IMMUNOHISTOCHEMICAL AND IMMUNOELECTRON MICROSCOPIC INVESTIGATION OF TAU-POSITIVE NEURONS LACKING TANGLE-FORMATION IN PROGRESSIVE SUPRANUCLEAR PALSY

Tau-positive neurons lacking tangle-formation (TNLT) show diffuse or f ine granular cytoplasmic staining with the tau-immunohistochemistry, a nd are more frequently found in progressive supranuclear palsy (PSP) a nd corticobasal degeneration (CBD) than in Alzheimer's disease (AD). I n this study, the regional incidence and ultrastructure of TNLT in 9 P SP cases were examined. The regional proportion of TNLT in tau-positiv e neurons was especially high in the hippocampus and amygdala, althoug h the incidence of TNLT was dependent on the case and region. Ultrastr ucturally, numerous tau-positive ribosome-like granules were found in the perikarya and dendrites of TNLT, but paired helical filaments (PHF ) and straight tubules were not identified. These findings suggest tha t TNLT in PSP or CBD are not the early stage of neurofibrillary tangle s (NFT) unlike TNLT in AD, but are another form of abnormally phosphor ylated tau.