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221.
Vollmer C Schwartges I Obermiller K Beck C Picker O 《General physiology and biophysics》2012,31(1):27-37
This study was designed to compare the effects of different ways of administering carbon monoxide (intravenous and inhalative) on gastric mucosal oxygenation in a canine model of hemorrhage. Six chronically instrumented dogs were repeatedly anesthetized and randomized to each of the following protocols: In a first series the animals were ventilated either with 100 ppm carbon monoxide (CO) or without followed by hemorrhage and re-transfusion. In a second series a saturated CO solution was infused, compared to normal saline, again followed by hemorrhage and re-transfusion. In a control series, animals received either CO-saline or saline without any further intervention. Microvascular oxygenation of the gastric mucosa (μHbO2) was assessed continuously by tissue reflectance spectrophotometry. Cardiac output was measured intermittently and oxygen delivery (DO2) was calculated. The application of CO, inhalative and intravenous, increased carboxyhemoglobin levels without effect on μHbO2. Hemorrhage reduced μHbO2 in all groups, paralleled by a reduction in DO2 without any differences between groups related to the application of CO. Neither intravenous nor inhalative application of CO alters μHbO2 during physiological conditions or during hemorrhage. Thus, independent of the application way, low dose CO does not seem to modulate regional mucosal oxygenation in cytoprotective concentrations. 相似文献
222.
Daniele Kasper Elisabete Fernandes Albuquerque Palermo Christina Wyss Castelo Branco Olaf Malm 《Hydrobiologia》2012,694(1):87-98
Hydroelectric reservoirs can stratify, producing favorable conditions for mercury methylation in the hypolimnion. The methylmercury (MeHg) can be exported downstream, increasing its bioavailability below the dam. Our objective was to assess the mercury levels in plankton, suspended particulate matter (SPM) and fish collected upstream (UP) and downstream (DW) from the Reservatório de Samuel dam, an Amazonian reservoir that stratifies during half of the year. Mercury concentrations in both SPM and plankton were similar between the two sites, which could indicate there are no conditions favoring methylation at the moment of sampling (absence of stratification). Almost all mercury found in the muscle of fishes was in organic form, and differences of mercury levels between sites were dependent on the fishes trophic level. Herbivores showed similar mean organic mercury levels (UP = 117 μg g?1; DW = 120 μg g?1; n = 12), whereas omnivores (UP = 142 μg g?1; DW = 534 μg g?1; n = 27) and carnivores (UP = 545 μg g?1; DW = 1,366 μg g?1; n = 69) showed significantly higher values below the dam. The absence of a reservoir effect in herbivores is expected, since they feed on grassy vegetation, near the riverbanks, which is not much influenced by mercury in aquatic systems. On the other hand, the higher mercury levels below the dam observed for omnivores and carnivores suggest a possible influence of the reservoir since they feed on items that could be contaminated by MeHg exported from upstream. The results highlight the necessity of assessing areas downstream of reservoirs. 相似文献
223.
Garufi G Hendrickx AP Beeri K Kern JW Sharma A Richter SG Schneewind O Missiakas D 《Journal of bacteriology》2012,194(16):4312-4321
Lipoteichoic acid (LTA), a glycerol phosphate polymer, is a component of the envelope of Gram-positive bacteria that has hitherto not been identified in Bacillus anthracis, the causative agent of anthrax. LTA synthesis in Staphylococcus aureus and other microbes is catalyzed by the product of the ltaS gene, a membrane protein that polymerizes polyglycerol phosphate from phosphatidyl glycerol. Here we identified four ltaS homologues, designated ltaS1 to -4, in the genome of Bacillus anthracis. Polyglycerol phosphate-specific monoclonal antibodies were used to detect LTA in the envelope of B. anthracis strain Sterne (pXO1(+) pXO2(-)) vegetative forms. B. anthracis mutants lacking ltaS1, ltaS2, ltaS3, or ltaS4 did not display defects in growth or LTA synthesis. In contrast, B. anthracis strains lacking both ltaS1 and ltaS2 were unable to synthesize LTA and exhibited reduced viability, altered envelope morphology, aberrant separation of vegetative forms, and decreased sporulation efficiency. Expression of ltaS1 or ltaS2 alone in B. anthracis as well as in other microbes was sufficient for polyglycerol phosphate synthesis. Thus, similar to S. aureus, B. anthracis employs LtaS enzymes to synthesize LTA, an envelope component that promotes bacterial growth and cell division. 相似文献
224.
Oelze VM Koch JK Kupke K Nehlich O Zäuner S Wahl J Weise SM Rieckhoff S Richards MP 《American journal of physical anthropology》2012,148(3):406-421
For the Early Iron Age western Hallstatt culture, which includes the site of Magdalenenberg in southwest Germany, it has been proposed that people were mobile and maintained far reaching social and trading networks throughout Europe. We tested this hypothesis by analyzing multiple isotopes (strontium, oxygen, sulfur, carbon, and nitrogen) of the preserved skeletons from the Magdalenenberg elite cemetery to determine diets and to look for evidence of mobility. The analysis of carbon, nitrogen, and sulfur isotope ratios in collagen of humans (n = 50) and associated domestic fauna (n = 10) indicates a terrestrial-based diet. There was a heterogeneous range of isotope values in both strontium (0.70725 to 0.71923, n = 76) and oxygen (13.4‰ to 18.5‰, n = 78) measured in tooth enamel. Although many of the individuals had values consistent with being from Hallstatt culture sites within southwest Germany, some individuals likely originated from further afield. Possible areas include the Alps of Switzerland and Austria or even locations in Italy. Our study strongly supports the assumption of far reaching social and economic networks in the western Hallstatt culture. 相似文献
225.
Carberry K Wiesenfahrt T Geisler F Stöcker S Gerhardus H Überbach D Davis W Jorgensen E Leube RE Bossinger O 《Development (Cambridge, England)》2012,139(10):1851-1862
The nematode Caenorhabditis elegans is an excellent model system in which to study in vivo organization and function of the intermediate filament (IF) system for epithelial development and function. Using a transgenic ifb-2::cfp reporter strain, a mutagenesis screen was performed to identify mutants with aberrant expression patterns of the IF protein IFB-2, which is expressed in a dense network at the subapical endotube just below the microvillar brush border of intestinal cells. Two of the isolated alleles (kc2 and kc3) were mapped to the same gene, which we refer to as ifo-1 (intestinal filament organizer). The encoded polypeptide colocalizes with IF proteins and F-actin in the intestine. The apical localization of IFO-1 does not rely on IFB-2 but is dependent on LET-413, a basolateral protein involved in apical junction assembly and maintenance of cell polarity. In mutant worms, IFB-2 and IFC-2 are mislocalized in cytoplasmic granules and accumulate in large aggregates at the C. elegans apical junction (CeAJ) in a DLG-1-dependent fashion. Electron microscopy reveals loss of the prominent endotube and disordered but still intact microvilli. Semiquantitative fluorescence microscopy revealed a significant decrease of F-actin, suggesting a general role of IFO-1 in cytoskeletal organization. Furthermore, downregulation of the cytoskeletal organizer ERM-1 and the adherens junction component DLG-1, each of which leads to F-actin reduction on its own, induces a novel synthetic phenotype in ifo-1 mutants resulting in disruption of the lumen. We conclude that IFO-1 is a multipurpose linker between different cytoskeletal components of the C. elegans intestinal terminal web and contributes to proper epithelial tube formation. 相似文献
226.
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228.
Marine fisheries as ecological experiments 总被引:1,自引:0,他引:1
There are many examples of ecological theory informing fishery management. Yet fisheries also provide tremendous opportunities
to test ecological theory through large-scale, repeated, and well-documented perturbations of natural systems. Although treating
fisheries as experiments presents several challenges, few comparable tests exist at the ecosystem scale. Experimental manipulations
of fish populations in lakes have been widely used to develop and test ecological theory. Controlled manipulation of fish
populations in open marine systems is rarely possible, but fisheries data provide a valuable substitute for such manipulations.
To highlight the value of marine fisheries data, we review leading ecological theories that have been empirically tested using
such data. For example, density dependence has been examined through meta-analysis of spawning stock and recruitment data
to show that compensation (higher population growth) occurs commonly when populations are reduced to low levels, while depensation
(the Allee effect) is rare. As populations decline, spatial changes typically involve populations contracting into high-density
core habitats while abandoning less productive habitats. Fishing down predators may result in trophic cascades, possibly shifting
entire ecosystems into alternate stable states, although alternate states can be maintained by both ecological processes and
continued fishing pressure. Conversely, depleting low trophic level groups may affect central-place foragers, although these
bottom–up effects rarely appear to impact fish—perhaps because many fish populations have been reduced to the point that they
are no longer prey limited. Fisheries provide empirical tests for diversity–stability relations: catch data suggest that more
diverse systems recover faster and provide more stable returns than less diverse systems. Fisheries have also provided examples
of the tragedy of the commons, as well as counter-examples where common property resources have been managed successfully.
We also address two barriers to use of fisheries data to answer ecological questions: differences in terminology for similar
concepts and misuse of records of fishery landings (catch data) as a proxy for biomass trends. 相似文献
229.
Wartenberg D Vödisch M Kniemeyer O Albrecht-Eckardt D Scherlach K Winkler R Weide M Brakhage AA 《Journal of Proteomics》2012,75(13):4038-4049
The isoprenoid alcohol farnesol represents a quorum-sensing molecule in pathogenic yeasts, but was also shown to inhibit the growth of many filamentous fungi. In order to gain a deeper insight into the antifungal activity of farnesol, we performed 2D-differential gel electrophoretic analysis (2D-DIGE) of Aspergillus nidulans exposed to farnesol. We observed an increased abundance of antioxidative enzymes and proteins involved in protein folding and the ubiquitin-mediated protein degradation. A striking finding was the strong up-regulation of a dehydrin-like protein (DlpA). Expression analyses suggested the involvement of DlpA in the cellular response to oxidative, osmotic and cold stress. In line with these data, we demonstrated that dlpA expression was regulated by the MAP kinase SakA/HogA. The generation of both a dlpA Tet(on) antisense RNA-producing A. nidulans strain (dlpA-inv) and a ΔdlpA deletion mutant indicated a role of DlpA in conidiation and stress resistance of dormant conidia against heat and ROS. Furthermore, the production of the secondary metabolite sterigmatocystin was absent in both strains dlpA-inv and ΔdlpA. Our results demonstrate the complexity of the farnesol-mediated stress response in A. nidulans and describe a farnesol-inducible dehydrin-like protein that contributes to the high tolerance of resting conidia against oxidative and heat stress. 相似文献
230.
Rob J Vandebriel Hilda JI De Jong Eric R Gremmer Olaf H Klungel Jan-Willem Cohen Tervaert Wout Slob Jan Willem Van Der Laan Henk Van Loveren 《Arthritis research & therapy》2012,14(2):R90