[Comparative estimation of the EGFP effects on the development of embryos obtained by reciprocal crossing of C57BL/6-Tgn(ACTbEGFP01Osb/J and C57BL/6 mice].

The effect of enhanced green fluorescent protein (EGFP) on the in vitro viability of early embryos of C57BL/6--Tgn(ACTbEGFP010sb/J mice has been studied. The number of viable ova in hemizygous females (-/egfp) has been shown to decrease. Irrespective of the EGFP level, it has no deleterious effect on the early development of embryos obtained by reciprocal crossing of hemizygous (-/egfp) and wild-type (-/-) mice.

[The nonmonotonicity changes of ornithine decarboxylase activity in spleen following exposure to gamma-irradiation on rats].

Exposure of rats to ionizing radiation caused in spleen nonmonotonous (as a function of time and of dose) changes in the activity of ornithine decarboxylase [ODC EC 4.1.1.17], an initial and rate limiting enzyme in polyamine synthesis. At physiological concentration polyamines (putrescine, spermidine, spermine) act as regulators of growth, proliferation and differentiation. ODC activity as well as spleen mass were studied in 2 h, 1, 7, 30 and 90 days after the exposure of rats to single-dose whole-body gamma-irradiation at the doses of 0.1, 1, 2, 6 Gy as well as 1, 7, 30, 90 day following fractionated one at a dose of 6 Gy (2 Gy three times in a week). Fractionating irradiation dose (2 Gy x 3) results in activation of ODC activity on day 30 after irradiation in contrast to the sharp decrease in the level of ODC activity on the same term after the single-dose exposure to gamma-irradiation at a dose of 6 Gy. The radiation activation of ODC precedes the renewal of organ mass. A possibility to apply a concept about nonmonotonic responses of mammalian cells and tissues to the action of ionizing radiation for analyzing dose-response processes of radiation damage and postradiation reparation of organism is discussed.

[The effect of X-rays and artificial hypotermia on lipids in rat neocortex].

Lipid content of tissue and of fraction of microsomes in neocortex of Wistar rats was studies under artificial hypothermia, after X-ray irradiation in dose 8 Gy under conditions of normothermia and artificial hypothermia in 48 h. The condition of artificial hypothermia get by cooling of rats to 15-18 degrees C. It was shown, that in fraction of microsomes of hypothermia rats the content of phosphatidylinositol was decreased, and in 48 h after cooling of rats the amount of protein, total and individual phospholipids was increased. The lipid content in tissue and in fraction of microsomes of rats, which were irradiated in normotermia, had no changes after 48 h. In fraction of microsomes of rats, which were irradiated after hypothermia, the amount of protein, total phospholipids, sphingomyelin, phosphatidylcholine and phosphatidylserine is increased trustworthy. Thus, we think, that radioprotective effect of hypotermia may be connected with the accumulation of proteins and of phospholipids in the endoplasmic reticulum membranes of neocortex.

[The effect of hypothermia on the rat radioresistance].

The cooling of Wistar rats up to 15-19 degrees C under a condition hypoxia-hypercapnia increased the radioresistance with a dose reduction factor (DRF) of 1.4. To elucidate the mechanisms of hypothermia radioprotective effect was evaluated the functional state of rat neocortex using a electroencephalogram (EEG) as well as was studied the lipid composition of neocortex under the conditions of both normothermia and hypothermia. At 19-20 degrees C the activity within a wide range of frequencies in EEG was suppressed; the nonregular slow waves were recorded against a background of "silence". The reduction of EEG spectrum with increasing temperature began with the low frequencies. At 26-28 egresC the contribution of theta-rhythm (an indicator of brain activity level) in EEG reaches the normothermia value, from this point the rat brain starts to functionate as a whole system. At normothermia the similarity of neocortex lipid composition in nonhibernators (rats) and hibernators (ground squirrels) mammalians was noted. The difference is only in a higher content of phosphatidylinositol in rats. Rats falling into hypothermia state as well as ground squirrels into torpor is followed by a decrease of cholesterol content and the absence of significant changes of the phospholipid composition in neocortex tissues.

[Nonmonotonous metabolic response of mammalian cells and tissues to ionizing radiation]. / Nemonotonnost' metabolicheskogo otveta kletok i tkanei mlekopitaiushchikh na vozdeistvie ioniziruiushchei radiatsii.

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. It was also assumed that living systems have the property of responding to stress agents by nonmonotonous changes in metabolism. In the case of acute irradiation, this response manifests itself as oscillations of metabolic parameters about the control. The oscillations occur with a particular amplitude and periods, which vary with radiation dose, and damp out with time. As a result, in a fixed time interval, the dose-response curve may be nonmonotonous. Reverse dose-response relationships are also possible. In the case of chronic irradiation, the metabolic and functional parameters oscillate throughout irradiation time, and a modification of the response occurs. A prolong exposure to ionizing radiation causes strong changes in the metabolism of lipids of cell membranes, organelles and chromatin, as well as in the functional properties of some mammalian cells and tissues. The necessity of constructing quantitative models for explaining the nonmonotonous dose-response dependence is discussed.

[Ornithine decarboxylase in the organs of rats under chronic exposure to gamma radiation at a low dosage rate]. / Ornitindekarboksilaza v organakh krys v usloviiakh khronicheskogo vozdeistviia gamma-izlucheniia maloi moshchnosti doz.

Chronic exposure of rats to gamma-irradiation at the dose rates of 1.1, 2.1, and 12.9 cGy/d in the dose ranges of 9-165, 17-315, and 100-2000 cGy, respectively, modified the ornithine decarboxylase (ODC) activity in the radiosensitive (thymus, spleen) and radioresistant (lung) organs. A nonmonotonic dependence of the ODC activity on the cumulative radiation doses was observed: a decrease in the ODC activity caused by low cumulative radiation doses (after 8 days of exposure) gave way to the level that was close to the control (after 45 and 90 days); after 150 days of exposure, the activity of ODC increased in some organs (spleen and lung). It was suggested that this nonmonotonicity has its origins in the radiation triggering the regulatory systems of the cell homeostasis.

[The effect of the mutant genes Ta, Ra and Sd on early embryogenesis in mice]. / Vliianie mutantnykh genov Ta, Ra, Sd na rannii émbriogenez myshei.

We studied early embryonic mortality of mice from mutant stocks Tabby (Ta, X-chromosome) and RaSd (RaSd/++, chromosome 2) maintained in the heterozygous state in F1 CBA x C57B1/6 hybrid. Tabby and RaSd mice were reciprocally crossed with F1 mice and examined for the morphological status of embryos washed from the oviduct on the third day of pregnancy, when the stage of eight blastomeres is normally attained. Mortality was evaluated from the number of embryos which did not reach the expected stage by this time. The results have shown that 2-4 cell embryos, which have received gene Ta with the X-chromosome of the female parent, differed from embryos with F1 genotype at the same stage of development by their increased mortality rate, whereas among embryos obtained from RaSd, the mortality was mainly observed before cleavage. Death of embryos receiving the mutant gene from hemizygous Ta males or heterozygous RaSd/++ males was not significantly different from the mortality of embryos without these mutations.

[Effects of single gamma-irradiation on the activity of ornithine decarboxylase in the thymus and pulmonary tissue]. / Vliianie odnokratnogo gama-oblucheniia na aktivnost' ornitindekarboksilazy v timuse i legochnoi tkani.

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. A nonmonotonous type of the dose-response curve was observed 7 days after irradiation: the radiation effect with a low dose (0.1 Gy) was opposite to that with sublethal doses (1-6 Gy).

[Effects of chronic gamma irradiation on the activity of adenylate cyclase in rat lung tissue]. / Vliianiie khronicheskogo gama-oblucheniia na aktivnost' adenilattsiklazy legochnoi tkani krys.

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.

[The effect of the dose rate on the development of rat pups under chronic gamma irradiation]. / Vliianie moshchnosti dozy na razvitie krysiat pri khronicheskom gamma-obluchenii.

Chronic exposure of rat pups to gamma radiation, during their intensive growth, at a dose rate of 0.01, 0.11 and 0.5 cGy/day did not affect their development throughout a two-month period of observation. At a dose rate of 12.9 cGy/day rat growth was inhibited during the first 15 days. With further exposure at the same dose rate (over a period of up to five months) the rate of rat pup growth was restored, which indicated the presence of adaptation processes.

[The dynamics of the ornithine decarboxylase activity in chronically gamma-irradiated rats]. / Dinamika aktivnosti ornitindekarboksilazy pri nepreryvnom gamma-obluchenii krys.

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 data obtained indicate that adaptation is possible, at a metabolic level, with the restricted chronic gamma-irradiation of animals.

[The possible participation of the cAMP system in the activation of ornithine decarboxylase in rat tissues following nonlethal fractionated gamma-irradiation]. / O vozmozhnom uchasti sistemy tsAMF v aktivatsii ornitindekarboksilazy v tkaniakh krys posle neletal'nogo fraktsionirovannogo gamma-oblucheniia.

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.

[The stimulating action of low doses of ionizing radiation on glucokinase synthesis in the liver of developing rats]. / Stimuliruiushchee deistvie malykh doz ioniziruiushchei radiatsii na sintez gliukokinazy v pecheni razvivaiushchikhsia krys.

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]. / Ornitindekarboksilaznaia aktivnost' v tkaniakh krys v otdalennye sroki posle oblucheniia.

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]. / Mekhanizmy narusheniia gormonal'noi reguliatsii adenilattsiklazy plazmaticheskikh membran pecheni krysy v khode rannego ontogeneza v usloviiakh oblucheniia in vitro.

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. The radiation-induced derangement of membrane lipids, where AC functions, is shown.

[Possible effect of natural radioactivity on the induction of glucokinase synthesis in the liver of developing rats]. / K voprosu o vozmozhnom vliianii estestvennoi radioaktivnosti na induktsiiu sinteza gliukokinazy v pecheni razvivaiushchikhsia krys.

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]. / Issledovanie radiatsionnogo narusheniia sinteza fermentov v perinatal'nyi period ontogeneza.

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. The radiation inhibition of G-6-P-ase synthesis was relieved by the injection of thyroxine. A dependence was shown between the radiation increase of TAT activity and changes in cAMP system (increase of cAMP level, decrease of phosphodiesterase activity, intensification of response of adenylate cyclase complex to biogenic amines). A suggestion is put forward that the radiation damage of the enzymes under study is mediated by a change in the number of hormonal inductors.

[Possible effect of natural background radiation on the development of mammals]. / O vozmozhnom vliianii estestvennogo fona ioniziruiushchei radiatsii na razvitie mlekopitaiushchikh.

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.