Bacopa monnieri extract increases rat coronary flow and protects against myocardial ischemia/reperfusion injury

Background: This study explored Bacopa monnieri, a medicinal Ayurvedic herb, as a cardioprotectant against ischemia/reperfusion injury using cardiac function and coronary flow as end-points. Methods: In normal isolated rat hearts, coronary flow, left ventricular developed pressure, heart rate, and functional recovery were measured using the Langendorff preparation. Hearts were perfused with either (i) Krebs-Henseleit (normal) solution, (control), or with 30, 100 μg/ml B. monnieri ethanolic extract (30 min), or (ii) with normal solution or extract for 10 min preceding no-perfusion ischemia (30 min) followed by reperfusion (30 min) with normal solution. Infarct volumes were measured by triphenyltetrazolium staining. L-type Ca2+-currents (ICa, L) were measured by whole-cell patching in HL-1 cells, a mouse atrial cardiomyocyte cell line. Cytotoxicity of B. monnieri was assessed in rat isolated ventricular myocytes by trypan blue exclusion. Results: In normally perfused hearts, B. monnieri increased coronary flow by 63 ± 13% (30 μg/ml) and 216 ± 21% (100 μg/ml), compared to control (5 ± 3%) (n = 8–10, p < 0.001). B. monnieri treatment preceding ischemia/reperfusion improved left ventricular developed pressure by 84 ± 10% (30 μg/ml), 82 ± 10% (100 μg/ml) and 52 ± 6% (control) compared to pre- ischemia/reperfusion. Similarly, functional recovery showed a sustained increase. Moreover, B. monnieri (100 μg/ml) reduced the percentage of infarct size from 51 ± 2% (control) to 25 ± 2% (n = 6-8, p < 0.0001). B. monnieri (100 μg/ml) reduced ICa, L by 63 ± 4% in HL-1 cells. Ventricular myocyte survival decreased at higher concentrations (50–1000 μg/ml) B. monnieri. Conclusions: B. monnieri improves myocardial function following ischemia/reperfusion injury through recovery of coronary blood flow, contractile force and decrease in infarct size. Thus this may lead to a novel cardioprotectant strategy

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Laterality of leaf cutting in the attine ant Acromyrmex echinatior

International audienceWe tested the idea that leaf-cutting ants preferentially use one of their mandibles in the leading position when cutting leaves. We recorded the mandible position of both paint-marked and unmarked foragers from a laboratory colony of Acromyrmex echinatior during foraging bouts in two experiments 1 year apart (2012 and 2013). Both types of ants were ambidextrous in 2012, and so were unmarked ants in 2013. In contrast, marked ants in 2013 had a preference for leading with their right mandible. The individual laterality of these latter ants ranged from ambidexterity to about 70 % use of the preferred leading mandible. In 2013, we also estimated the cutting rate (length cut per second spent cutting) and harvesting rate (leaf area harvested per second spent cutting) of cutting events for marked foragers. Despite significant positive correlations between head size and both cutting and harvesting rates, the intensity of lateralization was better explained by cutting and harvesting rates than by head size. Specifically, the most lateralized foragers were the slowest and harvested the smallest leaf area per second. We interpret this association as evidence that lateralization was stronger for ants for which cutting was more challenging

Mating systems and avoidance of inbreeding depression as evolutionary drivers of pollen limitation in animal-pollinated self-compatible plants

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Constraints imposed by pollinator behaviour on the ecology and evolution of plant mating systems

International audienceMost flowering plants rely on pollinators for their reproduction. Plant-pollinator interactions, although mutualistic, involve an inherent conflict of interest between both partners and may constrain plant mating systems at multiple levels: the immediate ecological plant selfing rates, their distribution in and contribution to pollination networks, and their evolution. Here, we review experimental evidence that pollinator behaviour influences plant selfing rates in pairs of interacting species, and that plants can modify pollinator behaviour through plastic and evolutionary changes in floral traits. We also examine how theoretical studies include pollinators, implicitly or explicitly, to investigate the role of their foraging behaviour in plant mating system evolution. In doing so, we call for more evolutionary models combining ecological and genetic factors, and additional experimental data, particularly to describe pollinator foraging behaviour. Finally, we show that recent developments in ecological network theory help clarify the impact of community-level interactions on plant selfing rates and their evolution and suggest new research avenues to expand the study of mating systems of animal-pollinated plant species to the level of the plant-pollinator networks

Assortative mating can help adaptation of flowering time to a changing climate: Insights from a polygenic model

International audienceSeveral empirical studies report fast evolutionary changes in flowering time in re-sponse to contemporary climate change. Flowering time is a polygenic trait under as-sortative mating, since flowering time of mates must overlap. Here, we test whether assortative mating, compared with random mating, can help better track a changing climate. For each mating pattern, our individual- based model simulates a popula-tion evolving in a climate characterized by stabilizing selection around an optimal flowering time, which can change directionally and/or fluctuate. We also derive new analytical predictions from a quantitative genetics model for the expected genetic variance at equilibrium, and its components, the lag of the population to the optimum and the population mean fitness. We compare these predictions between assortative and random mating, and to our simulation results. Assortative mating, compared with random mating, has antagonistic effects on genetic variance: it generates positive as-sociations among similar allelic effects, which inflates the genetic variance, but it de-creases genetic polymorphism, which depresses the genetic variance. In a stationary environment with substantial stabilizing selection, assortative mating affects little the genetic variance compared with random mating. In a changing climate, assorta-tive mating however increases genetic variance compared to random mating, which diminishes the lag of the population to the optimum, and in most scenarios translates into a fitness advantage relative to random mating. The magnitude of this fitness advantage depends on the extent to which genetic variance limits adaptation, being larger for faster environmental changes and weaker stabilizing selection

Comparative study of the efficiency of buffer zones and harvest discarding on gene flow containment in oilseed rape. A modelling approach

International audienceOilseed rape (OSR) genes can escape fields in space via pollen and seeds and in time via volunteers resulting from seeds lost before or during oilseed rape harvests. Previous simulation studies and field observations showed that co-existence at the landscape level of contrasting OSR varieties such as genetically modified (GM) and non-GM varieties require costly measures that are difficult to implement, such as isolation distances between OSR fields and stringent volunteer control in all fields and road margins. In the present study, two local strategies, non-GM buffer zones aroundGMfields and discarding the harvest of boundary plants of non-GM fields, were tested in a simulation study using the GENESYS model. This model, which was modified here to improve the prediction of volunteer reproduction and pollen dispersal, quantifies the effects of cropping system on gene flow in landscapes over the years. The evaluation of the improved model version with independent field observations showed that cross-pollination of fieldswas accurately predicted up to 50m and systematically underestimated above that distance, though fields were still ranked correctly. A corrective factor should therefore be applied to predictions in case of low regional OSR and GM proportions (which result into large distances between fields). To study the effects of the two local strategies, simulations were carried out in four contrasted case studies, based on different landscapes, regional OSR and GM proportions, cropping systems and OSR varieties. In these situations, harvest discarding was needless when volunteers were well controlled because the GM impurity in non- GM harvests was well below the EU labelling thresholds; it was useless when OSR contained male-sterile plants or when the landscape was infested by volunteers because large parts of the fields had to be discarded to respect impurity thresholds, which is financially unacceptable. Buffer zones were useful if the non-GM varieties comprised male-sterile plants or if the non-GM fields were small, but only if volunteers were well controlled and harvest impurity was already close to the labelling threshold. Buffer zones appeared considerably more efficient in reducing harvest impurity than harvest discarding because they not only increase the distance between GM and non-GM fields but also diminish the proportion of GM pollen in the total pollen cloud over landscapes. Harvest discarding could possibly be interesting for isolated OSR crops surrounded by bare ground or small crops, an effect that was not tested here. The present study showed that efforts should be dedicated to characterizing and modelling of gene flowat the landscape level, aswell as the collection of datasets for the evaluation of these models in many landscapes and configurations. Local measures tested here are insufficient for ensuring harvest purity. Therefore, future work should focus on finding additional measures are necessary to manage OSR volunteers which constitute the major risk factor for OSR harvest purity

Pollination ecology and inbreeding depression control individual flowering phenologies and mixed mating

International audienceWe analyze evolution of individual flowering phenologies by combining an ecological model of pollinator behavior with a genetic model of inbreeding depression for plant viability. The flowering phenology of a plant genotype determines its expected daily floral display which, together with pollinator behavior, governs the population rate of geitonogamous selfing (fertilization among flowers on the same plant). Pollinators select plant phenologies in two ways: they are more likely to visit plants displaying more flowers per day, and they influence geitonogamous selfing and consequent inbreeding depression via their abundance, foraging behavior and pollen carryover among flowers on a plant. Our model predicts two types of equilibria at stable intermediate selfing rates for a wide range of pollinator behaviors and pollen transfer parameters. Edge equilibria occur at maximal or minimal selfing rates and are constrained by pollinators. Internal equilibria occur between edge equilibria and are determined by a trade-off between pollinator attraction to large floral displays and avoidance of inbreeding depression due to selfing. We conclude that unavoidable geitonogamous selfing generated by pollinator behavior can contribute to the common occurrence of stable mixed mating in plants

A first step for modelling pollen dispersal at the landscape level: determining the shape of dispersal functions at long-distance. The case of oilseed rape

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Ex ante evaluation of gene flow in oilseed rape with cropping sytem models

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