EFFECTS OF TEMPERATURE: CELLULAR SYSTEMS 



783 



interpreted on the basis of two antagonistic actions of cyanide: there is 

 the usual block of oxidations, leading to an almost complete suppression 

 of respiration at 4.5 mM, and there is the oxidation of the cyanide itself 

 by the muscle preparation. As the cyanide concentration becomes higher, 

 the oxygen consumption due to its own oxidation begins to overshadow 

 the respiratory depression. Furthermore, the temperature coefficient of 



+ 100 



Fig. 15-7. Effects of temperature on the inhibitions of 

 frog muscle respiration joroduced by different concen- 

 trations of cyanide. The figures on the curves are cya- 

 nide concentrations in millimolar. (From Elhnger, 1924.) 



the cyanide oxidation is presumably high so that this reaction is partic- 

 ularly dominant at the higher temperatures. These experiments well 

 illustrate the complex behavior of a system wherein more than one effect 

 of the inhibitor is observed. They also emphasize the necessity of consid- 

 ering the metabolism of the inhibitor in studies of this type. 



The inhibition of trypanosome respiration by cyanide has been claimed 

 to be independent of temperature variations (Brand and Johnson, 1947) 

 but if the results in all the species studied are averaged, it may be seen 

 that there is quite constantly a small increase in the inhibition as the tem- 

 perature is raised from 28. 5^ to 37.5°. At 1 mM cyanide the mean increase 



