Vol 46, No 12 (2019)

Proton-beam irradiation (1, 2, and 4 Gy, 150 MeV) of hybrid male mice F1 (CBA × C57BL/6J) has changed their adaptive behavior in a different ways. The irradiated mice performed significantly less successfully than control ones in the puzzle-box test at those stages when the underpass to the safe box compartment was masked by wood shavings, and they had to dig to get to it. At the same time, they were significantly more successful at the stages when the underpass was masked by a light plug, which should be removed as it blocked the entrance. A reduction in neurogenesis in two proliferative forebrain zones had been demonstrated in irradiated mice.

Examples of the use of different types of chromosome aberrations as diagnostic indicators to solve the practical problems of radioecology were considered. The classifications of the chromosome aberrations used to estimate the clastogenic effect of factors of radiation and chemical nature according to the results of cytogenetic studies with uniform staining of the chromosomes were analyzed. Some terminological inconsistency and ambiguity when designating various types and categories of chromosome aberrations, reflecting the clastogenic effect, was detected. It was demonstrated that this inconsistency can complicate the use of such cytogenetic indices in radioecological practice. According to the results of the Allium test using a digital imaging system, original microimages demonstrating the configurations of aberrant chromosomes used in classifications were obtained.

A correlation between the effectiveness of the radioprotective action of cysteamine with the radiosensitivity of cells and their ability to recover from radiation damage was demonstrated for diploid yeast cells of S. cerevisiae. To demonstrate the involvement of the recovery processes in the mechanism for radioprotective action of the T1023 compound in animals, data on the survival of clonogenic bone marrow cells of mice exposed to ionizing radiation are presented. It is shown that the radioprotective effect of this compound can be realized not only at the physicochemical stage of formation of radiation damage due to a decrease in the oxygen content in tissues but also due to the post-radiation cell recovery at the biochemical stage. This is confirmed by the presence of the sigmoid part of the dose-response curve in the region of low doses of ionizing radiation.

The radiosensitizing effect of niclosamide against human rectal adenocarcinoma cells SW837 and human sigmoid colon carcinoma cells COLO 320 HSR and the underlying molecular mechanisms were investigated in this study. The survival rate of tumor cells under treatment with niclosamide, γ-radiation, and their combination was evaluated. The level of MDR1, Bcl-2, β-catenin, and γH2AX histone, a marker of DNA double-strand breaks (DSBs), was determined by flow cytometry using immunocytochemical methods. It was shown that the combined treatment with niclosamide and γ-radiation led to more intense tumor cell death than when niclosamide and γ-radiation were used separately. A decrease in the level of β-catenin was detected in the cells of the COLO 320 HSR line under treatment with niclosamide, which was more intense under combined treatment with niclosamide and irradiation. At the same time, the content of β-catenin in the cells of the SW837 line remained unchanged under treatment with niclosamide and γ-radiation and under their combined use. Niclosamide did not lead to the formation of DNA DSBs in unirradiated cells and did not increase their level 1 h after radiation exposure. The treatment of the cells with niclosamide before irradiation led to the fact that 24 h after irradiation the level of γH2AX histone, reflecting the number of DNA DSBs, was 1.6 times higher than that in intact cells and the cells exposed only to radiation. This evidences the inhibition of DNA DSB repair induced by γ-radiation. Thus, niclosamide possesses a radiosensitizing effect on human colorectal cancer cells, which is based on inhibition of DNA DSB repair. The inhibition of the Wnt/β-catenin signaling pathway under treatment with niclosamide is not detected in all types of tumor cells.

The effects of 29 substances, including known antioxidants, anti-radiation agents, amino acids, and vitamins, on the luminescence intensity of E. coli K12 MG1655 (pSoxS-lux) and MG1655 (pKatG-lux) bacterial cells induced by paraquat and peroxide, respectively, were studied. The luminescence of biosensors occurs as a result of activation of the soxS and katA gene promoters in response to an increase in the concentration of superoxide radicals and H₂O₂ in the cell. In the case of an antioxidant effect exerted by a substance under study, the intensity of the induced luminescence decreases, and in the case of a prooxidant effect, the luminescence intensity increases. Antioxidant activity was exhibited by 23 of 29 substances (79%) on the pKatG-lux biosensor and 22 of 29 substances (76%) on the pSoxS-lux biosensor. The studied anti-radiation agents (ten substances) showed different degrees of pro- and antioxidant activity. Lithium salt of glutathione disulfide, glutoxim, ginestein, and indraline significantly reduced the level of induced luminescence in both biosensors; magnesium salt of glutathione disulfide, zinc salt of reduced glutathione, and molixane, only in the pSoxS-lux biosensor; and cistamine and 5-AED, only in the pKatG-lux biosensor. Among the anti-radiation agents, a high prooxidant activity on the pKatG-lux biosensor at low concentrations was shown by lithium and magnesium salts of glutathione disulfide, zinc salt of reduced glutathione, molixane, and indralin (B-190); and on the pSoxS-lux biosensor, by genistein, cystamine, and 5-АED. The applicability of lux-biosensors for primary evaluation of the potential antioxidant and radioprotective activity of chemicals is discussed.

A comparison of sequential extraction methods proposed by F.I. Pavlotskaya [1, 2] and A. Tessier [3] for fractionation of technogenic (¹³⁷Cs and ⁹⁰Sr) and natural (²²⁶Ra, ²³²Th, and ²³⁸U) radionuclides from soils was performed. It is shown that both methods provide comparable results in the extraction of various forms of occurrence of technogenic radionuclides. Furthermore, both methods indicate a significantly higher availability of ⁹⁰Sr to plants and its greater ability to migrate with downward soil solution flows in comparison with ¹³⁷Cs. However, when used for the assessment of the occurrence forms of natural heavy radionuclides, the two methods provide inconsistent results. The Tessier sequential extraction method indicates higher contents of compounds available to plants and mobile compounds in comparison with the Pavlotskaya method. A possible reason behind this may be the soil chemistry complexity of radionuclides such as ²³²Th and ²³⁸U that feature polyvalence and a strong tendency for hydrolysis and complex formation; in addition, their behavior may be affected by various carriers. These elements form a broad range of compounds that change one into another with changes in the chemical conditions; this complicates accurate comparison of the composition of their forms extracted by reagents used in the above methods.