Search PubMed⌕ Search

Biomedical subjects

S Yoshida

Publications and source records attributed to S Yoshida.

At least 433 records · Page 24Linked to original sources
PubMed1999

Cysteine biosynthesis in Saccharomyces cerevisiae: a new outlook on pathway and regulation.

Using a Saccharomyces cerevisiae strain having the activities of serine O-acetyl-transferase (SATase), O-acetylserine/O-acetylhomoserine sulphydrylase (OAS/OAH SHLase), cystathionine beta-synthase (beta-CTSase) and cystathionine gamma-lyase (gamma-CTLase), we individually disrupted CYS3(coding for gamma-CTLase) and CYS4 (coding for beta-CTSase). The obtained gene disruptants were cysteine-dependent and incorporated the radioactivity of (35)S-sulphate into homocysteine but not into cysteine or glutathione. We concluded, therefore, that SATase and OAS/OAH SHLase do not constitute a cysteine biosynthetic pathway and that cysteine is synthesized exclusively through the pathway constituted with beta-CTSase and gamma-CTLase; note that OAS/OAH SHLase supplies homocysteine to this pathway by acting as OAH SHLase. From further investigation upon the cys3-disruptant, we obtained results consistent with our earlier suggestion that cysteine and OAS play central roles in the regulation of sulphate assimilation. In addition, we found that sulphate transport activity was not induced at all in the cys4-disruptant, suggesting that CYS4 plays a role in the regulation of sulphate assimilation.

Biological Transport↗
PubMed1999

Reconstitution of active recombinant Shiga toxin (Stx)1 from recombinant Stx1-A and Stx1-B subunits independently produced by E. coli clones.

Escherichia coli clones expressing recombinant Shiga toxin (Stx)1-A and recombinant Stx1-B subunits, were established. Culture supernatants of these clones were examined for inhibitory activity on in vitro protein synthesis using luciferase as a reporter enzyme. Culture supernatant of the clone expressing Stx1-A, but not Stx1-B, showed the inhibitory activity. Neither recombinant Stx1-A nor Stx1-B showed Vero cell cytotoxicity. For reconstitution of biologically active toxin, the culture supernatants of the Stx1-A clone and the Stx1-B clone were mixed. The reconstituted recombinant Stx1 showed both Vero cell cytotoxicity and inhibition of in vitro protein synthesis.

Animals↗
PubMed1999

Isothiazolone derivatives selectively inhibit telomerase from human and rat cancer cells in vitro.

The telomere hypothesis postulates stabilization of telomere length and telomerase activation as key events in cellular immortalization and carcinogeneses. Accordingly, telomerase has been suggested as a novel and highly selective target for design of antitumor drugs. Screening of a chemical library including 16 000 synthetic compounds yielded six that strongly inhibited telomerase activity in extracts of cultured human cells, including four isothiazolone derivatives and two unrelated compounds. The most potent inhibitor was 2-[3-(trifluoromethyl)phenyl]isothiazolin-3-one (TMPI), a concentration of 1.0 microM inhibited telomerase activity by 50% according to a telomere repeat amplification protocol (TRAP) assay. Analysis using partially purified telomerase from AH7974 rat hepatoma cells demonstrated noncompetitive inhibition with the telomere-repeat primer and mixed inhibition with the dNTPs; the inhibition constant was 2.5 microM. TMPI did not inhibit eukaryotic DNA polymerase alpha, beta, or human immunodeficiency virus reverse transcriptase (HIV RT). Thus, inhibition by TMPI was highly selective for telomerase. Inhibition by TMPI was quenched by 1 mM of dithiothreitol or glutathione, suggesting that TMPI inhibits telomerase by acting at a cysteine residue. TMPI inhibition of this enzyme may find application as an antineoplastic agent.

Animals↗
PubMed1999

Protease M/neurosin mRNA is expressed in mature oligodendrocytes.

No proteases have been identified to be oligodendrocyte-specific though there are phenomena in which proteases may be committed. We have cloned a cDNA for mouse homologue of protease M/neurosin, serine protease, and localized its mRNA in the mouse brain. The cDNA and the deduced amino acid sequences were 66% identical to those of human protease M/neurosin. In situ hybridization histochemistry revealed that the mRNA was localized in the mature oligodendrocytes which expressed proteolipid protein mRNA. Developmentally, protease M/neurosin mRNA was expressed by oligodendrocytes 2 to 7 days after the maturation. Thus, protease M/neurosin may be important to the processes occurring after the maturation of oligodendrocytes such as myelination or turnover of the proteins in the myelin.

Amino Acid Sequence↗
PubMed1999

cDNA cloning and expression of a novel serine protease in the mouse brain.

A cDNA for a novel serine protease, termed brain type granzyme K (B-GRK) was cloned from the mouse brain. The cDNA codes a protein similar to granzyme K (GRK) but completely different at the N-terminus. Genomic Southern and PCR analysis of the gene suggests B-GRK is the alternative transcription form of GRK. B-GRK and GRK have a different organ-specific expression pattern: B-GRK is expressed in the brain, while GRK is expressed in the spleen. The recombinant fusion protein was detected in the neuro2a cells transfected with a plasmid containing B-GRK sequence. The mRNA for B-GRK/GRK was detected in cerebral cortex, hippocampus and diencephalon of the mouse brain. In situ hybridization for B-GRK/GRK revealed that several regions in the forebrain and hypothalamus express the mRNA. Developmental analysis showed that in the prenatal stage, the mRNA was expressed also in pituitary and pineal body in addition to the brain.

Amino Acid Sequence↗
PubMed1999

Lack of repetition priming effect on visual event-related potentials in schizophrenia.

BACKGROUND: The present study was designed to assess, using event-related potentials, whether aberrant semantic processing reported in schizophrenia results from primary semantic overactivation or contextual dysregulation. METHODS: The visual event-related brain potentials were compared between 9 schizophrenic subjects and 16 normal control subjects performing two kinds of semantic categorization tasks with different nontarget stimuli: 1) nontargets comprising words, pseudowords, and unpronounceable foreign letters and 2) nontargets comprising initial presenting words, immediate repetition words, and delayed repetition words. RESULTS: Schizophrenic subjects showed no evidence suggestive of a greater negative potential associated with words and pseudowords, but they did show a lack of amplitude change associated with immediately repeated words relative to that in control subjects. CONCLUSIONS: These results suggest that aberrant semantic activation in schizophrenia results mainly from a failure to utilize information from preceding words or context, and could explain the increased N400 to the congruent or related words recently reported in this disease.

Adult↗
PubMed1999

Involvement of thioredoxin in rheumatoid arthritis: its costimulatory roles in the TNF-alpha-induced production of IL-6 and IL-8 from cultured synovial fibroblasts.

Thioredoxin (TRX) is a cellular reducing catalyst induced by oxidative stress and is involved in the redox regulation of transcription factors such as NF-kappaB. We found that the serum TRX concentration was elevated in patients with rheumatoid arthritis (RA) as compared with values from healthy individuals and patients with osteoarthritis (33.6 +/- 35.1 vs 11.8 +/- 6.6 ng/ml, p < 0.01). Moreover, the TRX concentration in the synovial fluid (SF) was much more elevated in RA patients than in osteoarthritis patients (103.4 +/- 53.3 vs 24.6 +/- 17.4 ng/ml, p < 0.001). Multiple regression analysis revealed that the serum C-reactive protein value was better correlated with the linear combination of SF TNF-alpha and SF TRX values than with SF TNF-alpha alone, suggesting that TRX might play a subsidiary role in the rheumatoid inflammation. We thus examined the effect of TRX on the TNF-alpha-induced IL-6 and IL-8 production using rheumatoid synovial fibroblast cultures. The extents of IL-6 and IL-8 production in response to TNF-alpha were greatly augmented by TRX as compared with TNF-alpha alone. TRX alone did not have such effects. We also found that TRX appeared to accelerate the nuclear translocation of NF-kappaB, a major transcriptional regulator for production of IL-6 and IL-8 on stimulation with TNF-alpha. Consistent with these findings, the IkappaBalpha phosphorylation at Ser32 and its subsequent degradation in response to TNF-alpha was facilitated by TRX. These findings indicate that the elevated TRX concentration in SF of RA patients might be involved in the aggravation of rheumatoid inflammation by augmenting the NF-kappaB activation pathway.

Adjuvants, Immunologic↗
PubMed1999

Stable expression of human beta1,4-galactosyltransferase in plant cells modifies N-linked glycosylation patterns.

beta1,4-Galactosyltransferase (UDP galactose: beta-N-acetylglucosaminide: beta1,4-galactosyltransferase; EC 2.4.1. 22) catalyzes the transfer of galactose from UDP-Gal to N-acetylglucosamine in the penultimate stages of the terminal glycosylation of N-linked complex oligosaccharides in mammalian cells. Tobacco BY2 cells lack this Golgi enzyme. To determine to what extent the production of a mammalian glycosyltransferase can alter the glycosylation pathway of plant cells, tobacco BY2 suspension-cultured cells were stably transformed with the full-length human galactosyltransferase gene placed under the control of the cauliflower mosaic virus 35S promoter. The expression was confirmed by assaying enzymatic activity as well as by Southern and Western blotting. The transformant with the highest level of enzymatic activity has glycans with galactose residues at the terminal nonreducing ends, indicating the successful modification of the plant cell N-glycosylation pathway. Analysis of the oligosaccharide structures shows that the galactosylated N-glycans account for 47.3% of the total sugar chains. In addition, the absence of the dominant xylosidated- and fucosylated-type sugar chains confirms that the transformed cells can be used to produce glycoproteins without the highly immunogenic glycans typically found in plants. These results demonstrate the synthesis in plants of N-linked glycans with modified and defined sugar chain structures similar to mammalian glycoproteins.

Agrobacterium tumefaciens↗
PubMed1999

Injury induces neuropsin mRNA in the central nervous system.

We have shown that neuropsin is expressed in the neurons of the limbic system in the adult mouse. After the central nervous system was injured by incision or intraperitoneal kainate injection, neuropsin mRNA was induced in the peri-lesioned region. The cells in which neuropsin mRNA was induced were localized mainly in axon fiber pathways and closely associated to proteolipid protein (PLP) mRNA expressing oligodendrocytes.

Animals↗
PubMed1999

Late pathologic changes in guinea pig kidneys irradiated with conventional fractionation and hyperfractionation.

PURPOSE: The aim of this study was to determine the differences in renal damage particularly associated with the effect of a small dose per fraction with a constant total dose. METHODS AND MATERIALS: Guinea pigs, 12-week-old English Hartley females, were used. The animals were divided into five groups according to irradiation schedule: No irradiation (control group); 2.0 Gy x 1/day, 5 fraction (f)/week (wk), 40 f, total 80 Gy (Group CF-2.0 [CF = conventional fractionation]); 1.0 Gy x 2/day, 10 f/wk, 80 f, total 80 Gy (Group HF-1.0 [HF = hyperfractionation]); 3.0 Gy x 1/day, 5 f/wk, 27 f, total 81 Gy (Group CF-3.0); and 1.5 Gy x 2/day, 10 f/wk, 54 f, total 81 Gy (Group HF-1.5). Only unilateral irradiation was performed. A histologic analysis was performed before irradiation and at 6 and 12 months after the completion of irradiation. The severity and severity ratios of urinary tubule atrophy, the number of large nuclei per unit area in the renal tubules, the average diameter of the glomeruli, and the number of cells composing the glomerulus were used as parameters for evaluating renal damage. RESULTS: In Groups CF-2.0 and CF-3.0 (the conventional fractionation [CF] groups), all the renal tubules showed severe atrophy 12 months after irradiation. On the other hand, only 20% of the renal tubules showed slight atrophy in Group HF-1.0 at 12 months. In Group HF-1.5, 70% of the renal tubules were atrophic at 12 months. The number of large nuclei markedly increased in Groups HF-1.0 and HF-1.5 (the hyperfractionation [HF] groups) at 12 months, whereas the number was very low in the CF groups at 12 months. Only in Group HF-1.0 had the average diameter of glomeruli not shrunk at 12 months. The number of cells composing the glomerulus in the CF groups markedly decreased at 12 months. The number of cells in the HF groups was also reduced, however the reduction was not as severe as that observed in the CF groups. CONCLUSION: 1.0 Gy per fraction delivered by HF greatly reduces renal damage even in the 80 Gy-irradiated kidney, which is one of the most radiosensitive organs.

Animals↗
PubMed1999

Crystal structure of neuropsin, a hippocampal protease involved in kindling epileptogenesis.

Neuropsin is a novel serine protease, the expression of which is highly localized in the limbic areas of the mouse brain and which is suggested to be involved in kindling epileptogenesis and hippocampal plasticity. The 2.1-A resolution crystal structure of neuropsin provides the first three-dimensional view of one of the serine proteases highly expressed in the nervous system, and reveals a serine protease fold that exhibits chimeric features between trypsin and nerve growth factor-gamma (NGFgamma), a member of the kallikrein family. Neuropsin possesses an N-glycosylated "kallikrein loop" but forms six disulfide bonds corresponding to those of trypsin. The ordered kallikrein loop projects proline toward the active site to restrict smaller residues or proline at the P2 position of substrates. Loop F, which participates in forming the S3/S4 sites, is similar to trypsin rather than NGFgamma. The unique conformations of loops G and H form an S1 pocket specific for both arginine and lysine. These characteristic loop structures forming the substrate-binding site suggest the novel substrate specificity of neuropsin and give a clue to the design of its specific inhibitors.

Amino Acid Sequence↗
PubMed1999

New lead compounds for brassinosteroid biosynthesis inhibitors.

The first brassinosteroid biosynthesis inhibitor is reported. Among newly synthesized triazole derivatives, 4-(4-chlorophenyl)-2-phenyl-3-(1,2,4-triazoyl)butan-2-ol (6) was found to inhibit the growth of cress seedlings, and this inhibition was recovered by the treatment of brassinolide, suggesting that compound 6 primarily inhibits brassinosteroid biosynthesis.

Butanols↗
PubMed1999

Delayed visual NA potential in remitted schizophrenia: a new vulnerability marker for psychotic relapse under low-dose medication.

BACKGROUND: Lasting cognitive dysfunction throughout remission has been regarded as a biological vulnerability in schizophrenia, which may produce psychotic relapses with characteristic symptoms. Our hypothesis was that an abnormality in event-related potentials (ERPs) may be a neurophysiological marker of vulnerability to psychotic relapse in remitted schizophrenia. We conducted a 2-year follow-up study after evaluating ERP abnormalities to find a new ERP marker for schizophrenic relapse. METHODS: Visual ERPs were recorded from outpatients with remitted schizophrenia under maintenance pharmacotherapy (n = 44) and normal controls (n = 20) during a letter discrimination task. Based on the prospective study, the patients were divided into a relapse group (n = 20) and a nonrelapse group (n = 24). ERP findings that related to psychotic relapse within 2 years were analyzed. RESULTS: Compared with controls, the relapsers showed ERP abnormalities in the NA, N2, and P3 components, and the nonrelapsers in the P3 component. The peak latency of the NA potential was delayed significantly in the relapse group relative to the nonrelapse group, and predicted a psychotic relapse with about 90% probability. CONCLUSIONS: The delayed NA, which reflects early perceptual disorganization, may be a promising neurophysiological predictor of psychotic relapse in remitted schizophrenia under maintenance pharmacotherapy.

Adult↗
PubMed1999

Schizosaccharomyces pombe stt3+ is a functional homologue of Saccharomyces cerevisiae STT3 which regulates oligosaccharyltransferase activity.

The Saccharomyces cerevisiae STT3 (ScSTT3) gene encodes a protein which is involved in protein glycosylation via the regulation of oligosaccharyltransferase activity. We have cloned and isolated the Schizosaccharomyces pombe STT3 homologous gene (Spstt3+). The Spstt3+ gene encodes a protein consisting of 749 amino acid residues which has significant homology with ScStt3p and the mouse Stt3p-homologue Itm1p. Disruption of the Spstt3+ gene shows that this gene is essential for growth. Like Itm1, Spstt3+ partially suppressed the temperature sensitivity of the stt3-1 mutation of S. cerevisiae, indicating that Spstt3+ is a functional and structural homologue of the ScSTT3 gene.

Amino Acid Sequence↗