WEEK 1: Pigments and Lipids Flashcards
what is an artefact pigment?
Deposits produced as result of chemical reaction in tissue
what is an endogenous pigment?
Produced within tissue and have a physiological function or are a by-product of normal metabolic process
what is an exogenous pigment?
Gain access to body accidentally with no physiological function. Usually minerals, enter by inhalation or implantation in skin during industrial exposure
what are 3 artefact pigments?
formalin, malarial, mercury pigments.
what are 4 endogenous pigments? (8 altogether)
bile, lipofuscin, melanin, iron, calcium, copper, uric acid and urates pigments.
How is bile pigment produced? What colour?
breakdown of RBC’s, more specifically when Hb is recycled. Yellow (bilirubin), green (biliverdin). Liver diseases or haemolytic disease.
What is lipofuscin pigment? How is it produced?
‘wear and tear’ pigment due to lipid oxidisation. It is a normal process but excess is linked to PNS and CNS diseases.
Brown pigment.
where is lipofuscin pigment found?
found in heart muscle, liver and brain
How is lipofuscin stained?
Stained by Sudan black, Periodic Acid-Schiff (PAS), Schorl’s, Long Ziehl-Neelsen technique.
what is melanin?
the pigment that is a product of melanocytes. It is black/brown.
where is melanin pigment found?
Eye, skin, hair, brain and melanoma
what is iron pigment stored as?
It is stored as protein haemosiderin in ferric state Fe3+. Fine brown colour.
where is haemosiderin found in the body?
liver, spleen and marrow
what is haemosiderin?
an iron storage complex in cells/tissue as opposed to circulating in the blood. The iron is from the breakdown of erythrocytes.
how is iron, in the ferric state, stained?
it is stained with Perls Prussian Blue staining
how does Perls Prussian Blue stain work?
- dilute hydrochloric acid releases ferric ions from binding proteins by partial denaturation of protein.
- the metal reacts with potassium ferrocyanide to form ferric ferrocyanide, an insoluble bright blue pigment
what is the chemical equation for Perls Prussian Blue staining with ferric iron?
ferric iron + potassium ferrocyanide —> ferric ferrocyanide or Prussian Blue
what is haemochromatosis?
Haemochromatosis is a disorder in which the body can build up too much iron in the skin, heart, liver, pancreas, pituitary gland, and joints. Too much iron is toxic to the body. IT IS GENETIC
who is affected by haematochromatosis?
females after menopause or males aged 40-60
what are some initial symptoms of haemochromatosis?
- fatigue
- weakness
- arthropathy affecting various joints
- nonspecific abdominal problems
- erectile dysfunction
- heart problems
what are some advanced symptoms of haemochromatosis?
- diabetes
- bronzing of the skin !!
- hepatomegaly
- arthropathy
- impotence
- amenorrhoea or hypogonadism
- cirrhosis
- diabetes mellitus
- cardiac disease
- neurological or psychiatric symptoms
how is haemochromatosis investigated?
initially by assessing iron stores. Further investigation includes genetic testing, liver biopsy, MRI
what is haemosiderosis?
haemosiderosis is a term used to describe an overload of iron in your organs or tissues. Also referred to as secondary haemochromatosis. IT IS NOT GENETIC (acquired)
what causes haemosiderosis?
blood transfusion
- excessive iron medication
- thalassemia
- liver disease
- congestive heart failure
- repeated episodes of bleeding
how is haemosiderosis treated?
treated with iron chelating agents
where is calcium absorbed?
in the GIT with use of vitamin D.
what stains are used to detect calcium?
Von Kossa and Alizarin red
how is uric acid produced?
from the breakdown of purine nucleotides
what problems occur with high uric acids or crystallisation?
kidney disease, overweight, diabetes.
crystallisation in joints - gout
urate crystals
why might you need a polarising microscope?
The polarizing microscope is particularly useful in the study of birefringent materials such as crystals - urate crystals
what is melanoma?
cancer - over production of melanin. The melanin pigment is much deeper in the skin than it should be - usually very close to surface
what is polarised light?
Polarised light has electric fields oscillating in one direction, whereas unpolarised light has electric field oscillating in all directions
what are 3 exogenous pigments?
carbon, silica and asbestos pigments.
how does a polarising microscope work?
Polarized light microscopes work by converting unpolarized light to polarized light. One way in which this can be achieved is by absorption of light vibrational movement in one specific direction.
define birefringent material
Birefringence is the optical property of a material having two distinct indices of refraction
how are lipids defined?
by their solubility in fat solvents and their insolubility in water.
which 2 fixatives can NOT be used to fixate lipids?
osmium tetroxide, potassium dichromate
what is a neutral fat?
Neutral fats are described as neutral because they are uncharged and do not contain acidic or basic groups. They are nonpolar and hydrophobic.
what is lysochrome?
a fat soluble dye that have high affinity to fats but is relatively insoluble in aq solvent, so is therefore used in staining.
what are some dyes using the lysochrome method?
- Sudan-type dyes (Sudan I-IV or Sudan black)
- Oil Red O
- Nile Blue
