Biomedical subjects

X Zhou

Publications and source records attributed to X Zhou.

At least 73 records · Page 4Linked to original sources

PubMed2003

T helper 2 immunity to hepatitis B surface antigen primed by gene-gun-mediated DNA vaccination can be shifted towards T helper 1 immunity by codelivery of CpG motif-containing oligodeoxynucleotides.

Gene-gun-mediated DNA immunization usually induces predominant T helper 2 (Th2) type immune response. As oligodeoxynucleotides (ODN)-containing unmethylated CpG motifs can activate the innate immune system in a Th1-biased way, the potential of codelivery of CpG motifs-containing ODN (CpG-ODN) with plasmid DNA to switch the gene-gun-mediated Th2 immune response was evaluated in this study. Here we show that codelivery of CpG-ODN with plasmid DNA at certain ratio (10/1) can enhance the Th1 humoral and cell-mediated immune responses in gene-gun-mediated DNA immunization in BALB/c mice, including increasing the hepatitis B surface antigen-specific total immunoglobulin G (IgG), IgG2a subclass, cytotoxic T-cell lymphocyte activity as well as interferon-gamma (IFN-gamma) secretion. Taken together, these results demonstrate that codelivery of CpG-ODN with recombinant plasmid DNA by gene gun can shift the gene-gun-mediated DNA immune response from Th2 towards Th1.

Adjuvants, Immunologic↗

PubMed2003

Self-setting kinetics of new type calcium phosphate bioactive bone cement: a thermokinetics study.

Thermokinetics method was used to study the self-setting kinetics of a new kind of calcium phosphate cement (CPC) in the present study. A calcium-deficient hydroxyapatite CPC was developed by using alpha-TCP and other calcium phosphate bioceramics. The mixing liquids used were deionized water and 0.25 M NaH2PO4/Na2HPO4, respectively. The calorimetric curves, heat evolution curves and total heat evolution in the setting and hardening process of CPC were determined. It has been found that mixing liquids, reaction temperature had influences on the calorimetric curves and heat evolution, and mixing liquids exhibited the greatest influence on the kinetics of CPC during the self-setting and hardening process. Based on the calorimetric curves obtained, the kinetic model equation was simulated, and the reaction control step was determined.

Bone Cements↗

PubMed2002

A host-specific bacteria-to-plant signal molecule (Nod factor) enhances germination and early growth of diverse crop plants.

Lipo-chitooligosaccharides (LCOs), or Nod factors, are host-specific bacteria-to-plant signal molecules essential for the establishment of a successful N(2)-fixing legume-rhizobia symbiosis. At submicromolar concentrations Nod factors induce physiological changes in host and non-host plants. Here we show that the Nod factor Nod Bj V(C18:1,MeFuc) of Bradyrhizobium japonicum 532C enhances germination of a variety of economically important plants belonging to diverse botanical families: Zea mays, Oryza sativa (Poaceae), Beta vulgaris (Chenopodaceae), Glycine max, Phaseolus vulgaris (Fabaceae), and Gossypium hirsutum (Malvaceae), under laboratory, greenhouse and field conditions. Similar increases in germination were observed for filtrates of genistein-induced cultures of B. japonicum 532C, while non-induced B. japonicum, induced Bj 168 (a nodC mutant of B. japonicum deficient in Nod factor synthesis) or the pentamer of chitin did not invoke such responses, demonstrating the role of Nod factor in the observed effects. In addition, three out of four synthetic LCOs evaluated also promoted germination of corn, soybean and Arabidopsis thaliana seeds. LCO also enhanced the early growth of corn seedlings under greenhouse conditions. These findings suggest the possible use of LCOs for improved crop production.

Bacteria↗

PubMed2002

Electrochemical characterization of polyacetylene ionomers and polyelectrolyte-mediated electrochemistry toward interfaces between dissimilarly doped conjugated polymers.

The electrochemical characterization of thin films of the ionically functionalized polyacetylene analogues poly(tetramethylammonium 2-cyclooctatetraenylethanesulfonate) (P(A)) and poly[(2-cyclooctatetraenylethyl)trimethylammonium trifluoromethanesulfonate] (P(C)) is reported along with an electrochemical approach to the fabrication of interfaces between dissimilarly doped conjugated polymers. Such interfaces are of interest because of the central role analogous interfaces based on silicon play in conventional microelectronics. The cationically functionalized P(C) can be both oxidatively (p-type) and reductively (n-type) doped to a conductive state, whereas the anionically functionalized P(A) can only be p-type doped. The voltammetry of P(C) displays relatively sharp waves with minimal history or relaxation effects. In contrast, the voltammetry of P(A) exhibits broader doping waves and a dependence on electrochemical history. The apparent formal potentials reported in 0.075 M Me4NBF4/CH3CN were -1.04 V versus SCE for the n-doping of P(C) and 0.40 and 0.30 V versus SCE for the p-doping of P(C) and P(A), respectively. These values depend on electrolyte concentration consistent with a Donnan potential due to the selective partitioning of ions between the electrolyte and polymer. Electrochemical quartz crystal microbalance data demonstrate that the p-type doping of P(A) and the n-type doping of P(C) proceed with the loss of ions from the polymer film and the formation of the internally compensated state. Voltammetry in tetrabutylammonium poly(styrenesulfonate)/CH3CN supporting electrolyte is also reported. It is demonstrated how a polyanion supporting electrolyte in concert with a conjugated ionomer can be used to control redox chemistry by governing the sign of ions available for charge compensation. In particular, we demonstrate the self-limiting oxidation of P(A) to inhibit deleterious overoxidation and prepare the precisely internally compensated state; the selective oxidation of P(A) over P(C), despite their similar apparent formal potentials; and the inhibition of the reoxidation of the n-doped form of P(C). The use of such polyelectrolyte-mediated electrochemistry in the fabrication of interfaces between dissimilarly doped conjugated polymers is discussed.

Journal Article↗

PubMed2002

Comparison of the structures of natural and re-established populations of Ascaris in humans in a rural community of Jiangxi, China.

To compare the structures of natural and re-established populations of Ascaris in humans, universal (mass) chemotherapy was carried out at the beginning and the end of the study year using pyrantel pamoate. Worms expelled within 48 h of treatment were collected, their sex determined, and measurements made of length, width and weight. Length was used as the criterion for estimating the developmental stage of the worms. In comparison with the natural population, the reestablished population displayed similar sex ratio as well as distribution patterns among individuals and age groups of the host. However, the mean worm burden of the re-established population was significantly decreased, with a reduction of burdens in children aged 5-9 years. Also, the re-established population showed significant changes in population structure and worm measurements in that it comprised more immature and less fertile males, less fertile and more senile females, smaller and lighter males, larger (but not heavier) females than the natural population. The results suggested that the reestablished Ascaris population did not restore to its original status in relation to mean density, composition and fecundity. Therefore, universal treatment once a year should decrease the transmission of Ascaris in humans. Combined with previous results for the same study sites, the present findings also indicated that caution is warranted to avoid misleading conclusions when using prevalence and faecal egg counts as parameters for evaluating the success of control programmes.

Adolescent↗

PubMed2002

Chlamydia pneumoniae IgA titres and coronary heart disease; prospective study and meta-analysis.

AIMS: To examine associations between Chlamydia pneumoniae IgA titres and incident coronary heart disease, and to compare them with associations previously reported between C. pneumoniae IgG titres and coronary heart disease. METHODS AND RESULTS: We measured serum concentrations of C. pneumoniae IgA antibodies in 502 coronary heart disease cases and in 1005 age- and town-matched controls 'nested' in a community-based prospective study of 5661 British men (mean follow-up in controls, 16 years), and conducted a meta-analysis of published prospective studies to place our findings in context. Two hundred and twenty-one (44%) of the cases were in the top third of C. pneumoniae IgA titres compared with 336 (33%) of the controls, yielding an odds ratio for coronary heart disease of 1.84 (95% confidence interval 1.40-2.43) which was largely unchanged after adjustment. In aggregate, the present study and nine previously reported prospective studies of C. pneumoniae IgA titres involved 2283 cases, yielding a combined odds ratio for coronary heart disease of 1.25 (1.03-1.53), with no significant heterogeneity among the ten studies (chi(2)9=7.8; P>0.1). This combined odds ratio is compatible with that previously reported for C. pneumoniae IgG titres and coronary heart disease (1.15, 0.97-1.36). CONCLUSION: Neither C. pneumoniae IgA titres nor IgG titres are strongly predictive of coronary heart disease in the general population.

Adult↗

PubMed2001

Clinical applications of plasma shock wave lithotripsy in treating postoperative remnant stones impacted in the extra- and intrahepatic bile ducts.

BACKGROUND: Choledochofiberscopy with basket extraction has been used widely to treat postoperative remnant stones in the bile duct system. However, it remains difficult to extract stones impacted in the bile duct system or stones too large to pass through the T-tube fistula. This report describes the efficacy and safety of plasma shock wave lithotripsy (PSWL) in fragmenting and eliminating such remnant stones from the bile duct. METHODS: In 52 patients, 117 remnant stones were fragmented with PSWL and subsequently extracted with choledochofiberscopy. The efficacy and safety of PSWL were observed during and after the procedure. RESULTS: After 116 of 117 remnant stones (99.1%) impacted in the extra- and intrahepatic bile ducts were fragmented successfulIy with PSWL, they were extracted with choledochofiberscopy. There were no significant complications during and after the procedure. CONCLUSION: It appears that PSWL is an effective and safe method for fragmenting remnant stones impacted in the bile duct system and stones too large to pass through the T-tube fistula.

Adult↗

PubMed2001

Ephrins stimulate neurite outgrowth during early cortical neurogenesis.

The Eph receptor ligands, the ephrins, are membrane-bound molecules that play important roles in establishing intercellular communication after neurogenesis by regulating cell migration, axon pathfinding, and topographic mapping. In diverse systems, such as embryonic day 17.5 (E17.5) hippocampal and cortical neurons, repulsive/inhibitory mechanisms underlie these cellular effects. However, although ligand/receptor expression occurs far earlier, during brain neurogenesis, little is known about potential ephrin functions in initial process outgrowth. We have examined ligand/receptor expression in E13.5 cortex in vivo and in culture, using alkaline phosphatase (AP)-conjugated reagents and RNase protection assay. B ephrins are highly expressed, including B1, B2, and B3, whereas A ephrins exhibit low expression levels. In contrast, the Eph receptors demonstrate an opposite pattern, exhibiting high levels of Eph A3, A4, and A5 mRNA transcripts and low levels of the B-class receptors. To examine effects on neurite outgrowth, soluble ephrins were incubated with antihuman IgG antibody, producing oligomeric agonist complexes, and dried onto culture dishes. Unexpectedly, both ephrin A and B complexes increased process outgrowth: Seventy to eighty percent of neuronal precursors exhibited long neurites on ephrins, whereas only 5-10% of cells had neurites on IgG control substrates, indicating that ephrins stimulated neuritogenesis by early cortical neurons. These observations suggest that ephrin ligand/receptor systems play ontogenetic roles not previously considered, activating mechanisms other than cellular repulsion. Ephrin systems may induce initial process elaboration by early cortical neurons that is restricted at later stages by well-characterized repulsive signaling mechanisms.

Animals↗

PubMed2001

Systemic sclerosis (scleroderma): specific autoantigen genes are selectively overexpressed in scleroderma fibroblasts.

The pathogenesis of systemic sclerosis (SSc) involves complex interactions between activated fibroblasts eventually leading to fibrosis, and impaired immune tolerance characterized by a variety of circulating SSc-specific autoantibodies. The expression of autoantigens in fibroblasts, a key target tissue in SSc, may play an important role in this process. To obtain a global view of this process, we examined gene expression profiles of SSc dermal fibroblasts using cDNA microarrays. The results show that dermal fibroblasts from SSc patients obtained from either affected or unaffected skin displayed a characteristic pattern of increased SSc autoantigen gene expression compared with that from normal controls. In particular, fibrillarin (p = 0.028), centromeric protein B (p = 0.01), centromeric autoantigen P27 (p = 0.042), and RNA polymerase II (220 kDa; p = 0.02) were significantly overexpressed in SSc fibroblasts. Quantitative RT-PCR confirmed overexpression of these autoantigens and also revealed increased levels of DNA topoisomerase I transcripts in SSc fibroblasts compared with normal control fibroblasts (p = 0.0318). The polymyositis/scleroderma autoantigen gene was overexpressed in some SSc patients (p = 0.09). To examine the specificity of these overexpressed autoantigen genes for SSc and its tissue specificity for fibroblasts, cDNA microarrays of dermal fibroblasts from patients with eosinophilic fasciitis and scleromyxedema were studied as well as PBMC and muscle biopsies from SSc patients. None of these tissues showed significant alterations in gene expression of SSc-specific autoantigens. Therefore, SSc-associated autoantigen genes are selectively overexpressed in SSc dermal fibroblasts, a major tissue involved in disease pathogenesis.

Autoantigens↗

PubMed2001

[Genetic polymorphism analysis of apolipoprotein CII microsatellite DNA (TG) n (AG) m in patients with coronary heart disease].

OBJECTIVE: To investigate the relationship between the polymorphism of apolipoprotein CII (apoCII) microsatellite DNA (TG) n (AG) m and coronary heart disease (CHD). METHODS: The apoCII microsatellite DNA (TG) n(AG)m genotypes of 108 patients with CHD and 231 healthy persons were detected by using polymerase chain reaction (PCR) and high voltage denatured polyacrylamid gels electrophoresis. RESULTS: The allele frequency distribution was significantly different between controls and patients with CHD (chi 2 = 19.93, P < 0.05). The allele 17 frequency in CHD group was remarkably higher than that in controls (chi 2 = 13.98, P < 0.01). The concentrations of TG and HDL-C among different genotype groups were significantly different. The levels of TG in 17/29 group and 17/30 group were higher than those in other groups (P < 0.05), while the concentration of HDL-C was lower (P < 0.05). CONCLUSION: The allele 17 of apoCII may be an independent risk factor for CHD in Han population.

Adult↗

PubMed2001

A flexible light-directed DNA chip synthesis gated by deprotection using solution photogenerated acids.

Oligonucleotide microarrays or oDNA chips are effective decoding and analytical tools for genomic sequences and are useful for a broad range of applications. Therefore, it is desirable to have synthesis methods of DNA chips that are highly flexible in sequence design and provide high quality and general adoptability. We report herein, DNA microarray synthesis based on a flexible biochip method. Our method simply uses photogenerated acid (PGA) in solution to trigger deprotection of the 5'-OH group in conventional nucleotide phosphoramidite monomers (i.e. PGA-gated deprotection), with the rest of the reactions in the synthesis cycle the same as those used for routine synthesis of oligonucleotides. The complete DNA chip synthesis process is accomplished on a regular DNA synthesizer that is coupled with a UV-VIS projection display unit for performing digital photolithography. Using this method, oDNA chips containing probes of newly discovered genes can be quickly and easily synthesized at high yields in a conventional laboratory setting. Furthermore, the PGA-gated chemistry should be applicable to microarray syntheses of a variety of combinatorial molecules, such as peptides and organic molecules.

DNA↗

PubMed2001

Functional cloning of Src-like adapter protein-2 (SLAP-2), a novel inhibitor of antigen receptor signaling.

In an effort to identify novel therapeutic targets for autoimmunity and transplant rejection, we developed and performed a large-scale retroviral-based functional screen to select for proteins that inhibit antigen receptor-mediated activation of lymphocytes. In addition to known regulators of antigen receptor signaling, we identified a novel adaptor protein, SLAP-2 which shares 36% sequence similarity with the known Src-like adaptor protein, SLAP. Similar to SLAP, SLAP-2 is predominantly expressed in hematopoietic cells. Overexpression of SLAP-2 in B and T cell lines specifically impaired antigen receptor-mediated signaling events, including CD69 surface marker upregulation, nuclear factor of activated T cells (NFAT) promoter activation and calcium influx. Signaling induced by phorbol myristate acetate (PMA) and ionomycin was not significantly reduced, suggesting SLAP-2 functions proximally in the antigen receptor signaling cascade. The SLAP-2 protein contains an NH2-terminal myristoylation consensus sequence and SH3 and SH2 Src homology domains, but lacks a tyrosine kinase domain. In antigen receptor-stimulated cells, SLAP-2 associated with several tyrosine phosphorylated proteins, including the ubiquitin ligase Cbl. Deletion of the COOH terminus of SLAP-2 blocked function and abrogated its association with Cbl. Mutation of the putative myristoylation site of SLAP-2 compromised its inhibitory activity and impaired its localization to the membrane compartment. Our identification of the negative regulator SLAP-2 demonstrates that a retroviral-based screening strategy may be an efficient way to identify and characterize the function of key components of many signal transduction systems.

Adaptor Proteins, Signal Transducing↗

PubMed2001

The microtubule cytoskeleton participates in control of beta2 integrin avidity.

Leukocyte avidity is regulated by cytoskeletal constraints, which keep beta(2) integrins in an inactive mode. Releasing these constraints results in increased lateral mobility and clustering of integrins, effectively activating adhesion. At least part of the constraint on beta(2) integrins is due to actin; whether other cytoskeletal components are involved has not previously been investigated. Microtubules are a candidate for control of integrin rearrangement, because they modulate focal adhesions, which are sites of interaction between integrins and the cytoskeleton. Here we report that both depolymerization of microtubules by colchicine or nocodazole and stabilization of microtubules by taxol increased the lateral mobility of beta(2) integrins, activating adhesion. Increased integrin mobility was accompanied by an increase in tyrosine phosphorylation of paxillin, a biochemical event associated with activation of beta(2) integrins. Further, C3 exoenzyme, an inhibitor of Rho, blocked induction of integrin mobility by nocodazole, but not by taxol, suggesting that there are multiple microtubule-dependent pathways to integrin rearrangement, only some of which require Rho activity. Taken together, our data suggest that a dynamic microtubule system is required to regulate integrin-cytoskeleton interactions. Furthermore, these data demonstrate that microtubules participate in control of integrin rearrangement, one of the earliest steps in activation of integrin-mediated adhesion.

Animals↗

PubMed2001

Secondary-structure-favored hydrophobic-polar lattice model of protein folding.

Protein folding is studied using a two-dimensional lattice model with the Hamiltonian including both hydrophobic interactions and main chain hydrogen bond interactions of amino acids. Since compact conformations have different designabilities and only highly designable conformations can act as native structural candidates [H. Li, R. Helling, C. Tang, and N. Wingreen, Science 273, 666 (1996)], it is shown that hydrophobic interaction alone is insufficient to explain the appearance of a high proportion of regular secondary structures, especially beta sheets whose content decreases with increasing designability, but interactions of main chain hydrogen bonds can account for this. Thus the emergence of only a small number of structure types (folds) among all possible structures can be understood to some extent.

Hydrogen Bonding↗

PubMed2001

Cloning and characterization of a histone deacetylase, HDAC9.

Histone deacetylase (HDAC) catalyzes the removal of the acetyl group from the lysine residues in the N-terminal tails of nucleosomal core histones. Eight human HDACs have been identified so far. Here, we report the identification of a ninth member of the HDAC family, designated HDAC9. HDAC9 is a class II HDAC and its gene resides on human chromosome 7. HDAC9 has several alternatively spliced isoforms. One of these isoforms is histone deacetylase-related protein or myocyte enhancer-binding factor 2-interacting transcriptional repressor that we and others have previously reported and which does not possess an HDAC catalytic domain. The longest of the HDAC9 isoforms contains 1,011 aa. The isoform, designated HDAC9a, is 132 aa shorter at the C terminus than HDAC9. Also, we have identified isoforms of HDAC9 that lack the nuclear localization signal. Similar to histone deacetylase-related protein, HDAC9 transcripts are expressed at high levels in brain and skeletal muscle. The ratio of HDAC9 and HDAC9a transcripts differs among the tissues examined. HDAC9 and HDAC9a contain the HDAC catalytic domain, and Flag-tagged HDAC9 and HDAC9a possess deacetylase activity. HDAC9 and HDAC9a also repress myocyte enhancer-binding factor 2-mediated transcription. In the present study, we have identified HDAC9 and a number of alternatively spliced isoforms of HDAC9 with potentially different biological activities.

Alternative Splicing↗

PubMed2001

Application of a LRT model to acid rain control in China.

For further control of acid rain and SO2 pollution in China, acid rain control zones and sulfur dioxide pollution control zones were designated where acid rain or serious SO2 pollution occurs or may occur. In this study, sulfur deposition in east China was computed through a policy-oriented, two-dimensional Eulerian model for long-range transport and deposition of SO2 and SO4(2-). The model predictions were in accordance with the wet deposition monitored. Results show that concentrations of SO2 and SO4(2-) are higher in north China than those in the south, and high deposition of sulfur occurs in most areas of North China, in the lower reaches of the Changjiang (Yangtze) River and around Chongqing and Guiyang in southwest China. Total emission of SO2 from the modeling region (from 19 degrees N to 42 degrees N, and from 104 degrees E to 124 degrees E) was about 20 million tons in 1995. The model predicts that 48% of this deposits within the region as dry deposition, 38% deposits as wet deposition, and only about 14% was transported out of the region. The modeling results of sulfur deposition were directly applied in designating acid rain control zones in China, and the emission-deposition relationship derived was also used to formulate middle- and long-range planning programs for regional acid rain control in China.

Acid Rain↗

PubMed2001

A malignant phenotype of hypertrophic cardiomyopathy caused by Arg719Gln cardiac beta-myosin heavy-chain mutation in a Chinese family.

Mutations of the cardiac beta-myosin heavy-chain (beta-MHC) gene cause hypertrophic cardiomyopathy (HCM). Recent genotype-phenotype correlation studies have shown that mutations carry prognostic significance. We studied five unrelated Chinese families with hypertrophic cardiomyopathy. Exons 3-27 and 40 of the beta-MHC gene were screened with both the polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) method and the cycle sequencing of the PCR products. A previously reported heterozygous mutation Arg719Gln (arginine-->glutamine in codon 719) in exon 19 was found in one family. The proband is a 30-year-old female diagnosed at age of 25 years when she presented with symptoms of chest pain, palpitations, and frequent incidents of dizziness and syncope. A two-dimensional echocardiogram showed moderate asymmetrical septal hypertrophy with left atrial enlargement. There was no obstruction of the left ventricular outflow tract (LVOT). The patient also developed atrial fibrillation. The proband's mother and one of her sisters had similar clinical manifestations and both died suddenly at the age of 38 years. In addition, two silent nucleotide substitutions (ACT63ACC, TTT244TTC) in the cardiac beta-MHC gene were identified in the other four families. These synonymous mutations did not cosegregate with the disease in the families and they were also present in the 60 healthy and age-matched control subjects. Of the five families studied, we did not find any missense mutation in the remaining four families. The missense mutation Arg719Gln found in the Chinese family is associated with a malignant phenotype of severe clinical symptoms and poor survival prognosis. This mutation also causes atrial enlargement and atrial fibrillation. Our study provides further evidence that the mutation, which alters the charge of the myosin heavy chain, is associated with a serious clinical outcome.

Adult↗

PubMed2001

Vital bleaching with whitening strips: summary of clinical research on effectiveness and tolerability.

Rapid innovation in vital bleaching has increased the popularity of tooth whitening among dental professionals and patients. A broad range of peroxide-based treatments are currently available including those that are professionally-administered (in-office), professionally-dispensed (custom-tray-based systems), and self-directed (over-the-counter). Recently, a novel, flexible polyethylene bleaching strip was introduced that delivers a hydrogen peroxide bleaching gel to the anterior dentition. This "trayless" system, available in professional-strength and over-the-counter versions, reportedly offers advantages with respect to overall peroxide dose, contact time, and ease-of-use compared to other delivery systems. This paper reviews the relevant published clinical research on whitening strips tested among a broad range of patients commonly encountered in contemporary dental practices.

Age Factors↗