Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HISTOPATH MIDTERMS > CHAPTER 7: CHEMICAL FIXATIVES PART 1 > Flashcards

CHAPTER 7: CHEMICAL FIXATIVES PART 1 Flashcards

1
Q
  • Aldehydes
  • Act by creating covalent chemical bonds between proteins in tissue
  • Anchors soluble proteins to the cytoskeleton, and lends additional rigidity to the tissue
A

Crosslinking Fixatives

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q
  • Commonly used cross-linking fixative
  • Good for immunohistochemical techniques
  • Long term storage and good tissue penetration
  • Vapor form is used for cell smears
A

Formaldehyde

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Standard solution of Formaldehyde

A

10% neutral buffered formalin / 3.7%-4.0% formaldehyde in phosphate buffered saline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Made with formaldehyde but the percentage denotes a different formaldehyde concentration

A

Formalin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

10% neutral buffered formalin is equivalent to __% formaldehyde

A

4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q
  • Most widely used fixative for routine histology
  • Buffered to pH 7 with phosphate buffer
  • Immunohistochemistry and interphase FISH
  • Contains 10% methanol to retard the formation of higher polymers that eventually fall out of solution as paraformaldehyde (deposits of white powder)
A

10% Neutral buffered formalin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Routine fixation with 10% Neutral buffered formalin

A
  1. Dissect specimen ASAP and immerse in a large volume of fixative
  2. Place at 4 degC and fix overnight
  3. Wash tissue well in several changes of Phosphate Buffered Saline (PBS); tissue may be stored in cold PBS for short period of time (2 or 3 days) and will be safe in ethanol since there is no danger of bacterial degradation
  4. Should not be stored in 70% ethanol for extended period; instead, store in PBS with sodium azide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Fixation time of small tissues (10x10x3) in 10% Neutral buffered formalin

a. 12-24 hours
b. 8-12 hours (overnight)
c. 24 hours
d. 2-4 weeks

A

a. 12-24 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

T/F: Fixation with formaldehyde is largely complete within 24 hours, although cross-linking still occurs for at least 2 weeks

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

T/F: At temperatures normally used for fixation (20-22°C), native DNA and RNA react with formaldehyde.

A

False (do not react)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

If reaction mixtures are heated at about 45 deg C (RNA) and 65 deg C (DNA), reaction begins due to _______.

A

uncoiling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

T/F: Only at elevated temperatures used when tissues are infiltrated with paraffin or resin, can a reaction with any remaining fixative take place.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Advantages of 10% Neutral buffered formalin

A
  1. It is cheap, readily available, easy to prepare, and relatively stable, especially if stored in buffered solution.
  2. It is compatible with many stains, and therefore can be used with various staining techniques depending upon the need of the tissues
  3. It does not over-harden tissues, even with prolonged periods of fixation, as long as solutions are regularly changed.
  4. It penetrates tissue well
  5. It preserves fat and mucin, making them resistant to subsequent treatment with fat solvents, and allowing them to be stained for demonstration
  6. It preserves glycogen
  7. It preserves but does not precipitate proteins, thereby allowing tissue enzymes to be studied. It does not make tissues brittle and is therefore recommended for nervous tissue preservation.
  8. It allows natural tissue colors to be restored after fixation by immersing formalin-fixed tissues in 70% alcohol for one hour and is therefore recommended for colored tissue photography.
  9. It allows frozen tissue sections to be prepared easily.
  10. It does not require washing out, unless tissues have stayed in formalin for excessively long periods of time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

If unbuffered, Formalin reduces neutrophilic and eosinophilic staining of cells. It also forms abundant brown pigment granules on blood-containing tissues, e.g., spleen, due to blackening of hemoglobin.

False/True
True/False
Both True
Both False

A

False/True (basophilic and eosinophilic)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Prolonged fixation may produce:

a. Bleaching and loss of natural tissue colors
b. Fat dispersal into fluid
c. Loss of glycogen and urate crystals

A

AOTA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

FACTORS THAT INFLUENCE FORMALIN FIXATION

A

1) Post-Mortem / Post-Surgical Interval
2) Composition of Fixative
3) Volume of Fixative
4) Fixation Time (24 hours in NBF)
5) Temperature
6) Tissue Thickness (3-5mm)
7) Post-Fixation Storage (for necessary delay, 3 days in the cold in 70% ethanol)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Mixture of fixatives that is useful for electron cytochemistry

A

Karnovsky’s paraformaldehyde- glutaraldehyde

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

-Mixture of fixative
- Rapid, preserve morphology and enzyme activity at low concentration
- Used for immersion fixation of surgical biopsies

A

Acrolein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

remove white paraformaldehyde deposits

A

10% methanol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

If added to formaldehyde, it prevents decomposition to formic acid or precipitation to paraformaldehyde (but unsuitable for EM due to protein denaturation)

A

Methanol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Change fluid fixative every _____ to prevent bleaching of tissues

A

3 months

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Immerse tissues in _______ after fixation to restore its natural colors

A

70% alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

T/F: Saturated alcoholic picric acid or 1% potassium hydroxide in 80% alcohol can remove brown/black crystalline precipitate formed by formic acid with blood.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

______ can be added to prevent dispersion of fat into fluid

A

Cadmium/Cobalt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

T/F: Magnesium carbonate or calcium can buffer/neutralize acid reaction due to formic acid formation to prevent explosion

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

T/F: Cadmium acetate can buffer formalin without leaving deposits on the tissue parts exposed to it

A

False (leave deposits)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Secondary fixation of formalin-fixed tissues (1-2 hours) in Helly’s fluid for _______ or in _______ for 4-16 hours to improve staining and produce firmer and harder consistency.

A
  • 4-6 hours
  • Formol sublimate
28
Q

T/F: Prevent deposition of hematin from acidic formalin by maintaining alkaline pH

A

False (neutral)

29
Q

T/F: Wash tissue in demineralized water if post-fixed in osmic acid to prevent hypotonicity and bleaching

A

False (Do not wash in demineralized water)

30
Q

Fixation of tissue blocks less than or equal to ______ thickness is usually complete in 6-12 hours at room temperature

A

5 mm

31
Q

pH of 10% Formal-Saline

A

6.8

32
Q

Widely used prior to introduction of Phosphate Buffered Formalin

A

10% Formal-Saline

33
Q

Fixation time of 10% Formal-Saline

A

12-24 hours

34
Q
  • Central nervous tissues and general post-mortem tissues for histochemical examination
  • Preservation of lipids (phospholipids)
A

10% Formal-Saline

35
Q

Advantages of 10% Formal-Saline

A
  1. It penetrates and fixes tissues evenly.
  2. It preserves microanatomic and cytologic details with minimum shrinkage and distortion.
  3. Large specimens may be fixed for a long time provided that the solution is changed every three months.
  4. It preserves enzymes and nucleoproteins.
  5. It demonstrates fats and mucin.
  6. It does not over-harden tissues, thereby facilitating dissection of the specimen.
  7. It is ideal for most staining techniques, including silver impregnation
  8. It allows natural tissue color to be restored upon immersion in 70% alcohol.
35
Q

Advantages of 10% Formal-Saline

A
  1. It penetrates and fixes tissues evenly.
  2. It preserves microanatomic and cytologic details with minimum shrinkage and distortion.
  3. Large specimens may be fixed for a long time provided that the solution is changed every three months.
  4. It preserves enzymes and nucleoproteins.
  5. It demonstrates fats and mucin.
  6. It does not over-harden tissues, thereby facilitating dissection of the specimen.
  7. It is ideal for most staining techniques, including silver impregnation
  8. It allows natural tissue color to be restored upon immersion in 70% alcohol.
36
Q

T/F: 10% Formal-Saline is a rapid fixative

A

False (slow; 24 hours or longer)

37
Q

Formal-saline fixed tissues tend to shrink during alcohol dehydration; this may be reduced by __________

A

secondary fixation

38
Q

T/F: Acid dye stains more brightly than when fixed with mercuric chloride

A

False (less brightly)

39
Q

One of the advantages of formol saline is that the 4. metachromatic reaction of amyloid is reduced.

A

False (disadvantage)

40
Q

pH of 10% Neutral-Buffered Formalin

A

7.4

41
Q

Best fixative for tissues containing iron pigments and for elastic fibers which do not stain well after Susa, Zenker’s or chromate fixation

A

10% Neutral-Buffered Formalin

42
Q

T/F: 10% Neutral-Buffered Formalin requires no post-treatment after fixation and goes directly into 80% alcohol for processing

A

True

43
Q

T/F: 10% Neutral-Buffered Formalin requires no post-treatment after fixation and goes directly into 80% alcohol for processing

A

True

44
Q

Disadvantages of 10% Neutral-Buffered Formalin

A
  1. It is longer to prepare; hence, is time-consuming.
  2. Positivity of mucin to PAS is reduced.
  3. It may produce gradual loss in basophilic staining of cells
  4. Reactivity of myelin to Weigert’s iron hematoxylin stain is reduced.
  5. It is inert towards lipids, especially neutral fats and phospholipids.
45
Q

The following statements about Unbuffered Zinc Formalin are true except for:

  1. Devised as alternatives to mercuric chloride formulations
  2. Said to give improved results with immunohistochemistry
  3. Zinc sulphate is more corrosive than zinc chloride

a. 1
b. 2
c. 3

A

c. 3

46
Q

Fixation time of Formol-Corrosive (Formol-Sublimate)

A

3-24 hours

46
Q

Fixation time of Formol-Corrosive (Formol-Sublimate)

A

3-24 hours

47
Q

Recommended for routine post-mortem tissues

A

Formol-Corrosive (Formol-Sublimate)

48
Q

It is excellent for many staining procedures including silver reticulum methods

A

Formol-Corrosive (Formol-Sublimate)

49
Q

It is excellent for many staining procedures including silver reticulum methods

A

Formol-Corrosive (Formol-Sublimate)

50
Q

Cytological structures and blood cells are well preserved. There is no need for “washing-out”. Tissues can be transferred directly from fixative to
alcohol.

a.10% Formal-Saline
b.10% Neutral-Buffered Formalin
c. Formol-Corrosive (Formol-Sublimate)

A

c. Formol-Corrosive (Formol-Sublimate)

51
Q

It fixes lipids, especially neutral fats and
phospholipids

A

Formol-Corrosive (Formol-Sublimate)

52
Q

Disadvantages of Formol-Corrosive (Formol-Sublimate)

A
  1. Penetration is slow; hence, tissue sections should not be more than 1 cm thick.
  2. It forms mercuric chloride deposits.
  3. It does not allow frozen tissue sections to be made.
  4. It inhibits the determination of the extent of tissue decalcification.
53
Q
  • Suited for paraffin embedding and sectioning, and immunocytochemical analysis
  • Allows for subsequent immune-detection of certain antigens and should be therefore used when objective is to study morphology and protein expression simultaneously
A

Paraformaldehyde

54
Q

Polymerized form of formaldehyde, usually obtained as fine white powder; depolymerizes to formalin when heated

A
55
Q

Polymerized form of formaldehyde, usually obtained as fine white powder; depolymerizes to formalin when heated

A

Paraformaldehyde

56
Q

4% Paraformaldehyde-1% Glutaraldehyde in 0.1M Phosphate Buffer

A

Karnovsky’s Fixative

57
Q
  • Suitable for use when preparing samples for LM in resin embedding and sectioning, and for EM
  • Should always be prepared fresh
A

Karnovsky’s Fixative

58
Q
  • Made up of 2 formaldehyde residues, linked by a 3-carbon chain
  • Causes rapid and irreversible changes, fixes quickly, well suited for EM
  • It fixes well at 4 deg C and it gives best overall cytoplasmic and nuclear detail
A

Glutaraldehyde

59
Q

Causes deformation of alpha-helix structure in
proteins (not good for immunohistochemical staining)

A

Glutaraldehyde

60
Q

most efficient aldehyde blockers

A

Ethanolamine and lysine

61
Q

4% Glutaraldehyde is used for small tissue fragments and needle biopsies (2-4 hours @ RT). 2.5% Glutaraldehyde is used for larger tissues less than 4mm thick (6-8 hours up to 24 hours)

a. FALSE/TRUE
b. TRUE/FALSE
c. BOTH TRUE
d. BOTH FALSE

A

d. BOTH FALSE

62
Q

Advantages of Glutaraldehyde over Formalin

A
  1. It has a more stable effect on tissues, giving a firmer texture with better tissue sections, especially of central nervous tissues.
  2. It preserves plasma proteins better.
  3. It produces less tissue shrinkage.
  4. It preserves cellular structures better; hence, is recommended for electron microscopy.
  5. It is more pleasant and less irritating to the nose.
  6. It does not cause dermatitis.
62
Q

Advantages of Glutaraldehyde over Formalin

A
  1. It has a more stable effect on tissues, giving a firmer texture with better tissue sections, especially of central nervous tissues.
  2. It preserves plasma proteins better.
  3. It produces less tissue shrinkage.
  4. It preserves cellular structures better; hence, is recommended for electron microscopy.
  5. It is more pleasant and less irritating to the nose.
  6. It does not cause dermatitis.
62
Q

Advantages of Glutaraldehyde over Formalin

A
  1. It has a more stable effect on tissues, giving a firmer texture with better tissue sections, especially of central nervous tissues.
  2. It preserves plasma proteins better.
  3. It produces less tissue shrinkage.
  4. It preserves cellular structures better; hence, is recommended for electron microscopy.
  5. It is more pleasant and less irritating to the nose.
  6. It does not cause dermatitis.
63
Q

Disadvantages of Glutaraldehyde over Formaldehyde

A
  1. It is less stable.
  2. It penetrates tissues more slowly.
  3. It tends to make tissue (i.e., renal biopsy) more brittle
  4. It is more expensive.
  5. It reduces PAS positivity of reactive mucin. This may be prevented by immersing glutaraldehyde- fixed tissues in a mixture of concentrated glacial acetic acid and aniline oil.

HISTOPATH MIDTERMS (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions