Biomedical subjects

D N Wang

Publications and source records attributed to D N Wang.

At least 19 recordsLinked to original sources

PubMed2006

Highly sensitive long-period fiber-grating strain sensor with low temperature sensitivity.

A long-period fiber-grating sensor with a high strain sensitivity of -7.6 pm/microepsilon and a low temperature sensitivity of 3.91 pm/ degrees C is fabricated by use of focused CO(2) laser beam to carve periodic grooves on a large- mode-area photonic crystal fiber. Such a strain sensor can effectively reduce the cross-sensitivity between strain and temperature, and the temperature-induced strain error obtained is only 0.5 microepsilon/ degrees C without using temperature compensation.

Journal Article↗

PubMed2006

Simple system for optical short-pulse generation in both active mode-locking and self-seeding schemes.

A simple system that simultaneously supports active mode-locking and self-seeding schemes for wavelength-tunable optical short-pulse generation is proposed. The system consists of a gain-switched Fabry-Perot laser diode, an erbium-doped fiber amplifier, a tunable optical filter, and two circulators. The mode-locked optical pulses exhibit good stability, a high side-mode suppression ratio of more than 31 dB over a wide wavelength tuning range of 42 nm, and a pulse width of around 35 ps at a repetition frequency of approximately 2.8 GHz.

Journal Article↗

PubMed2005

Pharmacological studies of the large-scaled purified genistein from Huaijiao (Sophora japonica-Leguminosae) on anti-osteoporosis.

In this report, we used genistein that was extracted from a Chinese herbal medicine Huaijiao (Sophora japonica-Leguminosae) to evaluate its pharmacological function on anti-osteoporosis. This genistein is purified in a large-scale production from Huaijiao by a state-of-art method as described by Tian et al. [2004. The preparation of genistein and LC-MS/MS on-line analysis. Drug Devel. Res. 61, 6-12]. Chemical structure of the isolated genistein was examined by using various techniques including nuclear magnetic resonant spectrum, infrared absorption spectrum, ultraviolet absorption spectrum and mass spectrum, and was proved to be identical to those purified from soybean in a small scale as previously reported. We randomly divided female SD rats into 6 groups, including control, ovariectomized model, Nilestriol-treated, and three level of dosages of genistein-treated. We evaluated the pharmacological effects of genistein against osteoporosis by measuring the bone density of femur and bone mineral group including calcium, phosphorous, and magnesium. The consequences of genistein treatment on bone histology and morphology were also determined by measuring the trabcular area, thickness and number. Our results indicated that treatment with a 4.5 or 9 mg/kg dosage of genistein could also prevent osteoporosis significantly at the 4th week after treatment. In comparison with the anti-osteoporosis effects of soybean genistein, the genistein extracted from Huaijiao has the same beneficial effect on anti-osteoporosis.

Animals↗

PubMed2005

Continuous wavelength-tunable optical short-pulse generation by use of two Fabry-Perot laser diodes in a mutual injection-seeding scheme.

A simple system for producing continuous and widely wavelength-tunable optical short pulses in a mutual injection-seeding scheme is presented. The system exhibits a good side-mode suppression ratio of greater than 32.7 dB over a large wavelength tuning range of 33.8 nm. The system is easy to operate and convenient for continuous wavelength tuning.

Journal Article↗

PubMed2005

Oridonin-induced apoptosis in leukemia K562 cells and its mechanism.

Oridonin, an extract from the Chinese herb Rabdosia rubescens, is currently one of the most important traditional Chinese herbal medicines. Recently oridonin has been reported to have anti- tumor effects in a large variety of malignant diseases. In this study, we investigated the apoptotic inducing effect of oridonin in leukemia K562 cells and its mechanism. Cell growth inhibition was measured using a microculture tetrazolium assay, apoptosis was measured by flow cytometry and electron microscopy as well as by DNA fragmentation analysis. Telomerase activity was measured by TRAP-enzyme- linked immunosorbent assay, and the expression of Bcl-2 and Bax proteins was detected by western blot analysis. The results showed that oridonin could inhibit the proliferation and induce apoptosis on leukemia K562 cells remarkably. Telomerase activity as well as Bcl-2 expression was down- regulated, while Bax expression was up-regulated concurrently, when apoptosis ocurred. We therefore conclude that oridonin demonstrated anti-proliferative and apoptosis-inducing effects on K562 cells in vitro, and that changes in bcl-2 and bax protein levels as well as telomerase activity may play an important role in its mechanism of action.

Antineoplastic Agents↗

PubMed2003

Wavelength-tunable optical short-pulse generation by mutual pulse injection seeding of two gain-switched Fabry-Perot laser diodes.

A simple and robust system is presented to generate wavelength-tunable optical short pulses by use of two gain-switched Fabry-Perot laser diodes in a mutual pulse injection-seeding scheme. The operating wavelength of the optical pulses is flexibly selected by adjustment of a tunable filter, and its intensity is enhanced with an erbium-doped fiber amplifier. The side-mode suppression ratio achieved by the system is larger than 26 dB over a wavelength region of 25 nm and higher than 31 dB within an 18-nm wavelength.

Journal Article↗

PubMed2001

High-yield expression and functional analysis of Escherichia coli glycerol-3-phosphate transporter.

The glycerol-3-phosphate (G3P) transporter, GlpT, from Escherichia coli mediates G3P and inorganic phosphate exchange across the bacterial inner membrane. It possesses 12 transmembrane alpha-helices and is a member of the Major Facilitator Superfamily. Here we report overexpression, purification, and characterization of GlpT. Extensive optimization applied to the DNA construct and cell culture has led to a protocol yielding approximately 1.8 mg of the transporter protein per liter of E. coli culture. After purification, this protein binds substrates in detergent solution, as measured by tryptophan fluorescence quenching, and its dissociation constants for G3P, glycerol-2-phosphate, and inorganic phosphate at neutral pH are 3.64, 0.34, and 9.18 microM, respectively. It also shows transport activity upon reconstitution into proteoliposomes. The phosphate efflux rate of the transporter in the presence of G3P is measured to be 29 micromol min(-1) mg(-1) at pH 7.0 and 37 degrees C, corresponding to 24 mol of phosphate s(-1) (mol of protein)(-1). In addition, the glycerol-3-phosphate transporter is monomeric and stable over a wide pH range and in the presence of a variety of detergents. This preparation of GlpT provides ideal material for biochemical, biophysical, and structural studies of the glycerol-3-phosphate transporter.

Biological Transport↗

PubMed2001

Monomeric state and ligand binding of recombinant GABA transporter from Escherichia coli.

The gamma-aminobutyric acid (GABA) transporter from Escherichia coli was homologously overexpressed and purified to homogeneity with a yield of 1.0 mg per liter culture. The purification procedure consists of a cobalt affinity column, proteolytic cleavage of His- and myc-tags, and size-exclusion chromatography. The purified transporter exists as a monomer in FOS-Choline 12 detergent, with a Stokes radius of 45 A for the protein-detergent complex. In detergent solution the protein binds substrates, as indicated by tryptophan fluorescence quenching. Its dissociation constants (K(d)) for GABA, muscimol and nipecotic acid are 13.8, 13.3 and 27.9 microM, respectively. This protein preparation provides ideal starting materials for future biochemical, biophysical and structural studies of the GABA transporter.

Bacterial Proteins↗

PubMed2001

Purification and characterization of human erythrocyte glucose transporter in decylmaltoside detergent solution.

The facilitative glucose transporter from human erythrocyte membrane, Glut1, was purified by a novel method. The nonionic detergent decylmaltoside was selected for solubilization on the basis of its efficiency to extract Glut1 from the erythrocyte membrane and its ability to maintain the protein in a monodisperse state. A positive, anion-exchange chromatography protocol produced a Glut1 preparation of 95% purity with little copurified lipid. This protein preparation exhibited cytochalasin B binding in detergent solution, as measured by tryptophan fluorescence quenching. The transporter existed as a monomer in decylmaltoside, with a Stokes radius of 50 A and a molecular mass of 147 kDa for the protein-detergent complex. We screened detergent, pH, additive, and lipid and have found conditions to maintain Glut1 monodispersity for 8 days at 25 degrees C or over 5 weeks at 4 degrees C. This Glut1 preparation represents the best available material for two- and three-dimensional crystallization trials of the human glucose transporter protein.

Chromatography, Ion Exchange↗

PubMed2001

[The new antiendotoxin strategies].

Lipopolysaccharide(LPS) is important in the pathogenesis of sepsis infected by gram-negative bacteria in humans, and part or all of this pathophysiology is mediated by a complex secondary inflammatory response. Administration of purified LPS or a variety of LPS-free recombinant mediators can reproduce much of the pathophysiology of gram-negative sepsis. There has been an explosion of new information over the last several years regarding the interactions of LPS with proteins and cells. Blocking sepsis at the bacterial toxin level is appealing because it is upstream, so that the secondary pathologic inflammatory cascade may be limited or prevented. A variety of antiendotoxin strategies have been proposed. Therapies under investigation include agents that bind and neutralize LPS, agents or systems that enhance LPS clearance, and agents that inhibit LPS interaction with serum elements or cellular receptors.

Acute-Phase Proteins↗

PubMed2001

[Cloning of secondary lymphoid-tissue chemokine (SLC) and its expression in prokaryotic system].

The total RNA from lymphoid tissue in Chinese was extracted, and the gene encoding the mature peptide of secondary lymphoid-tissue chemokine (SLC) was cloned by RT-PCR. Nucleotide sequence analysis showed that there is only one nucleotide different from that reported, but it doesn't alter the amino acid encoded. The SLC cDNA was inserted into an expression vector pET-28a(+) under T7 promoter and constructed recombinant plasmid pET28a-SLC. pET28a-SLC was transformed to E. coli BL21(DE3) and the expression strain was gotten. After inducing with IPTG for 3-5 hours the bacterium were sonicated. After centrifuging the supernatant was analysed by SDS-PAGE. An obvious expression band about 18 kD can be seen. The expressed product was purified by Ni2+ affinity chromatography column, and the purity is up to 90 percent.

Chemokine CCL21↗

PubMed2000

Interlaboratory study of identification and quantitation of multiresidue pyrethroids in agricultural products by gas chromatography-mass spectrometry.

This paper deals with the different GC-MS analytical conditions adopted by four laboratories in an attempt to confirm the accuracy of the GC-electron-capture detection (ECD) analytical results during the international collaborative study for the establishment of the AOAC Official Method 998. 01. What is especially noted is that two laboratories have conducted comparative analysis of the respective 12 blind samples with both methods of GC-ECD and GC-MS, and the analytical results of the two methods turn out to be basically identical. This fully demonstrates that GC-MS is not only an effective confirmation tool in the analysis of the pyrethroid residues but also of sufficient sensitivity regarding the maximum residue limit of determination prescribed by FAO/WHO. Moreover, its selectivity is better than GC-ECD.

Gas Chromatography-Mass Spectrometry↗

PubMed2000

Trimeric ring-like structure of ArsA ATPase.

ArsA protein is the soluble subunit of the Ars anion pump in the Escherichia coli membrane which extrudes arsenite or antimonite from the cytoplasm. The molecular weight of the subunit is 63 kDa. In the cell it hydrolyzes ATP, and the energy released is used by the membrane-bound subunit ArsB to transport the substrates across the membrane. We have obtained two-dimensional crystals of ArsA in the presence of arsenite on negatively-charged lipid monolayer composed of DMPS and DOPC. These crystals have been studied using electron microscopy of negatively-stained specimens followed by image processing. The projection map obtained at 2.4 nm resolution reveals a ring-like structure with threefold symmetry. Many molecular assemblies with the same ring-shape and dimensions were also seen dispersed on electron microscopy grids, prepared directly from purified ArsA protein solution. Size-exclusion chromatography of the protein sample with arsenite present revealed that the majority of the protein particles in solution have a molecular weight of about 180 kDa. Based on these experiments, we conclude that in solution the ArsA ATPase with substrate bound is mainly in a trimeric form.

Adenosine Triphosphatases↗

PubMed2000

[Cloning of the zot gene of Vibrio cholerae and its expression in Escherichia coli].

The zot gene encoding Zonula occludens toxin was amplified from classic Vibrio cholerae genomic DNA by PCR. The result of sequencing indicated that zot gene encodes 399 amino acid residues. The sequence of zot gene was a little bit different from that of reported including 14 nucleotides and four amino acid residues. The expression plasmid pET-ZOT was constructed by inserting zot gene into plasmid pET-28a(+) containing the T7 promoter. The expression plasmid was induced into E. coli BL21 (DE3) and expression strain BLZOT was selected. SDS-PAGE analysis revealed that the ZOT protein was expressed and accumulated up to above 15% of bacterial soluble protein after induced by IPTG. A protein of 47 kD was expressed as including body. Western blot analysis revealed that the expressed protein was ZOT.

Base Sequence↗

PubMed1996

[Effect of new zhengtian pill on 5-hydroxytryptamine content in platelet and plasma of migraine patients].

Changes of 5-hydroxytryptamine (5-HT) content in platelet and plasma before and after New Zhengtian Pill (NZTP) therapy in migraine patients were assayed with fluorospectrophotometry. Results showed that during the period of attack, the platelet 5-HT level of patients in comparing with normal control group, was increased (P < 0.05) but the plasma 5-HT level decreased (P < 0.01) and the ratio of the platelet and plasma 5-HT was abnormal P < 0.01. While during the intermittent period the 5-HT was increased both in platelet and plasma and the ratio of intra- and extra-platelet 5-HT was normal. Also, in comparing with before treatment, the post-treatmental plasma levels of 5-HT in patients with or without acute attack were all increased, the above-mentioned 5-HT ratio was also resumed obviously (P < 0.05). This study revealed that both the plasma 5-HT and platelet 5-HT levels and their ratio of patients in acute attack period were abnormal, which might be the pathogenetic basis of migraine. It suggested the mechanism of NZTP in treating migraine might be through its action on absorption, releasing and metabolism of 5-HT by platelet and maintaining a physiologic balance in them.

Adolescent↗

PubMed1995

Purification and two-dimensional crystallization of bacterial cytochrome oxidases.

A novel strategy which employes chromatography on an immobilized metal ion has been developed for the purification of bacterial cytochrome c and quinol oxidases. Many bacterial oxidase complexes appear to have a natural affinity to bind to the chelated copper ion. A combination of three different chromatographic principles (anion exchange, metal-affinity and gel filtration) makes an effective tool chest for the preparation of homogeneous and protein-chemically pure bacterial oxidases. These preparations have been used for two-dimensional crystallization. Until now, crystals have been obtained using the Paracococcus denitrificans and Rhodobacter sphaeroides cytochrome aa3 and the Escherichia coli cytochrome bo. The crystals diffract to approximately 2.5 nm in negative stain and have potential for further structural studies.

Bacteria↗

PubMed1995

[Study on ultrastructure of platelets in migraine patients with blood stasis type].

To study the relationship between ultrastructure of platelets and migraine patients with blood stasis type (MBS). The morphologic appearance and aggregation of platelets in MBS patients were examined before and after treatment with Tongbike oral liquor (20 cases in treated group and.10 in control). The results showed that the MBS patients' platelets appeared irregular, easy to aggregate and adhere to red cells, which was more severe when ADP was added, but improved after treated with Chinese medicinal herbs. According to the results it was assumed that platelets from MBS patients were in an abnormal activated state, the abnormal morphology and functional disturbance might be the pathologic basis of MBS. Tongbike oral liquor could markedly improve the morphologic and functional state of platelets, which was relevant to the inhibition of platelet aggregation and the inducing of platelet depolymerization.

Adolescent↗

PubMed1994

Three-dimensional map of the dimeric membrane domain of the human erythrocyte anion exchanger, Band 3.

The electroneutral exchange of chloride and bicarbonate across the human erythrocyte membrane is facilitated by Band 3, a 911 amino acid glycoprotein consisting of a 43 kDa N-terminal cytosolic domain that binds the cytoskeleton, haemoglobin and glycolytic enzymes and a 52 kDa C-terminal membrane domain that mediates anion transport. Electron microscopy and three-dimensional image reconstruction of negatively stained two-dimensional crystals of the dimeric membrane domain revealed a U-shaped structure with dimensions of 60 x 110 A, and a thickness of 80 A. The structure is open on the top and at the sides, with the monomers in close contact at the base. The basal domain is 40 A thick and probably spans the lipid bilayer. The upper part of the dimer consists of two elongated protrusions measuring 25 x 80 A in projection, with a thickness of 40 A. The protrusions form the sides of a canyon, enclosing a wide space that narrows down and converges into a depression at the centre of the dimer on the top of the basal domain. This depression may represent the opening to a transport channel located at the dimer interface. Based on the available protein-chemical data, the two protrusions face the cytosolic side of the membrane and they appear to be dynamic.

Amino Acid Sequence↗