PolyribosomesProtein BiosynthesisRibosomesCentrifugation, Density GradientPuromycinPeptide BiosynthesisCell FractionationPoly ALeucineRNA, MessengerCell-Free SystemCarbon IsotopesRibonucleasesMembranesRNA, RibosomalCytoplasmReticulocytesTritiumRNAFragile X Mental Retardation ProteinPulvinusPactamycinRibonucleoproteinsMicroscopy, ElectronUridinePeptide Chain Elongation, TranslationalAmino AcidsLumicolchicinesLiver