Fig. 21. A zonula occludens “tight” junctional area (TJ) between nonpigmented epithelial cells in Macaca mulatta as seen by the freeze-fracture technique. It shows a network of anastomosing grooves (arrows) on the outer plasmalemmal leaflet, giving a quilted effect. A few fragments of the complementary strands from the inner leaflet (P-face) are still adherent. (X 60,500; Courtesy of Dr. Guiseppina Raviola)