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Biomedical subjects

E Sanz

Publications and source records attributed to E Sanz.

At least 19 recordsLinked to original sources
PubMed2007

Solubility of KF and NaCl in water by molecular simulation.

The solubility of two ionic salts, namely, KF and NaCl, in water has been calculated by Monte Carlo molecular simulation. Water has been modeled with the extended simple point charge model (SPC/E), ions with the Tosi-Fumi model and the interaction between water and ions with the Smith-Dang model. The chemical potential of the solute in the solution has been computed as the derivative of the total free energy with respect to the number of solute particles. The chemical potential of the solute in the solid phase has been calculated by thermodynamic integration to an Einstein crystal. The solubility of the salt has been calculated as the concentration at which the chemical potential of the salt in the solution becomes identical to that of the pure solid. The methodology used in this work has been tested by reproducing the results for the solubility of KF determined previously by Ferrario et al. [J. Chem. Phys. 117, 4947 (2002)]. For KF, it was found that the solubility of the model is only in qualitative agreement with experiment. The variation of the solubility with temperature for KF has also been studied. For NaCl, the potential model used predicts a solubility in good agreement with the experimental value. The same is true for the hydration chemical potential at infinite dilution. Given the practical importance of solutions of NaCl in water the model used in this work, whereas simple, can be of interest for future studies.

Computer Simulation↗
PubMed2006

A potential model for methane in water describing correctly the solubility of the gas and the properties of the methane hydrate.

We have obtained the excess chemical potential of methane in water, over a broad range of temperatures, from computer simulation. The methane molecules are described as simple Lennard-Jones interaction sites, while water is modeled by the recently proposed TIP4P/2005 model. We have observed that the experimental values of the chemical potential are not reproduced when using the Lorentz-Berthelot combining rules. However, we also noticed that the deviation is systematic, suggesting that this may be corrected. In fact, by introducing positive deviations from the energetic Lorentz-Berthelot rule to account indirectly for the polarization methane-water energy, we are able to describe accurately the excess chemical potential of methane in water. Thus, by using a model capable of describing accurately the density of pure water in a wide range of temperatures and by deviating from the Lorentz-Berthelot combining rules, it is possible to reproduce the properties of methane in water at infinite dilution. In addition, we have applied this methane-water potential to the study of the solid methane hydrate structure, commonly denoted as sI, and find that the model describes the experimental value of the unit cell of the hydrate with an error of about 0.2%. Moreover, we have considered the effect of the amount of methane contained in the hydrate. In doing so, we determine that the presence of methane increases slightly the value of the unit cell and decreases slightly the compressibility of the structure. We also note that the presence of methane increases greatly the range of pressures where the sI hydrate is mechanically stable.

Journal Article↗
PubMed2006

The decrease of NAD(P)H has a prominent role in dopamine toxicity.

We characterized dopamine toxicity in human neuroblastoma SH-SY5Y cells as a direct effect of dopamine on cell reductive power, measured as NADH and NADPH cell content. In cell incubations with 100 or 500 microM dopamine, the accumulation of dopamine inside the cell reached a maximum after 6 h. The decrease in cell viability was 40% and 75%, respectively, after 24 h, and was not altered by MAO inhibition with tranylcypromine. Dopamine was metabolized to DOPAC by mitochondrial MAO and, at 500 microM concentration, significantly reduced mitochondrial potential and oxygen consumption. This DA concentration caused only a slight increase in cell peroxidation in the absence of Fe(III), but a dramatic decrease in NADH and NADPH cell content and a concomitant decrease in total cell NAD(P)H/NAD(P)+ and GSH/GSSG and in mitochondrial NADH/NAD+ ratios. Dopaminechrome, a product of dopamine oxidation, was found to be a MAO-A inhibitor and a strong oxidizer of NADH and NADPH in a cell-free system. We conclude that dopamine may affect NADH and NADPH oxidation directly. When the intracellular concentrations of NAD(P)H and oxidized dopamine are similar, NAD(P)H triggers a redox cycle with dopamine that leads to its own consumption. The time-course of NADH and NADPH oxidation by dopamine was assessed in cell-free assays: NAD(P)H concentration decreased at the same time as dopamine oxidation advanced. The break in cell redox equilibrium, not excluding the involvement of free oxygen radicals, could be sufficient to explain the toxicity of dopamine in dopaminergic neurons.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2006

Protective effect of N-(2-propynyl)-2-(5-benzyloxy-indolyl) methylamine (PF9601N) on mitochondrial permeability transition.

PF9601N, N-(2-propynyl)-2-(5-benzyloxy-indolyl) methylamine, an monoamine oxidase (MAO) B inhibitor, has shown neuroprotective properties against dopaminergic toxins. To elucidate the mechanisms involved in this protection, the effect of PF9601N on mitochondria was assessed. PF9601N prevents mitochondrial swelling, drop in the electrical potential and oxidation of sulfhydryl groups, glutathione and pyridine nucleotides induced by Ca(2+). These observations demonstrate the protective effect of PF9601N on the induction of mitochondrial permeability transition. This protection is due to the interaction of the secondary protonated amino group in the molecule with pore-forming structures and to its antioxidant property, rather than to inhibition of MAO B activity. PF9601N also prevents the release of cytochrome c from mitochondria, suggesting its potential inhibitory effect on mitochondria-mediated apoptosis. The low IC(50) value for this inhibition, in comparison with deprenyl, make it a more efficient compound than propargylamines and other amines in protecting the bioenergetic functions of mitochondria.

Animals↗
PubMed2005

Effect of temperature and organic nutrients on the biodegradation of linear alkylbenzene sulfonate (LAS) during the composting of anaerobically digested sludge from a wastewater treatment plant.

Limits on the application of biosolids (anaerobically processed sludges from wastewater treatment plants) as fertilizers for the amendment of soil are becoming greater because of the accumulation of recalcitrant substances, making necessary the use of techniques that bring the concentration of xenobiotics to lower concentrations than those permitted. In general, the biosolids composting process is sufficient to reduce the usual concentration of linear alkylbenzene sulfonates (LAS) to low levels. In this work, an assessment is made on the effect of temperature in the capacity of enriched bacterial populations to biodegrade LAS, together with the influence that the available nutrients may have in the biodegradation of these compounds. The results show that the microbial metabolism of LAS was not observed in the thermophilic range. The optimum temperature for the biodegradation of LAS appears to be around 40 degrees C, this is, the lowest assayed here, and at this temperature the differences in the biodegradation of LAS among the nutritionally supplemented cultures are small.

Alkanesulfonic Acids↗
PubMed2005

Evaluation of a focused sonication probe for arsenic speciation in environmental and biological samples.

Arsenic speciation analysis suffers in general from high sample handling time required by sample preparation. In a previous work, ultrasonic probe has been proved to reduce sample treatment time for arsenic extraction in rice to only a few minutes. Base upon the obtained results, here several extraction media for chicken, fish and soil samples (SEAS G6RD-CT2001-00473) have been studied and evaluated employing the same technique. Chicken sample needed an enzymatic treatment in order to liberate the species linked to the protein matrix. Extraction of the major species in fish, AsB, was quantitatively achieved in water in 1 min. Also 1 min was enough to leach about 85% of species present in soils and sediments, mainly the inorganic ones, using H(3)PO(4). In all cases, no inter-conversion among As species was observed. The five species found in those samples were separated using an improved HPLC-ICP-MS method in only 11 min, with detection limits at the ng l(-1) level. The proposed methods were validated by analysing several Certified Reference Materials: SRM 1,568 a rice flour, CRM-627 tuna fish tissue, SOIL-7 soil and MURST-ISS-A1 Antarctic sediment.

Animals↗
PubMed2005

A potential model for the study of ices and amorphous water: TIP4P/Ice.

The ability of several water models to predict the properties of ices is discussed. The emphasis is put on the results for the densities and the coexistence curves between the different ice forms. It is concluded that none of the most commonly used rigid models is satisfactory. A new model specifically designed to cope with solid-phase properties is proposed. The parameters have been obtained by fitting the equation of state and selected points of the melting lines and of the coexistence lines involving different ice forms. The phase diagram is then calculated for the new potential. The predicted melting temperature of hexagonal ice (Ih) at 1 bar is 272.2 K. This excellent value does not imply a deterioration of the rest of the properties. In fact, the predictions for both the densities and the coexistence curves are better than for TIP4P, which previously yielded the best estimations of the ice properties.

Journal Article↗
PubMed2005

Rate of homogeneous crystal nucleation in molten NaCl.

We report a numerical simulation of the rate of crystal nucleation of sodium chloride from its melt at moderate supercooling. In this regime nucleation is too slow to be studied with "brute force" molecular-dynamics simulations. The melting temperature of ("Tosi Fumi") NaCl is approximately 1060 K. We studied crystal nucleation at T = 800 and 825 K. We observe that the critical nucleus formed during the nucleation process has the crystal structure of bulk NaCl. Interestingly, the critical nucleus is clearly faceted, the nuclei have a cubical shape. We have computed the crystal-nucleation rate using two completely different approaches, one based on an estimate of the rate of diffusive crossing of the nucleation barrier, the other based on the forward flux sampling and transition interface sampling methods. We find that the two methods yield the same result within an order of magnitude. However, when we compare the extrapolated simulation data with the only available experimental results for NaCl nucleation, we observe a discrepancy of nearly five orders of magnitude. We discuss the possible causes for this discrepancy.

Journal Article↗
PubMed2005

The melting temperature of the most common models of water.

The melting temperature of ice I(h) for several commonly used models of water (SPC, SPC/E,TIP3P,TIP4P, TIP4P/Ew, and TIP5P) is obtained from computer simulations at p = 1 bar. Since the melting temperature of ice I(h) for the TIP4P model is now known [E. Sanz, C. Vega, J. L. F. Abascal, and L. G. MacDowell, Phys. Rev. Lett. 92, 255701 (2004)], it is possible to use the Gibbs-Duhem methodology [D. Kofke, J. Chem. Phys. 98, 4149 (1993)] to evaluate the melting temperature of ice I(h) for other potential models of water. We have found that the melting temperatures of ice I(h) for SPC, SPC/E, TIP3P, TIP4P, TIP4P/Ew, and TIP5P models are T = 190 K, 215 K, 146 K, 232 K, 245 K, and 274 K, respectively. The relative stability of ice I(h) with respect to ice II for these models has also been considered. It turns out that for SPC, SPC/E, TIP3P, and TIP5P the stable phase at the normal melting point is ice II (so that ice I(h) is not a thermodynamically stable phase for these models). For TIP4P and TIP4P/Ew, ice I(h) is the stable solid phase at the standard melting point. The location of the negative charge along the H-O-H bisector appears as a critical factor in the determination of the relative stability between the I(h) and II ice forms. The methodology proposed in this paper can be used to investigate the effect upon a coexistence line due to a change in the potential parameters.

Journal Article↗
PubMed2004

Tracing the phase diagram of the four-site water potential (TIP4P).

We present here the phase diagram for one of the most popular water models, the four-point transferable intermolecular potential (TIP4P) model. We show that TIP4P model, does indeed provide a qualitatively correct description of the phase diagram of water. The melting line of the five-point transferable intermolecular potential (TIP5P) at low pressures is also presented.

Letter↗
PubMed2004

Phase diagram of water from computer simulation.

The phase diagram of water as obtained from computer simulations is presented for the first time for two of the most popular models of water, TIP4P and SPC/E. This Letter shows that the prediction of the phase diagram is an extremely stringent test for any water potential function, and that it may be useful in developing improved potentials. The TIP4P model provides a qualitatively correct description of the phase diagram, unlike the SPC/E model which fails in this purpose. New behavior not yet observed experimentally is predicted by the simulations: the existence of metastable reentrant behavior in the melting curves of the low density ices (I,III,V) such that it could be possible to transform them into amorphous phases by adequate changes in pressure.

Journal Article↗
PubMed2004

Drug utilisation in outpatient children. A comparison among Tenerife, Valencia, and Barcelona (Spain), Toulouse (France), Sofia (Bulgaria), Bratislava (Slovakia) and Smolensk (Russia).

INTRODUCTION: Scarce information about comparative diagnostic and therapeutic patterns in paediatric outpatients of different countries is found in the literature. OBJECTIVE: To describe the similarities and differences observed in diagnosis and therapeutic patterns of paediatric patients of seven locations in different countries. DESIGN: Cross-sectional, prospective, international comparative, descriptive study. PATIENTS AND METHODS: A randomly selected sample of 12,264 paediatric outpatients seen in consultation rooms of urban and rural areas and attended by paediatricians or general practitioners of the participating locations. Data on patient demographic information, diagnosis and pharmacological treatment were collected using pre-designed forms. Diagnoses were coded using the ICD-9 and drugs according to the ATC classification. RESULTS: Among the ten most common diagnoses, upper respiratory tract infections are in the first position in all locations; asthma prevalence is highest in Tenerife (8.4%). Tonsillitis, otitis, bronchitis and dermatological affections are the most common diagnoses in all locations. Pneumonia is only reported in Sofia (3.8%) and Smolensk (2.3%). The average number of drugs prescribed per child varied from 1.3 in Barcelona to 2.9 in Smolensk. There are no great differences in the profile of pharmacological groups prescribed, but a considerable range of variations in antibiotic therapy is observed: prescription of cephalosporins is low in Smolensk (0.7%) and higher in the other locations, from 16.5% (Bratislava) to 28% (Tenerife). Macrolides prescriptions range from 12.6% (Toulouse) to 24.7% (Smolensk), except in Sofia where they drop to 5.6%. Trimethoprim and its combinations are used in Smolensk (23.3%), Sofia (11.8%) and Bratislava (8.7%). Check-up consultations are not recorded in Smolensk and Bratislava, whereas in Toulouse these visits account for 16.2% of all consultations and in the other locations the percentage varies from 6.1% (Tenerife) to 1.9% (Sofia). Homeopathic treatments are registered only in Toulouse. CONCLUSION: Except in asthma prevalence, there are no great differences in diagnostic maps among locations. Significant variations in the number of drugs prescribed per child and antibiotic therapies are observed. Areas for improvement have been identified.

Bulgaria↗
PubMed2004

Computer simulation study of the global phase behavior of linear rigid Lennard-Jones chain molecules: comparison with flexible models.

The global phase behavior (i.e., vapor-liquid and fluid-solid equilibria) of rigid linear Lennard-Jones (LJ) chain molecules is studied. The phase diagrams for three-center and five-center rigid model molecules are obtained by computer simulation. The segment-segment bond lengths are L = sigma, so that models of tangent monomers are considered in this study. The vapor-liquid equilibrium conditions are obtained using the Gibbs ensemble Monte Carlo method and by performing isobaric-isothermal NPT calculations at zero pressure. The phase envelopes and critical conditions are compared with those of flexible LJ molecules of tangent segments. An increase in the critical temperature of linear rigid chains with respect to their flexible counterparts is observed. In the limit of infinitely long chains the critical temperature of linear rigid LJ chains of tangent segments seems to be higher than that of flexible LJ chains. The solid-fluid equilibrium is obtained by Gibbs-Duhem integration, and by performing NPT simulations at zero pressure. A stabilization of the solid phase, an increase in the triple-point temperature, and a widening of the transition region are observed for linear rigid chains when compared to flexible chains with the same number of segments. The triple-point temperature of linear rigid LJ chains increases dramatically with chain length. The results of this work suggest that the fluid-vapor transition could be metastable with respect to the fluid-solid transition for chains with more than six LJ monomer units.

Journal Article↗
PubMed2004

Pharmacological treatment of acute otitis media in children. A comparison among seven locations: Tenerife, Barcelona and Valencia (Spain), Toulouse (France), Smolensk (Russia), Bratislava (Slovakia) and Sofia (Bulgaria).

OBJECTIVE: To describe patterns observed in the treatment of acute otitis media (AOM) in several locations of five countries. PATIENTS AND METHODS: Cross-sectional, descriptive study. Random sample of 12,264 paediatric outpatients seen by paediatricians or general practitioners (GPs). Data on patient demographics, diagnoses and treatment were collected. Diagnoses were coded by ICD-9 and drugs by ATC classification. Patients diagnosed with AOM (ICD-9 codes: 381 and 382) were selected for analysis. RESULTS: Cases of AOM (873) accounted for 7.1% of the sample. There is a clear variation in the percentage of children diagnosed with AOM and treated with antibiotics in the different locations, antibiotic prescriptions being higher in Barcelona (93% of children), and lowest in Smolensk (56.4 % of children were treated without antibiotics). The antibiotics used varied widely: ampicillin use is almost limited to Smolensk (26.7%) and Bratislava (13.8%), whereas amoxicillin plus clavulanic acid is the choice in Toulouse (33.8%), Valencia (30.2%) and Barcelona (28.9%), and cephalosporins are more frequently prescribed in Tenerife (51.7%). Finally, macrolides are used in Barcelona (18.3%), Valencia (17.5%) and Tenerife (13.6%), but not prescribed in Toulouse or Sofia. Prescriptions of anti-inflammatory drugs were only relevant in Valencia (31.7%), Tenerife (27.2%) and Toulouse (17.4%) and of otological preparations in Sofia, where almost each child received ear drops (91.9%). Nasal preparations are commonly used only in Sofia (41.9%), Bratislava (65.5%) and Smolensk (68.6%). CONCLUSION: Despite the general agreement of most guidelines, wide differences in the treatment of uncomplicated AOM in children are observed. Non-antibiotic therapy for AOM and the use of first-choice antibiotics should be more actively encouraged in the primary care centres. Studies to measure prevailing rates of antibiotic resistance in these populations are needed.

Acute Disease↗
PubMed2004

[Diagnosis and management of necrotizing tracheobronchitis].

OBJECTIVE: Necrotizing tracheobronchitis has been described as a complication of mechanical ventilation of newborns with respiratory failure. Neonates with necrotizing tracheobronchitis present a diverse clinical spectrum from asymptomatic disease to severe airway obstruction that causes 45% of mortality. The objective of our study is to analyze our experience in the management of these patients. MATERIAL AND METHODS: In the last three years we have treated eight patients with necrotizing tracheobronchitis The mean age was 0.84 +/- 0.95 months, gestational age of 37.43 +/- 2.3 weeks. The mean weight was 3.07 +/- 1.04 kg. Five patients had a congenital heat disease (62.5%) and three have a respiratory failure (37.5%). We have analyzed the contributing factors, symptoms, diagnosis, treatment and results. RESULTS: All patients presented episodes of shock with treatment of drugs. Five patients have conventional ventilation (62.5%) while three have high frequency oscillatory ventilation (37.5%). There were not significant differences in the ventilator parameters of both groups (PMA, PIP, PEEP). Three patients were supported by ECMO when they developed necrotizing tracheobronchitis. The treatment was bronchoscopic removal of necrotic tissue. There was not any complication after the procedure. A patient suffered a stenosis in the left main bronchus. Three patients have died during follow-up for different causes. The time of pursuit is of 10.33 +/- 7.61 months. CONCLUSIONS: Necrotizing tracheobronchitis may be increasing in the Neonatal Intensive Care Units, due to a bigger survival of patient with serious respiratory failure and shock. Hypotension and shock seems to be a major contributing factor in the development of this lesion. Bronchoscopy is necessary for treatment and survival of the patients.

Bronchitis↗
PubMed2002

Characterization of sparsomycin resistance in Streptomyces sparsogenes.

The antitumor antibiotic sparsomycin, produced by Streptomyces sparsogenes, is a universal translation inhibitor that blocks the peptide bond formation in ribosomes from all species. Sparsomycin-resistant strains were selected by transforming the sensitive Streptomyces lividans with an S. sparsogenes library. Resistance was linked to the presence of a plasmid containing an S. sparsogenes 5.9-kbp DNA insert. A restriction analysis of the insert traced down the resistance to a 3.6-kbp DNA fragment, which was sequenced. The analysis of the fragment nucleotide sequence together with the previous restriction data associate the resistance to srd, an open reading frame of 1,800 nucleotides. Ribosomes from S. sparsogenes and the S. lividans-resistant strains are equally sensitive to the inhibitor and bind the drug with similar affinity. Moreover, the drug was not modified by the resistant strains. However, resistant cells accumulated less antibiotic than the sensitive ones. In addition, membrane fractions from the resistant strains showed a higher capacity for binding the drug. The results indicate that resistance in the producer strain is not connected to either ribosome modification or drug inactivation, but it might be related to an alteration in the sparsomycin permeability barrier.

Antibiotics, Antineoplastic↗
PubMed2001

Diabetes abolishes the gender difference in vasopressin-mediated potentiation of sympathetic vasoconstriction.

Electrical field stimulation (4 Hz, 0.2 ms pulse duration, at a supramaximal voltage of 70 V, for 1 s) of isolated rat tail artery segments produced contraction which was lower in female than in male rats, and was reduced by streptozotocin-induced diabetes in both genders. This contraction was potentiated by vasopressin (10(-12)-10(-10) M) more in normoglycemic male than in normoglycemic female rats, and this effect of vasopressin was increased by the cyclooxigenase inhibitor meclofenamate (10(-5) M) in female control rats, but not in diabetic female, or control and diabetic male rats, and it was not modified by the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 10(-4) M). Endothelin-1 (10(-10)-3 x 10(-9) M) also potentiated the contraction to electrical stimulation. This potentiation was similar in all experimental groups, and it was not modified by meclofenamate or L-NAME. These results suggest that the potentiating effect of vasopressin, but not that of endothelin-1, on the sympathetic vasoconstriction, is lower in females than in males, probably by an increased release of vasodilating prostanoids, and this release may be reduced by diabetes in females.

Animals↗