寄生虫身体形变的关键因素
<p> 寄生虫身体形变的关键因素 <span word="Crafty">Crafty</span> <span word="parasites">parasites</span> <span word="frequently">frequently</span> <span word="undergo">undergo</span> <span word="dramatic">dramatic</span> <span word="shape">shape</span> <span word="changes">changes</span> <span word="during">during</span> <span word="their">their</span> <span word="life">life</span> <span word="cycles">cycles</span> <span word="that">that</span> <span word="enable">enable</span> <span word="them">them</span> <span word="to">to</span> <span word="adapt">adapt</span> <span word="to">to</span> <span word="different">different</span> <span word="living">living</span> <span word="conditions">conditions</span> <span word="and">and</span> <span word="thrive">thrive</span>. <span word="But">But</span> <span word="these">these</span> <span word="transformations">transformations</span> <span word="might">might</span> <span word="not">not</span> <span word="be">be</span> <span word="as">as</span> <span word="difficult">difficult</span> <span word="as">as</span> <span word="they">they</span> <span word="appear">appear</span>, <span word="according">according</span> <span word="to">to</span> <span word="a">a</span> <span word="study">study</span> <span word="in">in</span> <span word="The">The</span> <span word="Journal">Journal</span> <span word="of">of</span> <span word="Cell">Cell</span> <span word="Biology">Biology</span>. <span word="African">African</span> <span word="sleeping">sleeping</span> <span word="sickness">sickness</span> <span word="is">is</span> <span word="a">a</span> <span word="disease">disease</span> <span word="caused">caused</span> <span word="by">by</span> <span word="a">a</span> <span word="species">species</span> <span word="of">of</span> <span word="parasite">parasite</span> <span word="known">known</span> <span word="as">as</span> <span word="Trypanosoma">Trypanosoma</span> <span word="brucei">brucei</span> <span word="that">that</span> <span word="is">is</span> <span word="transmitted">transmitted</span> <span word="by">by</span> <span word="the">the</span> <span word="tsetse">tsetse</span> <span word="fly">fly</span>. <span word="The">The</span> <span word="single">single</span>-<span word="celled">celled</span> <span word="parasite">parasite</span> <span word="has">has</span> <span word="a">a</span> <span word="kinetoplast">kinetoplast</span>, <span word="which">which</span> <span word="houses">houses</span> <span word="the">the</span> <span word="cell">cell</span> <span word="s">s</span> <span word="mitochondrial">mitochondrial</span> <span word="DNA">DNA</span>, <span word="and">and</span> <span word="a">a</span> <span word="protruding">protruding</span> <span word="flagellum">flagellum</span> <span word="that">that</span> <span word="is">is</span> <span word="crucial">crucial</span> <span word="for">for</span> <span word="cell">cell</span> <span word="movement">movement</span>. <span word="T">T</span>. <span word="brucei">brucei</span> <span word="undergoes">undergoes</span> <span word="major">major</span> <span word="changes">changes</span> <span word="in">in</span> <span word="shape">shape</span> <span word="and">and</span> <span word="form">form</span> <span word="during">during</span> <span word="its">its</span> <span word="developmental">developmental</span> <span word="cycle">cycle</span>. <span word="In">In</span> <span word="one">one</span> <span word="phase">phase</span>, <span word="known">known</span> <span word="as">as</span> <span word="the">the</span> <span word="trypomastigote">trypomastigote</span> <span word="stage">stage</span>, <span word="the">the</span> <span word="kinetoplast">kinetoplast</span> <span word="is">is</span> <span word="located">located</span> <span word="posterior">posterior</span> <span word="to">to</span> <span word="the">the</span> <span word="nucleus">nucleus</span> <span word="and">and</span> <span word="almost">almost</span> <span word="all">all</span> <span word="of">of</span> <span word="the">the</span> <span word="flagellum">flagellum</span> <span word="is">is</span> <span word="connected">connected</span> <span word="to">to</span> <span word="the">the</span> <span word="cell">cell</span>. <span word="In">In</span> <span word="the">the</span> <span word="epimastigote">epimastigote</span> <span word="stage">stage</span>, <span word="on">on</span> <span word="the">the</span> <span word="other">other</span> <span word="hand">hand</span>, <span word="the">the</span> <span word="kinetoplast">kinetoplast</span> <span word="is">is</span> <span word="anterior">anterior</span> <span word="to">to</span> <span word="the">the</span> <span word="nucleus">nucleus</span>, <span word="and">and</span> <span word="only">only</span> <span word="part">part</span> <span word="of">of</span> <span word="the">the</span> <span word="flagellum">flagellum</span> <span word="is">is</span> <span word="fastened">fastened</span> <span word="to">to</span> <span word="the">the</span> <span word="cell">cell</span>. <span word="T">T</span>. <span word="brucei">brucei</span> <span word="s">s</span> <span word="close">close</span> <span word="relatives">relatives</span> <span word="come">come</span> <span word="in">in</span> <span word="many">many</span> <span word="different">different</span> <span word="shapes">shapes</span>, <span word="indicating">indicating</span> <span word="that">that</span> <span word="the">the</span> <span word="parasites">parasites</span> <span word="have">have</span> <span word="also">also</span> <span word="altered">altered</span> <span word="their">their</span> <span word="morphology">morphology</span> <span word="during">during</span> <span word="evolution">evolution</span>. <span word="When">When</span> <span word="researchers">researchers</span> <span word="from">from</span> <span word="the">the</span> <span word="University">University</span> <span word="of">of</span> <span word="Oxford">Oxford</span> <span word="reduced">reduced</span> <span word="the">the</span> <span word="expression">expression</span> <span word="of">of</span> <span word="a">a</span> <span word="protein">protein</span> <span word="called">called</span> <span word="ClpGM">ClpGM</span>6 <span word="in">in</span> <span word="T">T</span>. <span word="brucei">brucei</span> <span word="trypomastigotes">trypomastigotes</span>, <span word="the">the</span> <span word="cells">cells</span> <span word="switched">switched</span> <span word="to">to</span> <span word="an">an</span> <span word="epimastigote">epimastigote</span>-<span word="like">like</span> <span word="morphology">morphology</span>. <span word="The">The</span> <span word="kinetoplast">kinetoplast</span> <span word="was">was</span> <span word="close">close</span> <span word="to">to</span> <span word="the">the</span> <span word="nucleus">nucleus</span> <span word="or">or</span> <span word="anterior">anterior</span> <span word="to">to</span> <span word="it">it</span>, <span word="and">and</span> <span word="a">a</span> <span word="long">long</span> <span word="section">section</span> <span word="of">of</span> <span word="the">the</span> <span word="flagellum">flagellum</span> <span word="extended">extended</span> <span word="beyond">beyond</span> <span word="the">the</span> <span word="cell">cell</span>. <span word="The">The</span> <span word="parasites">parasites</span> <span word="weren">weren</span> <span word="t">t</span> <span word="identical">identical</span> <span word="to">to</span> <span word="epimastigotes">epimastigotes</span> -- <span word="they">they</span> <span word="lacked">lacked</span> <span word="a">a</span> <span word="distinctive">distinctive</span> <span word="surface">surface</span> <span word="protein">protein</span> <span word="found">found</span> <span word="at">at</span> <span word="this">this</span> <span word="life">life</span> <span word="stage">stage</span> -- <span word="but">but</span> <span word="they">they</span> <span word="were">were</span> <span word="able">able</span> <span word="to">to</span> <span word="survive">survive</span> <span word="and">and</span> <span word="reproduce">reproduce</span> <span word="for">for</span> <span word="more">more</span> <span word="than">than</span> 40 <span word="generations">generations</span>. <span word="ClpGM">ClpGM</span>6 <span word="resides">resides</span> <span word="in">in</span> <span word="the">the</span> <span word="flagellar">flagellar</span> <span word="attachment">attachment</span> <span word="zone">zone</span> <span word="and">and</span> <span word="likely">likely</span> <span word="helps">helps</span> <span word="fasten">fasten</span> <span word="the">the</span> <span word="flagellum">flagellum</span> <span word="to">to</span> <span word="the">the</span> <span word="cell">cell</span> <span word="body">body</span>. <span word="Loss">Loss</span> <span word="of">of</span> <span word="ClpGM">ClpGM</span>6 <span word="shortened">shortened</span> <span word="the">the</span> <span word="flagellar">flagellar</span> <span word="attachment">attachment</span> <span word="zone">zone</span>, <span word="which">which</span> <span word="helps">helps</span> <span word="determine">determine</span> <span word="cell">cell</span> <span word="size">size</span> <span word="and">and</span> <span word="shape">shape</span>. <span word="The">The</span> <span word="study">study</span> <span word="suggests">suggests</span> <span word="that">that</span> <span word="dramatic">dramatic</span> <span word="morphological">morphological</span> <span word="changes">changes</span> <span word="during">during</span> <span word="the">the</span> <span word="life">life</span> <span word="cycle">cycle</span> <span word="and">and</span> <span word="during">during</span> <span word="parasite">parasite</span> <span word="evolution">evolution</span> <span word="may">may</span> <span word="result">result</span> <span word="from">from</span> <span word="adjustments">adjustments</span> <span word="in">in</span> <span word="the">the</span> <span word="levels">levels</span> <span word="of">of</span> <span word="a">a</span> <span word="few">few</span> <span word="key">key</span> <span word="proteins">proteins</span>, <span word="rather">rather</span> <span word="than">than</span> <span word="from">from</span> <span word="wholesale">wholesale</span> <span word="changes">changes</span> <span word="in">in</span> <span word="the">the</span> <span word="parasite">parasite</span> <span word="s">s</span> <span word="protein">protein</span> <span word="or">or</span> <span word="DNA">DNA</span> <span word="content">content</span>.</p>
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