Radial Bands in the Optic Nerve Myelin Sheath

Abstract

WHILE examining the histochemistry of the optic nerve, we observed beaded transverse band-like areas, which were more dense than the other areas in the myelin sheath in osmium-tetroxide-fixed tissues (Fig. 1 A, arrows), These beads of dark areas in the myelin sheath were fairly constantly observed in cross as well as in longitudinal sections. The bands became very clear when the osmium-tetroxide-treated, paraffin-embedded sections were cleared in xylol, immersed in turpentine or dioxane for 1½ h, and then cleared again in xylol and mounted in dibutylphthalate polysterene xylene mounting medium. With this procedure, banded arrangements of beads were clearly seen (Fig. 1 B, arrows), and the lipid material which is in between these beads had been extracted, whereas the beads themselves were left unextracted. This suggests that these dark beaded areas in the myelin sheaths of the optic nerve, which are seen in osmium-tetroxide-treated material, are resistant to fat solvents. It is probable that these banded areas are made up of some kind of proteolipid or polysaccharide material which is resistant to fat solvents.