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.
The present study evaluated the effects of proton and gamma-ray ionizing radiation on the mouse eye. The aim of this work was to analyze radiation-mediated retinoid oxidation in the retina and retinal pigment epithelium (RPE). The findings from this analysis can be used to develop a noninvasive method for rapid assessment of the effects of ionizing radiation. Comparative fluorescence and chromatographic analyses of retinoids before and after irradiations were performed. The fluorescent properties of chloroform extracts from irradiated mouse retina and RPE exhibited an increase in fluorescence intensity in the short-wave region of the spectrum (λ < 550 nm). This change is due to increased retinal and RPE retinoid oxidation and degradation products after radiation exposure. Comparative analyses of radiation effects demonstrated that the effect of proton exposure on the retina and RPE was higher than that of gamma-ray exposure. The present study revealed a new approach to assessing the level of radiation exposure in ocular tissues.
We investigated the possibility of using water-soluble fitomelanin to improve the reproductive activity of intact male mice and restore male reproductive activity, reduced by effects of ionizing radiation. In the experiment, to stimulate the reproductive activity of male mice, they were given a course of melanin in liquid form, orally. The experiment was conducted with fitomelanin with water solubility not less than 80% and the concentration of paramagnetic centers not less than 8*1017 spin/g, dissolved in the distilled water at an effective concentration. Animals were consuming fitomelanin dissolved in their drinking water, for 8-10 days before the mating and within the mating period. The stimulating effect was achieved in case of a course intake of melanin, in concentration 12.5-50 mg per 100 ml of drinking water, thus increasing the number of animals per litter in intact mice in 1.34 times at and in mice with reproductive activity compromised by radiation exposure in 1.23 times.
Purpose: Investigation of the dose–time–effect dependency of the behavior of mice and rats after irradiation with accelerated protons and comparison of these data with the morphological changes in the hippocampus and the cerebellum of rodents.
Material and methods: Experiments were performed on outbred adult female ICR mice (CD-1), SPF categories, body weight 30–35 g, of the age of 10 weeks – total number 61 animals, and on 39 male Sprague Dawley outbred rats weighing 190–230 g, aged 6.5–7.5 weeks. The animals were irradiated with accelerated protons with energy of 70 MeV on the medical beam of the phasotron of the Joint Institute for Nuclear Research (Dubna). Mice were placed in individual containers and irradiated 4 ones at a time. Irradiation was performed in a modified Bragg peak at doses of 0.5; 1; 2.5 and 5 Gy in caudocranial and craniocaudal direction. Rats were divided into 2 groups: intact control and group irradiated with 170 MeV protons at a dose of 1 Gy, dose rate of 1 Gy / min in the craniocaudal direction. The behavioral responses of experimental animals were tested in the Open Field test on days 1, 7, 14, 30, 90 in rats and on days 8, 30, and 90 in mice. Quantitative analysis of the dilution of Purkinje cells in the rat cerebellum was made, as well as morphological changes in the rat hippocampal neurons. It was shown a development of structural changes after irradiation with protons in neurons of different severity at different times after exposure: after 30 and 90 days.
Results: In the period of 1–8 days after proton irradiation of mice and rats in non-lethal doses (0.5–5.0 Gy), there is a dose-independent decrease in the main indicators of the spontaneous locomotor activity of rodents.
By the 90th day after irradiation, there is a clear tendency to normalize the indicators of OIR in all groups of irradiated animals, while the ES remains elevated.
Disruption of motor activity of rodents irradiated with protons in the early period and its relative normalization in the late post-irradiation period occur on the background of an increased number of morphologically altered and dystrophic neurons in the hippocampus and rarefied of Purkinje cells in the cerebellum.
Conclusion: The complex hierarchical structure of the central nervous system, the dependence of its function on the state of the whole organism and its hormonal background, as well as on the state of the blood supply and other factors, along with its high plasticity, require complex physiological, morphological and neurochemical approaches in analyzing the radiobiological effect of corpuscular radiation, taking into consideration the unevenness in dose distribution during irradiation.
