Module 4: Lipid Staining

Question 1

What main type of tissue is adipose tissue?

Answer 1

Connective tissue

Question 2

What does adipose do?

Answer 2

Stores fat, pads organs, thermoregulation, is reserve energy supply

Question 3

What are the two main types of fat and what do they do?

Answer 3

White fat - thermoregulation in adults

Brown fat - thermoregulation in newborns

Question 4

Where does stored fat come from? (3)

Answer 4

Dietary fat as triglycerides in blood stream

Synthesized by liver and adipocytes by breaking down glycogen

Question 5

When may lipids be present in stainable amounts?

Answer 5

Adipose tissue
Degenerating cells
Fat hydrolysis in disease
Cholesterol
Complex lipids in brain tissue in disease

Question 6

What does adipose look like in a normal paraffin section?

Why?

Answer 6

Network of fibers and nuclei, fibrous connective tissue

Alcohol, xylene, and fat solvents remove the lipid during processing

Question 7

How can fat be demonstrated?

Answer 7

Fat soluble dyes (oil red O)
Other stain methods (Nile blue, histochemical, immunohistochemical)
Polarized light (unique refraction)
Osmium tetroxide - blackens

Question 8

What is the principle of fat soluble dyes like oil red O?

Answer 8

Selective/preferential solubility

Physical staining

Question 9

What is selective/preferential solubility?

Answer 9

The dye is more soluble in the lipid than it is in its solvent
Lipid takes up the stain

Question 10

How are sections made for oil red O?

Answer 10

Prepared frozen, fresh or fixed (formalin)

Usually cut at 10 microns

Question 11

What is used to mount slides after staining for oil red O? Why?

Answer 11

Aqueous mounting media
Miscible with water
Resinous is miscible with xylene which destroys fat

Question 12

What are the requirements for fat soluble dyes?

Answer 12

Highly colored
More soluble in fat than solvent
Not water soluble
Solvent must not remove fat

Question 13

What are other stains that can demonstrate lipids?

Answer 13

Sudan III
Sudan IV
Sudan black B

Question 14

What are the common solvents in fat soluble dyes?

Answer 14

Propylene/ethylene glycol
Triethyl phosphate
70% alcohol
70% alcohol + acetone
Isopropyl alcohol

Question 15

Why are fat stains performed? What can they detect?

Answer 15

Fatty changes in tissue in disease or degradation (metabolic disorders, toxins like alcohol or organic solvents)
Fatty emboli (bone fracture or crush injury)
Liposarcoma

Question 16

What is liposarcoma

Answer 16

Tumors arising from fat cells

Question 17

What are the main reagents in oil red O?

Answer 17

Oil red O
Harris hematoxylin
Lithium carbonate

Question 18

What are the results of an oil red O?

Answer 18

Blue nuclei
Red fat
Blue or gray background

Question 19

What is a good control for oil red O?

Answer 19

Frozen section containing adipose

Question 20

Why should fat stains be done in closed containers?

Answer 20

Evaporation will cause precipitation on the slides

Question 21

Why would acid alcohol not be used to differentiate hematoxylin?

Answer 21

The alcohol would remove the fat

Question 22

Why should slides not be blotted or pressed to remove coverslip air bubbles?

Answer 22

It will displace the fat droplets

Question 23

Which of the following tissues would be acceptable forlipid demonstration?

a. paraffin of formalin fixed tissue
b. frozen of formalin fixed tissue
c. paraffin of Bouin’s fixed tissue
d. frozen of 70% alcohol stored

Answer 23

b. frozen section of formalin fixed tissue

Question 24

Which fixative can be used to demonstrate lipids by blackening unsaturated bonds?

a. Bouin’s
b. Zenker’s
c. B-5
d. Osmium tetroxide

Answer 24

d. Osmium tetroxide

Question 25

Which mounting media would be acceptable to use for cover slipping sections stained using oil red O?

a. Glycerin jelly
b. Canada Balsam
c. Permount
d. D.P.X

Answer 25

a. Glycerin jelly

Question 26

What staining theory explains the ability of oil red O to demonstrate lipids?

a. adsorption
b. preferential solubility
c. covalent bonds
d. porosity

Answer 26

b. selective solubility

Question 27

Which of the following solvents would be inappropriate for use when demonstrating fine fat droplets using oil red O?

a. isopropyl alcohol
b. propylene glycol
c. triethyl phosphate
d. ethylene glycol

Answer 27

a. isopropyl alcohol

Question 28

List 4 criteria for preferentially soluble dyes

Answer 28

1. Highly colored
2. More soluble in substance to demonstrate than the solvent its dissolved in
3. Not soluble in water
4. Solvent does not destroy fat

Question 29

List 4 commonly used preferentially soluble dyes

Answer 29

1. oil red O
2. Sudan III
3. Sudan IV
4. Sudan black B

Question 30

Fatty changes in tissue occur in _______, _______ disorders that usually occur as a result of the introduction of _______; _______ or _______. The tissues that are commonly affected are _______, _______, _______

Answer 30

chronic metabolic
toxins, hypoxia, or diabetes
liver, kidney, and heart

Question 31

Keep stain lids tightly closed to avoid evaporation of solvent which could lead to _______ on the section

Answer 31

precipitation

Question 32

Sections stained for the demonstration of lipids should not be _______ or _______ to remove air bubbles as these will _______ droplets of lipids

Answer 32

blotted
pressed
displaced