Hydra transplantation phenomena and the mechanism of Hydra head regeneration: II. Properties of the head activation

摘要

Measurementsweremadeofthea€?headactivationa€?intransplantedfragmentsofHydratissue.Themeasurementsconfirmthatheadactivationisgradedinthebodyandthatactivationincreasesduringheadregeneration.Experimentsoftwodifferentsortsshowthatregeneration-specificactivationincreaseisconfinedtothepresumptiveheadzone.Whenheadformationisinitiatedandsubsequentlyblocked,theactivationdecaysbacktoitsoriginallevelinabout12hr;thisisthreetimesfasterthantheactivationdecayobservedinbodytissuemovedtoamorebasalposition.Experimentsonfootformationphenomenashowasimilarlabilitydifference.Itthusappearsthatregeneration-specificactivationincreaseinvolvesamechanismdifferentfromtheoneresponsibleforthegradientofactivationinthebody.Cuttingproducesalocalincreaseoftheheadand/orfootactivationlevel;thisincreasedecaysinabout12hr.TheseresultsandthoseoftheprecedingpaperareconsistentwithaversionoftheGierer-Meinhardtmodelwhichalsoaccountsfortheregulationofthehead/bodyproportioninHydra.