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A Péqueux

Publications and source records attributed to A Péqueux.

8 recordsLinked to original sources
PubMed2004

Uptake of cadmium through isolated perfused gills of the Chinese mitten crab, Eriocheir sinensis.

Using the perfusion method, we compared cadmium accumulation and influx across the gills of the euryhaline Chinese mitten crab Eriocheir sinensis, exposed to 4.8 microM cadmium in the incubation medium (OUT). Cadmium influx was not observed across posterior gills while it ranged from 0.15 to 6.82 nmol Cd g(-1) gill w.w. h(-1) across anterior ones. For these respiratory gills, a strong increase (40 times) was observed when calcium was removed in both incubation and perfusion media while the lack of sodium in the perfusion medium resulted in a 46 times decrease. For crabs acclimated 15 days to artificial seawater, cadmium influx across anterior gills showed a 21 times decrease when compared with freshwater acclimated ones. On the other hand, after 3 h of perfusion, we detected cadmium accumulation in both types of gills, ranging from 3.8 to 68 nmol Cd g(-1) gill w.w. in anterior gills and from 2.1 to 39 nmol Cd g(-1) gill w.w. in posterior ones. Such accumulations represent between 61.3 and 100% of the total uptake of cadmium through the gills. From these results, we suggest that cadmium can penetrate more easily into the hemolymph space through the 'respiratory' type epithelium present in the anterior gills but absent in the posterior ones. This metal uptake is likely to occur at least in part through the same pathways as calcium. On the contrary, cadmium seems to be sequestered inside the posterior gills, perhaps in the cuticle of the salt-transporting type epithelium.

Animals↗
PubMed2000

High pressure and glycolytic flux in the freshwater Chinese crab, Eriocheir sinensis.

The hexose part of glycolysis has been studied in the freshwater Chinese crab Eriocheir sinensis exposed to high pressure (101 ATA, i.e. 1000 m depth) at 14 degrees C and in normoxic conditions. Glycolytic fluxes (from glucose, JA and from Glucose 6 Phosphate, JB) have been determined using NADH depletion during the conversion of dihydroxy acetone phosphate into alpha-glycerol phosphate. Measurements have been performed at 14 and 19 degrees C. Pressure exposure induces an increase of glycolytic flux and a decrease of the time needed for the transition from aerobic to anaerobic glycolysis. As a consequence pressure-exposed crabs have a higher potential to increase glycolytic flux than control animals at atmospheric pressure. It is concluded that high pressure known to alter numerous enzymes individually, can also modify an overall metabolic pathway.

Analysis of Variance↗
PubMed1981

[Presence of carbonic anhydrase in 2 fish of the Kerguelen archipelago, Channichthys rhinoceratus lacking hemoglobin, and Notothenia megellanica with a normal blood formulation].

An antarctic hemoglobin-free Fish, living in the Kerguelen archipelago, Channichthys rhinoceratus, is devoid of carbonic anhydrase in the blood but has a high content of this enzyme in the gills which appears to be twice that of another normal species living in the same area. Notothenia magellancia. This enzyme appears to play an important role in the osmoregulation of the Channichthyidae.

Acetazolamide↗
PubMed1980

Electro-mechanical properties of human erythrocyte membranes: the pressure-dependence of potassium permeability.

Electrical breakdown of cell membranes is interpreted in terms of an electro-mechanical model. It postulates for certain finite membrane areas that the actual membrane thickness depends on the voltage across the membrane and the applied pressure. The magnitude of the membrane compression depends both on the dielectric constant and the compressive, elastic modulus transverse to the membrane plane. The theory predicts the existence of a critical absolute hydrostatic pressure at which the intrinsic membrane potential is sufficiently high to induce "mechanical" breakdown of the membrane. The theoretically expected value for the critical pressure depends on the assumption made both for the pressure-dependence of the elastic modulus of the membrane and of the intrinsic membrane potential. It is shown that the critical pressure is expected at about 65 M Pa. The prediction of a critical pressure could be verified by subjecting human erythrocytes to high pressures (up to 100 M Pa) in a hyperbaric chamber. The net potassium efflux in dependence on pressure was used as an criterion for breakdown. Whereas the potassium net efflux was linearly dependent on pressure up to 60 M Pa, a significant increase in potassium permeability was observed towards higher pressure in agreement with the theory. The increase in the net potassium efflux above 60 M Pa was reversible, as indicated by measurements in which the same erythrocyte sample was subjected to several consecutive pressure pulses. Temperature changes in the erythrocyte suspension during compression and decompression were so small (less than 2 degrees C) that they could not account for the observed effects.

Erythrocyte Membrane↗
PubMed1978

Effects of high hydrostatic pressures on the activity of the membrane ATPases of some organs implicated in hydromineral regulation.

1. The effects of high hydrostatic pressures have been studied on the ATPases extracted from tissues implicated in iono- and osmoregulation of a frog and various teleostean fishes. Pressure affects enzyme activity in the same qualitative way, whatever the tissue and the species considered. 2. The Mg2+ ATPase activity is maximally enhanced at 250 kg/cm2. A slight inhibition is observed at higher pressures up to 1000 kg/cm2. 3. The (Na+ + K+)ATPase is little affected by low pressures but strongly inhibited at 500 kg/cm2 and more. 4. The results are discussed in terms of pressure effects on the recently described protein-lipid interaction linked to ATPase activity.

Adenosine Triphosphatases↗