Biomedical subjects

T Yui

Publications and source records attributed to T Yui.

At least 19 recordsLinked to original sources

PubMed2001

Crystalline behavior of chitosan organic acid salts.

The crystal structures of chitosan acid salts were studied by X-ray diffraction measurements on a fiber diagram and a new procedure to obtain an anhydrous polymorph of chitosan was found. The salts prepared by immersing a chitosan into a mixture of acid solution and isopropanol were classified into two types (Types I and II) depending on their conformation. Molecular conformation of the Type I salt retains the extended 2-fold helical structure of the original chitosan, but that of Type II salt is a twisted 2-fold helix. All the Type II salts changed to the anhydrous "Annealed" polymorph of chitosan when soaking in 75% aqueous isopropanol, but when the Type I salts were immersed in the solution, they returned to the hydrated "Tendon" polymorph which is that of the original chitosan. The strange transformation observed in Type II salt may be related to the stability of the molecular conformation of chitosan in the salt.

Acids↗

PubMed2001

Immune thrombocytopenia in an elderly patient treated successfully by pulse therapy with cyclophosphamide.

Thrombocytopenia due to immune mechanisms is rare and difficult to manage in elderly patients. We describe a case of an 89-year-old female with severe immune thrombocytopenia (ITP) who rapidly improved by pulse therapy with cyclophosphamide. She was admitted to our hospital because she had arthralgia in both sides of her femoral region since January 1999, aphthous stomatitis and ecchymosis of the leg since April 1999, and bloody phlegm in July 1999. On admission, her peripheral blood count revealed severe thrombocytopenia (0.1 x 10(4)/microl). Her megakaryocyte count from bone marrow was increased to 512/microl without abnormal cells. Systemic lupus erythematosus was suspected because of strong positive protein in the urine in addition to the clinical and hematological findings described above, but she was negative for all the autoantibodies examined. Finally, she was diagnosed as having ITP on the basis of high platelet associated immunoglobulin G in addition to hematological and physical findings and she was treated with prednisolone. It was difficult to maintain her platelet count with only prednisolone, but 600 mg of cyclophosphamide rapidly increased her platelet count in spite of tapering the prednisolone. In September 2000, her platelet count was kept within normal limits by administration of 15 mg/day of prednisolon. It is suggested that immunosuppressive therapy for ITP using high-dose cyclophosphamide is useful in elderly patients as well as in juvenile adult patients.

Aged↗

PubMed2000

Molecular modeling study of highly branching (1-->3)-alpha-D-glucan, a model polysaccharide for cariogenic glucan, using the N-H mapping method.

A systematic search for possible regular helical structures of a highly branching (1-->3)-alpha-D-glucan was done using the n-h mapping technique, combined with MM3-generated relaxed-residue energy map calculations with respect to the conformations of the backbone glycosidic linkages. The alpha-D-glucan, consisting of a (1-->3)-alpha-linked backbone with alpha-D-glucose side residues attaching to an O6 atom of every second backbone residue, was considered as a model polysaccharide of a branching part of the glucan produced by oral bacteria, which was known to be related to dental plaque formation and to contribute to dental caries. The potential energy surfaces of the trisaccharide repeating unit of the branching alpha-D-glucan indicated that (1-->6)-alpha-linked side residues did not appear to interfere significantly with the backbone stereochemistry, probably due to a further separation of the three-bond-linked side residue compared with an ordinary two-bond-linked residue. Based on the n-h maps of the branching alpha-D-glucan, the side residues, when involved in a complete helix, mostly contributed additional stabilizations to particular helical structures. It was found by checking the typical helix models that formation of hydrogen bonds involving side residues was probably a major cause of the stabilization. This hydrogen bonding was expected to increase insolubility for the glucan chain--a typical, physical property observed for the bacterial alpha-D-glucan--by introducing its backbone stereochemistry as an additional stiff feature.

Carbohydrate Conformation↗

PubMed1997

Chain conformational analysis of beijeran by n-h map calculations.

Possible regular helix models of beijeran, a new acidic heteropolysaccharide consisting of a trisaccharide as a repeating unit, were investigated. Conformational analyses of the three component disaccharides were first carried out by calculating their relaxed-residue energy maps with respect to the glycosidic bond rotations, phi and psi. A search for possible beijeran chain conformations was carried out by calculating the two-dimensional map of the helix parameters; n (the number of asymmetric units per a fiber repeat) and h (the axial rise per the unit), on the basis of the phi-psi conformations taken from the low energy regions of each of the three energy maps. The n-h values of the helix models with low steric energies were mostly found to be around the experimental values (n = 2 and h = 1.20-1.25 nm), which may support the present methodology. It was also suggested that the internal flexibility of beijeran chain allowed it to conform in diverse helical structures, each of which were reasonably in accord with the observed n-h values. The three representative helix models were finally proposed for the beijeran chain conformation in the crystal structure.

Azotobacter↗

PubMed1997

X-ray study of beijeran sodium salts, a new galacturonic acid-containing exo-polysaccharide.

X-Ray fiber diffraction patterns were obtained from oriented films of sodium salts of a new uronic acid-containing polysaccharide (beijeran) both in its native, poly [-->3)-alpha-D-GalA-(1-->3)-beta-L-Rha-(1-->3)-alpha-D-Glc-O6Ac-(1 -->], and deacetylated forms. Initially the stretched films of both polysaccharides were amorphous, but the crystallinity was much improved by annealing at high temperature. The deacetylated specimen had higher crystallinity than the native. Both films showed similar X-ray fiber patterns indicating that these polysaccharides had similar unit cell dimensions and that the O-acetyl groups in the native beijeran chain did not disturb the regular array in the crystal having space group P21. All the visible reflections could be indexed in terms of a monoclinic unit cell with dimensions a = 1.277, b = 1.611, c (fiber axis) = 2.437 nm, and gamma = 96.79 degrees. The fiber axis length and the presence of (002) and (006) reflections indicated that the conformation was made up of two trisaccharide residues, in an extended two-fold helix.

Carbohydrate Conformation↗

PubMed1997

An evaluation of crystal structure of mannan I by X-ray powder diffraction and molecular mechanics studies.

The present study reports the re-examination of the crystal structure of mannan I by the X-ray powder diffraction study combined with the miniature crystal model simulation. A primary objective of this study was to investigate an adequate chain staggering position along the fiber axis. Among the several crystal structure models proposed for mannan I, that derived from the electron diffraction study of the single crystals was adopted as a starting model. The X-ray crystallographic residuals were calculated for the single crystal structure at different chain staggering positions, while the ab projection was kept invariant. In a similar fashion, the miniature crystal models consisting of seven mannotetraoses were constructed, each having different chain staggering values and the three-dimensional structures of all the models were subsequently optimized by using the MM3(92) program without introducing any constraint. Both the X-ray residual and lattice energy plots with respect to the chain staggering position showed the common minima around the -0.25 x c chain staggering. The minimum models were subjected to a search for preferred orientations of O2 and O6 hydroxyl groups. It was found that the hydroxyl groups present inside the minicrystal tended to rotate into particular orientations during the structure optimizations to form the O5-H-O2 and O3-H-O6 intermolecular hydrogen bonds between the adjacent oligomers in an alternative direction.

Cell Wall↗

PubMed1996

Chain conformation of deacetylated beijeran calcium salt.

A well-defined X-ray fiber diffraction pattern was obtained from a stretched film of the calcium salt of a new uronic acid containing polysaccharide designated as beijeran in the deacetylated form, poly[-->3)-alpha-D-GalUA-(1-->3)-beta-L-Rham-(1-->3)-alpha-D -Glc-(1-->]. The oriented film showed no diffraction spots, indicating it to be amorphous. However, when annealed at high temperature, the film exhibited high crystallinity. All the visible reflections could be indexed in terms of a monoclinic unit cell with the following dimensions: a = 1.297; b = 1.676; c (fiber axis) = 2.509 nm; and gamma = 106.50 degrees. The length of the fiber axis and the absence of meridional reflections at any odd layer line indicate that an extended two-fold helical conformation was made up of two trisaccharide residues.

Acylation↗

PubMed1995

Conformation of an arabinoxylan isolated from the rice endosperm cell wall by X-ray diffraction and a conformational analysis.

The chain conformation of an arabinoxylan isolated from the rice endosperm cell wall, which was composed of the linear backbone of a 1,4-linked beta-xylose residue highly substituted at the C3 position with alpha-L-arabinofuranose, was studied by X-ray fiber diffraction and a conformational analysis. From the X-ray results the polysaccharide was suggested to take an extended left-handed, three-fold helical structure which is not a desirable conformation to make a complex firmly associated with cellulose or xyloglucan that was elucidated to be present in the cell wall. A conformational analysis, using the PFOS force field for the O-alpha-L-arabinofuranose-(1-->3)-beta-D-xylose residue and O-alpha-L-arabinofuranose-(1-->3)-[(1-->4)-beta-D-xylose residue]3, in which the arabinose residue was linked to the C3 position of the middle residue of the xylotriose residue, and using the PS79 computer program for the arabinoxylan indicated that the backbone xylan chain could not take a two-fold helix similar to that of cellulose because of significant steric interaction between the arabinose side chain and the backbone. Thus, the left-handed, three-fold helix was found to be reasonable.

Carbohydrate Conformation↗

PubMed1994

Dependence of complex formation of (1-->3)-beta-D-glucan with congo red on temperature in alkaline solutions.

The formation of a complex between (1-->3)-beta-D-glucan and congo red in dilute alkaline solutions (0.1 and 0.15 M sodium hydroxide) where the glucan takes an ordered conformation was studied by measuring visible absorption spectra of the solutions at various temperatures between 15 and 35 degrees C. The average number of the glucose residues forming the binding site to accommodate one dye molecule decreased with increasing temperature or decreasing alkaline concentration, suggesting possible conformational changes of the glucan chain. The complex formation constant, K, increased with increasing temperature, and thermodynamical parameters, delta H degrees and delta S degrees, for the complex formation in 0.1 M and 0.15 M aqueous NaOH solutions were obtained at 25 degrees C to be 14 kcal/mol and 77 e.u. (0.1 M), and 12 kcal/mol and 68 e.u. (0.15 M), respectively. These results indicate that the driving force for the complex formation is entropic in nature stemming from the decrease of "iceberg formation".

Congo Red↗

PubMed1993

Cloning and sequence analysis of an esterase gene from Pseudomonas sp. KWI-56.

The gene encoding an esterase from Pseudomonas sp. KWI-56 was cloned and sequenced. The nucleotide sequence contained an open reading frame encoding a polypeptide comprising 262 amino acids, whose molecular weight agreed well with the value obtained by SDS-PAGE. Comparison of the amino acid sequence with those of the other homologous enzymes suggested that Ser-92 and His-24l might be included in the catalytic triad.

Amino Acid Sequence↗

PubMed1992

Molecular and crystal structure of konjac glucomannan in the mannan II polymorphic form.

A probable crystal structure of konjac glucomannan (mannose:glucose ratio = 1.6) is proposed based on X-ray data and constrained linked-atom least-squares model refinement. The structure crystallizes in the mannan II polymorphic form, in an orthorhombic unit-cell with a = 9.01 A, b = 16.73 A, c (fiber axis) = 10.40 A, and a probable space group I222. The backbone conformation of the chain is a two-fold helix stabilized by intramolecular O-3-O-5' hydrogen bonds, with the O-6 rotational position gt. The unit cell contains four chains with antiparallel packing polarity and eight water molecules which reside in crystallographic positions. Intermolecular hydrogen bonds occur exclusively between chains and water molecules, establishing a three-dimensional hydrogen-bond network in the crystal structure. The glucose residues replace mannoses in the structure in isomorphous fashion, although some disorder appears possible. A structure having alternating gg-gt O-6 rotational positions and conforming to space group P222 appears to describe the disorder regions of the crystal. The reliability of the structure analysis is indicated by the X-ray residuals R = 0.276 and R" = 0.223.

Carbohydrate Conformation↗

PubMed1992

Molecular and crystal structure of the regenerated form of (1----3)-alpha-D-mannan.

The crystal structure of the hydrated form of (1----3)-alpha-D-mannan, obtained by solid-state deacetylation of the partially O-acetylated mannan, was analyzed by combined X-ray diffraction and stereochemical-model refinement techniques. The structure crystallizes in a four-chain, monoclinic unit cell with parameters a = 11.33 A, b = 18.36 A, c (fiber repeat) = 8.25 A, and gamma = 101.75 degrees, and the most probable space group is P2(1). In the most probable structure the chain-backbone conformation is a two-fold helix, but with all four O-6 rotational positions nonequivalent. The chains pack with antiparallel polarity and are connected by pairs of intermolecular hydrogen bonds that form an infinite, zig-zag sheet. There are 16 water molecules in the unit cell, generally embedded between the sheets in crystallographic positions, providing additional hydrogen bonding and establishing a three-dimensional hydrogen-bond network in the crystal structure. The reliability of the structure analysis is indicated by the X-ray residual R" = 0.281, based on 98 hkl reflection intensities.

Acetylation↗

PubMed1992

Molecular and crystal structure of (1----3)-alpha-D-glucan triacetate.

A crystal and molecular structure for GTA I, the low temperature polymorph of (1----3)-alpha-D-glucan triacetate, is proposed on the basis of X-ray diffraction analysis of well-oriented films, combined with stereochemical model refinement. The unit cell is monoclinic with parameters a = 30.17 A, b = 17.42 A, c (fibre axis) = 12.11 A, and beta = 90 degrees C. The probable space group is P2(1) with b axis unique. Six molecular chains pass through the unit cell with alternating polarity and with three independent chains comprising the asymmetric unit. The chain axes are located in a hexagonal packing arrangement. The chain backbone conformation is a left-handed, three-fold helix, but all nine O(6) acetyl groups of the asymmetric unit are in non-equivalent rotational positions. The most probable structure is indicated by X-ray residuals R = 0.261 and R" = 0.283, based on 62 reflection intensities (41 observed and 21 unobserved).

Glucans↗

PubMed1989

[Eosinophil kinetics].

The kinetics of 111In-oxine labeled eosinophils were studied in 3 cases of reactive eosinophilia and were compared with those of neutrophils in patients with CML and neutrophilia. The disappearance curve of the labeled eosinophils consists of two exponential components. There was a slightly increase of radioactivity between these two components, suggesting the presence of recirculation. The disappearance rate of eosinophils was faster than that of neutrophils in CML and neutrophilia. In the cases of eosinophilia and CML, the marginal pool was larger than the circulating pool. In CML, the marginal pool was the largest among these three disorders. The granulocyte turnover rate in eosinophilia was less than in CML or chronic neutrophilia. It is suggested that the migration of eosinophils is less active than that of neutrophils.

Adolescent↗

PubMed1989

Signet cell carcinoma of the stomach in a patient with acquired immunodeficiency syndrome: a case report.

A case of signet cell carcinoma associated with AIDS is presented. A 50-year old Japanese man with hemophilia A was suffering from human immunodeficiency virus (HIV) infection, the result of multiple injections of clotting factor concentrates. A diagnosis of signet cell carcinoma of the stomach was reached upon endoscopic and histological examinations. Opportunistic infections of esophageal candidiasis and candida septicemia occurred. The patient died of repeated gastrointestinal bleeding and cachexia. Although there is a possibility of the patient having a coincidential carcinoma along with AIDS, the HIV infection, perhaps, had a role in causing signet cell cercinoma.

Acquired Immunodeficiency Syndrome↗

PubMed1989

[Acute promyelocytic leukemia with a history of RAEB in transformation and the 15/17 translocation].

A 34-year old female was admitted to our clinic because of fever and general fatigue on March 26, 1987. On admission, peripheral blood (PB) revealed pancytopenia. Bone marrow smears revealed 9. 0% of promyelocytic cells with or without Auer rods. Diagnosis of RAEB in transformation was made. Chromosome study of the bone marrow cells showed t(15; 17) in 3 out of 20 cells analysed. After 3 months, the leukemic cells were observed in PB and increased in number. Then the patient showed bleeding tendency and fibrin degradation products (FDP) increased up to 40 micrograms/ml. And the leukemic cells were over 30% in PB at the end of July, 1987. The diagnosis of APL with DIC was made. To our knowledge, this is the first case of APL with a history of MDS with t(15; 17).

Adult↗

PubMed1989

[Bone marrow aplasia without blast crisis in a case of CML of 10-year survival].

A case of chronic myelogenous leukemia (CML) of 10-year survival in described. A 44-year old male was admitted to our hospital because of general malaise, abdominal fullness and fever in February, 1977. On physical examination, giant splenomegaly and hepatomegaly were detected. Peripheral blood examination revealed leukocytosis without hiatus leukemia , normochromic macrocytic anemia and thrombocytosis. NAP rate and score were 16% and 22. Cytogenetic analysis of PB without stimulator revealed 46, XY, Ph1. Then he was diagnosed as having a typical type of Ph1-positive CML. He had been successfully treated over 9 years by intermittent administration of busulfan. However, anemia suddenly progressed in February, 1986 followed by leukopenia and thrombocytopenia. Hemorrhage was not detected by the examination. Though he had been received blood transfusion, the anemia progressed rapidly. He was died of cachexia on 4th of August, 1987. The postmortem examination revealed bone marrow aplasia with no signs of blast crisis nor myelofibrosis. Secondary hemochromatosis was seen in the liver, spleen, pancreas and some other organs.

Adult↗

PubMed1988

Application of the sum peak method to determine the perturbed angular correlation parameters in biological specimens.

The counting rate of a sum peak formed by two gamma-ray emissions in radioactive decay of a nuclide depends on its integral attenuation factor G22. Therefore, in the "sum peak method", the G22 value for the specimen in question can be obtained merely from sum peak measurements using one radiation detector when the resolution time and the geometry are fixed. The procedure to determine the G22 values is described for specimens containing 111In, together with the detailed relationships between the sum peak counting rates and the values of G22.

Animals↗