Induction of the alpha-type keratinization by hydrocortisone in embryonic chick skins grown in a chemically defined medium: An electron microscopic study☆

[摘要] Previousbiochemicalanalysesshowedthedifferentialaccumulationoftheepidermalstructuralprotein,whichyieldedS-carboxymethylatedepidermalproteinA(SCMEpA),inthehydrocortisone-inducedinvitrokeratinizationof13-dayembryonicchicktarsometatarsalskingrowinginachemicallydefinedmedium(Sugimotoetal.,1974).Finestructuralfeaturesofsuchaninvitrokeratinizationprocesswerestudiedbyelectronmicroscopyinthepresentwork.After2daysofculturewithhydrocortisone(0.02or0.2μM),developmentofthetonofilamentbundlesoccurredtosomeextent,butthekeratinizedlayerwasnotformed.Keratinizationwasobservedafter4daysofculturewithhydrocortisone(0.02or0.2μM).Desmosomesandtonofilamentbundleswereprominentinthecytoplasmofthebasalandintermediatecelllayersoftheepidermis.Keratohyalingranulesandlipiddropletsappearedintheupperlayer.Degradationofcellularorganellessuchasnucleiandmitochondriathenproceeded,leavingonlyfilamentbundlesandelectron-denseamorphousmassesinthecytoplasm.Thickenedcellularenvelopes,whicharecharacteristicofkeratinizedcells,werealsoobserved.Thesefeaturesarecharacteristicofalpha-typekeratinizationwhichiscommonforotherbodysurfaces.Beta-typekeratinization,typicalofnormalembryonicscales,wasnotobservedevenafter6daysofculturewithhydrocortisone.Keratinizationofembryonicsubperidermofbeta-typedidnotoccureither.Theseultrastructuralobservationsclearlyshowedthathydrocortisoneinducedthealpha-typekeratinization.ItwasalsosuggestedthatSCMEpAwascloselyrelatedtoalpha-typekeratinization.

[学科分类] 生物科学（综合）