A microscopic method was developed to study the role of platelets in fibrin formation. Perfusion of adhered platelets with plasma under coagulating conditions at a low shear rate (250(-1)) resulted in the assembly of a star-like fibrin network at the platelet surface. The focal fibrin formation on platelets was preceded by rises in cytosolic Ca(2+), morphologic changes, and phosphatidylserine e...

Previously, we found that LDL-receptor related protein-1 on macrophages mediated shear stress-dependent clearance of von Willebrand factor. In control experiments, however, we observed that von Willebrand factor also binds to macrophages independently of this receptor under static conditions, suggesting the existence of additional clearance-receptors. In search for such receptors, we focused on...

Glycoprotein llb-IRa (ctnbB3) and the vitronectin receptor (ct~B3), two integrins that share the common #3 subunit, have been reported to function as promiscuous receptors for the RGD-containing adhesive proteins fibrinogen, vitronectin, fibronectin, yon Willebrand factor, and thrombospondin. The present study was designed to establish a cell system for the expression of either GP IIb-IIIa or t...

We studied the role of von Willebrand factor in coronary thrombosis in normal, heterozygous, and homozygous von Willebrand's disease pigs by producing coronary stenosis with a Goldblatt clamp positioned around the left anterior descending coronary artery. Flow velocity was assessed by a 20-MHz Doppler velocity probe distal to the Goldblatt clamp. Myocardial extracellular potassium levels were m...

Studies of the functional properties and intravascular survival of normal and desialylated human Factor VIIIlvon Willebrand factor protein have been performed. The purified normal protein, possessing both procoagulant activity and ristecetin-induced platelet-aggregating activity, contains 154 = 15 nmol of sialic acid/mg of protein and 28 f 3 mol of Sk&k acid/m01 of 200,000 molecular weight subu...

The antibiotic ristocetin only aggregates platelets in the presence of plasma von Willebrand factor. Platelets from patients with Bernard-Soulier syndrome do not aggregate upon addition of ristocetin although, in contrast to von Willebrand's disease, plasma levels of factor VIII complex (factor VIII clotting activity, von Willebrand factor activity, and von Willebrand antigen) are normal. The m...

We identified three novel mutations (p.Gly39Arg, p.Lys157Glu, p.Cys379Gly) and one previously known mutation (p.Asp141Asn) in the von Willebrand factor propeptide from three von Willebrand disease patients. All four mutations impaired multimerization of von Willebrand factor, due to reduced oxidoreductase activity of isomeric propeptide. These mutations resulted in the endothelial reticulum ret...

S UMMA R Y. Rapid and relevant evaluation of platelet function is often clinically important. By means of fluorescent labelled chicken antibodies (which do not bind to Fc-receptors) against fibrinogen and von Willebrand factor and flow cytometry, we have determined the time course of ligand association to platelets after stimulation with adenosine 5’-diphosphate and ristocetin respectively. The...

Platelet-type von Willebrand disease (PT-VWD) is a rare autosomal dominant bleeding disorder which is due to a mutation in the gene encoding for platelet glycoprotein Ibalpha (GPIbalpha) resulting in enhanced affinity for von Willebrand factor (VWF). PT-VWD is often mistakenly diagnosed as type 2B VWD for the similarities between these two conditions. We characterized a new case of PT-VWD and e...