Genotypes of the mannan-binding lectin gene and susceptibility to visceral leishmaniasis and clinical complications

Background. Visceral leishmaniasis (VL) is almost always lethal if not treated, but most infections with the causative agents are clinically silent. Mannan-binding lectin (MBL), an opsonin, is a candidate molecule for modifying progression to VL because it may enhance infection with intracellular pathogens. Mutations in the MBL2 gene decrease levels of MBL and may protect against development of VL. This case-control study examines genotypes of MBL2 and levels of MBL in individuals presenting with different outcomes of infection with Leishmania chagasi.Methods. Genotypes for MBL2 and levels of serum MBL were determined in uninfected control subjects (n=76) and in individuals presenting with asymptomatic infection (n=90) or VL (n=69).Results. Genotypes resulting in high levels of MBL were more frequent (odds ratio [OR], 2.5 [95% confidence interval {CI}, 1.3-5.0]; P=.006) among individuals with VL than among those with asymptomatic infections and were even more frequent (OR, 3.97 [95% CI, 1.10-14.38];P=.043) among cases of VL presenting with clinical complications than among those with uneventful courses. Serum levels of MBL were higher (P=.011) in individuals with VL than in asymptomatic infections.Conclusions. Genotypes of the MBL2 gene predict the risk for developing VL and clinical complications in infections with L. chagasi.

Effect of 17 beta-estradiol and alendronate on the removal torque of osseointegrated titanium implants in ovariectomized rats

Background: This study investigated the influence of estrogen deficiency and its treatment with estrogen and alendronate on the removal torque of osseointegrated titanium implants.Methods: Fifty-eight female Wistar rats received a titanium implant in the tibia metaphysis. After 60 days, which was needed for implant osseointegration, the animals were randomly divided into five groups: control (CTLE; N = 10), sham surgery (SHAM; N = 12), ovariectomy (OVX; N = 12), ovariectomy followed by hormone replacement (EST; N = 12), and ovariectomy followed by treatment with alendronate (ALE; N = 12). The CTLE group was sacrificed to confirm osseointegration, whereas the remaining groups were submitted to sham surgery or ovariectomy according to their designations. After 90 days, these animals were also sacrificed. Densitometry of femur and lumbar vertebrae was performed by dual-energy x-ray absorptiometry (DXA) to confirm systemic impairment of the animals. All implants were subjected to removal torque.Results: Densitometric analysis of the femur and lumbar vertebrae confirmed a systemic impairment of the animals, disclosing lower values of bone mineral density for OVX. Analysis of the removal torque of the implants showed statistically lower values (P <0.05) for the OVX group in relation to the other groups. However, the group treated with alendronate (ALE group) presented significantly higher torque values compared to the others.Conclusion: According to this study, estrogen deficiency was observed to have a negative influence on the removal torque of osseointegrated implants, whereas treatment with alendronate

Penetration of 38% hydrogen peroxide into the pulp chamber in bovine and human teeth submitted to office bleach technique

This study evaluated the pulp chamber penetration of peroxide bleaching agent in human and bovine teeth after office bleach technique. All the teeth were sectioned 3 mm apical of the cement-enamel junction and were divided into 2 groups, A (70 third human molars) and B (70 bovine lateral incisors), that were subdivided into A1 and B1 restored by using composite resin, A2 and B2 by using glass ionomer cement, and A3 and B3 by using resin-modified glass ionomer cement; A4, A5, B4, and B5 were not restored. Acetate buffer was placed in the pulp chamber, and the bleaching agent was applied for 40 minutes as follows: A1-A4 and B1-B4, 38% hydrogen peroxide exposure and A5 and B5, immersion into distilled water. The buffer solution was transferred to a glass tube in which leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined by spectrophotometer and converted into microgram equivalents of hydrogen peroxide. Data were submitted to analysis of variance and Dunnett, Kruskal-Wallis, and Tukey tests (5%). A higher level of hydrogen peroxide penetrated into the pulp chamber in resin-modified glass ionomer cements in bovine (0.79 +/- 0.61 mu g) and human (2.27 +/- 0.41 mu g) groups. The bleaching agent penetration into the pulp chamber was higher in human teeth for any experimental situation. The penetration of the hydrogen peroxide depends on restorative materials, and under the conditions of this study human teeth are more susceptible to penetration of bleaching agent into the pulp chamber than bovine teeth.

Microstructure and corrosion resistance of inorganic-organic (ZrO2-PMMA) hybrid coating on stainless steel

Zirconia-polymethylmetacrylate hybrids prepared by a sol-gel method were deposited by dip-coating on stainless steel to improve the resistance against wet corrosion. The effect of the concentration of polymethylmetacrylate and the number of coating applications on the microstructure and corrosion performance of coated samples was investigated. The microstructural properties of samples was analyzed by scanning electron and atomic force microscopy, adhesion tests and profilemeter measurements. The electrochemical corrosion was evaluated through potentiodynamic polarization curves at room temperature. Results show that the sample prepared with 17 vol.% of polymethylmethacrylate has a maximum corrosion resistance, smaller roughness, are hermetic and adherent to the substrate. This film increases the life time of the stainless steel by a factor 30. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Influence of diet on assimilation and turnover of C-13 in the tissues of broiler chickens

1. The C-13 turnover rates of the liver and thoracic pectoral muscle of growing broilers were determined by feeding diets with varying C-13 content.2. Male chicks ( 1- d- old) were subjected to treatments based on free choice of 5 different mixes of energy and protein sources from plants with C-3 and C-4 photosynthetic pathways that had differing C-13 content. Rice bran ( R) and soybean meal ( S) were the C-3 sources, while maize ( C) and maize gluten meal ( G) were the C-4 sources. Choices were R + S, C + G, R + G, C + S or R + C +G + S. The 6th treatment was a complete feed ( CF) that was similar to a commercial broiler feed.3. The isotopic composition of the birds' tissues was representative of the isotopic composition of the diets. The assimilation was faster for C-3, in both liver and muscle, than for C-4 diets, and give the delta per mil difference between the diet and tissues.4. The liver is the most active metabolic tissue and gave more rapid isotope turnover than in muscle.

ANISOTROPY OF ELECTRICAL-PROPERTIES IN ALPHA-FE2O3 CERAMICS

Electrical conductivity and thermoelectric power measurements carried out in a heamatite ceramic showed a strong anisotropy in directions normal and parallel to the uniaxial pressing direction. This behaviour is similar to that verified in alpha-Fe2O3 single crystal. The results suggest that the extended structural defects, generated during sintering, disturb the magnetic order on the (001) planes of alpha-Fe2O3 and limit the mobility of n type carriers.

Surface protection of fluoroindate glasses by sol-gel dip-coated SnO2 thin layers

SnO2 coatings were deposited by a sol-gel dip-coating process to shield fluoroindate glasses (40In-F-3:16BaF(2):20SrF(2):20ZnF(2):2NaF:2GaF(3)) against corrosion in aqueous environments. The effect of the number of coating applications and of the withdrawal speed on the thickness, density and roughness of tin oxide films was investigated by X-ray reflectivity. Film thickness increases both with the number of coating applications and the withdrawal speed. The aqueous leaching of uncoated and SnO2-coated fluoroindate glasses was studied by scanning electron microscopy (SEM) and infrared spectroscopy (FTIR), showing that the glass surface was protected against hydrolytic attack. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Structural and phenomenological characterization of the thermoreversible sol-gel transition of a zirconyl aqueous precursor modified by sulfuric acid

The thermoreversible sol-gel transition is well-known in biological and organic polymeric systems but has not been reported for inorganic systems. In this paper we put in evidence a thermoreversible sol-gel transition for zirconyl chloride aqueous solutions modified by sulfuric acid in the ratio 3:1 Zr:SO4. The synthesis conditions are detailed and a variety of experimental techniques (turbidimetry, dynamic rheology, and EXAFS) have been employed for investigating the thermal reversibility and the chemical structure of this new material. Turbidimetric measurements performed for solutions containing different concentrations of precursor have evidenced that the sol-gel transformation temperature increases from 50 to 80 degrees C as the concentration of zirconyl chloride decreases from 0.22 to 0.018 mol L-1. A more detailed study has been done for the sample with [Zr] = 0.156 mol L-1, in which the sol-gel-sol transformation has been repeated several times by a cyclic variation of the temperature. The mechanical properties of this sample, evaluated by measuring the storage and the loss moduli, show a change from liquid like to viscoelastic to elastic behavior during the sol-gel transition and vice versa during the gel-sol one. In situ EXAFS measurements performed at the Zr K-edge show that no change of the local order around Zr occurs during the sol-gel-sol transition, in agreement with the concept of physical gel formation. We have proposed for the structure of the precursor an inner core made of hydroxyl and oxo groups bridging together zirconium atoms surrounded in surface by complexing sulfate ligands, the sulfate groups act as a protective layer, playing a key role in the linking propagation among primary particles during sol-gel-sol transition.

Effect of age on seed digestion in parrots (Amazona aestiva)

The objective of this study was to compare the capacity of adult (more than 3 yr old) and young (less than 1 yr old) true parrots to digest seeds that are normally included in their diet in captivity, particularly soybean, sunflower, and corn. All the seeds were offered for 5 d with an interval of 15 d between different diets. The seeds of soybean and corn were boiled for 15 min and soaked in water at ambient temperature for 12 h before being fed to the birds. There were no differences in the digestibilities of crude protein and fats (ether extract) among animals, but the digestibilities of dry matter and crude fiber by the adult animals were higher than those of the young ones. The digestibility of carbohydrate (nitrogen-free extract) by adult birds was higher only for sunflower seeds. It is concluded that the capacity of parrots to digest fiber may change according to the age of the animal. Since the digestion of fiber depends on the action of microorganisms, these results suggest that the colonization of the gastrointestinal tract is delayed or very slow in young parrots.

Structure of SnO2 alcosols and films prepared by sol-gel dip coating

To obtain SnO2 films to be used for surface protection of fluoride glasses, a non-aqueous sol-gel route for the preparation was developed. An ethanolic SnO2 colloidal suspension was prepared by thermohydrolysis of SnCl4 solution at 70 degreesC. By using this procedure, redispersable powders with nanometer sized particles were obtained. Films were obtained by dip coating on glass and mica substrates. The structures of the ethanolic precursor suspension and films were compared to those of similar samples prepared by the classical aqueous sol-gel route. Comparative analyses performed by photon correlation spectroscopy demonstrated that the powders obtained by freeze-drying are fully redispersable either in aqueous or in alcoholic solutions at pH greater than or equal to 8. As prepared sols and redispersed colloidal suspensions have hydrodynamic radius distribution (2-14 nm) with an average size close to 7 nm. The variations in film structures with firing temperature were investigated by small-angle X-ray scattering and X-ray reflectometry. The experimental results show that the films have a two level porous structure composed of agglomerates of primary colloidal particles. The sintering of the primary particles leads to the densification of agglomerates and to the formation of inter-agglomerate spatially correlated pores. The volume fraction of intra-agglomerate pores is reduced from approximate to 50% to approximate to 30% by the precipitation of precursor salts partially hydrolyzed in ethanolic solution. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Gelation of siloxane-poly(oxypropylene) composites

The viscoelastic properties of siloxane-poly(oxypropylene) (PPO) nanocomposites prepared by the sol-gel process has been analyzed during gelation by dynamic rheological measurements. The changes of storage and loss moduli, complex viscosity and phase angle has been measured as a function of time showing the newtonian viscosity of the sol in the initial step of gelation, and its progressive transformation to a viscoelastic gel. The rheologic properties have been correlated to mass fractal, nearly linear growth models and percolation theory. This study, completed by quasi-elastic light scattering and Si-29 solid state nuclear magnetic resonance measurements, shows that the mechanisms of gelation of siloxane-PPO hybrids depend on the molecular weight of the polymer and on the pH of the hybrid sol. For hybrids prepared in acid medium, a polymerization involving silicon reactive species located at the extremity of the polymer chains and presenting a functionality f = 2 occurs, forming a fractal structure during the first stage of sol-gel transition. For samples prepared under neutral pH, the fractal growth is only observed for hybrids containing short polymer chains (M-w similar to 130 gmol(-1)). The fractal dimensionality determined from the change in the rheological properties, indicates that the fractal growth mechanism changes from reaction-limited to diffusion-limited aggregation when the molecular weight of the PPO increases from 130 to 4000 gmol(-1) and as catalyst conditions change from acidic to neutral. Near the gel point, these hybrid gels have the typical scaling behavior expected from percolation theory. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Nanostructure and properties of ZnO films produced by the pyrosol process

Indium doped ZnO films were deposited by the pyrosol process on glass substrates at different temperatures from solutions containing In/Zn molar ratios up to 10%. The nanostructure of the films was investigated using grazing-incidence small angle X-ray scattering (GISAXS). The mass density was determined by X-ray reflectivity and the composition by X-ray photoelectron spectroscopy. The GISAXS measurements revealed an anisotropic pattern for films deposited at 573 and 623 K and a isotropic one for those deposited at higher temperatures. The anisotropic patterns indicate the presence of elongated nanopores with their long axes perpendicular to the film surface. In contrast, the isotropic nature of GISAXS patterns of films grown at high temperatures (673 and 723 K) suggests the presence of spherical voids. The pore size distribution function determined from the isotropic patterns indicates a multimodal size distribution. on the other hand, the measured mass density of the doped films with isotropic nanotexture is higher than that of the anisotropic films while the electric resistivity is significantly lower. This is in agreement with the detected strong reduction of the void density and specific surface area at approximately constant pore size.

Preparation of ceramic membranes from surface modified tin oxide nanoparticles

The preparation of crack-free SnO2 supported membranes requires the development of new strategies of synthesis capable to allow controlled changes of surface chemistry and to improve the processability of supported layers. In this way, the controlled modification of the SnO2 nanoparticle surface by adding capping molecules like Tiron(R) ((OH)(2)C6H2(SO3Na)(2)) during the sol-gel process was studied, aiming to obtain high performance membranes. Colloidal suspensions were prepared by hydrolyzing SnCl4.5H(2)O aqueous solution with NH4OH in presence of Tiron(R). The effect of the amount of Tiro(R) (from I to 20 wt.%) on the structural features of nanoparticles, powder redispersability and particle-solution interface properties was investigated by X-ray powder diffraction (XRPD), extended X-ray absorption fine structure (EXAFS), quasi-elastic light scattering and electrophoretic mobility measurements. XRPD and EXAFS results showed that the addition of Tiron(R) up to 20 wt.% to colloidal suspensions does not affect the crystallite size of SnO2 primary particles, determined around 2-3 nm. This value is comparable to the hydrodynamic size measured after redispersion of powder prepared with amount of Tiro(R) higher than 7.5 wt.%, indicating the absence of condensation reactions between primary particles after the initial precipitation step. As a consequence the powder with amount of Tiron(R) > 7.5 wt.%, can be fully redispersed in aqueous solution at pH greater than or equal to I I until a nanoparticle concentration of 6 vol.%. The electrophoresis measurements showed a decrease of the isoelectric point by increasing the amount of grafted Tiron(R) at the SnO2 nanoparticle surface, resulting in negatively charged particle-solution interface in all the studied pH range (2-11). These features govern the gelation process favoring the preparation of crack-free SnO2 supported membranes. The control exercised by Tiron(R) modifying agent in the aggregation process allows the fine-tuning of the porosity, from 0.124 to 0.065 cm(3) g(-1), and mean pore size, from 6.4 to 1.9 nm, as the amount of grafted molecules increases from 0 to 10 wt.%. In consequence, the membrane cut-off determined by filtration of polyethylene glycol standard solutions can be screened from 1500 to 3500 g mol(-1). (C) 2002 Elsevier B.V. B.V. All rights reserved.

Structure of luminescent mono and di-urethanesil nanocomposites doped with Eu3+ ions

A structure modeling of two families of sol-gel derived Eu3+-doped organic/inorganic hybrids based on the results of small-angle X-ray scattering experiments is reported. The materials are composed of poly(oxyethylene) chains grafted at one or both ends to siloxane groups and are called mono- and di-urethanesils, respectively. A theoretical function corresponding to a two-level hierarchical structure model fits well the experimental Scattering curves. The first level corresponds to small siloxane clusters embedded in a polymeric matrix. The secondary level is associated to the existence of siloxane cluster rich domains surrounded by a cluster-depleted polymeric matrix. Results show that increasing europium doping favors the growth of the secondary domains. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Thermostimulated sol-gel transition in suspensions of sulfate zirconium oxychloride

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)