X-ray-induced breaks in the X chromosomes in Drosophila lines of various radiosensitivities

The frequency of X-ray induced X-chromosome breaks has been studied in females of the line rad (2) 201G1 hypersensitive to radiation and in females of the control line selected from the same population. The frequency of X-chromosome breaks was judged based on the frequency of X0 males occurrence. Synergism of the effects of X-rays (at doses 0.1, 0.5 and 1.0 kr) and of hyperthermia (+37 degrees C, 5.5 hours) applied after irradiation served as an indirect evidence for the functioning of DNA repair systems. It is demonstrated that radiosensitivity of mature oocytes of the lines compared was equal and that hyperthermia applied after irradiation increased the latter effect in both lines. Young oocytes of the control line were radioresistant, and hyperthermia applied after irradiation enhanced its effect. Opposite to them, young oocytes of the rad line females were radiosensitive. They did not differ from mature oocytes in the frequency of X-chromosome losses. Synergism of the two factors (irradiation and hyperthermia) was not registered in young oocytes. On the basis of the results obtained, it may be concluded that radiosensitivity of young oocytes in the hypersensitive line is conditioned by the failure of DNA repair systems and that the rad (2) 201G1 gene may be considered, in relation to the genes controlling DNA repair, as a suppressor functioning selectively at a certain stage of oogenesis.     

Radiobiological method of studying the structure of the partially diploid area in T4 bacteriophage]

The mechanism of cross-reactivation after UV-irradiation was examined using different deletion mutants as recipients. A model of the rescue mechanism of partly diploid area was suggested. The method of cross-reactivation in demonstrated to permit an easy determination of the orientation of duplicated genes.     

Lethal and mutagenic photodynamic effect of acridine orange on bacteriophage cd]

Both acridine-sensitized inactivation and mutagenesis in phage sd have been studied and compared with the effect of other mutagens. Inactivation curve was not stictly exponential, with a small shoulder at short light doses and deviation of survival lower than 10(-5). The lethal effect was not reactivated by multiplicity reactivation. Photodynamic damage in phage sd was accompanied by the increase of the rise (but not of the latent) period in the one-step curve of phage multiplication and increase of the burst size. Experiments were carried out at dye concentration of 1-10(-5) M or lower; a strong dark effect of the dye being observed under 2-fold increase of the dye concentration. Plaque-type mutants were formed up to the maximum approximately 1% at the survival approximately 2--10(-5); in comparison with other mutagens photo-sensitized mutagenesis in phage sd was lower. The significant increase in the number of plaque mutants was observed after the illumination of phage fraction surviving the pre-treatment with higher acridine orange concentration (greater than or equal to 2-10(-5)M).     

Element Composition of Iris sibirica L. in In Vitro Culture

Russian Journal of Bioorganic Chemistry - The development of biotechnological methods for producing medicinal plants, preserving the valuable elemental and chemical composition of the group, is one...     

Spontaneous differentiation of cultured human pulmonary adenocarcinoma cells

During cultivation of the cells of dimorphous poorly differentiated glandular and squamous cell pulmonary carcinoma, one can see the predominance of the cells of poorly differentiated pulmonary adenocarcinoma with a gradual transition to a high-differentiated pulmonary adenocarcinoma. The cells of high-differentiated pulmonary adenocarcinoma exhibited marked capacity for agglutination induced by PHA and Con A, as well as high levels of dehydrogenase and hydrolase activity.