Discussion 241 



Mollison: Yes, but once the reticulocyte stage is over, apparently 

 they cannot do it any more. 



Amoroso: Can anyone give us information with regard to the nature 

 of the stainable material within the red cells ; is it nuclear material ? 



Mollisoti: Yes, it has been shown to be ribonucleoprotein. 



Amoroso: Well, might not that be an indication of the importance of 

 nuclear particles in the synthesis of these essential substances of the 

 red cells? 



Mollison: It is merely that they synthesize haem while they still 

 have got some reticulum, for example, and once they have lost this they 

 cannot synthesize haem any more. 



Amoroso : So the reticulum is important in respect of that particular 

 property? 



Mollison: Yes. 



Amoroso: Then there is pertinence to Dr. Krohn's suggestion that the 

 nucleus may be the deciding factor or a deciding factor. 



Mollison: It appears that the life-span of the red cell is limited once 

 it loses the ability to synthesize enzymes, and this presumably happens 

 when it loses its nucleus. 



Wislocki: With respect to the question of the factors limiting the age 

 or life-span of a uniform strain of cells, would not one of the most perfect 

 objects for such a study be unicellular organisms rather than mam- 

 malian cells ? Perhaps amoebae would be suitable. 



Mollison: Well, they are mortal, aren't they? 



Yemm: I do not know about other unicellular organisms, but many 

 bacteria can be frozen and dried, and still survive. What their longevity 

 is, I do not know, but they can be stored in a dry condition for a very 

 long time. 



Parkes: Yes, they come into a rather special category. 



Dempsey: There is some work which has been done on the amoeba, 

 I believe, which is perhaps pertinent here. When nuclei have been 

 removed the cell immediately loses its ability to feed and be mobile. 

 A nucleus may then be transplanted back into that enucleated cell and 

 immediately it begins to crawl away and resume its functions. 



I should like to direct a question to Dr. Parkes. In a slide he showed, 

 the analogy of the brick wall in which the bricks were flying out was 

 very suggestive to me. Would you care to elaborate on that concept a 

 little more and explain perhaps whether he conceives the membrane 

 of the red cell as becoming attenuated or smaller as this lipid is lost ? 

 Or does it get holes in it as was suggested by the slide ? I am reminded 

 of the fact that there are some electron micrographs which purport to 

 show holes in the red cell membrane. 



Parkes: Yes, I can answer that particular question. One of the things 

 Lovelock dealt with was cell volume, and the decreasing cell volume 

 parallels the loss of lipoprotein, and according to Lovelock the cell is 

 shrinking to fill up the holes which, as you say, are shown by electron 

 micrographs. 



While we are on that point, there is one other thing and that is that 

 Dr. Mollison showed a slide of the effects of repeated washing, and 



