MIYA, MARCUS AND PHELPS 



since there is opportunity for greater heat loss and this increased 

 metabolism is sufficient to result in the same end body tempera- 

 ture. Further, this increased metabolic rate resulting from the low 

 temperature stress might eventually lead to exhaustion of body re- 

 serves and subsequent death (Selye, 1950). 



Another possibility to account for variations in results is a 

 psychological factor. Since immunized non-challenged mice are able 

 to survive low ambient temperatures when caged individually but 

 not when challenged with an infectious disease agent and main- 

 tained individually at low ambient temperatures, one must speculate 

 concerning the extent that the factor of isolation contributes to in- 

 creased mortality observed. Psychological factors cannot be dis- 

 regarded in assessing this problem. 



In some instances, zymosan or endotoxin treatment resulted in 

 increased mortality ratios. This was noted consistently when the 

 challenge agent was K. pneumoniae or the strain of Coxsackie virus, 

 but not as apparent when S. aureus was used. This paradox, if real, 

 requires further investigation, since nonspecific immunizing agents 

 are known either to enhance or depress resistance depending on the 

 time of administration; yet our observations suggest that the dosage 

 and administration time optimal for a given ambient temperature 

 may not be optimal for another ambient temperature. 



The relationship of zymosan to properdin, shown to exist by 

 Pillemer et al. (1956), deserves attention with regard to speculation 

 concerning the extent the properdin system plays in the observed 

 results with zymosan incur experiments. The dosage of 9 mgm sub- 

 cutaneously is in excess of that reported by Ross (1956) to stimulate 

 increases in properdin levels in mice. Ross injected the material 

 intravenously, and the colloidal nature of zymosan certainly would 

 limit the amount employed in order to avoid pulmonary embolic 

 complications. Recently, lakovleva and Remezov (1960) reported 

 that mice exposed to the cold have greater than normal levels of 

 properdin 72 hours post- exposure. The properdin level increasing 

 action of zymosan added to the levels obtainable by cold exposure 

 should insure mice of a high properdin level. However, since the 

 serum of mice lacks complement components (Rice and Crowson, 

 19 50) and has been shown to be devoid of bactericidal activity 



192 



