The influence of axial structures on chick somite formation☆

[摘要] Theinfluenceoftheaxialstructuresonsomiteformationwasinvestigatedbyculturing,onanutritiveagarsubstrate,segmentalplatesfromchickembryoshaving8to20pairsofsomites.Inthefirstsetofexperiments,segmentalplatewasexplantedtogetherwithadjacentnotochordandapproximatelythelateralhalvesoftheneuraltubeandnoderegion.Theseexplantsformed18to20somiteswithin30hr.Inasecondseriesofexperiments,thenotochordandneuraltubewereincludedasbefore,butfurtherregressionmovementsintheexplantswerepreventedbyremovingthenoderegion.Theseexplantsformedonly11.9±1.1somites.Finally,explantsofsegmentalplatethatincludednoneuraltube,notochord,ornoderegionweremade.Theseexplantshadformed10.7±1.1somites14to17hrlater.Whensuchexplantswereculturedforperiodslongerthan17hr,therewasamarkedtendencyforthemoreposteriorsomitestodisperseandforallofthesomitestodevelopapeculiar“hollow”morphology.Itwasconcludedfromtheseresultsthatduringtheperiodofdevelopmentwhenchickembryospossess8to20pairsofsomites,thesegmentalplatemesoderm(1)representsabout12prospectivesomites,(2)maysegmentintoitsfullcomplementofsomiteswithoutfurthercontactwiththeaxialstructures,but(3)requirescontinuedintimatecontactwiththeaxialstructuresfornormalsomitemorphologicdifferentiationandstability.

[学科分类] 生物科学（综合）