VVG Flashcards
What is the classification of Verhoeff Van Gieson stain?
Connective tissue stain
What is the target component of VVG?
Elastin fibers
What is the mechanism of staining of VVG?
van der Waals forces
What are the positive controls that can be used for VVG?
Aorta, skin, lung, and internal controls
What is the purpose of ordering a VVG stain?
To demonstrate pathologic elastin fibers
To demonstrate normal elastic tissues (ID of veins and arteries)
To demonstrate blood vessels in tumours (e.g., venous invasion of colorectal cancers)
Is elastin birefringent?
Yes weakly
What colour does elastin have autofluorescence as?
Yellow
Are elastin fibers produced by the body after puberty?
No
What is the general composition of an elastin fiber?
The outer shell (microfibrillar) that comprises 8% of the fibre and is polar with mostly negatively charged reactive groups
The inner core (elastin) which comprises 92% of the fibre, is apolar, and has a few amino acids with ionizable side-chains
What are van der Waals forces?
An electrostatic attraction between the electrons of one atom and the nucleus of another atom
What kinds of fixatives can be used when staining elastin?
NBF or Zenker
How thick should sections be cut for elastin staining?
4-5 micrometers
What is the name of the solution used to stain the elastin?
Verhoeff’s hematoxylin
Is the Verhoeff’s hematoxylin in VVG applied regressively or progressively?
Regressively
What is the function of the hematoxylin in Verhoeff’s hematoxylin?
It is the elastin stain
What is the function of the ferric chloride in Verhoeff’s hematoxylin?
It acts as a mordant and an oxidizing agent
What is the function of the iodine in Verhoeff’s hematoxylin?
It acts as a mordant, an oxidizing agent, and a trapping agent
What type of chemical property assists in converting hematoxylin to hematein?
Oxidation
Does a mordant have more affinity for the dye or the tissue?
It has affinity for both
Why is mordant differentiation used instead of acid differentiation in VVG?
It’s more gentle on the elastin fibers
How is the dye-mordant bond broken in VVG during mordant differentiation?
You use excess mordant in solution which competes with the mordant in the tissue for the dye molecule. The dye is attracted to the larger amount of mordant in the solution and gets removed from the tissue. This breaks the dye-mordant bond.
What acts as the differentiator in VVG?
Excess mordant (ferric chloride)
How are elastin fibers able to retain the dye longer than other tissue components when using mordant differentiation in VVG?
They have the strongest affinity with the iron Hx
In what order must you add the reagents when preparing verhoeff’s hematoxylin working solution?
5% Alcoholic hematoxylin (5 ml)
10% ferric chloride (2 ml)
Lugol iodine (2 ml)
Why must the reagents for verhoeff’s hematoxylin working solution be added in a specific order?
If not, the solution will be over-oxidized
