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Biomedical subjects

H Miyai

Publications and source records attributed to H Miyai.

At least 19 recordsLinked to original sources
PubMed2000

Cardiovascular pharmacological studies on JTV-506, a new potassium channel opener. 1st communication: effects on myocardium and vasculature.

The effects of JTV-506 ((-)-(3S,4R)-2,2-bis(methoxymethyl)-4-[(1,6-dihydro-1-methyl-6-oxo-3- pyridazinyl)amino]-3-hydroxychroman-6-carbonitrile hemihydrate, CAS 170148-29-5), a novel coronary vasodilator, on hemodynamics, cardiac function and cardiac oxygen consumption were evaluated in anesthetized dogs. In anesthetized, open-chest dogs, JTV-506 (0.3-10 micrograms/kg i.v.) induced a marked increase in coronary blood flow in a dose dependent manner, while at these doses it had smaller effects on vertebral and mesenteric blood flow and almost no effect on renal blood flow. JTV-506 (1-10 micrograms/kg i.v.) showed a tendency to decrease oxygen consumption of the heart and elevate myocardial oxygen pressure without cardiac suppression. Effects of JTV-506 on hemodynamics and the respiratory system following i.v. administration (0.3-300 micrograms/kg) were investigated in spontaneously breathing anesthetized dogs. The effective dose to induce hemodynamic changes was more than 3 micrograms/kg. JTV-506 did not have a crucial influence on electrocardiogram. JTV-506 caused marked increase in coronary blood flow and myocardial oxygen pressure with slight change in blood pressure. It is concluded that JTV-506 is a potent vasodilator, with particularly pronounced effect on vasculature of the heart. These results suggest that JTV-506 may be useful in the treatment of angina pectoris.

Anesthesia↗
PubMed2000

Cardiovascular pharmacological studies on JTV-506, a new potassium channel opener. 2nd communication: effects on blood pressure in conscious animals.

The effects of JTV-506 ((-)-(3S,4R)-2,2-bis(methoxymethyl)-4-[(1,6-dihydro-1-methyl-6-oxo-3- pyridazinyl)amino]-3-hydroxychroman-6-carbonitrile hemihydrate, CAS 170148-29-5), a novel coronary vasodilator, on blood pressure were evaluated in conscious dogs and rats. In conscious dogs, JTV-506 (0.01-1 mg/kg p.o.), levcromakalim (0.01-1 mg/kg p.o.) and nifedipine (3-30 mg/kg p.o.) elicited an increase in double product, whereas nicorandil (1-10 mg/kg p.o.) did not affect the double product. The JTV-506-induced increase in double product was abolished by a beta-blocker, propranolol, suggesting that this increase in double product may be due to augumentation of heart rate by sympathetic nerves which mediate the baroreflex. The doses at which JTV-506 increased coronary blood flow in a previous study were lower than the doses required to increase the double product. JTV-506 did not have a crucial influence on electrocardiogram. In conscious rats, orally administered JTV-506, levcromakalim, nicorandil and nifedipine reduced blood pressure and increased heart rate dose dependently. These effects were more remarkable in hypertensive rats than in normotensive rats. JTV-506, a new potassium channel opener, seems to be relatively free of any hemodynamic effects.

Animals↗
PubMed1999

Effects of the new potassium channel opener JTV-506 on coronary vessels in vitro and in vivo.

The vascular effects of JTV-506 ((-)-(3S,4R)-2.2-bis(methoxymethyl)- 4-[(1,6-dihydro-l-methyl-6-oxo-3-pyridazinyl)amino]-3-hydroxychroman+ ++-6- carbonitrile hemihydrate, CAS 170148-29-5), a new potassium channel opener, was evaluated in isolated coronary arteries and anesthetized dogs. JTV-506 (1 nmol/l-3 mumol/l) produced a concentration-dependent relaxation in porcine isolated epicardial large coronary arteries precontracted with KCl (30 mmol/l), phenylephrine (3 mumol/l), histamine (3 mumol/l), serotonin (5-HT; 300 nmol/l), prostaglandin F2 alpha (PGF2 alpha; 10 mumol/l), U-46619 (100 nmol/l), endothelin-1 (ET-1; 30 nmol/l) and Bay K-8644 (100 nmol/l). JTV-506 was 2.5-8.5 and 13.3-81.5 times more potent than levcromakalim (CAS 94535-50-9) and nicorandil (CAS 65141-46-0), respectively, but was less potent than nifedipine (CAS 21829-25-4). JTV-506 and levcromakalim produced almost a complete relaxation in arteries precontracted with various kinds of vasoconstrictor, except for KCl. In contrast, nifedipine produced about 80-90% relaxation in arteries, precontracted with PGF2 alpha, U-46619 and ET-1. Thus, this potassium channel opener can be characterized as an agonist-nonselective vasorelaxant. The relaxing effects of JTV-506 and levcromakalim on coronary arteries precontracted with 30 mmol/l KCl was competitively antagonized by 3 mumol/l glibenclamide, an ATP-sensitive potassium (KATP) channel blocker. In canine isolated epicardial large coronary arteries, 10 mumol/l JTV-506, 10 mumol/l levcromakalim, 100 mumol/l nicorandil and 0.1 mumol/l nifedipine eliminated 10 mmol/l 3,4-diaminopyridine-induced rhythmic contractions. In anesthetized dogs, when administered directly into the coronary artery, JTV-506 induced dose-dependent increases in coronary arterial diameter and coronary blood flow. These results suggest that JTV-506 elicits coronary vasorelaxation through activation of the KATP channel. It is expected that JTV-506 might be useful in the treatment of coronary vasospasm in angina pectoris.

Anesthesia↗
PubMed1998

Differential expression of collagen IV isoforms in experimental glomerulosclerosis.

Expansion of the glomerular mesangial matrix (MM), thickening of the glomerular basement membrane (GBM), and eventually the development of glomerulosclerosis are often seen in immunologically mediated kidney diseases. In addition to quantitative changes in the extracellular matrix (ECM), qualitative changes in ECM molecules may contribute to alterations in the composition of the glomerular matrix. The expression of collagen IV, alpha 1-5(IV) mRNA, and polypeptides was therefore investigated during the development of chronic graft-versus-host disease (GvHD) in mice, a model for lupus nephritis, and in chronic serum sickness (CSS) in rats, a model for membranous nephropathy. Immunohistochemical studies showed increased mesangial expression of alpha 1 and alpha 2 early in the disease, but only late in the GBM. In contrast, alpha 3 and alpha 4 increased in the GBM during disease, but not in the MM. The mRNA levels for all collagen IV chains were increased in isolated glomeruli before morphological alterations were detectable. The mRNA increase was earlier and more profound for alpha 3, alpha 4 and alpha 5 than for alpha 1 and alpha 2. Expression of alpha 3(IV) was greatest in GvHD, whereas expression of alpha 4 was greatest in CSS. As determined by in situ hybridization (ISH), alpha 1 mRNA was observed dispersed in the glomerulus, but alpha 3, alpha 4, and alpha 5 mRNAs were mainly located in cells at the periphery of the glomerular tuft. The changes in the relative abundance of collagen IV mRNA in disease states may perturb the collagen IV network, altering glomerular structure and function, and may thereby play a central role in the development of glomerulonephritis and glomerulosclerosis.

Animals↗
PubMed1998

Effect of JTV-506, a novel vasodilator, on experimental angina model in rats.

The antianginal effects of JTV-506, a newly synthesized 2,2-bis-methoxymethyl benzopyran-derivative potassium channel opener, were evaluated in experimental angina models in rats and compared with those of levcromakalim, nicorandil, and nifedipine. JTV-506 (0.01-0.1 mg/kg, i.d.) dose-dependently inhibited S-wave elevation induced by injection of methacholine but caused almost no changes in blood pressure or heart rate. Other vasodilators including levcromakalim, nicorandil, and nifedipine, when administered intraduodenally, also inhibited the S-wave elevation and elicited a decrease in blood pressure. Oral administration of JTV-506 (1 and 3 mg/kg), levcromakalim (1 and 3 mg/kg), and nicorandil (30 mg/kg) significantly inhibited the S-wave depression induced by intravenous administration of arginine vasopressin (AVP). Thus JTV-506 exerts a potent protective effect on angina pectoris models to an extent similar to those of levcromakalim, nicorandil, and nifedipine, whereas its action on systemic blood pressure is different from that of other vasodilators, including reference potassium channel openers. These results suggest that JTV-506 may clinically be useful as an antianginal agent.

Administration, Oral↗
PubMed1997

Y-26763 protects the canine heart from a stunning injury through opening of the KATP channels.

The present study describes the protective effects of the ATP-sensitive K+ (KATP) channel opener Y-26763 ((-)-(3S,4R-4-(N-acetyl-N-hydroxyamino)-6-cyano-3,4-dihydro-2,2-dimethyl -2H-1-benzopyran-3-ol), on a model of reversible ischemia/reperfusion injury ('stunned' myocardium). Stunning was caused by 10-min occlusion of the left circumflex coronary artery followed by 3-h reperfusion in pentobarbital anesthetized beagle dogs. This procedure reduced by over 80% myocardial segment function measured by sonomicrometry in control preparations. Y-26763, administered 10 min before the left circumflex coronary artery occlusion, at a dose (3 micrograms/kg, i.v.) lacking significant systemic hemodynamic effects, produced a rapid and marked (80%) recovery of the shortening of the ischemic segment. By contrast, nifedipine (1 microgram/kg plus 0.2 microgram/kg per min, i.v.) did not ameliorate postischemic function. Glibenclamide, administered before Y-26763 at a dose (0.3 mg/kg, i.v.) that did not affect adversely hemodynamics and stunning injury negated the beneficial action of Y-26763. However, glibenclamide failed to do so when administered 2 min before starting reperfusion. The ischemia/reperfusion areas, which were measured by digital image analysis with NIH image software, were similar among experimental groups. Overall, these results indicate that Y-26763 protects the canine myocardium from reversible ischemia/reperfusion injury, probably through activation of myocardial KATP channels which appear to be involved in affording protection during the ischemic insult and not at the reperfusion.

Adenosine Triphosphate↗
PubMed1997

Polymorphism of extracellular superoxide dismutase (EC-SOD) gene: relation to the mutation responsible for high EC-SOD level in serum.

Extracellular superoxide dismutase (EC-SOD) with amino acid substitution R213G generated by the nucleotide substitution 760C-->G in the heparin binding domain is responsible for the high EC-SOD level in serum. We identified the two DNA polymorphic sites in the coding region of EC-SOD gene related to the 760C-->G and determined the allele frequencies. The polymorphism were A and G at nucleotide position (nt.) 241 and C and T at nt. 280 near the N-terminal. The haplotype frequencies in Japanese were 241A280C: 0.45, 241G280T: 0.37, and 241G280C: 0.18. The haplotype of 241A280T did not exist. The mutation 760C-->G must occur on the allele having the haplotype of 241G280T.

Extracellular Space↗
PubMed1995

The protective effect of probucol on adriamycin nephrosis in the rat.

Recent research has indicated the role of reactive oxygen species (ROS) in experimental nephritis. We examined the role of ROS and the effect of probucol, an anti-hyperlipidemic drug with antioxidant activity, on adriamycin (ADR)-induced nephrosis in the rat. Fourteen days after single intravenous injection of ADR (7.5 mg/kg b.w.), a nephrotic state was observed. Compared with the normal control values, the total kidney glutathione content was lower on day 5, but significantly higher on day 14 in the ADR-injected rats. Feeding ADR-injected rats with food containing 1% probucol was effective in reducing urinary protein excretion. Serum lipid peroxide level and kidney total glutathione content, both of which increased on day 14 in the ADR-injected rats, were also decreased significantly by concomitant probucol treatment. During long-term observation period of 18 weeks, probucol treatment relieved both urinary protein excretion and the progression of renal impairment. These protective effects of probucol suggest a role of ROS in the induction and progression of ADR nephrosis.

Animals↗
PubMed1993

Production of an interleukin-8-like chemokine by cytokine-stimulated rat NRK-49F fibroblasts and its suppression by anti-inflammatory steroids.

Normal rat kidney fibroblasts (NRK-49F cells) stimulated with interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) produced mainly cytokine-induced neutrophil chemoattractant (CINC) which is the rat counterpart of human gro/melanoma growth stimulatory activity. In addition, the cytokine-stimulated cells produced two minor neutrophil chemoattractants which are highly related to murine macrophage inflammatory protein-2 in their NH2-terminal amino acid sequences. IL-1 beta was a stronger stimulator than TNF-alpha, and addition of both the cytokines into the NRK-49F cell culture caused an additive stimulation for rat gro/CINC production. The anti-inflammatory steroids (dexamethasone, prednisolone and hydrocortisone) at 10(-9)-10(-6) M significantly suppressed the production of rat gro/CINC by the IL-1 beta-stimulated NRK-49F cells in a dose-dependent manner. The relative potencies of the inhibitory activity of the steroids on the rat gro/CINC production were dexamethasone > prednisolone > hydrocortisone. On the other hand, the non-steroidal anti-inflammatory drugs (indomethacin and piroxicam) at 10(-7)-10(-5) M showed no apparent inhibitory effect on rat gro/CINC production by NRK-49F cells stimulated with IL-1 beta.

Amino Acid Sequence↗
PubMed1993

Expression of interleukin 6 and major histocompatibility complex molecules in tubular epithelial cells of diseased human kidneys.

BACKGROUND: Interleukin-6 (IL-6) exerts multiple effects on infiltrated inflammatory cells and on structural cells in tissues. We previously reported that IL-6 expression is increased in the area of glomerular and tubular inflammation and tubular atrophy (Lab Invest 65:61, 1991). In the present study, we investigated the expression of IL-6 and HLA molecules in the tubules of patients with renal diseases, and correlate it with the morphological findings. EXPERIMENTAL DESIGN: Specific monoclonal antibodies and indirect immunofluorescence microscopy were used to identify IL-6, HLA-ABC, and -DR molecules, CD-2+ and CD-8+ lymphocytes and macrophages, in renal tissues obtained by biopsy from 41 patients that were divided into three groups on the basis of clinical, functional, and histologic findings. Group 1 included 12 patients with signs of acute renal disease and prevalent acute tubulointerstitial lesions. Group 2 included 19 patients with signs of chronic renal disease and histologic lesions of glomerulo- and tubulointerstitial nephritis. Group 3 included 10 patients that developed an acute renal disease treated with corticosteroids. When the acute symptoms subsided and the renal biopsy was performed, lesions characteristic of chronic tubulointerstitial nephritis were found. RESULTS: IL-6 was localized in all or in some cells of injured proximal tubules, including atrophic tubules. In one-third of specimens, there was more IL-6 in tubular cells than in infiltrated cells. The strongest expression of IL-6, HLA-ABC, and DR molecules was found in group 1, and the weakest in group 3. In the area with tubulointerstitial lesions, tubular IL-6 colocalized with HLA-ABC. Colocalization of IL-6 and HLA-DR was more evident in tubulointerstitial lesions of patients in group 2. In both groups 1 and 2, the distribution of IL-6 was statistically correlated with that of HLA-ABC and with interstitial infiltration of inflammatory cells. In group 2, there was statistical correlation between the expression of IL-6 and HLA-DR. The expression of IL-6 and of HLA molecules decreased in group 3. CONCLUSIONS: These results suggest that tubular IL-6 may be involved in the pathogenesis of tubulointerstitial nephritis.

Fluorescent Antibody Technique↗
PubMed1993

Plasma levels of superoxide dismutase and its isomers in patients with chronic renal disease.

To evaluate the significance of Cu,Zn-superoxide dismutase (SOD) in chronic renal disease, we evaluated the plasma SOD activity and analyzed the plasma Cu,Zn-SOD isomers employing gel column chromatography. The plasma SOD activity was determined as the biological activity using the nitrite method and the Cu,Zn-SOD concentration was assayed from the immunological activity using enzyme-linked immunosorbent assay (ELISA). The subjects comprised 185 patients with chronic glomerular disease and 20 hemodialysis patients. Plasma from 170 healthy persons was employed as a control. Both the plasma biological activity and plasma level of Cu,Zn-SOD determined by ELISA were elevated in patients with chronic glomerular disease. In hemodialysis patients, a marked increase in Cu,Zn-SOD level (ELISA) was noted in comparison with the increase in SOD biological activities. Gel column chromatography demonstrated a marked increase in Cu,Zn-SOD monomer which was enzymatically inactive. From these results, we conclude that a marked elevation of the plasma level of Cu,Zn-SOD in hemodialysis patients was caused by an increase in the enzymatically inactive Cu,Zn-SOD monomer.

Adult↗
PubMed1989

Synergism between interleukin-1 beta and tumor necrosis factor-alpha in production by 3T3 cells of a chemotactic factor for rat polymorphonuclear leukocytes.

Recombinant human interleukin-1 beta (IL-1) and tumor necrosis factor-alpha (TNF) synergistically stimulated BALB/c 3T3 cells to produce a chemotactic factor for rat polymorphonuclear leukocytes (PMNs), whereas an addition of 10(-11)-10(-8) M IL-1 or TNF alone to the cell culture resulted in a slight increase in the production of chemotactic factor. The partially purified factor was not a chemokinetic but chemotactic factor for PMNs when analyzed by checkerboard analysis. The partially purified factor was trypsin sensitive and heat stable; its isoelectric point was 8.5-10, and its molecular weight was about 10 kDa as estimated by gel filtration. These results suggest that fibroblasts may participate in PMN migration to the inflammatory site where both IL-1 and TNF are released by activated inflammatory cells, including macrophages.

Animals↗
PubMed1989

Effect of acute-phase proteinase inhibitors on chemotaxis of rat polymorphonuclear leukocytes in vitro.

Rat serum obtained at 24 h after subcutaneous injection of carrageenin significantly suppressed chemotaxis of rat polymorphonuclear leukocytes (PMNs) in vitro. alpha 2 Acute-phase macroglobulin (alpha 2APM), alpha 1 proteinase inhibitor (alpha 1 PI) and cysteine-proteinase inhibitors (CPIs) are present at high concentration in the 24-h serum and known as acute-phase reactants in rats. These acute-phase proteinase inhibitors were purified from inflamed rat serum or exudate and their effect on PMN chemotaxis was studied by Boyden's method in vitro. alpha 2 APM (4 mg/ml) significantly suppressed PMN chemotaxis while alpha 1M was without effect, though both alpha 2APM and alpha 1M had a similar anti-proteinase activity. The results suggest that alpha 2APM suppressed PMN chemotaxis through the mechanism unrelated to its anti-proteinase activity. On the other hand, alpha 1PI (1 and 3 mg/ml) slightly but significantly suppressed PMN chemotaxis, whereas CPI-1 and CPI-2 had no inhibitory effect. These results suggest that alpha 2APM and alpha 1PI play a role in suppression of PMNs infiltration into the inflammatory site in the late-phase of acute inflammation.

Animals↗