Search PubMed⌕ Search

Biomedical subjects

K Shirato

Publications and source records attributed to K Shirato.

At least 37 records · Page 2Linked to original sources
PubMed2001

Microvolt T wave alternans in human cardiac hypertrophy: electrical instability and abnormal myocardial arrangement.

INTRODUCTION: Although T wave alternans (TWA) is a promising risk marker for myocardial electrical instability, it remains unclear how the presence of TWA is related to myocardial damage. METHODS AND RESULTS: TWA was measured in 28 patients with hypertrophic cardiomyopathy (HCM), 29 patients with hypertensive left ventricular hypertrophy (HLVH), and 15 normal volunteers using a CH2000 system. The amplitude of TWA (Valt) was measured at the lead with the maximum amplitude. Cardiac biopsy was performed in 12 HCM patients, who were divided into two groups (severe and mild) based on histologic findings of myocardial disarray and fibrosis. TWA was positive (Valt > 1.9 microV) in 61% of HCM and 31% of HLVH, despite a nearly identical left ventricular mass index (176 +/- 65 g/m2 vs 175 +/- 39 g/m2). Valt at heart rate = 110 beats/min was significantly greater in HCM with severe disarray and fibrosis than in HCM with mild disarray and in HLVH. CONCLUSION: In HCM patients, a positive TWA test probably is related to abnormal myocardial arrangement (disarray) and/or fibrosis, and it may reflect electrical instability of the myocardium.

Aged↗
PubMed2001

Interleukin-1beta is an autocrine growth factor of rat glomerular epithelial cells in culture.

BACKGROUND: The proliferation of glomerular epithelial cells (GEC) is usually observed in crescentic glomerulonephritis. However, the regulation of GEC proliferation is not fully understood. Although it is known that interleukin-1beta (IL-1beta) has a mitogenic effect on mesangial cells and is produced by mesangial cells, the effect of this cytokine on GEC proliferation is not known. We investigated whether cultured rat GEC could produce IL-1beta, and the role of IL-1beta on GEC proliferation. METHODS: Cultured rat GEC from 24th to 36th passage were used. GEC proliferation was evaluated with a colorimetric assay using the tetrazolium salt. GEC were incubated in K1 medium for 72 h and IL-1beta in the culture supernatants was measured by specific enzyme-linked immunosorbent assay (ELISA). IL-1beta in GEC supernatants was examined by immunoblot analysis. IL-1beta mRNA expression in GEC was examined by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: IL-1beta showed a mitogenic effect on GEC, while interferon-gamma (IFN-gamma) and heparin inhibited GEC proliferation. Moreover, GEC proliferation cultured with K1 medium was partially inhibited by anti-IL-1beta neutralizing antibody. Amounts of IL-1beta in the culture supernatants increased over time (24-72 h). K1 medium increased IL-1beta production by GEC, while IFN-gamma or heparin did not change IL-1beta production. Immunoblot analysis revealed 17 kD protein of IL-1beta in the concentrated GEC supernatants. RT-PCR also demonstrated mRNA expression of IL-1beta in GEC. CONCLUSIONS: Our data indicate that IL-1beta is an autocrine growth factor for GEC and may have an important role in the regulation of GEC proliferation.

3T3 Cells↗
PubMed2001

Cultured rat glomerular epithelial cells show gene expression and production of transforming growth factor-beta: expression is enhanced by thrombin.

BACKGROUND: Glomerular crescents play an important role in progressive glomerular injury. The lesions consist of epithelial cells, macrophages, and deposits of fibrin and extracellular matrix. Transforming growth factor beta (TGF-beta) contributes to the modulation of cell growth and extracellular matrix synthesis. Thrombin is involved in fibrin formation in crescents. The purpose of this study was to examine whether glomerular epithelial cells (GEC) could produce TGF-beta, and if so, to clarify the role of TGF-beta in GEC proliferation. We also investigated whether thrombin could modulate the production of TGF-beta and extracellular matrix by GEC. METHODS: Bioassay using the TGF-beta-dependent mink pulmonary epithelial cell line (CCL-64), immunoblot analysis, and reverse transcriptase polymerase chain reaction (RT-PCR) were used to demonstrate TGF-beta production by rat GEC. TGF-beta gene expression was examined by RT-PCR in GEC incubated with thrombin, and type IV collagen and fibronectin were quantified by enzyme immunoassay in culture supernatants of GEC incubated with thrombin or TGF-beta. RESULTS: TGF-beta activity was demonstrated in GEC supernatants by bioassay. Immunoblot analysis of concentrated culture supernatants using anti-TGF-beta antibody revealed a 12.5-kDa protein, which was compatible with TGF-beta. Concentrated GEC supernatants inhibited GEC proliferation as well as porcine TGF-beta. RT-PCR demonstrated TGF-beta gene expression in GEC. Thrombin (0.5-5.0 U/ml) enhanced TGF-beta mRNA expression in a dose-dependent manner. Thrombin (5.0 U/ml) and porcine TGF-beta (5.0 ng/ml) stimulated the production of type IV collagen and fibronectin by GEC. CONCLUSIONS: Rat GEC produce TGF-beta in vitro. Thrombin may participate in the progression of glomerulosclerosis in crescentic glomerulonephritis through the stimulation of TGF-beta production by GEC.

Animals↗
PubMed2001

Nonselective endothelin receptor antagonist initiated soon after the onset of myocardial infarction may deteriorate 24-hour survival.

To investigate the effects of endothelin blockade initiated immediately after the onset of myocardial infarction on survival and left ventricular remodeling, treatment with the nonselective receptor antagonist TAK-044 (n = 22) or saline (n = 19) for 3 weeks was initiated immediately after coronary ligation in rats. The 24-h survival rate was significantly lower in the TAK-044 group than in the saline group. The systolic blood pressure 24 h after the onset of myocardial infarction was similar in the saline and TAK-044 groups, although it was significantly lower in the TAK-044 group during the 3-week protocol. Heart weight/tibial length was significantly increased in the TAK-044 group compared with the saline group. As all deaths in the TAK-044 group occurred within 24 h after myocardial infarction, we performed additional experiments using a separate group of rats 12-16 h after myocardial infarction. Plasma and myocardial endothelin-1 levels were significantly increased, and a bolus injection of TAK-044 significantly reduced left ventricular dP/dtmax in these rats that had had a myocardial infarction compared with sham-operated rats. Endothelin receptor blockade initiated immediately after the onset of myocardial infarction may deteriorate acute-phase survival and left ventricular remodeling. Inhibition of the positive inotropic action of endothlin-1 may partially explain the increased 24-h mortality.

Animals↗
PubMed2001

Stretch and quick release of rat cardiac trabeculae accelerates Ca2+ waves and triggered propagated contractions.

Rapid shortening of active cardiac muscle [quick release (QR)] dissociates Ca2+ from myofilaments. We studied, using muscle stretches and QR, whether Ca2+ dissociation affects triggered propagated contractions (TPCs) and Ca2+ waves. The intracellular Ca2+ concentration was measured by a SIT camera in right ventricular trabeculae dissected from rat hearts loaded with fura 2 salt, force was measured by a silicon strain gauge, and sarcomere length was measured by laser diffraction while a servomotor controlled muscle length. TPCs (n = 27) were induced at 28 degrees C by stimulus trains (7.5 s at 2.65 +/- 0.13 Hz) at an extracellular Ca2+ concentration ([Ca2+]o) = 2.0 mM or with 10 microM Gd3+ at [Ca2+]o = 5.2 +/- 0.73 mM. QR during twitch relaxation after a 10% stretch for 100-200 ms reduced both the time between the last stimulus and the peak TPC (PeakTPC) and the time between the last stimulus and peak Ca2+ wave (PeakCW) and increased PeakTPC and PeakCW (n = 13) as well as the propagation velocity (Vprop; n = 8). Active force during stretch also increased Vprop (r = 0.84, n = 12, P < 0.01), but Gd3+ had no effect (n = 5). These results suggest that Ca2+ dissociation by QR during relaxation accelerates the initiation and propagation of Ca2+ waves.

Actin Cytoskeleton↗
PubMed2001

Secretion and gene expression of secretory leukocyte protease inhibitor by human airway submucosal glands.

Submucosal glands were isolated within 4 h of death from tracheae and bronchi obtained from autopsied lungs, and the secretory response of secretory leukocyte protease inhibitor (SLPI) was examined with ELISA and a secretory index. Although human neutrophil elastase (HNE) at low concentrations increased SLPI secretion above the control level (i.e., 149% of control level at 10(-11) M), HNE at high concentrations significantly decreased it below the control level (i.e., 16% of control level at 10(-7) M). The decrease in SLPI concentration was shown to result from the degradation of SLPI by excessive HNE. Methacholine induced significant secretion (i.e., 363% of control level at 10(-5) M) that was abolished by both M(1) and M(3) receptor antagonists. A semiquantitative analysis of SLPI mRNA by RT-PCR and Southern blot showed that compared with the superficial epithelium, submucosal glands had a 30-fold or higher level of SLPI mRNA. Both HNE and methacholine significantly increased the level of SLPI mRNA in submucosal glands in a dose-dependent manner (i.e., 357% of control level at 10(-7) M and 175% of control level at 10(-5) M, respectively). These findings indicate that human airway submucosal glands can transcribe 30-fold or more SLPI mRNA than the superficial epithelium and that SLPI mRNA transcription and secretion are regulated by both HNE and muscarinic receptors.

Adult↗
PubMed2001

Role of GABA within the nucleus tractus solitarii in the hypoxic ventilatory decline of awake rats.

The purpose of this study was to examine our hypothesis that gamma-aminobutyric acid (GABA) in the nucleus tractus solitarii (NTS) may be related to the hypoxic ventilatory decline (HVD) and that chemoreceptor stimulation was essential to activate this mechanism. We used unanesthetized, freely moving rats in this study. An in vivo microdialysis technique was used to measure the extracellular GABA concentration ([GABA]o), and an in vivo microinjection technique was used to examine the effects of the GABA agonists and antagonists on the ventilation during hypoxia. The GABA agonists injected into the NTS attenuated the ventilation during hypoxia. By hypoxic exposure, [GABA]o was increased during the HVD. However, by carotid body denervation (CBD), this GABA increase was abolished. Although GABA antagonists microinjected into the NTS during the HVD phase significantly increased the depressed ventilation, this effect on the ventilation was abolished by CBD. These results suggest that the GABA in the NTS has a pivotal role in the HVD and that this mechanism is not activated without chemoreceptor stimulation.

Animals↗
PubMed2001

Increased expression of heme oxygenase-1 and bilirubin accumulation in foam cells of rabbit atherosclerotic lesions.

Heme oxygenase-1 (HO-1) catalyzes the regiospecific oxidative degradation of heme to biliverdin IXalpha, iron, and carbon monoxide. Biliverdin IXalpha is subsequently reduced to bilirubin IXalpha by biliverdin reductase. HO-1 expression is induced under various disease conditions, including atherosclerosis, but it is unknown whether HO-1 catalyzes heme breakdown in the regions at risk. Using hypercholesterolemic rabbits fed a cholesterol-enriched diet, we attempted to demonstrate the involvement of HO-1 induction and bilirubin IXalpha production in atherosclerotic regions. Expression levels of HO-1 mRNA were elevated in the aortas of hypercholesterolemic rabbits. In situ hybridization and immunohistochemistry revealed that mRNA and protein of HO-1 are induced in endothelial cells and foam cells (lipid-filled macrophages) in atherosclerotic lesions. Furthermore, immunohistochemistry with the use of an anti-bilirubin-IXalpha monoclonal antibody, 24G7, demonstrated accumulation of bilirubin IXalpha in foam cells, indicating that heme is actually degraded in atherosclerotic lesions. Remarkably, bilirubin IXalpha, like HO-1 protein, is predominantly accumulated in the perinuclear regions of foam cells. These results provide the first in vivo evidence of the colocalization of HO-1 and bilirubin IXalpha in foam cells, suggesting a role of HO-1 induction in the modulation of macrophage activation in atherosclerosis.

Animals↗
PubMed2001

Effect of whole-body x-irradiation on antigen-induced airway response in sensitized guinea pigs.

The objectives of this study were to test the hypothesis that x-irradiation inhibits the late asthmatic response (LAR) without influencing the early asthmatic response (EAR) and to examine the mechanism of the inhibitory effect. Twenty sensitized guinea pigs were irradiated at a dose of 8 Gy. The next day, one-half of the animals were injected intravenously with spleen cells (2 x 10(8)) collected from unirradiated sensitized guinea pigs, whilst the other half were injected with vehicle only. Ten additional unirradiated sensitized guinea pigs also received vehicle only. Antigen inhalation challenge took place two days later. Pulmonary resistance was measured for 6 h after antigen exposure, and bronchoalveolar lavage and lung fixation were then undertaken. The area under the percentage pulmonary resistance curve 2-6 h after allergen inhalation was used for analysis of the LAR, while the maximal percentage change in pulmonary resistance was used for analysis of the EAR. Irradiation abolished the LAR (364.4+/-49.4 versus 62.8+/-10.4) without inhibiting the EAR (229.3+/-27.2 versus 278.7+/-40.2) and significantly inhibited the accumulation of eosinophils and lymphocytes in the airways. Transfer of spleen cells restored the LAR (334.4+/-66.8) and the recruitment of cells to the levels seen in unirradiated sensitized guinea pigs. In addition, transfer of only CD4+ T-lymphocytes separated from the spleen cells restored the LAR (439.4+/-62.1) and the cell infiltration into the airways. These inhibitory effects of x-irradiation were due to decreases in numbers of CD4+ T-lymphocytes.

Airway Resistance↗
PubMed2001

Declining trend in the in-hospital case-fatality rate from acute myocardial infarction in Miyagi Prefecture from 1980 to 1999.

The case-fatality rate from acute myocardial infarction (AMI) appears to have been declining in recent decades, so the present study reviewed the trend in in-hospital case-fatalities from AMI in Miyagi Prefecture, Japan, 1980-1999. The causes of death and the effects of gender and age on the trend were also analyzed. From the AMI registration database of the Miyagi Study Group for AMI, 12,961 cases of AMI were analyzed. The 30-day in-hospital case-fatality was calculated from the data for 1980-1999: data for causes of death were available for 1980-1997, and the data concerning primary percutaneous transluminal coronary angioplasty (PTCA) for AMI were available for 1997-1999. The in-hospital case-fatality rate declined from 17.0% in the early 80s to 7.3% in the late 90s (approximately 57% reduction). The in-hospital case-fatality rate was higher in female patients. Rhythm failure substantially decreased in the late 1980s. Pump failure is decreasing, but is still the biggest problem. The in-hospital case-fatality rate was significantly lower in patients received PTCA. The declining trend in the in-hospital case-fatality rate suggests the benefits of current therapeutic procedures, including primary PTCA, for AMI. Pump failure is an important target for further decreasing the trend.

Adult↗
PubMed2001

Effect of transient stretch on intracellular Ca2+ during triggered propagated contractions in intact trabeculae.

Transient stretch of cardiac muscle during a twitch contraction may dissociate Ca2+ from myofilaments into the cytosol at the moment of quick release of the muscle. We studied the effect of stretch and quick release of trabeculae on changes in intracellular Ca2+ ([Ca2+]i) during triggered propagated contractions (TPCs). Trabeculae were dissected from the right ventricle of 9 rat hearts. [Ca2+]i was measured using electrophoretically injected fura-2. Force was measured using a silicon strain gauge and sarcomere length was measured using laser diffraction techniques. Reproducible TPCs (n = 13) were induced by trains of electrical stimuli (378 +/- 19 ms interval) for 7.5 s at [Ca2+]o of 2.0 mM (27.9 +/- 0.2 degrees C). The latency of the TPC force and the underlying increase in [Ca2+]i was calculated from the time (TimeF) between the last stimulus and the peak of TPC force (PeakF), or the time (TimeCa) between the last stimulus and the peak of the increase in [Ca2+]i during the TPCs (PeakCa). As a result of a 10% increase in muscle length for 150-200 ms during the last stimulated twitches, TimeF and TimeCa decreased and PeakF and PeakCa increased significantly (n = 13). In addition, transient stretch sometimes induced a twitch contraction subsequent to the accelerated TPC and its underlying increase in [Ca2+]i. These results suggest that Ca2+ binding and dissociation from the myofilaments by the stretch and quick release of muscle may modulate the TPC force and the underlying increases in [Ca2+]i and play an important role in the induction of arrhythmias.

Actin Cytoskeleton↗
PubMed2001

[Angiography of pulmonary hypertension].

In the present report, we reviewed articles on pulmonary angiography for patients with pulmonary hypertension. The use of a non-ionic, low-osmolarity agent and improvements in catheters reduced periprocedual complications, but attention should be paid to the pre-existing poorer physical state. Digital pulmonary angiography has similar diagnostic power to conventional angiography. Wedged pulmonary angiography could demonstrate distal lesions of the pulmonary artery which couldn't be detected by conventional pulmonary angiography. Typical pulmonary angiograms from pulmonary hypertension due to pulmonary embolism, primary pulmonary hypertension, collagen diseases, Takayasu's arteritis and porto-pulmonary hypertension were shown. Pulmonary angiography is relatively less valuable than before because of advances in other diagnostic imaging tools, but still remains the gold standard.

Angiography, Digital Subtraction↗
PubMed2000

The mouse L-histidine decarboxylase gene: structure and transcriptional regulation by CpG methylation in the promoter region.

To investigate the regulation of mouse L-histidine decarboxylase (HDC) gene expression, we isolated genomic DNA clones encoding HDC. Structural analysis revealed that the mouse HDC gene was composed of 12 exons, spanning approximately 24 kb. Northern blotting analysis indicated that, among the cell lines examined, a high level of HDC gene expression was restricted to mature mast cell lines and an erythroblastic cell line. The gene was induced strongly in the mouse immature mast cell line P815 after incubation in the peritoneal cavity of BDF1 mice. We observed that the promoter region was demethylated in the HDC-expressing cell lines and in induced P815 cells. Interestingly, forced demethylation by 5-azacytidine (5-azaC) treatment induced high expression of HDC mRNA in P815 cells. The activity of a mouse HDC promoter-reporter construct stably transfected in P815 cells was repressed by in vitro patch-methylation. This low promoter activity of the patch-methylated reporter construct was restored after 5-azaC treatment, which demethylated the patch-methylated promoter. These results indicate that DNA methylation state of the promoter region controls HDC gene expression.

3T3 Cells↗
PubMed2000

Regulation of murine airway eosinophilia and Th2 cells by antigen-conjugated CpG oligodeoxynucleotides as a novel antigen-specific immunomodulator.

The characteristic features of bronchial asthma reflect the orchestrated activity of Th2 cells. Oligodeoxynucleotides containing CpG motifs (CpG) have recently been highlighted as an immunomodulator that biases toward a Th1-dominant phenotype. We have previously reported that intratracheal coadministration of CpG and allergen inhibited airway eosinophilia and hyperresponsiveness in a synergistic manner. To substantiate the synergism between CpG and Ag, we introduced a covalently linked conjugate between CpG and Ag and examined the efficacy on airway eosinophilia and Th2 cytokine production. We found that the conjugated form of CpG plus Ag was 100-fold more efficient in regulating airway eosinophilia than the unconjugated mixture. The inhibitory effects lasted for at least 2 mo. The inhibition of airway eosinophilia by the conjugate was Ag specific and associated with an improvement of the airway hyperresponsiveness and the unresponsiveness of the Ag-specific Th2 cells in the regional lymph nodes. The CpG-Ag conjugate was 100-fold more effective than the unconjugated mixture for inducing in vitro Th1 differentiation in an IL-12-dependent manner. Our data show that CpG conjugated to Ag can work as a novel Ag-specific immunomodulator and imply that inhalation of allergen-CpG conjugate could be a desensitization therapy for patients with bronchial asthma.

Adjuvants, Immunologic↗
PubMed2000

Repression of heme oxygenase-1 by hypoxia in vascular endothelial cells.

Heme oxygenase 1 (HO-1), a rate-limiting enzyme in heme catabolism, has been reported to be induced by hypoxia. Unexpectedly, here we show that expression of HO-1 mRNA is repressed by hypoxia in primary cultures of human umbilical vein endothelial cells (HUVECs), but is increased by cobalt chloride (CoCl(2)) that is known to mimic hypoxia. Under the culture conditions used, the DNA-binding and transactivation activities of hypoxia-inducible factor 1 were increased in HUVECs by hypoxia or CoCl(2). Therefore, hypoxia and cobalt showed opposing effects on HO-1 mRNA expression, despite activation of hypoxia-inducible factor 1. The half-life of HO-1 mRNA was not changed by hypoxia, but was significantly prolonged by CoCl(2). Hypoxia also represses HO-1 mRNA expression in human coronary artery endothelial cells and astrocytes. The repression of HO-1 expression may represent the adaptation to hypoxia in certain cell types.

Cell Hypoxia↗
PubMed2000

Long-term right ventricular volume overload increases myocardial fluorodeoxyglucose uptake in the interventricular septum in patients with atrial septal defect.

BACKGROUND: Several studies have shown that long-term right ventricular (RV) overload in animal models alters myocardial energy substrate metabolism. However, whether long-term RV volume overload alters this metabolism in the human is unclear. METHODS AND RESULTS: We performed positron emission tomography with [(18)F]fluorodeoxyglucose (FDG) and single-photon emission tomography (SPECT) with [(201)Tl]TlCl (Tl) and [(123)I]15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) in 11 patients with atrial septal defect (ASD) and 11 control subjects. In the FDG study, we calculated myocardial metabolic rate of glucose (MMR) in interventricular septum (IVS) and left ventricular (LV) free wall. MMR was significantly increased in IVS compared with LV free wall in the ASD patients (420+/-35 versus 333+/-32 mol x kg(-1) x min(-1); P<0.05) but not in the control group (347+/-27 versus 357+/-25 mol x kg(-1) x min(-1)). In both ASD and control groups, SPECT count was not significantly different between IVS and LV free wall in Tl (ASD, 160+/-11 versus 177+/-12; control, 141+/-12 versus 157+/-14 counts per 15 minutes) and BMIPP studies (ASD, 203+/-14 versus 212+/-18; control, 162+/-16 versus 176+/-16 counts per 15 minutes). MMR in the IVS/LV free wall ratio in the ASD group significantly correlated with indices related to RV volume overload. CONCLUSIONS: Given the assumption that long-term RV volume overload did not affect the lumped constant, the present study suggests that, unlike myocardial perfusion or fatty acid analogue uptake, myocardial glucose utilization in IVS relative to LV free wall is increased in relation to long-term RV volume overload in patients with ASD.

Adult↗