POIK3LOTHERMIC ADAPTATIONS 

 DISCUSSION 



HUDSON: Dr. Prosser, do you see any signifiance in the 

 lower blocking temperature of the peripheral nerves compared 

 with the higher parts of the CNS, since functionally, as far as the 

 animal is conceirned, if the cord is not responding it would not 

 do any good to have the nerves responding? 



PROSSER: I am not sure that I can give you any offhand answer. 

 Certainly, the complex behavior which permits feeding and escape 

 from predators would be very necessary for survival. Perhaps this 

 means merely that integration is the important thing. This cold- 

 hardiness of peripheral nerves has been seen before; synaptic 

 transmission shows cold block at a higher temperature than nerve 

 conduction. 



ADAMS: Dr. Prosser, do you see any change in the lower 

 lethal temperature in poikilothermio vertebrates as a result of 

 acclimation to higher temperatures, or the converse? One of the 

 questions, of course, in homeothermic literature is the inter- 

 relationship of cold and heat acclimatization. 



PROSSER: Yes, Precht has reported cases where acclima- 

 tion occurred in both directions. But the curves of Fry and his 

 associates are quite clear in showing a change in the lower lethal 

 temperature with acclimation which may or may not be parallel 

 to the change in the high lethal temperature. Both of his curves 

 shift in the same direction. 



HART: Do lower lethal and upper lethal temperatures both 

 change in the same direction? 



PROSSER: Yes. I wish we knew more about the mechanism 

 of this process. I have a feeling that we need to use stress tests. 

 We have been looking at changes in the tolerated mid- range of 

 temperature. There are virtually no data on the critical tempera- 

 tures of enzyme functions. We know very little about changes in 

 denaturation temperatures. Dr. Jansky is doing something with this 

 and might want to comment on it. 



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