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Biomedical subjects

A Durán

Publications and source records attributed to A Durán.

At least 19 recordsLinked to original sources
PubMed2007

Imatinib mesylate induces hypophosphatemia in patients with chronic myeloid leukemia in late chronic phase, and this effect is associated with response.

Imatinib is the drug of first choice for most patients with chronic phase chronic myeloid leukemia (CML). Although it is generally well tolerated, a number of hematological and nonhematological side-effects have been described. We report here that imatinib induces hypophosphatemia in a high proportion of our series of CML patients previously treated with interferon alpha, and that this previously unreported side effect is associated with response.

Adolescent↗
PubMed2006

Photocatalytic degradation of pollutants from Elcogas IGCC power station effluents.

The aim of this work is to improve the quality of water effluents coming from Elcogas IGCC power station (Puertollano, Spain) with the purpose of fulfilling future more demanding normative, using heterogeneous photocatalytic oxidation processes (UV/H(2)O(2)/TiO(2) or ZnO). The efficiency of photocatalytic degradation for the different catalysts (TiO(2) and ZnO) was determined from the analysis of the following parameters: cyanides, formates and ammonia content. In a first stage, the influence of two parameters (initial concentration of H(2)O(2) and amount of catalyst) on the degradation kinetics of cyanides and formates was studied based on a factorial experimental design. pH was always kept in a value >9.5 to avoid gaseous HCN formation. The degradation of cyanides and formates was found to follow pseudo-first order kinetics. Experimental kinetic constants were fitted using neural networks (NNs). The mathematical model reproduces experimental data within 90% of confidence and allows the simulation of the process for any value of parameters in the experimental range studied. Moreover, a measure of the saliency of the input variables was made based upon the connection weights of the neural networks, allowing the analysis of the relative relevance of each variable with respect to the others. Results showed that the photocatalytic process was effective, being the degradation rate of cyanides about five times higher when compared to removal of formates. Finally, the effect of lowering pH on the degradation of formates was evaluated after complete cyanides destruction was reached (10 min of reaction). Under the optimum conditions (pH 5.2, [H(2)O(2)]=40 g/l; [TiO(2)]=2g/l), 100% of cyanides and 92% of initial NH(3) concentration are degraded after 10 min, whereas 35 min are needed to degrade 98% of formates.

Catalysis↗
PubMed2006

Solar photocatalytic degradation of reactive blue 4 using a Fresnel lens.

The heterogeneous photocatalytic degradation of reactive blue 4 dye (RB4) solutions under Fenton reagent and TiO(2) assisted by concentrated solar light irradiation using a Fresnel lens has been studied. Multivariate experimental design was applied to study the kinetic process. The efficiency of photocatalytic degradation was determined from the analysis of color and total organic carbon (TOC) removal. Factorial experimental design allowed to determine the influence of four parameters (pH and initial concentrations of TiO(2), Fe(II) and H(2)O(2)) on the value of the decoloration kinetic rate constant. Experimental data were fitted using neural networks (NNs). The mathematical model reproduces experimental data within 86% of confidence and allows the simulation of the process for any value of parameters in the experimental range studied. Also, a measure of the saliency of the input variables was made based upon the connection weights of the neural networks, allowing the analysis of the relative relevance of each variable with respect to the others. Results showed that acidic pHs (pH=3.6) are preferred for the complete dye decoloration. The optimum catalyst concentration is 1.2g TiO(2)/l. The use of a low cost catalyst and its activation using a Fresnel lens to concentrate solar energy significantly accelerates the degradation process when compared with direct solar radiation alone and can offer an economical and practical alternative for the destruction of environmental organic compounds.

Hydrogen Peroxide↗
PubMed2006

Fresnel lens to concentrate solar energy for the photocatalytic decoloration and mineralization of orange II in aqueous solution.

The decoloration and mineralization of the azo dye orange II under conditions of artificial ultraviolet light and solar energy concentrated by a Fresnel lens in the presence of hydrogen peroxide and TiO(2)-P25 was studied. A comparative study to demonstrate the viability of this solar installation was done to establish if the concentration reached in the focus of the Fresnel lens was enough to improve the photocatalytic degradation reaction. The degradation efficiency was higher when the photolysis was carried out under concentrated solar energy irradiation as compared to UV light source in the presence of an electron acceptor such us H(2)O(2) and the catalyst TiO(2). The effect of hydrogen peroxide, pH and catalyst concentration was also determined. The increase of H(2)O(2) concentration until a critical value (14.7 mM) increased both the solar and artificial UV oxidation reaction rate by generating hydroxyl radicals and inhibiting the (e(-)/h(+)) pair recombination, but the excess of hydrogen peroxide decreases the oxidation rate acting as a radical or hole scavenger and reacting with TiO(2) to form peroxo-compounds, contributing to the inhibition of the reaction. The use of the response surface methodology allowed to fit the optimal values of the parameters pH and catalyst concentration leading to the total solar degradation of orange II. The optimal pH range was 4.5-5.5 close to the zero point charge of TiO(2) depending on surface charge of catalyst and dye ionization state. Dosage of catalyst higher than 1.1 gl(-1) decreases the degradation efficiency due to a decrease of light penetration.

Azo Compounds↗
PubMed2005

Photo-Fenton-assisted ozonation of p-Coumaric acid in aqueous solution.

The degradation of p-Coumaric acid present in olive oil mill wastewater was investigated as a pretreatment stage to obtain more easily biodegradable molecules, with lower toxicity that facilitates subsequent anaerobic digestion. Thus, photo-Fenton-assisted ozonation has been studied and compared with ozonation at alkaline pH and conventional single ultraviolet (UV) and acid ozonation treatments. In the combined process, the overall kinetic rate constant was split into various components: direct oxidation by UV light, direct oxidation by ozone and oxidation by hydroxyl radicals. Molecular and/or radical ozone reaction was studied by conducting the reaction in the presence and absence of tert-butylalcohol at pHs 2, 7 and 9. Ozone oxidation rate increases with pH or by the addition of Fenton reagent and/or UV radiation due to generation of hydroxyl radicals, *OH. Hydrogen peroxide and ferrous ion play a double role during oxidation since at low concentrations they act as initiators of hydroxyl radicals but at high concentrations they act as radical scavengers. Finally, the additional levels of degradation by formation of hydroxyl radicals have been quantified in comparison to the conventional single processes and an equation is proposed for the reaction rate as a function of studied operating variables.

Coumaric Acids↗
PubMed2004

Modelling soot and SOF emissions from a diesel engine.

Modelling of soot and SOF emissions from a typical European turbocharged diesel engine has been made. The model consists of a detailed kinetic mechanism with 472 reactions (120 chemical species) and data from the thermodynamic diagnostic procedure of the combustion process of the engine. The forward kinetic constants were obtained from literature and the background constants from a self-developed non-linear fitting routine based on the Marquardt algorithm. The dilution and mixing processes inside the engine are represented by a simple Wiebe function. The system of ordinary differential equations is solved with the Rosenbrock method for rigid systems and using the interpolating Lagrange polynomials to calculate the heat capacity of each species at the corresponding temperature. The kinetic model has been implemented in Digital Visual Fortran 6.0. The model has been executed for five different fuels and three mixtures of biodiesel and reference diesel operating under three diverse conditions from the European transient urban/extraurban Certification Cycle and the results of soot and SOF predicted are compared with experimental data.

Air Pollutants↗
PubMed2004

Saccharomyces cerevisiae Bni4p directs the formation of the chitin ring and also participates in the correct assembly of the septum structure.

In Saccharomyces cerevisiae cytokinesis is efficiently achieved when a concerted series of events take place at the neck region, leading to septum formation. Here it is shown that Bni4p plays a crucial role in this process. Deltabni4 mutants contain normal amounts of chitin and show normal chitin synthase III (CSIII) activity, but are partially resistant to Calcofluor White (CFW), probably due to the striking pattern of chitin distribution. CFW vital staining shows that chitin is synthesized in daughter cells and that it is also asymmetrically deposited at the mother-side of the neck in large-budded cells. This specific pattern coincides with that of Chs4p and Chs3p proteins. Alternatively, staining of unbudded cultures confirmed that Bni4p directs early chitin ring assembly, but is no longer required for the chitin deposition that occurs late in the cell cycle at cytokinesis. Consequently, this work provides a strategy to genetically discriminate between the absence of chitin synthesis (Deltachs3 mutant) and failure in chitin ring assembly (Deltabni4 mutants). The characterization of double mutants affected in chitin synthesis and primary septum (PS) assembly (Deltamyo1 and Deltachs2) provides evidence for the cooperation of Bni4p in PS formation besides its role in chitin ring assembly. In addition, it is shown that the chitin ring, but not the late deposition of chitin, cooperates in the correct assembly of the actomyosin ring and the PS when the biological function of the septins is compromised. We conclude that Bni4p is not only required for the assembly of the chitin ring, but is also involved in septum architecture and the maintenance of neck integrity.

Cell Cycle Proteins↗
PubMed2003

Competitive diesel engine emissions of sulphur and nitrogen species.

NO(x), nitrate and sulphate emissions from a typical European passenger car diesel engine have been measured testing eight different fuels under five steady operating conditions (reproducing modes of the European transient urban/extraurban certification cycle). It is confirmed that nitrogen species compete with sulphur compounds to be adsorbed by diesel particulate matter (DPM) before being emitted into the atmosphere. This competition is found to increase with engine load, and is explained on the basis of the different specific surface and adsorption capacity of soot particles under different operating modes. When a high specific surface is available, as occurs in low load modes, both nitrates and sulphates are adsorbed by soot particles. On the contrary when a small surface is accessible, like in high load modes, sulphates are selectively adsorbed. This is specially important since sulphates are responsible for hydrocarbon retention in DPM due to the scrubbing effect.

Adsorption↗
PubMed2003

Effect of aluminium and sulphate on anaerobic digestion of sludge from wastewater enhanced primary treatment.

The combined and individual effects of aluminium and sulphate at concentrations of 1,000 mg/l as Al(OH)3, and 150 mgSO4(2-)/L as K2SO4, respectively, on the anaerobic digestion of sludge from enhanced primary treatment (EPT) were evaluated in 1 L capacity semi continuous reactors. It was found that at 59 days, aluminium inhibits the specific methanogenic activity (SMA) of methanogenic and acetogenic bacteria resulting in a 50% to 72% decrease. Sulphate also inhibits (48% to 65%) the SMA of the same type of bacteria. Methanogenic and acetogenic bacteria were able to adapt, to a different extent, to the assayed concentrations of aluminium and sulphate. However, the combination of aluminium and sulphate resulted in a higher inhibition, especially of the hydrogenophilic methanogenic bacteria. Indeed, this effect remained during the time of the experiment, maintaining an inhibition of 44% at 114 days. Feeding with EPT sludge led to a bigger decrease in SMA of each bacterial group, with respect to the other treatments with time. It is concluded that the acidification of anaerobic reactors fed with EPT sludge is due, among other causes, to the concurrent presence of aluminium and sulphate.

Aluminum↗
PubMed2001

Simulation of atmospheric PAH emissions from diesel engines.

Simulation of atmospheric PAH emissions in a typical European passenger car diesel engine at steady conditions or under a certification cycle is made using in-house software. It is based on neural fitting of experimental data from eight different fuels tested under five operating steady conditions (reproducing modes of the European transient urban/extraurban certification cycle). The software allows the determination of PAH emissions as a function of the fuel composition parameters (aromatic content, cetane index, gross heat power, nitrogen and sulphur content) and operation conditions (torque and engine speed). The mathematical model reproduces experimental data with a maximum error of 20%. This tool is very useful, since changes in parameters can be made without experimental cost and the trend in modifications in PAH emissions is immediately obvious.

Air Pollutants↗
PubMed2001

Comparison of peripheral arterial reconstruction in diabetic and non-diabetic patients: a prospective clinic-based study.

UNLABELLED: To assess the efficacy and safety of lower extremity arterial reconstruction in diabetic and non-diabetic subjects during a 3-year period. A prospective clinic-based study between 1994-1999 in Area 7, Madrid, with a population of 569307 and an estimated diabetic population of 37932 (15505 men and 22427 women). The level of arterial reconstruction and associated risk factors were ascertained. RESULTS: A total of 588 peripheral revascularization surgical procedures were performed in 481 patients. The diabetic patients (n=174, 36.2%) underwent 222 surgical procedures (including 48 follow-on operations, 21.6%), and 307 non-diabetic subjects underwent 366 surgical procedures (59 follow-on operations, 16.1%). The numbers of surgical procedures per 100000 people at risk and year were 18.8 and 1.8 for non-diabetic men and women, respectively, and 145.1 and 29.0 for men and women with diabetes mellitus (7.7- and 16.2-fold, respectively). Age at reconstruction surgery was 2 and 5 years earlier in non-diabetic than in diabetic men and women, respectively. Diabetic patients had a higher neuropathy score (P<0.05) and were less frequently smokers (P<0.05) than non-diabetic subjects. Diabetic subjects more frequently had distal reconstruction while proximal arterial reconstruction was more often performed in non-diabetic subjects. Between 64.6 and 80.4% of people with diabetes and 82.3 and 88.9% of non-diabetic subjects had no complications during their in-hospital stay. Distal amputation simultaneous to arterial reconstruction was the most frequent morbidity of people with diabetes during the study (P<0.05). Despite a graft occlusion rate after femoropopliteal revascularization significantly higher than in non-diabetic people (P<0.05), diabetic people more often required lower extremity amputations (LEAs) for the same level of bypass (P<0.01). Cumulative limb salvage rates were lower in diabetic patients than in non-diabetic subjects at femoropopliteal (49.2 vs. 89.7%; P<0.001), femorodistal (73.5 vs. 95.2%; P<0.01), and distal reverse (77.9 vs. 87.3%; P<0.05) arterial reconstruction, at the end of the third year, but similar after aorto-iliac reconstruction (93.1 vs. 97.5%). A higher neuropathy score and the presence of foot ulcers were associated to significantly lower limb salvage in diabetic patients (P<0.05), but not in non-diabetic people. Survival rates after 3 years were similar between diabetic and non-diabetic populations after aorto-iliac (93.1 vs. 97.5%), femoropopliteal (97.2 vs. 90.3%), and distal reverse (93.2 vs. 98.1%) revascularization, and slightly lower in diabetic compared to non-diabetic patients after femorodistal revascularization (82.1 vs. 96.3%; P<0.05). CONCLUSION: Although limb salvage after arterial reconstruction is lower in diabetic than in non-diabetic subjects, particularly in those with a higher neuropathy score, this surgical approach can be applied in both diabetic and non-diabetic subjects with otherwise similar outcome.

Aged↗
PubMed2001

Chromium accumulation by two Streptomyces spp. isolated from riverine sediments.

Strains designated R22 and R25, isolated from Salí River sediments, Argentina, were highly resistant to chromium. These strains were shown by 16S rRNA sequencing studies to be Streptomyces spp.; this affiliation was consistent with morphological and chemical characteristics. Growth of strains R22 and R25 in medium containing 100 mg l(-1) chromate was reduced by only 23% and 34%, respectively, compared with growth in medium without added chromium. Streptomyces sp. strains R22 and R25 both accumulated chromium with yields of 10.0 and 5.6 mg Cr g(-1) of dry weight, respectively, and a chromate concentration of 50 mg ml(-1). Cell fractionation studies with strain R22 showed that the great majority of the chromium were associated with the cell wall fraction. Streptomyces strains R22 and R25 may have applications in bioremediation of chromium contamination.

Biodegradation, Environmental↗
PubMed2000

Characterization of the chitin biosynthesis process as a compensatory mechanism in the fks1 mutant of Saccharomyces cerevisiae.

Deletion of the 1,3-beta-D-glucan synthase gene FKS1 in Saccharomyces cerevisiae induces a compensatory mechanism that is reflected in a significant increase in chitin synthase III (CSIII) activity, leading to high rates of chitin synthesis. Deregulation of CSIII activity is mainly due to the intracellular delocalization of Chs3p and Chs4p, the two main components of the CSIII active complex.

Carrier Proteins↗
PubMed2000

A family of multifunctional thiamine-repressible expression vectors for fission yeast.

A series of thiamine-repressible shuttle vectors has been constructed to allow a more efficient DNA manipulation in Schizosaccharomyces pombe. These high-copy-number vectors with regulatable expression (pJR) are based on the backbone of the pREP-3X, pREP-41X and pREP-81X plasmids. The pJR vectors are all uniform in structure, containing: (a) sequences for replication (ori) and selection (AmpR) in Escherichia coli; (b) the f1 ori sequence of the phage f1 for packaging of ssDNA, making them suitable for site-directed mutagenesis; and (c) the ars1 sequence for replication in S. pombe. The pJR vectors differ among them in: (a) the selectable marker (Saccharomyces cerevisiae LEU 2 gene, which complements S. pombe leu1- gene and S. pombe ura4+ and his3+ genes); (b) the thiamine-repressible nmt1 promoter (3X, 41X and 81X with extremely high, moderate or low transcription efficiency, respectively); and (c) the multiple cloning site (two multiple cloning sites, with 12 restriction sites each). The expression level of the pJR vectors has been analysed using the beta-galactosidase gene as reporter. Three levels of expression for each nmt1 promoter version, with any selectable marker and for either repressed or induced conditions, have been found. The expression is dependent on the distance to the initiation codon, varying from 0.001 to 15 times the activity characterized for the pREP plasmids. Also, the gene expression has been found to be extremely sensitive to the nucleotide sequence prior to the initiation codon, being up to 50-fold higher with an A/T sequence than with a G/C sequence. Finally, the beta-galactosidase mRNA levels were found to be similar in each nmt1 series, suggesting a translational effect on gene expression. As a result, any of these 18 new vectors allow performing gene expression in fission yeast, as well as a more versatile cloning, sequencing and mutagenesis, directly in the plasmid without the need for subcloning into intermediary vectors.

Base Sequence↗
PubMed2000

Schizosaccharomyces pombe ehs1p is involved in maintaining cell wall integrity and in calcium uptake.

The Schizosaccharomyces pombe mutant ehs1-1 mutant was isolated on the basis of its hypersensitivity to Echinocandin and Calcofluor White, which inhibit cell wall synthesis. The mutant shows a thermosensitive growth phenotype that is suppressed in the presence of an osmotic stabiliser. The mutant also showed other cell wall-associated phenotypes, such as enhanced sensitivity to enzymatic cell wall degradation and an imbalance in polysaccharide synthesis. The ehs1 + gene encodes a predicted integral membrane protein that is 30% identical to Saccharomyces cerevisiae Mid1p, a protein that has been proposed to form part of a calcium channel. As expected for such a function, we found that ehs1+ is involved in intracellular Ca2+ accumulation. High external Ca2+ concentrations suppressed all phenotypes associated with the ehs1 null mutation, suggesting that the cell integrity defects of ehs1 mutants result from inadequate levels of calcium in the cell. We observed a genetic relationship between ehs1+ and the protein kinase C homologue pck2+. pck2+ suppressed all phenotypes of ehs1-1 mutant cells. Overproduction of pck2p is deleterious to wild-type cells, increasing 1,3-beta-D-glucan synthase activity and promoting accumulation of extremely high levels of Ca2+. The lethality associated with pck2p, the increase in 1,3-beta-D-glucan synthase production and the strong Ca2+ accumulation are all dependent on the presence of ehs1p. Our results suggest that in fission yeast ehs1p forms part of a calcium channel that is involved in the cell wall integrity pathway that includes the kinase pck2p.

Amino Acid Sequence↗
PubMed2000

Proper ascospore maturation requires the chs1+ chitin synthase gene in Schizosaccharomyces pombe.

We have cloned chs1+, a Schizosaccharomyces pombe gene with similarity to class II chitin synthases, and have shown that it is responsible for chitin synthase activity present in cell extracts from this organism. Analysis of this activity reveals that it behaves like chitin synthases from other fungi, although with specific biochemical characteristics. Deletion or overexpression of this gene does not lead to any apparent defect during vegetative growth. In contrast, chs1+ expression increases significantly during sporulation, and this is accompanied by an increase in chitin synthase activity. In addition, spore formation is severely affected when both parental strains carry a chs1 deletion, as a result of a defect in the synthesis of the ascospore cell wall. Finally, we show that wild-type, but not chs1-/chs1-, ascospore cell walls bind wheatgerm agglutinin. Our results clearly suggest the existence of a relationship between chs1+, chitin synthesis and ascospore maturation in S. pombe.

Base Sequence↗