The submicroscopic organization of vertebrate nerve fibres: An electron microscope study of myelinated and unmyelinated nerve fibres

摘要: Abstract 1. I. Thin serial frozen sections of fresh peripheral and central myelinated nerve fibres from the frog, rat, cat rabbit, in addition to spinal cord segments frog were examined with electron microscope after freezing-drying or fixation osmium. Supplementary investigations included parallel observations by phase contrast microscopy examination thin embedded nerve, replica-adhesion dissociation preparations. The following structures are described internode portion nerves: 1.1. a) myelin sheath separates into layered membranes which closely resemble lamellae fixed whole nerve. Lamellar this type an average thickness 80 A a granular fine structure have been found all types. By means ultracentrifugation these laminated can be warped reproducible fashion, indicating that they probably preformed sheath. Dissociation fresh, unfixed rod shaped granules 60–80 long is produced trypsin digestion. concentric sheath, consisting individual layers approximately thick, could confirmed types examined. 1.2. b) Oblique clefts corresponding Schmidt-Lantermann incisures observed further structural details neurilemma membrane, its associated fibre bundles Schwann cells noted. Numerous opaque, oval bodies (0.5–1 μ) internal close cell. 1.3. c) An arrangement for obtaining successive diffraction patterns micrographs restricted areas same object specimen holder RCA EMU microscope, without breaking vacuum. With arrangement, characteristic cross-grating Kikuchi line recorded crystalline resembling osmium evidence available suggests products formed during process fixation. 1.4. d) axon frozendried fixed, contains filaments indefinite length, diameter 100–200 regularly spaced axial discontinuities. These show predominantly longitudinal within aggregate form compact neurofibrils. Dense corpuscles clear vesicular also seen axon. 2. In preparations lateral funiculus rat cords, new submicroscopic diameters ranging between 0.1 1 μ, identified as their connection larger structure. fusiform enlargements occupied dense nuclei, consist single tubular 100 variable number other structures. finest membrane only one filament. thick exhibits fibres. 3. Unmyelinated sympathetic chains constituted nodose filaments, having invested 60–100 thick. slender nuclei attached membranes. II. findings presented here indicate elements fundamentally similar, point common pattern organization sizes so-called unmyelinated