Abstract
The formation of junctional complexes and the location of actin and cytokeratin were examined in bovine embryos which were being transformed in vitro into blastocysts. In 16-cell embryos and morulae, gap junctions were observed between some pairs of blastomeres, though not very often. In early blastocysts, however, three kinds of junctions, Le., zonula occludens, predesmosomes and gap junctions were found between each pair of trophoblast cells. Gap junctions were seen between a pair of inner-cell-mass cells, and between a trophoblast cell and an inner-cell-mass cell, also. In expanded blastocysts, zonula ocdudens, zonula adherens, desmosomes and gap junctions were found between each pair of trophoblast cells, while predesmosomes and gap junctions were found between each pair of inner-cell-mass cells, and between a trophoblast cell and an inner-cellmass cell. Meanwhile, actin and cytokeratin fluorescences were observed throughout the cytoplasm of embryos at the 16-cell through blastocyst stages, and they were more prevalent in the ectoplasmic zone of trophoblast cells in blastocysts.
