[Effect of gamma-irradiation and neutrons on DNA-membrane complexes in mammalian cells]. / Vozdeistvie gamma-izlucheniia i neitronov na DNK-membrannye kompleksy kletok mlekopitaiushchikh.

The first results of the radiobiological studies obtained in a biophysical channel of the IBR-2 reactor at the Joint Institute for Nuclear Research are presented in this report. A study was made of the DNA-membrane complex sedimentation after exposure of Chinese hamster cells V79-4 to gamma-rays within a wide range of doses. The assumption, that had earlier been forwarded by the authors, of the role of double-strand DNA breaks in the alteration of a relative rate of the complex sedimentation upon irradiation of cells with doses above 50 Gy was confirmed.

[Double-stranded DNA breaks and inactivation of mammalian cells in relation to the LET of the radiation--comparison between experiment and theory]. / Dvunitevye razryvy DNK i inaktivatsiia kletok mlekopitaiushchikh v zavisimosti ot LPE izluchenii--sravnenie mezhdu éksperimentami i teoriei.

In experiments on Chinese hamster cells the survival curves and the yield of double-strand DNA breaks were determined after irradiation at different LET. The comparison of the experimental results and the survival curves calculated on the basis of Günter-Schultz's theory of radiation inactivation of cells has demonstrated that radiation-induced double-strand DNA breaks are responsible for the lethal effect of radiation on cells.

[Use of multicellular spheroids in studies based on the NSD (nominal standard dose) concept]. / Ispol'zovanie mnogokletochnykh sferoidov v issledovaniiakh po kontseptsii NSD.

The authors discuss the possibility of application of multicellular spheroids as a model system in studies based on NSD conception. The death rate of spheroids from cells of Chinese hamster V79-4 was shown to depend upon cumulative dose of gamma- and neutron (0.7 MeV)-radiation (the number of fractions was 1, 5 and 10). With fractionated irradiation, the reoxygenation effect was observed. A good coincidence was obtained between the dependence of the cumulative dose upon the number of fractions for multicellular spheroids and clinical data.

[Damage by gamma rays and heavy ions to superhelical structures of nuclear DNA]. / Povrezhdenie gamma-luchami i tiazhelymi ionami superspiral'nykh struktur iadernoi DNK.

Chinese hamster cells (V79-4), human lymphocytes and mouse ascites cell were exposed to gamma-rays and heavy ions (4He and 12C). Sedimentation of complexes containing DNA was studied after cell lysis by centrifugation in a neutral sucrose gradient. The distinctions noted after irradiation with gamma-rays and heavy ions are consistent with the idea of the superhelical organization of DNA into discrete and membrane-bound compact units. According to the estimates made the diameter of these complexes was approximately 0.2 micron and DNA content, about 2 X 10(9) dalton.

[Multicellular spheroids for use in radiobiological experiments]. / Mnogo kletochnye sferoidy kak ob"ekt dlia radiobiologicheskikh éksperimentov.

Cell spheroids are conglomerates of closely arranged cells with reciprocal effects among them. Spheroids are histologically similar to nodulary tumours. Cells constituting these spheroids are heterogenous in their sensitivity to X-rays and fast neutrons. Radiosensitivity of cells in a small spheroid is lower than that of similar cells grown in a monolayer.