DISCUSSION 425 



studies of human beings and dogs, showed (1) a marked increase in the incidence 

 of the abnormal lymphocytes following exposure to extremely small doses of 

 radiation from the cyclotron (doses difficult or impossible to measure) , and (2) a 

 peak incidence of these lymphocytes during an approximately 2-week post- 

 exposure period. [Ingram, H., Barnes, S. W., Science, 113: 32, 1951.] 



Altman : 



Our group at the University of Rochester, including K. Salomon, G. W. 

 Casarett, T. R. Noonan, and J. B. Hursh, has investigated the effect of total- 

 body x-radiation on the biosynthesis of hemoglobin in rats with the use of a 

 different precursor, namely alpha-C ''-glycine. We have failed to observe any 

 depression of hemoglobin synthesis 24 hr after radiation with 300 r and 600 r, 

 but rather have observed an increased C^^ incorporation in hemoglobin, even as 

 late as 48 hr after radiation. Whether this increase is due to stimulation of 

 hemoglobin synthesis or increased availability of precursor cannot be stated at 

 this time. Administration of alpha-C ^''-glycine 7 days after radiation with 600 r 

 showed marked depression of hemin synthesis and significant depression of 

 globin synthesis. The apparent discrepancy between our findings and those 

 reported by Jones cannot be completely evaluated, since in our experiments 

 chemically pure hemin and globin were isolated, whereas in the experiments 

 reported by Jones radioactive Fe was determined in the red cell without previous 

 isolation of hemin. 



Fishler: 



In relation to Jones's remarks regarding Hennesy's data on Fe*^ uptake into 

 the red cells of the irradiated rat, I should like to add that Hennesy has recently 

 found that cysteine intravenously administered does not seem to protect against 

 the x-ray-induced depression of Fe^^ uptake into the red cells. 



Hevesy: 



Jones has obtained beautiful results. It looks as though the effect of radi- 

 ation on tumors is proportional to the dose. Jones mentioned the figure 0.18 

 per cent per roentgen diminution of the rate of the formation of desoxyribo- 

 nucleic acid, and with 300 r the diminution then is about 50 per cent. In other 

 words, there is proportionality between the dose and the depression of the rate 

 of formation of desoxyribonucleic acid, up to this level of radiation. If the dose 

 is further increased, proportionality no longer follows. With 2000 r only 75 

 per cent diminution or less in desoxyribonucleic acid formation is found. 



If a rat is inoculated with two tumors which are separated from each other as 

 far as possible, and then one tumor is irradiated with 1000 r, the other tumor re- 

 ceiving no more than 2-3 r, the rate of incorporation of P^^ into the desoxyribo- 

 nucleic acid of the protected tumor can be shown to be affected almost as strongly 

 as is the rate of incorporation into the directly irradiated tumor. If, however, 

 the volume increase of the tumor in the postirradiation state is determined, the 

 protected tumor is to a minor extent prevented from growing, whereas this is not 

 true for the directly irradiated tumor. 



