMOX activity and endogenous CO production, represented by excreted CO and carboxyhemoglobin levels, during pregnancy (Embryonic Days 12.5-15.5) to nonpregnant controls. Micro-ultrasound was used to monitor maternal abdominal aorta diameters as well as blood flow velocities and diameters of fetal umbilical arteries. Tin mesoporphyrin, a potent HMOX inhibitor, was used to inhibit HMOX activity. Changes in maternal vascular tone were monitored by tail cuff blood pressure measurements. Effects of HMOX inhibition on placental structures were assessed by histology. We showed that maternal tissue and placental HMOX activity and CO production were significantly elevated during pregnancy. When HMOX in the placenta was inhibited, maternal and fetal hemodynamics underwent significant changes, with maternal blood pressures increasing. We concluded that increases in maternal tissue and placental HMOX activity contribute to the regulation of peripheral vascular resistance and therefore are important for the maintenance of normal maternal vascular tone and fetal hemodynamic functions during pregnancy.

    View details for DOI 10.1095/biolreprod.107.064899

    View details for Web of Science ID 000254217500020

    View details for PubMedID 18094356

  • Standardized bench method for evaluating the efficacy of phototherapy devices ACTA PAEDIATRICA Vreman, H. J., Wong, R. J., Murdock, J. R., Stevenson, D. K. 2008; 97 (3): 308-316

    Abstract

    As phototherapy (PT) devices employ a variety of broadband light sources, we developed and tested a standardized bench method for evaluating the efficacy of some devices.To evaluate efficacy, we quantified the in vitro photodegradation rate (expressed as t1/2) of unconjugated bilirubin in solution at 37 degrees C during exposure to a given light source at its mean delivered irradiance to the 2D body surface area (BSA) of newborn models. Reproducibility (between-day variation) of the method was determined at irradiance levels from 10 to 70 microW/cm2/nm on three different days.Between-day t1/2 measurements had coefficients of variation from 3% to 10%. When t1/2 values were normalized to the exposable 2D horizontal BSA, halogen lamp devices, without and with fiberoptics, were least effective (t1/2=60-108 min and 100-126 min for preterm and term models, respectively). Fluorescent tube devices had t1/2=19-78 min and 25-78 min, for preterm and term models, respectively. Light-emitting diode (LED)-based devices yielded the shortest t1/2 values (16-24 min) for preterm and term newborn models.We demonstrated the applicability of the method through the determination of the efficacy of several commercially available PT devices. This standardized method is reproducible and effectively evaluates the relative in vitro efficacy of various devices and may guide further in vitro and in vivo evaluations of devices.

    View details for DOI 10.1111/j.1651-2227.2007.00631.x

    View details for Web of Science ID 000253504300012

    View details for PubMedID 18241292

  • Statin treatment increases formation of carbon monoxide and bilirubin in mice: a novel mechanism of in vivo antioxidant protection CANADIAN JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY Muchova, L., Wong, R. J., Hsu, M., Morioka, O., Vitek, L., Zelenka, J., Schroeder, H., Stevenson, D. K. 2007; 85 (8): 800-810

    Abstract

    Heme oxygenase (HO) has a central role in cellular antioxidant defences and vascular protection, and it may mediate pleiotropic actions of drugs used in cardiovascular therapy. We investigated whether long-term use of statins upregulates HO activity and increases carbon monoxide (CO) and bilirubin levels in vivo. Adult FvB mice were given atorvastatin or rosuvastatin (5 mg/kg) daily by i.p. injections for 1, 2, or 3 weeks. HO activity, tissue CO, bilirubin, and antioxidant levels, total plasma bilirubin, and carboxyhemoglobin (COHb) were measured. Fold changes in heart HO activity significantly increased after 1, 2, and 3 weeks of atorvastatin (1.24 +/- 0.06 (p < or = 0.05); 1.29 +/- 0.26 (p < or = 0.03); 1.33 +/- 0.08 (p < 0.01), respectively) and 2 and 3 weeks of rosuvastatin (1.23 +/- 0.20 (p < or = 0.03); 1.63 +/- 0.42 (p < 0.01), respectively). Heart tissue CO and COHb levels also increased after 3 weeks with atorvastatin (1.30 +/- 0.24 (p < or = 0.05); 1.92 +/- 0.17 (p < or = 0.001), respectively) and rosuvastatin (1.47 +/- 0.13 (p < or = 0.004); 1.63 +/- 0.12 (p < or = 0.001), respectively). Significant increases in heart antioxidant levels were observed after statin treatment and corroborated by heart bilirubin content elevations. Antioxidant level increases were abolished by treatment with an HO inhibitor. These findings suggest that the induction of HO and the production of its products, CO and bilirubin, may be a mechanism by which statins exert antioxidant actions and confer cardioprotection in vivo.

    View details for DOI 10.1139/Y07-077

    View details for Web of Science ID 000250261400006

    View details for PubMedID 17901890

  • (TA)(n) UGT 1A1 promoter polymorphism: A crucial factor in the pathophysiology of jaundice in G-6-PD deficient neonates PEDIATRIC RESEARCH Kaplan, M., Renbaum, P., Vreman, H. J., Wong, R. J., Levy-Lahad, E., Hammerman, C., Stevenson, D. K. 2007; 61 (6): 727-731

    Abstract

    Increased heme catabolism has been reported in glucose-6-phosphate dehydrogenase (G-6-PD)-normal neonates who were also homozygous for (TA)7/(TA)7 (UGT1A1*28) uridine diphosphoglucuronate-glucuronosyltransferase 1A1 (UGT) promoter polymorphism (Gilbert syndrome). As G-6-PD deficiency is associated with increased hemolysis, we hypothesized that in G-6-PD-deficient neonates who also have the (TA)7/(TA)7 UGT promoter genotype, steady-state hemolysis would be even further increased. Male G-6-PD-deficient neonates were sampled for plasma total bilirubin (PTB), blood carboxyhemoglobin corrected for inhaled carbon monoxide in ambient air (COHbc) (an index of heme catabolism), and UGT (TA)n promoter genotype determination and compared with previously published G-6-PD-normal neonates. Although COHbc values were higher in the G-6-PD-deficient than in the G-6-PD-normal cohorts (0.97 +/- 0.32% of total Hb (tHb) versus 0.76 +/- 0.19% of tHb, p < 0.001), PTB values were similar (9.2 +/- 3.4 mg/dL versus 8.9 +/- 3.0 mg/dL, respectively, p = 0.3). Within the G-6-PD-deficient group, although COHbc values were alike between the three UGT promoter genotypes, PTB was higher in the (TA)7/(TA)7 homozygotes (11.1 +/- 4.0 mg/dL) compared with (TA)6/(TA)7 heterozygotes (9.1 +/- 3.2 mg/dL, p = 0.03) and wild-type (TA)6/(TA)6 homozygotes (8.8 +/- 3.4 mg/dL, p = 0.02). In the steady state, similar rates of hemolysis, but increased PTB in the G-6-PD- deficient, (TA)7/(TA)7 homozygotes, imply that (TA)7/(TA)7, homozygosity is central to increased PTB.

    View details for DOI 10.1203/pdr.0b013e31805365c5

    View details for Web of Science ID 000246787300019

    View details for PubMedID 17426648

  • The role of Bach1 in the induction of heme oxygenase by tin mesoporphyrin BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Abate, A., Zhao, H., Wong, R. J., Stevenson, D. K. 2007; 354 (3): 757-763

    Abstract

    Tin mesoporphyrin (SnMP), a competitive heme oxygenase (HO) inhibitor, also induces HO-1 mRNA and protein expression by a mechanism that is not fully understood. We examined whether the induction by SnMP is mediated by a de-repression of Bach1, a transcription factor that suppresses the HO-1 gene. Incubation of NIH3T3-HO-1-luc cells with SnMP attenuated HO activity with a concomitant increase in HO-1 mRNA and protein and a decrease in Bach1 and HO-2 proteins, which was not due to transcriptional down-regulation, but accelerated protein decay. Similarly, HO-1 protein degradation was increased by SnMP, despite of an elevation in HO-1 transcription. Transfection of Bach1 shRNA in Hepa cells raised basal HO-1 expression significantly, and SnMP treatment further increased HO-1 mRNA. In conclusion, SnMP induces HO-1 expression not only by de-repressing the HO-1 promoter by binding Bach1, but also by accelerating Bach1 degradation.

    View details for DOI 10.1016/j.bbrc.2007.01.050

    View details for Web of Science ID 000244284300021

    View details for PubMedID 17257585

  • American Pediatric Society presidential address 2006: Science on the edge with life in the balance PEDIATRIC RESEARCH Stevenson, D. K. 2006; 60 (5): 630-635
  • Expression and regulation of heme oxygenase isozymes in the developing mouse cortex PEDIATRIC RESEARCH Zhao, H., Wong, R. J., Nguyen, X., Kalish, F., Mizobuchi, M., Vreman, H. J., Stevenson, D. K., Contag, C. H. 2006; 60 (5): 518-523

    Abstract

    Heme oxygenase (HO), the rate-limiting enzyme in heme degradation, plays a role in neonatal jaundice. Understanding the regulation of the developmental expression patterns of the two HO isozymes, HO-1 and HO-2, is essential for targeting HO to control pathologic jaundice, and uncovering the fundamental role that they play in mammalian development. Here we characterized the ontogeny of HO-1 and HO-2 expression in the developing mouse cortex by in vivo bioluminescence imaging, quantitative RT-PCR, and Western blot. HO-2, the predominant isoform in the adult cortex, was relatively stable throughout all ages. HO-1 was observed to be progressively down-regulated in an age-related manner. HO-1 expression in the adult cortex was also the lowest among the eight adult tissues analyzed. Because there is a 283-bp CpG island region in the HO-1 promoter, we hypothesized that methylation of the island is responsible for the age-related HO-1 down-regulation in the cortex. Methylation status was assessed using regular and quantitative methylation-specific PCR and the CpG island was found to be hypomethylated at all ages. Therefore, we conclude that HO-1 gene expression in the cortex is developmentally-regulated and that methylation of the HO-1 CpG island is not associated with the down-regulation of the gene.

    View details for DOI 10.1203/01.PDR.0000242374.21415.f5

    View details for Web of Science ID 000241570300003

    View details for PubMedID 16966352

  • Concentration of carbon monoxide (CO) in postmortem human tissues: Effect of environmental CO exposure JOURNAL OF FORENSIC SCIENCES Vreman, H. J., Wong, R. J., Stevenson, D. K., Smialek, J. E., Fowler, D. R., Li, n. L., Vigorito, R. D., Zielke, H. R. 2006; 51 (5): 1182-1190

    Abstract

    We studied how carbon monoxide (CO) is distributed within the human body through quantitation of CO concentrations in postmortem tissue samples from fatalities including possible CO exposure. Stored, frozen tissues were diced, sonicated in water, and 0.01-8.0 mg wet weight (ww) tissues were incubated with sulfosalicylic acid in CO-purged, septum-sealed vials. CO released into the headspace was quantitated by reduction gas chromatography. Mean tissue CO concentrations (pmol/mg ww) from subjects diagnosed to have no known CO exposure (control, N=14), died from fire (N=13), and CO asphyxiation (N=7), respectively, were: adipose (2;13;9), brain (3;13;65), muscle (15;97;297), heart (30;99;371), kidney (22;432;709, lung (54;690;2638), spleen (73;1366;3548), and blood (162;2238;5070). Carboxyhemoglobin concentrations were 1.4%, 25.2%, and 69.1% of total hemoglobin, respectively. We conclude that measurements of CO concentration in a variety of tissues can be used as markers for the degree of exogenous CO exposure and the identification of possible causes of death.

    View details for DOI 10.1111/j.1556-4029.2006.00212.x

    View details for Web of Science ID 000240773700038

    View details for PubMedID 17018107

  • Tissue-specific effects of statins on the expression of heme oxygenase-1 in vivo BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS HSU, M., Muchova, L., Morioka, I., Wong, R. J., Schroder, H., Stevenson, D. K. 2006; 343 (3): 738-744

    Abstract

    Heme oxygenase-1 (HO-1) plays a central role in antioxidant and anti-inflammatory actions, which may be mediated through its formation of biliverdin/bilirubin and carbon monoxide. HMG-CoA reductase inhibitors (statins) induce in vitro HO-1 expression and are reported to have pleiotropic benefits that reduce oxidative stress in the vasculature. We characterized the effects of statins on in vivo HO-1 expression in various extravascular tissues: liver, lung, brain, and heart. Adult mice were orally administered simvastatin, lovastatin, atorvastatin, or rosuvastatin. HO activity significantly increased in a statin- and tissue-specific manner, with all statins increasing heart and lung activity within 24 h. Significant elevations of HO-1 protein and mRNA were also observed in heart and lung after atorvastatin treatment. We conclude that in vivo HO-1 induction is statin- and tissue-specific. Through this pathway, statins may confer antioxidant and anti-inflammatory actions in the vasculature and extravascular systems.

    View details for DOI 10.1016/j.bbrc.2006.03.036

    View details for Web of Science ID 000236976800010

    View details for PubMedID 16563347

  • Systemic effects of orally-administered zinc and tin (IV) metalloporphyrins on heme oxygenase expression in mice PEDIATRIC RESEARCH Morioka, I., Wong, R. J., Abate, A., Vreman, H. J., Contag, C. H., Stevenson, D. K. 2006; 59 (5): 667-672

    Abstract

    Some metalloporphyrins (Mps) inhibit heme oxygenase (HO), the rate-limiting enzyme in the production of bilirubin, and are potential compounds for the treatment of neonatal jaundice. We studied the safety and efficacy of Mps following oral administration. Adult HO-1-luc reporter mice were administered 30 micromol/kg body weight of tin mesoporphyrin (SnMP), zinc bis glycol deuteroporphyrin (ZnBG), or zinc protoporphyrin (ZnPP), or vehicle by oral gavage. Bilirubin production was measured as total body carbon monoxide (CO) excretion (VeCO). HO activity was quantitated via CO measurements by gas chromatography. HO-1 protein was determined by Western blot. HO-1 transcription levels were assessed by in vivo bioluminescence imaging. A significant 28% decrease in bilirubin production occurred within 3 h of SnMP treatment and persisted beyond 48 h. Bilirubin production decreased 15% and 9% by 3 h after administration of ZnBG and ZnPP, respectively, but returned to baseline within 48 h. Maximal inhibition of liver, spleen, and intestine HO activity was seen at 3 h with inhibitory effects decreasing in the order: SnMP > or = ZnBG > or = ZnPP. After SnMP treatment, HO-1 transcription increased 5.7-fold after 24 h. Furthermore, liver and spleen HO-1 protein significantly increased 3.7- and 2.0-fold, respectively, after 24 h. HO-1 transcription and protein were not affected in ZnBG- or ZnPP-treated mice. We conclude that the three Mps are absorbed at different rates in the mouse and affect bilirubin production and HO-1 expression in a tissue- and time-dependent manner.

    View details for DOI 10.1203/01.pdr.0000215088.71481.a6

    View details for Web of Science ID 000237003800009

    View details for PubMedID 16627879

  • Transcutaneous bilirubinometry: A noninvasive tool for studying newborn jaundiced rats before and after exposure to light PEDIATRIC RESEARCH Vreman, H. J., Wong, R. J., Chan, M. L., Young, B. W., Stevenson, D. K. 2006; 59 (2): 203-209

    Abstract

    The homozygous Gunn rat is the most frequently used animal model for the study of neonatal jaundice. We evaluated the applicability of noninvasive transcutaneous bilirubin (TcB) measurements as an index of serum total bilirubin (STB) levels in neonatal rats by comparison to invasive STB measurements. TcB measurements were made during the first 96 h of life with the Model 101 Minolta/Air-Shields Jaundice Meter (JM) and SpectRx BiliCheck System (BC). Measurements with both devices displayed parallel TcB profiles, rapidly rising within 24 h, increasing during the next 6 h, then leveling off after 30 h. Linear regressions for the JM (n = 60) were as follows: STB (mg/dL) = 0.79 (JM) - 0.01 (units, r = 0.95, head); STB (mg/dL) = 0.82 (JM) + 1.51 (units, r = 0.95, upper back); and STB (mg/dL) = 0.74 (JM) + 1.60 (units, r = 0.91, lower back). Mean bias +/- imprecision were as follows: -0.02 +/- 3.99 mg/dL, -0.01 +/- 3.90, and 0.01 +/- 4.28 at the head, upper back, and lower back, respectively. For the BC, only lower back measurements were taken, and the regression was as follows: STB (mg/dL) = 0.77 (BC) + 1.65 mg/dL, (r = 0.93, n = 29) with a mean bias +/- imprecision of -1.08 +/- 3.08 mg/dL. When pups were exposed to light, correlations remained strong but intercepts increased. These results demonstrate that noninvasive TcB measurements correlate highly with STB in the Gunn rat during the first 96 h of life and after exposure to light. We conclude that JM measurements at the head and BC at the lower back reflect STB most reliably and consistently. Thus, in addition to being a useful tool for evaluating jaundice in human neonates, TcB methodology can be used successfully for the noninvasive monitoring of jaundice in neonatal Gunn rats pre- and postlight exposure.

    View details for DOI 10.1203/01.pdr.000196737.73851.8a

    View details for Web of Science ID 000234764100008

    View details for PubMedID 16439579

  • The effectiveness of oral tin mesoporphyrin prophylaxis in reducing bilirubin production after an oral heme load in a transgenic mouse model BIOLOGY OF THE NEONATE DeSandre, G. H., Wong, R. J., Morioka, I., Contag, C. H., Stevenson, D. K. 2006; 89 (3): 139-146

    Abstract

    Neonatal jaundice is commonly encountered and rarely associated with morbidity and mortality. Nonetheless, infants with glucose-6-phosphate dehydrogenase deficiency often have hemolysis (a heme load) caused by an environmental oxidant trigger, thus increasing their risk for serious morbidity. The use of tin mesoporphyrin (SnMP) has been proposed for interdicting the development of severe hyperbilirubinemia in a variety of conditions.We studied the in vivo effects of prophylactic oral SnMP on heme oxygenase (HO) activity and bilirubin production, as indexed by the excretion rate of carbon monoxide (VeCO), following a subsequent oral heme load.Adult mice were exposed serially to heme and assessed for in vivo bilirubin production rates, HO-1 transcription and protein, and HO activity. The effect of prophylaxis with a single oral dose of SnMP prior to an oral heme load was assessed by measuring VeCOand tissue HO activities.After serial heme exposures, VeCO, HO-1 transcription and protein, and liver and spleen HO activities increased incrementally. After pretreatment with oral SnMP, bilirubin production decreased in response to an oral heme load. Also, heme-mediated increases in liver, spleen, and intestine HO activities were significantly dampened.A single oral dose of SnMP results in durable inhibition of bilirubin production and HO activity for at least 24 h in a mouse model of oral heme loading. Further studies are needed to fully elucidate the duration of this protection against hyperbilirubinemia due to a delayed heme load and any long-term consequences of prophylaxis with SnMP on HO-1 transcription and HO-1 protein.

    View details for DOI 10.1159/000088717

    View details for Web of Science ID 000235915600001

    View details for PubMedID 16205054

  • Inhaled nitric oxide for premature infants with severe respiratory failure NEW ENGLAND JOURNAL OF MEDICINE Van Meurs, K. P., Wright, L. L., Ehrenkranz, R. A., Lemons, J. A., Ball, M. B., Poole, W. K., Perritt, R., Higgins, R. D., Oh, W., Hudak, M. L., Laptook, A. R., Shankaran, S., Finer, N. N., Carlo, W. A., Kennedy, K. A., Fridriksson, J. H., Steinhorn, R. H., Sokol, G. M., Konduri, G. G., Aschner, J. L., Stoll, B. J., D'Angio, C. T., Stevenson, D. K., Oh, W., Hensman, A., Gingras, D., Stoll, B. J., Jain, L., Hale, E., Seabrook, I., Sokol, G., Lorant, D., Appel, D. D., Miller, L., Chriscinske, D., Attwood, J., Steinhorn, R., Sautel, M., Van Meurs, K., Ball, B., Proud, D., Carlo, W. A., Cosby, S. S., Johnson, R. B., Fridriksson, J., Warner, B., Mersmann, M., Alexander, B., Shively, J., Mincey, H., Hoover, M., Sapienz, S., Stephenson, E., Finer, N. N., Rasmussen, M. R., Henderson, C., Demetrio, C., Rich, W., Joseph, C., Hudak, M., Osbeck, S., Case, E., Kellum, A., Hogans, L., D'Angio, C. T., Reubens, L., Hutton, G., Laptook, A., Madison, S., Hensley, G., Miller, N., Metoyer, G., Kennedy, K., McDavid, G., Emerson, D., Konduri, G., Paquette, M., Wong, S., Aschner, J., O'Shea, T. M., Peters, N., Hansell, B. J., Griffin, J., Adams, C., Shankaran, S., Bara, R. A., Muran, G., Weekfall, W., Ehrenkranz, R. A., Gettner, P., Caldwell, A., Oh, W., Fanaroff, A. A., Goldberg, R. N., Stoll, B. J., Lemons, J. A., Stevenson, D. K., Carlo, W. A., Donovan, E. F., Finer, N. N., Duara, S., Phelps, D. L., Laptook, A. R., TYSON, J. E., O'Shea, T. M., Shankaran, S., Ehrenkranz, R. A., Jobe, A., Poole, W. K., Hastings, B., Petrie, C., Higgins, R. D., Wright, L. L., McClure, E., BULAS, D., Mertens, D., Slovis, T., Avery, G., D'Alton, M., Poole, W. K., Fletcher, J. C., Gleason, C. A., Redmond, C. 2005; 353 (1): 13-22

    Abstract

    Inhaled nitric oxide is a controversial treatment for premature infants with severe respiratory failure. We conducted a multicenter, randomized, blinded, controlled trial to determine whether inhaled nitric oxide reduced the rate of death or bronchopulmonary dysplasia in such infants.We randomly assigned 420 neonates, born at less than 34 weeks of gestation, with a birth weight of 401 to 1500 g, and with respiratory failure more than four hours after treatment with surfactant to receive placebo (simulated flow) or inhaled nitric oxide (5 to 10 ppm). Infants with a response (an increase in the partial pressure of arterial oxygen of more than 10 mm Hg) were weaned according to protocol. Treatment with study gas was discontinued in infants who did not have a response.The rate of death or bronchopulmonary dysplasia was 80 percent in the nitric oxide group, as compared with 82 percent in the placebo group (relative risk, 0.97; 95 percent confidence interval, 0.86 to 1.06; P=0.52), and the rate of bronchopulmonary dysplasia was 60 percent versus 68 percent (relative risk, 0.90; 95 percent confidence interval, 0.75 to 1.08; P=0.26). There were no significant differences in the rates of severe intracranial hemorrhage or periventricular leukomalacia. Post hoc analyses suggest that rates of death and bronchopulmonary dysplasia are reduced for infants with a birth weight greater than 1000 g, whereas infants weighing 1000 g or less who are treated with inhaled nitric oxide have higher mortality and increased rates of severe intracranial hemorrhage.The use of inhaled nitric oxide in critically ill premature infants weighing less than 1500 g does not decrease the rates of death or bronchopulmonary dysplasia. Further trials are required to determine whether inhaled nitric oxide benefits infants with a birth weight of 1000 g or more.

    View details for Web of Science ID 000230267300004

    View details for PubMedID 16000352

  • Monitoring age-related susceptibility of young mice to oral Salmonella enterica serovar typhimurium infection using an in vivo murine model PEDIATRIC RESEARCH Burns-Guydish, S. M., Olomu, I. N., Zhao, H., Wong, R. J., Stevenson, D. K., Contag, C. H. 2005; 58 (1): 153-158

    Abstract

    Neonates and young children are acutely susceptible to infections by gastrointestinal bacterial pathogens, such as Salmonella enterica serovar Typhimurium (S. typhimurium). To reveal age-related differences in susceptibility to this pathogen, we used in vivo bioluminescence imaging (BLI) to monitor the progression of infection in neonatal (1-wk-old), suckling (2-wk-old), juvenile (4-wk-old), and adult (6-wk-old) BALB/c mice. Mice were orally infected with various doses of a bioluminescent-labeled wild-type or mutant S. typhimurium strain, and progression of infection was monitored by BLI for 2 wks. We found that neonatal and suckling mice were more susceptible to the wild-type strain at inoculum sizes 4 and 2 log(10)'s lower for neonatal and suckling mice, respectively, than those for adult mice. At the lower inocula, newborn mice showed disseminated systemic infection as indicated by the pattern of photon emission assessed by BLI, whereas no bioluminescent signals were detectable in adult mice. In addition, an orgA(-) mutant strain of S. typhimurium with reduced virulence in adult mice produced systemic infection in newborn, suckling, and juvenile mice. Furthermore, as low as 3 log(10) CFU could be detected by BLI in tissue. The present study demonstrates that susceptibility to S. typhimurium infection decreases with age. Also, we established that BLI can be used to monitor the progression of infection in mice. Thus, this model of age-related susceptibility to S. typhimurium using BLI can be used to advance our understanding of the mechanisms involved in newborn susceptibility to infection.

    View details for DOI 10.1203/01.PDR.0000157725.44213.C4

    View details for Web of Science ID 000230252200028

    View details for PubMedID 15774831

  • Phototherapy: Current methods and future directions SEMINARS IN PERINATOLOGY Vreman, H. J., Wong, R. J., Stevenson, D. K. 2004; 28 (5): 326-333

    Abstract

    Phototherapy is the most common therapeutic intervention used for the treatment of hyperbilirubinemia. Although it has become a mainstay since its introduction in 1958, a better understanding of the photobiology of bilirubin, characteristics of the phototherapy devices, the efficacy and safety considerations of phototherapy applications, and improvements in spectroradiometers and phototherapy devices are necessary for more predictable and improved clinical practices and outcomes. A step forward in instituting consistent, uniform, and effective use of phototherapy is the recent American Academy of Pediatrics clinical guideline on the management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation, which outlines a clinical strategy for the diagnosis of hyperbilirubinemia and contains direct recommendations for the application of phototherapy. This article reviews the parameters that determine the efficacy of phototherapy, briefly discusses current devices and methods used to deliver phototherapy, and speculates on future directions and studies that are still needed to complement our presently incomplete knowledge of the facets of this common mode of therapy.

    View details for DOI 10.1053/j.semperi.2004.09.003

    View details for Web of Science ID 000226212000003

    View details for PubMedID 15686263

  • A primer on neonatal jaundice. Advances in pediatrics Stevenson, D. K., Wong, R. J., DeSandre, G. H., Vreman, H. J. 2004; 51: 263-288

    View details for PubMedID 15366777

  • Effects of metalloporphyrins on heme oxygenase-1 transcription: correlative cell culture assays guide in vivo imaging. Molecular imaging Hajdena-Dawson, M., Zhang, W., Contag, P. R., Wong, R. J., Vreman, H. J., Stevenson, D. K., Contag, C. H. 2003; 2 (3): 138-149

    Abstract

    Heme oxygenase (HO) is the rate-limiting step in the heme degradation pathway and is a potential target for the control, or prevention, of pathologic jaundice in neonates. Metalloporphyrins (Mps), a diverse set of synthetic derivatives of heme, can competitively inhibit the HO enzymes. However, certain Mps are phototoxic and some increase transcription of HO-1, the inducible HO isozyme. Therefore, effective development of this class of compounds as therapeutics for treating pathologic jaundice will require rapid and integrated biological screens to identify the most efficacious and safe Mps. To study the safety of these compounds, we assessed their cytotoxic effects and measured luciferase activity by bioluminescent imaging (BLI) as an index of HO-1 transcription, first in live cell cultures and then in living transgenic reporter mice. A total of 12 Mps were first evaluated in the correlative cell culture assay. Based on results from this study, 2 Mps, zinc protoporphyrin (ZnPP) and zinc bis glycol porphyrin (ZnBG), were selected for further studies in the live animal model. In vitro BLI showed ZnPP to be a strong inducer of HO-1 transcription in comparison to ZnBG, which showed minimal induction. Cytotoxicity studies revealed that ZnPP was phototoxic, whereas ZnBG had no effect on cell viability. In vivo BLI showed that both ZnPP and ZnBG had minimal effects on the levels of HO-1 transcription in the animals. Furthermore, serum enzyme assays indicated that neither caused detectable liver toxicity. These findings, and especially those with ZnBG, support the use of selected Mps as therapies for pathologic jaundice. Coupling the high throughput advantage of cell culture with the capability of imaging for whole-body temporal analyses could accelerate and refine the preclinical phases of drug development. Thus, this study serves as a model for understanding the effects of specific compounds in relation to defined targets using an integrated approach.

    View details for PubMedID 14649057

  • Heme oxygenase-2 protects against lipid peroxidation-mediated cell loss and impaired motor recovery after traumatic brain injury JOURNAL OF NEUROSCIENCE Chang, E. F., Wong, R. J., Vreman, H. J., Igarashi, T., Galo, E., Sharp, F. R., Stevenson, D. K., Noble-Haeusslein, L. J. 2003; 23 (9): 3689-3696

    Abstract

    After traumatic brain injury (TBI), substantial extracellular heme is released from hemoproteins during hemorrhage and cell injury. Heme oxygenase (HO) isozymes are thought to detoxify the pro-oxidant heme to the potent antioxidant, bilirubin. HO-1, the inducible isozyme, is expressed in glial populations after injury and may play a protective role. However, the role of HO-2, the predominant and constitutively expressed isozyme in the brain, remains unclear after TBI. We used a controlled cortical impact injury model to determine the extent and mechanism of damage between HO-2 knock-out (KO) (-/-) and wild-type (WT) (+/+) mice. The specific cellular and temporal expressions of HO-2 and HO-1 were characterized by immunocytochemistry and Western blots. HO-2 was immunolocalized in neurons both before and after TBI, whereas HO-1 was highly upregulated in glia only after TBI. HO activity determined by gas chromatography using brain sonicates from injured HO-2 KO mice was significantly less than that of HO-2 wild types, despite the induction of HO-1 expression after TBI. Cell loss was significantly greater in KO mice in areas including the cortex, the CA3 region of hippocampus, and the lateral dorsal thalamus. Furthermore, motor recovery after injury, as measured by the rotarod assay and an inclined beam-walking task, was compromised in the KO mice. Finally, brain tissue from injured HO-2 KO mice exhibited decreased ability to reduce oxidative stress, as measured with an Fe(2+)/ascorbic acid-mediated carbon monoxide generation assay for lipid peroxidation susceptibility. These findings demonstrate that HO-2 expression protects neurons against TBI by reducing lipid peroxidation via the catabolism of free heme.

    View details for Web of Science ID 000182700100016

    View details for PubMedID 12736340

  • Selection of potential therapeutics based on in vivo spatiotemporal transcription patterns of heme oxygenase-1 JOURNAL OF MOLECULAR MEDICINE-JMM Zhang, W. S., Contag, P. R., Hardy, J., Zhao, H., Vreman, H. J., Hajdena-Dawson, M., Wong, R. J., Stevenson, D. K., Contag, C. H. 2002; 80 (10): 655-664

    Abstract

    Heme oxygenase (HO), a key catabolic enzyme in the conversion of heme to bilirubin, is an ideal target for reducing bilirubin production and preventing pathological jaundice in newborn infants. Metalloporphyrins (Mps) have been well characterized as competitive inhibitors of HO and have been evaluated as potential chemopreventive agents for neonatal jaundice. However, in addition to reducing HO activity, many Mps have been shown to increase HO-1 transcription, which would likely reduce their potential therapeutic utility. The differential effects of Mps on the transcription of HO-1 were therefore evaluated in living transgenic (Tg) reporter mice. Of the compounds evaluated, we observed that zinc bis-glycol porphyrin (ZnBG), a potent inhibitor of HO enzyme activity, did not alter HO-1 transcription patterns in Tg mice. Whole body images of HO-1 transcription patterns did, however; reveal increases in HO-1 transcription in Tg mice after treatment with other Mps, heme and cadmium chloride (CdCl(2)). Intravenous injections of CdCl(2) resulted in expression patterns that differed in tempo and location from those observed in Tg mice treated with intraperitoneal injections. Spatiotemporal analyses of transcriptional regulation in living animals accelerated the assessment of an adverse effect of Mps by revealing different patterns of HO-1 transcription. Among the known inhibitors of HO enzyme activity that were evaluated in this study, ZnBG did not significantly affect HO-1 transcription and therefore may be well suited for the prevention of neonatal jaundice.

    View details for DOI 10.1007/s00109-002-0375-x

    View details for Web of Science ID 000179446600007

    View details for PubMedID 12395150

  • Carbon monoxide and bilirubin production in neonates SEMINARS IN PERINATOLOGY Stevenson, D. K., Vreman, H. J., Wong, R. J., Contag, C. H. 2001; 25 (2): 85-93

    Abstract

    Neonatal hyperbilirubinemia is a normal postnatal phenomenon resulting from a transitional imbalance between the production and elimination of bilirubin in the neonate. Bilirubin has been shown to be not only a potent antioxidant, but also toxic at excessive concentrations. As a result, the biology of bilirubin, its production, regulation, and measurements have been the focus of extensive studies. Bilirubin, carbon monoxide, and iron are derived from the degradation of heme, a ubiquitous two-step pathway catalyzed by the enzyme, heme oxygenase. It has been shown that these metabolically active products from the heme catabolic pathway may, in turn, influence many other biologic processes. This report provides a brief overview of these interrelationships in the hope that it may provide insight into the central role this pathway plays in the existence of most organisms.

    View details for Web of Science ID 000168272000008

    View details for PubMedID 11339670

  • FETAL HEMOGLOBIN OF TRANSFUSED NEONATES AND SPECTROPHOTOMETRIC MEASUREMENTS OF OXYHEMOGLOBIN AND CARBOXYHEMOGLOBIN JOURNAL OF CLINICAL MONITORING Mahoney, J. J., Wong, R. J., Vreman, H. J., Stevenson, D. K. 1991; 7 (2): 154-160

    Abstract

    The records of 32 neonates in an intensive care unit were examined retrospectively to determine if fetal hemoglobin concentrations could be predicted on the basis of gestational or postnatal age, or on the volume of red blood cell transfusions. In nontransfused neonates, the correlation between measured concentrations of fetal hemoglobin and post-natal age was r = 0.53 with a 17.2 standard error of prediction. In these same neonates, the correlation between measured fetal hemoglobin divided by birth weight and gestational age was r = 0.70, with a 9.6 standard error of prediction. A three-variable regression equation (the latter two variables plus calculated fetal hemoglobin) was found to have a high correlation with data for measured fetal hemoglobin (r = 0.97) and a relatively low 8.4 standard error of prediction. In transfused neonates, however, measured hemoglobin concentrations divided by birth weight correlated poorly with gestational age (r = 0.30 and a 12.4 standard error of prediction). In addition, the transfused neonates had low correlations when fetal hemoglobin concentrations alone were compared with the total volume of red blood cell transfusions (r = 0.35) and with postnatal age (r = 0.18) and the standard errors of prediction were all approximately 17. The correlations found between concentrations of fetal hemoglobin and age in transfused neonates were poorer than those reported in earlier nontransfused infant studies. Previous studies have also shown that neonatal blood containing fetal hemoglobin interferes with the spectrophotometric measurements of carboxyhemoglobin and oxyhemoglobin. Because of the imprecision in the predictions of fetal hemoglobin using age, weight, or the volume of transfusion, we conclude that fetal hemoglobin should be measured if accurate spectrophotometric determinations of carboxyhemoglobin and oxyhemoglobin are desired.

    View details for Web of Science ID A1991FH21600004

    View details for PubMedID 1712833

  • Could genetic polymorphisms related to oxidative stress modulate effects of heavy metals for risk of human preterm birth? Reproductive toxicology Shachar, B. Z., Carmichael, S. L., Stevenson, D. K., Shaw, G. M. 2013; 42: 24-26

    Abstract

    Human preterm birth (PTB) is a complex medical outcome influenced by a combination of genetic and environmental factors. Research on the causative factors of PTB has mostly focused on demographic, socio-behavioral and environmental risk factors. Recent studies turn the spotlight on the effects of heavy metals exposure on adverse pregnancy outcomes. Here we present and evaluate the hypothesis that heavy metals may cause PTB through oxidative stress, and that this effect may be modified by polymorphisms in genes related to oxidative stress. Indeed, accumulating data suggest that the risk of PTB is correlated with polymorphisms in genes involved in detoxification, oxidative stress and lipid metabolism. These and other polymorphisms have independently been associated with susceptibility to the adverse effects of heavy metals.

    View details for DOI 10.1016/j.reprotox.2013.06.072

    View details for PubMedID 23811355

  • Evaluation of window-tinting films for sunlight phototherapy. Journal of tropical pediatrics Vreman, H. J., Slusher, T. M., Wong, R. J., Schulz, S., Olusanya, B. O., Stevenson, D. K. 2013; 59 (6): 496-501

    Abstract

    We evaluated nine semi-transparent plastic window-tinting films for their ability to block ultraviolet A (UVA) and infrared (IR) radiation and transmit therapeutic blue light (400-520 nm) for treating jaundiced newborns. For indoor testing, three light sources (TL/52 special blue fluorescent, Black Light UVA and IR heat lamps) were positioned above each film and measured successively using a thermocouple thermometer, UVA radiometer and blue light irradiance meter, placed below each film. For outdoor testing, the same setup was used with the sun at zenith and a cloudless sky. Compared with unfiltered radiation, blue light transmission through films ranged from 24 to 83%, UVA transmission was 0.1-7.1% and reductions in IR heat were 6-12°C and 5-10°C for heat lamp and sun, respectively. The data suggest that most of the relatively low-cost window-tinting films tested can effectively reduce sunlight UV and IR and offer a range of significant attenuations of therapeutic blue light.

    View details for DOI 10.1093/tropej/fmt062

    View details for PubMedID 23880667

  • The effect of hematocrit on the efficacy of phototherapy for neonatal jaundice PEDIATRIC RESEARCH Lamola, A. A., Bhutani, V. K., Wong, R. J., Stevenson, D. K., McDonagh, A. F. 2013; 74 (1): 54-60

    Abstract

    Background:The therapeutic phototherapy action spectrum ranges from 420 to 500nm. However, a recent report of improved efficacy offluorescent "turquoise"light (~490 nm) compared toblue light(~450 nm) underscores the need to define an optimal action spectrum for precision-targeted phototherapy using very narrow wavelength ranges.Methods:We used a current semi-empirical model of theoptical properties of skinfor robust calculations of the fraction of light absorbed by bilirubin at various wavelengths that could be confounded by hemoglobin, melanin and skin thickness. Applying assumptions regarding the wavelength dependence of bilirubin photochemistry, "action spectra"wereassembled from the calculated values.Results:All the calculated action spectra displayed a peak between 472 and 480 nm (most at 476 nm), which is a significant shift from the well-reported 460 nm absorption peak of bilirubin. Interestingly, the relative amplitudes of the action spectra showed an inverse relationship with hematocrit.Conclusion:We speculate that narrow range of light at 476 nmshould be 60% more effective than blue (broad-band) fluorescent lamps. Because hemoglobin serves as a major competitor of bilirubin for light absorption, the calculations also predict that the efficacy of phototherapy is dependent on the hematocrit.A high hematocrit could reduce therapeutic efficiency.Pediatric Research (2013); doi:10.1038/pr.2013.67.

    View details for DOI 10.1038/pr.2013.67

    View details for Web of Science ID 000321795300009

    View details for PubMedID 23604171

  • Predischarge Screening for Severe Neonatal Hyperbilirubinemia Identifies Infants Who Need Phototherapy JOURNAL OF PEDIATRICS Bhutani, V. K., Stark, A. R., Lazzeroni, L. C., Poland, R., Gourley, G. R., Kazmierczak, S., Meloy, L., Burgos, A. E., Hall, J. Y., Stevenson, D. K. 2013; 162 (3): 477-?

    Abstract

    To test whether the combined use of total plasma/serum bilirubin (TSB) levels and clinical risk factors more accurately identifies infants who receive phototherapy than does the use of either method alone.We recruited healthy infants of ?35 weeks' gestation at 6 centers that practiced universal predischarge TSB screening. Transcutaneous bilirubin (TcB) was measured at 24 hours, with TSB at 24-60 hours and at 3- to 5- and 7- to 14-day follow-up visits. Clinical risk factors were identified systematically.Of 1157 infants, 1060 (92%) completed follow-up, and 982 (85%) had complete datasets for analysis. Infant characteristics included 25% were nonwhite and 55% were Hispanic/Latino; >90% were breastfed. During the first week, jaundice was documented in 84% of subjects. Predischarge TSB identified the 41 (4.2%) and 34 (3.5%) infants who received phototherapy before and after discharge, respectively. Prediction of postdischarge phototherapy was similar for combined clinical risk factors (earlier gestational age [GA], bruising, positive direct antiglobulin test, Asian race, exclusive breastfeeding, blood type incompatibility, jaundice extent) and age-adjusted TSB (area under the curve [AUC] = .86 vs .87), but combined screening was better (AUC = .95). TcB/TSB combined with GA alone was equally predictive (AUC = .95; 95% CI .93-.97).Jaundice is present in 4 of 5 (84%) healthy newborns. Predischarge TcB/TSB (adjusted for postnatal age) combined with specific clinical factors (especially GA) best predicts subsequent phototherapy use. Universal implementation of this strategy in the US should improve outcomes of healthy newborns discharged early.

    View details for DOI 10.1016/j.jpeds.2012.08.022

    View details for Web of Science ID 000315790100010

    View details for PubMedID 23043681

  • High Quality Genome-Wide Genotyping from Archived Dried Blood Spots without DNA Amplification. PLoS One St Julien KR, Jelliffe-Pawlowski LL, Shaw GM, Stevenson DK, O'Brodovich HM, Krasnow MA, Stanford BPD Study Group (Gould JB, Oehlert JW, Quaintance C, Wang H, Lazzeroni L, Hoffman T, Witte J, Lorey F) 2013; 8 (5): e4710

    View details for PubMedID 23737996

  • Peptidomic Identification of Serum Peptides Diagnosing Preeclampsia. PloS one Wen, Q., Liu, L. Y., Yang, T., Alev, C., Wu, S., Stevenson, D. K., Sheng, G., Butte, A. J., Ling, X. B. 2013; 8 (6): e65571

    Abstract

    We sought to identify serological markers capable of diagnosing preeclampsia (PE). We performed serum peptide analysis (liquid chromatography mass spectrometry) of 62 unique samples from 31 PE patients and 31 healthy pregnant controls, with two-thirds used as a training set and the other third as a testing set. Differential serum peptide profiling identified 52 significant serum peptides, and a 19-peptide panel collectively discriminating PE in training sets (n?=?21 PE, n?=?21 control; specificity?=?85.7% and sensitivity?=?100%) and testing sets (n?=?10 PE, n?=?10 control; specificity?=?80% and sensitivity?=?100%). The panel peptides were derived from 6 different protein precursors: 13 from fibrinogen alpha (FGA), 1 from alpha-1-antitrypsin (A1AT), 1 from apolipoprotein L1 (APO-L1), 1 from inter-alpha-trypsin inhibitor heavy chain H4 (ITIH4), 2 from kininogen-1 (KNG1), and 1 from thymosin beta-4 (TMSB4). We concluded that serum peptides can accurately discriminate active PE. Measurement of a 19-peptide panel could be performed quickly and in a quantitative mass spectrometric platform available in clinical laboratories. This serum peptide panel quantification could provide clinical utility in predicting PE or differential diagnosis of PE from confounding chronic hypertension.

    View details for PubMedID 23840341

  • Introductory address for the John Howland Award recipient, Philip A. Pizzo, MD PEDIATRIC RESEARCH Stevenson, D. K. 2012; 72 (3): 321-323

    View details for DOI 10.1038/pr.2012.82

    View details for Web of Science ID 000308280500014

    View details for PubMedID 22717691

  • The Need for Technologies to Prevent Bilirubin-Induced Neurologic Dysfunction Syndrome SEMINARS IN PERINATOLOGY Bhutani, V. K., Stevenson, D. K. 2011; 35 (3): 97-100

    Abstract

    Dramatic improvements in the overall socioeconomic conditions have yet to impact the unacceptably high maternal (approximately 1500 maternal deaths daily, worldwide) and neonatal morbidity and mortality (more than 10,000 deaths per daily 200,000 live-births, worldwide) in the developing nations. Thus, nations with emerging markets have unique health-societal needs. All infants require a safer transition from a birthing facility to home during the first week after birth and providing for a nurturing environment to prevent neonatal illnesses is integral to "good clinical practice." The unmonitored occurrence of severe hyperbilirubinemia and kernicterus are emblematic of a fractured maternal child healthcare system. The "know-do" gaps that span private versus public health care systems in the emerging markets have led us to conclude that building an interdisciplinary leadership approach to provide innovative strategies and affordable technologies will help bridge and access existing social barriers in the micro- and macro-health environments. Thus, unfettered access, global benchmarks, and culturally relevant strategies are dependent on evidence-based affordable technologies to successfully transform societal health care practices. Implementation of jaundice-related technologies should serve as a template for other affordable newborn health products.

    View details for DOI 10.1053/j.semperi.2011.02.002

    View details for Web of Science ID 000292057900001

    View details for PubMedID 21641481

  • Heme Oxygenase-1 Deletion Affects Stress Erythropoiesis PLOS ONE Cao, Y., Kusy, S., Luong, R., Wong, R. J., Stevenson, D. K., Contag, C. H. 2011; 6 (5)

    Abstract

    Homeostatic erythropoiesis leads to the formation of mature red blood cells under non-stress conditions, and the production of new erythrocytes occurs as the need arises. In response to environmental stimuli, such as bone marrow transplantation, myelosuppression, or anemia, erythroid progenitors proliferate rapidly in a process referred to as stress erythropoiesis. We have previously demonstrated that heme oxygenase-1 (HO-1) deficiency leads to disrupted stress hematopoiesis. Here, we describe the specific effects of HO-1 deficiency on stress erythropoiesis.We used a transplant model to induce stress conditions. In irradiated recipients that received hmox(+/-) or hmox(+/+) bone marrow cells, we evaluated (i) the erythrocyte parameters in the peripheral blood; (ii) the staining intensity of CD71-, Ter119-, and CD49d-specific surface markers during erythroblast differentiation; (iii) the patterns of histological iron staining; and (iv) the number of Mac-1(+)-cells expressing TNF-?. In the spleens of mice that received hmox(+/-) cells, we show (i) decreases in the proerythroblast, basophilic, and polychromatophilic erythroblast populations; (ii) increases in the insoluble iron levels and decreases in the soluble iron levels; (iii) increased numbers of Mac-1(+)-cells expressing TNF-?; and (iv) decreased levels of CD49d expression in the basophilic and polychromatophilic erythroblast populations.As reflected by effects on secreted and cell surface proteins, HO-1 deletion likely affects stress erythropoiesis through the retention of erythroblasts in the erythroblastic islands of the spleen. Thus, HO-1 may serve as a therapeutic target for controlling erythropoiesis, and the dysregulation of HO-1 may be a predisposing condition for hematologic diseases.

    View details for DOI 10.1371/journal.pone.0020634

    View details for Web of Science ID 000291097600112

    View details for PubMedID 21655188

  • Quantitating carbon monoxide production from heme by vascular plant preparations in vitro PLANT PHYSIOLOGY AND BIOCHEMISTRY Vreman, H. J., Wong, R. J., Stevenson, D. K. 2011; 49 (1): 61-68

    Abstract

    Heme in animals is mainly degraded enzymatically, producing a predictable amount of carbon monoxide (CO). Under some conditions, alternative sources of CO production are important, such as lipid peroxidation and photo-oxidation. Less is known about CO production in plants as a reflection of enzymatic activity or coupled oxidation, but a sensitive assay for CO production in plants would be a valuable tool to explore the various sources in plants as the conditions of the reactions and mechanisms are defined. Using gas chromatography, we determined the requirements for heme-supported in vitro CO generation by exogenous reactants (NADPH, tissue supernatant, oxygen), optimum reaction conditions (time, temperature, pH, light), and effects of various cofactors and substrates using supernatants from Spinacia oleracea (spinach) leaf and Solanum tuberosa (potato) tuber homogenates. We then determined the CO production rate distribution between organ (root, stem, leaf, flower, fruit) supernatants in a number of commercially available plant species. CO production ranged from 4-65 nmol CO/h/g fresh weight and occurred in all vascular plant tissues examined, with the highest rates in chloroplast-containing tissues. In spinach leaves, CO production was concentrated (>2-fold) in the particulate fraction, whereas in potato tubers, the particulate fraction accounted for <50% of the rates in homogenates. We conclude that gas chromatography is uniquely suited for the determination of CO production in pigmented, heterogeneous plant tissue preparations.

    View details for DOI 10.1016/j.plaphy.2010.09.021

    View details for Web of Science ID 000286998800009

    View details for PubMedID 21055958

  • Heptavalent Pneumococcal Conjugate Vaccine Immunogenicity in Very-Low-Birth-Weight, Premature Infants PEDIATRIC INFECTIOUS DISEASE JOURNAL D'Angio, C. T., Heyne, R. J., O'Shea, T. M., Schelonka, R. L., Shankaran, S., Duara, S., Goldberg, R. N., Stoll, B. J., Van Meurs, K. P., Vohr, B. R., Das, A., Li, L., Burton, R. L., Hastings, B., Phelps, D. L., Sanchez, P. J., Carlo, W. A., Stevenson, D. K., Higgins, R. D. 2010; 29 (7): 600-606

    Abstract

    The heptavalent pneumococcal CRM197 conjugate vaccine (PCV-7) has been incompletely studied in very-low-birth-weight (< or =1500 g) infants.To assess PCV-7 immunogenicity in very-low-birth-weight, premature infants. We hypothesized that the frequency of postvaccine antibody concentrations > or =0.15 microg/mL would vary directly with birth weight.This was a multicenter observational study. Infants 401 to 1500 g birth weight and <32 0/7 weeks gestation, stratified by birth weight, were enrolled from 9 National Institute of Child Health and Human Development Neonatal Research Network centers. Infants received PCV-7 at 2, 4, and 6 months after birth and had blood drawn 4 to 6 weeks following the third dose. Antibodies against the 7 vaccine serotypes were measured by enzyme-linked immunosorbent assay.Of 369 enrolled infants, 244 completed their primary vaccine series by 8 months and had serum obtained. Subjects were 27.8 +/- 2.2 (mean +/- standard deviation) weeks gestation and 1008 +/- 282 g birth weight. Twenty-six percent had bronchopulmonary dysplasia and 16% had received postnatal glucocorticoids. Infants 1001 to 1500 g birth weight were more likely than those 401 to 1000 g to achieve antibody concentrations > or =0.15 microg/mL against the least 2 immunogenic serotypes (6B: 96% vs. 85%, P = 0.003 and 23F: 97% vs. 88%, P = 0.009). In multiple logistic regression analysis, lower birth weight, postnatal glucocorticoid use, lower weight at blood draw, and Caucasian race were each independently associated with antibody concentrations <0.35 microg/mL against serotypes 6B and/or 23F.When compared with larger premature infants, infants weighing < or =1000 g at birth have similar antibody responses to most, but not all, PCV-7 vaccine serotypes.

    View details for DOI 10.1097/INF.0b013e3181d264a6

    View details for Web of Science ID 000279348900004

    View details for PubMedID 20234331

  • ELEVATED EXHALED CARBON MONOXIDE CONCENTRATION IN HEMOGLOBINOPATHIES AND ITS RELATION TO RED BLOOD CELL TRANSFUSION THERAPY PEDIATRIC HEMATOLOGY AND ONCOLOGY James, E. B., Vreman, H. J., Wong, R. J., Stevenson, D. K., Vichinsky, E., Schumacher, L., Hall, J. Y., Simon, J., Golden, D. W., Harmatz, P. 2010; 27 (2): 112-121

    Abstract

    In this study, the authors examined a possible role of measurements of end-tidal carbon monoxide (CO), corrected for inhaled CO (ETCOc), as a noninvasive screening tool for hemoglobinopathies and as an indicator for when transfusions would be required in patients receiving chronic transfusions. ETCOc measurements were obtained in subjects with sickle cell disease (n = 18), thalassemia (n = 21), and healthy controls (n = 62). ETCOc values less than 3 parts per million (ppm) yielded a positive predictive value of 93% and negative predictive value of 94% in identifying hemoglobinopathies. Subsequently, 7 subjects with thalassemia had laboratory parameters and ETCOc measured over 2 transfusion cycles. ETCOc values were 4.90 +/- 0.32 ppm (mean +/- SD), with 89% of values being above normal (>or=3 ppm). Pretransfusion ETCOc levels significantly correlated with pretransfusion reticulocyte count (r = .96, P <.001), but not with pretransfusion hemoglobin (r = .44, P = .16) or pretransfusion soluble transferrin receptors (sTfR, r = .52, P = .10). In conclusion, we found that patients with hemoglobinopathies have ETCOc values above the range for healthy controls and ETCOc measurements can be used as an adjunct to hemoglobin measurements to determine the proper timing of transfusions.

    View details for DOI 10.3109/08880010903536227

    View details for Web of Science ID 000275286100004

    View details for PubMedID 20201692

  • Neonatal brain structure on MRI and diffusion tensor imaging, sex, and neurodevelopment in very-low-birthweight preterm children DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY Rose, J., Butler, E. E., Lamont, L. E., Barnes, P. D., Atlas, S. W., Stevenson, D. K. 2009; 51 (7): 526-535

    Abstract

    The neurological basis of an increased incidence of cerebral palsy (CP) in preterm males is unknown. This study examined neonatal brain structure on magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) at term-equivalent age, sex, and neurodevelopment at 1 year 6 months on the basis of the Amiel-Tison neurological examination, Gross Motor Function Classification System, and Bayley Scales of Infant Development in 78 very-low-birthweight preterm children (41 males, 37 females; mean gestational age 27.6 wks, SD 2.5; mean birthweight 1021 g, SD 339). Brain abnormalities on MRI and DTI were not different between males and females except in the splenium of the corpus callosum, where males had lower DTI fractional anisotropy (p=0.025) and a higher apparent diffusion coefficient (p=0.013), indicating delayed splenium development. In the 26 infants who were at higher risk on the basis of DTI, males had more abnormalities on MRI (p=0.034) and had lower fractional anisotropy and a higher apparent diffusion coefficient in the splenium (p=0.049; p=0.025) and right posterior limb of the internal capsule (PLIC; p=0.003; p=0.033). Abnormal neurodevelopment was more common in males (n=9) than in females (n=2; p=0.036). Children with abnormal neurodevelopment had more abnormalities on MRI (p=0.014) and reduced splenium and right PLIC fractional anisotropy (p=0.001; p=0.035). In children with abnormal neurodevelopment, right PLIC fractional anisotropy was lower than left (p=0.035), whereas in those with normal neurodevelopment right PLIC fractional anisotropy was higher than left (p=0.001). Right PLIC fractional anisotropy correlated to neurodevelopment (rho=0.371, p=0.002). Logistic regression predicted neurodevelopment with 94% accuracy; only right PLIC fractional anisotropy was a significant logistic coefficient. Results indicate that the higher incidence of abnormal neurodevelopment in preterm males relates to greater incidence and severity of brain abnormalities, including reduced PLIC and splenium development.

    View details for DOI 10.1111/j.1469-8749.2008.03231.x

    View details for Web of Science ID 000266696900007

    View details for PubMedID 19459915

  • Inhaled Nitric Oxide for Preterm Premature Rupture of Membranes, Oligohydramnios, and Pulmonary Hypoplasia AMERICAN JOURNAL OF PERINATOLOGY Chock, V. Y., Van Meurs, K. P., Hintz, S. R., Ehrenkranz, R. A., Lemons, J. A., Kendrick, D. E., Stevenson, D. K. 2009; 26 (4): 317-322

    Abstract

    We sought to determine if inhaled nitric oxide (iNO) administered to preterm infants with premature rupture of membranes (PPROM), oligohydramnios, and pulmonary hypoplasia improved oxygenation, survival, or other clinical outcomes. Data were analyzed from infants with suspected pulmonary hypoplasia, oligohydramnios, and PPROM enrolled in the National Institute of Child Health and Development Neonatal Research Network Preemie Inhaled Nitric Oxide (PiNO) trial, where patients were randomized to receive placebo (oxygen) or iNO at 5 to 10 ppm. Outcome variables assessed were PaO (2) response, mortality, bronchopulmonary dysplasia (BPD), and severe intraventricular hemorrhage (IVH) or periventricular leukomalacia (PVL). Twelve of 449 infants in the PiNO trial met criteria. Six infants received iNO and six received placebo. The iNO group had a mean increase in PaO (2) of 39 +/- 50 mm Hg versus a mean decrease of 11 +/- 15 mm Hg in the control group. Mortality was 33% versus 67%, BPD (2/5) 40% versus (2/2) 100%, and severe IVH or PVL (1/5) 20% versus (1/2) 50% in the iNO and control groups, respectively. None of these changes were statistically significant. Review of a limited number of cases from a large multicenter trial suggests that iNO use in the setting of PPROM, oligohydramnios, and suspected pulmonary hypoplasia improves oxygenation and may decrease the rate of BPD and death without increasing severe IVH or PVL. However, the small sample size precludes definitive conclusions. Further studies are required to determine if iNO is of benefit in this specific patient population.

    View details for DOI 10.1055/s-0028-1104743

    View details for Web of Science ID 000264506400012

    View details for PubMedID 19067285

  • Commentary on the bilirubin supplement JOURNAL OF PERINATOLOGY Stevenson, D. K. 2009; 29: S2-S3

    View details for DOI 10.1038/jp.2008.220

    View details for Web of Science ID 000263604400002

    View details for PubMedID 19177055

  • Safe and effective devices for use in the neonatal intensive care unit: NICHD Workshop Summary. Biomed Instrum Technol Raju TNK, Stevenson DK, Higgins, RD, Stark AR 2009; 43: 408-18
  • Readmission for neonatal jaundice in California, 1991-2000: Trends and implications PEDIATRICS Burgos, A. E., Schmitt, S. K., Stevenson, D. K., Phibbs, C. S. 2008; 121 (4): E864-E869

    Abstract

    We sought to describe population-based trends, potential risk factors, and hospital costs of readmission for jaundice for term and late preterm infants.Birth-cohort data were obtained from the California Office of Statewide Health Planning and Development and contained infant vital statistics data linked to infant and maternal hospital discharge summaries. The study population was limited to healthy, routinely discharged infants through the use of multiple exclusion criteria. All linked readmissions occurred within 14 days of birth. International Classification of Diseases, Ninth Revision, codes were used to further limit the sample to readmission for jaundice. Hospital discharge records were the source of diagnoses, hospital charges, and length-of-stay information. Hospital costs were estimated using hospital-specific ratios of costs to charges and adjusted to 1991.Readmission rates for jaundice generally rose after 1994 and peaked in 1998 at 11.34 per 1000. The readmission rate for late preterm infants (as a share of all infants) over the study period remained at <2 per 1000. Factors associated with increased likelihood of hospital readmission for jaundice included gestational age 34 to 39 weeks, birth weight of <2500 g, male gender, Medicaid or private insurance, and Asian race. Factors associated with a decreased likelihood of readmission for jaundice were cesarean section delivery and black race. The mean cost of readmission for all infants was $2764, with a median cost of $1594.Risk-adjusted readmission rates for jaundice rose following the 1994 hyperbilirubinemia guidelines and declined after postpartum length-of-stay legislation in 1998. In 2000, the readmission rate remained 6% higher than in 1991. These findings highlight the complex relationship among newborn physiology, socioeconomics, race or ethnicity, public policy, clinical guidelines, and physician practice. These trend data provide the necessary baseline to study whether revised guidelines will change practice patterns or improve outcomes. Cost data also provide a break-even point for prevention strategies.

    View details for DOI 10.1542/peds.2007-1214

    View details for Web of Science ID 000254576800064

    View details for PubMedID 18381515

  • Neonatal microstructural development of the internal capsule on diffusion tensor imaging correlates with severity of gait and motor deficits DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY Rose, J., Mirmiran, M., Butler, E. E., Lin, C. Y., Barnes, P. D., Kermoian, R., Stevenson, D. K. 2007; 49 (10): 745-750

    Abstract

    Neonatal microstructural development in the posterior limbs of the internal capsule (PLIC) was assessed using diffusion tensor imaging (DTI) fractional anisotropy (FA) in 24 very-low-birthweight preterm infants at 37 weeks' gestational age and compared with the children's gait and motor deficits at 4 years of age. There were 14 participants with normal neonatal FA values (seven females, seven males; born at 27.6 weeks [SD 2.3] gestational age; birthweight 1027g [SD 229]) and 10 participants with low FA values in the PLIC (four females, six males; born at 28.4 weeks [SD 2.0] gestational age; birthweight 1041g [SD 322]). Seven of the 10 children with low FA and none of the children with normal FA had been diagnosed with CP by the time of gait testing. Among children with low neonatal FA, there was a strong negative correlation between FA of the combined left and right side PLIC and log NI (r=-0.89, p=0.001) and between FA and GMFCS (r=-0.65, p=0.04) at 4 years of age. There was no correlation between FA and gait NI or GMFCS at 4 years of age among children with normal neonatal FA. This preliminary study suggests neonatal DTI may be an important predictor of the severity of future gait and motor deficits.

    View details for Web of Science ID 000249660400007

    View details for PubMedID 17880643

  • Beware of the weaker sex: Don't get too close to your twin brother PEDIATRICS Stevenson, D. K., Tyson, J. E. 2007; 120 (3): 638-639

    View details for DOI 10.1542/peds.2007-0950

    View details for Web of Science ID 000249232000021

    View details for PubMedID 17766536

  • Neurodevelopmental outcomes of premature infants with severe respiratory failure enrolled in a randomized controlled trial of inhaled nitric oxide JOURNAL OF PEDIATRICS Hintz, S. R., Van Meurs, K. P., Perritt, R., Poole, W. K., Das, A., Stevenson, D. K., Ehrenkranz, R. A., Lemons, J. A., Vohr, B. R., Heyne, R., Childers, D. O., Peralta-Carcelen, M., Dusick, A., Johnson, Y. R., Morris, B., Dillard, R., Vaucher, Y., Steichen, J., Adams-Chapman, I., Konduri, G., Myers, G. J., De Ungria, M., Tyson, J. E., Higgins, R. D. 2007; 151 (1): 16-22

    Abstract

    We hypothesized that inhaled nitric oxide (iNO) would not decrease death or neurodevelopmental impairment (NDI) in infants enrolled in the National Institute of Child Health and Human Development Preemie iNO Trial (PiNO) trial, nor improve neurodevelopmental outcomes in the follow-up group.Infants <34 weeks of age, weighing <1500 g, with severe respiratory failure were enrolled in the multicenter, randomized, controlled trial. NDI at 18 to 22 months corrected age was defined as: moderate to severe cerebral palsy (CP; Mental Developmental Index or Psychomotor score Developmental Index <70), blindness, or deafness.Of 420 patients enrolled, 109 who received iNO (52%) and 98 who received placebo (47%) died. The follow-up rate in survivors was 90%. iNO did not reduce death or NDI (78% versus 73%; relative risk [RR], 1.07; 95% CI, 0.95-1.19), or NDI or Mental Developmental Index <70 in the follow-up group. Moderate-severe CP was slightly higher with iNO (RR, 2.41; 95% CI, 1.01-5.75), as was death or CP in infants weighing <1000 g (RR, 1.22; 95% CI, 1.05-1.43).In this extremely ill cohort, iNO did not reduce death or NDI or improve neurodevelopmental outcomes. Routine iNO use in premature infants should be limited to research settings until further data are available.

    View details for DOI 10.1016/j.jpeds.2007.03.017

    View details for Web of Science ID 000247851900007

    View details for PubMedID 17586184

  • Inhaled nitric oxide in infants > 1500 g and < 34 weeks gestation with severe respiratory failure JOURNAL OF PERINATOLOGY Van Meurs, K. P., Hintz, S. R., Ehrenkranz, R. A., Lemons, J. A., Ball, M. B., Poole, W. K., Perritt, R., Das, A., Higgins, R. D., Stevenson, D. K. 2007; 27 (6): 347-352

    Abstract

    Inhaled nitric oxide (iNO) use in infants >1500 g, but <34 weeks gestation with severe respiratory failure will reduce the incidence of death and/or bronchopulmonary dysplasia (BPD).Infants born at <34 weeks gestation with a birth weight >1500 g with respiratory failure were randomly assigned to receive placebo or iNO.Twenty-nine infants were randomized. There were no differences in baseline characteristics, but the status at randomization showed a statistically significant difference in the use of high-frequency ventilation (P=0.03). After adjustment for oxygenation index entry strata, there was no difference in death and/or BPD (adjusted relative risk (RR) 0.80, 95% confidence interval (CI) 0.43 to 1.48; P=0.50), death (adjusted RR 1.26, 95% CI 0.47 to 3.41; P=0.65) or BPD (adjusted RR 0.40, 95% CI 0.47 to 3.41; P=0.21).Although sample size limits our ability to make definitive conclusions, this small pilot trial of iNO use in premature infants >1500 g and <34 weeks with severe respiratory failure suggests that iNO does not affect the rate of BPD and/or death.

    View details for DOI 10.1038/sj.jp.7211690

    View details for Web of Science ID 000246905800005

    View details for PubMedID 17443204

  • Interobserver reliability and accuracy of cranial ultrasound scanning interpretation in premature infants JOURNAL OF PEDIATRICS Hintz, S. R., Slovis, T., Bulas, D., Van Meurs, K. P., Perritt, R., Stevenson, D. K., Poole, W. K., Das, A., Higgins, R. D. 2007; 150 (6): 592-596

    Abstract

    To assess interobserver reliability between 2 central readers of cranial ultrasound scanning (CUS) and accuracy of local, compared with central, interpretations.The study was a retrospective analysis of CUS data from the National Institute of Child Health and Human Development (NICHD) trial of inhaled nitric oxide for premature infants. Interobserver reliability of 2 central readers was assessed with kappa or weighted kappa. Accuracy of local, compared with central, interpretations was assessed by using sensitivity and specificity.CUS from 326 infants had both central reader and local interpretations. Central reader agreement for grade 3/4 intraventricular hemorrhage (IVH), grade 3/4 IVH or periventricular leukomalacia (PVL), grade of IVH, and degree of ventriculomegaly was very good (kappa = 0.84, 0.81, 0.79, and 0.75, respectively). Agreement was poor for lower grade IVH and for PVL alone. Local interpretations were highly accurate for grade 3/4 IVH or PVL (sensitivity, 87%-90%; specificity, 92%-93%), but sensitivity was poor-to-fair for grade 1/2 IVH (48%-68%) and PVL (20%-44%).Our findings demonstrate reliability and accuracy of highly unfavorable CUS findings, but suggest caution when interpreting mild to moderate IVH or white matter injury.

    View details for DOI 10.1016/j.jpeds.2007.02.012

    View details for Web of Science ID 000246939700011

    View details for PubMedID 17517240

  • The potential Salmonella aroA(-) vaccine strain is safe and effective in young BALB/c mice NEONATOLOGY Burns-Guydish, S. M., Zhao, H., Stevenson, D. K., Contag, C. H. 2007; 91 (2): 114-120

    Abstract

    Due to the increased susceptibility of neonates to pathogens including those with mutations, the use of live vaccine strategies in the human population may present a potential risk to the young.The specific aim of this study was to assess the risk that prospective Salmonella enterica serovar Typhimurium vaccine strains pose for the neonate and determine whether the strains are an effective vaccine by assessing the adaptive immune response.To evaluate the susceptibility of young mice to potential vaccine strains, S. typhimuriumaroA(-) and Delta phoP mutant strains were labeled by chromosomal insertion of the lux operon--this serves as a readily traceable marker of infection using noninvasive imaging methods. BALB/c mice ages 1, 2, 4, and 6 weeks of age were fed the bioluminescent aroA(-) or Delta phoP strains and the course of infection was monitored by in vivobioluminescence imaging. In addition, blood samples were collected post-inoculation to assess the IgG response of mice to S. typhimurium LPS.Young BALB/c mice were not susceptible to the aroA(-) strain in contrast to their susceptibility to the Delta phoP strain at a dose of 10(9) colony forming units. Delivery by oral feeding of the aroA(-) and Delta phoP strains in young mice also produced a robust IgG anti-LPS response.Here, we report that young 2-week-old mice orally fed the bioluminescent aroA(-) S. typhimurium strain were not susceptible to infection and elicited a protective immune response.

    View details for DOI 10.1159/000097128

    View details for Web of Science ID 000244967400006

    View details for PubMedID 17344661

  • Apigenin decreases hemin-mediated heme oxygenase-1 induction FREE RADICAL BIOLOGY AND MEDICINE Abate, A., Yang, G., Wong, R. J., Schroder, H., Stevenson, D. K., Dennery, P. A. 2005; 39 (6): 711-718

    Abstract

    Hemin is a strong inducer of heme oxygenase-1 (HO-1) expression in vitro and in vivo. Whereas moderate overexpression of HO-1 is protective against oxidative stress, uncontrolled levels of HO-1 can be detrimental. Therefore, we evaluated the effects of apigenin (APG), a flavonoid involved in a number of phosphorylation pathways and also known to inhibit inducible genes, such as iNOS and COX-2, on HO-1 expression. Incubation of mouse embryonic fibroblasts with APG (5--40 microM) decreased hemin-induced HO-1 protein and mRNA expression. APG also reduced the induction of HO-1 promoter activity, as assessed by bioluminescence imaging, in NIH3T3 cells transfected with the 15-kb HO-1 promoter fused with the reporter gene luciferase (HO-1-luc). Furthermore, through the use of specific inhibitors, APG's effect was found to be unrelated to its PKC, CK 2, PI 3 K, p38, or ERK inhibitory activities. Quercetin (10--40 microM), also a flavonoid, also inhibited hemin-induced HO-1 expression. Additionally, in vivo studies using HO-1-luc transgenic mice showed that APG (50 mg/kg) decreased hemin-induced HO activity and HO-1 protein expression in the liver. These results suggest that hemin-induced HO-1 expression can be attenuated by flavonoids, such as APG.

    View details for DOI 10.1016/j.freeradbiomed.2005.01.020

    View details for Web of Science ID 000231583500002

    View details for PubMedID 16109301

  • Determination of carbon monoxide (CO) in rodent tissue: Effect of heme administration and environmental CO exposure ANALYTICAL BIOCHEMISTRY Vreman, H. J., Wong, R. J., Kadotani, T., Stevenson, D. K. 2005; 341 (2): 280-289

    Abstract

    Carbon monoxide (CO), produced endogenously during heme degradation, is considered a messenger molecule in vascular and neurologic tissues. To study this role, it is important to determine CO concentration in target tissues pre- and post-perturbations. Here, we describe a sensitive and reproducible method, which is linear and accurate, and provide some examples of its application for quantitation of CO concentrations in tissues pre- and post-perturbations. Tissues from adult rats and mice were sonicated (20% w/w), and volumes representing 0.04-8 mg fresh weight (FW) were incubated at 0 degrees C for 30 min with sulfosalicylic acid. CO liberated into the headspace was quantitated by gas chromatography. Tissue CO concentrations (mean+/-SD, pmol CO/mg FW) were as follows: blood (47+/-10, 45+/-5), muscle (4+/-4, 10+/-1), kidney (5+/-2, 7+/-2), heart (6+/-3, 6+/-1), spleen (11+/-3, 6+/-1), liver (4+/-1, 5+/-1), intestine (2+/-1, 4+/-2), lung (2+/-1, 3+/-1), testes (1+/-1, 2+/-1), and brain (2+/-1, 2+/-0) in untreated rat (n=3) and mouse (n=5), respectively. Between the rat and the mouse, only CO concentrations in the muscle and spleen were significantly different (p0.05). Endogenous CO generation, after administration of heme arginate to mice (n=3), increased CO concentrations by 0-43 pmol/mg FW. Exposure of mice (n=3) to 500 ppm CO for 30 min yielded significantly elevated CO concentrations by 4-2603 pmol/mg FW in all tissues over the native state. While blood had the highest CO concentration for all conditions, muscle, kidney, heart, spleen, and liver, all rich in hemoglobin and/or other CO-binding hemoproteins, also contained substantial CO concentrations. Intestine, lung, testes, and brain contained the lowest CO concentrations.

    View details for DOI 10.1016/j.ab.2005.03.019

    View details for Web of Science ID 000229460800011

    View details for PubMedID 15907874

  • Cesarean delivery rates and neonatal morbidity in a low-risk population OBSTETRICS AND GYNECOLOGY Gould, J. B., Danielsen, B., Korst, L. M., Phibbs, R., Chance, K., Main, E., Wirtschafter, D. D., Stevenson, D. K. 2004; 104 (1): 11-19

    Abstract

    To estimate the relationship between case-mix adjusted cesarean delivery rates and neonatal morbidity and mortality in infants born to low-risk mothers.This retrospective cohort study used vital and administrative data for 748,604 California singletons born without congenital abnormalities in 1998-2000. A total of 282 institutions was classified as average-, low-, or high-cesarean delivery hospitals based on their cesarean delivery rate for mothers without a previous cesarean delivery, in labor at term, with no evidence of maternal, fetal, or placental complications. Neonatal mortality, diagnoses, and therapeutic interventions determined by International Classification of Diseases, 9th Revision, Clinical Modification codes, and neonatal length of stay were compared across these hospital groupings.Compared with average-cesarean delivery-rate hospitals, infants born to low-risk mothers at low-cesarean delivery hospitals had increased fetal hemorrhage, birth asphyxia, meconium aspiration syndrome, feeding problems, and electrolyte abnormalities (P <.02). Infused medication, pressors, transfusion for shock, mechanical ventilation, and length of stay were also increased (P <.001). This suggests that some infants born in low-cesarean delivery hospitals might have benefited from cesarean delivery. Infants delivered at high-cesarean delivery hospitals demonstrated increased fetal hemorrhage, asphyxia, birth trauma, electrolyte abnormalities, and use of mechanical ventilation (P <.001), suggesting that high cesarean delivery rates themselves are not protective.Neonatal morbidity is increased in infants born to low-risk women who deliver at both low- and high-cesarean delivery-rate hospitals. The quality of perinatal care should be assessed in these outlier hospitals.III

    View details for DOI 10.1097/01.AOG.0000127035.64602.97

    View details for Web of Science ID 000225414600004

    View details for PubMedID 15228995

  • Continuous, noninvasive, and localized microvascular tissue oximetry using visible light spectroscopy ANESTHESIOLOGY Benaron, D. A., Parachikov, I. H., Friedland, S., Soetikno, R., Brock-Utne, J., van der Starre, P. J., Nezhat, C., Terris, M. K., Maxim, P. G., Carson, J. J., Razavi, M. K., Gladstone, H. B., Fincher, E. F., Hsu, C. P., Clark, F. L., Cheong, W. F., Duckworth, J. L., Stevenson, D. K. 2004; 100 (6): 1469-1475

    Abstract

    The authors evaluated the ability of visible light spectroscopy (VLS) oximetry to detect hypoxemia and ischemia in human and animal subjects. Unlike near-infrared spectroscopy or pulse oximetry (SpO2), VLS tissue oximetry uses shallow-penetrating visible light to measure microvascular hemoglobin oxygen saturation (StO2) in small, thin tissue volumes.In pigs, StO2 was measured in muscle and enteric mucosa during normoxia, hypoxemia (SpO2 = 40-96%), and ischemia (occlusion, arrest). In patients, StO2 was measured in skin, muscle, and oral/enteric mucosa during normoxia, hypoxemia (SpO2 = 60-99%), and ischemia (occlusion, compression, ventricular fibrillation).In pigs, normoxic StO2 was 71 +/- 4% (mean +/- SD), without differences between sites, and decreased during hypoxemia (muscle, 11 +/- 6%; P < 0.001) and ischemia (colon, 31 +/- 11%; P < 0.001). In patients, mean normoxic StO2 ranged from 68 to 77% at different sites (733 measures, 111 subjects); for each noninvasive site except skin, variance between subjects was low (e.g., colon, 69% +/- 4%, 40 subjects; buccal, 77% +/- 3%, 21 subjects). During hypoxemia, StO2 correlated with SpO2 (animals, r2 = 0.98; humans, r2 = 0.87). During ischemia, StO2 initially decreased at -1.3 +/- 0.2%/s and decreased to zero in 3-9 min (r2 = 0.94). Ischemia was distinguished from normoxia and hypoxemia by a widened pulse/VLS saturation difference (Delta < 30% during normoxia or hypoxemia vs. Delta > 35% during ischemia).VLS oximetry provides a continuous, noninvasive, and localized measurement of the StO2, sensitive to hypoxemia, regional, and global ischemia. The reproducible and narrow StO2 normal range for oral/enteric mucosa supports use of this site as an accessible and reliable reference point for the VLS monitoring of systemic flow.

    View details for Web of Science ID 000221551300018

    View details for PubMedID 15166566

  • End tidal carbon monoxide levels are lower in women with gestational hypertension and pre-eclampsia. Journal of perinatology Kreiser, D., Baum, M., Seidman, D. S., Fanaroff, A., Shah, D., Hendler, I., Stevenson, D. K., Schiff, E., Druzin, M. L. 2004; 24 (4): 213-217

    Abstract

    The possible role of heme oxygenase and its byproduct carbon monoxide (CO) in the regulation of blood pressure is under investigation. The aim of this study was to compare end tidal breath CO (ETCO) levels in women with gestational hypertension (GH) or pre-eclampsia to the levels in healthy pregnant and nonpregnant women.We prospectively performed ETCO measurements corrected for ambient CO (ETCOc) in two medical centers (Stanford, CA and Cleveland, OH). A Natus CO-Stat End Tidal Breath Analyzer (Natus Medical Inc., San Carlos, CA) was used. The study group included a convenience sample of 31 women with GH/pre-eclampsia (PE). Control groups included 46 nonpregnant healthy women, 44 first-trimester and 48 third-trimester pregnant healthy women.Mean+/-SD ETCOc measurements were significantly lower in the GH/PE group compared to first-trimester (p=0.004) and third-trimester (p=0.001) normotensive pregnant and nonpregnant women (p=0.002) (1.36+/-0.30 vs 1.76+/-0.47, 1.72+/-0.42 and 1.78+/-0.54 ppm, respectively). The ETCOc values were < or =1.6 ppm in 89% of GH/PE women compared with, respectively, only 45, 54, and 46% of nonpregnant, first- and third-trimester normotensive pregnant women (p<0.05). ETCO measurements were not influenced by maternal age, parity, ethnicity, body mass index, gestational age or presence of household smokers. In the two centers, the controls had a similar mean ETCOc and the differences found remained significant when results for each center were analyzed separately.ETCOc levels were found to be significantly lower in women with GH/PE. Further investigation is required to determine if the lower CO levels reflect a deficient compensatory response to the increase in blood pressure or whether these are primary changes of significance to our understanding of the pathogenesis of GH/PE.

    View details for PubMedID 15014533

  • Characterization of coelenterazine analogs for measurements of Renilla luciferase activity in live cells and living animals. Molecular imaging Zhao, H., Doyle, T. C., Wong, R. J., Cao, Y., Stevenson, D. K., Piwnica-Worms, D., Contag, C. H. 2004; 3 (1): 43-54

    Abstract

    In vivo imaging of bioluminescent reporters relies on expression of light-emitting enzymes, luciferases, and delivery of chemical substrates to expressing cells. Coelenterazine (CLZN) is the substrate for a group of bioluminescent enzymes obtained from marine organisms. At present, there are more than 10 commercially available CLZN analogs. To determine which analog is most suitable for activity measurements in live cells and living animals, we characterized 10 CLZN analogs using Renilla luciferase (Rluc) as the reporter enzyme. For each analog, we monitored enzyme activity, auto-oxidation, and efficiency of cellular uptake. All CLZN analogs tested showed higher auto-oxidation signals in serum than was observed in phosphate buffer or medium, mainly as a result of auto-oxidation by binding to albumin. CLZN-f, -h, and -e analogs showed 4- to 8-fold greater Rluc activity, relative to CLZN-native, in cells expressing the enzyme from a stable integrant. In studies using living mice expressing Rluc in hepatocytes, administration of CLZN-e and -native produced the highest signal. Furthermore, distinct temporal differences in signal for each analog were revealed following intravenous or intraperitoneal delivery. We conclude that the CLZN analogs that are presently available vary with respect to hRluc utilization in culture and in vivo, and that the effective use of CLZN-utilizing enzymes in living animals depends on the selection of an appropriate substrate.

    View details for PubMedID 15142411

  • Gestational pattern of heme oxygenase expression in the rat PEDIATRIC RESEARCH Kreiser, D., Kelly, D. K., Seidman, D. S., Stevenson, D. K., Baum, M., Dennery, P. A. 2003; 54 (2): 172-178

    Abstract

    Fetal growth is influenced by many intrinsic and extrinsic factors. Our objective was to determine the pattern of heme oxygenase (HO) expression in the pregnant rat and to study its association with fetal growth and growth factors. Uterine tissues were obtained from nonpregnant and from time-mated rats at 7, 13, 16, 19, and 21 d of pregnancy. Placental tissue was obtained on d 13, 16, 19 and 21 of pregnancy. Tissues were evaluated for HO activity, HO-1, HO-2, leptin and vascular endothelial growth factor protein, and HO-1 and HO-2 mRNA. HO activity in both the uterus and placenta peaked on d 21 of pregnancy. In the uterus, HO-1 and HO-2 protein and total mRNA levels peaked on d 16 of pregnancy, whereas, in the placenta, HO-1 and HO-2 protein levels peaked on d 19. Additionally, placental HO-1 mRNA peaked on d 16, but placental HO-2 mRNA declined toward the end of pregnancy. Placental leptin and vascular endothelial growth factor protein levels followed a similar pattern to placental HO-1 and peaked on d 16. We conclude that there is a clear uterine and placental gestational pattern of HO expression in the rat. This pattern is comparable to that of vascular endothelial growth factor and leptin.

    View details for DOI 10.1203/01.PDR.0000072516.83498.07

    View details for Web of Science ID 000184407700005

    View details for PubMedID 12736392

  • Ethical considerations in neuroimaging and its impact on decision-making for neonates BRAIN AND COGNITION Stevenson, D. K., Goldworth, A. 2002; 50 (3): 449-454

    Abstract

    Neuroimaging can now provide information about structure and function. Despite new and improved neuroimaging technologies applicable to the newborn, predictions about later cognition, learning, social and emotional behavior, and neuromuscular capabilities, based on images of a fetus inside or a newborn outside the womb, are fraught with difficulties that go beyond technical ones. The interpretation of neuroimages may be necessary but it is not sufficient for decision-making related to the withholding or withdrawing of medical support for neonates. As the explanatory reach of neuroimaging increases, there will still need to be consideration of ethical issues as they relate to the best interests of the neonate and the neonate's parents, the quality of life of the neonate and non-beneficial treatment. Once this is appreciated, the boundary between the technical and the ethical will be less often disputed.

    View details for Web of Science ID 000180058100009

    View details for PubMedID 12480489

  • The jaundiced newborn. Understanding and managing transitional hyperbilirubinemia. Minerva pediatrica Stevenson, D. K., Wong, R. J., Hintz, S. R., Vreman, H. J. 2002; 54 (5): 373-382

    Abstract

    Neonatal jaundice is one of the most common conditions diagnosed by the pediatrician. This normally benign transitional phenomenon is a dynamic balance between the production and elimination of bilirubin. These processes can be exacerbated by a number of pathophysiologic conditions, which cause either an increase in bilirubin production rates, such as hemolysis, or a decrease in bilirubin elimination rates, such as bilirubin conjugation defects. The most dangerous circumstance for an infant is the combination of increased bilirubin production with impaired elimination. These infants are at considerable risk for developing excessive and potentially dangerous hyperbilirubinemia and subsequent kernicterus. Therefore, the importance of early recognition of the imbalance is paramount. In this review, we will discuss the various risk factors associated with hyperbilirubinemia and describe strategies for the diagnosis and management of transitional hyperbilirubinemia.

    View details for PubMedID 12244276

  • Heme oxygenase-1 modulates fetal growth in the rat LABORATORY INVESTIGATION Kreiser, D., Nguyen, X., Wong, R., Seidman, D., Stevenson, D., Quan, S., Abraham, N., Dennery, P. A. 2002; 82 (6): 687-692

    Abstract

    Intrauterine growth restriction is associated with increased perinatal morbidity and mortality as well as with lifelong cardiovascular and metabolic complications. Deficiency of heme oxygenase 1 (HO-1) is associated with growth restriction in mice and in humans, suggesting a role for HO-1 in fetal growth and maintenance of pregnancy. We hypothesized that modulation of HO-1 in the pregnant rat would alter fetal growth. In pregnant dams, placental HO activity was significantly inhibited with zinc deuteroporphyrin IX 2,4 bis glycol, and HO-1 protein was increased by transducing adenoviral human HO-1. Inhibition of HO-1 by zinc deuteroporphyrin IX 2,4 bis glycol resulted in a significant decrease in pup size, whereas transfection with hHO-1 resulted in increased pup size. Furthermore, the expression of IGF binding protein-1 and its receptor paralleled the expression of HO-1 in the placenta and were significantly modulated by modification of HO-1 along with the expression of vascular endothelial growth factor. These observations demonstrate that HO-1 modulates fetal growth by its effects on placental growth factors.

    View details for DOI 10.1097/01.LAB.0000017167.26718.F2

    View details for Web of Science ID 000176317600002

    View details for PubMedID 12065678

  • In vivo patterns of heme oxygenase-1 transcription. Journal of perinatology Contag, C. H., Stevenson, D. K. 2001; 21: S119-24

    Abstract

    Gene fusions composed of specific promoters and bioluminescent reporter genes can be used to assess gene expression patterns using whole-body imaging in living animal models. A transgenic mouse model was developed using the regulatory elements of the heme oxygenase promoter to drive luciferase as the reporter gene. In these transgenic mice, heme oxygenase (HO)-1 expression was apparent in neuronal tissues of neonates but not adults as measured by whole-body imaging, and in adults transcription of the reporter gene was inducible by known inducers of HO-1 transcription. Whole-body imaging of luciferase activity was then used to evaluate the effects of metalloporphyrins (Mps) on the transcription of the reporter gene. Some of the Mps, which are potent inhibitors of HO activity, did not activate the reporter gene above background. These Mps are ideally suited as chemotherapeutics that may target bilirubin production rates by inhibiting HO activity, but not result in a net increase in output from the HO gene. In contrast, known inducers of HO transcription did increase luciferase activity as did some of the other Mps that have been examined. Using whole-body in vivo transcriptional assays may facilitate rapid screening of potential therapeutic compounds for both desired and untoward effects.

    View details for PubMedID 11803432

  • Understanding newborn jaundice. Journal of perinatology Stevenson, D. K., Dennery, P. A., Hintz, S. R. 2001; 21: S21-4

    View details for PubMedID 11803411

  • The biology of bilirubin production. Journal of perinatology Dennery, P. A., Weng, Y. H., Stevenson, D. K., Yang, G. 2001; 21: S17-20

    Abstract

    Heme oxygenase (HO), the rate-limiting enzyme in bilirubin production, has been identified from the late 1960s. This enzyme has been shown to have many other roles in recent years. The inducible form is regulated by oxidative stress, inflammation, and heavy metals, among others, and is cytoprotective in many instance. Nonetheless, there are instances when HO-1 can be deleterious due to the release of iron from the reaction. Another important by-product, carbon monoxide, is a vasodilator and a neurotransmitter and has been implicated in signal transduction pathways. More recently, nonenzymatic, signaling roles of HO have been suggested. This may serve to regulate the endogenous activity of this enzyme when cellular heme levels are low.

    View details for PubMedID 11803410

  • Just when you thought it was safe... PEDIATRIC RESEARCH Hintz, S. R., Stevenson, D. K. 2001; 50 (6): 676-677

    View details for Web of Science ID 000172398500004

    View details for PubMedID 11726720

  • Alternative metalloporphyrins for the treatment of neonatal jaundice. Journal of perinatology Vreman, H. J., Wong, R. J., Stevenson, D. K. 2001; 21: S108-13

    View details for PubMedID 11803430

  • Prediction of hyperbilirubinemia in near-term and term infants. Journal of perinatology Stevenson, D. K., Fanaroff, A. A., Maisels, M. J., Young, B. W., Wong, R. J., Vreman, H. J., MacMahon, J. R., Yeung, C. Y., Seidman, D. S., Gale, R., Oh, W., Bhutani, V. K., Johnson, L. H., Kaplan, M., Hammerman, C., Nakamura, H. 2001; 21: S63-72

    Abstract

    The purpose of this study was to determine whether end-tidal carbon monoxide (CO) corrected for ambient CO (ETCOc), as a single measurement or in combination with serum total bilirubin (STB) measurements, can predict the development of hyperbilirubinemia during the first 7 days of life.From nine multinational clinical sites, 1370 neonates completed this cohort study from February 20, 1998 through February 22, 1999. Measurements of both ETCOc and STB were performed at 30+/-6 hours of life; STB also was measured at 96+/-12 hours and subsequently following a flow diagram based on a table of hours of age-specific STB. An infant was defined as hyperbilirubinemic if the hours of age-specific STB was greater than or equal to the 95th percentile as defined by the table at any time during the study.A total of 120 (8.8%) of the enrolled infants became hyperbilirubinemic. Mean STB in breast-fed infants was 8.92+/-4.37 mg/dl at 96 hours versus 7.63+/-3.58 mg/dl in those fed formula only. The mean ETCOc at 30+/-6 hours for the total population was 1.48+/-0.49 ppm, whereas those of nonhyperbilirubinemic and hyperbilirubinemic infants were 1.45+/-0.47 and 1.81+/-0.59 ppm, respectively. Seventy-six percent (92 of 120) of hyperbilirubinemic infants had ETCOc greater than the population mean. An ETCOc greater than the population mean at 30+/-6 hours yielded a 13.0% positive predictive value (PPV) and a 95.8% negative predictive value (NPV) for STB > or =95th percentile. When infants with STB > or =95th percentile at <36 hours of age were excluded, the STB at 30+/-6 hours yielded a 16.7% PPV and a 98.1% NPV for STB >75th percentile. The combination of these two measurements at 30+/-6 hours (either ETCOc more than the population mean or STB >75th percentile) had a 6.4% PPV with a 99.0% NPV.This prospective cohort study supports previous observations that measuring STB before discharge may provide some assistance in predicting an infant's risk for developing hyperbilirubinemia. The addition of an ETCOc measurement provides insight into the processes that contribute to the condition but does not materially improve the predictive ability of an hours of age-specific STB in this study population. The combination of STB and ETCOc as early as 30+/-6 hours may identify infants with increased bilirubin production (eg, hemolysis) or decreased elimination (conjugation defects) as well as infants who require early follow-up after discharge for jaundice or other clinical problems such as late anemia. Depending on the incidence of hyperbilirubinemia within an institution, the criteria for decision making should vary according to its unique population.

    View details for PubMedID 11803421

  • Differing pathogenesis of perinatal bilirubinemia in glucose-6-phosphate dehydrogenase-deficient versus -normal neonates PEDIATRIC RESEARCH Kaplan, M., Hammerman, C., Renbaum, P., Levy-Lahad, E., Vreman, H. J., Stevenson, D. K. 2001; 50 (4): 532-537

    Abstract

    The objective was to compare the contribution to perinatal bilirubinemia of hemolysis and UDP-glucuronosyltransferase (UGT) gene promoter polymorphism, seen in Gilbert's syndrome, between glucose-6-phosphate dehydrogenase (G-6-PD)-deficient and -normal neonates. Serum total bilirubin (STB) values from 52 G-6-PD-deficient and 166 G-6-PD-normal term, male neonates, sampled within 3 h of delivery (first sample) and on d 3 (second sample), were analyzed in relation to blood carboxyhemoglobin corrected for inspired CO (COHbc), an accurate index of hemolysis, and UGT promoter genotype. COHbc values (% total Hb) were greater in G-6-PD-deficient neonates than controls: first sample 1.00 +/- 0.25% versus 0.84 +/- 0.24%, p < 0.0001; second sample 0.83 +/- 0.20% versus 0.76 +/- 0.19%, p = 0.002. First sample COHbc and STB values did not correlate in either the G-6-PD-deficient or control groups, whereas second sample COHbc values correlated significantly with corresponding STB values in the control population only (r = 0.28, p = 0.0007). At second sampling, there was a higher allele frequency of the variant UGT promoter among those with STB values > or =75th percentile than those <75th among the G-6-PD-deficient neonates (0.60 versus 0.33, respectively, p = 0.025), but not controls (0.31 versus 0.40, respectively, p = 0.24). Among those infants with at least one variant UGT promoter allele, STB values were higher in the G-6-PD-deficient neonates than controls at second sampling only (181 +/- 56 microM versus 149 +/- 46 microM, respectively, p = 0.03). Both within and between the G-6-PD-deficient and control groups, our data demonstrate changing and differing contributions of hemolysis and UGT promoter polymorphism to bilirubinemia during the first 3 d of life.

    View details for Web of Science ID 000171092600018

    View details for PubMedID 11568299

  • Prediction of hyperbilirubinemia in near-term and term infants PEDIATRICS Stevenson, D. K., Fanaroff, A. A., Maisels, M. J., Young, B. W., Wong, R. J., Vreman, H. J., MacMahon, J. R., Yeung, C. Y., Seidman, D. S., Gale, R., Oh, W., Bhutani, V. K., Johnson, L. H., Kaplan, M., Hammerman, C., Nakamura, H. 2001; 108 (1): 31-39

    Abstract

    The purpose of this study was to determine whether end-tidal carbon monoxide (CO) corrected for ambient CO (ETCOc), as a single measurement or in combination with serum total bilirubin (STB) measurements, can predict the development of hyperbilirubinemia during the first 7 days of life.From 9 multinational clinical sites, 1370 neonates completed this cohort study from February 20, 1998, through February 22, 1999. Measurements of both ETCOc and STB were performed at 30 +/- 6 hours of life; STB also was measured at 96 +/- 12 hours and subsequently following a flow diagram based on a table of hours of age-specific STB. An infant was defined as hyperbilirubinemic if the hours of age-specific STB was greater than or equal to the 95th percentile as defined by the table at any time during the study.A total of 120 (8.8%) of the enrolled infants became hyperbilirubinemic. Mean STB in breastfed infants was 8.92 +/- 4.37 mg/dL at 96 hours versus 7.63 +/- 3.58 mg/dL in those fed formula only. The mean ETCOc at 30 +/- 6 hours for the total population was 1.48 +/- 0.49 ppm, whereas those of nonhyperbilirubinemic and hyperbilirubinemic infants were 1.45 +/- 0.47 ppm and 1.81 +/- 0.59 ppm, respectively. Seventy-six percent (92 of 120) of hyperbilirubinemic infants had ETCOc greater than the population mean. An ETCOc greater than the population mean at 30 +/- 6 hours yielded a 13.0% positive predictive value (PPV) and a 95.8% negative predictive value (NPV) for STB >/=95th percentile. When infants with STB >95th percentile at <36 hours of age were excluded, the STB at 30 +/- 6 hours yielded a 16.7% PPV and a 98.1% NPV for STB >75th percentile. The combination of these 2 measurements at 30 +/- 6 hours (either ETCOc more than the population mean or STB >75th percentile) had a 6.4% PPV with a 99.0% NPV. Conclusions. This prospective cohort study supports previous observations that measuring STB before discharge may provide some assistance in predicting an infant's risk for developing hyperbilirubinemia. The addition of an ETCOc measurement provides insight into the processes that contribute to the condition but does not materially improve the predictive ability of an hours of age-specific STB in this study population. The combination of STB and ETCOc as early as 30 +/- 6 hours may identify infants with increased bilirubin production (eg, hemolysis) or decreased elimination (conjugation defects) as well as infants who require early follow-up after discharge for jaundice or other clinical problems such as late anemia. Depending on the incidence of hyperbilirubinemia within an institution, the criteria for decision making should vary according to its unique population.

    View details for Web of Science ID 000169571400025

    View details for PubMedID 11433051

  • Serum bilirubin levels at 72 hours by selected characteristics in breastfed and formula-fed term infants delivered by cesarean section ACTA PAEDIATRICA Hintz, S. R., Gaylord, T. D., Oh, W., Fanaroff, A. A., Mele, L., Stevenson, D. K. 2001; 90 (7): 776-781

    Abstract

    The present multicenter study analysed the relative impact of maternal and infant factors on serum bilirubin levels at 72 +/- 12 h in exclusively breastfed vs formula-fed term infants. End-tidal carbon monoxide levels corrected for ambient air (ETCOc), an index of bilirubin production, were measured in exclusively breastfed (B = 66) or formula-fed (F = 210) term infants at 2-8 h of age. Inclusion criteria included cesarean section to ensure a 3 d hospitalization, birthweight > or = 2,500 g, gestational age >37 wk and absence of any illness. The ETCOc for B infants and F infants did not differ significantly (1.3 +/- 0.7 ppm vs 1.3 +/- 0.8 ppm). The serum bilirubin level at 72 +/- 12 h was significantly higher in B infants than in F infants (8.5 +/- 3.4mg dl(-1) vs 6.7 +/- 3.4mg dl(-1) p < 0.001), as was the percentage weight loss from birthweight. Serum bilirubin levels were significantly higher in infants who were male, who did not have meconium-stained amniotic fluid, and in those whose mothers were insulin-dependent diabetics or hypertensive. There was no difference between groups in the need for phototherapy or exchange transfusion.Although higher bilirubin levels were observed in group B at 72 +/- 12 h compared with group F, this finding was not of clinical or therapeutic consequence in this study. The lack of difference in ETCOc between the groups may be a factor of the timing of ETCOc measurement in this study, or may suggest that early increased bilirubin production is not a significant contributor to jaundice observed in exclusively breastfed infants. Key words: bilirubin, breastfeeding, jaundice

    View details for Web of Science ID 000170367700013

    View details for PubMedID 11519981

  • Unique effects of zinc protoporphyrin on HO-1 induction and apoptosis BLOOD Yang, G., Nguyen, X., Ou, J., Rekulapelli, P., Stevenson, D. K., Dennery, P. A. 2001; 97 (5): 1306-1313

    Abstract

    Zinc protoporphyrin (ZnPP), a naturally occurring molecule, is increased in iron deficiency and lead intoxication. ZnPP can also induce heme oxygenase (HO-1), the enzyme it competitively inhibits. In cultured cells (HA-1), ZnPP was the strongest HO-1 inducer of any metalloporphyrin (MP) tested. This was not due to increased oxidative stress, enhanced binding at metal response element, nor increased binding at activator protein-1 (AP-1) or SP-1 sites on HO-1. Only ZnPP, however, increased binding of nuclear proteins to early growth response-1 (Egr-1) protein consensus sequence. Pretreatment of HA-1 with cycloheximide inhibited ZnPP-induced HO-1 messenger RNA (mRNA) by 55%. Incubation with antisense Egr-1 oligomers decreased ZnPP-induced HO-1 expression by 47%. Furthermore, the level of HO-1 mRNA induction by ZnPP was 2-fold less in Egr-1-deficient fibroblasts than in wild-type cells. Because no Egr-1 binding site was previously identified on the HO-1 promoter, HA-1 cells were transfected with HO-1 CAT constructs containing segments of a 12.5-kb enhancer region of HO-1. A 196-bp fragment (RH) located approximately 9.5 kb upstream of the transcription start site mediated HO-1 induction by ZnPP alone. DNase I footprinting analysis further revealed that nuclear proteins bound to a 50-bp sequence in the RH. Within this sequence, a novel 9-bp region with 78% homology to the Egr-1 consensus sequence was identified further suggesting that Egr-1 partially mediates HO-1 induction by ZnPP. Lastly, increased apoptosis and nuclear localization were only seen with ZnPP, suggesting that increased ZnPP in disease states may serve as a cellular signaling mechanism.

    View details for Web of Science ID 000167117500019

    View details for PubMedID 11222374

  • Neonatal hyperbilirubinemia. New England journal of medicine Dennery, P. A., Seidman, D. S., Stevenson, D. K. 2001; 344 (8): 581-590

    View details for PubMedID 11207355

  • Rapid in vivo functional analysis of transgenes in mice using whole body imaging of luciferase expression TRANSGENIC RESEARCH Zhang, W. S., Feng, J. Q., Harris, S. E., Contag, P. R., Stevenson, D. K., Contag, C. H. 2001; 10 (5): 423-434

    Abstract

    The use of transgenic animals in biomedical research is increasing rapidly and may be the best means of determining gene function. Generating transgenic animals typically requires time-consuming screening processes, and gene function is assessed by an array of difficult phenotypic and biochemical assays performed ex vivo. To address the unmet need in transgenic research for functional assays performed with ease in living animals, we demonstrate here that in vivo detection of luciferase enzyme as a transcriptional reporter facilitates rapid screening for both the presence and function of transgenes in intact living mice. Using this approach we identified three bioluminescent transgenic founders where the transgene consisted of the heme oxygenase promoter fused to the modified coding sequence of the luciferase gene. These founders were identified from 183 pups and confirmed by PCR analysis. Identification of HO-1-luc homozygotes from back- crossed F2 littermates was then accelerated by in vivo imaging. In another transgenic mouse line, where the transgene was comprised of the bone morphogenic-4 (BMP4) promoter fused to the modified luciferase gene, we were able to identify transgenic animals and in each line we were able to visualize patterns of expression in living animals over time. The light production from these transgenic mice indicated that the desired DNA fragment was functional and different expression profiles apparent at different ages and after gene induction.

    View details for Web of Science ID 000171405600005

    View details for PubMedID 11708652

  • Bedside functional imaging of the premature infant brain during passive motor activation JOURNAL OF PERINATAL MEDICINE Hintz, S. R., Benaron, D. A., Siegel, A. M., Zourabian, A., Stevenson, D. K., Boas, D. A. 2001; 29 (4): 335-343

    Abstract

    Changes in regional brain blood flow and hemoglobin oxygen saturation occur in the human cortex in response to neural activation. Traditional functional radiologic methods cannot provide continuous, portable measurements. Imaging methods, which use near-infrared light allow for non-invasive measurements by taking advantage of the fact that hemoglobin is a strong absorber at these wavelengths.To test the feasibility of a new optical functional imaging system in premature infants, and to obtain preliminary brain imaging of passive motor activation in this population.A new optical imaging system, the Diffuse Optical Tomography System (DOTS), was used to provide real-time, bedside assessments. Custom-made soft flexible fiberoptic probes were placed on two extremely ill, mechanically ventilated 24 week premature infants, and three healthier 32 week premature infants. Passive motor stimulation protocols were used during imaging.Specific movement of the arm resulted in reproducible focal, contralateral changes in cerebral absorption. The data suggest an overall increase in blood volume to the imaged area, as well as an increase in deoxyhemoglobin concentration. These findings in premature infants differ from those expected in adults.In the intensive care setting, continuous non-invasive optical functional imaging could be critically important and, with further study, may provide a bedside monitoring tool for prospectively identifying patients at high risk for brain injury.

    View details for Web of Science ID 000170867600010

    View details for PubMedID 11565203

  • Sex differences in outcomes of very low birthweight infants: the newborn male disadvantage ARCHIVES OF DISEASE IN CHILDHOOD Stevenson, D. K., Verter, J., Fanaroff, A. A., Oh, W., Ehrenkranz, R. A., Shankaran, S., Donovan, E. F., Wright, L. L., Lemons, J. A., TYSON, J. E., Korones, S. B., Bauer, C. R., Stoll, B. J. 2000; 83 (3): F182-F185

    Abstract

    To determine the differences in short term outcome of very low birthweight infants attributable to sex.Boys and girls weighing 501-1500 g admitted to the 12 centres of the National Institute of Child Health and Human Development Neonatal Research Network were compared. Maternal information and perinatal data were collected from hospital records. Infant outcome was recorded at discharge, at 120 days of age if the infant was still in hospital, or at death. Best obstetric estimate based on the last menstrual period, standard obstetric factors, and ultrasound were used to assign gestational age in completed weeks. Data were collected on a cohort that included 3356 boys and 3382 girls, representing all inborn births from 1 May 1991 to 31 December 1993.Mortality for boys was 22% and that for girls 15%. The prenatal and perinatal data indicate few differences between the sex groups, except that boys were less likely to have been exposed to antenatal steroids (odds ratio (OR) = 0.80) and were less stable after birth, as reflected in a higher percentage with lower Apgar scores at one and five minutes and the need for physical and pharmacological assistance. In particular, boys were more likely to have been intubated (OR = 1.16) and to have received resuscitation medication (OR = 1.40). Boys had a higher risk (OR > 1.00) for most adverse neonatal outcomes. Although pulmonary morbidity predominated, intracranial haemorrhage and urinary tract infection were also more common.Relative differences in short term morbidity and mortality persist between the sexes.

    View details for Web of Science ID 000165126200005

    View details for PubMedID 11040165

  • Reduction of the NO-mediated response in the rat aorta by metalloporphyrins CANADIAN JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY Vreman, H. J., Haenen, G. R., Stevenson, D. K., Bast, A. 2000; 78 (6): 457-461

    Abstract

    Metalloporphyrins (MPs) have been found to affect the production of carbon monoxide (CO) and nitric oxide (NO). Unlike that for CO, little is known about the mechanism of action of MPs on the NO system. We determined the in vitro ability of ferrous protoporphyrin (heme, FePP), zinc protoporphyrin (ZnPP), and bilirubin (BR) to scavenge NO. Heme and ZnPP were studied in the rat aortic ring system for their ability to affect phenylephrine-induced contraction and methacholine-stimulated relaxation. Heme was found to be a good NO scavenger with a ks = 0.53 +/- 0.19 x 10(4) M(-1)xs(-1) (n = 6). ZnPP and BR did not scavenge NO. Neither heme nor ZnPP treatment affected the phenylephrine response as measured by -logEC50 and the maximal effect. However, heme and ZnPP treatments decreased the -logEC50 and the maximal effects of methacholine, therefore decreasing vasorelaxation. We conclude that when ZnPP is administered in vivo blood pressure should be carefully monitored.

    View details for Web of Science ID 000087770700003

    View details for PubMedID 10914634

  • Haem oxygenase activity in human umbilical cord and rat vascular tissues PLACENTA Vreman, H. J., Wong, R. J., Kim, E. C., Nabseth, D. C., Marks, G. S., Stevenson, D. K. 2000; 21 (4): 337-344

    Abstract

    Carbon monoxide (CO) has been shown to affect vascular tone in smooth muscle cells and thus, may regulate regional or systemic blood pressure as well as fetoplacental vascular tone and fetal blood delivery. To assess the potential of vascular tissue to produce CO, we determined haem oxygenase (HO) activity through in vitro quantitation of CO production with gas chromatography and its inhibition by 33-66 microm of chromium mesoporphyrin (CrMP) in homogenate preparations of rat aorta and vena cava and human umbilical cord tissues. We compared these results to HO activity in rat heart and liver. We also discuss normalization of HO activity on a per mg protein as well as per g fresh weight (FW) tissue basis. We found that both rat vascular tissue HO activities (per g FW) were equal, but greater than that of heart (x3) and less than that of liver (x0.2). For human cord tissues, HO activities of artery and vein were equal, but greater than that of Wharton's jelly. Also, HO activity in rat vascular tissues was 3x greater than that of the human cord tissues. HO activity was completely inhibited by CrMP in rat heart (90 per cent) and liver (96 per cent), but incompletely (50-66 per cent) in both rat and human vascular tissues. We established that it is unlikely that other non-haem CO-generating processes account for this unique insensitivity of HO to CrMP inhibition. In fact, high concentrations of other potent metalloporphyrin inhibitors affected vascular tissue HO even less. We found that the degree of in vitro HO inhibition appeared to be related to the concentration of haem in the reaction medium. We conclude that the presence of HO activity in cord tissues supports the possibility that CO plays a role in fetoplacental blood flow regulation.

    View details for Web of Science ID 000087666000006

    View details for PubMedID 10833368

  • Noninvasive functional imaging of human brain using light JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM Benaron, D. A., Hintz, S. R., Villringer, A., Boas, D., Kleinschmidt, A., Frahm, J., Hirth, C., Obrig, H., van Houten, J. C., Kermit, E. L., Cheong, W. F., Stevenson, D. K. 2000; 20 (3): 469-477

    Abstract

    Analysis of photon transit time for low-power light passing into the head, and through both skull and brain, of human subjects allowed for tomographic imaging of cerebral hemoglobin oxygenation based on photon diffusion theory. In healthy adults, imaging of changes in hemoglobin saturation during hand movement revealed focal, contralateral increases in motor cortex oxygenation with spatial agreement to activation maps determined by functional magnetic resonance imaging; in ill neonates, imaging of hemoglobin saturation revealed focal regions of low oxygenation after acute stroke, with spatial overlap to injury location determined by computed tomography scan. Because such slow optical changes occur over seconds and co-localize with magnetic resonance imaging vascular signals whereas fast activation-related optical changes occur over milliseconds and co-localize with EEG electrical signals, optical methods offer a single modality for exploring the spatio-temporal relationship between electrical and vascular responses in the brain in vivo, as well as for mapping cortical activation and oxygenation at the bedside in real-time for clinical monitoring.

    View details for Web of Science ID 000085829700005

    View details for PubMedID 10724111

  • Carbon monoxide detection and biological investigations. Transactions of the American Clinical and Climatological Association Stevenson, D. K., Vreman, H. J., Wong, R. J., Dennery, P. A., Contag, C. H. 2000; 111: 61-75

    Abstract

    Even though the heme degradation pathway consists of only two reactions, it and its major enzyme (i.e. HO), nonetheless, impact other processes not only through the removal of excess heme, but also through the production of several metabolically active compounds. Thus CO and biliverdin along with reactive iron, Fe2, are the primordial products of this ancient, highly conserved reaction. That every component of the heme catabolic pathway is directly or indirectly related to other reactions involving oxygen or light is, perhaps, no accident of nature. That a fundamentally destructive event can be linked with a multiplicity of synthetic events and various biological effects, depending on the timing and location of the HO activity, is testament to the economy and the ultimate beauty of nature. Furthermore, the interaction of the heme catabolic pathway with that of the NOS system may lead to even more exciting avenues of research. It may be shown that the integrity of the heme catabolic pathway, which is ever present and plays a role in every tissue, is central to the existence of most complex organisms.

    View details for PubMedID 10881332

  • Validation of the natus CO-Stat (TM) end tidal breath analyzer in children and adults JOURNAL OF CLINICAL MONITORING AND COMPUTING Vreman, H. J., Wong, R. J., Harmatz, P., Fanaroff, A. A., Berman, B., Stevenson, D. K. 1999; 15 (7-8): 421-427

    Abstract

    The performance of a point-of-care, noninvasive end tidal breath carbon monoxide analyzer (CO-Stat End Tidal Breath Analyzer, Natus Medical Inc.) that also reports end tidal carbon dioxide (ETCO2) and respiratory rate (RR), was compared to established, marketed (predicate) devices in children (n = 39) and adults (n = 48) who are normal or at-risk of elevated CO excretion.Concentrations of end tidal breath CO (ETCO), room air CO, ETCO corrected for inhaled CO (ETCOc), ETCO2, and RR were measured with the CO-Stat analyzer and the data compared to those obtained from the same subjects using the Vitalograph BreathCO monitor (Vitalograph, Inc.) for ETCOc and the Pryon CO2 monitor (SC210 and SC300, Pryon Corp) for ETCO2 and RR. Adults and children were studied at three medical centers. The data were analyzed by paired t-tests and linear regression. Bias and imprecision between the CO-Stat analyzer and the predicate devices was calculated by the method of Bland and Altman.Paired t-tests, performed on the three parameters measured with the CO-Stat analyzer and predicate devices showed that only the ETCOc values in the adults and the ETCO2 values in the children were significantly different (lower, p < or = 0.0001, and higher, p < or = 0.0001, respectively). The mean bias and imprecision of the CO-Stat analyzer for adult ETCOc and children ETCO2 measurements were -0.9 +/- 1.2 ppm and 0.4 +/- 0.6%, respectively. Linear regression analysis for the ETCOc results in children and adults had a high degree of correlation (r = 0.91 and 0.98, respectively).We conclude that in a clinical environment the Natus CO-Stat End Tidal Breath Analyzer performs at least as well as predicate devices for the measurements of ETCOc, ETCO2, and RR.

    View details for Web of Science ID 000086962600004

    View details for PubMedID 12578038

  • Effects of skin-to-skin holding on general movements of preterm infants CLINICAL PEDIATRICS Constantinou, J. C., Adamson-Macedo, E. N., Stevenson, D. K., Mirmiran, M., Fleisher, B. E. 1999; 38 (8): 467-471

    Abstract

    The study objective was to test the hypothesis that the effect of skin-to-skin (STS) holding increases the ratio of rest to activity in low birth weight preterm infants. Ten infants with birthweight < 2,000 grams were videotaped before and after STS holding. Video recordings were analyzed to determine the number of general movements. We found no statistically significant difference between the percentage of general movements over the two periods. We conclude that the ratio of rest-activity before and after STS holding does not change as measured by occurrence of general movements.

    View details for Web of Science ID 000081864400005

    View details for PubMedID 10456242

  • Bilirubin toxicity and differentiation of cultured astrocytes. Journal of perinatology Rhine, W. D., SCHMITTER, S. P., Yu, A. C., Eng, L. F., Stevenson, D. K. 1999; 19 (3): 206-211

    Abstract

    To study the toxicity of bilirubin in primary cultures of newborn rat cerebral cortical astrocytes.Primary cultures of newborn rat astrocytes were incubated at bilirubin concentrations of 0, 1, 5, 10, 25, 50, 100, 200, and 2000 microM, at a bilirubin:albumin molar ratio of 1.7. Bilirubin toxicity was determined by changes in cellular morphology, trypan blue staining, and lactate dehydrogenase (LDH) release into the culture medium at various times of incubation. To determine if differentiation of astrocytes affects bilirubin toxicity, cultures were treated with dibutyryl cyclic adenosine monophosphate.All three indices of toxicity showed a bilirubin concentration dependence. LDH release in experimental cultures was significantly elevated (p < 0.05) above that of control cultures by 24 hours at bilirubin concentrations of > or = 100 microM. The absolute amount of LDH release differed significantly between the 200 and 2000 microM cultures from 1.5 to 24 hours, after which duration of exposure appeared to take over and all cultures approached maximum. LDH release for the lower concentrations all reached maximum by 120 hours, except for the 1 microM cultures, which showed no significant elevation above control throughout the study period. At 100 and 200 microM bilirubin, LDH release by untreated cells was significantly higher (p < 0.05) than release by treated cells by 36 hours.Undifferentiated astrocytes appeared to be more sensitive to bilirubin toxicity, which may correlate with the greater susceptibility of newborns to kernicteric injury. Studies with primary astrocyte culture may provide insight into how bilirubin sensitivity changes with brain development as well as the cellular and biochemical mechanisms of bilirubin encephalopathy.

    View details for PubMedID 10685223

  • Bedside imaging of intracranial hemorrhage in the neonate using light: Comparison with ultrasound, computed tomography, and magnetic resonance imaging PEDIATRIC RESEARCH Hintz, S. R., Cheong, W. F., van Houten, J. P., Stevenson, D. K., Benaron, D. A. 1999; 45 (1): 54-59

    Abstract

    Medical optical imaging (MOI) uses light emitted into opaque tissues to determine the interior structure. Previous reports detailed a portable time-of-flight and absorbance system emitting pulses of near infrared light into tissues and measuring the emerging light. Using this system, optical images of phantoms, whole rats, and pathologic neonatal brain specimens have been tomographically reconstructed. We have now modified the existing instrumentation into a clinically relevant headband-based system to be used for optical imaging of structure in the neonatal brain at the bedside. Eight medical optical imaging studies in the neonatal intensive care unit were performed in a blinded clinical comparison of optical images with ultrasound, computed tomography, and magnetic resonance imaging. Optical images were interpreted as correct in six of eight cases, with one error attributed to the age of the clot, and one small clot not seen. In addition, one disagreement with ultrasound, not reported as an error, was found to be the result of a mislabeled ultrasound report rather than because of an inaccurate optical scan. Optical scan correlated well with computed tomography and magnetic resonance imaging findings in one patient. We conclude that light-based imaging using a portable time-of-flight system is feasible and represents an important new noninvasive diagnostic technique, with potential for continuous monitoring of critically ill neonates at risk for intraventricular hemorrhage or stroke. Further studies are now underway to further investigate the functional imaging capabilities of this new diagnostic tool.

    View details for Web of Science ID 000077706500009

    View details for PubMedID 9890608

  • Simultaneous production of carbon monoxide and thiobarbituric acid reactive substances in rat tissue preparations by an iron-ascorbate system CANADIAN JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY Vreman, H. J., Wong, R. J., Sanesi, C. A., Dennery, P. A., Stevenson, D. K. 1998; 76 (12): 1057-1065

    Abstract

    Most of the carbon monoxide (CO) produced by mammals is a product of the heme oxygenase (HO) reaction, the rate-limiting step in the heme degradation pathway leading to the generation of bilirubin in man. However, some CO is derived from other sources. We studied the association of CO production with lipid peroxidation in tissue preparations from adult male Wistar rats. Supernatants, from 20% tissue homogenates in potassium phosphate buffer, centrifuged for 1 min at 13,000 x g, were incubated for 30 min at 37 degrees C in septum-sealed vials in the dark with ascorbate (100 microM) and Fe(II) (6 microM) and (or) Fe(III) (60 microM). Butylated hydroxytoluene (BHT, 100 microM) was added for the blank reaction. CO produced into the headspace was quantitated by gas chromatography. Thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD), and lipid hydroperoxides (LOOH) in the reaction medium were quantitated by spectrophotometry. Of the tissues studied, CO and TBARS formation was greatest for brain, followed by kidney, lung, spleen, and blood, but no CO or TBARS formation was detected for testes, intestine, liver, and heart. Cell fractionation studies indicated that these differences might be due to the presence of endogenous soluble antioxidants in the latter tissues. Furthermore, these studies demonstrated that CO was exclusively generated by subcellular fractions that contained membranes. The magnitude of the rate of product formation in brain supernatants depended on the concentration of Fe(II) and (or) Fe(III). The formation of CO, TBARS, CD, and LOOH increased linearly with time for up to 30 min, but the rates of product formation were different. Product formation was completely inhibited by BHT (100 microM), biliverdin (50 microM), bilirubin (50 microM), citrate (100 microM), and the Fe(II) chelators, desferrioxamine mesylate (100 microM) and diethylenetriaminepentaacetate, but not by 10 microM of the HO inhibitor, zinc deuteroporphyrin bis glycol. We conclude that CO generation is associated with the process of in vitro lipid peroxidation in tissues with limited antioxidant reserves.

    View details for Web of Science ID 000079780100001

    View details for PubMedID 10326826

  • Very low birth weight outcomes of the National Institute of Child Health and Human Development Neonatal Research Network, January 1993 through December 1994 AMERICAN JOURNAL OF OBSTETRICS AND GYNECOLOGY Stevenson, D. K., Wright, L. L., Lemons, J. A., Oh, W., Korones, S. B., Papile, L. A., Bauer, C. R., Stoll, B. J., TYSON, J. E., Shankaran, S., Fanaroff, A. A., Donovan, E. F. 1998; 179 (6): 1632-1639

    Abstract

    Our purpose was to determine the mortality and morbidity rates for infants weighing 501 to 1500 g according to gestational age, birth weight, and gender.Perinatal data were collected prospectively on an inborn cohort from January 1993 through December 1994 by 12 participating centers of the National Institute of Child Health and Human Development Neonatal Research Network and were compared with the corresponding data from previous reports. Sociodemographic factors, perinatal events, and the neonatal course to 120 days of life, discharge, or death were evaluated.Eighty-three percent of infants survived until discharge to home or to a long- term care facility (compared with 74% in 1988). Survival to discharge was 49% for infants weighing 501 to 750 g at birth, 85% for those 751 to 1000 g, 93% for those 1001 to 1250 g, and 96% for those 1251 to 1500 g. The majority of deaths occurred within the first 3 days of life. Mortality rates were greater for male than for female infants. Respiratory distress syndrome was the most frequent pulmonary disease (52%). Chronic lung disease (defined as an oxygen requirement at 36 weeks after conception) developed in 19%. Thirty-two percent of infants had evidence of intracranial hemorrhage. Periventricular leukomalacia was noted in 6% of infants who had ultrasonography after 2 weeks. The average duration of hospitalization for survivors was 68 days (122 days for surviving infants weighing 501 to 750 g, compared with an average of 43 days for surviving infants 1251 to 1500 g). Among infants who died, the average length of stay was 19 days.The mortality rate for infants weighing between 501 and 1500 g at birth continues to decline. This increase in survival is not accompanied by an increase in medical morbidity. There are interactions between birth weight, gestational age, sex, and survival rates.

    View details for Web of Science ID 000077702500056

    View details for PubMedID 9855609

  • Light-emitting diodes: A novel light source for phototherapy PEDIATRIC RESEARCH Vreman, H. J., Wong, R. J., Stevenson, D. K., Route, R. K., Reader, S. D., Fejer, M. M., Gale, R., Seidman, D. S. 1998; 44 (5): 804-809

    Abstract

    High intensity light-emitting diodes (LEDs) are being studied as possible light sources for the phototherapy of hyperbilirubinemic neonates. These power-efficient, low heat-producing light sources have the potential to deliver high intensity light of narrow wavelength band in the blue-green portion of the visible light spectrum, which overlaps the absorption spectrum of bilirubin (BR). We compared the efficacy between single LEDs of different color and then constructed a prototype phototherapy device using 300 blue LEDs. The efficacy of this device was compared with that of conventional phototherapy devices by measuring the in vitro photodegradation of BR in human serum albumin. When blue, blue-green, green, and white LEDs were compared, the blue light was the most effective in degrading BR by 28% of dark control, followed by blue-green (18% of control), and then white light (14% of control). Green light was the least effective (11% of control). The prototype device with three focused arrays, each with 100 blue LEDs, generated greater irradiance (> 200 microW.cm-2.nm-1) than any of the conventional devices tested. It also supported the greatest rate of BR photodegradation. We conclude that light from LEDs should be considered a more effective treatment for hyperbilirubinemia than light from presently used phototherapy devices. Furthermore, the unique characteristics of this light source may make it especially suitable for use in safe and lightweight home phototherapy devices.

    View details for Web of Science ID 000076607700027

    View details for PubMedID 9803466

  • Strategy for lipid suppression in lactate imaging using STIR-DQCT: A study of hypoxic-ischemic brain injury MAGNETIC RESONANCE IN MEDICINE Nakai, T., Rhine, W. D., Okada, T., Stevenson, D. K., Spielman, D. M. 1998; 40 (4): 629-632

    Abstract

    In vivo lactate detection using gradient enhanced double quantum coherence transfer (DQCT) was significantly improved by addition of short-time-inversion-recovery (STIR). Phantom studies demonstrated lipid suppression down to the background noise level with 33% loss of lactate signal. In vivo studies using a rabbit model of hypoxic and unilateral-ischemic brain injury showed reduction down to 29 +/- 11% in lipids with inversion times between 140 and 170 ms. Lactate signals on the ischemic side were 51 +/- 53% higher than the nonischemic side at the peak of hypoxia. STIR-DQCT can be a useful robust method of obtaining metabolic maps of lactate in vivo.

    View details for Web of Science ID 000076080900015

    View details for PubMedID 9771580

  • Stationary headband for clinical time-of-flight optical imaging at the bedside PHOTOCHEMISTRY AND PHOTOBIOLOGY Hintz, S. R., Benaron, D. A., van Houten, J. P., Duckworth, J. L., Liu, F. W., Spilman, S. D., Stevenson, D. K., Cheong, W. F. 1998; 68 (3): 361-369

    Abstract

    Conventional brain-imaging modalities may be limited by high cost, difficulty of bedside use, noncontinuous operation, invasiveness or an inability to obtain measurements of tissue function, such as oxygenation during stroke. Our goal was to develop a bedside clinical device able to generate continuous, noninvasive, tomographic images of the brain using low-power nonionizing optical radiation. We modified an existing stage-based time-of-flight optical tomography system to allow imaging of patients under clinical conditions. First, a stationary head-band consisting of thin, flexible optical fibers was constructed. The headband was then calibrated and tested, including an assessment of fiber lengths, the existing system software was modified to collect headband data and to perform simultaneous collection of data and image reconstruction, and the existing hardware was modified to scan optically using this headband. The headband was tested on resin models and allowed for the generation of tomographic images in vitro; the headband was tested on critically ill infants and allowed for optical tomographic images of the neonatal brain to be obtained in vivo.

    View details for Web of Science ID 000075986500022

    View details for PubMedID 9747590

  • Diffusion and perfusion magnetic resonance imaging of the evolution of hypoxic ischemic encephalopathy in the neonatal rabbit JOURNAL OF MAGNETIC RESONANCE IMAGING D'Arceuil, H. E., de Crespigny, A. J., Rother, J., Seri, S., Moseley, M. E., Stevenson, D. K., Rhine, W. 1998; 8 (4): 820-828

    Abstract

    Hypoxic-ischemic encephalopathy (HIE) can result from neonatal asphyxia, the pathophysiology of which is poorly understood. We studied the acute evolution of this disease, using magnetic resonance imaging in an established animal model. HIE was induced in neonatal rabbits by a combination of common carotid artery (CCA) ligation and hypoxia. Serial diffusion and perfusion-weighted magnetic resonance images were acquired before, during, and after the hypoxic interval. Focal areas of decreased apparent diffusion coefficient (ADC) were detected initially in the cortex ipsilateral to CCA ligation within 62 +/- 48 min from the onset of hypoxia. Subsequently, these areas of decreased ADC spread to the subcortical white matter, basal ganglia (ipsilateral side), and then to the contralateral side. Corresponding perfusion-weighted images showed relative cerebral blood volume deficits which closely matched those regions of ADC change. Our results show that MRI diffusion and perfusion-weighted imaging can detect acute cell swelling post-hypoxia in this HIE model.

    View details for Web of Science ID 000080143600010

    View details for PubMedID 9702883

  • Ethical dilemmas in the delivery room SEMINARS IN PERINATOLOGY Stevenson, D. K., Goldworth, A. 1998; 22 (3): 198-206

    Abstract

    The decision to withhold or withdraw life support in the neonatal intensive care unit (NICU) is common but is never routine. Often, moral demands make such decisions difficult and emotionally exhausting. But, what is perhaps more challenging from the moral point of view is the transition from the delivery room to the NICU. A satisfactory analysis of the moral issues of delivery room practices must include a discussion of quality of life, the best interest of the infant, the best interests of the family members, and futile treatment. Although these topics are relevant in any discussion of the moral justification of the omission, withdrawal, or use of treatment for patients, they are especially telling when entertained in the context of the transition of the fetus to a newborn. This article uses these four topics as a moral compass for certain decisions made in the delivery room.

    View details for Web of Science ID 000074456600004

    View details for PubMedID 9650227

  • Bioluminescent indicators in living mammals NATURE MEDICINE Contag, P. R., Olomu, I. N., Stevenson, D. K., Contag, C. H. 1998; 4 (2): 245-247

    View details for Web of Science ID 000072249800043

    View details for PubMedID 9461201

  • Neonatal hypoglycemia, part II: Pathophysiology and therapy CLINICAL PEDIATRICS Halamek, L. P., Stevenson, D. K. 1998; 37 (1): 11-16

    Abstract

    Contemporary research is elucidating both the molecular mechanisms of hypoglycemia-induced neuronal injury and its corresponding clinical manifestations. Recognizing and screening those neonates at highest risk of hypoglycemia-induced injury is an important skill for all physicians responsible for the care of newborns. Appropriate therapy, consisting of either oral or intravenous glucose, should never be delayed while one is awaiting laboratory confirmation of a "low" glucose level.

    View details for Web of Science ID 000071577400002

    View details for PubMedID 9475694

  • Supplemental oxygen may decrease progression of prethreshold disease to threshold retinopathy of prematurity. Journal of perinatology Gaynon, M. W., Stevenson, D. K., Sunshine, P., Fleisher, B. E., Landers, M. B. 1997; 17 (6): 434-438

    Abstract

    The optimum level of oxygen saturation for infants with prethreshold retinopathy of prematurity (ROP) is unknown. We reviewed our conversion rate from prethreshold to threshold ROP between 1985 and 1993 during which time target levels of oxygen saturation rose in a stepwise fashion. A retrospective study of 153 infants with prethreshold ROP was performed at Stanford University between 1985 and 1993 that showed that target minimum oxygen saturation rose from 92% (1985-1987) to 95% (1988) to 96% (1989) to 99% (1990-1993). In addition, we looked at 26 infants between 1994 and 1996 who were excluded from the STOP-ROP study and who were not receiving supplemental oxygen in an effort to maintain equipoise for that study. Infant characteristics were tabulated, and rates of progression from prethreshold to threshold ROP were calculated. Rates of progression to threshold varied little between 1985 and 1989 (average 37%), but dropped to 7% for the period between 1990 and 1993. From 1994 through 1996 the rate of progression to threshold disease rose again, to 38%. Moderate supplemental oxygen (target saturation 99% with PO2 no higher than 100 mm Hg) was associated with regression of prethreshold ROP, without appearing to arrest retinal vascular maturation.

    View details for PubMedID 9447528

  • Visualizing gene expression in living mammals using a bioluminescent reporter PHOTOCHEMISTRY AND PHOTOBIOLOGY Contag, C. H., Spilman, S. D., Contag, P. R., Oshiro, M., Eames, B., Dennery, P., Stevenson, D. K., Benaron, D. A. 1997; 66 (4): 523-531

    Abstract

    Control of gene expression often involves an interwoven set of regulatory processes. As information regarding regulatory pathways may be lost in ex vivo analyses, we used bioluminescence to monitor gene expression in living mammals. Viral promoters fused to firefly luciferase as transgenes in mice allowed external monitoring of gene expression both superficially and in deep tissues. In vivo bioluminescence was detectable using either intensified or cooled charge-coupled device cameras, and could be detected following both topical and systemic delivery of substrate. In vivo control of the promoter from the human immunodeficiency virus was demonstrated. As a model for DNA-based therapies and vaccines, in vivo transfection of a luciferase expression vector (SV-40 promoter and enhancer controlling expression) was detected. We conclude that gene regulation, DNA delivery and expression can now be noninvasively monitored in living mammals using a luciferase reporter. Thus, real-time, noninvasive study of gene expression in living animal models for human development and disease is possible.

    View details for Web of Science ID A1997YC04200026

    View details for PubMedID 9337626

  • Imaging - Tissue optics SCIENCE Benaron, D. A., Cheong, W. F., Stevenson, D. K. 1997; 276 (5321): 2002-2003

    View details for Web of Science ID A1997XG74800051

    View details for PubMedID 9221510

  • Development of jaundice in Korean neonates after Cesarean section ACTA PAEDIATRICA JAPONICA Lee, C. S., Vreman, H. J., Choi, J. H., Yun, C. K., Stevenson, D. K. 1997; 39 (3): 309-311

    Abstract

    The aim of the project was to determine the physiologic mechanisms of later- and higher-peak transitional plasma bilirubin levels in Korean infants. Blood carboxyhemoglobin, corrected for inhaled CO (COHbc), as an index of bilirubin production, and plasma total bilirubin levels in 40 healthy term Korean infants delivered by Cesarean section were measured throughout the first week of life. The COHbc levels were significantly higher in the Korean neonates than in previously studied Caucasian neonates. Moreover, COHbc levels decreased by 28% during the first 7 days of life from 0.85 +/- 0.20 to 0.61 +/- 0.34% (P < 0.025). This pattern parallels a 15% decrease in total hemoglobin from 181 +/- 23 to 154 +/- 53 g/L (P < 0.05). In contrast, plasma bilirubin concentrations more than doubled from 80 +/- 32 to 172 +/- 48 mumol/L (4.7 +/- 1.8 to 10.0 +/- 2.8 mg/dL; P < 0.001), remaining unchanged between days 4 and 7. Both increased production and decreased elimination of bilirubin contribute to physiologic jaundice in Korean infants.

    View details for Web of Science ID A1997XM62300003

    View details for PubMedID 9241890

  • Neonatal severity of illness scoring systems: A comparison CLINICAL PEDIATRICS Fleisher, B. E., Murthy, L., Lee, S., Constantinou, J. C., Benitz, W. E., Stevenson, D. K. 1997; 36 (4): 223-227

    Abstract

    Several different scoring systems have been developed to predict neonatal morbidity and mortality. In this investigation we compared the utility of four severity of illness scoring systems (SISS) as predictors of days on ventilatory (DOV), length of hospital stay (LOS), and mortality in very-low-birth weight (VLBW) premature infants who required mechanical ventilation. The SISS assessed were the Score for Neonatal Acute Physiology (SNAP); the Score for Neonatal Acute Physiology-Perinatal Extension (SNAP + PE); Clinical Risk Index for Babies (CRIB), and the Sinkin Score at 12 hours (SS12). Results revealed significant correlations among the SS12, SNAP, SNAP + PE, CRIB, birth weight (BW), DOV, and LOS. However, none of the systems we assessed offered striking advantage over BW in a VLBW ventilated group.

    View details for Web of Science ID A1997WU89500007

    View details for PubMedID 9114994

  • The value of neurophysiologic approaches in the anticipation and evaluation of neonatal hypoglycemia. Acta paediatrica Japonica; Overseas edition Halamek, L. P., Benaron, D. A., Stevenson, D. K. 1997; 39: S33-43

    Abstract

    The association of low blood glucose with central nervous system (CNS) injury was first described in 1937 by Hartmann and Jaudon. In the early 60 years since publication of these observations the effects of hypoglycemia upon the brain remain poorly understood. Technology capable of accurately determining plasma glucose concentrations has been developed. Investigators have sought to establish critical values below which glucose levels should not be allowed to fall. Despite these efforts the definitive level of glucose capable of producing brain injury in any particular patient remains unknown. Glucose homeostasis within the neonatal CNS represents a dynamic process consisting of many interrelated variables including gestational and chronologic age, genotype, relative health, blood flow, metabolic rate and availability of other suitable substrates. New technique for assessing the glucose delivery: consumption ratio and directly monitoring the cellular consequences of glucose deprivation within discrete regions of the brain will help to answer the question 'How long is too low and how long is too long?'

    View details for PubMedID 9200877

  • The risk of carbon monoxide poisoning after prolonged laparoscopic surgery OBSTETRICS AND GYNECOLOGY Nezhat, C., Seidman, D. S., Vreman, H. J., Stevenson, D. K., Nezhat, F., Nezhat, C. 1996; 88 (5): 771-774

    Abstract

    To evaluate whether thermal energy produced by laser and bipolar electrosurgery during laparoscopic procedures significantly elevates blood carboxyhemoglobin levels.We prospectively studied 27 healthy nonsmoking patients, mean +/- standard deviation (SD) age 39.1 +/- 8.0 years (range 22-56), scheduled for laparoscopic procedures in which smoke was generated. Prolonged operative laparoscopy involved high-flow carbon dioxide insufflation, intensive evacuation of intra-abdominal smoke, and controlled hyperventilation with 50-100% oxygen. Laser and bipolar electrosurgery were used in all cases. Blood samples were drawn before and after surgery. Carboxyhemoglobin concentrations were measured using a highly accurate gas chromatography method.The mean +/- SD duration of surgery was 141 +/- 72 minutes (range 45-300). The mean +/- SD carboxyhemoglobin levels were 0.70 +/- 0.15% (range 0.44-1.20%) before surgery and 0.58 +/- 0.20% (range 0.30-1.33%) after surgery. A significant decrease (P < .001) in carboxyhemoglobin concentrations occurred during surgery (mean +/- SD, 20 +/- 11%; range 3-46%). The carboxyhemoglobin level was increased at the end of surgery in only one woman. In only one patient did the levels exceed 1% (1.33%), still well below the human threshold tolerance level of 2%. The Spearman correlation coefficient between carboxyhemoglobin concentrations and duration of surgery was r = 0.308 (P = .12).Carbon monoxide (CO) poisoning is not associated with even prolonged laparoscopic surgical procedures. This may be attributed to aggressive smoke evacuation that minimizes exposure to CO, and to active elimination of CO by ventilation with high oxygen concentrations.

    View details for Web of Science ID A1996VP61400006

    View details for PubMedID 8885911

  • Nitrovasodilator therapy for severe respiratory distress syndrome. Journal of perinatology Benitz, W. E., Rhine, W. D., Van Meurs, K. P., Stevenson, D. K. 1996; 16 (6): 443-448

    Abstract

    Improved gas exchange in infants with severe respiratory distress syndrome has been reported in association with infusion of nitroprusside and during inhalation of nitric oxide. To evaluate the association between nitrovasodilator therapy and clinical improvement in premature neonates with severe respiratory distress syndrome, we reviewed the courses of 22 infants with severe respiratory distress syndrome who were treated with sodium nitroprusside for at least 24 hours. These infants had birth weights of 2049 +/- 828 gm (range 720 to 3430 gm), gestational ages of 32.5 +/- 3.5 weeks (range 25 to 38 weeks), high ventilator settings before treatment (FIO2 of 100%, peak inspiratory pressures of 37.8 +/- 6.1 cm H2O [range 30 to 50 cm H2O], and mean airway pressures of 18.0 +/- 3.3 cm H2O [range 12.3 to 26 cm H2O]), and low pretreatment PaO2 of 49.3 +/- 9.4 mm Hg (range 27 to 69 mm Hg). Baseline oxygenation indexes were 39.4 +/- 12.1 (range 18.6 to 66.7). Nitroprusside infusion was temporally associated with increased PaO2, decreased PaCO2, and reduced oxygenation index. Potentially beneficial changes were inconsistent in infants with pulmonary interstitial emphysema and were greatest in infants treated with end-expiratory pressures of at least 4 cm H2O. These observations provide a basis for the hypothesis that nitrovasodilator therapy produces improvement in gas exchange in premature infants with severe respiratory distress syndrome.

    View details for PubMedID 8979182

  • Hepatic heme oxygenase is inducible in neonatal rats during the early postnatal period PEDIATRIC RESEARCH Tom, D. J., Rodgers, P. A., Shokoohi, V., Stevenson, D. K., Dennery, P. A. 1996; 40 (2): 288-293

    Abstract

    Heme oxygenase (HO) is the rate-limiting enzyme in the catabolism of heme to bilirubin. Cobalt chloride (CoCl2) and many other agents that generate oxidant stresses induce the HO-1 isoform. Furthermore, HO-1 has been shown to protect against oxidant stress in vitro and in vivo by mechanisms involving increased ferritin synthesis. However, little is known about the inducibility of hepatic HO-1 during the very early postnatal period, and whether HO-1 induction is associated with increased ferritin synthesis in neonates. Therefore, we studied hepatic HO-1 mRNA, HO-1 protein concentration, total HO activity, and ferritin protein levels in neonatal rats. Neonatal rats 0-5 d of age were injected with 250 mumol/kg body weight of CoCl2. 6H2O in saline or with an equal volume of saline in age-matched controls. Liver samples were collected 4 h after injection for HO-1 mRNA analysis and 20 h after injection for analysis of HO-1 protein concentration, total HO activity, and ferritin protein levels. In CoCl2-treated rats, hepatic HO-1 mRNA was 3-10 times the levels in control rats (p < 0.05), HO-1 protein concentration was 2-5 times the levels in control rats (p < 0.05), and total HO activity was higher by 20-80% than in control rats (p < 0.05). There were no differences in hepatic ferritin protein levels between CoCl2-treated neonatal rats and controls; however, in CoCl2-treated adult rats, hepatic ferritin protein levels were 1.6 times the levels in controls (p < 0.05). Thus, neonatal rats can up-regulate hepatic HO-1 mRNA, HO-1 protein concentration, and total HO activity in response to CoCl2; however, no upregulation of hepatic ferritin protein levels was observed in neonatal rats after CoCl2 administration or subsequent HO-1 induction. We speculate that neonatal rats induce hepatic HO-1 and up-regulate ferritin by different mechanisms than do adult rats.

    View details for Web of Science ID A1996UY05100016

    View details for PubMedID 8827779

  • Interlaboratory variability of bilirubin measurements CLINICAL CHEMISTRY Vreman, H. J., Verter, J., Oh, W., Fanaroff, A. A., Wright, L. L., Lemons, J. A., Shankaran, S., TYSON, J. E., Korones, S. B., Bauer, C. R., Stoll, B. J., Papile, L. A., Donovan, E. F., Ehrenkranz, R. A., Stevenson, D. K. 1996; 42 (6): 869-873

    Abstract

    During an 8-month study, 14 laboratories used automated analytical systems to measure total bilirubin concentrations in lyophilized bovine specimens containing 38, 169, and 253 micromol/L bilirubin (2.2, 9.9, and 14.8 mg/dL, respectively). The measured mean +/- SD (n, range) were: 39 +/- 7 micromol/L (n = 90, 31-53) [2.3 +/- 0.4 mg/dL (1.8-3.1)]; 176 +/- 29 micromol/L (n = 89, 146-222) [10.3 +/- 1.7 mg/dL (8.5-13.0)]; and 260 +/- 43 micromol/L (n = 103, 208-316) [15.2 +/- 2.5 mg/dL (12.1-18.5)]. In comparison with target values, measurements were consistently lower at 4, higher at 6, and within +/- 4% at 4 laboratories for each of the three concentrations. The measured values for each concentration remained fairly constant during the study at each laboratory. We conclude that bilirubin measurements differed significantly from the established target values at most of the participating laboratories.

    View details for Web of Science ID A1996UQ78300007

    View details for PubMedID 8665677

  • Duration of action and tissue distribution of zinc protoporphyrin in neonatal rats PEDIATRIC RESEARCH Rodgers, P. A., Seidman, D. S., Wei, P. L., Dennery, P. A., Stevenson, D. K. 1996; 39 (6): 1041-1049

    Abstract

    Zinc protoporphyrin IX (ZnPP) has been shown to inhibit heme oxygenase (HO) activity effectively in vivo and has potential in the treatment of neonatal jaundice. Because this is a transitional or temporary condition lasting only several days, an effective chemopreventive agent with a relatively short duration of action would be desirable for the treatment of severe neonatal jaundice. To determine the effective duration of action of ZnPP, we administered either 40 nmol/g of body weight ZnPP or 5 microL/g body weight diluent intraperitoneally to neonatal rats 24-36 h after birth. Between 0 and 21 d after ZnPP dosing, the duration of action was investigated through measurements of serum bilirubin and hepatic and splenic HO inhibition, which were correlated to measurements of ZnPP distribution. Significant (p < 0.05) hepatic HO inhibition, ranging from 27 to 51%, was observed in the liver between 1 and 4 d after dosing, concurrent with a 23-28% reduction in serum bilirubin levels, and was associated with ZnPP tissue concentrations of 27-38 nmol/g. Splenic HO was not inhibited measurably by the much lower concentrations of ZnPP found in the spleen (2.8-20.1 nmol/g) between 0 and 21 d after dosing. Furthermore, HO isoform 1 (HO-1) induction was apparently not a confounding factor in the duration of action of ZnPP, because the modest increases in HO-1 protein levels were not sustained longer than 24 h after ZnPP administration. Our findings demonstrated that the duration of action of ZnPP in neonatal rats is less than 1 wk. The reduction in serum bilirubin levels, the short duration of action and minimal confounding effects suggest that ZnPP may be an effective chemopreventive agent for the treatment of severe neonatal jaundice.

    View details for Web of Science ID A1996UN55500018

    View details for PubMedID 8725267

  • A model for detecting early metabolic changes in neonatal asphyxia by 1H-MRS JOURNAL OF MAGNETIC RESONANCE IMAGING Nakai, T., Rhine, W. D., Enzmann, D. R., Stevenson, D. K., Spielman, D. M. 1996; 6 (3): 445-452

    Abstract

    In newborn rabbits, the early cerebral metabolic changes caused by hypoxic-ischemic (H-I) insult was examined by using volume localized 1H-MRS (STEAM). Partial ischemia was caused by unilateral carotid artery ligation, and hypoxia was induced by 10% oxygen inspiration for 150 minutes. Lactate immediately increased after hypoxia induction and almost disappeared 120 to 150 minutes after removal of hypoxia in both H-I and hypoxia-only experiments. Lactate production correlated well with decrease of the blood oxygen saturation. More lactate was produced on ischemic side 50 minutes post-hypoxia induction in H-I study. Ischemia alone did not cause any significant lactate production. Lactate caused by hypoxia can be dynamically monitored by localized 1H-MRS. Existence of regional ischemia can induce greater anaerobic glycolysis and may affect the pattern of brain injury under hypoxia. 1H-MRS is a sensitive tool to detect the acute metabolic change caused by H-I insult.

    View details for Web of Science ID A1996UM58400004

    View details for PubMedID 8724409

  • Evaluation of neonatal jaundice: monitoring the transition in bilirubin metabolism. Journal of perinatology Stevenson, D. K., Vreman, H. J., Benaron, D. A. 1996; 16 (3): S62-7

    View details for PubMedID 8817441

  • Neonatal intracranial ischemia and hemorrhage: Diagnosis with US, CT, and MR imaging RADIOLOGY Blankenberg, F. G., Norbash, A. M., Lane, B., Stevenson, D. K., Bracci, P. M., Enzmann, D. R. 1996; 199 (1): 253-259

    Abstract

    To assess the usefulness of ultrasound (US), computed tomography (CT), and magnetic resonance (MR) imaging in the detection of intracranial hemorrhage and ischemia in newborns.Seventy-six neonates who underwent US within 72 hours of CT or MR examination were studied. Four observers rated images for the presence of germinal matrix hemorrhage (GMH), intraventricular hemorrhage (IPH), extraaxial hemorrhage, and hypoxic-ischemic encephalopathy.In 39% of neonates, CT and MR imaging provided greater confidence than US for the diagnosis or exlusion of neonatal ischemia or hemorrhage. Kappa analysis revealed significantly better interobserver agreement with CT than with US for the detection of GMH, IVH, IPH, and cortical infarction or ischemia (P <.005). Interobserver agreement was significantly better with MR imaging than with US for the detection of GMH, IVH, and cortical infarction or ischemia (P < .005).Sensitivity and interobserver agreement are better with MR imaging and CT than with US for the detection of neonatal cortical ischemia or infarction.

    View details for Web of Science ID A1996UB58400040

    View details for PubMedID 8633155

  • Characterization of porphyrin heme oxygenase inhibitors CANADIAN JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY Vreman, H. J., Cipkala, D. A., Stevenson, D. K. 1996; 74 (3): 278-285

    Abstract

    Synthetic metalloporphyrin derivatives of heme have been identified as competitive inhibitors of heme oxygenase, the rate-limiting enzyme in the heme degradation pathway that produces equimolar quantities of carbon monoxide, biliverdin, and bilirubin. Therefore, administration of metalloporphyrin has been proposed as one means to prevent excessive hyperbilirubinemia in human neonates. Tin proto- and meso-porphyrin have been studied for the suppression of neonatal jaundice. However, these compounds are also photosensitizers. This property may limit the clinical use of these compounds, particularly in infants being exposed simultaneously to phototherapy. Via measurements of carbon monoxide, we have studied the photooxidative, metabolic, and inhibitory characteristics of metalloporphyrins that have not yet been studied for this purpose: deuteroporphyrin bisglycol (DBG), iron deuteroporphyrin bisglycol (FeBG), tin deuteroporphyrin bisglycol (SnBG),tin deuteroporphyrin (SnDP), chromium deuteroporphyrin (CrDP), and zinc deuteroporphyrin (ZnDP). Of the six compounds, SnDP, SnBG, and DBG were significantly photoreactive in vitro. Furthermore, in vitro measurements of brain, liver, and spleen heme oxygenase activity inhibition indicated that, of the nonphotoreactive compounds, CrDP and ZnDP were the most potent inhibitors. Only FeBG served as a substrate for the heme oxygenase reaction. The concentration for 50% inhibition with the three tissues ranged from 0.6 to 1.3 microM for CrDP and from 11.0 to 13.5 microM for ZnDP. When 25 mumol CrDP and 50 mumol ZnDP per kilogram body weight were administered to rats given a heme load of 30 mumol/kg body weight, the total body carbon monoxide excretion due to the administered heme load was reduced by 46 and 32%, respectively, at t = 7.5 h, when the experiment was terminated in order to measure heme oxygenase activity. Brain heme oxygenase activity was not affected by the metalloporphyrin treatment. However, both CrDP and ZnDP inhibited liver tissue heme oxygenase activity to 5 and 20%, respectively, whereas only CrDP inhibited spleen tissue heme oxygenase, to 7% of untreated control. Thus, CrDP appears to be the most attractive of the six compounds and deserves further study.

    View details for Web of Science ID A1996UP79000008

    View details for PubMedID 8773407

  • Imaging brain injury using time-resolved near infrared light scanning PEDIATRIC RESEARCH VANHOUTEN, J. P., Benaron, D. A., Spilman, S., Stevenson, D. K. 1996; 39 (3): 470-476

    Abstract

    Conventional brain imaging modalities are limited in that they image only secondary physical manifestations of brain injury, which may occur well after the actual insult to the brain and represent irreversible structural changes. A real-time continuous bedside monitor that images functional changes in cerebral blood flow or oxygenation might allow for recognition of brain tissue ischemia or hypoxia before the development of irreversible injury. Visible and near infrared light pass through human bone and tissue in small amounts, and the emerging light can be used to form images of the interior structure of the tissue and measure tissue blood flow and oxygen utilization based on light absorbance and scattering. We developed a portable time-of-flight and absorbance system which emits pulses of near infrared light into tissue and measures the transit time of photons through the tissue. Images can then be reconstructed mathematically using either absorbance or scattering information. Pathologic brain specimens from adult sheep and human newborns were studied with this device using rotational optical tomography. Images generated from these optical scans show that neonatal brain injuries such as subependymal and intraventricular hemorrhages can be successfully identified and localized. Resolution of this system appears to be better than 1 cm at a tissue depth of 5 cm, which should be sufficient for imaging some brain lesions as well as for detection of regional changes in cerebral blood flow and oxygenation. We conclude that light-based imaging of cerebral structure and function is feasible and may permit identification of patients with impending brain injury as well as monitoring of the efficacy of intervention. Construction of real-time images of brain structure and function is now underway using a fiber optic headband and nonmechanical rotational scanner allowing comfortable, unintrusive monitoring over extended periods of time.

    View details for Web of Science ID A1996TX02600015

    View details for PubMedID 8929868

  • Evaluation of a fully automated end-tidal carbon monoxide instrument for breath analysis CLINICAL CHEMISTRY Vreman, H. J., Baxter, L. M., Stone, R. T., Stevenson, D. K. 1996; 42 (1): 50-56

    Abstract

    We evaluated a novel, portable breath sampler/CO-quantifying instrument [Baby's Breath Carbon Monoxide Analyzer (BB); Natus Medical], developed for use at the bedside or with gas samples collected into bags. Bench tests demonstrated that the CO measurements were linear, accurate, and precise when compared with gas chromatography (GC) results. In vivo tests (n = 30) performed with adults showed excellent correlation between end-tidal breath CO measurements (ETCO) corrected for inhaled CO (ETCOc) as determined by BB and GC. Breath sampling efficiency was 96%. ETCOc measurements and blood carboxyhemoglobin fractions (% of total hemoglobin) corrected for inhaled CO (COHbc) correlated strongly: COHbc = 0.25 ETCOc--0.01 microL/L CO (r2 = 0.97, Sy/x = 0.47, SE slope = 0.01, n = 30). The imprecision, assessed by the mean of the population's CV for triplicate determinations, was 11%. Measurements with healthy and hemolytic term newborns showed that ETCOc values of > 3 microL/L correlated with known hemolytic conditions. We conclude that this instrument is clinically reliable and can be used to noninvasively measure ETCO in neonates and adults.

    View details for Web of Science ID A1996TR04000012

    View details for PubMedID 8565232

  • Is Carbon Monoxide Poisoning a Risk During Prolonged Laparoscopic Surgery? The Journal of the American Association of Gynecologic Laparoscopists Seidman, D. S., Nezhat, C. R., Vreman, H. J., Stevenson, D. K., Brock-Une, J. G. 1996; 3 (4, Supplement): S45

    Abstract

    We evaluated whether prolonged laparoscopic procedures performed with high-flow carbon dioxide (CO2) insufflation, intensive evacuation of intraabdominal smoke, and controlled hyperventilation with 50% to 90% oxygen results in significant elevation in blood carboxyhemoglobin levels. Twenty-seven healthy, nonsmoking women (mean ± SD age 39.1 ± 8.0 yrs, range 22-56 yrs) undergoing laparoscopic procedures in which smoke was generated participated. In all cases both the CO2 laser and bipolar electrosurgery were used extensively. The mean ± SD duration of surgery was 141 ± 72 minutes (range 45-300 min). Blood samples were drawn before and after surgery. Carboxyhemoglobin concentrations were measured using a highly accurate gas chromatography method. The mean ± SD carboxyhemoglobin levels were 0.70% ± 0.15% (range 0.44-1.20%) before and 0.58% ± 0.20% (range 0.30-1.33%) after surgery. The concentrations decreased significantly during surgery (mean ± SD 20% ± 11%, range 3-46%, p <0.001). In only one woman the level increased at the end of surgery. This also occurred when levels exceeded 1% (1.33%). The correlation coefficient (r) between carboxyhemoglobin concentrations and duration of surgery was 0.324. We concluded that carbon monoxide poisoning is not associated with prolonged laparoscopic surgical procedures. This may be attributed to aggressive smoke evacuation that minimized exposure and to elimination of CO2 through hyperventilation.

    View details for PubMedID 9074233

  • Photonic detection of bacterial pathogens in living hosts MOLECULAR MICROBIOLOGY Contag, C. H., Contag, P. R., Mullins, J. I., Spilman, S. D., Stevenson, D. K., Benaron, D. A. 1995; 18 (4): 593-603

    Abstract

    The study of pathogenic processes is often limited to ex vivo assays and cell-culture correlates. A greater understanding of infectious diseases would be facilitated by in vivo analyses. Therefore, we have developed a method for detecting bacterial pathogens in a living host and used this method to evaluate disease processes for strains of Salmonella typhimurlum that differ in their virulence for mice. Three strains of Salmonella were marked with bioluminescence through transformation with a plasmid conferring constitutive expression of bacterial luciferase. Detection of photons transmitted through tissues of animals infected with bioluminescent Salmonella allowed localization of the bacteria to specific tissues. In this manner progressive infections were distinguished from those that were persistent or abortive. We observed patterns of bioluminescence that suggested the caecum may play a pivotal role in Salmonella pathogenesis. In vivo efficacy of an antibiotic was monitored using this optical method. This study demonstrates that real time non-invasive analyses of pathogenic events and pharmacological monitoring can be performed in vivo.

    View details for Web of Science ID A1995TL35800001

    View details for PubMedID 8817482

  • HYPERBILIRUBINEMIA RESULTS IN REDUCED OXIDATIVE INJURY IN NEONATAL GUNN-RATS EXPOSED TO HYPEROXIA FREE RADICAL BIOLOGY AND MEDICINE Dennery, P. A., McDonagh, A. F., Spitz, D. R., Rodgers, P. A., Stevenson, D. K. 1995; 19 (4): 395-404

    Abstract

    Bilirubin is a potent antioxidant in vitro. To determine whether bilirubin also is an antioxidant in vivo, we studied markers of oxidative injury in the Gunn rat model exposed to hyperoxia. Homozygous jaundiced males were mated with heterozygous nonjaundiced females to obtain both jaundiced and nonjaundiced pups within a litter. Once delivered, the pups and their mother were placed in air (21% O2) or hyperoxia (> 95% O2) for 3 d. Both jaundiced and nonjaundiced pups were removed from the chambers daily. Animals were sacrificed and blood was drawn for determination of serum bilirubin, blood thiobarbituric acid-reactive substances (TBARS) by fluorescence assay, serum hydroperoxides, and serum protein oxidation. Tissues (liver, lung, and brain) were assayed for lipid peroxides (TBARS, conjugated dienes [CD], loss of polyunsaturated fatty acid content [PUFA]). We also measured a wide range of serum antioxidants including superoxide dismutase, catalase, glutathione, vitamins A, C, and E, and uric acid. Blood TBARS were significantly decreased in the jaundiced pups compared to the nonjaundiced pups on day 3 of hyperoxia, and blood TBARS were inversely correlated to serum bilirubin on day 3 of hyperoxia (R2 +/- .89). Similar decreases in serum lipid hydroperoxides and serum protein carbonyl content were detected in the jaundiced pups as compared to their nonjaundiced littermates. Other serum antioxidants were not increased in jaundiced animals compared to nonjaundiced animals. Relative lung weight was lower in jaundiced pups exposed to hyperoxia compared to similarly exposed nonjaundiced pups, suggesting a reduction in hyperoxia-induced lung edema. We detected no significant effects of bilirubin on parameters of lipid peroxidation in solid tissues. We conclude that serum bilirubin protects against serum oxidative damage in the first days of life in neonatal Gunn rats exposed to hyperoxia. We speculate that bilirubin is a functionally important transitional antioxidant in the circulation of human neonates and that it may be involved in modulation of injury due to hyperoxia.

    View details for Web of Science ID A1995RN64800001

    View details for PubMedID 7590389

  • INDIVIDUALIZED DEVELOPMENTAL CARE FOR VERY-LOW-BIRTH-WEIGHT PREMATURE-INFANTS CLINICAL PEDIATRICS Fleisher, B. E., Vandenberg, K., Constantinou, J., Heller, C., Benitz, W. E., Johnson, A., Rosenthal, A., Stevenson, D. K. 1995; 34 (10): 523-529

    Abstract

    Forty very-low-birth-weight neonatal intensive care unit (NICU) infants with birth weights < or = 1,250 g were randomly assigned to treatment or control groups. Behavior of the treatment infants was systematically evaluated, and individualized developmentally oriented care plans were implemented to enhance stability. Treatment babies required fewer days of intermittent mandatory ventilation and continuous positive airway pressure and achieved full enteral feedings sooner. Length of hospital stay and hospital charges were less for treatment than control infants. There were favorable effects on treatment infants' behavioral performance at 42 weeks' postconceptional age. These results support the hypothesis that behaviorally sensitive, developmentally oriented care improves medical and neurodevelopmental outcome in the NICU.

    View details for Web of Science ID A1995RZ28800003

    View details for PubMedID 8591679

  • HOSPITAL READMISSION DUE TO NEONATAL HYPERBILIRUBINEMIA PEDIATRICS Seidman, D. S., Stevenson, D. K., Ergaz, Z., Gale, R. 1995; 96 (4): 727-729

    Abstract

    Severe neonatal hyperbilirubinemia can occur without apparent reason in term healthy breast-fed infants and some develop kernicterus. The aim of our study was to assess the incidence of severe hyperbilirubinemia in term healthy newborns discharged from the hospital. From January 1 through December 31, 1994, 6705 infants were delivered at Bikur-Cholim and Misgav-Ladach Community Hospitals. All 1448 newborns discharged with a serum bilirubin level > 10.0 mg/dL were instructed to return to the hospital within 3 days for follow-up, as well as bilirubin determination. Twenty-one newborns with a bilirubin level > 18.0 mg/dL were identified and readmitted at mean +/- standard deviation (SD) 5.5 +/- 1.8 (range, 5 to 10 days of life). This represents 1.7% of the 1220 infants who returned for follow-up examination. Mean +/- SD serum bilirubin levels at readmission were 19.6 +/- 2.5 mg/dL. All but one of the infants were breast-fed. No cases of ABO incompatibility were found and two newborns were glucose-6-phosphate dehydrogenase (G6PD)-deficient. Sepsis work-up and direct Coomb's tests were negative in all cases. None had hemolysis or were found to have any cause for hyperbilirubinemia other than breast-feeding. Phototherapy was provided in all but two cases, and an exchange transfusion was performed in one case. Three additional infants, with bilirubin levels < 10 mg/dL at discharge, were readmitted due to hyperbilirubinemia. One was diagnosed with neonatal hepatitis. We conclude that, based on our study population, 0.36% of term infants may subsequently develop severe neonatal hyperbilirubinemia in the first postnatal week.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1995RY67700021

    View details for PubMedID 7567338

  • ADVANCES IN THE DIAGNOSIS AND TREATMENT OF NEONATAL HYPERBILIRUBINEMIA CLINICS IN PERINATOLOGY Yao, T. C., Stevenson, D. K. 1995; 22 (3): 741-?

    Abstract

    Many controversies remain regarding the role of bilirubin in the developing human. Although kernicterus and cognitive impairment have been linked to hyperbilirubinemia, more recent studies have suggested that there might actually be beneficial effects of bilirubin at a cellular level; thus, the need to better understand the molecular and cellular physiology of this molecule is important. The attempted management of serum or tissue levels of bilirubin may either have implications for long-term neurologic development or interfere with normal body stress responses. Production of CO via heme catabolism also warrants further investigation regarding its role in cell to cell communication or in other important cellular reactions. New methods are being developed to better detect CO under a variety of experimental conditions, as well as to estimate total bilirubin production by measuring the COHb level of pulmonary excretion of CO. The development of new drugs to modulate bilirubin production is the subject of ongoing research. Although some metalloporphyrins already have been used clinically, the advantages and disadvantages of each drug still require further study. These new drugs are not only raising fascinating research questions about heme and bilirubin metabolism, but they may soon revolutionize the way we approach the diagnosis and management of neonatal jaundice, and provide new pharmacologic tools for exploring other aspects of metabolism.

    View details for Web of Science ID A1995RW70000012

    View details for PubMedID 8521691

  • RECOMBINANT-HUMAN-ERYTHROPOIETIN (RHUEPO) INCREASES TOTAL BILIRUBIN PRODUCTION IN PREMATURE-INFANTS CLINICAL PEDIATRICS Baxter, L. M., Vreman, H. J., Ball, B., Stevenson, D. K. 1995; 34 (4): 213-216

    View details for Web of Science ID A1995QR60000007

    View details for PubMedID 7789015

  • NEONATAL JAUNDICE - WHAT NOW CLINICAL PEDIATRICS Dennery, P. A., Rhine, W. D., Stevenson, D. K. 1995; 34 (2): 103-107

    View details for Web of Science ID A1995QH23900007

    View details for PubMedID 7729104

  • Carbon monoxide and carboxyhemoglobin. Advances in pediatrics Vreman, H. J., Mahoney, J. J., Stevenson, D. K. 1995; 42: 303-334

    View details for PubMedID 8540431

  • SEMIPORTABLE ELECTROCHEMICAL INSTRUMENT FOR DETERMINING CARBON-MONOXIDE IN BREATH CLINICAL CHEMISTRY Vreman, H. J., Stevenson, D. K., Oh, W., Fanaroff, A. A., Wright, L. L., Lemons, J. A., Wright, E., Shankaran, S., TYSON, J. E., Korones, S. B., Bauer, C. R., Stoll, B. J., Papile, L. A., Donovan, E. F., Ehrenkranz, R. A. 1994; 40 (10): 1927-1933

    Abstract

    Measurements of carbon monoxide (CO) in breath can be used for the diagnosis of hemolytic disease. A small, semiportable, easy-to-operate CO instrument was developed at Stanford University and tested at 12 Neonatal Research Network Centers of the National Institute of Child Health and Human Development. A syringe pump delivers 7.7 mL of sample per minute through an activate carbon filter to an electrochemical (EC) sensor having a sensitivity of 0.10 +/- 0.01 V per 1 microL/L CO in air. The electronically processed sensor signal is displayed on a digital multimeter. For a typical end-tidal CO measurement, corrected for inhaled CO, three 10- to 12-mL breath and room air samples are manually or mechanically collected and analyzed. CO determination in breath samples from 108 healthy, 1-day-old infants of nonsmoking mothers compared favorably with determinations by gas chromatography (GC), 1.3 +/- 0.8 vs 1.2 +/- 0.8 (mean +/- SD), respectively, with a regression equation of EC = 0.95 GC+0.13 (r2 = 0.98). The results demonstrate that the EC-CO instrument yields results that are comparable with those obtained by the more difficult to perform GC assay.

    View details for Web of Science ID A1994PL01600013

    View details for PubMedID 7923774

  • BILIRUBIN PRODUCTION IN HEALTHY TERM INFANTS AS MEASURED BY CARBON-MONOXIDE IN BREATH CLINICAL CHEMISTRY Stevenson, D. K., Vreman, H. J., Oh, W., Fanaroff, A. A., Wright, L. L., Lemons, J. A., Verter, J., Shankaran, S., TYSON, J. E., Korones, S. B., Bauer, C. R., Stoll, B. J., Papile, L. A., OKAH, F., Ehrenkranz, R. A. 1994; 40 (10): 1934-1939

    Abstract

    To describe total bilirubin production in healthy term infants, we measured the end-tidal breath CO, corrected for ambient CO (ETCOc), with an automated sampler and electrochemical (EC) CO instrument. For infants of mothers with a negative Coombs' test, the ETCOc was 1.3 +/- 0.7 microL/L (n = 397) and the serum bilirubin on day 3 postpartum was 73 +/- 35 mg/L (n = 381). In contrast, the ETCOc for infants with ABO or Rh incompatibility, a positive direct Coombs' test, and bilirubin > 130 mg/L (n = 9) was significantly higher, 1.8 +/- 0.8 microL/L, than for those who had a positive Coombs' test result but whose bilirubin was < or = 130 mg/L (n = 12), 1.0 +/- 0.5 microL/L (P < 0.05). At 2 to 8 h postpartum seven term babies from mothers with insulin-dependent diabetes had ETCOc of 1.8 +/- 0.7 microL/L, significantly higher than that in the other term infants [1.3 +/- 0.7 microL/L (n = 390), P < 0.04]. Their bilirubin concentration at 72 +/- 12 h was also higher: 121 +/- 45 mg/L (n = 7) vs 73 +/- 34 mg/L (n = 374; P = 0.03). We conclude that ETCOc measurements may be helpful in understanding the mechanisms of jaundice in healthy term infants in a variety of conditions.

    View details for Web of Science ID A1994PL01600014

    View details for PubMedID 7923775

  • CARBOXYHEMOGLOBIN DETERMINED IN NEONATAL BLOOD WITH A COOXIMETER UNAFFECTED BY FETAL OXYHEMOGLOBIN CLINICAL CHEMISTRY Vreman, H. J., Stevenson, D. K. 1994; 40 (8): 1522-1527

    Abstract

    Measurements of carboxyhemoglobin (COHb) for clinical purposes are routinely made with CO-oximeters. However, fetal hemoglobin (HbF) interferes with this spectrophotometric method. The manufacturer (Ciba Corning Diagnostics) of a new CO-oximeter (CCD 270) claims that COHb measurements with this instrument are insignificantly affected by HbF. We examined this claim through CO-oximeter analysis of cord blood/adult blood mixtures and compared the results with those obtained by gas chromatography (GC). We also studied the influence of oxygen and bilirubin concentrations. Measurements of COHb with CCD 270 were significantly lower than the GC measurements, but the differences were not clinically important. Linear regression analysis of HbF and COHb measurements (n = 68) showed significant correlation (P < 0.0001) between the two factors for the older CCD 2500 CO-oximeter (R2 = 0.56), but not for the CCD 270 (R2 = 0.06) or GC (R2 = 0.02). Bilirubin concentrations, which affected COHb measurements with CCD 2500, did not significantly affect CCD 270 measurements. We conclude that COHb measurements with CCD 270 CO-oximeter are not affected by HbF or bilirubin concentrations.

    View details for Web of Science ID A1994PA07300009

    View details for PubMedID 7519133

  • Maternal transmission of human immunodeficiency virus-1. Obstetrical & gynecological survey Paz, I., Seidman, D. S., Mashiach, S., Stevenson, D. K. 1994; 49 (8): 577-584

    Abstract

    The dramatic increase in the number of women of childbearing age infected with human immunodeficiency virus (HIV) has led to the revelation of another terrible consequence of the human immunodeficiency virus (HIV) pandemic; maternal transmission of HIV to the fetus. Over 90 per cent of the children who are infected with HIV contract the virus from their mother. Viral transmission may occur in utero, during labor when the newborn is exposed to maternal blood and body fluids or postnatally, mainly via breast-feeding. However, the risk of infection for a baby whose mother is an HIV carrier is not yet clear. The determination of the HIV status of the newborn remains a major diagnostic problem as the routine test, which detects antibodies to HIV, is of limited value in evaluating newborns. A summary of all of the large prospective long-term follow-up studies reported to date, shows an overall transmission rate of 22.4 per cent, with a 95 per cent confidence interval of 20.5 to 24.0 per cent. However, it is difficult to refer to the wide range of reported transmission rates, from 9.1 to 55.0 per cent, as they are confounded by the differing distribution of risk factors. The risk of maternal to newborn transmission must, therefore, be determined according to the specific characteristics of each parturient population.

    View details for PubMedID 7970451

  • KERNICTERUS IN A FULL-TERM INFANT PEDIATRICS Penn, A. A., Enzmann, D. R., Hahn, J. S., Stevenson, D. K. 1994; 93 (6): 1003-1006

    View details for Web of Science ID A1994NP67800024

    View details for PubMedID 7794295

  • Effect of phototherapy for neonatal jaundice on cognitive performance. Journal of perinatology Seidman, D. S., Paz, I., Stevenson, D. K., Laor, A., Danon, Y. L., Gale, R. 1994; 14 (1): 23-28

    Abstract

    Phototherapy for neonatal hyperbilirubinemia was introduced to our medical center in March 1971. To assess the influence of phototherapy on subsequent cognitive outcome, we compared the intelligence test scores at 17 years of age of subjects born 4 months before and 10 months after the introduction of phototherapy. The intelligence quotient score (mean +/- SE) at 17 years for 84 subjects with severe neonatal hyperbilirubinemia was 108 +/- 2 for those treated by phototherapy and 107 +/- 2 for controls matched for gestational age and birth weight. The confounding effect on intelligence quotient scores of perinatal factors (bilirubin concentrations, gestational age, birth weight, Apgar score) and demographic characteristics (ethnic origin, socioeconomic status, paternal education) was taken into account in a multiple logistic regression analysis by using a General Linear Models procedure. Phototherapy was found to have no independent effect on intelligence quotient scores after adjustment for the effect of confounding factors. We conclude that for full-term newborn infants with neonatal hyperbilirubinemia, phototherapy had neither a beneficial nor an adverse effect on intellectual ability in late adolescence.

    View details for PubMedID 8169674

  • MEASUREMENT OF CARBOXYHEMOGLOBIN AND TOTAL HEMOGLOBIN BY 5 SPECIALIZED SPECTROPHOTOMETERS (CO-OXIMETERS) IN COMPARISON WITH REFERENCE METHODS CLINICAL CHEMISTRY Mahoney, J. J., Vreman, H. J., Stevenson, D. K., VanKessel, A. L. 1993; 39 (8): 1693-1700

    Abstract

    We measured total hemoglobin (CtHb) and carboxyhemoglobin (COHb) in 100 patients' blood samples by using five specialized spectrophotometers (CO-oximeters)--IL 482 CO-Oximeter, Corning 2500 CO-oximeter, Radiometer OSM 3 Hemoximeter, Corning 270 CO-oximeter, and the AVL 912 CO-Oxylite--and compared the results with those obtained with the manual cyanmethemoglobin method and a gas-chromatographic (GC) method, respectively. For the CtHb measurements, the differences between the cyanmethemoglobin method and the CO-oximeters were not clinically important for any model. For the blood COHb measurements, the direction of the bias relative to GC was dependent on COHb concentration. In general, the CO-oximeters underestimated COHb concentration for COHb > 2.5% of total hemoglobin but overestimated COHb concentration for COHb < or = 2.5%. We conclude that all five CO-oximeters compared favorably with the reference methods for CtHb and for high concentrations of COHb. However, the inaccuracy of CO-oximeters for low-concentration (< or = 2.5%) COHb measurements may make these instruments unsuitable for some applications.

    View details for Web of Science ID A1993LT22800025

    View details for PubMedID 8353959

  • GD-DTPA MR DETECTION OF BLOOD-BRAIN-BARRIER OPENING IN RATS AFTER HYPEROSOMOTIC SHOCK JOURNAL OF COMPUTER ASSISTED TOMOGRAPHY Rhine, W. D., Benaron, D. A., Enzmann, D. R., Chung, C., GONZALESMENDEZ, R., Sayre, J. R., Stevenson, D. K. 1993; 17 (4): 563-566

    Abstract

    Detection of blood-brain barrier (BBB) opening in neonates has required invasive methods not clinically applicable. We set out to develop a noninvasive approach to detect such opening.Wistar rats were studied using MRI with Gd-DTPA contrast before and after injection of hyperosmotic solutions known to produce barrier opening. Arabinose was given via right carotid artery to produce unilateral barrier opening; urea was given via tail vein to produce bilateral opening; controls received normal saline. Next, all animals received Gd-DTPA via tail vein.Animals receiving carotid hyperosmotic injections showed increased signal in the ipsilateral brain hemisphere; those receiving venous hyperosmotic injections showed increased signal bilaterally. Similar increases were not found prior to administration of hyperosmotic agent or in saline controls. In both cases, barrier opening was detectable using the relative partitioning of Gd-DTPA between intrabarrier and extrabarrier structures, even in the absence of a hemispheric control.We conclude that MRI with Gd-DTPA contrast allows noninvasive detection of BBB opening in the rat.

    View details for Web of Science ID A1993LM74900008

    View details for PubMedID 8331226

  • PREDICTION OF THE DEVELOPMENT OF LOW-BIRTH-WEIGHT PRETERM INFANTS BY A NEW NEONATAL MEDICAL INDEX JOURNAL OF DEVELOPMENTAL AND BEHAVIORAL PEDIATRICS Korner, A. F., Stevenson, D. K., Kraemer, H. C., Spiker, D., Scott, D. T., Constantinou, J., DiMiceli, S. 1993; 14 (2): 106-111

    Abstract

    A new neonatal medical index (NMI) was used to predict the mental and motor development of low birth weight, preterm infants up to 3-years-old. The NMI is a summary score of only a few clinically salient items that are readily available on brief chart review. The sample consisted of 512 of 608 infants randomly assigned to the control group of the eight-site Infant Health and Development Program and on whom the complete set of developmental outcome measures was available. The developmental tests administered were the Bayley Scales at 12 and 24 months and the Stanford-Binet at 3 years. The findings indicated the NMI was predictive of later cognitive and motor development, and in infants born weighing less than 1500 g, the effects of neonatal medical complications continued to adversely influence these children's development to at least 3 years of age. In the heavier babies the developmental effects of sociodemographic factors predominated by 24 months and beyond.

    View details for Web of Science ID A1993KW12800005

    View details for PubMedID 8473525

  • OPTICAL TIME-OF-FLIGHT AND ABSORBENCY IMAGING OF BIOLOGIC MEDIA SCIENCE Benaron, D. A., Stevenson, D. K. 1993; 259 (5100): 1463-1466

    Abstract

    Imaging the interior of living bodies with light may assist in the diagnosis and treatment of a number of clinical problems, which include the early detection of tumors and hypoxic cerebral injury. An existing picosecond time-of-flight and absorbance (TOFA) optical system has been used to image a model biologic system and a rat. Model measurements confirmed TOFA principles in systems with a high degree of photon scattering; rat images, which were constructed from the variable time delays experienced by a fixed fraction of early-arriving transmitted photons, revealed identifiable internal structure. A combination of light-based quantitative measurement and TOFA localization may have applications in continuous, noninvasive monitoring for structural imaging and spatial chemometric analysis in humans.

    View details for Web of Science ID A1993KP97800039

    View details for PubMedID 8451643

  • SELECTION OF METALLOPORPHYRIN HEME OXYGENASE INHIBITORS BASED ON POTENCY AND PHOTOREACTIVITY PEDIATRIC RESEARCH Vreman, H. J., Ekstrand, B. C., Stevenson, D. K. 1993; 33 (2): 195-200

    Abstract

    The heme oxygenase inhibitor, tin protoporphyrin, is being studied for the prevention of neonatal jaundice. This potential drug, however, is also a photosensitizer that could cause serious and unknown side effects when administered to newborns. Therefore, we have developed in vitro and in vivo procedures for the screening and further characterization of potentially safe heme oxygenase inhibitors. The ideal inhibitor: 1) contains a biocompatible metal, 2) is not degraded in tissues, 3) is a highly potent inhibitor of heme oxygenase, and 4) does not participate in photochemical reactions. Proto- and mesoporphyrin derivatives with the tin, zinc, manganese, chromium, nickel, and magnesium were screened in vitro for suitability. Chromium protoporphyrin and mesoporphyrin were further studied in vitro and in vivo and were found to meet the ideal criteria. Chromium mesoporphyrin appeared to be the most potent in vitro inhibitor of adult Wistar rat tissue heme oxygenase. Four mumol of chromium protoporphyrin or chromium mesoporphyrin/kg body weight, administered intraperitoneally to adult male Wistar rats given a heme load through intraperitoneal administration of 30 mumol heme/kg body weight, caused significant suppression of hemolysis-induced increase in carbon monoxide production to 72 and 44% of control, respectively, 5.5 h after treatment. At t = 6 h, the tissue heme oxygenase activity, measured in vitro, was significantly reduced to 33 and < 5% in liver and to 22 and < 5% in spleen after the administration of chromium protoporphyrin and mesoporphyrin, respectively, but was not reduced in brain. The results show that there exist effective metalloporphyrin heme oxygenase inhibitors without photosensitizing properties.

    View details for Web of Science ID A1993KH83500018

    View details for PubMedID 8433895

  • ROLE OF LIPID-PEROXIDATION IN METALLOPORPHYRIN-MEDIATED PHOTOTOXIC REACTIONS IN NEONATAL RATS PEDIATRIC RESEARCH Dennery, P. A., Vreman, H. J., Rodgers, P. A., Stevenson, D. K. 1993; 33 (1): 87-91

    Abstract

    Our group previously demonstrated dose-dependent mortality in neonatal rats treated with tin protoporphyrin and light. We hypothesize that lipid peroxidation may be responsible for the toxic effects of photosensitizing metalloporphyrins. Neonatal rat blood samples with or without metalloporphyrins (40 mM) were exposed to cool white light (20 microW/cm2/nm) for 30 min at 37 degrees C. In the in vivo model, neonatal rat pups were given injections of 40 mumol of either tin protoporphyrin (4 mM), zinc protoporphyrin/kg body weight, or saline and placed over cool white light. The control animals were similarly treated but kept in the dark. After 3 h, the animals were killed, and their tissues were analyzed for malondialdehyde, conjugated dienes, and disappearance of polyunsaturated fatty acids as indices of lipid peroxidation. In all cases, the known photosensitizer tin protoporphyrin was associated with increased conjugated dienes in the liver and disappearance of polyunsaturated fatty acids and increased malondialdehyde in the liver and brain when animals were exposed to light. Zinc protoporphyrin was not associated with increased lipid peroxidation in the light except in the case of blood in vitro where malondialdehyde levels increased. We conclude that lipid peroxidation plays a role in metalloporphyrin-mediated phototoxicity in neonatal rat tissues.

    View details for Web of Science ID A1993KE70500018

    View details for PubMedID 8433867

  • INHIBITION OF HEME OXYGENASE AFTER ORAL VS INTRAPERITONEAL ADMINISTRATION OF CHROMIUM PORPHYRINS LIFE SCIENCES Vallier, H. A., Rodgers, P. A., Stevenson, D. K. 1993; 52 (10): PL79-PL84

    Abstract

    The effects of chromium porphyrins on suckling rat heme oxygenase activity were compared following oral vs intraperitoneal dosing. Chromium protoporphyrin (CrPP), chromium mesoporphyrin (CrMP), or chromium deuteroporphyrin 2,4 bis glycol (CrBG) were administered at 40 mumol/kg to 2-week old suckling rats either orally or intraperitoneally. Six hours after intraperitoneal dosing, CrPP and CrMP had significantly reduced hepatic and splenic heme oxygenase activity by more than 55%. CrBG effectively reduced hepatic heme oxygenase activity by 42%. More importantly, only CrMP was an effective inhibitor of hepatic heme oxygenase activity 6 hr after oral administration. In the first reported comparison of chromium porphyrin efficacy in vivo, our data suggest that chromium porphyrins, and particularly CrMP, may be effective in chemopreventive strategies for the treatment of neonatal jaundice.

    View details for Web of Science ID A1993KM67000009

    View details for PubMedID 8445977

  • RACE, ETHNICITY, AND THE PROPENSITY FOR NEONATAL JAUNDICE - INTRODUCTION CLINICAL PEDIATRICS Stevenson, D. K., Brown, A. K. 1992; 31 (12): 706-707

    View details for Web of Science ID A1992KD27700001

    View details for PubMedID 1360343

  • THE CARBOXYHEMOGLOBIN METHOD FOR ESTIMATING BILIRUBIN PRODUCTION IN NEONATES - JAPANESE STUDIES CLINICAL PEDIATRICS Stevenson, D. K. 1992; 31 (12): 708-711

    View details for Web of Science ID A1992KD27700002

    View details for PubMedID 1451376

  • DELAYED COMPLIANCE INCREASE IN INFANTS WITH RESPIRATORY-DISTRESS SYNDROME FOLLOWING SYNTHETIC SURFACTANT PEDIATRIC PULMONOLOGY ARMSBY, D. H., Bellon, G., Carlisle, K., Rector, D., Baldwin, R., Long, W., Stevenson, D. K., Ariagno, R. L. 1992; 14 (4): 206-213

    Abstract

    Recent research has demonstrated that Exosurf (EXSF), a newly synthesized artificial surfactant, increases survival when administered endotracheally to premature infants with RDS. This study examines the effects of EXSF on static respiratory system compliance (Crs). Thirty-four patients received two doses of EXSF in this rescue protocol. Crs (mL/cmH2O/kg) did not significantly change within the first 4 hours after either dose. However, Crs values did increase significantly (paired Student's t-test, P = 0.005) when data collected after the second dose (0.36 +/- 0.13 mL/cmH2O/kg) were compared to first week follow-up data (0.51 +/- 0.21 mL/cmH2O/kg). Crs data collected between 2 and 4 weeks after treatments were again not significantly different from non-concurrent control data collected at 3-4 weeks of life. The measurement of Crs in infants receiving EXSF may have been affected by an increase in lung inflation, which could mask an increase in Crs. We speculate that improved lung inflation may occur with less barotrauma in the first week of life due to surfactant replacement treatment and may in part explain the improved Crs seen at 1 week of age. Many investigators using different surfactants, dosing schedules, and pulmonary function methodologies to evaluate lung mechanics have reported that the improvement in compliance after surfactant treatment usually follows the clinical improvement in gas exchange. Additional studies are needed to explain the mechanism of early improvement following surfactant replacement in infants with RDS.

    View details for Web of Science ID A1992KD24300002

    View details for PubMedID 1484754

  • MATURATION OF JEJUNOILEAL GRADIENTS IN RAT INTESTINE - THE ROLE OF INTRALUMINAL NUTRIENTS BIOLOGY OF THE NEONATE Castillo, R. O., Feng, J. J., Stevenson, D. K., Kwong, L. K. 1992; 62 (5): 351-362

    Abstract

    Jejunoileal gradients of intestinal function are thought to be established during the third week of life in the rat when postnatal intestinal maturation occurs. In order to investigate the normal development of jejunoileal gradients and whether either the absence of intraluminal nutrients or the form in which they are provided affected the development of jejunoileal gradients, gradients for mucosal DNA, protein, lactase and sucrase were studied in suckling rats undergoing normal weaning and compared to gradients in rats receiving no intraluminal nutrients or rats receiving nutrients in elemental form. In suckling animals, preexisting jejunoileal gradients for DNA and protein persisted through the weaning period, gradients for lactase formed by rapid decline of ileal function and sucrase gradients formed by rapid increase in jejunal activities. Intraluminal nutrients in elemental form resulted in the formation of jejunoileal gradients similar to those in intestines of normally weaned rats. The lack of intraluminal nutrients resulted in no qualitative differences in the expression of jejunoileal gradients for sucrase, but provision of elemental nutrients resulted in increased jejunoileal differences for this enzyme. The lack of intraluminal nutrients resulted in no gradients for DNA, less pronounced jejunoileal differences for protein and delayed maturational decline of ileal lactase which prevented development of jejunoileal gradients for the enzyme. These studies indicate that the formation of jejunoileal gradients in the maturing rat intestine for the parameters investigated require intraluminal nutrients regardless of the form in which they are provided for their normal expression.

    View details for Web of Science ID A1992JZ80300005

    View details for PubMedID 1467373

  • NONINVASIVE METHODS FOR ESTIMATING INVIVO OXYGENATION CLINICAL PEDIATRICS Benaron, D. A., Benitz, W. E., Ariagno, R. L., Stevenson, D. K. 1992; 31 (5): 258-273

    Abstract

    Clinical signs of hypoxia and hyperoxia are nonspecific and unreliable, yet both are potentially injurious. Noninvasive methods of oxygen assessment fill the gap between clinical observation and invasive tests, helping physicians deliver sufficient oxygen with minimum toxicity. Potential sites for oxygen measurement vary between the blood and the mitochondria; each method measures at a different site and detects different types of hypoxia and hyperoxia. Thus, values obtained by two different methods are not equivalent, giving each method unique strengths and weaknesses. We review two clinical methods (pulse oximetry and transcutaneous oximetry), as well as four experimental methods (near-infrared spectrophotometry, magnetic resonance spectroscopy, magnetic resonance saturation imaging, and time-of-flight absorbance spectrophotometry). The principles of each method and the clinical situations in which each succeeds or fails are discussed. A fundamental understanding of each method can help in deciding which methods, if any, are appropriate for a given patient and how best to correct observed oxygenation problems once they are discovered.

    View details for Web of Science ID A1992HU95600001

    View details for PubMedID 1582091

  • EFFECTS OF MICROWAVE-RADIATION ON ANTIINFECTIVE FACTORS IN HUMAN-MILK PEDIATRICS Quan, R., Yang, C., Rubinstein, S., LEWISTON, N. J., Sunshine, P., Stevenson, D. K., Kerner, J. A. 1992; 89 (4): 667-669

    Abstract

    In intensive care nurseries it has become common practice to use microwave thawing of frozen human milk for more rapid accessibility. Twenty-two freshly frozen human milk samples were tested for lysozyme activity, total IgA, and specific secretory IgA to Escherichia coli serotypes 01, 04, and 06. The samples were heated by microwave for 30 seconds at a low- or high-power setting and then reanalyzed. One-mL aliquots of 10 additional human milk samples were microwaved at low (20 degrees C to 25 degrees C), medium (60 degrees C to 70 degrees C), and high (greater than or equal to 98 degrees C) setting before the addition to each of 1 mL of diluted E coli suspension. E coli growth was determined after 3 1/2 hours of incubation at 37 degrees C. Microwaving at high temperatures (72 degrees C to 98 degrees C) caused a marked decrease in activity of all the tested antiinfective factors. E coli growth at greater than or equal to 98 degrees C was 18 times that of control human milk. Microwaving at low temperatures (20 degrees C to 53 degrees C) had no significant effect on total IgA, specific IgA to E coli serotypes 01 and 04, but did significantly decrease lysozyme and specific IgA to E coli serotype 06. Even at 20 degrees C to 25 degrees C, E coli growth was five times that of control human milk. Microwaving appears to be contraindicated at high temperatures, and questions regarding its safety exist even at low temperatures.

    View details for Web of Science ID A1992HM25100018

    View details for PubMedID 1557249

  • Anthropometry and bilirubin production. Journal of perinatology Stevenson, D. K., Ochikubo, C. G., Rodgers, P. A., Kerner, J. A. 1991; 11 (4): 340-342

    Abstract

    Anthropometric measurements and total bilirubin formation (TBF) estimates were performed on infants born to normal and diabetic mothers. Although we do not exclude the theoretical possibility of a low-frequency occurrence of increased TBF in macrosomic infants of normal mothers, we can conclude that infants of mothers whose diabetes is well managed may have normal TBF.

    View details for PubMedID 1770390

  • INVITRO AND INVIVO CHARACTERISTICS OF A HEME OXYGENASE INHIBITOR - ZNBG AMERICAN JOURNAL OF THE MEDICAL SCIENCES Vreman, H. J., Lee, O. K., Stevenson, D. K. 1991; 302 (6): 335-341

    Abstract

    The authors evaluated the in vitro and in vivo efficacy and photosensitizing effects of zinc deuteroporphyrin 2,4-bis glycol (ZnBG) as an inhibitor of adult Wistar rat tissue heme oxygenase (HO) activity and bilirubin production. Concentrations of 0.02-0.05 microM ZnBG inhibited the HO activity in postmitochondrial supernatants of liver, spleen, brain, and kidney by at least 50%. Administration of 4 mumole ZnBG/kg body weight to adult rats significantly reduced the total body carbon monoxide (CO) excretion, an index of bilirubin formation, from 1 to 6 hours posttreatment. At 6 hours posttreatment, the HO activity in postmitochondrial supernatants of the liver and spleen, but not of the brain, was significantly lowered. ZnBG also behaved as an in vitro photooxidizer by degrading, in the presence of cool white light, the reduced form of nicotinamide adenine dinucleotide phosphate and histidine to CO and other nonidentified products. ZnBG also enhanced the natural photodegradation of bilirubin. Furthermore, administration of ZnBG to 1-day-old neonatal rats caused mortality within 12 hours in light-exposed animals, with a lethal dose 50 of 23 microM/kg body weight.

    View details for Web of Science ID A1991GU87600002

    View details for PubMedID 1772116

  • OBSERVATIONS ON NEONATAL HYPERBILIRUBINEMIA NEW YORK STATE JOURNAL OF MEDICINE Stevenson, D. K., Brown, A. K. 1991; 91 (11): 477-478

    View details for Web of Science ID A1991GN36000003

    View details for PubMedID 1771041

  • A STUDY OF NEPHROTOXIN-INDUCED ACUTE TUBULAR-NECROSIS WITH P-31 MAGNETIC-RESONANCE SPECTROSCOPY MAGNETIC RESONANCE IN MEDICINE Schutz, T., GONZALEZMENDEZ, R., Nabseth, D. C., Tune, B. M., Jardetzky, O., Stevenson, D. K. 1991; 18 (1): 159-168

    Abstract

    Phosphorus magnetic resonance spectroscopy (31P MRS) was used to obtain in vivo spectra from rat kidneys undergoing acute tubular necrosis induced by a nephrotoxic dose of cephaloridine (CLD). Spectra were obtained 0, 24, and 48 h after injection of CLD (experimental group, n = 6) or saline vehicle (control group, n = 6). The nephrotoxicity of CLD was demonstrated by severely increased serum creatinine levels and the development of extensive proximal tubular necrosis in the CLD-injected rats, and the lack of such changes in the controls. 31P MRS showed an increase in the inorganic phosphate region signal (Pi, p = 0.004) and a decrease in the phosphodiester region signal (PDE, p = 0.01) in the experimental group by 48 h, whereas these parameters did not vary significantly in the control group during the experiment. Significant correlations were found between serum creatinine and the same two 31P MRS parameters. In summary, rat kidneys which have developed severe CLD-induced proximal tubular necrosis exhibit changes in the 31P spectrum 48 h after administration of the drug. The causes of these changes were not determined.

    View details for Web of Science ID A1991EZ54700015

    View details for PubMedID 2062227

  • ALTERED MATURATION OF SMALL INTESTINAL FUNCTION IN THE ABSENCE OF INTRALUMINAL NUTRIENTS - RAPID NORMALIZATION WITH REFEEDING AMERICAN JOURNAL OF CLINICAL NUTRITION Castillo, R. O., Feng, J. J., Stevenson, D. K., Kwong, L. K. 1991; 53 (2): 558-561

    Abstract

    The absence of intraluminal nutrients during weaning in rats was shown to result in altered intestinal growth and maturation. In this study intestinal length, mucosal weight, DNA, protein, and total disaccharidase activities were significantly lower in animals sustained by intravenous nutrients over the normal weaning age than were normally weaned controls but were greater than preweaning values. Absorptive capacity for sucrose (assessed by hydrogen-gas production) was diminished, directly linking incomplete maturation of sucrase to diminished intestinal function. To determine whether these alterations were permanent, rats previously deprived of intraluminal nutrients over the weaning period were refed. Eight days after refeeding, all variables except total lactase had attained values found in normally weaned age-matched controls, including absorptive capacity for sucrose. Although intestinal growth and maturation is abnormal in the absence of intraluminal nutrients during weaning, the abnormalities are not permanent and are rapidly corrected upon refeeding.

    View details for Web of Science ID A1991EU94600027

    View details for PubMedID 1899174

  • ORAL-ADMINISTRATION OF ZINC DEUTEROPORPHYRIN IX 2,4 BIS GLYCOL INHIBITS HEME OXYGENASE IN NEONATAL RATS DEVELOPMENTAL PHARMACOLOGY AND THERAPEUTICS Vallier, H. A., Rodgers, P. A., Stevenson, D. K. 1991; 17 (3-4): 220-222

    Abstract

    Zinc deuteroporphyrin IX 2,4 bis glycol (ZnBG) has been shown to be a potent inhibitor of heme oxygenase (HO) in vitro. Oral administration, which has been minimally effective with other metalloporphyrins, could be clinically advantageous for prevention of neonatal hyperbilirubinemia. Therefore, we examined the effect of oral administration of ZnBG on tissue HO activity and tissue ZnBG concentrations. Suckling rats at 2 weeks of age received ZnBG at 40 mumol/kg BW via gastric gavage. Rats were killed with anesthetic over-dose after 60 min. ZnBG was detected in the portal and systemic circulation (n = 12), and the liver, kidney, spleen, and intestine (n = 8). ZnBG concentrations of 7.9 nmol/g liver and 1.7 nmol/g spleen corresponded to 67 and 72% inhibition of control HO activity (n = 9; p less than 0.0005) respectively.

    View details for Web of Science ID A1991JJ26500017

    View details for PubMedID 1841841

  • ABSORPTION OF ZINC DEUTEROPORPHYRIN-IX 2,4-BIS-GLYCOL BY THE NEONATAL RAT SMALL-INTESTINE INVIVO DEVELOPMENTAL PHARMACOLOGY AND THERAPEUTICS Vallier, H. A., Rodgers, P. A., Castillo, R. O., Stevenson, D. K. 1991; 17 (1-2): 109-115

    Abstract

    Zinc deuteroporphyrin IX 2,4-bis-glycol (ZnBG) is a potent inhibitor of heme oxygenase and may be useful in the prevention of neonatal jaundice. Enteral administration could be advantageous clinically, but it has been only minimally effective with other metalloporphyrins in rats and humans. Thus, the absorption of ZnBG by the small intestine in vivo was examined. ZnBG was administered enterally at 40 mumol/kg to 2-week-old suckling rats via in situ catheterization of the small intestine. Within 15 min ZnBG was absorbed by the small intestine, as it was measured in portal and systemic venous plasma, intestine, kidney, liver, and spleen. Concentrations exceeding 5.0 microM were found in plasma within 30 min, and 9.4 microM was found in the liver after 30 min. A total of 4.6% of the administered ZnBG dose was measured in plasma and tissues.

    View details for Web of Science ID A1991HK86500014

    View details for PubMedID 1811916

  • ZINC PROTOPORPHYRIN ADMINISTRATION FOR SUPPRESSION OF INCREASED BILIRUBIN PRODUCTION BY IATROGENIC HEMOLYSIS IN RHESUS NEONATES JOURNAL OF PEDIATRICS Vreman, H. J., Rodgers, P. A., Stevenson, D. K. 1990; 117 (2): 292-297

    Abstract

    We studied the effect of intravenous zinc protoporphyrin (ZnPP) administration on total body carbon monoxide excretion (VeCO), (an index of heme degradation), blood carboxyhemoglobin level, plasma bilirubin level, and tissue homogenate heme oxygenase activity 24 hours after delivery of rhesus neonates treated at 12 hours of age with heat-damaged erythrocytes (32 mumol heme/kg birth weight). All neonates were delivered by cesarean section and received ampicillin and gentamicin to suppress intestinal flora. The control group (n = 4) was treated with saline solution and ZnPP solvent; the erythrocyte-treated control group (n = 4) received erythrocytes and ZnPP solvent; and two experimental groups received erythrocytes and one dose of 10 (n = 3) or 40 (n = 4) mumol ZnPP/kg body weight, respectively. At 24 hours, administration of erythrocytes alone doubled the VeCO (p less than 0.05), carboxyhemoglobin level, (p less than 0.05), and plasma total bilirubin level (p less than 0.05). Treatment with ZnPP, 40 mumol/kg body weight, caused a significant decrease in VeCO (p less than 0.05), carboxyhemoglobin (p less than 0.05), bilirubin (p less than 0.05), and spleen heme oxygenase (p less than 0.05). Treatment of the erythrocyte-loaded animals with ZnPP, 10 mumol/kg body weight, also significantly (p less than 0.05) lowered VeCO and spleen heme oxygenase activity but did not cause a significant lowering of blood carboxyhemoglobin or plasma bilirubin concentration. We conclude that ZnPP is an effective, dose-dependent in vivo inhibitor of heme oxygenase in the newborn rhesus with latrogenic hemolysis, and that it suppresses both bilirubin production and subsequent accumulation.

    View details for Web of Science ID A1990DU14800025

    View details for PubMedID 2380831

  • A COMPARISON OF TOCOLYSIS WITH NIFEDIPINE OR RITODRINE - ANALYSIS OF EFFICACY AND MATERNAL, FETAL, AND NEONATAL OUTCOME AMERICAN JOURNAL OF OBSTETRICS AND GYNECOLOGY Ferguson, J. E., Dyson, D. C., Schutz, T., Stevenson, D. K. 1990; 163 (1): 105-111

    Abstract

    Nifedipine, a dihydropyridone calcium entry blocker, has been used with increasing frequency in the treatment of preterm labor. We studied 66 patients in this prospective, randomized trial to evaluate the efficacy and maternal, fetal, and neonatal outcome associated with tocolysis with nifedipine or ritodrine. Delivery was delayed for 48 hours, 7 days, and until the thirty-sixth week of gestation in 84%, 70%, and 41%, respectively, of patients in the nifedipine group, compared with 72%, 63%, and 52% of patients in the ritodrine group (difference not significant). Maternal side effects were more common and more serious in the group of patients who received ritodrine compared with those who received nifedipine (18 of 38 versus 5 of 38, p less than 0.01); however, fetal and neonatal outcome appeared to be similar when the groups were compared. On the basis of this study, it appears that tocolysis with either nifedipine or ritodrine is equally efficacious; however, maternal side effects are less common with nifedipine treatment. We conclude that nifedipine may have a role in the treatment of preterm labor but suggest further careful evaluation of this agent before it is considered for routine clinical use.

    View details for Web of Science ID A1990DR23400027

    View details for PubMedID 2197860

  • DEVELOPMENTAL BIOLOGY OF HEME OXYGENASE CLINICS IN PERINATOLOGY Rodgers, P. A., Stevenson, D. K. 1990; 17 (2): 275-291

    Abstract

    The regulation of heme oxygenase activity in the developing neonate is essential to the control of bilirubin production as well as intracellular heme and hemoprotein metabolism. The coordinated activity of the microsomal enzymes, heme oxygenase and NADPH-cytochrome c (P450) reductase, and the cytosolic enzyme biliverdin reductase is responsible for the degradation of heme. The complete reaction sequence requires oxygen and NADPH, and produces bilirubin and carbon monoxide in equimolar amounts. Although heme oxygenase expresses a rather broad range of substrate affinities, the oxidative degradation of heme is exclusively alpha-specific. Heme oxygenase is found in several tissues, with significant activity levels in the liver, spleen, and erythropoeitic tissue. Heme oxygenase activity is inducible by heme and other metalloporphyrins, hormones, starvation, stress, toxins, and xenobiotics. Heme oxygenase induction is generally considered to be the result of an increased protein synthesis and gene transcription. This hypothesis is supported by recent studies of the heme oxygenase gene that identified inducer element binding sites responsive to metal administration, heat shock, and nutrient availability. In the developing fetus and neonate, hepatic heme oxygenase activity and mRNA levels are elevated above that of the adult. This suggests that the elevated heme catabolism observed in neonates may be associated with an increased transcription of the heme oxygenase gene. The apparent induction of hepatic heme oxygenase during the neonatal period is probably the result of tissue-specific and time-dependent transcriptional regulating factors including potentially hormones and heme. Several metalloporphyrins, such as the tin and zinc porphyrin complexes, inhibit heme oxygenase activity and thus have therapeutic potential for the treatment of neonatal jaundice. Recent studies suggest that the meso- and bis-glycol derivatives of these metalloporphyrins may be more potent inhibitors of heme oxygenase activity in vitro and in vivo than the protoporphyrin structures. As structural analogues of heme, however, these compounds may also have other less desirable effects on the regulation of heme and hemoprotein metabolism, particularly in the developing neonate.

    View details for Web of Science ID A1990DM55000003

    View details for PubMedID 2196131

  • LIMITING TREATMENT FOR EXTREMELY PREMATURE, LOW-BIRTH-WEIGHT INFANTS (500 TO 750-G) AMERICAN JOURNAL OF DISEASES OF CHILDREN Young, E. W., Stevenson, D. K. 1990; 144 (5): 549-552

    Abstract

    Despite impressive recent advances in neonatology, outcomes for extremely premature, very-low-birth-weight infants (500 to 750 g) remain uneven. In a situation of inherent uncertainty, treating patients vigorously could do violence to the moral principles of nonmaleficence and (distributive) justice. Equally, failing to treat patients vigorously because of concerns about nonmaleficence and (distributive) justice could violate the principle of patient-centered beneficence. Compounding this dilemma is the legacy of the "Baby Doe Regulations." International perspectives on this particular quandary are provided. We assert that at Stanford (Calif) University the "individualized prognostic strategy" rather than the "wait until certainty" approach prevails. Four concluding questions are posed: Why is prevention not encouraged more than after-the-fact heroic intervention? Is it possible to develop a more rational view of stopping aggressive therapy once having started? Can we ignore the finitude of our medical resources? Is there a need to redefine the nature of autonomy?

    View details for Web of Science ID A1990DB96200021

    View details for PubMedID 2330921

  • METALLOPORPHYRIN-ENHANCED PHOTODEGRADATION OF BILIRUBIN INVITRO AMERICAN JOURNAL OF DISEASES OF CHILDREN Vreman, H. J., Stevenson, D. K. 1990; 144 (5): 590-594

    Abstract

    Solutions of bilirubin containing human serum albumin were exposed in vitro in the presence of 10 mumols/L of tin and zinc metalloporphyrins at 37 degrees C for 30 minutes to light sources used clinically for phototherapy of neonates. Bilirubin in the model solutions was photodegraded to approximately 60% of dark control in cool white light (17 microW/cm2 per nanometer). The presence of zinc protoporphyrin and zinc mesoporphyrin further reduced the bilirubin concentration slightly, but the tin analogues caused a significant enhancement of degradation to 35% and 25% of dark control, respectively. The results provide evidence that the zinc and tin metalloporphyrins are photosensitizers capable of enhancing the native photodegradation of bilirubin in biologic matrices, but that the tin compounds are more potent. The metalloporphyrin time course, dose-response curve, oxygen effects, and efficacy of phototherapy light sources were also studied.

    View details for Web of Science ID A1990DB96200030

    View details for PubMedID 2330928

  • CARBON-MONOXIDE PRODUCTION BY NONBACTERIAL SOURCES AFTER HEME FEEDING OF NEONATAL RATS BIOLOGY OF THE NEONATE Stevenson, D. K., HAMORI, C. J., Carlton, R. R., Castillo, R. O., Kerner, J. A., Vreman, H. J. 1990; 57 (3-4): 238-242

    Abstract

    We determined the relative potential for nonbacterial CO production after oral heme feeding of 12-hour-old rats. The intestinal flora was eliminated by treatment with kanamycin, ampicillin, and neomycin. CO excretion (VeCO) was measured after oral administration of heme (0.64 mumol/animal). Antibiotic treatment alone did not significantly affect the VeCO of rats gavaged with saline. Heme administration increased (p less than 0.05) the VeCO during t = 1-11 h with a peak at 3 h. Antibiotic treatment reduced this VeCO (p less than 0.05) during t = 2-8 h, but its level (peak at t = 2-3 h) was still significantly (p less than 0.05) above its nonheme control. The results confirm that bacterial degradation of heme is an important source of CO in suckling rats not pretreated with broad-spectrum antibiotics. However, oral heme feeding of gut-sterilized animals yielded transiently significantly increased VeCO. HO-mediated degradation of enteral heme is a likely nonbacterial source of CO and possibly bilirubin in the neonate.

    View details for Web of Science ID A1990CR41700015

    View details for PubMedID 2322605

  • REGULATION OF INTESTINAL ONTOGENY BY INTRALUMINAL NUTRIENTS JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Castillo, R. O., Feng, J. J., Stevenson, D. K., Kerner, J. A., Kwong, L. K. 1990; 10 (2): 199-205

    Abstract

    Major events in gastrointestinal ontogeny occur in the infant rat in association with weaning, resulting in striking alterations in small intestinal structure and function. Although the dietary changes attendant to weaning are not essential for the initiation of these events, dietary nutrients have been shown to participate in the maturation of some intestinal parameters. In order to define more precisely the role of intraluminal nutrients in the regulation of small intestinal ontogeny, a longitudinal study was conducted using a unique animal model in which intraluminal nutrients were excluded from the intact maturing intestine in vivo throughout the entire weaning period without major compromise in nutritional status. The absence of intraluminal nutrients over the weaning period resulted in diminished lengthening and accretion of mucosal mass, suggesting a slower rate of intestinal growth. Lower mucosal DNA, protein, and mitotic indices in intestines of animals receiving no intraluminal nutrients suggested that the lack of intraluminal nutrients resulted in the blunting of the striking increases in cellular proliferation normally exhibited by the developing intestinal mucosa at this time. Maturation of intestinal lactase-phlorizin hydrolase and maltase-glucoamylase was not affected by the absence of intraluminal nutrients. Although the appearance of sucrase-isomaltase was not altered by the absence of intraluminal nutrients, activity levels rose to only 50% of control levels. These data suggest that during this period of rapid intestinal maturation, intestinal growth is more dependent upon intraluminal nutrients than are the characteristic enzymic alterations normally expressed during this period.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1990CM93700010

    View details for PubMedID 2303970

  • THE USE OF ANTIBIOTICS IN NEONATES WEIGHING LESS THAN 1200 GRAMS PEDIATRIC INFECTIOUS DISEASE JOURNAL Prober, C. G., Stevenson, D. K., Benitz, W. E. 1990; 9 (2): 111-121

    View details for Web of Science ID A1990CT73000009

    View details for PubMedID 2179837

  • HEME CATABOLISM IN RHESUS NEONATES INHIBITED BY ZINC PROTOPORPHYRIN DEVELOPMENTAL PHARMACOLOGY AND THERAPEUTICS Rodgers, P. A., Vreman, H. J., Stevenson, D. K. 1990; 14 (4): 216-222

    Abstract

    The effect of zinc (II) protoporphyrin IX (ZnPP) administration (40 mumol/kg, i.v.) on neonatal heme catabolism and the associated bilirubin production was investigated in rhesus (Macaca mulatta) neonates. Carbon monoxide excretion rates (VECO), tissue heme oxygenase activity, and plasma bilirubin concentrations were measured during a 26-hour postnatal period. In ZnPP-treated neonates (n = 4), VECO values were significantly (p = 0.002) diminished by 24% within 24 h. When compared to controls (n = 3), tissue heme oxygenase activity in ZnPP-treated neonates was greatly reduced in both liver (94% inhibition, p = 0.047) and spleen (48% inhibition, p = 0.077), but essentially unaffected in the kidney and brain. Although not statistically significant, peak (24-hour) neonatal plasma bilirubin concentrations tended to be lower (23%). These results suggest ZnPP may be efficacious in reducing heme catabolism associated with neonatal jaundice.

    View details for Web of Science ID A1990DV23600004

    View details for PubMedID 2397675

  • INVITRO GENERATION OF CARBON-MONOXIDE FROM ORGANIC-MOLECULES AND SYNTHETIC METALLOPORPHYRINS MEDIATED BY LIGHT DEVELOPMENTAL PHARMACOLOGY AND THERAPEUTICS Vreman, H. J., GILLMAN, M. J., Downum, K. R., Stevenson, D. K. 1990; 15 (2): 112-124

    Abstract

    Tin protoporphyrin (SnPP) and analogs are being studied as possible agents for the prevention of neonatal hyperbilirubinemia through inhibition of heme oxygenase. Because SnPP is a photosensitizer, we studied its role in the photogeneration of carbon monoxide (CO) from organic compounds in vitro. Generation of CO occurred in the presence of 5 microM SnPP and cool white light (19 muW/cm2/nm or 29 W/m2) from SnPP alone, human serum albumin, glucose, histidine, ethanolamine, medium-chain triglycerides, the reduced form of nicotinamide-adenine dinucleotide phosphate (NADPH), and human plasma. More detailed studies with human serum albumin and NADPH established that the photogeneration of CO is nearly linear with time and irradiance. It is curvilinear with respect to the SnPP concentration at the concentrations tested, and it is dependent on the presence of O2 in the reactor headspace. Cool white light generated less CO from human serum albumin and NADPH than equidistantly placed blue and green phototherapy light sources. Comparison of SnPP with other metalloporphyrin heme oxygenase inhibitors indicates that tin mesoporphyrin is most and zinc protoporphyrin least photoreactive.

    View details for Web of Science ID A1990EV12100009

    View details for PubMedID 2078972

  • MORTALITY OF METALLOPORPHYRIN-TREATED NEONATAL RATS AFTER LIGHT EXPOSURE DEVELOPMENTAL PHARMACOLOGY AND THERAPEUTICS Hintz, S. R., Vreman, H. J., Stevenson, D. K. 1990; 14 (3): 187-192

    Abstract

    Tin protoporphyrin (SnPP) has been used to suppress hyperbilirubinemia in human neonates through inhibition of heme oxygenase. Some of the subjects exhibited mild erythema upon receiving phototherapy. SnPP and three proposed alternatives, tin mesoporphyrin (SnMP), zinc protoporphyrin (ZnPP) and zinc mesoporphyrin (ZnMP) are potential photosensitizers. We therefore studied the phototoxic effects of these compounds in the neonatal rat model. Fed Wistar rats (24-36 h old) were injected intraperitoneally with up to 40 mumol SnPP/kg body weight, 30 mumol SnMP/kg body weight, 60 mumol ZnPP/kg body weight, or 45 mumol ZnMP/kg body weight. The animals were placed over cool white light (20 microW/cm2/nm) for 12 h. Light exposure resulted in SnPP dose-dependent mortality, and the LD50 was determined to be 11.7 mumol/kg body weight. No deaths were observed in pups treated with up to 20 mumol SnMP/kg; treatment with 30 mumol SnMP/kg resulted in a 40% mortality rate. No fatalities were observed among the light-exposed ZnPP- or ZnMP-treated pups. No deaths were observed among control pups treated with the highest metalloporphyrin doses and kept in the dark; similarly, no mortality was observed in untreated light-exposed control animals. We conclude that (1) SnPP and SnMP are potentially fatal phototoxic substances in the neonatal rat; (2) ZnPP and ZnMP may be safer drugs for neonatal rats receiving light exposure, and (3) further studies are needed to fully assess the photobiological hazards of metalloporphyrin administration to humans.

    View details for Web of Science ID A1990DG27100006

    View details for PubMedID 2364856

  • CONTINUOUS PARENTERAL INFUSION OF VITAMIN-E PHARMACOKINETICS AND BILIRUBIN PRODUCTION IN PREMATURE NEONATES ANNALS OF THE NEW YORK ACADEMY OF SCIENCES Stevenson, D. K., Vreman, H. J., Ferguson, J. E., Lenert, L. A., Leonard, M. B., Gale, R. 1989; 570: 352-357

    Abstract

    We conclude that 5 mg/kg of vitamin E, administered intra-arterially as an 8-hour continuous infusion, significantly and predictably raises serum vitamin E levels into the supraphysiologic range with no apparent side effects. In a group of premature infants whose initial serum vitamin E levels were generally greater than or equal to 0.5 mg/dL, no decrease in bilirubin production was observed. Thus, vitamin E deficiency probably does not play a prominent role in jaundice of prematurity.

    View details for Web of Science ID A1989CV07100032

    View details for PubMedID 2629604

  • The education of scientific physicians. Journal of perinatology Stevenson, D. K. 1989; 9 (4): 442-443

    View details for PubMedID 2593019

  • NIFEDIPINE PHARMACOKINETICS DURING PRETERM LABOR TOCOLYSIS AMERICAN JOURNAL OF OBSTETRICS AND GYNECOLOGY Ferguson, J. E., Schutz, T., PERSHE, R., Stevenson, D. K., Blaschke, T. 1989; 161 (6): 1485-1490

    Abstract

    Nifedipine, a calcium entry blocker, has known relaxing effects on the myometrium. Thirteen women in preterm labor received nifedipine for tocolysis. Blood samples obtained serially during treatment and at the time of delivery were assayed for maternal and neonatal nifedipine concentrations. The peak concentration of nifedipine during sublingual therapy ranged from 23.4 to 197.9 ng/ml and reflected substantial interpatient variability. The mean (+/- SD) measurable trough value in patients who received 20 mg of nifedipine orally every 6 hours was 7.2 +/- 5.5 ng/ml. The maternal mean half-life of nifedipine was 81 minutes (range 49 to 137 minutes). At delivery, neonatal nifedipine levels were nondetectable in 6 of the 11 neonates available for study; in 5, values ranged from 29.5 to 1.8 ng/ml. From these results we conclude that both sublingual and oral nifedipine treatment results in variable but usually measurable maternal plasma concentrations and that placental transfer of nifedipine occurs.

    View details for Web of Science ID A1989CG73300010

    View details for PubMedID 2603904

  • INVITRO INHIBITION OF ADULT-RAT INTESTINAL HEME OXYGENASE BY METALLOPORPHYRINS PEDIATRIC RESEARCH Vreman, H. J., GILLMAN, M. J., Stevenson, D. K. 1989; 26 (4): 362-365

    Abstract

    We determined the inhibitory effects of concentrations of tin- and zinc protoporphyrin (1-100 microM) and mesoporphyrin (0.1-10 microM) on the in vitro heme oxygenase (HO) (E.C.1.14.99.3) activity in liver, spleen, and intestine 13,000 x g tissue supernatants from fasted adult male Wistar rats through measurement of carbon monoxide by gas chromatography. All four metalloporphyrins inhibited intestinal HO, under the light-limited conditions of these experiments. The zinc porphyrins showed a clear concentration dependency over the entire range, reducing activity to near zero levels at their highest concentrations. The tin porphyrins reduced HO activity to 26% of initial levels, but the inhibition was not clearly concentration dependent. Liver and spleen supernatants exhibited concentration dependent inhibition by all four metalloporphyrins. We also assessed the effect of light on HO activity measurements. HO determinations in the light (8 microW/cm2/nm) yielded higher HO activity than for reactions performed in the dark. The presence of light and SnPP appeared to stimulate the HO activity of intestinal preparations thus overcoming the observed inhibition. Light and SnPP also decreased to a lesser degree the inhibition for the spleen preparation, but not for the liver. We conclude that heme oxygenase activity measurements via CO determination need to be conducted in the absence of light, in particular when photosensitizers are present. Furthermore, it appears that intestinal HO behaves in a quantitatively different way from other tissues, under varying conditions of metalloporphyrin inhibition and light exposure.

    View details for Web of Science ID A1989AR78400015

    View details for PubMedID 2797950

  • VANCOMYCIN PHARMACOKINETICS IN VERY LOW BIRTH-WEIGHT NEONATES PEDIATRIC INFECTIOUS DISEASE JOURNAL Leonard, M. B., Koren, G., Stevenson, D. K., Prober, C. G. 1989; 8 (5): 282-286

    Abstract

    The pharmacokinetics of vancomycin hydrochloride was studied in 12 very low birth weight infants. The gestational age (mean +/- SD) was 25.9 +/- 1.3 weeks and body weight was 769.2 +/- 151.5 g at the time of initiation of the study. Vancomycin was infused over a period of 60 minutes in a dosage of 14.2 +/- 3.2 mg/kg once daily in 10 patients, twice daily in 1 patient and every 36 hours in 1 patient for a mean of 10.5 +/- 4.9 days. Serial blood samples were obtained and the concentration time data were fitted to a one-compartment open model using the ADAPT computer program. A significant positive correlation was found between postconceptional age and vancomycin clearance (P less than 0.005) and between vancomycin elimination half-life and plasma creatinine (P less than 0.01). A negative correlation existed between plasma creatinine and vancomycin clearance (P less than 0.005), between postconceptional age and plasma creatinine (P less than 0.005) and between vancomycin half-life and postconceptional age (P less than 0.01). On the basis of these findings a vancomycin dosage of 15 mg/kg every 24 hours for infants less than 1000 g should yield concentrations within the accepted therapeutic range. This susceptible population requires frequent monitoring of vancomycin concentrations because of the high degree of interpatient variability and the continuous maturation of renal function.

    View details for Web of Science ID A1989U613900006

    View details for PubMedID 2657617

  • STABLE INDIVIDUAL-DIFFERENCES IN DEVELOPMENTALLY CHANGING PRETERM INFANTS - A REPLICATED STUDY CHILD DEVELOPMENT Korner, A. F., Brown, B. W., DiMiceli, S., Forrest, T., Stevenson, D. K., Lane, N. M., Constantinou, J., Thom, V. A. 1989; 60 (2): 502-513

    Abstract

    In a longitudinal study with the Neurobehavioral Maturity Assessment (NB-MAP), developmental changes and stability of individual differences were assessed in 2 independent samples of preterm infants ranging from 32 weeks conceptional age to term. Individual stability of response was assessed using regression analysis with repeated measures on subjects. The large majority of the functions tested showed highly significant developmental gains with age and highly significant individual stability of performance across age. These findings replicated well across the 2 cohorts. The results are discussed in the light of the neurobiological stage of development of preterm infants during the last 8 weeks prior to term.

    View details for Web of Science ID A1989T356100020

    View details for PubMedID 2924664

  • THE USE OF METALLOPORPHYRINS FOR THE CHEMOPREVENTION OF NEONATAL JAUNDICE AMERICAN JOURNAL OF DISEASES OF CHILDREN Stevenson, D. K., Rodgers, P. A., Vreman, H. J. 1989; 143 (3): 353-356

    Abstract

    Decreasing bilirubin formation is an important strategy for the prevention of neonatal jaundice. The stannic porphyrins, in particular tin protoporphyrin and tin mesoporphyrin, have been proposed for this purpose because these compounds competitively inhibit heme oxygenase, the rate-limiting enzyme in the heme-degrading pathway. However, these compounds are not only potent inhibitors of heme oxygenase but are also photosensitizers, which can generate cytotoxic oxygen species, such as singlet oxygen. Therapeutic regimens designed to avoid the phototoxicity caused by these and other metalloporphyrins have been suggested. An alternative approach would be the development of derivatives of tin protoporphyrin or other heme analogs that are less phototoxic and are stronger inhibitors of heme oxygenase. However, our understanding of the molecular basis of heme oxygenase inhibition is still limited. The response of heme oxygenase to specific inhibitors varies a great deal and depends on the organ and stage of development. This may be a result of the differing proportions of heme oxygenase isoenzymes in different organs. These questions and others need to be systematically answered so we may better understand and treat disturbances in heme homeostasis. In addition, administration of these compounds may have other metabolic consequences directly and indirectly related to their potent, long-lasting inhibition of heme oxygenase. The significance of such effects, whether transient or permanent, needs to be elucidated.

    View details for Web of Science ID A1989T561300024

    View details for PubMedID 2644817

  • THE REAL CHALLENGE OF BABY DOE - CONSIDERING THE SANCTITY AND QUALITY OF LIFE CLINICAL PEDIATRICS Stevenson, D. K. 1989; 28 (3): 119-122

    View details for Web of Science ID A1989T798500002

    View details for PubMedID 2920487

  • INTERPRETING THE CARBOXYHEMOGLOBIN CONCENTRATION IN FETAL CORD BLOOD JOURNAL OF DEVELOPMENTAL PHYSIOLOGY Leonard, M. B., Vreman, H. J., Ferguson, J. E., Smith, D. W., Stevenson, D. K. 1989; 11 (2): 73-76

    Abstract

    We calculated the fetal-to-maternal carboxyhaemoglobin concentration ratio in 19 mother-infant pairs at the time of term delivery. Mothers, who had a less than 10% drop in their carboxyhaemoglobin concentration during labour, had an average ratio of 1.40 +/- 0.19. For mothers whose carboxyhaemoglobin concentrations dropped by 10% or more during labour, the average fetal-to-maternal carboxyhaemoglobin concentration ratio was 1.83 +/- 0.48. There was a strong correlation (r = 0.82) between the percent change in maternal carboxyhaemoglobin concentration during labour and the fetal-to-maternal carboxyhaemoglobin concentration ratio at the time of delivery. We conclude that increased CO elimination during labour may be accompanied by rapid changes in the maternal carboxyhaemoglobin concentration, leading to a spuriously high fetal-to-maternal carboxyhemoglobin concentration ratio at the time of delivery.

    View details for Web of Science ID A1989AJ93800003

    View details for PubMedID 2778293

  • A CONCURRENT EPIDEMIC OF RESPIRATORY SYNCYTIAL VIRUS AND ECHOVIRUS-7 INFECTIONS IN AN INTENSIVE-CARE NURSERY PEDIATRIC INFECTIOUS DISEASE JOURNAL Wilson, C. W., Stevenson, D. K., Arvin, A. M. 1989; 8 (1): 24-29

    Abstract

    We describe concurrent outbreaks of respiratory syncytial virus (RSV) and Echovirus 7 (Echo 7) infections in a neonatal intensive care unit, including infants who had dual infections. Seventy-three infants were identified as having RSV from January through June, 1984. During the same surveillance period Echo 7 was cultured from 20 infants, and 6 infants had concurrent RSV and Echo 7 and RSV were isolated, but not concurrently. This dual outbreak of RSV and Echo 7 infections persisted for months despite infection control measures. Control procedures were complicated by: (1) cases of RSV infection at less than 72 hours of age, which had not previously been reported and which led to the reintroduction of RSV into "clean" areas; (2) the lack of a rapid diagnostic test for enterovirus infection; (3) the number of infants who were asymptomatic with each infection; and (4) the logistical problems of handling a dual pathogen outbreak in a confined setting. These problems were compounded by the many risk factors associated with nosocomial infections found in neonatal intensive care settings such as prolonged hospitalizations, endotracheal or nasogastric tubes and contact with many ancillary care personnel.

    View details for Web of Science ID A1989R833000007

    View details for PubMedID 2922234

  • CARBON-MONOXIDE EXCRETION AS AN INDEX OF BILIRUBIN PRODUCTION IN RHESUS-MONKEYS JOURNAL OF MEDICAL PRIMATOLOGY Vreman, H. J., Rodgers, P. A., Gale, R., Stevenson, D. K. 1989; 18 (6): 449-460

    Abstract

    The role of increased heme catabolism in neonatal hyperbilirubinemia was investigated in rhesus (Macaca mulatta) neonates through the measurement of carbon monoxide excretion rates (VECO), blood carboxyhemoglobin content (HbCO), and plasma bilirubin concentrations. Neonatal values were compared to those of adult rhesus monkeys. These indices of bilirubin production responded appropriately to administration of NEM-damaged erythrocytes and tin protoporphyrin. Our results indicate that VECO measurements are a valid index of changes in bilirubin production in the newborn rhesus monkey.

    View details for Web of Science ID A1989CG06100003

    View details for PubMedID 2614809

  • ZINC PROTOPORPHYRIN INHIBITS CO PRODUCTION IN RATS JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION HAMORI, C. J., Vreman, H. J., Rodgers, P. A., Stevenson, D. K. 1989; 8 (1): 110-115

    Abstract

    We studied the effect of zinc protoporphyrin (ZnPP) on in vivo total bilirubin production, as measured by the excretion rate of carbon monoxide (VeCO), in adult rats. A single subcutaneous dose of ZnPP (40 mumol/kg) suppressed the VeCO between 2-12 h posttreatment, with maximum suppression of approximately 20% by 4 h. The heme oxygenase activity in the liver and spleen of the ZnPP-treated rats was significantly inhibited at 12 h compared with that of the controls. The in vitro inhibition of heme oxygenase activity by the addition of exogenous ZnPP to native rat liver and spleen tissue preparations was observed, as evidenced by suppressed CO production. This in vitro inhibition of heme oxygenase activity by ZnPP was further confirmed by finding decreased bilirubin formation, as measured directly by high-performance liquid chromatography. This study demonstrates that ZnPP can inhibit in vivo liver and spleen heme oxygenase activity and suppress CO production in the rat, as well as inhibit in vitro heme oxygenase activity in native rat tissues.

    View details for Web of Science ID A1989T010800020

    View details for PubMedID 2732855

  • NEONATAL BILIRUBIN PRODUCTION AFTER PRETERM LABOR TOCOLYSIS WITH NIFEDIPINE DEVELOPMENTAL PHARMACOLOGY AND THERAPEUTICS Ferguson, J. E., SCHUTZ, T. E., Stevenson, D. K. 1989; 12 (3): 113-117

    Abstract

    We studied the in vivo total bilirubin production, as indexed by the carboxyhemoglobin level (HbCO), of infants whose mothers had ritodrine (RIT) tocolysis or underwent tocolysis with the calcium channel blocker, nifedipine (NIF). No difference in HbCO between the infant groups was detected: NIF 0.67 +/- 0.31% saturation and RIT 0.88 +/- 0.47% saturation. We conclude that NIF is unlikely to cause a clinically important increase in total bilirubin production when used at doses sufficient for tocolysis.

    View details for Web of Science ID A1989U271600001

    View details for PubMedID 2721333

  • CARBOXYHEMOGLOBIN AS MEASURED BY GAS-CHROMATOGRAPHY AND WITH THE IL-282 AND IL-482 CO-OXIMETERS CLINICAL CHEMISTRY Vreman, H. J., Mahoney, J. J., VanKessel, A. L., Stevenson, D. K. 1988; 34 (12): 2562-2566

    Abstract

    We measured the concentration of carboxyhemoglobin (HbCO) in original and CO-tonometered blood samples from 53 intensive-care patients with IL 282 and IL 482 CO-Oximeters and by gas chromatography (GC), finding very strong correlations among the three methods for HbCO concentrations greater than 2.5%. For concentrations within the normal reference interval (less than or equal to 2.5%), however, the correlation between CO-Oximetry and GC is poor (r2 less than 0.26). The capillary mode of the IL 482 has a consistently lower correlation with any other method or mode. The correlations of measurements between the CO-Oximeters for total hemoglobin and oxyhemoglobin were excellent (r2 greater than or equal to 0.98). Correlations for methemoglobin were lower, owing to its low concentrations in the samples. We conclude that the IL 482 and the IL 282 are analytically equivalent for all analytes measured, but that both instruments differentiate poorly between HbCO values that fall within the reference interval.

    View details for Web of Science ID A1988R284000043

    View details for PubMedID 3197302

  • OXYTOCIN-INDUCED LABOR CHARACTERISTICS AND UTERINE ACTIVITY AFTER PREINDUCTION CERVICAL PRIMING WITH PROSTAGLANDIN-E2 INTRACERVICAL GEL OBSTETRICS AND GYNECOLOGY Ferguson, J. E., Ueland, F. R., Stevenson, D. K., UELAND, K. 1988; 72 (5): 739-745

    Abstract

    Labor characteristics and quantitation of uterine activity resulting from oxytocin induction of labor after intracervical prostaglandin E2 (PGE2) gel priming have not been previously reported. Forty-seven women with modified Bishop scores of 5 or less received preinduction priming with 0.5 mg of intracervical PGE2 gel. Oxytocin was used to induce labor after priming, and uterine activity was quantitated. A matched group of control patients was managed identically but did not receive PGE2 gel. In the gel group, modified Bishop scores improved significantly and in two patients (4%), priming alone induced labor. No uterine hyperstimulation or fetal heart rate abnormalities occurred during priming. Cesarean sections for all indications and those for failed induction were less common in the gel group. The length of the active phase and the second stage of labor were significantly shorter in the gel group. Uterine activity was similar in both groups. The data suggest a primary cervical action of the gel.

    View details for Web of Science ID A1988Q648700012

    View details for PubMedID 3173925

  • EFFECTS OF ORAL-ADMINISTRATION OF TIN AND ZINC PROTOPORPHYRIN ON NEONATAL AND ADULT-RAT TISSUE HEME OXYGENASE ACTIVITY JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Vreman, H. J., Hintz, S. R., Kim, C. B., Castillo, R. O., Stevenson, D. K. 1988; 7 (6): 902-906

    Abstract

    The purpose of this study was to investigate if oral metalloporphyrin treatment could suppress intestinal heme oxygenase (HO) activity and thus prevent HO-mediated heme degradation in this organ. Six hours after a single 40 mumol/kg oral dose of tin protoporphyrin (TP), zinc protoporphyrin (ZP), or heme to adult rats, no significant difference in the HO activity of the intestine was observed relative to control tissues. Moreover, the activity was not inhibited by in vitro exposure to 40 microM TP or ZP. Liver and spleen HO activity was also not significantly inhibited in vivo after oral administration of metalloporphyrins; however, in vitro exposure to TP or ZP decreased the HO activity of preparations from these organs significantly. Like adults, the intestinal HO activity of neonates was not inhibited effectively by oral administration of either metalloporphyrin. The results of subsequent in vitro exposure of control neonatal tissue preparations to ZP or TP was similar to those using adult tissue preparations. Even at 100 microM, only ZP seemed to have some in vitro inhibitory effect on the intestinal HO of suckling rats. We conclude that intestinal HO is less inhibitable by TP or ZP reaching the intestine via the stomach in concentrations at least 30-fold greater than those achieved after parenteral 40 mumol/kg doses, which cause significant hepatic and splenic HO inhibition. Intestinal absorption and enterohepatic circulation of heme, TP, and ZP do not seem to occur in amounts sufficient to consistently and significantly affect HO activity in liver or spleen.

    View details for Web of Science ID A1988Q638900019

    View details for PubMedID 3199276

  • SUPPRESSION OF CARBON-MONOXIDE EXCRETION BY ZINC MESOPORPHYRIN IN ADULT WISTAR RATS - EVIDENCE FOR POTENT INVIVO INHIBITION OF BILIRUBIN PRODUCTION RESEARCH COMMUNICATIONS IN CHEMICAL PATHOLOGY AND PHARMACOLOGY HAMORI, C. J., Vreman, H. J., Stevenson, D. K. 1988; 62 (1): 41-48

    Abstract

    We studied the effect of zinc mesoporphyrin on the CO excretion rate (VeCO) and liver heme oxygenase activity of adult rats. A subcutaneous dose of 4 mumol/kg significantly lowered the VeCO between 4 and 12 hours after injection. The liver heme oxygenase activity of treated animals was significantly lower 12 hours after treatment. These findings demonstrate that zinc mesoporphyrin is a potent inhibitor of in vivo total bilirubin production, as measured by the VeCO.

    View details for Web of Science ID A1988Q715300004

    View details for PubMedID 3205979

  • PLASMA PRORENIN AND RENIN IN CHILDHOOD AND ADOLESCENCE AMERICAN JOURNAL OF DISEASES OF CHILDREN Wilson, D. M., Stevenson, D. K., LUETSCHER, J. A. 1988; 142 (10): 1070-1072

    Abstract

    We studied 108 subjects (age range, 4 to 76 years) to determine the effect of age on prorenin (inactive renin), active renin, and plasma renin activity in normal children, adolescents, and adults. Children and adolescents had lower prorenin concentrations and higher plasma renin activity and active renin concentrations than did adults. Prorenin concentrations were positively correlated with age over the range of 4 to 76 years, while plasma renin activity and active renin concentration were negatively correlated with age. Plasma prorenin and active renin concentrations from umbilical cord blood samples obtained from 11 newborns and arterial samples obtained from five infants were higher than those in samples obtained from children or adults.

    View details for Web of Science ID A1988Q324900024

    View details for PubMedID 3052031

  • END-STAGE PERIVENTRICULAR LEUKOMALACIA - MR EVALUATION RADIOLOGY Baker, L. L., Stevenson, D. K., Enzmann, D. R. 1988; 168 (3): 809-815

    Abstract

    A prospective study was performed to assess the capabilities of magnetic resonance (MR) imaging in evaluation of end-stage periventricular leukomalacia (PVL) in six children, aged 31-54 months, in whom PVL had been documented by neurologic ultrasonography during the neonatal period. Eight children of similar age (four premature infants and four full-term infants) with normal neurologic development served as controls. A characteristic triad of PVL abnormalities was seen on MR images: (a) abnormally increased periventricular white-matter signal intensity on the first and second echo images of a T2-weighted sequence (repetition time = 2,000-2,400 msec, echo times = 20 or 30 and 80 msec), most commonly observed in the trigone regions of the lateral ventricles bilaterally; (b) marked loss of periventricular white matter in these regions of abnormal signal intensity, predominantly in the periatrial regions; and (c) compensatory focal ventricular enlargement adjacent to regions of abnormal signal intensity. In patients with the classic periatrial distribution of PVL lesions, general correlation between the degree of neurologic impairment and the severity of MR abnormalities was demonstrated. MR imaging was useful in detecting subtle forms of PVL in cases in which neurologic damage was subclinical.

    View details for Web of Science ID A1988P738600041

    View details for PubMedID 3406411

  • RELATIONSHIP BETWEEN BREATH AND TOTAL-BODY HYDROGEN EXCRETION RATES IN NEONATES JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Modler, S., Kerner, J. A., Castillo, R. O., Vreman, H. J., Stevenson, D. K. 1988; 7 (4): 554-558

    Abstract

    Our study examined the relationship of H2 excreted in breath to total body H2 excreted by neonates. We report simultaneously measured end-tidal H2 concentrations, plus breath H2 and total body H2 (breath H2 plus flatus H2) excretion rates in 10 neonates. End-tidal H2 concentrations varied from 2.4 to 192 ppm. Breath H2 excretion rates ranged from 0.20 to 6.5 and total body H2 excretion rates from 0.29 to 15.0 ml/h. The fractional breath H2 excretion in these infants was 48% (range 33-69%), compared with 21% reported in adults. The correlation coefficient for end-tidal derived H2 excretion and directly measured breath H2 excretion rates was 0.95 (p less than 0.001). We conclude that the proportion of total H2 excreted in the breath of neonates is increased compared with adults, suggesting that caution must be exercised when interpreting newborn breath H2 measurements and using adult norms.

    View details for Web of Science ID A1988N975500013

    View details for PubMedID 3397846

  • EFFECT OF BUPIVACAINE HYDROCHLORIDE ON BILIRUBIN PRODUCTION IN NEONATAL RATS BIOLOGY OF THE NEONATE Gale, R., Vreman, H. J., Ferguson, J. E., Stevenson, D. K. 1988; 54 (1): 45-48

    Abstract

    The rate of bilirubin production was studied in 12-hour-old rats exposed to bupivacaine HCl by subcutaneous injection. The bilirubin production was estimated by measuring the excretion rate of carbon monoxide (VeCO) using an open flow-through system. No significant difference was found between the VeCO of bupivacaine HCl-treated and control animals, or between the levels of bilirubin in the pooled blood of treated (0.92 +/- 0.32 SE mg/dl) and control (1.0 +/- 0.28 SE mg/dl) animals. These negative findings support the clinical studies which have not demonstrated an association between epidural anesthesia with bupivacaine HCl and neonatal jaundice.

    View details for Web of Science ID A1988P486300005

    View details for PubMedID 3207780

  • CORRELATION OF CARBON-MONOXIDE AND BILIRUBIN PRODUCTION BY TISSUE-HOMOGENATES JOURNAL OF CHROMATOGRAPHY-BIOMEDICAL APPLICATIONS Vreman, H. J., Stevenson, D. K., HENTON, D., Rosenthal, P. 1988; 427 (2): 315-319

    View details for Web of Science ID A1988N905000013

    View details for PubMedID 3410913

  • SN-PROTOPORPHYRIN - A CONSIDERATION OF THE 1ST CLINICAL-TRIAL IN HUMAN NEONATES PEDIATRICS Stevenson, D. K., Vreman, H. J. 1988; 81 (6): 881-882

    View details for Web of Science ID A1988N642600026

    View details for PubMedID 3285317

  • INVITRO CARBON-MONOXIDE PRODUCTION BY THE SMALL-INTESTINE OF SUCKLING AND ADULT WISTAR RATS - EFFECT OF PARENTERAL TIN-PROTOPORPHYRIN DEVELOPMENTAL PHARMACOLOGY AND THERAPEUTICS Kim, C. B., Hintz, S. R., Vreman, H. J., Stevenson, D. K. 1988; 11 (3): 166-172

    Abstract

    Single subcutaneous doses (25 mumol/kg body weight) of tin-protoporphyrin (TP), a potent competitive inhibitor or heme oxygenase (HO), were administered to both suckling and adult Wistar rats. The effect of TP on the carbon monoxide excretion rate (VeCO), an index of total bilirubin formation, and on in vitro carbon monoxide (CO) production by the small intestine were evaluated. Whereas the VeCO of the adult group was decreased (p less than 0.0005) after TP, that of the suckling rat was unchanged. Gradients of CO production along the small intestine were observed in sucklings as well as adults; however, these gradients were in opposite directions. Intestinal CO production was greatest in the adult duodenum, decreasing distally; conversely, the CO production was greatest in the suckling ileum, decreasing proximally. No significant difference in CO production between control and TP-treated adult intestinal mucosa was observed. In sucklings, a significant reduction of intestinal CO production in the TP-treated rats was detected in the duodenum only (p less than 0.05). The results suggest that suckling rats differ from adults in terms of the capacity to produce CO and the direction of the gradient of CO production along the intestine. We conclude that (1) TP may not substantially decrease the in vivo production of CO by the small intestine at a dose which inhibits hepatic and splenic heme oxygenase, and (2) because after a heme load, heme is excreted into the intestine after TP administration, heme-degrading, CO-producing processes in the intestine may contribute to an animal's VeCO under such conditions.

    View details for Web of Science ID A1988N081100006

    View details for PubMedID 3383729

  • NEPHROLITHIASIS FOLLOWING INUTERO DIURETIC EXPOSURE - AN UNUSUAL CASE PEDIATRICS Fischer, A. F., Parker, B. R., Stevenson, D. K. 1988; 81 (5): 712-714

    View details for Web of Science ID A1988N207600021

    View details for PubMedID 3282218

  • INTERFERENCE OF FETAL HEMOGLOBIN WITH THE SPECTROPHOTOMETRIC MEASUREMENT OF CARBOXYHEMOGLOBIN CLINICAL CHEMISTRY Vreman, H. J., RONQUILLO, R. B., Ariagno, R. L., Schwartz, H. C., Stevenson, D. K. 1988; 34 (5): 975-977

    Abstract

    We measured the concentration of carboxyhemoglobin (HbCO) in blood samples from 32 neonates by spectrophotometry (IL282 CO-Oximeter) and gas chromatography, finding a strong positive correlation (r = 0.89) between the concentration of fetal hemoglobin (Hb F) and HbCO as measured by spectrophotometry, but not by gas chromatography. Thus, Hb F interferes with the determination of HbCO by spectrophotometric techniques by falsely increasing apparent HbCO in direct proportion to Hb F. We conclude that, when Hb F is known or suspected to be present, blood HbCO cannot be reliably determined by methods based on spectrophotometry.

    View details for Web of Science ID A1988N563700035

    View details for PubMedID 2453310

  • Outcome of neonates with birth weights of less than 801 grams. Journal of perinatology Stevenson, D. K., Petersen, K. R., Yates, B. L., Benitz, W. E., Gale, R. 1988; 8 (2): 82-87

    Abstract

    The follow-up results of intensive care for 68 infants with birth weights less than 801 g treated at Stanford University Hospital were reviewed. The overall survival rate for these infants was 35%, but was 50% for those infants who had been successfully resuscitated in the delivery room and were admitted to the Intensive Care Nursery. Infants under 601 g in weight or less than 25 weeks gestation were more likely to die in the delivery room, but survival among those admitted to the Intensive Care Nursery did not depend on birth weight or gestational age. One-minute and 5-minute Apgar scores less than 5 and interstitial emphysema were associated with increased risk of neonatal death. Only two of 22 survivors (9%) were severely handicapped and another eight (36%) had remediable disabilities at 2 years of age. No infant developed hydrocephalus and only one infant had spasticity. We suggest that the low incidence of major handicaps among survivors encourages the vigorous resuscitation of infants weighing less than 801 g at birth, yet strategies must be developed that will minimize both prolonged dying and the cost of intensive care for nonviable infants.

    View details for PubMedID 2461442

  • COMPARISON OF BILIRUBIN PRODUCTION IN JAPANESE AND CAUCASIAN INFANTS JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Fischer, A. F., Nakamura, H., Uetani, Y., Vreman, H. J., Stevenson, D. K. 1988; 7 (1): 27-29

    Abstract

    Bilirubin production, as indexed by serum carboxyhemoglobin (HbCOc), was studied in a group of normal term Japanese infants and Caucasian controls during the second to third day of life. Stringent entry criteria were employed in order to eliminate infants with hemolysis or other known causes of increased bilirubin production. The mean HbCOc of the Japanese infants (0.69 +/- 0.15% sat) was significantly higher than that of the Caucasian infant (0.58 +/- 0.17% sat). The serum total bilirubin was also significantly higher in Japanese infants (11.1 +/- 3.0 mg/dl versus 8.0 +/- 2.2 mg/dl). This difference may be attributable to environmental and/or genetic factors.

    View details for Web of Science ID A1988L212500007

    View details for PubMedID 3335981

  • HEME OXYGENASE ACTIVITY AS MEASURED BY CARBON-MONOXIDE PRODUCTION ANALYTICAL BIOCHEMISTRY Vreman, H. J., Stevenson, D. K. 1988; 168 (1): 31-38

    Abstract

    A method is described for the in vitro determination of heme oxygenase (HO) activity in animal tissue preparations through determination of carbon monoxide production. Tissue homogenates were centrifuged and the 13,000g supernatants were incubated in septum-sealed vials with methemalbumin in the presence and absence of NADPH at 37 degrees C for 15 min. The reaction was terminated by quick-freezing to -78 degrees C and the amount of carbon monoxide released into the headspace was determined by gas chromatography with a reduction gas detector. The CO produced through mediation of NADPH is used as a measure of HO activity and is expressed as nanomoles of CO produced per hour per milligram protein. The method permits analysis of as little as 2 microliter normal rat tissue homogenate representing 0.4 mg liver tissue (approx 40 micrograms total protein). The assay rate is 10-15 duplicate samples per hour with a precision of 3% for sample (4.47 +/- 0.13 SD nmol CO/h/mg protein) and 6% for blank reactions (0.59 +/- 0.10 nmol CO/h/mg protein) for 10 microliter liver supernatant. Various reaction parameters were studied. The method was used to compare HO activity in several tissue homogenates from normal rats and rats treated with COCl2.

    View details for Web of Science ID A1988L731600005

    View details for PubMedID 3364715

  • REFRACTORY NEONATAL HYPOXEMIA - DIAGNOSTIC EVALUATION AND PHARMACOLOGIC MANAGEMENT RESUSCITATION Benitz, W. E., Stevenson, D. K. 1988; 16 (1): 49-64

    Abstract

    Hypoxemia refractory to oxygen administration and assisted ventilation is found in many clinical conditions and results from a variety of pathophysiologic disorders. Recent clinical and laboratory experience has demonstrated that the choice of therapy for an infant with refractory hypoxemia depends upon identification of the underlying etiologic and pathophysiologic conditions. The ideal therapies for many of these conditions have not yet been defined. We have provided, based on our experience, guidelines for selection of the most appropriate of the currently available therapies for many of these patients.

    View details for Web of Science ID A1988M299000005

    View details for PubMedID 2831603

  • LACK OF INHIBITION OF INTESTINAL HEME OXYGENASE BY ANTIBIOTICS AND TIN-PROTOPORPHYRIN PEDIATRIC RESEARCH Hintz, S. R., Kim, C. B., Vreman, H. J., Stevenson, D. K. 1988; 23 (1): 50-53

    Abstract

    We assessed the in vivo and in vitro effects of antibiotics and tin-protoporphyrin (TP) on intestinal heme oxygenase (HO) activity using a gas chromatographic assay. This method measures the carbon monoxide produced from heme in the presence of NADPH. After in vivo administration of kanamycin (10 mg/kg body weight), ampicillin (200 mg/kg body weight) or neomycin (60 mg/kg body weight) with or without TP (65 mumol/kg body weight) to suckling rats, no significant difference in HO activity along the small intestine was observed. In vitro exposure of adult rat intestinal preparations to the antibiotics showed no significant decrease in HO activity between control and experimental tissue preparations. A concentration-dependent stimulatory effect of neomycin was observed. Subcutaneous administration of TP (25 mumol/kg body weight) to adult male Wistar rats revealed no significant inhibition of the intestine. However, in vitro addition of TP (12.5 microM) to the control tissue preparations of adult Wistar rats revealed highly significant inhibition in liver and spleen when compared to the unexposed control tissues. In contrast, when TP was added to control intestinal preparations no inhibition was observed. These findings suggest that suckling rat intestinal heme oxygenase is not inhibited by in vivo treatment with high concentrations of kanamycin, ampicillin, or neomycin. Furthermore, these antibiotics are not in vitro inhibitors of adult rat intestinal HO. Finally, adult rat intestinal HO is not inhibited either in vivo or in vitro by a concentration of TP that significantly inhibits liver and spleen activity.

    View details for Web of Science ID A1988L542200010

    View details for PubMedID 3340445

  • EFFECT OF EPIDURAL ANALGESIA WITH BUPIVACAINE HYDROCHLORIDE ON NEONATAL BILIRUBIN PRODUCTION OBSTETRICS AND GYNECOLOGY Gale, R., Ferguson, J. E., Stevenson, D. K. 1987; 70 (5): 692-695

    Abstract

    We evaluated the rate of bilirubin production in vivo in newborns whose mothers received an epidural block with bupivacaine hydrochloride during labor and delivery. Bilirubin production was estimated in 23 full-term newborns whose mothers were treated with bupivacaine and in 20 controls by determining the end-tidal carbon monoxide concentration and the blood carboxyhemoglobin level corrected for ambient carbon monoxide. No significant difference was found between the mean end-tidal carbon monoxide concentrations for the bupivacaine-treated and the control groups (1.3 +/- 0.5 and 1.4 +/- 0.7 microL/kg/hour, respectively), or between the mean blood carboxyhemoglobin levels corrected for ambient carbon monoxide (0.54 +/- 0.17 and 0.52 +/- 0.18% saturation, respectively). These negative findings support the clinical studies, which have failed to demonstrate a causative connection between bupivacaine and neonatal jaundice.

    View details for Web of Science ID A1987K565800005

    View details for PubMedID 3116476

  • A TECHNIQUE FOR THE ADMINISTRATION OF RIBAVIRIN TO MECHANICALLY VENTILATED INFANTS WITH SEVERE RESPIRATORY SYNCYTIAL VIRUS-INFECTION CRITICAL CARE MEDICINE Frankel, L. R., Wilson, C. W., Demers, R. R., Parker, J. R., LEWISTON, N. J., Stevenson, D. K., Smith, D. W. 1987; 15 (11): 1051-1054

    Abstract

    Fifteen infants with respiratory syncytial virus pulmonary infection admitted to our pediatric ICU from December 1, 1985 through April 30, 1986, required mechanical ventilation. These patients were placed on an open trial of ribavirin therapy. We describe a technique for the safe delivery of aerosolized ribavirin to these infants while on the ventilator. The agent was delivered for 16 h/day for 7 days. Modifications of the ventilator circuit were needed to prevent the condensation of the drug in the ventilator tubing and to allow for the safe and effective operation of the ventilator. A common ventilator strategy was used for all patients. The highest positive inspiratory pressure generated was 42 +/- 9.5 (SD) cm H2O, the highest PEEP was 5.9 +/- 3.2 cm H2O, the duration of ventilation was 10.7 +/- 8.5 days, and exposure to fraction of inspired oxygen was greater than or equal to 0.6 for 55.3 h. Ribavirin levels were measurable in two patients, thereby demonstrating that the drug was in fact delivered and absorbed. Our preliminary results demonstrate that ribavirin can be delivered to the patients with respiratory syncytial viral infections who require mechanical ventilation; however, further studies are indicated to evaluate the efficacy and dose responsiveness, alterations in pulmonary dynamics, and safety of ribavirin in delivery to infants requiring ventilation.

    View details for Web of Science ID A1987K928100012

    View details for PubMedID 3677748

  • CARBON-MONOXIDE GENERATION FROM TIN-PROTOPORPHYRIN AND ZINC-PROTOPORPHYRIN BY TISSUE-HOMOGENATES BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Vreman, H. J., Stevenson, D. K. 1987; 148 (1): 417-421

    Abstract

    Both heme and tin-protoporphyrin (TP), but not zinc-protoporphyrin (ZP), supported significant NADPH-stimulated, concentration-dependent CO production in all tissues. These rates, for 400 microM substrate, ranged: for heme 0.52 (intestine) to 4.18 (spleen); for TP 0.08 (kidney) to 0.71 (liver); and for ZP 0.01 (liver) to 0.25 (kidney) nmoles CO/hr/mg protein. All three metalloporphyrins (400 microM) supported concentration-dependent CO production in the absence of NADPH. The rates ranged: for heme 0.31 (kidney) to 0.80 (spleen); for TP 0.41 (kidney) to 1.04 (intestine); and for ZP 0.12 (kidney) to 0.51 (spleen) nmoles/hr/mg protein. We conclude that both TP and ZP are subject to in vitro degradation by 13,000 x g supernatants of adult rat organs via CO-producing reactions.

    View details for Web of Science ID A1987K353100060

    View details for PubMedID 3675588

  • THE CONSEQUENCES OF UNCERTAINTY - AN EMPIRICAL-APPROACH TO MEDICAL DECISION-MAKING IN NEONATAL INTENSIVE-CARE JAMA-JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION Fischer, A. F., Stevenson, D. K. 1987; 258 (14): 1929-1931

    View details for Web of Science ID A1987K235300026

    View details for PubMedID 3309387

  • Metabolic emergencies of the newborn: hypoxemia and hypoglycemia. Comprehensive therapy Frankel, L., Stevenson, D. K. 1987; 13 (10): 14-19

    View details for PubMedID 3315406

  • CARBON-MONOXIDE PRODUCTION IN VENTILATED PREMATURE-INFANTS WEIGHING LESS THAN 1500-G ARCHIVES OF DISEASE IN CHILDHOOD Fischer, A. F., Ochikubo, C. G., Vreman, H. J., Stevenson, D. K. 1987; 62 (10): 1070-1072

    Abstract

    Mean pulmonary excretion rate of carbon monoxide in 13 premature babies on ventilators was significantly higher (p less than 0.001) than that of 19 healthy infants born at full term. This correlated with carboxyhaemoglobin concentrations in blood, indicating that the premature infants on ventilators produced abnormally large amounts of bilirubin.

    View details for Web of Science ID A1987K271300022

    View details for PubMedID 3674926

  • TIN-PROTOPORPHYRIN INHIBITS CARBON-MONOXIDE PRODUCTION IN ADULT MALE WISTAR RATS WITH COMMON BILE-DUCT LIGATION JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION MCMILLAN, J. J., Vreman, H. J., Stevenson, D. K. 1987; 6 (5): 795-798

    Abstract

    The excretion rate of CO (VeCO), an index of total bilirubin production, and the total plasma bilirubin level are significantly elevated by 72 h after ligation of the common bile duct in adult male Wistar rats. At 72 and 96 h, rats prepared in this manner were subcutaneously injected with 50 mumol/kg body weight of tin-protoporphyrin IX (TP) (n = 5) or saline (n = 6). At 120 h after surgery, the VeCO had fallen from the pretreatment level in the TP-treated animals by 22% (P less than 0.025) compared with no significant change in the saline-treated controls. The plasma total bilirubin level of the experimental animals had also declined by 32% (p less than 0.0005) compared with their pretreatment level. The hyperbilirubinemia of the saline-treated controls was not significantly modified. These results suggest that TP reduces bilirubin production and plasma total bilirubin levels in adult rats with surgically created obstructive jaundice.

    View details for Web of Science ID A1987J694100024

    View details for PubMedID 3694375

  • CARBOXYHEMOGLOBIN CONCENTRATION AS AN INDEX OF BILIRUBIN PRODUCTION IN NEONATES WITH BIRTH WEIGHTS LESS THAN 1,500 GRAMS - A RANDOMIZED DOUBLE-BLIND COMPARISON OF SUPPLEMENTAL ORAL VITAMIN-E AND PLACEBO JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Fischer, A. F., Inguillo, D., Martin, D. M., Ochikubo, C. G., Vreman, H. J., Stevenson, D. K. 1987; 6 (5): 748-751

    Abstract

    A randomized double-blind study of the efficacy of oral vitamin E supplementation as a prophylactic treatment for hyperbilirubinemia was undertaken in preterm infants weighing less than 1,500 g. Hemoglobin (Hb) levels, blood carboxyhemoglobin saturation (HbCOc), end-tidal carbon monoxide concentration (ETCO), and serum total bilirubin levels were determined in each subject on the first and third days of the study. We found no differences between the vitamin E-treated and placebo-treated groups with respect to Hb, HbCOc, ETCO, or serum bilirubin levels on day 1 or 3. In addition, we reanalyzed our data to compare those infants who had low vitamin E levels at birth with those who had vitamin E levels greater than 0.4 mg/dl on day 1. We still observed no differences in Hb, HbCOc, ETCO, or serum bilirubin levels on day 1 or 3. The results of our study suggest that supplemental oral vitamin E therapy has no major effect on bilirubin production during the first 3 days of life in premature infants weighing less than 1,500 g at birth.

    View details for Web of Science ID A1987J694100015

    View details for PubMedID 3320325

  • Immediate management of the asphyxiated infant: facilitating the cardiorespiratory transition from fetus to newborn. Journal of perinatology Stevenson, D. K., Frankel, L. R., Benitz, W. E. 1987; 7 (3): 221-225

    Abstract

    The authors discuss the possible ways of managing the asphyxiated infant by considering the respiratory circumstances of the fetus and newborn. However, they conclude that further multicenter clinical trials are required to evaluate the efficacy of the various methods of management of delayed transition in cardiorespiratory function after birth.

    View details for PubMedID 3504458

  • RECOVERY OF EXOGENOUS HEME AS CARBON-MONOXIDE AND BILIARY HEME IN ADULT-RATS AFTER TIN PROTOPORPHYRIN TREATMENT JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Hintz, S. R., Kwong, L. K., Vreman, H. J., Stevenson, D. K. 1987; 6 (2): 302-306

    Abstract

    We studied the effect of tin protoporphyrin (TP) on bilirubin production in adult Wistar rats by quantifying in vivo carbon monoxide (CO) excretion and the simultaneous excretion of biliary heme after common bile duct cannulation. A known amount of heme was injected intravenously as red blood cells (RBC) damaged with a sulfhydryl inhibitor, N-ethylmaleimide. The recovery of heme as CO or biliary heme in the cannulated animals was calculated as the molar percent of heme recovered over heme injected. For cannulated controls (n = 4), the recovery was 89 +/- 6% SD, and no heme appeared in bile. Cannulated rats treated with TP (n = 4) had 64 +/- 11% recovered as CO and 30 +/- 11% as heme in bile. Our findings suggest that TP is an effective in vivo inhibitor of exogenous heme catabolism and bilirubin production in adult rats. Furthermore, this inhibition results in increased excretion of heme into the bile proportional to the degree of inhibition.

    View details for Web of Science ID A1987G188100025

    View details for PubMedID 3694354

Conference Proceedings


  • NICHD Conference on Kernicterus: Research on Prevention of Bilirubin-Induced Brain Injury and Kernicterus: Bench-to-Bedside--Diagnostic Methods and Prevention and Treatment Strategies. Stevenson, D. K., Wong, R. J., Vreman, H. J., McDonagh, A. F., Maisels, M. J., Lightner, D. A. 2004: 521-525

    Abstract

    In July 2003, the National Institute of Child Health and Human Development (NICHD) organized a consensus conference, where a group of experts were invited to review and discuss the current state of knowledge regarding neonatal hyperbilirubinemia and identify areas in which where future research should be directed. This paper summarizes the presentations addressing the current methodologies for direct and noninvasive assessments of serum total bilirubin concentrations as well as prevention and treatment strategies for the management of neonatal hyperbilirubinemia.

    View details for PubMedID 15129227

  • Neonatal hypoglycemia .1. Background and definition Halamek, L. P., Benaron, D. A., Stevenson, D. K. SAGE PUBLICATIONS INC. 1997: 675-680

    Abstract

    Hypoglycemia in the neonate remains a common problem. The association of low blood glucose concentrations and abnormal development has prompted extensive research into the anticipation, evaluation, and treatment of neonatal hypoglycemia. Glucose homeostasis in the fetus and neonate is a developmentally regulated dynamic process involving a number of intricate physiologic mechanisms. In addition, the determination of glucose concentrations is dependent upon both the type of tissue analyzed and the limitations of the specific method employed. The complexity of glucose metabolism makes it difficult to precisely define "normal" and "abnormal" glucose levels in preterm and term neonates.

    View details for Web of Science ID A1997YK31400001

    View details for PubMedID 9415833

  • Carbon monoxide and bilirubin production in neonates Stevenson, D. K., Vreman, H. J. AMER ACAD PEDIATRICS. 1997: 252-254

    View details for Web of Science ID A1997XP05000015

    View details for PubMedID 9240808

  • SOURCES OF CARBON-MONOXIDE (CO) IN BIOLOGICAL-SYSTEMS AND APPLICATIONS OF CO DETECTION TECHNOLOGIES Rodgers, P. A., Vreman, H. J., Dennery, P. A., Stevenson, D. K. W B SAUNDERS CO. 1994: 2-10

    Abstract

    Carbon monoxide is produced from a variety of sources in biological systems. Heme oxygenase and heme oxygenase-like activity is the predominant source in mammals, and may be equally important in plants and lower animals. The enzyme appears to be ubiquitous, highly conserved throughout phylogeny, and tightly regulated during development. This and other evidence suggests that heme oxygenase has an important physiological role, of which CO production may be a part. Other minor sources of CO include the oxidation of organic molecules. This includes the following: (1) auto-oxidation of phenols, flavenoids, and halomethanes; (2) photo-oxidation of organic compounds; and (3) lipid peroxidation of membrane lipids. No longer thought of as a waste product only, recent studies suggest that in the central nervous system cellular CO production can influence cGMP levels through effects on soluble guanylyl cyclase activity. Cellular CO production may also be linked to cell-cell interactions, and may be important in the cell's response to environmental changes. Whether CO will have a place similar to nitric oxide in cellular metabolism is still unclear, but it is apparent that these metabolic relationships will become increasingly complex. Cellular heme oxygenase activity results in the equimolar production of CO and bilirubin for each molecule of heme degraded. The CO thus formed diffuses into the blood, is carried via hemoglobin, and is excreted in the lungs. Therefore, CO production can be assessed clinically by measuring the rate of total body CO excretion, blood COHb levels, and end-tidal CO concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1994MY45700002

    View details for PubMedID 8209283

  • RESOLUTION OF NEAR-INFRARED TIME-OF-FLIGHT BRAIN OXYGENATION IMAGING Benaron, D. A., Stevenson, D. K. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1994: 609-617

    View details for Web of Science ID A1994BA42S00081

    View details for PubMedID 8079765

  • TOMOGRAPHIC TIME-OF-FLIGHT OPTICAL IMAGING DEVICE Benaron, D. A., Ho, D. C., Spilman, S., VANHOUTEN, J. P., Stevenson, D. K. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1994: 207-214

    Abstract

    Time-resolved optical imaging has been used to image phantoms, animals, and humans, and offers the potential for the production of functional images of human tissues, such as the oxygenation of brain during stroke. We had previously reported a transmission scanner, and now give an early report on conversion to a rotational tomographic scanner with a non-parallel ray geometry similar to early CAT scanners. Initial scans show that 1) spatial imaging in turbid media using time-of-flight measurements, non-recursive algorithms, and standard tomographic geometry is possible, 2) separation of absorbance and scattering as an image is attainable, a key step in performing spatially-resolved chemometric analysis, 3) imaging of multiple objects buried within scattering material is feasible, demonstrating that equations derived for homogeneous media can be applied in at least some cases to inhomogeneous media such as tissue-like phantoms, and 4) imaging of brain pathology produces recognizable images with sufficient resolution for diagnostic decisions. We conclude that optical tomography is feasible for clinical use and that conversion of the present mechanically scanning device to a clinical scanner should be possible with retention of the current processing algorithms. Such a clinical scanner should ultimately be able to generate images in a few minutes with centimeter resolution at the center of living human brain.

    View details for Web of Science ID A1994BC72H00025

    View details for PubMedID 7597945

  • NON-RECURSIVE LINEAR ALGORITHMS FOR OPTICAL IMAGING IN DIFFUSIVE MEDIA Benaron, D. A., Ho, D. C., Spilman, S., VANHOUTEN, J. P., Stevenson, D. K. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1994: 215-222

    Abstract

    Optical imaging has been used to image phantoms, animals, and humans. It offers the potential for the production of functional images of tissues, such as oxygenation of brain during stroke. Fast algorithms are needed to allow diagnostically useful images to be generated under realistic conditions, including the likelihood that transmission geometries will not be possible. We proposed a linear algorithm, while less than ideal, may allow rapid reconstruction of images and avoid the pitfalls of recursive, nonlinear solutions. Such techniques may also facilitate the use of varied but physiologic imaging geometries. We found that linear backprojection tomography is feasible for clinical use. Conversion of the present mechanically scanning device to a clinical scanner should be possible with retention of the current processing algorithms. Such a clinical scanner should ultimately be able to generate images in less than one minute with centimeter resolution at the center of living human brain.

    View details for Web of Science ID A1994BC72H00026

    View details for PubMedID 7597946