Staining of Pigments Flashcards
What are pigments?
Any of the various colouring agents deposited as cytoplasmic inclusions or granules within tissues and cells
Pigments can be coloured, thus not always requiring staining with biological dyes
How are pigments classified?
Three Groups:
* Artifact
* Endogenous
* Exogenous
Each group has distinct origins and characteristics
What are artifact pigments?
Produced during tissue processing, commonly from fixation
Usually lie on top of tissue, with exceptions like formalin pigment
Name examples of artifact pigments.
- Formalin pigment
- Mercury pigment
- Chrome pigment
Formalin pigment is an acid hematin and birefringent
What are hematogenous pigments?
Derived from blood, includes:
* Hemoglobin
* Hemosiderin
* Bile pigments
Hemoglobin breaks down into heme and globin
What is the Prussian Blue reaction used for?
Detection of ferric (Fe3+) iron in tissues
Forms a bright blue pigment called Prussian Blue when Fe3+ reacts with ferrocyanide
What is the significance of melanin?
A brown-black pigment derived from tyrosine, present in skin, hair, and certain parts of the CNS
Variations in melanin amount contribute to differences in color among individuals
Which minerals can be demonstrated with special stains?
- Calcium (Ca2+)
- Ferrous/Ferric (Fe2+/Fe3+)
- Cupric (Cu2+)
- Phosphate (PO4^3-)
- Carbonate (CO3^2-)
Some metallic elements like silver, lead, and copper can be deposited pathologically
What is the appearance of carbon as an exogenous pigment?
A black pigment that resists bleaching and extraction procedures
Insoluble in concentrated sulfuric acid
True or False: Formalin pigment can be removed using saturated alcoholic picric acid.
True
This is done before staining to prevent interference
Fill in the blank: Hemosiderin is a _______ form of ferric iron.
storage
It is usually found in small amounts in specific organs
What condition is characterized by excess iron storage due to defects in iron absorption?
Hemochromatosis
What type of fixative should be used when demonstrating hemosiderin?
Buffered neutral formalin
What reagent is used in Perl’s Prussian Blue Technique?
A solution of equal parts HCl and potassium ferrocyanide
What is the purpose of the Turnbull Blue Stain?
The detection of ferrous (Fe2+) iron in tissues
What is the fixative used for the Turnbull Blue Stain?
Alcohol or 10% NBF
What color indicates the presence of ferrous iron in Turnbull Blue Stain results?
Blue
What technique is primarily used for the demonstration of melanin?
Masson-Fontana technique
What is the fixative used in the Masson-Fontana technique?
10% NBF
What is the result of the Masson-Fontana technique for melanin?
Melanin and argentaffin granules appear black, nuclei appear pink
What is used to differentiate between melanin and argentaffin granules?
Melanin Bleaching
What are some strong oxidizing agents that can bleach melanin?
- KMnO4
- H2O2 (hydrogen peroxide)
What is the purpose of the Mallory Bleach Technique?
To distinguish between melanin and argentaffin granules
What is the result of the Mallory Bleach Technique after washing in running tap water?
Removes KMnO4
What is the most useful bleaching agent mentioned?
KMnO4
Followed by 1% oxalic acid.
What does KMnO4 do in the Mallory bleach technique?
Oxidizes melanin.
What is the interpretation of a Masson-Fontana stain on a bleached slide?
No granules seen for melanin, golden brown granules seen for argentaffin granules.
What condition can cause the deposit of urate crystals?
Gout.
What fixative is required for the Gomori Methenamine Silver Method?
Absolute alcohol.
What is the main principle of the Gomori Methenamine Silver Method?
Urates are stained black by reacting with silver, which is then reduced to its metallic form.
What are the reagents used in the Gomori Methenamine Silver Method?
- Silver nitrate, 5%
- Methenamine solution, 3%
- Sodium borate, 5%
- Sodium thiosulphate solution, 3%
- Light green solution.
What color do urates stain in the Gomori Methenamine Silver Method?
Black.
What is the background color in the Gomori Methenamine Silver Method?
Green.
What is hydroxyapatite?
A calcium phosphate salt and the main mineral component of bone and teeth.
What are the two main methods used for calcium demonstration?
- Von Kossa
- Alizarin Red S.
What is the principle behind the Von Kossa Technique?
The method depends on the replacement of calcium by silver, which is then reduced to metal form.
What type of fixative is preferred for the Von Kossa Technique?
Alcohols.
What is the result of the Von Kossa stain?
Calcium salts appear black/brown.
What is the purpose of Alizarin Red S?
Used to demonstrate calcium in tissue sections.
What is the principle of the Alizarin Red S method?
Calcium forms an alizarin red S-calcium complex in a chelation process.
What color do calcium deposits stain with Alizarin Red S?
Orange-red.
What is the background color when using Alizarin Red S?
Green.
True or False: Alizarin Red S is more sensitive for small amounts of calcium than Von Kossa.
True.
What is the likely cause of a marked black precipitate in a section of ileum stained with Masson-Fontana?
Using the silver immediately after preparation.
What is the significance of calcium in coronary arteries?
Marker for coronary arterial disease (CAD).
