Fixation

Question 1

A good fixative will:

a. render cell constituents soluble
b. minimize differences in tissue refractive indices
c. protect tissue agains alteration by subsequent processing
d. minimally affect tissue metabolic processes

Answer 1

c. protect tissue agains alteration by subsequent processing

Question 2

Stock neutralized formalin is prepared in the laboratory by storing the solution over a laver of calcium carbonate. The solution withdrawn from this stock container will:

a. become acidic
b. become alkaline
c. remain neutral
d. exhibit metachromasia

Answer 2

a. become acidic

Question 3

For a good fixation of specimens for EM, it is recommended that the tissue segment be no larger than:

a. 1mm3
b. 2mm3
c. 1cm3
d. 2cm3

Answer 3

a. 1mm3

Question 4

A universal fixative used for routine purposes that allows a broad spectrum of staining procedures is: a. zenker fluid

b. zamboni PAF
c. 10%NBF
d. Carnoy solution

Answer 4

c. 10%NBF

Question 5

Zinc-formalin fixatives:

a. give poor ultrastructural preservation
b. can be used to preserve enzymes
c. result in poor nuclear detain
d. will not coagulate tissue proteins

Answer 5

a. give poor ultrastructural preservation

Question 6

A good fixative for routine use is one that:

a. makes tissue more permeable to fluids
b. is hypotonic to the tissue constituents
c. enhances putrefaction of tissue components
d. promotes tissue autolysis

Answer 6

a. makes tissue more permeable to fluids

Question 7

When fixing tissue with formaldehyde or gluteraldehyde, proper enzyme activity and preservation of structure depend upon all of the following EXCEPT:

a. pH
b. time and temperature
c. concentration and purity of the reagent
d. type of tissue

Answer 7

d. type of tissue

Question 8

A proper fixative is characterized by:

a. the absence of shrinking or swelling
b. inactivation of tissue enzyme
c. slow tissue penetration
d. the absence of distortion or dissolution

Answer 8

c. slow tissue penetration

Question 9

Coagulant fixatives:

a. change the spongework of proteins into meshes
b. produce fewer artifacts than noncoagulant fixatives
c. act very slowly to fix tissues
d. leave protein likage unaffected

Answer 9

a. change the spongework of proteins into meshes

Question 10

A fixative that produces a diffuse brownish black pigment is:

a. bouin
b. carnoy
c. zenker
d. alcohol

Answer 10

c. zenker

Question 11

The BEST preservation of staining properties during long-term storage, tissue should be stored in:

Answer 11

70% ethanol

Question 12

sections of breast carcinoma were fixed in a saline solution in the microwave oven. Microscopic examination of H&E sections show marked pyknotic, overstained nuclei. The staining results were most likely caused by the:

a. use of saline for fixation
b. solutions temperature exceeding 55C
c. use of plastic container in the microwave
d. presence of carcinoma in the breast tissue

Answer 12

b. solutions temperature exceeding 55C

heat affects staining

Question 13

If asked to cut cryostat sections of tissue fixed in Zenker solution, the histotechnologist should:

a. section the tissue as is
b. explain that frozen sections containing mercuric chloride cannot be made
c. treat the tissue with iodine, hypo and water before freezing
d. use a solution of 30% sucrose to infiltrate the tissue before freezing

Answer 13

c. treat the tissue with iodine, hypo and water before freezing

Question 14

which of the following fixatives is recommended for both the Heidehain and Mallory aniline blue stains?

Answer 14

Zenker fluid

Question 15

For optimum staining results, Bouin or Zenker fixation is recommended for:

Answer 15

most trichrome stains

Question 16

which of the following should be selected when it is desirable to preserve RBC in tissue?

a. zenker
b. bouin
c. carnoy
d. B-5

Answer 16

d. B-5

Question 17

alcohol, rather than water, is used as the solvent in some fixatives because alcohol:

a. helps precipitate proteins
b. decreases tissue shrinkage
c. increases lipid preservation
d. eliminated the need for dehydration

Answer 17

a. helps precipitate proteins

Question 18

when preparing Helly solution, formalin should be added:

a. when other ingredients are combined
b. before adding mercuric chloride
c. when ready to use
d. 24hrs before use

Answer 18

c. when ready to use

if added before use, it will affect future staining

Question 19

Picric acid was used alone as a fixative for a section of liver. he tissue most likely will show:

a. extrem swelling
b. excessive hardening
c. an increased uptake of eosin
d. hydrolysed nucleic acids

Answer 19

d. hydrolysed nucleic acids

Question 20

Electron micrographs of a tissue section reveal electron-lucent membranes. This is most likely indicates that:

a. fixation was done in Bouin solution
b. the osmolarity of the fixative was incorrect
c. the specimen was not post-fixed in osmium tetroxide
d. sections were stained with uranyl acetate

Answer 20

c. the specimen was not post-fixed in osmium tetroxide

Question 21

Paraffin block canintaining tissue in Bouin solution are retrieve from storage after several years. New section are cut and stained with H&E, but no nuclear staining is present, although the nuclei of the original slides were well staining. To prevent this from happening in the future on stored tissue:

a. neutralize the picric acid before processing
b. be sure that the pH of the Bouin solution is at neutrality
c. make certain that the formalin does not contain formic acid
d. store blocks at 20C

Answer 21

a. neutralize the picric acid before processing

Question 22

fixatives producing covalent bonding that tend to mask antigenic sites and hamper immunohistochemial localization contain:

a. mercury
b. phosphates
c. aldehydes
d. alcohols

Answer 22

c. aldehydes

reason behind HIER and IER

Question 23

For which of the following techniques are frozen sections of fixed tissue preferred?

a. autoradiography of steroid hormones
b. enxyme histochemistry of muscle bx
c. fat stains of liver
d. flurescent antibody techniques

Answer 23

a.autoradiography of steroid hormones

Question 24

In immuno-electron microscopy (IEM), a fixative other than osmium tetroxide is used because osmium would:

a. blacken the antigen
b. block entrance of the gold label
c. destroy the antigenicy of the sample
d. decrease membrane preservation

Answer 24

c. destroy the antigenicy of the sample

Question 25

helly fixative prepared 3 weeks before is now discolored and turbid. The most likely reason for this is:

a. the presence of acetic acid in the fixative
b. improper solution buffering
c. the premature addition of formaldehyde
d. chemical oxidation

Answer 25

c. the premature addition of formaldehyde

Question 26

A small amount of white precipitate is noticed in the bottom of the lab’s strock 37-40% formaldehyde container. The most appropriate action is:

a. discard de solution
b. disregard the precipitate
c. acidify the solution slightly
d. add methanol to the solution

Answer 26

b. disregard the precipitate

Question 27

a tissue block of unfixed hemorrhagic spleen is fixed for 24hrs in formalin that was prepared 6 months ago. H&E staining show a granular black pigment on the surface of the tissue. This problem can be prevented by:

a. washing the tissue prior to fixation
b. ensuring that the formalin contains buffering agents
c. using an iodine solution on the processor
d. using only freshly prepared solutions

Answer 27

b. ensuring that the formalin contains buffering agents

Question 28

Pap smears that have been fixed with spray fixative are submited to the lab. the smears are staining without an other treatment. The most likely result will be:

a. excellent cytological detain
b. the loss of cells from the slide
c. cells showing air-drying artifact
d. nuclei that appear foggy and lack detail

Answer 28

d. nuclei that appear foggy and lack detail