Search PubMed⌕ Search

Biomedical subjects

A Suzuki

Publications and source records attributed to A Suzuki.

At least 109 records · Page 6Linked to original sources
PubMed2001

No relationship between--141C Ins/Del polymorphism in the promoter region of dopamine D2 receptor and extrapyramidal adverse effects of selective dopamine D2 antagonists in schizophrenic patients: a preliminary study.

Previous studies have shown that subjects without Del alleles of the--141C Ins/Del polymorphism in the promoter region of the dopamine D2 receptor (DRD2) gene have lower DRD2 density that those with one or two Del alleles. The present study aims to investigate the relationship between the -141C Ins/Del polymorphism and extrapyramidal adverse effects of bromperidol and nemonapride, antipsychotic drugs with a selective and potent DRD2 antagonistic property, in schizophrenic inpatients. Twenty-seven patients were treated with bromperidol at a fixed-dose of 6, 12 or 18 mg/day, and 25 patients were treated with nemonapride at a fixed-dose of 18 mg/day. The duration of treatment with these drugs was 3 weeks. The Ins and Del alleles were determined by PCR. Extrapyramidal adverse effects were assessed by the Udvalg for Kliniske Undersøgelser side effects rating scale. The subjects consisted of 38 homozygotes of the Ins allele and 14 heterozygotes of the Ins and Del alleles. There were no significant differences in the incidence or severity of extrapyramidal adverse effects between patients with and without the Del allele. It is possible that this result was due to a lack of statistical power. However, the present study suggests that the--141C Ins/Del polymorphism is not related to the development of extrapyramidal adverse effects during acute-phase treatment with antidopaminergic agents.

Adult↗
PubMed2001

Amino acid residues in ribonuclease MC1 from bitter gourd seeds which are essential for uridine specificity.

The ribonuclease MC1 (RNase MC1), isolated from seeds of bitter gourd (Momordica charantia), consists of 190 amino acids and is characterized by specific cleavage at the 5'-side of uridine. Site-directed mutagenesis was used to evaluate the contribution of four amino acids, Asn71, Val72, Leu73, and Arg74, at the alpha4-alpha5 loop between alpha4 and alpha5 helices for recognition of uracil base by RNase MC1. Four mutants, N71T, V72L, L73A, and R74S, in which Asn71, Val72, Leu73, and Arg74 in RNase MC1 were substituted for the corresponding amino acids, Thr, Leu, Ala, and Ser, respectively, in a guanylic acid preferential RNase NW from Nicotiana glutinosa, were prepared and characterized with respect to enzymatic activity. Kinetic analysis with a dinucleoside monophosphate, CpU, showed that the mutant N71T exhibited 7.0-fold increased K(m) and 2.3-fold decreased k(cat), while the mutant L73A had 14.4-fold increased K(m), although it did retain the k(cat) value comparable to that of the wild-type. In contrast, replacements of Val72 and Arg74 by the corresponding amino acids Leu and Ser, respectively, had little effect on the enzymatic activity. This observation is consistent with findings in the crystal structure analysis that Asn71 and Leu73 are responsible for a uridine specificity for RNase MC1. The role of Asn71 in enzymatic reaction of RNase MC1 was further investigated by substituting amino acids Ala, Ser, Gln, and Asp. Our observations suggest that Asn71 has at least two roles: one is base recognition by hydrogen bonding, and the other is to stabilize the conformation of the alpha4-alpha5 loop by hydrogen bonding to the peptide backbone, events which possibly result in an appropriate orientation of the alpha-helix (alpha5) containing active site residues. Mutants N71T and N71S showed a remarkable shift from uracil to guanine specificity, as evaluated by cleavage of CpG, although they did exhibit uridine specificity against yeast RNA and homopolynucleotides.

Amino Acid Sequence↗
PubMed2001

Essential role of the nonreducing terminal alpha-mannosyl residues of the N-linked carbohydrate chain of bovine zona pellucida glycoproteins in sperm-egg binding.

It has been proposed that mammalian sperm bind species-specifically to carbohydrate chains of zona pellucida glycoproteins at fertilization. Although the sperm ligand carbohydrate chains have been characterized in mice and pigs, the existence of the ligands of other mammals remains unclear. In order to explore the bovine sperm ligand, two in vitro competition assay methods were applied. As a result, a high-mannose-type carbohydrate chain, Manalpha1-6(Manalpha1-3)Manalpha1-6(Manalpha1-3)Manbeta1-4GlcNAcbeta1-4GlcNAc, which is the major neutral chain in bovine egg zona glycoproteins, was shown to possess bovine sperm ligand activity. When nonreducing terminal alpha-mannosyl residues were eliminated from the zona glycoproteins by alpha-mannosidase digestion, the ligand activity was reduced, indicating that the alpha-mannosyl residues play an essential role in bovine sperm-egg binding. The number of sperm binding to eggs was reduced to about one-half after fertilization. The ligand-active high-mannose-type chain may be buried after fertilization, since its amount remains unchanged. Pretreatment of bovine sperm with the sperm ligand-carbohydrate chain significantly inhibited penetration of the sperm into oocyte and the male pronucleus formation. Thus, a correlation between the sperm ligand activity and in vitro fertilization rate was observed.

Animals↗
PubMed2001

Development of hematopoietic cells from embryonic stem cells.

Embryonic stem cells are pluripotent stem cells that can differentiate into all somatic cell lineages and germ lineage cells in vivo. In vitro differentiation capacity of the cells is rather limited compared with the in vivo pluripotency. However, differentiation into hematopoietic lineages is easily obtained, and it is a powerful tool to investigate hematopoietic development and differentiation. In this article, we describe a differentiation induction method that we established, the OP9 system, a unique method using the macrophage colony-stimulating factor-deficient stromal cell line OP9. The utility of the OP9 system includes hematopoietic development, differentiation, B-cell formation, osteoclast formation, and so on. The usefulness and limits of embryonic stem cell-derived hematopoietic cells in cell therapy are also discussed.

Animals↗
PubMed2001

Association between TaqI A dopamine D2 receptor polymorphism and therapeutic response to bromperidol: a preliminary report.

The relationship between TaqI A dopamine D2 receptor (DRD2) polymorphism and therapeutic response to bromperidol, a selective dopamine antagonist, was investigated in 30 acutely exacerbated schizophrenic inpatients. Patients were treated with bromperidol 6-18 mg/day for 3 weeks. Clinical symptoms were evaluated by the Brief Psychiatric Rating Scale (BPRS) before and 3 weeks after the treatment. The TaqI A genotypes were determined with the PCR method. There was no significant difference in the percentage improvement of total BPRS or 5-subgrouped symptoms (positive, negative, anxiety-depression, excitement and cognitive symptoms) after the 3-week treatment between the patients with A1 alleles (n=18) and those with no A1 allele (n=12). Although the present study is preliminary, it is suggested that the TaqI A DRD2 polymorphism is not associated with therapeutic response to bromperidol in schizophrenic patients.

Adult↗
PubMed2001

Glutamine and alpha-ketoglutarate are metabolite signals involved in nitrate reductase gene transcription in untransformed and transformed tobacco plants deficient in ferredoxin-glutamine-alpha-ketoglutarate aminotransferase.

Transformed tobacco (Nicotiana tabacum L.) plants with varying activities of the key enzyme of ammonia assimilation, ferredoxin-glutamine-alpha-ketoglutarate aminotransferase (Fd-GOGAT; EC 1.4.7.1), were used to examine the roles of ammonium, glutamine (Gln) and alpha-ketoglutarate (alpha-KG) in the regulation of nitrate reductase (NR; EC 1.6.6.1) transcript abundance. In wild-type leaf discs, NR mRNA abundance was increased following feeding with NO3-, sucrose and alpha-KG and decreased by feeding Gln. In air, leaves with decreased GOGAT accumulated Gln and alpha-KG simultaneously; this was accompanied by increased NR transcripts. The inhibition of NR transcription by Gln observed in leaf-disc experiments was therefore not observed in the low-Fd-GOGAT plants that accumulate Gln in vivo. The results suggest that the negative effect of Gln on NR transcript abundance was offset by high alpha-KG and that the relative amounts of alpha-KG and Gln are more important in controlling NR gene transcription than the concentration of either metabolite alone.

Amino Acid Oxidoreductases↗
PubMed2001

Dynamic changes in protein components of the tight junction during liver regeneration.

The construction of the hepatocyte tight junction is one of the most important events during liver regeneration leading to the reorganization of the bile canaliculi and the repolarization of hepatocytes after cell division. To understand this event at the molecular level, we examined the expression of tight junction proteins by Western blot analysis and their cellular localization by immunofluorescence microscopy in regenerating rat liver after two-thirds hepatectomy. The levels of tight junction components such as claudin-3, ZO-1 and atypical protein kinase C (PKC)-specific interacting protein (ASIP) increased two- to three-fold over control levels in coordination with a peak 2-3 days after partial hepatectomy, whereas occludin levels remained unchanged. The bile canaliculi outlined by tight junction components and actin filaments reveal significant morphological changes from 2-3 days after partial hepatectomy. During this period, claudin-3/ZO-1 and ASIP/ZO-1 were nearly co-localized, whereas occludin was locally reduced or almost absent on the bile canaliculi outlined by ZO-1 staining. The uncoupled localization of F-actin and tight junction components was often observed. The function of hepatocytes, as revealed by the serum bile acids level, was distorted temporally at an early stage of regeneration but mostly restored 3 days after partial hepatectomy. These observations suggest that the de novo construction of tight junctions proceeds mainly 2-3 days after partial hepatectomy in parallel with the cell polarization required for hepatocyte function. However, the complete normalization of the composition of the tight junction components, such as occludin and the association with F-actin, requires additional time, which may support the regeneration of fully polarized normal hepatocytes.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Prevalence of A-to-G mutation at nucleotide 3243 of the mitochondrial tRNA(Leu(UUR)) gene in Japanese patients with diabetes mellitus and end stage renal disease.

The A-to-G mutation at nucleotide 3243 of the mitochondrial tRNA(Leu(UUR)) gene (mt.3243A>G) is associated with both diabetes mellitus and myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Recently, this mutation was found in three diabetic subjects with progressive kidney disease, suggesting that it may be a contributing factor in the development of kidney disease in patients with diabetes. The aim of this study was to evaluate the contribution of this mutation to the development of end stage renal disease (ESRD) in patients with diabetes. The study group consisted of 135 patients with diabetes and ESRD. The control group consisted of 92 non-diabetic subjects with ESRD who were receiving hemodialysis. The mt.3243A>G mutation was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). We found the mt.3243A>G mutation in eight patients (8/135; 5.9%), all of whom were initially diagnosed with type II diabetes. Five of the eight patients were subsequently also diagnosed with MELAS. We did not find the mutation in any of the 92 nondiabetic subjects with ESRD. The prevalence of this mutation was 6.5-fold higher in patients with diabetes and ESRD than in those with diabetes alone (8/135 vs 5/550, respectively; chi2 = 13.704; P = 0.0002). The mt.3243A>G mutation may be a contributing genetic factor in the development of ESRD in Japanese patients with diabetes.

Adult↗
PubMed2001

T cell-specific loss of Pten leads to defects in central and peripheral tolerance.

PTEN, a tumor suppressor gene, is essential for embryogenesis. We used the Cre-loxP system to generate a T cell-specific deletion of the Pten gene (Pten(flox/-) mice). All Pten(flox/-) mice develop CD4+ T cell lymphomas by 17 weeks. Pten(flox/-) mice show increased thymic cellularity due in part to a defect in thymic negative selection. Pten(flox/-) mice exhibit elevated levels of B cells and CD4+ T cells in the periphery, spontaneous activation of CD4+ T cells, autoantibody production, and hypergammaglobulinemia. Pten(flox/-) T cells hyperproliferate, are autoreactive, secrete increased levels of Th1/Th2 cytokines, resist apoptosis, and show increased phosphorylation of PKB/Akt and ERK. Peripheral tolerance to SEB is also impaired in Pten(flox/-) mice. PTEN is thus an important regulator of T cell homeostasis and self-tolerance.

Animals↗
PubMed2001

Stimulation of sodium-dependent inorganic phosphate transport by activation of Gi/o-protein-coupled receptors by epinephrine in MC3T3-E1 osteoblast-like cells.

Recent data have shown that activation of Gi-protein-coupled receptors in osteoblast-like cells enhances the proliferation and differentiation of these cells. In the present study, we investigated the effect of epinephrine, an agonist of Gi-protein-coupled receptors in MC3T3-E1 cells, on Pi transport, type III Pi transporter expression, and the signaling mechanism(s) involved in this response. Epinephrine time- and dose-dependently stimulated sodium-dependent Pi transport and this effect was dependent on RNA and protein synthesis. This effect was associated with a related time-dependent increase in Pit-1 mRNA expression. Kinetic analysis indicated that the change in Pi transport activity induced by epinephrine was due to alteration in the maximal rate of Pi transport. Investigation of Pi transport stimulation by several adrenergic agonists and its inhibition by spiperone suggest that the effect of epinephrine on Pi transport was mediated by alpha1-adrenergic receptors. Pertussis toxin, which inactivates Gi/o proteins, significantly blunted the stimulatory effect of epinephrine on Pi transport. Analysis of the signaling pathways involved in this response has suggested a major role of protein kinase C and a small contribution from the mitogen-activated protein kinase Erk (MAPK(erk)). The results show that, in MC3T3-E1 osteoblast-like cells, activation of Gi/o-protein-coupled receptors induces stimulation of Pi transport. This effect is mediated by activation of protein kinase C and the MAPK(erk) pathway and probably involves the synthesis of Pit-1 transporters.

3T3 Cells↗
PubMed2001

Pressure-induced denaturation of monomer beta-lactoglobulin is partially irreversible: comparison of monomer form (highly acidic pH) with dimer form (neutral pH).

This study was conducted to assess the effect of high hydrostatic pressure on monomer beta-lactoglobulin (BLg) at acid pH by fluorescence spectroscopy under pressure and by circular dichroism (CD) and (1)H NMR spectroscopies after release of pressure. The intrinsic (tryptophan) fluorescence measurement and the study of 8-anilinonaphthalene-1-sulfonate (ANS) binding to BLg indicated that at pH 2.0 the recovery of center of spectral mass or ANS fluorescence was almost complete upon pressure release. No difference in (1)H NMR spectra was observed between pressurized and unpressurized BLg. In addition, NMR detection of the H/D exchange of aromatic protein indicated that the conformation of the vicinity of tryptophan residues could be refolded almost completely after release of pressure. These results seemingly confirm that the pressure-induced denaturation of BLg at pH 2.0 is reversible. However, cis-parinaric acid binding ability of pressurized BLg was largely lost, although its retinol binding ability was the same as its unpressurized one. Furthermore, CD spectra of the far-UV region and 2D NMR spectra evidently revealed the difference in the conformation of the molecule between unpressurized and pressurized BLg. These results are interpreted as an existence of partially fragile structure in the BLg molecule by high pressure.

Circular Dichroism↗
PubMed2001

Effects of genetic polymorphism of CYP1A2 inducibility on the steady-state plasma concentrations of trazodone and its active metabolite m-chlorophenylpiperazine in depressed Japanese patients.

The effects of a genetic polymorphism of inducibility of cytochrome P450 (CYP) 1A2 on the steady-state plasma concentrations of trazodone and its active metabolite, m-chlorophenylpiperazine, were studied in order to clarify if these steady-state plasma concentrations are dependent on the CYP1A2 polymorphism. Fifty-eight Japanese depressed patients received trazodone 150 mg/day at bedtime. The steady-state plasma concentrations of trazodone and m-chlorophenylpiperazine were measured in duplicate using high performance liquid chromatographic method, and were corrected to the mean body weight for analyses. A point mutation from guanine (wild type) to adenine (mutated type) at position -2964 in the 5'-flanking region of CYP1A2 gene was identified by polymerase chain reaction fragment length polymorphism method. The mean steady-state plasma concentration of trazodone, but not m-chlorophenylpiperazine was significantly (P<0.05) lower in smokers than in non-smokers. Twenty-two smokers had 16 homozygotes of the wild type allele, 5 heterozygotes of the wild type and mutated alleles, and one homozygote of the mutated allele. There was no significant difference in the mean steady-state plasma concentration of trazodone or m-chlorophenylpiperazine between smokers with no mutation and those with mutation, although one homozygote of the mutated allele had the highest steady-state plasma concentration of trazodone in smokers. The present study thus suggests that CYP1A2 polymorphism does not necessarily have predictive value of the steady-state plasma concentration of trazodone or m-chlorophenylpiperazine in most of the smokers treated with trazodone.

Adult↗
PubMed2001

SADS: A new component of Fas-DISC is the accelerator for cell death signaling and is downregulated in patients with colon carcinoma.

Fas is the death receptor, transducing cell death signaling upon stimulation by Fas ligand. During Fas-initiated cell death signaling, the formation of Fas-death inducing signaling complex (Fas-DISC) is the first step. Here we have identified a new component of Fas-DISC which we call 'small-accelerator for death signaling' (SADS). SADS cDNA encodes a 150 amino acid polypeptide (Mr = 16,700). During Fas-mediated cell death, SADS enhances the interaction of Fas-death domain-interactive factors (FADD) and procaspase-8, and deletion mutant analysis has identified FADD- and caspase-8-interactive domains in SADS. Inhibition or removal of SADS delays Fas-mediated cell death. In addition, we demonstrate the deletion or mutation of SADS in patients with colon carcinoma and that exogenous SADS expression in human colon carcinoma SW480 cells that lack SADS leads to re-acquisition of Fas-mediated cell death. Here, we propose that SADS is one of the cell death-associated factors and enhances Fas-DISC formation, especially FADD and procaspase-8 recruitment.

Apoptosis↗
PubMed2001

High-yield selection and extraction of two promoter-defined phenotypes of neural stem cells from the fetal human brain.

Neural stem and precursor cells reside in the ventricular lining of the fetal forebrain, and may provide a cellular substrate for brain repair. To selectively identify and extract these cells, we infected dissociated fetal human brain cells with adenoviruses bearing the gene for green fluorescence protein (GFP), placed under the control of enhancer/promoters for two genes (nestin and musashi1) that are expressed in uncommitted neuroepithelial cells. The cells were then sorted by fluorescence-activated cell sorting (FACS) on the basis of E/nestin- or P/musashi1-driven GFP expression. Both P/musashi1:hGFP- and E/nestin:EGFP-sorted cells were multipotent: limiting dilution with clonal expansion as neurospheres, in tandem with retroviral lineage analysis and xenograft to E17 and P0-2 rat forebrain, revealed that each phenotype was able to both self-renew and co-generate neurons and glia. Thus, fluorescent genes placed under the control of early neural promoters allow neural stem cells to be specifically targeted, isolated, and substantially enriched from the fetal human brain.

Adenoviridae↗
PubMed2001

Deletion of Pten in mouse brain causes seizures, ataxia and defects in soma size resembling Lhermitte-Duclos disease.

Initially identified in high-grade gliomas, mutations in the PTEN tumor-suppressor are also found in many sporadic cancers and a few related autosomal dominant hamartoma syndromes. PTEN is a 3'-specific phosphatidylinositol-3,4,5-trisphosphate (PI(3,4,5)P3) phosphatase and functions as a negative regulator of PI3K signaling. We generated a tissue-specific deletion of the mouse homolog Pten to address its role in brain function. Mice homozygous for this deletion (PtenloxP/loxP;Gfap-cre), developed seizures and ataxia by 9 wk and died by 29 wk. Histological analysis showed brain enlargement in PtenloxP/loxP;Gfap-cre mice as a consequence of primary granule-cell dysplasia in the cerebellum and dentate gyrus. Pten mutant cells showed a cell-autonomous increase in soma size and elevated phosphorylation of Akt. These data represent the first evidence for the role of Pten and Akt in cell size regulation in mammals and provide an animal model for a human phakomatosis condition, Lhermitte-Duclos disease (LDD).

Animals↗
PubMed2001

A rapid monitoring system of human herpesviruses reactivation by LightCycler in stem cell transplantation.

To establish a practical monitoring system of human herpesviruses reactivation in patients undergoing stem cell transplantation, we developed a new, very rapid, highly sensitive, and quantitative PCR assay for accurate measurement of human cytomegalovirus (CMV), human herpesvirus 6 (HHV-6) and Epstein-Barr virus (EBV) DNA using LightCycler. The LightCycler system revealed that there was a linear correlation in the wide range of viral template DNA at the indicated number of PCR cycles. Peripheral blood cells were collected from 16 patients undergoing stem cell transplantation. The cut-off level of CMV and HHV-6 was assessed as 10(2) copies/microg and that of EBV as 10(3). High numbers of CMV genomes were detected in 3/13 patients after transplant, and reactivation of HHV-6 was frequently seen, whereas none of the patient showed an elevation of EBV genome copies until the end of the observation period. In the present study, the reactivation of beta herpesviruses is associated with the occurrence of thrombotic microangiopathy (TMA) in two patients undergoing allogeneic BMT. Therefore, it may contribute in clarifying the pathological potential of human herpesviruses using a large number of clinical samples. Our results suggest that this system may be useful for monitoring viral reactivation.

Adolescent↗