Biomedical subjects

H Terada

Publications and source records attributed to H Terada.

At least 73 records · Page 4Linked to original sources

PubMed2000

Structure and characterization of the genes for murine choline/ethanolamine kinase isozymes alpha and beta.

Choline/ethanolamine kinase (CK/EK) is the first enzyme in phosphatidylcholine/phosphatidylethanolamine biosynthesis in all animal cells. The highly purified CKs from mammalian sources and their recombinant gene products so far were all shown to have EK activity also, indicating that both activities reside on the same protein. CK/EK in most animal cells exists as several isoforms, for two of which (alpha and beta) their cDNAs have been cloned from both the rat and mouse, and they are found to be separate gene products. The physiological significance for the existence of more than one CK/EK enzyme, however, remains to be clarified. In this study, we isolated mouse genes encoding both types of CK/EK isozyme and determined their entire structure. The 5'-flanking promoter regions were found to have quite different features from each other, indicating that their expression could be under distinct control. Comparison of the nucleotide sequence between the corresponding coding exons showed the best homology (75%) residing on exon VIII. A search of the database resulted in the possible existence of 17 different origins of eukaryotic CK and/or EK, each of which presumably contained the entire amino acid sequence. Multialignment of their putative amino acid sequences led to an identification of the novel consensus sequence possibly required for the expression of either CK or EK activity, which corresponded to the sequence within exons VII and VIII of CK/EK-alpha and -beta genes from the mouse. This sequence was localized in close proximity to the C-terminal region of the general (Brenner's) phosphotransferase concensus sequence which was also completely conserved in all of the putative eukaryotic CK/EK proteins. The results demonstrated that, while both CK/EK-alpha and -beta genes were composed of 11 major exons, the size of their genes was quite different: 40 kb for CK/EK-alpha, whereas it was only 3.5 kb for CK/EK-beta.

Amino Acid Sequence↗

PubMed1999

Increased cytosolic Ca(2+) concentration in endothelial cells by calmodulin antagonists.

Many functions of endothelial cells are Ca(2+)/calmodulin dependent, whereas the role of calmodulin in the regulation of cytosolic Ca(2+) ([Ca(2+)](i)) remains largely unexplained. In the present study, effects of various calmodulin antagonists on [Ca(2+)](i) were investigated in cultured aortic endothelial cells loaded with the Ca(2+)-sensitive dye fura-2/AM, and were compared with those of calmodulin-dependent protein kinase II (CaM kinase II) inhibitors. The calmodulin antagonists W-7, calmidazolium and fendiline provoked dose-dependent increases in [Ca(2+)](i). However, the CaM kinase II inhibitors KN-93 and lavendustin C had no effect on [Ca(2+)](i). In the absence of extracellular Ca(2+), pretreatment of cells with bradykinin (BK) and thapsigargin completely prevented W-7-stimulated increase in [Ca(2+)](i). Alternatively, pretreatment with W-7 also completely blocked BK- and thapsigargin-stimulated increases in [Ca(2+)](i). The time course of the Ca(2+)-response in W-7 treated cells was identical to that in thapsigargin-treated cells, but not that in BK-stimulated cells, suggesting that calmodulin antagonists could share a common signaling pathway with thapsigargin to increase [Ca(2+)](i) in endothelial cells. These findings indicate that calmodulin is involved in the regulation of [Ca(2+)](i), and may play an important role in the uptake of Ca(2+) to intracellular stores.

Animals↗

PubMed1999

Lack of association between alpha1-antichymotrypsin polymorphism and late-onset depressive disorder.

Late-onset depressive disorder (LOD) has been thought to be associated with dementia. Recently, it was reported that the position-15 (alanine) polymorphism of the alpha1-antichymotrypsin gene (ACT*A) was a risk factor for Alzheimer's disease. We wondered whether the ACT*A allele frequency might be elevated in LOD. ACT genotyping was performed as described by Kamboh et al. (Kamboh, M.I., Sanghera D.K., Ferrell R.E., DeKosky, S.T., 1995. APO* E4-associated Alzheimer's disease risk is modified by alpha1-antichymotrypsin polymorphism. Nature Genetics 10, 486-488) in 153 patients with depressive disorders and 107 healthy controls. The patients were subdivided into those with early-onset and late-onset, using 50 years as the cut-off age. There was no statistically significant difference in the age of onset of depressive disorders according to the ACT genotype. There was also no significant association between early-/late-onset depressive disorders and the ACT genotype. In addition, there was no association between the apolipoprotein E epsilon 4 allele and the ACT genotype in LOD. Our results suggest that there is no association between the ACT*A allele and LOD.

Adolescent↗

PubMed1999

Functional expression of the tandem-repeated homodimer of the mitochondrial ADP/ATP carrier in Saccharomyces cerevisiae.

The mitochondrial ADP/ATP carrier (AAC) is believed to function as a dimer. To characterize the oligomeric state of the yeast type 2 AAC (yAAC2), we tried to express its tandem-repeated homodimer, in which the C-terminus of the first repeat was fused to the N-terminus of the second repeat, in yeast mitochondria. The tandem dimer was expressed in the mitochondrial membrane at the same level as that of yAAC2, being inserted into the mitochondrial membrane as in yAAC2, and it showed very similar transport activity to that of yAAC2. It was suggested that the two carrier molecules in a dimeric form are located in the membrane facing each other in the same orientation.

Dimerization↗

PubMed1999

Fluctuation of the first loop facing the matrix of the mitochondrial ADP/ATP carrier deduced from intermolecular cross-linking of Cys56 residues by bifunctional dimaleimides.

The effects of six thiol-specific cross-linker dimaleimides, in which the distance of the two maleimide groups ranged from 7.7 to 16. 8 A, on bovine heart mitochondria were studied at pH 7.2 and 0 degrees C. None of the dimaleimides affected mitochondrial proteins, but they caused significantly specific intermolecular cross-linking of the 30 kDa ADP/ATP carrier in submitochondrial particles. All the cross-links were found to be formed specifically between two Cys56 residues in the first loop facing the matrix, as we observed previously in intermolecular disulfide bridge formation catalyzed by copper o-phenanthroline [Majima, E., Ikawa, K., Takeda, M., Hashimoto, M., Shinohara, Y., and Terada, H. (1995) J.Biol. Chem. 270, 29548-29554]. The dimerization was dependent on the cross-linking span of the dimaleimides, being maximum with the dimaleimide having a span of about 12 A. Cross-linking took place in the m-state carrier, but not in the c-state carrier, and inhibited ADP transport via the ADP/ATP carrier. We suggest that a pair of first loops with Cys56 residues in the dimer form of the m-state carrier fluctuates widely with a most probable distance between them of about 12 A, and that this fluctuation modulates the transport activity of the ADP/ATP carrier.

Adenosine Diphosphate↗

PubMed1999

Expression of the bovine heart mitochondrial ADP/ATP carrier in yeast mitochondria: significantly enhanced expression by replacement of the N-terminal region of the bovine carrier by the corresponding regions of the yeast carriers.

To characterize the transport mechanism mediated by the mammalian mitochondrial ADP/ATP carrier (AAC), we tried to express bovine heart mitochondrial AAC (bhAAC) in Saccharomyces cerevisiae. The open reading frame of the bhAAC was introduced into the haploid strain WB-12, in which intrinsic AAC genes were disrupted. Growth of the transformant was very low in glycerol medium, and a little amount of bhAAC was detected in the mitochondrial membrane. For improvement of bhAAC expression in WB-12, we introduced DNA fragments encoding chimeric bhAACs, in which the N-terminal region of the bhAAC extending into the cytosol was replaced by the corresponding regions of the type 1 and type 2 yeast AAC isoforms (yAAC1 and yAAC2). These transformants grew well, and the amounts of the chimeric bhAACs in their mitochondria were as high as that of yAAC2. The carriers expressed showed essentially the same ADP transport activities as that of AAC in bovine heart mitochondria.

Amino Acid Sequence↗

PubMed1999

Potent antiperoxidation activity of the bisbenzylisoquinoline alkaloid cepharanthine: the amine moiety is responsible for its pH-dependent radical scavenge activity.

The bisbenzylisoquinoline alkaloid cepharanthine, which has been considered to exhibit antiperoxidation activity due to its membrane stabilizing effect, was found to scavenge radicals such as .OH and DPPH (1,1-diphenyl-2-picrylhydrazyl) in solution, and to inhibit lipid peroxidation in mitochondria and liposomes by Fe2+/ADP. The antiperoxidation activity of cepharanthine in rat liver mitochondria initiated by Fe2+/ADP at pH 7.4 was much greater than that of alpha-tocopherol, its half-inhibitory concentration being about 23 microM. However, cepharanthine was effective only at neutral pH values such as pH 7.4, not in a moderately acidic pH region below pH 6.5. Accordingly, the neutral form of the deprotonated amine moiety in the tetrahydroisoquinoline ring is concluded to be responsible for the radical scavenging activity of cepharanthine. There are two amine moieties in the cepharanthine molecule, but we specified the effective amine moiety from the antiperoxidation activities of the imine analogs of cepharanthine.

Alkaloids↗

PubMed1999

Structure and NIR feature of QCC: a laboratory analog of carbon dust.

We have produced thin films of quenched carbonaceous composite (QCC) by hydrocarbon plasma deposition. The effect of thermal annealing on QCC has been investigated to understand how QCC, as a laboratory analog of carbon dust, is transformed in the warm environment around evolved stars. Spectroscopic measurements have indicated that, by heating, the proportion of aromatic sp2 CH bonds increases relative to sp3 CH bonds. Carbon onion-like spherules of approximately 10 nm in diameter are found with electron microscopic images after "graphitization" of thermal annealing.

Astronomical Phenomena↗

PubMed1999

Effect of endogenous nitric oxide on energy metabolism of rat heart mitochondria during ischemia and reperfusion.

The effects of ischemia and postischemic reperfusion on the functions of the heart and its mitochondria were studied with special attention to the effect of nitric oxide (NO) by treatment of rat hearts with the nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) or its noninhibitory isomer N(G)-nitro-D-arginine methyl ester (D-NAME). NO generated during reperfusion caused increase in coronary flow (CF), but had no effect on the left ventricular pressure (LVP) or heart rate (HR). The ATP level of the heart decreased during ischemia and was not completely restored by introduction of oxygen during reperfusion due to damage of complexes I and II of the respiratory chain of mitochondria by NO. Inhibition of the respiratory chain resulted in generation of hydrogen peroxide, and NO and NO-derived species generated after production of NO caused further damage of various proteins in mitochondria, such as complexes I and II of the respiratory chain and pyruvate dehydrogenase (PDH). These results suggested that NO generated on reperfusion was the primary cause of mitochondrial dysfunction by damage of complexes I and II of the respiratory chain, with consequent increase of CF in the heart.

Adenosine Triphosphate↗

PubMed1999

A single cell model of myocardial reperfusion injury: changes in intracellular Na+ and Ca2+ concentrations in guinea pig ventricular myocytes.

To investigate the contribution of the changes in intracellular Na+ and Ca2+ concentrations ([Na+]i and [Ca2+]i) to myocardial reperfusion injury, we made an ischemia/reperfusion model in intact guinea pig myocytes. Myocardial ischemia was simulated by the perfusion of metabolic inhibitors (3.3 mM amobarbital and 5 microM carbonyl cyanide m-chlorophenylhydrazone) with pH 6.6 and reperfusion was achieved by the washout of them with pH 7.4. [Na+]i increased from 7.9 +/- 2.0 to 14.0 +/- 3.4 mM (means +/- S.E., p < 0.01 ) during 7.5 min of simulated ischemia (SI) and increased further to 18.8 +/- 3.0 mM at 7.5 min after reperfusion. [Ca2+]i, expressed as the ratio of fluo 3 fluorescence intensity, increased to 133 +/- 8% (p < 0.01) during SI and gradually returned to the control level after reperfusion. Intracellular pH decreased from 7.53 +/- 0.04 to 6.31 +/- 0.04 (p < 0.01) and recovered quickly after reperfusion. Reperfusion with the acidic solution or the continuous perfusion of hexamethylene amiloride (2 microM) prevented the reperfusion-induced increase in [Na+]i. When the duration of SI was prolonged to 15 min, the cell response after reperfusion varied, 16 of 37 cells kept quiescent, 21 cells showed spontaneous Ca2+ waves, and 4 cells out of these 21 cells became hypercontracted. In quiescent cells, both [Na+]i and [Ca2+]i decreased immediately after reperfusion. In cells with Ca2+ waves, [Na+]i transiently increased further at the early phase of reperfusion, while [Ca2+]i declined. In hypercontracted cells, [Na+]i increased as much as in 'Ca2+ wave' cells, but [Ca2+]i increased extensively and both ion concentrations continued to increase. Reperfusion with the Ca2+-free solution prevented both the [Ca2+]i increase and morphological change. In the presence of ryanodine (10 microM), the increase in [Ca2+]i after reperfusion was augmented and some cells became hypercontracted. We concluded that (1) Na+/H+ exchange is active both during SI and reperfusion, resulting in the additional [Na+]i elevation on reperfusion, (2) the [Na+]i level after reperfusion and the following Ca2+ influx via Na+/Ca2+ exchange are crucial for reperfusion cell injury, and (3) the Ca2+ buffering capacity of sarcoplasmic reticulum would also contribute to the Ca2+ regulation and cell injury after reperfusion.

Amiloride↗

PubMed1999

The relation between the action potential duration, the increase in resting tension, and ATP content during metabolic inhibition in guinea pig ventricular muscles.

To investigate whether the action potential duration (APD) or resting tension was dependent on global ATP content, and whether they were preferentially dependent on glycolytic ATP, APD and resting tension were measured under various metabolic inhibition with corresponding measurement of ATP content in guinea pig ventricular muscles. Oxidative phosphorylation was inhibited by either hypoxic perfusion, the perfusion of sodium cyanide, or 2,4-dinitrophenol. Glycolysis was blocked by the perfusion of iodoacetic acid, and hypoxia with variable glycolytic activities was achieved by hypoxic perfusion in the presence of glucose (5, 10, and 50 mM). APD began to decrease when ATP content decreased to less than 3 mM/kg w.w. from the control level of 4.35 mM/kg w.w. APD shortened significantly and resting tension increased steeply, when ATP content decreased below 1 mM/kg w.w. The dependence of APD and the increase in resting tension on ATP content was not affected by the mode of metabolic block, that is, the inhibition of glycolysis and/or oxidative phosphorylation. Though other factors can affect APD and resting tension, we found no evidence of functional ATP compartmentation, with respect to APD and the increase in resting tension during metabolic inhibition.

2,4-Dinitrophenol↗

PubMed1999

The effect of intravenous or subarachnoid lidocaine on glutamate accumulation during transient forebrain ischemia in rats.

UNLABELLED: We studied whether IV or subarachnoid (SA) lidocaine would influence the increase in extracellular glutamate concentration in the hippocampal CA1 and the cerebral cortex during transient forebrain ischemia in rats by using the dialysis electrode method. Fifty-four Sprague-Dawley rats were assigned to one of six treatment groups: IV lidocaine 5 mg/kg, IV lidocaine 10 mg/kg, IV 0.9% saline 0.5 mL/kg, SA lidocaine 5 mg/kg, SA lidocaine 10 mg/kg, and SA 0.9% saline 0.5 mL/kg (n = 9 in each group). Transient forebrain ischemia was induced by hemorrhagic hypotension and carotid artery occlusion, 15 min after administration of lidocaine or saline. The maximal values of glutamate concentration and the areas under glutamate concentration curves in the CA1 were significantly less in the IV lidocaine 10 mg/kg group than the IV saline group, whereas those in the CA1 and the cortex were significantly less in the SA lidocaine 5 and 10 mg/kg groups than the SA saline group. The accumulation of glutamate in the CA1 or the cortex during transient forebrain ischemia was attenuated by IV or SA lidocaine. We conclude that the neuroprotective effect of lidocaine against transient cerebral ischemia involves the suppression of the increase in extracellular glutamate concentration. IMPLICATIONS: IV or subarachnoid lidocaine was demonstrated to suppress glutamate accumulation in the hippocampus and the cortex during transient forebrain ischemia in rats by using the dialysis electrode method. Lidocaine can have a neuroprotective effect through the suppression of the increase in extracellular glutamate concentration.

Anesthetics, Local↗

PubMed1999

[Significance of atrial fibrillation, left atrial thrombus and severity of stenosis for risk of systemic embolism in patients with mitral stenosis].

The prognostic significance of atrial fibrillation, left atrial thrombus and the severity of mitral stenosis (MS) for systemic embolism was evaluated in 142 consecutive patients with MS (male 61, female 81; mean age 51 +/- 10 years) who were referred for cardiac catheterization. The relationships between systemic embolization, atrial fibrillation, left atrial thrombus and the size of mitral valve area obtained by the echocardiographic or Doppler method, or cardiac catheterization (Gorlin's formula) were studied. The effects of mitral regurgitation (MR) (Sellers II < or =) on systemic embolism or left atrial thrombus were also evaluated. Atrial fibrillation was observed in 117 patients (87%), 30 (28%) of whom had a history of systemic embolism. Four of 18 patients (22%) with sinus rhythm had a history of systemic embolism. Left atrial thrombus was observed in 63 patients (45%), including 17 (27%) with a history of systemic embolism. Seventeen (22%) of 76 patients without left atrial thrombus had a history of systemic embolism. Left atrial thrombus was detected in 17 of 41 (41%) patients with severe MS [mitral valve area (MVA) < or = 1.0 cm2], 8 of 25 (32%) patients with moderate MS (1.1 < MVA < or = 1.5 cm2), 2 of 14 (14%) patients with mild MS (MVA > or = 1.6 cm2), and embolization was complicated in 11% of cases of severe MS, 32% of cases of moderate MS and 21% of cases of mild MS. There was no significant difference between the 3 groups. Left atrial thrombus was more frequently observed in patients without MR than with MR (44% vs 13%, p < 0.05), but there was no significant difference in the incidence of embolism between the groups (28% vs 22%). Positive therapy intervention should be considered to prevent systemic embolism regardless of the presence or absence of sinus rhythm, MR, left atrial thrombus or severity of stenosis.

Atrial Fibrillation↗

PubMed1998

Isolation and characterization of cDNA encoding rat heart type acetyl-CoA carboxylase.

We isolated and characterized cDNA clones encoding the entire open reading frame (ORF) of a protein consisting of 2456 amino acids with a molecular mass of 276069 Da from rat heart. As the deduced amino acid sequence showed 85% homology with that of human type 2 acetyl-CoA carboxylase (ACC2), we concluded that the cDNA clones encode rat heart type ACC2. Using the identified cDNA fragments and the reported cDNA fragment of rat type 1 ACC (ACC1), we determined the steady state transcript levels of ACC1 and ACC2 in various rat tissues quantitatively by Northern blot analysis. The transcript level of ACC2 was high in heart, skeletal muscle and brown adipose tissue, which require high energy and mainly metabolize fatty acids, whereas that of ACC1 was high in white adipose tissue, which stores fatty acids.

Acetyl-CoA Carboxylase↗

PubMed1998

Cationic uncouplers of oxidative phosphorylation are inducers of mitochondrial permeability transition.

To determine whether cationic uncouplers of oxidative phosphorylation induce permeability transition in mitochondria, the effects of the divalent cationic sulfhydryl cross-linker copper-o-phenanthroline (Cu(OP)2) and the cyanine dye tri-S-C4(5) on rat liver mitochondria were examined. Like Ca2+, they accelerated mitochondrial respiration with succinate and induced mitochondrial swelling when inorganic phosphate (Pi) was present in the incubation medium. The acceleration of respiration and swelling were inhibited by the SH-reagent N-ethylmaleimide, and by the specific permeability transition inhibitor cyclosporin A (CsA). In addition, these cations, like Ca2+, induced release of ADP entrapped in the mitochondrial matrix space, and the morphological change of mitochondria induced by these cations was essentially the same as that induced by Ca2+. It is concluded that the uncoupling actions of Cu(OP)2 and tri-S-C4(5) are due to induction of permeability transition in the inner mitochondrial membrane.

Adenosine Diphosphate↗

PubMed1998

Binding of the fluorescein derivative eosin Y to the mitochondrial ADP/ATP carrier: characterization of the adenine nucleotide binding site.

As the SH-reactive fluorescein derivative eosin-5-maleimide (EMA) specifically labels Cys159 in the second loop facing the matrix space (loop M2) of the ADP/ATP carrier in bovine heart submitochondrial particles [Majima, E., Koike, H., Hong, Y.-M., Shinohara, Y., and Terada, H. (1993) J. Biol. Chem. 268, 22181-22187], we studied the interaction of non-SH-reactive eosin Y, an analog of EMA, with the carrier under various conditions to characterize its binding. Eosin Y was found to inhibit ADP transport by binding to loop M2 in submitochondrial particles, but not in mitochondria. Its Ki for transport (0.33 microM) was found to be very similar to its Kd (0.53 microM) for specific binding to the carrier. Bound eosin Y was displaced by the transport substrates ADP and ATP, but not by untransportable GTP, suggesting that eosin Y bound to the specific binding site of ADP and ATP. The three-dimensional structure and electrostatic features of eosin Y were very similar to those of ADP, and the hydrophobic property and divalent charge of eosin Y were very important for its binding to the carrier. Based on these results, the features of the binding site of the transport substrates are considered.

Adenine Nucleotides↗

PubMed1998

Quantitative determinations of the steady state transcript levels of hexokinase isozymes and glucose transporter isoforms in normal rat tissues and the malignant tumor cell line AH130.

The steady state transcript levels of the four hexokinase (HK) isozymes and four glucose transporter (GLUT) isoforms were determined quantitatively by Northern analysis of RNA samples from rat tissues using synthetic fragments of the RNAs encoding the HK isozymes and GLUT isoforms. Results showed that the levels of HK isozyme transcripts were low in rat tissues, the level of that most highly expressed, the type I isozyme (HKI), in the brain being 0.025% of the total poly(A)+ RNA. A good correlation was found between the reported HK activities and the total amounts of transcripts encoding all HK isozymes in various tissues, showing that the HK activities in tissues can be estimated from the total amount of transcripts encoding HK isozymes. The proposed associated expressions of HK isozymes and GLUT isoforms in particular tissues were confirmed at their transcript levels. The steady state transcript levels of type II HK and the type 1 GLUT isoform in the malignant tumor cell line AH130 were also determined quantitatively.

Animals↗

PubMed1998

Keratoprosthesis in pemphigoid and Stevens-Johnson syndrome.

Keratoprosthesis was implanted in 17 eyes with ocular pemphigoid and 7 eyes with Stevens-Johnson syndrome and followed for 6 months to 6 years. Visual outcomes and complications were compared. Pemphigoid was found to have a much better prognosis than did Stevens-Johnson syndrome. Keratoprosthesis is now firmly indicated in elderly pemphigoid patients whose vision in both eyes has become reduced to hand movements or less due to a corneal opacity.

Adult↗