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Biomedical subjects

V Vicente

Publications and source records attributed to V Vicente.

At least 145 records · Page 8Linked to original sources
PubMed1986

Detection of anomalies in cell-surface carbohydrates on thrombasthenic platelets using 125I-labeled lectins.

The composition of carbohydrates on the surface of platelets from a patient with Glanzmann's thrombasthenia and from seven normal donors were determined and compared. To this end, binding studies were performed using nine different purified 125I-labeled lectins; Concanavalin A, P-Phytohaemagglutinin, Wheat Germ Agglutinin, Dolichos biflorus, Pisum sativum, Ricinus communis II Agglutinin, Tetragonolobus purpureus, Lens culinaris and Soybean Agglutinin. These studies show that thrombasthenic platelets bear significantly decreased numbers of receptors for Concanavalin A and Lens culinaris, both with a specificity for D-mannose, and Ricinus communis II, with specificity for D-galactose. There were no detectable differences in the numbers of other lectin receptors. These results provide further evidence of molecular defects in thrombasthenic platelets. Moreover, the use of 125I-labeled lectins, as shown here, provides a fast and reliable technique for identifying abnormalities in the carbohydrate composition on the surface of platelets in various thrombopathies.

Blood Platelet Disorders↗
PubMed1986

Activation of kinin-prekallikrein system after infusion of factor VIII concentrates in hemophilic patients.

Possible changes in the kinin-prekallikrein system after infusion of factor VIII concentrate were studied in seven patients with severe hemophilia. The functional and immunological activities of factors XI and XII, prekallikrein, high molecular weight kininogen, and C-1-esterase inhibitor were measured before and at 0.5, 2, 6, and 12 hours after infusion of 50 U/kg of factor VIII concentrate. A significant decrease (P less than 0.05) in the functional and immunological activities of prekallikrein was observed at 0.5 and 2 hours after factor VIII administration. The other proteins did not change. The results suggest that the kinin system is activated after infusion of high doses of factor VIII concentrate, although clinical evidence of such activation by these changes was not detected.

Antigens↗
PubMed1986

Controlled trial of desmopressin in liver cirrhosis and other conditions associated with a prolonged bleeding time.

The synthetic vasopressin derivative desmopressin (DDAVP) shortens a prolonged bleeding time (BT) in patients with uremia, congenital platelet dysfunction, and von Willebrand disease. To establish the limits of the clinical usefulness of DDAVP, a controlled randomized study was carried out in 53 patients and ten volunteers with different conditions that have in common a prolonged BT. DDAVP significantly shortened the BT in 21 cirrhotics (P less than .01), in eight patients with unclassified prolonged BT (P less than .05) and in ten volunteers taking the antiplatelet drugs aspirin (P less than .05) and ticlopidine. The BT changes were not statistically significant in 15 patients with severe thrombocytopenia nor in nine with congenital platelet dysfunction, even though a few patients with storage pool deficiency responded with a marked BT shortening. Our findings indicate that DDAVP might be given when biopsies or other surgical procedures must be carried out in patients with prolonged BT. However, the compound is often ineffective in patients with thrombocytopenia or congenital platelet dysfunction.

Adolescent↗
PubMed1986

New congenital deficiency of high molecular weight kininogen and prekallikrein (Fitzgerald trait). Study of response to DDAVP and venous occlusion.

The prolonged partial thromboplastin time observed in the plasma of a 36 year old asymptomatic man was related to the reduced prekallikrein activities (coagulant; antigenic; and amidolytic) and the absence of coagulant and immunologic activities of high molecular weight kininogen (HMWKg). The patient's plasma also exhibited impaired surface-mediated fibrinolysis and impaired generation of kallikrein. The coagulation defect was identified as the "Fitzgerald trait". The levels of CH50, C2, C4 and C-1 inactivator were normal. Venous occlusion in the patient gave rise to a normal release of extrinsic plasminogen activator from the vascular endothelium. The administration of DDAVP led to a FVIII/VWF response which was similar to that obtained in healthy subjects. No alteration could be observed in the contact phase proteins after DDAVP administration.

Adult↗
PubMed1985

Protein C deficiency--response to danazol and DDAVP.

We studied a Spanish family in which one of the female members presented recurrent thrombophlebitis in both legs after three different deliveries. Biological and antigenic activity of protein C was decreased (35% and 42% respectively). Reduced protein C levels were also observed in 6 other family members. Administration of danazol (600 mg/day) in two patients with protein C deficiency elevated this protein and discontinuation of the drug resulted in a reduction of protein C to pretreatment values. The proposita showed a normal fibrinolytic activity and infusion of DDAVP produced a similar response of FVIII/VWF and plasminogen activator to those observed in healthy subjects.

Antithrombin III↗
PubMed1985

Studies on platelet surface carbohydrates in normal and uraemic platelets using 125I-labelled lectins.

Binding studies with six different purified 125I-labelled lectins, concanavalin A (con A), wheat germ agglutinin (WGA), Ricinus communis agglutinin II (RCA II), Dolichos biflorus (DB), Tetranolobus purpureus (TP) and P-phyto-hemagglutinin (P-PHA), were used to investigate the surface topography of carbohydrates in platelets from uraemic and normal subjects. Compared with normal the uraemic platelets, bear significantly decreased (more than 2.5-fold) numbers of receptors for P-PHA (N-acetyl D-galactosamine specificity) and Con A (specificity glucose, mannose). The number of WGA, RCA, II, DB and TP receptors in uraemic platelets did not differ from the number in normal platelets. Binding studies with 125I-labelled lectins provide further evidence of molecular defects in uraemic platelets. Moreover, this method might provide a fast and reliable technique for identifying abnormalities in the surface topography of carbohydrates on platelets in several pathological states.

Adult↗
PubMed1985

Regulation of the cytosolic and melanosome-bound tyrosinase activities in Harding-Passey mouse melanoma.

Mouse melanoma tyrosinases exist in the cytoplasm of melanocytes and also in a particulate form, bound to melanosomes. The cytosolic isoenzyme activity is not expressed in the melanocytes in vivo. One of the mechanisms for the activity regulation is the existence of a soluble inhibitor. This inhibition is non-competitive with regard to L-dopa. Particulate tyrosinase can be solubilized from the melanosome by several agents, Brij 35 and Triton X-100 being the most effective ones. Melanin accumulation in the organelle produces a competitive inhibition of the activity.

Animals↗
PubMed1984

Congenital deficiency of vitamin K-dependent coagulation factors and protein C.

A 15-month-old girl from Coimbra (Portugal) had a history of numerous hemorrhagic episodes with multiple bruises, hematomas but not hemarthroses. On serial testing she showed deficiency of factors II, VII, IX, X and protein C. Malabsorption-induced vitamin K deficiency, liver disease or ingestion of a coumarin compound were excluded. An absence of detectable abnormalities was found among her relatives. Consanguinity was not present. The immunologic assay, immunoelectrophoresis or antibody neutralization, revealed much higher levels of these factors than the clotting assay. The non-physiological activator (Echis carinatus venom) produced higher levels of prothrombin activation than those detected by physiological activation. Two-dimensional immunoelectrophoresis of the patient's plasma in calcium showed that prothrombin had the same mobility as acarboxyprothrombin. No significant response to large doses of intravenous vitamin K3 (6 mg) was observed. Transfusion of 120 ml of frozen fresh plasma led to an immediate increase in the procoagulant activities of vitamin K dependent protein, similar to that found after perfusion of plasma plus vitamin K3. The results obtained from this patient suggest a defect in the gammacarboxylation mechanism inside the hepatocyte.

Blood Coagulation Disorders↗