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30 results on '"Chang, Chong W."'

11. Effect of Fluoride on Ribosomes from Corn Roots. Changes with Growth Retardation.

Author

Chang, Chong W.

Subjects
*ORGANELLES, *CORN, *RIBOSOMES, *FLUORIDES, *FLUORINE compounds, *CHROMATOGRAPHIC analysis
Abstract

Growth inhibition caused by fluoride was further studied by analyzing free and bound ribosomes, and the ribosomal components in corn roots. Ribosomes were isolated by differential centrifugation. Ribosomal components were analyzed by column chromatography and electrophoresis. Fluoride reduces the amounts of both free and bound ribosomes. Fluoride also modifies the RNA to protein ratio of bound ribosomes more than that of free ribosomes. Fluoride does not affect base ratios of the ribosomal RNA, but reduces its content and changes the structure of the ribosomal protein moiety. [ABSTRACT FROM AUTHOR]

Published
1970
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13. Effect of Fluoride on Nucleic Acids and Growth in Germinating Corn Seedling Roots.

Author

Chang, Chong W. and Thompson, C. Ray

Subjects
FLUORIDES, NUCLEIC acids, CORN, SEEDLINGS, PLANT roots, RNA
Abstract

Corn seeds were treated with 0.01 M sodium fluoride for various time periods. The treated seeds were germinated and grown until the seedling roots reached a standard size of 12 ±3 mm. Analyses were made for RNA and DNA contents of 3-mm seedling root tips. Determinations also were made for growth rate, rate of cell elongation, cell multiplication, and tissue maturity of 12-mm roots. RNA contents of 3-mm root tips were found to be directly proportional to the growth rates of the entire seedling root of corn seeds treated with sodium fluoride for various periods of time. The RNA content was reduced on a cell basis and was independent of the root tip cell number. The amount of DNA was not related to the growth rate of the intact seedling roots. Since fluoride reduced the number of mitotic figures, it was likely that fluoride inhibited DNA synthesis during the interphase of the mitotic cycle. Growth by cell multiplication was inhibited more than that by cell elongation in the sample treated with fluoride for a scorter period. The two types of growth, however, showed a similar level of growth reduction in the sample treated with fluoride for a longer period. Fluoride seemed to reduce the rates of cellular elongation and multiplication not more than about 40 per cent of the control value in these tissues under present experimental conditions. Fluoride also induced maturity in the seedling roots in proportion to the periods of fluoride treatment. [ABSTRACT FROM AUTHOR]

Published
1966
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14. Site of Fluoride Accumulation in Navel Orange Leaves 1

Author

Chang, Chong W. and Thompson, C. Ray

Subjects
Citrus, Fluorides, Chloroplasts, Articles, In Vitro Techniques
Abstract

Fluoride-polluted navel orange leaves, Citrus sinensis (Linn.) Osbeck, were fractionated into the subcellular components in hexane/carbon tetrachloride mixtures having various densities. Fluoride was determined at each fraction. Analyses were also made for the subcellular distribution of chlorophyll, nitrogen, and DNA to assess the extent of cross-contamination of each component. The fraction containing cell wall, nuclei, and partly broken cells apparently contained a major amount of fluoride. However, if allowance was made for the cross-contamination of chloroplasts and chloroplast fragments, the fraction of chloroplasts was found to be the site of the highest fluoride accumulation. When each particulate component was washed with water after drying, the combined washings contained more than 50% of the total fluoride of the isolated fractions. The usual method of subcellular fractionation with aqueous solvent shifted the major site of fluoride accumulation from the fraction of chloroplasts to that of the supernatant.

Published
1966

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