114 FACTORS AFFECTING CILIARY ACTIVITY 



the action of ACh on the cilia was a primary and not a secondary- 

 effect. 



Experiments on the effect of ACh on ciliary movement have 

 also been carried out on some other animals. For example, in 

 coelenterates the cilia of the tentacles of Metridium were slowed 

 by ACh (10-* and 10"^ g/ml) (ten Cate, Coomans and Walop, 

 1955), while in protozoa, both flagellates and ciliates have been 

 shown to have acetyl cholinesterase activity. Biilbring, Lourie 

 and Pardoe (1949) estimated that Trypanosoma rhodesiense 

 contained 2-4 to 8-6 /xg of ACh/g (wet weight) of tissue, and 

 demonstrated in vitro synthesis of ACh using trypanosome 

 material ; they could neither detect nor obtain synthesis of ACh in 

 the non-flagellate Plasmodium. In the ciliate Tetrahymena 

 pyriformis Seaman (1950) and Seaman and Houlihan (1951) have 

 shown the presence of an ACh -esterase which is inhibited by 

 eserine (10"'') and diisopropylfiuorophosphate (DFP) (10"' mol). 

 The movement of living Tetrahymena is reversibly inhibited by 

 both eserine and DFP at a concentration of 4xl0~^mol; this 

 seems rather a high concentration, but it does not affect the rate 

 of glycolysis of the cells. Seaman (1951) has further demonstrated 

 by differential centrifugation that the ACh-esterase activity is 

 located in the fibrillar system of the pellicle. Although Tibbs 

 (1960) was able to demonstrate ACh-esterase activity in sperm 

 of the trout and perch, he could not detect any activity in homo- 

 genates of Polytoma uvella, Polytomella caeca or Tetrahymena 

 pyriformis. 



The effect of ACh on these protozoan cilia may not be very 

 specific, for it has also been found to affect the reversal response 

 in Paramecium. Miiller and Toth (1959) found that both 

 ACh bromide and eserine sulphate affect the duration of the 

 reversal response caused by the addition of ^^ mol KCl. At low 

 concentrations of ACh (lO"*) and eserine (lO^^ and 10"^) the 

 duration of reversal of the ciliary beat was lengthened by up to 

 200 per cent, while at higher concentrations the response did not 

 last as long as in the control animals. Bayer and Wense (1936a) 

 have extracted ACh from Paramecium. 



Evidence for a direct effect of ACh on ciliary beating is not 

 very convincing in spite of all these reports. The effect of 

 adrenaline, and also of serotonin in molluscs, is larger and more 



