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Fixation Flashcards

1
Q

What does non-additive fixation means?

A

Fixing agent is not incorporated into the tissue

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2
Q

What does additive fixation means?

A

chemical constituent of the fixative is taken in and becomes part of the tissue

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3
Q

What is the mechanism of additive fixation?

A

forming cross-links or molecular complexes and giving stability to the protein

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4
Q

What is the mechanism of non-additive fixation?

A

Alters the tissue composition and stabilizes the tissue by removing the bound water attached to H-bonds of certain groups within the protein molecule

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5
Q

Fixation temperature for Electron Microscopy and Histochemistry

A

4°C

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6
Q

Fixation temperature using autotechnicon

A

40°C

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7
Q

Temperature for manual fixation

A

Room temperature

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8
Q

Penetration rate of formalin

A

1 mm/hr

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9
Q

Fixative volume for maximum effective fixation

A

20x the volume of the specimen

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10
Q

Enumerate the 5 NUCLEAR fixatives:

A

Carnoy’s
Bouin’s
Newcomer’s
Heidenhain’s Susa
Flemmings with HAc (Acetic acid)

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11
Q

Enumerate the 4 CYTOPLASMIC fixatives:

A

Regaud’s/Moller’s
Orth’s
Formalin with post chroming
Flemmings without HAc (Acetic acid)

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12
Q

How to make 1 Liter of 10% formalin?

A

100 ml of 37%-40% formalin + 900 ml distilled water

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13
Q

Disadvantage of formalin

A

Prolonged storing causes precipitation of formaldehyde to paraformaldehyde

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14
Q

Remedy to prevent the precipitation of formaldehyde

A

Add 10% methanol

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15
Q

Primary goal of fixation

A

Preserve tissue

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16
Q

Secondary goal of fixation

A

Hardens tissue
Protects tissue from trauma of further handling

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17
Q

Why do we need to achieve hardening of tissue?

A

To facilitate easy cutting of specimen into thin slices

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18
Q

Factors involved in fixation: (7)

A
  1. Correct size and thickness
  2. pH
  3. Osmolality
  4. Concentration of fixative
  5. Observe correct volume
  6. Time & duration
  7. Temperature
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19
Q

Factors to be considered when choosing the appropriate fixative: (5)

A
  1. Urgency of the case
  2. Type of tissue to be processed
  3. Tissue structure to be studied
  4. Staining technique
  5. Type of section to be studied
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20
Q

Factors that retard/slow fixation process: (4)

A
  1. Cold temperature
  2. Presence of blood and mucus
  3. Size and thickness of specimen
  4. Presence of Fats
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21
Q

Remedy for presence of blood and/or mucus in the tissue

A

Wash the tissue with NSS

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22
Q

Remedy for specimens with fats

A

Cut the specimen thinly to ensure rapid entry or penetration of fixative

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23
Q

Factors that accelerates fixation:

A
  1. Size and thickness
  2. Heat application
  3. Agitation
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24
Q

Problems encountered during fixation

A
  1. Loss of substances soluble in fixing agents
  2. Inadequate fixation
  3. Over fixation
  4. Presence of Artifacts
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25
Q

Ideal pH of fixative

A

pH 6-8

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26
Q

Ideal osmolality of fixative (by the book)

A

Slightly hypertonic

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27
Q

Ideal osmolality of fixative in real setting

A

Isotonic

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28
Q

Correct size and thickness of specimen

A

3x2 cm, 3-5mm thick

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29
Q

Recommended size for large specimens like lungs

A

1-2cm

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30
Q

Ratio of fixative volume to specimen

A

15-20:1

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31
Q

Which fixative must be 5-10x the volume of the specimen if used

a. Mercuric Chloride
b. Bouin’s
c. Formol Zenkers/Zenker’s formol
d. Osmium tetroxide

A

D. Osmium tetroxide

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32
Q

Formaldehyde/Formalin Fixatives (4)

A
  1. 10% formol saline
  2. 10% Neutral Buffered formalin
  3. Formol corrosive/Formol sublimate
  4. Alcoholic Formalin/Gendres
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33
Q

Classification of fixatives according to action/purpose that preserves cell parts

A

Cytological fixative

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34
Q

What are the 2 cytological fixative?

A
  1. Nuclear Fixatives
  2. Cytoplasmic fixatives
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35
Q

Classification of fixatives according to action/purpose that preserves tissues and cells in general

A

Microanatomical

36
Q

Classification of fixatives according to action/purpose that preserves chemicals

A

Histochemical

37
Q

Aldehyde fixatives under Formaldehyde/Formalin: (5)

A
  1. 10% Formalin
  2. 10% Formol Saline
  3. 10% Neutral Buffered Formalin
  4. Formol Corrosive/Formol Sublimate
  5. Alcoholic Formalin/Gendres
38
Q

Formaldehyde fixative that is routinely used

A

10% formalin

39
Q

Formaldehyde fixative that is used for CNS and post mortem tissues. NSS is used as diluent

A

10% formol saline

40
Q

Formaldehyde fixative that is used for tissues with iron pigments.

A

10% Neutral Buffered Formalin

41
Q

Composition of 10% Neutral Buffered Formalin

A

10% formalin + Sodium phosphate (buffer)

42
Q

Formaldehyde fixative that is best for lipids and neutral phospholipids

A

Formol corrosive/Formol sublimate

43
Q

Composition of formol sublimate

A

Formaldehyde + Mercuric chloride

44
Q

Formaldehyde fixative that is used for microincineration and sputum specimens

A

Alcoholic formalin/Gendres

45
Q

Composition of Gendres fixative

A

Formaldehyde + 95% Ethanol + Glacial HAc +Picric acid

46
Q

Aldehyde fixative that is used for Electron microscopy

A

Glutaraldehyde

47
Q

Amount of glutaraldehyde used for small tissue fragments/needle biopsies

A

2.5% Glutaraldehyde

48
Q

Amount of glutaraldehyde used for larger tissues less than 4mm thick

49
Q

Aldehyde fixative that is the smallest aldehyde

50
Q

Aldehyde fixatives: (3)

A
  1. Formaldehyde/Formalin
  2. Glutaraldehyde
  3. Glyoxal
51
Q

Metallic Fixatives: (3)

A
  1. Mercuric Chloride Fixatives
  2. Chromate Fixatives
  3. Lead fixatives
52
Q

Most common metallic fixative

A

Mercuric Chloride

53
Q

Metallic fixative that is excellent for Trichrome staining & tissue photography

A

Mercuric Chloride

54
Q

How do you remove excess mercuric fixatives:

A

Wash using alcoholic iodine

55
Q

Disadvantage of mercuric chloride fixative

A

Toxic and leaves excess black mercury deposit

56
Q

Mercuric chloride fixative that is used for liver, spleen, connective tissues and nuclei

A

Zenker’s Fluid

57
Q

Mercuric chloride fixative that is used for bone marrow

58
Q

Mercuric chloride fixative that is used for tumor skin biopsies

A

Heidenhain’s Susa

59
Q

Mercuric chloride fixative that is used for pituitary gland, bone marrow, spleen, and liver

A

Helly’s Fluid/Zenker Formol

60
Q

Substitute for mercuric chloride but is also toxic

A

Zinc sulfate

61
Q

Mercuric Chloride fixatives: (5)

A
  1. Zenker’s fluid
  2. B5
  3. Heidenhain’s susa
  4. Helly’s fluid/Zenker formol
  5. Zinc sulfate
62
Q

Chromate fixatives: (4)

A
  1. 1-2% Chromic acid
  2. 3% Potassium Dichromate
  3. Regaud’s Fluid/Moeller’s
  4. Orth’s fluid
63
Q

Chromate fixative that is used for carbohydrate

A

1-2% Chromic acid

64
Q

Chromate fixative that is used for lipids and mitochondria

A

3% Potassium Dichromate

65
Q

Chromate fixative that is used for mitochondria, RBC, colloid containing tissues

A

Regaud’s Fluid/Moeller’s

66
Q

Chromate fixative that is used for Ricketssiae & other bacteria, tissue necrosis

A

Orth’s fluid

67
Q

Metallic fixative that is used for Acid mucopolysaccharides and tissue mucin

A

Lead fixative

68
Q

Fixative that is excellent for glycogen demonstration

A

Picric acid fixative

69
Q

Three (3) uses of Picric acid

A
  1. Fixative
  2. Decalcifying agent
  3. Stain
70
Q

Fixative that imparts yellow color

A

Picric acid

71
Q

This is used to wash out excess amount of picric acid fixative

A

50-70% alcohol

72
Q

Picric acid fixative: (3)

A
  1. Bouin’s fluid
  2. Brasil’s
  3. Hollande’s
73
Q

Picric acid fixative that is used for for embryos, pituitary biopsies, and endometrial curetting

A

Bouin’s fluid

74
Q

Picric acid fixative that is not recommended for kidney structures and not compatible with Feulgen’s stain

A

Bouin’s fluid

75
Q

Picric acid fixative that is excellent for glycogen

A

Brasil’s

76
Q

Picric acid fixative that is used for gastrointestinal tract biopsies and endocrine tissues

A

Hollande’s

77
Q

Alcohol fixatives: (3)

A
  1. 95% Isopropyl Alcohol
  2. Carnoy’s
  3. Newcomer’s
78
Q

Alcohol fixative that is used for touch preparations

A

95% isopropyl alcohol

79
Q

Alcohol fixative that is the most rapid ftissue ixative

A

Carnoy’s

80
Q

Alcohol fixative that is used for chromosomes, lymph glands, and brain tissues

A

Carnoy’s

81
Q

Alcohol fixative that aids in rabies diagnosis together with acetone

A

Carnoy’s

82
Q

Alcohol fixative that is used for mucopolysaccharides and nuclear protein

A

Newcomer’s

83
Q

Uses of Acetone: (2)

A
  1. Fixative
  2. Dehydrating Agent
84
Q

Fixative that is used for phosphatases, lipases, and brain tissues

85
Q

Fixative that must be used at ice cold temperature

86
Q

Fixative that easily evaporates and dissolves fat

87
Q

Fixative that is used for electron microscopy and used for myelin and peripheral nerves

A
  1. Osmium Tetroxide
  2. Glutaraldehyde
  3. Paraformaldehyde

histoopaathh (7 decks)

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