Search PubMed⌕ Search

Biomedical subjects

Feng Chen

Publications and source records attributed to Feng Chen.

At least 109 records · Page 6Linked to original sources
PubMed2005

Development of competitive direct ELISA for gossypol analysis.

Anti-gossypol monoclonal antibody was purified from cell culturing supernatant by ammonium sulfate precipitation and Protein A AffinityPak. The antigen (i.e., gossypol) was labeled with horseradish peroxidase through Schiff-base formation. Both the purified antibody and the enzyme-labeled gossypol were employed to develop a competitive direct enzyme-linked immunosorbent assay (cdELISA) for gossypol analysis. I50 value, the concentration of gossypol causing 50% inhibition of the maximum ELISA signal in the competitive standard curve, was 0.067 microg/mL, whereas the detection limit for gossypol was 0.005 microg/mL. We also observed a good correlation (R2= 0.96, P < 0.05) between the cdELISA method and the AOCS official method for "free" gossypol (extractable gossypol and gossypol derivatives by 70% acetone) analysis of cottonseed meals. This indicates that the newly developed cdELISA could be a valuable and feasible alternative for determination of "free" gossypol, especially when the available sample is limited with relatively low gossypol concentration.

Antibodies, Monoclonal↗
PubMed2005

Isolation and purification of baicalein, wogonin and oroxylin A from the medicinal plant Scutellaria baicalensis by high-speed counter-current chromatography.

The medicinal plant Scutellaria baicalensis Georgi has been used widely in traditional Chinese medicine for anti-inflammation, anticancer, antiviral and antibacterial infections, reducing the total cholesterol level and decreasing blood pressures. A high-speed counter-current chromatography (HSCCC) method was developed for the preparative separation and purification of three bioactive flavonoids, namely, baicalein, wogonin and oroxylin A, from S. baicalensis Georgi. Preparative HSCCC with a two-phase solvent system composed of n-hexane-ethyl acetate-n-butanol-water (1:1:8:10, v/v/v/v) was successfully performed by increasing the flow-rate of the mobile phase stepwise from 1.0 to 2.0 ml min(-1) after 4 h. The components purified and collected were analyzed by high-performance liquid chromatography. The method yielded 144.8 mg of baicalein at 95.7% purity, 50.2 mg of wogonin at 98.5% purity, and 12.4 mg of oroxylin A at 93.2% purity from 500 mg of the crude extract in a one-step separation. The recoveries of baicalein, wogonin and oroxylin A were 92.7%, 91.6% and 92.5%, respectively.

Chromatography, High Pressure Liquid↗
PubMed2005

Preparation of controllable crystalline titania and study on the photocatalytic properties.

Nanocrystalline TiO(2) catalysts with different anatase/rutile ratios and high surface area (113-169 m(2)/g) have been prepared at low temperature by the microemulsion-mediated hydrothermal method. The samples were characterized by x-ray diffraction (XRD), Fourier transform (FT)-IR spectra, UV-vis diffuse reflectance spectra, and nitrogen adsorption-desorption methods. The contents of anatase and rutile phases in the TiO(2) powders have been successfully controlled by simply changing the proportion of Cl(-) and SO(4)(2-) in the aqueous phase of the microemulsion. A proposed mechanism involving bidentately chelated sulfate is discussed to explain the variation of the crystalline phase in the TiO(2) powder. The photodegradation of methyl orange (MO) in water has been investigated over titanium dioxide consisting of different anatase/rutile ratios. The catalyst containing 74.2% anatase showed the highest photocatalytic activity, which is due to a synergistic effect between anatase and rutile. The synergism was also found for the photodegradation of MO with physically mixed anatase and rutile as catalysts.

Journal Article↗
PubMed2005

Synthesis, characterization, and pharmacokinetic evaluation of a potential MRI contrast agent containing two paramagnetic centers with albumin binding affinity.

A dinuclear gadolinium(III) complex of an amphiphilic chelating ligand, containing two diethylenetriamine-N,N,N',N'',N''-pentaacetate (DTPA) moieties bridged by a bisindole derivative with three methoxy groups, has been synthesized and evaluated as a potential magnetic resonance imaging (MRI) contrast agent. Nuclear magnetic relaxation dispersion (NMRD) measurements indicate that at 20 MHz and 37 degrees C the dinuclear gadolinium(III) complex has a much higher relaxivity than [Gd(DTPA)] (6.8 vs 3.9 s(-1) mmol(-1)). The higher relaxivity of the dinuclear gadolinium(III) complex can be related to its reduced motion and larger rotational correlation time relative to [Gd(DTPA)]. In the presence of human serum albumin (HSA) the relaxivity value of the noncovalently bound dinuclear complex increases to 15.2 s(-1) per mmol of Gd3+, due to its relatively strong interaction with this protein. The fitted value of the binding constant to HSA (Ka) was found to be 10(4) M(-1). Because of its interaction with HSA, the dinuclear complex exhibits a longer elimination half-life from the plasma, and a better confinement to the vascular space compared to the commercially available [Gd(DTPA)] contrast agent. Transmetalation of the dinuclear gadolinium(III) complex by zinc(II) has been investigated. Biodistribution studies suggest that the complex is excreted by the renal pathway, and possibly by the hepatobiliary route. In vivo studies indicated that half of the normal dose of the gadolinium(III) complex enhanced the contrast in hepatic tissues around 40 % more effectively than [Gd(DTPA)]. The dinuclear gadolinium(III) complex was tested as a potential necrosis avid contrast agent (NACA), but despite the binding to HSA, it did not exhibit necrosis avidity, implying that binding to albumin is not a key parameter for necrosis-targeting properties.

Animals↗
PubMed2005

Effect of chitosan on the biological properties of sweet basil (Ocimum basilicum L.).

The effect of the treatment of chitosan at various concentrations (0.01%, 0.05%, 0.1%, 0.5%, and 1%) upon sweet basil (Ocimum basilicum L.) before seeding and transplanting was investigated in aspects of the amount of phenolic and terpenic compounds, antioxidant activity, and growth of the basil, as well as the phenylalanine ammonia lyase (PAL) activity. The total amount of the phenolic and terpenic compounds increased after the chitosan treatment. Especially, the amounts of rosmarinic acid (RA) and eugenol increased 2.5 times and 2 times, respectively, by 0.1% and 0.5% chitosan treatment. Due to the significant induction of phenolic compounds, especially RA, the corresponding antioxidant activity assayed by the DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging test increased at least 3.5-fold. Also, the activity of PAL, a key regulatory enzyme for the phenylpropanoid pathway, increased 32 times by 0.5% chitosan solution. Moreover, after the elicitor chitosan treatment, the growth in terms of the weight and height of the sweet basil significantly increased about 17% and 12%, respectively. Our study demonstrates that an elicitor such as chitosan can effectively induce phytochemicals in plants, which might be another alternative and effective means instead of genetic modification.

Antioxidants↗
PubMed2005

Peroxisome proliferator activated receptor-gamma ligands induced cell growth inhibition and its influence on matrix metalloproteinase activity in human myeloid leukemia cells.

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is one of the best characterized nuclear hormone receptors (NHRs) in the superfamily of ligand-activated transcriptional factors. PPAR-gamma ligands have recently been demonstrated to affect proliferation, differentiation and apoptosis of different cell types. The present study was undertaken to investigate PPAR-gamma ligands induced cell growth inhibition and its influence on matrix metalloproteinase MMP-9 and MMP-2 activities on leukemia K562 and HL-60 cells in vitro. The results revealed that PPAR-gamma expression was detectable in the two kinds of leukemia cells; Both 15-deoxy-delta(12,14)-prostaglandin J2(15d-PGJ2) and troglitazone (TGZ) have significant growth inhibition effects on these two kinds of leukemia cells. These two PPAR-gamma ligands could inhibit the leukemic cell adhesion to the extracellular matrix (ECM) proteins and the invasion through matrigel matrix. The expressions of MMP-9 and MMP-2 as well as their gelatinolytic activities in both HL-60 and K562 cells were inhibited by 15d-PGJ2 and TGZ significantly. We therefore conclude that PPAR-gamma ligands 15d-PGJ2 and TGZ have significant growth inhibition effects on myeloid leukemia cells in vitro, and that PPAR-gamma ligands can inhibit K562 and HL-60 cell adhesion to and invasion through ECM as well as downregulate MMP-9 and MMP-2 expressions. The data suggest that PPAR-gamma ligands may serve as potential anti-leukemia reagents.

Antineoplastic Agents↗
PubMed2005

Synthetic lethality of retinoblastoma mutant cells in the Drosophila eye by mutation of a novel peptidyl prolyl isomerase gene.

Mutations that inactivate the retinoblastoma (Rb) pathway are common in human tumors. Such mutations promote tumor growth by deregulating the G1 cell cycle checkpoint. However, uncontrolled cell cycle progression can also produce new liabilities for cell survival. To uncover such liabilities in Rb mutant cells, we performed a clonal screen in the Drosophila eye to identify second-site mutations that eliminate Rbf(-) cells, but allow Rbf(+) cells to survive. Here we report the identification of a mutation in a novel highly conserved peptidyl prolyl isomerase (PPIase) that selectively eliminates Rbf(-) cells from the Drosophila eye.

Amino Acid Sequence↗
PubMed2005

Isolation and purification of the bioactive carotenoid zeaxanthin from the microalga Microcystis aeruginosa by high-speed counter-current chromatography.

High-speed counter-current chromatography was successfully applied for the first time to the isolation and purification of the bioactive carotenoid zeaxanthin from the cyanobacterium Microcystis aeruginosa. The crude zeaxanthin was obtained by extraction with organic solvents after the microalgal sample had been saponified. Preparative high-speed counter-current chromatography with a two-phase solvent system composed of n-hexane-ethyl acetate-ethanol-water (8:2:7:3, v/v/v/v) was successfully performed yielding zeaxanthin at 96.2% purity from 150 mg of the crude extract in a one-step separation. The recovery of zeaxanthin was 91.4%. This was also the first report that zeaxanthin was successfully separated and purified from microalgae.

Chromatography, High Pressure Liquid↗
PubMed2005

Dynamic susceptibility contrast-enhanced perfusion MR imaging at 1.5 T predicts final infarct size in a rat stroke model.

The purpose of the present animal experiment was to determine whether source images from dynamic susceptibility contrast-enhanced perfusion weighted imaging (DSC-PWI) at a 1.5T MR scanner, performed early after photochemically induced thrombosis (PIT) of cerebral middle artery (MCA), is feasible to predict final cerebral infarct size in a rat stroke model. Fifteen rats were subjected to PIT of proximal MCA. T2 weighted imaging (T2WI), diffusion-weighted imaging (DWI), and contrast-enhanced PWI were obtained at 1 h and 24 h after MCA occlusion. The relative lesion size (RLS) was defined as lesion volume/brain volume x 100% and measured for MR images, and compared with the final RLS on the gold standard triphenyl tetrazolium chloride (TTC) staining at 24 h. One hour after MCA occlusion, the RLS with DSC-PWI was 24.9 +/- 6.3%, which was significantly larger than 17.6 +/- 4.8% with DWI (P < 0.01). At 24 h, the final RLS on TTC was 24.3 +/- 4.8%, which was comparable to 25.1 +/- 3.5%, 24.6 +/- 3.6% and 27.9 +/- 6.8% with T2WI, DWI and DSC-PWI respectively (P > 0.05). The fact that at 1 h after MCA occlusion only the displayed perfusion deficit was similar to the final infarct size on TTC (P > 0.05) suggests that early source images from DSC-PWI at 1.5T MR scanner is feasible to noninvasively predict the final infarct size in rat models of stroke.

Animals↗
PubMed2005

The small heat shock protein alpha B-crystallin is a novel inhibitor of TRAIL-induced apoptosis that suppresses the activation of caspase-3.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor alpha family of cytokines that preferentially induces apoptosis in transformed cells, making it a promising cancer therapy. However, many neoplasms are resistant to TRAIL-induced apoptosis by mechanisms that are poorly understood. We demonstrate that the expression of the small heat shock protein alpha B-crystallin (but not other heat shock proteins or apoptosis-regulating proteins) correlates with TRAIL resistance in a panel of human cancer cell lines. Stable expression of wild-type alpha B-crystallin, but not a pseudophosphorylation mutant impaired in its assembly and chaperone function, protects cancer cells from TRAIL-induced caspase-3 activation and apoptosis in vitro. Furthermore, selective inhibition of alpha B-crystallin expression by RNA interference sensitizes cancer cells to TRAIL. In addition, wild-type alpha B-crystallin promotes xenograft tumor growth and inhibits TRAIL-induced apoptosis in vivo in nude mice, whereas a pseudophosphorylation alpha B-crystallin mutant impaired in its anti-apoptotic function inhibits xenograft tumor growth. Collectively, these findings indicate that alpha B-crystallin is a novel regulator of TRAIL-induced apoptosis and tumor growth. Moreover, these results demonstrate that targeted inhibition of alpha B-crystallin promotes TRAIL-induced apoptosis, thereby suggesting a novel strategy to overcome TRAIL resistance in cancer.

Apoptosis↗
PubMed2005

Simultaneous separation and purification of five bioactive coumarins from the Chinese medicinal plant Cnidium monnieri by high-speed counter-current chromatography.

Cnidium monnieri (L.) Cusson is a well-known Chinese medicinal plant, which has been used for the treatment of impotence, frigidity, and skin-related diseases, and exhibits strong antipruritic, antiallergic, antidermatophytic, antibacterial, antifungal, and antiosteoporotic activities. A high-speed counter-current chromatography method was developed for the separation and purification of five bioactive coumarins from this plant. The crude coumarins were obtained by ethanol extraction from the dried fruits of Cnidium monnieri (L.) Cusson under sonication. High-speed counter-current chromatography with the two-phase solvent systems n-hexane-ethyl acetate-ethanol-water (5:5:4:6, v/v) and n-hexane-ethyl acetate-ethanol-water (5:5:6:4, v/v) was successfully performed with stepwise elution. The five relatively pure coumarins were obtained from 500 mg of the crude extract in a single run. Their purities were 90.6-98.9%, and the recoveries were 85.7-94.2%.

Chromatography, High Pressure Liquid↗
PubMed2005

Isolation and proteomic analysis [corrected] of cell wall-deficient Haematococcus pluvialis mutants.

The green alga Haematococcus pluvialis has a plant-like cell wall consisting of glycoproteins and cellulose that is modified during the cell cycle and under various conditions. These features allow Haematococcus to be used as a model organism for studying cell wall biology. Development of the Haematococcus model is hampered by the absence of mutants that could provide insight into the biosynthesis and assembly of wall components. Haematococcus mutants (WM#537 and WM#2978) (WM--wall mutant) with defective cell walls were obtained by chemical mutagenesis. WM#537 features a secondary wall of considerably reduced thickness, whereas WM#2978 possesses a somewhat reduced secondary wall with little intervening space between the wall and plasmalemma. 2-DE revealed that a majority of the cell wall proteins were present in the wild-type and mutant cell walls throughout the cell cycle. PMF identified 55 wall protein orthologs from these strains, including a subset of induced proteins known to be involved in wall construction, remodeling, and defense. Down-regulation of certain wall proteins in the two mutants was associated with the wall defects, whereas overexpression of other proteins may have compensated for the defective walls in the two mutants.

Algal Proteins↗
PubMed2005

A tetracycline-regulated adenovirus encoding dominant-negative caspase-9 is regulated in rat brain and protects against neurotoxin-induced cell death in vitro, but not in vivo.

Caspase-9 is a critical downstream effector molecule involved in apoptosis, a cell death process thought to be involved in the demise of dopamine (DA) neurons in the substantia nigra (SN) affected by Parkinson's disease (PD). In this study, we determined that a tetracycline-regulated adenovirus harboring a dominant-negative form of caspase-9 (Casp9DN) and the marker gene, enhanced green fluorescent protein (EGFP), under the control of a bidirectional promoter could each be regulated in vitro and in vivo by doxycycline. We next observed that Casp9DN gene delivery significantly protected against TNFalpha and cycloheximide-induced chromatin condensation in HeLa cells and prevented chromatin condensation and the appearance of the early apoptotic marker annexin V in 6-hydroxydopamine (6-OHDA) treated MN9D cells, a dopaminergic cell line. Effects of Casp9DN on DA neurons in vivo were also assessed. DA neurons were retrogradely labeled with fluorogold (FG) and transduced with Casp9DN and EGFP or EGFP alone. A progressive lesion of DA neurons was induced by striatal injection of 6-OHDA 1 week later. At 2 weeks post-lesion, a morphometric analysis of FG+ neurons in the SN revealed that the mean cell diameter of FG labeled neurons in the Casp9DN group was 8% and 21% larger than the EGFP and PBS groups, respectively (P <0.05). However, there was no difference among the treatment groups in the number of neurons remaining in the lesioned SN. These results suggest that while inhibiting apoptosis at the level of caspase-9 is protective in vitro, it is not protective against 6-OHDA-induced cell death in vivo.

Adenoviridae↗
PubMed2005

Molecular diagnosis of human cancer type by gene expression profiles and independent component analysis.

The precise diagnosis of cancer type based on microarray data is of particular importance and is also a challenging task. We have devised a novel pattern recognition procedure based on independent component analysis (ICA). Different from the conventional cancer classification methods, which are limited in their clinical applicability of cancer diagnosis, our method extracts explicitly, by ICA algorithm, a set of specific diagnostic patterns of normal and tumor tissues corresponding to a set of biomarkers for clinical use. We validated our procedure with the colon and prostate cancer data sets and achieved good diagnosis (>90%) on the data sets studied here. This technique is also suitable for the identification of diagnostic expression patterns for other human cancers and demonstrates the feasibility of simple and accurate molecular cancer diagnostics for clinical implementation.

Algorithms↗
PubMed2005

Apoptotic effect of oridonin on NB4 cells and its mechanism.

The anti-proliferation effects of oridonin on acute promyelocytic leukemia (APL) cells and its mechanisms were studied in vitro. NB4 cells as well as fresh leukemia cells obtained from APL patients in culture medium were treated with different concentrations of oridonin. Cell growth inhibition, apoptosis and related pathways were assessed by MTT assay as well as flow cytometry (FCM) and western blot analysis. The data revealed that oridonin (over 16 micromol/L) could inhibit the growth of NB4 cells by induction of apoptosis. Marked changes of cell apoptosis were observed very clearly by using electron microscopy and DNA fragmentation analysis after the cells exposed to oridonin for 48 h; Western blotting showed cleavage of the caspase-3 zymogen protein (32-kDa) with the appearance of its 20-kDa subunit as well as a cleaved 89-kDa fragment of 116-kDa PARP when apoptosis occurred. The expression of Bcl-2 was down-regulated remarkably accompanied by the disruption of the mitochondrial membrane potential (delta(psi)m). The anti-proliferative and apoptosis-inducing effects by oridonin in fresh APL cells were also found remarkably using Trypan Blue dye exclusion method and Wright's staining. We concluded that oridoning has significant anti-proliferative and apoptosis-inducing effects on NB4 cells by activation of caspase-3 and cleavage of PARP as well as by down regulation of Bcl-2 and disruption of the delta(psi)m. Furthermore, oridonin demonstrated apparent cell growth inhibition effects on fresh APL cells in vitro. The results indicated that oridonin may serve as a potential anti-leukemia reagent.

Antineoplastic Agents↗
PubMed2005

Necrosis avid contrast agents: functional similarity versus structural diversity.

Two categories of necrosis-avid contrast agents (NACAs), namely porphyrin- and nonporphyrin-based complexes, have thus far been discovered as necrosis-targeting markers for noninvasive magnetic resonance imaging (MRI) identification of acute myocardial infarction, assessment of tissue or organ viability, and therapeutic evaluation after interventional therapies. In addition to necrosis labeling, other less-specific functions, such as first-pass perfusion, blood pool contrast effect, hepatobiliary contrast enhancement (CE), adrenal and spleen CE, and renal functional imaging, also are demonstrated with NACAs. Despite various investigations with a collection of clues in favor of certain hypotheses, the mechanisms of such a unique targetability for NACAs still remain to be elucidated. However, a few things have become clear that porphyrin-like structures are not necessary for necrosis avidity and the albumin binding is not the supposed driving force but only a parallel nonspecific feature shared by both NACAs and non-NACA substances. Although the research and development of NACAs still remain in preclinical stage at a relatively small scale, their significance rests upon striking enhancement effects, which may warrant their eventual versatile clinical applications. The present review article is intended to summarize the cumulated facts about the evolving research on this topic, to demonstrate experimental observations for better understanding of the mechanisms, to trigger broader public interests and more intensive research activities, and to advocate, toward both academics and industries, further promotion of preclinical and clinical development of this unique and promising class of contrast agents.

Animals↗