THE INFLUENCE OF PRESSURE, TEMPERATURE AND URETHANE ON THE LUMINESCENT FLASH OF MNEMIOPSIS LEIDYI

Abstract

Using small segments of excised meridional canals of Mnemiopsis leidyi, luminescent flashes induced by square wave electrical pulses of precise voltage and duration have been accurately recorded with the aid of a photomultiplier-amplifier and dual beam cathode ray oscillograph. Analyses of more than 8000 flashes, under various conditions of temperature, hydrostatic pressure, urethane concentration, and frequency of repetitive stimulation, have led to the following generalizations. 1. The time course of luminescence intensity in an individual flash at a given temperature is not appreciably altered by increased pressures which greatly reduce the flash maximum. 2. The latent period between time of stimulation and onset of response is like-wise not significantly altered by pressure, within the sensitivity of the methods employed. 3. In a series of consecutive flashes, at frequencies of one per 3 seconds to 4 per second, the initial effect of increased pressure is always to reduce the maximum intensity of the flash; detectable reductions are caused by relatively slight pressures, of less than 100 psi. 4. A series of pressure increases in increments of several hundred psi is less inhibitory on flash intensities than a sudden increase to the highest pressure involved. Sudden increases of 1000 to 5000 psi temporarily abolish the flash, whereas with gradual increases to these pressures, the flash may persist, though at reduced intensity. 5. Under a sustained pressure, a process of adaptation frequently occurs, whereby on continued repetitive stimulation the initially inhibited flash recovers and then facilitates, sometimes to much higher intensities than prior to compression. 6. On sudden decompression, part way or all the way to. atmospheric pressure, the initial effect is always an increase in flash intensity over that occurring under pressure, or sometimes over that occurring prior to compression. The only exception occurs when excitability has disappeared completely, as occasionally happens. 7. The recovery process after pressure assumes a variety of unpredictable patterns; in some instances the first one to three flashes are excessively high ("over-shoot"), followed by rapidly decreasing flash maxima, whereas in other instances a gradual facilitation and decline take place. 8. Excess luminescence intensity in the recovery phase is independent of maintaining repetitive stimulation during the preceding period under pressure. 9. Excitability that has been lost through fatigue or unknown causes can be restored in some instances by subjecting the specimen to pressures of 3000 to 5000 psi for periods of 1 to 5 minutes. 10. Qualitatively the same results of pressure are observed at various temperatures between 15 and 35° C. Any definite influence of temperature on the effects of pressure is obscured by variations in the quantitative effect of a given pressure on different specimens and on the same specimen in different physiological states. 11. Urethane, in concentrations between 0.05 and 0.5 M, causes a progressively increasing reduction of flash maxima with duration of exposure of the drug, and at rates that increase with drug concentration and temperature. Qualitatively the same phenomena are observed with respect to the influence of pressure on the flash in the presence as in the absence of urethane. 12. The Mnemiopsis photogenic system is particularly sensitive to destructive effects of urethane and of elevated temperatures, thereby obscuring the possible existence of reversible thermal inactivation reactions and the possible influence of pressure thereon.