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A Medina

Publications and source records attributed to A Medina.

At least 19 recordsLinked to original sources
PubMed2006

Variability and characterization of mycotoxin-producing Fusarium spp isolates by PCR-RFLP analysis of the IGS-rDNA region.

In the present report, a total of 75 Fusarium spp isolates (35 of the Gibberella fujikuroi species complex, 26 of F. oxysporum, 7 of F. graminearum, 5 of F. culmorum, 1 of F. cerealis, and 1 of F. poae) from different hosts were characterized morphologically, physiologically and genetically. Morphological characterization was performed according to macroscopic and microscopic aspects. Physiological characterization was based on their ability to produce fumonisin B1 (FB1), fumonisin B2 (FB2), zearalenone (ZEA) and type B trichothecenes (deoxynivalenol, nivalenol and 3-acetyldeoxynivalenol). FB1, FB2, and ZEA were determined by liquid chromatography and trichothecenes by gas chromatography. Molecular characterization of isolates was carried out using an optimized and simple method for isolation of DNA from filamentous fungi and polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) of the intergenic spacer region (IGS) of the rDNA. The results indicated that G. fujikuroi complex isolates can be divided into low and high fumonisin producers. The haplotypes obtained with HhaI, EcoRI, AluI, PstI and XhoI enzymes provided very characteristic groupings of G. fujikuroi isolates as a function of host type and fumonisin producing capacity. F. graminearum, F. culmorum and F. cerealis isolates were high ZEA and type B trichothecene producers, while F. oxysporum and the G. fujikuroi complex isolates did not show this ability. The haplotypes obtained with CfoI, AluI, HapII, XhoI, EcoRI and PstI enzymes permitted to discern these five Fusarium species and G. fujikuroi complex isolates but the restriction patterns of the IGS region did not show any relationship with the geographic origin of isolates.

DNA, Fungal↗
PubMed2006

Transmission electron microscopy and theoretical analysis of AuCu nanoparticles: atomic distribution and dynamic behavior.

Though the application of bimetallic nanoparticles is becoming increasingly important, the local atomistic structure of such alloyed particles, which is critical for tailoring their properties, is not yet very clearly understood. In this work, we present detailed study on the atomistic structure of Au-Cu nanoparticles so as to determine their most stable configurations and the conditions for obtaining clusters of different structural variants. The dynamic behavior of these nanoparticles upon local heating is investigated. AuCu nanoparticles are characterized by high resolution transmission electron microscopy (HRTEM) and energy filtering elemental composition mapping (EFECM), which allowed us to study the internal structure and the elemental distribution in the particles. Quantum mechanical approaches and classic molecular dynamics methods are applied to model the structure and to determine the lowest energy configurations, the corresponding electronic structures, and understand structural transition of clusters upon heating, supported by experimental evidences. Our theoretical results demonstrate only the core/shell bimetallic structure have negative heat of formation, both for decahedra and octahedral, and energetically favoring core/shell structure is with Au covering the core of Cu, whose reverse core/shell structure is not stable and may transform back at a certain temperature. Experimental evidences corroborate these structures and their structural changes upon heating, demonstrating the possibility to manipulate the structure of such bimetallic nanoparticles using extra stimulating energy, which is in accordance with the calculated coherence energy proportions between the different configurations.

Alloys↗
PubMed2006

Fumonisin production in rice cultures of Fusarium verticillioides under different incubation conditions using an optimized analytical method.

Fumonisin B1 (FB1) and fumonisin B2 (FB2) are the main members of a family of mycotoxins produced by various fungal species belonging to the Gibberella fujikuroi complex. The present work shows the results of a comparative study of various clean-up and derivatization procedures for analysis of fumonisins in rice cultures. Fumonisins were extracted from rice with acetonitrile/water (50/50, v/v). For clean-up, three solid-phase extraction procedures were assayed (C18 cartridge, SAX cartridge, and a combination of both). Two reagents (o-phthaldialdehyde and 4-fluoro-7-nitro-benzofurazan) were studied comparatively for formation of fluorescent derivatives. The separation was carried out by LC using a fluorescence detector. The best procedure for analysis of fumonisins in rice involved clean-up with C18 cartridge and derivatization with o-phthaldialdehyde. The limit of detection was 0.010 mg kg(-1) for both toxins. In the 10-500 mg kg(-1) spiking level range, the recovery rates for FB1 and FB2 in rice varied from 94.6% to 103.6% and from 96.3% to 101.9%, respectively. The optimized analytical method for determination of fumonisins in rice was applied to the study of FB1 and FB2 production by four isolates of the G. fujikuroi species complex in rice cultures carried out at different temperatures and water activities to establish the influence of strain and environmental conditions on fumonisin production in this cereal. In general, fumonisin production was the highest at 20 degrees C and lowest at 37 degrees C. Four of the five assayed water activity (aw) values (0.97, 0.98, 0.99, and 1.0) did not affect significantly fumonisin accumulation but fumonisins were not detected in cultures when aw was 0.96.

Chromatography, Liquid↗
PubMed2005

Dynamical characterization of rotationally hindered species in liquids.

The rotational dynamics of HCl in liquid Ar has been studied by means of molecular-dynamics simulations. We calculate the lifetimes of weakly bound HCl-Ar dimers induced by the anisotropic pair interaction. It is shown that, although lifetimes are small with respect to the reorientational decorrelation, the time interval between the breaking down and formation of the next dimer is negligibly small. Thus, with respect to the rotational dynamics of the probe, the effect is similar to that and eventually would cause a time-stable complex. This provokes a peculiar hindered rotation of the diatomic in the liquid which is macroscopically embodied in the infrared spectrum of the solution as a Q-branch nonexistent otherwise.

Journal Article↗
PubMed2005

Simultaneous imbibition-heat convection process in a non-Darcian porous medium.

In the present work, the nonisothermal imbibition process in a porous medium was numerically analyzed using a non-Darcian model for the momentum equation and energy equations for the wetting and dry zones. In order to show the thermal character of the problem, we assume initially that the porous medium is found at a uniform temperature T0 and suddenly begins the imbibition process into the porous medium with a penetrating fluid at temperature T1. The physical influence of nondimensional parameters such as Peclet number, Pe, effective heat capacity number, beta(w), porous Reynolds number, Re(p), and the inertial coefficient of the porous medium, F, serve us to evaluate the position and velocity of the imbibition front as well as temperature profiles in both zones. In particular, for values of Re(p)F/beta(w)>>1, we recover a type of nonisothermal Washburn law. The numerical predictions show that the imbibition front and the temperature fields strongly depend on the above nondimensional parameters, revealing a clear deviation of the simple Washburn law.

Journal Article↗
PubMed2005

Occurrence of mycotoxin producing fungi in bee pollen.

The natural mycobiota occurring in bee pollen is studied in the present report with special attention to analyze the incidence of fungal species that are potential producers of mycotoxins. A total of 90 ready-to-eat bee pollen samples were analyzed. Eighty-seven samples were collected in stores placed in different Spanish areas and three were from Buenos Aires (Argentina). The statistical results (ANOVA) showed that yeasts and Penicillium spp. were the predominant fungi. With regard to the potential mycotoxin producing species, Penicillium verrucosum, Aspergillus niger aggregate, Aspergillus carbonarius, Aspergillus ochraceus, Aspergillus flavus, Aspergillus parasiticus and Alternaria spp. were found. The last genus was isolated very frequently. The potential ability for producing ochratoxin A (OTA) and aflatoxins B(1), B(2), G(1) and G(2) was studied by culturing in vitro the isolates followed by analysis of these mycotoxins in culture extracts by HPLC with fluorescent detection. It was found that 100%, 53.3%, 33.3% and 25% of the isolates of A. carbonarius, A. ochraceus, P. verrucosum and A. niger aggregate, respectively, produced OTA. Moreover, 28.6% of the isolates from the A. flavus plus A. parasiticus group were able to produce aflatoxin B(1). Aflatoxin B(2) was detected in only 10% of the cultures. Aflatoxins G(1) and G(2) were not detected in cultures under the assayed conditions. This is the first report carried out on the natural mycobiota occurring in bee pollen in general and on the toxigenic capability of these isolates in particular.

Aflatoxins↗
PubMed2005

Natural convection in tilted cylindrical cavities embedded in rocks.

This paper presents a theoretical investigation of the low Rayleigh number conjugate natural convection in a slender tilted cylindrical cavity which is embedded in a solid that is subject to a uniform vertical temperature gradient. Two cases have been analyzed; a fluid-filled cavity and a cavity filled with a fluid-saturated porous medium. The temperature of the solid and the velocity, temperature, and pressure in the cavity have been determined by analytically solving the coupled problems within and around the cavity. The effect of the ratio of the thermal conductivity of the material in the cavity to the thermal conductivity of the solid on the structure of the convection flow is discussed. The theoretical results for convection in the fluid-filled cavity are shown to be in good agreement with experimental PIV measurements.

Journal Article↗
PubMed2005

Application of Aspergillus niger-treated agrowaste residue and Glomus mosseae for improving growth and nutrition of Trifolium repens in a Cd-contaminated soil.

The microbial transformation of sugar beet (SB) agrowaste with or without rock-phosphate (RP) has utility for the improvement of plant growth in a Cd (5 microg g-1) artificially contaminated soil, particularly when the soil is co-inoculated with arbuscular mycorrhizal (AM) fungus Glomus mosseae isolated from a Cd-polluted area. Under such Cd-polluted conditions, the limited growth, mineral nutrition, symbiotic developments (nodulation and AM-colonization) and soil enzymatic activities were stimulated using SB or SB+RP as soil amendments and G. mosseae as inoculant. G. mosseae enhanced plant establishment in a higher extent in amended soil; it is probably due to the interactive effect increasing the potential fertility of such compounds and its ability for decreasing Cd transfer from soil to plant. The amount of Cd transferred from soil solution to biomass of AM-colonized plants ranged from 0.09 microg Cd g-1 (in SB+RP-amended soil) to 0.6 microg Cd g-1 (in non-amended soil). Nodule formation was more sensitive to Cd than AM-colonization, and both symbioses were stimulated in amended soils. Not only AM-colonization but also amendments were critical for plant growth and nutrition in Cd-polluted soil. The high effectiveness of AM inoculum increasing nutrients and decreasing Cd in amended soil indicated the positive interaction of these treatments in increasing plant tolerance to Cd contamination.

Agriculture↗
PubMed2005

Relationship between oxidative stress parameters and atherosclerotic signs in the carotid artery of stable renal transplant patients.

Reactive oxygen species (ROS) may participate in atheroma plaque formation, which may be noninvasively diagnosed by Doppler ultrasound of carotid artery. We sought to determine the relationship between the presence of carotid artery lesions and oxidative parameters to identify factors that may influence these lesions in renal transplant patients. Fifty renal transplanted patients with stable renal function and without diabetes mellitus were studied for more than 1 year posttransplantation. Echo Doppler examination of the carotid artery was performed to assess the intimal media thickness (IMT), atheroma plaques, calcification, and stenosis. Data were collected on oxidative parameters: malondialdehyde (MDA), glutathione peroxidase (GPx), catalase, superoxide dismutase (SOD), glutathione reductase (GR), and lipid profile. The serum GPx level among patients without atheroma plaques, calcification, or stenosis was higher than in those with ultrasound signs. The LDL cholesterol fraction was lower in patients with no ultrasound signs of atherosclerotic lesions; total cholesterol values showed the same behavior. In conclusion, transplanted patients with atheromatous plaques, calcification, and carotid stenosis have a greater degree of hypercholesterolemia and lower antioxidant activity (lower GPx). Recipient age was the principal risk factor for the presence of increased IMT, atheroma plaque, calcification, and/or stenosis of carotid artery in renal transplant patients.

Adult↗
PubMed2004

Infrared spectral profiles in liquids and atom-diatom interactions.

Molecular dynamics simulations of the infrared spectrum of a generic simple polar diatomic in a liquid nonpolar solvent allow to reproduce the different prototypical experimental line shapes of this kind of systems. This is feasible by using different solute-solvent anisotropic potentials at fixed thermodynamic conditions. In the limit cases, the rotation of the diatomic is explained in terms of a quasifree motion or a rotational diffusion evolution and the spectra show a doublet structure formed by P and R branches or a unique collapsed branch, respectively. When the profile contains three branches, including an intense Q branch in the vicinity of the center of the band, rotational evolution presents a particular hindering that can be understood by studying the influence on rotational spectral densities of the different time scales involved in rotational relaxation. Cancellation/enhancement effects among spectral density terms arising from intermediate and long times (0.4-1 ps) are essential to understand rotational hindering.

Journal Article↗
PubMed2004

Effect of wollastonite ceramics and bioactive glass on the formation of a bonelike apatite layer on a cobalt base alloy.

A biomimetic method was used to promote a bioactive surface on a cobalt base alloy (ASTM F-75). The metallic substrates were alkali treated and some of the samples were subsequently heat treated. The treated samples were immersed in simulated body fluid (SBF) on granular particles of either bioactive glass or wollastonite. For comparative purposes, no bioactive system was used in some tests. Three different methods were used for the immersion of the samples in SBF: 1) 21 days in SBF, 2) 21 days in 1.5 SBF, and 3) 7 days in SBF followed by 14 days in 1.5 SBF (re-immersion method). A bonelike apatite layer was formed on all the samples placed on wollastonite and bioactive glass particles. The morphology of the apatite layer formed by using the re-immersion method and wollastonite closely resembled the existing bioactive systems. No apatite layer was observed on the samples treated without bioactive material and soaked for 21 days in SBF or 1.5 SBF, apart from the substrates treated by using the re-immersion method. The heat treatment delayed the apatite formation in all the cases studied.

Alloys↗
PubMed2004

Improvement of soil characteristics and growth of Dorycnium pentaphyllum by amendment with agrowastes and inoculation with AM fungi and/or the yeast Yarowia lipolytica.

The effectiveness of two microbiologically treated agrowastes [dry olive cake (DOC) and/or sugar beet (SB)] on plant growth, soil enzymatic activities and other soil characteristics was determined in a natural soil from a desertified area. Dorycnium pentaphyllum, a legume plant adapted to stress situations, was the test plant to evaluate the effect of inoculation of native arbuscular mycorrhizal (AM) fungi and/or Yarowia lipolytica (a dry soil adapted yeast) on amended and non-amended soils. Plant growth and nutrition, symbiotic developments and soil enzymatic activities were limited in non-amended soil where microbial inoculations did not improve plant development. The lack of nodules formation and AM colonization can explain the limited plant growth in this natural soil. The effectiveness and performance of inocula applied was only evident in amended soils. AM colonization and spores number in natural soil were increased by amendments and the inoculation with Y. lipolytica promoted this value. The effect of the inoculations on plant N-acquisition was only important in AM-inoculated plants growing in SB medium. Enzymatic activities as urease and protease activities were particularly increased in DOC amended soil meanwhile dehydrogenase activity was greatest in treatments inoculated with Y. lipolytica in SB added soil. The biological activities in rhizosphere of agrowaste amended soil, used as indices of changes in soil properties and fertility, were affected not only by the nature of amendments but also by the inoculant applied. All these results show that the lignocellulosic agrowastes treated with a selected microorganism and its further interaction with beneficial microbial groups (native AM fungi and/or Y. lipolytica) is a useful tool to modify soil physico-chemical, biological and fertility properties that enhance the plant performance probably by making nutrients more available to plants.

Agriculture↗
PubMed2003

[Detection of cardiovascular risk factors in the reformed primary care network in Catalonia. Comparison between the years 1995 and 2000].

OBJECTIVES: To know if much the detection and control of cardiovascular risk factors (FRCV) have been incorporated in primary care settings (PCS) on 2000 and compare them with 1995 results. Design and participants. A descriptive cross-sectional study of a random sample of 5,875 of clinical histories (CH) of patients aged 15 and over attended during 2000 in PCS, which had been in operation for over three years. MEASUREMENTS AND MAIN RESULTS: Whether were recorded values, levels, diagnoses and control related to: blood pressure, cholesterol, glucose, weight, size, tobacco and alcohol consumption, in order to compare 1995 and 2000 results obtained with the same methodology. Cholesterol levels (57.3%), blood pressure values (52.9%) and glucose levels (51.3%) are the most recorded variables in CH. Obese diabetics and high blood pressure patients are the most studied with a mean of 3.6 records in the CH related others CRF. Smoking (41.7%) and hypertension (32.9%) are the most frequents diagnoses. The 32.3% of the high blood pressure patients have optimum control and 42.9% acceptable control. The 31.2% hyperlipaemia and the 34.1% diabetic patients are controlled. Compared with 1995, the main variations observed are: an increase of the records of cholesterol levels and glucose levels and a decrease of the others, especially in tobacco and alcohol consumption screening. Diabetes and obesity diagnosis decrease and smoking and excessive alcohol consumption increase have been also observed. Screening age and sex group differences are maintained. CONCLUSIONS: The results suggest that may be a change in CRF screening performance is happening and the influencial factors would be study.

Adolescent↗
PubMed2003

[Transbronchial needle aspiration in bronchogenic carcinoma with visible lesions: diagnostic yield and cost].

BACKGROUND: Transbronchial needle aspiration (TBNA) is a bronchoscopic technique whose usefulness in diagnosing endobronchial lesions has not yet been clearly established. OBJECTIVE: We aimed to determine whether the diagnostic yield of fiberoptic bronchoscopy could be increased, without a negative impact on diagnostic costs, if TBNA were used in combination with conventional diagnostic techniques (bronchial washings and bronchial brushings and forceps biopsy). PATIENTS AND METHODS: The cases of 130 patients diagnosed with bronchogenic carcinoma with endoscopically visible lesions were analyzed retrospectively. All had undergone conventional diagnostic procedures; TBNA was also performed if the bronchoscopist considered it was indicated. The final cost was calculated in euros for each diagnosis as the sum of the cost of the procedures needed to reach the diagnosis, including both endoscopic procedures and others (transthoracic needle aspiration, lymph node biopsy). Diagnostic yield and costs in cases diagnosed using only conventional techniques were compared to the yield and costs in cases in which both conventional techniques and TBNA were used. RESULTS: TBNA was performed in 49 patients and provided the diagnosis in 85.7%. Conventional techniques led to cytological and histological diagnosis in 80.2% of the cases, and the combination of conventional techniques and TBNA gave a diagnosis in 89.7% (P=.01). Significant differences were observed in extrinsic compression (conventional 37.5%; conventional+TBNA 100%; P=.01), submucosal infiltration (conventional 54.6%; conventional+TBNA 85%; P=.03), and exophytic mass with necrosis (conventional 80%; conventional+TBNA 100%; P=.01). The mean (SD) cost of diagnosis was euros 381.60 (euros 156.53) using conventional techniques and euros 413.25 (euros 112.91) for conventional techniques in combination with TBNA. By adding TBNA, costs decreased for diagnoses of submucosal infiltration, exophytic mass with necrosis and extrinsic compression, although the saving was significant only for extrinsic compression. CONCLUSION: The diagnostic yield of TBNA is high for endoscopically visible bronchial anomalies suggesting neoplasm, particularly when the lesion is due to extrinsic compression, submucosal infiltration, or exophytic mass with necrosis.

Biopsy, Needle↗
PubMed2001

Frizzled-7 signalling controls tissue separation during Xenopus gastrulation.

Cell signalling through Frizzled receptors has evolved to considerable complexity within the metazoans. The Frizzled-dependent signalling cascade comprises several branches, whose differential activation depends on specific Wnt ligands, Frizzled receptor isoforms and the cellular context. In Xenopus laevis embryos, the canonical beta-catenin pathway contributes to the establishment of the dorsal-ventral axis. A different branch, referred to as the planar cell polarity pathway, is essential for cell polarization during elongation of the axial mesoderm by convergent extension. Here we demonstrate that a third branch of the cascade is independent of Dishevelled function and involves signalling through trimeric G proteins and protein kinase C (PKC). During gastrulation, Frizzled-7 (Fz7)-dependent PKC signalling controls cell-sorting behaviour in the mesoderm. Loss of zygotic Fz7 function results in the inability of involuted anterior mesoderm to separate from the ectoderm, which leads to severe gastrulation defects. This result provides a developmentally relevant in vivo function for the Fz/PKC pathway in vertebrates.

Animals↗
PubMed2001

Application of free and Ca-alginate-entrapped Glomus deserticola and Yarowia lipolytica in a soil-plant system.

This study was performed to investigate the applicability of microbial inoculants entrapped in alginate gel. Glomus deserticola (AM) was inoculated into soil microcosms, enriched with rock phosphate, as either free form or entrapped in calcium alginate alone or in combination with a P-solubilizing yeast culture (Yarowia lipolytica). Plant dry weight, soluble P acquisition, and mycorrhizal index were equal in treatments inoculated with free and alginate-entrapped AM. Dual inoculation with entrapped G. deserticola and free cells of Y. lipolytica significantly increased all analyzed variables. Highest rates of the latter were obtained when both fungal microorganisms were applied co-entrapped in the carrier. The yeast culture behaved as a 'mycorrhiza helper microorganism' enhancing mycorrhization of tomato roots. These results indicate that dual inoculation with an AM fungus and a P-solubilizing microorganism co-entrapped in alginate can be an efficient technique for plant establishment and growth in nutrient deficient soils.

Agriculture↗