Macromolecular structure of the Schwann cell membrane. Perinodal microvilli.
The macromolecular structure of perinodal Schwann cell membrane was examined with freeze-fracture electron microscopy. Perinodal microvillous-like processes of Schwann cells exhibit an asymmetrical partitioning of intramembranous particles (IMPs), with a moderate (approximately 900/microns2) density of particles on P-faces and a lower (approximately 300/microns2) density of IMPs on E-faces. The densities of IMPs observed on the fracture faces of perinodal processes are similar to those within the outer membrane of the Schwann cell proper. On both fracture faces of the perinodal processes and the Schwann cell membrane proper, a high (approximately 45%) percentage of the IMPs displayed a large (greater than or equal to 9.6 nm) diameter. Specialized junctions (i.e., gap junctions, tight junctions) between adjacent perinodal Schwann cell processes or between perinodal processes and nodal axolemmal were not observed.
D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure; D005614:Freeze Fracturing; D008854:Microscopy, Electron; D008871:Microvilli / Q000648:ultrastructure; D011901:Ranvier's Nodes / Q000648:ultrastructure*; D051381:Rats; D011919:Rats, Inbred Strains; D012583:Schwann Cells / Q000648:ultrastructure*; D013127:Spinal Nerves / Q000648:ultrastructure