Myogenic fusion and the duration of the post-mitotic gap (G1)☆

[摘要] Thedecreasedgrowthrateobservedinoldermusclecultureshasbeenattributedtothewithdrawalofcellsfromtheproliferativepoolbyfusion.Thepossibilitywasexaminedthatthisdecreasereflectschangesinthecellcycleaswell.Beforefusion,thecycleisrelativelyshortanduniform(10.0±2.7hr)becominggreatlyextendedandmorevariable(19.2±8.5hr)inculturesundergoingfusion.Mostoftheincreaseingenerationtimeisintroducedbyalong,variableG1phase,thatphasetowhichfusionisrestricted.Thesestage-specificcyclecharactersticsareafunctionofchangesoccurringinthemedium,ratherthanoftimeinculture.Oldercultures,refedfreshmediumacquirethecellcyclecharacteristicsofyoungercultures,andconversely,earlyculturesfedmediumcollectedfromolderculturesexhibitcyclemeasurementstypicalofoldercultures.AlthoughthemeanG1timealmostdoublesatthetimeoffusion,thereisnoevidencethatcellsactuallywithdrawfromthecyclepriortofusion.Continuouslabelingbeforeandaftertheinitiationoffusionindicatethatatallstagesvirtually100%ofthemononucleatedcellsincorporate3H-TdR.SincefusionoccursinG1,itseemsreasonabletoassumethatsomepreparationforfusionoccursduringthisphaseandtheprobabilityoffusionincreaseswithprotractionofG1.

[学科分类] 生物科学（综合）