PAS Stains

Question 1

What dyes make up a PAS stain

Answer 1

• Periodic acid
• Schiffs reagent

Question 2

Purpose of PAS Stains

Answer 2

To visualise Carbohydrates (glycogen, glycoproteins) and Neutral Mucins

Question 3

The function of the Periodic acid

Answer 3

To oxidise the glycol groups of polysaccharides and turn them into di-aldehyde groups

Question 4

Purpose of the schiffs reagent

Answer 4

To bind and react to the newly formed di-aldehyde groups, thus forming unstable covalent bonds

Question 5

how does water washing affect the stain after the schiffs reagent has been applied

Answer 5

washes sulfonic acid away and creates a magenta colour

Question 6

what is the function of Mayers Hx in PAS stains

Answer 6

nuclear counterstain

Question 7

what carbs are stained and where are they found?

Answer 7

Neutral mucins = goblet cells/ sebaceous glands
Polysaccharides = Glycogen deposits in skeletal muscle and liver
Glycoproteins = basement membranes (extracellular matrix)

Question 8

What tissues are typically stained with PAS

Answer 8

Liver, Skeletal Muscle, GIT, Kidneys,

Question 9

What is the histochemical basis of PAS staining

Answer 9

REDOX reactions (periodic acid oxidising glycol groups converting them to di-aldehyde groups for the schiffs reagent to bind to)

Question 10

What is a Diastase PAS stain (PAS-D)

Answer 10

A PAS stain that has been treated with saliva that allows for better differentiation of glycogen from other PAS positive elements