Time-lapse fluorescence imaging of two-needle separation orthogonal to the interpolar spindle axis (transverse stretching). The fluorescent signal is from X-rhodamine–labeled tubulin incorporated into spindle microtubules. We are not sure of the origin of what appear to be microtubule bundles aligned orthogonal to the interpolar axis of the stretched spindle but suspect they might be formed from newly nucleated microtubules that reorient as chromosomes are stretched by the needles. The time interval between each frame is 600 ms, and elapsed time is shown as seconds:milliseconds. The video is shown at 10 frames/s. The series was acquired on an Eclipse TE2000e inverted microscope using a 20× NA 0.75 objective at ∼20°C. Bar, 20 µm.
