The zitter rat: membranous abnormality in the Schwann cells of myelinated nerve fibers

Abstract

Ultrastructural alterations of the Schwann cells were chronologically examined in zitter and in control rats. The membranous abnormalities closely involving the nuclear membranes of the Schwann cells and mesaxons were constantly observed in the zitter rats. These structures consisted of scroll- or whirl-like unit membrane accumulations directly extending to the nuclear envelope. Occasionally, similar membranous structure were observed in association with the endoplasmic reticulum, lysosome or mitochondria in the cytoplasm of the Schwann cells. In the control rats, whirl-like membranous structures in the nuclear membranes of the Schwann cells were observed only intermittently at 1, 5 and at 7 days of age in the developing process. In conclusion, we postulate that the zitter rat, which is an established animal model for hypomyelination of the central nervous system (CNS), has some inherited abnormality related to the membrane biosynthesis and its regulation in Schwann cells as well as in oligodendrocytes.