Figure 5.

Oligodendrocyte–axon interactions affect distribution and transport of axonal mitochondria. a–c, The distribution and transport rates of axonal mitochondria were compared in slice cultures of wild-type (WT) and myelin-deficient (MD) rats; myelin-deficient axons have Na⁺ channel clusters, but lack paranodal loops and compact myelin. Vertical bar, 300 s; horizontal bar, 10 μm. d, In contrast to wild-type myelinated axons, mean mitochondrial transport speed was identical in internodal and nodal-like axoplasm of myelin-deficient fibers. e–g, The mean size (e), normalized size (f), and length (g) of axonal mitochondria were similar in node-like (NL) and internodal axoplasm of myelin-deficient fibers. Mean mitochondria size in nodal-like and all axoplasm were significantly larger than mean mitochondrial size in wild-type axons. *p = 0.05, **p < 0.001; n, number of mitochondria (d, g) or axons (e, f). e, f, Bars, Mean + SEM. d, g, Boxes, Median with first and third quartiles. PNP, nodal–paranodal; Inter, internodal; Juxta, juxtaparanodal; Antero, anterograde; Retro, retrograde.