160 J. SOSKA, L. BENES, V. DRASIL, Z. KARPFEL, E. PALECEK AND M. SKALKA 



Table IV. The effect of partial hepatectomy and of totalbody irradiation 

 on the content of free deoxyribosides + deoxyribotides in liver 



The hepatectomy followed 24 hr after irradiation, the rats were killed 48 hr after 

 irradiation and/or 24 hr after hepatectomy. 



following partial hepatectomy is delayed even by irradiation before 

 hepatectomy. 



In the third experiment (Table V), the rats were irradiated 2 hr after 

 hepatectomy and sacrificed later, 28 hr following hepatectomy. The 

 difference in the level of free deoxyribonucleotides in the hejjatecto- 

 mized irradiated and hepatectomized non-irradiated rat livers was still 

 higher than in the preceding experiments, which again indicates a lack 

 of DNA-precnrsors after irradiation. The differences in the content of 

 polymerized DNA in the respective gi'oups of rat-livers were small 

 (Table V, column 5). At the same time, the content of free "ribonucleo- 

 tides -1- ribonucleosides" (all acid-soluble material, absorbing light at 

 260 m/x) was almost constant in all groups (column 6) and it was only 

 the "ribonucleoside" content (column 7); (the part of this material, 

 passing a Dowex 1 column, acetate form, at pH 7,0) that changed more 

 conspicuously. These results agree in general with those of Jafife et al. 

 (1959). 



An attempt was made to find the differences in the content of the 

 individual substances by means of pajier chromatography. In all 

 experimental groups, a substance was found in the liver, corresponding 

 by mobility in l)utanol-ammonia system and by microbiological activity 

 to deoxycytidine, in accordance with the results of Schneider and 

 Brownell (1957). Purine deoxynucleotides were not found in any group. 

 But in the livers of non-irradiated rats, a distinct spot of an additional 

 deoxyriboside was found. So far it is only known that this substance 

 contains a pyrimidine, but it is probably neither deoxyuridine nor 

 thymidine, but most probably deoxymethylcytidine. 



Deoxyril)onucleotides were chromatographed in the isobutyric acid- 

 ammonia system. Because of the complex pattern of deoxynucleotides 

 detected on the chromatogram, the individual substances could not be 

 identified. It could only be seen that the number and intensity of the 



