782 ADVENTURES IN RADIOISOTOPE RESEARCH 



0.126 

 0.024 

 0.097 

 0.104 

 0.175 

 0.033 



A quantitative comparison of these data with the values from in vivo 

 experiments is made more difficult by, among other things, the time 

 of experiment for sarcoma sections being 4 hr whereas the radioactive 

 nucleic acid is probably formed chiefly during the first hour. Yet the 

 conclusion can be drawn from the results that the amount of nucleic acid 

 built up in the sarcoma sections is about one-twentieth of that synthetized 

 in vivo in the sarcoma. The incorporation is markedly inhibited by poisons 

 such as cyanide, fluoride or monoiodoacetic acid, whereas colchicine, 

 oestrogenic substances and caffeine do not exercise any appreciable 

 effect. 



Summary 



If sarcoma sections are shaken for 4 hr at 37° C with blood, plasma or bicar- 

 bonate-Ringer's solution which contains radioactive sodium phosphate, the deoxy- 

 ribonucleic acid extracted from the sections and then purified exhibits radio- 

 activity. The ratio of the specific activity of the desoxyribonucleic acid P to that 

 of the free P isolated from the sarcoma tissue has been found to be on the average 

 1000. The metabolism of desoxyribonucleic acid in sarcoma sections is therefore 

 about one-twentieth of that found in a living animal in a 2 hr experiment. 



Cyanide, fluoride and monoiodoacetic acid inhibit the formation of radio- 

 active desoxyribonucleic acid, but colchicine, oestrone, diethylstilboestrol and 

 caffeine do not. 



