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G W Chen

Publications and source records attributed to G W Chen.

At least 19 recordsLinked to original sources
PubMed2004

Diallyl disulfide (DADS) induced apoptosis undergo caspase-3 activity in human bladder cancer T24 cells.

Diallyl disulfide (DADS), one of the major components of garlic (Allium sativum), is well known to have chemopreventative activity against human cancer such as colon, lung and skin. But the exact mechanism of the action is still unclear. In this study, we investigated how DADS--induced cell cycle arrest and apoptosis in T24 human bladder cancer cells in vitro. Apoptosis induction, cell viability, cell cycle arrest, caspases-3, -9 activity and gene expression were measured to determine their variation by flow cytometric assay, western blot, and determination of caspase-3 activity, PCR and cDNA microarray. There are significant differences in cell death (decreased viable cells then increased the amounts of apoptosis) of T24 cells that were detected between DADS (5-75 microM) treated and untreated groups. A significant increase was found in apoptosis induction when cells were treated with DADS (50 microM) compared to without DADS treated groups. DADS also promoted caspase-3 activity after exposure for 1, 3, 6, 12, and 24 h, which led to induce apoptosis. DADS also increased the product of intracellular hydrogen peroxide. Furthermore, the DADS-induced apoptosis on T24 cells was blocked by the broad-spectrum caspase inhibitor, z-VAD-fmk and antioxidant (catalase). DADS also increased cyclin E and decreased CDK2 gene expression which may lead to the G2/M arrest of T24 cells.

Allyl Compounds↗
PubMed2002

Effects of garlic components diallyl sulfide and diallyl disulfide on arylamine N-acetyltransferase activity and 2-aminofluorene-DNA adducts in human promyelocytic leukemia cells.

Two components of garlic, diallyl sulfide (DAS) and diallyl disulfide (DADS), inhibited arylamine N-acetyltransferase (NAT) activity and 2-aminofluorene-DNA adduct in human promyelocytic leukemia cells (HL-60). The NAT activity was measured by high performance liquid chromatography assaying for amounts of N-acetyl-2-aminofluorene (2-AAF) and remaining 2-aminofluorene (2-AF). Cellular cytosols and intact cell suspensions were assayed. The inhibition of NAT activity and 2-AF-DNA adduct formation in human leukemia cells by DAS and DADS were dose-dependent and were directly proportional. The data also indicated that DAS and DADS decrease the apparent values of Km and Vmax from human leukemia cells in both assays. This is the first report of garlic components affecting human leukemia cell NAT activity and 2-AF-DNA adduct formation.

Allyl Compounds↗
PubMed2001

Novel transmembrane GTPase of non-small cell lung cancer identified by mRNA differential display.

The technique of differential display was used previously to profile the gene expression patterns of non-small cell lung cancer, and several genes differentially expressed were thus identified. In this report, we demonstrate that a DNA fragment of 347-bp length, up-regulated in tumor tissues, showed 100% sequence similarity to human cDNA FLJ20693 for a 370-residue protein. The gene product of cDNA FLJ20693 was postulated to be a shorter isoform of transmembrane GTPase, termed TG370, based upon the results of searching for sequence homology. The nucleotide sequence alignment also indicated that the cDNA FLJ20693 and the cDNA for 741-residue human mitofusin 1 (TG741) possibly resulted from the event of alternative splicing from which a 127-bp region was retained in the latter. Analysis of the genome sequence confirmed the speculation that both cDNAs were mapped to the same chromosomal position composing of 18 exons, of which the 127-bp region of TG741 constituted exon 11. The alternative splicing in all lung cancer cell lines was also observed to occur nearly in all tissue specimens examined. The up-regulated expression of transmembrane GTPase was subsequently found in tumor tissues from at least five of seven non-small cell lung cancer patients. Also, a distinct PCR product was initially detected in cell line H520, and further sequence analysis identified the presence of the 86-bp region mapped to the genome sequence immediately followed by exon 10. To evaluate the retention of 86-bp region, it was found that, besides the predicted 486-bp product, an unexpected 332-bp product was concomitantly observed and identified as the result of exon 8 deletion. The expression and subcellular localization of the full-length TG741 and other shorter isoforms were detected by flow cytometry using three polyclonal antibodies. It was concluded that the full-length TG741 located at plasma membrane with its NH(2)-terminal domain exposed extracellularly and the shorter isoforms retained at cytosol. Finally, the up-regulation of transmembrane GTPase in tumor tissues was further illustrated using immunohistochemical staining.

Adenocarcinoma↗
PubMed2001

Luteolin inhibits the growth and arylamine N-acetyl-transferase activity in Neisseria gonorrhoeae.

Growth inhibition and arylamine N-acetyltransferase (NAT) activity in Neisseria gonorrhoeae were inhibited by luteolin, a drug which originated from herbs. The growth inhibition was based on changes in optical density (OD) using a spectrophotometer, and arylamine NAT activity with 2-aminofluorene (2-AF) was determined using high pressure liquid chromatography. The inhibition of growth in N. gonorrhoeae demonstrated that luteolin elicited a dose-dependent growth inhibition in the N. gonorrhoeae cultures. Suspensions of N. gonorrhoeae with or without specific concentrations of luteolin cotreatment showed different percentages of 2-AF acetylation. The data indicated that there was reduced NAT activity associated with increased levels of luteolin in N. gonorrhoeae suspensions. Time-course experiments showed that NAT activity measured from intact N. gonorrhoeae cells was inhibited by luteolin for at least 4 h. Using standard steady-state kinetic analysis, it was demonstrated that luteolin was a possible uncompetitive inhibitor to NAT activity in N. gonorrhoeae. This report is the first to show that luteolin can inhibit N. gonorrhoeae NAT activity.

Arylamine N-Acetyltransferase↗
PubMed2001

Amantadine-resistant influenza A virus in Taiwan.

BACKGROUND AND PURPOSE: Amantadine and rimantadine have been used for treatment and prophylaxis of influenza A virus infection. We examined the amantadine susceptibility of field isolates of influenza A virus in Taiwan from 1996 to 1998 to monitor the presence of resistant strains. METHODS: Eighty-four field isolates of influenza A virus were examined for resistance to amantadine by plaque inhibition assay. Virus isolates with amantadine 50% inhibitory concentrations (IC50) greater than 0.9 microgram were chosen for sequence analysis of the M gene that is the molecular target for amantadine/rimantadine. Reverse transcription-polymerase chain reaction (RT-PCR) was used to amplify the viral RNA. RT-PCR products were examined and purified by agarose gel electrophoresis for further sequence analysis. The Genetics Computer Group Sequence Analysis Package and the neighbor-joining method listed in the Molecular Evolutionary Genetic Analysis package were used for phylogenetic analysis. RESULTS: One field strain was amantadine resistant (IC50 > 10 micrograms/mL), with a mutation (position 31, serine to asparagine) in the M2 protein. The resistant virus was isolated from a non-immunocompromised child without a history of amantadine/rimantadine treatment. None of the family members reported previous exposure to amantadine/rimantadine. CONCLUSIONS: In this series, amantadine-resistant influenza A (H1N1) virus was isolated from a non-immunocompromised Taiwanese child without a known history of exposure to this drug. Resistant field isolates were rare. Due to the increasing use of amantadine/rimantadine in Taiwan, continued surveillance for amantadine/rimantadine-resistant influenza A viruses is warranted.

Amantadine↗
PubMed2001

[Clinical and experimental study on treatment of moderate and advanced malignant tumors with tianfoshen oral liquid].

OBJECTIVE: To investigate the clinical efficacy of Tianfoshen oral liquid (TFS) in treating moderate and advanced malignant tumors and its mechanism. METHODS: Therapeutic effect of TFS in treating 71 patients of malignant tumor was analyzed with the criteria, including quality of life, 3-year survival rate and immune function. And experimental studies of inhibitory effect on tumor clone primordial cells and tumor growth rate of TFS on human gastric tumor (MGC803) cell, human liver cancer (SMMC7721) cell and mice galactophore cancer (EMT6) cell by colony forming method and dye exclusion test respectively were also conducted. RESULTS: Clinical study showed that in the 71 cases treated, the total remission rate was 45.1%, the effective rate 71.8%, with improvement in quality of life and immune function, the 1-, 2- and 3-year survival rate being 78.5%, 38.5% and 10.8% respectively and the mean survival time 24.2 months. Experimental study showed that TFS could kill the cancer cells directly, inhibit the proliferation of single clonogenic cell, and had a broad-spectrum dose-dependent inhibitory action on various tumors with significant difference in comparing with the effects of the control (P < 0.05). CONCLUSION: TFS had obvious therapeutic effect to moderate and advanced tumors, its anti-tumor effect was related to the enhancement of immune function and tumor inhibiting or direct killing action.

Adult↗
PubMed2000

Syntheses and biological evaluation of new glyco-modified angucyclin-antibiotics.

The synthesis of novel aquayamycin-derived angucycline antibiotics 13a-d has been achieved. Glycosylation of aquayamycin (6) using 2-selenoglycosyl acetate 7 as glycosyl donor proceeded in excellent yield but attempts to reductively remove the selenyl group led to rearrangement or further aromatization of the aglycon. As a consequence of these results, it became possible to prepare urdamycinone B (10) starting from aquayamycin (6). In addition, silyl protected D-olivals 12a,b were attached to the C-glycoside domain of aquayamycin (6) under protic conditions. As expected, the hydroxy and phenol groups of the benz[a]anthracene framework of 6 did not react under the glycosylation conditions employed. Stepwise removal of the silyl protecting group starting with tetrabutyl ammonium fluoride followed by use of the HF/pyridine complex suppressed a possible rearrangement of the aglycon and successfully terminated the sequence. The new angucycline-antibiotics 13a and 13b are some of the most potent xanthine oxidase inhibitors known and show cytotoxic activity with ED50-values in the range of 12.6-2.9x 10(-6) M.

Animals↗
PubMed2000

Effects of berberine on arylamine N-acetyltransferase activity and 2-aminofluorene-DNA adduct formation in human leukemia cells.

Berberine is an alkaloid occurring in the plant genera Berberis and Coptis. Although berberine had been demonstrated to have antineoplastic function by inhibiting DNA-synthesis in activated lymphocytes, there is no available information to address berberine affects on human leukemia cell N-acetyltransferase (NAT) activity and 2-aminofluorene (AF)-DNA adduct formation. Thus, berberine was tested for inhibition of arylamine NAT activity and AF-DNA adduct formation in human leukemia cells. The NAT activity was measured by a high performance liquid chromatography assaying for the amounts of N-acetyl-2-aminofluorene (AAF) and N-acetyl-p-aminobenzoic acid (N-Ac-PABA) and the remaining AF and p-aminobenzoic acid (PABA). The NAT activity and AF-DNA adduct formation in human leukemia cells were inhibited by berberine in a dose-dependent manner, i.e. the higher the concentration of berberine, the higher the inhibition of NAT activity and AF-DNA adduct. The data also indicate that berberine decreased the apparent values of Km and Vmax from human leukemia cells in both cytosol and intact cells.

Antineoplastic Agents↗
PubMed2000

Effects of caffeic acid, chlorogenic acid and ferulic acid on growth and arylamine N-acetyltransferase activity in Shigella sonnei (group D).

Arylamine N-acetyltransferase (NAT) activities with 2-aminofluorene (2-AF) as substrates were determined in Shigella sonnei (group D) collected from patients with diarrhoeal disease. The NAT activity was determined using an acetyl CoA recycling assay and high pressure liquid chromatography. Inhibition of growth studies from S. sonnei (group D) demonstrated that caffeic acid (CA), chlorogenic acid (CGA) and ferulic acid (FA) elicited a dose-dependent bactericidal effect in S. sonnei (group D) cultures, i.e. the greater the concentration of CA, CGA and FA, the greater the inhibition of growth of S. sonnei (group D). Cytosols or suspensions of S. sonnei (group D) with and without selected concentrations of CA, CGA and FA co-treatment showed different percentages of 2-AF acetylation. The data indicated that there was reduced NAT activity associated with increased CA, CGA and FA in Shigella dysenteriae (group D) cytosols and intact cells. For the cytosol and intact bacteria examinations, the apparent values of K(m) and Vmax decreased after being co-treated with 400 microM CA, CGA and FA. This report is the first demonstration of plant phenolic inhibition (CA, CGA and FA) of arylamine NAT activity and growth in the bacterium S. sonnei (group D).

Arylamine N-Acetyltransferase↗
PubMed1999

Effects of berberine on arylamine N-acetyltransferase activity in human bladder tumour cells.

Berberine was used to determine inhibition of arylamine N-acetyltransferase (NAT) activity in human bladder tumour cells. The NAT activity was measured by HPLC assaying for the amounts of N-acetyl-2-aminofluorene (AAF) and N-acetyl-p-aminobenzoic acid (N-Ac-PABA) and remaining 2-aminofluorene (AF) and p-aminobenzoic acid (PABA). Two assay systems were performed, one with cellular cytosols, the other with intact bladder tumour cell suspensions. The NAT activity in human bladder tumour cells was inhibited by berberine in a dose-dependent manner, that is, the higher the concentration of berberine, the higher the inhibition of NAT activity. The values of apparent Km and Vmax calculated from cytosol NAT and intact cells were also decreased by berberine. This report is the first demonstration to show berberine did affect human bladder tumour cell NAT activity.

4-Aminobenzoic Acid↗
PubMed1999

Effects of berberine on arylamine N-acetyltransferase activity in human colon tumor cells.

Berberine was used to determine loss of viable cells and inhibition of arylamine Nacetyltransferase (NAT) activity in a human colon tumor (adenocarcinoma) cell line. The viable cells were determined by trypan blue exclusion under a light microscope. The NAT activity was measured by high performance liquid chromatography for the amounts of N-acetyl-2-aminofluorene (AAF), N-acetyl-p-aminobenzoic acid (N-Ac-PABA), and the remaining 2-aminofluorene (AF) and p-aminobenzoic acid (PABA). The viability and NAT activity in a human colon tumor cell line was inhibited by berberine in a dose-dependent manner, i.e., the higher the concentration of berberine, the higher the inhibition of NAT activity and cell death. The NAT activities measured in the intact human colon tumor cells were decreased over 50% by AAF and NAc-PABA production from acetylation of AF and PABA. The apparent values of Kmoff and Vmax of NAT from colon tumor cells were also inhibited by berberine in cytosols and in intact cells. This report is the first to show that berberine did affect human colon tumor cell NAT activity.

4-Aminobenzoic Acid↗
PubMed1999

Purification and characterization of an arylamine N-acetyltransferase from Lactobacillus acidophilus.

N-acetyltransferase from Lactobacillus acidophilus was purified by ultrafiltration, DEAE-Sephacel, gel filtration chromatography on Sephadex G-100, and DEAE-5pw on high performance liquid chromatography, as judged by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) on a 12% (w/v) slab gel. The purified enzyme was thermostable at 37 degrees C for 1 h with a half-life of 32 min at 37 degrees C, and displayed optimum activity at 37 degrees C and pH 7.0. The K(m) and Vmax values for 2-aminofluorene were 0.842 mM and 2.406 nmol/min/mg protein, respectively. Among a series of divalent cations and salts, Zn2+, Ca2+, Fe2+, Mg2+, and Cu2+ were demonstrated to be the most potent inhibitors. The enzyme had a molecular mass of 44.9 kD. The three chemical modification agents, iodoacetamide, phenylglyoxal, and diethylpyrocarbonate, all exhibited dose-, time-, and temperature-dependent inhibition effects. Preincubation of purified N-acetyltransferase with acetyl coenzyme A (AcCoA) provided significant protection against the inhibition of iodoacetamide and diethylpyrocarbonate, but only partial protection against the inhibition of phenylglyoxal. These results indicate that cysteine, histidine, and arginine residues are essential for this bacterial activity, and the first two are likely to reside on the AcCoA binding site, but the arginine residue may be located close to the AcCoA binding site. This report is the first demonstration of acetyl CoA:arylamine N-acetyltransferase in L. acidophilus.

Arylamine N-Acetyltransferase↗
PubMed1998

Effects of garlic compounds diallyl sulfide and diallyl disulfide on arylamine N-acetyltransferase activity in strains of Helicobacter pylori from peptic ulcer patients.

Arylamine N-acctyltransferase (NAT) activities with p-aminobenzoic acid (PABA) and 2-aminofluorene (2-AF) were determined in the bacterium Helicobacter pylori collected from peptic ulcer patients. Two assay systems were performed, one with cellular cytosols, the other with intact cell suspensions. Cytosols or suspensions of H. pylori with or without specific concentrations of diallyl sulfide (DAS) or diallyl disulfide (DADS) co-treatment showed different percentages of 2-AF and PABA acetylation. The data indicated that there was decreased NAT activity associated with increased levels of DAS or DADS in H. pylori cytosols and suspensions. Viability studies on H. pylori demonstrated that DAS or DADS elicited dose-dependent bactericide affects on H. pylori cultures. The data also indicated that DAS and DADS decreased the apparent values of K(m) and Vmax of NAT enzyme from H. pylori in both systems examined. This report is the first demonstration that garlic components can affect H. pylori growth and NAT activity.

Allyl Compounds↗
PubMed1998

Effects of aspirin on arylamine N-acetyltransferase activity in Klebsiella pneumoniae.

This study was designed to assess the effects of aspirin on arylamine N-acetyltransferase (NAT) activities in the bacterium Klebsiella pneumoniae using high performance liquid chromatography to measure the acetylation of 2-aminofluorene (2-AF) with or without aspirin. Cytosols or suspensions of K. pneumoniae with or without specific concentrations of aspirin co-treatment showed different percentages of 2-AF acetylation. The data indicated that there was decreased NAT activity associated with increased levels of aspirin in K. pneumoniae cytosols and in intact bacteria. For the cytosol examination, the apparent values of Km and Vmax decreased 0.59- and 0.58-fold after co-treated with 40 microM aspirin, respectively, for 2-AF. For the intact bacteria examination, the apparent values of Km and Vmax decreased 0.60- and 0.67-fold after co-treated with 40 microM aspirin, respectively, for 2-AF. This report is the first demonstration to show that aspirin can decrease N-acetyltransferase activity in the bacterium K. pneumoniae.

Acetylation↗
PubMed1997

Arylamine N-acetyltransferase activity in Staphylococcus aureus.

N-Acetyltransferase (NAT) activities were determined by incubation of Staphylococcus aureus cytosols with p-aminobenzoic acid (PABA) or 2-aminofluorene (2-AF) followed by high pressure liquid chromatography assays. The NAT activities from S. aureus were found to be 0.67 +/- 0.04 nmol/min/mg protein for the acetylation of 2-AF and 0.46 +/- 0.02 nmol/min/mg protein for the acetylation of PABA. The apparent K(m) and Vmax values obtained were 2.85 +/- 0.65 mM and 7.51 +/- 0.86 nmol/min/mg protein for 2-AF, and 2.35 +/- 0.39 mM and 9.43 +/- 0.78 nmol/min/mg protein for PABA, respectively. The optimal pH value for the enzyme activity was 7.0 for both substrates tested. The optimal temperature for enzyme activity was 37 degrees C for both substrates. The NAT activity was inhibited by iodoacetamide at 0.25 mM, and activity was reduced 50%. At 1.0 mM iodoacetamide activity was inhibited more than 90%. Among a series of divalent cations and salts, Zn2+, Ca2+, and Fe2+ were demonstrated to be the most potent inhibitors. The molecular weight of NAT from S. aureus was found to be 44.9 kDa. This report is the first demonstration of acetyl CoA: arylamine NAT activity in S. aureus.

Arylamine N-Acetyltransferase↗
PubMed1993

Secondary hyperalgesia is not affected by wound infiltration with bupivacaine.

The purpose of this study was to determine the effects of wound infiltration with bupivacaine on incisional pain and the zone of secondary hyperalgesia. Twenty-eight healthy parturients were studied in a double-blind randomized trial. At the time of Caesarean section one wound edge was infiltrated with saline 0.9% and the other with bupivacaine 0.25%. After 24 hr, visual analogue scores were obtained for incisional pain and the zone of secondary pain around the incision was measured. Patients served as their own controls. Visual analogue scores for the bupivacaine side of the wound were less than for the saline side (P < 0.05). The zone of secondary pain was similar overall for both sides of the wound. It is concluded that the bupivacaine-infiltrated side of the wound was less painful than the saline-injected side 24 hr postoperatively. The zone of pain measured around the wound edges was unaffected by bupivacaine or saline.

Adult↗
PubMed1993

[Effect of different preparation crafts on the content of baicalin in shuanghuanglian (SHL) injection].

The content of baicalin is stable when baicalin is added quantitatively in preparation. The time of extraction of the effective components of SHL with alcohol and the concentration of alcohol have little effect on the content of baicalin. The components can be extracted once, and the content of alcohol is preferably 85%. The pH level has greater influence on the content of baicalin, and should be controlled between 7.0 to 8.0. 0.2% activated carbon is suitable in preparation.

Charcoal↗