ADENOSINE TRIPHOSPHATE 109 



of Sperm tail ATP-ase is dependent on the concentration of Mg+"^ 

 and Ca++ and can be inhibited by salyrgan. 



Models of cilia and flagella have been prepared by the glycerine- 

 extraction techniques pioneered by Szent Gyorgyi (1949) and 

 Weber (1953) in work on the part played by ATP in muscle 

 contraction. Glycerine -extracted models of flagella of sperma- 

 tozoa and trypanosomes made by HoflPmann-Berling (1954, 1955) 

 were found to show a spontaneous alternation of contraction and 

 relaxation when ATP was added. This beating activity was 

 suppressed by small quantities of ATP-ase inhibitors like salyrgan 

 (5xlO~^) and germanin (2x10""^). Similar models of sperm of 

 the squid and various mammals have been prepared by Bishop 

 (1958a, c, f) and by Bishop and Hoffmann-Berling (1959). They 

 all responded to ATP, and the mammalian sperm models also 

 contracted with ADP and inosine triphosphate (ITP), but not 

 with pyrophosphate or other inorganic ions. In all cases the 

 response was a rhythmic flagellation with a similar frequency and 

 amplitude to that in fresh sperm. In this more recent work, no 

 correlation was found between ATP concentration and either 

 frequency or amplitude, although Hoffmann-Berling (1954) 

 believed that ATP concentration controlled the frequency of 

 contraction. 



Alexandrov and Arronet (1956) found that cilia of the frog 

 palate epithelium which had been extracted with glycerine for 

 several days were immobile until ATP was added, but then burst 

 into activity, with a rate of beat which was often similar to that of 

 normal cilia. Rhythmic contraction occurs even when the cilia 

 are isolated from the basal protoplasm. The reactivated cilia 

 sometimes beat synchronously, but the normal metachronal 

 co-ordination was lost. Cilia of Vorticella could also be reactivated 

 with ATP after being frozen and dried (Levine, 1959). 



Perhaps the most interesting thing about these reactivated 

 models of cilia and flagella is that they show repeated contractions, 

 while muscle models only show a single contraction; there is 

 relaxation of the cilia models but not of muscle models. It seems 

 that the ability to perform alternate contractions and relaxations 

 must be built into the contractile mechanism of these organelles, 

 for much of the cilium structure, including the cell membrane 

 with its special properties of selective permeability, is destroyed in 



