Figure 2.

Toluidine blue stained plastic embedded sections of rat sciatic nerve showing stages of axonal degeneration after crush injury. (a) Cross section from a control rat showing the normal axon density and bimodal distribution of large and small myelinated axons. The myelinated axons are surrounded by compact myelin and protein staining of the cytoskeletal and mitochondrial components in the axoplasm is evident. Two Schwann cells (*) have been sectioned at the middle of the internode through their cytoplasm and nucleus and axons sectioned through Schmidt-Lanterman incisures are present (arrows). Clusters of nonmyelinated axons (arrrowheads) are present and a blood vessel (v) is located along the lower boarder of the section. (b) Cross section obtained distal to crush injury. There is a decreased density of axons in the section with very few axons exhibiting normal axoplasm staining. Axons in early stages of axonal degeneration (*) are identifiable by the loss of axoplasm and axolemma staining with the myelin sheath still intact. Many axons are in later stages of axonal degeneration (arrows) demonstrating the progression of myelin collapse to form ovoids. Nucleated cells (arrowheads) present are consistent with dedifferentiated Schwann cells, macrophages or fibroblasts.