Inhibition of dynein/dynactin, kinesin-5, or both suppresses regional variation of poleward microtubule flux. (A) Spindle treated with excess p50/dynamitin. (B and C) Speckle trajectories color coded according to the velocity histogram (C); the flux rate of the specific spindle shown is mean ± SD = 2.33 ± 0.60 μm/min (N = 2,702 trajectories). (D and E) Mean and SD (error bars) of speckle velocities within regions in D. (F) Normalized flux rate along the pole-to-pole axis of control (average over 11 spindles) versus p50/dynamitin-treated spindles (average over seven spindles). (G) Flux rates at different monastrol concentrations. (H) Spindle treated with 200 μM monastrol. (I and J) Speckle trajectories color coded according to the velocity histogram (J); the flux rate of the spindle shown is mean ± SD = 0.89 ± 0.30 μm/min (N = 3,085 trajectories). (K and L) Mean and SD (error bars) of speckle velocities within regions in K. (M) Normalized flux rate distribution along the pole-to-pole axis of control and monastrol-treated spindles (average over 17 spindles treated with 20–200 μM monastrol). (N) Spindle treated with both 200 μM monastrol and excess p50/dynamitin. (O and P) Speckle trajectories color coded according to the velocity histogram (P); the flux rate of the spindle shown is mean ± SD = 1.59 ± 0.38 μm/min (N = 7,214 trajectories). (Q and R) Mean and SD (error bars) of speckle velocities within regions in Q. (S) Normalized flux rate distribution along the pole-to-pole axis of control versus monastrol + p50/dynamitin–treated spindles (average over six spindles). Bars, 10 μm.