Search PubMed⌕ Search

Biomedical subjects

L Zheng

Publications and source records attributed to L Zheng.

At least 19 recordsLinked to original sources
PubMed2003

Characterization of three Toll-like genes from mosquito Aedes aegypti.

Three Toll-related genes (AeToll1A, AeToll1B and AeToll5) were cloned and characterized from the yellow fever vector mosquito, Aedes aegypti. All three genes exhibited high levels of amino acid sequence similarity with Drosophila melanogaster (Dm)Toll1 and DmTehao (Toll5). AeToll1A and AeToll1B are 1124 and 1076 amino acid residues long, respectively. Both contain a carboxyl extension downstream of the Toll/interleukin-1 receptor (TIR) domain. AeToll5 is 1007 residues long and, like DmTehao, lacks the carboxyl terminal extension. Expression of these three genes was examined throughout development and after immune challenge. Both AeToll1A and AeToll5, like their Drosophila counterparts, activate transcription of drosomycin promoter in both Aedes and Drosophila cell lines. Deletion of the carboxyl extension of AeToll1A did not result in a further elevated level of the antifungal response. The intracellular signalling process appears to be species specific based on two observations. (1) DmToll is completely inactive in an Aedes cell line, suggesting a higher specificity requirement for DmToll in the intracellular signalling process. (2) Only one of three amino acid residues essential for DmToll function is required for AeToll1A function.

Aedes↗
PubMed2003

Comparative analysis of microsatellite loci in four fruit fly species of the genus Ceratitis (Diptera: Tephritidae).

The possibility to cross-species amplify microsatellites in fruit flies of the genus Ceratitis was tested with the polymerase chain reaction (PCR) by analysing 23 Ceratitis capitata (Wiedemann) microsatellite markers on the genomic DNA of three other economically important, congeneric species: C. rosa (Karsch), C. fasciventris (Bezzi) and C. cosyra (Walker). Twenty-two primer pairs produced amplification products in at least one of the three species tested. The majority of the products were similar, if not identical in size to those expected in C. capitata. The structures of the repeat motifs and their flanking sequences were examined for a total of 79 alleles from the three species. Sequence analysis revealed the same repeat type as the homologous C. capitata microsatellites in the majority of the loci, suggesting their utility for population analysis across the species range. A total of seven loci were differentially present/absent in C. capitata, C. rosa, C. fasciventris and C. cosyra, suggesting that it may be possible to differentiate these four species using a simple sequence repeat-based PCR assay. It is proposed that medfly-based microsatellite markers could be utilized in the identification and tracing of the geographical origins of colonist pest populations of the four tested species and in the assessment of their risk and invasive potentials; thereby assisting regulatory authorities in implementing quarantine restrictions and other pest control measures.

Alleles↗
PubMed2002

Increased soluble CD14 in bronchoalveolar lavage fluid of stable lung transplant recipients.

Macrophages, neutrophils and infection have been implicated in the genesis of the bronchiolitis obliterans syndrome (BOS) post lung transplantation. sCD14 is a soluble form of a shed-cell surface protein. It is capable of promoting cytokine-induced inflammation and it's presence in clinically stable lung transplant recipients (LTR) might be important as an early marker of BOS. Bronchalveolar lavage (BAL) and blood samples were taken from 26 stable LTR, at or near their best forced expiratory volume in one second who were free from infection. sCD14 levels were measured via enzyme-linked immunosorbent assay. Cell counts were performed on unfiltered BAL. LTR neutrophil count, BAL sCD14 and serum sCD14 levels were higher than controls (median 3.8% versus 1.3%, p<0.05; 11.5 ng x mL(-1) versus 6 ng x mL(-1), p<0.001; 6.2 microg x mL(-1) versus 2.4 microg x mL(-1), p<0.05, respectively). BAL albumin and sCD14 correlated (regression coefficient: 0.77, p<0.001). In this hypothesis-generating, cross-sectional study, the authors have described for the first time soluble CD14 levels in the bronchoalveolar lavage and serum of stable lung transplant recipients, and show that these are elevated compared to controls. This is a practicable candidate marker system, which can be tested for a predictive role in bronchiolitis obliterans syndrome following lung transplantation. The origin of this cellular protein and its temporal relationship to the development of the bronchiolitis obliterans syndrome remains to be elucidated in more definitive longitudinal studies, which should include other measurements potentially relevant to the innate immune system, such as bronchoalveolar lavage endotoxin levels.

Adult↗
PubMed2002

Overexpression of matrix metalloproteinase-8 and -9 in bronchiectatic airways in vivo.

The progressive bronchial dilatation in bronchiectasis is likely to be the result of continued airway matrix destruction, although little is known about the role of neutrophil matrix metalloproteinases (MMPs) in this process. Immunohistochemistry has been used to investigate the expression and cellular localisation of MMP-8 and MMP-9 in bronchiectatic airways in vivo. Endobronchial biopsies were taken from 25 bronchiectatic patients, and from the right lower lobe in 14 control subjects. MMP-8, MMP-9, neutrophils and macrophages were stained with monoclonal antibodies and quantified as positive cell x mm(-2) of the lamina propria by using an image analysis system. There were significantly higher densities of MMP-8 and MMP-9 positive cells in the lamina propria of bronchiectatic than control airways. In bronchiectatic airways, the densities of MMP-8 and MMP-9 positive cells correlated with each other and with neutrophil density, but not with macrophage density. In control airways, a significant correlation was found between MMP-8 with neutrophil and MMP-9 with macrophage densities. An overexpression of neutrophil matrix metalloproteinases in bronchiectatic airways could help explain the continuation of airway destruction in bronchiectasis. In view of the clinical availability of matrix metalloproteinase antagonists, the results presented here could have a significant impact on the development of novel therapies of this untreatable disease.

Aged↗
PubMed2001

A soluble dominant negative fibroblast growth factor receptor 4 isoform in human MCF-7 breast cancer cells.

Fibroblast growth factor receptors (FGFRs) are receptor tyrosine kinases encoded by four closely related genes. FGFR 1, 2, and 3 have a number of isoforms derived by alternative splicing, alternative initiation and exon switching; however, FGFR4 has been reported to encode a single intact receptor with three extracellular immunoglobulin (Ig)-like domains, a transmembrane domain, and a split intracellular kinase. Here we describe a novel C-terminally truncated soluble isoform of FGFR4 expressed by human epithelial breast cancer MCF-7 cells. This isoform results from failure of splicing of intron 4 resulting in an mRNA species that encodes an in-frame premature stop codon. Cells transfected with the corresponding cDNA containing intron 4 express a truncated releasable protein that is identified in conditioned media. This soluble FGFR4 isoform (sFGFR4) abrogates the effect of FGF-1-induced MAPK phosphorylation and PRL gene activation. These findings represent the first description of an endogenous soluble C-terminally truncated FGFR4 isoform with FGF modulatory properties.

3T3 Cells↗
PubMed2001

When genetic distance matters: measuring genetic differentiation at microsatellite loci in whole-genome scans of recent and incipient mosquito species.

Genetic distance measurements are an important tool to differentiate field populations of disease vectors such as the mosquito vectors of malaria. Here, we have measured the genetic differentiation between Anopheles arabiensis and Anopheles gambiae, as well as between proposed emerging species of the latter taxon, in whole genome scans by using 23-25 microsatellite loci. In doing so, we have reviewed and evaluated the advantages and disadvantages of standard parameters of genetic distance, F(ST), R(ST), (delta mu)(2), and D. Further, we have introduced new parameters, D' and D(K), which have well defined statistical significance tests and complement the standard parameters to advantage. D' is a modification of D, whereas D(K) is a measure of covariance based on Pearson's correlation coefficient. We find that A. gambiae and A. arabiensis are closely related at most autosomal loci but appear to be distantly related on the basis of X-linked chromosomal loci within the chromosomal Xag inversion. The M and S molecular forms of A. gambiae are practically indistinguishable but differ significantly at two microsatellite loci from the proximal region of the X, outside the Xag inversion. At one of these loci, both M and S molecular forms differ significantly from A. arabiensis, but remarkably, at the other locus, A. arabiensis is indistinguishable from the M molecular form of A. gambiae. These data support the recent proposal of genetically differentiated M and S molecular forms of A. gambiae.

Animals↗
PubMed2001

Astrocytes, not microglia, are the main cells responsible for viral persistence in Theiler's murine encephalomyelitis virus infection leading to demyelination.

The BeAn strain of Theiler's murine encephalomyelitis virus (TMEV) persists in the CNS and produces a chronic inflammatory demyelinating disease that is an animal model for human multiple sclerosis (MS). The mechanisms leading to TMEV-induced demyelination are still under study but most likely involve both immune-mediated and virus induced damage to cells in the CNS, both depending on viral persistence. It is therefore important to identify the cells in which continued virus production is permitted. In this study, we looked at virus infection in primary astrocytes, microglia and oligodendrocytes, derived from brains of neonatal susceptible SJL/J mice. As evidenced by Western blots and immunocytochemistry, we were able to detect viral antigens in all these brain-derived cells. In addition, we extended the study to spinal cord tissues from mice suffering TMEV-induced disease. Immunohistochemistry staining with anti-TMEV sera and antibodies to specific cell markers detected viral antigens in all these cells. We then asked the question whether viral antigen present in these cells, particularly in microglia/macrophages, represented true viral replication or not. By using different techniques, including immunoprecipitation experiments and the very sensitive method of negative RNA detection through RNase protection assay, we show that both astrocytes and oligodendroglia permit de novo viral replication and viral protein synthesis but with only minimal cytopathic effects. Of these two cell types, astrocytes carry the brunt of viral replication. In microglia, on the other hand, viral replication is restricted since only minimal amounts of negative RNA copies can be demonstrated, while there are clear signs that some of these cells undergo apoptosis. These findings show that the main cell for viral replication is the astrocyte, rather than the microglia/macrophage. Most of the viral antigen present in macrophages, therefore, is probably the result of phagocytosis, rather than actual viral replication. In view of the demonstrated presence of viral replication in astrocytes and of great amounts of viral antigens in microglia/macrophages, it is possible that both types of cells act as antigen presenting cells during this immunopathological disease.

Animals↗
PubMed2001

Solid-phase analysis method for (S)-[18F]fluorocarazolol and its metabolites.

(S)-[18F]Fluorocarazolol is a radiopharmaceutical developed to quantitatively assess beta-adrenergic receptors in vivo via positron emission tomography imaging. Since radioactive metabolites of (S)-[18F]fluorocarazolol rapidly appear in the plasma, methods for conveniently and reliably evaluating plasma for (S)-[18F]fluorocarazolol content are required. Here we present methods and validation of an approach using commercial extraction cartridges that is faster and more convenient than an approach using internal-surface reverse-phase chromatography but yields comparable results.

Adrenergic beta-Antagonists↗
PubMed2001

BRCA1 mediates ligand-independent transcriptional repression of the estrogen receptor.

Mutational inactivation of BRCA1 confers a cumulative lifetime risk of breast and ovarian cancers. However, the underlying basis for the tissue-restricted tumor-suppressive properties of BRCA1 remains poorly defined. Here we show that BRCA1 mediates ligand-independent transcriptional repression of the estrogen receptor alpha (ERalpha), a principal determinant of the growth, differentiation, and normal functional status of breasts and ovaries. In Brca1-null mouse embryo fibroblasts and BRCA1-deficient human ovarian cancer cells, ERalpha exhibited ligand-independent transcriptional activity that was not observed in Brca1-proficient cells. Ectopic expression in Brca1-deficient cells of wild-type BRCA1, but not clinically validated BRCA1 missense mutants, restored ligand-independent repression of ERalpha in a manner dependent upon apparent histone deacetylase activity. In estrogen-dependent human breast cancer cells, chromatin immunoprecipitation analysis revealed the association of BRCA1 with ERalpha at endogenous estrogen-response elements before, but not after estrogen stimulation. Collectively, these results reveal BRCA1 to be a ligand-reversible barrier to transcriptional activation by unliganded promoter-bound ERalpha and suggest a possible mechanism by which functional inactivation of BRCA1 could promote tumorigenesis through inappropriate hormonal regulation of mammary and ovarian epithelial cell proliferation.

Adenocarcinoma↗
PubMed2001

Stimulation of eukaryotic flap endonuclease-1 activities by proliferating cell nuclear antigen (PCNA) is independent of its in vitro interaction via a consensus PCNA binding region.

Interaction between human flap endonuclease-1 (hFEN-1) and proliferating cell nuclear antigen (PCNA) represents a good model for interactions between multiple functional proteins involved in DNA metabolic pathways. A region of 9 conserved amino acid residues (residues Gln-337 through Lys-345) in the C terminus of human FEN-1 (hFEN-1) was shown to be responsible for the interaction with PCNA. Our current study indicates that 4 amino acid residues in hFEN-1 (Leu-340, Asp-341, Phe-343, and Phe-344) are critical for human PCNA (hPCNA) interaction. A conserved PCNA interaction motif in various proteins from assorted species has been defined as Q(1)X(2)X(3)(L/I)(4)X(5)X(6)F(7)(F/Y)(8), although our results fail to implicate Q(1) (Gln-337 in hFEN-1) as a crucial residue. Surprisingly, all hFEN-1 mutants, including L340A, D341A, F343A, and F344A, retained hPCNA-mediated stimulation of both exo- and flap endonuclease activities. Furthermore, our in vitro assay showed that hPCNA failed to bind to the scRad27 (yeast homolog of FEN-1) nuclease. However, its nuclease activities were significantly enhanced in the presence of hPCNA. Four additional Saccharomyces cerevisiae scRad27 mutants, including multiple alanine mutants and a deletion mutant of the entire PCNA binding region, were constructed to confirm this result. All of these mutants retained PCNA-driven nuclease activity stimulation. We therefore conclude that stimulation of eukaryotic hFEN-1 nuclease activities by PCNA is independent of its in vitro interaction via the PCNA binding region.

Amino Acid Motifs↗
PubMed2001

Cloning, expression patterns, and chromosome localization of three human and two mouse homologues of GABA(A) receptor-associated protein.

Type A receptors of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter, contain alpha, beta, delta, gamma, and rho subunits. The gamma subunit has four subtypes: gamma1, gamma2, gamma3, andgamma4. GABA(A) receptor-associated protein (GABARAP) was previously demonstrated to act as a linker protein between microtubules and the gamma2 subunit of GABA(A) receptors. However, no other linker proteins have been identified as mediating the linkage of microtubules and the remaining subunits of GABA(A) receptors. In this study we identified three human paralogues (GABARAPL1, GABARAPL2, and GABARAPL3) and two mouse orthologues (Gabarapl1 and Gabarapl2) of human GABARAP, all of which encoded 117 amino acids, as does Gabarapl. The expression patterns of GABARAPL1, GABARAPL2, and GABARAP in 16 adult tissues showed that they were expressed ubiquitously. The expression levels of GABARAPL1 as a 2.3-kb transcript were very high in brain, heart, peripheral blood leukocytes, liver, kidney, placenta, and skeletal muscle, very low in thymus and small intestine, and moderate in other tissues tested. The unique 1.35-kb transcript of GABARAPL2 was expressed at high levels in heart, brain, testis, prostate, ovary, spleen, and skeletal muscle, at very low levels in lung, thymus, and small intestine, and moderately in other tissues tested. For GABARAP, a 1.3-kb transcript was abundantly expressed in all tested tissues with small variation. The expression patterns of Gabarapl1 and Gabarapl2 were similar to those of their counterparts in human. In addition, GABARAPL1 was localized to human chromosome 12p12.3 and GABARAPL2 to 16q22.3-q24.1 by RH mapping, while GABARAP and GABARAPL3 were found to be localized at chromosomes 17p13.2 and 15q25.1, respectively, by searching the related databases. Sequence comparison of the cDNAs and their corresponding genomic sequences shows that GABARAP, GABARAPL1, and GABARAPL2 are composed of four exons each, while GABARAPL3 is distributed only at one exon.

Adaptor Proteins, Signal Transducing↗
PubMed2001

The death effector domain-associated factor plays distinct regulatory roles in the nucleus and cytoplasm.

Homophilic interactions of death effector domains (DEDs) are crucial for the signaling pathways of death receptor-mediated apoptosis. The machinery that regulates proper oligomerization and autoactivation of procaspase-8 and/or procaspase-10 during T lymphocyte activation determines whether the cells will undergo caspase-mediated apoptosis or proliferation. We screened a yeast two-hybrid library by using the DEDs contained in the prodomains of procaspase-8 and procaspase-10 and isolated a DED-associated factor (DEDAF) that interacts with several DED-containing proteins but does not itself contain a DED. DEDAF is highly conserved between human and mouse (98% amino acid identity) and is homologous to a nuclear regulatory protein YAF-2. DEDAF is expressed at the highest levels in lymphoid tissues and placenta. DEDAF interacts with FADD, procaspase-8, and procaspase-10 in the cytosol as well as with the DED-containing DNA-binding protein (DEDD) in the nucleus. At the cell membrane, DEDAF augmented the formation of CD95-FADD-caspase-8 complexes and enhanced death receptor- as well as DED-mediated apoptosis. In the nucleus, DEDAF caused the DEDD protein to relocalize from subnuclear structures to a diffuse distribution in the nucleoplasm. Our data therefore suggest that DEDAF may be involved in the regulation of both cytoplasmic and nuclear events of apoptosis.

Amino Acid Sequence↗
PubMed2001

The retinoblastoma gene: a prototypic and multifunctional tumor suppressor.

Genome instability has been implicated in the generation of multiple somatic mutations that underlie cancer. Germline mutation in the retinoblastoma (RB) gene leads to tumor formation in both human and experimental animal models, and reintroduction of wild-type RB is able to suppress neoplastic phenotypes. Rb governs the passage of cells through the G1 phase-restriction point and this control is lost in most cancer cells. Rb has also been shown to promote terminal differentiation and prevent cell cycle reentry. Recent studies implicate Rb in mitotic progression, faithful chromosome segregation, checkpoint control, and chromatin remodeling, suggesting that Rb may function in the maintenance of genome integrity. It is likely that Rb suppresses tumor formation by virtue of its multiple biological activities. A single protein capable of performing multiple antioncogenic functions may be a common characteristic of other tumor suppressors including p53 and BRCA1/2.

Animals↗
PubMed2001

MR imaging-guided radiofrequency thermal ablation in the porcine brain at 0.2 T.

The aim of this study was to test the hypotheses that (a) MR imaging-guided radiofrequency (RF) thermal ablation is safe and feasible in porcine brain using an open C-arm-shaped low-field MR system, and that (b) induced thermal lesion size can be predicted using low-field MR imaging. Magnetic resonance-guided RF ablation was performed in the cerebral frontal lobes of six pigs. An 18-G monopolar RF electrode was inserted into the porcine brain using MR image guidance and RF was then applied for 10 min. After post-procedure imaging (T2-weighted, T1-weighted before and after gadodiamide administration), the pigs were killed and the brains were used for pathologic examination. Successful RF electrode placement was accomplished in all cases without complications; total magnet time ranged from 73 to 189 min. The thermal lesion size varied from 10 to 12 mm perpendicular to the electrode track and was easily visualized on T2-weighted and enhanced T1-weighted images. Enhanced T1-weighted imaging demonstrated the highest brain-to-RF thermal lesion contrast-to-noise ratio with an average of 1.5 +/- 1.6. Enhanced T1-weighted imaging never underestimated pathologic lesion diameter with a mean difference of 2.3 +/- 1.0 mm and a radiologic/pathologic correlation of 0.69. Magnetic resonance imaging-guided RF thermal ablation is feasible and safe in the porcine brain using an open MR low-field system. Induced-thermal lesion size can best be monitored using enhanced T1-weighted images. In the future, RF ablation under low-field MR guidance may offer an alternative treatment option for primary and secondary brain tumors.

Animals↗
PubMed2001

Labelling and binding of poly-(L-lysine) to functionalised gold surfaces. Combined FT-IRRAS and XPS characterisation.

We compare herein the interfacial reactivity of self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA), 1-undecanethiol (UDT) and 11-mercaptoundecanol (MUD) on gold surfaces towards aqueous solutions of poly-(L-lysine) (PL). Liquid-phase labelling of PL with the alkyne dicobalt hexacarbonyl cluster 1 combined with analysis of the substrates by Fourier transform infrared reflection-absorption spectroscopy (FT-IRRAS) and X-ray photoelectron spectroscopy (XPS) revealed that irreversible binding of PL occurred in all cases. However, the mechanism of binding involved differed markedly from one monolayer to the other. The main mode of interaction of PL to MUA SAM was of electrostatic nature between the terminal carboxylate of MUA and the ammonium groups of PL. For a similar number of bound thiolate molecules, the UDT adsorbed layer was found less continuous than the MUA one, allowing a higher fraction of PL to directly bind to the gold surface. As for MUD, very little thiolate molecules were adsorbed, leaving bare gold surface areas for non specific adsorption of PL.

Journal Article↗
PubMed2001

Degumming of ramie fibers by alkalophilic bacteria and their polysaccharide-degrading enzymes.

Three strains of alkalophilic bacteria, Bacillus sp. NT-39, NT-53 and NT-76, were selected for the degumming of ramie fibers and production of polysaccharide-degrading enzymes. After 48 h of incubation with the strains, the loss of the gum might amount to 5.0% or more of the fibers and a number of polysaccharide-degrading enzymes were secreted to the culture supernatants. The residual gum of the fibers decreased to 9.4% after 5 h of enzymatic degumming. Analysis of gum contents and enzyme activities revealed that pectate lyase and xylanase played an important role in the degradation of residual gum. Enzymatic degumming resulted in an increment of 5.4 ISO units in fiber brightness, whereas the reduction in bundle breaking tenacity of the fibers was less than 5.%. The results confirmed that degumming of ramie fibers by alkalophilic bacteria and their enzymes had substantial advantages.

Bacillus↗
PubMed2001

Sexual behaviour and contraceptive use among unmarried, young women migrant workers in five cities in China.

This paper reports the results of exploratory research on reproductive and sexual health knowledge and sexual behaviour of young, unmarried women who migrate to cities from rural areas for work, and their access to and needs in relation to family planning in Beijing, Guangzhou, Shanghai, Guiyang and Taiyuan, in China. Focus group discussions were conducted with 146 young women aged 16-25 and 58 in-depth interviews with key informants. Some of the young female migrant workers were sexually active and living with their boyfriends, most of whom expected to marry each other. Most of the women lacked basic information about reproduction and contraception, and did not know where or how to obtain contraception. There were social, psychological and economic barriers to accessing services. Only a small proportion of those who were unmarried were using contraception, so induced abortion was often the outcome of unprotected premarital sex. Pleasing male partners also played an important role in unprotected sex. The training, attitudes and approach of the entire family planning service system in relation to unmarried and young people in China, including this migrant population, needs to be reorientated so as to provide them with appropriate and adequate services.

Abortion, Induced↗