[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.

[Characteristics of the descendants of male dogs exposed to chronic combined gamma-irradiation and in the postradiation period]. / Kharakteristika potomstva sobak-samtsov v protsesse khronicheskogo, sochetannogo gamma-oblucheniia i v postradiatsionnyi period.

A study was made of the descendants of 12 male dogs subjected to gamma-irradiation during six years at dose-rates of 0.0034 Gy/day and 0.0017 Gy/day + additional annual exposures to gamma-radiation three times a year each of 0.42 Gy. The observations were made during 3 years after the end of irradiation. It was shown that the descendants reflected the regularities of the disorders revealed in fathers' spermatogenesis. The radiobiological effects were function of dose--rate and cumulative radiation dose. The changes were mainly noted during embryogenesis and manifested by the sterility, mortinatality and the decreased number of puppies in the postreity.

[Functional activity of the testes of dogs exposed to chronic gamma irradiation over a 3-year course]. / Funktsional'naia aktivnost' semennikov sobak pri khronicheskom gamma-obluchenii v techenie trekh let.

During three years 36 male dogs were exposed to chronic irradiation with a total dose of 21, 62 and 125 rad per year. tin addition to this irradiation at a dose rate of 62 rad per year, some dogs were also exposed to acute irradiations three times a year with a dose of 42, 8 and 8 rad and 42, 42 and 42 rad (at the combined irradiation the total doses were 120 and 190 rad per year). The study of the functional activity of testes gave the following results. The males that were chronically irradiated with a total dose of 125 rad per year showed hypospermia after 8-10 months of the experiment. The dogs that were exposed to combined irradiation displayed oligospermia after 5-7 months of the experiment which persisted throughout the period of 3 years. These effects depended on the dose rate, total dose and scheme of irradiation.

Physiological and hematological effects of chronic irradiation.

The information available for assessing radiation hazard involved in prolonged space missions is so far insufficient. Therefore, a three-year experiment was carried out in which 180 dogs were exposed to irradiation, simulating the dose value and rate of exposure that may occur in a real space flight of long duration. The exposure included a chronic irradiation (with dose rates of 21, 62 and 125 rads/year) and a combined irradiation during which the animals were exposed to chronic and acute irradiations with a dose of 8 or 42 rads applied three times every year, the annual total dose being 120 or 188 rads, respectively. Insignificant hematopoietic changes, e.g. the ratio of red to white blood cells, their decrease in the peripheral blood, were found. Distinct changes in the reproductive function were noted. The general condition of the animals was satisfactory. Most animals endured well an additional physical load and retained conditioned reflexes developed before irradiation. The experimental findings suggest that the effects are early symptoms of the first stage of chronic radiation damage.