Lipid Staining Flashcards
How are lipids classified?
- Simple Lipids
- Compound Lipids
- Derived Lipids
What is the fixative of choice for lipid histochemistry?
Formal calcium
While formaldehyde and formalin can fix lipids, they may alter some lipids upon extended storage
What is the Oil Red O staining method used for?
Demonstrating neutral lipids, particularly triglycerides, in frozen sections
It yields bright red staining of lipids
What are the properties of effective dyes for lipid demonstration?
- More soluble in tissue fat than in dye solvent
- Not water soluble
- Strongly colored
- Acts with tissue constituents by solution
What are the four solvents commonly used in lipid staining?
- 70% alcohol
- Herxheimer’s Fluid (acetone + 70% ethanol)
- Isopropanol
- Polyethylene glycol
What is Osmium Tetroxide used for in lipid histochemistry?
To chemically fix lipids and reveal lipid-rich structures in light microscopy
It binds to double bonds in unsaturated lipids, resulting in a black color
What is the principle of the Osmium Tetroxide method?
Osmium tetroxide chemically combines with fat, blackening it
This method allows paraffin embedding of tissues
What is the result of using the Sudan Black B technique?
Demonstration of lipids using a diazo dye that is lipid soluble
It is used for staining fat in tissue sections
What are common sources of error in lipid techniques?
Exposure to alcohols, acetone, chloroform, xylene, and paraffin can destroy lipid droplets
Proper handling and technique are crucial for accurate results
Fill in the blank: Lipids are soluble only in _______.
organic solvents
True or False: Most lipids can be fixed using formaldehyde without alteration.
False
Extended storage may remove or alter some lipids
What is the expected color of fat globules when stained with Oil Red O?
Intense red
Nuclei will appear blue when counterstained with Harris’ Hematoxylin
What is the significance of using fresh frozen material in lipid studies?
It gives the best results for enzyme, carbohydrate, and lipid studies
Fresh samples preserve lipid integrity better than fixed samples
What is the primary purpose of the Sudan Black B technique?
Demonstrates neutral lipids in tissue sections
What type of dyes are Sudan Black B and Sudan IV classified as?
Lysochrome dyes
What is the recommended fixative for fat fixation in tissue sections?
Formalin, preferably with 1% Calcium chloride
What is the staining result for fat using Sudan Black B?
Blue-black
What color do nuclei stain when using Sudan Black B?
Red
True or False: Sudan IV is preferred over Sudan III because of its darker staining.
True
What is the main disadvantage of Sudan IV compared to Oil Red O?
More orange shade and less intense stain
What is the main application of Sudan dyes in hemopathology?
Aids in differentiating granulocyte precursors from leukocytes
What is the critical step in the Sudan Black B procedure after staining?
Differentiate in 85% propylene glycol
Why should alcoholic-based fixatives not be used with Sudan Black B?
They dissolve fat
What is the appearance of lipids when stained with Oil Red O?
Red
What is the color of fat droplets when stained with Sudan IV?
Orange/red
What technique is used to demonstrate triglycerides in frozen sections?
Sudan Black B technique
Fill in the blank: The cytoplasm will appear _______ due to the effect of osmium.
Gray
What should the thickness of frozen sections be for the Sudan Black B technique?
10 um
What type of lipids may resist routine paraffin embedding after fixation?
- Phospholipids
- Lipofuchsins
- Granules of leukocytes
What is the general procedure for fixing unfixed tissue before using Sudan Black B?
Fix the cut and mounted sections in calcium-formalin for 1 minute
