Immunohistochemistry and PAS reaction of agouti subplacenta in midgestation. (A) Cytotrophoblast (cyt tr) and syncytiotrophoblast (syn tr) immunostain for cytokeratin. Fetal mesenchyme (mes) and wall of blood vessel (bv) are cytokeratin negative. (B) Fetal mesenchyme and wall of blood vessel immunostain for vimentin. Trophoblast is vimentin negative. (C) PAS reaction in the absence of amylase is strong in syncytiotrophoblast and negative in cytotrophoblasts (although their basal lamina gives a positive reaction). (D) Following treatment with amylase there is only a moderate decrease in the positive reaction of syncytiotrophoblast. Scale bars: 40 μm.