Endocrinologia experimentalis最新文献

Rats were subjected to acute immobilization (IMO) for 1 or 2 h and killed by decapitation. The hypothalamic supraoptic and paraventricular nuclei were isolated by dissection technique and the activity of acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) was assayed. A period of 1 or 2 h of IMO resulted in a significant increase of AChE activity only in the supraoptic nucleus, while no change of ChAT activity occurred. Acute IMO of 1 or 2 h duration resulted in an increase of AChE activity in supraoptic nucleus.

Tritiated vasopressin analogue, [8-L-arginine, 9-desglycineamide]-vasopressin was prepared from its diiodo-derivative by means of catalytic reductive dehalogenation. The reaction products were purified by reversed-phase HPLC resulting in a labelled peptide with high specific radioactivity (629 TBq/mmol).

Methylmercury (MeHg) treatment intramuscularly at doses of 10 and 20 micrograms separately/day/mouse for 30 days affected the weight of body and organs like testes, vas deferens and seminal vesicles in mice. Diminution of testosterone in serum was also associated with an accumulation of cholesterol in testes and reduction in seminal vesicle fructose. Altered spermatogenesis and Leydig cell morphology in testes and the changes in histoarchitecture of seminal vesicle and vas deferens indicated androgen deficiency in treated mice. Thus, the data suggested that MeHg administration to mice induced androgen deprived effect to target organs probably by blocking Leydig cell function.

The effect of endogenous opioid peptides (beta-endorphin, leucine-enkephalin, dynorphin 1-13 on the release of thyrotropin releasing hormone (TRH) from the rat stomach in vitro was studied. The rat stomach was incubated in the medium 199 with 1.0 mg/ml of bacitracin (pH 7.4) (medium) and the amount of TRH released into the medium was measured by radioimmunoassay. The release of TRH from the rat stomach was inhibited significantly in a dose-related manner with the addition of endogenous opioid peptides, but not affected with naloxone. However, the inhibitory effect of endogenous opioid peptides on TRH release from the rat stomach was prevented by the addition of naloxone. These findings suggest that endogenous opioid peptides inhibit TRH release from the rat stomach in vitro.

Experimental hyperthyroidism (thyroxine administration for 21 days) caused a significant decrease in ash mass, bone density and mineral content in the femora of mice, the same degree of reduction in individual measures of bone mass being found in oophorectomized and intact mice treated with thyroxine. It may be suggested that estrogens did not protect the skeleton against the resorbing action of thyroxine or triiodothyronine.

It has been shown that prolonged muscular exercise reduces insulin concentration in the portal vein and in the abdominal aorta. However, the reduction in the portal vein is much more pronounced than in the aorta and it indicates that the exercise reduces not only insulin secretion but also its removal.

Thyrotropin (TSH) levels in plasma were estimated with the aid of immunoradiometric assay in two groups of healthy male subjects aged 21-22 years in two experiments: 1. acute (30 min) exposure to 4 degrees C in a cold room; 2. insulin (0.01 U per kg i.v.) hypoglycemia at room temperature and at 55 degrees C. Immediately after cold exposure a decrease of TSH level was found (P less than 0.01), while no changes were observed during 30 min exposure. After insulin injection a significant decrease (P less than 0.05 to less than 0.001) of TSH level was found at 45 to 120 min irrespectively of the ambient temperature. In addition, increased levels of noradrenaline and decreased levels of growth hormone after cold exposure are presented.

The aim of this paper is the identification of beta-lipotropin (beta/LPH) as a peptide present in intraglandular colloid (the holocrine secretion of cells in the marginal half of the bovine pituitary intermediate lobe). beta/LPH, although not an opioid peptide itself, contains the peptide beta-endorphin. The methodology used allowed detection of beta/LPH when present in the samples in sufficient amounts.

The erythrocytes were used as a model system to study insulin receptors in diabetic patients with highly increased insulin resistance. The specific binding of 125I-insulin to erythrocytes of these patients was markedly reduced. When erythrocytes prepared from non-diabetic subjects were exposed to serum of these patients, the decrease of insulin binding was reproduced. The binding of insulin showed a displacement curve that is parallel to the control values over the same range of hormone concentration, even in the case when control erythrocytes were preincubated with serum of diabetics with increased insulin resistance. These results indicate the presence of certain component in blood plasma of examined patients which alters insulin binding to receptors. The developed assay provides an efficient method for detection and identification of substances presented in the serum which can influence the binding of insulin to the specific sites as well as its biological effects.