Chlorpromazine, triflupromazine, and chlordiazepoxide were studied for their effect on a conditioned avoidance response in rats at selected times following 500-, 1000-, and 10 000-rad whole-body doses of mixed gamma-neutron radiations. The ED 50 of the drugs increased in the rats receiving 1000 rads and decreased in those receiving 10 000 rads when compared to unirradiated controls. Although the dose-respone curve may be altered in irradiated rats, the three drugs studied remained effective even after radiation doses associated with central nervous system damage.

Mice (C57BL and C3H) and Sprague-Dawley rats were exposed to 250 kVp x-rays or 14 MeV neutrons, and mortality data were collected for 30 days thereafter. The whole-body, bilateral x-irradiations over the range of 378-918 rads (midline tissue dose) were delivered at approximately 21 rads/minute. The whole-body rotational neutron irradiations utilized midline tissue doses in the range from 282 to 707 rads. C57BL mice and Sprague-Dawley rats were exposed at a neutron dose rate which varied from 15 to 35 rads/minute (average ∼20 rads/minute). C3H mice were exposed at 15-50 (average ∼20 rads/minute) or 3-5 rads/minute to investigate the possibility of dose-rate effects. Mortality or survival time differences were not observed between sexes, and reported values represent combined groupings. The ${\rm LD}_{50/30}$ values for x-rays and 14 MeV neutrons, respectively, were: C57BL mice, 680 and 432 rads; C3H mice, 704 and 537 (3-5 rads/minute) or 480 (15-50 rads/minute); Sprague-Dawley rats, 810 and 494 rads. The relative biological effectivenesses (RBE) for 14 MeV neutrons using 30-day mortality as the end point for comparison and 250 kVp x-rays as the reference radiation were 1.6, 1.5, and 1.6 for C57BL mice, C3H mice, and Sprague-Dawley rats, respectively. A dose-rate effect was evident since the ${\rm LD}_{50/30}$ value for C3H mice exposed at 15-50 rads/minute was significantly lower (480 rads) than that of mice exposed at 3-5 rads/minute (537 rads). Of the strains studied only the mean survival time of C3H mice was significantly less when exposed to 14 MeV neutrons at 15-50 rads/minute than when exposed to x-rays.

The chinchilla's acute mortality response to mixed gamma-neutron radiations of the AFRRI-TRIGA reactor and 250-kVp x-rays was studied. Unilateral whole-body irradiations were accomplished at doses from 200 to 639 rads of mixed gamma-neutron radiations and from 357 to 1786 rads of x-rays. All radiations were delivered at approximately 20 rads/min and reported as midline doses. The ${\rm LD}_{50(30)}$ values calculated for the mixed gamma-neutron radiations and for the x-rays were 295 rads and 490 rads, respectively. With 30-day median lethality as the end point, the RBE of the mixed gamma-neutron radiations was 1.7. The wide lethal dose range obtained was attributed to a high degree of variation in age and weight of the chinchillas. At the supralethal doses of radiation associated with the gastrointestinal mode of radiation death in mice and rats (3 to 5 days mean survival times), the mean survival times for the chinchillas ranged between 6.3 and 9.6 days.

The effect of 200, 1000, and 5000 rads of mixed gamma-neutron radiations on total blood reducing sugar and blood glucose levels in guinea pigs was investigated 2 and 24 hours, and 9, 22, and 60 days postirradiation. In addition, the effectiveness of insulin and tolbutamide in these animals was evaluated before and after irradiation. Glucose increased to a lesser degree and later than did the nonglucose fraction of the blood sugar. Insulin and tolbutamide were at least as effective in irradiated animals as in unirradiated ones except after 5000 rads, when tolbutamide was significantly less effective. These results suggest that: (1) insufficient insulin is released by the pancreas in response to elevated blood sugar levels following irradiation; (2) the pancreas does produce insulin at these times and is able to release it in response to tolbutamide; and (3) a decrease in insulin production occurs following supralethal doses of radiation.

The effectiveness of four anticonvulsants was tested in male CF 1 mice exposed to 500-, 1000-, and 10,000-rad doses of mixed gamma-neutron radiations. Prevention of the hind leg extensor component of a maximal convulsion induced by electroshock was selected as the end point for effective anticonvulsant activity of diphenylhydantoin, phenobarbital, and mephenytoin. Prevention of convulsions induced by pentylenetetrazol was the end point of effective anticonvulsant activity of trimethadione. The effectiveness of the drugs was evaluated by comparing the ED 50 's to the ED 50 value for unirradiated controls. The anticonvulsants tested by electroshock showed a tendency toward increasing effectiveness after 500- and 1000-rad doses of radiation and a significantly increased effectiveness following 10,000 rads. Trimethadione effectiveness in irradiated mice was similar to that in unirradiated controls at all doses and times tested.

Total protein-bound carbohydrates (PBC), as neutral hexoses, were quantified in the plasma of C 3 H mice as a function of time relative to whole-body exposure to either monoenergetic 14-MeV neutrons or mixed gamma-neutron radiations delivered at a rate of approximately 20 rads/min. The reported doses, 365 to 530 rads, were those which yielded survivors under the stress of daily bleeding. A striking difference was observed between those radiosensitive animals which died after exposure and the more resistant individuals which, although exposed to identical doses, survived the observation period. In the former population, the PBC concentration rose to high values and remained elevated until the death of the animal. By contrast, the survivors showed little change in PBC, deviating only slightly from their preirradiation base-line values. The mean preirradiation PBC concentration in the mice which survived 30 days, while statistically significant (p < 0.01) only at the lowest reported dose, was consistently lower than that of those which died during the same period. The magnitude of the difference was inversely related to the radiation dose. The refinement of these data to provide an index to radiosensitivity prior to and prognosis after irradiation in otherwise healthy individuals is proposed.

Immunoelectrophoretic analyses were made on sera of C3H mice after steady-state whole-body exposures to <tex-math>${\rm LD}_{20(30)}$</tex-math> or <tex-math>${\rm LD}_{80(30)}$</tex-math> doses of monoenergetic 14-MeV neutrons or mixed gamma-neutron radiations. Marked differences were seen in the <tex-math>$\beta _{2}\text{-globulin}$</tex-math> response of the animals to the two sources during the first week postirradiation as tested by immunoelectrophoresis in agar gel. Monoenergetic 14-MeV neutron radiation at all doses resulted in augmentation of a <tex-math>$\beta _{2}\text{-globulin}$</tex-math> such that the precipitin line extended into the α-region. This qualitative increase was clearly evident by the third postirradiation day and appeared to be at its maximum by the fifth day. In the LD 20 groups, there were signs of return to normal on the sixth and seventh days, but the increased component persisted throughout the experimental period in the <tex-math>${\rm LD}_{80}$</tex-math> animals. By contrast, the mixed gamma-neutron radiations produced little change in this <tex-math>$\beta _{2}\text{-globulin}$</tex-math> and that only after 5 days at the higher dose level. Specific staining of the immunoelectrophoretic patterns revealed the affected globulin to be a glycoprotein.