Showing papers by "University of Extremadura published in 2008"

The auxin influx carrier LAX3 promotes lateral root emergence

Abstract: Lateral roots originate deep within the parental root from a small number of founder cells at the periphery of vascular tissues and must emerge through intervening layers of tissues We describe how the hormone auxin, which originates from the developing lateral root, acts as a local inductive signal which re-programmes adjacent cells Auxin induces the expression of a previously uncharacterized auxin influx carrier LAX3 in cortical and epidermal cells directly overlaying new primordia Increased LAX3 activity reinforces the auxin-dependent induction of a selection of cell-wall-remodelling enzymes, which are likely to promote cell separation in advance of developing lateral root primordia

A genome-wide association study identifies colorectal cancer susceptibility loci on chromosomes 10p14 and 8q23.3

Abstract: To identify colorectal cancer (CRC) susceptibility alleles, we conducted a genome-wide association study. In phase 1, we genotyped 550,163 tagSNPs in 940 familial colorectal tumor cases (627 CRC, 313 high-risk adenoma) and 965 controls. In phase 2, we genotyped 42,708 selected SNPs in 2,873 CRC cases and 2,871 controls. In phase 3, we evaluated 11 SNPs showing association at P < 10(-4) in a joint analysis of phases 1 and 2 in 4,287 CRC cases and 3,743 controls. Two SNPs were taken forward to phase 4 genotyping (10,731 CRC cases and 10,961 controls from eight centers). In addition to the previously reported 8q24, 15q13 and 18q21 CRC risk loci, we identified two previously unreported associations: rs10795668, located at 10p14 (P = 2.5 x 10(-13) overall; P = 6.9 x 10(-12) replication), and rs16892766, at 8q23.3 (P = 3.3 x 10(-18) overall; P = 9.6 x 10(-17) replication), which tags a plausible causative gene, EIF3H. These data provide further evidence for the 'common-disease common-variant' model of CRC predisposition.

Land Surface Emissivity Retrieval From Different VNIR and TIR Sensors

Abstract: This paper discusses the application and adaptation of two existing operational algorithms for land surface emissivity (epsiv) retrieval from different operational satellite/airborne sensors with bands in the visible and near-infrared (VNIR) and thermal IR (TIR) regions: (1) the temperature and emissivity separation algorithm, which retrieves epsiv only from TIR data and (2) the normalized-difference vegetation index thresholds method, in which epsiv is retrieved from VNIR data.

Characteristics of the research on reverse logistics (1995–2005)

Abstract: This paper aims to describe and analyse the main characteristics of articles on reverse logistics published in the production and operations management field, in order to determine the evolution of this current research over recent years and improve our understanding of this issue. We built up a database with the articles on reverse logistics published in the most relevant journals within the period 1995–2005, and we have explored the topic, the methodology and the techniques of analysis, as well as other relevant aspects of the research. We have evaluated the first decade of research on reverse logistics, observing what has been done and how, where and by whom it has been carried out. The result is an extensive review of the research works that have created and developed the reverse logistics concept, outlining some directions of research for the near future and offering practical help to those who begin to research on this topic.

Mechanical properties of calcium phosphate scaffolds fabricated by robocasting

Abstract: The mechanical behavior under compressive stresses of β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) scaffolds fabricated by direct-write assembly (robocasting) technique is analyzed. Concentrated colloidal inks prepared from β-TCP and HA commercial powders were used to fabricate porous structures consisting of a 3-D tetragonal mesh of interpenetrating ceramic rods. The compressive strength and elastic modulus of these model scaffolds were determined by uniaxial testing to compare the relative performance of the selected materials. The effect of a 3-week immersion in simulated body fluid (SBF) on the strength of the scaffolds was also analyzed. The results are compared with those reported in the literature for calcium phosphate scaffolds and human bone. The robocast calcium phosphate scaffolds were found to exhibit excellent mechanical performances in terms of strength, especially the HA structures after SBF immersion, indicating a great potential of this type of scaffolds for use in load-bearing bone tissue engineering applications. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 2008

Uniform and water stable magnetite nanoparticles with diameters around the monodomain-multidomain limit

Abstract: A direct method for the preparation of uniform magnetite nanoparticles with sizes around 30?nm and stable in aqueous media at pH 7 has been developed. This method is based on the precipitation of an iron (II) salt (FeSO4) in the presence of a base (NaOH) and a mild oxidant (KNO3). Reaction rate seems to be controlled by the iron salt concentration and the presence of ethanol in the media. Thus lower iron concentration and a water/ethanol ratio equal to one lead to the formation of the smallest particles, 30?nm in diameter. Colloidal suspensions of these particles were directly obtained by simple ultrasonic treatment of the powders leading to very stable ferrofluids at pH 7. Sulphate anions present at the particle surface seem to be responsible for the colloidal stability, providing a biocompatible character to the suspensions. The structural, morphological and magnetic characterization of the nanoparticles is also described and suggests that the smallest particles have a diameter close to the limit between monodomain?multidomain magnetic structure, which could account for the high powder absorption of magnetic fields. According to this calorimetric experiments resulted in specific power absorption rates of ca 80?95?W?g?1, which are among the highest values reported in the literature and make these nanoparticles very interesting for hyperthermia.

Measuring efficiency in education: an analysis of different approaches for incorporating non-discretionary inputs

Abstract: Measuring efficiency in the education sector is a highly complex task. One of the reasons is that the main resource of schools (the type of students they have) lie outside of their control, which means that it must be treated differently to other factors in analysis. This study examines the different options available in the literature for incorporating non-controllable inputs in a data envelopment analysis in order to determine the most appropriate model for evaluating schools. Our empirical study presents the results obtained using the model proposed by Fried et al . (1999), though we use bootstrap techniques to avoid problems of bias in the estimations.

Effects of malaria double infection in birds: one plus one is not two.

Abstract: Avian malaria parasites are supposed to exert negative effects on host fitness because these intracellular parasites affect host metabolism. Recent advances in molecular genotyping and microscopy have revealed that coinfections with multiple parasites are frequent in bird-malaria parasite systems. However, studies of the fitness consequences of such double infections are scarce and inconclusive. We tested if the infection with two malaria parasite lineages has more negative effects than single infection using 6 years of data from a natural population of house martins. Survival was negatively affected by both types of infections. We found an additive cost from single to double infection in body condition, but not in reproductive parameters (double-infected had higher reproductive success). These results demonstrate that malaria infections decrease survival, but also have different consequences on the breeding performance of single- and double-infected wild birds.

The Water Hyacinth, Eichhornia crassipes: an invasive plant in the Guadiana River Basin (Spain)

Abstract: The recent invasion of water hyacinth Eichhornia crassipes (C. Mart.) Solms (1883) in the Guadiana River Basin (Spain) is described and the distribution of this Amazonian floating plant is analyzed from a geobotanical and chorological perspective. Georeferenced locations of invasion in Spain and Portugal are presented and the relative growth rate (RGR) and doubling time (DT) indexes defined by Gopal (1987) were calculated. The sexual reproductive cycles were determined in order to evaluate the invasive capacity at these latitudes. Predictive models of the plant's potential distribution in the Guadiana River were constructed based on expert knowledge and using a Geographic Information System, on the basis of the water's physico-chemical parameters. Given the size of the potential area of distribution, it seems necessary to make provision for an important increase and subsequent maintenance in the level of the means and logistics targeted at the prevention and control of this weed.

The architecture of the left lateral atrial wall: A particular anatomic region with implications for ablation of atrial fibrillation

Abstract: AIMS We examined the left lateral ridge (LLR) between the orifices of the left pulmonary veins and the left atrial appendage for a better understanding of its structural composition relevant to ablations for atrial fibrillation (AF). METHODS AND RESULTS The LLR and its surrounding areas were studied in 40 heart specimens by dissection and histological sections. The LLR is a fold of the atrial wall with a mean width that was narrower superiorly than inferiorly (P < 0.001). Its myocardial thickness at the antero-superior level was thicker than at the postero-inferior level (2.8 +/- 1.1 vs. 1.7 +/- 0.8 mm, P < 0.001). Transmurally from subepicardium to subendocardium, the LLR comprises myofibres from the leftward extension of Bachmann's bundle together with the inferior branches of the septopulmonary bundle and the septoatrial bundle. The vein or ligament of Marshall is located on the epicardial aspect of the LLR. The Marshall structures and autonomic nervous system are in close proximity (<3 mm) to the endocardial surface at the superior level of the ridge in 70% of specimens. CONCLUSION The variability in width and thickness of the LLR, its proximity to Marshall structures and autonomic nerves, and myofibre arrangement may be significant in the fibrillatory process and spread of AF activity.

Basketball game-related statistics that discriminate between teams’ season-long success

Abstract: The aim of the present study was to identify the game-related statistics that discriminate between season-long successful and unsuccessful basketball teams participating in the Spanish Basketball League (LEB1). The sample included all 145 average records per season from the 870 games played between the 2000–2001 and the 2005–2006 regular seasons. The following game-related statistics were gathered from the official box scores of the Spanish Basketball Federation: 2- and 3-point field-goal attempts (both successful and unsuccessful), free-throws (both successful and unsuccessful), defensive and offensive rebounds, assists, steals, turnovers, blocks (both made and received), and fouls (both committed and received). To control for season variability, all results were normalized to minutes played each season and then converted to z-scores. The results allowed discrimination between best and worst teams’ performances through the following game-related statistics: assists (SC=0.47), steals (SC=0.34), a...

Polymorphisms of human N-acetyltransferases and cancer risk.

Abstract: Human arylamine N-acetyltransferases (CoASAc; NAT, EC 2.3.1.5) NAT1 and NAT2 play a key role in the metabolism of drugs and environmental chemicals and in the metabolic activation and detoxification of procarcinogens. Phenotyping analyses have revealed an association between NAT enzyme activities and the risk of developing several forms of cancer. As genotyping procedures have become available for NAT1 and NAT2 gene variations, hundreds of association studies on NAT polymorphisms and cancer risk have been conducted. Here we review the findings obtained from these studies. Evidence for a putative association of NAT1 polymorphism and myeloma, lung and bladder cancer, as well as association of NAT2 polymorphisms with non-Hodgkin lymphoma, liver, colorectal and bladder cancer have been reported. In contrast, no consistent evidence for a relevant association of NAT polymorphisms with brain, head & neck, breast, gastric, pancreatic or prostate cancer have been described. Although preliminary data are available, further well-powered studies are required to fully elucidate the role of NAT1 in most human cancers, and that of NAT2 in astrocytoma, meningioma, esophageal, renal, cervical and testicular cancers, as well as in leukaemia and myeloma. This review discusses controversial findings on cancer risk and putative causes of heterogeneity in the proposed associations, and it identifies topics that require further investigation, particularly mechanisms underlying association of NAT polymorphisms and risk for subsets of cancer patients with specific exposures, putative epistatic contribution of polymorphism for other xenobiotic-metabolising enzymes such as glutathione S-transferases of Cytochrome P450 enzymes, and genetic plus environmental interaction.

Ocean surface winds drive dynamics of transoceanic aerial movements.

Abstract: Global wind patterns influence dispersal and migration processes of aerial organisms, propagules and particles, which ultimately could determine the dynamics of colonizations, invasions or spread of pathogens. However, studying how wind-mediated movements actually happen has been hampered so far by the lack of high resolution global wind data as well as the impossibility to track aerial movements. Using concurrent data on winds and actual pathways of a tracked seabird, here we show that oceanic winds define spatiotemporal pathways and barriers for large-scale aerial movements. We obtained wind data from NASA SeaWinds scatterometer to calculate wind cost (impedance) models reflecting the resistance to the aerial movement near the ocean surface. We also tracked the movements of a model organism, the Cory's shearwater (Calonectris diomedea), a pelagic bird known to perform long distance migrations. Cost models revealed that distant areas can be connected through “wind highways” that do not match the shortest great circle routes. Bird routes closely followed the low-cost “wind-highways” linking breeding and wintering areas. In addition, we found that a potential barrier, the near surface westerlies in the Atlantic sector of the Intertropical Convergence Zone (ITCZ), temporally hindered meridional trans-equatorial movements. Once the westerlies vanished, birds crossed the ITCZ to their winter quarters. This study provides a novel approach to investigate wind-mediated movements in oceanic environments and shows that large-scale migration and dispersal processes over the oceans can be largely driven by spatiotemporal wind patterns.

Arginase I Induction by Modified Lipoproteins in Macrophages: A Peroxisome Proliferator-Activated Receptor-γ/δ-Mediated Effect that Links Lipid Metabolism and Immunity

Abstract: Macrophages are phagocytic cells that play essential roles in innate immunity and lipid homeostasis. The uptake of modified lipoproteins is an important early event in the development of atherosclerosis. We analyzed the ability of modified low-density lipoprotein (LDL) (oxidized and acetylated) to alter the expression and activity of arginases (ArgI and ArgII) in macrophages. We show that ArgI expression is potently induced by both oxidized and acetylated LDL in macrophages. We further show that this effect is mediated by peroxisome proliferator-activated receptors (PPAR). ArgI expression is highly responsive to agonists for PPARgamma and PPARdelta but not PPARalpha. Moreover, the induction of ArgI by both PPAR agonists and IL-4 is blocked in macrophages from PPARgamma- and PPARdelta-deficient mice. Functionally, PPAR activity induces macrophage activation toward a more Th2 immune phenotype in a model of Leishmania major infection. We show that PPARgamma and -delta ligands promote intracellular amastigote growth in infected macrophages, and this effect is dependent on both PPAR expression and Arg activity. Collectively, our results strongly suggest that ArgI is a key marker of the alternative program triggered by PPAR in macrophages.

Contribution of culture media to oxidative stress and its effect on human oocytes

Abstract: The adverse effects of reactive oxygen species (ROS) on many aspects of reproduction are well documented. However, much less is known regarding the contribution of culture media to the oxidative stress of gametes during assisted reproductive techniques. This study measured the generation of ROS by culture media during IVF procedures and its effects on human oocytes. Commercially supplied culture media generated ROS at various rates, depending on the composition, whereas follicular fluid generated ROS at a much lower level. The incubation of cumulus-oocyte complexes (COC) in culture media induced marked lipid peroxidation compared with levels found in freshly retrieved COC. This plasma membrane damage, measured with the quenching of cis-parinaric acid fluorescence assay, was attenuated by supplementation of the medium with alpha-tocopherol or catalase. Moreover, there was an association between ROS production by culture medium and thiolic content consumption within the oocytes, suggesting that the intracellular reduced glutathione pool was partially depleted during in-vitro manipulation. The results show that culture medium could damage oocytes (and consequently embryo development) depending on their composition, and it is proposed that current IVF protocols could be revised in order to decrease ROS generation.

Mathematical modelling of thin-layer infrared drying of wet olive husk

Abstract: The thin-layer infrared drying behaviour of wet olive husk (WOH) was experimentally investigated at the temperature range from 80 °C to 140 °C. The drying rate was found to increase with temperature, hence reducing the total drying time. In particular, as drying temperature was raised from 80 °C up to 140 °C, the time necessary to reduce the moisture content of the sample from 91.97 wt% down to 8.69 wt% (dry basis) changed from 105 min to 35 min. Using a non-linear regression (Marquart's method) and multiple regression analysis, a mathematical model for the thin-layer infrared drying process of WOH was proposed. The values of the diffusivity coefficients at each temperature were obtained using Fick's second law of diffusion. They varied from 5.958 × 10 −9 m 2 /s to 1.589 × 10 −8 m 2 /s over the temperature range. The temperature dependence of the effective diffusivity coefficient was described following an Arrhenius-type relationship. Activation energy for the moisture diffusion was determined as 21.30 kJ/mol.

Hydrogen sulfide raises cytosolic calcium in neurons through activation of L-type Ca2+ channels.

Abstract: Hydrogen sulfide (H(2)S) concentration can be maintained in cell cultures within the range reported for rat brain by repetitive pulses of sodium hydrogen sulfide. Less than 2 h exposure to H(2)S concentrations within 50 and 120 microM (i.e., within the upper segment of the reported physiological range of H(2)S in rat brain), produces a large shift of the intracellular calcium homeostasis in cerebellar granule neurons (CGN) in culture, leading to a large and sustained increase of cytosolic calcium concentration. Only 1 h exposure to H(2)S concentrations within 100 and 300 microM raises intracellular calcium to the neurotoxic range, with nearly 50% cell death after 2 h. L-type Ca(2+) channels antagonists nimodipine and nifedipine block both the H(2)S-induced rise of cytosolic calcium and cell death. The N-methyl-D-aspartate receptor antagonists (+)-MK-801 and DL-2-amino-5-phosphonovaleric acid afforded a nearly complete protection against H(2)S-induced CGN death and largely attenuated the rise of cytosolic calcium. Thus, H(2)S-induced rise of cytosolic calcium eventually reaches the neurotoxic cytosolic calcium range, leading to glutamate-induced excitotoxic CGN death. The authors conclude that H(2)S is a major modulator of calcium homeostasis in neurons as it induces activation of Ca(2+) entry through L-type Ca(2+) channels, and thereby of neuronal activity.