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John F Cockrem - One of the best experts on this subject based on the ideXlab platform.
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individual variation and repeatability of Corticosterone responses of little penguins eudyptula minor sampled in two successive years at oamaru new zealand
General and Comparative Endocrinology, 2017Co-Authors: John F Cockrem, Paul D Barrett, Jane E Candy, Philippa Agnew, Murray A PotterAbstract:Plasma Corticosterone concentrations increase when birds experience a stressor, and plasma Corticosterone responses to a capture and handling stressor have been measured in many species of birds. Whilst it is assumed that the reported Corticosterone responses reflect the inherent sensitivity of each bird to the stressor, responses of the same birds have rarely been measured at intervals of one or more years. The current study was conducted to measure the repeatability in two successive years of Corticosterone responses of little penguins (Eudyptula minor) at Oamaru, New Zealand. There was a wide range of individual Corticosterone responses to capture and restraint in 96 little penguins in 2012 and 50 penguins sampled at the same time of year in 2013. There were significant repeatabilities for the ranks of Corticosterone at 15, 30 and 60min (r=0.416±0.160, r=0.636±0.115 and r=0.380±0.166 respectively) and for the ranks of integrated Corticosterone responses (r=0.594±0.126) for 23 birds sampled in both years. There were no significant relationships between the size of Corticosterone responses and age, body weight or condition index. Mean Corticosterone concentrations at 60min were 114.22±6.65ng/ml in 2012 and 116.94±6.42ng/ml in 2013. Mean Corticosterone responses did not differ between two successive years and were greater than responses of other penguin species. Penguins are well suited to long term studies in which Corticosterone responses are measured annually as potential measures of changing marine environmental conditions.
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Corticosterone responses and personality in birds individual variation and the ability to cope with environmental changes due to climate change
General and Comparative Endocrinology, 2013Co-Authors: John F CockremAbstract:Birds can respond to an internal or external stimulus with activation of the HPA axis and secretion of Corticosterone. There is considerable individual variation in Corticosterone responses, and individual responses can be very different from the mean response for a group of birds. Corticosterone responses and behavioural responses to environmental stimuli are determined by individual characteristics called personality. It is proposed that birds with low Corticosterone responses and proactive personalities are likely to be more successful (have greater fitness) in constant or predictable conditions, whilst birds with reactive personalities and high Corticosterone responses will be more successful in changing or unpredictable conditions. The relationship between Corticosterone responses and fitness thus depends on the prevailing environmental conditions, so birds with either low or high Corticosterone responses can have the greatest fitness and be most successful, but in different situations. It is also proposed that birds with reactive personalities and high Corticosterone responses will be better able to cope with environmental changes due to climate change than birds with proactive personalities and relatively low Corticosterone responses. Phenotypic plasticity in Corticosterone responses can be quantified using a reaction norm approach, and reaction norms can be used to determine the degree of plasticity in Corticosterone responses of individual birds, and mean levels of plasticity in responses of species of birds. Individual Corticosterone responses and personality, and reaction norms for Corticosterone responses, can in future be used to predict the ability of birds to cope with environmental changes due to climate change.
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inverse urinary Corticosterone and testosterone metabolite responses to different durations of restraint in the cane toad rhinella marina
General and Comparative Endocrinology, 2012Co-Authors: Edward Jitik Narayan, Jeanmarc Hero, John F CockremAbstract:Non-invasive measurement of urinary Corticosterone and testosterone metabolites in amphibians provides opportunities for endocrine studies of responses to physiological and psychological stressors. Typically, Corticosterone metabolite concentrations increase in frog urine within 1-2h of a mild capture and handling stress protocol. However, no study has investigated the effect of duration of manual restraint on the changes in Corticosterone and reproductive hormones in amphibians. We quantified urinary Corticosterone and testosterone metabolite responses for 8h following various durations of manual restraint (control, 5, 15 or 30min) in adult male cane toads (Rhinella marina) under controlled laboratory conditions. All toads had a Corticosterone stress response over 8h to our standard capture and handling stressor. The mean Corticosterone stress response was significantly higher after 15 or 30min restraint in comparison to the control (no restraint) or to 5min restraint. Manual restraint for 5, 15 or 30min caused a significant reduction in urinary testosterone concentrations over 8h. We also provide a novel method of quantifying plasticity in Corticosterone stress responses in amphibians with respect to restraint duration using the concept of a "reaction norm". The reaction norm, which was calculated as slope of the regression line of integrated Corticosterone response against restraint duration, was 9.69 (pg Corticosterone/μg creatinineh)/min for male toads. In summary, Corticosterone and testosterone responses to restraint are affected by restraint duration in male toads. Glucocorticoid reaction norms can be applied to study the change in physiological stress hormonal response with respect to restraint duration in other amphibian species.
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individual variation and repeatability in urinary Corticosterone metabolite responses to capture in the cane toad rhinella marina
General and Comparative Endocrinology, 2012Co-Authors: Edward Jitik Narayan, John F Cockrem, Frank C Molinia, Jeanmarc HeroAbstract:Urinary Corticosterone metabolite enzyme-immunoassay (EIA) can be used for the non-invasive assessment of baseline levels and Corticosterone responses in amphibians. In this study, urinary Corticosterone responses of wild male cane toads (Rhinella marina) to confinement and repeated handling were measured to quantify individual variation in Corticosterone responses for the first time in an amphibian species. Urine samples were collected at 0 h in the wild, hourly from 2 to 8 h after transfer into captivity, and again at 12 and 24 h in captivity. Toads were then held in captivity and subjected to the same sampling protocol on three occasions at 14 days intervals to quantify variation in Corticosterone metabolite responses within and between toads. Baseline and individual Corticosterone metabolite responses in male cane toads were generally consistent, with high statistical repeatabilities for 0 h (r = 0.630), 6 h (r = 0.793), 12 h (r = 0.652) and 24 h (r = 0.721) Corticosterone metabolite concentrations, and for the total and corrected integrated Corticosterone responses (r = 0.567, p = 0.033; r = 0.728, p = 0.014 respectively). Urinary Corticosterone responses appear to be a stable, repeatable trait within individuals. Corticosterone responses in amphibians can be more readily measured when urine rather than plasma samples are collected, and the protocol established in the current study can now be applied to the study of variation in Corticosterone responses in other amphibians.
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urinary Corticosterone metabolite responses to capture and captivity in the cane toad rhinella marina
General and Comparative Endocrinology, 2011Co-Authors: Edward Jitik Narayan, John F Cockrem, Jeanmarc HeroAbstract:Abstract Urinary Corticosterone metabolite responses to capture have recently been shown for the first time in amphibians, and in the present study urinary Corticosterone metabolite responses to capture and to confinement in captivity were measured in adult cane toads ( Rhinella marina ) in Queensland, Australia. An adrenocorticotropic hormone (ACTH) challenge was used to provide a biological validation for urinary Corticosterone metabolite concentrations measured by radioimmunoassay (RIA). Urinary Corticosterone metabolite increased 1–2 days after ACTH but not saline injection and then returned to initial values, indicating that the RIA could detect changes in Corticosterone secretion in toads. Urinary Corticosterone metabolite responses to short-term capture and restraint in plastic bags were first apparent 2 h after capture of wild toads. Toads held communally in captivity for 5 days had elevated urinary Corticosterone metabolite concentrations. Mean Corticosterone concentrations declined significantly after a further 7 days in individual housing chambers. There was no sex difference in urinary Corticosterone metabolite responses of toads to ACTH challenge, short-term capture or captivity. The relative amount of variation in the mean Corticosterone responses was quantified by calculating coefficients of variation (CV) for each mean Corticosterone response. Mean Corticosterone at 0 min was more variable for captive toads than wild toads. Furthermore, initial Corticosterone concentrations (0 min) were more variable than concentrations during the ACTH challenge, short-term capture and captivity. There was little change in the amount of variation of mean Corticosterone levels between male and female toads with increasing time in captivity (12–29 days). This study has shown individual Corticosterone responses of amphibians for the first-time, and has provided a novel method for quantifying the relative amount of variation in amphibian Corticosterone responses.
John C Wingfield - One of the best experts on this subject based on the ideXlab platform.
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Influence of winter on endocrine state and behavior in European blackbirds (Turdus merula)
Zeitschrift für Tierpsychologie, 2010Co-Authors: Hubert Schwabl, John C Wingfield, Donald S. FarnerAbstract:and Summary Plasma levels of luteinizing hormone (LH), testosterone, 5α–dihydrotestosteronc (5α–DHT) and Corticosterone in wintering European blackbirds (Turdus merula) were analysed according to sex and age, and under two environmental conditions that reflect availability and the degree of competition for food. Circulating levels of LH, basal in all groups, appeared to be unaffected by more intense competition. However, levels of testosterone increased in males, whereas females had higher levels of 5α–DHT than of testosterone. This suggests a function of these hormones in aggressive behavior for procurement of food. Plasma concentrations of Corticosterone were positively correlated with time elapsed between capture and procurement of blood sample. They were significantly elevated in first–year birds and females but not in adult males during times of reduced availability of food. This could reflect greater stress in first–year birds and females than in adult males, indicating higher costs of wintering in the breeding area for low–ranking individuals. This differential effect of severe winter conditions according to age and sex could be among the ultimate factors in selection for partial migration in the population. Zusammenfassung Wir analysierten die Plasmakonzentrationen von luteinisierendem Hormon (LH), Testosteron, 5α–Dihydrotestosteron (5α–DHT) und Corticosteron im Brutgebiet uberwinternder Amseln nach Alter und Geschlecht sowie zwei Umwelttemperaturen, die das Nahrungsangebot und das Ausmas aggressiver Auseinandersetzungen widerspiegeln. Die Plasmaspiegel von LH waren im Vergleich zu den Konzentrationen wahrend der Brutzeit bei alien Gruppen sehr niedrig und wurden von den beiden Umweltsituationen nicht beeinflust. Im Gegensatz dazu waren bei Mannchen die Plasmaspiegel von Testosteron bei Nahrungsknappheit erhoht. Die Testosteronspiegel der Weibchen waren sehr niedrig, und es deutete sich kein Einflus der jeweiligen Umweltsituation an. Jedoch waren bei Weibchen die Konzentrationen von 5α–DHT hoher als die von Testosteron. Hohere Androgenspiegel wahrend Zeiten mit gesteigerten aggressiven Auseinandersetzungen konnten auf eine Funktion dieser Hormone in der Steuerung aggressiven Verhaltens auserhalb der Brutzeit hindeuten. Die Plasmakonzentrationen von Corticosteron waren mit der Dauer des Fangstresses positiv korreliert. Bei erstjahrigen Individuen und Weibchen, nicht aber bei adulten Mannchen, waren sie bei Futterknappheit deutlich erhoht. Dieses Ergebnis konnte damit erklart werden, das niedrigrangige Jungvogel und Weibchen bei Kalteeinbruchen groseren Belastungen unterworfen sind als adulte Mannchen. Dies konnte einer der Selektionsfaktoren sein, die zur Evolution von Teilzugverhalten in der untersuchten Amselpopulation fuhrten.
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Corticosterone is not correlated with nest departure in snowy owl chicks nyctea scandiaca
General and Comparative Endocrinology, 2006Co-Authors: Michael L Romero, Mike Maples, Denver W. Holt, John C WingfieldAbstract:Abstract Snowy owl chicks typically depart from nests at approximately 18 days of age, but 3 weeks before taking their first flight. High concentrations of Corticosterone have been implicated in behavioral changes in many species, leading us to assess Corticosterone’s role in chick nest departure. Corticosterone titers in free-living chicks, however, do not predict this departure event. Baseline Corticosterone concentrations decrease as chicks age. By 13 days, Corticosterone concentrations are 50% of concentrations in 1-day-old chicks. Baseline concentrations, however, do not differ between departed and nest-bound chicks. Furthermore, Corticosterone concentrations become significantly elevated 30 min after collecting the baseline sample, indicating that chicks are able to mount a Corticosterone response to handling. This stress-induced rise in Corticosterone also did not differ between departed and nest-bound chicks. Brood sizes varied, possibly resulting in increased stress in chicks from larger broods. Although many chicks died before reaching departure age, brood sizes at time of nest departure ranged from 1 to 10 chicks. Brood size was not correlated with age of nest departure or individual Corticosterone concentrations. These data indicate that it is unlikely that Corticosterone plays a role in triggering nest departure in snowy owl chicks.
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plasma Corticosterone increases during migratory restlessness in the captive white crowned sparrow zonotrichia leucophrys gambelli
Hormones and Behavior, 2004Co-Authors: Mėta M Landys, John C Wingfield, Marilyn RamenofskyAbstract:Plasma Corticosterone increases during the period of spring migration in a variety of bird species. Long-distance migrants show elevations in Corticosterone specifically in association with the stage of flight, suggesting that Corticosterone may support flight-related processes, for example, locomotor activity and/or energy mobilization. The pattern of Corticosterone secretion as it relates to migratory flight has hitherto not been clearly described in migrants that frequently interrupt flight to refuel, for example, the Gambel's white-crowned sparrow (Zonotrichia leucophrys gambelii). The Gambel's white-crowned sparrow fuels by day and expresses peak migratory activity during the first few hours of night. To determine if plasma Corticosterone increases in association with the stage of migratory flight also in this short-bout migrant, we induced captive white-crowned sparrows to enter into the migratory condition by placing photosensitive birds on long days (16L:8D) and then evaluated birds for plasma Corticosterone and locomotor activity during four time points of the day. Patterns found in long-day birds were compared to those observed in short-day controls (8L:16D). Differences in energy metabolism as determined from plasma metabolites were also evaluated. We found that locomotor activity and Corticosterone were significantly elevated at the onset of the dark period, but only in long-day birds. Plasma β-hydroxybutyrate (a ketone body) was also elevated. Thus, findings suggest that plasma Corticosterone and ketogenesis increase in association with migratory restlessness in a short-bout migrant. In fact, Corticosterone may play a regulatory role, because it shows a trend to increase already before night-time activity.
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maternal Corticosterone is transferred to avian yolk and may alter offspring growth and adult phenotype
General and Comparative Endocrinology, 2004Co-Authors: Lisa S Hayward, John C WingfieldAbstract:Many environmental perturbations may elevate plasma Corticosterone in laying birds, including disease, poor body condition, high predator density, anthropogenic disturbance, and/or food scarcity. When adverse conditions are not dire enough to dictate foregoing reproduction, maternal Corticosterone in egg yolk may phenotypically engineer offspring so as to maximize success under the constraints of the local environment. We tested the hypotheses that Corticosterone in avian egg yolk should correlate with Corticosterone in maternal circulation at the time of laying, and that high Corticosterone in yolk should then influence offspring development and adult phenotype. We implanted female Japanese quail (Coturnix coturnix japonica) with Corticosterone-filled or empty implants and measured concentrations of Corticosterone in the yolk of their eggs. Then we incubated the eggs and raised the chicks to test for effects on growth and hypothalamo-pituitary-adrenal response to capture and restraint in adult offspring. We found that Corticosterone implants significantly increased Corticosterone in yolk. Furthermore, chicks of Corticosterone-implanted mothers grew more slowly than controls and showed higher activity of the hypothalamo-adrenal axis in response to capture and restraint as adults. These results suggest that stress experienced by a laying bird has significant effects on offspring development and adult phenotype, possibly mediated by the transfer of maternal Corticosterone to yolk.
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changes in plasma Corticosterone and adrenocortical response to stress during the breeding cycle in high altitude flycatchers
General and Comparative Endocrinology, 2003Co-Authors: Maria E Pereyra, John C WingfieldAbstract:Abstract Plasma Corticosterone levels were monitored in a breeding population of Dusky Flycatchers ( Empidonax oberholseri ) at Tioga Pass, in the eastern Sierra Nevada. Seasonal changes in baseline plasma Corticosterone levels were largely related to changes in reproductive status. Levels in both sexes were highest during the period preceding the female’s initiation of a clutch. Females, alone, incubated, but males provided food regularly for their incubating mates. Excepting transient peaks in female Corticosterone levels that immediately preceded ovipositions, steep declines in baseline levels of Corticosterone in both sexes corresponded to the onset of parental attentiveness. Serial measurements of plasma Corticosterone levels over a 1-h period of restraint, indicated that these declines originate at the level of the hypothalamo–pituitary–adrenal response system. Increases in stress-induced plasma Corticosterone were significantly greater during the period preceding clutch initiation (prenesting) than during the nesting period (incubation and nestling periods). Despite the changes in Corticosterone between prenesting and nesting periods, variability in Corticosterone levels during both stages was negatively correlated with body condition (body mass and fat, corrected for size), and level of parental investment. Highest levels of plasma Corticosterone were observed in lighter, leaner flycatchers, and during the hours when self-foraging activities were highest; lowest levels were seen in heavier, fatter birds, and those foraging for chicks. This relationship between Corticosterone and parental care extended to a small number of accessory males that were acting as helpers at the nest. These results suggest that variation in the length of the reproductive cycle and degree of parental investment may help to explain the level of adaptive modulation of the adrenal stress response in species that breed in unpredictable environments.
Jeanmarc Hero - One of the best experts on this subject based on the ideXlab platform.
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inverse urinary Corticosterone and testosterone metabolite responses to different durations of restraint in the cane toad rhinella marina
General and Comparative Endocrinology, 2012Co-Authors: Edward Jitik Narayan, Jeanmarc Hero, John F CockremAbstract:Non-invasive measurement of urinary Corticosterone and testosterone metabolites in amphibians provides opportunities for endocrine studies of responses to physiological and psychological stressors. Typically, Corticosterone metabolite concentrations increase in frog urine within 1-2h of a mild capture and handling stress protocol. However, no study has investigated the effect of duration of manual restraint on the changes in Corticosterone and reproductive hormones in amphibians. We quantified urinary Corticosterone and testosterone metabolite responses for 8h following various durations of manual restraint (control, 5, 15 or 30min) in adult male cane toads (Rhinella marina) under controlled laboratory conditions. All toads had a Corticosterone stress response over 8h to our standard capture and handling stressor. The mean Corticosterone stress response was significantly higher after 15 or 30min restraint in comparison to the control (no restraint) or to 5min restraint. Manual restraint for 5, 15 or 30min caused a significant reduction in urinary testosterone concentrations over 8h. We also provide a novel method of quantifying plasticity in Corticosterone stress responses in amphibians with respect to restraint duration using the concept of a "reaction norm". The reaction norm, which was calculated as slope of the regression line of integrated Corticosterone response against restraint duration, was 9.69 (pg Corticosterone/μg creatinineh)/min for male toads. In summary, Corticosterone and testosterone responses to restraint are affected by restraint duration in male toads. Glucocorticoid reaction norms can be applied to study the change in physiological stress hormonal response with respect to restraint duration in other amphibian species.
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individual variation and repeatability in urinary Corticosterone metabolite responses to capture in the cane toad rhinella marina
General and Comparative Endocrinology, 2012Co-Authors: Edward Jitik Narayan, John F Cockrem, Frank C Molinia, Jeanmarc HeroAbstract:Urinary Corticosterone metabolite enzyme-immunoassay (EIA) can be used for the non-invasive assessment of baseline levels and Corticosterone responses in amphibians. In this study, urinary Corticosterone responses of wild male cane toads (Rhinella marina) to confinement and repeated handling were measured to quantify individual variation in Corticosterone responses for the first time in an amphibian species. Urine samples were collected at 0 h in the wild, hourly from 2 to 8 h after transfer into captivity, and again at 12 and 24 h in captivity. Toads were then held in captivity and subjected to the same sampling protocol on three occasions at 14 days intervals to quantify variation in Corticosterone metabolite responses within and between toads. Baseline and individual Corticosterone metabolite responses in male cane toads were generally consistent, with high statistical repeatabilities for 0 h (r = 0.630), 6 h (r = 0.793), 12 h (r = 0.652) and 24 h (r = 0.721) Corticosterone metabolite concentrations, and for the total and corrected integrated Corticosterone responses (r = 0.567, p = 0.033; r = 0.728, p = 0.014 respectively). Urinary Corticosterone responses appear to be a stable, repeatable trait within individuals. Corticosterone responses in amphibians can be more readily measured when urine rather than plasma samples are collected, and the protocol established in the current study can now be applied to the study of variation in Corticosterone responses in other amphibians.
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urinary Corticosterone metabolite responses to capture and captivity in the cane toad rhinella marina
General and Comparative Endocrinology, 2011Co-Authors: Edward Jitik Narayan, John F Cockrem, Jeanmarc HeroAbstract:Abstract Urinary Corticosterone metabolite responses to capture have recently been shown for the first time in amphibians, and in the present study urinary Corticosterone metabolite responses to capture and to confinement in captivity were measured in adult cane toads ( Rhinella marina ) in Queensland, Australia. An adrenocorticotropic hormone (ACTH) challenge was used to provide a biological validation for urinary Corticosterone metabolite concentrations measured by radioimmunoassay (RIA). Urinary Corticosterone metabolite increased 1–2 days after ACTH but not saline injection and then returned to initial values, indicating that the RIA could detect changes in Corticosterone secretion in toads. Urinary Corticosterone metabolite responses to short-term capture and restraint in plastic bags were first apparent 2 h after capture of wild toads. Toads held communally in captivity for 5 days had elevated urinary Corticosterone metabolite concentrations. Mean Corticosterone concentrations declined significantly after a further 7 days in individual housing chambers. There was no sex difference in urinary Corticosterone metabolite responses of toads to ACTH challenge, short-term capture or captivity. The relative amount of variation in the mean Corticosterone responses was quantified by calculating coefficients of variation (CV) for each mean Corticosterone response. Mean Corticosterone at 0 min was more variable for captive toads than wild toads. Furthermore, initial Corticosterone concentrations (0 min) were more variable than concentrations during the ACTH challenge, short-term capture and captivity. There was little change in the amount of variation of mean Corticosterone levels between male and female toads with increasing time in captivity (12–29 days). This study has shown individual Corticosterone responses of amphibians for the first-time, and has provided a novel method for quantifying the relative amount of variation in amphibian Corticosterone responses.
Mónica B. Martella - One of the best experts on this subject based on the ideXlab platform.
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influence of the rearing system on yolk Corticosterone concentration in captive greater rheas rhea americana
Zoo Biology, 2016Co-Authors: Natalia S Della Costa, Juan Manuel Busso, Cristian Hansen, Joaquín Luis Navarro, Raul Hector Marin, Mónica B. MartellaAbstract:Many environmental conditions elevate plasma Corticosterone in laying birds, leading to elevated hormone accumulation in the egg. We investigated whether maternal yolk Corticosterone levels in Greater Rheas differ between fresh eggs collected from an intensive (IRS) and a semi-extensive (SRS) rearing system. After HPLC validation, yolk Corticosterone was measured using a Corticosterone (125) I radio-immunoassay kit. Results (mean ± SE) showed that eggs collected from the IRS exhibited a significantly higher Corticosterone concentration than eggs from SRS (89.88 ± 8.93 vs. 45.41 ± 5.48 ng/g yolk, respectively). Our findings suggest that rearing conditions under an intensive scheme (e.g., small pens with bare ground, no direct foraging and handling) might be perceived as more stressful for Greater Rhea females than semi-extensive rearing conditions (e.g., low animal density distributed in extensive areas and direct foraging), which would result in the transfer of higher yolk Corticosterone levels. A better understanding of environmental conditions and female traits that affect yolk Corticosterone deposition provides a background for future studies concerning the roles of maternal Corticosterone on offspring development. Zoo Biol. 35:246-250, 2016. © 2016 Wiley Periodicals, Inc.
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Physiological stress in captive Greater rheas (Rhea americana): highly sensitive plasma Corticosterone response to an ACTH challenge.
General and Comparative Endocrinology, 2009Co-Authors: Alvina Leche, Juan Manuel Busso, Cristian Hansen, Joaquín Luis Navarro, Raul H. Marin, Mónica B. MartellaAbstract:Up to the present no studies have been conducted either on baseline concentrations of adrenal hormones or on hormonal responses to stress in Greater rhea (Rhea americana) and most ratite species. The aims of this work were to assess the presence of Corticosterone in plasma of Greater rhea, to validate a Corticosterone 125I-radioimmunoassay for determining Corticosterone levels in plasma samples and to study the activation of the adrenal gland after an adrenocorticotrophic hormone (ACTH) challenge. Six captive Greater rhea juveniles of 10 months of age received an intravenous ACTH injection. Blood samples were taken at 0 min (baseline pre-ACTH levels), and post-injection at 15, 30, 60 min and at 24 and 48 h. The high pressure liquid chromatography (HPLC) analysis of pooled plasma showed that Corticosterone is the glucocorticoid found in the plasma of Greater rhea. Biochemical assays of standard validation (e.g., parallelism, exogenous Corticosterone recovery) showed that measurements of Corticosterone present in the plasma of the Greater rhea provided by commercial Corticosterone 125I-radioimmunoassay were accurate and precise. ACTH challenge induced a more than 40-fold increase in plasma Corticosterone at 60 min post-ACTH (from 4.0 to 166.5 ng/ml, on average). The Corticosterone response to ACTH in Greater rhea was higher than is usual in birds, an apparently typical characteristic of ratites.
Edward Jitik Narayan - One of the best experts on this subject based on the ideXlab platform.
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inverse urinary Corticosterone and testosterone metabolite responses to different durations of restraint in the cane toad rhinella marina
General and Comparative Endocrinology, 2012Co-Authors: Edward Jitik Narayan, Jeanmarc Hero, John F CockremAbstract:Non-invasive measurement of urinary Corticosterone and testosterone metabolites in amphibians provides opportunities for endocrine studies of responses to physiological and psychological stressors. Typically, Corticosterone metabolite concentrations increase in frog urine within 1-2h of a mild capture and handling stress protocol. However, no study has investigated the effect of duration of manual restraint on the changes in Corticosterone and reproductive hormones in amphibians. We quantified urinary Corticosterone and testosterone metabolite responses for 8h following various durations of manual restraint (control, 5, 15 or 30min) in adult male cane toads (Rhinella marina) under controlled laboratory conditions. All toads had a Corticosterone stress response over 8h to our standard capture and handling stressor. The mean Corticosterone stress response was significantly higher after 15 or 30min restraint in comparison to the control (no restraint) or to 5min restraint. Manual restraint for 5, 15 or 30min caused a significant reduction in urinary testosterone concentrations over 8h. We also provide a novel method of quantifying plasticity in Corticosterone stress responses in amphibians with respect to restraint duration using the concept of a "reaction norm". The reaction norm, which was calculated as slope of the regression line of integrated Corticosterone response against restraint duration, was 9.69 (pg Corticosterone/μg creatinineh)/min for male toads. In summary, Corticosterone and testosterone responses to restraint are affected by restraint duration in male toads. Glucocorticoid reaction norms can be applied to study the change in physiological stress hormonal response with respect to restraint duration in other amphibian species.
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individual variation and repeatability in urinary Corticosterone metabolite responses to capture in the cane toad rhinella marina
General and Comparative Endocrinology, 2012Co-Authors: Edward Jitik Narayan, John F Cockrem, Frank C Molinia, Jeanmarc HeroAbstract:Urinary Corticosterone metabolite enzyme-immunoassay (EIA) can be used for the non-invasive assessment of baseline levels and Corticosterone responses in amphibians. In this study, urinary Corticosterone responses of wild male cane toads (Rhinella marina) to confinement and repeated handling were measured to quantify individual variation in Corticosterone responses for the first time in an amphibian species. Urine samples were collected at 0 h in the wild, hourly from 2 to 8 h after transfer into captivity, and again at 12 and 24 h in captivity. Toads were then held in captivity and subjected to the same sampling protocol on three occasions at 14 days intervals to quantify variation in Corticosterone metabolite responses within and between toads. Baseline and individual Corticosterone metabolite responses in male cane toads were generally consistent, with high statistical repeatabilities for 0 h (r = 0.630), 6 h (r = 0.793), 12 h (r = 0.652) and 24 h (r = 0.721) Corticosterone metabolite concentrations, and for the total and corrected integrated Corticosterone responses (r = 0.567, p = 0.033; r = 0.728, p = 0.014 respectively). Urinary Corticosterone responses appear to be a stable, repeatable trait within individuals. Corticosterone responses in amphibians can be more readily measured when urine rather than plasma samples are collected, and the protocol established in the current study can now be applied to the study of variation in Corticosterone responses in other amphibians.
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urinary Corticosterone metabolite responses to capture and captivity in the cane toad rhinella marina
General and Comparative Endocrinology, 2011Co-Authors: Edward Jitik Narayan, John F Cockrem, Jeanmarc HeroAbstract:Abstract Urinary Corticosterone metabolite responses to capture have recently been shown for the first time in amphibians, and in the present study urinary Corticosterone metabolite responses to capture and to confinement in captivity were measured in adult cane toads ( Rhinella marina ) in Queensland, Australia. An adrenocorticotropic hormone (ACTH) challenge was used to provide a biological validation for urinary Corticosterone metabolite concentrations measured by radioimmunoassay (RIA). Urinary Corticosterone metabolite increased 1–2 days after ACTH but not saline injection and then returned to initial values, indicating that the RIA could detect changes in Corticosterone secretion in toads. Urinary Corticosterone metabolite responses to short-term capture and restraint in plastic bags were first apparent 2 h after capture of wild toads. Toads held communally in captivity for 5 days had elevated urinary Corticosterone metabolite concentrations. Mean Corticosterone concentrations declined significantly after a further 7 days in individual housing chambers. There was no sex difference in urinary Corticosterone metabolite responses of toads to ACTH challenge, short-term capture or captivity. The relative amount of variation in the mean Corticosterone responses was quantified by calculating coefficients of variation (CV) for each mean Corticosterone response. Mean Corticosterone at 0 min was more variable for captive toads than wild toads. Furthermore, initial Corticosterone concentrations (0 min) were more variable than concentrations during the ACTH challenge, short-term capture and captivity. There was little change in the amount of variation of mean Corticosterone levels between male and female toads with increasing time in captivity (12–29 days). This study has shown individual Corticosterone responses of amphibians for the first-time, and has provided a novel method for quantifying the relative amount of variation in amphibian Corticosterone responses.
