Specialized cell contacts in the developing nerves of mouse embryos.

In mouse embryos, special focal contacts between axons and Schwann cells, axons and fibroblasts as well as Schwann cells and fibroblasts are visible during the outgrowth of nerves. These rather seldom contacts exhibit a uniform structure. Axons and Schwann cells from small finger-like protrusions projecting into coated pits of Schwann cells and fibroblasts. The narrow intercellular space in the contact zone is crossed by fine filaments.