182 



J. N. Davidson 



Claude (1946). From the figures shown in Table VII, it is 

 clear that in agreement with the results of Marshak and 

 Calvet (1949) and of Barnum and Huseby (1950), the nuclear 

 RNA has a much higher activity than the cytoplasmic 

 RNA. It also appears that of the cytoplasmic fractions the 

 ribonucleotide phosphorus in the small granules has a lower 

 activity than that in the large granules or the supernatant 

 fluid. This is in general agreement with the results of Jeener 

 (1949) and of Barnum and Huseby (1950) who used ^^p. 



Table VII 



Activities of Phosphorus Fractions Separated by Ionophoresis from 

 THE Ribonucleotide Fractions in a Schmidt-Thannhauser Separation 

 OF Isolated Nuclei and Cytoplasmic Components Obtained from Rat 



Liver Tissue 



10 fxc. ^-P per 100 g. body weight were injected two hours before kilhng. 



Reichard (1950), however, using ^^N in regenerating rat liver, 

 found no difference in the incorporation of the isotope into 

 the purines of the RNA in mitochondria, microsomes, and 

 "cell sap," i.e. the supernatant fluid in the differential 

 centrifugation procedure. The reason for this discrepancy is 

 not yet clear. 



Neither Jeener nor Barnum and Huseby isolated the 

 separate nucleotides in their fractionation procedures. This 

 has now been done by Mclndoe and Smellie using the iono- 

 phoresis technique, and the results are shown in Table VII, 



