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Biomedical subjects

A Muraoka

Publications and source records attributed to A Muraoka.

At least 19 recordsLinked to original sources
PubMed2001

Endovascular stent grafting for the treatment of blunt thoracic aortic injury.

OBJECTIVE: Recent advances of endovascular stent-grafting (ESG) provide a new therapeutic option with minimum surgical damage for blunt aortic injury (BAI) during its acute phase. To clarify the effectiveness of ESG for BAI, a prospective clinical study at a university hospital was conducted. METHODS: All patients with blunt thoracic injury underwent thoracic contrast-enhanced computed tomographic (CT) scan. Six patients age 48.8 +/- 19.8 years, with Injury Severity Scores of 35.8 +/- 8.1, and with BAI were treated according to our protocol. The stent-graft covered by woven Dacron was placed at the injury site. Endoleakage was then checked by aortography and CT scan was again performed once a day on days 7 through 14. RESULTS: All patients had injury of the aortic isthmus. ESG placement was performed within 8 hours after injury except in one (48 hours). The operating time was 159.5 +/- 21.1 minutes and bleeding volume was 105 +/- 26.6 mL. No endoleakage was found. Repeat CT scan revealed disappearance of hematoma. All patients except one had an event-free clinical course. One patient died because of rupture of the ascending aorta on day 6; however, autopsy revealed evidence of the healing process at the injury site sealed by ESG. CONCLUSION: An ESG is a valid therapeutic option with minimal surgical invasion for patients with acute-phase aortic injury.

Adult↗
PubMed2001

Nitric oxide donating compounds inhibit HCl-induced gastric mucosal lesions mainly via prostaglandin.

Prostaglandin (PG) and nitric oxide (NO) have been known to inhibit the lesion formation induced by necrotic agents. However, no clear correlation between PG and NO has been shown in the gastroprotective action against necrotic agent-induced gastric mucosal lesions in rats. Thus, the present study was performed to clarify this correlation. Gastric mucosal lesions were induced by the oral administration of 0.6 M HCl in rats. 16,16-Dimethyl PGE2 (0.3-3 microg/kg, p.o.; dim-PGE2), sodium nitrite (0.3 and 1 mg/kg, s.c.) and sodium nitroprusside (30 and 100 microg/kg, i.v.; SNP) dose-dependently inhibited the lesion formation. Orally administered sodium nitrite or SNP (3 mg/kg) also significantly inhibited the lesion formation. The gastroprotective action by dim-PGE2 was not affected by the pre-treatment with N(G)-nitro-L-arginine methylester (10 mg/kg, i.v.). The gastroprotective effect by sodium nitrite or SNP was markedly attenuated by the pre-treatment with indomethacin (10 mg/kg, s.c.). These findings suggest that NO donating compounds inhibit the HCl-induced mucosal lesions mainly through prostaglandin, but dim-PGE2 directly inhibits the lesions without involvement of NO in rats.

16,16-Dimethylprostaglandin E2↗
PubMed2000

Involvement of nitric oxide from nerves on diarrhea induced by castor oil in rats.

Nitric oxide (NO) is involved in the mechanism of castor oil-induced diarrhea. This study was performed to elucidate the source of NO. Diarrhea was induced by oral administration of castor oil in rats. Diarrhea was significantly inhibited by the pre-treatment with a relatively selective nerve NO synthase inhibitor, 7-nitroindazole. This effect was attenuated by the treatment with L-arginine. Capsaicin-sensitive afferent nerve degeneration did not affect the diarrhea. N(G)-Nitro-L-arginine methylester significantly inhibited diarrhea even in capsaicin-pretreated rats. These data suggest, at least in part, the involvement of NO from nerves on the diarrhea induced by castor oil in rats.

Animals↗
PubMed1998

Type IIa early gastric cancer with proliferation of xanthoma cells.

We report a type IIa early gastric cancer associated with xanthoma cell proliferation in a 61-year-old man. The patient was admitted to our hospital because of a gastric polyp detected at a medical checkup. An irregular protruding lesion with xanthoma cell proliferation was detected endoscopically. Histological examination showed a well differentiated tubular adenocarcinoma in the mucosa associated with xanthoma cell proliferation. The distribution of the xanthoma cells in the stroma corresponded closely with that of the cancer cells. Neither atypism nor mitotic figures were recognized in the xanthoma cells. In an immunohistochemical study, almost all the xanthoma cells were stained positive for alpha 1-antitrypsin, while relatively few exhibited positive S-100 protein staining. Specific monocyte chemotactic and activating factor immunoreactivity was present only in the xanthoma cells, and not in the cancer cells. On the basis of these findings, it was speculated that the gastric cancer cells may have caused the xanthoma cell proliferation via an autocrine mechanism i.e., by a chemical mediator acting in a paracrine or juxtacrine manner.

Adenocarcinoma↗
PubMed1998

Partial adenine phosphoribosyltransferase deficiency detected by ureterolithiasis.

A 30-year-old woman was admitted to our hospital because of recurrent ureterolithiasis. She was suspected of having adenine phosphoribosyltransferase (APRT) deficiency based on the presence of 2,8-dihydroxyadenine (DHA) crystals in her urinary sediment, infrared spectrophotometric analysis of the excreted stone, and then the definitive diagnosis by gene analysis. A pedigree study indicated only a slight possibility of this disease in the family. From these results, we consider that urinary sediment and stone analysis should be used for screening while gene analysis should be employed for definitive diagnosis of APRT deficiency, so that the complications of this condition can be prevented.

Adenine↗
PubMed1997

Cloning and chromosomal localization of a gene (GPR18) encoding a novel seven transmembrane receptor highly expressed in spleen and testis.

Using the techniques of relaxed stringency polymerase chain reaction and genomic library screening, we have isolated homologous canine and human genes that encode a novel putative seven transmembrane G-protein-linked receptor. The gene encodes an open reading frame (ORF) of 993 bp. The sequences of the canine and human ORFs are highly conserved, sharing 89% nucleotide identity and 92% amino acid similarity between the two species. Northern blot analysis demonstrates that mRNA transcripts of the gene are abundantly expressed in testis and spleen with a lesser degree of expression observed in several other tissues associated with endocrine and immunologic/hematologic function. The gene, designated GPR18, was localized to human chromosome 13q32 using fluorescence in situ hybridization.

Amino Acid Sequence↗
PubMed1997

[Involvement of nitric oxide, which was synthesized by constitutive nitric oxide synthase, and prostaglandin on diarrhea induced by castor oil in rats].

To clarify the mechanism of castor oil-induced diarrhea, this study was performed by using rats in relation to nitric oxide (NO) and prostaglandin (PG). Castor oil induced diarrhea in all rats within 3 hr in the control group. The pretreatment of NG-nitro-L-arginine methyl ester prevented the diarrhea, and this effect was attenuated by the combined treatment of L-arginine. Amino-guanidine inhibiting inducible NO synthase had no effect on the diarrhea, but dexamethasone, an inhibitor of both inducible NO synthase and phospholipase A2 that synthesizes PGs, significantly prevented it. Indomethacin, an inhibitor of cyclooxygenase that synthesizes PGs, also significantly prevented diarrhea. Therefore, the mechanism of the preventive effect by dexamethazone on diarrhea was suggested to be the inhibition of PGs generation. From the above results, it became clear that PG and NO, especially that synthesized by constitutive NO synthase, are involved in the mechanism of diarrhea induction by castor oil in rats.

Animals↗
PubMed1996

Acute gastric anisakiasis: 28 cases during the last 10 years.

Anisakiasis is a disease which occurs following eating raw fish infected with anisakis larvae. Many cases have been reported from Japan and from other countries with increasing opportunities of eating raw fish such as "sushi" and "sashimi." We have reviewed 28 patients with acute gastric anisakiasis during the last 10 years from November 1984 to October 1994. This disease has rarely been detected in persons over 60 years of age and in patients with gastric surgery. Therefore it is postulated that gastric acid secretion influences the activities of anisakis larvae. An alkaline gastric pH could interfere with the toxicity of anisakis larvae.

Adult↗
PubMed1996

Canine H(+)-K(+)-ATPase alpha-subunit gene promoter: studies with canine parietal cells in primary culture.

H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase) is the principal enzyme responsible for the process of gastric acid secretion. This enzyme is expressed in a cell-type-specific manner in gastric parietal cells. To explore the mechanisms regulating its expression, we transfected differentiated canine parietal cells in primary culture with H(+)-K(+)-ATPase-luciferase reporter genes and assessed transcriptional activities. Deletional analysis of the 5'-flanking region of this gene demonstrated a remarkable increment in transcriptional activity associated with a segment between bases -54 to -45 (5' GCTCCGCCTC 3') relative to the transcriptional initiation site. Gel shift assays with competition and supershift analysis demonstrated that this segment is specifically bound by the transcription factor Sp1. A point mutation, eliminating Sp1 binding, diminished basal transcriptional activity by 80%, indicating that this Sp1 binding site is important for constitutive transcriptional activity. Although these studies indicate that Sp1 is required to maintain a high concentration of the H(+)-K(+)-ATPase gene in the parietal cell, its cell-type-specific expression must rely on other elements because Sp1 is a ubiquitously expressed transcription factor.

Animals↗
PubMed1996

[Emergency coronary artery bypass grafting (CABG) in a case of coronary occlusion secondary to long segmental dissection of left anterior descending artery after percutaneous transluminal coronary angioplasty (PTCA)].

A 60-year-old man with unstable angina underwent PTCA at left anterior descending artery (LAD) #6, which had stenosis of 90%. Subsequently, a long segmental dissection formed from #6 to #7 and the patients was scheduled for CABG. On the day before the expected date of CABG, he had an angina attack and a 12 lead electrocardiogram (ECG) showed ST segment and T wave elevation in V1-3. Coronary angiograms revealed 99% stenosis in LAD #6 and immediately rePTCA was performed at the site. RePTCA improved the stenosis to 50%, but ECG showed an inverted T wave in V3,4 and emergency CABG was performed, with the saphenous vein at LAD #8 and high lateral artery. Some authors have stated that CABG is not useful for long segmental coronary dissection, but we conclude that CABG should be definitely considered in such a case, because this procedure resolves pressure gradients at before-and-after entry and the bypass grafts will be never occluded whenever anastomosis (intima-adventitia-graft) is performed.

Angioplasty, Balloon, Coronary↗
PubMed1995

Analysis of the structural features of the C-terminus of GLUT1 that are required for transport catalytic activity.

C-terminally truncated and mutated forms of GLUT1 have been constructed to determine the minimum structure at the C-terminus required for glucose transport activity and ligand binding at the outer and inner binding sites. Four truncated mutants have been constructed (CTD24 to CTD27) in which 24 to 27 amino acids are deleted. In addition, point substitutions of R468-->L, F467-->L and G466-->E have been produced. Chinese hamster ovary clones which were transfected with these mutant GLUT1s were shown, by Western blotting and cell-surface carbohydrate labelling, to have expression levels which were comparable with the wild-type clone. Wild-type levels of 2-deoxy-D-glucose transport activity were retained only in the clone transfected with the construct in which 24 amino acids were deleted (CTD24). The CTD25, CTD26 and CTD27 clones showed markedly reduced transport activity. From a kinetic comparison of the CTD24 and CTD26 clones it was found that the reduced transport was mainly associated with a reduced Vmax. value for 2-deoxy-D-glucose uptake but with a slight lowering of the Km. These data establish that the 24 amino acids at the C-terminus of GLUT1 are not required for the transport catalysis. However, the point mutations of F467L and G466E (26 and 27 residues from the C-terminus) did not significantly perturb the kinetics of 2-deoxy-D-glucose transport. The substitution of R468L produced a slight, but significant, lowering of the Km. The ability of the truncated GLUt1s to bind the exofacial ligand, 2-N-4-(1-zai-2,2,2-trifluoroethyl)benzoyl-1,3-bis-(D-mannos- 4-yl-oxy) -2-propylamine (ATB-BMPA), and the endofacial ligand, cytochalasin B, were assessed by photolabelling procedures. The ability to bind ATB-BMPA was retained only in the CTD24 truncated mutant and was reduced to levels comparable with those of the non-transfected clone in the other mutant clones. Cytochalasin B labelling was unimpaired in all four mutated GLUT1s. These data establish that a minimum structure at the C-terminus of GLUT1, which is required for the conformational change to expose the exofacial site, includes amino acids at positions Phe-467 and Arg-468; however, these amino acids are not individually essential.

Affinity Labels↗
PubMed1995

Epidermal growth factor induces H+,K+-ATPase alpha-subunit gene expression through an element homologous to the 3' half-site of the c-fos serum response element.

Epidermal growth factor (EGF) acutely inhibits acid secretion; however, prolonged administration of EGF has been reported to increase acid production. We undertook these studies to examine whether the physiological effects of EGF on acid secretion are mediated by regulation of gastric H+,K+-ATPase, the principle enzyme responsible for acid secretion. EGF in concentrations equivalent to those in plasma increased H+,K(+)-ATPase alpha-subunit mRNA levels. Using H+,K(+)-ATPase-luciferase constructs transfected into primary cultured parietal cells, a significant step up in EGF inducibility was observed between bases -162 and -156 (5'-GACATGG-3') relative to the cap site. This EGF response element (ERE) conferred EGF inducibility when linked to homologous and heterologous promoters. The ERE is homologous to the 3' half-site of the c-fos serum response element to which rNFIL-6, rE12, and SRE-ZBP bind. Electrophoretic mobility shift assays using an ERE probe and parietal cell nuclear extracts revealed a specific DNA-protein complex, the formation of which was changed by neither E12 and NFIL-6 consensus oligonucleotides nor antibodies for NFIL-6, SRE-ZBP, and E12. Our studies indicate that EGF induces gastric H+,K(+)-ATPase alpha-subunit gene expression via an interaction between a specific ERE and a novel transcriptional factor and that this may be a physiologic mechanism by which EGF regulates acid secretion.

Aminopyrine↗
PubMed1995

Glycine-extended progastrin processing intermediates induce H+,K(+)-ATPase alpha-subunit gene expression through a novel receptor.

Biologically active amidated gastrin is synthesized by carboxyl-terminal alpha-amidation of a glycine-extended progastrin post-translational processing intermediate (G-Gly). Although plasma levels of G-Gly are equivalent to those of gastrin, G-Gly has essentially no acute effect on gastric acid secretion. However, we have observed that inhibition of gastrin amidation leads to increased plasma concentrations of G-Gly and enhanced gastric acid secretion. We hypothesized, therefore, that G-Gly might have a chronic effect to increase H+,K(+)-ATPase expression in gastric parietal cells. In the present studies, we observed that a 2-day preincubation with G-Gly significantly enhanced histamine-stimulated [14C]aminopyrine uptake by isolated canine gastric parietal cells but acutely administered G-Gly had no effect. On Northern blot analysis, both G-Gly and gastrin dose-dependently increased H+,K(+)-ATPase alpha-subunit gene expression with maximal induction (225 +/- 35 and 170 +/- 29% of basal, mean +/- S.E.) achieved at concentrations of 10(-9) M G-Gly and 10(-8) M gastrin, respectively. Using an H+,K(+)-ATPase alpha-subunit gene-luciferase chimeric reporter construct transfected into primary cultured parietal cells, we observed that both G-Gly and gastrin increased luciferase activity in a manner similar to that obtained by Northern blot analysis. L365,260, a specific gastrin/CCKB receptor antagonist, completely reversed the stimulation of luciferase activity induced by gastrin but had no effect on G-Gly-stimulated activity. Gastrin increased [Ca2+]i, although G-Gly did not, however, genistein (a tyrosine kinase inhibitor) significantly reduced induction of luciferase activity by both G-Gly and gastrin. Specific binding of 125I-Leu15-G2-17-Gly to gastric parietal cells was dose-dependently displaced by G2-17-Gly but not by gastrin nor L365,260. Gastrin peptides truncated at the carboxyl- (G1-13) and amino terminus (G5-17-Gly) both induced H+,K(+)-ATPase alpha-subunit gene expression and inhibited 125I-Leu15-G2-17-Gly binding, but were less potent than G2-17-Gly. These data indicate that G-Gly may have a functional role in potentiating gastric acid secretagogue action via enhanced expression of the gene responsible for H+ generation through action at a novel receptor that can be distinguished from the gastrin/CCKB receptor. Thus, both the substrate and product of the terminal progastrin processing reaction appear to have complementary functions in regulation of gastric acid secretion.

Aminopyrine↗
PubMed1995

delta-Aminolevulinic acid dehydratase deficiency porphyria (ADP) with syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in a 69-year-old woman.

delta-Aminolevulinic acid dehydratase deficiency porphyria (ALAD porphyria, ADP) with syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in a 69-year-old woman is reported. The patient was admitted to our hospital complaining of slight cough with low-grade fever, and treated with piperacillin sodium, resulting in complete resolution of the symptoms, following a diagnosis of bronchopneumonia. Thereafter, however, she began to complain of vomiting, abdominal pain, facial numbness and paresis of the extremities with gait disturbance, and became comatose with hyponatremia (serum Na concentration 119 mEq/L) in a few days. Laboratory tests revealed an antidiuretic hormone (ADH) level of 13.5 pg/mL, plasma osmolality 218 mOsm/KgH2O, urinary osmolality 429 mOsm/KgH20, urinary Na concentration > 20 mEq/L, and no abnormalities of thyroid, adrenal or renal function. Neither edema nor dehydration was evident. These data indicated the presence of SIADH. No abnormalities suggestive of malignant or infectious diseases such as lung cancer, pneumonia and Guillain-Barré syndrome were evident from laboratory and roentgenographic findings. As the cause of SIADH, therefore, porphyria was suspected. Metabolites and activities of enzymes in the heme biosynthetic pathway were examined, and very low activity of delta-aminolevulinic acid dehydratase (ALA-D) (0.14 mumol PBG/mL RBC/h) was found. The patient was neither an alcoholic nor a heavy smoker, and she had no past history of heavy metal intoxication, photosensitivity or tyrosinemia. On the basis of these data and clinical features, she was diagnosed as having ADP. We consider this to be the first case of ADP reported in Japan.

Abdominal Pain↗
PubMed1994

Substitution of tyrosine 293 of GLUT1 locks the transporter into an outward facing conformation.

Tyrosines 292 and 293 in the mammalian glucose transporter GLUT1 have been substituted by either isoleucine or phenylalanine. Chinese hamster ovary clones that were transfected with Tyr-292-->Ile, Tyr-292-->Phe, Tyr-293-->Ile, and Tyr-293-->Phe constructs of GLUT1 were shown, by Western blotting and cell surface carbohydrate labeling, to have expression levels that were comparable with the wild type. The Vmax for 2-deoxy-D-glucose transport was markedly reduced only as a result of the Tyr-293-->Ile mutation. The ability of the Tyr-293-->Ile mutated GLUT1 to bind the exofacial ligand 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis-(D-mannos- 4-yloxy)-2- propylamine (ATB-BMPA) and the endofacial ligand cytochalasin B were assessed by photolabeling procedures. The ability to bind the bis-mannose compound was unimpaired, whereas the ability to bind cytochalasin B was totally abolished, and the level of labeling was lower than in the nontransfected clone. Affinities of the wild-type and Tyr-293-->Ile GLUT1 for D-glucose, the exofacial ligands (ATB-BMPA and 4,6-O-ethylidene-D-glucose), and the endofacial ligand (cytochalasin B) were assessed by the ability of these agents to displace the radioactive ATB-BMPA photolabel. These data indicated that the Tyr-293-->Ile substitution produced no change in the affinity for D-glucose, a relatively small enhancement in the affinity for exofacial ligands, but a large approximately 300-fold reduction in affinity for cytochalasin B, suggesting that the mutated GLUT1 is locked in an outward facing conformation. The observation that the Tyr-293-->Ile mutant transporter can bind nontransported C4 and C6 substituted hexose analogues but cannot catalyze transport is interpreted as indicating that Tyr-293 is involved in closing the exofacial site around C4 and C6 of D-glucose in the transport catalysis process.

Affinity Labels↗
PubMed1994

Substitution at Pro385 of GLUT1 perturbs the glucose transport function by reducing conformational flexibility.

The mammalian glucose transporter, GLUT1, is capable of alternating between two conformations which expose either an outward- or inward-facing ligand binding site. The possibility that these conformational changes are related to the presence of prolines and glycines in transmembrane region 10 was investigated by site-directed mutagenesis. Chinese hamster ovary clones which were transfected with Pro385-->Ile and Pro385-->glycine mutations of GLUT1 were shown, by Western blotting and cell surface carbohydrate labelling, to have expression levels which were comparable with the wild type. The transport activity was markedly reduced as a result of the Pro385-->isoleucine but not in the Pro385-->glycine mutation. The loss of transport activity in the Pro385-->isoleucine clone was associated with loss of labeling by the exofacial photoaffinity ligand, 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis(D-mannos-4 -yloxy)-2- propylamine (ATB-BMPA), but there was no loss in labeling by the inside site-directed ligand cytochalasin B. These results suggest that the transporter cannot adopt the outward-directed conformation in the Pro385-->isoleucine clone. By contrast, the glycine substitution for proline at this position resulted in a retention of the ligand binding properties at both inside and outside sites. We suggest a putative mode of operation of the transporter which involves conformational flexibility about the prolines in transmembrane segment 10 such that helices 11 and 12 can alternately either pack against the outside (ATB-BMPA binding) site in helices 7, 8, and 9 or against the inner (cytochalasin B binding) site at the base of transmembrane segment 10.

Amino Acid Sequence↗
PubMed1992

Site-directed mutagenesis of GLUT1 in helix 7 residue 282 results in perturbation of exofacial ligand binding.

The structure-function relationship of the HepG2/erythrocyte-type glucose transporter (GLUT1) has been studied by in vitro site-directed mutagenesis. Chinese hamster ovary clones in which glucose transporters were transfected were shown by Western blotting with a GLUT1 anti-COOH-terminal peptide antibody to have expression levels of Gln282----Leu, Asn288----Ile, and Asn317----Ile mutations that were comparable with the wild type. All three mutant GLUT1 clones had high 2-deoxy-D-glucose transport activity compared with a nontransfected clone, suggesting that these residues are not absolutely required for the transport function. We have examined the possibility that the inner and outer portions of the transport pathway are structurally separate by measuring the interaction of the mutant transporters with the inside site-specific ligand cytochalasin B and the outside site-specific ligand 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis(D-mannos-4 -yloxy)-2- propylamine (ATB-BMPA). All three mutant GLUT1 clones showed high levels of cytochalasin B labeling, and the N288I and N317I mutants showed high levels of ATB-BMPA labeling. In contrast to the transport and cytochalasin B labeling results, the transmembrane helix 7 Gln282----Leu mutant was labeled by ATB-BMPA to a level that was only 5% of the level observed in the wild type. We have confirmed that this mutant was defective in the outer site by comparing the inhibition of wild-type and mutant 2-deoxy-D-glucose transport by the outside site-specific ligand 4,6-O-ethylidene-D-glucose. 4,6-O-Ethylidene-D-glucose inhibited wild-type transport with a Ki of approximately 12 mM, but this was increased to greater than 120 mM in the Gln282----Leu mutant. Thus, of the 3 residues mutated in this study, only glutamine 282 substitution causes a major perturbation in function, and this is a specific and striking reduction in the affinity for the outside site-specific ligands ATB-BMPA and 4,6-O-ethylidene-D-glucose.

Amino Acid Sequence↗