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Biomedical subjects

Wei Cheng

Publications and source records attributed to Wei Cheng.

At least 37 records · Page 2Linked to original sources
PubMed2005

Adsorption of dissolved natural organic matter by modified activated carbons.

Adsorption of dissolved natural organic matter (DOM) by virgin and modified granular activated carbons (GACs) was studied. DOM samples were obtained from two water treatment plants before (i.e., raw water) and after coagulation/flocculation/sedimentation processes (i.e., treated water). A granular activated carbon (GAC) was modified by high temperature helium or ammonia treatment, or iron impregnation followed by high temperature ammonia treatment. Two activated carbon fibers (ACFs) were also used, with no modification, to examine the effect of carbon porosity on DOM adsorption. Size exclusion chromatography (SEC) and specific ultraviolet absorbance (SUVA(254)) were employed to characterize the DOMs before and after adsorption. Iron-impregnated (HDFe) and ammonia-treated (HDN) activated carbons showed significantly higher DOM uptakes than the virgin GAC. The enhanced DOM uptake by HDFe was due to the presence of iron species on the carbon surface. The higher uptake of HDN was attributed to the enlarged carbon pores and basic surface created during ammonia treatment. The SEC and SUVA(254) results showed no specific selectivity in the removal of different DOM components as a result of carbon modification. The removal of DOM from both raw and treated waters was negligible by ACF10, having 96% of its surface area in pores smaller than 1 nm. Small molecular weight (MW) DOM components were preferentially removed by ACF20H, having 33% of its surface area in 1--3 nm pores. DOM components with MWs larger than 1600, 2000, and 2700 Da of Charleston raw, Charleston-treated, and Spartanburg-treated waters, respectively, were excluded from the pores of ACF20H. In contrast to carbon fibers, DOM components from entire MW range were removed from waters by virgin and modified GACs.

Adsorption↗
PubMed2005

Synthesis and biological evaluation of a natural ester sintenin and its synthetic analogues.

Synthesis of 3-(3,4-dimethoxyphenyl)propyl-3-(3,4-dimethoxyphenyl) propanoate (18), a cytotoxic natural ester, was carried out by a convenient synthetic path with a total yield of 49%. Sixteen of its analogues (19-34) were also prepared. Seventeen unsaturated derivatives of 18, compounds 1-17, were also synthesized to examine the structure-activity relationship of this type of ester. All of the synthetic compounds were passed through the cytotoxicity screenings on human tumor cell lines, such as PC-3, Hela, A549, BEL7404, CNE, and KB. Some of the esters exhibited moderate inhibitory effects on these tumor cell lines. The phenolic derivatives exhibited the highest cytotoxicity among these derivatives, while the unsaturated esters were more cytotoxic than the saturated analogues. Some of the compounds also exhibited inhibition on alpha-glucosidase.

Antineoplastic Agents↗
PubMed2005

[Target-controlled infusion of remifentanil and propofol during operation with suspension laryngoscopy].

OBJECTIVE: To evaluate target-controlled infusion (TCI) of remifentail-propofol and the balanced anesthesia of fentanyl-isoflurane during the operation with suspension laryngscope. METHODS: Sixty ASA I-II patients scheduled for the surgery through suspension laryngoscopy were randomly divided into two groups: TCI group and control group. In TCI group, anesthesia was maintained with TCI remifentanil-propofol which was stopped at the end of operation. The target plasma concentration of remifentanil was set at 6 microg/L and propofol at 3 mg/L. In control group, anesthesia was induced with intravenous fentanl 2.5 microg/kg and propofol 1-2 mg/kg, maintained with fentanl 0.03 microg.kg(-1). min(-1) and 1% isoflurane which was stopped at the end of surgery. Intubation was facilitated with succinylcholine 1-1.5 mg/kg.MAP, HR, ECG, S(p)O(2) and P(ET)CO(2) were monitored during anesthesia. The following parameters were recorded and compared between two groups: (1) the changes in blood pressure (BP), heart rate(HR) and S(p)O(2) at different time point; (2) recovery profile including the time of response to verbal commands, autonomous breathing, tracheal extubation, orientation recovery, discharging from PACU after operation; (3) OAAS scores after operation; (4) postoperative complications; (5) unexpected events and awareness during operation. RESULT: (1) The hemodynamics were stable while the target plasma concentration of remifentanil was set at 6 microg/L and propofol at 3 mg/L. (2) During tracheal intubation, suspension laryngoscope was inserted, and extubation MAP was significantly lower in TCI group than that in control group; (3) There were no significant differences in hemodynamic values and S(p)O(2) of different time points between two groups. Study group was faster than control group on recovery profile including the time of response to verbal commands, autonomous breathing, tracheal extubation, orientation recovery and discharging from PACU. There was respectively one unexpected event in both groups. CONCLUSION: Remifentanil supplemented with isoflurane anesthesia can achieve the optimal hemodynamic stability during the operation with suspension laryngoscopy and better recovery profile from anesthesia than fentanyl.

Adolescent↗
PubMed2005

[Preparation and determination of 1-O-acetylbritannilactone in Inula Britannica L].

To prepare reference substance for quality control of Inula Britannica L., 1-O-acetylbritannilactone was extracted and separated from chloroform extraction of Inula Britannica L. Chemical structure of the 1-O-acetylbritannilactone product was elucidated by ultraviolet spectrometry (UV), infrared spectroscopy (IR), nuclear magnetic resonance (NMR) and mass spectrometry (MS), and the results were in agreement with the reference. The purity of the 1-O-acetylbritannilactone product was 99.5%, which satisfies the need of reference substances of traditional Chinese medicines. A method of high performance liquid chromatography-evaporative light scattering detection (HPLC-ELSD) is described for the determination of 1-O-acetylbritannilactone in Inula Britannica L. The chromatographic conditions include Hypersil ODS-2 column, a mixture of methanol-water (52: 48, v/v) with the flow rate of 1.0 mL/min used as mobile phase. The temperature of drift tube of the ELSD was 90 degrees C. Flow rate of carrier gas was 2.5 L/min. Linear range of 1-O-acetylbritannilactone was 1.37 - 8.21 microLg (r = 0.999 8). The average recovery of 1-O-acetylbritannilactone was 100.2% with the relative standard deviation (RSD) of 1.3% (n = 6). The method is simple, accurate, time saving and reproducible.

Chromatography, High Pressure Liquid↗
PubMed2005

[Study on the relationship between DNA damage and polymorphisms of metabolizing enzymes of vinyl chloride monomer-exposed workers].

OBJECTIVE: To explore the relationship between DNA damage induced by vinyl chloride monomer (VCM) and polymorphisms of metabolizing enzymes of VCM. METHODS: Comet assay was employed to detect DNA damage, the workers were divided into two groups based on the status of DNA damage. Case-control design was used to investigate the relationship between the genetic polymorphisms of metabolizing enzymes and DNA damage. Genotypes of CYP2E1 c1/c2 and mEH4 His139Arg were identified by the PCR-RFLP, null genotypes of GST T1 and GST M1 were detected by PCR. RESULTS: The genotypes of CYP2E1 c1c2 and c2c2 were significantly associated with DNA damages (P < 0.01). A prominent risk increasing of DNA damage was observed for those individuals having a high or low VCM exposure and possessing the CYP2E1 c1c2 and c2c2 genotypes (OR 4.92, 95% CI 1.35-13.85 and OR 2.57, 95% CI 1.01-6.59). CONCLUSION: Cumulative exposure dose and polymorphism of metabolizing enzymes may modulate the DNA damage of VCM-exposed workers. possessing the CYP2E1 c1c2 and c2c2 genotypes (OR 4.92, 95% CI 1.35-13.85 and OR 2.57, 95% CI 1.01-6.59). CONCLUSION: Cumulative exposure dose and polymorphism of metabolizing enzymes may modulate the DNA damage of VCM-exposed workers.

Adolescent↗
PubMed2004

Glycerophosphoinositol, a novel phosphate source whose transport is regulated by multiple factors in Saccharomyces cerevisiae.

Git1p mediates the transport of the phospholipid metabolite, glycerophosphoinositol, into Saccharomyces cerevisiae. We report that phosphate limitation and inositol limitation affect GIT1 expression and Git1p transport activity via distinct mechanisms that involve multiple transcription factors. GIT1 transcript levels and Git1p activity are greater in cells starved for phosphate, with or without inositol limitation, than in cells only limited for inositol. Furthermore, the kinetics of GIT1 transcript accumulation and Git1p activity upon transfer of cells to phosphate starvation media are different from those obtained upon transfer of cells to inositol-free media. Pho2p and Pho4p are required for GIT1 expression and for Git1p transport activity under all growth conditions tested. In contrast, Ino2p and Ino4p are required for full GIT1 expression when inositol is limiting, with or without phosphate limitation, but not when only phosphate is limiting. Greatly reduced transport activity was detected in ino2Delta and ino4Delta cells under all growth conditions. A 300-base pair region of the GIT1 promoter containing potential Pho4p binding sites was shown to be required for full GIT1 expression. Git1p appears to act as a H(+)-symporter, and neither inositol nor phosphate effectively compete with glycerophosphoinositol for transport by Git1p. Glycerophosphoinositol was shown previously to support the growth of an inositol auxotroph. Remarkably, we now report that glycerophosphoinositol can act as the sole source of phosphate for the cell, providing functional relevance for the regulation of Git1p transport activity by phosphate.

Base Sequence↗
PubMed2004

DNA-binding orientation and domain conformation of the E. coli rep helicase monomer bound to a partial duplex junction: single-molecule studies of fluorescently labeled enzymes.

The SF1 DNA helicases are multi-domain proteins that can unwind duplex DNA in reactions that are coupled to ATP binding and hydrolysis. Crystal structures of two such helicases, Escherichia coli Rep and Bacillus stearothermophilus PcrA, show that the 2B sub-domain of these proteins can be found in dramatically different orientations (closed versus open) with respect to the remainder of the protein, suggesting that the 2B domain is highly flexible. By systematically using fluorescence resonance energy transfer at the single-molecule level, we have determined both the orientation of an E.coli Rep monomer bound to a 3'-single-stranded-double-stranded (ss/ds) DNA junction in solution, as well as the relative orientation of its 2B sub-domain. To accomplish this, we developed a highly efficient procedure for site-specific fluorescence labeling of Rep and a bio-friendly immobilization scheme, which preserves its activities. Both ensemble and single-molecule experiments were carried out, although the single-molecule experiments proved to be essential here in providing quantitative distance information that could not be obtained by steady-state ensemble measurements. Using distance-constrained triangulation procedures we demonstrate that in solution the 2B sub-domain of a Rep monomer is primarily in the "closed" conformation when bound to a 3'-ss/ds DNA, similar to the orientation observed in the complex of PcrA bound to a 3'-ss/ds DNA. Previous biochemical studies have shown that a Rep monomer bound to such a 3'-ss/ds DNA substrate is unable to unwind the DNA and that a Rep oligomer is required for helicase activity. Therefore, the closed form of Rep bound to a partial duplex DNA appears to be an inhibited form of the enzyme.

Adenosine Triphosphatases↗
PubMed2004

Transport, location, and quantal release monitoring of single cells on a microfluidic device.

A novel microfluidic device has been developed for on-chip transport, location, and quantal release monitoring of single cells. The microfluidic device consists of a plate of PDMS containing channels for introducing cells and stimulants and a glass substrate into which a cell micro-chamber was etched. The two tightly reversibly sealed plates can be separated for respective cleaning, which significantly extends the lifetime of the microchip that is frequently clogged in cell analysis experiments. Using hydraulic pressure, single cells were transported and located on the microfluidic chip. After location of a single PC12 cell on the microfluidic chip, the cell was stimulated by nicotine that was also introduced through the micro-channels, and the quantum release of dopamine from the cell was amperometricly detected with our designed carbon fiber microelectrode. The results have demonstrated the convenience and efficiency of using the microfluidic chip for monitoring of quantal release from single cells and have offered a facile method for the analysis of single cells on microfluidic devices.

Journal Article↗
PubMed2004

Probing single-stranded DNA conformational flexibility using fluorescence spectroscopy.

Single-stranded DNA (ssDNA) is an essential intermediate in various DNA metabolic processes and interacts with a large number of proteins. Due to its flexibility, the conformations of ssDNA in solution can only be described using statistical approaches, such as flexibly jointed or worm-like chain models. However, there is limited data available to assess such models quantitatively, especially for describing the flexibility of short ssDNA and RNA. To address this issue, we performed FRET studies of a series of oligodeoxythymidylates, (dT)N, over a wide range of salt concentrations and chain lengths (10 < or = N < or = 70 nucleotides), which provide systematic constraints for testing theoretical models. Unlike in mechanical studies where available ssDNA conformations are averaged out during the time it takes to perform measurements, fluorescence lifetimes may act here as an internal clock that influences fluorescence signals depending on how fast the ssDNA conformations fluctuate. A reasonably good agreement could be obtained between our data and the worm-like chain model provided that limited relaxations of the ssDNA conformations occur within the fluorescence lifetime of the donor. The persistence length thus estimated ranges from 1.5 nm in 2 M NaCl to 3 nm in 25 mM NaCl.

DNA, Single-Stranded↗
PubMed2004

[Study of mechanism on loss of some components from basement membrane in epithelial-interstitial junction in cutaneous pseudoepitheliomatous hyperplasia lesion].

OBJECTIVE: To investigate the relationship between the formation of pseudoepitheliomatous hyperplasia (PEH) and the mechanism of loss of some components from the basement membrane in epithelial interstitial junction (EIJ) in the treatment of cutaneous wounds, when formation of PEH lesion was induced. METHODS: Morphological change in epithelial tissue was observed with histopathologic method and electronic microscopy in 11 specimens of PEH lesions and 6 specimens of normal skin adjacent to PEH (PEH-N) from 11 patients with injured skin. The expression characteristics and distribution of pan-cytokeratin (p-CK), matrix metalloproteinase-2 (MMP-2), MMP-3, MMP-9, proliferating cell nuclear antigen (PCNA), epithelial cadherin(E-Cad) and beta-catenin(beta-Cat) in EMJ were detected with immunohistochemical methods. RESULTS: Epithelial cells expressing P-CK presented squamous epithelialization and extended into deep layer of mesenchyma. In epithelium-mesenchyma junction, where IV type collagen and laminin were weakly expressed, the protein contents of p-CK, E-Cad, MMP-2, MMP-3 MMP-9 were decreased, whilst the immunochemical staining of beta-Cat and PCNA was apparently increased. In the junction, epithelial basal cells were observed to migrate and to depart from basal membrane; epithelial islands and isolated epithelial cells expressing p-CK in mesenchyma could be observed. Ultrastructural observation revealed deformation of epithelial basal cells, increment of nucleus/cytoplasm ratio, loosened intercellular junctions, decrement of electronic density of BM and derangement of BM structure could be observed. CONCLUSION: Reduction in the capability of epithelial basal cells adhesion, differentiation and formation of basement membrane and cytokeratin in PEH associated with wound may be the crucial cause which controls epithelial cells migration into mesenchyma. That the contents of ColIV and LN were decreased may not be associated with MMPs, but with enhancement of the ratio of beta-Cat/E-Cad signal might be the important mechanism of dedifferentiation of epithelial basal cells and the loss of ability of structure formation and cellular migration.

Basement Membrane↗
PubMed2004

Determination of methyl tert-butyl ether (MTBE) in Chinese fuels by gas chromatography/mass spectrometry and gas chromatography/flame ionization detector.

A method was developed to determine the concentration of methyl tert-butyl ether(MTBE) in gasoline, diesel and heating oil by gas chromatography(GC) with mass spectrometry(GC-MS) or flame ionization detection (FID). The diluted gasoline was directly injected into the GC, and the complete separation of MTBE from co-eluting hydrocarbons was not required. GC/MS or GC/FID method can be used to analyze MTBE in different concentration range and have good consistency.

Carcinogens↗
PubMed2004

[Determination of the content of wear metal in lubrication oil by ICP-AES].

An analytical method for determining wear metal elements directly by ICP-AES was proposed in this paper. The optimum condition was selected. The Conostan S-21 and Conostan 75 (oil-base standard samples) prepared by multi-element oil-base reserved standard samples were applied to make calibration curve. Oil samples were diluted 5 times by kerosene. The contents of wear metals in lubrication oil were determined by ICP-AES. The relative standard deviation (RSD) of all elements was less than 1%. In addition, the authors represented the analytical efficacy of Leeman labs multi-track profile ICP, and its rapid and accurate characters of simultaneous multi-element measurement.

Calibration↗
PubMed2002

The 2B domain of the Escherichia coli Rep protein is not required for DNA helicase activity.

The Escherichia coli Rep protein is a 3' to 5' SF1 DNA helicase required for replication of bacteriophage phiX174 in E. coli, and is structurally homologous to the E. coli UvrD helicase and the Bacillus stearothermophilus PcrA helicase. Previous crystallographic studies of Rep protein bound to single-stranded DNA revealed that it can undergo a large conformational change consisting of an approximately 130 degrees rotation of its 2B subdomain about a hinge region connected to the 2A subdomain. Based on crystallographic studies of PcrA, its 2B subdomain has been proposed to form part of its duplex DNA binding site and to play a role in duplex destabilization. To test the role of the 2B subdomain in Rep-catalyzed duplex DNA unwinding, we have deleted its 2B subdomain, replacing it with three glycines, to form the RepDelta2B protein. This RepDelta2B protein can support phiX174 replication in a rep(-) E. coli strain, although the growth rate of E. coli containing the repDelta2B gene is approximately 1.5-fold slower than with the wild-type rep gene. Pre-steady-state, single-turnover DNA unwinding kinetics experiments show that purified RepDelta2B protein has DNA helicase activity in vitro and unwinds an 18-bp DNA duplex with rates at least as fast as wild-type Rep, and with higher extents of unwinding and higher affinity for the DNA substrate. These studies show that the 2B domain of Rep is not required for DNA helicase activity in vivo or in vitro, and that it does not facilitate DNA unwinding in vitro.

Adenosine Triphosphatases↗
PubMed2002

Initiation and re-initiation of DNA unwinding by the Escherichia coli Rep helicase.

Helicases are motor proteins that couple conformational changes induced by ATP binding and hydrolysis with unwinding of duplex nucleic acid, and are involved in several human diseases. Some function as hexameric rings, but the functional form of non-hexameric helicases has been debated. Here we use a combination of a surface immobilization scheme and single-molecule fluorescence assays--which do not interfere with biological activity--to probe DNA unwinding by the Escherichia coli Rep helicase. Our studies indicate that a Rep monomer uses ATP hydrolysis to move toward the junction between single-stranded and double-stranded DNA but then displays conformational fluctuations that do not lead to DNA unwinding. DNA unwinding initiates only if a functional helicase is formed via additional protein binding. Partial dissociation of the functional complex during unwinding results in interruptions ('stalls') that lead either to duplex rewinding upon complete dissociation of the complex, or to re-initiation of unwinding upon re-formation of the functional helicase. These results suggest that the low unwinding processivity observed in vitro for Rep is due to the relative instability of the functional complex. We expect that these techniques will be useful for dynamic studies of other helicases and protein-DNA interactions.

Adenosine Triphosphatases↗
PubMed2002

Sinonasal undifferentiated carcinoma and nasopharyngeal-type undifferentiated carcinoma: two clinically, biologically, and histopathologically distinct entities.

Sinonasal undifferentiated carcinoma (SNUC) is a rare aggressive neoplasm arising in the nasal cavity and paranasal sinuses. Primary sinonasal nasopharyngeal-type undifferentiated carcinoma (PSNPC) is an even rarer tumor that has not been adequately reported. Both tumors have been reported to be associated with Epstein-Barr virus (EBV). We studied the clinicopathologic features and EBV status of 36 SNUC and 13 PSNPC patients from Taiwan, an EBV endemic area. The median age of SNUC patients was 53 years (range 20-76 years), with a male/female ratio of approximately 2:1. Five patients had histories of previous nasopharyngeal carcinoma treated with irradiation 6-26 years earlier. The most common locations were nasal cavity and ethmoid sinus. Orbital and intracranial invasion and distant metastasis were frequent findings. The median survival was 10 months. All 36 tumors were negative for EBER-1 by in situ hybridization. The median age of PSNPC patients was 58 years (range 36-75 years), with a male/female ratio of approximately 2:1. The most common location is nasal cavity. Eight patients achieved disease-free survival. Eight tumors had the morphology of lymphoepithelioma, whereas significant inflammatory infiltrate was not detected in the other five tumors. All 13 tumors were positive for EBER-1 by in situ hybridization. Because of the difference in the relation with EBV, prognosis, and response to radiotherapy, SNUC and PSNPC should be considered as two entirely different entities. The most important criteria for PSNPC are vesicular nuclei, syncytial pattern, spindle cells, and absence of necrosis.

Adult↗
PubMed2002

Superoxide anion impairs contractility in cultured aortic smooth muscle cells.

We examined the effects of superoxide anion (O) generated by xanthine plus xanthine oxidase (X/XO) on the intracellular Ca(2+) concentration ([Ca(2+)](i)) and muscle contractility in cultured bovine aortic smooth muscle cells (BASMC). Cells were grown on collagen-coated dish for the measurement of [Ca(2+)](i). Pretreatment with X/XO inhibited ATP-induced Ca(2+) transient and Ca(2+) release-activated Ca(2+) entry (CRAC) after thapsigargin-induced store depletion, both of which were reversed by superoxide dismutase (SOD). In contrast, Ca(2+) transients induced by high-K(+) solution and Ca(2+) ionophore A-23187 were not affected by X/XO. BASMC-embedded collagen gel lattice, which was pretreated with xanthine alone, showed contraction in response to ATP, thapsigargin, high-K(+) solution, and A-23187. Pretreatment of the gel with X/XO impaired gel contraction not only by ATP and thapsigargin, but also by high-K(+) solution and A-23187. The X/XO-treated gel showed normal contraction; however, when SOD was present during the pretreatment period. These results indicate that O(2)(-) attenuates smooth muscle contraction by impairing CRAC, ATP-induced Ca(2+) transient, and Ca(2+) sensitivity in BASMC.

Adenosine Triphosphate↗
PubMed2002

Gastrin, somatostatin, G and D cells of gastric ulcer in rats.

AIM: To investigate the relationship among gastrin, somatostatin, G and D cells in gastric ulcer and in its healing process in rats. METHODS: Fourty-nine Wistar rats were divided into 7 groups. The gastric ulcer model was induced by acetic acid successfully. The gastrin and the somatostatin in rat plasma, gastric fluid and antral tissue were measured by radioimmunoassay(RIA). G and D cells in antral mucosa were analyzed with polyclonal antibody of gastrin and somatostatin by immunohistochemical method and Quantimet 500 image analysis system. RESULTS: In gastric ulcer, the level of gastrin in plasma, gastric fluid, and antral tissue increased, that of somatostatin declined, and the disorder gradually recovered to the normal level in the healing process. Immunohistochemical technique of G and D cells in antral mucosa demonstrated that the number of G cells increased and that of D cells decreased, both areas of G and D cells declined, the ratio of number and area of G/D increased in gastric ulcer, and the disorder gradually recovered in the healing process. CONCLUSION: In gastric ulcer, the increased gastrin secreted by G cells, the declined somatostatin secreted by D cells, and the disordered G/D cell ratio can lead to gastrointestinal dysfunction.

Animals↗