PAA is injected into the equatorial region of a prometaphase NRK cell. A large aggregate near the chromosomes is initially spherical in shape. However, following chromosomal segregation, it elongates perpendicular to the spindle axis and moves rapidly into the newly formed spindle midzone before the initiation of cortical ingression. The aggregate resumes a spherical shape and remains stationary in the midzone during anaphase, but becomes highly elongated during cytokinesis. It is eventually severed by the ingressing furrow, and dispersed into the two daughter cells as small aggregates. Interestingly, the PAA probe fails to show a dumbbell shape as expected for the bisection by a narrow constricting ring, but becomes highly elongated along the spindle axis, suggesting widespread lateral compressive forces. Total time of recording, 60 minutes. |