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BACKGROUND: Posttraumatic chain disruption may be caused by blunt head trauma, barotrauma, or a penetrating foreign body. In cases of severe damage to the incus, or its absence, a titanium prosthesis is a good option for reconstructing the ossicular chain. METHODS: A retrospective analysis was performed on 24 cases of posttraumatic ossicular chain disruption that had been treated with a titanium partial or total ossicular replacement prosthesis. Air conduction, bone conduction, and air-bone gap were measured before, 6-12 months after, and more than 2 years after the operation. Hearing thresholds were calculated as the mean of 4 frequencies (0.5, 1, 2, and 4 kHz). RESULTS: The most common cause of ossicular chain disruption was blunt head trauma due to a traffic accident (9 of 24 cases), and there were also a diverse group of foreign bodies which caused damage. In cases where the incus was absent, or significantly damaged, titanium ossiculoplasties were performed (partial or total ossicular replacement prosthesis depending on the presence of the stapes superstructure). Analysis showed a significant improvement in average air conduction threshold and in air-bone gap after surgery (P < .05). Closure of the air-bone gap to within 20 dB was observed in 67% of patients. CONCLUSIONS: Although posttraumatic ossicular chain disruption is not common, it is suspected whenever conductive hearing loss persists for several months after injury. In such cases, ossiculoplasty with a titanium prosthesis is likely to provide satisfactory audiological results. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations give atomically detailed information on structure and dynamics in amphiphilic bilayer systems on timescales up to about 1 μs. The reorientational dynamics of the C-H bonds is conventionally verified by measurements of 13C or ²H nuclear magnetic resonance (NMR) longitudinal relaxation rates R1, which are more sensitive to motional processes with correlation times close to the inverse Larmor frequency, typically around 1-10 ns on standard NMR instrumentation, and are thus less sensitive to the 10-1000 ns timescale motion that can be observed in the MD simulations. We propose an experimental procedure for atomically resolved model-free estimation of the C-H bond effective reorientational correlation time τe, which includes contributions from the entire range of all-atom MD timescales and that can be calculated directly from the MD trajectories. The approach is based on measurements of 13C R1 and R1p relaxation rates, as well as ¹H-13C dipolar couplings, and is applicable to anisotropic liquid crystalline lipid or surfactant systems using a conventional solid-state NMR spectrometer and samples with natural isotopic composition. The procedure is demonstrated on a fully hydrated lamellar phase of 1-palmitoyl-2-oleoyl-phosphatidylcholine, yielding values of τe from 0.1 ns for the methyl groups in the choline moiety and at the end of the acyl chains to 3 ns for the g1 methylene group of the glycerol backbone. MD simulations performed with a widely used united-atom force-field reproduce the Te-profile of the major part of the acyl chains but underestimate the dynamics of the glycerol backbone and adjacent molecular segments. The measurement of experimental τe-profiles can be used to study subtle effects on C-H bond reorientational motions in anisotropic liquid crystals, as well as to validate the C-H bond reorientation dynamics predicted in MD simulations of amphiphilic bilayers such as lipid membranes. [ABSTRACT FROM AUTHOR]

The solution structure of the phosphocholine (PC) head group in 1,2-dipropionyl-sn-glycero-3-phosphocholine (C3-PC) in 30 mol. % dimethylsulfoxide (DMSO)-water solutions has been determined by using neutron diffraction enhanced with isotopic substitution in combination with computer simulation techniques. By investigating the atomic scale hydration structure around the PC head group, a unique description of the displacement of water molecules by DMSO molecules is detailed around various locations of the head group. Specifically, DMSO molecules were found to be the most prevalent around the onium portion of the head group, with the dipoles of the DMSO molecules being aligned where the negatively charged oxygen can interact strongly with the positively charged lipid group. The phosphate group is also partially dehydrated by the presence of the DMSO molecules. However, around this group the bulkier positive end of the DMSO dipole is interacting with negatively charged groups of the lipid head group, the DMSO layer shows no obvious ordering as it cannot form hydrogen bonds with the oxygen atoms in the PO4 group such as water molecules can. Interestingly, DMSO-water contacts have also increased in the presence of the lipid molecule relative to DMSO-water contacts observed in pure DMSO/water solutions at similar concentrations. [ABSTRACT FROM AUTHOR]

Reversed lipid liquid crystalline nanoparticles (LCNPs) of the cubic micellar (I2) phase have high potential in drug delivery applications due to their ability to encapsulate both hydrophobic and hydrophilic drug molecules. Their interactions with various interfaces, and the consequences for the particle structure and integrity, are essential considerations in their effectiveness as drug delivery vehicles. Here, we have studied LCNPs formed of equal fractions of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and glycerol dioleate in the presence of different fractions of the stabilizer Polysorbate 80. We have used a combination of ellipsometry, quartz crystal microbalance with dissipation monitoring and neutron reflectometry to reveal the structure and composition of the adsorbed layer on both anionic silica and cationic (aminopropyltriethoxysilane) silanized surfaces. For both types of surfaces, there is a spread near-surface layer comprising lipid and polymer as well as a sparse coverage of intact particles. The composition of the near-surface layer is very close to that of the particles, in contrast to the lipid bilayer observed with related systems. The interaction is stronger for cationic than anionic surfaces, which is rationalized in terms of the negative zeta potential of the LCNPs. The work shows that the attachment of and spreading from LCNPs is influenced by the properties of the surface, the internal structure, composition and stability of the particles as well as the nature of the stabilizer. [ABSTRACT FROM AUTHOR]

Sensing and manipulating living cellsusing vertical nanowire devicesrequires a complete understanding of cell behavior on these substrates.Changes in cell function and phenotype are often triggered by eventstaking place at the plasma membrane, the properties of which are influencedby local curvature. The nanowire topography can therefore be expectedto greatly affect the cell membrane, emphasizing the importance ofstudying membranes on vertical nanowire arrays. Here, we used supportedphospholipid bilayers as a model for biomembranes. We demonstratethe formation of fluid supported bilayers on vertical nanowire forestsusing self-assembly from vesicles in solution. The bilayers were foundto follow the contours of the nanowires to form continuous and locallyhighly curved model membranes. Distinct from standard flat supportedlipid bilayers, the high aspect ratio of the nanowires results ina large bilayer surface available for the immobilization and studyof biomolecules. We used these bilayers to bind a membrane-anchoredprotein as well as tethered vesicles on the nanowire substrate. Thenanowire-bilayer platform shown here can be expanded from fundamentalstudies of lipid membranes on controlled curvature substrates to thedevelopment of innovative membrane-based nanosensors. [ABSTRACT FROM AUTHOR]