Showing papers by "Kyoto University published in 1990"

Solutions able to reproduce in vivo surface-structure changes in bioactive glass-ceramic A-W.

Abstract: High-strength bioactive glass-ceramic A-W was soaked in various acellular aqueous solutions different in ion concentrations and pH. After soaking for 7 and 30 days, surface structural changes of the glass-ceramic were investigated by means of Fourier transform infrared reflection spectroscopy, thin-film x-ray diffraction, and scanning electronmicroscopic observations, in comparison with in vivo surface structural changes. So-called Tris buffer solution, pure water buffered with trishydroxymethyl-aminomethane, which had been used by various workers as a "simulated body fluid," did not reproduce the in vivo surface structural changes, i.e., apatite formation on the surface. A solution, ion concentrations and pH of which are almost equal to those of the human blood plasma--i.e., Na+ 142.0, K+ 5.0, Mg2+ 1.5, Ca2+ 2.5, Cl- 148.8, HCO3- 4.2 and PO4(2-) 1.0 mM and buffered at pH 7.25 with the trishydroxymethyl-aminomethane--most precisely reproduced in vivo surface structure change. This shows that careful selection of simulated body fluid is required for in vitro experiments. The results also support the concept that the apatite phase on the surface of glass-ceramic A-W is formed by a chemical reaction of the glass-ceramic with the Ca2+, HPO4(2-), and OH- ions in the body fluid.

Cloning and expression of a cDNA encoding an endothelin receptor

Abstract: Endothelins are a newly described peptide family consisting of three peptides (ET-1, ET-2 and ET-3) which are the most potent vasoconstrictive peptides known. They are crucial in the regulation of vascular smooth muscle tone. The diverse functions of endothelins are thought to be mediated by interaction with many different receptors coupled to the inositol phosphate/calcium ion messenger pathway. However, because of the structural resemblance of the three peptides, the presence and nature of multiple endothelin receptors remain to be elucidated. We report here the cloning of a complementary DNA encoding a bovine endothelin receptor, which has a transmembrane topology similar to that of other G protein-coupled receptors and shows specific binding, with the highest selectivity to ET-1 in animal cells transfected with the cloned cDNA. This receptor messenger RNA is widely distributed in the central nervous system and peripheral tissues, particularly in the heart and lung. Our results support the view that there are other receptor subtypes.

Cadherins: A Molecular Family Important in Selective Cell-Cell Adhesion

Abstract: PERSPECTIVES AND SUMMARY 237 SELECTIVE C LL ADHESION 238 CELL-CELL ,a,DHESION MOLECULES 239 CADHERINS 240 cDNA TRANSFECTION STUDIES ON CADHERIN FUNCTION 242 BINDING SPECIFICITIES OF CADHERINS 242 MOLECULAR BASIS FOR CADHERIN-MEDIATED SELECTIVE ADHESION ..... 244 SPECIES-SPECIFICITIES OF CADHERINS 245 TRANSMEMBRANE CONTROL OF CADHERIN FUNCTION 246 ROLE OF CADHERINS 1N MORPHOGENESIS 248

Ca, P‐rich layer formed on high‐strength bioactive glass‐ceramic A‐W

Abstract: Glass-ceramic A-W, containing crystalline apatite and wollastonite in a MgO-CaO-SiO2 glassy matrix shows high bioactivity as well as high mechanical strength, but other ceramics containing the same kinds of crystalline phases in different glassy matrices do not show the same bioactivity. In order to investigate the bone-bonding mechanism of this type of glass-ceramic, surface structural changes of the glass-ceramics after exposure to simulated body fluid were analyzed with various techniques. A solution with ion concentrations which are almost equal to those of the human blood plasma was used as the simulated body fluid, instead of Tris-buffer solution hitherto used. For analyzing the surface structural changes, thin-film x-ray diffraction was used in addition to conventional techniques. It was found that a bioactive glass-ceramic forms a Ca, P-rich layer on its surface in the fluid but nonbioactive ones do not, and that the Ca, P-rich layer consists of carbonate-containing hydroxyapatite of small crystallites and/or defective structure. These findings were common to those of Bioglass-type glasses. So, we conclude that the essential condition for glass and glass-ceramic to bond to bone is the formation of the surface apatite layer in the body environment but it is not essential to contain apatite within the material. Bioactivity of glass and glass-ceramic can be evaluated in vitro by examining the formation of the surface apatite layer in the simulated body fluid described above.

Crystalizing the $q$-analogue of universal enveloping algebras

Abstract: For an irreducible representation of theq-analogue of a universal enveloping algebra, one can find a canonical base atq=0, named crystal base (conjectured in a general case and proven forA n, Bn, Cn andD n). The crystal base has a structure of a colored oriented graph, named crystal graph. The crystal base of the tensor product (respectively the direct sum) is the tensor product (respectively the union) of the crystal base. The crystal graph of the tensor product is also explicitly described. This gives a combinatorial description of the decomposition of the tensor product into irreducible components.

Surface chemistry of bioactive glass-ceramics

Abstract: General principles governing the bioactivity of glass-ceramics are discussed on the basis of surface chemical studies of glass-ceramic A–W containing crystalline apatite and wollastonite, and related materials. The apatite phase in the glass-ceramics did not play an important role in forming chemical bond of the glass-ceramic to the bone. An apatite layer formed on the surface of the glass-ceramic in vivo was responsible for the bonding of the glass-ceramic to the bone. It was shown that a chemical bond between apatite crystals in the body environment can give a fairly strong bond. The surface apatite layer was shown to be formed by a chemical reaction of calcium and silicate ions dissolved from the glass-ceramic with the surrounding body fluid. A P2O5-free CaO·SiO2 glass also formed the surface apatite and bonded to the bone. The same type of apatite layer as the surface apatite was formed even on the surfaces of various kinds of ceramics, metals and polymers, when they were placed near a glass dissolving the calcium and silicate ions in a simulated body fluid. These results show that bioactive materials having various functions can be obtained using glasses and glass-ceramics based on the simple components of CaO and SiO2.

Regions of the skeletal muscle dihydropyridine receptor critical for excitation-contraction coupling.

Abstract: IT is thought that in skeletal muscle excitation–contraction (EC) coupling, the release of Ca2+ from the sarcoplasmic reticulum is controlled by the dihydropyridine (DHP) receptor in the transverse tubular membrane, where it serves as the voltage sensor1–3. We have shown previously4 that injection of an expression plasmid carrying the skeletal muscle DHP receptor complementary DNA3 restores EC coupling and L-type calcium current that are missing in skeletal muscle myotubes from mutant mice with muscular dysgenesis5–9. This restored coupling resembles normal skeletal muscle EC coupling4, which does not require entry of extracellular Ca2+ (refs 10, 11). By contrast, injection into dysgenic myotubes of an expression plasmid carrying the cardiac DHP receptor cDNA12 produces L-type calcium current and cardiac-type EC coupling13, which does require entry of extracellular Ca2+ (refs 14–16). To identify the regions responsible for this important functional difference between the two structurally similar DHP receptors, we have expressed various chimaeric DHP receptor cDNAs in dysgenic myotubes. The results obtained indicate that the putative cytoplasmic region between repeats II and III of the skeletal muscle DHP receptor3 is an important determinant of skeletal-type EC coupling.

Circulating CD8 + cytotoxic T lymphocytes specific for HTLV-I pX in patients with HTLV-I associated neurological disease

Abstract: The human T-lymphotropic virus type I (HTLV-I), the first human retrovirus to be characterized, is associated with adult T-cell leukaemia and a chronic progressive disease of the central nervous system termed tropical spastic paraparesis, or HTLV-I-associated myelopathy. Only 1% of individuals infected with HTLV-I develop clinical disease however. The various manifestations of an HTLV-I infection may be related to differences in the genetic backgrounds of individuals, infection with variant strains of HTLV-I, differences in viral tropism or host immune response to the virus. Whereas the humoral response to HTLV-I is well characterized, little is known about the human cellular immune response, such as the production of cytotoxic T lymphocytes. Here we report the presence of high levels of circulating HTLV-I-specific cytotoxic T lymphocytes in patients with HTLV-I associated neurological disease but not in HTLV-I seropositive individuals without neurological involvement. These cytotoxic T lymphocytes are CD8+, HLA class I- restricted and predominantly recognize the HTLV-I gene products encoded in the regulatory region pX. These findings suggest that HTLV-I-specific cytotoxic T lymphocytes may contribute to the pathogenesis of associated neurological disorders associated with HTLV-I.

Lignin biochemistry: Biosynthesis and biodegradation *

Abstract: Lignin biosynthesis via shikimate-cinnamate pathways in plants, and the biosynthetic differences of guaiacyl-and syringyl lignins between gymnosperms and angiosperms have been elucidated by tracer experiments using 14C labeled precursors and the following enzyme reactions. The formation of guaiacyl lignin but not syringyl lignin in gymnosperms was attributed to the following factors; absence of ferulate-5-hydroxylase, poor affinity of O-methyltransferase toward 5-hydroxyferulate, and lack of activation and/or reduction of sinapatc. A mechanism of lignin-carbohydrate complexes formation in wood cell walls was elucidated based on the reaction of the quinone methide of guaiacylglycerol-β-guaiacyl ether with sugars, and the analysis of DHP-polysaccharide complexes. The main cleavage mechanisms of side chains and aromatic rings of lignin model compounds and synthetic lignin (DHP) by white-rot fungi and their enzymes, lignin peroxidase and laccase have been elucidated using 2H, 13C and 18O-labeled lignin substructure dimcrs with 18O2 and H2 18O. Side chains and aromatic rings of these substrates were cleaved via aryl cation radical and phenoxy radical intermediates, in reaction mediated only by lignin peroxidase/H2O2 and laccase/O2.

Oncogenic transformation by the tax gene of human T-cell leukemia virus type I in vitro

Abstract: Human T-cell leukemia virus type I (HTLV-I) is a causative agent of adult T-cell leukemia (ATL). To elucidate the role of HTLV-I in leukemogenesis, we examined the biological activity of a defective HTLV-I provirus with the env-pX 3' long terminal repeat region cloned from leukemic cells of an ATL patient. Transfection experiments showed growth stimulation of NIH 3T3 cells--growing beyond the saturation density and growing in soft agar. Since the pX sequence is known to encode three proteins, Tax, Rex, and p21x, the biological activity of each pX gene was examined separately. The growth-stimulating activity was induced only by the tax gene in NIH 3T3 cells and Rat-1 cells. Furthermore, the tax gene induced tumorigenicity in nude mice when introduced into Rat-1 cells. Thus, a transcriptional transactivator gene of HTLV-I, tax, is clearly identified as a viral oncogene without a cellular homolog. The transforming activity of tax, possibly via a transcriptional deregulation of cell growth control, may play an important role in leukemogenesis of ATL in addition to its aberrant stimulation of the interleukin 2 system.

Shared binary decision diagram with attributed edges for efficient Boolean function manipulation

Abstract: The efficiency of Boolean function manipulation depends on the form of representation of Boolean functions. Binary decision diagrams (BDDs) are graph representations proposed by S.B. Akers (1978) and R.E. Bryant (1985). BDDs have some properties which can be used to enable efficient Boolean function manipulation. The authors describe a technique of more efficient Boolean function manipulation that uses shared binary decision diagrams (SBDDs) with attributed edges. The implements include an ordering algorithm of input variables and a method of handling 'don't care'. A Boolean function manipulator using the above methods is developed and it is shown that the manipulator is very efficient in terms of speed and storage. >

Vacuum-ultraviolet reflectance and photoemission study of the metal-insulator phase transitions in VO 2 , V 6 O 13 , and V 2 O 3

Abstract: Vacuum-ultraviolet reflectance and photoemission spectra of ${\mathrm{VO}}_{2}$, ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$, ${\mathrm{V}}_{6}$${\mathrm{O}}_{13}$, and ${\mathrm{V}}_{2}$${\mathrm{O}}_{5}$ are measured in order to investigate the 3d-band structures and electron-correlation effects. In the case of ${\mathrm{VO}}_{2}$, drastic changes in the 3d (${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ and ${\mathit{d}}_{\mathrm{?}}$) -band structures are found in both spectra through the metal-insulator phase transition. The ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ and ${\mathit{d}}_{\mathrm{?}}$ bands are found at the Fermi level and ${\mathit{E}}_{\mathit{B}}$=1.3 eV in the photoemission spectra of metallic ${\mathrm{VO}}_{2}$. In the insulating phase, the ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ valence band in the photoemission spectra becomes empty and a rise of the ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ conduction band by about 0.5 eV is found in the reflectance spectra. This band shift through the phase transition may be a driving force of the metal-insulator transition of ${\mathrm{VO}}_{2}$. The optical band gap between the ${\mathit{d}}_{\mathrm{?}}$ valence and ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ conduction bands is obtained as 0.7 eV in the insulating phase, to which the ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$-${\mathit{d}}_{\mathrm{?}}$ correlation energy contributes partially.The splitting of the ${\mathit{d}}_{\mathrm{?}}$ band is also found in the insulating phase. This splitting energy is about 2.5 eV, while the bandwidth of the ${\mathit{d}}_{\mathrm{?}}$ band is about 1.5 eV. This large band splitting is mainly due to the correlation energy of ${\mathit{d}}_{\mathrm{?}}$ electrons of about U(${\mathit{d}}_{\mathrm{?}}$,${\mathit{d}}_{\mathrm{?}}$)=2.1 eV. On the other hand, no drastic change is found in the 3d-band structures of ${\mathrm{V}}_{6}$${\mathrm{O}}_{13}$ and ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$ except for slight changes in the bandwidths. Furthermore, the density of states at the Fermi level is rather low in these materials even in the metallic phase. These facts support the view that the electron-correlation effects are important and Mott-type metal-insulator transitions are induced in ${\mathrm{V}}_{6}$${\mathrm{O}}_{13}$ and ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$. Resonant photoemission from V3d and O2p bands are observed as the photon energy is swept through the 3p\ensuremath{\rightarrow}3d optical-absorption transition. The resonance profiles of V3d bands show the characteristic antiresonance dip, while those of O2p bands show rather broad and simple enhancements. The multiplet structures in the 3p core photoemission spectra of ${\mathrm{VO}}_{2}$ and ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$ are quantitatively analyzed with use of results from the calculations of Yamaguchi et al.

Apatite coating on ceramics, metals and polymers utilizing a biological process

Abstract: A novel method of apatite coating is presented. The main characteristics of the method are that the apatite layer obtained consists of bone-like apatite and can be coated on various substrates including ceramics, metals and organic polymers. Coating is carried out in a simulated body fluid, the ion concentrations, temperature and pH of which are adjusted to almost equal to those of human blood plasma, using a plate of CaO, SiO2-based glass as a source of nucleating agent of apatite on the surfaces of substrates. The apatite layer obtained, formed in a similar environment to that in the body, is thus expected to show higher bone-bonding ability than that formed by conventional methods, and this method is applicable to various materials having different mechanical properties.

Farnesylated gamma-subunit of photoreceptor G protein indispensable for GTP-binding.

Abstract: TRANSDUCIN, composed of subunits Tα, Tβ and Tγ, is a member of a heterotrimeric G-protein family, and transduces the light signal in visual cells. We have recently found that bovine Tβγ can be separated into two components, Tβγ-1 and Tβγ-2, each of which has its own γ-subunit, Tγ-1 and Tγ-2, respectively1. Tβγ-2 enhances the binding of GTP to Tα in the presence of metarhodopsin II by about 30-fold compared with Tβγ-1 (ref. 1). Here we show that a farnesyl moiety is attached to a sulphur atom of the C-terminal cysteine of Tγ-2 (active form), a part of which is additionally methyl-esterified at the α-carboxyl group. In Tγ-1 (inactive form), however, such modifications are missing. Thus, the farnesyl moiety attached to the γ-subunit is indispensable for the GTP-binding activity of transducin. This suggests that a similar modification may occur in the γ-subunits of other heterotrimeric G proteins involved in biological signal transduction processes.

Novel potential mitotic motor protein encoded by the fission yeast cut7 + gene

Abstract: THE structure equivalent to higher eukaryotic centrosomes in fission yeast, the nuclear membrane-bound spindle pole body, is inactive during interphase. On transition from G2 to M phase of the cell cycle, the spindle pole body duplicates; the daughter pole bodies seed microtubules which interdigitate to form a short spindle that elongates to span the nucleus at metaphase1–5. We have identified two loci which, when mutated, block spindle formation. The predicted product of one of these genes, cut7+ (ref. 6), contains an amino-terminal domain similar to the kinesin heavy chain head domain7,8, indicating that the cut7+ product could be a spindle motor. The cut7+ gene resembles the Aspergillus nidulans putative spindle motor gene bimC (ref. 9), both in terms of its organization with a homologous amino-terminal head and no obvious heptad repeats and in the morphology of the mutant phenotype. But we find no similarity between the carboxy termini of these genes, suggesting that either the cut7+ gene represents a new class of kinesin genes and that fission yeast may in addition contain a bimC homologue, or that the carboxy termini of these mitotic kinesins are not evolutionary conserved and that the cut7+ gene belongs to a subgroup of bimC-related kinesins.

Storm-Time Magnetospheric Currents Inferred from Mid-Latitude Geomagnetic Field Variations

Abstract: Both D and H components of geomagnetic field data from 10 mid-latitude stations are used to examine the storm-time magnetospheric current system by deriving the longitudinally symmetric and asymmetric components of the fields. The asymmetry in D component suggests that net downward and upward field-aligned currents exist in the morning sector and from the evening to the early morning sector, respectively, when the IMF is southward. It also suggests the appearance of a net downward current in the afternoon sector at the developing stage of the storm-time ring current. These suggestions are confirmed by Magsat observation over the ionosphere since the direction of disturbances over the ionosphere is not the opposite but the same as that on the ground. This downward current signature co-exists with that of the morning sector during the southward IMF, suggesting that two different current systems co-exist at the developing phase of the ring current. One is the so-called partial ring current system whereas the other is the current system controlled by the IMF-Bz. A systematic phase shift of asymmetry in local time is seen in the dusk-side H but not in the D component, indicating that the contribution from westward drifting ring current particles can not be neglected as a cause for the H component asymmetry.

Quantitative evaluation of molecular orientation in thin Langmuir-Blodgett films by FT-IR transmission and reflection-absorption spectroscopy

Abstract: By a comparison of infrared reflection-absorption (RA) and transmission intensities, a method for the quantitative evaluation of molecular orientation in thin Langmuir-Blodgett (LB) films has been developed. The enhancement factors for the RA to transmission absorption intensities of hypothetical isotropic films were theoretically calculated by using Hansen's optical formulas for thin multilayer films. By combination of these values with the experimentally determined intensity ratios of the RA to transmission spectra for uniaxially oriented LB films, the orientation angles of the transition moments of major infrared bands were evaluated. Application of this method to the 7-monolayer LB film of cadmium stearate deposited on AG (for RA measurements) and on ZnSe (for transmission measurements) substrates gave reasonable tilt angles for the molecular chain as compared to those reported by other investigators and to the data from the X-ray analysis. This method will be discussed in detail and the various factors which influence the accuracy of the orientation analysis will also be covered.

Binding of the Drosophila sex-lethal gene product to the alternative splice site of transformer primary transcript.

Abstract: SOMATIC sexual differentiation in Drosophila melanogaster is accomplished by a hierarchy of genes1–5 of which one, Sex-lethal (Sxl)6,7, is required for the functional female-specific splicing of the transcripts of the immediately downstream regulatory gene, transformer (tra). The first exon of the tra primary transcript is spliced to one of two acceptor sites. Splicing to the upstream site yields a messenger RNA which is neither sex-specific nor func-tional, but that produced after splicing to the downstream acceptor site yields a functional female-specific mRNA. Here we address the question of how the Sxl gene product determines the alternative splicing of tra primary transcripts. One suggestion is that non-sex-specific splicing to the upstream acceptor is blocked in female flies by sex-specific factors8, but neither the identity of the female-specific factors nor the mechanism of the blockage has been specified. We have now performed co-transfection experiments in which Sxl complementary DNA and the tra gene are expressed in Drosophila Kc cells. Moreover, we find that female Sxl-encoded protein binds specifically to the tra transcript at or near the non-sex-specific acceptor site, implying that the female Sxl gene product is the trans-acting factor that regulates the alternative splicing.