Ochratoxin a in human breast milk, maternal and placental blood from Cochabamba-Bolivia / Presencia de ocratoxina a en leche, placenta y sangre materna en Cochabamba-Bolivia

The nephrotoxic and carcinogenic mycotoxin Ochratoxin A (OTA) is a contaminant in a wide variety of foods. Mothers who ingest food contaminated with OTA during the gestation and lactation period can transfer this mycotoxin to the fetus as to the infant, respectively. To quantify the transmission of Ochratoxin A from mother to newborn and to infant, samples were taken from maternal blood and umbilical cord of women at the moment of delivery and breast milk of ladies in lactation period in the city of Cochabamba-Bolivia. From a total of 31 samples of maternal plasma and its respective cord, 4 were positive in both sample types (incidence 13%, 12% allowable relative error to the population at 95% confidence). Maternal plasma samples had a range of 0.3-10.2 ng of Ochratoxin A/ml with a mean of 3.0 ng/ml (+/- SD=3,0). Similarly, in the umbilical cord plasma Ochratoxin A was also detected with values of 0.3 to 1.7 ng/ml and with a mean of 0.7+/- 0.65 ng/ml. In two samples the concentrations of ochratoxin A were higher in umbilical cord blood (0,5 and 1.7 ng/mL) than their corresponding pairs of maternal blood (0.3 and 1.3 ng /ml, respectively) with an average concentration ratio of 1.5 ng/ml. Two other samples presented positive in ochratoxin A in umbilical cord blood and negative in their corresponding pairs of maternal blood confirming the transfer of the mycotoxin through human placental barrier. Out of 29 samples the breast milk samples from the Bolivian mothers collected during the summer period, 13 (44.8%) were found positive in a ranged from 20.2 to 146.1 ng/l. Concerning the samples collected in the winter season, only one (2.4%) out of 42 had a measurable ochratoxin A concentration of 28.3 ng/1, and seven samples showed traces of the toxin, below the detection limit

La micotoxina nefrotóxica y cancerígena Ocratoxina A (OTA) es un contaminante en una amplia variedad de alimentos. Las madres que ingieren alimentos contaminados con OTA durante el período de gestación y lactancia pueden transferir esta micotoxina al feto y al bebé, respectivamente. Para cuantificar la transmisión de la ocratoxina A de la madre al feto y al niño, se tomaron muestras de sangre materna y cordón umbilical de mujeres en el momento del parto y de leche materna de madres en el período de lactancia en la ciudad de Cochabamba-Bolivia. De un total de 31 muestras de plasma materno y su respectivo cordón umbilical, 4 resultaron positivas en ambos tipos de muestra, (incidencia 13%, error admisible de 12% respecto a la población con 95% de confianza). Las muestras de plasma materno se encontraron en un rango de 0,3 a 10,2 ng/ml con una media de 3,0 ng/ml (+/- SD = 3,0). De igual manera, en el plasma de cordón umbilical se detectó también OTA en cuatro muestras, con valores de 0,3 a 1,7 ng/ml y con una media de 0,7 ng/ml (+/- SD=0.65). En dos muestras las concentraciones de ocratoxina A eran mayores en la sangre del cordón umbilical (0,5 y 1,7 ng/ml) que sus correspondientes pares de la sangre materna (0,3 y 1,3 ng/ml, respectivamente) con una relación de concentraciones promedio de 1,5. Otras dos muestras presentaron positivo en OTA en la sangre del cordón umbilical y negativo en sus correspondientes pares de sangre materna. Confirmándose así el traspaso de esta micotoxina a través de la barrera placentaria humana. De otra parte, de un total de 29 muestras de leche materna humana colectadas de madres bolivianas durante la estación de verano, 13 (44.8 %) se encontraron positivas en un rango de 20,2 a 146,1 ng/l. Respecto a las muestras de leche colectadas durante la estación de invierno solo 1 (2,4%) de 42 fueron positivas en ocratoxina a una concentración de 28,3 ng/l y siete muestras mostraron trazas de la toxina por debajo del límite de detección

1H nuclear spin relaxation of liquid water from molecular dynamics simulations.

We have investigated the nuclear spin relaxation properties of (1)H in liquid water with the help of molecular dynamics simulations. We have computed the (1)H nuclear spin relaxation times T1 and T2 and determined the contribution of the different interactions to the relaxation at different temperatures and for different classical water models (SPC/E, TIP3P, TIP4P, and TIP4P/2005). Among the water models considered, the TIP4P/2005 model exhibits the best agreement with the experiment. The same analysis was performed with Car-Parrinello ab initio molecular dynamics simulations of bulk water at T = 330 K, which provided results close to the experimental values at room temperature. To complete the study, we have successfully accounted for the temperature-dependence of T1 and T2 in terms of a simplified model, which considers the reorientation in finite angle jumps and the diffusive translation of water molecules.

A continuous mixture of two different dimers in liquid water.

It is hitherto thought that liquid water is composed of tetrahedrally coordinated molecules with an asymmetric interaction of the central molecule with neighboring molecules. Kühne et al., Nat. Commun., 2013, 4, 1450 suggested that this asymmetry, energetic rather than geometric, is the cornerstone to reconcile the homogeneous and inhomogeneous viewpoints of liquid water. In order to investigate the geometric origin of that asymmetry, we have scrutinized Molecular Dynamics (MD) simulations of water through a careful analysis of the five-dimensional probability distribution function of Euler angles in which the relative positions and orientations of water molecules are obtained. We demonstrate that, beyond the ubiquitous tetrahedral structure with well-defined molecular dimers, there is a series of possible molecular orientations that define the structure. These orientations are generated by rotating the neighboring molecule around the O-H axis that is involved in the hydrogen bond scheme. Two of the possible orientations have a higher probability, giving rise to two kinds of dimers: one close to the lowest energy of a water dimer in vacuum with an almost perpendicular alignment of the dipole moment, and another one with a parallel orientation of the dipole moment which is less tightly bound. These two different dimers have an effect on the orientation of further water dipole moments up to a distance of ≈6 Å. Liquid water can therefore be described as a continuous mixture of two kinds of dimers where the hydrogen bonds have the same geometry but the interaction energies are different due to a different mutual orientation of the dipoles of the participating water molecules.

Insights into the determination of molecular structure from diffraction data using a Bayesian algorithm.

The determination of the molecular ordering in a liquid is still a controversial subject. There is no general consensus either on the methods to obtain reliable liquid structures or on the way to analyze them. Regardless of the method, it is very important to have a realistic molecular structure available that allows simulations to faithfully reproduce the sample features, and that minimizes the computing time in structure refinements. However, attention is not always paid to this point and molecular models coming from general force-fields are frequently used to undertake many of the analyses. We propose in this work to use a Bayesian scheme to fit the experimental data and produce reliable molecular models that can be used as the starting point of any simulation or refinement. The algorithm behind the proposed method is based on a Markov chain Monte Carlo procedure, as many other refinement programs such as reverse Monte Carlo or empirical potential structure refinement.

Characterization of the Methane-Graphene Hydrophobic Interaction in Aqueous Solution from Ab Initio Simulations.

In this article, the interaction between a methane molecule and a graphene plane in liquid water has been characterized employing DFT-based free energy Molecular Dynamics calculations. This system represents a good model to understand the generic interaction between a small hydrophobic solute (methane molecule) and an extense hydrophobic surface (graphene plane). The structural and dynamical properties of graphene and methane hydration water are analyzed and found to be closely related to the main features of the potential of mean force. The results could be used in coarse-grained models to take into account the effect of the hydrophobic interaction in realistic systems relevant to experiment.

Specific ion effects in aqueous eletrolyte solutions confined within graphene sheets at the nanometric scale.

The underlying mechanisms of specific ion effects on structure and dynamics of aqueous solutions have been long debated. On the other hand, the role of polarization at hydrophobic interfaces when aqueous electrolytes are present is of great importance, as it has been observed at the air-vapor interface. In this work, we have explored influence of ionic species on microscopical properties of aqueous sodium halide solutions constrained inside a double layer graphene channel, as a model for a realistic hydrophobic interface. Our systems have been simulated by molecular dynamics techniques, explicitly including polarization in water molecules and ions. Water and ionic density profiles showed the tendency of ionic species to occupy the whole space available, in good agreement with spectroscopic experimental data. The exception to this general behavior was fluoride, which preferred to stay away from interfaces. Two main regions were defined: interfaces and the central part of the slab, the bulklike region. Ionic hydration numbers at interfaces were lower than those at the bulklike area by about one to two units. We have also analyzed water-ion orientations and polarization distributions and obtained a marked dependence on ionic concentration. Residence time of anions suffered important fluctuations and tended to be largest at interfaces. Large variations of the static permittivity between interfacial and bulklike regions were observed. Ionic diffusion was found to be between 10(-5) and 10(-6) cm(2) s(-1) and showed to be mainly dependent on the concentration, whereas the type of anion considered and the polarizability had significantly less relevance. Conductivities were found to be dependent on ionic concentrations and the polarizabilities of anions, as well as on the spatial direction considered.

Effects of concentration on structure, dielectric, and dynamic properties of aqueous NaCl solutions using a polarizable model.

The study of NaCl solutions in water at finite concentration, explicitly including polarization in water molecules and ions, has been carried out by molecular dynamics simulations. A comparison of the RPOL polarizable model with the rigid SPC/E potential for water has been included. Structure obtained with the two models does not show significant differences, although some deviations in the NaNa radial distribution functions at all concentrations are observed. Dielectric properties such as total and molecular dipole moment correlation functions revealed decay times of the order of 10 ps, roughly independent of concentration. The analysis of electric conductivity by means of current-current correlation functions also included the calculation of cross terms corresponding to dipole moment-current correlations, which proved to be non-neglectable at short times and especially relevant at high concentrations (m=4 mol kg(-1)). Frequency dependent dielectric constants and conductivities have been computed and the role of cross correlations has been analyzed. In all cases both concentration and cross correlations have significant influence in the results.

Molecular dynamics simulations of supercritical water confined within a carbon-slit pore.

We report the results of a series of molecular dynamics simulations of water inside a carbon-slit pore at supercritical conditions. A range of densities corresponding from liquid (0.66gcm;{-3}) to gas environments (0.08gcm;{-3}) at the supercritical temperature of 673K were considered. Our findings are compared with previous studies of liquid water confined in graphene nanochannels at ambient and high temperatures, and indicate that the microscopic structure of water evolves from hydrogen bond networks characteristic of hot dense liquids to looser arrangements where the dominant units are water monomers and dimers. Water permittivity was found to be very small at low densities, with a tendency to grow with density and to reach typical values of unconfined supercritical water at 0.66gcm;{-3}) . In supercritical conditions, the residence time of water at interfaces is roughly similar to that of water in the central regions of the slabs, if the size of the considered region is taken into account. That time span is long enough to compute dynamical properties such as diffusion or spectral densities. Water diffusion in supercritical states is much faster at low densities, and it is produced in such a way that, at interfaces, translational diffusion is mainly produced along planes parallel to the carbon walls. Spectral frequency shifts depend on several factors, being temperature and density effects the most relevant. However, we can observe corrections due to confinement, important both at the graphene interface and in the central region of the water slab.

Dynamics of water nanodroplets and aqueous protons in non-ionic reverse micelles.

We present a study of the microscopic dynamics of water trapped in reverse non-ionic micelles by means of a series of molecular dynamics simulations. The analysis of the effects of micellar confinement on spectroscopical properties of an excess proton has also been considered. Our micelles were microemulsions made with the neutral surfactant diethylene glycol monodecyl ether [CH(3)(CH(2))(11)(OC(2)H(4))(2)OH]. Simulation experiments including the proton species were performed using a multistate empirical valence bond Hamiltonian model. Diffusion of water in the micelle is markedly slower than that in the bulk liquid, in the same fashion as happens with reorientational dynamics. Spectral densities of hydrogens revealed a blue-shift of the OH-stretching vibration together with a split of the main band into two components. Absorption lineshapes of the solvated proton in the vicinity of the internal surface of the micelle indicate the coexistence of Eigen-like and Zundel-like structures and a tendency to red-shifting (compared to the aqueous unconstrained excess proton case) of the two relevant spectral bands (around 2000 and 2500 wavenumbers) mainly due to the slower dynamics of proton vibrations in water near interfaces.

Liquid water confined in carbon nanochannels at high temperatures.

Structure, hydrogen bonding, electrostatics, dielectric, and dynamical properties of liquid water confined in flat graphene nanochannels are investigated by molecular dynamics simulations. A wide range of temperatures (between 20 and 360 degrees C) have been considered. Molecular structure suffers substantial changes when the system is heated, with a significant loss of structure and hydrogen bonding. In such case, the interface between adsorbed and bulk-like water has a marked tendency to disappear, and the two preferential orientations of water nearby the graphite layers at room temperature are essentially merging above the boiling point. The general trend for the static dielectric constant is its reduction at high temperature states, as compared to ambient conditions. Similarly, residence times of water molecules in adsorbed and bulk-like regions are significantly influenced by temperature, as well. Finally, we observed relevant changes in water diffusion and spectroscopy along the range of temperatures analyzed.

Molecular dynamics simulation of liquid water confined inside graphite channels: dielectric and dynamical properties.

Electric and dielectric properties and microscopic dynamics of liquid water confined between graphite slabs are analyzed by means of molecular dynamics simulations for several graphite-graphite separations at ambient conditions. The electric potential across the interface shows oscillations due to water layering, and the overall potential drop is about -0.28 V. The total dielectric constant is larger than the corresponding value for the bulklike internal region of the system. This is mainly due to the preferential orientations of water nearest the graphite walls. Estimation of the capacitance of the system is reported, indicating large variations for the different adsorption layers. The main trend observed concerning water diffusion is 2-fold: on one hand, the overall diffusion of water is markedly smaller for the closest graphite-graphite separations, and on the other hand, water molecules diffuse in interfaces slightly slower than those in the bulklike internal areas. Molecular reorientational times are generally larger than those corresponding to those of unconstrained bulk water. The analysis of spectral densities revealed significant spectral shifts, compared to the bands in unconstrained water, in different frequency regions, and associated to confinement effects. These findings are important because of the scarce information available from experimental, theoretical, and computer simulation research into the dielectric and dynamical properties of confined water.

Molecular simulation of liquid water confined inside graphite channels: thermodynamics and structural properties.

We carried out molecular dynamics simulations to describe the properties of water inside a narrow graphite channel. Two stable phases were found: a low-density one made of water clusters adsorbed on the graphite sheets and a liquid one that fills the entire channel, forming several layers around a bulk-like region. We analyzed the interfacial structure, orientational order, water residence times in several regions, and hydrogen bonding of this last water phase, calculating also a quantity of electrochemical interest, the probability of electron tunneling through interfacial water. The results are in good qualitative agreement with the available experimental data.

Density and temperature effects on the orientational and dielectric properties of supercritical water.

The influence of temperature and density changes on the reorientational motions and dielectric properties of supercritical water is investigated by molecular dynamics simulations. A rigid simple point charged potential has been used to model water-water interactions. This model has revealed to be very satisfactory to reproduce thermodynamic, diffusive, and static dielectric properties of supercritical water. Reorientation times of water molecules have been computed along specific molecular directions and compared with available experimental data. The imaginary part of the frequency dependent dielectric constant, spectral densities of states, and residence times of water molecules in their first hydration shells are also evaluated.

Prognostic value of Pulsatility Index in acute intracerebral hemorrhage.

OBJECTIVE: To investigate whether data obtained by transcranial Doppler (TCD) have prognostic value in patients with intracerebral hemorrhage (ICH). METHODS: A prospective study of patients with an acute (<12 hours from onset of symptoms) spontaneous supratentorial ICH was conducted. Mortality was assessed at 30-day follow-up. TCD parameters were obtained from both middle cerebral arteries: systolic, diastolic, and mean velocities and Pulsatility Index (PI) from the affected and unaffected hemispheres. The following variables were included in a univariate analysis: age, sex, hematoma volume, hypodense volume around the hematoma, total volume, midline shift, ventricular size, Glasgow Coma Scale score, intraventricular hemorrhage, body temperature, white cell count, blood glucose, mean blood pressure, and TCD data. A multivariate analysis was performed with variables that showed significance in the univariate analysis. Receiver-operator characteristic (ROC) curves were obtained. RESULTS: Forty-eight patients (age 66.5 +/- 12.5 years; 28 men) were studied. Mortality at 30 days was 31%. The only predictor of mortality was the Glasgow Coma Scale score (odds ratio [OR] 0.67, CI 0.53 to 0.84, p = 0.001), whereas the PI from the unaffected hemisphere was correlated with mortality (OR 2.3, CI 0.92 to 5.72, p = 0.07). The area under the ROC curve was 0.92. A cutoff for PI from the unaffected hemisphere of 1.75 showed a specificity of 94% and a sensitivity of 80% as a predictor of death at 30 days. CONCLUSIONS: The PI of the unaffected hemisphere may be a predictor of death in acute ICH. These findings suggest that intracranial hypertension is the most likely cause of death in most patients with ICH.

Transfer of ochratoxin A during lactation: exposure of suckling via the milk of rabbit does fed a naturally-contaminated feed.

The transfer of ochratoxin A from the blood to the milk of lactating rabbit does and subsequently the exposure of their sucklings to the mycotoxin were investigated. An effective transfer of ochratoxin A from blood to milk was shown in lactating rabbit does fed a naturally-contaminated diet (10-20 g/kg of body weight/day) throughout a lactation period of 19 days. The ochratoxin A concentrations in plasma and in milk did not significantly change throughout the lactation period with a mean milk/plasma concentration ratio of 0.015. These variables were however significantly correlated (p < 0.05), as were the ingested amounts and milk concentrations. At slaughter, the highest concentration of ochratoxin A accumulated in the body of the rabbit does were found in kidney (1.2 g/kg) followed by liver (158 ng/kg), mammary gland (105 ng/kg) and muscle (38 ng/kg). A linear relationship was found between the ochratoxin A concentrations in milk and in the plasma of the sucklings, indicating an effective transfer of the toxin to the sucklings. If the same is true in humans, the exposure of the breast-fed infant to the toxin, which has been largely reported in the literature, should be a major matter of concern for human health.

[Cerebral venous thrombosis. Study of 17 cases]. / Trombosis venosa cerebral. Estudio de 17 casos.

BACKGROUND: We undertook this study to determine the clinical, neuroimaging findings, etiologies and final outcome of 17 patients with cerebral venous thrombosis diagnosed in a single center. PATIENTS AND METHODS: In this retrospective study we analyzed the clinical and neuroimaging findings of patients with cerebral venous thrombosis collected at our hospital from 1980 to 1997. The diagnosis of cerebral venous thrombosis was made by angiography and/or magnetic resonance imaging. Final outcome was assessed with the modified Rankin scale and patients were included in two groups. Differences between groups were tested using uni and multivariate analysis. RESULTS: Seventeen patients (10 women) with a mean age of 41.9 years were analyzed. The most frequent clinical pattern was focal cerebral signs (70.5%) followed by symptoms/signs of increased intracranial pressure (12%) and diffuse encephalopathy (12%). The diagnosis of cerebral venous thrombosis was made by conventional angiography in 12 cases (70.5%) and by magnetic resonance imaging in 5 (29.5%). The most frequent site of venous occlusion was superior sagittal sinus (47%) followed by lateral sinus (35%). Etiologies were hematologic disease (29%), neoplasms (23.5%), oral contraceptives (12%), infection (12%) and unknown in 18%. The majority of the patients (59%) had minor neurological sequelae during follow-up. A decreased level of consciousness and neoplasm were associated with a worse functional outcome. CONCLUSIONS: In our series the most frequent clinical pattern was focal cerebral signs and the main etiology was hematologic disease. A relatively good prognosis was observed in those patients. A decreased level of consciousness and presence of neoplasm were the factors associated with a bad prognosis in these cases.

Spontaneous primary intraventricular hemorrhage: clinical data, etiology and outcome.

The clinical features, etiology, and neurological outcome in patients with primary intraventricular hemorrhage (PIVH) have rarely been reported. We retrospectively reviewed the clinical data, complementary examinations, outcome, computed tomography (CT) blood amount, and ventricle size of 13 patients (mean age 60 years, five men). We defined PIVH as hemorrhage detected by CT in the ventricular system only. The major symptoms included headache (n = 13), decreased level of consciousness (n = 9), and nausea/vomiting (n = 7). The cause was unknown in five patients; and was associated with arterial hypertension in five, vascular malformations in two, and tumor in one, although arteriography was performed in only five patients. Outcomes were death in three, asymptomatic in six, mild disability in three, and moderate disability in one. Prognosis was not related to clinical or CT data. Clinical features can suggest the diagnosis of PIVH, but cerebral CT is required for confirmation.

[Immunologic profile of patients with renal transplantation in Panama]. / Perfil inmunologico del paciente con trasplante renal en Panama.

We are presenting the immunologic pattern of 100 patients with kidney transplant made from 1990-2000 at CHM CSS Dr.AAM. Eighty nine were alive related donors. Most of them were from blood group O, donors and receptors. They came from Panama, Chiriqui and Colon. Many of the donors were siblings. The grades of compatibility in frequency were D, C, A & B. For locus HLA-A the most common gen was A2 for transplanted patients and for the rest of the Panamanian population is A24. For the locus HLA-B were B35 and B38 respectively and for the locus HLA-C the most common gen was C4, and C3 for the rest of the population.