Fig. 4.

Return of myelin sheaths represents true remyelination. A) Electron micrograph of myelinated axons from cerebellum at 10 DIV. Scale bar — 1 μm. B) Electron micrograph of remyelinated axons from cerebellum at 25 DIV, after LPC treatment on day 10. Note the thinner myelin per axon, especially in relation to their axon diameter. Scale bar — 1 μm. C) Electron micrograph showing a node of Ranvier present in cerebellar cultures that were allowed to remyelinate. Thus, compact myelin forms with mature paranodal structures. Scale bar — 1 μm. D) Quantification of G ratios showing larger G ratios (thinner myelin) for remyelinated axons (dark grey) than that of myelinated axons (pale grey), per axon diameter. These regression lines are significantly different using the maximum likelihood ratio test, p < 0.01 (counted from 6 cerebellar slices per group). E–F) Frequency distribution graphs of internode length in myelinated (E) and remyelinated (F) axons in the cerebellum (pale grey) and spinal cord (dark grey). There is a left shift for remyelinated axons showing that these have shorter internodes. (N = 4 experiments, a minimum of 80 internodes counted per group.) Comparisons of myelination and remyelination frequency-distribution data for both cerebellum and spinal cord is significant with p < 0.01 (Kolmogorov–Smirnov Test).