166 THE BIOLOGY OF HYDRA : 1961 



23. Slater, E. C. 1949. A respiratory catalyst required for the reduction of cyto- 



chrome c by cytochrome b. Biochem. }. 45: 14-30. 



24. Welsh, J. H. 1955. On the nature and action of coelenterate toxins. Deep Sea 



Research, Suppl. 3: 287-297. 



25. Welsh, J. H., and P. B. Prock. 1958. Quaternary ammonium bases in the coelen- 



terates. Biol. Bull. 115: 551-561. 



26. Welsh, J. H. 1960. 5-Hydro.xytrytamine in coelenterates. Nature 186: 811-812. 



DISCUSSION 



WELSH: Were these serotonin values on a dry weight or wet 

 weight basis? 



KLINE: Dry weight basis. 



WELSH: What do you say about the heat and pH stabihty of the 

 succinoxidase inhibitor? 



KLINE: It is stable at pH 5.8 and 8, and since one step in the 

 purification of the inhibitor is a pH 4 precipitation it has appre- 

 ciable stability even at this pH. 



Heat stability is an interesting point. We felt that the inhibitor 

 from Hydra littoralis could have been a phospholipase A. Phospho- 

 lipase As are heat stable and the succinoxidase inhibitor in snake 

 venom is believed to be this enzyme. We heated separately some 

 Crotalus adamanteus venom and our inhibitor at pH 5.8 in a boil- 

 ing water bath for 15 minutes. The venom lost none of its effec- 

 tiveness against succinoxidase while the purified inhibitor from 

 Hydra lost about 75% of its activity. 



EAKIN: What is its behavior on dialysis? 



KLINE: Essentially all of the activity is non-dialyzable. 



LENHOFF: Does the inhibitor do anything to mitochondria? 



KLINE: We have done one or two preliminary studies and there 

 seems to be some effect on the mitochondria, but as yet we have 

 done too little to make any definite statements. 



MARTIN: Have you ever tried to extract active substances from 

 the nematocyst-poor parts of the Hydra? And if so, did they show 

 any similarity with the nematocyst content? 



