GRE阅读模拟在线练习附答案二百七十四

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　　The complications frequently accompanyingdiabetes, such as impairment of vision and ofkidney function,are now thought to result from thelack of continuous control of blood glucoseconcentrations. The healthy pancreas, in responseto increases in blood glucose concent-ration, releases small quantities of insulin throughout theday and thereby maintains the concentrationwithin physiological limits (normoglycemia). But the diabetic generally receives only one largedose daily.The diabetic's blood glucose concentration can thus fluctuate greatly during theinterval between doses, and it has been suggested that the complications result from theperiods of high concentrations of blood glucose (hyperglycemia). Many investigators thusbelieve that restoration of normoglycemia might halt the pro-gression of such complicationsand perhaps even reverse them.

　　There are three primary techniques that have been investigated for restoration ofnormoglycemia. They are:transplantation of whole,healthy pancreases;transplantation ofislets of Langerhans, that portion of the pancreas that actually secretes insulin;andimplantation of artificial pancreases.There has, in fact, been a great deal of success in thedevelop-ment of these techniques and each seems, on the whole, promising. Nonetheless, itwill undoubtedly be many years before any one of them is accepted as a treatment fordiabetes.

　　To many people. the obvious approach would seem to be simply to transplant pancreasesfrom cadavers in the same manner that kidneys and other organs are routinely transplanted. That was the rationale in 1966 when the first recorded pancreas transplant was performed. Between 1966 and 1975, there were forty-six pancreas trans-plants in forty-five other patients　　in the United States and five other countries. But only one of these patients is still alive witha functioning graft, and surgeons have found that the procedure is not as simple as they oncethought.

　　The surviving patient has required no insulin since the operation. Another patient survived 638 days without requiring insulin. And one patient survived a transplantation for more than ayear, but died when he chose not to take the immuno-suppressive drugs. These results, thoughmeager, suggest that the procedure has the potential for success.

　　The rest of the patients, however, either rejected the transplant or died within a short period. There does not appear to be any technical problem with the procedure. Rather, most of thepatients were already so severely debilitated by the compli-cations of diabetes that they couldnot withstand, the surgery and the immunosuppressive regimen required to preventrejection. More than half of the patients, furthermore, also required a kidney transplant. Mostinvestigators now agree that the simultaneous transplantation of both organs is too great ashock to the patient and greatly increases the total risk.

　　Which of the following best states one of the main conclusions of the passage?

　　A.Although the techniques for pancreas transplants appear to be theoretically correct, thereare problems that must be solved before the operation can be used as a treatment fordiabetes.

　　B.Although the techniques for pancreas transplants are still being developed, theexperimental results show that the operation will be a successful treatment for diabetes inthe near future.

　　C.Although pancreas transplants are reliable, many diabetics are reluctant to undergo theoperation because of the side effects of immunosuppressive drugs.

　　D.Although pancreas transplants alone are not generally successful, the operation can be usedin conjunction with other procedures to treat diabetes.

　　E.Although pancreas transplants have not been successful in treating diabetes, researchindicates that other procedures may soon be developed.

　　According to the passage, widely spaced doses of insulin can cause.

　　A.reversal of normal kidney function

　　B.delay in the onset of diabetes

　　C.radical changes in the concentration of blood glucose

　　D.restoration of normoglycemia

　　E.marked variations in the islets of Langerhans

　　According to the passage, a periodic high concentration of blood glucose in diabeticsis a possible cause of

　　A.deterioration of the pancreas

　　B.damage to the eyes and kidneys

　　C.rejection of transplanted organs

　　D.inadequate secretion of insulin

　　E.increased production of blood cells

　　It can be inferred from the passage that one of the important contributing causes ofthe failure of most pancreas transplants has been the

　　A.reluctance of patients to cooperate with physicians

　　B.imperfect techniques used in the operations

　　C.scarcity of immunosuppressive drugs

　　D.unavailability or healthy pancreases

　　E.weakened condition of the patients

　　The author provides information that would answer which of the following questions?

　　I. What is hyperglycemia?

　　II. What is one cause of hyperglycemia?

　　III. What are some of the organs that can be adversely affected by hyperglycemia?

　　A.I only

　　B.II only

　　C.I and III only

　　D.II and III only

　　E.I, II, and III

　　On the basis of the information in the passage, which of the following can be inferredabout the islets of Langerhans?

　　I. They are important for the normal control of blood glucose concentration.

　　II. They can be transplanted independently of other pancreatic cells.

　　III. They regulate immunosuppressive reactions.

　　A.I only

　　B.III only

　　C.I and II only

　　D.I and II only

　　E.I, II, and III

　　The passage suggests that the author considers the data concerning the success ofpancreas transplants to be

　　A.invalid

　　B.indirect

　　C.inaccurate

　　D.insufficient

　　E.inappropriate

　　正确答案:A C B E E C D

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