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Biomedical subjects

A Goto

Publications and source records attributed to A Goto.

At least 19 recordsLinked to original sources

Molecular mechanisms of endothelin-1-induced cell-cycle progression: involvement of extracellular signal-regulated kinase, protein kinase C, and phosphatidylinositol 3-kinase at distinct points.

Although it is well established that endothelin-1 (ET-1) has not only vasoconstrictive effects but also mitogenic effects, which seem to be implicated in vascular remodeling, little is known about the molecular mechanisms by which ET-1 induces cell-cycle progression. In this study, we examined the effects of ET-1 on the cell-cycle regulatory machinery, including cyclins, cyclin-dependent kinase (cdk), and cdk inhibitors in NIH3T3 cells. ET-1 increased cyclin D1 protein (5.1+/-1.9-fold increase, 8 hours after stimulation, P<0.05), cdk4 kinase activity (2.8+/-0. 5-fold increase, 12 hours after stimulation, P<0.01), and cdk2 kinase activity (2.1+/-0.4-fold increase, 16 hours after stimulation, P<0.05) in a time- and dose-dependent manner. ET-1-induced increase in cyclin D1 protein, and cdk4 kinase activity was not significantly inhibited by an inhibitor of the mitogen-activated protein kinase kinase 1/2, PD98059, nor by the protein kinase C inhibitor calphostin C, whereas ET-1-induced upregulation of cyclin D1 protein and cdk4 kinase activity was significantly inhibited by the phosphatidylinositol 3-kinase inhibitor LY294002. In contrast, ET-1-induced activation of cdk2 kinase was significantly inhibited by PD98059, calphostin C, and LY294002. ET-1 increased 3H-thymidine uptake in a time-dependent fashion (0 hours, 4216+/-264 cpm per well; 8 hours, 5025+/-197 cpm per well; 16 hours, 9239+/-79 cpm per well, P<0.001 versus 0 hours). ET-1-induced increase in 3H-thymidine uptake was significantly inhibited by PD98059, calphostin C, and LY294002. These results suggest that ET-1-induced cell-cycle progression is, at least in part, mediated by the extracellular signal-regulated kinase, protein kinase C, and phosphatidylinositol 3-kinase and that those pathways may be involved in the progression of the cell cycle at distinct points.

3T3 Cells

Effects of hypertension, diabetes mellitus, and hypercholesterolemia on endothelin type B receptor-mediated nitric oxide release from rat kidney.

BACKGROUND: Although endothelin-1 is a potent vasoconstrictor peptide, stimulation of endothelin type B receptor (ETBR) causes bidirectional changes in vascular tone, ie, vasodilation and vasoconstriction. Roles of ETBR in pathological conditions are largely unknown. METHODS AND RESULTS: We studied the effect of BQ-3020, a highly selective ETBR agonist, on renal vascular resistance and nitric oxide (NO) release in the isolated, perfused kidney of rats with hypertension, diabetes mellitus, and hypercholesterolemia. Immunohistochemistry of endothelial NO synthase and ETBR was also examined. Infusion of BQ-3020 at concentrations of </=10(-10) mol/L reduced renal perfusion pressure in Dahl salt-resistant (R) rats but increased renal perfusion pressure in Dahl salt-sensitive (S) rats (10(-10) mol/L: -10.3+/-0. 6% versus 11.2+/-1.5%, R versus S; P<0.01). BQ-3020 caused a dose-dependent release of NO in both R and S rats, although the level of NO release in S rats was lower, as detected by chemiluminescence (10(-10) mol/L: 10.7+/-0.7 versus 3.1+/-0.4 fmol/min per gram of kidney, R versus S; P<0.01). Similar effects of BQ-3020 were observed in streptozotocin-induced diabetic rats and diet-induced hypercholesterolemic rats. Expression of endothelial NO synthase decreased in S rats but not in diabetic or hypercholesterolemic rats. In contrast, expression of ETBR in the endothelium was decreased in all 3 disease models compared with that in the vascular smooth muscle cell. CONCLUSIONS: These results suggest that impaired NO release in response to stimulation of ETBR is due, at least in part, to a decrease in endothelial ETBR and may play a role in vascular dysfunction usually associated with arteriosclerosis-related diseases.

Animals

Antiarrhythmic effect and its underlying ionic mechanism of 17beta-estradiol in cardiac myocytes.

1. The effects of oestrogens on action potential and membrane currents were examined in single guinea-pig atrial myocytes. 2. 17Beta-estradiol (3-10 microM) shortened the action potential duration without significant changes in the resting membrane potential. E-4031 (1 microM) markedly prolonged the action potential duration and induced early afterdepolarization, and 17beta-estradiol (10 microM) abolished it. 3. When cells were perfused in isoproterenol-containing solution, action potentials due to abnormal automaticity caused by membrane depolarization developed, and were also inhibited by 17beta-estradiol. 4. Under voltage clamp conditions, the voltage-dependent Ca2+ currents consisted of both T-(I(Ca,T)) and L-type (I(Ca,L)). 17Beta-estradiol reduced I(Ca,L) concentration-dependently, while it (10 microM) suppressed I(Ca,T) only by approximately 10%. 17Beta-estradiol did not affect time courses of I(Ca,L) inactivation, but it shifted the steady-state inactivation curve to more negative potentials. 5. 17Beta-estradiol (10 microM) did not affect the time-dependent K+ current (I(K)), referred to as I(Kr) and I(Ks) and inwardly rectifying K+ current. However, 17beta-estradiol (30 microM) or diethylstilbestrol (10 microM) inhibited K+ currents. 6. DES and ethinylestradiol (EES) also suppressed I(Ca,L), but testosterone and progesterone failed to inhibit I(Ca,L) The potency of the inhibitory effect on I(Ca,L) was DES> EES> 17beta-estradiol. 7. 17Beta-estradiol and DES also inhibited the cyclic AMP-enhanced I(Ca,L), but cyclic GMP in the pipette or pretreatment of L-NAME could not block the effects of oestrogen on I(Ca,L). 8 These results suggest that oestrogen specifically has antiarrhythmic effects, possibly by acting the L-type Ca2+ channels. The antiarrhythmic effects of oestrogens may contribute to the cardioprotective actions of oestrogens.

Action Potentials

Hypoxia-induced adrenomedullin production in the kidney.

BACKGROUND: Adrenomedullin (AM) is a newly discovered peptide that has a potent vasorelaxant activity. To investigate its potential roles in hypoxia-induced renal injury, we examined whether AM production in the kidney increased under hypoxic conditions. METHODS: The AM transcript levels in Madin-Darby canine kidney (MDCK) cells, rat vascular smooth muscle cells (VSMCs), and rat mesangial cells were assessed by Northern blot analyses under normoxic and hypoxic conditions. The AM peptide in culture media was measured by radioimmunoassay. The effects of hypoxia on accumulation of cAMP in VSMCs were also examined. The stability of AM transcripts under normoxic and hypoxic conditions was compared in the presence of actinomycin D. The effects of hypoxia on AM promoter activity was assessed by transient transfection assays using the AM promoter subcloned upstream of luciferase gene. RESULTS: The expression of AM transcripts increased significantly in MDCK cells, rat VSMCs, and rat mesangial cells under hypoxic conditions without changes in the stability of AM transcripts; however, the AM promoter activity under hypoxic was not elevated significantly. The accumulation of AM peptide in culture media also increased significantly under hypoxic conditions in MDCK cells (2.2 +/- 0.1 fmol/10(5) cells in normoxia vs. 3.5 +/- 0.3 fmol/10(5) cells in hypoxia, 6 hr after hypoxia induction, P < 0.001), and in rat VSMCs (5.5 +/- 0.3 fmol/10(5) cells in normoxia vs. 7.8 +/- 0.4 fmol/10(5) cells in hypoxia, 8 hr after hypoxia induction, P < 0.01). Under hypoxic conditions, cAMP levels in rat VSMCs increased significantly compared with those under normoxic conditions (13.3 +/- 1.4 pmol/well vs. 4.6 +/- 0.4 pmol/well, P < 0.01). CONCLUSIONS: Renal parenchymal cells as well as renal vessels may produce AM under hypoxic conditions.

Adrenomedullin

Role of free radicals in the pathogenesis of lipid-induced glomerulosclerosis in rats.

BACKGROUND: We examined whether a high-cholesterol (HC) diet causes glomerulosclerosis in rats, and investigated the role of free radicals and lipid peroxidation in lipid-induced glomerulosclerosis. METHODS: The rats were given a normal diet, a HC diet, or a HC diet with antioxidants and radical scavengers. Serum levels of lipid, lipid peroxide (LOOH), urinary excretion of protein (UP), and urinary norepinephrine excretion (UNE) were measured. The glomerular sclerosing score was used to evaluate the renal injury. RESULTS: Blood pressure, total cholesterol, and LOOH were increased by a HC diet, as were UP and UNE. The HC diet induced renal injury. Treatment with superoxide dismutase, dimetylthiourea as a scavenger of hydroxyl radical (OH.), defferoxamine masilate as an iron chelator, or vitamin E inhibited the increases in blood pressure, LOOH, UP, and UNE, whereas total cholesterol was not affected. The production of superoxide anion (O2-.) by neutrophil and LOOH in the kidney was increased, and superoxide dismutase and hydrogen peroxide in the kidney were decreased. Almost all of these changes were attenuated by vitamin E; however, the O2-. production was not inhibited. OH. was increased by the HC diet, and it was normalized with the treatments. Furthermore, the sclerosing score was partially suppressed by the treatments. Ferric iron was stained in the proximal tubulus, and it was not observed in the treated rats. CONCLUSIONS: The data suggest that lipid peroxidation is involved in the pathogenesis of lipid-induced glomerulosclerosis and that O2-. and OH. may play a role in the process.

Animals

Pressor hyperreactivity to mental and hand-grip stresses in patients with hypercholesterolemia.

OBJECTIVE: To investigate the role of hypercholesterolemia in the regulation of blood pressure. SUBJECTS AND METHODS: We compared blood pressure responses to arithmetic stress and hand-grip tests in normotensive patients with hypercholesterolemia n = 15) and a mean (+/- SEM) age of 49 +/- 3 years, and normal cholesterolemic controls (n = 22) aged 48 +/- 1 years. Blood pressure and heart rate were measured throughout the tests. We examined the intracellular Ca2+ concentration in platelets with or without low-density-lipoprotein stimulation (2.9 nmol/l, 10 mg/ml). The plasma nitrite plus nitrate and cyclic GMP were determined before and at the end of each test to evaluate nitric oxide production and activity. RESULTS: Both tests showed that systolic/diastolic blood pressure was higher in the hypercholesterolemic patients than in the normal controls (stress test: 139 +/- 3/91 +/- 4 versus 127 +/- 2/80 +/- 3 mmHg, P < 0.01/P < 0.05; hand-grip test: 164 +/- 5/106 +/- 5 versus 144 +/- 3/88 +/- 3 mmHg, P < 0.01/P < 0.01). The intracellular Ca2+ concentration in platelets and the increase in response to low-density-lipoprotein stimulation were higher in the hypercholesterolemic patients (without stimulation: 72 +/- 3 versus 64 +/- 3 nmol/l, P < 0.01; with 2.9 nmol/l stimulation: 145 +/- 21 versus 89 +/- 6 nmol/l, P < 0.01). The increase in Ca2+ in response to 2.9 nmol/ml stimulation with low-density lipoprotein was positively related to the increase in mean blood pressure in response to the stress test (r = 0.56, P < 0.002). Nitric oxide production appeared to be increased in the hypercholesterolemic patients (65 +/- 5 versus 51 +/- 4 mmol/l, P < 0.05), and was not affected significantly by the tests. In contrast, cyclic GMP was lower in the patients and was increased significantly in the normal controls by the hand-grip test (P < 0.05). As a result, plasma cyclic GMP was lower in the patients (1.9 +/- 0.2 versus 2.5 +/- 0.1 nmol/l, P < 0.01). The ratio of plasma cyclic GMP to nitric oxide was also lower in the hypercholesterolemic patients at rest (P < 0.05), and at the end of the mental stress (P < 0.02) and hand-grip (P < 0.001) tests. CONCLUSIONS: Patients with hypercholesterolemia showed an exaggerated blood pressure response to both mental stress and exercise, even if resting blood pressure was normal. Increases in the intracellular Ca2+ concentration can contribute to these excessive responses. A disproportionately lower level of cyclic GMP to nitric oxide in plasma may also be involved in these abnormal responses.

Baroreflex

High salt intake potentiates the renal vascular and glomerular damage caused by low doses of angiotensin II in uni-nephrectomized rats.

OBJECTIVE: We recently reported that the renin-angiotensin system plays an important role in the progression of vascular and kidney injuries, even in Dahl salt-sensitive rats with volume-dependent hypertension. In this study, we investigated whether a high-salt diet increases susceptibility to kidney injury induced by angiotensin II in normotensive, uni-nephrectomized Sprague-Dawley rats, which mimics the condition of salt-volume repletion and blunted renin-angiotensin system. METHODS: The rats were fed either a low-salt (0.3% NaCl) or a high-salt (4% NaCl) diet and divided into five groups: two control groups with a low-salt or a high-salt diet without angiotensin II infusion (saline infusion), and three angiotensin II groups (angiotensin II infusion, 10 or 50 ng/kg per min with high-salt diet, 50 ng/kg per min with low-salt diet, subcutaneously). The rats were kept on these regimes for 8 weeks. The blood pressure was measured every week. Functional and morphological alterations in the kidney were assessed at the end of the experiment RESULTS: There were no differences in the arterial blood pressures of the five experimental groups. However, angiotensin II infusion increased the weights of the heart and aortic walls in a dose-dependent manner in the high-salt groups. There was also a dose-dependent increase in proteinuria, N-acetyl-beta-D-glucosaminidase activity (NAG) excretion, and additional glomerular and arterial injuries in the kidney, associated with angiotensin II infusion in the high-salt groups. In the rats given a higher dose of angiotensin II, the high-salt diet significantly increased the weights of the heart and aortic walls and exacerbated the renal function and morphological injuries, compared to the low-salt group. High-salt diet alone increased the kidney and heart weights. However, it did not significantly influence the results of the morphological and functional study. On the other hand, angiotensin II infusion on a low-salt diet showed a trend towards glomerular damage; however, the effects were small and not significant. Similarly, there were few effects of angiotensin II infusion on morphology and functional study on a low-salt diet CONCLUSION: These data clearly show that a high-salt intake increases susceptibility of the kidney to injuries induced by low doses of angiotensin II in normotensive, uni-nephrectomized rats.

Angiotensin II

Relations of vascular calcium channels with blood pressure and endothelium in hypertension and with aging.

To investigate the relationships between the activity in potential operated Ca2+ channels (POC), blood pressure, and endothelium in hypertension, we tested the contractile responses to a Ca2+ channel agonist Bay K 8644 (BAY K) in aorta from deoxycorticosterone-acetate-saline (DOCA-S) and reduced renal mass-saline (RRM-S) hypertensive rats. The effects of mechanical rubbing, N omega-Nitro-L-Arginine Methyl Ester (l-NAME) and indomethacin were also examined. Sensitivity to BAY K increased in experimental rats before they became hypertensive and contractile responses were enhanced as hypertension developed. Force development to BAY K was correlated with blood pressure levels. Endothelium removal enhanced the contractile response to BAY K. L-NAME, but not indomethacin, potentiated the response to BAY K. Contractile response to BAY K was negatively correlated with relaxation to acetylcholine. An enhanced contractile response to BAY K was observed also in aged rats. Enhanced activation of vascular POC in hypertension results from elevated blood pressure and partly from diminished inhibitory action of endothelium. Senescence also enhances vascular POC activity.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy

[Investigation about usefulness of serum antibody of Helicobacter pylori and serum pepsinogen I/II ratio as a marker of the judgment after eradication therapy].

To clarify that serum antibody of Helicobacter pylori (H. pylori) and serum pepsinogen I/II ratio are useful or not as a marker of the judgment after eradication therapy, we followed up 84 cases who received eradication therapy comparing with culture and histology (Carnoy's fixation and immunostaining using anti-H. pylori antibody, MIA method). Successful eradication was recognized in 45 of 84 cases (successful group), and remaining 39 cases were unsuccessful (unsuccessful group). Titers of serum H. pylori antibody went down gradually in the successful group, on the other hand, they did not go down constantly and often re-went up in the unsuccessful group. The difference of the various rate of titers in the both groups became clear statistically since 6 months after eradication therapy (p < 0.05). Supposing that cut-off rate of titer was 60% of pre-eradicated titer, sensitivity, specificity, and accuracy were 86.2%, 77.7%, and 84.2%, respectively, at 6 months after eradication therapy. Serum pepsinogen I/II ratio increased regardless of successful or unsuccessful eradication, but the various rate of serum pepsinogen I/II ratio was different in both groups at 1 month and 3 months after eradication therapy (p < 0.05). Serum antibody of H. pylori and serum pepsinogen I/II ratio could be a marker of the judgment after eradication therapy, especially the various rate of serum antibody of H. pylori is useful for the monitor of H. pylori infection in the long term.

Adolescent

Increase in intracellular hydrogen peroxide and upregulation of a nuclear respiratory gene evoked by impairment of mitochondrial electron transfer in human cells.

We have investigated an interorganelle communication pathway between the nucleus and mitochondria. We loaded a stress specific to mitochondria of human fibroblast cells by antimycin A (AA), an inhibitor of the mitochondrial cytochrome bc1 complex. AA inhibited cellular respiration in a dose-dependent manner. When the respiratory capacity was reduced to 50-70% of the original one, mRNA levels of cytochrome c1 as well as cytochrome b increased at 24 h after AA treatment, resulting in maintenance of the cell viability. In contrast, the cells retaining less than 40% of the original capacity showed no increase in either mRNA level and were targeted for death. Intracellular H2O2 level monitored by the fluorescence of dichlorofluorescein increased within 3 h in both the cases, although this increase was higher in the cells where the mRNA levels increased. An antioxidant N-acetylcysteine repressed the increases of not only H2O2 but also cytochrome c1 mRNA levels. These results suggest that the cells can respond to a limited impairment of electron transfer by promoting expression of nuclear and mitochondrial genes, probably through an H2O2-dependent signaling pathway.

Acetylcysteine

Prostaglandin D2 inhibits inducible nitric oxide synthase expression in rat vascular smooth muscle cells.

Vascular smooth muscle cells (VSMCs) as well as macrophages have been shown to generate a substantial amount of NO in inflammatory vascular lesions. Prostaglandin (PG) D2 (PGD2) is produced by inflammatory cells, including mast cells and macrophages. We investigated whether PGD2 modulates NO metabolism in rat VSMCs. PGD2 at a concentration of 10(-7) mol/L or greater dose-dependently inhibited nitrite accumulation in the medium of cultured VSMCs stimulated with interleukin 1beta (IL-1beta). In a dose-response analysis of IL-1beta and nitrite accumulation, PGD2 was seen to decrease the maximal ability of VSMCs to generate NO, arguing against competition by PGD2 at cytokine receptors. Northern analysis showed that PGD2 suppresses induction of inducible NO synthase (iNOS) mRNA in IL-1beta-stimulated VSMCs, with consequent inhibition of iNOS protein expression in Western analysis. A thromboxane A2 (TXA2) analogue, U46619 (10(-5) mol/L), produced less inhibition of NO generation than did PGD2. Neither the PGI2 analog carbaprostacyclin nor PGE1 showed any inhibition. PGD2 dose-dependently inhibited NO generation despite the addition of the TXA2 antagonist SQ29548. PGJ2, delta12-PGJ2, and 15-deoxy-delta12,14-PGJ2, all metabolites of PGD2, were as potent as or slightly stronger than PGD2 in the inhibition of NO generation. These data suggest that PGD2 suppresses NO generation in VSMCs by inhibiting iNOS mRNA expression, most likely through the cascade of the PGJ2 series rather than through the TX receptor or cAMP upregulation. Such action makes it likely that PGD2 regulates NO metabolism in vascular lesions.

Animals

Somatosensory homunculus as drawn by MEG.

We studied a detailed somatosensory representation map of the human primary somatosensory cortex using magnetoencephalography. Somatosensory-evoked magnetic fields following tactile stimulation of multiple points in the right hemibody (including the tongue, lips, fingers, arm, trunk, leg, and foot) were analyzed in five normal subjects. We were able to estimate equivalent current dipoles (ECDs) following stimulation of the tongue, lips, fingers, palm, forearm, elbow, upper arm, and toes in most subjects and those following the stimulation of the chest, ankle, and thigh in one subject. The ECDs were located in the postcentral gyrus and generally arranged in order along the central sulcus, which is compatible with the somatosensory "homunculus." Linear distances, averaged in five subjects, from the receptive area of the thumb to that of the tongue, little finger, forearm, upper arm, and toes were estimated to be 2.42 +/- 0.28, 1.25 +/- 0.28, 2.21 +/- 0.72, 2.75 +/- 0.63, and 5.29 +/- 0.48 cm, respectively. The moment of each ECD, which suggested the size of the cortical areas responsive to the stimulation, was also compatible with the bizarre proportion of the homunculus with a large tongue, lips, and fingers. According to these results, we were able to reproduce a large part of the somatosensory homunculus quantitatively on an individual brain MRI.

Brain Mapping

Relevance of periglomerular myofibroblasts in progression of human glomerulonephritis.

To clarify the pathological and clinical significance of periglomerular alpha-smooth muscle actin (alpha-SMA)-positive cells, we examined 51 needle-biopsy specimens from patients with human glomerulonephritis. Immunoelectron microscopy confirmed these cells were myofibroblasts showing characteristic features with abundant alpha-SMA-positive thin myofilaments. Nonsclerotic glomeruli with periglomerular myofibroblasts were larger in the Bowman's capsular planar area than nonsclerotic glomeruli without periglomerular myofibroblasts (24.7 +/- 6.0 x 10(3) microm2 v 19.9 +/- 8.5 x 10(3) microm2; P < 0.01). We studied the correlation between the clinical prognosis and the extent of periglomerular myofibroblasts in 24 patients with IgA nephropathy. Patients were divided into two groups; those with plasma creatinine levels within normal range at biopsy and significantly elevated at follow-up were designated group 1 (poor prognosis), and patients with plasma creatinine levels within normal range at biopsy and not significantly elevated at follow-up were designated group 2 (fair prognosis). In the kidneys of group 1 patients, periglomerular alpha-SMA was expressed more intensively than it was in the kidneys of group 2 patients (alpha-SMA expression score, 1.0 +/- 0.48 v 0.52 +/- 0.54; P < 0.05). These findings indicate that periglomerular myofibroblasts appeared surrounding the nonsclerotic hypertrophic glomeruli, which may lead finally to glomerulosclerosis. This report suggests that interaction between the glomerular cells and the periglomerular myofibroblasts may have a role in the progression of glomerular diseases.

Actin Cytoskeleton

Detection of the ongoing sorting of ancestrally polymorphic SINEs toward fixation or loss in populations of two species of charr during speciation.

The FokI family of short interspersed repetitive elements (SINEs) has been found only in the genomes of charr fishes (genus Salvelinus). In an analysis of the insertion of FokI SINEs using PCR, we characterized six loci at which FokI SINEs have been inserted into the genomes of Salvelinus alpinus (Arctic charr) and/or S. malma (Dolly Varden). An analysis of one locus (Fok-223) suggested that a sister relationship exists between S. alpinus and S. malma and the SINE at this locus might have been inserted in a common ancestor of these two species, being fixed in all extant populations examined. By contrast, SINEs at two other loci (Fok-211 and Fok-206) were present specifically in the genome of S. alpinus, with polymorphism among populations of this species. Moreover, the presence or absence of the SINEs of the other three loci (Fok-214, Fok-217, and Fok-600) varied among populations of these two species. The most plausible interpretation of this result is that SINEs, which were ancestrally polymorphic in the genome of a common ancestor of these two species, are involved in an ongoing process of differential sorting and subsequent fixation in the various populations of each species.

Animals

Ouabain-like factor.

Accumulated evidence has suggested that several sodium pump inhibitors, similar to cardiotonic steroids, are present in the human body. Ouabain-like factor, the most appealing candidate, has been found to be increased with high sodium intake and hypervolaemia, and in essential hypertension, mineralocorticoid hypertension, and pregnancy-induced hypertension. Furthermore, blocking the action of ouabain-like factor with digibind or a novel anti-ouabain agent lowers blood pressure in several models of hypertension. Several important questions remain, however, before it can be concluded that ouabain-like factor is indeed involved in the regulation of sodium homeostasis and blood pressure.

Animals