Weigert's elastic stain
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Weigert's elastic stain is a combination of stains used in histology which is useful in identifying elastic fibers. Often orcein or a combination of resorcinol and fuchsine are used for staining. For counterstaining cell nuclei nuclear fast red or hematoxylin is also used. After applying elastic fibers show up blue coloured while cell nuclei gets red or blue.
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This stain is used to demonstrate elastin fibres in a tissue. The stain used is resorcinol fuchsin which is a mixture of a basic fuchsin complex (made of rosaniline, pararosaniline and magenta II) combined with resorcinol and ferric chloride. The stain is initially brown, but following a rinse in water it turns purple. Counter stain used is Van Gieson's.
The mechanism of staining is not fully understood, but the basic fuchsin complex can be described as an 'iron resorcin lake' which binds to elastin. This is thought to be enhanced by the oxidation of disulfide bonds to produce negatively charged sulfonic acid groups.
To stain the tissue, it is placed face down in a petri dish resting on a piece of wooden stick. Stain is deposited slowly under the lower end of the slide and the dye moves up the tissue by capillary action. This is covered with the lid of the petri dish and left to be absorbed for 30-60 minutes. Differentiation is in 90% alcohol for 30-60 seconds. Section is counterstained in Van Gieson's for 45-60 seconds and blotted dry. It is then rinsed directly in absolute alcohol. (Van Gieson's consists of Picric Acid which is soluble in alcohol, and acid fuchsin which is soluble in water, hence the blotting dry and alcohol rinse are necessary).
