Vol 63, No 2 (2023)

Evaluation of age effect on the frequency of radiation-induced translocations, registered using FISH in circulating T-lymphocytes in the long-term period after exposure, is both of theoretical and practical interest for the purposes of biodosimetry. The objective of our study was to analyze the dose dependence of the translocation frequency in the peripheral blood T-lymphocytes in donors of different age who were exposed in the Techa Riverside settlements (n = 197). In cytogenetic studies, whole chromosome painting probes were used to stain three pairs of chromosomes. A total of 104,721 genome equivalents (GE) were calculated and 2,540 translocations were found. For each donor, the individual absorbed doses in organs and tissues at the time of blood sampling were calculated using the Techa River Dosimetry System. In addition, doses to T-lymphocytes and their progenitors were calculated using the innovative modelling approach with due account of age related-dynamics of T-lymphocytes. The age dependence of the translocation frequency was associated particularly with these doses. The main sources of donor exposure were ^89,90Sr, accumulating in bones and irradiating the bone marrow almost locally. To assess the parameters of the dose-effect relationship, linear regression model was used. After taking into account background values, the lowest frequency of translocations per 1000 GE per Gy was found in donors aged 0–5 years at the time of exposure (9.3 ± 1.3), which is statistically significantly lower than in children aged 6–18 years (15.3 ± 1.5), but not in adults (11.9 ± 2.9). The value for adults (>18 years) was characterized by the maximum scatter, but was close to the values obtained in an international study of nuclear enterprise personnel after external exposure (11.6 ± 1.6). The values of the background translocation frequencies registered in various age groups correspond to the published data obtained in a joint international study on unexposed donors. We have also confirmed the absence of sex-effect on the frequency of translocations.

We studied the cytogenetic effects in the bone marrow cells of root voles (Alexandromys (Microtus) oeconomus Pall.), which lived in areas contaminated with uranium and radium, as a result of the operation of radium mining (radium site) and the storage of its waste (uranium-radium site) (Komi Republic). The level and nature of mutational effects in voles from radioactively contaminated areas indicates the persistence of an increased frequency of chromosome aberrations and the appearance of individuals with an altered karyotype, which indicates genetic instability. When determining the nature of the dynamics of the mutation process in the studied populations, a high frequency of cells with micronuclei was noted in voles from the radium area, with the exception of the phase of population decline. In experiments with the use of provocative factors of chemical (urethane) and radiation (acute γ-irradiation) nature, an increase in the stability of bone marrow cells of animals living in conditions of increased background radiation has been shown.

The participant of the minor fractions of the liver phospholipids in the mechanism of adaptation for four species of wild rodents caught in the different years in the Chernobyl accident zone at the areas with level of the dose rate of the external γ-irradiation from 0.02 to 200 mR/h in 1987 is studied in dependence on the radioresistance of species. At first year after accident the growth of the lysoforms of phospholipids share and sphingomyelin involved in the apoptosis process and the increase of cardiolipin taking part in the interaction of DNA with membrane is revealed, During 5 years after the accident there is the increase of the sum share of phosphatidylinositol and phosphatidylserine taking part in the calcium ion transport and in regulation of the inner cell processes. Data obtained and analysis of literature allow us to conclude that the change of proportion of the minor fractions of phospholipids in liver of the wild rodents living at areas with the increased radiation level causing the adaptive reorganizations in the cell metabolism are the base for formation of the new subpopulations in these territories having the lipid peroxidation regulatory system different from norm.

We have analyzed the kinetics of seed germination of the model plant Arabidopsis thaliana after γ-irradiation at doses of 50, 100 and 150 Gy. The following lines were selected as study objects: abi3-8 with a mutation in the ABI3 gene and with reduced sensitivity to the natural form of abscisic acid and aba3-1 genotype with a mutation in the ABA3 gene and a reduced level of endogenous abscisic acid. Wild type Col-8 was used as a control. To study the effect of γ-radiation on various aspects of seed germination (germinability, germination time and rate, synchrony of germination, etc.), the germination kinetics was assessed using the Germinationmetrics package for the R programming environment. Control and irradiated seeds (radiation source – ⁶⁰Co) were grown on half-strength Murashige-Skoog medium under controlled conditions. Germination was assessed during the first six days after transfer to the phytotron by the rupture of the endosperm and the appearance of a root. In total, three independent experiments were carried out with three biological replications in each. A more pronounced effect of γ-radiation at a dose of 150 Gy on all studied genotypes was noted. Germination clustering showed that the distribution of the percentage of seed germination by day depends more on the genotype than on the dose of exposure. The best indicators of germination, speed and time interval between germination of 10% to 90% of seeds were noted for non-irradiated seeds of the abi3-8 line. The results obtained and a comparative analysis with previously published data suggest that the assessment of germination kinetics using the Germinationmetrics package for R is a clear and quite informative tool for studying the effect of ionizing radiation and other abiotic factors on various aspects of seed germination.

The analysis of dosimetric parameters of internal irradiation and biological effects in monogastric animals (rats, guinea pigs, pigs) caused by orally received “hot” radioactive particles causing ulcerative necrotic lesions of the gastrointestinal tract is presented. Mathematical models of particle transport and formation of absorbed doses in the digestive tract have been developed. The features of the deep distribution of absorbed doses in the mucous membrane depending on the spectral characteristics of β-radiation of radionuclides that are part of silicate particles are given. It is shown that the main factors in the formation of ulcerative lesions of the digestive tract were the uneven distribution of particles in the contents and the concentration of particles in certain areas of the mucous membrane, followed by the formation of high local dose loads. A dosi-metric scale of extremely severe, severe, medium and mild acute radiation ulcerative gastroenterocolitis is proposed, which allows extrapolating the results of model experiments on scenarios of radioactive contamination of the environment by particles of various genesis. The results obtained can be taken into account in the tasks of radiation safety.

In urban ecosystems to the west of the Elektrostal Heavy Machinery Plant, 6 years after the radiation incident, local areas with a total area of 0.2 km² with an increased equivalent dose rate of γ radiation of 0.15–0.40 μSv/hour and a high specific activity of ¹³⁷Cs reaching 8328–8740 Bq/kg in the upper soil horizons were identified. Statistically significant direct correlations were noted between the specific activity of ¹³⁷Cs in a layer of 0–10 cm of soil and the equivalent dose rate of γ radiation at the surface and height of 1 meter. The types of vertical distribution of ¹³⁷Cs in soils of polluted urban ecosystems, including those on which earth decontamination works were carried out, have been determined. The calculated ¹³⁷Cs transfer coefficients increase in row of tree: Salix alba < Sórbus aucupária < Ácer platanoídes < Malus domestica < Alnus incana < Ácer negúndo; and grassy vegetation: Týpha angustifólia < Artemísia vulgáris < Tussilágo fárfara < Cirsium arvense < Urtíca dióica.