Three-dimensional imaging of a long-period stacking ordered phase in Mg₉₇Zn₁Gd₂ using high-voltage electron microscopy

Spatial configurations and lateral morphology of the 14H long-period stacking ordered (LPSO) phase have been studied by single tilt-axis electron tomography using high-voltage scanning transmission electron microscopy (STEM) operated at 1 MV. A "Quonset hut-like" lateral shape of the LPSO was found in a tomogram of a specimen as thick as 1.7 μ m. The reconstructed volume reveals spatial distribution of residual particulate precipitates of (Mg, Zn)3Gd phase 20-30 nm in diameters. The precipitates act as a source of solute elements for the formation and growth processes of 14H LPSO. 1 MV-STEM realizes enough resolution for imaging the morphology of LPSO as well as high electron transmittance (∼4.1 μ m) without any obvious electron irradiation damages on microstructures

Toxin-induced pore formation is hindered by intermolecular hydrogen bonding in sphingomyelin bilayers

Sticholysin I and II (StnI and StnII) are pore-forming toxins that use sphingomyelin (SM) for membrane binding. We examined how hydrogen bonding among membrane SMs affected the StnI- and StnII-induced pore formation process, resulting in bilayer permeabilization. We compared toxin-induced permeabilization in bilayers containing either SM or dihydro-SM (lacking the trans 4 double bond of the long-chain base), since their hydrogen-bonding properties are known to differ greatly. We observed that whereas both StnI and StnII formed pores in unilamellar vesicles containing palmitoyl-SM or oleoyl-SM, the toxins failed to similarly form pores in vesicles prepared from dihydro-PSM or dihydro-OSM. In supported bilayers containing OSM, StnII bound efficiently, as determined by surface plasmon resonance. However, StnII binding to supported bilayers prepared from dihydro-OSM was very low under similar experimental conditions. The association of the positively charged StnII (at pH 7.0) with unilamellar vesicles prepared from OSM led to a concentration-dependent increase in vesicle charge, as determined from zeta-potential measurements. With dihydro-OSM vesicles, a similar response was not observed. Benzyl alcohol, which is a small hydrogen-bonding compound with affinity to lipid bilayer interfaces, strongly facilitated StnII-induced pore formation in dihydro-OSM bilayers, suggesting that hydrogen bonding in the interfacial region originally prevented StnII from membrane binding and pore formation. We conclude that interfacial hydrogen bonding was able to affect the membrane association of StnI- and StnII, and hence their pore forming capacity. Our results suggest that other types of protein interactions in bilayers may also be affected by hydrogen-bonding origination from SMs

A Role for the Cysteine-Rich 10 kDa Prolamin in Protein Body I Formation in Rice

The rice prolamins consist of cysteine-rich 10 kDa (CysR10), 14 kDa (CysR14) and 16 kDa (CysR16) molecular species and a cysteine-poor 13 kDa (CysP13) polypeptide. These storage proteins form protein bodies (PBs) composed of single spherical intracisternal inclusions assembled within the lumen of the rough endoplasmic reticulum. Immunofluorescence and immunoelectron microscopy demonstrated that CysR10 and CysP13 were asymmetrically distributed within the PBs, with the former concentrated at the electron-dense center core region and the latter distributed mainly to the electron-lucent peripheral region. These results together with temporal expression data showed that the formation of prolamin-containing PB-I in the wild-type endosperm was initiated by the accumulation of CysR10 to form the center core. In mutants deficient for cysteine-rich prolamins, the typical PB-I structures containing the electron-dense center core were not observed, and instead were replaced by irregularly shaped, electron-lucent, hypertrophied PBs. Similar, deformed PBs were observed in a CysR10 RNA interference plant line. These results suggest that CysR10, through its formation of the central core and its possible interaction with other cysteine-rich prolamins, is required for tight packaging of the proteins into a compact spherical structure

Development of a New Bioartificial Liver Support System Using a Radial-flow Bioreactor

There is an increasing number of patients with severe liver disease that requires whole organ transplantation or living-related split liver transplantation. This has resulted in a shortage of donor organs, which is particularly problematic and still awaits resolution. Bioartificial liver (BAL) support systems have been developed with the aim of supporting patients with life-threatening liver disease until their liver recovers. Here, we describe a high performance three-dimensional rat hepatocyte culture system using a radial-flow bioreactor (RFB) with a polyvinyl alcohol (PVA) membrane as a small-scale BAL support system. Hepatocytes from male Sprague-Dawley rat livers were isolated and divided into two groups as follows. Group A: isolated hepatocytes were maintained in culture medium as controls; and group B: isolated hepatocytes were injected into the medium chamber of the RFB-PVA culture system. Sampling was carried out every 48 h to analyze the concentrations of ammonia and albumin in the medium. Light and electron microscopic examination of hepatocytes explanted from the PVA membrane was also performed. Albumin production and urea synthesis by cells in group B were both significantly higher than in group A. Hematoxylin-Eosin staining of the cells in group B showed that three-dimensional cell masses were attached to the PVA membrane. It also showed that the cells were stably proliferating in the porous spaces of the PVA. Scanning electron microscopic images of group B also showed clusters of hepatocytes attached to the PVA membrane. Hepatocyte clusters growing in the RFB-PVA culture system retained their biological function and were stable in the porous spaces of the PVA membrane. This cell culture system may be useful for the development of new BAL support systems

光重合型プラスチック暫間充填材の臨床的評価

Fermit, a kind of a visible-light-cured resin, has recently been used as a temporary filling material. This clinical study was done to determine whether or not Fermit was superior to Dura Seal which was previously reported by us in this journal. The prepared cavities were sealed with Fermit for an average of 11.0 days. Fermit was found to have the same properties as Dura Seal, except for many losses of the seal (17.6% of the total) and difficulty in filling

Detailed Comparison of Deuterium Quadrupole Profiles between Sphingomyelin and Phosphatidylcholine Bilayers

AbstractLipid rafts are microdomains rich in sphingomyelin (SM) and cholesterol (Chol). The essential question is why natural lipid rafts prefer SM rather than saturated diacyl glycerophosphocholine, although both form ordered membranes with Chol in model systems. Hence in this study, we synthesized site-specifically deuterated 1-palmitoyl-2-stearoyl-sn-glycero-3-phosphocholines that match the acyl chain length of stearoyl-SM (SSM), and compared their deuterium quadrupole coupling profiles in detail. The results suggest a deeper distribution of Chol in the SSM membranes, a lower entropic penalty upon accommodation of Chol in SSM membranes, and a higher thermal stability of acyl-chain orders in the SSM-Chol bilayers than in the 1-palmitoyl-2-stearoyl-sn-glycero-3-phosphocholine-Chol system at various Chol concentrations. The entropy effect and thermal stability should render SM a more preferred raft constituent than saturated diacyl glycerophosphocholine. Our data also demonstrate that the selective and comprehensive deuteration strategy is indispensable for accurate comparison of order profiles

Multilayerization of Organophotocatalyst Films that Efficiently Utilize Natural Sunlight in a One-Pass-Flow Water Purification System

A full-spectrum visible-light-responsive organophotocatalyst membrane array is designed and employed for a one-pass-flow water purification system. Whereas previous photocatalyst systems required strong light source, the present design manages with natural sunlight intensity, owing to multilayerization of a newly optimized low-absorbance organophotocatalyst. The design of the system is to utilize natural-sunlight-equivalent visible light with 1 m² of irradiation area to process 1 ton/day of water. A 1/3300 scale module of the system was constructed and experimentally demonstrated its viability. The reactor part of the flow system contains 24 stacked layers of organic-semiconductor-laminated Nafion film. The organic semiconductor is a bilayer of metal-free phthalocyanine (H₂<i>Pc</i>, p-type semiconductor) and 3,4,9,10-perylenetertacarboxylic-bisbenzimidazole (PTCBI, n-type semiconductor). Transparent Nafion functions as mechanical support and absorbent of trimethylamine, which was chosen as a typical contaminant of underground water in coastal areas. The reactor was irradiated for only 1 h/day by visible light (10 mW/cm²). The light intensity at the bottom layer was estimated to be 0.1 mW/cm², which was sufficient intensity (internal quantum efficiency was 0.15.) for the photocatalytic reaction, due to the optimized absorbance and photocatalytic quantum efficiency of each layer. The inlet TMA concentration was 3 ppm, while that of the outlet was less than 0.03 ppm for the first day of the operation of the system with and without the bilayer. Without the bilayer, the TMA concentration of the outlet flow increased after 20 days. With the bilayer, the TMA concentration of the outlet flow remained at less than 0.03 ppm for the 40-day experimental period due to its photocatalysis. The turnover number of photocatalytic reaction was calculated to be 1.8 × 10⁴