ERα immunoreactivity (h-151 antibody) in early (17 h) and late trophoblast cultures (93 h). Dividing cells in [A] exhibit distinct surface staining (arrow). Cell in [B] shows moderate cytoplasmic and perinuclear immunoreactivity (arrowhead), and cell in [C] exhibits strong nuclear staining without surface expression. [D] Early syncytium shows traces of cytoplasmic ERα staining (compare with E). [E] No ERα staining of mature syncytium.