Key Role of Staphylococcal Fibronectin-Binding Proteins During the Initial Stage of Staphylococcus aureus Keratitis in Humans

ObjectivesStaphylococcus aureus is one of the main causes of bacterial keratitis in humans. This study was aimed at investigating the mechanisms of S. aureus adhesion to the human corneal epithelium involved during the initial stage of infectious keratitis.MethodsHuman corneas stored in a specific active storage machine that restores a normal pluristratified epithelium were used to assess S. aureus adhesion level to intact and injured tissues using immunostaining. S. aureus adhesion to immobilized fibronectin was measured in microtiter plate. Internalization of S. aureus clinical isolates recovered from keratitis was assessed on human corneal epithelial HCE-2 cells.ResultsSuperficial corneal injury unmasked fibronectin molecules expressed within the human corneal epithelium. S. aureus adhesion level was increased by 117-fold in the area of injured epithelium (p < 0.0001). The deletion of staphylococcal fnbA/B genes decreased by 71% the adhesion level to immobilized fibronectin (p < 0.001). The deletion of fnbA/B genes and the incubation of the corneas with anti-fibronectin blocking antibodies prior to the infection significantly reduced the S. aureus adhesion level to injured corneal epithelium (p < 0.001). Finally, S. aureus clinical isolates triggered its internalization in human corneal epithelial cells as efficiently as the 8325-4 wt.ConclusionS. aureus was almost unable to bind the intact corneal epithelium, whereas a superficial epithelial injury of the corneal epithelium strongly increased S. aureus adhesion, which is mainly driven by the interaction between staphylococcal fibronectin-binding proteins and unmasked fibronectin molecules located underneath the most superficial layer of the corneal epithelium.

Synthesis of a Compound Phosphorus-Nitrogen Intumescent Flame Retardant for Applications to Raw Lacquer

Raw lacquer (RL) is a natural polymer compound with highly promising applications; however, its inflammable attribute restricts the industrial applications. In this study, melamine is used to formulate tri (1-melamine-2-propanol) phosphate (FR-1), after which it is synthesized with ammonium phosphate (FR-2) and diatomite to form a compound phosphorus-nitrogen intumescent flame retardant (IFR). Next, IFR is used as the filling agent that then cross-links with RL, and as such RL/IFR membranes are formed after the curing. The limiting oxygen index (LOI) measurement, the vertical combustion test (UL-94), the microshape calorimetric analysis (CCT), and the thermal gravimetric analysis (TGA) are conducted to examine the combustion resistance and thermal stability of the membranes. Fourier transform infrared spectroscopy (FT-IR) and electron scanning microscope (SEM) are performed to separately characterize the structure and compatibility; the mechanical properties of the membranes are also evaluated. The vertical combustion test results confirm that with 30 wt% of IFR, RL/IFR membranes acquire 12.3% higher LOI and a vertically combustion of V-0 level. The TGA indicates that RL/IFR membranes demonstrate a greater adhesion level, a higher rigidity, and better luster than pure RL membranes.

EPDM/SBR Blends for Skim Compound of Steel Cord Conveyor Belt: Mechanical Properties, Thermal Stability and Adhesion Level

In this paper, the influence of some ingredient concentrations such as SBR ratio, DCP/S, CBS/DPG accelerator, EPDM-g-AM and cord surface on mechanical, thermal aging properties and adhesion between rubber compounds and cord have been investigated. The results showed that with suitable ingredients loading such as EPDM/SBR is 85/15 phr, DCP/S is 2.0/1.5 phr and EPDM-g-AM content is 2.0 phr with respect to rubber, the vulcanizates had good mechanical properties, thermal stability and adhesion level to the zinc/copper galvanized cord. The highest tensile strength, elongation at break and pull out strength reached 18.1 MPa, 432% and 60.3 N/mm respectively, and the highest retention after thermal aging at 150°C for 168 hours was about 0.76.

Characterization of the role of yadK in the pathogenesis of enterohaemorrhagic E. coli O157:H7

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 can use serious diarrhea and haemolytic uremic syndrome. Various factors including adhesins contribute to pathogenesis of EHEC. Previous studies suggested that yadK gene, which encodes a putative fimbrial adhesin in EHEC, may be involved in response of EHEC to acid stress. To characterize role of yadK protein in the pathogenesis of EHEC, recombinant yadK protein was generated and used to immunize rabbit to obtain anti-yadK antiserum, which was able to specifically recognize over-expressed yadK protein in EHEC. Western blotting with anti-yadK revealed a higher level of yadK expression in EHEC under acid adapted-acid stress compared to EHEC under unstressed conditions, which confirmed earlier yadK mRNA studies and indicated that yadK is upregulated in EHEC under acid stress. Finally, we observed that anti-yadK antiserum was able to specifically reduce adhesion of acid stressed EHEC to human epithelial cells compared to adhesion level of unstressed EHEC.

Characterization of the role of yadK in the pathogenesis of enterohaemorrhagic E. coli O157:H7

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 can use serious diarrhea and haemolytic uremic syndrome. Various factors including adhesins contribute to pathogenesis of EHEC. Previous studies suggested that yadK gene, which encodes a putative fimbrial adhesin in EHEC, may be involved in response of EHEC to acid stress. To characterize role of yadK protein in the pathogenesis of EHEC, recombinant yadK protein was generated and used to immunize rabbit to obtain anti-yadK antiserum, which was able to specifically recognize over-expressed yadK protein in EHEC. Western blotting with anti-yadK revealed a higher level of yadK expression in EHEC under acid adapted-acid stress compared to EHEC under unstressed conditions, which confirmed earlier yadK mRNA studies and indicated that yadK is upregulated in EHEC under acid stress. Finally, we observed that anti-yadK antiserum was able to specifically reduce adhesion of acid stressed EHEC to human epithelial cells compared to adhesion level of unstressed EHEC.

Corrosion Behavior of Al7Cu0.2Si0.2Zn0.2Mg0.1 Complex Concentrated Alloy, in 3wt% and 5wt% Na Cl Solution

Complex concentrated alloys (CCAs) are new types of materials, where the equimolar rule proposed by high entropy alloys (HEAs) is modified in relation to the potential of the obtained structures. CCAs expend the compositional space of the conventional alloys, revealing new pathways for material design. The Al7Cu0.2Si0.2Zn0.2Mg0.1 alloy was prepared in an induction furnace, in controlled atmosphere and was cast in a copper ingot mold. The resulting samples of Al7Cu0.2Si0.2Zn0.2Mg0.1 were analysed by chemical, structural, and corrosion resistance. Furthermore, the alloy has been subjected to mechanical tests of hardness, elongation and tensile strength. The corrosion immersion tests were performed in 3wt% and 5wt% NaClsolution, and corrosion indices were measured periodically. The obtained corrosion film was analized by SEM-EDS to determine the composition and structural behaviour. Depending on the adhesion level, the corrosion film remained stable or partially broken and separated in the solution. The sample weight loss presented large variations between the various experimental conditions, but the general tendency was the decrease in the weight of the samples during the corrosion tests. The formation of oxide and chloride layers, during the corrosion process, determined only the dealloying in Al. Other elements remained in initial concentrations. Overall, the resistance of the alloy in saline environment seems to be promising, with significant improvement over the comparable compositions of 2000 and 7000 series aluminium alloys.

Experimental prototyping of the adhesion braking control system design concept for a mechatronic bogie

The dynamic parameters of a roller rig vary as the adhesion level changes. The change in dynamics parameters needs to be analysed to estimate the adhesion level. One of these parameters is noise emanating from wheel–rail interaction. Most previous wheel–rail noise analysis has been conducted to mitigate those noises. However, in this paper, the noise is analysed to estimate the adhesion condition at the wheel–rail contact interface in combination with the other methodologies applied for this purpose. The adhesion level changes with changes in operational and environmental factors. To accurately estimate the adhesion level, the influence of those factors is included in this study. The testing and verification of the methodology required an accurate test prototype of the roller rig. In general, such testing and verification involve complex experimental works required by the intricate nature of the adhesion process and the integration of the different subsystems (i.e. controller, traction, braking). To this end, a new reduced-scale roller rig is developed to study the adhesion between wheel and rail roller contact. The various stages involved in the development of such a complex mechatronics system are described in this paper. Furthermore, the proposed brake control system was validated using the test rig under various adhesion conditions. The results indicate that the proposed brake controller has achieved a shorter stopping distance as compared to the conventional brake controller, and the brake control algorithm was able to maintain the operational condition even at the abrupt changes in adhesion condition.

The Role of a Dipeptide Transporter in the Virulence of Human Pathogen, Helicobacter pylori

Helicobacter pylori harbors a dipeptide (Dpp) transporter consisting of a substrate-binding protein (DppA), two permeases (DppB and C), and two ATPases (DppD and F). The Dpp transporter is responsible for the transportation of dipeptides and short peptides. We found that its expression is important for the growth of H. pylori. To understand the role of the Dpp transporter in the pathogenesis of H. pylori, the expression of virulence factors and H. pylori-induced IL-8 production were investigated in H. pylori wild-type and isogenic H. pylori Dpp transporter mutants. We found that expression of CagA was downregulated, while expression of type 4 secretion system (T4SS) components was upregulated in Dpp transporter mutants. The DppA mutant strain expressed higher levels of outer membrane proteins (OMPs), including BabA, HopZ, OipA, and SabA, and showed a higher adhesion level to gastric epithelial AGS cells compared with the H. pylori 26695 wild-type strain. After infection of AGS cells, H. pylori ΔdppA induced a higher level of NF-κB activation and IL-8 production compared with wild-type. These results suggested that in addition to supporting the growth of H. pylori, the Dpp transporter causes bacteria to alter the expression of virulence factors and reduces H. pylori-induced NF-κB activation and IL-8 production in gastric epithelial cells.

The microbiome of oral cavity patients with periodontitis, adhesive and biofilm forming properties

The microbiome of oral cavity in healthy people and patients with periodontitis was analyzed to determine their adhesive properties and the ability to form biofilms. The study involved 2 groups: healthy, 18 people, and an experimental group, 20 patients with chronic generalized periodontitis moderate severity of the disease. The average age of the studied people was 35-45 years. Material - dental plaque, scraping from the mucous membrane of the back of the tongue, the contents of the periodontal groove and periodontal pocket, as well as oral fluid. The main method of diagnostic was bacteriological. The average adhesion index (AAI) was used to determine adhesion level of microorganisms to epithelial cells of oral cavity’s mucous membrane. The microbiota’s ability to form biofilm was tested on glass and plastic surface. The microbiota of oral cavity of patients with periodontitis was characterized by decrease in the frequency of bacteria of the genera: Streptococcus, Peptostreptococcus, Peptococcus, and an increase in Staphylococcus aureus, Veillonella spp., Bacillus spp. The microbiota of the oral cavity of patients with generalized periodontitis has a greater ability to adhere to the cells of the mucous membrane than in healthy people, while their ability to form biofilms and exhibit pathogenic properties is enhanced. The biofilm formation of microorganisms in healthy and sick people differs both on glass and on plastic surfaces.

INVESTIGATION OF THE CARRIER LIFETIME IN NEUTRON-DOPED SILICON DEPENDING ON THE CONCENTRATION OF THE INITIAL BORON

The dependence of the lifetime of charge carriers ()in monocrystalline silicon on the concentration of light copper and post-diffusion cooling is discussed. The results obtained are explained by the redistribution of non-basic carriers at the adhesion level. In the compensated “p-Si” and the control “p-Si”, the relaxation process occurs in different wasy   98s for “p-Si”, and   5s for “p-Si”.At the same time ,with the growth of te initial concentration of charge carriers (in this case boron-B ) in the compensated silicon, an increase (with equal values ) is observed, which is due to a different degree of micro –uniformity in conductivity in the studied samples.