Retraction of membrane tethers.

Washed platelets (3 × 10⁸/mL) were perfused through VWF-coated (100 μg/mL) microcapillary tubes at 150 s⁻¹and the wall shear rate increased to 1800 s⁻¹ to induce tether detachment. (A,B) (i) Membrane tethers formed on immobilized VWF. The white arrowheads refer to the tether attachment point. (ii-vii) The tether attachment point releases its contact with the VWF matrix, causing the platelet to translocate in the direction of flow. Tethers either remained extended, actively participating in the translocation process (A), or alternatively, retracted back into the body of the cell (B). Tether retraction occurred through the formation of flat, ball-like structures along the length of the tether (arrowheads) while receding into the cell body. (C) Scanning electron micrographs demonstrating the early (i) and late phases (ii) of tether retraction (scale bar equals 1 μm).