Surface coat of the palatal shelf epithelium during palatogenesis in mouse embryos.

The palatal shelf epithelium of NMRI-mouse embryos was examined by electron microscopy during palatogenesis (day 14 + 2 hrs p.c. to day 14 + 10 hrs p.c.). A ruthenium red positive surface coat was observed on the epithelium of the vertically projected and horizontally rotated palatal processes. The surface coat on the tips of these processes was especially thick and was observed to be shed after fusion. The localization and the quantitative changes of the ruthenium red positive material during closure of the palatal shelves suggest that the surface coat may be involved in the initial process of palatal epithelial adhesion.