Seasonal variation in glucocorticoid and mineralocorticoid receptors in metabolic tissues of the house sparrow (Passer domesticus)

© 2014 Elsevier Inc. Glucocorticoid hormones like corticosterone (CORT) play essential metabolic roles at both baseline and stress-induced concentrations, and CORT titers vary seasonally in patterns occurring across many different vertebrate species. It has been hypothesized that CORT may vary seasonally due to changing energy requirements at different times of year. However, hormone effects are dependent on binding to receptors in target tissues, and receptors might also vary seasonally. CORT alters metabolism primarily through binding to two receptors, the high-affinity mineralocorticoid receptor (MR) and low-affinity glucocorticoid receptor (GR). We quantified GR and MR in metabolic tissues (liver, kidney, omental and subcutaneous fat, and gastrocnemius and pectoralis muscle) of wild-caught house sparrows (Passer domesticus) to assess these tissues\u27 capacity to respond to CORT-mediated metabolic demands. We quantified receptors using radioligand binding assays in early and late winter, pre-egg-laying, breeding, late breeding and molt (n= 12 at each stage). MR binding did not vary significantly in any tissue over the course of the year. Because MR is associated with baseline CORT effects, this suggests that changing hormone titers may primarily regulate baseline CORT effects on metabolism. Seasonal modulation of GR binding occurred in every tissue but omental fat, though peak receptor density did not coincide with peak stress-induced CORT concentrations measured previously. Because GR is associated with stress-induced CORT effects, these data demonstrate seasonal patterns in stress-induced CORT are not driven by metabolic needs alone, although at different times of year sparrows may vary which tissue types respond to increased energy demands resulting from exposure to stressors

Chronic stress alters concentrations of corticosterone receptors in a tissue-specific manner in wild house sparrows (Passer domesticus)

© 2014. Published by The Company of Biologists Ltd. The physiological stress response results in release of glucocorticoid hormones such as corticosterone (CORT). Whereas short-term activation of this response helps animals cope with environmental stressors, chronic activation can result in negative effects including metabolic dysregulation and reproductive failure. However, there is no consensus hormonal profile of a chronically stressed animal, suggesting that researchers may need to look beyond hormone titers to interpret the impacts of chronic stress. In this study, we brought wild house sparrows (Passer domesticus) into captivity. We then compared glucocorticoid and mineralocorticoid receptor concentrations in sparrows exposed either to a standardized chronic stress protocol (n=26) or to standard husbandry conditions (controls; n=20). We used radioligand binding assays to quantify receptors in whole brain, liver, kidneys, spleen, gonads, gastrocnemius and pectoralis muscle, omental and subcutaneous fat, and bib and back skin. In most tissues, CORT receptors did not differ between controls and stressed animals, although we found marginal increases in receptor density in kidney and testes in stressed birds at some time points. Only in pectoralis muscle was there a robust effect of chronic stress, with both receptor types higher in stressed animals. Increased pectoralis sensitivity to CORT with chronic stress may be part of the underlying mechanism for muscle wasting in animals administered exogenous CORT. Furthermore, the change in pectoralis was not paralleled by gastrocnemius receptors. This difference may help explain previous reports of a greater effect of CORT on pectoralis than on other muscle types, and indicate that birds use this muscle as a protein reserve

Unanswered Prayers: A Study of Apologia for God in the Matter of Prayer

Many Christian writers and thinkers take up the vexing issue of unanswered prayer and thereby use various rhetorical strategies to address the intersection of pertinent teaching about prayer, and the disjunctive, problematic life experiences concerning the experience of unanswered prayer. Our investigation uses the ancient rhetorical genre of apologia as a lens to better understand the tactics and stances taken up by those who seek to guide members of faith communities toward reconciliation between perceived biblical teaching and actual life experiences concerning unanswered prayer. Our study incorporates an analysis of both the formal and conceptual strategies utilized by rhetors who seek to repair, or account for, breaches in lived-faith and understood teaching by religious communities through investigation of representative contemporary rhetors who address prayer

Seasonal variation in corticosterone receptor binding in brain, hippocampus, and gonads in House Sparrows (Passer domesticus)

Abstract.-Both baseline and stress-induced concentrations of corticosterone (CORT) vary seasonally in a predictable fashion in many wild birds. Hypotheses about why these patterns exist include the behavior hypothesis, which predicts that animals will down-regulate stress-induced CORT when CORT-induced behaviors are too likely to cause reproductive failure; and the preparative hypothesis, which posits that baseline and stress-induced CORT will both be high at times of year with a higher incidence of predictable stressors. We tested predictions made by the behavior and predictive hypotheses about the CORT sensitivity of tissues involved in breeding: whole brain, hippocampus, and gonads. We used radioligand binding assays to examine glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) binding in free-living House Sparrows (Passer domesticus) at several different life history stages. We found lowest GR binding in whole brain during breeding; this suggests relative insensitivity of brain tissue to CORT at this time of year, which is consistent with predictions made by the behavior hypothesis. We found highest GR binding in whole brain in the pre-egg-laying period, which is consistent with the preparative hypothesis, given that this life stage is associated with a predictable increase in the likelihood of stressful events such as threats to territory and nest sites. However, we found no seasonal changes in GR or MR binding in gonads or hippocampus. Our results suggest that down-regulation of brain GR could be one way birds limit the negative effects of CORT release on breeding behavior, but further studies are necessary to understand the anatomic specificity of these changes.© 2013 by The American Ornithologists\u27 Union. All rights reserved

Chronic exposure to a low dose of ingested petroleum disrupts corticosterone receptor signalling in a tissue-specific manner in the house sparrow (Passer domesticus)

© The Author 2014. Stress-induced concentrations of glucocorticoid hormones (including corticosterone, CORT) can be suppressed by chronic exposure to a low dose of ingested petroleum. However, endocrine-disrupting chemicals could interfere with CORT signalling beyond the disruption of hormone titres, including effects on receptors in different target tissues. In this study, we examined the effects of 6 weeks of exposure to a petroleum-laced diet (1% oil weight:food weight) on tissue mass and intracellular CORT receptors in liver, fat, muscle and kidney (metabolic tissues), spleen (an immune tissue) and testes (a reproductive tissue). In the laboratory, male house sparrows were fed either a 1% weathered crude oil (n = 12) or a control diet (n = 12); glucocorticoid receptors and mineralocorticoid receptors were quantified using radioligand binding assays. In oil-exposed birds, glucocorticoid receptors were lower in one metabolic tissue (liver), higher in another metabolic tissue (fat) and unchanged in four other tissues (kidney, muscle, spleen and testes) compared with control birds. We saw no differences in mineralocorticoid receptors between groups. We also saw a trend towards reduced mass of the testes in oil-exposed birds compared with controls, but no differences in fat, kidney, liver, muscle or spleen mass between the two groups. This is the first study to examine the effects of petroleum on CORT receptor density in more than one or two target tissues. Given that a chronic low dose of ingested petroleum can affect stress-induced CORT titres as well as receptor density, this demonstrates that oil can act at multiple levels to disrupt an animal\u27s response to environmental stressors. This also highlights the potential usefulness of the stress response as a bioindicator of chronic crude oil exposure

Unanswered Prayers: A Study of Apologia for God in the Matter of Prayer

Many Christian writers and thinkers take up the vexing issue of unanswered prayer and thereby use various rhetorical strategies to address the intersection of pertinent teaching about prayer, and the disjunctive, problematic life experiences concerning the experience of unanswered pray-er. Our investigation uses the ancient rhetorical genre of apologia as a lens to better understand the tactics and stances taken up by those who seek to guide members of faith communities toward reconciliation between perceived biblical teaching and actual life experiences concerning unan-swered prayer. Our study incorporates an analysis of both the formal and conceptual strategies utilized by rhetors who seek to repair, or account for, breaches in lived-faith and understood teaching by religious communities through investigation of representative contemporary rhetors who address prayer

Access to the General Curriculum of Middle School Students with Mental Retardation: An Observational Study

The IDEA requires participation and progress in the general curriculum by all students. However, there is limited knowledge about the degree to which students with mental retardation have such access. This study examined the degree to which middle school students with mental retardation have access to the general curriculum and the impact of the classroom setting and the student's level of ability on such access. Findings indicated that students with mental retardation were most likely to participate with the general curriculum in the general education classroom and were less likely to engage in activities linked to a standard if they had more severe disabilities. Many students were engaged in activities in the general curriculum, but there was room for improvement in providing curricular modifications to promote access

Does corticosterone regulate the onset of breeding in free-living birds?: The CORT-Flexibility Hypothesis and six potential mechanisms for priming corticosteroid function

© 2015 Published by Elsevier Inc. For many avian species, the decision to initiate breeding is based on information from a variety of environmental cues, including photoperiod, temperature, food availability, and social interactions. There is evidence that the hormone corticosterone may be involved in delaying the onset of breeding in cases where supplemental cues, such as low food availability and inclement weather, indicate that the environment is not suitable. However, not all studies have found the expected relationships between breeding delays and corticosterone titers. In this review, we present the hypothesis that corticosterone physiology mediates flexibility in breeding initiation (the CORT-Flexibility Hypothesis ), and propose six possible corticosterone-driven mechanisms in pre-breeding birds that may delay breeding initiation: altering hormone titers, negative feedback regulation, plasma binding globulin concentrations, intracellular receptor concentrations, enzyme activity and interacting hormone systems. Based on the length of the breeding season and species-specific natural history, we also predict variation in corticosterone-regulated pre-breeding flexibility. Although few studies thus far have examined mechanisms beyond plasma hormone titers, the CORT-Flexibility Hypothesis is grounded on a solid foundation of research showing seasonal variation in the physiological stress response and knowledge of physiological mechanisms modulating corticosteroid effects. We propose six possible mechanisms as testable and falsifiable predictions to help clarify the extent of HPA axis regulation of the initiation of breeding