Luiz Alfredo Pavanin

Determination of chromium (III) using a homogenous mixture of water-ethanol-methylisobutylketone solvents.

The use of organic solvents to increase metal ion determination sensitivity by atomic absorption spectrophotometry with flame is quite common. The most employed organic solvent is 4-methyl-2-pentanona (methylisobutylketone, MIBK) which optimizes sample vaporization and combustion. In this work, we present the use of a homogeneous mixture of water-ethanol-MIBK solvents (1:14:10 v/v, respectively), named the single-phase solution instead of employing pure organic solvents to determine chromium (III) ions by atomic absorption spectrophotometry with flame. The analytical calibration curve in single-phase solution evaluated up to 8 mugml(-1) was linear and was described as Abs=0.0048 C(Cr(III))-0.0010 (r(2)=0.9998). Stability in the measurement as well as an increase in sensitivity more than twice as high when compared to determinations exclusively made in aqueous solutions were observed. The exactness of the determinations was evaluated with the same steel standards.

The ruthenium complex cis-(dichloro)tetrammineruthenium(III) chloride induces apoptosis and damages DNA in murine sarcoma 180 cells.

Ruthenium(III) complexes are increasingly attracting the interest of researchers due to their promising pharmacological properties. Recently, we reported that the cis-(dichloro)tetrammineruthenium(III) chloride compound has cytotoxic effects on murine sarcoma 180 (S-180) cells. In an effort to understand the mechanism responsible for their cytotoxicity, study we investigated the genotoxicity, cell cycle distribution and induction of apoptosis caused by cis-(dichloro)tetrammineruthenium(III) chloride in S-180 tumour cells. cis-(dichloro)tetrammineruthenium(III) chloride treatment induced significant DNA damage in S-180 cells, as detected by the alkaline comet assay. In the cell cycle analysis, cis-(dichloro)tetrammineruthenium(III) chloride caused an increase in the number of cells in G1 phase, accompanied by a decrease in the S and G2 phases after 24 h of treatment. In contrast, the cell cycle distribution of S-180 cells treated with cis-(dichloro)tetrammineruthenium(III) chloride for 48 h showed a concentration-dependent increase in the sub-G1 phase (indicating apoptosis), with a corresponding decrease in cells in the G1, S and G2 phases. In addition, cis-(dichloro)tetrammineruthenium(III) chloride treatment induced apoptosis in a time-dependent manner, as observed by the increased numbers of annexin V-positive cells. Taken together, these findings strongly demonstrate that DNA damage, cell cycle changes and apoptosis may correlate with the cytotoxic effects of cis-(dichloro)tetrammineruthenium(III) chloride on S-180 cells.

The compound cis-(dichloro)tetrammineruthenium(III) chloride induces caspase-mediated apoptosis in K562 cells

Ruthenium(III) complexes are increasingly attracting the interest of researchers due to their promising pharmacological properties. In the present study, we investigated the ability of cis-(dichloro)tetrammineruthenium(III) chloride to produce lethal effects in human chronic myelogenous leukemia K562 cells. The MTT tetrazolium reduction test and the trypan blue exclusion assay revealed that the IC(50) for the compound after 48 h of incubation with K562 cells was approximately 10.74 and 73.45 microM, respectively. Interestingly, it was observed that this compound exhibits mild cytotoxicity towards MRC-5 human fibroblast cells (IC(50)>383 microM). Flow cytometric analysis revealed that cis-(dichloro)tetrammineruthenium(III) chloride was capable of change cell cycle distribution since the percentage of cells in the G1, S and G2 phases decreased. In addition, treatment with this compound induced apoptotic cell death in K562 cells, demonstrated by increased DNA content in the sub-G1-peak and a significant increase in caspase-3 activity. Assay using cyclosporin A, an inhibitor of the mitochondrial permeability transition pore (MPT) showed that the preincubation of K562 cells with this inhibitor had not effect on cis-(dichloro)tetrammineruthenium(III) chloride induced caspase-3 activation. In summary, cis-(dichloro)tetrammineruthenium(III) chloride displayed a significant cytotoxic effect through cell cycle arrest and apoptotic induction in K562 cells, which suggests that cis-(dichloro)tetrammineruthenium(III) chloride might have therapeutic potential against leukemia.

Genotoxicity of Water From the Paraguay River Near Cáceres-MT, Brazil in the Drosophila Wing-Spot Test

The genotoxic activity of surface water samples from four sites along the Paraguay River, near Cáceres, Mato Grosso State, Brazil, was investigated using the Drosophila melanogaster Somatic Mutation and Recombination test (SMART). Effluents from sanitary sewers and agroindustrial effluents (residual effluents from slaughterhouses, leather tanneries, and dairies) flow into the Paraguay River, and directly or indirectly contaminate water from sampling sites 1–3. Site 4 was an upriver reference site that received no domestic or agroindustrial discharges. Water was collected at 4 time periods: September 2003 and August 2004 (periods of low water or drought); and April 2004 and March 2005 (periods of high water or flood). Chromium concentrations above statutory limits were detected at sites 1–3 (August 2004), and sites 1, 2 and 4 (March 2005). Sulfur compounds were also detected at sites 1–3. The SMART performed using standard (ST) cross flies detected genotoxic responses in only two samples, the August 2004 site 1 sample and the March 2005 site 2 sample. Many more samples were positive using high bioactivation (HB) cross flies: site 1 (all collection periods), site 2 (September 2003 and April 2004), and site 3 (September 2003 and August 2004). Mutant frequency comparisons between marker‐heterozygous and balancer‐heterozygous flies from the HB cross indicated that the positive genotoxic responses for the site 2 (April 2004) and site 3 (September 2003) samples were due mainly to mitotic recombination. Our findings indicate that the section of the Paraguay River within the urban perimeter of Cáceres is contaminated with genotoxic agents. Environ. Mol. Mutagen., 2008.

Cytotoxic and Genotoxic Effects of cis-Tetraammine(oxalato)Ruthenium(III) Dithionate on the Root Meristem Cells of Allium cepa

Ruthenium complexes have attracted much attention as possible building blocks for new transition-metal-based antitumor agents. The present study examines the mitotoxic and clastogenic effects induced in the root tips of Allium cepa by cis-tetraammine(oxalato)ruthenium(III) dithionate {cis-[Ru(C2O2)(NH3)4]2(S2O6)} at different exposure durations and concentrations. Correlation tests were performed to determine the effects of the time of exposure and concentration of ruthenium complex on mitotic index (MI) and mitotic aberration index. A comparison of MI results of cis-[Ru(C2O2)(NH3)4]2(S2O6) to those of lead nitrate reveals that the ruthenium complex demonstrates an average mitotic inhibition eightfold higher than lead, with the frequency of cellular abnormalities almost fourfold lower and mitotic aberration threefold lower. A. cepa root cells exposed to a range of ruthenium complex concentrations did not display significant clastogenic effects. Cis-tetraammine(oxalato)ruthenium(III) dithionate therefore exhibits a remarkable capacity to inhibit mitosis, perhaps by inhibiting DNA synthesis or blocking the cell cycle in the G2 phase. Further investigation of the mechanisms of action of this ruthenium complex will be important to define its clinical potential and to contribute to a novel and rational approach to developing a new metal-based drug with antitumor properties complementary to those exhibited by the drugs already in clinical use.

Cytotoxic effects of the compound cis-tetraammine(oxalato)ruthenium(III) dithionate on K-562 human chronic myelogenous leukemia cells.

Chemotherapy is a common treatment for leukemia. Ruthenium complexes have shown potential utility in chemotherapy and photodynamic therapy. The identification of new chemotherapeutics agents is critical for further progress in the treatment of leukemia. Ruthenium complexes generally have lower toxicities compared to cisplatin attributed to their specific accumulation in cancer tissues. Based on these evidences, in the present work we studied the cytotoxic activity of the ruthenium(III) compound cis-tetraammine(oxalato)ruthenium(III) dithionate - {cis-[Ru(C2O4)(NH3)4]2(S2O6)} against human chronic myelogenous leukemia cells (K-562) tumor cell line. The tested compound induces cell death in a dose and time dependent manner on K-562 cells. It is found that the effect was improved linearly while prolonging the incubation time. Compared to the cell cycle profiles of untreated cells, flow cytometric analysis indicated the sub-G1 arresting effect of ruthenium compound on K-562 cells. In our study, {cis-[Ru(C2O4)(NH3)4]2(S2O6)} shows a significant increase in tailed cells in any of the concentrations tested compared with negative control. Consequently, the concentration of {cis-[Ru(C2O4)(NH3)4]2(S2O6)} might be associated cytotoxicity with direct effect on K-562 cells DNA. Thus, it can be deducted that ruthenium-based compounds present selectivity to enter both tumor and normal cells. Additional studies are needed to determine the molecular mechanisms of the active components and to evaluate the potential in vivo anticancer activity of the cis-tetraammine(oxalato)ruthenium(III) dithionate.

AVALIAÇÃO DA QUALIDADE DA ÁGUA E CARACTERIZAÇÃO DE SEDIMENTOS DO RIO UBERABINHA EM UBERLÂNDIA - MG

The environmental changes in the river basin are instruments for the planning of water resources management. This study had the objective of evaluating water quality parameters of the Uberabinha River, Uberlândia MG, Brazil, with the characterization of the marginal sediments. Four samplings were carried out and five evaluation points were established. The points were chosen in areas that characterize natural runoff conditions and where anthropogenic interferences are significant. Twenty three water quality parameters and thirteen sediment characterization parameters were analyzed. The calculated IQA was compared to the figures provided by the Minas Gerais Water Management Institute. The results confirmed the effect of the contamination at the points sampled and the evolution of the water quality of the river in relation to the classes established in the framework. The dendogram of the results of the analysis of the sediment samples showed three groups of contaminants for specific sources of contamination.