An alginate lyase functional coating catalysis-independent to prevent P. aeruginosa adhesion

Bacterial colonisation of indwelling devices remains a serious threat in clinical field as it is commonly associated to persistent infections, called biomaterial-associated infections (BAI). Pseudomonas aeruginosa is the most common gram-negative bacillus associated with BAI and its emergence as a nosocomial pathogen is a growing concern. This opportunistic pathogen can produce a capsule-like polysaccharide called alginate that contributes to mucoid biofilm structure and persistent nature of infections. Given alginate's contribution to bacterial virulence, it has long been considered as a promising target for interventional therapies. Alginate lyase, an enzyme able to degrade alginate, has been shown to detach mucoid biofilms from abiotic surfaces and increase their antibiotic susceptibility. In this work, a new approach for alginate lyase was explored. Instead of using this enzyme for the treatment of pre-established mucoid biofilms, the ability of alginate lyase to prevent P. aeruginosa adhesion to a surface was investigated. For that purpose, a polydopamine (pDA) dip-coating strategy was applied for functionalization of biomaterials with alginate lyase. Polycarbonate (PC) substrates were immersed in an alkaline solution of dopamine to form a thin layer of pDA and then transferred into a solution of alginate lyase. Surface characterization was performed with XPS, contact angle measurement and SEM. Two reference strains of P. aeruginosa, a mucoid strain (ATCC 39324) and a non-mucoid (27853) as well as four clinical isolates, were used to assess the anti-adhesive properties of the functional coatings. Surface characterization confirmed the successful and efficient grafting of alginate lyase onto pDA-coated PC substrates. Untreated PC substrates allowed the adhesion of both reference strains and most of bacteria were found alive on these surfaces. Polydopamine-coated substrates had no significant effect on bacterial adhesion compared to the unmodified substrates. Substrates functionalized with alginate lyase exhibited anti-adhesive properties, causing a significant inhibition of the mucoid strain adhesion. Interestingly, substrates immobilized with this enzyme also proved to inhibit the adhesion of the non-mucoid strain and pDA-coated PC substrates immobilized with heat-inactivated enzyme also prevented the attachment of both bacterial strains. These results suggested that alginate lyase immobilized on pDA-coated substrates was able to impair P. aeruginosa adhesion regardless its mucoid phenotype and therefore it could be applied in a different context than cystic fibrosis. For instance, this enzyme could be used to develop functional coatings able to prevent P. aeruginosa infections associated to biomaterials. To confirm this hypothesis, the attachment of 4 clinical strains of P. aeruginosa, isolated from peritoneal dialysis catheters, on alginate lyase functional coatings were also evaluated. Alginate lyase immobilized on the substrates impaired the attachment of the clinical strains with the exception of one as its adhesion to the unmodified PC was already low. In this work, the versatile chemistry of polydopamine was successfully exploited to functionalize biomaterial surfaces with alginate lyase to impart them with anti-adhesive properties. The antibacterial performance of these alginate functional coatings was catalysis-independent which highlights the importance of further studies to better understand its mechanism of action against P. aeruginosa strains

Cardiovascular Responses to High Intensity Aerobic and Anaerobic Exercises

Please view abstract in the attached PDF file

Achromatizing a liquid-crystal spectropolarimeter: Retardance vs Stokes-based calibration of HiVIS

Astronomical spectropolarimeters can be subject to many sources of systematic error which limit the precision and accuracy of the instrument. We present a calibration method for observing high-resolution polarized spectra using chromatic liquid-crystal variable retarders (LCVRs). These LCVRs allow for polarimetric modulation of the incident light without any moving optics at frequencies >10Hz. We demonstrate a calibration method using pure Stokes input states that enables an achromatization of the system. This Stokes-based deprojection method reproduces input polarization even though highly chromatic instrument effects exist. This process is first demonstrated in a laboratory spectropolarimeter where we characterize the LCVRs and show example deprojections. The process is then implemented the a newly upgraded HiVIS spectropolarimeter on the 3.67m AEOS telescope. The HiVIS spectropolarimeter has also been expanded to include broad-band full-Stokes spectropolarimetry using achromatic wave-plates in addition to the tunable full-Stokes polarimetric mode using LCVRs. These two new polarimetric modes in combination with a new polarimetric calibration unit provide a much more sensitive polarimetric package with greatly reduced systematic error.Comment: Accepted in PAS

Metabolic Responses to High Intensity Aerobic and Anaerobic Exercises

Please view abstract in the attached PDF file

Interface modification of clay and graphene platelets reinforced epoxy nanocomposites: a comparative study

The interface between the matrix phase and dispersed phase of a composite plays a critical role in influencing its properties. However, the intricate mecha-nisms of interface are not fully understood, and polymer nanocomposites are no exception. This study compares the fabrication, morphology, and mechanical and thermal properties of epoxy nanocomposites tuned by clay layers (denoted as m-clay) and graphene platelets (denoted as m-GP). It was found that a chemical modification, layer expansion and dispersion of filler within the epoxy matrix resulted in an improved interface between the filler mate-rial and epoxy matrix. This was confirmed by Fourier transform infrared spectroscopy and transmission electron microscope. The enhanced interface led to improved mechanical properties (i.e. stiffness modulus, fracture toughness) and higher glass transition temperatures (Tg) compared with neat epoxy. At 4 wt% m-GP, the critical strain energy release rate G1c of neat epoxy improved by 240 % from 179.1 to 608.6 J/m2 and Tg increased from 93.7 to 106.4 �C. In contrast to m-clay, which at 4 wt%, only improved the G1c by 45 % and Tg by 7.1 %. The higher level of improvement offered by m-GP is attributed to the strong interaction of graphene sheets with epoxy because the covalent bonds between the carbon atoms of graphene sheets are much stronger than silicon-based clay

Emotional Well‐Being of Living Kidney Donors: Findings From the RELIVE Study

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109345/1/ajt12906.pd

Signaling in Secret: Pay-for-Performance and the Incentive and Sorting Effects of Pay Secrecy

Key Findings: Pay secrecy adversely impacts individual task performance because it weakens the perception that an increase in performance will be accompanied by increase in pay; Pay secrecy is associated with a decrease in employee performance and retention in pay-for-performance systems, which measure performance using relative (i.e., peer-ranked) criteria rather than an absolute scale (see Figure 2 on page 5); High performing employees tend to be most sensitive to negative pay-for- performance perceptions; There are many signals embedded within HR policies and practices, which can influence employees’ perception of workplace uncertainty/inequity and impact their performance and turnover intentions; and When pay transparency is impractical, organizations may benefit from introducing partial pay openness to mitigate these effects on employee performance and retention

Fusion of Seashell Nacre and Marine Bioadhesive Analogs: High-Strength Nanocomposite by Layer-by-Layer Assembly of Clay and L -3,4-Dihydroxyphenylalanine Polymer

No abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56017/1/949_ftp.pd

Bidirectional regulation of bone formation by exogenous and osteosarcoma-derived Sema3A

Semaphorin 3A (Sema3A), a secreted member of the Semaphorin family, increases osteoblast differentiation, stimulates bone formation and enhances fracture healing. Here, we report a previously unknown role of Sema3A in the regulation of ectopic bone formation and osteolysis related to osteosarcoma. Human recombinant (exogenous) Sema3A promoted the expression of osteoblastic phenotype in a panel of human osteosarcoma cell lines and inhibited the ability of these cells to migrate and enhance osteoclastogenesis in vitro. In vivo, administration of exogenous Sema3A in mice after paratibial inoculation of KHOS cells increased bone volume in non-inoculated and tumour-bearing legs. In contrast, Sema3A overexpression reduced the ability of KHOS cells to cause ectopic bone formation in mice and to increase bone nodule formation by engaging DKK1/β-catenin signalling. Thus, Sema3A is of potential therapeutic efficacy in osteosarcoma. However, inhibition of bone formation associated with continuous exposure to Sema3A may limit its long-term usefulness as therapeutic agent