Are you K B Thomas?

Claim your profile

Publications (4)15.04 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Reports on von Willebrand factor (vWF) in hemolytic-uremic syndrome (HUS) are not unequivocal. Because of potential pathogenic implications, we examined the ability of vWF to bind to collagen in vitro, which reflects its function. Plasma vWF antigen (vWF:Ag) and collagen-binding activity (vWF:CBA) were measured by enzyme-linked immunosorbent assay in children with (1) diarrhea-associated (D+) HUS (n = 27), (2) chronic renal insufficiency (CRI) (n = 8), (3) gastroenteritis (GE) not associated with HUS (n = 15), (4) immune thrombocytopenia (ITP) (n = 40) and from controls (n = 35). Structural vWF was evaluated by multimer analysis. Children with D+ HUS had vWF:Ag of 2.53 and vWF:CBA of 1.98 U/mL. The corresponding values for patients with ITP were 1.35 and 1.82 U/mL, with CRI 1.55 and 1.55 U/mL, and with GE 1.68 and 2.10 U/mL; all values were higher than in controls (1.04 and 1.16 U/mL). The mean ratio of vWF:CBA to vWF:Ag ratio in controls was 1.13; only children with HUS had a dysfunctional vWF, as indicated by a low ratio of 0.78; the ratio was elevated in children with ITP (1.36) and GE (1.27) and was normal in those with CRI (1.06). No ultralarge molecular multimers of vWF were detected in any group, including HUS. The very high concentration of plasma vWF:Ag in HUS probably reflects endothelial cell damage or irritation. In contrast to all other groups, only children with HUS had a dysfunctional vWF, caused either by a primary (due to enterohemorrhagic Escherichia coli) or secondary (due to consumption of functionally active vWF) process. This abnormality was not obvious as structural anomaly by multimer analysis.
    Seminars in Thrombosis and Hemostasis 07/2001; 27(3):287-92. · 4.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: von Willebrand factor (vWF) antigen (vWF:Ag) and vWF-collagen binding activity (vWF:CBA) were measured in plasma by parallel quantitative ELISAs in normal newborns and infants (n = 71). The medians for vWF:Ag (IU/ml) and vWF:CBA (U/ml), respectively, were 1.46 and 1.91 for 2-7 day-old (n = 43), 1.22 and 1.40 for 2-4 week-old (n = 14), 1.22 and 1.15 for 2-6-month-old (n = 14) infants and 0.98 and 1.08 (n = 36) in normal adults. Elevated levels of vWF:Ag, but particularly vWF:CBA were seen for up to 4 weeks of life reaching adult levels between 2 and 6 months of life. The elevated levels of the vWF parameters indicate that caution should be exercised when interpreting laboratory data and diagnosing von Willebrand disease in newborns and young infants and warrant the use of age-specific reference ranges. The efficient haemostasis observed during early neonatal life may in part be due to the increased ability of vWF to interact with collagen.
    Acta Paediatrica 07/1995; 84(6):697-9. · 1.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A screening project to identify candidate molecular defects causing von Willebrand disease type IIC (VWD IIC) in a German family was carried out using polymerase chain reaction (PCR) amplification of all 52 exons of the von Willebrand factor (VWF) gene, subsequent electrophoresis of single and double stranded DNA and direct sequencing of PCR products with aberrant electrophoretic patterns. Only one candidate mutation, G550R, caused by a G-->A transition, was detected in exon 14 of the pro-VWF gene sequence. This mutation was not found on 200 chromosomes of normal individuals. The propositus was homozygous for the mutation and for an extended intragenic haplotype, composed of eight polymorphic markers. Further family members were heterozygous for the mutation and were phenotypically normal or only mildly affected, in accordance with the recessive pattern of inheritance for VWD type IIC. The mutation could influence one of the presumed active centers for the suspected multimerizing enzymatic activity of pro-VWF localized in the D1 and D2 domain, which corresponds to exon 5 and exon 14 of the VWF gene.
    Human Genetics 06/1995; 95(6):681-6. · 4.63 Impact Factor
  • R Schneppenheim, K B Thomas, A H Sutor
    [Show abstract] [Hide abstract]
    ABSTRACT: Von Willebrand disease (vWD), a disorder of primary hemostasis, represents the most frequently inherited bleeding diathesis, It is caused by a quantitative reduction or a qualitative abnormality, or both, of von Willebrand factor (vWF), a glycoprotein normally found in plasma, endothelial cells, subendothelial cell space, megakaryocytes and platelets. Patients with vWD represent a heterogeneous group with different phenotypes and with clinical symptoms that vary in severity. Many of the described types and subtypes of vWD are caused by mutations and aberrations of the vWF gene. The aim of this article is to highlight the impact of gene analysis on the current knowledge of the inheritance of vWD as well as on the structure-function relationship of vWF, and to focus on the available diagnostic laboratory tests and treatment options for patients with vWD, especially in childhood.
    Seminars in Thrombosis and Hemostasis 02/1995; 21(3):261-75. · 4.22 Impact Factor