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T Hamamoto

Publications and source records attributed to T Hamamoto.

At least 55 records · Page 3Linked to original sources
PubMed1997

Expression of human telomerase RNA is an early event of stomach carcinogenesis.

Expression of human telomerase RNA (hTR) and telomerase activity in gastric cancer and corresponding non-cancerous mucosa were studied. Telomerase activity was detected in 23 (88%) of 26 carcinoma tissues. Although all tumor specimens and non-cancerous mucosa expressed various levels of hTR, 21 (81%) of 26 cases expressed hTR at a higher level in the tumor than that in the corresponding mucosa. All 8 gastric carcinoma cell lines also expressed hTR at high levels. Nine (35%) of 26 non-cancerous mucosa showed telomerase activity and all of them contained intestinal metaplasia. The incidence of telomerase-positive mucosa in grade 2 intestinal metaplasia was significantly higher than that in grade 0 or grade 1 intestinal metaplasia, whereas hTR overexpression was found in grade 0 or grade 1 intestinal metaplasia as well as grade 2 intestinal metaplasia. The degree of Helicobacter pylori infection increased in parallel with the level of hTR expression and telomerase positivity. These results overall suggest that Helicobacter pylori infection may be a strong trigger for hTR overexpression in intestinal metaplasia, and this may lead to telomerase reactivation.

Adult↗
PubMed1997

Posttranscriptional modification of tRNA in psychrophilic bacteria.

Posttranscriptional modification in tRNA is known to play a multiplicity of functional roles, including maintenance of tertiary structure and cellular adaptation to environmental factors such as temperature. Nucleoside modification has been studied in unfractionated tRNA from three psychrophilic bacteria (ANT-300 and Vibrio sp. strains 5710 and 29-6) and one psychrotrophic bacterium (Lactobacillus bavaricus). Based on analysis of total enzymatic hydrolysates by liquid chromatography-mass spectrometry, unprecedented low amounts of modification were found in the psychrophiles, particularly from the standpoint of structural diversity of modifications observed. Thirteen to 15 different forms of posttranscriptional modification were found in the psychrophiles, and 10 were found in L. bavaricus, compared with approximately 29 known to occur in bacterial mesophiles and 24 to 31 known to occur in the archaeal hyperthermophiles. The four most abundant modified nucleosides in tRNA from each organism were dihydrouridine, pseudouridine, 7-methylguanosine, and 5-methyluridine. The molar abundances of the latter three nucleosides were comparable to those found in tRNA from Escherichia coli. By contrast, the high levels of dihydrouridine observed in all three psychrophiles are unprecedented for any organism in any of the three phylogenetic domains. tRNA from these organisms contains 40 to 70% more dihydrouridine, on average, than that of the mesophile E. coli or the psychrotroph L. bavaricus. This finding supports the concept that a functional role for dihydrouridine is in maintenance of conformational flexibility of RNA, especially important to organisms growing under conditions where the dynamics of thermal motion are severely compromised. This is in contrast to the role of modifications contained in RNA from thermophiles, which is to reduce regional RNA flexibility and provide structural stability to RNA for adaptation to high temperature.

Base Composition↗
PubMed1997

Altered microsatellites in incomplete-type intestinal metaplasia adjacent to primary gastric cancers.

AIM: To investigate the presence of genetic instability in precancerous lesions of the stomach. METHODS: Fifteen cases of sporadic gastric cancers with a background of intestinal metaplasia were studied by microsatellite assay at nine loci. Altered metaplastic mucosa was microdissected, reconstructed topographically, and examined immunohistochemically with an anti-p53 antibody, comparing its positive area with foci of microsatellite instability in each individual. RESULTS: Alterations at one or more loci were observed in seven of 15 cancers (46.7%) and four of 15 intestinal metaplasias (26.7%). Two cases of replication error positive phenotype had no microsatellite alterations in their metaplastic mucosa. All the microsatellite alterations in the metaplastic mucosa were restricted to incomplete-type intestinal metaplasia around the respective cancers. Moreover, in one case, an identical pattern of microsatellite alteration was detected in the cancer tissue and in the adjacent metaplastic mucosa, suggesting the sequential development of gastric cancer from intestinal metaplasia. Frequent alteration was found at the locus D1S191 (1q), indicating that this locus might be altered early in the development of intestinal-type gastric cancer. No significant association between microsatellite instability and p53 immunoreactivity was observed in the cases examined. CONCLUSION: These results indicate that microsatellite instability may be an early event in stomach carcinogenesis, especially in intestinal-type cancers.

Adenocarcinoma↗
PubMed1997

Cloning and expression of purine nucleoside phosphorylase I gene from Bacillus stearothermophilus TH 6-2.

Bacillus stearothermophilus TH 6-2 has two kinds of purine nucleoside phosphorylases (Pu-NPase I and Pu-NPase II). The Pu-NPase I is a functional homolog of eukaryotic purine nucleoside phosphorylases that can catalyze the phosphorolysis of inosine and guanosine, but not adenosine, the primary substrate of Pu-NPase II. The Pu-NPase I gene of TH 6-2 has been cloned, sequenced, and expressed in E. coli. The gene corresponded to an open reading frame of 822 nucleotides that translates into a putative 274-amino acid protein with a molecular weight of 29,637. The deduced amino terminus sequence completely coincided with that found for the purified enzyme. The cloned gene was overexpressed in E. coli by using the trc promoter to produce an active enzyme in large quantities. The amino acid sequence of Pu-NPase I shared 50% similarity with those of human and mouse purine nucleoside phosphorylases.

Amino Acid Sequence↗
PubMed1997

Cloning of purine nucleoside phosphorylase II gene from Bacillus stearothermophilus TH 6-2 and characterization of its gene product.

Bacillus stearothermophilus TH 6-2 has two kinds of purine nucleoside phosphorylases (Pu-NPases). The type I enzyme (Pu-NPase I) is a functional and structural homolog of eukaryotic purine nucleoside phosphorylases that catalyze the phosphorolysis of inosine, guanosine, and their derivatives. The type II enzyme (Pu-NPase II) is a minor enzyme that efficiently phosphorolyzes adenosine and its derivatives rather than other purine nucleosides like Escherichia coli Pu-NPase. The gene coding for Pu-NPase II (punB gene) has been cloned and sequenced from TH 6-2 strain. The deduced amino acid sequence of Pu-NPase II shared 54% identity with that of E. coli enzyme, while it had no significant homology to that of Pu-NPase I or eukaryotic enzymes. By producing the Pu-NPase II in E. coli cells, the Pu-NPase II has been purified and characterized.

Amino Acid Sequence↗
PubMed1997

Growth inhibitory effect of interferon-beta is associated with the induction of cyclin-dependent kinase inhibitor p27Kip1 in a human gastric carcinoma cell line.

The effect of IFN-beta on cell growth and the mechanism of growth modulation was examined in human gastric carcinoma cell lines. IFN-beta inhibited the cell growth of TMK-1 cells, whereas it did not affect the growth of the other three cell lines (MKN-7, -28, and -45). The number of apoptotic cells in IFN-beta-treated TMK-1 cells was 2-fold the number of those in control TMK-1 cells, whereas the induction of apoptosis was not observed in IFN-beta-treated MKN-28 cells. IFN-beta enhanced the expression of cyclin-dependent kinase inhibitor p27Kip1 at mRNA and protein levels. The increased p27Kip1 bound preferentially to CDK6. The phosphorylation level of retinoblastoma protein in TMK-1 cells was reduced by IFN-beta treatment. IFN-beta did not affect the expression of cell cycle regulators in MKN-28 cells. These results suggest that the induction of p27Kip1 by IFN-beta might confer inhibition of cell growth, leading to subsequent apoptosis in TMK-1 cells.

Adenocarcinoma↗
PubMed1997

[Application of gene gun for local-regional cancer].

We studied the in vivo gene transfusion using a gene gun, formerly used in plants and culture cells. The hand-held type gene gun (Helios Gene Gun System) is simple and convenient for effective gene transfection in living animals. This method has some advantages in that there is no need for use of viral vector, independence on the cell cycle and local inducement of plural genes. There is a great possibility for application to local-regional cancer.

Animals↗
PubMed1996

Marked elevation of plasma carcinoembryonic antigen and stomach carcinoma.

BACKGROUND: This study was undertaken to clarify the relationship between marked elevation of plasma carcinoembryonic antigen (CEA) and signet ring cell carcinoma of the stomach. METHODS: To elucidate the contributing factor of extreme elevation of plasma CEA value, the histologic and biochemical records for 310 cases of stomach carcinoma, including 202 advanced and 108 early, collected between 1980 to 1994 from the San-in Rosai Hospital and Tottori University Hospital were studied. Immunohistochemical localization of CEA in the stomach was performed using a peroxidase antiperoxidase (PAP) staining technique. RESULTS: Among 310 cases of gastric carcinoma, 44 (14%) had abnormal plasma CEA values. The positivity rates of early and advanced gastric carcinoma were 3.7% (4/18) and 19% (40/202), respectively. Concerning advanced gastric carcinoma, 20 cases had more than 51 ng/mL, and 20 cases had between 5 ng/mL and 50 ng/mL. Four cases with plasma CEA values of more than 1,000 ng/mL had histological signet ring cell carcinoma (one case), and poorly differentiated adenocarcinoma with signet ring cell carcinoma (2 cases). Three cases of signet ring cell carcinoma or poorly differentiated adenocarcinoma of the stomach were massive local infiltration rather than hepatic metastasis. Among 40 cases with elevated plasma CEA, a multivariate regression analysis showed that only one variable (lymph node metastasis) was an independent factor (P < 0.05). Significantly higher rates of peritoneal metastasis (P < 0.0001) and lymph node metastasis (P < 0.05) were observed in patients with marked elevations of plasma CEA than in patients with moderate elevations of plasma CEA. No correlation was obtained between plasma CEA value and several biochemical tests. CONCLUSIONS: Marked elevation of plasma CEA may be found in the absence of liver metastasis from signet ring or poorly differentiated gastric carcinoma. Patients with marked elevations of CEA also had lymphatic and peritoneal dissemination.

Adenocarcinoma↗
PubMed1996

Characterization of malate dehydrogenase from deep-sea psychrophilic Vibrio sp. strain no. 5710 and cloning of its gene.

A metabolic key enzyme malate dehydrogenase (MDH) was purified from a deep-sea psychrophilic bacterium, Vibrio sp. strain no. 5710. The enzyme displayed an optimal activity shifted toward lower temperature and a pronounced heat lability. A gene encoding this enzyme was isolated and cloned. Recombinant Escherichia coli cells harboring the isolated clone expressed MDH activity with temperature stability identical to that of the parental psychrophile. Nucleotide sequencing of the gene revealed that its primary sequence was similar to that of a mesophile E. coli MDH (78% amino acid identity), for which the three-dimensional structure is known. The enzyme is thus suitable for the analysis of molecular adaptations to low temperatures.

Adaptation, Physiological↗
PubMed1996

Inhibitory properties of a novel human Kunitz-type protease inhibitor homologous to tissue factor pathway inhibitor.

In a previous report, we described the molecular cloning, expression, and partial characterization of a second human tissue factor pathway inhibitor (TFPI), which we designated as TFPI-2 [Sprecher, C. A., et al. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 3353-3357]. Recombinant TFPI-2 inhibited the amidolytic activity of trypsin as well as that of factor VIIa in complex with tissue factor. TFPI-2 recently has been shown to be identical to placental protein 5 (PP5), a glycoprotein originally isolated from placenta that exhibits serine protease inhibitory activity. In the present study, we have examined TFPI-2/PP5 for its ability to inhibit a number of serine proteases involved in blood coagulation and fibrinolysis, inasmuch as TFPI-2/PP5 prolonged the coagulation time of human plasma induced by either tissue factor or contact activation in a dose-dependent manner. In addition to its ability to inhibit the amidolytic and proteolytic activities of the factor VIIa-tissue factor complex, TFPI-2/PP5 strongly inhibited the amidolytic activities of human factor XIa, human plasma kallikrein, and human plasmin with Ki values of 15, 25, and 3 nM, respectively. TFPI-2/PP5 was also a weak inhibitor of the activation of factor X by a complex of human factor IXa and poly(lysine) with an apparent Ki of 410 nM. Heparin markedly enhanced the ability of TFPI-2/PP5 to inhibit factor VIIa-tissue factor both in the solution phase and on cell surfaces. In addition, heparin augmented the inhibition of human factor Xa amidolytic activity at relatively high levels (10-100 nM) of TFPI-2/PP5. No significant inhibition of glandular kallikrein, urinary plasminogen activator, tissue plasminogen activator, human activated protein C, human factor Xa, human thrombin, or leukocyte elastase was observed when these proteases were incubated with TFPI-2 in the absence of heparin.

Amino Acid Sequence↗
PubMed1996

The energy transmission in ATP synthase: from the gamma-c rotor to the alpha 3 beta 3 oligomer fixed by OSCP-b stator via the beta DELSEED sequence.

ATP synthase (F0F1) is driven by an electrochemical potential of H+ (delta microH+). F0F1 is composed of an ion-conducting portion (F0) and a catalytic portion (F1). The subunit composition of F1 is a alpha 3 beta 3 gamma delta epsilon. The active alpha 3 beta 3 oligomer, characterized by X-ray crystallography, has been obtained only from thermophilic F1 (TF1). We proposed in 1984 that ATP is released from the catalytic site (C site) by a conformational change induced by the beta DELSEED sequence via gamma delta epsilon-F0. In fact, cross-linking of beta DELSEED to gamma stopped the ATP-driven rotation of gamma in the center of alpha 3 beta 3. The torque of the rotation is estimated to be 420 pN x A from the delta microH+ and H(+)-current through F0F1. The angular velocity (omega) of gamma is the rate-limiting step, because delta microH+ increased the Vmax of H+ current through F0, but not the Km(ATP). The rotational unit of F0 (= ab2c10) is pi/5, while that in alpha 3 beta 3 is 2 pi/3. This difference is overcome by an analog-digital conversion via elasticity around beta DELSEED with a threshold to release ATP. The alpha beta distance at the C site is about 9.6 A (2,8-diN3-ATP), and tight Mg-ATP binding in alpha 3 beta 3 gamma was shown by ESR. The rotational relaxation of TF1 is too rapid (phi = 100 nsec), but the rate of AT(D)P-induced conformational change of alpha 3 beta 3 measured with a synchrotron is close to omega. The ATP bound between the P-loop and beta E188 is released by the shift of beta DELSEED from gamma RGL. Considering the viscosity resistance and inertia of the free rotor (gamma-c), there may be a stator containing OSCP (= delta of TF1) and F0-d to hold free rotation of alpha 3 beta 3.

Amino Acid Sequence↗
PubMed1996

The inhibition of human factor VIIa-tissue factor by antithrombin III-heparin is enhanced by factor X on a human bladder carcinoma cell line.

Previous studies have shown that antithrombin III-heparin effectively inhibited the factor VIIa-tissue factor complex. Herein, we show that the neutralization of factor VIIa in complex with the cell surface tissue factor by antithrombin III-heparin was markedly enhanced by plasma levels of factor X. Active site-mutated factor X (S376A factor X) and factor Xa previously inactivated with dansyl-Glu-Gly-Arg-chloromethyl ketone were as effective as plasma-derived factor X in this reaction, indicating that the active site serine residue of factor Xa was not involved in this mechanism. Furthermore, Gla-domainless factor X had no effect in this system, emphasizing the importance of the factor X Gladomain in this reaction. Antibody experiments revealed that this effect was not due to trace levels of a tissue factor pathway inhibitor contaminating either the factor X or antithrombin III preparations. The presence of heparin in this system was essential, as deletion of heparin resulted in a factor VIIa-tissue factor neutralization rate essentially identical to that observed for antithrombin III alone. Plasma levels of factor IX also accelerated the inhibition of factor VIIa-tissue factor by antithrombin III-heparin, although its effect was not as pronounced as that of factor X. Other vitamin K-dependent plasma proteins including protein S, protein C and prothrombin failed to augment the inhibition of factor VIIa-tissue factor by antithrombin III-heparin. Factor X did not enhance the neutralization rate of factor VIIa-tissue factor by antithrombin III-heparin when a carboxyl-terminal truncated tissue factor construct (TF1-219) was used, even in the presence of mixed phospholipids. Our collective finding suggest that antithrombin III and factor X bind to heparin at distinct sites on the heparin molecule resulting in a transient ternary complex of antithrombin III-heparin-factor X that represents the anticoagulant species. Factor X conceivably guides complex to a phosphatidylserine-rich site on the cell surface in close proximity to the factor VIIa-tissue factor complex and facilitates rapid neutralization of factor VIIa. Our findings also suggest that the effect of heparin on the regulation of the extrinsic pathway of blood coagulation may be more profound than previously recognized.

Antithrombin III↗
PubMed1996

The effect of heparin on the regulation of factor VIIa-tissue factor activity by tissue factor pathway inhibitor.

Tissue factor pathway inhibitor (TFPI) inhibits factor VIIa-tissue factor and factor Xa through its first and second Kunitz-type domains, respectively. Previous studies have shown that heparin binds to TFPI at two sites and enhances the inhibitory activity of TFPI towards factor Xa. We have studied the effect of heparin of the TFPI-mediated inhibition of factor VIIa-relipidated tissue factor amiodolytic activity and factor VIIa-tissue factor proteolytic activity towards factor IX and factor X on a human bladder carcinoma cell line, J82. The inhibitory activity of full-length TFPI on factor VIIa-tissue factor amidolytic and proteolytic activities was greatly enhanced by heparin, whereas the inhibitory activity of a truncated form of TFPI lacking the third Kunitz-type domain and carboxy-terminal tail (TFPI1-161) was not affected by heparin. Optimal inhibition of factor VIIa-tissue factor by TFPI was observed at 0.1 U/ml heparin. Heparin enhanced the inhibitory activity of TFPI towards factor Xa even in the presence of factor VIIa-tissue factor complexes in solution phase. In addition, heparin augmented the ability of TFPI to inhibit factor VIIa-tissue factor amidolytic activity in the presence of active-site mutated factor X (S376A factor X). Our collective results suggest that heparin may play a significant role in augmenting the physiological regulation of factor VIIa-tissue factor activity by TFPI.

Animals↗
PubMed1996

Induction of cytochrome P-450-linked monooxygenase system in rat liver microsomes by xiao-chaihu-tang.

The administration of Xiao-Chaihu-Tang (TJ-9) for 2 weeks induced a 25% increase in the content of cytochrome P-450 in female rat liver microsomes, while the content in male rats remained unchanged. The enzymatic activities toward various xenobiotics were stimulated in female rats, the levels being in the range of 125-250% of those in the control rats. Among these xenobiotics, the metabolic rates for substrates of cytochrome P-450 2E1 were significantly enhanced in female rats. On the other hand, the activities toward various xenobiotics in male rats were unchanged. When 3-methylcholanthrene was given to rats for a week, the augmentation of cytochrome P-450 content and the stimulation of xenobiotic metabolism were observed. However, co-administration of TJ-9 did not alter the effect of 3-methylcholanthrene described above.

Administration, Oral↗
PubMed1996

Purification and characterization of purine nucleoside phosphorylase and pyrimidine nucleoside phosphorylase from Bacillus stearothermophilus TH 6-2.

The purine nucleoside phosphorylase (Pu-NPase) and the pyrimidine nucleoside phosphorylase (Py-NPase) have been purified from Bacillus stearothermophilus TH 6-2. The Pu-NPase is a trimer of 30-kDa subunits and the Py-NPase is a dimer of 46-kDa subunits. The isoelectric points of Pu-NPase and Py-NPase were pH 4.3 and 4.6, respectively. The Pu-NPase could catalyze the phosphorolysis of inosine and guanosine, but not adenosine. the Py-NPase could phosphorolyze both uridine and thymidine.

Amino Acid Sequence↗
PubMed1996

Molecular cloning and expression of the pyrimidine nucleoside phosphorylase gene from Bacillus stearothermophilus TH 6-2.

The pyrimidine nucleoside phosphorylase (Py-NPase) of Bacillus stearothermophilus TH 6-2 is a dimer of 46-kDa subunits and catalyzes the reversible phosphorolysis of uridine and thymidine. The gene encoding this pyrimidine nucleoside phosphorylase (pyn gene) has been cloned and sequenced from B. stearothermophilus TH 6-2. The pyn gene corresponded to an open reading frame of 1299 nucleotides that translates into a putative 433 amino acid protein with a molecular weight of 46,271. The deduced amino terminal sequence of Py-NPase coincided with that previously found for the purified enzyme. The deduced amino acid sequence of Py-NPase shared significant similarity with those of human and Escherichia coli thymidine phosphorylases. The cloned pyn gene was overexpressed in E. coli cells to produce an active enzyme in large quantities that accounted for approximately 20% of the total protein.

Amino Acid Sequence↗