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Biomedical subjects

M S Mitskevich

Publications and source records attributed to M S Mitskevich.

29 records · Page 2Linked to original sources
PubMed1979

Light and electron microscopical investigations on the tanycyte differentiation during the perinatal period in the rat.

The differentiation of tanycytes was studied light and electron microscopically during the perinatal period in rats, the time when functional connections between hypothalamus and hypophysis are established. The 3rd ventricle is slit-like between 16 and 18 days of the prenatal period. Its wall is formed by intensively proliferating matrix cells with apical processes, ovoid perikarya and a basal process. The ventral region of the 3rd ventricle becomes funnel-shaped on the 20th day of the prenatal period. As the cells differentiate, the apical process becomes shorter and broader. Moreover, on day 20 of prenatal life cells without apical processes appear. Their number increases during the postnatal period. The concentration of endoplasmic reticulum, mitochondria, polysomes, lipid droplets, dense bodies (lysosomes), lamellated and multivesicular bodies increases. Initially the cells are similar but from the 3rd day of postnatal life differentiation occurs in different regions of the infundibular recess. After the 5th day, there are no marked changes in the structure and distribution of these cells.

Animals↗
PubMed1976

[Effect of metopirone and glucocorticoids on the glycogen content in the adrenals of rat fetuses].

Metopiron, hydrocortisone and dexamethazone are able to influence different links of the hypothalamo-hypohysial-adrenal system and induce the inhibition of glucocorticoid function. Changes in glycogen content in the adrenal gland and liver of rat foetuses under the effect of the drugs in question were studied. It was shown that metopiron exerted no marked influence on the level of glycogen in the adrenal gland and decreased 2.5 times that in the liver. On the contrary, hydrocortisone and dexamethazone increased the glycogen content 2 times in the adrenal gland and did not change that in the liver. The results obtained agree with the hypothesis on the relation between the glycogen level in the adrenal gland and the level of its hormonal activity and are considered as an additional proof of the functioning of hypothalamo-hypophysial-adrenal system during the last days of the rat prenatal development.

Adrenal Glands↗
PubMed1975

Glycogen content in the adrenals and liver of rat embryos depending on the level of adrenocorticotropic functions.

The functional state of the adrenals of rats during prenatal development was studied. The accumulation of glycogen in the adrenals and liver in 15.5-21.5-day old embryos was used as the index. The maximum glycogen concentration in the adrenals and the minimum in the liver were detected in 15.5-16.5-day embryos, i.e., before the adrenals had begun to produce glucocorticoids. A sharp decrease in glycogen in the adrenals was observed in 17.5-day embryos, and an appreciable accumulation in the liver in 18.5-day embryos, which coincides with the beginning of the glucocorticoid function. Decapitation and encephalectomy performed at an age of 17.5-19.5 days of development of the embryos, were invariably accompanied by a significant increase in the glycogen content in the adrenals and a decrease in its level in the liver in the case of investigation after two days. This indicates an active participation of the hypothalamo-pituitary system in the regulation of the adrenocortical function in the late days of embryonic development.

Adrenal Glands↗
PubMed1974

[Several aspects of the problem of the development of hormonal regulation during prenatal development].

Some general aspects of the problem of hormonal control mechanisms in prenatal life are discussed. An analysis is performed on the basis of both the literary and author's data pertaining to the development of hypothalamo-hypophysial-adrenal, hypothalamo-hypophysial-thyroid and hypothalamo-hypophysial-gonadal functions during the foetal life. Experimental evidences of the activity of these functions in foetuses are provided. Neuroendocrine mechanisms are considered as a system of coordinated and intercontrolling links where the relative autonomy, the self-regulation of lower levels is coupled with the centralized control of higher levels. A concept is put forward to the effect that interactions between individual links play an important part in the formation of these mechanisms. If it is so, organizing influences, or stimuli, may emanate both from higher levels of control towards the lower ones and vice versa. Hormonal influences in early ontogenesis are characterized by the fact that, besides direct effects at the same developmental stage, they ensure the maturation of higher levels of neuroendocrine mechanisms which perform hormonal control in adults.

Animals↗
PubMedDate not supplied

[The development of neuroendocrine regulation in ontogeny].

Published and author's data on hypothalamic control over the most important endocrine functions during mammalian ontogenesis were reviewed. The data presented indicates that adenohypophyseotropic protein neurohormones are synthesized and accumulated in hypothalamus long before birth. At the end of the prenatal period most of hypothalamic neurohormones reached the adenohypophysis and were involved in regulation of the tropic hormones secretion. Exceptionally, regulative properties of thyroliberin and somatostatin are only manifested in immature-born animals (rats) in early postnatal period.

Adaptation, Physiological↗
PubMedDate not supplied

[Role of the hypothalamus and pituitary gland in the development of pancreatic islet sensitivity to glucose in fetal rats].

Differences in the pattern of the development of three enzymes of the plasma membrane have been established. The activity of Na, K-ATPase progressively increases, that of adenylate cyclase decreases, whereas the activity of 5-nucleotidase undergoes only slight changes during embryogenesis. Differences between these enzymes were also found with respect to the development of their sensitivity to the regulatory effects of catecholamines. Adrenaline reactivity of adenylate cyclase may be detected already in embryogenesis; it is lower than that in definite muscle tissue increasing during further ontogenesis. Catecholamine reactivity was not found in Na, K-ATPase and 5-nucleotidase up to the 17th day of incubation of chick embryos. The effect of adrenalin was observed at later stages of ontogenesis, it may be initiated by exogeneous cAMP and protein kinase. At postembryonic stages, similarity in the behavior of these enzymes was found with respect to the presence and pattern of their reaction to adrenalin (stimulation), as well as with respect to temporal dynamics of the effect. The data obtained indicate the existence of close connections between these enzymes, which are realized in the sequence adrenoreceptor-adenylate cyclase-cAMP-protein kinase-effector proteins.

Adrenocorticotropic Hormone↗