Radiobiologiia最新文献

In studying the dose (0.1-6 Gy) and time (2 h to 180 days) dependence of ornithine decarboxylase activity, it was found that deviations from the control were more pronounced in the thymus than in the pulmonary tissue. The radiation effect was a function of dose and time after irradiation. A nonmonotonous type of the dose-response curve was observed 7 days after irradiation: the radiation effect with a low dose (0.1 Gy) was opposite to that with sublethal doses (1-6 Gy).

Conditions have been developed for cloning cells-precursors of rat bone marrow haemopoietic stroma, that form in culture dense and sparse fibroblast colonies (CFU-F) at a plating efficiency of 10(-4). Radiosensitivity of rat bone marrow CFU-F, with 60Co-gamma-irradiation in vitro, is characterized by the values of Do and n of 1.87 Gy and 1.4 respectively for all clones; 0.65 Gy and 6.7 for dense clones, and 4.27 Gy and 1.0 for sparse clones. This confirms the observed heterogeneity of CFU-F population consisting of highly radiosensitive and radioresistant subpopulations. The parameters of rat bone marrow CFU-F are nearly the same with irradiation both in vivo and in vitro; with in situ irradiation, the oxygen effect comes into play in a radiosensitive subpopulation of CFU-F; the OER values are 1.6, 2.6 and 0.9 for all, dense and sparse clones respectively.

In experiments with Chinese hamster cells at exponential and stationary growth phases, it has been shown that the postirradiation incubation of irradiated cells in a medium with low pH (up to 6.0) promotes the recovery of cells from potentially lethal damages; it has also been found that the recovery from sublethal radiation damages does not depend on the medium pH. The long-term incubation of nonirradiated cells with low pHc causes death of part of cells.

Growth kinetics of LY-S and LY-R cells (radiosensitive and radioresistant sublines of murine lymphoma L5178Y) has been investigated after beta-irradiation at cumulative doses of 1.5 to 20 cGy and dose rates of 0.8-10 mGy/h. It has been found that after 48 h culture in a complete medium the number of cells differed 5 times, whereas after X- and gamma-irradiation, Do values differed 1.62 times. Using the growth rate as the end point in evaluating the combined effect of beta-irradiation (10 cGy) and subsequent X-irradiation with lethal doses, we observed an increased relative cell number, in comparison to that after X-irradiation alone (an "adaptive response", using this criterion), in LY-S cells irradiated with a dose of 2 Gy. In contrast, when reproductive death of LY-S and LY-R cells the end-point analyzed, the lethal effect of consecutive beta- and X-irradiation in LY-S cells was higher than that expected for X-radiation alone (the synergistic effect).

Injection of prodigiozan to mice 24 h before irradiation caused, by the time of the radiation effect, a decrease in the number of haemopoietic cells-precursors (CFUs and CFU-HM) in the bone marrow and an increase in the functional activity of stromal cell-precursors--the haemopoietic microenvironment of transfer units (HMTU); in the spleen, the number of CFUs decreased, but the number of CFU-HM increased considerably. During the postirradiation period, the haemopoietic and stromal precursors were damaged to a lesser extent, and CFUs, CFU-HM and HMTU recovered more readily in prodigiozan-protected animals than in unprotected mice; the HMTU restoration preceded the increase in CFUs and CFU-HM levels.

The method is proposed for primary evaluation of the ability of drugs of various genesis to affect the accumulation of radionuclides in cells. Extracts of mycelium of wood-rotting Basidiomycetes were shown to prevent 137Cs accumulation in cultures of human embryo fibroblast.

In experiments with albino male rats, a study was made of the influence of age on the incidence of osteosarcomas induced by 90Sr. It was shown that the incidence of tumors decreases exponentially with age.

A study was made of deviations, beyond 1 sigma and 1.5 sigma of a mean value (M) of a donor group, in individual immunological parameters (for instance, the number of CD5+, CD2+, CD4+, CD8+, CD25+ and B-cells; alpha 1-thymosin concentration; and autoantibody titers to antigens of epithelial reticulum cell cytoplasm) in patients suffered acute radiation sickness (ARS) and liquidators of Chernobyl NPP accident. The radiation damage to the immune system was reliably detected in the affected subjects examined: they exhibited a decrease in the alpha 1-thymosin level below M = -1.5 sigma and in absolute B cellularity below M = -1 sigma; and increase in the number of CD25+ cells and in the level of serum autoantibodies to antigens of thymus epithelial reticulum cell cytoplasm. When several parameters selected were examined simultaneously the frequency of recording the deviations in merely one of them markedly increased.

The human fibroblasts were gamma-irradiated with low doses (0.07-0.21 Gy). After a short time interval (3 h), a study was made of the postirradiation viability of cells (by the trypan blue dye exclusion method); post-N-methyl-N'-nitro-nitrosoguanidine-DNA synthesis (by 3H-thymidine incorporation immediately after the mutagen treatment) and postirradiation induction of DNA single-strand breaks (by alkaline elution of cells lysed on the membrane filters). The preirradiation of cells with low doses of gamma-rays was shown to render the cells resistance to induction of DNA breaks by the following exposure to gamma-radiation. The survival rate increased; DNA synthesis was resistant to alkylation damage in these cells, as compared to nonirradiated cells.