Endocrinologia experimentalis最新文献

Non-steroidal antiandrogens (NAA), flutamide and hydroxy-flutamide were used to study involvement of androgenic receptors in feedback control of gonadotropin secretion in males. In castrated animals these blockers inhibited the uptake of tritiated testosterone (T) by the hypothalamus and adenohypophysis. In male rats with intact gonads the NAA were found to reduce inhibitory effects of circulating endogenous androgens on the hypothalamus and pituitary gland which resulted in the increase of plasma LH, FSH and T levels, enhanced pituitary sensitivity to intravenously injected LHRH, increased activity of testicular steroid-delta 5-3 beta-ol-dehydrogenase. Endocrine response appeared the most pronounced in rats and was less marked in other animals species, and also in humans. No response was revealed in hypophysectomized male rats. Deafferentation of mediobasal hypothalamus by Halász knife had no impact on increased plasma T level following exposure to NAA. Furthermore, electrolytic destruction of arcuate nucleus and median eminence prevented or diminished significantly stimulation of LH, FSH and T secretion in NAA treated male rats. The results of this study suggest that androgenic receptors of mediobasal hypothalamus and pituitary gland are involved in control of gonadotropin secretion by circulating male sex hormones.

In 5 patients after total thyroidectomy followed by radioiodine ablation the frequency analysis of EEG based on fast Fourier transformation was performed and the results obtained during hypothyroid state and after the substitution treatment with thyroid hormones were compared. During the hypothyroid state the most remarkable finding was the increase of percentage representation of fast frequencies in beta 1 and beta 2 bands, while such values in alpha band including a dominant frequency in that band were reciprocally decreased. After the period of treatment with triiodothyronine during which clinically euthyroid state has been achieved (i.e. decrease of Achilles tendon reflex time, decrease of TSH and of T3 level) no significant changes in the distribution of EEG frequencies spectrum were found, but in all patients a dominant frequency in alpha band was increased at least for 1 Hz. Only after the treatment with thyroxine (Eltroxin Glaxo) the interrelations between individual frequencies of EEG spectrum returned to the normal range and a further increase in dominant alpha frequency was found. The correlation between a dominant frequency in alpha band and thyroxine level in serum was highly significant. These findings are in agreement with our previous observations in 43 subjects where a dominant alpha frequency in healthy controls was always higher than that in hypothyroid subjects and was significantly related to T4 level. The findings of continuing EEG signs of brain hypothyroidism even after achieving of clinical euthyroidism and normal peripheral parameters under increased serum T3 and low T4 level are in full agreement with experimental observations on the importance of local deiodination of T4 in brain tissue and on the risk of hypothyroxinemia.(ABSTRACT TRUNCATED AT 250 WORDS)

TSH receptors of plasma membrane fractions of human cold thyroid adenoma and perinodular thyroid tissues (PTT), assumed by pathohistological analysis to be normal, were examined. In perinodular thyroid tissues (PTT) obtained by partial thyroidectomy from twelve euthyroid female patients 125I-TSH binding (as determined by equilibrium binding analysis on particulate plasma membrane preparations) was found to be significantly increased as compared with scintigraphically cold thyroid nodular tissues (CTN). In all examined thyroid tissues Scatchard analysis of TSH binding revealed two kinds of binding sites: these with high affinity showed a significantly increased dissociation constant (Kd1), while these with low affinity showed a decreased dissociation constant (Kd2) in PTT as compared with CTN. The capacity of low affinity binding sites in PTT was found to be decreased in comparison with CTN tissues. These results suggest that the changes in affinity of TSH receptors sites as well as iodine deficiency of thyroid tissues may be an important events in functional status of analysed perinodular and cold nodular thyroid tissues.

The authors investigated the effect of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) on the local healing process following an artificial fracture of the rat tibia and on the general posttraumatic response of the skeleton to local trauma. The results showed a significant increase in dry weight of fractured tibias as compared with contralateral intact bones which was due to the newly formed callus. 1,25(OH)2D3 significantly increased the weights of tibias which can be explained by its stimulatory effect on callus formation. The uptake of 85Sr into bones resembling the metabolic pathways of calcium was significantly higher in fractured bones as compared with intact ones. 1,25(OH)2D3 significantly reduced the uptake of 85Sr. There was a significantly higher whole body retention of 85Sr in the rats with fractured bones. The administration of 1,25(OH)2D3 significantly reduced the retention of 85Sr in the fractured bone and the concomitant reduction of the whole body retention of 85Sr most likely reflected the increase in intestinal calcium absorption induced by 1,25(OH)2D3 with the consequent decrease in the specific activity of 85Sr administered in a single injection. The general posttraumatic response was reflected by increased dry weight of non-fractured bones. 1,25(OH)2D3 showed a contributory effect on this increase which may indicate that the general response consisted in increased bone formation. The uptake of 85Sr in non-fractured bones was reduced which was also most probably due to a decrease of specific activity of 85Sr. 1,25(OH)2D3 significantly accentuated the reduction of the uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of tryptophane and arginine residues of rat liver receptors for the specific binding of 3,5,3'-triiodothyronine (T3) was studied by chemically modifying the receptor molecule. Soluble T3 receptor fraction was prepared from purified rat liver nuclei and the kinetics of the modification of a tryptophane indol ring of nuclear receptor by N-bromsuccinimide (NBS) in the presence of excess -SH protecting agent was examined. Moreover the kinetics of the formation of N5-(4-oxo-1,3-diazospiro[4,4]non-2-ylidene)-I-ornithine or N7,N8-(1,2-dihydroxycyclohexyl-1,2-ylene)-L-arginine from arginine residue(s) of nuclear receptor by 1,2-cyclohexanedione was investigated. The efficiency of the reactions were followed spectrophotometrically and the modified nuclear receptor fraction separated from chemical modifiers on a Sephadex G-25 column was assayed at pH 8.0 for T3 specific binding. The T3 specific binding was tested by Scatchard plot analysis. No changes in nuclear receptor Ka or MBC were observed after 1,2-cyclohexanedione treatment. Tryptophanyl residue(s) of the receptor molecule may play an effective role in the maintaining the nuclear receptor in a conformation optimal for T3 binding.

Experimental data support the hypothesis that insulin deficiency increases the degradation of glycosaminoglycans (GAGs) and decreases their synthesis. The purpose of this study was to investigate the effect of streptozotocin-induced experimental diabetes on mucopolysaccharide content of the articular and periarticular tissues as well as on the urine GAGs excretion. In two groups (A and B) of ten white Wistar rats, experimental diabetes was induced after administration of streptozotocin in a dose of 65 and 45 mg/kg of body weight, respectively. The animals of group A (short term diabetes) and B (long term diabetes) were sacrificed on the 8th and 87th day of the experimental procedure respectively. GAGs were determined in urine specimens collected before and on the 8th day in group A and before and on 3rd, 8th, 16th, 23rd, 36th, 52nd, 71st and the 87th day in group B. At the end of the experiment articular and periarticular tissue specimens were examined for changes in their mucopolysaccharides content and compared to a group of five animals of the same age and dietary conditions (control group, C). We found a marked increase (P less than 0.001) of urine GAGs excretion during streptozotocin-induced diabetes as compared to the respective values before the experiment in both groups, while in group B a positive relationship (P less than 0.001) between 24 hour urine GASGs excretion, and the duration of diabetes was observed. The histochemistry of the articular and periarticular tissues revealed marked decrease in GAGs content, as well as hardening of the tendons.

The aim of the present review is to summarize the question of the co-existence of two or more releasing hormones within a neuron or nucleus of the avian central nervous system (CNS). Furthermore, we attempt to differentiate between the character and functional significance of hypothalamic and of extrahypothalamic releasing hormone containing neurons. In order to approach these important questions, we have to summarize the localization and distribution of the different releasing hormone immunoreactive (RH-IR) structures in the avian brain, compared to the much more thoroughly investigated mammalian releasing hormone system. This mini-review comprises data obtained by immunohistochemical approach, exclusively. Other data, based on radioimmunoassay or other morphological methods, will be omitted here.

This study examined whether or not the electrophysiological effect of amiodarone on the heart is mediated through its action on thyroxine metabolism. Serum thyroid hormones and ECG were evaluated before and serially during amiodarone (15 subjects) and benziodarone (15 subjects) administration. Both amiodarone and benziodarone shifted the peripheral conversion of thyroxine (P less than 0.001 for amiodarone and P less than 0.001 for benziodarone) towards reverse triiodothyronine and away from triiodothyronine, whilst TSH levels initially fell and then rose with both drugs. After amiodarone the heart rate decreased (P less than 0.025), whilst the PR (P less than 0.005) and the QT interval (P less than 0.005) corrected for the heart rate increased. By contrast with benziodarone only the PR interval decreased (P less than 0.05). Since both drugs had roughly similar effects on thyroid hormone metabolism but different ones on the ECG, our results provide indirect evidence against the hypothesis that the antiarrhythmic effects of amiodarone are mediated through a decrease in the serum T3 presented to the peripheral tissues.

The effects of salmon calcitonin on calcium overload and its deposition in the rat aorta was studied. Calcitonin administered 4 days to rats i.p. in doses of 10 IU/kg body weight blocked the development of calcinosis induced by a single dose of vitamin D3 (300,000 IU/kg body weight, orally). This was demonstrated biochemically, histochemically and by electron microscopic methods.