Environmental heterogeneity at two spatial scales affects litter diversity-decomposition relationships

The effects of biodiversity on ecological processes have been experimentally evaluated mainly at the local scale under homogeneous conditions. To scale up experimentally based biodiversity-functioning relationships, there is an urgent need to understand how such relationships are affected by the environmental heterogeneity that characterizes larger spatial scales. Here, we tested the effects of an 800-m elevation gradient (a large-scale environmental factor) and forest habitat (a fine-scale factor) on litter diversity-decomposition relationships. To better understand local and landscape scale mechanisms, we partitioned net biodiversity effects into complementarity, selection, and insurance effects as applicable at each scale. We assembled different litter mixtures in aquatic microcosms that simulated natural tree holes, replicating mixtures across blocks nested within forest habitats (edge, interior) and elevations (low, mid, high). We found that net biodiversity and complementarity effects increased over the elevation gradient, with their strength modified by forest habitat and the identity of litter in mixtures. Complementarity effects at local and landscape scales were greatest for combinations of nutrient-rich and nutrient-poor litters, consistent with nutrient transfer mechanisms. By contrast, selection effects were consistently weak and negative at both scales. Selection effects at the landscape level were due mainly to nonrandom overyielding rather than spatial insurance effects. Our findings demonstrate that the mechanisms by which litter diversity affects decomposition are sensitive to environmental heterogeneity at multiple scales. This has implications for the scaling of biodiversity-ecosystem function relationships and suggests that future shifts in environmental conditions due to climate change or land use may impact the functioning of aquatic ecosystems.

Disgust sensitivity relates to attitudes toward gay men and lesbian women across 31 nations

Previous work has reported a relation between pathogen-avoidance motivations and prejudice toward various social groups, including gay men and lesbian women. It is currently unknown whether this association is present across cultures, or specific to North America. Analyses of survey data from adult heterosexuals ( N = 11,200) from 31 countries showed a small relation between pathogen disgust sensitivity (an individual-difference measure of pathogen-avoidance motivations) and measures of antigay attitudes. Analyses also showed that pathogen disgust sensitivity relates not only to antipathy toward gay men and lesbians, but also to negativity toward other groups, in particular those associated with violations of traditional sexual norms (e.g., prostitutes). These results suggest that the association between pathogen-avoidance motivations and antigay attitudes is relatively stable across cultures and is a manifestation of a more general relation between pathogen-avoidance motivations and prejudice towards groups associated with sexual norm violations.

Study of the ultrastructure of Enterococcus faecalis and Streptococcus mutans incubated with salivary antimicrobial peptides

OBJECTIVES

Enterococcus faecalis has been associated with root canal infections, while Streptococcus mutans has a central role in the etiology of dental caries. One of the main reasons of endodontic failure has been associated to the presence of E. faecalis and the formation of biofilms. S. mutans inhabits the oral cavity, specifically the dental plaque, which is a multispecies biofilm formed on the hard surfaces of the tooth. The biofilm formation is the main factor determining the pathogenicity of numerous bacteria. Natural antimicrobial peptides in the saliva protect against pathogenic bacteria and biofilms. The aim of this study was to assess the ultrastructural damage induced by salivary peptides in bacteria involved in biofilms has not been previously studied.

MATERIAL AND METHODS

Enterococcus faecalis and S. mutans incubated with cystatin C, chromogranin A, or histatin 5 were morphologically analyzed and counted. The ultrastructural damage was evaluated by transmission electron microscopy (TEM).

RESULTS

A decrease in bacterial numbers was observed after incubation with cystatin C, chromogranin A, or histatin 5, compared to the control group (P <  0.001). Ultrastructural damage in E. faecalis and S. mutans incubated with salivary peptides was found in the cell wall, plasma membrane with a decreased distance between the bilayers, a granular pattern in the cytoplasm, and pyknotic nucleoids.

CONCLUSIONS

This study demonstrated that salivary peptides exert antibacterial activity and induce morphological damage on E. faecalis and S. mutans. Knowledge on the ultrastructural damage inflicted by salivary antimicrobial peptides on two important bacteria causing dental caries and root canal infections could aid the design of new therapeutic approaches to facilitate the elimination of these bacteria.

Chilean Version of the Empathy Quotient (EQ) Scale: Adaptation and Psychometric Properties

We evaluated the psychometric properties of the empathy quotient (EQ) scale translated to Spanish in Chile. We estimated its structural validity, and its construct validity with other convergent measures of empathy and attachment, as well an inversely associated construct such as aggression. We used a general sample of students and community individuals (n = 336). Participants completed the EQ, Interpersonal Reactivity Index (IRI), and Buss-Perry Aggression Questionnaire (BPAQ). Another exclusively community group (n = 102) completed Collins Adult Attachment scale and the EQ. CFA and ESEM analyses confirmed the structural model fit of the data to three previously reported dimensions of the EQ: cognitive empathy (CE), emotional reactivity (ER) and social skills (SS). Sex-differences in emotional reactivity, and the predicted relationships with the convergent measures were observed. The current Chilean version of the EQ resulted in an appropriate multidimensional measurement of empathy. Finally, providing a specific social skills dimension extends the traditional conception of cognitive and affective empathy to the social realm in the Chilean context.

Influence of soil redox state on mercury sorption and reduction capacity

We investigated the mechanisms of interactions between divalent aqueous Hg and rock samples originating from an outcropping rock formation, the Albian Tégulines Clay (France, Aube). Two solid samples collected at two different depths (7.7 and 21.2 m depth) in the rock formation were selected since, in situ, they had and were still experiencing contrasting redox conditions, and thus had different mineralogy with regards to the minerals containing redox-sensitive elements, in particular iron. The sample that was the closer to the surface was under oxidizing conditions and contained goethite and siderite, while the deeper one was under reducing conditions and had more siderite, together with pyrite and magnetite. The redox state of the samples was preserved throughout the present study by careful conditioning, preparation, and use them under O₂-free conditions. The two samples had similar affinity for Hg, with a retention coefficient (R_D) ranging between 10² and 10⁶ mol·kg^-1 when the aqueous Hg concentration ranged between 4.4 and 10⁷ ng·L^-1 with the lowest concentration for the highest R_D. However, the mechanisms of interaction differed. In the oxidized sample, no change in Hg redox state was observed, and the retention was due to reversible adsorption on the mineral phases (including organic matter). In contrast, upon interaction with the deeper and reduced sample, Hg was not only adsorbed on the mineral phases, but part of it was also reduced to dissolve elemental Hg. This reduction was attributed to magnetite and siderite and highlights the influence of mineralogy on the geochemical cycle of Hg.

Optimization of Diabetic Macular Edema Management in the Real World: A Model of Excellence in Retina Units: The EMUREX Initiative

PURPOSE

To define and develop a model of excellence for the clinical management of diabetic macular edema (DME) patients in a real-world setting.

METHODS

A multidisciplinary joint commission (5 ophthalmologists, 1 nurse, and 1 pharmaceutic) established a series of preliminary recommendations based on clinical guidelines and DME activity results from 8 Pilot Hospitals (PH). These were validated by members of each PH and a group of DME patients in discussion workshops. Thus, the validated guideline (VG) took into consideration different aspects, namely, main core points (ranging 0-100), criteria, and indicators. Finally, each PH own setting was compared to the VG in order to settle down a starting point to clinical excellence.

RESULTS

Mean PH score was 51.5 (range 30-65). As compared to their maximum, main points that showed best scores were Clinical Guidelines and Protocols (78%) and Portfolio of Services (73%). Topics reaching close to 50% scoring included Resources (55%), Innovation (54%), Care Process (53%), Organization (52%), and Leadership (50%). Lowest scores were observed in the Strategic Alliances (46%) and Staff (37%) points.

CONCLUSIONS

Analysis of each PH by the VG delivered a global vision of the starting situation, especially focused in the identification of the different improvement areas. In order to further extend this model into the Public Health System, the effect of implementing it in different hospitals should be assessed to analyze its impact on daily clinical practice and health economics.

Microbially Mediated Release of As from Mekong Delta Peat Sediments

Peat layers within alluvial sediments are considered effective arsenic (As) sinks under reducing conditions due to the binding of As(III) to thiol groups in natural organic matter (NOM) and the formation of As-bearing sulfide phases. However, their possible role as sources of As for anoxic groundwaters remains unexplored. Here, we perform laboratory experiments to provide evidence for the role of a sediment peat layer in releasing As. Our results show that the peat layer, deposited about 8,000 years ago in a paleomangrove environment in the nascent Mekong Delta, could be a source of As to porewater under reducing conditions. X-ray absorption spectroscopy (XAS) analysis of the peat confirmed that As was bound to NOM thiol groups and incorporated into pyrite. Nitrate was detected in peat layer porewater, and flow-through and batch experiments evidenced the release of As from NOM and pyrite in the presence of nitrate. Based on poisoning experiments, we propose that the microbially mediated oxidation of arsenic-rich pyrite and organic matter coupled to nitrate reduction releases arsenic from this peat. Although peat layers have been proposed as As sinks in earlier studies, we show here their potential to release depositional- and/or diagenetically-accumulated As.

Structural, mechanical, spectroscopic and thermodynamic characterization of the copper-uranyl tetrahydroxide mineral vandenbrandeite

The full crystal structure of the copper-uranyl tetrahydroxide mineral (vandenbrandeite), including the positions of the hydrogen atoms, is established by the first time from X-ray diffraction data taken from a natural crystal sample from the Musonoi Mine, Katanga Province, Democratic Republic of Congo. The structure is verified using first-principles solid-state methods. From the optimized structure, the mechanical and dynamical stability of vandenbrandeite is studied and a rich set of mechanical properties are determined. The Raman spectrum is recorded from the natural sample and determined theoretically. Since both spectra have a high-degree of consistence, all spectral bands are rigorously assigned using a theoretical normal-coordinate analysis. Two bands in the Raman spectra, located at 2327 and 1604 cm⁻¹, are recognized as overtones and a band at 1554 cm⁻¹ is identified as a combination band. The fundamental thermodynamic functions of vandenbrandeite are computed as a function of temperature using phonon calculations. These properties, unknown so far, are key-parameters for the performance-assessment of geological repositories for storage of radioactive nuclear waste and for understanding the paragenetic sequence of minerals arising from the corrosion of uranium deposits. The thermodynamic functions are used here to determine the thermodynamic properties of formation of vandenbrandeite in terms of the elements and the Gibbs free-energies and reaction constants for a series of reactions involving vandenbrandeite and a representative subset of the most important secondary phases of spent nuclear fuel. Finally, from the thermodynamic data of these reactions, the relative stability of vandenbrandeite with respect to these phases as a function of temperature and in the presence of hydrogen peroxide is evaluated. Vandenbrandeite is shown to be highly stable under the simultaneous presence of water and hydrogen peroxide.

The experimental full crystal structure of vandenbrandeite is stablished for the first time and verified using first-principles methods. A detailed mechanical, spectroscopic and thermodynamic characterization is obtained from the optimized structure.

Retention of arsenic, chromium and boron on an outcropping clay-rich rock formation (the Tégulines Clay, eastern France)

The retention behavior of three toxic chemicals, As, Cr and B, was investigated for an outcropping rock formation, the Albian Tégulines Clay (France, Aube). At a shallow depth, Tégulines Clay is affected by weathering processes leading to contrasted geochemical conditions with depth. One of the main features of the weathering is the occurrence of a redox transition zone near the surface. Batch sorption experiments of As(V), As(III), Cr(VI) and B were performed on samples collected at two depths representative either of oxidized or reduced mineral assemblages. Batch sorption experiments highlighted a distinct behavior between As, Cr and B oxyanions. Cr(VI) retention behavior was dominated by redox phenomena, notably its reduction to Cr(III). The in-situ redox state of the Tégulines Clay samples has a significant effect on Cr retention. On the contrary, As(V) reduction into As(III) is moderate and its retention slightly affected by the in-situ redox state of the Tégulines Clay. As(V) retention is higher than As(III) retention in agreement with literature data. B retention is strongly related to its natural abundance in the Tégulines clay samples. Distribution coefficient of B corrected from its natural content is expected to be very low for in-situ conditions. Finally, the retention and mobility of these oxyanions were affected by clay mineralogy, natural abundance, and reducing capacity of the Tegulines Clay.

Becquerelite mineral phase: crystal structure and thermodynamic and mechanical stability by using periodic DFT

The structure, thermodynamic and mechanical properties of becquerelite mineral, Ca(UO₂)₆O₄(OH)₆·8H₂O, were studied by means of theoretical solid-state calculations based on density functional theory using plane waves and pseudopotentials. The positions of the hydrogen atoms in the unit cell of becquerelite mineral were optimized theoretically since it was not possible to determine them from X-ray diffraction data by structure refinement. The structural results, including the lattice parameters, bond lengths and X-ray powder pattern, were found to be in excellent agreement with their experimental counterparts. The fundamental thermodynamic properties of becquerelite mineral, including specific heat, entropy, enthalpy and Gibbs free energy, were then computed by performing phonon calculations at the computed optimized structure. Since the experimental values of these properties are unknown, their values were predicted. The values obtained for the isobaric specific heat and entropy of becquerelite at the temperature of 298.15 K were 148.4 and 172.3 J K⁻¹ mol⁻¹, respectively. The computed thermodynamic properties were combined with those of the corresponding elements in order to obtain the enthalpy and Gibbs free energy of formation as a function of temperature. The availability of these thermodynamic properties of formation allowed to determine the enthalpies and free energies and associated reaction constants of a series of reactions involving becquerelite and other uranyl containing materials. Futhermore, knowledge of these properties permitted the study of the thermodynamic stability of becquerelite with respect to a rich set of secondary phases of spent nuclear fuel, including dehydrated schoepite, schoepite, metaschoepite, studtite, metastudtite, rutherfordine and soddyite under different conditions of temperature. Becquerelite is shown to be highly stable in the presence of hydrogen peroxide. It is the second most stable phase under intermediate hydrogen peroxide concentrations (after schoepite), and the fourth most stable phase under high hydrogen peroxide concentrations (after studtite, schoepite and metaschoepite). Finally, the equation of state and elastic properties of this mineral, unknown to date, were determined. The crystal structure of becquerelite was found to be stable mechanically and dynamically. Becquerelite can be described as a brittle material exhibiting large anisotropy and large compressibility in the direction perpendicular to the sheets characterizing the structure of this layered uranyl containing material. The dependence of the elastic properties of becquerelite with respect to the strain orientation is shown to be analogous to that of schoepite mineral. The calculated bulk modulus is also very similar to that of schoepite, B ∼ 31 GPa.

The full crystal structure of becquerelite mineral phase was successfully determined using theoretical solid-state methods for the first time. Additionally, a complete study of its thermodynamic and mechanical properties and stability is reported.

[Recommendations of health care users and professionals to achieve a timely access to HIV diagnosis]

BACKGROUND

Early HIV (human immunodeficiency virus) diagnosis optimizes therapies aimed at reducing viral load, increasing survival, lowering health costs and reducing the number of people infected with the virus. In Chile, despite widespread and readily available HIV testing, infected people continue to get tested in a late fashion and are usually diagnosed in advanced stages of the disease.

AIM

To determine the elements that facilitate or impede a timely HIV testing and to evaluate how to improve the access to HIV testing.

MATERIAL AND METHODS

Descriptive, in-depth interviews to 30 participants with unknown serology, 15 participants diagnosed at AIDS stage and 15 health care professionals working at a primary healthcare settings.

RESULTS

Users and professionals formulated three suggestions to improve timely access to ELISA test for HIV diagnosis. Namely, to inform users and professionals about the characteristics of the disease and diagnostic test, to offer fast and easy access to HIV testing, and to train the whole healthcare team about obtaining informed consent for testing.

CONCLUSIONS

These recommendations should be implemented at healthcare centers to attain a timely HIV diagnosis.

Evaluación chilena del Inventario de Comportamientos de la Pareja que Provocan Celos

El presente estudio muestra la adaptación al contexto local del Inventario de Comportamientos de la Pareja que Provocan Celos (ICPC) creado en Holanda por Dijkstra, Barelds y Groothof (2010). Un pilotaje del inventario arrojó alta consistencia interna y estabilidad test-retest. Se administró el cuestionario a un grupo de 366 personas y 31 participantes completaron el retest. Un análisis factorial exploratorio permitió diferenciar las particularidades del instrumento en su configuración original y el contexto local, convergiendo en tres dimensiones: comportamiento infiel, comportamiento sospechoso y atracción mediática. Los resultados indicaron similares valores de consistencia interna para las dimensiones locales y las dimensiones de la escala original, así como los mismos patrones de correlación de las dimensiones entre sí; al igual que diferencias sexuales esperables desde el marco evolucionario, siendo las mujeres quienes responden con mayores valores en dos de las dimensiones de este constructo, reflejando una fuerte reacción basal a las situaciones que amenazan una relación valorada. 

Interlayer collapse affects on cesium adsorption onto illite

Cesium adsorption onto Illite has been widely studied, because this clay is especially relevant for Cs migration-retention in the environment. The objective of this study is to analyze how Cs adsorption onto Illite is affected by structural changes produced by the presence of different exchangeable cations--and specifically interlayer collapse. Cs sorption isotherms were carried out with Illite previously exchanged with Na, K, or Ca, at a broad enough range of ionic strength, for the determination of the possible affect of the electrolyte on the structure of Illite. In the presence of Ca, the maximum sorbed Cs was unexpectedly high (900 mequiv · kg(-1)) given the cationic exchange capacity commonly accepted for Illite (near 200 mequiv · kg(-1)). This was explained by the expansion of Illite layers (decollapse) induced by large hydrated cations such as Ca(2+) that may facilitate cation uptake--especially Cs(+), which is a highly selective cation. In the presence of Ca (and most probably of other divalent cations), Cs accessibility to exchange positions is increased. Both experimental evidence and the modeling of Cs sorption onto Illite supported the hypothesis of decollapse. Our results demonstrate the requirement of accounting for Illite decollapse especially for high Cs loadings, because of the potential prediction errors for its migration. Ignoring the Illite decollapse could lead the biased estimation of selectivity coefficients and consequently the erroneous prediction of sorption/migration behavior of Cs, and possibly other contaminants, in the environment.

Assessment of the Behavioral Inhibition System and the Behavioral Approach System: Adaptation and Validation of the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ) in a Chilean Sample

The goal of the present study is to estimate the psychometric properties of the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ; Torrubia, Ávila, Moltó, & Caseras, 2001) in a sample of Chilean college students. The main hypothesis is that the instrument would show appropriate levels of reliability and validity, in light of previous validation studies. A pilot study was conducted in order to generate the adapted version of the questionnaire, which was then applied to a student sample from different undergraduate careers (n = 434). The results show the expected levels of reliability (test-retest and internal consistency). The factorial validity does not comply with the expected model, suggesting a further consideration of the structure of the questionnaire. External validity is appropriate, as the questionnaire shows the expected correlations with other personality measures. It is concluded that the SPSRQ is adequate for the context of validation, and this study contributes to the generalization of the questionnaire, since the results are consistent with the expected psychometric properties that have been reported in the literature.

Contribution of ion binding affinity to ion selectivity and permeation in KcsA, a model potassium channel

Ion permeation and selectivity, key features in ion channel function, are believed to arise from a complex ensemble of energetic and kinetic variables. Here we evaluate the contribution of pore cation binding to ion permeation and selectivity features of KcsA, a model potassium channel. For this, we used E71A and M96V KcsA mutants in which the equilibrium between conductive and nonconductive conformations of the channel is differently shifted. E71A KcsA is a noninactivating channel mutant. Binding of K(+) to this mutant reveals a single set of low-affinity K(+) binding sites, similar to that seen in the binding of K(+) to wild-type KcsA that produces a conductive, low-affinity complex. This seems consistent with the observed K(+) permeation in E71A. Nonetheless, the E71A mutant retains K(+) selectivity, which cannot be explained on the basis of just its low affinity for this ion. At variance, M96V KcsA is a rapidly inactivating mutant that has lost selectivity for K(+) and also conducts Na(+). Here, low-affinity binding and high-affinity binding of both cations are detected, seemingly in agreement with both being permeating species in this mutant channel. In conclusion, binding of the ion to the channel protein seemingly explains certain gating, ion selectivity, and permeation properties. Ion binding stabilizes greatly the channel and, depending upon ion type and concentration, leads to different conformations and ion binding affinities. High-affinity states guarantee binding of specific ions and mediate ion selectivity but are nonconductive. Conversely, low-affinity states would not discriminate well among different ions but allow permeation to occur.

Pyrolysis of a waste from the grinding of scrap tyres

The fibres that are used to reinforce tyres can be recovered as a waste in the process of grinding of scrap tyres. In this paper beneficiation through pyrolysis is studied since the fibres are made up of polymers with a small amount of rubber because the latter is difficult to separate. The experiments were performed at three temperatures (400, 550 and 900°C) in a horizontal oven. The three products - gas, oil and char - obtained from the pyrolysis were investigated. The composition of the gas was analyzed by means of gas chromatography. The oil was studied by gas chromatography and infrared spectroscopy. The char porous structure was determined by N(2) adsorption. In addition, the topography of the chars was studied by means of scanning electron microscopy (SEM). The products resulting from the pyrolysis of the fibres were compared with those obtained from scrap rubber.

Ion binding to KcsA: implications in ion selectivity and channel gating

Binding of K+ and Na+ to the potassium channel KcsA has been characterized from the stabilization observed in the heat-induced denaturation of the protein as the ion concentration is increased. KcsA thermal denaturation is known to include (i) dissociation of the homotetrameric channel into its constituent subunits and (ii) protein unfolding. The ion concentration-dependent changes in the thermal stability of the protein, evaluated as the Tm value for thermal-induced denaturation of the protein, may suggest the existence of both high- and low-affinity K+ binding sites of KcsA, which lend support to the tenet that channel gating may be governed by K+ concentration-dependent transitions between different affinity states of the channel selectivity filter. We also found that Na+ binds to KcsA with a KD similar to that estimated electrophysiologically from channel blockade. Therefore, our findings on ion binding to KcsA partly account for K+ over Na+ selectivity and Na+ blockade and argue against the strict “snug fit” hypothesis used initially to explain ion selectivity from the X-ray channel structure. Furthermore, the remarkable effects of increasing the ion concentration, K+ in particular, on the Tm of the denaturation process evidence that synergistic effects of the metal-mediated intersubunit interactions at the channel selectivity filter are a major contributor to the stability of the tetrameric protein. This observation substantiates the notion of a role for ions as structural “effectors” of ion channels.

Occupancy of nonannular lipid binding sites on KcsA greatly increases the stability of the tetrameric protein

KcsA, a homotetrameric potassium channel from prokaryotes, contains noncovalently bound lipids appearing in the X-ray crystallographic structure of the protein. The binding sites for such high-affinity lipids are referred to as "nonannular" sites, correspond to intersubunit protein domains, and bind preferentially anionic phospholipids. Here we used a thermal denaturation assay and detergent-phospholipid mixed micelles containing KcsA to study the effects of different phospholipids on protein stability. We found that anionic phospholipids stabilize greatly the tetrameric protein against irreversible, heat-induced unfolding and dissociation into subunits. This occurs in a phospholipid concentration-dependent manner, and phosphatidic acid species with acyl chain lengths ranging 14 to 18 carbon atoms are more efficient than similar phosphatidylglycerols in protecting the protein. A docking model of the KcsA-phospholipid complex suggests that the increased protein stability originates from the intersubunit nature of the binding sites and, thus, interaction of the phospholipid with such sites holds together adjacent subunits within the tetrameric protein. We also found that simpler amphiphiles, such as alkyl sulfates longer than 10 carbon atoms, also increase the protein stability to the same extent as anionic phospholipids, although at higher concentrations than the latter. Modeling the interaction of these simpler amphiphiles with KcsA and comparing it with that of anionic phospholipids serve to delineate the features of a hydrophobic pocket in the nonannular sites. Such pocket is predicted to comprise residues from the M2 transmembrane segment of a subunit and from the pore helix of the adjacent subunit and seems most relevant to protein stabilization.

Exploring the relationship between vagal tone and event-related potentials in response to an affective picture task

The present study is the first to investigate the relationship between vagal tone level and event-related potentials (ERPs) in adults. Numerous studies have shown a relationship between vagal tone and the individual differences between a variety of psychophysiological, affective, and social outcomes. This suggests that vagal tone can be related to how people process relevant affective social information at the brain level. This study aimed to assess whether the ERP response varies between high and low vagal tone groups, in the face of salient affective information. In the experimental cohort, two groups were separated according to their vagal tone level. ERPs were recorded while individuals performed an affective picture task that included positive, neutral, and negative emotional stimuli. Differences between the high and low vagal tone groups were observed at the early posterior negativity for both positive and negative valences, and at the late positive potential for all the categories. It can be concluded that differences between high and low vagal tone levels are related to differences in the ERPs at early, middle, and late latencies. The results are discussed with respect to the effect of differences between the vagal tone conditions on various stages of information-processing.

Association between total immunoglobulin E and antibody responses to naturally acquired Ascaris lumbricoides infection and polymorphisms of immune system-related LIG4, TNFSF13B and IRS2 genes

The 13q33-34 region harbours a susceptibility locus to Ascaris lumbricoides, although the underlying genes are unknown. Immunoglobulin (Ig)E and IgG confer protective immunity and here we sought to investigate in an endemic population whether LIG4, TNFSF13B and IRS2 genes influence IgE and IgG levels against Ascaris and the ABA-1 allergen as a putative resistance marker. Mite-allergic asthmatic patients were analysed for potential relationships between Ascaris predisposition and allergy. One thousand and sixty-four subjects from Cartagena, Colombia, were included. Single nucleotide polymorphisms (SNPs) were genotyped using TaqMan assays. Antibody levels were measured by enzyme-linked immunosorbent assay. Linear and logistic regressions were used to model effects of genotypes on antibody levels. The GG genotype of LIG4 (rs1805388) was associated with higher IgE levels to Ascaris compared with other genotypes. TNFSF13B (rs10508198) was associated positively with IgG levels against Ascaris extract and IgE levels against ABA-1. In asthmatics, IRS2 (rs2289046) was associated with high total IgE levels. Associations held up after correction by population stratification using a set of 52 ancestry markers, age, sex and disease status. There was no association with asthma or mite sensitization. In a tropical population, LIG4 and TNFSF13B polymorphisms are associated with specific IgE and IgG to Ascaris, supporting previous linkage studies implicating the 13q33 region. Our results suggest that genes protecting against parasite infections can be different to those predisposing to asthma and atopy.

[Prevalence of drug abuse among children in basic schools]

BACKGROUND

Peer methodology (PM) is an adaptation of the privileged access interviewer methodology and is used for prevalence studies. PM estimates higher drug consumption frequencies among school and college students than self reports, since it minimizes underreporting.

AIM

To assess drug abuse among students using PM.

MATERIAL AND METHODS

A random sample of 234 school students of middle and low-middle socioeconomic status, aged 9 to 14 years (53% women) were interviewed using PM about drug consumption.

RESULTS

The frequency of illicit drug consumption during the last year was 29% and 15% during the last month (current consumption). The consumption of tobacco and alcohol was 20% and 18% respectively during the last year. The figures for the last month were 11% and 8% respectively. The beginning age for smoking and alcohol consumption were 11.1 +/-1.5 and 11.3+/- 1.8 years respectively. The frequency of illicit drug consumption was 3.5%. Illicit drug users began illicit drug consumption at earlier ages their non user peers.

CONCLUSIONS

There is a high frequency of illicit drug consumption among school age children.

Psicología Evolucionaria: un marco integrador para la disciplina Psicológica en el Bicentenario de Darwin

El objetivo del artículo es presentar los principios de la Psicología Evolucionaria y sus aportes a la comprensión de la condición humana. Se revisan brevemente los conceptos fundamentales de esta perspectiva, haciendo hincapié en la concepción de la mente como una adaptación, explicitando su articulación a través de la selección natural y sexual. Se ejemplifican las emociones como una adaptación destinada a la supervivencia, y algunas diferencias entre hombres y mujeres como producto de la selección sexual. La discusión se orienta al valor integrador de la perspectiva evolucionaria, dejando atrás el debate entre la naturaleza y la crianza, además de reconocer su alto potencial como un marco de convergencia interdisciplinaria, que fomenta la investigación y trasciende las barreras disciplinarias clásicas.    

Inverse modeling of multicomponent reactive transport through single and dual porosity media

Compacted bentonite is foreseen as buffer material for high-level radioactive waste in deep geological repositories because it provides hydraulic isolation, chemical stability, and radionuclide sorption. A wide range of laboratory tests were performed within the framework of FEBEX (Full-scale Engineered Barrier EXperiment) project to characterize buffer properties and develop numerical models for FEBEX bentonite. Here we present inverse single and dual-continuum multicomponent reactive transport models of a long-term permeation test performed on a 2.5 cm long sample of FEBEX bentonite. Initial saline bentonite porewater was flushed with 5.5 pore volumes of fresh granitic water. Water flux and chemical composition of effluent waters were monitored during almost 4 years. The model accounts for solute advection and diffusion and geochemical reactions such as aqueous complexation, acid-base, cation exchange, protonation/deprotonation by surface complexation and dissolution/precipitation of calcite, chalcedony and gypsum. All of these processes are assumed at local equilibrium. Similar to previous studies of bentonite porewater chemistry on batch systems which attest the relevance of protonation/deprotonation on buffering pH, our results confirm that protonation/deprotonation is a key process in maintaining a stable pH under dynamic transport conditions. Breakthrough curves of reactive species are more sensitive to initial porewater concentration than to effective diffusion coefficient. Optimum estimates of initial porewater chemistry of saturated compacted FEBEX bentonite are obtained by solving the inverse problem of multicomponent reactive transport. While the single-continuum model reproduces the trends of measured data for most chemical species, it fails to match properly the long tails of most breakthrough curves. Such limitation is overcome by resorting to a dual-continuum reactive transport model.

Protein-promoted membrane domains

The current notion of biological membranes encompasses a very complex structure, made of dynamically changing compartments or domains where different membrane components partition. These domains have been related to important cellular functions such as membrane sorting, signal transduction, membrane fusion, neuronal maturation, and protein activation. Many reviews have dealt with membrane domains where lipid-lipid interactions direct their formation, especially in the case of raft domains, so in this review we considered domains induced by integral membrane proteins. The nature of the interactions involved and the different mechanisms through which membrane proteins segregate lipid domains are presented, in particular with regard to those induced by the nAChR. It may be concluded that coupling of favourable lipid-lipid and lipid-protein interactions is a general condition for this phenomenon to occur.

Lumbar Bone Mineral Density in Renal Transplant Patients on Neoral and Tacrolimus: A Four-Year Prospective Study

BACKGROUND

This prospective study was designed to investigate the long-term evolution of bone mineral density (BMD) in kidney transplant recipients.

METHODS

In 86 patients with functioning grafts, 65 on tacrolimus-based immunosuppression and 21 on cyclosporine-based immunosuppression, laboratory parameters and BMD measurements in lumbar spine (L2-L4) and femoral neck (FN) were performed by DEXA in the first month after transplantation (baseline) and yearly thereafter up to the fourth year.

RESULTS

BMD did not change at 12 months in lumbar spine nor in the FN. Detailed analysis identified three patterns of BMD in lumbar spine at 12 months: BMD remained stable in 27 patients (31.4%), decreased >2% in 31 (36.0%) and increased >2% in 28 (32.6%). Patients with no change or gain presented a parallel increase of BMD in FN (P<0.001 in both groups). On multivariate analysis, the variables associated with no change or lumbar BMD loss were total prednisone dose in grams at 12 months (OR 1.402; 95% CI 1.038-1.893; P=0.028), calcitriol levels at 12 months (OR 0.936; 95% CI 0.892-0.982; P=0.007) and lumbar BMD at baseline (OR 1.006; 95% CI 1.002-1.010; P=0.002). Late treatment with calcium supplements and calcitriol did not improve osteopenia.

CONCLUSIONS

One third of patients had bone loss mainly during the first year of follow-up. Bone loss was associated to higher baseline BMD, high steroid dose, and lower calcitriol levels at 1 year. Late administration of calcitriol and calcium supplements did not improve posttransplant osteopenia. More than 50% of patients were osteopenic 4 years after transplantation.

The influence of a membrane environment on the structure and stability of a prokaryotic potassium channel, KcsA

The lack of a membrane environment in membrane protein crystals is considered one of the major limiting factors to fully imply X-ray structural data to explain functional properties of ion channels [Gulbis, J.M. and Doyle, D. (2004) Curr. Opin. Struct. Biol. 14, 440-446]. Here, we provide infrared spectroscopic evidence that the structure and stability of the potassium channel KcsA and its chymotryptic derivative 1-125 KcsA reconstituted into native-like membranes differ from those exhibited by these proteins in detergent solution, the latter taken as an approximation of the mixed detergent-protein crystal conditions.

A cysteine protease from Taenia solium metacestodes induce apoptosis in human CD4+ T-cells

Here we investigated whether the depletion of CD4+ lymphocytes, observed in mononuclear cells incubated with Taenia solium metacestode E/S products or with living cysts was due to apoptosis. Using the deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL), electron microscopy and DNA gel electrophoresis, we found signs of apoptosis in these cells. Results showed that cysteine protease activity was responsible for this effect, since E-64 prevented cell death in all cases. Electron microscopy studies showed that lymphocytes exhibited features of apoptosis such as cellular membrane integrity, strangling and fragmentation of nuclei, chromatin condensation, apoptotic bodies and loss of microvilli. In contrast, lymphocytes co-cultured with living metacestodes plus E-64 exhibited integrity of their structures. DNA fragmentation was detected by TUNEL assays and DNA gel electrophoresis. The results suggested that cell death induced by the cysteine protease from the T. solium metacestode may be involved in down-regulation of cell-mediated responses in infected hosts.

Probing the channel-bound shaker B inactivating peptide by stereoisomeric substitution at a strategic tyrosine residue

A synthetic peptide patterned after the sequence of the inactivating ball domain of the Shaker B K(+) channel, the ShB peptide, fully restores fast inactivation in the deletion Shaker BDelta6-46 K(+) channel, which lacks the constitutive ball domains. On the contrary, a similar peptide in which tyrosine 8 is substituted by the secondary structure-disrupting d-tyrosine stereoisomer does not. This suggests that the stereoisomeric substitution prevents the peptide from adopting a structured conformation when bound to the channel during inactivation. Moreover, characteristic in vitro features of the wild-type ShB peptide such as the marked propensity to adopt an intramolecular beta-hairpin structure when challenged by anionic phospholipid vesicles, a model target mimicking features of the inactivation site in the channel protein, or to insert into their hydrophobic bilayers, are lost in the d-tyrosine-containing peptide, whose behavior is practically identical to that of noninactivating peptide mutants. In the absence of high resolution crystallographic data on the inactivated channel/peptide complex, these latter findings suggest that the structured conformation required for the peptide to promote channel inactivation, as referred to above, is likely to be beta-hairpin.

Tyrosine phosphorylation of the inactivating peptide of the shaker B potassium channel: a structural-functional correlate

A synthetic peptide patterned after the sequence of the inactivating "ball" domain of the Shaker B K(+) channel restores fast (N-type) inactivation in mutant deletion channels lacking their constitutive ball domains, as well as in K(+) channels that do not normally inactivate. We now report on the effect of phosphorylation at a single tyrosine in position 8 of the inactivating peptide both on its ability to restore fast channel inactivation in deletion mutant channels and on the conformation adopted by the phosphorylated peptide when challenged by anionic lipid vesicles, a model target mimicking features of the inactivation site in the channel protein. We find that the inactivating peptide phosphorylated at Y8 behaves functionally as well as structurally as the noninactivating mutant carrying the mutation L7E. Moreover, it is observed that the inactivating peptide can be phosphorylated by the Src tyrosine kinase either as a free peptide in solution or when forming part of the membrane-bound protein channel as the constitutive inactivating domain. These findings suggest that tyrosine phosphorylation-dephosphorylation of this inactivating ball domain could be of physiological relevance to rapidly interconvert fast-inactivating channels into delayed rectifiers and vice versa.

Functional inactivation of the IGF-I and insulin receptors in skeletal muscle causes type 2 diabetes

Peripheral insulin resistance and impaired insulin action are the primary characteristics of type 2 diabetes. The first observable defect in this major disorder occurs in muscle, where glucose disposal in response to insulin is impaired. We have developed a transgenic mouse with a dominant-negative insulin-like growth factor-I receptor (KR-IGF-IR) specifically targeted to the skeletal muscle. Expression of KR-IGF-IR resulted in the formation of hybrid receptors between the mutant and the endogenous IGF-I and insulin receptors, thereby abrogating the normal function of these receptors and leading to insulin resistance. Pancreatic beta-cell dysfunction developed at a relative early age, resulting in diabetes. These mice provide an excellent model to study the molecular mechanisms underlying the development of human type 2 diabetes.

Thermodynamic analysis of helix-engineered forms of the activation domain of human procarboxypeptidase A2

Thermodynamic characterization of the activation domain of human procarboxypeptidase A2, ADA2h, and its helix-engineered mutants was carried out by differential scanning calorimetry. The mutants were engineered by changing residues in the exposed face of the two alpha helices in order to increase their stability. At neutral and alkaline pH the three mutants, alpha-helix 1 (M1), alpha-helix 2 (M2) and alpha-helix 1 and alpha-helix 2 (DM), were more stable than the wild-type domain, in the order DM, M2, M1 and wild-type. Under these conditions the CD and NMR spectra of all the variants are very similar, indicating that this increase in stability is not the result of gross structural changes. Calorimetric analysis shows that the stabilizing effect of mutating the water-exposed surfaces of the helices seems to be mainly entropic, because the mutations do not change the enthalpy or the increase in heat capacity of denaturation. The unfolding behavior of all variants changes under acidic conditions: whereas wild-type and M1 have a strong tendency to aggregate, giving rise to a beta conformation upon unfolding, M2 and DM unfold reversibly, M2 being more stable than DM. CD and NMR experiments at pH 3.0 suggest that a region involving residues of the second and third beta strands as well as part of alpha-helix 1 changes its conformation. It seems that the enhanced stability of the altered conformation of M2 and DM reduces the aggregation tendency of ADA2h at acidic pH.

Thermodynamic analysis of the structural stability of phage 434 Cro protein

Thermodynamic parameters describing the phage 434 Cro protein have been determined by calorimetry and, independently, by far-UV circular dichroism (CD) measurements of isothermal urea denaturations and thermal denaturations at fixed urea concentrations. These equilibrium unfolding transitions are adequately described by the two-state model. The far-UV CD denaturation data yield average temperature-independent values of 0.99 +/- 0.10 kcal mol(-)(1) M(-)(1) for m and 0.98 +/- 0.05 kcal mol(-)(1) K(-)(1) for DeltaC(p)()(,U), the heat capacity change accompanying unfolding. Calorimetric data yield a temperature-independent DeltaC(p)()(,U) of 0.95 +/- 0.30 kcal mol(-)(1) K(-)(1) or a temperature-dependent value of 1.00 +/- 0.10 kcal mol(-)(1) K(-)(1) at 25 degrees C. DeltaC(p)()(,U) and m determined for 434 Cro are in accord with values predicted using known empirical correlations with structure. The free energy of unfolding is pH-dependent, and the protein is completely unfolded at pH 2.0 and 25 degrees C as judged by calorimetry or CD. The stability of 434 Cro is lower than those observed for the structurally similar N-terminal domain of the repressor of phage 434 (R1-69) or of phage lambda (lambda(6)(-)(85)), but is close to the value reported for the putative monomeric lambda Cro. Since a protein's structural stability is important in determining its intracellular stability and turnover, the stability of Cro relative to the repressor could be a key component of the regulatory circuit controlling the levels and, consequently, the functions of the two proteins in vivo.

Effect of the inactivating "ball" peptide of Shaker B on intermediate conductance Ca(2+)-dependent inwardly rectifying K+ channels of HeLa cells

The patch-clamp technique was used to study the effect of intracellularly added inactivating "ball" peptide (BP) of the Shaker B K+ channel upon Ca(2+)-dependent inwardly rectifying K+ channels of the intermediate conductance type expressed in HeLa cells. Intracellular BP caused only moderate inhibition of outward K+ currents when assayed at an intracellular Ca2+ concentration of 100 nmol/l. Increasing intracellular Ca2+ levels led in itself to some voltage-dependent blockade of K+ currents, which was absent when high extracellular K+ was used. An additional strong blockade by intracellular BP was nevertheless observed both in Na(+)- and K(+)-rich extracellular solutions. A non-inactivating BP analogue had no effect. At this higher intracellular Ca2+ concentration the inhibition of these intermediate conductance Ca(2+)-dependent channels by BP was voltage-dependent, being absent at hyperpolarizing potentials, and could be relieved by increasing extracellular K+. These data suggest that BP acts at an internal pore site in Ca(2+)-dependent intermediate conductance K+ channels of HeLa cells, and that these might possess a receptor site for the peptide similar to that of other K+ channels such as Ca(2+)-activated maxi-K+ channels.

Dehydroepiandrosterone, pregnenolone and sex steroids down-regulate reactive astroglia in the male rat brain after a penetrating brain injury

Astrocytes are a target for steroid hormones and for steroids produced by the nervous system (neurosteroids). The effect of gonadal hormones and several neurosteroids in the formation of gliotic tissue has been assessed in adult male rats after a penetrating wound of the cerebral cortex and the hippocampal formation. The hormones testosterone, 17beta-estradiol and progesterone and the neurosteroids dehydroepiandrosterone, pregnenolone and pregnenolone sulfate resulted in a significant decrease in the accumulation of astrocytes in the proximity of the wound and in a decreased bromodeoxyuridine incorporation in reactive astrocytes. Of all steroids tested, dehydroepiandrosterone was the most potent inhibitor of gliotic tissue formation. These findings suggest that neurosteroids and sex steroids may affect brain repair by down-regulating gliotic tissue.

Inactivating peptide of the Shaker B potassium channel: conformational preferences inferred from studies on simple model systems

Previous studies on the interaction between the inactivating peptide of the Shaker B K+ channel (ShB peptide, H2N-MAAVAGLYGLGEDRQHRKKQ) and anionic phospholipid vesicles, used as model targets, have shown that the ShB peptide: (i) binds to the vesicle surface with high affinity; (ii) readily adopts a strongly hydrogen-bonded beta-structure; and (iii) becomes inserted into the hydrophobic bilayer. We now report fluorescence studies showing that the vesicle-inserted ShB peptide is in a monomeric form and, therefore, the observed beta-structure must be intramolecularly hydrogen-bonded to produce a beta-hairpin conformation. Also, additional freeze-fracture and accessibility-to-trypsin studies, which aimed to estimate how deeply and in which orientation the folded monomeric peptide inserts into the model target, have allowed us to build structural models for the target-inserted peptide. In such models, the peptide has been folded near G6 to configure a long beta-hairpin modelled to produce an internal cancellation of net charges in the stretch comprising amino acids 1-16. As to the positively charged C-terminal portion of the ShB peptide (RKKQ), this has been modelled to be in parallel with the anionic membrane surface to facilitate electrostatic interactions. Since the negatively charged surface and the hydrophobic domains in the model vesicle target may partly imitate those present at the inactivation 'entrance' in the channel protein [Kukuljan, M., Labarca, P. and Latorre, R. (1995) Am. J. Physiol. Cell Physiol. 268, C535-C556], we believe that the structural models postulated here for the vesicle-inserted peptide could help to understand how the ShB peptide associates with the channel during inactivation and why mutations at specific sites in the ShB peptide sequence, such as that in the ShB-L7E peptide, result in non-inactivating peptide variants.

Brain Ac39/physophilin: cloning, coexpression and colocalization with synaptophysin

Physophilin is an oligomeric protein that binds the synaptic vesicle protein synaptophysin constituting a complex that has been hypothesized to form the exocytotic fusion pore. Microsequencing of several physophilin peptides putatively identified this protein as the Ac39 subunit of the V-ATPase. Ac39 has recently been shown to be present in a synaptosomal complex which, in addition to synaptophysin, includes the bulk of synaptobrevin II, and subunits c and Ac115 of the V0 sector of the V-ATPase. We have cloned physophilin from mouse brain and found a differential region of 12 amino acids when compared with the previously reported sequence of Ac39 from bovine adrenal medulla. RT-PCR cloning from the bovine adrenal medulla demonstrates that sequencing errors occurred in the previous cloning study, and shows that the amino acid sequences of physophilin and Ac39 are completely identical. In situ hybridization in rat brain reveals a largely neuronal distribution of Ac39/physophilin mRNA which spatio-temporally correlates with those of subunit c and synaptophysin. Immunohistochemical analysis shows that Ac39/physophilin is mostly concentrated in the neuropil with a pattern identical to subunit A and very similar to synaptophysin. Double-labelling immunofluorescence shows a complete colocalization of Ac39/physophilin with subunit A and a partial colocalization with synaptophysin in the neuropil. Our findings bring anatomical support for the in vivo occurrence of the synaptophysin-Ac39/physophilin interaction and further suggest a coordinated transcription of V-ATPase and synaptophysin genes. A putative role of Ac39/physophilin in the inactivation of the V-ATPase by disassembly of its V1 sector is also discussed.

Survey for secondary dapsone and rifampicin resistance in Cuba

A total of 1211 Cuban multibacillary leprosy patients treated for at least 5 years were clinically and bacteriologically examined. They were being treated according to a 2-phase monotherapy regimen with RMP first and DADDS afterwards. On skin-smear examination 50 patients were found positive, of which 9 showed a BI of 3+ or higher at any site. With regard to the clinical status the only cases found with clinical signs of relapse were 5 out of 7 long-standing patients with BI of 4+ and 5+. A 6th patient of this high BI group who showed a good clinical condition, except for a heavy infiltration of both earlobes, was receiving a second RMP course when examined and biopsied for this research. These 9 patients were biopsied and susceptibility tests to RMP and DDS performed. The results showed that in 1 case the Mycobacterium leprae were resistant to both drugs; the organisms from 2 other patients were susceptible to RMP but low-grade resistant to DDS. Those from another patient were susceptible to RMP and fully resistant to DDS. In 3 other cases the bacilli did not multiply in any of the mice but 1 of these strains was from the patient taking a second RMP course, therefore this strain might also be susceptible to RMP and resistant to DDS. In the last 2 cases multiplication was only observed in 2 of the controls and in 1 of the 0.0001% DDS treated mice; therefore, these experiments were not conclusive, and the AFB recovered were inoculated into fresh mice to repeat the tests but these failed to multiply.

Synaptic and non-synaptic immunolocalization of GABA and glutamate acid decarboxylase (GAD) in cerebellar cortex of rat

The existence of a large number of GABA receptors in the cerebellar molecular layer, and the observation of numerous punctate immunoreactive deposits of GABA synthesizing enzyme (GAD) throughout this layer, could indicate the existence of numerous axon terminals that may be involved in neurotransmission modulated by GABA. These axon terminals may be different from those considered classically as cerebellar GABAergic axon terminals. Therefore, we have reinvestigated the localization of GABA- and GAD-immunoreactivities in the cerebellar cortex of the rat with the PAP method, using different antisera obtained from rabbits immunized with GABA, baclofen and GAD. The results observed in our investigation have demonstrated GABA- and GAD-immunoreactivities in the axon terminals considered classically as GABAergic, as well as in others which, until now, have not been considered GABAergic. This fact leads us to think that the distribution of GABA or molecules structurally similar to GABA is far more extended than previously thought in the cerebellum. We have also observed both GABA- and GAD-immunoreactivities within dendrites and glial cells. These facts suggest us a possible extrasynaptic release of GABA.