Directionally controlled spindle disassembly after mitosis in the diatom Pinnularia
Soranno, T.; Pickett-Heaps, J.
European Journal of Cell Biology 26(2): 234-243
1982
ISSN/ISBN: 0171-9335 PMID: 7067701 Document Number: 196701
Two aspects of late mitosis were investigated in Pinnularia spp. by EM. The 2 interdigitated half spindles that form the central spindle of this organism appear to separate before their disassembly. This separation is not dependent upon the cleavage furrow breaking the spindle as appears to be the case observing normal mitosis; it occurs even when cleavage is artificially prevented with cytochalasin D. After separation, the birefringence of each half spindle fades steadily from the overlap end (now, the free end) back to the pole. Disassembly commences .apprx. 1 1/2 min after the half spindles separate, synchronously in each daughter cell. Evidently, the microtubules in each half spindle are of uniform polarity and their disassembly, presumably influenced by this polarity, proceeds from only 1 end (the free end). The other end may be capped by polar structures. Because there is this pause between separation and the initiation of disassembly, breakdown of microtubules is probably not initiated merely by their ends becoming free in the cytoplasm.