Adhesive properties of plasma-circulating and platelet-derived microvesicles from healthy individuals.

BACKGROUND: Microvesicles (MVs) produced by platelets upon activation possess high procoagulant activity and represent a possible thrombotic risk marker. However, direct experimental evaluation of the adhesive properties of MVs and their potential role in thrombus growth is lacking. OBJECTIVES: We investigated integrin αIIbß3 status and adhesive properties of plasma-circulating and platelet-derived MVs from healthy individuals. METHODS: MVs were isolated from whole blood or produced from activated platelets. Flow cytometry was used for quantification of fluorescently labeled PAC-1 and fibrinogen binding to MVs. Confocal microscopy was used for evaluation of MVs adhesion to fibrinogen and for estimation of their involvement in whole blood thrombus formation in a parallel-plate flow chambers under arterial shear conditions. RESULTS AND CONCLUSIONS: Neither circulating plasma MVs, nor platelet-activation-produced MVs bound PAC-1. However, both types of MVs specifically and weakly bound fibrinogen (about 400 molecules of bound fibrinogen per MV versus >100,000 per non-procoagulant activated platelet). Still, the MVs did not adhere stably to the immobilized fibrinogen. Both types of MVs were weakly incorporated into a thrombus and did not affect thrombus formation: average thrombus height in the recalcified whole blood in the presence of platelet-activation-produced MVs was 4.19 ± 1.38 µm versus 4.87 ± 1.72 µm (n = 6, p > 0.05) in the control experiments. This suggests that MVs present in plasma of healthy individuals are not likely to be directly involved in thrombus formation under arterial flow conditions.

[PULMONARY AUTOGRAFT OPERATION IN PEDIATRIC PATIENTS].

Experience of performance of a pulmonary autograft operation (PAO, оperation of Ross) was analyzed, results were estimated, the ways of overcoming a procedure conduction problems were determined. Remote result was investigated in 151 patients: the aortal valve stenosis was diagnosed in 99 (65.6%) patients, insufficiency - in 42 (27.8%), combined aortal valve failure - in 10 (6.6%). Hospital lethality have constituted 3.6%, and a general one ­ 7.9%. Reoperations were performed in 52 patients. PAO constitutes one of surgical procedures for the aortal valve failure in children of different age. Improvement of surgical technique and application of a new procedures have promoted improvement of the investigation results ­ lethality lowering from 15.1 to 0.8%. Application of surgical modifications with the aortal radix strengthening have reduced the reoperations on neaortal valve risk trustworthy.