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DISCUSSION 



MANOiLOV : Did yoii administer nucleotides isolated from different organs and 

 tissues or are the phenomena observed characteristic for spleen and bone -marrow 

 alone ? 



Did the deoxyribonucleotides achiiinistered subcutaneously incorporate into 

 spleen DNA as such, or did they imdergo preliminary splitting up? 



SOSKA: The effect of deoxyribonucleotides on bone-marrow alone has been 

 studied. We have not studied as yet, whether the nucleotides administered are 

 broken down in tissues or not. 



xjtkin: How did you determine the mitotic index? 



SOSKA: A smear of Ijone-marrow from the sacrificed mouse was prepared and 

 stained according to Feulgen. The mitotic index was determined in a count of 

 8.000 to 10,000 nucleated cells. The proportion of the individual mitotic phases 

 was recorded. Dr. Karpfel found that, following exposure, the ratio of meta- 

 phases to prophases was changed. If, in the unirradiated mice, the ratio of meta- 

 phases to projDhases was 0-56, in animals irradiated with 500 r this ratio rose to 

 1-0 or 1-5. We found that administration of pyrimidine deoyxribonucleotides 

 following exposure brought changes in this picture, the ratio of metaphases to 

 prophases returning partially to normal. 



