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.     

Prenatal cocaine exposure induces deficits in Pavlovian conditioning and sensory preconditioning among infant rat pups.

Offspring derived from Sprague-Dawley dams that received daily sc injection of 40 mg/kg 3 cc–2 cocaine hydrochloride (C40) or saline (LC) from Gestational Days 8–20 were tested for first-order Pavlovian conditioning and sensory preconditioning at Postnatal Days 8 (P8), P12, and P21. Although C40 dams gained significantly less weight than LC dams, pup body weights did not differ between the 2 groups. Significant sensory preconditioning was obtained at P8 and P12 (but not at P21) in LC offspring, confirming previous reports (e.g., L. P. Spear et al; see record 1989-35900-001) of decline in performance in this task during ontogeny. In contrast, C40 offspring failed to exhibit sensory preconditioning at any test age. In addition, C40 pups tested at P8 did not display significant first-order conditioning. Taken together these results suggest a more general deficit in cognitive functioning rather than a delay in cognitive development in prenatally cocaine-exposed offspring. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of an objective mental workload assessment tool based on Rasmussen's skill–rule–knowledge framework

It is important to monitor operators’ mental workload during the operation phase. Physiological measurement approaches could record the operator's mental data continuously, and might be less interruptive on the work activities. However, these methods often require the attachment of physical sensors, which are not unobtrusive in the physical sense. Furthermore, the individual difference makes calibrating to each individual tedious and requires trained persons to use. Often high noise-to-signal ratio data are hard to analyze. Due to these factors, physiological workload measurements are hardly widely applied in practical fields. In this study, an objective, non-intrusive and performance-based mental workload predictive model was proposed with high validity (R² = 0.51), which can be applied during the operation phrase. This model, developed based on the Rasmussen's skill–rule–knowledge framework, is comprised of two novel cognitive indices, the attention required index and uncertainty index. It can be used as the basis for establishing an early online warning system automatically. Furthermore, this model also predicts the types of error-prone tasks. This kind of information is expected to provide managers and supervisors with opportunities to intervene and improve tasks before error occurred. Finally, the predictive model proposed in this paper requires more practical application in fields to be completed.     

Influence of alanine uptake on Staphylococcus aureus surface charge and its susceptibility to two cationic antibacterial agents,nisin and low molecular weight chitosan

Low molecular weight chitosan (LMWC) and nisin, recognized as cationic antibacterial agents (CAAs), inhibit bacterial growth by interacting with the anionically charged cell wall. In this study, alanine uptake significantly reduced the anionic cell surface charge, as determined by the zeta potential (ZP) measurements, of Staphylococcus aureus, resulting from the incorporation of d-alanine into the cell wall. Minimum inhibitory concentration (MIC) tests and growth inhibition curves revealed that LMWC and nisin possessed inverse antibacterial activity against three strains of S. aureus, depending on the strains’ net charge. A twofold reduction in the MIC value of nisin was obtained against S. aureus, inoculated in a 1.0% d- or l-alanine-augmented trypticase soy broth medium. A flocculation test demonstrated that neutralizing the anionic surface charge using d-alanine reduced the adsorption of S. aureus onto LMWC. Furthermore, the reduced surface net charge could enhance the colonization capacity of S. aureus on glass.     

BLAST-DVC: BitpLAne SelecTive distributed video coding

This paper presents a BitpLAne SelecTive (BLAST) distributed video coding (DVC) system. In the proposed system, the significance of each bitplane is measured at the decoder based on an estimated distortion-rate ratio that makes use of a correlation model for the original source information and the side information. Only the syndrome bits of the bitplanes that have estimated distortion-rate ratios higher than a target distortion-rate ratio, are transmitted and are used to decode the associated bitplanes. The remaining bitplanes are estimated using a minimum-distance symbol reconstruction scheme which makes use of the side information and the LDPCA-decoded bitplanes. Coding results and comparisons with existing DVC schemes and with H.264 intra- and inter-frame coding are presented to illustrate the performance of the proposed system.     

Influence of growth curve phase on electricity performance of microbial fuel cell by Escherichia coli

The microbial fuel cell of Escherichia coli can convert microorganism biochemistry energy into electrical energy. To realize the influence of the growth curve phase with respect to different culture times on electricity performance, three kinds of E. coli (BCRC No. 10322, 10675, 51534) are selected, and it is both required and important to improve the performance of the microbial fuel cell (MFC). Results show that the BCRC No. 51534 of E. coli would be a better choice because a larger open-circuit voltage of 0.88 V and a limiting current of 10.1 mA possessed by it would result in an excellent power density of 547 mW/m². In addition, the selection of culture timing set as at the middle of the logarithmic phase and phase transition from logarithmic to stationary is suggested because the growth curve is suitable for electricity generation of the MFC. These observations would be useful for the improvement of the MFC.     

Promotion of Pt-Ru/C catalysts driven by heat treated induced surface segregation for methanol oxidation reaction

Carbon supported Pt-Ru/C (1:1) alloy catalysts supplied by E-TEK are widely used for fuel cell research. Heat treatments in various atmospheres are conducted for the promotion of the methanol oxidation reaction (MOR) and the investigation of the structure-activity relationship (SAR) of the catalysts. The alloy structures, surface compositions, surface species, and electro-catalytic activities of the alloy catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV), respectively. The as-received Pt-Ru/C catalysts have a Ru rich in the inner core and Pt rich on the outer shell structure. Thermal treatments on the catalysts induce Ru surface segregation in different extents and thereby lead to their alteration of the alloying degrees. O₂ treatment results in obvious Ru segregation and formation of RuO₂. Catalysts treated in H₂ have the highest I_f/I_b value in the CV scans among all samples, indicating the catalysts have the excellent CO de-poisoning ability as evidenced by anodic CO stripping experiments. N₂ treatment may serve as an adjustment process for the surface composition and structure of the catalysts, which can suppress the surface Pt depletion (∼60% Pt on the surface), make the components stable and hence promote the MOR significantly.     

Flow Characteristics around a Circular Cylinder Placed Horizontally above a Plane Boundary

Flow characteristics around a circular cylinder positioned near a plane boundary (on which laminar boundary layer flow develops in the absence of circular cylinder), are investigated for Reynolds numbers R ranging from 7.8×102 to 1.15×104. Particle image velocimetry and fiber laser Doppler velocimetry were used to measure the velocity fields and velocity time histories, respectively. Flow structures are particularly revealed using flow visualization technique at R = 7.8×102 for gap ratios G/D (where G is the net gap between the surface of circular cylinder and the plane boundary), varying from 0 to 4. Based on the experimental results, the variation of Strouhal number of shedding vortex (or eddy) with G/D, the mechanism of vortex shedding suppression, and the streamwise velocity profiles of the upper shear layers and gap flows for small G/D are all discussed. Although the regular, alternate vortex shedding is suppressed for G/D<0.5, the periodicity could be detected due to the vortex (or eddy) shedding from the upper shear layer of the circular cylinder. Gap flow switching randomly is found and first put forward to be the main reason of multipeak or broadband spectral characteristics of the shedding event at a certain small gap ratio. It is also found that the streamwise velocity profiles of the upper shear layer, where periodic shedding eddies originate, exhibit well-behaved similarity. In addition, a unique similarity of mean streamwise velocity profiles of the gap flows is demonstrated for G/D ? 0.3. For R<4×103, the S increases as G/D decreases to its maximum around G/D ? 0.5 and then decreases as G/D decreases. For R ≥ 4×103, although most of the previous studies indicate that the S is insensitive to G/D, the present study shows that S still increases as G/D decreases but the variations of S are in a small range (i.e., 0.18 ? S ? 0.22).     

Fabrication of micro sensors on a flexible substrate

Flexible micro temperature and humidity sensors on parylene thin films were designed and fabricated using a micro-electro-mechanical-systems (MEMS) process. Based on the principles of the thermistor and the ability of a polymer to absorb moisture, the sensing device comprised gold wire and polyimide film. The flexible micro sensors were patterned between two pieces of parylene thin film that had been etched using O₂ plasma to open the contact pads. The sacrificial Cr spacer layer was removed from the Cr etchant to release the flexible temperature and humidity sensors from the silicon substrate. Au was used to form the sensing electrode of the sensors while Ti formed the adhesion layer between the parylene and Au. The thickness of the device was 7 ± 1 μm, so the sensors attached easily to highly curved surfaces. The sensitivities of the temperature and humidity sensor were 4.81 × 10⁻³ °C⁻¹ and 0.03 pF/%RH, respectively. This work demonstrates the feasibility and compatibility of thin film sensor applications based on flexible parylene. The sensor can be applied to fuel cells or components that must be compressed.