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GenPath Lab > Fixation > Flashcards

Fixation Flashcards

1
Q

What is the first step in histotechnology?

A

Fixation

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2
Q

What does fixation prevent?

A

Autolysis and putrefaction

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3
Q

Is fixation a reversible process?

A

No, it’s irreversible

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4
Q

What does fixation preserve?

A

Morphologic and chemical integrity

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5
Q

When should fixation be carried out?

A

As soon as possible after tissue removal

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6
Q

What does autolysis result from?

A

Intracellular enzymes release

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7
Q

What causes bacterial decomposition?

A

Microorganisms present

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8
Q

What is ischemia?

A

Reduced blood flow

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9
Q

What improves tissue preservation?

A

Early fixation

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10
Q

What are the two basic mechanisms involved in fixation?

A

Additive and Non-Additive

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11
Q

What does additive fixation do?

A

Forms cross-links

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12
Q

Examples of additive fixatives?

A

Formalin, Mercury, Osmium

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13
Q

What happens to improperly fixed tissues?

A

Poor staining and cutting

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14
Q

What is the importance of Acidity?

A

Formation of black, polarizable deposits in tissue

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15
Q

What is the ideal temperature for electron microscopy workouts?

A

0-4℃

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16
Q

What is a disadvantage of using Formalin at 60℃?

A

Increased risk of tissue distortion

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17
Q

What is the ideal thickness of a tissue block for electron microscopy?

A

1-2 mm2

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18
Q

What is the usual concentration of Formaldehyde solution used?

A

0.1

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19
Q

What is the usual duration of primary fixation in buffered formalin?

A

2-6 hours

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20
Q

How can the activity of some enzymes be restored after fixation?

A

Washing in running water

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21
Q

What is formaldehyde?

A

Fixative

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22
Q

What is glutaraldehyde?

A

Fixative

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23
Q

What is a metallic fixative?

A

Contains mercury, chromium, or lead

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24
Q

What is a compound fixative?

A

Made of two or more fixatives

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25
Q

What is the primary component of nuclear fixatives?

A

Glacial acetic acid

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26
Q

What pH do nuclear fixatives typically have?

A

4.6 or less

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27
Q

Name examples of nuclear fixatives.

A

Flemming’s, Carnoy’s, Bouin’s, Newcomer’s, Heidenhain’s Susa

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28
Q

Examples of lipid fixation agents?

A

Formal Saline 10%, Absolute Ethyl Alcohol, Acetone

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29
Q

What should be used to demonstrate lipids in tissues?

A

Cryostat or frozen sections

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30
Q

Effective fixative for lipid preservation?

A

Mercuric chloride and potassium dichromate

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31
Q

Which fixatives fix phospholipids?

A

Aldehydes

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32
Q

Post-fixing for improved lipid demonstration?

A

Imidazole osmium tetroxide

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33
Q

Fixative for cholesterol demonstration?

A

Digitonin

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34
Q

Recommended fixatives for glycogen?

A

Alcoholic fixatives

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35
Q

Better fixative in human skin for glycogen?

A

Alcoholic formaldehyde

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36
Q

Common fixatives for protein histochemistry?

A

Neutral buffered formol saline, formaldehyde vapor

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37
Q

Best fixatives for glycogen retention?

A

Rossman’s fluid, Cold absolute alcohol

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38
Q

Enhancement method for glycogen retention?

A

Celloidin coating

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39
Q

Useful mixture for electron cytochemistry?

A

Karnovsky Paraformaldehyde-glutaraldehyde

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40
Q

What is an optimal preservative that stabilizes cellular proteins?

A

Acrolein

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41
Q

Which fixative is most widely used?

A

10% formalin

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42
Q

What are aldehyde fixatives used for?

A

Routine paraffin sections

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43
Q

What is a pro of the fixative regarding tissue stability?

A

Stable in buffered solutions

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44
Q

What does the fixative preserve without precipitating?

A

Proteins

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45
Q

What is a con of the fixative related to tissue?

A

Can cause significant shrinkage

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46
Q

Why is the fixative recommended for nervous tissue preparation?

A

Does not make tissue brittle

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47
Q

Does the fixative overhard tissues?

A

No

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48
Q

Effect of unbuffered fixation

A

Reduces cell staining quality

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49
Q

Unbuffered fixation effects on blood tissues

A

Forms brown pigment granules

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50
Q

Consequences of prolonged fixation

A

Bleaching and loss of tissue colors

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51
Q

What is B. 10% Formol Saline?

A

Microanatomical fixative

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52
Q

Components of B. 10% Formol Saline?

A

40% Formaldehyde + NaCl + Distilled water

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53
Q

Recommended fixation time at 35 ℃?

A

24 hours

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54
Q

Pros of B. 10% Formol Saline?

A

Even penetration, preserves details

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55
Q

Cons of B. 10% Formol Saline?

A

Slow, tissue shrinkage

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56
Q

How does the tissue composition stabilize?

A

removing the bound water attached to H-bonds

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57
Q

What is the name of the alcohol fixative that is best carried out close to neutral pH?

A

Hydrogen Ion Concentration

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58
Q

What does increase the optical differentiation of cells and tissue components thereby rendering them more readily visible during examination?

A

inhibit bacterial decomposition

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59
Q

What destroys mitochondria and golgi bodies?

A

ntain glacial acetic acid

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60
Q

For what type of organism does precipitant fixatives ethanol and acetone give the best quantitative results using frozen tissues as the standard B.1.4

A

RNA

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61
Q

What do precipitant fixatives give the best quantitative results using frozen tissues as the standard B.1.4 Histochemical Fixatives?

A

ethanol and acetone

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62
Q

Formaldehyde is usually buffered to pH 7 with what?

A

phosphate buffer

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63
Q

What stains less brightly C. 10% Neutral Buffered Formalin or Phosphate Buffered Formalin?

A

acid dye

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64
Q

What are the pros of using the fixative?

A

Cheap, stable, compatible

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65
Q

What does the fixative preserve?

A

Fat, mucin, glycogen

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66
Q

What is a con of the fixative?

A

Causes allergic dermatitis

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67
Q

How does the fixative affect tissue?

A

May produce shrinkage

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68
Q

Why is the fixative recommended for nervous tissue?

A

Does not make brittle

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69
Q

Effect of unbuffered fixation on staining

A

Reduces basophilic and eosinophilic staining

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70
Q

Brown pigment granules formation cause

A

Blackening of hemoglobin

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71
Q

Consequences of prolonged fixation

A

Bleaching, color loss, fat dispersal

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72
Q

What is B. 10% Formol Saline made of?

A

40% Formaldehyde + NaCl + Distilled water

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73
Q

What is the recommended fixation time for B. 10% Formol Saline at 35 ℃?

A

24 hours

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74
Q

What are the main advantages of B. 10% Formol Saline?

A

Even penetration, minimal distortion

75
Q

What is a disadvantage of B. 10% Formol Saline?

A

Slow fixative

76
Q

What type of tissues is B. 10% Formol Saline recommended for?

A

Central nervous tissues

77
Q

What does the Formol-Corrosive fixative contain?

A

Mercuric chloride + Formaldehyde

78
Q

What is a pro of Formol-Corrosive fixative?

A

Minimal shrinkage and hardening

79
Q

What is a con of Formol-Corrosive fixative?

A

Slow penetration

80
Q

What are the components of Alcoholic Formalin (Gendre’s) Fixative?

A

95% ethyl alcohol, Formaldehyde, Glacial acetic acid

81
Q

What is a pro of Alcoholic Formalin?

A

Faster fixation

82
Q

What is a con of Alcoholic Formalin?

A

Gross hardening of tissues

83
Q

How is Glutaraldehyde composed?

A

2 formaldehyde residues linked by 3 carbon chains

84
Q

What is a pro of Glutaraldehyde over Formalin?

A

More stable effect on tissues

85
Q

Most common metallic fixative?

A

Mercuric Chloride

86
Q

Mercuric Chloride main issue with tissues?

A

Shrinkage

87
Q

Treat mercury deposits with?

A

0.5% iodine solution

88
Q

Mercuric Chloride tissue brightness?

A

Excellent trichrome staining

89
Q

Key advantage of Mercuric Chloride?

A

Preserves cell detail

90
Q

Consistency issue of fixed tissues?

A

Hard and brittle

91
Q

Mercuric Chloride Stock Solution ingredients?

A

Mercuric chloride, Potassium dichromate, Sodium sulfate, Distilled water

92
Q

Zenker’s Fluid key additive?

A

Glacial Acetic Acid

93
Q

Optimal fixation time for Zenker’s Fluid?

A

12-24 hours

94
Q

Zenker’s Fluid fixation quality?

A

Rapid and even

95
Q

Initial step to dezenkerize?

A

Water – 5 min

96
Q

How long to immerse in Lugol’s iodine?

A

5 min

97
Q

Zenker-Formol fixation time?

A

12-24 hours

98
Q

Components of Zenker-Formol?

A

Mercuric chloride, formaldehyde

99
Q

Pros of Zenker-Formol?

A

Excellent for pituitary

100
Q

Cons of Zenker-Formol?

A

Brown pigments, RBC lysis

101
Q

Main use of Heidenhain’s Susa?

A

Tumor biopsies

102
Q

What are the components of Heidenhain Susa fixative?

A

Mercuric chloride, Sodium chloride, Trichloroacetic acid, Glacial acetic acid, 40% Formaldehyde, Distilled water

103
Q

What is the fixation time for Heidenhain Susa fixative?

A

3-12 hours

104
Q

What is a pro of Heidenhain Susa fixative?

A

Rapid and even fixation

105
Q

What is a con of Heidenhain Susa fixative?

A

Poor RBC preservation

106
Q

What should be done after using Heidenhain Susa fixative?

A

Transfer to high-grade alcohol

107
Q

What is B-5 fixative used for?

A

Bone marrow biopsies

108
Q

What are the components of B-5 fixative?

A

Distilled water, Mercuric chloride, Anhydrous sodium acetate

109
Q

What is the fixation time for B-5 fixative?

A

1-2 hours

110
Q

What is a pro of B-5 fixative?

A

Rapid fixation

111
Q

What is a con of B-5 fixative?

A

Overfixation makes cutting difficult

112
Q

What is the main component of Regaud’s (Muller) Fluid?

A

Potassium dichromate & Formaldehyde

113
Q

What is Regaud’s fluid recommended for?

A

Chromatin, mitochondria, etc.

114
Q

What is a disadvantage of both Regaud’s Fluid and Orth’s Fluid?

A

Same as Regaud’s fluid

115
Q

What tissue structures does Orth’s Fluid preserve better than buffered formalin?

A

Myelin

116
Q

What happens to lead fixatives on prolonged staining?

A

Insoluble lead carbonate forms

117
Q

Which fixative dyes tissues yellow?

A

Picric acid fixative

118
Q

What can remove the color in the tissue?

A

Another acid dye or lithium carbonate

119
Q

What are the advantages of the fixative?

A

Glycogen demonstration, rapid fixation

120
Q

What are the disadvantages of the fixative?

A

Causes RBC hemolysis, not suitable for frozen tissues

121
Q

What may produce excessive staining?

A

Picric acid

122
Q

What stains less brightly C. 10% Neutral Buffered Formalin or Phosphate Buffered Formalin?

A

acid dye

123
Q

Does not cause what?

A

dermatitis

124
Q

What is the result of a prolonged fixation of Acetic Acid?

A

brittle and hard

125
Q

How long should tissue be washed with running water before processing?

A

several hours

126
Q

What method is highly explosive when dry Alters and dissolves lipids?

A

Interferes with Azure eosin

127
Q

When dry Alters and dissolves lipids Interferes with Azure eosin method?

A

Highly explosive

128
Q

Regaud’s Fluid components?

A

Potassium dichromate 3% + 40% Formaldehyde

129
Q

Regaud’s Fluid fixation time?

A

12-48 hours

130
Q

Pros of Regaud’s Fluid?

A

Penetrates well, hardens rapidly

131
Q

Cons of Regaud’s Fluid?

A

Deteriorates, poor glycogen penetration

132
Q

Orth’s Fluid components?

A

Potassium dichromate + Sodium sulfate + Formaldehyde

133
Q

Orth’s Fluid fixation time?

A

36-72 hours

134
Q

Pros of Orth’s Fluid?

A

Good for tissue necrosis, preserves myelin

135
Q

Lead fixatives used in?

A

4% aqueous solution of basic lead acetate

136
Q

Pros of Lead fixatives?

A

Recommended for acid mucopolysaccharides

137
Q

Picric acid fixative used in?

A

Strong saturated aqueous solution

138
Q

What can remove the yellow color from tissue?

A

Washing with ethanol

139
Q

What is a major advantage of this fixative?

A

Excellent for glycogen demonstration

140
Q

What causes RBC hemolysis?

A

Cons of the fixative

141
Q

What is a stable fixative’s benefit?

A

Precipitates all proteins

142
Q

What does picric acid produce?

A

Excessive staining

143
Q

Bouin’s Solution components?

A

Picric acid, Formaldehyde, Acetic Acid

144
Q

Bouin’s Solution fixation time?

A

6-24 hours

145
Q

Bouin’s Solution pros?

A

Minimal distortion

146
Q

Bouin’s Solution cons?

A

Poor penetration

147
Q

Brasil’s Fixative components?

A

Formaldehyde, Picric Acid, Alcohol, Trichloroacetic acid

148
Q

Glacial Acetic Acid pros?

A

Precipitates nucleoproteins

149
Q

Glacial Acetic Acid cons?

A

Destroys mitochondria

150
Q

Alcoholic Fixatives concentration?

A

70-100%

151
Q

Alcoholic Fixatives pros?

A

Preserves nuclear stains

152
Q

Methyl Alcohol use?

A

Fixing smears

153
Q

What is the fixation time for Ethyl Alcohol?

A

18-24 hours

154
Q

What is Carnoy’s Fluid primarily used for?

A

Fixing chromosomes

155
Q

What components make up Carnoy’s Fluid?

A

Absolute alcohol, Chloroform, Glacial acetic acid

156
Q

What is the fixation time for Carnoy’s Fluid?

A

1-3 hours

157
Q

What is a significant pro for Newcomer’s Fluid?

A

Better reaction in Feulgen stain

158
Q

What is the major drawback of Osmium Tetroxide?

A

Very expensive

159
Q

What is the common use of Flemming’s Solution?

A

Chrome-osmium acetic acid fixative

160
Q

What is the fixation time for Flemming’s Solution?

A

24-48 hours

161
Q

Flemming Solution pros

A

Excellent fixative

162
Q

Flemming Solution cons

A

Poor penetration

163
Q

Trichloroacetic acid pros

A

Precipitates proteins

164
Q

Trichloroacetic acid cons

A

Poor penetration

165
Q

Acetone use

A

Ice cold temp

166
Q

Acetone pros

A

Study enzymes

167
Q

Acetone cons

A

Evaporates rapidly

168
Q

Heat fixation pros

A

Better fixation

169
Q

Heat fixation cons

A

Tissue shrinkage

170
Q

Secondary fixation purpose

A

Improves staining

171
Q

Post chromatization purpose

A

Better staining

172
Q

What is washing out?

A

Removing excess fixative

173
Q

How does tap water affect tissue fixation?

A

Removes excess chromates

174
Q

What fixative does 50-70% alcohol wash out?

A

Bouin’s solution

175
Q

What does alcoholic iodine remove?

A

Excessive mercuric fixatives

176
Q

What factor slows down tissue fixation?

A

Size and thickness

177
Q

What does excess mucus prevent?

A

Complete penetration of fixative

178
Q

How should fatty tissues be handled?

A

Cut in thin sections

179
Q

What should be done with blood before fixing tissues?

A

Flush with saline

180
Q

How does temperature affect enzyme activity?

A

Cold inactivates enzymes

181
Q

What enhances the fixation process?

A

Agitation

182
Q

How does moderate heat affect fixation?

A

Accelerates but hastens autolysis

183
Q

How many fficults can Isopropyl Alcohol cut?

A

2

184
Q

Isopropyl Alcohol 95% Used for fixing what?

A

touch preparations

GenPath Lab (5 decks)

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