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Feeding State (feeding + state)
Selected AbstractsOrexins (hypocretins) actions on the GHRH/somatostatin-GH axisACTA PHYSIOLOGICA, Issue 3 2010M. López Abstract The secretion of growth hormone (GH) is regulated through a complex neuroendocrine control system that includes two major hypothalamic regulators, namely GH-releasing hormone (GHRH) and somatostatin (SST) that stimulate and inhibit, respectively, GH release. Classical experiments involving damage and electrical stimulation suggested that the lateral hypothalamic area (LHA) modulated the somatotropic axis, but the responsible molecular mechanisms were unclear. Evidence obtained during the last decade has demonstrated that orexins/hypocretins, a family of peptides expressed in the LHA controlling feeding and sleep, play an important regulatory role on GH, by inhibiting its secretion modulating GHRH and SST neurones. Considering that GH release is closely linked to the sleep,wake cycle and feeding state, understanding orexin/hypocretin physiology could open new therapeutic possibilities in the treatment of sleep, energy homeostasis and GH-related pathologies, such as GH deficiency. [source] Social Environment and Feeding State Influence Movement Decisions in a Web-building SpiderETHOLOGY, Issue 10 2009Maxence Salomon It is well recognized that feeding rate has a major influence on the amount of movement between microhabitats for many animals. However, the role of other extrinsic and intrinsic factors, and particularly how these factors may interact, is not well understood. This three-part study examines the movement decisions of a web-building spider, Latrodectus hesperus, by assessing microhabitat tenacity in established spiders and by testing how the presence of conspecific neighbours and the combined influence of individual feeding state (determined by prior feeding experience) and neighbour presence influence microhabitat residence time in unestablished spiders. The results show that naturally established spiders did not leave their microhabitats readily, emphasizing the importance of choosing a profitable location. Unestablished spiders stayed longer in microhabitats occupied by conspecifics than in unoccupied ones, and there was practically no cannibalism even though neighbours shared webs. Furthermore, feeding state and neighbour presence showed an interactive effect on microhabitat residence time. When spiders were housed alone, microhabitat residence time increased with feeding state. However, in the presence of conspecifics, spiders had a low propensity to move, regardless of feeding state. Together, these results demonstrate the combined importance of grouping dynamics and feeding state in shaping movement decisions. [source] Fasting modulates metabolic responses to cortisol, GH and IGF-I in Arctic charr hepatocytesJOURNAL OF FISH BIOLOGY, Issue 6 2005Ř. Aas-Hansen Hepatocytes in primary culture from fed and 2 month fasted Arctic charr Salvelinus alpinus were exposed to physiological doses of either cortisol, salmon growth hormone (GH), salmon insulin-like growth factor-I (IGF-I) or a combination of salmon GH and salmon IGF-I. Fasting significantly lowered medium glucose levels compared to the fed fish, but had no significant effects on hepatocyte glycogen content or on the activities of enzymes involved in the intermediary metabolism. Cortisol treatment had no effect on hepatocyte glycogen content or on the enzyme activities investigated, but resulted in a significant increase in medium glucose concentration in hepatocytes isolated from fasted, but not fed fish. GH and IGF-I treatments, both singly and in combination, significantly increased the glycogen content of hepatocytes isolated from fed fish, with less pronounced effects on hepatocytes isolated from fasted fish. The combination of GH and IGF-I significantly increased lactate dehydrogenase activity regardless of the feeding state and significantly reduced the phosphenolpyruvate carboxykinase activity and medium glucose concentration in hepatocytes isolated from fed fish. Further, GH and IGF-I significantly increased the activities of alanine aminotransferase and aspartate aminotransferase in hepatocytes isolated from fasted fish, but not fed fish. There were no effects of GH, IGF-I, or their combination, on glucose 6-phosphate dehydrogenase or 3-hydroxyacyl-CoA dehydrogenase activities. The results demonstrated that nutritional status of the animal modulates hepatocyte responsiveness to metabolic hormones, and suggested a role for GH and IGF-I in hepatic glycogen conservation. [source] | ||||||||||