The induction of DNA synthesis by frog egg cytoplasm

[摘要] Theearlyeffectsaredescribedofinjectingnucleifromembryonic,larval,andadultcellsofXenopuslaevisintounfertilizedeggsofthesamespecies.3H-thymidinewasinjectedintoeggsimmediately,oratintervals,aftertheinjectionofnuclei.AutoradiographyofthesectionedeggsshowedwhethertheinjectednucleihadsynthesizedDNAafterexposuretoeggcytoplasm.Thegreatmajorityofnucleifromgastrulaendodermcells,aswellasfromadultliver,brain,andbloodcells,synthesizedDNAatsometimeduringthe90minutesfollowinginjectionintoeggs.Inthecaseoftheliver,brain,andbloodcellnucleithisconstitutesaveryconsiderablechangeinfunction,sincenotmorethan1%ofthesecellsincorporate3H-thymidineina90-minuteperiodinvivo,andtheprocedureusedtopreparenucleifromthesecellsdidnotitselfinduceDNAsynthesis.Thischangeinnuclearfunctionisinducedbyexposingnucleitonormaleggcytoplasm.ThecytoplasmicinfluenceisnotClassspecificsinceover90%ofmouselivernucleiarealsoinducedtosynthesizeDNAafterinjectionintofrogs'eggs.Gastrula,liver,brain,andbloodcellnucleiinjectedintoeggscommenceDNAsynthesislater,andcontinueitforlonger,thantheeggnucleusofafertilizedegg.DNAsynthesiswasobservedintransplantedembryoniccellnucleiwhichweredestinedtopromoteabnormalaswellasnormaldevelopment.Liver,brain,andbloodcellnucleiswellupto60timesafterinjectionintoeggs,andthisincreaseinvolumetakesplaceatthesamerateasthatatwhichnucleiareinducedtosynthesizeDNA.Thesenucleiwerenotobservedtoentermitosisduringthe90minutesimmediatelyfollowinginjectionintounfertilizedeggs.

[学科分类] 生物科学（综合）