1,721,011 research outputs found
The ATTR-ACT trial
No full textLa transtiretina (TTR) è una proteina di trasporto con struttura tetramerica sintetizzata principalmente (99% circa) dal fegato, che a livello ematico trasporta la tiroxina e la proteina legante il retinolo1. Proprio dalla sua funzione deriva il nome “transtiretina” [transthyretin: TRANS(ports)THY(roxin) and RETIN(ol)].
Esistono due tipi di amiloidosi sistemiche derivate dal deposito della TTR (ATTR): una forma genetica nota come “amiloidosi ereditaria da TTR” (ATTRm) e una forma non ereditaria nota come amiloidosi da TTR “wild type” (ATTRwt, anche definita in passato come “amiloidosi sistemica senile”). Nel primo caso si tratta di una malattia ereditaria con trasmissione autosomica dominante in cui la presenza di una mutazione del gene della TTR conferisce alla proteina una conformazione più instabile; pertanto il tetramero risulta più suscettibile alla dissociazione in monomeri, passaggio essenziale per l’avvio del processo amiloidogenico. Tuttavia, anche se la mutazione è presente fin dalla nascita, e quindi per tutta la vita viene prodotta una proteina anomala, questa continua a mantenere la sua conformazione fino all’età adulta, quando la proteina comincia a precipitare in forma fibrillare e a formare i depositi. Tutto ciò suggerisce l’esistenza di ulteriori meccanismi fisiopatologici oltre all’instabilità intrinseca della proteina mutata
Effects of different levels of N- and P-deficiency on cell yield, okadaic acid, DTX-1, protein and carbohydrate dynamics in the benthic dinoflagellate Prorocentrum lima.
No full textProrocentrum lima (Ehrenberg) Dodge is a cosmopolitan epiphytic dinoflagellate that produces biotoxins which are causative of diarrhetic shellfish poisoning (DPS). Here we report on effects of several nitrogen (N) and phosphorous (P) limited conditions on cell yield, okadaic acid (OA) and dinophysistoxin-1 (DTX-1) contents synoptically with cell carbohydrate, exopolysaccharide (EPS) and cell protein concentrations in a P. lima strain isolated from the Sacca di Goro lagoon (Northern Adriatic Sea). Batch culture experiments
were set to assess changes induced by four nitrogen-limited levels (1/3-N, 1/10-N, 1/20-N, and 1/50-N) and four phosphorus-limited levels (1/3-P, 1/10-P, 1/20-P, and 1/50-P) with respect to control nutrient conditions (f/2 medium; NO3- and PO4 3- concentrations: 883 and 36.3 mM, respectively; N/P ratio: 24). Low nutrients availability determined lower cell yields starting from 1/10-N and 1/3-P levels and the pattern observed was dependent on nutrient dynamics, as shown byNand P analyses performed in culture media during growth. Final cell yield decreased significantly up to 4.7- and 5.6-fold under 1/50-N and 1/50 P-limited levels with respect to control values, while cell volume increased with respect to control (up to 30% and 35% for N- and P-experiment, respectively). On overall, OA concentration ranged from 6.69 to 15.80 pg cell-1, while DTX-1 ranged from 0.12 and 0.39 pg cell-1 resulting in unusual high OA/DTX-1 ratios. The study indicates that protein, carbohydrate, EPS, and toxin concentrations displayed remarkable different patterns under the two kinds of nutrient deficiencies. The main differences can be summarised as: (i) significant decrease of cell protein concentration (up to 2-fold) under N-limitation, conversely no
significant changes in protein concentration under P-limitation; (ii) significant increase of cell carbohydrate (up to 2.8-fold and 3.4-fold for N- and P-limitation, respectively) and cell OA amount (up to 1.9-fold and 2.3-fold, N- and P-limitation, respectively) under both N- and P-limitations, however different level-deficiency dependent patterns were displayed under the two nutrient conditions; (iii)
significant increase of EPS concentration (up to 6.50-fold) under P-limitation, conversely no significant changes in EPS concentration under N-limitation. Data presented here indicate that P. lima adopts different eco-physiological strategies to face N-limitation or P-limitation. This study provides the first evidence for an increase in EPS production by benthic dinoflagellates under P-limited conditions; the ecological significance of this increase is discussed
Test biologici e funzionali per il rilevamento delle palitossine.
No full textPer quanto riguarda la valutazione della tossicità associata alla presenza di biotossine nei molluschi bivalvi e in altri organismi acquatici, in Italia si fa riferimento alla normativa comunitaria in materia: Regolamento (EC) 853/2004 e s.m.i., che ne stabilisce i tenori massimi consentiti e Regolamento (EC) 2074/2005 e s.m.i., che decreta i metodi chimici e biologici di riferimento per diverse altre tossine, ma non per la palitossina (PLTX). I limiti di legge per la presenza di PLTX nei prodotti della pesca non sono ancora stati fissati, tuttavia lo European Food Safety Authority Panel on Contaminants in the Food Chain ha suggerito un limite di 30 μg/kg nei molluschi.
I test biologici hanno il vantaggio di identificare effetti tossici dovuti alla presenza di eventuali tossine non note o non attese, difficilmente identificabili con analisi chimiche. Il test biologico cui si fa riferimento nel suddetto decreto è il test sul topo per le tossine lipofile (mouse bioassay), che ha però una sensibilità piuttosto bassa, una riproducibilità limitata, può dare falsi positivi ed è stato ampiamente criticato per problemi di natura etica legati al benessere animale. Pertanto, nel 2011 la Commissione Europea ha stabilito che la cromatografia liquida abbinata a spettrometria di massa (Liquid Chromatography-Mass Spectrometry, LC-MS) sostituisca gradualmente il test sul topo e rappresenti il metodo standard per determinare la presenza di tossine lipofile nei molluschi; anche la PLTX può essere rilevata dal test sul topo, ma in maniera non sempre riproducibile, data la sua natura anfipatica.
Vista la crescente presenza di O. cf. ovata nel Mediterraneo e le possibili ripercussioni sulla salute umana, sarebbe particolarmente utile disporre di test semplici e rapidi in grado di dare informazioni attendibili sulla presenza di tossine nell’ambiente e/o negli organismi marini. Diversi metodi biologici e immunologici in grado di evidenziare la PLTX e i suoi analoghi in organismi marini, molluschi e microalghe sono già stati sviluppati, anche se nessuno è ancora stato validato. Tali metodi potrebbero essere utili o come screening preliminari cui far seguire le analisi strumentali o nel caso in cui i metodi strumentali non siano disponibili. Si elencano possibili metodi di identificazione delle PLTX con i relativi riferimenti bibliografici
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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