(PALM 306) Exam 3 Flashcards
A hypertonic solution will cause:
o cellular shrinkage
Which of the following is a general function of fixatives?
o protect tissue against distortion during subsequent processing
- This type of fixative will cross-link proteins forming a gel-like network
o Non-coagulant
- Fixatives alter proteins by changing their:
o Tertiary structure
- This term is defined as the change in the tertiary structure of proteins causing the molecule to become inactive and insoluble.
o Denaturation
- Microscopic examination of an H&E stained section of fallopian tube reveals very smudgy nuclei with nuclear bubbling. This is most likely caused by:
o Underfixation
- Buffering formalin to a neutral pH is accomplished by the addition of:
o Sodium phosphate, monobasic and dibasic
- 10% formalin contains what percentage of formaldehyde?
o 3.7-4%
- Select all of the fixatives that would be used for fixation in electron microscopy.
o Osmium tetroxide
o Glutaraldehyde
o Paraformaldehyde
- Which of the following fixatives penetrates slow and oxidizes carbohydrates?
o Chromic acid
- What is the recommended fixative-to-tissue volume ratio?
o 15-20 to 1
- Soluble carbohydrates are _______ during fixation.
o Lost
- Since formaldehyde is a gas, what is the maximum concentration that can be achieved in water?
o 37% - 40%
- A physical method of fixation primarily used for touch preparations and blood smears is:
o Desiccation
- Which of the following best describes cold ischemic time?
o The time from removal from the body to placement in fixative
- Which factor can affect the rate of penetration of fixatives?
o Type of fixative
o Heat
o Type of tissue
o Vacuum
- Match the fixative to it’s action.
o Zinc salts : Additive, coagulant
o Acetic acid : Nonadditive, coagulant
o Formaldehyde : Additive, noncoagulant
- Which of the following formalin solutions is recommended for central nervous system tissues?
o Formalin ammonium bromide
- This fixative is typically used as a replacement for mercury.
o Zinc salts
- Which of the following fixatives should be avoided for the demonstration of Helicobacter pylori?
o Glyoxal
- Additive fixatives:
o Chemically react with tissue
- Copper acetate may be used as a fixative to:
o Protect from RBC lysis
- Laboratory employees must periodically wear a formaldehyde badge to monitor exposure.
o True
- If tissue needs to be held in a solution prior to fixation, which type of solution would be the best choice?
o Isotonic
- What happens to tissue that has not been completely fixed and is exposed to alcohol on the processor?
o Alcohol will fix the tissue
- Which of the following formalin solutions is used as a dual purpose fixative for light microscopy and electron microscopy?
o Modified Millonig formalin
- This chemical is added to formaldehyde to prevent polymerization to paraformaldehyde .
o Methanol
- Mercuric chloride has been historically used as a fixative despite it’s hazards due to:
o Preservation of exceptional nuclear detail
- It is necessary to add buffer salts to formalin solutions to prevent:
o the formation of formalin pigment
- For optimal fixation and processing, tissue thickness at grossing should be:
o 3-4 mm
- What is the acceptable temperature range when using heat for fixation?
o 45°C - 68°C
- The recommended pH of fixative solutions used for electron microscopy is:
o 7.2 - 7.4
- How does formaldehyde react with insoluble carbohydrates, nucleic acids, and lipids?
o Traps them in cross-linked proteins
- One disadvantage of using formalin for fixation is that it will:
o Mask protein antigens for immunohistochemical staining
- Which of the following is the most common routine fixative?
o 10% neutral buffered formalin
- Which of the following can be used as both a fixative and a stain?
o Picric acid
- Microwave fixation is an example of what type of fixation?
o Physical
- Fixatives which remove molecularly bound water molecules from tissue proteins are categorized as:
o Nonadditive
- Which of the following may be used as a formaldehyde replacement?
o Glyoxal
- This fixative preserves up to 93% of lipids staining them black.
o Osmium tetroxide
- Formaldehyde is a poor fixative of:
o nucleic acids
- Which of the following is true of picric acid?
o Dissolves small calcifications
- Zinc salt precipitation can occur due to exposure to:
o Heat, pressure and vacuum on the processor
o Carbonates in tap water
o Phosphates in buffered formalin
- Which of the following tissue types would be most susceptible to autolysis?
o Small intestine
- Coagulant fixatives:
o Denature proteins forming a mesh-like permeable network
- Which of the following formalin solutions is recommended for the preservation of phospholipids?
o Calcium formalin
- When tissue is fixed with a second fixative, this is called:
o post-fixation
- A spleen specimen is fixed in 10% NBF for a prolonged period of time. A black to dark brown pigment is observed microscopically in the tissue. This was most likely caused by:
o the solution becoming acidic over time
- In which of the following circumstances would fixation be detrimental or contraindicated?
o Immunoflourescence
- A small amount of white precipitate is observed in the bottom of a 37% formaldehyde container. This precipitation could have been prevented by adding:
o Methanol
- Acid hematin, or formalin pigment, in tissue is caused by:
o acidic formalin, pH 5.5-6 or less
- Enzymatic destruction of tissue is called:
o Autolysis
- Which of the following fixatives will lyse RBCs?
o Acetic acid
- The chromate fixation pigment can be partially removed by treating with:
o Acidic alcohol
- Which is true of formaldehyde?
o penetrates quickly, cross-links slowly
- A delay in fixation should be no longer than:
o 30 minutes
- Which of the following fixation pigments cannot be prevented, but can be removed?
o Mercury
- Formalin pigment can be removed from tissue sections by treating with:
o alkaline alcohol
