Pigments and Lipids

Question 1

State the three types of pigment

Answer 1

Artefact
Endogenous (haematogenous/autogenous)
Exogenus

Question 2

Define Artefact pigment

Answer 2

Deposits produced as a result of chemical reaction in tissue

Question 3

Define Endogenous tissue

Answer 3

Produced within tissue
Have a physiological function or are a by-product of normal metabolic process

Question 4

Define exogenous tissue

Answer 4

Gain access to the body accidentally
No physiological function
Usually minerals, enter by inhalation or implantation on skin (during industrial exposure)

Question 5

Give examples of Artefact pigment

Answer 5

Formalin
Malarial
Mercury
Dichromate deposits

Question 6

Give examples of endogenous pigments

Answer 6

Bile pigments
Lipofuscin
Melanin
Iron
Calcium
Copper
Uric acid and urates

Question 7

Give three examples of conditions formed as a result of bile pigment accumulation

Answer 7

Obstructive/surgical Jaundice
Primary biliary cholangitis (PBC)
Cholestasis

Question 8

Outline obstructive jaundice

Answer 8

• A symptom of an underlying condition (involving the liver, gallbladder, or pancreas)
• Usually requires surgical intervention
• Accumulation of bile pigments
• Injury to bile duct/obstruction of bile flow
• Can cause hepatocellular damage and cirrhosis (eventually)

Question 9

Outline PBC

Answer 9

• Autoimmune disease of liver
• Results from a slow, progressive destruction of the small liver bile ducts, causing bile/other toxins to build up in liver

Question 10

Outline cholestasis

Answer 10

• A liver disease
• Bile cannot flow from liver to duodenum
• Obstructive: mechanical blockage in duct system due to gallstone or malignancy
• Metabolic: disturbances in bile formation due to genetic defects or medication

Question 11

Outline Haemosiderin

Answer 11

• Iron-storage complex in cells/tissues (not in blood circulation)
• Iron derived mainly from breakdown of erythrocytes (RBCs)
• Poorly available to supply iron when needed

Question 12

Outline Perls Prussian blue staining (ferric iron - Fe3+)

Answer 12

• Protocol chemicals: dilute hydrochloric acid (releasing ferric ions from binding proteins by partial denaturation of protein), potassium ferrocyanide
• Method stains mostly iron in ferric state, including ferritin and haemosiderin

Question 13

How does Perls Prussian blue staining work?

Answer 13

• Potassium ferrocyanide combines with ferric iron, forming prussian blue pigment (aka ferric ferrocyanide)
• Addition of hydrochloric acid increases iron availability within tissue

Question 14

What colour does Formalin pigment stain?

Answer 14

Brown/Black (once fixated in acid formalin)

Question 15

Where is formalin pigment often found?

Answer 15

Haemorrhagic tisdue

Question 16

What colour does malarial pigment stain?

Answer 16

Brown/black

Question 17

How to differentiate between formalin and malarial pigment?

Answer 17

Malarial pigment is found in RBCs with parasite

Question 18

What colour does mercury pigment stain?

Answer 18

Black

Question 19

What colour do dichromate deposits stain?

Answer 19

Yellow/brown

Question 20

Outline bile pigments

Answer 20

• Red/brown = bilirubin
• Green = biliverdin
• Result of RBCs breaking down
• Buildup suggests liver/haemolytic disease

Question 21

Outline Lipofuscin

Answer 21

• Brown
• ‘Wear and tear’
• Due to lipid oxidation near nucleus
• Found in the heart, liver, brain

Question 22

Outline melanin

Answer 22

• Black/brown
• Product of melanocytes
• Found in eye/skin/hair/brain/melanoma
• Dyed by Masson Fontana (black)

Question 23

Outline Iron

Answer 23

• Fine brown colour
• Blue after Prussian Blue reaction
• Stored as haemosiderin in ferric state (Fe3+)
• Found in liver, spleen, bone marrow

Question 24

State 3 iron store disorders

Answer 24

• Haemosiderin
• Haemosiderosis
• Haemochromatosis

Question 25

Outline Haemochromatosis

Answer 25

- Inherited condition - Iron levels slowly build up over many years - Symptoms: skin bronzing, fatigue, diabetes, cirrhosis - Ages 40-60/post menopause - Requires phlebotomy treatment

Question 26

Outline Haemosiderosis

Answer 26

- AKA secondary haemochromatosis - **Acquired** and less toxic than primary - Iron predominantly stored in reticuloendothelial system - Treated with iron chelating agents

Question 27

Outline Haemosiderin

Answer 27

- A symptom of a iron disorder - Too much can cause organ failure

Question 28

Outline calcium

Answer 28

- Stained black(?) - Absorbed via GIT (vit D) - Stained by von Kossa and Alizarin - Found in teeth/bone

Question 29

Outline copper

Answer 29

- Normally undetectable - An accumulation causes **Wilson's disease** - Specific stains required

Question 30

Outline Uric acid and urstes

Answer 30

- Use a polarising microscope, **birefringent** - Breakdown of purine nucleotides - High amounts can lead to joint crystallisation (gout), kidney diseases, diabetes

Question 31

Give examples of Exogenous pigments

Answer 31

Carbon Silica Asbestos

Question 32

Outline Carbon

Answer 32

- Most common exogenous pigment - Easily identified - Confused with melanin - Seen in lungs of smokers - Absorbed by phagocytes

Question 33

How to differentiate carbon and melanin?

Answer 33

Melanin bleach

Question 34

Outline Silica

Answer 34

- Intert angular masses - Same material as glass - In lungs (causes **silicosis** /fibrosis of lungs) - May be birefringent

Question 35

Outline Asbestos

Answer 35

- Long beaded fibres - Causes fibrosis - May lead to asbestosis and mesothelioma - Fibres become coated in protein sheaths containing haemosiderin (demonstrated by Prussian Blue)

Question 36

List unconjugated lipids

Answer 36

Neutral fats Waves Cholesterol esters Phosphoglycerides Sphingomyelins Ceramides Glycolipids

Question 37

List conjugated lipids

Answer 37

Fatty acids Steroids

Question 38

Define a lipid

Answer 38

Soluble in fat solvents BUT insoluble in water. They are hydrophobic.

Question 39

How to view lipids:

Answer 39

- Lysochrome method (staining using a dye very soluble in lipids, insoluble in aqueous solution) - Frozen, stained by Oil Red O or Sudan Black - Use of polarised light microscope (view oval fat bodies) - Osmium Tetroxide fixation (view the lipids as black)

Question 40

Briefly outline lipid storage disorders:

Answer 40

- AKA Lipidosis - a group of **inherited metabolic disorders** in which harmful amounts of fatty materials (lipids) accumulate in various cells and tissues - Particularly accumulate in CNS

Question 41

Give an example of a lipid storage disorder

Answer 41

Fabry disease (accumulation in kidney)