ULTRASTRUCTURE OF ORIENTED CELLS AND EXTRACELLULAR MATERIALS BETWEEN DEVELOPING FEATHERS

Regions between dermal condensations of early feather germs have been examined with the electron microscope. Fibroblasts in such places become elongated and oriented so as to point from one condensation toward the next. Bundles of collagen and anchor filaments occur near such cells. There is no unique orientation of the collagen, however; some bundles do parallel the intercondensation axis, but just as many run at a variety of angles to it. Intracellular microtubules and fine filaments parallel the long axis of the elongate fibroblasts. The basis of cell and collagen orientation and the possible significance of the orientation are discussed. On the basis of current information, it can only be hypothesized that the fibroblasts and some collagen bundles may orient between condensations in response to the same factors that determine feather germ pattern on the embryo. © 1969.