Pigments and Minerals Flashcards
Define what a pigment is
A pigment is a material that changes the colour or reflected or transmitted light as the result of wavelength-selective absorption
How are pigments defined in biology
Substances occurring in living matter that absorb visible light
Classify pigments
Endogenous
Exogenous
Artefact
Classify endogenous pigments
Haematogenous pigments
Non-haematogenous pigments
What are haematogenous pigments
Blood derived pigments
Give three examples of haematogenous pigments
Haemosiderins
Haemoglobin
Bile pigments
Give two examples of non-haematogenous pigments
Melanins
Lipofuscin
What are lipofuscins
(2)
Fine yellow-brown pigment granules composed of lipid-containing residues of lysosomal digestion.
It is considered to be one of the aging or “wear-and-tear” pigments
What are haemosiderins
(4)
Yellow or brown granules which normally appear intracellularly
Contain iron in the form of ferric hydroxide
Excessive in haemochromatosis
Deficient in anaemia
How can excess iron be dangerous in the body?
(3)
Excess iron absorption
Can’t excrete excess iron
Stores in the liver primarily and leads to fibrosis and cirrhosis
In your own words what are hemosiderins
(2)
Haemosiderins are iron-storage complexes
They are composed of partially digested ferritin and lysosomes
How does hemosiderin look on H&E
Brown deposits
What stain is used for hemosiderin (iron)?
Perls Prussian Blue
What are bile pigments
(2)
Bile is part of the breakdown product of rbcs
Bile appears browny on H&E but is more globular than iron
What stain is used for bile?
Fouchet’s Stain for Bile
How does Fouchet’s Stain for bile work?
Ferric chloride oxidises all bile pigment to green biliverdin
When would you see bile pigments
(2)
If there’s an obstruction in bile ducts ->bile will build up in hepatocytes
This is seen in fibrosis
Write a note on melanin
(6)
Found in the skin, brain, eye and hair
Different types, colours and amount in people
None in albinism, reduced amount in vitiligo
Associated with melanomas
Synthesised from tyrosine
Need to be able to identify malignant or benign processes
Write a note on melanin
(6)
Found in the skin, brain, eye and hair
Different types, colours and amount in people
None in albinism, reduced amount in vitiligo
Associated with melanomas
Synthesised from tyrosine
Need to be able to identify malignant or benign processes
How do we stain for melanin
(4)
An argentaffin reaction
Granules with melanin bind and reduce silver ions
Melanin is reduced by ferric ferricyanide
Then bleached with potassium permanganate
What is an argentaffin
A cell which takes up silver e.g. melanin
What do we do with a query melanoma
It will undergo immunohistochemistry
List the steps in an argentaffin reaction for melanin
(3)
Granules with melanin bind and reduce silver ions (Masson Fontana)
Reduce ferric ferricyanide (Schmorls)
Bleach with potassium permanganate
List the steps in an argentaffin reaction for melanin
(3)
Granules with melanin bind and reduce silver ions (Masson Fontana)
Reduce ferric ferricyanide (Schmorls)
Bleach with potassium permanganate
List three different ways of carrying out immunostaining for melanomas
S100 protein in melanocytes and neural cells
HMB45 – antigen on melanosomes
Tyrosinase enzyme or Melan A
Does an argentaffin reaction require a reducer?
NO
Does an argentaffin reaction require a reducer?
NO
What are the two types of silver reactions
Argentaffin reaction
Argyrophil reaction
What molecular markers can be used for melanin
BRAF
V600E
What stain is specific for melanin
Masson Fontana
How does a melanoma appear on cytology
Brown coloured cells -> melanin in cells that shouldnt have melanin
What is used to confirm the presence of melanocytes in cytology
Melan A -> carried out on body fluids where you wouldn’t expect to see melanocytes
Write a note on lipofuscin
(7)
Wear and tear pigment
Yellow colour
Lysosomal
Intracytoplasmic
Found in brain, liver and heart
Lipid breakdown products
Associated storage disease - ceroid lipofuscinosin
What histochemistry tests can be carried out for lipofuscin
(3)
Schmorls
Sudan Black B
Ziehl-Neelsen
How does lipofuscin look on H&E
Redish brown
What stain is most commonly used for lipofuscin
Schmorls
What stain is most commonly used for lipofuscin
Schmorls
How do exogenous pigments differ from endogenous pigments
(3)
They have no physiological functions
Gained by inhalation, ingestion, implantation etc
Most are classified as minerals and few are coloured
Give two examples of exogenous pigments
Carbon in the air
Tattoo pigment in the skin
Where can carbon be seen
Seen in the lung especially in dust cells -> lung macrophages
High amounts seen in people who live in industrial towns -> not seen often here
Where can tattoo pigment be seen
(2)
Tattoo pigment seen in the skin
Can be mistaken for melanoma if deep e.g. close to the epidermis
What causes artefact pigments
Due to chemical fixation -> less common today as we use buffered solutions
Give an example of an artefact pigment
Formalin
Write a note on formalin as a pigment
(3)
Brown pigment
Need to differentiate it from pathological pigments
Needs to be removed with picric alcohol
Define minerals
Naturally occuring homogenous inorganic substances having a definite chemical composition and characteristic crystalline structure, colour and hardness
Give three examples of minerals
Calcium
Copper
Iron
Write a note on calcium
Constituents of bones and teeth in the form of calcium phosphate
Write a note on calcium
Constituents of bones and teeth in the form of calcium phosphate
Write a note on calcium
Constituents of bones and teeth in the form of calcium phosphate
