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Biomedical subjects

Kunio Shirato

Publications and source records attributed to Kunio Shirato.

At least 55 records · Page 3Linked to original sources

Expression of the von Willebrand factor in atrial endocardium is increased in atrial fibrillation depending on the extent of structural remodeling.

BACKGROUND: The incidence of stroke in patients suffering atrial fibrillation (AF) is increased when left atrial enlargement occurs. Recently, the platelet adhesive molecule, von Willebrand factor (vWF), located in the atrial endocardium, has been shown to be increased in patients with a variety of heart diseases compared with patients who have no cardiac problems. METHODS AND RESULTS: We investigated the expression of vWF mRNA and protein in the endocardium as a possible prothrombotic alteration of AF in association with atrial structural remodeling. Atrial appendage specimens were obtained during either heart surgery or at an autopsy from AF patients with and without underlying heart disease. The immunohistochemical and in situ hybridization signals for vWF in the endocardium were well correlated and varied widely among the individual atrial appendages examined. The increased expression of vWF in the endocardium was associated with enlarged left atrial dimensions in mitral valvular disease or increased myocyte diameters in the underlying myocardium. Platelet adhesion/aggregation on the endocardium was always found under the fresh thrombi and was colocalized with strong vWF staining, but not necessarily with fibrinogen and/or fibrin staining. CONCLUSIONS: Endocardial overexpression of vWF may occur during the process of atrial structural remodeling contributing to the thrombotic predilection of AF in association with underlying heart disease.

Adult↗

Analysis of chronic heart failure registry in the Tohoku district: third year follow-up.

BACKGROUND: Because the real prognosis of Japanese patients with chronic heart failure (CHF) is still unknown, the aim of the present study was to clarify the prognosis and predictors for mortality of CHF patients using the Chronic Heart failure Analysis and Registry in Tohoku district (CHART). METHODS AND RESULTS: As of February 2003, 1,154 stable CHF patients with optimum standard therapy have been enrolled in the registry since February 2000 and of these, 175 died of some cause during the follow-up period (mean follow-up period, 1.9+/-0.9 years), giving 1- and 3-year all-cause mortality rates of 7.3% and 20.9%, respectively. Multivariate analysis showed that age at entry, diabetes, ventricular tachycardia, plasma concentration of brain natriuretic peptide (BNP), New York Heart Association (NYHA) functional class and rural residence were significantly associated with all-cause mortality (hazard ratio: 1.028, 1.940, 1.650, 1.001, 1.713, and 2.226). The 1-year all-cause mortality rates of CHF patients with a left ventricular ejection fraction <25%, left ventricular end-diastolic diameter > or =60 mm, BNP > or =500 pg/ml, NYHA > or = III, or with underlying coronary artery disease were 15.0%, 11.4%, 16.8%, 16.3%, and 10.8%, respectively. CONCLUSIONS: The prognosis of Japanese CHF patients with these predictors remains poor. A stratified approach is necessary to improve their survival and quality of life.

Aged↗

Rationale, design, and organization of the Diastolic Heart Failure Assessment Study in Tohoku District (DIAST).

BACKGROUND: High mortality and a high readmission rate characterize diastolic heart failure (DHF), but evidence-based therapeutic strategies have not been established for DHF. METHODS: The aim of a multicenter, randomized open trial (the Diastolic Heart Failure Assessment Study in Tohoku District, DIAST) is to evaluate the safety and prognostic efficacy of the multiple action non-selective beta-blocker carvedilol in 160 patients with DHF (left-ventricular ejection fraction > or =50%). The target dose of carvedilol is 10 mg twice a day and the mean follow-up is estimated to be 2 years. The primary endpoints are to evaluate (1) all-cause mortality or hospitalization, (2) cardiovascular mortality or hospitalization and (3) worsening heart failure. The secondary endpoints are to assess (1) cardiovascular events, (2) the individual components of the above combined endpoints, (3) the duration of hospitalization, (4) the functional class and exercise capacity and (5) the safety and tolerability. All patients' data are processed using an original registration system on an internet homepage. Several substudies to assess neurohumoral factors, heart rate variability, oxidative stress and sleep apnea will clarify the pathophysiology of DHF. CONCLUSIONS: The DIAST will contribute to establish therapeutic guidelines for DHF.

Diastole↗

Inferior vena cava filter is a new additional therapeutic option to reduce mortality from acute pulmonary embolism.

BACKGROUND: There are few reports that examine the current imaging and management techniques according to the severity of acute pulmonary embolism (APE) or that clarify whether the management strategy ameliorated the mortality from APE. METHODS AND RESULTS: The study group were 456 patients with APE who were clinically diagnosed before their death. The severity at diagnosis, and the imaging and management techniques were analyzed. Mortality from APE was 0.8% in patients without shock nor right ventricular overload, 2.7% in patients with right ventricular overload without shock, 15.6% in patients with shock, and 52.4% in patients with cardiopulmonary arrest (p<0.0001). In the more severe cases, pulmonary angiography and trans-thoracic echocardiography were used more frequently, whereas both ventilation and perfusion lung scans were used less frequently. Computed tomography was used widely, regardless of the severity. Thrombolytic therapy and catheter therapy were used more frequently in the more severe cases, but an inferior vena cava filter was the only management strategy that reduced the mortality from APE. CONCLUSIONS: The severity of APE at diagnosis affected the selection of both the diagnostic techniques and the type of management. Implantation of inferior vena cava filters reduced the mortality from APE.

Aged↗

Right ventricular systolic function and the manner of transformation of the right ventricle in patients with dilated cardiomyopathy.

BACKGROUND: Dilated cardiomyopathy (DCM) is generally considered to be accompanied by both left and right ventricular dysfunction, but most studies only analyze the left ventricular function. METHODS AND RESULTS: Biplane right ventriculography was performed in 13 control subjects and 13 patients with DCM and New York Heart Association functional class II. Three dimensions of the right ventricle (RV) (the long axis dimension (LA), the anterior - posterior dimension (AP), and the septum -free wall dimension (SF)) and 2 dimensions of the left ventricle (LV) (LA and AP) were examined to assess regional function. The group with DCM had a lower stroke volume index and RV ejection fraction. In the RV dimensional analysis, the group with DCM had a smaller SF and a larger AP at end-diastole, and larger AP and LA at end-systole. There was a significant linear negative correlation between SF of RV and AP of LV at end-diastole. CONCLUSION: In clinically well-controlled cases of DCM, RV systolic function is depressed, and the RV is compressed by the LV, becoming less thick than in the controls. This transformation results from some parallel interaction between the RV and a markedly enlarged LV.

Adolescent↗

Effects of tachycardia on regional wall motion in acute ischemic canine heart.

Tachycardia accompanies the preload reduction. Our aim is to assess the effect of the heart rate change on wall motion in ischemic heart. In 8 dogs with occlusion of left anterior descending artery, we changed the heart rate (heart rate 90, 120, and 150 beats/minute) after using UL-FS49, a selective bradycardic agent, with atrial pacing. Preload was changed by inferior vena caval occlusion at a heart rate of 90 beats/minute. With either an increase in heart rate or an inferior vena caval occlusion, the end-diastolic length was decreased, but the end-diastolic length relationships between the non-ischemic and the ischemic region made different lines from those of the heart rate change and inferior vena caval occlusion. When increasing the heart rate, isovolumetric shortening was unchanged in the non-ischemic region with more expansion in the ischemic region. While inferior vena caval occlusion at a heart rate of 90 beats/minute, isovolumetric shortening was increased in the non-ischemic region, with more expansion in the ischemic region. Both in tachycardia and by the inferior vena caval occlusion, ejectional shortenings decreased in the non-ischemic and ischemic regions. Our results suggest that, in ischemic heart, tachycardia changes both in the end-diastolic length relationship between the non-ischemic and the ischemic region and at the isovolumetric contraction phase. The changes seem to be not only due to the inferior vena caval occlusion, but also due to tachycardia itself.

Animals↗

Warfarin-intractable, intraatrial thrombogenesis in a 52-year-old woman with mitral stenosis and chronic atrial fibrillation.

Thromboembolic events are serious complications of atrial fibrillation (AF). We histologically investigated intraatrial thrombogenesis in a 52-year-old woman with mitral stenosis and chronic AF who had recurrent attacks of cerebral infarction despite continuous warfarin therapy. She underwent cardiac surgery for mitral valve replacement and maze procedure including left atrial thrombectomy. Macroscopic thrombi were found on the endocardium and their surfaces appeared rough and dark red in most areas. Histological examination showed that a single thrombus mass was composed of several tissue layers or blocks on the endocardium. Immunohistochemistry revealed stratum-like accumulations of small platelet aggregate/fibrin clot complexes in the superficial, fresh thrombus layers and multiple neovessel formation in the basal organized tissue layers. This case study suggests that intraatrial thrombi may develop in a stepwise fashion on the endocardium involving platelet aggregate/fibrin clot complex formation.

Adult↗

Deficit of CD38/cyclic ADP-ribose is differentially compensated in hearts by gender.

To elucidate whether myocardial CD38/cyclic ADP-ribose (cADPR) signaling plays a physiological role, we investigated the heart of CD38 knockout mice (CD38KO). In CD38KO, the myocardial cADPR content was reduced by 85% compared with wild-type mice (WT). Cardiac hypertrophy developed only in males. At 36 degrees C, none of the parameters for Ca(2+) transients and forces of the papillary muscles differed between WT and CD38KO. In contrast, at 27 degrees C, at which cADPR does not work, the peak [Ca(2+)](i) was increased and the decline in [Ca(2+)](i) was accelerated in CD38KO compared with WT. In CD38KO, the protein expression of SR Ca(2+) ATPase type2 (SERCA2) and the SERCA2-to-phospholamban ratio were increased compared with WT. The ryanodine receptor protein was increased only in female CD38KO compared with WT. These data suggest that the CD38/cADPR signaling plays an important role in intracellular Ca(2+) homeostasis in cardiac myocytes in vivo. Its deficiency was compensated differentially according to gender.

ADP-ribosyl Cyclase↗

Cytochrome P-450 metabolites but not NO, PGI2, and H2O2 contribute to ACh-induced hyperpolarization of pressurized canine coronary microvessels.

The endothelium-dependent hyperpolarization of cells has a crucial role in regulating vascular tone, especially in microvessels. Nitric oxide (NO) and prostacyclin (PGI2), in addition to endothelium-derived hyperpolarizing factor (EDHF), have been reported to hyperpolarize vascular smooth muscle in several organs. Studies have reported the hyperpolarizing effects of these factors are increased by a stretch in large coronary arteries. EDHF has not yet been identified and cytochrome P-450 metabolites and H2O2 are candidates for EDHF. With the use of the membrane potential-sensitive fluorescent dye bis-(1,3-dibutylbarbituric acid)trimethione oxonol [DiBAC4(3)], we examined whether NO, PGI2, cytochrome P-450 metabolites, and H2O2 contribute to ACh-induced hyperpolarization in pressurized coronary microvessels. Canine coronary arterial microvessels (60-356 mum internal diameter) were cannulated and pressurized at 60 cmH2O in a vessel chamber perfused with physiological salt solution containing DiBAC4(3). Fluorescence intensity and diameter were measured on a computer. There was a linear correlation between changes in the fluorescence intensity and membrane potential. ACh significantly decreased the fluorescence intensity (hyperpolarization) of the microvessels without any inhibitors. Endothelial damage caused by air perfusion abolished the ACh-induced decrease in fluorescence intensity. The inhibitors of NO synthase and cyclooxygenase did not affect the ACh-induced decreases in the fluorescence intensity. The addition of 17-octadecynoic acid, a cytochrome P-450 monooxygenase inhibitor, to those inhibitors significantly attenuated the ACh-induced decreases in fluorescence intensity, whereas catalase, an enzyme that dismutates H2O2 to form water and oxygen, did not. Furthermore, catalase did not affect the vasodilation produced by ACh. These results indicate that NO and PGI2 do not contribute to the ACh-induced hyperpolarization and that the cytochrome P-450 metabolites but not H2O2 are involved in EDHF-mediated hyperpolarization in canine coronary arterial microvessels.

Acetylcholine↗

Should increasing the dose or adding an AT1 receptor blocker follow a relatively low dose of ACE inhibitor initiated in acute myocardial infarction?

OBJECTIVE: Based on currently available clinical evidence, we should use high-dose angiotensin converting enzyme inhibitor (ACE-I) for patients with acute myocardial infarction (MI), initiating it at incremental doses to avoid excessive hypotension. Recent animal studies with acute MI models failed to demonstrate the superiority of the combination therapy of ACE-I and angiotensin receptor blocker (ARB) to high-dose ACE-I treatment with comparable blood pressure reductions, which however might be attributed to the initiation of the targeted doses from the beginning. The aim of this study was to compare the effect of increasing the dose of ACE-I with that of adding ARB following a relatively low dose of ACE-I on the survival and left ventricular (LV) remodeling after MI. METHODS: Rats underwent left coronary artery ligation and were treated with either ACE-I temocapril (5 mg/kg/day) or vehicle for 2 weeks, which was initiated 3 days after the surgery. The rats treated with temocapril were further randomly assigned to receive either high-dose temocapril (10 mg/kg/day) or combination therapy (temocapril 5 mg/kg/day+olmesartan 2.5 mg/kg/day), which was continued for another 6 weeks. RESULTS: Both treatments similarly reduced the blood pressure, improved survival and ameliorated LV enlargement. In contrast, several parameters of LV function were significantly ameliorated only by the high-dose ACE-I but not by the combination therapy. CONCLUSIONS: After the initiation of a relatively low dose of ACE-I in acute MI, increasing the dose of ACE-I or adding ARB may equally improve survival and LV remodeling in the setting of an equal hypotensive effect. Further study with a longer treatment protocol is required to determine whether the several favorable effects on LV function elicited only by the high-dose ACE-I treatment provide further beneficial effects on survival and LV remodeling compared with the combination therapy.

Angiotensin II Type 1 Receptor Blockers↗

Bach1 functions as a hypoxia-inducible repressor for the heme oxygenase-1 gene in human cells.

Heme oxygenase 1 (HO-1) catalyzes heme breakdown, eventually releasing iron, carbon monoxide, and bilirubin IXalpha. HO-1 is induced by its substrate heme and various environmental factors, which represents a protective response against oxidative stresses. Here we show that hypoxia represses HO-1 expression in three human cell types but induces it in rat, bovine, and monkey cells, indicating the inter-species difference in the hypoxic regulation of HO-1 expression. The hypoxia-mediated repression of HO-1 expression is consistently associated with the induction of Bach1, a heme-regulated transcriptional repressor, in human cells. Bach1 is a basic leucine zipper protein, forming a heterodimer with a small Maf protein. Expression of HO-1 was also reduced in human cells when exposed to interferon-gamma or an iron chelator desferrioxamine, each of which induced Bach1 expression. In contrast, induction of HO-1 expression by CoCl(2) is associated with reduced expression of Bach1 mRNA. Thus, expression of HO-1 and Bach1 is inversely regulated. We have identified a Maf recognition element in the human HO-1 gene that is required for repression of a reporter gene by hypoxia and targeted by Bach1. Therefore, Bach1 functions as a hypoxia-inducible repressor for the HO-1 gene, thereby contributing to fine-tuning of oxygen homeostasis in human cells.

Animals↗

Impact of hypercholesterolemia on acidosis-induced coronary microvascular dilation.

An increase in coronary flow conductance during acidosis is an important compensatory mechanism in various diseased conditions. On the other hand, hypercholesterolemia causes microvascular dysfunction as well as macrovascular disorders. We investigated the impact of hypercholesterolemia on the coronary microvascular response to acidosis. Coronary arterioles (< 150 microm) isolated from rabbit hearts were cannulated to micropipettes in a vessel chamber and the microvascular responses were observed. After preconstriction was established, the extravascular pH was gradually reduced from 7.4 to 7.0. The effects of glibenclamide, ATP-sensitive K(+) (K(ATP)) channel blocker, (1 microM, n = 4) or pertussis toxin (100 ng/mL, n = 7) on the acidosis-induced microvascular responses were examined. In another set of experiments, rabbits were randomly assigned to normal chow (NC group, n = 18) or high cholesterol (2 %) diet (HC group, n = 20). After 8 weeks of feeding, the responses of isolated coronary arterioles to acidosis, ADP, nitroprusside, and levcromakalim were examined in the two groups. Coronary arterioles significantly dilated as the pH was reduced and the dilation was significantly inhibited by glibenclamide or pertussis toxin. Acidosis-induced dilation in the HC group was significantly attenuated compared to the NC group (36.5 +/- 2.1 % vs 73.7 +/- 4.8 % at pH = 7.0 P < 0.05). There were no significant differences in the dilations by ADP, nitroprusside and levcromakalim between the two groups. In conclusion, acidosis-induced dilation of rabbit coronary arterioles is mediated by the activation of the pertussis toxin-sensitive G protein and K(ATP) channels, and the dilation of coronary arterioles is impaired in hypercholesterolemia. The impairment occurs upstream of K(ATP) channel opening.

Acidosis↗

Underdiagnosis and undertreatment of COPD in primary care settings.

OBJECTIVE: The aim of this study was to improve the detection of COPD in a primary care setting and to evaluate the subsequent management of these patients by general practitioners. METHODOLOGY: A two-step protocol was followed: patients were screened for airway obstruction and their subsequent management status reviewed. Screening spirometry was performed in 56 primary care settings (23 hospitals and 33 general practices). Inclusion criteria for screening subjects were: (i) > or =40-year-old smokers (both current and past smokers) and/or (ii) > or =40-year-old patients with respiratory symptoms of chronic cough and sputum. Patients with a previously diagnosed respiratory disease were excluded. In the second part of the study, the diagnosis and the subsequent management status of subjects with airway obstructive changes (FEV1/FVC <70%) were sought from their physician using a questionnaire 2 months after detection. RESULTS: A total of 1168 patients were screened, with 128 not analysed because of incomplete data, leaving 1040 patients. The percentages of current smokers, ex-smokers, and non-smokers among all analysed subjects were 41.7%, 29.8% and 28.5%, respectively. Airway obstructive changes (FEV1/FVC <70%) were found in 27.0% (n = 281) of all analysed subjects. Questionnaires for 194 subjects (with positive screening tests) were sent back by the participating physicians. Eighty-one per cent (n = 158) of the 194 subjects had COPD and 13.4% (n = 26) had asthma. Sixty-one per cent (n = 96) of the subjects with moderate to severe COPD according to international guidelines (FEV1 <80% predicted). However, 31.3% (n = 30) did not receive any clinical intervention (smoking cessation advice and/or drug administration). CONCLUSIONS: Screening spirometry in outpatients in a primary care setting can identify many COPD patients. However, COPD management appears to be poor in Japan.

Aged↗

Inhibition of matrix metalloproteinases prevents cardiac hypertrophy induced by beta-adrenergic stimulation in rats.

Insulin-like growth factor (IGF) -I is one of the candidates for cardiac hypertrophy induced by beta-adrenergic stimulation. However, the mechanisms by which the biologic actions of IGF-I are regulated under this condition remain unclear. IGF-I becomes bioavailable for its receptors upon its dissociation from IGF-binding protein (IGFBP) through IGFBP degradation. Because matrix metalloproteinases (MMPs) have been implicated in the degradation of IGFBPs, the authors investigated the role of MMPs in the regulation of the IGF-I action through the degradation of IGFBPs in cardiac hypertrophy induced by beta-adrenergic stimulation. They examined the expression of MMPs in cardiac tissues of rats infused with isoproterenol (3 mg/kg per day), the effect of a MMP inhibitor, SI-27 (5 mg/rat per day), on cardiac hypertrophy, and the expression of IGF-I and IGFBP-3. MMP-1 and -2 activities increased and IGFBP-3 was degraded in heart hypertrophied by isoproterenol. MMP inhibition caused a regression in the myocyte hypertrophy in association with the suppression of both IGF-I protein in myocytes and the degradation of IGFBP-3 protein. These results suggest that the induction of myocyte hypertrophy by isoproterenol is mediated, at least in part, by a modulation of the IGF-I axis.

Animals↗

Comparison of the efficacy of reperfusion therapies for early mortality from acute myocardial infarction in Japan: registry of Miyagi Study Group for AMI (MsAMI).

The current reperfusion strategy in Japan for acute myocardial infarction (AMI) is that the majority of early arrival patients are treated with primary percutaneous coronary intervention (PCI). However, the efficacy of primary PCI, intravenous thrombolysis (IV-T), intracoronary thrombolysis (IC-T) and rescue PCI has not been compared in the clinical situation. In the present study, 3,258 cases of AMI in 1992-2000 from the data base of the Miyagi Study Group for AMI were analyzed. These patients were hospitalized within 6 h of the onset of symptoms. IV-T and IC-T were initially performed in 120 and 441 patients, respectively, and 41 and 199 rescue PCI procedures, respectively, were needed. Primary PCI was performed in 1,822 cases, and no reperfusion therapy was done in 875 patients. The crude 30-day in-hospital mortality was 12.7% for IV-T, 3.7% for IC-T, 4.8% for primary PCI, 7.9% for rescue PCI, and 14.1% in patients who did not undergo reperfusion therapy. The covariate-adjusted odds ratio (95% confidence interval) was 0.38 (0.28-0.52) for primary PCI, 0.30 (0.15-0.60) for IC-T, 1.04 (0.51-2.10) for IV-T and 0.77 (0.46-1.30) for rescue PCI. The present data verify that primary PCI is superior to other reperfusion strategies in the real clinical situation and justifies the current unique strategy of reperfusion therapy for AMI used in Japan.

Adult↗

Greater impairment of right ventricular systolic function in patients with anterior myocardial infarction because of the extent of proximal lesions.

The present study examined the influence of the extent of the ischemic area on right ventricular (RV) systolic function and the relation between the RV global and regional systolic function in patients with anteroseptal myocardial infarction (MI). Biplane right ventriculography was performed in 15 subjects as the control group, and 46 patients with anteroseptal MI as the MI group. Three dimensions of the RV (the long axis dimension [LA], the anterior-posterior dimension [AP] and the septum-free wall dimension [SF]) were examined to assess regional function The MI group had a larger right ventricular end-systolic volume index and lower right ventricular ejection fraction than the control group. The more proximal the coronary lesion, the lower was the ejection fraction of the RV in the MI group. The MI group had lower percent shortening (% shortening) of the SF than the control group, but there were no significant change in the % shortening of AP and LA between the groups. The results suggest that the degree of impairment of RV systolic function depends on the extent of the infarcted area, and that the impairment is mainly from a reduction in the %shortening of the SF.

Aged↗

Characteristics and 1-year prognosis of medically treated patients with chronic heart failure in Japan.

The study was designed to characterize patients with chronic heart failure (CHF) in Japan in terms of the etiologies and prognosis. CHF was defined by ejection fraction (EF >or=50%), left ventricular diastolic dimension (LVDD >or=55 mm) or a past history of congestive heart failure. Among the 721 recruited patients, the most frequent etiology for CHF was dilated cardiomyopathy (DCM) in patients aged less than 59 years, and valvular heart disease (VHD) in those aged 70 years or more. The 1-year crude mortality was 8% overall and 12% in patients with myocardial infarction (MI). Sudden death accounted for 40% of the total deaths among all patients, and 60% in patients with MI. Multivariate logistic regression analysis showed that brain natriuretic peptide (BNP) was a consistent prognostic marker in CHF patients with a variety of etiologies. Total death and hospitalization because of heart failure were significantly less frequent in patients with BNP less than 100 pg/ml. In conclusion, the etiologies of Japanese CHF appear to be more diverse than those of other Western countries, but BNP is an excellent prognostic marker despite the etiological diversity. Sudden, unexpected death in CHF patients is also a serious problem in Japan. A nation-wide epidemiologic study should be done to characterize Japanese CHF.

Aged↗

Varieties of right ventricular diastolic function in patients with non-obstructive hypertrophic cardiomyopathy.

We examined whether differences in the location of myocardial hypertrophy influence the right ventricular diastolic function in patients with non-obstructive hypertrophic cardiomyopathy using cineangiography. Biplane right ventriculography was performed in 34 subjects (normal = 14, asymmetric septal hypertrophy = 9, apical hypertrophy = 11) during cardiac catheterization. In patients with asymmetric septal hypertrophy, compared with apical hypertrophy and normal groups, the indices of the right ventricular diastolic function including right ventricular peak filling rate and filling fraction of rapid filling phase were lower and the time to peak filling rate was prolonged. But in patients with apical hypertrophy, these indices were not significantly different compared with normal. There were no differences in right ventricular ejection fraction and cardiac index among the three groups. These data suggest that the location of the myocardial hypertrophy of the left ventricle is a significant factor affecting the right ventricular diastolic filling in non-obstructive hypertrophic cardiomyopathy.

Adult↗