Search PubMed⌕ Search

Biomedical subjects

H Akimoto

Publications and source records attributed to H Akimoto.

At least 127 records · Page 7Linked to original sources
PubMed1996

Heparin and heparan sulfate block angiotensin II-induced hypertrophy in cultured neonatal rat cardiomyocytes. A possible role of intrinsic heparin-like molecules in regulation of cardiomyocyte hypertrophy.

BACKGROUND: Heparan sulfate, one of the primary components of extracellular matrix, is a potent antigrowth factor in certain types of cells. To elucidate a possible role of endogenous heparin-like molecules in regulating cardiomyocyte hypertrophy, we investigated the effects of heparin and heparan sulfate on angiotensin (Ang) II-induced hypertrophy in cultured neonatal rat cardiomyocytes. METHODS AND RESULTS: Competitive [3H]heparin binding assay showed that cardiomyocytes had specific binding sites for heparin. In situ [3H]heparin binding assay demonstrated that heparin, which rapidly bound to the cardiomyocyte surface, was subsequently accumulated around the nuclei, suggesting that heparin might work in the nucleus. Cotreatment with heparin (20 micrograms/mL) completely inhibited increased cell surface area by Ang II (10(-6) mol/L). Increased [3H]leucine incorporation by Ang II was reduced by heparin dose-dependently. The inhibitory effect of heparin on Ang II-induced cardiomyocyte hypertrophy also was confirmed by Northern blot analysis: heparin dose-dependently inhibited skeletal alpha-actin and atrial natriuretic peptide gene expression, genetic markers for cardiomyocyte hypertrophy. Heparan sulfate showed similar inhibitory effects on cell surface area, [3H]leucine incorporation, and skeletal alpha-actin gene expression. Treatment with heparinase I or III, which specifically digests the disaccharide chains of endogenous heparin-like molecules, upregulated protein synthesis and skeletal alpha-actin and atrial natriuretic peptide gene expression in cardiomyocytes. CONCLUSIONS: Our findings in this study strongly suggest that heparin and heparan sulfate are potent inhibitors of cardiomyocyte hypertrophy and that endogenous heparin-like substances negatively regulate cardiomyocyte hypertrophy.

Angiotensin II↗
PubMed1996

Endothelin-3 induces hypertrophy of cardiomyocytes by the endogenous endothelin-1-mediated mechanism.

We have recently reported that endothelin-1 (ET-1) mediates angiotensin II-induced hypertrophy of cardiomyocytes as an autocrine/paracrine factor. In the present study, we examined whether endothelin-3 (ET-3) induces hypertrophy of cultured neonatal rat cardiomyocytes and whether endogenous ET-1 mediates this effect. ET-3 (10(-7) M) increased the cell surface area of cardiomyocytes after 48 h. ET-3 dose dependently (10(-9)-10(-7) M) stimulated protein synthesis as evaluated by [3H]leucine incorporation; the maximum response was 1.4-fold increase over the control at 10(-7) M. Since the response of cardiac hypertrophy is characterized by enhanced expression of fetal isoforms of muscle specific genes, the effect of ET-3 on steady state levels of mRNA for skeletal alpha-actin was evaluated by Northern blot analysis. ET-3 (10(-9)-10(-7) M) increased mRNA level for skeletal alpha-actin with a maximum response after 6 h. ET-3-induced [3H]leucine incorporation, skeletal alpha-actin mRNA and cell surface area were inhibited by a synthetic ETB receptor antagonist (BQ788). Interestingly, ET-3-induced skeletal alpha-actin gene expression and [3H]leucine incorporation were inhibited by a synthetic ETA receptor antagonist (BQ123) as well as by antisense oligonucleotides against peproET-1 mRNA. ET-3 (10(-7) M) transiently increased mRNA levels for ET-1 peaking at 30 min and stimulated the release of immunoreactive ET-1 from cardiomyocytes. These results suggest that endogenous ET-1 locally generated and secreted by cardiomyocytes may contribute to ET-3-induced cardiac hypertrophy as an autocrine/paracrine factor.

Actins↗
PubMed1996

Mild hypoxia induces hypertrophy of cultured neonatal rat cardiomyocytes: a possible endogenous endothelin-1-mediated mechanism.

Hypoxic or ischemic stresses on cardiomyocytes may cause a variety of compensatory responses including cell hypertrophy. In this study, we examined whether hypoxia induces hypertrophy of cardiomyocytes in vitro and whether hypoxia-induced hypertrophy is inhibited by an endothelin A receptor antagonist (BQ123). Neonatal rat cardiomyocytes were cultured in 10% O2/85% N2/5% CO2 or 95% N2/5% CO2 to produce a mild or severe hypoxic condition, respectively. Cardiomyocytes exposed to severe hypoxia revealed degenerative morphological changes and a decrease of cell number, suggesting the toxicity of severe hypoxia on cardiomyocytes. In contrast, cardiomyocytes with mild hypoxia developed hypertrophy; cell surface area of cardiomyocytes as evaluated by an image analyser system increased by 1.6-fold over control after 48 h. [3H]leucine incorporation into the cells was significantly increased by mild hypoxia but decreased by severe hypoxia, mRNA level of skeletal alpha-actin, a genetic marker of cardiac hypertrophy, up-regulated after 6-24 h by mild hypoxia. A transient increase of preproET-1 mRNA and a time-dependent increase of ET-1 protein in the culture medium were also observed in cardiomyocytes exposed to mild hypoxia. BQ123 partially inhibited either hypoxia-induced [3H]leucine incorporation or skeletal alpha-actin mRNA in a dose-dependent manner. These data suggest that mild hypoxia induces hypertrophy of cardiomyocytes and that activation of endogenous ET-1 may, at least in part, mediate this hypertrophic responses as an autocrine/ paracrine factor.

Actins↗
PubMed1996

Gene therapy for donor hearts: ex vivo liposome-mediated transfection.

OBJECTIVE: Liposomes may be an appropriate transfection vehicle for transplanted hearts, avoiding the use of viruses in immunosuppressed hosts and allowing transfection of nondividing cells. To study whether liposome-mediated transfection could be accomplished during transplantation, we used a liposome-reporter gene system in a rabbit model of allograft cardiac transplantation. METHODS: After aortic crossclamping, Stauffland donor hearts were injected with 10 ml Stanford cardioplegic solution; then a 1.3 to 2.0 mg/kg dose of chloramphenicol acetyl transferase in 1:1 deoxyribonucleic acid-liposome complexes was injected proximal to the aortic crossclamp for coronary artery perfusion. The hearts were transplanted into New Zealand White rabbit recipients in the heterotopic cervical position (n = 11 transplants). Recipients were sacrificed at 24 hours. Myocardial specimens (right and left ventricles) and vascular specimens (epicardial coronary artery, aortic root, and coronary sinus) from both the transplanted and native hearts were analyzed for chloramphenicol acetyl transferase protein by means of the enzymatic liquid scintillation assay (counts per minute per milligram of total protein). RESULTS: In the recipient, myocardial chloramphenicol acetyl transferase activity was significantly greater in treated donor hearts (mean 4.6 x 10(5) cpm/mg +/- 1.1 x 10(5) [standard error]) than in native hearts (mean 4.1 x 10(2) cpm/mg +/- 72 [standard error], p < 0.01, Mann-Whitney U test). In treated donor hearts, right and left ventricular specimens, as well as apical and basal myocardial specimens, were transfected equally. Chloramphenicol acetyl transferase activity in vascular specimens also indicated transfection (mean 5.4 x 10(5) cpm/mg +/- 2.5 x 10(5) [standard error]). Chloramphenicol acetyl transferase activity in the coronary sinus was comparable with that in the coronary arteries, which suggests that liposomes can transverse the coronary capillary beds. CONCLUSIONS: These findings demonstrate that ex vivo transfection of donor hearts with a liposome-reporter gene system results in significant in vivo expression of the transfected gene product after cardiac transplantation. Genetic alteration of myocardium and cardiac vasculature has potential clinical applications in the prevention of posttransplantation rejection, ischemia-reperfusion injury, and both transplant and nontransplant coronary artery disease.

Animals↗
PubMed1996

An anecdote in the dawn of Japanese psychiatry: the tragedy of Dr. Noboru Ishida.

This is a historical review of the tragic life of a psychiatrist in the dawn of Japanese psychiatry, who was sentenced to life imprisonment for first-degree murder by an American court and imprisoned in America. The purpose of this article is firstly to clarify the strange circumstances under which he was sentenced guilty in spite of his psychosis. In the author's opinion there appeared to be an incorrectness and injustice of the judicial decision in the American court from consideration to the documents of his trial. Secondly, the author would like to acknowledge Dr. Ishida's pioneering contributions of the Japanese psychiatry which, because of the circumstances, have been long buried in the history of Japanese psychiatry.

Anecdotes as Topic↗
PubMed1996

Transient elevation of nerve growth factor content in the rat hippocampus and frontal cortex by chronic ethanol treatment.

The nerve growth factor (NGF) content in the hippocampus and frontal cortex of chronic ethanol-treated rats was measured and compared with that of control rats, using a two-site enzyme immunoassay (EIA) system. The different time periods of chronic ethanol treatment caused transient elevation of the NGF content in both the hippocampus and frontal cortex. The NGF content in the hippocampus was significantly elevated in rats undergoing ethanol treatment of 2 weeks and 1 month. Nerve growth factor content of the 1 month treatment was higher than that of the 2 week treatment. However, a 3 month administration of ethanol reduced the NGF content to the control level. The NGF content in the frontal cortex increased significantly in the 2 week administration, but decreased to the control level in the 1 month administration. The increase of NGF may be caused by the proliferation of glial cells or the enhancement of neuronal production of NGF.

Animals↗
PubMed1996

Correlation between cerebral blood flow values obtained by Xenon/CT and Kety-Schmidt (N2O) methods.

The means of the cerebral blood flow (CBF) values obtained by the stable xenon enhanced CT (Xe/CT) method using two different CT scanners were compared with global CBF value obtained by the Kety-Schmidt (N2O) method as a reference. Xe/CT CBF values were obtained using a GE CT9200 (31 patients, 2 flow maps, 120 kV, absorption constant of 0.040) as well as a GE ProSeed Accell (38 patients, 4 flow maps, 80 kV, absorption constant of 0.028). The protocol of inhalation in the Xe/XT method consisted of 4 min wash-in and 4-min wash-out of 35% stable xenon. In the Kety-Schmidt method, 15% N2O gas was inhaled for 10 min. The N2O content of blood samples was measured using a van Slyke-Neill blood gas analyzer. We corrected all obtained CBF values for a PaCO2 of 34 mmHG (CBF34). The global CBF34 values obtained by the Kety-Schmidt method were linearly correlated with the CBF34 values obtained using the CT9200 and with those obtained using the ProSeed Accell, and the regression line equations were, respectively, Y = 0.64X + 13.7 (X: CT9200, Y: Kety-Schmidt, r = 0.666, p < 0.01) and Y = 0.99X + 11.2 (X: ProSeed Accell, Y: Kety Schmidt, r = 0.756, p < 0.01). Since the CBF values obtained by the Xe/CT method using different CT scanners are not always the same as the global CBF values obtained by the Kety-Schmidt method, CBF values obtained by the Xe/CT method should be corrected referring to the regression line obtained by applying both methods for each patient.

Adult↗
PubMed1996

Non-glutamate type pyrrolo[2,3-d]pyrimidine antifolates. II. Synthesis and antitumor activity of N5-substituted glutamine analogs.

The glutamic acid moiety of N-[4-[3-(2,4-diamino-7H-pyrrolo[2, 3-d]pyrimidin-5-yl)propyl]benzoyl]-L-glutamic acid (1b, TNP-351) and related compounds was replaced with some N5-substituted glutamines. Antifolates (4A-S) were effectively prepared by coupling pyrrolo[2,3-d]pyrimidine carboxylic acids (11a, b) with some properly protected N5-substituted glutamine derivatives (10A-S), which were prepared by coupling Boc-Glu-OMe (7) with various amines (8A-S) using a suitable condensing reagent, followed by hydrolysis. The inhibitory effects of the resulting products on dihydrofolate reductase (DHFR), thymidylate synthetase (TS) and the growth of murine fibrosarcoma Meth A cells in culture were examined. All N5-substituted glutamine analogs (4A-S) inhibited DHFR much more strongly than TNP-351 and some analogs exhibited the same potent growth inhibition of Meth A cells as TNP-351. Some typical analogs (4Bb, 4Db, 4F, 4Oa) were also examined for inhibitory effects on the growth of methotrexate (MTX)-resistant human CCRF-CEM cells in culture and for in vivo antitumor activities against murine leukemia and solid tumors. MTX-resistant cells, with a defect in transport and decreased polyglutamylation activity, showed little cross resistance to the analog (4Oa) having a tetrazole moiety as a substituent of glutamine, which exhibited potent antitumor activities. These results demonstrate that the antifolate analogs (4) with N5-substituted glutamine in place of glutamic acid are novel potent DHFR inhibitors with activity against MTX-resistant tumors. The potent antitumor activity of these analogs (4) may result from their effective uptake via reduced folate carrier in combination with their potent inhibition of DHFR.

Animals↗
PubMed1995

Analysis of zinc and other elements in rat pancreas, with studies in acute pancreatitis.

Determination of the concentration of certain elements makes it possible to investigate the physiology of the pancreas. We used X-ray fluorescence to determine the concentrations of zinc and other elements in the pancreas of normal (control) rats and those with cerulein-induced pancreatitis. Ten elements (Zn, Ni, Fe, P, Ca, Cl, S, K, Ti, and Mn) were detected in controls. In the early stage of acute pancreatitis, the pancreatic concentrations of Zn, Ni, Fe, and P were significantly decreased (P < 0.05) and those of Ca and Cl were significantly increased (P < 0.05), compared with control levels. However, levels of S, K, and Ti did not differ significantly from the control values. Mn was detected in only some samples. The serum levels of Zn and Fe were significantly elevated (P < 0.05) in acute pancreatitis. These observations indicate that Zn and these other nine elements could play an important role in acute pancreatitis.

Acute Disease↗
PubMed1995

Experimental study of liver injury after partial hepatectomy with intermittent or continuous hepatic vascular occlusion. Differences in tolerance to ischemia between normal and cirrhotic livers.

The degree of residual liver injury in normal and cirrhotic rats undergoing 70% hepatectomy with hepatic inflow occlusion was examined. The total duration of clamping was 60 min and animals were divided into 3 groups according to the ischemic modality: a 15-min intermittent clamping group (group I); a 30-min intermittent clamping group (group II), and a 60-min continuous clamping group (group III). In normal liver rats, the survival rates after operation in groups I, II and III were 90, 90 and 30%, respectively, compared to 70, 50 and 38%, respectively, in cirrhotic rats. The serum aspartate aminotransferase (AST) level increased markedly with prolongation of each period of clamping in rats with normal liver, showing higher AST levels than those with cirrhotic liver. The liver tissue adenosine-5'-triphosphate (ATP) levels and energy charge (EC) values decreased with prolongation of each period of clamping. Cirrhotic livers showed lower ATP levels and EC values than normal livers. Although there was no significant difference in the mitochondrial function between normal and cirrhotic livers in the group of the same form of ischemia, phosphorylative efficiency of mitochondria was maintained satisfactorily in normal groups I and II and in the cirrhotic group I. Even though cirrhotic livers showed a smaller necrotic response to ischemia than normal livers, they were more vulnerable to ischemia because of an inability to maintain energy metabolism. Therefore, when performing resection of a cirrhotic liver, a 15-min intermittent clamping method should be adopted.

Adenine Nucleotides↗
PubMed1995

Natriuretic peptides inhibit angiotensin II-induced proliferation of rat cardiac fibroblasts by blocking endothelin-1 gene expression.

The present study was aimed to test the role of endothelin-1 (ET-1) as a possible autocrine/paracrine growth factor for cardiac fibroblasts, and to examine its interaction with cardiac natriuretic hormones. Expression of preproET-1 (ppET-1) mRNA by cultured cardiac fibroblasts from neonatal rats was demonstrated by Northern blot analysis using cDNA for rat ppET-1 as a probe. Angiotensin II (ANG II) and ET-1 transiently (30 min) increased steady-state ppET-1 mRNA levels in cardiac fibroblasts. Both ET-1 and ANG II significantly stimulated [3H] thymidine incorporation into cardiac fibroblasts, whose effects were dose-dependently inhibited by an ETA receptor antagonist (BQ123), BQ123 also inhibited both ET-1- and ANG II-induced ppET-1 mRNA expression. Both atrial and brain natriuretic peptides (ANP, BNP), which activate particulate guanylate cyclase, inhibited ppET-1 mRNA expression and [3H]thymidine incorporation stimulated by ANG II and ET-1. Sodium nitroprusside, a soluble guanylate cyclase activator, and 8-bromocyclic GMP, a membrane-permeable cGMP derivative, similarly inhibited ppET-1 mRNA expression and [3H]-thymidine incorporation. BNP was more potent than ANP to inhibit ANG II- and ET-1-stimulated DNA synthesis, whereas BNP and ANP were almost equipotent in stimulating cGMP generation in cardiac fibroblasts. Our data demonstrated that ANG II and ET-1 upregulate ET-1 gene expression in rat cardiac fibroblasts partly via cyclic GMP-dependent mechanism, and that natriuretic peptides inhibit ANG II-stimulated proliferation of cardiac fibroblasts, possibly by inhibiting ET-1 gene expression. Our data suggest the possible role of endogenous ET-1 as an autocrine/paracrine growth factor for cardiac fibroblasts and its close interaction with natriuretic peptides in the regulation of cardiac fibrosis.

Angiotensin II↗
PubMed1995

Non-glutamate type pyrrolo[2,3-d]pyrimidine antifolates. I: Synthesis and biological properties of pyrrolo[2,3-d]pyrimidine antifolates containing tetrazole congener of glutamic acid.

Either the alpha- or gamma-carboxyl group of the glutamic acid moiety of N-[4-[3-(2,4-diamino-7H-pyrrolo[2,3-d]pyrimidin-5- yl)propyl]benzoyl]-L-glutamic acid (1b, TNP-351) and its related compound (1a) was replaced with a 1H-tetrazole ring, and the inhibitory effects of the resulting compounds on dihydrofolate reductase (DHFR) and the growth of murine fibrosarcoma Meth A cells were examined. The gamma-tetrazole analogs (2) were found to be much more potent DHFR inhibitors than TNP-351, and strongly inhibited the growth of Meth A cells. On the other hand, the alpha-tetrazole analogs (3) were much less active against Meth A cells, even though their DHFR-inhibitory activity was comparable to that of TNP-351. These findings suggest that the alpha-carboxyl group plays an important role in effective uptake via the reduced folate carrier, and a novel DHFR inhibitor could be obtained by chemically modifying the gamma-carboxyl moiety while leaving the alpha-carboxyl group intact.

Animals↗