Some results of radiobiological studies performed on Cosmos-110 biosatellite.

The experiment carried out on the Cosmos 110 biosatellite is a step further in radiobiological investigations performed in outer space and differs appreciably from flight experiments conducted on board the Vostok and Voskhod spacecraft. The difference lies, firstly, in the integral dose of cosmic radiation. According to the onboard dosimeter readings, it was 12 rad at an average dose rate of 500 mrad/day during the biosatellite flight, whereas in previous biological flight experiments, as is well known, the total dose was below 80 mrad (on a five-day flight of Vostok 5) at a dose rate of 80 to 20 mrad/day. Secondly, during the biosatellite mission, cosmic radiation originated not from the primary cosmic radiation as was the case in the Vostok and Voskhod flights but mainly from the Earth's radiation belts. Thirdly, the duration of the Cosmos 110 flight was far longer than that of any previous mission: the effect of weightlessness lasted for about 22 days. The paper presents results of investigations performed on E. coli K-12 lambda lysogenic bacteria, Tradescantia microspores, dry seeds of higher plants, different Chlorella strains and an intact plant of Tradescantia paludosa. The biological effect of space flight factors was evaluated by various physiological, cytogenetic, genetic and microbiological techniques. Similar to previous experiments carried out on board the Vostok 3-6 spacecraft, tests with lysogenic bacteria revealed a statistically significant induction of moderate bacteriophage. The induction value was shown to lag behind the mission duration dependence level. This seems to be related to a change of inducibility properties of lysogenic bacteria and a reduction of the yield range of phages per bacterial cell. Other tests (duration of the latent period, formation pattern of phage components) indicated no significant differences between test and control objects (N.N. Zhukov-Verezhnikov, N.I. Rybakov, V.A. Kozlov et al.). A study of protective properties of chemical compounds of different types in relation to the bacteriophage induction demonstrated that preparations of the aminothiolic group produced a high antimutagenic effect (V.A. Kozlov, N.I. Rybakov et al.). A postflight cytological analysis of Tradescantia paludosa microspores indicated their changes of three types: chromosome aberrations, mitotic disturbances and disorders of growth processes in the cell. Examinations of dry seeds of wheat, barley, pine and other plants, as well as of Allium cepa bulbs, gave evidence of a diverse effect of space flight factors on both physiological processes and hereditary structures of the objects. In some cases an increased percentage of seed germination, stimulation of their growth and a significant increase of aberrations were found. An investigation of the occurrence frequency of visible mutations in reaction cell cultures of different Chlorella strains (LARG-1, LARG-3 and others) showed no significant differences between the test and control material. Some cultures taken under a more detailed study indicated a delay with which cells entered the first sporulation and a greater amount of cells that divided into a lesser than usual number of autospores. In addition, test variants of the strains showed a slightly reduced survival of Chlorella cells. The reduction appeared to be statistically significant for the LARG-3 strain only (E.N. Vaulina et al.). A postflight examination of the appearance of the Tradescantia paludosa plant showed that it retained good turgor; its leaves were dark green and several bright flowers bloomed. No signs of its inhibition or etiolation were noted. As compared to the control, the test plant grew noticeably and the stem became crooked. Certain problems of biological indications of outer space are discussed.