title: Interlamellar tight junctions of central myelin. I. Developmental mechanisms during myelogenesis.
abstract: The process of myelination in the central nervous system (CNS) of the rat (optic nerve) was studied with the freeze-fracturing technique and ultrathin sectioning to obtain information on the developmental mechanisms of interlamellar tight junctions. Using a tilting cartridge for analysis of thin sections, it could be demonstrated that during the initial phase of wrapping a tight junction formation develops between the joining tips of the oligodendrocytic process. In tannic acid-stained samples these junctions appear as typical quintuple-layered membrane fusions, while in potassium permanganate-stained material membrane thickenings between the apposing glial tips are prevalent. The latter configuration represents the characteristic feature of the so-called radial component of central myelin. Using the freeze-fracturing technique, a biphasic mode of the myelinic tight junction assembly was detected. It is suggested that tight junctions represent a prerequisite of the myelination process.
mesh_terms: D000818:Animals; D001369:Axons / Q000648:ultrastructure*; D005614:Freeze Fracturing; D007365:Intercellular Junctions / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009186:Myelin Sheath / Q000502:physiology / Q000648:ultrastructure*; D009457:Neuroglia / Q000648:ultrastructure*; D009836:Oligodendroglia / Q000502:physiology / Q000648:ultrastructure*; D009900:Optic Nerve / Q000648:ultrastructure; D051381:Rats