Cloning Yields Human-Rabbit Hybrid Embryo

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日期: 2003-08-14 今日/总浏览: 1/4758 R; q* r% M2 q" J
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ScientistsinChinahave,forthefirsttime,usedcloningtechniquestocreatehybridembryosthatcontainamixofDNAfrombothhumansandrabbits,accordingtoareportinascientificjournalthathasreignitedthesmolderingethicsdebateovercloningresearch.
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Morethan100ofthehybrids,madebyfusinghumanskincellswithrabbiteggs,wereallowedtodevelopinlaboratorydishesforseveraldaysbeforethescientistsdestroyedthemtoretrieveso-calledembryonicstemcellsfromtheirinteriors.AlthoughscientistsinMassachusettshadpreviouslymixedhumancellsandcoweggsinasimilarattempttomakehybridembryosasasourceofstemcells,thoseexperimentswerenotsuccessful.
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Researcherssaidyesterdaytheywerehopefulthattherabbitworkwouldleadtoanewandplentifulsourceofembryonicstemcellsforresearchand,eventually,formedicaluse.Buttheologiansandothersdecriedtheworkasunethical.- G! @9 ?; n9 o" i% V" v
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Somewonderedaloudwhat,exactly,suchacreaturewouldbeifitweretransferredtoawombtodeveloptoterm.5 z; ]! `5 C+ E; O

) a" ~$ a: k3 W' u" Q7 \; mThevastmajorityoftheDNAintheembryosishuman,withasmallpercentageofgeneticmaterial--calledmitochondrialDNA--contributedbytherabbitegg.Nooneknowsifsuchanembryocoulddevelopintoaviablefetus,thoughsomeexperimentswithotherspeciessuggestitwouldnot.
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Congresshasbeenmullinglegislationforyearsthatwouldoutlawcertainhumancloningexperiments,withsomeopposedtoanycreationofclonedembryosforresearchandotherssympathetictoresearchusesaslongastheembryosarenotallowedtogrowintoclonedbabies.Nolawhasbeenpassed,however,inpartbecauseofresearchers'warningsthattheproposedrestrictionsaresofar-reachingthattheywouldhobbledevelopmentofnewmedicaltreatments.5 d1 S- S6 R% \: J& y

. V0 I1 }1 N' V! |! n+ E" D" eThenewwork,ledbyHuiZhenShengofShanghaiSecondMedicalUniversity,appearsinthelatestissueofCellResearchandwashighlightedinanewsreportinthejournalNature.CellResearchisapeer-reviewed--iflittle-knownintheUnitedStates--bimonthlyscientificjournalaffiliatedwiththeShanghaiInstituteofCellBiologyandtheChineseAcademyofSciences.Someresearchersyesterdaysaidtheywerefrustratedbythelackofdetailsinthepaper.
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* w/ N2 Z% i4 CTheteamsaiditretrievedforeskintissuefromtwo5-year-oldboysandtwomen,andfacialtissuefroma60-year-oldwoman,asasourceofskincells.TheyfusedthosecellswithNewZealandrabbiteggsfromwhichthevastmajorityofrabbitDNAhadbeenremoved.Morethan400ofthosenew,fusedentitiesgrewintoearlyembryos,andmorethan100survivedtotheblastocyststage--thepointatwhichcovetedstemcellsbegintoform., C6 ]/ b- T, V- u" Z
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Theapproachcouldhelpscientistswishingtomass-producehumanembryosassourcesofhumanembryonicstemcells.Stemcellscanmorphintoallkindsoftissuesandmaybeabletoreversetheeffectsofvariousdegenerativediseases.Buttomakeclonedembryos,scientistsneedbothnormalbodycells--suchasskincells--andeggcells,whichhavetheuniquecapacitytoreprogramthegenesinbodycellsandmakethembehaveasthoughtheywereembryocells.+ w& n3 ~/ i, h$ m5 U
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Becausehumaneggcellsaredifficultandcostlytoretrievefromwomen'sovaries--andbecausehumaneggretrievalposesriskstothedonors--scientistshavebeenwantingtoknowwhetheranimaleggsmayserveaswell.AmajorquestionhasbeenwhethertheremnantsofmitochondrialDNAthattypicallyremaininananimaleggwouldbecompatiblewiththenuclearDNAcontributedbythehumancell.  N' T* l7 s8 T5 ]8 @
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Thenewworksuggeststhattheanswertothatquestionisyes,scientistssaid--thoughwithanumberofcaveats.Mostimportant,researcherssaid,thepaperstopsshortofprovingbeyondadoubtthatthestemcellsretrievedfromthehybridembryosaretrulycapableofgrowingforlongperiodsoftimeinlabdishes,andthattheycanturnintoeveryknownkindofcell.5 K5 f6 i" ]0 g5 r4 Q' c

; x& H" o4 f+ Z. G8 \  q8 c7 _Evenso,saidDouglasMelton,aHarvardUniversitycellbiologistandcloningexpert,theworkisabigadvancebecauseitoffersanewsystemforexploringthemechanismsbywhicheggcellsgetadultcellstoactinembryonicways.Thatcouldprovidedeepinsightsintohumandevelopment,woundhealingandtissueregeneration.
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Henotedthatalthoughthisisthefirstcreationofahumanchimericembryo--areferencetothefabulouschimeraofGreekmythology,whichhadalion'shead,agoat'sbodyandaserpent'stail--itisnotthefirsttimescientistshaveblendedhumancellsintolabanimals.Somemice,forexample,havebeenendowedwithhumanbraincellsorportionsofthehumanimmunesystemforresearch.
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TheChinesework,Meltonsaid,isextremelyinteresting,andIhopetheypursueit." H4 L& ]: E4 s. L' h% A( J
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R.AltaCharo,anassociatedeanoflawandprofessorofbioethicsattheUniversityofWisconsinatMadison,notedthattheworkpassedmusterwithChineseethicsauthorities,whohaddemanded,amongotherthings,thattheembryosnotbeallowedtogrowmorethan14days." a# ?( w* a* o7 [+ A( v0 p
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Shortofputtingoneoftheseembryosintoawoman'sbodyfordevelopmenttoterm,Idon'tthinkthisworkharmsanyonealive,Charosaid.8 W, m0 J# M2 N) ^/ _" Y
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Shesaidtheexperimentsshouldforceopponentsofcloningresearchtoidentifymoreclearlythantheyhaveuntilnowexactlywheretheywoulddrawthelineagainsthumanembryocloning--ineffect:Howhumandoesanembryohavetobetohavethemoralstandingtheseadvocatesconferonembryos?& w/ Y. \* L! t

9 z9 V) E  M  M1 [+ U, ]& W2 g$ FRichardDoerflinger,oftheU.S.ConferenceofCatholicBishops,saidhefeltcertainthatthehuman-rabbitembryoswerehumanenoughtodeserveprotections.: ~5 Z3 O, D0 g# X" B& s  U

$ J# H8 e  ~# P# ?9 d) q4 ~5 JIthinkbecauseallthenuclearDNAishuman,Doerflingersaid,we'dconsiderthisanorganismofthehumanspecies.0 c8 p! `" d! g7 U8 L5 g6 U

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作者: Rick Weiss
) c  G  e3 l# u! U来源: Washington Post) z. j9 A8 p- d  Z4 q3 x# _1 L
发布者: 亦云