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Histopath LEC > ALDEHYDE FIXATIVES > Flashcards

ALDEHYDE FIXATIVES Flashcards

1
Q

• Gas produced by oxidation of methanol

A

Formaldehyde (Formalin)

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2
Q

Formaldehyde

Concentrations:
_____ gas form

______- stock concentration (causes overhardening of the external surfaces of tissues)

_____working solution; most commonly used

A

100%

• 37% to 40%

• 10%

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3
Q

Formaldehyde

Usually buffered to pH 7 with____

A

phosphate buffer

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4
Q

Advantages of formaldehyde

A

Cheap, readily available, and easy to prepare

Compatible with many stains

Penetrates tissue well

Allows natural tissue color to be restored

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5
Q

Disadvantages of formaldehyde

A

Irritating to the nose and eyes (allergic rhinitis); may cause Dermatitis

If unbuffered, may reduce both basophilic and eosinophilic staining

Prolonged fixation may cause bleaching of the specimen

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6
Q

Formaldehyde prolonged storage

EFFECTS

REMEDY

A

White formaldehyde ppt

  • Filter
  • Add 10% methanol (but dentures proteins thus unsuitable for EM)
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7
Q

Formaldehyde unbuffered

EFFECTS

REMEDY

A

Formation of Formic acid

Buffer or Methanol

  • 10% formol saline + Mg** / Ca** carbonate in jar with marbles
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8
Q

Formaldehyde action of formic acid w excess blood

EFFECTS

REMEDY

A

Formalin pigments brown / black precipitate

  • Saturated alcoholic picric acid
  • 1% KOH in 80& ROH
    blood
  • Kardasewitch’s Method
    (70% ETOH & 28% ammonia H202 70%
    ETOH & 28% ammonia water)
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9
Q

10% Formol-Saline

A

Saturated formaldehyde + 10% NaCl

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10
Q

Recommended for fixation of CNS tissues and general post mortem tissues for histochemical examination

A

10% Formol-Saline

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11
Q

Advantage: Ideal for Silver impregnation staining technique

Disadvantage: Slower; tissue shrinks during alcohol dehydration

A

10% Formol-Saline

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12
Q

10% Neutral Buffered Formalin (NBF)

A

Formaldehyde +

Na Dihydrogen Phosphate +

Disodium Hydrogen Phosphate

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13
Q

pH 7
Best general tissue fixative

A

10% Neutral Buffered Formalin (NBF)

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14
Q

Best for iron-containing pigments and elastic fibers which do not stain well after Susa, Zenker, or Chromate fixation

A

10% Neutral Buffered Formalin (NBF)

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15
Q

Disadvantage: Longer to prepare, inert to phospholipids and neutral fats

A

10% NBF

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16
Q

10% NBF

o Fixation Time:

A

4 to 24hrs

17
Q
  1. Formol-Corrosive (Formol Mercuric Chloride)
A

Saturated aq. Mercuric chloride + 40%
Formaldehyde

18
Q

Recommended for routine post mortem tissues and Silver Reticulum staining methods

A

Formol-Corrosive (Formol Mercuric Chloride)

19
Q

Advantage: does not need washing, fixes lipids

Disadvantage: Forms mercuric chloride deposits

A

Formol-Corrosive (Formol Mercuric Chloride)

20
Q

Has 95% ETOH, Picric acid, and GHAc

A

Gendre’s (Alcoholic Formalin)

21
Q

o
Advantage: good for microincineration techniques; Fixes sputum

A

Gendre’s (Alcoholic Formalin)

22
Q

For gastrointestinal (GI) tissues, prostate biopsies, and bone marrow (BM)

A

Hollande’s

23
Q

• Made up of 2 formaldehyde residues linked by 3 carbon chains; Container must be refrigerated

A

Glutaraldehyde

24
Q

For enzyme histochemistry and electron microscopy

A

Glutaraldehyde

25
Q

Advantage: more pleasant and less irritation compared to formalin

Disadvantage: less stable and more expensive than formalin

A

Glutaraldehyde

26
Q

Glutaraldehyde

Concentrations:

For immune electron microscopy

For small TSE fragments

Most common

For large TSE fragments

A

0.25%

2.5%

3%

4%

27
Q

• Polymer of Formalin
Powder in form, used in 4%

Plastic embedding
• For ultrathin and electron microscopy

A

Paraformaldehyde

28
Q

Acrolein in glutaraldehyde or formalin

For Electron Histochemistry & Electron
Immunocytochemistry

A

Karnovsky’s Paraformaldehyde /
Glutaraldehyde

29
Q

• Advantage: no smudging of nuclei and distortion of staining compared with formalin

• Disadvantage: reduced staining capacity
Remedy: increase staining time

A

40% Aqueous Glyoxal

Histopath LEC (37 decks)

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