Takamichi Miyazaki

Laminin E8 fragments support efficient adhesion and expansion of dissociated human pluripotent stem cells

Human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs) have the potential to provide an infinite source of tissues for regenerative medicine. Although defined xeno-free media have been developed, culture conditions for reliable propagation of hESCs still require considerable improvement. Here we show that recombinant E8 fragments of laminin isoforms (LM-E8s), which are the minimum fragments conferring integrin-binding activity, promote greater adhesion of hESCs and hiPSCs than do Matrigel and intact laminin isoforms. Furthermore, LM-E8s sustain long-term self-renewal of hESCs and hiPSCs in defined xeno-free media with dissociated cell passaging. We successfully maintained three hESC and two hiPSC lines on LM-E8s in three defined media for 10 passages. hESCs maintained high level expression of pluripotency markers, had a normal karyotype after 30 passages and could differentiate into all three germ layers. This culture system allows robust proliferation of hESCs and hiPSCs for therapeutic applications.

Comparison of defined culture systems for feeder cell free propagation of human embryonic stem cells

There are many reports of defined culture systems for the propagation of human embryonic stem cells in the absence of feeder cell support, but no previous study has undertaken a multi-laboratory comparison of these diverse methodologies. In this study, five separate laboratories, each with experience in human embryonic stem cell culture, used a panel of ten embryonic stem cell lines (including WA09 as an index cell line common to all laboratories) to assess eight cell culture methods, with propagation in the presence of Knockout Serum Replacer, FGF-2, and mouse embryonic fibroblast feeder cell layers serving as a positive control. The cultures were assessed for up to ten passages for attachment, death, and differentiated morphology by phase contrast microscopy, for growth by serial cell counts, and for maintenance of stem cell surface marker expression by flow cytometry. Of the eight culture systems, only the control and those based on two commercial media, mTeSR1 and STEMPRO, supported maintenance of most cell lines for ten passages. Cultures grown in the remaining media failed before this point due to lack of attachment, cell death, or overt cell differentiation. Possible explanations for relative success of the commercial formulations in this study, and the lack of success with other formulations from academic groups compared to previously published results, include: the complex combination of growth factors present in the commercial preparations; improved development, manufacture, and quality control in the commercial products; differences in epigenetic adaptation to culture in vitro between different ES cell lines grown in different laboratories.

Recombinant human laminin isoforms can support the undifferentiated growth of human embryonic stem cells

Human embryonic stem cells (hESCs) are thought to be a promising cell source for cell transplantation therapy. For such a clinical application, the hESCs should be manipulated using appropriate and qualified materials. In this study, we examined the efficacy of recombinant human laminin (rhLM) isoforms on the undifferentiated growth of hESCs. We first determined the major integrins expressed on the hESCs to reveal the preference of the hESCs for rhLMs, and found that the hESCs mainly expressed integrin alpha6beta1, which binds predominantly to laminin-111, -332 and -511/-521. When the hESCs were seeded onto rhLMs, the cells indeed adhered markedly to rhLM-332, and to rhLM-511 and rhLM-111 to a lesser extent. The hESCs proliferated on these three rhLMs for several passages while preserving their pluripotency. These results show that rhLM-111, -332, and -511 are good substrates to expand undifferentiated hESCs due to their high affinity to integrin alpha6beta1 expressed on hESCs.

Low damping constant for Co2FeAl Heusler alloy films and its correlation with density of states

Gilbert damping for the epitaxial Co2FeAl Heusler alloy films was investigated. Gilbert damping constant for the films was evaluated by analyzing the data of ferromagnetic resonance measured at the frequency of 2–20 GHz. Gilbert damping constant for the film without annealing was rather large, while it decreased remarkably with postannealing. Gilbert damping constant for the film annealed at 600 °C was ≃0.001. These behavior of Gilbert damping constant can be well explained by the fact that the density of states calculated from first principles decreases with increasing the degree of B2 order.

Study of the low temperature ordering of L10-Fe-Pt in Fe/Pt multilayers

In order to clarify the formation process of L10 Fe–Pt ordered phase in Fe (tFe)/Pt (tPt) multilayers, we have evaluated the activation energy of ordering (QS) and of atomic interdiffusion at Fe/Pt interfaces (QD). QS for the multilayers takes a minimum value of ∼0.7 eV when tFe=tPt, much lower than that of Fe–Pt disordered alloy films (1.2 eV). This value is almost the same with the activation energy QD of atomic interdiffusion at Fe/Pt interfaces. From these results, it is concluded that the interdiffusion at Fe/Pt interfaces which occurs at relatively low temperature dominates the formation process of L10 Fe–Pt in Fe/Pt multilayers.

Magnetic properties of rapidly quenched amorphous Fe-Sm alloys

Abstract The structural analysis and investigation of magnetic properties were carried out on rapidly quenched Fe 100− x Sm x (10.5 ⩽ x ⩽ 80) alloys. Amorphous alloys are fabricated in a wide composition range from x = 17 to 72.5. After heating the amorphous alloys up to 900 K, they transform into metastable phase I ( T c = 465 K)+ α-Fe ( x T c = 555 K)+α-Fe (20 ⩽ x ⩽ 33.3) and Fe 2 Sm+Sm ( x ⩾40). The composition dependence of Curie temperature and magnetization is found to be similar to that of amorphous Fe-(Nd, Pr) alloys. A maximum coercive force of about 1.1 kOe at 300 K and 12 kOe at 77 K is obtained in the x = 40 alloy. The rapid decrease in coercive force with raising temperature can be explained by the wall pinning model proposed by Gaunt. The pronounced composition dependence of these magnetic properties for the amorphous Fe-Sm alloys can be considered to be caused by the change in the short-range atomic order with Sm concentration on the basis of the results of X-ray structural analysis.

Spin glass in Fe‐Ni Invar alloys

Initial ac susceptibility χ was examined in the temperature range from 4.2 K to Curie temperatures for polycrystalline Fe100−xNix (20≤x≤50) alloys. The reentrant spin glass is found in x=30–45 alloys. The dependence of the freezing temperature Tg on the intensity of driving magnetic field (ac: 0–0.26 Oe; dc: 0–10 Oe) and on the frequency (140–9200 Hz) was studied for the Fe65Ni35 alloy. A strong magnetic relaxation is observed below Tg. These results are discussed based on the cluster model.

Material dependence of anomalous Nernst effect in perpendicularly magnetized ordered-alloy thin films

Material dependence of the anomalous Nernst effect (ANE) in perpendicularly magnetized ordered-alloy thin films is systematically investigated. The ANE was found to have a tendency to increase simply as uniaxial magnetic anisotropy increased at room temperature. The ANE increases as temperature increases from 10 to 300 K for all the materials. However, the signs of the ANE in Fe-based ordered-alloys (L10-FePt and L10-FePd) and in a Co/Ni multilayer are opposite to those in Mn-based ordered-alloys (L10-MnGa and D022-Mn2Ga). Ordered-alloys with larger uniaxial magnetic anisotropies reveal larger ANE and might be desirable for thermoelectric applications.

Microstructure of a carbon fiber-reinforced aluminum matrix composite fabricated by spark plasma sintering in various pulse conditions

Carbon fiber-reinforced aluminum composites were produced by spark plasma sintering in various pulse conditions. The pulse condition of spark plasma sintering affected the aluminum particle boundaries and aluminum/carbon fiber interfaces; the different fracture morphologies of aluminum oxide were observed on aluminum particles and interfacial aluminum carbide formation. We demonstrated the control of the quantity of aluminum carbide crystals by the alteration of pulse conditions. Finally, we propose the mechanism of local temperature increase in the spark plasma sintering process.

Low precessional damping observed for L10-ordered FePd epitaxial thin films with large perpendicular magnetic anisotropy

High-quality L10 ordered 20 nm-thick FePd epitaxial thin films with a large perpendicular magnetic anisotropy were fabricated using a SrTiO3 substrate. The uniaxial crystalline magnetic anisotropy constant Ku evaluated for the films annealed above 500 °C was 14 Merg/cm3. A very low effective damping constant, αeff = 0.007, was observed for FePd thin films annealed at 500 °C. This value is smaller than that of other Fe-based ordered alloys with a large perpendicular magnetic anisotropy.