242 1. lODOACETATE AND lODOACETAMIDE 



respiration is not simultaneously elevated much (Sbarra and Shirley, 1963). 

 It is even more surprising that pyruvate reverses to about the same degree 

 anaerobically, so its effects presumably are not mediated through the cycle. 



Streaming of Myxomycete Plasmodium 



This type of motility seems to be much more sensitive to inhibitors of 

 oxidations (e.g., cyanide or azide) than to iodoacetate. Allen and Price 

 (1950) found that low concentrations of iodoacetate stimulate the respira- 

 tion somewhat, 2 milf has no effect, and 5 niM inhibits 65%, but the flow 

 is not stopped until the Plasmodium disintegrates. The results of Ohta 

 (1954) are quite similar, except that 1 mM iodoacetate was found to inhibit 

 slightly. More recent work has emphasized that motility and motive force 

 are more sensitive to iodoacetate than is the respiration. In Physarum po- 

 lycephalnm a concentration of 1 mM has no effect on the respiration but 

 motihty is reduced significantly (Kamiya et al., 1957). Iodoacetate at 2 mM 

 almost abolishes motility and the protoplasmic viscosity increases so much 

 that measurements of motive force are impossible after 30 min. It has often 

 been assiuned that plasmodial movement is dependent on ATP, but Hatano 

 and Takeuchi (1960) reported that iodoacetate at 0.67 mM, which reduces 

 the motive force, has no significant effects on ATP or other phosphate frac- 

 tions, and that 1 mM seems to elevate the ATP level. The ATPase activity 

 is not altered by iodoacetate. 



Streaming of Avena Coleoptile Protoplasm 



The protoplasmic streaming in the epidermal cells of the coleoptile is 

 stimulated by 0.001 mM iodoacetate and relatively unaffected at 0.05 niM 

 unless the streaming is accelerated by auxin, in which case iodoacetate pre- 

 vents this stimulation (Sweeney and Thimann, 1942). Even up to 0.2 mM 

 there is no reduction of the auxin-accelerated streaming below the levels in 

 the absence of auxin. Malate is able to overcome partly the effect of iodo- 

 acetate on the auxin-induced streaming. This is a good example of how an 

 inhibitor can rather selectively depress an augmented activity without 

 significantly affecting the basal level of function, and such behavior leads 

 one to suspect that the pattern of metabolism is altered by the stimvilation. 

 Since 0.05 mM iodoacetate prevents growth completely, it is possible that 

 the interference with auxin-induced streaming is involved. 



Spermatozoal Motility 



Flagellar movement in general seems to depend on ATP and the usual 

 sources of ATP, but in bull spermatozoa the situation is not so clear. Lardy 

 and Phillips (1941) found that iodoacetate at concentrations of 0.25 mM 



