Вариант 8

Irritable bowel syndrome (ibs)

In some people the intestine changes activity with no apparent cause or explanation. These changes may be accompanied by considerable abdominal discomfort or pain, and are referred to as the irritable bowel syndrome. The intestinal activity may sometimes increase, causing diarrhoea, and sometimes decrease, causing constipation. The cause or causes are nor fully understood and are controversial, though some cases are believed to be due to food intolerance: eating foods which are not well tolerated by some individuals even

though most people find them harmless. These cases of IBS can, therefore, be controlled by suitable changes to the diet.

Unfortunately drug treatments for IBS are limited because it is such an unpredictable disorder. The movements of the intestine are regulated by acetylcholine, released from parasympathetic nerves, which increases activity, and by norepinephrine, released from sympathetic nerves, which decreases activity.

One approach to treating diarrhoeal phases of IBS is to use drugs which block the receptors for acetylcholine. These include atropine, hyoscine, dicyclomine, poldine, and propantheline. Since all these drugs block muscarinic receptors for acetylcholine, they will all produce side-effects due to blocking receptors in organs other than the gut.

Вариант 9

Research is under way in many laboratories to determine the extent of involvement and the precise role of platelets in atherosclerosis and thrombosis and in diseases such as diabetes, in which these are common complications. The studies involve not only the measurement of platelet survival time and the plasma content of platelet products but also the effects of particular drugs on these variables and on the incidence of heart attacks and other sequels of atherosclerosis. Some drugs, such as dipyridamole and sulfinpyrazone, seem to prolong the life span of platelets that would otherwise have a short survival time, but the discovery of this effect was largely fortuitous and the mechanism of he action of the two drugs in this respect is obscure. There are other drugs, such as aspirin, whose mode of action with respect to platelets is well under-stood, but unfortunately these drugs do not seem to be as effective in prolonging platelet survival. Both basic physiological and biochemical research and applied clinical studies can contribute to a better understanding of the role platelets play in atherosclerosis - the leading cause of death in advanced societies - and in other diseases and con-genital disorders.