Characterization and ATPase activity of human platelet actomyosin

Platelet actomyosin, partially purified by successive precipitation had a specific viscosity of 0,15 and a sensitivity to ATP of 60 %. The enzyme preparation was separated into the actin and myosin components and some myosin fragments by SDS-polyacrylamide gel electrophoresis. The ATPase activity of platelet actomyosin showed pH optima at pH 5.8 and pH 9.5. The influence of the concentrations of calcium and ATP on the ATPase activity was studied and evidence was obtained that Ca-ATP was the substrate. Non-competitive inhibition was brought about by free ATP. Competitive inhibition was observed in the presence of ADP

Factor VIII-related antigen in canine hemophilia and von Willebrand's disease: Variation when measured with different agaroses

The source of agarose used in the Laurell electroimmunoassay was found to produce variations in the factor VIII-related antigen levels of plasmas from dogs with von Willebrand's disease and hemophilia A. Similar artifactual variations in antigen were not observed for normal canine plasmas

Investigations on the relationship of factor VIII related antigen, factor VIII procoagulant activity and Von Willebrand factor activity using insolubilized rabbit antiserum

Insolubilized rabbit antifactor VIII sera removed factor VIII activity and factor VIII related antigen almost completely from normal plasma. This reduction was accompanied by a parallel decrease of the factors correcting the abnormal platelet retention and ristocetin aggregation in Von Willebrand's Disease. This indicated that rabbit antifactor VIII sera are indeed directed not only against factor VIII but also against the correcting factors on the abnormal platelet retention and ristocetin aggregation in Von Willebrand's Disease. In fluid phase assays antifactor VIII sera inhibited factor VIII activity only partly. Non inhibitory antibodies may be responsible for this. Prolonged immunization of a rabbit with factor VIII resulted in an antiserum, which inhibited factor VIII activity very potently. This can be explained by assuming that the functional site of the factor VIII molecule has a very conservative structure that has little changed in the course of evolution

Chorea in systemic lupus erythematosus and “lupus-like” disease: Association with antiphospholipid antibodies

Twelve patients with chorea from a population of 500 patients with SLE and “lupus-like” disease were reviewed. Clinical histories, including time relationships of chorea to the systemic illness and other neurologic manifestations, are reported. Chorea appeared early in the course of disease in most patients, but the development of cerebral infarctions or TIAs occurred subsequently in seven of nine patients demonstrating antiphospholipid antibodies. The relationship of chorea to the presence of these antibodies in nine of 12 patients and the therapeutic outcome are briefly discussed