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DISCUSSION 



Gray: Prof. Brachet, do you know the actual time-scale in which 

 DPN disappears after removal of the nucleus ? 



Brachet: Yes, there is a fall of about 25 per cent in the DPN content 

 of Amoeba within 24 hours. It is a fast phenomenon. We have not done 

 it yet in Acetabularia. 



Gray: Does DPN disappear both under aerobic and anaerobic 

 conditions ? 



Brachet: Our observations were made under aerobic conditions. It 

 will be difficult to test the effects of anaerobic conditions because, in 

 order to measure the DPN content of Amoeba, using a very sensitive 

 method, we have to cut about 4-5,000 amoebae for each experiment. 

 What we would really like to know is whether the distribution of DPN 

 would be altered in non-nucleated cytoplasm: there is a possibility that 

 part of the DPN may be linked to mitochondria. Perhaps only the free 

 DPN is attacked, while the DPN bound to the mitochondria is more or 

 less preserved. It may be that this loss of DPN, especially if it is soluble 

 DPN, is one of the causes of the poor utilization of carbohydrate 

 reserves. 



Davidson: I should like to raise one point in connection with nuclear 

 RNA : my colleagues and I believe that nuclear RNA is heterogeneous, 

 that at least two types of RNA, not just a single RNA, are present in 

 the nucleus. If we isolate cell nuclei by methods which avoid the use of 

 aqueous media, we can obtain perfectly clean cell nuclei from which 



