Hematopoietic Recovery in Endotoxin-Treated Lethally X-Irradiated BUB Mice

Abstract

Efforts to modify the radiation syndrome and prevent death from X-irradiation have consisted of several treatments which successfully combat bacteremia and hematopoietic failure. Effective procedures include treatment of the irradiated animal with antibiotics (1, 2), lead-shielding of hematopoietic organs during irradiation (3, 4), and injection of hematopoietic cell suspensions after irradiation (5, reviewed in 6). Treatment of mice with endotoxins of gram-negative bacteria also increases the number of animals surviving a lethal dose of X-irradiation (7-10). When a small dose of endotoxin is administered prior to irradiation, a marked increase in survival is accompanied by an increased resistance to endogenous and exogenous infection (10, 11) and an earlier recovery of hematopoietic tissues (12). Hematopoietic recovery has usually been measured in terms of the restoration of peripheral blood cells in animals exposed to varying doses of radiation (13), although estimations of the cellularity of bone marrow sections also indicate that the marrow recovers earlier in endotoxin-treated mice than in streptomycin-treated irradiated control animals (12). In view of the importance of hematopoietic recovery to the survival of irradiated animals, this investigation was undertaken to determine histologically the time and process of hematopoietic recovery in endotoxin-treated lethally X-irradiated mice.