排序方式: 共有99条查询结果,搜索用时 15 毫秒
31.
32.
Under a coalescent model for within-species evolution, gene trees may differ from species trees to such an extent that the gene tree topology most likely to evolve along the branches of a species tree can disagree with the species tree topology. Gene tree topologies that are more likely to be produced than the topology that matches that of the species tree are termed anomalous, and the region of branch-length space that gives rise to anomalous gene trees (AGTs) is the anomaly zone. We examine the occurrence of anomalous gene trees for the case of five taxa, the smallest number of taxa for which every species tree topology has a nonempty anomaly zone. Considering all sets of branch lengths that give rise to anomalous gene trees, the largest value possible for the smallest branch length in the species tree is greater in the five-taxon case (0.1934 coalescent time units) than in the previously studied case of four taxa (0.1568). The five-taxon case demonstrates the existence of three phenomena that do not occur in the four-taxon case. First, anomalous gene trees can have the same unlabeled topology as the species tree. Second, the anomaly zone does not necessarily enclose a ball centered at the origin in branch-length space, in which all branches are short. Third, as a branch length increases, it is possible for the number of AGTs to increase rather than decrease or remain constant. These results, which help to describe how the properties of anomalous gene trees increase in complexity as the number of taxa increases, will be useful in formulating strategies for evading the problem of anomalous gene trees during species tree inference from multilocus data. 相似文献
33.
Randa Bittar Élisabeth Aslangul Philippe Giral Lambert Assoumou Marc-Antoine Valantin Olga Kalmykova Marie-Christine Federspiel Corinne Cherfils Dominique Costagliola Dominique Bonnefont-Rousselot 《Comptes rendus biologies》2017,340(2):109-113
Background
We evaluated the effect of 45 days of rosuvastatin or pravastatin treatment on the distribution of HDL subfractions in HIV-1-infected individuals receiving boosted protease inhibitors (PIs) with cardiovascular risk.Methods
The distribution of HDL subclasses by gradient gel electrophoresis was blindly assessed in 74 HIV-1-infected individuals receiving boosted PIs at baseline and at day 45 of statin treatment, and compared with the distribution obtained in 63 healthy normolipidemic individuals taken as controls.Results
No significant modification appeared in HDL distribution between the two arms of statins for the HIV-1-infected individuals. Nevertheless, when compared to controls, HDL subfractions showed a significantly lower HDL2b proportion and significantly higher proportions of HDL2a and HDL3b (P < 0.001).Conclusion
No difference was observed in HDL distribution between pravastatin and rosuvastatin after 45 days treatment, in HIV-1-infected individuals under PIs. Nevertheless, when compared to healthy normolipidemic subjects, HDL distribution is clearly different, with a distribution in HIV-infected individuals under PIs associated with an increased cardiovascular risk. 相似文献34.
Janelle R. Thompson Mark A. Randa Luisa A. Marcelino Aoy Tomita-Mitchell Eelin Lim Martin F. Polz 《Applied microbiology》2004,70(7):4103-4110
Vibrios are ubiquitous marine bacteria that have long served as models for heterotrophic processes and have received renewed attention because of the discovery of increasing numbers of facultatively pathogenic strains. Because the occurrence of specific vibrios has frequently been linked to the temperature, salinity, and nutrient status of water, we hypothesized that seasonal changes in coastal water bodies lead to distinct vibrio communities and sought to characterize their level of differentiation. A novel technique was used to quantify shifts in 16S rRNA gene abundance in samples from Barnegat Bay, N.J., collected over a 15-month period. Quantitative PCR (QPCR) with primers specific for the genus Vibrio was combined with separation and quantification of amplicons by constant denaturant capillary electrophoresis (CDCE). Vibrio populations identified by QPCR-CDCE varied between summer and winter samples, suggesting distinct warm-water and year-round populations. Identification of the CDCE populations by cloning and sequencing of 16S rRNA genes from two summer and two winter samples confirmed this distinction. It further showed that CDCE populations corresponded in most cases to ~98% rRNA similarity groups and suggested that the abundance of these follows temperature trends. Phylogenetic comparison yielded closely related cultured and often pathogenic representatives for most sequences, and the temperature ranges of these isolates confirmed the trends seen in the environmental samples. Overall, this suggests that temperature is a good predictor of the occurrence of closely related vibrios but that considerable microdiversity of unknown significance coexists within this trend. 相似文献
35.
Randa A Zarban Umar F Shahul Hameed Muhammad Jamil Tsuyoshi Ota Jian You Wang Stefan T Arold Tadao Asami Salim Al-Babili 《Plant physiology》2022,188(2):1369
The obligate hemiparasitic weed Striga hermonthica grows on cereal roots and presents a severe threat to global food security by causing enormous yield losses, particularly in sub-Saharan Africa. The rapidly increasing Striga seed bank in infested soils provides a major obstacle in controlling this weed. Striga seeds require host-derived strigolactones (SLs) for germination, and corresponding antagonists could be used as germination inhibitors. Recently, we demonstrated that the common detergent Triton X-100 is a specific inhibitor of Striga seed germination by binding noncovalently to its receptor, S. hermonthica HYPO-SENSITIVE TO LIGHT 7 (ShHTL7), without blocking the rice (Oryza sativa) SL receptor DWARF14 (OsD14). Moreover, triazole ureas, the potent covalently binding antagonists of rice SL perception with much higher activity toward OsD14, showed inhibition of Striga but were less specific. Considering that Triton X-100 is not suitable for field application and by combining structural elements of Triton and triazole urea, we developed two hybrid compounds, KK023-N1 and KK023-N2, as potential Striga-specific germination inhibitors. Both compounds blocked the hydrolysis activity of ShHTL7 but did not affect that of OsD14. Binding of KK023-N1 diminished ShHTL7 interaction with S. hermonthica MORE AXILLARY BRANCHING 2, a major component in SL signal transduction, and increased ShHTL7 thermal specificity. Docking studies indicate that KK023-N1 binding is not covalent but is caused by hydrophobic interactions. Finally, in vitro and greenhouse tests revealed specific inhibition of Striga seed germination, which led to a 38% reduction in Striga infestation in pot experiments. These findings reveal that KK023-N1 is a potential candidate for combating Striga and a promising basis for rational design and development of further Striga-specific herbicides.Designed strigolactone antagonists inhibit Striga seed germination. 相似文献
36.
The response of the follicle cells of Rhodnius prolixus to JH in vitro was found to be independent of de novo macromolecular synthesis as exemplified by the failure of Actinomycin D, and puromycin to inhibit the response at any but the highest concentrations employed. C18 JH was found to be a more effective gonadotropin than C16 JH in this in vitro study. Neither methyl palmitate nor ecdysone mimiced or antagonised the action of JH on the follicle cells in vitro. Follicle cells of ovaries removed from allatectomised mated females failed to respond to C16 JH and ecdysone in vitro. 相似文献
37.
Randa Abboud Radu Popa Virginia Souza-Egipsy Carol S. Giometti Sandra Tollaksen Jennifer J. Mosher Robert H. Findlay Kenneth H. Nealson 《Applied microbiology》2005,71(2):811-816
Shewanella oneidensis MR-1 is a mesophilic bacterium with a maximum growth temperature of ≈35°C but the ability to grow over a wide range of temperatures, including temperatures near zero. At room temperature (≈22°C) MR-1 grows with a doubling time of about 40 min, but when moved from 22°C to 3°C, MR-1 cells display a very long lag phase of more than 100 h followed by very slow growth, with a doubling time of ≈67 h. In comparison to cells grown at 22°C, the cold-grown cells formed long, motile filaments, showed many spheroplast-like structures, produced an array of proteins not seen at higher temperature, and synthesized a different pattern of cellular lipids. Frequent pilus-like structures were observed during the transition from 3 to 22°C. 相似文献
38.
39.
Chandrabose Selvaraj Gurudeeban Selvaraj Randa Mohamed Ismail Rajendran Vijayakumar Alaa Baazeem Dong-Qing Wei Sanjeev Kumar Singh 《Saudi Journal of Biological Sciences》2021,28(7):3650-3659
Bacillus anthracis is a gram positive, deadly spore forming bacteria causing anthrax and these bacteria having the complex mechanism in the cell wall envelope, which can adopt the changes in environmental conditions. In this, the membrane bound cell wall proteins are said to progressive drug target for the inhibition of Bacillus anthracis. Among the cell wall proteins, the SrtA is one of the important mechanistic protein, which mediate the ligation with LPXTG motif by forming the amide bonds. The SrtA plays the vital role in cell signalling, cell wall formation, and biofilm formations. Inhibition of SrtA leads to rupture of the cell wall and biofilm formation, and that leads to inhibition of Bacillus anthracis and thus, SrtA is core important enzyme to study the inhibition mechanism. In this study, we have examined 28 compounds, which have the inhibitory activity against the Bacillus anthracis SrtA for developing the 3D-QSAR and also, compounds binding selectivity with both open and closed SrtA conformations, obtained from 100 ns of MD simulations. The binding site loop deviate in forming the open and closed gate mechanism is investigated to understand the inhibitory profile of reported compounds, and results show the closed state active site conformations are required for ligand binding specificity. Overall, the present study may offer an opportunity for better understanding of the mechanism of action and can be aided to further designing of a novel and highly potent SrtA inhibitors. 相似文献
40.
Jihane Pakradouni Wilfried Le Goff Claire Calmel Bénédicte Antoine Elise Villard Eric Frisdal Marianne Abifadel Joan Tordjman Christine Poitou Dominique Bonnefont-Rousselot Randa Bittar Eric Bruckert Karine Clément Bruno Fève Cécile Martinerie Maryse Guérin 《PloS one》2013,8(6)