Search PubMed⌕ Search

Biomedical subjects

T Tamura

Publications and source records attributed to T Tamura.

At least 469 records · Page 26Linked to original sources
PubMed1996

Newly identified pair of proteasomal subunits regulated reciprocally by interferon gamma.

Interferon (IFN) gamma induces replacements of the proteasomal subunits X and Y by LMP7 and LMP2, respectively, resulting in an alteration of the proteolytic specificity. We found a third pair of proteasome subunits expressed reciprocally in response to IFN-gamma. Molecular cloning of a cDNA encoding one subunit designated as Z, downregulated by IFN-gamma, showed that it is a novel proteasomal subunit with high homology to MECL1, which is markedly induced by IFN-gamma. Thus, IFN-gamma induces subunit replacements of not only X and Y by LMP7 and LMP2, respectively, but also of Z by MECL1, producing proteasomes responsible for immunological processing of endogenous antigens. When processed from their precursors, three pairs of the 10 homologous, but distinct, beta-type subunits of eukaryotic proteasomes, that is, X/LMP7, Y/LMP2, and Z/MECL1, have an NH2-terminal threonine residue, assumed to be part of a catalytic center. These findings suggest that the altered molecular organization of the proteasome induced by IFN-gamma may be responsible for acquisition of its functional change.

Amino Acid Sequence↗
PubMed1996

Structures of the rat proteasomal ATPases: determination of highly conserved structural motifs and rules for their spacing.

We have isolated rat cDNAs for all of the five known proteasomal ATPases. The protein sequences of rat TBP1, TBP7, MSS1, S4, and SUG1 predicted from the open reading frames consist of 439, 418, 433, 440, and 406 amino acid residues, respectively, and exhibit striking similarities to each human counterpart with only several amino acid substitutions. These five rat ATPases are also highly homologous with each other. The N-terminal region in rat TBP1, TBP7, and SUG1 contains a heptad repeat of hydrophobic amino acids reminiscent of a leucine zipper. Also, in the central region of each rat ATPase, we found four conserved motifs, Gx4GKT, DEID, SAT, and H/QRxGRx2R, that are characteristic of a large family of ATP-dependent RNA/DNA helicases. The spacing between individual motifs was strictly conserved in the rat ATPases. These findings suggest a common function of the rat proteasomal ATPases in ATP-dependent RNA/DNA unwinding.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1996

Three-year follow-up after implantation of metallic coronary-artery stents.

BACKGROUND: Coronary-artery stents are known to reduce rates of restenosis after coronary angioplasty, but it is uncertain how long this benefit is maintained. METHODS: We evaluated clinical and angiographic follow-up information for up to three years after the implantation of Palmaz-Schatz metallic coronary-artery stents in 143 patients with 147 lesions of native coronary arteries. RESULTS: The rate of survival free of myocardial infarction, bypass surgery, and repeated coronary angioplasty for stented lesions was 74.6 percent at three years. After 14 months, revascularization of the stented lesion was necessary in only three patients (2.1 percent). In contrast, coronary angioplasty for a new lesion was required in 11 patients (7.7 percent). Follow-up coronary angiography of 137 lesions at six months, 114 lesions at one year, and 72 lesions at three years revealed a decrease in minimal luminal diameter from 2.54 +/- 0.44 mm immediately after stent implantation to 1.87 +/- 0.56 mm at six months, but no further decrease in diameter at one year (in patients with paired angiograms, 1.95 +/- 0.49 mm at both six months and one year). Significant late improvement in luminal diameter was observed at three years (in patients with paired angiograms, 1.94 +/- 0.48 mm at six months and 2.09 +/- 0.48 mm at three years; P < 0.001). CONCLUSIONS: Clinical and angiographic outcomes up to three years after coronary-artery stenting were favorable, with a low rate of revascularization of the stented lesions. Late improvement in luminal diameter appears to occur between six months and three years.

Aged↗
PubMed1996

Transcriptional regulation of the c-fms proto-oncogene mediated by granulocyte/macrophage colony-stimulating factor (GM-CSF) in murine cell lines.

Differentiation of blood cells is paralleled by a timely ordered expression of cytokine receptor genes. We show here that the expression of the c-fms gene which encodes the lineage-specific receptor for macrophage colony-stimulating factor (M-CSF or CSF-1) is directly linked to ligand-mediated activation of the receptor for the granulocyte/macrophage colony-stimulating factor (GM-CSF). In interleukin-3 (IL-3) dependent multipotent progenitor cells, FDC-Pmix GMV#2 cells, GM-CSF treatment results in the rapid formation of full-length c-fms transcripts. Surprisingly, this upregulation of c-fms transcripts is also observed in mouse NIH3T3 fibroblasts stably transfected with genes coding for the alpha- and beta-subunits of the GM-CSF receptor. These results indicate a direct control by the GM-CSF receptor that takes place regardless of cell differentiation. Furthermore, a 2.1 kb genomic fragment containing the c-fms proximal promoter directs GM-CSF-inducible expression of a reporter gene, suggesting a regulation of c-fms gene expression on the transcriptional level.

3T3 Cells↗
PubMed1996

A new selenoprotein from human lung adenocarcinoma cells: purification, properties, and thioredoxin reductase activity.

We report the isolation and characterization of a new selenoprotein from a human lung adenocarcinoma cell line, NCI-H441. Cells were grown in RPMI-1640 medium containing 10% (vol/vol) fetal bovine serum and 0.1 microM [75Se]selenite. A 75Se-labeled protein was isolated from sonic extracts of the cells by chromatography on DE-23, phenyl-Sepharose, heparin-agarose, and butyl-Sepharose. The protein, a homodimer of 57-kDa subunits, was shown to contain selenium in the form of selenocysteine; hydrolysis of the protein alkylated with either iodoacetate or 3-bromopropionate yielded Se-carboxymethyl-selenocysteine or Se-carboxyethyl-selenocysteine, respectively. The selenoprotein showed two isoelectric points at pH 5.2 and pH 5.3. It was distinguished from selenoprotein P by N-glycosidase assay and by the periodate-dansylhydrazine test, which indicated no detectable amounts of glycosyl groups on the protein. The selenoprotein contains FAD as a prosthetic group and catalyzes NADPH-dependent reduction of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), and reduction of insulin in the presence of thioredoxin (Trx). The specific activity was determined to be 31 units/mg by DTNB assay. Apparent Km values for DTNB, Escherichia coli Trx, and rat Trx were 116, 34, and 3.7 microM, respectively. DTNB reduction was inhibited by 0.2 mM arsenite. Although the subunit composition and catalytic properties are similar to those of mammalian thioredoxin reductase (TR), the human lung selenoprotein failed to react with anti-rat liver TR polyclonal antibody in immunoblot assays. The selenocysteine-containing TR from the adenocarcinoma cells may be a variant form distinct from rat liver TR.

Adenocarcinoma↗
PubMed1996

Thrombotic occlusion of the coronary artery associated with accidental detachment of undeployed Palmaz-Schatz stent.

We describe a case of coronary stenting in which accidental detachment of the Palmaz-Schatz stent induced thrombotic occlusion of the coronary artery. This case suggests that careful consideration of the risk involving coronary occlusion is mandatory on deciding the therapeutic strategy of the cases in which the unexpanded coronary stent cannot be retrieved following successful deployment.

Adult↗
PubMed1996

2-D Crystallization of the Rhodococcus 20S Proteasome

The 2D crystallization method using a liquid-liquid interface has been applied to the Rhodococcus 20S proteasome. Two types of ordered arrays were obtained, both large enough for high-resolution analysis. The first one is a hexagonal close-packed array, whereas the second one has fourfold symmetry. By image analysis based on a real space correlation averaging technique, the close-packed array was found to be hexagonally packed but the molecules had complete rotational freedom. The fourfold array is, however, a true crystal with p4 symmetry. Lattice constants are a = b = 20.0 nm and the unit cell of this crystal contains two proteasomes. The diffraction pattern computed from the original picture shows the spots up to (4.5) that correspond to 3.1 nm resolution. After applying an unbending procedure, the diffraction pattern shows spots extending to 1.8 nm resolution.

Journal Article↗
PubMed1996

Protein and gene structures of 20S and 26S proteasomes.

The two types of proteasomes with apparent sedimentation coefficients of 20S and 26S consist of a number of heterogeneous polypeptides and are unusually large protein complexes of approximately 750 kDa and 2000 kDa, respectively. The 26S proteasome is a cylindrical caterpillar-shaped complex with a symmetrical assembly of a four-layered central 20S proteasome and two terminal 22S regulators each with a V-like structure. The central core and the terminal structures are formed by multiple polypeptides with molecular masses of 21-31 kDa and 28-112 kDa, respectively. We have been studying their detailed structures by protein-chemical and molecular biological techniques. In this review, we summarize the structural features of eukaryotic 20S and 26S proteasomes. We also discuss the possible function(s) of the terminal multi-protein regulator complex based on current information.

Animals↗
PubMed1996

Protein kinase C-dependent modulation of stimulatory guanine nucleotide binding protein of fetal rat skin keratinocytes.

Although the protein kinase C (PKC) activator, phorbol 12-myristate 13-acetate (PMA) has been known to induce heterologous desensitization of the epidermal adenylate cyclase, the precise mechanism of PMA action remains unknown. Effects of PMA on the receptor-G-protein-adenylate cyclase system of fetal rat skin keratinocytes (FRSK) were investigated. Choleratoxin catalysed the ADP ribosylation of 45 kDa and 52 kDa membrane proteins and islet activating protein (IAP) catalysed the ADP ribosylation of a 40 kDa membrane protein. Incubation of FRSK with PMA decreased the cholera toxin-catalysed ADP ribosylation of the membrane protein, but not the IAP-catalysed ADP ribosylation. The effect of PMA on the cholera toxin-catalysed ADP ribosylation was inhibited by the PKC inhibitor, H-7 (1-(5-isoquinolinesulfonyl)-2-methyl piperazine dihydrochloride). 1-Oleoyl-2-acetylglycerol (OAG), a membrane-permeable diacylglycerol analogue, also decreased the cholera toxin-catalysed ADP ribosylation, but 4-0-methyl PMA, a very weak PKC activator, had no effect. Keratinocytes are known to express the guanine nucleotide binding proteins, Gsalpha, Gi2alpha, and Gi3alpha. Immunoblot analysis of the PMA-treated FRSK showed no detectable difference in the amount of Gsalpha, Gi2alpha, Gi3alpha, or the beta subunit of the G-protein. PMA significantly decreased the beta-adrenergic adenylate cyclase response and cholera toxin-induced cyclic AMP accumulation, while it markedly increased forskolin-induced cyclic AMP accumulation. These results indicate that phorbol esters affect the stimulatory guanine nucleotide binding protein (Gs) of FRSK via a PKC-dependent pathway.

Adenosine Diphosphate Ribose↗
PubMed1996

Serum ferritin: a predictor of early spontaneous preterm delivery.

OBJECTIVE: To identify biochemical indices for iron and protein nutriture as well as acute-phase reactants as predictors of preterm delivery. METHODS: In this nested case-control study, serum samples were obtained at about 24 weeks' gestation from 94 indigent multiparas. These cases were defined based on having a spontaneous delivery of 32 weeks or less (n = 31) with two control groups, one delivering spontaneously at 33-36 weeks (n = 32) and the other delivering spontaneously at 37 weeks or more (n = 31). The concentrations of iron, ferritin, transferrin, transferrin saturation, and transferrin receptor were measured as indices of iron status. The concentrations of acute-phase reactants, including C-reactive protein, alpha-2-macroglobulin, beta-2-microglobulin and ceruloplasmin, were also measured, along with albumin, prealbumin, retinol-binding protein, copper, and zinc. RESULTS: Serum ferritin concentrations were negatively correlated with gestational age at birth (P = .034). For subjects having serum ferritin levels above the median compared with those below, the odds ratio of having an early spontaneous preterm delivery was 2.99 (95% confidence interval 1.13-7.89). The other indices, including iron status and the acute-phase reactants, were not significantly associated with gestational age at birth. CONCLUSION: Elevated serum ferritin levels during the second trimester are predictive of early spontaneous preterm delivery, possibly because these reflect an acute-phase reaction to subclinical infections that are closely associated with premature delivery.

Adolescent↗
PubMed1996

Effect of angiotensin-converting enzyme gene polymorphism on pregnancy outcome, enzyme activity, and zinc concentration.

OBJECTIVE: To evaluate the effect of angiotensin-converting enzyme (ACE) genotypes on pregnancy outcome, the incidence of pregnancy-induced hypertension, and changes in blood pressure (BP) during pregnancy; and the relationship between plasma ACE activities and plasma and erythrocyte zinc concentrations in each genotype. METHODS: The subjects (n = 191) were selected from 580 indigent African-American pregnant women who enrolled toward the end of a trial to evaluate the effect of zinc supplementation on pregnancy outcome. This selection resulted in 93 subjects who received zinc and 98 who received placebo. Sample size was calculated with a 0.50 correlation coefficient between plasma ACE activities and zinc levels and a power of 80%. This calculation indicated that the sample size in each ACE genotype should be more than 28. Angiotensin-converting enzyme genotypes were identified using polymerase chain reaction. Blood pressure, plasma ACE activities, and plasma and erythrocyte zinc concentrations were measured at each prenatal clinical visit. RESULTS: Pregnancy outcome, the incidence of pregnancy-induced hypertension, and BP were not different among the three ACE genotypes. There was no significant correlation between plasma ACE activities and zinc concentrations. Zinc supplementation did not have a significant effect on either plasma ACE activities or zinc concentrations, probably because of the small sample size in our study. CONCLUSION: There was no effect of ACE gene polymorphism on pregnancy outcome, the incidence of pregnancy-induced hypertension, or changes in BP during pregnancy. Among each ACE genotype, plasma ACE activities did not correlate significantly with plasma zinc concentrations.

Adolescent↗
PubMed1996

1,25-Dihydroxyvitamin D3 increased beta-adrenergic adenylate cyclase response of fetal rat keratinizing epidermal cells (FRSK cells).

Using fetal rat keratinizing epidermal cells (FRSK), the effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on adenylate cyclase system were investigated. The beta-adrenergic adenylate cyclase response was significantly increased by the stimulation of 1 x 10(-7) M 1,25(OH)2D3. The effect was observed by 6 h and continued for at least 48 h. The 1,25(OH)2D3-induced beta-adrenergic augmentation effect was dose-dependent and the maximal response was observed at a concentration of 1 x 10(-7) M 1,25(OH)2D3. Other adenylate cyclase systems (adenosine, prostaglandin E2 and histamine) were not affected by treatment with 1,25(OH)2D3. The thymidine incorporation in FRSK cells was not significantly affected by 1,25(OH)2D3 treatment. Forskolin-induced cyclic AMP accumulation was significantly increased by 1,25(OH)2D3 treatment. Cholera toxin-induced cyclic AMP accumulation was moderately increased, but this was statistically not significant. Northern blot hybridization showed that none of the mRNAs (the beta 2-adrenergic receptor, the alpha subunits of the stimulatory or inhibitory guanine nucleotide binding proteins, Gs alpha, Gi2 alpha, Gi3 alpha) were significantly altered by 1,25(OH)2D3 treatment. We have already reported that the beta-adrenergic response was increased by dexamethasone and inhibited by retinoids in FRSK cells. The addition of both 1,25(OH)2D3 and dexamethasone to the incubation medium resulted in an additive augmentation. On the other hand, the beta-adrenergic augmentation by the 1,25(OH)2D3 treatment was suppressed by the addition of all trans-retinoic acids. Our results indicate that 1,25(OH)2D3 induces beta-adrenergic augmentation without an alternation of thymidine incorporation of FRSK cells.

Adenylyl Cyclases↗
PubMed1996

Monitoring of heart and respiratory rates by photoplethysmography using a digital filtering technique.

An apparatus for simultaneously monitoring heart and respiratory rates was developed using photoplethysmography (PPG) and digital filters, and compared with conventional methods. The PPG signal, which includes both heart and respiratory components, was measured at the earlobe with an original transmission mode photoplethysmographic device. A digital filtering technique was used to distinguish heart and respiratory signals from the PPG signal. The cut-off frequency of the respiratory signal filter was selected automatically depending on the heart rate. Using digital filtering techniques, heart and respiratory signals were separated at rest and during exercise. The digital signal processor was employed to realize an adaptive and real-time filtering. The heart rate was calculated by the zero-crossing method and the respiratory rate from the peak interval of the filtered signal. To evaluate the newly developed monitor, an ECG for heart rate and a transthoracic impedance plethysmogram for respiratory rate were monitored simultaneously. To obtain higher heart and respiratory rates, exercise was performed on an electrical bicycle ergometer. Heart and respiratory rates calculated by the new method compare to those obtained from ECG and the transthoracic impedance plethysmogram. The maximum error of heart and respiratory rates was 10 beats/min and 7 breaths/min, respectively.

Adult↗
PubMed1996

Plasma ferritin and pregnancy outcome.

OBJECTIVE: Plasma ferritin is considered the best measure of total body iron, with low levels diagnostic of iron deficiency. High levels have been associated with inflammation and infection. We determined the relationship between plasma ferritin, birth weight, and preterm delivery. STUDY DESIGN: Plasma ferritin and hematocrit values were measured at 19, 26, and 36 weeks' gestational age and correlated with birth weight and preterm delivery (< or = 32 and < 37 weeks) in 580 indigent black women. RESULTS: Hematocrit levels measured at any gestational age did not correlate significantly with birth weight or preterm delivery. Regardless of the gestational age of sampling, ferritin levels in the lowest quartile did not correlate significantly with subsequent preterm delivery. However, at 26 weeks, compared with the three lower quartiles, ferritin levels in the highest quartile were significantly associated with preterm delivery < or = 32 weeks, 6.5% versus 2.3% (p = 0.02), with preterm delivery < 37 weeks, 14% versus 8% (p = 0.04), and with birth weight < 1500 gm, 6.5% versus 2.0% (p = 0.01). Plasma ferritin levels in the highest quartile at 19, 26, and 36 weeks were associated with birth weight < or = 2500 gm, 14% versus 8% (p = 0.03), 12% versus 7% (p = 0.05), and 10% versus 2% (p = 0.0001), respectively, compared with the lower quartiles. Ferritin levels in the highest quartile were always associated with a lower mean birth weight than were those in the lower three quartiles: 19 weeks, 2999 gm versus 3225 gm, (p = 0.002); 26 weeks, 3065 gm versus 3257 gm, (p = 0.005); and 36 weeks, 3182 gm versus 3323 gm, (p = 0.009). Regression analyses controlling for multiple potential confounders confirmed that at 26 weeks ferritin levels in the highest quartile had an odds ratio and 95% confidence interval for preterm birth < 37 weeks of 2.0 (1.1 to 3.8), preterm delivery < or = 32 weeks of 2.7 (0.99 to 7.6), birth weight < or = 1500 gm of 3.9 (1.2 to 12.2), and birth weight < or = 2500 gm of 2.0 (1.0 to 4.0) compared with the three lower ferritin quartiles. CONCLUSION: High, but not low, plasma ferritin levels, especially at 26 weeks, were strongly associated with subsequent preterm delivery and birth weight.

Adult↗
PubMed1996

Elevated amniotic fluid interleukin-6 levels at genetic amniocentesis predict subsequent pregnancy loss.

OBJECTIVE: Our purpose was to determine the proportion of pregnancy loss after genetic amniocentesis that is related to preexisting subclinical intrauterine inflammation. STUDY DESIGN: We accessed our bank of stored second-trimester amniotic fluid and maternal serum samples obtained from women undergoing genetic amniocentesis at our institution from 1988 to 1995 (N = 11,971). Interleukin-6 levels were measured by enzyme-linked immunosorbent assay in samples from every case resulting in spontaneous postprocedure loss (excluding fetal aneuploidy and anomalies) within 30 days after the procedure (n = 66) and from 66 normal control women delivered at term and matched for year of test, gestational age, maternal age, and indication for amniocentesis. RESULTS: Mean maternal serum interleukin-6 levels were the same in each group (0.02 +/- 0.07 ng/ml for cases and 0.06 +/- 0.25 ng/ml for controls, p = 0.45). Mean amniotic fluid interleukin-6 levels were higher in cases (4.0 +/- 13.1 ng/ml) than in controls (0.5 +/- 0.7 ng/ml, p = 0.04). The higher mean amniotic fluid interleukin-6 levels in the cases resulted from the inclusion of eight very high values (> or = 3 SD or > or = 2.5 ng/ml). When these samples were excluded, the means and range of values were the same in each group (0.4 +/- 0.4 ng/ml for cases and 0.5 +/- 0.7 ng/ml for controls, p = 0.58). Twelve percent (8/66) of the cases and 3% (2/66) of the controls had amniotic fluid interleukin-6 levels > or = 2.5 ng/ml (p = 0.048, odds ratio 4.1, 95% confidence interval 1.0 to 31.2). Although the overall correlation between maternal serum and amniotic fluid interleukin-6 levels was good (r = 0.50, p < 0.002), only one of the eight cases would have been identified by a maternal serum interleukin-6 level > or = 3 SD above the mean (> or = 0.8 ng/ml). CONCLUSION: Analysis of our complete unselected group of postamniocentesis pregnancy losses indicates that up to 12% may result from preexisting subclinical intrauterine inflammation. This inflammation is most likely localized and may not be identified by a maternal serum interleukin-6 level before the procedure.

Abortion, Spontaneous↗
PubMed1996

Exogenous motilin stimulates endogenous release of motilin through cholinergic muscarinic pathways in the dog.

BACKGROUND & AIMS: Exogenous motilin is believed to stimulate endogenous release of motilin, but this has not been studied in detail. The aim of this study was to investigate whether and by what mechanism exogenous motilin stimulates endogenous release of motilin in the dog. METHODS: Gastric and duodenal contractile activity in conscious dogs was monitored by chronically implanted force transducers. Plasma canine motilin (c-motilin) concentrations in response to exogenous porcine motilin (p-motilin) were determined by specific radioimmunoassay for c-motilin. The release of motilin from motilin cells obtained from canine duodenal mucosa was studied in vitro using a perifusion system. RESULTS: In vitro, c-motilin release was stimulated by carbachol but not by p-motilin, and the carbachol-induced c-motilin release was inhibited by atropine. In vivo, exogenous p-motilin stimulated endogenous c-motilin release and gastric and duodenal phase III-like contractions; this motilin-induced motilin release was inhibited by atropine, hexamethonium, and a 5-hydroxy-tryptamine 3 receptor antagonist. CONCLUSIONS: In the dog, exogenous motilin stimulates endogenous motilin release through muscarinic receptors on motilin-producing cells via preganglionic pathways involving 5-hydroxytryptamine 3 receptors.

Amino Acid Sequence↗
PubMed1996

Effects of competitive blood flow on arterial graft patency and diameter. Medium-term postoperative follow-up.

To identify predictors of arterial graft patency, we followed up 30 internal thoracic arterial grafts and 23 right gastroepiploic arterial grafts in situ with patency documented during postoperative angiography. After 24 months of follow-up on average, repeat angiography detected that one internal thoracic artery and two gastroepiploic arteries were anatomically occluded and that the other three gastroepiploic arteries were nonfunctioning. The logistic regression model identified a relationship between graft patency and competitive flow, which was detected as stenosis in the recipient coronary arteries (coefficients, p < 0.05; model, Hosmer-Lemeshow chi2 statistic 3.59, p = 0.89). The linear regression model demonstrated that changes in graft luminal diameter correlated with competitive flow (p < 0.01), smoking history (p < 0.05), and type of arterial grafts (p < 0.001) (R2 = 0.40, adjusted R2 = 0.36). The findings suggest a temporal relationship between competitive flow and prognosis of arterial graft.

Abdominal Muscles↗