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W Zhou

Publications and source records attributed to W Zhou.

At least 109 records · Page 6Linked to original sources
PubMed2000

Simultaneous activation of NADPH oxidase-related proton and electron currents in human neutrophils.

Generation of reactive oxygen species by the NADPH oxidase complex is an important bactericidal weapon of phagocytes. Phorbol myristate acetate (PMA) is a potent agonist for this "respiratory burst" in human neutrophils. Although stoichiometric H(+) efflux occurs during the respiratory burst, efforts to stimulate voltage-gated H(+) channels by PMA in whole-cell patch-clamped phagocytes have been unsuccessful. We have used a modification of the permeabilized-patch configuration that allows control of intracellular pH and preserves second-messenger pathways. Using this method, we show that PMA dramatically enhances and alters voltage-gated proton currents in human neutrophils. PMA produced four alterations in H(+) current properties, each of which increases the H(+) current at any given voltage: (i) a 40-mV negative shift in the H(+) conductance-voltage (g(H)-V) relationship; (ii) faster activation [smaller activation time constant (tau(act))] during depolarizing pulses; (iii) slower deactivation [larger deactivation time constant (tau(tail))] on repolarization; and (iv) a larger maximum H(+) conductance (g(H, max)). Inward current that directly reflects electron transport by NADPH oxidase was also activated by PMA stimulation. The identity of this electron current was confirmed by its sensitivity to diphenylene iodinium, an inhibitor of NADPH oxidase. Diphenylene iodinium also reversed the slowing of tau(tail) with a time course paralleling the inhibition of electron current. However, the amplitudes of H(+) and electron currents activated by PMA were not correlated. A complex interaction between NADPH oxidase and voltage-gated proton channels is indicated. The data suggest that PMA stimulation modulates preexisting H(+) channels rather than inducing a new H(+) channel.

Adult↗
PubMed2000

Overexpression of human alpha-synuclein causes dopamine neuron death in rat primary culture and immortalized mesencephalon-derived cells.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the appearance of intracytoplasmic inclusions called Lewy bodies (LB) in dopamine neurons in the substantia nigra and the progressive loss of these neurons. Recently, mutations in the alpha-synuclein gene have been identified in early-onset familial PD, and alpha-synuclein has been shown to be a major component of LB in all patients. Yet, the pathophysiological function of alpha-synuclein remains unknown. In this report, we have investigated the toxic effects of adenovirus-mediated alpha-synuclein overexpression on dopamine neurons in rat primary mesencephalic cultures and in a rat dopaminergic cell line - the large T-antigen immortalized, mesencephalon-derived 1RB3AN27 (N27). Adenovirus-transduced cultures showed high-level expression of alpha-synuclein within the cells. Overexpression of human mutant alpha-synuclein (Ala(53)Thr) selectively induced apoptotic programmed cell death of primary dopamine neurons as well as N27 cells. The mutant protein also potentiated the neurotoxicity of 6-hydroxydopamine (6-OHDA). By contrast, overexpression of wild-type human alpha-synuclein was not directly neurotoxic but did increase cell death after 6-OHDA. Overexpression of wild-type rat alpha-synuclein had no effect on dopamine cell survival or 6-OHDA neurotoxicity. These results indicate that overexpression of human mutant alpha-synuclein directly leads to dopamine neuron death, and overexpression of either human mutant or human wild-type alpha-synuclein renders dopamine neurons more vulnerable to neurotoxic insults.

Adenoviridae↗
PubMed2000

Relative reactivities of tethered functional groups in the interior of a zeolite

[reaction: see text] The reactions of singlet oxygen with substrates containing both sulfide and olefinic linkages have been examined. The dramatic increase in sulfoxide formation in the interior of the zeolite in comparison to solution is attributed to zeolite stabilization of the persulfoxide intermediate and concomitant inhibition of physical quenching of singlet oxygen.

Journal Article↗
PubMed2000

Investigation of the mechanism of action of microperoxidase-11, (MP11), a potential anti-cataract agent, with hydrogen peroxide and ascorbate.

The interaction of hydrogen peroxide, ascorbate and microperoxidase-11 (MP11), a ferriheme undecapeptide derived from cytochrome c, has been investigated using spectrophotometry, oxymetry, electron paramagnetic resonance (EPR), and mass spectroscopy techniques. It is shown that in 50 m M phosphate pH 7. 0-7.4 in the absence of other reactants H(2)O(2)induces a concentration-dependent decrease in absorption at the Soret band (399 nm) of the microperoxidase, with concomitant H(2)O(2)decomposition and oxygen evolution. The reaction causes irreversible heme degradation, concomitant with loss of enzymatic activity. Ascorbate effectively protects MP11 from degradation and inhibits oxygen evolution. At ascorbate concentrations greater than that of H(2)O(2), microperoxidase degradation is almost completely prevented. Mass spectrometry showed that H(2)O(2)oxidizes the microperoxidase to a monooxygenated product, which did not form if ascorbate was included in the reaction system. There appears to be a 1:1 relationship between H(2)O(2)degradation and ascorbate oxidation. EPR experiments revealed that an ascorbate radical was formed during the reaction. These reactions may be described by a scheme where a putative 'compound I' of the microperoxidase is reduced by ascorbate back to the original redox state (ferric) of the peroxidase in two one-electron steps, concomitantly with oxidation of the ascorbate to an ascorbate radical or in one two-electron transfer step forming dehydroascorbate. In the absence of ascorbate, the 'compound I' reacts further with the peroxide causing microperoxidase degradation and partial oxygen evolution. These observations are relevant to the interaction of ferrihemes with H(2)O(2)and ascorbic acid and may be pertinent for the potential application of MP11 as an anti-cataract agent.

Ascorbic Acid↗
PubMed2000

Identification of differentially expressed genes in nasopharyngeal carcinoma by means of the Atlas human cancer cDNA expression array.

PURPOSE: To investigate genes of critical areas, including cell cycle/growth control, apoptosis, oncogene/tumor suppressors and growth factor/cytokines, that are differentially expressed in nasopharyngeal carcinoma. METHODS: The Human Cancer cDNA Atlas, which contains 588 genes relating to tumor biology, was used to screen normal nasopharyngeal tissue, nasopharyngeal cancer (NPC). The reverse transcription/polymerase chain reaction was used to confirm the expression pattern of some genes identified by Atlas hybridization. RESULTS: The differentially expressed cell cycle/growth control regulators in NPC showed a stronger tendency toward cell proliferation with the up-regulation of cyclin D1, cyclin D2 etc. The expression pattern of apoptosis-related genes demonstrated the up-regulation of both anti-apoptotic factors such as the BCL-2-related protein A1, TRAF3, the inhibitor of apoptosis protein A1 (IAPI) and apoptotic pathway elements such as Fas/Apo-1, Apo-2 ligand etc. Among oncogenes/tumor suppressors, MDM2, STAT1 and STAT2 were found to be up-regulated in NPC. The expression profile of growth factors/cytokines showed the up-regulation of many growth-enhancing factors such as EGR1, tumor-derived growth factor 1, platelet-derived growth factor A chain etc. as well as Th1-type cytokines e.g. interleukin-1beta and interferons. A smaller number of genes were down-regulated in nasopharyngeal cancer, such as those encoding ERK1, Raf, secreted apoptosis-related protein 1, CD27BP, transforming growth factor beta2, pre-B-cell-stimulating factor homologue etc. CONCLUSION: The consistent tendency toward cell proliferation, the possibility of a stronger antiapoptotic force that operates on the normal apoptotic pathway, or the autocrine or paracrine growth factors may account for the development of NPC. Some genes are reported for the first time to have changed expression in nasopharyngeal carcinoma. The simple, quick, and high-throughput method of profiling gene expression by cDNA array hybridization provides us with a quick overview of key factors that may be involved in NPC, and may identify genes suitable for further study of carcinogenesis mechanism or targets for possible molecular diagnosis or therapy.

Apoptosis↗
PubMed2000

In situ localization of C3 synthesis in experimental acute renal allograft rejection.

Recent evidence has implicated complement in renal transplant injury and identified the kidney as a source of complement components. We therefore investigated the local gene expression of complement component C3, pivotal to complement activation pathways and a mediator of inflammatory injury, in a rat renal transplant model. By reverse transcriptase-polymerase chain reaction, the expression of C3 mRNA increased in two phases. The first phase coincided with post-ischemic injury over 2 days post-transplantation and was localized by in situ hybridization to vessels and glomerular mesangial cells in allogeneic and syngeneic (control) kidney transplants. In allografts only, a second phase was found in tubular epithelial cells, glomerular parietal cells, vessel walls and some infiltrating cells, which peaked on day 4 together with rapid influx of leukocytes, tubule cell damage, the induction of interleukin-2 and interferon-gamma mRNA, and the up-regulation of tumor necrosis factor-alpha and interleukin-1beta mRNA in the graft. In vitro studies showed that interleukin-2 and interferon-gamma up-regulate C3 production in renal tubule cells. We conclude that post-ischemic injury led to transient up-regulation of glomerular expression of C3 mRNA. Subsequent cellular rejection was associated with tubulointerstitial/glomerular parietal cell expression of C3 mRNA. This differential expression of local C3, immediately post-transplant or associated with acute rejection, may have implications for putative therapeutic complement inhibition in clinical transplantation.

Acute Disease↗
PubMed2000

First flight of the ASTROCULTURE (TM) experiment as a part of the U.S. Shuttle/MIR program.

A number of space-based experiments have been conducted to assess the impact of microgravity on plant growth and development. In general, these experiments did not identify any profound impact of microgravity on plant growth and development, though investigations to study seed development have indicated difficulty in plants completing their reproductive cycle. However, it was not clear whether the lack of seed production was due to gravity effects or some other environmental condition prevailing in the unit used for conducting the experiment. The ASTROCULTURE (TM) flight unit contains a totally enclosed plant chamber in which all the critically important environmental conditions are controlled. Normal wheat (Triticum aestivum L.) growth and development in the ASTROCULTURE (TM) flight unit was observed during a ground experiment conducted prior to the space experiment. Subsequent to the ground experiment, the flight unit was transported to MIR by STS-89, as part of the U.S. Shuttle/MIR program, in an attempt to determine if super dwarf wheat plants that were germinated in microgravity would grow normally and produce seeds. The experiment was initiated on-orbit after the flight unit was transferred from the Space Shuttle to MIR. The ASTROCULTURE (TM) flight unit performed nominally for the first 24 hours after the flight unit was activated, and then the unit stopped functioning abruptly. Since it was not possible to return the unit to nominal operation it was decided to terminate the experiment. On return of the flight unit, it was confirmed that the control computer of the ASTROCULTURE (TM) flight unit sustained a radiation hit that affected the control software embedded in the computer. This experience points out that at high orbital inclinations, such as that of MIR and that projected for the International Space Station, the danger of encountering harmful radiation effects are likely unless the electronic components of the flight hardware are resistant to such impacts.

Agriculture↗
PubMed2000

HRTEM investigation of mesoporous molecular sieves

High resolution transmission electron microscopic (HRTEM) studies of some typical mesoporous molecular sieves, such as MCM-41, SBA-2 and STAC-1, etc. are presented. Since the materials consist of amorphous silica and their unit cell dimensions are in a range of 1.5 to over 10 nm, the conventional X-ray diffraction method gives us very limited information about the detailed structures. On the other hand, HRTEM has been found to be the most powerful technique to detect the local structures and to image metal clusters inside the channels of these materials.

Journal Article↗
PubMed2000

Detection and sequencing of phosphopeptides affinity bound to immobilized metal ion beads by matrix-assisted laser desorption/ionization mass spectrometry.

Consecutive enzymatic reactions of analytes which are affinity bound to immobilized metal ion beads with subsequent direct analysis of the products by matrix-assisted laser desorption/ionization mass spectrometry have been used for detecting phosphorylation sites. The usefulness of this method was demonstrated by analyzing two commercially available phosphoproteins, beta-casein and alpha-casein, as well as one phosphopeptide from a kinase reaction mixture. Agarose loaded with either Fe3+ or Ga3+ was used to isolate phosphopeptides from the protein digest. Results from using either metal ion were complementary. Less overall suppression effect was achieved when Ga3+-loaded agarose was used to isolate phosphopeptides. The selectivity for monophosphorylated peptides, however, was better with Fe3+-loaded agarose. This technique is easy to use and has the ability to analyze extremely complicated phosphopeptide mixtures. Moreover, it eliminates the need for prior high-performance liquid chromatography separation or radiolabeling, thus greatly simplifying the sample preparation.

Amino Acid Sequence↗
PubMed2000

Tissue distribution and prevalence of Wolbachia infections in tsetse flies, Glossina spp.

Tsetse flies Glossina spp. (Diptera: Glossinidae) harbor three different symbiotic microorganisms, one being an intracellular Rickettsia of the genus Wolbachia. This bacterium infects a wide range of arthropods, where it causes a variety of reproductive abnormalities, one of which is termed cytoplasmic incompatibility (CI) that, when expressed, results in embryonic death due to disruptions in fertilization events. We report here that in colonized flies, Wolbachia infections can be detected in 100% of sampled individuals, while infections vary significantly in field populations. Based on Wolbachia Surface Protein (wsp) gene sequence analysis, the infections associated with different fly species are all unique within the A group of the Wolbachia pipientis clade. In addition to being present in germ-line tissues, Wolbachia infections have been found in somatic tissues of several insects. Using a Wolbachia-specific PCR-based assay, the tissue tropism of infections in Glossina morsitans morsitans Westwood, Glossina brevipalpis Newstead and Glossina austeni Newstead were analysed. While infections in G. m. morsitans and G. brevipalpis were limited to reproductive tissues, in G. austeni, Wolbachia could be detected in various somatic tissues.

Animals↗
PubMed2000

Risk of spontaneous abortion following induced abortion is only increased with short interpregnancy interval.

We set out to study the risk of spontaneous abortion following a first trimester induced abortion as a function of the interpregnancy interval between two pregnancies. The cohort study is based on the following databases: Danish national registries: the Medical Birth Registry (MBR), the Hospital Discharge Registry (HDR), and the induced Abortion Registry (IAR). All primigravid women in the time period from 1980 to 1982 were identified in the MBR, the HDR and the IAR. A total of 15 727 women who terminated the pregnancy with a first trimester induced abortion were selected as the induced abortion cohort, and 46 026 women who did not terminate the pregnancy with an induced abortion constituted the control cohort. By register linkage all subsequent pregnancies which were not terminated by induced abortion were identified from 1980 to 1994. Only women who had a non-terminated pregnancy following the index pregnancy were selected. Women whose first pregnancy was terminated following a first trimester induced abortion had a risk of spontaneous abortion of 11.0% vs. 9.4% in the control cohort. This relative difference of 1.17 was not statistically significant in logistic regression analyses. An increased risk was only found for women who had an interpregnancy interval of less than 3 months (OR=4.06, 95% C.I.=1.98-8.31). The abortion method, vacuum aspiration with dilatation or evacuation with dilatation did not modify this elevated risk. Overall the study did not show an increased risk of spontaneous abortion following one or more induced abortions, except for women with a short interpregnancy interval between an induced abortion and a subsequent pregnancy. We recommend women who have a first trimester induced abortion be advised to wait at least 3-6 months before trying to become pregnant again.

Journal Article↗
PubMed2000

Polymerization defects within human telomerase are distinct from telomerase RNA and TEP1 binding.

The minimal, active core of human telomerase is postulated to contain two components, the telomerase RNA hTER and the telomerase reverse transcriptase hTERT. The reconstitution of human telomerase activity in vitro has facilitated the identification of sequences within the telomerase RNA and the RT motifs of hTERT that are essential for telomerase activity. However, the precise role of residues outside the RT domain of hTERT is unknown. Here we have delineated several regions within hTERT that are important for telomerase catalysis, primer use, and interaction with the telomerase RNA and the telomerase-associated protein TEP1. In particular, certain deletions of the amino and carboxy terminus of hTERT that retained an interaction with telomerase RNA and TEP1 were nonetheless completely inactive in vitro and in vivo. Furthermore, hTERT truncations lacking the amino terminus that were competent to bind the telomerase RNA were severely compromised for the ability to elongate telomeric and nontelomeric primers. These results suggest that the interaction of telomerase RNA with hTERT can be functionally uncoupled from polymerization, and that there are regions outside the RT domain of hTERT that are critical for telomerase activity and primer use. These results establish that the human telomerase RT possesses unique polymerization determinants that distinguish it from other RTs.

Animals↗
PubMed2000

Induced abortion and low birthweight in the following pregnancy.

BACKGROUND: To examine whether induced abortion increases the risk of low birthweight in subsequent singleton live births. METHODS: Cohort study using the Danish Medical Birth Registry (MBR), the Hospital Discharge Registry (HDR), and the Induced Abortion Registry (IAR). All women who had their first pregnancy during 1980-1982 were identified in the MBR, the HDR, and the IAR. We included all 15,727 women whose pregnancy was terminated by a first trimester induced abortion in the induced abortion cohort and 46,026 women whose pregnancy was not terminated by an induced abortion were selected for the control cohort. All subsequent pregnancies until 1994 were identified by register record linkage. RESULTS: Low birthweight (<2500 g) in singleton term live births occurred more frequently in women with one, two, three or more previous induced abortions, compared with women without any previous induced abortion of similar gravidity, 2.2% versus 1.5%, 2.4% versus 1.7%, and 1.8% versus 1.6%, respectively. Adjusting for maternal age and residence at time of pregnancy, interpregnancy interval, gender of newborn, number of previous spontaneous abortions and number of previous low birthweight infants (control cohort only), the odds ratios (OR) of low birthweight in singleton term live births in women with one, two or more previous first trimester induced abortions were 1.9 (95% CI: 1.6, 2.3), and 1.9 (95% CI: 1.3, 2.7), respectively, compared with the control cohort of similar gravidity. High risks were mainly seen in women with an interpregnancy interval of more than 6 months. CONCLUSIONS: The findings suggest a positive association between one or more first trimester induced abortions and the risk of low birthweight in subsequent singleton term live births when the interpregnancy interval is longer than 6 months. This result was unexpected and confounding cannot be ruled out.

Abortion, Induced↗
PubMed2000

Sterol methyltransferase 1 controls the level of cholesterol in plants.

The side chain in plant sterols can have either a methyl or ethyl addition at carbon 24 that is absent in cholesterol. The ethyl addition is the product of two sequential methyl additions. Arabidopsis contains three genes-sterol methyltransferase 1 (SMT1), SMT2, and SMT3-homologous to yeast ERG6, which is known to encode an S-adenosylmethionine-dependent C-24 SMT that catalyzes a single methyl addition. The SMT1 polypeptide is the most similar of these Arabidopsis homologs to yeast Erg6p. Moreover, expression of Arabidopsis SMT1 in erg6 restores SMT activity to the yeast mutant. The smt1 plants have pleiotropic defects: poor growth and fertility, sensitivity of the root to calcium, and a loss of proper embryo morphogenesis. smt1 has an altered sterol content: it accumulates cholesterol and has less C-24 alkylated sterols content. Escherichia coli extracts, obtained from a strain expressing the Arabidopsis SMT1 protein, can perform both the methyl and ethyl additions to appropriate sterol substrates, although with different kinetics. The fact that smt1 null mutants still produce alkylated sterols and that SMT1 can catalyze both alkylation steps shows that there is considerable overlap in the substrate specificity of enzymes in sterol biosynthesis. The availability of the SMT1 gene and mutant should permit the manipulation of phytosterol composition, which will help elucidate the role of sterols in animal nutrition.

Amino Acid Sequence↗
PubMed2000

Induction of human fetal globin gene expression by a novel erythroid factor, NF-E4.

The stage selector protein (SSP) is a heteromeric complex involved in preferential expression of the human gamma-globin genes in fetal-erythroid cells. We have previously identified the ubiquitous transcription factor CP2 as a component of this complex. Using the protein dimerization domain of CP2 in a yeast two-hybrid screen, we have cloned a novel gene, NF-E4, encoding the tissue-restricted component of the SSP. NF-E4 and CP2 coimmunoprecipitate from extract derived from a fetal-erythroid cell line, and antiserum to NF-E4 ablates binding of the SSP to the gamma promoter. NF-E4 is expressed in fetal liver, cord blood, and bone marrow and in the K562 and HEL cell lines, which constitutively express the fetal globin genes. Enforced expression of NF-E4 in K562 cells and primary erythroid progenitors induces endogenous fetal globin gene expression, suggesting a possible strategy for therapeutic intervention in the hemoglobinopathies.

Amino Acid Sequence↗
PubMed2000

Upregulation of Kv1.3 K(+) channels in microglia deactivated by TGF-beta.

Microglial activation is accompanied by changes in K(+) channel expression. Here we demonstrate that a deactivating cytokine changes the electrophysiological properties of microglial cells. Upregulation of delayed rectifier (DR) K(+) channels was observed in microglia after exposure to transforming growth factor-beta (TGF-beta) for 24 h. In contrast, inward rectifier K(+) channel expression was unchanged by TGF-beta. DR current density was more than sixfold larger in TGF-beta-treated microglia than in untreated microglia. DR currents of TGF-beta-treated cells exhibited the following properties: activation at potentials more positive than -40 mV, half-maximal activation at -27 mV, half-maximal inactivation at -38 mV, time dependent and strongly use-dependent inactivation, and a single channel conductance of 13 pS in Ringer solution. DR channels were highly sensitive to charybdotoxin (CTX) and kaliotoxin (KTX), whereas alpha-dendrotoxin had little effect. With RT-PCR, mRNA for Kv1.3 and Kir2.1 was detected in microglia. In accordance with the observed changes in DR current density, the mRNA level for Kv1.3 (assessed by competitive RT-PCR) increased fivefold after treatment of microglia with TGF-beta.

Animals↗