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T Koga

Publications and source records attributed to T Koga.

At least 127 records · Page 7Linked to original sources

A novel NDP-6-deoxyhexosyl-4-ulose reductase in the pathway for the synthesis of thymidine diphosphate-D-fucose.

The serotype-specific polysaccharide antigen of Actinobacillus actinomycetemcomitans Y4 (serotype b) consists of D-fucose and L-rhamnose. Thymidine diphosphate (dTDP)-D-fucose is the activated nucleotide sugar form of D-fucose, which has been identified as a constituent of structural polysaccharides in only a few bacteria. In this paper, we show that three dTDP-D-fucose synthetic enzymes are encoded by genes in the gene cluster responsible for the synthesis of serotype b-specific polysaccharide in A. actinomycetemcomitans. The first and second steps of the dTDP-D-fucose synthetic pathway are catalyzed by D-glucose-1-phosphate thymidylyltransferase and dTDP-D-glucose 4,6-dehydratase, which are encoded by rmlA and rmlB in the gene cluster, respectively. These two reactions are common to the well studied dTDP-L-rhamnose synthetic pathway. However, the enzyme catalyzing the last step of the dTDP-D-fucose synthetic pathway has never been reported. We identified the fcd gene encoding a dTDP-4-keto-6-deoxy-D-glucose reductase. After purifying the three enzymes, their enzymatic activities were analyzed by reversed-phase high performance liquid chromatography. In addition, nuclear magnetic resonance analysis and gas-liquid chromatography analysis proved that the fcd gene product converts dTDP-4-keto-6-deoxy-D-glucose to dTDP-D-fucose. Moreover, kinetic analysis of the enzyme indicated that the Km values for dTDP-4-keto-6-deoxy-D-glucose and NADPH are 97.3 and 28.7 microM, respectively, and that the enzyme follows the sequential mechanism. This paper is the first report on the dTDP-D-fucose synthetic pathway and dTDP-4-keto-6-deoxy-D-glucose reductase.

Aggregatibacter actinomycetemcomitans↗

Virus-inducible expression of a host chemokine gene relies on replication-linked mRNA stabilization.

Analysis of the host response to viral infection generally has focused on the capacity of viruses to activate or repress transcription of cellular genes, and this approach is also characteristic of work on RNA viruses such as respiratory syncytial virus (RSV). In the present study, it appeared initially that RSV-driven expression of a critical immune regulator, the beta-chemokine RANTES (regulated upon activation, normal T cell expressed and secreted), in primary-culture airway epithelial cells also depended on inducible gene transcription because expression was accompanied by coordinate increases in transcriptional initiation rate and gene promoter activity. However, RSV-driven increases in RANTES gene transcription and promoter activity were small and transient relative to RANTES expression, and they were no different in size and duration than for inactivated RSV that was incapable of fully inducing RANTES expression. These findings suggested that the increase in RANTES gene transcription was not sufficient for inducible expression and that critical regulatory effects occurred at a posttranscriptional level. This type of mechanism for virus-inducible expression of RANTES was established when we found that replicating (but not inactivated) RSV markedly increased RANTES mRNA half-life (from 0.8 to 6.8 h). In addition, RNase protection assays of heterologous promoter/reporter plasmids indicate that basal instability of RANTES mRNA is mediated at least in part by nucleotides 11-389 of the RANTES gene, and this region is also the target for induction by virus. The distinct pathway for production of RANTES (in combination with cytokine-dependent expression of RANTES and related immune-response genes) may more effectively coordinate immune cell interaction with epithelial barrier cells to mediate host defense.

Bronchi↗

A novel dnaK operon from Porphyromonas gingivalis.

The nucleotide sequence of the dnaK operon cloned from Porphyromonas gingivalis revealed that the operon does not contain homologues of either dnaJ or grpE. However, there were two genes which encode small heat shock proteins immediately downstream from the dnaK and they were transcribed together with dnaK as one unit. The ATPase activity of the P. gingivalis DnaK was synergistically stimulated up to 40-fold in the simultaneous presence of Escherichia coli DnaJ and GrpE. These results suggest that the DnaK homologue of P. gingivalis, with its unique genetic structure and evolutionary features, works as a member of the DnaK chaperone system.

Adenosine Triphosphatases↗

Mucosally induced systemic T cell unresponsiveness to ovalbumin requires CD40 ligand-CD40 interactions.

CD40 ligand (CD40L) gene-disrupted (CD40L-/-) mice were employed to examine the role of costimulatory signals via CD40L-CD40 interactions in mucosally induced tolerance. CD40L-/- and control (CD40L+/+) mice of the same C57BL/6 x 129/J background were immunized orally with 25 mg of OVA before systemic challenge with OVA in CFA. While CD40L+/+ mice showed reductions in Ag-specific T cell responses including delayed-type hypersensitivity (DTH) and proliferative responses, CD40L-/- mice underwent normal T cell responses. Further, cytokine analysis of splenic CD4+ T cells showed that both Th1-type (e.g., IFN-gamma and IL-2) and Th2-type (e.g., IL-4, IL-5, IL-6, and IL-10) responses were maintained in CD40L-/- mice orally immunized with OVA, whereas these cytokine responses in CD40L+/+ mice were significantly reduced. In addition, splenic CD4+ T cells from CD40L-/- mice orally immunized with OVA provided B cell help in Ag-specific Ab-forming cells when the cells were cultured with naive B cells in the presence of Ag and CD40L-transfected cell lines. In contrast, an identical culture condition containing splenic CD4+ T cells from orally tolerized CD40L+/+ mice did not exhibit helper activity. Taken together, these findings indicate that CD40L and CD40 interactions are essential for the induction of systemic T cell unresponsiveness to orally administered Ag.

Administration, Oral↗

The site of the anti-emetic action of tachykinin NK1 receptor antagonists may exist in the medullary area adjacent to the semicompact part of the nucleus ambiguus.

NK1 receptor antagonists have been shown to act centrally and to produce a broad-spectrum anti-emetic action. To determine precisely the site of this action, we microinjected GR205171, an NK1 receptor antagonist, into the left medulla oblongata in decerebrate paralyzed dogs. The right medulla was transected 2.5 mm rostral to the obex to eliminate the emetic function of that half. Fictive retching induced by vagal stimulation was still observed after each of 32 injections (0.5-5 microgram in 1-30 microliter) in the area ventrolateral to the solitary complex in six dogs. Retching was also observed for 30 min or more after all but 2 of 30 injections (0.5-1 microgram in 0.5-1 microliter) in the area dorsal to the retrofacial nucleus in 17 dogs. In contrast, retching disappeared within 5-30 min after each of 20 injections (0.5-1 microgram in 1 microliter) in the area adjacent to the semicompact part of the nucleus ambiguus (scAMB) in 15 dogs. The threshold dose for abolition of the retching response was examined in seven dogs and was about 0.1 ng in 1 microliter. The maximum velocity of salivation occurred before the onset of retching and significantly decreased after its abolition. These results suggest that the site of the anti-emetic action of NK1 receptor antagonists may lie in a limited area adjacent to the scAMB, and that neurons in the site induce prodromal signs and retching in a sequential manner.

Animals↗

Expression of the SART-1 tumor rejection antigen in breast cancer.

We investigated in breast cancers the expression of the SART-1 gene encoding tumor rejection antigens. SART-1 mRNA was expressed in all of the samples tested. The SART-1(800) antigen was detectable in 20 of 50 (40%) breast cancer tissues and all breast cancer cell lines tested, but not in normal breast tissues. The SART-1(800)+ breast cancer cells transfected with HLA-A2601 or HLA-A2402 cDNA were recognized by the HLA-A26-restricted and SART-1-specific cytotoxic T lymphocytes (CTLs) or the HLA-A24-restricted and SART-1-specific CTLs, respectively. Among the 20 SART-1(800)+ tumors, 9 or 8 tumors expressed estrogen receptor or progesterone receptor, respectively. Therefore, the patients with HLA-A26 or -A24 haplotype might be appropriate candidates for specific immunotherapy with the SART-1 peptides independently or in combination with hormone therapy.

Antigens, Neoplasm↗

Role of Bcl-xL protein in differentiation and apoptosis of human middle ear cholesteatoma epithelium.

OBJECTIVE: To compare the mechanisms of proliferation, differentiation, and apoptosis in middle ear cholesteatoma epithelium with those of normal external ear canal epithelium. DESIGN: The localizations of the expression of Bcl-xL protein and involucrin and the presence of apoptotic cells were determined for tissue slices of middle ear cholesteatoma epithelium and compared with the findings for normal external ear canal epithelium. In addition, SCC-25/bcl-xL transfectants showing the overexpression of Bcl-xL were used to investigate the effect of this protein on the expression of involucrin, which is a marker of epithelial cell differentiation. MATERIALS: Cholesteatoma tissue specimens were surgically excised from 10 patients. Normal skin specimens collected from the external ear canal of the 10 patients were used as control specimens. RESULTS: The expression of Bcl-xL was detected in the vicinity of the basal cell layer of both the cholesteatoma epithelium and the normal external ear canal epithelium. Conversely, the expression of involucrin (ie, a marker of epithelial cell differentiation) increased in proportion to the shallowness of the epithelial layer. In situ labeling detected apoptotic cells in the spinous and granular cell layers of cholesteatoma tissue sections and similar findings in the normal external skin specimens. Western blot analysis confirmed that the expression of involucrin protein was the same in both wild-type SCC-25 cells and the SCC-25/bcl-xL transfectants. CONCLUSIONS: In both the cholesteatoma epithelium and the normal external ear canal epithelium, differentiation and apoptosis begin when the epithelial cells separate from the basal cells. The mechanisms behind these changes, at least in apoptosis, appear to be controlled by the expression of the Bcl-xL protein.

Adult↗

Proanthocyanidin-rich extract from grape seeds attenuates the development of aortic atherosclerosis in cholesterol-fed rabbits.

The aim of this study was to evaluate the antiatherosclerotic effect of proanthocyanidin-rich extracts from grape seeds in cholesterol-fed rabbits. Proanthocyanidin-rich extracts (0.1% and 1% in diets [w/w]) did not appreciably affect the changes in serum lipid profile of cholesterol-fed rabbits. The level of cholesteryl ester hydroperoxides (ChE-OOH) induced by 2,2'-azobis(2-amidinopropane-dihydrochloride (AAPH) were lower in the plasma of rabbits fed proanthocyanidin-rich extract plus cholesterol than in the plasma of rabbits fed cholesterol alone, but not in the low-density lipoprotein (LDL). Aortic malondialdehyde (MDA) content decreased in rabbits fed proanthocyanidin-rich extract. Feeding proanthocyanidin-rich extracts (0.1 and 1% in the diet) to rabbits significantly reduced severe atherosclerosis in the aorta. Immunohistochemical analysis revealed a decrease in the number of oxidized LDL-positive macrophage-derived foam cells in atherosclerotic lesions in the aorta of rabbits fed proanthocyanidin-rich extract. When proanthocyanidin-rich extract was administered orally to rats, proanthocyanidin was detected in the plasma by Porters method but not in the lipoproteins (LDL plus VLDL). In an in vitro experiment using human plasma, proanthocyanidin-rich extract added to the plasma inhibited the oxidation of cholesteryl linoleate in LDL, but not in the LDL isolated after the plasma and the extract were incubated in advance. These results suggested that proanthocyanidins, the major polyphenols in red wine, might trap reactive oxygen species in aqueous series such as plasma and interstitial fluid of the arterial wall, thereby inhibiting oxidation of LDL and showing an antiatherosclerotic activity.

Amidines↗

Effect of vitamin E on human aortic endothelial cell production of chemokines and adhesion to monocytes.

Epidemiological and clinical studies indicate that vitamin E may reduce the risk of cardiovascular disease (CVD). Modulation of adhesion molecule expression and chemokine production by vitamin E may contribute to its beneficial effect. In this study we found that the enrichment of confluent human aortic endothelial cells (HAEC) or U937 monocytic cells with increasing doses of vitamin E (d-alpha-tocopherol, 20, 40, and 60 micromol/l for 20 h) inhibited their adhesion when either or both cell types were stimulated with interleukin (IL)-1beta. Enrichment of HAEC with the same doses of vitamin E suppressed IL-1beta-stimulated expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and endothelial leukocyte adhesion molecule-1 (E-selectin). Supplementation with increasing doses of vitamin E up to 60 micromol/l was not effective in preventing spontaneous production of monocyte chemoattractant protein-1 (MCP-1), but supplementation with vitamin E at 60 micromol/l reduced IL-8 production significantly. However, IL-1beta-induced productions of both MCP-1 and IL-8 were dose-dependently suppressed by enrichment of cells with vitamin E. Vitamin E, at the doses used, did not significantly change the spontaneous production but dose-dependently inhibited the IL-1beta-induced production of inflammatory cytokine IL-6. We concluded that vitamin E could inhibit production of chemokines and inflammatory cytokines, in addition to inhibiting adhesion of HAEC to monocytes by reducing expression of adhesion molecules when cells were activated with an inflammatory cytokine. These mediators are actively involved in the pathogenesis of atherosclerosis. Therefore, their inhibition by vitamin E may contribute to vitamin E's reported reduction in risk of CVD.

Analysis of Variance↗

The tachykinin NK1 receptor antagonist GR205171 abolishes the retching activity of neurons comprising the central pattern generator for vomiting in dogs.

Tachykinin NK1 receptor antagonists are known to act centrally and to have broad-spectrum antiemetic effects, but their precise site of action has not yet been defined. To identify this site, the effects of the NK1 receptor antagonist GR205171 on the activities of neurons comprising the central pattern generator (CPG) for vomiting were observed in decerebrate paralyzed dogs. A non-respiratory neuron in each of nine dogs was considered to be a CPG neuron based on its response to abdominal vagal stimulation, its location in the CPG area in the reticular formation dorsomedial to the retrofacial nucleus, its firing patterns in prodromal and retching phases and its response to apomorphine. In response to vagal stimulation at 3-10 Hz, the firing of these neurons transiently increased at the onset of stimulation (fast component), gradually increased again (slow component), and finally developed into rhythmic bursts synchronous with retching bursts of the phrenic and abdominal muscle nerves. GR205171 (25-50 microg/kg, i.v.) abolished the slow component and retching bursts in the neurons, and the retching activities of both nerves, but did not change the fast component. The responses of these neurons to repetitive pulse-train vagal stimulation exhibited a vigorous 'wind-up' and finally developed into retching bursts. Both the 'wind-up' phenomenon and retching bursts disappeared after the application of GR205171. These results suggest that the site of the antiemetic action of NK1 receptor antagonists is located in the CPG or in the pathway connecting the solitary nucleus to the CPG.

Animals↗

Bactericidal activities of essential oils of basil and sage against a range of bacteria and the effect of these essential oils on Vibrio parahaemolyticus.

Basil and sage essential oils were examined for bactericidal activity against a range of Gram-positive and Gram-negative bacteria by viable count determinations. Generally, Gram-positive bacteria showed higher resistance to basil and sage essential oils than Gram-negative bacteria. Vibrio species showed a high sensitivity to both essential oils. Stationary growth phase cells of selected bacteria showed higher resistance to these essential oils than exponential growth phase cells. Basil-resistant (b21) and sage-resistant (s20) strains of Vibrio parahaemolyticus were isolated. Both strains showed higher resistance to heat and H2O2 than parent strain. Conversely, heat-adapted V. parahaemolyticus also showed a higher resistance to these essential oils than nonadapted cells.

Colony Count, Microbial↗

Increase of antioxidative potential of rat plasma by oral administration of proanthocyanidin-rich extract from grape seeds.

The effect of a single oral administration of proanthocyanidins, oligomeric and polymeric polyhydroxyflavan-3-ol units, on the antioxidative potential of blood plasma was studied in rats. Proanthocyanidin-rich extract from grape seeds was administered by intragastric intubation to fasted rats at 250 mg/kg of body weight. The plasma obtained from water- or proanthocyanidin-administered rats was oxidized by incubation with copper sulfate or 2, 2'-azobis(2-amidinopropane) dihydrochloride (AAPH) at 37 degrees C, and the formation of cholesteryl ester hydroperoxides (CE-OOH) was followed. The plasma obtained from proanthocyanidin-administered rats was significantly more resistant against both copper ion-induced and AAPH-induced formation of CE-OOH than that from control rats. The lag phase in the copper ion-induced oxidation of rat plasma was remarkably increased at 15 min after administration of proanthocyanidins and reached a maximum level at 30 min. When the plasma from proanthocyanidin-administered rat was hydrolyzed by sulfatase and beta-glucuronidase following analysis by high-performance liquid chromatography with electrochemical detection, metabolites of proanthocyanidins occurred in rat plasma at 15 min after administration, three peaks of which were identified as gallic acid, (+)-catechin, and (-)-epicatechin. These results suggest that the intake of proanthocyanidins, the major polyphenols in red wine, increases the resistance of blood plasma against oxidative stress and may contribute to physiological functions of plant food including wine through their in vivo antioxidative ability.

Administration, Oral↗

Isolation and characterization of the rml gene homologs from Porphyromonas gingivalis.

We cloned four genes from the Porphyromonas gingivalis chromosome, the gene products of which catalyze the anabolism of dTDP-L-rhamnose from D-glucose-1-phosphate when they were expressed in Escherichia coli. The amino acid sequences deduced from these genes showed significant homology to proteins encoded by the rml genes involved in dTDP-L-rhamnose biosynthesis in other gram-negative bacteria. Reverse transcriptase polymerase chain reaction analysis revealed that these four genes are expressed as a single transcript in P. gingivalis. To clarify the role of the rml gene homologs in this organism, construction of mutants defective in the rml gene homologs was attempted by allelic exchange. Unexpectedly, any mutants defective in the rml gene homologs were unable to be isolated, and the allelic exchange was possible only if the wild-type rml gene homologs were present on the chromosome. These results suggest that the rml gene homologs might be essential for the viability of P. gingivalis under the culture conditions used in this study.

Bacterial Proteins↗

Soluble E-selectin and eosinophil cationic protein are distinct serum markers that differentially represent clinical features of atopic dermatitis.

The serum levels of eosinophil cationic protein (ECP), soluble E-selectin (sE-selectin), soluble CD14 (sCD14) and interleukin (IL)-4 are known to be elevated in patients with atopic dermatitis (AD). However, little is known of the mutual relationship between these factors. To elucidate the clinical and mutual relevance of these markers, we examined the serum levels of ECP, sE-selectin, sCD14 and IL-4 as compared with eruption scores, itch scores, total IgE and numbers of peripheral eosinophils in patients with AD (n = 43), non-atopic eczema (n = 24) and urticaria (n = 13) and in normal individuals (n = 45). In 27 patients with AD the levels of these markers were compared before and after treatment. Levels of ECP were elevated only in the patients with AD, whereas the sE-selectin levels were higher not only in AD but also in non-atopic eczema in a severity-dependent manner. The levels of both markers significantly diminished after treatment. Significant correlations existed between ECP levels and numbers of eosinophils, sE-selectin levels and itch scores, and sE-selectin levels and IgE levels. No significant changes were observed in the sCD14 and IL-4 levels. Taken together, sE-selectin and ECP are good but distinct serum markers that reflect different clinical features of AD.

Adolescent↗