Fixation Flashcards
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
c. protect tissue agains alteration by subsequent processing
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 The solution withdrawn from this stock container will: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
a. become acidic
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
a. 1mm3
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
c. 10%NBF
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
a. give poor ultrastructural preservation
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
a. makes tissue more permeable to fluids
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
d. type of tissue
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
c. slow tissue penetration
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
a. change the spongework of proteins into meshes
A fixative that produces a diffuse brownish black pigment is:
a. bouin
b. carnoy
c. zenker
d. alcohol
c. zenker
The BEST preservation of staining properties during long-term storage, tissue should be stored in:
70% ethanol
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
b. solutions temperature exceeding 55C
heat affects staining
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
c. treat the tissue with iodine, hypo and water before freezing
which of the following fixatives is recommended for both the Heidehain and Mallory aniline blue stains?
Zenker fluid
For optimum staining results, Bouin or Zenker fixation is recommended for:
most trichrome stains
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
d. B-5
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
a. helps precipitate proteins
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
c. when ready to use
if added before use, it will affect future staining
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
d. hydrolysed nucleic acids
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
c. the specimen was not post-fixed in osmium tetroxide
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
a. neutralize the picric acid before processing
fixatives producing covalent bonding that tend to mask antigenic sites and hamper immunohistochemial localization contain:
a. mercury
b. phosphates
c. aldehydes
d. alcohols
c. aldehydes
reason behind HIER and IER
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
a.autoradiography of steroid hormones
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
c. destroy the antigenicy of the sample
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
c. the premature addition of formaldehyde
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
b. disregard the precipitate
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
b. ensuring that the formalin contains buffering agents
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
d. nuclei that appear foggy and lack detail
