Ultrastructure of myelin and axons in corpus callosum. (A) Cross and longitudinal sections of nerve fibers of control mice display a regular and compact myelin sheath. (B) In the corpus callosum of three-week-old Nestin-Pex5
−/− mice many axons are still myelinated while a subset already lacks a myelin sheath. The arrow in (B) indicates a swollen necrotic axon, surrounded by a normally appearing myelin sheath. (C) In 12-week-old Nestin-Pex5 knockout mice demyelination is even more pronounced than at three weeks. Similarly as at three weeks, an edematous necrotic axon, which is enwrapped by an apparently normal myelin sheath (arrow), is detected. In addition, large necrotic areas are observed (asterisk).