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.

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.

Perfusion of gills isolated from the hyper-hyporegulating crab Pachygrapsus marmoratus (Crustacea, Decapoda): adaptation of a method.

This paper reports the adaptation of a branchial perfusion technique to the gills of the small hyper-hyporegulating crab, Pachygrapsus marmoratus. The physiological quality of the preparation has been established and preliminary measurements of the transepithelial potential difference (PD) and sodium fluxes were reported. A clear-cut distinction has to be made between anterior and posterior gills. With symmetrical bathing conditions (same saline on both sides of the epithelium), a significant transepithelial PD was measured only in posterior gills isolated from crabs acclimated to dilute sea water. This hemolymph-side negative PD is shown to require biological energy and to be sensitive to ouabain. Na+ influx was larger than efflux, indicating the occurrence of a net inward of Na+. The active nature of the Na+ influx was established.

Effects of ions substitutions and of inhibitors on transepithelial potential difference and sodium fluxes in perfused gills of the crab Pachygrapsus marmoratus.

With the same saline on both sides of the epithelium, a spontaneous inside negative transepithelial potential difference (PD) was measured in perfused posterior gills of the euryhaline crab Pachygrapsus marmoratus acclimated to dilute sea water. The origin of the PD and the transport properties of the epithelium were investigated by ionic substitutions and by application of inhibitors. Diffusion of Na+ and Cl- ions at the apical side contributes to the establishment of the PD. Sodium cyanide (10(-2) M) added to the perfusion and incubation media almost completely inhibited the transepithelial PD and considerably decreased the Na+ influx. Internally perfused ouabain (5.10(-3) M) halved the PD and the Na+ influx but had no effect on the Na+ efflux. Externally applied amiloride (10(-3) M) also reduced the Na+ influx by 27%. All inhibitions were concentration-dependent. From these results, it has been concluded that the transepithelial PD and Na+ influx are, at least partly, generated by active, metabolic energy-requiring processes. The effect of ouabain supports the existence of a Na+/K+ exchange mechanism linked to the presence of Na(+)-K+ ATPase in the basolateral membrane of posterior gills. The effect of amiloride is discussed.

Ultrastructural changes in the gill epithelium of the green crab Carcinus maenas in relation to the external salinity.

Observation of semi-thin and ultrathin sections performed in the gills of green crabs (Carcinus maenas) kept in 100% and in dilute 30% sea water respectively reveals marked differences between the six anterior and the three posterior pairs of gills. The anterior gill lamellae are almost entirely lined by a thin pavement epithelium (0.9 to 3 mum thick) which does not undergo any noticeable change when crabs are acclimated from full to dilute sea water. This supports the view it is chiefly involved in the respiratory function. In addition to the pavement epithelium, the posterior gills exhibit small areas corresponding to a thick prismatic epithelium (10 mum) the ultrastructure of which is similar to that of most of the so-called 'salt transporting epithelia'. When submitted to reduced external salinity, this epithelium undergoes structural changes consisting of elaboration of an extensive apical plasma membrane infolding system, enlargement of the subcuticular compartment and close association of mitochondria with basolateral membrane infoldings. Pilaster cells exhibit ultrastructural features of either thin (respiratory) or thick (salt transporting) epithelial differentiation according to their localization within the gill. Their peculiar organization suggests they ensure, in addition, mechanical reinforcement of the gill lamellae against blood hydrostatic pressure. The fact that salt-transporting epithelium areas do not exceed, at most, 30% of the total lamellar surface is probably related to the weak osmoregulatory capabilities of the shore crab.

The ionic composition of the plasma and erythrocytes of deep sea fish.

This paper reports measurements of the plasma osmolarities, the main inorganic ions and the concentrations of plasma proteins in nine species of deep sea fish from depths of 900-4,000 m. Chloride and magnesium values are high compared to those of shallow water fish. These ions may be contaminants from sea water either contributing to, or resulting from, the animals' moribund condition. They may also contribute to the failure of isolated erythrocytes to show ionic regulation even after being restored to their normal high pressure.

A morphological study on gills of a crab acclimated to fresh water.

The gills of the fully euryhaline Chinese crab Eriocheir sinensis were studied by light and electron microscopy. In these Phyllobranchiates, the gills consist of a double row of lamellae extending laterally from a central shaft. Haemolymph flow pattern inside the gill is described and the existence of a complex secondary vascularization inside the platelets is reported. It is shown that important differences exist between the ultrastructure of the three anterior and the three posterior pairs of large gills. The epithelium of the posterior gills is much thicker and possesses an extensive elaboration of the plasma membranes in the form of infoldings, crypts and interdigitations, along which are packed numerous mitochondria. The presence of such a complex membrane system opening to the extracellular space and closely associated with mitochondria is common to all salt-transporting tissues. This study corroborates the idea that the posterior pairs of gills of Eriocheir sinensis are the only ones implicated in active Na+ uptake when the crab lives in dilute aquatic environment. The epithelium of anterior gills is much thinner and the cells poor in intracellular organelles. It seems to be involved essentially in respiration. Thus this work clearly corroborates the existence already suggested by physiological approach of a functional difference between the different pairs of E. sinensis branchiae with respect to their participation in the respiration and in the regulation of the blood ions content. Common to both types of gills is the presence of a lamellar septum separating the haemolymph space into two compartments. The part played by that structure in determining the pattern of haemolymph flow, together with periodic bridges forming pillars across the haemolymph space, is emphasized.

[Presence of carbonic anhydrase in 2 fish of the Kerguelen archipelago, Channichthys rhinoceratus lacking hemoglobin, and Notothenia megellanica with a normal blood formulation]. / La présence d'anhydrase carbonique chez 2 poissons de l'archipel des Kerguelen, Channichthys rhinoceratus exempt d'hémoglobine et Notothenia magellanica de formule sanguine normale.

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.

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.

Pressure-induced variations of K+-permeability as related to a possible reversible electrical breakdown in human erythrocytes.

Above a hydrostatic pressure of about 600 b a pronounced reversible increase in the net K+-efflux from human erythrocytes is observed. The effect is explained in terms of an electro-mechanical compression of the membrane, resulting in a reversible breakdown of the membrane.

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.

Effect of various ions on ATP determinations using the "luciferine-luciferase" system.

Various salts and buffers used in routine as part of the ATP extraction procedues induce an important inhibition of the peak light emission produced by the "luciferine-luciferase" system. The nature of the anion is more important in determining the inhibitory effect than the nature of the cation. The series obtained when placing the anions studied by order of increasing effectiveness is as follows Ac- less than Cl- less than I- less than ClO4-. KClO4 appears thus as a strong inhibitor of the enzyme activity. It appears moreover to act competitively with respect to ATP, one mole of inhibitor binding per mole of ATP active site. These results are discussed in connection with the use of the "luciferine-luciferase" system for ATP and other energy-rich compounds' concentration measurements.

Polarization variations induced by high hydrostatic pressures in the isolated frog skin as related to the effects on passive ionic permeability and active Na+ transport.

The effects of a wide range of hydrostatic pressures (from 50 to 1000 kg/cm2) have been investigated on the spontaneous potential difference (PD), the short-circuit current (SCC) and the activity of the membrane ATPases of the isolated abdominal skin from the frog Rana temporaria L. Two types of variations in PD are induced by pressure changes: short and transient potential variations which appear to be related to the pressure change (compression and decompression) and lasting variations which persist as long as pressure is applied and whose nature appears to be related to the pressure magnitude. Long-lasting potential changes have particularly been investigated. At pressures lower than 500 kg/cm2, the skin potential increases while a pressure over 500-600 kg/cm2 induces a depolarization. Both variations consecutively occur at 500 +/- 100 kg/cm2. These effects of pressure have been shown to be reversible up to about 800 kg/cm2. The question of the origin of the potential changes is discussed and it is proposed that the lasting hyperpolarization results from an effect on the passive permeabilities to Na+, K+ and Cl- ions inducing in turm a secondary readjustment (stimulation) of the Na+ active transport while the depolarization at high pressures reflects a direct inhibition of the Na+ pump. These interpretations are supported by experimental data on the effects of pressure on the short-circuit current and on the activity of the skin (Na+ + K+) ATPase.