Showing papers by "Nagoya University published in 1988"

A New Ambient Pressure Organic Superconductor Based on BEDT-TTF with TC Higher than 10 K (TC=10.4 K)

Abstract: An ambient pressure superconductivity of (BEDT-TTF)2Cu(SCN)2 was observed by d.c. magnetic susceptibility and electrical conductivity measurements. The superconducting critical temperature is the highest (TC=10.4 K) among the organic superconductors so far obtained, even though the anion has a positional disorder in the crystal.

Codon and amino-acid specificities of a transfer RNA are both converted by a single post-transcriptional modification.

Abstract: An Escherichia coli isoleucine transfer RNA specific for the codon AUA (tRNA2Ile or tRNAminorIle (ref. 1) has a novel modified nucleo-side, lysidine (L; ref. 2) (Fig. la) in the first position of the anticodon (position 34), which is essential for the specific recognition of the codon AUA (ref. 1). We isolated the gene for tRNA2Ile (ileX) and found that the anticodon is CAT, which is characteristic of the methionine tRNA gene. Replacement of L(34) of tRNA2Ile molecule enzymatically with unmodified C(34) resulted in a marked reduction of the isoleucine-accepting activity and, surprisingly, in the appearance of methionine-accepting activity. Thus, both the codon and amino-acid specificity of this tRNA are converted by a single post-transcriptional modification of the first position of the anticodon during tRNA maturation.

Chemistry of Maillard Reactions: Recent Studies on the Browning Reaction Mechanism and the Development of Antioxidants and Mutagens

Abstract: Publisher Summary In this chapter, the browning reaction mechanism, and the formation of antioxidants and mutagens are reviewed. The stages in browning reaction mechanism based on Hodge's scheme are described in detail. Different stages are initial stage involving the formation of glycosyl amino products followed by Amadori rearrangement, intermediate stage involving dehydration and fragmentation of sugars and final stage involving aldol condensation, polymerization, and formation of heterocyclic nitrogen compounds. Formation of free radicals and structure of novel free radicals in the initial stage are described in detail. The sugar fragmentation and carbonyl compounds in the formation of free radicals are effective in browning process. The steps in the intermediate stages described are Amadori rearrangement products, enolization and degradation of Amadori products and precursors of melanoidins. The final stage describes the chemistry of melanoidins. The chapter also discusses the antioxidants and Maillard reaction. The stability of foods increases when Maillard reactions occur. The stabilization is considered to be because of the antioxidative action of Maillard reaction products (MRPs). Conditions for induction of antioxidative activity are explained. Detailed explanation about the antioxidative property of reductones is presented. The antioxidative property of reductones is due to their reducing activity and metal cheating ability. Application of MRPs in practical food processing is also highlighted. The relationship between mutagen formation and browning of food is explained. The role of nitroso mutagens and antimutagens is also discussed. The chapter also discusses the need for more detailed information on the structure and properties of melanoidin to elucidate the mechanism of its antioxidative activity.

Mutations at twelve independent loci result in absence of outer dynein arms in Chylamydomonas reinhardtii.

Abstract: 35 strains of Chlamydomonas mutant missing the entire outer dynein arm were isolated by screening slow-swimming phenotypes. They comprised 10 independent genetic loci (odal-10) including those of previously isolated mutants oda38 and pf28. The 10 loci were distinct from pf13 and pf22, loci for nonmotile mutants missing the outer arm. These results indicate that at least 12 genes are responsible for the assembly of the outer dynein arms. There were no mutants lacking partial structures of the outer arm, suggesting that lack of a single component results in failure of assembly of entire outer arms. Temporary dikaryons derived from mating of two different oda strains often, but not always, recovered the wild-type motility within 2 h of mating. Hence, outer arms can be transported and attached to the outer doublets independently of flagellar growth.

Transport of Asian dust (KOSA) particles; importance of weak KOSA events on the geochemical cycle of soil particles

Abstract: Lidar measurements and airborne-particle collections were made during KOSARP 87 (‘KOSA’ Research Program of Nagoya University; April-May 1987) at Nagoya (35°N, 137°E) to investigate the vertical distribution of Asian dust (KOSA) particles and the transport of these particles. According to the lidar measurements, the highly concentrated particle layers with large depolarization ratio were frequently in the range from about 2 km to about 6 km. Electron microscope observations on the morphology of individual particles in the height range from near the ground to about 4400 m suggested that the particle layers contained many soil particles. It is reasonable to consider that KOSA particles were very frequently transported from Asian desert areas to the islands of Japan in the middle troposphere, even when the effect of the KOSA was not detected near the ground. This ‘background KOSA’ has concentrations of about 1.9 ~ 25 pg/m 3 at the layer peaks and one order of magnitude smaller than the values of severe KOSA. However, the contribution of the ‘weak KOSA’ to the global budget of soil particles is not negligible since the frequency of occurrence of ‘weak KOSA’ is high. The reaction of soil particles sampled on the vapour-deposited Ca thin-film suggested that some of the particles were coated by water or solution containing SO 2- 4 . Such particles can absorb various atmospheric gases, and therefore the KOSA particles can play an important role in the geochemical cycle of many chemical constituents, as chemical reaction sites in the atmosphere and as carriers of the chemical products. DOI: 10.1111/j.1600-0889.1988.tb00119.x

Curves, K3 Surfaces and Fano 3-folds of Genus ≤ 10

Abstract: A pair ( S , L ) of a K3 surface S and a pseudo-ample line bundle L on S with ( L 2 ) = 2 g − 2 is called a (polarized) K3 surface of genus g . Over the complex number field, the moduli space F g of those ( S , L )s is irreducible by the Torelli type theorem for K3 surfaces. A general K3 surface of genus 6 ≤ g ≤ 10 is still a complete intersection in a certain homogeneous space The homogeneous space X is the quotient of a simply connected semisimple complex Lie group G by a maximal parabolic subgroup P . This chapter describes the application of this to the description of birational type of F g for g ≤ 10 and the study of curves and Fano 3-folds.

Deformation and fracturing behaviour of discontinuous rock mass and damage mechanics theory

Abstract: The mechanical behaviour of a rock mass is strongly affected by discontinuities such as faults and joints. In this paper, a damage mechanics theory is proposed which deals with some sets of discontinuities distributed in a rock mass, for example, joint systems. In this theory, the distributed discontinuities are characterized by a second-order symmetric tensor, called the damage tensor. By introducing the damage concept, the deformation and fracturing behaviour of the rock mass can be reated in a framework of continuum mechanics. A numerical procedure is developed in order to implement the damage mechanics model by using the finite element method. The theory and numerical analysis are applied to several laboratory tests and a practical underground opening problem. Numerical results are compared with measured data.

Accumulation of indoxyl sulfate, an inhibitor of drug-binding, in uremic serum as demonstrated by internal-surface reversed-phase liquid chromatography.

Abstract: We quantified indoxyl sulfate in uremic serum by using internal-surface reversed-phase high-performance liquid chromatography. Its concentrations were markedly increased in chronic hemodialysis patients, and were significantly but weakly correlated with the concentrations of creatinine and beta 2-microglobulin in these patients' serum, and with the duration of their hemodialysis treatment. Indoxyl sulfate could not be removed effectively by conventional hemodialysis because of its strong binding to serum albumin. Equilibrium dialysis demonstrated that indoxyl sulfate inhibited the binding of salicylate to albumin, and that 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid inhibited the binding of indoxyl sulfate to albumin. In conclusion, indoxyl sulfate was markedly accumulated in uremic serum, and inhibited drug binding.

Accumulation of collagen III at the cleft points of developing mouse submandibular epithelium.

Abstract: The distribution of collagens I, III, IV and V was studied by immunoperoxidase staining of early developing mouse submandibular glands. Collagen I was always present in the extracellular matrices of the mesenchyme and at the epithelial-mesenchymal interfaces of the 12-day gland with no clefts and of the 13-day gland with a few definite clefts. Collagen III was found in a similar fashion to that of collagen I in the mesenchyme, but the distribution at the epithelial-mesenchymal interfaces was very different. In the mid 12-day gland with a round lobule, collagen III was distributed at every slightly indented site of basal epithelial surfaces. At the late 12-day stage, a few initial signs of cleft appeared on the surface, at which accumulation of collagen III became evident. Intense immunoreaction of collagen III in the early 13-day gland was seen at the bottom of every narrow cleft. No specific accumulation of collagens IV and V was observed in clefts of the late 12-day and early 13-day glands. Staining of collagen III in the 12-day gland cultured for 10 h in the presence of bovine dental pulp collagenase inhibitor, which has been shown to stimulate cleft initiation, was very prominent at the bottom of every narrow cleft. These observations suggest that collagen III works as a key substance for either in vitro or in vivo cleft initiation of the mouse embryonic submandibular epithelium.

Responses in muscle sympathetic activity to acute hypoxia in humans

Abstract: Responses in muscle sympathetic activity (MSA) to acute hypoxia were studied in 13 healthy male subjects under hypobaric hypoxic conditions at a simulated altitude of 4,000, 5,000, and 6,000 m. Efferent postganglionic MSA was recorded directly with a tungsten microelectrode inserted percutaneously into the tibial nerve. Heart rate (HR) and respiratory rate (RR) were counted respectively from the R wave of an electrocardiogram and from the respiratory tracing recorded by the strain-gauge method. The average values of the MSA burst rate and total activity of MSA (burst rate x mean burst amplitude) at 4,000, 5,000, and 6,000 m were 36.4 +/- 2.6, 39.1 +/- 3.1, and 40.2 +/- 4.2 (SE) bursts/min and 616 +/- 138, 794 +/- 190, and 764 +/- 227 arbitrary units, respectively. These values were significantly higher than the values of 27.1 +/- 2.9 bursts/min and 446 +/- 28 at sea level. HR increased significantly at altitudes, but RR did not show significant change. Under severe hypoxic conditions beyond 5,000 m, there were large interindividual differences in the MSA responsiveness to hypoxia. The results indicate that MSA is activated under hypoxia by stimulating the chemoreceptors. However, the central controlling mechanisms that would be affected by hypoxia may also influence the MSA responsiveness under severe hypoxia.

Heterogeneity in formation of lignin-XI : An autoradiographic study of the heterogeneous formation and structure of pine lignin

Abstract: Selective labeling of p-hydroxyphenyl-, guaiacyl-and syringylpropane moieties in protolignin was achieved by administration of corresponding 3H-labeled monolignol glucosides to differentiating xylem of pine. The growing process of the protolignin macromolecule in the specific morphological region was visualized by application of high resolution microautoradiography to the selectively labeled wood tissue. p-Hydroxyphenyl lignin is formed mainly in the compound middle lamella and cell corner in an early stage of cell wall differentiation. There are two peaks of deposition of guaiacyl lignin in the compound middle lamella at an early stage and in the secondary wall at a late stage. The content of condensed guaiacyl units is higher in the middle lamella than in the secondary wall lignin. Syringyl lignin is formed mainly in the inner layer of the secondary wall in a late stage as a minor structural moiety. During the formation of the cell wall, protolignin grows under definite biological regulations to a heterogeneous macromolecule which consists of various structural moieties arranged in a regular manner. The origin of the heterogeneous structure was explained as a result of the biogenesis of protolignin in the cell wall.

Arthroscopic meniscectomy for discoid lateral meniscus in children.

Abstract: We reviewed the cases of forty-six children who were less than fifteen years old and in whom total, subtotal, or partial arthroscopic meniscectomy was performed for symptomatic discoid lateral meniscus in fifty-three knees. The average length of follow-up was 31.2 months. A meniscal tear was evident in each knee. The extent of the meniscectomy depended on the site and shape of the tear, as did the symptoms and signs. We tried to establish the width of partial meniscectomy of a discoid meniscus that would prevent new tears.

Geometric realization of conformal field theory on Riemann surfaces

Abstract: Conformal field theory on a family of Riemann surfaces is formulated We derive equations of motion of vacua which are parametrized by moduli of Riemann surfaces and show that these vacua are characterized uniquely by these equations Our theory has a deep connection with Sato's theory of KP equations

Structure of the human tyrosine hydroxylase gene: alternative splicing from a single gene accounts for generation of four mRNA types.

Abstract: Tyrosine hydroxylase (TH) is a rate-limiting enzyme for catecholamine biosynthesis. Recently, Grima et al. (Nature (1987) 326, 707-711) and we (Biochem. Biophys. Res. Commun. (1987) 146, 971-975; Nucleic Acids Res. (1987) 15, 6733) reported four similar but distinct mRNAs that encode human TH. These mRNAs are constant for the major part, but are distinguishable from one another as to the insertion/deletion of 12-bp and 81-bp sequences near the N-terminus. We isolated genomic clones encoding the human TH gene and determined the nucleotide sequence. The human TH gene is split into 14 exons. The 12-bp insertion sequence is encoded by the 3'-terminal portion of the first exon. The 81-bp insertion sequence corresponds to the second exon. Taking into consideration also the results of Southern blot analysis of human genomic DNA, we concluded that the four types of human TH mRNA are produced through alternative splicing from a single gene. Two kinds of alternative splicing are involved: the alternative use of two donor sites in the first exon, and the inclusion/exclusion of the second exon. We propose a possible secondary structure for the latter alternative splicing pathway.

Enantioselective alkylation of carbonyl compounds. From stoichiometric to catalytic asymmetric induction

Abstract: Multinuclear organometallic species play a significant role in alkylation of carbonyl compounds. Enantioselective alkylation of aldehydes using a 1: 1 reagent/substrate stoichiometry is achievable by chirally modified lithium/magnesium binary organometallic reagents. For example, diethylmagnesium treated with di-O-lithio-(S)-2.2'- dihydroxy- 1, 1'-binaphthyl reacts with benzaldehyde in a THF- dimethoxyethane mixture at -100 OC to give (S)- 1-phenyl- 1- propanol in 92% ee. In the presence of a catalytic quantity of (4-3- exo-(dimethy1amino)isoborneol (DAIB), reaction of dialkylzincs and aldehydes in nonpolar media is accelerated greatly to lead to the corresponding S alcohols in very high enantiomeric excesses (up to 99% ee). The enantioselective catalysis involves fluxional organozinc species and the product-forming dinuclear intermediate possesses DAIB auxiliary, an aldehyde ligand, and three alkyl groups, where it is the bridging alkyl group, rather than the terminal alkyls, that migrates from zinc to the carbonyl carbon.