Effect of 5-bromodeoxyuridine on ultrastructure of developing limb-bud cells in vitro☆

[摘要] Limb-budcellsdifferentiateintochondrocytes,myocytes,fibrocytesandepithelialcellsinvivo.Whiledetailedmorphologicaldescriptionsofdevelopmentaleventshavebeenpresented,mechanismsgoverningdifferentiationofcellsinvivoarenotyetapparent.Limb-budcellscanbegrownintissuecultureandwilldifferentiateintothesamecelltypesasoccurinvivo.Chondrogenesisinvitroappearstomimicdifferentiationinvivoasevaluatedbothbiochemicallyandultrastructurally.IncorporationofH235SO4intoglycosaminoglycansincreasesmarkedlyonthefourthdayinculture.Atthesametime,cellsassumethemorphologyofmaturechondrocytesandsynthesizeextracellularmatrixcomposedof250–400Ã…proteoglycangranulesandpoorlycross-bandedcollagenfibers.Myocytescanbedetectedasearlyas21hrafterinitiationofcellculturesandcontaingiantpolysomesandthickandthinfilaments.Whenearlyembryoniclimb-budcellsaretreatedwith5-bromo-2′-deoxyuridine(BrdUrd),myogenesisisdiminishedanddifferentiationintochondrocytesispreventedirreversibly.IncorporationofH235SO4remainsdepressedthroughoutthecultureperioddespiteremovalofthedrugaftertheseconddayofgrowth.Developmentoforganellesassociatedwithsynthesisofextracellularmaterial(roughendoplasmicreticulumandGolgiapparatus)isnotpreventedbytreatinglimb-budcellswithBrdUrd.Extracellularmatrixconsistsprimarilyofbundlesofcollagenfibers.

[学科分类] 生物科学（综合）