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Continuous Dilution Culture System for Studies on Gene-Enzyme Regulation in Synchronous Cultures of Plant Cells

Robert R. Schmidt
In Vitro
Vol. 10, No. 5/6 (Nov. - Dec., 1974), pp. 306-320
Stable URL: http://www.jstor.org/stable/4291820
Page Count: 15
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Continuous Dilution Culture System for Studies on Gene-Enzyme Regulation in Synchronous Cultures of Plant Cells
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Abstract

A thermophilic species of Chlorella was used as a model for higher eucaryotic cells in the development of a continuous dilution system for maintenance of nearly constant environmental conditions during synchronous growth of cells cultured at high concentrations. An equilibrium (isopycnic) centrifugation procedure for selection of large numbers of highly synchronous daughter cells in Ficoll density gradients was also developed. By use of these two procedures, it was possible to show that genes of both inducible and biosynthetic enzymes are continuously available for transcription during the eucaryotic cell cycle. Moreover, with programmed changes in the culture conditions during synchronous growth, it was possible to change step patterns of biosynthetic enzymes to continuous patterns and vice versa. These results, coupled with studies with inhibitors of protein and RNA synthesis, indicate that gene transcription in at least some eucaryotes is responsive to changes in the external environment throughout the cell cycle.

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