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# The Response of the Beagle Dog to Cobalt-60 Gamma Radiation: Determination of the ${\rm LD}_{50(30)}$ and Description of Associated Changes

W. P. Norris, T. E. Fritz, C. E. Rehfeld and C. M. Poole
Radiation Research
Vol. 35, No. 3 (Sep., 1968), pp. 681-708
DOI: 10.2307/3572525
Stable URL: http://www.jstor.org/stable/3572525
Page Count: 28
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## Abstract

The ${\rm LD}_{50(30)}$ of ${}^{60}{\rm Co}\ \gamma \text{-radiation}$, given as a single, bilateral exposure at a rate of approximately 15 R/min to the whole body of 13-month-old, purebred beagle dogs, was determined to be 258 rads, expressed as the average absorbed dose. The method for computing radiation dose allows compensation for the individual variations in size of dogs. This has a significant effect on the overall result. Detailed examination of the dogs-by clinical methods, hematology, blood biochemistry, and gross and microscopic inspection of tissues-led to the conclusion that acute bacteremia, secondary to bone marrow damage was the primary cause of death. There were no sex-related differences. Bacteremia intervenes in the progression of the radiation syndrome as the granulocyte count approaches the critical level of about $1000\ \text{cells}/{\rm mm}^{3}$ of blood. Thus the complete expression of biologic response versus radiation dose is masked by the invasion of bacteria. The effect of such masking on the interpretation of data related to the ${\rm LD}_{50(30)}$ is discussed.

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