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Biomedical subjects

A I Nikitin

Publications and source records attributed to A I Nikitin.

At least 37 records · Page 2Linked to original sources
PubMed1986

[Progestagenic activity and the mechanism of the contraceptive action of mecygeprone].

Progestagenic activity of a modified analog of progesteron-6 alpha-methyl-cyclogexan-[1', 2', 16 alpha, 17 alpha]-pregn-4-en-3,20-dion including into mecygepron composition has been studied; its activity is proved to be 5 times as great as that of progesteron at any way of administration. Mecygepron affects processes of ovogenesis and early embryogenetic development in rats. A decreased number of washed out embryos is observed, while the number of lutein bodies specific for intact rats remains the same, decelerated rate of cleavage and increased number of unfertilized ova. In the mechanism of the changes observed an essential role plays a decreased secretion of lutropin resulting in a prolonged estrol cycle and, evidently, in intrafollicular overmaturation of the ova, which loose their ability to be fertilized. Besides, the disturbed hormonal balance under mecygepron influence can affect the character of the oviduct and uterine contents and, thus, prevent the normal development of the fertilized gametes.

Administration, Oral↗
PubMed1985

[Problems in the early differentiation of mammalian gonads (embryonic histogenesis and mechanisms of regulation)].

The results obtained for the last decades on the problem of early differentiation of mammalian gonads are elucidated. The data on the role of different tissue sources in origin of somatic elements in sex gonads are critically estimated. New data on participation of meiosis-regulating substances (that are produced by the mesonephros and its derivatives) in processes initiating and inhibiting meiosis are presented. The matters on the character of interrelations between the histostructural organization of embryonic gonads and their steroidsynthetic activity are considered. The modern notions on histogenesis of hormonally active stromal elements of the gonads are reported. The role of the data discussed for further investigation of pathogenesis of development of sex anomalies, of disorders in human reproductive function is regarded, as well as that for revealing histogenesis of gonadal tumours.

Animals↗
PubMed1979

[Change in the electrophysiological parameters of human oocytes in the process of maturation outside the body].

The dynamics of electrophysiological parameters (membrane potential--MP and resistance--R) of the human oocytes was studied during their in vitro maturation. The relationship was established between the changes of electrophysiological parameters and meiotic phases. The average value of MP of diplotene oocytes was 22.0 +/- 0.3 mV and that of R 2.0 +/- 0.5 mO. The membrane depolarization was observed upon the meiotic reinitiation. The MP of diakinesis--metaphase I oocytes amounted to 10.0 +/- 0.3 mV and R to 10.0 +/- 0.5 mO. At metaphase II the temporary membrane repolarisation was noted in some cases which, in some oocytes, was replaced by the increasing hyperpolarisation on the 2--3rd day of cultivation. The input membrane resistance increased on the 2--3rd day of cultivation.

Cells, Cultured↗
PubMed1979

[Cytogenetic analysis of human oocytes and the process of their maturation outside the body].

A cytogenetic analysis of human oocytes, after their removal from follicles and during extracorporeal maturation, has been performed. The heterogeneity of follicular oocytes according to the character of nuclear chromatin was established. It is probably related to the rate of reinitiation of meiosis in vivo and to the rate of atretic process. The dynamics of human ovum maturation in vitro was studied. 50.8% oocytes reached metaphase II in 46 hours of cultivation, but only 22.8% of these had no chromosomal aberrations. It is supposed that the high rate of chromosomal anomalies in vitro is a possible consequence of degenerative changes of oocytes that started still in vivo.

Cells, Cultured↗
PubMed1978

[Effect of insulin and prednisolone on the transport of organic substances in the kidneys of dogs].

Single injection of insulin (1 AU/kg) enhanced maximal glucose absorption, cardiotrast secretion and decreased sodium excretion without any changes of glomerular filtration in dogs. These effects depended on the direct action of insulin so far as the effect is expressed in the kidney only at the side of infusion when the preparation is administered into one of the renal arteries. Prednisolone had no significant effect on the glucose and cardiotrast transport in single injection (3--4 mg/kg) and 10-day (1.5--2 mg/kg daily) injections.

Animals↗