E. Tracz et al., PAIRED HELICAL FILAMENTS IN CORTICOBASAL DEGENERATION - THE FINE FIBRILLARY STRUCTURE WITH NANOVAN, Brain research, 773(1-2), 1997, pp. 33-44
Paired helical filaments (PHF) composed of hyperphosphorylated tau pro
teins are characteristic findings in neurodegenerative disorders, incl
uding Alzheimer's disease (AD) and corticobasal degeneration (CBD). Th
e filaments in CBD differ from those in AD by a reduced number of tau
isoforms and less stable ultrastructure. To further compare the ultras
tructure of both filaments, we employed a novel staining reagent, Nano
Van, as well as aurothioglucose and uranyl acetate. With commonly used
uranyl acetate, both kinds of filaments appeared as twisted ribbons 1
5-20-nm and 21-23-nm wide, respectively, without significant internal
substructure. With application of aurothioglucose, only few structural
details were apparent. With NanoVan, AD filaments showed similar stru
cture to that with uranyl acetate but CBD filaments displayed a highly
heterogeneous appearance consistent with the dissociation of the 20-2
5-nm-wide filaments along two longitudinal axes. This was evident by t
he presence of thinner, 12-13-nm-wide filaments and filaments that spl
ayed into two 20-25-nm-wide components at one or both ends. Moreover,
detection of a prominent, 7-8-nm-wide axial region distinguished up to
four protofilaments per one filament. Each protofilament appeared to
contain two 3-5-nm-wide fibrils separated by an approximately 1-nm-wid
e axial region. The results suggest that 3-5-nm fibrils are the smalle
st structural subunits of filaments in CBD and that NanoVan may be an
unique reagent in detecting eight-fibril organization in these less st
able filaments. (C) 1997 Elsevier Science B.V.