Pressure/temperature interactions in relation to development of high pressure convulsions in ectotherm vertebrates

Effects of hydrostatic pressure per se (101 ATA) on energetic processes in fish

Nucleotides concentrations (ATP, ADP, AMP) have been measured in brain and muscle of eels exposed to 101 ATA of hydrostatic pressure (HP) for 3 hr. Survival times (ST) and oxygen arterial content (CaO2) have been measured in trouts exposed to HP = 101 ATA. The results show that at HP = 101 ATA, AMP increases (P less than 0.05) and ATP decreases (-12%; NS) in muscle but are not modified in brain; ST values are similar in normoxic and hyperoxic conditions, and CaO2 are similar at 1 ATA and 101 ATA of HP. It is concluded that HP tends to decrease aerobic production of energy. This phenomenon is not due to a failure in O2 transport from ambient medium to the cell but to a possible perturbation of the aerobic cellular processes leading to energy production (Krebs cycle and/or respiratory chain coupled to oxidative phosphorylation.

Effects of hydrostatic pressure on the motor activity of fish from shallow water and 900 m depths; some results of Challenger cruise 6B/85

1. Two species of benthic fish from 900 m depths (90 atm pressure), Trachyscorpia cristulata echinata and Synaphobranchus kaupi, are shown to be adapted to their normal, high ambient pressure. 2. Their condition improves when they are restored to their normal pressure after experiencing decompression in a trawl and they undergo convulsions at 150 atm. 3. This contrasts with the response of shallow water species (Salmo salar, Pleuronectes platessa, Anguilla anguilla and Gadus morhua) which convulse at 93-114 atm and become immobilized and rigid at 150 atm.

Effects of high hydrostatic pressure per se, 101 atm on eel metabolism

Oxygen consumption (MO2) of confined eels was measured at atmospheric pressure, 1 atm, and at 101 atm of hydrostatic pressure per se (HP). The tolerance of the eels to hypoxia was studied at the two experimental pressures. At atmospheric pressure, when oxygen partial pressure (PWO2) fell below the critical pressure, Pc = 22.4 +/- 1.95 Torr, there was a linear PWO2-related decrease in MO2. At maximal hypoxia, the eels survived for several hours by their efficient anaerobic metabolism. At 101 atm of HP, as soon as the experimental pressure was attained, a linear PWO2-related decrease in MO2 was observed at PWO2 levels much higher than those considered as critical at atmospheric pressure. The relation MO2 = f (PWO2) was similar to that observed at 1 atm when PWO2 less than Pc, that is, when aerobic metabolism was insufficient to ensure the eels' energetic requirement. Moreover, the eels tolerated hypoxia much less well at 101 atm of HP than at 1 atm. In conclusion, the exposure of eels to 101 atm of HP induced a sharp decrease in aerobic metabolism; then, at 101 atm, the energetic requirements must be ensured by anaerobic processes which produced lactates in plasma whose values were similar to those observed at 1 atm when PWO2 less than Pc.

Hydrostatic pressure effects on the central nervous system: perspectives and outlook

The high pressure neurological syndrome (h.p.n.s.) represents a complex of behavioural changes observed in all vertebrates when exposed to progressively increasing pressures. The general characteristics of the syndrome will be described and discussed in the light of alternative hypotheses about its aetiology and biophysical characteristics. Recent investigations in this area have dealt with the problem of the discretion of the several stages of the h.p.n.s. in their dependence on compression parameters; with the problem of individual variability in sensitivity to h.p.n.s. development, the genetic basis thereof, and its implications from the point of view of personnel selection; and with exploration of the characteristics and nature of the antagonism between high pressure and general anaesthetics in the production of h.p.n.s. symptoms. A final part of the discussion will deal with the current status of investigations into the problem of hazard assessment, and with the several possible approaches to controlling the h.p.n.s. associated hazards encountered in deep diving operations.

Anesthetic antagonism of the effects of high hydrostatic pressure on locomotory activity of the brine shrimp Artemia

The locomotory activity of small groups of brine shrimp (Artemia salina) was studied under conditions of high hydrostatic pressure, varying temperatures and exposure to several gaseous anesthetics. Both compression and exposure to anesthesia reduced the animal's swimming activity, while temperature increased or decreased activity as it was raised or lowered from ambient. The effect of the anesthetics was less during periods of simultaneous exposure to high hydrostatic pressure. It is concluded that pressure antagonism of anesthesia is demonstrable in invertebrate organisms and may represent a fundamental interaction of these parameters in biological systems.