The precardiac areas and formation of the tubular heart in the chick embryo☆
[摘要] Smallfragmentsofmesodermandendodermhavebeentransplantedfromstage5donorembryoslabeledwiththymidine-3Htocorrespondingsitesinnonlabeledhosts.Thesefragmentshealinandparticipateinthenormaldevelopmentoftherecipientembryo.Thedistributionoftheimplantedcellsinthetubularheartatstage12hasbeendeterminedbyautoradiography,toprovideasetofcorrespondingpointsinthestage5precardiacmesodermandtheepimyocardialandendocardiallayersinthestage12heart.Thetubularhearthasbeensubdividedinto24definedregions,andtheboundariesofthoseregionshavebeenmappedinthestage5mesoderm.Theprocessofheartformationhasalsobeentracedthroughinterveningstagesbygraphicreconstructionandmicrodissectionofthemesodermlayerandbymarkingtheepimyocardialtroughsandforminghearttubewithparticlesofironoxide.Thepreepimyocardialmesodermisorganizedinthestage5embryointwoseparateregions,oneoneithersideoftheembryonicaxis,withagapofnoncardiogenicmesodermofabout0.8mmbetweenthem.Atthisstagepreendocardialcellsareorganizedintoareasgenerallysimilarinsizeandlocationtothepreepimyocardialregions,buttheyaremorewidelyscattered.Eachlateralheart-formingregioncanbesubdividedintoaseriesofcurvedbands.Therostromedialbandofeachheart-formingregionformsthetruncoconaltissueofthetubularheart.Themid-portiongivesrisetotheventriclesandthecaudolateralareaofeachregioncontributesthecellswhichformtheatria.Duringcardiogenesis,thepreepimyocardialmesodermbehavesasacoherentsheet.Itcondenses,stretches,folds,anddeforms,butitdoesnotloseitsintegrityasasheet,noritscontinuitywiththerestofthelayerofsplanchnicmesoderm.Itdoesnotbreakupintocellsorcellclusters.Endocardialcells,ontheotherhand,doshowsomeevidenceofdispersalassingletsandsmallgroupsduringformationofthehearttube.
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[效力级别] [学科分类] 生物科学（综合）
[关键词] [时效性]
