210 FREDERICK G. E. PAUTARD 



OSCILLATION OF GELS 



A phenomenon that appeared to be peculiar to flagellar gel speci- 

 mens was the sudden commencement of rhythmic oscillation of a 

 portion of the specimen in certain circumstances. This activity was 

 very sporadic and seemed to depend on critical conditions for suc- 

 cess. In general, the concentrations of ATP were higher (0.008iU) 

 than those normally used (0.003AI), the pH was above neutrality 

 (7.4 or thereabouts), and the concentration of KC1 was less than 

 usual (about 0.05M). In these circumstances, the gel specimen 

 changed shape as usual, but sometimes part of the gel envelope ex- 

 tended and contracted in a regular manner, a slow extension fol- 

 lowed by a sharp shortening twitch and a further extension, and so 

 on. A typical "twitch" of this kind of a gel from trout sperm flagella 

 is shown from a 16-mm cine record in Fig. 10. In the frames at 10a, 

 10b, and 10c, the extension of a portion of the gel envelope over 5 

 min can be seen. The frame at \0d shows the sudden change in posi- 

 tion of the gel extension (indicated by the arrowing) 6 sec (3 frames) 

 later. The complete event covers about 10 sec (5 frames), but the 

 speeding-up of the time lapse exposure during projection makes the 

 event appear as a sudden twitch of the gel. This kind of activity has 

 been observed for one or more areas of a specimen, but it occurs at 

 irregular intervals only and in occasional specimens from each prepa- 

 ration. 



Sometimes, however, the oscillatory behavior is more regular, and 

 two observations are drawn in the series in Fig. 11A and B. In the 

 first event shown in Fig. 11 A, a filamentous projection of the gel 

 envelope showed 16 cycles of extension and retraction with a period 

 of 5 sec, while in another case (the longest recorded) no fewer than 

 51 cycles of 3 sec period were observed in a lobe-shaped projection 

 from a fresh gel preparation (Fig. 11B). 



CONTRACTILITY OF GELS PRECIPITATED WITH MYOSIN 



"Synthetic" actomyosin can be made from actin and myosin pre- 

 pared separately and mixed in various proportions before precipita- 

 tion. Not only can actin and myosin from the same animal be made 

 to combine, but actins and myosins from different animals can be 

 coprecipitated to form gels which shrink in KC1 solutions when ATP 



