Fixation Flashcards
(184 cards)
1
Q
What is the first step in histotechnology?
A
Fixation
2
Q
What does fixation prevent?
A
Autolysis and putrefaction
3
Q
Is fixation a reversible process?
A
No, it’s irreversible
4
Q
What does fixation preserve?
A
Morphologic and chemical integrity
5
Q
When should fixation be carried out?
A
As soon as possible after tissue removal
6
Q
What does autolysis result from?
A
Intracellular enzymes release
7
Q
What causes bacterial decomposition?
A
Microorganisms present
8
Q
What is ischemia?
A
Reduced blood flow
9
Q
What improves tissue preservation?
A
Early fixation
10
Q
What are the two basic mechanisms involved in fixation?
A
Additive and Non-Additive
11
Q
What does additive fixation do?
A
Forms cross-links
12
Q
Examples of additive fixatives?
A
Formalin, Mercury, Osmium
13
Q
What happens to improperly fixed tissues?
A
Poor staining and cutting
14
Q
What is the importance of Acidity?
A
Formation of black, polarizable deposits in tissue
15
Q
What is the ideal temperature for electron microscopy workouts?
A
0-4℃
16
Q
What is a disadvantage of using Formalin at 60℃?
A
Increased risk of tissue distortion
17
Q
What is the ideal thickness of a tissue block for electron microscopy?
A
1-2 mm2
18
Q
What is the usual concentration of Formaldehyde solution used?
A
0.1
19
Q
What is the usual duration of primary fixation in buffered formalin?
A
2-6 hours
20
Q
How can the activity of some enzymes be restored after fixation?
A
Washing in running water
21
Q
What is formaldehyde?
A
Fixative
22
Q
What is glutaraldehyde?
A
Fixative
23
Q
What is a metallic fixative?
A
Contains mercury, chromium, or lead
24
Q
What is a compound fixative?
A
Made of two or more fixatives
25
What is the primary component of nuclear fixatives?
Glacial acetic acid
26
What pH do nuclear fixatives typically have?
4.6 or less
27
Name examples of nuclear fixatives.
Flemming's, Carnoy's, Bouin's, Newcomer's, Heidenhain's Susa
28
Examples of lipid fixation agents?
Formal Saline 10%, Absolute Ethyl Alcohol, Acetone
29
What should be used to demonstrate lipids in tissues?
Cryostat or frozen sections
30
Effective fixative for lipid preservation?
Mercuric chloride and potassium dichromate
31
Which fixatives fix phospholipids?
Aldehydes
32
Post-fixing for improved lipid demonstration?
Imidazole osmium tetroxide
33
Fixative for cholesterol demonstration?
Digitonin
34
Recommended fixatives for glycogen?
Alcoholic fixatives
35
Better fixative in human skin for glycogen?
Alcoholic formaldehyde
36
Common fixatives for protein histochemistry?
Neutral buffered formol saline, formaldehyde vapor
37
Best fixatives for glycogen retention?
Rossman’s fluid, Cold absolute alcohol
38
Enhancement method for glycogen retention?
Celloidin coating
39
Useful mixture for electron cytochemistry?
Karnovsky Paraformaldehyde-glutaraldehyde
40
What is an optimal preservative that stabilizes cellular proteins?
Acrolein
41
Which fixative is most widely used?
10% formalin
42
What are aldehyde fixatives used for?
Routine paraffin sections
43
What is a pro of the fixative regarding tissue stability?
Stable in buffered solutions
44
What does the fixative preserve without precipitating?
Proteins
45
What is a con of the fixative related to tissue?
Can cause significant shrinkage
46
Why is the fixative recommended for nervous tissue preparation?
Does not make tissue brittle
47
Does the fixative overhard tissues?
No
48
Effect of unbuffered fixation
Reduces cell staining quality
49
Unbuffered fixation effects on blood tissues
Forms brown pigment granules
50
Consequences of prolonged fixation
Bleaching and loss of tissue colors
51
What is B. 10% Formol Saline?
Microanatomical fixative
52
Components of B. 10% Formol Saline?
40% Formaldehyde + NaCl + Distilled water
53
Recommended fixation time at 35 ℃?
24 hours
54
Pros of B. 10% Formol Saline?
Even penetration, preserves details
55
Cons of B. 10% Formol Saline?
Slow, tissue shrinkage
56
How does the tissue composition stabilize?
removing the bound water attached to H-bonds
57
What is the name of the alcohol fixative that is best carried out close to neutral pH?
Hydrogen Ion Concentration
58
What does increase the optical differentiation of cells and tissue components thereby rendering them more readily visible during examination?
inhibit bacterial decomposition
59
What destroys mitochondria and golgi bodies?
ntain glacial acetic acid
60
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
RNA
61
What do precipitant fixatives give the best quantitative results using frozen tissues as the standard B.1.4 Histochemical Fixatives?
ethanol and acetone
62
Formaldehyde is usually buffered to pH 7 with what?
phosphate buffer
63
What stains less brightly C. 10% Neutral Buffered Formalin or Phosphate Buffered Formalin?
acid dye
64
What are the pros of using the fixative?
Cheap, stable, compatible
65
What does the fixative preserve?
Fat, mucin, glycogen
66
What is a con of the fixative?
Causes allergic dermatitis
67
How does the fixative affect tissue?
May produce shrinkage
68
Why is the fixative recommended for nervous tissue?
Does not make brittle
69
Effect of unbuffered fixation on staining
Reduces basophilic and eosinophilic staining
70
Brown pigment granules formation cause
Blackening of hemoglobin
71
Consequences of prolonged fixation
Bleaching, color loss, fat dispersal
72
What is B. 10% Formol Saline made of?
40% Formaldehyde + NaCl + Distilled water
73
What is the recommended fixation time for B. 10% Formol Saline at 35 ℃?
24 hours
74
What are the main advantages of B. 10% Formol Saline?
Even penetration, minimal distortion
75
What is a disadvantage of B. 10% Formol Saline?
Slow fixative
76
What type of tissues is B. 10% Formol Saline recommended for?
Central nervous tissues
77
What does the Formol-Corrosive fixative contain?
Mercuric chloride + Formaldehyde
78
What is a pro of Formol-Corrosive fixative?
Minimal shrinkage and hardening
79
What is a con of Formol-Corrosive fixative?
Slow penetration
80
What are the components of Alcoholic Formalin (Gendre’s) Fixative?
95% ethyl alcohol, Formaldehyde, Glacial acetic acid
81
What is a pro of Alcoholic Formalin?
Faster fixation
82
What is a con of Alcoholic Formalin?
Gross hardening of tissues
83
How is Glutaraldehyde composed?
2 formaldehyde residues linked by 3 carbon chains
84
What is a pro of Glutaraldehyde over Formalin?
More stable effect on tissues
85
Most common metallic fixative?
Mercuric Chloride
86
Mercuric Chloride main issue with tissues?
Shrinkage
87
Treat mercury deposits with?
0.5% iodine solution
88
Mercuric Chloride tissue brightness?
Excellent trichrome staining
89
Key advantage of Mercuric Chloride?
Preserves cell detail
90
Consistency issue of fixed tissues?
Hard and brittle
91
Mercuric Chloride Stock Solution ingredients?
Mercuric chloride, Potassium dichromate, Sodium sulfate, Distilled water
92
Zenker’s Fluid key additive?
Glacial Acetic Acid
93
Optimal fixation time for Zenker’s Fluid?
12-24 hours
94
Zenker’s Fluid fixation quality?
Rapid and even
95
Initial step to dezenkerize?
Water – 5 min
96
How long to immerse in Lugol’s iodine?
5 min
97
Zenker-Formol fixation time?
12-24 hours
98
Components of Zenker-Formol?
Mercuric chloride, formaldehyde
99
Pros of Zenker-Formol?
Excellent for pituitary
100
Cons of Zenker-Formol?
Brown pigments, RBC lysis
101
Main use of Heidenhain’s Susa?
Tumor biopsies
102
What are the components of Heidenhain Susa fixative?
Mercuric chloride, Sodium chloride, Trichloroacetic acid, Glacial acetic acid, 40% Formaldehyde, Distilled water
103
What is the fixation time for Heidenhain Susa fixative?
3-12 hours
104
What is a pro of Heidenhain Susa fixative?
Rapid and even fixation
105
What is a con of Heidenhain Susa fixative?
Poor RBC preservation
106
What should be done after using Heidenhain Susa fixative?
Transfer to high-grade alcohol
107
What is B-5 fixative used for?
Bone marrow biopsies
108
What are the components of B-5 fixative?
Distilled water, Mercuric chloride, Anhydrous sodium acetate
109
What is the fixation time for B-5 fixative?
1-2 hours
110
What is a pro of B-5 fixative?
Rapid fixation
111
What is a con of B-5 fixative?
Overfixation makes cutting difficult
112
What is the main component of Regaud’s (Muller) Fluid?
Potassium dichromate & Formaldehyde
113
What is Regaud's fluid recommended for?
Chromatin, mitochondria, etc.
114
What is a disadvantage of both Regaud’s Fluid and Orth’s Fluid?
Same as Regaud’s fluid
115
What tissue structures does Orth’s Fluid preserve better than buffered formalin?
Myelin
116
What happens to lead fixatives on prolonged staining?
Insoluble lead carbonate forms
117
Which fixative dyes tissues yellow?
Picric acid fixative
118
What can remove the color in the tissue?
Another acid dye or lithium carbonate
119
What are the advantages of the fixative?
Glycogen demonstration, rapid fixation
120
What are the disadvantages of the fixative?
Causes RBC hemolysis, not suitable for frozen tissues
121
What may produce excessive staining?
Picric acid
122
What stains less brightly C. 10% Neutral Buffered Formalin or Phosphate Buffered Formalin?
acid dye
123
Does not cause what?
dermatitis
124
What is the result of a prolonged fixation of Acetic Acid?
brittle and hard
125
How long should tissue be washed with running water before processing?
several hours
126
What method is highly explosive when dry Alters and dissolves lipids?
Interferes with Azure eosin
127
When dry Alters and dissolves lipids Interferes with Azure eosin method?
Highly explosive
128
Regaud’s Fluid components?
Potassium dichromate 3% + 40% Formaldehyde
129
Regaud’s Fluid fixation time?
12-48 hours
130
Pros of Regaud’s Fluid?
Penetrates well, hardens rapidly
131
Cons of Regaud’s Fluid?
Deteriorates, poor glycogen penetration
132
Orth’s Fluid components?
Potassium dichromate + Sodium sulfate + Formaldehyde
133
Orth’s Fluid fixation time?
36-72 hours
134
Pros of Orth’s Fluid?
Good for tissue necrosis, preserves myelin
135
Lead fixatives used in?
4% aqueous solution of basic lead acetate
136
Pros of Lead fixatives?
Recommended for acid mucopolysaccharides
137
Picric acid fixative used in?
Strong saturated aqueous solution
138
What can remove the yellow color from tissue?
Washing with ethanol
139
What is a major advantage of this fixative?
Excellent for glycogen demonstration
140
What causes RBC hemolysis?
Cons of the fixative
141
What is a stable fixative's benefit?
Precipitates all proteins
142
What does picric acid produce?
Excessive staining
143
Bouin's Solution components?
Picric acid, Formaldehyde, Acetic Acid
144
Bouin's Solution fixation time?
6-24 hours
145
Bouin's Solution pros?
Minimal distortion
146
Bouin's Solution cons?
Poor penetration
147
Brasil's Fixative components?
Formaldehyde, Picric Acid, Alcohol, Trichloroacetic acid
148
Glacial Acetic Acid pros?
Precipitates nucleoproteins
149
Glacial Acetic Acid cons?
Destroys mitochondria
150
Alcoholic Fixatives concentration?
70-100%
151
Alcoholic Fixatives pros?
Preserves nuclear stains
152
Methyl Alcohol use?
Fixing smears
153
What is the fixation time for Ethyl Alcohol?
18-24 hours
154
What is Carnoy’s Fluid primarily used for?
Fixing chromosomes
155
What components make up Carnoy’s Fluid?
Absolute alcohol, Chloroform, Glacial acetic acid
156
What is the fixation time for Carnoy’s Fluid?
1-3 hours
157
What is a significant pro for Newcomer’s Fluid?
Better reaction in Feulgen stain
158
What is the major drawback of Osmium Tetroxide?
Very expensive
159
What is the common use of Flemming’s Solution?
Chrome-osmium acetic acid fixative
160
What is the fixation time for Flemming’s Solution?
24-48 hours
161
Flemming Solution pros
Excellent fixative
162
Flemming Solution cons
Poor penetration
163
Trichloroacetic acid pros
Precipitates proteins
164
Trichloroacetic acid cons
Poor penetration
165
Acetone use
Ice cold temp
166
Acetone pros
Study enzymes
167
Acetone cons
Evaporates rapidly
168
Heat fixation pros
Better fixation
169
Heat fixation cons
Tissue shrinkage
170
Secondary fixation purpose
Improves staining
171
Post chromatization purpose
Better staining
172
What is washing out?
Removing excess fixative
173
How does tap water affect tissue fixation?
Removes excess chromates
174
What fixative does 50-70% alcohol wash out?
Bouin's solution
175
What does alcoholic iodine remove?
Excessive mercuric fixatives
176
What factor slows down tissue fixation?
Size and thickness
177
What does excess mucus prevent?
Complete penetration of fixative
178
How should fatty tissues be handled?
Cut in thin sections
179
What should be done with blood before fixing tissues?
Flush with saline
180
How does temperature affect enzyme activity?
Cold inactivates enzymes
181
What enhances the fixation process?
Agitation
182
How does moderate heat affect fixation?
Accelerates but hastens autolysis
183
How many fficults can Isopropyl Alcohol cut?
2
184
Isopropyl Alcohol 95% Used for fixing what?
touch preparations
