[The influence of UV-B radiation on reproductive function of Hordeum vulgare L. plants].

It has been shown that ultraviolet-B radiation induced acceleration of flowering and differentiation of sexual spike elements in barley. Increasing of pollen asynchronous development and variability of pollen grains with growing of pollen grain sterility were observed as well. The productivity of plants irradiated with UV-B radiation did not change. Considerable doses of irradiation resulted in decreasing of pollen sterility by intensification of haplontic cell selection. The influence of UV-B radiation on the plants can be considered as a genotoxical effects via formation of initial cell DNA damages and photoinduction.

[The radioadaptation condition at various stages of transition process, induced by gamma-irradiation in bacteria Escherichia coli JM 101]. / Sostoianie radioadaptirovannosti na raznykh stadiiakh indutsirovannogo ostrym gamma-oblucheniem perekhodnogo protsessa u bakterii Escherichia coli JM 101.

The dynamics of transition process caused by gamma-irradiation in bacterial Escherichia coli JM 101 culture was investigated. The bacteria radiostability at different phases of this process was defined. The received results testified to phase gamma-irradiation doze dependent character of bacteria population reaction. It was shown, that the increase of bacteria cell radioresistance occured at the postradiation restoration stage, whereas at the inhibition stage the radioresistance decreased.

[Soil drying as a model for the action of stress factors on the natural bacterial population]. / Vysushivanie pochvy: model' deistviia stressovykh faktorov na prirodnye populiatsii bakterii.

The drying of soil samples reduced the abundance (especially of predominant species) and the diversity of bacteria isolated from these samples, making easier the isolation of rare bacterial species. Some bacterial species that were minor before soil drying became dominant in dried soil samples. In general, soil drying allowed the diversity of soil bacteria to be determined more adequately. The bacteria that were isolated from dried soil samples turned out to be resistant to gamma radiation (with LD90 = 2.8-4.6 kGy) and desiccation. It is concluded that soil drying may serve as a model for the action of stress factors on natural bacterial populations. The hypothesis that periodic desiccation was the primary cause of formation of bacterial radioresistance in nature is discussed.

[The effect of gamma-radiation and desiccation on the viability of the soil bacteria isolated from the alienated zone around the Chernobyl Nuclear Power Plant]. / Vliianie gamma-izlucheniia i degidratatsii na vyzhivaemost' bakterii, izolirovannykh iz zony otchuzhdeniia Chernobyl'skoi AES.

Methylobacterium extorquens, M. mesophilicum, and Bacillus subtilis strains were found to be resistant to gamma-radiation, irrespective of whether they were isolated from the alienated zone around the Chernobyl Nuclear Power Plant or outside this zone. The LD90 of Methylobacterium and B. subtilis strains with respect to gamma-radiation was 2.0-3.4 and 3.7-4.4 kGy, respectively, whereas their LD99.99 values were 4.5-6.9 and more than 10 kGy, respectively. The high threshold levels of gamma-radiation for Methylobacterium and B. subtilis imply the efficient functioning of DNA repair systems in these bacteria. Unlike Bacillus polymyxa cells, the cells of M. extorquens, M. mesophilicum, and B. subtilis were also resistant to desiccation. Pseudomonas sp., Nocardia sp., and nocardioform actinomycetes were sensitive to both gamma-radiation and desiccation. Similar results were obtained when the bacteria studied were exposed to hydrogen peroxide and ultraviolet radiation. The results obtained indicate that the bacteria that are resistant to gamma-radiation are also resistant to desiccation, UV radiation, and hydrogen peroxide. The possibility of using simple laboratory tests (such as the determination of bacterial resistance to UV light and desiccation) for the evaluation of bacterial resistance to gamma-radiation is discussed.

[Epigenetic cell reactions induced by ionizing radiation]. / Epigeneticheskie reaktsii kletok na deistvie ioniziruiushchei radiatsii.

The importance of radiation modification of epigenetic activity in the general mechanism of radiobiological reactions is proved. The inheritable epigenetic changes induced by irradiation are one of the basic reasons of formation of the remote radiation pathology. It is noted that epigenetic inheritable changes of cells have the determined character distinguishing them from mutation changes, being individual and not directed. It is underlined the ability of ionizing radiation to modify a level of spontaneous genetic instability inherited in a number of cell generations on the epigenetic mechanism.

[In vitro repair of gamma-irradiated transforming Bacillus subtilis DNA by extracts of blue-green algae]. / Reparatsiia in vitro gamma-obluchennoi transformiruiushchei DNK Bacillus subtilis ékstraktami sine-zelenykh vodoroslei.

A cell-free extract from blue-green alga Anacystis nidulans contains enzymes which repair in vitro the transforming activity of gamma-irradiated Bacillus subtilis DNA. The level of restoration of the transforming activity depends on the protein concentration in the reaction mixture, the duration of incubation and on the dose of irradiation. The repair of gamma-induced lesions is most efficient in the presence of magnesium ions, NAD and ATP. The present data indicate that the repair of transforming DNA is performed with the participation of DNA polymerase and polynucleotide ligase which function in the cell-free extract of algae.

[Intracellular oxygen and the radiosensitization of cells of the blue-green alaga, Anacystis nidulans]. / Vnutrikletochnyi kislorod i radiosensibilizatsiia kletok sinezelenoi vodorosli Anacystis nidulans.

The photosynthetic system of the blue-green alga Anacystis nidulans was inactivated by 30% at a dose of 100 krad of gamma irradiation in N2. If the cells were irradiated in N2+2% CO2 in the light, their radiation sensitivity was increased with an oxygen enhancement ratio of 2.0. Neither light nor CO2 taken separately affected radiosensitization of the cells which increased almost to the same extent as under aerobic conditions in the presence of both light and CO2. The intracellular oxygen of the photosynthetic origin caused apparently the same radiosensitization as oxygen derived from the extracellular sources.