Cloning Yields Human-Rabbit Hybrid Embryo

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日期: 2003-08-14 今日/总浏览: 1/4750 \- C' a7 |% ]( }2 s8 p

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+ e- }4 _/ Z1 PScientistsinChinahave,forthefirsttime,usedcloningtechniquestocreatehybridembryosthatcontainamixofDNAfrombothhumansandrabbits,accordingtoareportinascientificjournalthathasreignitedthesmolderingethicsdebateovercloningresearch.
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Morethan100ofthehybrids,madebyfusinghumanskincellswithrabbiteggs,wereallowedtodevelopinlaboratorydishesforseveraldaysbeforethescientistsdestroyedthemtoretrieveso-calledembryonicstemcellsfromtheirinteriors.AlthoughscientistsinMassachusettshadpreviouslymixedhumancellsandcoweggsinasimilarattempttomakehybridembryosasasourceofstemcells,thoseexperimentswerenotsuccessful.! q. k  G1 C5 h: M2 _6 w$ \; X9 `1 w

, @# k6 j5 }5 R* `6 R6 Q/ K$ RResearcherssaidyesterdaytheywerehopefulthattherabbitworkwouldleadtoanewandplentifulsourceofembryonicstemcellsforresearchand,eventually,formedicaluse.Buttheologiansandothersdecriedtheworkasunethical.) Y' G" Q% J0 H" L3 j

+ C4 {  M  n/ @' Z3 p1 nSomewonderedaloudwhat,exactly,suchacreaturewouldbeifitweretransferredtoawombtodeveloptoterm.
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3 Q: `; l) u; Z8 m9 g  iThevastmajorityoftheDNAintheembryosishuman,withasmallpercentageofgeneticmaterial--calledmitochondrialDNA--contributedbytherabbitegg.Nooneknowsifsuchanembryocoulddevelopintoaviablefetus,thoughsomeexperimentswithotherspeciessuggestitwouldnot.
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Congresshasbeenmullinglegislationforyearsthatwouldoutlawcertainhumancloningexperiments,withsomeopposedtoanycreationofclonedembryosforresearchandotherssympathetictoresearchusesaslongastheembryosarenotallowedtogrowintoclonedbabies.Nolawhasbeenpassed,however,inpartbecauseofresearchers'warningsthattheproposedrestrictionsaresofar-reachingthattheywouldhobbledevelopmentofnewmedicaltreatments.# |' F3 ~% w) X5 O+ Z2 A

2 B5 q7 Z, j( s. g5 U9 hThenewwork,ledbyHuiZhenShengofShanghaiSecondMedicalUniversity,appearsinthelatestissueofCellResearchandwashighlightedinanewsreportinthejournalNature.CellResearchisapeer-reviewed--iflittle-knownintheUnitedStates--bimonthlyscientificjournalaffiliatedwiththeShanghaiInstituteofCellBiologyandtheChineseAcademyofSciences.Someresearchersyesterdaysaidtheywerefrustratedbythelackofdetailsinthepaper.
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! p" M5 E; A6 _2 S4 q9 }Theteamsaiditretrievedforeskintissuefromtwo5-year-oldboysandtwomen,andfacialtissuefroma60-year-oldwoman,asasourceofskincells.TheyfusedthosecellswithNewZealandrabbiteggsfromwhichthevastmajorityofrabbitDNAhadbeenremoved.Morethan400ofthosenew,fusedentitiesgrewintoearlyembryos,andmorethan100survivedtotheblastocyststage--thepointatwhichcovetedstemcellsbegintoform.
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; Q) x( q; l# ^0 R$ w) I4 E+ z# kTheapproachcouldhelpscientistswishingtomass-producehumanembryosassourcesofhumanembryonicstemcells.Stemcellscanmorphintoallkindsoftissuesandmaybeabletoreversetheeffectsofvariousdegenerativediseases.Buttomakeclonedembryos,scientistsneedbothnormalbodycells--suchasskincells--andeggcells,whichhavetheuniquecapacitytoreprogramthegenesinbodycellsandmakethembehaveasthoughtheywereembryocells." w9 w- s8 z8 R! y( @. T

! c' F- e+ j2 x$ Q  ^1 N& pBecausehumaneggcellsaredifficultandcostlytoretrievefromwomen'sovaries--andbecausehumaneggretrievalposesriskstothedonors--scientistshavebeenwantingtoknowwhetheranimaleggsmayserveaswell.AmajorquestionhasbeenwhethertheremnantsofmitochondrialDNAthattypicallyremaininananimaleggwouldbecompatiblewiththenuclearDNAcontributedbythehumancell.* ?! F  @" S# e  Q7 N8 x$ F
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Thenewworksuggeststhattheanswertothatquestionisyes,scientistssaid--thoughwithanumberofcaveats.Mostimportant,researcherssaid,thepaperstopsshortofprovingbeyondadoubtthatthestemcellsretrievedfromthehybridembryosaretrulycapableofgrowingforlongperiodsoftimeinlabdishes,andthattheycanturnintoeveryknownkindofcell.5 P' n1 V) H3 f5 |2 I

  E# Y# G9 T; t/ T% D# {( ^2 ^Evenso,saidDouglasMelton,aHarvardUniversitycellbiologistandcloningexpert,theworkisabigadvancebecauseitoffersanewsystemforexploringthemechanismsbywhicheggcellsgetadultcellstoactinembryonicways.Thatcouldprovidedeepinsightsintohumandevelopment,woundhealingandtissueregeneration.
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Henotedthatalthoughthisisthefirstcreationofahumanchimericembryo--areferencetothefabulouschimeraofGreekmythology,whichhadalion'shead,agoat'sbodyandaserpent'stail--itisnotthefirsttimescientistshaveblendedhumancellsintolabanimals.Somemice,forexample,havebeenendowedwithhumanbraincellsorportionsofthehumanimmunesystemforresearch./ a( S& ?. M8 `  s4 z$ i8 W

! P) z  o2 Z0 F+ D1 D5 `. ]TheChinesework,Meltonsaid,isextremelyinteresting,andIhopetheypursueit.
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8 `* V4 \. o+ `  [% s, F% x5 R: uR.AltaCharo,anassociatedeanoflawandprofessorofbioethicsattheUniversityofWisconsinatMadison,notedthattheworkpassedmusterwithChineseethicsauthorities,whohaddemanded,amongotherthings,thattheembryosnotbeallowedtogrowmorethan14days.
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  _5 L& l3 ?( nShortofputtingoneoftheseembryosintoawoman'sbodyfordevelopmenttoterm,Idon'tthinkthisworkharmsanyonealive,Charosaid.
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Shesaidtheexperimentsshouldforceopponentsofcloningresearchtoidentifymoreclearlythantheyhaveuntilnowexactlywheretheywoulddrawthelineagainsthumanembryocloning--ineffect:Howhumandoesanembryohavetobetohavethemoralstandingtheseadvocatesconferonembryos?
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( H9 T7 A# N9 F% X8 w9 URichardDoerflinger,oftheU.S.ConferenceofCatholicBishops,saidhefeltcertainthatthehuman-rabbitembryoswerehumanenoughtodeserveprotections.
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. e6 {7 @5 \" L' g& uIthinkbecauseallthenuclearDNAishuman,Doerflingersaid,we'dconsiderthisanorganismofthehumanspecies.
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作者: Rick Weiss5 e; r  K; d6 {6 ~1 V
来源: Washington Post
+ y5 o1 u0 }! p' j1 ~  C发布者: 亦云