Pellagra is:

Correct Answer: A

Rationale: The correct answer is A. Pellagra is caused by a deficiency of niacin, leading to symptoms like skin eruptions, digestive and nervous system disturbances, and mental deterioration. Choice B refers to beriberi, caused by thiamin deficiency. Option C describes pernicious anemia, caused by a lack of vitamin B12. Option D is incorrect as it includes all the above conditions, which is not the case. Overall, the key points to remember are the specific symptoms of pellagra and the deficiency of niacin as the cause.

Correct Answer: D

Rationale: The correct answer is D: Osteomalacia. Vitamin D3 is indicated for the treatment of osteomalacia, a condition characterized by softening of the bones due to a deficiency of vitamin D. It helps in the absorption of calcium and phosphorus, leading to proper bone mineralization. A: Hypercalcemia is not an indication for vitamin D3 as it can worsen the condition by increasing calcium levels further. B: Paget's disease is not a primary indication for vitamin D3 therapy. Treatment usually involves bisphosphonates. C: Hypophosphatemia is a condition where there is low phosphate levels, and treatment involves phosphate supplementation, not just vitamin D3.

Correct Answer: D

Rationale: The correct answer is D because plicamycin is indicated for testicular cancers refractory to standard treatment, Paget’s disease, and hypercalcemia of malignancy. Plicamycin inhibits bone resorption and reduces serum calcium levels in patients with hypercalcemia of malignancy. It also has cytotoxic effects on certain types of cancer cells, including testicular cancers. Therefore, it is used for all of the mentioned conditions. Choices A, B, and C are incorrect because plicamycin is not limited to only one specific condition, but rather can be used for multiple indications.

Correct Answer: A

Rationale: The correct answer is A: TRUE. Some microorganisms can indeed develop alternative metabolic pathways to bypass the inhibition caused by a drug. This is a common phenomenon known as drug resistance in microbial populations. Other choices are incorrect: B is false because drug resistance through alternative pathways is a known fact; C (All) is incorrect as not all microorganisms exhibit this behavior; and D (None) is incorrect as some microorganisms do develop alternative pathways to counter drug inhibition.

Correct Answer: B

Rationale: The correct answer is B: Inhibition of dihydropteroate synthase. Sulfonamides work by inhibiting dihydropteroate synthase, an enzyme involved in the folate synthesis pathway in bacteria. This disruption leads to a decrease in production of essential nucleotides, ultimately inhibiting bacterial growth. A: Inhibition of dihydropteroate reductase is incorrect as sulfonamides target dihydropteroate synthase, not reductase. C: Inhibition of cyclooxygenase is incorrect as this mechanism is related to NSAIDs, not sulfonamides. D: Activation of DNA gyrase is incorrect as this mechanism is associated with antibiotics like fluoroquinolones, not sulfonamides.