Biomedical subjects
Publications and source records attributed to E S Gevorkian.
Psychophysiological and cardiac hemodynamic changes were studied by computer registration and an analysis in tenth formers-entrants having a higher mental and emotional load during a school year. The changes in the above parameters were also studied when the formers were taking their school-leaving and entrance examinations.
Salivary Na+,K+-excretory function was studied in senior schoolchildren-entrants during an academic year and entrance examinations. The time course of changes in the salivary levels of Na+ and K+ in entrants during an academic year was undulating. In late October that is coincident with the beginning of lessons given by tutors, the salivary content of Na+ reduced while that of K+ increased. The second peak of decreased excretion rates for Na+ and increased excretion rates for K+ and that of less Na+/K+ ratios was observed in May on the eve of entrance examinations. On the eve of the examinations, 70% were observed to have tachycardia, elevated levels of integral parameters of cardiac rhythm regulation, a considerable reduction in the concentration of Na+, and an increase in the level of K+ with less Na+/K+ ratios. The pattern of the observed changes also retained in the postexamination period. On the eve of the examinations, 30% were found to have lowered levels of integral parameters of cardiac rhythm regulation and elevated levels of Na+. After an examination, there was a reduction in Na+ excretion which did not yet achieve the initial level. The mechanisms responsible for ionic shifts in the composition of saliva during psychoemotional stress are discussed.
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During examinations, cardiovascular and mental changes were studied in schoolchildren studying in middle (5-7) forms with a differentiated form of teaching. Cardiac hemodynamic values were calculated and a psychological testing for anxiety was performed in the examinees. During an examination session, the schoolchildren were ascertained to develop emotional stress characterized by a complex of psychophysiological and autonomic nervous changes.
The paper shows psychological and cardiac hemodynamic changes in students performing an hour mental test of a program on a computer. There are synchronous reductions in the magnitude of cardiac hemodynamic indices and in the activity of the sympathetic pattern of cardiac rhythm regulation in the examinees.
Effect of various concentrations of estradiol on activity of protein kinases A and C as well as of Ca(2+)-calmodulin kinase was studied in synaptosomes, their membrane and soluble fractions in vitro. Pharmacological concentrations of the hormone activated distinctly all the kinases studied, while physiological concentrations of estradiol increased markedly the activity of protein kinase C. These data suggest that protein kinase C is of importance for protein phosphorylation regulated by estradiol in rat brain cells.
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A possibility of phosphatidylinositides catabolism initiation was revealed in the rat brain synaptosome membranes during in vitro action of estradiol. It was shown that appreciable enhancement of diacylglycerol yield was observed at already 5th second of initiation, which decreased then until the 30th second and kept the sufficiently high level. The yield of free arachidonic acid had also enhanced. Analogous dynamics of alteration was observed during the action of pharmacological as well as physiological concentrations of hormone.
The effect of estradiol and progesterone on the activity of 3 regulatory enzymes of glycolysis (hexokinase, phosphofructokinase and pyruvate kinase) in the brain of female rats was studied in the initial phase of hormonal action. Steroids were capable of modifying epileptic activity caused by pentetrazol, the action of estradiol being epileptogenic, that of progesterone anticonvulsant. Hormone action modifying epileptic activity, probably results from changes in intracellular metabolism and from changes in electrogenesis of nerve cells, the second mechanism being predominant.
The availability of CDP-choline: diaglyceride phosphocholine transpherase activity in the rat liver nuclear membrane fraction is shown. It is established that the enzyme activity in nuclear membrane fraction makes up less than 1/3 of the analogous activity in microsomes. The hydrocortisone treatment of animals leads to an increase of the enzyme activity in microsomes and to a decrease in the nuclear membranes. The obtained data indicate the existence of the own enzyme of phosphatidyl choline synthesis in the nuclear membranes. This enzyme is, probably, responsible for the nuclear membrane structure when the functional status of cell changes.
It is shown that over 80% of nuclear neutral lipids are found in the nuclear membrane preparations, whereas only 7%--in chromatin. The injection of hydrocortisone to animals significantly decreases the neutral lipids content in both fractions. These results and the data obtained previously by the authors indicate the possible participation of nuclear membrane and chromatin lipids in the process of hormonal regulation of the genetic activity.
When isolating protein components of chromatin from the rat liver phospholipids are found in the fraction of nonhistone proteins but not in that of histone. Administration of hydrocortisone to animals evokes a reliable increase of the phospholipids of hydrocortisone to animals evokes a reliable increase of the phospholipids amount in the preparations of chromatin and labile-bound nonhistone proteins. In this case the fraction of phosphatidylcholine lowers considerably with a simultaneous increase of sphingomyelin and phosphatidylethanolamine. It is supposed that phospholipid metabolism in chromatin is controlled by hormones, which may be significant for mechanisms of the genetic apparatus activation by steroid hormones.
Preparations of chromatin and labile-bound nonhistone proteins were isolated from cockerel liver cells after treatment of birds with estradiol as well as from controls. Six protein fractions were obtained by means of column chromatography on DEAE cellulose: two of these fractions were quantitatively altered due to the hormonal effect. Electrophoretic separation of both total labile-bound nonhistone proteins and their hormone-dependent fractions showed that protein composition was altered after the estradiol treatment as compared with controls.
Effect of estradiol propionate on activity of seven enzymes from rabbit uterus was studied. Simultaneously with the known estrogen-induced enzymes, activity of some other enzymes from uterus cells (tyrosine transaminase, acetylcholinesterase, butyrylcholinesterase) was also studied. The hormone induced all the enzymes studied except of butyrylcholinesterase. After induction with the estrogen a new isoenzyme fraction was found in peroxidase: at the same time, content of isoenzymes of lactate dehydrogenase, tyrosine transaminase and acetylcholinesterase was increased.
After hydrocortisone administration some properties of rat liver chromatin were studied by means of melting technique and circular dichroism. Hydrocortisone caused a more than 2.5-fold increase in amount of the chromatin active fraction. Distinct differences were detected between circular dichroism spectra of total chromatin and of its active fraction as well as between differential curves of the chromatin active fraction melting in control and test samples. The difference was expressed as a decrease in temperature of melting in a low-point zone and as appearance of the secondary maxima in the region of nucleosomes melting. These data suggest that the decondensation of nucleosome-containing sites takes place which is considered as an indirect evidence of the chromatin activation.
Complexes containing DNA and various groups of non-histone proteins were isolated from rat liver cells. Deproteinized DNA was bound with the hydrocortisone-receptor complex at the highest rate in vitro. Non-histone proteins from the chromatin fraction did not bind with the hormone-receptor complex. Unsaturability of DNA in reaction with the complex appears to indicate the low specificity of binding.
The in vivo action of estradiol was shown to cause changes both in the total amount of phosphoinsitides and their individual fractions of rat synaptosomes. The maximum elevated levels of phosphoinositides was revealed on 1-hour exposure to the hormone. It is suggested the redistribution of phosphoinositides at the primary stage (1 hour postinjection) of exposure may rely on the initiation and functioning of the phosphoinositide mechanism, the ratio of triphosphoinositide to monophosphoinositide may be a peculiar indicator of the status of synaptosomal membranes for the functioning of this regulatory system.
Spermine decreased distinctly the activity of Ca2+ -phospholipid-dependent protein kinases, whereas not affected the protein kinase A activity. Content of cytosol estradiol receptors was drastically decreased in rat uterine in presence of the polyamine. The data obtained and literature data suggest that activation of estradiol receptors appears to occur after phosphorylation by means of Ca2+ - dependent protein kinases, which are regulated via phosphoinositide-involving mechanism, i.e. these receptors acquire the ability to bind hormones.