Ultrastructural studies of muscle from a patient with Lafora disease showed sheets of glycogen particles and fine granular-filamentous material between myofibrils. These structures were frequently intermingled and stained intensely with silver proteinate, a specific stain for polysaccharides. Methods for isolation of glycogen yielded excessive hexose-releasing material. In chromatographic analysis of a hydrolysate of this material, glucose was the only component sugar. Compared with action on normal muscle glycogen, phosphorylase was ineffective, β-amylase 50% less effective, but α-amylase normally effective in degrading the Lafora polyglucosan. Incubation of muscle homogenate or isolated polyglucosan with a mixture of glucosidases capable of completely degrading normal glycogen (Diazyme) resulted in only 30% digestion of the Lafora polyglucosan. The metabolic error causing the accumulation of anomalous polysaccharide in this generalized storage disease remainsobscure.
Coleman DL, Gambetti P, Di Mauro S, Blume RE. Muscle in Lafora Disease. Arch Neurol. 1974;31(6):396–406. doi:10.1001/archneur.1974.00490420062007
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