SPECIAL STAINS PART 10

Question 1

What does periodic acid Schiff (PAS) stain

Answer 1

1. Polysaccharides
2. Neutral mucus substance
3. Tissue basement membrane
4. fungal organisms

Question 2

what is the main polysaccharide identified in histology

Answer 2

Glycogen

Question 3

where is glycogen found

Answer 3

skeletal muscles
cardiac muscles
liver
kidney

Question 4

explain the general principle of PAS

Answer 4

The reactivity of the PAS technique is based on the structure of the monosaccharide
units.
The first reaction in the stain involves periodic acid acting as an oxidizing agent to oxidize the carbon-to-carbon bonds between two adjacent hydroxyl groups. This produces Schiff reactive aldehyde groups.
In the second reaction, the tissue section reacts with Schiff reagent. This comprises a mixture of basic fuchsin, hydrochloric acid, and sodium metabisulphite. The basic fuchsin in the mixture reacts with newly formed aldehyde groups in the tissue to
produce a bright magenta color.
Finally, when the section is rinsed in water, bound fuchsin molecules in the tissue then produce a bright magenta color. The intensity of the color is proportional to the concentration of hydroxyl groups originally present in the monosaccharide units.
Haematoxylin is then typically used as a counter stain to visualize other tissue elements. When PAS is used to demonstrate fungal organisms, however, a light
green counter stain is preferred.

Question 4

what does neutral mucus substances include

Answer 4

Glycoproteins
glycolipids
neutral mucins

Question 5

what does fungi have that makes it stain with PAS

Answer 5

High levels of carbohydrates. (Pas works on living fungi only)

Question 6

who uses PA stain

Answer 6

researchers studying glycogen storage diseases or diseases of the basement membrane may routinely examine PAS-stained tissues sections to evaluate these respective elements in tissues of interest.

Question 6

PAS helps with the diagnosis of which disease

Answer 6

1. Glycogen storage diseases: These are conditions in which excessive quantities of glycogen are stored in the liver, muscles, or kidney. PAS is often routinely used in the clinic to demonstrate glycogen accumulation in biopsies of these tissues.
2. Tumors: Glycogen granules can also be present in some tumors, including some of those that arise in tissues such as the pancreas, lung, and bladder.
3. Fungal infection: PAS can be used to visualize some fungal organisms in tissue sections.
4. Basement membranes: Since PAS can be used to highlight the basement membranes of tissues, it can be used to identify disorders in which there is weakness or improper functioning of basement membranes – such as in the case of some glomerular diseases in the kidney