96 CHARLES TERNER 



were only weakly labeled when l-C 14 -acetate, in the presence or ab- 

 sence of unlabeled glycerol, was the radioactive substrate. In addi- 

 tion, the labeling of the glycerol of the diglycerides occurred in bull 

 spermatozoa incubated with C 14 -glucose under both aerobic and 

 anaerobic conditions (Terner and Korsh, 1960, 1962). 



Although the cholesterol was almost free from radioactivity, the 

 ketosteroid fraction was radioactive. The latter (it had been separated 

 from a strongly radioactive mixture) was purified by repeated paper 

 chromatography in the Zaffaroni and Bush systems. Four radioactive 

 zones were detected by radioautography, and each of these gave a 

 positive Zimmerman reaction. 



The phosphatide fractions recovered from the silicic acid columns 

 were run on silicic acid impregnated paper (Marinetti et ah, 1957). 

 These were of much lower specific activity than the glycerides, but 

 they also became labeled under anaerobic as well as aerobic condi- 

 tions. At least one component was obtained in a state sufficiently 

 pure for identification by infrared spectrophotometry. It showed the 

 bands characteristic of lecithin (Freeman et ah, 1957). It had been 

 necessary to store the samples for long periods of time in order to 

 accumulate sufficient material, and there was much degradation as 

 shown by the appearance of lysolecithins. Therefore, no attempt 

 was made to isolate plasmalogens which have been reported to be 

 present in fresh spermatozoa (Lovern et ah, 1957). 



It is known that diglycerides are precursors of triglycerides and 

 phosphatides (Kennedy, 1957), and the relative specific activities of 

 the compounds isolated from the bull spermatozoa incubated with 

 radioactive substrates are in agreement with this order of events. 



On the question of the substrate of endogenous respiration Har- 

 tree and Mann (1959) have suggested that the fatty acids of the 

 acetalphosphatides present in ram and bull spermatozoa are the 

 substrates. Our studies show a rapid incorporation of glycerol into di- 

 glycerides and therefore suggest a rapid turnover of these compounds. 

 This makes it very probable that the glycerides constitute a readily 

 available source of substrate for the maintenance of the endogenous 

 respiration. In fact the amounts of diglyceride isolated were more 

 than sufficient to support respiration at a rate corresponding to a 

 Z ,oi —10 to —20 for one hour. 



A reappraisal of the role of aerobic and anaerobic glycolysis in 



