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131.
The anoxic layers of marine sediments are dominated by sulfate reduction and methanogenesis as the main terminal oxidation processes. The aim of this study was to analyze the vertical succession of microbial populations involved in these processes along the first 4.5 m of a tidal-flat sediment. Therefore, a quantitative PCR approach was applied using primers targeting the domains of Bacteria and Archaea, and key functional genes for sulfate reduction (dsrA) and methanogenesis (mcrA). The sampling site was characterized by an unusual sulfate peak at 250 cm depth resulting in separate sulfate-methane transition zones. Methane and sulfate profiles were diametrically opposed, with a methane maximum in the sulfate-depleted zone showing high numbers of archaea and methanogens. The methane-sulfate interfaces harbored elevated numbers of sulfate reducers, and revealed a slight increase in mcrA and archaeal 16S rRNA genes, suggesting sulfate-dependent anaerobic oxidation of methane. A diversity analysis of both functional genes by PCR-denaturing gradient gel electrophoresis revealed a vertical succession of subpopulations that were governed by geochemical and sedimentologic conditions. Along the upper 200 cm, sulfate-reducing populations appeared quite uniform and were dominated by the Deltaproteobacteria. In the layers beneath, an apparent increase in diversity and a shift to the Firmicutes as the predominant group was observed. 相似文献
132.
Clostridium thermocellum, a cellulolytic, thermophilic anaerobe, has potential for commercial exploitation in converting fibrous biomass to ethanol.
However, ethanol concentrations above 1% (w/v) are inhibitory to growth and fermentation, and this limits industrial application of the organism. Recent work with ethanol-adapted
strains suggested that protein changes occurred during ethanol adaptation, particularly in the membrane proteome. A two-stage
Bicine-doubled sodium dodecyl sulfate-polyacrylamide gel electrophoresis protocol was designed to separate membrane proteins
and circumvent problems associated with membrane protein analysis using traditional gel-based proteomics approaches. Wild-type
and ethanol-adapted C. thermocellum membranes displayed similar spot diversity and approximately 60% of proteins identified from purified membrane fractions
were observed to be differentially expressed in the two strains. A majority (73%) of differentially expressed proteins were
down-regulated in the ethanol-adapted strain. Based on putative identifications, a significant proportion of these down-regulated
proteins were involved with carbohydrate transport and metabolism. Approximately one-third of the up-regulated proteins in
the ethanol-adapted species were associated with chemotaxis and signal transduction. Overall, the results suggested that membrane-associated
proteins in the ethanol-adapted strain are either being synthesized in lower quantities or not properly incorporated into
the cell membrane. 相似文献
133.
Coppieters K Van Beneden K Jacques P Dewint P Vervloet A Vander Cruyssen B Van Calenbergh S Chen G Franck RW Verbruggen G Deforce D Matthys P Tsuji M Rottiers P Elewaut D 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(4):2300-2309
The glycosphingolipid alpha-galactosylceramide (alpha-GalCer) has been shown to be a potent activator of invariant NKT (iNKT) cells, rapidly inducing large amounts of both Th1 and Th2 cytokines upon injection in mice. The C-glycoside analog of alpha-GalCer (alpha-C-GalCer), by contrast, results in an enhanced Th1-type response upon activation of iNKT cells. We administered a single dose of these Ags to DBA/1 mice during the early induction phase of collagen-induced arthritis and demonstrated therapeutic efficacy of alpha-GalCer when administered early rather than late during the disease. Surprisingly, the Th1-polarizing analog alpha-C-GalCer also conferred protection. Furthermore, a biphasic role of IFN-gamma in the effect of iNKT cell stimulation was observed. Whereas in vivo neutralization of IFN-gamma release induced by either alpha-GalCer or alpha-C-GalCer early during the course of disease resulted in partial improvement of clinical arthritis symptoms, blockade of IFN-gamma release later on resulted in a more rapid onset of arthritis. Although no phenotypic changes in conventional T cells, macrophages, or APCs could be detected, important functional differences in T cell cytokine production in serum were observed upon polyclonal T cell activation, 2 wk after onset of arthritis. Whereas alpha-GalCer-treated mice produced significantly higher amounts of IL-10 upon systemic anti-CD3 stimulation compared with PBS controls, T cells from alpha-C-GalCer-treated mice, by contrast, produced substantially lower levels of cytokines, suggesting the involvement of different protective mechanisms. In conclusion, these findings suggest long-term, ligand-specific, time-dependent, and partially IFN-gamma-dependent immunomodulatory effects of iNKT cells in collagen-induced arthritis. 相似文献
134.
Tan W Wang Y Gold B Chen J Dean M Harrison PJ Weinberger DR Law AJ 《The Journal of biological chemistry》2007,282(33):24343-24351
135.
136.
In genomic research the ideal standard of free, informed, prior and explicit consent is sometimes difficult to apply. This has raised concern that important genomic research will be restricted. Different consent procedures have therefore been proposed. This paper explicitly examines the question how, in genomic research, the principles of solidarity and justice can be used to justify forms of diminished individual control over personal data and bio-samples. After a discussion of the notions of solidarity and justice and how they can be related to health care and genomic research, we examine how and in which situations these notions can form a strong moral basis for demanding certain financial sacrifices. Then we examine when these principles can justify consent procedures which diverge from the ideal standard. Because much genomic research is not expected to lead to immediate (clinical) benefits we also discuss the question of whether we can be obliged to make any sacrifices for future (not yet existing) patients. We conclude with the formulation of a number of conditions that have to be met before autonomy sacrifices can be reasonably demanded in genomic research. 相似文献
137.
Heart-type fatty acid-binding protein (H-FABP) is a major fatty acid-binding factor in skeletal muscles. Genetic lack of H-FABP
severely impairs the esterification and oxidation of exogenous fatty acids in soleus muscles isolated from chow-fed mice (CHOW-solei)
and high fat diet-fed mice (HFD-solei), and prevents the HFD-induced accumulation of muscle triacylglycerols (TAGs). Here,
we examined the impact of H-FABP deficiency on the relationship between fatty acid utilization and glucose oxidation. Glucose
oxidation was measured in isolated soleus muscles in the presence or absence of 1 mM palmitate (simple protocol) or in the
absence of fatty acid after preincubation with 1 mM palmitate (complex protocol). With the simple protocol, the mutation slightly
reduced glucose oxidation in CHOW-muscles, but markedly increased it in HFD-muscles; unexpectedly, this pattern was not altered
by the addition of palmitate, which reduced glucose oxidation in both CHOW- and HFD-solei irrespective of the mutation. In
the complex protocol, the mutation first inhibited the synthesis and accumulation of TAGs and then their mobilization; with
this protocol, the mutation increased glucose oxidation in both CHOW- and HFD-solei. We conclude: (i) H-FABP mediates a non-acute
inhibition of muscle glucose oxidation by fatty acids, likely by enabling both the accumulation and mobilization of a critical
mass of muscle TAGs; (ii) H-FABP does not mediate the acute inhibitory effect of extracellular fatty acids on muscle glucose
oxidation; (iii) H-FABP affects muscle glucose oxidation in opposing ways, with inhibition prevailing at high muscle TAG contents. 相似文献
138.
139.
The fast and accurate prediction of protein flexibility is one of the major challenges in protein science. Enzyme activity, signal transduction, and ligand binding are dynamic processes involving essential conformational changes ranging from small side chain fluctuations to reorientations of entire domains. In the present work, we describe a reimplementation of the CONCOORD approach, termed tCONCOORD, which allows a computationally efficient sampling of conformational transitions of a protein based on geometrical considerations. Moreover, it allows for the extraction of the essential degrees of freedom, which, in general, are the biologically relevant ones. The method rests on a reliable estimate of the stability of interactions observed in a starting structure, in particular those interactions that change during a conformational transition. Applications to adenylate kinase, calmodulin, aldose reductase, T4-lysozyme, staphylococcal nuclease, and ubiquitin show that experimentally known conformational transitions are faithfully predicted. 相似文献
140.