A modified NOR–silver impregnation technique for amyloid plaques and neurofibrillary tangles: comparative assessment

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Abstract
A modified nucleolar organizer region (NOR)-silver impregnation technique was recently introduced allowing the simultaneous staining of neurofibrillary tangles (NFT) and amyloid plaques (AP) in a single section. This impregnation technique proved to be very effective, rapid, of low cost, and to yield consistent results even in brain tissue fixed for long periods of time. In the present study, several silver impregnation and immunohistochemical techniques were applied and their reliability for the demonstration of NFT and AP was analysed. The modified NOR stain allowed the reliable and simultaneous demonstration of both amyloid plaques and neurofibrillary tangles; this method produced better results than the standard silver impregnation techniques. It is only in their early stages of formation that NFT cannot be detected by this method and, instead, immunohistochemistry for tau-2 is required. There was no significant difference in the staining properties for amyloid plaques between the modified NOR silver impregnation technique and the anti-beta-A4 immunostain.