[Evaluation of biological effectiveness of high-energy accelerated particles based on the study of cytogenetic disorders in murine sex cells]. / Otsenka biologicheskoi éffektivnosti vysokoénergeticheskikh uskorennykh zariazhennykh chastits na osnove tsitogeneticheskikh narushenii v polovykh kletkakh myshei.

The frequency of reciprocal translocations in spermatogonia of F1(CBAxC57Bl6) mice irradiated with 50 MeV protons, 4.2 GeV deuterons, 1.8 GeV/nucleon helium ions or 60Co gamma-rays was investigated. The relative biological effectiveness of these particles calculated by comparing the equieffective doses of reference and experimental radiations was less than 1.0 under the assumption of the linear dose-effect relationship. The RBE of the particles calculated by means of the nonparametric method largely depended on the doses applied.

[Assessment of the genetic risk of radiation by irradiation data from laboratory mammals]. / Otsenka geneticheskogo riska radiatsii po dannym oblucheniia u laboratornykh mlekopitaiushchikh.

An attempt has been made to assess quantitatively genetic risk of radiation for man based on mammalian (mostly mouse) data and using the direct method proposed by UNSCEAR. The parameter employed was induction of reciprocal translocations. Two assumptions were made: human radiosensitivity equals that of the mouse; and dose-response is linear. From observations with acute gamma irradiation the estimate of risk per 10(-2) Gy was as follows: 39 translocation heterozygotes are expected among one million F1 conceptions, 5 cases of multiple congenital anomalies, 25 abortions recorded and 49 unrecorded. Chronic gamma irradiation at dose rates of 1.3 X 10(-5), 1.7 X 10(-4) and 1.0 X 10(-4) Gy/min was 3 to 10 times less effective. Exposure to 4.2 GeV deuterons proved inferior in effectiveness to gamma irradiation. Chronic exposure to 4.1 MeV neutrons delivered at 8 X 10(-4) Gy/min showed 7 times the effectiveness of chronic gamma irradiation. Administration of tritiated water (from 37 to 37 X 10(2) kBq/g b.w.) to rats entailed a risk of the same order of magnitude as external chronic gamma irradiation. Reduction of genetic risk was achieved by pretreatment with either AFT-, ATP-serotonin mixtures or the molecular combinations, Adeturon and Cytriphos. Study of interspecies differences in genetic radiosensitivity showed decline in the following order: rat-rabbit-mouse-Syrian hamster. A dose-rate effect was most clearly seen in the rat, and least clearly in the rabbit. In female mice, examination of oocyte depletion indicated primary follicles to be highly susceptible to acute gamma irradiation; decrease in sensitivity was observed beginning with stage 4. Chronic gamma irradiation was found to be less effective.

[Effect of space flight factors on bone marrow cells in the rat]. / Deistvie faktorov kosmicheskogo poleta na kostnomozgovye kletki krys.

The effect of space flight factors, weightlessness in particular, on the genetic structures of bone marrow cells of rats flown for 18.5 days on Cosmos-1129 was investigated. Chromosome aberrations were measured on postflight days 6 and 25. The frequency of unstable chromosome aberrations was similar in the flight, synchronous and vivarium rats. Karyotyping of metaphase plates revealed chromosome aberrations in the flight and synchronous rats. Exposure to weightlessness did not influence the mutagenic effect in bone marrow cells of the rats.

[Chromosome translocations in the sex cells of mice subjected to chronic low-dose gamma-irradiation]. / Khromosomnye translokatsii v polovykh kletkakh myshi pri khronicheskom gamma-obluchenii s nizkoi moshchnost'iu dozy.

Translocation induction in mouse spermatogonia by continuous whole-body gamma irradiation (radium 226) was studied. Total doses, delivered at a rate of 13.0 +/- 1.3 X 10(-4) rad/min for various time intervals, were 97, 195, 294 and 442 rad. Cytological examination within 3 to 4 months after irradiation indicated the presence of translocations in 0.16, 0.30, 0.75 and 1.29 percent respectively, of primary spermatocytes at diakinesis metaphase I. Data on translocation induction (Y) as related to total irradiation dose (D) were best fitted to a second power parabola equation (Y=5.1 X 10(-6)D2 + 7.32 X 10(-4) X D). The results obtained confirm that chronic gamma irradiation is of low genetic efficiency, and support the suggestion that there exists a dose-rate threshold under which no more changes in exposure efficiency will occur.