Carbohydrate Staining Flashcards
What are the staining methods discussed for carbohydrates, mucosubstances, and amyloid in tissue specimens?
- PAS
- Alcian Blue
- Mucicarmine
- Colloidal Iron
- Congo Red
- Crystal Violet
- Thioflavine-T-Fluorescent techniques
Each method has unique principles and applications in histochemistry.
What is the primary monosaccharide found in the body that cannot be demonstrated in tissue sections?
Glucose
Due to its solubility in aqueous solutions and small molecular size, glucose does not remain detectable in fixed tissues.
What is the storage form of glucose in the body?
Glycogen
Glycogen is primarily stored in skeletal and cardiac muscle cells and can be rapidly converted to glucose for energy.
What staining method is best for demonstrating glycogen?
PAS – Periodic Acid Schiff technique
This method is effective for identifying glycogen due to its specific reaction with carbohydrate structures.
What is the purpose of the Alcian Blue staining method?
To stain sulfated and carboxylated acid glycoproteins
This method is particularly useful for identifying mucins in various tissue types.
What is the result of a PAS stain on basement membranes?
Magenta
This color indicates the presence of glycoproteins in the basement membrane structure.
What are the expected colors for the nuclei when performing a PAS stain?
Blue
Nuclei typically appear blue when counterstained with hematoxylin after PAS staining.
What is the role of periodic acid in the PAS staining method?
Oxidizes carbohydrates to yield aldehydes
This oxidation is essential for the subsequent reaction with Schiff reagent to produce a colored result.
What should be done after treating sections with Schiff reagent in PAS staining?
Wash thoroughly in running tap water
This step allows for full color development and removes unreacted Schiff reagent.
What is the expected result when using Alcian Blue at pH 2.5?
Turquoise blue for carboxylated and sulfated acid mucopolysaccharides
This result indicates the presence of mucins in the tissue.
What is the fixation requirement for Alcian Blue staining?
10% neutral buffered formalin or Bouin’s solution
Proper fixation is crucial for maintaining tissue morphology during staining.
What do the results of the Alcian Blue pH 1.0 method indicate?
Dark blue for sulfated mucins
This staining method is specifically tailored to identify sulfated forms of mucins.
What does Alcian Blue / PAS method differentiate?
Neutral mucins from acidic mucins.
Neutral mucins stain magenta, while acidic mucins stain blue.
What are common sources of error in staining with Alcian Blue?
Excessive background staining due to:
* pH above 2.5
* Dye impurities
* Excessive staining time
* Concentrated dye
* Inadequate rinsing post-staining
What is the purpose of Alcian Blue with hyaluronidase?
To differentiate epithelial from connective tissue mucins.
Staining will disappear for tissues containing hyaluronic acid after digestion.
What does Mucicarmine stain?
Epithelial mucin in tissue sections.
It is particularly useful in diagnosing adenocarcinomas.
What is the principle of Mucicarmine staining?
Aluminum forms a chelation complex with carmine, allowing it to bind to acid groups of mucins.
What are common sources of error in Mucicarmine staining?
Weak mucin staining likely due to:
* Exhausted or deteriorated mucicarmine
* Poor-quality powder
* Improper storage
What is the technique for Colloidal Iron staining?
- Deparaffinize and hydrate to distilled water.
- Rinse in 12% acetic acid.
- Stain in colloidal iron for 1 hour.
- Rinse in acetic acid.
- Immerse in ferro-cyanide-HCl solution.
- Counterstain and mount.
What does the Colloidal Iron method detect?
Carboxylated and sulfated mucopolysaccharides and glycoproteins.
What is the significance of Congo Red in diagnosing amyloid?
Congo Red stains amyloid deposits and shows green birefringence under polarized light.
What is the principle behind the Crystal Violet method for amyloid?
A rapid screening method that uses metachromatic staining due to the mucopolysaccharide content in amyloid.
What are the results of Thioflavine T staining for amyloid?
Fluoresces yellow to yellow-green.
Thioflavine T is a fluorescent dye that attaches to amyloid.
What is the purpose of the Alcian Blue stain?
To demonstrate acid mucopolysaccharides and glycoproteins in tissue sections.
What is a common source of error when using the Congo Red method?
Faint uptake of the Congo red dye may result from:
* Prolonged fixation in formaldehyde
* Extended storage of cut sections
* Unstable Congo red solutions
What is the purpose of using 12% acetic acid in the Colloidal Iron procedure?
To prevent dilution of colloidal iron and enhance staining results.
