Showing papers by "Kyoto University published in 1986"

A q-analogue of U(g[(N+1)), Hecke algebra, and the Yang-Baxter equation

Abstract: We study for g=g[(N+1) the structure and representations of the algebra Ŭ(g), a q-analogue of the universal enveloping algebra U(g). Applying the result, we construct trigonometric solutions of the Yang-Baxter equation associated with higher representations of g.

Chloroplast gene organization deduced from complete sequence of liverwort Marchantia polymorpha chloroplast DNA

Abstract: Chloroplasts contain their own autonomously replicating DNA genome. The majority of proteins present in the chloroplasts are encoded by nuclear DNA, but the rest are encoded by chloroplast DNA and synthesized by the chloroplast transcription–translation machinery1–4. Although the nucleotide sequences of many chloroplast genes from various plant species have been determined, the entire gene organization of the chloroplast genome has not yet been elucidated for any species of plants. To improve our understanding of the chloroplast gene system, we have determined the complete sequence of the chloroplast DNA from a liverwort, Marchantia polymorpha, and deduced the gene organization. As reported here the liverwort chloroplast DNA contains 121,024 base pairs (bp), consisting of a set of large inverted repeats (IRA and IRB, each of 10,058 bp) separated by a small single-copy region (SSC, 19,813 bp) and a large single-copy region (LSC, 81,095 bp). We detected 128 possible genes throughout the liverwort chloroplast genome, including coding sequences for four kinds of ribosomal RNAs, 32 species of transfer RNAs and 55 identified open reading frames (ORFs) for proteins, which are separated by short A+T-rich spacers (Fig. 1). Twenty genes (8 encoding tRNAs, 12 encoding proteins) contain introns in their coding sequences. These introns can be classified as belonging to either group I or group II, as described for mitochondria5. Interestingly, seven of the identified ORFs show high homology to unidentified reading frames (URFs) found in human mitochondria6,7.

Molecular distinction between fetal and adult forms of muscle acetylcholine receptor

Abstract: Distinct classes of acetylcholine receptor channels are formed when Xenopus oocytes are injected with combinations of the bovine α-, β-, γ- and δ- or the α-, β-, γ- and e-subunit-specific messenger RNAs. The conductance and gating properties of the two classes of channels, in conjunction with the developmental changes in the muscular contents of the mRNAs, suggest that replacement of the γ-subunit by the e-subunit is responsible for the functional alteration of the receptor during muscle development.

Existence of distinct sodium channel messenger RNAs in rat brain

Abstract: The sodium channel is a voltage-gated ionic channel essential for the generation of action potentials1–3. It has been reported that the sodium channels purified from the electric organ of Electrophorus electricus (electric eel)4,5 and from chick cardiac muscle6 consist of a single polypeptide of relative molecular mass (Mr) ∼260,000 (260K), whereas those purified from rat brain7 and skeletal muscle8 contain, in addition to the large polypeptide, two or three smaller polypeptides of Mr 37–45K. Recently, we have elucidated the primary structure of the Electrophorus sodium channel by cloning and sequencing the DNA complementary to its messenger RNA9. Despite the apparent homogeneity of the purified sodium channel preparations, several types of tetrodotoxin (or saxitoxin) binding sites or sodium currents have been observed in many excitable membranes10–19. The occurrence of distinguishable populations of sodium channels may be attributable to different states of the same channel protein or to distinct channel proteins. We have now isolated complementary DNA clones derived from two distinct rat brain mRNAs encoding sodium channel large polypeptides and present here the complete amino-acid sequences of the two polypeptides (designated sodium channels I and II), as deduced from the cDNA sequences. A partial DNA sequence complementary to a third homologous mRNA from rat brain has also been cloned.

Cloning, sequencing and expression of complementary DNA encoding the muscarinic acetylcholine receptor

Abstract: Cloning and sequence analysis of DNA complementary to porcine cerebral messenger RNA encoding the muscarinic acetylcholine receptor predict the complete amino-acid sequence of this protein. Expression of the complementary DNA produced functional muscarinic receptor in Xenopus oocytes. The muscarinic receptor is homologous with the beta-adrenergic receptor and rhodopsin in both amino-acid sequence and suggested transmembrane topography.

Quantum $R$ matrix for the generalized Toda system

Abstract: We report the explicit form of the quantumR matrix in the fundamental representation for the generalized Toda system associated with non-exceptional affine Lie algebras.

Expression of N-cadherin adhesion molecules associated with early morphogenetic events in chick development

Abstract: Selective adhesive properties of cells are thought to have a key role in animal morphogenesis1, but the molecular bases underlying these properties remain to be determined. Our studies have demonstrated that cell-type-specific adhesiveness resides in a class of cell-cell adhesion molecules, termed cadherins, which were defined as the molecular components of the Ca2+-dependent cell adhesion system (CADS)2,3. For example, a cadherin molecule identified in mouse teratocarcinoma cells, termed E-cadherin (this molecule seems to be identical to uvomorulin4 or cell-CAM 120/80 (ref. 5) and equivalent to chicken L-CAM6), was detected only in epithelial cells of various organs2,3; it did not cross-react with cadherins on other cell types7,8. We recently described a novel type of cadherin, N-cadherin, which is found in mouse cells and whose tissue distribution is distinct from that of E-cadherin3. In the present study, we have identified a molecular component of N-cadherin in the chicken and determined its distribution in the tissues of early embryos. The results suggest that expression of this adhesion molecule is associated with separation and sealing of cell layers in morphogenesis.

Expression of functional sodium channels from cloned cDNA

Abstract: The voltage-gated sodium channel is a transmembrane protein essential for the generation of action potentials in excitable cells. It has been reported that sodium channels purified from the electric organ of the electric eel, Electrophorus electricus, and from chick cardiac muscle consist of a single polypeptide of relative molecular mass (Mr) approximately 260,000, whereas those purified from rat brain and from rat and rabbit skeletal muscle contain, in addition to the large polypeptide, one or two smaller polypeptides of Mr 33,000-43,000. The primary structures of the Electrophorus sodium channel and two distinct sodium channel large polypeptides (designated as sodium channels I and II) from rat brain have been elucidated by cloning and sequencing the complementary DNAs. The purified sodium channel preparations from Electrophorus electroplax and from mammalian muscle and brain, when reconstituted into lipid vesicles or planar lipid bilayers, exhibit some functional activities. The successful reconstitution with the Electrophorus preparation would imply that the large polypeptide alone is sufficient to form functional sodium channels. However, studies with the rat brain preparation suggest that the smaller polypeptide of Mr 36,000 is also required for the integrity of the saxitoxin (STX) or tetrodotoxin (TTX) binding site of the sodium channel. Here we report that the messenger RNAs generated by transcription of the cloned cDNAs encoding the rat brain sodium channel large polypeptides, when injected into Xenopus oocytes, can direct the formation of functional sodium channels.

Visualization of the dynamic instability of individual microtubules by dark-field microscopy

Abstract: It has previously been shown that two populations of microtubules coexist in a dynamically unstable manner in vitro: those in one population elongate while those in the other shorten and finally disappear. This conclusion was based on changes in the number and length distribution of microtubules after dilution of the microtubule solution. Here, we demonstrate directly that growing and shortening populations coexist in steady-state conditions, by visualization of the dynamic behaviour of individual microtubules in vitro by dark-field microscopy. Real-time video recording reveals that both ends of a microtubule exist in either the growing or the shortening phase and alternate quite frequently between the two phases in a stochastic manner. Moreover, growing and shortening ends can coexist on a single microtubule, one end continuing to grow simultaneously with shortening at the other end. We find no correlation in the phase conversion either among individual microtubules or between the two ends of a single microtubule. The two ends of any given microtubule have remarkably different characteristics; the active end grows faster, alternates in phase more frequently and fluctuates in length to a greater extent than the inactive end. Microtubule-associated proteins (MAPs) suppress the phase conversion and stabilize microtubules in the growing phase.

A Soluble Active Rotater Model Showing Phase Transitions via Mutual Entertainment

Abstract: Some analytical results are obtained for a large population of limit·cycle oscillators modelled by a set of deterministic equations 1>i = WiNK'2;/j~lsin(

Dynamic hybrid position/force control of robot manipulators--Description of hand constraints and calculation of joint driving force

Abstract: For the application of robot manipulators to complex tasks, it is often necessary to control not only the position of a manipulator but also the force exerted by the hand on an object. For this purpose, Raibert and Craig have proposed the hybrid position/force control method. In this method, however, the manipulator dynamics has not been taken into account rigorously. The dynamic hybrid control method is proposed, which takes the manipulator dynamics into consideration. Constraints on the end effector are described by a set of constraint hypersurfaces. Then the basic equations for dynamic hybrid control are derived. It is shown that if the manipulator is not in a singular configuration, the desired position and force at the end effector can be simultaneously realized. Finally, a basic structure of the dynamic hybrid control system with a servo compensator is given.

Patch clamp measurements on Xenopus laevis oocytes: currents through endogenous channels and implanted acetylcholine receptor and sodium channels.

Abstract: Functional acetylcholine receptor (AChR) and sodium channels were expressed in the membrane of Xenopus laevis oocytes following injection with poly(A)+-mRNA extracted from denervated rat leg muscle. Whole-cell currents, activated by acetylcholine or by depolarizing voltage steps had properties comparable to those observed in rat muscle. Oocytes injected with specific mRNA, transcribed from cDNA templates and coding for the AChR of Torpedo electric organ, expressed functional AChR channels at a much higher density. Single-channel currents were recorded from the oocyte plasma membrane following removal of the follicle cell layer and the vitelline membrane from the oocyte. The follicle cell layer was removed enzymatically with collagenase. The vitelline membrane was removed either mechanically after briefly exposing the oocyte to a hypertonic solution, or by enzyme treatment with pronase. Stretch activated (s.a.) currents were observed in most recordings from cell-attached patches obtained with standard patch pipettes. S.a.-currents were evoked by negative or positive pressure (greater than or equal to 5 mbar) applied to the inside of the pipette, and were observed in both normal and mRNA injected oocytes indicating that they are endogenous to the oocyte membrane. The s.a.-channels are cation selective and their conductance is 28 pS in normal frog Ringer's solution (20 +/- 1 degree C). Their gating is voltage dependent, and their open probability increases toward more positive membrane potentials. The density of s.a.-channels is estimated to be 0.5-2 channels per micron 2 of oocyte plasma membrane. In cell-attached patches s.a.-currents are observed much less frequently when current measurement is restricted to smaller patches of 3-5 micron 2 area using thick-walled pipettes with narrow tips. In outside-out patches s.a.-currents occur much less frequently than in cell-attached or inside-out patches. AChR-channel and sodium channel currents were observed only in a minority of patches from oocytes injected with poly(A)+-mRNA from rat muscle. AChR-channel currents were seen in all patches of oocytes injected with specific mRNA coding for Torpedo AChR. In normal frog Ringer's solution (20 +/- 2 degrees C) the conductance of implanted rat muscle AChR-channels was 38 pS and that of sodium channels 20 pS. The conductance of implanted Torpedo AChR channels was 40 pS. The conductance of implanted channels was similar in cell-attached and in cell-free patches.(ABSTRACT TRUNCATED AT 400 WORDS)

Cloning of cDNA encoding the murine IgG1 induction factor by a novel strategy using SP6 promoter.

Abstract: Complementary DNA encoding the IgG1 induction factor, the first lymphokine directed to B lymphocytes, from a murine T-cell line has been cloned using a new strategy. The putative primary amino-acid sequence was deduced from the nucleotide sequence determined. The lymphokine synthesized by the direction of this cloned cDNA has many other functions, such as production of B-cell growth factor-1 and induction of Ia on B cells.

The NOD Mouse: Recessive Diabetogenic Gene in the Major Histocompatibility Complex

Abstract: Examination of the histocompatibility region of the nonobese diabetic (NOD) mouse with antibodies against class II glycoproteins (products of immune response genes of the major histocompatibility complex I-A and I-E), hybrid T-cell clones, and mixed-lymphocyte cultures and analysis of restriction fragment length polymorphisms indicate that the NOD mouse has a unique class II major histocompatibility complex with no expression of surface I-E, no messenger RNA for I-E alpha, and an I-A not recognized by any monoclonal antibodies or hybrid T-cell clones studied. In crosses of NOD mice with control C3H mice, the development of diabetes was dependent on homozygosity for the NOD mouse's unique major histocompatibility region.

Cloning of complementary DNA encoding T-cell replacing factor and identity with B-cell growth factor II

Abstract: Proliferation and maturation of antigen-stimulated B cells are regulated by several soluble factors derived from macrophages and T cells. These soluble factors are functionally divided into two groups: B-cell growth factor (BCGF), thought to be involved in B-cell proliferation; and B-cell differentiation factor (BCDF), responsible for maturation of activated B cells into immunoglobulin-secreting cells. This classification needs to be re-examined in the light of the recent cloning of complementary DNA encoding IgG1 induction factor (interleukin-4, IL-4) from the 2.19 mouse T-cell line. Recombinant IL-4 has BCGF and BCDF activities and affects B cells, T cells and mast cells (refs 7, 8; our unpublished data). Another well-characterized B-cell factor is T-cell replacing factor (TRF), which, when secreted by the murine T-cell hybridoma B151K12, is defined by two activities: induction of IgM secretion by BCL1 leukaemic B-cell line; and induction of secondary anti-dinitrophenol (DNP) immunoglobulin G (IgG) synthesis in vitro by DNP-prime B cells. Although TRF from B151K12 was classified as BCDF, purified TRF has BCGF-II activity. To elucidate the molecular properties of TRF we isolated cDNA encoding TRF from the 2.19 T-cell line and report here the structure and multiple activities of this lymphokine.

Reactions of alkenylchromium reagents prepared from alkenyl trifluoromethanesulfonates (triflates) with chromium(II) chloride under nickel catalysis.

Abstract: philicities in these complexes, with vanadium in complexes 4 and 5 exhibiting greater electrophilicity. Given the inclination of other 17-electron metal carbonyl complexes to undergo associative ligand displacement reactions, it seems ironic that the incorporation of a pentadienyl ligand, which would be expected to promote associative attack via $ 73 coordination changes, should lead instead to a series of compounds for which much lower rates of substitution are observed and for which the substitutions also take place via dissociative means. Additional kinetic, EPR, and structural studies are under way in attempts to better understand the unexpected behavior of these 17-electron complexes.

Formation of the volcanic front in subduction zones

Abstract: A model is proposed to understand the magma genesis beneath the volcanic front which overlies the dipping seismic zone with a constant depth of about 110 km in most subduction zones. It is suggested that the constant depth of 110 km is governed by the decomposition of amphibole in the mantle wedge. Hydrous phases in the subducted slab decompose at levels shallower than 100 km, that is, beneath the fore-arc region. The slab-derived H2O, enriched in incompatible elements with larger ionic radii, reacts with the overlying mantle wedge materials to form polluted amphibole peridotite. The polluted peridotite is transported downward on the slab by the induced convection in the mantle wedge. Amphibole in the dragged peridotite decomposes at a depth of about 110 km, just beneath the volcanic front. H2O released migrates upward to reform amphibole peridotite in the higher-temperature and lower-pressure region. When the front of amphibolization reaches a level at which the solidus temperature of amphibole peridotite is distributed, initial magmas are produced and rise as a form of mantle diapir. The mantle diapir stops rising to segregate a primary magma for lavas on the volcanic front.

Formation of a high-strength bioactive glass-ceramic in the system MgO―CaO―SiO2―P2O5

Abstract: Formation of a high-strength bioactive glass-ceramic in the system MgO-CaO-SiO2-P2O5 was investigated by observing the microstructure of the crystallized products. Crystallization of the parent glass in a bulk form led to the occurrence of large cracks in the crystallized product. This was attributed to the precipitation of fibrousβ-wollastonite crystals growing perpendicular to the outer surfaces of the glass after uniform precipitation of fine oxyapatite/fluoroapatite crystals. On the other hand, crystallization of the same glass in a powder compact led to the formation of a crack-free dense crystallized product due to uniform precipitation of both apatite and wollastonite fine crystals throughout the glass article. The uniform precipitation of the wollastonite crystals was attributed to the simultaneous formation of fine crystals in the individual glass particles.

Location of a δ-Subunit Region Determining Ion Transport Through the Acetylcholine Receptor Channel

Abstract: The combination of complementary DNA expression and single-channel current analysis provides a powerful tool for studying the structure — function relationship of the nicotinic acetylcholine receptor (AChR). Here we report that in an extracellular solution of low divalent cation concentration the bovine AChR channel has a smaller conductance than the torpedo AChR channel. Replacement of the δ-subunit of the torpedo AChR by the bovine δ-subunit reduces the channel conductance, making it similar to that of the bovine AChR channel. To locate the region within the δ-subunit responsible for the difference in channel conductance, we have constructed a series of chimaeric δ-subunit cDNAs composed of different combinations of the torpedo and bovine counterparts. The conductances of these AChR channels suggest that a region comprising the putative transmembrane segment M2 and the adjacent bend portion between segments M2 and M3 is involved in determining the rate of ion transport through the open channel.

Effects of Capsaicin on Lipid Metabolism in Rats Fed a High Fat Diet

Abstract: Effects of capsaicin, a pungent principle of hot red pepper, were studied in experiments using male rats fed a diet containing 30% lard. Capsaicin was supplemented at 0.014% of the diet. The level of serum triglyceride was lower when capsaicin was present in the diet than when it was not. Levels of serum cholesterol and pre-beta-lipoprotein were not affected by the supplementation of capsaicin. The perirenal adipose tissue weight was lower when capsaicin was present in the diet than when it was not. Hepatic enzyme activities of glucose-6-phosphate dehydrogenase and adipose lipoprotein lipase were lower in rats fed the 30% lard diet than in those fed a nonpurified diet. Activities of these two enzymes were higher when capsaicin was added to the diet than when it was not. Hepatic acetyl-CoA carboxylase, beta-hydroxyacyl-CoA dehydrogenase, and adipose hormone-sensitive lipase activities were not affected by capsaicin feeding. Lipid absorption was not affected by the supplementation of capsaicin. The perirenal adipose tissue weight and serum triglyceride were decreased as the level of capsaicin in the diet increased up to 0.021%. These results suggest that capsaicin stimulates lipid mobilization from adipose tissue and lowers the perirenal adipose tissue weight and serum triglyceride concentration in lard-fed rats.

Isolation and characterization of Schizosaccharomyces pombe cutmutants that block nuclear division but not cytokinesis.

Abstract: By examining cytological phenotypes of 587 temperature-sensitive mutants of the fission yeast Schizosaccharomyces pombe, we obtained 18 mutants which cause cell division in the absence of nuclear division. By genetic analyses, these novel nuclear division arrest mutants can be classified into nine complementation groups (designated cut1 – cut9). The cytological phenotype of cut mutants is similar but not identical to that of DNA topoisomerase II mutants (top2). The cut1+ gene was cloned by transformation and shown to complement cut2 as well as cut1, indicating a functional relationship between the two genes. The cut genes are required for nuclear division, but their mutant phenotypes differ from most of the previously identified mutants which block nuclear division and also the subsequent cytokinesis. Fluorescence microscopy indicates that the mitotic chromosomes formed in cut mutant cells are abnormal and fail to separate properly. We suggest that cut mutations, like top2, block mitotic chromosome formation and concomitantly nuclear division, but that cytokinesis proceeds independently of the defects in nuclear division, demonstrating uncoordinated mitotic pathways. A novel mutant nuc1 is also described which shows a cytological phenotype similar to the double mutant of DNA topoisomerases I and II but contains normal levels of both DNA topoisomerase activities.