Search PubMed⌕ Search

Biomedical subjects

M Tsuda

Publications and source records attributed to M Tsuda.

At least 73 records · Page 4Linked to original sources
PubMed2000

Antiarrhythmic efficacy of dipyridamole in treatment of reperfusion arrhythmias : evidence for cAMP-mediated triggered activity as a mechanism responsible for reperfusion arrhythmias.

BACKGROUND: Intracellular calcium overload is believed to play an important role in development of reperfusion arrhythmias. Dipyridamole, an inhibitor of cellular uptake of adenosine, may prevent or terminate reperfusion arrhythmias by reducing intracellular calcium overload. METHODS AND RESULTS: First, we tested for a preventive effect of dipyridamole. Sixty-one patients who underwent primary PTCA for treatment of acute anterior wall myocardial infarction were enrolled in this prospective study. Patients were divided into dipyridamole (DP) and nondipyridamole (non-DP) groups. The 2 groups had similar baseline characteristics. In the DP group, dipyridamole 0.5 mg/kg was infused intravenously for 3 minutes immediately before reperfusion during primary PTCA. Arrhythmias after reperfusion were analyzed from continuous ECG recordings. None of the patients in the DP group (n=23) had accelerated idioventricular rhythms (AIVR) or ventricular tachycardia (VT). In contrast, 7 (18.4%) had AIVR and 3 (7.9%) had VT in the non-DP group (n=38; P<0.01). Second, we tested for a termination effect of dipyridamole. Dipyridamole 0.5 mg/kg was infused intravenously while continuous ECG recordings were obtained in 9 patients who had either sustained AIVR (n=7) or sustained VT (n=2) after reperfusion of occluded coronary artery. Arrhythmias were terminated in all patients. CONCLUSIONS: These results indicate that administration of dipyridamole can prevent and terminate reperfusion arrhythmias such as AIVR and VT. cAMP-mediated triggered activity may, at least in part, be responsible for reperfusion-induced AIVR and VT.

Adenosine↗
PubMed2000

Roles for the protein tyrosine phosphatase SHP-2 in cytoskeletal organization, cell adhesion and cell migration revealed by overexpression of a dominant negative mutant.

SHP-2, a SRC homology 2 domain-containing protein tyrosine phosphatase, mediates activation of Ras and mitogen-activated protein kinase by various mitogens and cell adhesion. Inhibition of endogenous SHP-2 by overexpression of a catalytically inactive (dominant negative) mutant in Chinese hamster ovary cells or Rat-1 fibroblasts has now been shown to induce a marked change in cell morphology (from elongated to less polarized) that is accompanied by substantial increases in the numbers of actin stress fibers and focal adhesion contacts. Overexpression of the SHP-2 mutant also increased the strength of cell-substratum adhesion and resulted in hyperphosphorylation of SHPS-1, a substrate of SHP-2 that contributes to cell adhesion-induced signaling. Inhibition of SHP-2 also markedly increased the rate of cell attachment to and cell spreading on extracellular matrix proteins such as fibronectin and vitronectin, effects that were accompanied by enhancement of adhesion-induced tyrosine phosphorylation of paxillin and p130Cas. In addition, cell migration mediated by fibronectin or vitronectin, but not that induced by insulin, was impaired by overexpression of the SHP-2 mutant. These results suggest that SHP-2 plays an important role in the control of cell shape by contributing to cytoskeletal organization, and that it is an important regulator of integrin-mediated cell adhesion, spreading, and migration as well as of tyrosine phosphorylation of focal adhesion contact-associated proteins.

Animals↗
PubMed2000

A study on the mechanism of the proton transport in bacteriorhodopsin: the importance of the water molecule.

The mechanism of proton transport around the Schiff base in bacteriorhodopsin was investigated by ab initio molecular orbital (MO) calculations. Computations were performed for the case where there is a water molecule between the Schiff base and the Asp residue and for the case where there is no water molecule. Changes in the atomic configuration and potential energy through the proton transport process were compared between two cases. In the absence of water, the protonated Schiff base was not stable, and a proton was spontaneously detached from the Schiff base. On the other hand, a stable structure of the protonated Schiff base was obtained in the presence of water. This suggests that the presence of a water molecule is required for stability in the formation of a protonated Schiff base.

Aspartic Acid↗
PubMed2000

Antenatal ultrasonographic appearance of a cloacal anomaly.

BACKGROUND: Cloacal anomalies are rare abnormalities with highly variable forms, which makes them difficult to diagnose antenatally. We present a cloacal anomaly case with interesting antenatal ultrasonographic findings. CASE: A 24-year-old woman, gravida 1, para 0, presented at 23 weeks' gestation with ultrasonographic evidence of fetal ascites. Between 23 and 30 weeks' gestation, serial ultrasounds showed changing features of a cloacal anomaly, consisting of fetal ascites, a cystic pelvic mass, hydronephrosis, and oligohydramnios. CONCLUSION: Serial antenatal ultrasound helped diagnose changing features of a cloacal anomaly in our case, thus allowing directed antenatal counseling and appropriate perinatal treatment.

Adult↗
PubMed2000

Induction of clovamide by jasmonic acid in red clover.

The effect of jasmonic acid (JA) on the secondary metabolism of 5-day-old red clover seedlings was investigated. Induction of the formation of four compounds was found in roots after treatment with 50 microM JA for 48 h, while no induction was observed in the shoots. These compounds, whose formation was induced by JA addition, were isolated and identified as caffeoyl DOPA (clovamide), caffeoyltyrosine, p-coumaroyl DOPA and p-coumaroyltyrosine, by ion-spray MS and 1H NMR analyses, and by chemical synthesis. Among them, clovamide was the most abundant, while the other amides represented only a minor portion. Clovamide started to increase in amount 24-36 h after treatment and reached a maximum after 96 h (2.81 nmol/mg fr. wt.). The induction of their formation was observed even with 5 microM of JA, and the amount increased with concentrations up to 100 microM. Treatment with 1 mM CuCl2, which elicits accumulation of the phytoalexin maackiain in red clover, caused a decrease in clovamide amount.

Cyclopentanes↗
PubMed2000

Identification of the urease operon in Helicobacter pylori and its control by mRNA decay in response to pH.

We investigated the transcription of the urease gene cluster ureABIEFGH in Helicobacter pylori to determine the regulation of gene expression of the highly produced enzyme urease. Northern blot hybridization analysis demonstrated that cells of the wild-type strain grown in an ordinary broth had transcripts of ureAB, ureABI, ureI, ureIE' and ure'FGH, but cells of a ureI-disrupted mutant had only the ureAB transcript. When the wild-type cells were exposed to pH 8 for 30 min, very little mRNA was detected. However, when exposed to pH 6, a large amount of the ureIE" transcript, which was longer than the ureIE' transcript, together with the additional transcripts ureABIEFGH and ure'EFGH were detected. Rifampicin addition experiments demonstrated that urease mRNAs, and the ureIE' transcripts in particular, are more stable at pH 5.5 than at pH 7. In accord with these results, urease activity in the crude cell extract of the pH 5.5 culture was twice as much as that of the pH 7 culture, although the amounts of UreA and UreB detected by immunoblot analysis were similar. The transcription start point of ureI was identified by primer extension using a ureA promoter-deleted mutant, and a consensus sequence of RpoD-RNA polymerase was found in the ureI promoter. The 3' end of the ureIE" mRNA, determined using S1 nuclease mapping, revealed that the transcript is able to cover the majority of the ureE open reading frame (ORF) that might be sufficient for UreE activity. Based on the above results, we conclude that the urease gene cluster of H. pylori consists of two operons, ureAB and ureIEFGH, and that primary transcripts of the latter as well as the read-through transcript, ureABIEFGH, are cleaved to produce several species of mRNA. It has been suggested that the ureIEFGH operon is regulated post-transcriptionally by mRNA decay in response to environmental pH. We are tempted to speculate that the ureE" transcript present in acidic pH may contribute to produce an active product that can proceed the nickel incorporation to the active centre, the final step of urease biosynthesis.

Amino Acid Sequence↗
PubMed2000

cDNA cloning, genomic cloning, and tissue-specific regulation of mouse cerebroside sulfotransferase.

We have isolated a mouse cDNA clone encoding 3'-phosphoadenylylsulfate-galactosylceramide 3'-sulfotransferase (cerebroside sulfotransferase; CST; EC 2.8.2.11) from a kidney cDNA library, using a human CST cDNA clone [Honke, K., Tsuda, M., Hirahara, Y., Ishii, A., Makita, A. & Wada, Y. (1997) J. Biol. Chem. 272, 4864-4868] as a probe. A recombinant protein of the cloned cDNA showed CST activity. The deduced protein is composed of the same 423 amino acids as human CST and its sequence exhibits 84% identity with that of the human counterpart. Northern-blot analysis and subquantitative reverse transcription-PCR (RT-PCR) analysis showed that the CST gene is preferentially transcribed in stomach, small intestine, brain, kidney, lung, and testis, in that order. To examine differences in transcripts in various tissues, we isolated CST cDNA clones from stomach, small intestine, brain, kidney, and testis by 5'-RACE analysis. We found seven different nucleotide sequences in the 5'-UTR, while the DNA sequences of all the isolated cDNA clones were identical in the coding region. In addition, we isolated CST genomic DNA clones from a mouse genomic library. The clones covered all the 5'-UTR sequences and coding exons including 3'-UTR. RT-PCR analyses of CST mRNAs from various tissues confirmed that CST transcripts are tissue-specifically spliced by alternative use of multiple exons 1. These observations suggest that the tissue-specific expression of the CST gene is explained by alternative usage of multiple 5'-UTR exons flanked with tissue-specific promoters.

Amino Acid Sequence↗
PubMed2000

Cancer-associated alternative usage of multiple promoters of human GalCer sulfotransferase gene.

The galactosylceramide sulfotransferase (cerebroside sulfotransferase, CST) (EC 2.8.2.11) gene is highly expressed in human renal cancer cells. To elucidate the regulatory mechanism of its gene expression, we have determined the genomic organization of the human CST gene. The gene comprises at least four exons and spans about 20 kb. The coding region is located in exons 3 and 4. To determine the transcription initiation sites, 5'-rapid amplification of cDNA ends analysis was performed using mRNA obtained from four human renal cancer cell lines, SMKT-R1-R4, and normal human renal proximal tubular cells. We found four transcription initiation sites and alternative usage of six exons corresponding to the 5'-untranslated region in cancer cells. On the other hand, the only transcript beginning at exon 1a was observed in normal cells. Using reverse transcriptase-PCR analysis, we confirmed that all of the exons 1a-d, especially exons 1c and 1d, are used as a transcription initiation site in cancer cells, whereas only exons 1a and 1b, mostly 1a, are utilized in normal cells. Analyzing the protein production from the mRNA variants with different 5'-UTRs, we found that all the transcripts examined produced the identical proteins. These observations suggest that the aberrant usage of transcription initiation sites flanked with promoters/enhancers is involved in the cancer-associated expression of the CST gene. Furthermore, this gene was assigned to human chromosome 22q12 by means of fluorescence in situ hybridization.

Base Sequence↗
PubMed2000

Selective solubilization of high-molecular-mass neurofilament subunit during nerve regeneration.

A reduction in neurofilament (NF) protein synthesis and changes in their phosphorylation state are observed during nerve regeneration. To investigate how such metabolic changes are involved in the reorganization of the axonal cytoskeleton, we studied the injury-induced changes in the solubility and axonal transport of NF proteins as well as their phosphorylation states in the rat sciatic nerve. In the control nerve, 15-25% of high-molecular-mass NF subunit (NF-H) was recovered in the 1% Triton-soluble fraction when fractionated in the presence of phosphatase inhibitors. After a complete loss of NF proteins distal to the injury site (70-75 mm from the spinal cord) 1 week after injury, NF-H detected in the regenerating sprouts at 2 weeks or later exhibited higher solubility (>50%) and lower C-terminal phosphorylation level than NF-H in the control nerve. Solubility increase was also apparent with L-[35S]methionine-labeled NF-H that was in transit in the proximal axon at the time of injury. The low-molecular-mass subunit remained in the insoluble fraction in both the normal and the regenerating nerves, indicating that selective solubilization of NF-H rather than total filament disassembly occurs during regeneration.

Animals↗
PubMed2000

Abnormal intracellular localization of Bax with a normal membrane anchor domain in human lung cancer cell lines.

Proapoptotic Bax is a member of the Bcl-2 family proteins, which have a key role in regulating programmed cell death. The intracellular localization and redistribution of Bax are important in promoting apoptosis. Bax contains a BH3 domain heterodimerizing with Bcl-2 and a hydrophobic transmembrane segment to be inserted in specified organelle membranes. In this study, Bcl-2 showed cytoplasmic localization in all of ten human lung cancer cell lines tested. Interestingly, Bax was localized in the nucleus in 7 cell lines, although Bax lacks nuclear import signals. This may allow cancer cells to escape from apoptosis. Why Bax is able to exist in the nucleus is still unclear. We hypothesized that mutation in the BH3 domain and / or transmembrane segment of Bax possibly causes intracellular Bax distribution. We analyzed the sequence of the bax gene in these cell lines and found only a silent point mutation at codon 184 (TCG-->TCA) in the transmembrane segment in all cell lines. This finding indicates that changes in cellular localization of Bax in lung cancer cell lines do not depend on bax mutation and that Bax is possibly translocated into the nucleus without any mutation. This is the first report showing that Bax with the normal amino acid sequence can be localized in the nucleus in established lung cancer cell lines without any treatment of the cells.

Adenocarcinoma↗
PubMed2000

[Comparison between cytomegalovirus hepatitis and Epstein-Barr virus hepatitis in healthy adults].

In order to determine the factors responsible for the differentiation of cytomegalovirus (CMV) hepatitis and Epstein-Barr virus (EBV) hepatitis in previously healthy adults, the clinical features and laboratory data of both types of hepatitis were retrospectively analyzed. CMV hepatitis showed a tendency to increase in our department. In comparison with EBV hepatitis, CMV hepatitis occurred in significantly older hosts than EBV hepatitis. We found that lymphadenopathy, cough and sore throat was more common in EBV hepatitis than in CMV hepatitis. The number of peripheral white blood cell count and atypical lymphocytes, and serum GOT, GPT, LDH and CRP levels of CMV and EBV hepatitis showed no significant differences.

Adolescent↗
PubMed2000

Catalytic mechanism of class A beta-lactamase. I. The role of Glu166 and Serl30 in the deacylation reaction.

The tetrahedral intermediate formation process, which is the first step in the deacylation reaction by class A beta-lactamase, was investigated by the ab initio molecular orbital method. In this study, benzyl penicillin was used as the substrate. From the results of our molecular dynamics study of the structure of beta-lactam antibiotics-beta-lactamase complex, the substrate, Ser70, Lys73, Ser130, Glu166 and a water molecule for the deacylation reaction were considered for construction of a model for calculation. The calculation results indicated that Glu166 plays a role in holding a water molecule, which is necessary for the deacylation reaction, and that the hydrogen bond network among Lys73Nzeta, Ser130Ogamma, and the carboxyl group of the beta-lactam antibiotics was formed by the uptake of beta-lactam antibiotics by beta-lactamase. The activation energy for this reaction was 33.3 kcal/mol, and it is very likely that the reaction occurred at body temperature. Subsequent calculation results obtained by using the model excluding Ser130 and the carboxyl group of the substrate indicated that the activation energy for this reaction was 40.8 kcal/mol, which is 7.5 kcal/mol higher than that of the previous reaction. It was found that the hydrogen bond network plays an important role in decreasing the activation energy for the tetrahedral intermediate formation reaction. Lys73Nzeta, which is located at the edge of the hydrogen bond network, played a role in forming a hydrogen bond with Glu166Oepsilon in order to help the deacylation reaction. The role of amino acid residues around the active site of class A beta-lactamase was also discussed.

Acylation↗
PubMed2000

Pyrinodemins B-D, potent cytotoxic bis-pyridine alkaloids from marine sponge amphimedon sp.

New bis-pyridine alkaloids, pyrinodemins B-D (1-3), have been isolated together with pyrinodemin A (4) and related 3-alkyl pyridine alkaloids 5-8 from the Okinawan marine sponge Amphimedon sp. and the structures were elucidated from spectroscopic data. Pyrinodemins B-D (1-3) showed potent cytotoxicity, while compounds 5-8 exhibited antimicrobial activity.

Alkaloids↗
PubMed2000

[ATP receptors in pain].

Extracellular ATP has been known to activate sensory neurons via the ATP-gated ion channels P2X receptors, leading to the proposal that the P2X receptors may play a role in signal transduction of pain from the peripheral site to the spinal cord in vivo. P2X3 receptors are expressed in capsaicin-sensitive small-sized dorsal root ganglion (DRG) neurons, and they are involved in the generation of rapidly desensitizing inward current and evoking nocifensive behavior and thermal hyperalgesia. Heteromeric P2X2/3 (P2X2 and P2X3) receptor is expressed in capsaicin-insensitive primary afferent fibers, and its activation leads to the generation of slow desensitizing currents and induction of mechanical allodynia. In addition, accumulating information suggests the involvement of G protein-coupled ATP receptors in the modulation of the generation and transmission of pain.

Adenosine Triphosphate↗
PubMed2000

Triterpene phytoalexins from strawberry fruit.

Strawberry cv. Houkouwase is resistant to infection by Colletotrichum fragariae. The formation of antifungal compounds was observed in unripe fruit which had been wounded and inoculated with conidia of C. musae. Three antifungal compounds were isolated and identified as euscaphic acid, tormentic acid and myrianthic acid. Myrianthic acid inhibited the growth of C. musae at 3 microg, and euscaphic and tormentic acids showed inhibitory effects at 100 microg. A quantitative analysis of their contents showed that the triterpenes increased in wounded fruit, and in wounded and inoculated fruit, but not in non-treated fruit. These findings indicate that unripe fruit of Houkouwase produced the triterpenes as phytoalexins. The triterpene phytoalexins seem to be involved in the resistance of strawberry to the fungus.

Anti-Infective Agents↗