MICROTUBULE AND MICROFILAMENT DYNAMICS IN RAT EMBRYOS DURING THE 2-CELL BLOCK IN-VITRO

Developmental block of rat embryo is induced by phosphate at the late two-cell stage. The present study uses immunocytochemistry and laser s canning confocal microscopy to examine microtubule and microfilament d ynamics in blocked and nonblocked two-cell-stage rat embryos. Thin fib rous microtubules were distributed homogeneously in the cytoplasm in n onblocked embryos during the interphase of the two-cell stage and then translocated into mitotic spindles at the M-phase. In embryos blocked at the two-cell stage, much thicker fibrous microtubules were formed and distributed as rude meshwork structures in the cytoplasm. Microfil aments were distributed adjacent to nuclei and along the inside of the plasma membrane in nonblocked embryos during the two-cell stage, at M -phase, and at cleavage to the four-cell stage. In embryos blocked at the two-cell stage, however, microfilaments formed granules and disper sed in the cytoplasm. The distribution of microtubules and microfilame nts charged relative to the occurrence of two-cell block. In summary, these results indicate that both microtubules and microfilaments are c losely involved in the developmental block in two-cell rat embryos. (C ) 1998 Wiley-Liss, Inc.