[Certain mechanisms of development of types of body tolerance to acute hypobaric hypoxia].

The regulatory mechanisms of individual rat resistance to acute hypobaric hypoxia were studied using the functional indices of the central nervous system (neurochemical and behavioral) and the hematopoietic system. The resistance to hypoxia was evaluated by the time of attitudinal reflex maintenance and recovery after decompression to a simulated altitude of 11200 m. Animals with different types of tolerance to hypoxia demonstrated different metabolic backgrounds of neurochemical processes (which were most balanced in moderately resistant rats). This agrees with the differences in active behavior and adaptive efficiency of these animals exposed to mild open-field stress. High functional activity of erythropoiesis and early leukocytic response were observed in hypoxia-tolerant rats.

[The sexual peculiarities of organism resistance types to the acute hypobaric hypoxia repeated influences].

The experimental investigation of the differences of the rats males and females reactions individual peculiarities to the acute hypobaric hypoxia repeated influences carried out. The time of the pose reflex preservation and restoration and the hypobaric hypothermia value during the lifting to 11,200 m "altitude" used for the resistance to hypoxia criterions. In experiments was showed that the males some more reactivity than females. But low resistance to the first influence females adapted to the repeated influence hypoxia the most effective. They preserve compensator reserve of organism and quickly restore of the disturbed functions.

[Delayed effects of ionizing radiation on the skin as a function of dose]. / Otdalennye posledstviia vozdeistviia ioniziruiushchego izlucheniia na kozhu v zavisimosti ot dozy.

The article contains analysis of experimental and clinical data on delayed effects of different doses of ionizing radiation on the skin which in the row with the bone marrow, lens and other radiosensitive organs and critical tissues is one of the criteria of radiation risk for cosmonauts. According to the existing standard, maximal dose to the skin over the career may not exceed 1200 cSy. However, facts presented in the article testify the necessity to reform the standard since there is high probability of pathology including malignant tumor in delayed period after exposure to 1200 cSy. In view of the available data and present-day international recommendations, the maximal dose to the skin over the space career should not be higher than 600 cSy.

[State of cardiovascular system in immediate and delayed periods following exposure of organism to ionizing radiation]. / Sostoianie serdechno-sosudistoi sistemy v blizhaishem i otdalennom periodakh posle vozdeistviia na organizm ioniziruiushchikh izluchenii.

Data on the progress of radiation damages and the character of shifts in the cardiovascular functioning following exposure to ionizing radiation as a function of dose were analyzed. Reviewed were experimental and clinical material, and records of periodic medical examinations of persons who had worked long with sources of ionizing radiation. A plausible character of deviations in health and working ability of cosmonauts in flight and at the end of career due to cardiovascular disorders is described.

[Characteristic of organism reactivity during repeated hypoxic exposures of rats varying in resistance to ionizing radiation]. / Kharakteristika reaktivnosti organizma pri povtornykh gipoksicheskikh probakh u krys s razlichnoi ustoichivost'iu k ioniziruiushchemu izlucheniiu.

Wistar rats were used in the experiment on correlation of radiation sensitivity of the organism with tolerance of repeated acute hypoxia. Experimental rats (n = 100) were numbered and "raised" to 11,200 m thrice before exposure to 8.0 Gy with a dose rate of 3.0 Gy/min. Tolerance of hypobaric hypoxia was determined by the time of pose reflex sustention (PRST) and recovery (PRRT), the PRST/PRRT ratio, and the body temperature drop. Lethal effect was taken as the measure of radiation sensitivity. Controls were 58 rats exposed to equal radiation conditions but without preliminary testing by hypoxia. Unlike radiation sensitive rats, during second testing PRST in the radiation resistant specimens increased against PRRT shortening after termination of decompression and lessening the load on adaptative reaction (lower level of hypoxic hypothermia). The conclusion is that the method of repeated hypoxic tests enables to feature individual tolerance and adaptation of organism to the non-radiation factor in specimens distinguished by resistance to ionizing radiation.

[Evaluation of individual radiation resistance of rats based on reactions to non-radiation testing]. / Otsenka individual'noi radiorezistentnosti krys po reaktsiiam na testiruiushchee neradiatsionnoe vozdeistvie.

Presented are the data on radiation sensitivity of various groups of animals preliminary differentiated by their tolerance of acute hypoxia. The processes of blood forming system impairment and reparation are detailed. As was shown, highly resistant to hypoxia rats are distinguished by the best radiation resistance. Survivability of these rats was significantly higher as compared with other groups of animals. Recovery of blood formation by both the red and white chits following exposure to [symbol: see text] of the mean lethal dose proceeded more rapidly in the radiation resistant rats.

[Development of radiation injuries and recovery processes in the hematopoietic tissue of mice after repeated exposure to fast neutrons and gamma-irradiation]. / Nekotorye zakonomernosti formirovaniia radiatsionnogo porazheniia i razvitiia vosstanovitel'nykh protsessov v krovetvornoi tkani myshei posle povtornykh vozdeistvii bystrykh neitronov i gamma-izlucheniia.

A study was made of the number of CFUs and karyocytes in thigh bone and the concentration of functional cells in the peripheral blood of mice subjected to fast neutron- and gamma-irradiation four times at a 60-day interval (210 cGy per fraction). The regenerating potential decreased and the half-recovery time T1/2 increased in the haemopoietic tissue as the number of fractions and total absorbed dose increased. The dependence of T1/2 on the equivalent radiation dose was as follows: T1/2 = T1/2(0)e0.0009D.

[Radiation injury of hemopoiesis in alpine conditions depending upon the duration of adaptation]. / Luchevoe porazhenie gemopoéza v usloviiakh vysokogor'ia v zavisimosti ot dlitel'nosti adaptatsii.

A study was made of the disturbance of haemopoiesis in the small laboratory animals and dogs kept in Alpine conditions (3200 m) and exposed to ionizing radiation on days 3, 15, 22, 25 and 33 of adaptation. The radiation damage to haemopoiesis in Alpine conditions was shown to decrease at the beginning of the adaptation due to the intensification of the regenerating processes, which was manifested by the increase in the rate of DNA synthesis in the haemopoietic organs, and activation of erythropoiesis, myelopoiesis and lymphopoiesis. Later (after 30-35 days), a 2-4-fold increase was noted in the number of haemopoietic stem cells which improved the compensatory potency of the tissue under study and increased the total resistance of the organism.

[Effect of prolonged rotation on radiation injury to the body]. / Issledovanie vliianiia dlitel'nogo vrashcheniia na radiatsionnoe porazhenie organizma.

CBA mice were kept for three weeks in a rotating installation (velocity--7.5 rpm, rotation radius--110 cm, acceleration--0.07 g). As a result, their radiosensitivity reduced. The lethal effect and severity of radiation injury declined. The animals rotated and irradiated at a sublethal dose showed an enhancement of the reparation process in bone marrow and the thymus. Significant changes in radiosensitivity can be expected during an exposure to rotation and acceleration of 0.3--1.0 g.

[Clinical course of a radiation lesion under high-mountain conditions]. / Klinicheskoe techenie radiatsionnogo porazheniia v usloviiakh vysokogor'ia

The development and outcome of radiation disease were studied on dogs kept at an altitude of 3200 m above sea level. Clinical observations, morphological examinations of blood and bone marrow and measurements of blood coagulation parameters were carried out at different time intervals. Our findings demonstrated that irradiation of animals that followed a 25-day altitude acclimatization and their subsequent exposure to an altitude alleviated radiation disease. The clinical course of radiation disease aggravated in dogs that were reacclimatized to highlands after irradiation. It can be postulated that the dogs kept in highlands before and after irradiation developed a more intensive process of restoration, especially of erythropoiesis. They also showed a stable decrease of the blood coagulation rate and long persistence of high fibrinolytic activity of the blood.