Large-scale generation of differentiated cells to achieve regenerative medicine

The effects of microgravity and fluid dynamic stress on embryoid bodies generated from pluripotent stem cells induce and direct their differentiation. Using this hydrodynamic effect combined with exogenous factors and three-dimensional culture, a new technique has been developed to produce functional, effective, and safe hepatocytes for transplantation. The evolution of this technique will lead to automated production of a large number of differentiated cells and will significantly contribute to regenerative medicine.ArticleSTEM CELL RESEARCH & THERAPY. 5:10 (2014)journal articl

Hamiltonian decomposition for bulk and surface states

We demonstrate that a tight-binding Hamiltonian with nearest- and next-nearest-neighbor hopping integrals can be decomposed into bulk and boundary parts in a general lattice system. The Hamiltonian decomposition reveals that next nearest-neighbor hopping causes sizable changes in the energy spectrum of surface states even if the correction to the energy spectrum of bulk states is negligible. By applying the Hamiltonian decomposition to edge states in graphene systems, we show that the next nearest-neighbor hopping stabilizes the edge states.Comment: 5 pages, 4 figure

Berry's Phase for Standing Wave Near Graphene Edge

Standing waves near the zigzag and armchair edges, and their Berry's phases are investigated. It is suggested that the Berry's phase for the standing wave near the zigzag edge is trivial, while that near the armchair edge is non-trivial. A non-trivial Berry's phase implies the presence of a singularity in parameter space. We have confirmed that the Dirac singularity is absent (present) in the parameter space for the standing wave near the zigzag (armchair) edge. The absence of the Dirac singularity has a direct consequence in the local density of states near the zigzag edge. The transport properties of graphene nanoribbons observed by recent numerical simulations and experiments are discussed from the point of view of the Berry's phases for the standing waves.Comment: 6 pages, 4 figure

Soliton Trap in Strained Graphene Nanoribbons

The wavefunction of a massless fermion consists of two chiralities, left-handed and right-handed, which are eigenstates of the chiral operator. The theory of weak interactions of elementally particle physics is not symmetric about the two chiralities, and such a symmetry breaking theory is referred to as a chiral gauge theory. The chiral gauge theory can be applied to the massless Dirac particles of graphene. In this paper we show within the framework of the chiral gauge theory for graphene that a topological soliton exists near the boundary of a graphene nanoribbon in the presence of a strain. This soliton is a zero-energy state connecting two chiralities and is an elementally excitation transporting a pseudospin. The soliton should be observable by means of a scanning tunneling microscopy experiment.Comment: 7 pages, 4 figure

Freeze-thawing single human embryonic stem cells induce e-cadherin and actin filament network disruption via g13 signaling

Poor adhesion of single human embryonic stem (hES) cells after freeze-thawing causes death. To investigate mechanisms responsible for this, Rho-dependent protein kinase (ROCK) inhibitor Y-27632-treated and untreated single hES cells were analyzed for E-cadherin and F-actin distribution by immunostaining and phalloidin staining respectively and for G13 signaling pathway components by DNA microarray and quantitative polymerase chain reaction (PCR). Y-27632-treated cells clustered rapidly and maintained E-cadherin and F-actin distribution without losing Oct3/4. Immediately after thawing, E-cadherin in untreated hES cells dotted along the membrane and then displayed eccentric cytoplasmic localization. Bleb formation and early Oct3/4 loss occurred after F-actin network condensation in the cytoplasm. Microarray analyses and quantitative PCR indicated upregulation of two actin reorganization-associated components of the G13 signaling pathway, Arhgdib and Cdc42, in untreated cells. Considering these findings and that cell death was partly interrupted by Y-27632, E-cadherin and actin cytoskeleton network disruption through the G13 signaling pathway may cause hES cell death after freeze-thawing.ArticleCRYO LETTERS. 32(6):516-524 (2011)journal articl

GDP/GTP exchange reaction-stimulating activity of Rabphilin-3A for Rab3A small GTP-binding protein

AbstractRabphilin-3A is a putative target protein for Rab3A, a small GTP-binding protein particularly implicated in neurotransmitter release. Rabphilin-3A interacts more preferentially with GTP-Rab3A than with GDP-Rab3A. Moreover, Rabphilin-3A shows a weak activity to stimulate the GTPase activity of Rab3A and a strong activity to inhibit the Rab3A GTPase-activating protein (GAP)-stimulated GTPase activity of Rab3A. Here, we show that Rabphilin-3A has another activity to stimulate the GDP/GTP exchange reaction of Rab3A. Rabphifin-3A may keep Rab3A continuously in the GTP-bound form by converting again GDP-Rab3A, which may be converted from GTP-Rab3A by Rab3A GAP, to GTP-Rab3A, until the function of Rab3A is accomplished

Localization of Liv2 as an Immature Hepatocyte Marker in EB Outgrowth

The objective of this study was to establish Liv2, a surface marker of mouse immature hepatocytes (hepatoblasts), as a selection tool for embryonic stem (ES) cell–derived immature hepatocytes by acquiring basic data on Liv2 in normal mouse embryos and by confirming Liv2 expression in mouse ES-derived cells. The estimated molecular weight of Liv2 was 4045 kDa, and immunoreactivity was definitively detected in the cell membrane of fetal hepatocytes on embryonic day (E) 9.5, declined gradually until E12.5, and subsequently became undetectable. Liv2 was localized on and close to the cell membrane. Embryoid bodies (EB) were formed from mouse ES cells whose undifferentiated state was confirmed with immunostaining of Nanog by the hanging drop method. A few Liv2-positive cells occurred as a cluster in EB outgrowth on day 7, but only some of these were albumin (ALB)-positive on day 13. These cells had the same pattern of immunoreactivity, i.e., localization on the cell membrane, as immature hepatocytes in the developing liver, although there were other types of cells with a different pattern of immunoreactivity that were seen only as a granular pattern in the cytoplasm and without ALB or the neuronal marker nestin. These results suggest that Liv2 may be useful as a surface marker for immature hepatocytes derived from ES cells. This application would allow for the sole selection of immature hepatocytes and provide a useful tool for regenerative medicine

High Human T Cell Leukemia Virus Type-1(HTLV-1) Provirus Load in Patients with HTLV-1 Carriers Complicated with HTLV-1-unrelated disorders

<p>Abstract</p> <p>Background</p> <p>To address the clinical and virological significance of a high HTLV-1 proviral load (VL) in practical blood samples from asymptomatic and symptomatic carriers, we simultaneously examined VL and clonal expansion status using polymerase chain reaction (PCR) quantification (infected cell % of peripheral mononuclear cells) and Southern blotting hybridization (SBH) methods.</p> <p>Results</p> <p>The present study disclosed extremely high VL with highly dense smears with or without oligoclonal bands in SBH. A high VL of 10% or more was observed in 16 (43.2%) of a total of 33 samples (one of 13 asymptomatic carriers, 8 of 12 symptomatic carriers, and 7 of 8 patients with lymphoma-type ATL without circulating ATL cells). In particular, an extremely high VL of 50% or more was limited to symptomatic carriers whose band findings always contained at least dense smears derived from polyclonally expanded cells infected with HTLV-1. Sequential samples revealed that the VL value was synchronized with the presence or absence of dense smears, and declined at the same time as disappearing dense smears. Dense smears transiently emerged at the active stage of the underlying disease. After disappearance of the smears, several clonal bands became visible and were persistently retained, explaining the process by which the clonality of HTLV-1-infected cells is established. The cases with only oligoclonal bands tended to maintain a stable VL of around 20% for a long time. Two of such cases developed ATL 4 and 3.5 years later, suggesting that a high VL with oligoclonal bands may be a predisposing risk to ATL.</p> <p>Conclusion</p> <p>The main contributor to extremely high VL seems to be transient emergence of dense smears detected by the sensitivity level of SBH, corresponding to polyclonal expansion of HTLV-1-infected cells including abundant small clones. Major clones retained after disappearance of dense smears stably persist and acquire various malignant characteristics step by step.</p