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W Chen

Publications and source records attributed to W Chen.

At least 73 records · Page 4Linked to original sources
PubMed2004

Key influential factors for sludge pre-fermentation process design--a case study.

Sewage sludge pre-fermentation process produces readily biodegradable carbon, which is essential for reliable biological phosphorus removal and efficient denitrification. This bench scale study was to develop site-specific design parameters for a sludge fermentation process, and to look into the effects of various influential factors. The key factors investigated induded solids retention time (4-8 days), temperature (9-19 degrees C) and sludge concentrations (0.5%-4% DS). The optimum Volatile Fatty Adds yield was found at a sludge concentration of 1%-1.5% DS. A solid retention time of 4 days at 15-20 degrees C was found to be most cost effective. The fermentation reaction was temperature sensitive, which was found to be inefficient at temperature below 12-15 degrees C. Under the optimum conditions, 80-100 mgVFA g(-1) VSS can be generated from fermentation process, which will result in an increase of 20-24 mg l(-1) in the settled sewage based on average flow. A significant pathogen reduction level was also demonstrated over the fermentation period. Liquid sludge from the small rural wastewater treatment plants is often imported to a regional sludge treatment centre for more advanced treatment to comply with the Regulations. The suitability of this imported sludge for pre-fermentation process was also investigated in this study.

Biodegradation, Environmental↗
PubMed2004

Elicitation of both CD4 and CD8 T-cell-mediated specific immune responses to HCA587 protein by autologous dendritic cells.

We recently cloned a new member of cancer/testis antigen named HCA587, which was highly expressed in human hepatocellular carcinoma (HCC) tissues. To investigate it as a potential tumour-specific target for immunotherapy, the immunogenicity of this protein, especially the ability to induce specific cellular immune responses, was evaluated in the present study. As dendritic cells (DC) are the most potent antigen-presenting cells, DC-based vaccination has recently shown marked promise for the treatment of human malignancies by immunological intervention. Here, we demonstrate that autologous DC loaded with HCA587 protein could induce specific T-cell responses in healthy individuals by in vitro stimulations. Enzyme-linked immunospot analysis for interferon-gamma (IFN-gamma) secretion demonstrated HCA587-specific CD8(+) T cells in the antigen-stimulated peripheral blood lymphocytes, and the analysis of CD4(+) T cells by proliferation assay also showed antigen-specific reactivities in normal donors. Two-colour flow cytometric analysis of surface markers and intracellular cytokine expression demonstrated that HCA587-specific cytotoxic T lymphocytes exhibited a heterogeneous CD8(+)/CD56(+) expression, and a striking T-helper 1 cytokine bias (IFN-gamma(high)/IL-4(low)) was observed for both CD4(+) and CD8(+) HCA587-specific lymphocyte populations. We conclude that HCA587 is a potent immunogen that can induce CD4(+) and CD8(+) T-cell-mediated specific immune responses, and these findings propose HCA587 as a good candidate for the development of a therapeutic protein-based DC tumour vaccine for the treatment of HCC patients.

Antigens, Neoplasm↗
PubMed2004

Fractional Laplacian time-space models for linear and nonlinear lossy media exhibiting arbitrary frequency power-law dependency.

Frequency-dependent attenuation typically obeys an empirical power law with an exponent ranging from 0 to 2. The standard time-domain partial differential equation models can describe merely two extreme cases of frequency-independent and frequency-squared dependent attenuations. The otherwise nonzero and nonsquare frequency dependency occurring in many cases of practical interest is thus often called the anomalous attenuation. In this study, a linear integro-differential equation wave model was developed for the anomalous attenuation by using the space-fractional Laplacian operation, and the strategy is then extended to the nonlinear Burgers equation. A new definition of the fractional Laplacian is also introduced which naturally includes the boundary conditions and has inherent regularization to ease the hypersingularity in the conventional fractional Laplacian. Under the Szabo's smallness approximation, where attenuation is assumed to be much smaller than the wave number, the linear model is found consistent with arbitrary frequency power-law dependency.

Acoustics↗
PubMed2004

Clonal diversity and stability of subgingival Eikenella corrodens.

Eikenella corrodens is a commensal subgingival bacterium commonly found in both periodontally nondiseased and diseased subjects. The present study examined the clonal diversity and stability of subgingival E. corrodens over time. Ninety-five subjects were enrolled at the baseline examination, including 44 periodontally nondiseased subjects and 51 subjects with aggressive periodontitis. Twenty-two nondiseased subjects and 11 subjects with aggressive periodontitis were subsequently reexamined after an average interval of 14 months. Two subgingival plaque samples were obtained from each subject to determine the total cultivable bacteria. In addition, multiple E. corrodens isolates from each sample were recovered for clonal analysis by arbitrarily primed PCR. The mean numbers of distinct E. corrodens clones harbored by nondiseased subjects and subjects with aggressive periodontitis were 1.3 and 3.0, respectively. Thirty-nine percent of the nondiseased subjects and 63% of the subjects with aggressive periodontitis harbored multiple clones of E. corrodens. The numbers of distinct E. corrodens clones increased significantly (Mann-Whitney ranking test, P < 0.05) in sites from patients with aggressive periodontitis, in sites with pocket depths of 4 mm or greater, in sites with a clinical attachment loss of 2 mm or greater, and in sites coinfected with Porphyromonas gingivalis. Comparison of E. corrodens clones recovered at the baseline and those recovered at the follow-up examination showed that E. corrodens colonization was not stable. Thirty-eight of the 66 follow-up samples (58%) showed a complete change (including de novo colonization of the sites or complete elimination of the organism from the sites) of the subgingival E. corrodens clonal types between the baseline and the follow-up examinations. Our results suggest a complexity of subgingival microbiota not seen previously.

Adolescent↗
PubMed2004

Arginine stimulates intestinal cell migration through a focal adhesion kinase dependent mechanism.

BACKGROUND: L-Arginine is a nutritional supplement that may be useful for promoting intestinal repair. Arginine is metabolised by the oxidative deiminase pathway to form nitric oxide (NO) and by the arginase pathway to yield ornithine and polyamines. AIMS: To determine if arginine stimulates restitution via activation of NO synthesis and/or polyamine synthesis. METHODS: We determined the effects of arginine on cultured intestinal cell migration, NO production, polyamine levels, and activation of focal adhesion kinase, a key mediator of cell migration. RESULTS: Arginine increased the rate of cell migration in a dose dependent biphasic manner, and was additive with bovine serum concentrate (BSC). Arginine and an NO donor activated focal adhesion kinase (a tyrosine kinase which localises to cell matrix contacts and mediates beta1 integrin signalling) after wounding. Arginine stimulated cell migration was dependent on focal adhesion kinase (FAK) signalling, as demonstrated using adenovirus mediated transfection with a kinase negative mutant of FAK. Arginine stimulated migration was dependent on NO production and was blocked by NO synthase inhibitors. Arginine dependent migration required synthesis of polyamines but elevating extracellular arginine concentration above 0.4 mM did not enhance cellular polyamine levels. CONCLUSIONS: These results showed that L-arginine stimulates cell migration through NO and FAK dependent pathways and that combination therapy with arginine and BSC may enhance intestinal restitution via separate and convergent pathways.

Animals↗
PubMed2004

IL-1alpha stimulates cathepsin K expression in osteoclasts via the tyrosine kinase-NF-kappaB pathway.

Interleukin-1alpha (IL-1alpha) is a powerful activator of osteoclast cells. However, the underlying mechanism for this activation is unknown. In this study, we reveal that IL-1alpha up-regulates the expression of cathepsin K protein, a key protease in bone resorption, by five-fold. Northern blot analysis and promoter analysis show that this induction occurs at the transcriptional level, in a dose-responsive and time-dependent manner. No increase in expression occurs in the presence of either pyrrolidine dithiocarbamate (PDTC), a selective inhibitor of NF-kappaB, or Genistein, a protein tyrosine kinase inhibitor, suggesting that IL-1alpha up-regulation may be via the tyrosine kinase-NF-kappaB pathway to regulate cathepsin K expression. Antisense oligonucleotides to p65, but not the p50 subunit of NF-kappaB, suppress the IL-1alpha-induced expression of cathepsin K. We therefore conclude that IL-1alpha up-regulates cathepsin K gene expression at the transcription level, and this regulation may be via the tyrosine-kinase-NF-kappaB pathway.

Animals↗
PubMed2003

Global nature of dilute-to-dense transition of granular flows in a 2D channel.

The dilute-to-dense transition of granular flow of particle size d(0) is studied experimentally in a two-dimensional channel (width D) with confined exit (width d). Our results show that with fixed d and D there is a maximum inflow rate Q(c) above which the flow changes from dilute to dense and the outflow rate drops abruptly from Q(c) to a dense rate Q(d). A rescaled critical rate q(c) is found to be a function of a scaling variable lambda only: q(c) approximately F(lambda), where lambda identical with d/d(0) d/D-d. This form of lambda suggests that the dilute-to-dense transition is a global property of the flow, unlike the jamming transition which depends only on d/d(0). Furthermore, the transition is found to occur when the area fraction of particles near the exit exceeds a critical value which is close to 0.65+/-0.03.

Journal Article↗
PubMed2003

Cooperation between monocytes and breast cancer cells promotes factors involved in cancer aggressiveness.

In breast cancers, clinical symptoms of inflammation localised around the tumour at the time of diagnosis have been considered to have poor prognosis significance. In this study, the biological mechanisms responsible for the deleterious action of monocytes in cancer were investigated. The incubation of the breast-cancer-derived MDA-MB231 cells with monocytes resulted in an increase in factors involved in cell invasion (i.e. both cancer cells and monocytes-associated urokinase and Tissue Factor, and PAI-1 and MMP-9 secretion). Moreover, the functions of monocytes were also modified. Incubation of monocytes with MDA-MB231 cancer cells resulted in a downregulation in the secretion of the antiproliferative cytokine Oncostatin M, while the apoptotic factor TNF alpha was dramatically increased. However, MDA-MB231 cancer cells have been shown to be resistant towards the apoptotic action of TNF alpha. These findings demonstrate that incubation of MDA-MB231 cancer cells with monocytes induced a crosstalk, which resulted in an increased expression of factors involved in cancer cell invasiveness and in a modification of monocytes function against cancer cells, while inflammatory effects were increased.

Breast Neoplasms↗
PubMed2003

Grammatical and resource components of sentence processing in Parkinson's disease: an fMRI study.

BACKGROUND: Sentence comprehension requires linguistic processing as well as cognitive resources such as working memory (WM) and information-processing speed (IPS). The authors hypothesize that sentence comprehension difficulty in patients with mild PD is due to degradation of the large-scale neural network that supports cognitive resources during sentence processing. OBJECTIVE: To understand the neural basis for sentence comprehension difficulty in PD. METHOD: Regional brain activity with blood oxygenation level-dependent fMRI was monitored while seven PD patients and nine healthy seniors answered a simple probe about written sentences that vary in their grammatical and cognitive resource properties. RESULTS: Healthy seniors recruited posterolateral temporal and ventral inferior frontal regions of the left hemisphere, brain regions associated with grammatical processing that were also activated by PD patients. Healthy seniors also recruited left dorsal inferior frontal, right posterolateral temporal, and striatal regions that are associated with cognitive resources during sentence processing. Direct contrasts showed that striatal, anteromedial prefrontal, and right temporal regions are recruited to a significantly lesser degree in PD, but these patients have increased activation of right inferior frontal and left posterolateral temporal-parietal areas during sentence comprehension. CONCLUSION: These findings associate impaired sentence comprehension in PD with interruption of a large-scale network important for cognitive resources during sentence processing. These results also imply compensatory up-regulation of cortical activity that allows patients with mild PD to maintain sentence comprehension accuracy.

Aged↗
PubMed2003

Bile acids for viral hepatitis.

BACKGROUND: The viral hepatitides are common causes of liver diseases globally. Trials have assessed bile acids for patients with viral hepatitis, but no consensus was reached regarding their usefulness. OBJECTIVES: To assess the beneficial and harmful effects of bile acids for viral hepatitis. SEARCH STRATEGY: Searches were performed of the trial registers of The Cochrane Hepato-Biliary Group (September 2002), The Cochrane Library (Issue 2, 2002), MEDLINE (September 2002), EMBASE (September 2002), and The Chinese Biomedical Database (April 2001). SELECTION CRITERIA: Randomised clinical trials comparing any dose or duration of bile acids versus placebo or no intervention for viral hepatitis were included, irrespective of language, publication status, or blinding. DATA COLLECTION AND ANALYSIS: Two reviewers extracted the data independently. The methodological quality of the trials was evaluated with respect to generation of the allocation sequence, allocation concealment, double blinding, and follow-up. The outcomes were presented as relative risks (RR) or weighted mean differences (WMD) with 95% confidence intervals (CI). MAIN RESULTS: We identified 27 randomised trials of bile acids for hepatitis B or C; none were of high methodological quality. In one trial, ursodeoxycholic acid (UDCA) versus placebo for acute hepatitis B significantly reduced the risk of hepatitis B surface antigen positivity at the end of treatment and serum HBV DNA level at the end of follow-up. In another trial, UDCA versus no intervention for chronic hepatitis B significantly reduced the risk of having abnormal serum transaminase activities at the end of treatment. Twenty-five trials compared bile acids (21 trials UDCA; four trials tauro-UDCA) versus placebo or no intervention with or without co-interventions for chronic hepatitis C. Bile acids did not significantly reduce the risk of having detectable serum HCV RNA (RR 0.99, 95% CI 0.91 to 1.07), cirrhosis, or portal and periportal inflammation score at the end of treatment. Bile acids significantly decreased the risk of having abnormal serum alanine aminotransferase activity at the end of treatment (RR 0.82, 95% CI 0.76 to 0.90) and follow-up (RR 0.91, 95% CI 0.85 to 0.98). Bile acids significantly increased the Knodell score (WMD 0.20, 95% CI 0.08 to 0.31) at the end of treatment. No severe adverse events were reported. We did not identify trials including patients with hepatitis A, acute C, D, or E. REVIEWER'S CONCLUSIONS: Bile acids lead to a significant improvement in serum transaminase activities in hepatitis B and C. There is insufficient evidence either to support or to refute effects on viral markers, mortality, incidence of cirrhosis, or liver histology. Trials with high methodological quality are required.

Antiviral Agents↗
PubMed2003

Bile acids for primary sclerosing cholangitis.

BACKGROUND: Bile acids have been used for treating primary sclerosing cholangitis, but their beneficial and harmful effects remain unclear. OBJECTIVES: To assess the beneficial and harmful effects of bile acids for patients with primary sclerosing cholangitis. SEARCH STRATEGY: We searched The Cochrane Hepato-Biliary Group's Trials Register, The Cochrane Library, MEDLINE, EMBASE, and The Chinese Biomedical Database generally from inception through to May 2002. SELECTION CRITERIA: Randomised clinical trials comparing any dose or duration of bile acids versus placebo, no intervention, or another intervention were included. Trials were included irrespective of blinding, language, or publication status. DATA COLLECTION AND ANALYSIS: Two reviewers extracted the data. The methodological quality of the trials was evaluated with respect to the generation of the allocation sequence, allocation concealment, double blinding, and follow-up. The results were reported by intention-to-treat analysis. The outcomes were presented as relative risks (RR) or weighted mean differences (WMD), both with 95% confidence intervals (CI). MAIN RESULTS: We identified six randomised clinical trials, all with low methodological quality. Patients were treated for three months to six years (median two years). Five trials (183 patients) compared ursodeoxycholic acid versus placebo, and one trial (40 patients) compared ursodeoxycholic acid versus no treatment. Ursodeoxycholic acid did not significantly reduce the risk of death (RR 0.86; 95% CI 0.27 to 2.73); treatment failure including liver transplantation, varices, ascites, and encephalopathy (RR 0.94; 95% CI 0.63 to 1.42); liver histological deterioration (RR 0.89; 95% CI 0.45 to 1.74); or liver cholangiographic deterioration (RR 0.43; 95% CI 0.18 to 1.02). Ursodeoxycholic acid significantly improved serum bilirubin (WMD -14.6 micro mol/litre; 95% CI -18.7 to -10.6), alkaline phosphatases (WMD -506 IU/litre; 95% CI -583 to -430), aspartate aminotransferase (WMD -46 IU/litre; 95% CI -77 to -16), and gamma-glutamyltranspeptidase (WMD -260 IU/litre; 95% CI -315 to -205), but not albumin (WMD -0.20 g/litre; 95% CI -1.91 to 1.50). Ursodeoxycholic acid was well tolerated. REVIEWER'S CONCLUSIONS: Ursodeoxycholic acid leads to a significant improvement in liver biochemistry, but there is insufficient evidence to either support or refute its clinical effects in patients with primary sclerosing cholangitis. Large scale, high-quality randomised clinical trials are needed.

Cholagogues and Choleretics↗
PubMed2003

Infusion of in vitro-generated DN T regulatory cells induces permanent cardiac allograft survival in mice.

Previously, we have demonstrated that pretransplant donor lymphocyte infusion (DLI) can activate recipient-derived CD3+CD4-CD8- double negative T regulatory (DN Tr) cells which have a potent immune regulatory function in vitro and in vivo. Here we studied the regulatory ability of DN T cell clones generated from the spleens of nai;ve anti-L(d) transgenic TCR+ (2C x dm2)F1 mice. We were able to identify subsets of DN T cell clones that were able to kill anti-Ld CD8+ T cells, and therefore had regulatory properties, and DN T cells with no regulatory properties. Next, we investigated the ability of these in vitro generated DN T cell clones to enhance cardiac allograft survival. (2C x dm2)F1 transgenic mice were infused with either regulatory or non-regulatory DN T cell clones, or left untreated one day before receiving an Ld-mismatched cardiac grafts from (C57BL/6 x Balb/c)F1 mice. Injection of non-regulatory DN T clone cells did not prolong cardiac graft survival in (2C x dm2)F1 mice when compare to untreated controls. In contrast, all of the cardiac grafts survived more than 100 days in mice that received DN Tr clone cells prior to transplantation. These results demonstrate that DN Tr cells can be generated in vitro and protect cardiac allograft from rejection when infused into recipients prior to transplantation. They also suggest that DN Tr cells may provide a novel therapy for the treatment of allograft rejection.

Animals↗
PubMed2003

Common presence of Helicobacter DNA in the gallbladder of patients with gallstone diseases and controls.

BACKGROUND: Several species of Helicobacter colonise the biliary tract of animals and cause hepatobiliary diseases. Helicobacter species have also been identified in the gallbladder of a high proportion of Chilean patients with gallbladder cancer. AIM: To determine the presence of Helicobacter species, particularly Helicobacter pylori and Helicobacter bilis, in the gallbladder of patients with non-malignant gallbladder diseases and control patients. PATIENTS AND METHODS: DNA was extracted from gallbladder samples from 122 consecutive patients undergoing cholecystectomy. The presence of Helicobacter genus-specific or Helicobacter pylori and Helicobacter bilis species-specific DNA was determined by polymerase chain reaction and sequence analysis. The presence of Helicobacter pylori-specific immunoglobulin G in the serum (n=84) and bile (n=104) samples was determined by enzyme linked immunosorbent assay. RESULTS: Helicobacter DNA was detected in 61 (50.0%) gallbladder samples: 29 of 60 (48.3%) patients with symptomatic gallstone, six of 10 (60.0%) patients with asymptomatic gallstones, 11 of 15 (73.3%) patients with other biliary diseases, and 15 of 37 (40.5%) control patients, respectively. Among them, 39 samples were positive for Helicobacter pylori but none were positive for Helicobacter bilis. Sequence analysis of Helicobacter genus-positive samples showed that 56 samples were Helicobacter pylori and five were Helicobacter species 'Liver 3' strain. Overall, there was no significant difference in the detection rate of Helicobacter DNA or the levels of serum and bile Helicobacter pylori-specific immunoglobulin G in the various biliary disease groups compared with control patients. Neither was there any significant difference in the blood biochemistry and liver function tests between patients with positive and negative Helicobacter DNA detection. CONCLUSION: Helicobacter species' DNA are commonly present in the gallbladder of patients with gallstone diseases and in controls, implying that Helicobacter infection alone may not play a significant role in the formation of gallstones. However, our results do not exclude the possibility of Helicobacter infection as a cofactor in the development of gallstones.

Antibodies, Bacterial↗
PubMed2003

HLA-DRB1, DQB1 and DPB1 polymorphism in the Naxi ethnic group of South-western China.

Polymorphism of HLA-DRB1, DQB1 and DPB1 was revealed with a sequencing-based typing (SBT) method in unrelated healthy volunteers from the Naxi ethnic group. Among the 43 DRB1 alleles detected, the most common allele was DRB1*12021 with a frequency of 17%, followed by DRB1*08032, DRB1*09012 and DRB1*1404 with frequencies of 8.5%, 7.4% and 7.4%, respectively. Among 23 DQB1 alleles detected, the most frequent DQB1 allele was DQB1*03011/0309 (21.9%), followed by DQB1*0502 (16.4%) and DQB1*05031 (9.6%). For the DPB1 locus, the most common alleles were DPB1*0501 (25.5%), DPB1*0402 (14.6%) and DPB1*02012 (12.0%). The most common DRB1-DQB1-DPB1 haplotype was DRB1*1404-DQB1*05031-DPB1*0402 with a frequency of 5.26%, followed by the DRB1*08032-DQB1*06011-DPB1*1301 (3.51%). The distribution characteristics of the HLA class II alleles revealed that the Naxi ethnic group belonged to the Southern group of Chinese.

Alleles↗
PubMed2003

Comparative susceptibilities of diamondback moth (Lepidoptera: Plutellidae) and cabbage looper (Lepidoptera: Noctuidae) from Minnesota and south Texas to lambda-cyhalothrin and indoxacarb.

The susceptibility of early instars of diamondback moth, Plutella xylostella (L.), and early (first and second) and late instars (third and fourth) of cabbage looper, Trichoplusia ni (Hübner), from Minnesota and south Texas, to indoxacarb and lambda-cyhalothrin was determined in the laboratory. Susceptibilities of the two species from the two geographical locations to indoxacarb and lambda-cyhalothrin varied greatly. P. xylostella from Minnesota was as susceptible to indoxacarb as those from south Texas, whereas both early and late instar T. ni from south Texas were significantly more tolerant to indoxacarb than those from Minnesota. The LC50 values of indoxacarb for early and later instar T. ni at 48 h from south Texas were 4.3- and 34.0-fold greater than those from Minnesota, respectively. Similarly, early instar P. xylostella and late instar T. ni from south Texas were significantly less susceptible to lambda-cyhalothrin than those from Minnesota. Percentage mortality of the two insect species caused by the two insecticides varied with time of exposure and generally exhibited similar patterns of responses to different concentrations for each insecticide.

Animals↗
PubMed2003

Genetic association and cellular function of MC1R variant alleles in human pigmentation.

We have examined MC1R variant allele frequencies in the general population of South East Queensland and in a collection of adolescent dizygotic and monozygotic twins and family members to define statistical associations with hair and skin color, freckling, and mole count. Results of these studies are consistent with a linear recessive allelic model with multiplicative penetrance in the inheritance of red hair. Four alleles, D84E, R151C, R160W, and D294H, are strongly associated with red hair and fair skin with multinomial regression analysis showing odds ratios of 63, 118, 50, and 94, respectively. An additional three low-penetrance alleles V60L, V92M, and R163Q have odds ratios 6, 5, and 2 relative to the wild-type allele. To address the cellular effects of MC1R variant alleles in signal transduction, we expressed these receptors in permanently transfected HEK293 cells. Measurement of receptor activity via induction of a cAMP-responsive luciferase reporter gene found that the R151C and R160W receptors were active in the presence of NDP-MSH ligand, but at much reduced levels compared with that seen with the wild-type receptor. The ability to stimulate phosphorylation of the cAMP response element binding protein (CREB) transcription factor was also apparent in all stimulated MC1R variant allele-expressing HEK293 cell extracts as assessed by immunoblotting. In contrast, human melanoma cell lines showed wide variation in the their ability to undergo cAMP-mediated CREB phosphorylation. Culture of human melanocytes of known MC1R genotype may provide the best experimental approach to examine the functional consequences for each MC1R variant allele. With this objective, we have established more than 300 melanocyte cell strains of defined MC1R genotype.

Alleles↗