The Effect of pH Levels By Varying the Acidity of the Extracellular Solution on the Developmental Growth of a Zebrafish embryo, Brachydanio rerio
来自 : 蚂蚁淘
Background
Zebrafish,Brachydaniorerio,haveadistinctembryonicdevelopment.Theembryogoesthroughaprocesscalledepiboly.Epiboly,asdefinedinthesixtheditionofDevelopmentalBIOLOGy(Gilbert2000),isthemovementofepithelialsheets(usuallyoftheectodermcells)thatspreadasaunit,ratherthanindividually,toenclosethedeeperlayersoftheembryo.Epibolyenablesanembryotoprotecttheinnercellsfromextracellularvariations.AccordingtoProfessorRichardFluck,whoworkswithmedakaandisaDr.E.PaulandFrancesH.ReiffProfessorofBiologyatFranklinandMarshallCollege,itishisexperiencethatmedakaembryosaremoresusceptIBLetoexteriorenvironmentalchangepriortocompleteepiboly.Zebrafisharesupposedtobeevenmoresensitivetoenvironmentalchangethanmedaka.Objective
ThestudyofacidicpHlevelseffectingthedevelopmentofzebrafish.Thisisbeingdonetodetermineifacidrainhasanymajoreffectondevelopingembryos.Rainfall(pH5.6)hasamoreacidicvaluethanthatofnormalwater(pH7orneutral).TheEmbryomedium,whichisusedfordevelopingdechorionatedembryos,aswellastheotherHank"sstandardsolutionscanbeseenhere.AddinglessNaOHbuffersothatitwillbelessthanapH7.2levelwillchangetheembryomedium.Thisissupposedlyonlypertinentifthechorionhasbeenremoved.HopefullythechorionwillnothinderpHinteractions.TheslowadditionofNaOHwillenableforafairrangeofacidictooptimalpHreADInglevels.BytakingpicturesoftheembryospriortoexposuretovariouspHsolutionsandcomparingthesetopicturesofthesameembryosfurtheralongdevelopmentitwillhopefullyshowthatpHlevelhaseneffectonthedevelopmentoftheembryos.Procedure1)Zebrafishweremarbledthepreviousnightbeforecollectionofembryos-Themarblesinthetankbottompromotespawningwhenthenextdawncomes2)Embryoswereselectedfortwovaryingcellstagesofdevelopment-firstsetwerebetweenthe2-4cellstageofdevelopment-secondsetwasofembryosbetween64-128cellsindevelopment3)pHlevelsusedwere:7.2,6.6,6,5,and4.-pH7.2isthecontrolexperimentNote:EachofthesepHlevelswasappliedtoeachofthetwocellstagespreviouslymentioned.AnimagewastakenoftheinitialembryostocomparewiththedevelopingembryosinthevariouspHsolutions.Embryoswereobservedovera48hourperiod.Results
ItwasfoundthatthedifferenceinpHlevelsthatwereuseddidnothavestopdevelopment.TheonlysignificanteffectwasthatthelowerpHlevelscausedthezebrafishtodevelopslower.Thiswasobservedoveraperiodof48hours.Discussion
ThezebrafishshowednosignsofaltereddevelopmentduetothelevelsofpHusedinthisexperiment.Thismayhaveoccurredbecausetheembryoswerenotdechorionated.Perhapsdechorionatingthemwouldhaveproducedviableresults.AsitstandszebrafishareimpervioustothepHlevelsthatwereusedinthisexperiment.ItalmostcertainthatmuchmoreacidicpHlevelswouldhavedrasticeffectsonthedevelopmentofzebrafishbecausetheproteinlayersoftheembryoswouldbedisturbed.
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