ABSTRACT
The heterogeneity of mitotic microtubules in sea urchin eggs was investigated by indirect immunofluorescence using three anti-tubulin antibodies. We found that: (1) YL1/2 strongly stained both the spindle and aster, (2) D2D6 strongly stained the spindle but weakly stained the aster, and (3) DM1B stained only the aster. These results suggest that tubulin isoforms of the spindle are different from tubulin isoforms of the aster. In the eggs treated with a microtubule depolymerizing or stabilizing drug, the mitotic apparatus changed both morphologically and immunocytochemically. Astral microtubules depolymerized rapidly after the treatment with vinblastine, whereas spindle microtubules remained for a while, which were stained with DM1B as well as with YL1/2. On the other hand, after the treatment with hexylene glycol, many astral and spindle microtubules polymerized, and many miniasters appeared in the cytoplasm. DM1B stained the miniasters strongly and the mitotic apparatus weakly, whereas YL1/2 stained all of the spindle, amphiaster, and miniasters.
