Cloning Yields Human-Rabbit Hybrid Embryo

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日期: 2003-08-14 今日/总浏览: 1/475
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ScientistsinChinahave,forthefirsttime,usedcloningtechniquestocreatehybridembryosthatcontainamixofDNAfrombothhumansandrabbits,accordingtoareportinascientificjournalthathasreignitedthesmolderingethicsdebateovercloningresearch.2 p+ x* B  Z2 p% ]" i

% O* I/ K  ?$ r7 S7 L# LMorethan100ofthehybrids,madebyfusinghumanskincellswithrabbiteggs,wereallowedtodevelopinlaboratorydishesforseveraldaysbeforethescientistsdestroyedthemtoretrieveso-calledembryonicstemcellsfromtheirinteriors.AlthoughscientistsinMassachusettshadpreviouslymixedhumancellsandcoweggsinasimilarattempttomakehybridembryosasasourceofstemcells,thoseexperimentswerenotsuccessful., ~) r% Q/ b/ t

. b* J8 x" I' L9 u* iResearcherssaidyesterdaytheywerehopefulthattherabbitworkwouldleadtoanewandplentifulsourceofembryonicstemcellsforresearchand,eventually,formedicaluse.Buttheologiansandothersdecriedtheworkasunethical.
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Somewonderedaloudwhat,exactly,suchacreaturewouldbeifitweretransferredtoawombtodeveloptoterm.
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ThevastmajorityoftheDNAintheembryosishuman,withasmallpercentageofgeneticmaterial--calledmitochondrialDNA--contributedbytherabbitegg.Nooneknowsifsuchanembryocoulddevelopintoaviablefetus,thoughsomeexperimentswithotherspeciessuggestitwouldnot.4 P2 `7 ^2 T; Z4 p0 [4 S
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Congresshasbeenmullinglegislationforyearsthatwouldoutlawcertainhumancloningexperiments,withsomeopposedtoanycreationofclonedembryosforresearchandotherssympathetictoresearchusesaslongastheembryosarenotallowedtogrowintoclonedbabies.Nolawhasbeenpassed,however,inpartbecauseofresearchers'warningsthattheproposedrestrictionsaresofar-reachingthattheywouldhobbledevelopmentofnewmedicaltreatments.: N. ^# ^9 H3 p: ~2 s3 k$ _

, \1 [; z7 T7 b: zThenewwork,ledbyHuiZhenShengofShanghaiSecondMedicalUniversity,appearsinthelatestissueofCellResearchandwashighlightedinanewsreportinthejournalNature.CellResearchisapeer-reviewed--iflittle-knownintheUnitedStates--bimonthlyscientificjournalaffiliatedwiththeShanghaiInstituteofCellBiologyandtheChineseAcademyofSciences.Someresearchersyesterdaysaidtheywerefrustratedbythelackofdetailsinthepaper.( ?" B$ O, u$ \" t7 b- V) r

9 `, _1 ~& x8 i5 C# f3 dTheteamsaiditretrievedforeskintissuefromtwo5-year-oldboysandtwomen,andfacialtissuefroma60-year-oldwoman,asasourceofskincells.TheyfusedthosecellswithNewZealandrabbiteggsfromwhichthevastmajorityofrabbitDNAhadbeenremoved.Morethan400ofthosenew,fusedentitiesgrewintoearlyembryos,andmorethan100survivedtotheblastocyststage--thepointatwhichcovetedstemcellsbegintoform.
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Theapproachcouldhelpscientistswishingtomass-producehumanembryosassourcesofhumanembryonicstemcells.Stemcellscanmorphintoallkindsoftissuesandmaybeabletoreversetheeffectsofvariousdegenerativediseases.Buttomakeclonedembryos,scientistsneedbothnormalbodycells--suchasskincells--andeggcells,whichhavetheuniquecapacitytoreprogramthegenesinbodycellsandmakethembehaveasthoughtheywereembryocells., h2 v1 i  o/ ~: K6 t

" }" H$ E9 |2 x( R, gBecausehumaneggcellsaredifficultandcostlytoretrievefromwomen'sovaries--andbecausehumaneggretrievalposesriskstothedonors--scientistshavebeenwantingtoknowwhetheranimaleggsmayserveaswell.AmajorquestionhasbeenwhethertheremnantsofmitochondrialDNAthattypicallyremaininananimaleggwouldbecompatiblewiththenuclearDNAcontributedbythehumancell.
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Thenewworksuggeststhattheanswertothatquestionisyes,scientistssaid--thoughwithanumberofcaveats.Mostimportant,researcherssaid,thepaperstopsshortofprovingbeyondadoubtthatthestemcellsretrievedfromthehybridembryosaretrulycapableofgrowingforlongperiodsoftimeinlabdishes,andthattheycanturnintoeveryknownkindofcell.
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( I. {2 H$ L$ j8 C4 R( yEvenso,saidDouglasMelton,aHarvardUniversitycellbiologistandcloningexpert,theworkisabigadvancebecauseitoffersanewsystemforexploringthemechanismsbywhicheggcellsgetadultcellstoactinembryonicways.Thatcouldprovidedeepinsightsintohumandevelopment,woundhealingandtissueregeneration.
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8 C$ y$ \. R$ p' y7 ?! FHenotedthatalthoughthisisthefirstcreationofahumanchimericembryo--areferencetothefabulouschimeraofGreekmythology,whichhadalion'shead,agoat'sbodyandaserpent'stail--itisnotthefirsttimescientistshaveblendedhumancellsintolabanimals.Somemice,forexample,havebeenendowedwithhumanbraincellsorportionsofthehumanimmunesystemforresearch.
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$ L6 |( X0 d) {& q; kTheChinesework,Meltonsaid,isextremelyinteresting,andIhopetheypursueit.$ P7 l1 b9 y% m+ Z" [" M
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R.AltaCharo,anassociatedeanoflawandprofessorofbioethicsattheUniversityofWisconsinatMadison,notedthattheworkpassedmusterwithChineseethicsauthorities,whohaddemanded,amongotherthings,thattheembryosnotbeallowedtogrowmorethan14days.
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$ t3 w* z( C4 OShortofputtingoneoftheseembryosintoawoman'sbodyfordevelopmenttoterm,Idon'tthinkthisworkharmsanyonealive,Charosaid." F* @; q9 A- K2 k% \* S- j
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Shesaidtheexperimentsshouldforceopponentsofcloningresearchtoidentifymoreclearlythantheyhaveuntilnowexactlywheretheywoulddrawthelineagainsthumanembryocloning--ineffect:Howhumandoesanembryohavetobetohavethemoralstandingtheseadvocatesconferonembryos?/ e+ T# Y8 v2 ]2 q" V2 x
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RichardDoerflinger,oftheU.S.ConferenceofCatholicBishops,saidhefeltcertainthatthehuman-rabbitembryoswerehumanenoughtodeserveprotections.
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IthinkbecauseallthenuclearDNAishuman,Doerflingersaid,we'dconsiderthisanorganismofthehumanspecies.& @% F# h0 c! r$ I$ U
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- f# Y  ]/ L5 H, s: B8 e6 r作者: Rick Weiss# K  g2 F8 x4 B7 e& L2 K2 x
来源: Washington Post
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