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Biomedical subjects

G Zhang

Publications and source records attributed to G Zhang.

At least 361 records · Page 20Linked to original sources
PubMed1998

Augmentation of recombinant fibronectin polypeptide CH50 on the antitumor function of macrophages.

We prepared an anti-metastatic polypeptide, recombinant fibronectin polypeptide CH50, and finished the preliminary identification of its functions. In this paper, we studied the effect of this polypeptide on the function of macrophages. CH50 can significantly augment the production of nitric oxide(NO) by macrophages in a dose-dependent manner. The continuous presence of CH50 had a much stronger effect. In the presence of CH50, the cytotoxicity of macrophages to melanoma B16/F1 cells was significantly enhanced, and a stronger effect was obtained if CH50 was present continuously. CH50 polypeptide and IFN-gamma have a synergistic effect on the production of NO by macrophages and the cytotoxicity of macrophages on tumor cells. In the in vivo experiments, CH50 can inhibit the growth of tumor cells, and have a better effect in the presence of IFN-gamma. Our results suggest that recombinant fibronectin polypeptide CH50 has two functions: one is to inhibit the metastasis of tumor cells, and the other one is to augment the function of macrophages. And this polypeptide will be potentially useful in tumor therapy.

Animals↗
PubMed1998

Effect of fragment Asp1961-Glu1978 in fibronectin on the expression of triple-domain polypeptide in E. coli.

Two plasmids were constructed and used to express two triple-domain recombinant polypeptide of human fibronectin (FN). The cDNAs in plasmids code for two polypeptides, CH62 (Pro1239-Ser1515 of FN linked with Ala1690-Val2049 through Met) and CH63 (CH62 without Ile1850-Glu1978). The expression level of CH62 in E. coli was very low, but that of CH63 was very high. The results suggests that Asp1961-Glu1978 in FN is a key sequence influencing the expression of triple-domain polypeptide in E. Coli. After being dissolved and renatured, CH63 can be purified by heparin-agarose affinity chromatography. Both of the cell-binding domains in the recombinant polypeptide were functional. The production of CH63 provides a fundamental basis for further study of recombinant products with better anti-metastasis function.

Animals↗
PubMed1998

Effect of sulfhydryl oxidoreduction on permeability of cardiac tetrodotoxin-insensitive sodium channel.

Effects of sulfhydryl oxidizing and reducing agents on permeability of the tetrodotoxin (TTX)-insensitive Na-channel were investigated in guinea-pig ventricular myocytes using the whole-cell patch-clamp technique. Mercury chloride (HgCl2) at 1-100 microM irreversibly blocked Na+ currents with no significant changes in the gating kinetics. In contrast, the hydrophilic sulfhydryl oxidizing agent, thimerosal at 50-100 microM little affected Na+ permeation through the Na-channel. The Hg2+-induced block of Na+ current could be readily reversed by 1,4-dithiothreitol (DTT), an agent that reduces disulfide bonds. These results indicate that the formation of sulfur-Hg-sulfur bridge is essential for Hg2+ block. Pretreatment with DTT prevented the Hg2+ block of Na+ current, whereas Zn2+ and Cd2+ retained their abilities to block Na+ current after DTT treatment. An application of Zn2+ or Cd2+ resulted in the restoration of Hg2+ sensitivity of the DTT-treated channel. A conformational model for the Na-channel with multiple free sulfhydryl groups and native disulfide bonds could account for our experimental data regarding the effects of sulfhydryl modifying agents on the channel permeability. We conclude that the cardiac TTX-insensitive Na-channel contains functionally important free sulfhydryl groups and disulfide bonds which are accessible from the extracellular side by an aqueous pathway. These sulfhydryls would be capable of modulating the Na-channel permeability by affecting the conformation of channel pore region.

Algorithms↗
PubMed1998

Orphanin FQ is the major OFQ1-17-containing peptide produced in the rodent and monkey hypothalamus.

In order to investigate the processing of OFQ containing peptides in the hypothalamus we have developed a sensitive and quantitative radioimmunoassay for OFQ. We fractionated rodent and monkey hypothalamic extracts by reversed-phase high performance liquid chromatography and found that the extracts contained multiple peaks of OFQ immunoreactivity with the major peak co-eluting with synthetic OFQ1-17. Mouse hypothalamic extracts were also fractionated by SDS-PAGE to determine the apparent molecular weights of molecules containing the OFQ peptide. Multiple peaks of OFQ immunoreactivity, ranging in size from approximately 1 to 30 kilodaltons, were detected by this method. These results suggest that OFQ1-17 is processed to smaller peptides in mouse and monkey hypothalamic neurons.

Amino Acid Sequence↗
PubMed1998

Study on a fluorescence-enhanced system of 1,2,4-trihydroxyanthroquinone-Be(2+)-DNA.

Fluorescence-enhancement of 1,2,4-trihydroxyanthroquinone (THAQ)-Be2+ complex enhanced by nucleic acid was studied. Experimental results revealed that double-stranded DNA can enhance remarkably the fluorescence intensity of THAQ-Be2+, while RNA cannot. Based on these results, a fluorescence method for the selective determination of DNA in the presence of RNA was developed. Maximum fluorescence intensity was found in the pH range 3.6-4.5 with maximum excitation and emission wavelengths at 510 and 565 nm, respectively. Under optimum conditions, the calibration graph was linear over the range 0.08-18 micrograms ml-1 for double-stranded fish sperm DNA (fsDNA) with the detection limit being 2.75 x 10(-8) g ml-1. The method was applied for the determination of DNA in synthetic samples. The relative S.D. for five replicates was within 4%. In addition, the interaction mechanism of THAQ-Be2+ with DNA was also discussed.

Anthraquinones↗
PubMed1998

Caspase inhibition prevents staurosporine-induced apoptosis in CHO-K1 cells.

Apoptosis is a distinct form of programmed cell death that plays an important role in many biological processes. Although the phenotypes of apoptotic cells are well documented, little is known of the central mechanism leading to programmed cell death. Over the past few years, a number of ICE/CED-3 family proteases (also termed caspases) have been discovered and implicated as the common effectors of apoptosis. In this report, we demonstrate that induction of apoptosis in CHO-K1 cells by staurosporine, a broad spectrum inhibitor of protein kinases, results in an increase in DEVD-dependent protease activity. These events were followed by nuclear DNA fragmentation and cell death. Inhibition of the DEVD-cleaving activity by a synthetic tetrapeptide inhibitor DEVD-CHO, blocked staurosporine-induced downstream apoptotic phenotypes, such as morphological characteristics and DNA fragmentation. These results suggest that staurosporine-induced apoptosis in CHO-K1 cells is mediated through the CPP32/caspase-3-like cysteine proteases.

Journal Article↗
PubMed1998

An investigation of neural networks in thyroid function diagnosis.

We investigate the potential of artificial neural networks in diagnosing thyroid diseases. The robustness of neural networks with regard to sampling variations is examined using a cross-validation method. We illustrate the link between neural networks and traditional Bayesian classifiers. Neural networks can provide good estimates of posterior probabilities and hence can have better classification performance than traditional statistical methods such as logistic regression. The neural network models are further shown to be robust to sampling variations. It is demonstrated that for medical diagnosis problems where the data are often highly unbalanced, neural networks can be a promising classification method for practical use.

Bayes Theorem↗
PubMed1998

DNA vector chemistry: the covalent attachment of signal peptides to plasmid DNA.

The nuclear entry of exogenous DNA in mammalian cells is critical for efficient gene transfer. A novel technique was developed for the covalent attachment of cationic peptides to double-stranded DNA using a cyclo-propapyrroloindole cross-linker. The attachment of the SV40 large T antigen nuclear localization signal peptide induced the nuclear accumulation of the conjugated DNA in digitonin-permeabilized cells via the classical pathway for the nuclear transport of karyophilic proteins. Increased nuclear uptake of the modified DNA, however, did not occur after it was microinjected into the cytoplasm of cultured cells. This demonstration that the covalent modification of DNA with a signal peptide alters its behavior and interaction with other cellular factors portends the potential of DNA vector chemistry to enhance the efficiency of cellular gene transfer.

Antigens, Polyomavirus Transforming↗
PubMed1998

A cytosolic factor is required for mitochondrial cytochrome c efflux during apoptosis.

Treatment of HL-60 cells with staurosporine (STS) induced mitochondrial cytochrome c efflux into the cytosol, which was followed by caspase-3 activation and apoptosis. Consistent with these observations, in vitro experiments demonstrated that, except for cytochrome c, the cytosol of HL-60 cells contained sufficient amounts of all factors required for caspase-3 activation. In contrast, treatment of HCW-2 cells (an apoptotic-resistant HL-60 subclone) with STS failed to induce significant amounts of mitochondrial cytochrome c efflux, caspase-3 activation, and apoptosis. In vitro assays strongly suggested that a lack of cytochrome c in the cytosol was the primary limiting factor for caspase-3 activation in HCW-2 cells. To explore the mechanism which regulates mitochondrial cytochrome c efflux, we developed an in vitro assay which showed that cytosolic extracts from STS-treated, but not untreated, HL-60 cells contained an activity, which we designated 'CIF' (cytochrome c-efflux inducing factor), which rapidly induced cytochrome c efflux from HL-60 mitochondria. In contrast, there was no detectable CIF activity in STS-treated HCW-2 cells although the mitochondria from HCW-2 cells were responsive to the CIF activity from STS-treated HL-60 cells. These experiments have identified a novel activity, CIF, which is required for cytochrome c efflux and they indicate that the absence of CIF is the biochemical explanation for the impaired ability of HCW-2 cells to activate caspase-3 and undergo apoptosis.

Apoptosis↗
PubMed1998

The efficient expression of intravascularly delivered DNA in rat muscle.

Previous studies have demonstrated that muscle can take up and express naked DNA or RNA. This study demonstrates that the pDNA can be delivered to and expressed within skeletal muscle when injected rapidly, in a large volume and when all blood vessels leading into and out of the hindlimb are occluded. The additional use of collagenase, papaverine and ischemia raised expression moderately but was not critical. These results demonstrate that a nonviral method can lead to high levels of expression in the muscles of adult animals large than mice.

Animals↗
PubMed1998

Characterization of a second transcription initiation element (STIE) in the human interleukin-1 beta (IL-1beta) gene.

Interleukin-1-beta (IL-1beta) is a significant mediator in the inflammation process. Although the human IL-1beta genomic sequence has been known for several years, our understanding of its molecular regulation of transcription remains incomplete. We are reporting a new transcription initiation element that is located within intron 1 and exon 2 of the human IL-1beta gene. Different lengths of the human IL-1beta gene fragment (-685 to +550) were cloned upstream from a chloramphenical acetyltransferase (CAT) gene to make the IL-1beta promoter/CAT reporter constructs. Transient CAT expression with these constructs in the human monocytic leukemia cell line THP1 illustrates an important positive regulatory element exists within the region from +387 to +550. Using electromobility shift assays and by DNase I footprinting analysis, we identified three nuclear factor binding sites (+448 to +502, +513 to +531, and +539 to +548). Functional studies show that CAT production is undetectable when the 19 bp region (+513 to +531) is removed, and CAT production is diminished when the 10-bp region (+539 to +548) is deleted. The region containing these sites is likely to initiate a new transcript starting at +559 of exon 2. This second transcript of the IL-1beta gene shares the same reading frame with the previously recognized cDNA transcript.

Base Sequence↗
PubMed1998

Identification and characterization of Escherichia coli DNA helicase II mutants that exhibit increased unwinding efficiency.

Using a combination of both ethyl methanesulfonate and site-directed mutagenesis, we have identified a region in DNA helicase II (UvrD) from Escherichia coli that is required for biological function but lies outside of any of the seven conserved motifs (T. C. Hodgman, Nature 333:22-23, 1988) associated with the superfamily of proteins of which it is a member. Located between amino acids 403 and 409, alterations in the amino acid sequence DDAAFER lead to both temperature-sensitive and dominant uvrD mutations. The uvrD300 (A406T) and uvrD301 (A406V) alleles produce UV sensitivity at 44 degrees C but do not affect sensitivity to methyl methanesulfonate (MMS). In contrast, the uvrD303 mutation (D403AD404A) causes increased sensitivity to both UV and MMS and is dominant to uvrD+ when present at six to eight copies per cell. Several of the alleles demonstrated a strong antimutator phenotype. In addition, conjugal recombination is reduced 10-fold in uvrD303 strains. Of all of the amino acid substitutions tested, only an alanine-to-serine change at position 406 (uvrD302) was neutral. To determine the biochemical basis for the observed phenotypes, we overexpressed and purified the UvrD303 protein from a uvrD delta294 deletion background and characterized its enzymatic activities. The highly unusual UvrD303 protein exhibits a higher specific activity for ATP hydrolysis than the wild-type control, while its Km for ATP binding remains unchanged. More importantly, the UvrD303 protein unwinds partial duplex DNA up to 10 times more efficiently than wild-type UvrD. The DNA binding affinities of the two proteins appear comparable. Based on these results, we propose that the region located between amino acids 403 and 409 serves to regulate the unwinding activity of DNA helicase II to provide the proper balance between speed and overall effectiveness in the various DNA repair systems in which the protein participates.

Adenosine Triphosphatases↗
PubMed1998

Rapid and sensitive assay for detection of enterotoxigenic Bacteroides fragilis.

Bacteroides fragilis is an obligatory anaerobic, gram-negative bacterium found among the normal intestinal flora of humans. Enterotoxigenic strains of B. fragilis (ETBF) have been associated with diarrheal diseases in humans and animals. The enterotoxin of ETBF induces fluid changes in ligated intestinal segments and cytotoxic response in HT29/C1 cells. By using a pair of monoclonal antibodies (MAbs; MAb C3 and MAb 4H8) specific for the lipopolysaccharide of B. fragilis, an assay based on immunomagnetic separation (IMS) in combination with PCR (IMS-PCR) was developed. After DNA extraction, a 294-bp fragment was amplified. The specificity of the IMS-PCR assay was evaluated by adding previously isolated and confirmed ETBF strains to normal fecal samples. All fecal samples to which ETBF strains were added were positive, showing a 100% specificity. The spiked fecal samples were also used for evaluation of the sensitivity of the assay. The detection limit was found to be approximately 50 CFU/g of feces. By this method 10 clinical fecal samples (5 from patients with diarrhea and 5 from healthy controls) were examined. The results of PCR were in accordance with the results of the HT29/C1 cell assay for all samples. The minimum time to retrieval of the final result by the IMS-PCR method is 36 h. The proposed IMS-PCR assay is rapid and sensitive for the direct detection of ETBF in stool samples.

Animals↗
PubMed1998

Presence of antibodies to heat stress proteins in workers exposed to benzene and in patients with benzene poisoning.

Heat shock or stress proteins (Hsps) are a group of proteins induced by a large number of xenobiotics, many of which are common in the working and living environment. The biological significance of the presence of antibodies against Hsps in humans is presently unknown. In the present study, 112 workers were selected and divided into four groups on the basis of their level of occupational exposure to benzene: a control group, two groups of workers exposed to either low (< 300 mg/m3) or high concentrations of benzene (> 300 mg/m3) and a group of workers who had experienced benzene poisoning. Blood samples from these workers were assayed for the number of peripheral white blood cells, concentration of hemoglobin, activities of serum superoxide dismutase (SOD), lymphocyte DNA damage and finally for the presence of antibodies to different human heat-shock proteins (Hsp27, Hsp60, Hsp71 and Hsp90). Benzene-poisoned workers showed a high incidence of antibodies against Hsp71 (approximately 40%) which was associated with a decrease in white blood cells (3.84+/-1.13 x 10(9)versus 7.68+/-1.84 x 10(9) in controls) and with an increase in activities of serum SOD (138.43+/-23.15 micro/ml) and lymphocyte DNA damage (18.7%). These data suggest that antibodies against Hsps can potentially be useful biomonitors to assess if workers are experiencing or have experienced abnormal xenobiotic-induced stress within their living and working environment.

Adult↗
PubMed1998

[Epidemiological study on risk factors of Chlamydia trachomatis infection in pregnant women].

54 Pregnant women and 216 without were detected for anti-Chlamydial antibodies, using indirect hemagglutination test on a 1:4 matched Case-control study to look for risk factors of Chlamydia trachomatis infection. A total number of 26 independent variables were selected for analysis, in which 8 factors were confirmed as associated factors by single variable analysis. Of the above 8 factors, 4 were significantly correlated to the infection under the multifactorial conditional logistic regression model, which were: extramarital sex life, history of urogenital tract infection, age of sexual intercourse debut and the use of intrauterus contraception.

Adult↗