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65 Cards in this Set
- Front
- Back
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Fixation |
Stabilizes protein so resistant to further change |
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Additive Fixation |
Bond Disruption and chemical combination(link) with fixative molecule possible change to electrical charge or tertiary structure |
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Nonadditive Fixation |
No combination, acts on tissue only Denatures proteins by dissociating water groups -> coagulates or precipitates proteins |
examples: alcohol, acetone |
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Functions of Fixation |
1. Kills tissue 2. Stabilizes tissue 3. Emphasizes refractive index differences 4. Enhances staining 5. Firms tissue |
List 5 |
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Why is Killing Tissue important? |
Prevents postmortem decay (autolysis, putrefaction) |
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Why is Tissue Stabilization important? |
cellular structures and relationships are kept intact |
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Why is emphasizing refractive differences important? |
Increases visibility |
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Microwave Fixation function
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instantaneously heats to stabilize and denature protein |
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Microwave Fixation process |
1. large specimen in saline 2. 2mm blocks in saline heated to 50-68c or 45-55c Saline used to be used now aldehydes (formaldehyde) |
2 stage fixation |
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Microwave Fixation Troubleshooting Results |
Overheated (68c+): overstained nuclei, protein denaturation, loss of antigenicity Underheated: poor fixation |
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Dessication |
Air drying for Wright staining |
rarely used |
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Additive Fixation Reagents |
Mercuric Chloride Chromium Trioxide Picric Acid Formaldehyde Glutaraldehyde Glyoxl Osmium Tetroxide ZincSulfate Chloride |
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Nonadditive Fixation Reagents |
Methyl alcohol
Ethyl alcohol Acetone |
organic compounds |
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What happens when fixative adds to NH2 or COOH? |
Charges and pH can change |
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How to affect penetration rate |
heat, not concentration |
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Penetration speed high-to-low fixatives |
formaldehyde, acetic acid, mercuric chloride, methyl alcohol, osmium tetroxide, picric acid |
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Best way to store tissues |
NBF indefinitely or 70% alc to stop crosslinking for IHC |
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Hypertonic/ Hypotonic/ Isotonic |
more conc/less conc/equal conc compared to cell |
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Nucleus Fixation |
Acetic alcohol and Carnoy solution fix NAs (nuclear proteins) Nuclear bubbling with formalin fixation |
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Nuclear Bubbling |
chromatin strands and intervening clear spaces after formalin fixation |
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Lipid Fixation |
Osmium textroxide or chromic acid only both change chemical reactivity |
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Carbohydrate Fixation |
usually lost, glycogen retention prob due to entrapment |
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https://www.leicabiosystems.com/knowledge-pathway/fixation-and-fixatives-1-the-process-of-fixation-and-the-nature-of-fixatives/ |
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Acetic Acid |
noncoagulant / additive rapid penetration softens tissue precipitates and preserves nucleoproteins lyses RBC used alone swells protein and can counteract shrinking |
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Formaldehyde |
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Black Acid Hematin
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Black Acid hematin removal |
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Glutaraldehyde |
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Glyoxl |
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Mercuric Chloride |
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Osmium Tetroxide |
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Picric Acid |
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Potassium Dichromate |
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Zinc Salts |
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Zinc Sulfate |
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B-5 Fixative |
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Bouin Solution |
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Gendre Solution |
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Hollande Solution
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Formaldehyde-glutaraldehyde |
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Zenker & Helly solution |
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Orth Solution |
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Zamboni Solution |
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Zinc Formalin Solutions |
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Aqueous Zinc Formalin (and unbuffered) |
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Alcoholic Zinc Chloride Formalin |
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Acetone |
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Methanol |
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Ethanol |
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Alcoholic Formalin |
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Carnoy Solution |
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Methacarn Solution |
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Clarke Fluid |
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Saline |
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Michel Medium |
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Michel Transport Medium |
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EM Fixatives |
Osmium Tetroxide Primary Aldehyde (form-,glut-) Primary Buffered PAF fixation (Zamboni) |
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Malarial Pigment removal |
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Mercury Pigment removal |
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Zinc Precipitate |
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Chromate Pigment |
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Good Fixation Traits |
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Delayed Fixation Traits |
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Incomplete Fixation Traits |
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What group does formaldehyde bind to?
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NH2, amino groups |
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https://www.studyblue.com/notes/note/n/fixation/deck/6616425 |
F |
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Mordant |
A mordant is a chemical that serves as a link between the dye and the substrate. The result is an insoluble compound that helps adhere the dye to the cells. |
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