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Biomedical subjects

M Dechavanne

Publications and source records attributed to M Dechavanne.

At least 73 records · Page 4Linked to original sources
PubMed1986

Identification of two distinct regions within the binding sites for fibrinogen and fibronectin on the IIb-IIIa human platelet membrane glycoprotein complex by monoclonal antibodies P2 and P4.

The effect of two monoclonal antibodies P2 (LyP 2) or P4 (LyP 4), specific for the platelet membrane glycoprotein IIb/IIIa complex, on binding of 125I-labelled fibrinogen or 125I-labelled fibronectin to thrombin-stimulated platelets was studied. These monoclonal antibodies are directed against different determinants on the IIb-IIIa complex and react only with the complex and not with the individual glycoproteins. Fibrinogen binding to thrombin-stimulated platelets was significantly inhibited by P2 but not by P4. Fibronectin binding to thrombin-stimulated platelets was significantly inhibited by P4 but only poorly by P2. These results indicate the presence of specific regions on the glycoprotein IIb-IIIa complex which act as binding sites for fibrinogen or fibronectin. Other authors [Haverstick et al. (1985) Blood 66, 946-952; Ginsberg et al. (1985) J. Biol. Chem. 260, 4133-4138] have shown that a tetrapeptide, Arg-Gly-Asp-Ser, inhibited the binding of fibrinogen, fibronectin, and von Willebrand factor (vWf) to stimulated platelets and that fibrinogen competes with vWf and fibronectin for binding. These findings, together with previous studies, therefore indicate the presence of specific regions as well as a common region in the binding sites for fibrinogen and fibronectin on the IIb-IIIa complex.

Adenosine Diphosphate↗
PubMed1986

Effects of linoleic acid and gamma-linolenic acid intake on platelet functions in elderly people.

Sixteen old subjects were given daily dietary supplement of lg of linoleic acid and lg of gamma-linolenic acid (primerose oil) or 2g of linoleic acid (sunflower oil) for periods of two months. Haemostatic parameters, platelet aggregation, exogenous and endogenous arachidonic acid metabolism were investigated before and after the intake. Diets did not induce any significant change in haemostatic parameters (bleeding time, levels of anti-thrombin III, plasminogen and plasma beta-TG and PF4). Platelet rich plasma aggregation induced by collagen and arachidonic acid were significantly reduced after linoleic acid (18:2n-6) intake. In contrast, gamma-linolenic acid (18:3n-6) supplement did not alter aggregation. However, thromboxane B2 formation (under stimulation) and vitamin E level in platelets (but not in plasma) were decreased after 18:3n-6 as compared to 18:2n-6 intake. The mechanism of thromboxane B2 decrease is unclear. Nevertheless, we may speculate that beneficial effect of this decrease could be counterbalanced by the decreased platelet vitamin E. We conclude that intake of 18:2n-6 or 18:3n-6 does not affect much platelet functions in elderly people.

8,11,14-Eicosatrienoic Acid↗
PubMed1986

Pharmacokinetic studies of standard heparin and low molecular weight heparin in patients with chronic renal failure.

The disappearance of the anticoagulant activities of a standard commercial heparin and of a low molecular weight (LMW) heparin (PK 10169), administered as single intravenous injections, was studied in patients with chronic renal failure. Heparin and LMW heparin anticoagulant activities were determined by activated partial thromboplastin time (APTT) and chromogenic assays of anti-Xa and anti-IIa activities. Following heparin injection, a fast initial decay of anticoagulant activities preceded a slow convex disappearance curve, in semilogarithmic plots. These experimental data are in agreement with a model based on a predominant saturable mechanism of elimination of heparin in patients with renal failure. The disappearance of LMW heparin anti-Xa activity was obviously different, with linear or concave elimination curves, and longer apparent half-life. Taken together, our kinetic data and those previously reported in normal subjects strongly suggest that the mechanism of elimination of the LMW heparin studied is not saturable (at least for the tested dosages), and that the kidneys play a minimal role in the elimination.

Adolescent↗
PubMed1985

Plasma thrombospondin in patients with chronic renal failure, liver disease and splenectomy.

Thrombospondin (TSP), is a major constituent of human blood platelet alpha-granules. Stimulation of platelets causes the release of TSP in parallel with other alpha-granule constituents such as beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) but the thrombospondin plasma in vivo half life is significantly greater than beta-TG and PF4. The aim of this study was to assay TSP levels in plasma of patients with chronic renal failure (CRF), liver disease (LD) and following splenectomy. The TSP values were then compared to the patients plasma levels of two traditional markers of platelet activation, beta-TG and PF4, and to fibronectin (FN) and von Willebrand factor (VIII:vWF). Plasma TSP levels (67.6 +/- 16.9 ng/ml) assayed in 14 CRF patients were significantly higher (p less than 0.05) than those measured in 28 donors (55.5 +/- 11.7 ng/ml). No correlation was observed, in CRF patients, between the TSP level and PF4 (2.5 +/- 1.5 ng/ml), beta-TG (131.1 +/- 21 ng/ml), FVIII:vWF (252 +/- 85%), or FN (102 +/- 33%) plasma levels. The TSP plasma level in CRF patients was significantly correlated (p less than 0.02) with that of fibrinopeptide A (4.1 +/- 1.9 ng/ml). Although the beta-TG (23.5 +/- 6.9 ng/ml) and PF4 (2.9 +/- 2 ng/ml) plasma levels in six LD patients were normal, the TSP levels (82.5 +/- 39.1 ng/ml) were significantly increased (p less than 0.01). Thrombospondin plasma levels (77.1 +/- 20.1 ng/ml) in 14 patients having undergone splenectomy were significantly increased (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Tandem separation of labelled human blood platelet membrane glycoproteins by anion-exchange and gel fast protein liquid chromatography.

Studies were made of the separation of surface-labelled platelet glycoproteins, solubilized in a non-ionic detergent (Berol 185), on a Mono Q anion-exchange column, coupled to a Superose 12 gel fast protein liquid chromatographic column. Peaks eluted from the anion-exchange and gel columns were subjected to electrophoresis on sodium dodecyl sulphate-polyacrylamide gels in the presence (non-reducing conditions) or absence (reducing conditions) of disulphide bridges. Labelled electrophoresed glycoprotein bands were rendered visible by fluorography or indirect autoradiography. Platelet membrane glycoproteins Ib, IIb, IIIa, IIIb, V and IX were identified by their apparent molecular weights and their surface labelling characteristics. It was concluded that tandem chromatography can be used to separate platelet membrane proteins and glycoproteins rapidly and with good resolution.

Blood Platelets↗
PubMed1985

Identification and characterization of fragments of major glycoproteins from platelet membrane after chymotrypsin treatment.

Human platelets were surface-labeled by the periodate/NaB3H4 method or by lactoperoxidase-catalysed iodination with 125I. The labeled platelets were treated with chymotrypsin under conditions known to give platelets which aggregate with fibrinogen without stimulation with ADP. Platelets and supernatant were then analysed by various gel electrophoretic techniques including isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing or non-reducing conditions and two-dimensional non-reduced/reduced sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by fluorography or indirect autoradiography. Chymotrypsin-treatment of surface-labeled platelets degraded the major glycoproteins Ib, IIb and IIIa but also GP120(4.9-5.4), GPIc and GPV. The membrane-bound fragments of GPIb, IIb and IIIa could be identified and also the supernatant fragments of GPIb and GPV. GPIIIa was also cleaved within a loop structure formed by disulfide bond(s). The fact that remnants of both GPIIb and IIIa are left on chymotrypsin-treated platelets which aggregate spontaneously with fibrinogen may indicate that a complex formed by these remnants constitutes the fibrinogen-binding site on platelets.

Adult↗
PubMed1985

Prostaglandin E2-like activity of 20:3n-9 platelet lipoxygenase end-product.

5,8,11-Icosatrienoic acid (20:3n-9), a fatty acid associated with platelet hyperactivity, was oxygenated by platelet lipoxygenase. The end-product of this pathway was purified by high-performance liquid chromatography (HPLC) and characterized as 12-hydroxy-5,8,10-icosatrienoic acid [12-OH-20:3(5,8,10)] by capillary gas-liquid mass spectrometry. When tested upon platelet aggregation, 12-OH-20:3(5,8,10) exhibited a biphasic effect. At low concentrations (below 5 X 10(-7) M) it potentiated aggregation but inhibited it at higher levels, a pattern similar to that obtained with prostaglandin E2. However, since the amounts of 12-OH-20:3(5,8,10) generated under thrombin stimulation are in the range of concentrations with potentiating effects, it seems that the 12-OH derivative is responsible for the hyperaggrebility of 20:3n-9-rich platelets.

8,11,14-Eicosatrienoic Acid↗
PubMed1985

One-step procedure for the rapid isolation of mouse monoclonal antibodies and their antigen binding fragments by fast protein liquid chromatography on a mono Q anion-exchange column.

A one-step chromatographic procedure was used to isolate rapidly mouse IgG monoclonal antibodies (mAbs) (IgG1, IgG2a, IgG2b) contained in ascites fluids and Fab fragments contained in papain-treated mAb suspensions. Chromatographic separations were performed on an anion-exchange Mono Q column connected to a fast protein liquid chromatographic (FPLC) system. Detection of mAb or their antigen binding fragments (Fab) in eluted peaks was performed using sodium dodecyl sulphate-polyacrylamide gel electrophoresis together with a silver or a Coomassie Brillant Blue R 250 staining technique and solid phase radioimmunoassay with 125I-labelled sheep anti-mouse antibodies directed against total immunoglobulins. Rapid assessment of the purity of isolated mAbs and their Fab fragments was performed by gel permeation chromatography on a TSK G 3000 SW column. Mouse mAbs and their Fab fragments were rapidly isolated (25 min), in a functionally active state, to a high degree of purity on the FPLC-Mono Q system compared to the time taken by other techniques.

Animals↗
PubMed1985

In vitro incorporation and metabolism of some icosaenoic acids in platelets. Effect on arachidonic acid oxygenation.

Three icosaenoic acids (20:3(n-6), 20:5(n-3) and 20:3(n-9)) which may arise in platelet phospholipids under certain dietary conditions and which may affect platelet functions have been taken up by human platelets. Each acid was pre-coated onto delipidated albumin and then incubated with platelets isolated from their plasma. The distribution study of each acid in cellular lipids revealed that around 80% of the acid taken up was located in phospholipids, of which the bulk was in phosphatidylcholine. The percentage incorporation of each acid into the different glycerophospholipids was similar to their endogenous percentage profiles, therefore simulating the in vivo situation. The icosaenoic acids then incorporated were liberated from phospholipids when platelets were incubated with thrombin or calcium ionophore A23187 and subsequently oxygenated through the cyclooxygenase and/or lipoxygenase pathway. Whereas 20:3(n-6) was readily converted into cyclooxygenase products, 20:5(n-3) was more specifically converted into lipoxygenase products, and this latter conversion was comparable to that of 20:3(n-9) which is not a prostanoid precursor. Finally, only 20:3(n-6)- or 20:5(n-3)-rich platelets exhibited a reduced availability of endogenous arachidonic acid from phospholipids when induced by thrombin. It is concluded that inhibitory polyunsaturated fatty acids (20:3(n-6) and 20:5(n-3)) could act both by reducing prostaglandin H2/thromboxane A2 production from endogenous arachidonic acid and in generating platelet inhibitory substances (cyclooxygenase and/or lipoxygenase products of 20:3(n-6) and 20:5(n-3)). On the other hand, 20:3(n-9), a fatty acid which potentiates platelet aggregation through its lipoxygenase end product, could produce sufficient amounts of this compound to enhance the aggregation when platelets are triggered with inducers of phospholipase activity such as thrombin or calcium ionophore.

Arachidonic Acid↗
PubMed1985

Platelet membrane glycoprotein abnormalities in patients with myeloproliferative disorders and secondary thrombocytosis.

Carbohydrate-specific surface labelling and 125I-labelled lectin binding techniques, in combination with one- or two-dimensional (non-reduced/reduced) SDS-polyacrylamide gel electrophoresis have been used with platelets from patients with myeloproliferation disorders and secondary thrombocytosis and from healthy donors. In essential thrombocythaemia platelet membrane glycoproteins were significantly less sialylated than in normals (particularly GP Ib and IIIa). Increased binding of 125I-labelled Lens culinaris lectin to thrombospondin and GP IIIa indicated a defect in the glucose/mannose glycosylation of the platelet glycoproteins in essential thrombocythaemia. In polycythaemia vera and in chronic myeloid leukaemia the terminal sialic acid of glycoprotein IIIb was labelled slightly more than normal. In chronic myeloid leukaemia there was increased labelling of the penultimate galactose/N-acetylgalactosamine residues of GP Ib, IIb, IIIa and IIIb. In comparison to myeloproliferative disorders, platelets from patients with secondary thrombocytosis showed no significant changes, except for platelets from two patients with idiopathic thrombocytopenic purpura which showed an increased sialylation of all surface glycoproteins.

Blood Platelets↗
PubMed1985

Intravenous plasmin-treated gammaglobulin therapy in idiopathic thrombocytopenic purpura. Results in 40 patients.

A study of the effects of high-dose IV plasmin-treated IgG was undertaken in 40 patients (30 children and 10 adults) with idiopathic thrombocytopenic purpura (ITP). After a first course of treatment, a success therapy (platelet counts greater than 100 X 10(9)/l) was observed in 21 patients. The results after additional courses of pH 4 treated IgG in 7 patients tended to indicate that the 2 kinds of concentrates might induce similar platelet responses. No significant side-effects were observed. Platelet associated (PA), IgG, IgM and C3 levels were determined before therapy and on the 7th day after the first infusion (day 8) in 27 patients (36 courses). In spite of great variability, overall results showed a significant decrease in PA IgG (P less than 0.05), PA IgM (P less than 0.01) and PA C3 (P less than 0.001) at day 8. A significant inverse relationship was found between either PA IgG, or PA IgM or PA C3 levels, and platelets counts (respectively, r = -0.57, -0.55, -0.66, P less than 0.001). Our results also showed that pretreatment platelet counts were higher in patients with success therapy (25.8 +/- 16.9 X 10(9)/l) than in others (11.3 +/- 12.1 X 10(9)/l, P less than 0.001). This suggested that pretreatment platelet counts could help predicting the platelet response.

Adolescent↗
PubMed1984

Inhibition of platelet aggregation and thromboxane synthesis after intake of small amount of icosapentaenoic acid.

Elderly people ingested 150 mg/day of icosapentaenoic acid (20:5n-3) or a placebo for one month. Platelet aggregation, platelet arachidonate metabolism and the fatty acid composition of both plasma and platelet lipids were investigated before and after the intake. Platelet aggregation induced by collagen, epinephrine or low concentrations of ADP was significantly reduced after 20:5n-3 intake. Besides, the main oxygenated product formation from endogenous platelet arachidonate under thrombin stimulation was markedly decreased after the 20:5n-3 supplementation. Such a decrease was absent after placebo. Moreover, no modification in the fatty acid composition of both plasma lipids and platelet phosphatidylcholine could be observed. We conclude that intake of low amounts of 20:5n-3 by elderly people, is able to lower their platelet sensitivity to aggregating agents, probably by decreasing the endogenous formation of platelet thromboxane A2, although no modification in the fatty acid composition was detected.

Adenosine Diphosphate↗