The role of weightlessness in the genetic damage from preflight gamma-irradiation of organisms in experiments aboard the Salyut 6 orbital station.

The effect of weightlessness on chromosomal aberration frequency in preflight irradiated Crepis capillaris seeds, on the viability, fertility and mutation frequency in Arabidopsis thaliana, and on the frequency of nondisjunction and loss of X chromosomes in pre-flight irradiated Drosophila melanogaster gametes was studied aboard the Salyut 6 orbital station. The following effects were observed: a flight-time dependent amplification of the effects of preflight gamma-irradiation in A. thaliana with respect to all the parameters studied; unequal effects in seeds and seedlings Crepis capillaris; and a significant increase in the frequency of nondisjunction and loss of chromosomes during meiosis in Drosophila females. These observations are discussed in terms of the data of ground-based model experiments and flight experiments with a different time of exposure of objects to weightlessness. An attempt is made to elucidate the role of weightlessness in the modification of ionizing radiation effects.

Development of higher fungi under weightlessness.

The development of Polyporus brumalis basidomycete cultures, both in the dark and in the light, was studied in the 17 day experiment on the orbital station Salyut 5 and in the 20 day experiment on the orbital station Salyut 6. In the first experiment the test tube cultures were exposed to weightlessness beginning from the stage of the fruiting body primordium. In the second experiment the culture was exposed in large containers at the stage of mycelium growth. In the first experiment fruiting bodies that had formed in light had stems and caps approximating the appearance and anatomical structure of the control culture. The fruiting bodies and caps were oriented towards the light. Some structural changes in the hymenophore were observed. Fruiting bodies developed in the dark had twisted stems and no caps. In the second experiment no fruiting bodies were formed in the dark. Light-optical and electron-microscopic studies of Polyporus brumalis growth under weightlessness were carried out.

Biological investigations on the orbital station "Salyut-5".

Genetic and embryological investigations were continued on the orbital station Salyut-5. The effect of space flight factors on dry Crepis capillaris (L) Wallr seeds and seedlings, dry Arabidopsis thaliana (L) Heynh seeds, Polyporus brumalis Pers. ex. Fries culture as well as on spawn development and fish behaviour was studied. Space flight factors are shown to have adverse effects with respect to some characteristics in seeds and seedlings, and to change the morphology of the fungus. Fishes appear to adapt themselves to weightlessness.

Biological investigations of higher and lower plants aboard Soyuz 19.

Biological investigations carried out aboard Soyuz 19 consisted of three independent complex experiments. All biological materials aboard the spacecraft were kept in "Biocat" thermostats which maintained the required temperature. The objective of the experiment "Genetic investigations" was to determine the effect of space flight factors on the heredity of lower (Chlamydomonas reinhardi Dang) and higher (Crepis capillaris (L) Wallr and Arabidopsis thaliana (L) Heynh) plants, and on the radiosensitivity of plant seeds and the radiation effect of prior gamma-irradiation. The space flight factors decreased the survival of Chlamydomonas cells and A. thaliana plants of the first generation. They decreased the germination of seeds, increased the rate of chlorophyll mutations and embryonal lethals, produced no effect on the rate of visible mutations in unicellular algae, increased the rate of chromosome aberrations in root meristem cells C. capillaris, induced disturbances in mitosis of unicellular algae and modified the effect of prior gamma-irradiation. The experiment "Growth of micro-organisms" was conducted with a culture of Proteus vulgaris in a growth chamber. After return to the laboratory the experimental and control variants were studied for twenty-two tests. The control and experimental material differed in the average cell size, biomass distribution, the character of haemotaxis, the rate of cell migration over the substratum surface, dehydrogenase activity, ribosomal aggregation, and ultrastructural peculiarities of cells. The experiment "Embryological investigations" was carried out to study the effect of space flight factors on embryogenesis of the bony fish Brachyodanio rerio. No abnormalities were noted in the course or rate of the development of spawn cultivated in a special thermostat.

Biological experiments on the orbital station Salyut 4.

Two series of experiments were carried out on the orbital station Salyut 4: one series consisted of two experiments (30 and 62 days respectively) designed to study the effect of space-flight factors on the growth and development of Drosophila melanogaster, strain D-32, and the second series consisted of two experiments (24-33 days) designed to study the effect of space-flight factors on the growth and development of the dwarf pea, variety "Pioneer". Analysis of the progeny from flies exposed to space flight showed an increase in the rate of visible mutations for y, ct, w and vg loci over those observed in the earth control. Space flight factors produced no noticeable effect on the first growth stages of pea plants. Later on growth stopped and most of the plants died under weightless conditions at the age of 2-3 weeks. Possible causes of their death during flight are discussed on the basis of anatomo-morphological, cytological and biochemical analyses of experimental and control plants.

The influence of variable gravitational fields on the embryonic development of some ecaudate amphibians.

The fertilized eggs of the frog Rana temporaria immediately after fertilization were rotated on a clinostat in the vertical plane at the rate of 0.66 rotations per minute with a radius of 20 mm for 2.5 hours. A wide spectrum of developmental anomalies was found (33% in the experiment, 14% in the control) which, in the authors' opinion, result from abnormalities in the cortical reaction of symmetrization. These abnormalities manifest themselves in the irregular distribution of cortical pigment and in eccentric division lines.