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T Aoyama

Publications and source records attributed to T Aoyama.

At least 109 records · Page 6Linked to original sources
PubMed1998

Relationship between structure and substrate-chain-length specificity of mitochondrial very-long-chain acyl-coenzyme A dehydrogenase.

Very-long-chain acyl-coenzyme A dehydrogenase (VLCAD) is one of four enzymes which catalyze the initial step of the mitochondrial beta-oxidation with different but overlapping substrate-chain-length specificities. A450P, a variant of VLCAD identified in a patient with VLCAD deficiency, showed abnormal substrate-chain-length specificity. Based on this mutation, we studied the relationship between the structure and substrate-chain-length specificity of VLCAD. When VLCAD was treated with trypsin, a homodimer protein of a 48-kDa polypeptide deprived of both the amino-terminal 22 amino acids and the carboxyl-terminal 145 amino acids of VLCAD was obtained. Six Ala450 variants and tryptic-VLCAD exhibited similar substrate specificities. Effects of long-chain acyl-CoA on the tryptic cleavage and changes in the catalytic properties by deprivation of the carboxyl-terminal region suggest that this region interacts with the fatty acyl moiety of long-chain acyl-CoA. Thus, both Ala450 and the carboxyl-terminal region, which are not shared by other acyl-CoA dehydrogenases, are likely to be the determinating factors in the substrate-chain-length specificity of VLCAD.

Acyl Coenzyme A↗
PubMed1998

Life without white fat: a transgenic mouse.

We have generated a transgenic mouse with no white fat tissue throughout life. These mice express a dominant-negative protein, termed A-ZIP/F, under the control of the adipose-specific aP2 enhancer/promoter. This protein prevents the DNA binding of B-ZIP transcription factors of both the C/EBP and Jun families. The transgenic mice (named A-ZIP/F-1) have no white adipose tissue and dramatically reduced amounts of brown adipose tissue, which is inactive. They are initially growth delayed, but by week 12, surpass their littermates in weight. The mice eat, drink, and urinate copiously, have decreased fecundity, premature death, and frequently die after anesthesia. The physiological consequences of having no white fat tissue are profound. The liver is engorged with lipid, and the internal organs are enlarged. The mice are diabetic, with reduced leptin (20-fold) and elevated serum glucose (3-fold), insulin (50- to 400-fold), free fatty acids (2-fold), and triglycerides (3- to 5-fold). The A-ZIP/F-1 phenotype suggests a mouse model for the human disease lipoatrophic diabetes (Seip-Berardinelli syndrome), indicating that the lack of fat can cause diabetes. The myriad of consequences of having no fat throughout development can be addressed with this model.

Adipose Tissue↗
PubMed1998

Inducible expression of lectin-like oxidized LDL receptor-1 in vascular endothelial cells.

Endothelial dysfunction, or activation, elicited by oxidized LDL (Ox-LDL) or its lipid constituent, has been implicated in the initiation and progression of atherosclerosis. We have recently identified a C-type lectin-like molecule, designated lectin-like Ox-LDL receptor-1 (LOX-1), which acts as a cell-surface receptor for Ox-LDL in cultured vascular endothelial cells. In this study, we provide evidence that LOX-1 expression can be upregulated by tumor necrosis factor-alpha (TNF-alpha) and phorbol 12-myristate 13-acetate (PMA) in cultured bovine aortic endothelial cells. TNF-alpha and PMA upregulated LOX-1 protein and mRNA in a time- and dose-dependent manner. Nuclear runoff assay revealed that TNF-alpha stimulates transcription of the LOX-1 gene. Chinese hamster ovary K1 cells stably expressing LOX-1 internalized 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-labeled Ox-LDL but did not significantly internalize acetylated LDL (Ac-LDL), which was effectively suppressed by excess amounts of unlabeled Ox-LDL but not by Ac-LDL. Upregulated expression of LOX-1 by TNF-alpha and PMA was associated with increased uptake of DiI-Ox-LDL that cannot be blocked by excess amounts of unlabeled Ac-LDL. Taken together, LOX-1 is a receptor specific for Ox-LDL, and enhanced uptake of Ox-LDL via this novel receptor on vascular endothelial cells may play an important role in endothelial activation in atherogenesis.

Animals↗
PubMed1998

Purification of a novel endothelin-converting enzyme specific for big endothelin-3.

Endothelin-3 (ET-3), a potent vasoactive peptide, is considered to be produced from big ET-3 by endothelin-converting enzyme (ECE) like the other members of the endothelin family (ET-1 and ET-2). We purified a novel ECE from bovine iris microsomes. The purified enzyme, a 140 kDa protein by SDS-PAGE analysis, converted big ET-3 to ET-3 but not big ET-1, with a Km value of 0.14 microM for big ET-3. The conversion to ET-3 was confirmed with sandwich EIA by monoclonal antibodies, the elution profile of HPLC, and intracellular calcium mobilization in CHO-K1 cells expressing recombinant human ET(B) receptors. The conversion activity was inhibited by an inhibitor of neutral endopeptidase 24.11 (NEP) phosphoramidon. These results show that ECE-3 purified from bovine iris is a novel metalloprotease totally different from ECE-1 or ECE-2, in that the enzyme is highly specific for big ET-3.

Animals↗
PubMed1998

Structural characterization of the virB operon on the hairy-root-inducing plasmid A4.

The hairy-root-inducing plasmid A4 (pRiA4) is capable of conferring tumorigenic symptoms on plants upon infection by its host bacterium, Agrobacterium rhizogenes. The virB operon on pRiA4 has been sequenced and found to be composed of 11 genes, virB1 to virB11, whose products mostly appear to be associated with the cell membrane. A novel structural characteristic is frequent overlappings between the translation termination and initiation codons of adjacent genes. This is indicative of fine tuning of relative translation frequencies for each VirB protein. These results support the view that VirB multisubunit complexes provide facilities for T-DNA transfer at the bacterial cell membrane. The structural organization of the pRiA4 virB operon was essentially identical to that of the previously reported virB operons of tumor-inducing plasmids, pTiC58 and pTiA6, and the corresponding VirB proteins of the three plasmids were extremely homologous to one another. On the basis of the structural similarity of each VirB protein, the phylogenetic relationship among pRiA4, pTiC58, and pTiA6 is discussed.

Bacterial Proteins↗
PubMed1998

High affinity binding of oxidized LDL to mouse lectin-like oxidized LDL receptor (LOX-1).

We cloned mouse LOX-1 cDNA to take advantage of a gene-targeting technique to clarify the role of LOX-1 in vivo. Mouse LOX-1 was composed of 363 amino acids and had a C-type lectin domain type II membrane protein structure. Mouse LOX-1 had triple repeats of the sequence in the extracellular "Neck domain," which is unlike human and bovine LOX-1. LOX-1 bound oxidized LDL with two classes of binding affinity in the presence of serum. The binding component with the higher affinity showed the lowest value of Kd among the known receptors for oxidized LDL. In the absence of serum, the high affinity component disappeared, suggesting that an unknown co-factor in serum is essential for efficient uptake of oxidized LDL by endothelial cells. A low concentration of unlabeled oxidized LDL displaced 125I-labeled oxidized LDL more efficiently in the presence of serum than in the absence of serum. The co-factor in the serum may be involved in the pathophysiology of atherosclerosis in addition to the oxidation of LDL.

Amino Acid Sequence↗
PubMed1998

Very-long-chain acyl-CoA dehydrogenase subunit assembles to the dimer form on mitochondrial inner membrane.

This paper describes the process of dimer assembly of mitochondrial very-long-chain acyl-CoA dehydrogenase (VLCAD) subunit. Mature VLCAD is a homodimer of a 70-kDa protein associated with the mitochondrial membrane. Newly synthesized VLCAD was present as a monomer and the major fraction was associated with the mitochondrial inner membrane. The association of VLCAD subunit with the mitochondrial membrane was observed early during dimer formation. In contrast, a VLCAD monomeric mutant S583W, a novel mutation identified from a patient with VLCAD deficiency, did not associate with the mitochondrial membrane after import and the major fraction remained in the mitochondrial matrix. These results suggest that association of VLCAD protein with mitochondrial inner membrane is necessary for dimer assembly and formation of mature VLCAD.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed1998

Altered constitutive expression of fatty acid-metabolizing enzymes in mice lacking the peroxisome proliferator-activated receptor alpha (PPARalpha).

Peroxisome proliferator-activated receptor alpha (PPARalpha) is a member of the steroid/nuclear receptor superfamily and mediates the biological and toxicological effects of peroxisome proliferators. To determine the physiological role of PPARalpha in fatty acid metabolism, levels of peroxisomal and mitochondrial fatty acid metabolizing enzymes were determined in the PPARalpha null mouse. Constitutive liver beta-oxidation of the long chain fatty acid, palmitic acid, was lower in the PPARalpha null mice as compared with wild type mice, indicating defective mitochondrial fatty acid catabolism. In contrast, constitutive oxidation of the very long chain fatty acid, lignoceric acid, was not different between wild type and PPARalpha null mice, suggesting that constitutive expression of enzymes involved in peroxisomal beta-oxidation is independent of PPARalpha. Indeed, the PPARalpha null mice had normal levels of the peroxisomal acyl-CoA oxidase, bifunctional protein (hydratase + 3-hydroxyacyl-CoA dehydrogenase), and thiolase but lower constitutive expression of the D-type bifunctional protein (hydratase + 3-hydroxyacyl-CoA dehydrogenase). Several mitochondrial fatty acid metabolizing enzymes including very long chain acyl-CoA dehydrogenase, long chain acyl-CoA dehydrogenase, short chain-specific 3-ketoacyl-CoA thiolase, and long chain acyl-CoA synthetase are also expressed at lower levels in the untreated PPARalpha null mice, whereas other fatty acid metabolizing enzymes were not different between the untreated null mice and wild type mice. A lower constitutive expression of mRNAs encoding these enzymes was also found, suggesting that the effect was due to altered gene expression. In wild type mice, both peroxisomal and mitochondrial enzymes were induced by the peroxisome proliferator Wy-14,643; induction was not observed in the PPARalpha null animals. These data indicate that PPARalpha modulates constitutive expression of genes encoding several mitochondrial fatty acid-catabolizing enzymes in addition to mediating inducible mitochondrial and peroxisomal fatty acid beta-oxidation, thus establishing a role for the receptor in fatty acid homeostasis.

17-Hydroxysteroid Dehydrogenases↗
PubMed1998

Catalytic and FAD-binding residues of mitochondrial very long chain acyl-coenzyme A dehydrogenase.

Very long-chain acyl-CoA dehydrogenase (VLCAD) is one of four flavoproteins which catalyze the initial step of the mitochondrial beta-oxidation spiral. By sequence comparison with other acyl-CoA dehydrogenases, Glu-422 of VLCAD has been presumed to be the catalytic residue that abstracts the alpha-proton in the alphabeta-dehydrogenation reaction. Replacing Glu-422 with glutamine (E422Q) caused a loss of enzyme activity by preventing the formation of a charge transfer complex between VLCAD and palmitoyl-CoA. This result provides further evidence for Glu-422 being part of the active site of VLCAD. F418L is a disease-causing mutation in human VLCAD deficiency. Unlike wild-type VLCAD, F418L and F418V contained no bound FAD when expressed at extremely high levels in the baculovirus expression system. Although F418T and F418Y bound FAD at a level similar to that of wild-type VLCAD, both showed reduced Vmax values toward palmitoyl-CoA, most likely due to a decrease in the rate of enzyme-bound FAD reduction. These data suggest that Phe-418 is involved in the binding and subsequent reduction of FAD. FAD-deficient VLCADs (F418L, F418V, and apo-VLCAD) showed increased sensitivity to trypsinization. Loss of FAD may change the folding of VLCAD subunit.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed1998

Molecular cloning and characterization of a mitochondrial peroxisome proliferator-induced acyl-CoA thioesterase from rat liver.

We have previously reported the purification and characterization of the peroxisome proliferator-induced very-long-chain acyl-CoA thioesterase (MTE-I) from rat liver mitochondria [L.T. Svensson, S.E. H. Alexson and J.K. Hiltunen (1995) J. Biol. Chem. 270, 12177-12183]. Here we describe the cloning of the corresponding cDNA. One full-length clone was isolated that contained an open reading frame of 1359 bp encoding a polypeptide with a calculated molecular mass of 49707 Da. The deduced amino acid sequence contains a putative mitochondrial leader peptide of 42 residues. Expression of the cDNA in Chinese hamster ovary cells, followed by immunofluorescence, immunoelectron microscopy and Western blot analyses, showed that the product was targeted to mitochondria and processed to a mature protein of 45 kDa, which is similar to the molecular mass of the protein isolated from rat liver mitochondria. The recombinant enzyme showed the same acyl-CoA chain-length specificity as the isolated rat liver enzyme. Sequence analysis showed no similarity to known esterases, but a high degree (approx. 40%) of identity with bile acid-CoA:amino acid N-acyltransferase cloned from human and rat liver. A putative active-site serine motif (Gly-Xaa-Ser-Xaa-Gly) of several carboxylesterases and lipases was identified. Western and Northern blot analyses showed that MTE-I is constitutively expressed in heart and is strongly induced in liver by feeding rats with di(2-ethylhexyl)phthalate, a peroxisome proliferator, suggesting a role for the enzyme in lipid metabolism.

Amino Acid Sequence↗
PubMed1998

[Two cases of coronary artery aneurysm including one case of the left main coronary artery aneurysm].

We report two cases of coronary artery aneurysm including one case of the left main coronary artery aneurysm. The coronary angiogram of one patient, a 68-year-old male, having anterior chest pain on exertion, revealed left anterior descending coronary artery (segment 6) aneurysm of 7 mm in diameter with 90% stenosis distal to the aneurysm and 75% stenosis in the right coronary artery (segment 2). The coronary angiogram of another patient, a 69-year-old female, having chest pain unrelated to exertion, revealed left main coronary artery aneurysm of 25 mm in diameter and delayed filling of contrast medium into the left anterior descending coronary artery. We decided to operate by the reason of not only significant coronary artery stenosis but risks of myocardial infarction due to embolization into distal coronary arteries and rupture of the aneurysm. We performed coronary artery bypass graftings using the great saphenous veins and closure of the coronary arteries running into and out the aneurysm under cardiopulmonary bypass. It is recommended that ligation of the coronary arteries connecting to the aneurysm or resection of the aneurysm followed by coronary artery bypass grafting is performed before developing myocardial infarction or rupture of aneurysm.

Aged↗
PubMed1998

Detection of a drug-drug interaction on population-based phenobarbitone clearance using nonlinear mixed-effects modeling.

OBJECTIVE: Nonlinear mixed-effects modeling (NONMEM) was used to estimate the effects of drug drug interaction on phenobarbitone clearance values, using 648 serum levels gathered during the routine clinical care of 349 pediatric and adult epileptic patients (age range, 0.4-33.3 years). Patients received phenobarbitone as monotherapy or in combination with either of the antiepileptic drugs carbamazepine or valproic acid. RESULTS: The final model describing phenobarbitone clearance was CL = 52.3 x TBW(-0.567) x CO, where CL is clearance (ml x kg(-1) x h(-1)), TBW is total body weight (kg) and CO is a scaling factor for concomitant medication with a value of 1 for patients on phenobarbitone monotherapy, 46.4(-1/TBW) for those patients receiving concomitant carbamazepine and 0.642 for those patients receiving concomitant valproic acid. Phenobarbitone CL was highest in the very young and decreased in a weight-related fashion in children, with minimal changes observed in adults. This pattern was consistent whether phenobarbitone was administered alone or coadministered with carbamazepine or valproic acid. When phenobarbitone was coadministered with carbamazepine or valproic acid, phenobarbitone CL decreased compared with that in monotherapy. Its magnitudes in the presence of carbamazepine are maximal in early childhood (about 54%) and decreased in a weight-related fashion in older children, with minimal changes observed in adults. Concomitant administration of phenobarbitone and valproic acid resulted in a 35.8% decrease of phenobarbitone CL.

Adolescent↗
PubMed1998

Activated partial thromboplastin time is a predictive parameter for further miscarriages in cases of recurrent fetal loss.

OBJECTIVE: To determine whether clinically routine clotting tests such as activated partial thromboplastin time (aPTT), prothrombin time (PT), or fibrinogen can be used to predict further miscarriages. DESIGN: Prospective study. SETTING: Nagoya City University Hospital, Nagoya, Japan. PATIENT(S): A total of 261 patients with a history of two consecutive first-trimester spontaneous abortions who had no antiphospholipid antibodies or other autoimmune diseases and no anatomic anomalies were examined for aPTT, PT, and fibrinogen before becoming pregnant again. INTERVENTION(S): Blood tests were performed before pregnancy. Patients then were followed up during subsequent pregnancy and their outcomes were compared with their previous blood test results. MAIN OUTCOME MEASURE(S): Activated partial thromboplastin time, PT, and fibrinogen were measured by coagulation time methods. RESULT(S): Fifty-eight of 261 patients (22.2%) had a subsequent miscarriage. Mean (+/-SD) values for preconception aPTT in individuals whose subsequent pregnancies ended in success and failure were 88.2%+/-23.4% and 99.3%+/-26.4%, respectively. The difference was statistically significant. Respective values were 106.8%+/-22.8% and 106.3%+/-21.4% for PT and 245+/-61.1 mg/dL and 259.1+/-57 mg/dL for fibrinogen. These findings were not significantly different. CONCLUSION(S): A shortened aPTT before conception is associated with further miscarriages in patients with a history of recurrent spontaneous abortions who have no antiphospholipid antibodies.

Abortion, Habitual↗
PubMed1998

Recurrent abortion and moderate or strong antiphospholipid antibody production.

OBJECTIVE: To investigate the treatment outcome for women suffering recurrent miscarriages associated with strong or moderate antiphospholipid antibody (aPL) production. METHODS: Sixty-seven pregnancies in 61 women demonstrating at least one kind of aPL with a history of recurrent miscarriages were treated with: (1) aspirin (ASA) alone; (2) prednisolone (PSL) and ASA; and (3) PSL, ASA, heparin and/or immunoglobulin (IgG). For comparison purposes the aPL-positive patients were divided into two groups, strongly and moderately-positive. IgG and IgM antibodies against PE and five negatively-charged phospholipids were measured by ELISA between 1987 and 1993. Beta2-glycoprotein I (beta2GPI) dependent anticardiolipin antibodies were measured by ELISA since 1993. Lupus anticoagulant was measured by a diluted aPTT method since 1993. RESULTS: Out of a total of 16 (50%) patients strongly-positive for aPL and 47 out of 51 (92.2%) moderately-positive demonstrated a successful outcome. The live birth rate moderate group was significantly higher than in the strongly-positive cases (P < 0.0005). In the cases exhibiting moderate aPL production, 28 out of 30 (93.3%) receiving PSL and ASA and 14 out of 15 (93.3%) treated with ASA alone successfully gave birth. None of the 14 given ASA alone suffered preterm delivery or IUGR. In contrast 12 (36.4%) and 6 (18.2%) of the 33 patients treated with the PSL combination therapy suffered from preterm delivery and IUGR, respectively. CONCLUSIONS: The live birth rate in patients strongly positive for aPL is lower than that in patients with moderate aPL production even if treatment is performed during pregnancy. However, ASA is useful to treat cases with moderate aPL so that distinction of the two groups is warranted.

Abortion, Habitual↗
PubMed1998

Reversal of severe hypertrophic cardiomyopathy and excellent neuropsychologic outcome in very-long-chain acyl-coenzyme A dehydrogenase deficiency.

Very-long-chain acyl-coenzyme A dehydrogenase (VLCAD) deficiency is a disorder of fatty acid beta oxidation that reportedly has high rates of morbidity and mortality. We describe the outcome of a 5-year-old girl with VLCAD deficiency who was first seen at 5 months of age with severe hypertrophic cardiomyopathy, hepatomegaly, encephalopathy, and hypotonia. Biochemical studies indicated VLCAD deficiency caused by a stable yet inactive enzyme. Molecular genetic analysis of her VLCAD gene revealed a T1372C (F458L) missense mutation and a 1668 ACAG 1669 splice site mutation. After initial treatment with intravenous glucose and carnitine, the patient has thrived on a low-fat diet supplemented with medium-chain triglyceride oil and carnitine and avoidance of fasting. Her ventricular hypertrophy resolved significantly over 1 year, and cognitively, she is in the superior range for age. Clinical recognition of VLCAD deficiency is important because it is one of the few directly treatable causes of cardiomyopathy in children.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed1998

Quality evaluation of radiographic contrast media in large-volume prefilled syringes and vials.

RATIONALE AND OBJECTIVES: The authors compared the particle contaminations of radiographic contrast media packaged in large-volume prefilled syringes and vials. MATERIALS AND METHODS: Particle counting was performed for four contrast media packaged in large-volume prefilled syringes (iohexol, ioversol, ioversol for angiography, and ioxaglate) and three contrast media packaged in vials (iohexol, ioversol, and ioxaglate). X-ray emission spectrometry was performed to characterize the individual particles. The amount of silicone oil in the syringe was quantified with infrared spectrophotometry. RESULTS: The particle contamination in syringes containing ioversol was higher than that in syringes containing iohexol or ioxaglate. Particle contamination in the vials was relatively low, except with ioxaglate. X-ray emission spectrometry of the components of the syringe and vial showed that the source of particles was internal material released from the rubber stopper or inner surface. CONCLUSION: The particle counts for contrast media packaged in syringes and vials varied considerably among the different contrast media and were related to the amount of silicone oil on the inner surface and rubber piston of the syringe.

Contrast Media↗
PubMed1998

Amino acid and nucleotide sequences of human peroxisomal enoyl-CoA hydratase: 3-hydroxyacyl-CoA dehydrogenase cDNA.

Deficiency of enoyl-CoA hydratase: 3-hydroxyacyl-CoA dehydrogenase (peroxisomal bifunctional enzyme), one of the enzymes of the peroxisomal beta-oxidation system, leads to clinical manifestations resembling Zellweger syndrome with hypotonia, psychomotor delay, hepatomegaly, typical facial appearance and accumulation of very long-chain fatty acids. The nucleotide sequence of the human peroxisomal enoyl-CoA hydratase: 3-hydroxyacyl-CoA dehydrogenase cDNA has been reported by Hoefler and colleagues; however, we have found some amino acid differences from our originally isolated cDNA. Contrary to the findings described in a previous paper, we report here the cDNA sequence of human peroxisomal enoyl-CoA hydratase: 3-hydroxyacyl-CoA dehydrogenase in which there are 9 authenticated amino acid alterations.

3-Hydroxyacyl CoA Dehydrogenases↗