The distribution of desmosomes and ruthenium red-bound cell surface carbohydrates during palatal closure in the hamster.

The distribution of ruthenium red (RR)-bound cell surface carbohydrates and desmosomes was studied during epithelial adhesion and seam formation stages of palatal development in the hamster. Before closure, RR-positive material was observed on the plasma membrane of the superficial cells and in the intercellular spaces of the palatal epithelium. At the time of initial contact, RR-bound substance was absent or reduced on the outer plasma membrane and desmosomes were forming between the epithelial cells of the opposing palatal shelves. Except in the oral and nasal triangular areas, RR-positive material was absent in the epithelial seam. Quantitative analysis showed a three-fold increase in the number of desmosomes from the vertical stage to the epithelial fusion stage which correlated well with the disappearance of RR-bound material. Desmosome formation appears crucial during initial adhesion between epithelia of the opposing palatal shelves and during the formation and maintenance of the seam.