Expression of coagulation-related genes in TS and DT cells and in E8.5 microdissected placenta and embryos determined by semiquantitative RT-PCR. Placenta consisting of trophoblast shell were carefully peeled from the surrounding decidual tissue and separated from Reichert's membrane, visceral yolk sac, and the embryo proper. Dihydrofolate reductase (DHFR; housekeeping gene) and fibroblast growth factor 4 (FGF4; expressed only by the embryo) were included as controls.