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Biomedical subjects

J W Liu

Publications and source records attributed to J W Liu.

At least 19 recordsLinked to original sources
PubMed2007

Characterization of endothelial-like cells derived from human mesenchymal stem cells.

BACKGROUND: Blood-derived endothelial progenitor cells (EPC) have been used to treat ischemic disease. However, the number of EPC that can be obtained from adult blood is limited. OBJECTIVE: To characterize endothelial-like cells obtained from human bone marrow and determine their ability to stimulate new blood vessel formation in vivo. METHODS: Mononuclear cells (MNC) were isolated from human bone marrow or umbilical cord blood and cultured in endothelial growth medium (EGM-2). Mesenchymal stem cells (MSC) were isolated from bone marrow and induced to differentiate into endothelial-like cells (MSCE), or adipocytes or osteocytes by growth in EGM-2, adipogenic or osteogenic medium. RESULTS: Cells obtained by culturing bone marrow MNC in EGM-2 formed cord- or tube-like structures when grown on Matrigel(TM) and expressed several endothelial marker proteins. However, cell morphology and the profile of endothelial marker protein expression were different from those of cord blood-derived EPC (cbEPC). Cells with a similar phenotype were obtained by differentiation of MSC into MSCE, which was accompanied by an increase of endothelial marker proteins and a diminished capacity to differentiate into adipocytes. Subcutaneous implantation of MSCE in collagen plugs in non-obese diabetic-severe combined immunodeficient (NOD-SCID) mice resulted in formation of functional blood vessels that had incorporated the MSCE. CONCLUSIONS: Our results show that MSCE and cbEPC are different cell types. The formation of functional blood vessels by MSCE, combined with high yields and a reduced capacity to differentiate into other cell types compared with MSC, makes these cells potentially useful for autologous therapy of ischemic disease.

Adipocytes↗
PubMed2006

Maximum independent set on diluted triangular lattices.

Core percolation and maximum independent set on random graphs have recently been characterized using the methods of statistical physics. Here we present a statistical physics study of these problems on bond diluted triangular lattices. Core percolation critical behavior is found to be consistent with the standard percolation values, though there are strong finite size effects. A transfer matrix method is developed and applied to find accurate values of the density and degeneracy of the maximum independent set on lattices of limited width but large length. An extrapolation of these results to the infinite lattice limit yields high precision results, which are tabulated. These results are compared to results found using both vertex based and edge based local probability recursion algorithms, which have proven useful in the analysis of hard computational problems, such as the satisfiability problem.

Journal Article↗
PubMed2006

Evaluation of the rpoB macroarray assay to detect rifampin resistance in Mycobacterium tuberculosis in Beijing, China.

The aim of this study was to evaluate the modified rifampin oligonucleotide (RIFO) macroarray method to detect mutations in the hot-spot region of the rpoB gene, associated with rifampin (RIF) resistance in Mycobacterium tuberculosis. The study sample included 123 strains of M. tuberculosis isolated in the Beijing, China, area in 2002-2005, including 73 RIF-resistant and 40 pansusceptible strains. The genotypic assay successfully identified 91.8% of the RIF-resistant strains, whereas no mutations were found in RIF-susceptible strains. The most frequently detected rpoB mutations were in the codons 516, 526, and 531, together accounting for 74% of RIF-resistant strains. Spoligotyping subdivided all strains into 11 unique profiles and 3 profiles shared by 3, 4, and 103 strains, respectively. The 113 strains belonged to the Beijing family genotypes, defined by the specific spoligotype signature (absence of signals 1-34) and deletion of the RD105 region. The rpoB S531L (TCG-->TTG) mutation was found in 57.4% of the RIF-resistant strains of the Beijing genotype. A mutation in the rpoB hot-spot region was found in 51 of the 55 (92.7%) multidrug-resistant strains (i.e., resistant to at least RIF and isoniazid), thus demonstrating the added utility of the modified RIFO method to predict multidrug resistance. The RIFO method is relatively simple to perform and allows straightforward interpretation of results; consequently, it can be used in clinical diagnostic laboratories as a fast complement to phenotypic methods.

Antibiotics, Antitubercular↗
PubMed2005

Analysis of STR polymorphisms in the Chao Shan population in South China.

Chao Shao area is a littoral under the jurisdiction of Guangdong province, abutting on Fujian. Historically, the area was relatively isolated from other parts of China until 1990s, when it started to take a small number of immigrants from other regions. People residing in this area speak in unique dialect and have distinct lifestyle. Allele frequencies for the 15 short tandem repeats (STR) loci included in the AmpFLSTR Identifiler kit were obtained from a sample of 144 unrelated Chinese born and living in the Chao Shan area, South China.

China↗
PubMed2005

Global analysis of endothelial cell line proliferation patterns based on nutrient-depletion models: implications for a standardization of cell proliferation assays.

It is known that cell populations growing in different environmental conditions may exhibit different proliferation patterns. However, it is not clear if, despite the diversity of the so-observed patterns, inherent cellular growth characteristics of the population can nevertheless be determined. This study quantifies the proliferative behaviour of the permanent endothelial human cell line, Eahy926, and establishes to which extent the estimation of the cell proliferation rate depends on variations of the experimental protocols. Cell proliferation curves were obtained for cells cultured over 16 days and the influences of cell seeding densities, foetal bovine serum content and frequency of culture medium changes were investigated. Quantitative dynamic modelling was conducted to evaluate the kinetic characteristics of this cell population. We proposed successive models and retained a nutrient-depletion toxicity dependant model, which takes into account the progressive depletion of nutrients, as well as the increase of toxicity in the cell culture medium. This model is shown to provide a very good and robust prediction of the experimental proliferation curves, whatever are the considered frequency of culture medium changes and serum concentrations. Thus, the model enables an intrinsic quantification of the parameters driving in vitro EAhy926 proliferation, including proliferation, nutrient consumption and toxicity increase rates, rather independently of the experiments design. We therefore propose that such models could provide a basis for a standardized quantification of intrinsic cell proliferation kinetics.

Cell Count↗
PubMed2005

Characteristics of patients suffering from tuberculous pleuritis with pleural effusion culture positive and negative for Mycobacterium tuberculosis, and risk factors for fatality.

SETTING: A 2500-bed hospital. OBJECTIVES: To clarify characteristics of tuberculous pleuritis (TP) with pleural effusion culture positive and negative for Mycobacterium tuberculosis (PECP-MT and PECN-MT) and to identify risk factors for fatality. PATIENTS AND METHODS: Retrospective analysis of TP patients with PECP-MT and PECN-MT, and review of medical charts of deceased patients. RESULTS: Of 126 patients enrolled (28 PECP-MT and 98 PECN-MT), those with PECP-MT had a higher prevalence of steroid use (SU) (14.3% vs. 2.0%; P = 0.022) and concurrent tuberculosis involving another site (7.2% vs. 0.0%; P = 0.048), increased neutrophils (36.4% vs. 16.6%; P = 0.020) and decreased glucose levels (mean 88.7 vs. 127.6 g/dl; P = 0.012) in pleural effusion, and a higher fatality rate (28.0% vs. 3.1%; P < 0.001). Deceased patients (n = 10) were older (mean 74.2 vs. 64.4 years; P = 0.047), had a higher incidence of acute renal failure (ARF) (50.0% vs. 11.7%; P = 0.007), and a higher prevalence of malignancy (40.0% vs. 6.3%; P = 0.006), history of stroke (30.0% vs. 7.2%; P = 0.048) and SU (20.0% vs. 1.8%; P = 0.034). CONCLUSION: SU, concurrent tuberculosis involving another site, increased neutrophils and decreased glucose levels in pleural effusion may be predictive factors for PECP-MT. Malignancy, ARF and SU, and perhaps being elderly or history of stroke, are risk factors for fatality in patients with TP.

Age Factors↗
PubMed2004

Gene expression spectra in human leukemia HL-60 cells treated with EGCG.

To decipher the molecular mechanism of EGCG induced HL-60 cell apoptosis, alterations of gene expression spectra in HL-60 cell line cells after treatment with EGCG were screened by cDNA chip, and analyzed with the GenePix 3.0 twice; and the cDNA chip results further identified by RT-PCR. Ninety-seven genes among the total 8398 (1.15%) showed consistent significant differential expression in the duplicated cDNA chip assessments. Thirty-nine genes (40.2%) were up-regulated and 58 genes (59.8%) were down-regulated; and the randomly selected four performed RT-PCR results agreed with the cDNA chip data. The results suggest that the apoptosis of HL-60 cells induced by EGCG is a progressive transformation process regulated by a variety of genes.

Base Sequence↗
PubMed2004

Optimization of submerged culture requirements for the production of mycelial growth and exopolysaccharide by Cordyceps jiangxiensis JXPJ 0109.

AIMS: The objective of the present study was to investigate the optimal culture requirements for mycelial growth and exopolysaccharide production by Cordyceps jiangxiensis JXPJ 0109 in submerged culture. METHODS AND RESULTS: The effects of medium ingredients (i.e. carbon and nitrogen sources, and growth factor) and other culture requirements (i.e. initial pH, temperature, etc.) on the production of mycelia and exopolysaccharide were observed using a one-factor-at-a-time method. More suitable culture requirements for mycelial growth and exopolysaccharide production were proved to be maltose, glycerol, tryptone, soya bean steep powder, yeast extract, medium capacity 200 ml in a 500-ml flask, agitation rate 180 rev min(-1), seed age 4-8 days, inoculum size 2.5-7.5% (v/v), etc. The optimal temperatures and initial pHs for mycelial growth and exopolysaccharide production were at 26 degrees C and pH 5 and at 28 degrees C and pH 7, respectively, and corresponding optimal culture age were observed to be 8 and 10 days respectively. According to the primary results of the one-factor-at-a-time experiments, the optimal medium for the mycelial growth and exopolysaccharide production were obtained using an orthogonal layout method to optimize further. Herein the effects of medium ingredients on the mycelial growth of C. jiangxiensis JXPJ 0109 were in the order of yeast extract > tryptone > maltose > CaCl2 > glycerol > MgSO4 > KH2PO4 and the optimal concentration of each composition was 15 g maltose (food-grade), 10 g glycerol, 10 g tryptone, 10 g yeast extract, 1 g KH2PO4, 0.2 g MgSO4, and 0.5 g CaCl2 in 1 l of distilled water, while the order of effects of those components on exopolysaccharide production was yeast extract > maltose > tryptone > glycerol > KH2PO4 > CaCl2 > MgSO4, corresponding to the optimal concentration of medium was as follows: 20 g maltose (food-grade), 8 g glycerol, 5 g tryptone, 10 g yeast extract, 1 g KH2PO4, and 0.5 g CaCl2 in 1 l of distilled water. CONCLUSIONS: Under the optimal culture requirements, the maximum exopolysaccharide production reached 3.5 g l(-1) after 10 days of fermentation, while the maximum production of mycelial growth achieved 14.5 g l(-1) after 8 days of fermentation. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the submerged culture requirements for mycelial growth and exopolysaccharide in C. jiangxiensis, and this two-step optimization strategy in this study can be widely applied to other microbial fermentation processes.

Carbon↗
PubMed2003

Evolution of an organophosphate-degrading enzyme: a comparison of natural and directed evolution.

Organophosphate-degrading enzyme from Agrobacterium radiobacter P230 (OPDA) is a recently discovered enzyme that degrades a broad range of organophosphates. It is very similar to OPH first isolated from Pseudomonas diminuta MG. Despite a high level of sequence identity, OPH and OPDA exhibit different substrate specificities. We report here the structure of OPDA and identify regions of the protein that are likely to give it a preference for substrates that have shorter alkyl substituents. Directed evolution was used to evolve a series of OPH mutants that had activities similar to those of OPDA. Mutants were selected for on the basis of their ability to degrade a number of substrates. The mutations tended to cluster in particular regions of the protein and in most cases, these regions were where OPH and OPDA had significant differences in their sequences.

Amino Acid Sequence↗
PubMed2003

Inhibition of liver cancer cell proliferation and migration by a combination of (-)-epigallocatechin-3-gallate and ascorbic acid.

A mixture of (-)-epigallocatechin-3-gallate (EGCG) and ascorbic acid exhibited 73.2% inhibition of SMMC-7721 cell proliferation in a soft agar colony formation assay, which was much higher than EGCG (40.4%) or ascorbic acid (12.4%) alone. In the cell migration assay, the mixture also significantly suppressed the migration of SMMC-7721 cells by 65.9% while EGCG and/or ascorbic acid did by 28.9% and 18.7%, respectively. Ascorbic acid was able to enhance the antioxidant activity of EGCG by decreasing the intracellular oxidative stress according to fluorographic analysis of oxidative stress. In conclusion, the combination of EGCG and ascorbic acid can strongly suppress the proliferation and metastasis of liver cancer cells, possibly with a mechanism associated with the scavenging of reactive oxygen species. All these events add to our knowledge of liver cancer chemotherapy.

Antioxidants↗
PubMed2003

The high value of high-resolution computed tomography in predicting the activity of pulmonary tuberculosis.

SETTING: A 2500-bed medical centre in southern Taiwan. OBJECTIVE: To study the clinical value of high-resolution computed tomography (HRCT) in predicting the activity of pulmonary tuberculosis (TB). DESIGN: HRCTs were performed prospectively in 148 patients whose chest radiographs (CXRs) showed highly suspicious signs of pulmonary TB, predominantly upper lung field infiltration. The HRCT findings, interpreted independently by a pulmonologist and a radiologist, were used to predict the activity of pulmonary TB. RESULTS: Pulmonologist-interpreted and radiologist-interpreted HRCTs showed high sensitivity (both 93%), specificity (83 vs. 88%), accuracy (86 vs. 90%), positive predictive values (76 vs. 83%) and negative predictive values (both 95%). Kappa statistic indicates good inter-reader agreement. CONCLUSION: HRCT has a high value in predicting the activity of pulmonary TB. It is a useful tool in this regard when a patient with suspected pulmonary TB lacks microbiologic proof, when clinical condition makes invasive diagnosis impossible or when a patient has completed anti-tuberculosis treatment with no compatible unequivocal CXR.

Adult↗
PubMed2003

Tuberculous wrist in the era of effective chemotherapy: an eleven-year experience.

BACKGROUND: The chronic course and non-specific clinical manifestations of tuberculous (TB) wrist often cause failure to make a timely diagnosis. OBJECTIVE: To better understand the rarely encountered TB wrist. PATIENTS AND METHODS: Retrospective review and analysis of cases of TB wrist between 1986 and 1997 in a medical centre in southern Taiwan. RESULTS: Thirty-seven cases (16 definitive, 13 probable and eight possible) of TB wrist (25 men, 12 women; mean age, 56.3 +/- 13.0 years) were found among a total of 4970 cases of tuberculosis. The most common presenting sign and symptom (mean duration 9.4 months) were local swelling and pain over the affected wrist. The mean white blood cell (WBC) count in peripheral blood was 7.04 x 10(9)/l, and the erythrocyte sediment rates (ESR) in seven of 31 patients who had ESR assayed were normal. Forty-six per cent of the patients had abnormal chest X-ray, and 35% had had previous manipulation of the affected wrist. CONCLUSION: Physicians should have a high index of suspicion for TB wrist among patients with chronic arthritis, even when their peripheral WBC count and ESR are normal. An abnormal chest X-ray and/or a history of previous manipulation of the affected wrist could be important clues for possible TB wrist.

Adult↗
PubMed2002

Nosocomial blood-stream infection in patients with end-stage renal disease: excess length of hospital stay, extra cost and attributable mortality.

Patients with end-stage renal disease undergoing haemodialysis are at high risk of nosocomial blood-stream infection (BSI), but data on the associated costs in this patient population are not available. Therefore, we conducted a retrospective matched (1:2) case-control study of such patients undergoing haemodialysis from January 1998 to December 1998 in a medical centre in southern Taiwan to determine the excess length of hospital stay, attributable mortality, and the extra cost caused by nosocomial BSI. The excess length of hospital stay was 30 days for cases vs. 16 days for controls (P<0.001), the mortality rate was 26.3% for cases vs. 0 for controls (P=0.003) (attributable mortality being 26.3%), and the median of overall costs was 131,584 dollars NT for cases vs. 65,282 dollars NT for controls (P<0.001). Based on these findings, we believe that an effective programme to minimize nosocomial BSI in this patient population would greatly reduce their medical and economic burdens.

Case-Control Studies↗
PubMed2002

Experience with a bone bank operation and allograft bone infection in recipients at a medical centre in southern Taiwan.

To assess the contamination rate of allograft bones at retrieval and the infection rate of the implanted allograft bone, we audited a bone bank retrospectively and reviewed the medical charts of allograft bone recipients between June 1999 and June 2000 at a medical centre in southern Taiwan. The bone bank did its utmost to minimize allograft contamination with hospital-acquired pathogens by adopting purposefully designed criteria for selection of donors. This protocol included sterilization with soaking of the retrieved allograft in a solution of a first-generation cephalosporin before storage and prophylaxis in recipients with first-generation cephalosporin. The contamination rates at allograft retrieval from living and cadaveric donors were 2.7% and 12.4%, respectively (P<0.001). Culture of 262 specimens taken at allograft implant revealed 12 (4.6%) positive for culture. Of the 12 patients implanted with allograft bones positive for culture, nine (75.0%) had allograft bone infection, while three (25.0%) did not. Among the 250 recipients with sterile allograft bones, four (1.6%) were found to have allograft infection. None of the cases of infection required removal of the allograft bones, and all cases were successfully treated with tailored antimicrobial therapy based on susceptibility tests on isolated bacteria. The overall infection rate was 5.0%, which compared favourably with those in other series. A prospective cohort study is needed to determine which of the varied sterilization methodologies gives the best and/or most cost-effective outcome.

Adult↗
PubMed2002

Streptococcus pneumoniae bacteremia in southern Taiwan.

Streptococcus pneumoniae bacteremia was diagnosed in 33 patients between June 1999 and November 2000 at the Chang Gung Memorial Hospital-Kaohsiung in southern Taiwan. Antimicrobial susceptibility and serotyping of the clinical isolates were performed. Pneumonia was diagnosed in 19 patients, primary bacteremia in 13, and meningitis in one. The most common serotypes were types 14, 3, and 23F. Fourteen (42.4%) isolates of S. pneumoniae were non-susceptible to penicillin. High antimicrobial resistance rates were found to erythromycin (81.9%), tetracycline (69.7%), clindamycin (69.7%), trimethoprim-sulfamethoxazole (33.1%), and chloramphenicol (12.1%). The mortality was 42.4% and liver cirrhosis was an independent risk factor for mortality (odds ratio = 9.998; 95% confidence interval, 1.011-98.85; p=0.049). All isolated strains were covered by 23-valent the pneumococcal vaccine. Given the increasing prevalence of penicillin non-susceptible S. pneumoniae infection in the community, ongoing periodic monitoring of the evolutionary clinical situation is needed. Results of this study suggest that patients with liver cirrhosis should be inoculated with pneumococcal vaccine.

Adult↗
PubMed2002

[Purification and characterization of L-amino acid oxidase from Agkistrodon halys pallas venom].

L-amino acid oxidase (LAO, EC 1.4.3.2) is widely found in snake venoms and is thought to contribute to the toxicity in envenoming. By using of Sephadex G-150, DEAE-Sepharose CL-6B and FPLC Superose 12 chromatography, a protein with L-amino acid oxidase activity was purified and characterized from Agkistrodon haly Pallas venom. Its molecular mass was 57 kD as determined by SDS-PAGE analysis under both reducing and non-reducing conditions, and its pI was about 4.9. The protein catalysed the stereospecific oxidative deamination of L-amino acid substrate. It inhibited the platelet aggregation induced by ADP and collagen dose-dependently, even at low concentrations of 0.2 micromol/L and 0.08 micromol/L, respectively. The LAO had antibacterial effect to E.coli K12D31, and the effective concentration was as low as 0.03 g/L. Furthermore, the LAO showed cytotoxicity in crystal violet assay and apoptosis-inducing activity in the A549 cells. After 24h treatment with 5 mg/L LAO, the typical DNA fragmentation pattern of apoptotic cells was observed by using of agrose gel electrophoresis.

Agkistrodon↗
PubMed2001

Effect of conjugated linoleic acid on fungal delta6-desaturase activity in a transformed yeast system.

Conjugated linoleic acid (CLA; 18:2), a group of positional and geometric isomers of linoleic acid (LA; 18:2n-6), has been shown to modulate immune function through its effect on eicosanoid synthesis. This effect has been attributed to a reduced production of n-6 polyunsaturated fatty acid (PUFA), the precursor of eicosanoids. Since delta6-desaturase is the rate-limiting enzyme of the n-6 PUFA production, it is our hypothesis that CLA, which has similar chemical structure to LA, interacts directly with delta6-desaturase. A unique and simple model, i.e., baker's yeast (Saccharomyces cerevisiae) transformed with fungal delta6-desaturase gene, previously established, was used to investigate the direct effect of CLA on delta6-desaturase. This model allows LA to be converted to y-linolenic acid (GLA; 18:3n-6) but not GLA to its metabolite(s). No metabolites of CLA were found in the lipids of the yeast transformed with delta6-desaturase. The inability to convert CLA to conjugated GLA was not due to the failure of yeast cells to take up the CLA isomers. CLA mixture and individual isomers significantly inhibited the activity of delta6-desaturase of the transformed yeast in vivo. Even though its uptake by the yeast was low, CLA c9,t11 isomer was found to be the most potent inhibitor of the four isomers tested, owing to its high inhibitory effect on delta6-desaturase. Since CLA did not cause significant changes in the level of delta6-desaturase mRNA, the inhibition of GLA production could not be attributed to suppression of delta6-desaturase gene expression at the transcriptional level.

Fatty Acid Desaturases↗