Protoplasmic streaming as a process of jet propulsion☆

[摘要] Protoplasmicstreamingisproposedtobegenerallyacountercurrentprocessinwhichtubularandvesicularmembranouselementsoftheendoplasmjet-propelthemselvesinthedirectionofstreamingbyapumpingactioninwhichthecytoplasmicmatrixisejectedintheoppositedirection.Movementofinclusionswiththejet-propelledmembranouselementsapparentlydependsuponthefactthattheyaremembraneencapsulatedandenmeshedinadensenetworkoftheseelements,forwhichtheyhaveahighaffinity.Circulationofmatrixbetweenmassivelamellarelementsoftheendoplasmicreticulumalsoseemstobeaccomplishedbyapumpingactionoftheconstituentdouble-membranelamellae.Therecoilofthesemassiveelementsandofmembrane-encapsulatedorganellesmaybethebasisfortheirtranslationalandrotationalmovements.Thepumpingofmatrixbymembranouselementsissuggestedtobeanaccompanimentofmetabolicactivityattheirsurfacesandtheprimitivebasisforcellcirculations.Inthisview,theveryelementsresponsibleforsynthesesandothermetabolicreactions,alsoprovidethechannelsandmotiveforceforpartitioning,exposing,circulating,andtransportingboththesubstratesuponwhichtheyactandtheproductsoftheiractions.Whenprotoplasmicstreaminginvariousformsisanalyzedasacountercurrentprocessinvolvingjetpropulsion,itsmanymanifestationscanbeformulatedasmerevariationsonacommontheme,aspostulatedinthefollowing:1.1.Cyclosisofplant-cellprotoplasmreflectsthecontinuouscountercurrentcirculationofmatrixthroughtheluminaofcounter-movingmembranouselements.2.2.Astersformbyjetpropulsionofmembranouselementsinwardalongtheraystotheclearhyalinecentralregionwheretheyaccumulateasagelledmass.3.3.“Peristaltic”flowofaxoplasmand“dammingup”ofconstrictedneuronsoccurasaresultofthetemporary“pileup”ofjet-propelledelementsoftheaxonalendoplasmicreticulum(andaccompanyinginclusions)atthenodesofRanvierandotherconstrictedregions.4.4.Myxomyceteshuttlestreamingprimarilyreflectstheback-and-forthcountercurrentcirculationofmatrixthroughtheluminaofelementsoftheendoplasmicreticulum.Thematrixandjet-propelledelementsalternatelyaccumulateingreateramountsatoppositeendsofthestream.5.5.Protoplasmicstreaminginfungalhyphae,viewedasaprocessofmassexchangeratherthanofbulktransfer,resolvesthelong-standingenigmaofwherethestreamingprotoplasmgoesto.Membranouselementsandinclusionsmakeheadwaytocertainregionsattheexpenseofmatrixwhich,beingretrojectedintandem,accumulatesatotherregions.Thecyclesofwaxingandwaningofvacuolarsizeatoppositeextremitiesofhyphaeinwhichreversalsofstreamingoccur,reflecttheaccumulationandevacuationofmatrixretrojectedfromoneendtotheotherbythejet-propelledelements.6.6.Thecountercurrentbasisofprotoplasmicstreamingisrevealedinorganismswhichfeedbyfilamentstreaming.Whenonlyaninterfacialfilmseparatestheprotoplasmfromthemedium,asinaforaminiferanreticulopod,themovementofretrojectedmatrixismanifestedbecauseitcarriesthefilmandadheringparticulatematterbacktothecellbodywithitbyadhesivedrag.Agradientofdynamicinterfacialtensionprobablypromotestheflowofthefilm.

[学科分类] 生物科学（综合）