Effect of HZE particles and space hadrons on bacteriophages.

The effect of high energy (HZE) particles and high energy hadrons on T4Br+ bacteriophage was analyzed. The experiments were done in orbital flight, on high mountains, on an accelerator, and with an alpha particle source. We studied the survival rate of the bacteriophage, the mutation frequency, the mutation spectrum and the revertability under the action of chemical mutagens with a known mechanism of action on DNA. It was found that the biological efficiency of HZE particles and high energy hadrons is greater than that of gamma radiation. The spectra of mutations produced by these mutations and the mechanisms of their action are also different. These effects were local, because of the mode of interaction of the radiant energy with biological objects, and depended on the linear energy transfer (LET). The modes have now been experimentally defined.

A review and comparative analysis of the biological damage induced during space flight by HZE particles and space hadrons.

We have studied the somatic and genetic effects of heavy ions (HZE particles) and the very high energy hadrons of space radiation on various organisms ranging in complexity from bacteriophage to man. Experimental data were obtained in space, on high mountains and in a proton accelerator at energies of 76 GeV. In all these experiments local micro- and macroradiational damage was observed. This damage was characterized by severity over large local regions and for the most part was due to cascades of secondary particle bundles resulting from the collision of very high energy space hadrons with atomic nuclei rather than from cellular hits from relatively low energy single HZE particles. At present there does not appear to be any effective way to provide shielding against these cosmic hadrons.

Genetic effects of space hadrons on bacteriophage under Alpine conditions.

A dried film culture of bacteriophage T4Br + was kept in a lead bioblock for 366 days under Alpine conditions at an altitude of 6100 m above sea level to study the genetic effect of space hadrons. In the gelatin-like film under study we discovered some film plots with markedly reduced bacteriophage survival. In such plots, the mutation frequency exceeded the spontaneous background mutation rate 60-100 times. The spectrum of r mutations as classified into standard groups rI, rII and rIII differed from that found for other model radiation systems such as gamma-ray radiation in buffer or nutrient broth, and hadron and HZE particle radiation under space flight conditions. Reversion analysis of 159 rII mutants showed that 54.4% had small and elongated deletions, 23.16% had point mutations, and 22.5% of all the mutants had both small deletion and point mutations.

Genetic effects of cosmic radiation on bacteriophage T4Br+ (on materials of biological experiment "Soyuz-Apollo").

During the experiment "Spore-ring Forming Fungi Biorhythm" of the Apollo-Soyuz test project the Rhythm-1 apparatus contained a dried film culture of bacteriophage T4Br+, growing cultures of Actinomyces and plastic nuclear particle detectors. The following were studied: the frequency of induction of r mutations in the bacteriophage film per 2 X 10(4) surviving particles, the spectrum of mutant types obtained (rI, rII, rIII), and the possible molecular mechanisms for the occurrence of rII mutants with due regard to the registered tracks of heavy nuclear particles. The studies showed that the local radiation due to heavy nuclear particle tracks plays a major role in space radiation damage.

Apollo-Soyuz Test Project on biorhythm of zone-forming fungi: preliminary work.

The purpose of the experiment was to study general and local effects of space flight factors on the rhythm of cellular activity and on the morphological and genetic properties of biological objects. The Pushchino strain, Actinomyces levoris Kras 17-225A-IBFM, isolated at the Institute of Biological Physics, Moscow, was chosen as the main biological object. Under appropriate conditions it gives distinct and continuous rings of spore formation reflecting its intrinsic high degree of synchronism in changing its reproduction forms seen with the unaided eye as transparent rings (vegetative growth) alternate with convex white rings (spore-formation growth). As an additional test object, a film culture of bacteriophage T4Br+ developed at the institute was used. The strains were placed together in one bioblock together with plastic detectors for detecting nuclear particles. The film culture of bacteriophage enabled us to amplify the area of registration of local radiation effects by studying the genetic effects of these: frequency of mutations, induced radiation, their spectrum, subsequent revertability under the action of chemical mutagens with known mechanisms of action on DNA molecules.

Peculiarities of biological action of hadrons of space radiation.

Biological investigations in space enable one to make a significant contribution on high-energy hadrons to biological effects under the influence of factors of space flights. Physical and molecular principles of the action of high-energy hadrons are analysed. Genetic and somatic hadron effects produced by the secondary radiation from 70 GeV protons have been studied experimentally. The high biological effectiveness of hadrons, great variability in biological effects, and specifically of their action, are associated with strong interactions of high-energy hadrons. These are the probability of nuclear interaction with any atom nucleus, generation of a great number of secondary particles (among them, probably, highly effective multicharged and heavy nuclei, antiprotons, pi(-)-mesons), and the spatial distribution of secondary particles as a narrow cone with extremely high density of particles in its first part. The secondary radiation generated by high- and superhigh-energy hadrons upon their interaction with the spaceship is likely to be the greatest hazard of radiation to the crew during space flights.

Estimation of the biological danger of the very high energy component of space radiation.

In modelling the action of the high energy component of space radiation in a space ship, the secondary radiation resulting from the interaction of 76 GeV protons with a target was used. The radiation flow consisted of neutrons, mesons of different kinds and charges, protons and gamma-quanta of wide energy spectrum. We studied the influence of radiation on the survival of E. coli B and T4Br+ bacteriophage, on the growth, dry weight and survival of Vicia faba, on the frequency of chromosome aberrations, and number of cells with abnormal mitoses, on the rate of post-irradiation recovery according to these characteristics, and also on the yield of the r-mutants of T4Br+ bacteriophage, their distribution and biochemical identification. The probability of strong interactions with intra-nuclear cascade processes was minor. Their action on the background of the main mass of radiation with an RBE of less than 1 could be considerably masked. Nevertheless, the RBE of combined secondary radiation was sufficiently greater than 137Cs radiation; from approximate curves, it was from 1.2 to 4.0 times as great and in single experimental points it was more than 5. The spectrum of mutation was also different.