Electrokinetic properties and surface membrane sialic acid status of platelets in idiopathic thrombocytopenic purpura (ITP)

An experience of oseltamivir phosphate (tamiflu™) in a pediatric patient with chronic idiopathic thrombocytopenic purpura: a case report

We report a pediatric patient with chronic idiopathic thrombocytopenic purpura who suffered from an influenza A (H1N1) virus infection. A 13-year-old girl presented with fever, coughing, and generalized petechiae. The influenza A antigen was positive in her pharyngeal aspirate. She was successfully treated with neuraminidase inhibitor oseltamivir phosphate. Her platelet counts progressively increased with oseltamivir phosphate without another blood product or agent. We suggest that oseltamivir phosphate can be used in patients with immune thrombocytopenic purpura who present with influenza virus A infection. We also suggest that oseltamivir phosphate can be effective in patients with immune thrombocytopenic purpura. Large study groups are needed to confirm the relationship between idiopathic thrombocytopenic purpura and neurominidase inhibitors.

Unstimulated platelets evoke calcium responses in human umbilical vein endothelial cells

Interactions between human platelets and human umbilical vein endothelial cells (HUVEC) were studied by monitoring changes in cytosolic [Ca2+]i in both cell types. Confluent monolayers of Fura-2-loaded HUVEC, grown on gelatin-coated coverslips, responded to repeated addition of a suspension of unstimulated platelets by transient increases in cytosolic [Ca2+]i. These platelet-evoked Ca2+ responses were not caused by products secreted from the platelets and were insensitive to inhibitors of platelet activation and/or platelet aggregation. The platelet-evoked rises in [Ca2+]i in endothelial cells, similarly as the thrombin-evoked rises, were blocked by preincubation of HUVEC with the phospholipase C inhibitor U73122 or the Ca2+ influx blocker Ni2+. In contrast, treatment with the protein tyrosine kinase inhibitor genistein was without effect. Video imaging experiments, in which the fluorescence signal was analysed from the individual cells of an endothelial monolayer, showed that only 2-20% of the cells, scattered over the monolayer, responded to the addition of platelets by a transient increase in [Ca2+]i, whereas most of the cells responded to thrombin. This leads to the conclusion that unstimulated platelets can activate HUVEC putatively by mechanical interaction with individual endothelial cells in the monolayer.

Electrokinetic behaviour and surface sialic acid status of blood platelets in essential thrombocythaemia (ET)

We have previously reported, for platelets from patients with idiopathic thrombocytopenic purpura, that there was in increased electrophoretic mobility that was related to their increased sialic acid content. Heterogeneity in the circulating platelet pool of patients with essential thrombocythaemia (platelet counts 600-1000 x 10(9)/l) has also been investigated by preparative continuous flow electrophoresis (CFE). The surface charge-dependent separation profiles of all the patients' platelets showed marked anodal shifts compared with the profiles of platelets from age- and sex-matched control subjects separated under identical conditions. The increase above normal in the net electronegativity of the patients' platelets could not be accounted for by differences in surface neuraminidase-labile or total platelet sialic acid content.