Aim. To study the effect of the blood components on clot contraction dynamics in vitro.Methods. The original method based on the optical detection of changes in the blood clot volume over time was used. Whole blood, as well as reconstructed samples using washed platelets, erythrocytes, purified fibrinogen, platelet-poor and platelet-rich plasma were studied.Results. Blood clot contraction has a non-linear kinetics, reflecting the complexity of the underlying mechanisms. Platelets increase the blood clot contraction, while the red blood cells have an inhibitory effect. Blocking the fibrin and platelets interaction using the RGDS peptide, an integrin αIIbβ3 antagonist, reduces the extent and rate of clot contraction. The exogenous Ca2+ is not required for contraction, but its addition stabilizes clots by inhibiting the erythrocytes. Thrombin has a dose-dependent effect and increases the rate and extent of contraction. In blood samples of patients taking warfarin, blood clot contraction was delayed.Conclusion. The blood clot contraction is a process which depends on many factors, including the blood cell composition, amount of fibrinogen, the endogenous thrombin activity and platelets interaction with fibrin; understanding the mechanisms of the blood clot contraction could form the basis for the development of novel approaches to the hemostatic disorders treatment.

Aim. To characterize the influence of psychoemotional stress on a white blood cells number in peripheral blood and clotting parameters. Methods. Lymphocytes, granulocytes, monocytes blood counts and coagulological testing were performed in fifty-one students (26 males and 25 females) during the midyear examinations. Psychological tests were used to reveal stress resistance and predisposition to stress. Results. The higher monocyte counts were found in male group under stress compared to control group. Meanwhile, female group under stress showed higher percentage of granulocytes and lower percentage of lymphocytes compare to control group. Sex differences in stationary speed of clot formation were found in stress and non-stress groups. Both sex groups showed an association of psychoemotional stress and hemostasis parameters, the differences in male group were more marked. Conclusion. The obtained data suggest that psychoemotional stress modulates immune cells and hemostasis parameters in healthy volunteers.