EFFECTS OF POST-IREADIATION INJECTION OF YEAST 



SODIUM RIBONUCLEATE AND ITS NUCLEOTIDES ON 



THE DIFFERENTIAL COUNT OF BONE-MARROW 



H. MAISIN 

 Cliniques Universitaires St. Raphael, Institut du Cancer, Louvain, Belgium 



SUMMAEY 



We have counted the total number of marrow cells per mg of marrow, the number of 

 white and red ceU precursors and the number of reticular cells at different time-intervals 

 after a LD50 and a LD^oo X-ray dose in rats of our strain, control irradiated, or injected 

 with j^east RNA or its nucleotides directly after irradiation. Nucleotides are toxic at 

 LD^oo- In the ribonucleate- or nucleotide-injected rats we were able to show a general 

 faster regeneration of the marrow red and white precuirsors but particularly of the white; 

 the regeneration of the red precursors is no longer possible after LD^oo? that of the white 

 is reduced. It was not possible to show a definite regeneration of the reticular cells but 

 their transformation into white and red precursors must have been facilitated. 



The significance of these results is discussed. 



'0^ 



Maisin et al. (1960) were the first to establish that post-irradiation injection 

 of yeast ribonucleic acid and its nucleotides was sufficient to decrease the 

 mortality of rats irradiated with LDgj^gp) of X-rays. Detre and Finch (1958) 

 had observed the same fact in mice also with yeast RNA. Formerly Pan je vac 

 et al. (1958) had shown that isologous highly polymerized nucleic acids ex- 

 tracted from spleen and liver improve significantly the survival of lethaUy 

 irradiated rats. Yeast RNA was only active against the meduUary syndrome 

 (Maisin et al., 1960). The dose reduction factor is not very high, it is -^ 1-12 

 (Maisin et al., 1962). Experiments of Soska et al. (1958-59) with deoxyribo- 

 nucleotides injected in mice after irradition had furthermore shown prevention 

 of the decrease in red cells, induced a more rapid regeneration of white cells 

 and stimulated the mitotic index of bone-marrow. 



Personally, we were interested in confirming this medullary protection in 

 the bone-marrow of our rats by cytological evidence and to see which 

 precursors would be better protected. We irradiated rats with 500 r-LD50(30) 

 and 600 r-LD^oQ^^Q), the former were injected, after irradiation, with yeast 

 nucleotides, the latter, with yeast sodium ribonucleate. Indeed from a survival 

 point of view, yeast nucleotides were toxic at 600 r. We did not examine the 

 marrow of our rats later than the 6th day at 600 r (because they die) or 500 r 

 (because the regeneration of the marrow is already started). 



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