Formation and evolution of early-type galaxies. II. Models with quasi-cosmological initial conditions

In this study, with the aid of N-Body simulations based on quasi-cosmological initial conditions, we have followed the formation and evolution of two models of early-type galaxies, from their separation from global expansion of the Universe to their collapse to virialized structures, the formation of stars and subsequent nearly passive evolution. The cosmological background we have considered is the Standard CDM. The models have significantly different nitial total mass. Particular care has been paid to the star formation process, heating and cooling of gas, and chemical enrichment. In both models star formation is completed within the first Gyrs of evolution. The structural properties of the present-day models are in good agreement with current observations. The chemical properties, mean metallicity and metallicity gradients also agree with available observational data. Finally, conspicuous galactic winds are found to occur. The models conform to the so-called revised monolithic scheme, because mergers of substructures have occurred very early in the galaxy life. Our results agree with those obtained in other similar recent studies, thus strengthening the idea that the revised monolithic scheme is the right trail to follow in the forest of galaxy formation and evolution.Comment: 21 pages, 19 figures, 3 tables. To be published on Astronomy & Astrophysics (accepted April 12, 2006

Formation and Evolution of Early-Type Galaxies: Spectro-Photometry from Cosmo-Chemo-Dynamical Simulations

One of the major challenges in modern astrophysics is to understand the origin and the evolution of galaxies, the bright, massive early type galaxies (ETGs) in particular. Therefore, these galaxies are likely to be good probes of galaxy evolution, star formation and, metal enrichment in the early Universe. In this context it is very important to set up a diagnostic tool able to combine results from chemo-dynamical N-Body-TSPH (NB-TSPH) simulations of ETGs with those of spectro-photometric population synthesis and evolution so that all key properties of galaxies can be investigated. The main goal of this paper is to provide a preliminary validation of the software package before applying it to the analysis of observational data. The galaxy models in use where calculated by the Padova group in two different cosmological scenarios: the SCDM, and the Lambda CDM. For these models, we recover their spectro-photometric evolution through the entire history of the Universe. We computed magnitudes and colors and their evolution with the redshift along with the evolutionary and cosmological corrections for the model galaxies at our disposal, and compared them with data for ETGs taken from the COSMOS and the GOODS databases. Starting from the dynamical simulations and photometric models at our disposal, we created synthetic images from which we derived the structural and morphological parameters. The theoretical results are compared with observational data of ETGs selected form the SDSS database. The simulated colors for the different cosmological scenarios follow the general trend shown by galaxies of the COSMOS and GOODS. Within the redshift range considered, all the simulated colors reproduce the observational data quite well.Comment: 28 pages, 28 figures, accepted for pubblication by A&

Exchange of functional domains between a bacterial conjugative relaxase and the integrase of the human adeno-associated virus

Endonucleases of the HUH family are specialized in processing single-stranded DNA in a variety of evolutionarily highly conserved biological processes related to mobile genetic elements. They share a structurally defined catalytic domain for site-specific nicking and strand-transfer reactions, which is often linked to the activities of additional functional domains, contributing to their overall versatility. To assess if these HUH domains could be interchanged, we created a chimeric protein from two distantly related HUH endonucleases, containing the N-terminal HUH domain of the bacterial conjugative relaxase TrwC and the C-terminal DNA helicase domain of the human adeno-associated virus (AAV) replicase and site-specific integrase. The purified chimeric protein retained oligomerization properties and DNA helicase activities similar to Rep68, while its DNA binding specificity and cleaving-joining activity at oriT was similar to TrwC. Interestingly, the chimeric protein could catalyse site-specific integration in bacteria with an efficiency comparable to that of TrwC, while the HUH domain of TrwC alone was unable to catalyze this reaction, implying that the Rep68 C-terminal helicase domain is complementing the TrwC HUH domain to achieve site-specific integration into TrwC targets in bacteria. Our results illustrate how HUH domains could have acquired through evolution other domains in order to attain new roles, contributing to the functional flexibility observed in this protein superfamily.This work was supported by the Medical Research Council (MRC) grant MR/N022890/1 to EH and grant 1001764 to RML; National Institutes of Health (NIH) grant RO1-GM09285 to CRE; Spanish Ministry of Economy and competitiveness (MINECO) grant BIO2013-46414-P to ML and AFM is supported by a Doc.Mobility fellowship from the Swiss National Science Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

A Genome-Wide Characterization of MicroRNA Genes in Maize

MicroRNAs (miRNAs) are small, non-coding RNAs that play essential roles in plant growth, development, and stress response. We conducted a genome-wide survey of maize miRNA genes, characterizing their structure, expression, and evolution. Computational approaches based on homology and secondary structure modeling identified 150 high-confidence genes within 26 miRNA families. For 25 families, expression was verified by deep-sequencing of small RNA libraries that were prepared from an assortment of maize tissues. PCR–RACE amplification of 68 miRNA transcript precursors, representing 18 families conserved across several plant species, showed that splice variation and the use of alternative transcriptional start and stop sites is common within this class of genes. Comparison of sequence variation data from diverse maize inbred lines versus teosinte accessions suggest that the mature miRNAs are under strong purifying selection while the flanking sequences evolve equivalently to other genes. Since maize is derived from an ancient tetraploid, the effect of whole-genome duplication on miRNA evolution was examined. We found that, like protein-coding genes, duplicated miRNA genes underwent extensive gene-loss, with ∼35% of ancestral sites retained as duplicate homoeologous miRNA genes. This number is higher than that observed with protein-coding genes. A search for putative miRNA targets indicated bias towards genes in regulatory and metabolic pathways. As maize is one of the principal models for plant growth and development, this study will serve as a foundation for future research into the functional roles of miRNA genes

Online trapping and enrichment ultra performance liquid chromatography-tandem mass spectrometry method for sensitive measurement of "arginine-asymmetric dimethylarginine cycle" biomarkers in human exhaled breath condensate.

BACKGROUND: Exhaled breath condensate (EBC) is a biofluid collected non invasively that, enabling the measurement of several biomarkers, has proven useful in the study of airway inflammatory diseases, including asthma, COPD and cystic fibrosis. To the best of our knowledge, there is no previous report of any analytical method to detect ADMA in EBC. OBJECTIVES: Aim of this work was to develop an online sample trapping and enrichment system, coupled with an UPLC-MS/MS method, for simultaneous quantification of seven metabolites related to "Arginine-ADMA cycle", using the isotopic dilution. METHODS: Butylated EBC samples were trapped in an online cartridge, washed before and after each injection with cleanup solution to remove matrix components and switched inline into the high pressure analytical column. Multiple reaction monitoring in positive mode was used for analyte quantification by tandem mass spectrometry. RESULTS: Validation studies were performed in EBC to examine accuracy, precision and robustness of the method. For each compound, the calibration curves showed a coefficient of correlation (r(2)) greater than 0.992. Accuracy (%Bias) was <3% except for NMMA and H-Arg (<20%), intra- and inter-assay precision (expressed as CV%) were within \ub120% and recovery ranged from 97.1 to 102.8% for all analytes. Inter-day variability analysis on 20 EBC of adult subjects did not demonstrate any significant variation of quantitative data for each metabolite. ADMA and SDMA mean concentrations (\u3bcmolL(-1)), measured in EBC samples of asthmatic adolescents are significantly increased (p<0.0001) than in normal controls (0.0040\ub10.0021 vs. 0.0012\ub10.0005 and 0.0020\ub10.0015 vs. 0.0002\ub10.0001, respectively), as well the ADMA/Tyr (0.34\ub10.09 vs. 0.12\ub10.02, p<0.0001) and the SDMA/Tyr ratio (0.10\ub10.04 vs. 0.015\ub10.004, p<0.0001). CONCLUSIONS: The proposed method features simple specimen preparation, maintenance of an excellent peak shape of all metabolites and reduced matrix effects as well mass spectrometer noise. Moreover, the possibility to perform different cycles of enrichment, using large injection volumes, compensated for the low concentration of analytes contained in EBC, leading to a good analytical sensitivity. Preliminary data obtained from asthmatic and healthy adolescents, demonstrated that the analytical method applied to EBC seems suitable not only for research purposes, but also for clinical routinely analysis

ASYMMETRIC DIMETHYLARGININE (ADMA) IN EXHALED BREATH CONDENSATE AND SERUM OF ASTHMATIC CHILDREN.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor and uncoupler of nitric oxide synthase. By promoting the formation of peroxynitrite, ADMA is believed to contribute to several aspects of asthma pathogenesis (ie, airway inflammation, oxidative stress, bronchial hyperresponsiveness, and collagen deposition). The aim of the present study was to compare this mediator in healthy children and children with asthma using the completely noninvasive exhaled breath condensate (EBC) technique