为什么有些地方长毛发有些地方却不长?
<p><span word="Why">Why</span> <span word="can">can</span> <span word="millions">millions</span> <span word="of">of</span> <span word="hairs">hairs</span> <span word="grow">grow</span> <span word="from">from</span> <span word="our">our</span> <span word="heads">heads</span>, <span word="and">and</span> <span word="yet">yet</span> <span word="our">our</span> <span word="palms">palms</span> <span word="and">and</span> <span word="the">the</span> <span word="soles">soles</span> <span word="of">of</span> <span word="our">our</span> <span word="feet">feet</span> <span word="are">are</span> <span word="as">as</span> <span word="bare">bare</span> <span word="as">as</span> <span word="anything">anything</span>? <span word="It">It</span> <span word="all">all</span> <span word="comes">comes</span> <span word="down">down</span> <span word="to">to</span> <span word="a">a</span> <span word="special">special</span> <span word="molecule">molecule</span> <span word="in">in</span> <span word="our">our</span> <span word="bodies">bodies</span>, <span word="according">according</span> <span word="to">to</span> <span word="the">the</span> <span word="scientists">scientists</span> <span word="who">who</span> <span word="have">have</span> <span word="found">found</span> <span word="it">it</span>.</p><p>为什么数以百万计的头发可以从我们的头上长出来，而我们的手掌和脚底却是光秃秃的？据发现这一问题的科学家表示，一切都归结于我们体内的一种特殊分子。</p><p><span word="The">The</span> <span word="hairless">hairless</span> <span word="regions">regions</span> <span word="of">of</span> <span word="our">our</span> <span word="skin">skin</span> <span word="secrete">secrete</span> <span word="a">a</span> <span word="special">special</span> <span word="type">type</span> <span word="of">of</span> <span word="molecule">molecule</span> <span word="known">known</span> <span word="as">as</span> <span word="an">an</span> <span word="inhibitor">inhibitor</span>. <span word="This">This</span> <span word="particular">particular</span> <span word="one">one</span> <span word="is">is</span> <span word="a">a</span> <span word="protein">protein</span> <span word="named">named</span> <span word="Dickkopf">Dickkopf</span> 2 (<span word="DKK">DKK</span>2). <span word="These">These</span> <span word="effectively">effectively</span> <span word="brick">brick</span>-<span word="up">up</span> <span word="the">the</span> <span word="WNT">WNT</span> <span word="pathway">pathway</span>, <span word="which">which</span> <span word="is">is</span> <span word="in">in</span> <span word="charge">charge</span> <span word="of">of</span> <span word="triggering">triggering</span> <span word="hair">hair</span> <span word="growth">growth</span> <span word="in">in</span> <span word="our">our</span> <span word="bodies">bodies</span>.</p><p>我们皮肤的无毛区域分泌一种特殊的分子，称为抑制剂。这种特殊的蛋白质叫做<span word="Dickkopf">Dickkopf</span> 2(<span word="DKK">DKK</span>2)。这些物质有效地堵塞了<span word="WNT">WNT</span>通路，而<span word="WNT">WNT</span>通路负责刺激我们体内的毛发生长。</p><p><span word="Scientists">Scientists</span> <span word="at">at</span> <span word="the">the</span> <span word="University">University</span> <span word="of">of</span> <span word="Pennsylvania">Pennsylvania</span> <span word="School">School</span> <span word="of">of</span> <span word="Medicine">Medicine</span> <span word="believe">believe</span> <span word="certain">certain</span> <span word="animals">animals</span> <span word="have">have</span> <span word="evolved">evolved</span> <span word="to">to</span> <span word="produce">produce</span> <span word="DKK">DKK</span>2 <span word="in">in</span> <span word="certain">certain</span> <span word="parts">parts</span> <span word="of">of</span> <span word="their">their</span> <span word="bodies">bodies</span>, <span word="depending">depending</span> <span word="on">on</span> <span word="what">what</span> <span word="will">will</span> <span word="best">best</span> <span word="help">help</span> <span word="different">different</span> <span word="creatures">creatures</span> <span word="to">to</span> <span word="survive">survive</span>.</p><p>宾夕法尼亚大学医学院的科学家们认为，某些动物已经进化到在身体的某些部位产生<span word="DKK">DKK</span>2，这取决于哪种物质最有助于不同的生物生存。</p><p>"<span word="In">In</span> <span word="this">this</span> <span word="study">study</span>, <span word="we">we</span>'<span word="ve">ve</span> <span word="shown">shown</span> <span word="the">the</span> <span word="skin">skin</span> <span word="in">in</span> <span word="hairless">hairless</span> <span word="regions">regions</span> <span word="naturally">naturally</span> <span word="produces">produces</span> <span word="an">an</span> <span word="inhibitor">inhibitor</span> <span word="that">that</span> <span word="stops">stops</span> <span word="WNT">WNT</span> <span word="from">from</span> <span word="doing">doing</span> <span word="its">its</span> <span word="job">job</span>," <span word="Professor">Professor</span> <span word="Sarah">Sarah</span> <span word="E">E</span>. <span word="Millar">Millar</span>, <span word="an">an</span> <span word="author">author</span> <span word="of">of</span> <span word="the">the</span> <span word="study">study</span> <span word="published">published</span> <span word="in">in</span> <span word="the">the</span> <span word="journal">journal</span> <span word="Cell">Cell</span> <span word="Reports">Reports</span>, <span word="commented">commented</span>.</p>
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