In this study, we examined hormonal regulation of the distribution profiles of leukocyte subpopulations in the peripheral blood of rats. Flow cytometric analysis revealed significant and selective changes in the numbers and the percentages of peripheral blood leukocyte subpopulations which were a function of diurnal variations in hormone secretion and hormonal changes induced by acute stress. Changes in numbers and percentages of leukocyte subpopulations, which varied with time of day, were similar to changes observed under stress conditions. At the beginning of the rat's active period, and after 1 h of restraint stress, there was a significant reduction in numbers of leukocytes and lymphocytes. This reduction was primarily accounted for by a decrease in numbers of B cells, natural killer cells, monocytes (diurnal study), and helper T cells (diurnal study). There was also a significant decrease in the percentage of lymphocytes which was mirrored by an increase in the percentage of neutrophils in the peripheral blood. Peripheral blood leukocyte numbers were inversely related to plasma corticosterone levels. These results suggest that the endocrine system plays a role in the regulation of immune cell turnover and/or redistribution between immune compartments under conditions of normal daily experiences, namely, the diurnal cycle, and mild acute stress. They also suggest that these effects are selective for certain subpopulations of leukocytes.
"Lymphopenia response is reported to be a strategy that allows lymphocytes to move to sites of greatest potential for pathogens entry into the body such as epithelia of gills, skin and intestines; this help fish to mitigate infection from foreign pathogens  . Simultaneously, the circulating neutrophils are increased to attack pathogens that enter the body  . "
"This supposition is supported by a series of studies wherein individuals predictably alter their circulating leukocytes profile in response to exogenous GC administration (e.g. Dhabhar et al. 1994). However, a clear positive relationship between elevated GC and HLR has remained difficult to detect, especially in wild populations, as M€ uller, Jenni-Eiermann & Jenni (2011) failed to show a significant positive relationship between these two parameters. "
[Show abstract][Hide abstract] ABSTRACT: 1.There is growing need for reliable biomarkers of the physiological stress response in basic ecological investigations and conservation-specific applications. One effect of stress hormone secretion is the alteration of circulating leukocytes, specifically an increase in the heterophil: lymphocyte ratio (HLR). There have been numerous studies and reviews of the relationship between the stress response and HLR, yet the data have not been systematically analyzed across studies.2.Here, we performed meta-analyses of studies in which paired values of plasma corticosterone (CORT) and HLR were available to investigate the relationship between these parameters. Specifically, we analyzed CORT and HLR as baseline measures between treatment (or “stressed” populations) and control (or “reference” populations). Additionally, we investigated the relationship within CORT and HLR to identify temporal patterns of the response as a result of the duration of the stressor.3.Across studies, we identified that CORT and HLR are significantly elevated in populations subjected to environmentally stressful conditions. While not significantly different, CORT tended to be more elevated than HLR in the stressed populations.4.We found that there is a significant, negative relationship between CORT and the temporal duration of environmental stress. Additionally, we found a significant breakpoint in this response at 85 days of stress duration, above which there is not a clear relationship between CORT and duration. This indicates that the CORT response to environmental stress attenuates.5.We found a small but positive significant relationship between HLR and temporal duration of environmental stress. This suggests that the elevation of HLR in response to environmental stress does not decrease over time.6.Our data identified that data gaps of wild populations of species exist, and that more studies pairing physiological stress responses will further our understanding of how populations respond to environmental challenges. We found that CORT and HLR responded differently to stress, depending on captivity status, whether the study population was the domestic chicken, and the sex of the study population.This article is protected by copyright. All rights reserved.
"While glucocorticoids are often assayed to evaluate the physiological response to stress by the hypothalamic–pituitary–adrenal (HPA) axis, another increasingly common method of assessing physiological stress involves quantification of circulating leukocyte ratios—neutrophil to lymphocyte ratios in mammals, amphibians, and some fishes, and heterophil to lymphocyte (H:L) ratios in birds, reptiles, and other fish species (reviewed in Davis et al., 2008). Studies in poultry have demonstrated a causal relationship between the main circulating glucocorticoid , corticosterone (CORT), and H:L ratios (Gross and Siegel, 1983), with higher CORT resulting in increased movement of lymphocytes out of circulation into more peripheral tissues, thereby—in association with a rise in circulating heterophils—generating an increase in circulating H:L ratios (Dhabhar et al., 1994, 1996). This relocation of leukocytes is thought to be a mechanism for redistributing cells to locations where their actions are required during a stress response. "
[Show abstract][Hide abstract] ABSTRACT: Glucocorticoids and leukocyte ratios have become the most widespread variables employed to test hypotheses regarding physiological stress in wild and captive vertebrates. Little is known, however, regarding how these two indices of stress covary in response to stressors, their repeatability within individuals, and differences in response time upon capture. Furthermore, few studies compare stress indices between captive and wild populations, to assess potential alteration of stress physiology in captivity. To address these issues, we examined corticosterone (CORT) and heterophil to lymphocyte (H:L) ratios in two ecotypes of the garter snake Thamnophis elegans. We found that CORT and H:L ratios were not correlated within individuals, and both variables showed little or no repeatability over a period of months. CORT levels, but not H:L ratios, were higher for individuals sampled after ten min from the time of capture. However, both variables showed similar patterns of ecotypic variation, and both increased over time in gravid females maintained in captivity for four months. We suggest that CORT and H:L ratios are both useful, but disparate indices of stress in this species, and may show complex relationships to each other and to ecological and anthropogenic variables.
Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 04/2014; 174. DOI:10.1016/j.cbpa.2014.03.023 · 1.97 Impact Factor
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