Stability and contractility of membrane tethers.

Washed platelets (3 × 10⁸/mL) were perfused through VWF-coated (100 μg/mL) microcapillary tubes at 150 s⁻¹ as described in “Materials and methods.” Once a tether attachment point (black arrowheads) is formed between a translocating platelet and the VWF matrix, this becomes the single point of contact during tether elongation. As a result, the cell body is able to move freely either in a side-to-side swinging motion (white arrows) induced by collision with other translocating platelets (A) or in a rotational manner around the axis of the tether (B). The tether attachment point is able to sustain stable platelet adhesion during tether contraction where the cell body is pulled against the resistive drag of flow (C). (D) Time-dependent contraction of tethers from 3 representative platelets.