/ Project Title: 14, Scope: Effects of Radiation on Living Organisms Early and Late Effects of Radiation of Different Qualityand at Different Dose Rate (Cont'd.) RX-03-Ol-(a)_ to the intercomparison and standardization of neutron dosimetry methods and instrumentation for radiotherapy and radiobiology as well as for radiation protection. (Bond, Rossi) The mechanism of action of radiation carcinogenesis in the rat is studied by observing the mammary neoplastic response to chemical carcinogens and radiation in relation to a comparative study of neutron and x radiation; the effect of dose rate; and the interaction of hormonal stimulation of mammary tissue and chemical and physical carcinogens. The dose-response relationships of rat mammary carcinogenesis and exposure to neutrons are studied at neutron dose ranges of 0.125 to 8 rads. The possible ''sparing effect'' of Lowering the dose rate on mammary carcinogenesis is investigated, Various strains of rats are studied for their differing responses ta x radiation and chemical carcinogens in regard to the hormonal status’ of each strain. (Shellabarger) Another study, investigating radiation effects on the central nervous system is aimed at obtaining basic information on the response of the mammalian central nervous system to x-ray doses in the therapeutic range and studying the comparative radiosensitivity of the elasmobranch and mammalian central nervous system related to differences in structure and function, This information should have practical value in the planning of patient radiotherapy and in furthering the understanding of basic neurophysiology. In the mammalian CNS studies monkeys, age 12 weeks cto 4 years, have received whole and partial brain x-ray exposures to the hand-face area of the cortex as well as the visual cortex in single and multiple doses ranging from 150 to 67,000 rads, Clinical and EEG evaluation are combined with serial sacrifice at post-irradiation periods from 24 hours to 96 weeks. Normal histological procedures and electron microscopy are combined with special techniques of statistical evaluation of alterations in the dendritic plexus and synaptic area to correlate changes in function as Special techniques of frequency analysis of photomeasured by the EEG, In addition, the loss in in the EEG analysis. used are response evoked visual acuity in trained animals is being measured following x irradiation A short-term objective is the accumulation of of both visual cortices. data on the relationship of radiation dose to the pathogenesis of radiation lLesiong decre and loss of function, In particular, the dose threshold for in visual acuity and reduction in photo-evoked response is e -#fhese studies are in collaboration with Roizin, Columbia University; ooks Air Force Base; and Graham, University of Puget Sound. The morphology of the elasmobranch as compared to the mammal (the location of astrocytes are grouped in intimate contact with vessels in sharks as opposed to being scattered at greater distances in mammals) (See Continuation Sheet) 1119259 RX- 166