Emesis ED50 of Neutron Irradiation and Prophylactic Effectiveness.
Final rept. 1 Jan 79-31 Dec 84,
SCHOOL OF AEROSPACE MEDICINE BROOKS AFB TX
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Two neutron emesis experiments were conducted at the Armed Forces Radiobiology Research Institute AFRRI. In both experiments described as Phase I and Phase II the radiation dose required to cause emesis in 50 of subjects ED50 was determined for both neutron reactor and gamma reactor source radiation. Emesis onset, offset and duration times post-exposure are reported. Neutrons were maximized from the reactor by passing the beam through a 15.25 cm 6 in. thick lead wall to filter out gamma photons. Gamma rays were maximized by thermalizing neutrons in 30.5 cm 12 in. of water, then absorbing the thermal neutrons in a gadolinium-cadmium shield. In Phase I, 28 dogs were exposed to radiation 12 were exposed to gamma photons at the rate of 0.69 Gymin and 16 were exposed to neutrons at 1.2 Gymin. In Phase II, 58 dogs in 3 groups were exposed to radiation 19 were exposed in the gamma group at 0.75 Gymin, 20 were exposed in the undrugged neutron group at 1.62 Gymin, and 19 were exposed in the drug-treated neutron group. The drugged group received, 40-min pre-exposure, a combination of thiethylperazine, promethazine, and cimetidine which was previously shown to raise a 60 Co gamma ED50 by 85. The drugs were ineffective against neutron irradiation.