Abstract. RNA which dissociated from purified cerebral polyribosomes of adult rats in the presence of EDTA was isolated by fractionation in a discontinuous sucrose gradient. The yield was 2% of the total polyribosomal RNA. The base composition resembled the complementary values for rat DNA and was very different from base compositions of ribosomal RNA and transfer RNA. This RNA fraction contained a large proportion of molecules which were rapidly labeled in vivo and hybridized to homologous DNA. The polyribosomal RNA preparation also exhibited high template activity in a cerebral cell-free system which had previously been stripped of the capacity to incorporate amino acids in the absence of added messenger RNA (mRNA). Sedimentation analysis revealed only two peaks, with coefficients of approximately 8 S and 16 S. The data indicate that RNA with the properties of mRNA can be selectively isolated from cerebral polyribosomes under mild conditions which avoid degradation.Numerous studies support the concept that alterations in RNA and protein synthesis are associated with information transfer and storage in the central nervous system. Activation of the synthesis of specific proteins is suggested by the reports that new RNA with altered base composition, presumably mRNA, is formed during the acquisition phase of learning. [1][2][3][4] These findings indicate that successful isolation of undegraded mRNA from brain may lead to definitive studies on the relationship between protein synthesis and the specialized functions of this organ.Previous investigations from this laboratory revealed that cerebral cortex of the adult rat contains a high proportion of mRNA-ribosome complexes which readily dissociate in media of low Mg2+ concentration.56 The same studies indicated that purified cerebral polyribosomes were devoid of measurable RNase activities. These results suggested that mRNA species present in unstable cerebral polyribosomes might be readily extracted in their native state. The present report provides experimental support for this prospect.Materials and Methods. Polyribosomes, pH 5 fraction and ribosomal factors:Polyribosomes were isolated from cerebral cortical gray matter of young adult male rats (42 days old) without the use of a detergent.6 About 85% of the total polyribosomes in cerebral postmitochondrial supernatants were recovered in this 'free' polyribosome fraction.7 The purified polyribosomes contained no detectable RNase activities.6 The 644
We Have recently reported that chronic electroconvulsive seizures (ECS) lead to a long‐lasting increase (up to 6 weeks) in the activity of monoamine oxidase (MAO) in the brain of rats (Pryor and Otis, 1970). Other investigators have shown increased levels of norepinephrine (NE) and 5‐HT, more rapid clearance of intracisternally‐injected [3H]HNE (Kety, Javoy, Thierry, Julou and Glowinski, 1967), and increased tyrosine hydroxylase activity (Musacchio, Julou, Kety and Glowinski, 1969) at 24 h after a series of two ECS daily for 7 days. Together, these data suggest a sustained activation of the 5‐HT and/or NE systems following chronic ECS. We now report the results of a series of experiments in which some of the potential variables that may be involved in the MAO response were investigated and that indicate some biochemical specificity of the response. In these experiments, succinate dehydrogenase (SDH) activity was also assayed to assess possible nonspecific effects of repeated seizures on mitochondrial metabolism and catechol O‐methyltransferase (COMT) activity was determined to see if this extracellular degradative enzyme for NE was affected in the same way as MAO located intracellularly in the mitochondria.
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