title: Myelin structure and composition of myelinated tissue in the African lungfish.
abstract: To analyze myelin structure and the composition of myelinated tissue in the African lungfish (Protopterus dolloi), we used a combination of ultrastructural and biochemical techniques. Electron microscopy showed typical multilamellar myelin: CNS sheaths abutted one another, and PNS sheaths were separated by endoneurial collagen. The radial component, prominent in CNS myelin of higher vertebrates, was suggested by the pattern of staining but was poorly organized. The lipid and myelin protein compositions of lungfish tissues more closely resembled those of teleost than those of higher vertebrates (frog, mouse). Of particular note, for example, lungfish glycolipids lacked hydroxy fatty acids. Native myelin periodicities from unfixed nerves were in the range of those for higher vertebrates rather than for teleost fish. Lungfish PNS myelin had wider inter-membrane spaces compared with other vertebrates, and lungfish CNS myelin had spaces that were closer in value to those in mammalian than to amphibian or teleost myelins. The membrane lipid bilayer was narrower in lungfish PNS myelin compared to other vertebrates, whereas in the CNS myelin the bilayer was in the typical range. Lungfish PNS myelin showed typical compaction and swelling responses to incubation in acidic or alkaline hypotonic saline. The CNS myelin, by contrast, did not compact in acidic saline but did swell in the alkaline solution. This lability was more similar to that for the higher vertebrates than for teleost.
authors.affiliation: Department of Neuropathology, Harvard Medical School, Boston, MA 02115, USA. kirschnd@bc.edu
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Kirschner
authors.forename: Jothie
authors.initials: J
authors.lastname: Karthigesan
authors.forename: Oscar A
authors.initials: OA
authors.lastname: Bizzozero
authors.forename: Bela
authors.initials: B
authors.lastname: Kosaras
authors.forename: Hideyo
authors.initials: H
authors.lastname: Inouye
mesh_terms: D000818:Animals; D002490:Central Nervous System / Q000737:chemistry; D004577:Electron Probe Microanalysis; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D005399:Fishes / Q000378:metabolism*; D006017:Glycolipids / Q000737:chemistry; D008051:Lipid Bilayers / Q000032:analysis; D008055:Lipids / Q000032:analysis; D008854:Microscopy, Electron; D009185:Myelin Proteins / Q000032:analysis; D009186:Myelin Sheath / Q000737:chemistry* / Q000648:ultrastructure*; D017933:Peripheral Nervous System / Q000737:chemistry; D014018:Tissue Distribution
chemical_list: D005227:Fatty Acids; D006017:Glycolipids; D008051:Lipid Bilayers; D008055:Lipids; D009185:Myelin Proteins