[Nonmonotonous metabolic response of mammalian cells and tissues to ionizing radiation].

Changes in the activity of ornithindecarboxylase in various tissues and in the amount of catecholamine in rat hypothalamus by the action of acute and chronic ionizing radiation were studied. A nonmonotonous relationship between the metabolic parameters of animal tissues and cells and the radiation dose was revealed. It was assumed that the nonmonotonous character of the dose-response dependence results from the nonmonotonous time course of the metabolic response to irradiation.

Nuclear and chromatin lipids: metabolism in normal and gamma-irradiated rats.

The data on nuclear and chromatin lipid metabolism are reviewed. The amount of neutral lipids and phospholipids in nuclei of rat thymus, liver and neocortex neuron as well as the amount of lipids in rat thymus and liver chromatin are described. The metabolic responses of nuclear and chromatin lipids from thymus to different doses and dose rates of gamma-irradiation of rats are discussed.

Nonmonotonous Changes in Metabolic Parameters of Tissues and Cells under Action of Ionizing Radiation on Animal.

A nonmonotonous relationship between changes of metabolic parameters of tissues and cells of animal and radiation dose were discussed. Under acute irradiation of animals the nonmonotonous dose-response curve for metabolic parameters of tissues and cells were found. The nonmonotonous dose-response curves of metabolic and functional tissues and cells parameters were also revealed upon chronic irradiation of animals at a low dose-rate.

Ornithine decarboxylase in organs of rat following chronic gamma-irradiation at low dose-rates.

Purpose: To investigate the consequence of continuous low dose-rate exposure to gamma-rays on ornithine decarboxylase (ODC EC 4.1.1.

[Ornithine decarboxylase in the organs of rats under chronic exposure to gamma radiation at a low dosage rate].

Chronic exposure of rats to gamma-irradiation at the dose rates of 1.1, 2.1, and 12.

[The catecholaminergic system in the hypothalamus in the chronic gamma irradiation of rats].

Drastic changes in the level of catecholamines (dophamine and noradrenaline) in the central regulatory area of the sympathetic-adrenal system-hypothalamus--caused by continuous gamma irradiation of rats were observed. The irradiation was performed with the doses of 9 to 165 cGy at a rate of 1.1 cGy/day and with the doses of 17 to 315 cGy at a rate of 2.

[Effects of chronic gamma irradiation on the activity of adenylate cyclase in rat lung tissue].

Different phase changes were observed in adenylate cyclase (AC) activity of pulmonary tissue plasma membranes under chronic gamma-irradiation of rats at a dose-rate of 12.9 cGy/day. Comparison of AC basal activity with the data reported earlier on changes in ornithine decarboxylase activity under similar radiation conditions showed unidirectional changes which indicated that cAMP-dependent processes were possibly involved in radiation modification of ornithine decarboxylase.

[Effects of single gamma-irradiation on the activity of ornithine decarboxylase in the thymus and pulmonary tissue].

In studying the dose (0.1-6 Gy) and time (2 h to 180 days) dependence of ornithine decarboxylase activity, it was found that deviations from the control were more pronounced in the thymus than in the pulmonary tissue. The radiation effect was a function of dose and time after irradiation.

[The effect of the dose rate on the development of rat pups under chronic gamma irradiation].

Chronic exposure of rat pups to gamma radiation, during their intensive growth, at a dose rate of 0.01, 0.11 and 0.

[The dynamics of the ornithine decarboxylase activity in chronically gamma-irradiated rats].

Ornithine decarboxylase activity changes in some tissues of chronically gamma-irradiated rats (0.54 cGy/h). The radiation effect is a function of the life span of continuously exposed animals.

[The possible participation of the cAMP system in the activation of ornithine decarboxylase in rat tissues following nonlethal fractionated gamma-irradiation].

A study was made of the activity of adenylate cyclase and cAMP-phosphodiesterase in rat thymus and liver various time intervals following nonlethal fractionated gamma-irradiation (2 Gy three times at a week interval). There was a positive correlation between the activity of cAMP metabolism enzymes and the radiation modification of ornithine decarboxylase (ODC) observed before. It is suggested that cAMP system is involved in ODC activity regulation in the exposed tissue.

[Adenylate cyclase activity of the plasma membranes of lung tissue at lengthy periods following non-lethal gamma-irradiation of rats].

Basal and stimulated activity of adenylate cyclase (cyclizing ATP-pyrophosphate lyase, E.C. 4.

[The stimulating action of low doses of ionizing radiation on glucokinase synthesis in the liver of developing rats].

Taking spontaneous glucokinase synthesis as an example the authors showed an increase in the rate of enzymatic differentiation against the insignificantly increased natural radiation background, which might serve as a supporting evidence of the previously obtained data confirming the necessity of the natural radioactive background for the development of mammals.

[Ornithine decarboxylase activity in rat tissues in the late periods after irradiation].

Ornithine decarboxylase activity in some rat tissues was shown to grow at remote times after gamma irradiation (60Co) with nonlethal doses. The authors suggest that ornithine decarboxylase activity should be used as a biochemical marker of remote effects of ionizing radiation.

[Mechanisms of the disorder of the hormonal regulation of plasma membrane adenylate cyclase in the rat liver during early ontogeny under in vitro irradiation].

Possible reasons for the previously detected inhibitory effect of gamma-radiation (100-1000 Gy in vitro) on isoproterenol-stimulated activity of adenylate cyclase (AC) of the liver plasma membranes of a 20-day-old rat fetus were investigated. It was discovered that the number of beta-adrenergic receptors was reduced. Analysis of basal and fluorine-stimulated activities of AC attests to the radiation-induced damage to catalytic and N-regulatory proteins.

[Possible effect of natural radioactivity on the induction of glucokinase synthesis in the liver of developing rats].

A decrease in the induced synthesis of glucokinase in the liver, at the time of spontaneous appearance of the enzyme, was observed in suckling rats kept for 10 days in a chamber with a decreased (by 10 times) natural radiation background. No changes were noted in the glucokinase synthesis induction after restoration of natural radioactivity by introducing of uranium salts.

[Radiation disorder of enzyme synthesis in the perinatal period of ontogeny].

A change of enzymatic differentiation in the rat liver during the perinatal developmental period after gamma-irradiation on the 7-9th and 19th days of embryogenesis in doses 0.5, 2 and 6 Gr has been shown on the example of glucose-6-phosphatase (G-6-P-ase) and tyrosine aminotransferase (TAT). The protein-synthesizing machinery was not damaged at these doses.

[Possible effect of natural background radiation on the development of mammals].

The deceleration of the development of young rats during the postnatal ontogenesis under conditions of a low-background chamber (a 10-fold decrease in the natural radiation background) was detected using the criterion of individual growth of the body weight for 10 days of observation. The administration, to the low-background chamber, of uranium salts which restore the natural background (all other experimental conditions being retained) removed the effect observed.

On the mechanism of a radiation-induced change in enzymic differentiation during development.

In experiments on glucose-6-phosphatase and tyrosine aminotransferase it was shown that radiation induces changes in enzymic differentiation in perinatal rat liver. A study was made of the probable reasons for the observed changes. It was shown that the macromolecular system of the protein enzyme synthesis was not damaged by the radiation doses used.

[Radiation modulation of the activity of the enzymatic systems in isolated plasma membranes in early ontogeny].

The activity of adenylate cyclase (Ac), cAMP phosphodiesterase (PDE) and 5'-nucleotidase was studied in plasma membranes from the liver of rat embryo of the 20th day of development normally and after exposure to ionizing radiation. Gamma-irradiation of plasma membranes with doses ranging from 0.1 to 100 kR was shown to inhibit the activity of Ac, this effect being more pronounced during stimulation with higher doses of isoproterenol.

[Hepatic adenosine-3',5'-monophosphate metabolism in newborn rats irradiated during the period of organogenesis].

The adenylate cylcase (AC) and phosphodiesterase (PDE) activities, as well as the 3'5'-AMP (cAMP) fund were studied in the liver of newborn rats, intact, and after irradiation on the 9th day of the embryonic development. A decrease of AC and PDE activities was noted with a dose of 50 r. The stationary level of cAMP in the tissue remained unchanged.