LATE BIOLOGICAL EFFECTS OF HEAVY CHARGED PARTICLES: CATARACTS, VASCULAR INJURY AND LIFE SHORTENING IN MICE E. J. Ainsworth - J. G. Jose - M. E. Barker - E. L. Alpen Donner Laboratory, Lawrence Berkeley Laboratory and School of Optometry University of California, Berkeley, California 94720 Manned space flights are now a reality and may increase in the future in connection with use of advanced technologies, such as satellite power systems (SPS) to generate electricity. However, many of the risks associated with extended habitation in a space environment remain undetermined. Of particular concern at this time are the hazards to space workers that might result from exposure to high energey heavy ion particles (HZE). Less is known about the biological consequences of HZE than about other types of radiations encountered in space. Conventional types of shielding used for radiation protection do not shield out these particles. No data are available currently to assess lens damage and repair after low doses of HZE particles. Thus, more information is needed about biological effects of HZE in order to assess their potential adverse health hazards. Of considerable importance are the potential effects of HZE particles on the crystalline lens of the eye, because this tissue has proven susceptible to x-and gamma rays and particularly susceptible to the action of other forms of high LET radiation such asfission-spectrum neutrons. Because carcinogenic effects and blood vessel (vascular) damage are also of great importance for radiation risk assessment, several animal experiments are in progress to evaluate dose-response relationships for tumor-induction/promotion and for vascular injury. This presentation concentrates on cataract productions, yet preliminary results on carcinogenic and vascular effects are presented for perspective. A fundamental question addressed by several ongoing studies at Berkeley is the extent to which the biological effects of HZE particles are more or less hazardous than fission neutrons, because fission neutrons and densely ionizing alpha particles are considered the most hazardous radiations to man. The three radiation sources we use in these studies are 250 kVp x-ray machine, the Lawrence Berkeley Laboratory Bevalac, and the 184 inch cyclotron. All mice evaluated for cataracts by slit-lamp biomicroscopy were given either head only or upper body exposures to charged particles or x-irradation. Fully stripped heavy charged-particles were obtained from the Lawrence Berkeley Laboratory Bevalac, a national facility. The Bevalac combines two accelerators; the SuperHILAC, a heavy ion linear accelerator and the Bevatron, a protron synchrotron. Particles are first accelerated to appropriately 7-9 MeV in the SuperHILAC and are then injected into the Bevatron thru a transfer line where maximum energies obtained are in the range of 2 GeV.12C, 20Ne, 1+0 Ar, 5GFe ions were extracted from the Bevalac at a preselected energy. Eye examinations were performed by first sedating each animal with Diabutal. Dilation was achieved by the use of one drop of 1% Tropicamide. The lenses were then observed with a slit-lamp biomicroscope, and assigned a severity score of 0.0-4.0. The observer did not know the type or dose of radiation that the animals had received. Preirradiation screening of animals for "spontaneous cataracts" was accomplished on many animals and the number rejected was nil. Cataract evaluations have been done on several strains of hybrid mice involved in five different experiments, only two of which were dedicated cataract experiments. In Experiment II animals were irradiated with 10-100 rad of spread Bragg peak argon ions (570 MeV) and were evaluated at 7,8,9 and 18 months after irradiation. Nearly 44% (48/108) of the mouse eyes developed some opacification by
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