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Biomedical subjects

T H Wang

Publications and source records attributed to T H Wang.

At least 19 recordsLinked to original sources
PubMed2006

Quantum size effect on surface photovoltage spectra: alpha-Fe(2)O(3) nanocrystals on the surface of monodispersed silica microsphere.

A new method for the preparation of Fe(2)O(3) nanoparticle/SiO(2) microsphere composites is described, in which fine alpha-Fe(2)O(3) nanocrystals were prepared by forced hydrolysis of FeCl(3) aqueous solution. The structure and optical spectra of these alpha-Fe(2)O(3) nanocrystals have been studied. Their visible optical absorption can be enhanced by their adsorptions on the surface of SiO(2) microspheres and thereafter simple packing of these microspheres to the aggregated structures. The size-dependent photogenerated surface photovoltage spectra (SPS) of these composites were studied, and quantum confinement effects of the SPS properties were observed. The transport of photoinduced charges between nanocrystals with intrinsic electronic nature of confined states accounts for this phenomenon. These results are helpful in understanding the relationship among d-d transition and charge-transfer transition in transition metal oxides and find applications in photovoltaic devices.

Journal Article↗
PubMed2006

Molecular epidemiology of long-term colonization of Candida albicans strains from HIV-infected patients.

Twenty-one Candida albicans isolates from three HIV-infected patients were collected over a period of 3 years and characterized for fluconazole susceptibility, infectivity and genetic relatedness. Fluconazole resistance was found in five isolates, four exhibited dose-dependent susceptibility and the remainder were fully susceptible to this agent. Pulsed-field gel electrophoresis of SfiI restriction digests of the genomic DNA from the isolates revealed that isolates from the same swab specimen were identical despite differences in susceptibility to fluconazole and isolates recovered over time from the three patients retained clonally related DNA fingerprints within each patient. This small-scale study confirms the persistence of oral colonization of C. albicans strains in HIV-infected patients. Clinical data also suggests that the primary infecting strain may become a persistent colonist in the oral cavity once the immune function of the patient has been restored.

Adult↗
PubMed2005

Single-crystalline Sb-doped SnO2 nanowires: synthesis and gas sensor application.

The synthesis of semiconducting Sb-doped SnO2 nanowires in mass production by an in situ doping approach are reported, and the ethanol sensing results demonstrated that Sb-doped SnO2 nanowires have a promising application for the fabrication of gas sensors with low resistance, and quick response and recovery times.

Journal Article↗
PubMed2005

Antisense inhibition of xylitol dehydrogenase gene, xdh1 from Trichoderma reesei.

AIMS: To inhibit xylitol dehydrogenase (XDH) in Trichoderma reesei by antisense inhibition strategy and construct novel strains capable of accumulating xylitol. METHODS AND RESULTS: The xdh1 antisense expression plasmid pGTA-xdh was constructed by inserting xdh1 DNA fragment inversely between the gpdA promoter and the trpC terminator from Aspergillus nidulans into a pUC19 plasmid backbone. Trichoderma reesei protoplasts were co-transformated with pGTA-xdh and hygromycin B resistance plasmid pAN7-1. Of 20 transformants screened from the selective medium, one transformant with the highest xylitol accumulation, designated ZY15, showed a distinct reduction (c. 52%) in XDH activity compared with the original strain Rut-C30. The results of Southern hybridization and PCR assay showed that the antisense expression cassette of xdh1 was integrated into the genome of T. reesei. The RT-PCR analysis proved that antisense RNA effectively inhibited XDH expression (c. 65%). Xylitol accumulation (2.37 mg ml(-1)) of ZY15 was five times higher than that (0.46 mg ml(-1)) of the original strain Rut-C30. CONCLUSIONS: Strain ZY15 successfully downregulated XDH production and exhibited xylitol accumulation in xylose liquid medium. SIGNIFICANCE AND IMPACT OF THE STUDY: This study contributed to the budding field of fungal genetics in two points. First, it confirmed that antisense RNA strategy could be used as a means of reducing gene expression in the filamentous fungus T. reesei. Secondly, it verified that the strategy appears most promising for creating novel filamentous fungi strains capable of accumulating intermediary metabolites.

Antisense Elements (Genetics)↗
PubMed2004

Construction of a yeast one-hybrid system with the xylanase2 promoter from Trichoderma reesei to isolate transcriptional activators.

AIMS: To construct a yeast one-hybrid system and isolate transcriptional activators. METHODS AND RESULTS: A 1.1-kb promoter region of xylanase2 from Trichoderma reesei was cloned by PCR and sequenced (GenBank accession number: AY263380). Sequence analysis revealed that typical binding sites for several transcription factors in filamentous fungi, such as CREI, XLNR, ALCR, AREA and CCAAT enhancer, are located in the promoter. To isolate xyn2 transcription factors, the reporter plasmid of a yeast one-hybrid system was constructed on the backbone of the plasmid pRS415 containing the leu2 selective marker, with the xyn2 promoter region and Saccharomyces cerevisiae his4 as a reporter gene. The reporter gene contained 123-bp minimal promoter region. The S. cerevisiae H158 strain containing the reporter plasmid was transformed with a T. reesei expression cDNA library, and 34 transformants were collected from SC-Leu-His-Ura plates. The isolation of the gene ace2 from several transformants showed that the one-hybrid system approach was successful. Then, approx. 59 mg l(-1) of ace2 was overexpressed in Escherichia coli BL21. SIGNIFICANCE AND IMPACT OF THE STUDY: The yeast one-hybrid system is suitable for isolating transcription factors of filamentous fungi. ACE II is a main and universal transcriptional activator that controls cellulase and hemicellulase transcription regulation in T. reesei.

Alcohol Oxidoreductases↗
PubMed2003

Contribution of the gastrointestinal tract below the stomach to the 13C-urea breath test.

BACKGROUND: Graham et al. [Lancet, I (1987) 1174] found a late increase of 13C enrichment in the 13C-urea breath test 120 min after administration of labeled urea to patients without Helicobacter pylori infection. This may give false positive results. AIM: We designed this study to elucidate the contribution of the gastrointestinal tract below the stomach to the 13C-urea breath test. PATIENTS: Twenty-eight patients with dyspeptic symptoms who gave their consent were enrolled. METHODS: Patients underwent the 13C-urea breath tests both via the mouth (as usual) and the duodenum (labeled urea introduced to the second portion). Breath samples were collected at baseline, 5, 15, 30, 45, 60, 90, 120, 150 and 180 min for analysis. H. pylori status was defined by the CLOtest and by histological examination. RESULTS: There was no late increase in 13C enrichment of 13C-urea breath test for eight H. pylori negative patients either via the mouth or the duodenum. For those H. pylori positive patients, seventeen had no late rise 13C enrichment of the 13C-urea breath test via the duodenum and three patients had a rise after 15 min. CONCLUSIONS: No late rise in 13CO2 excretion to cause a positive 13C-urea breath test up to 180 min after the administration of labeled urea was found in the present study.

Adult↗
PubMed2001

Effect of mouth washing on the.

BACKGROUND: Mouth washing is often mentioned as a possible method to eliminate the interference of urease activity in the oral cavity before the [13C]-urea breath test (UBT). However, the effectiveness of mouth washing prior to testing has not been demonstrated clearly in the literature. Thus, the present study was designed to examine the consistency of the [13C]-UBT and the effects of mouth washing on it. METHODS: A total of 101 healthy volunteers underwent the [13C]-UBT three times. The first and second tests used a standard protocol and collected samples at 5, 10, 15 and 30 min. In the third test, the procedure was the same except that mouth washing was omitted. RESULTS: We used 5 permil (/1000) as the cut-off value and there were 21 (20.8%) positive cases. The kappa values for the samples collected at 5, 10, 15 and 30 min between the first and second tests were 0.68, 0.97, 1 and 1, respectively, and all showed good consistency, except for the sample collected at 5 min. Judging from the mean value of the [13C] enrichment of the first and second tests (with mouth washing) and the third test (without mouth washing), 50 (63.3%), 15 (18.8%), 0 and 0 cases at 5, 10, 15 and 30 min, respectively, changed from negative to positive. There were 14 (17.5%) and six (7.5%) cases at 15 and 30 min, respectively, whose [13C] enrichment changed from less than 3 (negative) to between 3 and 5 (border zone). CONCLUSIONS: These results indicate that mouth washing had an important effect on samples obtained at 5 and 10 min, while this influence decreased at 15 min and was lowest at 30 min.

Adult↗
PubMed2001

Situational leadership style as a predictor of success and productivity among Taiwanese business organizations.

The present study was an evaluation of the impact of Taiwanese leadership styles on the productivity of Taiwanese business organizations. Specifically, it looked at the impact that both adaptive and nonadaptive leaders have on 6 measures of productivity: absenteeism, turnover rate, quality of work, reject rates, profitability, and units produced. The results indicated that the greater the level of adaptability, the more productive the organization is likely to be. Although not all of the computed correlations were statistically significant, they were all in the predicted directions. In particular, the findings for units produced and reject rates were consistently statistically significant. The study was also an examination of the usefulness of the Leadership Effectiveness and Adaptability Description (LEAD) questionnaire (P. Hersey & K. Blanchard, 1988), which appeared to be an accurate predictor of adaptability and valid for use in Taiwan. The final part of this study was an investigation of whether successful companies were more likely to have a greater percentage of adaptive leaders than unsuccessful companies. The data supported this expectation, although it is suggested that caution be used in the interpretation of this particular finding because it could have several different explanations. Overall, the evidence supported the value of adaptive leadership styles in high-technology industries in Taiwan.

Adaptation, Psychological↗
PubMed2001

Weibull modeling of the Fenton's oxidation process.

A modified version of the two-parameter Weibull survival curve is used to investigate its applicability to analyze the influence of the Fenton's Reagent on the decomposition of 2,4-dinitrophenol solutions (DNP). Fenton's Reagent is one type of advanced oxidation processes (AOPs) in which strong oxidants, hydroxyl radicals, are generated. Fenton's Reagent was maintained at a ratio of 0.5 mM H2O2 to 0.1 mM Fe2+ at the start of all experiments. By varying the initial DNP concentration, we are not only able to correlate parameters (a) and (b) defined in the modified curve to the Fenton's oxidation process, but also interpret their physical significance on the process. The scale parameter (a) can be used to illustrate the rate of the decomposition of DNP in solutions. The imbalance between decomposition rate and initial DNP concentration can be easily observed with the aid of parameter (a). By defining a specific decomposition rate function, the shape parameter (b) indicates the strength of the oxidation power provided by the Fenton's Reagent. When (b) > 1, the existence of a maximum specific decomposition rate shows a sufficient supply of the hydroxyl radicals, whereas a first-order decomposition of DNP is obtained when (b) = 1. A lack of oxidation power becomes obvious if (b) < 1, showing a high dose of initial DNP in a solution. Knowing the physical interpretation of both parameters, they are further applied to design the Fenton's oxidation process.

2,4-Dinitrophenol↗
PubMed2001

Measuring Fenton's reaction kinetics at one-second intervals.

The concept of quench flow has been implemented to design a simple and yet easy-to-operate device to measure Fenton's reaction kinetics at one-second intervals. 2,4-dinitrophenol (DNP) was used as a model compound in this study. Experimental results show that more than 40% of DNP can be decomposed within the first second, followed by a stagnant reaction for a period of 29 seconds. Subsequently, a 5% drop in the ADMI (American Dye Manufacturing Index) color value was observed. The initial specific rates of DNP concentration and the ADMI color value were the same, indicating that ADMI color value can be potentially used as a process parameter in designing a computerized Fenton's oxidation process. The scanning spectrum recorded a reaction pattern with constant rates of decolorization and degradation of DNP occurring between 5 and 29 seconds, irrespective of different Fe2+/H2O2 ratios. Such a reaction pattern has not been reported elsewhere.

2,4-Dinitrophenol↗
PubMed2001

Familial risk of asthma among adolescents and their relatives in Taiwan.

Although family studies have established that asthma has a hereditary basis, little evidence has been presented about the family risk of simple asthma (AS or nonatopic asthma) and asthma with other atopic diseases (AWAD or atopic asthma) after adjusting for potential risk factors. In this study, data were collected on demographic variables and a wide range of known risk factors for asthma. Study participants were asthmatic adolescents and controls, and their relatives. The role of a familial history of asthma and atopic diseases in predicting asthma risk among asthmatic adolescents and their relatives was evaluated in a population-based family study conducted in southern Taiwan. Asthma risk factor data were collected through telephone interviews with students' parents for 207 asthmatic adolescents 11-16 years of age, their 1600 relatives, and 207 nonasthmatic adolescents in the control group and their 1638 relatives. The results show (after adjusting potential confounders) that a family history of asthma is highly associated with asthma in adolescents. Having two or more family members with asthma was associated with a 3.4-fold (95% confidence interval [CI] = 1.0-12.0) increased risk of asthma among adolescents. Logistic regression was used to assess the effects of having an asthmatic relative and the effect of atopic diseases among relatives of cases. Having a family history of asthma and other atopic conditions, such as rhinitis and atopic dermatitis (adjusted odds ratio [AOR] = 3.64, 95% CI = 2.29-5.74 and AOR = 1.94, 95% CI = 1.53-2.46, respectively), was found to be a significant predictor of asthma in children. Along with a history of allergic rhinitis or atopic dermatitis, familial risks of asthma occurring in adolescents with and without other atopic diseases will be analyzed separately. A critical finding was the significant difference in a risk of asthma and atopic diseases among the relatives of asthma cases with atopic diseases and controls. However, for relatives of asthma cases without atopic diseases compared to control probands, AORs were highly significant for family history of asthma, but not for the family history of atopic diseases. These findings suggest that both forms of asthma may be hereditary, but there are differences in their modes of inheritance. Atopic status itself did not predispose a child to AS. A concomitant inheritance of a predisposition to asthma and atopic condition for AWAD cases was suggested.

Adolescent↗
PubMed2001

Identification of shared populations of human immunodeficiency virus type 1 infecting microglia and tissue macrophages outside the central nervous system.

Infection of microglia and other cells of the macrophage/monocyte lineage in the central nervous system (CNS) by human immunodeficiency virus type I (HIV-1) underlies the development of giant cell encephalitis (GCE). It is currently unknown whether GCE depends on the emergence of virus populations specifically adapted to replicate in cells of the monocyte/macrophage lineage and whether this also leads to the specific targeting of macrophages in other nonlymphoid tissues. Autopsy samples from lymph node, brain (frontal region), lung, and full-thickness colon sections were obtained from nine study subjects with GCE and from nine without. The two groups showed no significant differences in CD4 counts, disease progression, or treatment history before death. Genetic relatedness between variants recovered from lymph node and nonlymphoid tissues was assessed by sequence comparison of V3 and p17(gag) regions using a newly developed method that scores the sample composition at successive nodes in a neighbor-joining tree. The association index enabled objective, numerical comparisons on the degree of tissue compartmentalization to be made. High proviral loads and p24 antigen expression in the brain were confined to the nine individuals with GCE. GCE was also associated with significantly higher proviral loads in colon samples (median of the GCE(+) group: 1,010 copies/10(6) cells; median of GCE(-) group, 10/10(6) cells; P = 0.006). In contrast, there were no significant differences in proviral load between the GCE(+) and GCE(-) groups in lymph node or lung samples, where HIV infection was manifested predominantly by infiltrates of lymphoid cells. V3 sequences from brain samples of individuals with GCE showed the greatest compartmentalization from those of lymph node, although samples from other tissues, particularly the colon, frequently contained variants phylogenetically related to those found in brain. The existence of shared, distinct populations of HIV specifically distributed in cells of the monocyte/macrophage lineage was further indicated by immunocytochemical detection of CD68(+), multinucleated giant cells expressing p24 antigen in samples of lung and colon in two individuals with GCE. This study provides the basis for future investigation of possible phenotypic similarities that underline the shared distributions of HIV variants infecting microglia and tissue macrophages outside the CNS.

Amino Acid Sequence↗
PubMed2001

Evidence for alterations in circulating low-molecular-weight antioxidants and increased lipid peroxidation in smokers on hemodialysis.

BACKGROUND/AIM: Cardiovascular disease is the major cause of mortality in dialysis patients, accounting for about 40% of deaths in most large registries. Oxidative stress has been strongly implicated in the pathogenesis of these events. As end-stage renal disease is a state of elevated free radical activity, the aim of the present study was to investigate the negative impact of smoking in 57 male hemodialysis patients. METHODS: The patients, who were 20-85 years of age (mean age 51.0 +/- 14 years), had been on hemodialysis for at least 6 months before participating in this study. Fasting blood sampling for serum lipid, albumin, urate and lipophilic antioxidants such as tocopherols, carotenes, ascorbate and lipid peroxides was performed. RESULTS: The plasma malondialdehyde (MDA) concentration was significantly higher in hemodialysis patients who smoked compared to hemodialysis patients who were nonsmokers (1.92 +/- 0.52 vs. 1.59 +/- 0.42 nmol/ml, p = 0.006). No association was found between levels of MDA in smokers and parameters such as body mass index, serum cholesterol, serum triglycerides and smoking index. There were no significant differences in the plasma levels of uric acid, alpha-tocopherol, gamma-tocopherol, delta-tocopherol, alpha-carotene, beta-carotene and retinol between the two groups. A significantly lower level of plasma ascorbate was observed in hemodialysis patients who smoked compared to the nonsmoking hemodialysis patients or healthy controls (4.59 +/- 4.0 vs. 9.57 +/- 4.0 and 10.16 +/- 4.6 microg/ml, p < 0.05). Moreover, in smokers, the plasma levels of ascorbate were negatively correlated with the levels of plasma MDA (r = -0.43, p < 0.001) of each patient. Partial correlation analysis of the plasma levels of the measured antioxidants and the smoking index revealed a negative correlation between the plasma levels of lipid-normalized lycopene and the smoking index (r = -0.53, p < 0.05). CONCLUSION: Our data suggest that cigarette smoking further increases plasma-circulating products of lipid peroxidation, which are already increased in nonsmoking hemodialysis patients as compared to matched healthy controls. The lower plasma levels of ascorbate in hemodialysis patients who smoke suggest that these patients may be more susceptible to oxidative tissue damage caused by smoking.

Adult↗
PubMed2001

[Role of conditioned growth medium for ventricular fibroblasts in promoting fibroblast collagen synthesis and proliferation].

Ventricular fibroblasts were cultured using conditioned growth medium for ventricular fibroblasts (FCGM). The rate of the total collagen synthesis of ventricular fibroblasts was measured by assaying the incorporation rate of [3H]-proline, whereas the proliferation of ventricular fibroblasts was assessed by determining the incorporation rate of [3H]-TdR and the expression of c-fos genes. FCGM significantly increased the [3H]-proline incorporation rate and [3H]-TdR incorporation rate of fibroblasts in a dose-dependent manner. Furthermore, FCGM promoted the c-fos gene expression of fibroblasts, which attained its maximum in 1 h. BQ123, an ETA receptor antagonist, partially blocked the above effects of FCGM, but AT1 receptor antagonist CV11974 and alpha-adrenergic receptor antagonist regitin did not. It is suggested that the ventricular fibroblast has an autorine function in promotion of collagen synthesis and proliferation of fibroblasts by secreting endothelin and other bioactive substances.

Animals↗
PubMed2001

[Effect of aldosterone on the secretion of endothelin by ventricular fibroblasts].

Using cell culture, radioimmunoassay for endothelin and RT-PCR, the effect of aldosterone on the endothelin secretion of ventricular fibroblasts was studied. The results showed that aldosterone (1 x 10(-7) mol/L) promoted the expression of ppET-1 mRNA, which began to increase in 2 hours and attained the highest level in 4 hours, thereafter decreased; aldosterone increased the endothelin level in ventricular fibroblasts and fibroblast conditioned growth medium (FCGM) as well, which was blocked by spironolactone (1 x 10(-6) mol/L), an aldosterone receptor antagonist. The results suggest that aldosterone can increase endothelin secretion by ventricular fibroblasts, which can be inhibited by its receptor antagonist spironolactone.

Aldosterone↗
PubMed2001

[Role of mitogen-activated protein kinase in the inhibition of myocardial hypertrophy by nitric oxide in renovascular hypertensive rats].

The aim of this study was to examine the effects of L-arginine, a nitric oxide (NO) precursor, on protein expression of endothelial nitric oxide (eNOS), nitrite/nitrate content, protein expression of mitogen-activated protein kinase phosphatase-1 (MKP-1) and the activity of mitogen-activated protein kinase (MAPK) in cardiac tissues in renovascular hypertensive rats (RHR). The Goldblatt renovascular hypertensive model was established by two-kidney one clip method. The rats were divided into four groups, respectively treated with 50, 150 and 450 mg/kg L-arginine and 150 mg/kg L-arginine plus 10 mg/kg L-NAME (an eNOS inhibitor) (i.p.). Another group did not receive specific treatment from the 5th week after renal artery constriction. Control group was sham-operated. Mean arterial blood pressure (MABP) and the ratio of left ventricular weight to body weight (LVW/BW) were measured 8 weeks after treatment. eNOS protein expression, nitrite/nitrate content, MKP-1 protein expression and MAPK activity in cardiac tissues were detected using Western blot analysis, enzyme-reduction method and substrate in-gel kinase assay, respectively. It was found that L-arginine significantly inhibited the increase of MABP and LVW/BW, attenuated the activity of MAPK, increased protein expression of eNOS and MKP-1 and potentiated production of NO in cardiac tissue with the most effective dosage of 150 mg/kg, and these effects of L-arginine could be inhibited by L-NAME. These results suggest that MKP-1 may play an important role in the NO-induced inhibition of myocardial hypertrophy. The anti-hypertrophic effects of L-arginine may involve increase of eNOS protein expression and NO production, potentiation of MKP-1 protein expression, and inhibition of MAPK activity in the cardiac tissue of RHR.

Animals↗
PubMed2001

Renal oncocytoma in acquired renal cystic disease.

Renal oncocytoma is a rare benign tumor of the kidney that accounts for about 5% of renal tumors. Acquired renal cystic disease (ARCD) is commonly seen in dialyzed patients. However, the occurrence of renal oncocytoma in ARCD has rarely been reported. We report such a case in a 67-year-old man who had hypertension-associated end-stage renal disease and had received regular hemodialysis for 5 years. Radiologic diagnostic studies demonstrated a renal mass in the left atrophic cystic kidney that increased in size from 2 cm to 4 cm during 2 years of follow-up. Under the diagnosis of renal cell carcinoma, he received left radical nephrectomy. The pathologic examination revealed renal oncocytoma with a well-cirumscribed, homogenous, mahogany-brown tumor on a background of ARCD. Although patients with ARCD have a higher incidence of renal malignancies, renal oncocytoma may occur in these patients and may be managed conservatively.

Adenoma, Oxyphilic↗