Bernard Simon

Laboratory system enabling long-term exposure (⩾ 30 d) to hydrostatic pressure (⩽ 101 atm) of fishes or other animals breathing water

A high-pressure water-circulation system is described which enables fish (or other animals breathing water) to be maintained at pressures up to 101 atm for at least one month. A typical experiment, measuring the oxygen consumption of the eelAnguilla anguilla over a period of 31 d, revealed a metabolic acclimation to pressure in this fish. This system has numerous advantages; e.g. it is possible to reproduce in situ environmental conditions at depth, thus enabling the study of the problems of pressure adaptation, and also to simulate vertical migrations of animals, allowing the study of associated physiological phenomenon.

Hydrostatic pressure induces a state resembling histotoxic hypoxia in Anguilla anguilla

Abstract 1. 1. Energy metabolism (substrates, enzyme activities) was studied in white muscle and liver of yellow freshwater eels ( Anguilla anguilla L.) exposed for 3 hr to 100 atm hydrostatic pressure in normoxic conditions and at constant water temperature. 2. 2. In the two tissues explored, a decrease occurred in glycogen content (the anaerobic substrate) and an accumulation of total fatty acids (exclusive aerobic substrate). Concomitant changes in substrate contents, decreased of cytochrome c oxidase activity and increased lactate dehydrogenase activity were observed. 3. 3. When complemented with observations (ATP, oxygen consumption) from previous studies, results were in agreement with an alteration of aerobic energy production and an activation of the anaerobic pathway. In fish, hydrostatic pressure appeared to induce a state resembling histotoxic hypoxia.

Effects of Hydrostatic Pressure on Energy Metabolism and Osmoregulation in Crab and Fish

This review will focus on the effects of hydrostatic pressure on the oxidative metabolism and on the energy production of the eel Anguilla anguilla, in comparison with the results of investigations conducted on the other powerful euryhaline species, the chinese crab Eriocheir sinensis. Anguilla and Eriocheir were chosen as being both aquatic ectotherms with comparable life modes, the eel being however “preadapted” to high pressure while the crab normally never encounters high levels of pressure during its life cycle. Comparison between both species should lead to better knowledge of the biological effects of hydrostatic pressure per se. Experimental evidence suggests that the oxygen consumption ṀO2 decrease observed in both animal species during exposure to 101 ATA hydrostatic pressure and which follows a transient increase, likely results from a decrease in O2 use at the cell level. That idea of an alteration of aerobic metabolism during the first hours under pressure is substantiated by a set of experiments on the eel. However, results indicate that, after some days under pressure, the shallow water fish is quite able to acclimate perfectly to high pressure. The hypothesis that pressure induces a state resembling histotoxic hypoxia during the first hours of exposure is put forward and discussed. The second part of the review focuses on some results showing that osmoregulation is also concerned with hydrostatic pressure. Results obtained on the freshwater eel clearly establish the occurrence of a Na+ balance impairment at the tissue level induced by a long-term (30 days) exposure to pressure. It is interesting to point out that this impairment occurs at the same time when a new state of energetic metabolism results from adjustments of intertissue coupling of anaerobic and aerobic metabolisms induced by pressure. It is shown that the physiological processes involved in the control of the hydromineral balance in the chinese crab (which never experiences high-pressure exposure in the course of its life cycle) are outstandingly resistant to pressure by comparison with other crustaceans like the crayfish and the shore crab. Disturbances in hydromineral balance and energetic metabolism in the chinese crab are rapidly resorbed and adjusted to a new state of activity.

High hydrostatic pressure (101 ATA) changes the metabolic design of yellow freshwater eel muscle

The glycolytic pathway has been studied in the white muscle of yellow freshwater eel (Anguilla anguilla L.) exposed to high hydrostatic pressure (101 ATA) for 1 month. Using appropriate substrates and auxiliary enzymes to drive the flux towards glycerol phosphate, fluxes of glucose (JA) then of glucose 6-phosphate (JB) have been measured. The maximum acceleration during the transition from JA to JB was measured as the response time, tm; the metabolic reprise, which gives information about the rapidity of a given metabolic change, was calculated as r (JB:JA):tm, i.e the ratio of the fluxes over the response time. An estimation in vivo has been performed for each parameter. Acclimatization to high pressure induces a significant increase in the fluxes (PB0.05), but the ratio JB:JA remains constant. As the metabolic response time tm decreases, there is a significant increase in the metabolic reprise r (60%, PB0.01) which means that muscle from acclimatized fish has the capacity to increase the glycolytic flux 1.6-times more than control fish muscle. These modifications in the metabolic design in pressure acclimatized fish are discussed and the hypothesis is raised that pressure may optimize energy production to prepare eel physiology to the new environment encountered during migration from freshwater to seawater and thus to a new type of energy demand.

Effects of long-term exposure to 101 ATA hydrostatic pressure on blood, gill and muscle composition and on some enzyme activities of the FW eel (Anguilla anguilla L.)

Abstract 1. 1. The study was set up to investigate the effects of long-term exposure (30 days) at 101 ATA of hydrostatic pressure (HP), in normoxic conditions and at constant temperature, on enzyme activities involved in energy production and ionic transfers. 2. 2. Measurements of activities of LDH, PFK, IDH and CPK in liver, red and white muscle seem to show that HP induces an improvement of aerobic pathway in red muscle and anaerobic pathway in white muscle; in liver no significant change is observed. 3. 3. At the same time, there appears an increase of plasma Na + , Cl − and Mg 2+ contents; in muscle and gill, only Na + and Cl − increase under pressure. Concomitantly with the changes in ion contents, there is a decrease in maximum activity of gill (Na + + K + )ATPase and Mg 2+ ATPase activity. 4. 4. The results agree with a Na + balance impairment occurring at the tissue level at the same time when a new state of energetic metabolism results from adjustments of intertissue coupling of anaerobic and aerobic metabolisms induced by a long-term exposure to hydrostatic pressure.

Muscle energetics in yellow freshwater eels (Anguilla Anguilla L.) exposed to high hydrostatic pressure (101 ATA) for 30 days

Abstract 1. 1. Yellow freshwater eels were exposed for 30 days to hydrostatic pressure, HP (101 atmospheres absolute, ATA). Enzyme activities, nucleotides and substrates were measured in white and red muscle of pressure-exposed and control fish. 2. 2. After 30 days under pressure, enzymes activities, substrates and nucleotide tissue content are similar or increased when compared to control fish. 3. 3. These resuts show that the freshwater eel is ablet to acclimate to high pressure and to improve P O ratio. 4. 4. The process of pressure acclimation is not an adaptation to the energetic state observed after some hours under HP, but a return to that observed before compression.

Ethanol concentrations in plasma and tissues of freshwater eel (Anguilla anguilla) exposed to 101 ATA of hydrostatic pressure

Abstract 1. 1. Ethanol concentrations have been measured in liver, white and red muscles, and plasma of eels exposed for 3 hr at 101 ATA hydrostatic pressure (HP) in normoxic (series I) and anoxic (series II) conditions. 2. 2. In normoxic conditions, only trends to increase ethanol concentrations are observed, mainly in plasma, under pressure. In anoxic conditions, ethanol concentration significantly increases (P 3. 3. The obtained results are in agreement with an ethanol production induced by the particular hypoxia (histotoxic hypoxia) due to pressure and are discussed at a metabolic point of view.