Regulation of surface architecture by symbiotic bacteria mediates host colonization

Microbes occupy countless ecological niches in nature. Sometimes these environments may be on or within another organism, as is the case in both microbial infections and symbiosis of mammals. Unlike pathogens that establish opportunistic infections, hundreds of human commensal bacterial species establish a lifelong cohabitation with their hosts. Although many virulence factors of infectious bacteria have been described, the molecular mechanisms used during beneficial host–symbiont colonization remain almost entirely unknown. The novel identification of multiple surface polysaccharides in the important human symbiont Bacteroides fragilis raised the critical question of how these molecules contribute to commensalism. To understand the function of the bacterial capsule during symbiotic colonization of mammals, we generated B. fragilis strains deleted in the global regulator of polysaccharide expression and isolated mutants with defects in capsule expression. Surprisingly, attempts to completely eliminate capsule production are not tolerated by the microorganism, which displays growth deficits and subsequent reversion to express capsular polysaccharides. We identify an alternative pathway by which B. fragilis is able to reestablish capsule production and modulate expression of surface structures. Most importantly, mutants expressing single, defined surface polysaccharides are defective for intestinal colonization compared with bacteria expressing a complete polysaccharide repertoire. Restoring the expression of multiple capsular polysaccharides rescues the inability of mutants to compete for commensalism. These findings suggest a model whereby display of multiple capsular polysaccharides provides essential functions for bacterial colonization during host–symbiont mutualism

ETG de Referencia en Chile, simetría: Estudio de Caso

El presente artículomuestra parte de los resultados de una investigación que estudió la circulación y progresión del Espacio de Trabajo Geométrico de Referencia de Chile,en tercero y cuarto básico, en torno a las Transformaciones Isométricas. En este artículo nos referimos a una de las Actividades Sugeridas por el Ministerio de Educación de Chile, en el Programa de Estudio de cuarto año básico. En esta se identifican los elementos epistemológicos y procesos cognitivos que la actividad moviliza -a la luz de la teoría del Espacio de Trabajo Geométrico propuesta por Alain Kuzniak et al

Talk the talk, walk the walk: Defining Critical Race Theory in research

Over the last decade there has been a noticeable growth in published works citing Critical Race Theory (CRT). This has led to a growth in interest in the UK of practical research projects utilising CRT as their framework. It is clear that research on 'race' is an emerging topic of study. What is less visible is a debate on how CRT is positioned in relation to methodic practice, substantive theory and epistemological underpinnings. The efficacy of categories of data gathering tools, both traditional and non-traditional is a discussion point here to explore the complexities underpinning decisions to advocate a CRT framework. Notwithstanding intersectional issues, a CRT methodology is recognisable by how philosophical, political and ethical questions are established and maintained in relation to racialised problematics. This paper examines these tensions in establishing CRT methodologies and explores some of the essential criteria for researchers to consider in utilising a CRT framework. © 2012 Copyright Taylor and Francis Group, LLC

A 3D Voronoi+Gapper Galaxy Cluster Finder in Redshift Space to z∼ 0.2 I: an Algorithm Optimized for the 2dFGRS

This paper is the first in a series, presenting a new galaxy cluster finder based on a three-dimensional Voronoi Tesselation plus a maximum likelihood estimator, followed by gapping-filtering in radial velocity(VoML+G). The scientific aim of the series is a reassessment of the diversity of optical clusters in the local universe. A mock galaxy database mimicking the southern strip of the magnitude(blue)-limited 2dF Galaxy Redshift Survey (2dFGRS), for the redshift range 0.009 N g ≥ 5, and 14% with N g < 5. The ensemble of VoML+G clusters has a ~59% completeness and a ~66% purity, whereas the subsample with N g ≥ 10, to z ~ 0.14, has greatly improved mean rates of ~75% and ~90%, respectively. The VoML+G cluster velocity dispersions are found to be compatible with those corresponding to "Millennium clusters" over the 300–1000 km s−1 interval, i.e., for cluster halo masses in excess of ~3.0 × 1013 M ⊙ h −1

Aortic valve replacement in neonates and infants: An analysis of the Society of Thoracic Surgeons Congenital Heart Surgery Database

ObjectiveWe sought to describe early outcomes of aortic valve replacement in neonates and infants across a large multicenter cohort.MethodsNeonates and infants in the Society of Thoracic Surgeons Congenital Heart Surgery Database undergoing nontruncal aortic valve replacement with the Ross-Konno procedure, Ross procedure, or homograft replacement from 2000 to 2009 were included. Preoperative characteristics, operative data, and early outcomes are described.ResultsA total of 160 patients (43 neonates, 117 infants) from 47 centers were included. Society of Thoracic Surgeons–defined preoperative risk factors were present in 76 patients (48%) and were most prevalent in neonates (67%) and patients undergoing homograft aortic valve replacement (93%). Concomitant arch repair or mitral valve surgery was performed in 30 patients (19%) and 19 patients (12%), respectively. Postoperative mechanical circulatory support was used in 17 patients (11%). Overall in-hospital mortality was 18% and was highest for neonates (28%) and patients undergoing homograft aortic valve replacement (40%). Concomitant arch repair was associated with higher in-hospital mortality (33% vs 15%, P = .02), whereas concurrent mitral valve surgery was not (21% vs 18%, P = .73). Postoperative mechanical circulatory support was also associated with increased in-hospital mortality (65% vs 13%, P < .0001).ConclusionsNeonates and infants undergoing aortic valve replacement are a high-risk group, with hospital mortality comparable with some of the highest risk procedures in this age group. The requirement for arch repair or postoperative mechanical circulatory support was associated with an increased risk of death in this cohort

Probiotic bacteria regulate intestinal epithelial permeability in experimental ileitis by a TNF-dependent mechanism

Background: We previously showed that the probiotic mixture, VSL#3, prevents the onset of ileitis in SAMP/YitFc (SAMP) mice, and this effect was associated with stimulation of epithelial-derived TNF. The aim of this study was to determine the mechanism(s) of VSL#3-mediated protection on epithelial barrier function and to further investigate the "paradoxical" effects of TNF in preventing SAMP ileitis. Methods: Permeability was evaluated in SAMP mice prior to the onset of inflammation and during established disease by measuring transepithelial electrical resistance (TEER) on ex vivo-cultured ilea following exposure to VSL#3 conditioned media (CM), TNF or VSL#3-CM + anti-TNF. Tight junction (TJ) proteins were assessed by qRT-PCR, Western blot, and confocal microscopy, and TNFRI/TNFRII expression measured in freshly isolated intestinal epithelial cells (IEC) from SAMP and control AKR mice. Results: Culture with either VSL#3-CM or TNF resulted in decreased ileal paracellular permeability in pre-inflamed SAMP, but not SAMP with established disease, while addition of anti-TNF abrogated these effects. Modulation of the TJ proteins, claudin-2 and occludin, occurred with a significant decrease in claudin-2 and increase in occludin following stimulation with VSL#3-CM or TNF. TNF protein levels increased in supernatants of SAMP ilea incubated with VSL#3-CM compared to vehicle, while IEC-derived TNFR mRNA expression decreased in young, and was elevated in inflamed, SAMP versus AKR mice. Conclusions: Our data demonstrate that the previously established efficacy of VSL#3 in preventing SAMP ileitis is due to direct innate and homeostatic effects of TNF on the gut epithelium, modulation of the TJ proteins, claudin-2 and occludin, and overall improvement of intestinal permeability. © 2012 Corridoni et al

Modeling and Testing Superconducting Artificial CPW Lines Suitable for Parametric Amplification

Achieving amplification with high gain and quantum-limited noise is a difficult problem to solve. Parametric amplification using a superconducting transmission line with high kinetic inductance is a promising technology not only to solve this problem but also adding several benefits. When compared with other technologies, they have the potential of improving power saturation, achieving larger fractional bandwidths and operating at higher frequencies. In this type of amplifiers, selecting the proper transmission line is a key element in their design. Given current fabrication limitations, traditional lines such as coplanar waveguides (CPW), are not ideal for this purpose since it is difficult to make them with the proper characteristic impedance for good matching and slow-enough phase velocity for making them more compact. Capacitively-loaded lines, also known as artificial lines, are a good solution to this problem. However, few design rules or models have been presented to guide their accurate design. This fact is even more crucial considering that they are usually fabricated in the form of Floquet lines that have to be designed carefully to suppress undesired harmonics appearing in the parametric process. In this article we present, firstly, a new modelling strategy, based on the use of electromagnetic-simulation software, and, secondly, a first-principles model that facilitate and speed the design of CPW artificial lines and of Floquet lines made out of them. Then, we present comparisons with experimental results that demonstrate their accuracy. Finally, the theoretical model allows to predict the high-frequency behaviour of the artificial lines showing that they are good candidates for implementing parametric amplifiers above 100 GHz.Comment: 7 pages, 11 figures, submitted to IEEE Transactions on Applied Superconductivit

Varamiento de Cetáceos en la costa sur del Perú (2016-2021)

Twenty stranding events of cetaceans are reported in four places of southern coast at Peru: Mejía (Arequipa), Punta Coles (Moquegua) and the sites of Ite, Llostay and Los Palos (Tacna). Observations of these events were carried out during 2016-2021. Identified species are: Balaenoptera musculus, Megaptera novaeangliae, Tursiops truncatus, Delphinus delphis, Phocoena spinipinnis, and Lagenorhynchus obscurus. The identification was made using a key of skulls and performing standard morphometric measurements in freshly beached whole animals. Mysticeti's weight was also estimated. Observations included information about clues of interaction between fisheries and cetaceans. Strandings of Mysticeti only occurred in Los Palos, while the species with more landings was Phocoena spinipinnis. Precisely, in the present work, remains of this species are reported for Mejía, Ite, and Los Palos.Se presenta evidencia de diecisiete varamientos de cetáceos producidos en las siguientes localidades: Mejía (Arequipa), Punta Coles (Moquegua), asi como Ite, Llostay y Los Palos (Tacna). Los varamientos se registraron en el periodo 2016-2021. Las especies identificadas fueron: Balaenoptera musculus, Megaptera novaeanglieae, Tursiops truncatus, Delphinus delphis, Phocoena spinipinnis, y Lagenorhynchus obscurus. En el caso de Mysiticeti se estimó la masa de animales frescos varados, así como la causa aparente de varamiento por interacción con las pesquerías. Los Palos fue la única localidad con varamientos de Mysticeti, mientras que la especie con mayor número de varamiento fue Phocoena spinipinnis, la cual se reporta para las localidades de Mejía (Arequipa), Ite y Los Palos (Tacna)

Crystal structures from the Plasmodium peroxiredoxins: new insights into oligomerization and product binding

<p>Abstract</p> <p>Background</p> <p><it>Plasmodium falciparum </it>is the protozoan parasite primarily responsible for more than one million malarial deaths, annually, and is developing resistance to current therapies. Throughout its lifespan, the parasite is subjected to oxidative attack, so <it>Plasmodium </it>antioxidant defences are essential for its survival and are targets for disease control.</p> <p>Results</p> <p>To further understand the molecular aspects of the <it>Plasmodium </it>redox system, we solved 4 structures of <it>Plasmodium </it>peroxiredoxins (Prx). Our study has confirmed <it>Pv</it>Trx-Px1 to be a hydrogen peroxide (H₂O₂)-sensitive peroxiredoxin. We have identified and characterized the novel toroid octameric oligomer of <it>Py</it>Trx-Px1, which may be attributed to the interplay of several factors including: (1) the orientation of the conserved surface/buried arginine of the NNLA(I/L)GRS-loop; and (2) the <it>C</it>-terminal tail positioning (also associated with the aforementioned conserved loop) which facilitates the intermolecular hydrogen bond between dimers (in an A-C fashion). In addition, a notable feature of the disulfide bonds in some of the Prx crystal structures is discussed. Finally, insight into the latter stages of the peroxiredoxin reaction coordinate is gained. Our structure of <it>Py</it>Prx6 is not only in the sulfinic acid (RSO₂H) form, but it is also with glycerol bound in a way (not previously observed) indicative of product binding.</p> <p>Conclusions</p> <p>The structural characterization of <it>Plasmodium </it>peroxiredoxins provided herein provides insight into their oligomerization and product binding which may facilitate the targeting of these antioxidant defences. Although the structural basis for the octameric oligomerization is further understood, the results yield more questions about the biological implications of the peroxiredoxin oligomerization, as multiple toroid configurations are now known. The crystal structure depicting the product bound active site gives insight into the overoxidation of the active site and allows further characterization of the leaving group chemistry.</p