PubMed · 391998
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L A Kamentsky. 1979. Future directions for flow cytometry.. https://doi.org/10.1177/27.12.391998
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The effects of the flavonoids quercetin and myricetin, and the antihepatotoxic agent silymarin, on hydrogen peroxide-mediated DNA damage in human lymphocytes were determined using alkaline single-cell gel electrophoresis (the comet assay). Treatment with hydrogen peroxide increased the levels of DNA strand breaks and oxidised pyrimidine bases in these cells. Quercetin was protective at concentrations above 10 microM and myricetin decreased oxidant-induced DNA strand breakage at concentrations of 100 microM. Cellular metabolism may alter the antioxidant efficacy of the flavonoids. Silymarin had no protective effect at any of the concentrations tested. None of these flavonoids was itself genotoxic. Neither alpha-tocopherol nor beta-carotene decreased hydrogen peroxide-induced DNA breakage. The differences in effectiveness of these dietary compounds against oxidative DNA damage may be explained by differences in their chemical structure or location within the cell.
Two human tumor cell lines that are deficient in the mismatch repair protein hMSH2 show little or no increase in mutation rate relative to that of a mismatch repair-proficient cell line when the cells are maintained in culture conditions allowing rapid growth. However, mutations accumulate at a high rate in these cells when they are maintained at high density. Thus the mutator phenotype of some mismatch repair-deficient cell lines is conditional and strongly depends on growth conditions. These observations have implications for tumor development because they suggest that mutations may accumulate in tumor cells when growth is limited.
Bovine cytochrome P450c17 monooxygenase was produced in a 30-L fermenter by Saccharomyces cerevisiae GRF18 (YEp-Toku1), harboring the GAL10 promoter, and using conditions of medium cell density culture. Upon addition of D-galactose as an inducer and FeCl3 as a cofactor, cells began to produce the P450 hemoprotein. The yield of this enzyme reached a maximum after 31 h but its formation continued for more than 60 h after induction. The amount of P450c17 produced was 4.7-fold as compared to shake flask experiments.