EPILOGUE 289 



phosphagen system would prove of greater advantage to an inverte- 

 brate sperm than to a mammalian germ cell. 



When the wealth of metabolic information concerning glycolytic 

 processes in sperm is considered, it is particularly refreshing to have 

 the remarkable comparative survey of qualitative and quantitative 

 aspects of respiratory pigments presented here by Gonse. It is sur- 

 prising, moreover, to learn of the general similarity of the cyto- 

 chromes, pyridine nucleotides, and flavoproteins when compared in 

 sperm of the bull, dog, and clam, Spisula. Whereas the relative pro- 

 portions of cytochromes may differ significantly, total concentration 

 and turnover number appear about the same. All three species carry 

 equivalent quantities of cytochromes, i.e., approximately 2.5 X 10 6 

 molecules per sperm (see also Perry et al., 1960). Cytochrome oxidase 

 content is relatively large in the sperm of the dog and bull. From re- 

 sults with DNP, specific respiratory inhibitors, Amytal and antimy- 

 cin A, and the less specific inhibitor, azide, it would seem that clam 

 sperm are much more sensitive to uncoupling than are mammalian 

 sperm. Oxidative phosphorylation, while yielding a greater amount 

 of energy available (as ATP) for motility, does so at a slower and less 

 accessible rate, owing to compartmentation according to Gonse, than 

 is the case with glycolysis. One may, on this basis, account for the 

 preferential utilization of glycolysis over oxidative respiration by 

 mammalian sperm under aerobic conditions in the presence of suit- 

 able substrate. 



A new twist to the fate of degradation products of the Embden- 

 Meyerhof glycolytic scheme in sperm has been outlined by Terner. 

 A considerable portion of the pyruvate is regarded as being con- 

 verted, by dismutation, to lactate, acetyl CoA and carbon dioxide, 

 under both aerobic and anaerobic conditions. Confirmation of this 

 metabolic pathway in sperm would seem to be indicated before one 

 speculates just how general the process might be. Whether or not. 

 however, acetyl CoA is thus made available for synthesis in sperm, 

 Terner reports on the presence of strongly labeled diglycerides, and 

 less intensely labeled triglycerides and phosphatid, in bull sperm in- 

 cubated with C 14 -gl UC ose. Flipse also finds evidence of synthetic 

 activity, if this is what is is, in bull sperm, namely, the formation of 

 the dipeptide carnosine in cells exposed to C 14 -histidine. It would be 

 interesting to know whether sperm homogenates or extracts can per- 



