Time of origin of Mauthner's neuron in Xenopus laevis embryos

[摘要] ThetimeofthelastDNAreplicationoftheMauthner'sneuronprecursorcellhasbeeninvestigatedusingradioautography.EmbryosofXenopuslaeviswerelabeledatdifferentstagesofearlydevelopmentbysinglemicroinjectionsoftritiatedthymidine.Labelingtimesweredesignedtocovertheentireperiodofdevelopmentbetweengastrulaandhatchingstages.Theembryoswerefixedatlaterstages(41to44,accordingtoNieuwkoopandFaber,1967),whentheMauthnerneuroncanbereadilydistinguishedbyitscharacteristicallylargesizeandlargenucleolus.Mauthnerneuronsofembryoswhichreceivedtritiatedthymidinefromstage10(beginningofgastrulation)tostage12(advancedgastrula,mediumyolkplug)werealwayslabeled.Thoseembryoswhichreceivedtheisotopeatorafterstage1212(advancedgastrula,smallyolkplug)wereneverfoundlabeled.TheseresultsimplythatthelastDNAreplicationofthecelldestinedtogiverisetotheMauthnerneuronoccursduringthelastgastrulastages.ThislastDNAreplicationimmediatelyproceedsthetimeoftheso-called“histogeneticdetermination”oftheMauthnerneuronproposedtocorrespondtostage13(slitblastopore)byStefanelli(1951).ThereforeitappearsthatthedevelopmentalprogramoftheMauthnerneuroninvolvesaremarkablyearlycessationofDNAreplicationcloselyfollowedbyhistogeneticdetermination.Thisistheearliestknowneventofthistypeforaspecific,wellcharacterizedneuronintheamphibianembryo.

[学科分类] 生物科学（综合）