Radiobiologiia最新文献

In experiments with mice a study was made of the favourable effect of a single dose of a mixture of extracts from Archangelica officinalis and Ledum palustre on the severity of radiation injury induced by fractionated gamma irradiation (doses of 1 and 4 Gy, cumulative dose of 12 Gy). Injection of the mixture prior to the first dose of 4 Gy (given 3 times at a 2-7 day interval) caused a significant decrease in the damaging effect with respect to both the survival rate and the average life expectancy of exposed mice. With fractionated irradiation, the protective effect of the extract mixture increased with decreasing efficiency of the cumulative radiation dose. The results obtained indicate that the mixture used protects the animals from the injury to both the gastrointestinal tract and the haemopoietic system.

A single dose of 6-methyluracil (50 mg/kg) administered intraperitoneally to BALB and SHK mice prior to X irradiation (5.0 Gy) produced a pronounced radioprotective effect which was dependent upon the initial antioxidant status of the body, but independent of the effect of the agent on postirradiation leukopenia dynamics. The radioprotective effect of 6-methyluracil was conditioned by its influence on lipid peroxidation regulation and was displayed by the normalization of the antioxidant activity of lipids of radiosensitive organs and tissues and by high activity of superoxide dismutase in the liver and erythrocytes.

The effect of subliminal streptozotocin doses of rat pancreas cells was studied 1 and 3 months after 1-Gy gamma irradiation. Streptozotocin injected to irradiated animals caused a drastic decrease in beta-cell function which was manifested by hyperglycemia and less intensive secretion and lesser content of insulin in isolated pancreatic islands, as compared to control.

A comparative study was made of modification of the effects of UV-, X- and fission neutron-radiation by DNA-topoisomerase II and spermidine. The efficiency of the studied agents was the highest with UV-radiation of cells. Being insignificantly efficient in changing the radiosensitivity of cells, novobiocine and spermidine suppressed significantly the recovery of cells from radiation damages which were realized as chromosome aberrations upon X-ray dose fractionation. Adriamycin removed completely the effect of dose fractionation. Chromatin condensation was noted in cells after the treatment thereof with the agents under study. The authors discuss the possible mechanism of interaction between DNA-topoisomerase II and repair processes in mammalian cells.

The effect of gas hypoxic mixture, containing 8% of O2 (GHM-8), on the ability of cell precursors of haemopoietic stroma (which form colonies (clones) of fibroblasts (CFU-F) in a culture, and are present in the bone marrow of adult rats) to repair potentially lethal and sublethal radiation damages has been investigated. The recovery of CFU-F from potentially lethal damages, that was studied after their delayed survival in a culture following irradiation of animals, proceeds at nearly the same rate in cells irradiated both in the air and in hypoxic conditions (GHM-8). Fractionated irradiation reduces the radioprotective effect of GHM-8 for CFU-F, particularly for the radioresistant subpopulation; the ability of CFU-F to recover from sublethal radiation damages decreases.

The method of flow cytometry was used to study conformation changes in rat hepatocyte chromatin exposed to various doses of X-rays and fission neutrons (mean energy of 0.85 MeV). Chromatin decondensation induces by both X-rays and neutrons was shown to be a function of dose. The saturation effect was observed for X-rays doses ranging from 4 to 6 Gy; for fission neutrons no saturation effect was noted within the dose range from 0.5 to 4 Gy. The initial chromatin level, that changed during the cell cycle and upon ageing, influence induction of conformation changes in the chromatin. The authors discuss the dependence of the processes of repair and fixation of damages to hereditary cell structure on the chromatin conformation at the time of exposure.

The ability of cell precursors of the haemopoietic stroma (CFU-F), that are present in the bone marrow of adult rats, to recover from potentially lethal and sublethal radiation damages has been investigated. The highest reparability, with respect to potentially lethal damages, is displayed by the most radioresistant CFU-F population, that forms loose colonies (clones) in a culture; the slope of the dose-response curve, not the extrapolation number, changes, and heterogeneity of the CFU-F population is observed. The results obtained confirm the presence of heterogeneity in the population of CFU-F, that was revealed in studying their radiosensitivity by the formation of dense and loose fibroblast colonies in a culture.

Local fractionated exposure of a rabbit eye to fast neutrons of 3 Gy (1.5 x 2) and 7.5 Gy (1.5 x 5) induces early reactions of all structural elements of retina, among which dose-dependent degradation of photoreceptor membrane discs and damages to pigmentoepitheliocytes are of prime importance. Further pathomorphogenesis is connected with the surpassing degeneration of a radial glia with respect to destruction of interneuronal synapses and a minor part of neurons. The postirradiation (one and six months after 7.5 Gy irradiation) changes in the blood-retinal barrier are responsible for the disturbances in the glioneuronal complex.

The method of luminol-dependent chemiluminescence was used to study the affect of gamma radiation on activation of cells of thymus and bursa of Fabricius upon their adhesion on kapron. Thymocyte activation by adhesion on glass or kapron provoked chemiluminescence which was connected with the development in cells of active oxygen forms. The chemiluminescence amplitude was shown to increase with adhesion of thymocytes exposed to 1-5 Gy radiation and to decrease after a dose of 10 Gy. In cells of bursa of Fabricius, the analogous response to activation or irradiation was not observed.

With the use of two genetically labeled lines of Djungarian hamster cells and the method of hybrid selection on a HAT-selective medium it was found that in the irradiated mixed culture of the above cell lines, cells were formed that survived in the conditions of total destruction of irradiated parent cells. The chromosome analysis showed that about 45% of the survived cells were hybrids resulting from the radiation-induced fusion of two initial cell lines. These hybrid cells were capable of reproduction. A subline of hybrid cells was isolated. It is assumed that the radiation-induced process of cell fusion and the formation of viable somatic hybrids might be essential for the survival of cell population in the course of tumor radiotherapy.