Search PubMed⌕ Search

Biomedical subjects

H Hashimoto

Publications and source records attributed to H Hashimoto.

At least 613 records · Page 34Linked to original sources
PubMed1995

Mutagenic activity of topoisomerase I inhibitors

Topoisomerase I-directed agents are now in Phase I and II clinical trials and show great promise as potentially important agents for cancer chemotherapy. Because of their mechanism of action they may also be potential mutagens; however, their mutagenicity and oncogenicity still remain to be elucidated. We have previously shown that VP-16, a topoisomerase II-directed agent, induces sister chromatid exchanges and gene deletions and/or rearrangements in vitro. These observations may account for both the cytotoxic effects of topoisomerase II-directed agents as well as their recently reported leukemonogenic potential. To evaluate the potential mutagenicity of topoisomerase I-directed drugs, we measured mutant frequencies at the hypoxanthine phosphoribosyl transferase locus of the V79 Chinese hamster fibroblast cell line treated with the topoisomerase I-directed drugs camptothecin and topotecan, and compared these results with mutant frequency obtained with the topoisomerase II-directed drug VP-16 and an alkylating agent, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). All of these drugs showed a dose-dependent increase in mutant frequency at the hypoxanthine phosphoribosyl transferase locus. At a dose producing approximately 30% survival, VP-16, camptothecin, and topotecan induced mutant frequencies of 11.3 x 10(-6), 4.9 x 10(-6), and 2.7 x 10(-6), respectively, whereas the spontaneous mutant frequency at this locus was 0.3 x 10(-6). In contrast, the alkylating agent MNNG produced a mutant frequency of 562 x 10(-6) at 26% survival dose. The molar mutagenic potencies, expressed as mutant frequency/mol-h exposure, for VP-16, camptothecin, topotecan, and MNNG at approximately 30% survival dose were 0.9, 8.2, 2.3, and 56.8, respectively. On Southern blot analysis after EcoRI, PstI, or HindIII digestion, 6 of 12 independent thioguanine-resistant mutants induced by topotecan showed gene deletions or rearrangements. In contrast, five of five independent spontaneous mutants and six of six independent mutants induced by MNNG demonstrated the same restriction pattern as the parental V79 cells. These results indicate that the mutant frequency and the mutagenic potential of topoisomerase I and II active agents are quantitatively similar. The results further demonstrate that topoisomerase I and II active agents introduce mutations characterized by gene deletions and rearrangements, whereas spontaneous mutations and those induced by alkylating agents appeared to be more characteristically associated with point mutations. Thus, clinical use of the topoisomerase I and II active agents is expected to cause similar mutagenic effects that could potentially lead to secondary malignancies.

Journal Article↗
PubMed1994

Molecular cloning and functional expression of a mouse cytochrome P-450 (Cyp3a-13): examination of Cyp3a-13 enzyme to activate aflatoxin B1 (AFB1).

A cDNA encoding a novel member of the cytochrome P-450 superfamily, Cyp3a-13, has been isolated from mouse liver cDNA library by hybridization screening. The Cyp3a-13 encoded 503 amino acid residues and shared 71% amino acid identity with Cyp3a-11. When Cyp3a-13 cDNA was expressed in CR119 cells which had been established as a cell line stably expressing NADPH-cytochrome P-450 reductase cDNA of guinea pigs, aflatoxin B1-dependent cytotoxicity was observed. This cytotoxicity was enhanced by alpha-naphthoflavone (7,8-benzoflavone), which is known to augment the CYP3A enzymatic activity. The results indicate that CYP3A in mice, which are relatively insensitive to aflatoxin B1, can activate aflatoxin B1 to a genotoxic product.

Aflatoxin B1↗
PubMed1994

A novel form of mouse cytochrome P450 3A (Cyp3a-16). Its cDNA cloning and expression in fetal liver.

A complementary DNA clone coding for a novel form of cytochrome P450, Cyp3a-16, in mouse fetal livers was isolated and completely sequenced. This clone encoded a polypeptide of 504 deduced amino acids and showed 87.3% and 66.6% amino acid identities with mouse Cyp3a-11 and Cyp3a-13, respectively. Cyp3a-16 transcript was detectable before birth and remarkably diminished five weeks after birth in mice. We conclude that Cyp3a-16 is a fetal- and puberty-specific cytochrome P450 in mice.

Amino Acid Sequence↗
PubMed1994

Transglucosylation with 6'-chloro-6'-deoxysucrose and immobilized isomaltulose-producing microorganisms using 2,2-dimethyl-1,3-dioxolane-4-methanol and its related compounds as acceptors. Steric and chemical requirement of the glucosyl acceptor.

Enantioselective and diastereoselective alpha-D-glucosylation of 2,3-O-isopropylidene-erythritol was observed in transglucosylation with a synthetic donor using three kinds of immobilized isomaltulose-producing microorganisms. Several related compounds, including an 2,3-O-isopropylidenated aldotetrose dimethyl dithioacetal and an aldotetronic acid ester were also glucosylated in moderate or good yield, depending on the microorganism utilized. Steric as well as functional group factors are discussed in relation to the substrate specificity of the glucosyl acceptor.

Carbohydrate Conformation↗
PubMed1994

Cerulenin-resistant mutants of Saccharomyces cerevisiae with an altered fatty acid synthase gene.

Cerulenin, an antifungal antibiotic produced by Cephalosporium caerulens, is a potent inhibitor of fatty acid synthase in various organisms, including Saccharomyces cerevisiae. The antibiotic inhibits the enzyme by binding covalently to the active center cysteine of the condensing enzyme domain. We isolated 12 cerulenin-resistant mutants of S. cerevisiae following treatment with ethyl methanesulfonate. The mechanism of cerulenin resistance in one of the mutants, KNCR-1, was studied. Growth of the mutant was over 20 times more resistant to cerulenin than that of the wild-type strain. Tetrad analysis suggested that all mutants mapped at the same locus, FAS2, the gene encoding the alpha subunit of the fatty acid synthase. The isolated fatty acid synthase, purified from the mutant KNCR-1, was highly resistant to cerulenin. The cerulenin concentration causing 50% inhibition (IC50) of the enzyme activity was measured to be 400 microM, whereas the IC50 value was 15 microM for the enzyme isolated from the wild-type strain, indicating a 30-fold increase in resistance to cerulenin. The FAS2 gene was cloned from the mutant. Sequence replacement experiments suggested that an 0.8 kb EcoRV-HindIII fragment closely correlated with cerulenin resistance. Sequence analysis of this region revealed that the GGT codon encoding Gly-1257 of the FAS2 gene was altered to AGT in the mutant, resulting in the codon for Ser. Furthermore, a recombinant FAS2 gene, in which the 0.8 Kb EcoRV-HindIII fragment of the wild-type FAS2 gene was replaced with the same region from the mutant, when introduced into FAS2-defective S. cerevisiae complemented the FAS2 phenotype and showed cerulenin resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Identification and characterization of parathyroid hormone/parathyroid hormone-related peptide receptor in cultured astrocytes.

Parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor expressed in rat cultured cortical type I astrocytes was identified and characterized. Northern blot analysis demonstrated that the PTH/PTHrP receptor mRNA is expressed in astrocytes. A human PTH fragment, PTH [1-34], stimulated adenylate cyclase with the EC50 value of 3 nM, but not phospholipase C. PTH [1-34] changed the morphology of protoplasmic type astrocytes into process-bearing ones. Thus, type I astrocytes possess PTH/PTHrP receptor that is coupled to an adenylate cyclase-activating system but not to phospholipase C.

Adenylyl Cyclases↗
PubMed1994

Cultured rat astrocytes possess Na(+)-Ca2+ exchanger.

Na(+)-Ca2+ exchange activity in its reverse mode was demonstrated in cultured rat astrocytes. Combination of ouabain (1 mM) and monensin (20 microM) caused a marked increase in 45Ca2+ uptake in astrocytes. 45Ca2+ uptake was also stimulated by lowering the external Na+ concentration. Ouabain plus monensin-stimulated 45Ca2+ uptake was blocked by 3,4-dichlorobenzamil (IC50, 16 microM), an inhibitor of Na(+)-Ca2+ exchanger, but not by nifedipine (0.1 microM). The stimulated-45Ca2+ uptake was observed even in K(+)-free medium, and external K+ at 5-10 mM caused a 2.2-fold increase in the uptake. Microspectrofluorimetry using the Ca(2+)-sensitive dye fura-2 showed that ouabain plus monensin increased intracellular Ca2+ concentration in single astrocytes. The Ca2+ signal was dependent on external Ca2+ (EC50, 1.4 mM), and blocked by 20 microM 3,4-dichlorobenzamil, but not by Ca2+ channel blockers (Cd2+, 20 microM; Ni2+, 100 microM). Antiserum of cardiac Na(+)-Ca2+ exchanger recognized 160 and 120-135 kDa proteins on SDS-polyacrylamide gel electrophoresis of astrocyte homogenate. Northern blot analysis revealed the presence of mRNA for the exchanger protein in astrocytes. These findings indicate that Na(+)-Ca2+ exchanger which is modulated by K+ is present in cultured rat astrocytes.

Amiloride↗
PubMed1994

Unique T cell differentiation markers: gangliosides with cholera toxin receptor activity on murine fetal thymocytes.

Cholera toxin B subunit receptors (CTBR; gangliosides GM1a and GM1b-GalNAc-Gal) and GM1b-type gangliosides were examined during T cell development in BALB/c mice by FACS or TLC immunostaining. Sixty-two percent of CD4-8- early fetal thymocytes express CTBR [58% low affinity (GM1a+), 4% high affinity (GM1a2+)] at 13 days gestation (Day 13); GM1a2+ was expressed preferentially on Thy-1+ fetal thymocytes after Day 13. GM1a2+ Thy-1+ cells increased from 4% on Day 13 to 95% on Day 17. Surface GM1a2+ decreased beginning on Day 15 while GM1b-GalNAc-Gal (and CD4 and CD8) increased. GM1b-type+ cells increased from 8% on Day 13 to 51% on Day 17 and then decreased to 16% at 4 weeks; few asialo GM1+ cells (< 5%) are seen during gestation. Thus, synthesis of GM1a- and GM1b-type series was active until Days 15 and 17, respectively, and then was suppressed; GM1b-GalNAc-Gal was synthesized from GM1b following Gestational Day 15. GM1a- and GM1b-type identify immature T cells in mice, while GM1b-GalNAc-Gal identifies mature T cells.

Animals↗
PubMed1994

Functional and morphological effects of tumour necrosis factor alpha in an interleukin 6-producing pulmonary large cell carcinoma with sarcomatoid features.

We established a clonal cell line, HAT.MC8, derived from a human pulmonary large cell carcinoma with sarcomatoid features. This cell line was successfully maintained in a protein-free medium and exhibited sarcomatoid fibroblastic features in vitro. The cells constitutively produced a large amount of interleukin 6 (IL-6) in vitro. Tumour necrosis factor alpha (TNF-alpha) not only stimulated HAT.MC8 cells to produce IL-6, but also induced a morphological change from sarcomatoid fibroblastic to epithelial features. Although this change was related to actin and zonula adherens, there was no evidence that E-cadherin participated in the change. Interleukin 1 beta (IL-1 beta) had a stimulatory effect on IL-6 production by HAT.MC8 cells, but no influence on the morphology of the cells.

Carcinoma, Non-Small-Cell Lung↗
PubMed1994

Tunicamycin inhibits prostaglandin F2 alpha receptor-mediated phosphoinositide hydrolysis in cultured rat astrocytes.

Effect of tunicamycin, an inhibitor of N-linked glycosylation, on prostaglandin (PG) F2 alpha-stimulated phosphoinositide (PI) hydrolysis was examined in cultured rat astrocytes. Pretreatment of cultured astrocytes with tunicamycin (25-250 ng/ml) inhibited subsequent PGF2 alpha (1 microM)-stimulated PI-hydrolysis in concentration- and time-dependent manners. The inhibition completely recovered after removal of tunicamycin and re-incubation for 12 h. Tunicamycin pretreatment (100 ng/ml for 12 h) significantly blocked [35S]methionine incorporation into cultured astrocytes, but cell viability was not affected under the condition. Inhibitors of processing of N-linked sugar chains such as bromoconduritol, 1-deoxymannojirimycin, and swainsonine had no effect on PI response to PGF2 alpha. These observations suggest that PGF2 alpha receptor is N-linked glycosylated.

Animals↗
PubMed1994

Klinefelter's syndrome and rheumatoid arthritis. Report of a case and review of the literature.

Our case report describes a patient with Klinefelter's syndrome (KFS) associated with rheumatoid arthritis (RA). He had active RA in 1985 but his arthritis almost subsided in 1993 without intensive treatments for RA as well as KFS. Recently, the lower levels of testosterone in male RA patients, especially at the active phase has been reported. However, it is still questionable whether hypogonadism is a predisposing factor or just a consequence of disease. Since our case had a mild clinical course, and since the incidence of RA associated with KFS is very rare in comparison with other rheumatic diseases, may suggest that the low levels of testosterone are not a predisposing factor to the activity of RA.

Adult↗
PubMed1994

Angiographic follow-up after successful percutaneous coronary angioplasty for chronic total coronary occlusion: experience in 110 consecutive patients.

Percutaneous transluminal coronary angioplasty (PTCA) was performed in 110 consecutive patients (111 vessels) with chronically occluded coronary arteries and was successful in 69 patients (69 vessels). Successful initial PTCA was related to the extent of coronary artery disease, the morphology of the proximal surface of the occlusion site, and the clinical duration of occlusion. Repeat angiography was performed for 62 patients, with successful initial PTCA and demonstrated restenosis in 34 (55%) patients, of whom 11 had total occlusion. Repeat PTCA was performed in 30 patients and was successful in 80%. Follow-up angiography after repeat PTCA was carried out in all patients who underwent successful second PTCA, and, it demonstrated re-restenosis in 7 (29%) patients. In this study, among 111 total occlusions, 28 vessels undergoing successful initial PTCA and 17 undergoing successful repeat PTCA were free from restenosis or re-restenosis at the time of follow-up angiography.

Adult↗
PubMed1994

Effects of alcohol on lipoprotein lipase, hepatic lipase, cholesteryl ester transfer protein, and lecithin:cholesterol acyltransferase in high-density lipoprotein cholesterol elevation.

The mechanism whereby alcohol increases high-density lipoprotein cholesterol (HDL-C) levels is unclear. Lipoprotein lipase (LPL), hepatic lipase (HL), cholesteryl ester transfer protein (CETP) and lecithin:cholesterol acyltransferase (LCAT) act on lipoprotein metabolism. The purpose of the present study is to determine which one or what combination of these factors is responsible for the rise in HDL-C levels following alcohol ingestion. After 3 weeks of abstinence, 12 men consumed 0.5 g/kg bw of alcohol per day for 4 weeks; 13 abstaining men served as controls. Mean plasma total cholesterol (TC) levels were unchanged in either group throughout the study. Among the alcohol consumers, plasma triglycerides (TG), HDL-C, apolipoprotein (apo) A-I and A-II levels increased significantly after 3 weeks of alcohol loading but were unchanged in the control group. High-density lipoprotein3 cholesterol (HDL3-C) levels increased significantly in the alcohol consumers after 4 weeks of alcohol loading whereas high-density lipoprotein2 cholesterol (HDL2-C) levels were unaffected. In the controls, neither HDL2-C nor HDL3-C changed significantly. Post-heparin plasma (PHP) LPL activity and mass increased significantly (P < 0.01) after the alcohol ingestion (controls remained unchanged) without changing LPL specific activity. HL, CETP and LCAT activities were unaffected in both groups. We conclude that of the factors considered, LPL contributed the most to the alcohol-induced rise in HDL-C.

Adult↗
PubMed1994

Analysis of function of a human antigen-presenting cell by xenogeneic interaction with mouse T cells.

A human B cell line, ARH, was transfected with a murine major histocompatibility complex class II gene (I-A(k)). One of the transfectants, ARH5.5, which strongly expresses I-A(k) molecules was found to be capable of presenting soluble antigens to I-A(k)-restricted, antigen-specific murine helper T cell (Th) clones. When ARH5.5 was treated with either chloroquine or paraformaldehyde prior to the antigen pulse, it failed to present a protein antigen, ovalbumin, but retained the ability to present a peptide, indicating that the presentation was dependent on processing. The xenogeneic interaction of co-stimulatory molecules on the human antigen presenting cell (APC) and the murine Th cell was assessed by using antibodies against adhesion molecules. We found that the xenogeneic interaction of LFA-1/ICAM-1 acted as a strong co-stimulator of the antigen presentation by ARH5.5, while that of CD2/LFA-3 had only little stimulatory effect. These results suggest that the interaction between some of the adhesion molecules on APC and Th can cross the species barrier. The experimental system presented here is simple and useful for analyzing human APC function, separately from T cell function, especially when the dysfunction of APC associated with viral infection with human tropism is considered.

Amino Acid Sequence↗