STRUCTURAL AND CHEMICAL ARCHITECTURE OF HOST CELLS 61 



indicate that uricase and acid phosphatase were associated with vesicles 

 derived from tlie submicroscopic lamellar structures of the cytoplasm. Their 

 fractions of liver cytoplasm and correlation of different substances with 

 particle size are given in Table VI. Data of this tyjje on host cells used in 



TABLE VI 

 The Pkoperties of Fractions of Rat Liver Cytoplasm " 



°' Kuff et al. (1956). * Diphosphopyridine nucleotide. 



virus infections could be of considerable value in analyzing the degree of 

 purification of a derived virus preparation. 



Using polyvinyl pjrrrolidone-sucrose to stabilize mitochondria and differ- 

 ential centrifugation as a method of separation, evidence has been obtamed 

 to show that there is indeed a class of small mitochondria, called lysosomes, 

 containing a high concentration of the hydrolytic enzymes, acid phosphatase, 

 ribonuclease, deoxyribonuclease, cathepsin, etc. (de Duve, 1957; Novikoff, 

 1957). However, these workers have concluded that the true extent of 

 biochemical heterogeneity of mitochondria will require a great deal of 

 additional study before a satisfactory clarification is attained. It may be 

 noted that, although it had been claimed that there is a class of small mito- 

 chondria rich in UNA, the presence of this nucleic acid appears to stem 

 largely, if not completely, from microsomal contamination. 



5. Chemical Composition of MitocJwndria 



The mitochondria isolated from many animal tissues contain protein, 

 phospholipids, other fatty acid derivatives, and RNA. Their coenzyme 

 content is summarized m Table VII. 



In normal rat Uver the mitochondrial fraction comprises 23 to 26 % of the 

 total nitrogen and 30 to 33 % of the total protein, figures which may increase 

 shghtly after correction for mitochondria (succinoxidase activity) present in 

 the nuclear fraction. In many other tissues these values are considerably less. 

 On disruption of mitochondria by sonic vibration 60 % of the mitochondrial 



