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Biomedical subjects

M A García

Publications and source records attributed to M A García.

At least 19 recordsLinked to original sources
PubMed2007

Ground laser remote sensing measurements of a Saharan dust outbreak in Central Spain. Influence on PM10 concentrations in the lower and upper Spanish plateaus.

This paper presents the hourly evolution of a severe Saharan dust outbreak, (SDO), affecting Central Spain over July 23-24, 2004 measured with a laser remote sensing device at a location close to the Guadarrama mountain range foothills and its impact on PM10 levels (particles with an aerodynamic diameter below 10 microm) recorded at four contrasting monitoring stations located in the upper and lower Spanish plateau, some 170km apart. During the period of study the Saharan dust layer, (SDL), presented significant hourly variability in height (3600-1500m), depth (1500-700m) and aerosol dust loading (extinction coefficient, EC, 0.22-1.28km(-1)). Overnight layering was generally observed whereas a well mixed layer prevailed in the afternoon. The (SDO) impact on the lower levels took place approximately 12h after the (SDL) was initially observed and triggered by a descending dust enriched, evidencing the important role of subsidence over the presence of dust in lower altitudes. During the event, PM10 levels at all the stations exceeded EU air quality daily mean standards, 50 microgm(-3), on 2-4days. The maximum values ranged from 185 to 245 microgm(-3) depending on the monitoring station. The impact on PM10 spread from 2days in the upper plateau to 3-4 in the lower plateau, in agreement with the geographical location of the monitoring stations with respect to the southwest origin of the intrusion. The impact was even more dramatic on PM10 hourly concentrations, leading to maximum hourly peaks ranging from 322 to 598 microgm(-3) again depending on the monitoring station. Correlations between EC vertical profiles and PM10 hourly concentrations at the monitoring stations showed the great influence of the (SDO) on surface concentrations. The best linear fits corresponded to the extinction coefficients in the lower altitudes (close to the lower range of the device 500-650m), EC2, yielding satisfactory correlation coefficients ranging from 0.68 to 0.71. The low variability of the slope of each individual linear fit, 19.2%, shows the similar impact of (SDO) on the PM10 hourly concentrations recorded in the area under study.

Air Movements↗
PubMed2006

No evidence of association between genetic variants of the PDCD1 ligands and SLE.

PDCD1, an immunoreceptor involved in peripheral tolerance has previously been shown to be genetically associated with systemic lupus erythematosus (SLE). PDCD1 has two ligands whose genes are located in close proximity on chromosome 9p24. Our attention was drawn to these ligands after finding suggestive linkage to a marker (gata62f03, Z=2.27) located close to their genes in a genome scan of Icelandic families multiplex for SLE. Here, we analyse Swedish trios (N=149) for 23 single nucleotide polymorphisms (SNPs) within the genes of the PDCD1 ligands. Initially, indication of association to eight SNPs was observed, and these SNPs were therefore also analysed in Mexican trios (N=90), as well as independent sets of patients and controls from Sweden (152 patients, 448 controls) and Argentina (288 patients, 288 controls). We do not find support for genetic association to SLE. This is the first genetic study of SLE and the PDCD1 ligands and the lack of association in several cohorts implies that these genes are not major risk factors for SLE.

Antigens, CD↗
PubMed2006

Fe impurities weaken the ferromagnetic behavior in Au nanoparticles.

In this Letter, we report on a crucial experiment showing that magnetic impurities reduce the ferromagnetic order temperature in thiol-capped Au glyconanoparticles (GNPs). The spontaneous magnetization of AuFe GNPs exhibits a fast decrease with temperature that contrasts with the almost constant value of the magnetization observed in Au NPs. Moreover, hysteresis disappears below 300 K. Both features indicate that Fe impurities reduce the high local anisotropy field responsible for the ferromagnetic behavior in Au GNPs. As a consequence, the amazing ferromagnetism in Au NPs should not be associated with the presence of magnetic impurities.

Journal Article↗
PubMed2006

Vitreous SiO2-CaO coatings on Ti6Al4V alloys: reactivity in simulated body fluid versus osteoblast cell culture.

Vitreous coatings of the SiO(2)-CaO system have been prepared on Ti6Al4V substrates by the sol-gel method. The textural parameters (porosity and roughness) and thickness of the films obtained increase when the concentration of the precursor solutions is raised. In vitro studies of these coatings have been performed using two approaches: soaking in simulated body fluid, and by growing osteoblasts on these materials. The results of both studies show differences in terms of chemical reactivity. While in simulated body fluid the coatings were dissolved without forming a bioactive surface, when osteoblast-like cells grew on the coatings they were more stable. Furthermore, cell culture assays show biocompatible behavior of these coatings making them of potential interest for clinical applications. The effect of the textural parameters of the obtained coatings on the cell functions (attachment, spreading, proliferation and differentiation) has also been studied. The results show an increase in these cell parameters as the roughness and porosity of the coatings increase.

Alkaline Phosphatase↗
PubMed2006

Origin of orbital ferromagnetism and giant magnetic anisotropy at the nanoscale.

The origin of orbital magnetism recently observed in different nanostructured films and particles is discussed as a consequence of spin-orbit coupling. It is shown that contact potentials induced at the thin film surface by broken symmetries, as domain boundaries in self-assembled monolayers, lead to orbital states that in some cases are of large radius. The component of the angular momentum normal to the surface can reach very high values that decrease the total energy by decreasing spin-orbit interaction energy. Intraorbital ferromagnetic spin correlations induce orbital momenta alignment. The estimated values of the magnetic moments per atom are in good agreement with the experimental observations in thiol capped gold films and nanoparticles.

Journal Article↗
PubMed2006

Impact of protein kinase PKR in cell biology: from antiviral to antiproliferative action.

The double-stranded RNA-dependent protein kinase PKR is a critical mediator of the antiproliferative and antiviral effects exerted by interferons. Not only is PKR an effector molecule on the cellular response to double-stranded RNA, but it also integrates signals in response to Toll-like receptor activation, growth factors, and diverse cellular stresses. In this review, we provide a detailed picture on how signaling downstream of PKR unfolds and what are the ultimate consequences for the cell fate. PKR activation affects both transcription and translation. PKR phosphorylation of the alpha subunit of eukaryotic initiation factor 2 results in a blockade on translation initiation. However, PKR cannot avoid the translation of some cellular and viral mRNAs bearing special features in their 5' untranslated regions. In addition, PKR affects diverse transcriptional factors such as interferon regulatory factor 1, STATs, p53, activating transcription factor 3, and NF-kappaB. In particular, how PKR triggers a cascade of events involving IKK phosphorylation of IkappaB and NF-kappaB nuclear translocation has been intensively studied. At the cellular and organism levels PKR exerts antiproliferative effects, and it is a key antiviral agent. A point of convergence in both effects is that PKR activation results in apoptosis induction. The extent and strength of the antiviral action of PKR are clearly understood by the findings that unrelated viral proteins of animal viruses have evolved to inhibit PKR action by using diverse strategies. The case for the pathological consequences of the antiproliferative action of PKR is less understood, but therapeutic strategies aimed at targeting PKR are beginning to offer promising results.

Animals↗
PubMed2005

Metallic magnetic nanoparticles.

In this paper, we reviewed some relevant aspects of the magnetic properties of metallic nanoparticles with small size (below 4 nm), covering the size effects in nanoparticles of magnetic materials, as well as the appearance of magnetism at the nanoscale in materials that are nonferromagnetic in bulk. These results are distributed along the text that has been organized around three important items: fundamental magnetic properties, different fabrication procedures, and characterization techniques. A general introduction and some experimental results recently obtained in Pd and Au nanoparticles have also been included. Finally, the more promising applications of magnetic nanoparticles in biomedicine are indicated. Special care was taken to complete the literature available on the subject.

Anisotropy↗
PubMed2005

Identification of a nuclear export signal in the KSHV latent protein LANA2 mediating its export from the nucleus.

LANA2 is a latent protein detected in Kaposi's sarcoma-associated herpesvirus (KSHV)-infected B cells that inhibits p53-dependent transcriptional transactivation and apoptosis and PKR-dependent apoptosis, suggesting an important role in the transforming activity of the virus. It has been reported that LANA2 localizes into the nucleus of both KSHV-infected B cells and transiently transfected HeLa cells. In this study, we show that LANA2 is a nucleocytoplasmic shuttling protein that requires a Rev-type nuclear export signal located in the C-terminus to direct the protein to the cytoplasm, through an association with the export receptor CRM1. In addition, a functional protein kinase B (PKB)/Akt phosphorylation motif partially overlapping with the nuclear export signal was identified. Nuclear exclusion of LANA2 was negatively regulated by the phosphorylation of threonine 564 by Akt. The ability of LANA2 to shuttle between nucleus and cytoplasm has implications for the function of this viral protein.

Active Transport, Cell Nucleus↗
PubMed2005

Ground level ozone concentrations at a rural location in northern Spain.

A systematic analysis of surface ozone observations at a rural area of the upper Spanish plateau is presented. A near four-year study of ozone concentrations was carried out between February 2000 and October 2003. Diurnal and monthly variations of ozone are studied. The peak concentration levels are obtained between 13:00 and 15:00 GMT and the lowest levels at 4:00 and 5:00 GMT. The highest values together with a slight increase in data variability are found from April to August, when spring and summer maxima are appreciated. The relationship between synoptic-scale atmospheric transport patterns and the maximum ozone concentrations was also examined. Analysis of the 500-hPa synoptic weather patterns revealed that the highest values occur during continental and Atlantic ridges in summer and, to a lesser extent, during troughs in the east-northeast of the Iberian Peninsula in spring. Our approach entailed calculating 3-day isobaric backward air mass trajectories at the observational site sorted on the following main origins: European continent, African continent, Atlantic Ocean and local. The assessment of the results showed the influence of local conditions on the daily maximum ozone concentrations. Moreover, continental air masses provide certain evidence of long-range transport added to the local or regional contribution of the main cities affecting the sampling site. Conversely, Atlantic trajectories show the least contribution to ozone levels.

Air Movements↗
PubMed2005

Analysis of forced wheezes in asthma patients.

BACKGROUND: Spirometric parameters can be normal in many stable asthma patients, making a diagnosis difficult at certain times in the course of disease. OBJECTIVES: The present study aims to find differences and similarities in the acoustic characteristics of forced wheezes among asthma patients with and without normal spirometric values. METHODS: Eleven chronic asthma patients (8 men/3 women) with moderate-to-severe airway obstruction (FEV1 48.4%), 9 stable asthma patients (6 males/3 females) with normal spirometry (FEV1 84.0%) and a positive methacholine test and 14 healthy subjects (8/6) were enrolled in the study. A contact sensor was placed on the trachea, and wheezes were detected by a modified Shabtai-Musih algorithm in a time-frequency representation. RESULTS: More wheezes were recorded in obstructive asthma patients than in stable asthma and control subjects: nonstable asthma 13.6 (13.3), stable asthma 3.5 (3.0) and control subjects 2.5 (2.1). The mean frequency of all wheezes detected was higher in control subjects than in either stable or non-stable asthma patients. The change in the total number of wheezes after terbutaline inhalation was more pronounced in nonstable asthma patients than in stable asthmatics and control subjects. CONCLUSIONS: This study confirms that wheeze recording during forced expiratory maneuvers can be a complementary measure to spirometry to identify asthma patients.

Acoustics↗
PubMed2005

Interface double-exchange ferromagnetism in the Mn-Zn-O system: new class of biphase magnetism.

In this Letter, we experimentally show that the room temperature ferromagnetism in the Mn-Zn-O system recently observed is associated with the coexistence of Mn(3+) and Mn(4+) via a double-exchange mechanism. The presence of the ZnO around MnO(2) modifies the kinetics of MnO(2)-->Mn(2)O(3) reduction and favors the coexistence of both Mn oxidation states. The ferromagnetic phase is associated with the interface formed at the Zn diffusion front into Mn oxide, corroborated by preparing thin film multilayers that exhibit saturation magnetization 2 orders of magnitude higher than bulk samples.

Journal Article↗
PubMed2005

Ozone concentrations at a high altitude station in the Central Massif (Spain).

In order to contribute to current knowledge of ozone concentrations and transport across the Central Massif, a monitoring station was installed at 1780 m on the upper Spanish plateau about 55 km from the city of Madrid. Ozone concentrations and standard meteorological variables were measured in June and July 2002. A smoothed ozone hourly cycle was obtained with mean values of 120 and 110 microgm(-3) during day-time and night-time, respectively. The highest ozone concentrations were recorded in the SE-S-SW wind sectors, proving the influence of transport from the Madrid urban plume to the upper plateau. This assumption was also supported by the satisfactory correlation between ozone peaks obtained at the monitoring site and those recorded in a representative station on the foothill located on the lower plateau during episodic situations. To assess the contribution of long-range transport, backward air mass trajectories were computed each day of measurements at 820 hPa. The lowest ozone mean was linked to Atlantic Ocean air masses, and the highest to air masses from Central Europe.

Air Movements↗
PubMed2004

Permanent magnetism, magnetic anisotropy, and hysteresis of thiol-capped gold nanoparticles.

We report on the experimental observation of magnetic hysteresis up to room temperature in thiol-capped Au nanoparticles with 1.4 nm size. The coercive field ranges from 860 Oe at 5 K to 250 Oe at 300 K. It is estimated that the Au atoms exhibit a magnetic moment of mu=0.036mu(B). However, Au nanoparticles with similar size but stabilized by means of a surfactant, i.e., weak interaction between protective molecules and Au surface atoms, are diamagnetic, as bulk Au samples are. The apparent ferromagnetism is consequently associated with 5d localized holes generated through Au-S bonds. These holes give rise to localized magnetic moments that are frozen in due to the combination of the high spin-orbit coupling (1.5 eV) of gold and the symmetry reduction associated with two types of bonding: Au-Au and Au-S.

Journal Article↗
PubMed2004

Low-grade MgO used to stabilize heavy metals in highly contaminated soils.

Low-grade MgO may be an economically feasible alternative in the stabilization of heavy metals from heavily contaminated soils. The use of MgO is described acting as a buffering agent within the pH 9-11 range, minimizing heavy metals solubility and avoiding the redissolution that occurs when lime is used. The effectiveness of LG-MgO has been studied as stabilizer agent of heavily polluted soils mainly contaminated by the flue-dust of the pyrite roasting. The use of LG-MgO as a reactive medium ensures that significant rates of metal fixation, greater than 80%, are achieved. The heavy metals leachate from the stabilized soil samples show a concentration lower than the limit set to classify the waste as non-special residue. Regardless of the quantity of stabilizer employed (greater than 10%), LG-MgO provides an alkali reservoir that allows guaranteeing long-term stabilization without varying the pH conditions.

Environmental Pollution↗
PubMed2003

Patterns in the precision of quantitative data from multicomponent gas chromatographic or gas chromatographic-mass spectrometric analysis.

The dispersion of the quantitative results in the analysis of volatile compounds from multicomponent mixtures by different fractionation techniques (solid-phase microextraction and direct thermal desorption) followed by GC or GC-MS presents nonrandom patterns related to the existence of different factors in the fractionation process or in the chromatographic separation which affect, to a different extent, the recovery of the sample components. Statistical techniques have been used to show the relative importance of these factors. The improvement in data precision achieved by using volatile compound concentration ratios is discussed.

Chromatography, Gas↗
PubMed2003

The concentrations and bioconcentration factors of copper and zinc in edible mushrooms.

Copper and zinc contents have been determined in up to 28 species of edible mushrooms from different sites in the province of Lugo (NW Spain). Two hundred thirty-eight collected samples were analyzed by an anodic stripping voltammetric technique using a drop mercury as the working electrode. The results showed that the element concentrations were species-dependent, and the highest metal levels corresponded to the following species: Calvatia utriformis (235.5 mg Cu/kg), Macrolepiota procera (217.8 mg Cu/kg), and Agaricus macrosporus (217.7 mg Cu/kg) and Calvatia utriformis (265.8 mg Zn/kg), Lactarius delicious (231.0 mg Zn/kg), and Agaricus macrosporus (221.3 mg Zn/kg) for Cu and Zn, respectively. All mushroom species bioaccumulated copper and zinc. Nevertheless, some individual samples of the species, such as Hydnum repandum, Cantharellus cibarius, and Coprinus comatus, were bioexclusors (BCF < 1). The hymenophore in mushrooms showed higher mean metal levels than the rest of the fruit bodies, with statistically significant differences. The copper and zinc concentrations were compared to literature data and levels set by legislation. It can be concluded that the consumption of these mushrooms cannot be considered a toxicological risk, and they provide an important nutritional requirement to the diet.

Agaricales↗
PubMed2003

Assessment of drinking water contamination at springs along the road to Santiago (NW Spain).

With the aim of assessing the potability of drinking water, 31 different springs sited along the road to Santiago "The French Way" in Galicia (NW Spain) were studied. Twenty-one parameters, according to Spanish Legislation have been determined by Official Methods. It was observed that the parameters: pH, nitrate, ammonia, total coliforms, fecal coliforms and fecal streptococcus did not always comply with the levels established by Spanish Legislation. The bacteriological characters were the most restrictive of the sanitary quality of drinking water, only 19% of the springs were drinkable during all the study. According to the Factorial Analysis in Principal Component applied to the obtained results, it was concluded that the parameters: conductivity, hardness, dry residue, nitrate and fecal coliforms can be very indicative for assessing water sanitary quality.

Ammonia↗