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Biomedical subjects

K Tamura

Publications and source records attributed to K Tamura.

At least 649 records · Page 36Linked to original sources
PubMed1995

[Hamartomatous polyposis syndrome].

The hamartomatous polyposis syndromes, which comprise Peutz-Jeghers syndrome, juvenile polyposis, and Cowden's disease, occur less frequently. These disorders are characterized by multiple hamartomatous polyps in the gastrointestinal tract, and distinctive extraintestinal manifestations. We have recognized that these have inheritance with autosomal dominant trait by genetic studies. Most of them have high malignant potential which make transformation to neoplasms in gastrointestinal tract and extraintestinal organs. It is necessary for patients with these disorders to manage appropriately. Therefore, we must understand their natural histories and pathological characterization. Because affected patients and their first degree relatives belong to high risk groups of malignant neoplasms, we have to intensively survey them through their lifetime.

Adenomatous Polyposis Coli↗
PubMed1995

[In vitro antibacterial activities of carbapenems and other antibiotics against Pseudomonas aeruginosa determined using low-amino-acid agar].

MICs of imipenem (IPM), panipenem (PAPM), cefozopran (CZOP), cefpirome (CPR), gentamicin (GM), tobramycin (TOB) and amikacin (AMK) against Pseudomonas aeruginosa were determined using Mueller-Hinton agar and low-amino-acid agar. On Mueller-Hinton agar, the antibacterial activity of TOB was superlative, followed in order by GM, CZOP, IPM, AMK, PAPM and CPR, whereas on low-amino-acid agar, the order changed to IPM, PAPM, TOB, CZOP, GM, AMK and CPR. The largest decrease of MICs was seen with PAPM on low-amino-acid agar, and the antibacterial activity of PAPM was not stronger than that of IPM. The growth of P. aeruginosa on the low-amino-acid agar were significantly weaker than that on Mueller-Hinton agar, hence the evaluation of appearance colonies was difficult and misjudgement may result. Based on the above observations, we believe further investigations are needed before the application of low-amino-acid agar becomes routine.

Agar↗
PubMed1995

Combination therapy with mucosal protective agent for the eradication of Helicobacter pylori.

OBJECTIVE: To investigate the effect of plaunotol in combination with proton-pump inhibitors on Helicobacter pylori eradication in patients with gastric ulcer. PATIENTS AND METHODS: We studied 65 H. pylori-positive gastric ulcer patients. They were randomly assigned to five treatment groups: omeprazole (group I, n = 8), lansoprazole (group II, n = 13), lansoprazole+plaunotol (group III, n = 12), lansoprazole+clarithromycin (group IV, n = 16) and lansoprazole+plaunotol+clarithromycin (group V, n = 16). Ulcer status was diagnosed by endoscopy and H. pylori status by culture, histology, a urease test and a urea breath test at baseline, and after 8 and 12 weeks. The clearance and eradication rates were compared in each group. RESULTS: The healing rates in groups I-V were 100, 92, 100, 100 and 100%, respectively; clearance rates were 0, 23, 42, 50 and 75%, respectively; and eradication rates were 0, 0, 8, 38 and 69%, respectively. CONCLUSION: Combination therapy with plaunotol is efficacious for the eradication of H. pylori in gastric ulcer patients.

Anti-Bacterial Agents↗
PubMed1995

[Possibility for clinical use of mitral valve allograft: an experimental histopathological study in consideration with aortic valve allograft].

Morphologic studies were made on antibiotic preserved mitral valve allograft implanted in 8 sheep for 12 to 24 weeks. All allograft showed severe deterioration of connective tissue due to autolysis and immunological/inflammatory reactions. Compared with aortic valve allograft, mitral valve allograft failed more quickly and more severely, presumably because of differences in structure (presence of chordae tendineae and increased surface area of leaflets) and in closing pressure. The durability of cardiac valve allograft is influenced by the degree of preservation of collagen and elastic fibers in the graft. attenuation of immunologic reactions and control of fibrous sheathing.

Animals↗
PubMed1995

Horizontal transmission of group-I ribozymes: viruses as a carrier of the introns.

The nucleotide sequences of two self-splicing group I introns found in viruses that infect the eukaryotic green alga Chlorella were compared with those of 19 nuclear group I introns of 11 green algae, 1 red alga, 2 yeasts and 1 protist. The similarity ranging from 69.5% to 89.0% in any comparison strongly suggested a close relatedness of these introns. Since this kind of viruses infect algal cells residing in protists such as Paramecium, they may serve as a mediator to spread group I introns horizontally among organisms of different phylogenetic kingdoms.

Animals↗
PubMed1995

Similarities and differences in tRNA identity between Escherichia coli and Saccharomyces cerevisiae: evolutionary conservation and divergence.

Identity elements, which allow correct recognition of tRNAs by their cognate aminoacyl-tRNA synthetase, have been well elucidated in Escherichia coli to begin to see a pattern for tRNA recognition. We examined the identity elements of several tRNA species from Saccharomyces cerevisiae and Thermus thermophilus using in vitro transcripts. Comparison of identity elements among different organisms indicates not only conservation but also evolutionary divergence of tRNA recognition.

Amino Acyl-tRNA Synthetases↗
PubMed1994

Ultrastructural study on NOS-immunoreactive nerve terminals in the rat coeliac ganglion.

Nerve terminals immunoreactive for nitric oxide synthase (NOS) were studied in the rat coeliac-superior mesenteric ganglion by electron microscopy using a pre-embedding immunostaining method. The immunoreactive material was distributed in the axoplasmic matrix and was not specifically associated with any subcellular organelle. In most NOS-immunoreactive axon terminals numerous small clear vesicles (35-50 nm) were seen, and in some terminals a small number of large granular vesicles (70-120 nm) were intermingled with small clear vesicles. Most NOS-immunoreactive axon terminals formed axodendritic as well as axo-somatic synapses with non-immunoreactive ganglion neurones, and axo-axonic contacts were very scarce. These results suggest that NO may be released at the synaptic sites from the axon terminals and may affect ganglion neurones.

Amino Acid Oxidoreductases↗
PubMed1994

The role of the CCA sequence of tRNA in the peptidyl transfer reaction.

Peptidyl transfer is a key step in the process of protein biosynthesis. To examine the role of the universal CCA terminal sequence of tRNA in the process of peptidyl transfer, various mutant transcripts of Escherichia coli valine tRNA were constructed. Peptidyl transferase activity, monitored by the 'fragment reaction' with a slight modification, was decreased by mutation at any one base of CCA. The effect of mutation was moderate in the UCA, CUA and CCG mutants. Replacement of A76 by a pyrimidine nucleotide, or replacement of either C74 or C75 by a purine nucleotide caused a marked decrease in the activity. These findings suggested that the universal CCA terminus of tRNA makes a functional interaction with ribosomal RNA by base-pairing.

Acetylation↗
PubMed1994

Role of the CCA terminal sequence of tRNA(Val) in aminoacylation with valyl-tRNA synthetase.

All known tRNAs have a universal CCA sequence at the 3'-terminal. To study the role of this terminal sequence in the aminoacylation process, base substitutions were introduced into a transcript of Escherichia coli valine tRNA and the effects on the aminoacylation activity with valyl-tRNA synthetase were evaluated. Substitution of the terminal adenosine residue at position 76 by C or U caused a 5-7-fold decrease of valine charging activity in Vmax/Km, while substitution by G resulted in about a 300-fold decrease. In addition, these mutations gave rise to an appreciable level of misaminoacylation with threonine. ATP hydrolysis activity during threonylation was lower in the terminal adenosine mutants than in the wild-type. Mutations introduced at positions 75 and 74 also caused threonylation instead of reducing valylation, albeit to a much smaller extent. These results indicate that the CCA sequence, especially the base portion of the terminal adenosine residue, plays an important role not only in amino-acylation efficiency with valine but also in preventing misaminoacylation by hydrolyzing misactivated threonyl-tRNA(Val).

Acylation↗
PubMed1994

Selective 8-hydroxyguanine formation in pancreatic DNA due to a single intravenous administration of 4-hydroxyaminoquinoline 1-oxide in rats.

8-Hydroxyguanine (8-OHG) formation, a possible initiating event, was determined in pancreatic and liver DNA and compared with the genesis of acinar cell and hepatocyte necrosis in male Wistar rats given a single intravenous administration of 4-hydroxyaminoquinoline 1-oxide (4-HAQO). At the non-necrotic but tumorigenic dose of 7.0 mg/kg body weight, 8-OHG was selectively generated in pancreatic DNA, in the absence of acinar cell necrosis, at the 6 and 24 h time points and repaired by the 48 h time point. When rats were exposed to 4-HAQO at a necrotic dose of 14.0 mg/kg body weight, 8-OHG was also selectively formed in pancreatic DNA with the same time-dependence of generation and repair, while acinar cell necrosis became evident at the 24 h time point and progressed thereafter. Whereas no hepatocyte necrosis was detected in any rats, 8-OHG values for liver DNA merely expressed slight increases only at the 24 and 48 h time points in rats given 14.0 mg/kg body weight of 4-HAQO. The present data suggest that formation of oxidative DNA damage, assayed by 8-OHG, in pancreatic DNA is independent from toxicity and may be involved, along with quinoline adducts, in mutational events underlying 4-HAQO-induced rat acinar cell carcinogenesis.

4-Hydroxyaminoquinoline-1-oxide↗
PubMed1994

Interaction of tacrolimus(FK506) and its metabolites with FKBP and calcineurin.

Tacrolimus(FK506) is a strong immuno-suppressant and shows its activity through inhibiting IL-2 mRNA transcription by forming pentameric complex with intracellular receptor(FK506 binding protein 12 kDa or FKBP12), Ca2+, calmodulin, and calcineurin. Here, we report the binding activity to FKBP12, the pentameric complex formation and Con-A response inhibiting activities of 7 metabolites. C15-demethylated metabolite(M-3) needed higher quantity to compete in Con-A assay and in pentamer formation assay, although it binds more strongly to FKBP12. The result suggests that the ability to form a pentameric complex is not a two step reaction with the first binding to FKBP12, but a single step reaction by components for the pentamer formation.

Animals↗
PubMed1994

Inhibitory effect of clentiazem (TA-3090) on platelet aggregation--alone and in combination with aspirin or ticlopidine.

Clentiazem (a novel calcium antagonist) and its basic metabolites (MB1-MB7) showed inhibitory effects on collagen-induced platelet aggregation in human platelets. All the basic metabolites (IC50:8-22 micrograms/ml) had much stronger inhibitory effects than clentiazem itself (IC50:53 micrograms/ml), but the acidic metabolites (MA1-MA4) had no inhibitory effects even at 300 micrograms/ml. Other calcium antagonists (diltiazem, verapamil, nicardipine and nimodipine) also showed similar inhibitory effects although nicardipine and nimodipine were less active than the other drugs. The inhibitory effect of clentiazem was enhanced in the presence of aspirin or ticlopidine. Diltiazem and nicardipine also exhibited a similar potentiation of the anti-platelet effect in combination with aspirin or ticlopidine. Clentiazem also inhibited collagen-induced thromboxane B2 production by the platelets, and this inhibition by clentiazem was additively enhanced by the presence of aspirin. When both clentiazem and aspirin were orally administered to rats, platelet aggregation was additively inhibited. These results indicate that a combination therapy with clentiazem plus aspirin or clentiazem plus ticlopidine may be useful for the prevention and/or treatment of thrombotic disorders.

Animals↗
PubMed1994

Self-splicing group I introns in eukaryotic viruses.

We report the occurrence of self-splicing group I introns in viruses that infect the eukaryotic green alga Chlorella. The introns contained all the conserved features of primary sequence and secondary structure previously described for the group IB introns. The Chlorella viral introns (approximately 400 nt) self-spliced in vitro, yielding the typical group I intron splicing intermediates and products. Contrasting to eukaryotic nuclear group I introns, all of which are located in the rRNA genes, these introns were inserted in genes encoding proteins. In one case, the exons encoded a protein showing significant homology to the eukaryotic transcription factor SII (TFIIS), which may be important for viral gene expression. In another case, the gene for the open reading frame (ORF) of a 14.2 kDa polypeptide with unknown functions contained the intron. Scattered distribution of these introns among the viral species and their structural similarity to the group I introns of algae and protists indicated horizontal intron transmission. These eukaryotic viral introns offer an opportunity to understand how group I introns reach organisms of different phylogenetic kingdoms.

Amino Acid Sequence↗
PubMed1994

Spinal cord tumor appearing as unusual pain.

STUDY DESIGN: The authors report two cases of spinal cord tumors characterized by unusual pain, which is recurrent abdominal pain or cervical angina. METHODS: These unusual pains were improved after removal of tumors in the patients. CONCLUSIONS: The authors conclude that the pain was caused by vascular compression, bleeding in the tumor, or incomplete block of the cerebrospinal fluid flow. They recommend the use of osteoplastic laminectomy, because anatomic structure and spinal function should be preserved in young patients.

Abdominal Pain↗
PubMed1994

Escherichia coli seryl-tRNA synthetase recognizes tRNA(Ser) by its characteristic tertiary structure.

To investigate the sequence requirements of Escherichia coli tRNA(Ser) for recognition by seryl-tRNA synthetase, various mutants of unmodified tRNA(Ser) were constructed. Substitution of G2.C71 by C2.G71, but not by A2.U71 or U2.A71, impaired the serine-accepting activity, indicating that this position is not involved in recognition by seryl-tRNA synthetase, but contributes to discrimination from other tRNAs processing C2.G71 such as tRNA(Leu). Other nucleotides characteristic of tRNA(Ser), including the discriminator base, were not involved in recognition by seryl-tRNA synthetase. The anticodon was not involved, as suggested by its sequence variety within the isoacceptors. The long variable arm composed of over ten nucleotides, which is a characteristic feature of tRNA(Ser) together with tRNA(Leu) and tRNA(Tyr), was stem-length-specifically, but not sequence-specifically, important for recognition. In order to introduce a sufficient serine-accepting activity to a tRNA(1LEU) transcript in vitro, besides the change from C2.G71 to G2.C71, the following elements had to be changed to those characteristic of tRNA(Ser): the sequence in the D-loop, the stem pairing pattern of the variable arm, the tertiary base-pair 15.48 and the nucleotide at position 59 in the T psi C-loop. None of the nucleotides at these changed positions was involved in base-specific recognition, indicating that seryl-tRNA synthetase selectively recognizes tRNA(Ser) on the basis of its characteristic tertiary structure rather than the nucleotides specific to tRNA(Ser).

Base Sequence↗