Figure 3.

Electron micrographs of sciatic nerve cross-sections from control and PDTC treated rats. (A) Large and small myelinated axons and nonmyelinated axons in a control. The myelinated axons are surrounded by compact myelin, Schwann cell cytoplasm and basal lamina. Several small clusters of nonmyelinated axons (na) are present on the left border with each group of axons encircled by the basal lamina of a nonmyelinating Schwann cell. (B-D) Sections from a rat exposed to oral pyrrolidine dithiocarbamate and maintained on a 200 ppm copper diet for 47 weeks. (B) A demyelinated axon (a) surrounded by the processes of an associated Schwann cell (s) possessing a basal lamina. A nonmyelinated axon and its associated Schwann cell (ns) that has been sectioned through its nucleus are also present. A large elongated nucleated cell (m) with pseudopodia and no basal lamina is consistent with an activated macrophage. (C) A thinly myelinated axon (a) is surrounded by persistent basal lamina (arrow). The associated nucleated cell (n) appears to be either a myelinating Schwann cell sectioned through its nucleus and a Schmidt-Lanterman incisure (arrowhead) or a macrophage that has infiltrated under the basal lamina ensheathment and is inserting a process between the myelin lamellae (arrowhead). (D) A remyelinating axon and its current Schwann cell is surrounded by persistant basal lamina (arrows) of previous Schwann cells and the process of a supernumerary Schwann cell (arrowheads).