Myrmecophaga tridactyla , mid gestation placenta. (A) Vimentin. Villi with positive connective tissue, enlarged mesenchymal cells (mc) and fetal capillaries (cap). Cellular (ct) and syncytial (syn) trophoblast were immunonegative, as well as trophoblast of trabeculae (trab). Remnants of the maternal vessel endothelium were absent. (B) Toluidine blue. Villi with two layers of trophoblast and hypertrophied mesenchymal cells. (C,D) TEM. The interhaemal barrier along the intervillous space (ivs) was thin and syncytial. Trophoblast cells occurred. Fetal capillaries with endothelium (endo) were near the surface (E) TEM. Trabeculae had solid strands of cellular trophoblast with large nuclei and liquid droplets (ld) and connective tissue (con tiss). (F) PCNA. Proliferation activity was high in trophoblast cell clusters of villi and trabeculae (white arrows). Also, proliferation occurred in hypertrophied mesenchymal cells and endothelia of the villi (black arrows).