Inhibition of palatal fusion in vitro by β‐2‐thienylalanine

The effect of β‐2‐thienylalanine on palatal fusion was studied in vitro. Palatal shelves were dissected from 13‐ and 14‐day C57BL/6J mouse embryos and placed on agar‐solidified Eagle's medium containing equimolar concentrations of β‐2‐thienylalanine and phenylalanine. Closure of the palate proceeded normally in these explants—the marginal edges of the shelves fused to form an epithelial band, which then broke down and permitted mesenchymal continuity of the palatal processes. However, fusion was delayed, or completely inhibited, in all explants grown on medium supplemented with 2 mM β‐2‐thienyla‐lanine alone. The degree of inhibition depended on the stage of development of the embryo from which the palatal shelves were obtained—explants from early 13‐day embryos showed no adherence of the midpalatal epithelium, but 14‐day explants formed an epithelial band along the full length of the palate. Numerous mitotic figures, as well as areas of active cartilage and bone proliferation, demonstrated that the cultures were viable in the presence of the analogue.