Cholesterol is essential to the body as a component of cellular membranes and a source of steroid hormones, but excess cholesterol is a risk factor for atherosclerosis. ATP-binding cassette protein A1 (ABCA1) and ABCG1 play important roles in cholesterol homeostasis by removing excess cholesterol from peripheral tissues including macrophages and functioning in reverse cholesterol transport to the liver. Thus, ABCA1 and ABCG1 can be targets of drugs for atherosclerosis and hyperlipidemia. ABCA1 mediates the efflux of cholesterol and phosphatidylcholine (PC) to apolipoprotein A-I (apoA-I), which forms preβ-high density lipoprotein (HDL). ABCG1 mediates the efflux of cholesterol and sphingomyelin (SM) to preβ-HDL and HDL. Cholesterol and SM form ordered microdomains (raft domains, detergent-resistant membranes) in the plasma membrane. It was assumed that SM influences the membrane dynamics, so the cellular SM level was changed, and the effects of lipid raft on the efflux of cholesterol mediated by ABCA1 and ABCG1 were examined. It was demonstrated that the ABCA1- and ABCG1-mediated efflux of cholesterol is inverse and is correlated with the cellular SM level, respectively. The expression of ABCA1 or ABCG1 increased the amount of cholesterol available to cold methyl-β-cyclodextrin extraction even in the absence of apoA-I or HDL. These suggest that ABCA1 and ABCG1 reorganize the plasma membrane and generate more loosely packed domains, which facilitate apoA-I- or HDL-dependent cholesterol efflux, and that the membrane environment modulates the efflux of cholesterol mediated by ABCA1 and ABCG1.

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Interaction of apolipoprotein (apo) A-I with lipid membrane is involved in a large number of processes in lipoprotein metabolism and cholesterol homeostasis. This review discusses the molecular mechanisms of interaction of apoA-I with lipid membrane in view of their structures. Lipid-free apoA-I is folded into two domains, comprising an Nterminal part forming a four-helix bundle and a discrete C-terminal part. It is well known that insertion of a proline residue into a protein sequence disruptsα-helix structure. Perturbation of the helix bundle structure occurs by the proline insertion into the putative helical region in the N-terminal domain, suggesting that the substituted residue is part of the helix bundle. In lipid-binding, apoA-I recognizes headgroup separation (hydrated space) between phospholipid molecules at the lipid membrane. ApoA-I initially binds to lipid through the C-terminal domain, followed by a conformational opening of the helix bundle with an accompanying increase inα-helical content. The transition from random coil toα-helix has been shown to produce a large negative enthalpy (exothermic heat) that drives lipid binding. Despite a lack of the C-terminal domain, which is critical for lipid-binding, perturbation of the helix bundle structure restored the lipidbinding ability by exposing a potential lipid-binding region in the N-terminal domain.

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Neural cells such as neurons and glias in the central nervous system (CNS) appear in a multi-process with a large cell surface. Accordingly the CNS is a cholesterol-rich organ that accounts for approximately 25% of total body cholesterol in humans. As circulating plasma lipoproteins is segregated by the blood-brain barrier (BBB) from the CNS of vertebrates, a unique system for intercellular cholesterol transport functions in the brain. This review article describes the contribution of apoE/HDL generation by astrocytes to cholesterol homeostasis in the brain.

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We prepared a novel rubbed fluorinated polyimide membrane using a rubbing machine with a rubbing cloth and determined the surface properties of the rubbed membrane using an atomic force microscope and contact angle measurements. In addition, we evaluated the cell adhesion behavior on the rubbed polyimide membrane using a phase contrast microscope. Interestingly, a rubbed polyimide surface having a micrometer-scale grooved pattern was prepared by the rubbing method, and the morphologies of cells attached to the rubbed surface were threedimensional multicellular spheroids, while the cells on an unrubbed surface showed two-dimensional monolayers. This initial study indicates that the rubbing method without any chemical modification is simple and can easily produce large surface areas, suggesting that the rubbing may become a novel cell culture method.

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In order to meet the diversifying demand for the cell manipulation in the rapid progress of cell engineering, we developed a novel technique to control living adherent cells on a culture substrate by irradiating light onto multiple points simultaneously. Among them, we developed a functional cell culture surface, on which polyethylene glycol as a cell adhesion inhibitor is immobilized via a photo-responsive polymer. In clear contrast to the conventional cell patterning using the previously patterned substrate, the cell-adhesive area can be appended even after cell seeding just by irradiating light. Additionally to the simple cell patterning, construction of patterned co-culture system was demonstrated by using the substrate.

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For achievement of regenerative medicine, ex vivo expansion of stem cells which can be differentiated to various cells is very important. However, it is very difficult to efficiently and safely culture some stem cells such as hematopoietic stem cells in cord blood or human embryonic stem cells. Therefore, the culture systems are investigated by many researchers. Here the state-of-arts of culture of stem cells and in particle development of biomaterials or expansion of stem cells is discussed.

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Cell micropatterning techniques have greatly contributed to fundamental studies of cell biology. However, they have nly limited application to regenerative medicine so far. One of the most significant challenges in the field of regenerative medicine is introducing blood vascular systems into artificial tissue constructs. Recently, we have developed the technique called cell transfer printing, which has the potential to solve the issue. In this paper, we describe the preparation of a micropatterned substrate by photocatalytic lithography and its surface characterization, and then provide a brief overview of transfer printing of micropatterned endothelial cells. Possible mechanisms of cell transfer printing and its further prospects are also discussed.

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The liposome-assisted refolding of recombinant microbial transglutaminase (MTG) was achieved by using the dilution method. The analysis of the partly-denatured MTG by using the calcein-trapping immobilized liposome chromatography showed the interaction between the MTG and liposome under the above condition. The effect of the addition of liposome was then investigated, resulting that the refolding yield of MTG was improved from 66% at control to 82% by adding the liposome with suitable membrane fluidity and surface charge density.

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An electrolyte-entrapping liposome was immobilized on an Au electrode to design and develop an immobilized-liposome sensor (ILS) system for the detection of the damage of proteins. Three kinds of proteins, such as bovine carbonic anhydrase, lysozyme and chitosanase, were used as model analytes. The proteins treated by a denaturant (guanidium hydrochloride, GuHCl) were applied to the ILS analysis, resulting that the significant electrical signals could effectively be detected due to the interaction between the liposome and GuHCl-denatured protein. The diffusion currents normalized by protein concentrations were linearly correlated with local hydrophobicity of proteins evaluated by the conventional aqueous two-phase partitioning method. The ILS system can, therefore, be utilized as a useful tool for an on-line monitoring to conformational changes of proteins.

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The influences of the addition of glycolipid analogues to the vesicle membrane composed of nonionic surfactant Span80 on the membrane characteristics of the vesicle were investigated. The analogues examined were as follows: N-[O-(D-glucopyranosyl)-6-oxyhexyl]-3,5-bis(dodecyloxy)benzamide (Glc-L6-2), N-[O-(D-glucopyranosyl)-6-oxyhexyl]- 3,4,5-tris(dodecyloxy)benzamide (Glc-L6-3) and 3,4,5-tris(dodecyloxy)benzyl-D-glucopyranoside (Glc-Bn-3). The membrane fluidity of Span80 vesicle was compared with some phospholipid liposomes by measuring the fluorescence anisotropy (1/P value) with 1,6-diphenyl-1,3,5-hexatrien. The fluidity of Span80 vesicle was higher than those of the liposomes because of very lower phase-transition temperature (–40 ℃) of the Span80 vesicle. The addition of each glycolipid analogue decreased the membrane fluidities of the Span80 vesicles with the order of the additive systems of Glc-L6-2, Glc-L6-3 and Glc-Bn-3. The effects of the additive glycolipid analogues to Span80 vesicle on the formation ratio and the initial burst of the vesicle were evaluated by measuring the leakage of the Brilliant blue tracer entrapped in the vesicle. The addition of either Glc-L6-3 or Glc-Bn-3 of 0.2 ～ 0.3 wt% also enhanced the vesicle formation and inhibited the initial burst of the vesicle. Thus, the fluidity, formation and initial burst of Span80 vesicle were controlled by incorporating the glycolipid analogues to the vesicle membrane.

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Many water purification plants using MF or UF membrane filtration processes have been constructed and in operation throughout the world. Feed water quality of these plants may change site by site from the view points of suspended particles (turbidity) and characteristics of natural organic matter (NOM). One of the important issues that affect membrane filtration performance is “membrane fouling”. To overcome “membrane fouling”, we studied the design of both pure water permeability and membrane surface pore size distribution. As a result, TORAY has achieved to obtain the series of low fouling hollow fiber membranes by unique composite hollow fiber membrane morphologies. These composite hollow fiber membranes are made from high strength supporting layer and low fouling layers, which determine the surface pore size. Based on this technology, TORAY line-upped three PVDF hollow fiber membrane modules, which should be selected for water purification plant depending on the feed water qualities. The hollow fiber membranes are successfully made into extremely large casing type modules, which have 8inches diameter, 2 meter length and 75 square meter surface area. These modules make it possible to achieve small footprint area of membrane filtration plants, low cost and stable operation.

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