Abundància i persistència de Faecalibacteriun prausnitzii en la Malaltia de Crohn

Faecalibacterium prausnitzii és un del bacteris anaeròbis més abundants entre les espècies comensals del tracte intestinal humà sa. Aquesta espècie és una de les principals productores de butirat a l'intestí (que és la principal font d’energia per als colonòcits), però també s'ha suggerit que pot produir compostos antiinflamatoris i intervenir en la regulació de vàries rutes metabòliques de l’hoste. F. prausnitzii és un bacteri difícil de cultivar, ja que presenta una elevada sensibilitat a l'oxigen i presenta uns requeriments nutricionals molt exigents, el que ha compromès considerablement el nombre d’estudis basats en aïllats d’aquesta espècie. No obstant això, en els darrers anys l’interès en aquest bacteri està creixent ja que s’ha evidenciat que les poblacions de F. prausnitzii són variables en diferents grups d'edat i que es veuen reduïdes en certs trastorns intestinals com ara la malaltia inflamatòria intestinal i el càncer colorectal. L’objectiu d'aquest treball ha estat aprofundir en el rol que desenvolupa F. prausnitzii com un dels principals bacteris comensals del tracte intestinal humà. En primer lloc, s’ha dissenyat, optimitzat i validat un nou mètode molecular per determinar l’abundància d’aquesta espècie en mostres del tracte gastrointesinal, i s’ha demostrat la seva possible aplicació per ajudar al diagnòstic de la malaltia de Crohn. En segon lloc, s’ha dut a terme un estudi de les característiques filogenètiques i fenotípiques dels aïllats de F. Prausnitzii disponibles en l'actualitat a fi de coneixre’n millor la diversitat genètica i fenotípica i dilucidar quins factors són crucials en comprometre la població d’aquest bacteri en un intestí malalt. L’anàlisi de les soques ha revelat que F. prausnitzii inclou Principalment dos filogrups, nutricionalment versàtils i molt sensibles a canvis en les condicions ecològiques que pot patir l’intestí de l’hoste sota certes malalties intestinals. En conclusió, els resultat obtinguts en aquest estudi mostren que F. prausnitzii és una espècie ben establerta al còlon sa, amb una elvada versatilitat metabòlica ja que és capaç d’ interactuar amb carbohidrats de diferent estructura i complexitat. S’ha corroborat que aquest microorganisme seria un bon indicador de salut intestinal ja que la seva abundància es veu significativament reduida en pacients amb malaltia de Crohn. Aquests resultats concorden amb els obtinguts per proves fisiològiques que mostren una elevada sensibilitat de l’espècie a determinades condicions relacionades amb malalties intestinals. Estudis futurs s’orientaran a comprendre millor quins factros derrivats de la interacció amb l’hoste també determinen la persistència d’aquesta espècie en un intestí sa o malalt.

Investigation of defect formation and electronic transport in microcrystalline silicon deposited by hot-wire CVD

We have investigated doped and undoped layers of microcrystalline silicon prepared by hot-wire chemical vapour deposition optically, electrically and by means of transmission electron microscopy. Besides needle-like crystals grown perpendicular to the substrate's surface, all of the layers contained a noncrystalline phase with a volume fraction between 4% and 25%. A high oxygen content of several per cent in the porous phase was detected by electron energy loss spectrometry. Deep-level transient spectroscopy of the crystals suggests that the concentration of electrically active defects is less than 1% of the undoped background concentration of typically 10^17 cm -3. Frequency-dependent measurements of the conductance and capacitance perpendicular to the substrate surface showed that a hopping process takes place within the noncrystalline phase parallel to the conduction in the crystals. The parasitic contribution to the electrical circuit arising from the porous phase is believed to be an important loss mechanism in the output of a pin-structured photovoltaic solar cell deposited by hot-wire CVD.

Raman microstructural analysis of silicon-on-insulator formed by high dose oxygen ion implantation: As-implanted structures

A microstructural analysis of silicon-on-insulator samples obtained by high dose oxygen ion implantation was performed by Raman scattering. The samples analyzed were obtained under different conditions thus leading to different concentrations of defects in the top Si layer. The samples were implanted with the surface covered with SiO2 capping layers of different thicknesses. The spectra measured from the as-implanted samples were fitted to a correlation length model taking into account the possible presence of stress effects in the spectra. This allowed quantification of both disorder effects, which are determined by structural defects, and residual stress in the top Si layer before annealing. These data were correlated to the density of dislocations remaining in the layer after annealing. The analysis performed corroborates the existence of two mechanisms that generate defects in the top Si layer that are related to surface conditions during implantation and the proximity of the top Si/buried oxide layer interface to the surface before annealing.

Synthesis, binding affinity and SAR of new benzolactam derivatives as dopamine D3 receptor ligands

A series of new benzolactam derivatives was synthesized and the derivatives were evaluated for theiraffinities at the dopamine D1, D2, and D3 receptors. Some of these compounds showed high D2 and/orD3 affinity and selectivity over the D1 receptor. The SAR study of these compounds revealed structuralcharacteristics that decisively influenced their D2 and D3 affinities. Structural models of the complexesbetween some of the most representative compounds of this series and the D2 and D3 receptors wereobtained with the aim of rationalizing the observed experimental results. Moreover, selected compoundsshowed moderate binding affinity on 5-HT2A which could contribute to reducing the occurrence of extrapyramidalside effects as potential antipsychotics.

A short motif in Drosophila SECIS Binding Protein 2 provides differential binding affinity to SECIS RNA hairpins

Selenoproteins contain the amino acid selenocysteine which is encoded by a UGA Sec codon. Recoding UGA Sec requires a complex mechanism, comprising the cis-acting SECIS RNA hairpin in the 3′UTR of selenoprotein mRNAs, and trans-acting factors. Among these, the SECIS Binding Protein 2 (SBP2) is central to the mechanism. SBP2 has been so far functionally characterized only in rats and humans. In this work, we report the characterization of the Drosophila melanogaster SBP2 (dSBP2). Despite its shorter length, it retained the same selenoprotein synthesis-promoting capabilities as the mammalian counterpart. However, a major difference resides in the SECIS recognition pattern: while human SBP2 (hSBP2) binds the distinct form 1 and 2 SECIS RNAs with similar affinities, dSBP2 exhibits high affinity toward form 2 only. In addition, we report the identification of a K (lysine)-rich domain in all SBP2s, essential for SECIS and 60S ribosomal subunit binding, differing from the well-characterized L7Ae RNA-binding domain. Swapping only five amino acids between dSBP2 and hSBP2 in the K-rich domain conferred reversed SECIS-binding properties to the proteins, thus unveiling an important sequence for form 1 binding.

Synthesis, binding affinity, and molecular docking analysis of new benzofuranone derivative as pontential antipsychotics

The complex etiology of schizophrenia has prompted researchers to develop clozapine-related multitargetstrategies to combat its symptoms. Here we describe a series of new 6-aminomethylbenzofuranones in aneffort to find new chemical structures with balanced affinities for 5-HT2 and dopamine receptors. Throughbiological and computational studies of 5-HT2A and D2 receptors, we identified the receptor serine residuesS3.36 and S5.46 as the molecular keys to explaining the differences in affinity and selectivity betweenthese new compounds for this group of receptors. Specifically, the ability of these compounds to establishone or two H-bonds with these key residues appears to explain their difference in affinity. In addition, wedescribe compound 2 (QF1004B) as a tool to elucidate the role of 5-HT2C receptors in mediating antipsychoticeffects and metabolic adverse events. The compound 16a (QF1018B) showed moderate to high affinitiesfor D2 and 5-HT2A receptors, and a 5-HT2A/D2 ratio was predictive of an atypical antipsychotic profile.

Rat splanchnic net oxygen consumption. Energetic implications

1. The blood flow, PO2, pH and PCO2 have been estimated in portal and suprahepatic veins as well as in hepatic artery of fed and overnight starved rats given an oral glucose load. From these data the net intestinal, hepatic and splanchnic balances for oxygen and bicarbonate were calculated. The oxygen consumption of the intact animal has also been measured under comparable conditions. 2. The direct utilization of oxygen balances as energy equivalents when establishing the contribution of energy metabolism of liver and intestine to the overall energy expenses of the rat, has been found to be incorrect, since it incorporates the intrinsic error of interorgan proton transfer through bicarbonate. Liver and intestine produced high net bicarbonate balances in all situations tested, implying the elimination (by means of oxidative pathways, i.e. consuming additional oxygen) of high amounts of H+ generated with bicarbonate. The equivalence in energy output of the oxygen balances was then corrected for bicarbonate production to 11-54% lower values. 3. Intestine and liver consume a high proportion of available oxygen, about one-half in basal (fed or starved) conditions and about one-third after gavage, the intestine consumption being about 15% in all situations tested and the liver decreasing its oxygen consumption with gavage.

Bistability of mitochondrial respiration underlies paradoxical reactive oxygen species generation induced by anoxia

Increased production of reactive oxygen species (ROS) in mitochondria underlies major systemic diseases, and this clinical problem stimulates a great scientific interest in the mechanism of ROS generation. However, the mechanism of hypoxia-induced change in ROS production is not fully understood. To mathematically analyze this mechanism in details, taking into consideration all the possible redox states formed in the process of electron transport, even for respiratory complex III, a system of hundreds of differential equations must be constructed. Aimed to facilitate such tasks, we developed a new methodology of modeling, which resides in the automated construction of large sets of differential equations. The detailed modeling of electron transport in mitochondria allowed for the identification of two steady state modes of operation (bistability) of respiratory complex III at the same microenvironmental conditions. Various perturbations could induce the transition of respiratory chain from one steady state to another. While normally complex III is in a low ROS producing mode, temporal anoxia could switch it to a high ROS producing state, which persists after the return to normal oxygen supply. This prediction, which we qualitatively validated experimentally, explains the mechanism of anoxia-induced cell damage. Recognition of bistability of complex III operation may enable novel therapeutic strategies for oxidative stress and our method of modeling could be widely used in systems biology studies.

Meissner effect and critical fields in an inhomogeneous Ba2HoCu3O7-x high-Tc superconductor

The Meissner and diamagnetic shielding effects and the upper, lower, and thermodynamical critical fields have been studied in a Ba2HoCu3O7-x sample using magnetization measurements in fields up to 55 kOe. The diamagnetic shielding curve shows the existence of a transition at Tc=91.5 K followed by a broad transition extending from 85 to 25 K which may be related to inhomogeneities in the oxygen content of the sample. A rather low flux expulsion (13.5%) is observed which we attribute to flux pinning or trapping. We show that the coexistence of superconducting and nonsuperconducting regions within the sample at temperatures just below Tc leads to strong reductions in the critical magnetic fields.

Rat splanchnic net oxygen consumption. Energetic implications

1. The blood flow, PO2, pH and PCO2 have been estimated in portal and suprahepatic veins as well as in hepatic artery of fed and overnight starved rats given an oral glucose load. From these data the net intestinal, hepatic and splanchnic balances for oxygen and bicarbonate were calculated. The oxygen consumption of the intact animal has also been measured under comparable conditions. 2. The direct utilization of oxygen balances as energy equivalents when establishing the contribution of energy metabolism of liver and intestine to the overall energy expenses of the rat, has been found to be incorrect, since it incorporates the intrinsic error of interorgan proton transfer through bicarbonate. Liver and intestine produced high net bicarbonate balances in all situations tested, implying the elimination (by means of oxidative pathways, i.e. consuming additional oxygen) of high amounts of H+ generated with bicarbonate. The equivalence in energy output of the oxygen balances was then corrected for bicarbonate production to 11-54% lower values. 3. Intestine and liver consume a high proportion of available oxygen, about one-half in basal (fed or starved) conditions and about one-third after gavage, the intestine consumption being about 15% in all situations tested and the liver decreasing its oxygen consumption with gavage.

Evidence for oxygen-island formation on Al(111): Cluster-model theory and x-ray photoelectron spectroscopy

The O 1s x-ray photoelectron spectroscopy spectrum for Al(111)/O at 300 K shows two components whose behavior as a function of time and variation of detection angle are consistent with either (a) a surface species represented by the higher binding-energy (BE) component and a subsurface species represented by the lower BE component, or (b) small close-packed oxygen islands with the interior atoms represented by the lower BE component and the perimeter atoms by the higher BE component. We have modeled both situations using ab initio Hartree-Fock wave functions for clusters of Al and O atoms. For an O atom in a threefold site, it was found that a below-surface position gave a higher O 1s BE than an above-surface position, incompatible with interpretation (a). This change in the O 1s BE could arise because the bond for O to Al may have a more covalent character when the O is below the surface than when it is above the surface. We present evidence consistent with this view. An O adatom island with all the O atoms in threefold sites gives calculated O 1s BE's which are significantly higher for the perimeter O atoms. Further, the results for an isolated O island without the Al substrate present also give higher BE¿s for the perimeter atoms. Both these results are consistent with interpretation (b). Published scanning-tunneling-microscopy data supports the suggestion that the chemisorbed state consists of small, close-packed islands, whereas the presence of two vibrational modes in high-resolution electron-energy-loss spectroscopy data has been interpreted as representing surface and subsurface oxygen atoms. In light of the present results, we suggest that a vibrational interpretation in terms of interior and perimeter adatoms should be considered.

TGF-β dependent regulation of oxygen radicals during transdifferentiation of activated hepatic stellate cells to myofibroblastoid cells

Background: The activation of hepatic stellate cells (HSCs) plays a pivotal role during liver injury because the resulting myofibroblasts (MFBs) are mainly responsible for connective tissue re-assembly. MFBs represent therefore cellular targets for anti-fibrotic therapy. In this study, we employed activated HSCs, termed M1-4HSCs, whose transdifferentiation to myofibroblastoid cells (named M-HTs) depends on transforming growth factor (TGF)-β. We analyzed the oxidative stress induced by TGF-β and examined cellular defense mechanisms upon transdifferentiation of HSCs to M-HTs. Results: We found reactive oxygen species (ROS) significantly upregulated in M1-4HSCs within 72 hours of TGF-β administration. In contrast, M-HTs harbored lower intracellular ROS content than M1-4HSCs, despite of elevated NADPH oxidase activity. These observations indicated an upregulation of cellular defense mechanisms in order to protect cells from harmful consequences caused by oxidative stress. In line with this hypothesis, superoxide dismutase activation provided the resistance to augmented radical production in M-HTs, and glutathione rather than catalase was responsible for intracellular hydrogen peroxide removal. Finally, the TGF-β/NADPH oxidase mediated ROS production correlated with the upregulation of AP-1 as well as platelet-derived growth factor receptor subunits, which points to important contributions in establishing antioxidant defense. Conclusion: The data provide evidence that TGF-β induces NADPH oxidase activity which causes radical production upon the transdifferentiation of activated HSCs to M-HTs. Myofibroblastoid cells are equipped with high levels of superoxide dismutase activity as well as glutathione to counterbalance NADPH oxidase dependent oxidative stress and to avoid cellular damage.

Biogeochemical processes controlling oxygen and carbon isotopes of diatom silica in Late Glacial to Holocene lacustrine rhythmites

Biogeochemical cycles and sedimentary records in lakes are related to climate controls on hydrology and catchment processes. Changes in the isotopic imposition of the diatom frustules (δ 18 O diatom and δ 13 C diatom ) in lacustrine sediments can be used to reconstruct palaeoclimatic and palaeoenvironmental changes. The Lago Chungará (Andean Altiplano, 18°15 ′ S, 69°10 ′ W, 4520 masl) diatomaceous laminated sediments are made up of white and green multiannual rhythmites. White laminae were formed during short-term diatom super-blooms, and are composed almost exclusively of large-sized Cyclostephanos andinus.These diatoms bloom during mixing events when recycled nutrients from the bottom waters are brought to the surface and/or when nutrients are introduced from the catchment during periods of strong runoff. Conversely, the green laminae are thought to have been deposited over several years and are composed of a mixture of diatoms (mainly smaller valves of C. andinus and Discostella stelligera ) and organic matter. These green laminae reflect the lake's hydrological recovery from a status favouring the diatom super-blooms (white laminae) towards baseline conditions. δ 18 O diatom and δ 13 C diatom from 11,990 to 11,530 cal years BP allow us to reconstruct shifts in the precipitation/evaporation ratio and changes in the lake water dissolved carbon concentration, respectively. δ 18 O diatom values indicate that white laminae formation occurred mainly during low lake level stages, whereas green laminae formation generally occurred during high lake level stages. The isotope and chronostratigraphical data together suggest that white laminae deposition is caused by extraordinary environmental events. El Niño-Southern Oscillation and changes in solar activity are the most likely climate forcing mechanisms that could trigger such events, favouring hydrological changes at interannual-to-decadal scale. This study demonstrates the potential for laminated lake sediments to document extreme pluriannual events.