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Hokkaido University Collection of Scholarly and Academic Papers (130.615 recursos)

HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.

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Mostrando recursos 1 - 15 de 15

  1. Generation of Bilateral Symmetry in the Ectoderm of the Tubifex Embryo : Involvement of Cell–cell Interactions

    Nakamoto, Ayaki; Arai, Asuna; Shimizu, Takashi
    In embryos of the oligochaete annelid Tubifex, most ectodermal tissues are derived from four bilateral pairs of embryonic stem cells called teloblasts (ectoteloblasts N, O, P and Q). Ectoteloblasts are generated on both left and right sides of the embryo through an invariable sequence of cell divisions of a proteloblast, NOPQ, and they are positioned in a mirror symmetric pattern relative to the embryonic midline. This mirror symmetry of ectoteloblast arrangement gives rise to the generation of bilateral symmetry in the ectoderm. Here we review results of our recent experiments on Tubifex tubifex that were designed to gain an insight...

  2. Embryonic expression of a decapentaplegic gene in the oligochaete annelid Tubifex tubifex

    Matsuo, Kei; Shimizu, Takashi
    We have cloned and characterized the expression of a decapentaplegic homologue (designated Ttu-dpp) from the oligochaete annelid Tubifex tubifex. RT-PCR analysis and in situ hybridization revealed that Ttu-dpp begins to be expressed around the time of the onset of ectodermal germ band (GB) elongation (i.e., the onset of gastrulation). At this time, Ttu-dpp expression is detected in the anteriormost part of the GBs. As development proceeds and the GBs elongate, the domain of Ttu-dpp-expressing cells extends posteriorly. Then Ttu-dpp-expressing cells within the GB are divided into two groups: one group occurs along the ventral midline and coincides with the domain...

  3. An optical telemetry system for underwater recording of electromyogram and neuronal activity from non-tethered crayfish

    Tsuchida, Yoshikazu; Hama, Noriyuki; Takahata, Masakazu
    We have developed an optical telemetry system for recording electrical signals associated with muscle and neuronal activities from freely walking crayfish under water. The device was made from conventional electronic parts which are commercially available, utilizing infrared light (880 nm) for signal transmission. Two or four channels of biological signals were multiplexed, the voltage of each data point modulated to the duration of subcarrier pulses and further to the interval of narrower carrier pulses that directly drove the infrared light emission diode (IRLED) under water. The light-pulse modulated signals were received by photodiodes and demodulated to restore the original two...

  4. Modification of statocyst input to local interneurons by behavioral condition in the crayfish brain

    Hama, N.; Takahata, M.
    Posture control by statocysts is affected by leg condition in decapod crustaceans. We investigated how, in the crayfish brain, the synaptic response of local interneurons to statocyst stimulation was affected by leg movements on and off a substratum. The magnetic field stimulation method permitted sustained stimulation of statocyst receptors by mimicking body rolling. The statocyst-driven local interneurons were classified into four morphological groups (Type-I–IV). All interneurons except Type-IV projected their dendritic branches to the parolfactory lobe of the deutocerebrum where statocyst afferents project directly. Type-I interneurons having somata in the ventral-paired lateral cluster responded invariably to statocyst stimulation regardless of...

  5. Further exploration into the adaptive design of the arthropod "microbrain" : I. Sensory and memory-processing systems

    Mizunami, Makoto; Yokohari, Fumio; Takahata, Masakazu
    Arthropods have small but sophisticated brains that have enabled them to adapt their behavior to a diverse range of environments. In this review, we first discuss some of general characteristics of the arthropod "microbrain" in comparison with the mammalian "megalobrain". Then we discuss about recent progress in the study of sensory and memory-processing systems of the arthropod "microbrain". Results of recent studies have shown that (1) insects have excellent capability for elemental and context-dependent forms of olfactory learning, (2) mushroom bodies, higher olfactory and associative centers of arthropods, have much more elaborated internal structures than previously thought, (3) many genes...

  6. End-Crosslinking Gelation of Poly(amide acid) Gels studied with Scanning Microscopic Light Scattering

    Furukawa, Hidemitsu; Kobayashi, Mizuha; Miyashita, Yoshiharu; Horie, Kazuyuki
    Network formation in the gelation process of end-crosslinked poly(amide acid) gels, which are the precursor of end-crosslinked polyimide gels, was studied by scanning dynamic light scattering. The gelation process is essentially non-reversible due to the formation of covalent bonds. The molecular structure formed in the gelation process is controlled by varying the equivalence ratio of end-crosslinker to oligomer during the preparation. It was found that a couple of relaxation modes are observed in the gelation point even for semi-rigid poly(amide acid) solutions. This is similar to flexible polymer solutions and convenient to characterize the molecular structure in the gelation processes....

  7. Phylogeny and Evolution of Butterflies of the Genus Parnassius : Inferences from Mitochondrial 16S and ND1 Sequences

    Katoh, Toru; Chichvarkhin, Anton; Yagi, Takashi; Omoto, Keiichi
    Phylogenetic relationships among species of the genus Parnassius and its related taxa were analyzed by comparing nucleotide sequences of mitochondrial 16S ribosomal RNA (504 sites) and NADH-dehydrogenase subunit 1 (469 sites). In the phylogenetic trees, Parnassius was found to be most closely related to Hypermnestra helios, whereas Archon apollinus, which has been classified in the tribe Parnassiini together with Parnassius and Hypermnestra, was more closely related to members of the tribe Zerynthiini. Within the Parnassius clade, six major clades corresponding to species groups were well supported, although the phylogenetic relationships among them were not clear. Although the results of the...

  8. Amphipathic alpha-helix mediates the heterodimerization of soluble guanylyl cyclase.

    Shiga, Takumi; Suzuki, Norio
    Soluble guanylyl cyclase (soluble GC) is an enzyme consisting of α and β subunits and catalyzes the conversion of GTP to cGMP. The formation of the heterodimer is essential for the activity of soluble GC. Each subunit of soluble GC has been shown to comprize three functionally different parts: a C-terminal catalytic domain, a central dimerization domain, and an N-terminal regulatory domain. The central dimerization domain of the β1 subunit, which contains an N-terminal binding site (NBS) and a C-terminal binding site (CBS), has been postulated to be responsible for the formation of α/ β heterodimer. In this study, we...

  9. Diverse forms of guanylyl cyclases in medaka fish -- their genomic structure and phylogenetic relationships to those in vertebrates and invertebrates.

    Yamagami, Sayaka; Suzuki, Norio
    Fish species such as medaka fish, fugu, and zebrafish contain more guanylyl cyclases (GCs) than do mammals. These GCs can be divided into two types: soluble GCs and membrane GCs. The latter are further divided into four subfamilies: (i) natriuretic peptide receptors, (ii) STa/guanylin receptors, (iii) sensory-organ-specific membrane GCs, and (iv) orphan receptors. Phylogenetic analyses of medaka fish GCs, along with those of fugu and zebrafish, suggest that medaka fish is a much closer relative to fugu than to zebrafish. Analyses of nucleotide data available on a web site ( of GCs from a range of organisms from bacteria to...

  10. Molecular regulation of gonadotropin secretion by gonadotropin-releasing hormone in salmonid fishes

    Ando, Hironori; Urano, Akihisa
    Gonadotropin-releasing hormone (GnRH) plays a central role in the control of reproductive function in vertebrates. In salmonids, salmon GnRH (sGnRH) secreted by preoptic GnRH neurons regulates gonadal maturation through stimulation of synthesis and release of pituitary gonadotropins (GTHs). In addition, several lines of our evidence indicate that sGnRH is involved in spawning behavior, and serves to integrate the gonadal maturation with the reproductive behavior. A growing number of studies show that the effects of GnRH are mediated by multiple subtypes of GnRH receptors, successive multiple signaling pathways, and finally multiple transcription factors which act cooperatively to stimulate transcription of GTH...

  11. Complementary structural information of positive- and negative-ion MSn spectra of glycopeptides with neutral and sialylated N-glycans

    Deguchi, Kisaburo; Ito, Hiroki; Takegawa, Yasuhiro; Shinji, Nagai; Nakagawa, Hiroaki; Nishimura, Shin-Ichiro
    Positive- and negative-ion MSn spectra of chicken egg yolk glycopeptides binding a neutral and a sialylated N-glycan were acquired by using electrospray ionization linear ion trap time-of-flight mass spectrometry (ESI-LIT-TOFMS) and collision-induced dissociation (CID) with helium as collision gas. Several characteristic differences were observed between the positive- and negative-ion CID MSn (n = 2, 3) spectra. In the positive-ion MS2 spectra, the peptide moiety was presumably stable, but the neutral N-glycan moiety caused several B-type fragmentations and the sialylated N-glycan almost lost sialic acid(s). In contrast, in the negative-ion MS2 spectra, the peptide moiety caused several side-chain and N-glycan residue...

  12. Temperature adaptation in Dictyostelium: role of Δ5 fatty acid desaturase

    Saito, Tamao; Kato, Atsushi; Ochiai, Hiroshi; Morita, Naoki
    Membrane fluidity is critical for proper membrane function and is regulated in part by the proportion of unsaturated fatty acids present in membrane lipids. The proportion of these lipids in turn varies with temperature and may contribute to temperature adaptation in poikilothermic organisms. The fundamental question posed in this study was whether the unsaturation of fatty acids contributes to the ability to adapt to temperature stress in Dictyostelium. First, fatty acid composition was analysed and it was observed that the relative proportions of dienoic acids changed with temperature. To investigate the role of dienoic fatty acids in temperature adaptation, null...

  13. Gel friction: A model based on surface repulsion and adsorption

    Gong, Jianping; Osada, Yoshihito
    A model describing the frictional force produced when a polymer gel is sliding on a solid surface has been proposed from the viewpoint of solvated polymer repulsion and adsorption theory at a solid surface. General relations for the frictional force f expressed as functions of the normal loading P, sliding velocity v, the polymer volume fraction Φ, or the elastic modulus E of the gel, etc., have been derived by applying scaling relations to the model. For the repulsive case, f is ascribed to the viscous flow of solvent at the interface and f is theoretically demonstrated to be proportional...

  14. Elucidation of stability determinants of cold-adapted monomeric isocitrate dehydrogenase from a psychrophilic bacterium, Colwellia maris, by construction of chimeric enzymes

    Watanabe, Seiya; Yasutake, Yoshiaki; Tanaka, Isao; Takada, Yasuhiro
    To elucidate determinants of differences in thermostability between mesophilic and psychrophilic monomeric isocitrate dehydrogenases (IDHs) from Azotobacter vinelandii (AvIDH) and Colwellia maris (CmIDH), respectively, chimeric enzymes derived from the two IDHs were constructed based on the recently resolved three-dimensional structure of AvIDH, and several characteristics of the two wild-type and six chimeric IDHs were examined. These characteristics were then compared with those of dimeric IDH from Escherichia coli (EcIDH). All recombinant enzymes with a (His)6-tag attached to the N-terminal were overexpressed in the E. coli cells and purified by Ni2+-affinity chromatography. The catalytic activity (kcat) and catalytic efficiency (kcat/Km) of...

  15. Biochemical characterization of human kallikrein 8 and its possible involvement in the degradation of extracellular matrix proteins

    Rajapakse, Sanath; Ogiwara, Katsueki; Takano, Naoharu; Moriyama, Akihiko; Takahashi, Takayuki
    Human kallikrein 8 (KLK8) is a member of the human kallikrein gene family of serine proteases, and its protein, hK8, has recently been suggested to serve as a new ovarian cancer marker. To gain insights into the physiological role of hK8, the active recombinant enzyme was obtained in a pure state for biochemical and enzymatic characterizations. hK8 had trypsin-like activity with a strong preference for Arg over Lys in the P1 position, and its activity was inhibited by typical serine protease inhibitors. The protease degraded casein, fibronectin, gelatin, collagen type IV, fibrinogen, and high-molecular-weight kininogen. hK8 also converted human single-chain...

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