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951.
Stadthagen G Sambou T Guerin M Barilone N Boudou F Korduláková J Charles P Alzari PM Lemassu A Daffé M Puzo G Gicquel B Rivière M Jackson M 《The Journal of biological chemistry》2007,282(37):27270-27276
Mycobacteria produce two unusual polymethylated polysaccharides, the 6-O-methylglucosyl-containing lipopolysaccharides (MGLP) and the 3-O-methylmannose polysaccharides, which have been shown to regulate fatty acid biosynthesis in vitro. A cluster of genes dedicated to the synthesis of MGLP was identified in Mycobacterium tuberculosis and Mycobacterium smegmatis. Overexpression of the putative glycosyltransferase gene Rv3032 in M. smegmatis greatly stimulated MGLP production, whereas the targeted disruption of Rv3032 in M. tuberculosis and that of the putative methyltransferase gene MSMEG2349 in M. smegmatis resulted in a dramatic reduction in the amounts of MGLP synthesized and in the accumulation of precursors of these molecules. Disruption of Rv3032 also led to a significant decrease in the glycogen content of the tubercle bacillus, indicating that the product of this gene is likely to be involved in the elongation of more than one alpha-(1-->4)-glucan in this bacterium. Results thus suggest that Rv3032 encodes the alpha-(1-->4)-glucosyltransferase responsible for the elongation of MGLP, whereas MSMEG2349 encodes the O-methyltransferase required for the 6-O-methylation of these compounds. 相似文献
952.
Nicolas Le Novère 《BMC systems biology》2007,1(1):28-3
Computational neurobiology was born over half a century ago, and has since been consistently at the forefront of modelling
in biology. The recent progress of computing power and distributed computing allows the building of models spanning several
scales, from the synapse to the brain. Initially focused on electrical processes, the simulation of neuronal function now
encompasses signalling pathways and ion diffusion. The flow of quantitative data generated by the "omics" approaches, alongside
the progress of live imaging, allows the development of models that will also include gene regulatory networks, protein movements
and cellular remodelling. A systems biology of brain functions and disorders can now be envisioned. As it did for the last
half century, neuroscience can drive forward the field of systems biology. 相似文献
953.
Competition for pollination is thought to be an important factor structuring flowering in many plant communities, particularly
among plant taxa with morphologically similar and easily accessible flowers. We examined the potential for heterospecific
pollen transfer (HPT) in a community of four Acacia species in a highly seasonal tropical habitat in Mexico. Partitioning of pollen flow among sympatric species appears to be
achieved, in part, through segregation of flowering in seasonal time, and interspecific differences in pollinator guilds.
However, two coflowering species (Acacia macracantha and Acacia angustissima) shared multiple flower visitors, raising the possibility of HPT. Each of these coflowering species showed high intraspecific
daily synchrony in pollen release, but dehisce at different times of day. Pollinators rapidly harvested available pollen from
one species before abandoning it to visit the flowers of the second later in the day. The activity of shared pollinators,
predominantly bees, is thus structured throughout the day, and potential for HPT reduced. Suggestive evidence in favour of
a resource partitioning explanation for this pattern is provided by the fact that A. macracantha showed significantly greater intraspecific synchrony when coflowering with a potential competitor (A. angustissima) than when flowering alone. We discuss our results in light of previous work on coflowering acacia assemblages in Tanzania
and Australia.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Nigel E. RaineEmail: |
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Objective: We evaluated the effect of adipocyte‐derived lipoprotein lipase (LPL) on macrophage activation and monocyte adhesion and the role of fatty acids in these effects. Research Methods and Procedures: 3T3‐L1 adipocytes were incubated with heparin or insulin to induce LPL secretion; then adipocyte conditioned media (CM) were added to cultured J774 macrophages or human aortic endothelial cells (HAECs). Macrophage cytokine production and monocyte adhesion to HAECs were determined. Results: Incubation of macrophages with heparin‐ or insulin‐treated adipocyte CM increased tumor necrosis factor α, interleukin‐6, and nitric oxide production by these cells. LPL neutralization and heparinase treatment prevented these effects. Addition of active LPL or palmitate to cultured macrophages replicated these effects. Blockade of leptin also reduced the effect of insulin‐treated adipocyte CM on macrophage inflammatory changes. Induction of macrophage cytokine secretion by leptin was prevented by LPL immunoneutralization. Finally, addition of CM of heparin‐ or insulin‐treated adipocytes to HAECs stimulated monocyte adhesion to these cells, an effect that was abrogated by an anti‐LPL antibody. This effect was reproduced by treating HAECs with active LPL or palmitate. Discussion: These results point to an effect of LPL‐mediated lipolysis in macrophage activation and monocyte adhesion. 相似文献
959.
Vandewalle G Schmidt C Albouy G Sterpenich V Darsaud A Rauchs G Berken PY Balteau E Degueldre C Luxen A Maquet P Dijk DJ 《PloS one》2007,2(11):e1247
Background
Relatively long duration retinal light exposure elicits nonvisual responses in humans, including modulation of alertness and cognition. These responses are thought to be mediated in part by melanopsin-expressing retinal ganglion cells which are more sensitive to blue light than violet or green light. The contribution of the melanopsin system and the brain mechanisms involved in the establishment of such responses to light remain to be established.Methodology/Principal Findings
We exposed 15 participants to short duration (50 s) monochromatic violet (430 nm), blue (473 nm), and green (527 nm) light exposures of equal photon flux (1013ph/cm2/s) while they were performing a working memory task in fMRI. At light onset, blue light, as compared to green light, increased activity in the left hippocampus, left thalamus, and right amygdala. During the task, blue light, as compared to violet light, increased activity in the left middle frontal gyrus, left thalamus and a bilateral area of the brainstem consistent with activation of the locus coeruleus.Conclusion/Significance
These results support a prominent contribution of melanopsin-expressing retinal ganglion cells to brain responses to light within the very first seconds of an exposure. The results also demonstrate the implication of the brainstem in mediating these responses in humans and speak for a broad involvement of light in the regulation of brain function. 相似文献960.
Recent contributions of in vitro models to our understanding of hepatitis C virus life cycle 总被引:1,自引:0,他引:1
Hepatitis C virus is a human pathogen responsible for liver diseases including acute and chronic hepatitis, cirrhosis and hepatocellular carcinoma. Its high prevalence, the absence of a prophylactic vaccine and the poor efficiency of current therapies are huge medical problems. Since the discovery of the hepatitis C virus, our knowledge of its biology has been largely punctuated by the development of original models of research. At the end of the 1980s, the chimpanzee model led to cloning of the viral genome and the definition of infectious molecular clones. In 1999, a breakthrough was achieved with the development of a robust in vitro replication model named 'replicon'. This system allowed intensive research into replication mechanisms and drug discovery. Later, in 2003, pseudotyped retroviruses harbouring surface proteins of hepatitis C virus were produced to specifically investigate the viral entry process. It was only in 2005 that infectious viruses were produced in vitro, enabling intensive investigations into the entire life cycle of the hepatitis C virus. This review describes the different in vitro models developed to study hepatitis C virus, their contribution to current knowledge of the virus biology and their future research applications. 相似文献