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At least 73 records · Page 4Linked to original sources
PubMed1978

[Sister chromatid exchanges following incorporation of bromine into cytosine DNA nucleotides. I. Combined use of 5-bromdeoxycytidine and thymidine for the purpose of incorporating bromine into DNA cytosine].

In the cultured in vitro human blood lymphocytes treated with 5-bromodeoxycytidine (BrdC) plus thymidine (dT) in concentrations of 0.05 mM and 0.4 mM, respectively, metaphases of the second division, containing chromosomes with differentially stained sister chromatids appear after a 30 hours treatment, attaining 85 per cent at 36 hours. Under the treatment with BrdC or BrdU alone, the similar percentage of metaphases is observed at 28 hours. Similar results are obtained if, at 16--18 hours, the culture medium, containing BrdC plus dT is either replaced with a medium free of both the precursors, or supplied once more vith (0.05 mM) or dC(0.05 mM). The The observed slowing movement of cells through out the cell cycle, due to the treatment with BrdC plus dT, is explained by the inhibitory effect of dT on DNA synthesis which is manifested as BrdC catabolism. It is concluded that BrdC administered together with the cell cycle-slowing doses of thymidine is predominantly incorporated into cytosine of DNA.

Bromodeoxycytidine↗
PubMed1995

[Comparison of low-dose cytosine arabinoside and aclarubicin in combination with granulocyte colony-stimulating factor to intermediate-dose cytosine arabinoside and mitoxantrone with or without etoposide in the treatment of relapsed acute myeloid leukemia].

We used a new chemotherapy regimen for the treatment of 18 consecutive patients with relapsed AML. The regimen consisted of low-dose cytosine arabinoside (Ara-C), low-dose aclarubicin and concurrent use of G-CSF (CAG regimen). Fifteen out of 18 patients (83%) achieved complete remission (CR). Median CR duration and median survival were 6 months and 15 months, respectively. These results were similar to those of previously reported salvage therapies for relapsed AML including intensive chemotherapy consisting of intermediate-dose Ara-C and sequential mitoxantrone with or without etoposide (MC/MEC), which we previously adopted. Myelosuppression and non-hematological toxicities were apparently lower and less frequent compared to MC/MEC. The CAG regimen seems promising for the treatment of relapsed AML with its low toxicity contributing to a high quality of life for the patient.

Aclarubicin↗
PubMed1997

Cystosine-rich strands of the insulin minisatellite adopt hairpins with intercalated cytosine+.cytosine pairs.

Previously, we reported the high resolution NMR structure of the hairpin G-quartet structure formed by the G-rich strand of the insulin minisatellite of repeat sequence, (ACAG4TGTG4/TGTC4ACAC4) located upstream of the human insulin gene. Here, we report structural studies on the C-rich strand of this insulin minisatellite. First, we show by high resolution NMR that (C4TGTC4) forms a hairpin dimer with intercalated C+.C pairs (referred to as the hairpin i-motif); 340 NOE distance constraints uniquely define the nature of hairpin folding and the pattern of C+.C intercalation. Second, we show by one-dimensional NMR spectroscopy and molecular modeling studies that (C4TGTC4ACA4TGTC4) forms an intramolecularly folded hairpin with intercalated C+.C pairs. Third, we demonstrate by in vitro replication studies that several such hairpin i-motifs are present in long (C4TGTC4ACA)n (n>/=6) sequences, even in the presence of their complementary strands. Finally, we discuss structural and biological significance of the hairpin i-motifs formed by the C-rich strands of the insulin minisatellite.

Base Sequence↗
PubMed1978

Photochemistry of cytosine derivatives. 2. Photohydration of cytosine derivatives. Proton magnetic resonance study on the chemical structure and property of photohydrates.

Photohydrates of cytidine and cytidylic acids have been definitively characterized to be isomeric 6-hydroxy-5,6-dihydrocytosine derivatives. It has also been demonstrated by nuclear magnetic resonance spectroscopy that (1) the stereochemistry of photohydration is random, (2) the C5-H trans to the C6-OH undergoes a rapid selective exchange in the presence of proton acids, and (3) the dehydration of photohydrates is a trans-elimination. The mechanism of these processes is discussed.

Cytidine↗
PubMed2002

The antimalarial and cytotoxic drug cryptolepine intercalates into DNA at cytosine-cytosine sites.

Cryptolepine, a naturally occurring indoloquinoline alkaloid used as an antimalarial drug in Central and Western Africa, has been found to bind to DNA in a formerly unknown intercalation mode. Evidence from competition dialysis assays demonstrates that cryptolepine is able to bind CG-rich sequences containing nonalternating CC sites. Here we show that cryptolepine interacts with the CC sites of the DNA fragment d(CCTAGG)(2) in a base-stacking intercalation mode. This is the first DNA intercalator complex, from approximately 90 solved by X-ray crystallography, to bind a nonalternating (pyrimidine-pyrimidine) DNA sequence. The asymmetry of the drug induces a perfect stacking with the asymmetric site, allowing for the stability of the complex in the absence of hydrogen bonding interactions. The crystal structure of this antimalarial drug-DNA complex provides evidence for the first nonalternating intercalation and, as such, provides a basis for the design of new anticancer or antimalarial drugs.

Alkaloids↗
PubMed2004

Characterization of cytosine methylated regions and 5-cytosine DNA methyltransferase (Ehmeth) in the protozoan parasite Entamoeba histolytica.

The DNA methylation status of the protozoan parasite Entamoeba histolytica was heretofore unknown. In the present study, we developed a new technique, based on the affinity of methylated DNA to 5-methylcytosine antibodies, to identify methylated DNA in this parasite. Ribosomal DNA and ribosomal DNA circles were isolated by this method and we confirmed the validity of our approach by sodium bisulfite sequencing. We also report the identification and the characterization of a gene, Ehmeth, encoding a DNA methyltransferase strongly homologous to the human DNA methyltransferase 2 (Dnmt2). Immunofluorescence microscopy using an antibody raised against a recombinant Ehmeth showed that Ehmeth is concentrated in the nuclei of trophozoites. The recombinant Ehmeth has a weak but significant methyltransferase activity when E.histolytica genomic DNA is used as substrate. 5-Azacytidine (5-AzaC), an inhibitor of DNA methyltransferase, was used to study in vivo the role of DNA methylation in E.histolytica. Genomic DNA of trophozoites grown with 5-AzaC (23 microM) was undermethylated and the ability of 5-AzaC-treated trophozoites to kill mammalian cells or to cause liver abscess in hamsters was strongly impaired.

5-Methylcytosine↗
PubMed2001

Transcription-induced cytosine-to-thymine mutations are not dependent on sequence context of the target cytosine.

We showed previously that transcription of a plasmid-borne kan allele increases C-to-T mutations in the nontranscribed strand. Using two new plasmid-borne kan alleles, one cmp allele, and a chromosomal kan allele, we found in this study that transcription-induced mutations are not limited to specific genes, alleles, or locations and are likely to be a general property of transcript elongation in Escherichia coli.

Alleles↗
PubMedDate not supplied

[Anomalies in the dielectric properties of cytosine monohydrate monocrystals and textured anhydrous cytosine polycrystals].

Measurements were taken of dielectric constants of cytozin-monohydrate monocrystals and nonaqueous cytozin polycrystals within a wide temperature range (77-410 K) and along different crystallographic directions. A number of anomalies were found in dielectric constant of these compounds, as well as phase transition of cytozin-monohydrate into nonaqueous modification. Energies of hydrogen bonds OHN and OHO in monocrystals of cytozin-monohydrate and approximate relaxation time were estimated.

Chemical Phenomena↗
PubMed1978

Daunomycin, cytosine arabinoside and 6-thioguanine (DAT) vs vincristine, cytosine arabinoside and 6-thioguanine (VAT) in the induction treatment of acute nonlymphocyte leukemia: a randomized collaborative study.

One hundred patients were entered in a cooperative study comparing the efficacy of two different regimens in the induction treatment of acute nonlymphocytic leukemia (ANLL). Patients were randomly allocated to receive either the DAT or VAT combination; half of the patients were also randomized to receive CNS prophylaxis including intrathecal methotrexate + prednisone and cranial irradiation. Consolidation and maintenance therapy were uniform in responding patients. Out of 82 evaluable patients 41 (50%) attained complete remission (CR) with no significant difference between the two regimens. Median remission duration was slightly longer in the DAT group (32.5 vs 22 weeks); median survival was 34 weeks for all evaluable patients with no difference between the two schedules. Meningeal relapse occurred only in two patients after 19 and 99 weeks of continuous remission. Fourteen patients are still alive after 61 to greater than or equal to 155 weeks, of whom seven are in their initial remission (six in the DAT and one in the VAT group). We conclude that 1) DAT and VAT are equally effective in inducing CR in a high proportion of ANLL patients; 2) until marrow remission can be prolonged significantly, preventing CNS leukemia will not have any significant impact of the course of ANLL.

Adolescent↗