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At least 973 records · Page 54Linked to original sources
PubMed2005

Proton exchange membrane and electrode surface areas as factors that affect power generation in microbial fuel cells.

Power generation in microbial fuel cells (MFCs) is a function of the surface areas of the proton exchange membrane (PEM) and the cathode relative to that of the anode. To demonstrate this, the sizes of the anode and cathode were varied in two-chambered MFCs having PEMs with three different surface areas (A (PEM)=3.5, 6.2, or 30.6 cm(2)). For a fixed anode and cathode surface area (A (An)=A (Cat)=22.5 cm(2)), the power density normalized to the anode surface area increased with the PEM size in the order 45 mW/m(2) (A (PEM)=3.5 cm(2)), 68 mW/m(2) (A (PEM)=6.2 cm(2)), and 190 mW/m(2) (A (PEM)=30.6 cm(2)). PEM surface area was shown to limit power output when the surface area of the PEM was smaller than that of the electrodes due to an increase in internal resistance. When the relative cross sections of the PEM, anode, and cathode were scaled according to 2A (Cat)=A(PEM)=2A (An), the maximum power densities of the three different MFCs, based on the surface area of the PEM (A (PEM)=3.5, 6.2, or 30.6 cm(2)), were the same (168+/-4.53 mW/m(2)). Increasing the ionic strength and using ferricyanide at the cathode also increased power output.

Bacteria, Anaerobic↗
PubMed1990

Expression of spasmolysin (FIM-A.1): an integumentary mucin from Xenopus laevis.

In the past, a unique type of precursor for a secretory protein was discovered. It contains a central repetitive domain rich in threonine residues and terminal cysteine-rich domains. Due to striking homologies of these terminal domains with pancreatic spasmolytic polypeptide, originally the name "prepro-spasmolysin" was proposed. Here we show that the mature protein has a MW of about 130 kDa, consisting of about 70% carbohydrate and 30% protein. Similar O-linked glycoproteins have been found in mucins from human intestine. For this and numerous other reasons we decided to rename this glycoprotein "frog integumentary mucin A.1" (FIM-A.1). Furthermore, analysis of the protein with specific antibodies against the predicted C-terminal end indicates that FIM-A.1 is probably not processed at pairs of basic residues. In situ hybridization as well as immunofluorescence studies revealed that FIM-A.1 is expressed and stored exclusively in mature mucous glands of Xenopus laevis skin. Only cone cells at the proximal part of these glands do not synthesize FIM-A.1. In contrast, all other physiologically active peptides from X. laevis skin investigated so far are synthesized in granular glands. A hypothetical function of FIMs for defense against microbial infections is discussed.

Amino Acid Sequence↗
PubMed1992

Purification and characterization of wheat alpha-gliadin synthesized in the yeast, Saccharomyces cerevisiae.

The development of efficient methods for production and purification of plant seed storage proteins in heterologous microbial hosts would facilitate structure-function studies of these proteins. This report describes such methods applied to the production and isolation of wheat alpha-gliadin, a prolamine-type seed storage protein, from Saccharomyces cerevisiae. Beginning with the vector, growth conditions, and extraction methods of Neill et al. [Gene 55 (1987) 303-317], we implemented several improvements to increase the yields of alpha-gliadin per volume of yeast cell culture. The CYCl::Gli-A2-Y transcriptional fusion vector, pAY31 (Neill et al., 1987), was modified by replacing the ARS1 region of replication with that of the 2 mu plasmid of yeast. We formulated a new medium, a derivative of synthetic defined (SD) medium supplemented with several nitrogen sources, that allows both selection for maintenance of plasmids and growth to high cell densities. Stationary phase cultures of cells bearing the modified expression vector, and grown in this medium with glycerol and lactate as carbon sources, contain significantly higher levels of alpha-gliadin than log-phase cultures grown in SD glucose. Sonication in 80% ethanol selectively and efficiently extracts the alpha-gliadin from cell pellets of small- or large-scale cultures, allowing the purification of several hundred micrograms of the wheat protein per liter in just a few high-yield steps. The alpha-gliadin isolated from yeast elutes at the same position in HPLC as the A-gliadin fraction purified from wheat flour. N-terminal amino acid (aa) sequencing reveals that the signal peptide is removed from the gliadin precursor in yeast cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed2005

Simulation of antibiotic pharmacodynamic exposure for the empiric treatment of nosocomial bloodstream infections: a report from the OPTAMA program.

OBJECTIVE: We developed a model to predict the pharmacodynamic exposure of antibiotics against bacteria commonly implicated in nosocomial bloodstream infections to determine which dosage regimens would provide the greatest likelihood of obtaining a bactericidal effect. METHODS: Pharmacodynamic exposures were simulated for 5000 subjects receiving standard doses of ceftazidime, cefepime, piperacillin/tazobactam, meropenem, imipenem, or ciprofloxacin. Exposures were indexed to the MICs of bacteria weighted by their prevalence in causing nosocomial bloodstream infections, derived from 2002 SENTRY data. Enterococci were excluded. MIC data were derived from the 2003 Meropenem Yearly Surveillance Test Information Collection resistance study. The probabilities of achieving bactericidal exposures (ie, target attainment) for each antibiotic regimen were compared. The effect of increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) on attainment of bactericidal targets was tested. RESULTS: All dosage regimens except ciprofloxacin and ceftazidime 1 g q8h achieved >90% likelihood of bactericidal exposure. The rank order of target attainment was as follows: imipenem 500 mg q6h, 100.0%; imipenem 1 g q8h, 99.9%; cefepime 2 g q12h, 99.4%; meropenem 1 g q8h, 98.4%; cefepime 1 g q12h, 98.2%; piperacillin/tazobactam 3.375 g q6h, 97.9%; piperacillin/tazobactam 4.5 gq8h, 95.0%; ceftazidime 2 g q8h, 94.2%; ceftazidime 1 g q8h, 71.7%; ciprofloxacin 400 mg q8h, 63.3%; and ciprofloxacin 400 mg q12h,63.0%. Target attainments dropped to <90% for all agents when MRSA was modeled at > or =10% prevalence. CONCLUSIONS: The results of this model analysis suggest that standard doses of the carbapenems, piperacillin/tazobactam, and cefepime, and higher doses of ceftazidime, may provide optimal likelihood of achieving bactericidal exposure against pathogens implicated in nosocomial bloodstream infections, excluding MRSA and enterococci. When MRSA rates are > or =10%, therapy with an antibiotic that has activity against this phenotype should be empirically initiated.

Anti-Bacterial Agents↗
PubMed2006

Interleukin-22: a novel T- and NK-cell derived cytokine that regulates the biology of tissue cells.

Interleukin (IL)-22, discovered in 2000, is a member of the IL-10 family of cytokines. The major sources of IL-22 are activated T1- and NK-cells. IL-22 acts via a heterodimeric receptor complex consisting of IL-22R1 and IL-10R2. Neither resting nor activated immune cells express IL-22R1 or respond to IL-22. In contrast, tissue cells at outer body barriers, i.e. of the skin, kidney, and the digestive and respiratory systems are targets of this cytokine. IL-22 functions by promoting the anti-microbial defense, protecting against damage, and re-organizing non-immune tissues. Furthermore, IL-22 induces acute phase reactants. These findings indicate that IL-22 represents a novel type of immune mediator that, although produced by immune cells, regulates tissue protection and homeostasis.

Humans↗
PubMed2004

Role of PPARgamma in macrophage biology and atherosclerosis.

Macrophages carry out key functions by defending a host from microbial invaders and by clearing endogenous cellular debris. Molecules that are essential for the recognition, phagocytosis and clearance of pathogens also mediate the uptake and degradation of pathogenic lipoproteins. During atherogenesis, for example, scavenging trapped lipoproteins leads to the formation of foam cells and subsequently the activation of these lipid-laden macrophages. Although they are initially clinically silent, these fatty streaks evolve into complex inflammatory plaques that cause significant morbidity and mortality. Thus, interventions that decrease foam cell formation and reduce the inflammatory response of macrophages could become effective therapies for coronary artery disease. Thiazolidinediones (TZDs) might be developed as anti-atherogenic agents on the basis of their actions as ligands for peroxisome proliferator-activated receptor-gamma (PPARgamma).

Animals↗
PubMed2005

Biological and chemical interactions with U(VI) during anaerobic enrichment in the presence of iron oxide coated quartz.

Microcosm experiments were performed to understand chemical and biological interactions with hexavalent uranium (U(VI)) in the presence of iron oxide bearing minerals and trichloroethylene (TCE) as a co-contaminant. Interactions of U(VI) and hydrous iron oxide moieties on the mineral oxide surfaces were studied during enrichments for dissimilatory iron reducing (DIRB) and sulfate reducing bacteria (SRB). Microbes enriched from groundwater taken from the Test Area North (TAN) site at the Idaho National Laboratory (INL) were able to reduce the U(VI) in the adsorption medium as well as the iron on quartz surfaces. Early in the experiment disappearance of U(VI) from solution was a function of chemical interactions since no microbial activity was evident. Abiotic removal of U(VI) was enhanced in the presence of carbonate. As the experiment proceeded, further removal of U(VI) from solution was associated with the fermentation of lactate to propionate and acetate. During later phases of the experiment when lactate was depleted from the growth medium in the microcosm containing the DIRB enrichments, U(VI) concentrations in the solution phase increased until additional lactate was added. When additional lactate was added and fermentation proceeded, U(VI) concentrations in the liquid phase again returned to near zero. Similar results were shown for the SRB enrichment but lower uranium concentrations were seen in the liquid phase, while in the enrichment with carbonate a similar increase in uranium concentration was not seen. Chemical and biological interactions appear to be important on the mobilization/immobilization of U(VI) in an iron oxide system when TCE is present as a co-contaminant. Interestingly, TCE present in the microcosm experiments was not dechlorinated which was probably an effect of redox conditions that were unsuitable for reductive dechlorination by the microbial culture tested.

Adsorption↗
PubMed2003

Unexpected catalytic site variation in phosphoprotein phosphatase homologues of cofactor-dependent phosphoglycerate mutase.

The cofactor-dependent phosphoglycerate mutase (dPGM) superfamily contains, besides mutases, a variety of phosphatases, both broadly and narrowly substrate-specific. Distant dPGM homologues, conspicuously abundant in microbial genomes, represent a challenge for functional annotation based on sequence comparison alone. Here we carry out sequence analysis and molecular modelling of two families of bacterial dPGM homologues, one the SixA phosphoprotein phosphatases, the other containing various proteins of no known molecular function. The models show how SixA proteins have adapted to phosphoprotein substrate and suggest that the second family may also encode phosphoprotein phosphatases. Unexpected variation in catalytic and substrate-binding residues is observed in the models.

Amino Acid Sequence↗
PubMed2003

Importance of atmospherically deposited nitrogen to the annual nitrogen budget of the Neuse River estuary, North Carolina.

Wet deposition of nitrogen, as NH(4)(+), NO(3)(-), and organic N, contributes up to 50% of the total externally supplied or 'new' N flux to the Neuse River Estuary (North Carolina). Excessive nitrogen (N) loading to N-sensitive waters such as the Neuse River Estuary has been linked to changes in microbial and algal community composition and function (harmful algal blooms), hypoxia/anoxia, and fish kills. In a 4-year study from July 1996 to July 2000, the weekly wet deposition of NH(4)(+), NO(3)(-), and dissolved organic N was calculated, based on concentration and precipitation measurements, at 11 sites on a northwest-southeast transect in the watershed. Data from this period indicate that the annual mean total wet atmospherically deposited (AD)-N flux was 11 kg ha(-1) year(-1). Deposition was fairly evenly distributed between nitrate, ammonium, and organics (32%, 32%, and 36%, respectively). Seasonally, the summer (June-August) months contained the highest weekly wet total N deposition; this trend was not driven by precipitation amount. Estimates of watershed N retention and in-stream riverine processing revealed that the AD-N flux contributed an estimated 20% (range of 15-51%) of the total 'new' N flux to the estuary, with direct deposition of N to the estuary surface accounting for 6% of the total 'new' N flux. This study did not measure the dry depositional flux, which may double the contribution of AD-N to the estuary. The AD-N is an important source of 'new' N to the Neuse River Estuary as well as other estuarine and coastal ecosystems downwind of major emission sources. As such, AD-N should be included in effective nutrient mitigation and management efforts for these N-sensitive waters.

Air Pollutants↗
PubMed1988

Specific sequestering agents for the actinides. 16. Synthesis and initial biological testing of polydentate oxohydroxypyridinecarboxylate ligands.

Chemical and biological similarities of plutonium(IV) and iron(III) suggested that octadentate ligands containing hydroxamate or catecholate functional groups, which are found in microbial iron chelating agents (siderophores), would be effective and relatively selective complexing agents for actinide(IV) ions. However, their usefulness for in vivo chelation of actinide(IV) is limited, because catechol and hydroxamate are such weak acids that the potential for octadentate binding of actinide(IV) cannot be achieved at physiological pH. The structurally similar monoprotic and more acidic 1-hydroxy-2(1H)-pyridinone (1,2-HOPO) group was, therefore, incorporated into multidentate ligands. Treatment of 1,2-dihydro-1-hydroxy-2-oxopyridine-6-carboxylic acid (5) with phosgene in THF solution gives the active ester poly[1,2-dihydro-1,2-dioxopyridine-6-carboxylate], which upon treatment with excess anhydrous dimethylamine gave a 60% yield of N,N-dimethyl-1,2-dihydro-1-hydroxy-2-oxopyridine-6-carboxamide (6). A similarly reactive intermediate was prepared from 5 and an equimolar amount of phosgene in N,N-dimethylacetamide. Combined in situ with 1,3-propanediamine, benzylamine, spermine, spermidine, 1,3,5-tris(aminomethyl)benzene, or desferrioxamine B and excess triethylamine, the latter intermediate gave the corresponding amides in isolated yields ranging from 16% to 60%. The free ligands, their Zn(II) complexes, and the ferric complex of 3,4,3-LIHOPO were administered to mice [30 mumol/kg intraperitoneally 1 h after Pu(IV)-238 citrate, kill at 24 h]. Net Pu removal [Pu excretion (treated)-PU excretion (control)], expressed as percent of injected Pu, was as follows: Na salts and Zn(II) complexes, respectively, of 3-LIHOPO (54, 56), 3,4-LIHOPO (58, 60), 3,4,3-LIHOPO (73, 76); Na salts of MEHOPO (46), DFO-HOPO (78); Fe(III) complex of 3,4,3-LIHOPO (79). DFO-HOPO and 3,4,3-LIHOPO and its Zn(II) and Fe(III) complexes promoted significantly more Pu excretion than CaNa3-DTPA (61% of injected Pu). Preliminary findings on the acute toxicity of the poly(HOPO) ligands and HOPO monomers are presented in an appendix. The biological data indicate strongly that the aqueous solubility and relatively high acidity of the octadentate HOPO ligands, 3,4,3-LIHOPO and DFO-HOPO allow them to form complete eight-coordinate complexes with Pu(IV) ion.

Actinoid Series Elements↗
PubMed1999

Anti-Helicobacter pylori agents. 3. 2-[(Arylalkyl)guanidino]-4-furylthiazoles.

A series of 2-[(arylalkyl)guanidino]-4-[(5-acetamidomethyl)furan-2-yl]thiazole s and some 4-acetamidomethyl positional isomers were synthesized and evaluated for antimicrobial activity against Helicobacter pylori. Among the compounds that had potent antimicrobial activity (MIC < 0. 1 microgram/mL), compounds 31 and 36 additionally possessed H2 antagonist and gastric antisecretory activities. Though compound 51, an analogue incorporating a methyl group onto the furan nucleus of 36, and compound 54, a positional isomer of 51, also showed potent anti-H. pylori activity, the H2 antagonism profile was eliminated from these compounds. Thus, two types of potent anti-H. pylori agents could be derived from the same scaffold.

Animals↗
PubMed2000

Circulating endothelial cells in vascular disorders: new insights into an old concept.

The endothelial contribution to vascular disorders has been widely documented in experimental models. However, its implication in human pathology is difficult to investigate, owing to the paucity of noninvasive methods and of specific endothelial markers. The enumeration of circulating endothelial cells (CEC) released in peripheral blood after vascular injury represents a direct exploration of the endothelium. For this purpose, we have produced a monoclonal antibody (S-Endo 1), which recognizes CD 146, a molecule expressed on all types of human endothelial cells but absent from haemopoietic cells. Using this antibody, we have designed a specific and sensitive immunocapture test, which allowed us to detect high numbers of CEC in thrombotic, infectious or immunological disorders, while CEC were found to be very rare ( < 3/ml) in normal subjects. This quantitative approach using CEC might prove useful as a marker of vascular wall injury. Their enumeration is of interest in the clinical follow-up of vascular disorders, in the evaluation of therapeutic effectiveness or in the direct diagnosis of infectious diseases involving intra-endothelial microbial agents. Furthermore, an immunological and/or functional study of CEC could allow one to assess their procoagulant and proadhesive properties, as well as their viability, opening new perspectives for CEC investigation in vascular pathology.

Antigens, CD↗
PubMed2000

Effects of areca nut extracts on the functions of human neutrophils in vitro.

Aqueous extracts of ripe areca nut without husk (ripe ANE) and fresh and tender areca nut with husk (tender ANE) were examined for their effects on the defensive functions of human neutrophils. Exposure of peripheral blood neutrophils to ripe ANE and tender ANE inhibited their bactericidal activity against oral pathogens, including Actinobacillus actinomycetemcomitans and Streptococcus mutans, in a dose-dependent manner. At the concentrations tested, ripe and tender ANEs did not significantly affect the viability of neutrophils as verified by their ability to exclude trypan blue dye. However, both ANEs inhibited the production of bactericidal superoxide anion by neutrophils as measured by cytochrome c reduction. Moreover, the ripe ANE inhibited neutrophils more effectively than did tender ANE. Arecoline, a major alkaloid of areca nut, only exhibited an inhibitory effect on the functions of neutrophils when high concentrations were used. Therefore, arecoline could not be used to explain the inhibitory effects observed for ANEs. In conclusion, our results demonstrated that ripe and tender ANEs reduced the antibacterial activity and the superoxide anion production of neutrophils. This effect may contribute to a less efficient elimination of bacteria from the periodontal environment. Inhibition of the antimicrobial functions of neutrophils may alter the microbial ecology of the oral cavity, and this may be one possible mechanism by which areca nut compromises the oral health of users of areca nut products.

Aggregatibacter actinomycetemcomitans↗
PubMed2000

Pathways for lipid antigen presentation by CD1 molecules: nowhere for intracellular pathogens to hide.

A crucial feature of peptide antigen presentation by major histocompatibility complex (MHC) class I and II molecules is their differential ability to sample cytosolic and extracellular antigens. Intracellular viral infections and bacteria that are taken up in phagosomes, but then escape from the endocytic compartment efficiently, enter the class I pathway via the cytosol. In contrast, phagosome-resident bacteria yield protein antigens that are sampled deep in the endocytic compartment and presented in a vacuolar acidification-dependent pathway mediated by MHC class II molecules. Despite this potential for antigen sampling, microbes have evolved a variety of evasive mechanisms that affect peptide transport in the MHC class I pathway or blockade of endosomal acidification and inhibition of phagosome-lysosome fusion that may compromise the MHC class II pathway of antigen presentation. Thus, besides MHC class I and II, a third lineage of antigen-presenting molecules that bind lipid and glycolipid antigens rather than peptides exists and is mediated by the family of CD1 proteins. CD1 isoforms (CD1a, b, c, and d) differentially sample both recycling endosomes of the early endocytic system and late endosomes and lysosomes to which lipid antigens are differentially delivered. These CD1 pathways include vacuolar acidification-independent pathways for lipid antigen presentation. These features of presenting lipid antigens, independently monitoring various antigen-containing intracellular compartments and avoiding certain evasive techniques employed by microbes, enable CD1 molecules to provide distinct opportunities to function in host defense against the microbial world.

Animals↗
PubMed2005

Bioactive microbial metabolites.

The short history, specific features and future prospects of research of microbial metabolites, including antibiotics and other bioactive metabolites, are summarized. The microbial origin, diversity of producing species, functions and various bioactivities of metabolites, unique features of their chemical structures are discussed, mainly on the basis of statistical data. The possible numbers of metabolites may be discovered in the future, the problems of dereplication of newly isolated compounds as well as the new trends and prospects of the research are also discussed.

Animals↗