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Biomedical subjects

U Ikeda

Publications and source records attributed to U Ikeda.

At least 127 records · Page 7Linked to original sources
PubMed1998

A case of Cushing's syndrome due to ACTH-independent bilateral macronodular hyperplasia associated with excessive secretion of mineralocorticoids.

A 74-year-old man developed Cushing's syndrome and hypokalemia due to ACTH-independent bilateral macronodular adrenocortical hyperplasia (AIMAH) with excessive secretion of mineralocorticoid hormones. Plasma concentrations of weak mineralocorticoids were high. The increase in plasma cortisol did not have a diurnal rhythm, and was not suppressed by a high dose of dexamethasone. Plasma ACTH was undetectable, but plasma cortisol was increased by ACTH administration. The concentrations of mineralocorticoids, especially deoxycorticosterone and corticosterone were increased, and augmented the response to ACTH administration. Plasma renin activity and aldosterone concentrations were rather suppressed. Both adrenal glands, with a total weight of 110 g, were enlarged and contained several macronodules. These nodules were composed of hyperplasia of small cortical cells and usual clear cells. This is a rare case of ACTH-independent bilateral macronodular adrenocortical hyperplasia because there were excessive secretion of mineralocorticoid and hypokalemia.

Adrenal Cortex↗
PubMed1998

Induction of torsades de pointes by dobutamine infusion in a patient with idiopathic long QT syndrome.

We used a provocative test with dobutamine infusion to diagnose long QT syndrome (LQTS) in a girl with a history of syncope. When dobutamine was infused at a rate of 10 microg/kg/min, the QT interval corrected for heart rate (QTc) was prolonged from 460 ms to 620 ms with abnormal TU complexes and torsades de pointes developed. In 5 control subjects the QTc did not change significantly during low-dose dobutamine infusion. Low-dose dobutamine, in addition to isoproterenol, may be useful for evaluation of prolongation of the QT interval and abnormal TU complexes in patients in whom LQTS is suspected.

Adolescent↗
PubMed1998

Endothelial cell damage and angiotensin-converting enzyme insertion/deletion genotype in elderly hypertensive patients.

OBJECTIVES: The purpose of this study was to investigate the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) genotype and endothelial cell dysfunction or hypercoagulable state in elderly hypertensive patients. BACKGROUND: Angiotensin-converting enzyme (ACE) insertion/ deletion (I/D) polymorphism was recently reported to be associated with various cardiovascular diseases. However, the precise mechanism of this association remains unknown, and some confounding factors might also affect the association. Endothelial cell dysfunction and coagulation activation play important roles in both the atherosclerotic process and the onset of cardiovascular events. METHODS: We identified the ACE I/D genotype and measured the plasma levels of markers of endothelial cell damage (von Willebrand factor [vWF] and thrombomodulin) and of coagulation activation (prothrombin fragment F1 + 2 [F1 + 2]) in 318 asymptomatic elderly patients with hypertension, aged 59-93 years. RESULTS: The vWF level was significantly higher in those with the DD genotype (n = 54) than in those with the II genotype (n = 131, p < 0.0001) or with the ID genotype (n = 133, p < 0.0001). The TM levels were also higher in patients with the ID genotype (p < 0.005) and the DD genotype (p < 0.01) than in those with the II genotype. There were no differences in F1 + 2 level among the groups. Positive correlations of systolic blood pressure with levels of both vWF and thrombomodulin were found predominantly in patients with the II genotype (both p < 0.001), but no correlation was noted in those with the DD genotype. CONCLUSIONS: Considering the increased plasma levels of both endothelial cell-derived markers in the hypertensive patients with ACE DD genotype, we speculate that the ACE D allele is a risk factor for the development of hypertensive cardiovascular disease associated with endothelial cell damage.

Aged↗
PubMed1997

Serotonin inhibits nitric oxide synthesis in rat vascular smooth muscle cells stimulated with interleukin-1.

We investigated the effects of serotonin (5-hydroxytryptamine; 5-HT) on nitric oxide (NO) synthesis in vascular smooth muscle cells. We measured the production of nitrite, a stable metabolite of NO, and the expression of inducible NO synthase protein in cultured rat vascular smooth muscle cells. Incubation of the cultures with interleukin-1beta (10 ng/ml) caused a significant increase in nitrite production. 5-HT inhibited nitrite production by interleukin-1beta -stimulated vascular smooth muscle cells in a concentration-dependent manner (10(-8)-10(-5) M). 5-HT-induced inhibition of nitrite production was accompanied by decreased inducible NO synthase protein accumulation in vascular smooth muscle cells. Addition of the 5-HT2 receptor antagonist ketanserin, but not the 5-HT1A receptor antagonist spiroxatrine, inhibited the effect of 5-HT. On the other hand, the 5-HT2 receptor agonist alpha-methyl-5-HT, but not the 5-HT1A receptor agonist (+/-)-8-hydroxy-2-(di-n-propylamino) tetralin, decreased interleukin-1beta-induced nitrite production by vascular smooth muscle cells. 5-HT significantly increased protein kinase C activity in vascular smooth muscle cells, and the protein kinase C inhibitor calphostin C dose-dependently abolished the effect of 5-HT on nitrite production. After protein kinase C activity was functionally depleted by treatment of cells with phorbol 12-myristate 13-acetate for 24 h, the effect of 5-HT was abolished. These results indicate that 5-HT acts on 5-HT2 receptors and inhibits NO synthesis in interleukin-1beta-stimulated vascular smooth muscle cells at least partially through a protein kinase C-dependent pathway.

Animals↗
PubMed1997

SOCS-1/JAB/SSI-1 can bind to and suppress Tec protein-tyrosine kinase.

Tec is the prototype of a recently emerging subfamily among nonreceptor type protein-tyrosine kinases and is known to become tyrosine-phosphorylated and activated by a wide range of cytokine stimulations in hematopoietic cells. Although Tec was recently shown to be involved in the cytokine-driven activation mechanism of c-fos transcription, it is yet obscure how Tec relays the signals from cell surface receptors to the nucleus. To identify signaling molecules acting downstream of Tec, we have looked for Tec-interacting proteins (TIPs) by using the yeast two-hybrid system. Here we report the identification and characterization of a novel protein, TIP3, which has been simultaneously identified by other groups as SOCS-1, JAB, or SSI-1. TIP3 carries one Src homology 2 domain with a sequence similarity to that of CIS. In 293 cells, TIP3 associates with Tec and suppresses its kinase activity. Interestingly, TIP3 can also down-regulate the activity of Jak2 but not that of Lyn. We propose that SOCS-1/JAB/SSI-1/TIP3 is a novel type of negative regulator to a subset of protein-tyrosine kinases.

Amino Acid Sequence↗
PubMed1997

Promoter of the Na,K-ATPase alpha3 subunit gene is composed of cis elements to which NF-Y and Sp1/Sp3 bind in rat cardiocytes.

Na,K-ATPase alpha subunit has three isoforms whose expression is regulated developmentally and hormonally. Na,K-ATPase alpha3 subunit gene (Atpla3) is expressed only in brain and neonatal heart in a rat. The purpose of this study is to analyze cis-acting elements and trans-acting factors regulating the transcription of Atpla3 in cultured neonatal rat cardiocytes. Transient transfection assays with Atpla3-luciferase chimeric construct and a series of 5' sequential deletion mutations revealed the existence of positive regulatory elements from -74 to -59 and from -59 to -39. A factor was identified to bind across -59 by gel retardation assay. Methylation interference and DNase I footprinting analyses revealed the binding region from -74 to -53 (positive regulatory element (PRE) 1). The binding factor was identified to be NF-Y by gel retardation assay using specific antibody. Gel retardation and methylation interference analyses revealed that factors bind to two other elements from -54 to -43 (PRE2) and from -25 to -13 (PRE3). The binding factors were identified to be Sp1/Sp3 using specific antibodies. The functions of above-mentioned three elements were examined by transient transfection assay with various combinations of mutations. They all regulated the transcription positively and a synergistic enhancement of it was observed. Roles of NF-Y in the transcriptional activation and synergy are discussed.

Animals↗
PubMed1997

Tranilast inhibits contraction of rat aortic smooth muscle.

Recently, the anti-allergic drug tranilast has been shown to reduce the rate of coronary restenosis after percutaneous transluminal coronary angioplasty. In this study, we investigated the effect of tranilast on contraction of and Ca2+ movement in vascular smooth muscle. We measured the isometric force and fura-2-estimated intracellular Ca2+ concentrations ([Ca2+]i) of rat aortic strips. Exposure of aortic strips to tranilast (0-500 microM) dose-dependently inhibited endothelin-1-induced increases in tension and [Ca2+]i elevation of the strips. Similar inhibition by tranilast was observed in response to high K+ stimulation. These results suggest that tranilast inhibits the contraction of vascular smooth muscle by inhibiting Ca2+ mobilization, which might be related to its preventive effect on coronary restenosis after percutaneous transluminal coronary angioplasty.

Animals↗
PubMed1997

Tranilast inhibits the growth of rat mesangial cells.

We investigated the effects of tranilast on the growth of cultured rat mesangial cells. The number of mesangial cells increased fivefold during a 5-day incubation in RPMI 1640 with 20% fetal bovine serum. The number of cells was significantly lower in the presence of tranilast than in its abscence. Tranilast (0 approximately 500 microM) inhibited platelet-derived growth factor (PDGF)-induced DNA synthesis of rat mesangial cells cultured in RPMI 1640 medium containing 0.5% fetal bovine serum in a dose-dependent manner. The inhibition of DNA synthesis by tranilast was not affected by the presence of indomethacin (1 microg/ml) or N(G)-monomethyl-L-arginine (0.5 mM). Tranilast did not stimulate nitrite oxide synthesis in PDGF-stimulated cells. Mitogen-activated protein kinase activity in mesangial cells was significantly increased by exposure to PDGF, while the effect was significantly suppressed in the presence of tranilast. The present study revealed that tranilast inhibits the growth of rat mesangial cells, independently of nitric oxide or prostacycline synthesis.

Animals↗
PubMed1997

Effect of mitral valvuloplasty in mitral stenosis on coagulation activity.

We investigated the plasma levels of molecular markers for the status of thrombin generation and fibrinolysis in patients with mitral stenosis before and after percutaneous mitral valvuloplasty. Our results show that percutaneous mitral valvuloplasty results in decreased coagulation activity, suggesting that percutaneous mitral valvuloplasty is also useful for prevention of systemic embolism in patients with mitral stenosis.

Blood Coagulation↗
PubMed1997

Monocytes modulate the fibrinolytic balance of endothelial cells.

Cultured endothelial cells (ECs) produced a constitutive plasminogen activator inhibitor-I (PAI-1), whereas primary culture of monocytes from blood did not produce a detectable amount of PAI-1. Addition of monocytes to ECs caused the accumulation of a large amount of PAI-1 in the supernatant in a dose- and time-dependent manner. Having almost no effect on the production of tissue-type plasminogen activator (t-PA), monocytes decreased the potential fibrinolytic activity of ECs. The 6 hours conditioned medium obtained from the coculture system between monocytes and either ECs or paraformaldehyde-fixed ECs had almost the same effect on the other ECs to produce PAI-1 and t-PA as monocytes that were direct contact with ECs. In addition, this effect was specifically inhibited by using two antibodies against interleukin-1 beta and tumor necrosis factor-alpha. These results indicate that interleukin-1 beta and tumor necrosis factor-alpha induced by the coculture are mostly responsible for decreasing the fibrinolytic activity of ECs.

Cells, Cultured↗
PubMed1997

Biochemical markers of coagulation activation in mitral stenosis, atrial fibrillation, and cardiomyopathy.

Advances in the understanding of the biochemistry of the mechanism of hemostasis have led to the development of sensitive methods for determining levels of markers which reflect thrombin activity (thrombin-antithrombin III complex, fibrinopeptide A, F1 + 2 fragment), active fibrinolysis (D-dimer, plasmin-alpha 2-plasmin inhibitor complex), and platelet activity (platelet factor 4, beta-thromboglobulin) in vivo. Measurement of these markers may be useful in identifying patients with various cardiovascular disorders at high risk of thromboembolism.

Atrial Fibrillation↗
PubMed1997

Nitric oxide and cardiac failure.

Cardiac myocytes express two types of nitric oxide (NO) synthase, eNOS and iNOS. eNOS activity is regulated by the contractile state of the heart, while iNOS expression is induced by cytokines. Nitric oxide induced by cytokines causes negative inotropic and lethal effects on cardiac myocytes. Expression of iNOS in the myocardium is increased in patients with dilated cardiomyopathy with clinical evidence of heart failure. Several neurohumoral factors activated in chronic heart failure augment cardiac iNOS expression and could cause cardiac dysfunction and cell damage.

Animals↗
PubMed1997

Lack of association between the insertion/deletion polymorphism of the angiotensin-converting enzyme gene and vasospastic angina.

BACKGROUND AND HYPOTHESIS: It has been suggested that the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene is an independent risk factor for coronary atherosclerosis and myocardial infarction, but its relation to vasospastic angina has not been fully proven. In the present study, we investigated the possible relationship between the ACE I/D genotype and vasospastic angina. METHODS: We explored the distribution of the ACE genotype in 20 patients with vasospastic angina without fixed coronary artery stenosis, 55 angina patients with fixed coronary artery stenosis, and 30 control subjects without coronary artery disease. RESULTS: The frequency of the DD genotype in patients with vasospastic angina (DD: 30.0%, ID: 20.0%, II: 50.0%) did not differ from that in the control subjects (DD: 23.3%, ID: 26.7%, II: 50.0%), while the frequency in patients with coronary artery stenosis (DD: 43.7%, ID: 21.8%, II: 34.5%) was significantly higher than that in the control subjects. The frequency of the D allele also did not differ between patients with vasospastic angina (0.40) and control subjects (0.37), while the frequency was significantly higher in patients with coronary artery stenosis (0.55). CONCLUSIONS: These findings suggest that the ACE DD genotype is a potent genetic risk factor for organic coronary artery disease, while it confers no appreciable increase in risk of vasospastic angina. These results also suggest the diversity of the pathogenesis of vascular lesions in these two types of coronary artery disease.

Aged↗
PubMed1997

Natriuretic peptides modulate nitric oxide synthesis in cytokine-stimulated cardiac myocytes.

In patients with congestive heart failure, plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels are frequently increased, but whether natriuretic peptides act directly on the heart has not been clarified. We investigated the effects of natriuretic peptides on nitric oxide (NO) synthase activity in cardiac myocytes. We measured the production of nitrite, a stable metabolite of nitric oxide, and the expression of inducible NO synthase (iNOS) mRNA and protein in cultured neonatal rat cardiac myocytes. Incubation of cardiac myocytes for 24 h with interleukin-1beta (IL-1beta) caused a significant increase in NO production. ANP, BNP and 8-bromo-cGMP, but not C-type natriuretic peptide (CNP), augmented NO synthesis in IL-1beta-stimulated cardiac myocytes in dose- and time-dependent manners. The same effects of ANP and BNP were observed at different doses of IL-1beta. Simultaneous incubation with IL-1beta in the presence of the NOS inhibitor NG-monomethyl-l-arginine or the RNA synthesis inhibitor actinomycin D for 24 h completely inhibited ANP- and BNP- as well as IL-1beta-induced nitrite production. ANP- BNP-induced NO synthesis in IL-1beta-stimulated cells were accompanied by increased iNOS mRNA and protein levels. The cGMP-dependent protein kinase inhibitor Rp-8-Br-cGMPS completely inhibited the effects of ANP and BNP. These findings indicate that both ANP and BNP up-regulate IL-1beta-induced iNOS expression in cardiac myocytes, which is at least partially mediated via activation of cGMP-dependent protein kinase.

Animals↗
PubMed1997

Cardiac abnormalities and cytosine-thymine-guanine trinucleotide repeats in myotonic dystrophy.

This study investigated the correlation between cardiac abnormalities and cytosine-thymine-guanine (CTG) trinucleotide repeat expansion in patients with myotonic dystrophy (MD). We studied 18 patients with the adult form of classical MD and 18 age-matched control subjects. In patients with MD, left ventricular systolic function at rest was not different from that in normal subjects. On the other hand, of Doppler parameters of diastolic function, mitral inflow peak early velocity and atrial velocity were significantly lower, and deceleration time and isovolumic relaxation time were significantly longer in patients with MD compared with normal controls. No significant correlation was observed between these diastolic parameters and CTG repeat expansion in the patients, although the parameters showed a positive correlation with age and neurologic symptom duration. Electrocardiographic conduction abnormalities were detected in 42% of patients. These patients showed a significantly longer symptom duration, although the size of CTG repeats was not different between the patients with and without conduction abnormalities. This study demonstrated that, in patients with MD, significant alterations in ventricular diastolic function (myocardial myotonia) occur in addition to conduction abnormalities. The size of CTG expansion is not a predictor of these cardiac involvements.

Adult↗
PubMed1997

Adenosine stimulates nitric oxide synthesis in vascular smooth muscle cells.

OBJECTIVE: The aim was to investigate the effects of adenosine on nitric oxide (NO) synthesis in vascular smooth muscle cells. METHODS: NO and cAMP synthesis was measured in confluent rat vascular smooth muscle cells in culture at passage 5-10, using Griess reagent and an enzyme immunoassay kit, respectively. The expression of inducible NO synthase mRNA was assayed by Northern blotting. RESULTS: Incubation of cultures with interleukin-1 beta (10 ng/ml) for 24 h caused a significant increase in nitrite production. The interleukin-1 beta-induced nitrite production by vascular smooth muscle cells was significantly increased by adenosine or its stable analogue, 2-chloroadenosine, in a dose-dependent manner. The adenosine A2a receptor antagonist, KF17837, but not the A1 receptor antagonist, DPCPX, significantly inhibited 2-chloroadenosine-mediated nitrite production. The 2-chloroadenosine-mediated nitrite production by interleukin-1 beta-stimulated cells was accompanied by increased inducible NO synthase mRNA accumulation. In the presence of dibutyryl-cAMP (1 mM), interleukin-1 beta-induced nitrite accumulation was further increased, but the effect of 2-chloroadenosine was not additive or synergistic. Addition of 2-chloroadenosine dose-dependently increased intracellular cAMP levels of vascular smooth muscle cells. CONCLUSIONS: These results indicate that adenosine acts on A2 receptors and augments NO synthesis in interleukin-1 beta-stimulated vascular smooth muscle cells, at least partially through a cAMP-dependent pathway.

2-Chloroadenosine↗