RNA- and protein-synthesizing capacity of isolated oocytes of the sea urchin Lytechinus pictus☆

[摘要] Uridine-14Candvaline-14CincorporationintomacromoleculesbysuspensionsofeggsofLytechinuspictuscontainingvaryingproportionsofoocytesweremeasuredbyscintillationcountingandwerelocalizedwithinthecellsbyautoradiography.Matureeggsincorporatedalmostnouridine-14Cwhileoocytesincorporatedappreciableamounts.Valine-14Cincorporationbysuspensionsofmatureeggsin9experiments,rangedfrom1.91μμmolesto3.39μμmoles,andaveraged2.37μμmolesper104eggsin15minutes.Thecorrespondingvaluesobtainedin10experimentswithsuspensionscontainingvariousamountsofoocytesrangedfrom6.12μμmolesto97.8μμmolesandaveraged37.9μμmoles,namely,approximately16timesthatofthematureeggs.Dactinomycinsignificantlyinhibiteduridine-14Cincorporationbutdidnotsuppressvaline-14Cincorporationbythematureeggsortheoocytes.Infouroftheexperiments(onewithamatureeggsuspension)dactinomycinstimulatedvaline-14Cincorporationbythree-tofourfoldbutin10others(twowithmatureeggsuspensions)therewasnosignificantdifferencefromthecontrol.Additionalevidencethattheincorporationofvaline-14Crepresentssynthesisratherthanexchangeorabsorptiveprocesseswasprovidedbyademonstrationthatittakesplaceonpolyribosomes.Autoradiographsconfirmedthatthematureeggsdidnotincorporateuridine-14Candincorporatedonlyslightquantitiesofvaline-14C,eveninthemixedsuspensionswithoocytes.Theoocytesincorporateduridine-14Cprimarilyinthenucleolus,andthiswaspreventedbydactinomycin.Valine-14Cwasincorporated,bytheoocytes,principallyinthecytoplasmandnucleolus.Inseaurchinsthen,theoocytesappeartoundergoaconsiderableamountofintrinsicproteinandRNAsynthesis.Thisisincontrasttothesituationinmanyotherorganismsinwhichtheoocyteapparentlyobtainsmuchmaterialfromothertissues.

[学科分类] 生物科学（综合）