CORRELATION BETWEEN MORPHOLOGICAL STRUCTURE 259 



time after injection. The problem is of course to get enough radioactivity incor- 

 porated at the very short times for without this it is not possible to study the 

 pattern of labelling. 



HoLTER : I think that we need not be afraid of the short time of 3 min. The group 

 at the Department of Terrestrial Magnetism of the Carnegie Institution in Wash- 

 ington found in E. coli incorporation times of the order of seconds, so I don't 

 expect there is any reason to believe that in higher organisms it should go so much 

 slower than in E. coli. 



Campbell : There is only one snag, it is presumably easier for the amino acids 

 to get to the site of protein synthesis in E. coli than it is in this case. 



Allfrey : I think that one answer to Dr. Davis's question comes from the work 

 of Dr. Friedrich-Frekse's department at Tubingen. In this department they have 

 shown that exposure to U.V. or X-irradiation affects protein synthesis and they have 

 deduced that the laying down of protein proceeds from one end of the chain ; if 

 it is interrupted by irradiation at any stage, then the synthesis of that particular 

 chain is stopped. 



Porter: It is an extraordinary thing but I do not believe anyone has observed 

 in electron micrographs of liver cells any evidence of accumulation of material 

 within the extremely flat cysternae of the ER. I imagine that it could be brought 

 out by physiological experiments. 



Williams: I wonder whether you could tell us anything about the serum 

 albumin in the mitochondria. Firstly, is it readily released and secondly, does it 

 incorporate amino acids rapidly ? 



Campbell: The answer to the second question is that we don't know. As to the 

 serum albumin being readily released, once again Peters has done a considerable 

 amount of work on this with the chick liver and we have worked on the rat. Serum 

 albumin is released with DOC so it is certainly held in quite nicely. 



Mitchell : Can you tell us more about the lipid membrane that you men- 

 tioned. I believe that Dr. Siekevitz in his very nice Ciba Foundation review said 

 that he did not think that the membrane of the reticulum had very much lipid in 

 it. 



Siekevitz: If you isolate liver microsomes and test for phospholipid you find a 

 great deal, but if you isolate the pancreas microsomes you find very little, using the 

 same methods of extraction. 



