PubMed Health⌕ Search

Biomedical subjects

D Zhang

Publications and source records attributed to D Zhang.

At least 55 records · Page 3Linked to original sources
PubMed2003

The high-pathogenicity island is absent in human pathogens of Salmonella enterica subspecies I but present in isolates of subspecies III and VI.

In this study we tested 74 Salmonella strains of all eight Salmonella groups and were able to demonstrate the presence of two high-pathogenicity island types in strains of Salmonella groups IIIa, IIIb, and VI. Most high-pathogenicity island-positive isolates produced yersiniabactin under iron-limited conditions and were positive for the high-molecular-weight proteins HMWP1 and HMWP2.

3' Flanking Region↗
PubMed2003

Synthesis, electronic properties, and applications of indium oxide nanowires.

Single-crystalline indium oxide nanowires were synthesized using a laser ablation method and characterized using various techniques. Precise control over the nanowire diameter down to 10 nm was achieved by using monodisperse gold clusters as the catalytic nanoparticles. In addition, field effect transistors with on/off ratios as high as 10(4) were fabricated based on these nanowires. Detailed electronic measurements confirmed that our nanowires were n-type semiconductors with thermal emission as the dominating transport mechanism, as revealed by temperature-dependent measurements. Furthermore, we studied the chemical sensing properties of our In(2)O(3) nanowire transistors at room temperature. Upon exposure to a small amount of NO(2) or NH(3), the nanowire transistors showed a decrease in conductance of up to five or six orders of magnitude, in addition to substantial shifts in the threshold gate voltage. Our devices exhibit significantly improved chemical sensing performance compared to existing solid-state sensors in many aspects, such as the sensitivity, the selectivity, the response time and the lowest detectable concentrations. We have also demonstrated the use of UV light as a "gas cleanser" for In(2)O(3) nanowire chemical sensors, leading to a recovery time as short as 80 seconds.

Crystallization↗
PubMed2003

Mouse models of human cancer web-based resources.

The Mouse Models of Human Cancers Consortium (MMHCC) is a collaborative program designed to derive and characterize mouse models of human malignancies. To enhance information and resource exchange among the MMHCC investigators and other cancer research scientists, the NCI Center for Bioinformatics (NCICB, http://ncicb.nci.nih.gov/) has developed web-based resources that are freely available to the cancer research community. These resources include a website (http://emice.nci.nih.gov) and databases for cancer models (http://cancermodels.nci.nih.gov) and cancer images (http://cancerimages.nci.nih.gov).

Animals↗
PubMed2002

Chromosomal localization of 5S and 18S-5.8S-25S ribosomal DNA sites in five Asian pines using fluorescence in situ hybridization.

Fluorescence in situ hybridization (FISH) was employed on mitotic metaphase chromosome preparations of five Asian Pinus species: Pinus tabuliformis, Pinus yunnanensis, Pinus densata, Pinus massoniana and Pinus merkusii, using simultaneously DNA probes of the 18S rRNA gene and the 5S rRNA gene including the non-transcribed spacer sequences. The number and location of 18S rDNA sites varied markedly (5-10 pairs of strong signals) among the five pines. A maximum of 20 major 18S rDNA sites was observed in the diploid genome (2n = 24) of P. massoniana. The 5S rDNA FISH pattern was less variable, with one major site and one minor site commonly observed in each species. The differentiation of rDNA sites on chromosomes among the five pines correlates well with their phylogenic positions in Pinus as reconstructed from other molecular data. P. densata, a species of hybrid origin, resembles its parents ( P. tabuliformis and P. yunnanensis), including some components characteristic of each parent in its pattern. However, the species is unique, showing new features resulting possibly from recombination and genome reorganization.

Asia↗
PubMed2002

A crossover, add-on trial of talampanel in patients with refractory partial seizures.

The authors report a double-blind, placebo-controlled, crossover study of talampanel in 49 patients with refractory partial seizures. Three doses of talampanel were investigated based on differences in patients' concomitant antiepileptic drug usage. Talampanel showed efficacy in reducing seizure frequency (p = 0.001) with a median seizure reduction of 21%. Eighty percent of patients had fewer seizures on talampanel than on placebo. Dizziness (52%) and ataxia (26%) were the only significant adverse events.

Adult↗
PubMed2002

Thrombostasin: purification, molecular cloning and expression of a novel anti-thrombin protein from horn fly saliva.

Thrombostasin (TS), a novel protein found in the saliva of Haematobia irritans (horn fly), was purified by high-performance liquid chromatography from the saliva of field-collected insects. This protein, which inhibits thrombin, accounts for anti-clotting activity in horn fly saliva [J. Med. Entomol. 37 (2000) 416] and is the first purified anti-hemostatic factor described from the Stomoxyinae, a large group of blood-feeding insects that are major pests of livestock world-wide. The purified TS had an apparent molecular weight of 16.7 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and revealed two isoelectric groups with isoelectric points (pIs) of approximately 4.6 and 4.8. Mass spectroscopy analysis, however, resulted in at least three major isoforms that range in mass from 9213 to 9274 Da. A 243-bp coding sequence was obtained from cDNA by using a degenerate primer deduced from the N-terminal sequence of the purified TS. The conceptual translation of the 243-bp sequence showed that the 81-amino-acid peptide, whose first 30 amino acids match those of the N-terminal sequence, had a predicted mass of 9213 Da with pI 4.14. A full-length TS cDNA was generated by rapid amplification of cDNA ends of the 5' and sequential polymerase chain reaction (PCR) amplification. It contained a 5'-end 12-bp segment preceding the putative ATG start codon, followed by a 54-bp sequence corresponding to a secretory signal and an additional 228-bp coding sequence preceding residues revealed by N-terminal sequencing of purified TS. The fidelity of the PCR-generated TS sequence was confirmed in genomic DNA and by biological activity of recombinant TS produced in a baculovirus expression system. Database comparisons revealed no homology between TS and other known molecules. Because of the paucity of other anti-hemostatic factors in horn fly saliva, TS may play a critical role in maintenance of the ectoparasitic lifestyle of horn flies.

Amino Acid Sequence↗
PubMed2002

Multidrug-resistance-associated protein MGr1-Ag is identical to the human 37-kDa laminin receptor precursor.

We report the isolation and functional characterization of the gene encoding MGr1-Ag, a multidrug-resistance-associated protein. A lambdagt11 cDNA library derived from colorectal carcinoma SW480 cells was screened with monoclonal antibody MGr1. DNA homology analysis of 22 positive clones (designated R1-R22) suggested human 37-kDa laminin receptor precursor (37LRP, R7/R9/R15/R16/R19/R20) and a novel gene (R22) as candidate genes encoding MGr1-Ag. Western blot analysis showed that anti-R20 serum reacted with a unique protein band that was consistent with MGr1-Ag, while anti-R22 serum could not react with MGr1-Ag. The coding gene for MGr1-Ag was amplified using reverse transcription-PCR. Sequence analysis revealed that the MGr1-Ag and 37LRP genes shared the same coding sequence. An in vitro drug sensitivity assay indicated that down-regulation of 37LRP by an antisense technique could significantly enhance the cytotoxicity of anticancer drugs to gastric cancer cells. Thus we draw the conclusion that MGr1-Ag is identical to 37LRP.

Carcinoma↗
PubMed2002

Cloning and molecular characterization of two mosquito iron regulatory proteins.

Iron regulatory proteins (IRPs) control the synthesis of various proteins at the translational level by binding to iron responsive elements (IREs) in the mRNAs. Iron, infection, and stress can alter IRP/IRE binding activity. Insect messenger RNAs for ferritin and succinate dehydrogenase subunit b have IREs that are active translational control sites. We have cloned and sequenced cDNAs encoding proteins from the IRP1 family for the mosquitoes, Aedes aegypti and Anopheles gambiae. Both deduced amino acid sequences show substantial similarity to human IRP1 and Drosophila IRP1A and IRP1B, and all of the residues thought to be involved in aconitase activity and iron-sulfur cluster formation are conserved. Recombinant A. aegypti IRP1 binds to transcripts of the IREs of mosquito or human ferritin subunit mRNAs. No significant change in A. gambiae IRP1 messenger RNA could be detected during the various developmental stages of the life cycle, following iron loading by blood feeding, or after bacterial or parasitic infections. These data suggest that there is no change in gene transcription. Furthermore, bacterial challenge of A. gambiae cells did not change IRP1 protein levels. In contrast, IRP1 binding activity for the IRE was elevated following immune induction. These data show that changes in IRP1/IRE binding activity occur as part of the insect immune response.

Aedes↗
PubMed2002

Inclusion of Vpr accessory gene in a plasmid vaccine cocktail markedly reduces Nef vaccine effectiveness in vivo resulting in CD4 cell loss and increased viral loads in rhesus macaques.

We compared the immunogenicity of plasmid vaccines containing multiple human immunodeficiency virus (HIV) antigens and found that covaccination with plasmids expressing HIV-1 14 kDa vpr gene product profoundly reduces antigen-specific CD8-mediated cytotoxic T-cell activity (CTL). Interestingly, Th1 type responses against codelivered antigens (pGag-Pol, pNef, etc.) encoded by the plasmid vaccines were suppressed. This suggested that vpr might compromise CD8 T-cell immunity in vivo during infection. A pilot primate vaccine study was designed to test the hypothesis to compare the following groups: unvaccinated controls, animals vaccinated without simean immunodeficiency virus (SIV)-Nef antigen plasmid, and animals covaccinated with the identical plasmid antigen and a plasmid construct encoding SIV Vpr/Vpx. Animals were subsequently challenged intrarectally with pathogenic SIVmac251 after the final vaccination of a multiple immunization protocol. Control animals were all infected and exhibited high viral loads and rapid CD4+ T-cell loss. In contrast, the Nef plasmid-vaccinated animals were also infected but exhibited preservation of CD4+ T-cells and a multilog reduction in viral load compared with controls. Animals covaccinated multiple times with the Nef vaccine and pVpr/Vpx plasmid suffered rapid and profound loss of CD4+ T-cells. These results have important implications for the design of multicomponent and particle vaccines for HIV-1 as well as for our understanding of HIV/SIV pathogenesis in vivo.

Animals↗
PubMed2002

Maternal smoking during pregnancy and nicotine and cotinine concentrations in maternal and neonatal hair.

OBJECTIVE: Conflicting data have been reported in the association between maternal smoking and adverse effects during pregnancy and in neonates. Some studies, conducted on a limited number of patients have evaluated maternal consumption and fetal exposure by measuring nicotine and cotinine in the hair. Our aims were to evaluate the relationship among maternal cigarette consumption, fetal smoking exposure and outcome of pregnancy in a population of pregnant women who smoked. DESIGN: Mothers smoking during pregnancy were included at their first prenatal visit and followed prospectively. Maternal data (demographic variables, obstetrical history and cigarette consumption), neonatal data and birth indicators (number of weeks of gestation, type of delivery, weight) were collected. Hair samples from the mothers and the babies were collected at birth. SETTING: The present study was conducted in the Department of Obstetrics of the University Hospital Robert Debré in Paris. POPULATION: A total of 254 women smokers were included in the study and 182 mother/neonate pairs were analyzed after exclusion of 50 babies whose hair samples were inadequate and 22 for various other reasons. METHODS: Nicotine and cotinine concentrations in the maternal and neonatal hair were measured at birth by radio-immunoassay. MAIN OUTCOME MEASURES: Cigarette consumption was based on self reporting and quantified each trimester. It was expressed more precisely during the third trimester by the mean number per cigarette per day. Nicotine and cotinine concentrations in the maternal and neonatal hair at birth were also analysed. RESULTS: Nicotine and cotinine concentrations in maternal hair were associated with cigarette consumption during the third trimester of pregnancy (P < 0.003 and P < 0.01, respectively). In neonates, only cotinine concentrations were associated to maternal cigarette consumption (P < 0.0001). This association remained significant in a multivariate analysis, which included maternal cotinine hair concentrations and the ethnic group. CONCLUSIONS: Our results have shown a strong relationship between maternal cigarette consumption and fetal exposure to smoking measured by cotinine concentrations in neonatal hair. Further studies are required to look for associations between fetal exposure and adverse pregnancy outcome.

Adult↗
PubMed2001

Cell cycle genes as targets of retinoid induced ovarian tumor cell growth suppression.

We have examined the effect of all-trans-retinoic acid (RA) on cell cycle gene expression in RA sensitive CA-OV3 and RA resistant SK-OV3 ovarian carcinoma cell lines. Gene expression was analysed by multiprobe RNAse protection, Western blotting and in vitro kinase assays. No differences were observed between RA sensitive and RA resistant ovarian carcinoma cells in the levels of expression of many cell cycle genes including cyclin A, B and E, cdk 2,4 and 6, E2F-1, E2F-2, E2F-3, E2F-4, E2F-5, DP-1 and DP-2. However, RA sensitive CA-OV3 cells expressed higher levels of p53, p27, p21, and p16 compared to RA resistant SK-OV3 cells. In addition, RA treatment of CA-OV3 cells resulted in a significant decrease in hyperphosphorylated RB and RB-2/p130 and corresponding significant increases in the levels of hypophosphorylated and/or partially phosphorylated RB-2/p130 protein and hypophosphorylated RB. Also, RA treatment increased expression of the cdk inhibitor p27 and decreased activity of cdk 2, cdk 4 and cdk 6. Finally, amounts of p27-cyclin E and RB-2/p130-E2F4 complexes were found to increase in CA-OV3 cells growth arrested by RA. These results suggest that the pocket protein pathways are critical targets for retinoid suppression of ovarian carcinoma cell growth.

Blotting, Western↗
PubMed2001

[Preparation of decalcified bone matrix, bone cement and bone morphogenetic protein composite].

OBJECTIVE: To investigate the most excellent composite proportion and the most convenient composite method of decalcified bone matrix (DBM), bone cement (BC) and bovine bone morphogenetic protein (bBMP) composite. METHODS: The canine DBM and the bBMP were prepared beforehand. First mix the bBMP and DBM together with the proportion of 1:25 with adsorption and directly, then add BC with different weight proportion and finally the complex material was examined by biomechanics, scan electron microscope, determination of bone inductive activity and implanted into the canine femoral defect caused by microwave-induced hyperthermia. RESULTS: The bBMP had strong bone inductive activity and had no affect for this function when combined with DBM with different method. There were irregular gaps in the composite and most of them with diameter less than 100 microns and the porosity of the composite was less than 20% when the proportion of DBM was 40%. So it was unfavorable for the new bone to form and the new blood vessels to reconstruct. The DBM and BC could not be combined together when the proportion of DBM was 80%. While the biomechanical intensity of the composite decreased and the qualities of the new bone forming and new blood vessels reconstructing improved successively when the proportion of DBM was from 50% to 75%. CONCLUSION: It is the most convenient that bBMP is combined with DBM directly while its bone inductive activity could not be affected. The composite material not only has high biomechanical intensity, but also is favorable for new bone to form and new blood vessels to reconstruct when the proportion of DBM is 50% and 60%. So it is favorable for bone repair in the places where need to bear a load. However it is also favorable for bone repair in the places where do not need to bear a load when the proportion of DBM is 75%.

Animals↗
PubMed2001

CD4 promotes breadth in the TCR repertoire.

A diverse population of MHC class II-restricted CD4 lineage T cells develops in mice that lack expression of the CD4 molecule. In this study, we show that the TCR repertoire selected in the absence of CD4 is distinct, but still overlapping in its properties with that selected in the presence of CD4. Immunization of mice lacking CD4 caused the clonal expansion of T cells that showed less breadth in the range of Ag-binding properties exhibited by their TCRs. Specifically, the CD4-deficient Ag-specific TCR repertoire was depleted of TCRs that demonstrated low-affinity binding to their ligands. The data thus suggest a key role for CD4 in broadening the TCR repertoire by potentiating productive TCR signaling and clonal expansion in response to the engagement of low-affinity antigenic ligands.

Animals↗
PubMed2001

Characterization of fortilin, a novel antiapoptotic protein.

Apoptosis is meticulously controlled in living organisms. Its dysregulation has been shown to play a key role in a number of human diseases, including neoplastic, cardiovascular, and degenerative disorders. Bcl-2 family member proteins and inhibitors of apoptosis proteins are two major negative regulators of apoptosis. We report here the characterization of novel antiapoptotic protein, fortilin, which we identified through yeast two-hybrid library screening. Sequence analysis of fortilin revealed it to be a 172-amino acid polypeptide highly conserved from mammals to plants. Fortilin is structurally unrelated to either Bcl-2 family member proteins or inhibitors of apoptosis proteins. Northern blot analysis showed the fortilin message to be ubiquitous in normal tissue but especially abundant in the liver, kidney, and small intestine. Western blot analysis using anti-fortilin antibody showed more extensive expression in cancerous cell lines (H1299, MCF-7, and A549) than in cell lines derived from normal tissue (HEK293). Immunocytochemistry using HeLa cells transiently expressing FLAG-tagged fortilin and immunohistochemistry using human breast ductal carcinoma tissue and anti-fortilin antibody both showed that fortilin is predominantly localized in the nucleus. Functionally, the transient overexpression of fortilin in HeLa cells prevented them, in a dose-dependent fashion, from undergoing etoposide-induced apoptosis. Consistently, U2OS cells stably expressing fortilin protected the cells from cell death induced by etoposide over various concentrations and durations of exposure. In addition, fortilin overexpression inhibited caspase-3-like activity as assessed by the cleavage of fluorogenic substrate benzyloxycarbonyl-DEVD-7-amido-4-(trifluoromethyl)coumarin. Furthermore, the antisense depletion of fortilin from breast cancer cell line MCF-7 was associated with massive cell death. These data suggest that fortilin represents a novel antiapoptotic protein involved in cell survival and apoptosis regulation.

Amino Acid Sequence↗
PubMed2001

p53-dependent suppression of uridine phosphorylase gene expression through direct promoter interaction.

Uridine phosphorylase (UPase) is a key enzyme in the pyrimidine salvage pathway. It reversibly catalyzes the catabolism of uridine to uracil; controls the homeostatic regulation of uridine concentration in plasma and tissues; and plays a role in the intracellular activation of 5-fluorouracil. We cloned the murine UPase gene promoter, a 1703-bp fragment, and determined the transcription initiation sites located at +1 and +92 bp of the cDNA sequence. Through transient expression analysis of the 5'-flanking region of UPase gene, we have evaluated the promoter activity for a series of fragments with 5'- to 3'-deletion in murine breast cancer EMT-6 cells and immortalized murine fibroblast NIH 3T3 cells. Cotransfection of the UPase promoter constructs (from -1619 to -445) containing p53 binding motif with the wild-type p53 construct resulted in a significant reduction of luciferase activity; however, this effect disappeared with the additional deletion of the -445 to -274 sequence to suggest the existence in this promoter region of a putative p53 recognition element. Similar cotransfection in murine embryo fibroblasts p53-/- confirmed the inhibitory role of p53 on the UPase promoter activity. The specificity of the interaction is demonstrated by nuclear protein-specific binding to the putative p53 recognition sequence using gel mobility shift assay and DNase I footprinting analysis. These data indicate the UPase gene is a novel target of p53, and its expression is down-regulated by p53 at the promoter level.

3T3 Cells↗
PubMed2001

Granzyme A activates an endoplasmic reticulum-associated caspase-independent nuclease to induce single-stranded DNA nicks.

The cytotoxic T lymphocyte protease granzyme A (GzmA) initiates a novel caspase-independent cell death pathway characterized by single-stranded DNA nicking. The previously identified GzmA substrate SET is in a multimeric 270-420-kDa endoplasmic reticulum-associated complex that also contains the tumor suppressor protein pp32. GzmA cleaved the nucleosome assembly protein SET after Lys(176) and disrupted its nucleosome assembly activity. The purified SET complex required only GzmA to reconstitute single-stranded DNA nicking in isolated nuclei. DNA nicking occurred independently of caspase activation. The SET complex contains a 25-kDa Mg(2+)-dependent nuclease that degrades calf thymus DNA and plasmid DNA. Thus, GzmA activates a DNase (GzmA-activated DNase) within the SET complex to produce a novel form of DNA damage during cytotoxic T lymphocyte-mediated death.

Amino Acid Sequence↗