764 



SPERM, OVA, AND PREGNANCY 



cerning human sperm may be, they have 

 some merit. New avenues of investigation 

 are opened by a broader approach. More- 

 over, some advantage is gained by attempts 

 to relate certain aspects of the apparently 

 exotic behavior of human sperm to the meta- 

 bolic patterns and principles common to 

 other mammalian tissues. Many issues are 

 yet to be resolved, including the question of 

 the utilization of oxidative substrates vis-d- 

 vis their jiermeability, and the recently 

 announced difference in sensitivity of hu- 

 man sperm to endogenous versus exogenous 

 hydrogen jieroxide (Wales, White, and 

 Lamond, 1959 ». Tests might be applied to 

 determine whether peroxide is produced in 

 accordance with the scheme noted above or 

 whether it may arise from endogenous ni- 

 trogenous sources, comparable to its forma- 

 tion from exogenous aromatic amino acids, 

 as previously noted (Tosic, 1947; VanDe- 

 mark, Salisbury and Bratton, 1949; Tosic 

 and W^alton, 19501. 



F. METABOLIC-THERMODVX.\MIC 

 INTERRELATIONS 



Underlying much of the above discussion 

 are many quantitative data pertaining to 

 the metabolic and thermodynamic proper- 

 ties of sperm. Rates of oxygen consumption 



TABLE 13.12 

 Vital statistics of hull spermatozoa 

 (Data obtained in buffered saline, 37°C.; calcu- 

 lations based on free-energy change of hydrolysis 

 of —8 kcal. per mole of adenosine triphosphate.) 



* Based on fragmented cells and expressed as 

 net result of balance between hydrolysis and syn- 

 thesis of ATP. 



and of fructolysis have been determined for 

 sperm of a wide variety of species (Mann, 

 1954). Values have also been obtained for 

 heat production (Bertaud and Probine, 

 1956; Clarke and Rothschild, 1957; Roths- 

 child, 1959), ATP hydrolysis, and the en- 

 ergy requirements for flagellar movement. 

 Some of these properties for one species 

 are tentatively summarized in a table of 

 vital statistics for bull spermatozoa (Table 

 13.12). Expressed on a per sperm basis, the 

 energy, in ergs, calculated for substrate 

 utilization and heat production indicate a 

 wide thermodynamic safety factor in the 

 balance sheet between energy generated and 

 that required. 



In Rothschild's exacting study (1959) in 

 which he has demonstrated the changes in 

 sperm heat production with variations in 

 environmental factors, including pH, tonic- 

 ity, and centrifugation, attention is drawn 

 to the narrow margin between the free- 

 energy change of anaeorbic glycolysis which 

 is associated with ATP synthesis and the 

 energy expenditure involved in flagellation. 

 The data suggest that in bull sperm under 

 anaerobic conditions the rate of ATP syn- 

 thesis does not keep pace with that of ATP 

 hydrolysis. 



Although adequate data are available for 

 the ATP-splitting activity of sperm frag- 

 ments and siierni extracts (see Nelson, 1954; 

 Burnasheva, 1958), the rate of ATP hy- 

 drolysis in whole sperm is difficult to assess, 

 inasmuch as the value of inorganic phos- 

 phate liberated is the net result of hydrol- 

 ysis over synthesis or the phosphorylation of 

 ADP. This is clearly indicated in Table 

 13.12, in which the energy from ATP-split- 

 ting is seen to be insufficient for the energy 

 requirements of movement. This procedural 

 quandary was noted by Lardy, Hansen and 

 Phillips (1945) who demonstrated in aero- 

 bic suspensions of bull sperm an increase in 

 nucleotide-phosphate release in the presence 

 of cyanide, an inhibitor of phosphorylation 

 processes. 



G. BIOSYNTHETIC ACTIVITY 



Although spermatozoa are generally re- 

 garded as fully differentiated by the time 

 they reach the epididymis, some questions 

 have arisen with respect to their biosyn- 



