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Tadashi Yoshida

Publications and source records attributed to Tadashi Yoshida.

67 records · Page 4Linked to original sources
PubMed2003

Origin of oxysterols in hepatic bile of patients with biliary infection.

OBJECTIVES: Oxysterols are ubiquitous in the body and are potential cytotoxic agents in addition to being metabolic regulators. Although bile contains high concentrations of cholesterol, oxysterol concentrations in bile and the effect of infection on oxysterol levels have not been measured, nor has their origin been studied. The purpose of this study was to determine if infection of the biliary tract was associated with increased concentrations of oxysterols in the bile and, if so, which oxysterols showed a significant change. METHODS: Hepatic bile was obtained from eight patients with biliary tract disease by means of a naso-biliary catheter. Oxysterols were extracted and purified by solid-phase extraction, derivatized and measured by gas chromatography-mass spectrometry. RESULTS: The following were quantified in hepatic bile: 7-alpha-hydroxycholesterol, 7-beta-hydroxycholesterol, cholestan-3-beta,5-alpha,6-beta-triol, 25-hydroxycholesterol, 26-hydroxycholesterol, 7-ketocholesterol, and 7-alpha-hydroxy-4-cholesten-3-one. Total oxysterols in hepatic bile ranged from 0.133 mumol/L to 7.748 mumol/L (1.47 +/- 2.55 mumol/L). Levels of 7-alpha-hydroxycholesterol and 7-beta-hydroxycholesterol were increased in infected bile (14.2 +/- 15.1 x 10(-3)% of cholesterol vs 1.9 +/- 0.5 x 10(-3)% of cholesterol, p < 0.05, and 22.0 +/- 25.0 x 10(-3)% of cholesterol vs 1.6 +/- 1.2 x 10(-3)% of cholesterol, p < 0.05, respectively). Serum C-reactive protein levels correlated positively with biliary levels of 7-alpha-hydroxycholesterol (R = 0.948), 7-beta-hydroxycholesterol (R = 0.976), cholestan-3-beta,5-alpha,6-beta-triol (R = 0.823), 7-alpha-hydroxy-4-cholesten-3-one (R = 0.846,) and 7-ketocholesterol (R = 0.973). Different oxysterols were found in gallstones, chiefly 3-keto-cholest-4-ene (624 +/- 316 parts per million [ppm] of dry weight), 3-keto-cholesta-4,6-diene (240 +/- 329 ppm) and 7-keto-cholesterol (77 +/- 81 ppm). Incubation of human leukocytes with model bile in the presence of bacterial lipopolysaccharide resulted in changes in sterol composition, including increases in oxysterols. We have identified and quantified oxysterols from uninfected and infected human hepatic bile and from gallstones and gallbladder bile. Biliary infection may be involved in the biogenesis of oxysterols in bile through the production of reactive oxygen species from activated leukocytes.

Aged↗
PubMed2003

The long, but not the short, presequence of human coproporphyrinogen oxidase is essential for its import and sorting to mitochondria.

Nucleotide sequence analyses of human coproporphyrinogen oxidase (CPO) have shown two possible translation initiation eodons (TICs) in the region upstream from the region coding the mature polypeptide. These TICs lead to the precursor polypeptides of CPO (long and short pCPOs), which have 110 and 10 amino acids (long and short) presequences, respectively. To determine which TIC is the real one, import reactions to mitochondria of the two pCPOs synthesized using in vitro transcription-translation system were analyzed. The results showed that the long pCPO was imported into mitochondria and sorted properly to the intermembrane space, whereas the short pCPO was not. We also found several miss-readings in the reported nucleotide sequence of mouse CPO gene. This correction revealed that mouse pCPO has also a longer presequence, which are very similar to the long presequence of human. These results indicate that the long, but not short, presequence is the real one.

5' Untranslated Regions↗
PubMed2002

Cryogenic absorption spectra of hydroperoxo-ferric heme oxygenase, the active intermediate of enzymatic heme oxygenation.

Using radiolysis with (32)P enriched phosphate as an internal source of ionizing radiation, the formation of hydroperoxo-ferric complex from oxy-ferrous precursor with a high yield was monitored at 77 K in heme oxygenase (HO) by means of optical absorption spectroscopy. Well-resolved absorption spectra (maxima at 421 nm, 530 nm, 557 nm) of hydroperoxo-ferric intermediate of this heme enzyme were measured in 70% glycerol/buffer frozen glasses. After annealing at 210-215 K this complex converts to the product complex, alpha-meso hydroxyheme-HO. No heme degradation products were formed in control experiments with ferric HO or other heme proteins.

Catalysis↗
PubMed2002

Catalytic mechanism of heme oxygenase through EPR and ENDOR of cryoreduced oxy-heme oxygenase and its Asp 140 mutants.

Heme oxygenase (HO) catalyzes the O(2)- and NADPH-cytochrome P450 reductase-dependent conversion of heme to biliverdin, Fe, and CO through a process in which the heme participates both as a prosthetic group and as a substrate. In the present study, we have generated a detailed reaction cycle for the first monooxygenation step of HO catalysis, conversion of the heme to alpha-meso-hydroxyheme. We employed EPR (using both (16)O(2) and (17)O(2)) and (1)H, (14)N ENDOR spectroscopies to characterize the intermediates generated by 77 K radiolytic cryoreduction and subsequent annealing of wild-type oxy-HO and D140A, F mutants. One-electron cryoreduction of oxy-HO yields a hydroperoxoferri-HO with g-tensor, g = [2.37, 2.187, 1.924]. Annealing of this species to 200 K is accompanied by spectroscopic changes that include the appearance of a new (1)H ENDOR signal, reflecting rearrangements in the active site. Kinetic measurements at 214 K reveal that the annealed hydroperoxoferri-HO species, denoted R, generates the ferri-alpha-meso-hydroxyheme product in a first-order reaction. Disruption of the H-bonding network within the distal pocket of HO by the alanine and phenylalanine mutations of residue D140 prevents product formation. The hydroperoxoferri-HO (D140A) instead undergoes heterolytic cleavage of the O-O bond, ultimately yielding an EPR-silent compound II-like species that does not form product. These results, which agree with earlier suggestions, establish that hydroperoxoferri-HO is indeed the reactive species, directly forming the alpha-meso-hydroxyheme product by attack of the distal OH of the hydroperoxo moiety at the heme alpha-carbon.

Aspartic Acid↗
PubMed2002

Identification of a renal proximal tubular cell-specific enhancer in the mouse 25-hydroxyvitamin d 1alpha-hydroxylase gene.

The active form of vitamin D is synthesized by 25-hydroxyvitamin D 1alpha-hydroxylase (1alpha-hydroxylase), which is expressed predominantly in renal proximal tubular cells. To clarify the mechanism of cell-specific gene expression of this enzyme, the 5'-flanking region of the mouse 1alpha-hydroxylase gene was investigated. Investigation began with mRNA expression of 1alpha-hydroxylase in cultured cells, including LLC-PK1, NIH/3T3, HepG2, MDCK, and OK cells. Expression of 1alpha-hydroxylase mRNA was restricted in LLC-PK1 cells. Several lengths of the 5'-flanking region of 1alpha-hydroxylase gene were linked to a pGL3-basic luciferase vector and introduced into these cells. Only LLC-PK1 cells had a substantial luciferase activity. Deletion analyses revealed that luciferase activity was detected in constructs extending from the transcription initiation site to -1652 to -105 bp, whereas further deletion to -80 bp resulted in a marked decrease in activity. The region from -105 to -80 bp contained two ternary complex factor-1 (TCF-1) sites, and mutations in the proximal TCF-1 site decreased the activity. Electrophoretic mobility shift assay demonstrated binding of LLC-PK1 nuclear proteins to this region. Tests of enhancer function in LLC-PK1 cells indicated that the 26-bp fragment behaved as a classical enhancer, i.e., independently of position and orientation. Moreover, a decoy oligonucleotide corresponding to this region substantially inhibited the promoter activity of 1alpha-hydroxylase gene. This study suggests that the -105 to -80 bp element of mouse 1alpha-hydroxylase gene contains an enhancer to be necessary for renal proximal tubular cell-specific expression.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed2002

Characterization of five phyllosphere bacteria isolated from Rosa rugosa leaves, and their phenotypic and metabolic properties.

Five gram-negative bacteria, all of which were Enterobacteriaceae, were isolated from the phyllosphere of green or senescing leaves of Rosa rugosa, and their phenotypic and physiological characteristics were examined. Partial 16S rDNA sequences led to identification of these isolates as Pantoea agglomerans, Klebsiella terrigena, Erwinia rhapontici, and two strains of Rahnella aquatilis. Interestingly, these phyllosphere bacteria had certain phenotypic and physiological convergences, while they showed their own metabolic properties toward phenolic compounds of plant origin. In particular, the two Ra. aquatilis isolates from the green leaves had a substrate-inducible gallate decarboxylase activity in the resting cells that had been cultured in 1 mM gallic acid- or protocatechuic acid-containing medium. The other three isolates from the senescing leaves did not have this enzyme activity. Simple phenolics that the Ra. aquatilis decarboxylatively produced from benzoic acid derivatives had better antimicrobial activities than those of the substrates.

Antifungal Agents↗
PubMed2002

Antigen presentation by Peyer's patch cells can induce both Th1- and Th2-type responses depending on antigen dosage, but a different cytokine response pattern from that of spleen cells.

The Th1 and Th2 preference induced by cells from the Peyer's patch (PP) and spleen (SPL) with various doses of an antigen was examined. The same splenic T cell receptor-transgenic CD4+ T cells were first incubated with PP or SPL cells in the presence of various doses of an antigen, and the cytokine response was observed after secondary stimulation. A Th2-type pattern was only obtained for primary stimulation at 10 microM of the antigen with PP cells, whereas a Th1 pattern was induced at both higher and lower concentrations. SPL cells in the presence of 0.1 to 1 microM of the antigen induced the secretion of Th2-type cytokines. Ten and 100 microM of the antigen plus SPL cells did not induce the release of a large quantity of cytokines. PP cells induced a different cytokine pattern at the antigen concentration that induced a similar level of T cell proliferation with SPL cells. Our findings suggest that the antigen-dose dependent development of Th1/Th2 cells is differentially modulated by the antigen-presentation function of cells in PP and SPL.

Animals↗
PubMed2002

[A case of spindle cell type hepatocellular carcinoma responding to hepatic intra-arterial infusion chemotherapy].

We report herein a case of spindle cell type hepatocellular carcinoma responding to hepatic intra-arterial infusion chemotherapy. A 50-year-old woman was hospitalized for right epigastralgia. A computed tomography scan demonstrated cloudy liver tumor with a diameter of 12 cm in S5 and S8. Surgery was performed based on the diagnosis of liver tumor. However, because the tumor was also present in the left lobe, we did only a biopsy for a part of tumor. From the pathological findings, this was diagnosed as a spindle cell type hepatocellular carcinoma. After the operation, hepatic intra-arterial injection therapy of continuous infusion with 5-FU was conducted for two weeks. A small reduction in the tumor was seen with computed tomography after the completion of two courses.

Administration, Oral↗
PubMedDate not supplied

Modulation of the T cell response to beta-lactoglobulin by conjugation with carboxymethyl dextran.

We have previously prepared beta-lactoglobulin (beta-LG)-carboxymethyl dextran (CMD) conjugates with water-soluble carbodiimide and achieved reduced immunogenicity of beta-LG. In the present study, to elucidate the mechanism for the reduced immunogenicity of beta-LG, we investigated changes in the T cell response to beta-LG after conjugation with CMDs differing in molecular weight (about 40 and 162 kDa). Lymph node cells from BALB/c, C3H/He, and C57BL/6 mice that had been immunized with beta-LG or the conjugates were stimulated with beta-LG, and the in vivo T cell response was then evaluated by BrdU (5-bromo-2'-deoxyuridine) ELISA as the ex vivo proliferative response. T cells from the conjugate-immunized mice showed a lower proliferative response than those from the beta-LG-immunized mice. T cell epitope scanning, using synthesized peptides, showed that the T cell epitope profiles of the conjugates were similar to those of beta-LG, whereas the proliferative response to each epitope was reduced. These results indicate that the lower in vivo T cell response with the conjugates was not due to induction of conjugate-specific T cells, but due to a decrease in the number of beta-LG-specific T cells. After the lymph node cells from beta-LG-immunized mice had been stimulated with beta-LG or the conjugates, the efficiency of the antigen presentation of the conjugate to beta-LG-specific T cells was evaluated by BrdU ELISA as the in vitro proliferative response. The antigen presentation of beta-LG to the T cells was reduced by conjugation with CMD. In addition, conjugation with CMD enhanced the resistance of beta-LG to cathepsin B and cathepsin D, which suggest that conjugation with CMD inhibited the degradation of beta-LG by proteases in APC and led to suppression of the generation of antigenic peptides including T cell epitopes from beta-LG. It is therefore considered that the suppressive effect on the generation of T cell epitopes reduced the antigen presentation of the conjugates and that this reduction led to a decrease in the number of beta-LG-specific T cells in vivo. As a result, the decreased help to B cells by T cells would have reduced the antibody response to beta-LG. We conclude that suppression of the generation of T cell epitopes by conjugation with CMD is important to the mechanism for the reduced immunogenicity of beta-LG.

Adjuvants, Immunologic↗