Metachromasia

Metachromasia is a phenomenon observed in certain biological materials where they change color when stained with specific dyes. This property is particularly significant in the field of histology and cytology, where it is used to identify and differentiate between various types of tissues and cellular components.

Mechanism

Metachromasia occurs due to the interaction between the dye molecules and the biological material. When a metachromatic dye binds to certain substances, such as glycosaminoglycans or amyloid, the dye molecules aggregate, leading to a shift in the dye's absorption spectrum. This shift results in a color change that is different from the dye's original color. For example, the dye toluidine blue appears blue in solution but stains certain tissues purple or red.

Applications

Metachromasia is widely used in histopathology to identify and study various tissue components. It is particularly useful in diagnosing diseases that involve the accumulation of specific substances, such as mucopolysaccharidoses and amyloidosis. The technique is also employed in cytology to examine cellular structures and identify abnormalities.

Common Metachromatic Dyes

Several dyes are known for their metachromatic properties, including:

• Toluidine blue
• Methylene blue
• Crystal violet
• Thionine

Related Techniques

Metachromasia is often used in conjunction with other staining techniques to provide a comprehensive analysis of tissue samples. Some related techniques include:

• Hematoxylin and eosin staining
• Periodic acid–Schiff stain
• Masson's trichrome stain

See Also

• Histology
• Cytology
• Histopathology
• Glycosaminoglycan
• Amyloid
• Toluidine blue
• Methylene blue
• Crystal violet
• Thionine