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Biomedical subjects

Y Muto

Publications and source records attributed to Y Muto.

At least 19 recordsLinked to original sources
PubMed1992

The secondary structure of the colicin E3 immunity protein as studied by 1H-1H and 1H-15N two-dimensional NMR spectroscopy.

By performing 1H-1H and 1H-15N two-dimensional (2D) nuclear magnetic resonance (NMR) experiments, the complete sequence-specific resonance assignment was determined for the colicin E3 immunity protein (84 residues; ImmE3), which binds to colicin E3 and inhibits its RNase activity. First, the fingerprint region of the spectrum was analyzed by homonuclear 1H-1H HOHAHA and NOESY methods. For the identification of overlapping resonances, heteronuclear 1H-15N (HMQC-HOHAHA, HMQC-NOESY) experiments were performed, so that the complete 1H and 15N resonance assignments were provided. Then the secondary structure of ImmE3 was determined by examination of characteristic patterns of sequential backbone proton NOEs in combination with measurement of exchange rates of amide protons and 3JHN alpha coupling constants. From these results, it was concluded that ImmE3 contains a four-stranded antiparallel beta-sheet (residues 2-10, 19-22, 47-49, and 71-79) and a short alpha-helix (residues 31-36).

Amino Acid Sequence↗
PubMed1992

Recognition of an antiparallel beta-sheet structure of human epidermal growth factor by its receptor. Site-directed mutagenesis studies of Ala-30 and Asn-32.

The Ala-30 and Asn-32 residues involved in the major antiparallel beta-sheet structure of human epidermal growth factor (hEGF) were substituted with various amino acid residues, and the receptor-binding affinities of the nine variant hEGFs were determined by the use of human KB cells. The Ala-30----Arg, Ala-30----His and Ala-30----Phe substitutions drastically reduced the binding affinity, suggesting that the side chain in position 30 of Ala-30 of hEGF is required to be small for the receptor binding. The Asn-32----Asp substitution significantly reduced the binding affinity, while the Asn-32----His variant could bind to the receptor as well as to the wild-type hEGF. Therefore, it seems to be important for receptor binding that the side chain in position 32 does not have a negative charge but does have an NH group. Thus, we propose that, in the ligand-receptor complex, the receptor recognizes, on one side of the antiparallel beta-sheet structure of hEGF, a wider contact area than previously suggested.

Alanine↗
PubMed1992

A site-directed mutagenesis study on the role of isoleucine-23 of human epidermal growth factor in the receptor binding.

The isoleucine-23 residue of human epidermal growth factor (hEGF) was substituted by a variety of amino acid residues and the receptor-binding activities of variant hEGFs were determined by the use of human KB cell. Tight receptor binding was found of variants with hydrophobic amino acid residues in position 23. The size of the isoleucine residue was nearly optimum for the receptor binding as compared with other hydrophobic residues. The structure analysis by two-dimensional nuclear magnetic resonance spectroscopy showed that the substitution at position 23 only slightly affected the tertiary structure of hEGF. These indicate that the side chain of isoleucine residue in position 23, which is exposed on the protein surface, directly binds to a hydrophobic pocket of the receptor.

Amino Acid Sequence↗
PubMed1992

Genetic analysis of a Japanese family with normotriglyceridemic abetalipoproteinemia indicates a lack of linkage to the apolipoprotein B gene.

Normotriglyceridemic abetalipoproteinemia is a rare familial disorder characterized by an isolated deficiency of apoB-100. We have previously reported a patient with this disease, who had normal apoB-48 but no apoB-100. To elucidate the genetic abnormalities in this family, we studied the linkage of apoB gene using three genetic markers. The proband and her affected brother showed completely different apoB gene alleles, suggesting that the apoB gene itself is not related to this disorder in this family. By contrast, an American case had a point substitution in the apoB gene generating an in-frame stop codon. These results indicate that this disorder can be caused by defect(s) of either an apoB gene or other genes.

Abetalipoproteinemia↗
PubMed1992

Guanine-nucleotide binding activity, interaction with GTPase-activating protein and solution conformation of the human c-Ha-Ras protein catalytic domain are retained upon deletion of C-terminal 18 amino acid residues.

A truncated human c-Ha-Ras protein that lacks the C-terminal 18 amino acid residues and the truncated Ras protein with the amino acid substitution Gly-->Val in position 12 were prepared by an E. coli overexpression system. The truncated Ras protein showed the same guanine-nucleotide binding activity and GTPase activity as those of the full-length Ras protein. Further, the same extent of GTPase activity enhancement due to GTPase-activating protein was observed for the truncated and full-length Ras proteins. In fact, two-dimensional proton NMR analyses indicated that the tertiary structure of the truncated Ras protein (GDP-bound or GMPPNP-bound) was nearly the same as that of the corresponding catalytic domain of the full-length Ras protein. Moreover, a conformational change around the effector region upon GDP-->GMPPNP exchange occurred in the same manner for both proteins. These observations indicate that the C-terminal flanking region (18 amino acid residues) of the Ras protein does not appreciably interact with the catalytic domain. Therefore, the truncated Ras protein is suitable for studying the molecular mechanism involved in the GTPase activity and the interaction with the GTPase-activating protein. On the other hand, an active form of the truncated Ras protein, unlike that of the full-length Ras protein, did not induce neurite outgrowth of rat pheochromocytoma PC12 cells. Thus, membrane anchoring of the Ras protein through its C-terminal four residues is not required for the interaction of Ras and GAP, but may be essential for the following binding of the Ras-GAP complex with the putative downstream target.

Animals↗
PubMed1992

In vitro susceptibility of clinical isolates of Bacteroides fragilis and Bacteroides thetaiotaomicron in Japan.

A nationwide survey of the susceptibility of 433 isolates of Bacteroides fragilis and 149 isolates of Bacteroides thetaiotaomicron was conducted from December 1986 through November 1989 in Japan. These strains were collected from 16 university hospitals and one metropolitan hospital. Metronidazole was the most active drug against both species, with no resistant isolates found. The activity of imipenem and sulbactam-cefoperazone was good, with very low resistance rates determined in Bacteroides fragilis (1.4% and 1.6%, respectively) and in Bacteroides thetaiotaomicron (3.4% for both drugs), and was comparable to that of metronidazole. Cefoxitin, cefmetazole, cefotetan, cefbuperazone, latamoxef and ceftizoxime were found to be more active against Bacteroides fragilis, for which resistance rates were 3.2 to 9.5%, than against Bacteroides thetaiotaomicron, for which resistance rates were 18.1 to 21.8%. Rates of piperacillin resistance in the two species were 12.9% and 26.8%, respectively. Clindamycin was very active at a low concentration (MIC50 of 0.39 to 1.56 mg/l), but 24% and 27.5% of Bacteroides fragilis and Bacteroides thetaiotaomicron isolates, respectively, were resistant to this agent.

Anti-Bacterial Agents↗
PubMed1992

A 1H-15N NMR study of human c-Ha-ras protein: biosynthetic incorporation of 15N-labeled amino acids.

A 1H-15N NMR study was performed on the GDP-bound form of a truncated human c-Ha-ras oncogene product (171 amino acid residues). Resonance cross peaks of the backbone amide 1H-15N nuclei of a uniformly 15N-labeled protein were observed with heteronuclear single-quantum coherence spectroscopy (HSQC). In order to resolve overlapping cross peaks, selective 15N-labeling of one or two types of amino acid residues (Ala, Arg, Asx, Glx, Gly, His, Ile, Leu, Lys, Met, Phe, Ser, Thr, Tyr and/or Val) was carried out using appropriate E. coli mutant strains. By this procedure, all the backbone 1H-15N cross peaks were classified into amino acid types.

Amino Acids↗
PubMed1992

Spontaneous bacterial peritonitis due to Clostridium perfringens in a patient with liver cirrhosis and pure red cell aplasia.

A 63-year-old man with decompensated liver cirrhosis and pure red cell aplasia complained of pyrexia, abdominal distention and abdominal pain. A diagnosis of spontaneous bacterial peritonitis (SBP), Conn's syndrome, was made upon the isolation of an anaerobe Clostridium perfringens from both ascitic fluid and peripheral blood. The bacteria were found to be susceptible to piperacillin, and administration of the antimicrobial agent markedly improved his SBP. The anaerobes should be kept in mind as one of the possible pathogens of SBP, although anaerobic infection has been reported to be quite rare in the disease.

Clostridium Infections↗
PubMed1992

Changes in brain monoamine metabolism in rats with acute ischemic hepatic failure under artificial cardiopulmonary management.

A study was conducted to investigate changes in monoamine metabolism in the brain of rats with acute ischemic hepatic failure (AHF) induced by two-stage hepatic devascularization. Strict artificial cardiopulmonary management was used to exclude possible confounding effects of hypotension, hypothermia and hypoxemia that often appear in AHF. Rats were put in an incubator at 34 degrees C before the ligation of the hepatic artery (second stage operation), tracheotomized and ventilated artificially throughout the remaining experimental periods. No significant difference was observed in physiological parameters, including body temperature, pulse rate and systolic arterial blood pressure or PaO2 between AHF and sham operated rats. Brain levels of norepinephrine (NE) and its metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG), dopamine (DA) and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA), and serotonin (5-hydroxytryptamine, 5HT) and its metabolite 5-hydroxyindoleacetic acid (5HIAA) were determined by HPLC-voltametry. AHF rats showed significantly higher MHPG, DOPAC, 5HIAA and lower NE levels in the brain compared to controls. In addition, a significant negative correlation between NE and tyrosine (Tyr), a significant positive correlation between MHPG and Tyr or phenylalanine (Phe), and a significant positive correlation between DOPAC and Tyr or Phe were observed. In conclusion, the changes in monoamine metabolism in the brain of AHF rats are clearly induced specifically by hepatic failure itself, possibly through an altered metabolism of amino acids.

Animals↗
PubMed1992

Rupture of embolised coeliac artery pseudoaneurysm into the stomach: is coil embolisation an effective treatment for coeliac anastomotic pseudoaneurysm?

An elderly woman with an anastomotic pseudoaneurysm of the coeliac artery, after previous treatment of a thoraco-abdominal aortic aneurysm, was treated by stainless steel coil embolisation. One year later, the embolised pseudoaneurysm ruptured into the stomach and total gastrectomy and aneurysmorraphy was necessary. She is leading a normal life 6 months later.

Aged↗
PubMed1992

A modified technique for endoscopic mucosal resection of small early gastric carcinomas.

Endoscopic gastric mucosal resection (EGMR) is increasingly employed in early gastric cancer to remove the tumour with the surrounding mucosa and part of the submucosa after submucosal saline injection and staining to define the extent of the lesion. This study presents preliminary experience with a modified EGMR technique in five patients which allows more precise targeting and resection of the lesions. The time required for this procedure was less than 30 minutes in each case. All lesions were completely removed. In two patients, however, tumour growth invaded the submucosa and these patients therefore underwent subsequent surgery. Three patients with carcinoma confined to the mucosa were tumour-free at follow-up with repeat endoscopy and biopsy after 7 to 23 months.

Adenocarcinoma↗
PubMed1992

Conjugal transfer of imipenem resistance in Bacteroides fragilis.

Transfer of imipenem resistance in Bacteroides fragilis was studied. Clinical isolate B. fragilis 10-73 was highly resistant to imipenem. Imipenem resistance was transferred from 10-73 to B. fragilis strain TM4000 at a frequency of 10(-6)/input recipient by a filter mating technique. The resistance could also be retransferred. B. fragilis 10-73 and both primary and secondary transcipients produced an imipenem-hydrolyzing metallo-beta-lactamase. Acquisition of imipenem resistance correlated with the appearance of plasmid DNA with a size (ca. 13.6 kb) similar to that of the donor strain. TM4000 transformed by electroporation with purified DNA of the 13.6-kb plasmid pBFUK1 produced the metallo-beta-lactamase and was resistant to imipenem. Transfer was resistant to DNase treatment and no transfer was seen with a sterile filtrate of the donor culture. It is suggested that gene transfer in B. fragilis has the properties of a conjugation system rather than those of transformation or transduction.

Anti-Bacterial Agents↗
PubMed1992

[A case of Legionella pneumonia with myelodysplastic syndrome].

A 40-year-old man was admitted with high fever and cough. Pneumonic shadows of the left middle and lower lung fields increased rapidly, and his blood gases worsened. Initial treatment with cefmenoxime, piperacillin, and minocycline was ineffective. Administration of rifampicin was started for suspected legionella pneumonia, but it did not control the spread of the pneumonia shadows. After addition of an antifungal agent and trimethoprim-sulfamethoxazole, his symptoms gradually improved. Isolation of Legionella pneumophila from sputum specimens collected on the 4th day of admission confirmed the diagnosis on day 10. The patient was then given oral rifampicin plus cefmenoxime to prevent mixed infection, and showed a satisfactory improvement. Legionella pneumonia developed secondary to compromise of the patient's immunity due to steroid therapy for MDS. After recovering from Legionella pneumonia, the patient subsequently developed tuberculous pleurisy and Pneumocystis carinii pneumonia, which were cured by antituberculous therapy and trimethoprim-sulfamethoxazole. However, acute hepatitis followed by hepatic failure developed, and he died on day 121 after admission.

Adult↗
PubMed1992

[Flow cytometric determination of active oxygen produced by neutrophils in patients with inflammatory diseases].

We investigated active oxygen (H2O2) production by neutrophils in patients with inflammatory diseases such as connective tissue disease and respiratory tract infection. The analysis was done by flow cytometry using as small volume of whole-blood as 100 microliters. H2O2 production as well as C-reactive protein (CRP) were increased in connective tissue diseases, and was decreased after steroid therapy. In a case of neuro-Behçet's disease, changes in H2O2 production was observed in agreement with those in clinical symptoms such as gait disturbance. H2O2 production as well as CRP and neutrophil count were increased in acute respiratory tract infection, but in chronic patients H2O2 production alone was rather reduced. In stages of enhanced H2O2 production, tissue damage or inflammation may exist, the degree of which seems to be well reflected by H2O2 production. During stages of impaired H2O2 production, care should be taken to prevent infections. Using flow cytometry, H2O2 production can be easily determined as one of functions of neutrophils.

C-Reactive Protein↗
PubMed1992

[Cytofluorometric analysis of DNA content in proliferating cells of coronary arteriosclerotic lesions].

Cytofluorometric determination of DNA content was done on paraffin-embedded tissues of 19 cases of coronary arteriosclerotic lesions including fibrocellular intimal thickening lesions (FT) or atherosclerosis (AS). DNA distribution pattern of medial smooth muscle cells of coronary arteries with FT and AS was all diploid. The average proliferative index (PI) of both medial smooth muscle cells of coronary arteries with FT and AS was 4.8 +/- 0.6. DNA distribution patterns of intimal cells of coronary arteries with FT and AS were also diploid. The average PI of intimal cells of coronary arteries with FT and AS was 8.4 +/- 1.0 and 9.1 +/- 0.7, respectively. These results suggest that intimal cellular proliferation plays an important role in the development of atherosclerosis.

Cell Division↗
PubMed1992

CD30/Ki-1-positive anaplastic large cell lymphoma preceded by Hodgkin's disease.

A 59-year-old man was initially diagnosed as having Hodgkin's disease, nodular sclerosis type, and complete remission was achieved after combination chemotherapy. One year later, he developed a high fever and recurrence of the Hodgkin's disease was diagnosed. Salvage chemotherapy was ineffective, and the patient died. Autopsy specimens showed infiltration of lymphoma cells into multiple organs. Lymph nodes showed characteristics of non-Hodgkin's lymphoma, with expansion of anaplastic large cells; this differed from the histological features at initial diagnosis. Immunohistochemical staining was positive for CD30/Ki-1, but negative for CD15 (LeuM1). These findings were compatible with Ki-1 lymphoma, suggesting that this may be a case of CD30/Ki-1 lymphoma preceded by Hodgkin's disease and that a certain proportion of Ki-1 lymphomas and Hodgkin's disease may share the same cellular origin.

Antigens, CD↗