Alimentary tract hormones

PTHrP is released during lactation and its levels increase about 10,000-fold over the levels found in the serum of nonlactating women. Receptors for PTHrP are present in the intestinal epithelium and the hormone may play a physiologic role in the development of the alimentary tract. However, infants raised on soy milk formulas that do not contain the hormone are healthy thus, the hormone is not essential. 

The actions of thyrocalcitonin on the alimentary tract do not appear to be of major significance. Aliapoulios and Munson (Al) found that administration of the hormone to rats produced the expected hypocalcemia, even when the entire gastrointestinal tract had been removed. Clearly, changes in calcium absorption or fecal loss cannot be relevant to the immediate drop in plasma calcium level. However, previous fasting, or the administration of a low-calcium diet for some days, appears to sensitize the rat to the effects of thyrocalcitonin (H4, Kl). 

Originally, it was thought that these compounds could provide the structural basis for the design of pesticides because it is unlikely that insects would develop resistance to their own or closely related hormones [120]. However, this has proven not to be the case. Most insects possess enzymes such as mixed function oxidases and esterases in their alimentary tract and haemolymph which are, among other functions, important for the metabolism of plant toxins [121, 122]. For example, insects which have developed resistance to insecticides may also show resistance to JH... 

Pressor hormone, of posterior pituitary, activity, VII, 385, 390 circulatory, VII, 390, 405 hyperglycemic, VIII, 233, 234 oxytocic, VIII, 228 amino acids in, VII, 383 composition, VII, 385 diabetes insipidus and, VIII, 245 effect on alimentary tract, VIII, 218-225... 

Cells which stain with silver salts and which are found in several sites in the alimentary tract. They synthesize the hormone serotonin. 

Crystalline insulin, C45Hj90i4NxiS.3H20, has been obtained by various methods, including the addition of pyridine to insulin solutions at pH 5-6. The potency of the crystalline hormone is very little greater than that of some of the amorphous preparations, namely, 23-26 international units per mg. Chemically, insulin belongs to the peptides, which may explain its destruction in the alimentary tract, when given by the mouth. 

The existence of chemical factors controlling secondary sexual characters in the male had long been inferred from the more obvious consequences of castration, before or after puberty. Early attempts by Brown-S quard and others to obtain active extracts from testicular tissue were inconclusive, mainly for two reasons the preparations were administered by the alimentary tract, from which the hormones are only absorbed with difficulty and no exact method of chemical assay was available. Since 1930, Moore and others have shown that androgenic activity may be detected by the increased growth of the comb and wattles in castrated birds (capons) and Korenchevsky has based a method of assay on the increased growth of the prostate and seminal vesicles evoked when the hormone is injected into castrated rodents. Aided by these tests, four natural androgens have been isolated, and various artificial androgens have been synthesised. 

A major role of vitamin D is to maintain the concentrations of calcium and phosphorus in the blood, primarily by enhancing the absorption of dietary calcium from the alimentary tract and regulating the interchange of calcium between blood and bone. It is likely that there are other cellular roles as yet little understood. The active form of vitamin D responsible for the hormone-like functions described above is 1,25-dihydroxycholecalciferol. Cholecalciferol, whether absorbed from the diet or synthesized in the skin, is first hydroxylated in the liver to 25-hydroxycholecalciferol. This is the main form of the hormone circulating in the blood, bound to a sterol binding protein. A further hydroxylation occurs in the kidneys to give 1,25-... 

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