Homeostatic hormones

Leptin is a homeostatic hormone. It inhibits food intake and promotes energy expenditnre. Therefore, in the face of a loss in body fat, the levels of leptin decrease and food intake is stimnlated. In contrast, if body fat stores increase, the levels of leptin increase as well and food intake is decreased and energy expenditure increased. Therefore, leptin tends to maintain body weight within fairly close limits. Since ob/ob mice are genetically deficient in leptin, it follows that administration of leptin shonld tend to restore normal body weight. That is exactly what happens. Injection of leptin into ob/ob mice reduces their food intake dramatically and they tend toward the body weights of their normal littermates. In these mice at least, leptin is a powerful force for treatment of obesity. 

Leptin a polypeptide hormone produced by and released from adipose tissue its levels are inversely correlated with body weight a homeostatic hormone. 

Interaction of PTH, calcitonin, and serum concentrations of calcium and phosphate in calcium and phosphate homeostasis. [Modified and reproduced, with permission, from A. W. Norman, Vitamin D The Calcium Homeostatic Hormone. Academic Press, New York, 1979.]... 

Homeostatic Hormones. Insulin is produced by beta cells found in the islets of Langerhans that are dispersed throughout the pancreas. The islet cells constitute only 1% of total pancreatic tissue. Each islet contains about 3000 endocrine cells with a core of beta cells surrounded by other endocrine cells such as the glucagon-secreting alpha cells, the somatostatin-secreting delta cells, and the pancreatic polypeptide-secreting PP cells. The beta cells first synthesize a 109-amino-acid preproinsulin that is subsequently processed to an 86-amino-acid proinsulin. The... 

Fig. 2. Homeostatic control of blood Ca " level where PTH is parathyroid hormone [9002-64-6], CC, cholecalciferol, ie, vitamin D HCC, hydroxycholecalciferol DHCC, dihydroxycholecalciferol CaBP, calcium-binding protein NAD PH, protonated nicotinarnide-adenine dinucleotide...

The volume of extracellular fluid is direcdy related to the Na" concentration which is closely controlled by the kidneys. Homeostatic control of Na" concentration depends on the hormone aldosterone. The kidney secretes a proteolytic enzyme, rennin, which is essential in the first of a series of reactions leading to aldosterone. In response to a decrease in plasma volume and Na" concentration, the secretion of rennin stimulates the production of aldosterone resulting in increased sodium retention and increased volume of extracellular fluid (51,55). 

A. W. Norman, Vitamin D—The Calcium Homeostatic Steroid Hormone, Academic Press, Inc., New York, 1979, p. 3. 

Among vertebrate species, the neuro-endocrine-immime system is responsible for many complex, inter-related physiological processes including neuronal, homeostatic, reproductive and immune functions. There are four main types of hormone polypeptides, eicosanoids, steroids and thyroid hormones. Reflecting the inter-dependency of the neiiro-endocrine and immune systems, hormones, neuropeptides and other neiirotransmitters are known to be produced by some immune cells and play a role in the regulation of the immune system, while endocrine and nervous tissues express receptors for many substances produced by the immune system. The major focus of interest in endocrine disruption has... 

Brain structure below the thalamus and main portion of the ventral region of the diencephalon, controlling homeostatic and nonhomeostatic basic body and brain functions, including circadian and feeding rhythms, energy metabolism, thermogenesis, sympathoadrenal, and neuroendocrine outflow (secretion of hormones by the pituitary gland), behavioral state and memory functions. 

HORMONES TRANSDUCE SIGNALS TO AFFECT HOMEOSTATIC MECHANISMS... 

Electrolytes are involved in many metabolic and homeostatic functions, including enzymatic and biochemical reactions, maintenance of cell membrane structure and function, neurotransmission, hormone function, muscle contraction, cardiovascular function, bone composition, and fluid homeostasis. The causes of electrolyte abnormalities in patients receiving PN may be multifactorial, including altered absorption and distribution excessive or inadequate intake altered hormonal, neurologic, and homeostatic mechanisms altered excretion via gastrointestinal and renal losses changes in fluid status and fluid shifts and medications. 

Each cell is surrounded by a plasma membrane that separates the cytoplasmic contents of the cell, or the intracellular fluid, from the fluid outside the cell, the extracellular fluid. An important homeostatic function of this plasma membrane is to serve as a permeability barrier that insulates or protects the cytoplasm from immediate changes in the surrounding environment. Furthermore, it allows the cell to maintain a cytoplasmic composition very different from that of the extracellular fluid the functions of neurons and muscle cells depend on this difference. The plasma membrane also contains many enzymes and other components such as antigens and receptors that allow cells to interact with other cells, neurotransmitters, blood-borne substances such as hormones, and various other chemical substances, such as drugs. 

Regarding the adrenal steroids, the behavioral activation of hormonal secretion in stress is part of a mechanism for restoring homeostatic balance. For example, an encounter with a predator may require rapid evasive action, in which neural activity and rapidly mobilized hormones such as epinephrine play a role. Adrenal steroid secretion is slower, reaching a peak minutes after the stressful event, and therefore is not expected to play a role in coping with the immediate situation. If the evasive action is successful and... 

Nickel is considered essential to animals because it is present in the fetus or newborn, is homeostatically regulated, the metabolic pool of nickel is specifically influenced by hormonal substances or pathologic processes, certain metalloproteins contain nickel, and because nickel deficiency has been induced experimentally in certain species of birds and animals (NAS 1975 USPHS 1977 Kirchgessner and Schnegg 1980). In general, the nickel deficiency syndrome can be cured or prevented by trace amounts of nickel (NAS 1975). However, nickel administration may not be successful in reversing all abnormalities produced by nickel deprivation (USPHS 1977). 

Because melatonin is sold over the counter and its production is not the subject of strict regulation as is that of prescribed medications, it is in wide use, but insufficient scientifically controlled information is available. Another consequence of the popularity and availability of the hormone is its use in a wide array of situations in which its efficacy has not been proven yet for instance, as treatment for neurodegenerative diseases or as a sleep-inducing medication. It also has been tried as an antidepressant, but that effect is still unclear. The administration of melatonin to patients with bipolar depression, especially to rapid cyclers, is of interest, especially if its use is associated with the presumed decrease in nocturnal hormonal levels and increase in sensitivity to light (Lewy et al. 1985). The possibility that melatonin also serves as a stabilizer of rhythm in these patients is in accord with the homeostatic effect of several other hormones that have been previously discussed here. 

Evidence of noradrenergic involvement in panic disorder includes results from studies on the growth hormone axis, the cardiovascular system, and the homeostatic control of the noradrenergic axis. A review of these three areas is presented below. To illustrate the manner in which the environment may interact with the noradrenergic axis, the review of these three areas integrates research on panic disorder with research on children who may be at risk for panic disorder and with research on nonhuman primate models of human anxiety states. 

Maintenance of red cell volume is critical to having an adequate oxygen supply to the tissues [10]. Healthy individuals finely balance erythropoiesis and erythrocyte loss and maintain constant hematocrit. The glycoprotein hormone erythropoietin is the principal controller of the homeostatic mechanism that links tissue oxygen delivery to red cell production. While hypothesized as early as 1863, unequivocal evidence of erythropoietin was first published in 1953. A few years later, scientists showed that animals subjected to bilateral nephrectomy were unable to mount an erythropoietin response to hypoxia. Indeed, the kidneys produce about 90% of circulating erythropoietin. 

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