Antibacterial and Antibiofilm Activities of Novel Antimicrobial Peptides against Multidrug-Resistant Enterotoxigenic Escherichia Coli

Post-weaning diarrhea due to enterotoxigenic Escherichia coli (ETEC) is a common disease of piglets and causes great economic loss for the swine industry. Over the past few decades, decreasing effectiveness of conventional antibiotics has caused serious problems because of the growing emergence of multidrug-resistant (MDR) pathogens. Various studies have indicated that antimicrobial peptides (AMPs) have potential to serve as an alternative to antibiotics owing to rapid killing action and highly selective toxicity. Our previous studies have shown that AMP GW-Q4 and its derivatives possess effective antibacterial activities against the Gram-negative bacteria. Hence, in the current study, we evaluated the antibacterial efficacy of GW-Q4 and its derivatives against MDR ETEC and their minimal inhibition concentration (MIC) values were determined to be around 2~32 μg/mL. Among them, AMP Q4-15a-1 with the second lowest MIC (4 μg/mL) and the highest minimal hemolysis concentration (MHC, 256 μg/mL), thus showing the greatest selectivity (MHC/MIC = 64) was selected for further investigations. Moreover, Q4-15a-1 showed dose-dependent bactericidal activity against MDR ETEC in time–kill curve assays. According to the cellular localization and membrane integrity analyses using confocal microscopy, Q4-15a-1 can rapidly interact with the bacterial surface, disrupt the membrane and enter cytosol in less than 30 min. Minimum biofilm eradication concentration (MBEC) of Q4-15a-1 is 4× MIC (16 μg/mL), indicating that Q4-15a-1 is effective against MDR ETEC biofilm. Besides, we established an MDR ETEC infection model with intestinal porcine epithelial cell-1 (IPEC-1). In this infection model, 32 μg/mL Q4-15a-1 can completely inhibit ETEC adhesion onto IPEC-1. Overall, these results suggested that Q4-15a-1 may be a promising antibacterial candidate for treatment of weaned piglets infected by MDR ETEC.     

Detecting Sybil attacks in Wireless Sensor Networks using neighboring information

As the prevalence of Wireless Sensor Networks (WSNs) grows in the military and civil domains, the need for network security has become a critical concern. In a Sybil attack, the WSN is subverted by a malicious node which forges a large number of fake identities in order to disrupt the network’s protocols. In attempting to protect WSNs against such an attack, this paper develops a scheme in which the node identities are verified simply by analyzing the neighboring node information of each node. The analytical results confirm the efficacy of the approach given a sufficient node density within the network. The simulation results demonstrate that for a network in which each node has an average of 9 neighbors, the scheme detects 99% of the Sybil nodes with no more than a 4% false detection rate. The experiment result shows that the Sybil nodes can still be identified when the links are not symmetric.     

Comments on "Software process representation and analysis for framework instantiation"

When studying [T.C. Oliveira et al. (2004)], we found an error and some ambiguous parts. In this paper, we state those errors.     

Adjusting Sink Location to Reduce End-to-End Delay in Low-Duty-Cycle Wireless Sensor Networks

Low-duty-cycle mechanisms can reduce the energy consumption significantly in wireless sensor networks (WSNs). Sensors stay dormant most of the time to save their energy and wake up based on their needs. However, such a technique, while prolonging the network lifetime, sets excessive challenges for reducing the end-to-end (E2E) delay within the network. In this paper, the centralized cluster-based location finding (CCLF) algorithm is proposed to reduce the high latency in low-duty-cycle WSNs by finding a suitable position for the sink. The algorithm is mainly composed of three steps:a) the cluster construction, b) the fast look-up table (FLU-table) construction, and c) the sink location decision. The simulation results show that the performance of the CCLF algorithm is significantly similar to that of the optimal algorithm. Moreover, the CCLF algorithm requires less operation time compared with the optimal algorithm.     

Improving routing distance for geographic multicast with Fermat points in mobile ad hoc networks

In mobile ad hoc networks (MANETs), each node has the ability to transmit, receive, and route packets, and also moves through the field either randomly or in accordance with a pre-planned route. For enhancing the performance of MANETs, reducing the routing distance is a primary concern. For either ad hoc or static networks, the problem of minimizing the overall routing distance during multicasting is NP-complete. Therefore, it is difficult to determine an optimal solution. This paper presents an efficient geographic multicast protocol, designated as GMFP, based on the use of Fermat points. The objective of GMFP is to improve the overall routing distance for multicast tasks. Through a series of simulations, it is shown that GMFP outperforms the conventional Position-Based Multicast protocol and FERMA protocol in terms of the total routing distance, the packet transmission delay, the packet delivery ratio, and the node energy consumption. The performance improvements provided by GMFP are apparent as the scale of the network topology increases.     

Large arrays of microcavity plasma devices for active displays and backlighting

Developments of the past several years in the technology of microcavity plasma devices having characteristic dimensions of 10-100 /spl mu/m suggests their applicability to the next generation of active and passive displays. Two examples of device structures that are well suited for economically manufactured arrays of large active area are presented. Arrays as large as 500/spl times/500 (2.5/spl middot/10/sup 5/) pixels of Si inverted pyramid microplasma devices, with emitting apertures of 50/spl times/50 /spl mu/m/sup 2/ and designed for AC or bipolar excitation, have been designed and operated successfully in the rare gases at pressures up to and beyond one atmosphere. Multilayer Al/nanostructured Al/sub 2/O/sub 3/ microplasma devices having 100-300 /spl mu/m diam. cylindrical microcavities are robust and operate in the abnormal glow mode for rare gas or Ar/2-5% N/sub 2/ mixture pressures of 500-700 torr. Grown by a wet chemical process, the nanoporous Al/sub 2/O/sub 3/ dielectric yields a lightweight, flexible structure that produces intense visible or ultraviolet emission when driven by sinusoidal AC or bipolar voltage waveforms.     

IL-8 as a Potential Therapeutic Target for Periodontitis and Its Inhibition by Caffeic Acid Phenethyl Ester In Vitro

Salivary levels of interleukin-8 (IL-8) are elevated in patients with periodontitis. Caffeic acid phenethyl ester (CAPE) improves the periodontal status in subjects. However, whether CAPE can reduce IL-8 expression is unclear. We collected saliva to determine proinflammatory cytokine levels and used subgingival calculus and surrounding tissues from patients with periodontitis for oral microbiota analysis via 16s ribosomal RNA gene sequencing. THP-1 cells were stimulated with sterile-filtered saliva from patients, and target gene/protein expression was assessed. IL-8 mRNA expression was analyzed in saliva-stimulated THP-1 cells treated with CAPE and the heme oxygenase-1 (HO-1) inhibitor tin-protoporphyrin (SnPP). In 72 symptomatic individuals, IL-8 was correlated with periodontal inflammation (bleeding on probing, r = 0.45; p < 0.001) and disease severity (bleeding on probing, r = 0.45; p < 0.001) but not with the four oral microbiota species tested. Reduced salivary IL-8 secretion was correlated with effective periodontitis treatment (r = 0.37, p = 0.0013). In THP-1 cells, saliva treatment induced high IL-8 expression and IKK2 and nuclear factor-κB (NF-κB) phosphorylation. However, the IKK inhibitor BMS-345541, NF-κB inhibitor BAY 11-7082, and CAPE attenuated saliva-induced IL-8 expression. CAPE induced HO-1 expression and inhibited IKK2, IκBα, and NF-κB phosphorylation. Blocking HO-1 decreased the anti-inflammatory activity of CAPE. The targeted suppression of IL-8 production using CAPE reduces inflammation and periodontitis.     

Sensor Position Determination with Flying Anchors in Three-Dimensional Wireless Sensor Networks

This paper presents a range-free position determination (localization) mechanism for sensors in a three-dimensional wireless sensor network based on the use of flying anchors. In the scheme, each anchor is equipped with a GPS receiver and broadcasts its location information as it flies through the sensing space. Each sensor node in the sensing area then estimates its own location by applying basic geometry principles to the location information it receives from the flying anchors. The scheme eliminates the requirement for specific positioning hardware, avoids the need for any interaction between the individual sensor nodes, and is independent of network densities and topologies. The performance of the localization scheme is evaluated in a series of simulations performed using ns-2 software and is compared to that of the Centroid and Constraint range-free mechanisms. The simulation results demonstrate that the localization scheme outperforms both Centroid and Constraint in terms of a higher location accuracy, a reduced localization time, and a lower beacon overhead. In addition, the localization scheme is implemented on the Tmote Sky for validating the feasibility of the localization scheme.