The primary, long term goal of the proposed research is an improved, more quantitative understanding of how blood cells are affected by passage through both physiological and extracorporeal (artificial) systems. Within this general context it is proposed to investigate the following specific subjects: (1) shear-induced alterations of normal human platelets; (2) influence of particular drugs, plasma proteins and lipids on shear tolerance of normal platelets; (3) mechanical properties of red cell membrane in both normal and diseased cells and the relationship of these properties to molecular constituents and membrane ultrastructure; (4) effects of metabolic inhibitors on deformability of polymorphonuclear leukocytes and erythrocytes.