Biomedical subjects

J Kiraku

Publications and source records attributed to J Kiraku.

10 recordsLinked to original sources

PubMed2000

Increases in intracellular calcium of arterial smooth muscle cells in transgenic mice overexpressing Na+/H+ exchanger.

We produced transgenic mice overexpressing Na+/ H+ exchanger as a model of salt-sensitive hypertension and reported that dietary salt loading elevates blood pressure in these transgenic mice. We speculate that this blood pressure elevation may be attributed to the elevation of intraarterial smooth muscle Ca2+ concentration through Na+/Ca2+ exchange. To test this hypothesis, we measured the isometric tension of aortic rings and intracellular free calcium ([Ca2+]i) of cultured smooth muscle cells. In the transgenic mice, the aortic ring contraction induced by 5 mM caffeine (percentage of 60 mM K-induced contraction) was significantly greater than control mice (60.1 +/- 5.5% vs. 44.8 +/- 3.1%). The mean [Ca2+]i in vascular smooth muscle cells (VSMCs) of transgenic mice (123.1 +/- 19.7 nM) was higher than those in VSMCs of control mice (66.6 +/- 7.2 nM). These observations suggest that dietary salt loading increases the concentration of calcium in arterial smooth muscle cells in this transgenic mice. These findings are helpful in tracing the causes of salt-sensitive hypertension.

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PubMed2000

Unclassified connective tissue disease presenting as cardiac tamponade: a case report.

This report describes a case of cardiac tamponade as the initial manifestation of unclassified connective tissue disease (UCTD). A 68-year-old Japanese woman was admitted to hospital because of dyspnea and edema. She had undergone a radical left mastectomy for the treatment of breast cancer 18 years before. On admission, bilateral leg edema, hepatomegaly, and a paradoxical pulse were noted on physical examination. The erythrocyte sedimentation rate was elevated and the C-reactive protein was 2.8 mg/dl. Antinuclear antibodies and anti-SS-A/Ro antibodies were present. The scl-70 and anticentromere antibodies were elevated. Chest radiography showed cardiomegaly. Echocardiography revealed a large pericardial effusion, but the pericardial fluid did not contain malignant cells or bacteria. She did not meet the diagnostic criteria for any known connective tissue diseases, so was diagnosed with cardiac tamponade due to UCTD. Prednisolone (30 mg/day) was administered, which resulted in a gradual resolution of the pericardial effusion. Although connective tissue diseases are known to cause pericardial effusion, cardiac tamponade as the initial manifestation of the disease in the absence of other symptoms is quite rare.

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PubMed1999

Dietary salt loading increases nitric oxide synthesis in transgenic mice overexpressing sodium-proton exchanger.

We studied the role of nitric oxide (NO) synthesis in amelioration of blood pressure elevation during dietary salt loading in transgenic mice overexpressing sodium proton exchanger. Systolic blood pressure rose after starting salt loading only in the high-salt group of transgenic mice. However, this elevation of blood pressure was not continued. Urinary excretion of inorganic nitrite and nitrate in the high-salt group of transgenic mice was significantly higher than in the high-salt group of control mice. These results suggest that increased NO synthesis in response to salt loading is one of the anti-hypertensive mechanisms in transgenic mice overexpressing sodium proton exchanger.

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PubMed1998

Remission of hypertension: retrospective observations over a period of 20 years.

To clarify the background and outcome of hypertensive patients who have remission of their elevated blood pressure (BP) after a course of antihypertensive drug therapy, we designed a retrospective observational study. The clinical records of 106 hypertensive men and women (BP, 164.3/104.4 mmHg) given antihypertensive drug treatment and subsequently examined every 1 to 3 mo for more than 20 yr were reviewed. The patients were divided into two groups: those who had remission (R-group) and those who did not have remission (N-group). Patients were considered in remission if no significant elevation in BP was observed for more than 1 yr after withdrawing their medication. Remissions ranging in duration from 1.6 to 21.7 yr (average duration, 6.3 yr) occurred in 19 of 106 patients (17.9%). However, anti-hypertensive drug treatment was eventually restarted in 17 of the 19 patients. Before treatment, comparison of the R-group and N-group revealed no differences with respect to age, body weight, BP, or serum creatinine. In contrast, the proportion of patients who lacked high-voltage deflections in their electrocardiograms (ECG) as well as that of patients whose BP was well-controlled by a single medication was significantly greater in the R-group than in the N-group (12/19 vs. 22/87, p < 0.05 and 10/19 vs. 13/87, p < 0.001, respectively). In addition, body weight in the R-group decreased significantly by the time drug therapy was withdrawn (p < 0.01). Finally, significantly more patients (14 of 19 patients) entered remission in the spring and summer (p < 0.05) than at other times of the year. We conclude that remission occurs in a subset of well-controlled hypertensive patients and may persist for several years or more. However, in the majority of patients, antihypertensive drug treatment will usually need to be restarted at some point. Patients who lack ECG high-voltage deflections and who are successfully treated with a single therapeutic agent are most likely to experience remission. Moreover, it appears that withdrawing patients from drug therapy in the spring or summer is more likely to yield a favorable outcome than at other times of the year.

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PubMed1998

[Transient mitral regurgitation induced by vagal stimulation in rabbits: a Doppler echocardiographic study].

Cervical vagal stimulation in rabbits frequently causes systolic murmur with bigeminy due to premature ventricular contractions. The bigeminy disappears in a few minutes, but the systolic murmur persists for a few days. The present study used Doppler echocardiography to examine whether or not this systolic murmur is due to mitral regurgitation. Electrocardiographic monitoring was performed on anesthetized rabbits forced into the supine position. Doppler echocardiography was performed in the animals which showed systolic murmur 6 hours, 3 days, and 1, 2, 3 and 4 weeks after vagal stimulation. Six hours after vagal stimulation, phonocardiography detected systolic click and late systolic murmur, and Doppler echocardiography detected marked mitral regurgitation. The systolic murmur and mitral regurgitation were attenuated and the papillary muscle was swollen 3 days after vagal stimulation. The mitral regurgitation disappeared within a week and swelling of the papillary muscle improved 3 weeks after vagal stimulation. Doppler echocardiography confirmed that the systolic murmur observed in rabbits after vagal stimulation is due to transient mitral regurgitation.

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PubMed1997

Increase in erythrocyte volume in patients with chronic atrial fibrillation.

Non-anemic macrocytosis is occasionally observed in patients with a history of alcoholism or chronic liver disease. Recently we reported that patients with atrial fibrillation (AF) had larger erythrocytes than normal subjects. In the present study, we examined the temporal changes in hematologic measurements during the development of AF in 88 male patients (chronic AF: 49, paroxysmal AF: 39), and compared alcohol intake among the groups. The mean corpuscular volume of erythrocytes was significantly greater in chronic AF patients, both before (98.1 +/- 6.1 (SD) fl p < 0.05) and after onset (within 6 months: 98.4 +/- 7.1 fl p < 0.05; 1 year: 98.6 +/- 6.2 fl p < 0.01), compared with 300 age-matched male control subjects with sinus rhythm (95.9 +/- 3.6 fl). Hematocrit increased significantly with development of AF in both chronic and paroxysmal AF patients (p < 0.005). Mean daily alcohol consumption did not differ significantly among the control, chronic AF and paroxysmal AF groups. Our findings indicate that erythrocyte size is already larger in patients with chronic AF before the condition develops.

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PubMed1997

[Trends in the prescriptions for antihypertensive drugs in elderly patients].

We compared trends in the prescription of antihypertensive drugs in elderly patients with those in middle-aged patients. We analyzed prescriptions given to 141 patients with hypertension who were 65 years old or older (mean age, 73 years) and to 511 patients with hypertension who were 64 years old or younger (mean age, 59 years). The numbers of drugs prescribed did not differ between the elderly and the non-elderly patients. In both groups, about 50% of patients were given prescriptions for one antihypertensive drug, about 40% were given prescriptions for two drugs, and about 10% were given prescriptions for three drugs. Calcium antagonists were the agents most commonly prescribed as monotherapy (51.4% and 56.4% in the non-elderly and elderly respectively; n.s.); followed by beta-blockers (32.2% and 25.6%; n.s.). Diuretics were prescribed less often to non-elderly patients than to elderly patients (5.1% and 10.0%; p < 0.01). When prescriptions for more than one antihypertensive agent were included in the analysis, calcium antagonists were still the most commonly prescribed agents (63.8% and 66.4%; n.s.), followed by the beta-blockers (53.3% and 66.4%; p < 0.05). Diuretics were less commonly prescribed to non-elderly patients (13.5% and 21.3%; p < 0.005), while ACE inhibitors (19.0% and 11.6%; p < 0.005) and beta-blockers (52.3% and 44.0; p < 0.05) were more commonly prescribed to non-elderly patients. When we classified the data according to the time of the first visit, we found that patients whose first visit was earlier were more likely to have been given a prescription for a diuretics, whether they were elderly or non-elderly. Calcium antagonists were the most commonly prescribed agents in all time periods studied, followed by beta-blockers. Comparison of our results with those of a similar study done at our clinic in 1990 showed that the use of calcium antagonist monotherapy doubled in both groups (non-elderly: 26.4% in 1990 to 51.4% in 1995, p < 0.001; elderly: 29.5% in 1990 to 56.4% in 1995, p < 0.001) and that the use of diuretics declined markedly (non-elderly; 20.3% to 5.1%, p < 0.001; elderly: 30.2% to 10.0%, p < 0.001). A similar trend was seen when prescriptions for more than one antihypertensive drug were included in the analysis.

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PubMed1997

[Experimental study on the pathogenesis of mitral annular calcification: calcium deposits in mitral complex lesions induced by vagal stimulation in rabbits].

Cervical vagal stimulation in rabbits frequently causes peculiar mitral complex lesions which are detected by deposition of colloidal carbon. The present study examined the effects of vagal stimulation on the calcium (Ca) contents in the mitral complex lesions. Anesthetized rabbits were forced into the supine position with electrocardiographic monitoring. The animals were divided into those with vagal stimulation (n = 37), and those without manipulation as controls (n = 25). Colloidal carbon (1 ml) was intravenously injected into the animals on the next day. All animals were sacrificed after 1 week. After perfusion of the heart by heparinized saline, Ca content per g myocardium in the mitral annulus, papillary muscle, free wall or apex in the left ventricle was measured by the atomic absorption method. Immediately after vagal stimulation, bigeminy due to premature ventricular contractions was observed in 76%, and systolic murmur was heard in 30%. Mitral complex lesions detected by carbon deposits were found in 73% of the rabbits with vagal stimulation. Ca content in the mitral annulus or papillary muscle was significantly greater than that in the free wall or apex (p < 0.001). Ca content in the mitral annulus was significantly greater in the rabbits with vagal stimulation than in the control group (p < 0.001). In the former group, Ca content in the mitral annulus in animals with mitral complex lesions was significantly greater than that in those without mitral complex lesions (p < 0.01). These results suggest that these mitral complex lesions might provide an experimental model of mitral annular calcification, and that the autonomic nervous system and arrhythmia might be involved in the mechanism of this calcification.

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PubMed1997

[QRS axis shift in deep breathing].

We examined changes in mean QRS axis of electrocardiogram during the deep breathing test in outpatients with hypertension, ischemic heart disease, and/or diabetes mellitus. The mean age of all patients (n = 596; male 327, female 269) was 63.0 years (male 62.7 years, female 63.4 years). The average of the mean QRS axis in all patients was shifted to the right during deep inspiration. The changes in mean QRS axis during deep breathing test were more than 60 degrees in 27 patients (4%) (mean age: 70.0 years), 30-59 degrees in 118 patients (20%) (mean age: 65.5 years), and 0-29 degrees in 451 patients (76%) (mean age: 61.9 years). These results suggest that the changes in mean QRS axis during deep breathing are greater in the aged patients.

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PubMed1996

[Experimental production of tricuspid valve and papillary muscle lesions by premature ventricular contractions due to ventricular stimulation in rabbits].

Ventricular bigeminy or trigeminy can spontaneously occur in anesthetized rabbits forced into the supine position. Premature ventricular contractions (PVCs) of this type are characterized by a long coupling time and superimposition of the following P waves. Rabbits with PVCs of this type frequently develop peculiar mitral complex lesions which are detected by deposition of colloidal carbon. This study examined the effects on the tricuspid complex of artificial PVCs induced by left ventricular pacing in rabbits. Anesthetized rabbits were forced into the supine position under electrocardiographic monitoring. The animals were divided into those with spontaneous PVCs, those with artificial PVCs, and those without PVCs as controls. Colloidal carbon (1 ml) was intravenously injected into the animals the next day. All animals were sacrificed after 1 week. Tricuspid complex lesions were found in 2.0% of animals with spontaneous PVCs, in 17.6% of those with artificial PVCs, and in none of the controls. These results indicate that artificial PVCs induced by left ventricular pacing can cause peculiar tricuspid complex lesions.

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