Lecture 4 - Staining Tissue Sections Flashcards
What are the primary objectives of staining in histology?
Staining aims to make cell structure visible, show variation in cell and tissue structure, and indicate the chemical nature of cellular/tissue components.
What are the three types of staining mentioned in the lecture, and how do they differ?
The types of staining include non-vital (staining of fixed, processed, sectioned dead tissue), histochemical (using biochemical reactions to detect functional groups), and lyochrome (staining of neutral lipids/fats).
Explain the role of chromophores in effective dyes and name three common chromophore groups.
Chromophores are groups that make an organic compound colored. Common chromophore groups include Nitro, Azo, and Quinonoid groups.
What is an auxochrome, and why is it important in the interaction between dye and tissue?
An auxochrome allows the dye to interact with the tissue. Common auxochrome groups include hydroxyl and amino groups.
How does the Society of Dyers and Colourists categorize and index dyes, and why is it relevant to histology?
The society categorizes and indexes dyes according to dye structure (Color Index). This is relevant for consistency and comparability in histological use.
Describe the mechanisms of staining, specifically focusing on how dyes may bind directly or indirectly to tissue.
Dyes may bind directly via chemical bonds or indirectly with a mordant linking the dye to the tissue. Indirect attachment involves progressive or regressive staining.
What are the factors influencing the depth of colorization by dyes in tissue sections?
The depth of colorization is affected by chemical affinity, tissue density, tissue permeability, and the molecular size of the dye.
Explain the differential actions of dyes and their effects on tissue staining depth.
Differential actions depend on the strength of interaction, tissue density, and tissue permeability. Different dyes may produce varying staining depths.
What structures does Haematoxylin stain, and why is it considered a basic dye?
Haematoxylin stains nuclei due to their negative charge, and it is considered a basic dye as it has a positive charge.
Why is Eosin used as a counterstain in Haematoxylin and Eosin staining, and what does it typically interact with in tissues?
Eosin is used to counterstain and interacts with positively charged structures in tissues.
What are the characteristics of a good histochemistry stain, and why is it important for detection at the cellular level?
A good histochemistry stain should produce a visible colored product, create an insoluble product localized in tissue, be highly sensitive, and detect substances within the tissue environment.
What does the Periodic acid-Schiff (PAS) technique identify, and what is the two-step chemical reaction involved?
PAS identifies the presence of neutral sugar like glycogen, glycoproteins, and neutral mucins. The two-step reaction involves oxidation of sugar molecules and reaction with Schiff’s reagent.
How does the Diastase/PAS method contribute to identifying glycogen in tissue, and what is the role of diastase?
The Diastase/PAS method involves treating sections with diastase to hydrolyze glycogen. Comparing PAS stained and diastase-treated PAS sections allows specific identification of glycogen.
What is the purpose of Alcian Blue staining, and how can it be fine-tuned for selective staining of different acid mucins?
Alcian Blue staining identifies acid mucins. Its pH can be adjusted for selective staining; at pH 2.5, all acid mucins stain, while at pH 1, only strongly sulphated mucins stain.
How is Combined Alcian blue/PAS staining useful, and what does it allow the identification of in tissues?
Combined Alcian blue/PAS staining allows the identification of mucins and glycogen in tissues, enhancing specificity.
In histochemistry, what is the significance of staining for carbohydrates, and provide examples of conditions where such staining is useful.
Staining for carbohydrates is significant in conditions like glycogen storage diseases, tumor diagnosis, fungal infections, and highlighting abnormalities in basement membranes.
What are the different types of mucins, and what distinguishes neutral mucins from acidic mucins?
Neutral mucins are uncharged (e.g., in stomach, bronchus), weakly acidic mucins contain sialic acid (sialomucin), and acid mucins contain carbohydrate-bound sulfate groups (sulfomucin).
Explain the steps involved in the Periodic acid-Schiff (PAS) technique and how it reveals the presence of neutral sugars.
The technique involves oxidation of sugar molecules, creating aldehyde branches. These aldehyde groups react with Schiff’s reagent to form a magenta-colored product.
How does the Alcian Blue staining technique selectively stain different classes of acid mucins?
Alcian Blue staining can be fine-tuned by varying pH. At pH 2.5, all acid mucins stain, while at pH 1, only strongly sulphated mucins stain.
What are the potential applications of histochemistry in various pathological conditions, and how does it aid in diagnosis?
Histochemistry applications include identifying glycogen storage diseases, tumor differentiation, visualizing fungal infections, and highlighting basement membrane abnormalities for diagnostic purposes.
