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Lazarus M, Sergiel A, Ferenčaković M, Orct T, Kapronczai L, Pađen L, Janz DM, Reljić S, Zwijacz-Kozica T, Zięba F, Selva N, Huber Đ. Stress and reproductive hormones in hair associated with contaminant metal(loid)s of European brown bear (Ursus arctos). CHEMOSPHERE 2023; 325:138354. [PMID: 36907481 DOI: 10.1016/j.chemosphere.2023.138354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 03/06/2023] [Accepted: 03/07/2023] [Indexed: 06/18/2023]
Abstract
Environmental contaminants like arsenic (As), cadmium (Cd), mercury (Hg) or lead (Pb) may disrupt hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes due to their endocrine toxicity potential. Resulting long-term physiological stress or adverse effects on wildlife reproduction and ontogeny may cause detrimental effects at the individual and population levels. However, data on environmental metal(loid)s' impact on reproductive and stress hormones in wildlife, especially large terrestrial carnivores, are scarce. Hair cortisol, progesterone and testosterone concentrations were quantified and modelled with hair As, Cd, total Hg, Pb, biological, environmental and sampling factors to test for potential effects in free-ranging brown bears (Ursus arctos) from Croatia (N = 46) and Poland (N = 27). Testosterone in males (N = 48) and females (N = 25) showed positive associations with Hg and an interaction between Cd and Pb, but a negative association with interaction between age and Pb. Higher testosterone was found in hair during its growth phase compared to quiescent phase. Body condition index was negatively associated with hair cortisol and positively associated with hair progesterone. Year and conditions of sampling were important for cortisol variation, while maturity stage for progesterone variation (lower concentrations in cubs and yearlings compared to subadult and adult bears). These findings suggest that environmental levels of Cd, Hg and Pb might influence the HPG axis in brown bears. Hair was shown to be a reliable non-invasive sample for investigating hormonal fluctuations in wildlife while addressing individual and sampling specificities.
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Affiliation(s)
- Maja Lazarus
- Institute for Medical Research and Occupational Health, Zagreb, Croatia.
| | - Agnieszka Sergiel
- Institute of Nature Conservation of Polish Academy of Sciences, Kraków, Poland.
| | | | - Tatjana Orct
- Institute for Medical Research and Occupational Health, Zagreb, Croatia.
| | | | - Lana Pađen
- Faculty of Veterinary Medicine, University of Zagreb, Croatia.
| | - David M Janz
- Toxicology Centre, University of Saskatchewan, Saskatoon, Canada; Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Canada.
| | - Slaven Reljić
- Faculty of Veterinary Medicine, University of Zagreb, Croatia.
| | | | | | - Nuria Selva
- Institute of Nature Conservation of Polish Academy of Sciences, Kraków, Poland; Departamento de Ciencias Integradas, Facultad de Ciencias Experimentales, Centro de Estudios Avanzados en Física, Matemáticas y Computación, Universidad de Huelva, Huelva, Spain.
| | - Đuro Huber
- Institute of Nature Conservation of Polish Academy of Sciences, Kraków, Poland; Faculty of Veterinary Medicine, University of Zagreb, Croatia.
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Babic NL, Johnstone CP, Reljić S, Sergiel A, Huber Đ, Reina RD. Evaluation of physiological stress in free-ranging bears: current knowledge and future directions. Biol Rev Camb Philos Soc 2023; 98:168-190. [PMID: 36176191 PMCID: PMC10086944 DOI: 10.1111/brv.12902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 08/25/2022] [Accepted: 08/31/2022] [Indexed: 01/12/2023]
Abstract
Stress responses, which are mediated by the neurogenic system (NS) and hypothalamic-pituitary-adrenal (HPA) axis help vertebrates maintain physiological homeostasis. Fight-or-flight responses are activated by the NS, which releases norepinephrine/noradrenaline and epinephrine/adrenaline in response to immediate stressors, whilst the HPA axis releases glucocorticoid hormones (e.g. cortisol and corticosterone) to help mitigate allostatic load. There have been many studies on stress responses of captive animals, but they are not truly reflective of typical ranges or the types of stressors encountered by free-ranging wildlife, such as responses and adaptation to environmental change, which are particularly important from a conservation perspective. As stress can influence the composition of age and sex classes of free-ranging populations both directly and indirectly, ecological research must be prioritised towards more vulnerable taxa. Generally, large predators tend to be particularly at risk of anthropogenically driven population declines because they exhibit reduced behavioural plasticity required to adapt to changing landscapes and exist in reduced geographic ranges, have small population sizes, low fecundity rates, large spatial requirements and occupy high trophic positions. As a keystone species with a long history of coexistence with humans in highly anthropogenic landscapes, there has been growing concern about how humans influence bear behaviour and physiology, via numerous short- and long-term stressors. In this review, we synthesise research on the stress response in free-ranging bear populations and evaluate the effectiveness and limitations of current methodology in measuring stress in bears to identify the most effective metrics for future research. Particularly, we integrate research that utilised haematological variables, cardiac monitors and Global Positioning System (GPS) collars, serum/plasma and faecal glucocorticoid concentrations, hair cortisol levels, and morphological metrics (primarily skulls) to investigate the stress response in ursids in both short- and long-term contexts. We found that in free-ranging bears, food availability and consumption have the greatest influence on individual stress, with mixed responses to anthropogenic influences. Effects of sex and age on stress are also mixed, likely attributable to inconsistent methods. We recommend that methodology across all stress indicators used in free-ranging bears should be standardised to improve interpretation of results and that a wider range of species should be incorporated in future studies.
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Affiliation(s)
- Natarsha L Babic
- School of Biological Sciences, Monash University, 25 Rainforest Walk, Clayton, 3800, Victoria, Australia
| | - Christopher P Johnstone
- School of Biological Sciences, Monash University, 25 Rainforest Walk, Clayton, 3800, Victoria, Australia
| | - Slaven Reljić
- Faculty of Veterinary Medicine, University of Zagreb, Heinzelova 55, Zagreb, 10000, Croatia
| | - Agnieszka Sergiel
- Institute of Nature Conservation, Polish Academy of Sciences, Adama Mickiewicza 33, Krakow, 31120, Poland
| | - Đuro Huber
- Faculty of Veterinary Medicine, University of Zagreb, Heinzelova 55, Zagreb, 10000, Croatia.,Institute of Nature Conservation, Polish Academy of Sciences, Adama Mickiewicza 33, Krakow, 31120, Poland
| | - Richard D Reina
- School of Biological Sciences, Monash University, 25 Rainforest Walk, Clayton, 3800, Victoria, Australia
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Whiteman JP, Harlow HJ, Durner GM, Regehr EV, Amstrup SC, Pagano AM, Ben‐David M. The acute physiological response of polar bears to helicopter capture. J Wildl Manage 2022; 86:e22238. [PMID: 35915725 PMCID: PMC9324155 DOI: 10.1002/jwmg.22238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Revised: 02/25/2022] [Accepted: 03/29/2022] [Indexed: 11/28/2022]
Abstract
Many wildlife species are live captured, sampled, and released; for polar bears (Ursus maritimus) capture often requires chemical immobilization via helicopter darting. Polar bears reduce their activity for approximately 4 days after capture, likely reflecting stress recovery. To better understand this stress, we quantified polar bear activity (via collar‐mounted accelerometers) and body temperature (via loggers in the body core [Tabd] and periphery [Tper]) during 2–6 months of natural behavior, and during helicopter recapture and immobilization. Recapture induced bouts of peak activity higher than those that occurred during natural behavior for 2 of 5 bears, greater peak Tper for 3 of 6 bears, and greater peak Tabd for 1 of 6 bears. High body temperature (>39.0°C) occurred in Tper for 3 of 6 individuals during recapture and 6 of 6 individuals during natural behavior, and in Tabd for 2 of 6 individuals during recapture and 3 of 6 individuals during natural behavior. Measurements of Tabd and Tper correlated with rectal temperatures measured after immobilization, supporting the use of rectal temperatures for monitoring bear response to capture. Using a larger dataset (n = 66 captures), modeling of blood biochemistry revealed that maximum ambient temperature during recapture was associated with a stress leukogram (7–26% decline in percent lymphocytes, 12–21% increase in percent neutrophils) and maximum duration of helicopter operations had a similar but smaller effect. We conclude that polar bear activity and body temperature during helicopter capture are similar to that which occurs during the most intense events of natural behavior; high body temperature, especially in warm capture conditions, is a key concern; additional study of stress leukograms in polar bears is needed; and additional data collection regarding capture operations would be useful.
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Affiliation(s)
- John P. Whiteman
- Department of Biological Sciences, Old Dominion University Hampton Boulevard Norfolk VA 23529 USA
| | - Henry J. Harlow
- Department of Zoology and Physiology, University of Wyoming University Avenue Laramie WY 82071 USA
| | - George M. Durner
- Alaska Science Center, US Geological Survey University Drive Anchorage AK 99508 USA
| | - Eric V. Regehr
- Polar Science Center University of Washington NE 40th Street Seattle WA 98105 USA
| | | | - Anthony M. Pagano
- Alaska Science Center, US Geological Survey University Drive Anchorage AK 99508 USA
| | - Merav Ben‐David
- Department of Zoology and Physiology, University of Wyoming University Avenue Laramie WY 82071 USA
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Wilson AE, Michaud SA, Jackson AM, Stenhouse G, McClelland CJR, Coops NC, Janz DM. Protein biomarkers in serum as a conservation tool to assess reproduction: a case study on brown bears ( Ursus arctos). CONSERVATION PHYSIOLOGY 2021; 9:coab091. [PMID: 34888057 PMCID: PMC8651255 DOI: 10.1093/conphys/coab091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 10/26/2021] [Accepted: 11/01/2021] [Indexed: 06/13/2023]
Abstract
Monitoring the reproductive characteristics of a species can complement existing conservation strategies by understanding the mechanisms underlying demography. However, methodology to determine important aspects of female reproductive biology is often absent in monitoring programs for large mammals. Protein biomarkers may be a useful tool to detect physiological changes that are indicative of reproductive state. This study aimed to identify protein biomarkers of reproductive status in serum collected from free-ranging female brown bears (Ursus arctos) in Alberta, Canada, from 2001 to 2018. We hypothesized that the expression of proteins related to reproduction in addition to energetics and stress can be used to answer specific management-focused questions: (i) identify when a female is pregnant, (ii) detect if a female is lactating, (iii) determine age of sexual maturity (i.e. primiparity) and (iv) assess female fertility (i.e. reproduction rate). Furthermore, we investigated if silver spoon effects (favourable early life conditions provide fitness benefits through adulthood) could be determined using protein expression. A target panel of 19 proteins with established relationships to physiological function was measured by peptide-based analysis using liquid chromatography and multiple reaction monitoring mass spectrometry and their differential expression was evaluated using a Wilcoxon signed-rank test. We found biomarkers of pregnancy (apolipoprotein B-100 and afamin), lactation (apolipoprotein B-100 and alpha-2-macroglobulin) and sexual maturity (corticosteroid-binding globulin), but there were no statistically significant relationships with protein expression and fertility. The expression of proteins related to reproduction (afamin) and energetics (vitamin-D binding protein) was associated with the nutritional quality of the individual's present habitat rather than their early life habitat. This study highlights potential biomarkers of reproductive status and provides additional methods for monitoring physiological function in wildlife to inform conservation.
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Affiliation(s)
- Abbey E Wilson
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan S7N 5B4, Canada
| | - Sarah A Michaud
- The University of Victoria Genome BC Proteomics Centre, 4464 Markham St #3101, Victoria, British Columbia V8Z 7X8, Canada
| | - Angela M Jackson
- The University of Victoria Genome BC Proteomics Centre, 4464 Markham St #3101, Victoria, British Columbia V8Z 7X8, Canada
| | - Gordon Stenhouse
- Grizzly Bear Program, fRI Research, 1176 Switzer Drive, Hinton, Alberta T7V 1V3, Canada
| | | | - Nicholas C Coops
- Department of Forest Resource Management, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - David M Janz
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan S7N 5B4, Canada
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Boonstra R, Bodner K, Bosson C, Delehanty B, Richardson ES, Lunn NJ, Derocher AE, Molnár PK. The stress of Arctic warming on polar bears. GLOBAL CHANGE BIOLOGY 2020; 26:4197-4214. [PMID: 32364624 DOI: 10.1111/gcb.15142] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 04/15/2020] [Accepted: 04/23/2020] [Indexed: 05/25/2023]
Abstract
Arctic ecosystems are changing rapidly in response to climate warming. While Arctic mammals are highly evolved to these extreme environments, particularly with respect to their stress axis, some species may have limited capacity to adapt to this change. We examined changes in key components of the stress axis (cortisol and its carrier protein-corticosteroid binding globulin [CBG]) in polar bears (Ursus maritimus) from western Hudson Bay (N = 300) over a 33 year period (1983-2015) during which time the ice-free period was increasing. Changing sea ice phenology limits spring hunting opportunities and extends the period of onshore fasting. We assessed the response of polar bears to a standardized stressor (helicopter pursuit, darting, and immobilization) during their onshore fasting period (late summer-autumn) and quantified the serum levels of the maximum corticosteroid binding capacity (MCBC) of CBG, the serum protein that binds cortisol strongly, and free cortisol (FC). We quantified bear condition (age, sex, female with cubs or not, fat condition), sea ice (breakup in spring-summer, 1 year lagged freeze-up in autumn), and duration of fasting until sample collection as well as cumulative impacts of the latter environmental traits from the previous year. Data were separated into "good" years (1983-1990) when conditions were thought to be optimal and "poor" years (1991-2015) when sea ice conditions deteriorated and fasting on land was extended. MCBC explained 39.4% of the variation in the good years, but only 28.1% in the poor ones, using both biological and environmental variables. MCBC levels decreased with age. Changes in FC were complex, but more poorly explained. Counterintuitively, MCBC levels increased with increased time onshore, 1 year lag effects, and in poor ice years. We conclude that MCBC is a biomarker of stress in polar bears and that the changes we document are a consequence of climate warming.
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Affiliation(s)
- Rudy Boonstra
- Centre for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
| | - Korryn Bodner
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
| | - Curtis Bosson
- Centre for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
| | - Brendan Delehanty
- Centre for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
| | - Evan S Richardson
- Wildlife Research Division, Science and Technology Branch, Environment and Climate Change Canada, Winnipeg, MB, Canada
| | - Nicholas J Lunn
- Environment and Climate Change Canada, Biological Sciences Building, University of Alberta, Edmonton, AB, Canada
| | - Andrew E Derocher
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Péter K Molnár
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
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Wilson AE, Michaud SA, Jackson AM, Stenhouse G, Coops NC, Janz DM. Development and validation of protein biomarkers of health in grizzly bears. CONSERVATION PHYSIOLOGY 2020; 8:coaa056. [PMID: 32607241 PMCID: PMC7311831 DOI: 10.1093/conphys/coaa056] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 04/09/2020] [Accepted: 05/31/2020] [Indexed: 06/11/2023]
Abstract
Large carnivores play critical roles in the maintenance and function of natural ecosystems; however, the populations of many of these species are in decline across the globe. Therefore, there is an urgent need to develop novel techniques that can be used as sensitive conservation tools to detect new threats to the health of individual animals well in advance of population-level effects. Our study aimed to determine the expression of proteins related to energetics, reproduction and stress in the skin of grizzly bears (Ursus arctos) using a liquid chromatography and multiple reaction monitoring mass spectrometry assay. We hypothesized that a suite of target proteins could be measured using this technique and that the expression of these proteins would be associated with biological (sex, age, sample location on body) and environmental (geographic area, season, sample year) variables. Small skin biopsies were collected from free-ranging grizzly bears in Alberta, Canada, from 2013 to 2019 (n = 136 samples from 111 individuals). Over 700 proteins were detected in the skin of grizzly bears, 19 of which were chosen as targets because of their established roles in physiological function. Generalized linear mixed model analysis was used for each target protein. Results indicate that sample year influenced the majority of proteins, suggesting that physiological changes may be driven in part by responses to changes in the environment. Season influenced the expression of proteins related to energetics, reproduction and stress, all of which were lower during fall compared to early spring. The expression of proteins related to energetics and stress varied by geographic area, while the majority of proteins that were affected by biological attributes (age class, sex and age class by sex interaction) were related to reproduction and stress. This study provides a novel method by which scientists and managers can further assess and monitor physiological function in wildlife.
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Affiliation(s)
- Abbey E Wilson
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan S7N 5B3, Canada
| | - Sarah A Michaud
- The University of Victoria Genome BC Proteomics Centre, 4464 Markham St #3101, Victoria, British Columbia V8Z 7X8, Canada
| | - Angela M Jackson
- The University of Victoria Genome BC Proteomics Centre, 4464 Markham St #3101, Victoria, British Columbia V8Z 7X8, Canada
| | - Gordon Stenhouse
- Foothills Research Institute, Grizzly Bear Program, 1176 Switzer Drive, Hinton, Alberta T7V 1V3, Canada
| | - Nicholas C Coops
- Department of Forest Resource Management, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - David M Janz
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan S7N 5B3, Canada
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Wilson AE, Fair PA, Carlson RI, Houde M, Cattet M, Bossart GD, Houser DS, Janz DM. Environment, endocrinology, and biochemistry influence expression of stress proteins in bottlenose dolphins. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2019; 32:100613. [PMID: 31382157 DOI: 10.1016/j.cbd.2019.100613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/15/2019] [Accepted: 07/24/2019] [Indexed: 10/26/2022]
Abstract
Natural and anthropogenic stressors have been reported to impact the health of marine mammals. Therefore, investigation of quantifiable biomarkers in response to stressors is required. We hypothesized that stress protein expression would be associated with biological and health variables in wild and managed-care bottlenose dolphins (Tursiops truncatus). To test this hypothesis, our study objectives were to (1) determine if stress proteins in skin, white blood cells (WBCs), and plasma could be measured with an antibody-based microarray, (2) measure stress-protein expression relative to biological data (location, sex, age, environment), and (3) determine if stress-protein expression was associated with endocrine, hematological, biochemical and serological variables and gene expression in bottlenose dolphins. Samples were collected from two wild groups (n = 28) and two managed-care groups (n = 17). Proteins involved in the HPA axis, apoptosis, proteotoxicity, and inflammation were identified as stress proteins. The expression of 3 out of 33 proteins was significantly (P < 0.05) greater in skin than plasma and WBCs. Male dolphins had significantly greater expression levels for 10 proteins in skin compared to females. The greatest number of stress-associated proteins varied by the dolphins' environment; nine were greater in managed-care dolphins and 15 were greater in wild dolphins, which may be related to wild dolphin disease status. Protein expression in skin and WBCs showed many positive relationships with measures of plasma endocrinology and biochemistry. This study provides further understanding of the underlying mechanisms of the stress response in bottlenose dolphins and application of a combination of novel methods to measure stress in wildlife.
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Affiliation(s)
- Abbey E Wilson
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan S7N 5B3, Canada
| | - Patricia A Fair
- National Oceanic and Atmospheric Administration, National Ocean Service, Center for Coastal Environmental Health & Biomolecular Research, 219 Fort Johnson Road, Charleston, SC 29412, United States of America; Department of Public Health Sciences, Medical University of South Carolina, 221 Fort Johnson Road, Charleston, SC 29412, United States of America
| | - Ruth I Carlson
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan S7N 5B3, Canada
| | - Magali Houde
- Aquatic Contaminants Research Division, Environment and Climate Change Canada, 105 McGill Street, Montreal, Quebec H2Y 2E7, Canada
| | - Marc Cattet
- RGL Recovery Wildlife Health & Veterinary Services, 415 Mount Allison Crescent, Saskatoon, Saskatchewan S7H 4A6, Canada
| | - Gregory D Bossart
- Georgia Aquarium, 225 Baker St NW, Atlanta, GA 30313, United States of America; Division of Comparative Pathology, Miller School of Medicine, University of Miami, PO Box 016960 (R-46), Miami, FL 33101, United States of America
| | - Dorian S Houser
- National Marine Mammal Foundation, 2240 Shelter Island Dr, San Diego, CA 92106, United States of America
| | - David M Janz
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan S7N 5B3, Canada.
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Desantis LM, Bowman J, Faught E, Boonstra R, Vijayan MM, Burness G. Corticosteroid-binding globulin levels in North American sciurids: implications for the flying squirrel stress axis. CAN J ZOOL 2018. [DOI: 10.1139/cjz-2017-0300] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Corticosteroid-binding globulin (CBG) helps to regulate tissue bioavailability of circulating glucocorticoids (GCs), and in most vertebrates, ≥80%–90% of GCs bind to this protein. New World flying squirrels have higher plasma total cortisol levels (the primary corticosteroid in sciurids) than most vertebrates. Recent research suggests that flying squirrels have either low amounts of CBG or CBG molecules that have a low binding affinity for cortisol, as this taxon appears to exhibit very low proportions of cortisol bound to CBG. To test whether CBG levels have been adjusted over evolutionary time, we assessed the levels of this protein in the plasma of northern (Glaucomys sabrinus (Shaw, 1801)) and southern (Glaucomys volans (Linnaeus, 1758)) flying squirrels using immunoblotting, and compared the relative levels among three phylogenetically related species of sciurids. We also compared the pattern of CBG levels with cortisol levels for the same individuals. Flying squirrels had higher cortisol levels than the other species, but similar levels of CBG to their closest relatives (tree squirrels). We conclude that CBG levels in flying squirrels have not been adjusted over evolutionary time, and thus, the uncoupling of CBG levels from cortisol concentrations may represent an evolutionary modification in the lineage leading to New World flying squirrels.
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Affiliation(s)
- Lanna M. Desantis
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON K9L 0G2, Canada
| | - Jeff Bowman
- Ontario Ministry of Natural Resources and Forestry, Trent University, DNA Building, Peterborough, ON K9L 1Z8, Canada
| | - Erin Faught
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Rudy Boonstra
- Centre for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
| | | | - Gary Burness
- Department of Biology, Trent University, Peterborough, ON K9L 0G2, Canada
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Desantis LM, Bowman J, Vijayan MM, Burness G. Seasonal changes in acute stressor-mediated plasma glucocorticoid regulation in New World flying squirrels. Gen Comp Endocrinol 2018; 266:78-86. [PMID: 29763585 DOI: 10.1016/j.ygcen.2018.04.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Revised: 04/13/2018] [Accepted: 04/25/2018] [Indexed: 10/16/2022]
Abstract
Southern flying squirrels have higher circulating cortisol levels than most vertebrates. However, regulation of tissue exposure to cortisol by the hormone's carrier protein, corticosteroid-binding globulin (CBG), appears to be altered due to lower-than-expected CBG expression levels, and a reduced affinity for cortisol. To assess the capacity of flying squirrels to regulate acute stress-mediated cortisol levels, we used the dexamethasone (DEX) suppression test followed by the adrenocorticotropic hormone (ACTH) stimulation test in both the breeding and non-breeding seasons, and quantified resultant changes in plasma cortisol and relative CBG levels. Regulation of cortisol via negative feedback, and the acute stress response appeared to function as they do in other vertebrates during the breeding season, but response to DEX in the non-breeding season showed that the sensitivity of the negative feedback mechanism changed across seasons. The relatively high concentrations of DEX required to induce negative feedback suggests that southern flying squirrels have a reduced sensitivity to cortisol compared with other vertebrates, and that high circulating cortisol levels may be required to compensate for low target tissue responsiveness in this species. Cortisol, but not CBG levels, were higher during the non-breeding than breeding season, and females had higher cortisol and CBG levels than males. Our data suggest that flying squirrel cortisol levels are regulated by negative feedback at a higher set point than in related species. Seasonal changes in cortisol levels, target tissue sensitivity to DEX, and in the capacity to respond to stressors appear to be part of the underlying physiology of southern flying squirrels, and may be required to maximize fitness in the face of tradeoffs between survival and reproduction.
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Affiliation(s)
- Lanna M Desantis
- Environmental & Life Sciences Graduate Program, Trent University, Peterborough, ON K9J 0G2, Canada.
| | - Jeff Bowman
- Ontario Ministry of Natural Resources and Forestry, Trent University, DNA Building, Peterborough, ON K9J 0G2, Canada
| | - Mathilakath M Vijayan
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Gary Burness
- Department of Biology, Trent University, Peterborough, ON K9L 0G2, Canada
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Atkinson S, Crocker D, Houser D, Mashburn K. Stress physiology in marine mammals: how well do they fit the terrestrial model? J Comp Physiol B 2015; 185:463-86. [PMID: 25913694 DOI: 10.1007/s00360-015-0901-0] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 03/23/2015] [Accepted: 04/09/2015] [Indexed: 12/28/2022]
Abstract
Stressors are commonly accepted as the causal factors, either internal or external, that evoke physiological responses to mediate the impact of the stressor. The majority of research on the physiological stress response, and costs incurred to an animal, has focused on terrestrial species. This review presents current knowledge on the physiology of the stress response in a lesser studied group of mammals, the marine mammals. Marine mammals are an artificial or pseudo grouping from a taxonomical perspective, as this group represents several distinct and diverse orders of mammals. However, they all are fully or semi-aquatic animals and have experienced selective pressures that have shaped their physiology in a manner that differs from terrestrial relatives. What these differences are and how they relate to the stress response is an efflorescent topic of study. The identification of the many facets of the stress response is critical to marine mammal management and conservation efforts. Anthropogenic stressors in marine ecosystems, including ocean noise, pollution, and fisheries interactions, are increasing and the dramatic responses of some marine mammals to these stressors have elevated concerns over the impact of human-related activities on a diverse group of animals that are difficult to monitor. This review covers the physiology of the stress response in marine mammals and places it in context of what is known from research on terrestrial mammals, particularly with respect to mediator activity that diverges from generalized terrestrial models. Challenges in conducting research on stress physiology in marine mammals are discussed and ways to overcome these challenges in the future are suggested.
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Affiliation(s)
- Shannon Atkinson
- School of Fisheries and Ocean Sciences, Juneau Center, University of Alaska Fairbanks, 17101 Pt. Lena Loop Road, Juneau, AK, 99801, USA,
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Cattet M, Macbeth BJ, Janz DM, Zedrosser A, Swenson JE, Dumond M, Stenhouse GB. Quantifying long-term stress in brown bears with the hair cortisol concentration: a biomarker that may be confounded by rapid changes in response to capture and handling. CONSERVATION PHYSIOLOGY 2014; 2:cou026. [PMID: 27293647 PMCID: PMC4732478 DOI: 10.1093/conphys/cou026] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 05/26/2014] [Accepted: 05/29/2014] [Indexed: 05/19/2023]
Abstract
The measurement of cortisol in hair is becoming important in studying the role of stress in the life history, health and ecology of wild mammals. The hair cortisol concentration (HCC) is generally believed to be a reliable indicator of long-term stress that can reflect frequent or prolonged activation of the hypothalamic-pituitary-adrenal axis over weeks to months through passive diffusion from the blood supply to the follicular cells that produce the hair. Diffusion of cortisol from tissues surrounding the follicle and glandular secretions (sebum and sweat) that coat the growing hair may also affect the HCC, but the extent of these effects is thought to be minimal. In this study, we report on a range of factors that are associated with, and possibly influence, cortisol concentrations in the hair of free-ranging brown bears (Ursus arctos). Through two levels of analyses that differed in sample sizes and availability of predictor variables, we identified the presence or absence of capture, restraint and handling, as well as different methods of capture, as significant factors that appeared to influence HCC in a time frame that was too short (minutes to hours) to be explained by passive diffusion from the blood supply alone. Furthermore, our results suggest that HCC was altered after hair growth had ceased and blood supply to the hair follicle was terminated. However, we also confirmed that HCC was inversely associated with brown bear body condition and was, therefore, responsive to diminished food availability/quality and possibly other long-term stressors that affect body condition. Collectively, our findings emphasize the importance of further elucidating the mechanisms of cortisol accumulation in hair and the influence of long- and short-term stressors on these mechanisms.
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Affiliation(s)
- Marc Cattet
- Canadian Wildlife Health Cooperative, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5B4
- Corresponding author: Canadian Wildlife Health Cooperative, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5B4. Tel: +1 306 966 2162.
| | - Bryan J. Macbeth
- Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4Z6
| | - David M. Janz
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5B4
| | - Andreas Zedrosser
- Department of Environmental and Health Studies, Telemark University College, 3800 Bø, Norway
| | - Jon E. Swenson
- Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, NO-1432 Ås, Norway
| | - Mathieu Dumond
- Department of Environment, Government of Nunavut, Kugluktuk, Nunavut, Canada X0B 0E0
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12
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Ware JV, Nelson OL, Robbins CT, Carter PA, Sarver BAJ, Jansen HT. Endocrine rhythms in the brown bear (Ursus arctos): Evidence supporting selection for decreased pineal gland size. Physiol Rep 2013; 1:e00048. [PMID: 24303132 PMCID: PMC3835004 DOI: 10.1002/phy2.48] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 07/09/2013] [Accepted: 07/10/2013] [Indexed: 12/21/2022] Open
Abstract
Many temperate zone animals adapt to seasonal changes by altering their physiology. This is mediated in large part by endocrine signals that encode day length and regulate energy balance and metabolism. The objectives of this study were to determine if the daily patterns of two important hormones, melatonin and cortisol, varied with day length in captive brown bears (Ursus arctos) under anesthetized and nonanesthetized conditions during the active (March-October) and hibernation periods. Melatonin concentrations varied with time of day and season in nonanesthetized female bears despite exceedingly low nocturnal concentrations (1-4 pg/mL) in the active season. In contrast, melatonin concentrations during hibernation were 7.5-fold greater than those during the summer in anesthetized male bears. Functional assessment of the pineal gland revealed a slight but significant reduction in melatonin following nocturnal light application during hibernation, but no response to beta-adrenergic stimulation was detected in either season. Examination of pineal size in two bear species bears combined with a phylogenetically corrected analysis of pineal glands in 47 other species revealed a strong relationship to brain size. However, pineal gland size of both bear species deviated significantly from the expected pattern. Robust daily plasma cortisol rhythms were observed during the active season but not during hibernation. Cortisol was potently suppressed following injection with a synthetic glucocorticoid. The results suggest that melatonin and cortisol both retain their ability to reflect seasonal changes in day length in brown bears. The exceptionally small pineal gland in bears may be the result of direct or indirect selection.
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Affiliation(s)
- Jasmine V Ware
- Departments of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University Pullman, Washington, 99164
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13
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Chow BA, Donahue SW, Vaughan MR, McConkey B, Vijayan MM. Serum immune-related proteins are differentially expressed during hibernation in the American black bear. PLoS One 2013; 8:e66119. [PMID: 23825529 PMCID: PMC3692520 DOI: 10.1371/journal.pone.0066119] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 05/01/2013] [Indexed: 11/23/2022] Open
Abstract
Hibernation is an adaptation to conserve energy in the face of extreme environmental conditions and low food availability that has risen in several animal phyla. This phenomenon is characterized by reduced metabolic rate (∼25% of the active basal metabolic rate in hibernating bears) and energy demand, while other physiological adjustments are far from clear. The profiling of the serum proteome of the American black bear (Ursus americanus) may reveal specific proteins that are differentially modulated by hibernation, and provide insight into the remarkable physiological adaptations that characterize ursid hibernation. In this study, we used differential gel electrophoresis (DIGE) analysis, liquid chromatography coupled to tandem mass spectrometry, and subsequent MASCOT analysis of the mass spectra to identify candidate proteins that are differentially expressed during hibernation in captive black bears. Seventy serum proteins were identified as changing by ±1.5 fold or more, out of which 34 proteins increased expression during hibernation. The majority of identified proteins are involved in immune system processes. These included α2-macroglobulin, complement components C1s and C4, immunoglobulin μ and J chains, clusterin, haptoglobin, C4b binding protein, kininogen 1, α2-HS-glycoprotein, and apoplipoproteins A-I and A-IV. Differential expression of a subset of these proteins identified by proteomic analysis was also confirmed by immunodetection. We propose that the observed serum protein changes contribute to the maintenance of the hibernation phenotype and health, including increased capacities for bone maintenance and wound healing during hibernation in bears.
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Affiliation(s)
- Brian A. Chow
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Seth W. Donahue
- Department of Mechanical Engineering, Colorado State University, Fort Collins, Colorado, United States of America
| | - Michael R. Vaughan
- Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States of America
| | - Brendan McConkey
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
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14
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Macbeth BJ, Cattet MRL, Obbard ME, Middel K, Janz DM. Evaluation of hair cortisol concentration as a biomarker of long-term stress in free-ranging polar bears. WILDLIFE SOC B 2012. [DOI: 10.1002/wsb.219] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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15
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Vongraven D, Aars J, Amstrup S, Atkinson SN, Belikov S, Born EW, DeBruyn TD, Derocher AE, Durner G, Gill M, Lunn N, Obbard ME, Omelak J, Ovsyanikov N, Peacock E, Richardson E, Sahanatien V, Stirling I, Wiig Ø. A circumpolar monitoring framework for polar bears. URSUS 2012. [DOI: 10.2192/ursus-d-11-00026.1] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Bechshøft TØ, Rigét FF, Sonne C, Letcher RJ, Muir DCG, Novak MA, Henchey E, Meyer JS, Eulaers I, Jaspers VLB, Eens M, Covaci A, Dietz R. Measuring environmental stress in East Greenland polar bears, 1892-1927 and 1988-2009: what does hair cortisol tell us? ENVIRONMENT INTERNATIONAL 2012; 45:15-21. [PMID: 22572112 PMCID: PMC3366040 DOI: 10.1016/j.envint.2012.04.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 03/13/2012] [Accepted: 04/07/2012] [Indexed: 04/18/2024]
Abstract
Hair sampled from 96 East Greenland polar bears (Ursus maritimus) over the periods 1892-1927 and 1988-2009 was analyzed for cortisol as a proxy to investigate temporal patterns of environmental stress. Cortisol concentration was independent of sex and age, and was found at significantly higher (p<0.001) concentrations in historical hair samples (1892-1927; n=8) relative to recent ones (1988-2009; n=88). In addition, there was a linear time trend in cortisol concentration of the recent samples (p<0.01), with an annual decrease of 2.7%. The recent hair samples were also analyzed for major bioaccumulative, persistent organic pollutants (POPs). There were no obvious POP related time trends or correlations between hair cortisol and hair POP concentrations. Thus, polar bear hair appears to be a relatively poor indicator of the animal's general POP load in adipose tissue. However, further investigations are warranted to explore the reasons for the temporal decrease found in the bears' hair cortisol levels.
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Affiliation(s)
- T Ø Bechshøft
- Department of Bioscience, Aarhus University, Box 358, Frederiksborgvej 399, 4000 Roskilde, Denmark.
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17
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Johnstone CP, Reina RD, Lill A. Interpreting indices of physiological stress in free-living vertebrates. J Comp Physiol B 2012; 182:861-79. [PMID: 22415475 DOI: 10.1007/s00360-012-0656-9] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 02/22/2012] [Accepted: 02/24/2012] [Indexed: 10/28/2022]
Abstract
When vertebrate physiological ecologists use the terms 'stress' or 'physiological stress', they typically mean the level of hypothalamus-pituitary-adrenal (HPA-) axis activation. Measurements of stress hormone concentrations (e.g. glucocorticoids in blood, urine or faeces), leukocytes (e.g. the neutrophil-lymphocyte ratio or heterophil equivalent), immunofunction (e.g. innate, cell-mediated or humoral immunity measures) and regenerative anaemia (e.g. mean erythrocyte volume and red blood cell distribution width) have all been used to estimate HPA-axis activity in free-living vertebrates. Stress metrics have provided insights into aspects of autecology or population regulation that could not have been easily obtained using other indices of population wellbeing, such as body condition or relative abundance. However, short- and long-term stress (often problematically termed acute and chronic stress, respectively) can interact in unpredictable ways. When animals experience trapping and handling stress before blood, faeces and/or urine is sampled, the interaction of short- and long-term stress can confound interpretation of the data, a fact not always acknowledged in studies of stress in free-living vertebrates. This review examines how stress metrics can be confounded when estimates of HPA-axis activation are collected for free-living vertebrates and outlines some approaches that can be used to help circumvent the influence of potentially confounding factors.
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Affiliation(s)
- Christopher P Johnstone
- School of Biological Sciences, Monash University, Clayton Campus, Melbourne, VIC 3800, Australia.
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Kumar BS, Chung BC, Kwon OS, Jung BH. Discovery of common urinary biomarkers for hepatotoxicity induced by carbon tetrachloride, acetaminophen and methotrexate by mass spectrometry-based metabolomics. J Appl Toxicol 2011; 32:505-20. [PMID: 22131085 DOI: 10.1002/jat.1746] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 08/25/2011] [Accepted: 08/26/2011] [Indexed: 01/02/2023]
Abstract
Liver toxicity represents an important healthcare issue because it causes significant morbidity and mortality and can be difficult to predict before symptoms appear owing to drug therapy or exposure to toxicants. Using metabolomic techniques, we discovered common biomarkers for the prediction of hepatotoxicity in rat urine using mass spectrometry. For this purpose, liver toxicity was induced by 5 days of oral administration of carbon tetrachloride (1 ml kg(-1) per day), acetaminophen (1000 mg kg(-1) per day) and methotrexate (50 mg kg(-1) per day). Serum levels of alkaline phosphatase aspartate aminotransferase, alanine aminotransferase and histopathology in liver tissue were then checked to demonstrate liver toxicity. Global metabolic profiling with UPLC-TOF-MS (ultraperformance liquid chromatography-mass spectrometry), multivariate analysis (partial least square-discriminant analysis, hierarchical analysis) and database searching were performed to discover common biomarkers for liver toxicity induced by these three compounds. Urinary concentrations of the newly discovered biomarkers were then quantified to confirm them as biomarkers of hepatotoxicity with targeted metabolic profiling using GC (gas chromatography)-MS and CE (capillary electrophoresis)-MS. In the results, steroids, amino acids and bile acids were metabolically changed between the control and drug-treated groups in global metabolic profiling; 11β-hydroxyandrosterone, epiandrosterone, estrone, 11-dehydrocorticosterone, glycine, alanine, valine, leucine, dl-ornithine, 3-methylhistidine, cholic acid and lithocholic acid were selected as liver toxicity biomarkers after performing targeted metabolic profiling. In conclusion, we discovered metabolite biomarkers belonging to three different metabolic pathways to check for liver toxicity with mass spectrometry from a metabolomics study that could be used to evaluate hepatotoxicity induced by drugs or other toxic compounds.
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Affiliation(s)
- Bhowmik Salil Kumar
- Biomolecular Functional Research Center, Korea Institute of Science and Technology, Cheongryang, Seoul, Republic of Korea
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Bechshøft TØ, Sonne C, Dietz R, Born EW, Novak MA, Henchey E, Meyer JS. Cortisol levels in hair of East Greenland polar bears. THE SCIENCE OF THE TOTAL ENVIRONMENT 2011; 409:831-4. [PMID: 21144554 PMCID: PMC3019279 DOI: 10.1016/j.scitotenv.2010.10.047] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 10/22/2010] [Accepted: 10/27/2010] [Indexed: 05/19/2023]
Abstract
To demonstrate the ability to assess long-term hypothalamic-pituitary-adrenocortical (HPA) axis activity in polar bears (Ursus maritimus), a pilot study was conducted in which cortisol concentrations was analyzed in hair from 7 female (3-19 years) and 10 male (6-19 years) East Greenland polar bears sampled in 1994-2006. The hair was chosen as matrix as it is non-invasive, seasonally harmonized, and has been validated as an index of long-term changes in cortisol levels. The samples were categorized according to contamination: eight were clean (2 females, 6 males), 5 had been contaminated with bear blood (2 F, 3 M), and 4 with bear fat (3 F, 1 M). There was no significant difference in cortisol concentration between the three categories after external contamination was removed. However, contaminated hair samples should be cleaned before cortisol determination. Average hair cortisol concentration was 8.90 pg/mg (range: 5.5 to 16.4 pg/mg). There was no significant correlation between cortisol concentration and age (p=0.81) or sampling year (p=0.11). However, females had higher mean cortisol concentration than males (females mean: 11.0 pg/mg, males: 7.3 pg/mg; p=0.01). The study showed that polar bear hair contains measurable amounts of cortisol and that cortisol in hair may be used in studies of long-term stress in polar bears.
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Affiliation(s)
- TØ Bechshøft
- Department of Arctic Environment, National Environmental Research Institute, Aarhus University, Box 358, Frederiksborgvej 399, 4000 Roskilde, Denmark
- Corresponding author: , Tel: +45 4630 1952, Fax: +45 4630 1914
| | - C Sonne
- Department of Arctic Environment, National Environmental Research Institute, Aarhus University, Box 358, Frederiksborgvej 399, 4000 Roskilde, Denmark
| | - R Dietz
- Department of Arctic Environment, National Environmental Research Institute, Aarhus University, Box 358, Frederiksborgvej 399, 4000 Roskilde, Denmark
| | - EW Born
- Greenland Institute of Natural Resources, Box 570, 3900 Nuuk, Greenland
| | - MA Novak
- Department of Psychology, University of Massachusetts, Tobin Hall, 135 Hicks Way, Amherst, MA 01003-9298, USA
| | - E Henchey
- Department of Biochemistry, University of Massachusetts, Amherst, MA 01003, USA
| | - JS Meyer
- Department of Psychology, University of Massachusetts, Tobin Hall, 135 Hicks Way, Amherst, MA 01003-9298, USA
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Chow BA, Hamilton J, Cattet MR, Stenhouse G, Obbard ME, Vijayan MM. Serum corticosteroid binding globulin expression is modulated by fasting in polar bears (Ursus maritimus). Comp Biochem Physiol A Mol Integr Physiol 2011; 158:111-5. [DOI: 10.1016/j.cbpa.2010.09.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 09/16/2010] [Accepted: 09/20/2010] [Indexed: 10/19/2022]
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