1,720,958 research outputs found
Vibrio interactions with bivalve hemocytes and analysis of the Crassostrea gigas microbiota
No full textMy PhD project aimed at investigating the molecular mechanisms at the basis of the interaction between Vibrio bacteria and shellfish in the bivalve models Crassotrea gigas and Mytilus galloprovincialis and to study the composition and dynamics of bivalve microbiota.
Previous studies suggested that persistence of entrapped bacteria inside bivalve tissues depends, at least in part, on their capacity to survive to the hemolymph bactericidal activity, that is exerted by both hemocytes and serum soluble factors. In the first part of my PhD work, hemocytes of M. galloprovincialis were challenged with different pathogenic Vibrio strains (V. aestuarianus 01/032, V. aestuarianus 02/041, V. tasmaniensis LGP32, V. harveyi VH2, V. tapetis CECT 4600 and V. coralliilyticus ATCC BAA 450) in the presence or in the absence of the extrapallial protein present in M. galloprovincialis serum (MgEP), and of the whole hemolymph serum. In addition, C. gigas hemocytes were exposed to the bivalve pathogens V. aestuarianus 01/032 and V. aestuarianus 02/041 under the same conditions to better understand molecular basis of bacteria-hemolymph interactions in oysters. We observed that MgEP promotes D- mannose sensitive adhesion to and killing by hemocytes of the bivalve pathogens V. aestuarianus 01/032, V. aestuarianus 02/041, V. tasmaniensis LGP32 and V. coralliilyticus ATCC BAA 450. In addition, in the presence of M. galloprovincialis EP protein (MgEP), C. gigas haemocytes killed V. aestuarianus 01/032 and V. aestuarianus 02/041 almost as efficiently as mussel phagocytes. These findings suggest that the different sensitivity of Vibrio strains to the antibacterial activity of oyster (susceptible to Vibrio infection) and mussel (resistant to Vibrio infection) haemolymph might partly depend on the fact that C. gigas serum lacks MgEP-like opsonins. These results may have important implications for improving bivalve depuration strategies and prevent diseases affecting bivalve production worldwide.
In the second part of my thesis work, I studied the microbial communities associated to contrasting C. gigas samples collected during mortality episodes in different European sites. Real-time PCR targeting oyster pathogens (e.g. Ostreid herpesvirus 1 [OshV-1] and V. aestuarianus) and 16SrRNA gene-based microbial profiling were applied on a large number of C. gigas samples (n=525 and n=101 for qPCR and 16SrRNA gene profiling analysis, respectively) to extensively investigate the patterns and dynamics of oyster microbiota during mortality events. Comparative analysis of contrasting (e.g. infected vs not infected) C. gigas samples conducted using these methods revealed that oyster experiencing mortality outbreaks displayed signs of microbiota disruption associated with the presence of previously undetected potential pathogenic microbial species mostly belonging to genus Vibrio and Arcobacter. This represents to our knowledge, the largest study conducted so far to determine the composition and dynamics of farmed oyster microbiota
Shift in Immune Parameters After Repeated Exposure to Nanoplastics in the Marine Bivalve Mytilus
Full text linkBivalves are widespread in coastal environments subjected to a wide range of environmental fluctuations: however, the rapidly occurring changes due to several anthropogenic factors can represent a significant threat to bivalve immunity. The mussel Mytilus spp. has extremely powerful immune defenses toward different potential pathogens and contaminant stressors. In particular, the mussel immune system represents a significant target for different types of nanoparticles (NPs), including amino-modified nanopolystyrene (PS-NH2) as a model of nanoplastics. In this work, the effects of repeated exposure to PS-NH2 on immune responses of Mytilus galloprovincialis were investigated after a first exposure (10 μg/L; 24 h), followed by a resting period (72-h depuration) and a second exposure (10 μg/L; 24 h). Functional parameters were measured in hemocytes, serum, and whole hemolymph samples. In hemocytes, transcription of selected genes involved in proliferation/apoptosis and immune response was evaluated by qPCR. First exposure to PS-NH2 significantly affected hemocyte mitochondrial and lysosomal parameters, serum lysozyme activity, and transcription of proliferation/apoptosis markers; significant upregulation of extrapallial protein precursor (EPp) and downregulation of lysozyme and mytilin B were observed. The results of functional hemocyte parameters indicate the occurrence of stress conditions that did not however result in changes in the overall bactericidal activity. After the second exposure, a shift in hemocyte subpopulations, together with reestablishment of basal functional parameters and of proliferation/apoptotic markers, was observed. Moreover, hemolymph bactericidal activity, as well as transcription of five out of six immune-related genes, all codifying for secreted proteins, was significantly increased. The results indicate an overall shift in immune parameters that may act as compensatory mechanisms to maintain immune homeostasis after a second encounter with PS-NH2
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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