General Pathology Practice Questions

Q: Oil Red O staining is used for which type of specimen preparation?

Frozen section. **Explanation:** **1. Why Frozen Section is Correct:** Oil Red O is a lysochrome (fat-soluble) dye used to demonstrate **neutral lipids and triglycerides**. The fundamental principle of lipid staining is that the dye must be more soluble in the lipid than in its solvent. In routine histological processing (paraffin embedding), specimens undergo dehydration with **alcohol** and clearing with **xylene**. These organic solvents dissolve lipids, leaving behind empty vacuoles (as seen in adipocytes). To preserve lipids within the tissue, the specimen must bypass these solvents. **Frozen sections** (using a cryostat) are the gold standard because they maintain the chemical integrity of lipids, allowing the Oil Red O to physically dissolve into the fat droplets, staining them bright red. **2. Why Other Options are Incorrect:** * **Alcohol & Formalin fixed specimens (C & D):** While formalin itself does not dissolve lipids, the subsequent processing steps required for paraffin embedding (dehydration via graded alcohols and clearing agents) remove the lipids entirely. * **Glutaraldehyde fixed specimen (B):** This is primarily used for Electron Microscopy to provide superior protein cross-linking but does not prevent lipid loss during the routine dehydration required for light microscopy. **High-Yield Clinical Pearls for NEET-PG:** * **Sudan Black B:** Another common lipid stain; it is more sensitive for phospholipids and myelin. * **Clinical Application:** Oil Red O is used to diagnose **Fat Embolism Syndrome** (in lung/kidney biopsies) and to identify lipid-rich tumors like liposarcomas or xanthomas. * **Osmium Tetroxide:** The only fixative that also acts as a stain for lipids, turning them black (used in EM). * **Mounting:** Always use **aqueous mounting media** (e.g., glycerin jelly) for lipid stains, as organic mounting media will dissolve the stain.

Question 1

Central to apoptosis is the utilization of?

Accepted Answer

Caspases

Answer

Nitrous oxide

Answer

Adenyl cyclase

Answer

c-AMP

Question 2

Arrange the steps in apoptosis in sequence of occurrence:

Accepted Answer

Removal of BCL-2, Release of cytochrome c in cytoplasm, Activation of APAF-1, Caspase activation

Answer

Caspase activation, Activation of APAF-1, Release of cytochrome c in cytoplasm, Removal of BCL-2

Answer

Release of cytochrome c in cytoplasm, Activation of APAF-1, Caspase activation, Removal of BCL-2

Answer

Removal of BCL-2, Activation of APAF-1, Caspase activation, Release of cytochrome c in cytoplasm

Question 3

What is the initial manifestation of most cell injuries?

Accepted Answer

Cellular swelling

Answer

Necrosis

Answer

Apoptosis

Answer

Chromatin condensation

Question 4

An elderly male's autopsy reveals brown atrophy of the liver. Microscopic examination shows a finely granular, yellow-brown pigment that frequently encircles the nucleus. Brown atrophy is attributed to the accumulation of which substance?

Accepted Answer

Lipofuscin

Answer

Melanin

Answer

Hemosiderin

Answer

Hematin

Question 5

What is the cause for caseous necrosis in Tuberculosis?

Accepted Answer

High lipid content

Answer

Hydrolytic enzymes

Answer

Mycolic acid

Answer

Hydrophobic changes by the bacterial wall

Question 6

All of the following are methods of cellular adaptation EXCEPT?

Accepted Answer

Dysplasia

Answer

Atrophy

Answer

Hyperplasia

Answer

Hypertrophy

Question 7

In apoptosis, permeabilization of which membrane occurs?

Accepted Answer

Mitochondrial membrane

Answer

Nuclear membrane

Answer

Cytoplasmic membrane

Answer

Lysosome

Question 8

Which cation is found in extremely high concentrations in cells that have undergone coagulative necrosis?

Accepted Answer

Calcium

Answer

Potassium

Answer

Iron

Answer

Cobalt

Question 9

Annexin V is a marker of?

Accepted Answer

Apoptosis

Answer

Necrosis

Answer

Gangrene

Answer

Aging

Question 10

Oil Red O staining is used for which type of specimen preparation?

Accepted Answer

Frozen section

Answer

Glutaraldehyde fixed specimen

Answer

Alcohol fixed specimen

Answer

Formalin fixed specimen

General Pathology — MCQs

General Pathology — MCQs

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