Flashcards in BL - Investigative Techniques (done to slide 29) Deck (17):
How is cut tissue preserved to stop it from rotting?
Formalin is used
What is used to allow tissue to be cut very thinly for microscopy? (5 micrometers)
Melted paraffin which sets hard when cooled
What does haematoxylin stain and what colour does it stain it?
It stains the nucleus blue
What colour does eosin stain things, and what does it stain?
Cytoplasm and extracellular matrix, pink
What is a "frozen section"?
A specimen is placed on a metal disc and then frozen to -20 to -30 degrees C. It is then stained with H+E. It is very fast, but technical quality is low.
Two samples are taken from two different patients and viewed using polarised light microscopy. One shows long thin crystals and one shows rhomboid crystals. Which is gout?
Long thin = gout.
Rhomboid = pseudogout
True or false - fluorescent microscopy can be used to diagnose cancer?
True or false - confocal microscopy is never combined with fluorescent microscopy?
False, they often are.
What makes confocal microscopy different to normal microscopy?
A pinhole is placed art the confocal plane of the lens to eliminate out of focus light, which enables sharper 3D images to be created.
How does immunohistochemical staining work?
Antigens in the cells of a tissue section can be detected by labelled antibodies binding to them.
Describe the process of autoradiography.
A photographic emulsion is used to visualise molecules labelled with radioactive marker. The marker is first injected into the live animal/cell culture. The histological section is then coated with the emulsion.
True or false - higher frequency (shorter wavelength) gives a better resolution?
Why does transmission electron microscopy have a better resolution than light microscopy?
The wavelength is 1 nanometre compared to light microscopy which uses 400 nanometres.
Why do some portions of an image created by TEM seem dark?
These portions have absorbed electrons, while the beam has passed straight through the light sections.
How is a sample prepared for viewing with a TEM?
Fix with glutaraldehyde, embed in epoxy resin, stain (eg. Osmium tetroxide), use microtome with diamond knives.
What is "freeze fracture electron microscopy"?
The tissue is frozen to -160 degrees C and fractured by hitting it with a knife edge. The fracture line passes through the plasma membrane, exposing its interior.