14 Questions
What is the effect of sulfur dioxide on basic fuchsin?
Sulfur dioxide converts basic fuchsin into colorless leukofuchsin.
What is the purpose of adding thionyl chloride in the preparation of Schiff reagent?
To release sulfur dioxide.
What is the temperature at which the basic fuchsin solution should be cooled before adding thionyl chloride?
50°C
What is the purpose of adding activated charcoal to the Schiff reagent?
To decolorize the solution.
How long should the solution stand in the dark after adding thionyl chloride?
12 hours
What is the purpose of adding sodium or potassium metabisulfite in the De Tomasi-Coleman Method?
To release sulfur dioxide.
What type of macromolecules are composed of monosaccharide units joined by covalent bonds?
Polysaccharides
What is the main polysaccharide identified through histology staining using PAS?
Glycogen
What type of substances can be demonstrated using the PAS stain?
Carbohydrates and other substances
What is the essential component of Schiff reagent?
Basic fuchsin
What type of diseases can be diagnosed using the PAS stain?
Glycogen storage diseases
In what type of tissues can glycogen granules be present?
Some tumors, including those that arise in tissues such as the pancreas, lung, and bladder
What type of organisms can be visualized using the PAS stain?
Some fungal organisms
What type of abnormalities can be highlighted using the PAS stain?
Abnormal basement membrane abnormalities
Study Notes
Periodic Acid Schiff (PAS) Reaction
- A histochemical stain that demonstrates carbohydrates and other substances in tissue.
- Used to demonstrate the following substances:
- Polysaccharides, such as glycogen, found in skeletal muscle, cardiac muscle, liver, and kidney.
- Neutral mucus substances, including glycoproteins, glycolipids, and neutral mucins, produced by epithelial cells.
- Tissue basement membranes, which anchor and support epithelium and endothelium to underlying connective tissue.
- Fungal organisms, which contain high levels of carbohydrate in their cell walls.
Applications of PAS Stain
- Diagnosis of glycogen storage diseases, which involve excessive glycogen storage in the liver, muscles, or kidney.
- Detection of glycogen granules in some tumors, such as those in the pancreas, lung, and bladder.
- Visualization of fungal organisms in tissue sections.
- Highlighting abnormal basement membrane abnormalities, such as in glomerular diseases in the kidney.
Schiff Reagent
- Essential component is basic fuchsin, a mixture of three dyes (rosanilin, pararosanilin, and magenta II).
- Sulfur dioxide converts basic fuchsin into colorless leukofuchsin, which can be restored to magenta-colored basic fuchsin by reoxidation.
- Can be prepared in different ways, including using thionyl chloride, sodium or potassium metabisulfite, or sulfur dioxide gas.
Methods of Preparing Schiff Reagent
Barger and de Lamater Method (1948)
- Dissolve 1 g basic fuchsin in 400 ml boiling distilled water.
- Cool to 50°C and filter.
- Add 1 ml thionyl chloride to the filtrate.
- Let stand in the dark for 12 hours.
- Add 2 gm activated charcoal to decolorize, shake, and filter into a brown stock bottle.
- Store in the dark at 0 to 4°C.
De Tomasi-Coleman Method (1939)
- Dissolve 1 gm basic fuchsin in 200 ml boiling distilled water.
- Cool to 50°C and filter.
- Add 20 ml 1 M HCl to the warm filtrate.
- Cool to 25°C.
- Add 1 gm anhydrous sodium or potassium metabisulfite.
- Let stand in the dark for 16 to 24 hours.
- Add 2 gm activated charcoal to decolorize, shake, and filter.
This quiz covers the Periodic Acid Schiff (PAS) reaction, a histochemical stain used to demonstrate carbohydrates and other substances in tissue.
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