% . ' the NTS, are expesed te high energy x-irradiatien at six expesure peints straddling a previeusly determined 1509/3 ef 500 rep. Animals are 2th under the 2 MEV Van der Graaf exposed at the National Institutes of unit at the time the animals are expesed to weapon irradiatien. Sub-project .2.3. Nineteen hundred and twenty Walter Reed - BAGG strain ef mice. Only female mice are exposed, weighing appreximately 25.0 grams at expesure. The axes for animal placement parallel that fer the ' swine, and, as such, en ene axis the total dose ef irradiatiqn consists ef at least BOF neutren flux (south axis). This is feasible on the basis ef weapen geemetry and without sophisticated shielding other than te avoid the thermal flux and te prevent blast injury. The second axis fer animal place- ment is such that the total dose of irradiation delivered censists of 80% gamma with 20% neutren flux centamination (west axis). Animals are exposed in aluminum and lead hemispheres (ITR-1167, Operation TEAPOT-Classified) in such a fashion that there are fifteen aliminum stations on each axis and en the south axis there are fifteen lead hemispheres, Dispesitien is such that the statiens cover a dose range ef 300 to 1000 rem, with forty mice at each point. As s00n as pessible after exposure the mice are recovered and returned to the animal facility. Twenty mice frem each peint will be simply ebserved, with death as an endpoint, for thirty days (LDso/ ). Ten mice fren each point are te be sacrificed at. 9 hours, and ten Vice sacrificed serially ever the 30 day ebservatien period. At sacrifice the fellewing are carried eut: 1. net spleen weight 2. thymus weight 3. small intestine weight 4. total peripheral white cell count 5. differential white cell count 6. gress body weight 7. ‘tetal bene marrew count ef the right femur 8. and appropriate histological sectiens are fixed as demanded. Control mice for serial sacrifice are given identical field handling and exposure cenditiens, but without actual radiatien exposure. At Walter ee Reed Army Institute ef Research, after return from NTS, mice ef the same strain, age, weight, etc. are to be subjected te an We analysis of parameters identical to the field study. estimates even more reliable. Sub-preject 4.2.4. study with | 4.4 should make RBE See Program 2 experimental plan. nae °°

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