An Erratum to this paper has been published: https://doi.org/10.1134/S1547477125010017

Assessing the role of social factors in the formation of radioresistance in chronic exposure and finding ways to increase it are important for understanding the mechanisms of the damaging effects of radiation and developing practical methods for reducing radiation risk in professionals exposed to ionizing radiation and patients undergoing radiation therapy. In this work, we investigated the ability to influence the lifespan of animals exposed to γ-radiation fractionally for a long time by replacing drinking water from tap water to distilled water. Female ICR mice (CD-1) were exposed to total 60Co γ-radiation weekly in fractions for 33 weeks starting at nine weeks of age. The dose of a single irradiation was 50 mGy, and the average dose rate was 2 mGy/s. The total radiation dose was 1.65 Gy. The control nonirradiated mice and irradiated animals were divided into two groups. The first received tap water, and the second received distilled water throughout the experiment. Nonirradiated animals kept on tap water showed a statistically insignificant (log-rank test, p = 0.483) reduction in average life expectancy compared to mice kept on distilled water. In animals after exposure to 60Co γ-radiation, a statistically significant (p = 0.0013) decrease in life expectancy was noted when kept on tap water and statistically insignificant (p = 0.1511) when kept on distilled water. Tap water and irradiation showed a clear synergy with a combined effect on the body of mice, expressed in a more than threefold decrease in the period of post-radiation shortening of the life expectancy. Distilled water reduced the rate of death of irradiated animals and modified the rate of death of nonirradiated animals. Our data demonstrate that the reduction in the life expectancy of mice kept on tap water caused by long-term fractionated irradiation can be reduced when animals are kept on distilled water.

We designed a study with the objective to determine the long-term radiation effects of gamma rays, originating from a single shot of Co60 at a dose of 2 Gy on the 7-month-old male mice of the ICR line in 30 days after the irradiation. The aim of this study was to characterize the behavior of animals using the Open Field test, immuno-hematological status, and morpho-functional changes in the central nervous system of mice. Irradiated animals displayed significantly different behavior in the OF in comparison with the control group. The radiation damage was confirmed by assessing the ratio of leukocytes in the peripheral blood of mice at a later date after exposure to Co60. After irradiation, a decrease in the glioneuronal complex was observed in the irritated group as well as histological changes of brain cells. To sum up, not only was the hematological status of mice altered upon the total gamma irradiation, but also their behavior, which was most probably due to significant alterations in the CNS. Study of influence of ionizing radiation on female mice, comparison between different age groups. Open Field test on the 30 days after 2 Gy of γ-rays and histological analysis indicated changes in behavioral patterns, leucocytes, and brain tissue.

The bio-effect of long-term fractionated γ-irradiation with a low total dose was assessed by the criteria of lifespan and death rate in certain life periods. The experiment was made with 40 female ICR (CD-1) mice. Fractionated irradiation of the animals with γ-quants 60Co (50 mGy×33 wks) brought about reduction of the mice mean life by more than 150 days. The total dose of 1.65 Gy is approximate to the admissible career dose limit for cosmonauts. Untimely deaths, in comparison with the control mice, were observed both in the early and terminal periods. Also, body mass of the irradiated animals was increased throughout the follow-up time. The data can be used for evaluation of the risks of tumor and cardiovascular diseases from chronic irradiation of crews during long-term exploration missions.

The aim of this research was to study behavioral reactions and morphological changes in the brain of adult female Sprague Dawley rats after exposure to 170 MeV and 70 MeV protons and gamma radiation (60Co) at a dose of 1 Gy. The analysis of the behavioral reactions in the T-maze showed that exposure to ionizing radiation with different LETs led to an increase in number of repeated entries into the arms of the maze in the spontaneous alternation test. In the Open Field test a decrease in overall motor activity in the group of irradiated animals (70 MeV protons at the Bragg peak) was observed. A decrease in the number of standing positions was seen in all groups of irradiated animals. Morphological analysis showed the development of early amyloidosis, autolysis of the ependymal layer, an increase in the number of neurodegenerative changes in various structures of the brain, and the development of neuronal hypertrophy on the 30th day after irradiation in the cerebellum and hippocampal hilus. Exposure to protons at a dose of 1 Gy leads to the development of structural and functional disorders of the central nervous system of animals on the 30th day after irradiation. These data indicate a damage of short-term memory, a decrease in motor activity and exploratory behavior of animals. With an increase in LET, there is an increase in the number of amyloid plaques in the forebrain of rats, autolysis of the ependymal layer of the ventricles, and the development of dystrophic changes. Investigations of behavioral reactions and morphological changes in various parts of the brain of adult rats on the 30th day after influence of ionizing radiation with different physical characteristics at a dose of 1 Gy. Various negative patho-morphological and cognitive-behavioral changes observed.

Fluorescence and chromatographic analysis of bisretinoids from the retina and retinal pigment epithelium of mouse eyes was carried out before and after exposure to accelerated protons in the Bragg peak. It has been shown that ionizing radiation at doses of 1–4 Gy leads to a shift in the short-wave region of the maximum of the fluorescence spectrum in the chloroform extract obtained from both the retinal pigment epithelium and the retina. Chromatographic analysis of these extracts has shown a change in the relative content of individual bisretinoids. The obtained spectral and chromatographic data indicate that the exposure of mice to accelerated protons in the Bragg peak at doses of 1–4 Gy leads to radiation oxidation of bisretinoids in eye tissues.

The experiments were performed with outbred CD-1 male mice (SPF category). Total irradiation at 1.0; 2.5 and 5.0 Gy by protons with the average energy of 170 MeV was conducted in a level medical beam of the phasotron at the Joint Institute of Nuclear Investigations. Targets were 2 points of in-depth dose distribution, i.e. beam entrance of the object, and modified Bragg peak. As a physical protector, the comb filter increases linear energy transfer (LET) of 170 MeV entrance protons from 0.49 keV/μm to 1.6 keV/μm and, according to the bone marrow test, doubles the biological effectiveness of protons when comparing radiation doses that cause 37% inhibition of blood cell formation in the bone marrow. Physical protection increases dose rate from 0.37 Gy/min for entrance protons to 0.8 Gy/min for moderated protons which more than in thrice reduces time of irradiation needed to reach an equal radiobiological effect.