1,720,966 research outputs found
Investigation of factors involved in the interaction between Quahog Parasite Unknown (QPX) and its host, the hard clam Mercenaria mercenaria
Get PDFQPX (Quahog parasite unknown) is a protistan parasite affecting the hard clam Mercenaria mercenaria along the Northeastern coast of the United States. The geographic distribution and occurrence of disease epizootics suggests the involvement of environmental parameters and host genotype in disease development. Field investigations and laboratory transmission studies revealed some variations in the susceptibility of different hard clam stocks to QPX infection. Histological observations demonstrated that clams mount marked inflammatory responses against the infection that can sometimes lead to the healing of infected individuals. This study investigated host-pathogen interactions in QPX disease by studying individual components of the tripartite interaction: The pathogen, the host and the environment. Methods were developed to investigate virulence factors of the parasite QPX. Constitutive defense factors and immune response to QPX challenge in hard clams exhibiting different susceptibility to the parasite were also assessed using cellular, biochemical and molecular approaches. Finally, integrative approaches were used to determine the effect of environmental parameters (temperature, salinity, dissolved oxygen) on constitutive and QPX-induced clam defenses as well as on QPX itself. Results demonstrated that QPX produces virulence factors that are cytotoxic to M. mercenaria hemocytes. QPX cytotoxicity appears to be induced by clam factors and QPX extracellular products modulated host response against the parasite. In vitro growth of QPX was significantly reduced at temperatures above and below optimal levels ranging from 20 øC to 23 øC. QPX appeared to tolerate a wide range of salinities (22 to 37 psu) and parasite growth was only significantly affected at very low salinity (15 psu). Different QPX isolates displayed various levels of cytotoxicity against clam hemocytes and had different temperature optima supporting previous studies suggesting the existence of different QPX strains. This study also demonstrated the presence of constitutive compounds in clam tissues that significantly inhibited (mantle, gills) or stimulated (adductor muscle) QPX growth in vitro. Difference in anti-QPX activity was also observed in plasma from different clam populations and was associated to their respective susceptibility to QPX. Molecular investigations of clam response to QPX led to the identification of several stress- and defense-related genes such as ferritin, metallothionein, defensins, lectins and a thioester-containing protein (or TEP). Components of signaling pathways (such as NF-kB) were also characterized and their transcriptional regulation was correlated to the abundance of some humoral transcripts. Further investigation of the modulation of hemolymph parameters and transcriptional regulation of ferritin and metallothionein during bacterial and QPX challenge indicated difference in clam response according to the challenge. Similarly, comparison of host response among QPX-resistant and. susceptible clam broodstocks exhibited significant difference. Effective response of resistant clams against QPX led to the elimination of the parasite and the restoration of constitutive defense status whereas susceptible clams exhibited a strong modulation characterized by an acute phase response but appeared less effective to eliminate QPX after 28 days. Finally, results demonstrated significant effect of temperature and salinity on clam constitutive defenses and also on host. pathogen interaction and QPX disease dynamics. For instance, low temperature (13 øC) impeded clam defenses causing QPX disease development whereas changes in hemolymph parameters among QPX-infected clams maintained at 21 øC were related to significant healing processes. Higher QPX-associated mortality was also observed in infected clams maintained at high salinity (30 psu) compared to 15 psu. Overall, this study provided essential insights on QPX virulence, M. mercenaria defenses and effects of environmental parameters on host. pathogen interactions and provided perspectives for the remediation of QPX disease. The results not only improved our knowledge of cellular and molecular pathways involved during QPX disease, but also generated important information on M. mercenaria defenses, and enhanced our understanding of invertebrate immunity in general. Generated molecular information significantly enhanced public databases and allowed the development of new tools for the investigation of M. mercenaria transcriptome
Investigation of factors involved in the interaction between Quahog Parasite Unknown (QPX) and its host, the hard clam Mercenaria mercenaria
No full textQPX (Quahog parasite unknown) is a protistan parasite affecting the hard clam Mercenaria mercenaria along the Northeastern coast of the United States. The geographic distribution and occurrence of disease epizootics suggests the involvement of environmental parameters and host genotype in disease development. Field investigations and laboratory transmission studies revealed some variations in the susceptibility of different hard clam stocks to QPX infection. Histological observations demonstrated that clams mount marked inflammatory responses against the infection that can sometimes lead to the healing of infected individuals. This study investigated host-pathogen interactions in QPX disease by studying individual components of the tripartite interaction: The pathogen, the host and the environment. Methods were developed to investigate virulence factors of the parasite QPX. Constitutive defense factors and immune response to QPX challenge in hard clams exhibiting different susceptibility to the parasite were also assessed using cellular, biochemical and molecular approaches. Finally, integrative approaches were used to determine the effect of environmental parameters (temperature, salinity, dissolved oxygen) on constitutive and QPX-induced clam defenses as well as on QPX itself. Results demonstrated that QPX produces virulence factors that are cytotoxic to M. mercenaria hemocytes. QPX cytotoxicity appears to be induced by clam factors and QPX extracellular products modulated host response against the parasite. In vitro growth of QPX was significantly reduced at temperatures above and below optimal levels ranging from 20 øC to 23 øC. QPX appeared to tolerate a wide range of salinities (22 to 37 psu) and parasite growth was only significantly affected at very low salinity (15 psu). Different QPX isolates displayed various levels of cytotoxicity against clam hemocytes and had different temperature optima supporting previous studies suggesting the existence of different QPX strains. This study also demonstrated the presence of constitutive compounds in clam tissues that significantly inhibited (mantle, gills) or stimulated (adductor muscle) QPX growth in vitro. Difference in anti-QPX activity was also observed in plasma from different clam populations and was associated to their respective susceptibility to QPX. Molecular investigations of clam response to QPX led to the identification of several stress- and defense-related genes such as ferritin, metallothionein, defensins, lectins and a thioester-containing protein (or TEP). Components of signaling pathways (such as NF-kB) were also characterized and their transcriptional regulation was correlated to the abundance of some humoral transcripts. Further investigation of the modulation of hemolymph parameters and transcriptional regulation of ferritin and metallothionein during bacterial and QPX challenge indicated difference in clam response according to the challenge. Similarly, comparison of host response among QPX-resistant and. susceptible clam broodstocks exhibited significant difference. Effective response of resistant clams against QPX led to the elimination of the parasite and the restoration of constitutive defense status whereas susceptible clams exhibited a strong modulation characterized by an acute phase response but appeared less effective to eliminate QPX after 28 days. Finally, results demonstrated significant effect of temperature and salinity on clam constitutive defenses and also on host. pathogen interaction and QPX disease dynamics. For instance, low temperature (13 øC) impeded clam defenses causing QPX disease development whereas changes in hemolymph parameters among QPX-infected clams maintained at 21 øC were related to significant healing processes. Higher QPX-associated mortality was also observed in infected clams maintained at high salinity (30 psu) compared to 15 psu. Overall, this study provided essential insights on QPX virulence, M. mercenaria defenses and effects of environmental parameters on host. pathogen interactions and provided perspectives for the remediation of QPX disease. The results not only improved our knowledge of cellular and molecular pathways involved during QPX disease, but also generated important information on M. mercenaria defenses, and enhanced our understanding of invertebrate immunity in general. Generated molecular information significantly enhanced public databases and allowed the development of new tools for the investigation of M. mercenaria transcriptome.Advisor(s): Bassem Allam. Committee Member(s): Anne E. McElroy; Jackie L. Collier; Mark D. Fast; Susan E. Ford; Arnaud TanguyStony Brook University Libraries. SBU Graduate School in Department of Marine and Atmospheric Science. Lawrence Martin (Dean of Graduate School)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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