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.

[答案与考点解析]

1. 【答案】A

【考点解析】本题是一道审题定位题。本题的题干比较奇怪，没有明确指出本题答案信息在原文中的确切位置。在大多数情况下，考生会迷失解题思路。我们一再重申：考生在迷失解题思路时一定要多想一想全文的中心主旨句，以及各段的主题句。本文的中心主旨句是第二段的尾句，本题的正确选项A恰恰是来自于本句。这再次说明我们在迷失解题思路时应该首先想到全文的中心主旨句或每段的主题句。

2. 【答案】C

【考点解析】这是一道细节推导题。通过本题题干中的“widely spaced doses of insulin”可将本题的答案信息来源确定在首段的第三、四句。因为这两句话提到了“doses of insulin”。通过仔细阅读和理解第三、四句，就可推导出本题的正确选项C。考生在解题时一定要善于理解和把握题干和原文所进行的同义词替换。

3. 【答案】B

【考点解析】这是一道句间关系题。通过题干中的“periodic high concentration”可将本题的答案信息来源迅速确定在第一段的第四句。通过仔细阅读和理解第四句，尤其是把第四句中的“complication”和第一句中的“complications”进行连贯的理解，就可推导出本题的正确选项B。考生在解题时要善于发现和理解句子之间的关系。

4. 【答案】D

【考点解析】这是一道细节推导题。通过题干中的“failure”一词可推断本题的正确答案信息在倒数第二段尾句的前后，因为该句所谈论的中心话题是“success”。又根据题干中的“most”一词将本题的答案信息确定在尾段的第三句，因为该句中含有“most”一词。通过阅读和理解尾段第三句，可推导出本题的正确答案是D。考生在解题时要注意灵活理解题干和原文所表达的内容，千万不能生硬地进行理解。

5. 【答案】D

【考点解析】本文是一道词汇理解题。本题题干中的“success”将本题的答案信息来源确定在倒数第二段的尾句。该句中的“meager”(不足的，贫乏的)暗示本题的正确选项是D。考生在解题时一定要对关键词加以重视并进行合理的推断。

[参考译文]

通常与糖尿病相伴的并发症，如视力和肾功能的损害，现在被认为是由于无法连续控制血液中的葡萄糖浓度所导致的。健康的胰脏，在血糖浓度增加时，会在整个白天不断地释放出少量的胰岛素，从而使血糖浓度维持在生理限度之内(正常血糖量)。但是糖尿病患者一般是每天得到一次大剂量胰岛素的注射。这样在两次注射之间，糖尿病患者的血糖浓度会发生很大波动，而且目前已被指出，并发症可能就是源于这些高血糖浓度时期(高血糖)。因此，许多研究人员相信，恢复正常的血糖浓度或许能阻止这些并发症的发展，并进而可能减轻并发症。

为了恢复正常的血糖浓度，已对三种主要的技术进行了研究。它们分别是：健康胰脏的整个移植;胰岛部分的移植，胰岛是胰腺中实际分泌胰岛素的部分;以及人造腺的移植。事实上，这些技术的发展都获得了成功，而且从整体上讲，每种技术都大有希望。然而，毫无疑问地，在任何一种技术被接受用作糖尿病患者的治疗手段之前，还会有很多年的时间。

对多数人而言，显而易见的方法看来可能是从尸体中移植胰腺，就象移植肾脏和其它器官那样。这便是1966年第一例胰腺移植手术的理论基础。在1966年至1975年间，在美国和另外五个国家，共有45名其它病人进行了46例胰腺移植手术。但目前，只有其中一个病人尚在人世，而且移植的胰腺功能健全。因此，手术医生们发现，手术过程并不像他们先前想象的那么简单。

幸存的病人从那次手术之后不再需要注射胰岛素。另一个病人在不需要注射胰岛素的情况下活了638天。还有一名病人在移植之后存活了一年，但他决定不服用免疫药物之后就死去了。这些结果，尽管为数不多，可也表明了手术过程有潜在成功的可能。

然而，其余的病人或者出现排异反应，或者在很短一段时期后死去。在手术过程中，看起来是不存在任何技术问题的。不过，大多数的病人都由于糖尿病的并发病已经很衰弱，以至于无法经受手术和为防止排异反应所需的免疫抑制疗程。另外，一大半病人还需要进行肾脏移植。目前，多数研究人员都认为同时移植两个器官对病人自身系统影响太大，而且极大地增加了整体的风险。