Nuclear transplantation studies on the early gastrula (Rana pipiens): I. Nuclei of presumptive endoderm☆

[摘要] PreviouslypublishedstudiesshowedthatthenuclearchangesassociatedwithendodermaldifferentiationarewelladvancedatthelategastrulastageinRanapipiens.Inthepresentinvestigationanattemptwasmadetodeterminewhenindevelopmentthisprocessofnuclear“differentiation”begins.Presumptiveendodermnucleifromthevegetalpoleregionofearlygastrulaeweretestedbytransplantationintoenucleatedeggs.Forcomparison,controltransferswereperformedwithnucleifromtheundeterminedanimalpoleregionofblastulae.Therecipienteggsdevelopedasfollows:1.1.Cleavage:Controlandexperimentaltransfersgaveaboutthesameresults.Approximately60%ofthetransfersineachseriesledtotheformationofcompleteblastulae.2.2.Embryonicdifferentiation:Eightypercentofthecompleteblastulaeresultingfromthecontroltransfersdevelopednormallytolarvalstages.Inthecaseofthetransfersofpresumptiveendodermnuclei,52%oftheblastulaedevelopednormally.Themajorityoftheremainingembryosdisplayedabnormalitiesinpostneurulastagesandfailedtoattainthelarvalstage.Afewoftheseabnormalembryos(5)showedextremedeficienciesintheectodermalderivatives.Inthemajority,however,thedeficiencieswerenotrelatedtotheendodermaloriginofthenucleiinanyobviousfashion.3.3.Larvaldevelopment:Allembryoswhichpassedthroughtheembryonicstagesnormallywerereareduntiltheydiedorreachedmetamorphosis.Intheirlarvaldevelopmentthenuclear-transplantanimalsdidnotdifferfromtheirnormallyfertilizedcontrols.Apossibleexceptiontothisconclusionismentionedonpage261.Theresultssummarizedabovearecomparedwiththosepreviouslyobtainedbyusintransplantationstudiesonnucleifromolderdonors;andwiththeresultsofexperimentsonXenopuslaevisnucleirecentlyreportedbyFischbergetal.,1958.

[学科分类] 生物科学（综合）