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Biomedical subjects

T Ohta

Publications and source records attributed to T Ohta.

At least 937 records · Page 52Linked to original sources
PubMed1992

[Extensive radical surgery for carcinomas of the head of the pancreas].

Since 1973, we have applied extensive radical surgery for the head of the pancreas in order to improve not only the resection rate but also the surgical therapeutic results. The main points of our surgical procedure are as follows: (1) complete resection of surrounding connective tissues in retroperitoneum including extrapancreatic neural plexus. (2) extensive lymph node dissection, and (3) combined resection of the portal vein. As a result, our 3-year survival rate has increased to 31.4% and the 5-year survival rate to 27.9% in patients who underwent the macroscopically complete resection. These surgical therapeutic results are not satisfactory, but we have had 10 patients who survived more than 3 years. It is also true, however, that this procedure is extremely invasive and requires careful, long-term nutritional management after surgery. Therefore, the cooperation of not only the patients themselves but also their families is indispensable for the success of the treatment.

Humans↗
PubMed1992

[Effect of daily energy intake and amount of walking on body weight reduction and its maintenance].

The relationship of daily energy intake and the amount of walking performed, based on pedometer readings, for effective body weight reduction were studied based on results of a weight reduction program at the Aichi Prefectural Center of Health Care from 1983 to 1990. In addition, a follow-up study based on a mailed questionnaire was performed, to further determine the relationship to maintenance of body weight reduction of energy intake and amount of walking after the conclusion of program. The subjects were two-hundred and forty middle-aged obese women who were placed on a 5-month weight reduction program consisting of diet (1500 kcal/day) and exercise (10000 walk steps/day). At the end of the program, the mean energy intake and the mean number of steps per day had reached target levels and the mean body weight reduction was 4.2 kg. The relationship of energy intake, and the number of steps walked at the end of program to the amount of reduction in body weight during the program was analyzed by multiple regression analysis, and the amount of walking expressed in the number of steps necessary for weight reduction were calculated for various energy intakes. A follow-up study was performed in 1988, with sixty-six women responding to the mailed questionnaire. Since the end of the program, body weight increase of 1.1 kg occurred, but body weight was still lower than initially. Although mean energy intake increased after the program, a level about 200 kcal less than at the beginning of the program was being maintained, so the effect of diet recommendation in the program appeared to be retained.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Bilateral distal anterior cerebral artery aneurysms associated with polycystic kidney and liver disease; a case report].

A patient who had bilateral distal anterior cerebral artery aneurysms and a right middle cerebral artery aneurysm in association with polycystic kidney and liver disease is reported. A 57-year-old woman was referred to our center with headache and disturbance of consciousness. On admission, her level of consciousness as evaluated by the Japan Coma Scale was 10. CT revealed subarachnoid hemorrhage, especially in the interhemispheric fissures. Right carotid angiography demonstrated bilateral distal anterior cerebral artery aneurysms and a right middle cerebral artery aneurysm. All three aneurysms were clipped in a one-stage procedure. The patient was discharged without any neurological deficits two weeks after the operation. Bilateral distal anterior cerebral artery aneurysms are extremely rare. This is the first report of such aneurysms and a right middle cerebral artery aneurysm in association with polycystic kidney and liver disease. The etiology of these aneurysms is discussed.

Cerebral Angiography↗
PubMed1992

[A case of enchondroma protuberance with destroying the rib bone].

A 42-year-old female was referred to our hospital because of a tumor shadow in the right lung fields. Tomography revealed a tumor which had destroyed the right 4th rib. Under the diagnosis of malignant tumor, she was treated by radical en bloc excision. The pathological diagnosis was enchondroma.

Adult↗
PubMed1992

The "duct-ectatic" variant of mucinous cystic neoplasm of the pancreas: clinical and radiologic studies of seven cases.

Seven cases of the "duct-ectatic" variant of mucinous cystic neoplasm of the pancreas are presented. This new entity, the duct-ectatic variant of mucinous cystic neoplasm of the pancreas, probably masquerades as pancreatic pseudocyst clinically and radiologically. However, it has the characteristic pathologic findings of the classic "megacystic" type of mucinous cystic neoplasm. If there are cysts visualized on pancreaticogram which are in a diffusely duct-ectatic configuration and are in communication with the main pancreatic duct, the duct-ectatic variant of mucinous cystic neoplasm should be strongly suspected rather than the pancreatic pseudocyst.

Adult↗
PubMed1992

[Carotid stenosis complicated by coronary disease; a case report].

A 66-year-old-man with carotid stenosis complicated by coronary disease is reported. He suffered from mild motor weakness on the right side and speech disturbance. Radiological examination revealed 90% stenosis at the cervical portion of the left internal carotid artery, and two-vessel coronary disease. In order to prevent intraoperative cardiac stroke, initial percutaneous coronary angioplasty (PTCA), was performed and the subsequent carotid endarterectomy (CEA) was performed successfully. Preoperative symptoms gradually improved and he was discharged as ambulatory. Because atherosclerosis is always systemic, patients with carotid artery disease should be examined for coronary disease. We recommend greater use of coronary angiography and, when a lesion is found, the use of PTCA, which is a safer method in terms of preventing intraoperative cardiac stroke of CEA than any other method.

Aged↗
PubMed1992

[Pneumonectomy in a case of chronic hemodialysis].

A 60-year-old male was referred to our hospital due to a well-delineated tumor (4 x 4 x 3 cm) in the left hilar region demonstrated by chest X-ray examination. Bronchofiberscopic biopsy showed evidence of well moderately differentiated epidermoid carcinoma. Since the tumor infiltrated to a part of the pericardium, left pneumonectomy and partial resection of pericardium were performed. The disease was p-T2, N1, M0, and state II. Anemia was corrected with Erythropoietin, and hemodialysis was performed for 3 consecutive days before operation. Hemodialysis 3 times per week was initiated from 2 days after operation. Hyperkalemia was successfully treated by GI therapy (continuous intravenous infusion of glucose+insulin). His postoperative course was good without bleeding and infection. He was discharged 37 days after operation and has been observed on an outpatient basis. With an increased and aging patients on chronic hemodialysis, the operations for various malignant tumors have been increasing. However, there are few reports on operation for lung cancer and no report on pneumonectomy in such patients in Japan. We performed pneumonectomy for lung cancer detected in a patient on chronic hemodialysis for 4 years and obtained good results.

Carcinoma, Squamous Cell↗
PubMed1991

Mucosal dysplasia of the liver and the intraductal variant of peripheral cholangiocarcinoma in hepatolithiasis.

Four cases are reported of the intraductal variant of peripheral cholangiocarcinoma among surgical specimens from 32 cases of hepatolithiasis. The cancers arose from the periphery of the stone-containing bile duct and spread chiefly along the luminal surface. Microscopically, these tumors showed papillary proliferation and therefore were diagnosed as the intraductal spreading type of peripheral cholangiocarcinoma. Mucosal dysplasia also was noticed in the vicinity of the tumors. In six other cases, mucosal dysplasia was observed in the periphery of the stone. Immunohistochemically, anti-CA 19-9 staining was observed diffusely in the cytoplasm of dysplastic lesions and carcinomas. Anti-carcinoembryonic antigen staining was restricted to the luminal surface and/or the supranuclear region of the cytoplasm in carcinomas. It was not identified in dysplastic cells. These results suggest that the mucosal dysplasia occasionally observed near stones is a precursor of the intraductal spreading type of peripheral cholangiocarcinoma in the presence of hepatolithiasis. The authors hypothesize that the lining epithelium of the large bile duct, when persistently exposed to biochemically altered bile, may undergo a carcinomatous transformation through a stage of mucosal dysplasia.

Adenoma, Bile Duct↗
PubMed1991

Identification of a unique specificity determinant of the colicin E3 immunity protein.

Plasmid immunity to a nuclease-type colicin is defined by the specific binding of an immunity (or inhibitor) protein, Imm, to the C-terminal nuclease domain, T2A, of the colicin molecule. Whereas most regions of colicin operons exhibit extensive sequence identity, the small plasmid region encoding T2A and Imm is exceptionally varied. Since immunity is essential for the survival of the potentially lethal colicin plasmid (Col), we inferred that T2A and Imm must have co-evolved, retaining their mutual binding specificities. To evaluate this co-evolution model for the col and imm genes of ColE3 and ColE6, we attempted to obtain a stabilized clone from a plasmid which had been destabilized with a non-cognate immunity gene. A hybrid Col, in which the immE3 gene of the ColE3 was replaced with immE6 from ColE6, was lethal to the host cells upon SOS induction. From among this suicidal cell population, we isolated a stabilized, i.e., evolved, clone which produced colicin E3 (E3) stably and exhibited immunity to E3. This change arose from only a single mutation in ImmE6, from Trp48 to Cys, the same residue as in the ImmE3 sequence. In addition, we constructed a series of chimeric genes through homologous recombination between immE3 and immE6. Characterization of these chimeric immunity genes confirmed the above finding that colicins E3 and E6 are mostly distinguished by only Cys48 of the ImmE3 protein.

Amino Acid Sequence↗
PubMed1991

Stimulation of the Na+/K+ pump by external [K+] is regulated by voltage-dependent gating.

Wild-type and mutants with alpha-subunits truncated at the N terminus of Na+/K+ pumps of Torpedo electroplax were expressed in Xenopus oocytes by injection of cRNAs encoding for one of the alpha-subunits and for the beta-subunit. Currents generated by the pump were investigated under voltage clamp in Na(+)-free solution, a condition where stimulation by external [K+] is the only voltage-dependent and rate-determining step in the pump cycle (Rakowski, R. F., Vasilets, L. A., LaTona, J., and Schwarz, W. (1991) J. Membr. Biol. 121, 177-187). Voltage dependence of the apparent Km value for pump stimulation and of maximum transport activity was investigated. Truncation of the intracellular N-terminal end of the alpha-subunit at the trypsin-accessible site (alpha delta K37, leaving Lys37) leads to nearly complete inhibition of pump current at physiological potentials, whereas ouabain binding capacity is retained indicating an essential involvement of the N-terminal end in the process of ion translocation. Truncation at the N-terminal end leaving Lys28 (alpha delta K28) or Thr29 (alpha delta T29) leads to removal of 6 or 7 lysine residues, respectively, and has no effect on maximum transport activity. On the other hand, the mutated pumps with alpha delta K28 or alpha delta T29 exhibit more pronounced voltage dependences for stimulation of pump current by external [K+] compared with the wild-type Torpedo pump. In particular, a pronounced increase in voltage dependence of the apparent affinity of pump stimulation is obtained by the removal of the Lys28. The results support the view that the lysine-rich region in the N-terminal end affects the cation binding to the pump molecule and that Lys28 is important.

Animals↗
PubMed1991

Gene structure of heat shock proteins 61KDa and 12KDa (thermophilic chaperonins) of thermophilic bacterium PS3.

Heat shock proteins 60 (hsp60) and 10 (hsp10) are essential for the formation and restoration of many supramolecular structures. For reconstitution of these structures, we isolated stable hsps of 61kDa and 12kDa, which are similar to hsp60 and hsp10, respectively, from the supernatant fraction of thermophilic bacterium PS3 by ATP-Agarose chromatography. Using synthetic DNA of the deduced sequence, the 1.6kbp double stranded DNA encoding both proteins was obtained by the polymerase chain reaction (PCR). The complete sequence of the resulting reading frames showed high homology to those of the genes encoding GroEL (hsp60) and GroES (hsp10) of E. coli, and hsp60s and hsp10s of several other species. The genes for the 12K and 61K were present in the same operon. 61K was also partially similar to the F1 alpha subunit of thermophilic ATP synthase, which is highly reconstitutable to form the alpha beta complex.

Amino Acid Sequence↗
PubMed1991

The 'lysine cluster' in the N-terminal region of Na+/K(+)-ATPase alpha-subunit is not involved in ATPase activity.

The alpha-subunit of the Na+/K(+)-ATPases from several animal species have markedly similar amino acid sequences. However, the N-terminal sequences of the alpha-subunit are rather divergent except for lysine-rich sequences, the 'lysine cluster'. Here we report that the alpha-subunit from frog (Rana catesbeiana) has an N-terminal sequence with the 29 amino acid residues shorter than that of the Xenopus alpha-subunit deduced from its cDNA and hence lacks the 'lysine cluster'. Nevertheless, the Rana enzyme still exhibits ATPase activity. The ATP-dependent Na+ transport activity of the Rana enzyme was similar to that of the dog enzyme, which contains the 'lysine cluster'. Moreover, the Torpedo alpha-subunits deprived of the 'lysine cluster' by means of two gene deletions showed the same Na+/K(+)-ATPase activities as that of the wild type when expressed in Xenopus oocytes from their mRNAs. These results strongly suggest that the 'lysine cluster' in the N-terminal region of the alpha-subunit is not involved in the ATPase and ion transport activities. Since an active alpha-subunit was translated in Xenopus oocytes from mRNA lacking the N-terminal region including the 'lysine cluster', these regions were proved not to function as a membrane insertion signal sequence.

Adenosine Triphosphatases↗
PubMed1991

Role of diversifying selection and gene conversion in evolution of major histocompatibility complex loci.

Genes at the major histocompatibility complex (MHC) in mammals are known to have exceptionally high polymorphism and linkage disequilibrium. In addition, these genes form highly complicated gene families that have evolved through gene conversion and unequal crossing-over. It has been shown recently that amino acid substitution at the antigen recognition site (ARS) is more rapid than synonymous substitution, suggesting some kind of positive natural selection working at the ARS. It is highly desirable to know the interactive effect of gene conversion and natural selection on the evolution and variation of MHC gene families. A population genetic model is constructed that incorporates both selection and gene conversion. Diversifying selection is assumed in which sequence diversity is enhanced not only between alleles at the same locus but also between duplicated genes. Expressed and nonexpressed loci are assumed as in the class I gene family of MHC, with gene conversion occurring among all loci. Extensive simulation studies reveal that very weak selection at individual amino acid sites in combination with gene conversion can explain the unusual pattern of evolution and polymorphisms. Here both gene conversion and natural selection contribute to enhancing polymorphism.

Alleles↗
PubMed1991

Sequence of gene choB encoding cholesterol oxidase of Brevibacterium sterolicum: comparison with choA of streptomyces sp. SA-COO.

The nucleotide (nt) sequence of the cholesterol oxidase (Cho)-encoding gene (choB) cloned from Brevibacterium sterolicum ATCC21387 was determined. The sequence contained an open reading frame with a G + C content of 64.9 mol% that would encode a protein of 552 amino acids (aa). Comparison of the nt sequence of choB and deduced aa sequence to those of the Cho-encoding gene (choA) of Streptomyces sp. strain SA-COO showed identities of 64% and 58%, respectively. N-terminal aa sequence analysis of the extracellular enzyme of B. sterolicum confirmed that the mature enzyme consisted of 507 aa with a predicted Mr of 54,902, and was preceded by a 45-aa signal sequence.

Amino Acid Sequence↗
PubMed1991

D-lactate dehydrogenase is a member of the D-isomer-specific 2-hydroxyacid dehydrogenase family. Cloning, sequencing, and expression in Escherichia coli of the D-lactate dehydrogenase gene of Lactobacillus plantarum.

The gene encoding D-lactate dehydrogenase (D-lactate: NAD+ oxidoreductase, EC 1.1.1.28) of Lactobacillus plantarum has been sequenced, and expressed in Escherichia coli cells with an inducible expression plasmid, in which the 5'-noncoding region of the gene was replaced with the tac promoter. Comparison of the sequence of D-lactate dehydrogenase with L-lactate dehydrogenases, including the L. plantarum L-lactate dehydrogenase, showed no significant homology. In contrast, the D-lactate dehydrogenase is homologous to E. coli D-3-phosphoglycerate dehydrogenase and Lactobacillus casei D-2-hydroxyisocaproate dehydrogenase. This indicates that D-lactate dehydrogenase is a member of a new family of 2-hydroxyacid dehydrogenases recently proposed, being distinct from L-lactate dehydrogenase and L-malate dehydrogenase, and strongly suggests that the new family consists of D-isomer-stereospecific enzymes. In the reductive reaction, the enzyme showed a broad substrate specificity, although pyruvate was the most favorable of all 2-ketocarboxylic acids tested. In particular, hydroxypyruvate is effectively reduced by the enzyme, the reaction rate, and Km value being comparable to those in the case of pyruvate, indicating that the enzyme has not only D-lactate dehydrogenase activity but also D-glycerate dehydrogenase activity. The conserved residues in this family appear to be the residues involved in the substrate binding and the catalytic reaction, and thus to be targets for site-directed mutagenesis.

Alcohol Oxidoreductases↗
PubMed1991

Application of an anhydrotrypsin-immobilized precolumn for selective separation of peptides having arginine or lysine at their C-termini by column-switching high-performance liquid chromatography.

A column-switching high-performance liquid chromatographic (CS-HPLC) system which consisted of an anhydrotrypsin (AHT)-immobilized diol-silica precolumn and a reversed-phase analytical column was developed for the selective separation of peptides having Arg or Lys at their C-termini. Tuftsin (Thr-Lys-Pro-Arg) could be enriched almost quantitatively on the precolumn when loaded with water as a carrier solvent and the precolumn was washed with 10-30 mM acetate buffer (pH 5.0). An investigation of the affinity characteristics of 55 peptides to the AHT precolumn showed that among twelve peptides having Arg or ArgNH2 at their C-termini and more than four amino acid residues, ten were retained almost quantitatively on the precolumn, and eight out of nine peptides having Lys at their C-termini were less retained. The peptide having D-Arg at its C-termini was not retained. However, twelve out of thirty peptides having no Arg or Lys at their C-termini were also retained, but the retention was greatly decreased, in contrast to the Arg peptides, when the precolumn was washed with 20 mM calcium chloride solution. The results indicate that the CS-HPLC system equipped with an AHT precolumn offers new selectivity in the HPLC selectivity in the HPLC separation of peptides.

Amino Acid Sequence↗
PubMed1991

Site-directed mutants, at position 166, of RTEM-1 beta-lactamase that form a stable acyl-enzyme intermediate with penicillin.

Class A beta-lactamases are known to hydrolyze substrates through a Ser70-linked acyl-enzyme intermediate, although the detailed mechanism remains unknown. On the basis of the tertiary structure of the active site, the role of Glu166 of class A enzymes was investigated by replacing the residue in RTEM-1 beta-lactamase with Ala, Asp, Gln, or Asn. All the mutants, in contrast to the wild-type, accumulated a covalent complex with benzylpenicillin which corresponds to an acyl-enzyme intermediate. For the Asp mutant, the complex decayed slowly and the hydrolytic activity was slightly retained both in vivo and in vitro. In contrast, the other mutants lost the hydrolytic activity completely and their complexes were stable. These results indicate that the side-chain carboxylate of Glu166 acts as a special catalyst for deacylation. Residues for deacylation have not been identified in other acyl enzymes, such as serine proteases and class C beta-lactamases. Furthermore, the acyl-enzyme intermediates obtained are so stable that they are considered to be ideal materials for crystallographic studies for elucidating the catalytic mechanism in more detail. In addition, the mutants can more easily form inclusion bodies than the wild-type, when they are produced in a large amount, suggesting that the residue also plays an important role in proper folding of the enzyme.

Acylation↗