1,721,031 research outputs found
Experimental and Computational Analysis of a Tuned Exhaust System for a Small Two-Stroke Engine
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Interaction between probiotics and intestinal human epithelial cells: adhesion and induction of immune-related genes.
No full textHuman gut is the largest body surface in contact with the external environment. It is a complex ecosystem combining gastrointestinal epithelium, immune cells and resident microbiota. Together, they cooperate to build up physical and chemical barriers to protect the host from potentially harmful microorganisms [1]. Probiotics may improve host health by modulating mucosal immune functions (e.g. mucin secretion, cytokine balance and antimicrobial peptides production).
We previously developed an in vitro system that simulates the human gastro-intestinal (GI) tract, in which bacterial stress tolerance was examined. Lactobacillus plantarum WCFS1 [2], relative mutant strains (ΔctsrR, ΔftsH, Δhsp18.55) [3,4], and commercial probiotics exhibited appreciable survival to stresses of the human GI tract. Here we study the interaction of these bacterial strains with human colonic cells in terms of colonization ability and immune modulation.
The adhesion propriety of the bacteria was analyzed on monolayers of differentiated and polarized Caco-2 cells. Intestinal cells were overlaid with bacteria in a ratio of 103:1 (bacteria: epithelial cells). The number of cell-associated bacteria was determined by CFU count on MRS plates. Among the three mutants analysed, ΔctsR showed significantly higher adherence with respect to wild type strain, similarly to the considerable adhesion of commercial probiotics. By qRT-PCR, the expression profile of a set of immune-related genes was analysed in Caco-2 cells, treated with either live or heat-inactivated bacteria. We observed up-regulation of HBD-2 and MUC-2 genes upon treatment with heat-killed cells of ΔftsH strain and differential induction of IL-6 and IL-8 genes by all the tested strains.
References
1.Liévin-Le Moal V and Servin AL (2006) Clin Microbiol Rev 19: 315-337.
2.Kleerebezem M et al (2003) Proc Natl Acad Sci USA 100:1990–1995.
3.Fiocco D et al (2010) J Bacteriol 192:896-900.
4. Capozzi V et al (2011) Res Microbiol 162:419
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Analisi dei meccani di tolleranza agli stress in un microrganismo probiotico modello.
No full textUna caratteristica comune a tutti gli organismi viventi è la capacità di rispondere agli stress. Questa è particolarmente importante nei microrganismi probiotici che, durante il transito nel tratto gastro-intestinale (GI), devono affrontare condizioni particolari come elevata acidità e salinità. L’analisi dei meccanismi molecolari alla base della resistenza agli stress in microrganismi probiotici, permette l’identificazione di marcatori utili per la selezione di probiotici con caratteristiche migliori. Lactobacillus plantarum (Lp), un batterio lattico (LAB), è una specie versatile, riscontrabile in una varietà di nicchie ambientali: per esempio è naturalmente presente nella saliva e nel tratto GI dell’uomo. Alcuni specifici ceppi di Lp sono stati selezionati e commercializzati sulla base di proprietà probiotiche (1). Lp ha la capacità di sopravvivere ad un ampio spettro di stress abiotici; è perciò plausibile che abbia sviluppato diversi e complessi meccanismi di tolleranza agli stress. La flessibilità ecologica di Lp è confermata dall’ampiezza del suo genoma, uno dei più grandi tra i LAB e tra le specie probiotiche più comuni.
Molti batteri vivono in un ambiente dinamico, in cui temperatura e disponibilità di nutrienti variano frequentemente. L’adattamento ai cambiamenti si realizza attraverso network di regolazione globale che controllano l'espressione simultanea di numerosi geni. La risposta allo shock termico consiste in una reazione biologica generale che protegge la cellula aumentandone la termo-tolleranza. La regolazione della risposta allo shock termico varia tra le diverse specie batteriche. In Bacillus subtilis, considerato microrganismo modello per i Gram-positivi, i cosiddetti reguloni della heat shock response sono classificati in base allo specifico elemento regolatore. La classe III, ad esempio, raggruppa i geni controllati dal repressore trascrizionale CtsR.
Scopo di questa ricerca è stato caratterizzare in Lp, i geni ctsR e ftsH, codificanti per proteine coinvolte nella regolazione della risposta allo stress termico. Analizzando il genoma di Lp sono stati individuati i geni potenzialmente regolati da CtsR. Per alcuni di questi geni è già nota l’associazione ai meccanismi di risposta agli stress; per altri non è confermato il loro coinvolgimento. Per verificare il controllo trascrizionale da parte di CtsR, è stato generato un ceppo mutante per delezione di ctsR, in cui si è analizzato il pattern di espressione dei possibili geni target. Per alcuni geni, il ruolo regolatore di CtsR è stato confermato mediante saggi di DNA binding ed analisi del promotore. Il gene ftsH, codificante per una proteina di membrana con funzione di proteasi e chaperone molecolare, è stato identificato come uno dei geni regolati da CtsR (2). Il profilo di espressione di ftsH e ctsR è stato studiato in condizioni di crescita sia ottimali che di stress. È stato prodotto un ceppo mutante di Lp in cui ftsH è stato inattivato. Il fenotipo dei mutanti per ctsR e ftsH è stato studiato e confrontato con quello wild-type, soprattutto in relazione alla tolleranza a vari stress abiotici, tipici degli habitat di Lp. Entrambi i mutanti risultano termosensibili. Sono stati inoltre valutati aspetti morfologici, proprietà autolitiche e capacità di formare biofilm.
Questo studio contribuisce a chiarire il complesso network regolativo che consente a Lp di rispondere agli stress ambientali e può rivelarsi utile per future applicazioni medico-biotecnologiche, quali la selezione di ceppi con migliori proprietà probiotiche e/o performances di starter alimentare.
Bibliografia
1. Cunningham-Rundles et al. (2000) Am. J. Gastroenterol. 95, 22–25.
2. Fiocco et al. (2009) J. Bacter. 191 (5), 1688–1694
Ultrastructural and functional study of the Liver Pigment cells from Rana esculenta L
No full textA study of the liver pigment cells of Rana esculenta L....
Mushroom Tyrosinase in Polyelectrolyte Multilayers as an Optical Biosensor for o-diphenols
No full textDetermination of phenolic derivatives is very important in medical, food and environmental samples
because of their relevant significance in health care and pollution monitoring. Tyrosinase-based biosensors
are promising tools for this purpose because of several advantages with respect to currently used
detection methods.
A key aspect in the development of a biosensor is the effective immobilization of the enzyme. In this
work, ordered tyrosinase films on an optical transparent support were immobilized by a “layer-by-layer”
(LbL) assembly, alternating the enzyme with the polycation polymer poly(dimethyldiallylammonium
chloride). As confirmed by UV–vis spectroscopy, the LbL deposition allowed a high loading of enzyme.
The immobilized tyrosinase functionality was proven and its kinetic parameters were spectrophotometrically
determined. The prepared biosensor was used to optically detect the o-diphenolic compound
L-3,4-dihydroxyphenyl-alanine (L-DOPA) and exhibited good repeatability and time stability. The sensing
properties of the system were studied by means of both absorption and fluorescence spectroscopy.
The bioassay based on the absorbance measurements gave a LOD of 23uM and a linear response up to
350uM. The bioassay based on the fluorescence measurements gave a LOD of 3uM and a linear response
in the range of tens of micromolar (the exact value depends on the number of mushroom tyrosinase
layers). Biosensor sensitivity could be modulated varying the number of the immobilized enzyme layers
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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