六级冲刺练习阅读（119）
<p> <span word="There">There</span> <span word="is">is</span> <span word="evidence">evidence</span> <span word="that">that</span> <span word="the">the</span> <span word="usual">usual</span> <span word="variety">variety</span> <span word="of">of</span> <span word="high">high</span> <span word="blood">blood</span> <span word="pressure">pressure</span> <span word="is">is</span>, <span word="in">in</span> <span word="part">part</span>, <span word="a">a</span> <span word="familial">familial</span> <span word="disease">disease</span>. <span word="Since">Since</span> <span word="families">families</span> <span word="have">have</span> <span word="similar">similar</span> <span word="genes">genes</span> <span word="as">as</span> <span word="well">well</span> <span word="as">as</span> <span word="similar">similar</span> <span word="environments">environments</span>, <span word="familial">familial</span> <span word="diseases">diseases</span> <span word="could">could</span> <span word="be">be</span> <span word="due">due</span> <span word="to">to</span> <span word="shared">shared</span> <span word="genetic">genetic</span> <span word="influences">influences</span>, <span word="to">to</span> <span word="shared">shared</span> <span word="environmental">environmental</span> <span word="factors">factors</span>, <span word="or">or</span> <span word="to">to</span> <span word="both">both</span>. <span word="For">For</span> <span word="some">some</span> <span word="years">years</span>, <span word="the">the</span> <span word="role">role</span> <span word="of">of</span> <span word="one">one</span></p><p> <span word="environment">environment</span> <span word="factor">factor</span> <span word="commonly">commonly</span> <span word="shared">shared</span> <span word="by">by</span> <span word="families">families</span>, <span word="namely">namely</span> <span word="dietary">dietary</span> <span word="salt">salt</span> , <span word="has">has</span> <span word="been">been</span> <span word="studied">studied</span> <span word="at">at</span> <span word="Brookhaven">Brookhaven</span> <span word="National">National</span> <span word="Laboratory">Laboratory</span>. <span word="These">These</span> <span word="studies">studies</span> <span word="suggest">suggest</span> <span word="that">that</span> <span word="long">long</span> <span word="excess">excess</span> <span word="salt">salt</span> <span word="intake">intake</span> <span word="can">can</span> <span word="lead">lead</span> <span word="to">to</span> <span word="high">high</span> <span word="blood">blood</span> <span word="pressure">pressure</span> <span word="in">in</span> <span word="man">man</span> <span word="and">and</span> <span word="animals">animals</span>. <span word="Some">Some</span> <span word="individuals">individuals</span>, <span word="however">however</span>, <span word="and">and</span> <span word="some">some</span> <span word="rats">rats</span> <span word="consume">consume</span> <span word="large">large</span> <span word="amounts">amounts</span> <span word="of">of</span> <span word="salt">salt</span> <span word="without">without</span> <span word="developing">developing</span> <span word="high">high</span> <span word="blood">blood</span> <span word="pressure">pressure</span>. <span word="No">No</span> <span word="matter">matter</span> <span word="how">how</span> <span word="strictly">strictly</span> <span word="all">all</span> <span word="environmental">environmental</span> <span word="factors">factors</span> <span word="were">were</span> <span word="controlled">controlled</span> <span word="in">in</span> <span word="these">these</span> <span word="experiments">experiments</span>, <span word="some">some</span> <span word="salt">salt</span>-<span word="fed">fed</span> <span word="animals">animals</span> <span word="never">never</span> <span word="developed">developed</span> <span word="hypertension">hypertension</span> <span word="whereas">whereas</span> <span word="a">a</span> <span word="few">few</span> <span word="rapidly">rapidly</span> <span word="developed">developed</span> <span word="very">very</span> <span word="severe">severe</span> <span word="hypertension">hypertension</span> <span word="followed">followed</span> <span word="by">by</span> <span word="early">early</span> <span word="death">death</span>. <span word="These">These</span> <span word="marked">marked</span> <span word="variations">variations</span> <span word="were">were</span> <span word="interpreted">interpreted</span> <span word="to">to</span> <span word="result">result</span> <span word="from">from</span> <span word="differences">differences</span> <span word="in">in</span> <span word="genetic">genetic</span> <span word="constitution">constitution</span>.</p><p> <span word="By">By</span> <span word="mating">mating</span> <span word="long">long</span> <span word="successive">successive</span> <span word="generations">generations</span> <span word="of">of</span> <span word="those">those</span> <span word="animals">animals</span> <span word="that">that</span> <span word="failed">failed</span> <span word="to">to</span> <span word="develop">develop</span> <span word="hypertension">hypertension</span> <span word="from">from</span> <span word="salt">salt</span> <span word="intake">intake</span>, <span word="a">a</span> <span word="resistant">resistant</span> <span word="strain">strain</span> <span word="has">has</span> <span word="been">been</span> <span word="evolved">evolved</span> <span word="in">in</span> <span word="which">which</span> <span word="consumption">consumption</span> <span word="of">of</span> <span word="large">large</span> <span word="quantities">quantities</span> <span word="of">of</span> <span word="salt">salt</span> <span word="fails">fails</span> <span word="to">to</span> <span word="influence">influence</span> <span word="the">the</span> <span word="blood">blood</span> <span word="pressure">pressure</span> <span word="significantly">significantly</span>. <span word="In">In</span> <span word="contrast">contrast</span>, <span word="by">by</span> <span word="mating">mating</span> <span word="only">only</span> <span word="animals">animals</span> <span word="that">that</span> <span word="quickly">quickly</span> <span word="develop">develop</span> <span word="hypertension">hypertension</span> <span word="from">from</span> <span word="salt">salt</span>, <span word="sensitive">sensitive</span> <span word="strain">strain</span> <span word="has">has</span> <span word="also">also</span> <span word="been">been</span> <span word="developed">developed</span>.</p><p> <span word="The">The</span> <span word="availability">availability</span> <span word="of">of</span> <span word="these">these</span> <span word="two">two</span> <span word="strains">strains</span> <span word="permits">permits</span> <span word="investigations">investigations</span> <span word="possible">possible</span>. <span word="They">They</span> <span word="provide">provide</span> <span word="a">a</span> <span word="plausible">plausible</span> <span word="laboratory">laboratory</span> <span word="model">model</span> <span word="on">on</span> <span word="which">which</span> <span word="to">to</span> <span word="investigate">investigate</span> <span word="some">some</span> <span word="clinical">clinical</span> <span word="aspects">aspects</span> <span word="of">of</span> <span word="the">the</span> <span word="human">human</span> <span word="hypertension">hypertension</span>. <span word="More">More</span> <span word="important">important</span>, <span word="there">there</span> <span word="might">might</span> <span word="be">be</span> <span word="the">the</span> <span word="possibility">possibility</span> <span word="of">of</span> <span word="developing">developing</span> <span word="methods">methods</span> <span word="by">by</span> <span word="which">which</span> <span word="genetic">genetic</span> <span word="susceptibility">susceptibility</span> <span word="of">of</span> <span word="human">human</span> <span word="beings">beings</span> <span word="to">to</span> <span word="high">high</span> <span word="blood">blood</span> <span word="pressure">pressure</span> <span word="can">can</span> <span word="be">be</span> <span word="defined">defined</span> <span word="without">without</span> <span word="waiting">waiting</span> <span word="for">for</span> <span word="its">its</span> <span word="appearance">appearance</span>. <span word="Radioactive">Radioactive</span> <span word="sodium">sodium</span> 22 <span word="was">was</span> <span word="an">an</span> <span word="important">important</span> <span word="tool">tool</span> <span word="in">in</span> <span word="working">working</span> <span word="out">out</span> <span word="the">the</span> <span word="characteristics">characteristics</span> <span word="of">of</span> <span word="the">the</span> <span word="sodium">sodium</span> <span word="chloride">chloride</span> <span word="metabolism">metabolism</span>.</p>
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