238 J. tibbs 



ing motility since Hoffmann-Berling (1958) has also shown that in 

 glycerized models prepared from the stalks of Vorticella gracilis cal- 

 cium ions but not ATP induce contraction, whereas the addition of 

 ATP to the contracted models causes relaxation and with calcium 

 ions still present sets up a cycle of alternate contraction and relaxa- 

 tion. 



In the case of the sperm tail it is not easy to say whether ATP is 

 split during a contractile process or not. The extraction and behavior 

 of functional material should do something to clarify the situation. 

 Pautard (1957) has described an extract from perch sperm flagella 

 which forms a gel contracting or extending in ATP depending upon 

 whether potassium chloride is present or not. Bishop (1958a) has ob- 

 tained from bull testes a preparation which hydrolyzes ATP and 

 undergoes superprecipitation in the presence of ATP and magnesium 

 ions. This last experiment seems to link contraction with the ATP- 

 splitting step. 



In the case of muscle, inhibition of the ATPase by either natural 

 or artificial systems results in relaxation, and activation of the enzyme 

 in the presence of substrate produces contraction. It seemed likely 

 that by inhibiting the flagellar ATPase before the sperm had been 

 allowed to swim, it might be possible to prepare tails in which all the 

 contractile material was in the same state, that immediately preceding 

 ATP breakdown. Activation of the enzyme of this preparation in the 

 presence of ATP might then produce a second state, the two states 

 being distinguishable from each other by a change in flagellar volume. 

 There existed then the possibility of detecting such a difference by 

 the optical method of Cleland (1952), which has been used to meas- 

 ure the swelling of mitochondria. 



The first requirement for this experiment was a system which 

 could be used to inhibit the flagellar enzyme reversibly. p-Chloro- 

 mercuribenzoate, found by Engelhardt and Burnasheva (1957) to in- 

 hibit an ATPase preparation from sperm, did not produce a high 

 enough degree of inhibition to warrant a more detailed investigation 

 into the reversibility of its action. 



In the absence of activator, the sperm tail enzyme has a much re- 

 duced activity (Tibbs, 1959). Pyrophosphate and ethylenediamine- 

 tetraacetic acid (EDTA) both inhibit the ATPase of muscle presuma- 

 bly by the removal of activator, although in the case of EDTA the in- 



