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Hormones Act (hormones + act)

Distribution by Scientific Domains

Life Sciences	60%
Medical Sciences	40%

Selected Abstracts

The use of leukocyte profiles to measure stress in vertebrates: a review for ecologists

FUNCTIONAL ECOLOGY, Issue 5 2008
A. K. Davis
Summary 1A growing number of ecologists are turning to the enumeration of white blood cells from blood smears (leukocyte profiles) to assess stress in animals. There has been some inconsistency and controversy in the ecological literature, however, regarding their interpretation. The inconsistencies may stem partly from a lack of information regarding how stress affects leukocytes in different taxa, and partly from a failure on the part of researchers in one discipline to consult potentially informative literature from another. 2Here, we seek to address both issues by reviewing the literature on the leukocyte response to stress, spanning the taxa of mammals (including humans), birds, amphibians, reptiles and fish. 3We show that much of the early literature points to a close link between leukocyte profiles and glucocorticoid levels. Specifically, these hormones act to increase the number and percentage of neutrophils (heterophils in birds and reptiles), while decreasing the number and percentage of lymphocytes. This phenomenon is seen in all five vertebrate taxa in response to either natural stressors or exogenous administration of stress hormones. For the ecologist, therefore, high ratios of heterophils or neutrophils to lymphocytes (,H : L' or ,N : L' ratios) in blood samples reliably indicate high glucocorticoid levels. Furthermore, this close relationship between stress hormones and N : L or H : L ratios needs to be highlighted more prominently in haematological assessments of stress, as it aids the interpretation of results. 4As with hormone assays, there are challenges to overcome in the use of leukocytes profiles to assess levels of stress; however, there are also advantages to this approach, and we outline each. Given the universal and consistent nature of the haematological response to stress, plus the overwhelming evidence from the veterinary, biomedical and ecological literature reviewed here, we conclude that this method can provide a reliable assessment of stress in all vertebrate taxa. [source]

Distribution of sex steroid hormone receptors in the brain of an African cichlid fish, Astatotilapia burtoni

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 16 2010
Lauren A. Munchrath
Abstract Sex steroid hormones released from the gonads play an important role in mediating social behavior across all vertebrates. Many effects of these gonadal hormones are mediated by nuclear steroid hormone receptors, which are crucial for integration in the brain of external (e.g., social) signals with internal physiological cues to produce an appropriate behavioral output. The African cichlid fish Astatotilapia burtoni presents an attractive model system for the study of how internal cues and external social signals are integrated in the brain as males display robust plasticity in the form of two distinct, yet reversible, behavioral and physiological phenotypes depending on the social environment. In order to better understand where sex steroid hormones act to regulate social behavior in this species, we have determined the distribution of the androgen receptor, estrogen receptor alpha, estrogen receptor beta, and progesterone receptor mRNA and protein throughout the telencephalon and diencephalon and some mesencephalic structures of A. burtoni. All steroid hormone receptors were found in key brain regions known to modulate social behavior in other vertebrates including the proposed teleost homologs of the mammalian amygdalar complex, hippocampus, striatum, preoptic area, anterior hypothalamus, ventromedial hypothalamus, and ventral tegmental area. Overall, there is high concordance of mRNA and protein labeling. Our results significantly extend our understanding of sex steroid pathways in the cichlid brain and support the important role of nuclear sex steroid hormone receptors in modulating social behaviors in teleosts and across vertebrates. J. Comp. Neurol. 518:3302,3326, 2010. © 2010 Wiley-Liss, Inc. [source]

Effect of thyroid hormones on stress ulcer formation

ANZ JOURNAL OF SURGERY, Issue 9 2002
Ayhan Koyuncu
Background: Stress ulcers are gastric mucosal lesions that may cause life-threatening upper gastrointestinal bleeding. Although it is known that hyperthyroid status prevents stress ulcer formation, the effect of thyroid hormones given just as the stress is beginning has not been studied. The aim of this study was to assess the effect of thyroid hormone supplementation on gastric stress ulcers at the beginning of the restraint stress. Methods: Thyroid hormones were administered to rats 2 days before or at the beginning of the restraint stress. The linear length of the gastric mucosal lesions, mucosal pH and thyroid hormone levels were measured and histopathological examinations were carried out. Results: It was found that both triiodothyronin and thyroxin reduce the length and depth of the stress ulcers (P < 0.001). Conclusion: Although the mechanisms by which the thyroid hormones act on stress ulcers are uncertain, current experimental studies suggest that thyroid hormones reduce the formation of stress ulcers in rats when given before or at the beginning of the stress. [source]

The intracrine hypothesis and intracellular peptide hormone action

BIOESSAYS, Issue 4 2003
Richard N. Re
There is evidence that many peptide growth factors and hormones act in the intracellular space after either internalization or retention in their cells of synthesis. These factors, commonly called intracrines, are structurally diverse while sharing some common functional features. Reports of intracellular peptide hormone binding and action are reviewed here. Also, this laboratory has made proposals regarding the origin and actions of intracrines and these areas are further explored. Intracrine interactions and the relationship of intracrines to transcription factors are discussed. The intracellular/intracrine renin,angiotensin system (iRAS) is reviewed to illustrate the intracrine analogue of a well-established physiological system. The role of intracrine action in metazoan development is also considered. BioEssays 25:401,409, 2003. © 2003 Wiley Periodicals, Inc. [source]

Glucose homeostasis and the gastrointestinal tract: insights into the treatment of diabetes

DIABETES OBESITY & METABOLISM, Issue 1 2008
D. Maggs
The gastrointestinal tract is increasingly viewed as a critical organ in glucose metabolism because of its role in delivering glucose to the circulation and in secreting multiple glucoregulatory hormones that, in concert with insulin and glucagon, regulate glucose homeostasis. Under normal conditions, a complex interplay of these hormones acts to maintain plasma glucose within a narrow range despite large variations in the availability of glucose, particularly during transition from the fasting to fed state. In the fed state, the rate at which nutrients are passed from the stomach to the duodenum, termed gastric emptying rate, is a key determinant of postprandial glucose flux. In patients with diabetes, the regulation of glucose metabolism is disrupted resulting in fasting and postprandial hyperglycaemia. Elucidation of the role of the gastrointestinal tract, gut-derived glucoregulatory peptides and gastric emptying rate offers a new perspective on glucose homeostasis and the respective importance of these factors in the diabetes state. This review will highlight the importance of the gastrointestinal tract in playing a key role in glucose homeostasis, particularly in the postprandial period, and the role of established or new therapies that either leverage or modify gastrointestinal function to improve glycaemic state. [source]