1000 resultados para Structure peptidique secondaire
Resumo:
To evaluate whether environmental heterogeneity contributes to the genetic heterogeneity in Anopheles triannulatus, larval habitat characteristics across the Brazilian states of Roraima and Pará and genetic sequences were examined. A comparison with Anopheles goeldii was utilised to determine whether high genetic diversity was unique to An. triannulatus. Student t test and analysis of variance found no differences in habitat characteristics between the species. Analysis of population structure of An. triannulatus and An. goeldii revealed distinct demographic histories in a largely overlapping geographic range. Cytochrome oxidase I sequence parsimony networks found geographic clustering for both species; however nuclear marker networks depicted An. triannulatus with a more complex history of fragmentation, secondary contact and recent divergence. Evidence of Pleistocene expansions suggests both species are more likely to be genetically structured by geographic and ecological barriers than demography. We hypothesise that niche partitioning is a driving force for diversity, particularly in An. triannulatus.
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Species range shifts in response to climate and land use change are commonly forecasted with species distribution models based on species occurrence or abundance data. Although appealing, these models ignore the genetic structure of species, and the fact that different populations might respond in different ways because of adaptation to their environment. Here, we introduced ancestry distribution models, that is, statistical models of the spatial distribution of ancestry proportions, for forecasting intra-specific changes based on genetic admixture instead of species occurrence data. Using multi-locus genotypes and extensive geographic coverage of distribution data across the European Alps, we applied this approach to 20 alpine plant species considering a global increase in temperature from 0.25 to 4 °C. We forecasted the magnitudes of displacement of contact zones between plant populations potentially adapted to warmer environments and other populations. While a global trend of movement in a north-east direction was predicted, the magnitude of displacement was species-specific. For a temperature increase of 2 °C, contact zones were predicted to move by 92 km on average (minimum of 5 km, maximum of 212 km) and by 188 km for an increase of 4 °C (minimum of 11 km, maximum of 393 km). Intra-specific turnover-measuring the extent of change in global population genetic structure-was generally found to be moderate for 2 °C of temperature warming. For 4 °C of warming, however, the models indicated substantial intra-specific turnover for ten species. These results illustrate that, in spite of unavoidable simplifications, ancestry distribution models open new perspectives to forecast population genetic changes within species and complement more traditional distribution-based approaches.
Resumo:
Trois constats majeurs sont à l'origine de notre étude. Premièrement, les processus d'acquisition mobilisés par l'enseignement bilingue ont fait l'objet de très peu de recherches, alors que les résultats issus de ce type d'enseignement ont été largement explorés et ont globalement reçu une évaluation positive. Deuxièmement, l'apprentissage de la langue seconde (L2) et le bénéfice qu'il peut tirer d'un enseignement bilingue reste l'objet privilégié pour la plupart des études, alors que les particularités et les enjeux de l'apprentissage des disciplines dites "non linguistiques" (DNL) (telles l'histoire, la physique ou les mathématiques) restent largement inexplorées. Troisièmement, l'intégration a été souvent étudiée au niveau du curriculum scolaire pour dégager les interrelations entre enseignement de la L2 et enseignement des DNL, mais l'intégration demandait encore à être décrit de manière détaillée en tant qu'incorporation de l'apprentissage des savoirs disciplinaires et linguistiques et en tant que travail intégré des savoirs linguistiques et disciplinaires.Notre analyse s'inscrit alors dans une triple perspective prenant en compte ces trois axes de recherche : une perspective interactionniste et située de l'apprentissage des langues permettant d'envisager les processus d'acquisition mobilisés par l'enseignement bilingue in situ ; une perspective bi-plurilingue qui invite à étudier les spécificités de l'enseignement bilingue et s'affilie à une didactique du plurilinguisme valorisant un travail bilingue et intégré en classe ; une perspective des DNL permettant de considérer les enjeux de l'enseignement bilingue pour l'apprentissage des DNL, et non seulement pour l'apprentissage de la L2, et de considérer le travail intégré des savoirs linguistiques et disciplinaires.Ainsi, notre étude vise la description des pratiques effectives en classe bilingue s'appuyant sur l'analyse d'un important corpus d'interactions enregistrées dans diverses classes du secondaire II, orientée vers une méthodologie à caractère ethnographique et basée sur une démarche empirique et descriptive, ainsi que sur les outils de l'analyse conversationnelle appliquée à l'apprentissage des L2.Dans ce contexte, notre travail repose sur l'hypothèse que l'enseignement bilingue profite non seulement à l'apprentissage des savoirs linguistiques, mais également à celui des savoirs disciplinaires, lorsqu'il se base sur un travail intégré de la dimension linguistique et disciplinaire de cet apprentissage, et qu'un travail dans les deux langues en présence contribue à une intégration forte des savoirs linguistiques et disciplinaires. Il vise alors l'examen de l'articulation entre travail disciplinaire et travail linguistique dans différentes DNL et activités, ainsi que l'élaboration bilingue des concepts disciplinaires.D'abord, nos analyses montrent deux manières d'aborder l'élaboration des concepts disciplinaires dans les classes bilingues observées, le mode unilingue et le mode bilingue, et mettent en lumière l'apport du mode bilingue ou travail bilingue à l'élaboration des savoirs disciplinaires. Puis, la description détaillée de séquences-types permet de dégager les fonctionnements spécifiques à un enseignement bilingue et intégré, ainsi que les degrés et les procédés d'intégration des savoirs linguistiques et disciplinaires dans l'apprentissage en classe bilingue.En résumé, nos observations montrent que le bénéfice de l'enseignement bilingue réside dans l'attention particulière portée aux enjeux linguistiques des DNL et dans le travail linguistique, lorsqu'il est orienté vers un but disciplinaire. Aussi, cette orientation s'affirme dans la dynamique entre travail sur la dimension disciplinaire et travail sur la dimension linguistique.
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Malaria is responsible for more deaths around the world than any other parasitic disease. Due to the emergence of strains that are resistant to the current chemotherapeutic antimalarial arsenal, the search for new antimalarial drugs remains urgent though hampered by a lack of knowledge regarding the molecular mechanisms of artemisinin resistance. Semisynthetic compounds derived from diterpenes from the medicinal plant Wedelia paludosawere tested in silico against the Plasmodium falciparumCa2+-ATPase, PfATP6. This protein was constructed by comparative modelling using the three-dimensional structure of a homologous protein, 1IWO, as a scaffold. Compound 21 showed the best docking scores, indicating a better interaction with PfATP6 than that of thapsigargin, the natural inhibitor. Inhibition of PfATP6 by diterpene compounds could promote a change in calcium homeostasis, leading to parasite death. These data suggest PfATP6 as a potential target for the antimalarial ent-kaurane diterpenes.
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House re-invasion by native triatomines after insecticide-based control campaigns represents a major threat for Chagas disease vector control. We conducted a longitudinal intervention study in a rural section (Area III, 407 houses) of Pampa del Indio, northeastern Argentina, and used wing geometric morphometry to compare pre-spray and post-spray (re-infestant bugs) Triatoma infestanspopulations. The community-wide spraying with pyrethroids reduced the prevalence of house infestation by T. infestans from 31.9% to < 1% during a four-year follow-up, unlike our previous studies in the neighbouring Area I. Two groups of bug collection sites differing in wing shape variables before interventions (including 221 adults from 11 domiciles) were used as a reference for assigning 44 post-spray adults. Wing shape variables from post-spray, high-density bug colonies and pre-spray groups were significantly different, suggesting that re-infestant insects had an external origin. Insects from one house differed strongly in wing shape variables from all other specimens. A further comparison between insects from both areas supported the existence of independent re-infestation processes within the same district. These results point to local heterogeneities in house re-infestation dynamics and emphasise the need to expand the geographic coverage of vector surveillance and control operations to the affected region.
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Genetic differentiation is a consequence of the combination of drift and restriction in gene flow between populations due to barriers to dispersal, or selection against individuals resulting from inter-population matings In phytophagous insects, local adaptation to different kinds of host plants can sometimes lead to reproductive isolation and thus to genetic structuring, or even to speciation Acanthoscelides. obtectus Say is a bean bruchid specialized on beans of the Phaseolus vulgaris group, attacking both wild and domesticated forms of P vulgaris., and P coccineus This study reveals that the genetic structure of populations of this bruchid is explained mainly by their geographical location and is not related to a particular kind (wild or domesticated) of bean In contrast, the species of bean might have led, to some extent, to genetic structuring in these bruchids, although our sampling is too limited to address such process unambiguously. If confirmed, it would corroborate preliminary results found for the parasitoid species that attack Acanthoscelides species, which might show a genetic structure depending on the species of host plant
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This paper identifies the key sectors in greenhouse gas emissions of the Uruguayan economy through input-output analysis. This allows to precisely determine the role played by the different productive sectors and their relationship with other sectors in the relation between the Uruguayan productive structure and atmospheric pollution. In order to guide policy design for GHG reduction, we decompose sectors liability between the pollution generated through their own production processes and the pollution indirectly generated in the production processes of other sectors. The results show that all the key polluting sectors for the different contaminants considered are relevant because of their own emissions, except for the sector Motor vehicles and oil retail trade, which is relevant in CO2 emissions because of its pure, both backward and forward, linkages. Finally, the best policy channels for controlling and reducing GHGs emissions are identified, and compared with the National Climate Change Response Plan (NCCRP) lines of action.
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One of the criticisms leveled at the model of dispersed city found all over the world is its unarticulated, random, and undifferentiated nature. To check this idea in the Barcelona Metropolitan Region, we estimated the impact of the urban spatial structure (CBD, subcenters and transportation infrastructures) over the population density and commuting distance. The results are unfavorable to the hypothesis of the increasing destructuring of cities given that the explanatory capacity of both functions improves over time, both when other control variables are not included and when they are included.
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In populations of various ant species, many queens reproduce in the same nest (polygyny), and colony boundaries appear to be absent with individuals able to move fi eely between nests (unicoloniality). Such societies depart strongly from a simple family structure and pose a potential challenge to kin selection theory, because high queen number coupled with unrestricted gene flow among nests should result in levels of relatedness among nestmates close to zero. This study investigated the breeding system and genetic structure of a highly polygynous and largely unicolonial population of the wood ant Formica paralugubris. A microsatellite analysis revealed that nestmate workers, reproductive queens and reproductive males (the queens' mates) are all equally related to each other, with relatedness estimates centring around 0.14. This suggests that most of the queens and males reproducing in the study population had mated within or close to their natal nest, and that the queens did not disperse far after mating. We developed a theoretical model to investigate how the breeding system affects the relatedness structure of polygynous colonies. By combining the model and our empirical data, it was estimated that about 99.8% of the reproducing queens and males originated from within the nest, or from a nearby nest. This high rate of local mating and the rarity of long-distance dispersal maintain significant relatedness among nestmates, and contrast with the common view that unicoloniality is coupled with unrestricted gene flow among nests.
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Salivary gland polytene chromosomes of 4th instar Anopheles darlingi Root were examined from multiple locations in the Brazilian Amazon. Minor modifications were made to existing polytene photomaps. These included changes to the breakpoint positions of several previously described paracentric inversions and descriptions of four new paracentric inversions, two on the right arm of chromosome 3 and two on the left arm of chromosome 3 that were found in multiple locations. A total of 18 inversions on the X (n = 1) chromosome, chromosome 2 (n = 7) and 3 (n = 11) were scored for 83 individuals from Manaus, Macapá and Porto Velho municipalities. The frequency of 2Ra inversion karyotypes in Manaus shows significant deficiency of heterozygotes (p < 0.0009). No significant linkage disequilibrium was found between inversions on chromosome 2 and 3. We hypothesize that at least two sympatric subpopulations exist within the An. darlingi population at Manaus based on inversion frequencies.
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Host-cell factor 1 (HCF-1) is an unusual transcriptional regulator that undergoes a process of proteolytic maturation to generate N- (HCF-1(N)) and C- (HCF-1(C)) terminal subunits noncovalently associated via self-association sequence elements. Here, we present the crystal structure of the self-association sequence 1 (SAS1) including the adjacent C-terminal HCF-1 nuclear localization signal (NLS). SAS1 elements from each of the HCF-1(N) and HCF-1(C) subunits form an interdigitated fibronectin type 3 (Fn3) tandem repeat structure. We show that the C-terminal NLS recruited by the interdigitated SAS1 structure is required for effective formation of a transcriptional regulatory complex: the herpes simplex virus VP16-induced complex. Thus, HCF-1(N)-HCF-1(C) association via an integrated Fn3 structure permits an NLS to facilitate formation of a transcriptional regulatory complex.
Resumo:
Geography as a school subject is specifically thought for and by the schools. The contents of the school subject, nowadays, do not reflect the concerns and the evolution of the discipline as such. Nevertheless, official curricula set school objectives that address issues affecting the world and people's lives. These issues are coherent with the ones addressed by geography as a social science, that is to say the study of how people and their environment interact and how societies are interconnected through space. On an every day basis, Geography as a school subject is most of the time reduced to accumulating knowledge outside any given context. This knowledge may even be partially untrue or old and the related activities focus on low cognitive tensions. These practices do not contribute to the learners' understanding of the world because it does not allow them to build a geographical competence, which they. will need as future citizens in order to make responsible choices when they are confronted to questions related to how the locations of human and physical features are influenced by each other and how they interact across space. The central part of the text relies on the ideas and the processes discussed in the publications, which constitute the published file; it is divided into two parts. The first part (chapter 4) presents a didactic approach, which gives meaningful insights into Geography as a school subject and shows a brief account of the theoretical background that supports it. This socio-constructivist approach relies on the main following features: a priming stage (élément déclencheur), which presents geographical knowledge as an issue to be explored, discussed or solved; the issue is given to learners;. the planning of the teaching-learning sequence in small units launched by the main issue in the priming stage ; the interconnections of geographical knowledge with integrative concepts ; the synthetic stage or reporting stage where final concepts and knowledge are put together in order to be learned. Such an approach allows learners to re-invest the knowledge they have built themselves. This knowledge is organised by geographical integrative concepts, which represent true thinking operative tools and with which key issues in the geographical thinking are associated. The second part of the text (chapter 5) displays the didactic principles that governed the conception of the new initial training course for the future upper secondary school teachers at the HEP Vaud. The ambition of this course is to prepare future teachers to plan and realize the teaching of geography that provides pupils with the tools to understand better how people and their environment interact and how societies are interconnected through space. One of the tools for the teachers is the conceptual framework, whose most salient interest is to be relevant at every stage of the preparation and planning of the teaching, including the necessary epistemological reflection that should always be present. The synthesis of the text starts with a short account of the first evaluation of the new course. Various reflections on the future concerns and issues, that the didactics and methodology of Geography will be confronted with, constitute the synthesis.
Resumo:
Members of the human APOBEC3 family of editing enzymes can inhibit various mobile genetic elements. APOBEC3A (A3A) can block the retrotransposon LINE-1 and the parvovirus adeno-associated virus type 2 (AAV-2) but does not inhibit retroviruses. In contrast, APOBEC3G (A3G) can block retroviruses but has only limited effects on AAV-2 or LINE-1. What dictates this differential target specificity remains largely undefined. Here, we modeled the structure of A3A based on its homology with the C-terminal domain of A3G and further compared the sequence of human A3A to those of 11 nonhuman primate orthologues. We then used these data to perform a mutational analysis of A3A, examining its ability to restrict LINE-1, AAV-2, and foreign plasmid DNA and to edit a single-stranded DNA substrate. The results revealed an essential functional role for the predicted single-stranded DNA-docking groove located around the A3A catalytic site. Within this region, amino acid differences between A3A and A3G are predicted to affect the shape of the polynucleotide-binding groove. Correspondingly, transferring some of these A3A residues to A3G endows the latter protein with the ability to block LINE-1 and AAV-2. These results suggest that the target specificity of APOBEC3 family members is partly defined by structural features influencing their interaction with polynucleotide substrates.