HZE PARTICLE EFFECTS IN-SPACE

Among the various particulate components of ionizing radiation in spac e, heavy ions (the so-called HZE particles) have been of special conce rn to radiobiologists. To understand the ways by which HZE particles o f cosmic radiation interact with biological systems, methods have been developed to precisely localize the trajectory of an HZE particle rel ative to the biological object and to correlate the physical data of t he particle with the biological effects observed along its path. In a variety of test systems, injuries were traced back to the traversal of a single HZE particle, such as somatic mutations and chromosomal aber rations in plant seeds, development disturbances and malformations in insect and salt shrimp embryos, or cell death in bacterial spores. In the latter case, a long-ranging killing effect around the particle's t rack was observed. Whereas, from spaceflight experiments, substantial information has been accumulated on single HZE particle effects in res ting systems and in a few embryonic systems, there is a paucity of dat a on cosmic radiation effects in whole tissues or animals, especially mammalians.