[Bio-objects and biological methods of space radiation effects evaluation].

The unique conditions of space experiments place austere requirements to bio-objects and biological methods of radiation effects evaluation. The paper discusses suitability of a number of bio-objects varying in stage of evolution and metabolism for space researches aimed to state common patterns of the radiation damage caused by heavy ions (HI), and character of HI-cell interaction. Physical detectors in space experiments of the BIOBLOCK series make it possible to identify bio-objects hit by space HI and to set correlation between HI track topography and biological effect. The paper provides an all-round description of the bio-objects chosen for two BIOBLOCK experiments (population of hydrophyte Wolffia arrhiza (fam. duckweed) and Lactuca sativa seeds) and the method of evaluating effects from single space radiation HI. Direct effects of heavy ions on cells can be determined by the criteria of chromosomal aberrations and delayed morphologic abnormalities. The evaluation results are compared with the data about human blood lymphocytes. Consideration is being given to the procedures of test-objects' treatment and investigation.

[Survivability and morphologic anomalies in higher plants wolffia arrhiza following exposure to heavy ions of the galactic space radiation]. / Vyzhivaemost' i morfologicheskie anomalii u vysshikh rastenii (vol'fii beskornevoi) posle vozdeistviia tiazhelykh ionov galakticheskogo kosmicheskogo izlucheniia.

Experimental data on the effects of spaceflight factors, space radiation in particular, on higher plant Wolffia arrhiza firstly exposed in the "Bioblock" assembly and measurements made by physical track detectors of heavy ions (HI) are presented. Death of individual Wolffia plants and morphologic anomalies were the basic evaluation criteria. The peculiar feature of this biological object consists in the possibility to reveal delayed effects after 1-2 months since space flight as Wolffia has a high rate of vegetative reproduction. German investigators through microscopic examination of track detectors performed identification of individual plants affected by HI. With specially developed software and a coordinate system of supposition of biolayers and track detectors with the accuracy of 1 micron, tracks and even separate sections of individual HI tracks were determined in biological objects. Thereafter each Wolffia plant hit by HI was examined and data were compared with other variants. As a result, correlation between Wolffia death rate and morphologic anomalies were determined at different times post flight and topography of HI tracks was found. It is hypothesized that morphological anomalies in Walffia were caused by direct hits of plant germs by heavy ions or close passage of particles.

[Chromosome aberrations as a bio-dosimetric test of space radiation (experimental data from the seeds of higher plants)]. / Khromosomnye aberratsii kak biodozimetricheskii test kosmicheskoi radiatsii (éksperimental'nye dannye na semenakh vysshykh rastenii)]

The authors analyzed the data about seeds of higher plants obtained in space experiments from several days to a year and a half in duration, and ground-based simulation studies on beams of accelerated heavy ions by the universal biological criterion of the chromosome aberrations. The criterion was also used to compare these data with those about lymphocytes in human peripheric blood in vitro. The number of aberrant cells, including cells with multiple aberrations, grew with mission duration, absorbed dose, and fluence of heavy charged particles as well as the topography of particles traverse of cells. Methodical dimensions of the test-object as a detector to evaluate the biological effects of and risk from space radiation in long-term space missions are considered.

Particle trajectories in seeds of Lactuca sativa and chromosome aberrations after exposure to cosmic heavy ions on Cosmos Biosatellites 8 and 9.

The potentially specific importance of the heavy ions of the galactic cosmic radiation for radiation protection in manned spaceflight continues to stimulate in situ, i.e., spaceflight experiments to investigate their radiobiological properties. Chromosome aberrations as an expression of a direct assault on the genome are of particular interest in view of cancerogenesis being the primary radiation risk for man in space. In such investigations the establishment of the geometrical correlation between heavy ions' trajectories and the location of radiation sensitive biological substructures is an essential task. The overall qualitative and quantitative precision achieved for the identification of particle trajectories in the order of approximately 10 micrometers as well as the contributing sources of uncertainties are discussed. We describe how this was achieved for seeds of Lactuca sativa as biological test organisms, whose location and orientation had to be derived from contact photographies displaying their outlines and those of the holder plates only. The incidence of chromosome aberrations in cells exposed during the COSMOS 1887 (Biosatellite 8) and the COSMOS 2044 (Biosatellite 9) mission was determined for seeds hit by cosmic heavy ions. In those seeds the incidence of both single and multiple chromosome aberrations was enhanced. The results of the Biosatellite 9 experiment, however, are confounded by spaceflight effects unrelated to the passage of heavy ions.

[Effect of outer space factors on lettuce seeds (Lactuca sativa) flown on "Kosmos" biosatellites]. / Vliianie faktorov otkrytogo kosmosa na semena salata (Lactuca sativa) éksponirovannye na biosputnikakh serii "Kosmos".

The effect of cosmic radiation on air-dry lettuce (Lactuca sativa) seeds was investigated. It was attempted to discriminate the effects of cosmic ionizing radiation per se and its combination with solar light radiation. It was found that the number of aberrant cells in the seeds exposed to solar light was smaller than that of cells chielded with 0.0008 to 0.0035 g/cm2 foil which could be attributed to photoreactivity.

Reliability of trajectory identification for cosmic heavy ions and cytogenetic effects of their passage through plant seeds.

The potentially specific importance of the study of heavy ions from galactic cosmic rays for the understanding of radiation protection in manned spaceflight continues to stimulate spaceflight experiments in order to investigate the radiobiological properties of these ions. Chromosome aberrations as an expression of a direct assault on the genome are of particular interest in view of carcinogenesis as the primary radiation risk for man in space. An essential technical ingredient of such spaceflight experiments is the visual nuclear track detector which permits identification of those biological test organisms which have been affected by cosmic heavy ions. We describe such a technique and report on an analysis of the qualitative and quantitative reliability of this identification of particle trajectories in layers of biological test organisms. The incidence of chromosome aberrations in cells of lettuce seeds, Lactuca sativa, exposed during the Kosmos 1887 mission, was determined for seeds hit by cosmic heavy ions. In those seeds the incidence of both single and multiple chromosome aberrations was enhanced.

[Effect of single exposure of the seeds of Lactuca sativa to heavy ions of galactic cosmic radiation at orbital manned space stations "Saliut-6" and "Saliut-7"]. / Vliianie odinochnykh popadanii tiazhelykh ionov galakticheskikh kosmicheskikh luchei na semena Lactuca sativa, eksponirovannye na orbita'lnykh pilotiruemykh stantsiiakh "Saliut-6" i "Saliut-7".

This paper presents the results of measuring single heavy ions (HI) of galactic cosmic rays during 40- to 457-day flights of manned orbital stations Salyut-6 and Salyut-7. Cytogenetic analysis of Lactuca sativa seeds showed a significant increase of aberrant cells and cells with multiple chromosome aberrations in seeds hit with HI compared to non-hit++ seeds during flights of 123 to 457 days in duration. There was a good correlation between curves showing aberrant cells as a function of flight of the dose absorbed, viz. 16.0 to 63.4 mGy. These findings suggest a high biological effectiveness of heavy ions of galactic cosmic rays.

Biological effects of galactic radiation HZE particles in experiments on the orbital station Salyut 7.

Lettuce (Lactuca sativa) seeds were flown on-board the orbital station Salyut 7 for 66-457 days. It was found that a single heavy charged particle (HZE) hitting a seed only slightly affects the subsequent plant growth. However, morphological anomalies of varying type in primordial leaves and roots were observed that show good correlation with the location of the particle track. The most severe damage detected by light and an electron microscopy were "channels" in dry and soaked seeds. The appearance of "channels" seems to be related to the LET of the incident particle. This finding is of considerable importance for assessment of space flight radiation hazard.

Effects of prolonged exposure of lettuce seeds to HZE particles on orbital stations.

In a study of the biological effects of cosmic HZE particles, lettuce (Lactuca sativa) seeds were flown on the orbital stations Salyut 6 and 7 for varying periods of time (from 40 to 457 days). The dependence of the biological damage on flight duration, physical parameters and the fact of passage of an HZE particle through the seed was estimated using the criterion of the frequency of aberrant cells. The arrangement of the flight biological container Biobloc made it possible to trace the location of tracks of individual HZE particles with Z > or = 6 and LET 200 keV/um. In seeds hit by HZE particles, for all exposure times, a statistically significant much higher yield of aberrant cells and also of cells containing multiple chromosome aberrations was observed than in the control material. The frequency of aberrant cells is markedly higher (by a factor of 1,5) in seeds hit than in non-hit ones. The changes of the yield of aberrant cells as a function of the absorbed dose (3.2-63.4 mGy) and the fluence (4.8-44.2 particles/cm2) are linear for the exposure duration ranging from 40 to 457 days.

Results on Artemia cysts, lettuce and tobacco seeds in the Biobloc 4 experiment flown aboard the Soviet Biosatellite Cosmos 1129.

Artemia cysts, lettuce and tobacco seeds were flown aboard the Cosmos 1129 for 19 days. A correlative method was used in order to determine the passage of cosmic heavy ions (HZE particles) through the biological test objects. This space flight resulted in a decrease on hatchability, nucleic acid and protein synthesis in hydrated Artemia cysts. HZE particle effects on plant cellular chromosomes are confirmed. In tobacco seeds, a stimulating effect on germination rate and a higher frequency of abnormalities were observed. Dormant biological objects are a very suitable material to study cosmic ray effects: these objects can be arranged in monolayers and sandwiched between visual track detectors in order to determine the passage of the cosmic heavy ions (HZE particles). On the other hand this method allows us to study effects of microgravity and those of the protonic component of cosmic rays in the objects not hit by the HZE articles.

[Cytogenetic effects in experimental exposure to the heavy charged particles of galactic cosmic radiation on the Kosmos-1129 biosatellite]. / Tsitogeneticheskie éffekty pri vozdeistvii tiazhelykh zariazhennykh chastits galakticheskogo kosmicheskogo izlucheniia v éksperimente na biosputnike "Kosmos-1129".

The experiment was carried out on lattice (Lactuca sativa) seeds flown in a biocontainer equipped with plastic detectors to record heavy charged particles (HCP). The purpose of the experiment was to determine the yield of aberrant cells as a result of irradiation, and to identify this effect as a function of HCP topography in the seed. The cytogenetic examination of flight seedlings revealed a significant difference between the seeds which were hit with HCP and those that remained intact. This indicates a significant contribution of the heavy component of galactic cosmic rediation into the radiobiological effect. The relationship between the radiobiological effect and the HCP topography in the seed was established: zones of the root and stem meristema proved to be most sensitive targets.

Effects of prolonged exposure to space flight factors for 175 days on lettuce seeds.

We have studied the effects of prolonged (up to 175 days) exposure of Lactuca sativa seeds to space flight factors, including primary cosmic radiation heavy ions. The data obtained evidence a significant fourfold increase of spontaneous mutagenesis in seeds both with regard to the total number of aberrant cells as well as the formation of single cells with multiple aberrations. Comparison of the present experiment with earlier works shows that the frequency of such aberrations increases with the duration of the flight.

Development capacity of artemia cysts and lettuce seeds flown in Cosmos 936 and directly exposed to cosmic rays.

Developmental capacity of Artemia cysts and chromosomal aberration frequency in lettuce seeds, flown aboard Cosmos 936 have been investigated. Biological objects were located inside or outside the spacecraft. Lettuce seeds were stuck on plastic plates and sandwiched in cellulose sheets in order to discriminate the objects hit by the cosmic heavy ions from the ones not hit. The absorbed dose inside the spacecraft was about 650 mrad. Biological objects were located at different levels in the "outside" container; absorbed doses were 1.5 rad for lettuce seeds and 30 rad for Artemia cysts. There was no change in hatch-ability of Artemia cysts located inside or outside the spacecraft when eggs were tested 2-4 months after recovery, but a marked decrease was observed in eggs 9 months after the space flight. Survival of larvae and adults was normal in "inside" eggs, but decreased in "outside" eggs. Space flight also resulted in a higher frequency of single chromosomal aberrations in cells developed from "inside and outside", hit and non-hit seeds. This highest percentage of multiple chromosomal aberrations occurred in seeds hit by the heavy ions.

Radiobiological investigations in Cosmos 782 space flight (Biobloc SF1 experiment).

Several biological objects were flown in Cosmos 782 in order to investigate the effects of HZE cosmic particles and other environmental factors of space. Space flight results in chromosomic aberrations in lettuce seeds, decreased germination rate and increased frequency of abnormalities in tobacco seeds and decreased developmental capacity in Artemia eggs. In lettuce and tobacco seedlings, changes were observed not only in seeds hit by heavy ions but also in nonhit seeds. The results indicate that exposure to the space environment can induce important changes in biological objects and emphasize the usefulness of investigations carried out on organisms less complex than mammals.

Effect of weightlessness and of artificial gravity on irradiated lettuce seeds.

In our previous studies on board the artificial earth satellite Cosmos 368, the cosmic apparatus Zond 8 and the orbital station Salyut it has been demonstrated that space-flight factors (SFF) have a definite effect on poorly active biological systems, such as dry lettuce seeds. The technical possibilities on board the biosatellite Cosmos 782 (the availability of an on-board centrifuge) allowed us to obtain some new data concerning the mechanisms of the SFF effects. Irradiated seeds of lettuce (Lactuca sativa L.) were exposed in space flight for 22 days either to weightlessness conditions only or to a centrifugal field. Data have been obtained characterizing the cytogenetical and physiological processes in seeds of various series of the experiment. An attempt is made to analyse the role of individual SFF in the changes observed.

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.