gre阅读练习每日一篇(五十)
<p> 掌握了<span word="gre">gre</span>阅读里的长难句，到了实战演习的时候了。<span word="gre">gre</span>阅读练习每日一篇帮助<span word="gre">gre</span>考生循序渐进地进行练习和总结。希望<span word="gre">gre</span>考生在进行<span word="gre">gre</span>阅读练习时，也按着考试时候的时间规定自己的练习，这样才能有效果。</p><p> <span word="For">For</span> <span word="some">some</span> <span word="time">time</span> <span word="scientists">scientists</span> <span word="have">have</span> <span word="believed">believed</span> <span word="that">that</span> <span word="cholesterol">cholesterol</span> <span word="plays">plays</span> <span word="a">a</span> <span word="major">major</span> <span word="role">role</span> <span word="in">in</span> <span word="heart">heart</span> <span word="disease">disease</span> <span word="because">because</span> <span word="people">people</span> <span word="with">with</span> <span word="familial">familial</span> <span word="hypercholesterolemia">hypercholesterolemia</span> , <span word="a">a</span> <span word="genetic">genetic</span> <span word="defect">defect</span>, <span word="have">have</span> <span word="six">six</span> <span word="to">to</span> <span word="eight">eight</span> <span word="times">times</span> <span word="the">the</span> <span word="normal">normal</span> <span word="level">level</span> <span word="of">of</span> <span word="cholesterol">cholesterol</span> <span word="in">in</span> <span word="their">their</span> <span word="blood">blood</span> <span word="and">and</span> <span word="they">they</span> <span word="invariably">invariably</span> <span word="develop">develop</span> <span word="heart">heart</span> <span word="disease">disease</span>. <span word="These">These</span> <span word="people">people</span> <span word="lack">lack</span> <span word="cell">cell</span>-<span word="surface">surface</span> <span word="receptors">receptors</span> <span word="for">for</span> <span word="low">low</span>-<span word="density">density</span> <span word="lipoproteins">lipoproteins</span> , <span word="which">which</span> <span word="are">are</span> <span word="the">the</span> <span word="fundamental">fundamental</span> <span word="carriers">carriers</span> <span word="of">of</span> <span word="blood">blood</span> <span word="cholesterol">cholesterol</span> <span word="to">to</span> <span word="the">the</span> <span word="body">body</span> <span word="cells">cells</span> <span word="that">that</span> <span word="use">use</span> <span word="cholesterol">cholesterol</span>. <span word="Without">Without</span> <span word="an">an</span> <span word="adequate">adequate</span> <span word="number">number</span> <span word="of">of</span> <span word="cell">cell</span>-<span word="surface">surface</span> <span word="receptors">receptors</span> <span word="to">to</span> <span word="remove">remove</span> <span word="LDLs">LDLs</span> <span word="from">from</span> <span word="the">the</span> <span word="blood">blood</span>, <span word="the">the</span> <span word="cholesterol">cholesterol</span>-<span word="carrying">carrying</span> <span word="LDLs">LDLs</span> <span word="remain">remain</span> <span word="in">in</span> <span word="the">the</span> <span word="blood">blood</span>, <span word="increasing">increasing</span> <span word="blood">blood</span> <span word="cholesterol">cholesterol</span> <span word="levels">levels</span>. <span word="Scientists">Scientists</span> <span word="also">also</span> <span word="noticed">noticed</span> <span word="that">that</span> <span word="people">people</span> <span word="with">with</span> <span word="familial">familial</span> <span word="hypercholesterolemia">hypercholesterolemia</span> <span word="appear">appear</span> <span word="to">to</span> <span word="produce">produce</span> <span word="more">more</span> <span word="LDLs">LDLs</span> <span word="than">than</span> <span word="normal">normal</span> <span word="individuals">individuals</span>. <span word="How">How</span>, <span word="scientists">scientists</span> <span word="wondered">wondered</span>, <span word="could">could</span> <span word="a">a</span> <span word="genetic">genetic</span> <span word="mutation">mutation</span> <span word="that">that</span> <span word="causes">causes</span> <span word="a">a</span> <span word="slowdown">slowdown</span> <span word="in">in</span> <span word="the">the</span> <span word="removal">removal</span> <span word="of">of</span> <span word="LDLs">LDLs</span> <span word="from">from</span> <span word="the">the</span> <span word="blood">blood</span> <span word="also">also</span> <span word="result">result</span> <span word="in">in</span> <span word="an">an</span> <span word="increase">increase</span> <span word="in">in</span> <span word="the">the</span> <span word="synthesis">synthesis</span> <span word="of">of</span> <span word="this">this</span> <span word="cholesterol">cholesterol</span>-<span word="carrying">carrying</span> <span word="protein">protein</span>?</p><p> <span word="Since">Since</span> <span word="scientists">scientists</span> <span word="could">could</span> <span word="not">not</span> <span word="experiment">experiment</span> <span word="on">on</span> <span word="human">human</span> <span word="body">body</span> <span word="tissue">tissue</span>, <span word="their">their</span> <span word="knowledge">knowledge</span> <span word="of">of</span> <span word="familial">familial</span> <span word="hypercholesterolemia">hypercholesterolemia</span> <span word="was">was</span> <span word="severely">severely</span> <span word="limited">limited</span>. <span word="However">However</span>, <span word="a">a</span> <span word="breakthrough">breakthrough</span> <span word="came">came</span> <span word="in">in</span> <span word="the">the</span> <span word="laboratories">laboratories</span> <span word="of">of</span> <span word="Yoshio">Yoshio</span> <span word="Watanabe">Watanabe</span> <span word="of">of</span> <span word="Kobe">Kobe</span> <span word="University">University</span> <span word="in">in</span> <span word="Japan">Japan</span> <span word="in">in</span> 1980. <span word="Watanabe">Watanabe</span> <span word="noticed">noticed</span> <span word="that">that</span> <span word="a">a</span> <span word="male">male</span> <span word="rabbit">rabbit</span> <span word="in">in</span> <span word="his">his</span> <span word="colony">colony</span> <span word="had">had</span> <span word="ten">ten</span> <span word="times">times</span> <span word="the">the</span> <span word="normal">normal</span> <span word="concentration">concentration</span> <span word="of">of</span> <span word="cholesterol">cholesterol</span> <span word="in">in</span> <span word="its">its</span> <span word="blood">blood</span>. <span word="By">By</span> <span word="appropriate">appropriate</span> <span word="breeding">breeding</span>, <span word="Watanabe">Watanabe</span> <span word="obtained">obtained</span> <span word="a">a</span> <span word="strain">strain</span> <span word="of">of</span> <span word="rabbits">rabbits</span> <span word="that">that</span> <span word="had">had</span> <span word="very">very</span> <span word="high">high</span> <span word="cholesterol">cholesterol</span> <span word="levels">levels</span>. <span word="These">These</span> <span word="rabbits">rabbits</span> <span word="spontaneously">spontaneously</span> <span word="developed">developed</span> <span word="heart">heart</span> <span word="disease">disease</span>. <span word="To">To</span> <span word="his">his</span> <span word="surprise">surprise</span>, <span word="Watanabe">Watanabe</span> <span word="further">further</span> <span word="found">found</span> <span word="that">that</span> <span word="the">the</span> <span word="rabbits">rabbits</span>, <span word="like">like</span> <span word="humans">humans</span> <span word="with">with</span> <span word="familial">familial</span> <span word="hypercholesterolemia">hypercholesterolemia</span>, <span word="lacked">lacked</span> <span word="LDL">LDL</span> <span word="receptors">receptors</span>. <span word="Thus">Thus</span>, <span word="scientists">scientists</span> <span word="could">could</span> <span word="study">study</span> <span word="these">these</span> <span word="Watanabe">Watanabe</span> <span word="rabbits">rabbits</span> <span word="to">to</span> <span word="gain">gain</span> <span word="a">a</span> <span word="better">better</span> <span word="understanding">understanding</span> <span word="of">of</span> <span word="familial">familial</span> <span word="hypercholesterolemia">hypercholesterolemia</span> <span word="in">in</span> <span word="humans">humans</span>.</p>
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