Histology Staining Techniques

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40 Questions

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

Modifier

What is the main function of an Auxochrome?

To ionize the dye

At what pH range do both dyes and tissues ionize?

pH 3-10

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

DNA, RNA, and phospholipids

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

Adsorption

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

Permeability

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

Regressive staining

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

Progressive staining

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

Because their structures are not distinguishable

What is the purpose of histological techniques in tissue examination?

To distinguish tissue components

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

Due to absorption of light by the dye

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

Sensitivity

What is vital staining used for?

To stain living cells

What is the basis of elective solubility in staining?

Solubility of stain in tissue fluids

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

Because the nuclear membrane is impermeable to dyes

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

Lysochromes

What is the primary product of benzene?

Dyes

What is the function of chromophores in dyes?

To bear the color of the dye

What is the main characteristic of most lysochromes?

Lipid solubility

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

Chemical reaction producing a true dye

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

Quinonoid

What is the function of auxochromes in dyes?

To increase the intensity of the color

What is the purpose of enzyme histochemistry in tissue staining?

To produce a colored substance at the site of activity

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

Argentaffin tissue

What type of dye is Basic fuchsin?

Basic or cationic dye

What is the source of carmine, a natural dye?

Cochineal insect

What is the characteristic of acidic or anionic dye?

It gives negatively charged colored dye ions

What is the characteristic of amphoteric dye?

It is cationic below certain pH and anionic above it

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

To react with tissue components to produce a colored substance

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

Neutral dye

What type of staining technique is most commonly used?

Staining with dyes

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

Argyrophil tissue

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

Indirect staining

Which of the following fixatives favors basic dyes?

Formaldehyde

What is the purpose of an accentuator in tissue staining?

To increase the staining power and selectivity of dyes

What is the role of an accelerator in tissue staining?

To act like an accentuator

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

To hold dyes in combination with tissues or bacteria

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

Leuco-dye

What is the purpose of differentiation in tissue staining?

To de-stain over-stained tissue

What is the effect of fixation on tissue staining?

It assists tissue-dye interaction

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.

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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