Discussion of ``2004 IMS Medallion Lecture: Local Rademacher complexities and oracle inequalities in risk minimization'' by V. Koltchinskii

Discussion of ``2004 IMS Medallion Lecture: Local Rademacher complexities and oracle inequalities in risk minimization'' by V. Koltchinskii [arXiv:0708.0083]Comment: Published at http://dx.doi.org/10.1214/009053606000001037 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

p53-dependent stimulation of redox-related genes in the lymphoid organs of γ-irradiated mice—identification of Haeme-oxygenase 1 as a direct p53 target gene

Recent data showed that p53 stimulates the expression of genes encoding not only pro- but also antioxidant enzymes. It was suggested that antioxidant genes could be induced under physiologic levels of stress while the prooxidant ones respond to higher level of stress. Results presented in this article illustrate an additional degree of complexity. We show that the expression of Haeme-oxygenase 1 (HO-1), a stress-inducible gene that codes for an enzyme having antioxidant properties, is stimulated in a p53-dependent manner in the thymus and spleen of irradiated mice. We prove that HO-1 is a direct p53 target gene by showing that the p53RE identified within human and mouse genes is specifically bound by p53. The threshold of irradiation dose required to induce a significant response of HO-1 in the lymphoid organs of the irradiated mice is higher than that for Waf1/p21 that encodes an universal inhibitor of cell cycle. Moreover, induction of HO-1 occurs later than that of Waf1/p21. Finally, the higher stimulation of HO-1 is reached when Waf1/p21 stimulation starts to decrease

Nuevos precursores Al-X-Mo/W (X = Al, Co, V) vía síntesis reticular: Caracterización por 27Al NMR y Raman Microprobe. Aplicación en desulfurización oxidativa (ODS)

Se investigó la actividad de nuevos precursores trimetálicos obtenidos por síntesis reticular, en dos diferentes reacciones de desulfurización oxidativa (ODS): difenilsulfuro a difenilsulfona en presencia de H2O2 y de dibenzotiofeno DBTs mediante terbutilhidroperóxido (t-BuOOH). Se prepararon diversas fases de fórmula general A113-[XMo6] (X= Al (III), Co(III), V(V) y Al13-P[WO4]n combinando el isopolication Keggin [AlO4Al12(OH)24(H2O)12]7+ (Al13) e iso ó heteropolimetalatos del tipo: [XMo6O24H6]3-; [Co2Mo10H4]6-; [WO4]n , [PW9O34]9-, [V2W4]6-. La caracterización se llevó a cabo por XRD, 27Al NMR, FTIR y Raman Microprobe. La estabilidad térmica se estudió por TGA-DTA. Los tests catalíticos se realizaron en batch entre 75 y 80 °C. Los resultados preliminares indican que la actividad ODS aumenta con la densidad electrónica del sustrato, siendo mayor para difenilsulfuro que para DBT. Los catalizadores a base de heteropolimolibdatos presentan una mejor performance en ambas reacciones, mientras el heteroátomo parece mejorar la polarización del enlace Mo-O2t. Catalizadores a base de iso y politungstatos no mostraron actividad excepto aquel conteniendo P como heteroátomo. Asimismo se comprobó por Raman Microprobe, que las fases empleadas conservan su estructura después de la reacción, mostrando la interesante posibilidad de reutilización

Genome Sequences of Two Tunisian Field Strains of Avian <I>Mycoplasma, M. meleagridis<I> and <I>M. gallinarum<I>

International audienceMycoplasma meleagridis and Mycoplasma gallinarum are bacteria that affect birds, but little is known about the genetic basis of their interaction with chickens and other poultry. Here, we sequenced the genomes of M. meleagridis strain MM_26B8_IPT and M. gallinarum strain Mgn_IPT, both isolated from chickens showing respiratory symptoms, poor growth, reduction in hatchability, and loss of production

Mycoplasma mycoides, from "mycoides Small Colony" to "capri". A microevolutionary perspective

<p>Abstract</p> <p>Background</p> <p>The <it>Mycoplasma mycoides </it>cluster consists of five species or subspecies that are ruminant pathogens. One subspecies, <it>Mycoplasma mycoides </it>subspecies <it>mycoides </it>Small Colony (MmmSC), is the causative agent of contagious bovine pleuropneumonia. Its very close relative, <it>Mycoplasma mycoides </it>subsp. <it>capri </it>(Mmc), is a more ubiquitous pathogen in small ruminants causing mastitis, arthritis, keratitis, pneumonia and septicaemia and is also found as saprophyte in the ear canal. To understand the genetics underlying these phenotypic differences, we compared the MmmSC PG1 type strain genome, which was already available, with the genome of an Mmc field strain (95010) that was sequenced in this study. We also compared the 95010 genome with the recently published genome of another Mmc strain (GM12) to evaluate Mmc strain diversity.</p> <p>Results</p> <p>The MmmSC PG1 genome is 1,212 kbp and that of Mmc 95010 is ca. 58 kbp shorter. Most of the sequences present in PG1 but not 95010 are highly repeated Insertion Sequences (three types of IS) and large duplicated DNA fragments. The 95010 genome contains five types of IS, present in fewer copies than in PG1, and two copies of an integrative conjugative element. These mobile genetic elements have played a key role in genome plasticity, leading to inversions of large DNA fragments. Comparison of the two genomes suggested a marked decay of the PG1 genome that seems to be correlated with a greater number of IS. The repertoire of gene families encoding surface proteins is smaller in PG1. Several genes involved in polysaccharide metabolism and protein degradation are also absent from, or degraded in, PG1.</p> <p>Conclusions</p> <p>The genome of MmmSC PG1 is larger than that of Mmc 95010, its very close relative, but has less coding capacity. This is the result of large genetic rearrangements due to mobile elements that have also led to marked gene decay. This is consistent with a non-adaptative genomic complexity theory, allowing duplications or pseudogenes to be maintained in the absence of adaptive selection that would lead to purifying selection and genome streamlining over longer evolutionary times. These findings also suggest that MmmSC only recently adapted to its bovine host.</p

Comparative genomic and proteomic analyses of two Mycoplasma agalactiae strains: clues to the macro- and micro-events that are shaping mycoplasma diversity

Background: While the genomic era is accumulating a tremendous amount of data, the question of how genomics can describe a bacterial species remains to be fully addressed. The recent sequencing of the genome of the Mycoplasma agalactiae type strain has challenged our general view on mycoplasmas by suggesting that these simple bacteria are able to exchange significant amount of genetic material via horizontal gene transfer. Yet, events that are shaping mycoplasma genomes and that are underlining diversity within this species have to be fully evaluated. For this purpose, we compared two strains that are representative of the genetic spectrum encountered in this species: the type strain PG2 which genome is already available and a field strain, 5632, which was fully sequenced and annotated in this study. Results: The two genomes differ by ca. 130 kbp with that of 5632 being the largest (1006 kbp). The make up of this additional genetic material mainly corresponds (i) to mobile genetic elements and (ii) to expanded repertoire of gene families that encode putative surface proteins and display features of highly-variable systems. More specifically, three entire copies of a previously described integrative conjugative element are found in 5632 that accounts for ca. 80 kbp. Other mobile genetic elements, found in 5632 but not in PG2, are the more classical insertion sequences which are related to those found in two other ruminant pathogens, M. bovis and M. mycoides subsp. mycoides SC. In 5632, repertoires of gene families encoding surface proteins are larger due to gene duplication. Comparative proteomic analyses of the two strains indicate that the additional coding capacity of 5632 affects the overall architecture of the surface and suggests the occurrence of new phase variable systems based on single nucleotide polymorphisms. Conclusion: Overall, comparative analyses of two M. agalactiae strains revealed a very dynamic genome which structure has been shaped by gene flow among ruminant mycoplasmas and expansion-reduction of gene repertoires encoding surface proteins, the expression of which is driven by localized genetic micro-events

Improvement of HDS catalysts through the modification of the oxidic precursor with 1,5-pentanediol: Gas phase sulfidation and thiophene conversion

AbstractThe performance, in thiophene HDS, of a CoMo/Al2O3 catalyst was successfully improved through chemical modification of its oxidic precursor by impregnation with 1,5-pentanediol solution. The gas phase activation with a H2/H2S mixture was followed by thermogravimetric analysis coupled with a rapid chromatograph; the catalysts were characterized at different steps of the activation using X-ray photoelectron spectroscopy (XPS). It appeared that the addition of the organic agent retards the sulfidation of the supported metals, leading to a simultaneous sulfidation of Co and Mo atoms. This induces the formation of smaller MoS2 slabs and thus an increase in the number of active CoMoS sites, directly correlated with the better HDS performance of the modified solid. The role of 1,5-pentanediol is likely to inhibit, at low temperature, the adsorption of H2S on the solid and thus the sulfidation of the supported metals