Toshiyuki Takagi

Bio: Toshiyuki Takagi is an academic researcher from Tohoku University. The author has contributed to research in topics: Eddy-current testing & Eddy current. The author has an hindex of 49, co-authored 837 publications receiving 14331 citations. Previous affiliations of Toshiyuki Takagi include Osaka Prefecture University & Russian Academy of Sciences.

Visfatin: a protein secreted by visceral fat that mimics the effects of insulin.

Abstract: Fat tissue produces a variety of secreted proteins (adipocytokines) with important roles in metabolism. We isolated a newly identified adipocytokine, visfatin, that is highly enriched in the visceral fat of both humans and mice and whose expression level in plasma increases during the development of obesity. Visfatin corresponds to a protein identified previously as pre-B cell colony-enhancing factor (PBEF), a 52-kilodalton cytokine expressed in lymphocytes. Visfatin exerted insulin-mimetic effects in cultured cells and lowered plasma glucose levels in mice. Mice heterozygous for a targeted mutation in the visfatin gene had modestly higher levels of plasma glucose relative to wild-type littermates. Surprisingly, visfatin binds to and activates the insulin receptor. Further study of visfatin's physiological role may lead to new insights into glucose homeostasis and/or new therapies for metabolic disorders such as diabetes.

Visfatin : A protein secreted by visceral fat that mimics the effects of insulin

Abstract: Recent studies of obesity show that fat tissue fulfills an endocrine function by producing a variety of secreted proteins, called adipocytokines, that may play key metabolic roles. The present investigators have isolateda newly identified adipocytokine, visfatin, from visceral fat of both mice and humans. Expression of visfatin in the plasma increases as obesity develops. This substance corresponds to a protein identified as preB cell colony-enhancing factor (PBEF), a cytokine expressed in lymphocytes. In a study of 101 human males and females, plasma levels of PBEF correlated closely with the amount of visceral fat as estimated by computed tomography. Correlation with the amount of subcutaneous fat was weak. Significant elevations of PBEF mRNA were also found in KKAy mice, which serve as a model for obesity-related type 2 diabetes. These mice become obese at age 6 to 12 weeks and, at the same time, plasma PBEF levels increase significantly, as do levels of PBEF mRNA in visceral fat. Levels in subcutaneous fat change very little. Mice fed a high-fat diet had higher plasma PBEF concentrations than those fed normal chow. When recombinant visfatin was administered intravenously to c57BL/6J mice, plasma glucose decreased within 30 minutes in a dose-dependent manner. The same effect was noted in insulin-resistant obese KKAy mice, mimicking the effect of insulin injection. Visfatin also had insulin-like effects on cultured cells. In both strains of mice, chronic exposure to visfatin, using adenovirus, significantly lowered plasma levels of both glucose and insulin. Visfatin was found to bind to-and activate-the insulin receptor but in a way different from insulin. These studies indicate that visfatin shares properties of insulin both in vitro and in vivo. In addition to helping to understand glucose and lipid homeostasis and adipocyte proliferation, visfatin may prove to be a useful target when developing drug treatments for diabetes.

Structural and magnetic phase transitions in shape-memory alloys Ni 2 + x Mn 1 − x Ga

Abstract: The Heusler-type alloy ${\mathrm{Ni}}_{2+x}{\mathrm{Mn}}_{1\ensuremath{-}x}\mathrm{Ga}$ exhibits well defined shape memory properties in a ferromagnetic state, which means that the martensitic transition temperature is lower than the Curie point of this material. The change of composition makes these characteristic temperatures approach each other. To study this behavior, the measurements of specific heat, ac magnetic susceptibility, and dc resistivity were performed. The phase diagram of the cubic ferromagnet describing possible structural and magnetic transitions is obtained theoretically. This diagram is compared with experimental data on ${\mathrm{Ni}}_{2+x}{\mathrm{Mn}}_{1\ensuremath{-}x}\mathrm{Ga}.$ An estimate is given of the magnetic-field influence on the temperature of martensitic transformation in the studied alloys.

The atypical M2 segment of the beta subunit confers picrotoxinin resistance to inhibitory glycine receptor channels.

Abstract: Purified preparations of the inhibitory glycine receptor (GlyR) contain alpha and beta subunits, which share homologous primary structures and a common transmembrane topology with other members of the ligand-gated ion channel superfamily. Here, a beta subunit-specific antiserum was shown to precipitate the [3H]strychnine binding sites localized on alpha subunits from membrane extracts of both rat spinal cord and mammalian cells co-transfected with alpha and beta cDNAs. Further, inhibition of alpha homo-oligomeric GlyRs by picrotoxinin, a non-competitive blocker of ion flow, was reduced 50- to 200-fold for alpha/beta hetero-oligomeric receptors generated by cotransfection. Site-directed mutagenesis identified residues within the second predicted transmembrane segment (M2) of the beta subunit as major determinants of picrotoxinin resistance. These data implicate the M2 segment in blocker binding to and lining of the GlyR chloride channel.

Shape memory ferromagnets

Abstract: In ferromagnetic alloys with shape memory large reversible strains can be obtained by rearranging the martensitic domain structure by a magnetic field. Magnetization through displacement of domain walls is possible in the presence of high magnetocrystalline anisotropy, when martensitic structure rearrangement is energetically favorable compared to the reorientation of magnetic moments. In ferromagnetic Heusler alloys Ni2+xMn1–xGa the Curie temperature exceeds the martensitic transformation temperature. The fact that these two temperatures are close to room temperature offers the possibility of magnetically controlling the shape and size of ferromagnets in the martensitic state. In Ni2+xMn1–xGa single crystals, a reversible strain of ~6% is obtained in fields of ~1 T.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

SPAdes, a new genome assembly algorithm and its applications to single-cell sequencing ( 7th Annual SFAF Meeting, 2012)

Abstract: The lion's share of bacteria in various environments cannot be cloned in the laboratory and thus cannot be sequenced using existing technologies. A major goal of single-cell genomics is to complement gene-centric metagenomic data with whole-genome assemblies of uncultivated organisms. Assembly of single-cell data is challenging because of highly non-uniform read coverage as well as elevated levels of sequencing errors and chimeric reads. We describe SPAdes, a new assembler for both single-cell and standard (multicell) assembly, and demonstrate that it improves on the recently released E+V-SC assembler (specialized for single-cell data) and on popular assemblers Velvet and SoapDeNovo (for multicell data). SPAdes generates single-cell assemblies, providing information about genomes of uncultivatable bacteria that vastly exceeds what may be obtained via traditional metagenomics studies. SPAdes is available online ( http://bioinf.spbau.ru/spades ). It is distributed as open source software.

Inflammation and insulin resistance

Abstract: Over a hundred years ago, high doses of salicylates were shown to lower glucose levels in diabetic patients. This should have been an important clue to link inflammation to the pathogenesis of type 2 diabetes (T2D), but the antihyperglycemic and antiinflammatory effects of salicylates were not connected to the pathogenesis of insulin resistance until recently. Together with the discovery of an important role for tissue macrophages, these new findings are helping to reshape thinking about how obesity increases the risk for developing T2D and the metabolic syndrome. The evolving concept of insulin resistance and T2D as having immunological components and an improving picture of how inflammation modulates metabolism provide new opportunities for using antiinflammatory strategies to correct the metabolic consequences of excess adiposity.