Biomedical subjects

C M Li

Publications and source records attributed to C M Li.

At least 19 recordsLinked to original sources

PubMed2006

Spectral power distribution and quantum yields of Sm3+-doped heavy metal tellurite glass under the pumping of blue lighting emitting diode.

Quantum yields for multichannel transition emissions have been determined in Sm3+-doped heavy metal tellurite glass under the pumping of blue lighting emitting diode for the first time. To achieve this goal, the necessary fluorescence spectra were measured and calibrated in an integrating sphere, which was connected to a CCD detector with a 400 microm-core optical fiber. The spectral power distribution of the sample under the blue LED pumping was derived from the measured spectra firstly, and then the quantum yields for the visible emissions of Sm3+ were calculated based on the distribution and the total quantum yields in visible region is 7.55%. For accurate measurements, integrating sphere method is proved to be a reliable and reproducible way to characterize luminescence and laser materials.

Glass↗

PubMed2006

Sensitive electrochemical enzyme immunoassay microdevice based on architecture of dual ring electrodes with a sensing cavity chamber.

A novel electrochemical detection architecture was investigated for enzyme immunoassay sensors. Microchips with dual-ring working and counter electrodes, and a sensing cavity chamber were made on glass slides. The glass surface of the microchip was coated by 3-aminopropyltriethoxysilane (APTES). Goat IgG, as a example, was covalently captured on APTES-modified glass surfaces through glutaraldehyde (GA) as a cross-linker. Enzyme substrate, p-aminophenyl phosphate (PAPP) was prepared by electrolysis. The enzyme conversion from home-synthetic PAPP to p-aminophenol (PAP) was examined by differential pulse voltammetry (DPV). A competitive inhibition enzyme-linked immunosorbant assay (ELISA) was designed to test the system. Experimental results demonstrate that a detection limit of 118 fg/ml of goat IgG and a dynamic range of 118 fg/ml to 1.18 ng/ml, up to five orders of magnitude could be achieved. Due to its novel architecture design and electronic detection scheme, the method can be used to fabricate portable electrochemical ELISA lab-on-chip systems. The technology could have great potential in clinical diagnostic applications.

Animals↗

PubMed2006

Changes in the expression of Fas on T lymphocytes after allogeneic fetal thymus transplantation in systemic lupus erytematosus mice.

BACKGROUND: Systemic lupus erythematosus (SLE) is an autoimmune disorder that can produce inflammation in many organ systems. The rate of spontaneous apoptosis in lymphocytes from human SLE patients has been reported to be increased both in vivo and in vitro. Studies of fetal thymus transplantation in an autoimmune syndrome indicate that cellular immunity can be reconstituted and regulatory T cell functions can be normalized. OBJECTIVES: The aim of this study was to assess changes in Fas expression on T lymphocytes following fetal thymus transplant. METHODS: (B/CxB6) F1 (H-2d/h) female F1 mice were assigned to groups designated transplantation, normal, and control. Mice in the transplantation and control groups received parental BALB/c lymphocytes intravenously. Thirty days after injection of the lymphocytes, each F1 mouse in the transplantation group received a fetal thymus graft under the right renal capsule. Mice in the control group did not receive thymus transplant and mice in the normal group received neither parental lymphocytes nor a fetal thymus graft. All mice received cyclosporin A at 2 mg/kg daily for the first 12 days after transplantation or starting on the corresponding day. Thirty days after thymus transplantation, F1 mice were sacrificed and expression of Fas in peripheral blood lymphocytes was analyzed by flow cytometry. RESULTS: The percentage of CD4Fas+ T lymphocytes was significantly increased in the control group and the transplantation group compared with the normal group. Corresponding significant differences were observed for CD8Fas+, CD4CD25Fas', and CD45RB(low)Fas+ T lymphocytes. CONCLUSIONS: In this study, we found that fetal thymus transplantation had a significant effect on the expression of Fas by T cell subtypes in SLE mice.

Animals↗

PubMed2005

Impedance labelless detection-based polypyrrole protein biosensor.

A simple and sensitive electrochemical immunosensor with impedance labelless detection and novel data processing method was investigated. One-step copolymerization was used to electrochemically deposit an antibody impregnated polypyrrole film on a glassy carbon electrode surface for the immunosensor. Impedance measurements provided a labelless or reporterless method to detect antibody (Ab)-antigen (Ag) interactions. Dimensionless analysis was employed to successfully process the measured impedance data. Since the method derived unit impedance change to eliminate or reduce the variation of the bulk electronic properties of Ab/polypyrrole films, the signal to noise ratio (S/N) was significantly improved for high sensitivity and specificity. Nonspecific binding effect was studied by array electrode chips and was found out that the polypyrrole electrode without antibody attachment had much stronger nonspecific binding effect than the Ab/polypyrrole electrode; incubation followed by thoroughly washing significantly reduced the nonspecific interference. 10 pg/ml detection limit and superior specificity were achieved by the method, demonstrating a highly sensitive labelless immunosensor in comparison with the detection limit of ng -microgram/ml for the reported polypyrrole based immunosensors. The electrochemical immunosensors presented in this paper, due to its simplicity, low cost, high sensitivity and superior specificity, could be an invaluable tool for clinical diagnostics and could have potential applications in drug discovery, environmental and food analysis.

Antibodies↗

PubMed2005

Type II vanilloid receptor signaling system: one of the possible mechanisms for the rise in asthma cases.

The prevalence of asthma keeps on increasing worldwide, especially in western societies over last 40 years. The mechanism of asthma is unclear. Recently, concern about indoor air pollution as a risk factor for asthma has been arisen. In present study, 25 Kun Ming male mice were placed in an air chamber containing respective formaldehyde (FA) concentration of 0, 0.5, 1.0, 3.0 mg/m3,and 3.0 mg/m3 with Capsazepine (CPZ, a specific antagonist of vanilloid receptor)-pretreatment in five testing groups (n=5 per group) for inhale experiments. The inhaled groups were exposed to gaseous FA for 6 hours each day in 10 successive days. After exposure, the concentrations of IL4 in blood serum and broncho alveolar lavage fluid (BALF) were measured. Experimental results showed that the IL4 level in serum was too low to be detected; and the concentrations of IL4 in BALF increased in a dose-dependent manner. However, for the CPZ-pretreated group the IL4 level in BALF decreased significantly (compared with 3.0 mg/m3 FA inhaled group, p<0.01). This paper describes experimental animal methods to probe IL4 level, an important indicator for IgE response. The studies in this paper indicated that gaseous FA might induce acquired atopy by type II VR1 signaling system. These findings suggested that indoor air pollutants such as FA might be key risk factors for the rise in asthma cases, and type II VR1 signaling system might be one of the mechanisms for the rise.

Animals↗

PubMed2005

Efficient probe immobilization on poly (dimethylsiloxane) for sensitive detection of proteins.

Chemical surface modification methods were investigated to activate surface of poly-(dimethylsiloxane) (PDMS) for probe immobilization in enzyme-linked immunosorbent assay (ELISA). The investigations started from dramatization of PDMS surface with (3-aminopropyl)-triethoxysilane (APTES). Amino groups generated by APTES were either derived into carboxyl group by Succinic acid anhydride (SAA), then captured the protein through the heterobifunctional cross-linker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), or directly reacted with homobifunctional cross-linker, glutaraldehyde (GA). Rabbit IgG, Goat IgG, Human IgA and Rat IgG were covalently immobilized on PDMS by both methods, and examined through well-organized competitive inhibition ELISA. The results demonstrated that both GA and EDC based methods had good covalent immobilization capability, and the EDC method had higher efficiency than the GA method. The competitive ELISA with probe immobilization through EDC had a detection limit of pg/ml level. The method was proved to be applicable for immobilization of different proteins. The topography of the immobilized protein properties was studied by atomic force microscope (AFM), demonstrating that the immobilization by GA had protein conglomeration, resulting in poorer uniformity and lower immobilization efficiency than EDC method. The possible reason is protein inter-molecule crossing linkage by the homobifunctional group of GA. Due to its simplicity, low cost, and high immobilization efficiency, EDC based immobilization method could provide great potential for making ELISA protein chips based on PDMS.

Animals↗

PubMed2005

Treating chemical mechanical polishing (CMP) wastewater by electro-coagulation-flotation process with surfactant.

The effect of surfactants on the treatment of chemical mechanical polishing (CMP) wastewater by electro-coagulation-flotation (ECF) process was studied. Two surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) were employed in this study to compare the effect of cationic (CTAB) and anodic (SDS) surfactants on ECF. The cationic surfactant can enhance the removal of the turbidity, but anodic surfactant cannot. It can be explained by the hetero-coagulation theory. Moreover, the addition of CTAB in CMP wastewater can reduce the sludge volume and the flotation/sedimentation time in ECF process. The residual turbidity and dissolved silicon dropped with the increase of charge loading. No CTAB pollution problem exists after the ECF process.

Cetrimonium↗

PubMed2005

Impact of bond order loss on surface and nanosolid mechanics.

An analytical solution shows that a competition between bond order loss and the associated bond strength gain of the lower coordinated atoms near the edge of a surface dictates the mechanics of the surface and, hence, a nanosolid. Bond order loss lowers the activation energy for atomic dislocation, whereas bond strength gain enhances the energy density or mechanical strength in the region near the surface. Therefore, the surface is harder than the bulk interior at temperatures far below the melting point (T(m)), and the surface becomes softer at temperatures close to the surface T(m) that drops because of bond order loss. Matching predictions to measurements reveals that a transition happens to the Hall-Petch relationship for a nanosolid when the effect of bond order loss becomes dominant, and the critical size of the Hall-Petch transition depends intrinsically on the bond nature of the specimen and the ratio of T/T(m), where T is the temperature of operation.

Journal Article↗

PubMed2005

Impedance labelless detection-based polypyrrole DNA biosensor.

Microelectrodes were fabricated to study impedance labelless detection of DNA hybridization. The probe molecule was attached onto the platinum microelectrode surface by electrochemically copolymerizing pyrrole and the probe oligonucleotides. Measured impedance complexes showed that an electrochemical redox-reaction occurred and the electron-transfer resistance increased after DNA hybridization. It was proposed that the hybridization of DNA in the conductive polymer matrix slowed down the anionic doping/undoping process, resulting impedance changes for the target DNA detection. Impedance measurements were conducted at the complementarily hybridized probe oilgomer-attached polypyrrole film electrodes in different anionic solutions to exam the anionic effects. Results showed that higher concentration and smaller size of anions had the lower electron-transfer resistance. The results not only provide further evidence to support the detection mechanism proposed, but also offer a method to improve the signal to noise ratio for the DNA biosensor. The research also tested the specificity of the methods and experimental results, indicating good specificity of the method. A concept array chip was fabricated and used to demonstrate the capability of the labelless detection method. Nano-Molar concentrations were detected and showed fairly linear responses versus the target molecule concentrations. The method is simple and inexpensive. The technique based genosensors could have potential applications in clinical diagnosis, drug discovery, environmental and food analysis.

Base Sequence↗

PubMed2004

Porous carbon composite/enzyme glucose microsensor.

An enzyme glucose microsensor using a glucose oxidase-immobilized porous carbon/Teflon composite microelectrode was developed. The microsensor was fabricated by etching a platinum microelectrode (platinum, radius of 25 and 50 micrometers) in hot aqua regia to create a cavity at the tip and then packing a porous carbon/Teflon composite, which was made from acetylene black and Teflon emulsion, into the cavity. Nafion was impregnated into the inner surface of porous carbon/Teflon composite electrode following immobilization of Os(bpy)3+2/+3 as electron transfer mediators. The loading amount of Os(bpy)3+2/+3 in the Nafion/porous carbon/Teflon composite electrode was found to be 7.0x10(-8) mole cm(-2), which is much higher than that in polymer modified electrodes reported in literatures. The microsensor was further dipped overnight in buffer solution containing glucose oxidase for enzyme modification. With both glucose oxidase and mediators in the porous carbon/Teflon composite surface, the sensor performance was evaluated in buffer solutions containing different glucose concentrations and serum samples for glucose determination. The microsensor showed directly electrochemical glucose oxidation on the Os(bpy)3+2/+3 impregnated enzyme/porous carbon/Teflon composite surface with linear response over concentration range of 0-15 mM and Machaelis behavior. Reliability and reproducibility were conducted in serum samples and glucose buffer solution, and the results demonstrated there was no significant decrease of amperometric response in air-saturated solution for one month. The sensor demonstrated potential in clinical diagnostic applications.

Biosensing Techniques↗

PubMed2004

Porous carbon composite/enzyme glucose microsensor.

Biosensing Techniques↗

PubMed2003

Leiocyclocin C and D, two cyclopeptides from Goniothalamus leiocarpus.

Two new cyclopeptides, leiocyclocin C (1) and D (2), were isolated from the seeds of Goniothalamus leiocarpus (Annonaceae). Their structures were determined as cyclo-(Gly1-Ser-Pro2-Tyr2-Gly2-Tyr1-Pro1-Pro3) and cyclo-(Gly1-Leu-Pro1-Gly2-Phe-Tyr-Pro2), respectively, by means of spectral and chemical methods.

Annonaceae↗

PubMed2002

Response heterogeneity of human macrophages to ATP is associated with P2X7 receptor expression but not to polymorphisms in the P2RX7 promoter.

A region 2 kb upstream of exon 1 of the P2X7 gene was sequenced using DNA from nine healthy individuals who exhibited three different ATP response phenotypes (i.e. high, low and interferon gamma-inducible). Five single nucleotide polymorphisms were identified within the nine donor promoter sequences but none were associated with a specific ATP response phenotype. A P2X7 loss of function polymorphism (1513 in exon 13) was also screened for within donor DNA but no response associations were identified. ATP response phenotype was positively associated with P2X(7) receptor expression, as assessed by flow cytometry, but not with any identified receptor or promoter gene polymorphisms.

Adenosine Triphosphate↗

PubMed2001

ATP-mediated killing of Mycobacterium bovis bacille Calmette-Guérin within human macrophages is calcium dependent and associated with the acidification of mycobacteria-containing phagosomes.

We previously demonstrated that extracellular ATP stimulated macrophage death and mycobacterial killing within Mycobacterium bovis Bacille Calmette-Guérin (BCG)-infected human macrophages. ATP increases the cytosolic Ca(2+) concentration in macrophages by mobilizing intracellular Ca(2+) via G protein-coupled P2Y receptors, or promoting the influx of extracellular Ca(2+) via P2X purinoceptors. The relative contribution of these receptors and Ca(2+) sources to ATP-stimulated macrophage death and mycobacterial killing was investigated. We demonstrate that 1) ATP mobilizes Ca(2+) in UTP-desensitized macrophages (in Ca(2+)-free medium) and 2) UTP but not ATP fails to deplete the intracellular Ca(2+) store, suggesting that the pharmacological properties of ATP and UTP differ, and that a Ca(2+)-mobilizing P2Y purinoceptor in addition to the P2Y(2) subtype is expressed on human macrophages. ATP and the Ca(2+) ionophore, ionomycin, promoted macrophage death and BCG killing, but ionomycin-mediated macrophage death was inhibited whereas BCG killing was largely retained in Ca(2+)-free medium. Pretreatment of cells with thapsigargin (which depletes inositol (1,4,5)-trisphosphate-mobilizable intracellular stores) or 1,2-bis-(2-aminophenoxy)ethane-N, N, N',N'-tetraacetic acid acetoxymethyl ester (an intracellular Ca(2+) chelator) failed to inhibit ATP-stimulated macrophage death but blocked mycobacterial killing. Using the acidotropic molecular probe, 3-(2,4-dinitroanilino)-3'-amino-N-methyl dipropylamine, it was revealed that ATP stimulation promoted the acidification of BCG-containing phagosomes within human macrophages, and this effect was similarly dependent upon Ca(2+) mobilization from intracellular stores. We conclude that the cytotoxic and bactericidal effects of ATP can be uncoupled and that BCG killing is not the inevitable consequence of death of the host macrophage.

Adenosine Triphosphate↗

PubMed2001

Quantitative detection of N(7)-(2-hydroxyethyl)guanine adducts in DNA using high-performance liquid chromatography/electrospray ionization tandem mass spectrometry.

High-performance liquid chromatography (HPLC) was combined with electrospray ionization tandem mass spectrometry (ESI-MS/MS) to develop a sensitive and selective method for the quantitative measurement of N(7)-(2-hydroxyethyl)guanine (N(7)-HEG) adducts in DNA obtained from ethylene oxide-exposed biological samples. Selected reaction monitoring (SRM) was used as the detection mode while the fragmentation product ion at m/z 152 generated from the precursor protonated N(7)-HEG (m/z 196) was monitored. The detection limits for N(7)-HEG were estimated by twofold serial dilution and determined to be 4 fmol in neat standard solution and 16 fmol when a matrix effect is considered. When the mass spectrometer was operated in the selected ion monitoring mode using only the first quadrupole (without MS/MS function), the detection limits increased to 128 fmol and 1 pmol (when matrix effect is considered), respectively. A good linear correlation (R(2) = 0.999) was observed for signal intensities obtained by injecting 16 fmol--33 pmol of N(7)-HEG into the HPLC/ESI-MS/MS system. Hep G2 cells were incubated for 8 h with medium containing various concentrations of ethylene oxide (ranging from 0.05 to 5.0 mM). A dose-response relationship was established, indicating that the adduct formation increases with the exposure level. The method shows potential, although the detection limit needs to be lowered for practical applications, for use in monitoring N(7)-HEG formation in other biological systems.

Carcinoma, Hepatocellular↗

PubMed2001

A nonsense mutation is responsible for the RNA-negative phenotype in human citrullinaemia.

Citrullinaemia is an inborn error of metabolism resulting from a deficiency of argininosuccinate synthetase. Previous studies of RNA of argininosuccinate synthetase of citrullinaemia patients using S1 nuclease analysis have identified a class of so-called RNA-negative alleles in which no stable mRNA can be detected. To investigate the nature of mutation responsible for such a phenotype, a compound heterozygous citrullinaemia carrying an RNA-negative allele and an allele with a 3' splice site mutation in intron 6 (IVS6-2A>G) was analysed. Using sequences of a DNA polymorphism and the IVS6-2A>G mutation as markers, approximately equal amounts of pre-mRNAs from allelic genes were detected suggesting that RNA-negative phenotype could not be the result of defect in transcription initiation. A C-to-T transition converting the CGA arginine codon at residue 279 to a TGA termination codon (R279X) was identified by cDNA sequencing. No accumulation of partially spliced pre-mRNAs containing introns immediately upstream and downstream of the nonsense mutation was observed. In addition, no mRNA species of abnormal size was detected when cDNA from the RNA-negative allele was analysed. Hence, there is no indication of nonsense-associated altered splicing (NAS). The most likely event responsible for the RNA-negative phenotype appears to be nonsense-mediated mRNA decay (NMD).

Alleles↗

PubMed2001

Non-clostridial gas gangrene caused by Klebsiella pneumoniae: a case report.

A 45-y-old man was hospitalized due to pain and swelling of the right leg for 3 d. Bullae developed with gas formation involving multiple compartments of the entire limb 46 h later. Klebsiella pneumoniae was recovered from blood and surgical specimens. The patient died on Day 8 despite amputation and antibiotic therapy.

Amputation, Surgical↗

PubMed2001

Transforming growth factor-beta(1) modifies fibroblast growth factor-2 production in type II cells.

Transforming growth factor (TGF)-beta(1) is an inflammatory cytokine that plays multiple roles in pulmonary fibrosis. In vascular epithelium, it has been shown to regulate production and activity of fibroblast growth factor (FGF)-2, a potent type II cell mitogen in the lung. Such a relationship could have important consequences in prefibrotic change in the lung alveolus, where reepithelialization of alveolar surfaces is crucial. The goal of this study was to determine if FGF-2 production by alveolar type II cells is modulated by TGF-beta(1) or FGF-1, another type II cell mitogen. Isolated rat type II cells were exposed to 0 to 40 ng/mL of TGF-beta(1) or 0 to 500 ng/mL of FGF-1 in serum-free medium for 1 to 3 days. Using a specific immunoassay, significant increases in FGF-2 protein in type II cell lysates were achieved after 1 day of exposure to 100 ng/mL of FGF-1 and after 3 days of treatment with 8 ng/mL of TGF-beta(1). Similarly, transcripts for FGF-2 were dramatically increased with TGF-beta(1) or FGF-1, as were those for FGF receptor (FGFR)-1. These interactions were dramatically effected by the addition of heparin, a model sulfated extracellular matrix (ECM). Heparin as low as 0.01 mg/mL significantly downregulated expression of TGF-beta(1) and FGF-1-stimulated FGF-2 and FGFR-1. These results demonstrate important regulatory links between FGF-2, sulfated ECMs, and both TGF-beta(1) and FGF-1, which could contribute to the modulation of normal cell turnover, development, and repair processes attendant to fibrosis in the lung.

Animals↗