Histotech. Fixation Questions
Potassium dichromate increase availability of which of the following groups for binding dye? a. SH b. COOH c. NH2 d. OH
-COOH
The volume of fixative should exceed the volume of the tissue by?
15-20 times
The recommended minimum time for fixation in formalin is: a. 1 hr to 3 hr b. 4 hr to 5 hr c. 6 hr to 8 hr d. 9 hr to 10 hr
6 hour to 8 hour
The ratio of stock solution to acid in Zenker fixative is:
95 parts stock to 5 parts acetic acid
What is in a Zenker?
Mercuric chloride, potassium dichromate, glacial acetic acid
Formaldehyde cross-links proteins by reacting with which of the following groups? a. NH2 b. COOH c. S=S d. OH
NH2
What fixative is preferred to preserve chromaffin granules?
Orth
Electron microscopic studies on a section of tumor fixed in 10% neurtral-buffered formalin revealed very poor cell preservation. This could be prevented in the future by: a. postfixing the tissue in os. tetroxide b. fixing some of the tumor in glutaraldehyde solution c. holding in saline until the need for electron microscopy can be determined d. washing the tissue in running water prior to placing in osmium
B
H&E- stained sections of the liver fixed in 10% neutral-buffered formalin showed a marked difference in staining between the periphery and center of the tissue. More nuclear bubbling is also noted in the center part of the section. This is most likely due to: a. underdehydration during processing b. incomplete fixation prior to beginning dehydration c. poor paraffin infiltration d. overheat embedding paraffin
B
Hollande solution is a modification of which of the following? a. Carnoy b. Zamboni c. Bouin d. Orth
Bouin
What is the preferred fixative for connective tissue?
Bouin
Which of the following fixatives contains picric acid, formalin, and acetic acid?
Bouin
Which of the following is a nonaqueous fixative?
Carnoy
A good fixative should penetrate slowly. [T\F]
F
The volume of the fixative should exceed the volume of the tissue by 1 to 2 times. [T\F]
F; 15-20 times
Acetic acid is a useful addition to many compound fixatives because of its shrinking action. [T/F]
F; Acetic acid swells tissue which counteract shrinking
Formalin ammonium bromide is a very good fixative for connective tissue. [T\F]
F; CNS
The fixing fluid considered best for the preservation of nuclear detail is buffered formalin. [T\F]
F; Carnoy solution preferred for nuclear fixation due to acetic acid
Fat is well preserved by Carnoy solution. [T\F]
F; Fat is dissolved by Carnoy solution, which contains absolute alcohol, acetic acid, and chloroform
Since formalin is a coagulant fixative it is considered an excellent fixative for paraffin embedding. [T\F]
F; Formalin is a noncoagulating fixative and was not considered by Baker to be excellent for paraffin embedding.
Helly, Zenker, and Orth solutions all contain mercury. [T\F]
F; Orth does not contain mercury chloride (postassium dichromate)
Bouin solution contains picric acid, formaldehyde, and hydrochloric acid. [T\F]
F; acetic acid
Zenker fixative contains formaldehyde, mercuric chloride, and potassium dichromate. [T\F]
F; acetic acid, mercuric chloride, and potassium dichromate (Helly has formalin)
If one wishes to prevent the formation of a pigment, formalin solutions must be buffered to a pH above 7 .0. [T\F]
F; buffering at neutrality above is not indicated
B-5 fixative contains formaldehyde and potassium dichromate. [T\F]
F; formalin and mercuric chloride
10% formalin is a 1:4 dilution of commercial formalin. [T\F]
F; it is a 1:10 dilution
Formalin fixation stabilizes lipids. [T\F]
F; lipids are preserved by formalin, but they are not made insoluble; subsequent processing will remove the lipid
Which of the following fixatives contain formalin, potassium dichromate, and mercuric chloride? Zenker Helly Carnoy Orth
Helly
A fixative stops autolysis and putrefaction. [T\F]
T
Acetone is sometimes used when a rapid-acting fixative is needed. [T\F]
T
Any fixative containing mercuric salts will leave a pigment in the tissue. [T\F]
T
Chrome pigment can be prevented by washing the tissues with water following fixation. [T\F]
T
Concentrated commercial solution of formaldehyde are 37% to 40% by weight of the gas formaldehyde dissolved in water [T/F].
T
Formalin pigment can be removed from tissue by immersion in alcoholic picric acid. [T\F]
T
Glutaraldehyde is frequently used to fix specimen for EM. [T/F]
T
Glyoxal fixatives are rapid-acting compared to formaldehyde. [T\F]
T
Heat and desiccation are methods of fixation T/F
T
Orth solution is the best fixative for pheochromocytomas when immunohistochemistry is not to be performed. [T\F]
T
Osmium tetroxide chemically fixes fat [T/F].
T
Tissue left in a fixative beyond the defined time may become excessively hard [T/F]
T
Zinc is a satisfactory replacement for mercury in some fixative solutions. [T\F]
T
Acetic acid is an excellent nuclear fixative. [T/F]
T; Acetic acid is added to many fixatives because of its ability to fix nucleoprotins
Formalin penetrates rapidly but fixes slowly. [T\F]
T; Formalin penetrates and adds very quickly, but it fixes very slowly because it takes a long time to cross-link the tissue proteins
Fixation in Helly solution will preserve erythrocytes, while fixation in Zenker solution will not. [T\F]
T; Helly solution will reserve erythrocytes, but Zenker will not because it contains acetic acid
If tissue have been fixed in an aqueous fixative, uric acid crystals cannot be demonstrated [T/F].
T; Uric acid crystals are water solube and cannot be demonstrated following fixation with an aqueous fixative
Mercury pigment may be removed from tissue by immersion in sodium thiosulfate. [T\F]
T; removed with iodine and sodium thiosulfate
What fixative is preferred for the demonstration of muscle cross-striations by the PTAH technique?
Zenker
Tissue must be washed in running water after fixation in: a. Zenker solution b. absolute alcohol c. glyoxal d. formalin
Zenker, because a pigment may be formed when tissue is taken from a chromate-containing solution directly into an alcoholic solution?
H&E stained sections fixed in formalin show a brown microcrystalline deposit lying on top of the tissue. It is especially heavy in bloody areas of the tissue. This pigment can most likely be removed by treating the tissue with: a. running water b. iodine and sodium thiosulfate c. potassium permanganate d. alcoholic picric acid
alcoholic picric acid
Formaldehyde reacts with protein side chains by combining with the: a. carboxyl group b. thiol group c. amino group d. phenolic group
amino group
Putrefaction of tissue is caused by: a. enzymatic activity b. bacterial action c. aqueous fixatives d. overfixation
b
To prepare a 10% solution of formalin, which of the following amounts of water should be added to 100 mL of stock formaldehyde? a. 1,000 mL b. 900 mL c. 450 mL d. 10 mL
b
When alcohol is used as the primary fixative, one should expect: a. fat preservation b. excessive shrinkage c. very soft tissue d. slow penetration
b
Substitution of alcohol as the diluting solution for formaldehyde results in: a. slower fixation b. less harder tissue c. better retention of fats d. better preservation
better preservation of glycogen
After fixing tissue in Bouin solution, the excess picric acid is frequently removed by washing in: a. running water b. absolute alcohol c. 50% to 70% alcohol d. phosphate buffer
c
Commercial stock formaldehyde solutions contain: a. 4% formaldehyde b. 10% formaldehyde c. 37% to 40% formaldehyde d. 98% to 100% formaldehyde
c
For best results when using formalin as a routine fixative, it must be made: a. acidic b. basic c. neutral d. isoelectric
c
Formalin pigment may be removed from tissue by a. running water b. alcoholic iodine c. alcoholic picric acid d. potassium permanganate
c
Generally, an increase in the temperature of the fixative solution: a. decreases the tissue autolysis b. decreases the fixative penetration c. increases the speed of fixation d. increases the volume of fixative needed
c
H&E-stained section of liver fixed in the microwave oven showed marked pyknotic, overstained nuclei. This can probably be prevented in the future by ensuring that the temperature is kelp below: a. 25 C b. 37 C c. 55 C d. 75 C
c
10% formalin is the same as: a. 3 7% to 40% formaldehyde b. 10% formaldehyde c. 4% formaldehyde d. 1% formaldehyde
c; 10% formalin is a 1:10 dilution of 37% to 40% formaldehyde; there for 10% solution is the same as 3.7% to 4% formaldehyde
At the time of embedding, a white deposit is noted on tissue fixed in unbuffered zinc formalin and then transferred to phosphate-buffered formalin. One possible explanation could be that the tissue was: a) left in the zinc formalin too long b) subjected to incompatible fixatives c) transferred to buffered formalin without washing d) not washed before placing in 70% alcohol
c; Zinc will be precipitated by phosphates present in buffered formalin, so the tissue must be washed before transferring
The fixation used by the laboratory is being changed from formalin to glyoxal. It will most likely be necessary to: a. wash tissue before processing b. decrease routine staining timing c. check for correct staining of H. pylori d. monitor lab. personnel for exposure monthly
c; glyoxal is not a satisfactory fixative if silver stains for H. pylori are needed, as stains is unsatisfactory
Which of the following is nonadditive fixative? a. mercuric chloride b. osmium tetroxide c. formaldehyde d. ethyl alcohol
ethyl alcohol
Methylene bridges are formed during the reaction of certain tissue groups with: a. osmium tetroxide b. formaldehyde c. picric acid d. chromium trioxide
formaldehyde
What type of sections are needed for enzyme histochemistry?
frozen sections
How should specimens for immunofluorescence be prepared?
frozen without fixation
Precipitate left in tissue that have been fixed in solution containing mercuric chloride may be removed by immersion in? -running water -sodium thiosulfate -weak ammonia water -iodine
iodine (gram or lugol)
To prevent polymerization of formaldehyde, which of the following is added to the commercial stock solutions? a. methyl alcohol b. formic acid c. paraformaldehyde d. sodium phosphate
methyl alcohol
Which of the following fixatives will leave the tissue protein uncoagulated? a. Zenker b. osmium tetroxide c. B-5 d. zinc formalin
osmium tetroxide
Which of the following must be used under a hood because it readily vaporizes and will fix the nasal mucosa? a. chromic acid b. formaldehyde c. zinc sulfate d. osmium tetroxide
osmium tetroxide
What 2 fixatives are used for EM?
osmium tetroxide and Zamboni
Polymerized formaldehyde is known as: a. glutaraldehyde b. paraformaldehyde c. paraldehyde d. acetaldehyde
paraformaldehyde
A disadvantage of osmium tetroxide fixation is that osmium: a. fixes fat poorly b. penetrates poorly c. coagulates tissue proteins d. impedes staining with basic dyes
penetrates poorly
Depending on the reagent used, which of the following may cause tissue to become overhardened? a. prolonged fixation b. abbreviated fixation c. inadequate dehydration d. incomplete clearing
prolonged fixation
Zinc salts are added to some formalin fixatives to: a. prevent the loss of cytoplasmic structures b. provide superior nuclear detail c. decrease tissue shrinkage d. keep tissue from overhardening
provide superior nuclear detail
H&E stained sections fixed in formalin show a brown microcrystalline deposit lying on top of the tissue. This can most likely be prevented in the future by: a) filtering the hematoxylin solution before use b) decreasing the time in formalin solution c) raising the pH of the formalin above 6.0 d) washing the tissue after fixation
raising the pH of the formalin above 6.0
The primary purpose of fixation is to?
stop enzymatic action
Tissue fixed in glutaraldehyde is not satisfactory for: a. the periodic acid-Schiff (PAS) reaction b. electron microscopy c. argentaffin stains d. routine H&E stains
the PAS reaction
For immunofluorescence, the tissue should be: a. fixed in formalin b. fixed in alcohol c. fixed in B-5 d. unfixed
unfixed
Fixatives containing chromate salts usually require: a. additional fixation b. washing in water c. washing in alcohol d. no special treatment
washing in water
The permissible exposure limit (PEL) for formaldehyde is currently: a. 0.5 ppm b. 0.75 ppm c. 1.0 ppm d. 2.0 ppm
0.75
Carnoy fluid is prepared with acetic acid, alcohol, and: a. chloroform b. formalin c. acetone d. osmium tetroxide
a
Which of the following tissue changes occur if acetic acid is used alone as a fixative? a. swelling b. shrinkage c. overhardening d. poor nucleoprotein preservation
a
Blocked tissue, which had been fixed in Bouin solution, is pulled from the file after being stored for several years. New sections are cut and stained with H&E. No nuclear staining is noted on the new sections, although the original sections stained very well. The most likely explanation is that the: a) picric acid was not removed sufficiently before blocking b) pH of the fixative was wrong at the time of fixation c) formaldehyde used in the solution contained formic acid d) paraffin used in embedding has broken down
a, if picric acid is not removed sufficiently (preferable neutralized), staining will be affected in blocks after prolonged storage
H&E-stained sections FAIL to reveal uric acid crystals on a case with a clinical diagnosis of gout. One possible explanation for the false-negative result could be that the specimen was fixed in a solution other than: a. absolute alcohol b. B-5 solutiobn c. buffered formalin d. Bouin solution
a; Urate crystals are water soluble, so a nonaqueous fixative, such as absolute alcohol, must be used
The first and most important procedure in the preparation of a tissue for microscopic examination is the choice of: a. fixative b. dehydrating agent c. clearing agent d. staining technique
a; because often the fixative determines which special stain can be done on the tissue
Formalin pigment would almost certainly be formed when the pH of the formalin is: a.5 b.6 c.7 d.8
a; formalin pigment tends to form if the pH of the solution drops below 6 and is so would most definately form in a solution of pH of 5
Fats are usually preserved best if the tissue is fixed in: a. osmium tetroxide b. Camoy c. Bouin d. Helly
a; os. tetroxide is the only fixative soultion that will chemically fix fats, making them insoluble in the processing reagents
Absolute alcohol is indicated as a primary fixative if the tissue is to be processed for the demonstration of: a. fat b. immunofluorescence c. enzymes d. urate crystals
d
A good fixative for central nervous system tissue to be stained with silver or gold techniques is: a. Zenker solution b. neutral-buffered formalin c. Bouin solution d. formalin ammonium bromide
d; Formalin ammonium bromide is a good fixative for central nervous system tissue, especially when the Cajal astrocyte procedure is to be performed
