[Correlation between the movement of trophoblast cells invading the implantation site and the microfilament system--with special reference to the nidation site on day 15 post-coitus].

Trophoblast cells invading into decidual tissue of implantation sites of 21 cases in early stage of gestation were morphologically studied in order to clarify the correlation between integrity of the microfilament system and the various biological statuses. Especially, trophoblast cells of ovum at 15 day post coitus were mainly analyzed, since the migrating direction of the cells could be easily identified. 1. Syncytiotrophoblast cells migrating to maternal vessel were in slender shape toward the vessel. Thin and thick filaments connecting to dense body in tip of the cell run parallel with the cell axis. Thus, it is suggested that trophoblast cell migrates in decidual tissue by the joint work of its own actin and myosin in the tip of the cell. 2. Trophoblast cells making close contact with maternal cell such as endothelial cell, decidual cell and gland cell were relatively stable. The cells mainly put into action to project the cytoplasmic processes by thin filament, beneath the cytomembrane, running parallel with the cytomembrane and by thin filament, in the cytoplasmic process, running parallel with the axis of the cytoplasmic process in order to exchange information with maternal cell or to destroy the maternal cell.