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Biomedical subjects

N Okamura

Publications and source records attributed to N Okamura.

At least 199 records · Page 11Linked to original sources
PubMed1985

Serogrouping of Bacteroides vulgatus by the agglutination test.

The agglutination technique was used to establish a serological classification scheme for Bacteroides vulgatus strains isolated from normal human feces and clinical specimens, especially from ulcerative colitis patients. Absorbed antisera to 10 strains of B. vulgatus were prepared. These 10 absorbed antisera were species specific. Of 90 B. vulgatus strains tested, 55 (61%) were agglutinated by one or more of these 10 absorbed antisera. A total of 27 serological patterns were grouped into 18 serogroups; 10 of these serogroups contained only one group component, whereas the other 8 serogroups were composed of more than one component. This serological classification could be used to study the epidemiology of this organism.

Adult↗
PubMed1984

Changes in protein phosphorylation in guinea pig polymorphonuclear leukocytes by treatment with membrane-perturbing agents which stimulate superoxide anion production.

Phosphorylation of proteins was examined in guinea pig polymorphonuclear leukocytes in relation to the effects of membrane-perturbing agents, which stimulate superoxide anion production, and their inhibitors. The phosphorylation was detected by 32P autoradiography after separation by two-dimensional electrophoresis of proteins phosphorylated in 32P-preloaded cells. Though phosphorylation of various proteins was stimulated by each of the membrane-perturbing agents, the stimulation was especially marked in six proteins. Phorbol myristate acetate and digitonin enhanced the phosphorylation of the six proteins, while myristate and concanavalin A increased the phosphorylation of five and three proteins, respectively, out of the six proteins. p-Bromophenacyl bromide, an inhibitor of phospholipase A2, inhibited the stimulatory effect of phorbol myristate acetate on both superoxide anion production and protein phosphorylation. Trifluoperazine, a calmodulin inhibitor, also inhibited the effect of phorbol myristate acetate on both, except for an increase in the phosphorylation of one out of the six proteins. alpha-Methylmannoside, an inhibitor of concanavalin A binding, inhibited the stimulation of the phosphorylation of the three proteins by concanavalin A. The results indicate that the activation of superoxide anion production by the membrane-perturbing agents in guinea pig polymorphonuclear leukocytes is accompanied by the phosphorylation of, at least some of, these six proteins.

Animals↗
PubMed1983

Activation of spermatozoan adenylate cyclase by a low molecular weight factor in porcine seminal plasma.

The ejaculated porcine spermatozoa were fractionated into the cytosol, membrane, midpiece plus tail (flagella) and head fractions, and their adenylate cyclase activities were measured. About 65% of the total activity was located in the flagella fraction. For all the fractions, Mn2+-dependent adenylate cyclase activity was about 20 times higher than Mg2+-dependent activity, and guanine nucleotides, fluoride, and other reagents tested did not activate adenylate cyclase. The results suggest that the GTP-dependent regulatory subunit is absent in porcine spermatozoa. The porcine seminal plasma was found to stimulate the adenylate cyclase activity in spermatozoa. The stimulating factor in porcine seminal plasma was partially purified by gel filtration and the molecular weight of the factor appeared to be between 200 and 300. The partially purified factor is heat stable and is not inactivated by treatment with Pronase, trypsin, phospholipase A2 or D but is inactivated by acid hydrolysis. It is easily soluble in water, partially soluble in methanol, and insoluble in ethanol, ethyl ether, chloroform, or acetone. The activation of sperm adenylate cyclase by the factor occurred without a time lag. The activating effect was dose-dependent, saturated at high dose, and ascribed to the increase of the maximal velocity (Vmax). The effect of the factor appears to be limited to adenylate cyclase in spermatozoa; the factor activated adenylate cyclase both in porcine and bovine spermatozoa but failed to activate those in other porcine tissues. The factor was shown to activate the enzyme not only in the ejaculated spermatozoa but also in the epididymal sperm. The factor was also found to elevate the cAMP level in the intact porcine spermatozoa. The factor enhanced the motility of corpus and cauda epididymal spermatozoa. These findings indicate the possibility that this factor initiates the spermatozoan motility upon ejaculation through directly activating adenylate cyclase.

Adenylyl Cyclases↗
PubMed1983

Changes in nervous system glycolipids during metamorphosis of Xenopus laevis.

Qualitative and quantitative changes occurring in the myelin marker glycolipids, cerebrosides, sulfatides, and monogalactosyl diglyceride, in the nervous system (brain, spinal cord, and tail) of Xenopus laevis during its metamorphic stages were analyzed by normal and reverse-phase high performance liquid chromatography. The concentration of these glycolipids increased rapidly in brain until the tadpole reached the middle of metamorphosis, fluctuated slightly, decreased until metamorphosis was completed, and increased once more as the frog matured. Similar changes were observed in the spinal cord, but the decrease of glycolipids occurred at a later stage of metamorphosis. The glycolipid level in tail nerve reached a peak at the beginning of metamorphosis and then rapidly decreased. The ratios of hydroxycerebroside and hydroxysulfatide to respective nonhydroxylipids in brain, spinal cord, and tail remained constant throughout the metamorphic change but differed in each tissue. The tail contained the highest ratio. The glycolipids in sciatic nerve generated during the metamorphosis had an even higher hydroxyl lipid/nonhydroxy lipid ratio. The cerebrosides contained extremely high concentrations of monounsaturated fatty acids with very long carbon chains (C22-C25) and this homolog composition remained almost unchanged throughout metamorphosis. These results indicate that active degradation of these glycolipids, and probably of myelin, occurs but the glycolipid composition of myelin appears to remain the same throughout the metamorphic process. The significance of these findings is discussed from a morphological standpoint.

Animals↗
PubMed1983

Further characterization of the heat-stable factor in the alpha-hydroxylation and oxidation of lignoceric acid in brain: effect of acidic amino acids and hexose-phosphates on brain fatty acid metabolism.

Lignoceric acid and other very long-chain fatty acids are converted to alpha-hydroxy fatty acids and ceramide in brain. These fatty acids are also oxidized and produce glutamic acid and other water-soluble products. All of these metabolic conversions are catalyzed by a rat brain particulate fraction and require NADPH, heat-labile factor, and heat-stable factor. The heat-stable factor was prepared from calf cerebellum. Glucose 6-phosphate and N-acetylaspartic acid have previously been identified as active components of the heat-stable factor. We report in this manuscript that glutamic acid, glutamine, aspartic acid, and gamma-aminobutyric acid as well as inorganic phosphate and adenosine nucleotides are also active components of the heat-stable factor. When the amino acids, glucose 6-phosphate, AMP, and phosphoric acid were combined, full activity of the heat-stable factor for the formation of cerebronate (by alpha-hydroxylation) and glutamate (presumably by beta-oxidation) from lignoceric acid was recovered. The role of the acidic amino acids in the metabolic conversion of lignoceric acid in brain appears to be their conversion to the corresponding alpha-keto acids and then incorporation into the TCA cycle. Glucose 6-phosphate is also likely to be involved in the TCA cycle through the Emden-Meyerhof pathway. Inorganic phosphate and AMP seemingly are used to produce ATP. However, the addition of up to 20 mM ATP alone did not replace the heat-stable factor.

Amino Acids↗
PubMed1983

Purification and characterization of the heat-stable factors essential for the conversion of lignoceric acid to cerebronic acid and glutamic acid: identification of N-acetyl-L-aspartic acid.

The conversion of lignoceric acid to cerebronic acid, ceramides, cerebrosides, and glutamic acid is catalyzed by a rat brain particulate preparation. The heat-stable factor, prepared from calf cerebellum, together with the heat-labile factor, a pyridine nucleotide, and Mg2+ are essential to all of these metabolic pathways. Our previous work showed that the heat-stable factor is composed of at least two components, HSF-1 and HSF-2, and identified HSF-2 as D-glucose-6-phosphate. In the current investigation, HSF-1 was further purified and found to be N-acetyl-L-aspartic acid. In addition, it was discovered that a third component, HSF-3, is also required for heat-stable factor activity. A reconstituted system composed of N-acetylaspartic acid, glucose-6-phosphate, and HSF-3 fully replaced the heat-stable factor essential for the conversion of lignoceric acid to cerebronic acid and glutamic acid. The reconstituted heat-stable factor did not show the initial time lag always observed with the crude heat-stable factor.

Animals↗
PubMed1983

HeLa cell invasiveness and O antigen of Shigella flexneri as separate and prerequisite attributes of virulence to evoke keratoconjunctivitis in guinea pigs.

Many rough mutants selected from isogenic smooth virulent and avirulent strains of Shigella flexneri were examined for virulence, using tissue culture infection and Sereny tests. Many of the rough mutants isolated from a virulent smooth strain were capable of penetrating tissue culture cells but incapable of producing a positive Sereny test. In contrast, we could not obtain from smooth avirulent strains any rough mutants capable of penetrating HeLa cells. Chemical analysis of lipopolysaccharide of some representative rough strains showed several patterns of sugar composition with a range of from Ra to Re chemotypes. There was no correlation between HeLa cell invasiveness and chemotypes of lipopolysaccharides, thus indicating little significance of oligosaccharides of the rough core as well as O antigens in the ability of S. flexneri to penetrate HeLa cells. When these invasive rough strains were given O antigen genes from a smooth avirulent Shigella Hfr strain, most of the transconjugants that expressed O antigens regained the ability to evoke keratoconjunctivitis in guinea pigs. We also examined the chromosomal loci of HeLa cell invasion by transferring carbohydrate fermentation genes of Escherichia coli K-12 Hfr and found two chromosomal loci, the rha and lac-gal regions, which control the ability to penetrate HeLa cells. These results suggested that O antigens and ability to penetrate tissue culture cells are independent and prerequisite attributes of virulence in Shigella flexneri to evoke keratoconjunctivitis in guinea pigs.

Animals↗
PubMed1982

Modifying effect of vinblastine on superoxide anion production by membrane perturbing agents in polymorphonuclear leukocytes.

Superoxide anion production in peritoneal polymorphonuclear leukocytes obtained from guinea pigs was stimulated by in vitro treatment with membrane-perturbing agents, such as cytochalasin D, concanavalin A, phorbol myristate acetate, myristate, digitonin, and NaF. Vinblastine modified these stimulating effects on the superoxide anion production, but its modifying effect was not uniform. The effect of cytochalasin D was stimulated by vinblastine at the concentration of 10(-5)-10(-7) M, whereas it was inhibited at the concentration of 10(-4) M. At 10(-4)-10(-5) M, vinblastine was inhibitory to the effect of concanavalin A, and lower concentrations had no significant effect. Stimulation of the superoxide anion production by phorbol myristate acetate and myristate was further enhanced by vinblastine at any concentration in the range of 10(-4)-10(-8) M with peaks at 10(-6) and 10(-5) M, respectively. Vinblastine had little effect on the stimulation of the superoxide anion production by digitonin and NaF throughout the concentration range examined. The mechanism of the interaction of these membrane-perturbing stimulants and vinblastine is discussed.

Animals↗