Orcein

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Orcein staining of liver tissue. The elastic fibres in the portal tract are a deeper brown (left). Similarly, the copper-associated protein in the hepatocytes adjacent to the portal tract are a similar deep brown.
Orcein staining of liver tissue showing several hepatocytes containing positive 'ground glass' cytoplasm.

A collective name for several similar lichen-derived dyes (although some synthetic ones are availble). Orcein is chemically similar to litmus. It is sometimes called Shikata orcein after the Japanese researcher who first described its use in 1974 to stain the hepatitis B surface antigen in histological slides.[1] It is used as a special stain in histopathology, particularly in liver tissue where orcein binds to elastic fibres, hepatitis B surface antigen and copper-binding proteins, the common factor amongst these apparently diverse substances is a relative richness in sulfhydrl groups.[2] Victoria Blue staining is an alternative to orcein.

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