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The title compound, [Zn2(C2H3O2)2(C8H9N4S)2], is a centrosymmetric dinuclear molecule with two acetate bridging ligands in a syn-syn arrangement. The Zn(II) atom is five-coordinated in a trigonal-bipyramidal configuration by three thiosemicarbazone atoms (two N and one S) and by an O atom from each of the two acetate groups.
The cell cycle specificity of chromatid breakage induced by inhibitors of DNA synthesis depends on the mechanism of drug action. 5-Hydroxy-2-formylpyridine thiosemicarbazone, hydroxyurea, and guanazole, compounds that inhibit ribonucleotide reductase, do not cause chromatid breakage during G(2) phase. In contrast, two active antitumor agents, arabinosylcytosine and 5-azacytidine, which are either incorporated into polynucleotides or affect DNA polymerase, produce chromatid breakage during G(2) phase. All of these agents except guanazole also induce breakage in S phase.
The antiviral drug methisazone (N-methylisatin beta-thiosemicarbazone) was tested for its effect on immune responses to sheep erythrocytes and on hemopoietic colony-forming cell (granulocyte-macrophage progenitor cell) responses to complete Freund's adjuvant in mice. Suppressive activity was demonstrated in both systems, the immune system being more readily and more consistently susceptible. Evidence is presented which suggests that the insoluble particulate form of the drug has both stimulatory and suppressive effects on the colony-forming cell system, whereas the soluble form is only suppressive. Methisazone increased the mortality from ectromelia in adjuvant-treated animals.
Methisazone (N-methylisatin beta-thiosemicarbazone) was shown to inhibit the development of hemopoietic colonies in vitro when incorporated in the culture medium. The activity of methisazone was compared with that of several antimetabolic and antibiotic drugs. Although methisazone reduced the number of colonies, it did not affect the size of those colonies which did develop, and evidence is presented which shows that it acted only at the early stages of colony development. Some implications of these findings are briefly discussed.
The two nucleic acid-dependent nucleoside triphosphate phosphohydrolases, previously purified from vaccinia virus cores, were shown to be immunologically distinct enzymes. Antiserum prepared against purified phosphohydrolase I and antiserum prepared against purified phosphohydrolase II only neutralized the activity of that enzyme used as antigen. Both enzymes were induced in HeLa cells after vaccinia infection. DNA-cellulose chromatography was used to purify the two phosphohydrolases from the cytoplasms of infected cells. The enzymes were identified by their different substrate specificities, nucleic acid dependence, and neutralization with specific antiserum. A third chromatographically separable nucleic acid-dependent phosphohydrolase similar to phosphohydrolase I in substrate specificity but not neutralizable by antiserum to either phosphohydrolase I or II, was also isolated from infected cells. No nucleic acid-dependent nucleoside triphosphate phosphohydrolase activity was detected by similar methods from uninfected HeLa cells. Formation of these virus-induced enzymes was prevented by actinomycin D and cycloheximide, indicating a requirement for de novo RNA and protein synthesis, respectively. The kinetics of induction and inhibition by cytosine arabinoside, an inhibitor of DNA synthesis, suggested that synthesis of the phosphohydrolases is a late viral function. Rifampin, an inhibitor of vaccinia virus growth which prevents virion assembly, had no inhibitory effect on the induction of the phosphohydrolases. This result was consistent with the finding that these enzymes exist in a soluble as well as in a particulate form in the cytoplasm of infected cells. Addition of another specific anti-poxviral drug, isatin-beta-thiosemicarbazone, to vaccinia-infected cells partially inhibited induction of the phosphohydrolases.
Ribonucleotide reductase plays a central role in cell proliferation by supplying deoxyribonucleotide precursors for DNA synthesis and repair. The holoenzyme is a protein tetramer that features two large (hRRM1) and two small (hRRM2 or p53R2) subunits. The small subunit contains a di-iron cluster/tyrosyl radical cofactor that is essential for enzyme activity. Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone, 3-AP) is a new, potent ribonucleotide reductase inhibitor currently in phase II clinical trials for cancer chemotherapy. Ferric chloride readily reacts with Triapine to form an Fe(III)-(3-AP) complex, which is reduced to Fe(II)-(3-AP) by DTT. Spin-trapping experiments with 5,5-dimethyl-1-pyrroline-N-oxide prove that Fe(II)-(3-AP) reduces O2 to give oxygen reactive species (ROS). In vitro activity assays show that Fe(II)-(3-AP) is a much more potent inhibitor of hRRM2/hRRM1 and p53R2/hRRM1 than Triapine. Electron paramagnetic resonance measurements on frozen solutions of hRRM2 and p53R2 show that their tyrosyl radicals are completely quenched by incubation with Fe(II)-(3-AP). However, the enzyme activity is maintained in protein samples supplemented with catalase alone or in combination with superoxide dismutase. Furthermore, catalase alone or in combination with superoxide dismutase markedly decreases the antiproliferative effect of Triapine in cytotoxicity assays. These results indicate that Triapine-induced inhibition of ribonucleotide reductase is caused by ROS. We suggest that ROS may ultimately be responsible for the pharmacologic effects of Triapine in vivo.
BACKGROUND: Noninvasive assessment of regional myocardial perfusion at rest and after stress is important for the objective evaluation of the effects of coronary artery disease and its response to therapy. Centers that do not have cyclotrons rely on generator-produced radioisotopes for assessment of regional myocardial perfusion with positron emission tomography (PET). The aim of the present study was to develop and implement an approach to quantify regional myocardial perfusion using copper(II) pyruvaldehyde bis-(N4-thiosemicarbazone) (PTSM) labeled with the generator-produced, positron-emitting radionuclide 62Cu (t1/2 = 9.7 minutes). METHODS AND RESULTS: Regional perfusion was estimated from dynamic PET scans after intravenous administration of 62Cu-PTSM in 21 studies in 13 intact dogs evaluated over a wide range of myocardial flow values. In 15 interventions in nine dogs, regional perfusion was also estimated with H2(15)O. Regional perfusion with 62Cu-PTSM was estimated from dynamic blood and tissue time-activity curves, along with the model parameter k1 (forward rate of transport) and the PET parameter FBM (fraction of blood pool activity observed in tissue), using a two-compartment kinetic model. Arterial blood activity was corrected for red blood cell-associated 62Cu. In 44 comparisons, estimates of regional perfusion with 62Cu-PTSM correlated well with estimates obtained with concomitantly administered radiolabeled microspheres (y = 0.90x +/- 0.15, r = 0.95, p < 0.05) over a flow range from 0.23 to 6.14 ml/g per minute. In five healthy human volunteers evaluated at rest with H2(15)O and 62Cu-PTSM, regional perfusion estimated with 62Cu-PTSM was not significantly different from that obtained with H2(15)O (1.05 +/- 0.36 versus 0.96 +/- 0.28 ml/g per minute). 62Cu-PTSM provided high-quality images of the heart. CONCLUSIONS: The results of this study demonstrate that quantification of regional myocardial perfusion is feasible using generator-produced 62Cu-PTSM. Since 62Cu-PTSM can be used to estimate perfusion in the brain, kidney, and tumors as well as in the heart, it is an attractive tracer for centers that rely on generator-produced tracers for the evaluation of perfusion with PET.
Pseudopregnant and cyclic rats were injected for 5 to 26 days with daily doses of 5 and/or 3 mg of 5-bromo-2-thienyl-ethyl-ketone thiosemicarbazone (70026) starting on Day 0 (the day of oestrus). The vaginal smear cytology, record of ovulation and ability to breed and conceive were compared with the results for corn oil-injected controls. Both doses of 70026 were found to cause a reappearance of pro-oestrous and/or oestrous vaginal smears within 4 to 6 days in the pseudopregnant rats, but ovulations did not occur. The 5-mg dose of 70026 inhibited ovulation and interrupted the oestrous cycle in cyclic rats, even though the daily 3-mg dose seemed to have little effect on ovulation, ovarian cyclicity, breeding or conception. In spite of the absence of an ovulation accompanying the induced pro-oestrous and/or oestrous vaginal smears in the pseudopregnant rats, the pattern of the vaginal smears suggested the occurrence of a 'delayed pseudopregnancy' in most of the pseudopregnant rats treated daily with 3 mg, but in few of those treated with 5 mg, 70026.
The more significant bioactivities of a variety of semicarbazones (anti-protozoa, anticonvulsant) and thiosemicarbazones (antibacterial, antifungal, antitumoral, antiviral) and their metal complexes are reviewed together with proposed mechanisms of action and structure-activity relationships. Clinical or potential pharmacological applications of these versatile compounds are discussed.
Hydrogenation of 4-N-substituted thiosemicarbazonic acid acetylpyrazine derivatives with NaBH4 in dry ethanol led to seventeen new compounds. The in vitro tuberculostatic activity investigations of the 15 synthesized compound were carried out. MIC few of i.v. compounds were lower than 32 micrograms/cm3.
The human colon adenocarcinoma-derived cell line CaCo-2 male Swiss mice and male Sprague-Dawley rats were used as model systems to study the effects of nickel (II), 5-methyl-2-furaldehyde thiosemicarbazone ligand and their complex. The stimulation effect of the complex was obtained with low concentrations from 3.7 x 10(-7) to 3.7 x 10(-6) M, while inhibiting effects occurred from 3.7 x 10(-5) to 3.7 x 10(-4) M. This study showed that Ni (II) is toxic for cultured cells. Our data suggest that the comple; according to the toxicity assays in mice and carcinogenesis assays in rats, could be used as an antimitotic agent.
The antineoplastic agent, 3-ethoxy-2-oxobutyraldehyde bis(thiosemicarbazonato) copper(II), undergoes a pseudo-first-order decomposition in the presence of viable Ehrlich ascites tumor cells. Physical and chemical methods show that the copper is reduced in this process, that thiols are involved in the reaction, and that the thiosemicarbazone ligand is displaced from the copper ion. The widespread distribution of the cell-bound copper suggests several modes of cytotoxicity.
Forty-five condensation products of furan-, pyrrole-, and N-methyl pyrrole-alpha-carboaldehyde with N4-3-or 4-substituted phenyl semicarbazides and thiosemicarbazides were designed and synthesized to optimize the antiulcer activity. Quantitative structure-activity relationships reveal that in the series of semicarbazones increase in hydrophobicity of molecules and introduction of electron-repelling groups onto the phenyl ring raise the antiulcer activity; Generally, the activity of semicarbazones is higher than that of the corresponding thiosemicarbazones. The large spans between activity and toxicity of compounds No. 17 and 30 led to further investigation of pharmacological actions.
A number of 3-oxo and 3-thiosemicarbazono analogues of 1-aryl-1-ethylthio-nonanes and related compounds were synthesized. Solutions of the thiosemicarbazones in deuterochloroform were shown by PMR spectroscopy to exist principally in the anti configuration at equilibria except when an ortho-methoxy group was present in the aryl ring. In this case intramolecular hydrogen bonding probably accounts principally for the presence of equal amounts of anti and syn isomers. Evaluation of these compounds for anti-convulsant properties revealed that 1-(2-aminoethylthio)-1-(2-chlorophenyl)nonan-3-one hydrochloride (6a) and sodium 2-(N-acetylamino)-3-[1-(2-chlorophenyl)-3-oxononylthio]propionate (6c) were active and thus they could serve as prototype molecules for future development.
The copper complex of 3-ethoxy-2-oxobutyraldehyde bis(thiosemicarbazone) or CuKTS is reduced and dissociated upon reaction with Ehrlich cells. Titration of the cells with the complex leads to the specific binding of copper to metallothionein with 1 to 1 displacement of its complement of zinc. Under conditions of complete titration of metallothionein, 1.25-2.5 nmol CuKTS/10(7) cells, cellular DNA synthesis is rapidly inhibited but no long term effects on cell proliferation are observed. The kinetics of redistribution of Cu and Zn in Ehrlich cells in culture and in animals were studied after pulse reaction of CuKTS with cells. After exposure of cells to the noncytotoxic concentration of 2.5 nmol of CuKTS/10(7) cells, nonmetallothionein bound copper is lost rapidly from the cells, after which copper in metallothionein decays. New zinc metallothionein is made as soon as exposed cells are placed in culture. New synthesis stops when the level of zinc in metallothionein reaches control levels. A second pulse treatment of cells with CuKTS to displace zinc from metallothionein again stimulates new synthesis of the protein to restore its normal concentration. The kinetics of metal metabolism in Ehrlich cells exposed to 5.5 nmol of CuKTS/10(7) cells, which inhibits cell proliferation, are qualitatively similar except there is a pronounced lag before new zinc metallothionein is synthesized. The Ehrlich ascites tumor in mice responds to CuKTS similarly to cells in culture. It is also shown that cultured Ehrlich cells do not make extra zinc metallothionein in the presence of high levels of ZnCl2, and fail to accumulate copper in the presence of large concentrations of CuCl2.
Each of three ribonucleoside diphosphate reductase inhibitors was used as a third drug in combination with selected antitumor platinum (Pt) agents and cyclophosphamide (CY) in the treatment of advanced L1210 leukemia in C57BL/6 x DBA/2 mice. Each was synergistic with the various Pt plus CY combinations but the effect was highly schedule dependent. The collective cure rate was 68% when hydroxyurea (HU) was given as a single injection with Pt plus CY; the cure rate was 15% when HU was administered on a divided-dose schedule with Pt plus CY. The collective cure rate was 53% when guanazole was given as a single injection with Pt plus CY, but was only 8% when it was given on a divided-dose schedule with Pt plus CY. The effect of 4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone, when used as a third drug with the various Pt plus CY regimens, was not schedule dependent as assessed by the collective cure rate. A therapeutic synergy between CY and each of the three ribonucleoside diphosphate reductase inhibitors was also observed.
The nature of the inhibition of Ehrlich tumor cell ribonucleotide reductase by combinations of agents directed at the non-heme iron-containing component and the effector-binding component was studied with the use of isobolograms. From these studies, it was determined that the combinations of pyrazoloimidazole (IMPY) and dialdehyde of inosine, IMPY and deoxyguanosine triphosphate (dGTP), IMPY and deoxyadenosine triphosphate (dATP), and IMPY and deoxythymidine triphosphate (dTTP) gave synergistic inhibition of cytidine diphosphate reductase. The combination of dATP and dGTP also gave synergistic inhibition. The combinations of hydroxyurea and IMPY, 4-methyl-5-aminoisoquinoline thiosemicarbazone (MAIQ) and IMPY, and dialdehyde of inosine and dialdehyde derivative of 5'-deoxyinosine gave antagonistic inhibition. Other combinations utilizing MAIQ and dATP, MAIQ and dGTP, MAIQ and dTTP, hydroxyurea and dGTP, and hydroxyurea and dTTP gave inhibition which was additive.
Three novel series of 2,6-di-tert-butyl-1,4-benzoquinone derivatives were synthesized: 4-[(3,4-disubstituted-2,3-dihydrothiazol-2-ylidene) hydrazono]-2,6-di-tert-butyl-2,5-cyclohexadien-1-ones, 4-[(3-substituted-5-carbethoxy-4-methyl-2,3-dihydrothiazol-2- ylidene)hydrazono]-2,6-di-tert-butyl-2,5-cyclohexadien-1-one s, and 4-[(3-substituted-4-oxothiazolidin-2-ylidene)hydrazono]-2,6- di-tert- butyl-2,5-cyclohexadien-1-ones. These compounds were prepared by cyclization of the new 4-(N-substituted thiocarbamoylhydrazono)-2,6-di-tert-butyl-2,5-cyclohexadien- 1-ones with phenacyl bromides, ethyl alpha-chloroacetoacetate and ethyl bromoacetate, respectively. Antimicrobial testing of the prepared compounds and of the key intermediate thiosemicarbazones was performed. Some of the compounds revealed higher activity than streptomycin.