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Biomedical subjects

M Dechavanne

Publications and source records attributed to M Dechavanne.

At least 19 recordsLinked to original sources
PubMed1996

A nonsense mutation in the GPIIb heavy chain (Ser 870-->stop) impairs platelet GPIIb-IIIa expression.

Glanzmann thrombasthenia (GT) is a rare autosomal recessive bleeding disorder, caused by a quantitative or qualitative defect of the GPIIb-IIIa integrin (alpha IIb beta 3), which functions as the platelet fibrinogen receptor. We report a case of type I GT due to a homozygous mutation resulting in Ser 870 to stop codon substitution. This residue is located near the proteolytic cleavage site of proGPIIb. The mutation results in a GPIIb truncated of 138 amino acids, including transmembrane and intracytoplasmic domains. Cotransfection of an expression vector containing the mutant GPIIb and wild-type GPIIIa showed that the mutant Ser 870-->stop GPIIb was able to associate to GPIIIa. However, this heterodimer failed to mature as shown by endoglycosidase-H digestion and was therefore not expressed at the COS-7 cell surface. This report is the first description of a homozygous nonsense mutation in the GPIIb gene and highlights the role of the GPIIb light chain.

Adolescent↗
PubMed1996

Platelet-aggregation inhibition and hemodynamic effects of beraprost sodium, a new oral prostacyclin derivative: a study in healthy male subjects.

The antiaggregation and hemodynamic effects of the new prostacyclin analogue beraprost sodium were investigated in a randomized, placebo-controlled, double-blind clinical trial of Latin-square design. Twelve healthy Caucasian males randomly received 8-day oral treatments of 20, 40, and 60 micrograms of beraprost sodium and a placebo. One-week washout periods followed each treatment. Pharmacokinetic and pharmacodynamic measurements were performed on days 1 and 8 for each period of treatment. All three doses of beraprost sodium significantly inhibited platelet aggregation on day 8 (compared with placebo) during the 1st h after drug intake. Incubation of the 60-micrograms beraprost sodium samples with ADP (2, 5, and 10 microM) and collagen (1.25 micrograms/mL) decreased platelet aggregation by 10, 19, 16, and 6 +/- 4% (mean +/- SE), respectively, compared with placebo. No significant hemodynamic effects on blood pressure, heart rate, and digital pulse were observed. The 60-micrograms dose of beraprost sodium did significantly decrease the IRZ index (which may reflect the left ventricular pre-ejection period) on days 1 and 8. Some subjects experienced headache and facial flushing, effects that were dose dependent and reversible. Beraprost sodium at 20- to 60-micrograms doses exerts platelet antiaggregation (day 8 of therapy) and slight hemodynamic (days 1 and 8 of treatment) effects in Caucasian males. Beraprost sodium hemodynamic effects and potential benefits in patients with cardiovascular disease should be explored further.

Administration, Oral↗
PubMed1996

Open trial of intravenous tissue plasminogen activator in acute carotid territory stroke. Correlations of outcome with clinical and radiological data.

BACKGROUND AND PURPOSE: Pilot studies using early thrombolytic therapy in stroke have suggested that recombinant tissue plasminogen activator (rTPA) might be effective. While large, double-blind, randomized studies are needed, open trials could generate hypotheses concerning (1) the clinical correlations of outcome, (2) the significance of CT scan data during the first week, and (3) the use of adjunctive therapies. METHODS: We performed an open trial of intravenous rTPA on patients referred to our emergency service with all types of ischemic stroke in the carotid territory. All patients between 20 and 81 years hospitalized during 1994 with completed stroke in the internal carotid artery territory and a baseline Scandinavian Stroke Scale score lower than 48, even with severe disturbances of consciousness, were included. The inclusion time was within 7 hours after stroke onset. A 0.8-mg/kg dose of rTPA was infused for 90 minutes. Intravenous heparin was given either immediately at efficient dosage or after 24 hours. Mannitol was used in patients with severe presentation. The Scandinavian Stroke Scale evaluation was done at baseline, 3 hours, and 1, 7, 30, and 90 days. The CT scan was performed before the treatment and at days 1 (24 +/- 6 hours) and 7. RESULTS: Forty-three consecutive patients met the criteria of the protocol. The mean age at inclusion was 65 +/- 10.4 years, and the mean interval to treatment was 232 +/- 79 minutes. At day 90, 25 patients (58.1%) exhibited a complete regression of symptoms, and 3 had moderate neurological sequelae. Thirteen patients had severe neurological sequelae, 11 with infarcts and 2 with secondary parenchymal hematomas. Two patients died (4.6%), 1 with hematoma. The overall hematoma rate was 6.9%. Excellent outcome at day 90 was significantly correlated with major neurological improvement at day 1. Intravenous immediate heparin versus delayed heparin after 24 hours improved the ischemic outcome but not the overall outcome. Reinfarction syndromes after major neurological improvement, likely to be rethrombosis syndromes, were observed in 3 patients (6.9%). For the day 1 CT scan, poor outcome was associated with the presence of structured and homogeneous hypodensities likely to represent classic infarcts, as confirmed by day 7 CT scan. Conversely, total recovery was significantly associated with the absence of any image or with unstructured hypodensities, a particular type of image characterized by its heterogeneous darkness and often polylobar shape. This type of image disappeared at day 7 in 17.6% of the cases and is likely to represent reperfusion images and/or incomplete ischemic damage. CONCLUSIONS: The results obtained in this open, small study suggest safety and effectiveness of rTPA thrombolysis at the dose of 0.8 mg/kg within 7 hours in acute strokes of the carotid territory, including highly serious baseline neurological presentations, until age 81 years and under special therapeutic conditions. Complete recovery is significantly associated with major neurological improvement during the first 24 hours and the presence of a particular type of image at day 1 CT scan characterized by an unstructured hypodensity, often polylobar and heterogeneous, which is likely to correspond to reperfusion images.

Adult↗
PubMed1996

[Diagnosis of venous thrombosis and/or pulmonary embolism by determination of d-dimers using ELISA. Review based on a study of 80 consecutive patients hospitalized in an emergency unit].

The sensitivity and specificity of an ELISA method (Fibrinostika Fbdp Organon Teknika) for assay of D-dimers in the diagnosis of deep vein thrombosis and/or pulmonary embolism was studied in 80 consecutive patients seen at an emergency unit. Fifty-six of the patients presented clinical signs of deep vein thrombosis. Diagnosis was confirmed in 26 of the 56 patients with a D-dimer level above 370 ng/ml (sensitivity 92.3%) and 370 ng/ml for 13 of 30 patients with a negative venous ultrasound Doppler examination (specificity 43.3%). The positive predictive value was 58.5% and the negative predictive value was 87%. There was a significant difference in the level of D-dimers between distal and proximal deep vein thrombosis. In 40 cases with suspected pulmonary embolis, either alone or with suspected deep vein thrombosis, diagnosis was made in only 4 of 9 with a highly or intermediately probable ventilation/perfusion scan. D-dimer level was always above 3,000 ng/ml. Coupling the ELISA dimer test with noninvasive explorations improves negative predictive value but can also avoid invasive explorations (venography, pulmonary angiography) in certain patients. A D-dimer test as sensitive as the ELISA test and as rapid as the latex test remains to be described.

Adolescent↗
PubMed1995

Combined factor IX and protein C deficiency in a child: thrombogenic effects of two factor IX concentrates.

We have recently described an unusual situation which involved a combination of a factor IX and a protein C deficiency in a young child who presented, according to the bleeding tendency, as a hemophilia B patient. In this particular hemophiliac, baseline prothrombin fragment F1 + 2 levels were unexpectedly elevated and increased after an injection of a very high purity factor IX concentrate. This observation raised a question regarding the substitution schedule in the case of repeated injections of factor IX, since the thrombotic tendency has been a major concern with some factor IX concentrates. We monitored factor IX, prothrombin fragment F1 + 2, and D-dimer plasma levels before and during the 6 hr following the injection of an immunopurified factor IX concentrate. The results showed an increase in the F1 + 2 levels after the factor IX injection, but an increase lower than previously observed with an ion-exchange chromatography-purified concentrate. Furthermore, the F1 + 2 level returned to baseline value 6 hr after administration. This factor IX concentrate seems to be best for use in the patient where repeated injections are involved (as employed during surgery). Moreover, the data point out the advantage of a monoclonal antibody-purified factor IX concentrate over less purified concentrates in a specific situation, with regard to the thrombogenic risk.

Antibodies, Monoclonal↗
PubMed1995

Quantitative immunochemistry of endothelial cells in cutaneous tissue.

In vivo endothelial cell exploration in human pathology has been limited by the lack of a suitable procedure for quantification of endothelial molecule expression. The objective of the present study was the development of a precise, simple and rapid image analysis method to quantify dermis endothelial cells and associated molecules. Cutaneous tissue sections were labelled by immunoperoxidase procedure using a monoclonal anti-von Willebrand factor (vWF) antibody, which identifies endothelial cells. The image analysis programme was tested to quantify final reaction deposit (DAB) with reference to different anti-vWF antibody concentrations. The entire biopsy section was acquired, field by field. Analysis was restricted to three dermis zones geodesically defined from epidermis. Optical density and area measurements were performed in whole area and in positive areas. This work demonstrated the feasibility of endothelial cell study assisted by image analysis. Surface labelled by anti-vWF antibody at saturating concentration may be considered as an endothelial reference surface, and thus may be useful for future quantification of other endothelial molecules.

Antibodies, Monoclonal↗
PubMed1995

Molecular study of Glanzmann thrombasthenia in 3 patients issued from 2 different families.

In an effort to further understand Glanzmann thrombasthenia (GT) 3 patients from 2 different families were studied. After biochemical and immunological analysis these patients were classified as type I. We observed in the first family a new restriction site for Stu I in exon II of the glycoprotein (GP) IIIa gene caused by a homozygous nonsense mutation: 62 Arg to stop codon. The parents were heterozygotes for this mutation. We found in the second family a previously described nonsense mutation: 584 Arg to stop codon in exon 17 of the GPIIb gene. The father and his two affected sons were heterozygous for this genetic defect. This mutation 62 Arg to stop codon is a new description of a genetic defect associated with GT. Furthermore, the discovery of the same mutation in 3 affected families from different ethnic groups raises the possibility of either a hot spot mutation in the CG dinucleotide region of GPIIb gene, or an ancient mutant allele present in diffuse populations at a relatively high frequency.

Amino Acid Sequence↗
PubMed1994

Increased plasma free gamma carboxyglutamic acid levels during deep vein thrombosis and intravascular disseminated coagulation.

Gammacarboxyglutamic acid (gla) is a non essential amino acid synthesized in presence of vitamin K, predominantly found in coagulation and bone proteins. In 14 cases of deep vein thrombosis and in 11 cases of disseminated intravascular coagulation, compared to 19 normal subjects and 9 patients hospitalized for leg pain, free plasma gla levels were found significantly elevated (respectively 372 +/- 244 and 559 +/- 361 versus 146 +/- 34 and 120 +/- 40 pmol/mL). In six paired plasma and serum, gla levels were similar. These results suggest an involvement of blood coagulation in gla generation with need of a catabolism of the activated factors. A significant decrease was noticed during vitamin K antagonist therapy and liver disease, both instances in which the synthesis of gla containing coagulation factors is affected. During hepatocellular carcinoma with elevated desgamma carboxyprothrombin, gla was found normal, denying an global impairement of the vitamin K metabolism.

1-Carboxyglutamic Acid↗
PubMed1994

Increased thrombosis incidence in a family with an inherited protein S deficiency and a high oxygen affinity hemoglobin variant.

Inherited protein S deficiency and the presence of a rare high oxygen affinity hemoglobin variant: Hb Rainier [beta 145 (HC2) Tyr-->Cys] were found in a family. Among 16 studied members, nine were found as carriers of protein S deficiency (type I with decrease of total, free, and activity levels). Six subjects carried the high-affinity hemoglobin variant, which displayed an increase of blood viscosity. Four members combined both abnormalities. Three had thrombotic accidents before the age of 30. We suggest the combination of protein S deficiency and the presence of this hemoglobin variant can lead to a severe primary hypercoagulable state with pathological consequences compared to each genetic defect alone.

Adult↗
PubMed1994

Expression of adhesion molecules in endothelial cells during allogeneic bone marrow transplantation.

Endothelial cell activation during allogeneic bone marrow transplantation, mainly in acute graft-versus-host disease (aGvHD) was studied in 23 recipients and 5 controls using anti-von Willebrand factor (vWF) antibody, antibodies to endothelial leukocyte adhesion molecule-1 (ELAM-1), vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), and anti-HLA-DQ antibody, by immunohistological staining of skin. vWF extravasation, ELAM-1 and VCAM-1 expression were present in most recipients with a cutaneous rash which was confirmed as an aGvHD by histological examination (documented aGvHD) (p = 0.005 for vWF extravasation and ELAM-1 expression and p = 0.03 for VCAM-1 expression in comparison with the controls). In recipients with a rash, the cases displaying vWF extravasation and ELAM-1 expression were significantly more numerous in those with a documented aGvHD than in those without histological features of aGvHD (p = 0.01). vWF extravasation and ELAM-1 occurred concomitantly (p < 0.01). This study demonstrates that, during the course of skin aGvHD following bone marrow transplantation, there is transient expression of ELAM-1 and VCAM-1 by endothelial cells and simultaneous vWF extravasation, indicating an intense inflammation with endothelial cell participation.

Acute Disease↗
PubMed1993

Increased thrombin generation in a child with a combined factor IX and protein C deficiency.

We report a quantitative protein C deficiency combined with a factor IX deficiency in a one-year-old boy. The inheritance of the two deficiency states was independent, the factor IX defect coming from the mother and the protein C defect from the father. Both factor IX activity and antigen were below 1%, and protein C activity as well as antigen were close to 27% of normal values. This association raises a real therapeutic and prognostic question. Protein C deficiency is indeed associated with a significant thrombotic risk and some factor IX concentrates seem to carry a potential thrombogenicity, particularly following infusion of repeated doses. We evaluated in this patient the potential activation of the coagulation system by measuring the levels of prothrombin fragment F1 + 2 at the basal state and after a single administration of 20 U/kg of a high purity factor IX concentrate. We found an unexpected basal activation of the hemostatic system before infusion (F1 + 2 = 1.6 nmol/L), which further increased during 8 hours. Despite the clinical predominant expression of the hemophilic trait, our results seem to assess the biologic prevalence of the protein C deficiency. This emphasizes the need for a careful follow-up after infusions of repeated doses of factor IX, as used during a surgical procedure. Furthermore, this raises the question of the prognosis because the risk of thrombotic manifestations associated with a protein C deficiency increases with age. Finally, these results highlight a part of the in vivo activation process of prothrombin in case of failure of the intrinsic pathway of coagulation. The protein C defect seems to be responsible for an upregulation of the prothrombin activation through the extrinsic pathway.

Factor IX↗
PubMed1993

Substitution of cysteine for phenylalanine 751 in mature von Willebrand factor is a novel candidate mutation in a family with type IIA von Willebrand disease.

Type IIA is a variant form of von Willebrand disease (vWD) characterized by the absence of von Willebrand factor (vWF) high molecular weight multimers in plasma. Most of the candidate missense mutations potentially responsible for type IIA vWD have been found clustered within a short segment of vWF, lying between Gly742 and Glu875 of the mature subunit. The present work reports a single heterozygous T-->G transversion in eight patients from a large type IIA vWD family, resulting in the substitution Phe751-->Cys. The absence of this mutation in 100 normal vWF genes as well as the lack, in these patients, of any other abnormality within the whole exon 28 encoding amino acids 463-921 of mature vWF, provide a strong support that this non-conservative mutation may be at the origin of the disease in this family. The presence of an additional cysteine at position 751 may induce a conformational change of the vWF subunit affecting either its 'in vivo' sensitivity to proteolytic cleavage or, more likely, its intracellular transport as suggested by the abnormal multimeric pattern of platelet vWF observed in these patients.

Cysteine↗
PubMed1993

Results of splenectomy for idiopathic thrombocytopenic purpura. Review of 72 cases.

Seventy-two patients underwent splenectomy for idiopathic thrombocytopenic purpura between 1979 and 1990. Mean age at splenectomy was 36.4 years (range 11-73). Indications for splenectomy were corticodependence in 21 cases and resistance to steroids in 44 cases. Thirty-five patients had platelet kinetic studies by 51Cr alloplatelets; 22 of them had splenic sequestration. Hematologic results were evaluated on discharge, at 3 months and in the long term (median follow-up 5.4 years). We had no mortality, morbidity was seen in 7% of the cases. None of the patients suffered from secondary infectious complications. 89% had good results on discharge (> 120 x 10(9)/l), 72.6% at 3 months and 90% on long-term follow-up. Factors associated with good response to splenectomy included a high postoperative platelet count (more than 120 x 10(9)/l on discharge), younger age at the time of surgery, preoperative corticodependence and predominantly splenic sequestration.

Adolescent↗
PubMed1993

Thrombomodulin is synthesized by osteoblasts, stimulated by 1,25-(OH)2D3 and activates protein C at their cell membrane.

We have previously shown that protein S, a vitamin K-dependent protein, is a bone matrix component synthesized and secreted by osteoblasts. Because protein S is a cofactor of protein C in inhibiting factor Va and VIIIa, we have looked for the presence of the proteins related to the anticoagulant protein C system in human MG 63 osteosarcoma cells and in human adult osteoblast-like cells. Using immunoblotting, we have shown that protein C, factor V, and C4b binding protein are not secreted by these cells. We have shown by enzyme-linked immunoassay, immunocytochemistry, and immunoprecipitation of labeled proteins that thrombomodulin, a transmembrane glycoprotein involved with thrombin in the activation of protein C, is present at the cell surface of osteoblasts. Moreover, using a protein C activation system where thrombin and protein C are added to the cells, we have shown that protein C could be activated at the osteoblast cell surface. This activation of exogenous protein C, reflecting the activity of thrombomodulin, as well as the expression of the thrombomodulin antigen, is regulated by some bone resorption-enhancing factors. 1,25-dihydroxyvitamin D3 and retinoic acid increase thrombomodulin expression and activity in a dose-dependent manner whereas tumor necrosis factor alpha and interleukin 1 decrease these parameters. Because thrombomodulin is known to inhibit single-chain urokinase-type plasminogen activator, a molecule present in the osteoblast microenvironment, these findings suggest that thrombomodulin could play a role in the regulation of bone resorption by modulating the plasmin system.

Calcitriol↗