Camptothecin
Mostrando 13-24 de 154 artigos, teses e dissertações.
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13. Camptothecin cytotoxicity in mammalian cells is associated with the induction of persistent double strand breaks in replicating DNA.
Camptothecin is a specific topoisomerase I poison and is highly cytotoxic to eukaryotic cells. In the present study, we show, using a pulse field gel electrophoresis assay, that camptothecin induces DNA double strand breaks (DSBs) specifically in newly replicated DNA. Camptothecin induces these replication associated DNA DSBs in a dose-dependent manner. At l
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14. Biosynthesis of Camptothecin. In Silico and in Vivo Tracer Study from [1-13C]Glucose1
Camptothecin derivatives are clinically used antitumor alkaloids that belong to monoterpenoid indole alkaloids. In this study, we investigated the biosynthetic pathway of camptothecin from [1-13C]glucose (Glc) by in silico and in vivo studies. The in silico study measured the incorporation of Glc into alkaloids using the Atomic Reconstruction of Metabolism s
The American Society for Plant Biologists.
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15. Camptothecin, a specific inhibitor of type I DNA topoisomerase, induces DNA breakage at replication forks.
The structure of replicating simian virus 40 minichromosomes, extracted from camptothecin-treated infected cells, was investigated by biochemical and electron microscopic methods. We found that camptothecin frequently induced breaks at replication forks close to the replicative growth points. Replication branches were disrupted at about equal frequencies at
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16. Characterization of an altered DNA catalysis of a camptothecin-resistant eukaryotic topoisomerase I.
We investigated topoisomerase I activity at a specific camptothecin-enhanced cleavage site by use of a partly double-stranded DNA substrate. The cleavage site belongs to a group of DNA topoisomerase I sites which is only efficiently cleaved by wild-type topoisomerase I (topo I-wt) in the presence of camptothecin. With a mutated camptothecin-resistant form of
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17. Role of DNA topoisomerase I in the transcription of supercoiled rRNA gene.
The fraction DE-B obtained by fractionating an extract from rat mammary adenocarcinoma cells on a DEAE-Sephadex column was used for transcribing linear and supercoiled rRNA gene (rDNA). This fraction, which is known to contain RNA polymerase I and essential transcription factors, also contains DNA topoisomerase I activity. Inhibition of this topoisomerase ac
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18. Molecular and cytotoxic effects of camptothecin, a topoisomerase I inhibitor, on trypanosomes and Leishmania.
Parasites pose a threat to the health and lives of many millions of human beings. Among the pathogenic protozoa, Trypanosoma brucei, Trypanosoma cruzi, and Leishmania donovani are hemoflagellates that cause particularly serious diseases (sleeping sickness, Chagas disease, and leishmaniasis, respectively). The drugs currently available to treat these infectio
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19. A Microbiological Assay for Estimating Concentrations of Camptothecin Lactone in Mouse Tissues
The marked sensitivity of the yeast Hansenula wingei NRRL Y-2340 strain 5 to a new antineoplastic alkaloid served as the basis for a logarithmic-ratio microbiological assay which has been developed for the estimation of concentrations of camptothecin lactone (or cytotoxic equivalents) in tissues of mice. The utility of this assay has been demonstrated by pre
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20. Characterization of a mammalian mutant with a camptothecin-resistant DNA topoisomerase I.
DNA topoisomerase I was purified to near homogeneity from a clonal line of human lymphoblastic leukemia cells, RPMI 8402, that is resistant to camptothecin, a cytotoxic alkaloid from Camptotheca acuminata, and compared with that of the parent wild-type cells. As assayed by relaxation of the supercoiled plasmid DNA and by formation of enzyme-linked DNA breaks
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21. Transcription of adenovirus and HeLa cell genes in the presence of drugs that inhibit topoisomerase I and II function.
The requirements for topoisomerases in transcription of adenovirus and HeLa cell genes were analyzed using drugs that specifically inhibit either topoisomerases I or II. Cleavage of viral DNA by topoisomerases in the presence of either camptothecin or VM26 was used to determine drug concentrations that led to maximal inhibition of ligation in the cleavage an
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22. Spatial organization of topoisomerase I-mediated DNA cleavage induced by camptothecin–oligonucleotide conjugates
Triple helix-forming oligonucleotides covalently linked to topoisomerase I inhibitors, in particular the antitumor agent camptothecin, trigger topoisomerase I-mediated DNA cleavage selectively in the proximity of the binding site of the oligonucleotide vector. In the present study, we have performed a systematic analysis of the DNA cleavage efficiency as a f
Oxford University Press.
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23. Involvement of DNA topoisomerase I in transcription of human ribosomal RNA genes.
Treatment of HeLa cells with a DNA topoisomerase I-specific inhibitor, camptothecin, results in rapid cessation of the synthesis of the 45S rRNA precursor. The inhibition of rRNA synthesis is reversible following drug removal and correlates with the presence of camptothecin-trapped topoisomerase I-DNA abortive complexes, which can be detected as topoisomeras
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24. Tissue-Specific Expression of the β-Subunit of Tryptophan Synthase in Camptotheca acuminata, an Indole Alkaloid-Producing Plant1
Camptothecin is an anticancer drug produced by the monoterpene indole alkaloid pathway in Camptotheca acuminata. As part of an investigation of the camptothecin biosynthetic pathway, we have cloned and characterized a gene from C. acuminata encoding the β-subunit of tryptophan (Trp) synthase (TSB). In C. acuminata TSB provides Trp for both protein syn
American Society of Plant Physiologists.