Here, we report the measurement of an eABR (electrically evoked auditory brainstem response) by using a custom-developed BAM (bionic auditory membrane) for a novel artificial cochlear system. The BAM is an acoustic sensor designed as a trapezoidal and flexible membrane made of a piezoelectric material to convert acoustic waves to electrical signals with frequency selectivity. The signal from the BAM was used as an electrical source to stimulate the auditory nerves in a cochlea. The stimulating characteristics were investigated by measuring the eABR in guinea pigs. The results showed that the developed system could realize the perception of peak sound pressure levels and frequency of the acoustic wave. Consequently, we accumulated fundamental knowledge for developing a fully implantable artificial cochlea based on the BAM.
Among the several functions of the nasal cavity, temperature and humidity adjustments are important for preserving the trachea and lungs. The functions of the nasal cavity have been clarified in experiments investigating the conditions in the nasal cavity. However, the difficulties of noninvasive measurements have rendered nasal cavity simulations an attractive alternative. Data are readily obtained from a simulated result. In this study, airflow, temperature, and humidity transfer in the human nasal cavity were investigated in a nasal cavity wall model of temperature and humidity transport. The simulated result was verified by comparison with experimental data. A reasonable agreement was attained between experimental data and a model incorporating the latent heat effect. The model simulates heat and water exchange in the nasal cavity. In all cases, the temperature and humidity of the inhaled air were adjusted to suitable physiological values. Temperature and humidity gradients were highest at the front of the nasal cavity. The influence of latent heat was clarified by comparing simulation results with and without latent heat under several inhaled air conditions. In the hot-humid inhaled air case, temperature in the Kiesselbach area was increased by latent heat of condensation, and relative humidity declined. In the other inhaled air cases, the temperature in the Kiesselbach area was decreased by latent heat of evaporation, while relative humidity increased. Latent heat effect was particularly influential in the hot inhaled air case.
Glycosylation is one of the most important protein post-translational modifications. O-glycosylation plays important roles in biological functions. There are several variations of O-glycosylation, with each having a different function. In this work, in order to discriminate sugar types in O-glycosylation from protein primary sequences, the characteristics of the sequences around the glycosylated sites were extracted. Fucose (Fuc) and xylose (Xyl) were discriminated with high accuracy by the position-specific scoring matrix (PSSM) based on the amino acid propensities around the glycosylated sites. It was suggested that the characteristics of the sequences modified by Fuc and Xyl could be extracted. However, the discrimination of N-acetylgalactosamine (GalNAc) and N-acetylglucosamine (GlcNAc) was inaccurate, and it was considered that the characteristics could not be extracted because information from the primary sequences was insufficient. The results indicate that PSSM based on protein primary sequences can effectively discriminate some sugar types in O-glycosylation.
Fluid shear stress (SS) is well known to cause morphological changes in vascular endothelial cells (ECs) accompanied by alteration in actin cytoskeletal structure and distribution of focal adhesions. Recent studies have shown that spatial SS gradient also has effects on EC morphology, but the detailed mechanisms of EC responses to SSG remain unclear. In the present study, we sought morphological responses of ECs under SS and uniform SSG condition using a newly developed flow chamber. Confluent ECs were exposed to SS with SSG for 24 hours. Focal adhesions of the EC under SS without SSG were localized in the cell periphery. In contrast, focal adhesions were expressed not only in the periphery but also in interior portion of cells after exposure to SS with SSG. Unlike ECs exposure to SS developed thick actin filaments aligned to the direction of flow no development of thick actin filaments but thin and short filaments were observed in ECs after 24-hour exposure to SS with SSG. Since the distribution of focal adhesion is of critical importance for development of actin filaments and cell morphological changes, these results suggest that SSG suppresses redistribution of focal adhesions, resulting in the inhibition of EC morphological changes and development of thick actin filaments in response to flow.
In the present study, we address theoretical approaches for the experimental results to investigate the flow dynamics of λDNA through a nanochannel in which two nanoelectrodes are integrated. In order to elucidate the relationship between the longitudinal ionic current and the electrophoresis of λDNA in the specific micro/nanofluidics, we develop a theoretical model for the macroscopic fluid dynamics in a Lagrangian framework. The measured current change associated with a single molecule translocation through the channel is explained by the principle of the Coulter counter that allowed to predict the conformation of λDNA. We also analyze the local velocity of λDNA passing through a nanoscaled confined channel. A result from the model is in considerable agreement with the experimental observations for the electrophoretic flow of λDNA. The basic knowledge obtained here may be useful in developing electrical methods for controlling the electrophoretic velocity of single-molecule DNA for realizing the nanopore sequencer.
In this study, the influence of phospholipid and protein constituents on friction and wear behavior of artificial hydrogel cartilage was investigated. A sliding pair of an ellipsoidal specimen of poly (vinyl alcohol) (PVA) hydrogel and a flat specimen of PVA hydrogel was evaluated in simplified reciprocating friction test. Dipalmitoylphosphatidylcholine (DPPC) was selected as a phospholipid constituent and was dispersed in saline as liposome. Fluorescent-labeled albumin and γ-globulin were used as protein constituents in lubricants at concentration of 0.7 wt%. After reciprocating friction test, the boundary film formed on the surface of PVA hydrogel and the worn surface of PVA hydrogel were observed by using fluorescent microscope and confocal laser scanning microscope, respectively. When only albumin or γ-globulin was added to lubricant, adhesive wear pattern was frequently observed and large breaking-off of surface structure of PVA hydrogel occurred. Lubricants that contain both proteins and 0.01wt% DPPC showed reduction of friction and suppression of large breaking-off of surface structure of PVA hydrogel. Meanwhile, under coexistence of protein and 0.02wt% DPPC, friction increased compared to that for lubricants that contain 0.01wt% DPPC and the adhesive wear patterns became obvious. Therefore, both the concentration and the relative ratio of proteins to phospholipids are important factors to function adequately as excellent boundary lubricant for PVA hydrogel.
A deformation analysis of a liquid-filled spherical microcapsule indented by a sharp truncated-cone indenter was conducted, in which a circumferential wrinkling model was introduced in the dimpled region near the indenter tip. The initial stretch of the membrane of an alginate-poly(L)lysine-alginate microcapsule was determined by fitting the calculated and measured force-displacement curves. In the fitting procedure, the effect of the membrane permeability in the experiment on the force-displacement curve was taken into account. The calculated deformed shape of the indented microcapsule was almost identical to the experimentally observed one. The influences of the initial stretch on the force-displacement relationship, transmural pressure-displacement relationship, and deformation shape before membrane rupture due to the indenter-tip piercing were demonstrated. The importance of taking the initial stretch into account in the mechanical characterization of microcapsules or cells was shown.
The objective of this study was to simulate the movements of the bones involved in human forearm rotation. We developed a biomechanical arm model comprising bone, muscle, and ligament components. Computed tomography (CT) scans of a human arm were used to determine the morphology of the humerus, ulna, radius, and hand bones. Magnetic resonance (MR) images were used to create muscle spring models simulating the pronator teres, pronator quadratus, and supinator muscles. Twenty-seven ligaments connecting the bone components were approximated by wire models. We also created several ligament rupture models by eliminating some of the 27 ligaments. Ligaments were removed according to the following four stages: Stage a-I, only dorsal triangular fibrocartilage complex (TFCC); Stage b-I, only palmar TFCC; Stage II, both dorsal and palmar TFCC; Stage III, both dorsal and palmar TFCC plus distal interosseous membrane. In the complete 27-ligament model and in the ligament rupture models, the forearm was rotated to 90° supination and 85° pronation for comparison. In supination, the rupture of the palmar TFCC (Stage b-I) caused a larger difference between the two types of models than the rupture of the dorsal TFCC (Stage a-I). The distal radioulnar joint instability and radial laxity occurred for Stage III rather than Stage II. The distal radioulnar joint was more stable and radial laxity was less pronounced during pronation in the presence of the pronator quadratus muscle than during supination in the absence of this muscle. These findings were in good accord with previous study results.