Platelet-dependent fibrin formation under flow. Coverslips with or without adhered platelets were perfused with pooled plasma under recalcification at a low shear rate of 250 s−1. (A) Representative phase-contrast images taken at 580-640 seconds after start (ie, during the first minute of fibrin formation). Image recording with a Nikon Diaphot 200 microscope as described in “Methods.” Right panels show differential, subtracted images (bars, 10 μm). Note the parallel fibrin fibers in the direction of flow on perfusion with tissue factor (1pM). (B) High magnification images of star-like fibrin fibers on platelets. (C) Quantification of fibrin fibers from subtracted images. Increases in mean pixel intensity are shown. (D) Thrombin activity in plasma samples collected from the flow chamber outlet. Means ± SE (n = 3-4 experiments); ***P < .001 vs control.
