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Biomedical subjects

Z Wang

Publications and source records attributed to Z Wang.

At least 577 records · Page 32Linked to original sources
PubMed2000

Identification of a complex that binds to the CD154 3' untranslated region: implications for a role in message stability during T cell activation.

CD154 expression is regulated throughout a time course of CD3-dependent T cell activation by differential mRNA decay. To understand the molecular basis of the "stability" phase of this pathway, experiments were conducted to identify sequences and specific complexes important in this regulation. Gel retardation assays using extracts from both Jurkat T cells and CD3-activated CD4(+) T cells revealed a major complex (complex I) that bound a 65-bp highly CU-rich region of the CD154 3' untranslated region. The specificity of the CU-rich element for complex-I formation was confirmed by disruption of this complex by oligo(dCT) competition. Formation of complex I strongly correlated with CD154 mRNA stability across a time course of T cell activation. UV cross-linking identified a major oligo(dCT)-sensitive species at approximately 90 kDa that showed induced and increased expression in extracts from 24- and 48-hr anti-CD3-activated T cells, respectively. This protein was absent in equivalent extracts from resting or 2-h-activated T cells. Using an in vitro decay assay, we found that a CD154-specific transcript was more rapidly degraded in 2-h-activated extract and stabilized in the 24- and 48-h extracts compared to extracts from resting T cells. Disruption of complex I resulted in the rapid decay of a CD154-specific transcript demonstrating a functional role for complex I in mRNA stabilization in vitro. These studies support a model of posttranscriptional regulation of CD154 expression being controlled in part by the interaction of a poly(CU)-binding complex with a specific sequence in the 3' untranslated region.

3' Untranslated Regions↗
PubMed2000

Leptin resistance of adipocytes in obesity: role of suppressors of cytokine signaling.

Liver-derived hyperleptinemia induced in normal rats by adenovirus-induced gene transfer causes rapid disappearance of body fat, whereas the endogenous adipocyte-derived hyperleptinemia of obesity does not. Here we induce liver-derived hyperleptinemia in rats with adipocyte-derived hyperleptinemia of acquired obesity caused by ventromedial hypothalamus lesioning (VMH rats) or by feeding 60% fat (DIO rats). Liver-derived hyperleptinemia in obese rats caused only a 5-7% loss of body weight, compared to a 13% loss in normoleptinemic lean animals; but in actual grams of weight lost there was no significant difference between obese and lean groups, suggesting that a subset of cells remain leptin-sensitive in obesity. mRNA and protein of a putative leptin-resistance factor, suppressor of cytokine signaling (SOCS)-1 or -3, were both increased in white adipose tissues (WAT) of VMH and DIO rats. Since transgenic overexpression of SOCS-3 in islets reduced the lipopenic effect of leptin by 75%, we conclude that the increased expression of SOCS-1 and -3 in WAT of rats with acquired obesity could have blocked leptin's lipopenic action in the leptin-resistant WAT population.

Adenoviridae↗
PubMed2000

Fluorinated building blocks. The discovery of a stable difluoroallenyl indium and the synthesis of gem-difluoroallenyl and -propargyl synthons in aqueous media

The synthesis of two highly functional fluorinated motifs, TIPS-C triple bond C-CF2-, and CF2=C=C(TIPS)- is described. This approach is mediated by a room-temperature stable ethereal solution of a difluoroallene indium intermediate. This intermediate may be used as "stock solution" in the reaction with aqueous HCHO, to yield CF2=C=C(TIPS)CH2OH, and in a reaction with a Schiff base to produce the corresponding beta,beta-difluorohomopropargylamine. The synthetic potential of CF2=C=C(TIPS)CH2-OH has been demonstrated by its conversion to a difluorodihydrofuran derivative by a facile and efficient 5-endo-trig cyclization. Homopropargylic gem-difluoro alcohols are synthesized by addition of indium to a mixture of an aldehyde and TIPS-C triple bond C-CF2Br in predominantly aqueous media.

Journal Article↗
PubMed2000

Lung cancer and environmental tobacco smoke in a non-industrial area of China.

We report results from a population-based case-control study of lung cancer and environmental tobacco smoke (ETS) among never-smokers conducted in 2 rural prefectures of China, including 200 female and 33 male lung cancer cases, and 407 female and 114 male controls, matched on age, sex and prefecture of current residence. The odds ratio (OR) for ever-exposed to ETS was 1.19 (95% CI 0.7-2.0), with a significant trend (p<0.05) with increasing exposure. ORs were 1.00, 1.04, 1.13 and 1.51 for non-exposed, <10, 10-19 and >/=20 pack-years of ETS exposure, respectively. Excess risks were limited to ETS exposures in childhood (</=18 years of age). The OR for ever-exposed to ETS in childhood, adjusting for ETS exposure in adulthood, was 1. 52 (95% CI 1.1-2.2), with a significant trend (p<0.01) with increasing pack-years of childhood exposure, 1.00, 1.43, 1.81 and 2. 95, respectively. After adjustment for ETS in childhood, there was no excess risk from adult ETS exposure. The OR for ever-exposed to ETS in adulthood was 0.90 (95% CI 0.-1.4). These results were not affected by adjustment for type of residential dwelling, type or amount of fuel used, perceived indoor smokiness, or measures of socioeconomic status, or omitting next-of-kin respondents.

Adult↗
PubMed2000

Lung cancer and indoor air pollution in rural china.

PURPOSE: Indoor air pollution has been linked with lung cancer in China. In contrast to previous studies conducted in urban areas with high levels of industrial pollution, we undertook a lung cancer case-control study in a rural area of China, where residents live in underground dwellings. We evaluated the effects of radon, wood and coal combustion, cooking oil fumes, and environmental tobacco smoke on lung cancer risk.METHODS: We enrolled 886 lung cancer cases (656 males, 230 females) diagnosed between 1994-98, aged 30-75 years and 1765 frequency matched population-based controls from two prefectures in Gansu Province in Northwestern China. We conducted interviews with subjects or next of kin on smoking, housing characteristics, fuel use and cooking practices. Year-long radon detectors were placed in current and former homes of subjects.RESULTS: Subjects primarily used coal (22%), wood (56%) or a combination of both (22%) for heating. Odds Ratios (OR) for lung cancer rose with increasing percent of time that coal was used to heat homes over the past 30 years (ORs = 1.00, 1.17, 1.35, 1.23 compared to wood only, adjusted to smoking, P for trend = 0.025). Among non-smoking females and males, the OR for ever exposed to environmental tobacco smoke was 1.19, 95% CI = 0.7-2.0 with a significant trend for increasing years of exposure. Fumes from cooking with rapeseed oil increased the risk of lung cancer (OR = 1.56, 95% CI = 1.0-2.5) among non-smoking women. Among these women, occasional and frequent eye and throat irritation during cooking appeared to be associated with increased risk of lung cancer (ORs = 1.00, 1.42, 2.28, p trend < 0.01), whereas, increasing level of smokiness during cooking did not appear to affect risk.CONCLUSIONS: There is a suggestion that coal used for heating, environmental tobacco smoke, and cooking oil fumes contribute to the risk of lung cancer in this rural area of China.

Journal Article↗
PubMed2000

Progesterone regulates human telomerase reverse transcriptase gene expression via activation of mitogen-activated protein kinase signaling pathway.

Emerging evidence indicates that sex steroid hormones regulate telomerase in target tissues. We have reported that estrogen activates telomerase through transactivation of the telomerase catalytic subunit, human telomerase reverse transcriptase (hTERT). Progesterone usually antagonizes estrogen action in reproductive organs, but the effect on telomerase remains unclear. In this study, we examine the effects of progesterone on the gene expression of hTERT in breast and endometrial cancer cell lines expressing progesterone receptor. Progesterone significantly induced hTERT mRNA expression within 3 h after exposure. This transient effect peaked at 12 h and then decreased. In contrast, exposure to progesterone for > 48 h antagonized estrogen effects and inhibited the estrogen-induced activation of hTERT expression; the cyclin-dependent kinase inhibitor p21/Waf1/Cip1 plays an integral role in this inhibition. Thus, progesterone exerts diverse effects on hTERT mRNA expression in a time-dependent manner. We also found that the mitogen-activated protein kinase signaling pathway mediates both the short-term and long-term effects of progesterone on hTERT gene expression. These findings support the notion that hTERT gene is a target of both estrogen and progesterone.

Breast Neoplasms↗
PubMed2000

High-performance polyethylene glycol-coated solid-phase microextraction fibers using sol-gel technology.

The sol-gel method is applied for the preparation of solid-phase microextraction (SPME) fibers. An electron microscopy experiment suggested a porous structure for Superox-4 (polyethylene glycol, PEG) coating. SPME-GC analyses provided evidence that the sol-gel fibers have some advantages, such as high velocities of mass transfer, efficient extraction rates. high thermal stability, long life span, and spacious range of application for both polar and non-polar analytes. Efficient SPME-GC analyses of benzene-toluene-ethylbenzene-xylenes, phenols, phthalic diesters, naphthalene congeners and pesticides were achieved using sol-gel-coated PEG fibers.

Chromatography, Gas↗
PubMed2000

Stereocontrolled syntheses of deoxyribonucleosides via photoinduced electron-transfer deoxygenation of benzoyl-protected ribo- and arabinonucleosides.

The stereocontrolled, de novo syntheses of beta-2'-deoxy-, alpha-2'-deoxy-, beta-3'-deoxy-, and beta-2', 3'-dideoxyribonucleosides are described. Strategically protected ribose, arabinose, and xylose glycosylation precursors were synthesized bearing C2-esters capable of directing Vorbrüggen glycosylation. The key step is the regioselective deoxygenation of the desired hydroxyl group as either the benzoyl- or 3-(trifluoromethyl)benzoyl derivative. This deoxygenation is accomplished via a photoinduced electron-transfer (PET) mechanism using carbazole derivatives as the photosensitizer. The syntheses of the desired deoxynucleoside generally proceed in three steps from a common, readily available precursor.

Arabinonucleosides↗
PubMed2000

Identification of ENV determinants in V3 that influence the molecular anatomy of CCR5 utilization.

The V3 loop of the ENV glycoprotein exerts a dominant influence on the interaction of gp120 with coreceptors. Primary env genes cloned from sequential isolates from two seroconverters revealed Pro-->Ala conversion in the conserved GPG motif of the V3 crown in seven of 17 R5 ENV. ENV containing the GPG motif in the V3 crown had fusogenic activity with chimeric receptors containing either the N terminus or loops of CCR5, whereas those with the GAG variant utilized only the former. Site-directed mutagenesis of multiple primary and prototypic R5 env genes demonstrated that the GPG motif was necessary for dual utilization of the N terminus and body of CCR5 in both gain and loss-of-function experiments. All ENV containing the GPG V3 crown showed CCR5 binding in the presence of soluble CD4, whereas it was not detected with the GAG variants. Molecular dynamic simulations of a V3 peptide predicts that the Pro-->Ala substitution results in a conformational change with loss of the crown structure. These studies demonstrate that sequences in the third hypervariable region determine the specificity of coreceptor utilization for fusion, and that a conserved motif in the crown directly influences the molecular anatomy of the interaction between gp120 and CCR5.

Amino Acid Motifs↗
PubMed2000

Molecular evidence for a role of Shaw (Kv3) potassium channel subunits in potassium currents of dog atrium.

We previously described an ultrarapid delayed rectifier current in dog atrial myocytes (IKur,d) with properties resembling currents reported for Kv3.1 channels in neural tissue; however, there was no direct molecular evidence for Shaw subfamily (Kv3) subunit expression in the heart. To identify the molecular basis of IKur,d, we cloned a full-length cDNA (dKv3.1) from canine atrium with homology-based reverse transcription (RT)- polymerase chain reaction (PCR) cloning techniques. A 1755 bp full-length cDNA (dKv3.1) was obtained, with 94.2 % homology to rat brain Kv3.1 (rbKv3.1). The deduced amino acid sequence had 99.3 % homology with rbKv3.1. Heterologous expression of dKv3.1 in Xenopus oocytes produced currents with activation voltage dependence, rectification, and activation and deactivation kinetics that strongly resemble native IKur,d. Like IKur,d, dKv3.1 was found to be highly sensitive to extracellular 4-aminopyridine (4-AP) and tetraethylammonium (TEA). RNase protection assays, Western blots and immunohistochemical studies demonstrated the presence of dKv3.1 transcripts and proteins in dog atrial preparations and isolated canine atrial myocytes. Protein corresponding to the Kv1.5 subunit, which can also carry ultrarapid delayed rectifier current, was absent. Unlike neural tissues, which express two splice variants (Kv3.1a and Kv3.1b), canine atrium showed only Kv3.1b transcripts. Whole-cell patch-clamp studies showed that IKur,d is absent in canine ventricular myocytes, and immunohistochemical and Western blot analysis demonstrated the absence of dKv3.1 protein in canine ventricle. We conclude that the Shaw-type channel dKv3.1 is present in dog atrium, but not ventricle, and is the likely molecular basis of canine atrial IKur,d.

4-Aminopyridine↗
PubMed2000

Casein kinase II phosphorylation of caldesmon downregulates myosin-caldesmon interactions.

It is well-known that caldesmon (CaD) is a substrate for casein kinase II (CKII), and the phosphorylation of CaD by CKII regulates the interaction of CaD with myosin. However, the functionally relevant CKII phosphorylation site(s) on CaD and the precise role of CaD phosphorylation by CKII in mediating CaD's function have remained elusive. In this study, we demonstrate that Ser-26 is the major CKII phosphorylation site on CaD, while Ser-73 is of relatively minor importance. Moreover, the phosphorylation of Ser-26 and Ser-73 reduced CaD's ability to bind myosin by 45% and 27%, respectively, suggesting that the interaction of CaD with myosin is downregulated, at least in part, by the phosphorylation of these serine residues by CKII. Our results also demonstrate that there are at least four myosin-binding motifs within the amino-terminal region of CaD, located between residues 1-23, 34-43, 44-53, and 86-115, respectively. The myosin-binding motif between residues 44-53 contributes to strong myosin binding, while the three other myosin-binding motifs are responsible for weak myosin binding. The sequences between residues 24-33 and 54-85 on CaD are not required for the binding of CaD to myosin; thus, both Ser-26 and Ser-73 are located outside of the myosin-binding motifs. It is therefore likely that the downregulation of myosin-CaD interactions by CKII phosphorylation is due to phosphorylation-induced conformational changes in the adjacent myosin-binding motifs on CaD, rather than by the direct modification of these myosin-binding motifs by CKII.

Animals↗
PubMed2000

Nicotine is a potent blocker of the cardiac A-type K(+) channels. Effects on cloned Kv4.3 channels and native transient outward current.

BACKGROUND: Nicotine is a main constituent of cigarette smoke and smokeless tobacco, known to increase the risk of sudden cardiac death. This study aimed at establishing ionic mechanisms underlying potential electrophysiological effects of nicotine. METHODS AND RESULTS: Effects of nicotine on Kv4.3 and Kv4.2 channels expressed in Xenopus oocytes were studied at the whole-cell and single-channel levels. The effects of nicotine on the transient outward K(+) current (I:(to)) were studied by use of whole-cell patch-clamp techniques in canine ventricular myocytes. Nicotine potently inhibited Kv4 current. The concentration for half-maximal inhibition (IC(50)) was 40+/-4 nmol/L, and the current was abolished by 100 micromol/L nicotine. The IC(50) for block of native I:(to) was 270+/-43 nmol/L. The steady-state activation properties of Kv4.3 and I:(to) were unaltered by nicotine, whereas positive shifts of the inactivation curves were observed. Of the total inhibition of Kv4.3 and I:(to) by nicotine, 40% was due to tonic block and 60% was attributable to use-dependent block. Activation, inactivation, and reactivation kinetics were not significantly changed by nicotine. Nicotine reduced single-channel conductance, open probability, and open time but increased the closed time of Kv4.3. The effects of nicotine were not altered by antagonists to various neurotransmitter receptors, indicating direct effects on I:(to) channels. CONCLUSIONS: Nicotine is a potent inhibitor of cardiac A-type K(+) channels, with blockade probably due to block of closed and open channels. This action may contribute to the ability of nicotine to affect cardiac electrophysiology and induce arrhythmias.

Animals↗
PubMed2000

Evolutionarily conserved features of the arginine attenuator peptide provide the necessary requirements for its function in translational regulation.

Neurospora crassa arg-2 mRNA contains an evolutionarily conserved upstream open reading frame (uORF) encoding the Arg attenuator peptide (AAP) that confers negative translational regulation in response to Arg. We examined the regulatory role of the AAP and the RNA encoding it using an N. crassa cell-free translation system. AAPs encoded by uORFs in four fungal mRNAs each conferred negative regulation in response to Arg by causing ribosome stalling at the uORF termination codon. Deleting the AAP non-conserved N terminus did not impair regulation, but deletions extending into the conserved region eliminated it. Introducing many silent mutations into a functional AAP coding region did not eliminate regulation, but a single additional nucleotide change altering the conserved AAP sequence abolished regulation. Therefore, the conserved peptide sequence, but not the mRNA sequence, appeared responsible for regulation. AAP extension at its C terminus resulted in Arg-mediated ribosomal stalling during translational elongation within the extended region and during termination. Comparison of Arg-mediated stalling at a rare or common codon revealed more stalling at the rare codon. These data indicate that the highly evolutionarily conserved peptide core functions within the ribosome to cause stalling; translational events at a potential stall site can influence the extent of stalling there.

Amino Acid Sequence↗
PubMed2000

Exaggerated response to endotoxin in mice lacking the Duffy antigen/receptor for chemokines (DARC).

Duffy antigen/receptor for chemokines (DARC) is a promiscuous receptor for chemokines that is required for Plasmodium vivax infection of erythroid cells. This receptor is expressed by subsets of endothelial, as well as erythroid cells. Selection for protection from malaria infection resulted in an erythroid-specific defect, suggesting that DARC may play a critical role in endothelial biology. Mice with targeted disruption of this gene were generated, and the function of DARC in inflammation was explored. RNA from spleens of homozygous mutant mice lacked DARC transcripts, which were abundant in wild-type (+/+) and heterozygote (+/-) mice. DARC(-/-) mice lacked developmental abnormalities and were healthy at 1 year. Whereas hematologic parameters were within normal ranges, erythrocytes from nullizygous mice lacked CXC and CC chemokine-binding activity. Challenge with lipopolysaccharide resulted in significantly increased inflammatory infiltrates in lung and liver of nullizygous mice. These results suggest that DARC modulates the intensity of inflammatory reactions as a sink for chemokines. (Blood. 2000;96:1681-1684)

Animals↗
PubMed2000

TIMP-2 is required for efficient activation of proMMP-2 in vivo.

Matrix metalloproteinases (MMPs) are synthesized as latent proenzymes. A proteolytic cleavage event involving processing of the cysteine-rich N-terminal propeptide is required for their full activation. Previous in vitro studies indicated that activation of proMMP-2 can occur through formation of a trimolecular complex between MMP-14, TIMP-2, and proMMP-2 at the cell surface. Using TIMP-2-deficient mice and cells derived from them, TIMP-2 was shown to be required for efficient proMMP-2 activation both in vivo and in vitro. The requirement for TIMP-2 was not cell-autonomous as exogenously added TIMP-2 could restore activation of proMMP-2 to TIMP-2-deficient cells. Mutant mice were overtly normal, viable, and fertile on the C57BL/6 background, indicating that both TIMP-2 and activated proMMP-2 are dispensable for normal development.

Animals↗
PubMed2000

Adduct formation or metathesis reactions of silver complexes containing the fluorinated ligands [HB(3,5-(CF3)2Pz)3]- and [CF3SO3]-: formation of silver adducts containing unsupported silver-germanium bonds.

A mixture of [HB(3,5-(CF3)2Pz)3]Ag(eta 2-toluene) and [(Me)2ATI]GeCl in CH2Cl2, rather than undergoing metathesis, formed a 1:1 adduct [HB(3,5-(CF3)2Pz)3]Ag<--GeCl[(Me)2ATI] (1, where [HB(3,5-(CF3)2Pz)3] = hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate and [(Me)2ATI] = N-methyl-2-(methylamino)troponiminate) featuring a silver-germanium bond. Solutions of 1 (in CH2Cl2 or toluene) did not precipitate AgCl even after several days. However, it easily underwent metathesis with CF3SO3Ag, leading to the chloride-free product [HB(3,5-(CF3)2Pz)3]Ag<--Ge(OSO2CF3)[(Me)2ATI] (2). Compounds 1 and 2 were characterized by X-ray crystallography. The Ag-Ge bond distances of 1 and 2 are 2.4215(9) and 2.4116(10) A, respectively.

Journal Article↗
PubMed2000

The role of Mg2+ cofactor in the guanine nucleotide exchange and GTP hydrolysis reactions of Rho family GTP-binding proteins.

The biological activities of Rho family GTPases are controlled by their guanine nucleotide binding states in cells. Here we have investigated the role of Mg(2+) cofactor in the guanine nucleotide binding and hydrolysis processes of the Rho family members, Cdc42, Rac1, and RhoA. Differing from Ras and Rab proteins, which require Mg(2+) for GDP and GTP binding, the Rho GTPases bind the nucleotides in the presence or absence of Mg(2+) similarly, with dissociation constants in the submicromolar concentration. The presence of Mg(2+), however, resulted in a marked decrease in the intrinsic dissociation rates of the nucleotides. The catalytic activity of the guanine nucleotide exchange factors (GEFs) appeared to be negatively regulated by free Mg(2+), and GEF binding to Rho GTPase resulted in a 10-fold decrease in affinity for Mg(2+), suggesting that one role of GEF is to displace bound Mg(2+) from the Rho proteins. The GDP dissociation rates of the GTPases could be further stimulated by GEF upon removal of bound Mg(2+), indicating that the GEF-catalyzed nucleotide exchange involves a Mg(2+)-independent as well as a Mg(2+)-dependent mechanism. Although Mg(2+) is not absolutely required for GTP hydrolysis by the Rho GTPases, the divalent ion apparently participates in the GTPase reaction, since the intrinsic GTP hydrolysis rates were enhanced 4-10-fold upon binding to Mg(2+), and k(cat) values of the Rho GTPase-activating protein (RhoGAP)-catalyzed reactions were significantly increased when Mg(2+) was present. Furthermore, the p50RhoGAP specificity for Cdc42 was lost in the absence of Mg(2+) cofactor. These studies directly demonstrate a role of Mg(2+) in regulating the kinetics of nucleotide binding and hydrolysis and in the GEF- and GAP-catalyzed reactions of Rho family GTPases. The results suggest that GEF facilitates nucleotide exchange by destabilizing both bound nucleotide and Mg(2+), whereas RhoGAP utilizes the Mg(2+) cofactor to achieve high catalytic efficiency and specificity.

Dose-Response Relationship, Drug↗