Growth of step bunches on a Si(001) vicinal face with drift of adatoms

金沢大学総合メディア基盤センターOn a Si(001) vicinal face, where the direction of fast surface diffusion alternates on consecutive terraces, step bunching has been observed under direct current heating. By using a one-dimensional step model with drift of adatoms, we study growth laws of step bunches. If evaporation is negligible, the average number N of steps in a bunch increases with time as N ∝ tβ with β less than and double approximate 1/2. The growth exponent β weakly depends on the repulsive interaction potential between steps. When steps at a distance l interact with the repulsive potential ζ ∝ 1/l ν, the average step distance in a bunch lb decreases as lb ∝ N-α with α ≈ 3/2(ν + 2). The exponents α and β are related as β ≈ 1/(2 + α). The simulation results are consistent with experiment if we take account of both logarithmic and ν = 2 potentials, which are expected in this system. The growth rate of the bunch size with step-down drift is faster than that with step-up drift. If evaporation of adatoms is significant, the difference of the growth rate in the opposite drift directions becomes small. The apparent exponent β depends on the drift direction, and is larger with step-up drift. © 2004 The Physical Society of Japan

Mammalian Lgl Forms a Protein Complex with PAR-6 and aPKC Independently of PAR-3 to Regulate Epithelial Cell Polarity

AbstractBackground: Epithelial cells have apicobasal polarity and an asymmetric junctional complex that provides the bases for development and tissue maintenance. In both vertebrates and invertebrates, the evolutionarily conserved protein complex, PAR-6/aPKC/PAR-3, localizes to the subapical region and plays critical roles in the establishment of a junctional complex and cell polarity. In Drosophila, another set of proteins called tumor suppressors, such as Lgl, which localize separately to the basolateral membrane domain but genetically interact with the subapical proteins, also contribute to the establishment of cell polarity. However, how physically separated proteins interact remains to be clarified.Results: We show that mammalian Lgl competes for PAR-3 in forming an independent complex with PAR-6/aPKC. During cell polarization, mLgl initially colocalizes with PAR-6/aPKC at the cell-cell contact region and is phosphorylated by aPKC, followed by segregation from apical PAR-6/aPKC to the basolateral membrane after cells are polarized. Overexpression studies establish that increased amounts of the mLgl/PAR-6/aPKC complex suppress the formation of epithelial junctions; this contrasts with the previous observation that the complex containing PAR-3 promotes it.Conclusions: These results indicate that PAR-6/aPKC selectively interacts with either mLgl or PAR-3 under the control of aPKC activity to regulate epithelial cell polarity

Vertical oxide semiconductor field-effect transistor with extremely low off-state current

Oxide semiconductor field-effect transistors (OSFETs) are actively developed for display applications. An OSFET exhibits a lower off-state current than a silicon FET and enables low-frequency driving. We developed the measurement method and revealed the OSFET exhibits an extremely low off-state current [1]. In addition, we discovered a c-axis aligned crystalline indium-gallium-zinc oxide (CAAC-IGZO) which was unique crystal morphology [2]. A display with a backplane formed using CAAC-IGZO FETs achieves low power consumption owing to idling-stop driving that allows an extremely low refresh rate [3]. Please click Download on the upper right corner to see the full abstract

Discrimination of Stem Cell Status after Subjecting Cynomolgus Monkey Pluripotent Stem Cells to Naïve Conversion

Experimental animal models have played an indispensable role in the development of human induced pluripotent stem cell (iPSC) research. The derivation of high-quality (so-called “true naïve state”) iPSCs of non-human primates enhances their application and safety for human regenerative medicine. Although several attempts have been made to convert human and non-human primate PSCs into a truly naïve state, it is unclear which evaluation methods can discriminate them as being truly naïve. Here we attempted to derive naïve cynomolgus monkey (Cm) (Macaca fascicularis) embryonic stem cells (ESCs) and iPSCs. Several characteristics of naïve Cm ESCs including colony morphology, appearance of naïve-related mRNAs and proteins, leukaemia inhibitory factor dependency, and mitochondrial respiration were confirmed. Next, we generated Cm iPSCs and converted them to a naïve state. Transcriptomic comparison of PSCs with early Cm embryos elucidated the partial achievement (termed naïve-like) of their conversion. When these were subjected to in vitro neural differentiation, enhanced differentiating capacities were observed after naïve-like conversion, but some lines exhibited heterogeneity. The difficulty of achieving contribution to chimeric mouse embryos was also demonstrated. These results suggest that Cm PSCs could ameliorate their in vitro neural differentiation potential even though they could not display true naïve characteristics

A phospho-switch controls RNF43-mediated degradation of Wnt receptors to suppress tumorigenesis.

Funder: Japan Foundation for Applied Enzymology; doi: https://doi.org/10.13039/100008695Funder: Pancreas Research Foundation of Japan Collaborative Research Project Program of the Medical Institute of Bioregulation, Kyushu University, Japan Joint Research Program of the Institute for Molecular and Cellular Regulation, Gunma University, Japan Grant for Joint Research Project of the Research Institute for Microbial Diseases Osaka UniversityFunder: European Research Council (ERC (639050) and the Interpark Bio-Convergence Center Grant Program.Frequent mutation of the tumour suppressor RNF43 is observed in many cancers, particularly colon malignancies. RNF43, an E3 ubiquitin ligase, negatively regulates Wnt signalling by inducing degradation of the Wnt receptor Frizzled. In this study, we discover that RNF43 activity requires phosphorylation at a triplet of conserved serines. This phospho-regulation of RNF43 is required for zebrafish development and growth of mouse intestinal organoids. Cancer-associated mutations that abrogate RNF43 phosphorylation cooperate with active Ras to promote tumorigenesis by abolishing the inhibitory function of RNF43 in Wnt signalling while maintaining its inhibitory function in p53 signalling. Our data suggest that RNF43 mutations cooperate with KRAS mutations to promote multi-step tumorigenesis via the Wnt-Ras-p53 axis in human colon cancers. Lastly, phosphomimetic substitutions of the serine trio restored the tumour suppressive activity of extracellular oncogenic mutants. Therefore, harnessing phospho-regulation of RNF43 might be a potential therapeutic strategy for tumours with RNF43 mutations

Cilostazol attenuates ischemia?reperfusion-induced blood?brain barrier dysfunction enhanced by advanced glycation endproducts via transforming growth factor-β1 signaling

We investigated the effects of cilostazol, a selective inhibitor of phosphodiesterase 3, on blood-brain barrier (BBB) integrity against ischemia-reperfusion injury enhanced by advanced glycation endproducts (AGEs). We used in vitro BBB models with primarily cultured BBB-related cells from rats (brain capillary endothelial cells, astrocytes and pericytes), and subjected cells to either normoxia or 3-h oxygen glucose deprivation (OGD)/24-h reoxygenation with or without AGEs. Treatment of AGEs did not affect the transendothelial electrical resistance (TEER) in the BBB model under normoxia, but there was a significant decrease in TEER under 3-h OGD/24-h reoxygenation conditions with AGEs. Cilostazol inhibited decreases in TEER induced by 3-h OGD/24-h reoxygenation with AGEs. Immunocytochemical and Western blot analyses showed that AGEs reduced the expression of claudin-5, the main functional protein of tight junctions (TJs). In contrast, cilostazol increased the expression of claudin-5 under 3-h OGD/24-h reoxygenation with AGEs. Furthermore, while AGEs increased the production of extracellular transforming growth factor (TGF)-β1, cilostazol inhibited the production of extracellular TGF-β1 and restored the integrity of TJs. Thus, we found that AGEs enhanced ischemia-reperfusion injury, which mainly included decreases in the expression of proteins comprising TJs through the production of TGF-β1. Cilostazol appeared to limit ischemia-reperfusion injury with AGEs by improving the TJ proteins and inhibiting TGF-β1 signaling

Si(001)微斜面での通電加熱時のステップ束の形成と成長則 : 結晶成長理論Ⅰ

金沢大学総合メディア基盤センターWith a Si(001) vicinal face in mind, we study step bunching induced by drift of adatoms taking account of the alternation of anisotropic diffusion coefficient. The step bunching occurs irrespective of the drift direction. We perform simulation of a one-dimensional step flow model and analyze growth law of the bunch size and size dependence of the step distance in a bunch