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11 Cards in this Set
- Front
- Back
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What does H&E stain? |
Haemotoxylin - a positively charged basic dye that stains acidic structures blue or purple. Eosin - stains basic structures pink or red. |
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What does Masson-Fontana stain? |
Stains melanin black, used to identify malignant melanoma |
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What does Periodic Acid-Sciff stain? |
Stains mucin and glycogen |
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What are the ideal criteria for fixation? |
1. Kills cells rapidly, avoiding cell structure destruction. 2. Quick, even penetration of the tissue. 3. Does not shrink or swell cells. 4. Prevent moisture loss. 5. Safe to use. 6. Reasonably priced. |
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Name four different fixation types and their benefits/downfalls. |
Quick freezing - disrupts structure, maintains antigen, quick. Formalin - useful for light microscopy Aldehydes - useful for immunohistochemistry, maintain structure but change antigen. Alcohol - disrupts structure but changes antigen. |
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What are two key methods of histological specimen collection? |
1. Exfoliative cytology - collect exfoliated cells by brushing, scraping or washing e.g. cervical broom. 2. Fine needle aspiration |
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Explain the basic principle of immunohistochemistry. |
A specific protein is identified in a fixed tissue sample by incubating an epitope specific primary antibody with the tissue. If the protein is present, the antibody binds. Then a secondary antibody is added to the incubation and labelled with a fluorescent tag. If the primary antibody has bound, after washing an X-ray image will show where the markers are and thus the location of the protein in the tissue. |
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Explain confocal microscopy. |
Increases resolution and contrast by adding a pinhole on the confocal plane of the lens to eliminate out of focus light. This is good because it allows imaging of thick samples (unlike EM) and allows field depth control. |
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Explain Electron Microscopy and its benefits and downfalls. |
Electron Microscopy is performed on thin specimens. The sample is dehydrated and fixed in plastic, preserving its structure. Then, electrons are directed at the sample in a 'beam' giving an image based on scattering. TEM - greater magnification but requires thinner samples. SEM - focuses on the surface so doesn't require magnification, has better field depth. |
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Describe in situ hybridisation. |
A technique that uses pre-made complementary DNA, RNA or primers to detect the specific sequence in a small section of tissue which allows you to determine the structure and number of sequences in a tissue. |
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DNA Microarray |
DNA oligonucleotides are spotted on a chip and target hybridisation occurs with the incubation of fluorescent-labelled probes, allowing gene profilingof the individual. Helps identify SNPs. |
