Biomedical subjects

C X Zhang

Publications and source records attributed to C X Zhang.

At least 55 records · Page 3Linked to original sources

PubMed1995

Expression of the complementary-strand transcripts from BamHI-A region of the Epstein-Barr virus genome in various induced virus-carrying B cell lines.

The complementary-strand transcripts from Epstein-Barr virus BamHI-A-I fragments (also called the BARF0 RNAs) were first found in a nasopharyngeal carcinoma passaged in nude mice, c15, and soon proved to exist in various EBV-associated tumors and virus-carrying B cell lines. The data from previous studies revealed that the BARF0 transcripts have a highly spliced structure, whereas the evidence about their in vivo translational products remains few. The BARF0 RNA is also somehow considered as a new member of the viral latent transcripts. In order to know further about its transcriptional profile, we investigated its transcription in several EBV-carrying B cell lines during different viral stages. Our results show that (1) at least some of the BARF0 transcripts are transcribed during the viral lytic stage in the tested inducible lines; (2) the major lytic BARF0 mRNA appears heterogeneous in size (2.5 to 4.2 kb) among different lines; (3) in P3HR1 and Akata lines, the major BARF0 transcript is highly spliced and sensitive to both an inhibitor of the viral DNA polymerase and of protein synthesis. The identification of such lytic BARF0 RNAs may help us to understand further about their complex gene expression.

Animals↗

PubMed1995

Asbestos causes DNA strand breaks in cultured pulmonary epithelial cells: role of iron-catalyzed free radicals.

Asbestos causes pulmonary fibrosis and various malignancies by mechanisms that remain uncertain. Reactive oxygen species in part cause asbestos toxicity. However, it is not known whether asbestos-induced free radical production causes alveolar epithelial cell (AEC) cytotoxicity by inducing DNA strand breaks (DNA-SB). We tested the hypothesis that asbestos-induced AEC injury in vitro is due to iron-catalyzed free radical generation, which in turn causes DNA-SB. We found that amosite asbestos damages cultured human pulmonary epithelial-like cells (WI-26 cells) as assessed by 51Cr release and that an iron chelator, phytic acid (500 microM), attenuates these effects. A role for iron causing these effects was supported by the observation that ferric chloride-treated phytic acid did not diminish WI-26 cell injury. Production of hydroxyl radical-like species (.OH) was assessed based upon the .OH-dependent formation of formaldehyde (HCHO) in the presence of dimethyl sulfoxide. A variety of mineral dusts induced significant levels of .OH formation (nmol HCHO at 30 min: carbonyl iron, 85 +/- 21; amosite asbestos, 14 +/- 2; chrysotile asbestos, 7 +/- 1; titanium dioxide, 2.5 +/- 0.5). Phytic acid significantly diminished the asbestos-induced .OH production. DNA damage to AEC was assessed by the alkaline unwinding, ethidium bromide fluorometric technique. Hydrogen peroxide caused dose-dependent DNA-SB in WI-26 cells after a 30-min exposure period [50% effective dose (ED50): 5 microM] that was similar to other cell lines. Amosite asbestos induced dose-dependent DNA-SB in WI-26, A549, and primary isolated rat alveolar type II cells maintained in culture for 7-10 days (alveolar type I-like). Lower doses of amosite (0.5-5 micrograms/ml or 0.25-2.5 micrograms/cm2) caused significant WI-26 cell DNA-SB after prolonged exposure periods (> or = 2 days). Phytic acid ameliorated DNA damage in all three cultured AEC. There was a direct correlation between mineral dust-induced .OH production at 30 min and DNA-SB in WI-26 cells at 4 h (P < 0.0005). These data suggest that mineral dusts can be directly genotoxic to relevant target cells of asbestos, AEC. Furthermore, these results provide additional support for the premise that iron-catalyzed free radicals mediate asbestos-induced pulmonary toxicity.

Asbestos↗

PubMed1994

[A study on changes of plasma endothelin-1 level in patients with chronic cor pulmonale].

The level of plasma endothelin-1 (ET-1) was measured with radioimmunoassay in 36 patients with chronic pulmonale before and after treatment. The results showed that ET-1 level was significantly higher in cor pulmonale patients (P < 0.001) and decreased significantly after treatment (P < 0.001), but was still higher than that in controls (P < 0.002). There was significant negative correlation between PaO2, pH and ET-1 level. A significant positive correlation was found between ET-1 level and PaCO2. The results suggest that ET-1 may play an important role in the pathophysiological process of chronic cor pulmonale and the drugs which can influence plasma ET-1 level may be used in the treatment of the disease.

Aged↗

PubMed1994

[Hepatitis C virus RNA in tumor tissues of Chinese liver cancer patients].

A total of 38 specimens of liver cancer and pericancerous tissues from 30 hepatocellular carcinoma patients were studied for hepatitis C virus (HCV) RNA by RT-PCR using primers from the s'non-coding regions of HCV viral genome. Serum anti-HCV of these patients was also assayed as a marker of infection. The results showed that 10/30 (33.3%) hepatocellular carcinoma (HCC) patients were infected by HCV, while 23/30 (76.7%) by hepatitis B virus (HBV). The HCV RNA from liver cancer tissues were characterized by type II and III through restriction enzyme digestion. Sequencing of the 5'-NC regions amplified revealed that this region was conserved. Since 8 of the 10 HCV infected HCC patients were coinfected with HBV, chronic infection caused by HCV and HBV might be one of the factors leading to HCC.

Adult↗

PubMed1993

Micellar electrokinetic capillary chromatography theory based on conventional chromatography.

From the definitions of retention time (tR) and resolution (Rs) in conventional chromatography, two fundamental equations for the retention behaviour and resolution of neutral solutes are derived and proved to be valid in all cases of micellar electrokinetic capillary chromatography (MECC). Two parameters, phase velocity ratio (Pr) and column availability (Aco), are introduced to reveal clearly the relationships and differences between MECC and conventional chromatography. The tR and Rs values may be either positive or negative in MECC. A negative tR indicates that the solute migrates toward the positive electrode and a positive tR toward the negative electrode. Rs > 0 means that the solute with a smaller value of the capacity factor (k') in the pair of solutes reaches the detector first, while Rs < 0 means that the elution order is the opposite. MECC can be classified into eight cases depending on the values of Pr for convenience of discussion. So far, MECC was usually performed in case IV and the resolution was poorer than that in conventional chromatography for given values of theoretical plate number, selectivity and k'. However, a better resolution can be obtained in cases II, VI and VIII when Pr < (1-k')/2. Cases VI, VIII and II are preferable to case IV for high resolution and should be more frequently employed in the future.

Chemical Phenomena↗

PubMed1993

Crystallization and preliminary X-ray diffraction studies of Theiler's virus (GDVII strain).

Theiler's murine encephalomyelitis virus (TMEV) is a member of the picornavirus family. Mice infected with TMEV serve as models for the study of human neurological diseases including multiple sclerosis. Preparations of the GDVII strain of Theiler's virus have been crystallized using the hanging drop technique. When exposed to high intensity synchrotron radiation, these monoclinic crystals diffracted X-rays to at least 3.0 A resolution. The unit cell has a C-centered lattice with dimensions: a = 575.2 A, b = 324.0 A and c = 558.4 A, beta = 108.2 degrees. The molecular mass and cell dimensions imply that there is an entire virus particle per asymmetric unit, suggesting the presence of 60-fold non-crystallographic redundancy. This GDVII crystal form appears to be suitable for high-resolution structure determination.

Crystallization↗

PubMed1993

Determination of 3-methylflavone-8-carboxylic acid, the main metabolite of flavoxate, in human urine by capillary electrophoresis with direct injection.

The effects of tetraalkylammonium salts and sodium dodecyl sulphate on the migration behaviour of human urinary components and other negatively charged or neutral solutes were investigated. The sulphate acted mainly on hydrophobic and positively charged substances, whereas the ammonium salts acted mainly on negatively charged solutes. By choosing the components of the eluent carefully, the free and conjugate forms of 3-methylflavone-8-carboxylic acid (MFA) in human urine, the major metabolites of flavoxate, could be simultaneously determined without pretreatment, using fenprofen as an internal standard. The calibration curve of MFA was linear in the range 1-50 micrograms/ml and the detection limit was 0.2 microgram/ml, which covered the urine levels encountered in pharmacokinetic studies. The intra-day and inter-day precisions of the method, expressed as the relative standard deviation, were less than 2 and 3%, respectively. This method was successfully applied to an excretion study of MFA in eight healthy volunteers, and the results were in agreement with data in the literature obtained by gas chromatography.

Adult↗

PubMed1993

Analysis of Epstein-Barr virus gene transcription in lymphoma induced by the virus in the cottontop tamarin by construction of a cDNA library with RNA extracted from a tumour biopsy.

Inoculation of the cottontop tamarin with Epstein-Barr virus (EBV) gives rise to the development of mono- and/or oligoclonal large cell malignant lymphoma. A cDNA library was generated with the RNA extracted from an EBV-induced tamarin lymphoma biopsy in order to study the transcripts expressed in the tumour tissue. Fifteen EBV-specific cDNA clones were localized in the corresponding viral genomic fragments. Among them, two correspond to the EBNA-2 gene, and two others to the latent membrane protein gene. The majority of the cDNA clones were localized in the BamHI A fragment which has not been associated with latent expression. Furthermore, cDNAs were also found from the BamHI D and I fragments. Sequence analysis of the cDNAs localized in BamHI A showed that they correspond to a rightward transcript in the BALF-3 region, with the one clone that was sequenced containing four exons and three introns. The above results were confirmed by testing three different biopsies with the rapid amplification of cDNA ends-PCR method.

Animals↗

PubMed1993

A potential transforming growth factor alpha/epidermal growth factor receptor autocrine circuit in placental cytotrophoblasts.

A potential autocrine loop involving transforming growth factor alpha (TGF-alpha) and the epidermal growth factor (EGF) receptor (EGFR) in benign placental cytotrophoblasts was examined. EGFR were localized to villous cytotrophoblasts and syncytiotrophoblasts in frozen sections throughout gestation using immunoperoxidase (IP) and autoradiography with 125I-EGF. EGF and TGF-alpha stimulated uptake of [3H]-thymidine in cultured cytotrophoblasts from first and second trimester placentae, demonstrating both functional EGFR and the mitogenic ability of either growth factor in these cells. Using IP, TGF-alpha was localized consistently throughout gestation to cytotrophoblasts with little or no staining of syncytiotrophoblasts in formalin-fixed sections. Variable staining of villous stromal cells and intense staining of maternal decidua were also observed. TGF-alpha production by cultured cytotrophoblasts was confirmed in vitro via IP analysis of cytotrophoblasts cultured in serum-free media and enzyme-linked immunosorbent assay analysis of cytotrophoblast serum-free conditioned media. The results suggest that a TGF-alpha/EGFR autocrine loop stimulates proliferation of benign cytotrophoblasts.

Cells, Cultured↗

PubMed1992

Three-dimensional structure of Theiler murine encephalomyelitis virus (BeAn strain).

Depending on the strain, Theiler murine encephalomyelitis virus (TMEV) may cause acute encephalitis or chronic demyelinating disease, which is associated with viral persistence in mice. Persistent central nervous system infection and demyelination by the less-virulent TMEV has provided a useful animal model for the human demyelinating disease multiple sclerosis. The less-virulent BeAn strain of TMEV was crystallized and its atomic structure was determined by x-ray crystallography. The alpha-carbon coordinates of the closely related Mengo virus were used to calculate the initial phases to 3.5 A resolution and the interpretable electron density map was produced by 10 cycles of 30-fold noncrystallographic molecular replacement averaging. The structure revealed a high degree of overall structural similarity to Mengo virus as well as substantial differences in the surface loops. These structural changes might be correlated with TMEV host-specific recognition, pH-related stability, and neurovirulence.

Animals↗

PubMed1992

Transcriptional expression of the viral genome in the Epstein-Barr virus-induced tamarin lymphoma and the corresponding lymphoblastoid tumour lines.

Inoculation of the cottontop tamarin with Epstein-Barr virus (EBV) invariably gives rise to mono- or oligoclonal large cell lymphoma occurring at multiple sites, and which resembles to a certain extent B cell lymphoma that occurs in the immunodeficient patient. The viral transcriptional pattern in tamarin tumour biopsies and in the corresponding tumour cell lines was investigated by means of the synthesis of radioactive single-stranded cDNA. It was found that the EBV transcripts came mainly from the fragments BamH1-H, BamH1-S, BamH1-A and EcoR1-Dhet. Transcripts from a few other early or late genes, namely BARF1, BSLF1/BMLF1, BBLF-4, BLLF1 and BXLF2, were also detected in one of the three biopsies tested. It would be important to characterize the transcripts that originate from the region where viral latent expression has not previously been observed. Our results also revealed that there is a sharp increase in EBV transcription in the tumour cell lines derived from the tamarin lymphomas. Simultaneously, the copy number of the viral genome was found to be amplified. Such a significant change in viral activity might be indicative of a close virus-host cell interaction in vivo.

Animals↗

PubMed1992

Mapping of B-cell epitopes on the polypeptide chain of the Epstein-Barr virus major envelope glycoprotein and candidate vaccine molecule gp340.

The Epstein-Barr virus (EBV) major envelope glycoprotein gp340 is the subject of current efforts to develop an EBV subunit vaccine. The importance of gp340-specific humoral immunity has been highlighted by studies of natural infection in humans and gp340 immunization of experimental animals. The former studies have demonstrated the presence of gp340-specific serum antibodies which mediate EBV neutralization, complement fixation, and antibody-dependent cellular cytotoxicity. The latter studies have often shown a correlation between the induction of gp340-specific EBV-neutralizing antibodies and protection from virus challenge. We have used a series of bacterial beta-galactosidase-gp340 fusion proteins and overlapping synthetic peptides from the gp340 open reading frame to map the positions of B-cell epitopes within the gp340 primary amino acid sequence. The data reported here indicate the presence of B-cell epitopes within the carboxy-terminal third of the gp340 polypeptide chain. These epitopes could not be detected with a peptide enzyme-linked immunosorbent assay, thereby suggesting that they are discontinuous. Affinity purification of antibodies with a gp340 fusion protein from the carboxy terminus of the gp340 polypeptide chain has been used to show that these antibodies are not EBV neutralizing in vitro. The consequences of these findings for future EBV vaccine development are considered.

Amino Acid Sequence↗

PubMed1991

Histopathologic comparison between human oral squamous cell carcinomas and their xenografts in nude mice.

Tumor portions were obtained from 11 oral squamous cell carcinomas and used to produce tumors in a xenogeneic gnotobiotic nude mouse model system. The tumors that developed were examined histologically. The cellular features and tumor growth patterns were compared between the original oral squamous cell carcinoma (T0) and the tumor that developed in the xenogeneic host (T1). The T1 tumors were more highly differentiated in comparison with the T0 tumors. The T1 tumors exhibited less cellular pleomorphism and a more uniform pattern of stratification. The cells in the T1 tumors exhibited an increased mitotic index but did not contain abnormal mitoses. The T1 tumors usually exhibited nodular growth patterns rather than the infiltrating pattern exhibited by the parenchyma of the T0 tumors. The desmoplastic reaction was markedly reduced in the T1 tumors. The results indicated that the gnotobiotic nude mouse model system either selects for or induces a more differentiated pattern of tumor growth than that found in the original human oral squamous cell carcinomas.

Adult↗

PubMed1991

Recombination between satellite and genomic RNAs of turnip crinkle virus.

New recombinant molecules formed from satellite and genomic RNAs of turnip crinkle virus (TCV) have been characterized. Known collectively as sat-RNA CX, these molecules are composed of a nearly full-length segment of a previously characterized TCV satellite RNA (sat-RNA D) at the 5' end joined to variable lengths of TCV genomic RNA 3' terminal sequence. Sat-RNA CX molecules fall into two classes: molecules of 420 to 435 bases and larger species of 501 to 506 bases. The TCV sequence at the junction of the larger molecules is purine-rich and is similar to a motif found at the 5' ends of the TCV satellite RNAs and at the junctions of some TCV defective interfering RNAs. The TCV sequence at the junction of the smaller sat-RNA CX molecules is pyrimidine-rich and is similar to the sequence at the right side of a junction of one TCV defective interfering RNA as well as sequence immediately downstream of the internal initiation site of the 1.45-kb TCV subgenomic RNA. We propose that the latter motif is another putative signal recognized by the viral replicase during the generation of defective interfering and recombinant RNAs in the TCV system.

Base Sequence↗

PubMed1991

Cell-specific expression of the glucocorticoid receptor within granular convoluted tubules of the rat submaxillary gland.

The submaxillary gland, a heterogeneous tissue composed essentially of two functionally distinct cell types (tubular epithelial and acinar), offers an interesting system in which to study the mechanisms of steroid-dependent growth and differentiation. One cell type, the granular convoluted tubular (GCT) cell, secretes a large number of physiologically important polypeptides, including epidermal and nerve growth factors. Two steroids, androgens and glucocorticoids, greatly influence the growth, differentiation, and secretory activity of GCT cells. Because glucocorticoids can partially mimic or potentiate androgen effects, it has been thought that glucocorticoids act via androgen receptors. Since the presence of glucocorticoid receptors is a prerequisite for glucocorticoid action, we have investigated the presence and cellular distribution of glucocorticoid receptors within the rat submaxillary gland. Binding experiments using [3H]dexamethasone revealed the presence of high affinity binding sites in rat submaxillary tissue homogenates. Most of these sites were specifically competed by dexamethasone, corticosterone, and a pure glucocorticoid agonist RU 28362. Neither testosterone nor dihydrotestosterone competed for glucocorticoid binding. The cellular distribution of glucocorticoid receptors within the submaxillary gland was investigated by immunocytochemistry, using two highly specific glucocorticoid receptor antibodies. The receptor was localized in the GCT cells, but not in the acinar cells of rat and mouse submaxillary tissue sections. In GCT cells, the glucocorticoid receptor colocalized with several secretory polypeptides, including epidermal growth factor, nerve growth factor, alpha 2u-globulin, and atrial natriuretic factor. These data suggest that the submaxillary gland is a target for glucocorticoid action and that at least part of the glucocorticoid effects on this tissue are mediated by bona fide glucocorticoid receptors.

Adrenalectomy↗

PubMed1990

[A new method of measuring the cytotoxicity by spectrophotometer for amalgam of different cupric quantity].

The authors developed a new measuring cytotoxic method for biomaterials using violet-spectrophotometer. The principle of this test is that the more the cell exist the higher the concentration of stain occur. Base this phenomena, we may calculate the relative growth rate and evaluated the toxic grade of the tested materials according to the absorption in spectrophotometer. The merits are that it can avoid subjective factor of the operator; collect all cells tested; be more sensitive, simple and accurate than the cell growth rate test, agar overlay test and molecular filter test. Three kinds of different cupric quantity amalgam are tested using new measuring cytotoxic method. The content of copper is 6%, 13% and 24.6% respectively. The result shows that there is no evident cytotoxicity for these three materials after 2 days, but the cytotoxicity appeared and increased as the contacting time between the extract of material and cell goes on. On the other hand, as the content of copper increased. The cell relative growth rate decreased. It indicated that there may be certain relationship between the content of copper and cell growth rate.

Animals↗

PubMed1989

[A comparison between Chinese panax quinquefolius and imported Panax quinquefolius--analysis of composition of essential oil in Panax quinquefolius].

The content of essential oil of Panax quinquefolius from different producing area ranges from 0.04 to 0.097%. Twenty compounds were separated and identified from these essential oils by GC-MS. Chinese Panax quinquefolius is similar to imported Panax quinquefolius in the composition and content of essential oil.

Gas Chromatography-Mass Spectrometry↗

PubMed1988

Pituitary-specific expression and glucocorticoid regulation of a proopiomelanocortin fusion gene in transgenic mice.

The product of a single gene encoding proopiomelanocortin (POMC) is differentially processed to produce corticotropin and alpha-melanotropin in anterior and intermediate pituitary cells, respectively. Hormonal control of POMC gene transcription and of corticotropin or alpha-melanotropin release is also tissue-specific; for example, glucocorticoids specifically inhibit anterior but not intermediate pituitary POMC transcription. Outside the pituitary gland, very low levels of POMC mRNAs are present in brain, testes, ovaries, and placenta. We have used transgenic mice to identify POMC 5' flanking sequences that are sufficient for tissue-specific expression and glucocorticoid regulation in anterior and intermediate pituitary cells. Three lines of transgenic mice were established, each carrying 50-75 copies (per cell) of a chimeric rPOMCneo gene constituted of rat POMC promoter sequences and of bacterial neomycin-resistance coding sequence. High levels of rPOMCneo transcripts were detected in pituitaries of mice from all three lineages. In situ hybridization revealed that the ratio of intermediate to anterior pituitary transcripts was similar for the transgene and endogenous POMC mRNA. rPOMCneo transcripts were not detected in any other tissue except at very low levels in the testes in two transgenic lines. Endogenous mouse POMC mRNA increased in response to depletion of plasma glucocorticoids (adrenalectomy) and decreased after glucocorticoid treatment; rPOMCneo transcripts were altered to the same extent by these treatments in all three lines. Intermediate pituitary and testicular rPOMCneo transgene expression was not altered by these treatments. Thus, no more than 769 base pairs of the rat POMC promoter are required for pituitary-specific expression and for specific glucocorticoid inhibition of the POMC gene in the anterior pituitary.

Animals↗