Dynamical Boson Stars

The idea of stable, localized bundles of energy has strong appeal as a model for particles. In the 1950s John Wheeler envisioned such bundles as smooth configurations of electromagnetic energy that he called {\em geons}, but none were found. Instead, particle-like solutions were found in the late 1960s with the addition of a scalar field, and these were given the name {\em boson stars}. Since then, boson stars find use in a wide variety of models as sources of dark matter, as black hole mimickers, in simple models of binary systems, and as a tool in finding black holes in higher dimensions with only a single killing vector. We discuss important varieties of boson stars, their dynamic properties, and some of their uses, concentrating on recent efforts.Comment: 79 pages, 25 figures, invited review for Living Reviews in Relativity; major revision in 201

The RSPO–LGR4/5–ZNRF3/RNF43 module controls liver zonation and size

LGR4/5 receptors and their cognate RSPO ligands potentiate Wnt/β-catenin signalling and promote proliferation and tissue homeostasis in epithelial stem cell compartments. In the liver, metabolic zonation requires a Wnt/β-catenin signalling gradient, but the instructive mechanism controlling its spatiotemporal regulation is not known. We have now identified the RSPO-LGR4/5-ZNRF3/RNF43 module as a master regulator of Wnt/β-catenin-mediated metabolic liver zonation. Liver-specific LGR4/5 loss of function (LOF) or RSPO blockade disrupted hepatic Wnt/β-catenin signalling and zonation. Conversely, pathway activation in ZNRF3/RNF43 LOF mice or with recombinant RSPO1 protein expanded the hepatic Wnt/β-catenin signalling gradient in a reversible and LGR4/5-dependent manner. Recombinant RSPO1 protein increased liver size and improved liver regeneration, whereas LGR4/5 LOF caused the opposite effects, resulting in hypoplastic livers. Furthermore, we show that LGR4(+) hepatocytes throughout the lobule contribute to liver homeostasis without zonal dominance. Taken together, our results indicate that the RSPO-LGR4/5-ZNRF3/RNF43 module controls metabolic liver zonation and is a hepatic growth/size rheostat during development, homeostasis and regeneration

Proteolytic activity and reduction of gliadin-like fractions by sourdough lactobacilli

Aims:  To characterize the peptide hydrolase system of Lactobacillus plantarum CRL 759 and CRL 778 and evaluate their proteolytic activity in reducing gliadin-like fractions. Methods and Results:  The intracellular peptide hydrolase system of Lact. plantarum CRL 759 and CRL 778 involves amino-, di- (DP), tri- (TP) and endopeptidase activities. These peptidases are metalloenzymes inhibited by EDTA and 1,10-phenanthroline and stimulated by Co2+. DP and TP activities of Lact. plantarum CRL 759 and CRL 778, respectively, were completely inhibited by Cu2+. Lactobacillus plantarum CRL 778 showed the highest proteolytic activity and amino acids release in fermented dough. The synthetic 31–43 α-gliadin fragment was hydrolysed to 36% and 73% by Lact. plantarum CRL 778 and CRL 759 respectively. Conclusions: Lactobacillus plantarum CRL 759 and CRL 778 have an active proteolytic system, which is responsible for the high amino acid release during sourdough fermentation and the hydrolysis of the 31–43 α-gliadin-like fragment. Significance and Impact of the Study:  This work provides new information of use when obtaining sourdough starters for bread making. Moreover, knowledge regarding lactobacilli capable of reducing the level of gliadin-like fractions, a toxic peptide for coeliac patients, has a beneficial health impact

Mechanisms involved in bile resistance in Lactobacillus reuteri, a probiotic bacteria

Lactobacillus (L.) reuteri CRL 1098 es una bacteria probiótica de probado efecto hipocolesterolemiante estrechamente relacionado con su actividad hidrolasa de sales biliares (HSB). La capacidad de L. reuteri para sobrevivir el pasaje a través del tracto intestinal y resistir los efectos tóxicos de los ácidos biliares (AB) es un factor clave para su función probiótica. El objetivo de este trabajo es revisar los aspectos más relevantes relacionados con la tolerancia a AB en esta cepa probiótica modelo.Utilizando técnicas fluorescentes se determinó que la acción deletérea de los AB en bacterias lácticas estaría estrechamente relacionada con la disipación de la fuerza protón motriz. La cepa CRL 1098 presentó elevada resistencia a AB siendo sólo sensible a altas concentraciones de ácido deoxicólico (ADC). Mediante estudios proteómicos se identificaron 25 proteínas diferencialmente expresadas cuando L. reuteri fue desafiado con ácido glicodeoxicólico (AGDC) y ADC. Se destaca la enzima citosina trifosfato (CTP) sintetasa, involucrada con la reparación del daño oxidativo del ADN y proteínas relacionadas con transcripción y traducción que fueron sobreexpresadas en presencia de AGDC y reprimidas en presencia de ADC, lo que explicaría la mayor toxicidad de este compuesto. Finalmente, se clonó y caracterizó el operón del gen hsb de CRL1098, lo que permitirá profundizar su influencia en la reducción de los niveles de colesterol sérico.Los resultados presentados en este trabajo proponen que los AB inducen una respuesta fisiológica compleja en L. reuteri y proporcionan nuevos conocimientos sobre los mecanismos implicados en la tolerancia a bilis en cepas probióticas.Fil: Bustos, Ana Yanina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santiago del Estero. Universidad Nacional de Santiago del Estero. Centro de Investigaciones y Transferencia de Santiago del Estero; ArgentinaFil: Fadda, S. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Font de Valdez, G. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Raya, R. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Taranto, MP. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentin

Analysis by Mass Spectrometry of the Polar Lipids from the Cellular Membrane of Thermophilic Lactic Acid Bacteria

Fast atom bombardment (FAB) technique was employed to determine the structure of polar lipids from the cellular membrane of Lactobacillus delbruekii ssp. bulgaricus and Streptococcus salivarius ssp. thermophilus. Analysis of spectra provided useful information about the molecular species and aminoacids constituents of the samples