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T Ueda

Publications and source records attributed to T Ueda.

At least 451 records · Page 25Linked to original sources
PubMed1997

Depression of T-cell epitope generation by stabilizing hen lysozyme.

Conformational stability of proteins is an important factor that determines their resistance/susceptibility to proteolytic digestion. Intracellular proteolysis is the key step in antigen presentation events for protein antigens; hence, it is likely that increasing protein stability reduces the antigenicity of proteins. We prepared three hen egg white lysozyme derivatives possessing different stabilities by chemical modification to clarify the relationship between conformational stability and the antigenicity of the protein. One of the derivatives was conformationally unstabilized by removing one intramolecular disulfide bond, whereas the two others were stabilized by the addition of an intramolecular cross-link. The antigenicity of these derivatives was evaluated using hen egg white lysozyme-specific T-cell hybridoma cells and a B-lymphoma cell line, A20, as antigen-presenting cells. With an increase in conformational stability, the T-cell response decreased. However, the reduction was not derived from the inefficiency of internalization to A20 cells nor the alteration of antigenicity by chemical modifications. Moreover, from analyses of their susceptibility to proteolysis and the kinetics of presentation of the T-cell epitope, it was confirmed that increasing protein stability led to the depression of T-cell epitope generation by increasing resistance to proteolysis. These results have an important implication in devising a new strategy for manipulating T-cell response by the stability of protein antigen.

Animals↗
PubMed1997

An oocyte-specific methylation imprint center in the mouse U2afbp-rs/U2af1-rs1 gene marks the establishment of allele-specific methylation during preimplantation development.

An oocyte-specific methylation imprint mark region, consisting of approximately 200 bp from the mouse imprinted gene U2afbp-rs, was identified within an area containing a CpG island and a short tandem repeat sequence. The oocyte-specific methylation was preserved in fertilized eggs and then expanded on the repressed maternal allele during preimplantation development until the adult methylation pattern was achieved by 12.5 days of embryonic development. These results indicate that the oocyte-specific imprinting mark region acts as a center in establishing the hypermethylated region on the repressed maternal allele. Furthermore, a region that is hypermethylated in both gametes was identified but its hypermethylation was conserved only on the maternal allele during preimplantation development, suggesting that some factor(s) inherited from oocytes may act to maintain hypermethylation on the maternal allele.

Alleles↗
PubMed1997

Screening for imprinted genes by allelic message display: identification of a paternally expressed gene impact on mouse chromosome 18.

A systematic screen termed the allelic message display (AMD) was developed for the hunting of imprinted genes. In AMD, differential display PCR is adopted to image allelic expression status of multiple polymorphic transcripts in two parental mouse strains, reciprocal F1 hybrids and pooled backcross progenies. From the displayed patterns, paternally and maternally expressed transcripts can be unequivocally identified. The effectiveness of AMD screening was clearly demonstrated by the identification of a paternally expressed gene Impact on mouse chromosome 18, the predicted product of which belongs to the YCR59c/yigZ hypothetical protein family composed of yeast and bacterial proteins with currently unknown function. In contrast with previous screening methods necessitating positional cloning efforts or generation of parthenogenetic embryos, this approach requires nothing particular but appropriately crossed mice and can be readily applied to any tissues at various developmental stages. Hence, AMD would considerably accelerate the identification of imprinted genes playing pivotal roles in mammalian development and the pathogenesis of various diseases.

Alleles↗
PubMed1997

Location of KAI1 on the short arm of human chromosome 11 and frequency of allelic loss in advanced human prostate cancer.

BACKGROUND: We recently isolated the KAI1 gene, a metastasis suppressor gene for prostate cancer, from human chromosome region 11p13-cen-containing rat prostate cancer cells. The present study was performed to further locate the region of the KAI1 gene on the short arm of chromosome 11, and to examine whether loss of this region is significant during progression of human prostate cancer. METHODS: The small portion of human chromosome 11 (i.e., 11p13-cen) was reintroduced into highly metastatic rat prostate cancer cells by using microcell-mediated chromosome transfer. Loss of heterozygosity (LOH) at polymorphic microsatellite loci on the human chromosome 11 was examined in human prostate cancer tissues. RESULTS: The minimum region of human chromosome 11 that contained the KAI1 gene was located on the proximal region of 11p11.2 divided by the D11S554 locus. The percentage of LOH or allelic imbalance at the D11S1344 locus, which is located on the same region as the KAI1 locus, in metastasis tissues from autopsy cases who died from metastatic prostate cancer was 70% (7 of 10 informative cases), whereas the percentages in primary tumors from the same cases and from cases with clinically localized prostate cancer were 33% (3 of 9 informative cases) and 8% (1 of 12 informative cases), respectively. CONCLUSIONS: These findings demonstrate a high frequency of LOH or allelic imbalance at the centromeric region of 11p, which contains the KAI1 gene in advanced prostate cancer.

Adenocarcinoma↗
PubMed1997

cDNA sequence of a translational elongation factor Ts homologue from Caenorhabditis elegans: mitochondrial factor-specific features found in the nematode homologue peptide.

The cDNA for a homologue of elongation factor Ts which probably functions in mitochondria has been sequenced from a nematode Caenorhabditis elegans. The deduced amino acid sequence (316 amino acids long) has a possible transit peptide sequence at the amino terminus and several common specific features for mammalian mitochondrial EF-Ts. The amino acid identities in the protein from C. elegans compared with those of bovine mitochondria and Escherichia coli are 29.5% and 24.0%, respectively. The C. elegans sequence was classified as a long EF-Ts (ca. 280 amino acids long) similar to peptides from mammalian mitochondria and eubacteria other than Thermus and cyanobacteria (except Spirulina platensis), rather than short EF-Ts (ca. 200 amino acids long) as those of Thermus, cyanobacteria and plastids.

Amino Acid Sequence↗
PubMed1997

The crystal structure of the nucleotide-free alpha 3 beta 3 subcomplex of F1-ATPase from the thermophilic Bacillus PS3 is a symmetric trimer.

BACKGROUND: F1-ATPase, an oligomeric assembly with subunit stoichiometry alpha 3 beta 3 gamma delta epsilon, is the catalytic component of the ATP synthase complex, which plays a central role in energy transduction in bacteria, chloroplasts and mitochondria. The crystal structure of bovine mitochondrial F1-ATPase displays a marked asymmetry in the conformation and nucleotide content of the catalytic beta subunits. The alpha 3 beta 3 subcomplex of F1-ATPase has been assembled from subunits of the moderately thermophilic Bacillus PS3 made in Escherichia coli, and the subcomplex is active but does not show the catalytic cooperativity of intact F1-ATPase. The structure of this subcomplex should provide new information on the conformational variability of F1-ATPase and may provide insights into the unusual catalytic mechanism employed by this enzyme. RESULTS: The crystal structure of the nucleotide-free bacterial alpha 3 beta 3 subcomplex of F1-ATPase, determined at 3.2 A resolution, shows that the oligomer has exact threefold symmetry. The bacterial beta subunits adopt a conformation essentially identical to that of the nucleotide-free beta subunit in mitochondrial F1-ATPase; the alpha subunits have similar conformations in both structures. CONCLUSIONS: The structures of the bacterial F1-ATPase alpha and beta subunits are very similar to their counterparts in the mitochondrial enzyme, suggesting a common catalytic mechanism. The study presented here allows an analysis of the different conformations adopted by the alpha and beta subunits and may ultimately further our understanding of this mechanism.

Amino Acid Sequence↗
PubMed1997

Inhibitory action of sphingosine or ceramide on amylase secretion from isolated rat pancreatic acini.

Sphingosine and ceramide, products of sphingomyelin hydrosis by sphingomyelinase, have recently been regarded as second messengers for cell biological actions. On the other hand, exocrine pancreas is a typical organ to perform regulatory secretion of digestive enzymes, depending upon extracellular signals. We investigated the effects of sphingosine or ceramide on amylase secretion from isolated rat pancreatic acini. Either sphingosine or cell-permeable ceramide inhibits CCK8- or carbachol-induced enzyme secretion from isolated rat pancreatic acini in a dose-dependent manner. Sphingosine or ceramide itself does not affect basal amylase secretion from the acini. Ceramide also inhibits NaF-induced amylase secretion, indicating that it acts post the activation of receptor-linked GTP-binding protein. In our experiments, ceramide inhibited Ca2+ ionophore-induced amylase secretion, but not phorbol ester-induced secretion. These results indicate that ceramide affects secretory processes post intracellular Ca2+ mobilization in the exocrine pancreas.

Amylases↗
PubMed1997

Affinity for alpha-tocopherol transfer protein as a determinant of the biological activities of vitamin E analogs.

alpha-Tocopherol transfer protein (alphaTTP), a product of the gene which causes familial isolated vitamin E deficiency, plays an important role in determining the plasma vitamin E level. We examined the structural characteristics of vitamin E analogs required for recognition by alphaTTP. Ligand specificity was assessed by evaluating the competition of non-labeled vitamin E analogs and alpha-[3H]tocopherol for transfer between membranes in vitro. Relative affinities (RRR-alpha-tocopherol = 100%) calculated from the degree of competition were as follows: beta-tocopherol, 38%; gamma-tocopherol, 9%; delta-tocopherol, 2%; alpha-tocopherol acetate, 2%; alpha-tocopherol quinone, 2%; SRR-alpha-tocopherol, 11%; alpha-tocotrienol, 12%; trolox, 9%. Interestingly, there was a linear relationship between the relative affinity and the known biological activity obtained from the rat resorption-gestation assay. From these observations, we conclude that the affinity of vitamin E analogs for alphaTTP is one of the critical determinants of their biological activity.

Animals↗
PubMed1997

A protein factor that inhibits ATP-dependent glutamate and gamma-aminobutyric acid accumulation into synaptic vesicles: purification and initial characterization.

Glutamate, the major excitatory neurotransmitter in the mammalian central nervous system, is transported into and stored in synaptic vesicles. We have purified to apparent homogeneity a protein from brain cytosol that inhibits glutamate and gamma-aminobutyric acid uptake into synaptic vesicles and have termed this protein "inhibitory protein factor" (IPF). IPF refers to three distinct proteins with relative molecular weights of 138,000 (IPF alpha), 135,000 (IPF beta), and 132,000 (IPF gamma), respectively. Gel filtration and sedimentation data suggest that all three proteins share an elongated structure, identical Stokes radius (60 A), and identical sedimentation coefficient (4.3 S). Using these values and a partial specific volume of 0.716 ml/g, we determined the native molecular weight for IPF alpha to be 103,000. Partial sequence analysis shows that IPF alpha is derived from alpha fodrin, a protein implicated in several diverse cellular activities. IPF alpha inhibits ATP-dependent glutamate uptake into purified synaptic vesicles with an IC50 of approximately 26 nM, while showing no ability to inhibit ATP-independent uptake at concentrations up to 100 nM. Moreover, IPF alpha inhibited neither norepinephrine uptake into chromaffin vesicles nor Na+-dependent glutamate uptake into synaptosomes. However, IPF alpha inhibited uptake of gamma-aminobutyric acid into synaptic vesicles derived from spinal cord, suggesting that inhibition may not be limited to glutamatergic systems. We propose that IPF could be a novel component of a presynaptic regulatory system. Such a system might modulate neurotransmitter accumulation into synaptic vesicles and thus regulate the overall efficacy of neurotransmission.

Adenosine Triphosphate↗
PubMed1997

p53 and MDM2 alterations in osteosarcomas: correlation with clinicopathologic features and proliferative rate.

BACKGROUND: Alterations of the p53 gene and of MDM2, a gene coding for a p53 binding protein, have been implicated in the pathogenesis of osteosarcoma (OS). METHODS: To determine the frequency of alterations of the p53/MDM2 pathway in OS and their possible correlation with clinicopathologic features, MDM2 copy number and p53 protein levels were determined in a series of 83 samples of OS by quantitative Southern blot analysis and immunohistochemistry, respectively. RESULTS: Positivity for p53 was found in 26.5% and MDM2 amplification in 6.6% of the samples analyzed in a mutually exclusive fashion with one exception. Overall, alterations of the p53/MDM2 pathway occurred in 34% of cases; p53 accumulation was not associated with a higher proliferative rate. The mean age of patients with p53 positive OS (40 years) was older than that of the p53 negative group (28 years) (P < 0.04). Furthermore, three of the four cases of OS arising in Paget's disease showed p53 accumulation. CONCLUSIONS: Alterations of the p53/MDM2 pathway are frequent in OS and usually represent mutually exclusive tumorigenic events. p53 does not appear to be a major determinant of proliferative rate in OS.

Adult↗
PubMed1997

The 'polysemous' codon--a codon with multiple amino acid assignment caused by dual specificity of tRNA identity.

In some Candida species, the universal CUG leucine codon is translated as serine. However, in most cases, the serine tRNAs responsible for this non-universal decoding (tRNA(Ser)CAG) accept in vitro not only serine, but also, to some extent, leucine. Nucleotide replacement experiments indicated that m1G37 is critical for leucylation activity. This finding was supported by the fact that the tRNA(Ser)CAGs possessing the leucylation activity always have m1G37, whereas that of Candida cylindracea, which possesses no leucylation activity, has A37. Quantification of defined aminoacetylated tRNAs in cells demonstrated that 3% of the tRNA(Ser)CAGs possessing m1G37 were, in fact, charged with leucine in vivo. A genetic approach using an auxotroph mutant of C.maltosa possessing this type of tRNA(Ser)CAG also suggested that the URA3 gene inactivated due to the translation of CUG as serine was rescued by a slight incorporation of leucine into the polypeptide, which demonstrated that the tRNA charged with multiple amino acids could participate in the translation. These findings provide the first evidence that two distinct amino acids are assigned by a single codon, which occurs naturally in the translation process of certain Candida species. We term this novel type of codon a 'polysemous codon'.

Amino Acids↗
PubMed1997

Effect of theophylline on adaptation of the heart to myocardial ischemia during percutaneous transluminal coronary angioplasty in patients with stable angina pectoris.

This study was designed to examine whether theophylline, an adenosine receptor antagonist, affects cardiac adaptation to ischemia during progression of repetitive balloon inflations of percutaneous transluminal coronary angioplasty (PTCA). Theophylline abolished this cardiac adaptation, suggesting that endogenous adenosine is a key mediator for cardiac adaptation during PTCA.

Adaptation, Physiological↗
PubMed1997

Detection of a prothrombotic state after acute aerobic exercise.

Angina, myocardial infarction, and sudden cardiac death are associated with thrombus formation in coronary arteries. It is generally believed that these conditions benefit from long-term exercise. However, the evidence for such amelioration or prevention is inconclusive and so is the mechanism through which long-term exercise exerts its beneficial effect on various ischaemic conditions. Because of the thrombotic events, the effects of exercise on platelet reactivity, blood coagulation and fibrinolysis have been extensively studied, but the findings are not consistent (1-9). This is mainly due to methodological problems. Analysis of platelet response to a variety of agonists and the dozen of coagulation and fibrinolysis variables makes the assessment of the overall platelet function, coagulation and fibrinolysis status extremely difficult.

Adult↗
PubMed1997

Altering substrate specificity of Bacillus sp. SAM1606 alpha-glucosidase by comparative site-specific mutagenesis.

The Bacillus sp. SAM1606 alpha-glucosidase with a broad substrate specificity is the only known alpha-glucosidase that can hydrolyze alpha,alpha'-trehalose efficiently. The enzyme exhibits a very high sequence similarity to the oligo-1,6-glucosidases (O16G) of Bacillus thermoglucosidasius and Bacillus cereus which cannot act on trehalose. These three enzymes share 80% identical residues within the conserved regions (CR), which have been suggested to be located near or at the active site of the alpha-amylase family enzymes. To identify by site-specific mutagenesis the critical residues that determine the broad substrate specificity of the SAM1606 enzyme we compared the CR sequences of these three glucosidases and selected five targets to be mutagenized in SAM1606 alpha-glucosidase, Met76, Arg81, Ala116, Gly273, and Thr342. These residues have been specifically replaced by in vitro mutagenesis with Asn, Ser, Val, Pro, and Asn, respectively, as in the Bacillus O16G. The 12 mutant enzymes with single and multiple substitutions were expressed and characterized kinetically. The results showed that the 5-fold mutation virtually abolished the affinity of the enzyme for alpha, alpha'-trehalose, whereas the specificity constant for the hydrolysis of isomaltose, a good substrate for both the SAM1606 enzyme and O16G, remained essentially unchanged upon the mutation. This loss in affinity for trehalose was critically governed by a Gly273 --> Pro substitution, whose effect was specifically enhanced by the Thr342 --> Asn substitution in the 5-fold and quadruple mutants. These results provide evidence for the differential roles of the amino acid residues in the CR in determining the substrate specificity of the alpha-glucosidase.

Amino Acid Sequence↗
PubMed1997

Molecular cloning and characterization of the chromosomal gene for human lactoperoxidase.

Lactoperoxidase (LPO) is an oxidoreductase secreted into milk, and plays an important role in protecting the lactating mammary gland and the intestinal tract of the newborn infants against pathogenic microorganisms. In this study, the human LPO chromosomal gene was molecularly cloned, and its gene organization was determined. The human LPO gene was found to be arranged with the myeloperoxidase (MPO) gene in a tail-to-tail manner. Similar to the human MPO and eosinophil peroxidase (EPO) genes, the human LPO gene is split by 11 introns and spans 28 kb. Unlike most introns in mammalian gene, the 5' splice donor sequence of intron 11 starts with GC instead of GT. When the minigene comprised of exon 11, intron 11 and exon 12 of the human LPO gene was introduced into COS cells, the correct splicing of the intron was found, suggesting the intron 11 of the human LPO gene is functional. The coding sequence of human LPO consists of 2136 bp, and codes for a protein of 712 amino acids. The amino acid sequence of human LPO has 51% similarity with those of both human MPO and EPO, suggesting that these peroxidase genes have evolved from a common ancestral gene. On the other hand, the nucleotide sequences of the 5' promoter regions of these peroxidase genes exhibit no similarity among them, which agrees with their tissue-specific expression.

Amino Acid Sequence↗
PubMed1997

Neoadjuvant chemotherapy for pediatric osteosarcoma patients.

BACKGROUND: Since the first trial for chemotherapy in children with osteosarcoma in 1977, the survival rate has gradually improved. Currently, more than 60% of all patients are cured, mainly because of the introduction of intensive chemotherapy using doxorubicin, high dose methotrexate, and cisplatin. The increased survival rates have promoted efforts to improve the quality of survival through the use of limb salvage surgery rather than amputation. Improvements in chemotherapeutic efficacy should result in a more favorable outcome and better function of the affected limb. The current study evaluated factors that influence chemotherapy so that a higher survival rate could be obtained. METHODS: Three chemotherapy regimens comprised of doxorubicin, high dose methotrexate, cisplatin, and ifosfamide were retrospectively analyzed in 67 pediatric osteosarcoma patients. Twenty-three patients were treated with chemotherapy comprised of high dose methotrexate and doxorubicin (OOS-A regimen), 25 were treated with OOS-A with the addition of cisplatin (OOS-B), and 19 were treated with OOS-B with the addition of ifosfamide (OOS-C). RESULTS: The OOS-A regimen was poorest in terms of survival (40.6%) compared with the OOS-B (67.5%) and OOS-C regimens (72.5%) (P < 0.001). There was no significant difference in survival between the OOS-B and OOS-C regimens. In the OOS-B regimen, patients who received a higher relative dose intensity showed a better prognosis. CONCLUSIONS: These findings show that doxorubicin, high dose methotrexate, and cisplatin are the most potent drugs and suggest that it is more important to maintain the dose intensity of the regimen to improve survival rather than add a new drug.

Adolescent↗