Hormonal effects on the development of glutamine synthetase in the embryonic chick retina☆
[摘要] Glutaminesynthetase(GS)activityintheneuralretinaofthechickembryoincreasesrapidlyduringthefinalperiodofembryonicdevelopment.MaturationalchangesoccurringinchickserumduringthisperiodwereshowntoenhanceprecociouslyGSactivitiesinorganculturesofretinafromearlyembryosinapatternstrikinglysimilartothenormalsequenceofGSdevelopmenttowardhatching.ThesignificanceofthisagreementbetweenpatternsofretinalGSintheembryoandinvitrowasdiscussedinrelationtorecentevidencesuggestingthatGSdevelopmentinculturedretinaacquiresaninsensitivitytoinhibitorsofRNAsynthesis.HormoneswereemployedtoexaminethepossibilitythatchangesinthesystemicenvironmentoftheembryomightparticipateincontrollingGSincreasesinsitu.Injectionsofestradiol,thyroxine,cortisone,andhydrocortisoneincreasedretinalGSactivitiestovaryingdegrees;hydrocortisonewasmosteffectiveinstimulatingprecociousGSdevelopmentintheembryo.TheinfluenceofendogenousthyroidhormoneonthenormalGSpatternwastestedwithpropylthiouracil(PTU),anantithyroidcompound;PTU-treatmentdepressedthenormalrapidincreaseofretinalGSactivitiesduringtheterminalphaseofembryonicdevelopment.HormonaleffectsonretinalGSwereexaminedfurtherinvitroinorgancultures,usingretinasfromearlyembryos.TheadrenalcorticoidswereshowntoadvanceprecociouslyGSactivitiesinretinaculturedunderappropriateconditions.HydrocortisoneelicitedmaximalGSdevelopmentinvitroinconcentrationscomparabletocirculatinglevelsofthissteroidintheadult.Finally,thepossibilitywastestedwhetherthyroidfunctionwasnecessaryfortheprecociousstimulationofretinalGSintheembryobyhydrocortisone.ItwasshownthathydrocortisoneorsubstanceswithsimilaractivityintheembryonicserumcouldprecociouslyenhanceretinalGSactivitiesintheembryointheabsenceofnormalserumlevelsofthyroidhormone.
[发布日期] [发布机构]
[效力级别] [学科分类] 生物科学（综合）
[关键词] [时效性]
