The significance of the latent period in thyroid hormone induced tissue regression during amphibian metamorphosis

[摘要] TailfindisksremovedfromtadpolesofRanapipiensthatwereimmersedinthyroxineortriiodothyroninefor3days(referredtoasdonors)werefusedtopremetamorphictailfinblocksthathadneverbeenexposedtothishormone(referredtoasrecipients)sothattripletswereformed,consistingofonerecipienttailblocksandwichedbetweentwodonortailfinblocks.Suchrecipienttailblocksrespondedwithcharacteristicresorptiveactivitywithin24or48hr,insteadoftheminimum72-hrlatentperiodnormallyinterveningindonorblocks,untilshrinkagewasinitiatedinresponsetotriiodothyronine(T3)ortetraiodothyronine(T4).ThepresenceofT3orT4hormonewasnotrequiredcontinuouslythroughoutthelatentperiod.Hormonecouldbewithdrawnafter30hrcontactinvivoandafter24hrcontactinvitrowithoutinterferingwiththerateoftissueregressionoftadpoletailfins,suggestingthatthe“latentperiod”probablydoesnotcoincidewiththe“criticalperiod”duringwhichsubtlebiochemicalchangespresumablyoccurthatprecederegressionofthetadpoletailduringmetamorphosis.Itissuggestedthatduringthelatentperiodactiveintermediatesmaybesynthesizedthataresubsequentlytransferredfromdonortailfinstorecipients,thusreducingthelatentperiodofthelatter.

[学科分类] 生物科学（综合）