MODULE 1 - Fixation Flashcards by SHAINA MAE CASPE

What are the factors involved in fixation?

Hydrogen ion concentration
Temperature
Thickness of tissue
Osmolality
Concentration & Duration of fixation
Volume

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Usual temperature used in fixation of surgical specimen

Room temperature

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Hydrogen ion concentration for fixation

Between pH of 6 and 8

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Temperature when using EM and histochemistry

0-4 degrees Celsius

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Formalin temperature when fixing tissues with tuberculosis

100 degrees Celsius

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Formalin temperature when rapid fixation of urgent biopsies

60 degrees Celsius

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Usual temperature when using tissue processors

40 degrees Celsius

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Thickness of tissue used in EM

1-2 mm2

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Thickness of tissue used in LM

2 cm2

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Tissue slices should not be

> 4-5 mm

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Thickness of lung specimen

2 cm

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In large solid tissues like uterus, it must be _______

open/sliced thinly

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In large solid tissues like brain, it should be _______

suspended whole in 10% buffered formalin (2-3 weeks)

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This type of solution may be used as holding solutions for tissues
to be transported to frozen sections or kidney biopsies for
special processing

Isotonic solution

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Type of solution to be used in fixation

Slightly hypertonic

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Hypertonic solution may cause

Cell shrinkage

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Hypotonic solution may cause

Cell swelling

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Slightly hypertonic solution is between

400-450 mo5m

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Amount of glutaraldehyde found to be effective in immunoEM

0.25%

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for EM, dyes tissue must be fixed for

3 hours

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Prolonged fixation causes

Shrinkage and hardening of tissues

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Ratio of fixative to tissue

20:1

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Effects of fixative in general

Harden soft and friable tissues
Resistant to damage
Acts as mordant and accentuator
Reduce risk of infection
Inhibit bacterial decomposition

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2 types of fixative according to composition

Simple and Compound

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3 types of fixatives according to action

Histochemical- preserves the chemical components like enzymes Cytological- preserves parts of nucleus Microanatomical- as a WHOLE/GENERAL

This allows general microscopic study of tissue structures without altering the structural pattern and normal intercellular relationships

MICROANATOMICAL

This preserve chemical components of cell and tissue like phosphates and lipases

HISTOCHEMICAL

This preserve specific part of the cell

CYTOLOGICAL

Type of cytological fixative that contains glacial acetic acid which preserves part of the nucleus

nuclear

Type of cytological fixative that do not contain glacial acetic acid and which preserves part of the cytoplasm

cytoplasmic

What is the pH of cytoplasmic fixative?

pH >4.6

What is the pH of nuclear fixative?

pH <4.6

Enumerate those under Nuclear fixatives

``` Flemming's with HAc Carnoy's Bouin's Newcomer's Heidenhain's susa ```

Enumerate those under Cytoplasmic fixatives

``` Flemmings without HAc Orth's Regaud's/Moller's Formalin with Post chroming Helly's ```

Enumerate those under Microanatomical fixatives

``` 10% formol saline 10% neutral buffered formalin Heidenhain's susas Formol sublimate/formol corrosive Bouin's Zenker's Brasil's ```

Enumerate those under Histochemical fixatives

10% formol saline Newcomer's Absolute ethyl alcohol Acetone

Which of the following group of fixatives belong to Nuclear Fixatives: A. 10% formol saline, 10% neutral buffered formalin, Heidenhain’s Susa, Formol sublimate/formol corrosive, Zenker’s, Bouin’s, Brasil’s B. Flemming’s, Bouin’s, Carnoy’s , New comer’s Heidenhain’s Susa C. Formol saline, absolute ethyl alcohol, acetone, new comers D. Flemming’s regauds, Kelly’s fluid, formalin, regald, moller’s, orth’s

Satisfactory for routine paraffin sections for EM and other histochemical and enzyme studies

Aldehyde fixatives

Formaldehyde/Formalin may form what pigment color on blood-containing tissues like spleen?

Brown

Alcoholic formalin is also known as

Gendre's solution

Enumerate all diluted forms of formalin

10% formol saline 10% neutral buffered formalin Formol sublimate/corrosive Alcoholic formalin

Percentage of commercially available formalin/formaldehyde

37-40%

What do you call the routine tissue fixative?

Formalin/formaldehyde

What is the penetration rate of formalin?

1 mm per hour

It is recommended for mailing specimens

Formalin/formaldehyde

Recommended for colloid tissue photography

formalin/formaldehyde

fumes are irritating, may cause allergic dermatitis on prolonged contact and may form brown pigment on blood containing tissues like spleen

Formaldehyde/Formalin

``` What method contains Saturated alcoholic picric acid? A. Kardasewitsch method B. Picric acid Method C. 1% KOH in 80% alcohol D. Lillie’s Method ```

``` What method contains 70% ethanol 28% ammonia water? A. Kardasewitsch method B. Picric acid Method C. 1% KOH in 80% alcohol D. Lillie’s Method ```

``` What method contains Hydrogen peroxide 28% ammonia water and acetone? A. Kardasewitsch method B. Picric acid Method C. 1% KOH in 80% alcohol D. Lillie’s Method ```

precipitation of white paraformaldehyde is due to and can cause

prolonged storage and turbidity

remedy for precipitation of white paraformaldehyde

add 10% methanol

Formaldehyde is usually buffered to what pH

pH 7 with phosphate buffer

10% formol saline is diluted with

distilled water with sodium chloride

10% formol saline is used for

general post mortem tissues and for CNS tissue and general post mortem tissues

10% Neutral Buffered Formalin or Phosphate Buffered formalin is used for

surgical post mortem and research specimens | for elastic fibers and for tissue with iron pigment

This is a combination of formaldehyde and mercuric chloride

Formol sublimate/corrosive

This is recommended for lipids, neutral fats and phospholipids

Formol sublimate/corrosive

This is used for sputum specimens and micro-incineration techniques

Alcohol formalin or Gendre's solution

Karnovsky’s paraformaldehyde-glutaraldehyde solution and Acrolein are for

electron cytochemistry

This is recommended for enzyme histochemistry

Glutaraldehyde

What percentage of glutaraldehyde solution is used for small fragment of tissues

2.5%

What percentage of glutaraldehyde solution is used for larger tissues less than 4mm thick

It is a fast-acting fixative and the smallest aldehyde fixative

Glyoxal

Glyoxal is supplied at what percentage of aqueous solution?

40%

When using glyoxal, surgical specimens are fixed within

4-6 hrs

When using glyoxal, small biopsy specimens are fixed within

45 mins

Penetrates poorly and produces shrinkage in tissue so it is | combine with other fixative.

Mercuric chloride

Mercuric chloride may form what color of deposits?

Black mercury deposits

Remedy for black mercury deposits

Alcohol iodine

What is the most common metallic fixatives and it preserves, _________

cell detail in tissue photography

Mercuric chloride is excellent for

Trichrome staining

Enumerate fixatives under mercuric chloride

Zenker's fluid Zenker's formol Heidenhain's susa B5

Zenker's fluid contain

mercuric chloride and glacial acetic acid

Zenker's fluid is used for fixing

liver, spleen, CT fibers and nuclei

Zenker's formol is also known as

Helly's fluid

Helly's fluid contains

potassium dichromate and 40% formaldehyde

Zenker's formol is used for

pituitary gland BM and blood containing organs like spleen and liver

Heidenhain’s Susa is used for

tumor-skin biopsies

B5 contains

anhydrous sodium acetate

B5 is used for

Bone marrow (BM)

``` Used for acid mucopolysaccharides and for tissue mucin A. Mercuric chloride B. Chromate fixatives C. Picric acid fixatives D. Lead fixatives ```

This type of fixative is used for CHO

Chromic acid

This type of fixative is used for rickettsia and other bacteria

Orth's

Moller's fluid is used for?

Chromatin, mitochondria, mitotic figures, Golgi body, RBC containing colloid tissues

Potassium dichromate preserves

lipids and mitochondria

Orth's fluid is used for

early degenerative process and tissue necrosis

Removal of mercuric deposits is also known as what process

DEZENKERIZATION

Major drawback of using picric acid fixative

Imparts yellow color

Picric acid fixative is excellent for

glycogen demonstration

Picric acid fixative acts as:

Fixative, stain, and decalcifying agent

Remedy for yellow color left by using Picric acid fixative

Lithium carbonate and 70% alcohol

Bouin's solution is excellent for preserving

embryos, pituitary biopsies and endometrial curettings.

Bouin's solution should never be used for _____ and it also abolishes _____.

Kidneys and Fuelgen's reaction

Hollande's solution is good for

GIT biopsies and endocrine tissues

Brasil’s Alcoholic Picformol is excellent for

glycogen

Bouin's solution is good for what stain?

Masson's trichrome

Glacial acetic acid is what type of fixative?

Compound fixative

Glacial acetic acid is used in? At what pH?

Nuclear fixative at pH <4.6

Glacial acetic acid is recommended for ____.

Nucleoproteins

GLACIAL ACETIC ACID solidifies at what temperature?

17 degrees celcius

What is the disadvantage of using alcohol fixatives?

glycogen polarization

Alcohol fixatives is both ____ & ____.

Fixative & dehydrating agent

___ is used as a raw material in making _______

acetone, shabu

``` Alcohol fixatives will: A. Preserve enzymes B. Denatures rapidly and precipitates proteins C. Preserve nucleoproteins D. Stain with Masson's trichome ```

The MOST RAPID fixative

Carnoy's fluid

``` It is used for CT mucins & umbilical cord. A. Lead fixatives B. Newcomer's C. 10% formalin D. Rossmann's ```

Ethyl alcohol is used for:

blood, tissue films and smears

Methyl alcohol is used for

wet and dry smears, blood smears and BM tissues

``` Touch preparation is under: A. Rossmann's B. Orth's C. Methyl Alcohol D. Isopropyl alcohol ```

Carnoy's fluid is used for

chromosomes, lymph glands, brain tissue (RABIES)

Newcomer's is used for

nuclear protein and mucopolysaccharides

Classified both as nuclear and histochemical fixative

Newcomer's

Alcohol fixatives is ideal for

small tissue fragments

``` Rapid in action and may be used in urgent biospecimen A. Rossmann's B. Carnoy's C. Isopropyl alcohol D. Methyl alcohol ```

Expensive and not commonly used.

Osmium tetroxide

OSMIUM TETROXIDE is used for

peripheral tissues like myelin and peripheral nerves

Required volume for osmium tetroxide

5-10 times the volume of tissue

Disadvantage of using osmium tetroxide

conjunctivitis and blindness

2 types of osmium tetroxide

1. Flemming's w/ HAc | 2. Flemming's w/o HAc

WEAK DECALCIFYING AGENT

Trichloroacetic acid

A compound fixative with double purpose?

Trichloroacetic acid- fixative and decalcifying agent

Fixatives that can be used for fixing brain tissues in diagnosis for rabies

Acetone and Carnoy's

Acetone A. fixes and dehydrates B. fixes and decalcify C. fixes and stains

Acetone is used at what temperature

-5-4 degrees Celsius

Disadvantages of acetone

Dissolves fats and evaporates easily

It is used as raw material in making shabu

ACETONE

A type of fixation used in frozen sections

Heat fixation

It Involves thermal coagulation of CHON and in micro, it is used for bacterial smears

Heat fixation

It is done to improve demonstration of substance, ensure complete hardening and for special staining

Secondary fixation

A secondary fixation with the use of potassium dichromate

Post chromatization

Post chromatization is used for,

cytologic preservations

Removal of excess fixative from the tissue after fixation to improve staining and remove artifacts

washing out

Type of washing out technique used to remove excess amount of picric acid/bouin’s

50-70% alcohol

Type of washing out technique used to remove Kelly’s, zenker’s, flemming’s, Remove excess chromate, formalin, osmic acid

Tap water

Type of washing out technique used to remove excess mercuric fixative

alcoholic iodine

Type of washing out technique used to remove excess amount of picric acid/bouin’s

50-70% alcohol

These factors will retard fixation

size and thickness, presence of mucus, blood, fats, and cold temperature

These factors will accelerate fixation

smaller and thin tissues, agitation, heating 37-56 degrees Celsius

``` inactivation of enzymes is due to: A. prolonged fixation B. incomplete washing of fixative C. wrong choice of fixative D. incomplete fixation ```

``` presence of artefacts on tissues is due to: A. prolonged fixation B. incomplete washing of fixative C. wrong choice of fixative D. incomplete fixation ```

``` Tissue are soft and feather like in consistency are due to: A. prolonged fixation B. incomplete washing of fixative C. wrong choice of fixative D. incomplete fixation ```

``` shrinkage and swelling of cells is due to: A. overfixation B. incomplete washing of fixative C. wrong choice of fixative D. incomplete fixation ```

Microwave Technique may be used for neurochemical substances in brain like

acetylcholine

What is the secondary goal of fixation?

Harden tissues for easy cutting and protect from further trauma

It is a technique that increases movement of molecules thereby accelerating fixation, staining, decalcification, immunohistochemistry and EM

Microwave technique

Ideal time to perform fixation is

20-30 minutes following interruption of blood supply

This refers to the period the tissue is exposed to formalin

Fixation time

Volume of osmium tetroxide for EM;

5-10 time the volume of tissue

Volume of tissue for museum preparations

not <50-100 times the volume of specimen

Autopsy materials should be fixed as soon after death as possible. If not possible, body must be placed in a mortuary ref. What should be the temperature of mortuary ref?

4 degrees Celsius

Hollow organs (stomach, intestine) should be

put cotton soaked in with specimen or it is completely open

To prevent floating of air-filled lungs in fixative, what should be done?

cover with several layers of gauze to keep it at bottom

Human Brain must undergo

intravascular perfusion- washing out of blood using ringer's lactate

Eyes should be dissected before they are fixed. True of False?

False

Hard tissues (cervix, uterine, fibroid etc.) must undergo what method?

Lendrum's method- immersing in 4% aqueous phenol for 1-3 days

Factors to be considered when choosing the right fixative

1. urgency 2. tissue structure 3. type of stain 4. type of specimen

This type of additive stabilizes tissue proteins A. Non-additive B. Additive

This type of additive involves alteration of tissue components A. Non-additive B. Additive

Examples of non-additive fixatives are:

Alcohol and acetone

``` Recommended for mailing specimens and colloid tissue photography A. formalin/formaldehyde B. Mercuric chloride C. Glutaraldehyde D. Picric Acid fixative ```

Disadvantages of using formalin/formaldehyde

1. irritating fumes 2. contact dermatitis 3. brown pigment on blood-containing tissue like spleen

``` It is used for fixing liver, spleen, CT fibers and nuclei A. Zenker's formol/Helly's B. Zenker's fluid C. B5 D. Heidenhain's susa ```

``` Zenker's fluid contains A. anhydrous sodium acetate B. Potassium dichromate and 40% formaldehyde C. Mercuric chloride and HAc D. TCA, Glac HAc & formalin ```

``` It is used for lipids, neutral fats and phospholipids A. Zenker's fluid B. B5 C. 10% Neutral buffered formalin D. Formol sublimate/corrosive ```

``` It is used for pituitary glands, BM and other blood-containing tissues A. Heidenhain's susa B. Zenker's Fluid C. Helly's fluid D. Alcoholic iodine ```

``` It is used for tumor skin biopsies A. Heidenhain's susa B. Formol sublimate C. Zenker's fluid D. Potassium dichromate ```

``` It is used for acid mucopolysaccharides and tissue mucin A. Potassium dichromate B. B5 C. Lead fixatives D. Glutaraldehyde ```

``` It is used for chromatin, mitochondria, mitotic figures, golgi bodies and RBC containing colloid tissues. A. Regaud's/Moller's B. Helly's C. Gendre's D. Alcoholic iodine ```

``` It is used for early degenerative processes and tissue necrosis. A. Moller's B. Helly's C. Orth's D. Zenker's ```

Fixatives used for enzyme histochemistry

4% formaldehyde | Formol saline

Fixatives used for EM and Electron histochemistry

Glutaraldehyde Osmium tetroxide Paraformaldehyde

Which of the following will remove picric acid/bouin's? A. Alcohol iodine B. 50-70% alcohol C. Tapwater

Which of the following will remove excess mercuric chloride? A. Alcohol iodine B. 50-70% alcohol C. Tapwater

Which of the following will remove zenker's? A. Alcohol iodine B. 50-70% alcohol C. Tapwater

adequate fixation time (book)

4-6 hrs

recommended size of the tissue (book)

2 cm2, and no more than 4 mm. thick.

rate of penetration for aldehyde fixative (book)

two to-three millimeter per hour

For solid material (e.g., liver) the longest dimension should not exceed (book)

10-15mm

commonly added to osmium tetroxide fixatives for electron | microscopy (book)

sucrose

Formaldehyde is normally used at what percent of solution? (book)

10%

Glutaraldehyde is normally used at what percent of solution? (book)

It destroys mitochondria and Golgi bodies of the cytoplasm. (book)

glacial acetic acid

Small endoscopic specimens are particularly susceptible to this type of damage. (book)

Drying of specimen

Purulent material, exudates or transudates should be marked and kept for possible cultures, smears and other bacteriologic examination. True or false? (book)

true

Human brains may be suspended by a (book)

cord tied under the Circle of Willis to prevent flattening

Intravascular perfusion (washing out of blood with Ringer's lactate) may lead to? (book)

artifact formation with loss of blood content

Frozen sections may lead to formation of (book)

ice crystal artifacts

prepared from stock solutions immediately before use because they are unstable (book)

Helly’s fluid

a well-known artifact that may be produced under acid | conditions. (book)

formalin pigment

Failure to arrest early autolysis of cells (book)

Failure to fix immediately, Insufficient fixative

Formalin pigment may be eliminated or reduced by (book)

fixation in phenol formalin

may be found in surgical specimens particularly in liver | biopsies, associated with an intense eosinophilic staining at the center of the tissue in H&E stained sections. (book)

Crush artifact

should be used for demonstrating lipid in tissues, followed by a general lipid stain. (book)

Cryostat or frozen sections

The most useful fixatives for preserving glycogen (book)

Rossman's fluid or cold absolute alcohol

commonly used fixatives for amino acid histochemistry (book)

Neutral buffered formal saline or formaldehyde vapor

commonly used in pathology for the demonstration of various antibodies (book)

Immunofluorescence techniques

Examples of organic solvents

alcohols and acetone

Example of Cross-linking reagents

paraformaldehyde

causes covalent cross-links between molecules, effectively gluing them together into an insoluble meshwork (book)

paraformaldehyde

variables that need to be considered when developing immunohistochemistry protocols (book)

Fixation method, time, and temperature

immunofluorescent (IF) staining is best done on (book)

frozen sections

Background auto fluorescence, to a greater or lesser degree, can be suppressed by a post-staining (book)

Sudan Black treatment

Microwave antigen retrieval is one of several so-called what method

‘HIER’ (heat induced epitope retrieval) methods

considered to be the major factor responsible for the effects of microwaves during tissue fixation. (book)

heat

After microwaving they should immediately be sliced to | _____ and placed in ______. (book)

2 mm, 70% ethanol

The chief advantage of microwave fixation (book)

tissue is heated right through the block in a very short time, thereby potentially allowing the study of cellular processes that proceed very rapidly.

microwave fixation is useful in preserving (book)

neurochemical substances in brain, such acetylcholine

Two types of chemical fixatives according to their mechanism of action

Crosslinking Fixatives (e.g., Aldehydes) and Precipitating (or denaturing) fixatives (e.g., alcoholic fixatives)

presence of buffer prevents

formalin pigmentation

can be used as a fixative for cell smears

formaldehyde vapor

what is the ratio in diluting the concentrated formalin in phosphate buffer?

1:10

“Overnight” fixation (i.e., 8-12 hours) is generally indicated for

10 mm thick slices of tissues

At what temperature does native DNA and RNA do not react with formaldehyde?

20-22 degrees Celsius

At what temperature does RNA and DNA consecutively reacts?

45 and 65 degrees Celcius

recommended for colored tissue photography

formalin

Formation of brown pigment granules on blood-containing tissues, e.g., spleen is due to:

blackening of hemoglobin

``` If there is a necessary delay in fixation, the tissue should be immersed in: A. Formalin/formaldehyde B. Cold phosphate-buffered saline (PBS) C. Formol sublimate D. Zenker's ```

``` Natural tissue colors may be restored by immersing tissues in _______ after fixation. A. 10% methanol B. 70% alcohol C. Lithium carbonate D. Glacial acetic acid ```

Brown or black crystalline precipitate formed by the action of formic acid with blood and can be removed from the sections prior to staining by treatment with?

saturated alcoholic picric acid or a 1% solution of potassium hydroxide in 80% alcohol

If fatty tissues are to be stored for a long time, what can be added to prevent dispersion of fat out into the fluid.

cadmium or cobalt salts

post-fixed in osmic acid may result in hypotonicity and bleaching, to prevent this, what should be done: A. must not be washed in demineralized water B. fix in 70% ethyl alcohol C. wash with tap water D. wash with 50-70% alcohol

Fixation of tissue blocks not exceeding 5 mm. in thickness is usually complete in ______ hours at room temperature. A. 6-12 B. 4-6 C. 24 D. 24-48

Fixation time of 10% Formal-Saline

12 – 24 hours

pH of 10% Formal-Saline

pH of 6.8

Paraformaldehyde is suitable for: A. lipids, neutral fats and phospholipids B. paraffin embedding, sectioning and immunocytochemical analysis C. general post mortem tissues D. iron pigmented tissues and elastic fibers

The most efficient aldehyde blockers are

ethanolamine and lysine

Solid specimens taken from patients with gout are usually fixed in

95% ethanol

appears to give the most usable | DNA fragments for polymerase chain reaction (PCR)

Ethanol

``` The color of the specimen can be preserved for photographic work using A. 70% alcohol B. 80% alcohol C. 90% alcohol D. 100% alcohol ```

Isopropyl Alcohol 95% is used for certain special staining procedures such as

Wright-Giemsa

What happens when lower concentrations (lower than 70-100%) of ethyl alcohol are used? A. cell shrinkage B. cell swelling C. RBC's become hemolyzed and WBC's are inadequately preserved. D. precipitation of proteins

fixation time of ethyl alcohol

18-24 hours

Carnoy’s Fixative fixation time

1-3 hours

Clarke’s solution has been used on

frozen sections and smears

``` It preserves nucleic acids but extracts lipids. A. Helly's B. Zenker's C. Clarke's D. Bouin's ```

Alcoholic formalin fixation time

12-24 hours

``` It can be used for fixation or post-fixation of large fatty specimens (particularly BREAST) A. Alcoholic formalin B. Zenker's fluid C. Helly's D. Acetone ```

Formol-acetic alcohol fixation time

1-6 hours

Newcomer's Fluid fixation time

12-18 hours at 3°C

``` It produces better reaction in Feulgen stain than Carnoy's fluid. A. Regaud's/Moller's B. Newcomer's C. Rossmann's D. Clarke's ```

``` It is recommended for renal tissue, fibrin, connective tissue and muscle. A. mercuric chloride B. lead fixatives C. potassium dichromate D. B5 ```

Zenker's Solution fixation time

12-24 hours

Trichome staining

Zenker's solution

It is recommended for congested specimens (such as lung, heart and blood vessels) and gives good results with PTAH. A. Zenker's fluid B. Potassium dichromated C. Helly's D. Newcomer's

Zenker-Formol (Helly’s) Solution fixation time

4 – 24 hours

``` This mixture enhances nuclear detail, which is important for identifying normal and abnormal cell types in bone marrow (hematopoietic tissue) specimens. A. Helly's B. Rossmann's C. B5 D. Lillie’s B-5 Fixative ```

Lillie’s B-5 Fixative fixation time

4-8 hours

Heidenhain's Susa Solution fixation time

3-12 hours

``` This method of staining elastic fibers is not possible in Susa fixed tissues. A. Romanowsky's B. Giemsa's C. Wright's D. Weigert's ```

``` traditionally used in electron microscopy both as a fixative and a heavy metal stain. A. Potassium dichromate B. Glacial acetic acid C. Chromic acid D. Osmium tetroxide ```

the most common chrome-osmium acetic acid fixative used

flemming's solution

``` It permanently fixes fat. A. Osmium tetroxide B. Flemming's solution C. Chromic acid D. Zenker's fluid ```

Flemming's solution's fixation time

24-48 hours

``` It is a strong oxidizing agent A. Osmium tetroxide B. Flemming's solution C. Chromic acid D. Zenker's fluid ```

Orth's Fluid Fixation time

36-72 hours

``` an explosive hazard in dry form A. Bouin's B. Glacial Acetic acid C. Picric Acid D. Osmium tetroxide ```

``` Prolonged storage in this acidic mixture causes hydrolysis and loss of stainable DNA and RNA. A. Bouin's B. Glacial Acetic acid C. Picric Acid D. Osmium tetroxide ```

Bouin's solution fixation time

4 – 18 hours

``` It is suitable for Aniline stains (Mallory's, Heidenhain's or Masson's methods). A. Picric Acid B. Glacial Acetic acid C. Bouin's D. Osmium tetroxide ```

It is the preferred fixative for tissues to be stained by Masson's trichrome for collagen, elastic or connective tissue. A. Picric Acid B. Gendre's solution C. Bouin's D. Osmium tetroxide

``` a reagent that is used for the precipitation of proteins and nucleic acids. A. Picric Acid B. Glacial Acetic acid C. TCA D. Osmium tetroxide ```

provides a stable medium for transport of fresh unfixed tissues, such as renal, skin and oral mucosa biopsies. A. Picric Acid B. Glacial Acetic acid C. TCA D. Michel's solution

Cryostat or frozen sections should be used in what tissues?

Lipids

``` Most usable for DNA fragments for PCR A. bouin's B. Formaldehyde C. ethanol D. Zenker's fluid ```

``` Traditionally the amount of fixative use is A. 10x the vol. of specimen B. 20-30x the vol. of the specimen C. 10-25 vol. of the specimen D. 5x vol. of the specimen ```

normally used in strong saturated aqueous solution (approximately 1%)

Picric acid

It is a form of secondary fixation where in the already fixed tissue is placed in 2.5-3% pot. dichromate

post chromatization

``` Aldehyde fixative recommended for preservation and storage of surgical specimen A. Phosphate buffered formalin B. Glutaraldehyde C. Alcohol formalin D. Formol corrosive ```

One of the advantage of this fixative is it fixed myelin and peripheral nerve as well

Osmium tetroxide

``` It is an excellent microanatomic fixative for pituitary gland, bone marrow, and blood containing organs A. Helly's soln B. Brasil's fluid C. Moller's fluid D. Orth's fluid ```

Low temperature retards fixation but prevent autolysis | True or false

True

This method of fixation involves thermal coagulation of protein and usually employed in frozen tissue section

Heat fixation

``` Alcohol formalin is also known as A. Moller's fluid B. Helley's fluid C. Gendre's fixative D. Formol sublimate ```

Tissue should not be more than 5mm thick except in lung edema True or false

true

Hard specimen must be immersed overnight with 4% aqueous sol'n True or false

false, dpat 1-3 days

Chromic acid and osmic acid is the component of flemming's soln without acetic acid True of false

True

``` Alcoholic fixative suitable for small tissue fragments such as currettings and biopsy material A. Carnoy's fluid B. Isopropyl acohol 95% C. Newcomer's fluid D. Ethyl alcohol ```

Water is used to remove picric acid fixative | True or false

False

Eyes as a specimen should not be dissected prior to fixation | True or false

True

Over fixation will result to shrinkage and swelling of cells and tissue structure True of false

True

``` Specific fixative recommended/utilize to fix nuclear structure A. Heidenhain's susa B. B5 fixative C. Zenker's formol D. Flemming's solution ```

Human brains shall be washed out with Ringer's lactate sol'n | True or False

True

This type of fixative does not need washing out process after fixation A. Bouin's sol'n's B. Bouin's solution

Wrong choice of fixative will result to removal of substances in the cells or structure True of false

True

``` Metallic fixative for preservation of cell detail in tissue photography A. mercuric chloride B. heidenhain's susa C. Zenker''s sol'n D. B5 fixative ```

Specific fixative for fixing brain tissue for rapid diagnosis of rabies

Acetone