Studies on the appearance and nature of a maturation-inducing factor in the cytoplasm of amphibian oocytes exposed to progesterone☆

[摘要] Full-grownoocytesofamphibiansrespondinvitrotoexogenousprogesteronebyundergoingphysiologicalmaturation(breakdownofthegerminalvesicle(GVBD),meiosis,andacquisitionofthecapacityforactivation).Bothcytoplasmand“cytosol”frommaturingoocyteshavebeenshowntoproducesimilareventswheninjectedintounstimulatedoocytes.Thisactivityappearedwithin4hrafterhormonetreatmentinRanapipiensandXenopuslaevisandrepresentstheearliestdetectable,specificresponseoftheoocyteyetobserved,i.e.,6–8hrbeforeGVBDinRana.Maturingoocytesretainedactivityaslongas100hrafterexposuretoprogesterone,andactivitywasalsoobtainedfromovulatedeggsandcleavingembryos.Inaddition,cytoplasmfromRanapipiens,Xenopuslaevis,orAmbystomamexicanumwaseffectiveininducingmaturationinoocytesofeachother,indicatingalackofspecificity.RecipientoocytesofXenopuslaevisconsistentlybegantomaturewithin1.5–3hrafterinjectionofmaturingcytoplasm,wellbeforeprogesterone-treatedcontrols.Thetimingoftheresponsewascloselyrelatedtothequantityofcytoplasmtransferred,suggestingthepresenceofbothaminimumandthresholdlevelofcytoplasmicfactor.SerialcytoplasmictransferinXenopusoocytesshowednosignificantlossofactivitythrough10injections.

[学科分类] 生物科学（综合）