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Biomedical subjects

J Caen

Publications and source records attributed to J Caen.

At least 91 records · Page 5Linked to original sources
PubMed1981

Monoclonal antibody to human platelet glycoprotein I. I. Immunological studies.

A monoclonal hybridoma antibody specific for platelet glycoprotein I complex is described. The nature od the antigen was determined by demonstration that it was chymotrypsin sensitive and gave a peak at 150 000 daltons on SDS-PAGE after immunoprecipitation. The expression of the antigen is restricted to platelets and megakaryocytes with at least 1.6 x 10(4) molecules of antigen per platelet. The antibody failed to bind to platelets from patients with Bernard Soulier syndrome, where there is known to be a deficiency of glycoprotein Ib/Is expression. Binding to platelets from patients with Glanzmann's thrombasthenia was normal.

Animals↗
PubMed1981

Glycoprotein-sialyltransferase activity of normal human, thrombasthenic and Bernard-Soulier platelets.

Some properties of the sialyltransferase activity of homogenates prepared from normal human platelets were investigated using asialo-fetuin as substrate. The enzyme activity was optimal at pH 6.5 and was stimulated by divalent cations in the order Mg2+ greater than Mn2+ greater than Ca2+. Buffers of high ionic strength strongly reduced the activity. ATP and ADP were not inhibitors at 0.1 mM concentration, but AMP, CTP and CMP reduced the activity by 15-30%. A native endogenous acceptor for the enzyme activity was located in the platelet homogenates. The range of fetuin-sialyltransferase activity found in platelets isolated from 6 normal donors was 79 +/- 39 pmol/h/mg protein (mean +/- SD). The platelets of patients with Glanzmann's thrombasthenia and the Bernard-Soulier syndrome, which are characterized by different membrane glycoprotein deficiencies, were shown to have fetuin-sialyltransferase activities within the normal range indicating that the membrane glycoprotein defects in the platelets of these patients are not associated with the absence of sialyltransferase activity.

Adenosine↗
PubMed1981

Defective alpha-granule production in megakaryocytes from gray platelet syndrome: ultrastructural studies of bone marrow cells and megakaryocytes growing in culture from blood precursors.

The ultrastructure and cytochemistry of megakaryocytes from two patients with a familial gray platelet syndrome are described. Although the Golgi zones appeared normally developed, the megakaryocytes lacked alpha-granules. Catalase-containing particles were normal in number. In immature megakaryocytes, granules measuring from 0.05-0.1 mu and having an electron-dense core occurred in the Golgi area. These granules, which are considered as the precursors of alpha-granules in normal megakaryocytes, appeared unable to mature, and their number decreased with the megakaryocyte maturation. The presence of dense material in distended demarcation membranes and/or vacuoles suggested that their content was discharged. It is suggested that myelofibrosis present in the bone marrow from these two patients may be related to the possible excretion of a polypeptide growth factor normally contained in the alpha-granules. Megakaryocytes grown by the plasma clot procedure from blood precursors isolated from the two patients also did not exhibit alpha-granules, which were replaced by vacuoles. Our findings suggest that the lack of alpha-granules in gray platelets may be related to a defective megakaryocyte-committed cell, and evidence is presented which suggests that the precursors of alpha-granules are produced but that their contents are then lost.

Blood Platelets↗
PubMed1980

[Interaction between the platelets and the vessel wall. Part 3: Investigation].

Numerous techniques are now suggested for the investigation of interactions between the platelets and the vessel wall. These techniques offer the possibility of precise diagnosis of the majority of haemorrhagic diseases of primary haemostasis. A critical study nevertheless shows that few tests of haemostasis are of use in defining a state predisposing to thrombosis and amongst others, biological study of the vessel remains very limited.

Animals↗
PubMed1980

[Interactions between the platelets and the vessel wall. Part 2: physiopathology (author's transl)].

The role of the blood platelets in the aetiogenesis of arterial lesions has been underlined in recent years by studies of platelet elastase and above all the mitogenic factor of smooth muscle cells. A truly thrombogenic theory of atherosclerosis can now be envisaged. In the context of arterial thromboses, it is interaction between the damaged vessel wall, the lesion most often being atherosclerosis, and blood platelets which gives rise to the thrombus. In certain conditions such as diabetes abnormalities in the interaction between platelets and vessel walls may favour the development of vascular lesions and thromboses. With regard to venous thrombosis, the participation of the vessel and/or platelets is less clear. However, recently described platelet procoagulant activities could activate coagulation mechanisms. Knowledge of diseases of primary haemostasis has benefited from studies of platelet-vessel interaction. Whilst the spontaneous haemorrhagic syndrome of major thrombocytopaenia remains mysterious, platelet membrane molecular abnormalities in thrombopathies such as Bernard Soulier syndrome or thrombasthenia offer an explanation for their mechanisms. By their interaction with the vessel, platelets finally participate in mechanisms of inflammation, immunological conflicts, disseminated intravascular coagulation and metastatic dissemination.

Arteries↗
PubMed1980

[Interactions between the platelets and the vessel wall. Part 1: Physiology (author's transl)].

The vessel wall plays an important role in the maintenance of balance between haemorrhage and thrombosis. The endothelial lining of a normal vessel wall is thrombo-resistant, in particular by virtue of prostacyclin, whilst the sub-endothelium with its collagen is thrombogenic. If the endothelium is pathologically or experimentally damaged, adhesion of the blood platelets becomes possible. This mechanism, presently studied at a molecular level itself, involves the Willebrand factor, the glycoproteins of the platelet membrane and constituents of the sub-endothelium which remain poorly defined. Platelet adhesion is responsible for cellular activation with the liberation of numerous intraplatelet constituents and synthesis of prostaglandins. Agregation between platelets involves complex biochemical phenomena which concern the platelet membrane and fibrinogen, contractile proteins and the cyclic AMP system, prostaglandins and ADP. The role of calcium in these different phenomena is very important.

Adenosine Diphosphate↗
PubMed1980

Immunochemical evidence for protein abnormalities in platelets from patients with Glanzmann's thrombasthenia and Bernard-Soulier syndrome.

Crossed immunoelectrophoresis of Triton X-100 solubilized proteins from normal and abnormal platelets was performed with rabbit antibodies raised against normal platelets. In Bernard-Soulier platelets protein 13 was not detected, and neither the amphiphilic (probably GP Ib) nor the hydrophilic (glycocalicin) glycocalicin-related proteins were seen when monospecific antiglycocalicin antiserum was used. The most prominent precipitate, 16, and platelet fibrinogen, 24 were not detected in platelets of two patients with type I thrombasthenia, whereas in one patient with type II thrombasthenia fibrinogen was clearly detected, but the amount of protein 16 remained severely reduced. Protein 16 was heavily labeled after lactoperoxidase-catalyzed (125)I iodination of normal platelets, and was precipitated by IgG-L, an alloantibody from a polytransfused thrombasthenic patient. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) or protein 16 cut out from immunoplates showed two (125)I-labeled glycoprotein bands, which migrate as GP IIb and GP IIIa. SDS-PAGE of (125)I-labeled type I thrombasthenic platelets showed no periodic acid-Schiff bands or peaks of radioactivity in the GP IIb and GP IIIa regions, whereas in the GP I region both the periodic acid-Schiff band intensity and the radiolabeling were within the normal range. Autoradiography after crossed immunoelectrophoresis of iodinated thrombasthenic platelets showed that the bulk of radioactivity was bound to protein 17. This glycoprotein, which was also present in normal and Bernard-Soulier platelets, migrates in the GP I region on SDS-PAGE. Thus, the bulk of radioactivity observed in the GP I region after SDS-PAGE is associated with protein 17 and not with glycocalicin.

Blood Platelet Disorders↗
PubMed1979

[Quantification of platelet associated IgG in thrombocytopenic purpura (authors transl)].

One hundred and twenty four tests of quantification of platelet associated IgG were done in patients with thrombocytopenia. The level was increased in 80% of the patients with ITP. The platelet associated IgG level does not seem a prognosis tool but is useful to follow the evolution. Platelet associated IgG levels higher than 600 x 10(-16) g/platelet were only observed in ITP (control less than 54 x 10(-16) g/platelet). Level lower than 600 x 10(-16) g/platelet were observed in systemic lupus erythematosus, chronic lymphocytic leukemia or chronic hepatitis. In defective thrombopoïesis, the levels were always normal.

Blood Platelets↗
PubMed1977

[Acquired Von Willebrand disease with chronic lymphocytic leukaemia and angiodysplasia (author's transl)].

The onset of an haemorragic syndrome in a patient with chronic lymphocytic leukaemia led to the diagnosis of acquired von Willebrand's disease secondary to an anti-von Willebrand factor antibody. Multiple angiodysplasia were shown by an arteriography done for a ruptured femoral arterial aneuvrism. The relationship between angiodysplasia and acquired von Willebrand disease are discussed.

Aged↗
PubMed1977

Effect of somatostatin on platelet aggregation and plasma factor VIII level in normal man.

As impairment in coagulation and platelet function has been reported following acute administration of somatostatin, a reevaluation of the effects of the cyclic and linear form of the peptide was undertaken. In vitro somatostatin had no effect by itself on platelet aggregation and no effect on ADP- or ristocetin-induced aggregation. In vivo ten healthy men infused with cyclic or linear somatostatin (loading dose of 250 microgram and three hour-infusion with 1,500 microgram) and five control subjects were investigated during the infusion and for three hours after the end of the infusion. With this dose, sufficient in man for maintaining plasma growth hormone and insulin at fasting levels under arginine stimulation, no abnormalities in platelet count, in ADP-induced platelet aggregation and in plasma VIII von Willebrand factor, factor VIII procoagulant activity and factor VIII related antigen levels were observed.

Adenosine Diphosphate↗
PubMed1977

Molecular defect in platelets from patients with bernard-soulier syndrome.

An IgG antibody isolated from the serum of a patient with the Bernard-Soulier syndrome induced platelet agglutination in the platelet-rich plasma of 50 normal subjects regardless of their ABO, KOa, KOb, HLA, or PlA1 types. This antibody was nonreactive with platelets from three other Bernard-Saulier syndrome patients. Indirect immunoprecipitation tests using this serum (or purified IgG) and soluble membrane antigens labeled with 125I that had been extracted from normal platelets by the nonionic detergent Nonidet P-40 gave a single radioactive peak at 150,000 MW in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These findings strongly suggest that the antigenic determinant reacting with this antibody is absent from platelets of Bernard-Soulier syndrome patients and that the deficient molecule is of 150,000 MW. The role of this molecule in subendothelial adhesion and macromolecular-mediated aggregations is discussed.

Antibodies↗
PubMed1976

[Reduction of Willebrand activity in patients with chronic kidney failure].

Decreased factor VIII von Willebrand activity in contrast with increased factor VIII procoagulant activity and increased concentrations of factor VIII related antigen, were found in the plasma of patients with chronic renal failure. This functional abnormality of the factor VIII protein is not improved by haemodialysis, but it is no longer found in patients with normally functioning grafted kidneys. It may at least partly explain the prolonged bleeding time commonly found in chronic renal failure.

Blood Coagulation Disorders↗