To prevent a common, adverse effect of prolonged use of phenytoin sodium (Dilantin), patients taking the drug are instructed to:

Correct Answer: D

Rationale: Phenytoin (Dilantin), an anticonvulsant, commonly causes gingival hyperplasia (gum overgrowth) with prolonged use. Practicing good dental hygiene and reporting gum swelling or bleeding (D) helps prevent and manage this. Avoiding crowds (A) relates to infection risk, not a common effect; fluid intake (B) addresses hydration, not specific to phenytoin; and diet (C) is unrelated, making D the correct preventive measure.

Correct Answer: B

Rationale: Albumin, a negatively charged protein, is primarily blocked by anionic proteoglycan clusters in the glomerular basement membrane (B), which repel it via charge. The fenestrated endothelium (A) filters small molecules, and filtration slits (C) between podocytes limit size, but the basement membrane's charge barrier is key. ‘None' (D) is incorrect as B is true, making B the correct answer.

Correct Answer: A

Rationale: Antidiuretic hormone (ADH) increases water reabsorption (A) in the collecting duct via aquaporin-2, concentrating urine. It doesn't affect sodium directly (B, D) or form AII (C), making A the primary role.

Correct Answer: B

Rationale: The descending limb (B) is passively permeable to water, allowing concentration via medullary osmosis. The proximal tubule (A) uses active sodium transport, collecting duct (C) requires ADH, and ascending limb (D) is impermeable, making B correct.

Correct Answer: B

Rationale: The PCT apical membrane reabsorbs bicarbonate via Na+/H+ exchange and carbonic anhydrase, making it permeable (B), not impermeable (A). False reflects this active process, making B correct.