Clot characteristics formed in whole blood remain unchanged in the presence of UHRA. Clotting was initiated by recalcifying human whole blood with 11.1 mM CaCl2. Clot samples were then processed for SEM imaging. (A) Clots formed in the presence of 500 µg/mL UHRA did not undergo detectable morphological changes. (B) However, clots formed in the presence of 100 µg/mL protamine showed thicker clot fibers, less platelet aggregates, and complete abnormality in clot architecture. Also, at this concentration of protamine, tiny clots were obtained as a result of the intrinsic anticoagulation effect of protamine. Clotting was inhibited at higher concentrations. Clot images were taken at 2 original magnifications, ×2500 and ×5000. Only images from the original magnification ×5000 are depicted. Scale bar, 4 µm.
