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　　SAMPLE 19

　　[醫(yī)學(xué)類]

　　The complications frequently accompanying diabetes, such as impairment of vision and of kidney function, are now thought to result from the lack of continuous control of blood glucose concentrations. The healthy pancreas, in response to increases in blood glucose concentration, releases small quantities of insulin throughout the day and thereby maintains the concentration within physiological limits (nomoglycemia). But the diabetic generally receives only one large dose daily. The diabetic’s blood glucose concentration can thus fluctuate greatly during the interval between doses, and it has been suggested that the complication result from the periods of high concentrations of blood glucose (hyperglycemia). Many investigators thus believe that restoration of normoglycemia might halt the progression of such complications and perhaps even reverse them.

　　There are three primary techniques that have been investigated for restoration of normoglycemia. They are: transplantation of whole, healthy pancreases; transplantation of islets of Langerthan, that portion of the pancreas that actually secretes insulin, and implantation of artificial pancreases. There has, in fact been a great deal of success in the development of these techniques and each seems, on the whole, promising. Nonetheless, it will undoubtedly be many years before any one of them is accepted as a treatment for diabetes.

　　To many people, the obvious approach would seem to be simply to transplant pancreases from cadavers in the same manner that kidneys and other organs are routinely transplanted. That was the rationale in 1966 when the first recorded pancreas was performed. Between 1960 and 1975, there were forty-six pancreas transplants in forty-five other patients in the United States and five other countries. But only one of these patients is still alive with a functioning graft and surgeons have found that the procedure is not simple as they once thought.

　　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 a year, but died when he chose not to take immunosuppressive drugs. These results, though meager, 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 the patients were already so severely debilitated by the complications of diabetes that they could not withstand the surgery and the immunosuppressive regimen required to prevent rejection. More than half of the patients, furthermore, also required a kidney transplant. Most investigators now agree that the simultaneous transplantation of both organs is too great a shock to the patient and greatly increases the total risk.

　　1. Which of the following best states one of the main conclusions of the text?

　　[A] Although the techniques for pancreas transplants appear to be theoretically correct, there are problems that must be solved before the operation can be used as a treatment for diabetes.

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

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

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

　　2. According to the text, 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.

　　3. According to the text, a periodic high concentration of blood glucose in diabetics is 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.

　　4. It can be inferred from the text that one of the important contributing causes of the failure of most pancreas transplants has been the

　　[A] reluctance of patients to cooperate with physicians.

　　[B] imperfect techniques used in the operation.

　　[C] scarcity of immunosuppressive drugs.

　　[D] weakened condition of the patients.

　　5. The text suggests that the author considers the data concerning the success of pancreas transplants to be

　　[A] invalid.

　　[B] indirect.

　　[C] inaccurate.

　　[D] insufficient.