Myelin Proteins, Glycoproteins, and Myelin‐Related Enzymes in Experimental Demyelination of the Rabbit Optic Nerve: Sequence of Events

Abstract

Wallerian degeneration of the rabbit optic nerve was investigated by the technique of retinal ablation which precludes edema, hemorrhage, or macrophage infiltration. After 8 days of degeneration, marked degradation of axons and some myelin abnormalities appeared in the optic nerve, optic chiasma, and optic tract. Myelin lesions were maximal 32 days after retinal destruction. The amount of material stained with a myelin dye decreased drastically between 32 and 90 days after the operation. Biochemical parameters gave the following sequence of events. The concentration of the major periodic acid--Schiff staining glycoproteins was decreased after 2 days, and 6 days later the presence of cholesterol esters was detected in the optic tissue. After 16 days of Wallerian degeneration, the specific activity of 2',3'-cyclic nucleotide 3'-phosphodiesterase not associated with myelin decreased, indicating a possible de-differentiation of oligodendrocytes. Degradation of myelin basic protein became significant at 32 days and the amount of myelin isolated decreased later. The loss of myelin basic protein coincided with a reduction of myelin periodicity as measured in purified fractions by electron microscopy. These results show that secondary myelin destruction in the absence of edema, hemorrhage, or macrophages is a very slow process, and in this situation myelin undergoes a selective and sequential loss of its constituents.

Effect of Reactive Oxygen Species on Myelin Membrane Proteins

“…On the other hand, it is known that infiltrating polymorphonuclear leukocytes release large amounts of reactive oxygen species into the medium (Babior, 1978) and thus the inflammatory reactions in the CNS may induce peroxidative changes in the myelin sheath. Furthermore, the shift toward heavier myelin fragments (similar to the shift observed in this investigation) has been reported in demyelinating conditions (Reigner et al, 1981;. Although the evidence is indirect it can be envisaged that the peroxidative reactions may be an important factor in the immune system-mediated dissolution of myelin.…”

Investigations on myelination in vitro: IV. „Myelin‐Like”︁ or Premyelin Structures in Cultures of Dissociated Brain Cells From 14–15‐Day‐Old Embryonic Mice

“…Periodicity measurements gave 102 A. Reigner et al [1981] found similar data for the periodicity of myelin isolated from rabbit optic nerve.…”

Abnormalities in brain myelin of rabbits with experimental autoimmune multiple sclerosis-like disease induced by immunization to gangliosides

“…The analysis of myelin obtained from the brains of MS patients showed an elevation in the ratio of heavy to light myelin fractions as compared to normal control myelin (Konat & Oflner 1982). Recently a similar shift in the buoyant density of myelin was observed in optic nerves from rabbits undergoing experimental demyelination (Reigner et al 1981). These reports prompted us to investigate the density distribution of myelin fragments isolated from the brains of rabbits with EAMSD.…”