Distribution of retrogradely transported fluorescent latex microspheres in rat lumbosacral ventral root axons following peripheral crush injury: a light and electron microscopic study.
The retrograde axonal transport of fluorescent latex microspheres, which are tracers extensively used for studying the neuronal connectivity in the CNS, was investigated in large myelinated lumbosacral ventral root nerve fibres of adult rats following peripheral crush injury. After crushing the sciatic nerve, a suspension of 30 nm red-fluorescent latex beads was injected in the crush region. Following postoperative survival times of 24, 48, 72 and 120 h, the animals were fixed by vascular perfusion using different types of paraformaldehyde-based fixatives. At shorter survival times, red-fluorescent granules were seen distributed mainly internodally in several axons, while at longer times (> 48 h) an accumulation at nodes of Ranvier, close to the paranodal myelin sheath, predominated. Photoconversion of the fluorescent labelling into a stable, highly electron dense reaction product was performed using diaminobenzidine, permitting ultrastructural observations. The electron dense material that formed over the fluorescent granules appeared in association with membrane-delimited bodies. In some bodies the electron dense material formed well-defined, solitary spheres of sizes corresponding to those of the latex beads. When located close to the paranodal myelin sheath, the bodies were often situated within larger membranous structures, which sometimes were partly engulfed by protrusions of the so called axon-Schwann cell network. At longer survival times, some bodies containing photoconversion reaction product appeared within the axon-Schwann cell network, thereby being segregated from the main axoplasm. The study introduces a new application for fluorescent latex microspheres. The used approach, combining light/fluorescence and electron microscopy, should be suitable for long term investigations of the fate of axonally transported non-neuronal substances.
Persson
H G
HG
Department of Anatomy and Cell Biology, University of Göteborg, Sweden.
Gatzinsky
K P
KP
D000818:Animals; D001369:Axons / Q000378:metabolism*; D005453:Fluorescence; D007840:Latex; D008161:Lumbosacral Region; D008297:Male; D008853:Microscopy / Q000379:methods; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008863:Microspheres; D009409:Nerve Crush; D059348:Peripheral Nerve Injuries; D051381:Rats; D017207:Rats, Sprague-Dawley; D013126:Spinal Nerve Roots / Q000378:metabolism* / Q000648:ultrastructure
D007840:Latex