Neural-mesodermal interactions subsequent to neural induction in Ambystoma☆

[摘要] Thisinvestigationconsideredthedifferentiationtendenciesofspecificanterior-posteriorregionsoftheneuralplateinanattempttoestablishtheregionaldifferentiationcapacityforAmbystomagracileneuroepithelium.Presumptiveneuraltissues(hindbrainandtrunkspinalcord)wereisolatedfromtheembryoatthetimeofprimaryinduction(stage11)topostneurulation(stage19)andculturedinvitroaloneorwithcombinationsofaxialmesoderm(notochordandsomite).Priortoprimaryinductiontheisolatedpresumptiveneuroepitheliumformedonlyatypicalepidermis.Immediatelysubsequenttothisinductionbothregions(hindbrainandtrunkcord)demonstratedunorganizedneuralhistogenesis,andtheformationoforganizedneuraltissueappearedlater(instage12–14isolates).Bystage15–16,thehistogenesisandorganogenesisoftheisolatedhindbrainresembledthatofthecontrol,whereastheisolatedtrunkcordformedonlyaprimitiveneuraltube.Neurogenesis,therefore,wasseparatedintotwodistinctevents,histogenesisfollowedbyorganogenesis.Thepresenceofsomitetissueenhancedhindbraindifferentiationconsiderably;notochordwaseffectivetoalimitedextent.Thecombinedeffectofbothtissuesonneurogenesiswasgreaterthanwithsomitealone.Theadditionofnotochordtotrunkspinalcordenhancedhistogenesistoagreaterextentthaneithersomitealoneorthecombinationofnotochordandsomite.Thetrunkneuraltissue,whetheraloneorincombinationwithmesoderm,neverdemonstratednormalspinalcordmorphology.Organogenesisoftheneuralregionsappearedtobetheresultofgradualandcumulativeeffectsbroughtaboutbythetissueenvironment,viz.,notochordandsomite.Thesequenceofeventsoccurringduringneurogenesis,aswellasthepossibleroleofthemesoderminconditioningtheneuraltissuemicroenvironment,isdiscussed.

[学科分类] 生物科学（综合）