Lectins as antimicrobial agents Breitenbach Barroso Coelho, L.C.; Marcelino dos Santos Silva, P.; Felix de Oliveira, W. ...
Journal of applied microbiology,
November 2018, 2018-Nov, 2018-11-00, 20181101, Volume:
125, Issue:
5
Journal Article
Peer reviewed
Open access
Summary
The resistance of micro‐organisms to antimicrobial agents has been a challenge to treat animal and human infections, and for environmental control. Lectins are natural proteins and some are ...potent antimicrobials through binding to carbohydrates on microbial surfaces. Oligomerization state of lectins can influence their biological activity and maximum binding capacity; the association among lectin polypeptide chains can alter the carbohydrate–lectin binding dissociation rate constants. Antimicrobial mechanisms of lectins include the pore formation ability, followed by changes in the cell permeability and latter, indicates interactions with the bacterial cell wall components. In addition, the antifungal activity of lectins is associated with the chitin‐binding property, resulting in the disintegration of the cell wall or the arrest of de novo synthesis from the cell wall during fungal development or division. Quorum sensing is a cell‐to‐cell communication process that allows interspecies and interkingdom signalling which coordinate virulence genes; antiquorum‐sensing therapies are described for animal and plant lectins. This review article, among other approaches, evaluates lectins as antimicrobials.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The purinergic system participates in the control of blood pressure. Hypertension promotes the occurrence of gastrointestinal disorders such as intestinal inflammation and gastric emptying delay. ...This study aimed i) to investigate the participation of the P2X7 receptor blocker Brilliant Blue G (BBG) on gastric emptying of solids and changes in oxidative stress in the gastric fundus, duodenum, and colon of spontaneously hypertensive rats (SHR) and ii) to study the putative relationship of this effect with the renin-angiotensin system. Rats were divided into five groups: Control, SHR, SHR+BBG, SHR+BBG+ATP, and SHR+BBG+ANG II. In the gastrointestinal tract, we assessed gastric emptying (GE) and oxidative stress markers (NOx, MPO, GSH, SOD). We observed a decrease in the GE rate (P<0.05) in SHR vs control rats (21.8±2.0% vs 42.8±3.5%). The decrease in GE was returned (P<0.05) to control levels by BBG in SHR rats (21.8±2.0% vs 41.6±3.2%). Co-administration of ATP or ANG II together with BBG bypassed the effect of the P2X7 antagonist on GE in SHR (P<0.05) (21.9±5.0% vs 25.6±3.0% vs 41.6±3.2%). The MPO activity increased (P<0.05) in the gastric fundus of SHR compared to control rats (6.12±2.26 vs 0.077±0.02 UMPO/mg tissue); this effect was prevented (P<0.05) by BBG (0.55±0.15 vs 6.12±2.26 UMPO/mg tissue). Data demonstrated that blockage of P2X7 receptors with BBG can improve the GE delay and oxidative stress biomarkers in SHR animals. This preventive effect of BBG on GE delay was abrogated by ANG II and ATP, thus prompting crosstalk between renin-angiotensin and the purinergic signaling systems underlying this phenomenon.
Zymomonas mobilis has long attracted attention owing to its capacity to ferment hexose to ethanol. From a taxonomic viewpoint, Z. mobilis is a unique species of the genus Zymomonas, separated into ...three subspecies, Z. mobilis subsp. mobilis, Z. mobilis subsp. pomaceae and Z. mobilis subsp. francensis on the basis of physiological tests, which are often unreliable owing to the genetic proximity among these species. Currently, the use of molecular techniques is more appropriate for identification of these bacterial subspecies. In this study, the 32 strains of Z. mobilis present in the UFPEDA bacterial collection were characterized using molecular techniques, such as sequencing of the 16S rDNA gene and its theoretical restriction profile, classifying them as members of the subspecies, Z. mobilis subsp. mobilis. In addition, anaerobic cultivations were performed, which showed the biological diversity of the strains in terms of growth, sugar consumption and ethanol production. From these results, it was possible to identify the strain Z‐2‐80 as a promising bacterium for use in the fermentation process.
Significance and Impact of the Study
Zymomonas mobilis is a bacterium of great relevance to biotechnology, owing to its capacity to ferment hexose to ethanol. On a molecular basis, 32 isolates were identified as Z. mobilis subsp. mobilis. However, intraspecific diversity was identified when these were grown under strictly anaerobic conditions. The results obtained from this study suggest a strain of Z. mobilis as an alternative for use in the fermentation process.
Significance and Impact of the Study:Zymomonas mobilis is a bacterium of great relevance to biotechnology, owing to its capacity to ferment hexose to ethanol. On a molecular basis, 32 isolates were identified as Z. mobilis subsp. mobilis. However, intraspecific diversity was identified when these were grown under strictly anaerobic conditions. The results obtained from this study suggest a strain of Z. mobilis as an alternative for use in the fermentation process.
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•A probabilistic description of the distance relay operation, applied to transmission line protection, is incorporated into a methodology to assess protection systems performance previously developed ...by the authors.•The new methodology allows quantifying the influence of the equipment failure rate on the transmission line protection system performance, as well as the influence of the fault location.•This methodology is applied to a transmission line protection scheme with one aided communication channel.•The methodology proves to be adequate (1) to quantify the benefits of using communication channels in transmission line protection; (2) to be used in a cost/benefit analysis, in order to establish adequate time to repair and service levels associated to communication channels.•Furthermore it shows adequate to assess different protection system architectures.
A performance analysis methodology for transmission line primary protection systems is presented, based on a probabilistic approach to protection system successful operation. The protection system operation is represented by reliability graphs, and a probabilistic model of the distance protection is considered. The system successful operation is described by tie-sets, and solutions are obtained from Monte Carlo simulation. The system elements are characterized by the reliability factors: equipment failure rate and time to repair. The system performance is assessed by the availability index.
The developed methodology is applied to a transmission line protection scheme with one aided communication channel. Results allow quantifying the influence of the fault location on the protection system performance. Results also show the influence of the equipment failure rate on the system performance. The developed methodology proves to be adequate to quantify the benefits of using communication channels in transmission line protection. Furthermore it is adequate to assess different protection system architectures. A comparative performance analysis, considering four different transmission line protection schemes, can be found in the Part II paper.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The significance of bottom-up controls on biological communities has been a long-standing topic of interest in ecology. However, before environmental effects on communities can be properly assessed, ...a thorough knowledge of the individual species' responses is required. We studied effects of food availability on population development and on different life-history traits in three species of bacterial-feeding nematodes,
Diplolaimelloides oschei,
Diplolaimelloides meyli (both Monhysteridae) and
Pellioditis marina (Rhabditidae), which co-occur on macrophyte detritus in the Westerschelde Estuary (SW Netherlands). The bacteria
Escherichia coli was offered in five food-availability treatments corresponding to initial cell densities from 3
×
10
10 cells ml
−
1
to 3
×
10
7 cells ml
−
1
. The three bacterial-feeding nematode species studied here showed differential responses to food availability, which agreed with the general idea that Rhabditidae have extreme colonization abilities under very high food availability, while Monhysteridae tend to have a somewhat slower population development and comparatively lower food requirements. Several life-history traits, including juvenile mortality and development time, did not exhibit a clear food-availability dependence, but bioenergetics-related parameters did. Results on the F1 generation may, however, be affected by strong maternal effects on life-history traits of their progeny. Patterns of food-availability dependence of population increase and size at maturity were similar in
P. marina. Both
Diplolaimelloides species, however, exhibited a large body size at maturity but a very low population increase at the highest food availability, suggesting a trade-off between biomass and reproduction. Comparison with published data on other nematode species reveals that nematode responses to food availability as well as to other environmental factors are highly species-specific.
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•Promoting voltage sags prediction in network planning procedures is advocated.•New voltage sag indices are proposed as planning criteria.•The indices are probabilistically evaluated using a voltage ...sag prediction method developed by the authors.•The methodology includes the probabilistic description of fault resistance and a solid basis for determining dip duration.•Percentile values of the voltage sags indices are extracted and used as network planning criteria.•The methodology is applied to the IEEE RTS network to assess the number of voltages sags within the operator's responsibility region.
This paper presents a stochastic approach for predicting voltage sags amplitude and duration in network planning. It is suggested that a targeted voltage sags index value is incorporated as additional planning criterion. The developed methodology is based on Monte Carlo simulation and considers the stochastic nature of power system faults, in space and time, as well as the probabilistic nature of successful operation by primary protection systems. Adequate voltage sags site indices for network site characterization in network planning are proposed. The concept of responsibility-sharing between network operators and network users is incorporated, by considering a voltage sag responsibility-sharing curve.
Simulation outcomes are time series of the proposed indices, which are statistically analyzed and presented as probability distribution functions. Site characterization is made using representative values, average and percentile, extracted from the computed distribution functions.
The methodology is applied to the IEEE RTS to assess the number of voltages sags within the operator's responsibility region, expected to occur in each network site. Average and percentile values are computed for all network sites, allowing to rank them according to the provided voltage quality, as sags are concerned.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Foliar application of 24-epibrassinolide (EBL) has been used in different crops to reduce the adverse effects of water stress, but no studies have been found with soybean crop in the flowering stage, ...involving this bioregulator. Thus, this work aimed to evaluate the efficiency of the 24-epibrassinolide on growth, physiological mechanisms and antioxidant defense in soybean in the flowering phase under drought stress and rehydration. The EBL mitigated the effect of water stress on the shoot growth of soybean plants. In irrigated plants, EBL promoted improvements in gas exchange, photosynthetic efficiency, chlorophyll synthesis, and increase in shoot biomass. Plants under water deficit treated with EBL showed reductions in stomatal conductance and photosynthesis similar to those found in plants without EBL. However, the EBL mitigated the damage caused by water deficit in soybean, which was evidenced by the reduction of physiological damage to relative water content, leaf water potential, and effective equantum efficiency of photosystem II (Φ
PSII
). In addition, EBL minimized oxidative stress in plants, stimulating greater activities of the antioxidant enzymes catalase (CAT) and ascorbate peroxidase (APX),lower electrolyte leakage, and lipid peroxidation, which contributed to the lower degradation of chlorophylls. The EBL contributed with the higher production of dry matter and grain production in plants subjected to stress followed by rehydration. This set of information suggests that EBL not only partially alleviated the deleterious effect of drought stress on soybean in the flowering stage, but also participated in the post-stress recovery of soybean plants, which promoted increased growth, dry matter, and yield.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•The proposed fault description is a useful tool for power system planning and design, when a stochastic approach of the power system faults characteristics is adopted.•Fault rate and individual ...fault characteristics, namely fault location, type and resistance, are modeled.•The model is able to reproduce atypical years, as happen in real transmission networks.•The fault resistance model is based on Weibull distribution, with parameters per voltage level.•The model is applied to short-circuit current computation and results are prone to specify network circuit breakers and current transformers probabilistically.
Correct modeling of power system faults is a key issue in a diversity of power system studies, such as in network planning, equipment specification and protection systems coordination. The present paper addresses the probabilistic description of faults, based on available data collected by transmission system operators for different voltage levels. Fault rate and individual fault characteristics are stochastically modeled, namely fault location, type and resistance. A fault resistance model is suggested, based on Weibull distribution, which parameters are set per voltage level. The proposed fault description is a useful tool for power system planning and design, when a stochastic approach of the power system faults characteristics is adopted. Time series of fault input data and simulation results are presented in a common format, so to allow using the same statistical tools as used in power system monitoring and field data reporting. The model is able to reproduce atypical years, as happen in real transmission networks. The developed fault model is used to generate stochastic short-circuit events, which are then used for short-circuit current computation. The methodology is applied to the IEEE RTS and simulation results are shown for the probability of amplitude and time constant values. These results are prone to be used to specify network circuit breakers and current transformers using a probabilistic approach.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•The methodology presented in the Part I paper for the performance analysis of transmission line protection systems, based on a probabilistic approach to system successful operation, is applied to ...four different protection schemes with aided communication channels operating in today's transmission networks.•The system performance takes into account equipment reliability factors: failure rate and time to repair.•New probabilistic performance indicators for transmission line protection are introduced, which are useful for protection system design.•The performance indicators allow quantifying the benefits of the different design options, such as redundancy or equipment sharing.•The new indicators can be used in a cost/benefit analysis, as well as to assess maintenance strategies and equipment reliability requirements.
Following the Part I paper, a comparative performance analysis is presented, considering four different transmission line protection schemes, equipped with aided communication channels. In the Part I paper, the performance analysis methodology was presented, which is based on a probabilistic approach to protection system successful operation. The system performance takes in account equipment reliability factors such as failure rate and time to repair, and is assessed by the availability index. In the present paper, new performance indicators are introduced, which are applicable to transmission line protection system design, as well as to describe its probabilistic operation in other power system studies.
Four different transmission line protection schemes with aided communication channels, operating in today's transmission networks, are compared. The results obtained for the performance indicators allow quantifying the benefits of the different design options. In particular, the effect of relay and communication channel redundancy, as well as communication channel sharing, is highlighted.
Furthermore, results show that the newly defined performance indicators can be used in a cost/benefit analysis, as well as to assess maintenance strategies and communication reliability requirements.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We present the results from the spectroscopic monitoring of WR 140 (WC7pd + O5.5fc) during its latest periastron passage in 2009 January. The observational campaign consisted of a constructive ...collaboration between amateur and professional astronomers. It took place at six locations, including Teide Observatory, Observatoire de Haute Provence, Dominion Astrophysical Observatory and Observatoire du Mont Mégantic. WR 140 is known as the archetype of colliding-wind binaries and it has a relatively long period (
8 yr) and high eccentricity (
0.9). We provide updated values for the orbital parameters, new estimates for the WR and O star masses and new constraints on the mass-loss rates and colliding-wind geometry.
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