Biomedical subjects

K Takeo

Publications and source records attributed to K Takeo.

At least 19 recordsLinked to original sources

PubMed1997

Ultrastructure of cholesterol gallstones as observed by electron microscopy after freeze-fracturing.

The ultrastructure of cholesterol gallstones (mixed type) was studied in detail for the first time under the transmission electron microscope after freeze-fracturing. Gallstones consisted essentially of cholesterol crystals, some impurities, and fluid. In accord with the theoretical 3.4 nm bilayered structure of cholesterol crystals, 3-4 nm periodicity of crystal layering was observed. However, gallstone cholesterol crystals were not perfect and often showed structural defects. Between crystals, complete edge-to-surface, edge-to-edge and surface-to-surface adhesions, and overall block-like aggregations were found. These may represent the structural basis for the stability of cholesterol crystal aggregation. The easy breakdown of cholesterol gallstones by extracorporeal shock wave lithotripsy is discussed in relation to their ultrastructure.

Aged↗

PubMed1997

Electron microscopy of biological specimens by the plasma-polymerization rapid-freeze replica method.

The plasma-polymerization replica method is a unique replica technique for transmission electron microscopy. In the present study, we used this method in combination with a rapid-freeze technique to observe T4 bacteriophages and hepatitis B virus core particles. The heads of T4 bacteriophages appeared hexagonal and measured approximately 110 nm in length. Striations in their tails were also visible, indicating that the resolution of the present method is better than 4 nm. The images corresponded well with those obtained by ice-embedding and negative staining methods, with respect to both morphology and size of the phage particle. Hepatitis B virus core particles observed by the present method appeared round, approximately 30 nm in diameter, with hollow centres. Again, the morphology and size of the particles corresponded well with those obtained by ice-embedding, negative staining, and ultrathin sectioning. From these results, we conclude that the plasma-polymerization rapid-freeze replica method provides a useful technique for observation of biological specimens in a natural state and at high resolution.

Aluminum Silicates↗

PubMed1996

Conformation of cyclic and linear (1 --> 2)-beta-D-glucans in aqueous solution.

The conformations of cyclic (1 --> 2)-beta-D-glucan chains having degree of polymerization (dp) 17 to 24 were characterized by means of small-angle X-ray scattering and Monte Carlo simulation. The results indicate that cyclic (1 --> 2)-beta-D-glucan chains adopt the shape of a doughnut-like ring with a thickness of about 10 A for all the samples. The diameter of the annulus for the cyclic glucan having dp 21 is estimated to be only about 4-5 A. Two linear (1 --> 2)-beta-D-glucans possessing dp 19 and 21 prepared by acid hydrolysis of a cyclic glucan and subsequent fractionation showed different scattering profiles from those obtained for cyclic glucans having the corresponding dp. Although the Monte Carlo simulation does not completely reproduce the scattering profiles observed by small-angle X-ray scattering, linear (1 --> 2)-beta-D-glucans seem to possess a characteristic cylindrical shape with cross-sectional diameters of 11.8 and 13.2 A for linear glucans of dp 19 and 21, respectively.

Chromatography, High Pressure Liquid↗

PubMed1996

Immune response to different doses of a hapten of fluorescein isothiocyanate analyzed by two-dimensional affinity electrophoresis.

The immune response to different doses of a hapten of fluorescein isothiocyanate (FITC) in BALB/c mice was analyzed by two-dimensional affinity electrophoresis (2-D AEP). The mice were immunized with different doses (0.5 microgram, 5 micrograms, 50 micrograms, 500 micrograms and 2.5 mg) of FITC-conjugated bovine serum albumin (BSA). The antibodies to FITC bovine serum albumin (BSA) were separated into a large number of IgG spots due to differences in their isoelectric points (pI) and binding affinity to FITC ligand immobilized in the gel. The IgG spots, showing identical affinity to the ligand but different pI, have been considered as an IgG family. The affinity and quantity of IgG families changed with the increase in FITC-BSA dosage. With a low dose (5 micrograms) most of the families showed high affinity (Kd < 1 microM < Kd < 50 microM) and low affinity (Kd > 50 microM) antibodies were produced. The increase of FITC-BSA up to 500 micrograms markedly increased the quantity of IgG spots showing a variety of affinity to FITC. However, 2.5 mg FITC-BSA did not increase the quantity and heterogeneity of IgG spots significantly. The changes in the heterogeneity and quantity of anti-FITC antibodies and the subclass switch were observed over the course of immunization. The heterogeneity and the quantity of IgG1, IgG2b and IgG3 antibodies increased markedly during the first and the second immunization, whereas an increase in the heterogeneity and the quantity of IgG2a antibody was observed in the third immunization. This suggests that the subclass switch to IgG1, IgG2b and IgG3 and the somatic mutation of IgG1, IgG2b and IgG3 occur during the first and the second immunization, but the subclass switch to IgG2a and the somatic mutation of IgG2a seem to occur later than that of the other IgG subclasses.

Animals↗

PubMed1996

A new type of growth exhibited by Trimmatostroma abietis.

Trimmatostroma abietis initially grew as hyphae when grown in various media containing yeast extract or bactopeptone. It grew as segmented elements (lumbricoid elements) characterized by bidirectional growth, when grown in Czapek-Dox broth or yeast nitrogen base supplemented with 1% glucose. A lumbricoid element usually was 10-70 microns in length, with transverse septation only and contained 3 to 15 cells. Growth and propagation, as revealed by time-lapse photomicrography occurred as follows. Elements usually grew by apical elongation without widening; after simple apical elongation adjacent parts of two central cells eventually started to grow, resulting in the separation of the element into two.

Microscopy, Electron↗

PubMed1996

Stationary phase development of Trimmatostroma abietis.

Processes of anamorph cell replication in Trimmatostroma abietis are described. Growth and conidiation are delimited on the basis of morphological, ultrastructural and ecological criteria. Cellular expansion shifts from bidirectional intercalary in exponential phase cells to isodiametric in late stationary phase cells, in the latter case with endogenous asexual reproduction. Ultrastructural similarities to dothideaceous black yeasts are discussed.

Cell Division↗

PubMed1996

Translocation of hepatitis B virus core particles through nuclear pores in transformed yeast cells.

In our previous transmission electron microscopic study of hepatitis B virus core antigen in transformed yeast cells, we observed core particles passing through the nuclear pores. We have now analyzed 1,421 nuclear pores in transformed yeast, and conclude that 1) translocation of core particles from the nucleus to the cytoplasm occurs through the nuclear pores; 2) translocation sites are located in the center of nuclear pores; 3) at least 95% of pores are involved in the translocation process; 4) proteins as large as 28 nm in diameter can cross the envelope; 5) translocation does not stop, but rather becomes more active during nuclear division in yeast cells.

Biological Transport, Active↗

PubMed1995

Molecular and crystal structures of two 1,6-anhydro-beta-maltotriose derivatives.

Crystal structures of two 1,6-anhydro-beta-maltotriose derivatives, 1,6-anhydro-beta-maltotriose nonaacetate and 6"-bromo-6"-deoxy-1,6-anhydro-beta-maltotriose octaacetate, have been determined. Both structures are isomorphous and belong to the orthorhombic system, space group of P2(1)2(1)2(1), with cell dimensions of a = 15.659(3) A, b = 20.587(6) A, c = 13.023(2) A and a = 15.402(7) A, b = 19.737(8) A, c = 13.481(5) A, respectively. Each molecule has three alpha-(1-->4)-linked glucose units, and two of them have a typical 4C1 chair conformation, while the glucose unit with the 1,6-anhydro bridge has a 1C4 chair-envelope intermediate conformation. In spite of introducing the 1,6-anhydro bridge and acetyl groups, the conformations of the glycosidic linkages in these molecules are almost the same as those of other alpha-(1-->4)-linked oligosaccharides. Crystal structures are stabilized by hydrophobic interactions and by a weak intermolecular hydrogen bond of C-H. . .O.

Acetates↗

PubMed1995

Synthesis of (1-->4)-beta-D-xylo-oligosaccharides of dp 4-10 by a blockwise approach.

Dibutyltin oxide-mediated regioselective chloroacetylation of methyl 1-thio-beta-xylobioside, followed by treatment of the product with 4-methylbenzoyl chloride-pyridine, gave methyl 4-O-chloroacetyl-2,3-di-O-(4-methylbenzoyl)-beta-D-xylopyranosyl-(1-->4) -2.3-di - O-(4-methylbenzoyl)-1-thio-beta-D-xylopyranoside (18) in 70% yield. Coupling of 18 with benzyl alcohol afforded the disaccharide benzyl beta-glycoside, which was O-dechloroacetylated to provide methyl 2,3-di-O-(4-methylbenzoyl)-beta-D-xylopyranosyl-(1-->4)-2,3-di-O-(4- methylbenzoyl)-1-thio-beta-D-xylopyranoside (20). A homologous series of (1-->4)-beta-D-xylo-oligosaccharides from the tetra- to the deca-saccharide have been synthesized in a blockwise manner by using 20 as the glycosyl acceptor, 18, methyl 1-thio-beta-xylobioside pentaacetate, and methyl 1-thio-beta-xylotrioside heptaacetate as the glycosyl donors, and a combination of N-iodosuccinimide-silver triflate as the promoter.

Carbohydrate Conformation↗

PubMed1995

Synthesis of 2- and 4-nitrophenyl beta-glycosides of beta-(1-->4)- D-xylo-oligosaccharides of dp 2-4.

2- and 4-Nitrophenyl beta-D-xylopyranosides (4 and 5) were transformed, via dibutyltin oxidemediated acylation, into the corresponding 2,3-di-O-benzoyl derivatives 11 and 15. Xylobiose and xylotriose were easily isolated by charcoal column chromatography from a commercially available material and converted into the di- and trisaccharide methyl 1-thio-beta-glycosides 36 and 37. The 2-and 4-nitrophenyl beta-glycosides of the beta-(1-->4)-D-xylo-oligosaccharides of dp 2-4 were synthesized by N-iodosuccinimide-silver triflate-promoted condensation using 11 and 15 as the glycosyl acceptors and ethyl 1-thio-beta-D-xylopyranoside triacetate 16, 36, and 37 as the glycosyl donors. Also described are an improved preparation of 4 and 5, and the synthesis of 1-naphthyl beta-D-xylopyranoside, as well as an alternative approach to the 2- and 4-nitrophenyl beta-xylobiosides.

Carbohydrate Sequence↗

PubMed1995

Unbudded G2 as well as G1 arrest in the stationary phase of the basidiomycetous yeast Cryptococcus neoformans.

Stationary-phase cells of Cryptococcus neoformans displayed two morphological characteristics: virtually all the cells were unbudded even in the early stationary phase and even when grown in rich media, and average cell size increased from that of exponential-phase cells. DNA contents for small and large stationary-phase cells were determined by quantitative fluorescence microscopy after DNA staining with propidium iodide or DAPI. Small cells contained G1 DNA, whereas large unbudded cells had either a G2 or G1 DNA content, indicating that Cr. neoformans can enter into the stationary phase from either the G1 or G2 period.

Cryptococcus neoformans↗

PubMed1995

Microheterogeneity of mouse antidextran monoclonal antibodies.

Mouse antidextran monoclonal antibodies showed microheterogeneity which was analyzed by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). Not only the heavy (H) chains but also the light (L) chains were heterogeneous in terms of isoelectric point (pI). The higher the pI, the more prominent the H chain spots. To demonstrate the cause of the microheterogeneity an IgG1 monoclonal antibody (mAb 35.8.2H) was examined especially for involvement of the sugar moiety in the microheterogeneity. The glycosylated region was determined in the Fc portion from serine 239 to methionine 309 by a glycan detection method using mild periodate oxidation, which confirms that the sugar chain is attached to the conserved glycosylation site of asparagine 297. However, charge heterogeneity of the H chain was not entirely attributed to the Fc because the papain digest of the antibody was separated into two Fc spots, a few Fd spots and two L chain spots by 2-D PAGE. This indicates that factors other than the sugar moiety are responsible for charge heterogeneity of IgG monoclonal antibody. On the other hand, the H chain isoforms of lower pI were shown to be more susceptible to V8 protease by peptide mapping. This result strongly suggests the occurrence of deamidation at glutamine or asparagine residues.

Amino Acid Sequence↗

PubMed1995

Conidial surface ultrastructure of human-pathogenic and saprobic Cladosporium species.

Freeze-fracturing of outer wall layers of Cladosporium conidia revealed two types of ultrastructure, coinciding with taxonomic characteristics. The outer conidial layers were essentially smooth in the human pathogenic species, C. bantianum, C. carrionii, and C. trichoides. In contrast, mosaic arrays of rodlets on conidia were observed with freeze-fracturing in the saprobic species, C. cladosporioides, C. coralloides, C. herbarum, C. sphaerospermum, and C. variabile. Conidia of C. elatum were an exception among the saprobic species as they had smooth surfaces. The present study supports the suggestion that the human pathogenic Cladosporium species should be transferred to another genus.

Cell Wall↗

PubMed1995

A structural model for the mechanisms of elicitor release from fungal cell walls by plant beta-1,3-endoglucanase.

The release of elicitor-active carbohydrates from fungal cell walls by beta-1,3-endoglucanase contained in host tissues has been implicated as one of the earliest processes in the interaction between soybean (Glycine max) and the fungal pathogen Phytophthora megasperma f. sp. glycinea leading to host defense responses such as phytoalexin production. The present study was conducted to evaluate the primary structure of the glucanase-released elicitor (RE). Gel-filtration chromatography of carbohydrates released from mycelial walls by purified soybean beta-1,3-endoglucanase resolved them into the four fractions (elicitor-active RE-I, -II, and -III and elicitor-inactive RE-IV). Sugar composition analysis indicated that all of the fractions were composed almost entirely of glucose. 1H- and 13C-nuclear magnetic resonance analysis indicated the presence of both beta-1,3- and beta-1,6-linkages for the elicitor-active RE-I, -II, and -III fractions and only beta-1,3 linkage for the elicitor-inactive RE-IV fraction. Methylation analysis and degradation studies employing beta-1,3-endo- and beta-1,3-exoglucanase further suggested that the basic structure of elicitor-active RE consists of beta-1,6-linked glucan backbone chains of various lengths with frequent side branches composed of beta-1,3-linked one or two glucose moieties. From these structural analyses of RE, a structural model of how RE is originally present in fungal cell walls and released by host beta-1,3-endoglucanase is also proposed.

Carbohydrate Sequence↗

PubMed1994

An antitumor, branched (1-->3)-beta-D-glucan from a water extract of fruiting bodies of Cryptoporus volvatus.

A water-soluble, (1-->6)-branched (1-->3)-beta-D-glucan (H-3-B) was isolated from a hot-water extract of the fruiting bodies of the fungus, Cryptoporus volvatus (Basidiomycetes). Enzymatic analysis using exo-(1-->3)-beta-D-glucanase and methylation analysis indicated that this polysaccharide has a main chain composed of beta-(1-->3)-linked D-glucopyranosyl residues, and single, beta-(1-->6)-linked D-glucopyranosyl residues attached as side chains to, on average, every fourth sugar residue of the main chain. This structure was confirmed by 13C NMR spectra of the glucan in Me2SO-d6. The weight-average molecular weight (Mw) of H-3-B was determined to be 44.0 x 10(4) by gel permeation chromatography equipped with a low-angle laser-light-scattering photometer. The electron microscopic observations showed that H-3-B and its sonicated sample (S-H-3-B, Mw = 13.7 x 10(4)) can be described as linear worm-like chains. The mass per unit length for native and sonicated H-3-B was determined to be 1750 and 1780 g mol-1 nm-1, respectively, from the contour lengths obtained by electron microscopy and the molecular weights. These values are in good agreement with that expected for the triple stranded structure. A sample denatured in 0.1 M NaOH and subsequently renatured by neutralization showed a mixture of linear and cyclic structures, and larger aggregates with less well-defined morphology. The H-3-B and S-H-3-B had antitumor activity against the Sarcoma 180 tumor.

Animals↗

PubMed1994

Molecular and crystal structure of (2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl)-(1-->3)- [2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl-(1-->6)]- (2,4-di-O-acetyl-beta-D-glucopyranosyl)- (1-->3)-1,2,4,6-tetra-O-acetyl-beta-D-glucopyranose.

Crystals of the tetrasaccharide, (2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl)-(1-->3)- [2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl-(1-->6)]- (2,4-di-O-acetyl-beta-D-glucopyranosyl)-(1-->3)- 1,2,4,6-tetra-O-acetyl-beta-D-glucopyranose, belong to the monoclinic system, space group P2(1), with a = 12.709(4), b = 27.767(9), c = 9.567(4) A, beta = 105.07(2) degrees, and Z = 2. The crystal structure was solved by the direct method and refined by the full-matrix least-squares procedure to an R-value of 0.071 for 302- observed reflections in the X-ray data. All the four D-glucopyranose residues have the usual 4C1 chair conformations. The torsional angles at two (1-->3)-beta-linkages were phi(O-5-1-O-1-C-3) = -74 degrees and psi (C-1-O-1-C-3-C-2) = -122 degrees between the nonreducing and the middle residues, and phi = -67 degrees, psi = -111 degrees between the middle and the reducing residues. The orientation about the (1-->6)-beta-linkage was found to be phi(O5-C1-O-1-C-6) = -77 degrees, theta(C1-O-1-C-6-C-5) = 160 degrees, and chi(O-1-C-6-C-5-O-5) = 63 degrees (gt conformation). The primary acetate groups at C-6 of the reducing and the (1-->6)-branched residues were in the gt conformations (O-5-C-5-C-6-O-6 = 81 degrees and 84 degrees, respectively). On the other hand, the gg conformation was observed for the primary acetate group in the nonreducing residue (O-5-C-5-C-6-O-6 = 78 degrees).

Carbohydrate Conformation↗

PubMed1994

Pleoanamorphic life cycle of Exophiala (Wangiella) dermatitidis.

The anamorph life cycle of the black yeast Exophiala (Wangiella) dermatitidis is described. The fungus is dimorphic, yeast cells being the prevalent form of propagation. The fungus is strongly hydrophilic, probably completing its anamorph life cycle in submersion. Adaptation to dry conditions is slow. Types of conidiogenesis comprise annellidic, phialidic and sympodial reproduction, in addition to isotropic development. Phialoconidia fail to germinate under the conditions tested, and thus may have a function other than dispersal. Sterile, multicellular bodies resembling a Capronia teleomorph are described.

Exophiala↗

PubMed1994

Conformation of (2-->1)-beta-D-fructan in aqueous solution.

The conformation and dilute solution properties of (2-->1)-beta-D-fructan in aqueous solution were studied by gel permeation chromatography, low-angle laser light-scattering photometry, viscometry, small-angle X-ray scattering and electron microscopy. Fractions covering a broad range of weight-average molecular weights (Mw) from 1.49 x 10(4) to 5.29 x 10(6) were obtained from a native sample by ultrasonic degradation and fractional precipitation. For Mw < 4 x 10(4), the intrinsic viscosity [eta] varies with Mw0.71, indicating that the fructan chain behaves as a random coil expanded by an excluded-volume effect in this molecular weight region. For Mw > 10(5), [eta] exhibits an unusually weak dependence on Mw and finally becomes almost independent of molecular weight. This behaviour is interpreted in terms of a globular conformation of the high-molecular-weight fructan molecules. Small-angle X-ray-scattering measurements and electron microscopic observations support this interpretation of the values of [eta] observed.

Aspergillus↗