1,720,958 research outputs found
Reactive oxygen species and oxylipin pathways: a unifying framework in oxidative stress.
No full textLo scopo della tesi è stato di studiare due tipi di stress ossidativo in due diversi modelli vegetali: il primo riguardava il coinvolgimento di specie attivate dell’ossigeno e l’attivazione della via delle ossilipine in piante di melo affette da fitoplasmosi, il secondo concerneva lo stress ossidativo in semi di caffè durante la conservazione e la germinazione
Involvement of plasma membrane peroxidases and oxylipin pathway in the recovery from phytoplasma disease in apple (Malus domestica)
No full textApple trees (Malus domestica) may be affected by apple proliferation (AP), caused by “Candidatus Phytoplasma mali”. Some plants can spontaneously recover from the disease, which implies the disappearance of symptoms through a phenomenon known as recovery. In this paper it is shown that NAD(P)H peroxidases of leaf plasma membrane-enriched fractions exhibited a higher activity in samples from both AP-diseased and recovered plants. In addition, an increase in endogenous SA was characteristic of the symptomatic plants, since its content increased in samples obtained from diseased apple trees. In agreement, phenylalanine ammonia lyase (PAL) activity, a key enzyme of the phenylpropanoid pathway, was increased too. Jasmonic acid (JA) increased only during recovery, in a phase subsequent to the pathological state, and in concomitance to a decline of salicylic acid (SA). Oxylipin pathway, responsible for JA synthesis, was not induced during the development of AP-disease, but it appeared to be stimulated when the recovery occurred. Accordingly, lipoxygenase (LOX) activity, detected in plasma membrane-enriched fractions, showed an increase in apple leaves obtained from recovered plants. This enhancement was paralleled by an increase of hydroperoxide lyase (HPL) activity, detected in leaf microsomes, albeit the latter enzyme was activated in either the disease or recovery conditions. Hence, a reciprocal antagonism between SA- and JA-pathways could be suggested as an effective mechanism by which apple plants react to phytoplasma invasions, thereby providing a suitable defense response leading to the establishment of the recovery phenomenon
Attività di perossidasi di superficie e via delle ossilipine in piante di melo soggette a recovery da fitoplasmosi
No full textApple trees (Malus domestica Borkh) may be affected by apple proliferation (AP), caused by ‘Candidatus Phytoplasma mali’. Some plants can spontaneously recover from the disease, which implies the disappearance of symptoms through a phenomenon known as recovery. Recovered apple trees show the disappearance of the symptoms and pathogens from the canopy, but not from the infected roots, where phytoplasmas persist viable and infectious. Recovery of apple plants is linked to an overproduction of hydrogen peroxide in the phloem tissues. The high levels of hydrogen peroxide in the canopy of recovered apple plants could have a direct antimicrobial effect on pathogens and/or a signalling function, in order to activate defence responses triggered by the phytormones jasmonate and salicylate. In general, it can be stated that salicylate promotes resistance against biotrophic pathogens, whereas the jasmonate pathway induces resistance against necrotrophic pathogens and herbivorous insects. Apple plants, infected by AP-disease, initially show an induced mechanism of defence mediated by salicylate but, subsequently, during the recovery, an increase of jasmonate, sinthesized by the oxylipin pathway, occurs
CHARACTERIZATION OF LIPASE ACTIVITY IN GREEN COFFEE BEANS DURING STORAGE AND GERMINATION
Full text linkLipase, green coffee, germination, storage, lipid
Coffee seeds possess an intermediate storage pattern, showing a non-quiescent behaviour
characterized by various metabolic reactions occurring during storage. In particular, lipase is the
main enzyme involved in the mobilization of triacylglycerols, providing energy and a source of
carbon skeleton during early stages of germination. During storage, the triacylglycerols might be involved in the generation of undesirable compounds (known as “off-flavours”), lowering both the viability of coffee seeds and the cup quality. In this work, the soluble protein fraction from coffee seeds and plantlets was extracted by acetone and then was utilised to assay lipase activity. Green coffee beans, harvested in Colombia, were stored at room temperature for 2-3 months, in order to verify the influence of prolonged storage on lipase activity. For germination experiments, the seeds were imbibed for 7 days at 30 °C and transferred in perlite at 28 °C and 90% R.H. for further 3 weeks. Lipase activity was detected by a colorimetric method based on specific degradation of a chromogenic substrate, at pH 8.2. Green coffee seeds exhibited an appreciable lipase activity that was slightly increased during storage. Such an activity was inhibited by tetrahydrolipstatin (THL) in
a concentration-dependent manner, while it was slightly stimulated by both EGTA and EDTA.
During the germination, after 10, 14, 17 and 21 days, lipase activity showed an initial increase that was followed by a gradual decrease. The effect of the presence or absence of the parchment (seed coat), during the first stages of germination, has also been investigated
Surface NADH peroxidases and oxilipin pathway are involved in the recovery from phytoplasma disease in apple
No full textPhytoplasmas are prokaryotic plant pathogens responsible for deterioration of several trees. In apple tree, the proliferation of the disease, caused by phytoplasmas, may undergo a spontaneous disappearance of symptoms, which are associated to hydrogen peroxide production in the phloem, a phenomenon called recovery. The aim of this work was to identify the biochemical pattern associated to the recovery by examining some enzymatic activities and metabolites in leaves from healthy, diseased and recovered plants. NAD(P)H oxidase/peroxidase, lipoxygenase, hydroperoxide lyase and phenylalanine ammonia lyase (PAL) activities were assayed. All these activities, except for PAL, were increased in leaves from recovered plants. Salicylate and jasmonate content was also determined, showing that the increase in recovered leaves was ascribed to jasmonate only. These results suggest that the activation of surface/plasma membrane redox systems is crucial in promoting the recovery process in apple tree, which then proceeds through the oxylipin pathway, leading to jasmonate. Conversely, salicylic acid appears to be involved only in the response to disease, but not in the subsequent recovery
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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