Acute exposure of mice to an environmental temperature of either 5 C or 37 C reduced the LD of a crude Serration marcescens endotoxin from a high of 2300 μg in mice housed at 30 C to an amount less than 40 μg. At 15 C or 32 C, the LD50 was, respectively, 880 μg and 550 |xg, while at 25 C it was 1200 jag. Control animals placed at each of these temperatures were able to maintain normothermic except for those at the high and low extremes where they became slightly hyperthermia and hypothermic. Following an injection of either twice the LD50 or a dose of 1000 (Xb, the thermoregulatory ability was upset at all temperatures except 30 C. Mice at temperatures below 30 C became progressively more hypothermic as the environment was increasingly cold and vice versa at higher temperatures. It is believed that endotoxin sensitizes mice to heat and cold rather than these temperatures sensitizing to endotoxin. After one week of acclimatization at 5 C or 37 C, the LD50 of endotoxin increased, respectively, to 790 μg and 260 μg. Indelibility of the liver enzyme tryptophan prolate, believed to play a role in an animal’s response to endotoxin, was evaluated at each environmental temperature. Only at the extremes was it suppressed.
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