REACTIVATION OF EXTRACTED SPERM CELL MODELS 



259 





o 



IO 

 ( M / 



IO 



IO " IO" 

 Mg + + Concentration (M/l) 



Fig. 5. Frequency as a function of Mg++ concentration in sea urchin 

 (O) and starfish # sperm models; 1 mM ATP, 10 mM histidine, pH 

 7.5. (After Kinoshita, 1958.) 



both ions sustain flagellation equally well. A similar monovalent 

 cationic indifference was noted by Nelson (1955) in his study of 

 ATPase activity of clam flagella and is consistent with evidence for 

 ionic requirements of comparable muscle preparations (Szent-Gyor- 

 gyi, 1951). 



Whereas reactivation of insect and mammalian sperm models re- 

 quires only exogenous nucleotide and Mg+ + , starfish and sea urchin 

 sperm need an additional factor, a plasticizing or chelating agent such 

 as histidine, cysteine, EDTA, or pyrophosphate (Fig. 6.) (Kinoshita, 

 1958). This suggests that a relaxing type of substance is essential to 

 the invertebrate sperm model as extracted; such an agent, along with 

 ATP, is necessary for oscillation. Kinoshita (1959) subsequently iso- 



