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Biomedical subjects

O Yasuda

Publications and source records attributed to O Yasuda.

At least 19 recordsLinked to original sources
PubMed2001

Direct inhibitory effect of adrenomedullin, calcitonin gene-related peptide, calcitonin, and amylin on cholecystokinin-induced contraction of guinea-pig isolated caecal circular smooth muscle cells.

We recently reported the direct inhibitory effect of adrenomedullin on caecal circular smooth muscle cells via cAMP system. This study was designed to determine whether the structurally related peptides to adrenomedullin (i.e.; calcitonin gene-related peptide (CGRP), calcitonin, and amylin) can inhibit the cholecystokinin octapeptide (CCK-8)-induced contractile response by exerting a direct action on guinea-pig caecal circular smooth muscle cells, and to compare the inhibitory potency of these peptides. In addition, to elucidate each intracellular mechanisms, the effects of an inhibitor of cAMP-dependent protein kinase, inhibitors of particulate or soluble guanylate cyclase on the each peptide-induced relaxation were investigated. Adrenomedullin, CGRP, calcitonin, and amylin inhibited the contractile response produced by CCK-8 in a dose-dependent manner, with IC50 values of 0.14 nM, 0.37 nM, 5.4 nM, and 160 nM, respectively. An inhibitor of cAMP-dependent protein kinase significantly inhibited the relaxation produced by all of these peptides. On the contrary, inhibitors of particulate or soluble guanylate cyclase did not have any significant effect on the relaxation produced by these peptides. In this study, we demonstrated the direct inhibitory effects of the structurally related peptides to adrenomedullin (i.e.; CGRP, calcitonin, and amylin) on the isolated caecal circular smooth muscle cells via cAMP system. The order of potency was as follows; adrenomedullin falling dots CGRP > calcitonin > amylin.

Adrenomedullin↗
PubMed2001

Elevated expression of type VIII collagen gene in the atherosclerotic plaque of the ApoE-deficient mouse.

The proliferation of smooth muscle cells (SMCs) is a key event in the development of atherosclerosis. To compare the nature of SMCs from advanced atherosclerotic lesions and normal aortic segments, we established SMC lines from plaque-containing portions (P) and non-plaque portions (NP) of aortas of apolipoprotein-E-deficient mice. Differential display showed several transcripts that were differentially expressed in P and NP lines. One of the transcripts whose expression was elevated in P lines compared to their NP counterparts was for type VIII collagen. Type VIII collagen transcripts were also readily detectable by RT-PCR in RNA isolated from plaques freshly dissected from apolipoprotein-E-deficient mice, but not in RNA isolated from the normal part of the aorta or from adventitia. In situ hybridization showed localization of Col8alpha1 transcripts near the luminal surface of the plaque. Thus, differential production of type VIII collagen in SMCs from atherosclerotic plaques continues when the cells are maintained in culture.

Animals↗
PubMed2000

Thyrotropin-releasing hormone interacts with vasoactive intestinal peptide-specific receptor in guinea pig cecal circular smooth muscle cells.

The relationship between thyrotropin-releasing hormone (TRH) binding sites and vasoactive intestinal peptide (VIP) receptors in circular muscle cells obtained from the guinea pig cecum was investigated using antagonists of VIP receptors and a selective receptor protection method. Both VIP10-28, a VIP antagonist, and atrial natriuretic peptide1-11 (ANP1-11), a VIP-specific receptor antagonist, completely inhibited 10(-5) M TRH-induced relaxation in a concentration-dependent manner. The muscle cells where cholecystokinin octapeptide (CCK-8) and TRH binding sites were protected completely preserved the inhibitory responses to TRH and ANP (a VIP-specific receptor agonist), and partially the inhibitory response to VIP. Peptide histidine isoleucine (PHI: a VIP-preferring receptor agonist) had no inhibitory effect on these cells. The muscle cells where CCK-8 and ANP (VIP-specific) receptors were protected completely preserved the inhibitory responses to TRH and ANP and partially the inhibitory response to VIP. PHI had no inhibitory effect on these cells. The muscle cells where CCK-8 and VIP receptors (both VIP-specific and VIP-preferring receptors) were protected preserved completely the inhibitory responses to TRH, VIP, ANP, and PHI. The muscle cells where CCK-8 and PHI (VIP-preferring) receptors were protected completely preserved the inhibitory response to PHI and partially the inhibitory response to VIP. TRH and ANP had no inhibitory effect on these cells. This study first demonstrates that TRH interacts with VIP-specific receptor in guinea pig cecal circular smooth muscle cells.

Animals↗
PubMed2000

Interaction between brain natriuretic peptide and atrial natriuretic peptide in caecal circular smooth muscle cells.

Guinea pig caecal circular smooth muscle cells were used to determine whether brain natriuretic peptide (BNP) can inhibit the contractile response produced by cholecystokinin-octapeptide (CCK-8). In addition, we examined the effect of an inhibitor of cAMP-dependent protein kinase, an inhibitor of particulate or soluble guanylate cyclase, an atrial natriuretic peptide (ANP) antagonist (ANP 1-11), and selective receptor protection on the BNP-induced relaxation of these muscle cells. The effect of BNP on cAMP formation was also examined. BNP inhibited the contractile response produced by CCK-8 in a dose-response manner, with an IC50 value of 8.5 nM, and stimulated the production of cAMP. The inhibitor of cAMP-dependent protein kinase and the inhibitor of soluble guanylate cyclase significantly inhibited the relaxation produced by BNP. In contrast, the inhibitor of particulate guanylate cyclase did not have any significant effect on the relaxation produced by BNP. ANP 1-11 significantly but partially inhibited the relaxation produced by BNP. The muscle cells where CCK-8 and ANP binding sites were protected completely preserved the inhibitory response to ANP, but partially preserved the inhibitory response to BNP. The muscle cells where CCK-8 and BNP binding sites were protected completely preserved the inhibitory response to both ANP and BNP. This study demonstrates that BNP induces relaxation of these muscle cells via both ANP binding sites coupled to soluble guanylate cyclase and distinct BNP binding sites coupled to adenylate cyclase.

Aminoquinolines↗
PubMed2000

Negative feedback regulation of activated macrophages via Fas-mediated apoptosis.

Apoptosis is a critical event for eliminating activated macrophages. Here we show that Fas-mediated apoptosis may participate in the mechanism of negative feedback regulation of activated macrophages. Cytokine-activated macrophages released high levels of nitric oxide (NO) that induced apoptosis in macrophages themselves. This NO-induced macrophage apoptosis was inhibited by a Fas-Fc chimeric molecule that binds to Fas ligand (FasL) and prevents its interaction with endogenous cell surface Fas. High levels of NO stimulated the release of the soluble form of FasL that was inhibited by a matrix metalloproteinase inhibitor KB-8301. High levels of NO also upregulated the expression of Fas mRNA in macrophages. In addition, macrophages isolated from Fas-lacking mice were resistant to NO-induced apoptosis. Finally, inhibition of apoptosis by a caspase inhibitor augmented peroxide production from activated macrophages. These findings suggest that high levels of NO released from activated macrophages may promote the Fas-mediated macrophage apoptosis that may be a negative feedback mechanism for elimination and the downregulation of activated macrophages in the vessel wall.

Animals↗
PubMed2000

Synthesis of N-4909 analogs. Part I. A stimulant of apolipoprotein E secretion in human hepatoma G2 cells.

Analogs of N-4909 (1), which had a stimulating activity for apolipoprotein E (apo E) secretion in Human hepatoma Hep G2 cells, were prepared and their activities examined. Cyclic analogs which had different kinds of amino acids or different number of amino acids from N-4909 (1) showed less effect on apo E secretion from Hep G2 cells. The length of acyl chain was found to be an important factor for the activity. Shorter chain reduced the activity. Linear analogs were also prepared. One of their analogs, N-5849 (17), which had six amino acids was found to have strong activity.

Apolipoproteins E↗
PubMed1998

Exogenous ouabain is accumulated in the adrenals and mimics the kinetics of endogenous digitalis-like factor in rats.

Ouabain has been isolated as an endogenous pathogenetic factor in salt-induced hypertension and has been shown to be rich in the adrenals. In this study, organ accumulation of orally administered [3H]ouabain was examined in rats. Exogenous [3H]ouabain was accumulated in high levels in the adrenals, especially in the zona intermedia, and was not metabolized in the rat. Accumulated [3H]ouabain mimicked the movement of "endogenous" digitalis-like factor, since 1) the plasma [3H]ouabain level decreased in bilaterally adrenalectomized rats, 2) the plasma [3H]ouabain level increased accompanied by a decrease in [3H]ouabain content in the adrenals in reduced renal mass hypertensive rats, and 3) [3H]ouabain levels in plasma and in the adrenals increased in spontaneously hypertensive rats, as compared with those in respective control animals. Moreover, the rat diet contained a relatively high amount of ouabain-like immunoreactivity (OLI), and the ratio of the [3H]ouabain content to OLI in each organ was comparable to that of the daily intake of dietary [3H]ouabain to OLI. Furthermore, high 3H-radioactivities were also observed in the adrenals of rats that ingested [3H]digoxin and [3H]digitoxin. These data suggest that exogenous ouabain, related cardiotonic glycosides of plant origin, or both accumulate in the adrenals and, at least in part, act as "endogenous" digitalis-like factor(s).

Adrenal Cortex↗
PubMed1997

Autoimmune pancreatitis as a new clinical entity. Three cases of autoimmune pancreatitis with effective steroid therapy.

The most common forms of chronic pancreatitis are related to alcohol ingestion, whereas the entity of non-alcohol-associated (idiopathic) pancreatitis is poorly understood. Autoimmunity has been suggested as a possible etiologic factor of idiopathic chronic pancreatitis. A total of 362 Japanese patients underwent endoscopic retrograde pancreatography (ERP) for suspected pancreatic disease, and 161 were diagnosed with chronic pancreatitis. Among them, we found three cases (1.86% incidence) of unique chronic pancreatitis, in which ERP revealed diffuse narrowing of the main pancreatic duct with an irregular wall. We diagnosed these three patients as having pancreatitis associated with an autoimmune mechanism morphologically and biochemically and started them on steroid therapy. The characteristics of the these three patients were as follows: hypergammaglobulinemia, eosinophilia, ultrasonography showing hypoehoic diffuse swelling in the pancreas (sausage-like appearance), ERP showing diffuse narrowing of the main pancreatic duct with irregular like thumbprint-like marks, reversible exocrine insufficiency, and positive anti-carbonic anhydrase II antibody. After one month of the treatment with steroids, pancreatitis dramatically improved morphologically and enzymatically. Here we describe these cases of the suspected autoimmune chronic pancreatitis. We must recognize the concept and the features of autoimmune pancreatitis in order to avoid unnecessary surgery as pancreatic cancer.

Aged↗
PubMed1997

Immunoelectron microscopic demonstration of regulated pathway for calcitonin and constitutive pathway for carcinoembryonic antigen in the same cells of human medullary carcinomas of thyroid glands.

The human medullary carcinomas are well known to secrete calcitonin (CT) as a neuroendocrine peptide and carcinoembryonic antigen (CEA) as a serum protein that is integrated into the cell membrane. This ultrastructural study is designed to elucidate whether CT and CEA are secreted via two different intracellular secretory pathways, a regulated pathway and a constitutive pathway. The immunoelectron microscopic postembedding method, performed on four cases of the human medullary carcinomas of the thyroid using plastic embedding material, disclosed two distinct different localization patterns for CT and CEA. CT was localized exclusively in dense cored secretory granules. CEA was present in the cell membrane and in the secretory vesicles. The secretory granules were completely negative for CEA. The trans-Golgi networks were also positive for CT and CEA. Electron microscopic double staining confirmed these localization in the same carcinoma cells. These observations suggest the presence of two distinct pathways in the endocrine cancer cells, i.e., the regulated pathway for CT and the constitutive pathway for CEA.

Biological Transport↗
PubMed1996

[Effect of estriol and bone mineral density of lumbar vertebrae in elderly and postmenopausal women].

To compare the efficacy of estriol (E3) in postmenopausal and senile osteoporosis, we administered orally 1 g/day calcium lactate either alone (control groups) or with 2 mg/day estriol (estrogen groups) for 10 months to 20 postmenopausal women aged 50-65 years and to 29 elderly women aged 70-84 years, and measured their bone mineral density of the lumbar vertebrae by dual energy X-ray absorptiometry. Out of 41 subjects who completed 10 months of treatment, 8 postmenopausal women and 12 elderly women in the estrogen groups had significant (p < 0.05) increases in bone mineral density (5.59 +/- 4.79% of the respective basal values). Ten postmenopausal women and 11 elderly women in the control groups had decreases bone mineral density (-4.02 +/- 7.00% and -3.26 +/- 4.60% of the respective basal values) at the 10th month. Genital bleeding as a side effect of estriol was seen in 6 out 29 elderly subjects at this dose. Moreover, decreases in the levels of calcium, total cholesterol, and triglycerides in serum, and an increase in the level of high-density lipoprotein-cholesterol were seen only in the elderly women receiving estriol. Although a lower dosage of estriol may be recommended for elderly subjects, these observations suggest that hormone replacement therapy with estriol is effective against degenerative osteoporosis, and that low-turnover bones in elderly women are also responsive to estriol.

Aged↗
PubMed1996

[Primary biliary cirrhosis with polymyositis successfully treated with prednisolone and ursodeoxycholic acid].

A 65-year-old woman was given a diagnosis of polymyositis in April 1991. She was treated with prednisolone until December 1993, at which time muscle strength had increased and high blood pressure had developed. In May 1994 she was hospitalized for muscle weakness and mild liver dysfunction. Prednisolone was given and the levels of hepatobiliary enzymes decreased. Immunological examination revealed strongly positive results for anti-mitochondria antibody and M-2 antibody, which lead to the diagnosis of primary biliary cirrhosis. administration of ursodeoxycholic acid in addition to prednisolone was followed by normalization of liver function and a decrease in the production of the autoantibodies. Although polymyositis can be complicated by autoimmune diseases, reports of complication by primary biliary cirrhosis are rare, here we report that treatment with the combination of ursodeoxycholic acid and prednisolone was successful in a patient with liver dysfunction and primary biliary cirrhosis.

Aged↗
PubMed1995

Lysophosphatidylcholine causes Ca2+ influx, enhanced DNA synthesis and cytotoxicity in cultured vascular smooth muscle cells.

The effects of lysophosphatidylcholine (LPC), a vasoactive phospholipid, on intracellular free calcium concentration ([Ca2+]i), DNA synthesis and cytotoxicity of vascular smooth muscle cells (VSMC) were studied. LPC from 10(-7) to 10(-5) mol/l dose-dependently induced a sustained increase in [Ca2+]i. In contrast to the response of [Ca2+]i induced by angiotensin II, that induced by LPC was totally abolished when extracellular Ca2+ was removed, was not affected by pretreatment of the cells with islet-activating protein, and was not desensitized by repeated addition. 8-(N,N-Diethylamino)octyl 3,4,5-trimethoxybenzoic acid (TMB-8), an inhibitor of Ca2+ release from intracellular Ca2+ stores, 1-(5-isoquinolinesulfonyl)-2-methylpiperadine dihydrochloride (H-7), an inhibitor of protein kinase C, KT5823, an inhibitor of protein kinase G, and Ca2+ channel blockers failed to suppress the LPC-induced increase in [Ca2+]i. LPC at 10(-5) mol/l caused significant stimulation of [3H]thymidine incorporation into VSMC, and at concentrations of 10(-5) mol/l and higher dose-dependently stimulated release of lactate dehydrogenase in cell culture supernatants. Moreover, digitonin mimicked the effects of LPC on [Ca2+]i, and also caused similar effects to those of LPC on DNA synthesis and cytotoxicity in VSMC. These observations suggest that LPC causes both cell growth and cell injury of VSMC, at least partly, through its detergent action, causing membrane leakiness and resultant [Ca2+]i overload in vitro, thus indicating the possible participation of LPC in atherosclerosis and/or injury of the vascular wall.

Animals↗
PubMed1995

Nitric oxide mediates cytotoxicity and basic fibroblast growth factor release in cultured vascular smooth muscle cells. A possible mechanism of neovascularization in atherosclerotic plaques.

To define the pathophysiological role of nitric oxide (NO) released from vascular smooth muscle cells (VSMC), we examined whether NO released from VSMC induces cytotoxicity in VSMC themselves and adjacent endothelial cells (EC) using a coculture system. Prolonged incubation with interleukin-1 (IL-1) induced large amounts of NO release and cytotoxicity in VSMC. NG-Monomethyl-L-arginine, an inhibitor of NO synthesis, inhibited both NO release and cytotoxicity induced by IL-1. In contrast, DNA synthesis in cocultured EC was not inhibited but rather stimulated by prolonged incubation with IL-1 or sodium nitroprusside (SNP), a NO donor. However, IL-1 and SNP did not stimulate but inhibited DNA synthesis in EC alone. On the other hand, conditioned medium from VSMC incubated for a long period with IL-1 or SNP stimulated DNA synthesis in EC alone. Furthermore, the concentration of basic fibroblast growth factor in the conditioned medium was increased and correlated with the degree of cytotoxicity in VSMC. These results indicate that NO released from VSMC induces VSMC death, which results in release of basic fibroblast growth factor, which then stimulates adjacent EC proliferation. Thus, NO released from VSMC may participate in the mechanism of neovascularization in atherosclerotic plaques.

Animals↗
PubMed1995

Role of parathyroid hormone-related protein in the proliferation of vascular smooth muscle cells.

Human parathyroid hormone-related protein(1-34) [hPTHrP(1-34)] inhibited [3H]thymidine incorporation into DNA of cultured vascular smooth muscle cells (VSMC) and increased intracellular cAMP accumulation, both in a concentration-dependent manner. The potency of hPTHrP(1-34) was similar to that of human parathyroid hormone(1-34) [hPTH(1-34)], but their antagonists, hPTHrP(7-34) and hPTH(3-34), showed no effect on VSMC DNA synthesis. The inhibitory effect of PTHrP on VSMC DNA synthesis was mimicked by dibutyryl-cAMP but not by dibutyryl-cGMP. These results suggest that PTHrP, as an autocrine and/or paracrine regulator, may inhibit VSMC DNA synthesis mediated at least partly by cAMP, a second messenger which has also been proposed to mediate vascular relaxation.

Animals↗
PubMed1994

FS2. a mamba venom toxin, is a specific blocker of the L-type calcium channels.

The peptide FS2 is a mamba venom toxin, consisting of 60 amino acids, three residues of which are different from those of calciseptine (CaS), a natural L-type Ca2+ channel blocker. The biological activities of synthetic FS2 for L-type Ca2+ channels were determined under comparisons to those of CaS and nitrendipine, a 1,4-dihydropyridine derivative. Similar to CaS, FS2 competitively inhibited the binding of [3H]nitrendipine to rat brain synaptosomal membranes on Lineweaver-Bulk plot, with Kd value of 210 nM, which was similar to that of CaS being 290 nM, but did not affect binding of an N-type Ca2+ channel ligand omega-[125I]-conotoxin GVIA to the membranes. Pretreatment of A7r5 cells with either FS2 or CaS at concentrations of 10(-8) M and greater for 5 min significantly and dose-dependently reduced 10(-6) M Bay K8644-induced increase in the cytosolic free Ca2+ concentration ([Ca2+]i) of the cells determined by the fluorescent Ca2+ indicator fura-2, with the half inhibitory concentrations (IC50) of 2.3 x 10(-8) and 2.7 x 10(-8) M, being similar to that of the IC50 value of nitrendipine (4.4 x 10(-8) M). These observations indicate that FS2, similar to CaS, is an active natural L-type Ca2+ blocker sharing the binding site on the channels with the 1,4-dihydropyridines.

Amino Acid Sequence↗
PubMed1993

Calciseptine binding to a 1,4-dihydropyridine recognition site of the L-type calcium channel of rat synaptosomal membranes.

Calciseptine (CaS) is a natural peptidic L-type Ca2+ channel blocker consisting of 60 amino acids with four disulfide bonds. The effects of synthetic CaS on the binding of various ligands to Ca2+ channels of rat brain synaptosomal membranes were studied. The membranes possessed specific binding sites for L-type Ca2+ channel ligands [3H]nitrendipine, [3H]diltiazem and [3H]verapamil, derivatives of 1,4-dihydropyridine, benzothiazepine and papaverine, respectively, and also for N-type Ca2+ channel ligand omega-[125I]-conotoxin GVIA (omega-[125I]CTX). Lineweaver-Bulk plot analysis disclosed that CaS competitively inhibited the binding of [3H]nitrendipine, with maximal binding capacity of 0.19 pmol/mg protein and dissociation constant (Kd) of 290 nM, being about 10(3) times the Kd value of [3H]nitrendipine. Similar to nitrendipine, CaS noncompetitively enhanced the binding of [3H]diltiazem, but did not affect the binding of [3']verapamil. CaS at up to 10.0 microM did not affect the binding of omega-[125I]CTX. These observations indicate that CaS shares the properties of 1,4-dihydropyridine derivatives, and allosterically modulates the binding of other L-type Ca2+ channel ligands.

Animals↗