244 Discussion 



Mollison: I do not think so; I think the main thing is anaerobic 

 glycolysis; red cells use dextrose quite rapidly. 



Parkes: I gathered from what you said, Dr. Mollison, that in your 

 later experiments you have got the red cell apparently stable at low 

 temperature. Is that right? 



Mollison: It looks like that; of course, it is for periods only of the order 

 of one year. 



Parkes: Two years, I thought. 



Mollison: Yes, we have found that during periods up to 21 months 

 there does not seem to be any progressive loss of red cells. 



Parkes: Yes. Originally, of course, there was a slow but steady loss, 

 wasn't there? 



Mollison: I think that was due to using too little glycerol. At — 20° C 

 we tried saline glycerol to start with but that was hopeless. The results 

 with glycerol citrate are far better but we still find some progressive 

 deterioration. I rather wonder how random molecular movement can 

 be blamed for this deterioration, because surely that should go on all the 

 time and thus the curves of viability should fall steadily. Since in fact 

 there is an early period of fairly rapid deterioration, followed by only 

 very slow deterioration,! cannot believe random molecular movement is 

 the chief or only factor responsible. 



Parkes: Not as compared with diffusion. 



Mollison: No. We do not understand at all well what is happening; 

 at — 20° C, for example, we do not understand why there should be 

 a progressive drop for three months and then, apparently, so little change 

 afterwards. 



Parkes: How then do you explain the fact that altering the medium 

 has stopped the slight but steady loss which previously occurred at 

 -20° C? 



Mollison: I think the red cells were bursting. We mixed them with 

 saline glycerol and thus there was, inside the cell, haemoglobin exerting 

 an osmotic effect, and outside, effectively nothing. Now we use citrate 

 which is a non-penetrating anion outside, which acts as a balance to the 

 haemoglobin. We find that the cells actually shrink in this medium. 

 I think in the other medium they were simply bursting. 



Parkes: They were swelling up at low temperature? 



Mollison: Oh yes. We know that potassium and sodium shifts across 

 the red cell membrane go on quite rapidly at — 20° C and occur even at 

 - 79° C. 



Parkes: Of course, that is just another form of physical dissolution 

 at low temperature, is it not ? Physical instability ? 



Mollison: Yes, it is physical instability but not dissolution. 



Parkes: Well, there are the two lots of cells, then, which are apparently 

 stable at — 79° C, because by some fluke apparently we hit upon op- 

 timal or at least adequate conditions for bull sperm almost immediately, 

 and they too appeared to be stable at — 79° C. The problem of the red 

 cell was more difficult but has, apparently, now been solved. 



Mollison: Yes, the only difference is that we now use more glycerol. 



Parkes: And a different medium otherwise? 



