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Accession Number:
AD0672738
Title:
COMPARATIVE HEMATOPOIETIC CYTOKINETICS IN RATS EXPOSED TO EITHER 250 KVP X RAY OR MIXED GAMMA-NEUTRON RADIATION,
Descriptive Note:
Corporate Author:
ARMED FORCES RADIOBIOLOGY RESEARCH INSTBETHESDA MD
Report Date:
1968-01-01
Pagination or Media Count:
30.0
Abstract:
The experiment was designed to obtain recovery and residual injury data on hematopoietic stem cells of 6 groups of polycythemic rats exposed to one of three relatively low doses 150, 200, and 250 rads from one of two radiation sources. The radiation sources were a 250 kVp x-ray generator and the AFRRI- TRIGA Mark F reactor. About 60 percent of the dose produced by the reactor was from gamma rays the remainder was from neutrons. In the polycythemic rats, the response of hematological stem cells to erythropoietin as measured by 59Fe uptake in the progeny of these cells, was utilized as a measure of the effects of the irradiation. Peripheral leukocyte counts were obtained to assess competitive stimulation of related blood cells upon the hypothesized multipotential stem cell pool. It was observed that stem cell injury increases significantly with increasing radiation dose as expressed in the first rapid recovery phase. Although recovery responses are dose dependent, they are independent of the type of radiation and, in general, the RBE of gamma-neutron radiation appears to be 1. A significant decrease in the recovery response is observed in animals subjected to a repeated dose of 200 or 250 rads after a 90- day rest period. Leukopoietic recovery, as noted in the circulatory blood, begins approximately 8 days after exposure. The data suggest that the postirradiation physiological adjustments in the rat initiated by recovery and subsequent cellular proliferation result in the early abortive cellular rise and its termination. In this investigation, the residual injury observed after a repeated radiation exposure could be the result of faulty recovery in a number of primitive progenitor cells.
Distribution Statement:
APPROVED FOR PUBLIC RELEASE
