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T Ohga

Publications and source records attributed to T Ohga.

27 records · Page 2Linked to original sources
PubMed1995

Chemosensitisation of spontaneous multidrug resistance by a 1,4-dihydropyridine analogue and verapamil in human glioma cell lines overexpressing MRP or MDR1.

Multidrug resistance phenotypes in human tumours are associated with the overexpression of the 170 kDa P-glycoprotein encoded by the multidrug resistance 1 (MDR1) gene, and also with that of the non-P-glycoprotein-mediated multidrug resistance gene, MRP, which encodes a 190 kDa membrane ATP-binding protein. We have previously reported that overexpression of MRP appears to be responsible for spontaneous multidrug resistance in some human glioma cell lines (Abe et al., Int. J. Cancer, 58, 860-864, 1994). In this study, we investigated whether chemosensitising agents of P-glycoprotein-mediated multidrug resistance such as verapamil, a biscoclaurine alkaloid (cepharanthine), and a dihydropyridine analogue (NIK250) could also reverse multidrug resistance in human glioma cells. The glioma cell lines were the two MRP-expressing cell lines, T98G and IN500, an MDR1-expressing cell line, CCF-STTG1, and the MRP1 MDR1-non-expressing cell line, IN157. Verapamil and NIK250 almost completely reversed drug resistance to vincristine, etoposide and doxorubicin in T98G cells, while they also reversed drug resistance to vincristine and etoposide, but only partially to doxorubicin in IN500 cells. Cepharanthine as well as verapamil and NIK250 reversed vincristine resistance in CCF-STTG1 cells, but cepharanthine only partially reversed drug resistance in T98G and IN500 cells. The cellular accumulation of [3H]etoposide increased about 2- and 3-fold compared with control in T98G cells in the presence of verapamil and NIK250 respectively. Furthermore, the release of doxorubicin from the nuclei of T98G cells was blocked by NIK250. However, NIK250 and verapamil caused no apparent increase in vincristine accumulation in T98G cells. NIK250 or verapamil might exert inhibitory effects upon MRP function, resulting in a reversal of MRP-mediated spontaneous multidrug resistance in cultured human glioma cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Isolation and characterization of chemotaxis mutants and genes of Pseudomonas aeruginosa.

Two chemotaxis-defective mutants of Pseudomonas aeruginosa, designated PC1 and PC2, were selected by the swarm plate method after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. These mutants were fully motile but incapable of swarming, suggesting that they had a defect in the intracellular signalling pathway. Computer-assisted capillary assays confirmed that they failed to show behavioral responses to chemical stimuli, including peptone, methyl thiocyanate, and phosphate. Two chemotaxis genes were cloned by phenotypic complementation of PC1 and PC2. From nucleotide sequence analysis, one gene was found to encode a putative polypeptide that was homologous to the enteric CheZ protein, while the other gene was cheY, which had been previously reported (M. N. Starnbach and S. Lory, Mol. Microbiol. 6:459-469, 1992). Deletion and complementation analysis showed that PC1 was a cheY mutant, whereas PC2 had a double mutation in the cheY and cheZ genes. A chromosomal cheZ mutant, constructed by inserting a kanamycin resistance gene cassette into the wild-type gene, changed its swimming direction much more frequently than did wild-type strain PAO1. In contrast, cheY mutants were found to rarely reverse their swimming directions.

Amino Acid Sequence↗
PubMed1993

Chemotaxis away from thiocyanic and isothiocyanic esters in Pseudomonas aeruginosa.

Negative chemotaxis, the movement of organisms away from chemicals, was investigated in Pseudomonas aeruginosa using a rapid videotape method. Digital image processing was used to detect changes in bacterial numbers near the mouth of a capillary containing a test chemical. P. aeruginosa was found to be repelled by thiocyanic and isothiocyanic esters including allyl isothiocyanate, ethyl thiocyanate, methyl isothiocyanate and methyl thiocyanate. Particularly, the movement of bacteria away from methyl thiocyanate was so drastic that bacterial numbers near the mouth of the capillary decreased by approximately 80% within 30 s after the start of observation. Mutant strains, fully motile but lacking positive chemotaxis, did not escape away from the esters, suggesting a common mechanism between positive and negative chemotaxes in this organism.

Chemotaxis↗
PubMed1992

Determination of free N-acetylamino acids in biological samples and N-terminal acetylamino acids of proteins.

N-Acetylamino acids were derivatized with 9-anthryldiazomethane to the corresponding esters. The anthryl esters were separated by high-performance liquid chromatography and detected fluorimetrically (excitation at 365 nm; fluorescence emission measured at 412 nm). N-Acetyl derivatives of Asn, Gln, Ser, Thr, Gly, Ala, Tyr, Pro, Met, Val, Ile and Leu as well as N-formyl-Met could be separated and identified in the same chromatographic run. The detection limit was from 0.10 pmol for AcGln to 5.5 pmol for AcIle and AcLeu. When the acetylamino acids listed above were added to the 700 g supernatant of a rat liver homogenate, the mean recovery was 72%. AcAla and AcTyr were found in free form in baker's yeast. Proteins with an acetylated N-terminus were digested by a protease, and the peptides formed were treated with an N-acylamino acid-releasing enzyme. This method was applied to end-group determination of four proteins (each 0.5 nmol).

Acetamides↗
PubMedDate not supplied

Spontaneous occurrence of vasculitis-like lesions in male reproductive tissues in mice: a histological study.

Vasculitis involving testes, epididymides, and vasa deferentia is considered to be a rare disease but has often been reported in man. In the present study, reproductive tissues of young and aged mice were examined to determine whether spontaneous vasculitis occurs in them. Testes, ductuli efferentes, epididymides, and vasa deferentia were obtained from young and aged BALB/c mice together with some nonreproductive organs for histological observation at the light microscopic level. The examination revealed that vasculitis-like lesions comparable to those in man were significantly present in the epididymides and vasa deferentia of aged but not young mice. However, no significant lesions were found in the testes and ductuli efferentes. Furthermore, other organs, such as salivary glands, thyroid glands, livers, pancreases, and kidneys, were also negative for the lesions. These results indicate that the epididymis and vas deferens are spontaneously apt to be affected by vasculitis-like lesions with advancing age, but that the lesions are not due to a systemic vasculitis disease.

Aging↗
PubMedDate not supplied

Preoperative therapy with insufficient effectiveness is related to unfavorable prognosis of patients with esophageal squamous cell carcinoma.

The disadvantage brought by the preoperative therapy with insufficient effectiveness for the patients with esophageal carcinoma has not been previously investigated. The aim of the current study was to show that the prognosis of patients with advanced esophageal carcinoma treated with preoperative therapy with insufficient effectiveness may be rather more unfavorable than that of patients without preoperative therapy. The subjects were 406 patients with esophageal squamous cell carcinomas of depth reaching to muscularis propria or adventitia but not to neighboring structures, who had been treated with esophagectomy and reconstruction. Although the proportions of lymphatic invasion and venous invasion in patients treated with preoperative therapy of insufficient effect were lower than those of patients without preoperative therapy, the 1-, 3- and 5-year survival rates in the former (62.2%, 32.0% and 23.1%, respectively) was significantly lower than in the latter (78.5%, 57.3% and 39.7%, respectively, p=0.01). A preoperative therapy with insufficient effectiveness may bring a more unfavorable prognosis of patients with esophageal squamous cell carcinoma.

Carcinoma, Squamous Cell↗