Ultrastructure of neurofibrillary tangles in Alzheimer's disease by means of tilt-stage electron microscopy.

Neurofibrillary tangles (NFT) in the brains of patients with Alzheimer's disease were examined by means of tilt-stage electron microscopy. Observing a longitudinal direction, constricted parts of the NFT did not move in an axial direction. In a transverse section, a fibril of the NFT consisted of globular subunits having a hollow structure in the center and did not appear as paired filaments. From these findings, it was considered that a fibril of NFT consists of twisted protofilaments made up of globular subunits and does not consist of paired helical filaments.