Review of Biological Effects of Acute and Chronic Radiation Exposure on Caenorhabditis elegans

Knowledge regarding complex radiation responses in biological systems can be enhanced using genetically amenable model organisms. In this manuscript, we reviewed the use of the nematode, Caenorhabditis elegans (C. elegans), as a model organism to investigate radiation’s biological effects. Diverse types of experiments were conducted on C. elegans, using acute and chronic exposure to different ionizing radiation types, and to assess various biological responses. These responses differed based on the type and dose of radiation and the chemical substances in which the worms were grown or maintained. A few studies compared responses to various radiation types and doses as well as other environmental exposures. Therefore, this paper focused on the effect of irradiation on C. elegans, based on the intensity of the radiation dose and the length of exposure and ways to decrease the effects of ionizing radiation. Moreover, we discussed several studies showing that dietary components such as vitamin A, polyunsaturated fatty acids, and polyphenol-rich food source may promote the resistance of C. elegans to ionizing radiation and increase their life span after irradiation.

Results of the study of cataracts in the exposed population in the Southern Urals

Epidemiological data have revealed a significant association between exposure to ionizing radiation, loss of optical lens function, and cataract formation. Residents of villages in the Southern Urals were chronically exposed to external and internal radiation in the range of «small» and «medium» doses as a result of two radiation accidents at the «Mayak» plant in the middle of the last century. Purpose. Тo investigate changes in the lens in individuals who have been chronically exposed to radiation over a long time. Material and methods. Аn analysis of the results of the examination by an ophthalmologist in the clinical Department of the URCRM of 583 people from among those who were subjected to chronic radiation exposure and their offspring was carried out. The examination was carried out according to a special in-depth program with photo fixation of changes in the lens (18 characteristics). Results. According to the results of the examination, grade 1 and 2 opacities were most often detected in all layers of the lens. More expressed changes in the lens significantly reduce vision and require earlier cataract surgery. Lens Opacities in the cortical layers are the most common type of lens pathology in the development of cataracts in all age categories. The frequency of nuclear cataracts in the study group of patients of the URCRM Clinic gradually increases with attained age from 0% under the age of 40 to 19-23% in the age groups with members aged over 70. The same tendency is observed in the increase in the intensity of yellow color in the staining of the lens nucleus. The largest changes in the posterior lens capsule were observed in the oldest age group (over the age of 80 - 22% of all the opacities at this age). Conclusion. The ophthalmological examination of patients affected by radiation accidents in the Ural region revealed an increase in cataract cases with an increase in age, which corresponds to the trends in the non-irradiated population. Key words: eye diseases; chronic radiation exposure; cortical cataract; nuclear cataract; posterior subcapsular cataract.

Effects of chronic radiation exposure on phytoplankton communities in special industrial reservoirs of Mayak PA

A comparative study of phytoplankton communities inhabiting six reservoirs in the Southern Urals with different levels of radioactive contamination is presented. Along with increasing the level of radioactive contamination, the diversity of the phytoplankton species is decreases, however the abundance of surviving species and their biomass did not depend on the level of radiation contamination in the studied reservoirs. There were found no signs of ecological regression of phytoplankton communities caused by radioactive contamination up to 6.5 kBq l-1 in the reservoirs of the Techa river Reservoir Cascade R-11, R-10, R-4 and R-3. Ecological regression of the phytoplankton community was observed in reservoirs R-17 and R-9, with a total activity of β-emitting radionuclides 470 kBq l-1 and higher, a total activity of α-emitting radionuclides 220 kBq l-1 and higher. Ecological regression of communities was registered as a decrease in species diversity, fluctuations in the number of algae in the high ranges, and the predominant development of one species. Reduction of species diversity in adverse conditions and violations of interspecies relationships in the community often leads to sharp fluctuations in the biomass and abundance. Moreover, the highest biomass of the algal communities can result from either excessive species gain or species loss. In the most contaminated R-9 (Karachai Lake) species diversity is dramatically decreased to monoculture of a single cyanobacteria species, dominant species could vary in different years of the study.

Apoptosis of Lymphocytes and Polymorphisms of Apoptosis Regulation Genes in Individuals Exposed to Chronic Radiation Exposure

Purpose: Study the apoptotic death of peripheral blood lymphocytes in long-term period in persons exposed to chronic radiation exposure, and analysis of association of the polymorphic regions rs4645878, rs2279115, rs28362491, rs664677, rs1042522, rs1801270, rs2279744 of the BAX, BCL2, NFkB, ATM, TP53, CDKN1A, MDM2 genes with apoptotic lymphocytes frequency in residents of the coastal villages of the Techa River. Material and methods: The study of apoptosis and genotyping was conducted in 390 persons exposed to chronic radiation exposure as a result of Mayak PA radioactive waste releases into the Techa–Iset–Tobol river system. The early stage of apoptosis was assessed on a flow cytometer by the presence of phosphatidylserine on the surface of the cell membranes using the Annexin V Apoptosis Detection Kit I and the late stage of apoptosis using the TUNEL method. Real-time PCR genotyping was performed of allelic variations of rs4645878, rs2279115, rs28362491, rs664677, rs1042522, rs1801270, rs2279744 of BAX, BCL2, NFkB, ATM, TP53, CDKN1A, MDM2 genes in a group of irradiated individuals. Results: The number of cells at the early stage of apoptosis is statistically significantly increased in individuals whose irradiation began during the period of intrauterine development and continued in the postnatal period compared to individuals exposed only in the postnatal period. At the same time, the number of lymphocytes at the stage of DNA fragmentation in the group irradiated in utero is lower than in the group irradiated postnatally and non-irradiated individuals. Also, a weak negative correlation between intrauterine doses of RBM irradiation and the doses of thymus and peripheral lymphoid organs with the number of cells in the late stage of apoptosis in individuals irradiated in utero. The influence of allelic variation rs4645878 of the BAX gene was established on the number of lymphocytes at the early stage of apoptosis in residents of coastal villages of the Techa River. A statistically significant decrease in the number of cells at an early stage of apoptosis is observed in C/C genotype carriers according to the allelic variation rs4645878 of the BAX gene compared with carriers of the T/T and T/C genotypes. Conclusion: Residents of coastal villages of the Techa River exposed to radiation during the period of prenatal development, there are differences in the frequency of apoptotic death of peripheral blood lymphocytes compared with non-irradiated persons and persons who were irradiated in the postnatal period. SNPs of apoptosis-regulating genes can modify the response of blood lymphocytes to radiation in a wide range of doses RBM.