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Biomedical subjects

C Leray

Publications and source records attributed to C Leray.

At least 55 records · Page 3Linked to original sources
PubMed1987

Topological distribution of aminophospholipid fatty acids in trout intestinal brush-border membrane.

The transbilayer distribution of aminophospholipids in trout intestinal brush-border membrane has been investigated using trinitrobenzene sulfonic acid (TNBS). In the middle intestine, phosphatidylethanolamine (PE) is symmetrically distributed between the two leaflets while 68% of the phosphatidylserine (PS) are located in the inner membrane leaflet. In the posterior intestine, 64% of the PE and 69% of the PS are located in the inner membrane leaflet. When asymmetrically distributed, the inner species of PE and PS have a higher content of 22:6(n-3) than the outer ones. This asymmetric distribution of docosahexaenoic acid in trout intestinal brush-border membrane might be related to the rod-like shape of the microvillus membrane and to its metabolism to hydroxylated derivatives.

Animals↗
PubMed1987

Influence of lipid environment on insulin binding in cultured hepatoma cells.

The influence of alterations of plasma membrane physico-chemical properties on insulin binding have been characterized in an insulin-sensitive rat hepatoma cell line adapted to grow for several generations in culture medium enriched with linoleic acid (18:2) or with 25-hydroxycholesterol. The cells took up 18:2 and 25-hydroxycholesterol added to the culture medium, without exhibiting any sign of intolerance or intoxication. These compounds respectively increased and decreased membrane fluidity at 37 degrees C. The cells demonstrated extensive changes in insulin binding parameters in response to experimental modifications of their membrane lipid composition. When determined at 4 degrees C, insulin receptors were present in the control cells at 136,000 sites/cell but this fell to 111,000 (P less than 0.05) in cells enriched in 18:2, and rose to 176,000 (P less than 0.001) in hydroxysterol-grown cells. According to a two-site model, the main effect of 18:2 was a significant increase of the number of high-affinity sites with a concomitant decrease of low-affinity sites. The hydroxysterol had the opposite effects on these parameters. The high-affinity insulin binding capacity of the hepatoma cells was affected by lipid supplementation in a similar way, whether it was determined at 4 degrees C or at 37 degrees C. Assuming a negative cooperativity model, 18:2 enhanced the degree of negative cooperativity among the sites, while 25-hydroxycholesterol reduced it. The time-course of insulin-induced receptor down-regulation was accelerated in the cells enriched in polyunsaturated fatty acids, but reduced in cells exposed to 25-hydroxycholesterol. These insulin-binding alterations cannot be directly related to modifications of cellular growth rate, receptor internalization or membrane fluidity per se, and are discussed as being more likely due to membrane lipid composition than to overall cell metabolism modifications.

Animals↗
PubMed1987

Effects of eicosatetraynoic acid on membrane lipids of trout liver and intestine.

After two months feeding either an (n-3) or an (n-6) fatty acid-rich diet, two groups of trout were switched to the (n-6) or the (n-3) fatty acid-rich diet, respectively. Half of each group was treated with 0.03% 5,8,11,14-eicosatetraynoic acid (ETYA) in the diet. Liver and intestinal brush border membrane lipids were analyzed. No effect was observed on their cholesterol content. ETYA induced an accumulation of 18:2(n-6), and it did not affect the 20:4(n-6) content but decreased the 22:5(n-6) content. ETYA induced an increase of 18:3(n-3) content in the brush border membrane and a decrease of the 22:6(n-3) content in the liver. Those results suggest that ETYA blocks mainly the delta 6-desaturase, which should have two different sites in the liver and one in the intestine.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1987

Dietary modifications of phospholipid composition and biophysical properties of the brush border membrane along the trout intestine.

Brush border membranes (BBM) are isolated from middle and posterior intestine of trout fed either an essential fatty acid-rich diet or a saturated one. The different phospholipid classes are separated, and their fatty acid composition is determined. Fluorescence anisotropy studies are performed using two lipid fluorophores, namely diphenylhexatriene (DPH) and trimethylamino-diphenylhexatriene (TMA-DPH). The results indicate that the usual parameters affecting the lipid fluidity such as the phospholipid:protein (PL:PROT), cholesterol:phospholipid (CHOL:PL), and sphingomyelin:phosphatidylcholine (SP:PC) ratios and the unsaturation of the acyl chains are sufficient to explain the fluidity values determined using DPH, but not those obtained with TMA-DPH as a probe. This fluorophore is assessed to be localized only in the external leaflet of the membrane. Hence, it will be affected by the composition of the major phospholipids of this leaflet, sphingomyelin and phosphatidylcholine.

Animals↗
PubMed1986

Isolation and characterization of brush-border membrane from trout intestine. Regional differences.

The isolation of brush-border membranes from trout enterocytes is described for both middle and posterior intestine. Both procedures are based on differential centrifugations combined with calcium precipitation. Classical marker enzymes are quantified and indicate a valuable purification of the membranes (13-18-fold). No difference appears when comparing the relative amounts of phospholipids, cholesterol and proteins in microvillus membranes isolated from either middle or posterior intestine. In contrast, the membranes isolated from middle intestine are more unsaturated than those from the posterior one, and their sphingomyelin/phosphatidylcholine ratio is lower. These differences are reflected by fluorescence anisotropy studies with diphenylhexatriene as lipid fluorophore which indicate a higher fluidity of the microvillus membranes from the middle intestine as compared with those from the posterior intestine. These results point out the importance of the fatty acyl chains and that of the relative amounts of phosphatidylcholine and sphingomyelin in controlling the fluidity of biological membranes in relation with their transport properties.

Animals↗
PubMed1985

Na transport and enzyme activities in the intestine of the freshwater and sea-water adapted trout (Salmo gairdnerii R.).

Unidirectional fluxes of Na+ obtained in perfused preparation and mucosal enzyme equipment (alkaline phosphatase, ouabain-sensitive Na+, K+-ATPase) have been determined in the middle and posterior intestine of freshwater (FW) and sea-water (SW) adapted trout. In FW, influxes and outfluxes were higher in the middle than in the posterior intestine, although net fluxes were similar. SW adaptation induced an increase of influxes and net fluxes mainly in the posterior intestine. SW adaptation decreased the alkaline phosphatase activity only in the posterior intestine. Na+,K+-ATPase activity was always higher in the middle than in the posterior intestine in FW and SW and increased in both parts by SW adaptation. Thus, it seems that SW adaptation of rainbow trout modifies Na intestinal absorption principally in its posterior part and in relation with the Na+, K+-ATPase activity.

Acclimatization↗
PubMed1985

Incidence of (n-3) essential fatty acid deficiency on trout reproductive processes.

A feeding experiment was conducted on rainbow trout broodstock for one year to investigate the influence of the quality of dietary lipids on egg and fry fatty acid composition, embryonic development and hatching efficiency. The broodstock were fed either a commercial control diet or a (n-3) fatty acid-deficient diet; their liver, eggs and fry were analysed to determine the fatty acid composition of their neutral and polar lipids. The fatty acid pattern in liver, eggs and fry was markedly different due to the qualitative difference of the dietary lipids. The most striking difference was the low amount of 22:6 (n-3) and the high levels of 20:4 (n-6) and 22:5 (n-6) in phospholipids of fish receiving the (n-3)-deficient diet containing a high level of 18:2 (n-6). While fertilization efficiency was equivalent in the first two days of development, whatever the diet, two peaks of mortality were observed, one at day 8 and the other at day 22 after fertilization, during the time the eggs produced by the deficient fish were incubated. A shorter period of vitellus resorption (50 vs 65 day) was observed in (n-3)-deficient alevins as compared to controls. Morphological study of the development of the (n-3)-deficient embryos showed some cleavage disorders at the 16 to 32-cell stage, a blocking effect before gastrulation, and later various alterations in organogenesis. It was concluded that (n-3) fatty acids, and especially 22:6 (n-3), play a crucial and specific role in trout embryo development. These fatty acids could be involved in cellular recognition processes through their oxygenated derivatives. The need for long-term nutritional deficiency to induce the reported biochemical and physiological alterations is discussed.

Animals↗
PubMed1982

Patterns of purine nucleotides in some North Sea fish erythrocytes.

1. The purine nucleotides were determined in the whole blood of 13 species of seawater teleosts and 3 species of selachians. 2. The ATP/ADP ratio ranged from 4 to 50 in the erythrocytes of the fish examined. 3. GTP is widely distributed in fish erythrocytes but its level ranged from 2 to 27 nmol/mg Hb, the highest value being observed in Conger. 4. Conger, Melanogrammus and Merlangus exhibited a GTP/ATP ratio higher than 1. The concentration of GTP per mol of Hb (physiologically most indicative) is higher than 1 in Conger, Melanogrammus, Merlangus and Pollachus, and close to 1 in Molva and Gadus.

Adenosine Triphosphate↗
PubMed1979

Interaction of adenosine and its phosphorylated derivatives with putative purinergic receptors in the gill vascular bed of rainbow trout.

1. The haemodynamic responses of trout gill to pulses of adenosine and related nucleotides were recorded in isolated trout head preparations. 2. Pulses of adenosine and related nucleotides induced a vasoconstriction of arterial gill vessels. Theophylline antagonized the resonse to adenosine but had not influence on its metabolism. 3. Dipyridamole and two adenosine deaminase inhibitors [deoxycoformycin and erythro-9(2-hydroxy-3-nonyl) adenine] had no effect on either the haemodynamic response of adenosine or its deamination and its uptake by gill tissues. 4. The adenosine response was neither mediated by cholinergic nor adrenergic receptors. 5. These results suggest the existence of extracellular "purinergic receptors" in the gills of trout.

Adenine Nucleotides↗
PubMed1979

AMP deaminase in the gill of trout (Salmo gairdneri R.). Modalities of an activation by cellular proteolytic enzymes.

1. The AMP deaminase activity present in a crude extract of trout gill increased with time. 2. Soybean trypsin inhibitor and alpha2-macroglobulin inhibited the AMP deaminase activation. NEM was also inhibitory at 10-3 M. 3. The activation process is followed by a decrease of activity which is inhibited by EGTA and enhanced by Mg2+. These two compounds were without effect on the activation process itself. 4. Trypsin induces a sharp activation of AMP deaminase in a fresh gill extract but is without effect on a fully activated extract. 5. Overall, the results suggest that neutral proteinases are implicated in AMP deaminase activation.

AMP Deaminase↗
PubMed1979

Aspects of purine metabolism in the gill epithelium of rainbow trout, Salmo gairdneri Richardson.

1. Enzymes interconnecting the adenylate pool were present in high concentration. 2. AMP and adenosine were easily deaminated by the corresponding enzymes whose high levels were detected. 3. Adenylate was hydrolyzed either by deamination to yield IMP which was further dephosphorylated to inosine or by dephosphorylation to adenosine followed by deamination to inosine. 4. Incubation of gill extract with [-14C]-AMP in the presence and absence of ATP but with adenosine deaminase inhibitors allowed demonstration that ATP controlled the balance between these pathways. 5. Some biochemical properties of 5'-nucleotidase. AMP deaminase and adenosine deaminase were defined. 6. Purine salvage enzymes were also estimated.

Adenosine↗
PubMed1979

Patterns of purine nucleotides in fish erythrocytes.

1. The purine nucleotides were determined in the whole blood of 9 fresh water teleosts and 2 marine selachians. 2. GTP and ATP accounted for 88-99% of the total erythrocytes purines. 3. The ATP/ADP ratio ranged from 11 to 60 in the erythrocytes of the fish examined. 4. GTP is widely distributed in fish erythrocytes but its level ranged from 1 to 33 nmol/mg Hb (0.4 to 9 mumol/ml erythrocyte). 5. Lepomis and Esox exhibited a GTP/ATP ratio as elevated as in Anguilla; moreover the concentration of GTP per mol of Hb (physiologically most indicative) is higher in Lepomis, Esox, Ictalurus and Silurus than in Anguilla.

Animals↗