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Biomedical subjects

Y Takeyama

Publications and source records attributed to Y Takeyama.

At least 109 records · Page 6Linked to original sources
PubMed1985

Enhancement of growth factor-induced DNA synthesis by colon tumor-promoting bile acids in Swiss 3T3 cells. Their different mode of action from that of phorbol esters.

In Swiss 3T3 cells, colon tumor-promoting deoxycholate (DOC) enhanced DNA synthesis which was induced by fibroblast growth factor (FGF) in the presence of insulin. This effect was observed only when DOC was added within 10 h after the addition of FGF. DOC by itself did not induce DNA synthesis irrespective of the presence or absence of insulin. Similar results were obtained with other colon tumor-promoting bile acids such as cholate, chenodeoxycholate and taurocholate. In contrast to these bile acids, 12-O-tetradecanoylphorbol-13-acetate (TPA) induced DNA synthesis fully without FGF in the presence of insulin. DOC did not affect TPA-induced DNA synthesis. Prolonged treatment of the cells with phorbol-12,13-dibutyrate caused the down-regulation of the phorbol ester receptor and rendered the cells unresponsive to TPA. In these cells, FGF still induced DNA synthesis in the presence of insulin, but the maximal level was reduced to about one third of that in the control cells. DOC did not enhance this DNA synthesis any more. DOC did not alter the binding of FGF to the cells. These results indicate that colon tumor-promoting bile acids enhance the mitogenic action of FGF and thereby stimulate DNA synthesis, although the phorbol ester substitutes for the mitogenic action of FGF.

Animals↗
PubMed1985

Studies on the phosphorylation of myelin basic protein by protein kinase C and adenosine 3':5'-monophosphate-dependent protein kinase.

The substrate specificity of protein kinase C was studied and compared with that of cyclic AMP-dependent protein kinase (protein kinase A) by using bovine brain myelin basic protein as a model substrate. This basic protein was phosphorylated at multiple sites by both of these protein kinases. In this analysis, the basic protein was thoroughly phosphorylated in vitro with [gamma-32P]ATP and each protein kinase, and then digested with trypsin. The resulting radioactive phosphopeptides were isolated by gel filtration followed by high performance liquid chromatography on a reverse-phase column. Subsequent amino acid analysis and/or sequential Edman degradation of the purified phosphopeptides, together with the known primary sequence of this protein, revealed that Ser-46 and Ser-151 were specifically phosphorylated by protein kinase C, whereas Thr-34 and Ser-115 were phosphorylated preferentially by protein kinase A. Both kinases reacted with Ser-8, Ser-11, Ser-55, Ser-110, Ser-132, and Ser-161 at various reaction velocities. Contrary to protein kinase A, protein kinase C appears to react preferentially with seryl residues that are located at the amino-terminal side close to lysine or arginine. The seryl residues that are phosphorylated commonly by these two protein kinases have basic amino acids at both the amino- and carboxyl-terminal sides. These results provide some clues to understanding the rationale that these kinases may show different but sometimes similar functions depending on the structure of target phosphate acceptor proteins.

Amino Acid Sequence↗
PubMed1985

Activation of cellular protein kinase C and mode of inhibitory action of phospholipid-interacting compounds.

12-O-Tetradecanoylphorbol-13-acetate (TPA), that is intercalated into the cell membrane, binds a roughly stoichiometric amount of protein kinase C to produce a catalytically active complex with phospholipid. Local anesthetics and other phospholipid-interacting compounds such as chlorpromazine inhibit profoundly this complex formation in a manner competitive with phospholipid but not with TPA. A tiny change of the membrane phospholipid bilayer structure that is caused by TPA appears to facilitate this unique phospholipid-protein kinase C interaction.

Anesthetics, Local↗
PubMed1985

Ultrastructure of the sarcoplasmic reticulum in the ischemic myocardium.

Fine structural changes in the sarcoplasmic reticulum (SR) in myocardial ischemia, induced by occlusion of the anterior descending branch of the left coronary artery in the canine heart, were studied by the freeze-fracture technique in situ and in vitro and compared to the alterations in Ca2+-stimulated ATPase activity and sodium dodecyl sulfate gel electrophoresis of the isolated SR. Both SR in situ and the isolated SR exhibited the typical intramembranous particles of 70-90 A in freeze-fracture replicas, and the numbers of particles were more numerous in the concave face (PF) than in the convex face (EF). The numbers of particles in the PF were 2748/micron 2 on the average. In ischemia for 1-2 hr, a significant decrease in the numbers of the particles was found in SR in situ, and corresponding changes were noted in the isolated SR. Decreases in Ca2+-stimulated ATPase activity and in the major protein band of ATPase were recognized simultaneously. The close correlation of the changing patterns between the reduction in Ca2+-ATPase and that in the intramembranous particle density during ischemia supports the suggestion that a large part of the intramembranous particles represents ATPase protein itself. The decrease in the particles of SR membrane indicates the degradation of ATPase in the process of ischemic myocardial necrosis.

Animals↗
PubMed1984

Analysis of structural proteins from biopsied human myocardium with special emphasis on methodology.

An analytical procedure for the quantitative determination of the structural proteins from a biopsied human cardiac muscle weighing approximately 1 mg was described to be applicable in clinical studies in 20 patients with various heart diseases. The principle of the method is glycerinization of heart muscle and analysis by SDS gel electrophoresis. In 6 control heart muscles obtained from patients having almost normal hearts, the pattern of the structural proteins was similar to that of the normal canine heart. Myosin heavy chain-actin ratio ranged 1.26 +/- 0.44. In 5 cases with secondary cardiac hypertrophy, the pattern of the structural proteins was the same as that of the control heart. In 4 cases with hypertrophic cardiomyopathy, an increase in myosin heavy chain was observed in 2 cases, while myosin heavy chain and alpha-actinin decreased in another 2 cases. Hypertrophy and severe disarray of myofibrils were noted in the former, and atrophy and degradation were done in the latter in electron microscopy. In 5 cases with dilated cardiomyopathies, the relative contents of myosin heavy chain and alpha-actinin was reduced in all cases together with atrophy and degradation of myofibrils.

Actinin↗
PubMed1983

Acid hydrolases in the initiation of ischemic myocardial necrosis.

Alterations in myocardial acid hydrolases in acute ischemia were studied in relation to the evolution of cardiac cellular necrosis by the determination of cathepsin D, acid phosphatase (AcPase), and beta-glucuronidase activities of the myocardial fractions and by electron microscopic cytochemical studies on AcPase in the canine heart. In the normal myocardium, the same level of activity of acid hydrolases was found in sarcoplasmic reticulum (SR) as in the lysosome fraction. In electron microscopy, AcPase reaction products were observed markedly in SR and moderately in lysosomes, in residual bodies, and in Golgi apparatus. In the ischemic myocardium, at 20 to 30 min after coronary ligation, activation of these enzymes was observed in both SR and lysosomes, and at 60 to 90 min they were decreased in the particles and, in turn, increased in the cytoplasm accompanying the ischemic fine structural changes. At 2 to 3 hr those acid hydrolase activities in the cytosol were decreased, indicating the loss of enzymes from necrotic myocardial cells. Acid hydrolases are the most important factor for the evolution of ischemic myocardial necrosis by being activated not only in lysosomes but also in SR and by being released to the cytoplasm to disintegrate the cellular structures.

Acid Phosphatase↗
PubMed1983

Electron microscopic cytochemical studies on acid phosphatase activity in acute myocardial ischemia.

Alterations in the localization and the intensity of acid phosphatase activity were studied electron microscopically in acute ischemic myocardial cells in the dog, in relation to processes of cellular degradation. In normal myocardial cells, the acid phosphatase activity was concentrated in the terminal cisternae, the longitudinal elements and the subsarcolemmal cisternae of the sarcoplasmic reticulum and the primary lysosomes. Activity was moderate in the secondary lysosomes, residual bodies and Golgi apparatus. As early as 15 min after coronary ligation the intensity of acid phosphatase activity increased in the enlarged lysosomes and the sarcoplasmic reticulum of the ischemic myocardial cells. Fine deposits of the reaction product were distributed in the sarcoplasm around lysosomes and the sarcoplasmic reticulum after 30 min, and the activity began to decrease in lysosomes and in the sarcoplasmic reticulum. One to 3 hours after ligation, intramitochondrial dense deposits appeared, and the reaction product decreased both in lysosomes and the sarcoplasmic reticulum. The fine reaction product, which leaked from lysosomes and the sarcoplasmic reticulum, was scattered in the sarcoplasm and was accompanied by fine structural changes indicating cellular necrosis. From these findings it is strongly suggested that acid hydrolases in lysosomes and the sarcoplasmic reticulum are closely related to the necrotic process in ischemic myocardial cells.

Acid Phosphatase↗
PubMed1982

Electron microscopic studies on the ATPase activity in myocardial infarction -changes in the early myocardial infarction.

Ultracytochemical changes in ATPase activity of ischemic myocardial cells were studied in the dog heart by electron microscopy in the early stage of myocardial infarction and compared to the fine structural alterations in the ischemic myocardium. 1) In the normal myocardial cell, ATPase activity was observed intensely in the terminal cisternae (TC) of the sarcoplasmic reticulum (SR), and moderately in the myofilaments in the longitudinal SR and around the gap junctions of the intercalated discs. 2) The most striking change in the ischemic myocardial cells was the reduction in the ATPase reaction product in the TC of the SR and along the gap junctions 60 min after coronary ligation, simultaneously with swelling of the TC and the appearance of mitochondrial dense deposits. The reaction product began to decrease at 30 min on the myofilaments, and for 3 to 12 hours no reaction product was observed except irreversible morphologic changes in 60 to 70% of the longitudinal SR in the ischemic subendocardial cells. 3) A decrease in ATPase activity was recognized in the early stage of myocardial ischemia simultaneously with the fine structural changes of myocardial cells and it is considered to be one of the signs of ischemic irreversibility.

Adenosine Triphosphatases↗
PubMed1980

Studies on the subcellular localization of electrolytes in normal and infarcted canine myocardium. With special reference to calcium ion.

1. Alterations in subcellular distribution of electrolytes were studied with particular emphasis on Ca++ in normal and ischemic myocardium produced by ligating the coronary artery in the dog, by means of the histochemical method using potassium pyroantimonate. 2. In the normal myocardium, the antimonate precipitates were observed most abundantly in TC of SR and on N-line within sarcomeric I-band, but found scarcely in mitochondria, M-line, Z-line, intercalated disc or T-system. 3. In the infarcted myocardium, the precipitates were strikingly increased in both number and size in disrupted mitochondria, while they were markedly decreased in swollen TC with the progress of ischemia. 4. Most of the precipitates in TC and on N-line were removed by chelation with EGTA but a few larger precipitates were consistently found mainly on N-line. And the presence of Ca++ in the antimonate precipitates was confirmed by energy dispersive X-ray microanalysis.

Animals↗
PubMed1978

Morphologic and biochemical studies on the experimental chronic ischemic myocardium with the Ameroid constrictor.

1. Morphologic as well as biochemical alterations in chronic ischemic myocardial tissue without infarction were studied in dogs utilizing the Ameroid constrictor. 2. Serum creatine kinase activity elevated at around three weeks after placing the Ameroid constrictor around the circumflex branch of the left coronary artery suggestive of myocardial tissue injury followed by the initial activation caused by surgery. 3. Subendocardial proliferation of connective tissue was observed in about 60% of the experiments, but the middle and the subepicardial muscles were morphologically intact. 4. The marked increase in glycogen particles was observed in the subendocardial muscle cells in most of the experiments, and mild features of myocardial cellular necrosis were found in approximately 60% of the experiments. 5. ATPase activities of the structural proteins as well as sarcoplasmic reticulum in the ischemic myocardium shoed relatively higher values than those in the non-ischemic myocardium. However, no substructural changes were observed in SDS gel electrophoresis in both the fractions. 6. The alterations in the chronic myocardial ischemia are supposed to be essentially the same as those in myocardial necrosis followed by acute coronary occlusion.

Adenosine Triphosphatases↗
PubMed1978

Studies of the cardiac sarcoplasmic reticulum in myocardial infarction.

1. Influence of ischemia on the biochemical properties of the sarcoplasmic reticulum (SR) was studied in the experimental myocardial infarction in the dog. 2. Ca2+ -uptake rate of SR decreased at around 90 minutes after coronary occlusion. This reduction was roughly in parallel with the reduction in the Ca+ -Mg2+ -stimulated ATPase activity. However, Ca2+ -binding rate of SR was kept within the range of that of the non-infarcted tissue through the time course of myocardial infarction. 3. Ca2+ -Mg2+ -stimulated ATPase activity decreased at around 3 hours after coronary occlusion to about 50% of that of the non-infarcted portion. 4. In SDS gel electrophoresis, the protein band with the largest molecular weight among three major components decreased at 3 hours after coronary occlusion, which is suggestive of ATPase. At 48 hours after coronary occlusion, the protein with the smallest molecular weight in the major proteins also decreased. 5. Ca2+ -uptake rate, Ca2+ -Mg2+ -stimulated ATPase activity and the substructural changes return to the normal level and pattern at around 28 days after coronary occlusion.

Adenosine Triphosphatases↗