Define what a mordant is and describe how mordants function in histopathology?
The correct answer and explanation is:
A mordant is a chemical substance used in histology and histopathology to bind and fix dyes to tissue sections. In histopathology, mordants play a crucial role in enhancing the interaction between tissue components and stains, helping to achieve more defined and consistent staining results. Mordants do not color the tissue by themselves; instead, they help in forming a stable bond between the tissue and the dye molecules, ensuring that the dye adheres effectively.
The process of using mordants in histopathology typically involves applying the mordant to tissue sections before staining. The mordant creates a bond with the tissue’s cellular or extracellular components, often proteins or other molecules, making the tissue more receptive to the dye. Once the mordant has bound with the tissue, the dye is added, and it interacts with the mordant, creating a stable and colored complex that allows for better visualization of cellular structures under a microscope.
One of the most common examples of mordants in histopathology is aluminum sulfate used with hematoxylin, a dye commonly used in histological staining. Hematoxylin by itself has limited ability to stain tissues, but when combined with aluminum sulfate as a mordant, it forms a complex that binds to nucleic acids, specifically DNA and RNA, in the cell’s nucleus. This process results in the characteristic purple-blue color of the cell’s nucleus.
The use of mordants is essential for achieving accurate and reproducible staining in tissue samples. Different mordants are chosen based on the type of tissue being studied and the specific dye used. For example, in a Gram stain used for bacterial classification, iodine acts as a mordant, forming a complex with the crystal violet dye, which helps in differentiating bacterial types.
In conclusion, mordants function in histopathology by facilitating the binding of dyes to tissue structures, which is key to the accurate visualization and identification of various cellular components during microscopic examination.