Cloning Yields Human-Rabbit Hybrid Embryo

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日期: 2003-08-14 今日/总浏览: 1/475/ E7 m# u+ _0 q# q' L
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: Z! {  I" M, lScientistsinChinahave,forthefirsttime,usedcloningtechniquestocreatehybridembryosthatcontainamixofDNAfrombothhumansandrabbits,accordingtoareportinascientificjournalthathasreignitedthesmolderingethicsdebateovercloningresearch.1 B3 r  `- t  Z' o2 g

% v- }: Z, {  r9 w2 H& k( bMorethan100ofthehybrids,madebyfusinghumanskincellswithrabbiteggs,wereallowedtodevelopinlaboratorydishesforseveraldaysbeforethescientistsdestroyedthemtoretrieveso-calledembryonicstemcellsfromtheirinteriors.AlthoughscientistsinMassachusettshadpreviouslymixedhumancellsandcoweggsinasimilarattempttomakehybridembryosasasourceofstemcells,thoseexperimentswerenotsuccessful.
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Researcherssaidyesterdaytheywerehopefulthattherabbitworkwouldleadtoanewandplentifulsourceofembryonicstemcellsforresearchand,eventually,formedicaluse.Buttheologiansandothersdecriedtheworkasunethical.
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( F" q% t  i" ySomewonderedaloudwhat,exactly,suchacreaturewouldbeifitweretransferredtoawombtodeveloptoterm., o$ e1 k, v  H

. p0 y3 K5 t* k  LThevastmajorityoftheDNAintheembryosishuman,withasmallpercentageofgeneticmaterial--calledmitochondrialDNA--contributedbytherabbitegg.Nooneknowsifsuchanembryocoulddevelopintoaviablefetus,thoughsomeexperimentswithotherspeciessuggestitwouldnot.
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Congresshasbeenmullinglegislationforyearsthatwouldoutlawcertainhumancloningexperiments,withsomeopposedtoanycreationofclonedembryosforresearchandotherssympathetictoresearchusesaslongastheembryosarenotallowedtogrowintoclonedbabies.Nolawhasbeenpassed,however,inpartbecauseofresearchers'warningsthattheproposedrestrictionsaresofar-reachingthattheywouldhobbledevelopmentofnewmedicaltreatments.7 ~" P0 s2 Z0 y  R& J

' c, j; t8 x5 b7 rThenewwork,ledbyHuiZhenShengofShanghaiSecondMedicalUniversity,appearsinthelatestissueofCellResearchandwashighlightedinanewsreportinthejournalNature.CellResearchisapeer-reviewed--iflittle-knownintheUnitedStates--bimonthlyscientificjournalaffiliatedwiththeShanghaiInstituteofCellBiologyandtheChineseAcademyofSciences.Someresearchersyesterdaysaidtheywerefrustratedbythelackofdetailsinthepaper.
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7 z! n7 \$ E1 S, }+ |$ p$ sTheteamsaiditretrievedforeskintissuefromtwo5-year-oldboysandtwomen,andfacialtissuefroma60-year-oldwoman,asasourceofskincells.TheyfusedthosecellswithNewZealandrabbiteggsfromwhichthevastmajorityofrabbitDNAhadbeenremoved.Morethan400ofthosenew,fusedentitiesgrewintoearlyembryos,andmorethan100survivedtotheblastocyststage--thepointatwhichcovetedstemcellsbegintoform.; u8 ~+ {: [+ Y5 ~8 s7 L: j8 \

( N* G* m2 r/ P+ V0 HTheapproachcouldhelpscientistswishingtomass-producehumanembryosassourcesofhumanembryonicstemcells.Stemcellscanmorphintoallkindsoftissuesandmaybeabletoreversetheeffectsofvariousdegenerativediseases.Buttomakeclonedembryos,scientistsneedbothnormalbodycells--suchasskincells--andeggcells,whichhavetheuniquecapacitytoreprogramthegenesinbodycellsandmakethembehaveasthoughtheywereembryocells.' K: [) S# w! P0 b, J# B
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Becausehumaneggcellsaredifficultandcostlytoretrievefromwomen'sovaries--andbecausehumaneggretrievalposesriskstothedonors--scientistshavebeenwantingtoknowwhetheranimaleggsmayserveaswell.AmajorquestionhasbeenwhethertheremnantsofmitochondrialDNAthattypicallyremaininananimaleggwouldbecompatiblewiththenuclearDNAcontributedbythehumancell.# h/ u+ B. e$ ]) ]( [/ M
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Thenewworksuggeststhattheanswertothatquestionisyes,scientistssaid--thoughwithanumberofcaveats.Mostimportant,researcherssaid,thepaperstopsshortofprovingbeyondadoubtthatthestemcellsretrievedfromthehybridembryosaretrulycapableofgrowingforlongperiodsoftimeinlabdishes,andthattheycanturnintoeveryknownkindofcell.
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Evenso,saidDouglasMelton,aHarvardUniversitycellbiologistandcloningexpert,theworkisabigadvancebecauseitoffersanewsystemforexploringthemechanismsbywhicheggcellsgetadultcellstoactinembryonicways.Thatcouldprovidedeepinsightsintohumandevelopment,woundhealingandtissueregeneration.
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4 I; g2 ~+ l- z5 I0 W- ZHenotedthatalthoughthisisthefirstcreationofahumanchimericembryo--areferencetothefabulouschimeraofGreekmythology,whichhadalion'shead,agoat'sbodyandaserpent'stail--itisnotthefirsttimescientistshaveblendedhumancellsintolabanimals.Somemice,forexample,havebeenendowedwithhumanbraincellsorportionsofthehumanimmunesystemforresearch., g" w" h# G& @' a* |% ?8 K2 e: z5 B
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TheChinesework,Meltonsaid,isextremelyinteresting,andIhopetheypursueit.
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R.AltaCharo,anassociatedeanoflawandprofessorofbioethicsattheUniversityofWisconsinatMadison,notedthattheworkpassedmusterwithChineseethicsauthorities,whohaddemanded,amongotherthings,thattheembryosnotbeallowedtogrowmorethan14days.4 l+ |% P% y8 G* k' ~# n
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Shortofputtingoneoftheseembryosintoawoman'sbodyfordevelopmenttoterm,Idon'tthinkthisworkharmsanyonealive,Charosaid.
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2 [: ~, E; O. WShesaidtheexperimentsshouldforceopponentsofcloningresearchtoidentifymoreclearlythantheyhaveuntilnowexactlywheretheywoulddrawthelineagainsthumanembryocloning--ineffect:Howhumandoesanembryohavetobetohavethemoralstandingtheseadvocatesconferonembryos?
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3 J7 q- K+ q. E" dRichardDoerflinger,oftheU.S.ConferenceofCatholicBishops,saidhefeltcertainthatthehuman-rabbitembryoswerehumanenoughtodeserveprotections.
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% P  _' M# w4 ]$ K; W- Q8 R- vIthinkbecauseallthenuclearDNAishuman,Doerflingersaid,we'dconsiderthisanorganismofthehumanspecies.
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作者: Rick Weiss
0 m/ V: S- Y% s  S" B. u来源: Washington Post% z! J+ X& k9 x, e' t' h2 x7 O) U
发布者: 亦云