Neuritic guidance by polyornithine-attached materials of ganglionic origin☆

[摘要] Dissociatedciliaryganglionicneuronsdonotsurviveincultureunlesssuppliedwithanappropriatesourceofciliaryneuronotrophicfactors(CNTF).Moreover,previousworkfromthisandotherlaboratorieshasshownthatpolyornithine(PORN)substratapersedonotallowneuriticdevelopmentfromsuchCNTF-supportedneurons.Neuriticformation,however,wouldtakeplaceifthePORNsubstratumiscoatedwithaneurite-promotingfactor(NPF)fromheartconditionedmedium.UndissociatedchickembryociliarygangliaexplantedonPORNsubstratawillalsoproducealavishradialneuriticoutgrowthonlyiftheyareCNTFsupportedandthesubstratumiscoatedwithNPF.IntheabsenceofexogenousNPFneuritesgrowradiallybutonlytoalimitedextent.Atadistanceofapproximately120μmfromtheexplant,neuritesswitchfromaradialtoacircularortangentialgrowthpattern,thusgivingrisetoaneuriticringalmostconcentricwithrespecttotheexplant.Time-lapsestudiesshowthattheneuriticringisgeneratedthroughacombinationofseveralbehaviorsthatneuritesdisplayuponreachingtheradial-to-circular“transitionzone,”includingbranchingandturningeitherclock-orcounterclockwise.Contributionsarealsomadebyinterneuriticbridgesarisingfromfusionoftangentialfilopodiafromadjacentgrowthcones.Theoverallbehaviorofneuriticoutgrowthsuggeststhattheexplantedciliarygangliaareabletoproducematerialsendowedwithneurite-promotingproperties,whichcoatthePORNsubstratumintheimmediatevicinityoftheganglia.Autoradiographicexperimentsusinggangliaprelabeledwitheither[3H]glucosamineor[14C]leucinedemonstratedtheexistenceofthesematerials.AperiganglionicterritoryofPORN-attachedmaterials(PAMs)ofganglionicorigincanberecognizedafewhoursafterexplantation,beforetheonsetofneuriticemergencefromtheganglion.ThisPAMterritorygrosslycorrespondstotheareathatafewhourslaterwillbeoccupiedbytheneuriticring.IftwogangliaareexplantedatadistanceapproximatelyequaltotwicethedistancenormallycoveredbyadenseperiganglionicPAMhalo,acontinuitybetweenthePAMterritoriesofbothgangliaisestablishedbeforetheonsetofneuriticoutgrowth.Thisoverlappinggeneratesan“avenueofpreferentialterrain”thatprovidesguidancetoneuritesbetweentheneighboringganglia.Thepossibilityisconsideredthatasimilarmechanismofneuriticguidancecouldalsooccurinvivo.

[学科分类] 生物科学（综合）

[关键词] CG;ciliary ganglion;CNTF;ciliary neuronotrophic factor;EE;embryo extract;HCM;heart-conditioned medium;HEBM;modified Eagle's basal medium;NPF;neurite-promoting factor;CG-NPF;ciliary ganglion-derived NPF;CM-NPF;conditioned medium-derived NPF;PAM;polyornithine-attached material;PORN;polyornithine