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D Zhang

Publications and source records attributed to D Zhang.

At least 253 records · Page 14Linked to original sources
PubMed2000

The transmembrane signal transduction in HEp-2 cells induced by bacterial adherence.

In order to understand the role of transmembrane signal transduction of host cells in the early steps of infection, the adherence of E. coli to HEp-2 cells and the change of activity of phospholipase C-gamma (PLC-gamma) induced by the adherence were investigated. The adherence of enteropathogenic E. coli (EPEC), strain E. 7, induced a significant increase of inositol-triphosphat (IP-3) level in HEp-2 cells. The adherence of the bacteria and the increase of IP-3 was kinetically correlated. Whereas the increase of IP3 level induced by the adherence of the control strain EPEC (H511), a non-piliated strain, was much meager than that by E7, a piliated strain. The results highlighted an important role of transmembrane signals like 1P-3 in the pathogenesis of EPEC.

Bacterial Adhesion↗
PubMed2000

[Indirect determination of iodide by flame atomic absorption spectrometry].

A new method was developed for the indirect determination of iodide by flame atomic absorption spectrometry (FAAS). Precipitation of CuI, obtained with the reaction of Cu+ with I, was dissolved in Na2S2O3. Copper content in the solution was determined by FAAS and the iodide content was calculated using the content of copper. The linear range of the proposed method is 0-800 micrograms. mL-1 of I-, and the relative standard derivation at 0.4 mL of I level is 0.7%. The proposed method was applied to determination of iodine in iodized tablets salt, cydiodine tablets and laver with a recovery range of 99.9%-100.3%.

Humans↗
PubMed1999

Human TATA-binding protein-related factor-2 (hTRF2) stably associates with hTFIIA in HeLa cells.

The TATA-binding protein (TBP)-related factor TRF1, has been described in Drosophila and a related protein, TRF2, has been found in a variety of higher eukaryotes. We report that human (h)TRF2 is encoded by two mRNAs with common protein coding but distinct 5' nontranslated regions. One mRNA is expressed ubiquitously (hTRF2-mRNA1), whereas the other (hTRF2-mRNA2) shows a restricted expression pattern and is extremely abundant in testis. In addition, we show that hTRF2 forms a stable stoichiometric complex with hTFIIA, but not with TAFs, in HeLa cells stably transfected with flag-tagged hTRF2. Neither recombinant human (rh)TRF2 nor the native flag.hTRF2-TFIIA complex is able to replace TBP or TFIID in basal or activated transcription from various RNA polymerase II promoters. Instead, rhTRF2, but not the flag.hTRF2-TFIIA complex, moderately inhibits basal or activated transcription in the presence of rhTBP or flag.TFIID. This effect is either completely (TBP-mediated transcription) or partially (TFIID-mediated transcription) counteracted by addition of free TFIIA. Neither rhTRF2 nor flag. hTRF2-TFIIA has any effect on the repression of TFIID-mediated transcription by negative cofactor-2 (NC2) and neither substitutes for TBP in RNA polymerase III-mediated transcription.

Amino Acid Sequence↗
PubMed1999

Bivariate analysis of the p53 pathway to evaluate Ad-p53 gene therapy efficacy.

BACKGROUND: Gene therapy of human tumors with adenovirus vectors presents a clinical research challenge and a potential opportunity in cancer therapy. One of the research challenges is that endpoints like tumor reduction, time to recurrence, and survival do not provide information about whether a potential therapeutic infects the targeted cells or whether the transferred gene functions or induces a cellular response. Therefore, a flow cytometric approach was developed for a wildtype, p53 encoding adenoviral vector (Ad-p53) that provides (1) the relative level of p53 transferred by p53 immunoreactivity, (2) mdm2 immunoreactivity as an assay of p53 activity, and (3) estimates of the percentage of infected cells by dual parameter analysis (p53 versus mdm2). METHODS: Three prostate cancer cell lines (PC-3, LNCaP, DU 145) that are null, wild-type, and mutant for p53, respectively, and two ovarian cancer cell lines (PA1, MDAH 2774) that are wild-type and mutant for p53, respectively, were tested for immunoreactivity and lack of cross-reactivity with the monoclonal antibodies, DO-7 (anti-p53) and IF2 (anti-mdm2). Optimal dual staining conditions for a flow cytometric assay employing saturating levels of antibody were developed and tested by infection of PC-3, PA1, and MDAH 2774 with Ad-p53 or a control virus, Ad-luc. Dual staining with DO-7 and propidium iodide was used to determine any biological effect of the transferred gene. RESULTS: Neither DO-7 nor IF2 showed appreciable cross-reactions by Western blot analysis of representative prostate or ovarian cell lines. By flow cytometric titration, DO-7 appears to be a high avidity antibody (saturation staining of 10(6) DU 145 cells with 0.5ug) whereas IF2 appears less so (optimum signal to noise ratio at 1ug/10(6) cells). Infection with Ad-p53 was detected at 6 to 48 hours post infection as a uniform relative increase in p53 levels over background p53 levels. Coincident increases in mdm2 immunoreactivity were also detected. DNA content measurements of PA1 and MDAH 2774 cells indicated that G1 arrest and/or apoptosis occurred subsequent to Ad-p53 infection. p53 and mdm2 levels and DNA content distributions for Ad-luc infected cells were equivalent to uninfected cells. CONCLUSIONS: A flow cytometric approach to measure the efficacy of an Ad-p53 gene therapy vector was developed that detects not only the gene transferred but also the activity of the transferred gene product.

Adenoviridae↗
PubMed1999

Loss of mitochondrial membrane potential is dependent on the apoptotic program activated: prevention by R-2HMP.

Recent evidence suggests that the mitochondrial membrane potential begins to decrease well before the cells commit to apoptotic death. By using cultured cerebellar granule cells, two types of apoptosis can be induced, one by adding cytosine arabinoside (Ara-c; p53-dependent apoptosis) and one by lowering the K(+) concentrations of the medium (p53-independent apoptosis). Cultures show clear signs of increased apoptosis (chromatin condensation as visualized with bis-benzamide) after 12 hr which increases with time up to 24 hr. A fluorescent probe, chloromethyl-tetramethylrhodamine methyl ester (CMTMR), a lipophilic, potentiometric dye, which when introduced into the media accumulates within mitochondria in proportion to the mitochondrial membrane potential, was added at various time points after the induction of apoptosis. In Ara-c-induced apoptosis, there was a shift in the distribution of cell populations towards low-intensity CMTMR fluorescence, whereas in control and low-K(+) cultures, there was no such shift. This effect was observed as early as 6 hr after adding Ara-c. The antiapoptotic drug R-N-2-heptyl-N-methylpropargylamine hydrochloride (R-2HMP) reversed this loss of mitochondrial membrane potential in Ara-c-induced apoptosis; the effect was antagonized by the S-2HMP.

Alkynes↗
PubMed1999

Genomic structure, chromosomal mapping, and promoter region analysis of murine uridine phosphorylase gene.

Uridine phosphorylase (UPase) plays an important role in the activation of 5-fluorouracil and in the regulation of tissue and plasma concentration of uridine, a potential biochemical modulator of 5-fluorouracil therapy. UPase expression is affected by the c-H-ras oncogene and various cytokines through unknown mechanisms. To understand its expression and regulation, we cloned the murine UPase gene, defined its genomic organization, determined its 5'- and 3'-end flanking sequences, and evaluated the promoter activity. The UPase gene contains nine exons and eight introns, spanning a total of approximately 18.0 kb. Its promoter lacks canonical TATA and CCAAT boxes, although a CAATAAAAA TATA-like box is seen from -41 to -49. Furthermore, IFN regulatory factor 1, c/v-Myb, and p53 binding sites are present in the promoter region, indicating that UPase expression may be directly regulated by cytokines and oncogene products. The 1.2-kb flanking fragment showed promoter activity driving the expression of the luciferase gene in various mammalian cells. A TGGGG repeat sequence is seen in the 3'-end flanking region. This element is considered to be a potential recombination consensus hot spot that may contribute to the encoding of different UPase isoforms present in different tissues, both normal and neoplastic.

3' Untranslated Regions↗
PubMed1999

[Production of HBV surface antigen-specific target cell].

OBJECTIVE: To analyze the hepatitis B virus surface antigen (HBsAg)-specific cytotoxic T-cell (CTL) response during hepatitis development and investigate the effect of some factors on CTL response. METHODS: The recombinant retrovirus plasmid PLXSN-S was tranferred into PA317 by electroporation and the pseudoviruses produced from PA317 were used to infect EL4. Clones which highly expressed HBsAg were selected with limited dilution. RESULTS: A clone expressing-HBsAg the highest (A = 0.85 in supernatant at 48th hour) was obtained which steadly expressed HBsAg in vitro after at least 100 passages. It worked very well when used as target cells in CTL response after C57 mice immunized with PLXSN-S and recombinant adenovirus vector (rAdv-B7-2-S). CONCLUSION: We constructed HBsAg-specific target cell line which steadly expressed HBsAg. It may play an important role in HBsAg CTL response and immunopathogenetic mechanisms of hepatitis B.

Animals↗
PubMed1999

Immunohistochemical detection of the lipid peroxidation product 4-hydroxynonenal after experimental brain injury in the rat.

This study examined the accumulation of the cytotoxic lipid peroxidation product 4-hydroxynonenal (HNE) after lateral fluid percussion (FP) brain injury in rats. A diffuse distribution of HNE-immunoreactivity (HNE-ir) was observed in the cortex and hippocampus of the ipsilateral, but not of the contralateral, hemisphere at 30 min, 6 h, 24 h, and 48 h after brain injury. The HNE-ir was well-localized in cell bodies of the ipsilateral cortex and the CA3 pyramidal layer in the ipsilateral hippocampus. Because HNE's interaction with certain proteins causes protein dysfunction and HNE, in vitro, causes neuronal cell damage, the present results suggest that HNE's interaction with neuronal proteins may contribute to neuronal damage in the ipsilateral cortex and hippocampus after brain injury.

Aldehydes↗
PubMed1999

The genomic organization and polymorphism analysis of the human Niemann-Pick C1 gene.

Niemann-Pick C (NP-C) is a fatal autosomal recessive storage disorder characterized by progressive neurodegeneration and variable hepatosplenomegaly. At the cellular level, cells derived from an affected individual accumulate unesterified cholesterol in lysosomes when cultured with low-density lipoprotein. The NP-C gene was identified at 18q11. The transcript is 4.9 kb encoding a 1278-amino-acid protein. We have defined the genomic structure of NPC1 along with the 5' flanking sequence. The NPC1 gene spans greater than 47 kb and contains 25 exons. Exons range in size from 74 to 788 bp with introns ranging in size from 0.097 to 7 kb. All intron/exon boundaries follow the GT/AG rule. The 5' flanking sequence has a CpG island containing multiple Sp1 sites indicative of a promoter region. The CpG island is located in the 5' flanking sequence, exon 1 and the 5' end of intron 1. We have also identified multiple single nucleotide polymorphisms in the coding and intronic sequences.

Base Sequence↗
PubMed1999

Immortalization of human prostate epithelial cells by HPV 16 E6/E7 open reading frames.

BACKGROUND: The exact pathogenesis for prostate cancer is not known. Progress made in prostate cancer research has been slow, largely due to the lack of suitable in vitro models. Here, we report our work on the immortalization of a human prostate epithelial cell line and show that it can be used as a model to study prostate tumorigenesis. METHODS: Replication-defective retrovirus harboring the human papillomavirus (HPV) type 16 E6 and E7 open reading frames was used to infect primary human prostate epithelial cells. Polymerase chain reaction, followed by Southern hybridization for the HPV 16 E6/E7, Western blot for prostatic acid phosphatase, telomeric repeat amplification protocol assay for telomerase activity, two-dimensional gels for cytokeratins, and cytogenetic analysis were undertaken to characterized the infected cells. RESULTS: The retrovirus-infected cell line, HPr-1, continued to grow in culture for more than 80 successive passages. Normal primary cells failed to proliferate after passage 6. HPr-1 cells bore close resemblance to normal primary prostate epithelial cells, both morphologically and biochemically. However, they possessed telomerase activity and proliferated indefinitely. Cytogenetic analysis of HPr-1 cells revealed a human male karyotype with clonal abnormalities and the appearance of multiple double minutes. CONCLUSIONS: The HPr-1 cells expressed prostatic acid phosphatase and cytokeratins K8 and K18, proving that they were prostate epithelial cells. They were benign in nude mice tumor formation and soft agar colony formation assay. The HPr-1 cell line is an in vitro representation of early prostate neoplastic progression.

Acid Phosphatase↗
PubMed1999

Characterization of PECI, a novel monofunctional Delta(3), Delta(2)-enoyl-CoA isomerase of mammalian peroxisomes.

We report here the identification and characterization of human and mouse PECI, a novel gene that encodes a monofunctional peroxisomal Delta(3),Delta(2)-enoyl-CoA isomerase. Human and mouse PECI were identified on the basis of their sequence similarity to Eci1p, a recently characterized peroxisomal Delta(3),Delta(2)-enoyl-CoA isomerase from the yeast Saccharomyces cerevisiae. Cloning and sequencing of the human PECI cDNA revealed the presence of a 1077-base pair open reading frame predicted to encode a 359-amino acid protein with a mass of 39.6 kDa. The corresponding mouse cDNA contains a 1074-base pair open reading frame that encodes a 358-amino acid-long protein with a deduced mass of 39.4 kDa. Northern blot analysis demonstrated human PECI mRNA is expressed in all tissues. A bacterially expressed form of human PECI catalyzed the isomerization of 3-cis-octenoyl-CoA to 2-trans-octenoyl-CoA with a specific activity of 27 units/mg of protein. The human and mouse PECI proteins contain type-1 peroxisomal targeting signals, and human PECI was localized to peroxisomes by both subcellular fractionation and immunofluorescence microscopy techniques. The potential roles for this monofunctional Delta(3),Delta(2)-enoyl-CoA isomerase in peroxisomal metabolism are discussed.

Amino Acid Sequence↗
PubMed1999

Nucleoside diphosphate kinase associated with membranes modulates mu-opioid receptor-mediated [35S]GTPgammaS binding and agonist binding to mu-opioid receptor.

The role of nucleoside diphosphate kinase (NDKP), which converts GDP to GTP, in the coupling of mu-opioid receptors to G protein was investigated in membranes of Chinese hamster ovary cells stably transfected with the cloned rat mu-opioid receptor (rmor). Endogenous NDPK activity in membranes was determined to be 0.60+/-0.02 micromol/mg protein/30 min UDP (at 10 mM), a competitive substrate of NDPK for GDP with no effect on guanine nucleotide binding to G proteins, reduced basal [35S]GTPgammaS binding and unmasked morphine-stimulated [35S]GTPgammaS binding to pertussis toxin-sensitive G proteins, indicating that [35S]GTPgammaS binding to NDPK accounts for part of its high basal binding. UDP increased the extent of morphine-induced increase in [35S]GTPgammaS binding in the presence of GDP, most likely by reducing basal binding and inhibiting conversion of GDP to GTP. ATP greatly reduced morphine-induced increase in [35S]GTPgammaS binding, whereas AMP-PCP (adenylyl-(beta,gamma-methylene)-diphosphoate tetralithium salt), which cannot serve as the phosphate donor for NDPK, did not, demonstrating that effects of ATP is mediated by the NDPK product GTP. In addition, GDP and ATP increased the Kd and lowered the Bmax of the agonist [3H]DAMGO ([D-Ala2,N-Me-Phe4,Gly5ol]-Enkephalin) for the mu-opioid receptor and GDP alone increased Kd, most likely through their conversion to GTP by NDPK. Addition of exogenous NDPK enhanced the inhibitory effects of GDP and combined GDP and ATP on [3H]DAMGO binding. Thus, NDPK appears to play a role in modulating signal transduction of and agonist binding to mu-opioid receptors.

Adenosine Triphosphate↗
PubMed1999

Transcriptional regulation of a receptor protein tyrosine phosphatase gene hPTP-J by PKC-mediated signaling pathways in Jurkat and Molt-4 T lymphoma cells.

The recently cloned type II receptor protein tyrosine phosphatase (RPTP) gene hPTP-J is a new member of the MAM (meprin, A5, PTPmicro) domain subfamily. We previously reported that hPTP-J mRNA was detected significantly in Jurkat T lymphoma cells and its expression was completely down-regulated by phorbol myristate acetate (PMA). In this study, we investigated what signaling pathways/molecules are involved in the transcriptional regulation of hPTP-J expression in Jurkat and Molt-4 T cell lines. The hPTP-J transcription was transiently up-regulated 20 min after the addition of PMA (20 ng/ml) to the Jurkat culture, followed by the complete down-regulation in 8 h after PMA addition. The transient up-regulation and the complete down-regulation induced by PMA was blocked by a PKC-specific inhibitor, GF109203X, suggesting that the regulatory effect of PMA on the hPTP-J transcription depends on protein kinase C activation. hPTP-J transcription was down-regulated not only by PMA but also by several signaling modulators including 1-oleoyl-2-acetylglycerol, forskolin, orthovanadate, manumycin and okadaic acid. Therefore, several signaling molecules such as protein tyrosine phosphatases, PP2A/CaMKIV and Ras are required for hPTP-J transcription in Jurkat and Molt-4 cells.

Cyclic AMP↗
PubMed1999

Translating clinical trial results into practice: the effect of an AIDS clinical trial on prescribed antiretroviral therapy for HIV-infected pregnant women.

BACKGROUND: The success of Pediatric AIDS Clinical Trials Group (PACTG) Protocol 076 in preventing vertical HIV transmission prompted intensive efforts to inform lay-persons and professionals about the trial's results. OBJECTIVE: To explore community responsiveness to these efforts by assessing temporal, maternal, and health care factors associated with prescribed antiretroviral therapy before and after PACTG Protocol 076. DESIGN: Retrospective cohort study. SETTING: New York State Medicaid program. PATIENTS: 2607 HIV-infected women who delivered a living child between January 1993 and September 1996. MEASUREMENTS: Adjusted odds of being prescribed antiretroviral treatment in the second or third trimester for women who delivered in period 1 (during the trial [January 1993 to February 1994]), period 2 (after the trial's end and announcement of the results to publication of the results [March 1994 to November 1994]), and period 3 (after publication of the trial results [December 1994 to September 1996]). RESULTS: The adjusted odds of being prescribed antiretroviral therapy increased 21% per month in period 2 and decreased to 3% per month in period 3. In all time periods, the adjusted odds of being prescribed antiretroviral therapy were at least 60% greater (P < 0.05) for women who were treated at an institution that performed HIV clinical trials, received HIV-focused ambulatory care, or had adequate prenatal care visits. After the trial, women receiving methadone treatment had at least twofold (95% CI, 1.5- to 4.3-fold) greater adjusted odds of being prescribed antiretroviral therapy than women who did not take any illicit drugs. Latin-American women, older women, and women born in the United States had greater adjusted odds (P < 0.05) of being prescribed treatment in period 3. CONCLUSION: Community practice responded rapidly to efforts to disseminate the results of PACTG Protocol 076; however, the absolute increase in prescribed therapy was greatest for women who had adequate prenatal visits or were receiving HIV-focused care, care at a site that performed clinical trials, or methadone therapy.

Adult↗
PubMed1999

Identification of RPE65 in transformed kidney cells.

The protein RPE65 has an important role in retinoid processing and/or retinoid transport in the eye. Retinoids are involved in cell differentiation, embryogenesis and carcinogenesis. Since the kidney is known as an important site for retinoid metabolism, the expression of RPE65 in normal kidney and transformed kidney cells has been examined. The RPE65 mRNA was detected in transformed kidney cell lines including the human embryonic kidney cell line HEK293 and the African green monkey kidney cell lines COS-1 and COS-7 by reverse transcription PCR. In contrast, it was not detected in human primary kidney cells or monkey kidney tissues under the same PCR conditions. The RPE65 protein was also identified in COS-7 and HEK293 cells by Western blot analysis using a monoclonal antibody to RPE65, but not in the primary kidney cells or kidney tissues. The RPE65 cDNA containing the full-length encoding region was amplified from HEK293 and COS-7 cells. DNA sequencing showed that the RPE65 cDNA from HEK293 cells is identical to the RPE65 cDNA from the human retinal pigment epithelium. The RPE65 from COS-7 cells shares 98 and 99% sequence identity with human RPE65 at the nucleotide and amino acid levels, respectively. Moreover, the RPE65 mRNA was detected in three out of four renal tumor cultures analyzed including congenital mesoblastic nephroma and clear cell sarcoma of the kidney. These results demonstrated that transformed kidney cells express this retinoid processing protein, suggesting that these transformed cells may have an alternative retinoid metabolism not present in normal kidney cells.

Amino Acid Sequence↗
PubMed1999

A novel labeling approach supports the five-transmembrane model of subunit a of the Escherichia coli ATP synthase.

Cysteine mutagenesis and surface labeling has been used to define more precisely the transmembrane spans of subunit a of the Escherichia coli ATP synthase. Regions of subunit a that are exposed to the periplasmic space have been identified by a new procedure, in which cells are incubated with polymyxin B nonapeptide (PMBN), an antibiotic derivative that partially permeabilizes the outer membrane of E. coli, along with a sulfhydryl reagent, 3-(N-maleimidylpropionyl) biocytin (MPB). This procedure permits reaction of sulfhydryl groups in the periplasmic space with MPB, but residues in the cytoplasm are not labeled. Using this procedure, residues 8, 27, 37, 127, 131, 230, 231, and 232 were labeled and so are thought to be exposed in the periplasm. Using inside-out membrane vesicles, residues near the end of transmembrane spans 1, 64, 67, 68, 69, and 70 and residues near the end of transmembrane spans 5, 260, 263, and 265 were labeled. Residues 62 and 257 were not labeled. None of these residues were labeled in PMBN-permeabilized cells. These results provide a more detailed view of the transmembrane spans of subunit a and also provide a simple and reliable technique for detection of periplasmic regions of inner membrane proteins in E. coli.

Amino Acid Sequence↗
PubMed1999

[Effects of high manganese on cerebral development of the offspring of rats].

Pregnant rats were divided into three groups. Two groups are exposed to manganese from drinking water contaminated with manganese in 10 and 2 g/L respectively. Cerebral development of the offspring of rats was studied. The results are as follows. (1) The thickness of frontal and parental cortex of high dose Mn-exposed groups was significantly reduced, but glial fibrillary acid protein (GFAP) and the densities of its products were increased. (2) Cingular cortex was thickened, GFAP and the density of its products of cingular cortex was increased in both Mn-exposed groups compared with the control group. (3) The area, GFAP and the densits of its products of corpus callosium in the high Mn-exposed group were significantly increased compared with those in both low Mn-exposed and control groups.

Animals↗