Histology Staining Techniques
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Questions and Answers

What type of group is added to a dye to alter its color?

  • Phosphoryl
  • Auxochrome
  • Chromophore
  • Modifier (correct)

    • What is the main function of an Auxochrome?

  • To strengthen the color of the dye
  • To ionize the tissue
  • To alter the color of the dye
  • To ionize the dye (correct)

    • At what pH range do both dyes and tissues ionize?

  • pH 3-6
  • pH 3-10 (correct)
  • pH 11-14
  • pH 7-10

    • What type of tissue components are acidic due to phosphoryl groups?

    <p>DNA, RNA, and phospholipids</p> Signup and view all the answers

    What is the property of solid objects that allows them to attract and hold other substances on their free surfaces?

    <p>Adsorption</p> Signup and view all the answers

    What is the term for the amount of time it takes for a tissue to stain?

    <p>Permeability</p> Signup and view all the answers

    What type of staining technique involves over-staining and then de-staining a tissue?

    <p>Regressive staining</p> Signup and view all the answers

    What is the term for the type of staining that achieves satisfactory differential coloration of the tissue without differentiation?

    <p>Progressive staining</p> Signup and view all the answers

    Why are tissues transparent and colorless when examined with a light microscope?

    <p>Because their structures are not distinguishable</p> Signup and view all the answers

    What is the purpose of histological techniques in tissue examination?

    <p>To distinguish tissue components</p> Signup and view all the answers

    What is the reason behind the coloration of tissues when stained with a dye?

    <p>Due to absorption of light by the dye</p> Signup and view all the answers

    What is the ability of a stain to demonstrate a tissue substance in low concentration?

    <p>Sensitivity</p> Signup and view all the answers

    What is vital staining used for?

    <p>To stain living cells</p> Signup and view all the answers

    What is the basis of elective solubility in staining?

    <p>Solubility of stain in tissue fluids</p> Signup and view all the answers

    What is the reason why the nucleus is not stained in vital staining?

    <p>Because the nuclear membrane is impermeable to dyes</p> Signup and view all the answers

    What is the term for substances that dissolve in tissue fluids?

    <p>Lysochromes</p> Signup and view all the answers

    What is the primary product of benzene?

    <p>Dyes</p> Signup and view all the answers

    What is the function of chromophores in dyes?

    <p>To bear the color of the dye</p> Signup and view all the answers

    What is the main characteristic of most lysochromes?

    <p>Lipid solubility</p> Signup and view all the answers

    What type of reaction is involved in producing a colored substance in tissue using Schiff's reagent?

    <p>Chemical reaction producing a true dye</p> Signup and view all the answers

    What is the type of chromophore group in basic and acid fuchsin?

    <p>Quinonoid</p> Signup and view all the answers

    What is the function of auxochromes in dyes?

    <p>To increase the intensity of the color</p> Signup and view all the answers

    What is the purpose of enzyme histochemistry in tissue staining?

    <p>To produce a colored substance at the site of activity</p> Signup and view all the answers

    What is the term for tissues that can reduce ammonical silver solution to form visible deposits?

    <p>Argentaffin tissue</p> Signup and view all the answers

    What type of dye is Basic fuchsin?

    <p>Basic or cationic dye</p> Signup and view all the answers

    What is the source of carmine, a natural dye?

    <p>Cochineal insect</p> Signup and view all the answers

    What is the characteristic of acidic or anionic dye?

    <p>It gives negatively charged colored dye ions</p> Signup and view all the answers

    What is the characteristic of amphoteric dye?

    <p>It is cationic below certain pH and anionic above it</p> Signup and view all the answers

    What is the purpose of using a pale or colorless solution in chemical production of a colored substance?

    <p>To react with tissue components to produce a colored substance</p> Signup and view all the answers

    What is the type of dye that has affinity for both basic and acidic structures?

    <p>Neutral dye</p> Signup and view all the answers

    What type of staining technique is most commonly used?

    <p>Staining with dyes</p> Signup and view all the answers

    What is the term for tissues that can reduce ammonical silver solution to form visible deposits only with the addition of an extraneous reducer?

    <p>Argyrophil tissue</p> Signup and view all the answers

    What type of staining requires an additional intermediate substance known as a mordant?

    <p>Indirect staining</p> Signup and view all the answers

    Which of the following fixatives favors basic dyes?

    <p>Formaldehyde</p> Signup and view all the answers

    What is the purpose of an accentuator in tissue staining?

    <p>To increase the staining power and selectivity of dyes</p> Signup and view all the answers

    What is the role of an accelerator in tissue staining?

    <p>To act like an accentuator</p> Signup and view all the answers

    What is the purpose of a trapping agent in tissue staining?

    <p>To hold dyes in combination with tissues or bacteria</p> Signup and view all the answers

    Which of the following is an example of a colorless leucobase?

    <p>Leuco-dye</p> Signup and view all the answers

    What is the purpose of differentiation in tissue staining?

    <p>To de-stain over-stained tissue</p> Signup and view all the answers

    What is the effect of fixation on tissue staining?

    <p>It assists tissue-dye interaction</p> Signup and view all the answers

    Study Notes

    The Theory of Staining

    • Tissues are transparent and colorless, making it difficult to distinguish different structures when examined with a light microscope.
    • Histological techniques are used to distinguish tissue components, which can cause changes in the tissue through alteration of contrast or color.

    Alteration of Contrast

    • Phase contrast and polarized microscope can be used to make parts of the tissue appear grey or black.
    • Impregnation methods can also be used to alter the contrast of tissue components.

    Alteration in Color (Histological Staining)

    • Histological staining involves the production of colors in tissue through dye-staining.
    • The coloration is due to the absorption of light by the dye.
    • A satisfactory staining method should combine high sensitivity and specificity.
    • Sensitivity refers to the capacity of the stain to demonstrate a tissue substance in low concentration.
    • Specificity or selectivity refers to the ability to discriminate between individual tissue components.

    Staining Processes

    • Vital Staining: Living cells can be stained by dissociation in the staining fluid (supra-vital) or by injection of dye into the living organism (intra-vital).
    • Elective Solubility: Based on the solubility of the stain in tissue fluids, substances that dissolve in tissue are known as lysochromes.
    • Chemical Production of Colored Substance in Tissue: Using a pale or colorless solution that reacts with tissue components to produce colored substances.
    • Metallic Impregnation: Metallic compounds are reduced by tissues to produce opaque, black deposits.
    • Staining with Dyes: Most staining techniques belong to this group, involving the use of natural or synthetic dyes.

    Staining with Dyes

    • Types and Structure of Dyes: There are two main types of dyes: natural dyes (e.g., carmine and haematoxylin) and synthetic dyes.
    • Chromophores: Are the color-bearing chemical groups in the compound, which are classified into three main types: quinonoid, azo-coupling, and nitro group.
    • Auxochromes: Are the ionizing groups that increase the intensity of the color, which are either acidic or basic.
    • Dye Characteristics: Dyes can be basic, acidic, neutral, or amphoteric, depending on the number of basic or acidic auxochromes they contain.
    • Modifiers: Additional chemical groups that alter the color of the dye or make it deeper.

    Mode of Action of Dye Staining

    • Chemical Dye Staining: Dye and tissues react together at the ordinary pH range, resulting in electropositive stain units combining with electronegative tissues and vice versa.
    • Physical Dye Staining: Dye combines with tissues by adsorption, which is affected by physical factors such as density and permeability.
    • Staining Techniques: There are four main staining techniques: progressive, regressive, direct, and indirect staining.

    General Factors in Tissue Staining

    • Effect of Fixation: Fixation can assist or hinder tissue-dye interaction, and may extract some tissue substances making subsequent staining ineffective.
    • Accentuators: Substances used to increase the staining power and selectivity of dyes, but differ from mordants.
    • Accelerators: Act like accentuators, used in metallic impregnation for the nervous system.
    • Trapping Agents: Hold dyes in combination with tissues or bacteria, preventing them from escaping during differentiation.
    • Differentiation: De-staining of over-stained tissue in regressive technique, brought about by washing, oxidizing agents, mordants, or dyes acting as differentiators.

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    Description

    This quiz covers the principles of histological staining techniques used to distinguish tissue components under a light microscope. It discusses alteration of contrast and color through different methods.

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