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Biomedical subjects

N I Riabchenko

Publications and source records attributed to N I Riabchenko.

At least 55 records · Page 3Linked to original sources
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[Thymidine excretion from thymocytes in irradiated and nonirradiated rats during endonucleolysis].

The concentration of free thymidine (dT), excreted from thymocytes of irradiated and nonirradiated rats, was determined after incubation of cells in various digestive buffers. The release of dT from thymocytes depended upon the rate of DNA fragmentation in conditions of chromatin endonucleolysis. The increase in the thymidine content, in conditions of chromatin endonucleolysis in buffers containing no calcium ions, was only noted in thymocytes of exposed rats: this was the consequence of chromatin DNA damages already available in these cells.

Animals↗
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[Structural organization of chromatin as a factor determining the rate of its endonucleolysis in irradiated and nonirradiated thymocytes].

A study was made of chromatin endonucleolysis in hypotonic thymocytes incubated in digestive buffers containing different concentrations of potassium, magnesium, calcium, and mercaptoethanol. Inhibition of endonucleolysis by univalent cation during the first 20 min of incubation was followed by intensive chromatin degradation. A decrease in free potassium content retarded chromatin degradation and enhanced the inhibiting effect of the univalent cations. The regularities of changes in the rate of chromatin endonucleolysis in different digestive buffers were similar with both exposed and intact thymocytes.

Animals↗
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[Effect of cycloheximide on the morphological and biochemical changes in chromatin in non-irradiated and irradiated rat thymocytes].

The level of chromatin degradation was studied and the method of electron-microscopy was used to estimate the changes in the ultrastructure of irradiated and nonirradiated thymocytes of rats treated with cycloheximide. The latter was found to decrease the degree of derangement of nuclear ultrastructure and the level of chromatin degradation in exposed animals and to increase the yield of these damages in thymocytes of nonirradiated animals. The electronmicroscopic determinations showed that the percentage of thymocytes with the impaired nucleus structure is twice as high as that of degraded chromatin. The causes of the quantitative disagreement between the morphological and biochemical indices of the interphase thymocyte death are discussed.

Animals↗
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[Enhancement by metronidazole of the antitumor effect of cyclophosphane].

In experiments on mouse tumors (sarcoma-180, Ehrlich ascites tumor and hemoblastosis La) the ability of metronidazole to enhance the antitumor chemotherapeutic action of cyclophosphane was investigated. It was shown that metronidazole (1000 mg/kg) injected 60 min before cyclophosphane administration can elicit an almost two-fold increase in its radioprotective efficiency. The chemosensitizing effect of metronidazole depends on the drug concentration and the tumor type.

Animals↗
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[Radiosensitizing and toxic action of metronidazole and isometronidazole (1-(2-hydroxyethyl)-2-methyl-4-nitroimidazole) on the cells of Ehrlich ascites cancer and hemoblastosis La in vitro].

A study was made of Ehrlich ascites tumor growth and life span of mice bearing hemoblastosis La after inoculation of tumor cells subjected, in anaerobic conditions, to the effect of gamma-radiation and/or metronidazole and isometronidazole. It was shown that the cytotoxic effect of isometronidazole was less manifest than that of metronidazole the radiosensitizing effect, with a reference to anoxic tumor cells in vitro, being nearly the same.

Anaerobiosis↗
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[Effect of metronidazole on the free thymidine content in the blood serum of irradiated mice].

The influence of a radiosensitizer, metronidazole, on the free thymidine content of blood serum of irradiated mice was studied in aerobic and hypoxic conditions. A heated metronidazole solution (1 mg/g) was administered intraperitoneally 30 min before irradiation of animals with a dose of 3 Gy. Thymidine concentration in blood serum was determined by the radioimmunological technique. The influence of metronidazole on the level of thymidinemia was only noted in the animals exposed under hypoxic conditions.

Acute Disease↗
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[Interphase death of thymus cells in combined radiation-thermal injury against a background of prophylactic administration of alpha-tocopherol and indomethacin].

The administration of alpha-tocopherol prior to radiation and thermal affection enhances chromatin degradation in thymocytes, increases the number of pyknomorphic cells in the critical zone of thymus, and enhances injury to erythrocyte membranes. The preventive administration of indomethacin does not influence the interphase cell death.

Animals↗
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[Viability of rat thymocytes as affected by radiation and combined radiation-heat damage].

A share of damaged (nonviable) cells of rat thymus was quantitatively estimated on days 1 and 3 following irradiation with doses of 1, 3 and 6 Gy and a combined treatment with radiation and heat. The percentage of nonviable thymocytes was higher after the combined treatment than after the effect of radiation alone delivered in equivalent doses.

Animals↗
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[Radiosensitizing and toxic effect of metronidazole and its ortho-isomer 1-(2-hydroxyethyl)-2-methyl-4-nitroimidazole on Escherichia coli B/r cells].

A study was made of the effect of metronidazole and isometronidazole on the survival rate of irradiated and nonirradiated E. coli B/r cells. These substances had similar radiosensitizing activity with regard to anoxic cells and did not sensitize cells irradiated in the air. At the same time, isometronidazole was found to be less toxic than metronidazole.

Aerobiosis↗
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[Radiosensitizing activity of maleic acid derivatives. Effect of maleic acid o-nitroanilide, anilide and diethyl ester on the survival of gamma-irradiated cells of Escherichia coli B/r].

Among three substances under study, only o-nitroanilide of maleic acid (oNAM) possessed a radiosensitizing activity. Radiosensitivity of E. coli B/r cells irradiated in the presence of Ar and oNAM was higher by 4.8 times than that of irradiated controls. The survival rate of E. coli B/r cells irradiated in the presence of oxygen was changed by 1.4 times by the effect of oNAM.

Aerobiosis↗
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[Degradation of DNA and chromatin in cells of mouse lymphoid organs after irradiation and PHA administration].

Phytohemagglutinin (PHA) administered to irradiated mice did not influence the postirradiation degradation of DNA and the yield of polydeoxynucleotides (PDN) in cells of thymus, spleen and bone marrow. The degree of degradation of DNA and chromatin was higher in the thymus as compared to other studied organs. A possible mechanism of the radiotherapeutic action of PHA is discussed.

Animals↗
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[Chromatin breakdown in the white blood cells of rats during irradiation and in combined radiation injury under cystamine protection].

The polydeoxyribonucleotide (PDN) level in leukocytes of peripheral blood of rats treated with cystamine adequately reflects the severity and outcome of radiation sickness. Preventive application of cystamine against the combined effect of ionizing radiation and heat decreased the PDN level in white blood cells but did not influence the survival of animals.

Animals↗
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[Sensitivity of DNA synthesis to gamma-irradiation in Ehrlich ascites carcinoma cells in stationary and logarithmic growth phases].

A study was made of the influence of gamma-radiation on DNA synthesis in cells of 3-day and 7-day Ehrlich ascites tumor cultures. DNA synthesis in cells of the 3-day culture was more sensitive to moderate radiation doses than those of the 7-day culture as was observed during the first 30 min after irradiation. After 3-hour postirradiation incubation, no appreciable difference was noted in radiosensitivity of DNA synthesis in the cells of the 3-day and 7-day cultures.

Animals↗