Biomedical subjects

M G Stepanov

Publications and source records attributed to M G Stepanov.

24 records · Page 2Linked to original sources

PubMed1984

[Androgen binding by skeletal muscle nuclei].

A study was made of 3H-19-nortestosterone binding by isolated nuclei and 0.4 M KCl nuclear extract of the rat skeletal muscle. Binding specificity was ascertained by incubation in the presence of various unlabeled steroids. The Kd values were measured for nuclei and 0.4 M KCl nuclear extract (11.6 +/- 2.5 nM and 9.9 +/- 1.6 nM, respectively). The amount of binding sites was 24.1 +/- 1.7 fmol/mg DNA or 13.7 +/- 1.0 fmol/g tissue. Enzymatic treatment with pronase and DNase shows that nuclear androgen receptors are proteins. DNA was noted to have a stabilizing effect. DNase treatment of nuclei during extraction with 0.4 M KCl was shown to significantly increase the amount of specifically bound radioactivity in the extract.

Androgens↗

PubMed1983

[Contractile proteins in the fractions of soluble and insoluble chromatin of liver and thymus].

The proteins corresponding in molecular weight and solubility in salt solutions to skeletal muscle actin and myosin were revealed in liver and thymus chromatin fragments. When the ionic strength reached 0.3, about 60% of the myosin-like protein identified by electrophoretic mobility of high chains and the K+-EDTA-ATPase activity was cosedimented with nucleohistones. In the presence of ATP or PPi and Mg2+ the solubility of myosin in such salt solutions increased up to 90%, which was paralleled with significant stimulation of RNA release from the nucleohistones. The conformity in the degree of extraction and sedimentation of RNA and intranuclear myosin was also observed in other solutions used during myosin purification. The supposition that the nuclear system of contractile proteins causes labile, ATP-dependent binding of RNA to chromatin is discussed. No essential differences in the actin or myosin contents in the fractions of soluble and non-soluble chromatin were detected.

Adenosine Triphosphatases↗

PubMedDate not supplied

[Changes in the secretion of gonadoliberin, gonadotropins, and ovarian hormones in rats under chronic exposure to low concentrations of methylmethacrylate].

Chronic influence of small concentrations of methylmethacrylate in inhalations (at the level of a maximum permissible dose of 50 mg/m3 and in its 10-fold excess) after short-term enhancement of the hypothalamo-hypophyseo-gonad system (in one month after exposure to a dose at maximum permissible concentration) is quickly followed by suppression of its function. The use of methylmethacrylate for 4 months revealed a decrease in ovarian mass, the blood level of progesterone and a rise of secretion of FSH and LH with a simultaneous decrease in the level of gonad-releasing hormone in the mediobasal hypothalamic structures. It indicates primary gonad damage of the reproductive system and preservation of a normal reaction of the hypothalamohypophyseal factor, responding by activation on the feedback principle. In 4 months a high embryotoxic and teratogenic effect of methylmethacrylate was observed.

Animals↗

PubMedDate not supplied

[Hormonal regulation of reproductive function in rats in response to cold stress in a context of chronic toluene poisoning].

Chronic toluene inhalation at a maximum permissible concentration (MPC) and 10-fold higher as well as cold stress result in a significant rise of blood prolactin in female rats. Cold stress in control animals causes a decrease in the level of gonad-releasing hormone (Gn-RH) in the hypothalamus. When exposed to toluene this reaction disappears. In 4 hours after estradiol administration control animals demonstrate an increase in the level of Gn-RH in the vascular organ of an end plate. Rats, exposed to toluene (in MPC concentration) and cold stress show a decrease in the level of hypothalamic Gn-RH. At a higher concentration of toluene the level of Gn-RH in the hypothalamus remains unchanged either after estradiol administration or in cold stress. Thus chronic toluene inhalation even at small concentrations changes hypothalamic reactivity in response to stress and hormonal stimuli.

Administration, Inhalation↗

PubMedDate not supplied

[Hormonal properties of new 17 alpha-hydroxyprogesterone derivatives].

The paper is devoted to an experimental study of the hormonal properties of two new derivatives of 17 alpha-oxyprogesterone--mepregenol monoacetate and mepregenol diacetate--for their possible use as minipills. Both compounds showed a high progestational activity which was much higher than that of progesterone and the activity of alpha-norgestrel in peroral administration. The above compounds made no inhibitory effect on hypophyseal gonadotropic function; on the contrary, they stimulated follitropine secretion. Besides, different dose-related influence of the steroids on a progesterone level was revealed: the use of small doses resulted in enhanced secretion and larger doses brought about the suppression of secretion. Thus, the new compounds of the progesterone series--mepregenol monoacetate and mepregenol diacetate--appear promising compounds for monohormonal contraception and for the management of conditions with lowered function of the corpus luteum.

17-alpha-Hydroxyprogesterone↗

PubMedDate not supplied

[Disruption of central regulation of reproductive function under the effect of unfavorable environmental factors].

Rat experiments have established that early unfavourable environmental influences cause a non-specific response of the central link of reproductive function regulation as manifested by the impaired circadian rhythm of gonado releasing hormone through the vascular organ of the lamina terminalis. It is suggested that this is induced by changes in prolactin production. Under unfavourable environmental influences there were insidious changes in the neuroendocrine regulation of reproductive function, which emerge with the involvement of additional damaging factors or functional tests. They are easily reversible and functional, but they may be regarded as the first signs of reproductive dysfunction.

Animals↗