Fig. 10.

Stereoscopic images of juxtamesaxonal membranes in glutaraldehyde-fixed (A) and formaldehyde-fixed WT mouse sciatic nerve (B) and in glutaraldehyde-fixed Cx29 ko mouse (C). A: rosettes of myelin P-face particles in glutaraldehyde-fixed JMIM (MP₁; light aqua overlay) and absence of rosettes where the second wrapping of myelin is exposed (MP₂). Orange overlay, axoplasm; pink overlay, tight junction; purple overlay, axon E-face; M, compact myelin. B: abundant 9-nm IMPs along the JMIM expansion (to right side of the tight junction, arrow and pink overlay) but almost no 9-nm IMPs on the continuation of the same membrane, which becomes the second wrapping of myelin to the left of the tight junction. Cx29 is labeled with 10-nm gold beads (yellow arrowhead). Ax, axoplasm (orange overlay); E, E-face of the JMAX (purple overlay); P, myelin P-face; dark aqua, myelin E-face; bottom green overlay, cytoplasm of myelin inner tongue; top green overlay, juxtamesaxonal myeloplasm. C: axolemma of myelinated axon from formaldehyde-fixed Cx29 ko mouse. Rosettes of 9-nm K_V1 E-face particles (purple overlays) are present, even though their normal coupling partners (Cx29 rosettes) are absent from the apposed myelin P-face (aqua overlay) (none present here or elsewhere). Also noteworthy, there are essentially no other large P-face particles (<50 per μm²) in the innermost myelin juxtaparanodal membrane, consistent with the proposal that, normally, there are virtually no channels other than Cx29 in the JPIM collars. Scale bars, 0.1 and 1 μm.