Squamous metaplasia and keratinization of chorionic epithelium of the chick embryo in egg and in culture☆

摘要

1.1.Experimentalproductioninovoandinvitroofakeratogenicmetaplasiainchorionicepitheliumofchickembryosisdescribed.Themetaplasiamanifesteditselfasanalterationoftheone-cell-thick,respiratory,chorioepithelialmembraneintoastratified,squamous,highlykeratinizedepithelium.2.2.Inovo,keratogenicmetaplasiaoccurredregularlyinfenestratedeggs,providedwithshellopeningsonthe8thto14thdayandincubatedunderconditionsofnear-saturationorsaturation-humidityuntilthe18thday.Thedegreeandextentofchangeweredirectlyrelatedtoover-allsizeoftheopenings,i.e.,tothefacilityofinterchangebetweeninsideandoutsideair.3.3.Invitro,metaplasticchangesoccurredinexplantsgrownfor8daysuponaplasmaclotbytheorganculturemethod,withoutfurtherexperimentalinterference.4.4.Therewerenokeratogenicchangesinfenestrated,well-sealedeggswhichindicatedthatmeredetachmentofthechorionicepitheliumfromtheshell,withoutprovisionofdirectaccesstooutsideair,didnotprovideconditionsnecessaryforthismetaplasticalteration.5.5.Keratogenicmetaplasiawasexpeditedandintensifiedbyslighttraumatotheexposedchorionicepitheliumandbysmalltissuegraftsplaceduponit.However,withoutprovisionofshellopenings,thesepromotingconditionsdidnot,bythemselvescausetypicalkeratogenicchanges.6.6.Othertypesofmorphogeneticchangesinmetaplasticchorionicepithelium,suchasmovementsofepithelialcellsintotheunderlyingmesenchymeandtheirformativeactivitiesthese,arebrieflydescribed.7.7.Thedevelopmentalstateofchorioniccellsatthetimeoftheirresponsetotheeffectiveconditions,andthepossiblenatureofthedirectstimulus,arediscussed.Itissuggestedthatalterationinthegaseousenvironmentofchorionicepithelium,consequentuponitsexposuretoatmosphericoxygen:carbondioxideproportions,mayhaveinitiatedthechainofeventsconducivetokeratogenicmetaplasia.