Role of mitotic asters in accumulation of pigment granules around nuclei in early amphibian embryos

Pigment granules accumulate around nuclei during the cleavage stage in amphibian embryos (Kobayakawa, J. Embryol. Exp. Morphol., 88:293–302, 1985). In Rana rugosa embryos, this unidirectional intracellular transport of pigment granules was found to occur mainly at each mitotic stage of 4th to 6th cell cycles in vegetal blastomeres. Immunocytochemical staining confirmed the growth of astral rays that fully develop at anaphase and telophase in each mitotic stage and also suggested an association of pigment granules with the microtubules. Microtubule inhibitors suppressed the accumulation of pigment granules, which appears to depend, around nuclei, on microtubular structures, probably astral rays in mitosis.