UNCLASSIFIED VI - BIOLOGY AND MEDICINE Research Activities Effects of X rays on frog retina. The University of California Radiation Laboratory has completed a study on the effect of X rays on animal retina. amined. Particularly the visual response to small doses of X rays was ex- Measurements on the bullfrog were made to determine the threshold intensity needed to-elicit a light stimulus and the adaptation and recovery after small doses of X rays. It was found that electrical response could be measured on the retina after 0.6 roentgens, that during exposure to X rays the sensitivity to light was reduced, and that recovery of the retThis ina after an X ray stimulus was slower than after a light stimulus. recovery phenomenon indicates that the effect is to a large extent revers“ible and that the phenomenon is one of the smallest reversible responses which has been observed with penetrating radiations. Biological synthesis of fatty acids. Research at the University of California at Los Angeles includes a project on the mechanism of metabolism in animals with respect to fatty acids in the body. It has been demonstrated for the first time that an "essential" fatty acid can be syn- thesized in the animal body. This “essential" acid--arachidonic--contains 20 carbon atoms. Synthesis was accomplished from carboxyl labeled acetate and a compound containing 18 carbon atoms. Further studies will be undertaken to elucidate the physiological significance of this reaction. Biological effects of radiation. At Los Alamos Scientific Laboratory, experiments have been undertaken to determine the biological effects of total-body KX radiation in mice. Pretreatment of mice with p-aminopropiophenone (an agent producing a pronounced hypoxia) or gluthathione, exerted a marked protective effect against total-body X radiation. A negligible degree of protection was found when mice so pretreated were exposed to thermal column radiation (thermal neutrons plus gamma contaminant). It is tentatively suggested that the lack of effect of these agents against thermal column exposure results from the fact that the majority of the ifonizations are produced along a short track and that under these conditions certain products produced by the ionization of water can be formed independently of molecular oxygen. On the basis of the data reported it.appears that agents which are protective against one type of ionizing radiation may not be of value against all types and that tissue oxygen tension may play a role in producing the marked differences observed in the relative effectiveness of neutrons and X rays in various tissues. Radiation effects on mortality. The effects of whole body ir- yadiation of male rats on mortality among their offspring is being studied by the AEC-University of Tennessee research group. Male rats were exposed to 300 roentgens of gamma rays from a cobalt 60 source, or to X rays at 250 Kilovolts peak voltage. The irradiated males were subsequently mated to UNCLASSIFIED 25 “OE ARCHIVES