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Biomedical subjects

G Li

Publications and source records attributed to G Li.

At least 271 records · Page 15Linked to original sources
PubMed2001

[The level of plasma-soluble Fas and its clinical value in patients with lung carcinoma].

OBJECTIVE: To explore the clinical value of plasma-soluble Fas (Fas) in patients with lung carcinoma. METHODS: Plasma-Fas level was measured by ELISA method. T lymphocyte phenotype was analysed by flow cytometry in 60 patients with lung cancer. RESULTS: The level of Fas was higher in 40% patients. There was no relationship between level of Fas and pathology. But level of Fas was associated with clinical stage, there was higher level of Fas in patients with advanced neoplastic disease than early stage. The frequencies of activated T cells (CD3+, HLA-DR+) and NK cells (CD16+, CD56+) were also significantly increased in advanced neoplastic patients. However, there was a significant decrease in helper T cells (CD4+, CD8-) in advanced patients. Primary diagnosed SCLC patients with elevated Fas often had good responses to chemotherapy. Plasma Fas level decreased to normal through effective therapy. CONCLUSIONS: There is a elevated plasma-Fas level in patients with lung cancer. It is associated with lymphocyte phenotype. Plasma-Fas may be used as a useful parameter in predicting response to therapy or disease activity.

Adult↗
PubMed2000

Taxol from Tubercularia sp. strain TF5, an endophytic fungus of Taxus mairei.

The diterpenoid taxol is an important anticancer agent used widely in the clinic. The purpose of this work was to identify a taxol-producing endophytic fungus (strain TF5) isolated from Taxus mairei and study its anticancer activities. Strain TF5 was identified as a Tubercularia sp. according to the morphology of the fungal culture, the mechanism of spore production and the characteristics of the spores. Strain TF5 produced taxol, when grown in potato dextrose liquid medium and analyzed by thin layer chromatography, high performance liquid chromatography, ultraviolet and mass spectrometry. The fungal taxol, which was isolated from the organic extract of the TF5 culture, had strong cytotoxic activity towards KB and P388 cancer cells in vitro, tested by the MTT assay. Observed with immunofluorescence and electron microscopy, the fungal taxol enhanced microtubule stability and bundling in culture cells and induced tubulin polymerization in vitro similar to the authentic taxol.

Animals↗
PubMed2000

bFGF induces differentiation and death of olfactory neuroblastoma cells.

Olfactory neuroblastoma (ONB) is a highly vascularized and malignant tumor arising in olfactory neuronal precursors from the paranasal sinuses. Previously, we showed that treatment of JFEN cells with transforming growth factor (TGF)-alpha caused them to differentiate and respond to chemical odorants, whereas basic fibroblast growth factor (bFGF) treated cells differentiated and died. In the present study we show that established ONB tumors treated with bFGF upregulate the bFGF receptor (FGFR1) prior to differentiation. This cellular differentiation was evidenced by bFGF-induced expression of the human runt homologue AML1 (PEBP2 alpha B, CBFA-2) that is highly expressed in developing olfactory neuroepithelium and TrkA, a preferred nerve growth factor receptor. Since TrkA is expressed in supporting cells, but not in mature olfactory neurons, we hypothesize that the expression of AML1 and TrkA in bFGF-treated JFEN cells induced supporting cell differentiation. Collectively, these results have implications for the treatment of patients afflicted with ONB.

Animals↗
PubMed2000

Photoreceptor regulated expression of Ca(2+)/calmodulin-dependent protein kinase II in the mouse retina.

The objective of this investigation is to determine mechanisms for regulation of retinal calmodulin kinase II (CaMKII). To this end, the expression and activity of CaMKII are examined in the retina of the rdta mouse, in which rod photoreceptors have been genetically ablated [47]. CaMKII levels are compared between rdta mice and the normal, littermate control mice. It is demonstrated that retinal CaMKII protein, enzyme activity and mRNA are significantly increased in response to the genetic ablation of rod photoreceptors. The data indicate that CaMKII expression/activity in amacrine and ganglion cells is negatively regulated by the rod photoreceptor-mediated visual input. The regulation appears to occur primarily at the transcriptional level. It is shown that the cytoplasmic polyadenylation element binding protein (CPEB), a regulatory factor for translation that is known to promote CaMKIIalpha translation in dendrites [83], is also present in the mouse retina. However, the polyadenylation-mediated translational control mechanism is not activated in this experimental paradigm.

Animals↗
PubMed2000

Chorion peroxidase-mediated NADH/O(2) oxidoreduction cooperated by chorion malate dehydrogenase-catalyzed NADH production: a feasible pathway leading to H(2)O(2) formation during chorion hardening in Aedes aegypti mosquitoes.

A specific chorion peroxidase is present in Aedes aegypti and this enzyme is responsible for catalyzing chorion protein cross-linking through dityrosine formation during chorion hardening. Peroxidase-mediated dityrosine cross-linking requires H(2)O(2), and this study discusses the possible involvement of the chorion peroxidase in H(2)O(2) formation by mediating NADH/O(2) oxidoreduction during chorion hardening in A. aegypti eggs. Our data show that mosquito chorion peroxidase is able to catalyze pH-dependent NADH oxidation, which is enhanced in the presence of Mn(2+). Molecular oxygen is the electron acceptor during peroxidase-catalyzed NADH oxidation, and reduction of O(2) leads to the production of H(2)O(2), demonstrated by the formation of dityrosine in a NADH/peroxidase reaction mixture following addition of tyrosine. An oxidoreductase capable of catalyzing malate/NAD(+) oxidoreduction is also present in the egg chorion of A. aegypti. The cooperative roles of chorion malate/NAD(+)oxidoreductase and chorion peroxidase on generating H(2)O(2) with NAD(+) and malate as initial substrates were demonstrated by the production of dityrosine after addition of tyrosine to a reaction mixture containing NAD(+) and malate in the presence of both malate dehydrogenase fractions and purified chorion peroxidase. Data suggest that chorion peroxidase-mediated NADH/O(2) oxidoreduction may contribute to the formation of the H(2)O(2) required for chorion protein cross-linking mediated by the same peroxidase, and that the chorion associated malate dehydrogenase may be responsible for the supply of NADH for the H(2)O(2) production.

Aedes↗
PubMed2000

De novo activation of the beta-phaseolin promoter by phosphatase or protein synthesis inhibitors.

The promoter for the phaseolin (phas) bean seed protein gene adopts an inactive chromatin structure in leaves of transgenic tobacco. This repressive architecture, which confers stringent spatial regulation, is disrupted upon transcriptional activation during embryogenesis in a process that requires the presence of both a transcription factor (PvALF) and abscisic acid (ABA). Toward determining the need for de novo synthesis of proteins other than PvALF in transcriptional activation we explored the effect of several eukaryotic protein synthesis inhibitors. Surprisingly, cycloheximide (CHX), emetine, and verrucarin A were able to induce transcription from the phas promoter in tobacco and bean leaf tissue in the absence of either PvALF or ABA. This induction was decreased by the replication inhibitors hydroxyurea and aphidicolin but not by genistein or mimosine. Since protein phosphatases and kinases are essential components of the ABA signal transduction pathway, it is conceivable that CHX is also capable of inducing phosphorylation of proteins usually involved in ABA-mediated activation. Interestingly, okadaic acid, an inhibitor of serine/threonine phosphatase, also strongly activated transcription from the phas promoter. In contrast, the protein synthesis inhibitors anisomycin and puromycin did not activate transcription from the phas promoter, nor did the tyrosine phosphatase inhibitors phenylarsine oxide and sodium orthovanadate. These discrete but different results on transcriptional activation may reflect specific modes of action of the inhibitors, or they may reflect differential interactions of the inhibitors or of downstream events resulting from inhibitor activity with presently unknown components of the transcriptional activation system.

Cycloheximide↗
PubMed2000

Mouse prenylated Rab acceptor is a novel Golgi membrane protein.

We have cloned a mouse prenylated Rab acceptor (mPRA), which interacts with various Rab proteins in the yeast two-hybrid system. This study investigated its intracellular localization and characterized the localization signal. The mPRA was found to be an integral membrane protein that was localized to the Golgi complex at steady state as determined by confocal fluorescence microscopy. With green fluorescent protein attached to the N-terminus of mPRA, the fusion protein was expressed in BHK cells and was shown to exhibit the same Golgi localization as the native mPRA. Systematic truncations from the N- and C-termini of mPRA revealed that the entire N-terminal half (91 residues) of the protein was dispensable for the Golgi localization. In contrast, deletion of only 5 residues from the C-terminus diminished the Golgi localization of mPRA, leading to its accumulation in the ER. The data indicate that the C-terminal half (94 residues) of mPRA is necessary and sufficient for proper folding, ER export, and Golgi localization. The Golgi localization of mPRA suggests that it may play a role in the structural organization and function of the Golgi complex.

Amino Acid Sequence↗
PubMed2000

Susceptibility to apoptosis is restored in human leukemia HCW-2 cells following induction and stabilization of the apoptotic effector Bak.

We demonstrate that treatment of HCW-2 cells, an apoptotic resistant variant of the human HL-60 promyelocytic leukemia cell line with phorbol-12-myristate acetate (PMA), induced differentiation along the monocytic lineage. During this process there was a dramatic increase in the mitochondrial levels of the apoptosis effector, Bak, due to the stabilization of bak mRNA, which was correlated with the sensitization of HCW-2 cells to respond to the apoptotic effect of staurosporine (STS). Treatment of PMA-differentiated, but not undifferentiated, HCW-2 cells induced processing of Bid, substantial efflux of cytochrome c from mitochondria to the cytosol, activation of caspase-3 and apoptosis. The biological significance of the increased mitochondrial Bak in differentiated HCW-2 cells was supported by the finding that transient transfection of a bak cDNA into HCW-2 cells conferred sensitivity to STS-triggered apoptosis, as determined by pro-caspase-3 processing, cytochrome c efflux and DNA fragmentation. Our results suggest that the induction of Bak, upon monocytic differentiation, may be a critical event that regulates the apoptotic sensitivity of differentiated HCW-2 cells. Oncogene (2000) 19, 4108 - 4116

Apoptosis↗
PubMed2000

Copper-catalyzed aminohalogenation using the 2-NsNCl(2)/2-NsNHNa combination as the nitrogen and halogen sources for the synthesis of anti-alkyl 3-chloro-2-(o-nitrobenzenesulfonamido)-3-arylpropionates.

New regio- and stereoselective aminohalogenation of cinnamic esters has been developed using the combination of 2-NsNCl(2)/2-NsNHNa as the nitrogen and chlorine sources and copper(I) triflate as the catalyst. The new procedure provides an efficient synthesis of anti-alkyl 3-chloro-2-(o-nitrobenzenesulfonamido)-3-phenylpropionate derivatives. Nine examples are presented with good yields (62-82%) and stereoselectivity ((5:1)-(30:1)).

Amination↗
PubMed2000

Regulatory domain conformational exchange and linker region flexibility in cardiac troponin C bound to cardiac troponin I.

Previously, we utilized (15)N transverse relaxation rates to demonstrate significant mobility in the linker region and conformational exchange in the regulatory domain of Ca(2+)-saturated cardiac troponin C bound to the isolated N-domain of cardiac troponin I (Gaponenko, V., Abusamhadneh, E., Abbott, M. B., Finley, N., Gasmi-Seabrook, G., Solaro, R.J., Rance, M., and Rosevear, P.R. (1999) J. Biol. Chem. 274, 16681-16684). Here we show a large decrease in cardiac troponin C linker flexibility, corresponding to residues 85-93, when bound to intact cardiac troponin I. The addition of 2 m urea to the intact cardiac troponin I-troponin C complex significantly increased linker flexibility. Conformational changes in the regulatory domain of cardiac troponin C were monitored in complexes with troponin I-(1-211), troponin I-(33-211), troponin I-(1-80) and bisphosphorylated troponin I-(1-80). The cardiac specific N terminus, residues 1-32, and the C-domain, residues 81-211, of troponin I are both capable of inducing conformational changes in the troponin C regulatory domain. Phosphorylation of the cardiac specific N terminus reversed its effects on the regulatory domain. These studies provide the first evidence that the cardiac specific N terminus can modulate the function of troponin C by altering the conformational equilibrium of the regulatory domain.

Animals↗
PubMed2000

Expression of a chimeric farnesyl diphosphate synthase gene in Artemisia annua L. transgenic plants via Agrobacterium tumefaciens-mediated transformation.

An Agrobacterium tumefaciens-mediated transformation system was developed for Artemisia annua L. Using this system a cDNA encoding farnesyl diphosphate synthase (FDS placed under a CaMV 35S promoter) was transferred into A. annua via A. tumefaciens strain LB4404. Leaf or leaf discs were used as explants to be infected with A. tumefaciens and an optimal concentration of 20 mg/l kanamycin was applied to select kanamycin resistant shoots. Forty-five lines of resistance kanamycin shoots transformed with FDS were established. Analysis of PCR showed that at least 20 shoots transformed with the FDS gene were PCR positive. Southern blot analysis suggested the foreign FDS gene had been integrated into the A. annua genome, and Northern blot analysis revealed that the foreign FDS gene expressed at the transcriptional level in five shoot lines (F-1, F-4, F-61, F-62 and F-73 shoot lines). Analysis of artemisinin demonstrated that about 8 approximately 10 mg/g DW of artemisinin were then detected in transgenic plants regenerated from five shoot lines, this is about 2-3 times higher than that in the control.

Journal Article↗
PubMed2000

Estrogen attenuates integrin-beta(3)-dependent adventitial fibroblast migration after inhibition of osteopontin production in vascular smooth muscle cells.

BACKGROUND: Previous in vitro studies have suggested that estrogen attenuates the vascular injury response by modulating vascular smooth muscle cell (VSMC) expression of soluble factor(s) directing migration of adventitial fibroblasts. Previous in vivo studies have established a role for osteopontin (OPN) and its integrin receptors after vascular injury. In this study, we examined OPN expression in activated VSMCs, its modulation by estrogen, and its effects on adventitial fibroblast migration. In addition, the relative functional roles of beta(1)- and beta(3)-integrin-matrix interactions were examined. METHODS AND RESULTS: Primary cultures of VSMCs and adventitial fibroblasts were derived from female Sprague-Dawley rats. Serum-activated VSMCs expressed high levels of OPN mRNA and secreted protein that was effectively inhibited by estrogen treatment (10(-7) mol/L). Compared with VSMCs, fibroblasts expressed similar levels of integrins alphanu and beta(1) and higher levels of integrin-beta(3). Exogenous OPN (5.0 to 40 microg/mL) directed fibroblast migration in a dose-dependent fashion. Anti-beta(3)-integrin antibody (F11) pretreatment markedly inhibited adventitial fibroblast migration directed by exogenous OPN or VSMC-conditioned medium in a dose-dependent manner. In contrast, anti-beta(1)-integrin antibody (Ha2/5) did not affect fibroblast migration. Similarly, pretreatment with either linear or cyclic RGD peptides (10 to 1000 micromol/L) inhibited fibroblast migration directed by OPN or VSMC-conditioned medium in a dose-dependent manner. CONCLUSIONS: These observations suggest that estrogen indirectly attenuates integrin-beta(3)-dependent adventitial fibroblast migration after inhibition of OPN expression in VSMCs.

Animals↗
PubMed2000

Purification and characterization of chorion peroxidase from Aedes aegypti eggs.

Previous study has shown that a peroxidase is present in the mature eggs of Aedes aegypti mosquitoes, and the enzyme is involved in the formation of a rigid and insoluble chorion by catalyzing chorion protein crosslinking through dityrosine formation. In this study, chorion peroxidase was solubilized from egg chorion by 1% SDS and 2 M urea and purified by various chromatographic techniques. The enzyme has a relative molecular mass of 63,000 as estimated by SDS-PAGE. Spectral analysis of the enzyme revealed the presence of the Soret band with a lambda(max) at 415 nm, indicating that chorion peroxidase is a hemoprotein. Treatment of the native enzyme with H2O2 in excess in the absence of reducing agents shifted the Soret band from 415 to 422 nm, and reduction of the native enzyme with sodium hydrosulfite under anaerobic conditions changed the Soret band from 415 to 446 nm. These results show that the chorion peroxidase behaves similarly to other peroxidases under oxidative and reductive conditions, respectively. Compared to other peroxidases, the chorion peroxidase, however, is extremely resistant to denaturing agents, such as SDS and organic solvents. For example, chorion peroxidase remained active for several weeks in 1% SDS, while horseradish peroxidase irreversibly lost all its activity in 2 h under the same conditions. Comparative analysis between mosquito chorion peroxidase and horseradish peroxidase showed that the specific activity of chorion peroxidase to tyrosine was at least 100 times greater than that of horseradish peroxidase to tyrosine. Chorion peroxidase is also capable of catalyzing polypeptide and chorion protein crosslinking through dityrosine formation during in vitro assays. Our data suggest that the characteristics of the chorion peroxidase in mosquitoes closely reflect its functions in chorion formation and hardening.

Aedes↗
PubMed2000

[Comparative study of pulmonary magnetic resonance angiography (MRA)].

Imaging was performed using a 1.0 Tesla superconducting MR system with a body coil. Two-dimensional(2D) turbo FLASH sequence and/or three-dimensional(3D) FISP sequence were carried out in 46 volunteers with 113 pulmonary MRA. The total MRAs were divided into 4 groups and analysed. The results showed: After Gd-DTPA was injected, the signal-to-noise ratio(SNR) of pulmonary 2D- and 3D-TOF MRA was increased in 46 normal pulmonary MR angiography cases(P < 0.01); the number of left and right pulmonary artery divisions identified was much greater than that before Gd-DTPA injection both in 2D- and 3D-MOF(except lingual segment of left lobe). It is suggested that Gd-DTPA may markedly promote the efficiency of pulmonary MRA.

Adolescent↗
PubMed2000

Modulation of Ca(2+)-dependent K(+) currents in mesenteric arterial smooth muscle cells by adenosine.

The effect of adenosine on Ca(2+)-dependent K(+) currents was studied in freshly isolated smooth muscle cells from rat mesenteric artery. Perforated-patch recordings showed that adenosine induced transient outward currents and an overall increase in the averaged currents at higher depolarizing potentials. The changes in current activity induced by adenosine could be blocked by iberiotoxin. The transient outward currents were not dependent directly on external Ca(2+) and could be induced after brief exposure to Ca(2+)-free solutions. In conventional whole-cell recordings, transient outward currents were also induced by adenosine when a low EGTA concentration of 0.1 mM was included in the pipette solution. Adenosine was not effective in inducing increases in outward currents when a higher concentration of 5.0 mM EGTA was used. Ryanodine and thapsigargin were also effective in blocking the effect of adenosine. These observations suggest that adenosine may activate Ca(2+)-dependent K(+) currents by inducing Ca(2+) release from ryanodine-sensitive channels in the sarcoplasmic reticulum of rat mesenteric arterial cells.

Adenosine↗
PubMed2000

[Study on the absorption of environmental contaminants in low-level exposure by pharmacokinetic analysis].

A dynamic generating toxic gas system and a nose-only exposure system were used for the pharmacokinetic study of inhaled environmental contaminants for benzene, toluene, xylene, ethylbenzene, chlorobenzene, styrene, isopropyl benzene, tetrachloroethylene, nonane and methylcyclohexane in male guinea pig. The change of these substances in blood with time was determined simultaneously by solid phase micro-extraction(SPME) gas chromatography (GC). The results showed that the fraction of absorption of benzene at low (121 micrograms/m3) exposure was 4.8 times higher than that at high(12.1 mg/m3) exposure. The pharmacokinetics of these substances were evaluated by using linear compartment models. The data showed that more styrene was absorbed than tetrachloroethylene at low-exposure. The metabolic elimination of these compounds at various exposure concentrations was extrapolated by using estimated pharmacokinetic parameters. Moreover, not only should the differences in absorption quantities be considered in evaluation of potential risk assessment, the metabolic elimination rates should also be considered although the exposure concentrations in gas for all chemicals were equal. The data presented in this paper was fundamental data used for risk assessment.

Air Pollutants↗
PubMed2000

Calcium/calmodulin-dependent protein kinase II containing a nuclear localizing signal is altered in retinal neurons exposed to N-methyl-D-aspartate.

This study investigated N-methyl-D-aspartate (NMDA) mediated cell death and its possible regulation by calcium/calmodulin-dependent protein kinase II (CaMKII) in the adult rat retina. To investigate cell death, the terminal deoxyribonucleotidyltransferase (TdT)-mediated biotin-16-dUTP nick-end labelling (TUNEL) method was used to detect fragmented DNA in fixed tissue sections of rat retina. The TUNEL assay confirmed that apoptosis occurs in the inner nuclear layer (INL) and ganglion cell layer (GCL) following NMDA injection. The level of antibody binding to CaMKII-alpha, the activity of CaMKII, and the mRNA level for the alpha(B) subunit of CaMKII were found to be elevated for short time periods (30 min, 2 h) after a single intravitreal injection of NMDA. In contrast to this, there was a decrease in CaMKII activity and in the CaMKII-alpha(B) mRNA levels at longer time periods (24 h) following injection of NMDA. These effects were specific for the mRNA for the alpha(B) subunit, an alternatively spliced product of the CaMKII-alpha gene, that contains a nuclear localizing signal (NLS) known to target this protein to the nucleus. It is suggested that regulated expression of CaMKII-alpha(B) could be involved in the NMDA-mediated cell death in retinal neurons.

Animals↗