Degenerating Myelin: Comparative Histochemical Studies Using Classical Myelin Stains and an Improved Marchi Technique Minimizing Artifacts

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Abstract
In this study on degenerating myelin, comparisons were made between different stains including Marchi, regular lipid, and Weil's stain for myelin sheaths. An improved technique was devised which minimized artifacts regularly seen in the classical stains for myelin and for degenerating myelin. An artifact referred to as “pseudo-Marchi dust” is eliminated by the method of handling and fixing brain and spinal cord tissue. Some discussion is included on the solubilities of various tissue constituents which may be affected by prior freezing of unreacted tissue. In view of this, the varying sequence of events in degenerative processes of the central nervous system (CNS) brought about by different etiologic factors, such as Wallerian degeneration, phalaris staggers and enzootic ataxia, might be re-evaluated by the use of several interrelated staining methods. The CNS diseases studied here using a number of staining techniques are considered to be the result of local toxic conditions rather than due to tract interruption. The present study suggests evaluations of the stained sections in terms of the histochemical reactions involved. The degenerative sequence in phalaris staggers appears to be different from that seen in enzootic ataxia in that tissues from sheep with phalaris staggers showing early and advanced neurological changes have differing patterns of lipid stainability and the combined staining procedures applied to CNS tissues from sheep with enzootic ataxia show characteristics more like the CNS tissues from sheep with advanced phalaris staggers than from early phalaris staggers. Characteristics of both conditions differ from the histological pattern reported for classical Wallerian degeneration.

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