- Excessive hardening - Removes calcium and iron

Fixatives (Wk 16, 17) Flashcards by E E

This does not affect spores and therefore tissue may still be infectious.

MICROWAVE

How well did you know this?

Not at all

Perfectly

Air drying of smears can lead to what 4 problems

Enlarged cells and nuclei
Indistinct cell boundaries
Pale chromatin staining
Overall pale staining

How well did you know this?

Not at all

Perfectly

A less toxic alternative to mercury.

ZINC SULFATE

How well did you know this?

Not at all

Perfectly

What is a coating fixative and its purpose

Wax coating that protects cells during transport or until they can be stained

Prevents air-dry effect

How well did you know this?

Not at all

Perfectly

Glutaraldehyde is usually used as a _% solution

How well did you know this?

Not at all

Perfectly

This causes proteins to swell.

ACETIC ACID

How well did you know this?

Not at all

Perfectly

Main effect of formalin on staining?

Decreased amino (+) groups

How well did you know this?

Not at all

Perfectly

Zinc sulphate fixation mechanism

Binds to histidine and cysteine residues to stabilize conformation of proteins

How well did you know this?

Not at all

Perfectly

Fixative that precipitates proteins without denaturing them

acetone

How well did you know this?

Not at all

Perfectly

Formalin is added to this fixative before use

How well did you know this?

Not at all

Perfectly

Routine use of B5

Bone marrow

How well did you know this?

Not at all

Perfectly

General category of fixatives which cause proteins to precipitate.

COAGULANT

How well did you know this?

Not at all

Perfectly

What is the working concentration of formalin

Max conc. of formaldehyde in solution = 40%

Diluted 1 in 10

Therefore, 10% neutral buffered formalin = 4% formaldehyde

How well did you know this?

Not at all

Perfectly

What are the 2 reactions that occur during fixation with formalin

Hemiacetal formation

2. Methylene bridge formation

How well did you know this?

Not at all

Perfectly

Transport media for short term (~1 hr) storage

Place on saline moistened gauze in sealed container on ice

Refrigeration

How well did you know this?

Not at all

Perfectly

Routine use of Zenker’s

Bone marrow

Lmyph nodes

How well did you know this?

Not at all

Perfectly

How to make formalin from paraformaldehyde

Dissolve in water; faster in neutral pH

How well did you know this?

Not at all

Perfectly

What is the primary purpose of a microanatomical fixative?

preservation of cellular and non-cellular structural elements

How well did you know this?

Not at all

Perfectly

2 cons of Bouin’s

Excessive hardening

- Removes calcium and iron

How well did you know this?

Not at all

Perfectly

These are formed when formaldehyde crosslinks proteins.

METHYLENE BRIDGES

How well did you know this?

Not at all

Perfectly

This reaction is used to demonstrate the adrenal medulla and tumours of it

Chromaffin reaction

How well did you know this?

Not at all

Perfectly

Typical fixatives for fluids

Ethanol
Saline in sterile container
Refrigeration

How well did you know this?

Not at all

Perfectly

4 common ingredients in Zenker’s

Mercuric chloride
Potassium dichromate
Sodium sulphate
Water

How well did you know this?

Not at all

Perfectly

Volume of fixative that should be used?

15-20x greater than tissue

How well did you know this?

Not at all

Perfectly

Term for nuclear shrinkage and increased basophilia.

PYKNOSIS

Formalin solutions mainly reacts with this functional group.

AMINO GROUPS

2 main routine uses of osmium tetroxide fixative

- Electron microscopy (as a fixative) | - Lipid stain (as a stain)

2 major aldehyde fixatives

- Formalin | - Glutaraldehyde

2 main glutaraldehyde differences compared to formalin

- Larger | - 2 aldehyde functional groups rather than 1

2 reactions involved in formalin fixation

1 - hemiacetal formation | 2 - methylene bridge formation

Transport media for long term storage

Michel's transport media

How to recognize and remove formalin pigment?

Found in bloody areas => brown Remove w/ alcoholic picric acid

Define methylene hydrate and what it's also known as

The form of formaldehyde in aqueous solution AKA methylene glycol

What is paraformaldehyde

White precipitate of formalin that forms spontaneously

3 common ingredients in Bouins

- Picric acid - Formalin - Acetic acid

Fixative that precipitates nucleic acids

acetic acid

Fixative that is appropriate for in situ hybridization b/c it inactivates RNases

Mercury

This fixative makes lipids black.

OSMIUM TETROXIDE

Routine use of Bouin's

Trichrome post-fix | Testicular biopsies

2 fixatives that contain mercury

Zenker's (Helly's) B5

What causes the formation of formalin pigment

Oxidation of formalin to formic acid (during storage) = lowers pH of solution Causes hgb to break down to hematein

Fixative of choice for hematopoietic tissues.

What is karyolysis

Nuclear chromatin fades or dissolves

Fixative useful in trichrome stain due to low pH (that's not Bouins)

Picric acid

The fixative which is also a commonly used dye is?

PICRIC ACID

Best fixative for antigen preservation

Zinc/alcohol

Typical fixatives for cell blocks

Formalin

Bouin's removes these 2 minerals

Calcium and iron

This fixative may result in free aldehydes.

GLUTARALDEHYDE

Effect of formalin fixation on eosin staining and why

Decreases eosin staining - hemiacetal and methylene bridge formation requires amino groups = used up = fewer sites for eosin to bind to - net increase in negative charges

How to neutralize osmium tetroxide

Large quantities of vegetable oil or sodium sulfite

This is used mainly to fix cytology smears.

ALCOHOL

4 advantages of making formalin from paraformaldehyde

- Very pure formalin - Doesn't easily re-polymerize - Methanol not required to prevent paraformaldehyde formation - Doesn't usually form formic acid

Typical fixatives for smears

Ethanol Ethanol/acetic acid Air dry Coating fixatives

Best for fixative for hematology specimens

Mercury

4 common ingredients in B5

- Mercuric chloride - Sodium acetate - Water - Formalin (add immediately before use)

Another word for polymerized formaldehyde

Paraformaldehyde

The one fixative that causes proteins to swell

Acetic acid

When used like this alcohol works well for enzyme Histochemistry.

COLD

The presence of this may lead to an artifact pigment which can be removed by alcoholic picric acid.

FORMIC ACID

Used to demonstrate adrenal medulla and tumors of it

Chromaffin reaction (dichromate fixative)

What is karyorrhexis

Fragmentation of nuclei

Main ingredients of this fixative: picric acid, formalin and acetic acid.

BOUINS

Fixation mechanism behind chromates

Attaches to phospholipids and renders them insoluble

This is added to prevent polymerization of formaldehyde.

METHANOL

Common ingredient in combination fixatives like Zenker's

Potassium dichromate

4 cons of Zenker's

- Toxic (mercury) - Hardening of tissues - Nonspecific silver precipitaes - Mercury artifacts

Difference between Zenker's and Helly's

Helly's - add formalin instead of acetic acid

Effect of glutaraldehyde fixation on PAS stain

False positives due to glutaraldehyde containing aldehyde groups

Fixative that may be used for frozen sections for enzyme histochemical rxns

Acetone

Chromates fixation mechanism

Attaches to phospholipids and renders them insoluble

Mercury fixation mechanism

Affects SH (thiol) groups of proteins

How to neutralize glutaraldehyde

Sodium bisulfite or sodium hydroxide

Which chemical may be used as a substitute for mercuric chloride in a fixative?

Zinc sulphate

Fixative that enhances nuclear staining

Mercury

Main routine use of glutaraldehyde fixative?

Electron microscopy

General fixative volume to tissue ratio

20:1

Difference between formaldehyde and formalin

Formaldehyde = gas Formalin = aqueous saturated solution of formaldehyde

Fixatives (Wk 16, 17) Flashcards

(78 cards)