Ectodermal-mesodermal interactions in the growth of limb buds in the chick embryo: Constancy and temporal limits of the ectodermal induction☆

[摘要] Heterochronousrecombinationsweremadeusingchickembryolimb-budmesoblastsandectodermalhullsofdifferingdevelopmentalstages.Anyfunctionalapicalectodermalridge(AER)wasfoundtoinduceoutgrowthoflimbpartsintherespondingmesodermintheirproperproximodistalsequence,regardlessoftherelativeagesoftheectodermandmesoderm.Itisconcluded,therefore,thattheinductivesignalemanatingfromtheAERremainsqualitativelyconstantfromstagetostageandfromleveltolevelduringlimb-budoutgrowth;informationforpropersequencingoflevel-specificpatternsinthelimbmustthereforebeprogrammedintrinsicallywithinthemesoderm.TheAERlosesthecapacitytoinducecompletelimbsfromyounglimb-budmesoblastsduringstage29.RecombinationofayoungectodermalhullwitholdermesodermdoesnotacceleratethelossoffunctionbytheAERand,conversely,itisunlikelythatprolongedassociationwithyoungmesodermcanprolongtheperiodoftheAER'sinductivepotency.Lossoffunctionthusoccursonaschedulethatisdeterminedintrinsicallywithintheectodermandthatisaffectedlittleornotatallbythestageoftheunderlyingmesoderm.

[学科分类] 生物科学（综合）