Principles of tinctorial properties
The ability of cellular elements and intercellular substance to take up dyes is called tinctorial properties. Depending on their chemical nature, pigments are divided into groups:
- Basic (cationic): interact with acidic components, such as nuclear chromatin and RNA-containing organelles. Striking examples include hematoxylin, methylene blue, and azure.
- Acidic (anionic): have an affinity for basic structures of the cytoplasm and fibrous components of connective tissue. These include eosin and acid fuchsin.
- Neutral: contain both components.
Overview method: hematoxylin and eosin
The most common method in laboratory and clinical practice is the combined use of hematoxylin and eosin (H&E). Hematoxylin forms strong bonds with the negative sugar-phosphate backbone of nucleic acids, imparting a violet-blue color to the nuclei. Eosin is responsible for contrasting cytoplasmic structures and protein granules, staining them in pinkish-red tones. This approach is sufficient for routine tasks, including the assessment of cellular composition and blood cell counting.
Special methods and impregnation
Special techniques are used for a more detailed study of morphology and the detection of specific compounds:
- Heidenhain's iron hematoxylin: used to reveal the striation of muscle fibers and intercalated discs of the myocardium.
- Silver nitrate impregnation: based on tissue argyrophilia; visualizes reticular fibers as a black network, nerve elements, and endocrinocytes.
- Sudan III: stains lipids orange in frozen sections, preventing their dissolution during standard tissue processing.
- Mallory's stain: clearly differentiates muscle fibers from connective tissue layers, staining the latter blue.
Basic dyes are blue (like the sky), acidic dyes are red (like a sunset). Hematoxylin loves nuclei, eosin loves cytoplasm.
Class and exam questions
Why does hematoxylin stain nuclei blue?
Hematoxylin is a basic dye and binds to the negatively charged sugar-phosphate backbone of nucleic acids, which predominate in the nucleus.
Which method is best suited for detecting fatty degeneration?
Sudan III staining is used on frozen sections, coloring lipids orange, since fats dissolve during standard tissue processing.
What are the results of Mallory's stain?
This method is demonstrative for the stroma: connective tissue layers are stained blue, making it easy to distinguish them from muscle tissue.
What else to study on this topic
- Autoradiography method with H³-uridine for studying transcription
- Best's carmine stain for glycogen detection
- Application of Giemsa stain in parasitology
- Cytological diagnostics using the Papanicolaou stain
- Immunohistochemistry and other modern tumor verification methods
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