Fast corroding,thin magnesium coating displays antibacterial effects and low cytotoxicity

Bacterial colonisation and biofilm formation are characteristics of implant-associated infections. In search of candidates for improved prosthetic materials, fast corroding Mg-based coatings on titanium surfaces were examined for their cytotoxic and antimicrobial properties. Human osteoblasts and Staphylococcus epidermidis were each cultured on cylindrical Ti samples coated with a thin layer of Mg/Mg₄₅Zn₅Ca, applied via magnetron sputtering. Uncoated titanium samples served as controls. S. epidermidis was quantified by counting colony forming units. The biofilm-bound fraction was isolated via ultrasonic treatment, and the planktonic fraction via centrifugation. Biofilm-bound S. epidermidis was significantly decreased by approximately four to five orders of magnitude in both Mg- and Mg₄₅Zn₅Ca-coated samples after seven days compared to the control. The osteoblast viability was within the tolerance threshold of 70% stated in DIN EN ISO 10993-5:2009-10 for Mg (~80%) but not for Mg₄₅Zn₅Ca (~25%). Accordingly, Mg-coated titanium was identified as a promising candidate for an implant material with antibacterial properties and low cytotoxicity levels. The approach of exploiting fast corrosion contrasts with existing methods, which have generally focused on reducing corrosion.     

Resting Membrane Potentials Recorded On-site in Intact Skeletal Muscles from Deep Sea Fish (Sigmops gracile) Salvaged from Depths up to 1.000 m

The effect of elevated ambient pressures in deep sea fish residing at certain bottom depths or even covering different depth levels during migration is poorly understood. Elevated pressures are known to influence membrane properties of various excitable tissues in many species. Reliable results on membrane properties require freshly isolated living cells and short decompression times. During a scientific cruise south of Japan, deep sea fish were sampled from depths up to 1.000 m by using the intelligent operative net sampling system IONESS. On-site electrophysiological recordings of resting membrane potentials were performed in freshly isolated skeletal muscles from Sigmops gracile. Experiments were conducted at various extracellular K+ concentrations to derive relative membrane ion permeabilities and estimate intracellular K+ concentrations [K+]i in the muscles studied. With increasing sampling depth, a tendency for depolarized resting membrane potentials was observed. This could be explained by an increase in relative Na+ over K+ resting membrane permeabilities. Fish samples from deeper sites also had larger [K+]i values compared with shallower sites. This study represents a first approach to perform sophisticated physiological live-cell experiments on board a fully operating ship. These data are expected to more realistically reflect the physiological state of biological preparations residing in the deep sea.     

Sequential depolarization of root cortical and stelar cells induced by an acute salt shock - implications for Na(+) and K(+) transport into xylem vessels

Early events in NaCl-induced root ion and water transport were investigated in maize (Zea mays L) roots using a range of microelectrode and imaging techniques. Addition of 100 mm NaCl to the bath resulted in an exponential drop in root xylem pressure, rapid depolarization of trans-root potential and a transient drop in xylem K(+) activity (A(K+) ) within ～1 min after stress onset. At this time, no detectable amounts of Na(+) were released into the xylem vessels. The observed drop in A(K+) was unexpected, given the fact that application of the physiologically relevant concentrations of Na(+) to isolated stele has caused rapid plasma membrane depolarization and a subsequent K(+) efflux from the stelar tissues. This controversy was explained by the difference in kinetics of NaCl-induced depolarization between cortical and stelar cells. As root cortical cells are first to be depolarized and lose K(+) to the environment, this is associated with some K(+) shift from the stelar symplast to the cortex, resulting in K(+) being transiently removed from the xylem. Once Na(+) is loaded into the xylem (between 1 and 5 min of root exposure to NaCl), stelar cells become more depolarized, and a gradual recovery in A(K+) occurs.     

Calibration of hyperelastic material properties of the human lumbar intervertebral disc under fast dynamic compressive loads

Under fast dynamic loading conditions (e.g. high-energy impact), the load rate dependency of the intervertebral disc (IVD) material properties may play a crucial role in the biomechanics of spinal trauma. However, most finite element models (FEM) of dynamic spinal trauma uses material properties derived from quasi-static experiments, thus neglecting this load rate dependency. The aim of this study was to identify hyperelastic material properties that ensure a more biofidelic simulation of the IVD under a fast dynamic compressive load. A hyperelastic material law based on a first-order Mooney-Rivlin formulation was implemented in a detailed FEM of a L2-L3 functional spinal unit (FSU) to represent the mechanical behavior of the IVD. Bony structures were modeled using an elasto-plastic Johnson-Cook material law that simulates bone fracture while ligaments were governed by a viscoelastic material law. To mimic experimental studies performed in fast dynamic compression, a compressive loading velocity of 1 m/s was applied to the superior half of L2, while the inferior half of L3 was fixed. An exploratory technique was used to simulate dynamic compression of the FSU using 34 sets of hyperelastic material constants randomly selected using an optimal Latin hypercube algorithm and a set of material constants derived from quasi-static experiments. Selection or rejection of the sets of material constants was based on compressive stiffness and failure parameters criteria measured experimentally. The two simulations performed with calibrated hyperelastic constants resulted in nonlinear load-displacement curves with compressive stiffness (7335 and 7079 N/mm), load (12,488 and 12,473 N), displacement (1.95 and 2.09 mm) and energy at failure (13.5 and 14.7 J) in agreement with experimental results (6551 ± 2017 N/mm, 12,411 ± 829 N, 2.1 ± 0.2 mm and 13.0 ± 1.5 J respectively). The fracture pattern and location also agreed with experimental results. The simulation performed with constants derived from quasi-static experiments showed a failure energy (13.2 J) and a fracture pattern and location in agreement with experimental results, but a compressive stiffness (1580 N/mm), a failure load (5976 N) and a displacement to failure (4.8 mm) outside the experimental corridors. The proposed method offers an innovative way to calibrate the hyperelastic material properties of the IVD and to offer a more realistic simulation of the FSU in fast dynamic compression.     

Grandparental effects in marine sticklebacks: transgenerational plasticity across multiple generations

Nongenetic inheritance mechanisms such as transgenerational plasticity (TGP) can buffer populations against rapid environmental change such as ocean warming. Yet, little is known about how long these effects persist and whether they are cumulative over generations. Here, we tested for adaptive TGP in response to simulated ocean warming across parental and grandparental generations of marine sticklebacks. Grandparents were acclimated for two months during reproductive conditioning, whereas parents experienced developmental acclimation, allowing us to compare the fitness consequences of short‐term vs. prolonged exposure to elevated temperature across multiple generations. We found that reproductive output of F1 adults was primarily determined by maternal developmental temperature, but carry‐over effects from grandparental acclimation environments resulted in cumulative negative effects of elevated temperature on hatching success. In very early stages of growth, F2 offspring reached larger sizes in their respective paternal and grandparental environment down the paternal line, suggesting that other factors than just the paternal genome may be transferred between generations. In later growth stages, maternal and maternal granddam environments strongly influenced offspring body size, but in opposing directions, indicating that the mechanism(s) underlying the transfer of environmental information may have differed between acute and developmental acclimation experienced by the two generations. Taken together, our results suggest that the fitness consequences of parental and grandparental TGP are highly context dependent, but will play an important role in mediating some of the impacts of rapid climate change in this system.     

A multicomponent method for Fusarium toxins in cereal based food and feed samples using HPLC-MS/MS

A reliable, sensitive and selective multicomponent method has been developed to determine 12 differentFusarium mycotoxins (trichothecenes type A and B, zearalenone) simultaneously in cereal and grain samples using liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS). The sample preparation based on a standard extraction step followed by two different kinds of solid phase clean-up (multifunctional MycoSep^® material) for trichothecenes, and an immuno-affinity purification which combined antibodies for aflatoxins, ochratoxin A and zearalenone (AOZ-IAC). For quantification of zearalenone (ZON) an internal standard (zearalanone, ZAN) was used, whereas for trichothecenes a recovery standard (verrucarol, VOL) was applied. The average recoveries for the trichothecenes ranged from 65% for nivalenol (NIV) up to 96% for deoxynivalenol (DON) and 89% for zearalenone. The limit of quantification is different for each of the individual trichothecenes and in the range of 1 ppb to 10 ppb.     

Supported organometallic complexes. Part 27: novel sol-gel processed rhodium(I) complexes: synthesis, characterization, and catalytic reactions in interphases

A novel T-silyl functionalized cationic (COD)(dppp)rhodium(I) complex was sol-gel processed with various amounts of the co-condensing agents MeSi(OMe)₂(CH₂)₆(OMe)₂SiMe and MeSi(OMe)₂(CH₂)₃(C₆H₄)(CH₂)₃(OMe)₂SiMe to give novel stationary phases for ‘Chemistry in Interphases’. The polysiloxane matrices and the integrity of the rhodium(I) complex centers were investigated by means of multinuclear solid-state NMR (¹³C, ²⁹Si, ³¹P) and EXAFS spectroscopies. Dynamic NMR measurements show an increasing mobility of the matrix and the reactive centers with a higher amount of the co-condensing component. The accessibility of the anchored rhodium(I) centers was scrutinized by the metal catalyzed hydrogenation of 1-hexene. All applied xerogels show remarkable activities and selectivities. An enhancement of the activities is achieved when polar solvents are used. SEM micrographs reveal the morphology of the hybrid materials and energy dispersive X-ray spectroscopy (EDX) suggests that the distribution of the elements is in satisfying agreement with the applied composition.