[Structural-functional characteristics of chromatin fractions in the regenerating liver of adult and old rats].

The transcriptional activity, nucleosomal patterns, and thermodenaturation parameters of low-active and active fractions of liver chromatin were studied in adult (6-8 mo) and old (26-28 mo) rats at 2, 4, and 6 weeks after partial hepatectomy. At 2 weeks postoperatively, there was a decrease in relative specific radioactivity (RSR) of the active chromatin fraction in adult rats, which returned to normal by the 4th week, while in the low-active fraction it was decreased throughout all the studied regeneration periods. The decrease of the low-active fraction RSR was attended with changes in the nucleosomal organization and DNA-protein interactions revealed by electrophoresis and thermodenaturation.

[Distribution of H3-hydrocortisone in subcellular fractions of the liver of rats of different ages].

The paper is concerned with the results of a study of the distribution of /3H/-hydrocortisone in hepatocytic organellae of adult and old rats. In subcellular fractions /3H/-hydrocortisone was distributed inhomogeneously: the greatest number of tracers was detected in the cytosol, less in microsomes, mitochondria, nuclei. Age differences are absent.

[Effect of partial hepatectomy on the state of liver chromatin in adult and old rats].

Partial hepatectomy in rats of two age groups--adult (6-8 months) and old (24-26 months)--is found to increase the intensity of [2-14C] orotic acid incorporation into RNA of the liver chromatin which reaches the maximum values 15 h after the operation simultaneously in animals of both groups. In the age groups under study the transcription activation is accompanied by an increase in the relative quantity of the active chromatin fraction. The study of the process of thermodenaturation of inactive and active chromatin fractions in the liver of adult rats after the partial hepatectomy has revealed no considerable shifts in the melting point and in distribution of the hyperchromism percentage within different temperature ranges as compared to the intact liver.

[Effect of electric stimulation of the hypothalamus on the transcription activity of chromatin in the rat liver during aging].

Age-dependent peculiarities of electric stimulation of hypothalamus were studied by means of estimation of active/inactive liver chromatin fractions, protein/DNA ratio in the latters, level of incorporation of 14C-orotic acid in total RNA and in chromatin RNA fractions. Electric stimulation of hypothalamus in adult rats led to an increase in the relative content of active chromatin fraction and in the rate of the labelled precursor incorporation into both chromatin fractions. In old animals the stimulation did not cause any redistribution of chromatin fractions and did not affect the rate of the labelled precursor incorporation into RNA.

[Effect of electrostimulation of the hypothalamus on protein biosynthesis in organs of adult and aged rats].

The effect of hypothalamus electrical stimulation on total protein biosynthesis was studied in skeletal muscle, heart, liver, adrenal cortex and thyroid gland of adult rats. In adult animals hypothalamus stimulation provokes a pronounced increase in 3H-leucine incorporation into total protein of all tissues, as well as into liver chromatin proteins. No significant changes were observed in protein biosynthesis when hypothalamus of old rats was stimulated.