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MT6321 HISTOPATH > U4 LEC: FIXATION PT. 2 > Flashcards

U4 LEC: FIXATION PT. 2 Flashcards

1
Q

Characteristics of a Good Fixative

A
  • cheap
  • stable
  • safe to handle
  • minimum distortion
  • minimum shrinkage
  • permit rapid and even penetration
  • harden tissues
  • minimal physical and chemical alteration of cells
  • insensitive to subsequent processing
  • subsequent application of many staining procedures
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2
Q

Characteristics of a Good Fixative

To produce minimum distortion, it must?

A

kill the cell quickly

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3
Q

Characteristics of a Good Fixative

To produce minimum shrinkage, it must?

A

inhibit bacterial decomposition and autolysis

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4
Q

Characteristics of a Good Fixative

To make cutting of sections easier, it must?

A

harden tissues

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5
Q

Characteristics of a Good Fixative

To cause minimal physical and chemical alteration of the cells, it must be?

A

isotonic

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6
Q

Characteristics of a Good Fixative

To render them insensitive to subsequent processing, it must make cell components?

A

insoluble to hypotonic solutions

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7
Q

Characteristics of a Good Fixative

To facilitate easier and more profitable examination, it must permit the?

A

subsequent application of many staining procedures

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8
Q

Fixatives in order of decreasing speed of penetration

A

Formaldehyde >
Acetic acid >
Mercuric chloride >
Ethyl/Methyl alcohol >
Osmium tetroxide >
Picric acid

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9
Q

Mechanism of Aldehyde Fixatives

A
  • form cross-links
  • mechanical strength
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10
Q

Mechanism of Aldehyde Fixatives

Cross linking between proteins create a?

A

gel

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11
Q

Mechanism of Aldehyde Fixatives

Cross linking retains?

A

cellular constituents in their in vivo relationships to each other

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12
Q

Mechanism of Aldehyde Fixatives

Gives mechanical strength to?

A

entire structure

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13
Q

Mechanism of Aldehyde Fixatives

Mechanical strength enables it to?

A

withstand subsequent processing

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14
Q

This is produced from the oxidation of methyl alcohol

A

Formaldehyde

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15
Q

Formaldehyde

Fixation time

A

24 hours

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16
Q

Most common Formaldehyde variant

A

10% Formalin

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17
Q

10% Formalin is also known as?

A

Neutral, Buffered Formalin

(for stain to easily enter tissue)

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18
Q

Characteristics of 10% Formalin

A
  • cheap, readily available, easy to prepare
  • relatively stable
  • compatible with many stains
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19
Q

10% Formalin

Fumes irritating to?

A

nose and eyes

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20
Q

10% Formalin

Solution irritating to?

A

skin

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21
Q

10% Formalin

For what sections?

A
  • Routine Paraffin
  • Electron Microscopy
  • Histochemistry
  • Enzyme
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22
Q

Most preferred fixative for Electron Microscopy

A

Electron microscopy

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23
Q

10% Formalin

Pigments removed by treatment with?

A

alcoholic picric acid

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24
Q

10% Formol-Saline

Diluent

A

10% NaCl Solution

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25
Q

10% Formol-Saline

Fixation of?

A

Central Nervous Tissues

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26
Q

10% Formol-Saline

What is used for histochemical examinations?

A

Post-Mortem tissues

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27
Q

10% Formol-Saline

Fixation time at body temp (35)

A

24 hrs

28
Q

10% Formol-Saline

Fixation time at room temp (24-25)

A

48 hrs

29
Q

Formaldehyde 40%

Total volume

A

100mL

30
Q

Formaldehyde 40%

NaCl

A

9 gm

31
Q

Formaldehyde 40%

Distilled water

A

900 mL

32
Q

This is used mainly for preservation and storage.

A

10% Neutral Buffered Formalin

33
Q

10% Neutral Buffered Formalin

Preservation and Storage of?

A
  • Surgical
  • Post-mortem
  • Research
34
Q

10% Neutral Buffered Formalin

Fixation time

A

4-24 hours

35
Q

10% Neutral Buffered Formalin

Sodium dihydrogen phosphate

A

3.5gm

36
Q

10% Neutral Buffered Formalin

Disodium hydrogen phosphate

A

6.5 gm

37
Q

10% Neutral Buffered Formalin

Formaldehyde 40%

A

100 mL

38
Q

10% Neutral Buffered Formalin

Distilled water

A

900 mL

39
Q

10% Neutral Buffered Formalin is the optimal choice for these reasons:

A
  • fast penetration
  • non-coagulant and additive
  • prevents alterations during processing
  • less shrinkage than other fixatives
  • not osmotically active
  • hardens tissue ebtter
  • stored indefinitely
  • cheap & stable
40
Q

10% Neutral Buffered Formalin

Fixative of choice for?

A

Immunohistochemistry and molecular tests

41
Q

10% Neutral Buffered Formalin

Disadvantages

A
  • longer time to prepare
  • reduced positivity of mucin to PAD
  • gradual loss in basophilic staining
  • reduced myelin reactivity to Weigert’s iron hematoxylin stain
  • inert towards lipids
42
Q

10% Neutral Buffered Formalin

Positivity of _____ to ____ is reduced

A

mucin, PAS

43
Q

10% Neutral Buffered Formalin

Produce gradual loss in?

A

basophilic staining

44
Q

10% Neutral Buffered Formalin

Reactivity of ________ to _______________ is reduced

A

myelin, Weigert’s iron hematoxylin stain

45
Q

10% Neutral Buffered Formalin

It is inert towards lipids, especially?

A

neutral fats and phospholipids

46
Q

This uses mercuric chloride as diluent.

A

Formol-Corrosive

47
Q

Other name of Formol-Corrosive

A

Formol-Sublimate

48
Q

Formol-Corrosive

Diluent

A

Sat. Aq. Mercuric Chloride

49
Q

Mercuric chloride can be used to demonstrate?

A

nerves

50
Q

Formol-Corrosive

Fixation time

A

3-24 hours

51
Q

Formol-Corrosive

Recommended for?

A

Routine Post-Mortem Tissues

52
Q

Formol-Corrosive

Brightens?

A

cytoplasmic and metachromic stains

53
Q

T/F: Formol-Corrosive penetrates rapidly.

A

False

slowly

54
Q

Polymerized form of formaldehyde obtained as white powder

A

Paraformaldehyde

55
Q

T/F: Paraformaldehyde can be depolymerized back when heated.

A

True

56
Q

Paraformaldehyde

Suitable for?

A
  • paraffin embedding and sectioning
  • immunocytochemical analysis
57
Q

Paraformaldehyde

can be stained for?

A

general histology

less vigorous ang degree of fixation than Bouin’s, less morphology quality

58
Q

This is a mixture of paraformaldehyde and glutaraldehyde.

A

Karnovsky’s fixative

59
Q

Karnovsky’s fixative

Sutaible for?

A
  • light microscopy in resin embedding and sectioning
  • electron microscopy
60
Q

Karnovsky’s fixative

This fixative should always be prepared?

A

fresh (on the spot)

61
Q

Glutaraldehyde

2.5% solution

A
  • small tissue fragments
  • needle aspirates
62
Q

Glutaraldehyde

4% solution

A

larger tissues

63
Q

Glutaraldehyde

used for?

A
  • Routine Light Microscopy
  • EM
64
Q

Glutaraldehyde

Advantages

A
  • preserve cell structures better
  • less irritating to nose and skin
65
Q

Glutaraldehyde

Disadvantages

A
  • expensive
  • less stable
  • slow penetration
66
Q

Mechanism of Metallic Fixatives

A

Mercuric Chloride and Lead mercuric salts bind with sulfhydryl groups in acidic solutions

67
Q
A

MT6321 HISTOPATH (15 decks)

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