72 



ROLAND FISCHER 



■■ ;"15Pw£ 



Fig. 3. Tadpoles of Xenopus levis Daudin 



biologically active substances may produce their specific effects by acting on 

 the enzyme which inactivates them." (Zupancic, 1953). We might assume then 

 that adsorption of our compounds on wool simulates the combination of the 

 "cationic head"-s of active compounds with the anionic sides of the cholines- 

 terase receptor. Some further data seem to support such an assumption. Janus 

 green B, a very potent inhibitor of cholinesterase, as well as certain quaternary 

 ammonium compounds, exhibit an affinity for wool (especially the quaternaries 

 display, the highest affinity, 7.0 mMol. X 10 _2 /gm. wool). 



Since Zupancic (1953) and Smith et al, (1952) among others, claim that 

 certain quaternaries, especially those antagonistic to tubocurarine, act by in- 

 hibiting cholinesterase, we suggest that wool protein in this study might be re- 

 garded as a model for the latter enzyme. 



According to Bergmann and Shimoni (1953), cholinesterase behaves towards 

 cations like a cation exchanger. Therefore, when the enzyme is built into the 

 nerve membrane, the latter will acquire properties of a "permselective" mem- 

 brane. 



It is clear, state Bergmann and Shimoni (1953), that in the nerve membrane 

 the resting potential is re-established long before the ion-exchange processes 

 are finished. Therefore, the recovery process must be dependent on a chemical 

 change in the membrane itself. A special mechanism must be available to re- 

 cover the resting conditions through readjustment of the original concentration 

 and activity of H+ in the hydrated membrane phase. This could be done by an 

 appropriate buffer, which would not prevent the original "acidification" re- 

 quired by the breakdown of selective permeability, but would react within a 

 measurable, though very short time. The usual buffers would not serve this 

 purpose. It is necessary to look for a fast chemical "buffering" reaction, cata- 



