Histotechnology Exam 1 Questions (chapter 1)

How should a gout specimen be processed? Should it be processed on the processor? Why?

1/2 placed in 100% alcohol and hand processed without formalin. Should not be placed on the processor, because formalin contains water, which dissolves urate crystals. Should be hand processed without formalin and stained with just Eosin.

What is the proper volume ratio of formalin to tissue?

15 to 20x more formalin to tissue volume.

What is commonly the osmolarity of fixatives?

340mOsm (salty)

Formaldehyde comes as a liquid that is _____% to _____%, which is considered 100% formalin.

37-40%

What size should sections of tissue be sampled that are being processed for routine processing (10-12 hours)?

3mm thick (thinner for shorter processing times)

At what pH does formaldehyde cross-link the amino groups?

7.0

What is commonly the pH of fixatives?

7.2-7.4

What size should sections of tissue be sampled that are being processed for whole mounts (36 hour processing)?

8mm thick

What non-additive fixative is used to transport tissue for testing in other labs?

Michels Transport Medium

If you receive a breast sample on a Friday night, what method must be performed to prevent exceeding the allowed formalin fixation time to perform the Her2 test?

Must place the tissue in 70% alcohol for one day and then place in formalin the following day.

How can mercury pigment be removed?

After hydrating cells in Gram or Lugol's solution for 5-10 minutes, wash briefly in running water, then place slides in 3-5% sodium thiosulfate for 3 minutes followed by a running water rinse.

What compound fixative is no longer used due to its mercury content which is a severe health hazard?

B-5

Name 2 compound fixatives?

B5 and Bouins

What event must occur for penetration of fixative to occur?

Blood supply must stop

What compound fixative is excellent when used with tissue that has to be stained with Masson trichrome stain?

Bouins Solution

What non-additive fixative contains absolute ethyl alcohol (60mL), chloroform (30 mL) , and acetic acid (10 mL). ***

Carnoy's solution

Name two methods of fixation?

Chemical reaction (formaldehyde) and physical (heat or dessication)

How can you prepare 10% formalin? What is commonly added to prevent the pH from dropping below 6.0? ****

Dilute 1 part 37% formaldehyde with 9 parts distilled water. Buffered to a pH of 7.0 with mono- or dibasic sodium phosphate.

If you spill 37% formaldehyde what should you do?

Evacuate IMMEDIATELY!!!! 1 inhalation could kill and the floor should be evacuated immediately.

True or False. If a physician is looking for gout in a toe specimen, they should place the tissue in sterile water until it reaches the technician to make touch preps?

False. Urate crystals are dissolved in water.

What method is used to stabilize proteins making it resistant to further damage?

Fixation

Which is stronger? Formaldehyde or Formalin?

Formaldehyde

Why would sodium phosphate buffer be added to 10% formalin?

To make the solution isotonic (pH 7.0).

How can formalin pigment be removed from sections?

Treat sections before staining with alcoholic picric acid or alkaline alcohol. After sections are hydrated, rinse in 70% ethanol (100 mL) and 3 mL of NH4OH for 10 minutes to 3 hours before staining.

True or False. You can over fix tissue?

True. Over fixation dries out the tissue and limits the quality. Can attempt steaming the sections to remedy over fixation.

True or False. When fixing a liver specimen, the fixation time should be doubled?

True. The enzymes found in the cytoplasm need to be fixed well.

If you spill 10% formalin what should you do?

Wipe up with paper towels and place them in the fume hood.

What simple aqueous fixative is good for the use of immunohistochemistry?

Zinc Salts (Zn SO4)

What are two causes of Post mortem putrefaction if the tissue is not fixed? *****

bacteria or mold

What factor causes autolysis if tissue is not fixed? ****

enzyme attack

What non-additive fixative is used to preserve urate crystals and glycogen and is known to shrink tissue?

ethanol

Name 2 non-additive fixatives?

ethyl alcohol, methyl alcohol, Carnoy's solution, and Michels transport medium.

What simple aqueous fixative is considered a additive fixative, fixes lipids but doesn't make them insoluble, and associated with an increased loss of lipids the longer the fixation time, rapid fixation time, hardens tissue, can cause pigment if the pH drops below 6.0? ****

formaldehyde

What three components make up Bouins Solution? ****

formaldehyde, picric acid, and acetic acid

What fixative is the fastest penetrating? slowest?

formalin; picric acid

What simple aqueous fixative is used from electron microscopy, has a unique smell, is slow penetrating, and usually stored in small vials (2-3 mL in a 5 mL vial).

glutaraldehyde

What three organs contain the highest levels of enzymes?

liver, kidney, and brain

What simple aqueous fixative is no longer used due to its toxicity and the fact that it can never be properly disposed of?

mercuric chloride

What non-additive fixative is used for touch preps and blood smears?

methanol

What is the name of a fixative that removes water from tissue? Give two examples

nonadditive fixative. Ex. alcohol or acetone

What simple aqueous fixative is used for electron microscopy as a post fixative, fixes fat, and is toxic?

osmium tetroxide

What simple aqueous fixative is used as a mordant and a fixative, is yellow, and in its dry form is considered a highly explosive material? ****

picric acid

When handling what fixative reagent should the bomb squad be contact if it becomes dry? Why?

picric acid is highly explosive

At what temperature are most fixatives performed at?

room temperature (20°C) up to 45°C

Name three factors that influence fixation?

temperature, size, and time

True or False. Poorly fixed tissue can result in poor staining later on?

true

What will be present in the center of tissue that has a lego appearance? What stage was interrupted to cause this to happen?

water will be present and the center will not be properly fixed. Alcohol was not able to properly penetrate the tissue. Alcohol removes water from tissue.

What are four functions of fixatives?

1. kills tissue to prevent putrefaction and autolysis 2. maintains proper relationship between intracellular and extracellular substances 3. preserves refractive indexes 4. enhances stains

What molar value is common in fixatives?

0.1 molar with pH 7.4

How quickly does formalin penetrate tissue?

1 mm per hour

What simple aqueous fixative is used for fixing nuclei-proteins, fast acting, is added to other fixatives to counteract shrinkage, and lyses red blood cells? Does not fix carbs or lipids.

acetic acid (5% acetic acid = vinegar)

Name 2 aqueous fixatives?

acetic acid, formaldehyde, glutaraldehyde, mercuric chloride, osmium tetroxide, picric acid, and zinc salts.

What is the name of a fixative that is combined with the protein molecule? Give an example.

additive fixative Ex. formaldehyde