286 INTRACELLULAR LUMINESCENCE 



ing pressure, provided correction is made for the decay of lumines- 

 cence during the intervening period of time, and at the higher tem- 

 peratures, provided correction is made also for a rate of thermal 

 inactivation of the system. 



Evidence of the transitory spikes and dips had been observed in 

 earlier studies with intact cells ( cf . discussion in Johnson, Eyring, and 

 Polissar, 1954), but quantitative records had not been made of them 

 or of the changes in intensity between steady-state levels. Data are 

 not yet available whereby, at various temperatures, quantitative com- 

 parisons can be made between spikes and dips in cells and extracts, 

 respectively. It appears that the transitory changes occur more rapidly 

 in the intact cells, as judged by the curves shown for 16° in Fig. 12. 

 The true magnitudes of the spike and dip in cells at 16° C are uncer- 

 tain because the half-second period of the recording instrument was 

 not fast enough to measure them accurately. Qualitatively, the results 

 obtained with extracts are remarkably similar to those obtained in 

 previous studies with intact cells. Quantitatively, the agreement is 

 close, at the one temperature for which data are presently available, 

 except that the time relations differ, i.e., changes in intensity follow- 

 ing changes in pressure take place faster in cells than in the extracts. 



Steady-state levels of intensity as a function of pressure at various 

 temperatures are plotted in Fig. 13, from the data of Fig. 12 and 

 similar experiments. For comparison, the pressure-temperature data 

 obtained with cells of P. phosphoreum in the initial study of this 

 relationship in luminous bacteria- (Brown, Johnson, and Marsland, 

 1942) are replotted in this figure. Corresponding effects of pressure 

 occur at temperatures a few degrees higher in extracts of A. fischeri 

 than in cells of P. phosphoreum, a difference that would be logically 

 expected on the basis of the difference in normal optimal tempera- 

 tures for luminescence in the two species, i.e., the normal optimum is 

 several degrees higher in cells and extracts of A. jischeri than in cells 

 of P. phosphoreum. As indicated earlier in the discussion, the bio- 

 logical effects of pressure may be expected to be related to the tem- 

 perature-activity curve of the specific system and conditions involved. 

 Thus, the increase in steady-state levels under pressure becomes pro- 

 gressively greater as the temperature is increased above the normal 

 optimum of the specific system. The most likely intei-pretation is that 



