Vol 63, No 3 (2023)

The results of large-scale radiation, genetic, cytogenetic and molecular genetic studies on the nature and frequency of heritable mutations of two sex-linked and three autosomal genes of Drosophila melanogaster after exposure to ⁶⁰Co γ-rays and 0.85 MeV neutrons are presented. Regularities were established for studied genes and radiations in the induction of five different types of recessively inherited mutations, which can be combined into two main classes - the class of chromosomal mutations in one way or another affecting the gene under study (changes leading to sterility of F₁ mutants, multilocus deletions, inversion or translocation breakpoint chromosome in the region of gene localization) and a class of “point” gene mutations with a complex spectrum of DNA changes detected by PCR and sequencing. In this report, the results of classical genetic and cytogenetic analysis of these classes of mutations are considered in detail and the frequency of their induction by γ-rays or neutrons is estimated per locus per dose unit (1 Gy). An important and unexpected result of the assessment was the fact that the frequency of “point” mutations turned out to be invariant (on average 1.15 E-06/locus/Gy) for the studied genes and radiations, in contrast to chromosomal mutations, where a pronounced locus-specificity is observed for individual types of mutations. At the same time, neutrons are two or more times more effective than γ-rays in inducing this class of mutations. It is significant that the ave-rage frequency of “point” mutations induction correlates with the average cDNA length of these genes (1.62 kb), but not with their average size (6.07 kb), indicating that the target for " point mutations is, obviously, not the entire DNA of the gene, but only the informational part of its exons. The dependence of the frequency of chromosomal mutations of one type or another on the position of the gene on the chromosome and in the three-dimensional space of the genome is discussed.

This work presents the results of the use of three-color FISH-staining of chromosomes (DNA probes to 1, 4 and 12 pairs of chromosomes) for the cytogenetic study of peripheral blood lymphocyte cultures of four patients at different times after irradiation in various emergency situations. All victims had initial dose estimations: one by EPR signal in the tooth enamel (1.12 Gy) and three by the dicentric frequencies (1.9; 3.2 and 4.3 Gy). There was a strong significant linear correlation between the observed translocation frequencies and the initial dose estimations. Retrospective indication of the dose by translocation frequencies was carried out with the help of own dose-effect curve, the obtained on the basis of experiments with the irradiation of blood of healthy donors in vitro. At the same time, dose estimates in the long terms after irradiation in three of these patients with the greatest lesion were significantly lower than they were established earlier (1.26; 2.06 and 2.47 Gy). The coincidence of the initial and repeated results was observed only in one remaining patient.

The review provides data from a number of authors on the risk of developing psychogenic disorders, mainly depression as the most severe pathology, after accidents at nuclear power plants: Three Mile Island, Chernobyl, Fukushima. At the same time, it is important to develop depression even many years after the accident. The second part of the review provides information on the development of depression in patients with head and neck cancer who received head radiotherapy. The number of pathologies in this group significantly exceeds the indicator of the development of pathologies in patients with other types of cancer. The role of non-coding RNAs in the pathogenesis of radio-induced depression is discussed. They are supposed to be used as targets for specific therapy of depression.

In experiments on mice, rats, guinea pigs and dogs, the effectiveness of metabolic correction of cerebral radiation syndrome with nicotinic and succinic acids and Esseentiale was evaluated. The animals were totally exposed to 5–8 and 16–20 MeV pulsed electron flux at doses of 85–110 or 500–570 Gy or to gamma irradiation at a dose of 100 Gy. The frequency and time of ataxia and convulsions, as well as the dynamics of animal death after radiation were recorded. Nicotinic and succinic acids (500 mg/kg each) and Esseenciale (20 mg/kg by nicotinamide) reduced the frequency and delayed the onset of ataxia and seizures equally in both small laboratory animals and dogs. In experiments on rats after exposure at a dose of 100 Gy under the influence of radiation and Essentiale, there was no significant change in animal cognitive function according to the decision-making test at the first presentation of a new deposit.

Ionizing radiation induces a complex of genetic, biochemical, structural and functional changes in the body. The inflammatory response development is acknowledged as one of the manifestations of systemic bodily response to ionizing radiation exposure, and this response, through the activation of immunity, acts both as protector and leads to the development of undesirable early, delayed and off-target effects. Its underlying molecular and cellular mechanisms are defined by DNA damage, free radical metabolic changes (primarily reactive oxygen and nitrogen species), oxidative stress development, inflammasome activation, “danger signals” release and pro-inflammatory cytokines production. The role of non-apoptotic cell death forms (ferroptosis and pyroptosis) is described in the genesis of post-radiation inflammatory response and subsequent tissue, organ, and system damages. The post-radiation inflammatory reaction’s ability to take form of a time-stable self-sustaining process – that increases the radiation-induced damage severity – due to the presence of a positive feedback between different components of its pathogenesis is noted.

The article presents the results of assessing the dose of external and internal irradiation of the tree tier of pine stands growing on the northern trace of the Belarusian sector of the 30-kilometer zone around the Chernobyl nuclear power plant at the present stage. It was found that in the most polluted experimental sites, the total dose of external and internal irradiation of the stand can reach 160 mGy/year. It is shown that internal irradiation is formed by beta radiation of radionuclides accumulated by aboveground phytomass, its contribution to the total dose can be 80%. The external irradiation of the stand is determined by the gamma radiation of ¹³⁷Cs located in the soil. The results obtained are important for understanding the processes of formation of radiation-induced effects and assessing the effects of irradiation of living organisms.

The year 2021 was marked with a significant date – 100 years ago, brilliant radiobiologist and geneticist N.V. Timofeeff-Ressovsky started his scientific work. Among the new directions developed by him from 1921 to 1981 were physical biology, basic principles of genetic engineering, amplifier principle, and population radiobiology. It is noteworthy that many of his ideas were developed in the former Department of Radiation Genetics and General Radiobiology of the Institute of Medical Radiology in Obninsk, which is now called the Experimental Sector of the A. Tsyb Medical Radiological Research Centrе. Our work reveals the interconnections of Timofeeff-Ressovsky’s works with the activities of his contemporaries and productive ideas of today.