278 INTRACELLULAR LUMINESCENCE 



maximum luminescence intensity is lowered. Similar effects have been 

 obtained with the urethan inhibition of oxygen consumption and 

 methylene blue reduction by Rhizobium trifoUi (Koffler, Johnson, and 

 Wilson, 1947). The action of higher members of a homologous series 

 of carbamates on luminescence, however, apparently involves a mech- 

 anism different from the one just discussed (Johnson, Flagler, Simp- 

 son, and McGeer, 1951). 



Reversal of Narcosis by Increased Hydrostatic Pressure 



According to the theory briefly described above, narcotics such as 

 alcohol and urethan promote a reversible denaturation that involves 

 a large volume increase of reaction in going from the initial (native) 

 state to the final (denatured) state of an essential enzyme. It is not 

 surprising, on this basis, to find that the inhibition caused by these 

 drugs is partially counteracted by increased pressure. Figure 9 illus- 

 trates the results of applying hydrostatic pressure to aliquot portions 

 of a suspension of luminous bacteria containing different concentra- 

 tions of alcohol, at the normal optimum temperature where pressure 

 has little effect on the intensity of luminescence in the absence of 

 the drug. At low concentrations of alcohol, the inhibition is virtually 

 abolished by pressure. With higher concentrations, the effects of pres- 

 sure are more complicated, possibly because of multiple equilibria 

 involved in the action of alcohol (vide infra), but in each case the 

 amount of inhibition is reduced by pressure. It is interesting to note 

 also that the "optimum pressure" in the presence of alcohol is rever- 

 sibly shifted by as much as several thousand pounds per square inch, 

 depending upon the concentration of alcohol. 



Although the narcosis of animals is a much more complicated phe- 

 nomenon than the inhibition of bacterial luminescence, the mech- 

 anisms involved at the molecular level are not fundamentally different. 

 It is not surprising, therefore, that salamander and frog larvae, when 

 narcotized in water containing appropriate concentrations of alcohol 

 or urethan, recover their activity and swim in apparently normal man- 

 ner when the pressure is increased from atmospheric up to between 

 2000 and 5000 psi (Johnson and Flagler, 1951). Moreover, observa- 

 tions made thus far indicate a close correlation between the action 

 of pressure on the inhibition of bacterial luminescence and on the 



