Discussion 243 



because work in a certain type of experimentation is applicable to the 

 living cell the biophysical system in that experimental technique is 

 living too? I think what it really comes to is that Lovelock only claimed 

 to have a very useful biophysical system to work on. 



Parkes: That is exactly what it does mean. 



Huggett: It does not deny Williams' point, that it may be dead in the 

 biological sense of the word. 



Villee: I think we could settle this only if someone can give a definition 

 of life which is acceptable to all of us and then we might decide whether 

 the red cell does or does not fit that definition. 



Dempsey: I thought we were having that trouble with the concept of 

 ageing! 



Amoroso: Is there any evidence that nerve cells grow and multiply? 



Krohn: Grow, but not multiply. 



Amoroso: Are they alive, according to Williams, or are they dead or 

 only partially alive ? 



Williams: I should think they have synthetic activities. 



Wislocki: With respect to the ageing of cells, I find the question 

 interesting as to the relative rates that they replace themselves, at the 

 cellular as well as at atomic levels. Neurons are permanent and do not 

 undergo division after birth, whereas other types of cells, such as leuko- 

 cytes and erythrocytes, are short-lived and frequently replaced. Never- 

 theless, at the molecular and atomic level of structure, all cells and 

 interstitial substances appear to be repeatedly renewed. The nature 

 of the replacement and the factors regulating it are topics of consider- 

 able importance with respect to the problems of ageing. To what degree 

 has the molecular and atomic turnover of the red cell been investigated ? 



Mollison: A great many different systems have been studied; for 

 example, there is evidence that red cells can synthesize cholesterol. 



Parkes: May I ask Dr. Mollison, when the red cell is about to fade 

 out in vivo, is it known what are the premonitory changes? 



Mollison: No, it is not known, unfortunately. We have one fact only; 

 that it is supposed to be more easily broken up by mechanical trauma, 

 and even that is not very well established. Perhaps the only other thing, 

 which has emerged from recent work at Oxford, is that it looks as though 

 its content of enzymes is getting low, but that evidence is rather in- 

 complete at the moment. 



Parkes: So when you get out a mixed population there is no method 

 of telling which are scheduled for demolition within the next week and 

 which are going on for another couple of months. 



Mollison: No, not at all. 



Huggett: Mollison, you said a few minutes ago that the red cell has an 

 anaerobic metabolism. If you have fresh blood, its cell reduces. Where 

 is the oxygen going? 



Mollison: It is thought that the utilization of oxygen is very small 

 in the absence of white cells. 



Huggett: That is the point, is it? It is not thought that it is used in 

 aerobic metabolism in preference to the anaerobic and can fall back 

 on it? 



