HOWARD M. LENHOFF 229 



16. LooMis, W. F. 1954. Environmental factors controlling growth in livdra. ]. Exp. 



Zool. 126: 223-234. 



17. LooMis, W. F. 1955. Glutathione control of the specific feeding reactions of 



h\dra. Ann. N. Y. Acad. Sci. 62: 209-228. 



18. LooMis, W. F. and H. M. Lenhoff. 1956. Growth and sexual differentiation 



of hydra in mass culture. /. Exp. Zool. 132: 555-574. 



19. MoNOD, J. 1956. Remarks on the mechanism of enzyme induction. In Enzymes: 



Units of Biological Structure and Function, edited by O. H. Gaebler. 

 Academic Press, Inc., New York, pp. 7-28. 



20. Park, H. D. 1953. In \V. F. Loomis, reference 17, p. 211. 



21. ScATCHARD, G. 1949. The attraction of proteins for small molecules and ions. 



Ann. N. Y. Acad. Sci. 51: 660-672. 



DISCUSSION 



LANE: Would you care to speculate about the nature of the gluta- 

 thione-receptors, and their location? 



LENHOFF: I can only guess that the receptor is a very specific 

 protein, probably a lipoprotein on the cell membrane. The evidence 

 is not too good concerning the location of the receptors on Hydra. 

 Experiments using isolated parts of Hydra show that some are lo- 

 cated on the tentacles, and others on the hypostome. We tried to 

 localize the receptor by radioautography using glutathione. But 

 the glutathione washes readily off. 



SLAUTTERBACK: Aren't you inhibiting the oxidative enzymes 

 severely when \'0u get down to 6 degrees and thus reduce the gen- 

 eral motility of the animal? 



LENHOFF: No doubt we are slowing down many reactions by 

 lowering the temperature, but the limiting reaction is the one that 

 we think causes this delay in mouth opening. 



SLAUTTERBACK: Are these animals still moving around actively? 



LENHOFF: Yes. In assaying the feeding reflex, we observe mouth 

 opening, tentacle waving and contraction. All these movements 

 seem normal as does contraction after a mechanical stimulus. 



BURNETT: Maybe you could explain this preliminary experiment. 

 We placed hydra in a 10~^' M solution of glutathione and waited 

 until all of them had closed their mouths and discontinued their 



