Paired Helical Filaments in Electron Microscopy of Alzheimer's Disease

Abstract

IN the light microscope, the characteristic change in the neurones of the cerebral cortex in Alzheimor's disease is the presence of dense bundles of argyrophilic fibrils. They are coiled into skeins or ‘squash racket’ shapes and appear to fill most of the perikaryal cytoplasm, sometimes giving the cell a swollen appearance. It has been suggested by Divry¹ that the fibrils are extra-cellular except in the later stages of the change. The fibrils stain with congo red, and this results in a type of birefringence suggesting the presence of longitudinally arranged micelles in the fibrillar bundles. These well-known findings would lead one to expect the presence of fine filaments associated with these cells in the electron microscope, and if intra-cellular, these might be neurofilaments, which are suggested by Gray and Guillery² to be the basis of neurofibrillary argyro-philia.