Effect of nocodazole on microtubule stability in MDA-MB-468 and MCF-7 cells. MDA-MB-468 (a–c) or MCF-7 (d–f) cells growing on coverslips were treated with diluent (a and d), 167 nM nocodazole (b and e), or 1 μM nocodazole (c and f) for 8 hours (by this time most MCF-7 cells had not yet accumulated in mitosis and thus remained adherent), fixed, stained with anti–α-tubulin, and visualized by fluorescence microscopy.