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HSTCYT > LESSON 2: FIXATION > Flashcards

LESSON 2: FIXATION Flashcards

1
Q

✓ first and most critical step in tissue processing
✓ fixing or preserving fresh tissue for examination
✓ should be done immediately to preserve cellular and tissue morphology

A

FIXATION

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2
Q

primary purpose of fixation

A

Preservation

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3
Q

secondary purpose of fixation

A

Protection

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4
Q

✓ capable of forming cross-links between proteins
➢ stabilizes tissue components making them insoluble to lysosomal enzymes
✓ capable of inactivating lysosomes

A

Fixative agents

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5
Q

Types of Fixative that becomes part of the cross-link itself

A

Additive

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6
Q

Types of Fixative that facilitates the removal of water in order for cross-links to form

A

Non-Additive

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7
Q

FIXATIVE AGENTS ARE RETARDED BY:

A
  • Increase in size and thickness
  • Presence of mucus
  • Presence of fats
  • Presence of blood
  • Decrease in temperature
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8
Q

FIXATIVE AGENTS ARE ENHANCED BY:

A

✓ Decrease in size and thickness
✓ Presence of agitation
✓ Presence of heat

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9
Q

pH considered in FIXATIVE AGENTS

A

6 to 8

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10
Q

Temperature considered in Routine Manual Fixation

A

Room Temp (20 to 22oC)

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11
Q

Temperature considered in Routine Automated Fixation

A

40 oC

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12
Q

Temperature considered in Electron Microscopy Fixation

A

0 to 4oC

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13
Q

Temperature considered in Formalin at very urgent biopsies

A

Formalin at 60 oC or 60 oC

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14
Q

Temperature considered in Formalin for the diagnosis of tuberculosis

A

Formalin at 100 oC or 100 oC

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15
Q

Temperature considered in DNA Fixation

A

65 oC

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16
Q

Temperature considered in RNA Fixation

A

45 oC

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17
Q

Size and Thickness in Light Microscopy

A

2cm2 by 0.4cm thick

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18
Q

Size and Thickness in Electron Microscopy

A

1 to 2 mm2

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19
Q

Size and Thickness in Lung Edema

A

1 to 2 cm thick

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20
Q

Osmolality in Light microscopy

A

slightly

hypertonic (400-450 mOsm)

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21
Q

Osmolality in Electron Microscopy

A 
more or
less isotonic (340 mOsm)
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22
Q

Concentration of Formaldehyde

A

10%

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23
Q

Concentration of Glutaraldehyde

A

3%

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24
Q

Volume in Routine Fixation

A

10 to 25 times the

volume of the specimen

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25
Q

Volume in Museum Fixation

A

50 to 100 times the

volume of the specimen

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26
Q

On Tissue/Organ Preparations an MT must cover this with several layers of gauze

A

Air-filled Lungs

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27
Q

On Tissue/Organ Preparations an MT must: Dilate this with cotton soaked in fixative
and Completely open specimen

A

Hollow Organs

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28
Q

On Tissue/Organ Preparations an MT must: ✓ Fix this first before sampling
✓ Suspend it by a cord tied under the Circle of Willis
✓ Intravascular perfusion using Ringer’s lactate

A

Brain

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29
Q

On Tissue/Organ Preparations an MT must: ✓ Fixed it whole

✓ Inject it formol-alcohol

A

Eyes

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30
Q

On Tissue/Organ Preparations an MT must:

Do Lendrum’s Method: washed out with running water overnight and immersed in 4% aq. phenol solution for 1-3 days

A

Hard Tissues

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31
Q

On Tissue/Organ Preparations an MT must:
✓ Stretch this with sutures on each end
✓ Lay it in flat moist filter paper

A

Muscles

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32
Q
  1. Cheap & economical
  2. Stable and safe to handle
  3. Fast acting, permits rapid an even penetration
  4. Inhibits bacterial decomposition & autolysis
  5. Must harden tissues
  6. At least isotonic
  7. Must render tissues insensitive to subsequent processing
  8. Must be compatible with many staining procedures
A

CHARACTERISTICS OF A GOOD FIXATIVE

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33
Q

A TYPE OF FIXATIVES According to Composition made up of only one component substance

A

Simple Fixatives

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34
Q

A TYPE OF FIXATIVES According to Composition made up of two or more fixatives

A

Compound Fixatives

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35
Q

A TYPE OF FIXATIVES According to Action: permit general microscopic study of tissue structures and normal intercellular relationship of tissues

A

Microanatomical Fixatives:

36
Q

A TYPE OF FIXATIVES According to Action: preserve specific cellular components

A

Cytological Fixatives

37
Q

Under Cytological Fixatives this
✓ preserve nuclear structures
✓ contain glacial HAc
✓ pH 4.6 or less

A

Nuclear Fixatives

38
Q

▪ high affinity to nuclear chromatin

▪ destroys mitochondria and Golgi bodies

A

glacial HAc

39
Q

Under Cytological Fixatives this
✓ preserve cytoplasmic structures
✓ do not contain glacial HAc
✓ pH of more than 4.6

A

Cytoplasmic Fixatives

40
Q

preserve chemical constituents

A

Histochemical Fixatives

41
Q

Histochemical Fixatives for Lipids

A

mercuric chloride or potassium dichromate

42
Q

Histochemical Fixatives for Phospholipids

A

Baker’s formol-calcium

43
Q

Histochemical Fixatives for Cholesterol

A

digitonin

44
Q

Histochemical Fixatives for Carbohydrates

A

alcoholic fixatives

45
Q

Histochemical Fixatives for Glycogen

A

Rossman’s fluid or cold absolute alcohol

46
Q

Histochemical Fixatives for Proteins

A

neutral buffered formol saline or formaldehyde vapor

47
Q

Histochemical Fixatives for Electron microscopy

A

double fixation

48
Q

Mixture of Fixatives for Electron Cytochemistry

A

Karnovsky’s paraformaldehydeglutaraldehyde solution

49
Q

Mixture of Fixatives for Acrolein

A

mixture of glutaraldehyde or fomaldehyde

50
Q

✓ rapid penetration, preserves morphology and enzyme
activity at low concentrations
✓ immersion fixation of surgical biopsies

A

Acrolein

51
Q 
• 10% Formol saline
• 10% Neutral buffered
formalin
• Heidenhain’s SuSa
• Formol sublimate/corrosive
• Zenker’s solution
• Zenker-formol/Helly’s
solution
• Bouin’s solution
• Brasil’s solution
A

MICROANATOMICAL

52
Q
  • Heidenhain’s SuSa
  • Newcomer’s
  • Bouin’s
  • Flemming’s
  • Carnoy’s
A

CYTOLOGIC - NUCLEAR

53
Q 
• Helly’s
• Orth’s
• Regaud’s/Muller’s
• Flemming’s
• Formalin with
post-chroming
A

CYTOLOGIC - CYTOPLASMIC

54
Q
  • 10% Formol saline
  • Absolute ethanol
  • Newcomer’s
  • Acetone
A

HISTOCHEMICAL

55
Q

for routine paraffin sections, electron microscopy, histochemistry and
enzyme studies

A

ALDEHYDE FIXATIVES

56
Q

▪ gas produced by the oxidation of methyl alcohol
▪ buffered at ph 7 to 8
→ hypoxia in tissues leads to acidity which favors the formation of
Formalin heme pigments (black, polarizable deposits)
▪ Pure Stock: 40% formalin
▪ Dilution: 1:10 (10% solution); 1:20 (5% solution)
▪ Concentration for fixation: 10% formalin
▪ Paraformaldehyde: white precipitate due to prolonged storage
→ may be removed by filtration or addition of 10% methanol

A

maldehyde (Formalin)

57
Q

▪ central nervous tissues and general post-mortem tissues for histochemical
examination
▪ ideal with most stains including silver impregnation
▪ duration of fixation: more than 24 hours (slow fixative)

A

10% Formol-Saline

58
Q

▪ preservation and storage of surgical, post-mortem and research specimens
▪ best fixative for frozen sections
▪ best fixative for iron pigments and elastic fibers

A

10% Neutral Buffered Formalin

59
Q

▪ routine post-mortem tissues
▪ for lipids, especially neutral fats and phospholipids
▪ no need for washing-out

A

Formol-Corrosive

60
Q

▪ used to fix sputum

▪ for the demonstration of immunoperoxidase activity

A

Alcoholic Formalin

61
Q

▪ made up of two formaldehyde residues linked by three carbon chains
▪ used in conjunction with osmium tetroxide
▪ Fixation time: ½ hour to 2 hours

A

Glutaraldehyde

62
Q

✓ most common metallic fixative
✓ tissue photography
✓ tissues contain black precipitates of mercury (except Susa)

A

Mercuric Chloride

63
Q

✓ fixing small pieces of liver, spleen, connective tissues fibers and nuclei

A

Zenker’s Fluid

64
Q

removal of mercuric deposits in tissues

A

De-zenkerization

65
Q

✓ pituitary gland, bone marrow and blood containing organs (spleen and
liver)

A

Zenker-formol

66
Q

✓ for tumor biopsies

A

Heidenhain’s Susa Solution

67
Q

✓ for bone marrow biopsies

A

B-5 Fixative

68
Q

✓ preserves carbohydrates

A

Chromic Acid

69
Q

✓ preserves lipids and mitochondria

A

Potassium Dichromate

70
Q

✓ demonstration of chromatin, mitochondria, mitotic figures, Golgi bodies, RBC and colloid-containing tissues

A

Regaud’s Fluid

71
Q

✓ study of early degenerative processes and tissue necrosis

✓ demonstrates Rickettsia and other bacteria

A

Orth’s Fluid

72
Q

✓ demonstration of acid mucopolysaccharides

A

Lead Fixatives

73
Q

Picrates are soluble in water, therefore, tissues should not be washed in running tap
water (use 70% alcohol instead)

A

PICRIC ACID FIXATIVES

74
Q

✓ fixation of embryos and pituitary biopsies

A

Bouin’s Solution

75
Q

✓ fixative for glycogen

A

Brasil’s Alcoholic Picroformol Fixative

76
Q

✓ fixation of nucleoproteins

A

GLACIAL ACETIC ACID

77
Q

Preserves but does not “fix” glycogen granules

A

95 % Ethanol

78
Q

For dry and wet smears, blood and bone marrow samples

A

Methanol

79
Q

for touch preparations

A

Isopropyl alcohol (95%)

80
Q

▪ most rapid fixative
▪ for chromosomes, lymph glands, urgent biopsies and brain tissue for the
diagnosis of rabies

A

Carnoy’s fluid

81
Q

demonstration of mucopolysaccharides and nucleoproteins

A

Newcomer’s

82
Q

Permanently fixes fats and recommended for fixing nuclear structures

A

Flemming’s (chrome-osmium HAc)

83
Q

For cytoplasmic structures

A

Flemming’s w/o acetic acid

84
Q

may also be used as a weak decalcifying agent

A

TRICHLOROACETIC ACID

85
Q

✓ use at cold temperature (-5 to 4oC)

✓ fixation of brain tissues for rabies diagnosis

A

ACETONE

86
Q

Under ALDEHYDE FIXATIVES this is a Routinely used fixative

A

Formaldehyde

87
Q

Used for electron microscopy

A

Glutaraldehyde

HSTCYT (6 decks)

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