Acute Lethal Responses of Goats and Sheep to Bilateral or Unilateral Whole-body Irradiation by Gamma-rays and Fission Neutrons

SummaryMan-sized goats were exposed either bilaterally or unilaterally and sheep, a quarter to a half that size were exposed bilaterally. Deaths from ‘gut injury’ occurred with haemoconcentration and gross injury to some portion of the gastro-intestinal tract. Deaths from ‘marrow failure’ occurred with thrombocytopoenia, haemorrhage and leucopoenia, and the consequent bacteraemia was regarded as the major cause of death, except in a minority which died from haemorrhage. The distribution of deaths with time after neutron-irradiation was different from that after gamma-irradiation. Following bilateral exposure the neutron : gamma R.B.E. for the LD 50/37 was 0·73 for goats and 0·83 for sheep. For death from ‘gut injury’, the neutron R.B.E. may be about 1·5. In goats the responses of lymphocytes to gamma- and neutron-irradiation were the same, but those of polymorphs and platelets were slightly different. The R.B.E. for each of these responses appeared to be similar to that for the LD 50/37.When goats were irradiated unilaterally either with gamma-rays or neutrons there was an unexpectedly small alteration in the LD 50/37 and RBE. In decedents and survivors, unilateral-irradiation caused the same changes in lymphocyte numbers as did bilateral, but polymorph and platelet counts recovered more rapidly whether the exposure was to neutrons or gamma-rays Unilateral neutron-irradiation was perhaps more effective than bilateral in causing ‘gut injury’.The sedatives that had to be used caused a transient polymorphonucleocytosis but otherwise had no effect on the response to irradiation.