Linkage between axonal ensheathment and basal lamina production by Schwann cells

RP Bunge, MB Bunge… - Annual review of …, 1986 - annualreviews.org
RP Bunge, MB Bunge, CF Eldridge
Annual review of neuroscience, 1986annualreviews.org
Theodor Schwann (1839) identified the cell that now bears his name in his efforts to
establish the cellular nature of all body parts. He considered the demonstration that the fatty
sheaths of peripheral nerve were related to cells particularly compelling support for his cell
theory. The question whether the fatty myelin sheath derived from the cell of Schwann during
development was debated during the ensuing century and finally was settled when the
resolution of the electron microscope allowed demon stration that the myelin sheath was …
Theodor Schwann (1839) identified the cell that now bears his name in his efforts to establish the cellular nature of all body parts. He considered the demonstration that the fatty sheaths of peripheral nerve were related to cells particularly compelling support for his cell theory. The question whether the fatty myelin sheath derived from the cell of Schwann during development was debated during the ensuing century and finally was settled when the resolution of the electron microscope allowed demon stration that the myelin sheath was formed from Schwann cell plasma membrane.
The resolution of the electron microscope was also required to demon strate the precise nature of ensheathment of unmyelinated nerve fibers (fibers of Remak). Ultrastructural studies established that these nerve fibers are provided with an investment of Schwann cell cytoplasm rather than a thin layer of myelin, as was often stated earlier. This cytoplasmic ensheathment has now been studied in considerable detail, although its functional contribution to the enclosed axon remains enigmatic. We know now that, with rare exceptions, Schwann cells encircle all nerve fibers in peripheral nerve. One Schwann cell either encloses one axon, with a myelin sheath and associated cytoplasm, or a number of unmyelinated axons, each one harbored within a furrow of cytoplasm. These Schwann cell-neurite units are further enveloped by a sleeve of basal lamina, and this
Annual Reviews