1,721,019 research outputs found
METABOLIC AND SYMBIOTIC INTERACTIONS IN AMINO ACID POOLS OF THE PEA APHID ACYRTHOSIPHON PISUM, PARASITIZED BY THE BRACONID APHIDIUS ERVI
No full textMetabolic and symbiotic interactions in the pea aphid Acyrthosiphon pisum parasitised by the braconid Aphidius ervi.
No full textAphidius ervi Haliday (Hymenoptera, Braconidae) is an endophagous parasitoid of the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera, Aphididae). This parasitoid strongly redirects host reproduction and metabolism to favour nutrition and development of its juvenile stages. Parasite-regulated biosynthesis and mobilization of nitrogen metabolites determine a significant increase of host nutritional suitability. The aim of the present study was mainly to investigate the temporal changes of A. pisum amino acid pools, as affected by A. ervi parasitism, and to assess the role of the aphid bacterial endosymbiont Buchnera in determining the observed changes. In parasitized aphids, we observed a very significant increase in total free amino acids, compared with synchronous non-parasitized controls, starting from day 4 after parasitization (+51%). This trend culminated with more than doubling the control value (+152%) on day 6 after parasitization. However, a significant “parasitism” effect was observed only for 10 of the 28 amino acids detected. Tyrosine accumulation was the most prominent parasitoid-induced alteration, with a fourfold increase over control levels registered on day 6. In parasitized hosts, the amino acid biosynthetic capacity of Buchnera was unaltered, or even enhanced for the phenolic pool, and contributed greatly to the definition and maintainance of host free amino acid pools. The hypertyrosinemic syndrome was not dependent on food supply of the aromatic nucleus but was induced by parasitism, which likely
enhanced the aromatic shuttle mediating phenylalanine transfer from bacteria to the host tissues, where tyrosine conversion occurs.
This process is likely associated with a selective disruption of the host’s functions requiring tyrosine, leading to the remarkable
accumulation of this amino acid. The possible mechanisms determining these parasitism-induced host alterations, and their nutritional significance for the developing parasitoid larva, are discussed
METABOLIC AND SYMBIOTIC INTERACTIONS IN AMINO ACID POOLS OF THE PEA APHID ACYRTHOSIPHON PISUM, PARASITIZED BY THE BRACONID APHIDIUS ERVI
No full textGoing 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
Interazioni fisiologiche e biochimiche nel sistema ospite-parassitoide Acyrthosiphon pisum - Aphidius ervi.
No full textBiochemical content in fatty acids and biological parameters of Harmonia axyridis reared on artificial diet
No full textA flightless strain of Harmonia axyridis (Pallas) (Coleoptera Coccinellidae) was fed, at the larval and/or adult stage, on a liverbased
artificial diet supplemented with lin-seed oil, which is rich in α-linolenic acid (C18:3n-3), an essential lipid for the fecundity
of different insect species, and other unsaturated fatty acids. Biochemical analyses revealed that, compared to Ephestia kuehniella
Zeller eggs (the control food for H. axyridis), the diet content of C18:3n-3 was higher (P < 0.05), whereas the content of linoleic
acid (C18:2n-6) was not significantly different (P > 0.05). The composition in fatty acids of H. axyridis newly-emerged females,
which were fed on the artificial diet during the larval stages, reflected the composition of the diet. In particular, these females
showed a higher concentration of α-linolenic acid compared to control females. Moreover, no difference was found for total fatty
acids between the control newly emerged females and those reared as larvae on the artificial diet. On this diet, fecund H. axyridis
adults were obtained, but the emergence rates and a number of quality parameters (including the development times, the weights
of the newly-emerged adults, the female fecundity and fertility) of the diet-fed H. axyridis were worse compared to the coccinellids
fed on E. kuehniella eggs. The diet may however be utilized for adult maintenance, in order to reduce production costs, or in
case of shortage of aphids or E. kuehniella eggs
METABOLIC AND SYMBIOTIC INTERACTIONS IN AMINO ACID POOLS OF THE PEA APHID ACYRTHOSIPHON PISUM, PARASITIZED BY THE BRACONID APHIDIUS ERVI
No full textVariations 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
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