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K Takeo

Publications and source records attributed to K Takeo.

At least 37 records · Page 2Linked to original sources
PubMed1998

Fine structure of hepatitis B virus surface antigen produced by recombinant yeast: comparison with HBsAg of human origin.

The ultrastructure of hepatitis B virus surface antigen (HBsAg) particles produced by recombinant yeast cells was examined using high-resolution negative staining, and ice embedding, electron microscopy. With negative staining, the HBsAg particles were spherical to slightly ovoid with a mean diameter of 27.5 nm and consisted of many subunits each 4 nm in diameter. Subunits were marked with a minute central pore. With ice embedding, particles were mostly spherical to ovoid, with a mean diameter of 23.7 nm and a 7-8 nm thick cortex surrounding an electron translucent core. Human HBsAg particles, examined using the same methods, were smaller, apparently because of molecular differences in polypeptide structure.

Electrophoresis, Polyacrylamide Gel↗
PubMed1998

Growth polarity transitions in a dimorphic fission yeast.

Fission yeast cells grow by extension at the ends (poles) and divide by transverse fission. It has previously been reported that Schizosaccharomyces japonicus var. japonicus can switch to unipolar, filamentous growth. Here it is shown that the yeast-to-mycelium transition is a gradual process involving a changeover to unipolar growth associated with asymmetric divisions, the development of large polarly located vacuoles, the modifications of the actin and microtubular cytoskeleton and the repression of cell separation after division. High concentrations of glucose in the medium or supplementation of the medium with caffeine or cAMP support the bipolar yeast phase, inhibit the transition to the mycelial phase and induce the conversion of hyphae to yeasts. These effects suggest that cAMP may be involved in the regulation of dimorphism. Temperatures below 18 degrees C or over 35 degrees C are restrictive for the mycelial phase and provoke a return to yeast phase.

Caffeine↗
PubMed1998

Environmentally controlled dimorphic cycle in a fission yeast.

The fission yeast Schizosaccharomyces pombe shows bipolar growth and is a convenient model for studying cell polarity and polar growth. This paper shows that the related Schiz. japonicus var. japonicus can switch to unipolar growth and can exist in both yeast and mycelial phases. On solid media, the yeast phase is unstable and prone to switch to the mycelial form, which shows unipolar growth by tip elongation. The hyphae can colonize the body of the substrate (true mycelium) or just its surface (pseudo-mycelium). The yeast-to-mycelium transition and the growth of the mycelium are regulated by a nutritional gradient and are associated with extensive vacuolation. The mycelium can convert into arthroconidia or return to the yeast phase in response to environmental changes. These environmentally controlled morphological transitions make Schiz. japonicus var. japonicus an attractive model for the investigation of cell polarity and morphogenesis.

Cell Polarity↗
PubMed1998

Antisporulating and respiration-inhibitory effects of essential oils on filamentous fungi.

Sporulation of four species of filamentous fungi, namely Aspergillus fumigatus, Fusarium solani, Penicillium expansum and Rhizopus oryzae, was suppressed by gaseous contact with citron, lavender and thyme oils and, to a lesser extent, by that of perilla and tea tree oils. Lemongrass and cinnamon bark oils were scarcely active. The antisporulating effect of the essential oils was not observed when they were applied as a solution, indicating that their vapours were the active form. Moreover, exposure of fungal cultures to vapours of the active essential oils caused curling of the tips of aerial hyphae (R. oryzae) or incomplete development of conidiophores (A. fumigatus). These antisporulating effects of the vapourizing essential oils seemed to be correlated with their respiration-inhibitory activity, rather than with their growth-inhibitory activity.

Fungi↗
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↗