[An EPR study of the joint action of sodium nitrite and whole-body irradiation on animal tissues]. / Issledovanie metodom EPR sovmestnogo deistviia nitrita natriia i obshchego oblucheniia na tkani zhivotnykh.

Changes in metabolic paramagnetic centers of the liver, kidney, spleen, brain and heart tissues, and blood after sodium nitrite intraperitoneal administration irradiation, or combined action of sodium nitrite and irradiation on mice, were studied using the EPR method. It was shown that irradiation of mice after sodium nitrite administration enhanced the effects induced by sodium nitrite alone: the levels of nitrosyl complexes Heme-NO in the tissues, cytochrome P-450 inhibition, and MetHb were higher.

[Markers of the metabolic changes arising as a result of ionizing radiation exposure]. / Markery metabolicheskikh izmenenii, voznikaiushchikh vsledstvie vozdeistviia ioniziruiushchei radiatsii.

Time-related changes have been studied in the content of extracellular DNA, Fe(3+)-transferrin (TF), and Cu(2+)-ceruloplasmin (CP) in the blood plasma and the activity of ribonucleotide reductase (RR) in the tumor cells and spleen of mice during the development of acute lympholeukosis P-388 and after ionizing irradiation. At the initial stages of leucosis P-388, the content of extracellular DNA increases, the TF and CP pools in the blood plasma enlarge, and the RR activity in the tumor cells and spleen of tumoral mice markedly increases. A dose-dependent increase in RR activity was also recorded in the spleen of 5-day-old rats within 15-30 min after irradiation. The causes of these changes and the possibility for these indices to be used in estimating leucosis risk are discussed. Radiation-induced increases in RR activity are discussed in relation to the SOS-response to DNA damage; an increased pool of deoxyribonucleotides is necessary for repair of DNA. The mean contents of extracellular DNA, TF and CP in the blood plasma were obtained from children of different ages degrees of radioactive contamination suffering the consequences of the accident at the Chernobyl' Nuclear Power Station (n = 155). Groups of children have been isolated with increased, sharply decreased, and close to normal levels of extracellular DNA, TF, and CP. The lowered TF pool was observed in children with thyroid glands damaged by incorporated radioactive iodine with the degree of suppression determined by the dose. For most children subject to general irradiation, the TF and CP pools in the blood were higher than in the control, suggesting an adaptive response to irradiation.

[Ribonucleotide reductase--a "target" of the action of nitrosomethylurea]. / Ribonukleotidreduktaza--"mishen'" deistviia nitrozometilmocheviny.

The antitumor and toxic effects of methylnitrosourea (MNU) are determined through its metabolic pathways. In organism MNU is subject to hydrolytic decomposition and denitrosation. It has been shown in vivo studies that MNU abdominal injections of therapeutic doses caused the inhibition of ribonucleotide reductase in mouse spleen, and therefore the DNA synthesis depress. The effect may apparently contribute to antitumor property of MNU. It has been estimated that destruction of M2 subunit of the enzyme is occurred. The relation between the loss of ribonucleotide reductase activity and the inhibition of protein synthesis was discussed. Besides, the cancerogenic and mutagenic properties of MNU were discussed as a result of imbalance of DNA precursor pools. Changes in contents of Fe(3+)-transferrin, ceruloplasmin, methemoglobin in blood and spleen of animals after MNU injections have been found. The changes were reversible after single MNU injection and became irreversible after multiple injections.

[Effect of metronidazole and local irradiation of the tumor on paramagnetic metal complexes of the liver and tumor tissues]. / Vliianie metronidazola i lokal'nogo oblucheniia opukholi na paramagnitnye metallokompleksy tkanei pecheni i opukholi.

A study was made of changes in the intensity of the ESR signals in tissues of sarcoma-37 and liver of mice after radiation of the tumor, administration of metronidazole, and after the combined effect of the two factors. The most pronounced changes in the ESR signals were induced by metronidazole. An appreciable increase in the content of nitrosyl complexes in the tumor was noted after the combined effect of metronidazole and radiation which was indicative of the radiation-induced formation of a large number of metronidazole anion-radicals in the tumor.