S1) Investigative Techniques Flashcards
Identify 3 requirements for light microscopy
- Formalin
- Paraffin
- Haematoxylin and Eosin
What role does formalin have in light microscopy?
Formalin preserves tissue to prevent it from rotting
What role does paraffin have in light microscopy?
Paraffin embeds the tissue in a substance that allows it to be sliced very thinly
What role does H&E have in light microscopy?
Haematoxylin and Eosin stains the tissue so that we can see cell components
Describe the process of producing a frozen section
- The surgical specimen is placed on a metal disc then frozen rapidly to -20°C to -30°C
- The specimen is cut open with a cryostat
- The tissue is then stained with H&E
Identify an advantage and a disadvantage of frozen sections
- Advantage: prepared more rapidly than traditional histology (10 minutes vs 16 hours)
- Disadvantage: technical quality of sections is much lower
Outline the process of fluorescent microscopy
- Specimen has fluorescent molecules (fluorophores) attached
- Fluorophores emit light when they are irradiated by a specific wavelength of light
- Colours observed can be different components of a cell or the different cell types within a tissue
When is fluorescent microscopy most commonly used?
Used in the differentiation of different cancer cell types
Outline the process of confocal microscopy
Often combined with fluorescent imaging:
- Fluorescent dye molecules are attached to specific parts of a sample
- Only the labelled parts can be seen in the confocal microscope
Identify and describe 3 advantages of confocal microscopy
- Produces a sharper image (blocks out of focus light)
- Captures 3D images of specimens
- Allows for imaging of live specimens (images taken at time intervals to create a time-lapse video)
Outline the process of autoradiography
A photographic emulsion is used to visualise molecules labelled with a radioactive marker:
- Marker is injected into the live animal/cell culture
- Histological section is coated with the emulsion
What is an ultrasound?
Ultrasound are sound waves with frequencies which are higher than those audible to humans (>20,000 Hz)
Describe the process of performing an ultrasound
- Ultrasonic images are sonograms and are made by sending pulses of ultrasound into tissue using a probe
- The sound echoes off the tissue
- Different tissues reflecting varying degrees of sound
- Echoes are recorded and displayed as an image
Describe the use and aim of the ultrasound
- Use: view internal body structures
- Aim: find a source of a disease or to exclude any pathology
Outline the process involved in Transmission Electron Microscopy
- Uses an electron beam generated in a vacuum
- The electron beam passes through the tissue
- Portions that the beam has passed through appear bright
- Portions that have absorbed or scatter electrons appear dark
Make a relative comparison of electron microscopy with light microscopy in terms of:
- Resolution
- Magnification
- Resolution: 400 x that of light microscopy
- Magnification: 250 x that of light microscopy
Outline the process involved in Freeze Fracture Electron Microscopy
- The tissue is frozen to -160°C and fractured by hitting with a knife edge.
- The fracture line passes through the plasma membrane exposing its interior which can then be imaged
Outline the process involved with Scanning Electron Microscopy
The electrons are reflected from the surface and received by a cathode ray tube (like a TV)
What is MRI?
MRI is a useful non-invasive and non-destructive diagnostic tool for imaging soft tissues such as the brain, heart and muscles, and for discovering tumors in many organs
