2,727 research outputs found

    The inositol pyrophosphate metabolism of Dictyostelium discoideum does not regulate inorganic polyphosphate (polyP) synthesis

    Get PDF
    Initial studies on the inositol phosphates metabolism were enabled by the social amoeba Dictyostelium discoideum. The abundant amount of inositol hexakisphosphate (IP6 also known as Phytic acid) present in the amoeba allowed the discovery of the more polar inositol pyrophosphates, IP7 and IP8, possessing one or two high energy phosphoanhydride bonds, respectively. Considering the contemporary growing interest in inositol pyrophosphates, it is surprising that in recent years D. discoideum, has contributed little to our understanding of their metabolism and function. This work fulfils this lacuna, by analysing the ip6k, ppip5k and ip6k-ppip5K amoeba null strains using PAGE, 13C-NMR and CE-MS analysis. Our study reveals an inositol pyrophosphate metabolism more complex than previously thought. The amoeba Ip6k synthesizes the 4/6-IP7 in contrast to the 5-IP7 isomer synthesized by the mammalian homologue. The amoeba Ppip5k synthesizes the same 1/3-IP7 as the mammalian enzyme. In D. discoideum, the ip6k strain possesses residual amounts of IP7. The residual IP7 is also present in the ip6k-ppip5K strain, while the ppip5k single mutant shows a decrease in both IP7 and IP8 levels. This phenotype is in contrast to the increase in IP7 observable in the yeast vip1Δ strain. The presence of IP8 in ppip5k and the presence of IP7 in ip6k-ppip5K indicate the existence of an additional inositol pyrophosphate synthesizing enzyme. Additionally, we investigated the existence of a metabolic relationship between inositol pyrophosphate synthesis and inorganic polyphosphate (polyP) metabolism as observed in yeast. These studies reveal that contrary to the yeast, Ip6k and Ppip5k do not control polyP cellular level in amoeba

    Concepciones culturales del VIH/Sida de adolescentes de Bolivia, Chile y MĂ©xico

    Get PDF
    OBJETIVO: Comprender las dimensiones culturales del VIH/Sida de estudiantes adolescentes. MÉTODOS: Estudio antropolĂłgico cognitivo. Realizado en Cochabamba (Bolivia), Talca (Chile) y Guadalajara (MĂ©xico) entre 2007 y 2008. Un total de 184 jĂłvenes (de 14 y 19 años de edad) fueron seleccionados por muestreo propositivo en centros de estudios de educaciĂłn media superior de cada paĂ­s. Fueron utilizadas las tĂ©cnicas de listados libres y el sorteo de montones. Se indagaron tĂ©rminos asociados al concepto VIH/Sida y grupos de dimensiones conceptuales. Posteriormente se aplicĂł anĂĄlisis de consenso mediante factorizaciĂłn de componentes principales y anĂĄlisis dimensional mediante conglomerados jerĂĄrquicos y escalas multidimensionales. RESULTADOS: Las diferencias entre los contextos fueron en el grado de consenso en relaciĂłn al tĂ©rmino de VIH/Sida, ya que fue mayor en Cochabamba. En Talca y Guadalajara los jĂłvenes mencionaron metĂĄforas de lucha frente a la enfermedad, mientras en Cochabamba se refirieron a la ayuda, apoyo y amor que las personas infectadas deberĂ­an recibir. Las coincidencias entre las conceptualizaciones de los jĂłvenes de los tres paĂ­ses fueron: los riesgos (las prĂĄcticas sexuales desprotegidas y el contacto con algunos grupos poblacionales especĂ­ficos), las consecuencias (muerte fĂ­sica y social, entendida Ă©sta Ășltima como el rechazo de la sociedad hacia los enfermos) y la prevenciĂłn de la enfermedad (con base en la informaciĂłn asĂ­ como uso del condĂłn). CONCLUSIONES: Para los estudiantes adolescentes el VIH/Sida es una enfermedad causada por prĂĄcticas sexuales y consumo de drogas que implica daño, dolor y muerte. Los programas preventivos del VIH/Sida para los adolescentes deben promover la bĂșsqueda de informaciĂłn sobre el tema con bases cientĂ­ficas, y no centrarse en las consecuencias emocionales y sociales de la enfermedad.OBJETIVO: Compreender as dimensĂ”es culturais do HIV/Aids por estudantes adolescentes. MÉTODOS: Estudo antropolĂłgico cognitivo realizado em Cochabamba (BolĂ­via), Talca (Chile) e Guadalajara (MĂ©xico), entre 2007 e 2008. O total de 184 jovens (de 14 e 19 anos de idade) foi selecionado por amostragem propositiva em centros de estudos de educação mĂ©dia superior de cada paĂ­s. Foram utilizadas tĂ©cnicas de listas livres e classificação da pilha. Foi feita a indagação de termos associados ao conceito HIV/Aids e grupos de dimensĂ”es conceituais. Posteriormente, fez-se anĂĄlise de consenso mediante a fatorização dos componentes principais e anĂĄlise dimensional mediante conglomerados hierĂĄrquicos e escalas multidimensionais. RESULTADOS: As diferenças entre os contextos foram no grau de consenso em relação ao termo HIV/Aids, que foi maior em Cochabamba. Em Talca e Guadalajara os jovens mencionaram metĂĄforas de luta diante da doença, enquanto em Cochabamba eles referiram ajuda, apoio e amor que as pessoas infectadas deveriam receber. As coincidĂȘncias entre as conceitualizaçÔes dos jovens dos trĂȘs paĂ­ses foram: os riscos (as prĂĄticas sexuais desprotegidas e o contato com alguns grupos populacionais especĂ­ficos), as conseqĂŒĂȘncias (morte fĂ­sica e social, entendida esta Ășltima como o rechaço da sociedade aos doentes) e a prevenção da doença (com base na informação e no uso do preservativo). CONCLUSIONES: Para os estudantes adolescentes, o HIV/Aids Ă© uma doença causada por prĂĄticas sexuais e uso de drogas que envolve dano, dor e morte. Os programas preventivos do HIV/Aids para os e as adolescentes devem promover a busca de informação com bases cientĂ­ficas sobre o tema, e nĂŁo sĂł a que se centra nas conseqĂŒĂȘncias emocionais e sociais da doença.OBJECTIVE: To understand the cultural dimensions of HIV/AIDS among adolescent students. METHODS: A cognitive anthropological study was undertaken in Cochabamba (Bolivia), Talca (Chile) and Guadalajara (Mexico), during 2007 and 2008. A total of 184 teenagers (from 14 to 19 years old) were selected by purposeful sampling at secondary schools in each country. Free association lists and pile sorts were utilized. Terms associated with the concept of HIV/AIDS and groups of conceptual dimensions were investigated. Subsequently, consensus analysis was performed using factorial principal components and dimensional analysis through hierarchical clusters and multidimensional scales. RESULTS: The differences between the country contexts were in the degree of consensus in relation to the term HIV/AIDS, which was greater in Cochabamba. In Talca and Guadalajara the youths mentioned metaphors of fighting against HIV/AIDS, while in Cochabamba participants talked about help, support and love that infected people should receive. The similarities among conceptions by youth from the three countries were: the risk factors (unprotected sexual practice and contact with specific population groups), the consequences (physical and social death, being the latter understood as social rejection of people living with HIV/AIDS) and the prevention of illness (based on information and condom use). CONCLUSIONS: For adolescent students, HIV/AIDS is a disease caused by sexual practices and drug use and involves harm, pain and death. HIV/AIDS prevention programs for adolescents should promote science based information on the topic and not concentrate only on the emotional and social consequences of HIV/AIDS

    Fractional Euler-Lagrange differential equations via Caputo derivatives

    Get PDF
    We review some recent results of the fractional variational calculus. Necessary optimality conditions of Euler-Lagrange type for functionals with a Lagrangian containing left and right Caputo derivatives are given. Several problems are considered: with fixed or free boundary conditions, and in presence of integral constraints that also depend on Caputo derivatives.Comment: This is a preprint of a paper whose final and definite form will appear as Chapter 9 of the book Fractional Dynamics and Control, D. Baleanu et al. (eds.), Springer New York, 2012, DOI:10.1007/978-1-4614-0457-6_9, in pres

    Release of Lungworm Larvae from Snails in the Environment: Potential for Alternative Transmission Pathways

    Get PDF
    Background: Gastropod-borne parasites may cause debilitating clinical conditions in animals and humans following the consumption of infected intermediate or paratenic hosts. However, the ingestion of fresh vegetables contaminated by snail mucus and/or water has also been proposed as a source of the infection for some zoonotic metastrongyloids (e.g., Angiostrongylus cantonensis). In the meantime, the feline lungworms Aelurostrongylus abstrusus and Troglostrongylus brevior are increasingly spreading among cat populations, along with their gastropod intermediate hosts. The aim of this study was to assess the potential of alternative transmission pathways for A. abstrusus and T. brevior L3 via the mucus of infected Helix aspersa snails and the water where gastropods died. In addition, the histological examination of snail specimens provided information on the larval localization and inflammatory reactions in the intermediate host. Methodology/Principal Findings: Twenty-four specimens of H. aspersa received ~500 L1 of A. abstrusus and T. brevior, and were assigned to six study groups. Snails were subjected to different mechanical and chemical stimuli throughout 20 days in order to elicit the production of mucus. At the end of the study, gastropods were submerged in tap water and the sediment was observed for lungworm larvae for three consecutive days. Finally, snails were artificially digested and recovered larvae were counted and morphologically and molecularly identified. The anatomical localization of A. abstrusus and T. brevior larvae within snail tissues was investigated by histology. L3 were detected in the snail mucus (i.e., 37 A. abstrusus and 19 T. brevior) and in the sediment of submerged specimens (172 A. abstrusus and 39 T. brevior). Following the artificial digestion of H. aspersa snails, a mean number of 127.8 A. abstrusus and 60.3 T. brevior larvae were recovered. The number of snail sections positive for A. abstrusus was higher than those for T. brevior. Conclusions: Results of this study indicate that A. abstrusus and T. brevior infective L3 are shed in the mucus of H. aspersa or in water where infected gastropods had died submerged. Both elimination pathways may represent alternative route(s) of environmental contamination and source of the infection for these nematodes under field conditions and may significantly affect the epidemiology of feline lungworms. Considering that snails may act as intermediate hosts for other metastrongyloid species, the environmental contamination by mucus-released larvae is discussed in a broader context

    Surveillance of iclaprim activity: In vitro susceptibility of gram-positive pathogens collected from 2012 to 2014 from the United States, Asia Pacific, Latin American and Europe

    Get PDF
    Iclaprim is a diaminopyrimidine, which inhibits bacterial dihydrofolate reductase, and it is highly active against Gram-positive pathogens including emerging drug-resistant pathogens. In vitro activity of iclaprim and comparators against 2814 Gram-positive clinical isolates from the United States, Asia Pacific, Latin American and Europe collected between 2012 and 2014 were tested. Susceptibility testing was performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Minimum inhibitory concentration (MIC) interpretations were based on CLSI and European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. MIC50/MIC90 for all S. aureus, methicillin susceptible S. aureus, methicillin resistant S. aureus, beta-hemolytic streptococci, and Streptococcus pneumoniae were 0.06/0.12, 0.06/0.12, 0.06/0.5, 0.06/0.25, and 0.06/2 ÎŒg/mL, respectively. Iclaprim was 8 to 32-fold more potent than trimethoprim, the only FDA approved dihydrofolate reductase inhibitor, against all Gram-positive isolates including resistant phenotypes. The MIC90 of iclaprim was also lower than most of the comparators including linezolid and vancomycin against Gram-positive pathogens. Iclaprim demonstrated potent activity against a contemporary collection (2012–2014) of Gram-positive clinical isolates from the United States, Asia Pacific, Latin America and Europe

    Smc5/6: a link between DNA repair and unidirectional replication?

    Get PDF
    Of the three structural maintenance of chromosome (SMC) complexes, two directly regulate chromosome dynamics. The third, Smc5/6, functions mainly in homologous recombination and in completing DNA replication. The literature suggests that Smc5/6 coordinates DNA repair, in part through post-translational modification of uncharacterized target proteins that can dictate their subcellular localization, and that Smc5/6 also functions to establish DNA-damage-dependent cohesion. A nucleolar-specific Smc5/6 function has been proposed because Smc5/6 yeast mutants display penetrant phenotypes of ribosomal DNA (rDNA) instability. rDNA repeats are replicated unidirectionally. Here, we propose that unidirectional replication, combined with global Smc5/6 functions, can explain the apparent rDNA specificity

    Two Earth-sized planets orbiting Kepler-20

    Get PDF
    Since the discovery of the first extrasolar giant planets around Sun-like stars, evolving observational capabilities have brought us closer to the detection of true Earth analogues. The size of an exoplanet can be determined when it periodically passes in front of (transits) its parent star, causing a decrease in starlight proportional to its radius. The smallest exoplanet hitherto discovered has a radius 1.42 times that of the Earth's radius (R Earth), and hence has 2.9 times its volume. Here we report the discovery of two planets, one Earth-sized (1.03R Earth) and the other smaller than the Earth (0.87R Earth), orbiting the star Kepler-20, which is already known to host three other, larger, transiting planets. The gravitational pull of the new planets on the parent star is too small to measure with current instrumentation. We apply a statistical method to show that the likelihood of the planetary interpretation of the transit signals is more than three orders of magnitude larger than that of the alternative hypothesis that the signals result from an eclipsing binary star. Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate. The outer planet could have developed a thick water vapour atmosphere.Comment: Letter to Nature; Received 8 November; accepted 13 December 2011; Published online 20 December 201

    Transit Photometry as an Exoplanet Discovery Method

    Full text link
    Photometry with the transit method has arguably been the most successful exoplanet discovery method to date. A short overview about the rise of that method to its present status is given. The method's strength is the rich set of parameters that can be obtained from transiting planets, in particular in combination with radial velocity observations; the basic principles of these parameters are given. The method has however also drawbacks, which are the low probability that transits appear in randomly oriented planet systems, and the presence of astrophysical phenomena that may mimic transits and give rise to false detection positives. In the second part we outline the main factors that determine the design of transit surveys, such as the size of the survey sample, the temporal coverage, the detection precision, the sample brightness and the methods to extract transit events from observed light curves. Lastly, an overview over past, current and future transit surveys is given. For these surveys we indicate their basic instrument configuration and their planet catch, including the ranges of planet sizes and stellar magnitudes that were encountered. Current and future transit detection experiments concentrate primarily on bright or special targets, and we expect that the transit method remains a principal driver of exoplanet science, through new discoveries to be made and through the development of new generations of instruments.Comment: Review chapte
    • 

    corecore