Vessel injury and thrombus formation are the cause of most ischemic coronary syndromes and, in this setting, activated platelets stimulate platelet recruitment to the growing thrombus. Recently, a constitutive nitric oxide synthase (NOS) has been identified in human platelets. To further define the capacity of platelets to produce nitric oxide (NO), as well as to study the role of this NO in pl...

Normal human platelets aggregated by thrombin undergo the release reaction and are not readily deaggregated by the combination of inhibitors hirudin, chymotrypsin, and prostaglandin E1 (PGE1). In contrast, thrombin-induced aggregates of platelets from patients with delta-storage pool deficiency (delta-SPD), which lack releasable nucleotides, are readily deaggregated by the same combination of i...

Factor VIII coagulant protein (VIII:C) functions as a critical cofactor with factor IXa, calcium ions, and phospholipid during the activation of factor X. In the course of this reaction, the activity of VIII:C is first increased and then is destroyed by one or more serine proteases that are part of the coagulation sequence. In this study, we have investigated the influence of platelets on the i...

• In influenza-immune subjects, H1N1 influenza virus–containing immune complexes can activate platelets through FcgRIIA. • H1N1 can also activate platelets through thrombin, independently of FcgRIIA, pointing to a role of coagulation in influenza infection. Platelets play crucial functions in hemostasis and the prevention of bleeding. During H1N1 influenza A virus infection, platelets display a...

To investigate whether platelet ABO antigens are intrinsic to platelets or adsorbed from plasma. the amount of A-antigen on washed platelets was determined and related to the Lewis and secretor phenotypes, as these genes control the amount A, B. or H antigen present in plasma. The A-antigen on platelets was quantitated using a platelet-erythrocyte mixed agglutination assay in 28 A1 individuals ...

BACKGROUND CD40 ligand (CD40L) expression on platelets is mediated by agonists, but the underlying mechanism is still unclear. METHODS AND RESULTS CD40L expression was measured in platelets from healthy subjects both with and without the addition of antioxidants or a phospholipase A2 (PLA2) inhibitor and in platelets from 2 patients with an inherited deficiency of gp91phox. Immunoprecipitatio...

The elements Ag, Au, Cd, Co, Cr, Cs, Mo, Rb, Sb, and Se were determined in platelets from seven normal donors. The results, in ng/g wet weight, for plasma-free platelets follow: "Pure" platelets: Ag = 29 +/- (18), au = 0.22 +/- (0.22), Cd = 6.2 +/- 3.4, Cs = 54.8 +/- 19.2, Cr = 6.1 +/- 2.5, Co = 7.5 +/- (5.0), Mo = 3.4 +/- 1.3, Rb = 10400 +/- 3000, Sb = 18 +/- (26), and Se = 782 +/- 127. "Impur...

About 60% of the platelets freeze proaddition or removal of the cryoprotective served in 6% dimethylsulfoxide retained agent. Platelets that retained the disc the discoid shape characteristic of fresh shape had a well-preserved ultrastructure, platelets. The remainder wore sphered. but sphered platelets showed extensive Platelet sphering occurred during freezing ultrastructural changes. and tha...

The role of platelets extends beyond hemostasis. The pivotal role of platelets in inflammation has shed new light on the natural history of conditions associated with acute or chronic inflammation. Beyond the preservation of vascular integrity, platelets are essential to tissue homeostasis and platelet-derived products are already used in the clinics. Unanticipated was the role of platelets in ...

The platelet membrane receptor for quinidine- and quinine-dependent antibodies was studied in three patients with the Bernard-Soulier syndrome (BSS) and in normal subjects with immunologic techniques based on the release of 51Cr from labeled platelets. The receptor could not be detected on BSS platelets but was present on platelets from each of 180 normal subjects. BSS platelets reacted normall...