Showing papers by "Kyoto University published in 1996"

The Sloan digital sky survey photometric system

Abstract: This paper describes the Sloan Digital Sky Survey photometric system, a new five-color (u' g' r' i' z') wide-band CCD system with wavelength coverage from 3000 to 11 000 A. The zero points will be based on an updated version of the spectrophotometric ABv system. This updated calibration, designated as AB95, is presented in this paper.

Defects of B-cell lymphopoiesis and bone-marrow myelopoiesis in mice lacking the CXC chemokine PBSF/SDF-1

Abstract: The chemokines are a large family of small, structurally related cytokines. The physiological importance of most members of this family has yet to be elucidated, although some are inducible inflammatory mediators that determine leukocyte chemotaxis. Pre-B-cell growth-stimulating factor/stromal cell-derived factor-1 (PBSF/SDF-1) is a member of the CXC group of chemokines PBSF/SDF-1 stimulates proliferation of B-cell progenitors in vitro and is constitutively expressed in bone-marrow-derived stromal cells. Here we investigate the physiological roles of PBSF/SDF-1 by generating mutant mice with a targeted disruption of the gene encoding PBSF/SDF-1. We found that mice lacking PBSF/SDF-1 died perinatally and that although the numbers of B-cell progenitors in mutant embryos were severely reduced in fetal liver and bone marrow, myeloid progenitors were reduced only in the bone marrow but not in the fetal liver, indicating that PBSF/SDF-1 is responsible for B-cell lymphopoiesis and bone-marrow myelopoiesis. In addition, the mutants had a cardiac ventricular septal defect. Hence, we have shown that the chemokine PBSF/SDF-1 has several essential functions in development.

Expression of the PD-1 antigen on the surface of stimulated mouse T and B lymphocytes

Abstract: A mAb J43 has been produced against the product of the mouse PD-1 gene, a member of the Ig gene superfamily, which was previously isolated from an apoptosis-induced T cell hybridoma (2B4.11) by using subtractive hybridization. Analyses by flow cytometry and immunoprecipitation using the J43 mAb revealed that the PD-1 gene product is a 50-55 kDa membrane protein expressed on the cell surface of several PD-1 cDNA transfectants and 2B4.11 cells. Since the molecular weight calculated from the amino acid sequence is 29, 310, the PD-1 protein appears to be heavily glycosylated. Normal murine lymphoid tissues such as thymus, spleen, lymph node and bone marrow contained very small numbers of PD-1(+) cells. However, a significant PD-1(+) population appeared in the thymocytes as well as T cells in spleen and lymph nodes by the in vivo anti-CD3 mAb treatment. Furthermore, the PD-1 antigen expression was strongly induced in distinct subsets of thymocytes and spleen T cells by in vitro stimulation with either anti-CD3 mAb or concanavalin A (Con A) which could lead T cells to both activation and cell death. Similarly, PD-1 expression was induced on spleen B cells by in vitro stimulation with anti-IgM antibody. By contrast, PD-1 was not significantly expressed on lymphocytes by treatment with growth factor deprivation, dexamethasone or lipopolysaccharide. These results suggest that the expression of the PD-1 antigen is tightly regulated and induced by signal transduction through the antigen receptor and do not exclude the possibility that the PD-1 antigen may play a role in clonal selection of lymphocytes although PD-1 expression is not required for the common pathway of apoptosis.

Preparation of bioactive Ti and its alloys via simple chemical surface treatment.

Abstract: A simple chemical method was established for inducing bioactivity of Ti and its alloys. When pure Ti, Ti-6A1-4V, Ti-6A1-2Nb-Ta, and Ti-15Mo-5Zr-3A1 substrates were treated with 10M NaOH aqueous solution and subsequently heat-treated at 600 degrees C, a thin sodium titanate layer was formed on their surfaces. Thus, treated substrates formed a dense and uniform bonelike apatite layer on their surfaces in simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. This indicates that the alkali- and heat-treated metals bond to living bone through the bonelike apatite layer formed on their surfaces in the body. The apatite formation on the surfaces of Ti and its alloys was assumed to be induced by a hydrated titania which was formed by an ion exchange of the alkali ion in the alkali titanate layer and the hydronium ion in SBF. The resultant surface structure changed gradually from the outermost apatite layer to the inner Ti and its alloys through a hydrated titania and titanium oxide layers. This provides not only the strong bonding of the apatite layer to the substrates but also a uniform gradient of stress transfer from bone to the implants. The present chemical surface modification is therefore expected to allow the use the bioactive Ti and its alloys as artificial bones even under load-bearing conditions.

Small scale cosmological perturbations: An Analytic approach

Abstract: Through analytic techniques verified by numerical calculations, we establish general relations between the matter and cosmic microwave background (CMB) power spectra and their dependence on parameters on small scales. Fluctuations in the CMB, baryons, cold dark matter (CDM), and neutrinos receive a boost at horizon crossing. Baryon drag on the photons causes alternating acoustic peak heights in the CMB and is uncovered in its bare form under the photon diffusion scale. Decoupling of the photons at last scattering and of the baryons at the end of the Compton drag epoch freezes the diffusion-damped acoustic oscillations into the CMB and matter power spectra at different scales. We determine the dependence of the respective acoustic amplitudes and damping lengths on fundamental cosmological parameters. The baryonic oscillations, enhanced by the velocity overshoot effect, compete with CDM fluctuations in the present matter power spectrum. We present new exact analytic solutions for the cold dark matter fluctuations in the presence of a growth-inhibiting radiation and baryon background. Combined with the acoustic contributions and baryonic infall into CDM potential wells, this provides a highly accurate analytic form of the small-scale transfer function in the general case.

The small GTP-binding protein Rho binds to and activates a 160 kDa Ser/Thr protein kinase homologous to myotonic dystrophy kinase.

Abstract: The small GTP-binding protein Rho functions as a molecular switch in the formation of focal adhesions and stress fibers, cytokinesis and transcriptional activation. The biochemical mechanism underlying these actions remains unknown. Using a ligand overlay assay, we purified a 160 kDa platelet protein that bound specifically to GTP-bound Rho. This protein, p160, underwent autophosphorylation at its serine and threonine residues and showed the kinase activity to exogenous substrates. Both activities were enhanced by the addition of GTP-bound Rho. A cDNA encoding p160 coded for a 1354 amino acid protein. This protein has a Ser/Thr kinase domain in its N-terminus, followed by a coiled-coil structure approximately 600 amino acids long, and a cysteine-rich zinc finger-like motif and a pleckstrin homology region in the C-terminus. The N-terminus region including a kinase domain and a part of coiled-coil structure showed strong homology to myotonic dystrophy kinase over 500 residues. When co-expressed with RhoA in COS cells, p160 was co-precipitated with the expressed Rho and its kinase activity was activated, indicating that p160 can associate physically and functionally with Rho both in vitro and in vivo.

Perisynaptic Location of Metabotropic Glutamate Receptors mGluR1 and mGluR5 on Dendrites and Dendritic Spines in the Rat Hippocampus

Abstract: Ionotropic and metabotropic (mGluR1a) glutamate receptors were reported to be segregated from each other within the postsynaptic membrane at individual synapses. In order to establish whether this pattern of distribution applies to the hippocampal principal cells and to other postsynaptic metabotropic glutamate receptors, the mGluR1a/b/c and mGluR4 subtypes were localized by immunocytochemistry. Principal cells in all hippocampal fields were reactive for mGluR5, the strata oriens and radiatum of the CA1 area being most strongly immunolabelled. Labelling for mGluR1b/c was strongest on some pyramids in the CA3 area, weaker on granule cells and absent on CA1 pyramids. Subpopulations of non-principal cells showed strong mGluR1 or mGluR5 immunoreactivity. Electron microscopic pre-embedding immunoperoxidase and both pre- and postembedding immunogold methods consistently revealed the extrasynaptic location of both mGluRs in the somatic and dendritic membrane of pyramidal and granule cells. The density of immunolabelling was highest on dendritic spines. At synapses, immunoparticles for both mGluR1 and mGluR5 were found always outside the postsynaptic membrane specializations. Receptors were particularly concentrated in a perisynaptic annulus around type 1 synaptic junctions, including the invaginations at 'perforated' synapses. Measurements of immunolabelling on dendritic spines showed decreasing levels of receptor as a function of distance from the edge of the synaptic specialization. We propose that glutamergic synapses with an irregular edge develop in order to increase the circumference of synaptic junctions leading to an increase in the metabotropic to ionotropic glutamate receptor ratio at glutamate release sites. The perisynaptic position of postsynaptic metabotropic glutamate receptors appears to be a general feature of glutamatergic synaptic organization and may apply to other G-protein-coupled receptors.

An Antimicrobial Peptide, Magainin 2, Induced Rapid Flip-Flop of Phospholipids Coupled with Pore Formation and Peptide Translocation†

Abstract: The effect of an antimicrobial peptide, magainin 2, on the flip-flop rates of phospholipids was investigated by use of fluorescent lipids, i.e., anionic N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)dipalmitoyl-l-α-phosphatidylethanolamine (NBD-PE), 1-oleoyl-2-[12-((7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)dodecanoyl]-l-α-phosphatidic acid (C12-NBD-PA), 1-oleoyl-2-[12-((7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)dodecanoyl]-l-α-phosphatidyl-l-serine (C12-NBD-PS), and zwitterionic 1-palmitoyl-2-[6-((7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)caproyl]-l-α-phosphatidylcholine (C6-NBD-PC). Their intrinsic flip-flop half-lives at 30 °C in the absence of the peptide were 1.1 h, ca. 7 h, ca. 8 days, and >2 days, respectively. The peptide accelerated the flip-flop half-lives of the fluorescent lipids to an order of minutes. Furthermore, the flip-flop was coupled with the membrane permeabilization and the peptide translocation [Matsuzaki, K., Murase, O., Fujii, N., & Miyajima, K. (1995) Biochemistry 34, 6521−6526], suggesting por...

Spontaneous Formation of Bonelike Apatite Layer on Chemically Treated Titanium Metals

Abstract: Generally, artificial materials implanted into bone defects are encapsulated by a fibrous tissue isolating them from the surrounding bone. Only limited kinds of ceramics are known to bond to living bone without forming the fibrous tissue, and already they are being used clinically as important artificial bones. However, they cannot be used under highly loaded conditions, since their fracture toughnesses are not so high as that of human cortical bone. The present study shows that even pure titanium metal and its alloys can bond to living bone, if their surfaces are pre-treated with alkali hydroxide solutions. Thus-treated metals are believed to be useful as artificial bones even under highly loaded conditions because of their high bone-bonding ability as well as high fracture toughness.

Regulation mechanism of ERM (ezrin/radixin/moesin) protein/plasma membrane association: possible involvement of phosphatidylinositol turnover and Rho-dependent signaling pathway.

Abstract: The ERM proteins, ezrin, radixin, and moesin, are involved in the actin filament/plasma membrane interaction as cross-linkers. CD44 has been identified as one of the major membrane binding partners for ERM proteins. To examine the CD44/ERM protein interaction in vitro, we produced mouse ezrin, radixin, moesin, and the glutathione-S-transferase (GST)/CD44 cytoplasmic domain fusion protein (GST-CD44cyt) by means of recombinant baculovirus infection, and constructed an in vitro assay for the binding between ERM proteins and the cytoplasmic domain of CD44. In this system, ERM proteins bound to GST-CD44cyt with high affinity (Kd of moesin was 9.3 +/- 1.6nM) at a low ionic strength, but with low affinity at a physiological ionic strength. However, in the presence of phosphoinositides (phosphatidylinositol [PI], phosphatidylinositol 4-monophosphate [4-PIP], and phosphatidylinositol 4.5-bisphosphate [4,5-PIP2]), ERM proteins bound with a relatively high affinity to GST-CD44cyt even at a physiological ionic strength: 4,5-PIP2 showed a marked effect (Kd of moesin in the presence of 4,5-PIP2 was 9.3 +/- 4.8 nM). Next, to examine the regulation mechanism of CD44/ERM interaction in vivo, we reexamined the immunoprecipitated CD44/ERM complex from BHK cells and found that it contains Rho-GDP dissociation inhibitor (GDI), a regulator of Rho GTPase. We then evaluated the involvement of Rho in the regulation of the CD44/ERM complex formation. When recombinant ERM proteins were added and incubated with lysates of cultured BHK cells followed by centrifugation, a portion of the recombinant ERM proteins was recovered in the insoluble fraction. This binding was enhanced by GTP gamma S and markedly suppressed by C3 toxin, a specific inhibitor of Rho, indicating that the GTP form of Rho in the lysate is required for this binding. A mAb specific for the cytoplasmic domain of CD44 also markedly suppressed this binding, identifying most of the binding partners for exogenous ERM proteins in the insoluble fraction as CD44. Consistent with this binding analysis, in living BHK cells treated with C3 toxin, most insoluble ERM proteins moved to soluble compartments in the cytoplasm, leaving CD44 free from ERM. These findings indicate that Rho regulates the CD44/ERM complex formation in vivo and that the phosphatidylinositol turnover may be involved in this regulation mechanism.

TAB1: An activator of the TAK1 MAPKKK in TGF-β signal transduction

Abstract: Transforming growth factor-β (TGF-β) regulates many aspects of cellular function. A member of the mitogen-activated protein kinase kinase kinase (MAPKKK) family, TAK1, was previously identified as a mediator in the signaling pathway of TGF-β superfamily members. The yeast two-hybrid system has now revealed two human proteins, termed TAB1 and TAB2 (for TAK1 binding protein), that interact with TAK1. TAB1 and TAK1 were co-immunoprecipitated from mammalian cells. Overproduction of TAB1 enhanced activity of the plasminogen activator inhibitor 1 gene promoter, which is regulated by TGF-β, and increased the kinase activity of TAK1. TAB1 may function as an activator of the TAK1 MAPKKK in TGF-β signal transduction.

Photorespiration protects C3 plants from photooxidation

Abstract: PLANTS absorb light for photosynthesis but as light can itself be dangerous to plants, they need to protect themselves against its damaging effects. Here we show that photorespiration can act as such a defence mechanism. We constructed transgenic tobacco plants enriched or reduced in plastidic glutamine synthetase (GS2), a key enzyme in photorespiration. Those transgenic plants having twice the normal amount of GS2 had an improved capacity for photorespiration and an increased tolerance to high-intensity light, whereas those with a reduced amount of GS2 had a diminished capacity for photorespiration and were photoinhib-ited more severely by high-intensity light compared with control plants. We conclude that photorespiration protects C3 plants from photoinhibition.

Theoretical Studies of GG-Specific Photocleavage of DNA via Electron Transfer: Significant Lowering of Ionization Potential and 5‘-Localization of HOMO of Stacked GG Bases in B-Form DNA

Abstract: Ab initio molecular orbital calculations of stacked DNA bases were performed at the 3-21G(*) and 6-31G* levels to elucidate the origin of the 5‘-GG-3‘ sequence specificity for the photocleavage of DNA in the presence of electron-accepting photosensitizers. Ionization potentials (IP) were estimated as Koopman's theorem values for 16 sets of two stacked nucleobases and seven sets of stacked nucleobase pair systems in a B-form geometry. It was found that the GG/CC system is the lowest among the 10 possible stacked nucleobase pairs and that approximately 70% of the HOMO is localized on the 5‘-G of 5‘-GG-3‘. These calculations indicate that the 5‘-G of 5‘-GG-3‘ is the most electron donating site in B DNA and suggest that one-electron transfer from DNA to an electron acceptor occurs most effectively at 5‘-GG-3‘ sites which are fully consistent with the experimental data. In order to know the fate of the cation radical, the vertical IPs were estimated for seven stacked nucleobase pairs. It was found that the GG/...

Expanded polyglutamine in the machado-joseph disease protein induces cell death in vitro and in vivo

Abstract: Recently, we identified a novel gene, MJD1, which contains an expanded GAG triplet repeat in Machado–Joseph disease. Here we report the induction of apoptosis in cultured cells expressing a portion of the MJD1 gene that includes the expanded GAG repeats. Cell death occurs only when the GAG repeat is translated into polyglutamine residues, which apparently precipitate in large covalently modified forms. We also created ataxic transgenic mice by expressing the expanded polyglutamine stretch in Purkinje cells. Our results demonstrate the potential involvement of the expanded polyglutamine as the common aetiological agent for inherited neurodegenerative diseases with GAG expansions.

The catenin/cadherin adhesion system is localized in synaptic junctions bordering transmitter release zones.

Abstract: Molecular mechanisms linking pre- and postsynaptic membranes at the interneuronal synapses are little known We tested the cadherin adhesion system for its localization in synapses of mouse and chick brains We found that two classes of cadherin-associated proteins, alpha N- and beta-catenin, are broadly distributed in adult brains, colocalizing with a synaptic marker, synaptophysin At the ultrastructural level, these proteins were localized in synaptic junctions of various types, forming a symmetrical adhesion structure These structures sharply bordered the transmitter release sites associated with synaptic vesicles, although their segregation was less clear in certain types of synapses N-cadherin was also localized at a similar site of synaptic junctions but in restricted brain nuclei In developing synapses, the catenin-bearing contacts dominated their junctional structures These findings demonstrate that interneuronal synaptic junctions comprise two subdomains, transmitter release zone and catenin-based adherens junction The catenins localized in these junctions are likely associated with certain cadherin molecules including N-cadherin, and the cadherin/ catenin complex may play a critical role in the formation or maintenance of synaptic junctions

Two chains of rhamnogalacturonan II are cross-linked by borate-diol ester bonds in higher plant cell walls

Abstract: Polysaccharide moiety of the boron-polysaccharide complex (T. Matoh, K. Ishigaki, K. Ohno, J. Azuma [1993] Plant Cell Physiol 34: 639–642) isolated from radish (Raphanus sativus) roots has been shown to be rhamnogalacturonan II by glycosyl-linkage analysis and the presence of diagnostic monosaccharides, including apiose, aceric acid, 2-O-methylfucose, and 3-deoxy-D-manno-2-octulosonic acid. Removal of boron from the complex reduced the molecular weight by one-half without causing a significant increase in the number of reducing end groups, indicating that boron, as boric acid, links two rhamnogalacturonan II chains together to form the boron-polysaccharide complex.

Cut2 proteolysis required for sister-chromatid separation in fission yeast

Abstract: ALTHOUGH mitotic cyclins are well-known substrates for ubiquitin-mediated proteolysis at the metaphase–anaphase transition1–4, their degradation is not essential for separation of sister chromatids5–8; several lines of evidence suggest that proteolysis of other protein(s) is required, however4,6,9–11. Here we report the anaphase-specific proteolysis of the Schizosaccharomyces pombe Cut2 protein, which is essential for sister-chromatid separation12,13. Cut2 is located in the nucleus, where it is concentrated along the short metaphase spindle. The rapid degradation of Cut2 at anaphase requires its amino-terminal region and the activity of Cut9 (ref. 14), a component of the 20S cyclosome/ anaphase-promoting complex (APC), which is necessary for cyclin destruction3,4,11. Expression of non-degradable Cut2 blocks sister-chromatid separation but not cell-cycle progression. This defect can be overcome by grafting the N terminus of cyclin B onto the truncated Cut2, demonstrating that the regulated proteolysis of Cut2 is essential for sister-chromatid separation.

Gravitational energy in spherical symmetry.

Abstract: Various properties of the Misner-Sharp spherically symmetric gravitational energy E are established or reviewed. In the Newtonian limit of a perfect fluid, E yields the Newtonian mass to leading order and the Newtonian kinetic and potential energy to the next order. For test particles, the corresponding H\'aj\'{\i}\ifmmode \check{c}\else \v{c}\fi{}ek energy is conserved and has the behavior appropriate to energy in the Newtonian and special-relativistic limits. In the small-sphere limit, the leading term in E is the product of volume and the energy density of the matter. In vacuo, E reduces to the Schwarzschild energy. At null and spatial infinity, E reduces to the Bondi-Sachs and Arnowitt-Deser-Misner energies, respectively. The conserved Kodama current has charge E. A sphere is trapped if Eg1/2r, marginal if E=1/2r, and untrapped if E1/2r, where r is the areal radius. A central singularity is spatial and trapped if Eg0, and temporal and untrapped if E0. On an untrapped sphere, E is nondecreasing in any outgoing spatial or null direction, assuming the dominant energy condition. It follows that E\ensuremath{\ge}0 on an untrapped spatial hypersurface with a regular center, and E\ensuremath{\ge}1/2${\mathit{r}}_{0}$ on an untrapped spatial hypersurface bounded at the inward end by a marginal sphere of radius ${\mathit{r}}_{0}$. All these inequalities extend to the asymptotic energies, recovering the Bondi-Sachs energy loss and the positivity of the asymptotic energies, as well as proving the conjectured Penrose inequality for black or white holes. Implications for the cosmic censorship hypothesis and for general definitions of gravitational energy are discussed. \textcopyright{} 1996 The American Physical Society.