Vinblastine Produces Uniaxial, Birefringent Crystals in Starfish Oocytes

The high degree of ultrastructural organization of microtubular crystals (1, 2) produced in mammalian cells by incubation with Vinca alkaloids, suggested that these crystals would be birefringent in polarized light. We now report the induction by vinblastine sulfate (VBL) of birefringent crystals in unfertilized oocytes of the starfish Pisaster ochraceous . Mature ovaries were removed, placed in filtered sea water at 1 1 ° to 13 ° C, and induced to spawn by application of an aqueous extract of starfish radial nerve (3) . Oocytes obtained in this manner developed from germinal vesicles to the metaphase spindle of meiosis I, which persisted for about an hour. Most of the oocytes then went on to form polar bodies, at which time further development was arrested; a few continued to develop parthenogenetically for many divisions, presumably activated by the radial nerve extract ; all eventually degenerated. In polarized light with rectified, strain-free optics, the mitotic spindle is the major birefringent structure found in these oocytes . All 11° to 13 °C, on addition of VBL (1 to 2 X 10-5 M), the mitotic spindle diminished in size and birefringence and disappeared within about 10 min, as we have noted previously in oocytes of the marine polychaete Pectinaria gouldi (4) . Within a few hours at higher concentrations of VBL (2 to 10 X 10 M), small birefringent spots appeared and gradually grew into square or rectangular crystals that were never seen in control cells . The