750 



ADVENTURES IN RADIOISOTOPE RESEARCH 



Table 7. — Formation of Nucleic Acid in Double 

 Sarcomas (time of Experiment, ]/» hr; dose 1500 r) 



Expt. 



Weight of 

 sarcoma 



(g) 



Activity of 1 mgm of nucleic acid P 

 as a percentage of 1 mgm of 



Liver P 



I 

 Plasma P Sarcoma P 



(a) Unirradiated sarcomas 



108: 1 

 108: 2 

 109 .. 



108: 1 

 108: 2 

 109 .. 



17 



27 

 41 



0.37 

 0.105 



0.042 



0.23 



0.058 

 0.098 



(b) Irradiated sarcomas 

 14 



24 

 27.5 



0.080 

 0.040 



0.044 

 0.110 



0.96 



0.326 



0.071 



0.332 



RESULTS 



In Table 1 are recorded the experimental results which were obtained 

 in the study of one sarcoma protected against the effects of radiation, 

 while Table 2 contains the corresponding data for the irradiated sar- 

 comas. Tables 3 and 4 contain the experimental results relating only 

 to the sarcomas which were far removed from each other (one near 

 the neck and the other near the tail). As a check, we have also investi- 

 gated the rate of formation of labelled desoxyribonucleic acid in double 

 sarcomas of unirradiated rats. The result of this experiment is seen in 

 Table 5, while Table 6 contains a summary of all results. 



By taking into account the studies of all the sarcomas in irradiated 

 lats it is found that the direct irradiation reduces the nucleic acid forma- 

 tion to 45 per cent of that taking place in the sarcomas in the control 

 animals, while the metabolism in the shielded sarcoma is only reduced 

 to 53 per cent. When only the widely separated sarcomas are considered, 

 the corresponding values are 35 and 47 per cent. 



From these results it follows that the synthesis of nucleic acid in these 

 sarcomas, which have not been exposed to X-rays, is also subject to 

 the action of X-rays, but the effect is somewhat less and is only about 

 four-fifths of that found in the study of the irradiated sarcoma. These 

 results correspond to the events occurring in the sarcoma within 2 hr 

 of the irradiation. 



We have also performed a few experiments in which the rats were 

 killed only t.^ hr after injection of the radioactively labelled phosphate 

 solution. In so far as conclusions can be drawn from the very few values 

 contained in Table 8, the nucleic acid formation is not very different 

 in the shielded and irradiated sarcomas in this i/4 hr experiment also. 



