Endokrinologie最新文献

The first interaction between target cell and hormone gives rise to hormonal imprinting, which accounts for greater responsiveness of the cell at later interactions. The mechanism of hormonal imprinting is obscure; we based experimental approach to its closer study on combined treatment of Tetrahymena, as model cells, with diiodotyrosine (T2), which stimulates the division, and cell growth inhibitors, which interfere with different stages of cell reproduction, and methylamine, which inhibits cluster formation in the membrane. Of these, actinomycin D and methylamine inhibited the growth of the Tetrahymena, while colchicine did not, and all three suppressed the division stimulating action of T2, but could not prevent hormonal imprinting, as demonstrated on later re-exposure to T2 of cells preexposed and not preexposed to T2 in combination with the inhibitors. It appears that the underlying mechanism of hormonal imprinting is highly complex, and involves many subcellular mechanisms and structures, but suppression of, or gross interference with, one or another of these cannot delete, only quantitatively reduce, the consequence of the first interaction with the hormone, i.e. hormonal imprinting.

The effect of hydrocortisone acetate on the maturity of male Labeo gonius was studied during spawning season. Maturation was inhibited and spermiation arrested. Reduction in the lobes of the testes, volume of the testes and gonadosomatic index were observed. The length of the testes was also reduced. The clumping of spermatozoa occurred in the middle part of the seminiferous lobules. The control group remained unchanged.

The seasonal changes observed in the neurons of the nucleus lateralis tuberis (NLT) of Clarias batrachus have been studied with particular reference to the testicular cycle throughout the year at 15 days interval. The neurons of the pars medialis (pm) and pars ventrocaudalis (pvc) subgroups of the four NLT components exhibited steady enlargements and degranulation, consistent with the spermatocyte enlargement. During spermiation phase (August), when the fishes spermiated, the neurons of pm and pvc attained their maximum size. Thus, a possible link existing between the hypothalamic nucleus (pm and pvc) and the testicular activity has been established.

Intermale aggression by pairing bandicoot rats (Bandicota bengalensis) in their home cage, continuously for three hours, stimulated the pineal gland activity, cytologically measured by decreasing cell population density and increasing nuclear size of the pinealocytes, in the socially subordinate animals. The pineal gland of the dominant animal was not perceptibly affected by aggression. It is suggested that during aggression, the subordinate rats perhaps suffered from psychosocial stress that might have caused hyperactivity of their pineal gland.

The effects of prolonged steroid suppression on adrenal 5 alpha-reductase and 11 beta-hydroxylase activities and corticosterone production in vitro was studied in adult male rats. Cortisone acetate was administered at a dose of 2.5 mg/rat daily for 30 days and after that time at a dose of 5 mg/rat every other day. Autopsies were performed on 3, 6, 9, 12, 15, 20, 30, 60 and 120 days of experiment. Cortisone treatment resulted in a decrease in corticosterone output by quartered adrenals and an earlier and more marked drop in corticosterone production by whole adrenal homogenates. Steroid suppression leads to a marked increase in adrenal 5 alpha-reductase activity assayed on 12,000 X g supernatant, however on 120 day of experiment activity of the enzyme was markedly lower if compared with the earlier time-interval studied. 11 beta-hydroxylase activity, as tested in mitochondrial fraction, on day 12 of experiment was even higher than in control rats and thereafter a marked decline occurred. The studies suggest that adrenal steroid 5 alpha-reductase activity may participate in adaptation of adrenals to a disturbed hormonal status of the organism induced by cortisone treatment.

Role of calcium (Ca2+) in the effects of thyroliberin (TRH) and somatostatin (SRIF) on the release of growth hormone (GH), prolactin (PRL) and thyroid stimulating hormone (TSH) from the rat adenohypophyseal cells in primary monolayer cultures has been studied. Decrease of extracellular Ca2+ diminished the stimulatory effects of TRH on TSH and PRL release. Ca2+ is also an important factor in the mechanism of SRIF action. Data obtained in the experiments with high Ca2+ levels in the medium indicate that some antagonistic interrelationship exists between Ca2+ and SRIF. These results suggest that the participation of cAMP alone is not sufficient for stimulus-secretion coupling. Another messenger, namely Ca2+, is necessary for the effects of hypothalamic hormones. On the other hand, the contribution of Ca2+ to the secretory process in mammotrophs, somatotrophs and thyrotrophs is not equal. PRL and TSH secretion is more dependent on the presence of extracellular Ca2+ than the release of GH.

The aim of the present investigation is to evaluate adrenomedullary hormones and blood glucose responses to intermale aggression in the bandicoot rat. Aggression elicited a rise in adrenaline and noradrenaline content of the adrenal gland and in blood glucose level in the subordinate rats. No significant change was marked in the dominant rats after aggression. It is suggested that during aggression the subordinate rats suffered from psychosomatic stress that resulted in hyperactivity of the adrenal medulla and consequently hyperglycemia.

The relationship between the ejection time from the left ventricle (LVET), the pre-ejection period (PEP) of the left ventricle, the Q-Kd interval, the course of the Achilles tendon reflex (ATR) and the thyroxine (T4) and triiodothyronine (T3) serum level in 184 patients with different grades of thyroid function was investigated. Some of these patients suffered from cardiac affection caused by thyrotoxicosis or ischemic heart disease. The significant inverse correlations between the T3 level and the duration of PEP, LVET, the Q-Kd interval and the ATR was revealed. An inverse relationship with T4 level was found only in the Q-Kd interval and ATR. In those instances, where there was a correlation with T4 and T3, higher values of correlation coefficients were observed in the correlation with T3. T4 concentration was higher in patients with cardiac affection. In thyrocardiacs was an increase in the quotient T4:T3, while in thyrotoxic patients without cardiac affection this quotient was rather decreased. The significance of disturbed T4 metabolism in development of cardiac affection in thyrotoxicosis is discussed with respect to ageing processes.

1. A relationship is established between different doses of intraperitoneally injected streptozotocin (SZ) and the degree of hyperglycemia and hyperlipemia. 2. Changes in serum level of glucose, cholesterol, triglycerides and NEFA were determined after intraperitoneal administration of three different doses (55 mg, 85 mg and 125 mg/kg body weight) of SZ. Cholesterol level was significantly (P less than 0.001) elevated after 72 hrs only in the animals which received 85 mg/kg and 125 mg/kg SZ. 3. Dose dependent changes in NEFA and triglycerides could be observed after 24 hrs of SZ administration. 4. Diabetic animals consistently showed triphasic blood sugar response, initial hyperglycemia at 5-7 hrs, profound hypoglycemia in between 8-12 hrs and finally an irreversible hyperglycemic state by 24 hrs and onwards. 5. Liver and muscle glycogen were continuously decreased except a significant rise at 12 hrs coinciding with hypoglycemic phase. During the experimental period SZ treated rats continuously lost weight, while control animals progressively gained weight. In summary these changes indicated that diabetogenicity is dose dependent and the severity can be judged by elevated lipid metabolites.