The Experts below are selected from a list of 129 Experts worldwide ranked by ideXlab platform
Nicholas A. Wright - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of a proposed technique to assess unscheduled DNA Synthesis and genotoxicity.
Gut, 1993Co-Authors: Robert A. Goodlad, Cy Lee, Malcolm R. Alison, C. E. Sarraf, M. A. Ghatei, S.r. Bloom, Nicholas A. WrightAbstract:Results from a recent, new assay suggest that omeprazole, a potent inhibitor of gastric acid secretion, is genotoxic. The principle of this assay is that the non-proliferating zone of surface gastric epithelial cells can be selectively removed by controlled digestion so that any incorporation of tritiated thymidine into these cells represents unscheduled DNA Synthesis. Parietal cells (which are located below the uppermost proliferating cells) and proliferating cells in semiconservative, regular DNA Synthesis could always be shown in the digested fraction, and as regular DNA Synthesis takes up a thousand fold more thymidine than unscheduled DNA Synthesis, any signal from unscheduled Synthesis would therefore be swamped. The digestion process was also uneven, as histological analysis showed denuded patches of mucosa, and gland like structures were seen in the digest. Quantification of the number of silver grains over the nuclei showed no increase in low level labelling after omeprazole administration, indicating that there was no unscheduled DNA Synthesis. The labelling index of undigested gastric tissue from omeprazole treated rats was not significantly different from that of the control group, despite an increase in the plasma gastrin value.
Robert A. Goodlad - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of a proposed technique to assess unscheduled DNA Synthesis and genotoxicity.
Gut, 1993Co-Authors: Robert A. Goodlad, Cy Lee, Malcolm R. Alison, C. E. Sarraf, M. A. Ghatei, S.r. Bloom, Nicholas A. WrightAbstract:Results from a recent, new assay suggest that omeprazole, a potent inhibitor of gastric acid secretion, is genotoxic. The principle of this assay is that the non-proliferating zone of surface gastric epithelial cells can be selectively removed by controlled digestion so that any incorporation of tritiated thymidine into these cells represents unscheduled DNA Synthesis. Parietal cells (which are located below the uppermost proliferating cells) and proliferating cells in semiconservative, regular DNA Synthesis could always be shown in the digested fraction, and as regular DNA Synthesis takes up a thousand fold more thymidine than unscheduled DNA Synthesis, any signal from unscheduled Synthesis would therefore be swamped. The digestion process was also uneven, as histological analysis showed denuded patches of mucosa, and gland like structures were seen in the digest. Quantification of the number of silver grains over the nuclei showed no increase in low level labelling after omeprazole administration, indicating that there was no unscheduled DNA Synthesis. The labelling index of undigested gastric tissue from omeprazole treated rats was not significantly different from that of the control group, despite an increase in the plasma gastrin value.
V. Subbarao - One of the best experts on this subject based on the ideXlab platform.
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Dehydroepiandrosterone inhibits DNA Synthesis of rat hepatocytes induced by partial hepatectomy or mitogen (ciprofibrate)
Cell proliferation, 1997Co-Authors: M. S. Rao, V. SubbaraoAbstract:In a previous study we have shown that dehydroepiandrosterone (DHEA) inhibits hepatocyte DNA Synthesis after short-term administration and induces hepatocellular carcinomas after long-term administration in the rat. It is not known whether DHEA is also capable of inhibiting replicative and mitogen-induced DNA Synthesis. In the present study, we have evaluated the effect of DHEA on DNA Synthesis in the rat liver after partial hepatectomy and mitogen administration. After partial hepatectomy, DHEA significantly inhibited DNA Synthesis at 20, 26, 32 and 38 h. Similarly, combined administration of ciprofibrate, a peroxisome proliferator and mitogen, and DHEA also resulted in significant hepatocyte DNA Synthesis. However, DHEA did not affect liver enlargement caused by ciprofibrate. This experimental system will serve as useful tool to evaluate the role of cell proliferation in carcinogenesis.
Sigurdur Gudmundsson - One of the best experts on this subject based on the ideXlab platform.
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different patterns of bacterial DNA Synthesis during postantibiotic effect
Antimicrobial Agents and Chemotherapy, 1995Co-Authors: Magnus Gottfredsson, Helga Erlendsdottir, Agust Gudmundsson, Sigurdur GudmundssonAbstract:Studies on bacterial metabolism during the postantibiotic effect (PAE) period are limited but might provide insight into the nature of the PAE. We evaluated the rate of DNA Synthesis in bacteria during the PAE period after a 1-h exposure of organisms in the logarithmic growth phase to various antibiotics. Staphylococcus aureus ATCC 25923 was exposed to vancomycin, dicloxacillin, rifampin, and ciprofloxacin ; Escherichia coli ATCC 25922 was exposed to gentamicin, tobramycin, rifampin, imipenem, and ciprofloxacin ; and Pseudomonas aeruginosa ATCC 25783 was exposed to imipenem, tobramycin, and ciprofloxacin. DNA Synthesis was determined by measuring the rate of [ 3 H]thymidine incorporation in S. aureus and E. coli and [ 3 H]adenine incorporation in P. aeruginosa. DNA Synthesis in S. aureus was suppressed during the PAE phase with vancomycin, dicloxacillin, and rifampin, it was suppressed in E. coli with rifampin, and it was suppressed in P. aeruginosa after exposure to tobramycin. Conversely, DNA Synthesis was relatively enhanced in the gram-negative bacilli after exposure to imipenem and in all three species after exposure to ciprofloxacin. However, DNA Synthesis in E. coli was only minimally affected after exposure to tobramycin and gentamicin. The differences in DNA Synthesis observed after exposure to various antimicrobial agents suggest multiple mechanisms for the PAE.
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different patterns of bacterial DNA Synthesis during postantibiotic effect
Antimicrobial Agents and Chemotherapy, 1995Co-Authors: Magnus Gottfredsson, Helga Erlendsdottir, Agust Gudmundsson, Sigurdur GudmundssonAbstract:Studies on bacterial metabolism during the postantibiotic effect (PAE) period are limited but might provide insight into the nature of the PAE. We evaluated the rate of DNA Synthesis in bacteria during the PAE period after a 1-h exposure of organisms in the logarithmic growth phase to various antibiotics. Staphylococcus aureus ATCC 25923 was exposed to vancomycin, dicloxacillin, rifampin, and ciprofloxacin ; Escherichia coli ATCC 25922 was exposed to gentamicin, tobramycin, rifampin, imipenem, and ciprofloxacin ; and Pseudomonas aeruginosa ATCC 25783 was exposed to imipenem, tobramycin, and ciprofloxacin. DNA Synthesis was determined by measuring the rate of [ 3 H]thymidine incorporation in S. aureus and E. coli and [ 3 H]adenine incorporation in P. aeruginosa. DNA Synthesis in S. aureus was suppressed during the PAE phase with vancomycin, dicloxacillin, and rifampin, it was suppressed in E. coli with rifampin, and it was suppressed in P. aeruginosa after exposure to tobramycin. Conversely, DNA Synthesis was relatively enhanced in the gram-negative bacilli after exposure to imipenem and in all three species after exposure to ciprofloxacin. However, DNA Synthesis in E. coli was only minimally affected after exposure to tobramycin and gentamicin. The differences in DNA Synthesis observed after exposure to various antimicrobial agents suggest multiple mechanisms for the PAE.
Cy Lee - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of a proposed technique to assess unscheduled DNA Synthesis and genotoxicity.
Gut, 1993Co-Authors: Robert A. Goodlad, Cy Lee, Malcolm R. Alison, C. E. Sarraf, M. A. Ghatei, S.r. Bloom, Nicholas A. WrightAbstract:Results from a recent, new assay suggest that omeprazole, a potent inhibitor of gastric acid secretion, is genotoxic. The principle of this assay is that the non-proliferating zone of surface gastric epithelial cells can be selectively removed by controlled digestion so that any incorporation of tritiated thymidine into these cells represents unscheduled DNA Synthesis. Parietal cells (which are located below the uppermost proliferating cells) and proliferating cells in semiconservative, regular DNA Synthesis could always be shown in the digested fraction, and as regular DNA Synthesis takes up a thousand fold more thymidine than unscheduled DNA Synthesis, any signal from unscheduled Synthesis would therefore be swamped. The digestion process was also uneven, as histological analysis showed denuded patches of mucosa, and gland like structures were seen in the digest. Quantification of the number of silver grains over the nuclei showed no increase in low level labelling after omeprazole administration, indicating that there was no unscheduled DNA Synthesis. The labelling index of undigested gastric tissue from omeprazole treated rats was not significantly different from that of the control group, despite an increase in the plasma gastrin value.
