title: Ultrastructural recognition of gap junctions between melanocytes in human vestibular organs by tannic acid containing fixative preparation and freeze-fracture technique.
abstract: BACKGROUND
  The purpose of the present study was to obtain additional information about the ultrastructural characteristics of gap junctions between melanocytes in human vestibular organs by using various ultrastructural techniques.
  
  
  METHODS
  All materials were obtained from patients with vestibular schwannoma. Glutaraldehyde-fixed specimens and specimens treated with fixative containing glutaraldehyde and tannic acid were processed for conventional ultrathin transmission electron microscopic (TEM) examination. Others were prepared for freeze-fracture replica and examined by TEM.
  
  
  RESULTS
  Gap junctions were present between adjacent subepithelial melanocytes. The gaps between the inner leaflets of the apposed plasma membranes at the gap junctions were 10-12 nm, and the gaps between the outer leaflets were 2-4 nm. The intercellular space between the apposed plasma membranes of gap junctions showed the deposition of high electron-dense material in specimens prepared with fixative containing glutaraldehyde and tannic acid. At the highest magnification specimens fixed by glutaraldehyde with or without tannic acid and cut obliquely to the plasma membranes showed periodic substructures with constant repeating lattices or a small porous structure at the junctions. Study by freeze fracture revealed that these gap junctions between melanocytes consisted of 100-200 aggregations of connexon particles that were approximately 8.8 nm in diameter.
  
  
  CONCLUSIONS
  We suggest that melanocytes may construct a cellular network involved in the maintenance of the homeostasis of human vestibular organs through the intimate transmission of various signals or intercellular informations via well-developed gap junctions.
authors.affiliation: Department of Otorhinolaryngology, Keio University, School of Medicine, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Masuda
authors.forename: K
authors.initials: K
authors.lastname: Yamazaki
authors.forename: Y
authors.initials: Y
authors.lastname: Toyama
authors.forename: J
authors.initials: J
authors.lastname: Kanzaki
authors.forename: Y
authors.initials: Y
authors.lastname: Hosoda
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005404:Fixatives; D005614:Freeze Fracturing; D017629:Gap Junctions / Q000648:ultrastructure*; D005976:Glutaral; D006801:Humans; D047348:Hydrolyzable Tannins; D008297:Male; D008544:Melanocytes / Q000648:ultrastructure*; D008854:Microscopy, Electron; D008875:Middle Aged; D009442:Neurilemmoma / Q000648:ultrastructure; D015837:Vestibular Diseases / Q000473:pathology; D014722:Vestibule, Labyrinth / Q000648:ultrastructure*
chemical_list: D005404:Fixatives; D047348:Hydrolyzable Tannins; D005976:Glutaral