Anatomy
1 questionsWhich type of glial cell is derived from mesodermal origin?
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 441: Which type of glial cell is derived from mesodermal origin?
- A. Macroglial cells
- B. Microglial cells (Correct Answer)
- C. Oligodendrocytes
- D. Ependymal cells
Explanation: ***Microglial cells*** - **Microglial cells** are unique among glial cells as they originate from **mesoderm**, specifically from **monocyte/macrophage precursors** in the bone marrow [1]. - They function as the **immune cells of the central nervous system (CNS)**, scavenging for plaques, damaged neurons, and infectious agents [1]. *Macroglial cells* - This is a broad category that includes **astrocytes, oligodendrocytes, and ependymal cells**, all of which are derived from **neuroectoderm**, not mesoderm [1]. - They perform various supportive roles but are distinct in origin from microglial cells [1]. *Oligodendrocytes* - **Oligodendrocytes** are derived from **neuroectoderm** and are responsible for forming the **myelin sheath** around axons in the CNS [2]. - Myelination is crucial for rapid and efficient nerve impulse conduction. *Ependymal cells* - **Ependymal cells** are derived from **neuroectoderm** and line the **ventricles of the brain** and the **central canal of the spinal cord**. - They play a role in the production and circulation of **cerebrospinal fluid (CSF)**.
Biochemistry
5 questionsWhat primarily forms the core of chylomicrons?
What is the primary role of calnexin and calreticulin in the endoplasmic reticulum?
Which gene is responsible for the production of COX type 3?
Transport of lipids from the intestine to other tissues is by -
Which method is used to separate a mixture of lipids?
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 441: What primarily forms the core of chylomicrons?
- A. Triglycerides and Cholesterol together
- B. Triglycerides (Correct Answer)
- C. Free fatty acids
- D. Triglyceride, Cholesterol and Phospholipids
Explanation: ***Triglycerides*** - Chylomicrons are primarily responsible for transporting **dietary triglycerides** from the intestines to other tissues. - Their large core, composed mainly of **triglycerides**, allows efficient transport of these hydrophobic molecules. *Triglycerides and Cholesterol together* - While **cholesterol** is present in chylomicrons, it is less abundant than **triglycerides** and primarily exists as **cholesterol esters** in the core. - The core is not an equal mixture; **triglycerides** overwhelmingly dominate the volume. *Free fatty acids* - **Free fatty acids** are transported in the blood primarily bound to **albumin**, not within the core of chylomicrons. - Chylomicrons typically carry **esterified fatty acids** as part of triglycerides. *Triglyceride, Cholesterol and Phospholipids* - **Phospholipids** form the outer monolayer of the chylomicron, along with apoproteins, making them **amphipathic**. - They do not constitute a core component but rather the **surface interface** with the aqueous environment.
Question 442: What is the primary role of calnexin and calreticulin in the endoplasmic reticulum?
- A. Degrade misfolded proteins
- B. Act as chaperones (Correct Answer)
- C. Serve as tumor markers
- D. Facilitate enzymatic reactions
Explanation: ***Act as chaperones*** - **Calnexin** and **calreticulin** are **chaperone proteins** located in the **endoplasmic reticulum (ER)**. - They bind to unfolded or misfolded glycoproteins to assist in their proper folding and assembly. - They are part of the **ER quality control system**, ensuring only properly folded proteins proceed to the Golgi apparatus. *Degrade misfolded proteins* - While misfolded proteins are eventually degraded through **ER-associated degradation (ERAD)**, this is not the primary function of calnexin and calreticulin. - These chaperones first attempt to **rescue and refold** proteins; degradation is a separate process involving other machinery. *Serve as tumor markers* - **Calnexin** and **calreticulin** are not typically used as **tumor markers** in clinical practice. - Their functions are related to protein quality control within the cell, not cancer detection. *Facilitate enzymatic reactions* - While some proteins in the ER are enzymes, **calnexin** and **calreticulin** themselves are not enzymes, nor do they primarily facilitate enzymatic reactions. - Their function is to ensure correct protein folding, distinct from direct catalytic activity.
Question 443: Which gene is responsible for the production of COX type 3?
- A. COX 3 gene
- B. COX 2 gene
- C. None of the above
- D. COX I gene (Correct Answer)
Explanation: ***COX I gene*** - COX-3 is an **alternatively spliced variant** of the **COX-1 gene** (specifically, a splice variant of the COX-1 mRNA that retains intron 1). - While it was initially thought to be a distinct gene, research has shown that it arises from the same genetic locus as COX-1. *COX 2 gene* - The COX-2 gene encodes for the **inducible cyclooxygenase enzyme**, which is responsible for prostaglandin synthesis during inflammation. - It is a separate gene from COX-1 and has distinct regulatory mechanisms and physiological roles. *COX 3 gene* - There is currently **no distinct gene in humans** specifically identified as "COX-3". - COX-3 refers to a protein isoform derived from the COX-1 gene, not a separate genetic locus. *None of the above* - This option is incorrect because COX-3 is indeed derived from the **COX-1 gene** through alternative splicing. - The existence of COX-3 as a distinct protein product has been demonstrated, although its precise physiological role in humans is still under investigation.
Question 444: Transport of lipids from the intestine to other tissues is by -
- A. Chylomicrons (Correct Answer)
- B. LDL
- C. HDL
- D. VLDL
Explanation: ***Chylomicrons*** - **Chylomicrons** are the **largest lipoprotein particles** that transport **dietary (exogenous) lipids** from the **intestine** to peripheral tissues - They are synthesized in **intestinal enterocytes** after fat absorption and enter the bloodstream via the **lymphatic system (thoracic duct)** - They carry **triglycerides (85-95%), cholesterol, phospholipids, and fat-soluble vitamins** (A, D, E, K) - **Apolipoprotein B-48** is the characteristic structural protein of chylomicrons - After delivering triglycerides to tissues (via lipoprotein lipase), chylomicron remnants are taken up by the **liver** *LDL (Low-Density Lipoprotein)* - LDL transports **cholesterol from the liver to peripheral tissues** (not from intestine) - It carries **endogenous cholesterol**, not dietary lipids from the intestine - Often called "**bad cholesterol**" due to its role in atherosclerosis - Contains **Apolipoprotein B-100** *HDL (High-Density Lipoprotein)* - HDL performs **reverse cholesterol transport** - moving excess cholesterol from peripheral tissues **back to the liver** - It does **not transport lipids from the intestine** to tissues - Called "**good cholesterol**" for its protective cardiovascular role - Contains **Apolipoprotein A-I and A-II** *VLDL (Very-Low-Density Lipoprotein)* - VLDL is synthesized in the **liver** (not intestine) and transports **endogenous triglycerides** to peripheral tissues - It carries lipids **from the liver**, not from the intestine - VLDL is converted to IDL and then LDL after losing triglycerides - Contains **Apolipoprotein B-100**
Question 445: Which method is used to separate a mixture of lipids?
- A. Electrophoresis
- B. Chromatography (Correct Answer)
- C. Isoelectric focusing
- D. PAGE
Explanation: ***Chromatography*** - **Chromatography** (e.g., thin-layer chromatography, gas chromatography, high-performance liquid chromatography) is widely used to separate lipids based on differences in their **polarity**, **molecular weight**, or **solubility** in various solvents. - This method allows for the isolation and identification of different lipid classes and individual lipid species from a complex mixture. *Electrophoresis* - **Electrophoresis** separates molecules based on their **charge** and **size** in an electric field, making it more commonly used for proteins and nucleic acids. - Lipids are generally **uncharged** or have very low charge, which makes them poorly suited for separation by standard electrophoretic methods without modification. *Isoelectric focusing* - **Isoelectric focusing** is a type of electrophoresis that separates molecules based on their **isoelectric point (pI)**, which is the pH at which a molecule has no net charge. - This technique is primarily used for **proteins** and **peptides**, as lipids typically lack ionizable groups necessary for establishing a distinct pI. *PAGE* - **PAGE** (Polyacrylamide Gel Electrophoresis) is a common method used to separate **proteins** and **nucleic acids** based on their size and charge. - Lipids are **hydrophobic** and do not readily migrate through an aqueous polyacrylamide gel matrix, making PAGE unsuitable for their direct separation.
Internal Medicine
1 questionsWhich of the following is true regarding carcinoid tumor?
NEET-PG 2015 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 441: Which of the following is true regarding carcinoid tumor?
- A. Associated with serotonin production
- B. Potentially malignant tumor
- C. Neuroendocrine tumor (Correct Answer)
- D. Most common site is lung
Explanation: ### Most common site is lung - Carcinoid tumors are more commonly found in the **gastrointestinal tract**, specifically the appendix and ileum, rather than the lungs [1]. - This statement is false as they can occur in the lungs but are not the most common site overall. ### Potentially malignant tumor - Carcinoid tumors can be classified as **malignant,** especially if they show aggressive behavior or metastasis. - Many carcinoid tumors, particularly those in the gastrointestinal tract, can be **non-functional** and less aggressive [1]. ### Neuroendocrine tumor - Carcinoid tumors are indeed a type of **neuroendocrine tumor**, arising from **neuroendocrine cells**. - This classification emphasizes their origin and potential for secretion of hormones like **serotonin**. ### Associated with serotonin production - Many carcinoid tumors produce **serotonin**, leading to symptoms like **carcinoid syndrome** when they metastasize, particularly to the liver [1]. - This statement is true, indicating their involvement in neuroendocrine secretions.
Pathology
1 questionsFibrosis associated with liver cirrhosis is mediated by -
NEET-PG 2015 - Pathology NEET-PG Practice Questions and MCQs
Question 441: Fibrosis associated with liver cirrhosis is mediated by -
- A. Platelet-Derived Growth Factor (PDGF)
- B. Transforming Growth Factor-beta (TGF-β) (Correct Answer)
- C. Vascular Endothelial Growth Factor (VEGF)
- D. Tumor Necrosis Factor-alpha (TNF-α)
Explanation: ***PDGF*** - Platelet-Derived Growth Factor (**PDGF**) is a critical mediator in the **fibrogenic response** associated with liver cirrhosis [1]. - It stimulates the **proliferation** and activation of hepatic stellate cells, leading to excessive **collagen deposition** and fibrosis [1][2]. *ICAM-1* - Intercellular Adhesion Molecule-1 (**ICAM-1**) primarily mediates **cell adhesion** and is involved in inflammatory processes, not directly in fibrosis. - While it may play a role in **leukocyte recruitment**, it does not contribute significantly to the fibrogenic pathway in liver cirrhosis. *PcAM-l* - **PCAM-1** (Platelet/endothelial cell adhesion molecule-1) is involved in **cell adhesion** and is primarily expressed on endothelial cells. - Its role is more associated with **angiogenesis** and inflammation, lacking direct involvement in the fibrogenic process of cirrhosis. *IFN-y* - Interferon-gamma (**IFN-y**) is a cytokine that predominantly has a role in **immune modulation** and does not directly induce fibroblast activation. - It may have regulatory effects on inflammation but does not lead to significant fibrosis associated with liver cirrhosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 31-32. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, pp. 830-832.
Pharmacology
2 questionsWhich of the following is non-selective 3rd generation Beta blocker ?
Beta-blockers should be used with caution in patients with?
NEET-PG 2015 - Pharmacology NEET-PG Practice Questions and MCQs
Question 441: Which of the following is non-selective 3rd generation Beta blocker ?
- A. Betaxolol
- B. Celiprolol
- C. Nebivolol
- D. Carvedilol (Correct Answer)
Explanation: ***Carvedilol*** - **Carvedilol** is a **non-selective beta-adrenergic antagonist** (blocks both β1 and β2 receptors) with **additional α1-adrenergic blocking activity**, making it a true **3rd generation beta-blocker**. - The α1-blockade provides **vasodilatory properties**, reducing peripheral vascular resistance and improving hemodynamics. - It has favorable effects on lipid metabolism and insulin sensitivity, making it particularly useful in heart failure and hypertension. - Its non-selective beta-blockade combined with vasodilation distinguishes it from selective 3rd generation agents. *Betaxolol* - **Betaxolol** is a **selective β1-adrenergic antagonist** without vasodilatory properties. - Classified as a **2nd generation beta-blocker** due to its cardioselectivity. - Primarily used in glaucoma and hypertension but lacks the non-selective profile and additional mechanisms of 3rd generation agents. *Celiprolol* - **Celiprolol** is a **β1-selective antagonist** with **β2-agonistic effects** providing vasodilation. - While classified as 3rd generation due to vasodilatory properties, it is **selective for β1**, not non-selective. - Its β2-agonism causes peripheral vasodilation but maintains β1-selectivity. *Nebivolol* - **Nebivolol** is a highly **selective β1-adrenergic antagonist** with **vasodilatory effects via nitric oxide (NO) release**. - Classified as 3rd generation due to NO-mediated vasodilation, but it is **β1-selective**, not non-selective. - The combination of high β1-selectivity and endothelial-mediated vasodilation makes it unique among 3rd generation agents.
Question 442: Beta-blockers should be used with caution in patients with?
- A. Hypertension
- B. CHF
- C. Conduction defect (Correct Answer)
- D. Glaucoma
Explanation: ***Conduction defect*** - Beta-blockers **slow heart rate** and **decrease AV nodal conduction**, which can worsen pre-existing conduction defects like **AV block** or **sick sinus syndrome**. - Their use can lead to **symptomatic bradycardia** or complete heart block in susceptible individuals. - This represents a **strong relative contraindication** requiring significant caution. *Hypertension* - Beta-blockers are a **first-line treatment for hypertension**, effectively lowering blood pressure by reducing cardiac output and renin release. - They are generally **well-tolerated** and beneficial in most hypertensive patients. *Glaucoma* - Topical beta-blockers, such as **timolol**, are a common treatment for open-angle glaucoma as they **reduce aqueous humor production**, thereby lowering intraocular pressure. - Systemic use of beta-blockers does not typically worsen glaucoma and may even offer some benefit. *CHF* - While certain beta-blockers (**carvedilol, metoprolol succinate, bisoprolol**) are now proven beneficial in **chronic heart failure with reduced ejection fraction (HFrEF)**, they do require careful use. - They must be **initiated at low doses and carefully titrated** to avoid acute decompensation, and are **contraindicated in acute decompensated heart failure**. - However, **conduction defects** represent a **stronger contraindication** where beta-blockers can cause life-threatening bradycardia or complete heart block, making it the best answer for conditions requiring the most caution.