Carbohydrates Flashcards
Which carbohydrates cannot be demonstrated in tissue sections?
- Glucose
- Oligosaccharides
What are the 4 groups of naturally occuring polysaccharides?
Group 1: Neutral polysaccharides
Group 2: Acid mucopolysaccharides
Group 3: Glycoproteins
Group 4: Glycolipids
What is the purpose of PAS?
Demonstrate glycogen, neutral mucopolysaccharides, basement membrane, and fungal infections
What is the principle of PAS?
Glycol groups are oxidized to aldehydes which react with the Schiff reagent to produce a colour
What will PAS positive structures stain?
Magenta
What will nuclei look like after staining with PAS?
Blue
What are the storing conditions of Schiffs reagent?
- sealed in dark cool (4C) place
What is the BEST fixative to use for PAS?
Alcohol or alcoholic picric acid
What is dPAS?
Diastase method, enzymatic treatment of sections with diastase to digest glycogen, followed by PAS.
What is the result of dPAS method?
Undigested sections - PAS positive magenta staining
Digested sections - No magenta
What is the purpose of Alcian blue at a pH of 2.5?
Demonstrate carboxylated and sulphated acid mucopolysaccharide
What is the purpose of Alcian Blue at a pH of 1.0?
Demonstration of sulphated mucins.
What is the ideal fixative to use for the Alcian blue methods?
- 10% NBF
- Bouins
What is the purpose of staining with both Alcian blue and PAS?
To distinguish neutral and acid mucosubstances
What is the purpose of treating slides with hyaluronidase prior to staining with Alcian Blue?
Remove hyaluronic acids which inhibits or reduces staining quality.
What is the purpose of staining with mucicarmine?
Demonstrate epithelium mucin or encapsulated fungi .
What does mucicarmine stain? Be specific!
carboxylated and sulphated mucins
What will mucins look like after staining with mucicarmine?
deep red
What is the counterstain used in mucicarmine?
metanil yellow
What is the purpose of using colloidal iron?
To demonstrate;
- acid mucins
- cryptococcus neoformans
- carboxylated and sulfated mucopolysaccharides
- glycoproteins
What is the principle of colloidal iron?
Histochemical reaction
Which fixatives are idea for colloidal iron?
- NBF
- Carnoy’s
what is the purpose of congo red?
demonstrate amyloid deposits in tissue sections.
Which fixatives should be avoided with colloidal iron?
Chromate fixatives
