1,721,033 research outputs found
Role of von Willebrand factor in the haemostasis
Full text linkvon Willebrand factor (VWF) is an adhesive and multimeric glycoprotein that found its historical origin in 1924, when the Finnish physician Erik von Willebrand first reported a family with a serious hereditary bleeding affecting consanguineous families. The proband was a five years old girl with severe bleeding since birth. Three sisters had died before the age of four, one living sister, aged three, also was severely affected. von Willebrand had thought that it was a disorder of platelet function or a vascular defect as a possible cause of the bleeding.
Since the original observations by Erik von Willebrand, the disease has been extensively studied and it was shown in the mid 1950s that impaired haemostasis was because of lack or an abnormality of a plasmatic factor - the von Willebrand factor – necessary for normal hemostasis
Study on the glucose-6-phosphate dehydrogenase degradative mechanism in developing rabbit erythroblasts
No full textMutations leading to premature termination codons in the Von Willebrand factor gene are associated with the decay of the mutant mRNAs
No full textGlucose-6-phosphate dehydrogenase activity in dorsal root ganglia of vitamin E - deficient rats.
No full textMutations leading to premature termination codons in the Von Willebrand factor gene are associated with allele-specific mRNAs decay
No full textA new candidate mutation, G1629R, in a patient with type 2A von Willebrand's disease: basic mechanisms and clinical implications
Full text linkType 2A von Willebrand's disease (VWD) refers to disease variants with decreased platelet-dependent function of von Willebrand factor (VWF) associated with the absence of high molecular weight (HMW) multimers. The candidate G1629R mutation, identified in an Italian patient with type 2A VWD, was expressed to confirm the relationship between phenotype and genotype. Plasma samples from the patient were studied after DDAVP or FVIII/VWF concentrate injections. Furthermore, an expression vector carrying the G1629R mutation was constructed by site-directed mutagenesis and transiently expressed in Cos-7 cells. The characteristics of the corresponding recombinant protein were analyzed. After 1-deamino-8-D-argine vasopressin (DDAVP) infusion, factor VIII and VWF activities increased and HMW VWF multimers were transiently observed in the patient's plasma. VWF activity increased only after administration of a dual FVIII/VWF concentrate. ADAMTS-13 activity did not change significantly before or after the therapies. Secretion, in culture medium, of the corresponding mutated protein (R1629-rVWF) was slightly decreased and this rVWF contained intermediate and HMW multimers. Furthermore, binding of R1629-rVWF to platelet GPIb was moderately reduced compared to that of the wild-type rVWF. Based on the DDAVP and in vitro expression results, we classified the G1629R mutation in group 2 type 2A mutations. Our findings could explain why DDAVP may only be partially effective and suggest that FVIII/VWF concentrates should be used in cases of prolonged mucosal bleeding and major surgery when functional VWF is required
Prevalence of type 2b "Malmo/New York" von Willebrand disease in Italy : the role of von Willebrand factor gene conversion
No full textMolecular diagnosis of von Willebrand disease.
No full textThe role of molecular characterization in the diagnosis of von Willebrand disease (VWD) is not essential if the patients have been extensively investigated using phenotypic analysis. On the other hand, if some of these phenotype assays are not available, the identification of the mutation causing the disease could be crucial for an accurate diagnosis. Nevertheless, there are several reasons for performing molecular analysis in patients phenotypically well characterized, e.g. to identify the mutation causing VWD can be useful for patients and their family members when prenatal diagnosis is required (type 3 or severe type 2). In this manuscript, we report the techniques used for the molecular characterization of suspected VWD patients. We describe the use of online von Willebrand factor database and online single nucleotide variation databases, the former to verify whether a candidate mutation has been previously identified in other VWD patients and the latter to ascertain whether a putative mutation has been reported earlier in healthy individuals. We listed the available in silico analysis tools, to determine the predicted pathogenicity of a sequence variant and to establish its possible negative effect on the normal splicing process. We also report the strategy that can be used to identify VWD type 2 patients' mutations in subjects who have been fully characterized using the phenotype assays
von Willebrand factor collagen binding assay in von Willebrand disease type 2A, 2B, and 2M
No full textBiochemical characterization of a recombinant von Willebrand factor (VWF) with combined type 2B and type 1 defects in the VWF gene in two patients with a type 2A phenotype of von Willebrand disease
No full textBackground: In a patient previously diagnosed with type 2A von Willebrand disease (VWD) [absence of high and intermediate molecular weight von Willebrand factor (VWF) multimers and markedly reduced ristocetin-induced platelet aggregation (RIPA)], an infusion test of desmopressin was followed by mild thrombocytopenia. This led to further laboratory investigations of his affected brother and of family members, who showed different phenotypic patterns compatible with type 1, 2A, 2B and an uncertain classification of VWD. The two brothers were compound heterozygotes (C275R/P1337L), whereas the others members of the family were heterozygous for C275R (a novel mutation in the D1 domain) or P1337L (a type 2B mutation in the A1 domain). Objective and methods: To evaluate the role of the combined effect of the two mutations in the two brothers, C275R and P1337L recombinant (r) VWFs were transiently expressed in COS-7 cells. Results: Recombinant VWF levels secreted in cell media were similar for wild-type (WT), P1337L and hybrid P1337L/WT rVWFs, reduced for hybrids C275R/P1337L and C275R/WT rVWFs, and strongly reduced for C275R rVWF. All rVWFs had a full set of multimers except C275R rVWF, which had only dimers. P1337L rVWF and C275R/P1337L rVWF showed the highest degree of binding to glycoprotein (GP) Ibα and the lowest to collagen, followed by P1337L/WT rVWF (with an intermediate level of binding to both ligands), and by WT rVWF with the lowest level of binding to GPIbα and the highest to collagen. Conclusion: These results suggest that the two compound heterozygous patients have a circulating VWF mainly mutated in the A1 domain (P1337L). This peculiar type 2B VWF variant showed a remarkably high affinity for the GPIbα platelet receptor, leading to the loss of high and intermediate molecular weight multimers and hence to decreased RIPA, as in type 2A VWD
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