Image analysis of blood platelets adhesion.

Adhesion of blood platelets is one of the major events in haemostatic and thrombotic processes. We studied adhesion of blood platelets on fibrinogen and fibrin dimer sorbed on solid support material (glass, polystyrene). Adhesion was carried on under static and dynamic conditions and measured as percentage of the surface covered with platelets. Within a range of platelet counts in normal and in thrombocytopenic blood we observed a very significant decrease in platelet adhesion on fibrin dimer with bounded active thrombin with decreasing platelet count. Our results show the imperative use of platelet poor blood preparations as control samples in experiments with thrombocytopenic blood. Experiments carried on adhesive surfaces sorbed on polystyrene showed lower relative inaccuracy than on glass. Markedly different behaviour of platelets adhered on the same adhesive surface, which differed only in support material (glass or polystyrene) suggest that adhesion and mainly spreading of platelets depends on physical quality of the surface. While on polystyrene there were no significant differences between fibrin dimer and fibrinogen, adhesion measured on glass support material markedly differed between fibrin dimer and fibrinogen. We compared two methods of thresholding in image analysis of adhered platelets. Results obtained by image analysis of spreaded platelets showed higher relative inaccuracy than results obtained by image analysis of platelets centres and aggregates.

Hemostyptic effect of oxidized cellulose on blood platelets.

Cellulose is one of the hemostyptic biomaterials, which are able to initiate or accelerate blood coagulation at the site of their application. It belongs to surgical sealants. The mechanism of its action is not clearly understood. We studied the participation of blood platelets in this mechanism. As a marker of platelet activation we used serotonin release reaction. Serotonin release in platelet rich plasma incubated with various concentrations of oxidized cellulose (0.5%-2.0%) started in about 20 min. Washed platelets were not directly activated by oxidized cellulose within one hour. Washed platelets reconstituted in plasma obtained from two patients with coagulation factor XII deficiency were activated by oxidized cellulose with a prolonged lag phase. Our results demonstrate the significant influence of factor XII on blood platelets activation by oxidized cellulose.

[Effect of oxidized cellulose on fibrin formation and blood platelets]. / Vliv oxidované celulózy na tvorbu fibrinu a krevní desticky.

BACKGROUND: Haemostyptic materials initiate and hasten blood clotting at the site of their application. The properties of haemostyptic materials are used for treatment of capillary and parenchymatous haemorrhage along with surgical treatment. Celluloses one of the biopolymers studied for a long time, suitable because of its biocompatibility and non-toxicity. METHODS AND RESULTS: In the submitted study the authors used microdispersed calcium-sodium salt of oxidized cellulose which is formed by oxidation of cellulose in position C6 (patent Alltracel Pharmaceuticals). The authors investigated the effect of oxidized cellulose on fibrin formation and platelets. Using the optic method of the surface plasmon resonance they investigated the initial stage of interaction between fibrinogen and oxidized cellulose. Oxidized cellulose retards and reduces the interaction of the immobilized fibrin monomer with fibrinogen. Fibrin formation was investigated spectrophotometrically at 350 nm. In the presence of cellulose the period of formation of fibrin gel was prolonged and its turbidity increased, depending on the concentration of the cellulose used. The platelet activation by cellulose was assessed by measuring the released serotonin. For the activation of platelets by cellulose the presence of plasma is necessary, rinsed platelets were not activated by cellulose. It was revealed that direct, interaction of rinsed platelets or fibrinogen with cellulose plays a secondary role. CONCLUSIONS: These data and the retarded activation of platelets in plasma with factor XII deficiency indicate that due to negatively charged oxidized cellulose probably activation of the contact coagulation system occurs and this leads to the activation of platelets and fibrin formation.