Fig. 5. Electron microscopic characterization of the poles in monopolar figures after -tubulin depletion. (A) Overall image of a monopolar prometaphase. The microtubules from the polar region defined by short centrioles (arrowheads) interacted with the kinetochores (k) of the chromosomes (ch) or passed through the chromosomal mass. (B1-4) Serial thin sections of a pole. The presence of four short centrioles (labelled 1 to 4) shows that, despite depletion of the major cellular -tubulin, centriole duplication but not separation took place. (C) Elongation of the centriole microtubules. The spindle microtubules resulted at least partly from the elongation of the distal ends of centriolar microtubules (arrowheads). Scale bars, 0.2 µm.