[Progress in studies on the oxidative metabolism of xenobiotics mediated by lipoxygenase from extrahepatic tissues].
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Glutathione↗
Biomedical subjects
Yue Wu
Publications and source records attributed to Yue Wu.
[Stimulatory response to the oxidation of benzidine and other xenobiotics mediated by lipoxygenase in the presence of phenothiazines].
OBJECTIVE: To test the possibility that certain efficient substrates for lipoxygenase (LOX) produce shuttle oxidants that stimulate the generation of reactive oxygen species from other chemicals. METHODS: Metabolic interactions were conducted in vitro between chlorpromazine (BZ) or other phenothiazines and benzidine or other xenobiotics mediated by soybean lipoxygenase (SLO) or purified human term placental lipoxygenase (HTPLO) in the presence of hydrogen peroxide, and the rates of xenobiotics oxidation were measured by spectroscopic analysis. RESULTS: Chlorpromazine cation radical (CPZ(*+)) generated by lipoxygenase triggered a rapid oxidation of benzidine to benzidine diimine cation. Under the experimental conditions used, the metabolic interaction resulted in a 42-fold greater stimulation than BZ alone in the rate of BZ oxidation. The magnitude of stimulation of benzidine oxidation exhibited a dependence on the pH of the reaction medium, amount of the enzyme, and concentration of chlorpromazine, BZ, and hydrogen peroxide. A number of other phenothiazines were also found to stimulate BZ oxidation, albeit to a lesser degree. Chlorpromazine cation radical stimulated the oxidation of all six other xenobiotics tested. The highest stimulation (94-fold) was noted in the oxidation of tetramethyl phenylenediamine to Wursters blue radical, while the lowest stimulatory response (2-fold) was observed in guaiacol. Preliminary data showed that purified HTPLO also displayed a similar stimulatory response to benzidine oxidation in the presence of chlorpromazine. CONCLUSION: Both soybean lipoxygenase and purified human term placental lipoxygenase can mediate stimulatory response to the oxidation of benzidine and other xenobiotics in the presence of phenothiazines.
Benzidines↗
Crossover of microscopic dynamics in metallic supercooled liquid observed by NMR.
Nuclear magnetic resonance is used to characterize local atomic motions in the glassy and supercooled liquid states of the bulk metallic glass system Pd43Ni10Cu27P20. The temperature dependence of the Knight shift reveals that certain local atomic motion decreases rapidly below a crossover temperature T(c) down to the glass transition temperature T(g). Above T(c) as well as below T(g) the mean-squared amplitude of local motions depends linearly on the temperature. The observed gradual transition below T(c) is inconsistent with heterogeneity effects. It reveals that qualitative changes of microscopic properties in the supercooled liquid take place at temperatures significantly above T(g).
Journal Article↗
Synthesis of CdS and ZnS nanowires using single-source molecular precursors.
Single-source molecular precursors were used to synthesize II-VI compound semiconductor nanowires for the first time. Cadmium sulfide and zinc sulfide nanowires were prepared using cadmium diethyldithiocarbamate, Cd(S2CNEt2)2, and zinc diethyldithiocarbamate, Zn(S2CNEt2)2, respectively, as precursors in a gold nanocluster-catalyzed vapor-liquid-solid growth process. High-resolution transmission electron microscopy studies show that the CdS and ZnS nanowires are single-crystal wurtzite structures with stoichiometric compositions. In addition, photoluminescence measurements demonstrate that these nanowires exhibit high-quality optical properties. The applicability of our approach to the synthesis of other compound and alloy semiconductors nanowires as well as nanowire heterostructures of these materials is discussed.
Journal Article↗
Directional sensing requires G beta gamma-mediated PAK1 and PIX alpha-dependent activation of Cdc42.
Efficient chemotaxis requires directional sensing and cell polarization. We describe a signaling mechanism involving G beta gamma, PAK-associated guanine nucleotide exchange factor (PIX alpha), Cdc42, and p21-activated kinase (PAK) 1. This pathway is utilized by chemoattractants to regulate directional sensing and directional migration of myeloid cells. Our results suggest that G beta gamma binds PAK1 and, via PAK-associated PIX alpha, activates Cdc42, which in turn activates PAK1. Thus, in this pathway, PAK1 is not only an effector for Cdc42, but it also functions as a scaffold protein required for Cdc42 activation. This G beta gamma-PAK1/PIX alpha/Cdc42 pathway is essential for the localization of F-actin formation to the leading edge, the exclusion of PTEN from the leading edge, directional sensing, and the persistent directional migration of chemotactic leukocytes. Although ligand-induced production of PIP(3) is not required for activation of this pathway, PIP(3) appears to localize the activation of Cdc42 by the pathway.
Actins↗
The density of AMPA receptors activated by a transmitter quantum at the climbing fibre-Purkinje cell synapse in immature rats.
We aimed to estimate the number of AMPA receptors (AMPARs) bound by the quantal transmitter packet, their single-channel conductance and their density in the postsynaptic membrane at cerebellar Purkinje cell synapses. The synaptic and extrasynaptic AMPARs were examined in Purkinje cells in 2- to 4-day-old rats, when they receive synaptic inputs solely from climbing fibres (CFs). Evoked CF EPSCs and whole-cell AMPA currents displayed roughly linear current-voltage relationships, consistent with the presence of GluR2 subunits in synaptic and extrasynaptic AMPARs. The mean quantal size, estimated from the miniature EPSCs (MEPSCs), was approximately 300 pS. Peak-scaled non-stationary fluctuation analysis of spontaneous EPSCs and MEPSCs gave a weighted-mean synaptic channel conductance of approximately 5 pS (approximately 7 pS when corrected for filtering). By applying non-stationary fluctuation analysis to extrasynaptic currents activated by brief glutamate pulses (5 mM), we also obtained a small single-channel conductance estimate for extrasynaptic AMPARs (approximately 11 pS). This approach allowed us to obtain a maximum open probability (Po,max) value for the extrasynaptic receptors (Po,max = 0.72). Directly resolved extrasynaptic channel openings in the continued presence of glutamate exhibited clear multiple-conductance levels. The mean area of the postsynaptic density (PSD) of these synapses was 0.074 microm2, measured by reconstructing electron-microscopic (EM) serial sections. Postembedding immunogold labelling by anti-GluR2/3 antibody revealed that AMPARs are localised in PSDs. From these data and by simulating error factors, we estimate that at least 66 AMPARs are bound by a quantal transmitter packet at CF-Purkinje cell synapses, and the receptors are packed at a minimum density of approximately 900 microm-2 in the postsynaptic membrane.
Age Factors↗
Magnetic alignment in nominally non-magnetic hexagonal metal hydrides: NMR.
Powders of three hexagonal metal-hydrides or -deuterides are found to align in 4.4-8.3 T magnetic fields used for NMR. The field-alignment is unexpected, since all three systems have very small susceptibilities, as demonstrated by sharp NMR lines. The extent of alignment runs from nearly complete to barely detectable in ZrBe2(H,D)x, LuD3, and YD3, respectively. The preferred alignment direction in ZrBe2(H,D)x is with the crystallites' c-axis perpendicular to B, while the c-axis and B tend to be parallel in LuD3 and YD3. The susceptibilities chi parallel and chi perpendicular are determined from bulk magnetization measurements in aligned ZrBe2H1.4 powder. The alignment must be considered for proper analysis of NMR spectra in these and related materials.
Journal Article↗
Myosin phosphatase and myosin phosphorylation in differentiating C2C12 cells.
C2C12 cells offer a useful model to study the differentiation of non-muscle cells to skeletal muscle cells. Myosin phosphorylation and changes in related enzymes, with an emphasis on myosin phosphatase (MP) were analyzed over the first 6 days of C2C12 differentiation. There was a transition from myosin phosphatase target subunit 1 (MYPT1), predominant in the non-muscle cells to increased expression of MYPT2. Levels of MYPT1/2 were estimated, and both isoforms were higher in non- or partially differentiated cells compared to the concentrations in the differentiated isolated myotubes from day 6. A similar profile of expression was estimated for the type 1 protein phosphatase catalytic subunit, delta isoform (PP1c delta). Phosphatase activities, using phosphorylated smooth and skeletal muscle myosins, were estimated for total cell lysates and isolated myotubes. In general, smooth muscle myosin was the preferred substrate. Although the expression of MYPT1/2 and PP1c delta was considerably reduced in isolated myotubes the phosphatase activities were not reduced to corresponding levels. Most of the MP activity was due to PP1c, as indicated by okadaic acid. In spite of relatively high expression of MYPT1/2 and PP1c delta, marked phosphorylation of non-muscle myosin (over 50% of total myosin) was observed at day 2 (onset of expression of muscle-specific proteins) and both mono- and diphosphorylated light chains were observed. Partial inhibition of MLCK by 1-(5-chloronaphthalene-1-sulphonyl)-1H-hexahydro-1,4-diazepine HCl (ML-9) or by a construct designed from the autoinhibitory domain of MLCK, resulted in an increase in small myotubes (3-5 nuclei) after 3 days of differentiation and a decrease in larger myotubes (compared to control). The effect of ML-9 was not due to a reduction in intracellular Ca2+ levels. These results suggest that phosphorylation of non-muscle myosin is important in growth of myotubes, either in the fusion process to form larger myotubes or indirectly, by its role in sarcomere organization.
Animals↗
Identification of cry1I-type genes from Bacillus thuringiensis strains and characterization of a novel cry1I-type gene.
A PCR-restriction fragment length polymorphism method for identification of cry1I-type genes from Bacillus thuringiensis was established by designing a pair of universal primers based on the conserved regions of the genes to amplify 1,548-bp cry1I-type gene fragments. Amplification products were digested with the Bsp119I and BanI enzymes, and four kinds of known cry1I-type genes were successfully identified. The results showed that cry1I-type genes appeared in 95 of 115 B. thuringiensis isolates and 7 of 13 standard strains. A novel cry1I-type gene was found in one standard strain and six isolates. The novel cry1I gene was cloned from B. thuringiensis isolate Btc007 and subcloned into vector pET-21b. Then it was overexpressed in Escherichia coli BL21(DE3). The expressed product was shown to be toxic to the diamondback moth (Plutella xylostella), Asian corn borer (Ostrinia furnacalis), and soybean pod borer (Leguminivora glycinivorella). However, it was not toxic to the cotton bollworm (Helicoverpa armigera), beet armyworm (Spodoptera exigua), or elm leaf beetle (Pyrrhalta aenescens) in bioassays. Subsequently, the Cry protein encoded by this novel cry gene was designated Cry1Ie1 by the B. thuringiensis delta-endotoxin nomenclature committee.
Bacillus thuringiensis↗
Phosphorylation of the myosin phosphatase target subunit by integrin-linked kinase.
A mechanism proposed for regulation of myosin phosphatase (MP) activity is phosphorylation of the myosin phosphatase target subunit (MYPT1). Integrin-linked kinase (ILK) is associated with the contractile machinery and can phosphorylate myosin at the myosin light-chain kinase sites. The possibility that ILK may also phosphorylate and regulate MP was investigated. ILK was associated with the MP holoenzyme, shown by Western blots and in-gel kinase assays. MYPT1 was phosphorylated by ILK and phosphorylation sites in the N- and C-terminal fragments of MYPT1 were detected. From sequence analyses, three sites were identified: a primary site at Thr(709), and two other sites at Thr(695) and Thr(495). One of the sites for cAMP-dependent protein kinase (PKA) was Ser(694). Assays with the catalytic subunit of type 1 phosphatase indicated that only the C-terminal fragment of MYPT1 phosphorylated by zipper-interacting protein kinase, and ILK inhibited activity. The phosphorylated N-terminal fragment activated phosphatase activity and phosphorylation by PKA was without effect. Using full-length MYPT1 constructs phosphorylated by various kinases it was shown that Rho kinase gave marked inhibition; ILK produced an intermediate level of inhibition, which was considerably reduced for the Thr(695)-->Ala mutant; and PKA had no effect. In summary, phosphorylation of the various sites indicated that Thr(695) was the major inhibitory site, Thr(709) had only a slight inhibitory effect and Ser(694) had no effect. The findings that ILK phosphorylated both MYPT1 and myosin and the association of ILK with MP suggest that ILK may influence cytoskeletal structure or function.
Amino Acid Sequence↗
Outcome of B-cell non-Hodgkin lymphoma protocol CCCG-B NHL97: a report from Chinese multi-center cooperative group.
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Adolescent↗
Cellular and molecular effects of alpha-tocopheryloxybutyrate: lessons for the design of vitamin E analog for cancer prevention.
alpha-Tocopherol and its synthetic derivative, a-tocopheryl succinate (alpha-TS), are known to inhibit proliferation of cancer cells. alpha-TS is considered a more desirable anticancer agent because of the ability to induce apoptosis. It has been established previously that the whole intact alpha-TS molecule is necessary for its pro-apoptotic activity. For this reason, alpha-TS is not suitable for oral use because the ester bond linking succinate to tocopherol is subject to hydrolysis by intestinal esterases. One approach to overcome this problem is to replace the ester bond with an ether bond, since the latter is resistant to esterase-mediated hydrolysis. alpha-Tocopheryloxybutyrate (alpha-TOB) is the ether analog of alpha-TS. In this study, we compared the potency of alpha-TS and alpha-TOB using a panel of bioassays: cell growth, TUNEL labelling for apoptosis, PARP cleavage, caspase-3 and caspase-9 activation, as well as Akt and JNK phosphorylation. The experiments were carried out in two human prostate cancer cell lines: LNCaP and PC-3. Our results showed that alpha-TOB was capable of inhibiting cell growth and inducing apoptosis, although alpha-TOB was less active than alpha-TS on an equimolar basis. In general, it took twice as much alpha-TOB as alpha-TS to achieve the same response. Nonetheless, these two compounds shared the same mechanism of targeting the Akt and JNK signaling pathways, and activating the intrinsic cell death mediators of caspase-9 and caspase-3. Cellular analysis of alpha-TS and alpha-TOB showed that alpha-TOB was taken up as efficiently as alpha-TS (if not more so), suggesting that the lower activity of alpha-TOB is an inherent property of the molecule and not due to impaired uptake. Additional evidence is provided to show that beta-TS may act at the membrane level to interfere with Akt phosphorylation, although the exact nature of this disruption remains unclear. The future design of new anticancer tocopherol analogs should incorporate the ether linkage of the side chain for esterase resistance as well as other structural modifications for enhanced blocking of membrane signaling.
Anticarcinogenic Agents↗