|
From a histological perspective the classification is a lot simpler, since the commonly used methods can only show the presence of amyloid in general rather than selectively colour individual types. For the limited differentiations possible between the various types it is necessary to block their staining reaction and compare the staining to an unblocked stained section. The possibilities are given in the chart below.
|Autoclave at 120°C for 30 min.||AA no longer stains with congo red.|
|Autoclave at 120°C for 2 hours.||AL no longer stains with congo red.
Pre-albumin related amyloid shows no change.
|Potassium permanganate oxidation.||AA and β2-microglobulin amyloid no longer stain with congo red.|
|Alkaline guanidine for 1 minute.||AA no longer stains with congo red|
|Alkaline guanidine for 2 hours.||AL and systemic senile amyloid no longer stain with congo red.
Familial amyloid protein retains congo red staining
Immunohistochemistry is the most definitive method for classification of amyloid types by identification of their predominant protein. Amyloid fibrils may also be solubilised and identified in solution, although that is outside the scope of StainsFile.
The methods used for demonstrating amyloid are listed below. Of these, the DMAB nitrite test is a histochemical method for tryptophan using p-dimethylaminobenzaldehyde. The metallic impregnations are rarely used. By far, the most common method and something of a standard, if that word can be applied to amyloid staining, is to use the direct cotton dye, congo red, with the green birefringence it usually imparts.
The term direct cotton dye is used in the textile industry to refer to those dyes which can colour cotton without requiring a mordant, i.e. by direct dyeing. They are usually acid dyes. In the Colour Index their functional name is "direct + colour + number". Some direct cotton dyes are suitable for staining amyloid, notably congo red (direct red 28) and sirius red F3B (direct red 80). Other direct cotton dyes, such as benzo scarlet 4BNS, sold under the proprietary name "amyloid red" (direct red 72), may also be successful. I would remind you that any staining method for amyloid may be unsuccessful, and that applies to congo red and the other direct cotton dyes as well.
|Toluidine blue birefringence|
|Crystal violet metachromasia|
|Congo red and sirius red F3B|
|Thioflavine T and S|
|DMAB-Nitrite for tryptophan|
Amyloid and Amyloidosis
http://en.wikipedia.org/wiki/Amyloid and http://en.wikipedia.org/wiki/Amyloidosis.
The charts were blended and reproduced under the Creative Commons licence.
Structure of amyloid
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Histological technique., Ed. 2.
Oxford University Press, London, England.
Cohen, A S, and Calkins, E, (1959).
Electron Microscopic Observations on a Fibrous Component in Amyloid of Diverse Origins
Nature, v. 183: p. 1202-1203.
Drury, R A, and Wallington, E A, (1967).
Carleton's histological technique., Ed. 4.
Oxford University Press, London, England.
Elghetany, M.T. & Saleem, M.,
Methods for staining amyloid in tissues: a review.,
Stain Technology, July 1988, pages 201-212.
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Histopathology: Selected Topics,
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Bailliere Tindall, London, England.
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Cellular Pathology, p.371
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The site of formation and ultrastructure of amyloid
American Journal of pathology, v. 43: p. 837.
Lendrum, A C, Slidders, W, and Fraser S, (1972).
Renal hyalin: A study of amyloidosis and diabetic fibrinous vasculosis with new staining methods,
Journal of Clinical Pathology, v. 25, P. 373
Wolman, M. (1971).
Amyloid, its nature and molecular structure: comparison of a new toluidine blue polarized light method with traditional procedures.
Laboratory Investigation, v. 25: p. 104-110.
Last updated January 2019