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FIXATION Flashcards

1
Q

most critical step in routine histopathology

A

fixation

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2
Q

goals of fixation

A
  1. preserve morphological and chemical integrity of the cell

2. harden and preserve tissue

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3
Q

action of fixatives

A
  1. preserves the tissue by stopping all cellular activities

2. prevent autolysis by inactivating lysosomal enzymes

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4
Q

fixation pH

A

6-8

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5
Q

fixation osmolality

A

slightly hypertonic

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6
Q

fixation rate of penetration

A

1 mm/hour

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7
Q

rapid fixation temp

A

60 C

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8
Q

routine histopath fixation temp

A

22-25 C

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9
Q

electron microscopy and histochem fixation temp

A

0-4 C

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10
Q

autotechnicon fixation temp

A

40 C

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11
Q

tb patients fixation temp

A

100 C

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12
Q

mercury refrigerator fixation temp

A

4 C

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13
Q

buffered formalin duration

A

2-6 hours

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14
Q

electron microscopy duration

A

3 hours

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15
Q

hastens fixation

A

small and loose tissues, agitation, heat, microwave, vacuum

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16
Q

retards fixation

A

fibrous tissues, blood, mucus, fats, and cold temp

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17
Q

routine histopath fixation volume

A

10-20x of the tissue

usually, 20:1

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18
Q

expensive fixation volume

A

5-10x of the tissue

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19
Q

museum fixation volume

A

50x of the tissue

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20
Q

brain special consideration (spc)

A
  1. tied at the circle of willis

2. fixed for 2-3 weeks in 10% neutral buffered formalin

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21
Q

large solid tissues (uterus) spc

A

cut open and sliced thinly

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22
Q

hollow organs spc

A

place cotton inside or open organs entirely

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23
Q

air filled lungs spc

A

covered with gauze

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24
Q

eyes spc

A

fixative is injected

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25
Q

hard tissues (nails) spc

A

immersed in tissue softeners

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26
Q

fixative that forms cross-links with the tissue

A

additive fixatives

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27
Q

fixative that removes water in the tissue

A

alcoholic/dehydrating agents

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28
Q

cytological fixative that preserves nucleus and chromatin. also contains glacial acetic acid

A

nuclear fixative

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29
Q

cytological fixative that preserves membrane bound organelles. should not contain glacial acetic acid.

A

cytoplasmic fixative

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30
Q

cytological fixative that preserves biochemical components (fats, enzymes).

A

histochemical

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31
Q 
microanatomical fixative (7)
1010 hfb zb
A 
10% formol saline
10% BNF
heidenhain's susa
formol sublimate
bouin's
zenker's
brasil's
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32
Q 
nuclear fixative (5)
fch nb
A 
flemming's
carnoy's
heidenhain's susa
newcomer's
bouin's
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33
Q

cytoplasmic (5)

fk fro

A 
flemming's w/o hoac
helly's
formalin
regaud's (moller's)
orth's
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34
Q

histochemical (4)

10 aan

A

10% formol saline
absolute ethanol
acetone
newcomer’s

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35
Q

fixation of CNS tissue, post-mortem tissues, and silver impregnation techniques

A

10% formol saline

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36
Q

routine histopath fixative, also for tissues with iron pigments and elastic fibers

A

10% BNF

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37
Q

fixative for silver reticulin methods and post-mortem tissues

A

formol sublimate

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38
Q

fixative for glycogen and sputum

A

alcohol formalin (gendre’s fixative)

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39
Q

fixative for enzyme histochem and electron microscopy, has 2 concs

A

glutaraldehyde

2.5% - small tissue fragments and needle biopsy
4% - larger tissue specimens

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40
Q

aldehyde fixative for ultrathin sections

A

paraformaldehyde

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41
Q

most common metallic fixative

A

mercuric chloride

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42
Q

process where we remedy black granule ppts from metallic fixatives

A

dezenkerization

43
Q

dezenkerization solution

A

96% alcohol and 5% sodium thiosulfate

44
Q

fixative of choice for cell detail preservation and tissue photography; permits brilliant metachromatic staining of cells

A

mercuric chloride

45
Q

fixative for small pieces of liver, spleen, and nuclei

A

zenker’s

46
Q

fixative for pituitary gland, bone marrow, and blood containing organs

A

helly’s / zenker’s formol

47
Q

fixative for skin tumor biopsy

A

heidenhain’s susa

susa:
Sublimat - mercuric chloride
Saure - acid

48
Q

fixative for bone marrow biopsies

A

B5 fixative

49
Q

this fixative is carcinogenic and used for carbohydrate preservation

A

chromate fixatives

50
Q

fixative for lipid and mitochondria demonstration

A

potassium dichromate

51
Q

fixative for golgi bodies and colloid containing tissues

A

regaud’s

52
Q

fixative for rickettsia demonstration, tissue necrosis, and myelin preservation

53
Q

forms lead carbonate precipitate and for acid mucopolysaccharides and mucins preservation

A

lead fixatives

54
Q

fixative that is explosive in dry forms, can also be used as a decalcifying agent

A

picric acid fixatives

55
Q

major disadvantage of picric acid fixative

A

yellow stain

56
Q

remedy for the major disadvantage of picric acid fixative

A

wash the tissue with 50-70% alcohol

57
Q

excellent fixative for glycogen and small tissue fragments

A

picric acid fixative

58
Q

true or false. since picric acid imparts a stain, this may also be used as a stain.

59
Q

fixative for embryo and pituitary biopsies

60
Q

fixative for glycogen

A

picroformol fixative

61
Q

fixative for GIT samples and endocrine tissues, has decalcifying properties too

A

hollande’s

62
Q

preferred fixative among all picric acid fixatives

A

picroformol fixative

63
Q

fixative that rapidly denatures and ppts protein

A

alcoholic fixatives

64
Q

fixative for dry and wet blood/blood marrow smears

disadv: can cause blindness

65
Q

fixative for touch preparation

A

isopropanol

66
Q

fixative for PCR, used for cytological smears (Pap smear, 95% ethanol), cant fix glycogen

67
Q

most rapid fixative (1-3 hrs)

A

carnoy’s

68
Q

fixative for chromosome, lymph nodes, brain tissue for rabies dx, and urgent biopsies

A

carnoy’s

69
Q

fixative for nuclear, histochemical, and biochemical

70
Q

fixative of choice for ultrathin sectioning

A

osmium tetroxide

71
Q

most common chrome-osmium acetic acid fixative,

excellent fixative for nuclear structures

A

flemming’s

72
Q

fixative that precipitates nucleoproteins and chromatin material

A

glacial acetic acid fixatives

73
Q

fixative for rabies dx and preservation of water-diffusible enzymes (lipases and phosphatases)

A

acetone fixatives

74
Q

fixation method for bacteriologic smears

A

heat fixation

75
Q

rapid physical method of fixation, demonstration of neurochemical substances in the brain (acetylcholine)

A

microwave fixation

76
Q

tissue is fixed on another fixative

A

secondary fixation

77
Q

secondary fixation using 2.5-3% potassium dichromate for 1 day

A

post chromatization

78
Q

ideal time to perform fixation:

A

within 20-30 mins

79
Q

most important reaction for maintaining tissue morphology

A

stabilization of proteins

80
Q

additive fixatives examples:

A

formalin, mercury, osmium tetroxide

81
Q

nonadditive fixatives examples:

A

alcoholic agents

82
Q

electron microscopy section thickness

83
Q

light microscopy section thickness

A

2 cm^2

not > 0.4 cm

84
Q

simple fixative example:

A

glacial acetic acid

solidification temp: 17 C

85
Q

compound fixative example:

A

zenker’s solution
2 major parts:
-mercuric chloride: shrinks tissue
-glacial acetic acid: swells tissue

86
Q

kind of fixatives that is used for general microscopic study

A

microanatomical fixatives

87
Q

kind of fixative that fixes specific parts of the cell

A

cytological fixatives

88
Q

usual fixation time for formalin

89
Q

formalin is produced from?

A

a gas produced by the oxidation of methanol

90
Q

stock solution, tends to overharden the outer surface of the tissue.
not meant to be used as fixative

A

40% formalin

91
Q

working solution (unstable, may produce artefacts)

A

10% formalin

92
Q

10% formalin artefacts:

white precipitates that may form after prolonged standing of solution at low temp

A

paraformaldehyde

93
Q

how to remove paraformaldehyde artifact?

A
  • filtration

- add 10% methanol

94
Q

10% formalin artefacts:

brown or black granules that may obscure microscopic details

A

acid formaldehyde hematin

95
Q

how to remove acid formaldehyde hematin

A
  • kardasewitsch method
  • lillie’s method
  • saturated alcoholic picric acid*
  • alcoholic KOH*
96
Q

fixative for lipids

A

formol-calcium

97
Q

fixative for electron cytochemistry

A

acrolein and kpg (karnovsky’s)

98
Q

disadvantage of using mercuric chloride:

A
  • causes tissue to shrink
  • decreases amount of demonstrable glycogen
  • corrodes all metals, except for nickel alloy
  • produces black granular deposits
99
Q

type of fixative that is generally recommended for glycogen

A

alcoholic fixatives

100
Q

disadvantage of using alcoholic fixatives

A

polarization (movement of glycogen granules towards the ends or poles of the cells)

101
Q

this fixative inhibits hematoxylin

A

osmium tetroxide

102
Q

storage conditions for osmium tetroxide

A

keep in a dark colored bottle to prevent evaporation

103
Q

both fixative and decalcifying agent

A

trichloroacetic acid

104
Q

fixative that is used at ice cold temp (-5 to 4 C)

Histopathology (11 decks)

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