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AP0509 Component 2 Exam > Pigments and Lipids > Flashcards

Pigments and Lipids Flashcards

1
Q

What are pigments?

A
  • self coloured materials, can be seen in unstained solution

- limited range of colour; yellow-brown or brown-black

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2
Q

Artefact pigments

A
  • deposit produced as a result of chemical reaction in tissue
  • not originally part of tissue
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3
Q

Exogenous pigments

A
  • present in original tissue
  • some pathological, some indicative of person’s lifestyle/employment
  • gain accidental access through industrial exposure; inhalation or implantation
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4
Q

Endogenous pigments

A
  • produced within tissue and have physiological function

- or by-product of normal metabolic process

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5
Q

Schmorl’s test

A
  • yellow pigment turning green = positive result

- may be difficult to see if reaction has occurred

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6
Q

Types of artefact pigments (5)

A
  • Formalin
  • Malarial
  • Mercury
  • Osmium
  • Dichromate deposits
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7
Q

Types of endogenous pigments (8)

A
  • Bile pigments
  • Lipofuscin
  • Melanin
  • Iron
  • Copper
  • Uric Acid and Urates
  • Calcium
  • Haemoglobin
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8
Q

Types of exogenous pigments (3)

A
  • Carbon
  • Asbestos
  • Silica
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9
Q

Formalin pigment

A
  • brown/black deposit following acid formalin fixation
  • most easily seen around old/degenerated blood in tissues
  • removed w/ picric acid
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10
Q

Malarial pigment

A
  • similar to formalin; formed in/near RBCs
  • also found in cytoplasm of macrophages that have ingested affected RBCs
  • parasite presence within RBCs helps identify pigment source
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11
Q

Mercury pigment

A
  • black deposit formed w/ mercury-containing fixatives
  • removed w/ iodine and sodium thiosulphate
  • less common in modern histology
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12
Q

Osmium pigment

A
  • very dense black pigment following osmium tetroxide fixation
  • removed by oxidation w/ hydrogen peroxide
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13
Q

Dichromate deposits

A
  • occurs when chrome salts reacts w/ alcohols and produces brown oxide
  • potassium dichromate fixation form yellow/brown deposits
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14
Q

Bile pigments

A
  • breakdown of bile pigments; range of colours in a healing bruise
  • difficult to identify; oxidation alters colour
  • only large deposits can appear in wax sections
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15
Q

Iron pigment

A
  • stored as haemosiderin in ferric state
  • fine brown colour; liver, spleen and marrow
  • Perl’s Prussian Blue; detects iron in haemosiderin by potassium ferrocyanide - dense blue precipitate
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16
Q

Melanin pigment

A
  • identified by reducing ability w/ Schmorl’s test
  • black/brown pigment; product of melanocytes
  • eye, skin, hair, brain and melanoma
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17
Q

Lipofuscin pigment

A
  • ‘wear and tear’ pigment due to lipid oxidation
  • most easily identified pigment
  • brown or lipochrome pigment
18
Q

Copper pigment

A
  • normally undetectable
  • accumulation (Wilson’s disease)
  • important in metabolism (oxidase enzymes)
19
Q

Calcium pigment

A
  • absorbed in GIT from food (vitamin D)

- demonstrated by Von Kossa (silver impregnation, non specific to calcium - black)

20
Q

Haemoglobin pigment

A
  • brownish colour in formalin fixed sections
  • Eosin in H&E gives orange/pink colour
  • free Hb is anamorphous or globular; strongly acidophilic
21
Q

Uric Acid and Urates pigment

A
  • urate crystals are birefringent
  • high uric acids (kidney diseases, overweight, diabetes)
  • breakdown of purine nucleotides
  • gout; crystallisation in joints
22
Q

Carbon pigment

A
  • dense, black pigment
  • most common of pigments; absorbed by phagocytes
  • acts as carrier for more dangerous materials; absorb chemicals onto their surface
  • seen in lungs of urban dwellers, smokers; skin from tattoos and needle tracks
23
Q

Asbestos pigments

A
  • brown pigments
  • cause fibrosis, may lead to asbestosis and mesothelioma
  • long beaded fibres
24
Q

Silica pigments

A
  • black-brown, depending on source of it
  • may be birefringent
  • miners, quarry workers, stonemasons exposed to it
25
Q

Types of conjugated lipids (7)

A
  • neutral fats
  • waxes
  • cholesterol esters
  • phosphoglycerides
  • sphingomyelins
  • ceramides
  • glycolipids
26
Q

Types of unconjugated lipids (2)

A
  • fatty acids

- steroids

27
Q

What are fats and lipids defined by?

A
  • solubility in fat solvents

- insolubility in water

28
Q

Why is fixation of lipids difficult?

A
  • all but 2 fixatives can be used (osmium tetroxide, potassium dichromate)
  • osmium tetroxide fixes lipids but also blackens them
29
Q

What does lush chrome staining rely on?

A
  • using a dye that’s very soluble in lipids but relatively insoluble in aqueous solvent
30
Q

What techniques are used with lysochrome methods?

A
  • Sudan dyes
  • Oil Red O
  • Nile blue
31
Q

Limitations of techniques with lab methods with lipids?

A
  • melting point 37oC; fluid in body, solid in section, may not stain/react with reagents
  • physical properties; pure lipids stain differently from mixtures
32
Q

What is applied after biopsy of lipids?

A
  • Sudan black B
  • Oil Red O
  • Polarised light (birefringence)
33
Q

Haemosiderin

A
  • found in spleen and liver
  • iron binding proteins (Fe3+)
  • destruction of old RBCs
34
Q

Diseases associated with haemosiderin

A
  • haemochromatosis

- haemosiderosis

35
Q

Haemochromatosis

A
  • autosomal recessive disorder
  • excessive absorption of iron
  • multi-organ disorder
  • liver (cirrhosis), heart (myopathy), pancreas (diabetes mellitus)
36
Q

Haemosiderosis

A
  • focal deposits
  • no genetic cause
  • alcoholism or thalassaemia (blood transfusions)
  • aka secondary haemochromatosis
37
Q

Solubility in lipid identification

A
  • section cut fixed, frozen tissue
  • subsequent short formalin fixation, neutral lipids preserved not fixed
  • traditional wax sectioning removes lipids. H&E gives -ve artefact image
  • no dehydration/clearing and sections mounted in aqueous mountants
38
Q

Lipid storage disorders (lipidosis)

A
  • metabolic inherited disorders (rare)
  • lipid accumulation in cells (overproduction, decreased metabolism)
  • varies in organs; particular in CNS
39
Q

Fabry disease

A
  • accumulation of lipids in kidney
40
Q

Osmium tetroxide fixation

A
  • uncommon in light microscopy, blackening lipids
41
Q

Microscopic examination in lipid identification

A
  • bright-field microscopy (H&E, Sudan-type stains, Oil Red O)
  • polarised light microscopy (oval fat bodies in urinary sediment examination - lipiduria

AP0509 Component 2 Exam (21 decks)

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