STRUCTURAL AND CHEMICAL ARCHITECTURE OF HOST CELLS 



59 



By either mechanism of origin of mitochondria, it may be expected that 

 the size and composition of the mitochondrial population within the cell will 

 vary as a function of the physiological and genetic state of the cell. Such a 

 situation bears many similarities to problems of virus multiplication. The 

 quantitative variability of a viruslike cytoplasmic particle containing DNA 

 has been studied in some detail in the case of the kappa factor multiplying in 

 the cytoplasm of Paramecium aurelia. 



Enzyme concentration 



■in relation to 



cell division 



and/or enzyme synthesis 



Enzyme concentration: 



increases 



remains constant 



decreases 



continued decrease 

 = irreversible change 



Fig. 7. Diagrams to illustrate a hypothetical mechanism of carcinogenesis in terms of 

 the deletion of a cytoplasmic particle or an enzyme contained therein (Potter et al., 

 1950). Each large circle represents a cell. The cross-hatched circles represent nuclei and 

 the small black dots represent one type of cytoplasmic particle. 



The problem is also of great interest from the point of view of carcino- 

 genesis. Potter et al. (1950) studied the composition of rat Hver as a result of 

 feeding the carcinogenic dimethylaminoazobenzene derivatives to rats. They 

 correlated the loss of succinoxidase, a mitochondrial enzyme, with the 

 increasing carcinogenicity of various compounds and concluded that car- 

 cinogens might produce irreversible changes by causing the deletion of 

 particular cytoplasmic inclusions during cell multiplication, as presented in 

 Fig.7_. 



A similar conclusion has been reached by Ephrussi and collaborators in 

 analyzing the respiration-deficient mutants of yeast produced by the action 

 of acriflavm. (Ephrussi, 1953). 



