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NeuroScience Associates

Campbell-Switzer Alzheimer Pathology Silver Stain Abstract

The first description of the result of this protocol was as an abstract submitted for the 17th Annual Meeting of the Society for Neuroscience.

ALZHEIMER PLAQUES AND TANGLES: A CONTROLLED AND ENHANCED SILVER STAINING METHOD. S.K. Campbell, R.C. Switzer, III, and T.L. Martin, Univ. of TN, Dept. Pathology & Medical Biology, Knoxville, TN 37920.

The hallmark neuropathological features of Alzheimers disease are the neuritic plaques and neurons with neurofibrillary tangles (nft). Traditionally, these features have best been histologically visualized by one of a number of protocols utilizing silver. Because of a lack of control in certain steps in many of these protocols, the silver methods are notorious for being capricious. In particular, erratic staining and other problems are common in methods that use a silver-diammine solution (silver nitrate and ammonium hydroxide). Furthermore, the step involving reduction (final development of silver impregnated structures) typically is not easily controlled.

We have combined the silver-pyridine-carbonate incubation step of Hicks (J Lab Clin Med 31:1375, 1946) with the physical development procedure of Gallyas (Acta Neuropathol Berl. 16:39, 1970) to achieve control of the staining reaction. This method works equally well on paraffin or freeze-cut sections. In addition to easily and consistently achieving a high quality staining of plaques and tangles, the contrast was greatly improved due to little or no staining of myelin. The longer the tissue had been in formalin, the less staining of myelin occurred. By adjusting the time in the developer, the density of staining can be controlled so that features of interest to a given investigator could be accentuated. We also found that the staining of glia and background neuropil could be reduced by increasing the amount of pyridine in the silver-pyridine-carbonate solution, thus allowing fuller development of the staining of plaques, especially minute ones. This yields spectacular sections that have dark plaques against a clear background, which makes these sections readily amenable for computer image analysis. Neurons with nft’s become more orange with increasing pyridine concentrations. With such enhancement, we have found that plaques occur in caudate and putamen more frequently than our other stains had led us to believe. This method allows a wide range of control of silver staining and a means of regulating the amount of staining of normal tissue elements.

A complete description was published by the US Patent Office “Histologic Analysis Method” patent # 5,192,688 in 1993.

Since this abstract was printed, this staining method has been quite valuable in revealing the AD-like pathology in the brains of various mouse models of AD. The high contrast image is ideally suited for image analysis to determine amyloid plaque burden.

Helpful links:

FAQ regarding silver stains:

Are silver stains all the same?

No. There are numerous silver staining protocols, each tailored to reveal specific features. "Silver Stains" are as unique as any other stain in that they are each specifically designed to stain a particular feature. Silver simply refers to the staining agent (Silver) which stains the designated feature black.

Does the Campbell-Switzer stain show the same features as the disintegrative degeneration stain?

No. Each method reveals a different set of features. The Campbell-Switzer method reveals the neuritic plaques and tangles of Alzheimer's pathology. The disintegrative degeneration stain shows the products of neuronal disintegrative degeneration.

How do the plaques revealed by the Campbell-Switzer stain in transgenic mouse models compare with staining using antibodies against different forms of amyloid?

Some antibodies show only a subset of plaques revealed by the Campbell-Switzer method, while others appear to be a one to one match. The Campbell-Switzer stain is unique in its ability to differentiate its staining of immature (diffuse) and mature (congophilic) plaques, allowing researchers a unique observational capability.

 

For further reference, please see: Stains