A blood-based biomarker to complement the clinical and neuropsychological assessments used to evaluate the risk of individuals with mild cognitive impairment (MCI) developing Alzheimer's disease (AD) would be invaluable. Previous pilot studies by our group identified elevated platelet membrane β-secretase activity in patients with AD and MCI, as compared to controls, and this activity was influ...

The expression of myeloid and megakaryocytic markers of differentiation has been studied in one K-562 cell subline, in its clones, and in the original cell line. Cytotoxicity, electron microscopy, immunofluorescence studies with a panel of polyclonal and monoclonal antibodies, and radioimmunoassays were performed on K-562 cells before and after induction with hemin, sodium butyrate, and 12-O-te...

Fibrinolytic activity was found to be associated with sonicated platelet membranes after separation from cytosol by differential centrifugation. This fibrinolytic activity was attributed to the presence of a plasminogen activator, which was immunochemically identified as urinary-type plasminogen activator (uPA) by antibody neutralization assay, immunoblotting, and immunofluorescence. The molecu...

To determine platelet Ca2+ transport entities involved in increased cytosolic Ca2+ in the platelets of hypertensive individuals, we studied the relations between blood pressure and Ca2+ transporters in platelet membranes from 22 white male volunteers 32 to 68 years old. We used thapsigargin, a specific inhibitor of the internal membrane Ca(2+)-ATPase, to differentiate between plasma membrane an...

Primary Haemostasis This involves platelet adhesion, via Von Willebrand factor (vWF), to the subendothelial collagen, with ensuing activation and aggregation of platelets, resulting in the formation of a platelet plug. When platelets become activated, phosphatidylserine (PS; previously platelet factor 3) becomes exposed on the platelet membrane and acts as a scaffold for the assembly of coagula...

There are several signal mechanisms involved in platelet activation, including specific receptors, G proteins, phosphatidyl inositol metabolism, synthesis of thromboxane A2 (TXA2) and other eicosanoids, changes in cytosolic calcium, and protein phosphorylation, in serine/threonine and tyrosine residues[2]. These signal mechanisms result in a conformational change in the GP IIb IIIa receptor, pl...

Studies are presented characterizing platelet CDCrel-1, a protein expressed to high levels by megakaryocytes and belonging to a family of conserved proteins, termed septin. Septin filaments originally were identified in yeast as essential for budding but have become increasingly associated with processes in higher eukaryotic cells involving active membrane movement such as cytokinesis and vesic...