title: Distribution and protein synthetic activities of neuronal free and membrane-bound ribosomes during postnatal development of rat cerebral cortex.
abstract: The distribution and amino acid incorporative activities of free and membrane-bound ribosomes in neuronal perikarya of rat cerebral cortex at successive stages of postnatal development were investigated. The relative proportion of neuronal membrane-bound ribosomes increased significantly between 6 and 18 days of age, reaching 50% of the total ribosomal population around day 18. In contrast to the neuronal fraction, the membrane-bound ribosomes in unfractionated cerebral cortex decreased from 50% at birth to 35% in 18-day-old pups. When tested in a cell-free amino acid incorporation system the activities of both free and membrane-bound ribosomes increased up to day 10 post partum. However, whereas the activity of free ribosomes reached a constant level at this age, that of the membrane-bound fraction continued to rise until 18th day after birth. Crossover experiments employing homologous or heterologous cell sap fractions showed that the preparation from the 18-day-old animals was more efficient in supporting protein synthesis in vitro, if compared with similar preparation from the neonatal animals. This was attributed to an enhanced aminoacylation of transfer RNA in neuronal cell sap of older compared with younger rats. The observed developmental alterations in the distribution and activities of free and membrane-bound ribosomes are discussed in relation to changes that occur in morphology and function of brain during the early postnatal period.
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation; D002540:Cerebral Cortex / Q000166:cytology*; D004247:DNA / Q000096:biosynthesis; D009474:Neurons / Q000378:metabolism; D012335:RNA, Ribosomal / Q000096:biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains; D012269:Ribosomal Proteins / Q000096:biosynthesis*; D012270:Ribosomes / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins; D004247:DNA