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Histopath > Fixation > Flashcards

Fixation Flashcards

1
Q

This process is
- done at 0-4 degrees C
- fixatives containing glutaraldehyde followed by secondary fixative, osmium tetroxide

A

ELECTRON MICROSCOPY

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2
Q
  • maximal preservation of enzyme activity to where it
    originates, while also preserving structural integrity
  • overnight fixation using 4% formaldehyde or formal-saline
A

ENZYME HISTOCHEMISTRY

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3
Q
  • fixed with acetone or formaldehyde for frozen sections
A

ENZYME HISTOCHEMISTRY

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4
Q
  • uses the principle of Ag-Ab reaction
  • epitopes (sites where the Ab will attach to) of antigens must be preserved for antibodies to bind on
    antigens to be detected
  • if prolonged fixation was performed, antigenicity of Ag will be lost because of the loss of epitope
A

IMMUNOFLUORESCENCE AND
IMMUNOHISTOCHEMISTRY

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5
Q
  • antigen retrieval can be done to bring back antigenicity using Heat-induced epitope retrieval
    (HIFR)
A

IMMUNOFLUORESCENCE AND
IMMUNOHISTOCHEMISTRY

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6
Q
  • employing the advantage of heat to fi tissue, microwaves aid in the fixation process by either allowing heat to permeate and fix the tissue itself (microwave fixation) or heat using microwave assists the permeation of a chemical fixative (microwave assisted fixation)
A

MICROWAVE FIXATION

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7
Q
  • use of chemical reagents to preserve tissues
  • chemical fixatives have their own different actions
    o cross-links with proteins, providing additional rigidity to the cells
    o denatures proteins
A

CHEMICAL FIXATION

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8
Q
  • Formaldehyde (product of the production of methanol) is sold as _______ w/v formaldehyde
    solution
A

FORMALDEHYDE AND FORMALIN in 10% concentration

35-40%

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9
Q
  • white powder; formaldehyde polymers
  • allows paraffin embedding and sectioning, and IHC
  • effects are reversible by excess water
  • avoids pigmentation produced by formalin
A

PARAFORMALDEHYDE

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10
Q
  • standard fixative for EM
  • less dangerous than para/formaldehyde;
    pleasing smell; less irritating
A

GLUTARALDEHYDE

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11
Q

GLUTARALDEHYDE
- 2%-
- 2.5% -
- 4% -

A

GLUTARALDEHYDE
- 2%- EM
- 2.5% - small tissue biopsies and needle biopsies
- 4% - for larger tissues less than 4mm thick

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12
Q
  • 4% paraformaldehyde – 1% glutaraldehyde in 0.1M
    Phosphate Buffer
A

KARNOVSKY’S FIXATIVE

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13
Q
  • suitable to use when tissues are to be embedded in
    resin
  • suitable fixative for EM because of the presence of
    glutaraldehyde
A

KARNOVSKY’S FIXATIVE

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14
Q
  • denatures CHONS
  • not routinely used for tissues as it can produce severe distortion on tissue samples, thus only used in
    slide samples which has a thickness around just a cell or 2 layers of cells
  • rarely used alone for fixing locks, unless studying nucleic acid
A

ALCOHOLIC FIXATIVES

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15
Q
  • good for cytologic smear fixation
  • used as 70& to 100% concentration
  • mixed with acetic acid, water, chloroforms to reduce distortions
A

ALCOHOLIC FIXATIVES

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16
Q

– general fixative for Peripheral Blood Smear (PBS), dry and wet smears, and Bone Marrow
Aspirates (BMA) smears

A

Methanol

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17
Q

– touch preps

A

95% Isopropanol

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18
Q

– used as a fixative and a
dehydrating agents

A

Ethanol (70-100%)

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19
Q

– preserves Nissl bodies, cytoplasmic granules,
nucleoproteins, nucleic acids; for fixing brain tissues for rabies dx

A

Carnoy’s Fluid (absolute alcohol in Chloroform)

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20
Q

– fixation or post- fixation of large
fatty specimens

A

Alcoholic Formalin

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21
Q

– can be used on frozen sections

A

Clarke’s solution

22
Q

– sometimes used for fixing
tissues for diagnostic cryostat

A

Formol – acetic Alcohol

23
Q

– enhances immunoperoxidase
studies; for glycogen and micro-incineration

A

Gendre’s Fluid

24
Q

– for fixing mucopolysaccharides
and nuclear proteins

A

Newcomer’s Fluid

25
Q
  • most common metallic fixative
  • used as a 5-7% aqueous solution
  • works by additive and coagulative means
  • it can incorporate itself in cells and precipitate CHONS, thus denaturing them in process
A

MERCURIC CHLORIDE

26
Q

– recommended for congested
specimens, and for trichrome staining and Phophotungstic acid Hematoxylin (PTAH) staining

A

Zenker’s solution

27
Q
  • excellent fixative
    for bone marrow, liver (to demonstrate extramedullary hematopoiesis), spleen, pituitary
    glands, and cardiac muscle
A

Zenker-Formol (Helly’s) Solution

28
Q

– for fixing hematopoietic BM
biopsies, and lymphoid tissues

A

Lillie’s B-5 fixative

29
Q

– for tumor biopsies of the skin;
permits easier sectioning of large blocks of fibrous connective tissue

A

Heidenhain’s Susa

30
Q
  • causes complete denaturation of CHONS
  • traditionally used in EM (fixative and stain); now, it act as secondary fixative
A

OSMIUM TETROXIDE; OSMIC ACID

31
Q
  • good fixative and stain for lipids
  • preserves cytoplasmic structures
  • penetrates at a slower rate vs. metallic fixatives
A

OSMIUM TETROXIDE; OSMIC ACID

32
Q
  • may give off a black stain
  • extremely volatile; prolonged exposure to vapors may cause conjunctivitis
A

OSMIUM TETROXIDE; OSMIC ACID

33
Q

OSMIUM-BASED FIXATIVES
1. _________________ – most common; permanent fixative for fat
2. _________________________________ – recommended for demonstrating mitochondria

A

OSMIUM-BASED FIXATIVES
1. Flemming’s Fluid – most common; permanent fixative for fat
2. Flemming’s w/out acetic acid – recommended for demonstrating mitochondria

34
Q

– good in preserving
mitochondria at pH 4.5-5.2

A

Chromic acid (1-2%)

35
Q

– recommended for demonstrating
mitochondria, mitotic figures, golgi bodies, RBC and colloid- containing tissues

A

Regaud’s fluid

36
Q

– recommended for studying early
degenerative processes and tissue necrosis; also advisable for demonstrating rickettsiae and other
bacteria

A

Orth’s Fluid

37
Q
  • performs almost as well as mercuric fixative; doesn’t harden as much
  • reacts with histones and basic proteins; precipitates al, proteins
A

PICRATE FIXATIVES

38
Q
  • good fixative for connective tissues, preserves glycogen well, extracts lipids
  • May impart a yellow pigments
    o removed using lithium carbonate or wash in
    alcohol in changes of 50-70%
A

PICRATE FIXATIVES

39
Q
  • recommended for fixing embryos and pituitary biopsies, also glycogen
A

Bouin’s Fluid

40
Q
  • recommended for gastrointestinal tract specimen and endocrine tissues; has some decalcifying properties
A

Hollande’s Solution

41
Q
  • highly recommended for glycogen
    and carbohydrate preservation; produces minimal distortion of micro-anatomical structures.
A

Gendre’s Fluid

42
Q
  • better and less messy than Bouin’s; excellent for preserving
    glycogen.
A

Brasil’s Alcoholic Picroformol Fixative

43
Q
  • Anhydrous
  • Freezes at 16°C
A

GLACIAL ACETIC ACID

44
Q
  • Enables cell swelling Precipitates and fixes nucleoproteins
  • Compounded with other fixatives to counteract the swelling effect
A

GLACIAL ACETIC ACID

45
Q
  • metallic fixative because of the presence of lead
  • Recommended for fixing acid mucopolysaccharides, mucin
  • May produce lead carbonate upon standing.
    o white ppt at the bottom; filtered out
A

LEAD FIXATIVES

46
Q
  • Fixative and decalcifying agent
A

TRICHLOROACETIC ACID (TCA)

47
Q
  • Precipitates proteins and nucleic acids
  • Used only on small pieces; penetrates poorly
A

TRICHLOROACETIC ACID (TCA)

48
Q
  • non-alcoholic
  • Not recommended as a morphological fixative
    because it is known to distort tissue
A

ACETONE

49
Q
  • Used in fixing cryostat sections and for tissues
    requiring enzyme preservation.
  • Used to fix tissues at cold temperatures (0-4°C)
A

ACETONE

50
Q
  • Recommended for fixing brain tissues to diagnose rabies
  • Preserves glycogen poorly; dissolves fats.
A

ACETONE

51
Q
  • Not a fixative
  • Stable medium for transporting fresh, unfixed tissues that will undergo frozen sectioning or IF studies.
  • Specimens can be kept in the solution for _ days until it can be delivered to a reference laboratory.
  • Not suitable for keeping tissues for ____.
  • Tissues in such solution must be kept at an ambient temperature of ______
A

MICHEL’S SOLUTION
- Not a fixative
- Stable medium for transporting fresh, unfixed tissues that will undergo frozen sectioning or IF studies.
- Specimens can be kept in the solution for 5 days until
it can be delivered to a reference laboratory.
- Not suitable for keeping tissues for FISH.
- Tissues in such solution must be kept at an ambient temperature of 4-22°C

Histopath (1 decks)

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