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DIFFERENTIAL METABOLISM OF RNA IN NEURONAL‐ENRICHED AND GLIAL‐ENRICHED FRACTIONS OF RAT CEREBRUM
Author(s) -
Flangas A. L.,
Bowman R. E.
Publication year - 1970
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1970.tb03373.x
Subject(s) - ficoll , cerebrum , cytidine , isopycnic , biochemistry , cytoplasm , rna , chemistry , differential centrifugation , parenchyma , microbiology and biotechnology , metabolism , cerebral cortex , biology , centrifugation , enzyme , central nervous system , in vitro , peripheral blood mononuclear cell , botany , neuroscience , gene , endocrinology
— Cerebral tissue of rat, disrupted by passage through a custom‐designed tissue press, was diluted to a 10% (w/v) cellular suspension in 10% (w/v) Ficoll and was then fractionated in the Spinco Model L ultracentrifuge into: (1) two enriched cellular layers ( alpha and beta ) in an isopycnic Ficoll gradient in the Spinco 40 angular rotor; or (2) into four layers (A, B, C, and D) in a discontinuous Ficoll gradient in the Spinco SW 39 swinging bucket rotor. The cellular composition of these layers was identified microscopically and enzymically as either glial‐enriched ( alpha and B layers) or neuronal‐enriched ( beta and C layers) fractions of cerebral cortex. Portions of the neuronal and glial fractions were used for determinations of total nitrogen, and for colorimetric determinations of carbonic anhydrase activity (a glial cell marker). These data established that glial contamination of the neuronal‐enriched layer averaged 6·5 per cent. The data also indicated glial enrichment of Layer B, although no quantitative assessment of the amount of neuronal contamination was possible. The kinetics of metabolism of RNA in the glial‐enriched and neuronal‐enriched fractions were studied from 0·5 to 16 h after‐intracisternal injection of either [ 3 H]cytidine or [ 3 H]orotic acid. In addition, the incorporation of [ 3 H]cytidine into crude nuclear and cytoplasmic components of the layers was studied by the use of 1 h pulses. Our findings indicated greater incorporation of [ 3 H]cytidine into nuclear fractions than into cytoplasmic fractions at 1 h and greater incorporation of both precursors into neuronal‐enriched fractions than into glial‐enriched fractions at all pulse times.