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Biomedical subjects

T Kamiyama

Publications and source records attributed to T Kamiyama.

At least 91 records · Page 5Linked to original sources
PubMed1994

Tetrafibricin, a novel non-peptide fibrinogen receptor antagonist, induces conformational changes in glycoprotein IIb/IIIa.

Arg-Gly-Asp (RGD) is an amino acid sequence in fibrinogen recognized by platelet glycoprotein (GP) IIb/IIIa. Recently, it was found that RGD peptide binding to GPIIb/IIIa leads to conformational changes in the complex that are associated with the acquisition of high-affinity fibrinogen-binding function. In this study, we found that tetrafibricin, a novel non-peptidic GPIIb/IIIa antagonist, induced similar conformational changes in GPIIb/IIIa as did RGD peptides. Tetrafibricin increased the binding of purified inactive GPIIb/IIIa to immobilized pl-80, a monoclonal antibody that preferentially recognizes ligand-occupied GPIIb/IIIa. Exposure of the pl-80 epitope by tetrafibricin was also observed on resting human platelets by flow cytometry. On intact platelets, the conformational changes transformed GPIIb/IIIa into a high-affinity receptor for fibrinogen and triggered subsequent platelet aggregation. Tetrafibricin is the first non-peptidic GPIIb/IIIa antagonist reported that has the capacity to induce conformational changes in GPIIb/IIIa.

Amino Acid Sequence↗
PubMed1994

Cyclothialidine, a novel DNA gyrase inhibitor. II. Isolation, characterization and structure elucidation.

Cyclothialidine is a novel DNA gyrase inhibitor produced by Streptomyces filipinensis NR 0484. It was isolated from the culture broth by charcoal adsorption, Diaion HP-21, Amberlite CG-50, DEAE Toyopearl, and Toyopearl HW-40 SF column chromatography. The structure of cyclothialidine was determined to be a unique twelve membered lactone by amino acid analysis and various 2D-NMR experiments. Cyclothialidine inhibited Escherichia coli DNA gyrase with an IC50 of 30 ng/ml.

Amino Acid Sequence↗
PubMed1994

Bacithrocins A, B and C, novel thrombin inhibitors.

Novel thrombin inhibitors, bacithrocins A, B and C, have been isolated from the culture broth of Bacillus laterosporus Laubach NR 2988. The structures of these inhibitors have been determined to be N-acyl-L-phenylalanyl-DL-arginal by the 2D-NMR experiments on their oxidation products and by amino acid analysis. Bacithrocin A inhibits thrombin, factor Xa and trypsin with IC50s of 48, 13 and 0.65 microM, respectively, which are similar to those of bacithrocins B and C. Bacithrocins prolong the clotting time induced by thrombin and factor Xa.

Amino Acid Sequence↗
PubMed1994

[Efficacy of transarterial embolization combined with percutaneous ethanol injection therapy for recurrent hepatocellular carcinoma].

One hundred and eighty-nine patients with hepatocellular carcinoma (HCC) underwent hepatectomy since 1987 to 1992 in our institute. Recurrences were detected on residual liver in 84 patients up to December 1993. Sixty-seven of 84 patients were treated with re-resection (group-O, n = 11), transarterial embolization (TAE) combined with percutaneous ethanol injection therapy (PEIT) (group-TP, n = 13), TAE alone (group-T, n = 34) and intraarterial chemotherapy (group-IA, n = 9). Among these 67 cases, the efficacy of treatment for recurrences was investigated. There was no significant difference in age, positive ratio of hepatitis B virus, ICG R15 and percentage of underlying liver cirrhosis among the 4 groups. However, the frequency of patients with 2 nodules or less, was significantly higher in group-O than in other groups. Cumulative 1-, 2- and 3-year survival rates (%) were 88.9, 64.8 and 51.9 in group-O, 92.1, 55.4 and 55.4 in group-TP, 70.9, 49.6 and 31.0 in group-T, and 16.9, 0 and 0 in group-IA, respectively. The survival rate after recurrences in group-TP was higher than in group-IA and group-T, and almost equivalent to that of group-O. Either re-resection or TAE combined with PEIT might assure- a favorable prognosis in patients with recurrent HCC.

Carcinoma, Hepatocellular↗
PubMed1994

[Efficacy of benzimidazole-type drugs on alveolar echinococcosis (AE)].

AE patients can be cured only by complete excision of the lesions. In Europe and the United States, however, benzimidazole-type drugs have been reported to be effective. We treated 37 patients (20 males and 17 females, mean age of 45.9 years) with mebendazole (MBZ) (n = 17) or albendazole (ABZ) (n = 20) according to the WHO chemotherapy protocol, and compared adverse reactions, drug concentrations, serological parameters, and measurable lesions by CT scan and/or X-ray examination. In the MBZ group, serological parameters were unaffected. One patient each had hepatic disorder and alopecia (12%), and 5 lesions in the liver and 3 in the lung gradually increased in size (105% in 1 year, 112% in 2 years), and showed NC (no response) in 6, PD (progressive disease) in 2. One case of released biliary obstruction were judged as PR (partial response) (Response rate: 11.1%). In the ABZ group, no adverse reactions were found and ELISA level decreased significantly in 10 out of 12 patients. One lesion in the liver, 3 in the lung, 1 in the chest wall and 1 in the retropancreatic region reduced in size significantly (Mean: 56%) (PR 3, NC 3; Response rate: 50.0%). ABZ was safer and more effective than MBZ.

Adult↗
PubMed1993

Tetrafibricin: a nonpeptidic fibrinogen receptor inhibitor from Streptomyces neyagawaensis (I). Its GPIIb/IIIa blockage on solid phase binding assay.

Tetrafibricin is a novel nonpeptidic fibrinogen receptor inhibitor isolated from Streptomyces neyagawaensis NR0577. Its competitive and selective fibrinogen receptor blockage was demonstrated in this study. Tetrafibricin competitively inhibited (Ki = 9.9 nM) the binding of biotinylated fibrinogen to purified active glycoprotein (GP) IIb/IIIa immobilized on plastic plate. When RGDS and tetrafibricin were added in combination, the inhibition was additive. The binding of other RGD-containing proteins, fibronectin and von Willebrand factor, to active GPIIb/IIIa were also completely inhibited by tetrafibricin. The fact that tetrafibricin did not inhibit the binding of von Willebrand factor to GPIb/IX indicates the specific blockage of tetrafibricin for GPIIb/IIIa. Fibrinogen receptor inhibition of tetrafibricin was also confirmed by its ability to inhibit 125I-fibrinogen binding to platelets stimulated with ADP. Because of its competitiveness and specificity, tetrafibricin can be used in a new structural model for the design of fibrinogen receptor inhibitors.

Adenosine Diphosphate↗
PubMed1993

Tetrafibricin: a nonpeptidic fibrinogen receptor inhibitor from Streptomyces neyagawaensis. (II). Its antiplatelet activities.

Tetrafibricin; a nonpeptidic fibrinogen inhibitor from microbial origin, showed potent antiaggregation activities on human platelet aggregation induced by either ADP, thrombin or collagen (IC50s = 5.6, 7.6 and 11 microM, respectively) in platelet rich plasma. The ability to inhibit aggregation in platelets treated with chymotrypsin confirmed the GPIIb/IIIa blockage of tetrafibricin. Tetrafibricin blocked the release of serotonin induced by ADP but it did not block the release reaction induced by thrombin. When added to platelets formerly aggregated with ADP, tetrafibricin caused rapid and complete deaggregation. As for the selectivity among other Arg-Gly-Asp -dependent integrins, tetrafibricin seems to be more specific for glycoprotein (GP) IIb/IIIa than RGDS is. This is because it had no effect on adhesion of bovine aortic endothelial cells to RGD-containing proteins. Tetrafibricin is the first nonpeptidic fibrinogen receptor inhibitor that may be valuable for the study on platelet aggregation inhibitors.

Adenosine Diphosphate↗
PubMed1993

Role of lipid peroxidation in acetaminophen-induced hepatotoxicity: comparison with carbon tetrachloride.

The effect of acetaminophen on lipid peroxidation in vivo and in vitro was studied in rat liver and the data were compared with those with carbon tetrachloride. Carbon tetrachloride increased diene conjugates in vivo and thiobarbituric acid reactive substance production in vitro in the liver microsomal incubation. These changes were further enhanced by ethanol that has previously been shown to increase carbon tetrachloride-induced hepatotoxicity. On the other hand, acetaminophen did not increase diene conjugates in vivo and inhibited thiobarbituric acid reactive substance production in vitro. These effects were minimally affected by ethanol which has previously been shown to inhibit acetaminophen-induced hepatotoxicity. Thus, lipid peroxidation may play a minimal role in acetaminophen-induced hepatotoxicity in contrast with carbon tetrachloride-induced hepatotoxicity.

Acetaminophen↗
PubMed1993

Establishment of a human small cell lung carcinoma cell line carrying amplification of c-myc gene and chromosomal translocation of t(3p;6p) and t(12q;17p).

A transplantable tumor and an in vitro culture cell line (GK-T3) were established from metastatic liver tissue of human small cell lung carcinoma (SCLC). Southern blot analysis revealed about 30-fold amplification of c-myc gene in the tumor cells in liver, xenografts, and in vitro cell line. The degree of c-myc amplification was essentially conserved through serial passages in nude mice and cultivation in vitro. The level of c-myc mRNA was significantly increased in these cells. Cytogenetically, numerical and complex structural abnormalities were observed in GK-T3 cells, including t(3p;6p), t(12q;17p), two homogeneously staining regions (hsrs) and several double minutes (dmins). These results suggest that activation of c-myc gene and alteration of gene(s) around these chromosomal breakpoints may play a role in tumorigenesis of GK-T3 SCLC.

Aged↗
PubMed1993

B-raf oncogene: activation by rearrangements and assignment to human chromosome 7.

cDNA clones presumably containing a transforming gene were isolated from transformed NIH3T3 cells, which were obtained by the transfection of DNA from peripheral blood lymphocytes of a familial adenomatous polyposis patient. Sequence analysis of the cDNA clones showed that the gene contained an activated B-raf, the 5' half of which was replaced by the human small nuclear ribonucleoprotein E protein gene and an unknown gene. A partial genomic physical map of the transforming gene was made on the basis of the physical map of the cDNA clones, indicating that rearrangements had occurred during the transfection. The human B-raf gene was shown to be located on chromosome 7 by Southern blotting analysis of rodent-human somatic cell hybrid DNA using the B-raf cDNA as a probe.

3T3 Cells↗
PubMed1993

Biological characterization of cyclothialidine, a new DNA gyrase inhibitor.

Cyclothialidine is a new DNA gyrase inhibitor isolated from Streptomyces filipinensis NR0484. Structurally, it belongs to a new class of natural products containing a unique 12-membered lactone ring that is partly integrated into a pentapeptide chain. Cyclothialidine was found to be one of the most active of all the DNA gyrase inhibitors tested in the DNA supercoiling reaction of Escherichia coli DNA gyrase; 50% inhibitory concentrations (in micrograms per milliliter) of 0.03 (cyclothialidine), 0.06 (novobiocin), 0.06 (coumermycin A1), 0.66 (norfloxacin), 0.88 (ciprofloxacin), and 26 (nalidixic acid) were found. In addition, DNA gyrases from gram-positive species were inhibited equally as well as DNA gyrase from E. coli. Cyclothialidine also inhibited the in vitro DNA replication directed from oriC of E. coli. Among the bacterial species tested, only Eubacterium spp. were inhibited by cyclothialidine, suggesting that it can enter the cells of Eubacterium and exert antibacterial activity through interference with the DNA gyrase within the cells, although its penetration into most bacterial cells appears to be poor. These results provide a basis for cyclothialidine to be a lead structure for novel antibacterial agents with DNA gyrase inhibitory activities.

Animals↗
PubMed1993

Carbamazepine-induced hyponatremia in a patient with partial central diabetes insipidus.

A 51-year-old Japanese man was referred for the evaluation of persistent hyponatremia. The serum sodium level remained around 120 mmol/l despite mild water restriction. His past history included chronic alcoholism, myocardial infarction and lumbar disc herniation. Carbamazepine (200 mg, b.i.d.) has been used for more than 8 years for low back pain. Serum sodium returned to normal after carbamazepine was stopped, and rechallenge produced acute symptomatic hyponatremia (117 mmol/l) on day 2 after a total dose of 600 mg. Hepatic, renal and endocrine function were within normal limits, and the response to a water load (20 ml/kg) was also normal. Partial central diabetes insipidus was diagnosed by his response to water restriction and nasal desmopressin administration. Polyuria and hypernatremia were not evident in this case, probably due to a combination of low solute intake and low, but not deficient, levels of plasma ADH. This case demonstrates that carbamazepine may cause acute hyponatremia even in central diabetes insipidus, probably by sensitizing the distal renal tubules.

Carbamazepine↗
PubMed1993

Tetrafibricin, a novel fibrinogen receptor antagonist. I. Taxonomy, fermentation, isolation, characterization and biological activities.

Tetrafibricin is a novel fibrinogen receptor antagonist produced by Streptomyces neyagawaensis NR0577. It was isolated from the culture broth by Diaion HP-21 adsorption, MeOH extraction, MCI GEL CHP-20P column chromatography, preparative HPLC and Toyopearl HW-40 SF column chromatography. The physico-chemical properties of tetrafibricin indicated that the structure of tetrafibricin is different from the known peptide fibrinogen receptor antagonists and closely related to the polyene macrolide antibiotics. Tetrafibricin strongly inhibited the binding of fibrinogen to its receptors with an IC50 of 46 nM. It also inhibited ADP-, collagen-, and thrombin-induced aggregation of human platelets with IC50s of 5.6, 11.0 and 7.6 microM, respectively.

Anti-Bacterial Agents↗