1,721,027 research outputs found
Latent inhibition in an insect: the role of aminergic signaling
Get PDFLatent inhibition (LI) is a decrement in learning performance that results from the nonreinforced pre-exposure of the to-beconditioned stimulus, in both vertebrates and invertebrates. In vertebrates, LI development involves dopamine and serotonin; in invertebrates there is yet no information. We studied differential olfactory conditioning of the proboscis extension response in the honeybee Apis mellifera, and we compared LI in individuals treated with antagonists of biogenic amines (dopamine, octopamine, and serotonin). An antagonist of octopamine receptors and two antagonists of serotonin receptors showed LI disruption. We thus provide evidence that serotonin would participate in the regulation of LI in honeybees.Fil: Fernandez, Vanesa Maribel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Giurfa, Martín. Université de Toulouse; Francia. Centre National de la Recherche Scientifique; FranciaFil: Devaud, Jean Marc. Université de Toulouse; Francia. Centre National de la Recherche Scientifique; FranciaFil: Farina, Walter Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentin
Influence of social and environmental context on bumblebee nutrition
No full textDepuis plusieurs décennies maintenant, la géométrie nutritionnelle a permis d’observer comment divers animaux équilibrent leur apport en plusieurs nutriments de manière simultanée afin de maximiser leurs performances générales. Cependant, chez les espèces sociales, tel que les fourmis ou les abeilles, la régulation nutritionnelle est assurée par une minorité d’individus qui choisissent leur nourriture en fonction non seulement de leurs propres besoins, mais aussi de ceux des autres membres de la colonie. Les besoins des autres membres peuvent varier selon l’âge, le sexe, la caste ou encore les conditions environnementales. Durant cette thèse, via l’approche de géométrie nutritionnelle, j’ai étudié comment les bourdons, Bombus terrestris, régulent leur prise de nutriments en fonction du contexte social et écologique. Pour cela j’ai mis au point des expériences dites de cafétéria, dans lesquelles des bourdons isolés ou en micro-colonies pouvaient réguler leurs régimes alimentaires à partir de plusieurs diètes artificielles, variées en concentrations de sucres, protéines et lipides. Dans le premier chapitre, j’ai mesuré la réponse des bourdons à chacun de ces macronutriments et ainsi confirmé qu’ils sont plus motivés aux sucres plutôt qu’aux lipides ou protéines. Ensuite j’ai laissé le temps à des bourdons isolés, de divers âges et castes, de composer leur régime alimentaire à partir de plusieurs diètes artificielles. Leur régulation nutritionnelle n’était ni âge ni taille dépendante. Les reines et les ouvrières convergeaient vers divers régimes, respectivement plus dirigés vers les protéines ou vers les sucres. Les butineuses, étudiées dans une troisième expérience faite en extérieur dans un tunnel de vol, démontrèrent une collecte nutritionnelle généraliste en visitant de manière non-aléatoire divers fleurs artificielle afin de composer un régime alimentaire précis. Dans le deuxième chapitre, j’ai étudié l’influence du couvain sur le comportement de collecte alimentaire des ouvrières. Quand contraintes à un régime alimentaire fixe, les micro-colonies sans couvain ne régulèrent plus les protéines, conduisant à la sur-collecte de ces dernières. Ainsi le couvain aide à la régulation nutritionnelle des ouvrières, ou bien ces dernières s’adaptent à leur présence. Dans le troisième chapitre, j’ai examiné l’effet de pressions environnementales sur le comportement et les performances des bourdons en observant leurs choix nutritionnels à plusieurs températures. À température optimale (30°C), les bourdons composèrent un régime alimentaire favorisant leurs fonctions reproductrices ; alors qu’à basse température ils cherchèrent du sucre pour améliorer leur survie ; et à haute température, il se concentrèrent sur la prise en eau et/ou lipides. Dans le contexte du fort déclin mondial des populations d'insectes, une meilleure compréhension du comportement nutritionnel des pollinisateurs est cruciale. Mieux comprendre le comportement des bourdons, commercialisés pour la pollinisation, permettrait d'améliorer leur activité de butinages et ainsi d’amoindrir la crise actuelle de pollinisation des plantes agricoles. )For a few decades, the development of nutritional geometry has brought new insights into how individual animals eat and balance their acquisition of multiple nutrients simultaneously to maximize overall fitness. Yet, in social species, such as ants and bees, diet balancing is ensured by a minority of individuals that need to choose foods in order to meet their own needs as well as those of all other colony members whose needs may differ according to age, sex, caste, and the environmental conditions. In this thesis, I used nutritional ecology to study how bumblebees Bombus terrestris balance their nutrient collection across social and ecological contexts. To do so I designed cafeteria experiments in which individual bees or micro-colonies could balance their diet from artificial diets varying in their composition of carbohydrates, proteins and lipids. In the first chapter, I measured the response of individual bumblebees to each of the three nutrients in food and confirmed they respond more to carbohydrates than to lipids or proteins. Then, we let individuals’ bees of various ages and castes time to self-compose their nutritional balance between varying diets that differ in their macronutrient’s concentration. Nutrient regulation was no age- nor body size-dependant. Queen and workers non-randomly converged to different nutritional diets, essentially toward proteins or carbohydrates, respectively. Foragers in a third similar experiment, but outside in a flight tunnel, demonstrated a generalist collect by non-randomly visiting several artificial flowers to compose a specific nutritional diet. In the second chapter, I studied the influence of brood on food collection by the workers. When constrained to single diets, micro-colonies without brood did not regulate proteins, resulting in their over-collection. In the third chapter I examined the effect of environmental pressures on behaviour and fitness, by observing nutritional choices of bumblebees at various temperatures. At optimal temperature (30°C), bees self-composed a diet to maximize their reproductive ability; while at low temperature, they searched for carbohydrates to prioritize survival; and at high temperature, they searched for water and/or lipid in diets. Bumblebees as pollinators have a noteworthy economic value since their domestication, and with the current widespread declines of wild bees, manipulating the nutritional behaviour of domesticated species could selectively increase foraging activity and mitigate the ongoing pollination crisis.
Genetically Expressed Cameleon in Drosophila melanogaster Is Used to Visualize Olfactory Information in Projection Neurons
No full textAbstractComplex external stimuli such as odorants are believed to be internally represented in the brain by spatiotemporal activity patterns of extensive neuronal ensembles. These activity patterns can be recorded by optical imaging techniques. However, optical imaging with conventional fluorescence dyes usually does not allow for resolving the activity of biologically defined groups of neurons. Therefore, specifically targeting reporter molecules to neuron populations of common genetic identity is an important goal. We report the use of the genetically encoded calcium-sensitive fluorescence protein cameleon 2.1 [1] in the Drosophila brain. We visualized odorant-evoked intracellular calcium concentration changes in selectively labeled olfactory projection neurons both postsynaptically in the antennal lobe, the primary olfactory neuropil, and presynaptically in the mushroom body calyx, a structure involved in olfactory learning and memory. As a technical achievement, we show that calcium imaging with a genetically encoded fluorescence probe is feasible in a brain in vivo. This will allow one to combine Drosophila's advanced genetic tools with the physiological analysis of brain function. Moreover, we report for the first time optical imaging recordings in synaptic regions of the Drosophila mushroom body calyx and antennal lobe. This provides an important step for the use of Drosophila as a model system in olfaction
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
- …
