Results of cytogenetic studies of seeds after their extended orbital flight aboard the Salyut orbital scientific station.

Air-dry seeds of Lactuca sativa (lettuce) with a different level of spontaneous mitagenesis were used in these experiments. A part of the seeds was given pre-flight gamma radiation in doses of 1 and 10 krads. Comparison of the results for the in-flight experiments, laboratory and "transport" control showed an increase of cells with chromosome aberrations and an increase of radiobiological effect in irradiated seeds flown aboard the Salyut scientific station. A comparative analysis was made of the cytogenetic changes in seeds after their exposure to different periods of weightlessness during the Cosmos 368, Zond 8 and Salyut missions. The effect of weightlessness of different duration on the development of cytogenetic changes in irradiated and unirradiated seeds is discussed.

The radiobiological effects of heavy ions on mammalian cells and bacteria.

The radiobiological effects of heavy ions have been studied in experiments with mouse corneal epithelium, liver cells of rats irradiated in vivo, and the bacterium Escherichia coli B. From exposure of E. coli B to radiations with different LET, the effectiveness of the modifying influence of anoxia and some other radioprotectors has been determined.

Influence of Cosmos 368 space flight conditions on radiation effects in yeasts, hydrogen bacteria and seeds of lettuce and pea.

Radiobiological studies have been carried out on board the Cosmos 368 satellite, launched on 8 October 1970 and returning to earth on 14 October 1970. Yeast diploid cells Saccharomyces ellipsoides, Megri strain 139-B, haploid cells Zygosaccharomyces Baili, hydrogen bacteria Hydrogenomonas eutropha, strain Z-1, Berlin variety lettuce seeds and Capital variety pea seeds were used in these experiments. The biological specimens were irradiated with gamma-rays at dose rates of 71.8 and 6.7 rad d-1 suring the packaging of containers and after returning the samples to the laboratory. It was found that both on pre-radiation and post-radiation exposure space flight factors did not greatly influence radiobiological effects.

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.

Characteristics of biological effects of cosmic radiation, model investigations.

In view of the probability of the influence of ionizing radiation on crewmen and the appropriate problem of creating adequate anti-radiation protection, it is necessary to investigate the peculiarities of biological effects of cosmic radiation. Under actual space flight conditions, cosmic radiation will affect the human organism in the complex along with other factors. Full imitation of cosmic radiation on the ground is impossible but it can exert influence on the human radiosensibilty. In this connection, the successful solution of the problem of obtaining appropriate information can be made by a reasonable combination of both ground radiobiological and medical-hygienic investigations and those carried out by using artificial earth satellites. The available experience in carrying out such research and its results are given in this report. Information on investigating the peculiarities of biological effects of protons in the wide spectrum of energy is also included. The report contains the data of observing immediate and later effects of radiation influence on higher animals and also on many biological objects arranged in various levels of evolution and biological organizations. The values of the RBE for protons are given.

Vestibular analyzer as a critical organ in the evaluation of radiation hazards during space flights.

During space flights the vestibular analyzer functions under conditions which are not usual for Earth environments. The vestibular analyzer periodically or constantly experiences the action of angular, linear or Coriolis acceleration combined with ionizing radiation. The quantitative evaluation of the functional state of the vestibular analyzer made it possible to obtain material on semicircular canal activity disturbances at different periods of radiation sickness and responses of the irradiated body, given various doses of gamma radiation, to angular and Coriolis acceleration. Experiments were performed on 250 rabbits and 22 dogs. Rabbits were exposed to the total gamma radiation at doses of 50, 100, 500, 800, 5000, 10000 rad; dogs experienced single and fractional radiation exposures at doses of 200 rad (gamma-rays) and at doses of 500 and 350 rad (protons of 510 MeV). Specific conditions under which the astronaut's vestibular analyzer is functioning during space missions and our own experimental results make it possible to state that the vestibular analyzer serves as the critical organ in evaluation of radiation hazards during space flights.