Dose-Rate Effects of Co60 Irradiation on Performance and Physiology in Monkeys.
LOVELACE FOUNDATION FOR MEDICAL EDUCATION AND RESEARCH ALBUQUERQUE N MEX
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One thousand rad Co60 was administered to 12 monkeys at 75 radmin and to 8 monkeys at 50 radmin while they performed a delayed match-to-sample, shock avoidance task. Only four at 75 radmin and two at 50 radmin showed early performance decrement andor early transient incapacitation PD-ETI, in contrast to 13 of 16 previously studied monkeys who showed PD-ETI with an average dose rate of 180 radmin. A dose-rate effect was concluded. When these three groups were compared with an untrained group exposed to a 4000-rad gamma-neutron pulse, all showed similar degrees of hypotension postirradiation. But the onset of hypotension was delayed and its rate of fall prolonged as dose rate decreased. Tentative interpretation was that radiation thresholds for the induction of PD-ETI exist for cumulative dose or 300 rad, midbody and dose rate or 30 radmin.