HISTOCHEMISTRY OF DEMYELINATION 



C. W. M. ADAMS and N. A. TUQAN 

 Guy*s Hospital, London 



Chemical changes in the myelin lipids cannot be detected during the 

 early phases of Wallerian degeneration (Rossiter). This is confirmed by 

 histochemical studies which show that the Marchi reaction does not 

 become positive until the stage of chemical dégradation of the rayelin 

 lipids. In the early phase of demyelination (first week) the sheath breaks 

 down into small lipid particles (Nobak) but the histochemical and bio- 

 chemical characteristics of thèse particles remain normal. For this reason 

 attention bas been directed to the proteins in demyelination. Myelin 

 contains both trypsin-re sis tant and trypsin-digestible proteins. It was 

 found that the trypsin-resistant protein of normal CNS myelin is a chloro- 

 form-soluble proteolipid while that in PNS myelin is insoluble in chloro- 

 form (TRPR, neurokeratin). However, no histochemical or biochemical 

 changes were detected in thèse trypsin-resistant proteins or their attached 

 lipids during demyelination. On the other hand, removal of the trypsin- 

 digestible protein by proteolytic enzymes releases lipid from myelin in 

 cryostat-cut tissues (Wolman). Investigation in vivo revealed that 

 proteolytic activity increases in the early stages of demyelination but 

 more as a resuit of libération of enzyme pre-existing in the normal nerve 

 than as a resuit of increased synthesis of enzyme. It is inferred that the 

 release of lipid by the digestion of protein is an important factor in the 

 early phase of demyelination. 



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