Publications by authors named "David C Ensminger"

13 Publications

  • Page 1 of 1

Short-term elevations in glucocorticoids do not alter telomere lengths: A systematic review and meta-analysis of non-primate vertebrate studies.

PLoS One 2021 1;16(10):e0257370. Epub 2021 Oct 1.

Department of Integrative Biology, University of California, Berkeley, CA, United States of America.

Background: The neuroendocrine stress response allows vertebrates to cope with stressors via the activation of the Hypothalamic-Pituitary-Adrenal (HPA) axis, which ultimately results in the secretion of glucocorticoids (GCs). Glucocorticoids have pleiotropic effects on behavior and physiology, and might influence telomere length dynamics. During a stress event, GCs mobilize energy towards survival mechanisms rather than to telomere maintenance. Additionally, reactive oxygen species produced in response to increased GC levels can damage telomeres, also leading to telomere shortening. In our systematic review and meta-analysis, we tested whether GC levels impact telomere length and if this relationship differs among time frame, life history stage, or stressor type. We hypothesized that elevated GC levels are linked to a decrease in telomere length.

Methods: We conducted a literature search for studies investigating the relationship between telomere length and GCs in non-human vertebrates using four search engines: Web of Science, Google Scholar, Pubmed and Scopus, last searched on September 27th, 2020. This review identified 31 studies examining the relationship between GCs and telomere length. We pooled the data using Fisher's Z for 15 of these studies. All quantitative studies underwent a risk of bias assessment. This systematic review study was registered in the Open Science Framework Registry (https://osf.io/rqve6).

Results: The pooled effect size from fifteen studies and 1066 study organisms shows no relationship between GCs and telomere length (Fisher's Z = 0.1042, 95% CI = 0.0235; 0.1836). Our meta-analysis synthesizes results from 15 different taxa from the mammalian, avian, amphibian groups. While these results support some previous findings, other studies have found a direct relationship between GCs and telomere dynamics, suggesting underlying mechanisms or concepts that were not taken into account in our analysis. The risk of bias assessment revealed an overall low risk of bias with occasional instances of bias from missing outcome data or bias in the reported result.

Conclusion: We highlight the need for more targeted experiments to understand how conditions, such as experimental timeframes, stressor(s), and stressor magnitudes can drive a relationship between the neuroendocrine stress response and telomere length.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0257370PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8486123PMC
October 2021

Repeated stimulation of the HPA axis alters white blood cell count without increasing oxidative stress or inflammatory cytokines in fasting elephant seal pups.

J Exp Biol 2021 Sep 28;224(18). Epub 2021 Sep 28.

Department of Integrative Biology, University of California, Berkeley, CA 94720-3200, USA.

The hypothalamic-pituitary-adrenal (HPA) axis controls the release of glucocorticoids, which regulate immune and inflammatory function by modulating cytokines, white blood cells and oxidative stress via glucocorticoid receptor (GR) signaling. Although the response to HPA activation is well characterized in many species, little is known about the impacts of HPA activation during extreme physiological conditions. Hence, we challenged 18 simultaneously fasting and developing elephant seal pups with daily intramuscular injections of adrenocorticotropin (ACTH), a GR antagonist (RU486), or a combination of the two (ACTH+RU486) for 4 days. We collected blood at baseline, 2 h and 4 days after the beginning of treatment. ACTH and ACTH+RU486 elevated serum aldosterone and cortisol at 2 h, with effects diminishing at 4 days. RU486 alone induced a compensatory increase in aldosterone, but not cortisol, at 4 days. ACTH decreased neutrophils at 2 h, while decreasing lymphocytes and increasing the neutrophil:lymphocyte ratio at 4 days. These effects were abolished by RU486. Despite alterations in white blood cells, there was no effect of ACTH or RU486 on transforming growth factor-β or interleukin-6 levels; however, both cytokines decreased with the 4 day fasting progression. Similarly, ACTH did not impact protein oxidation, lipid peroxidation or antioxidant enzymes, but plasma isoprostanes and catalase activity decreased while glutathione peroxidase increased with fasting progression. These data demonstrate differential acute (2 h) and chronic (4 days) modulatory effects of HPA activation on white blood cells and that the chronic effect is mediated, at least in part, by GR. These results also underscore elephant seals' extraordinary resistance to oxidative stress derived from repeated HPA activation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1242/jeb.243198DOI Listing
September 2021

Alpha- and beta- adrenergic receptors regulate inflammatory responses to acute and chronic sleep fragmentation in mice.

PeerJ 2021 24;9:e11616. Epub 2021 Jun 24.

Department of Biology, Western Kentucky University, Bowling Green, KY, United States of America.

Sleep is a recuperative process, and its dysregulation has cognitive, metabolic, and immunological effects that are largely deleterious to human health. Epidemiological and empirical studies have suggested that sleep fragmentation (SF) as result of obstructive sleep apnea (OSA) and other sleep abnormalities leads to pronounced inflammatory responses, which are influenced by the sympathetic nervous system (SNS). However, the underlying molecular mechanisms contributing to SNS regulation of SF-induced inflammation are not fully understood. To assess the effects of the SNS upon inflammatory responses to SF, C57BL/6j female mice were placed in automated SF chambers with horizontally moving bars across the bottom of each cage at specified intervals to disrupt sleep. Mice were first subjected to either control (no bar movement), acute sleep fragmentation (ASF), or chronic sleep fragmentation (CSF) on a 12:12-h light/dark schedule. ASF involved a bar sweep every 120 s for 24 h, whereas CSF involved a bar sweep every 120 s for 12 h (during 12 L; resting period) over a period of 4 weeks. After exposure to these conditions, mice received an intraperitoneal injection of either phentolamine (5 mg/kg BW; an α-adrenergic receptor blocker), propranolol (5 mg/kg BW; a β-adrenergic receptor blocker), or vehicle (saline). Serum corticosterone concentration, brain and peripheral cytokine (IL1β, TNFα, and TGFβ) mRNA expression, and body mass were assessed. ASF and CSF significantly elevated serum corticosterone concentrations as well as cytokine mRNA expression levels compared with controls, and mice subjected to CSF had decreased body mass relative to controls. Mice subjected to CSF and treated with phentolamine or propranolol had a greater propensity for a decrease in cytokine gene expression compared with ASF, but effects were tissue-specific. Taken together, these results suggest that both α- and β-adrenergic receptors contribute to the SNS mediation of inflammatory responses, and adrenergic antagonists may effectively mitigate tissue-specific SF-mediated inflammation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.7717/peerj.11616DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8236227PMC
June 2021

Launching a saliva-based SARS-CoV-2 surveillance testing program on a university campus.

PLoS One 2021 26;16(5):e0251296. Epub 2021 May 26.

University of California, Berkeley, California, United States of America.

Regular surveillance testing of asymptomatic individuals for SARS-CoV-2 has been center to SARS-CoV-2 outbreak prevention on college and university campuses. Here we describe the voluntary saliva testing program instituted at the University of California, Berkeley during an early period of the SARS-CoV-2 pandemic in 2020. The program was administered as a research study ahead of clinical implementation, enabling us to launch surveillance testing while continuing to optimize the assay. Results of both the testing protocol itself and the study participants' experience show how the program succeeded in providing routine, robust testing capable of contributing to outbreak prevention within a campus community and offer strategies for encouraging participation and a sense of civic responsibility.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0251296PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8153421PMC
June 2021

Elevated glucocorticoids during gestation suggest sex-specific effects on offspring telomere lengths in a wild lizard.

Comp Biochem Physiol A Mol Integr Physiol 2021 07 29;257:110971. Epub 2021 Apr 29.

Department of Biology, The Pennsylvania State University, Mueller Laboratory, University Park, PA 16802, United States of America; Intercollege Graduate Degree Program in Ecology, The Pennsylvania State University, University Park, PA 16802, United States of America.

The effects of maternal glucocorticoids (e.g. corticosterone, CORT) on offspring interest biologists due to increasing environmental perturbations. While little is known about the impact of maternal CORT on offspring fitness, it may modulate telomere length and compromise offspring health. Here, we use a modified real-time quantitative PCR assay to assess telomere length using small DNA quantities (<60 ng). We tested the hypothesis that increased maternal CORT during gestation decreases offspring telomere length. While CORT-driven telomere shortening is well established within individuals, cross-generational effects remain unclear. We treated wild-caught gravid female eastern fence lizards (Sceloporus undulatus) with daily transdermal applications of CORT, at ecologically relevant levels, from capture to laying. Maternal CORT treatment did not alter maternal telomere length, although baseline maternal CORT concentrations had a weak, negative correlation with maternal telomere length. There was no relation between mother and offspring telomere length. There was a trend for maternal CORT treatment to shorten telomeres of sons but not daughters. Our treatment replicated exposure to a single stressor per day, likely underestimating effects seen in the wild where stressors may be more frequent. Future research should further explore fitness consequences of maternal CORT effects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cbpa.2021.110971DOI Listing
July 2021

Fasting ameliorates oxidative stress: A review of physiological strategies across life history events in wild vertebrates.

Comp Biochem Physiol A Mol Integr Physiol 2021 06 26;256:110929. Epub 2021 Feb 26.

Department of Integrative Biology, University of California, Berkeley, USA. Electronic address:

Fasting is a component of many species' life history due to environmental factors or behavioral patterns that limit access to food. Despite metabolic and physiological challenges associated with these life history stages, fasting-adapted wild vertebrates exhibit few if any signs of oxidative stress, suggesting that fasting promotes redox homeostasis. Here we review mammalian, avian, reptilian, amphibian, and piscine examples of animals undergoing fasting during prolonged metabolic suppression (e.g. hibernation and estivation) or energetically demanding processes (e.g. migration and breeding) to better understand the mechanisms underlying fasting tolerance in wild vertebrates. These studies largely show beneficial effects of fasting on redox balance via limited oxidative damage. Though some species exhibit signs of oxidative stress due to energetically or metabolically extreme processes, fasting wild vertebrates largely buffer themselves from the negative consequences of oxidative damage through specific strategies such as elevating antioxidants, selectively maintaining redox balance in critical tissues, or modifying behavioral patterns. We conclude with suggestions for future research to better elucidate the protective effects of fasting on oxidative stress as well as disentangle the impacts from other life history stages. Further research in these areas will facilitate our understanding of the mechanisms wild vertebrates use to mitigate the negative impacts associated with metabolically-extreme life history stages as well as potential translation into therapeutic interventions in non-fasting-adapted species including humans.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cbpa.2021.110929DOI Listing
June 2021

Maternal corticosterone increases thermal sensitivity of heart rate in lizard embryos.

Biol Lett 2019 01;15(1):20180718

1 Intercollege Graduate Degree Program in Ecology, The Pennsylvania State University , University Park, PA 16802 , USA.

While it is well established that maternal stress hormones, such as corticosterone (CORT), can induce transgenerational phenotypic plasticity, few studies have addressed the influence of maternal CORT on pre-natal life stages. We tested the hypothesis that experimentally increased CORT levels of gravid female eastern fence lizards ( Sceloporus undulatus) would alter within-egg embryonic phenotype, particularly heart rates. We found that embryos from CORT-treated mothers had heart rates that increased faster with increasing temperature, resulting in higher heart rates at developmentally relevant temperatures but similar heart rates at maintenance relevant temperatures, compared with embryos of control mothers. Thus, maternal CORT appears to alter the physiology of pre-natal offspring. This may speed development and decrease the amount of time spent in eggs, the most vulnerable stage of life.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1098/rsbl.2018.0718DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6371906PMC
January 2019

Maternal stress alters the phenotype of the mother, her eggs and her offspring in a wild-caught lizard.

J Anim Ecol 2018 11 30;87(6):1685-1697. Epub 2018 Aug 30.

Department of Ecosystem Science and Management, Pennsylvania State University, University Park, Pennsylvania.

While biomedical researchers have long appreciated the influence of maternally derived glucocorticoids (GCs) on offspring phenotype, ecologists have only recently begun exploring its impact in wild animals. Interpreting biomedical findings within an ecological context has posited that maternal stress, mediated by elevations of maternal GCs, may play an adaptive role preparing offspring for a stressful or rigorous environment. Yet, the influence of maternal stress on offspring phenotype has been little studied in wild animals. We experimentally elevated GCs to ecologically relevant levels (mimicking increases in maternal stress hormones following a nonlethal predator encounter, a heat challenge, or a chasing or confinement stressor) in female eastern fence lizards Sceloporus undulatus during gestation. We tested the hypothesis that maternally derived stress hormones themselves are sufficient to alter offspring phenotype. Specifically, we examined the effects of experimentally elevated maternal GCs on fitness-relevant traits of the mother, her eggs and her subsequent offspring. We found that daily maternal GC elevation: (a) increased maternal antipredator behaviours and postlaying glucose levels; (b) had no effect on egg morphology or caloric value, but altered yolk hormone (elevated GC) and nutrient content; and (c) altered offspring phenotype including stress-relevant physiology, morphology and behaviour. These findings reveal that maternally derived GCs alone can alter offspring phenotype in a wild animal, changes that may be mediated via maternal behaviour, and egg hormone and nutrient content. Understanding the ecological consequences of these effects under different environmental conditions will be critical for determining the adaptive significance of elevated maternal GCs for offspring.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/1365-2656.12891DOI Listing
November 2018

A Vertically Integrated Online Radiology Curriculum Developed as a Cognitive Apprenticeship: Impact on Student Performance and Learning.

Acad Radiol 2016 Feb 21;23(2):252-61. Epub 2015 Dec 21.

Stritch School of Medicine, Loyola University Medical Center, 2160 S. First Ave., Maywood, IL 60546.

Rationale And Objectives: The principles of Collins' cognitive apprenticeship model were used to design a radiology curriculum in which medical students practice radiological skills using online case-based modules. The modules are embedded within clinical third-year clerkships, and students are provided with personalized feedback from the instructors. We describe the development of the vertical online radiology curriculum and evaluate its impact on student achievement and learning process using a mixed method approach.

Materials And Methods: The curriculum was developed over a 2-year period. Student participation was voluntary in the first year and mandatory in the second year. For quantitative curriculum evaluation, student metrics for voluntary versus mandatory groups were assessed using independent sample t tests and variable entry method regression analysis. For qualitative analysis, responses from a survey of students about the value of the curriculum were organized into defined themes using consensus coding.

Results: Mandatory participation significantly improved (p = .001) the mean radiology examination score (82 %) compared to the voluntary group (73%), suggesting that mandatory participation had a beneficial effect on student performance. Potential preexisting differences in underlying general academic performance were accounted for by including mean basic science grades as the first variable in the regression model. The significant increase in R(2) from .16 to .28 when number of radiology cases completed was added to the original model, and the greater value of the standardized beta for this variable, suggest that the curriculum made a significant contribution to students' radiology examination scores beyond their baseline academic performance. Five dominant themes about curricular characteristics that enhanced student learning and beneficial outcomes emerged from consensus coding. These themes were (1) self-paced design, (2) receiving feedback from faculty, (3) clinical relevance of cases, (4) gaining confidence in interpreting radiological images, and (5) transfer of conceptual knowledge to actual practice.

Conclusions: The vertically integrated online radiology curriculum can positively impact student performance and learning process in the context of the cognitive apprenticeship model.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.acra.2015.09.018DOI Listing
February 2016

Development of Dive Capacity in Northern Elephant Seals (Mirounga angustirostris): Reduced Body Reserves at Weaning Are Associated with Elevated Body Oxygen Stores during the Postweaning Fast.

Physiol Biochem Zool 2015 Sep-Oct;88(5):471-82. Epub 2015 Jul 1.

Department of Biology, Sonoma State University, Rohnert Park, California 94928; 2Extreme Physiology Laboratory, Department of Biology, Colorado State University, Fort Collins, Colorado 80523.

Developmental increases in dive capacity have been reported in numerous species of air-breathing marine vertebrates. Previous studies in juvenile phocid seals suggest that increases in physiological dive capacity during the postweaning fast (PWF) are critical to support independent aquatic foraging. Although there is a strong relationship between size at weaning and PWF duration and body reserves at weaning vary considerably, few studies have considered whether such variation in body reserve magnitude promotes phenotypic modulation of dive capacity development during the PWF. Phenotypic modulation, a form of developmental plasticity in which rates and degrees of expression of the developmental program are modulated by environmental factors, may enhance diving capacity in weanlings with reduced PWF durations due to smaller body reserves at weaning if reduced body reserves promote accelerated development of dive capacity. We longitudinally measured changes in blood and muscle oxygen stores and muscle metabolic enzymes over the first 8 wk of the PWF in northern elephant seals and determined whether rates of change in these parameters varied with body reserves at weaning. We assessed whether erythropoietin (EPO), thyroid hormones, serum nonesterified fatty acid levels, and iron status influenced blood and muscle oxygen store development or were influenced by body reserves at weaning. Although mass-specific plasma volume and blood volume were relatively stable across the fast, both were elevated in animals with reduced body reserves. Surprisingly, hemoglobin and mean corpuscular hemoglobin concentrations declined over the PWF while hematocrit remained stable, and these variables were not associated with body reserves or EPO. Swimming muscle myoglobin and serum iron levels increased rapidly early in the PWF and were not related to body reserves. Patterns in maximal activities of muscle enzymes suggested a decline in total aerobic and anaerobic metabolic capacity over the PWF, despite maintenance of fat oxidation capacity. These results suggest that only development of blood volume is increased in smaller weanlings and that extended fasting durations in larger weanlings do not improve physiological dive capacity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1086/682386DOI Listing
September 2016

Case study of an evaluation coaching model: exploring the role of the evaluator.

Eval Program Plann 2015 Apr 17;49:124-36. Epub 2015 Jan 17.

Loyola University Chicago, School of Education, 820 N Michigan Ave, Chicago, IL 60611, United States. Electronic address:

This study examined the role of the external evaluator as a coach. More specifically, using an evaluative inquiry framework (Preskill & Torres, 1999a; Preskill & Torres, 1999b), it explored the types of coaching that an evaluator employed to promote individual, team and organizational learning. The study demonstrated that evaluation coaching provided a viable means for an organization with a limited budget to conduct evaluations through support of a coach. It also demonstrated how the coaching processes supported the development of evaluation capacity within the organization. By examining coaching models outside of the field of evaluation, this study identified two forms of coaching--results coaching and developmental coaching--that promoted evaluation capacity building and have not been previously discussed in the evaluation literature.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.evalprogplan.2015.01.002DOI Listing
April 2015

Metabolic responses to adrenocorticotropic hormone (ACTH) vary with life-history stage in adult male northern elephant seals.

Gen Comp Endocrinol 2014 Aug 2;204:150-7. Epub 2014 May 2.

Dept. of Biology, Sonoma State University, 1801 E. Cotati Ave., Rohnert Park, CA 94928, USA. Electronic address:

Strong individual and life-history variation in serum glucocorticoids has been documented in many wildlife species. Less is known about variation in hypothalamic-pituitary-adrenal (HPA) axis responsiveness and its impact on metabolism. We challenged 18 free-ranging adult male northern elephant seals (NES) with an intramuscular injection of slow-release adrenocorticotropic hormone (ACTH) over 3 sample periods: early in the breeding season, after 70+ days of the breeding fast, and during peak molt. Subjects were blood sampled every 30 min for 2h post-injection. Breeding animals were recaptured and sampled at 48 h. In response to the ACTH injection, cortisol increased 4-6-fold in all groups, and remained elevated at 48 h in early breeding subjects. ACTH was a strong secretagogue for aldosterone, causing a 3-8-fold increase in concentration. Cortisol and aldosterone responses did not vary between groups but were correlated within individuals. The ACTH challenge produced elevations in plasma glucose during late breeding and molting, suppressed testosterone and thyroid hormone at 48 h in early breeding, and increased plasma non-esterified fatty acids and ketoacids during molting. These data suggest that sensitivity of the HPA axis is maintained but the metabolic impacts of cortisol and feedback inhibition of the axis vary with life history stage. Strong impacts on testosterone and thyroid hormone suggest the importance of maintaining low cortisol levels during the breeding fast. These data suggest that metabolic adaptations to extended fasting in NES include alterations in tissue responses to hormones that mitigate deleterious impacts of acute or moderately sustained stress responses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ygcen.2014.04.024DOI Listing
August 2014

Associations between formative practice quizzes and summative examination outcomes in a medical anatomy course.

Anat Sci Educ 2015 Jan-Feb;8(1):37-44. Epub 2014 Mar 4.

Program in Cell Biology, Neurobiology and Anatomy, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; Ralph P. Leischner Jr., M.D. Institute for Medical Education, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois.

Formative practice quizzes have become common resources for self-evaluation and focused reviews of course content in the medical curriculum. We conducted two separate studies to (1) compare the effects of a single or multiple voluntary practice quizzes on subsequent summative examinations and (2) examine when students are most likely to use practice quizzes relative to the summative examinations. In the first study, providing a single on-line practice quiz followed by instructor feedback had no effect on examination average grades compared to the previous year or student performances on similar questions. However, there were significant correlations between student performance on each practice quiz and each summative examination (r = 0.42 and r = 0.24). When students were provided multiple practice quizzes with feedback (second study), there were weak correlations between the frequency of use and performance on each summative examination (r = 0.17 and r = 0.07). The frequency with which students accessed the practice quizzes was greatest the day before each examination. In both studies, there was a decline in the level of student utilization of practice quizzes over time. We conclude that practice quizzes provide some predictive value for performances on summative examinations. Second, making practice quizzes available for longer periods prior to summative examinations does not promote the use of the quizzes as a study strategy because students appear to use them mostly to assess knowledge one to two days prior to examinations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ase.1442DOI Listing
September 2015
-->