1,720,967 research outputs found
In vitro growth inhibition studies of Photobacterium damselae subspecies piscicida, using various antibodies
No full textTwo recently isolated Photobacterium damselae subspecies piscicida (Pasteurella piscicida) isolates were tested against various antibody probes (prepared in rabbits, mice and sea bass) in in vitro growth inhibition studies using three media formulations. The best suppressive activity was noted with sea bass antibodies; this activity was influenced by the culture medium used for the growth of the pathogen and the virulence of the isolate. Results are discussed in view to future vaccine development
Development of an ELISA to detect Pasteurella piscicida in culture and in “spiked” fish tissue
No full textAn enzyme linked immunosorbent assay (ELISA) was developed to detect the presence of
Pasteurella piscicida. The test, after the preparation of the solid phase, takes less than 4 h to
complete and the same technique can be applied for both bacteria in culture and in tissue. The
limit of sensitivity for bacteria in culture was IO’ cells ml ’ or 10’ cells well ‘, if a plate reader
is available or 10’ cells ml-’ (IO3 cells well- ‘> visually. Similar sensitivity was achieved (IO’
cells well-’ with a plate reader, IO’ cells well- ’ visually) when the ELISA was performed on
tissue. The technique is specific and it offers a rapid, early and sensitive means of diagnosing
Pasteurellosis during outbreaks and screening large populations of fish for the presence of P.
piscicida. 0 1997 Elsevier Science B.V
Investigation of media formulations promoting Photobacterium damsela subsp. piscicida natural and novel antigen expression and recognition by sea bass (Dicentrarchus labrax, L.) immune sera
No full textPhotobacterium damsela ssp. piscicida (Phdp) isolates were grown in various bacteriological media, in eukaryotic cell culture media and in the presence of fish cells (resembling some aspects of in vivo growth environments). Bacterial cells, extracellular products (ECPs) and crude capsular polysaccharide were isolated and analysed by electrophoresis and Western blot using sea bass sera. Growth in bacteriological media conserved the synthesis of cell and extracellular components when these were compared with those prepared under near-in vivo growth conditions. In fact, synthesis of a larger range of cell components was induced after growth in bacteriological media. Certain media based on yeast extract and peptones from various sources and a specific salt formulation induced the synthesis of novel cell components at approximately 21.3 and 14 kDa. These antigens were recognized by sea bass sera collected after natural pasteurellosis outbreaks and other sea bass sera raised against live or inactivated Phdp cells. The ECPs of the pathogen were not good immunogens in their soluble form despite various treatments prior to immunization. The results are discussed with respect to vaccine development
Vaccination trials of sea bass (Dicentrarchus labrax, L.) against Photobacterium damsela subsp. piscicida, using antigens prepared in novel media
No full textBacterial cells of the marine fish pathogen Photobacterium damsela subsp. piscicida were grown in novel culture media. A mixture of whole cells and extracellular components was inactivated and used in bath, intraperitoneal (i.p.) and oral vaccination of sea bass, Dicentrarchus labrax, employing two sizes of fish. A commercial vaccine was used for comparative purposes. Control and immunized fish were either bath or intraperitoneally challenged 6 and 12 weeks post-vaccination. Small fish had significantly higher relative percentage survival with the novel vaccine mixture both at 6 and 12 weeks post-vaccination by bath, in comparison with the commercial vaccine. No protection was afforded at 6 or 12 weeks post-immunization by either vaccine after challenge via i.p. injection. Sea bass (1.5-2 g) intraperitoneally vaccinated with various adjuvanted vaccine mixtures were not protected against pasteurellosis. In contrast, larger sea bass (20 g) benefited from vaccination with the novel vaccine mixtures. Intraperitoneal challenge with the pathogen resulted in protection in both fish groups vaccinated with novel vaccine mixtures, whereas control fish suffered high mortalities (> 80%). Orally vaccinated fish were immersion challenged with the pathogen. At 6 and 12 weeks post-vaccination the control fish had a high mortality and the fish vaccinated with the novel vaccine mixture achieved good protection
The effect of novel growth media on the virulence and toxicity of cellular and extracellular components of the fish pathogen Photobacterium damselae subsp. piscicida
No full textNovel media for the preparation of antigens from the pathogen Photobacterium damselae subsp. piscicida were evaluated in respect to the promotion of synthesis of virulence factors. Certain formulations based on yeast extract and bacterial and / or fish peptone promoted the toxicity of ECPs and the virulence of bacterial cells administered via immersion or intraperitoneal injection. Crude capsular polysaccharide was proved to possess low toxicity. Heating of extracellular products abolished completely their toxicity, but freezing and PMSF treatment did not. Concentration of extracellular products using 12KD molecular weight cut-off dialysis membranes, influenced negatively the toxicity of extracellular products prepared in certain formulations
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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