The surface morphology of embryonic and adult chick lens-fiber cells

The surface morphology of lens fibers in embryonic and adult chicken lenses has been studied by scanning electron microscopy. As the elongating epithelial cells enter into a state of terminal differentiation they elaborate a number of cellular processes interconnecting neighboring fibers. The interlocking devices take the shapes of balls on a short stalk, tonguelike flaps, and fingerlike processes that fit into complementarily shaped sockets, imprints, and fingerprints, respectively, of adjoining fibers. Gap junctions comprising more than 50% of the fiber-cell membrane may serve as ultrastructural interlocking devices. The interlocking devices and gap junctions are probably necessary to maintain fiber order--a critical requirement for lens transparency. With increase maturation, the uniform morphology of the fibers and their interlocking devices is lost. The highly repetitive ordered alignment of young uniformly shaped fiber cells acts to minimize large-particle scatter. The results of this study show a progressive loss of uniform shape and order in chicken fibers of advanced maturity. This phenomenon of lens development may be the basis for the increase in light scattering seen in aged lenses of other species such as man.