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Acta Crystallographica. Section E,... Oct 2010In the title compound, [Cu(C(2)H(6)N(5))(2)](2)(SiF(6))(3), the asymmetric unit is composed of one [Cu(HL)(2)](3+) cation (where L is 3,5-diamino-1,2,4-triazole) and one...
In the title compound, [Cu(C(2)H(6)N(5))(2)](2)(SiF(6))(3), the asymmetric unit is composed of one [Cu(HL)(2)](3+) cation (where L is 3,5-diamino-1,2,4-triazole) and one and a half SiF(6) (2-) anions. The rather large positively charged guanazole ligand moiety promotes the low metal coordination number of 2 for the Cu(I) atom. The compound was obtained using the electrochemical alternating-current technique starting from an ethanol-methanol solution of CuSiF(6)·4H(2)O and guanazole. In the crystal, N-H⋯F hydrogen bonds play an important role in the formation of a three-dimensional network. As a result of these hydrogen bonds, there are also π-π inter-actions [centroid-centroid distance = 3.3024 (14) Å] involving one of the triazole groups in mol-ecules related by an inversion center, and short Cu⋯N inter-actions [2.909 (3) Å] involving an -NH(2) group, leading to the formation of a dimer-like arrangement.
PubMed: 21588872
DOI: 10.1107/S160053681004225X -
FEMS Yeast Research Mar 2022Schizosaccharomyces pombe is an established yeast model for studying the cellular mechanisms conserved in humans, such as the DNA replication checkpoint. The replication...
Schizosaccharomyces pombe is an established yeast model for studying the cellular mechanisms conserved in humans, such as the DNA replication checkpoint. The replication checkpoint deals with replication stress caused by numerous endogenous and exogenous factors that perturb fork movement. If undealt with, perturbed forks collapse, causing chromosomal DNA damage or cell death. Hydroxyurea (HU) is an inhibitor of ribonucleotide reductase (RNR) commonly used in checkpoint studies. It produces replication stress by depleting dNTPs, which slows the movement of ongoing forks and thus activates the replication checkpoint. However, HU also causes side effects such as oxidative stress, particularly under chronic exposure conditions, which complicates the studies. To find a drug that generates replication stress more specifically, we tested three other RNR inhibitors gemcitabine, guanazole and triapine in S. pombe under various experimental conditions. Our results show that guanazole and triapine can produce replication stress more specifically than HU under chronic, not acute drug treatment conditions. Therefore, using the two drugs in spot assay, the method commonly used for testing drug sensitivity in yeasts, should benefit the checkpoint studies in S. pombe and likely the research in other model systems.
Topics: Cell Cycle Proteins; Checkpoint Kinase 2; DNA Replication; Deoxycytidine; Enzyme Inhibitors; Guanazole; Humans; Hydroxyurea; Pyridines; Ribonucleotide Reductases; Schizosaccharomyces; Schizosaccharomyces pombe Proteins; Thiosemicarbazones; Gemcitabine
PubMed: 35262697
DOI: 10.1093/femsyr/foac014 -
The Journal of Biological Chemistry Jul 1985Several known inhibitors of mammalian ribonucleotide reductase were studied for their interactions with herpes simplex virus type 1 (HSV-1) ribonucleotide reductase....
Several known inhibitors of mammalian ribonucleotide reductase were studied for their interactions with herpes simplex virus type 1 (HSV-1) ribonucleotide reductase. MAIQ (4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone) produced apparent inactivation of HSV-1 ribonucleotide reductase. Only catalytically cycling, not resting, enzyme could be inactivated. Double reciprocal replots of the rates of inactivation versus the concentration of MAIQ indicated that a reversible complex with the enzyme was formed prior to inactivation. In the presence of 10 microM CDP, the maximum rate of inactivation was 20 per h (t1/2 = 3 min). The half-maximum rate was achieved at about 15 microM MAIQ. INOX (periodate-oxidized inosine) also appeared to inactivate HSV-1 ribonucleotide reductase. In contrast to MAIQ, it readily inactivated resting as well as cycling enzyme. CDP retarded the rates of inactivation by INOX. An initial reversible complex between INOX and enzyme was not detectable under the conditions used. IMPY (2,3-dihydro-1H-pyrazolo(2,3-a)imidazole) and guanazole (3,5-diamino-1,2,4-triazole) produced reversible inhibition. Although the data with both inhibitors were most consistent with the noncompetitive inhibition model (versus CDP), the data with guanazole were also marginally consistent with the uncompetitive model.
Topics: Guanazole; Inosine; Isoquinolines; Kinetics; Pyrazoles; Ribonucleotide Reductases; Simplexvirus; Triazoles
PubMed: 2991215
DOI: No ID Found -
Experimental Hematology Jul 2003Clinical heterogeneity among patients with sickle cell anemia (SCA) is influenced by the amount of fetal hemoglobin (HbF) within circulating erythrocytes. Current...
OBJECTIVE
Clinical heterogeneity among patients with sickle cell anemia (SCA) is influenced by the amount of fetal hemoglobin (HbF) within circulating erythrocytes. Current pharmacotherapy focuses on increasing HbF in order to reduce hemolysis and help prevent acute vaso-occlusive events. Hydroxyurea, a known S-phase-specific cytotoxic ribonucleotide reductase (RR) inhibitor, is an effective agent for HbF induction in patients with SCA, but the mechanisms by which hydroxyurea induces HbF in vivo have not been elucidated.
MATERIALS AND METHODS
We adapted an in vitro assay for HbF induction, growing burst-forming unit erythroid (BFU-E) colonies in methylcellulose from peripheral blood of children with SCA and extracting the hemoglobin for high-performance liquid chromatography analysis of HbF. Hydroxyurea and other known RR inhibitors, along with cytotoxic agents that are not RR inhibitors, were tested for the ability to induce HbF using this in vitro assay.
RESULTS
Hydroxyurea decreased the number of BFU-E colonies that grew in culture and significantly increased HbF from 13.6%+/-6.2% to 25.4%+/-8.0% at 50 microM HU (p=0.012). Three other known RR inhibitors also significantly induced HbF: 4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone (p=0.025), guanazole (p=0.008), and gemcitabine (p=0.028). Cytarabine and alkylating agents BCNU and 4-hydroperoxycyclophosphamide, which are cytotoxic agents but not RR inhibitors, reduced BFU-E colony number but did not significantly induce HbF.
CONCLUSION
Hydroxyurea and other RR inhibitors significantly induce HbF in vitro in human erythroid progenitor cells. Inhibition of RR may be a critical mechanism by which hydroxyurea increases HbF in vivo in patients with SCA.
Topics: Anemia, Sickle Cell; Child; Chromatography, High Pressure Liquid; Erythroid Precursor Cells; Fetal Hemoglobin; Humans; Hydroxyurea; In Vitro Techniques
PubMed: 12842703
DOI: 10.1016/s0301-472x(03)00086-9 -
Blood Jul 1975The clinical course of a patient with acute monocytic leukemia and prominent infiltration of the skin and testes is described. In vitro studies demonstrated that the...
The clinical course of a patient with acute monocytic leukemia and prominent infiltration of the skin and testes is described. In vitro studies demonstrated that the circulating monocyte precursors were capable of adherence to nylon fibers, and phagocytosis of bacteria and latex particles. In vivo, migration of leukemic cells to skin windows was observed. Extreme nuclear folding, marked surface activity, and morphologic features suggesting nuclear and cytoplasmic maturation were seen by light and electron microscopy. The presence of morphologically and functionally more differentiated monocytic cells may account for the marked tiuuse invasion in this patient and, possibly, in other patients with monocytic leukemia.
Topics: Bone Marrow Examination; Cell Adhesion; Cell Movement; Cerebrospinal Fluid; Cyclophosphamide; Daunorubicin; Drug Therapy, Combination; Guanazole; Hematopoietic Stem Cells; Humans; Latex; Leukemia, Monocytic, Acute; Male; Megakaryocytes; Microscopy, Electron; Microspheres; Middle Aged; Monocytes; Muramidase; Neutrophils; Nylons; Phagocytosis; Testis
PubMed: 1055611
DOI: No ID Found -
Journal of Bacteriology Aug 1991Chlamydiae are obligate intracellular bacteria that are dependent on eukaryotic host cells for ribonucleoside triphosphates but not deoxyribonucleotide triphosphates....
Chlamydiae are obligate intracellular bacteria that are dependent on eukaryotic host cells for ribonucleoside triphosphates but not deoxyribonucleotide triphosphates. Ribonucleotide reductase is the only enzyme known to catalyze the direct conversion of a ribonucleotide to a deoxyribonucleotide. Hydroxyurea inhibits ribonucleotide reductase by inactivating the tyrosine free radical present in the small subunit of the enzyme. In this report, we show that Chlamydia trachomatis growth is inhibited by hydroxyurea in both wild-type mouse L cells and hydroxyurea-resistant mouse L cells. Hydroxyurea was used as a selective agent in culture to isolate, by a stepwise procedure, a series of C. trachomatis isolates with increasing levels of resistance to the cytotoxic effects of the drug. One of the drug-resistant C. trachomatis isolates (L2HR-10.0) was studied in more detail. L2HR-10.0 retained its drug resistance phenotype even after passage in the absence of hydroxyurea for 10 growth cycles. In addition, L2HR-10.0 was cross resistant to guanazole, another inhibitor of ribonucleotide reductase. Results obtained from hydroxyurea inhibition studies using various host cell-parasite combinations indicated that inhibition of host cell and C. trachomatis DNA synthesis by hydroxyurea can occur but need not occur simultaneously. Crude extract prepared from highly purified C. trachomatis reticulate bodies was capable of reducing CDP to dCDP. The CDP reductase activity was not inhibited by monoclonal antibodies to the large and small subunits of mammalian ribonucleotide reductase, suggesting that the activity is chlamydia specific. The CDP reductase activity was inhibited by hydroxyurea. Crude extract prepared from drug-resistant L2HR-10.0 reticulate bodies contained an elevation in ribonucleotide reductase activity. In total, our results indicate that C. trachomatis obtains the precursors for DNA synthesis as ribonucleotides with subsequent conversion to deoxyribonucleotides catalyzed by a chlamydia-specific ribonucleotide reductase.
Topics: Adenine; Animals; Chlamydia trachomatis; Cytidine Diphosphate; DNA, Bacterial; Drug Resistance, Microbial; Guanazole; Hydroxyurea; L Cells; Mutation; Ribonucleotide Reductases; Selection, Genetic
PubMed: 1860812
DOI: 10.1128/jb.173.16.4932-4940.1991 -
Cancer Immunology, Immunotherapy : CII 1983In studies of antitumor antibody-cytotoxic agent conjugates as potential antitumor agents with improved tumor specificity, the toxic subunit A-chain of ricin was...
In studies of antitumor antibody-cytotoxic agent conjugates as potential antitumor agents with improved tumor specificity, the toxic subunit A-chain of ricin was conjugated with a monoclonal antibody to a tumor-associated antigen expressed weakly on murine leukemia L1210 cells and strongly on L1210/GZL cells, a guanazole-resistant subline of L1210, employing N-succinimidyl 3-(2-pyridyldithio)propionate as cross-linking agent. The conjugate (anti-L1210 conjugate) exhibited a potent concentration-dependent cytotoxicity against cultured L1210/GZL cells, and inhibited cell growth at concentrations over 0.8 micrograms/ml. The conjugate killed all L1210/GZL cells at a concentration of 100 micrograms/ml. Neither nonimmune conjugate similarly prepared from mouse nonimmune IgG nor unconjugated anti-L1210 IgG alone showed cytotoxicity against L1210/GZL cells. When (BALB/c X DBA/2)F1 mice inoculated with 1 X 10(5) L1210/GZL cells were treated with IP injections of 27 micrograms anti-L1210 conjugate 1 h and 5 days after tumor cell inoculation, a life-prolonging effect was observed. [Lifespan in treated animals as percentage of that in controls (T/C) = 146%]. However, when the dose per injection was increased to 50 micrograms per mouse, survival was the same as in the control group. Postmortem examination of mice that had been treated with 50 micrograms anti-L1210 conjugate revealed lesions with necrosis and hemorrhage in the liver parenchyma and the intestinal epithelium, respectively. A similar toxic effect on the host mice was also observed with nonimmune conjugate.
Topics: Animals; Antibodies, Monoclonal; Antibodies, Neoplasm; Antineoplastic Agents; Cell Transformation, Neoplastic; Female; Immunoglobulin G; Immunotherapy; Leukemia L1210; Lymphoma; Male; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Ricin
PubMed: 6559105
DOI: 10.1007/BF00199238 -
European Journal of Biochemistry Jun 1982
Characterization of the active site of ribonucleotide reductase of Escherichia coli, bacteriophage T4 and mammalian cells by inhibition studies with hydroxyurea analogues.
Topics: Animals; Binding Sites; Cattle; Chemical Phenomena; Chemistry; Escherichia coli; Fibroblasts; Guanazole; Hydroxyurea; In Vitro Techniques; Mice; Nitroso Compounds; Ribonucleotide Reductases; Structure-Activity Relationship; T-Phages; Thymus Gland
PubMed: 7049700
DOI: 10.1111/j.1432-1033.1982.tb06653.x