Showing papers by "University of Extremadura published in 1999"

Anatomy of the left atrium: implications for radiofrequency ablation of atrial fibrillation.

Abstract: Anatomy of the Left Atrium. Introduction: The feasibility of treating atrial fibrillation with radiofrequency ablation has revived interest in the structure of the left atrium, a chamber that has been neglected in many textbooks of anatomy. Methods and Results: We reviewed the gross structure of the left atrium by examining the septum, the appendage, and insertions of the pulmonary veins in normal hearts. The limited extent of the true septal component is relevant to procedures using the transseptal approach. On gross examination, the musculature of the atrial wall is composed of overlapping bundles of aligned fibers that, in the majority of hearts, are arranged in characteristic patterns with only minor individual variations. Muscular sleeves extend into the walls of the pulmonary veins to varying distances. The longest sleeves are in the left upper veins. Bachmann's bundle anteriorly, and other smaller bundles superiorly and posteriorly, bridge the septal raphe to blend with musculature of the right atrium. Tongues of left atrial musculature from the posterior wall also extend into the wall of the coronary sinus. Conclusion: The left atrium is more complex than usually conceived. Understanding its structure, and the arrangement of its musculature, will help in improving strategies for linear lesions when attempting to compartmentalize the chamber, or when placing focal lesions for ablating ectopic sources.

Bacteremic pneumonia due to staphylococcus aureus: a comparison of disease caused by methicillin-resistant and methicillin-susceptible organisms

Abstract: We performed a prospective study of all patients with bacteremic pneumonia due to Staphylococcus aureus over a period of 6 years during an outbreak of methicillin-resistant S. aureus (MRSA). Patients with bacteremic pneumonia due to MRSA (32 cases) or methicillin-susceptible S. aureus (MSSA; 54 cases) were compared. The patients with MRSA pneumonia were older and were more likely than those with MSSA pneumonia to have predisposing factors for acquisition of the infection. There were no differences in clinical findings, radiological pattern, or complications in clinical evolution among patients with MRSA and MSSA pneumonia. Mortality was significantly higher among MSSA-infected patients treated with vancomycin than among those treated with cloxacillin (47% vs. none; P<.01). Multivariate analysis (stepwise logistic regression method) showed a relationship between mortality and the following variables: septic shock (odds ratio [OR], 61), vancomycin treatment (OR, 14), and respiratory distress (OR, 8).

A Defect in Interleukin-10 Leads to Enhanced Malarial Disease in Plasmodium chabaudi chabaudi Infection in Mice

Abstract: Infection of interleukin-10 (IL-10)-nonexpressing (IL-10−/−) mice with Plasmodium chabaudi chabaudi (AS) leads to exacerbated pathology in female mice and death in a proportion of them. Hypoglycemia, hypothermia, and loss in body weight were significantly greater in female IL-10−/− mice than in male knockout mice and all wild-type (WT) mice during the acute phase of infection. At this time, both female and male IL-10−/− mice produced more gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), and IL-12p40 mRNA than their respective WT counterparts. Inactivation of IFN-γ in IL-10−/− mice by the injection of anti-IFN-γ antibodies or by the generation of IL-10−/− IFN-γ receptor−/− double-knockout mice resulted in reduced mortality but did not affect body weight, temperature, or blood glucose levels. The data suggest that IFN-γ-independent pathways may be responsible for these pathological features of P. chabaudi malaria and may be due to direct stimulation of TNF-α by the parasite. Since male and female knockout mice both produce more inflammatory cytokines than their WT counterparts, it is likely that the mortality seen in females is due to the nature or magnitude of the response to these cytokines rather than the amount of IFN-γ or TNF-α produced.

Immunocompetence and condition-dependent sexual advertisement in male house sparrows (Passer domesticus)

Abstract: Summary1. We tested the condition-dependent hypothesis of sexual advertisement in housesparrows (Passer domesticus). Male house sparrows have a bib of black featherswhich serves as both a badge of social status and as a cue for female choice. Wemanipulated environmental conditions during the premoult period of juvenilehouse sparrows kept in outdoor aviaries. Birds were assigned to two treatments dif-fering in the amount of dietary proteins, which are known to a•ect the expressionof immune response in birds. We tested whether birds in the protein-rich grouphad better immune responses and developed larger bibs than birds reared on a pro-tein-poor diet. We also checked whether immune response was a predictor of survi-val and parasite resistance.2. Individuals with higher cellular immune response at capture had greater prob-ability to survive during the 3months of the experiment, and they had a higherprobability to recover from infection with Haemoproteus sp. (a blood parasite).Conversely, birds with high immunoglobulin concentrations at capture had ahigher probability of mortality.3. Birds on the protein-rich diet had a higher cellular immune response comparedto birds in the protein-poor treatment. Humoral immune response showed theopposite pattern, being higher for birds in the protein-poor treatment. We did notfind any e•ect of food quality on the development of the badge, assessed as the sizeof the trait and its colour properties.4. In conclusion, our results support the view that immune defences are importantfor survival and parasite resistance in natural populations, and that they might becostly to produce. On the other hand, we did not find support for the condition-dependent hypothesis of sexual advertisement, suggesting that the badge may notbe a costly trait to produce. However, badge size could reflect other aspects of con-dition. The kind of pigments involved in colour signals may be the key factor deter-mining the production costs of such traits.Key-words: immune response, immunoglobulins, parasite resistance, sexual signals,survival, T-cell response.Journal of Animal Ecology (1999) 68, 1225–1234Introduction

Trend analysis of monthly precipitation over the iberian peninsula for the period 1921–1995

Abstract: In this study monthly and annual total precipitation records of the Iberian Peninsula are analyzed for trend. In order to take into account seasonality and serial correlation, the different months of the year are considered separately. The precipitation series were observed at forty meteorological stations scattered all over the Iberian Peninsula. The group of series were selected for their spatial and temporal representativeness. The long common period of seventy-five years (from January 1921 to December 1995) permits a reliable climatic investigation. The Wald and Wolfowitz (1943) test was applied to the series in order to detect serial correlation that could affect the subsequent trend analysis. Due to the long interval of time (one year) between consecutive data, the monthly total precipitation series for the different months showed no persistence. However, the annual total precipitation series showed a positive serial correlation. In order to detect possible trends in precipitation over the Iberian Peninsula, the Mann-Kendall test was applied to the annual and monthly series. This test is non-parametric and thus, has the advantage of being insensitive to the true (unknown) form of the distribution involved. No significant global trend was found in the annual total precipitation series. The only trend observed was a downward trend in twenty-one of the forty series of monthly total precipitation only for the month of March.

Monthly Modes of Variation of Precipitation over the Iberian Peninsula.

Abstract: An attempt is made to find the main monthly modes of variation of precipitation over the Iberian Peninsula. The modes of variation of precipitation were derived from principal component analysis. The dataset used consists of records of monthly precipitation from 40 meteorological stations over 74 yr (1919–92). The stations are spatially representative of most of the Iberian Peninsula. To take into account the seasonality of precipitation over the Iberian Peninsula, one analysis was performed separately for each calendar month. The modes of variation resulting from the different analyses were compared and clustered in groups according to their loading patterns. Seven main patterns were found to be of importance during various months of the year. These seven patterns explained more than 75% of the variance of the precipitation field from December to April. However, less than 20% of the total variance is explained for July and August. It is concluded that, depending on the month or season of interes...

On the quality of the data envelopment analysis model

Abstract: The user of data envelopment analysis (DEA) has little available guidance on model quality. The technique offers none of the misspecification tests or goodness of fit statistics developed for parametric statistical methods. Yet, if a DEA model is to guide managerial policy, the quality of the model is of crucial importance. This paper suggests four alternative purposes of DEA modelling, and offers four measures of the quality of a DEA model which reflect those purposes. Using Monte Carlo simulation methods, it explores the performance of DEA under a wide variety of assumptions. It notes that four issues will have an important influence on model results: the distribution of true efficiencies in the study sample; the size of the sample; the number of inputs and outputs included in the analysis; and the degree of correlation between inputs and outputs. The paper concludes that any judgement about the reliability of model results must be dependent on the objective of the analysis.

Preparation and Properties of Biodiesel from Cynara cardunculus L. Oil

Abstract: A study was made of the reaction of transesterification of Cynara cardunculus L. oil by means of methanol, using sodium hydroxide, potassium hydroxide, and sodium methoxide as catalysts. The objective of the work was to characterize the methyl esters for use as biodiesels in internal combustion motors. The operation variables used were methanol concentration (5−21 wt %), catalyst concentration (0.1−1 wt %), and temperature (25−60 °C). The evolution of the process was followed by gas chromatography, determining the concentration of the methyl esters at different reaction times. The biodiesel was characterized by determining its density, viscosity, high heating value, cetane index, cloud and pour points, Ramsbottom carbon residue, characteristics of distillation, and flash and combustion points according to ISO norms. The biodiesel with the best properties was obtained using 15% methanol, sodium methoxide as catalyst (1%), and 60 °C temperature. This biodiesel has very similar properties to those of diesel ...

Comparative in vitro and in vivo inhibition of cytochrome P450 CYP1A2, CYP2D6, and CYP3A by H2-receptor antagonists.

Abstract: The isozymes CYP1A2, CYP2D6, and CYP3A4/5 are involved in the majority of all cytochrome P450-mediated drug biotransformations. In this study we investigated the inhibition profiles of CYP1A2 (substrate: caffeine) CYP2D6 (substrate: dextromethorphan), and CYP3A4/5 (substrate: dextrorphan) by cimetidine, ranitidine, and the novel H2-receptor antagonist ebrotidine in human liver microsomes. The inhibitory effect of the drugs on the enzymes activities were as follows: CYP1A2: cimetidine >> ranitidine = ebrotidine; CYP2D6: cimetidine >>> ranitidine = ebrotidine; CYP3A4/5: ebrotidine > cimetidine >>> ranitidine. The inhibition of CYP3A4/5 enzyme activity by ebrotidine was competitive. To test whether the inhibitory effect of ebrotidine in CYP3A activity was also found in vivo, we analyzed the biodisposition of midazolam in 8 healthy volunteers. Midazolam biodisposition was significantly reduced when administered together with cimetidine (P < .05), whereas no significant inhibition was observed with ebrotidine or ranitidine compared with placebo. Psychomotor performance analysis revealed no significant effect of the observed reduction on midazolam biodisposition. We concluded that patients who are receiving treatment with drugs metabolized through CYP3A may experience enhanced drug effects as a result of pharmacokinetic interaction when treated concomitantly with cimetidine. In contrast, the effect of ranitidine or ebrotidine on CYP3A activity in vivo seems to have little clinical significance.

Relaciones entre la orientación de meta disposicional y la satisfacción con los resultados deportivos, las creencias sobre las causas de éxito en deporte y la diversión con la práctica

Abstract: Este trabajo analizo las propiedades psicometricas de una bateria de cuestionarios utilizado previamente en contextos deportivos britanicos y norteamericanos para medir: la orientacion de metas disposicional, las creencias sobre las causas de exito en deporte, la satisfaccion con los resultados deportivos y la diversion con la practica deportiva y las relaciones entre la orientacion de meta personal y las variables estudiadas. 90 chicos y 40 chicas practicantes de atletismo o tenis participaron en el estudio. Los resultados han mostrado una distribucion factorial semejantes a las obtenidas con los instrumentos originales. La consistencia interna de todas las escalas se ha mostrado aceptable y las relaciones entre la orientacion de meta disposicional, las creencias, la satisfaccion y la diversion, han mostrado que la orientacion al ego se encuentra relacionada con patrones motivacionales potencialmente poco adaptativos.

Different mechanisms of protection against apoptosis by valproate and Li

Abstract: Acute treatment with valproate and Li+ was found to protect cultured cerebellar granule cells against apoptosis induced by low K+ (5 mM). Because the protection was unaffected by MK801 (N-methyl-D-aspartate receptor inhibitor), an increase in glutamate release cannot be responsible for the observed neuroprotection. Insulin also protects against low-K+-induced apoptosis of cerebellar granule cells. This protection is totally dependent on LY294002 (a phosphatidylinositol 3-kinase inhibitor). These results suggest a role for phosphatidylinositol 3-kinase in the neuroprotection induced by insulin. Likewise, and in contrast with the results observed with Li+, the protection induced by valproate is also dependent on insulin and LY294002. Moreover, valproate (a branched-chain fatty acid) does not change the plasma membrane microviscosity under physiological conditions. These results suggest that valproate protects against low-K+-induced apoptosis by acting in the phosphatidylinositol 3-kinase/protein kinase B pathway. The protection by Li+ is independent of this transduction pathway.

Retinoic acid regulates programmed cell death through BMP signalling.

Abstract: rogrammed cell death by apoptosis is one of the major driving forces that shape and pattern the organs and tissues of a developing embryo. One of the best model systems for the study of apoptosis is the interdigital cell death (INZ) that occurs during the outgrowth of the vertebrate limb. However, although much has been learned about the cells involved in this process, the molecular mechanisms underlying INZ remain unclear. Retinoic acid (RA) and bone morphogenetic proteins (BMPs) are two of the signalling components known to be involved in INZ. However, the exact relationships between these two factors in controlling cell death remain unknown. Here we show that RA can control INZ by promoting BMP gene expression and simultaneously repressing the chondrogenic potential of BMPs. We found that RA-soaked beads implanted in the interdigital regions of the chick limb bud promoted apoptosis before the onset of physiological INZ (assessed by neutral red vital staining and TUNEL assay; Fig. 1a–c). Furthermore, interdigital web regression was accelerated (Fig. 1d,e). These effects were preceded by upregulation of different members of the BMP gene family (bmp-7, Fig. 1f,g and bmp-4, not shown). In accordance with these findings, the P

Resveratrol is a potent inhibitor of the dioxygenase activity of lipoxygenase.

Abstract: Resveratrol is a naturally occurring phytoalexin, present in grapes and other food products, with important antioxidant properties. Although still under debate, it is generally assumed that resveratrol has protective effects against heart diseases and probably tumor development. Lipoxygenase is a dioxygenase with peroxidase activity involved in the synthesis of mediators in inflammatory, atherosclerotic, and carcinogenic processes. Lipoxygenase activity is also involved in the generation of flavors and aromas in foods from animal or vegetal sources. The results presented here show that resveratrol was a potent inhibitor of the dioxygenase activity of lipoxygenase, with an IC(50) = 13 microM. Simultaneously, resveratrol was oxidized by the peroxidase activity of lipoxygenase with a V(max) = 0.28 microM min(-1) and a k(M) = 16.6 microM. Furthermore, oxidized resveratrol was as efficient a lipoxygenase inhibitor as in its reduced form. From the data obtained it can be concluded that both resveratrol and its oxidized form can act as inhibitors of the dioxygenase activity of lipoxygenase. In contrast, the hydroperoxidase activity of lipoxygenase was not inhibited by resveratrol. These results suggest that resveratrol may be used as an antioxidant food additive and as a pharmacological agent to prevent the generation of eicosanoids involved in pathological processes.

Science in america latina: A comparison of bibliometric and scientific-technical indicators

Abstract: Latin-American scientific achievement is generally under-represented in databases for a number of reasons pointed out in our study. In this paper we analyze Latin-American scientific production in terms of input (resources) and output (publications). The indicators used were: Gross Domestic Product (GDP), economically active population (EAP), percentage of GNP destined to R+D, and total number of researchers dedicated to R+D. These indicators were subjected to bivariant analysis to determine the degree of correlation with the number of ISI publications.

Wine distillery wastewater degradation. 1. Oxidative treatment using ozone and its effect on the wastewater biodegradability.

Abstract: Laboratory-scale experiments were conducted to investigate the impact of ozonation on the degradability of wine distillery wastewaters, usually called vinasses, with the goal of developing combined chemical−biological methods for their treatment. Chemical oxygen demand (COD), biological oxygen demand (BOD), total organic carbon (TOC), and ultraviolet absorbance at 254 nm (UV254) were taken as reference parameters to follow the pollution level. The vinasses were treated both directly and after being mixed with domestic sewage. Ozonation of pure vinasses required high ozone doses to achieve a significant efficiency for removing the organic matter. Mixing vinasses with domestic sewage allowed higher degradation rates with ozone. Ozone was also demonstrated to be an appropriate oxidizing agent to improve vinasses's biodegradability and organic matter removal. A mathematical model of the ozonation kinetics based on the film theory concept is also presented. Keywords: Wastewater treatment; ozonation; biodegrada...

Chemical Decomposition of 2,4,6-Trichlorophenol by Ozone, Fenton's Reagent, and UV Radiation

Abstract: The kinetics of the decomposition of 2,4,6-trichlorophenol by ozonation, by Fenton's reagent reaction, and by a polychromatic UV radiation is investigated from experiments performed in a batch reactor. In each oxidation system, the degree of removal of the organic compound from water is evaluated and the influence of the operating variables is established. The ozonation process is conducted at pH = 2 and in the presence of radical scavengers: In these conditions the kinetic constants and reaction orders for the direct reaction between ozone and that organic compound are deduced by using a model based in the film theory. The oxidation by Fenton's reagent (Fe2+ ion and H2O2), a generating system of hydroxyl radicals, leads to the evaluation of pseudo-first-order rate constants for the global reaction and to the determination of the kinetic constant for the direct radical reaction. Finally, the quantum yields in the photodecomposition process are determined from the rate equation, with the radiation flow ra...

Kinetic Models for Granular Flow

Abstract: The generalization of the Boltzmann and Enskog kinetic equations to allow inelastic collisions provides a basis for studies of granular media at a fundamental level. For elastic collisions the significant technical challenges presented in solving these equations have been circumvented by the use of corresponding model kinetic equations. The objective here is to discuss the formulation of model kinetic equations for the case of inelastic collisions. To illustrate the qualitative changes resulting from inelastic collisions the dynamics of a heavy particle in a gas of much lighter particles is considered first. The Boltzmann–Lorentz equation is reduced to a Fokker–Planck equation and its exact solution is obtained. Qualitative differences from the elastic case arise primarily from the cooling of the surrounding gas. The excitations, or physical spectrum, are no longer determined simply from the Fokker–Planck operator, but rather from a related operator incorporating the cooling effects. Nevertheless, it is shown that a diffusion mode dominates for long times just as in the elastic case. From the spectral analysis of the Fokker–Planck equation an associated kinetic model is obtained. In appropriate dimensionless variables it has the same form as the BGK kinetic model for elastic collisions, known to be an accurate representation of the Fokker–Planck equation. On the basis of these considerations, a kinetic model for the Boltzmann equation is derived. The exact solution for states near the homogeneous cooling state is obtained and the transport properties are discussed, including the relaxation toward hydrodynamics. As a second application of this model, it is shown that the exact solution for uniform shear flow arbitrarily far from equilibrium can be obtained from the corresponding known solution for elastic collisions. Finally, the kinetic model for the dense fluid Enskog equation is described.

Treatment of olive mill wastewaters by ozonation, aerobic degradation and the combination of both treatments

Abstract: The degradation of the pollutant organic matter present in olive oil mill wastewaters (OMW) is carried out by a single ozonation, a single aerobic degradation, and the combination of two successives steps: an ozonation followed by an aerobic degradation, and an aerobic degradation followed by an ozonation. In both single processes, the removal of this contaminant load is followed by means of global parameters which are directly related to the concentration of organic compounds in those effluents: chemical oxygen demand and total aromatic and phenolic contents. In the ozonation, an approximate kinetic study is performed which leads to the evaluation of the apparent kinetic constants for the aromatic reduction, kA. In the aerobic degradation, the kinetic study is conducted by using the Grau model, which is applied to the experimental data, and leads to the determination of the kinetic parameters of this model, K2 and n. In the combined processes, a higher COD global reduction is obtained by the successive stages, and an improvement in the removal of the organic material during the second treatment of both processes due to the pretreatment conducted is also observed. This enhancement is shown by an increase of the kinetic parameters (K2 and n in the aerobic degradation of the pre-ozonated wastewaters; the apparent constant kA in the ozonation of the wastewaters preliminary fermented aerobically), in relation to the values obtained for them in the single processes carried out at the same operating conditions. © 1999 Society of Chemical Industry

Equation of state of a multicomponent d – dimensional hard – sphere fluid

Abstract: A simple recipe to derive the compressibility factor of a multicomponent mixture of d-dimensional additive hard spheres in terms of that of the one-component system is proposed. The recipe is based (i) on an exact condition that has to be satisfied in the special limit where one of the components corresponds to point particles; and (ii) on the form of the radial distribution functions at contact as obtained from the Percus—Yevick equation in the three-dimensional system. The proposal is examined for hard discs and hard spheres by comparison with well-known equations of state for these systems and with simulation data. In the special case of d = 3, our extension to mixtures of the Carnahan—Starling equation of state yields a better agreement with simulation than the already accurate Boublik—Mansoori—Carnahan—Starling—Leland equation of state.