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W C Chang

Publications and source records attributed to W C Chang.

At least 127 records · Page 7Linked to original sources
PubMed1997

Evidence for arylamine N-acetyltransferase activity in the fungi Candida albicans.

N-acetyltransferase activities were determined in Candida albicans, which is a member of the normal flora of the mucous membranes in the respiratory, gastrointestinal and female genital tract. The N-acetylation of 2-aminofluorene and p-aminobenzoic acid by the N-acetyltransferase from Candida albicans was determined using high pressure liquid chromatography. The activities (mean +/- S.D.) of N-acetyltransferase from Candida albicans cytosols were 1.06 +/- 0.01 nmol/min per mg protein for the acetylation of 2-aminofluorene substrate, and not detectable levels of acetyl-p-aminobenzoic acid for the acetylation of p-aminobenzoic acid. The apparent kinetic constants Km and Vmax values were 0.17 +/- 0.06 mM and 1.43 +/- 0.42 nmol/min per mg protein, respectively, for 2-aminofluorene substrate. The optimum pH value for the enzyme activity was 8.0. The optimal temperature for the enzyme activity is 40 degrees C for 2-aminofluorene substrate. Among a series of divalent cations and salts, Fe2+, SCN-, I-, and NH4+ were demonstrated to be the most potent inhibitors. The N-acetyltransferase activity was inhibited by iodoacetamide: at 0.25 mM iodoacetamide, activity was reduced 50% and 1.0 mM iodoacetamide inhibited activity more than 90%. This is the first demonstration of acetyl CoA arylamine N-acetyltransferase activity in the yeast-like fungus Candida albicans.

4-Aminobenzoic Acid↗
PubMed1997

Transcriptional activation of human 12-lipoxygenase gene promoter is mediated through Sp1 consensus sites in A431 cells.

The functional 5' flanking region of the human 12-lipoxygenase in epidermoid carcinoma A431 cells was characterized. By a primer extension method, the transcription initiation sites were mapped at -47 adenosine, -48 guanosine and -55 guanosine upstream of the ATG translation start codon. Transient transfection with a series of 5' and 3' deletion constructs showed that the 5' flanking region spanning from -224 to -100 bp was important for the basal expression of 12-lipoxygenase gene. Gel mobility shift assays with antibodies of transcription factors showed that both Sp1 and Sp3 required highly GC-rich Sp1 sites within this region for binding. Disruption of two Sp1 recognition motifs residing at -158 to -150 bp and -123 to -114 bp by site-directed mutagenesis markedly reduced the basal 12-lipoxygenase promoter activity and abolished the retarded bands in a gel-shift assay, indicating that these two Sp1-binding sites were essential for gene expression. The same two Sp1-binding sites in this promoter region were also responsible for epidermal growth factor (EGF)-induced expression of 12-lipoxygenase gene. Moreover, EGF also induced the transcriptional activation of luciferase driven by SV40 early promoter, which contained rich Sp1-binding sites. Taken together, the results suggest that two specific Sp1 consensus sites are involved in the mediation of the basal promoter activity as well as EGF induction of the 12-lipoxygenase gene and that Sp1 and Sp3 transcription factors might have a role in their regulation.

Adenosine↗
PubMed1997

Human aldehyde dehydrogenase genes, ALDH7 and ALDH8: genomic organization and gene structure comparison.

The structure of two human aldehyde dehydrogenase genes, ALDH7 and ALDH8, have been determined. The ALDH7 gene spans about 20 kb of the human genomic DNA and is composed of 9 coding exons. The ALDH8 gene is over 10 kb in length and consists of at least 10 exons. The ALDH8 gene contains an in-frame stop codon at the 17th codon position from the first initiator Met. The coding region of the ALDH7 gene shows about 86% nucleotide identity with the corresponding region of the ALDH8 gene. The numbers and positions of the introns of the two genes are conserved, suggesting that gene duplication is involved in the expansion of the ALDH gene family. The human ALDH7 and -8 genes have a closer evolutionary relationship with the human ALDH3.

Aldehyde Dehydrogenase↗
PubMed1997

Overexpression of Ha-ras enhances the transcription of human arachidonate 12-lipoxygenase promoter in A431 cells.

The effect of transient transfection with expression vectors of Ha-ras on the promoter activity of 12-lipoxygenase in human epidermoid carcinoma A431 cells was studied. Overexpression of Ha-ras increased the promoter activity in a dose- and time-dependent manner, which correlated closely with the cellular expression of Ras protein. Promoters of different gene lengths for human 12-lipoxygenase were used to prepare the luciferase fusion vectors. Following transfection by Ha-ras for 68 h, an approx. 40-fold increase in luciferase reporter activity was observed in plasmids with the 5'-flanking region ranging from -951 to -224 bp upstream from translation starting site. There was no obvious stimulation in cells transfected with a vector-bearing promoter with a length of -100 bp. These results indicate that the promoter region ranging from -224 to -100 bp was important for the Ha-ras response. With the aid of additional 5'-deletion and site-directed mutagenesis, three Sp1 binding sequences residing at -169 to -161 bp, -158 to -150 bp and -123 to -114 bp were found to be critical for the Ha-ras response of activating the transcription of human 12-lipoxygenase gene.

Arachidonate 12-Lipoxygenase↗
PubMed1997

Epidermal growth factor enhances transcription of human arachidonate 12-lipoxygenase in A431 cells.

Epidermal growth factor (EGF), determined by immunoprecipitation and Western blot analysis, increased both enzyme activity and protein level of 12-lipoxygenase in the solubilized microsomes of human epidermoid carcinoma A431 cells, respectively. The EGF-induced expression of 12-lipoxygenase mRNA was inhibited by transcription inhibitors such as actinomycin D and 5,6-dichlorobenzimidazole riboside. Promoters of different lengths for human 12-lipoxygenase gene were used to prepare the luciferase fusion vectors. These construct plasmids were transiently transfected into A431 cells, and the induction of luciferase expression by EGF was examined. A 4- to 6-fold increase in luciferase reporter activity stimulated by EGF for 18 h treatment was observed in plasmids with the 5'-flanking region length of -951 bp and that of -224 bp upstream from translation starting site. The time-dependent induction of luciferase activity by EGF paralleled the EGF-induced enzyme activity and expression of 12-lipoxygenase protein. Taken together, the results of this study indicate that EGF enhanced the transcription of the human 12-lipoxygenase gene, resulting in an increase in the amount and activity of 12-lipoxygenase.

Arachidonate 12-Lipoxygenase↗
PubMed1997

The visible vessel on the bleeding gastric ulcer: an endoscopic-pathological study.

BACKGROUND AND STUDY AIMS: The visible vessel is an important endoscopic sign for predicting rebleeding in ulcers. Freeman has described a visible vessel with a high rate of rebleeding as a "pearl" color (whitish) compared with a darkly colored "sentinel" clot with a low rebleeding rate. Clarifying the color of visible vessels helps to distinguish high-risk bleeding ulcers. We conducted a retrospective study that compared pathological findings with endoscopic pictures to determine the significance of the visible vessel's color. PATIENTS AND METHODS: From January 1986 to December 1992, 110 patients who underwent endoscopy and received subtotal gastrectomies for ulcer bleeding were included in this study. Of these, 24 received endoscopic therapy before the operation. There were 94 males and 16 females, ranging in age from 30 to 90 years, with a mean age of 62.5 years. According to Freeman's report, a subgroup of visible vessels (IIav +) was defined as having either a "pearl-colored" collar around a red or black protruding mount or a "pearl-colored" mount on the ulcer base. The endoscopic findings were compared with the findings of the pathological specimens. RESULTS: The endoscopic findings on the stigmata of recent hemorrhage in the 110 patients revealed that 31 were of type IIa (including 18 type IIav+ and 13 type IIav-), 56 of type IIb, 18 of type IIc, and 5 of type III. Fifty-four patients (49,1%) were found from their pathological specimen to have an eroded vessel on their ulcer base. Type IIa patients had a higher percentage of eroded vessels. The percentages of eroded vessels in types IIa, IIb, IIc, and III were 67.7%, 46.4%, 33.3%, and 20 %, respectively (P < 0.05, Fisher's exact test). Of the 54 patients with an eroded vessel in their pathological specimen, 13 (24 %) were found to have some vessel wall above the ulcer base (six in type IIa, four in type IIb, two in type IIc, and one in type III). Among the six with vessel wall above the ulcer base in type IIa, five patients (83 %) were identified as type IIav+ under endoscopy. There was a greater frequency of having a vessel wall above the ulcer base in type IIav+ than in type IIav- (38.5% vs. 12.5%) among the 31 endoscopic type IIa patients. CONCLUSION: From this study, we determined that the wall of an eroded vessel on a gastric ulcer may protrude either above or below the ulcer base. A vessel wall on the ulcer base will appear pearl-colored under endoscopic view.

Female↗
PubMed1997

Relationship among colonocyte proliferation, differentiation, and apoptosis as a function of diet and carcinogen.

To determine the relationship among colonocyte proliferation, differentiation, and apoptosis as a function of fiber and carcinogen, we conducted a 2 x 2 factorial design study with two fibers (pectin or cellulose) and two injection protocols (azoxymethane or saline) in male Sprague-Dawley rats. Rats were killed six weeks after the injections, and in vivo cell proliferation was measured by incorporation of bromodeoxyuridine into DNA, differentiation by binding of the lectin Dolichos biflorus agglutinin, and apoptosis by immunoperoxidase detection of digoxigenin-labeled genomic DNA. In the proximal colon, pectin decreased differentiation and apoptosis, resulting in a greater number of cells per crypt column. In the distal colon, pectin increased cell proliferation, resulting in more crypts per millimeter of colon and a greater number of surface cells. Azoxymethane increased cell proliferation and decreased differentiation and apoptosis in the proximal and the distal colon. This resulted in a greater number of surface cells proximally and more crypts per millimeter of colon distally. These results illustrate the importance of considering all three parameters (proliferation, differentiation, and apoptosis) when evaluating neoplastic growth.

Animals↗
PubMed1997

Predictive value of proliferation, differentiation and apoptosis as intermediate markers for colon tumorigenesis.

In order to determine the prognostic significance of proliferation, differentiation, and apoptosis as intermediate markers for colon tumor development, these indices were measured during the promotion phase of tumorigenesis. Two hundred and sixty male Sprague-Dawley rats were provided with one of two fats (corn oil and fish oil) and two fibers (pectin and cellulose) plus or minus the carcinogen azoxymethane (AOM) and killed at two time points (18 and 36 wk) in a 2x2x2x2 factorial design. In vivo cell proliferation was measured immunohistochemically using incorporation of bromodeoxyuridine into DNA. Differentiation was assessed by binding of Dolichos biflorus agglutinin (DBA) to colonocytes. Apoptosis was measured by immunoperoxidase detection of digoxigenin-labeled genomic DNA. Adenocarcinoma incidence results at week 36 were 70.3% for corn oil + AOM and 56.1% for fish oil + AOM treatment (P < 0.05); no main effect of fiber was observed. At week 18, AOM treatment increased the number of cells per crypt column in the proximal colon compared with saline controls (P = 0.0358) and increased the proliferative zone in the distal colon compared with controls (P = 0.0073). However, changes in cell proliferation at week 18 did not predict the beneficial effect of fish oil versus corn oil. In contrast, DBA binding (the marker for differentiation) was higher in fish oil versus corn oil fed animals in both the proximal and distal colon and in each portion of the crypt (P = 0.0001). There were a greater number of apoptotic cells/crypt column in the proximal colon (P = 0.0019) and distal colon (P = 0.0358) with fish oil compared with corn oil, and indices of apoptosis also predicted certain fat/fiber interactions. Measurements of differentiation and apoptosis had greater prognostic value to detect dietary effects on tumor incidence than did measurements of cell proliferation.

Adenocarcinoma↗
PubMed1997

Obtaining clone-specific primer and probe for the immunoglobulin heavy-chain gene from paraffin-embedded tissue of B-cell lymphoma: technical considerations.

The complementarity determining region (CDR) III of the immunoglobulin heavy-chain (IgH) gene is a tumor-specific marker for B-cell malignancies that has been widely exploited for the monitoring of minimal residual disease in B-precursor acute lymphocytic leukemia. There are a number of technical problems in applying the same technology for B-cell non-Hodgkin's lymphoma (B-NHL). Several procedures have been useful in overcoming these unique problems encountered in obtaining the tumor-specific sequence of the IgH-CDRIII in B-NHL, including the use of denaturing gradient gel electrophoresis or micromanipulation of tissue sections in separating the tumor-specific CDRIII products from those of contaminating normal B-lymphocytes. Minor modifications of a commercial kit greatly improve the purity of the polymerase chain reaction (PCR) products for sequencing. Modifications of the 5'-ends of the VH and IH primers, coupled with the cycle sequencing technique, make it possible to obtain unambiguous sequences on direct sequencing of short PCR products. Computer informatics and programs that facilitate the design of tumor-specific primers and probes from CDRIII sequences are described.

DNA Primers↗
PubMed1997

Experimental study of steady and pulsatile flows in cerebral aneurysm model of various sizes at branching site.

Pulsatile and steady flow fields in cerebrovascular aneurysm models of various sizes are presented in terms of laser-Doppler velocimetry measurements and flow visualization. The bifurcation angle was 140 deg and volume flow rate ratio between the branches was 3:1. The mean, peak, and minimal Reynolds numbers based on the bulk average velocity and diameter of the parent vessel were 600, 800, and 280, respectively. It is found that among the tested sizes there exists a middle range of aneurysm sizes, above and below which the forced-vortex inside the aneurysmal model is weaker and lacking, respectively, whereas in the middle range of the tested sizes the forced vortex is stronger and the fluctuation level is higher near the dome. The present results also identify the major fluid dynamic factors of the aneurysmal promotion or rupture for the medium and larger aneurysms, respectively. Furthermore, the maximum fluctuation intensity is found to increase with aneurysm size. The locations of the maximum fluctuation intensity are found to occur in the bifurcation area or at the neck instead of intra-aneurysm.

Aneurysm, Ruptured↗
PubMed1997

A substance isolated from Cornus officinalis enhances the motility of human sperm.

The effects of a Chinese herb, Cornus officinalis, on the motility of human sperm was studied. An aqueous extract was prepared from the dried fruits of the herb and used in this study. The crude extract at a final concentration of 0.5 microgram/microliter in phosphate buffered saline (pH 7.4) increased sperm motility from 25.8 +/- 7.7% to 42.8 +/- 10.3% (i.e. 68% increase, n = 7), as determined by the computer-aided-sperm-analysis (CASA) method. The crude extract was fractionated by high-performance liquid chromatography (HPLC) into four fractions: C1, C2, C3 and C4. Their effects on sperm motility were further studied by CASA. Only the C4 fraction showed substantial stimulatory effects on sperm motility. At a concentration of 5 ng/microliter, C4 increased the sperm motility from 15.7 +/- 3.8% to 34.5 +/- 6.4% (i.e. 120% increase, n = 6) by CASA and from 14.9 +/- 4.3 to 28.5 +/- 8.1 (i.e. 91% increase, n = 8) by transmembrane migration ratio (TMMR) method. This result suggests that C4 is the active component in Cornus officinalis that enhances sperm motility.

Chromatography, High Pressure Liquid↗
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↗
PubMed1997

Perturbation of platelet adhesion to endothelial cells by plasminogen activation in vitro.

To investigate whether the endothelium-platelet interactions may be altered by plasminogen activation, cultured human umbilical vein endothelial cells (ECs) were treated with tissue-type plasminogen activator (t-PA) in the presence of plasminogen, and platelet adhesion to ECs was subsequently measured by using a tapered flow chamber. Our results demonstrated that platelets adhered more readily to t-PA treated EC monolayer than to the control monolayer at all shear stress levels tested. This phenomenon was treatment time-dependent and dose-dependent, and it could be blocked by adding plasmin inhibitors, such as epsilon-amino caproic acid and aprotinin. Adherent platelets on t-PA treated EC monolayer underwent more severe shape change than those on the control monolayer. While the extracellular matrix directly treated with t-PA attracted less platelets than the control matrix did, platelet adhesion to the matrix that was produced by t-PA-treated ECs was unaltered. These data suggest that t-PA treatment on ECs compromised antiplatelet-adhesion capability on their apical surface without altering the reactivity of their extracellular matrix towards platelets.

Blood Platelets↗
PubMed1997

Concurrent 5-fluorouracil, leucovorin, etoposide, cisplatin and radiotherapy for locally advanced non-small cell lung cancer.

BACKGROUND: The prognosis of Stage III unresectable non-small cell lung cancer may be improved by concurrent chemoradiotherapy. In this study, we attempted to evaluate the feasibility, tolerance, efficacy and toxicities of the combination of thoracic radiation and chemotherapy with a novel regimen that included 5-fluorouracil, leucovorin, etoposide and cisplatin (the FLEP regimen) in the treatment of this group of patients. PATIENTS AND METHODS: From July 1995 to September 1996, 20 untreated patients with locally advanced non-small cell lung cancer were enrolled in the study. Radiation at a dose of 44 Gy was initially delivered in daily fractions of 2 Gy 5 days a week to the tumor and mediastinum, followed by a boost to the tumor (20 to 26 Gy according to patients tolerance). Concurrently with thoracic irradiation, patients were treated with chemotherapy consisting of cisplatin at the dose of 60 mg/m2/d for 1 day, etoposide at the dose of 60 mg/m2/d for 2 days, and 5-FU 500 mg/m2/d plus leucovorin 50 mg/d infusion for 48 hours. Cycles of chemotherapy were repeated every 3 weeks for a maximum of 3 cycles. RESULTS: Seventeen of 20 patients were assessable. The overall response rate was 70.6% (95% confidence interval = 49-92%). No complete response was achieved. The median response duration for all responding patients is not yet estimable, with a range of 3.5 to 15.5+ months. Eleven patients remain progression-free for 4 to 15 months. The median survival for the entire group is not estimable. The major toxicity was esophagitis. Other grade 3 or 4 toxicities were not frequently observed. CONCLUSION: Combined-modality therapy with FLEP regimen and radiation is a promising treatment with a high response rate and acceptable toxicity for locally advanced non-small cell lung cancer.

Adult↗
PubMed1997

Evaluating the FONE FIM: Part I. Construct validity.

Rasch analysis was used in this paper to evaluate the Motor component of the FONE FIM, the telephone version of the Functional Independence Measure (FIM). For this purpose, 132 patients discharged from an inpatient geriatric assessment and rehabilitation program were assessed by trained research assistants using the FONE FIM. The results at 5 weeks post-discharge were compared to the observation FIMs (OBS FIMs) done at home 6 weeks post-discharge. These patients had an average age of 79 years and presented with multiple, complex medical problems and significant functional decline. The FONE FIM and the OBS FIM were shown to share a strikingly similar item hierarchy, based on Rasch item difficulty measures. Only bladder management and climbing stairs were misfitting items as indicated by item fit statistics. The same 13-item set and 4-point scales were shown to be psychometrically optimal for both the FONE FIM and the OBS FIM based on the person separation index. Further research is required to address the issue of the optimal item set and scale levels from psychometric and clinical perspectives.

Activities of Daily Living↗