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Cyclo-glycylproline (cGP), a cyclic dipeptide containing a condensation bond between glycine and proline, is produced by the cyclization of the N-terminal tripeptide of insulin-like growth factor-1. Previous studies have shown that cGP administration exerts a neuroprotective effect and enhances the regenerative ability in rats with ischemic brain injury. The efficacy of cGP is medicated by regulating the bioavailability of insulin-like growth factor-1 (IGF-1), however, the molecular mechanisms underlying the neuroprotective effects of cGP on brain damage remains to be elucidated. In the current study, we investigated the cGP-mediated molecular mechanism in human fetal neural stem cells (hfNSCs) exposed to oxidative stress, which is a key factor affecting the development of several brain diseases, including traumatic brain injury and Parkinson's disease. We found that cGP treatment attenuated oxidative stress-induced cell death in cultured hfNSCs in a dose-dependent manner. Transcriptome analysis revealed that under oxidative stress conditions, p53-mediated signaling was activated, accompanied by upregulation of mouse double minute 2 homolog (MDM2), a p53-specific E3 ubiquitin ligase, in cGP-treated hfNSCs. By using a comprehensive protein phosphorylation array, we found that cGP induced the activation of Akt signaling pathway, which enhanced the expression of MDM2, in hfNSCs exposed to oxidative stress. Moreover, the MDM2 inhibitor nutlin-3 inhibited the protective effect of cGP on oxidative stress-induced cell death and apoptosis. Therefore, cGP attenuates oxidative stress-induced cell death mediated by the interplay between IGF-1 signaling and the MDM2-p53 pathway in human NSCs. We revealed the molecular mechanism underlying cGP-induced neuroprotective properties in a model of brain damage.

Signaling pathways involving signal transducer and activator of transcription 3 (STAT3) play key roles in the aggressiveness of pancreatic ductal adenocarcinoma (PDAC), including their tumorigenesis, invasion, and metastasis. Cancer stem cells (CSCs) have been correlated with PDAC aggressiveness, and activation of STAT3 is involved in the regulation of CSC properties. Here, we investigated the involvement of interleukin-6 (IL-6) or the leukemia inhibitory factor (LIF)/glycoprotein 130 (gp130)/STAT3 pathway and their role in pancreatic CSCs. In PDAC CSC-like cells formed by culturing on a low attachment plate, autocrine/paracrine IL-6 or LIF contributes to gp130/STAT3 pathway activation. Using a gp130 inhibitor, we determined that the gp130/STAT3 pathway contributes to the maintenance of stemness features, the expression of membrane-type 1 matrix metalloproteinase (MT1-MMP), and the invasion of PDAC CSC-like cells. The gp130/STAT3 pathway also modulates the transforming growth factor (TGF)-β1/Smad pathway required for epithelial-mesenchymal transition induction through regulation of TGFβ-RII expression in PDAC CSC-like cells. Furthermore, chromatin immunoprecipitation assays revealed that p-STAT3 can access the active promoter region of

Fascin, an actin-bundling protein, is present in the filopodia and lamellipodia of growth cones. However, few studies have examined lamellipodial fascin because it is difficult to observe. In this study, we evaluated lamellipodial fascin. We visualized the actin meshwork of lamellipodia in live growth cones by super-resolution microscopy. Fascin was colocalized with the actin meshwork in lamellipodia. Ser39 of fascin is a well-known phosphorylation site that controls the binding of fascin to actin filaments. Fluorescence recovery after photobleaching experiments with confocal microscopy showed that binding of fascin was controlled by phosphorylation of Ser39 in lamellipodia. Moreover, TPA, an agonist of protein kinase C, induced phosphorylation of fascin and dissociation from actin filaments in lamellipodia. Time series images showed that dissociation of fascin from the actin meshwork was induced by TPA. As fascin dissociated from actin filaments, the orientation of the actin filaments became parallel to the leading edge. The angle of actin filaments against the leading edge was changed from 73° to 15°. This decreased the elasticity of the lamellipodia by 40%, as measured by atomic force microscopy. These data suggest that actin bundles made by fascin contribute to elasticity of the growth cone.

Indonesian ginger (Zingiber purpureum Rosc.), also known as Bangle, exhibits neurotrophic effects on cultured murine cortical neurons and in the adult mouse brain, but the underlying mechanisms remain unknown. Here, using human fetal neural stem cells (hfNSCs) as a model system for in vitro human neurogenesis, we show that Bangle extracts activate canonical WNT/&beta, catenin signaling. Bangle extract-treatment of hfNSCs not only promoted neuronal differentiation, but also accelerated neurite outgrowth from immature neurons. Furthermore, Bangle extracts induced expression of neurogenic genes and WNT signaling-target genes, and facilitated the accumulation of &beta, catenin in nuclei of hfNSC. Interestingly, altered histone modifications were also observed in Bangle-treated hfNSCs. Together, these findings demonstrate that Bangle contributes to hfNSC neurogenesis by WNT pathway and epigenetic regulation.

DNA methylation at the 5-position of cytosine bases (5-methylcytosine, 5mC) in genomic DNA is representative epigenetic modification and is involved in many cellular processes, including gene expression and embryonic development. The hydroxylation of 5mC provide 5-hydroxymethylcytosine (5hmC), the so-called sixth base rediscovered recently in mammalian cells, is also considered to act as an epigenetic regulator. We report herein the immunochemical assessment of 5hmC achieved by an enzyme-linked immunosorbent assay (ELISA) using our linker technology. The keys to this assay are 1) the immobilization of genomic DNA with the bifunctional linker molecule, and 2) quantitative analysis by using guaranteed standard samples containing defined amounts of 5hmC. We succeeded in the sensitive and quantitative detection of 5hmC as well as 5mC in HEK293T cells transfected with TET1, and also monitored the effect of ascorbate on the TET1 catalyzed conversion of 5mC to 5hmC. Our linker technology enables the rapid and stable immobilization of genomic samples and thus contributes to the realization of a reproducible 5hmC evaluation method.

Flavin adenine dinucleotide (FAD), synthesized from riboflavin, is redox cofactor in energy production and plays an important role in cell survival. More recently, riboflavin deficiency has been linked to developmental disorders, but its role in stem cell differentiation remains unclear. Here, we show that FAD treatment, using DMSO as a solvent, enabled an increase in the amount of intracellular FAD and promoted neuronal differentiation of human neural stem cells (NSCs) derived not only from fetal brain, but also from induced pluripotent stem cells. Depression of FAD‐dependent histone demethylase, lysine‐specific demethylase‐1 (LSD1), prevented FAD‐induced neuronal differentiation. Furthermore, FAD influx facilitated nuclear localization of LSD1 and its enzymatic activity. Together, these findings led us to propose that FAD contributes to proper neuronal production from NSCs in the human fetal brain during development.

Dermatan sulphate (DS), a glycosaminoglycan, is present in the extracellular matrix and on the cell surface. Previously, we showed that heparan sulphate plays a key role in the maintenance of the undifferentiated state in mouse embryonic stem cells (mESCs) and in the regulation of their differentiation. Chondroitin sulphate has also been to be important for pluripotency and differentiation of mESCs. Keratan sulphate is a marker of human pluripotent stem cells. To date, however, the function of DS in mESCs has not been clarified. Dermatan 4 sulfotransferase 1, which transfers sulphate to the C-4 hydroxyl group of N-acetylgalactosamine of DS, contributes to neuronal differentiation of mouse neural progenitor cells. Therefore, we anticipated that neuronal differentiation would be induced in mESCs in culture by the addition of DS. To test this expectation, we investigated neuronal differentiation in mESCs and human neural stem cells (hNSCs) cultures containing DS. In mESCs, DS promoted neuronal differentiation by activation of extracellular signal-regulated kinase 1/2 and also accelerated neurite outgrowth. In hNSCs, DS promoted neuronal differentiation and neuronal migration, but not neurite outgrowth. Thus, DS promotes neuronal differentiation in both mouse and human stem cells, suggesting that it offers a novel method for efficiently inducing neuronal differentiation.

In pancreatic cancer, morphologically and functionally heterogeneous cancer cells reside within the same patient. The heterogeneity is believed to promote metastasis and resistance to chemoradiotherapy. MIA PaCa-2, an established human pancreatic ductal adenocarcinoma (PDAC) cell line, contains round and spindle-shaped adherent cells, as well as, round floating cells. In this study, we aimed to assess if the floating cells might have greater metastatic potential and/or be more resistant to drug-induced apoptosis compared to adherent cells. Time-lapse analysis revealed that the two types of adherent cells transformed bilaterally, and some of the adherent, round cells converted to floating cells. Flow cytometry and electron microscopy showed that approximately 90% of the floating cells were viable. qRT-PCR analysis revealed that floating cells expressed lower levels of integrins and ATP-binding cassette (ABC) transporters than adherent cells. In contrast, except for vimentin, floating cells expressed more epithelial to mesenchymal transition markers than adherent cells. Floating cells included a larger population of G2/M-phase cells, and migration assays revealed a decreased migration ability by floating cells relative to adherent cells. A cell aggregation assay showed that the aggregative properties of the floating cells were lower than those of the adherent cells. In 3D culture, spheres derived from floating cells were more sensitive to anti-cancer drugs, including gemcitabine, 5-FU, and abraxane, than those derived from adherent cells. Expression levels of stemness markers in the spheres derived from floating cells were lower than those derived from adherent cells. Morphological characterization of human PDAC cell lines may help to clarify the series of alterations cancer cells undergo during the metastatic process and may contribute to the development of new PDAC diagnostics and more patient-specific treatments for those with PDAC.

Cancer stem cells (CSCs) are a small group of cells within a tumor that preserve stemness and enhance regrowth of cancer cells. CSCs have important implications in resistance to conventional therapies and tumor relapse, although their detailed properties remain unknown. Thus, CSCs represent promising targets to improve cancer treatment. So far, a number of cell surface markers containing glycans have been exploited to identify and isolate CSCs. Cell surface glycans are well-known markers for specific cell types and also play important cellular roles, such as regulation of cell signaling. In normal stem cells, including embryonic and tissue stem cells, glycan markers in an undifferentiated state have been identified. These markers are mostly known to regulate signaling pathways required for maintenance of stemness. In contrast, CSC-specific glycans have not been well characterized yet. In this review, we summarize functional commonalities between CSCs and normal stem cells in glycan-mediated signaling pathways. Identification of CSC-specific glycans may lead to early diagnosis and radical treatment of cancer.

Histone-modifying enzymes dynamically regulate the chromatin status and have been implicated in the fate specification of stem cells, including neural stem cells (NSCs), which differentiate into three major cell types: neurons, astrocytes, and oligodendrocytes. Lysine-specific demethylase 1 (LSD1, also known as KDM1A) catalyzes the demethylation of H3K4me1/2 and H3K9me1/2, and it was recently suggested that functional disruption of LSD1 links to various human diseases. However, the mechanism by which LSD1 regulates human neural development remains unclear. Here, we present evidence that specific inhibition of LSD1 suppresses the neurogenesis of cultured human fetal NSCs (hfNSCs) isolated from the human fetal neocortex. Notably, we found that LSD1 directly associates with the promoter of the HEYL gene, and controls the demethylation of H3K4me2, which is accompanied by repression of HEYL expression during hfNSC neuronal differentiation. Furthermore, we also showed that HEYL expression is sufficient to inhibit the neuronal differentiation of hfNSCs. This mechanism seems to be primate-specific because mouse NSCs do not exhibit the LSD1 inhibitor-induced upregulation of Heyl. Our findings suggest that LSD1 plays an important role in primate neurogenesis and may contribute to the characterization of an evolved primate brain.

Correlative light-electron microscopy of cells in a natural environment of aqueous liquid facilitates high-throughput observation of protein complex formation. ASEM allows the inverted SEM to observe the wet sample from below, while an optical microscope observes it from above quasi-simultaneously. The disposable ASEM dish with a silicon nitride (SiN) film window can be coated variously to realize the primary-culture of substrate-sensitive cells in a few milliliters of culture medium in a stable incubator environment. Neuron differentiation, neural networking, proplatelet-formation and phagocytosis were captured by optical or fluorescence microscopy, and imaged at high resolution by gold-labeled immuno-ASEM with/without metal staining. Fas expression on the cell surface was visualized, correlated to the spatial distribution of F-actin. Axonal partitioning was studied using primary-culture neurons, and presynaptic induction by GluRδ2-N-terminus-linked fluorescent magnetic beads was correlated to the presynaptic-marker Bassoon. Further, megakaryocytes secreting proplatelets were captured, and P-selectins with adherence activity were localized to some of the granules present by immuno-ASEM. The phagocytosis of lactic acid bacteria by dendritic cells was also imaged. Based on these studies, ASEM correlative microscopy promises to allow the study of various mesoscopic-scale dynamics in the near future.

High-throughput immuno-electron microscopy is required to capture the protein–protein interactions realizing physiological functions. Atmospheric scanning electron microscopy (ASEM) allowsin situcorrelative light and electron microscopy of samples in liquid in an open atmospheric environment. Cells are cultured in a few milliliters of medium directly in the ASEM dish, which can be coated and transferred to an incubator as required. Here, cells were imaged by optical or fluorescence microscopy, and at high resolution by gold-labeled immuno-ASEM, sometimes with additional metal staining. Axonal partitioning of neurons was correlated with specific cytoskeletal structures, including microtubules, using primary-culture neurons from wild typeDrosophila, and the involvement of ankyrin in the formation of the intra-axonal segmentation boundary was studied using neurons from anankyrin-deficient mutant. Rubella virus replication producing anti-double-stranded RNA was captured at the host cell’s plasma membrane. Fas receptosome formation was associated with clathrin internalization near the surface of primitive endoderm cells. Positively charged Nanogold clearly revealed the cell outlines of primitive endoderm cells, and the cell division of lactic acid bacteria. Based on these experiments, ASEM promises to allow the study of protein interactions in various complexes in a natural environment of aqueous liquid in the near future.

Single crystal eutectic composites have recently been researched and developed as the bulk materials. They are generally expected to be the most interesting and attractive as the high temperature, environmental resistant structural material in the field of aeronautics, aerospace and power generator technologies. They have high temperature strength characteristics, high creep and oxidation resistance as well as the fairly good machinability and manufacturability. An overview provides explain the National project of application of eutectic composites for 1700 °C-class gas turbine system that does not require thermal and environmental barrier coatings. Pure mode-I and -II, mixed-mode fracture toughness are investigated up to 1700 °C in air to determine materials reliability and also discussed fatigue crack growth characteristics in relation to materials durability. Key technical issues are summarized with prospects for a wide practical application.

Experimental studies were undertaken to assess the environmental effects on ultra-high temperature tensile creep behavior of directionally solidified Al2O3/Y3Al5O12(YAG) and Al2O3/GdAlO3(GAP) eutectic ceramics. Tensile creep deformation tests conducted under constant stress ranging 100–200 MPa at temperature range of 1673–1873 K at different environmental conditions consisting of air and at different water vapor pressure, p H 2 O , up to 0.6 MPa. These eutectic ceramics exhibited a stress exponent of about 4.9–11.6, indicative of tensile creep behavior characteristic of dislocation mechanism. The apparent activation energy for creep deformation was 737–984 kJ/mol of Al2O3/YAG and 957 kJ/mol of Al2O3/GAP in air, while it was 529–645 kJ/mol of Al2O3/YAG and 611 kJ/mol of Al2O3/GAP at p H 2 O = 0.06 MPa and 570–620 kJ/mol of Al2O3/YAG at p H 2 O = 0.6 MPa. The presence of moisture accelerated the creep rate by about 1.4–4 orders of magnitude for p H 2 O = 0.06 MPa, about five orders of magnitude for p H 2 O = 0.4 MPa and about 5–7 orders of magnitude for p H 2 O = 0.6 MPa as compared with that in air at 1773 K. Results of this study and reasonable estimates in changes of the water vapor pressure indicated accelerated creep behavior by the presence of moisture.

Behavior of thermo-mechanical fatigue (TMF) failure of a new generation titanium alloy matrix composite, SP700/SCS-6, was studied, based on a series of investigations on ; (i) mechanical properties under monotonic loading of the SP-700/SCS-6 composite and the matrix alloy; (ii) fiber push-out tests to represent the fiber/matrix interfacial strength at elevated temperatures ; (iii) isothermal low cycle fatigue (ILCF) tests, (iv) interfacial reaction zone to characterize the microscopic damage evolution under the TMF test and the thermal cycle test without external load. A special focus was paid to understand both the mechanisms of TMF failure, and the dissimilarities and the similarities between the TMF and ILCF failures. From the results of these tests, it was shown that the differences of damage characteristics may be concerned with the degradation of the fiber/matrix interface by the crack propagation and reaction layer due to thermal cycles. These systematic investigations showed that the lives and the failure mechanisms of the TMF should be clearly distinguished from those of the isothermal ILCF, whereas there were a few similarities between them. It was also suggested the difference should be primarily originated from the cracking by the repeat of the thermal cycle and the resultant change in fiber/matrix adhesion strength.

Compressive creep tests were conducted for an in-situ single-crystal alumina/yttrium aluminum garnet [Al 2 O 3 /Y 3 Al 5 O 12 (YAG)] eutectic composite for a specimen with a compressive axis with 0 or 90° to the solidified direction at temperatures between 1723 and 1923 K under stress ranges of 140–450 MPa in air environments. The single-crystal Al 2 O 3 /YAG eutectic exhibited a stress exponent of 5.4–10, indicative of compressive creep behavior characterized by a dislocation mechanism. Activation energies for creep deformation were 810–1024 kJ/mol, close to that for 42° from c -axis single-crystal Al 2 O 3 or single-crystal YAG, in agreement with that of self-diffusion for c -axis single-crystal Al 2 O 3 . The 0° specimen exhibited a slight decrease in creep rate by about half for a 90° specimen corresponding to results from crystal anisotropy in single-crystal Al 2 O 3 . The Larson–Miller method provided an effective means of comparing creep resistance of oxides on the basis of results obtained under different stresses and temperatures.

Efficacy of the Shinki bioclean room for preventing infection in neutropenic patients Aim of the study. To investigate the effectiveness of a new type of bioclean room named Shinki bioclean room (SBCR) for the prevention of infection during neutropenia after intensive chemotherapy in comparison with a standard laminar air flow room (LAFR). Background. Recently, a new industrial technology, wherein a dust-free and aseptic environment is created by circulating air containing nanometre order ultra fine water droplets with abundant negative air ions, has been developed in Japan. Methods. The air cleanliness of SBCR was examined by measuring airborne particles and microorganisms. Bacteriological samples for environment culture were taken by means of exposed settle-plates. In addition, the frequency of pneumonia and fever higher than 38°C were examined in 34 patients with acute leukaemia who received intensive chemotherapy in SBCR or LAFR. Results. The number of airborne particles (≥0·5 μm) was 70 particles/ft3, and that of airborne microorganisms was 0·00 colony forming unit/ft3 in SBCR, and neither bacteria nor fungi were detected. The numbers of colonies of bacteria and fungi on air settle-plates were fewer in the SBCR than in the LAFR regardless of the presence of patients or the nurse entering. The frequency of pneumonia during chemotherapy for acute leukaemia was lower in the SBCR group (0%, 0/19 cases) than in the LAFR group (27%, 4/15 cases) (P=0·0294) and the frequency of fever higher than 38°C also tended to be lower in the SBCR group (53%, 10/19 cases) than in the LAFR group (80%, 12/15 cases) (P=0·0973). Conclusion. The SBCR is equal or superior to LAFR in preventing infection during neutropenia. Other advantages for SBCR are a low level of noise (40 dB), easy control of temperature and humidity, and efficient removal of odour. In addition to the quiet and comfortable atmosphere, expected favourable effects of negative air ions may give higher quality of life for patients in SBCR than those in LAFR. Further studies will be needed to examine the safety, benefits and effects of the negative ion exposure.

The relationship between nutritional status and insulin-like growth factor binding protein-2 (IGFBP-2) gene expression in chickens was studied. Chickens (6 wk old) were food deprived for 2 d and then refed. IGFBP-2 mRNA in the brain was significantly decreased by food deprivation and levels did not increase when birds were refed for 24 h. Gizzard and hepatic IGFBP-2 mRNA levels were significantly increased by food deprivation and decreased by refeeding. Any nutrients tested decreased hepatic IGFBP-2 gene expression. In kidney, IGFBP-2 mRNA was detected but not influenced by food deprivation and refeeding. In another study, the influence of dietary protein source [isolated soybean protein vs. casein; crude protein (CP) 20%] and the supplementation of essential amino acids on IGFBP-2 gene expression of young chickens (5 wk old) was examined. The influence of feeding a low soybean protein diet (CP 5%) on tissue IGFBP-2 gene expression was also investigated. Hepatic IGFBP-2 mRNA was not detected in any group. Feeding the low protein diet for 7 d decreased brain IGFBP-2 mRNA level and increased gizzard IGFBP-2 level compared with chickens fed 20% protein diets. A significant interaction between protein source and amino acid supplementation was observed in gizzard IGFBP-2 mRNA level. In both casein-fed groups and in chickens fed 20% soybean protein diet without supplemental amino acids, the levels did not differ from one another or from the low protein diet-fed birds. The level was lower in chickens fed the amino acid-supplemented, 20% soybean protein diet. In conclusion, the response of IGFBP-2 gene expression to variations in nutritional status was rapid and different in several tissues of young chickens, which would help modulate the growth-promoting effect of circulating IGF-I by making the IGF-IGFBP complex.

Item does not contain fulltext The characteristics of pluripotent embryonic stem cells of human and mouse are different. The properties of human embryonic stem cells (hESCs) are similar to those of mouse epiblast stem cells (mEpiSCs), which are in a later developmental pluripotency state, the so-called "primed state" compared to mouse embryonic stem cells (mESCs) which are in a naive state. As a result of the properties of the primed state, hESCs proliferate slowly, cannot survive as single cells, and can only be transfected with genes at low efficiency. Generating hESCs in the naive state is necessary to overcome these problems and allow their application in regenerative medicine. Therefore, clarifying the mechanism of the transition between the naive and primed states in pluripotent stem cells is important for the establishment of stable methods of generating naive state hESCs. However, the signaling pathways which contribute to the transition between the naive and primed states are still unclear. In this study, we carried out induction from mESCs to mEpiSC-like cells (mEpiSCLCs), and observed an increase in the activation of Fas signaling during the induction. The expression of Fgf5, an epiblast marker, was diminished by inhibition of Fas signaling using the caspase-8 and -3 blocking peptides, IETD and DEVD, respectively. Furthermore, during the induction, we observed increased expression of 3-O sulfated heparan sulfate (HS) structures synthesized by HS 3-O-sulfotransferase (3OST), which are recognized by the HS4C3 antibody (HS4C3-binding epitope). Knockdown of 3OST-5 reduced Fas signaling and the potential for the transition to mEpiSCLCs. This indicates that the HS4C3-binding epitope is necessary for the transition to the primed state. We propose that Fas signaling through the HS4C3-binding epitope contributes to the transition from the naive state to the primed state.

In general, structural integrity depends on material performance under cyclic loading. It is therefore very important to characterize the fatigue strength characteristics of ceramic/metal joints for wide use in structural applications of engineering ceramics. In this work, in order to clarify the strength characteristics of alumina joints, static strength and cyclic fatigue tests were carried out for joints of Al 2 O 3 /Al 2 O 3 and Al 2 O 3 /Mo/SUS 304/Mo/Al 2 O 3 formed with Ticusil and Cu 80 Ti 20 fillers in vacuum. Static tests were conducted at room temperature and elevated temperature. Fatigue tests were conducted at constant stress ratio R (=0.1) and constant frequency f(=50 Hz) at room temperature. The strength characteristics of the joints of Al 2 O 3 /Al 2 O 3 formed using Ticusil were similar to the strength characteristics of Al 2 O 3 . The strength characteristics of the joints of Al 2 O 3 /Mo/SUS 304/Mo/Al 2 O 3 were mainly determined by those of the joint of Mo/Al 2 O 3 .

Effects of a surface layer with chill structure, specimen thickness, shape of mold and powder lubrication in a sleeve on fracture mechanic characteristics were investigated for aluminum alloy die castings ADC12 with two different types of molds (flat and staircase shapes). The results are as follows. In the case of a flat mold, a decrease of thickness improves mechanical properties. A surface layer with chill structure has a substantial influence on mechanical properties, but little influence on fracture toughness. In the case of the staircase mold, the mechanical properties are the same as for the flat mold. On the other hand, the powder lubrication in the sleeve improves the fracture toughness and reduces the scatter in fracture toughness. There is little influence of both the surface layer with chill structure and the specimen orientation on the fatigue crack growth resistance, but with decrease of specimen thickness, the fatigue crack growth resistance decreases, especially in the region of near-threshold fatigue crack growth rate. In addition, the lubricating method has no effect on the fatigue crack growth resistance for the staircase-shapes die castings.

The basic objective of this study is to establish the material design concepts for the coexistence of good high-temperature mechanical properties and super heat resistance in the systems of ceramic/metal and ceramic/ceramic functionally gradient materials (FGMs). Flexural and fracture toughness tests were conducted on gas-pressure combustion-sintered Cr 3 C 2 ceramic and its composites with Ni and TiC (Cr 3 C 2 /Ni, Cr 3 C 2 /TiC) in a vacuum environment up to 1 200°C using a newly developed materials testing system. Fracture characteristics were investigated on the basis of fracture mechanics and fractography. The toughness of Cr 3 C 2 can be improved by the addition of metallic particles. It is found that the principal mechanism of toughness improvement in these composites (ductile-phase reinforced ceramic matrix composites) is attributable to crack-tip plastic blunting by a ductile metallic phase.

The tensile deformation and damage behavior of 2024-T6 aluminum alloy reinforced by 2% and 10% SiC particles are studied. SEM (Scanning Electron Microscope) observation shows that the fracture occurs due to the dimple fracture of matrix, interfacial debonding of particle and matrix and particle cracking. These fracture processes are simulated numerically using Gurson's constitutive equation with large-deformation theory. It is shown that the nonuniform distributions of particles have a large effect on the microfracture process, and the effect of the initial debonding and particle cracking are discussed.

In order to study the influence of the grain size and PSZ reinforcement on fatigue strength characteristics of alumina, cyclic fatigue tests were carried out on sintered alumina (Al2O3) with a surface crack. The crack was introduced by Vicker's indentation method under two load levels, 98N and 294 N. Fatigue strength tests were conducted at a constant stress ratio R(=0. 1) and constant frequency f(=50 Hz). It is shown that there is large influence of grain size on fatigue strength characteristics and the larger-grained alumina has a longer fatigue life. It is also found that PSZ reinforcement is effective in enhancing the fatigue strength of alumina.

In order to study the influence of cyclic load on the crack propagation behavior of sintered alumina, static and cyclic fatigue crack growth tests were carried out over a wide range of fatigue crack growth rates. In the case of cyclic load, crack growth tests were conducted at a constant stress ratio R(=0. 1) and at three levels of frequencies f : 1 Hz, 10 Hz and 50 Hz. Further tests were carried out at a constant f(=10 Hz) and at three levels of R : 0. 1, 0. 5 and 0. 8. The crack growth rate da/dN as independent of frequency. In cases of R : 0. 1 and 0. 5, the crack growth rate in cyclic fatigue was higher than that in static fatigue. In the case of R=0. 8, the crack growth rate in cyclic fatigue was almost identical to that in static fatigue. The effective stress intensity factor range ΔKeff is also a useful parameter to evaluate the cyclic fatigue crack growth characteristics.

It is still essential for high strength engineering ceramics to improve fracture toughness for a wide use in primary structural applications. The purposes of this paper are to apply the ductile metallic phase toughening mechanism proposed previously to ceramics/metals functionally gradient materials (FGMs) and to confirm the possibility of improvement of fracture toughness without the reduction of strength. Fracture characteristics were investigated for symmetrically step by step graded FGMs (Cr3C2/Ni, TiC/Ni) on the basis of fracture mechanics and fractography. It was found that the ductile metallic phase toughening mechanism has a good potential for ceramics/metals FGMs.

Contains fulltext : 108814.pdf (Publisher’s version ) (Open Access) Maintenance of self-renewal and pluripotency in mouse embryonic stem cells (mESCs) is regulated by the balance between several extrinsic signaling pathways. Recently, we demonstrated that heparan sulfate (HS) chains play important roles in the maintenance and differentiation of mESCs by regulating extrinsic signaling. Sulfated HS structures are modified by various sulfotransferases during development. However, the significance of specific HS structures during development remains unclear. Here, we show that 3-O-sulfated HS structures synthesized by HS 3-O-sulfotransferases (3OSTs) and recognized by the antibody HS4C3 increase during differentiation of mESCs. Furthermore, expression of Fas on the cell surface of the differentiated cells also increased. Overexpression of the HS4C3-binding epitope in mESCs induced apoptosis and spontaneous differentiation even in the presence of LIF and serum. These data showed that the HS4C3-binding epitope was required for differentiation of mESCs. Up-regulation of the HS4C3-binding epitope resulted in the recruitment of Fas from the cytoplasm to lipid rafts on the cell surface followed by activation of Fas signaling. Indeed, the HS4C3-binding epitope interacted with a region that included the heparin-binding domain (KLRRRVH) of Fas. Reduced self-renewal capability in cells overexpressing 3OST resulted from the degradation of Nanog by activated caspase-3, which is downstream of Fas signaling, and was rescued by the inhibition of Fas signaling. We also found that knockdown of 3OST and inhibition of Fas signaling reduced the potential for differentiation into the three germ layers during embryoid body formation. This is the first demonstration that activation of Fas signaling is mediated by an increase in the HS4C3-binding epitope and indicates a novel signaling pathway for differentiation in mESCs.

Self-renewal of mouse embryonic stem cells (mESCs) is maintained by leukemia inhibitory factor (LIF)/signal transducer and activator of transcription (STAT3) signaling. However, this signaling control does not function in neither mouse epiblast stem cells (mEpiSCs) nor human ESCs (hESCs) or human induced pluripotent stem cells (hiPSCs). To date, the underlying molecular mechanisms that determine this differential LIF-responsiveness have not been clarified. Here, we show that the cell surface glycan LacdiNAc (GalNAcβ1-4GlcNAc) is required for LIF/STAT3 signaling. Undifferentiated state mESCs expressed LacdiNAc at a higher level than differentiated state cells. Knockdown of β4GalNAc-T3 reduced LacdiNAc expression and caused a decrease in LIF/STAT3 signaling that lessened the rate of self-renewal of mESCs. A biochemical analysis showed that LacdiNAc expression on LIF receptor (LIFR) and gp130 was required for the stable localization of the receptors with lipid raft/caveolar components, such as caveolin-1. This localization is required for transduction of a sufficiently strong LIF/STAT3 signal. In primed state pluripotent stem cells, such as hiPSCs and mEpiSC-like cells produced from mESCs, LacdiNAc expression on LIFR and gp130 was extremely weak and the level of localization of these receptors on rafts/caveolae was also low. Furthermore, knockdown of β4GalNAc-T3 decreased LacdiNAc expression and reduced the efficiency of reversion of primed state mEpiSC-like cells into naïve state mESCs. These findings show that the different LIF-responsiveness of naïve state (mESCs) and primed state (mEpiSCs, hESCs, and hiPSCs) cells is dependent on the expression of LacdiNAc on LIFR and gp130 and that this expression is required for the induction and maintenance of the naïve state.

The basic objective of this study is to establish the material design concepts for the coexistence of good mechanical properties with super heat-resistance in the systems of ceramic/metal and ceramic/ceramic FGMs. Flexural and fracture toughness tests were conducted on gas-pressure combustion sintered Cr3C2 ceramic and its composites with Ni and TiC (Cr3C2/Ni, Cr3C2/TiC) in a vacuum environment up to 1200°C using a newly developed materials testing system. Fracture characteristics were investigated on the basis of fracture mechanics and fractography. The toughness of Cr3C2 can be improved by the addition of metallic particles. It is found that the principal mechanism of toughness improvements in these composites (ductile-phase reinforced ceramic matrix composites) is attributed to crack tip blunting by a ductile metallic phase.

The fracture process of whisker-reinforced aluminum alloys is studied. First, tensile tests are carried out on specimens of various orientations. Dimple fracture occurs at the edge of the whisker fiber due to the stress concentration. It is also found that delamination occurs at the whisker matrix interface in the T-specimen. Then the fracture process is simulated by FEM. For the constitutive equation, Gurson's yield fuction is used. Void volume fraction is used as a fracture parameter and a conventional fracture analysis is carried out. Numerical results qualitatively agree with those of experiments. The delamination effect between the base metal and the whisker fiber is considered. It is concluded that the effect of the delamination is very small before fracture of the specimen.

In order to characterize the fatigue strength of various injection moulded thermoplastics, such as PA6, PA66, PES or PEEK, and short glass or short carbon fiber reinforced composites with those thermoplastics for matrix, fatigue tests were conducted under alternating plane bending stress at 20°C.The effects of the properties of matrices, the kind of reinforced fibers and the molecular or fiber orientation on the fatigue strength characteristics were investigated. The short fiber reinforcement of advanced thermoplastics was also discussed on the basis of the fractographic examinations.

Recently, we have identified two 3'-phosphoadenosine 5'-phosphosulfate (PAPS) transporters (PAPST1 and PAPST2), which contribute to PAPS transport into the Golgi, in both human and Drosophila. Mutation and RNA interference (RNAi) of the Drosophila PAPST have shown the importance of PAPST-dependent sulfation of carbohydrates and proteins during development. However, the functional roles of PAPST in mammals are largely unknown. Here, we investigated whether PAPST-dependent sulfation is involved in regulating signaling pathways required for the maintenance of mouse embryonic stem cells (mESCs), differentiation into the three germ layers, and neurogenesis. By using a yeast expression system, mouse PAPST1 and PAPST2 proteins were shown to have PAPS transport activity with an apparent K(m) value of 1.54 microM or 1.49 microM, respectively. RNAi-mediated knockdown of each PAPST induced the reduction of chondroitin sulfate (CS) chain sulfation as well as heparan sulfate (HS) chain sulfation, and inhibited mESC self-renewal due to defects in several signaling pathways. However, we suggest that these effects were due to reduced HS, not CS, chain sulfation, because knockdown of mouse N-deacetylase/N-sulfotransferase, which catalyzes the first step of HS sulfation, in mESCs gave similar results to those observed in PAPST-knockdown mESCs, but depletion of CS chains did not. On the other hand, during embryoid body formation, PAPST-knockdown mESCs exhibited abnormal differentiation, in particular neurogenesis was promoted, presumably due to the observed defects in BMP, FGF and Wnt signaling. The latter were reduced as a result of the reduction in both HS and CS chain sulfation. We propose that PAPST-dependent sulfation of HS or CS chains, which is regulated developmentally, regulates the extrinsic signaling required for the maintenance and normal differentiation of mESCs.

The elastic-plastic fracture tests on the base metal and the weldment of A286 steel, which was one of the candidate structural materials for superconducting generators, were performed at room temperature and cryogenic temperature. It was found that the elastic-plastic fracture toughness JIC and tearing modulus TJ for the base metal depend on both the specimen orientation and the test temperature. Also, JIC for the weldment was smaller than that of the base metal at cryogenic temperature. It was also shown from the fractographic observation that the JIC values can be evaluated by the stretched zone size.