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Biomedical subjects

Y L Chen

Publications and source records attributed to Y L Chen.

At least 19 recordsLinked to original sources
PubMed2006

Photocatalysis of 2,2',3,4,4',5'-hexachlorobiphenyl and its intermediates using various catalytical preparing methods.

Four etching solutions used on support materials and two coating methods of TiO(2) were conducted to investigate the effects of catalytical preparing methods on the photocatalysis of 2,2',3,4,4',5'-hexachlorobiphenyl (PCB congener 138). The results of XRD analyses confirmed that various etching solutions used on support substrates did not influence the characteristics of titanium(IV) oxide. The XRD patterns of crystallization for the catalysts before and after purification remained unchanged. Hydrofluoric acid used as an etching solution for the support substrates provided the best adhesion stability for the catalysts that demonstrated the highest photocatalytic efficiency for congener 138. Xenon and ultraviolet lamps were used to compare the irradiation effect on photocatalysis. The shortest half-lives of congener 138 were 7.4 and 12.2 h using xenon and UV reactors, respectively. Lower chlorinated biphenyls (lower congener numbers) were identified through the continuous dechlorination of congener 138. PCB congeners 99, 87, 66, 49, 28, 17, 9, and 7 were detected as a result of dechlorination from higher chlorinated congeners to lower chlorinated congeners along with the extension of exposure times. The concentrations of chloride ion were increased with increasing exposure time through dechlorination, while the concentrations of organic chlorine of congener 138 were decreased. Meta-dechlorination was the most commonly found mechanism for the photocatalysis of PCB 138. The activation energy of the photocatalysis of congener 138 was 70.8 kJ mol(-1).

Catalysis↗
PubMed2005

Factors affecting the biodegradation of PCP by Pseudomonas mendocina NSYSU.

A pentachlorophenol (PCP) degrading bacterium was isolated from PCP-contaminated soils and identified as Pseudomonas mendocina NSYSU (P. mendocina NSYSU). The main objectives of this study were to (1) clarify the factors affecting the ability and efficiency of PCP biodegradation by P. mendocina NSYSU, and (2) optimize the use of this bacterium in bioremediation of PCP. Microcosm experiments were conducted to fulfill the objectives. In batch cultures, P. mendocina NSYSU used PCP as its sole source of carbon and energy and was capable of completely degrading this compound. This was confirmed by the stoichiometric release of chloride ion. Moreover, P. mendocina NSYSU was able to mineralize a high concentration of PCP (150 mg/L). Results from the oxygen concentration experiment reveal that the growth of P. mendocina NSYSU was inhibited under low oxygen and anaerobic conditions. Results indicate that the optimal growth conditions for P. mendocina NSYSU include the following: slightly acidic (6<pH<7), aerobic, and relatively moderate ambient temperature (20 degrees C<temperature<30 degrees C) conditions. Addition of extra carbon sources (sodium acetate and glucose) could not enhance the PCP biodegradation. No PCP byproducts were detected after eight days of incubation in this study. This suggests that P. mendocina NSYSU is able to effectively biodegrade PCP and its biodegradation byproducts without the accumulation of inhibitory toxic compounds. Results from this study could be used to assist the optimization of its use in bioremediation of PCP.

Biodegradation, Environmental↗
PubMed2005

Particle size and magnetic field-induced optical properties of magnetic fluid nanoparticles.

Magnetite nanoparticles with diameters of 7, 9, and 12 nm have been prepared by a chemical coprecipitation method. The transmission of light through magnetic fluid containing these nanoparticles has been investigated as a function of film thickness with wavelength between 400 and 750 nm, and applied magnetic fields up to 275 Oe. The transmission threshold shifts to the lower wavelength side with decreasing magnetic fluid film thickness as well as the particle size. For a given film thickness, the transmittance increases with increasing magnetic field for films with a particle size of 7 and 9 nm, but decreases in the 12-nm film. This is attributed to the competition between the van der Waals and dipole-dipole interaction.

Journal Article↗
PubMed2005

Arbuscular mycorrhizal fungi associated with the Meliaceae on Hainan island, China.

Species richness, spore density, frequency of occurrence, and relative abundance of AM fungi were determined in rhizosphere soil samples from nine tropical rainforest sites on Hainan island, south China, and the arbuscular mycorrhizal (AM) status of members of the Meliaceae was examined. All 28 plant taxa investigated (25 species including two varieties of 1 species and three varieties of another) were colonized by AM fungi. The mean proportion of root length colonized was 56% (range 10-95%). Vesicles were observed in 27 and hyphal coils in 26 of the 28 plant taxa. Mycorrhizas were of the Paris-type or intermediate-type, with no Arum-type mycorrhizas observed. Species richness of AM fungi varied from 3 to 15 and spore density from 46 to 1,499 per 100 g rhizosphere soil. Of 33 AM fungal taxa in five genera isolated and identified, 18 belonged to Glomus, 9 to Acaulospora, 1 to Entrophospora, 2 to Gigaspora, and 3 to Scutellospora. Acaulospora and Glomus were the dominant genera identified. Glomus claroideum was the taxon most commonly isolated, with a frequency of occurrence of 56.5% and relative abundance of 10.4%. A positive correlation was found between percentage of root length colonization and species richness. However, there was no correlation between spore density and percentage of root length colonized by AM fungi.

China↗
PubMed2005

Cortical dysplasia associating with abnormal vasculature complicated with subdural haemorrhage.

Cortical dysplasia is a neuronal migration disorder occasionally associated with anomalous draining veins. However, to our knowledge, no intracranial haemorrhage in conjunction with this association has been reported in the literature. We herein report a 7-month-old baby girl with cortical dysplasia associated with an ipsilateral cortical draining vein and complicated with subdural haemorrhage, with the diagnosis made by computed tomography and magnetic resonance imaging. This case demonstrated that patients with this condition could have an excellent prognosis even when the anomalous veins coexist with intracranial haemorrhage. We postulate that venous rupture may be the cause of this condition and further discuss the possible pathophysiology.

Central Nervous System Vascular Malformations↗
PubMed2005

Utilization of the metal-cyano complex tetracyanonickelate (II) by Azotobacter vinelandii.

AIMS: The ability of Azotobacter vinelandii, a N(2)-fixing bacterium, to biodegrade tetracyanonickelate (TCN) was evaluated. METHODS AND RESULTS: The amounts of TCN were measured spectrophotometrically. Ammonia was determined colorimetrically by the indophenol method. The produced methane from TCN conversion by A. vinelandii was detected by gas chromatography. Results showed that A. vinelandii was able to biodegrade 1 mmol l(-1) of TCN. Ammonia and methane were detected during the process of TCN degradation. Effects of exogenous nitrogen sources on TCN degradation were addressed in this study. Results revealed that the addition of ammonia (1, 5 and 10 mmol l(-1)) into the reaction mixtures caused decrease of TCN degradation rate during a 24-h incubation period. This inhibition was also observed when nitrite (5 and 10 mmol l(-1)) was added, whereas TCN degradation still proceeded after the addition of nitrate at the same concentrations. Furthermore, the rate of TCN utilization was strikingly enhanced when 0.8% of glucose was added. CONCLUSIONS: Azotobacter vinelandii can degrade 1 mmol l(-1) of TCN into ammonia and methane. However, the inhibitory effects of exogenous ammonia and nitrite on TCN degradation by this bacterium were found in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report defining the capability of A. vinelandii to degrade TCN. This bacterium might have potential value in applied strategies for removing metal-cyano wastes. Furthermore, these findings would be helpful in designing a practical system inoculated with A. vinelandii for the treatment of TCN.

Ammonia↗
PubMed2003

Effects of soil pH, temperature and water content on the growth of Burkholderia pseudomallei.

Optimum conditions were determined for the growth of Burkholderia pseudomallei in natural soils or waters. It grows better in paddy soil, crop-covered and fallow field than in fresh and salty water. Although the optimal temperature and pH for the growth were 37 or 42 degrees C, and 6.5 or 7.5 in an environmental-mimicking soil medium, this bacterium can still grow at 4 degrees C, which was suggested to be related with the occurrence of melioidosis in some cold areas. In soil media with water content < 15. B. pseudomallei did not grow until 60 d of incubation, suggesting that water contents of soils in which it dwelled would be one important factor in determining the growth rate.

Bacteriological Techniques↗
PubMed2003

Detection of Burkholderia pseudomallei in rice fields with PCR-based technique.

Burkholderia pseudomallei Ara- in rice fields was detected using PCR-based techniques with 16S RNA and flagella gene primer sets. The sensitivity of these PCRs was at least 1 CFU/mL of B. pseudomallei Ara- preincubated into Ashdown's medium for 6 h. B. pseudomallei Ara- DNA from watery soil were more detectable than from dry soil. The distribution of this DNA was mainly found at a depth of 300-600 mm under crop-covered fields, but not detected in the location of soil close to the land surface. The results suggest that PCR based on 16S RNA and flagella gene primer sets can be applied to investigate the presence of B. pseudomallei Ara- in contaminated soil of rice fields.

Burkholderia pseudomallei↗
PubMed2003

Enhanced PCE dechlorination by biobarrier systems under different redox conditions.

The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to evaluate the (1) feasibility of enhancing PCE biodegradation using cane molasses and sludge cakes as the primary substrates under methanogenic and iron reducing conditions, and (2) potential of installation a sludge cake/cane molasses biobarrier to clean up PCE-contaminated aquifers. The biodegradability of sludge cake (from secondary wastewater treatment system) and cane molasses was tested using bioavailability experiments. Results show that biodegradable materials were released from sludge cake/cane molasses and utilized by microbial consortia. Based on the chemical oxygen demand (COD) tests, approximately 28 and 248 mg of biodegradable COD can be released from 1g of sludge cake and 1g of cane molasses under anaerobic conditions, which have the potential to convert 70 and 620 mg of PCE to ethylene (ETH), respectively. Reductive dechlorination was evaluated using microcosms containing primary substrates (sludge cake/cane molasses) and inocula (aquifer sediments). Results indicate that sludge cake and cane molasses can serve as the diffusion sources of primary substrates, and enhance the reductive dechlorination of PCE under methanogenic processes. However, results from this study were not sufficient enough to show that reductive dechlorination of PCE would occur under iron-reducing conditions. This indicates that more studies need to be performed to further evaluate the role of iron reduction on the PCE dechlorination. Results reveal that it is feasible and applicable to install a sludge cake or cane molasses biobarrier to clean up PCE contaminated aquifers. From an engineering point of view, the sludge cake/cane molasses biobarrier has the potential to become an environmentally and economically acceptable technology for PCE bioremediation.

Biodegradation, Environmental↗
PubMed2003

Remediation of PCE-contaminated aquifer by an in situ two-layer biobarrier: laboratory batch and column studies.

The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop an in situ two-layer biobarrier system consisting of an organic-releasing material layer followed by an oxygen-releasing material layer. The organic-releasing material, which contained sludge cakes from a domestic wastewater treatment plant, is able to release biodegradable organics continuously. The oxygen-releasing material, which contained calcium peroxide, is able to release oxygen continuously upon contact with water. The first organic-releasing material layer was to supply organics (primary substrates) to reductively dechlorinate PCE in situ. The second oxygen-releasing material layer was to release oxygen to aerobic biodegrade or cometabolize PCE degradation byproducts from the first anaerobic layer. Batch experiments were conducted to design and identify the components of the organic and oxygen-releasing materials, and evaluate the organic substrate (presented as chemical oxygen demand (COD) equivalent) and oxygen release rates from the organic-releasing material and oxygen-releasing materials, respectively. The observed oxygen and COD release rates were approximately 0.0368 and 0.0416 mg/d/g of material, respectively. A laboratory-scale column experiment was then conducted to evaluate the feasibility of this proposed system for the bioremediation of PCE-contaminated groundwater. This system was performed using a series of continuous-flow glass columns including a soil column, an organic-releasing material column, two consecutive soil columns, and an oxygen-releasing material column, followed by two other consecutive soil columns. Anaerobic acclimated sludges were inoculated in the first four columns, and aerobic acclimated sludges were inoculated in the last three columns to provide microbial consortia for contaminant biodegradation. Simulated PCE-contaminated groundwater with a flow rate of 0.25 L/d was pumped into this system. Effluent samples from each column were analyzed for PCE and its degradation byproducts. Results show that up to 99% of PCE removal efficiency was obtained in this passive system. Thus, the biobarrier treatment scheme has the potential to be developed into an environmentally and economically acceptable remediation technology for the in situ treatment of PCE-contaminated aquifer.

Bacteria, Aerobic↗
PubMed2003

Adsorption characteristics of benzene on biosolid adsorbent.

This study selected biosolids from a petrochemical wastewater treatment plant as the raw material. The sludge was immersed in 0 to 5 mol l(-1) of ZnCl2 solutions and pyrolyzed at different temperatures. When the sludge was pyrolyzed for 30 min at temperatures of 400, 500, 600, and 700 degrees C, the corresponding surface area of the biosolid adsorbent was 46, 401, 921, and 727 m2/g, respectively. Pore size analysis indicated that the mesopore (20 to 500 A) contributed more than the macropore and micropore in the sludge pyrolytic residue. When the benzene influent concentration was 800 ppmv, the adsorption capacity ranged from 59 to 164 mg/g for different biosolid adsorbents. A larger BET surface area and smaller average pore diameter yielded a larger benzene adsorption capacity.

Adsorption↗
PubMed2001

Down-regulation of Fas-L in glioma cells by ribozyme reduces cell apoptosis, tumour-infiltrating cells, and liver damage but accelerates tumour formation in nude mice.

Fas-L (CD95L, APO-1L) expresses in a variety of tumours and has been proposed to play a role in tumour formation and metastasis. The contribution of Fas-L to tumour growth, however, is not conclusive especially in systems using cells with over-expressed Fas-L. In this study we down-regulated the expression o Fas-L in human glioma cells by a hammerhead ribozyme (Fas-L(ribozyme)) targeting against Fas-L mRNA. Fas-L(ribozyme)-carrying cells exhibited slightly enhanced growth rate and less degree of spontaneous apoptosis in vitro as compared with vector controls. In nude mice, Fas-L(ribozyme)-carrying cells grew faster with lesser apoptosis, formed bigger tumour with significantly fewer infiltrating cells in the tumour area, and triggered relatively milder tumour-associated liver damage than vector controls did. Thus, down-regulation of Fas-L not only improved viability of glioma cells but also reduces local immune responses that may consequently affect tumour formation. Taken together, our findings imply that endogenous expression of Fas-L in malignant cells is not always growth promoting.

Animals↗
PubMed2001

Prothymosin alpha enhances protective immune responses induced by oral DNA vaccination against pseudorabies delivered by Salmonella choleraesuis.

Previously, we showed that vaccination with the glycoprotein D (gD) gene of pseudorabies virus (PrV) delivered by Escherichia coli induced protective immune responses. In this study, we report that oral DNA vaccination with attenuated Salmonella choleraesuis carrying the PrV gD gene conferred protective immunity in mice against PrV. Moreover, co-delivery of the prothymosin alpha gene carried by S. choleraesuis enhanced the vaccine efficacy. Our results thus demonstrate for the first time, to our knowledge, the effectiveness of oral DNA vaccination using S. choleraesuis as a delivery vehicle and the potential usefulness of prothymosin alpha as a DNA vaccine adjuvant.

Adjuvants, Immunologic↗
PubMed2001

Synthesis and antibacterial evaluation of certain quinolone derivatives.

A number of 7-substituted quinolone derivatives were synthesized and evaluated for antibacterial and cytotoxic activities. Preliminary results indicated that most compounds tested in this study demonstrated better activity against methicillin-resistant Staphylococcus aureus than norfloxacin. Among them, 1-(4-amino-2-fluorophenyl)-6-fluoro-1,4-dihydro-7-[4-[2-(4-methoxyphenyl)-2-hydroxyiminoethyl]-1-piperazinyl]-4-oxo-3-quinolinecarboxylic acid (11d) and its ketone precursor 10d exhibited significant activities against Klebsiella pneumoniae, methicillin-resistant S. aureus, erythromycin- and ampicillin-resistant Streptococcus pneumoniae, and vancomycin-resistant Enterococcus faecalis. Due to strong cytotoxicities of 11d (a mean log GI(50) of -5.40), compound 10d, with good antibacterial activities and low cytotoxicities (a mean log GI(50) of -4.67), is a more potential drug candidate.

Anti-Bacterial Agents↗
PubMed2001

Time-dependent reversal of long-term potentiation by low-frequency stimulation at the hippocampal mossy fiber-CA3 synapses.

Using mouse hippocampal slices, we studied the induction of depotentiation of long-term potentiation (LTP) at the mossy fiber synapses onto CA3 pyramidal neurons. A long train of low-frequency (1 Hz/900 pulses) stimulation (LFS) induced a long-term depression of baseline synaptic transmission or depotentiation of previously established LTP, which was reversible and was independent of NMDA receptor activation. This LFS-induced depotentiation was observed when the stimulus was delivered 1 or 10 min after LTP induction. However, when LFS was applied at 30 min after induction, significantly less depotentiation was found. The induction of depotentiation on one input was associated with a heterosynaptic reverse of the LTP induced previously on a separate pathway. In addition, this LFS-induced depotentiation appeared to be mediated by the activation of group 2 metabotropic glutamate receptors (mGluRs), because it was mimicked by the bath-applied group 2 agonist (2S,2'R,3'R)-2-(2', 3'-dicarboxycyclopropyl) glycine and was specifically inhibited by the group 2 antagonists (S)-alpha-methyl-4-carboxyphenylglycine and (alphaS)-alpha-amino-alpha-(1S,2S)-2-carboxycyclopropyl-9H-xanthine-9-propanic acid. Moreover, the induction of depotentiation was entirely normal when synaptic transmission is blocked by glutamate receptor antagonist kynurenic acid and was associated with a reversal of paired-pulse facilitation attenuation during LTP expression. Pretreatment of the hippocampal slices with G(i/o)-protein inhibitor pertussis toxin (PTX) prevented the LFS-induced depotentiation. These results suggest that the activation of presynaptic group 2 mGluRs and in turn triggering a PTX-sensitive G(i/o)-protein-coupled signaling cascade may contribute to the LFS-induced depotentiation at the mossy fiber-CA3 synapses.

Animals↗