STRUCTURAL AND CHEMICAL ARCHITECTURE OF HOST CELLS 



39 



In liver, about 45 % of the N and P and 36 % of the RNA are to be found 

 in the supernatant fluid after sedimentation of the particulate materials. 

 This nonparticulate RNA is also associated with protein, in almost all cells. 

 In genera], neither RNA nor DNA exists in the free state in uninfected celJs, 

 but only as nucleoprotein. However, the existence of a particle of free RNA 

 (Lindner et al., 1956) has been reported in some plants, 



TABLE I 

 Rat Liver Cell Fractions " 



Nitrogen 



Control 



Protein- 

 deficient 



Phosphorus 



Control 



Protein - 

 deficient 



Homogenate (mg./gm.) 19.8 24.0 3.3 3.1 



Nuclear fraction 4.54 4.56 0.56 0.55 



Mitochondria 5.14 3.99 0.40 0.36 



Microsomes 7.95 5.22 1.18 0.90 



Residual cytoplasm 12.95 11.17 1.56 1.63 



DNA 



Control 



Protein - 

 deficient 



RNA 



Control 



Protein - 

 deficient 



mg./gm. liver 

 Nuclei 



Mitochondria 

 Microsomes 

 Residual cytoplasm 



2.68 

 2.52 



3.06 

 3.26 



8.39 

 1.13 

 0.43 

 4.16 

 3.04 



8.03 

 0,96 

 0.56 

 3.49 

 3.78 



« Muntwyler et al. (1950). 



Mclndoe and Davidson (1952) have presented data on the distribution of 

 acid-insoluble P compounds of various types in animal nuclei. The nucleic 

 acid and phospholipid contents of the nuclei studied are given in Table II. 

 As can be seen, the ratios of RNA to DNA may vary from 0,05 in the 

 erythrocyte nucleus of a tumor-bearing fowl to 1,2 in the tumor nucleus of 

 the same bird. On the other hand, the ratios of RNA to nuclear mass vary 

 Uttle, i,e,, between 0,15 to 0,33, 



Osawa et al. (1957) have recently studied the nucleotide composition of the 

 acid-soluble fraction of calf thymus nuclei isolated in sucrose or by the 

 Behrens technique. Both types of nuclei have given similar patterns of 

 nucleotide distribution, although some nucleotides tend to be lost by the 

 former method. In addition nonaqueous nuclei contain substantially the 



