Which of the following statements concerning beta-adrenoceptor-blocking drugs are true:

Correct Answer: C

Rationale: Step 1: Beta-adrenoceptor-blocking drugs primarily work by blocking the beta-adrenergic receptors in the body. Step 2: By blocking these receptors, these drugs decrease heart rate, blood pressure, and contractility of the heart muscle. Step 3: These hemodynamic effects lead to decreased myocardial oxygen requirements at rest and during exercise, providing beneficial effects. Step 4: Choice C is correct as it accurately describes the main mechanism and beneficial effects of beta-adrenoceptor-blocking drugs. Step 5: Choices A, B, and D are incorrect as they do not accurately describe the primary mechanism or effects of beta-adrenoceptor-blocking drugs.

Correct Answer: A

Rationale: The correct answer is A: Radioiodines in the body emit mainly β radiations. This is because radioiodines typically decay by β- decay, releasing β particles. β radiation consists of electrons or positrons, which are emitted during the decay process. This type of radiation is commonly observed with radioiodines. Option B is incorrect because γ radiation is a type of electromagnetic radiation emitted by the nucleus, not by radioiodines in this case. Option C is incorrect because radioiodines predominantly emit β radiation, not an equal amount of β and γ. Option D is incorrect because radioiodines do emit radiation, particularly β radiation, and therefore are not completely safe in terms of radiation exposure.

Correct Answer: B

Rationale: The correct answer is B: Infiltration of leucocytes and phagocytic cells (phase of exudation). During the delayed, subacute phase of inflammation, infiltrating leukocytes, such as neutrophils and macrophages, play a crucial role in removing debris and pathogens. This phase is characterized by the migration of these cells to the site of injury, where they engulf and digest foreign substances. This process helps to clear the area of infection and promote tissue repair. Other choices are incorrect: A: Local vasodilatation and increased capillary permeability (phase of damage) - This describes the initial phase of inflammation, not the delayed subacute phase. C: Tissue degeneration and fibrosis occurrence (phase of proliferation) - This describes the later stages of inflammation involving tissue repair and remodeling, not the delayed subacute phase. D: All of the above - This is incorrect as choices A and C do not accurately describe the delayed, subacute

Correct Answer: A

Rationale: The correct answer is A: Granules in mast cells or basophils. Mast cells and basophils are well-known for storing histamine in their granules. Upon stimulation, these cells release histamine into the surrounding tissues. Histaminergic neurons (choice B) primarily release histamine in the brain and are not the main reservoir of tissue histamine. Enterochromaffin-like cells (choice C) are found in the stomach and release histamine into the bloodstream, not sequestering it in tissues. Therefore, the correct choice is A as most tissue histamine is indeed sequestered and bound in granules in mast cells or basophils.

Correct Answer: D

Rationale: The correct answer is D: Vitamin B1. This is a water-soluble vitamin, also known as thiamine. Water-soluble vitamins dissolve in water and are not stored in the body, so they need to be consumed regularly. Vitamin A (choice A), Vitamin E (choice B), and Vitamin D (choice C) are fat-soluble vitamins, meaning they are stored in the body's fat tissues and liver, not excreted in urine like water-soluble vitamins. Therefore, they are not water-soluble vitamins. Vitamin B1 (choice D) is crucial for energy metabolism and nerve function, making it a water-soluble vitamin that needs to be replenished regularly through diet.