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T Yanagishita

Publications and source records attributed to T Yanagishita.

At least 19 recordsLinked to original sources
PubMed1999

Generation of free radicals and the damage done to the sarcoplasmic reticulum during reperfusion injury following brief ischemia in the canine heart.

Free radical generation was studied by the electron spin resonance (ESR) technique using alpha-phenyl N tert butyl nitrone (PBN) in a brief ischemia-reperfusion model of the canine heart, and correlated with biochemical changes of the sarcoplasmic reticulum (SR). ESR spectra (aH=0.3-0.4mT, aN=1.43-1.58mT) were observed as PBN spin adducts, which peaked at levels 5-fold above the control levels at 5 min after reperfusion. The simulated coupling constants of PBN spin adducts suggested that the sample should contain at least 2 carbon-centered radicals at 5 min after reperfusion (radical A: aH=0.350mT, aN=1.485mT; radical B: aH=0.370mT, aN=1.615 mT). At this time point, a significant reduction in Ca-ATPase activity of the SR was found without degradation of the major ATPase protein. Superoxide dismutase (SOD) significantly reduced the intensity of the PBN spin adduct signals and preserved the Ca-ATPase activity of the SR to 80% of the control level. Reperfusion injury after brief ischemia may be the result of inactivation of intracellular Ca-ATPase by free radicals generated during reperfusion, and SOD contributes to the protective effect by scavenging the radicals.

Animals↗
PubMed1997

Changes in microsomal membrane phospholipids and fatty acids and in activities of membrane-bound enzyme in diabetic rat heart.

Diabetes mellitus is associated with alterations in lipid metabolism and cardiac dysfunction despite an absence of coronary arteriosclerotic changes. To investigate mechanisms of cardiac dysfunction in diabetic cardiomyopathy, we studied the relation between activities of membrane-bound enzymes and surrounding phospholipids in rats with diabetes induced with a single intravenous injection of streptozotocin (65 mg/kg). We found that total phospholipid content of sarcoplasmic reticulum membrane increased significantly 8 weeks after treatment with streptozotocin owing to increases in phosphatidylcholine and phosphatidylethanolamine, a decrease in arachidonic acid, and an increase in docosahexaenoic acid in the early stage of diabetes. Sarcolemmal Na+/K(+)-ATPase activity and the number of receptors decreased in isolated cardiomyocytes of diabetic rats 8 weeks after streptozotocin administration. The Ca2+ uptake of both sarcoplasmic reticulum and mitochondria decreased simultaneously in permeabilized, isolated cardiomyocytes from diabetic rats. The depression of membrane-bound enzyme activities was correlated with alterations in phospholipids, which are closely related to the microenvironment of membrane-bound enzymes and influence intracellular Ca2+ metabolism. Because these changes in phospholipids and fatty acids were reversible with insulin therapy, they are diabetes-specific and might be a cause of cardiac dysfunction in diabetes.

Animals↗
PubMed1997

Protective effect of captopril on ischemic myocardium.

The protective effect and mechanism of action of the angiotensin-converting enzyme inhibitor (ACE-I) captopril was investigated in organelles from ischemic myocardial cells in a canine coronary ligation model. Sarcoplasmic reticulum (SR) and mitochondrial fractions were extracted from ischemic and nonischemic myocardial cells from captopril- and saline-treated (control) hearts. Heart rate, cardiac output, and right ventricular systolic blood pressure were similar in the captopril-treated and control groups. Left ventricular systolic blood pressure (LVPs) decreased gradually to 89% of the baseline value after captopril administration, and to 78% of the baseline value after ligation. Ca-ATPase activity in the SR, the respiratory control ratio (RCR) in the mitochondria, and dinitrophenol (DNP)-stimulated ATPase activity were significantly higher in ischemic myocardium from the captopril-treated group than from the saline-treated (control) group. The SH group content of both organelles was higher in the captopril-treated group. Our results suggest that, in addition to their hemodynamic effects, ACE-I agents containing SH groups protect the myocardium from ischemic damage by preventing enzyme oxidation.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Reversal of early metabolic dysfunction in hypertensive rat left-ventricular myocytes by angiotensin-converting enzyme inhibition.

We evaluated the effects of angiotensin-converting enzyme (ACE) inhibition on metabolic changes in myocardial organelles, myocardial hypertrophy, and interstitial fibrosis in the early stage of hypertension. An ACE inhibitor, imidapril (2.5 mg/kg per day), a calcium-channel blocker, diltiazem (30 mg/kg per day), or vehicle was given to spontaneously hypertensive rats (SHRs) from 10 to 18 weeks of age. Single myocytes were isolated enzymatically from the left ventricles of these SHRs and normotensive Wistar-Kyoto (WKY) controls at 18 weeks of age. In single ventricular myocytes, enzyme activities in the sarcoplasmic reticulum (SR) and the sarcolemma (SL) and the mitochondrial respiratory control ratio (RCR) were determined. In 18-week-old SHRs receiving vehicle, myocardial hypertrophy and interstitial fibrosis developed, and SR Ca2+ AT-Pase activity and the mitochondrial RCR were significantly lower and SL Na+, K(+)-ATPase activity was significantly higher than in age-matched WKYs. However, compared with diltiazem, imidapril was better able to prevent the development of myocardial hypertrophy and interstitial fibrosis, to improve SR Ca(2+)-ATPase activity and the mitochondrial RCR, and to increase SL Na+, K(+)-ATPase activity. These results suggest that ACE inhibition can prevent the development of morphologic changes associated with hypertension-induced left ventricular remodeling, such as myocardial hypertrophy and interstitial fibrosis, and can counteract ongoing dysfunction of organelle metabolism early in the development of hypertension.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

The effects of dopamine, dobutamine and amrinone on mitochondrial function in cardiogenic shock.

The impairment of mitochondrial in non-infarcted myocardium under cardiogenic shock complicated by acute myocardial infarction was studied. We induced acute myocardial infarction in dogs by ligating the circumflex branch of the left coronary artery (LCX). On basis of left ventricular systolic pressure (LVPs) after 60 minutes, we divided the dogs into two groups: a group in which LVPs fell to below 70% of the pre-LCX ligation level, and a Control group in which LVPs remained more than 90%. The former group was further divided into four subgroups, depending on infusion of dopamine, dobutamine, amrinone or saline after 90 minutes. Mitochondria were prepared and mitochondrial respiratory activity determined. In the Saline group, hemodynamics became reduced to less than 70% of the preligation level after 120 minutes, however, in the Dopamine and Dobutamine groups, hemodynamics became restored to the preligation level. In the Amrinone group, LVPs decreased slightly, while cardiac output, LV Max. dp/dt and myocardial blood flow increased. In the Saline group, mitochondria in the non-infarcted myocardium functioned at a lower level of activity than that of the Control group. However, in the Dopamine, Dobutamine, and Amrinone groups, the mitochondria functioned at a higher level. Electron microscopy revealed mitochondrial damage in the Saline group only. The results indicate that an energy production disorder in the non-infarcted myocardium may have pathogenetic implications in cardiogenic shock associated with acute myocardial infarction, while dopamine, dobutamine, and amrinone improve mitochondrial function, and ultimately improve cardiac function.

Adenosine Triphosphatases↗
PubMed1995

Purification and characterization of a novel glycoprotein which has significant homology to heavy chains of inter-alpha-trypsin inhibitor family from human plasma.

Plasmapheresis with a dextran sulfate column is a treatment for patients with hypercholesteremia. When proteins bound to the column during the treatment were fractionated to prepare some known proteins, we found a 57 kDa glycoprotein designated GP57 which showed a new N-terminal amino acid sequence. Western-blot analysis of human plasma revealed that only a 120 kDa protein, GP120, reacted with anti-GP57 antibody. Since GP120 and GP57 had an identical N-terminal amino acid sequence, GP120 is probably the intact form of GP57. The isoelectric point of GP120 was 6.8. N-Glycanase treatment decreased the molecular weight of GP120 by 15 kDa. Neuraminidase and O-glycanase, however, did not affect the molecular weight. Amino acid sequence analyses of the lysylendopeptidase digest of GP120 revealed significant homology to the heavy chains of inter-alpha-trypsin inhibitor (ITI) family. Since GP120 showed no bikunin sequence, and chondroitinase treatment and alkaline treatment of GP120 did not affect its molecular weight, we concluded that GP120 was not a complex with bikunin. We designated GP120 as IHRP (ITI heavy chain-related protein).

Alpha-Globulins↗
PubMed1992

Study on reperfusion injury on sarcoplasmic reticulum in acute myocardial ischemia.

Reperfusion injury in early myocardial ischemia was studied in the dog with special reference to sarcoplasmic reticulum (SR) and contraction bands. Acute myocardial ischemia (I) was induced by occlusion of the left anterior descending coronary artery (LAD) for 10, 20 and 30 min followed by reperfusion for 15 min (R). Ca(++)-ATPase activity of SR in 10-min-R-Group was significantly reduced to 60% of control activity, but activity of 10-min-I-Group remained near the control level in subendomyocardium (Endo). ATPase activity in 30-min-I-Group diminished to 60% of control activity in Endo and it was similar for 30-min-R-Group. In ischemic myocardium, composition of major ATPase protein decreased significantly in 30-min-I-Group and similar reduction was observed in 20-min-R-Group in Endo. In morphology proportion of appearance of contraction bands in Endo was significantly increased in 20-min or longer-R-Groups. These results suggest that reperfusion injury is likely to occur when coronary artery is reflowed after 10 min of ischemia. This may be caused by increased intracellular Ca++ at a very early stage of reperfusion period, and reperfusion injury may be induced due to acceleration in the necrotic process of the membrane system in the myocytes during ischemia.

Animals↗
PubMed1992

Impairment of sarcolemmal permeability in the acute ischemic myocardium--a study with ionic lanthanum probe method.

Impairment of sarcolemmal permeability after the initiation of acute ischemic myocardial injury was studied using an ionic lanthanum (La3+) probe in electron microscopy. Acute ischemic myocardium was induced by ligation of the left anterior descending coronary artery in dogs. In normal cardiac myocytes La is localized exclusively in the extracellular space. i.e. on the glycocalyx, in the T-system and in intercalated discs, with normal fine structures. In ischemic myocardial cells, La deposits were found in the cytosolic space in 22% of subendocardial cells with mild to moderate, but non-necrotic, fine structural changes as early as 30 min. The number of myocytes with La deposition increased with advancing ischemic injury, and necrotic fine structural changes were recognized following ischemia for 60 min. These results indicate that deposition of La occurs before the appearance of irreversible morphologic alterations in ischemic myocardial cells, and suggest an increased permeability of the sarcolemma for Ca2+ and the development of degradation of plasma membrane integrity.

Animals↗
PubMed1989

Effects of leukocyte-derived oxidants on sarcolemmal Na,K,ATP-ase and calcium transport.

Our study demonstrated that the Na,K,ATPase activity and ouabain binding sites were reduced by oxidants. Sarcolemmal calcium transport was also inhibited by hydrogen peroxide and HOC1. The action of HOC1 on the sarcolemmal functions was 2-3 orders of magnitude more powerful than that of hydrogen peroxide. Effects of hydrogen peroxide consisted of two components, i.e., the first, highly sensitive one, most probably mediated by Fe-catalyzed, site-specific free radical formation, and the second, less potent action by (high concentrations of) hydrogen peroxide. Finally, very low concentrations of hydrogen peroxide potentiated Na,K,ATPase activities when assayed using myocytes.

Animals↗
PubMed1989

Increase vs. decrease of calcium uptake by isolated heart cells induced by H2O2 vs. HOCl.

Adult rat heart myocytes were labeled rapidly with exogenous [45Ca2+]. Addition of 2.5 mM H2O2 to the heart cell suspension raised the content of rapidly exchangeable intracellular Ca2+ twofold, whereas addition of 1-30 mM HOCl decreased the Ca2+ content. The H2O2-induced increase in Ca2+ content was dependent on the medium Na+, pH, and temperature but was not significantly affected by addition of verapamil, diltiazem, amiloride, or 3-aminobenzamide. The [3H]ouabain binding to myocytes was suppressed by H2O2, whereas the Ca2+ efflux from myocytes was not influenced. An uncoupler, carbonyl cyanide m-chlorophenylhydrazone, reduced Ca2+ content, implying that the H2O2-induced change in Ca2+ content was not directly related to ATP depletion. On the other hand, the H2O2-induced Ca2+ accumulation in myocytes was prevented by deferoxamine or o-phenanthroline. These results suggest that H2O2 inhibited Na+-K+-ATPase, resulting in an increase in intracellular Na+ concentration and stimulation of sarcolemmal Na+-Ca2+ exchange activity, which caused a transient net Ca2+ influx into myocytes. By contrast, HOCl decreased the Ca2+ content of the rapidly exchangeable pool below control levels and this action of HOCl was antagonized by 1,4-dithiothreitol. HOCl accelerated Ca2+ efflux from myocytes. Ca2+ uptake and Ca2+-ATPase of the isolated sarcoplasmic reticular (SR) fraction were highly sensitive to the action of HOCl. Ca2+ uptake by intracellular sites, studied with myocytes permeabilized with digitonin, was inhibited by both H2O2 and HOCl. Thus these results suggest that HOCl inhibits the SR Ca2+ pump, resulting in the observed acceleration of Ca2+ efflux from and decline in Ca2+ content of myocytes.

Animals↗
PubMed1989

Pharmacological intervention in oxidant-induced calcium pump dysfunction of dog heart.

Micromolar concentrations of HOCl, an oxidant produced by activated neutrophils, inhibited Ca2+ uptake and Ca2+ATPase of isolated dog heart sarcoplasmic reticulum (SR). DTT antagonized completely the HOCl effect only when it was given within 5 min after the addition of HOCl. When the pharmacological intervention was delayed, the recovery with DTT was not complete, and administration of DTT 30 min after the start of HOCl's reaction with SR resulted in only a small improvement in SR Ca2+ uptake. Although H2O2 and Fe ion-chelate (a free radical-generating procedure) also inhibited Ca2+ uptake and ATPase, the concentrations required were very large. The response of cardiac sarcolemmal and skeletal muscle SR calcium pumps to oxidants was similar to that of the cardiac SR calcium pump.

Animals↗
PubMed1989

Oxidant injury to isolated heart cells.

Recent evidence suggests that free radicals are generated in the heart during the reperfusion which follows ischemia. Intracellular accumulation of calcium has been postulated to be an important pathogenic factor in a number of disease states, including reperfusion injury. Therefore, in this study, the effects of various oxidants on calcium uptake by isolated rat heart cells were investigated. Ammonium persulphate, t-butyl hydroperoxide and phenazine methosulphate increased the number of cells in contracture in both a concentration dependent and time dependent manner, while 45Ca content of cardiomyocytes was decreased by oxidant in proportion to its concentration. Carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) dependent (mitochondrial) and CCCP independent (sarcoplasmic reticulum) 45Ca contents in chemically skinned myocytes were reduced by the oxidants. By contrast, hydrogen peroxide raised 45Ca content of cardiomyocytes and did not reduce sarcoplasmic reticulum 45Ca content, although mitochondrial 45Ca content was decreased. Release of 45Ca from mitochondria and sarcoplasmic reticulum in saponin treated myocytes was accelerated by hypochlorous acid and hydrogen peroxide. The authors conclude that oxidants other than hydrogen peroxide inhibited intracellular uptake of calcium and accelerated calcium release, thus raising the cytosolic calcium concentration and causing cell contracture. The net influx of calcium across sarcolemmal membrane was decreased by these oxidants.

Animals↗
PubMed1988

Impairment of mitochondrial respiratory activity in the early ischemic myocardium--with special reference to electron transport system.

Impairment of mitochondrial respiration in early myocardial ischemia was studied with special reference to myocellular irreversible injury. The technique used was total ligation of the left anterior descending coronary artery, followed by reconstruction of coronary blood flow, in the dog. State 3 respiratory activity reduced significantly to 76% of that of the non-ischemic myocardium in subendocardial muscle (Endo) as early as 30 min after occlusion, and at 60 min to 84% in the subepicardium (Epi). The activity was not recovered by reperfusion. The activity of complex I of sonicated submitochondrial particles decreased at 30 min to 67% in Endo and at 60 min to 71% in Epi, and was not recovered by reperfusion. Complex II and IV activities were kept in the control level until 60 min of ischemia. DNP-stimulated ATPase activity reduced to 79% in Endo at 15 min and to 70% in Epi at 30 min, but recovered significantly by reperfusion until 30 min of ischemia. Mitochondrial respiratory activity was impaired irreversibly in ischemia for 30 min in Endo and this spread to Epi later. Degradation of complex I is considered to be one of the causes of myocardial irreversibility in early ischemia.

Adenosine Triphosphatases↗
PubMed1988

Degrading process of acute ischemic myocardial cells.

1. Development of acute ischemic myocardial injury was studied in mongrel dogs, induced by ligation of left anterior descending coronary artery (LAD), by biochemical analysis of myocardial fractions such as sarcoplasmic reticulum (SR) and mitochondria (Mt) and by electron microscopic observation of ischemic myocardial cells with lanthanum probe method. 2. Irreversible injury of ischemic myocardium initiated in subendocardial muscle as early as 20 min after occlusion of LAD as expressed degradation of major ATPase protein and phosphatidylcholine and phosphatidylethanolamine of SR and irreversible impairment of state III respiratory and dinitrophenol (DNP)-ATPase activities of Mt, and these necrotic changes advanced to subepicardial layer at about 60 min. 3. Ultrastructural irreversible findings appeared later at about 60 min following inflow of lanthanum ions in ischemia for 30 min. 4. Activation of cathepsin B inside of SR under ischemic acidic metabolism and abnormal inflow of Ca++ into ischemic cardiac myocytes are suspective of very important factors for the initiation of myocardial ischemic injury in early myocardial ischemia.

Animals↗
PubMed1987

Alterations in phospholipids in acute ischemic myocardium.

Alterations in the phospholipid component of membranes were studied in acute myocardial ischemia with respect to sarcoplasmic reticulum (SR) and mitochondria (Mt) in the canine heart and compared with changes in the phospholipid composition of intact membrane treated with exogenous phospholipases (PLases) A2 and C, in order to examine the mechanism of ischemic degradation. As early as 30 min after coronary ligation, the total phospholipid content of SR and Mt decreased significantly, 16.0% and 5.6%, respectively. The patterns of SR and Mt phospholipids from the ischemic myocardia did not differ on the chromatograms from those of the non-ischemic myocardia, and no significant increases in lysophospholipids were found for up to 3 hrs. Among the components of phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) decreased mainly during ischemia, and depletion of PC exceeded that of PE in SR. PLase C hydrolysed phospholipids yielded no lysophospholipids, compared to the production of a large amount of lysophospholipids by PLase A2. It was concluded that degradation of membrane phospholipids occurs in the early stage of myocardial ischemia mainly in PC and PE, which are the major components of membrane phospholipids. This may be an expression of irreversible changes, and the activation of PLase C was considered to play an important role in their degradation.

Animals↗
PubMed1987

Degradation of the cardiac sarcoplasmic reticulum in acute myocardial ischemia.

The degradation of the sarcoplasmic reticulum (SR) in acute myocardial ischemia was studied with references to the regional irreversibility and to the mechanism of ischemic degradation by the measurements of Ca++-stimulated ATPase activity and composition of the major ATPase protein of the SR and activity of cathepsin B of the SR and lysosome (Ly) fractions. Ca++-stimulated ATPase activity decreased to 66% of that of the nonischemic portion at 20 min after coronary ligation in the subendocardium (Endo) and to 44% at 30 min in the subepicardium (Epi). Composition of the major ATPase protein decreased to 55% and 73% at 30 min in Endo and Epi, respectively. In both SR and Ly fractions cathepsin B exhibited the maximal activity at 6.0-6.5, and pH dependent. And incubation of the SR at pH 6.0 induced the degradation of the ATPase protein quite similarly to that in vivo ischemia. These results suggest that the degradation of the SR membrane of ischemic myocardial cells begins earlier in Endo 20 to 30 min after the cease of the coronary blood flow, and extends to Epi later. Cathepsin B is strongly conceivable to play an initial role of necrotic process of the ischemic myocardial cells by activation inside of the SR in ischemic acidic state.

Acute Disease↗
PubMed1986

Ultrastructural changes in the sarcoplasmic reticulum in acute myocardial ischemia.

We investigated the morphologic changes in the sarcoplasmic reticulum (SR) in acute myocardial ischemia, induced by occlusion of the coronary artery in the canine heart, by freeze-fracture of SR in situ and in vitro, and they were compared to the alterations in Ca++-stimulated ATPase activity and protein composition of the isolated SR. Both SR in situ and the isolated SR exhibited typical intramembranous particles with diameters of 70 to 90 A in freeze-fracture replicas. The intramembranous particle density of the P face in SR in situ was 3,319 +/- 75 (mean +/- SE) per micrometer2 and that in the isolated SR was 2,667 +/- 60; particles were more numerous on the concave (P) face than on the convex (E) face. In ischemia for 30 to 60 min a significant decrease in the number of particles was found in SR in situ, and the corresponding change was noted in the isolated SR. Simultaneous decreases in Ca++-stimulated ATPase activity and the major ATPase protein of the SR were recognized. The close correlation of the changing pattern between the reduction in Ca++-ATPase and that in intramembranous particle density during ischemia supports the suggestion that a large part of the intramembranous particles represent ATPase protein itself. Decrease in the SR membrane particles strongly suggests the degradation of ATPase protein in the process of ischemic myocardial injury.

Adenosine Triphosphatases↗