Dynein-mediated MB extension induces its coiling. (A) The MB length of resting platelets (PRP prepared from freshly drawn blood after a recovery period) and transiently activated platelets, present in PRP prepared from freshly drawn blood, was measured as described in the Materials and methods section. Platelets were grouped in five categories according to different coiling stages (stage 1, resting platelets, n = 66; stage 2, start of coiling, n = 31; stage 3, slightly coiled, n = 32; stage 4, more coiled, n = 33; and stage 5, maximum coiled, n = 16; data are presented as means ± SEM; *, P < 0.017; **, P < 0.38; ***, P < 0.033; ****, P < 0.0009). (B) Platelets prepared from freshly drawn blood with coiling MBs were diluted in PBS, 2.5 × 106/ml, and incubated with or without EHNA (1-mM final) for 10 min at RT, fixed, and stained for α-tubulin (Tub). Arrows indicate platelets having simultaneously coiled and resting MBs. Video 7. Bars, 2 µm.
