182 



LEONARD NELSON 



"interdigitation" and sliding, although the two sets of fibers involved 

 unquestionably differ in their solubility characteristics. Muscle spe- 

 cialists caution that even though a motile system possesses contractile 

 elements which exhibit ATPase activity, this evidence alone does 

 not justify the inference that the system is a muscle. Nevertheless, the 

 judicious application of muscle methodology to sperm investigations 

 may yield constructive information. For example, Burnasheva (1958), 

 after treating bull sperm with known actomyosin extractants ob- 

 tained "spermosin," a substance which on the basis of its reactions 

 with actin and ATP would be classified as a myosin-like protein (Fig. 

 8). In fact, myosin antibodies react to some degree with rat sperm at 

 the electron microscope level. Extraction of the frozen-dried sperm 

 with 50% glycerol does not appreciably diminish this reactivity, 

 while subsequent treatment with the actomyosin extractants abol- 



% 



'\ 



ACTOSPERMOSIN 



ACTOMYOSIN 



~~ 



~~ 



© © (D © © © © © 



Fig. 8. Viscosity changes with complex formation and addition of 

 ATP in system composed of extracted bull sperm protein and rabbit 

 muscle actin; analogous reactions of actomyosin shown at right. 1, F-actin; 

 2, spermosin; 3, spermosin + F-actin (ratio 12:1); 4, spermosin + F-actin 

 + ATP (4.23 X 10- 4 Af); 5, myosin; 6, myosin + F-actin (ratio 2:1); 7, 

 myosin + F-actin + ATP (4.23 X 10~ 4 M). (Redrawn from Burnasheva, 

 1958.) 



