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Biomedical subjects

T Tamura

Publications and source records attributed to T Tamura.

At least 397 records · Page 22Linked to original sources
PubMed1997

Initial experience with the Cordis stent: analysis of serial angiographic follow-up.

To evaluate the efficacy of the more flexible Cordis stent, a prospective angiographic follow-up study was performed. Implantation of the Cordis stent was attempted in 99 consecutive patients with 103 native coronary lesions from January 1994 to July 1995. Clinical success, defined as final diameter stenosis of < 50% without death, bypass surgery, or Q-wave myocardial infarction, was achieved in 88% of the patients. There were no in-hospital deaths. In-hospital subacute stent occlusion occurred in only one case. Follow-up angiograms were obtained in 86 (95%) eligible lesions. The minimal luminal diameter improved from 1.03 +/- 0.31 to 2.82 +/- 0.31 mm, but started to decrease at 1 mon (2.57 +/- 0.24 mm), and continued to decrease throughout the 6 mon (2.00 +/- 0.61 mm), the biggest reduction being between 1 and 3 mon (-0.57 +/- 0.50 mm). Angiographic restenosis (stenosis > or = 50%) occurred in 23% of the lesions; a revascularization procedure of the target lesion was required in 12% of the patients. Multivariate analysis identified age, diabetes mellitus, and preprocedural reference diameter to be predictors of angiographic restenosis. In conclusion, the Cordis stent can be implanted successfully with a low complication rate and a clinical outcome at least comparable to other stent studies.

Adult↗
PubMed1997

Genetic defect in T lymphocyte-specific homing into peripheral lymph nodes.

Lymphocytes circulating in the bloodstream home into lymph nodes (LN). T cells predominate in peripheral LN (PLN) and B cells in spleen or mucosal tissue, e.g. Peyer's patches (PP). DDD/1 mice are unique in marked paucity of LN cells, especially T cells. T cell frequency in PLN was 20-40% in this strain, compared to 60-80% in others. Immunohistochemistry confirmed the low density of T cells in the subcortical area but normal colonization of B cells in cortical area in PLN of DDD/1. In contrast, the T cell content of peripheral blood and spleen was higher in DDD/1 but that in PP was not significantly different compared to other strains. It was thus concluded that this abnormality in DDD/1 results from a homing defect of T cells into PLN but not from lymphopenia. Genetical analysis showed that the defect in T cell-specific homing was regulated by a single autosomal recessive gene, tentatively designated plt (paucity of lymph node T cells). Reciprocal bone marrow transplantation indicated that the plt phenotype may arise from some defect in PLN stroma but not in lymphocytes. An in vivo homing assay using fluorescence-labeled lymphocytes demonstrated that the homing defect was specific for T cells but not for B cells. A Stamper-Woodruff assay revealed that the binding between lymphocytes and PLN high endothelial venules was normal and that L-selectin and its ligand, peripheral node vascular addressin (PNAd), were expressed and functioned normally in DDD/1. These results taken together indicate that the T cell-specific homing into PLN is disturbed at a post-adhesion stage in DDD/1. The product of the plt locus may play a pivotal role at this stage.

Animals↗
PubMed1997

Immunocytochemical localization of vitamin D receptors in the shell gland of immature, laying, and molting hens.

It is accepted that vitamin D is involved in the control of egg calcification in hens. The goal of this study was to localize the vitamin D receptors (VDR) in hen shell gland and to determine whether their localization was dependent on reproductive function. Frozen sections of the shell gland of immature, laying, and molting hens were immunostained for VDR, and the VDR in these tissues were also examined by Western blot analysis. Both apical and basal cells of the mucosal epithelium as well as tubular gland cells showed a strong immunoreaction for VDR in the shell gland of laying hens. In the magnum and isthmus, the basal cells of the mucosal epithelium showed a moderately strong immunoreaction for VDR, whereas the immunoreactions in the apical cells of the mucosal epithelium and tubular gland cells were weak. In the shell gland of immature birds, both the mucosal epithelium and tubular gland cells showed a moderately strong VDR immunoreaction. In molting hens, the mucosal epithelial cells and tubular gland cells showed a strong VDR immunoreaction although the mucosal tissue was regressed. Western blot analysis indicated that the mucosal tissue of the shell gland of immature, laying, and molting hens contained two forms of immunoreactive VDR, which were approximately 58 and 60 kDa. Because VDR were richer in the shell gland than in other oviductal segments, these results suggest that in laying hens the shell gland tissues are one of the significant targets for vitamin D. It is likely that the amount of shell gland VDR increases during sexual maturation and immunoreactive VDR remain even during the molting phase.

Animals↗
PubMed1997

cDNA cloning and mRNA expression analysis of the human neuronatin. High level expression in human pituitary gland and pituitary adenomas.

The authors cloned the nearly complete cDNA of human neuronatin with the aid of an expressed sequence tag (EST) database, and analyzed its expression in various human tissues by Northern blot analysis. The nucleotide and deduced amino acid sequences of the human neuronatin showed a high similarity to those of rodents. The Northern blot analysis revealed that the human neuronatin message was expressed predominantly in the fetal brain in the brain-specific manner, but only faintly in the adult brain. Among the various adult human tissues examined, the anterior pituitary gland was shown to be the only place where the neuronatin mRNA was strongly expressed. Intense neuronatin expression was also observed in several human pituitary adenomas, including ACTH-producing, GH-producing, and nonfunctioning adenomas, but hardly detected in other brain tumors.

Adenoma↗
PubMed1997

Eradication of minimal residual disease during graft-versus-host reaction induced by abrupt discontinuation of immunosuppression following bone marrow transplantation in a patient with Ph1-ALL.

We observed a patient in whom graft-versus-host disease (GVHD) appeared to induce a positive effect. This 32-year-old male with Philadelphia chromosome-positive acute lymphoblastic leukemia received a bone marrow transplant (BMT) from an HLA-identical sibling donor. We analyzed the bone marrow with the reverse transcriptase-polymerase chain reaction to screen for the minor bcr/abl transcript, which indicates the presence of minimal residual disease (MRD). MRD was present in the pre- and post-transplant phases. There was no evidence of acute GVHD by post-transplant day 45. We abruptly discontinued the immunosuppressive therapy in an attempt to eliminate MRD by inducing an antileukemic reaction during GVHD. GVHD associated with diarrhea and liver dysfunction developed on day 64. On day 105, MRD disappeared and GVHD was treated with prednisolone and cyclosporin. The disappearance of MRD may have been due to the graft-versus-leukemia (GVL) effect mediated by the alloimmune response of donor T lymphocytes. These findings suggest that induction of the GVL effect may be useful for eliminating MRD after BMT in leukemia patients at high risk of recurrence of the disease.

Adult↗
PubMed1997

The effects of infusion of trieicosapentaenoyl-glycerol emulsion on extravascular lung water during myocardial ischemia and reperfusion in dogs.

To test the effects of eicosapentaenoic acid (EPA) infusion on pulmonary edema induced by coronary ligation and reperfusion, extravascular lung water (EVLW) was measured in situ by the thermal-dye double indicator dilution method in dogs. In the control group of five dogs, 30 mL of a 10% soybean oil emulsion was infused through a leg vein. One hour after infusion, the left anterior descending coronary artery below the first diagonal branch was ligated for 15 min and then reperfused for 30 min. In the EPA group, six dogs were similarly treated with an emulsion of a 10% trieicosapentaenoyl-glycerol (90% pure). EVLW, pulmonary capillary wedge pressure, mean pulmonary artery pressure, mean blood pressure, and cardiac index were measured before and 15 min after coronary ligation, and 15 min and 30 min after coronary reperfusion. There were no significant differences in the hemodynamic indices between the two groups. EVLW significantly increased up to two times of baseline during coronary ligation in the control group (P < 0.05) and more during reperfusion (P < 0.01), whereas EVLW did not increase in the EPA group. In conclusion, EPA inhibited EVLW accumulation and may be useful for ameliorating one of the ischemia-reperfusion-induced complications, pulmonary edema.

Animals↗
PubMed1997

Plasma and erythrocyte zinc concentrations and their relationship to dietary zinc intake and zinc supplementation during pregnancy in low-income African-American women.

OBJECTIVE: To evaluate the effects of usual dietary intake of zinc and of zinc supplementation during pregnancy on plasma and erythrocyte zinc concentrations. DESIGN: A randomized, double-blind, placebo-controlled trial. SUBJECTS: Low-income African-American women (n = 580) assigned randomly to groups at 19 weeks of gestation. INTERVENTION: A daily dose of zinc (25 mg) or a placebo until delivery. MAIN OUTCOME MEASURES: Plasma, erythrocyte, and dietary zinc levels. STATISTICAL ANALYSES: Multiple regression and repeated measures analysis of variance. RESULTS: In both the placebo and the supplemented groups, when all subjects were grouped by usual dietary zinc intake above or below the median (12 mg/day), results were the same: Women with high dietary zinc intake had higher erythrocyte zinc levels at the time of randomization and at all subsequent measurements during pregnancy than those who had low dietary zinc intake (P < or = .06; difference not significant for zinc-supplemented group); no difference was observed for plasma zinc levels. On the other hand, when the subjects were stratified at the median by total daily zinc intake (usual dietary zinc + 25 mg zinc supplement) during pregnancy, a significant difference in plasma zinc levels (P < .005) was found between women with high total zinc intake (mean = 38 mg/day) and low total intake (mean = 13 mg/day) at 26, 32, and 38 weeks of gestation; however, no such differences were found in erythrocyte zinc levels. APPLICATIONS: These results should help dietitians and other health professionals better understand the expected changes in plasma and erythrocyte zinc levels during pregnancy, and the relationship between dietary and supplemental zinc and zinc nutriture.

Adult↗
PubMed1997

Importance of left ventricular diastolic function on maintenance of exercise capacity in patients with systolic dysfunction after anterior myocardial infarction.

To investigate the role of left ventricular (LV) diastolic function in the maintenance of exercise capacity in patients with systolic dysfunction, symptom-limited cardiopulmonary exercise testing combined with radionuclide ventriculography was performed in 24 patients with an LV ejection fraction < 35% after anterior myocardial infarction. The ratio of pulmonary artery wedge pressure (PAWP) to LV end-diastolic volume (EDV), an index of global diastolic function, correlated significantly with peak oxygen consumption at peak exercise (r = -0.55; p = 0.006), whereas ejection fraction at peak exercise did not. The change in PAWP/EDV ratio from rest to peak exercise was related to the increases in stroke volume (r = -0.54; p = 0.006) and cardiac output (r = -0.51; p = 0.01) during exercise, but the change in ejection fraction was not. Resting hemodynamics did not differ between patients with preserved exercise capacity (group 1, n = 8) and those with exercise impairment (group 2, n = 16). At peak exercise, stroke volume, cardiac output, and EDV were significantly higher, and PAWP and PAWP/EDV ratio were significantly lower in group 1 than in group 2, but ejection fraction and end-systolic volume were similar in both groups. Although the incidences of hypertension, LV hypertrophy, and infarct-related coronary artery lesions did not differ between the two groups, group 2 had a significantly higher incidence of non-infarct-related coronary artery lesions than group 1 (p < 0.05). Thus in patients with LV systolic dysfunction after anterior myocardial infarction, the major cause of exercise impairment and failure to increase LV performance during exercise was diastolic dysfunction associated with the presence of non-infarct-related coronary artery lesions with the potential for exercise-induced ischemia of the noninfarcted areas.

Adult↗
PubMed1997

Impairment of signal transduction in T cells from old mice.

T cells from old mice showed impaired proliferative response to antigenic stimulation. To understand the mechanism underlying the age-related impairment of T cell functions, the signal transduction pathway was examined and compared between T cells from young and old mice, and between T cell clones established from a young and old mouse. The age-related changes in T cells were as follows: (1) reduction in the expression and the activation of protein tyrosine kinases associated with T cell receptor (TCR) after antigenic stimulation; (2) reduced phosphorylation of phospholipase C gamma 1 (PLC gamma 1); (3) reduced production of second messengers such as inositoltrisphosphate (IP3) and diacylglycerol (DAG); and (4) reduced influx of Ca2+ ion. Thus, a T cell clone established from an old mouse showed impaired proliferation by stimulation with anti-CD3 antibody, but was fully activated to the level of a T cell clone from a young mouse by stimulation with phorbol acetate myristate (PMA) plus ionomycin (INM). However, splenic T cells freshly prepared from old mice did not show full recovery by the same treatment. The results indicate that one major blockade in the signal transduction of T cells from old mice is present in the pathway just after TCR, but besides this, the blockade is also present in multiple sites down-stream, which can not be bypassed by stimulation with PMA plus INM.

Aging↗
PubMed1997

Stimulatory and inhibitory effects of neuropeptide Y on growth hormone secretion in acromegaly in vivo.

It has been reported that neuropeptide Y (NPY) affects growth hormone (GH) secretion in several animal species. With respect to the role of NPY in regulating GH release in humans, one previous study has reported that NPY inhibited GH secretion from cultured GH-secreting pituitary adenoma cells in vitro. However, since it has yet to be explored whether NPY affects GH secretion in acromegaly in vivo, in this study we attempted to examine the effect of intravenous (i.v.) bolus injection of 100 microg of human NPY on plasma GH levels in 15 patients with active acromegaly, trying to find a possible correlation among GH responses to NPY, thyrotropin-releasing hormone (TRH;500 microg, i.v.), luteinizing hormone-releasing hormone (LHRH;100 microg, i.v.), and bromocriptine (Br;2.5 mg, per os). NPY significantly increased GH secretion (more than twice the basal level) in 4 (27%) patients, and all of them were responsive to LHRH and non-responsive to Br. In contrast, 3 (20%) acromegalics showed a significant decrease in GH levels (less than half the baseline) after NPY, and all these patients were responsive to both TRH and Br. From these results, we hypothesize that the NPY-induced increase in GH release may be a feature of somatotroph-like pituitary adenoma causing acromegaly, whereas the NPY-induced decrease in GH secretion may be a feature of lactotroph-like adenoma.

Acromegaly↗
PubMed1997

A suppressive effect of dexamethasone (DEX) on adrenocorticotropin (ACTH) response to vasoactive intestinal peptide (VIP) in Cushing's disease: a parallel modulation by DEX of ACTH responses to VIP and corticotropin-releasing hormone.

We have previously reported and confirmed that vasoactive intestinal peptide (VIP) is a significant stimulator of ACTH and cortisol secretion in at least some patients with Cushing's disease. We have also found that the hormonal responses to corticotropin-releasing hormone (CRH) in VIP-responsive patients with Cushing's disease were higher than those in VIP non-responders, which suggested a linkage between the actions of CRH and VIP in this disorder. Therefore, in the present study we examined whether this linkage also exists after glucocorticoid treatment by testing the effect of dexamethasone (DEX) pretreatment (1.0 mg, intravenous bolus, 60 min before) on ACTH and cortisol responses to CRH (100 microg, i.v. bolus) and VIP (100 microg, i.v. bolus) in 7 patients with Cushing's disease who were responsive to both neuropeptides while under no DEX pretreatment. The results were that in 5 patients, DEX was able to significantly suppress the ACTH and cortisol responses to both CRH and VIP, and in the remaining 2 patients, DEX did not significantly affect the action of either CRH or VIP. This study is the first to demonstrate the parallel inhibition by DEX of ACTH and cortisol responses to CRH and VIP in Cushing's disease. Although the possibility cannot be excluded that VIP may act on CRH receptors in corticotropinomas as a partial agonist, it seems more likely that specific receptors for CRH and VIP, respectively, may concurrently express in substantial quantity in those corticotropinomas that are responsive to both neuropeptides.

Adrenocorticotropic Hormone↗
PubMed1997

Effect of smoking on the prevalence of albuminuria in Japanese men with non-insulin-dependent diabetes mellitus.

Smoking is a risk factor for diabetic nephropathy in patients with IDDM and potentially those with NIDDM. We investigated the relationship between renal involvement and cigarette smoking in 148 men with NIDDM. The presence of renal involvement was assessed by determining the overnight urinary albumin/creatinine ratio (mg/g, ACR). The patients were divided into three groups, normo-, micro-, and macroalbuminuria, based on the ACR (< 30, 30-300, and 300 < or = mg/g, respectively). The incidence of micro-/macroalbuminuria in 81 smokers was significantly higher than that in 21 ex-smokers (stopped smoking at least 10 years prior to the study) or 40 non-smokers (53.1, 33.3, and 20.0%, respectively). The prevalence of smoking in the groups of patients with normo-, micro-, and macroalbuminuria were 45, 73, and 76%, respectively. The relative risk (odds ratio) for the prevalence of micro-/macroalbuminuria associated with smoking was 4.5 (95% CI, 1.9-11.6, P < 0.001) in smokers and was 2.0 (not significant) in ex-smokers. Our results indicate that stricter counselling about the importance of quitting smoking will be necessary in patients with NIDDM to protect against the development of diabetic nephropathy.

Aged↗
PubMed1997

Immunobiological activities of chemically defined lipid A from Helicobacter pylori LPS in comparison with Porphyromonas gingivalis lipid A and Escherichia coli-type synthetic lipid A (compound 506).

Helicobacter pylori lipid A, characterised by a glucosamine beta (1-6) disaccharide 1-(2-aminoethyl)phosphate acylated by (R)-3-hydroxyoctadecanoic acid and (R)-3-(octadecanoyloxy)octadecanoic acid at the 2- and 2'-positions, respectively, exhibited no or very low endotoxic activities, i.e. lethal toxicity in galactosamine-loaded mice, pyrogenicity for rabbits and the activity of the Limulus test compared with Escherichia coli-type synthetic lipid A (compound 506), which possesses beta-(1-6)-linked glucosamine disaccharide 1,4'-bisphosphate, with two acyloxyacyl groups at the 2'- and 3'-positions and two 3-hydroxytetradecanoyl groups at the 2- and 3-positions. The endotoxic properties of H. pylori lipid A were also a little weaker than those of the low endotoxic lipid A of P. gingivalis, which has 1-phospho beta-(1-6)-linked glucosamine disaccharide with 3-hydroxy-15-methylhexadecanoyl and 3-hexadecanoyloxy-15-methylhexadecanoyl groups at the 2- and 2'-positions, respectively. Further, the mitogenic activity of H. pylori lipid A in murine splenic mononuclear cells was also less than those of P. gingivalis lipid A and compound 506. However, H. pylori lipid A induced comparable production of interleukin-6 (IL-6) by human peripheral blood mononuclear cells (PBMC) compared with P. gingivalis lipid A and compound 506. H. pylori lipid A also increased human natural killer cell activity, and strongly agglutinated rabbit erythrocytes. However, the lipid As of H. pylori and P. gingivalis showed lower activities in inducing tumour necrosis factor alpha (TNF-alpha) production by human PBMC and IL-8 production by human gingival fibroblasts than that of compound 506. The structural feature of H. pylori lipid A may be associated with low endotoxic properties and potent immunobiological activities.

Animals↗
PubMed1997

Antibacterial activity of trichorabdal A from Rabdosia trichocarpa against Helicobacter pylori.

Rabdosia trichocarpa is used in a popular home-made remedy for gastric and stomachic complaints in Japan. A diterpene, trichorabdal A from R. trichocarpa, showed a very strong in vitro antibacterial activity against Helicobacter pylori. With regard to the antibacterial activity of the extract and constituents of R. trichocarpa against H. pylori, the effect of traditional use of this plant for the treatment of gastritis is probably due to the suppression of H. pylori since the extract of R. trichocarpa particularly inhibits the growth of H. pylori. It could be a promising native herb treatment for patients with gastric complaints including gastric ulcer caused by H. pylori.

Anti-Bacterial Agents↗
PubMed1997

Self-compartmentalizing proteases.

Among the hundreds of proteases characterized so far, most of which are monomeric or dimeric, there is a small group that form compartments through self-association and that segregate their proteolytic active sites to the interior of these compartments. Although few in number, they represent the main agents of intracellular protein breakdown. They belong to different hydrolase families but have converged towards the same barrel-shaped architecture. Frequently, they are coupled to chaperone-like ATPases of similar quaternary structure that regulate the access to the proteolytic compartments and appear to have been recruited from the same branch of P-loop NTPases.

Amino Acid Sequence↗
PubMed1997

Tricorn protease exists as an icosahedral supermolecule in vivo.

Tricorn protease is the core enzyme of a recently discovered modular proteolytic system. We present evidence that tricorn protease exists in vivo in the form of a higher-order assembly, namely as an icosahedral capsid. Its size exceeds that of many virus particles and represents by far the largest known homooligomeric enzyme complex. Each capsid is built from 20 copies of the tricorn hexameric toroid and thus has a molecular weight of 14.6 MDa. Three-dimensional reconstructions of ice-embedded capsids from electron micrographs show that it is hollow and has large void volumes in its wall. We suggest that the tricorn capsid, in addition to its intrinsic proteolytic activity, serves as the organizing center of a multienzyme complex.

Archaeal Proteins↗
PubMed1997

Eubacterial proteasomes.

Proteasomes are large, multisubunit proteases with highly conserved structures. The 26S proteasome of eukaryotes is an ATP-dependent enzyme of about 2 MDa, which acts as the central protease of the ubiquitin-dependent pathway of protein degradation. The core of the 26S complex is formed by the 20S proteasome, an ATP-independent, barrel-shaped protease of about 700 kDa, which has also been detected in archaebacteria and, more recently, in eubacteria. Currently, the distribution of 20S proteasomes in eubacteria appears limited to the actinomycetes, while most other eubacteria contain a related complex of simpler structure.

Amino Acid Sequence↗