GRE阅读题目解析:胆固醇水平

　　P2

　　1

　　For some time scientists have believed that cholesterol plays a major role in heart disease because people with familial hypercholesterolemia, a genetic defect, have six to eight times the normal level of cholesterol in their blood and they invariably develop heart disease.

　　科学家们一度相信，胆固醇水平是心脏病的一个关键，因为有高胆固醇血家族病史的人群，血液中的胆固醇浓度是正常水平的六到八倍，而他们无一例外都得了心脏病，这是一种遗传缺陷。

　　(cholesterol 胆固醇【kə-'les-tə-ˌrōl, -ˌrȯl】

　　familial 家庭的，家族遗传的【fə-'mil-yəl, -'mi-lē-əl】

　　主干为加粗部分)

　　2

　　These people lack cell-surface receptors for low-density lipoproteins (LDL‘s), which are the fundamental carriers of blood cholesterol to the body cells that use cholesterol.

　　这类患者缺乏细胞表面的 低密度脂蛋白(LDL‘s)受体，这些受体是从血液中把胆固醇，运至有需要的细胞的主要载体。

　　3

　　Without an adequate number of cell-surface receptors to remove LDL‘s from the blood, the cholesterol-carrying LDL‘s remain in the blood, increasing blood cholesterol levels.

　　细胞表面缺乏足够数量的受体，运走血液中的 LDL’s，这些携带着胆固醇的 LDL‘s (蛋白)滞留在血液中，提高了血液的胆固醇水平。

　　4

　　Scientists also noticed that people with familial hypercholesterolemia appear to produce more LDL‘s than normal individuals.

　　科学家还注意到，患有遗传性高胆固醇血病的人群，在体内产生多于正常人水平的 LDL's 。

　　(hypercholesterolemia 血脂过高症)

　　5

　　How, scientists wondered, could a genetic mutation that causes a slow-down in the removal of LDL‘s from the blood also result in an increase in the synthesis of this cholesterol-carrying protein?

　　科学家好奇，一种基因突变如何能够减缓血液中的 LDL's 的运输，同时还合成了更多的，此种携带胆固醇的蛋白质?

　　6

　　Since scientists could not experiment on human body tissue, their knowledge of familial hypercholesterolemia was severely limited.

　　鉴于科学家们无法进行人体组织的实验，他们关于遗传性高胆固醇病的研究，严重受阻。

　　7

　　However, a breakthrough came in the laboratories of Yoshio Watanabe of Kobe University in Japan in 1980.

　　然而 1980 年，神户大学的 YW 所领导的实验室取得了突破。

　　8

　　Watanabe noticed that a male rabbit in his colony had ten times the normal concentration of cholesterol in its blood.

　　渡边注意到，他实验室里的一只雄兔，其血液中的胆固醇浓度是正常水平的十倍。

　　9

　　By appropriate breeding, Watanabe obtained a strain of rabbits that had very high cholesterol levels.

　　经过悉心培养，渡边得到了一个高胆固醇兔子家族。

　　(strain 家族，血统)

　　10

　　These rabbits spontaneously developed heart disease.

　　这些兔子都得了心脏病。

　　(spontaneously 自然地，自发的，非强迫的

　　科学家坦然作孽)

　　11

　　To his surprise, Watanabe further found that the rabbits, like humans with familial hypercholesterolemia, lacked LDL receptors.

　　渡边对后续发现惊讶不已，这些兔子和患有遗传性高胆固醇血病的人类一样，都缺乏 LDL 受体。

　　12

　　Thus, scientists could study these Watanabe rabbits to gain a better understanding of familial hypercholesterolemia in humans.

　　于是，科学家们可以通过研究渡边兔，更深入地了解人类的遗传性高胆固醇血病。

　　13

　　Prior to the breakthrough at Kobe University, it was known that LDL‘s are secreted from the liver in the form of a precursor, called very low-density lipoproteins (VLDL‘s), which carry triglycerides as well as relatively small amounts of cholesterol.

　　神户大学的研究取得进展以前，科学家们已经知道 LDL’s 的前体，是由肝脏分泌的 非常低密度脂蛋白 VLDL's ，它携带甘油三酯以及相对少量的胆固醇。

　　(triglyceride 甘油三酯【(ˌ)trī-'gli-sə-ˌrīd】)

　　14

　　The triglycerides are removed from the VLDL‘s by fatty and other tissues.

　　甘油三酯被脂肪组织和其他组织吸收。

　　15

　　What remains is a remnant particle that must be removed from the blood.

　　余下的物质必须从血液中清除。

　　16

　　What scientists learned by studying the Watanabe rabbits is that the removal of the VLDL remnant requires the LDL receptor.

　　通过研究渡边兔，科学家们认识到想要清除 VLDL 残余物，需要 LDL 受体。

　　17

　　Normally, the majority of the VLDL remnants go to the liver where they bind to LDL receptors and are degraded.

　　正常情况下，多数 VLDL 残余物在肝脏与 LDL 受体结合并分解。

　　18

　　In the Watanabe rabbit, due to a lack of LDL receptors on liver cells, the VLDL remnants remain in the blood and are eventually converted to LDL‘s.

　　渡边兔的肝细胞缺乏 LDL 受体，VLDL 残余物滞留在血液中，最终转变为 LDL's 。

　　19

　　The LDL receptors thus have a dual effect in controlling LDL levels.

　　可见，LDL 受体在控制 LDL 水平时发挥着双重作用。

　　20

　　They are necessary to prevent oversynthesis of LDL‘s from VLDL remnants and they are necessary for the normal removal of LDL‘s from the blood.

　　它在两种情况下都不可或缺：防止 VLDL 残余物被过度合成 LDL's ，以及清除血液中常规存在的 LDL's 。

　　21

　　With this knowledge, scientists are now well on the way toward developing drugs that dramatically lower cholesterol levels in people afflicted with certain forms of familial hypercholesterolemia.

　　了解到这些，科学家们都致力于寻找能够极大降低血液中胆固醇水平的新药，缓解那些深受遗传性高胆固醇血病折磨的病人的痛苦。

　　3. In the passage, the author is primarily concerned with

　　(A) presenting a hypothesis and describing compelling evidence in support of it

　　(B) raising a question and describing an important discovery that led to an answer

　　(C) showing that a certain genetically caused disease can be treated effectively with drugs

　　(D) explaining what causes the genetic mutation that leads to heart disease

　　(E) discussing the importance of research on animals for the study of human disease

　　选 B

　　提出一个问题，描述一项指向答案的重要发现。

　　提出的问题在句 5：基因突变为什么能一方面减缓 LDL 的运输，又增加血液中 LDL 的合成;

　　重要发现，就是神户大学的渡边实验室，很科学(怪人)家作风地养出了一群高胆固醇兔子，发现了其中的一些关联。

　　For the following question, consider each of the choices separately and select all that apply

　　4. The passage supplies information to answer which of the following questions EXCEPT ?

　　(A) Which body cells are the primary users of cholesterol?

　　(B) How did scientists discover that LDL‘s are secreted from the liver in the form of a precursor?

　　(C) Where in the body are VLDL remnants degraded?

　　选 AB

　　注意，选 EXCEPT 项。

　　A 哪一种人体细胞是胆固醇的主要使用者，没说

　　B 科学家们如何发现 LDL‘s 的前体是肝脏分泌的，文中只说科学家已经知道，没说怎么知道的

　　C 在什么器官或部位降解 VLDL，句 17 说了，肝

　　5. The passage implies that if the Watanabe rabbits had had as many LDL receptors on their livers as do normal rabbits, the Watanabe rabbits would have been

　　(A) less likely than normal rabbits to develop heart disease

　　(B) less likely than normal rabbits to develop high concentrations of cholesterol in their blood

　　(C) less useful than they actually were to scientists in the study of familial hypercholesterolemia in humans

　　(D) unable to secrete VLDL‘s from their livers

　　(E) immune to drugs that lower cholesterol levels in people with certain forms of familial hypercholesterolemia

　　选 C

　　注意题目逻辑，文章为什么要说渡边兔，或者说科学家为什么研究这些兔子。

　　A 很可能是成立的，但不符合作者和科学家们的用意，研究这些兔子是因为它们的症状跟某些人类症状相似，有借鉴意义，作者没有论证高胆固醇兔子发心脏病是不是必然。

　　B 可能成立，但不选，理由同上。

　　C 正确项。

　　D 噢。

　　E 掰掰。

　　6. The passage implies that Watanabe rabbits differ from normal rabbits in which of the following ways?

　　(A) Watanabe rabbits have more LDL receptors than do normal rabbits.

　　(B) The blood of Watanabe rabbits contains more VLDL remnants than does the blood of normal rabbits.

　　(C) Watanabe rabbits have fewer fatty tissues than do normal rabbits.

　　(D) Watanabe rabbits secrete lower levels of VLDL‘s than do normal rabbits.

　　(E) The blood of Watanabe rabbits contains fewer LDL‘s than does the blood of normal rabbits.

　　选 B

　　A 说反了，是 less 。

　　B 正确。残余物多。

　　C 无法判断。如果题目让我们推测一种比较可能的推论，尽管我们也觉得这些兔子很可能更胖，但还是应该专业地装傻，因为文中信息不足以做出这样的推论。

　　D 渡边兔分泌的 VLDL's 很可能跟正常的没区别，只是缺受体去吸收残余物 LDL’s 。

　　E 说反了，是 more 。

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