290 DAVID W. BISHOP 



form these synthetic activities, comparable to dinucleotide formation 

 by phosphorylases extracted from human sperm as reported by Hakim 

 (1959). 



The specific roles and interplay of a number of factors which can 

 affect sperm respiration, glycolysis, and motility, in vivo, have been 

 recorded by Salisbury in the excellent survey of bull sperm under a 

 variety of conditions. It is well to be reminded of the paradoxical 

 roles of K+, P0 4 , and C0 2 , essential in small amounts and in- 

 hibitory at high concentrations. Some of the historical indictment 

 has been lessened, also, against Ca++ as a divalent cation in diluting 

 media. From methods described here, coupled with those involving 

 studies of ionic balance noted above, there should soon unfold a 

 fairly complete account of the precise physiological control of me- 

 tabolism and motility of sperm in such significant biological niches 

 as the mammalian epididymis. 



In view of Salisbury's allusion to the so-called metabolic regulator 

 of Lardy and colleagues, it should be noted that many of their data 

 can be interpreted in terms of metabolic control mechanisms applica- 

 ble to other, more generalized, cells (Bishop, 1961). Uncoupling 

 agents and the relative concentrations and availability of inorganic 

 phosphate and ADP are significant factors. Salisbury's work points 

 up the inhibitory role of excess P, on respiration and phosphoryla- 

 tion, and Rothschild's findings suggest a low rate of phosphorylation 

 in freshly ejaculated sperm under anaerobic conditions as manifested 

 by a relatively high ADP to ATP ratio. 



Discussions such as we have had here concerning energy conver- 

 sion for motility, efficiency of substrate utilization, metabolic con- 

 trol of movement, and the like, always seem to skirt the issue — what 

 price motility? Dr. Carlson has come up with some answers. Any con- 

 ceptual model has its limitations, to be sure, and his is a simplified 

 model. But important connotations are implied by the relation of 

 energy procurement versus energy expenditure. Under what condi- 

 tions is it to the sperm's advantage to move at all? Nature may have 

 had this in mind when she designed the modus operandi of the he- 

 mipteran (Notonecta) sperm which remain immotile until activated 

 by female secretions, and of herring (Clupea) sperm which nor- 

 mally become motile only in the vicinity of the egg micropyle (Pantel 

 and de Sinety, 1906; Yanagimachi, 1957). The stirring-rod hypothesis 



