Seasonal serum glucose, progesterone, and Cortisol levels of black bears (<i>Ursus americanus</i>)

Harlow, Henry J.; Beck, Thomas; Walters, Lisa; Greenhouse, Shelley S.

doi:10.1139/z90-025

Cited by 50 publications

(38 citation statements)

References 19 publications

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“…Thus, further investigations are needed to explain the apparent interpopulation difference in E 2 between female polar bears from Svalbard and Canada. The cortisol concentrations in this study showed large variations between individuals, and the cortisol levels were higher than those reported for female black bears caught in foot snares during spring (March-May) (Harlow et al 1990). The concentrations may be elevated as a consequence of immobilization and handling, but there seemed to be no differential effect of handling between reproductive groups.…”

Section: Discussioncontrasting

confidence: 67%

“…The independent variables were capture date (Julian date), age (years, months), body mass (kilograms), ΣPCBs (nanograms per gram lipid weight), and PCB-118 (nanograms per gram lipid weight). Effects on plasma P 4 concentrations due to stress of handling were also examined, because stress-related cortisol production may lead to higher blood levels of adrenal P 4 (Harlow et al 1990;Plotka et al 1983). …”

Section: Polychlorinated Biphenyls and Reproductive Hormones In Femalmentioning

confidence: 99%

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Polychlorinated biphenyls and reproductive hormones in female polar bears at Svalbard.

Haave

Ropstad

Derocher

et al. 2003

Environ Health Perspect

117

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High concentrations of polychlorinated biphenyls (PCBs) in polar bears from Svalbard have increased concern for that population's reproductive health. We examined whether there were associations between the plasma concentrations of PCBs and reproductive hormones [progesterone (P 4 ) and 17β-estradiol (E 2 )] in free-living female polar bears from Svalbard. Concentrations of P 4 depended on reproductive status, and concentrations were lowest in females with offspring-females with cubs and females with yearlings. In these females, the P 4 concentrations were positively correlated with plasma ΣPCBs (sum of all analyzed polychlorinated biphenyl congeners) concentrations. The ΣPCBs concentrations explained 27% of the variation in the P 4 concentrations. There were no correlations between ΣPCBs and E 2 and cortisol in any of the groups of polar bears, or between ΣPCBs and P 4 in single polar bears. Although the ΣPCBs-P 4 relationship in female polar bears with offspring is not evidence per se of a direct cause-effect association, the results indicate that PCBs may affect levels of P 4 in polar bear females. There is a clear need to further assess the hormone balance and population health of polar bears at Svalbard.

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Section: Discussioncontrasting

confidence: 67%

Section: Polychlorinated Biphenyls and Reproductive Hormones In Femalmentioning

confidence: 99%

Polychlorinated biphenyls and reproductive hormones in female polar bears at Svalbard.

Haave

Ropstad

Derocher

et al. 2003

Environ Health Perspect

117

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“…None of the polar bears had extremely high levels of cortisol, and the individual variation may have been related to differences in chase time, but unfortunately, individual chase time was not recorded in this study. Cortisol levels were higher in black bears in winter than in summer, and generally higher than found for polar bears (Harlow et al, 1990). It is uncertain whether this difference in cortisol levels is due to less capture stress among polar bears or species variability.…”

Section: Discussionmentioning

confidence: 84%

Plasma Biochemical Values From Apparently Healthy Free-Ranging Polar Bears From Svalbard

Tryland

Brun

Derocher

et al. 2002

Journal of Wildlife Diseases

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To establish reference values for free-ranging polar bears (Ursus maritimus) at Svalbard, Norway, plasma samples from 15 females and 20 males were analyzed for 28 blood biochemistry parameters. Animals were chemically immobilized (Zoletil: tiletamine and zolazepam) on land at Barentsøya, Edgeøya, and the eastern coast of Spitsbergen in August 1998. All bears were apparently healthy, with ages ranging from 1-22 yr. Females had almost two times higher levels of lipase than males. Several parameters varied with age. Levels of alkaline phosphatase (ALP) and calcium (Ca) decreased with age, being significantly higher in young individuals (Ͻ6 yr) compared to middle-aged (6-13 yr) and older bears (Ͼ13 yr). Globulin was lower in animals Ͻ6 yr of age than in animals Ͼ13 yr of age, while the opposite was the case for albumin. Levels of ALP, Ca, and potassium decreased with age. We found no significant changes in total protein correlated to age, but total protein levels were higher in obese compared to lean individuals. Further, total protein levels were slightly lower and had greater variation compared to data from polar bears in captivity, which may reflect food availability for the latter group. The mean ratio between urea and creatinine was 10.9 and indicated these bears were fasting. These data provide a baseline from which to compare biochemical parameters in captive and free-ranging polar bears and will be especially valuable for future studies of polar bears at Svalbard.

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“…Upon entrance into Phase III, corticosterone levels in laboratory rats had risen by 19-fold (100). Overwintering black bears likewise experience increases in circulating cortisol; however, winter dormant raccoon dogs experienced a decline in plasma cortisol suggesting that they may use an alternative axis to stimulate lipolysis (246,391).…”

Section: Glucocorticoidsmentioning

confidence: 99%

Integrative Physiology of Fasting

Secor

Carey

2016

Comprehensive Physiology

138

144

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Extended bouts of fasting are ingrained in the ecology of many organisms, characterizing aspects of reproduction, development, hibernation, estivation, migration, and infrequent feeding habits. The challenge of long fasting episodes is the need to maintain physiological homeostasis while relying solely on endogenous resources. To meet that challenge, animals utilize an integrated repertoire of behavioral, physiological, and biochemical responses that reduce metabolic rates, maintain tissue structure and function, and thus enhance survival. We have synthesized in this review the integrative physiological, morphological, and biochemical responses, and their stages, that characterize natural fasting bouts. Underlying the capacity to survive extended fasts are behaviors and mechanisms that reduce metabolic expenditure and shift the dependency to lipid utilization. Hormonal regulation and immune capacity are altered by fasting; hormones that trigger digestion, elevate metabolism, and support immune performance become depressed, whereas hormones that enhance the utilization of endogenous substrates are elevated. The negative energy budget that accompanies fasting leads to the loss of body mass as fat stores are depleted and tissues undergo atrophy (i.e., loss of mass). Absolute rates of body mass loss scale allometrically among vertebrates. Tissues and organs vary in the degree of atrophy and downregulation of function, depending on the degree to which they are used during the fast. Fasting affects the population dynamics and activities of the gut microbiota, an interplay that impacts the host's fasting biology. Fasting-induced gene expression programs underlie the broad spectrum of integrated physiological mechanisms responsible for an animal's ability to survive long episodes of natural fasting.

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Seasonal serum glucose, progesterone, and Cortisol levels of black bears (Ursus americanus)

Cited by 50 publications

References 19 publications

Polychlorinated biphenyls and reproductive hormones in female polar bears at Svalbard.

Polychlorinated biphenyls and reproductive hormones in female polar bears at Svalbard.

Plasma Biochemical Values From Apparently Healthy Free-Ranging Polar Bears From Svalbard

Integrative Physiology of Fasting

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