192 research outputs found
Composition chimique et propriĂ©tĂ©s antibactĂ©riennes des huiles essentielles dâOcimum basilicum et dâHyptis suaveolens (L.) Poit rĂ©coltĂ©s dans la rĂ©gion de Dakar au SĂ©nĂ©gal
Les huiles essentielles des feuilles dâOcimum basilicumet dâHyptis suaveolens, rĂ©coltĂ©es dans la rĂ©gion de Dakar au SĂ©nĂ©gal ont Ă©tĂ© extraites par entraĂźnement Ă la vapeur et analysĂ©es en CPG et CPG-SM. Les monoterpĂšnes oxygĂ©nĂ©s dont lâestragol (38,78 %), le linalol (19,45 %) et le mĂ©thyl-eugĂ©nol (9,98 %) sont majoritaires dans lâhuile essentielle dâO. basilicum. Ils sont suivis dâun sesquiterpĂšne hydrocarbonĂ©: le bergamotĂšne (8,48 %). Par contre, lâhuile essentielle de H. suaveolensest essentiellement constituĂ©e de composĂ©s hydrocarbonĂ©s: le ÎČ-caryophyllĂšne (16,63 %), le sabinĂšne (11,30 %), le terpinolĂšne (8,58 %), le limonĂšne (8,45 %) et le bergamotĂšne (5,26 %). Les propriĂ©tĂ©s antimicrobiennes des huiles essentielles de ces plantes ont Ă©tĂ© testĂ©es in vitro sur cinq souches bactĂ©riennes (Staphylococcus aureus, Bacillus sp.,Salmonella sp., Escherichia coli, Streptococcus sp.). Une activitĂ© inhibitrice des huiles sur les souches Ă©tudiĂ©es a Ă©tĂ© observĂ©e. Toutefois, celle dâO.basilicumsâest rĂ©vĂ©lĂ©e plus active, particuliĂšrement contre Bacillus sp., Salmonella sp., et Escherichia coli.Mots-clĂ©s: Ocimum basilicum, Hyptis suaveolens, huiles essentielles, composition chimique, propriĂ©tĂ©s antimicrobiennes. Chemical composition and antimicrobial properties of the essential oils of Ocimum basilicum andHyptis suaveolensharvested from Dakar region in SenegalEssential oils of leaves from Ocimum basilicum and Hyptis suaveolens collected in the region of Dakar in Senegal have been extracted by steam distillation and analyzed by GC and GC-MS. The oxygenated monoterpenes which estragol (38.78%), linalool (19.45%) and methyl-eugenol (9.98%) constitute the major portion of the essential oils of O. basilicum followed by bergamotene (8.48%) which is a sesquiterpene hydrocarbon. Principal compounds of H.suaveolens essential oilsare: ÎČ-caryophyllene (16.63%), sabinene (11.30%), terpinolene (8.58%), limonene (8.45%) and bergamotene (5.26%).The antimicrobial properties of essential oils of these plants were tested in vitro against five bacterial strains (Staphylococcus aureus, Bacillussp, Salmonella sp., Escherichia coli, Streptococcus sp.). The inhibitory activity of the oils on the strains studied was observed. However, the essential oil of O. basilicum was more active, especially against Bacillus sp., Salmonella sp. and Escherichia coli.Keywords: Ocimum basilicum, Hyptis suaveolens, essential oils, chemical composition, antimicrobial properties
Tiques et hémoparasitoses du bétail au Sénégal. III. La zone Nord-soudanienne
Les auteurs rapportent les rĂ©sultats d'une Ă©tude sur les tiques et les hĂ©moparasitoses des bovins, des ovins et des caprins de la zone nord-soudanienne. Un dĂ©tiquage systĂ©matique de 40 bovins, 40 moutons et 40 chĂšvres est effectuĂ© pendant 15 mois dans le but de dĂ©terminer la dynamique des populations et de prĂ©ciser les sites prĂ©fĂ©rentiels de fixation des diffĂ©rentes espĂšces. Les espĂšces suivantes sont rĂ©coltĂ©es sur ces animaux : Hyalomma marginatum rufipes, H. truncatum, Rhipicephalus lunulatus, Rh. e evertsi, Rh. sulcatus, Rh. senegalensis, Boophilus decoloratus. Des Ă©tudes sont menĂ©es simultanĂ©ment sur les hĂ©moparasitoses, par rĂ©alisation de frottis de sang et de splĂ©nectomies. Chez les bovins, sont mis en Ă©vidence : Anaplasma marginale, Ehrlichia bovis, Theileria mutans, Th. velifera, Trypanosoma congolense, T. brucei et des microfilaires de Setaria labiatopapillosa. Babesia bigemina a Ă©tĂ© observĂ©e aprĂšs splĂ©nectomie. Les infections dĂ©celĂ©es chez les petits ruminants sont occasionnĂ©es par A. ovis, Th. ovis et T. vivax. Les valeurs de l'hĂ©matocrite d'animaux apparemment sains sont Ă©tudiĂ©es de mĂȘme que les variations saisonniĂšres de ce paramĂštre hĂ©matologique
The roles of static stability and tropical â extratropical interactions in the summer interannual variability of the North Atlantic sector
Summer seasonal forecast skill in the North Atlantic sector is lower than winter skill. To identify potential controls on predictability, the sensitivity of North Atlantic baroclinicity to atmospheric drivers is quantified. Using ERA-INTERIM reanalysis data, North Atlantic storm-track baroclinicity is shown to be less sensitive to meridional temperature-gradient variability in summer. Static stability shapes the sectorâs interannual variability by modulating the sensitivity of baroclinicity to variations in meridional temperature gradients and tropopause height and by modifying the baroclinicity itself. High static stability anomalies at upper levels result in more zonal extratropical cyclone tracks and higher eddy kinetic energy over the British Isles in the summertime. These static stability anomalies are not strongly related to the summer NAO; but they are correlated with the suppression of convection over the tropical Atlantic and with a poleward-shifted subtropical jet. These results suggest a non-local driver of North Atlantic variability. Furthermore, they imply that improved representations of convection over the south-eastern part of North America and the tropical Atlantic might improve summer seasonal forecast skill
The complete genome sequence of the phytopathogenic fungus Sclerotinia sclerotiorum reveals insights into the genome architecture of broad host range pathogens
Sclerotinia sclerotiorum is a phytopathogenic fungus with over 400 hosts including numerous economically important cultivated species. This contrasts many economically destructive pathogens that only exhibit a single or very few hosts. Many plant pathogens exhibit a âtwo-speedâ genome. So described because their genomes contain alternating gene rich, repeat sparse and gene poor, repeat-rich regions. In fungi, the repeat-rich regions may be subjected to a process termed repeat-induced point mutation (RIP). Both repeat activity and RIP are thought to play a significant role in evolution of secreted virulence proteins, termed effectors. We present a complete genome sequence of S. sclerotiorum generated using Single Molecule Real-Time Sequencing technology with highly accurate annotations produced using an extensive RNA sequencing data set. We identified 70 effector candidates and have highlighted their in planta expression profiles. Furthermore, we characterized the genome architecture of S. sclerotiorum in comparison to plant pathogens that exhibit âtwo-speedâ genomes. We show that there is a significant association between positions of secreted proteins and regions with a high RIP index in S. sclerotiorum but we did not detect a correlation between secreted protein proportion and GC content. Neither did we detect a negative correlation between CDS content and secreted protein proportion across the S. sclerotiorum genome. We conclude that S. sclerotiorum exhibits subtle signatures of enhanced mutation of secreted proteins in specific genomic compartments as a result of transposition and RIP activity. However, these signatures are not observable at the whole-genome scale
Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase
Pattern recognition receptors (PRRs) play a key role in plant and animal innate immunity. PRR binding of their cognate ligand triggers a signaling network and activates an immune response. Activation of PRR signaling must be controlled prior to ligand binding to prevent spurious signaling and immune activation. Flagellin perception in Arabidopsis through FLAGELLINâSENSITIVE 2 (FLS2) induces the activation of mitogenâactivated protein kinases (MAPKs) and immunity. However, the precise molecular mechanism that connects activated FLS2 to downstream MAPK cascades remains unknown. Here, we report the identification of a differentially phosphorylated MAP kinase kinase kinase that also interacts with FLS2. Using targeted proteomics and functional analysis, we show that MKKK7 negatively regulates flagellinâtriggered signaling and basal immunity and this requires phosphorylation of MKKK7 on specific serine residues. MKKK7 attenuates MPK6 activity and defense gene expression. Moreover, MKKK7 suppresses the reactive oxygen species burst downstream of FLS2, suggesting that MKKK7âmediated attenuation of FLS2 signaling occurs through direct modulation of the FLS2 complex
Cellular development and evolution of the mammalian cerebellum
\ua9 2023, The Author(s).The expansion of the neocortex, a hallmark of mammalian evolution 1,2, was accompanied by an increase in cerebellar neuron numbers 3. However, little is known about the evolution of the cellular programmes underlying the development of the cerebellum in mammals. In this study we generated single-nucleus RNA-sequencing data for around 400,000 cells to trace the development of the cerebellum from early neurogenesis to adulthood in human, mouse and the marsupial opossum. We established a consensus classification of the cellular diversity in the developing mammalian cerebellum and validated it by spatial mapping in the fetal human cerebellum. Our cross-species analyses revealed largely conserved developmental dynamics of cell-type generation, except for Purkinje cells, for which we observed an expansion of early-born subtypes in the human lineage. Global transcriptome profiles, conserved cell-state markers and gene-expression trajectories across neuronal differentiation show that cerebellar cell-type-defining programmes have been overall preserved for at least 160 million years. However, we also identified many orthologous genes that gained or lost expression in cerebellar neural cell types in one of the species or evolved new expression trajectories during neuronal differentiation, indicating widespread gene repurposing at the cell-type level. In sum, our study unveils shared and lineage-specific gene-expression programmes governing the development of cerebellar cells and expands our understanding of mammalian brain evolution
A molecular mechanism of artemisinin resistance in Plasmodium falciparum malaria
Artemisinins are the cornerstone of anti-malarial drugs. Emergence and spread of resistance to them raises risk of wiping out recent gains achieved in reducing worldwide malaria burden and threatens future malaria control and elimination on a global level. Genome-wide association studies (GWAS) have revealed parasite genetic loci associated with artemisinin resistance. However, there is no consensus on biochemical targets of artemisinin. Whether and how these targets interact with genes identified by GWAS, remains unknown. Here we provide biochemical and cellular evidence that artemisinins are potent inhibitors of Plasmodium falciparum phosphatidylinositol-3-kinase (PfPI3K), revealing an unexpected mechanism of action. In resistant clinical strains, increased PfPI3K was associated with the C580Y mutation in P. falciparum Kelch13 (PfKelch13), a primary marker of artemisinin resistance. Polyubiquitination of PfPI3K and its binding to PfKelch13 were reduced by the PfKelch13 mutation, which limited proteolysis of PfPI3K and thus increased levels of the kinase, as well as its lipid product phosphatidylinositol-3-phosphate (PI3P). We find PI3P levels to be predictive of artemisinin resistance in both clinical and engineered laboratory parasites as well as across non-isogenic strains. Elevated PI3P induced artemisinin resistance in absence of PfKelch13 mutations, but remained responsive to regulation by PfKelch13. Evidence is presented for PI3P-dependent signalling in which transgenic expression of an additional kinase confers resistance. Together these data present PI3P as the key mediator of artemisinin resistance and the sole PfPI3K as an important target for malaria elimination
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