1,721,117 research outputs found
A critical evaluation of the available methods for the determination of factor VIII von Willebrand.
No full textVon Willebrand factor (vWf) is the major component of the circulating factor VIII complex. The von Willebrand molecule includes factor VIII related antigen (VIIIR: Ag) which represents the molecular substrate of the von Willebrand activity expressed as Ristocetin cofactor (VIIIR:RCoF) activity. Several methods have been developed for VIIIR: Ag evaluation, among the first being the rocket-immunoelectrophoresis method of LAURELL. Radial immunodiffusion (MANCINI's method) was also used. Subsequently, radioimmunological assays, either as radioimmunoassay (RIA) or immunoradiometric assay (IRMA), were developed with improvements in sensitivity, so that levels of VIIIR: Ag lower than 0.1% of normal can be detected. More recently, an enzyme-linked immunosorbent assay (ELISA), characterized by the use of enzyme-conjugated antibody was proposed. This method shows a sensitivity similar to immunoradiometric methods but without using any dangerous reagent. Finally, a nephelometric method was proposed for factor VIII antigen evaluation. For a qualitative evaluation of von Willebrand factor crossed-immunoelectrophoresis and multimeric analysis can be used. In the first case, the use of precipiting antibodies against von Willebrand factor may demonstrate a peak with different characteristics related to the biochemical property of von Willebrand. Multimeric analysis in SDS-agarose gel electrophoresis followed by staining with labelled antifactor VIII antibodies gives information about different polymeric forms of circulating VIII/vW factor. Von Willebrand factor activity, expressed as its ability to induce platelet aggregation in the presence of the antibiotic Ristocetin, can be carried out using normal formalin fixed platelets, either with aggregometer or visual methods (glass slide test or tubes test and microtritation plate). The corrected evaluation of factor VIII complex by all these techniques together with the clotting activity assay allows a satisfactory study of factor VIII properties
Different platelet binding sites are probably involved in spontaneous platelet aggregation induced by IIB von Willebrand factor in normals and in IIB von Willebrand's disease patients.
No full textAssessment of von Willebrand factor propeptide improves the diagnosis of von Willebrand disease.
No full textOne of the more recent findings concerning Von Willebrand disease (VWD) is that a shorter Von Willebrand factor (VWF) survival either decides or modulates the VWD phenotype by downregulating circulating VWF levels. VWF survival is currently investigated with the desmopressin (DDAVP) test, a time-consuming strategy enabling the main pharmacokinetic parameters (e.g., VWF half-life elimination time and clearance) to be defined. An alternative now available involves assaying the VWF propeptide (VWFpp) in single steady-state blood samples, which reportedly increases as VWF survival decreases. This article demonstrates how measuring VWFpp and calculating the VWFpp-to-VWF:antigen ratio (VWFpp ratio) are good alternatives to DDAVP for investigating VWF survival. In type 1 VWD, the VWFpp ratio has been found normal in patients with pure quantitative VWF defects, markedly increased in cases with an isolated decline in VWF survival, and more or less increased in patients with both quantitative defects and a shorter VWF survival. The same applies to type 2B VWD, which is characterized by an increased VWFpp ratio and a shorter VWF survival, with values that appear inversely related. Exploring VWF half-life by assaying VWFpp is useful not only for the more precise characterization of VWD but also for defining its most appropriate treatment
Platelet aggregation and pseudothrombocytopenia induced by 1-desamino-8-D-arginine vasopressin (DDAVP) in type IIB von Willebrand's disease patient.
No full textOur study shows that the thrombocytopenia described in type IIB von Willebrand's disease (vWd) after 1-desamino-8-D-arginine vasopressin (DDAVP) infusion is, at least partially, a pseudothrombocytopenia. There was a discrepancy in platelet counts in blood anticoagulated with EDTA (less than 10 x 10(3)/microliters) or citrate (55 x 10(3)/microliters) in one patient with type IIB vWd and chronic thrombocytopenia (80 x 10(3)/microliters) after DDAVP infusion. Furthermore, DDAVP induced a normalization of patient's prolonged bleeding time. Spontaneous platelet aggregation (SPA) observed in platelet-rich plasma before DDAVP infusion was inhibited completely by monoclonal antibodies which block binding of fibrinogen, vWf and fibronectin to GPIIb-IIIa. SPA was partially inhibited by a monoclonal antibody which blocks the binding of vWf to GPIb. After DDAVP, in contrast, SPA partially persisted in the presence of anti-GPIIb-IIIa monoclonal antibodies but was completely inhibited by anti-GPIb monoclonal antibody. Therefore GPIb and GPIIb-IIIa complex seem to play a different role in SPA before and after DDAVP infusion into type IIB vWd.
I.F. 1,80
[Juvenile rheumatoid arthritis appearing after hepatitis. Causal or casual relationship].
No full textHigh fever, spleen and lymph node enlargement, and joint pains that assumed the character of rheumatoid arthritis in the ensuing months were noted after a viral hepatitis episode in a 21-year-old woman. Serious anaemia and myocarditis also appeared when the picture was at its worst. A lymphoma was suspected, and the spleen and some abdominal lymph nodes were removed. These displayed signs of intense follicular reaction unaccompanied by atypia. The possibility that juvenile rheumatoid arthritis may be triggered by hepatitis is examined
Potentiation of anticoagulant response to warfarin by sulphinpyrazone: a double-blind study in patients with prosthetic heart valves.
No full textThe effect of Sulphinpyrazone on the anticoagulant response to Warfarin was evaluated by a double-blind study in 11 patients with prosthetic heart valves. Six patients received Warfarin and Sulphinpyrazone and 5 Warfarin and placebo. Sulphinpyrazone potentiated the anticoagulant effect of Warfarin. Patients receiving Sulphinpyrazone needed about half the amount of Warfarin as compared to the control group. There were four bleeding episodes in the Sulphinpyrazone group and one episode in the control group. It was difficult to regulate the dose of Warfarin in patients also receiving Sulphinpyrazone
A model-based approach to the automatic diagnosis of von Willebrand disease
No full textVon Willebrand disease (VWD) is the most common inherited coagulation disorder to be seen in humans. It originates from a
deficiency and/or dysfunction of the von Willebrand factor (VWF), a large multimeric glycoprotein playing a central role in
the hemostasis process. VWD occurs in a large variety of forms, and its symptoms may range from sporadic nosebleeds and
mild bleeding from small lesions in skin, to acute thrombocytopenia or prolonged bleeding episodes. Diagnosing VWD may be
complicated because of the heterogeneous nature of the disorder. Two mechanistic models of VWD are proposed in this article,
and their performance is assessed using clinical data. Models allow for the automatic detection of the disease, as well as
for a quantitative assessment of VWF multimer distribution patterns, thus elucidating the critical pathways involved in the disease
recognition and characterization
1-Desamino-8-D-arginine vasopressin (DDAVP) infusion in type IIB von Willebrand's disease: shortening of bleeding time and induction of a variable pseudothrombocytopenia.
No full textWe have investigated the effects of 1-desamino-8-D-arginine vasopressin (DDAVP) infusion on platelet count and bleeding time in 4 patients with type IIB von Willebrand's disease (vWd). Three of four patients showed a normalization of the bleeding time within 1 h after the infusion, while bleeding time was not modified in the fourth. In accordance with the literature, thrombocytopenia was observed after DDAVP infusion, but this thrombocytopenia was due to the anticoagulants used for blood collection. In two patients (F.I., G.F.) no thrombocytopenia was observed when platelets were counted by fingerstick method but there was a 20% platelet decrease in blood samples collected in sodium citrate and a 50% decrease in samples collected in EDTA. Dramatic falls in platelet counts (70-95%) were observed in the additional two patients (C.A., D.Z.) after DDAVP infusion, when both sodium citrate or EDTA were used as anticoagulants. In the latter two patients there was also a 50% decrease in platelet count when the fingerstick method was used. The decrease in the patient's platelet count in EDTA samples after DDAVP infusion could be prevented, in part, by the previous additions of an anti GPIb monoclonal antibody and an anti GPIIb-IIIa monoclonal antibody. Thus, the thrombocytopenia observed in the four IIB vWd patients studied after DDAVP infusion seems to be, at least partially, a pseudothrombocytopenia depending on the calcium concentration in the blood samples and the availability of GPIb and GPIIb-IIIa receptors. These findings and the normalization of the bleeding time observed in three of the four patients has led us to reconsider the possible use of DDAVP in the treatment of our IIB vwd patients
FACTOR-VIII VONWILLEBRAND-FACTOR ABNORMALITIES DURING L-ASPARAGINASE TREATMENT IN PATIENTS WITH ACUTE LYMPHOBLASTIC-LEUKEMIA
No full textFactor VIII/von Willebrand factor (VIII/vWf) related properties were studied in 10 patients affected by acute lymphoblastic leukemia during L-asparaginase-vincristine-prednisone treatment. These properties remained within the normal range during the period of observation without any difference from the basal values. On the contrary, VIII:C activity was already increased before medication and showed gradual additional elevation during the observation period, reaching a peak 1 week after discontinuation of L-asparaginase administration. Crossed immunoelectrophoresis of vWf, performed weekly in 2 patients during the period of medication, demonstrated a normal pattern before the beginning of treatment, but an apparently faster migrating peak during L-asparaginase therapy, suggesting a qualitative abnormality of vWf. No abnormal bleeding tendency was found in any of the patients
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