Fixation Flashcards
1
Q
Acetic acid
A
Concentration: About 5% Fixation time: Overnight Additive: No Coagulant: No Hardens: No Acid dyes: Improves Basic dyes: Reduced Aftertreatment: None Carbohydrates: no effect Lipids: no effect Preserves nuclei Tissues shrink after dehydration if used alone
2
Q
Acetone
A
Concentration: Absolute Fixation time: A few hours Additive: No Coagulant: Yes Hardens: Yes Acid dyes: Neutral Basic dyes: Neutral Aftertreatment: None Carbohydrates: not fixed Lipids: not preserved Poor preservation, best for enzymes
3
Q
Chromic acid
A
Concentration: 1 - 3% Fixation time: Several hours Additive: Yes Coagulant: Yes Hardens: No Acid dyes: Improves Basic dyes: Reduced Aftertreatment: Wash well Carbohydrates: oxidized Lipids: oxidized Strong oxidizer, combines with reducing agent
4
Q
Potassium dichromate
A
Concentration: 1 - 3% Fixation time: Hours to weeks Additive: Yes Coagulant: No Hardens: Moderately Acid dyes: Improves Basic dyes: Reduced Aftertreatment: Wash well, can cause dark precipitate when transferred to ethanol Carbohydrates: no effect Best for lipids If ph is above 3.8
5
Q
Ethanol
A
Concentration: Absolute Fixation time: Several hours Additive: No Coagulant: Yes Hardens: Yes Acid dyes: Neutral Basic dyes: Neutral Aftertreatment: None Carbohydrates: not fixed unless attached to proteins Glycogen well preserved Lipids: not preserved, may dissolve Poor cytoplasmic preservation Fixes proteins through dehydration and precipitation
6
Q
Formaldehyde
A
Concentration: 4% aqueous Fixation time: Days Additive: Yes Coagulant: No Hardens: Yes Acid dyes: Not enhanced Basic dyes: Not enhanced Aftertreatment: None Carbohydrates: only fixes protein part Lipids: most dissolve through clearing Causes proteins to cross link preserving morphology Cleared with ethanol to removes salts after fixing Reacts with nitrogen in the proteins
7
Q
10% Neutral Buffered Formalin
A
10% formalin buffered with sodium dihydrogen phosphate and disodium hydrogen phosphate to pH 7.0
Reduces formalin pigment formation with bloody tissues
8
Q
Glutaraldehyde
A
Concentration: 4% aqueous Fixation time: Several hours Additive: Yes Coagulant: No Hardens: Yes Acid dyes: Not enhanced Basic dyes: Not enhanced Aftertreatment: aldehyde block needs to be used when staining for PAS Carbohydrates: not fixed, proteins attached will be Lipids: not fixed Used for electron microscopy Adds free aldehyde groups to the fixed tissue; can pose problems for immunolabeling
9
Q
Mercuric chloride
A
Concentration: Varies, often 6% Fixation time: 30 minutes to hours Additive: Yes Coagulant: Yes Hardens: Yes Acid dyes: Improves Basic dyes: Improves Aftertreatment: Rinse with Iodine to remove mercury pigment Excellent preservation
10
Q
Methanol
A
Concentration: Absolute Fixation time: Several hours Additive: No Coagulant: Yes Hardens: Yes Acid dyes: Neutral Basic dyes: Neutral Aftertreatment: None Carbohydrates: not fixed Lipids: not rpeserved, may dissolve Fixes proteins through dehydration and precipitation
11
Q
Osmium tetroxide
A
Concentration: Up to 1% Fixation time: A few hours Additive: Yes Coagulant: No Hardens: No Brittle: No Acid dyes: Poor Basic dyes: Good Aftertreatment: Wash well Carbohydrates: unaffected Lipids: preserved, reacts with double bond of unsaturated lipids, rendering them resistant to extraction by many solvents Excellent preservation Acts as mordant for lead staining, hematoxylin Penetrates poorly, need small tissue Reacts with C=C in unsaturated fatty acid chains of phospholipids
12
Q
Trichloroacetic acid
A
Concentration: About 2% Fixation time: A few hours Additive: Yes Coagulant: Yes Hardens: Yes Aftertreatment: None Carbohydrates: not affected Lipids: not affected Fixes by reactions between negatively charged chloroacetate anion and positively charged amino groups of proteins
13
Q
Zinc chloride
A
Concentration: Varies, perhaps 2-5% Fixation time: one or more hours Additive: Yes Coagulant: Yes Hardens: Yes Acid dyes: Some improvement Basic dyes: Some improvement Aftertreatment: None Alternative to mercuric chloride but inferior
14
Q
B5
A
Ingredients: Mercuric chloride DI Water Sodium Acetate 40% Formalin Clear with iodine Improves nuclear and cytoplasmic staining Used with trichromes
15
Q
Bouin’s picro formal acetic
A
Ingredients: Formalin Picric acid Clear with 70% ethanol Used as secondary fixation after formalin Used with trichromes
16
Q
Duboscp-Brasil
A
Ingredients: Picric acid Ethanol Formalin Acetic acid Increases staining of acid dyes Recommended for glycogen
17
Q
Carnoy’s
A
Ingredients: Ethanol Acetic acid Chloroform Clear with absolute ethanol Very rapid fixation Preserves glycogen
