title: Mechanism of the "dark" axonal degeneration in the central nervous system.
abstract: OBJECTIVE
  In the central nervous tissue, two types of transsection-resulted axonal degeneration are generally accepted: "watery" and "dark". The present paper deals with the assumption that the mechanism of this kind of "dark" axonal degeneration has a relationship with that of the "dark" neuronal degeneration.
  
  
  METHODS
  A minute stab wound is inflicted in the parietal cortex of the rat brain. From 1 h to 3 months postinjury, the resulted ultrastructural events in two distant regions of the corticospinal tract (internal capsule and C3 region of the corticospinal tract) are studied.
  
  
  RESULTS
  As a novel finding, the first morphological process of "dark" axonal degeneration was found to consists in a striking reduction of the distances between neighboring neurofilaments, which were readily distinguishable and apparently undamaged. This pattern (compacted ultrastructure) persisted for hours. By day 1 postinjury, the compacted axoplasmic elements aggregated into a homogenous and dense ("dark") mass in which hardly any ultrastructural elements could be distinguished. Surrounded by apparently normal or mildly abnormal myelin sheat, this mass underwent a non-isotropic shrinkage during the next three months. Morphological signs of phagocytosis were insignificant.
  
  
  CONCLUSIONS
  The ultrastructural events during the first day post-injury suggest a non-enzymatic mechanism as an alternative to the prevailing molecular-biological mechanism.
authors.forename: József
authors.initials: J
authors.lastname: Pál
authors.forename: Ferenc
authors.initials: F
authors.lastname: Gallyas
mesh_terms: D000818:Animals; D001369:Axons / Q000473:pathology* / Q000648:ultrastructure; D002490:Central Nervous System / Q000473:pathology* / Q000503:physiopathology*; D009186:Myelin Sheath / Q000473:pathology* / Q000648:ultrastructure; D009410:Nerve Degeneration / Q000473:pathology* / Q000503:physiopathology*; D010587:Phagocytosis; D051381:Rats; D017208:Rats, Wistar