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. 2009 Dec 14;187(6):831–845. doi: 10.1083/jcb.200907090

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© 2009 von Dassow et al.

This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.jcb.org/misc/terms.shtml). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).

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Figure 1. — Microtubules in live urchin embryos. All panels show single confocal sections. (A and A′) 16-cell purple urchin embryo; A′ shows a 2× enlarged view of the lower cell (indicated by white mark in A). Microtubules approach the cortex everywhere before anaphase onset (1 min, 30 s); during anaphase, just before furrowing, many astral microtubules penetrate both polar and equatorial cortex (arrowheads in A′). (B) Vegetal view, 28-cell sand dollar embryo; i–vi are 2× enlarged views as indicated. Astral microtubules frequently cross spindle midplane before and during anaphase (i–iii), approach within 1 µm of the equatorial surface before furrowing (ii–iv), and curve inward as the furrow ingresses (v and vi). Arrowheads point to exemplars. (C) Eight-cell sand dollar embryo; single microtubules grow as far as the cell surface in all directions (equatorially in the 01:56 frame, tropically in the 01:08 frame, and toward the pole in the 03:32 frame). Astral microtubules reach the polar cortex most densely in anaphase (08:48) but also reach the equator before furrowing (frame 10:48). (C′) Enlargement of successive frames for microtubules indicated by arrowheads in C (intensities squared to enhance contrast). Video 1 corresponds to A–C. Time is indicated in minutes:seconds.