1,720,966 research outputs found
Tyraminergic signaling in phytophagous insects: from physiology to pest control
No full textLe ammine biogene tiramina (TA) ed octopamina (OA) sono sostanze neurochimiche, essenziali negli invertebrati, che agiscono come sostituti dell'adrenalina e della noradrenalina. TA ed OA esercitano i loro effetti legando specifici recettori che appartengono alla superfamiglia dei recettori accoppiati a proteine G. I recettori tiramici (TAR) ed octopaminici (OAR) svolgono un ruolo importante nel modulare la biologia, la fisiologia e il comportamento degli insetti. In questa tesi di dottorato viene descritta la caratterizzazione del recettore della tiramina di tipo 1 (TAR1) in due insetti nocivi per le piante, Drosophila suzukii e Halyomorpha halys, con lo scopo di investigare il ruolo che il recettore esercita nel controllo dei tratti fisiologici e comportamentali oltre che testare TAR1 come possibile bersaglio per biopesticidi. Il TAR1 di D. suzukii si è rivelato un interessante bersaglio per biopesticidi, nello specifico i monoterpeni. Questi composti sono stati in grado di modulare quegli aspetti fisiologici e comportamentali di D. suzukii direttamente controllati da TAR1. In H. halys, la downregolazione di TAR1 attraverso RNAi ha evidenziato un possibile coinvolgimento del recettore nella percezione dei feromoni. Insieme, i dati presentati mostrano come TAR1 sia cruciale nel controllo di numerosi aspetti fisiologici e comportamentali degli insetti. Inoltre, questo recettore sembra essere un bersaglio per approcci innovativi e rispettosi dell'ambiente nel controllo dei parassiti.The biogenic amines tyramine (TA) and octopamine (OA) are neurochemicals essential in invertebrates that act as adrenaline and noradrenaline substitutes. They exert their effects by binding specific receptor proteins that belong to the superfamily of G-protein coupled receptors. Tyramine (TAR) and octopamine (OAR) receptors play important roles in modulating the biology, physiology and behavior of insect. This PhD thesis describes the characterization of the type 1 tyramine receptor (TAR1) in two insect pests, Drosophila suzukii and Halyomorpha halys, to dissect the receptor role in controlling physiological and behavioral traits as well as to examine TAR1 as possible target for biopesticides. D. suzukii TAR1 proved to be an interesting target for biopesticides, such as monoterpenes. These compounds were in fact able to modulate directly TAR1-controlled physiology and behavior. In H. halys, RNAi-mediated TAR1 downregulation suggested that the receptor involvement in pheromone perception. Together, the data described emphasize TAR1 as crucial in controlling and defining physiological and behavioral aspects in insects. Furthermore, this receptor appears an interesting target for innovative and environmental friendly in pest control
Monoterpenes-induced toxicity in nymphal stages of Halyomorpha halys
No full textIn this work, the toxic activity by fumigation of 10 monoterpenes was evaluated on Halyomorpha halys 2nd instar nymphs.
The results showed that (±)-limonene was the monoterpene with the highest insecticidal activity (LC50 0.48 μl l−1 air), followed by two phenolic monoterpenes eugenol and isoeugenol (LC50 0.41 and 0.55 μl l−1 air, respectively). In addition, the alcoholic monoterpenes α-terpineol and l -(−)-menthol and the ketonic monoterpene (+)-pulegone exhibited strong efficacy on H. halys 2nd instar nymphs (LC50 values 0.84, 1.15 and 0.48 μl l−1 air, respectively). These preliminary data indicate that essential oils and the individual terpenic components could be used as fumigants for the control of H. halys nymphs
Topical delivery of dsRNA in two hemipteran species: Evaluation of RNAi specificity and non-target effects
No full textDouble-stranded (ds) RNA-based technologies could provide novel and potential tool for pest management with efficiency and specificity of action. However, before applying this technique in the field, it is necessary to identify effective delivery methods and evaluate the non-target effects that may occur. In this article, we evaluated the effectiveness of dsRNA by topical delivery on a species of great agricultural interest, Halyomorpha halys. The specificity of action of the dsRNA was also investigated in Rhodnius prolixus, an insect phylogenetically close to H. halys. Of the three investigated genes (putative ATPase N2B, ATPase, serine/threonine-protein phosphatase PP1-β catalytic subunit, PP1, and IAP repeat-containing protein 7-B-like, IAP), IAP and ATPase were able to induce higher mortality in H. halys nymphs compared to the control, with specific concentrations for each gene targeted. However, when the same RNAs were topically delivered to both R. prolixus 2nd and 3rd instar nymphs, no gene silencing and mortality were observed. For this reason, to assess dsRNA application-mediated non-target effects, we injected both H. halys and R. prolixus specific dsRNA in R. prolixus 5th instar nymphs. When the dsRNA targeting H. halys IAP was microinjected into R. prolixus 5th instar nymphs, no mortality was observed, suggesting a strong RNAi specificity. Together, these data suggest that the topical delivery could be suitable for the dsRNA to control H. halys population. Furthermore, its specificity of action would allow treatments towards single harmful species with limited non-target effects
The Insect Type 1 Tyramine Receptors: From Structure to Behavior
Full text linkTyramine is a neuroactive compound that acts as neurotransmitter, neuromodulator, and neurohormone in insects. Three G protein-coupled receptors, TAR1-3, are responsible for mediating the intracellular pathway in the complex tyraminergic network. TAR1, the prominent player in this system, was initially classified as an octopamine receptor which can also be activated by tyramine, while it later appeared to be a true tyramine receptor. Even though TAR1 is currently considered as a well-defined tyramine receptor and several insect TAR1s have been characterized, a defined nomenclature is still inconsistent. In the last years, our knowledge on the structural, biochemical, and functional properties of TAR1 has substantially increased. This review summarizes the available information on TAR1 from different insect species in terms of basic structure, its regulation and signal transduction mechanisms, and its distribution and functions in the brain and the periphery. A special focus is given to the TAR1-mediated intracellular signaling pathways as well as to their physiological role in regulating behavioral traits. Therefore, this work aims to correlate, for the first time, the physiological relevance of TAR1 functions with the tyraminergic system in insects. In addition, pharmacological studies have shed light on compounds with insecticidal properties having TAR1 as a target and on the emerging trend in the development of novel strategies for pest control
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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