538 5. QUINONES 



by tlie fibroblast work discussed above. Yakar (1952) found c-mitoses in 

 onion and tiger lily root tips treated with 1 vaM p-benzohydroquinone, the 

 spindles inactivated, and the contracted chromosomes scattered throughout 

 the cytoplasm in closely appressed c-pairs, chromosomal breakage occurring 

 after 24 hr. 



An interesting idea was expressed by Reed (1949) with regard to the pos- 

 sible effects of the naturally occurring quinones on plant growth. Plants 

 with certain mineral deficiencies are dwarfed and poorly differentiated; 

 simultaneously an excess of quinones appears within the cells, due perhaps 

 to a shift in the intracellular redox potential. It was postulated that these 

 quinones might block mitosis and retard growth and differentiation. A 

 study of zinc-deficient walnut trees was done; the leaves here are curled 

 and dwarfed, and contain coacervated phenolic material and active poly- 

 phenol oxidase. Some of the palisade cells are blocked in mitosis and be- 

 come hypertrophied. He then tested the effect of phenanthraquinone at 

 0.00048 raM on the meristematic cells of Tradescantia buds and showed 

 chromosomal distortion and mitotic abnormalities. Some relation was 

 claimed to exist between these quinone effects and the changes seen in 

 the walnut leaves. The relation is indeed tenuous, but it is an intriguing 

 approach to morphological disturbances due to deficient nutrients in plants. 

 Actually the phenolic compounds or quinones occurring naturally in the 

 walnut leaves should be extracted and tested directly, since their actions 

 might be quite different from phenanthraquinone (even the effects of ju- 

 glone would be more informative). 



After presenting these investigations on antimitotic activity, one is 

 impressed by the need to determine more closely, if possible, the site or 

 sites of action for the induction of these mitotic inhibitions. At present 

 some workers are inclined to believe in a direct chromosomal action, others 

 in effects on the spindle, others in secondary effects subsequent to cell 

 edema due to actions on membrane mechanisms, and others to inhibition 

 of metabolic systems involved in mitotic movements. We lack studies on 

 (1) the metabolic changes occurring in cells undergoing disturbances in 

 mitosis, (2) the changes in SH groups or thiols within cells acted upon by 

 the quinones, (3) the exact chronological sequence of the effects in cells, 

 and (4) a quantitative comparison of these actions with those of other SH 

 reagents in order to determine more accurately how much the reaction 

 with these groups contributes to the mitotic interference. 



EFFECTS ON NEOPLASTIC CELLS 



As is the case with many substances which may inhibit neoplastic growth, 

 the quinones seem to be able under certain circumstances to induce tumors, 

 and we shall briefly consider this aspect before the inhibitory properties 



