Search PubMed⌕ Search

Biomedical subjects

J Vermylen

Publications and source records attributed to J Vermylen.

At least 145 records · Page 8Linked to original sources
PubMed1992

Influence of hydroxyethyl starch on coagulation in patients during the perioperative period.

The perioperative use of hydroxyethyl starch (HES) has been implicated as a possible cause of intracranial bleeding. The purpose of this study was to compare the influence on blood coagulation of the isovolemic replacement of 1-L blood loss with either 6% HES (molecular weight [MW] average: 450,000) or 5% human albumin during neurosurgery or lower abdominal surgery. Twenty patients scheduled for brain tumor surgery and 20 patients undergoing transabdominal hysterectomy were studied. The activated partial thromboplastin time, prothrombin time, fibrinogen concentration, factor VIII coagulant, von Willebrand factor antigen, platelet count, and the activated clotting time were compared after induction of anesthesia, after administration of 500 and 1000 mL of colloid solution, and 24 and 48 h postoperatively. All measured coagulation variables remained within physiologic range. Changes in coagulation indices were identical in neurosurgical and hysterectomy patients, except for a larger increase in fibrinogen concentration 24 and 48 h after hysterectomy. The acute phase reaction of factor VIII coagulant and von Willebrand factor, which plays a role in postoperative hypercoagulability, was attenuated by the use of HES. We conclude that isovolemic replacement of 1-L blood loss with either 6% HES (MW average: 450,000) or 5% human albumin does not interfere with normal hemostasis during and after neurosurgery or lower abdominal surgery.

Adult↗
PubMed1991

Continuous quantitative monitoring of mural, platelet-dependent, thrombus kinetics in the crushed rat femoral vein.

A new in vivo method to study the size and dynamics of a growing mural thrombus was set up in the rat femoral vein. The method uses a standardized crush injury to induce a thrombus, and a newly developed transilluminator combined with digital analysis of video recordings. Thrombi in this model formed rapidly, reaching a maximum size 391 +/- 35 sec following injury, after which they degraded with a half-life of 197 +/- 31 sec. Histological examination indicated that the thrombi consisted mainly of platelets. The quantitative nature of the transillumination technique was demonstrated by simultaneous measurement of the incorporation of 111In labeled platelets into the thrombus. Thrombus formation, studied at 30 min interval in both femoral veins, showed satisfactory reproducibility overall and within a given animal. With this method we were able to induce a thrombus using a clinically relevant injury and to monitor continuously and reproducibly the kinetics of thrombus formation in a vessel of clinically and surgically relevant size.

Animals↗
PubMed1991

Possible platelet contribution to pathogenesis of transient neonatal hyperammonaemia syndrome.

The pathogenesis of the transient neonatal hyperammonaemia syndrome is largely unknown. The role of platelet activation was investigated in three preterm infants with this syndrome by non-invasive methods. In all three infants, urinary concentrations of beta-thromboglobulin and 11-dehydrothromboxane B2 levels were much higher during the hyperammonaemia than those in ten control preterm infants. It is possible that transient platelet activation occurs in the portal system of these infants, thereby causing the hyperammonaemia.

Ammonia↗
PubMed1991

Thromboxane synthase inhibitors, thromboxane receptor antagonists and dual blockers in thrombotic disorders.

Thromboxane A2 (TXA2) plays a pivotal role in platelet activation and is involved in the development of thrombosis. Thromboxane synthase inhibitors suppress TXA2 formation and increase the synthesis of the antiaggregatory prostaglandins PGI2 and PGD2; however, accumulated PGH2 may interact with the platelet and vessel wall TXA2 receptor, thus reducing the antiplatelet effects of this class of drug. TXA2 receptor antagonists block the activity of both TXA2 and PGH2 on platelets and the vessel wall. Very recently, drugs possessing both thromboxane synthase-inhibitory and thromboxane receptor-antagonist properties have been developed. Paolo Gresele and colleagues explain here why these drugs can be more efficacious than traditional antiplatelet agents and review the available experimental studies involving these drugs.

Animals↗
PubMed1991

Bilateral carotid artery occlusion: clinical presentation and outcome.

In a 4-year period, 17 patients were diagnosed as having bilateral carotid artery obstruction on ultrasonic duplex examination. Twelve had been referred because of recent neurological symptoms and the remaining 5 during cardiac or peripheral vascular work-up. Three patients had a completely silent occlusion of their two carotid arteries. Cardiac and/or peripheral vascular symptoms were present in 11 subjects. Mean follow-up was 28 months. No further strokes occurred. The 3-year cumulative stroke-free survival by life-table analysis was 75%. Myocardial infarction was the cause of death in 2 of 4 patients. For some patients with bilateral carotid artery occlusion, the clinical outcome is better than anticipated.

Aged↗
PubMed1991

In vitro and in vivo evaluation of two factor VIII concentrates virally inactivated by solvent-detergent or by pasteurization.

The present study compares two new factor VIII preparations currently used in the treatment of haemophilia. A Factor VIII was partially purified from plasma obtained from unpaid voluntary Belgian donors in the blood transfusion centers of Lille and Amsterdam and virus-inactivated by exposure to solvent-detergent (FVIII-SD) or by pasteurization (FVIII-P) respectively. The factor VIII content and the purity of both preparations were assessed in vitro, whereas in vivo we studied the recovery and the plasma half-life of both concentrates. The higher purity of FVIII-SD was confirmed. Factor VIII-P preparations contained more factor VIII than mentioned on the label. Both preparations gave good in vivo recoveries and half-lives. Patients who did not have antibodies to hepatitis B, hepatitis C or HIV at the initial screening, remained negative after six months treatment with the new concentrates. No patients developed neutralizing factor VIII antibodies. Furthermore patients appreciated the ease of administration of both preparations. In conclusion both FVIII concentrates are suited for the treatment of haemophilia A patients.

Antibodies, Viral↗
PubMed1991

Platelet fatty acids and function in two distinct regions of Belgium: relationship to age and dietary habits.

We compared the dietary habits, fatty acid composition of plasma and platelet phospholipids, and platelet function in two groups of healthy Belgian male subjects, known to differ in their mortality rate from coronary heart disease (CHD). In the Walloon subjects, there was a larger intake of saturated and a lower intake of (n-6) polyunsaturated fats, confirmed by the fatty acid composition of plasma and platelet phospholipids. While plasma HDL and total cholesterol were similar in the present samples of the two communities, platelet aggregation to epinephrine was significantly higher in the Walloon subjects. When the two populations were divided into younger (28-54 years) and older (55-73 years) age groups, the older Walloon subjects exhibited platelet hyper-aggregability to most of the agonists, compared to the other three groups. In addition to dietary fats, alcohol and smoking habits, age was an important determinant of platelet phospholipid fatty acids and platelet reactivity. The present results reinforce those of previous studies, indicating that platelet behaviour is significantly affected by the main risk factors for CHD.

Aging↗
PubMed1991

Diagnostic significance of antinuclear antibodies in neurologic patients.

In a combined retrospective and prospective study, we tried to define the prevalence of antinuclear antibodies (ANA) and its clinical relevance in neurological patients. Three hundred twenty-seven neurological patients who had ANA determined because of suspicion of connective tissue disease (CTD), were retrospectively studied. Thirty (9.2%) were ANA positive, 20 (66%) of whom had CTD. Of 327 consecutively admitted patients, prospectively studied, 18 (5.5%) were ANA positive, 5 (28%) of whom had evidence of CTD. Systemic lupus erythematosus (SLE) was the most frequently diagnosed CTD. In a prospective study of 48 multiple sclerosis (MS) patients, only 1 had detectable ANA at a dilution of 1:40. Lupus anticoagulant (LA) was prospectively detected in 2 patients but was not associated with a vascular or autoimmune systemic disease.

Adult↗
PubMed1991

Generation of arachidonic acid metabolites from stimulated whole blood in patients with chronic myeloproliferative disorders.

We have evaluated the arachidonic acid (AA) metabolism in patients with myeloproliferative disorders (MPD). In essential thrombocythemia (ET), the generation of thromboxane B2 was found significantly reduced and inversely correlated with platelet count. Polycythemia vera (PV) patients showed an increased formation of this metabolite of AA. Prostaglandin E2 and 6-keto-PGF1 alpha generation were markedly reduced in patients with chronic myelogenous leukemia. Our study confirms that the arachidonate metabolism is frequently deranged in patients with MPD. The opposite changes in thromboxane formation in ET and PV could be one of the factors responsible for the different incidences of thrombotic and hemorrhagic complications in these diseases.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Measurement of von Willebrand factor antigen in plasma and platelets with an enzyme-linked immunosorbent assay based on two murine monoclonal antibodies.

Two murine monoclonal antibodies, raised against von Willebrand factor (vWF), were used to construct an enzyme-linked immunosorbent assay (ELISA), for quantitation of vWF antigen (vWFAg) in human plasma and platelets. This assay had a lower limit of sensitivity of 0.0001 IU/ml in buffer, and thus is one to two orders of magnitude more sensitive than other ELISA assays which have been reported. The intraassay, interassay and interdilution coefficients of variation were 4.1, 10.4 and 9.9%, respectively. In normal plasma (n = 20), the vWFAg level was 0.83 (range: 0.42-1.25) IU/ml. In normal washed platelets (n = 10), 0.35 (0.25-0.49) IU/10(9) platelets was found. In plasma obtained from various patient groups the following vWFAg levels (geometric mean and range) were observed: von Willebrand's disease (n = 19): 0.18 (0.02-0.77) IU/ml; patients with liver cirrhosis (n = 20): 3.73 (1.68-9.20) IU/ml; patients with pregnancy-induced hypertension (n = 20): 4.14 (2.28-7.44) IU/ml and patients with malignant disease (n = 10), 2.54 (1.51-5.60) IU/ml. A linear correlation was found between vWFAg levels measured with a polyclonal antibody based Laurell electroimmunoassay (r = 0.92, n = 58) or with a polyclonal antibody based ELISA (r = 0.94, n = 64). The present assay is based on stable and reproducible reagents and allows the specific measurement of vWFAg in plasma and in platelets. This assay may constitute a useful tool for the further investigation of clinical conditions associated with changes in vWFAg levels. In addition, its high sensitivity may facilitate a more detailed study of platelet vWFAg in normal and in pathological conditions.

Animals↗
PubMed1990

Detection of lupus-like anticoagulants by an enzyme-linked immunosorbent assay using a partial thromboplastin as antigen; a comparative study.

Clotting assays allow qualitative rather than quantitative detection of the lupus anticoagulant. We have therefore studied the usefulness of an ELISA using a commercial partial thromboplastin, Throombofax, as antigen; the results obtained on 146 selected patient plasmas were compared to the results of coagulation tests (kaolin clotting time, tissue thromboplastin inhibition test, activated partial thromboplastin time) and of ELISAs using cardiolipin or phosphatidylserine as antigen. While satisfactory agreement was found within the group of coagulation tests or that of ELISAs, only a moderate agreement was obtained between clotting tests and ELISAs, the best being with the partial thromboplastin ELISA using low plasma dilutions. The study further indicates that ELISA techniques cannot entirely replace coagulation tests for the detection of a lupus anticoagulant, even when a partial thromboplastin is used as antigen. On the other hand, coagulation tests are less sensitive than ELISAs for the detection of antiphospholipid antibodies.

Antigens↗
PubMed1990

Ridogrel, a combined thromboxane synthase inhibitor and receptor blocker, decreases elevated plasma beta-thromboglobulin levels in patients with documented peripheral arterial disease.

The combination of thromboxane synthase inhibition with thromboxane receptor antagonism has been shown to result in a strong inhibition of platelet aggregation and a prolongation of the bleeding time (Gresele et al., J. Clin Invest 1987; 80: 1435-45). Ridogrel is a single molecule that efficiently achieves both inhibitions in human volunteers. The present study was performed in patients with obstructive peripheral arterial disease and elevated plasma beta-thromboglobulin levels. Patients were treated with either 2 x 300 mg ridogrel or 2 x 300 mg placebo per day for 2 1/2 days, according to a double blind randomised parallel design. Plasma beta-thromboglobulin decreased significantly throughout active treatment starting within 2 h after administration; serum and urinary immunoreactive TxB2 levels and urinary 11-dehydro-TxB2 excretion were significantly lower and serum PGE2 and 6-keto-PGF1 alpha levels significantly higher with ridogrel; no changes were observed in the placebo-treated group. In conclusion this study demonstrates a reduction of platelet activation in vivo by ridogrel.

Aged↗
PubMed1990

Recombinant human erythropoietin increases blood pressure, platelet aggregability and platelet free calcium mobilisation in uraemic children: a possible link?

Recombinant human erythropoietin was administered to 10 uraemic children on chronic haemodialysis, all of whom responded by correcting their haemoglobin. In addition, they showed an increase in blood pressure; platelet aggregations, subnormal before therapy, improved during treatment. The intracellular free calcium concentration in platelets after thrombin stimulation also increased significantly during erythropoietin administration. We hypothesize that the effect of erythropoietin on platelet aggregability and on blood pressure may be due to an increase in the intracellular free calcium mobilisation in platelets and possibly in smooth muscle cells respectively.

Adolescent↗
PubMed1990

Lack of platelet response to collagen associated with an autoantibody against glycoprotein Ia: a novel cause of acquired qualitative platelet dysfunction.

Platelets from a patient with an acquired hemorrhagic disorder had a severely impaired response to collagen, whereas platelet aggregation to other agonists and coagulations tests were normal. No abnormalities of the patient's platelet membrane glycoproteins (GP) were seen. Treatment of the patient with immunosuppressive agents temporarily improved both the bleeding tendency and the collagen responsiveness of the platelets. An IgG was found to be present in the plasma, directed against a protein comigrating with GPIa, and coadsorbing with GPIa to insoluble collagen fibers in a Mg2+(-)dependent manner. Furthermore, GPIa was recognized by the patient's antibody when affinity-purified GPIa-IIa was used as antigen. Finally, the GPIa-IIa complex was immunoprecipitated from a platelet lysate by patient's plasma. In addition, purified platelet specific IgG's from the patient inhibited aggregation of normal platelets induced by collagen or by wheat germ agglutinin. We conclude that the lack of response to collagen of the patient's platelets may well be due to the presence of an autoantibody against GPIa.

Adult↗
PubMed1990

Guanine nucleotide-dependent inhibition of phospholipase C in human endothelial cells.

Treatment of intact human umbilical vein endothelial cells with NaF results in a dose-dependent biphasic response in both prostacyclin and inositol phosphate production: the stimulation observed with 10-20 mM NaF decreases with higher concentrations. High concentrations of NaF furthermore reduce thrombin- or A23187-stimulated prostacyclin production. Direct assay of phospholipase C activity in cell homogenates shows a similar biphasic response to NaF, also after chelation of Ca2+; addition of AlCl3 shifts the inhibition toward lower NaF concentrations. Guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) also causes a dose-dependent biphasic response in inositol phosphate formation in permeabilized cells and homogenates; a higher inhibitory concentration of GTP gamma S abolishes the stimulation of inositol phosphate production by low NaF concentrations. A high concentration of NaF furthermore inhibits the non-G-protein-dependent activation of phospholipase C by deoxycholate. NaF also induces a dose-dependent biphasic response in cyclic AMP formation in intact cells, indicating that the inhibition of phospholipase C at higher NaF concentrations does not result from a rise in cyclic AMP. The data are compatible with the existence of a guanine nucleotide-dependent, cyclic AMP-independent, phospholipase C-inhibitory pathway in endothelial cells.

1-Methyl-3-isobutylxanthine↗