Microbes and Accumulations Flashcards
What are accumulations
May be due to defects in packaging or transport or fats, protein, carbohydrates
Write about the processing of lipids
(5)
Lipids are processed differently to other tissues
Adipose tissue is used as an insulator
- will dissolve at high temperatures
Cannot process in the normal way
Needs thermal fixation
- freezing
Cryotomy is a technique used to cut sections for thermal fixation
Describe the method of lipid processing used in the lab
(5)
Tissue is received fresh into the laboratory
It is snap frozen in liquid nitrogen
Sections are cut at -20 degrees celsius and fixed in formalin
Transferred to isopropanol
Stained used oil red O or Sudan Black B
Describe the staining of lipids with H&E
Usually empty space with the nucleus staining purple
How does Oil Red O work?
(3)
Red hydrophobic dye
Works by solubility principle
The dye dissolves in isopropanol and is fat soluble i.e. will stain fat cells
How does sudan black B work
(2)
Slightly basic dye that combines with acidic groups in the lipid compounds
less commonly used in histology
Write about amyloid
(5)
Abnormal protein that is produced in the bone marrow
Aggregates of protein
A waxy translucent substance deposited under abnormal conditions
Not found in normal physiological tissue
Amyloidosis
Write about amyloid
(5)
Abnormal protein that is produced in the bone marrow
Aggregates of protein
A waxy translucent substance deposited under abnormal conditions
Not found in normal physiological tissue
Amyloidosis
What stain is used for amyloid
Congo red stain
Has an apple green birefringence under crossed polarised light
Why investigate infectious agents in histology
They are the most commonly investigated entities by special stains
Often incidental findings as most infectious agents are typed by microbiology
Can be identified on histology and cytology
May be non-viable no culture possible
What are the four infectious agents
Bacteria
Fungi
Viruses
Parasites and protozoa
How do we stain for microbes
Cant really use H&E
We use histochemistry stains and molecular methods to accurately subtype the species
Write about bacteria as accumulants
(4)
Bacteria are a large cohort of microorganisms
They have a number of shapes ranging from spheres to rods and spirals
Subtyped based on gram positive or negative
Mycobacterium has a lipid rich coat
Write about the gram stain in histology
Modified for histology samples - Gram Tworts
A type of differential stain
Gram positive retains the crystal violet dye due to the thick peptidoglycan cell wall
Gram negative do not retain dye
Background varying shades of blue/green
Write about the gram stain in histology
Modified for histology samples - Gram Tworts
A type of differential stain
Gram positive retains the crystal violet dye due to the thick peptidoglycan cell wall
Gram negative do not retain dye
Background varying shades of blue/green
