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

U4 LEC: FIXATION PT. 2 Flashcards

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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
10% Formol-Saline Fixation of?
Central Nervous Tissues
26
10% Formol-Saline What is used for histochemical examinations?
Post-Mortem tissues
27
10% Formol-Saline Fixation time at body temp (35)
24 hrs
28
10% Formol-Saline Fixation time at room temp (24-25)
48 hrs
29
Formaldehyde 40% Total volume
100mL
30
Formaldehyde 40% NaCl
9 gm
31
Formaldehyde 40% Distilled water
900 mL
32
This is used mainly for preservation and storage.
10% Neutral Buffered Formalin
33
10% Neutral Buffered Formalin Preservation and Storage of?
- Surgical - Post-mortem - Research
34
10% Neutral Buffered Formalin Fixation time
4-24 hours
35
10% Neutral Buffered Formalin Sodium dihydrogen phosphate
3.5gm
36
10% Neutral Buffered Formalin Disodium hydrogen phosphate
6.5 gm
37
10% Neutral Buffered Formalin Formaldehyde 40%
100 mL
38
10% Neutral Buffered Formalin Distilled water
900 mL
39
10% Neutral Buffered Formalin is the optimal choice for these reasons:
- 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
10% Neutral Buffered Formalin Fixative of choice for?
Immunohistochemistry and molecular tests
41
10% Neutral Buffered Formalin Disadvantages
- 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
10% Neutral Buffered Formalin Positivity of _____ to ____ is reduced
mucin, PAS
43
10% Neutral Buffered Formalin Produce gradual loss in?
basophilic staining
44
10% Neutral Buffered Formalin Reactivity of ________ to _______________ is reduced
myelin, Weigert's iron hematoxylin stain
45
10% Neutral Buffered Formalin It is inert towards lipids, especially?
neutral fats and phospholipids
46
This uses mercuric chloride as diluent.
Formol-Corrosive
47
Other name of Formol-Corrosive
Formol-Sublimate
48
Formol-Corrosive Diluent
Sat. Aq. Mercuric Chloride
49
Mercuric chloride can be used to demonstrate?
nerves
50
Formol-Corrosive Fixation time
3-24 hours
51
Formol-Corrosive Recommended for?
Routine Post-Mortem Tissues
52
Formol-Corrosive Brightens?
cytoplasmic and metachromic stains
53
T/F: Formol-Corrosive penetrates rapidly.
False slowly
54
Polymerized form of formaldehyde obtained as white powder
Paraformaldehyde
55
T/F: Paraformaldehyde can be depolymerized back when heated.
True
56
Paraformaldehyde Suitable for?
- paraffin embedding and sectioning - immunocytochemical analysis
57
Paraformaldehyde can be stained for?
general histology less vigorous ang degree of fixation than Bouin's, less morphology quality
58
This is a mixture of paraformaldehyde and glutaraldehyde.
Karnovsky's fixative
59
Karnovsky's fixative Sutaible for?
- light microscopy in resin embedding and sectioning - electron microscopy
60
Karnovsky's fixative This fixative should always be prepared?
fresh (on the spot)
61
Glutaraldehyde 2.5% solution
- small tissue fragments - needle aspirates
62
Glutaraldehyde 4% solution
larger tissues
63
Glutaraldehyde used for?
- Routine Light Microscopy - EM
64
Glutaraldehyde Advantages
- preserve cell structures better - less irritating to nose and skin
65
Glutaraldehyde Disadvantages
- expensive - less stable - slow penetration
66
Mechanism of Metallic Fixatives
Mercuric Chloride and Lead mercuric salts bind with sulfhydryl groups in acidic solutions
67

MT6321 HISTOPATH (15 decks)

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