All of the following statements regarding inhibitors of type III phosphodiesterase are true EXCEPT:

Correct Answer: C

Rationale: The correct answer is C. Type III phosphodiesterase inhibitors increase cAMP levels in cardiac myocytes, leading to positive inotropic and vasodilatory effects, reducing afterload. They are associated with the risk of cardiac arrhythmias due to their effects on cardiac contractility. However, they do not show significant cross-tolerance with beta-receptor agonists, as they act via a different mechanism. Therefore, choice C is incorrect.

Correct Answer: B

Rationale: The correct answer is B because Nimodipine and Cinnarizine are calcium channel blockers that affect brain blood flow by dilating cerebral blood vessels. Nimodipine specifically acts on cerebral arteries, while Cinnarizine works by reducing the influx of calcium ions into smooth muscle cells of the brain vasculature. Choice A, Aminalon and Picamilon, are not calcium channel blockers and do not directly influence brain blood flow. Choice C, Heparin and Warfarin, are anticoagulants and do not have a direct effect on brain blood flow through calcium channel blockade. Choice D, Vinpocetine and Nicergoline, are vasodilators that improve cerebral blood flow, but they do not act as calcium channel blockers.

Correct Answer: B

Rationale: Insulin is a polypeptide hormone, and as a protein-based molecule, it is susceptible to degradation by gastric juice, making option B correct. Gastric juice contains enzymes like pepsin that break down proteins. Option A is incorrect because polypeptides are not resistant to destruction by gastric juice. Option C is incorrect as insulin is indeed a polypeptide. Option D is incorrect as insulin is not immediately metabolized by cellular enzymes; instead, it plays a crucial role in regulating glucose metabolism.

Correct Answer: D

Rationale: The correct answer is D because the statement is false. The half-life of cortisol in circulation is around 60-90 minutes, not hours. Choice A is correct as cortisol is indeed synthesized from cholesterol. Choice B is correct as ACTH regulates cortisol secretion. Choice C is incorrect - most cortisol is inactivated in the liver.

Correct Answer: C

Rationale: The correct answer is C: Ethylenediamines; i.e. Suprastine. Ethylenediamines do not exhibit significant anticholinergic effects. Alkylamines, piperazines, and phenothiazines are known for their anticholinergic properties due to their chemical structures. Alkylamines have tertiary amines that cause anticholinergic effects. Piperazines have a bulky side chain that contributes to anticholinergic effects. Phenothiazines have a tricyclic structure that leads to anticholinergic activity. Therefore, C is the correct answer as ethylenediamines do not possess significant anticholinergic effects compared to the other categories.