524 5. QUINONES 



all of the quinone taken up is involved in the actions observed, and that a 

 large fraction may be combined with cell components of no immediate con- 

 sequence in mitosis. It establishes only an upper limit to the amount re- 

 quired. 



Amount (g/egg) Effect 



It would be highly desirable to have more thorough studies on the meta- 

 bolic alterations, if any, induced by the antimitotic concentrations of these 

 quinones. It is true that none of the enzymes tested is as sensitive to p-ben- 

 zoquinone as is cleavage in these eggs, but most of the important enzymes 

 have not been examined. The role of the plasma membrane in cleavage 

 has been largely ignored in most studies; it is entirely possible that effects 

 on permeability, membrane potentials, or organizing patterns could be of 

 importance, and work on membrane properties would also be highly de- 

 sirable before mechanistic interpretations are made. 



A comparison of the antimitotic and antidevelopmental potencies of 

 several quinones on the eggs and embryos of Tubifex and Paracentrotus is 

 shown in Table 5-6. The activities against each type of egg are roughly 

 parallel. The loss of potency upon methylation, especially of 1,4-naphtho- 

 quinone, is notable. 



Further correlations between structure and activity are provided in the 

 work of Druckrey and his colleagues (Druckrey et al., 1952, 1953) on the 

 eggs of Paracentrotus lividus (see accompanying tabulation). Phenolic 



„ , ^ Concentration (mi¥) for 50% 



oubstance .,.,.. . , 



mhibition ol cleavage 



