Effets de l'hivernage en banques sur la survie et la qualité reproductive des reines d'abeilles mellifères (Apis mellifera L.)

L'industrie apicole occupe une place cruciale au sein de l'économie canadienne et est en expansion depuis plusieurs années. Les conditions climatiques du pays entraînent cependant des pertes importantes de colonies et limitent l'élevage de reines tôt au printemps. Les apiculteurs doivent donc importer des reines d'autres pays afin de remplacer les colonies perdues, ce qui contribue à la dissémination d'agents pathogènes et de lignées d'abeilles ayant des traits génétiques indésirables pour l'apiculture canadienne. L'acquisition de reines locales au printemps est donc souhaitable et pourrait être facilitée par l'hivernage de reines en banques. En élevant des reines à la fin de l'été et en les regroupant dans une même colonie appelée banque durant la période hivernale, les apiculteurs auraient accès à des reines locales tôt au printemps. Cette technique est récente et les connaissances à ce sujet ont besoin d'être approfondies. Dans ce contexte, les objectifs de mon projet étaient d'évaluer l'effet de deux densités de reines (40 et 80) entreposées en banques sur leur survie hivernale et d'évaluer l'influence de l'hivernage des reines en banques sur leur qualité reproductive et leur performance en colonie. Nos résultats montrent que la survie hivernale des reines est supérieure à la densité la plus basse. L'hivernage des reines en banques n'affecte pas leur fertilité, mais réduit leur taille, leur poids et leur ponte durant leurs premières semaines en colonie au printemps. Néanmoins, après leurs premières semaines en colonie, les reines hivernées en banques regagnent une taille et un poids comparables à ceux de reines hivernées libres dans leur colonie respective. Ce projet démontre le potentiel de l'entreposage des reines en banques pour conserver des reines durant la période hivernale et ainsi assurer un approvisionnement en reines locales tôt au printemps. Cette méthode favorise aussi le maintien de traits génétiques adaptés aux besoins de l'industrie apicole canadienne.The beekeeping industry is a vital part of Canadian economy and has been expanding for several years. However, winter causes significant colony losses and limits the rearing of queens in early spring. As a result, beekeepers must import queens from other countries to replace lost colonies, which contributes to the spread of pathogens and undesirable genetic traits. Developing the country's autonomy towards queen imports in early spring is therefore essential and could be facilitated by overwintering queens in a bank colony. By rearing queens at the end of summer and grouping them in a colony called a bank during the winter period, beekeepers would have access to local queens in early spring. This method is recent and the knowledge on this subject needs to be broadened. In this context, the objectives of my project were to assess the effect of two densities of queens (40 and 80) stored in a bank colony on their winter survival and to evaluate the influence of overwintering queens in a bank colony on their reproductive quality and colony performance. Our results show that queen survival rate is higher at the lowest density. Overwintering queens in a bank colony does not compromise their fertility, but reduces their size, weight and oviposition during their first weeks in a colony in spring. Nevertheless, after their first weeks in the colony, queens overwintered in bank colonies regain a size and weight comparable to that of queens overwintered free in their respective colony. This project demonstrates the potential of storing queens in a bank colony during the winter period. This method ensures a supply of local queens early in the spring and maintains genetic traits corresponding to the needs of the Canadian beekeeping industry

Transforming Growth Factor: β Signaling Is Essential for Limb Regeneration in Axolotls

Axolotls (urodele amphibians) have the unique ability, among vertebrates, to perfectly regenerate many parts of their body including limbs, tail, jaw and spinal cord following injury or amputation. The axolotl limb is the most widely used structure as an experimental model to study tissue regeneration. The process is well characterized, requiring multiple cellular and molecular mechanisms. The preparation phase represents the first part of the regeneration process which includes wound healing, cellular migration, dedifferentiation and proliferation. The redevelopment phase represents the second part when dedifferentiated cells stop proliferating and redifferentiate to give rise to all missing structures. In the axolotl, when a limb is amputated, the missing or wounded part is regenerated perfectly without scar formation between the stump and the regenerated structure. Multiple authors have recently highlighted the similarities between the early phases of mammalian wound healing and urodele limb regeneration. In mammals, one very important family of growth factors implicated in the control of almost all aspects of wound healing is the transforming growth factor-beta family (TGF-β). In the present study, the full length sequence of the axolotl TGF-β1 cDNA was isolated. The spatio-temporal expression pattern of TGF-β1 in regenerating limbs shows that this gene is up-regulated during the preparation phase of regeneration. Our results also demonstrate the presence of multiple components of the TGF-β signaling machinery in axolotl cells. By using a specific pharmacological inhibitor of TGF-β type I receptor, SB-431542, we show that TGF-β signaling is required for axolotl limb regeneration. Treatment of regenerating limbs with SB-431542 reveals that cellular proliferation during limb regeneration as well as the expression of genes directly dependent on TGF-β signaling are down-regulated. These data directly implicate TGF-β signaling in the initiation and control of the regeneration process in axolotls

Global urban environmental change drives adaptation in white clover

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale

Modulation of monosodium urate crystal-induced responses in neutrophils by the myeloid inhibitory C-type lectin-like receptor: potential therapeutic implications

INTRODUCTION: Monosodium urate crystals (MSU), the etiological agent of gout, are one of the most potent proinflammatory stimuli for neutrophils. The modulation of MSU-induced neutrophil activation by inhibitory receptors remains poorly characterized. The expression of the myeloid inhibitory C-type lectin-like receptor (MICL) in neutrophils is downregulated by several proinflammatory stimuli, suggestive of a role for this receptor in neutrophil function. We thus investigated the potential role of MICL in MSU-induced neutrophil activation. METHODS: The expression of MICL was monitored in human neutrophils by flow cytometry and Western blot analysis after stimulation with MSU. Protein tyrosine phosphorylation was also assessed by Western blot analysis and the production of IL-1 and IL-8 by enzyme-linked immunosorbent assay. Changes in the concentration of cytoplasmic free calcium were monitored with the Fura-2-acetoxymethyl ester calcium indicator. MICL expression was modulated with an anti-MICL antibody in neutrophils and siRNA in the PLB-985 neutrophil-like cell line. RESULTS: MSU induced the downregulation of MICL expression in neutrophils. A diminution in the expression of MICL induced by antibody cross-linking or siRNA enhanced the MSU-dependent increase in cytoplasmic calcium levels, protein tyrosine phosphorylation and IL-8 but not IL-1 production. Pretreatment of neutrophils with colchicine inhibited the MSU-induced downregulation of MICL expression. CONCLUSIONS: Our findings strongly suggest that MICL acts as an inhibitory receptor in human neutrophils since the downregulation of MICL expression enhances MSU-induced neutrophil activation. Since MSU downregulates the expression of MICL, MICL may play a pathogenic role in gout by enhancing neutrophil effector functions. In support of this notion, colchicine counteracts the MSU-induced loss of MICL expression. Our findings thus also provide further insight into the potential molecular mechanisms behind the anti-inflammatory properties of this drug

Enfance et famille autochtones

Ce numéro explore les enjeux liés à l’enfance, aux jeunes et aux familles dans les communautés autochtones dans différents pays. Les articles publiés abordent notamment l’éducation formelle et informelle ainsi que les effets de la colonisation et du système de protection de la jeunesse sur les jeunes et les familles. Il comprend également deux articles hors thème qui questionnent : pour l’un, le lien au cœur des conjugalités occidentales contemporaines et pour l’autre, les associations d’enfants et de jeunes travailleurs au Burkina Faso