158 Discussion 



take rat cells which have established themselves in a mouse and intro- 

 duce them into a normal, non-irradiated mouse and see if they disappear. 

 Has this been done? 



Van Bekkum: Not yet. 



Spiegelman: I think this would test it very cleanly and directly. 



Lajtha: Can these irradiation and bone marrow transfusion experi- 

 ments be repeated before the mice die, in those mice which die, say after 

 50 days? Those mice which die only after 30 days will show some of 

 their original cells returning, which probably means that their immune 

 reaction starts killing off the donor cells. Now, could a repeat irradia- 

 tion and transfusion then be performed and thus elongate the life of the 

 animal? Furthermore, do you think that such a treatment could 

 "cure" an experimental leukaemia in the animals? 



Loutit: I suppose it could, but I have not done it, and I don't know 

 what the answer would be. 



Stocken: I would like to show a slide which is relevant to Cole's 

 proposition that nuclear material is concerned in the curative factor. 

 This slide (Table I) show s decreasing numbers of whole cells and varying 



Table I (Stocken) 



30 Days Survival of CBA Mice after 950 r X-rays 

 AND I.V. Injection of Spleen Fractions 



amounts of nuclei. I think it is reasonably clear that when the number of 

 whole cells is reduced to less than 30,000, the recovery does not take 

 place. You will notice that where 36,000,000 nuclei were put into the 

 mice no benefit was obtained. 



Hollaender: I would like to keep an open mind with regard to cell-free 

 extracts still possibly producing recovery. Even if you establish the 

 bone marrow and have tissue growing in the animal, the recovery 

 process as such may be a product of something which is given up by the 

 cells. I think we should keep searching, and I think some of the work 

 which Dr. Stapleton has done may be pertinent at this point. 



Stapleton: While we were studying prevention of death or recovery 

 in bacteria, we had some indication that precursors for RNA synthesis 

 might be involved. We wondered if an RNA polynucleotide fraction 

 from Esch. coli would stimulate recovery in bacteria. We prepared a 



