Electron microscopy of pathological alterations of quadriceps nerves in six-month-old PBGD^–/– mice. (a) A myelinated axon (A) is surrounded by basal lamina–covered Schwann cell profiles (arrows) reminiscent of bands of Büngner. Arrowheads point to empty basal laminae. (b) Schwann cells devoid of axon and myelin (arrows) form profiles reminiscent of bands of Büngner. Arrowheads point to Schwann cell basal laminae. (c) This axonal profile (asterisk) containing numerous vesicles (small arrows) is reminiscent of a growth cone usually found in injured nerves. Note the close association with a Schwann cell (large arrows). Arrowheads point to Schwann cell basal laminae. (d) Two small-caliber axons (asterisks), probably axonal sprouts, are in close association with a Schwann cell profile (arrows) reminiscent of a band of Büngner. Arrowheads point to Schwann cell basal laminae. Scale bars: 0.5 μm