Immuno-EM analysis of cross-sectioned DAPs and tethers. Perfusions were carried out over melamine-plated coverslips coated with dVWFA1. Immunolabeling as described in the legend to Figure 3. The electron micrographs show DAPs of various sizes (A-C), and cross-sectioned tethers (D-F) attached to the dVWFA1 substrate. (A-B) DAPs appear in cross-section as darker areas of the membrane closely juxtaposed to the adhesive substrate and with high density of GPIbα (arrowheads); the latter is also detected in the open canalicular system (OCS). (C) A DAP (arrowhead) is in close contact with the adhesive substrate while the surrounding platelet membrane is lifting away, suggestive of a nascent tether or PMP. (D-F) Visualization of GPIbα in cross-sectioned tethers. Scale bar in panels A to C = 200 nm; bars in panels D to F = 50 nm.