Biomedical subjects
Publications and source records attributed to H Shimokawa.
A genomic DNA clone (14.5 kbp) for amelogenin, a tooth enamel specific protein, has been isolated from a mouse genomic library. The nucleotide structure of this DNA was determined by the polymerase chain reaction and sequence analysis. The result indicated that the cloned DNA contained all the exons in addition to approximately 5.5 kbp of upstream sequence.
OBJECTIVE: We recently demonstrated that chronic treatment with interleukin-1 beta (IL-1 beta), a major inflammatory cytokine found in atherosclerotic lesions, induces coronary arteriosclerotic changes and vasospastic responses to serotonin and histamine in pigs in vivo and that those responses are partially mediated by platelet-derived growth factor (PDGF). This study was designed to examine, first, whether the effects of IL-1 beta are also partially mediated by fibroblast growth factor-2 (FGF-2), which is another important growth factor in atherosclerotic lesions, and, secondly, whether chronic treatment with FGF-2 per se also induces histological and functional changes in porcine coronary arteries in vivo. METHODS: Porcine coronary arteries were aseptically wrapped with cotton mesh absorbing IL-1 beta with or without neutralizing antibody to FGF-2. In a separate series of experiments porcine coronary arteries were chronically treated with FGF-2 itself in the same manner. Coronary vascular responses in vivo and histological changes were examined 2 weeks after the operation. RESULTS: Coronary vasospastic responses to serotonin and histamine and neointimal formation were induced at the site of the coronary artery where IL-1 beta was chronically and locally applied. These responses were significantly suppressed by co-treatment with a neutralizing antibody to FGF-2 but not by that with non-immune IgG. Immunostaining revealed the presence of FGF-2 in the endothelial cells, the thickened intima and the media at the IL-1 beta-treated site. Furthermore, chronic treatment with FGF-2 also induced coronary vasospastic responses to serotonin and histamine and neointimal formation. CONCLUSIONS: These results suggest that the vascular effects of IL-1 beta may also be mediated by FGF-2 in our swine model and that chronic treatment with FGF-2 also causes coronary arteriosclerotic changes and vasospastic responses in vivo.
Three cases of chronic atrial tachycardia associated with ventricular dysfunction and severe exercise intolerance markedly improved within a few weeks when ventricular rate was slowed. Slowing ventricular rate may improve symptoms and ejection fraction despite possible changes in myocyte and tissue structure.
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BACKGROUND: Endothelium-derived nitric oxide (NO) is believed to regulate myocardial perfusion and structural changes in the vascular wall. Our objective was to determine whether chronic inhibition of NO synthesis causes structural and functional changes in coronary arteries. METHODS AND RESULTS: Coronary vasomotor response was studied in pigs before and after chronic oral administration of the NO synthesis antagonist N omega-nitro-L-arginine methyl ester (L-NAME) 30 mg.kg-1.d-1 for 2 weeks. Chronic L-NAME treatment increased (P < .01) arterial pressure but did not alter baseline coronary blood flow (CBF), epicardial coronary diameter, or heart rate. Chronic L-NAME treatment augmented (P < .01) the decrease in CBF in response to intracoronary serotonin (30 micrograms/kg) from 5 +/- 14% to 40 +/- 5% but did not alter the CBF response to prostaglandin F2 alpha. The serotonin-induced decrease in CBF after acute L-NAME administration was still less before (1.3 +/- 0.4%) than after chronic L-NAME treatment (51 +/- 6%). Chronic L-NAME treatment attenuated the increase in CBF with bradykinin (100 ng/kg) but did not alter the CBF response to nitroglycerin (10 micrograms/kg). Compared with intact pigs without L-NAME treatment, L-NAME-treated pigs had significant thickening of the media in the microvessels (diameter, < 300 microns) but not in the large epicardial vessels. Chronic intracoronary infusion of L-NAME at 3 mg.kg-1.d-1 for 2 weeks, which did not produce arterial hypertension, caused similar microvascular medial thickening. CONCLUSIONS: These results indicate that chronic administration of L-NAME caused coronary microvascular structural changes and hyperreactivity to serotonin in pigs in vivo, suggesting an important role of defective NO synthesis in coronary microvascular disorders.
BACKGROUND: We previously reported that glibenclamide (a selective inhibitor of ATP-sensitive K+ channels [K+ATP channels]) inhibited metabolic coronary vasodilatation induced by beta 1-adrenoceptor stimulation. However, the role of K+ATP channels in metabolic coronary vasodilatation induced by tachycardia is still unknown. This study aimed to determine whether glibenclamide attenuates metabolic coronary vasodilatation induced by pacing-induced tachycardia. METHODS AND RESULTS: In anesthetized dogs, increasing heart rate from 103 +/- 1 to 160 beats per minute with atrial pacing increased coronary blood flow without altering arterial pressure and left ventricular pressure. Intracoronary infusion of glibenclamide at 1.5 and 5.0 micrograms.kg-1.min-1 did not alter basal coronary blood flow but significantly attenuated (P < .01) the tachycardia-induced coronary vasodilatation without altering the tachycardia-induced increase in myocardial oxygen consumption (MVO2). In conscious dogs, intracoronary glibenclamide at 5.0 micrograms.kg-1.min-1 attenuated (P < .05) coronary vasodilatation induced by ventricular pacing from 85 +/- 6 to 150 beats per minute. Glibenclamide markedly attenuated coronary vasodilation evoked with the K+ATP channel opener pinacidil. CONCLUSIONS: These data indicate that blockade of coronary vascular K+ATP channels with glibenclamide inhibited metabolic coronary vasodilatation induced by pacing tachycardia in dogs, suggesting that K+ATP channels are involved in the mechanism mediating metabolic coronary vasodilatation associated with pacing tachycardia.
BACKGROUND: Bradykinin causes endothelium-dependent vasodilation of isolated human coronary arteries in vitro. However, the effect of bradykinin on vasomotion of human coronary arteries in vivo has not been studied. The aim of this study was to examine whether bradykinin-induced vasodilation is altered at the atherosclerotic or spastic site of human coronary arteries in vivo. METHODS AND RESULTS: The effect of bradykinin on vasomotion of epicardial coronary arteries was evaluated in 8 patients with normal coronary arteries (control group), 14 patients with organic coronary stenosis (coronary artery disease [CAD] group), and 8 patients with vasospastic angina (VSA group). Changes in the diameter of epicardial coronary artery were assessed by quantitative coronary arteriography. Intracoronary administration of bradykinin at graded doses (60, 200, and 600 ng) dilated epicardial coronary arteries without altering arterial pressure or heart rate in all patients of either group. In the control group, vasomotor responses of the site where acetylcholine caused dilation were compared with the responses of the site where acetylcholine caused constriction. The magnitudes of bradykinin-induced dilation at the site with acetylcholine-induced dilation (mean +/- SD: 6 +/- 6%, 11 +/- 9%, and 15 +/- 9%) were comparable to that (3 +/- 6%, 8 +/- 8%, and 13 +/- 9%) at the site with acetylcholine-induced constriction. In the CAD group, vasomotor responses of the stenotic site (% diameter stenosis, 15% to 50%) and nonstenotic site were examined. The bradykinin-induced dilation at the stenotic site (0 +/- 4%, 3 +/- 8%, and 5 +/- 9%) was significantly less (P < .01) than at the nonstenotic site (3 +/- 4%, 8 +/- 6%, and 16 +/- 11%) and in the control group. Coronary vasodilation with nitrate at the stenotic site (20 +/- 11%) was comparable to that at the nonstenotic site (22 +/- 16%) and in the control group (21 +/- 10%). In the VSA group, vasomotor responses of the site with acetylcholine-induced spasm and the site without spasm were examined. The bradykinin-induced vasodilation at the spastic site (5 +/- 5%, 16 +/- 15%, and 33 +/- 17%) was comparable to that at the nonspastic site (4 +/- 8%, 12 +/- 14%, and 21 +/- 9%). Nitrate-induced dilation was comparable at the spastic site (51 +/- 19%) and the nonspastic site (32 +/- 13%). The ratio of bradykinin-induced vasodilation to nitrate-induced vasodilation at the spastic site was comparable to the control group. CONCLUSIONS: These results suggest that bradykinin causes vasodilation of human epicardial coronary arteries in vivo and that bradykinin-induced endothelium-dependent vasodilation is impaired at the stenotic site but is preserved at the angiographically normal site where endothelium-dependent vasodilation by acetylcholine is impaired and at the spastic site.
In the rat tibial bone marrow cavity, following colchicine injection, there is a phase of osteogenesis in which bone trabeculae replace the necrotic bone marrow tissues and fill the marrow cavity. The newly formed bone is subsequently resorbed by osteoclasts and normal bone marrow is restored. In this study, we correlated these morphologic events with the pattern of gene expression of bone sialoprotein (BSP), an extracellular matrix protein in mineralized tissues, to elucidate the possible functions of BSP in bone formation and resorption in vivo. The expressions of osteopontin (OPN) and type I collagen were also examined. Northern hybridization of the tibia demonstrated that OPN mRNA was gradually increased and expressed at a maximal level 10 days after colchicine injection (during the bone resorption process), while BSP mRNA expression already reached a maximal level at day 6 (during the initial process of bone formation). Its expression was, thus, quite temporary at the beginning of bone formation and different from that of type I collagen, which was continually elevated from days 6 to 10. In situ hybridization of the newly formed bone induced in the tibia revealed that BSP mRNA was evenly expressed in most osteoblasts and osteocytes, moreover in interconnecting colonies of spindle-shaped cells, possibly preosteoblasts, at day 6. At day 10, however, its expression became restricted to some cells on the bone surfaces, some osteoblasts, and most osteoclasts. These observations suggest that BSP may play an important role mainly in the initiation of bone formation and is also associated with the functions of osteoclast in vivo.
To elucidate the role of monocytes in the cytokine system in acute myocardial infarction (AMI), we examined the time courses of plasma concentrations and generation capacities of monocyte-related cytokines in 17 consecutive patients with uncomplicated AMI (from day 1 to 28) and in 10 control subjects. The concentrations of monocyte-related cytokines were measured by enzyme immunoassay with horseradish peroxidase. Cytokine generation capacity was evaluated by cytokine concentrations in the culture solution 24 hours after incubation of 0.5 ml whole blood with 5 micrograms lipopolysaccharide. Two distinct patterns of increases in the cytokine concentrations were noted: transient (plasma interleukin [IL]-6) and sustained (plasma macrophage colony-stimulating factor and generation capacities of IL-1 alpha, IL-6, granulocyte colony-stimulating factor, and tumor necrosis factor alpha). There was no significant increase in the concentrations of other cytokines. These results indicate that the concentrations of the monocyte-related cytokines dynamically change during the course of AMI, suggesting that they may contribute to the inflammatory and subsequent proliferative responses in AMI.
We examined the effects of aspirin on coronary hyperreactivity to autacoids after arterial balloon injury in miniature pigs. Coronary vasoconstriction induced by histamine and serotonin were examined angiographically before, 1 h, 1 week, and 1 month after balloon injury in 29 hypercholesterolemic miniature pigs. The animals were divided into three groups: group A, no treatment (n = 16); group B, pretreated with aspirin 50 mg/day for 2 days before injury (n = 7); and group C, treated with aspirin 50 mg/day for 2 days before and 5 days after injury (7 days in all) (n = 6). In group A, coronary vasoconstriction induced by autacoids was significantly greater at the injured than at the noninjured site at all times examined (p < 0.01). Hyperconstriction induced by the autacoids 1 h after injury were significantly less in groups B and C than in group A (p < 0.01). Hyperconstriction induced by autacoids 1 week after injury were significantly less in group B than in group A (p < 0.01) and were significantly less in group C than in group A (p < 0.01) or group B (p < 0.05). Treatment with aspirin for 2 or 7 days had no effect on the constrictive responses at the injured site 1 month after injury or on those at the noninjured site at all times examined. These results suggest that platelet-vessel wall interaction may play an important role in coronary hyperconstrictive responses to autacoids 1 h and 1 week after injury.
Endothelium-derived nitric oxide (EDNO) has been implicated in the modulation of coronary arterial tone. The aim of this study was to determine if metabolic coronary vasodilation induced by pacing tachycardia is altered by the inhibition of EDNO synthesis. Before and after the intracoronary infusion of an inhibitor of EDNO synthesis (N omega-nitro-L-arginine-methyl-ester, L-NAME), changes in coronary blood flow (CBF), regional myocardial blood flow (MBF), and myocardial oxygen consumption (MVO2) were measured in anesthetized dogs in response to atrial pacing tachycardia. Increasing the heart rate from 109 +/- 10 to 160 beats/min by pacing produced significant increases in CBF (p < 0.05), MVO2 (p < 0.05), and MBF in each sublayer of the myocardium (p < 0.05). L-NAME did not alter the pacing-induced increases in CBF, MVO2, or regional MBF. In addition, the ratio of the tachycardia-induced increase in CBF to the increase in MVO2 was not changed by L-NAME. The coronary vasodilation evoked by acetylcholine was attenuated by L-NAME (p < 0.05). However, the response to sodium nitroprusside was not altered. These results suggest that EDNO does not play a primary role in the mechanism mediating metabolic coronary vasodilation induced by pacing tachycardia in dogs.
L-Arginine analogues have been widely used to examine the role of endothelium-derived nitric oxide (NO) in vascular responses; however, the effects of the agents on coronary vasomotion are not fully understood. In this study, we examined the effects of the analogues on vasomotion of isolated porcine coronary arteries. Strips of the porcine coronary artery were suspended for isometric tension recording in Krebs-Henseleit solution. L-Arginine analogues, N omega-nitro-L-arginine methyl ester (L-NAME, 10(-9)-10(-3) M), NG-monomethyl-L-arginine (L-NMMA, 10(-9)-10(-3) M), and NG-nitro-L-arginine (L-NNA, 10(-9)-10(-3) M), caused dose-dependent contractions, which were greater in strips with than in those without endothelium. Those endothelium-dependent contractions were almost abolished by indomethacin (10(-5) M) and FeCl2 (10(-3) M). The latter reduces prostaglandin H2 to 12-heptadecatrienoic acid, which has no vasoconstrictor effect. These results indicate that the L-arginine analogues cause endothelium-dependent contractions that are mediated by prostaglandin endoperoxides and suggest that they have properties other than simple inhibition of NO synthesis in porcine coronary arteries.
The significance of the defective endothelial signal transduction in the impaired endothelium-dependent relaxations in atherosclerosis and related conditions was examined. Pertussis toxin-sensitive endothelium-dependent relaxations were prominently impaired in experimental atherosclerosis in pigs. The expression of endothelial Gi protein was reduced in atherosclerosis and related conditions in human coronary arteries. Thus, the dysfunction of pertussis toxin-sensitive G protein (Gi protein) may contribute to the impairment of the endothelium-dependent relaxations in atherosclerosis.
The aim of the present study was to investigate the effects of long-term blockade of nitric oxide synthesis with the L-arginine analogue N omega-nitro-L-arginine methyl ester (L-NAME) for 8 weeks on coronary vascular and myocardial structural changes. Four groups of Wistar-Kyoto rats were studied: those with no treatment, those treated with L-NAME 1 g/L (3.7 mmol/L in drinking water), those treated with L-NAME 0.1 g/L (0.37 mmol/L in drinking water), and those treated with L-NAME 1.0 g/L and hydralazine 120 mg/L (0.6 mmol/L in drinking water). After 8 weeks, the heart was excised, and the degrees of structural changes in coronary arteries (wall-to-lumen ratio and perivascular fibrosis), myocardial fibrosis, and myocyte size were quantified by an image analyzer. Chronic inhibition of nitric oxide synthesis increased arterial pressure compared with control animals. Chronic inhibition of nitric oxide synthesis caused significant microvascular remodeling (increased wall-to-lumen ratio and perivascular fibrosis). Cardiac hypertrophy was also observed after chronic inhibition of nitric oxide synthesis. Coadministration of hydralazine prevented arterial hypertension but did not affect microvascular remodeling and cardiac hypertrophy induced by the chronic inhibition of nitric oxide synthesis. In addition, chronic inhibition of nitric oxide synthesis caused scattered lesions of myocardial fibrosis, which was significantly attenuated by cotreatment with hydralazine. These results suggest that long-term blockade of nitric oxide synthesis caused coronary microvascular remodeling and cardiac hypertrophy in rats in vivo by a mechanism other than arterial hypertension. In contrast, arterial hypertension contributed to the development of myocardial fibrosis induced by long-term blockade of nitric oxide synthesis.
We recently demonstrated that chronic treatment with IL-1 beta induces coronary arteriosclerotic changes and vasospastic responses to autacoids in pigs in vivo and that those responses are importantly mediated by PDGF. The receptors for PDGF and other major growth factors are known to have tyrosine kinase activity. We therefore investigated the effects of a selective tyrosine kinase inhibitor, ST 638, on those responses induced by IL-1 beta in our swine model. Intimal thickening and coronary vasospastic responses to serotonin and histamine were induced at the site of the coronary artery where IL-1 beta was chronically and locally applied. These responses were significantly suppressed in a dose-dependent manner by cotreatment with ST 638. In addition, ST 494, which is an inactive form of ST 638, did not inhibit those responses. The treatment with ST 638 alone did not affect the coronary vasoconstricting responses to the autacoids. Immunoblotting using an antibody to phosphotyrosines confirmed the inhibitory effects of ST 638 on the tyrosine phosphorylations induced by IL-1 beta. These results thus suggest that tyrosine kinase activation may play an important role in mediating the effects of IL-1 beta, while also suggesting that ST 638 has an inhibitory effect on the arteriosclerotic changes and vasospastic responses to autacoids in our swine model in vivo.
Vascular endothelial cells play an important role in modulating cardiovascular function, by liberating several vasoactive substances, such as prostacyclin, endothelium-derived relaxing factor/nitric oxide, a hyperpolarizing substance, and vasoconstrictor substances. Their roles in the cardiovascular system include modulation of the contraction of the underlying vascular smooth muscle, interaction between blood components and blood vessel wall, vascular growth, as well as regulation of the cardiovascular system at several levels beyond the vascular wall. Alterations in the endothelial functions and the related processes are now known to be involved in the pathogenesis of many cardiovascular diseases, including hypertension and atherosclerosis. Thus, the impaired endothelial regulation of the cardiovascular system may have an important implication for the development and progression of many cardiovascular diseases.
Screening of a bovine odontoblast cDNA library from developing incisor with murine Msx-1 and Msx-2 cDNA probes led to the isolation of three positive clones. All of them encoded for a sequence of a protein containing 297 amino acids. The responsible gene was designated as bovine Msx-1 (bMsx-1) due to the high homology with the human MSX-1 and mouse Msx-1 sequences.
OBJECTIVES: The role of endothelin-1 (ET-1) in the pathogenesis of coronary artery spasm is not well understood. We aimed to determine if ET-1 is involved in serotonin-induced coronary spasm in the swine model. METHODS: In 10 miniature pigs, a segment of the left anterior descending coronary artery was denuded and irradiated with X-ray. Three months after endothelial denudation, coronary vasomotion was assessed in vivo by quantitative arteriography. RESULTS: Intracoronary serotonin at 10 micrograms/kg provoked coronary spasm (augmented narrowing of the luminal diameter) at the denuded site (diameter reduction 93 +/- 4%) but not at the non-denuded control site (19 +/- 4%, P < 0.01) associated with ST segment elevation in the region perfused by the denuded artery. Intracoronary administration of ET-1 at 25 ng/kg caused mild vasoconstriction of the denuded (26 +/- 4) and non-denuded site (16 +/- 3%, n.s.), but provoked ST segment elevation in the regions perfused by both the denuded and non-denuded arteries. The treatment with an endothelin antagonist (BQ123 0.1 mg/kg) significantly attenuated coronary vasoconstriction and ST segment elevation evoked with ET-1, but did not alter serotonin-induced vasoconstriction either at the denuded or control site. CONCLUSIONS: The results of this study suggest that endogenous ET-1 may not be involved in the pathogenesis of serotonin-induced coronary spasm in our swine model.