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Search Results: 1 - 10 of 412634 matches for " O. S. Leon "
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Nimesulide limits kainate-induced oxidative damage in the rat hippocampus
E. Candelario-Jalil,H. H. Ajamieh,S. Sam,G. Martinez,O. S. Leon
Quantitative Biology , 2007,
Abstract: Kainate induces a marked expression of cyclooxygenase-2 after its systemic administration. Because cyclooxygenase-2 activity is associated to the production of reactive oxygen species, we investigated the effects of nimesulide, a selective cyclooxygenase-2 inhibitor, on kainate-induced in vivo oxidative damage in the rat hippocampus. A clinically relevant dose of nimesulide (6 mg/kg, i.p.) was administered three times following kainate application (9 mg/kg, i.p.). After 24 h of kainate administration, the drastic decrease in hippocampal glutathione content and the significant increase in lipid peroxidation were attenuated in nimesulide-treated rats, suggesting that the induction of cyclooxygenase-2 is involved in kainate-mediated free radicals formation.
Characterization of Contaminants from a Sanitized Milk Processing Plant
Sara Cleto, Sónia Matos, Leon Kluskens, Maria Jo?o Vieira
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0040189
Abstract: Milk processing lines offer a wide variety of microenvironments where a diversity of microorganisms can proliferate. We sampled crevices and junctions where, due to deficient reach by typical sanitizing procedures, bacteria can survive and establish biofilms. The sampling sites were the holding cell, cold storage tank, pasteurizer and storage tank - transfer pump junction. The culturable bacteria that were isolated after the sanitation procedure were predominantly Pseudomonas spp., Serratia spp, Staphylococcus sciuri and Stenotrophomonas maltophilia. We assayed several phenotypic characteristics such as the ability to secrete enzymes and siderophores, as well as the capacity of the strains to form biofilms that might contribute to their survival in a mixed species environment. The Pseudomonas spp. isolates were found to either produce proteases or lecithinases at high levels. Interestingly, protease production showed an inverse correlation with siderophore production. Furthermore, all of the Serratia spp. isolates were strong biofilm formers and spoilage enzymes producers. The organisms identified were not mere contaminants, but also producers of proteins with the potential to lower the quality and shelf-life of milk. In addition, we found that a considerable number of the Serratia and Pseudomonas spp. isolated from the pasteurizer were capable of secreting compounds with antimicrobial properties.
Back and neck pain are related to mental health problems in adolescence
Clare S Rees, Anne J Smith, Peter B O'Sullivan, Garth E Kendall, Leon M Straker
BMC Public Health , 2011, DOI: 10.1186/1471-2458-11-382
Abstract: One thousand five hundred and eighty participants (mean age 14.1 years) from the Western Australian Pregnancy (Raine) Study provided cross-sectional spinal pain and CBCL data.As predicted, there was a high prevalence of back and neck pain in this cohort. On the whole, females reported more mental health difficulties than males. There were strong relationships between the majority of symptom scales of the CBCL and back and neck pain. Scores on the CBCL were associated with higher odds of comorbid back and neck pain.These findings strongly support the need to consider both psychological and pain symptoms when providing assessments and treatment for adolescents. Further research is required to inform causal models.Significant biological, emotional, intellectual and social changes take place during adolescence and mental health problems are relatively common in this age group. The population point- prevalence of mental health disorder in those aged between 13 and 17 years residing in Australia and the United States has been reliably estimated at around 11% - 12% [1,2]. Adolescent mental health problems may be short-term states, or persistent long-term patterns [3]. Persistent long-term patterns are of concern as they may be precursors of adult psychopathology. Many of the common forms of child and adolescent mental health problems are substantially correlated [4]. Notwithstanding this, many adult disorders, such as major depression and social phobia, definitely occur in childhood and adolescence, starting much earlier than used to be thought possible [5]. For example, major depression is a common and serious disorder of adolescence. Lifetime prevalence increases dramatically from 1% of the population under 12 to approximately 17% - 25% by the end of adolescence [6]. Genetic factors and exposure to early adversity in the form of socioeconomic disadvantage, parental mental illness or substance use, family dysfunction, and stressful life-events are key risk factors [6,7].
K-symplectic formalism on Lie algebroids
M. de Leon,D. Martin de Diego,M. Salgado,S. Vilari?o
Physics , 2009, DOI: 10.1088/1751-8113/42/38/385209
Abstract: In this paper we introduce a geometric description of Lagrangian and Hamiltonian classical field theories on Lie algebroids in the framework of k-symplectic geometry. We discuss the relation between Lagrangian and Hamiltonian descriptions through a convenient notion of Legendre transformation. The theory is a natural generalization of the standard one; in addition, other interesting examples are studied, in particular, systems with symmetry and Poisson sigma models.
Nonholonomic constraints in $k$-symplectic Classical Field Theories
M. de Leon,D. Martin de Diego,M. Salgado,S. Vilari?o
Physics , 2008, DOI: 10.1142/S0219887808003077
Abstract: A $k$-symplectic framework for classical field theories subject to nonholonomic constraints is presented. If the constrained problem is regular one can construct a projection operator such that the solutions of the constrained problem are obtained by projecting the solutions of the free problem. Symmetries for the nonholonomic system are introduced and we show that for every such symmetry, there exist a nonholonomic momentum equation. The proposed formalism permits to introduce in a simple way many tools of nonholonomic mechanics to nonholonomic field theories.
Abundant Molecular Gas in Tidal Dwarf Galaxies: On-going Galaxy Formation
J. Braine,P. -A. Duc,U. Lisenfeld,V. Charmandaris,O. Vallejo,S. Leon,E. Brinks
Physics , 2001, DOI: 10.1051/0004-6361:20011109
Abstract: [Abridged...] We investigate the process of galaxy formation as can be observed in the only currently forming galaxies -- the so-called Tidal Dwarf Galaxies, hereafter TDGs -- through observations of the molecular gas detected via its CO emission. These objects are formed of material torn off of the outer parts of a spiral disk due to tidal forces in a collision between two massive galaxies. Molecular gas is a key element in the galaxy formation process, providing the link between a cloud of gas and a bona fide galaxy. We have detected CO in 8 TDGs (two of them have already been published in Braine et al. 2000), with an overall detection rate of 80%, showing that molecular gas is abundant in TDGs, up to a few 10^8 M_sun. The CO emission coincides both spatially and kinematically with the HI emission, indicating that the molecular gas forms from the atomic hydrogen where the HI column density is high. A possible trend of more evolved TDGs having greater molecular gas masses is observed, in accord with the transformation of HI into H2.... Although higher spatial resolution CO (and HI) observations would help reduce the uncertainties, we find that TDGs require no dark matter, which would make them the only galaxy-sized systems where this is the case. Dark matter in spirals should then be in a halo and not a rotating disk. Most dwarf galaxies are dark matter-rich, implying that they are not of tidal origin....
Star Formation in Tidal Dwarf Galaxies
U. Lisenfeld,J. Braine,O. Vallejo,P. -A. Duc,S. Leon,E. Brinks,V. Charmandaris
Physics , 2001,
Abstract: Tidal Dwarf Galaxies (TDGs) are objects presently forming from gas which has been expelled from their parent galaxies during an interaction. We observed the CO emission of a sample of 11 TDGs, of which 8 were detected. The CO is found at the peak of the HI observations and has the same line velocity and width, indicating that the molecular gas is forming in situ instead of being torn from the parent galaxies. The presence of H$\alpha$ emission furthermore shows that stars are forming from this molecular gas. In order to investigate star formation in TDGs further, we compared their molecular gas content and star formation rate (SFR), traced by H$\alpha$, to those of spiral galaxies and classical dwarfs. The major difference between TDGs and classical dwarfs is the lower metallicity of the latter. The star formation efficiency (SFR per molecular gas mass) of TDGs lies in the range typical of spiral galaxies indicating that star formation is proceeding in a normal fashion from molecular gas.
Characterization of hexabundles: Initial results
J. J. Bryant,J. W. O'Byrne,J. Bland-Hawthorn,S. G. Leon-Saval
Physics , 2011, DOI: 10.1111/j.1365-2966.2011.18841.x
Abstract: New multi-core imaging fibre bundles -- hexabundles -- being developed at the University of Sydney will provide simultaneous integral field spectroscopy for hundreds of celestial sources across a wide angular field. These are a natural progression from the use of single fibres in existing galaxy surveys. Hexabundles will allow us to address fundamental questions in astronomy without the biases introduced by a fixed entrance aperture. We have begun to consider instrument concepts that exploit hundreds of hexabundles over the widest possible field of view. To this end, we have compared the performance of a 61-core fully-fused hexabundle and 5 lightly-fused bundles with 7 cores each. All fibres in the bundles have 100 micron cores. In the fully-fused bundle, the cores are distorted from a circular shape in order to achieve a higher fill fraction. The lightly-fused bundles have circular cores and five different cladding thicknesses which affect the fill fraction. We compare the optical performance of all 6 bundles and find that the advantage of smaller interstitial holes (higher fill fraction) is outweighed by the increase in modal coupling, cross-talk and the poor optical performance caused by the deformation of the fibre cores. Uniformly high throughput and low cross-talk are essential for imaging faint astronomical targets with sufficient resolution to disentangle the dynamical structure. Devices already under development will have between 100 and 200 lightly-fused cores, although larger formats are feasible. The light-weight packaging of hexabundles is sufficiently flexible to allow existing robotic positioners to make use of them.
Effects of pyruvate administration on infarct volume and neurological deficits following permanent focal cerebral ischemia in rats
A. Gonzalez-Falcon,E. Candelario-Jalil,M. Garcia-Cabrera,O. S. Leon
Quantitative Biology , 2007,
Abstract: Recent experimental evidences indicate that pyruvate, the final metabolite of glycolysis, has a remarkable protective effect against different types of brain injury. The purpose of this study was to assess the neuroprotective effect and the neurological outcome after pyruvate administration in a model of ischemic stroke induced by permanent middle cerebral artery occlusion (pMCAO) in rats. Three doses of pyruvate (250, 500 and 1000 mg/kg, i.p.) or vehicle were administered intraperitoneally 30 min after pMCAO. In other set of experiments, pyruvate was given either before, immediately after ischemia or in a long-term administration paradigm. Functional outcome, mortality and infarct volume were determined 24 h after stroke. Even when the lowest doses of pyruvate reduced mortality and neurological deficits, no concomitant reduction in infarct volume was observed. The highest dose of pyruvate increased cortical infarction by 27% when administered 30 min after pMCAO. In addition, when pyruvate was given before pMCAO, a significant increase in neurological deficits was noticed. Surprisingly, on the contrary of what was found in the case of transient global ischemia, present findings do not support a great neuroprotective role for pyruvate in permanent focal cerebral ischemia, suggesting two distinct mechanisms involved in the effects of this glycolytic metabolite in the ischemic brain.
Delayed treatment with nimesulide reduces measures of oxidative stress following global ischemic brain injury in gerbils
E. Candelario-Jalil,D. Alvarez,N. Merino,O. S. Leon
Quantitative Biology , 2007,
Abstract: Metabolism of arachidonic acid by cyclooxygenase is one of the primary sources of reactive oxygen species in the ischemic brain. Neuronal overexpression of cyclooxygenase-2 has recently been shown to contribute to neurodegeneration following ischemic injury. In the present study, we examined the possibility that the neuroprotective effects of the cyclooxygenase-2 inhibitor nimesulide would depend upon reduction of oxidative stress following cerebral ischemia. Gerbils were subjected to 5 min of transient global cerebral ischemia followed by 48 h of reperfusion and markers of oxidative stress were measured in hippocampus of gerbils receiving vehicle or nimesulide treatment at three different clinically relevant doses (3, 6 or 12 mg/kg). Compared with vehicle, nimesulide significantly (P<0.05) reduced hippocampal glutathione depletion and lipid peroxidation, as assessed by the levels of malondialdehyde (MDA), 4-hydroxy-alkenals (4-HDA) and lipid hydroperoxides levels, even when the treatment was delayed until 6 h after ischemia. Biochemical evidences of nimesulide neuroprotection were supported by histofluorescence findings using the novel marker of neuronal degeneration Fluoro-Jade B. Few Fluoro-Jade B positive cells were seen in CA1 region of hippocampus in ischemic animals treated with nimesulide compared with vehicle. These results suggest that nimesulide may protect neurons by attenuating oxidative stress and reperfusion injury following the ischemic insult with a wide therapeutic window of protection.
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