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Korneel Rabaey - One of the best experts on this subject based on the ideXlab platform.
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a novel shewanella isolate enhances corrosion by using metallic iron as the electron donor with fumarate as the electron acceptor
Applied and Environmental Microbiology, 2018Co-Authors: Jo Philips, Niels Van Den Driessche, Kim De Paepe, Antonin Prevoteau, Jeffrey A Gralnick, Jan Arends, Korneel RabaeyAbstract:The involvement of Shewanella sp. in biocorrosion is often attributed to their Fe(III) reducing properties, but they could also affect corrosion by using metallic iron as electron donor. Previously, we isolated Shewanella strain 4t3-1-2LB from an acetogenic community enriched with Fe(0) as sole electron donor. Here, we investigated its use of Fe(0) as electron donor with fumarate as electron acceptor and explored its corrosion Enhancing Mechanism. Without Fe(0), strain 4t3-1-2LB fermented fumarate to succinate and CO 2 , as was shown by the reaction stoichiometry and pH. With Fe(0), strain 4t3-1-2LB completely reduced fumarate to succinate and increased the Fe(0) corrosion rate 7.0 ± 0.6 times in comparison to abiotic controls (based on the succinate versus abiotic hydrogen formation rate). Fumarate reduction by strain 4t3-1-2LB was, at least in part, supported by chemical hydrogen formation on Fe(0). Filter-sterilized spent medium only increased the hydrogen generation rate 1.5 times, thus extracellular hydrogenase enzymes appear insufficient to explain the enhanced corrosion rate. Electrochemical measurements suggested that strain 4t3-1-2LB did not excrete dissolved redox mediators. Exchanging the medium and SEM imaging indicated cells were attached to Fe(0). Possibly, strain 4t3-1-2LB used a direct Mechanism to withdraw electrons from Fe(0), or favored chemical hydrogen formation on Fe(0) through maintaining low hydrogen concentrations. In co-culture with an Acetobacterium strain, strain 4t3-1-2LB did not enhance acetogenesis from Fe(0). This work describes a strong corrosion enhancement by a Shewanella strain through its use of Fe(0) as electron donor and gained insights in its corrosion Enhancing Mechanism. Importance Shewanella sp. are frequently found on corroded metal structures. Their role in microbial influenced corrosion has mainly been attributed to their Fe(III) reducing properties and, therefore, been studied with the addition of an electron donor (lactate). Shewanella sp., however, can also use solid electron donors, such as cathodes and potentially Fe(0). In this work, we show that the electron acceptor fumarate supported the use of Fe(0) as electron donor by Shewanella strain 4t3-1-2LB, which caused a 7.0 ± 0.6 times increase of the corrosion rate. The corrosion Enhancing Mechanism likely involved cell-surface associated components in direct contact with the Fe(0) surface, or maintenance of low hydrogen levels by attached cells, thereby favoring chemical hydrogen formation by Fe(0). This work sheds new light on the role of Shewanella sp. in biocorrosion, while the insights in the corrosion Enhancing Mechanism contribute to the understanding of extracellular electron uptake processes.
Akira Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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enhanced permeability of insulin across the rat intestinal membrane by various absorption enhancers their intestinal mucosal toxicity and absorption Enhancing Mechanism of n lauryl β d maltopyranoside
Journal of Pharmacy and Pharmacology, 2010Co-Authors: Tomomi Uchiyama, Takuya Fujita, Tetsuo Sugiyama, Yingshu Quan, Atsushi Kotani, Naoki Okada, Shozo Muranishi, Akira YamamotoAbstract:We have examined the in-vitro permeability characteristics of insulin in the presence of various absorption enhancers across rat intestinal membranes and have assessed the intestinal toxicity of the enhancers using an in-vitro Ussing chamber method. The absorption Enhancing Mechanism of n-lauryl-beta-D-maltopyranoside was studied also. The permeability of insulin across the intestinal membranes was low in the absence of absorption enhancers. However, the permeability was improved in the presence of enhancers such as sodium glycocholate and sodium deoxycholate in the jejunum, and sodium glycocholate, sodium deoxycholate, n-lauryl-beta-D-maltopyranoside, sodium caprate and ethylenediaminetetraacetic acid (EDTA) in the colon. Overall, the absorption Enhancing effects were greater on the colonic membrane than on the jejunal membrane. The intestinal membrane toxicity of these enhancers was characterized using the release of cytosolic lactate dehydrogenase from the colonic membrane. A marked increase in the release of lactate dehydrogenase was observed in the presence of sodium deoxycholate and EDTA. The release of lactate dehydrogenase in the presence of these absorption enhancers was similar to that seen with sodium dodecyl sulphate (SDS), used as a positive control, indicating high toxicity of these enhancers to the intestinal membrane. In contrast, sodium glycocholate and sodium caprate caused minor releases of lactate dehydrogenase, similar to control levels, suggesting low toxicity. In addition, the amount of lactate dehydrogenase in the presence of n-lauryl-beta-D-maltopyranoside was much less than that seen with sodium deoxycholate, EDTA and SDS. Therefore, sodium glycocholate, sodium caprate and n-lauryl-beta-D-maltopyranoside are useful absorption enhancers due to their high absorption Enhancing effects and low intestinal toxicity. To investigate the absorption Enhancing Mechanisms of n-lauryl-beta-D-maltopyranoside, the transepithelial electrical resistance (TEER), voltage clamp experiments and the circular dichroism spectra were studied. n-Lauryl-beta-D-maltopyranoside decreased the TEER values in a dose-dependent manner, suggesting that the enhancer may open the tight junctions of the epithelium, thereby increasing the permeability of insulin via a paracellular pathway. This speculation was supported by the findings that 20 mM n-lauryl-beta-D-maltopyranoside produced a greater increase in the paracellular flux rate than in the transcellular flux rate by the voltage clamp studies. Evaluating the circular dichroism spectra we found that insulin oligomers were not dissociated to monomers by the addition of n-lauryl-beta-D-maltopyranoside, but dissociation did occur with the addition of sodium glycocholate. Thus, the dissociation of insulin was not a major factor in the absorption Enhancing effect of n-lauryl-beta-D-maltopyranoside. These findings provide basic information to select the optimal enhancer for the intestinal delivery of peptide and protein drugs including insulin.
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improvement of intestinal absorption of water soluble macromolecules by various polyamines intestinal mucosal toxicity and absorption Enhancing Mechanism of spermine
International Journal of Pharmaceutics, 2008Co-Authors: Yang Gao, Hidemasa Katsumi, Toshiyasu Sakane, Takuya Fujita, Akira YamamotoAbstract:The absorption-Enhancing effects of three different polyamines, spermine (SPM), spermidine (SPD) and putrescine (PUT) on the intestinal absorption of water-soluble macromolecules were examined in rats. Fluorescein isothiocyanate-labeled dextrans (FDs) with different average molecular weights were chosen as models of water-soluble macromolecules and intestinal absorption of FDs with or without these polyamines was examined by an in situ closed loop method. The intestinal absorption of fluorescein isothiocyanate-labeled dextran with an average molecular weight of 4400 (FD4) was relatively low in the absence of these polyamines. However, its absorption was improved in the presence of 5-10mM SPM and 10mM SPD in the jejunum and 10mM SPM in the colon, while 10mM PUT had almost no absorption-Enhancing effect on the intestinal absorption of FD4. Overall, the Enhancing effects of these polyamines were greater in the jejunal membranes than in the colonic membranes. The absorption-Enhancing effect of SPM decreased as the molecular weights of FDs increased. The intestinal membrane toxicity of 10mM SPM was evaluated by measuring the amount of protein and activity of lactate dehydrogenase (LDH) released from the intestinal epithelial cells. We also observed the morphological changes of intestinal mucosa in the presence or absence of SPM. The results indicated that the amount of protein and LDH was not changed in the presence of 10mM SPM, although we observed a significant increase in these biological markers in the presence of 3% Triton X-100, as a positive control. Furthermore, we found no significant change in the intestinal membrane with 10mM SPM by the morphological observation. These findings suggested that 10mM SPM did not cause any significant membrane damage to the intestinal epithelium. To investigate the absorption-Enhancing Mechanism of SPM, the transepithelial electrical resistance (TEER) of the rat jejunal membranes was studied by using a diffusion chamber method. SPM decreased the TEER values in a concentration dependent manner and 10mM SPM had almost the same effect to decrease the TEER value compared with 10mM EDTA as a positive control. These findings suggest that SPM may loosen the tight junction of the epithelium, thereby increasing the intestinal absorption of drugs via a paracellular route. In summary, polyamines, especially SPM would be one of the suitable absorption enhancers with high effectiveness and low intestinal membrane toxicity.
Jo Philips - One of the best experts on this subject based on the ideXlab platform.
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a novel shewanella isolate enhances corrosion by using metallic iron as the electron donor with fumarate as the electron acceptor
Applied and Environmental Microbiology, 2018Co-Authors: Jo Philips, Niels Van Den Driessche, Kim De Paepe, Antonin Prevoteau, Jeffrey A Gralnick, Jan Arends, Korneel RabaeyAbstract:The involvement of Shewanella sp. in biocorrosion is often attributed to their Fe(III) reducing properties, but they could also affect corrosion by using metallic iron as electron donor. Previously, we isolated Shewanella strain 4t3-1-2LB from an acetogenic community enriched with Fe(0) as sole electron donor. Here, we investigated its use of Fe(0) as electron donor with fumarate as electron acceptor and explored its corrosion Enhancing Mechanism. Without Fe(0), strain 4t3-1-2LB fermented fumarate to succinate and CO 2 , as was shown by the reaction stoichiometry and pH. With Fe(0), strain 4t3-1-2LB completely reduced fumarate to succinate and increased the Fe(0) corrosion rate 7.0 ± 0.6 times in comparison to abiotic controls (based on the succinate versus abiotic hydrogen formation rate). Fumarate reduction by strain 4t3-1-2LB was, at least in part, supported by chemical hydrogen formation on Fe(0). Filter-sterilized spent medium only increased the hydrogen generation rate 1.5 times, thus extracellular hydrogenase enzymes appear insufficient to explain the enhanced corrosion rate. Electrochemical measurements suggested that strain 4t3-1-2LB did not excrete dissolved redox mediators. Exchanging the medium and SEM imaging indicated cells were attached to Fe(0). Possibly, strain 4t3-1-2LB used a direct Mechanism to withdraw electrons from Fe(0), or favored chemical hydrogen formation on Fe(0) through maintaining low hydrogen concentrations. In co-culture with an Acetobacterium strain, strain 4t3-1-2LB did not enhance acetogenesis from Fe(0). This work describes a strong corrosion enhancement by a Shewanella strain through its use of Fe(0) as electron donor and gained insights in its corrosion Enhancing Mechanism. Importance Shewanella sp. are frequently found on corroded metal structures. Their role in microbial influenced corrosion has mainly been attributed to their Fe(III) reducing properties and, therefore, been studied with the addition of an electron donor (lactate). Shewanella sp., however, can also use solid electron donors, such as cathodes and potentially Fe(0). In this work, we show that the electron acceptor fumarate supported the use of Fe(0) as electron donor by Shewanella strain 4t3-1-2LB, which caused a 7.0 ± 0.6 times increase of the corrosion rate. The corrosion Enhancing Mechanism likely involved cell-surface associated components in direct contact with the Fe(0) surface, or maintenance of low hydrogen levels by attached cells, thereby favoring chemical hydrogen formation by Fe(0). This work sheds new light on the role of Shewanella sp. in biocorrosion, while the insights in the corrosion Enhancing Mechanism contribute to the understanding of extracellular electron uptake processes.
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A novel Shewanella isolate enhances corrosion by using metallic iron as the electron donor with fumarate as the electron acceptor
'American Society for Microbiology', 2018Co-Authors: Jo Philips, Van Den Driessche Niels, De Paepe Kim, Prévoteau Antonin, Gralnick, Jeffrey A, Arends Jan, Rabaey KorneelAbstract:The involvement of Shewanella spp. in biocorrosion is often attributed to their Fe(III)-reducing properties, but they could also affect corrosion by using metallic iron as an electron donor. Previously, we isolated Shewanella strain 4t3-1-2LB from an acetogenic community enriched with Fe(0) as the sole electron donor. Here, we investigated its use of Fe(0) as an electron donor with fumarate as an electron acceptor and explored its corrosion-Enhancing Mechanism. Without Fe(0), strain 4t3-1-2LB fermented fumarate to succinate and CO2, as was shown by the reaction stoichiometry and pH. With Fe(0), strain 4t3-1-2LB completely reduced fumarate to succinate and increased the Fe(0) corrosion rate (7.0 +/- 0.6)-fold in comparison to that of abiotic controls (based on the succinate-versus-abiotic hydrogen formation rate). Fumarate reduction by strain 4t3-1-2LB was, at least in part, supported by chemical hydrogen formation on Fe(0). Filter-sterilized spent medium increased the hydrogen generation rate only 1.5-fold, and thus extracellular hydrogenase enzymes appear to be insufficient to explain the enhanced corrosion rate. Electrochemical measurements suggested that strain 4t3-1-2LB did not excrete dissolved redox mediators. Exchanging the medium and scanning electron microscopy (SEM) imaging indicated that cells were attached to Fe(0). It is possible that strain 4t3-1-2LB used a direct Mechanism to withdraw electrons from Fe(0) or favored chemical hydrogen formation on Fe(0) through maintaining low hydrogen concentrations. In coculture with an Acetobacterium strain, strain 4t3-1-2LB did not enhance acetogenesis from Fe(0). This work describes a strong corrosion enhancement by a Shewanella strain through its use of Fe(0) as an electron donor and provides insights into its corrosion-Enhancing Mechanism. IMPORTANCE Shewanella spp. are frequently found on corroded metal structures. Their role in microbial influenced corrosion has been attributed mainly to their Fe(III)-reducing properties and, therefore, has been studied with the addition of an electron donor (lactate). Shewanella spp., however, can also use solid electron donors, such as cathodes and potentially Fe(0). In this work, we show that the electron acceptor fumarate supported the use of Fe(0) as the electron donor by Shewanella strain 4t3-1-2LB, which caused a (7.0 +/- 0.6)-fold increase of the corrosion rate. The corrosion-Enhancing Mechanism likely involved cell surface-associated components in direct contact with the Fe(0) surface or maintenance of low hydrogen levels by attached cells, thereby favoring chemical hydrogen formation by Fe(0). This work sheds new light on the role of Shewanella spp. in biocorrosion, while the insights into the corrosion-Enhancing Mechanism contribute to the understanding of extracellular electron uptake processes
Thierry Rakotoarivelo - One of the best experts on this subject based on the ideXlab platform.
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privacy utility tradeoff in a guessing framework inspired by index coding
International Symposium on Information Theory, 2020Co-Authors: Yucheng Liu, Ni Ding, Parastoo Sadeghi, Thierry RakotoariveloAbstract:This paper studies the tradeoff in privacy and utility in a single-trial multi-terminal guessing (estimation) framework using a system model that is inspired by index coding. There are n independent discrete sources at a data curator. There are m legitimate users and one adversary, each with some side information about the sources. The data curator broadcasts a distorted function of sources to legitimate users, which is also overheard by the adversary. In terms of utility, each legitimate user wishes to perfectly reconstruct some of the unknown sources and attain a certain gain in the estimation correctness for the remaining unknown sources. In terms of privacy, the data curator wishes to minimize the maximal leakage: the worst-case guessing gain of the adversary in estimating any target function of its unknown sources after receiving the broadcast data. Given the system settings, we derive fundamental performance lower bounds on the maximal leakage to the adversary, which are inspired by the notion of confusion graph and performance bounds for the index coding problem. We also detail a greedy privacy Enhancing Mechanism, which is inspired by the agglomerative clustering algorithms in the information bottleneck and privacy funnel problems.
S Awazu - One of the best experts on this subject based on the ideXlab platform.
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absorption Enhancing Mechanism of edta caprate and decanoylcarnitine in caco 2 cells
Journal of Pharmaceutical Sciences, 1996Co-Authors: M Tomita, M Hayashi, S AwazuAbstract:The Mechanism of paracellular expansion by absorption enhancers, e.g., EDTA, sodium caprate (C10), and decanoylcarnitine (DC), was studied, the focus being on the process of actin microfilament contraction in the tight junction. The effects of various inhibitors such as KN-62 (a specific inhibitor of Ca2+/calmodulin dependent protein kinase), H7 (a protein kinase C (PKC) inhibitor), and W7 (a calmodulin antagonist) were examined on the paracellular expansion by the enhancers in Caco-2 cells. From the experimental results, the following Mechanisms were suggested. EDTA activates PKC by depletion of extracellular calcium via chelation resulting in expansion of the paracellular route. C10 increases the intracellular calcium level by an interaction with the cell membrane independent of cell polarity resulting in contraction with actin microfilament. DC interacts specifically with the apical membrane to increase the intracellular calcium level, but the mechanistic details subsequent to the increase of calcium are not clear.
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absorption Enhancing Mechanism of sodium caprate and decanoylcarnitine in caco 2 cells
Journal of Pharmacology and Experimental Therapeutics, 1995Co-Authors: M Tomita, M Hayashi, S AwazuAbstract:The Mechanism of action of the absorption enhancers such as sodium caprate (C10) and decanoylcarnitine (DC) was examined. Both C10 and DC increased the epithelial permeability of fluorescein isothiocyanate dextran 4000 and decreased the transepithelial electrical resistance in Caco-2 cell monolayer. Irrespective of the presence or absence of mucosal calcium, C10 rapidly increased intracellular calcium levels dose-dependently. Compound 48/80, a phospholipase C inhibitor, prevented the increases of the intracellular calcium level and permeability of fluorescein isothiocyanate dextran 4000 by C10. Furthermore, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride, a strong calmodulin inhibitor, also significantly decreased the Enhancing effect of C10. These results suggest that C10 releases calcium from intracellular stores via activation of phospholipase C in plasma membrane. The increase of the calcium levels was considered to induce the contraction of calmodulin-dependent actin microfilament, followed by dilatation of the paracellular route. Although DC also increased intracellular calcium levels, neither compound 48/80 nor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride decreased the Enhancing effect of DC. The Enhancing Mechanisms were different for C10 and DC.