Recombinant human erythropoietin is used to treat:

Correct Answer: C

Rationale: Recombinant human erythropoietin (EPO) treats anemia of chronic renal failure (C), stimulating red blood cell production in kidneys unable to produce endogenous EPO, improving quality of life in dialysis patients. It's not used for iron-deficient anemia (A); iron supplementation is needed. Sickle cell anemia (B) relies on hydroxyurea, not EPO. It treats AZT-related anemia (D) in HIV, countering marrow suppression. It's ineffective in clozapine-induced agranulocytosis (original E). EPO's targeted stimulation of erythropoiesis, monitored via hemoglobin levels, reduces transfusion needs, though hypertension and thrombosis risks require oversight.

Correct Answer: C

Rationale: Steroid hormone action involves diffusion into the cytoplasm and binding to an intracellular receptor (C), as lipophilic steroids (e.g., cortisol) cross membranes, bind nuclear receptors, and regulate gene expression. Option A describes tyrosine kinase receptors (e.g., insulin). Option B fits G-protein-coupled receptors (e.g., epinephrine). Option D involves JAK-STAT pathways (e.g., cytokines), not steroids. Option E (original) about ion channels applies to neurotransmitters. This genomic mechanism, slow but sustained, contrasts with rapid membrane receptor signaling, altering protein synthesis for effects like anti-inflammation, critical in endocrinology and pharmacology.

Correct Answer: A

Rationale: Bronchial smooth muscle (A) is not a nicotinic site; it's primarily muscarinic, responding to acetylcholine via G-protein-coupled receptors for bronchoconstriction. Nicotinic sites, ligand-gated ion channels, include adrenal medullary cells (B) for catecholamine release, parasympathetic (C) and sympathetic (original E) ganglia for autonomic transmission, and skeletal muscle (D) for contraction. Nicotinic receptors' rapid ionotropic action contrasts with muscarinic metabotropic effects, critical in pharmacology (e.g., nicotine mimics ACh at these sites). This distinction guides cholinergic drug targeting, like neuromuscular blockers (skeletal) vs. bronchodilators (smooth muscle).

Correct Answer: D

Rationale: The pH value is the negative log of the hydrogen ion (H⁺) concentration (D), defined as pH = -log[H⁺], measuring acidity (e.g., pH 7 = 10⁻⁷ M H⁺). Option A (log[OH⁻]) and B (-log[OH⁻]) relate to pOH, not pH. Option C (log[H⁺]) omits the negative, yielding incorrect values. Option E (original) about ratios is unrelated. This logarithmic scale, rooted in the water dissociation constant (pH + pOH = 14), quantifies acidity impacting drug ionization (e.g., weak acids in stomach), a cornerstone of pharmaceutical chemistry.

Correct Answer: A

Rationale: The particle size of the dispersed solid in a suspension is usually greater than 0.5 μm (A). Suspensions are heterogeneous systems with insoluble particles large enough to settle (e.g., oral antacids), distinguishing them from colloids (0.001-0.5 μm). Options B (0.4 μm), C (0.3 μm), and D (0.2 μm) fall below this threshold, while 0.1 μm (original E) is even smaller. This size ensures visible dispersion, requiring shaking before use, and impacts stability and bioavailability, as larger particles dissolve slower, a key consideration in pharmaceutical suspensions.