PubMed Health⌕ Search

Biomedical subjects

Q Zeng

Publications and source records attributed to Q Zeng.

At least 19 recordsLinked to original sources
PubMed1999

Sequence analysis of Pasteurella multocida major outer membrane protein (OmpH) and application of synthetic peptides in vaccination of chickens against homologous strain challenge.

Pasteurella multocida major outer membrane protein (OmpH) has been previously characterized as a porin. The native OmpH from strain X-73 (serotype 1) but not recombinant protein from Escherichia coli induced homologous protection in chickens. In this study OmpH sequences from 15 P. multocida serotypes as well as the CU vaccine strain were compared by sequence alignment and revealed high homology, with major variations confined to two discrete regions which were correspondingly predicted as two largest external loops. Secondary structures of OmpHs were predicted by sequence alignment of OmpHs with well defined porins and analyses of amphiphilicity, hydrophobic moment and antigenic index plots. Several synthetic peptides derived from predicted loop 2 and loop 5 of X-73 OmpH were synthesized as vaccine candidates. Vaccination studies in chickens showed that the cyclic synthetic peptide (Cyclic-L2) mimicking the predicted loop 2 induced 70% protection in chickens against strain X-73 challenge. This is the first report that a synthetic peptide mimicking the conformational epitopes of a native protein provide practical protection in target animal against bacterial infection.

Amino Acid Sequence↗
PubMed1998

The core metal-recognition domain of MerR.

MerR, the metalloregulatory protein of the mercury-resistance operon (mer) has unusually high affinity and specificity for ionic mercury, Hg(II). Prior genetic and biochemical evidence suggested that the protein has a structure consisting of an N-terminal DNA binding domain, a C-terminal Hg(II)-binding domain, and an intervening region involved with communication between these two domains. We have characterized a series of MerR deletion mutants and found that as little as 30% of the protein (residues 80-128) forms a stable dimer and retains high affinity for Hg(II). Biophysical measures indicate that this minimal Hg(II)-binding domain assumes the structural characteristics of the wild-type full-length protein both in the Hg(II) center itself and in an immediately adjacent helical protein domain. Our observations are consistent with the core Hg(II)-binding domain of the MerR dimer being constituted by a pair of antiparallel helices (possibly in a coiled-coil conformation) comprised of residues cysteine 82 through cysteine 117 from each monomer followed by a flexible loop through residue cysteine 126. These antiparallel helices would have a potential Hg(II)-binding site at each end. However, just as in the full-length protein, only one of these potential binding sites in the deleted proteins actually binds Hg(II).

Amino Acid Sequence↗
PubMed1998

Topoisomerase II-mediated site-directed alkylation of DNA by psorospermin and its use in mapping other topoisomerase II poison binding sites.

Psorospermin is a plant natural product that shows significant in vivo activity against P388 mouse leukemia. The molecular basis for this selectivity is unknown, although psorospermin has been demonstrated to intercalate into DNA and alkylate N7 of guanine. Significantly, the alkylation reactivity of psorospermin at specific sites on DNA increased 25-fold in the presence of topoisomerase II. In addition, psorospermin trapped the topoisomerase II-cleaved complex formation at the same site. These results imply that the efficacy of psorospermin is related to its interaction with the topoisomerase II-DNA complex. Because thermal treatment of (N7 guanine)-DNA adducts leads to DNA strand breakage, we were able to determine the site of alkylation of psorospermin within the topoisomerase II gate site and infer that intercalation takes place at the gate site between base pairs at the +1 and +2 positions. These results provide not only additional mechanistic information on the mode of action of the anticancer agent psorospermin but also structural insights into the design of an additional class of topoisomerase II poisons. Because the alkylation site for psorospermin in the presence of topoisomerase II can be assigned unambiguously and the intercalation site inferred, this drug is a useful probe for other topoisomerase poisons where the sites for interaction are less well defined.

Alkylation↗
PubMed1998

Design of new topoisomerase II inhibitors based upon a quinobenzoxazine self-assembly model.

A new class of pyridobenzophenoxazine compounds has been developed as topoisomerase II inhibitors for anticancer chemotherapy. These compounds were designed based on a proposed model of a quinobenzoxazine self-assembly complex on DNA. They showed excellent inhibitory effects on several tumor cell lines with nanomolar IC50 values. Their cytotoxic potency correlates with their ability to unwind DNA and inhibit topoisomerase II.

Antineoplastic Agents↗
PubMed1998

Requirement of Stat3 but not Stat1 activation for epidermal growth factor receptor- mediated cell growth In vitro.

Stimulation of epidermal growth factor receptor (EGFR) by ligand(s) leads to activation of signaling molecules including Stat1 and Stat3, two members of the signal transducers and activators of transcription (STAT) protein family. Activation of Stat1 and Stat3 was constitutive in transformed squamous epithelial cells, which produce elevated levels of TGF-alpha, and was enhanced by the addition of exogenous TGF-alpha. Targeting of Stat3 using antisense oligonucleotides directed against the translation initiation site, resulted in significant growth inhibition. In addition, cells stably transfected with dominant negative mutant Stat3 constructs failed to proliferate in vitro. In contrast, targeting of Stat1 using either antisense or dominant-negative strategies had no effect on cell growth. Thus, TGF-alpha/EGFR-mediated autocrine growth of transformed epithelial cells is dependent on activation of Stat3 but not Stat1.

Carcinoma, Hepatocellular↗
PubMed1998

Inhibition of human squamous cell carcinoma growth in vivo by epidermal growth factor receptor antisense RNA transcribed from the U6 promoter.

BACKGROUND: Squamous cell carcinomas of the head and neck (SCCHN), unlike normal mucosal squamous epithelial cells, overexpress epidermal growth factor receptor (EGFR) messenger RNA and protein. EGFR protein is required to sustain the proliferation of SCCHN cells in vitro. To determine whether EGFR expression contributes to tumor growth, we investigated the effect of suppressing EGFR expression in tumor xenografts through in situ expression of antisense oligonucleotides. METHODS: Intratumoral cationic liposome-mediated gene transfer was used to deliver plasmids capable of expressing sense or antisense EGFR sequences into human head and neck tumors, which were grown as subcutaneous xenografts in nude mice. The oligonucleotides were expressed under the control of the U6 RNA promoter. RESULTS: Direct inoculation of the EGFR antisense (but not the corresponding sense) plasmid construct into established SCCHN xenografts resulted in inhibition of tumor growth, suppression of EGFR protein expression, and an increased rate of apoptosis (programmed cell death). Sustained antitumor effects were observed for up to 2 weeks after the treatments were discontinued. CONCLUSION: These results suggest that interference with EGFR expression, using an antisense-based gene therapy approach, may be an effective means of treating EGFR-overexpressing tumors, including SCCHN.

Animals↗
PubMed1998

A single plasmid vector (pSTAR) mediating efficient tetracycline-induced gene expression.

A plasmid vector (pSTAR) has been constructed which confers neomycin resistance for selecting stably transfected cells, possesses a cloning cassette for placing a gene of interest under the control of the tetO DNA motif, and expresses rtTAnls which, upon association with tetracycline, binds to and drives gene expression from the tetO DNA motif. The plasmid pSTAR/LacZ, which has the gene for beta-galactosidase inserted into the cloning cassette, was transfected into Chinese hamster ovary (CHO) cells and selected for stably transfected cells. In pooled transfectants of CHO, tetracycline induced the expression of beta-galactosidase in 10-30% of cells. Using clonal transfectants, beta-galactosidase expression was induced by tetracycline in essentially every cell. Furthermore, induction of beta-galactosidase expression by tetracycline was both dose- and time-dependent. Similar tetracycline-induced beta-galactosidase expression is also observed in other cell types. The pSTAR vector is thus suited to facilitate the application of tetracycline-induced gene expression in diverse research areas.

Animals↗
PubMed1998

Downmodulation of TGF-alpha protein expression with antisense oligonucleotides inhibits proliferation of head and neck squamous carcinoma but not normal mucosal epithelial cells.

Interruption of an autocrine growth pathway involving TGF-alpha and EGFR may inhibit tumor growth and improve survival in head and neck cancer patients. We previously demonstrated that biopsy specimens and established cell lines from patients with squamous cell carcinoma of the head and neck (SCCHN) overexpress TGF-alpha and its receptor, epidermal growth factor receptor (EGFR) at both the mRNA and protein levels. Protein localization studies showed that TGF-alpha and EGFR are produced by the same epithelial cells in tissues from head and neck cancer patients further supporting a role for this ligand-receptor pair in an autocrine growth pathway. To confirm that TGF-alpha contributes to autocrine growth, we examined the effect of down regulation of TGF-alpha protein on SCCHN cell proliferation. Treatment of 6 SCCHN cell lines with antisense oligodeoxynucleotides targeting the translation start site of human TGF-alpha mRNA decreased TGF-alpha protein production by up to 93% and reduced cell proliferation by a mean of 76.2% compared to a 9.7% reduction with sense oligonucleotide (range P = 0.036-0.0001). TGF-alpha antisense oligonucleotide exposure also decreased TGF-alpha protein levels in normal oropharyngeal mucosal epithelial cells, however their growth rate was not affected. These findings indicate that TGF-alpha is participating in an autocrine signaling pathway in transformed, but not in normal mucosal epithelial cells, that promotes proliferation.

Base Sequence↗
PubMed1998

Mouse PRL-2 and PRL-3, two potentially prenylated protein tyrosine phosphatases homologous to PRL-1.

Protein tyrosine phosphatases (PTPs) play a fundamental role in regulating diverse cellular processes. PRL-1 is a unique nuclear PTP that is induced in mitogen-stimulated cells and regenerating liver. Database searches using the PRL-1 sequence led to the identification of mouse PRL-2 and PRL-3 which exhibit 87% and 76% identity to mouse PRL-1 in their amino acid sequences. All three mouse PRL proteins contain a C-terminal consensus sequence for prenylation. All PRL proteins bear significant sequence homology to Cdc14p and the recently identified tumor suppressor PTEN/MMAC1, in regions other than the conserved PTP signature motif. The nucleotide sequences of the coding regions of mouse PRL-2 and PRL-3 are, respectively, 71% and 62%, identical to mouse PRL-1, while the 5' un-translated regions of mouse PRL-1, PRL-2, and PRL-3 are much more divergent. Northern blot analysis revealed that PRL-2 is preferentially expressed in skeletal muscle, while PRL-3 is preferentially expressed in both skeletal muscle and heart, although both PRL-2 and PRL-3 are expressed at lower levels in other tissues.

Amino Acid Sequence↗
PubMed1998

A novel synaptobrevin/VAMP homologous protein (VAMP5) is increased during in vitro myogenesis and present in the plasma membrane.

cDNA clones encoding a novel protein (VAMP5) homologous to synaptobrevins/VAMPs are detected during database searches. The predicted 102-amino acid VAMP5 harbors a 23-residue hydrophobic region near the carboxyl terminus and exhibits an overall amino acid identity of 33% with synaptobrevin/VAMP1 and 2 and cellubrevin. Northern blot analysis reveals that the mRNA for VAMP5 is preferentially expressed in the skeletal muscle and heart, whereas significantly lower levels are detected in several other tissues but not in the brain. During in vitro differentiation (myogenesis) of C2C12 myoblasts into myotubes, the mRNA level for VAMP5 is increased approximately 8- to 10-fold. Immunoblot analysis using antibodies specific for VAMP5 shows that the protein levels are also elevated approximately 6-fold during in vitro myogenesis of C2C12 cells. Indirect immunofluorescence microscopy and immunoelectron microscopy reveal that VAMP5 is associated with the plasma membrane as well as intracellular perinuclear and peripheral vesicular structures of myotubes. Epitope-tagged versions of VAMP5 are similarly targeted to the plasma membrane.

Amino Acid Sequence↗
PubMed1998

Immunoreactive endothelin-1 and its receptors in human adrenal tissues.

To elucidate the pathophysiologic significance of endothelin-1 (ET-1) in adrenal and the mechanism for reduced responsiveness to exogenous ET-1 in aldosterone-producing adenoma (APA), we have investigated ET-1 receptors by radioligand binding assay (RBA) in human normal adrenal (NA), APA, idiopathic hyperaldosteronism (IHA), and pheochromocytoma (PHEO), immunoreactive (ir-) ET-1 content in NA, APA and PHEO by radioimmunoassay (RIA), and immunohistochemical staining of ET-1 with the peroxidase-anti-peroxidase (PAP) method in NA, APA, and PHEO. A single class of high-affinity binding sites for ET-1 was found in human NA and tumor tissues. Dissociation constant (Kd) values of ET-1 receptors were similar in NA, APA, and IHA, but maximal binding capacity (Bmax) of ET-1 receptors was lower in APA than in NA and IHA. Both Kd and Bmax in PHEO were higher than those in NA, APA, and IHA. Ir-ET-1 content in tumors of APA and PHEO were higher than in NA. Immunohistochemical staining was more intense in the tumor cells of APA and PHEO than in NA. These results suggest that the reduced response to exogenous ET-1 in APA could be related to downregulation of ET-1 receptors in the tumor. Increased ET-1 content and receptors may lead to hypersecretion of catecholamine in PHEO. ET-1 produced in normal and tumor adrenal tissues may regulate aldosterone and catecholamine secretion from adrenals in a paracrine/autocrine fashion.

Adrenal Gland Neoplasms↗
PubMed1998

Normalization of EGFR mRNA levels following restoration of wild-type p53 in a head and neck squamous cell carcinoma cell line.

Head and neck squamous cell carcinoma (HNSCC) is frequently characterized by mutation of the p53 tumor suppressor gene and increased expression of the epidermal growth factor receptor (EGFR). To determine the potential link between p53 and EGFR expression, we examined the effect of overexpressing wild-type p53 on EGFR mRNA levels in HNSCC. In these studies, a temperature-sensitive (ts) p53 mutant was transfected into an HNSCC line which contained a deletion of one allele of the p53 gene and a mutation of the remaining allele. Following selection, six clones were isolated, characterized by Southern blot analysis, and stable expression of mutant p53 protein was confirmed by immunoblotting of clones grown at the mutant temperature. Total RNA was isolated from transfectants grown at both wild-type or mutant temperatures followed by Northern blot analysis to determine levels of EGFR mRNA expression at the two p53 conformations. Clones grown at the wild-type temperature (32.5 degreesC) demonstrated a 69% 13% decrease in EGFR mRNA compared with the same cells grown at the mutant temperature (39.5 degreesC; p=0.006) indicating that restoration of wild-type p53 reduces EGFR mRNA levels in this HNSCC cell line. These findings suggest that abnormalities in p53 may contribute to activation of EGFR gene transcription.

Blotting, Northern↗
PubMed1998

Automated knowledge extraction from the UMLS.

This paper presents our work in extracting disease-chemical relationship knowledge from the UMLS Co-occurrence table (MRCOC) using an automated method. We evaluated the quality of the knowledge from UMLS MRCOC by comparing it with knowledge from other sources: For disease-lab chemical relationships, knowledge was obtained from a decision support system (DXplain) and our own knowledge base of medical terminology (MED) through automated processes. For disease-drug chemical relationships, knowledge was manually acquired from the medical literature. Evaluations showed that the UMLS MRCOC knowledge has good sensitivity, especially regarding disease-drug relationships. We are using this knowledge to produce disease-specific views of patients' electronic patient record.

Decision Support Systems, Clinical↗
PubMed1997

Testing homogeneity of intra-run variance parameters in immunoassay.

A common assumption in the analysis of immunoassay data is a similar pattern of within-run variation across runs of the assays. One makes this assumption without formal investigation of its validity, despite the widely acknowledged fact that accurate understanding of intra-run variation is critical to reliable calibration inference. We propose a simple procedure for a formal test of the assumption of the homogeneity of parameters that characterize intra-run variation based on representation of standard curve data from multiple assay runs by a non-linear mixed effects model. We examine the performance of the procedure and investigate the robustness of calibration inference to incorrect assumptions about the pattern of intra-run variation.

Calibration↗
PubMed1997

Inhibition of epidermal growth factor receptor gene expression and function decreases proliferation of head and neck squamous carcinoma but not normal mucosal epithelial cells.

Previous reports have shown that fresh tissues and cell lines from patients with squamous cell carcinoma of the head and neck (SCCHN) overexpress transforming growth factor alpha (TGF-alpha) and its receptor, the epidermal growth factor receptor (EGFR) at both the mRNA and protein levels. Protein localization studies confirm that TGF-alpha and EGFR are produced by the same epithelial cells in tissues from head and neck cancer patients further supporting an autocrine growth pathway. Using three strategies, we examined the hypothesis that downmodulation of EGFR would reduce the proliferation of SCCHN cells. We targeted EGFR mRNA using antisense oligonucleotides and the mature EGFR protein at two sites, the ligand-binding domain and the kinase domain, and determined the effects of this targeting on SCCHN proliferation. Treatment of several SCCHN cell lines with a pair of antisense oligodeoxynucleotides directed against the translation start site and first intron-exon splice junction of the human EGFR gene resulted in decreased EGFR protein production and inhibited growth by 86% compared to a 13% reduction in cells treated with sense oligonucleotides (P=0.03). Growth inhibition was specific for carcinoma cells since the same EGFR antisense oligonucleotides had no effect on the proliferation of normal mucosa cells harvested from non-cancer patients. Two monoclonal antibodies which block ligand binding to EGFR (MAbs 425 and 528) inhibited the growth of several SCCHN cell lines by up to 97% which suggests that EGFR is participating in an autocrine pathway in SCCHN that is, at least in part, external. An EGFR-specific tyrosine kinase inhibitor (PD 153035) was found to inhibit EGFR phosphorylation in SCCHN cell lines and to reduce growth by 68% although it had no effect on the growth rate of normal mucosal epithelial cells. These experiments indicate that EGFR gene expression and function is critical for SCCHN cell growth but not for growth of normal mucosa cells and therefore may serve as a tumor-specific target for preventive and therapeutic strategies in head and neck cancer.

Aged↗
PubMed1997

[Cross reaction of Trichinella spiralis larva antigens with sera of schistosomiasis japonica].

Cross reactions of T. spiralis muscular larva antigens (TsMLA) against several sera from patients with other parasitic diseases by ELIB (enzyme-linked immunoblotting technique) were studied. The proteins of 31-100 KDa were recognized by sera of two cases of acute schistosomiasis, while proteins of 44/45, 51/53, 62/64 and 100 KDa were recognized by sera of 11 cases of chronic schistosomiasis. The proteins of 60 KDa showed varied cross reactions against sera of five kinds of patients with other parasitic diseases (filariasis, hookworm diseases, paragonimiasis, ascariasis and clonorchiasis). Only the proteins of 45 KDa were recognized by six of fifteen cases of normal human sera. All of > 29 KDa proteins were recognized by sera of rabbit infected by T. spiralis. It is suggested that there were many antigens in Trichinellen muscular larva which shared in common with several other parasites. The cross reactions of TsMLA against Schistosoma japonicum may be differentiated on the positive reaction bands of 44/45, 51/53, 62/64 and 100 KDa proteins which was specific to the chronic schistosomiasis using the TsMLA by means of ELIB.

Animals↗