Characterization and clinical association of antibody inhibitory to HIV reverse transcriptase activity   总被引：7，自引：0，他引：7  

J Laurence  A Saunders  J Kulkosky 《Science (New York, N.Y.)》1987,235(4795):1501-1504

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INDUCED BIOTIN DEFICIENCY AS A POSSIBLE EXPLANATION OF OBSERVED SPONTANEOUS RECESSIONS IN MALIGNANCY     

Laurence WL 《Science (New York, N.Y.)》1941,94(2430):88-89

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High deleterious genomic mutation rate in stationary phase of Escherichia coli     

Loewe L  Textor V  Scherer S 《Science (New York, N.Y.)》2003,302(5650):1558-1560

In natural habitats, bacteria spend most of their time in some form of growth arrest. Little is known about deleterious mutations in such stages, and consequently there is limited understanding of what evolutionary events occur. In a deleterious mutation accumulation experiment in prolonged stationary phase of Escherichia coli, about 0.03 slightly deleterious mutations were observed per genome per day. This is over an order of magnitude higher than extrapolations from fast-growing cells, but in line with inferences from observations in adaptive stationary phase mutation experiments. These findings may affect understanding of bacterial evolution and the emergence of bacterial pathogenicity.  相似文献   

G protein-coupled receptors in Anopheles gambiae   总被引：3，自引：0，他引：3  

Hill CA  Fox AN  Pitts RJ  Kent LB  Tan PL  Chrystal MA  Cravchik A  Collins FH  Robertson HM  Zwiebel LJ 《Science (New York, N.Y.)》2002,298(5591):176-178

We used bioinformatic approaches to identify a total of 276 G protein-coupled receptors (GPCRs) from the Anopheles gambiae genome. These include GPCRs that are likely to play roles in pathways affecting almost every aspect of the mosquito's life cycle. Seventy-nine candidate odorant receptors were characterized for tissue expression and, along with 76 putative gustatory receptors, for their molecular evolution relative to Drosophila melanogaster. Examples of lineage-specific gene expansions were observed as well as a single instance of unusually high sequence conservation.  相似文献   

Deep Subseafloor Fungi as an Untapped Reservoir of Amphipathic Antimicrobial Compounds     

Marion Navarri  Camille Jégou  Laurence Meslet-Cladière  Benjamin Brillet  Georges Barbier  Ga?tan Burgaud  Yannick Fleury 《Marine drugs》2016,14(3)

The evolving global threat of antimicrobial resistance requires a deep renewal of the antibiotic arsenal including the isolation and characterization of new drugs. Underexplored marine ecosystems may represent an untapped reservoir of novel bioactive molecules. Deep-sea fungi isolated from a record-depth sediment core of almost 2000 m below the seafloor were investigated for antimicrobial activities. This antimicrobial screening, using 16 microbial targets, revealed 33% of filamentous fungi synthesizing bioactive compounds with activities against pathogenic bacteria and fungi. Interestingly, occurrence of antimicrobial producing isolates was well correlated with the complexity of the habitat (in term of microbial richness), as higher antimicrobial activities were obtained at specific layers of the sediment core. It clearly highlights complex deep-sea habitats as chemical battlefields where synthesis of numerous bioactive compounds appears critical for microbial competition. The six most promising deep subseafloor fungal isolates were selected for the production and extraction of bioactive compounds. Depending on the fungal isolates, antimicrobial compounds were only biosynthesized in semi-liquid or solid-state conditions as no antimicrobial activities were ever detected using liquid fermentation. An exception was made for one fungal isolate, and the extraction procedure designed to extract amphipathic compounds was successful and highlighted the amphiphilic profile of the bioactive metabolites.  相似文献   

Individual heterogeneity in erythrocyte susceptibility to Babesia divergens is a critical factor for the outcome of experimental spleen-intact sheep infections     

Laurence Malandrin  Maggy Jouglin  Emmanuelle Moreau    Alain Chauvin 《Veterinary research》2009,40(4)

Susceptibility of sheep erythrocytes to Babesia divergens was investigated in vitro and a high inter-individual variability in their ability to support parasite population development was demonstrated, with some individuals having refractory red blood cells (RBC). As neither changes in growth conditions nor the use of different B. divergens strains influenced the level of susceptibility, the main factor postulated for this variability is the erythrocyte itself. Sheep therefore represent an excellent in vitro model to study the parasite-erythrocyte interaction. In addition, the existence of refractory RBC should help in the identification of the erythrocyte components required for B. divergens development. Experimental infections were carried out on spleen-intact sheep characterized by refractory or fully susceptible erythrocyte types. These differences translated into the successful infection of only those animals with susceptible erythrocytes: infected animals showed no clinical signs, but maintained an asymptomatic persistent infection, as usually observed in the natural bovine host. Sheep therefore represent model organisms that can allow us to study interactions between B. divergens and its vertebrate host at different levels of biological organisation, from the target cell to the intact animal, and represent an experimental infection model of concomitant immunity. Only a low percentage (13%) of the sheep population tested possessed susceptible erythrocytes and the potential role of sheep as a natural host or reservoir of B. divergens is discussed.  相似文献   

The effect of seawater flow and temperature on metamorphosis and postlarval development in great scallop     

René Robert  Laurence Nicholas 《Aquaculture International》2000,8(6):513-530

Variations in growth and survival of hatchery-reared post-metamorphicjuveniles of great scallop Pecten maximus prompted anexamination of settlement and postlarval development. The effects ofseawater flow and temperature on great scallop metamorphosis andpostlarvae were studied over a 4–5 week period. In allexperiments, and regardless of environmental conditions, great scallopmetamorphosed after a 2–3 week period with values of 35 to70%. Subsequently, spat numbers increased slightly. Spatmortality generally occurred from the third week onward and reachedlevels as high as 30% by the fifth week under standardconditions. At 20 °C, however, 60% mortality levels wererecorded. Differences in spat growth rate, ranging from 37 to 45 mday^–1, were noticed at different seawater flow ratesbut no clear tendency could be discerned. Temperature affected spatgrowth with an increase in size from 24 m day^–1 at15 °C to 35 m day^–1 at 18 °C. Conversely,growth was suppressed at 20 °C (14 m day^–1).For optimal metamorphosis and postlarval development in great scallop, aseawater flow of 4.3 L h^–1 per sieve and a temperatureof 15 °C are recommended.  相似文献   

Habitat partitioning among three predatory fish in a temperate reservoir     

Samuel Westrelin  Julien Cucherousset  Romain Roy  Laurence Tissot  Frdric Santoul  Christine Argillier 《Ecology of Freshwater Fish》2022,31(1):129-142

The diversity of predatory species plays a key role in ecosystem functioning but our understanding of the mechanisms underlying their coexistence is limited, particularly in freshwater ecosystems. Northern pike Esox lucius, European perch Perca fluviatilis and pikeperch Sander lucioperca are three widespread predatory species in European lakes, where they often coexist. As potential competitors, we hypothesised that partitioning habitat is a determinant of species coexistence. This was tested by quantifying the variability of their habitat use in tracking adult individuals in the Bariousses reservoir (France, 86.6 ha, mean depth 7.1 m). Specifically, we investigated their distribution along the littoral–pelagic and depth axes along the daily cycle and across seasons. From littoral to pelagic waters were first found pike, then perch and finally pikeperch. Pike was the closest to the surface while pikeperch was the deepest. This general pattern was, however, variable across seasons with the three species located in the upper layer in summer during reservoir stratification. Individuals were more evenly distributed along the littoral–pelagic axis and closer to the bottom when water was mixing (autumn, winter). In summer, perch used more intensively in the pelagic zone during the daytime. Other species did not show any diel change of habitats. Our results highlighted that species coexistence is associated with habitat partitioning among these three predators, with perch showing a more variable behaviour regarding habitat characteristics. Now more than ever, in the context of global change which modifies habitats, it is of crucial importance to understand the coexistence mechanisms of species that shape ecosystems.  相似文献