[Estimation of genetic effects of chronic exposure to low-dose rate gamma-radiation by cytogenetic methods and DNA-comet assay]. / Otsenka geneticheskikh éffektov khronicheskogo vozdeistviia nizkointensivnogo gamma-izlucheniia tsitogeneticheskimi metodami i metodom DNK-komet.

The study of genetic effects in CBA/lac mice exposed for 1 year to constant low dose-rate gamma-radiation at a dose-rate 63 cGy/year has been carried out. We have shown the significant increase in the DNA breaks' level in spleen lymphocytes by comet-assay beginning from the total absorbed dose of 20 cGy. It is possible that the DNA breaks' level increase resulted from the structural rearrangement of chromatin or induction of lymphocyte proliferation. The results obtained by micronucleus test have proved that the mutagenic effect of chronic low dose-rate gamma-radiation depends on cell type and respectively on cell proliferation rate, cell differentiation, etc. So, by the end of experiment the significant increase in the frequency of PCE with micronuclei (MN) was observed. However, in contrast, the frequency of NCE with MN was not increased. No significant increase in the percent of lung cells with MN was registered.

[The estimation of molecular and cytogenetic effects in mice exposed to chronic low dose gamma-radiation]. / Otsenka molekuliarnykh i tsitogeneticheskukh éffektov khronicheskogo vozdeistviia nizkointensivnogo gamma-izlucheniia u myshei.

Molecular and cytogenetic parameters were estimated in male CBA/lac mice exposed to chronic low dose-rate gamma-radiation (62 cGy/year) for 40, 80, 120, 210, and 365 days. After 40 days of exposure (6.7 cGy), spleen lymphocyte susceptibility to hydrogen peroxide was shown to increase. However, beginning from the day 120 of the treatment (20.4 cGy), the opposite effect was observed. An increase in number of the DNA-protein crosslinks was recorded in spleen lymphocytes only on day 40 of the experiment. The number of DNA breaks increased significantly beginning from day 120 of the experiment, as shown by the DNA-comet method. On the day 210 of irradiation, the frequency of abnormal sperm heads in the mice significantly increased. The number of normochromatic micronucleated erythrocytes of the peripheral blood remained unchanged.

[Changes in the number of DNA-protein cross links in spleen lymphocytes of mice exposed to low intensity low dose gamma irradiation]. / Izmeneniia kolichestva DNK-belkovykh sshivok v limfotsitakh selezenki myshei pri vozdeistvii nizkointensivnogo gamma-izlucheniia v malykh dozakh.

Levels of DNA-protein cross-links (DPC) and DNA single-strand breaks (SSB) in spleen lymphocytes were studied in mice exposed to low-intensity gamma-radiation (1.7 mGy/day) for 1, 4, 10, 20, and 30 days. The spleen mass and count of lymphocytes isolated from this organ also has been investigated. The significant increase in the DPC level as compared to the control occurred on the 10-th and 30-th days of irradiation at doses of 1.7 and 5.1 cGy, accordingly. The number of spleen lymphocytes normalized to organ mass significantly decreased on the 4-th and 30-th days of the experiment. No increase was found in levels of alkali-labile sites and SSB. In contrast, the increase in the amount of duplex form DNA was recorded on the 4-th and 30-th days of the experiment. Our indicate that DPC formation after irradiation at low doses represents some form of cellular response to the damaging agent.

DNA-protein cross-links in cells of internal organs of rats after fractional irradiation at various doses.

The influence of daily fractional irradiation of male Wistar rats for 30 days on DNA-protein cross-links (DPC) in spleen, thymus, and liver cells was studied. The level of DPC depended strongly on the daily dose of irradiation and the studied organ. After irradiation at dose 0.5 Gy per day increased DPC level was detected in all organs. The highest level was in the lymphoid organs and the lowest in the liver. After irradiation at dose 0.3 Gy per day DPC formation was detected only in the thymus. The data suggest the existence of a dose threshold for DPC formation during fractional irradiation.