EFFECT OF SINGLE AND FRACTIONATED DOSES OF IRRADIATION 39 



DISCUSSION 



drasil: I should lilce to draw attention to some results by Dr. Karpfel. He found many 

 chromosome aberrations in bone-marrow cells which were injected into irradiated mice. 

 Furthermore he observed that the percentage of cells with chromosome aberrations is 

 much higher in allogenic (homologous) chimaeras than in syngeneic (isologous) chimaeras. 

 These results suggest an interaction between the irradiated host and the injected bone- 

 marrow cells, derived from a non-irradiated donor. 



KOLLER: How do you know that the cells showing chromosome-breaks are the non- 

 irradiated donor cells? 



drasil: The mice were given 1,000 or 1,200 r total-body irradiation, without bone-marrow 

 therapy very few dividing cells were seen in the marrow of such animals 24 and 44 hours 

 after irradiation. In those mice which were given bone-marrow from non-irradiated 

 donors, the number of cells in division was high. On this basis we may assume that the 

 dividing cells showing the chromosome injuries were derived from the non-irradiated 

 donor. 



roller: Dr. Ford of Harwell, in a very thorough work, demonstrated that bone-marrow 

 cells of irradiated mice show chromosome injuries and such cells may appear for several 

 days after irradiation. Ford's observation suggests that we should be very careful in our 

 interpretation regarding the identity of cells with injured chromosomes in the marrow of 

 iri'adiated animals, which received non-irradiated donor cells. 



