Search

La exposición a plaguicidas, durante todas las etapas de su uso, puede tener efectos adversos en la salud y el medio ambiente. Estos efectos no siempre están relacionados con lesiones inmediatas y aparentes, sino que pueden tardar incluso años en manifestarse. La utilización de biomarcadores en estudios epidemiológicos, como son las evaluaciones de daño genético, permiten la detección temprana de un riesgo incrementado de desarrollar diversas patologías, definiendo estados de prepatogénesis, como neoplasias, problemas reproductivos, malformaciones y enfermedades cardiovasculares. Los estudios de biomonitoreo en poblaciones agrícolas publicados desde la década de los años 70 indican resultados muy diversos, dada la amplia variedad de biomarcadores citogenéticos analizados y la heterogeneidad de las poblaciones incluidas en dichos estudios. En etapas previas de esta investigación se han descripto factores personales y contextuales vinculados con la exposición a plaguicidas entre trabajadores agrícolas, diseñado escalas de exposición a plaguicidas y descripto condiciones de salud percibida por agroaplicadores terrestres de la Provincia de Córdoba. Este trabajo presenta biomarcadores de daño citogenético, aportando nuevos elementos para la detección de grupos de riesgo, la comprensión de la red causal de las patologías asociadas a tales exposiciones y proponer herramientas preventivas.

The chemical and physical properties of the double perovskite Pb2FeMoO6 are systematically studied by means of structural and magnetic characterization. The compound crystallizes in the cubic Fm3̅m space group, with partial cation order involving iron and molybdenum at the perovskite B site. Structural and Mössbauer characterization points to the presence of nanometer-sized antiphase domains within the ordered matrix giving rise to two iron populations, characterized by different chemical environments, with the same weight but different valence (0.3 electrons) and inequivalent magnetic anisotropy. This structural feature deeply affects the properties of the compound: Mössbauer and EPR measurements show a high-temperature superparamagnetic-like behavior ascribed to weak magnetic interactions occurring between the antiphase domains and the rest of the sample. However, below 270 K ferrimagnetic ordering of the atomic moments is observed by neutron diffraction and SQUID magnetometry, with the onset of blocked long range magnetic interactions on the Mössbauer timescale involving both the antiphase domains and the ordered matrix below 230 K. The superparamagnetic-like behavior is ascribed to the presence of low anisotropy barriers, giving rise to an extremely thin hysteresis loop at 5 K, with a very small coercive field and remnant magnetization. The observed saturation magnetization of 1.75 μB per f.u. is in agreement with the magnetic structure determined by neutron diffraction, with the two symmetry independent sites producing a ferrimagnetic resultant μS = 1.59 μB. [ABSTRACT FROM AUTHOR]

In analyzing Mössbauer spectra by means of the integral transmission function, a correct evaluation of the recoilless factor of the source at the position of the sample is needed. A novel method to evaluate for a 57Co source is proposed. The method uses the standard transmission experimental set up and it does not need further measurements but the ones that are mandatory in order to center the Mössbauer line and to calibrate the Mössbauer transducer. Firstly, the background counts are evaluated by collecting a standard Multi Channel Scaling (MCS) spectrum of a tick metal iron foil absorber and two Pulse Height Analysis (PHA) spectra with the same life-time and setting the maximum velocity of the transducer at the same value of the MCS spectrum. Secondly, is evaluated by fitting the collected MCS spectrum throughout the integral transmission approach. A test of the suitability of the technique is presented, too. [ABSTRACT FROM AUTHOR]

We present a Mössbauer study of a S = 0 ground state magnetic Fe(III)-dimer in the presence of an applied 5 T longitudinal magnetic field, between 7.6 and 33 K. The values obtained for the isomer shift and the quadrupolar splitting are comparable with the ones of Fe(III) ions coordinated to eight oxygen ions. Regarding the spin dynamics, both intramultiplet and intermultiplet transitions are considered. In the chosen temperature range the rate of the former transitions is constant, within the errors, while the rate of the latter ones quickly increases with the temperature. [ABSTRACT FROM AUTHOR]

We report on the synthesis and characterization of BiFe0.5Mn0.5O3, a potential type-I multiferroic compound displaying temperature-induced magnetization reversal. Bulk samples were obtained by means of solid-state reaction carried out under the application of hydrostatic pressure of 6 GPa at 1100 °C. The crystal structure is a highly distorted perovskite with no cation order on the B site, where, besides a complex scheme of tilt and rotations of the TM-O6 octahedra, large off-centering of the bismuth ions is detected. Below T1 = 420 K the compound undergoes a first weak ferromagnetic transition related to the ordering of iron-rich clusters. At lower temperatures (just below RT) a complex thermally activated mechanism induces at first an enhancement of the magnetization at T2 = 288 K, then a spontaneous reversal giving rise to a negative response. The complementary use of powder neutron diffraction, superconducting quantum interference device magnetometry, and Mössbauer spectroscopy allowed us to propose as a possible interpretation of the overall magnetic behavior the presence of an uncompensated competitive coupling between nonequivalent clusters of weakly ferromagnetic interactions characterized by different critical temperatures and resultant magnetizations. [ABSTRACT FROM AUTHOR]

Ferritins are ubiquitous and conserved proteins endowed with enzymatic ferroxidase activity, that oxidize Fe(II) ions at the dimetal ferroxidase centre to form a mineralized Fe(III) oxide core deposited within the apo-protein shell. Herein, the in vitro formation of a heterodimetal cofactor constituted by Fe and Mn ions has been investigated in human H ferritin (hHFt). Namely, Mn and Fe binding at the hHFt ferroxidase centre and its effects on Fe(II) oxidation have been investigated by UV-Vis ferroxidation kinetics, fluorimetric titrations, multifrequency EPR, and preliminary Mössbauer spectroscopy. Our results show that in hHFt, both Fe(II) and Mn(II) bind the ferroxidase centre forming a Fe-Mn cofactor. Moreover, molecular oxygen seems to favour Mn(II) binding and increases the ferroxidation activity of the Mn-loaded protein. The data suggest that Mn influences the Fe binding and the efficiency of the ferroxidation reaction. The higher efficiency of the Mn-Fe heterometallic centre may have a physiological relevance in specific cell types (i.e. glia cells), where the concentration of Mn is the same order of magnitude as iron., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Doping of biocompatible nanomaterials with magnetic phases is currently one of the most promising strategies for the development of advanced magnetic biomaterials. However, especially in the case of iron-doped magnetic hydroxyapatites, it is not clear if the magnetic features come merely from the magnetic phases/ions used as dopants or from complex mechanisms involving interactions at the nanoscale. Here, we report an extensive chemical-physical and magnetic investigation of three hydroxyapatite nanocrystals doped with different iron species and containing small or no amounts of maghemite as a secondary phase. The association of several investigation techniques such as X-ray absorption spectroscopy, Mössbauer, magnetometry, and TEM allowed us to determine that the unusual magnetic properties of Fe 2+/3+ -doped hydroxyapatites (FeHA) occur by a synergy of two different phenomena: i.e., (i) interacting superparamagnetism due to the interplay between iron-doped apatite and iron oxide nanoparticles as well as to the occurrence of dipolar interactions and (ii) interacting paramagnetism due to Fe 3+ ions present in the superficial hydrated layer of the apatite nanophase and, to a lesser extent, paramagnetism due to isolated Fe 3+ ions in the apatite lattice. We also show that a major player in the activation of the above phenomena is the oxidation of Fe 2+ into Fe 3+ , as induced by the synthesis process, and their consequent specific positioning in the FeHA structure.

Improving cathode materials is mandatory for next-generation Li-ion batteries. Exploring polyanion compounds with high theoretical capacity such as the lithium metal orthosilicates, Li2MSiO4 is of great importance. In particular, mixed silicates represent an advancement with practical applications. Here we present results on a rapid solid state synthesis of mixed Li2(FeMnCo)SiO4 samples in a wide compositional range. The solid solution in the P21/n space group was found to be stable for high iron concentration or for a cobalt content up to about 0.3 atom per formula unit. Other compositions led to a mixture of polymorphs, namely Pmn21 and Pbn21. All the samples contained a variable amount of Fe(3+) ions that was quantified by Mössbauer spectroscopy and confirmed by the TN values of the paramagnetic to antiferromagnetic transition. Preliminary characterization by cyclic voltammetry revealed the effect of Fe(3+) on the electrochemical response. Further work is required to determine the impact of these electrode materials on lithium batteries.

We report a comprehensive study of the spontaneous magnetization reversal (MRV) performed on the disordered polycrystalline perovskite BiFe(0.5)Mn(0.5)O(3), an intriguing compound synthesized in high pressure-high temperature conditions. In disordered systems, the origin of MRV is not completely clarified, yet. In BiFe(0.5)Mn(0.5)O(3), compositional disorder involves the ions on the B-site of the perovskite determining the presence of mesoscopic clusters, characterized by high concentrations of iron or manganese and thus by different resultant magnetization. This leads to the observation of two singular fields H(1) and H(2) dependent on the degree of inhomogeneity, unpredictably changing from sample to sample due to synthesis effects. These fields separate different magnetic responses of the system; for applied fields H < H(1), the Fe and Mn clusters weakly interact in a competitive way, giving rise to MRV, while for an intermediate field regime the energy of this weak interaction becomes comparable to the energy of the system under field application. As a consequence, the zero field cooled magnetization thermal evolution depends on the sample degree of inhomogeneity. In this field regime, applied field Mössbauer spectroscopy indicates that the iron rich clusters are highly polarized by the field, while the largest part of the material, consisting of AFM clusters characterized by axial anisotropy and uncompensated moments, shows soft or hard magnetism depending on T. Above the higher singular field, the M(T) curves show the trend expected for a classical antiferromagnetic material and the competitive character is suppressed. The MRV phenomenon results to be highly sensitive on both the thermal and magnetic measurement conditions; for this reason the present work proposes a characterization strategy that in principle has a large applicability in the study of disordered perovskites showing similar phenomenology.

Objective: To determine the role of the habitual use of the most common artificial sweeteners (AS) in the development of urinary tract tumors (UTT) in Argentina., Methods: Case-control study of 197 patients with histologically confirmed UTT of transitional varieties, and 397 controls with acute, non-neoplastic, and non-urinary tract diseases, admitted to the same hospitals in Córdoba (Argentina) between 1999 and 2006. All subjects were interviewed about their use of AS and their exposure to other known or suspected risk factors for UTT., Results: Fifty-one UTT patients (26%) and 87 controls (22%) used AS. The risk of UTT was significantly increased in long-term (> or =10 years) AS users compared with none-AS users. The OR (95% CI) for long-term consumers was 2.18 (1.22-3.89) and for short-term users was 1.10 (0.61-2.00) after adjustment for age, gender, BMI, social status. and years of tobacco use., Conclusion: Regular use of AS for 10 years or more was positively associated with UTT.

A Food-Frequency questionnaire (FFQ) is the method chosen for estimating dietary intake in epidemiological studies because it can provide valid and reliable estimates of usual intake in a variety of populations. Colorectal cancer is associated with diet but no information about validity and reproducibility of dietary exposure assessment is available in Argentina. The purpose of the study is to evaluate the validity and reproducibility of the FFQ used in assessing the relationship between dietary intake and colorectal cancer. Selected nutrient intake, measured by two interviewer-administered FFQs, was compared with average intake derived from using four 24 hour dietary recalls (DR) as the reference method, for 62 control subjects from Córdoba, Argentina. Pearson's product-moment and Spearman correlation coefficients were used. Nutrient intakes were adjusted for energy, sex and age using tertiles of residuals from regression models. Weighted and unweighted kappa statistics were calculated for both FFQs versus DR. The mean correlation coefficients between DR and FFQs were 0.74. Agreement measurement (Kappa) varied from 0.51 to 0.74 for FFQ1 vs. FFQ2 to between 0.71 and 0.87 for FFQ1 and FFQ2. This study demonstrates an acceptable validity and reproducibility for this FFQ. The pattern of the correlation coefficients found in the present study indicates that the FFQ can provide an acceptable assessment of long-term dietary intake in the Argentine population and in other Latin-american areas.

The composition of food lipid, including total lipids, saturated, monosaturated, and polyunsaturated fatty acids was analysed in this study. Foods, which were frequently consumed in Argentina and include in this study were: lean and fatty red meats, "ossobucco" with or without bone marrow, lean and skinned chicken meager and fatty fish, several sausages (salami and blood sausage), several crackers, hand-made fatty bread, fried and baked biscuits, ice cream, milk-marmelade, edible oils and bovine tallow. The content of fatty acids grouped according to their families in the food and description of the formulation of each food are given in the current paper. The glossary will help to identify the preparation of foods and will be beneficial for the people in other countries of Latinoamérica.

In an effort to understand the mechanism of action of the DNA-intercalating antitumor agent 9-hydroxyellipticine (9-OH-E), we have examined the effects of this drug on the cell survival, macromolecular syntheses, and cell cycle progression in sensitive and resistant cells. Our results show that 9-OH-E toxicity on sensitive and resistant cells involves different mechanisms of action: the drug toxicity in the sensitive cells appears to result from lethal lesions mediated through the interaction of the drug with an intracellular protein, independently of any effect of the drug on the macromolecular syntheses; in the resistant cells, the cell death occurs concomitantly with the inhibition of these syntheses. Cell cycle progression analysis after 9-OH-E treatment showed that, in the sensitive cells, the drug is inducing a G1 and a G2 block, which are both released in the presence of 1 mM caffeine, without any effect on the 9-OH-E toxicity. In the resistant cells, a G2 block was also observed but only when the cells were resuming their growth after about a 30- to 40-h growth arrest. Caffeine release of this block, which again had no effect on 9-OH-E toxicity, was only observed when it was added from 40 to 60 h after 9-OH-E treatment, when the cells resumed their growth. Finally in the sensitive cells, cycloheximide exerted an inhibitory effect on 9-OH-E toxicity when it was added before and during the cell exposure to the drug. This effect was interpreted as indicating that 9-OH-E toxicity in the sensitive cells relies on a protein which is not induced by the drug but has to be present in the cells when the drug is added. The possible implication of DNA topoisomerases in 9-OH-E toxicity mechanism is discussed.