Yoshihiro Fujimura — Page 3

PubMed2002

[Von Willebrand factor-cleaving protease activity in patients of collagen disease with antiphospholipid antibodies].

Acquired thrombotic thrombocytopenic purpura (TTP), characterized by widespread thrombus formation in the microcirculation, is a ponderous complication of antiphospholipid syndrome. Recently, von Willebrand factor-cleaving protease (VWF-CPase) activity has been reported as a possible determinant for the occurrence of TTP. To clarify the role of VWF-CPase in the thrombus formation associated with antiphospholipid syndrome, we investigated plasma VWF-CPase activity in patients of collagen diseases with lupus anticoagulant (LA). Decreased plasma VWF-CPase activity less than 50% of the normal activity was observed in 25.7% (n = 18) in 70 patients with collagen diseases and 7 (10%) cases of them showed more lower VWF-CPase activity less than 25%. The IgG fractions obtained from 2 patients with the low VWF-CPase activity strongly inhibited the proteolytic reaction of normal VWF-CPase. There was no significant relationship between LA and plasma VWF-CPase activity. Thrombotic episodes, especially arterial thrombosis, were more frequently observed in LA-positive patients with low VWF-CPase activity. These results suggest that decreased activity of VWF-CPase, partly due to IgG type inhibitor to the enzyme activity may be an additional risk factor for arterial thrombosis in collagen disease patients with antiphospholipid antibodies.

ADAM Proteins↗

PubMed2002

[Shear stress-induced platelet aggregation in children with minimal change nephrotic syndrome].

Analysis of the hemostasis system using biochemical techniques in children with minimal change nephrotic syndrome (MCNS) has previously been restricted to in vitro assays. The recent introduction of measurement of shear stress-induced platelet aggregation (SIPA) using platelet-rich plasma (PRP) has facilitated detailed investigation of the hemostatic system in vivo. In order to further analyze the etiology of the thrombotic tendency exhibited by patients with childhood MCNS, we investigated SIPA at both low shear stress (L-SIPA) and high shear stress (H-SIPA) in 14 children with MCNS using PRP collected weekly after commencing prednisolone therapy. Seven patients were newly diagnosed cases of MCNS (ND) whereas the remainder had suffered a disease relapse (DR). Prior to prednisolone therapy L-SIPA, which was thought to be affected by fibrinogen (Fbg) levels, was significantly increased in both patient groups compared to normal controls (17.4 +/- 4.1% vs. 3.6 +/- 0.7%, ND vs control, p < 0.01: 11.7 +/- 3% vs. 2 +/- 0.7%, DR vs control, p < 0.01) with values declining at weekly intervals thereafter. Plasma Fbg levels in simultaneously collected samples followed a similar course. In contrast, H-SIPA, which was thought to be affected by von Willebrand factor (VWF), was significantly enhanced in MCNS patients after 1 week of prednisolone therapy compared to the controls (45 +/- 5.1% vs. 26.3 +/- 3.5%, ND vs normal, p < 0.05: 36.9 +/- 3.3% vs. 25.5 +/- 1.6%, DR vs. normal, p < 0.05). Plasma ristocetin cofactor and VWF antigen levels in simultaneously collected samples followed a similar course, whereas thrombin-antithrombin complex (TAT) levels remained constant. These results indicate that SIPA is enhanced in the acute stage of childhood MCNS, especially L-SIPA prior to the initiation of prednisolone therapy and H-SIPA after 1 week of prednisolone therapy, and that these phenomena may be affected by plasma Fbg and VWF levels, respectively. The enhanced SIPA may play an important thrombogenic role in the acute phase of childhood MCNS.

Adolescent↗