Joelle Ivy Rosser

All Publications

• Top 5 Things Health Professions Students Should Know About Ecology and Waste Management. AMA journal of ethics Rosser, J. I., Lavery, O. X., Christofferson, R. C., Nasoro, J., Mutuku, F. M., LaBeaud, A. D. 2024; 26 (2): E132-141

  Abstract

  The environments in which we live affect individual and community risk for disease transmission and illness severity. Communities' and neighborhoods' waste stream management designs and health care organizations' spatial and structural architecture also influence individuals' and communities' pathogenic vulnerabilities and how well health sector industrial hygiene practices support them. This article describes a One Health approach to planetary environmental health and suggests strategies for implementing a One Health or Planetary Health approach in the context of climate change.

  View details for DOI 10.1001/amajethics.2024.132

  View details for PubMedID 38306203

• Impact of the COVID-19 Pandemic on Tuberculosis Testing and Treatment at a Tertiary Hospital in Zambia. The American journal of tropical medicine and hygiene Rosser, J. I., Phiri, C., Bramante, J. T., Fwoloshi, S., Kankasa, C., Lungu, P., Chanda, R., Chipimo, P., Mulenga, L., Claassen, C. W., Chanda, D. 2023

  Abstract

  Globally, tuberculosis (TB) testing and treatment have declined dramatically during the COVID-19 pandemic. We quantified the change in TB visits, testing, and treatment compared with a 12-month pre-pandemic baseline at the national referral hospital's TB Clinic in Lusaka, Zambia, in the first year of the pandemic. We stratified the results into early and later pandemic periods. In the first 2 months of the pandemic, the mean number of monthly TB clinic visits, prescriptions, and positive TB polymerase chain reaction (PCR) tests decreased as follow: -94.1% (95% CI: -119.4 to -68.8%), -71.4% (95% CI: -80.4 to -62.4%), and -73% (95% CI: -95.5 to -51.3%), respectively. TB testing and treatment counts rebounded in the subsequent 10 months, although the number of prescriptions and TB-PCR tests performed remained significantly lower than pre-pandemic. The COVID-19 pandemic significantly disrupted TB care in Zambia, which could have long-lasting impacts on TB transmission and mortality. Future pandemic preparedness planning should incorporate strategies developed over the course of this pandemic to safeguard consistent, comprehensive TB care.

  View details for DOI 10.4269/ajtmh.22-0689

  View details for PubMedID 36913923

• Oral hymecromone decreases hyaluronan in human study participants. The Journal of clinical investigation Rosser, J. I., Nagy, N., Goel, R., Kaber, G., Demirdjian, S., Saxena, J., Bollyky, J. B., Frymoyer, A. R., Pacheco-Navarro, A. E., Burgener, E. B., Rajadas, J., Wang, Z., Arbach, O., Dunn, C. E., Kalinowski, A., Milla, C. E., Bollyky, P. L. 2022; 132 (9)

  Abstract

  BACKGROUNDHyaluronan (HA), an extracellular matrix glycosaminoglycan, has been implicated in the pathophysiology of COVID-19 infection, pulmonary hypertension, pulmonary fibrosis, and other diseases, but is not targeted by any approved drugs. We asked whether hymecromone (4-methylumbelliferone [4-MU]), an oral drug approved in Europe for biliary spasm treatment that also inhibits HA in vitro and in animal models, could be repurposed as an inhibitor of HA synthesis in humans.METHODSWe conducted an open-label, single-center, dose-response study of hymecromone in healthy adults. Subjects received hymecromone at 1200 (n = 8), 2400 (n = 9), or 3600 (n = 9) mg/d divided into 3 doses daily, administered orally for 4 days. We assessed safety and tolerability of hymecromone and analyzed HA, 4-MU, and 4-methylumbelliferyl glucuronide (4-MUG; the main metabolite of 4-MU) concentrations in sputum and serum.RESULTSHymecromone was well tolerated up to doses of 3600 mg/d. Both sputum and serum drug concentrations increased in a dose-dependent manner, indicating that higher doses lead to greater exposures. Across all dose arms combined, we observed a significant decrease in sputum HA from baseline after 4 days of treatment. We also observed a decrease in serum HA. Additionally, higher baseline sputum HA levels were associated with a greater decrease in sputum HA.CONCLUSIONAfter 4 days of exposure to oral hymecromone, healthy human subjects experienced a significant reduction in sputum HA levels, indicating this oral therapy may have potential in pulmonary diseases where HA is implicated in pathogenesis.TRIAL REGISTRATIONClinicalTrials.gov NCT02780752.FUNDINGStanford Medicine Catalyst, Stanford SPARK, Stanford Innovative Medicines Accelerator program, NIH training grants 5T32AI052073-14 and T32HL129970.

  View details for DOI 10.1172/JCI157983

  View details for PubMedID 35499083

• Reemergence of yellow fever virus in southeastern Brazil, 2017-2018: What sparked the spread? PLoS neglected tropical diseases Rosser, J. I., Nielsen-Saines, K., Saad, E., Fuller, T. 2022; 16 (2): e0010133

  Abstract

  BACKGROUND: The 2017-2018 yellow fever virus (YFV) outbreak in southeastern Brazil marked a reemergence of YFV in urban states that had been YFV-free for nearly a century. Unlike earlier urban YFV transmission, this epidemic was driven by forest mosquitoes. The objective of this study was to evaluate environmental drivers of this outbreak.METHODOLOGY/PRINCIPAL FINDINGS: Using surveillance data from the Brazilian Ministry of Health on human and non-human primate (NHP) cases of YFV, we traced the spatiotemporal progression of the outbreak. We then assessed the epidemic timing in relation to drought using a monthly Standardized Precipitation Evapotranspiration Index (SPEI) and evaluated demographic risk factors for rural or outdoor exposure amongst YFV cases. Finally, we developed a mechanistic framework to map the relationship between drought and YFV. Both human and NHP cases were first identified in a hot, dry, rural area in northern Minas Gerais before spreading southeast into the more cool, wet urban states. Outbreaks coincided with drought in all four southeastern states of Brazil and an extreme drought in Minas Gerais. Confirmed YFV cases had an increased odds of being male (OR 2.6; 95% CI 2.2-3.0), working age (OR: 1.8; 95% CI: 1.5-2.1), and reporting any recent travel (OR: 2.8; 95% CI: 2.3-3.3). Based on this data as well as mosquito and non-human primate biology, we created the "Mono-DrY" mechanistic framework showing how an unusual drought in this region could have amplified YFV transmission at the rural-urban interface and sparked the spread of this epidemic.CONCLUSIONS/SIGNIFICANCE: The 2017-2018 YFV epidemic in Brazil originated in hot, dry rural areas of Minas Gerais before expanding south into urban centers. An unusually severe drought in this region may have created environmental pressures that sparked the reemergence of YFV in Brazil's southeastern cities.

  View details for DOI 10.1371/journal.pntd.0010133

  View details for PubMedID 35130278

• The Effect of Healthcare Worker Density on Maternal Health Service Utilization in Sub-Saharan Africa. The American journal of tropical medicine and hygiene Rosser, J. I., Aluri, K. Z., Kempinsky, A., Richardson, S., Bendavid, E. 2022; 106 (3): 939-944

  Abstract

  Facility births and antenatal care (ANC) are key to improving maternal health. This study evaluates the relationship between physician and nurse/midwife densities and the use of key maternal health services in sub-Saharan Africa (SSA). We matched individual-level maternal health service indicators from Demographic and Health Surveys between 2008 and 2017, to country-level physician and nurse/midwife per-capita densities, across 35 SSA countries. We performed univariate and multivariate probit regression analyses to evaluate the association between healthcare worker (HCW) densities and facility births as our primary outcome and additional ANC services as secondary outcomes. We controlled for established maternal health predictors, including literacy, child marriage, reported problems accessing healthcare, GDP per capita, political instability, and government effectiveness scores. HCW density across SSA was low at 0.13 physicians and 0.91 nurses/midwives per 1,000 people, compared with 2010 worldwide mean densities of 1.33 and 3.07, respectively. The probability of facility birth increased by 9.8% (95% CI: 2.1-17.5%) for every additional physician per 1,000 people and 8.9% (95% CI: 7.1-9.7%) for every additional nurse/midwife per 1,000 people. HCW densities were also associated with increased likelihood of ANC by the respective provider type, and with antenatal testing for preeclampsia (urine and blood pressure checks). Other ANC services demonstrated variable relationships with HCW densities based on provider type. In 35 SSA countries, HCW density was positively associated with many key measures of maternal health service utilization including facility birth and ANC testing for preeclampsia.

  View details for DOI 10.4269/ajtmh.21-0727

  View details for PubMedID 35026729

• Case-control study evaluating risk factors for SARS-CoV-2 outbreak amongst healthcare personnel at a tertiary care center. American journal of infection control Rosser, J. I., Tayyar, R., Giardina, R., Kolonoski, P., Kenski, D., Shen, P., Steinmetz, L. M., Hung, L., Xiao, W., Bains, K., Morrison, T., Madison, A., Chang, S., Tompkins, L., Pinsky, B. A., Holubar, M. 2021

  Abstract

  BACKGROUND: Despite several outbreaks of SARS-CoV-2 amongst healthcare personnel (HCP) exposed to COVID-19 patients globally, risk factors for transmission remain poorly understood.METHODS: We conducted an outbreak investigation and case-control study to evaluate SARS-CoV-2 transmission risk in an outbreak among HCP at an academic medical center in California that was confirmed by whole genome sequencing.RESULTS: A total of 7/9 cases and 93/182 controls completed a voluntary survey about risk factors. Compared to controls, cases reported significantly more patient contact time. Cases were also significantly more likely to have performed airway procedures on the index patient, particularly placing the patient on high flow nasal cannula, continuous positive airway pressure (CPAP), or bilevel positive airway pressure (BiPAP) (OR=11.6; 95% CI=1.7-132.1).DISCUSSION: This study highlights the risk of nosocomial infection of SARS-CoV-2 from patients who become infectious midway into their hospitalization. Our findings also reinforce the importance of patient contact and aerosol-generating procedures as key risk factors for HCP infection with SARS-CoV-2.CONCLUSIONS: Re-testing patients for SARS-CoV-2 after admission in suspicious cases and using N95 masks for all aerosol-generating procedures regardless of initial patient SARS-CoV-2 test results can help reduce the risk of SARS-COV-2 transmission to HCP.

  View details for DOI 10.1016/j.ajic.2021.09.004

  View details for PubMedID 34536502

• Retrospective Review of Virologic and Immunologic Response in Treatment-Experienced Patients on Third-Line HIV Therapy in Lusaka, Zambia. Journal of the International Association of Providers of AIDS Care Zulu, P. M., Toeque, M., Hachaambwa, L., Chirwa, L., Fwoloshi, S., Siwingwa, M., Mbewe, M., Rosser, J. I., Stafford, K. A., Lindsay, B., Mulenga, L., Claassen, C. W. 2021; 20: 23259582211022463

  Abstract

  Established antiretroviral therapy (ART) programs in sub-Saharan Africa have well-defined first-and second-line therapies but no standard third-line ART regimen. The impact of third-line ART on patients with multiclass-resistant HIV in resource-limited settings has not been well characterized. We conducted a retrospective review of patients on third-line ART at the University Teaching Hospital in Lusaka, Zambia. We assessed virologic and immunologic outcomes following 6 months of third-line therapy and found among those with a documented viral load, viral suppression (≤1000 copies/ml) at 24 weeks was 95% (63/66) with a mean increase in CD4 count of 116 cells/mm3 and viral suppression of 63% (63/100) by imputation of missing data. This study suggests that third-line therapy is clinically and virologically effective among patients with multiclass-resistance in a resource-limited setting in sub-Saharan Africa.

  View details for DOI 10.1177/23259582211022463

  View details for PubMedID 34080454

• SARS-CoV-2 Seroprevalence in Healthcare Personnel in Northern California Early in the COVID-19 Pandemic. Infection control and hospital epidemiology Rosser, J. I., Roltgen, K., Dymock, M., Shepard, J., Martin, A., Hogan, C. A., Blomkalns, A., Mathew, R., Parsonnet, J., Pinsky, B. A., Maldonado, Y. A., Boyd, S. D., Chang, S., Holubar, M., Stanford Healthcare COVID-19 Workforce Response Group 2020: 1–27

  Abstract

  OBJECTIVE: We aimed to assess the magnitude of unidentified SARS-CoV-2 infections in our healthcare personnel (HCP) early in the COVID-19 pandemic and evaluate risk factors for infection in order to identify areas for infection control practice improvement in a northern California academic medical center.METHODS: We reviewed the anti-SARS-CoV-2 receptor binding domain (RBD) IgG serologic test results and self-reported risk factors for seropositivity among 10,449 asymptomatic HCP who underwent voluntary serology testing between April 20 and May 20, 2020.RESULTS: In total, 136 employees (1.3%) tested positive for SARS-CoV-2 IgG. This included 41 (30.1%) individuals who had previously tested positive for SARS-CoV-2 by nasopharyngeal reverse transcription polymerase chain reaction (RT-PCR) between March 13 and April 16, 2020. In multivariable analysis, employees of Hispanic ethnicity (OR = 2.01; 95% CI = 1.22-3.46) and those working in environmental services/food services/patient transport (OR = 4.81; 95% CI = 2.08-10.30) were at increased risk for seropositivity compared to other groups. Employees reporting a household contact with COVID-19 were also at higher risk for seropositivity (OR = 3.25; 95% CI = 1.47-6.44), but those with a work exposure were not (OR = 1.27; 95% CI = 0.58-2.47). Importantly, one-third of seropositive individuals reported no prior symptoms, no suspected exposures, and no prior positive RT-PCR test.CONCLUSION: In this study, SARS-CoV-2 seropositivity among HCP early in the northern California epidemic appeared to be quite low and was more likely attributable to community rather than occupational exposure.

  View details for DOI 10.1017/ice.2020.1358

  View details for PubMedID 33292895

• Characteristics and outcomes of coronavirus disease patients under nonsurge conditions, northern California, USA, March–April 2020 Emerging Infectious Diseases Ferguson, J., Rosser, J., Quintero, O., Scott, J., Subramanian, A., Gumma, M., Rogers, A., Kappagoda, S. 2020

  Abstract

  Limited data are available on the clinical presentation and outcomes of coronavirus disease (COVID-19) patients in the United States hospitalized under normal-caseload or nonsurge conditions. We retrospectively studied 72 consecutive adult patients hospitalized with COVID-19 in 2 hospitals in the San Francisco Bay area, California, USA, during March 13-April 11, 2020. The death rate for all hospitalized COVID-19 patients was 8.3%, and median length of hospitalization was 7.5 days. Of the 21 (29% of total) intensive care unit patients, 3 (14.3% died); median length of intensive care unit stay was 12 days. Of the 72 patients, 43 (59.7%) had underlying cardiovascular disease and 19 (26.4%) had underlying pulmonary disease. In this study, death rates were lower than those reported from regions of the United States experiencing a high volume of COVID-19 patients.

  View details for DOI 10.3201/eid2608.201776

• Cervical Cancer Stigma in Rural Kenya: What Does HIV Have to Do with It? JOURNAL OF CANCER EDUCATION Rosser, J. I., Njoroge, B., Huchko, M. J. 2016; 31 (2): 413–18

  Abstract

  Cervical cancer is a leading cause of cancer-related death amongst women in sub-Saharan Africa, largely due to the lack of early screening and treatment. In addition to poor access to screening services, inadequate uptake of available services is a barrier to early identification of precancerous lesions. Given that cervical cancer is caused by a sexually transmitted virus and is associated with HIV positivity, stigma is one of the potential barriers to the utilization of cervical cancer programs in sub-Saharan Africa. We conducted a cross-sectional survey of 419 women attending health facilities in rural western Kenya to measure levels of cervical cancer and HIV stigma and to measure the associations between cervical cancer stigma, HIV stigma, and HIV status. Women who qualified for cervical cancer screening were asked to complete an oral questionnaire using a modified 9-point HIV stigma scale. Low cervical cancer stigma was reported in this study, with only 85/419 (20.3 %) of respondents answering yes to at least one cervical cancer stigma question. However, cervical cancer stigma was highly correlated with HIV stigma (correlation coefficient 0.72) and was significantly lower in HIV-positive women (p < 0.001). Reducing cervical cancer stigma in the general population is an important part of promoting screening in sub-Saharan Africa.

  View details for DOI 10.1007/s13187-015-0843-y

  View details for Web of Science ID 000374285800029

  View details for PubMedID 25982550

• Cervical Cancer Screening Knowledge and Behavior among Women Attending an Urban HIV Clinic in Western Kenya JOURNAL OF CANCER EDUCATION Rosser, J. I., Njoroge, B., Huchko, M. J. 2015; 30 (3): 567–72

  Abstract

  Cervical cancer is a highly preventable disease that disproportionately affects women in developing countries and women with HIV. As integrated HIV and cervical cancer screening programs in Sub-Saharan Africa mature, we have an opportunity to measure the impact of outreach and education efforts and identify areas for future improvement. We conducted a cross-sectional survey of 106 women enrolled in care at an integrated HIV clinic in the Nyanza Province of Kenya 5 years after the start of a cervical cancer screening program. Female clinic attendees who met clinic criteria for cervical cancer screening were asked to complete an oral questionnaire assessing their cervical cancer knowledge, attitudes, and screening history. Ninety-nine percent of women had heard of screening, 70 % felt at risk, and 84 % had been screened. Increased duration of HIV diagnosis was associated with feeling at risk and with a screening history. Nearly half (48 %) of women said they would not get screened if they had to pay for it.

  View details for DOI 10.1007/s13187-014-0787-7

  View details for Web of Science ID 000360918700025

  View details for PubMedID 25595965

• Barriers to Cervical Cancer Screening in Rural Kenya: Perspectives from a Provider Survey JOURNAL OF COMMUNITY HEALTH Rosser, J. I., Hamisi, S., Njoroge, B., Huchko, M. J. 2015; 40 (4): 756–61

  Abstract

  Although cervical cancer is highly preventable through screening, it remains the number one cause of cancer-related death in Kenyan women due to lack of funding and infrastructure for prevention programs. In 2012, Family AIDS Care and Education Services in partnership with the Kenya Ministry of Health began offering free screening at eleven rural health facilities. We sought to explore why screening coverage remains low at some sites. We examined the barriers to screening through a survey of 106 healthcare staff. The most frequently cited barriers to service delivery included staffing shortages, lack of trained staff, insufficient space, and supply issues. The patient barriers commonly perceived by the staff included inadequate knowledge, wait time, discomfort with male providers, and fear of pain with the speculum exam. Despite multilateral efforts to implement cervical cancer screening, staff face significant challenges to service provision and increased education is needed for both providers and patients.

  View details for DOI 10.1007/s10900-015-9996-1

  View details for Web of Science ID 000357342800020

  View details for PubMedID 25677728

• Changing knowledge, attitudes, and behaviors regarding cervical cancer screening: The effects of an educational intervention in rural Kenya PATIENT EDUCATION AND COUNSELING Rosser, J. I., Njoroge, B., Huchko, M. J. 2015; 98 (7): 884–89

  Abstract

  Cervical cancer screening uptake may be influenced by inadequate knowledge in resource-limited settings. This randomized trial evaluated a health talk's impact on cervical cancer knowledge, attitudes, and screening rates in rural Kenya.419 women attending government clinics were randomized to an intervention (N=207) or control (N=212) group. The intervention was a brief health talk on cervical cancer. Participants completed surveys at enrollment (all), immediately after the talk (intervention arm), and at three-months follow-up (all). The primary outcomes were the change in knowledge scores and the final screening rates at three-months follow-up. Secondary outcomes were changes in awareness about cervical cancer screening, perception of personal cervical cancer risk, cervical cancer and HIV stigma, and screening acceptability.Mean Knowledge Scores increased by 26.4% (8.7 points increased to 11.0 points) in the intervention arm compared to only 17.6% (8.5 points increased to 10.0 points) in the control arm (p<0.01). Screening uptake was moderate in both the intervention (58.9%; N=122) and control (60.9%; N=129) arms, with no difference between the groups (p=0.60).A brief health talk increased cervical cancer knowledge, although it did not increase screening over simply informing women about free screening.Screening programs can increase patient understanding with just a brief educational intervention.

  View details for DOI 10.1016/j.pec.2015.03.017

  View details for Web of Science ID 000355708800011

  View details for PubMedID 25858634

  View details for PubMedCentralID PMC4437717

• Knowledge about cervical cancer screening and perception of risk among women attending outpatient clinics in rural Kenya INTERNATIONAL JOURNAL OF GYNECOLOGY & OBSTETRICS Rosser, J. I., Njoroge, B., Huchko, M. J. 2015; 128 (3): 211–15

  Abstract

  To evaluate cervical cancer knowledge, risk perception, and screening intention among women attending outpatient clinics in rural Kenya.A cross-sectional oral survey was conducted among non-pregnant women aged 23-64 years who attended one of 11 western Kenyan health facilities for any reason between March 25 and April 26, 2013. Demographic and clinical predictors were identified using bivariate and multivariate regression analyses.Among 419 participants, 327 (78.0%) had heard of cervical cancer screening. Nevertheless, their specific knowledge was low (mean score 8.6±2.4 [out of 15.0]). Overall, 288 (68.7%) women felt at risk for cervical cancer, and 333 (79.5%) stated that they would undergo screening if offered. Women who intended to undergo screening were less likely to attend a district hospital (adjusted odds ratio [AOR] 0.4; 95% confidence interval [CI] 0.2-0.6) and more likely to have been diagnosed with HIV more than 4 years previously (AOR 0.4; 95% CI 0.2-0.6). Additionally, increased screening acceptance was associated with high knowledge scores (P=0.004).Educational interventions to increase knowledge about cervical cancer might increase screening uptake in low-income settings. Additionally, improvements in services at local health facilities could have a large effect.

  View details for DOI 10.1016/j.ijgo.2014.09.006

  View details for Web of Science ID 000350096400006

  View details for PubMedID 25467908

  View details for PubMedCentralID PMC4329271

• Men's knowledge and attitudes about cervical cancer screening in Kenya BMC WOMENS HEALTH Rosser, J. I., Zakaras, J. M., Hamisi, S., Huchko, M. J. 2014; 14: 138

  Abstract

  A number of studies have identified male involvement as an important factor affecting reproductive health outcomes, particularly in the areas of family planning, antenatal care, and HIV care. As access to cervical cancer screening programs improves in resource-poor settings, particularly through the integration of HIV and cervical cancer services, it is important to understand the role of male partner support in women's utilization of screening and treatment.We administered an oral survey to 110 men in Western Kenya about their knowledge and attitudes regarding cervical cancer and cervical cancer screening. Men who had female partners eligible for cervical cancer screening were recruited from government health facilities where screening was offered free of charge.Specific knowledge about cervical cancer risk factors, prevention, and treatment was low. Only half of the men perceived their partners to be at risk for cervical cancer, and many reported that a positive screen would be emotionally upsetting. Nevertheless, all participants said they would encourage their partners to get screened.Future interventions should tailor cervical cancer educational opportunities towards men. Further research is needed among both men and couples to better understand barriers to male support for screening and treatment and to determine how to best involve men in cervical cancer prevention efforts.

  View details for DOI 10.1186/s12905-014-0138-1

  View details for Web of Science ID 000345718000001

  View details for PubMedID 25416335

  View details for PubMedCentralID PMC4254217

• Cancers That U.S. Physicians Believe the HPV Vaccine Prevents: Findings from a Physician Survey, 2009 JOURNAL OF WOMENS HEALTH Saraiya, M., Rosser, J. I., Cooper, C. 2012; 21 (2): 111–17

  Abstract

  There is strong scientific evidence that human papillomavirus (HPV) vaccines, which protect against two oncogenic HPV types (16 and 18), can prevent cervical, vaginal, and vulvar cancers in women. In addition, recent research has established that the HPV vaccine can prevent anal cancer and has implied that it may also prevent oropharyngeal cancers.A 2009 web-based survey of 1500 physicians from four specialties (pediatricians, family practitioners, internists, and obstetrician-gynecologists) explored knowledge about which female cancers the HPV vaccine was effective in preventing. Physician characteristics associated with the belief that the HPV vaccine prevents cervical, vaginal, vulvar, anal, and other cancers were examined using logistic regression models.Nearly all respondents (97.8%) identified cervical cancer as being prevented by the HPV vaccine; however, lower awareness that the vaccine prevents vaginal (23.8%), vulvar (27.8%), and anal cancer (28.4%) was found. Physician specialty was the most significant covariate identified, with obstetrician-gynecologists being more likely than other physicians to report that the HPV vaccine protected against vaginal (p<0.001), vulvar (p<0.001), and anal (p<0.001) cancers.Physicians may benefit from educational efforts clarifying which noncervical cancers can be prevented by the HPV vaccine. Education is needed across all medical specialties, but it is particularly important for pediatricians and family practitioners, the physicians most likely to administer the HPV vaccine to young adolescents.

  View details for DOI 10.1089/jwh.2011.3313

  View details for Web of Science ID 000300240400001

  View details for PubMedID 22216920

  View details for PubMedCentralID PMC5555392

• Effect of physiological levels of caffeine on Ca2+ handling and fatigue development in Xenopus isolated single myofibers. American journal of physiology. Regulatory, integrative and comparative physiology Rosser, J. I., Walsh, B., Hogan, M. C. 2009; 296 (5): R1512-7

  Abstract

  The purpose of the present study was to determine whether exposure to exogenous physiological concentrations of caffeine influence contractility, Ca(2+) handling, and fatigue development in isolated single Xenopus laevis skeletal muscle fibers. After isolation, two identical contractile periods (separated by 60-min rest) were conducted in each single myofiber (n = 8) at 20 degrees C. During the first contractile period, four fibers were perfused with a noncaffeinated Ringer solution, while the other four fibers were perfused with a caffeinated (70 microM) Ringer solution. The order was reversed for the second contractile period. The single myofibers were stimulated during each contractile period at increasing frequencies (0.16, 0.20, 0.25, 0.33, 0.50, and 1.0 tetanic contractions/s), with each stimulation frequency lasting 2 min until fatigue ensued, defined in this study as a fall in tension development to 66% of maximum. Tension development and free cytosolic [Ca(2+)] (fura-2 fluorescence spectroscopy) were simultaneously measured. There was no significant difference in the peak force generation, time to fatigue, cytosolic Ca(2+) levels, or relaxation times between the noncaffeinated and caffeinated trials. These results demonstrate that physiological levels of caffeine have no significant effect on Xenopus single myofiber contractility, Ca(2+) handling, and fatigue development, and suggest that any ergogenic effects of physiological levels of caffeine on muscle performance during contractions of moderate to high intensity are likely related to factors extraneous to the muscle fiber.

  View details for DOI 10.1152/ajpregu.90901.2008

  View details for PubMedID 19261915

  View details for PubMedCentralID PMC2689837