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  • 1
    ISSN: 1432-1076
    Keywords: Key words Chronic relapsing ; Thrombotic thrombocytopenic purpura ; Von Willebrand factor-cleaving protease ; Prophylactic treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The pentad of thrombocytopenia, haemolytic anaemia, mild renal dysfunction, neurological signs and fever, classically characterizes the syndrome of thrombotic thrombocytopenic purpura (TTP). TTP usually occurs in adults but also children have been described with this condition. The disorder may take a relapsing course, termed chronic relapsing TTP (CRTTP), which although very rare, may also begin in childhood. Deficiency of a recently identified enzyme, the von Willebrand factor (vWF)-cleaving protease, seems to play a major role in the development of TTP. We report on a 3-year-old boy with a dramatic but typical clinical course of CRTTP. At the time of diagnosis, neurological deficits and multiple cerebral infarctions had already occurred. In plasma, vWF-cleaving protease was completely absent, both during acute TTP and in remission. There was no protease inhibitor detected. Regular infusions of fresh frozen plasma were successfully given for replacement on a prophylactic basis. Conclusion Assay of von Willebrand factor-cleaving protease helps to diagnose a form of thrombotic thrombocytopenic purpura which may be managed by prophylactic treatment with fresh frozen plasma.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of muscle research and cell motility 20 (1999), S. 363-370 
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Phosphorylation of the regulatory light chain subunit of smooth muscle myosin is sufficient, but not necessary for muscle contraction. It has been suggested that thin-filament regulation may also contribute to the regulation of contraction. A hallmark feature of regulated thin filaments, previously described for vertebrate skeletal muscle, is the capacity of strong-binding or rigor-like cross bridges to “turn-on” the actin filament. Turned-on thin filaments stimulate cross-bridge attachment even in the absence of calcium. The present study utilized an in vitro sliding-filament motility assay to test for thin-filament regulation of both unphosphorylated and phosphorylated smooth muscle myosins. Regulated thin-filaments were reconstituted from skeletal muscle actin and chicken gizzard smooth muscle tropomyosin (TmCG), and then turned-on either (1) by rigor cross bridges at low concentrations of MgATP, or (2) by adding N-ethyl-maleimide-modified skeletal subfragment S1(NEM-S1), which forms rigor-like bonds in the presence of MgATP. For control actin·TmCG filaments, force production by unphosphorylated myosin was 0.5% of that produced by thiophosphorylated myosin. The force exerted on actin·Tm filaments by both unphosphorylated and phosphorylated myosins was increased by reducing the [MgATP] to 10–100 μM MgATP (rigor-dependent activation). Force was also increased by actin·TmCG filaments that had been turned-on by NEM-S1 binding, with force production by unphosphorylated myosin increased 80-fold vs. 2.3-fold for thiophosphorylated myosin. TmCG was required for increased force production with both low MgATP and NEM-S1. Unloaded filament velocity for NEM-S1-activated thin filaments was 0.72 μm/sec with unphosphorylated myosin compared to 1.24 μm/sec with thiophosphorylated myosin. Taken together, these results suggest that thin-filament regulation may play a role in the activation of both unphosphorylated and phosphorylated smooth muscle myosins and suggest a possible mechanism for activation of slowly cycling unphosphorylated cross bridges (i.e. latch-state) during tonic contractions of smooth muscle.
    Type of Medium: Electronic Resource
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