Figure 10.

Late-onset axonal degeneration in the spinal cord of FA2H^−/− mice. A–F, The spinal cord white matter of 18-month-old mice features scattered degenerated myelin sheaths characterized by splitting of myelin lamellae (arrows in B and E), degenerated axons that often display accumulations of fibrillary material (circle in B, black asterisk in C) or collapsed axon cylinders (E, arrows), and microcystic spaces (B, white arrow in C, black asterisk in D and F; compare with controls in A; all photos taken close to the anterior horn). These microcystic spaces are sometimes surrounded by remnants of myelin sheaths (black asterisk in D), indicating that they represent leftovers of degenerated myelinated axons. Care was taken to document these pathologic changes only in the vicinity of well preserved myelin sheaths as an internal control for adequate fixation. F, “Microcysts” appear ultrastructurally as empty gaps without a discernable wall structure. Scale bars: A, 20 μm; B, C, 10 μm; D, E, 0.5 μm; F, 210 μm.