María Pérez - Academia.edu (original) (raw)

Papers by María Pérez

OTM Workshops, 2008

This volume contains the papers presented at GADA 2008, the International Symposium on Grid Compu... more This volume contains the papers presented at GADA 2008, the International Symposium on Grid Computing,High-Performance and Distributed Applications. The purpose of the GADA series of conferences, held within the framework of the OnTheMove Federated Conferences (OTM), is to bring together researchers, developers, professionals and students in order to advance research and development in the areas of grid computing and distributed systems and applications. This year’s conference was held in Monterrey, Mexico, November 13-14, 2008.

Many initiatives exist with the goal of providing the required tools to improve energy efficiency... more Many initiatives exist with the goal of providing the required tools to improve energy efficiency of households. Encouraged by public administrations, supported by the private industry, and demanded by an environmentally-aware society, several systems are gaining attention, mainly, energy consumption sensors, smart meters, and energy management platforms. The latter pretend to increase their impact and engagement with emerging social networks focused on energy efficiency matters and applying knowledge engineering disciplines. This paper describes the current home energy efficiency ecosystem, outlines some missing pieces and advances required to achieve its potential outcome, and surveys the existing social media platforms.

Free radical biology & medicine, 2002

Hepatology (Baltimore, Md.), 2003

Chronic ethanol consumption causes increased oxidative damage in the liver. Induction of CYP2E1 i... more Chronic ethanol consumption causes increased oxidative damage in the liver. Induction of CYP2E1 is one pathway involved in how ethanol produces oxidative stress. Ethanol can cause protein accumulation, decreased proteolysis, and decreased proteasome activity. The objective of this study was to investigate the effect of inhibition of the proteasome activity on CYP2E1-dependent toxicity. HepG2 cells over-expressing CYP2E1 (E47 cells) were treated with arachidonic acid (AA) plus iron, agents important in development of alcoholic liver injury and which are toxic to E47 cells by a mechanism dependent on CYP2E1, oxidative stress, and lipid peroxidation. Addition of various proteasome inhibitors was associated with significant potentiation of the loss of cell viability caused by AA plus iron. Potentiation of toxicity was associated with increased oxidative damage as reflected by an increase in lipid peroxidation and accumulation of oxidized and nitrated proteins in E47 cells and an enhanced decline in mitochondrial membrane potential. Antioxidants prevented the loss of viability and the potentiation of this loss of viability by proteasome inhibition. CYP2E1 levels were elevated about 3-fold by the proteasome inhibitors. Inhibition of proteasome activity also potentiated toxicity of AA alone and toxicity after treatment to remove glutathione (GSH). Similar results were found in hepatocytes from pyrazole-treated rats with high levels of CYP2E1. In conclusion, proteasome activity plays an important role in modulating CYP2E1-mediated toxicity in HepG2 cells by regulating CYP2E1 levels and by removal of oxidized proteins. Such interactions may be important in CYP2E1-catalyzed toxicity of hepatotoxins and in alcohol-induced liver injury.

Journal of hepatology, 2005

Journal of medicinal chemistry, Jan 26, 2007

Journal of pineal research, 2007

Maternal cholestasis is usually a benign condition for the mother but induces profound placental ... more Maternal cholestasis is usually a benign condition for the mother but induces profound placental damage and may be lethal for the fetus. The aim of this study was to investigate the protective effects in rat maternal and fetal livers as also the placenta of melatonin or silymarin against the oxidative stress and apoptosis induced by maternal obstructive cholestasis during the last third of pregnancy (OCP). Melatonin or silymarin administration (i.e. 5 mg/100 g bw/day after ligation of the maternal common bile duct on day 14 of pregnancy) reduced OCP-induced lipid peroxidation, and prevented decreases in total glutathione levels. However, the protective effect on OCP-induced impairment in the GSH/GSSG ratio was mild in the placenta and fetal liver, while absent in maternal liver. Melatonin or silymarin also reduced OCP-induced signs of apoptosis (increased caspase-3 activity and Bax-alpha upregulation) in all the organs assayed. Moreover, melatonin (but not silymarin) upregulated several proteins involved in the cellular protection against the oxidative stress in rats with OCP. These included, biliverdin-IX alpha reductase and the sodium-dependent vitamin C transport proteins SVCT1 and SVCT2, whose expression levels were enhanced in maternal and fetal liver by melatonin treatment. In contrast, in placenta only biliverdin-IX alpha reductase and SVCT2 were upregulated. These results indicate that whereas the treatment of cholestatic pregnant rats with melatonin or silymarin affords a direct protective antioxidant activity, only melatonin has dual beneficial effects against OCP-induced oxidative challenge in that it stimulates the expression of some components of the endogenous cellular antioxidant defense.

Current gastroenterology reports, 2007

Functional dyspepsia (FD) is common in children, with as many as 80% of those being evaluated for... more Functional dyspepsia (FD) is common in children, with as many as 80% of those being evaluated for chronic abdominal pain reporting symptoms of epigastric discomfort, nausea, or fullness. It is known that patients with persistent complaints have increased comorbidities such as depression and anxiety. The interaction with psychopathologic variables has been found to mediate the association between upper abdominal pain and gastric hypersensitivity. These observations suggest that abnormal central nervous system processing of gastric stimuli may be a relevant pathophysiologic mechanism in FD. Despite increased understanding, no specific therapy has emerged; however, recent nonpharmacological-based options such as hypnosis may be effective. Novel approaches, including dietary manipulation and use of nutraceuticals such as ginger and Iberogast (Medical Futures Inc., Ontario, Canada), may also be considered.

Toxicology and applied pharmacology, Jan 15, 2008

Maternal cholestasis causes oxidative damage to the placental-fetal unit that may challenge the o... more Maternal cholestasis causes oxidative damage to the placental-fetal unit that may challenge the outcome of pregnancy. This has been associated with the accumulation of biliary compounds able to induce oxidative stress. However, other cholephilic compounds such as ursodeoxycholic acid (UDCA) and bilirubin have direct anti-oxidant properties. In the present study we investigated whether these compounds exert a protective effect on cholestasis-induced oxidative stress in placenta as compared to maternal and fetal livers, and whether this is due in part to the activation of anti-oxidant mechanisms involving vitamin C uptake and biliverdin/bilirubin recycling. In human placenta (JAr) and liver (HepG2) cells, deoxycholic acid (DCA) similar rates of free radical generation. In JAr (not HepG2), the mitochondrial membrane potential and cell viability were impaired by low DCA concentrations; this was partly prevented by bilirubin and UDCA. In HepG2, taurocholic acid (TCA) and UDCA up-regulated biliverdin-IX alpha reductase (BVR alpha) and the vitamin C transporter SVCT2 (not SVCT1), whereas bilirubin up-regulated both SVCT1 and SVCT2. In JAr, TCA and UDCA up-regulated BVR alpha, SVCT1 and SVCT2, whereas bilirubin up-regulated only SVCT2. A differential response to these compounds of nuclear receptor expression (SXR, CAR, FXR and SHP) was found in both cell types. When cholestasis was induced in pregnant rats, BVR alpha, SVCT1 and SVCT2 expression in maternal and fetal livers was stimulated, and this was further enhanced by UDCA treatment. In placenta, only BVR alpha was up-regulated. In conclusion, bilirubin accumulation and UDCA administration may directly and indirectly protect the placental-fetal unit from maternal cholestasis-induced oxidative stress.

Journal of pediatric gastroenterology and nutrition, 2010

Investigators may have concerns that parents will not allow their children to participate in plac... more Investigators may have concerns that parents will not allow their children to participate in placebo-controlled trials (PCTs). The aim of the present study was to identify potential differences between parental perceptions in families who successfully completed (CO) a clinical trial compared with those who were noncompleters (NC). Parents of both CO and NC children enrolled in pediatric gastrointestinal studies performed in the previous year were eligible. NC were defined as those who were screen failures or treatment nonresponders or had adverse events. One hundred seven parents were identified and mailed a 26-item questionnaire eliciting perceptions regarding participation in research. Questionnaires were sent 6 months after participation in research ended. Seventy-eight (69%) parents returned the survey. Characteristics included maternal responders (98%), English as primary language (97%), and education beyond high school (85%). Five parents (4.7%) had children involved in previous research trials. There were no significant differences in responses found between CO (n = 49; 63%) and NC (n = 29; 37%) in regard to importance of research, perceptions of risk to child, benefits to child, and more attention in the study. Statistical significance was approached in regard to the comfort with the research team, with a greater portion of CO stating that the researcher put the parent at ease and the NC feeling less positive about the interaction (P = 0.05). A positive perception about participation in research is not stratified by successful completion of a PCT. These results should encourage investigators and institutional review boards that if properly designed and conducted, pediatric PCTs can result in a positive experience for parents.

Medical mycology, 2014

Many bloodstream infections (BSI) in patients with central venous catheters (CVC) are not cathete... more Many bloodstream infections (BSI) in patients with central venous catheters (CVC) are not catheter-related (CR). Assessment of catheter involvement without catheter withdrawal has not been studied in candidemia. We assessed the value of conservative techniques to evaluate catheters as the origin of candidemia in patients with CVC in a prospective cohort study (superficial Gram stain and culture, Kite technique (Gram stain and culture of the first 1 cm blood drawn from the CVC), proportion of positive blood cultures (PPBCs), differential time to positivity (DTP), and minimal time to positivity (MTP)). All catheters were cultured at withdrawal. From June 2008 to January 2012, 22 cases fulfilled the inclusion criteria. CR-candidemia (CRC) was confirmed in 10. Validity values for predicting CRC were: superficial Gram stain (S, 30%; Sp, 81.83%; PPV, 60%; NPV, 56.3%; Ac, 57.1%), superficial cultures (S, 40%; Sp, 75%; PPV, 57.1%; NPV, 60%; Ac, 59.1%), Kite Gram stain (S, 33.3%; Sp, 66.7%; PPV, 50%; NPV, 50%; Ac, 50%), Kite culture (S, 80%; Sp, 66.7%; PPV, 66.7%; NPV, 80%; Ac, 72.7%), PPBC (S, 50%; Sp, 41.7%; PPV, 41.7%; NPV, 50.0%; Ac, 45.5%), DTP (S, 100%; Sp, 33.3%; PPV, 55.6%; NPV, 100%; Ac, 63.6%), and MTTP (S, 70%; Sp, 58.3%; PPV, 58.3%; NPV, 70%; Ac, 63.6%). While combinations of two tests improved sensitivity and NPV, more than two tests did not improve validity values. Classic tests to assess CR-BSI caused by bacteria cannot be reliably used to diagnose CRC. Combinations of tests could be useful, but more and larger studies are required.

Grid constitutes a new computing paradigm, which inherits a great number of its features from dis... more Grid constitutes a new computing paradigm, which inherits a great number of its features from distributed systems. This new paradigm enables resource-sharing across networks, being data one of the most important ones. Data-intensive grid systems are grid applications, whose major goal is to provide efficient access to data. Existing data-intensive applications have been used in several domains, such as physics, climate modeling, biology or visualization. The I/O problem is not completely solved in this kind of applications. This chapter presents MAPFS as a flexible and high-performance platform for data-intensive applications and, more specifically, for data grid applications.

Abstract. Grid computing,has become,one of the most,important topics appeared and widely develope... more Abstract. Grid computing,has become,one of the most,important topics appeared and widely developed in the computing,field in the last decade. One of the major goals of grid computing is to provide an efficient access to data, being data-intensive grid systems one of the most relevant grid applications. Existing data-intensive applications have been used in several domains, such as physics, climate modeling, biology or visualization. The I/O problem is not completely resolved in this kind of applications.

Neurotoxicology, 2006

This study addresses the participation of radiation-induced free radicals, mainly nitric oxide (N... more This study addresses the participation of radiation-induced free radicals, mainly nitric oxide (NO), in modulating the apoptotic response in an in vitro model of neural cortical precursor cells exposed to γ-radiation. Cortical cells obtained from rats at 17 gestational day (GD) were irradiated with a dose of 2 Gy. The percentage of apoptotic cells was significantly increased 4 h post-irradiation (pi). NO content showed a significant increase after 30 min pi and the rate of generation reached a maximum 1 h pi. Luminol-dependent chemiluminescence (CL) was significantly higher in cells after 2 h pi as compared to control cells and this profile was maintained up to 4 h pi. Supplementation with l-NAME significantly increased light emission. Administration of superoxide dismutase (SOD) following l-NAME addition prevented the observed changes due to l-NAME administration. The caspase inhibitor zDEVD-fmk significantly reduced the radical generation. Moreover, the cellular decrease in NO content occurred coincidentally with the rise in oxygen radical generation and the activation of caspase-3. In vitro irradiation of neural precursor cells allowed us to suggest that an early radiation-induced generation of NO could exert a neuroprotective role. However, despite this NO initial protective effect and its role modulating the response against γ-radiation, NO generation was not able of fully preventing radiation-induced apoptosis.

Telomeres and genomic damage repair. Their implication in human pathology. Telomeres, functional ... more Telomeres and genomic damage repair. Their implication in human pathology. Telomeres, functional complexes that protect eukaryotic chromosome ends, participate in the regulation of cell proliferation and could play a role in the stabilization of genomic regions in response to genotoxic stress. Their significance in human pathology becomes evident in several diseases sharing genomic instability as a common trait, in which