7 Hyped GM maize study faces growing scrutiny.docx

7 Hyped GM maize study faces growing scrutiny.docx

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7HypedGMmaizestudyfacesgrowingscrutiny

DisruptedsleepmaypredictAlzheimer’s

PoorsleeppatternslinkedtoformationofAlzheimer'splaques.

18October2012

NewOrleans,Louisiana

DisturbedsleeppaternscanpredictafutureAlzheimer'sdiagnosis.

StevePrezant/Corbis

Adisturbednight'ssleepmightsignalafuturediagnosisofAlzheimer’sdisease,accordingtofindingspresentedthisweekattheannualmeetingoftheSocietyforNeuroscienceinNewOrleans,Louisiana.

PatientswithAlzheimer’softencomplainofchangesintheirsleeppatternsduringtheearlystagesofthedisease.Inhealthypeople,forexample,daytimenapsusuallylastaround20minutes,buttheycanbeto3hourslonginpatientswithAlzheimer’sdisease.

RoxanneSterniczuk,aneurophysiologistatDalhousieUniversityinHalifax,Canada,andhercolleagueswantedtodeterminehowearlythesechangesoccurandiftheycouldpredictaperson’sfutureriskofdevelopingthedisease.

Sterniczukandhercolleaguesanalyseddatafromaround14,600healthypeople,collectedaspartoftheSurveyofHealth,AgeingandRetirementinEurope（SHARE）,along-termobservationalstudyofpeopleaged50andoverfrom12Europeancountries.Theylookedatvariousmeasuresofsleepquality,andusedthemtoproducea‘sleepdisturbanceindex’.

Theresearchersfoundthatparticipantswhoreportedsleepingrestlessly,feelingtiredduringthedayandtakingsleepmedicationweremorelikelytobediagnosedwithAlzheimer’swithinthenext2years,andthatthegreatertheextentoftheseproblems,themoreseverewerethesymptomsofthesubsequentdisease.

“Increaseddaytimesleepinesswasthebiggestpredictor,”saysSterniczuk.“Itwouldappearthatsubtlechangesinthesleep–wakecyclearetakingplacebeforeanydiseasepathology.”

Earlymarker

Alzheimer’sdiseaseischaracterizedbytwohallmarks—thedepositionofinsolubleplaquesmadeupofamyloid-ßprotein,whichaccumulateinthespacesaroundnervecells,andproteinaggregatescalledneurofibrillarytanglesthataredepositedinsidecells.

Sleepdisturbancesmaybeanearlymarkerforthebrainchangesthatoccurasthediseasedevelops,ortheymaycontributetoprogressionofthedisease,saysDavidHoltzman,aneurologistatWashingtonUniversitySchoolofMedicineinStLouis,Missouri,whostudiesAlzheimer’sdisease.“Eitherthatpathologyisbeginningtooccurduringageing,orsleepproblemsleadtoacceleratedAlzheimer’spathologyanddisease,”headds.

Lastmonth,HoltzmanandhiscolleaguesreportedthatinamousemodelofAlzheimer’sthesleep–wakecyclebreaksdownfollowingtheformationofamyloid-ßplaques,andthateliminatingtheplaquescausedthecycletoreturntonormal,suggestingthatplaqueformationcausesthesleepdisturbances1.Butheaddsthatdistinguishingbetweenthetwopossibilitiesinhumanswillrequirelong-termstudiestoassesshowbiologicalmarkersassociatedwithAlzheimer’sdiseasechangethroughlife.

Sterniczukisnowinvestigatingwhetherthechangesinsleeppatternsarerelatedtoalterationsingeneactivityinthesuprachiasmaticnucleus（视交叉上核）,aregionofthebrainthatcontrolsthecircadianrhythm（昼夜节律）andregulatesthesleep–wakecycle.

Sheemphasizeshowimportantitistofindwaystoaccuratelydiagnosetheconditionandidentifypeopleatriskofdevelopingit.“Wehaveanageingpopulationonourhands,andtheremaybeanAlzheimer’spandemic（大流行的）inthenext10–15yearsasthebabyboomersreachthetypicalageofdiagnosis,”shesays.

Journalname:

Nature

DOI:

doi:

10.1038/nature.2012.11620

DNAhasa521-yearhalf-life

Geneticmaterialcan'tberecoveredfromdinosaurs—butitlastslongerthanthought.

∙MattKaplan

Fewresearchershavegivencredence（信任）toclaimsthatsamplesofdinosaurDNAhavesurvivedtothepresentday,butnooneknewjusthowlongitwouldtakeforgeneticmaterialtofallapart（崩溃，破碎）.Now,astudyoffossilsfoundinNewZealandislayingthemattertorest—andputtinganendtohopesofcloningaTyrannosaurusrex（霸王龙）.

∙

∙Aftercelldeath,enzymesstarttobreakdownthebondsbetweenthenucleotidesthatformthebackboneofDNA,andmicro-organismsspeedthedecay.Inthelongrun,however,reactionswithwaterarethoughttoberesponsibleformostbonddegradation.Groundwaterisalmostubiquitous,soDNAinburiedbonesamplesshould,intheory,degradeatasetrate.

∙

∙DeterminingthatratehasbeendifficultbecauseitisraretofindlargesetsofDNA-containingfossilswithwhichtomakemeaningfulcomparisons.Tomakemattersworse,variableenvironmentalconditionssuchastemperature,degreeofmicrobialattackandoxygenationalterthespeedofthedecayprocess.

∙

∙Butpalaeogeneticists（古遗传学家）ledbyMortenAllentoftattheUniversityofCopenhagenandMichaelBunceatMurdochUniversityinPerth,Australia,examined158DNA-containinglegbonesbelongingtothreespeciesofextinct（灭绝的）giantbirdscalledmoa（恐鸟，已绝种的纽西兰巨鸟）.Thebones,whichwerebetween600and8,000yearsold,hadbeenrecoveredfromthreesiteswithin5kilometresofeachother,withnearlyidenticalpreservationconditionsincludingatemperatureof13.1ºC.ThefindingsarepublishedtodayinProceedingsoftheRoyalSocietyB.

∙

∙Diminishingreturns

∙Bycomparingthespecimens'（样本）agesanddegreesofDNAdegradation,theresearcherscalculatedthatDNAhasahalf-lifeof521years.Thatmeansthatafter521years,halfofthebondsbetweennucleotidesinthebackboneofasamplewouldhavebroken;afteranother521yearshalfoftheremainingbondswouldhavegone;andsoon.

∙

∙Theteampredictsthateveninaboneatanidealpreservationtemperatureof−5ºC,effectivelyeverybondwouldbedestroyedafteramaximumof6.8millionyears.TheDNAwouldceasetobereadablemuchearlier—perhapsafterroughly1.5millionyears,whentheremainingstrandswouldbetooshorttogivemeaningfulinformation.

∙

∙“ThisconfirmsthewidelyheldsuspicionthatclaimsofDNAfromdinosaursandancientinsectstrappedinamberareincorrect,”saysSimonHo,acomputationalevolutionarybiologistattheUniversityofSydneyinAustralia.However,although6.8millionyearsisnowhereneartheageofadinosaurbone—whichwouldbeatleast65millionyearsold—“WemightbeabletobreaktherecordfortheoldestauthenticDNAsequence,whichcurrentlystandsatabouthalfamillionyears,”saysHo.

∙

∙Thecalculationsinthelateststudywerequitestraightforward,butmanyquestionsremain.

∙

∙“Iamveryinterestedtoseeifthesefindingscanbereproducedinverydifferentenvironmentssuchas‘permafrost（永冻层）andcaves,”saysMichaelKnapp,apalaeogeneticistattheUniversityofOtagoinDunedin,NewZealand.

∙

∙Moreover,theresearchersfoundthatagedifferencesaccountedforonly38.6%ofthevariationinDNAdegradationbetweenmoa-bonesamples.“OtherfactorsthatimpactonDNApreservationareclearlyatwork,”saysBunce.“Storagefollowingexcavation（挖除）,soilchemistryandeventhetimeofyearwhentheanimaldiedarealllikelycontributingfactorsthatwillneedlookinginto.”Journalname:

Nature

DOI:

doi:

10.1038/nature.2012.11555

Rapidtestpinpointsnewborns'geneticdiseasesindays

Methodraiseshopesforroutinewhole-genomesequencinginneonatal（新生的）intensivecare（重症监护）.

MonyaBaker03October2012

AfasterDNAsequencingmachineandstreamlinedanalysisoftheresultscandiagnosegeneticdisordersindaysratherthanweeks,asreportedtodayinScienceTranslationalMedicine.

Uptoathirdofthebabiesadmittedtoneonatalintensivecareunitshaveageneticdisease.Althoughsymptomsmaybesevere,thegeneticcausecanbehardtopindown.Thousandsofgeneticdiseaseshavebeendescribed,butrelativelyfewtestsareavailable,andeventhesemaydetectonlythemostcommonmutations.

Whole-genomesequencingcouldtestformanydiseasesatonce,butitscost,thecomplexityoftheresultsandtheturnaroundtimeareprohibitive.Inwhattheyhopewillbeaprototypeforotherhospitals,aresearchteamledbyStephenKingsmoreatChildren’sMercyHospitalinKansasCity,Missouri,hasimplementedamuchfaster,simplersystemforfindingrelevantmutationsinwhole-genomesequencesthatisdesignedforphy’sicians（内科医生）withoutspecializedgenetictraining.

Thesekindsofinnovationwillhelpmorehospitalsbringsequencingintoclinicalcare,saysRichardGibbs,directorofthehumangenomesequencingcentreatBaylorCollegeofMedicineinHouston,Texas.“Alotofpeoplearegoingtorealizefromthisthatthefutureisnow.”

Sequencingfordisease

Sequencinghasbeenusedbeforetopinpointthecauseofmysteriousdiseases.In2011,Gibbsledateamthatsequenced14-year-oldtwinswithaneurologicalmovementdisorderandfoundawaytoimprovetheirtreatment.Inanotherinstance,whole-genomesequencingsuggestedthatamysteriouscaseofsevereinflammatoryboweldiseasehadageneticcauseandcouldberelievedthroughabonemarrowtransplant.Butboththeseexamplesrequiredseveralweeksandateamofexpertstoresolve.TheChildren’sMercyHospitalplanstoofferroutinesequencingintheneonatalintensivecareunitbytheendoftheyear.

Toorderatest,physicianswillchoosetermsfrompull-downboxestodescribetheinfant'ssymptoms.Softwarethencompilesalistofpotentialsuspectgenes.Afterthegenomeissequenced,thesoftwarehuntsforandanalysesmutationsinonlythosegenes,whichallowsittocompilealistofpossiblecausativemutationsmorequickly.TheteamhadearlyaccesstoanewDNAsequencingmachinefromsequencingcompanyIllumina,basedinSanDiego,California,thatcouldgenerateawholegenomewithin25hours.Theentireprocess,fr