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Biomedical subjects

M Osumi

Publications and source records attributed to M Osumi.

At least 91 records · Page 5Linked to original sources
PubMed1982

Digital processing methods for structural analysis of an electron micrograph.

Digital processing method using the scanning-densitometer with microcomputer provides a useful description system. It draws attention to the usefulness of local lattice averaging in clarifying images of periodic structures in crystals as well as crystalloids and para crystalline arrays in biological specimens. Digital processing of lattice images in crystal structures from the selected diffraction spots is successfully developed to the structural analysis of evaporated gold, graphitized carbon and human tooth enamel of hydroxyapatite. Furthermore, known microbody crystalloids in enzyme and icosahedral capsids in virus are confirmed and clarified by the procedure of selecting diffraction spectra transformed from the information taken with high resolution electron micrographs. The processed results can provide significant improvements in structural analysis of an electron micrograph.

Crystallography↗
PubMed1982

Identification and properties of the glucose transporter of human erythrocytes.

Several lines of studies were undertaken to clarify the identity of the glucose transporter of human erythrocytes. Peptide maps of zone 4.5 which is the main component of the purified transporter fraction, were different from those of band 3. Cytochalasin B bound to the purified transporter fraction but not to band 3. Antibody raised against the purified transporter fraction cross-reacted with zone 4.5 and moderately with band 7, but not with other erythrocyte membrane proteins. These results indicate that zone 4.5 is the transporter (or a part of the transporter) and is not a fragment of band 3. With ferritin antibody electron microscopy and freeze-fracture electron microscopy, the glucose transporter were found to evenly distributed in reconstituted liposomes. Further morphological analysis coupled with transport assays showed the distribution of the transporters was random and was satisfactorily fitted to Poisson distribution, indicating reversible association of the transporters does not occur in liposomes and is not necessary for transport activity. This communication summarises our recent studies on identification and properties of the glucose transporter of human erythrocytes. A full account of the studies is published elsewhere (22, 23).

Blood Glucose↗
PubMed1978

Subcellular localization of two long-chain acyl-coenzyme-A synthetases in Candida lipolytica.

Studies have been made on the subcellular localization of two long-chain acyl-coenzyme-A synthetases as well as glycerolphosphate acyltransferase and the acyl-CoA-oxidizing system in Candida lipolytica grown on oleic acid. Acyl-CoA synthetase I is distributed among different subcellular fractions, including microsomes and mitochondria where glycerolphosphate acyltransferase is located. On the other hand, acyl-CoA synthetase II is localized in microbodies where the acyl-CoA-oxidizing system is located. These results support our previous conclusion that acyl-CoA synthetase I is responsible for the production of acyl-CoA to be utilized for the synthesis of cellular lipids, while acyl-CoA synthetase II provides acyl-CoA that is exclusively degraded via beta-oxidation.

Candida↗
PubMed1977

Immobilization of yeast microbodies by inclusion with photo-crosslinkable resins.

Yeast microbodies containing FAD-dependent alcohol oxidase, catalase and D-amino acid oxidase were isolated from methanol-grown cells of Kloeckera sp. 2201 and immobilized intact in matrices formed by a short-time illumination of photo-crosslinkable resin oligomers. The relative activities of catalase, alcohol oxidase and D-amino acid oxidase of the gel-entrapped microbodies were 36, 76 and 31% respectively as compared with those of free microbodies. Immobilization enhance d the stability of catalase to a certain degree, but not that of alcohol oxidase. The pH/activity profiles of catalase and alcohol oxidase of the entrapped organelles showed more narrow pH optima than those of the free counterparts. D-Amino acid oxidase in immobilized microbodies showed a somewhat higher Km value for D-alanine than that in free ones. Immobilized microbodies oxidized two moles of methanol to form two moles of formaldehyde with consumption of one mole of molecular oxygen. Addition of 3-amino-1,2,4-triazole, an inhibitor of catalase, reduced the formation of formaldehyde to half the amount without change in the amount of oxygen consumed, indicating the synergic action of alcohol oxidase and catalase in methanol oxidation in the microbodies of living yeast cells.

Alcohol Oxidoreductases↗
PubMed1976

Development of Microbodies in the yeast Kloeckera growing on methanol.

A number of microbodies appear regularly in methanol-grown yeast cells, but rarely in ethanol- or glucose-grown cells. When one of representative methanol-utilizing yeasts, Kloeckera sp.no. 2201 (also known as Candida bodinii), was cultured on glucose and then transferred into a methanol medium, microbodies of small size could be observed in 2-h old cells. The number of microbodies per sectioned cell reached five to six after 4 h of cultivation. Though the number of microbodies did not change during prolonged cultivation, their size became larger with the passage of cultivation time. The activities of catalase and alcohol oxidase were confirmed in the particulate fractions throughout the cultivation period, whereas the activities of formaldehyde dehydrogenase and formate dehydrogenase were not detected in the particles. The activity of isocitrate lyase was detected in the particulate fractions only at the early growth phase.

Alcohol Oxidoreductases↗
PubMed1975

Microbody of methanol-grown yeasts. Localization of catalase and flavin-dependent alcohol oxidase in the isolated microbody.

Profuse appearance of microbodies was observed in the cells of methanol-utilizing yeasts in connection with the enhanced catalase activity. These microbodies were isolated successfully by means of sucrose gradient centrifugation from the methanol-grown cells of Kloeckera sp. no. 2201. Localization of a flavin-dependent alcohol oxidase as well as characteristic microbody enzymes (catalase and D-amino acid oxidase) were ascertained in the isolated microbodies, whereas formaldehyde and formate dehydrogenases were detected in the cytoplasmic region. Localization of catalase in the isolated microbody was also demonstrated by the cytochemical technique with 3,3'-diaminobenzidine.

Alcohol Oxidoreductases↗
PubMed1975

Development of microbodies in candida tropicalis during incubation in a n-alkane medium.

Development of microbodies in Candida tropicalis pK 233 was studied mainly by electron microscopical observation. The yeast cells, precultured on malt extract, scarcely contained microbodies and showed very low catalase activity. When the precultured cells were transferred to a n-alkane medium and incubated with shaking, the number of microbodies increased and concomitantly the activity of catalase was enhanced. That is, both the area ratio of microbodies in the cell and the ratio of microbodies to cytoplasm in area increased significantly during the utilization of n-alkanes for 8 hrs. Localization of catalase in the microbodies was demonstrated cytochemically by use of 3,3'-diaminobenzidine, but other organella in the cell, except for vacuoles appearing in the early growth phase and mitochondria, were not stained with this reagent. Microbodies seemed to grow by division. Biogenesis of microbodies in the yeast cells is also discussed.

3,3'-Diaminobenzidine↗
PubMed1975

Ultrastructure of methanol-utilizing yeast cells: appearance of microbodies in relation to high catalase activity.

Nine strains of methanol-utilizing yeasts belonging to the genera Candida, Hansenula, Kloeckera, Pichia, and Torulopsis were examined with respect to the interrelationship between their catalase content and ultrastructure. Methanol-grown cells of all the yeasts tested showed higher catalase activities than the respective ethanol- and glucose-grown cells. In connection with this, occurrence of a specific organelle surrounded by a single-unit membrane ("microbodies") was observed only in the methanol-grown cells. Several morphological differences were observed between the microbodies of methanol-utilizing yeasts and those of hydrocarbon-utilizing yeasts such as Candida tropicalis. That is, microbodies of methanol utilizers were large in size, existed in closely associated forms, and had crystalloid structures. Localization of catalase activity in these microbodies was demonstrated cytochemically by use of 3,3'-diaminobenzidene. Especially, 3,3'-diaminobenzidine reaction product accumulated heavily in crystalloids of yeast microbodies.

Candida↗
PubMed1975

Defective pyocin particles produced by some mutant strains of Pseudomonas aeruginosa.

Mutants of Pseudomonas aeruginosa, defective in the production of active R-type pyocins, were isolated from pyocinogenic strains and their products were characterized. Polysheath-like structures were found in induced lysates of 29 out of 42 mutants. Two mutants (strain P15-16 and M189) were found to produce special defective particles, which were characterized in detail. The other 11 mutants did not produce significant amounts of any structure visible under an electron microscope. Serum blocking powers were found in lysates from P15-16 and M189 to significant amounts. Defective particle produced by strain P15-16 lacked the sheath component, whereas M189 had morphological defects at the junction between sheath and baseplate, and also in the architecture of baseplate. Both defective particles could adsorb to the surface of bacteria, that were sensitive to pyocin, at the tip of their fibers without killing cells. All M189 particles attached to the bacteria had the extended sheaths. Therefore, attachment to the bacteria by fibers is not sufficient to kill cells, and contraction of sheath must occur after the initial adsorption by fibers for pyocin to express its biological activity. Defective particles of strain P15-16, which was derived from strain P15 (a pyocin R1 producer), could be converted to active forms by an in vitro complementation reaction with extracts from certain mutants originated from strain PAO (a pyocin R2 producer). This result indicated the exchangeability of components between R-type pyocins belonging to the different groups.

Adsorption↗