Until about five years ago, the very idea that peptide hormones might be made anywhere in the brain besides the hypothalamus was astounding- Peptide hormones, scientists thought, were made by endocrine glands and the hypothalamus was thought to be the brains’ only endocrine gland. What is more, because peptide hormones cannot cross the blood-brain barrier; researchers believed that they never got to any part of the brain other than the hypothalamus, where they were simply produced and then released into the bloodstream.
But these beliefs about peptide hormones were questioned as laboratory after laboratory found that antiserums to peptide hormones, when injected into the brain, bind in places other than the hypothalamus, indicating that either the hormones or substances that cross-react with the antiserums are present. The immunological method of detecting peptide hormones by means of antiserums, however, is imprecise. Cross-reactions are possible, and this method cannot determine whether the substances detected by the antiserums really are the hormones, or merely close relatives. Furthermore this method cannot be used to determine the location in the body where the detected substances are actually produced.
New techniques of molecular biology, however, provide a way to answer these questions. It is possible to make specific complementary DNA’s (cDNA’s) that can serve as molecular probes to seek out the messenger RNA’s (mRNA’s) of the peptide hormones. If brain cells are making the hormones, the cells will contain these mRNA’s. If the products the brain cells make resemble the hormones but are not identical to them, then the cDNA’s should still bind to these mRNA’s, but should not bind as tightly as they would to mRNA’s for the true hormones. The cells containing these mRNA’s can then be isolated and their mRNA’s decoded to determine just what their protein products are and how closely the products resemble the true peptide hormones.
The molecular approach to detecting peptide hormones using cDNA probes should also be much faster than the immunological method because it can take years of tedious purifications to isolate peptide hormones and then develop antiserums to them. Roberts, expressing the sentiment of many researchers, states: “I was trained as an endocrinologist. But it became clear to me that the field of endocrinology needed molecular biology input. The process of grinding out protein purifications is just too slow.”
If, as the initial tests with cDNA probes suggest, peptide hormones really are made in the brain in areas other than the hypothalamus, a theory must be developed that explains their function in the brain. Some have suggested that the hormones are all growth regulators, but Rosen’s work on rat brains indicates that this cannot be true. A number of other researchers propose that they might be used for intercellular communication in the brain.
1.Which of the following titles best summarizes the passage?
2.The passage suggests that a substance detected in brain by use of antiserums to peptide hormones may（ ）.
3.The passage implies that, in doing research on rat brains, Rosen discovered that （ ）.
4.Which of the following is a way in which the immunological method of detecting peptide hormones differs from the molecular method?
问题1选项
A.Is Molecular Biology the Key to Understanding Intercellular Communication in the Brain?
B.Molecular Biology: Can Researchers Exploit Its Techniques to Synthesize Peptide Hormones?
C.The Advantages and Disadvantages of the Immunological Approach to Detecting Peptide Hormones.
D.Peptide Hormones: How Scientists Are Attempting to Solve Problems of Their Detection.
问题2选项
A.have been stored in the brain for a long period of time and to Understand Their Function
B.play no role in the functioning of the brain
C.have been produced in some part of the body other than the brain
D.play an important role in the functioning of hypothalamus
问题3选项
A.peptide hormones are used for intercellular communication
B.complementary DNA’s do not bind to cells producing peptide hormones
C.products closely resembling peptide hormones are not identical to peptide hormone
D.some peptide hormones do not function as growth regulators
问题4选项
A.The immunological method uses substances that react with products of hormone-producing cells, whereas the molecular method uses substances that react with a specific component of the cells themselves.
B.The immunological method has produced results consistent with long-held beliefs about peptide hormones, whereas the molecular method has produced results that upset these beliefs.
C.The immunological method uses probes that can only bind with peptide hormones, whereas the molecular method uses probes that bind with peptide hormones and substances similar to them
D.The immunological method can only be used to test for the presence of peptide hormones within the hypothalamus, whereas the molecular method can be used throughout the brain.
第1题:
【选项释义】
Which of the following titles best summarizes the passage? 下面哪个标题最好地概括了这篇文章？
A. Is Molecular Biology the Key to Understanding Intercellular Communication in the Brain? A. 分子生物学是理解大脑细胞间通讯的关键吗？
B. Molecular Biology: Can Researchers Exploit Its Techniques to Synthesize Peptide Hormones? B. 分子生物学：研究人员能否利用其技术合成肽激素？
C. The Advantages and Disadvantages of the Immunological Approach to Detecting Peptide Hormones. C. 免疫学方法检测肽激素的优缺点。
D. Peptide Hormones: How Scientists Are Attempting to Solve Problems of Their Detection. D. 肽激素：科学家如何试图解决它们的检测问题。
【考查点】主旨大意题。
【解题思路】文章第一段说到了之前关于肽激素的一些研究看法，但第二段开头就出现了转折关系词but，本文的讨论点必然是在but之后出现。第一句说到But these beliefs about peptide hormones were questioned as laboratory after laboratory found that antiserums to peptide hormones, when injected into the brain, bind in places other than the hypothalamus, indicating that either the hormones or substances that cross-react with the antiserums are present.（但是，这些关于肽激素的观点受到了质疑，因为一个又一个的实验室都发现，抗血清肽激素被注射进大脑后，会在下丘脑以外的地方结合，这表明要么是激素，要么是与抗血清发生交叉反应的物质），可知下文不会讨论A选项中的“分子生物学与大脑间通讯”，也不会研究B选项“技术合成肽激素”，也不是讨论C选项“检测肽激素的优缺点”，而是把重心放在研究肽激素的位置，及怎样去检测它的位置，因此D选项“肽激素：科学家如何试图解决它们的检测问题”正确。
【干扰项排除】
A、B、C选项均不是文章主要讨论的问题，属于曲解原文。
第2题:
【选项释义】
The passage suggests that a substance detected in brain by use of antiserums to peptide hormones may（ ）. 这篇文章表明，通过使用抗血清肽激素在大脑中检测到的一种物质（ ）。
A. have been stored in the brain for a long period of time and to Understand Their Function A. 已经在大脑中储存了很长一段时间，并了解它们的功能
B. play no role in the functioning of the brain B. 对大脑的运作没有任何影响
C. have been produced in some part of the body other than the brain C. 是在身体的其他部位产生的，而不是大脑
D. play an important role in the functioning of hypothalamus D. 在下丘脑的功能中起重要作用
【考查点】事实细节题。
【解题思路】根据题干关键词antiserums to peptide hormones定位文章第二段首句But these beliefs about peptide hormones were questioned as laboratory after laboratory found that antiserums to peptide hormones, when injected into the brain, bind in places other than the hypothalamus, indicating that either the hormones or substances that cross-react with the antiserums are present.（但是，这些关于肽激素的观点受到了质疑，因为一个又一个的实验室都发现，抗血清肽激素被注射进大脑后，会在下丘脑以外的地方结合，这表明要么是激素，要么是与抗血清发生交叉反应的物质），说明这些物质是在下丘脑以外的地方结合形成的，因此C选项“是在身体的其他部位产生的，而不是大脑”正确。
【干扰项排除】
A、D选项均未在文中体现，属于无中生有；
B选项“对大脑的运作没有任何影响”，根据文章最后一段A number of other researchers propose that they might be used for intercellular communication in the brain.（其他一些研究人员提出，它们可能用于大脑中的细胞间通信），可知抗血清肽激素并非对大脑的运作没有任何影响，属于曲解原文。
第3题:
【选项释义】
The passage implies that, in doing research on rat brains, Rosen discovered that（ ）. 这篇文章暗示，在对老鼠大脑进行研究时，罗森发现（ ）。
A. peptide hormones are used for intercellular communication A. 肽激素用于细胞间通讯
B. complementary DNA’s do not bind to cells producing peptide hormones B. 互补DNA不与产生肽激素的细胞结合
C. products closely resembling peptide hormones are not identical to peptide hormone C. 类似肽激素的产品与肽激素并不完全相同
D. some peptide hormones do not function as growth regulators D. 有些肽激素没有生长调节剂的功能
【考查点】事实细节题。
【解题思路】根据题干关键词rat brains和Rosen定位文章最后一段第二句Some have suggested that the hormones are all growth regulators, but Rosen’s work on rat brains indicates that this cannot be true.（有些人认为这些激素都是生长调节剂，但Rosen对老鼠大脑的研究表明这不是真的），可知Rosen的研究表明这些激素并不是生长调节剂，因此D选项“有些肽激素没有生长调节剂的功能”正确。
【干扰项排除】
A、B、C选项虽在文章最后一段和第三段中有所体现，但并不属于罗森从老鼠大脑研究中所发现的内容，属于答非所问。
第4题:
【选项释义】
Which of the following is a way in which the immunological method of detecting peptide hormones differs from the molecular method? 以下哪一项是检测肽激素的免疫学方法不同于分子方法的方法？
A. The immunological method uses substances that react with products of hormone-producing cells, whereas the molecular method uses substances that react with a specific component of the cells themselves. A. 免疫学方法使用与产生激素的细胞产生反应的物质，而分子方法使用与细胞自身特定成分发生反应的物质。
B. The immunological method has produced results consistent with long-held beliefs about peptide hormones, whereas the molecular method has produced results that upset these beliefs. B. 免疫学方法产生的结果与长期以来人们对肽激素的看法一致，而分子方法产生的结果却颠覆了这些看法。
C. The immunological method uses probes that can only bind with peptide hormones, whereas the molecular method uses probes that bind with peptide hormones and substances similar to them. C. 免疫学方法使用的探针只能与肽激素结合，而分子方法使用的探针与肽激素及其类似物质结合。
D. The immunological method can only be used to test for the presence of peptide hormones within the hypothalamus, whereas the molecular method can be used throughout the brain. D. 免疫学方法只能用于测试下丘脑内肽激素的存在，而分子方法可以用于整个大脑。
【考查点】推理判断题。
【解题思路】题干中提到了两个检测肽激素的方式对比，文章第二段详细说明了第一种方法The immunological method of detecting peptide hormones by means of antiserums, however, is imprecise. Cross-reactions are possible, and this method cannot determine whether the substances detected by the antiserums really are the hormones, or merely close relatives.（然而，用抗血清来测定肽激素的免疫学方法是不精确的，可能产生交叉反应。而且这种方法不能确定抗血清检测到的物质是否真的是激素，有可能仅仅是近亲），符合A选项中“免疫学方法使用与产生激素的细胞产生反应的物质”的表述；第二个方法的描述出现在第三段New techniques of molecular biology, however, provide a way to answer these questions. It is possible to make specific complementary DNA’s (cDNA’s) that can serve as molecular probes to seek out the messenger RNA’s (mRNA’s) of the peptide hormones.（然而，分子生物学的新技术为这些问题提供了答案。科学家可以制造出特殊的互补DNA’s (cDNA’s)，以此作为分子探针，探寻出肽激素的信使RNA’s (mRNA’s)），此处说的“问题”就是第一种方法中说到的“近亲”问题，符合A选项中“分子方法使用与细胞自身特定成分发生反应的物质”的表述，因此A选项正确。
【干扰项排除】
B、C、D选项均未在文中体现，属于无中生有。
