Understanding three-dimensional effects in polarized observations with the ground-based ADMIRARI radiometer during the CHUVA campaign

Measurements of down-welling microwave radiation from raining clouds performed with the Advanced Microwave Radiometer for Rain Identification (ADMIRARI) radiometer at 10.7-21-36.5 GHz during the Global Precipitation Measurement Ground Validation ""Cloud processes of the main precipitation systems in Brazil: A contribution to cloud resolving modeling and to the Global Precipitation Measurement"" (CHUVA) campaign held in Brazil in March 2010 represent a unique test bed for understanding three-dimensional (3D) effects in microwave radiative transfer processes. While the necessity of accounting for geometric effects is trivial given the slant observation geometry (ADMIRARI was pointing at a fixed 30 elevation angle), the polarization signal (i.e., the difference between the vertical and horizontal brightness temperatures) shows ubiquitousness of positive values both at 21.0 and 36.5 GHz in coincidence with high brightness temperatures. This signature is a genuine and unique microwave signature of radiation side leakage which cannot be explained in a 1D radiative transfer frame but necessitates the inclusion of three-dimensional scattering effects. We demonstrate these effects and interdependencies by analyzing two campaign case studies and by exploiting a sophisticated 3D radiative transfer suited for dichroic media like precipitating clouds.

Symmetry controlled spin polarized conductance in Au nanowires

The fact that the resistance of propagating electrons in solids depends on their spin orientation has led to a new field called spintronics. With the parallel advances in nanoscience, it is now possible to talk about nanospintronics. Many works have focused on the study of charge transport along nanosystems, such as carbon nanotubes, graphene nanoribbons, or metallic nanowires, and spin dependent transport properties at this scale may lead to new behaviors due to the manipulation of a small number of spins. Metal nanowires have been studied as electric contacts where atomic and molecular insertions can be constructed. Here we describe what might be considered the ultimate spin device, namely, a Au thin nanowire with one Co atom bridging its two sides. We show that this system has strong spin dependent transport properties and that its local symmetry can dramatically change them, leading to a significant spin polarized conductance.

Polymorphism, crystallinity and hydrophilic-lipophilic balance of stearic acid and stearic acid-capric/caprylic triglyceride matrices for production of stable nanoparticles

There is an increasing interest in lipid nanoparticles because of their suitability for several administration routes. Thus, it becomes even more relevant the physicochemical characterization of lipid materials with respect to their polymorphism, lipid miscibility and stability, as well as the assessment of the effect of surfactant on the type and structure of these nanoparticles. This work focuses on the physicochemical characterization of lipid matrices composed of pure stearic acid or of mixtures of stearic acid-capric/caprylic triglycerides, for drug delivery. The lipids were analyzed by Differential Scanning Calorimetry (DSC), Wide Angle X-ray Diffraction (WAXD), Polarized Light Microscopy (PLM) and hydrophilic-lipophilic balance (HLB) in combination with selected surfactants to determine the best solid-to-liquid ratio. Based on the results obtained by DSC and WAXD, the selected qualitative and quantitative composition contributed for the production of stable nanoparticles, since the melting and the tempering processes provided important information on the thermodynamic stability of solid lipid matrices. The best HLB value obtained for stearic acid-capric/caprylic triglycerides was 13.8, achieved after combining these lipids with accepted surfactants (trioleate sorbitan and polysorbate 80 in the ratio of 10:90). The proposed combinations were shown useful to obtain a stable emulsion to be used as intermediate form for the production of lipid nanoparticles. (C) 2011 Elsevier B.V. All rights reserved.

Functional analysis of a novel missense NBC1 mutation and of other mutations causing proximal renal tubular acidosis

Mutations in the Na+-HCO3- cotransporter NBC1 cause severe proximal tubular acidosis (pRTA) associated with ocular abnormalities. Recent studies have suggested that at least some NBC1 mutants show abnormal trafficking in the polarized cells. This study identified a new homozygous NBC1 mutation (G486R) in a patient with severe pRTA. Functional analysis in Xenopus oocytes failed to detect the G486R activity due to poor surface expression. In ECV304 cells, however, G486R showed the efficient membrane expression, and its transport activity corresponded to approximately 50% of wild-type (WT) activity. In Madin-Darby canine kidney (MDCK) cells, G486R was predominantly expressed in the basolateral membrane domain as observed for WT. Among the previously identified NBC1 mutants that showed poor surface expression in oocytes, T485S showed the predominant basolateral expression in MDCK cells. On the other hand, L522P was exclusively retained in the cytoplasm in ECV304 and MDCK cells, and functional analysis in ECV304 cells failed to detect its transport activity. These results indicate that G486R, like T485S, is a partial loss of function mutation without major trafficking abnormalities, while L522P causes the clinical phenotypes mainly through its inability to reach the plasma membranes. Multiple experimental approaches would be required to elucidate potential disease mechanism by NBC1 mutations.

Particle acceleration and magnetic field structure in PKS 2155-304: optical polarimetric observations

In this paper, we present multiband optical polarimetric observations of the very-high energy blazar PKS 2155-304 made simultaneously with a HESS/Fermi high-energy campaign in 2008, when the source was found to be in a low state. The intense daily coverage of the data set allowed us to study in detail the temporal evolution of the emission, and we found that the particle acceleration time-scales are decoupled from the changes in the polarimetric properties of the source. We present a model in which the optical polarimetric emission originates at the polarized mm-wave core and propose an explanation for the lack of correlation between the photometric and polarimetric fluxes. The optical emission is consistent with an inhomogeneous synchrotron source in which the large-scale field is locally organized by a shock in which particle acceleration takes place. Finally, we use these optical polarimetric observations of PKS 2155-304 at a low state to propose an origin for the quiescent gamma-ray flux of the object, in an attempt to provide clues for the source of its recently established persistent TeV emission.

Morphological and quantitative study of ganglionated plexus of Calomys callosus trachea

Calomys callosus is a wild, native forest rodent found in South America. In Brazil, this species has been reported to harbour the parasitic protozoan Trypanosoma cruzi. The ganglionated plexus of this species was studied using whole-mount preparations of trachea that were stained using histological and histochemical methods. The histological methods were used to determine the position of the ganglia with respect to the trachea muscle and to determine the presence of elastic and collagen fibers. The histochemical method of NADH-diaphorase was used for morphometric evaluations of the plexus. The tracheal plexus lies exclusively over the muscular part of the organ, dorsal to the muscle itself. It varies in pattern and extent between animals. The average number of neurons was 279 and the cellular profile area ranged from 38.37 mu m(2) to 805.89 mu m(2). Acetylcholinesterase (AChE) histochemistry verified that both ganglia and single neurons lie along nerve trunks and are reciprocally interconnected with the plexus. Intensely AChE-reactive neurons were found to be intermingled with poorly reactive ones. Two longitudinal AChE-positive nerve trunks were also observed and there was a diverse number of ganglia along the intricate network of nerves interconnecting the trunks. A ganglion capsule of collagen and elastic fibers surrounding the neurons was observed. Under polarized light, the capsule appeared to be formed by Type I collagen fibers. (C) 2008 Elsevier B.V. All rights reserved.

Cell death and lumen formation in spheroids of MCF-7 cells

3D (three-dimensional) cell culture permits a more integrated analysis of the relationship between cells, inserting them into a structure more closely resembling the cellular microenvironment in vivo. The development of in vitro parameters to approximate in vivo 3D cellular environments makes a less reductionist interpretation of cell biology possible. For breast cells, in vitro 3D culture has proven to be an important tool for the analysis of luminal morphogenesis. A greater understanding of this process is necessary because alterations in the lumen arrangement are associated with carcinogenesis. Following lumen formation in 3D cell culture using laser scanning confocal microscopy, we observed alterations in the arrangement of cytoskeletal components (F-actin and microtubules) and increasing levels of cell death associated with lumen formation. The formation of a polarized monolayer facing the lumen was characterized through 3D reconstructions and the use of TEM (transmission electron microscopy), and this process was found to occur through the gradual clearing of cells from the medullary region of the spheroids. This process was associated with different types of cell death, such as apoptosis, autophagy and entosis. The present study showed that changes in the extracellular matrix associated with long periods of time in 3D cell culture lead to the formation of a lumen in MCF-7 cell spheroids and that features of differentiation such as lumen and budding formation occur after long periods in 3D culture, even in the absence of exogenous extracellular compounds.

Endogenous Hepatocyte Growth Factor Attenuates Inflammatory Response in Glycerol-Induced Acute Kidney Injury

Background: Hepatocyte growth factor (HGF) is overexpressed after acute kidney injury (AKI). The aim of this study was to evaluate the role of endogenous HGF in the progression of the inflammatory response in glycerol-induced AKI (Gly-AKI) in rats. Methods: Renal and systemic HGF expressions were evaluated during the development of Gly-AKI. Subsequently, the blockade of endogenous HGF was analyzed in rats treated with anti-HGF antibody concomitant to glycerol injection. Apoptosis, cell infiltration and chemokine and cytokine profiles were investigated. Results: We detected an early peak of renal and plasma HGF protein expressions 3 h after glycerol injection. The pharmacological blockade of the endogenous HGF exacerbated the renal impairment, the tubular apoptosis, the renal expression of monocyte chemoattractant protein-1 and the macrophage, CD43+, CD4+ and CD8+ T lymphocytes renal infiltration. The analysis of mRNA expressions of Th1 (t-bet, TNF-alpha, IL-1 beta) and Th2 (gata-3, IL-4, IL-10) cytokines showed a Th1-polarized response in Gly-AKI rats that was aggravated with the anti-HGF treatment. Conclusion: Endogenous HGF attenuates the renal inflammatory response, leukocyte infiltration and Th1 polarization after glycerol injection. The control of cellular immune response may partly explain the protective effect of endogenous HGF in the development of Gly-AKI. Copyright (C) 2008 S. Karger AG, Basel

Toll-like receptor 4 agonists adsorbed to aluminium hydroxide adjuvant attenuate ovalbumin-specific allergic airway disease: role of MyD88 adaptor molecule and interleukin-12/interferon-gamma axis

Background Epidemiological and experimental data suggest that bacteria] lipopolysaccharides (LPS) can either protect from or exacerbate allergic asthma. Lipopolysaccharides trigger immune responses through toll-like receptor 4 (TLR4) that in turn activates two major signalling pathways via either MyD88 or TRIF adaptor proteins. The LPS is a pro-Type 1 T helper cells (Th 1) adjuvant while aluminium hydroxide (alum) is a strong Type 2 T helper cells (Th2) adjuvant, but the effect of the mixing of both adjuvants on the development of lung allergy has not been investigated. Objective We determined whether natural (LPS) or synthetic (ER-803022) TLR4 agonists adsorbed onto alum adjuvant affect allergen sensitization and development of airway allergic disease. To dissect LPS-induced molecular pathways, we used TLR4-, MyD88-, TRIF-, or IL-12/IFN-gamma-deficient mice. Methods Mice were sensitized with subcutaneous injections of ovalbumin (OVA) with or without TLR4 agonists co-adsorbed onto alum and challenged with intranasally with OVA. The development of allergic lung disease was evaluated 24 h after last OVA challenge. Results Sensitization with OVA plus LPS co-adsorbed onto alum impaired in dose-dependent manner OVA-induced Th2-mediated allergic responses such as airway eosinophilia, type-2 cytokines secretion, airway hyper-reactivity, mucus hyper production and serum levels of IgE or IgG1 anaphylactic antibodies. Although the levels of IgG2a, Th1 -affiliated isotype increased, investigation into the lung-specific effects revealed that LPS did not induce a Th1 pattern of inflammation. Lipopolysaccharides impaired the development of Th2 immunity, signaling via TLR4 and MyD88 molecules and via the IL-12/IFN-gamma axis, but not through TRIF pathway. Moreover, the synthetic TLR4 agonists that proved to have a less systemic inflammatory response than LPS also protected against allergic asthma development. Conclusion Toll-like receptor 4 agonists co-adsorbed with allergen onto alum down-modulate allergic lung disease and prevent the development of polarized T cell-mediated airway inflammation.

The geodiamolide H, derived from Brazilian sponge Geodia corticostylifera, regulates actin cytoskeleton, migration and invasion of breast cancer cells cultured in three-dimensional environment

We are investigating effects of the depsipeptide geodiamolide H, isolated from the Brazilian sponge Geodia corticostylifera, on cancer cell lines grown in 3D environment. As shown previously geodiamolide H disrupts actin cytoskeleton in both sea urchin eggs and breast cancer cell monolayers. We used a normal mammary epithelial cell line MCF 10A that in 3D assay results formation of polarized spheroids. We also used cell lines derived from breast tumors with different degrees of differentiation: MCF7 positive for estrogen receptor and the Hs578T, negative for hormone receptors. Cells were placed on top of Matrigel. Spheroids obtained from these cultures were treated with geodiamolide H. Control and treated samples were analyzed by light and confocal microscopy. Geodiamolide H dramatically affected the poorly differentiated and aggressive Hs578T cell line. The peptide reverted HsS78T malignant phenotype to polarized spheroid-like structures. MCF7 cells treated by geodiamolide H exhibited polarization compared to controls. Geodiamolide H induced striking phenotypic modifications in Hs578T cell line and disruption of actin cytoskeleton. We investigated effects of geodiamolide H on migration and invasion of Hs578T cells. Time-lapse microscopy showed that the peptide inhibited migration of these cells in a dose-dependent manner. Furthermore invasion assays revealed that geodiamolide H induced a 30% decrease on invasive behavior of Hs578T cells. Our results suggest that geodiamolide H inhibits migration and invasion of Hs578T cells probably through modifications in actin cytoskeleton. The fact that normal cell lines were not affected by treatment with geodiamolide H stimulates new studies towards therapeutic use for this peptide.

Melting Regime of the Anionic Phospholipid DMPG: New Lamellar Phase and Porous Bilayer Model

Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG) at pH above the apparent pK of DMPG and concentrations in the interval 70-300 mM have been investigated by small (SAXS) and wide-angle X-ray scattering, differential scanning calorimetry, and polarized optical microscopy. The order. disorder transition of the hydrocarbon chains occurs along an interval of about 10 degrees C (between T(m)(on) similar to 20 degrees C and T(m)(off) similar to 30 degrees C). Such melting regime was previously characterized at lower concentrations, up to 70 mM DMPG, when sample transparency was correlated with the presence of pores across the bilayer. At higher concentrations considered here, the melting regime persists but is not transparent. Defined SAXS peaks appear and a new lamellar phase L(p) with pores is proposed to exist above 70 mM DMPG, starting at similar to 23 degrees C (similar to 3 degrees C above T(m)(on)) and losing correlation after T(m)(off). A new model for describing the X-ray scattering of bilayers with pores, presented here, is able to explain the broad band attributed to in-plane correlation between pores. The majority of cell membranes have a net negative charge, and the opening of pores across the membrane tuned by ionic strength, temperature, and lipid composition is likely to have biological relevance.

Polarization and Spectral Shift of Benzophenone in Supercritical Water

Monte Carlo simulation and quantum mechanics calculations based on the INDO/CIS and TD-DFT methods were utilized to study the solvatochromic shift of benzophenone when changing the environment from normal water to supercritical (P = 340.2 atm and T = 673 K) condition. Solute polarization increases the dipole moment of benzophenone, compared to gas phase, by 88 and 35% in normal and supercritical conditions, giving the in-solvent dipole value of 5.8 and 4.2 D, respectively. The average number of solute-solvent hydrogen bonds was analyzed, and a large decrease of 2.3 in normal water to only 0.8 in the supercritical environment was found. By using these polarized models of benzophenone in the two different conditions of water, we performed MC simulations to generate statistically uncorrelated configurations of the solute surrounded by the solvent molecules and subsequent quantum mechanics calculations on these configurations. When changing from normal to supercritical water environment, INDO/CIS calculations explicitly considering all valence electrons of the 235 solvent water molecules resulted in a solvatochromic shift of 1425 cm(-1) for the most intense transition of benzophenone, that is, slightly underestimated in comparison with the experimentally inferred result of 1700 cm(-1). TD-B3LYP/6-311+G(2d,p) calculations on the same configurations but with benzophenone electrostatically embedded in the 320 water molecules resulted in a solvatochromic shift of 1715 cm(-1) for this transition, in very good agreement with the experimental result. When using the unpolarized model of the benzophenone, this calculated solvatochromic shift was only 640 cm(-1). Additional calculations were also made by using BHandHLYP/6-311+G(2d,p) to analyze the effect of the asymptotic decay of the exchange functional. This study indicates that, contrary to the general expectation, there is a sizable solute polarization even in the low-density regime of supercritical condition and that the inclusion of this polarization is important for a reliable description of the spectral shifts considered here.

Observation of two-magnon bound states in the spin-1 anisotropic Heisenberg antiferromagnetic chain system NiCl2-4SC(NH2)(2)

Results of systematic tunable-frequency ESR studies of the spin dynamics in NiCl2-4SC(NH2)(2) (known as DTN), a gapped S = 1 chain system with easy-plane anisotropy dominating over the exchange coupling (large-D chain), are presented. We have obtained direct evidence for two-magnon bound states, predicted for S = 1 large-D spin chains in the fully spin-polarized (FSP) phase. The frequency-field dependence of the corresponding excitations was calculated using the set of parameters obtained earlier [S.A. Zvyagin, et al., Phys. Rev. Lett. 98 (2007) 047205]. Very good agreement between the calculations and the experiment was obtained. It is argued that the observation of transitions from the ground to two-magnon bound states might indicate a more complex picture of magnetic interactions in DTN, involving a finite in-plane anisotropy. (C) 2007 Elsevier B.V. All rights reserved.

Surface and Quantum Confinement Effects in ZnO Nanocrystals

ZnO nanocrystals are studied using theoretical calculations based on the density functional theory. The two main effects related to the reduced size of the nanocrystals are investigated: quantum confinement and a large surface:volume ratio. The effects of quantum confinement are studied by saturating the surface dangling bonds of the nanocrystals with hypothetical H atoms. To understand the effects of the surfaces of the nanocrystals, all saturation is removed and the system is relaxed to its minimum energy position. Several different surface motifs are reported, which should be observed experimentally. Spin-polarized calculations are performed in the nonsaturated nanocrystals, leading to different magnetic moments. We propose that this magnetic moment can be responsible for the intrinsic magnetism observed in ZnO nanostructures.

MAGNETO-OPTICAL ABSORPTION AND PHOTOMAGNETISM IN EUROPIUM CHALCOGENIDES

The absorption threshold in EuTe and EuSe was investigated as a function of applied magnetic field in the Faraday geometry. A well-resolved doublet of sharp dichroic lines was observed when the magnetic field induced ferromagnetic alignment of the spins in the crystal lattice. In contrast, at zero magnetic field only a broad and featureless absorption onset is seen. These results are fully explained in terms of a model of electronic transitions between localized states at the Eu lattice site and a tight-binding conduction band, which incorporates the formation of spin domains. Based on this model, predictions are made concerning the possibility of inducing magnetization of the spin lattices by illuminating the material with circularly polarized light.