The development of myofibrils in cultured muscle cells: A whole-mount and thin-section electron microscopic study☆

[摘要] ThedevelopmentofmyofibrilsinculturedmyotomecellsfromXenopusembryoswasstudiedwithwhole-mountandthin-sectionelectronmicroscopy.Forwholemount,thecellsweregrownonFormvar-coatedgrids,fixed,dehydrated,critical-pointdried,andexaminedwithaconventional(100kV)orahigh-voltage(1000kV)electronmicroscope.Nonstriatedbundlesof6-to8-nmmicrofilaments,similartostressfibersinnonmusclecells,appearpriortonascentmyofibrils.Thesebundlesrunthewholelengthofthecellandareinsertedintothecellcortex.Thetransitionfromstriatedregiontononstriatedregiononasinglenascentmyofibrilcanbeseeninbothwhole-mountandthin-sectionimages.Newsarcomeresappeartobeaddedatthedistalendofexistingones.Ourdataalsoindicatethatthesenewsarcomeresareformedonapreexistingbundleofthinfilaments.Thissuggeststhatthebundlesofmicrofilamentsareprecursorstomyofibrils.Evidenceforthishypothesiscamefromthefollowingobservations.(1)Nascentmyofibrilsareanchoredtothecellcortexviathinfilamentssimilartomicrofilamentbundles.(2)ThinfilamentsinnewlyformedsarcomeresareoftencontinuousthroughthemiddleoftheAband.LatertheybreaktoformtheHzone.(3)ThinfilamentsappeartobecontinuousthroughthedevelopingZband.LatertheyinteractwiththefilamentsintheZbandtoformthestaggeredappearance.

[学科分类] 生物科学（综合）