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Biomedical subjects

Feng Chen

Publications and source records attributed to Feng Chen.

At least 55 records · Page 3Linked to original sources
PubMed2006

Polymorphisms in DNA damage binding protein 2 (DDB2) and susceptibility of primary lung cancer in the Chinese: a case-control study.

DNA damage binding protein 2 (DDB2) is one of the major DNA repair proteins involved in the nucleotide excision repair (NER) pathway. Mutations in the DDB2 gene can cause a repair-deficiency syndrome xeroderma pigmentosum group E. Because tobacco carcinogens can cause DNA damage that is repaired by NER and suboptimal NER capacity is reported to be associated with lung cancer risk, we hypothesized that common variants in the DDB2 gene are associated with lung cancer risk. To test this hypothesis, we conducted a case-control study of 1010 patients with incident lung cancer and 1011 cancer-free controls and genotyped two DDB2 single nucleotide polymorphisms (SNPs) (rs830083 and rs3781620) that are in linkage disequilibrium with other untyped SNPs. We found that compared with the rs830083CC, subjects carrying the heterozygous rs830083CG genotype had a significantly 1.31-fold increased risk of lung cancer [95% confidence interval (CI) 1.08-1.60] and those carrying the homozygous rs830083GG genotype had a non-significantly 1.22-fold elevated risk (95% CI 0.89-1.67). In addition, effects of the combined rs830083CG/GG variant genotypes were more evident in young subjects, heavy smokers and subjects with a positive family history of cancer. These findings indicate, for the first time, that the DDB2 rs830083 polymorphism may contribute to the etiology of lung cancer. Further functional studies on this SNP and/or related variants are warranted to elucidate the underlying molecular mechanisms of the association.

Aged↗
PubMed2006

Statistical analysis of real-time PCR data.

BACKGROUND: Even though real-time PCR has been broadly applied in biomedical sciences, data processing procedures for the analysis of quantitative real-time PCR are still lacking; specifically in the realm of appropriate statistical treatment. Confidence interval and statistical significance considerations are not explicit in many of the current data analysis approaches. Based on the standard curve method and other useful data analysis methods, we present and compare four statistical approaches and models for the analysis of real-time PCR data. RESULTS: In the first approach, a multiple regression analysis model was developed to derive DeltaDeltaCt from estimation of interaction of gene and treatment effects. In the second approach, an ANCOVA (analysis of covariance) model was proposed, and the DeltaDeltaCt can be derived from analysis of effects of variables. The other two models involve calculation DeltaCt followed by a two group t-test and non-parametric analogous Wilcoxon test. SAS programs were developed for all four models and data output for analysis of a sample set are presented. In addition, a data quality control model was developed and implemented using SAS. CONCLUSION: Practical statistical solutions with SAS programs were developed for real-time PCR data and a sample dataset was analyzed with the SAS programs. The analysis using the various models and programs yielded similar results. Data quality control and analysis procedures presented here provide statistical elements for the estimation of the relative expression of genes using real-time PCR.

Analysis of Variance↗
PubMed2006

In vitro labeling and MRI of mesenchymal stem cells from human umbilical cord blood.

OBJECTIVE: The aim of this study was to label human umbilical cord blood mesenchymal stem cells (MSCs) with poly-l-lysine (PLL)-conjugated superparamagnetic iron oxide particles and to obtain magnetic resonance (MR) images of the labeled MSCs' suspension at 1.5 T. MATERIAL AND METHODS: PLL was conjugated with iron oxide to form superparamagnetic particles called Fe(2)O(3)-PLL. Human umbilical cord blood MSCs were isolated, purified, expanded and incubated with Fe(2)O(3)-PLL. Prussian blue stain was performed to show intracellular iron; spectrometry was used to quantify iron uptake within cells. Tetrazolium salt (MTT) assay was applied to evaluate toxicity and proliferation of MSCs labeled with various concentrations of Fe(2)O(3)-PLL. The cell apoptosis rate was determined by annexin V/propichium iodide (PI) double staining method. Vials containing cells underwent MR imaging (MRI) with T(1), T(2) and T(2)* weighted MRI. RESULTS: Iron-containing intracytoplasmatic vesicles could be observed clearly with Prussian blue staining in all samples except the unlabeled control. The iron content per cell determined by spectrometry was 64.51+/-10.32 pg. Among MSCs with and without labeling of various concentrations of Fe(2)O(3)-PLL, MTT values of light absorption had no statistically significant difference (Kruskal-Wallis test, chi(2)=10.35, P=.17). A concentration at 20 mug/ml of iron appeared most suitable for incubating cells. Of labeled and unlabeled MSCs, the early [annexin V-fluorescein isothiocyanate (FITC)-positive/PI-negative] and late (annexin V-FITC-positive/PI-positive) apoptotic cells were 10.34+/-0.43%/11.36+/-1.30% and 4.01+/-1.76%/2.98+/-1.37%, respectively, and there were no significant differences between them (P>.05). T(2) weighted image (WI) and T(2)*WI demonstrated significant decrease of signal intensity (SI) in vials containing 1 x 10(6) (1 day), 1x10(6) (8 days) and 5 x 10(5) labeled cells, in comparison with unlabeled cells (P<.05). The percentage change of SI (DeltaSI) was significantly higher in 10(6) labeled cells after 1-day culture than that in the same number of labeled cells after 8-day culture and that in 5 x 10(5) labeled cells, particularly on T(2)*WI (P<.05). Among pulse sequences, T(2)*WI demonstrated the highest DeltaSI (P<.05). CONCLUSION: The human umbilical cord blood MSCs can be labeled with Fe(2)O(3)-PLL without significant change in viability and apoptosis. The suspension of labeled MSCs can be imaged with standard 1.5-T MR equipment.

Cell Survival↗
PubMed2006

A quasiclassical trajectory study for the N(4S)+O2(X 3Sigmag-)-->NO(X 2Pi)+O(3P) reaction on the new 2A' and 4A' potential-energy surfaces.

A quasiclassical trajectory study with the sixth-order explicit symplectic algorithm of the N(4S)+O2(X 3Sigmag-)-->NO(X 2Pi)+O(3P) atmospheric reaction has been performed by employing the new 2A' and 4A' potential-energy surfaces reported by Sayos et al. [J. Chem. Phys. 117, 670 (2002)]. For the translational temperature considered up to 10,000 K, the larger relative translational energy and the higher rovibrational levels of O2 molecule with respect to the previous works have been taken into account, and a clearer database about the character of the total reaction cross section has been presented in this work. The dependence of microscopic rate constants on the vibrational level of O2 molecule at T=3000, 5000, and 10,000 K has been exhibited, and we can see that the values of log10 k(T,v,J) vary almost linearly with the vibrational level of O2 molecule. The thermal rate constants at the translational temperature between 300 and 10,000 K have been evaluated and compared with the experimental and previous theoretical results. It is found that the thermal rate constants determined in this work have a better agreement with the experimental data and can provide a more valid theoretical reference at the translational temperature considered for the title reaction.

Journal Article↗
PubMed2006

An ankyrin repeat-containing protein, characterized as a ubiquitin ligase, is closely associated with membrane-enclosed organelles and required for pollen germination and pollen tube growth in lily.

Exhibiting rapid polarized growth, the pollen tube delivers the male gametes into the ovule for fertilization in higher plants. To get an overall picture of gene expression during pollen germination and pollen tube growth, we profiled the transcription patterns of 1,536 pollen cDNAs from lily (Lilium longiflorum) by microarray. Among those that exhibited significant differential expression, a cDNA named lily ankyrin repeat-containing protein (LlANK) was thoroughly studied. The full-length LlANK cDNA sequence predicts a protein containing five tandem ankyrin repeats and a RING zinc-finger domain. The LlANK protein possesses ubiquitin ligase activity in vitro. RNA blots demonstrated that LlANK transcript is present in mature pollen and its level, interestingly contrary to most pollen mRNAs, up-regulated significantly during pollen germination and pollen tube growth. When fused with green fluorescent protein and transiently expressed in pollen, LlANK was found dominantly associated with membrane-enclosed organelles as well as the generative cell. Overexpression of LlANK, however, led to abnormal growth of the pollen tube. On the other hand, transient silencing of LlANK impaired pollen germination and tube growth. Taken together, these results showed that LlANK is a ubiquitin ligase associated with membrane-enclosed organelles and required for polarized pollen tube growth.

Ankyrin Repeat↗
PubMed2006

First preclinical evaluation of mono-[123I]iodohypericin as a necrosis-avid tracer agent.

PURPOSE: We have labelled hypericin, a polyphenolic polycyclic quinone found in St. John's wort (Hypericum perforatum), with( 123)I and evaluated mono-[(123)I]iodohypericin (MIH) as a potential necrosis-avid diagnostic tracer agent. METHODS: MIH was prepared by an electrophilic radioiodination method. The new tracer agent was evaluated in animal models of liver infarction in the rat and heart infarction in the rabbit using single-photon emission computed tomography (SPECT), triphenyltetrazolium chloride (TTC) histochemical staining, serial sectional autoradiography and microscopy, and radioactivity counting techniques. RESULTS: Using in vivo SPECT imaging, hepatic and cardiac infarctions were persistently visualised as well-defined hot spots over 48 h. Preferential uptake of the tracer agent in necrotic tissue was confirmed by perfect match of images from post-mortem TTC staining, autoradiography (ARX) and histology. Radioactivity concentration in infarcted tissues was over 10 times (liver; 3.51% ID/g in necrotic tissue vs 0.38% ID/g in normal tissue at 60 h p.i.) and over 6 times (myocardium; 0.36% ID/g in necrotic tissue vs 0.054% ID/g in normal tissue; ratios up to 18 for selected parts on ARX images) higher than in normal tissues. CONCLUSION: The results suggest that hypericin derivatives may serve as powerful necrosis-avid diagnostic agents for assessment of tissue viability.

Animals↗
PubMed2006

Magnetic resonance imaging after radiofrequency ablation in a rodent model of liver tumor: tissue characterization using a novel necrosis-avid contrast agent.

We exploited a necrosis-avid contrast agent ECIV-7 for magnetic resonance imaging (MRI) in rodent liver tumors after radiofrequency ablation (RFA). Rats bearing liver rhabdomyosarcoma (R1) were randomly allocated to three groups: group I, complete RFA, group II, incomplete RFA, and group III, sham ablation. Within 24 h after RFA, T1-weighted (T1-w) MRI was performed before and after injection of ECIV-7 at 0.05 mmol/kg and followed up from 6-24 h. Signal intensities (SIs) were measured with relative enhancement (RE) and contrast ratio (CR) calculated. The MRI findings were verified histomorphologically. On plain T1-w MRI the contrasts between normal liver, RFA lesion, residual and/or intact tumor were vague. Early after administration of ECIV-7, the liver SI was strongly enhanced (RE=40-50%), leaving the RFA lesion as a hypointense region in groups I and II. At delayed phase, two striking peri-ablational enhancement patterns appeared (RE=90% and CR=1.89%), i.e., "O" type of hyperintense rim in group I and "C" type of incomplete rim in group II. These MRI manifestations could be proven histologically. In this study, tissue components after RFA could be characterized with discernable contrasts by necrosis-avid contrast agent (NACA)-enhanced MRI, especially at delayed phase. This approach may prove useful for defining the ablated area and identifying residual tumor after RFA.

Animals↗
PubMed2006

The GABA(B) receptor allosteric modulator CGP7930, like baclofen, reduces operant self-administration of ethanol in alcohol-preferring rats.

GABA systems have been implicated as targets for ethanol at the cellular, molecular and behavioural level. The present study was designed to further examine the potential of the GABA(B) receptor as a target for regulating operant alcohol responding. Given that the prototypic agonist, baclofen, reduces the self-administration of alcohol, we hypothesized that the GABA(B) receptor allosteric modulator, CGP7930, might have similar actions but a reduced side-effect profile. In this context, inbred alcohol-preferring (iP) rats were trained to respond for 10% v/v ethanol in a fixed ratio paradigm; all drug testing was performed under an FR3 schedule. Both baclofen and CGP7930 independently reduced voluntary responding for 10% ethanol in a dose-related manner. Neither drug impacted upon responding for water. A combination of subthreshold doses of baclofen and CGP7930 was also able to reduce operant responding for ethanol, suggesting that CGP7930 is indeed acting to facilitate GABA(B) receptor-mediated signalling in this paradigm. These data demonstrate the potential of positive allosteric modulators of metabotropic GABA(B) receptors to regulate alcohol responding.

Alcohol Drinking↗
PubMed2006

OrthoMCL-DB: querying a comprehensive multi-species collection of ortholog groups.

The OrthoMCL database (http://orthomcl.cbil.upenn.edu) houses ortholog group predictions for 55 species, including 16 bacterial and 4 archaeal genomes representing phylogenetically diverse lineages, and most currently available complete eukaryotic genomes: 24 unikonts (12 animals, 9 fungi, microsporidium, Dictyostelium, Entamoeba), 4 plants/algae and 7 apicomplexan parasites. OrthoMCL software was used to cluster proteins based on sequence similarity, using an all-against-all BLAST search of each species' proteome, followed by normalization of inter-species differences, and Markov clustering. A total of 511,797 proteins (81.6% of the total dataset) were clustered into 70,388 ortholog groups. The ortholog database may be queried based on protein or group accession numbers, keyword descriptions or BLAST similarity. Ortholog groups exhibiting specific phyletic patterns may also be identified, using either a graphical interface or a text-based Phyletic Pattern Expression grammar. Information for ortholog groups includes the phyletic profile, the list of member proteins and a multiple sequence alignment, a statistical summary and graphical view of similarities, and a graphical representation of domain architecture. OrthoMCL software, the entire FASTA dataset employed and clustering results are available for download. OrthoMCL-DB provides a centralized warehouse for orthology prediction among multiple species, and will be updated and expanded as additional genome sequence data become available.

Animals↗
PubMed2006

Antiproliferation effects of oridonin on HPB-ALL cells and its mechanisms of action.

Oridonin, an ent-kaurane diterpenoid derived from the herbal Rabdosia rubescens, has been recently reported to have antitumor effects on a large variety of cancer cells. The present study was undertaken to investigate the in vitro antiproliferation and apoptosis inducing effects of oridonin on HPB-ALL cell lines and its mechanisms of action. HPB-ALL cells in culture medium in vitro were treated with different concentrations of oridonin (16-56 micromol/L). MTT assay was used to detect the cell growth inhibitory rate, and the cell viability was assessed by the trypan blue dye-exclusion method. Cell apoptosis and the mitochondrial membrane potential (delta psi m) were investigated by flow cytometry (FCM), Hoechst 33258 staining, and DNA fragmentation analysis. The expression of caspase-3 and different apoptosis modulators, including Fas and Bcl-2 family members, was analyzed by Western blotting. The results revealed that oridonin could significantly inhibit the growth of HPB-ALL cells and cause apoptosis, and the suppression was both time- and dose-dependent. After treatment with oridonin for 48 hr, the percentage of disruption of delta psi m gradually increased in a dose-dependent manner along with marked changes of cell apoptosis, and necrotic cells increased remarkably after the cells were treated with oridonin for 72 hr; Western blotting showed cleavage of the caspase-3 zymogen protein (32 kDa) with the appearance of its 20-kDa subunit when apoptosis occurred; expression of Bcl-2 and Bcl-XL was downregulated remarkably while expression of Bax and Bid was upregulated concurrently after the cells were treated with oridonin for 24 hr. Of note, the expressions of Fas and other Bcl-2 family members including Bak and Bad remained constant before and after apoptosis occurred. We therefore conclude that oridonin has significant antiproliferation effects on HPB-ALL cells by induction of apoptosis as well as directly causing cell necrosis and that oridonin-induced apoptosis on HPB-ALL cells is mainly related to the disruption of delta psi m and activation of caspase-3 as well as downregulation of anti-apoptotic protein Bcl-2, Bcl-XL, and upregulation of pro-apoptotic proteins Bax and Bid. The results indicate that oridonin may serve as a potential antileukemia reagent.

Antineoplastic Agents↗
PubMed2006

Isolation and purification of canthaxanthin from the microalga Chlorella zofingiensis by high-speed counter-current chromatography.

Certain microalgae are considered to be a potential source of canthaxanthin, which possesses strong antioxidant and anticancer activities. A high-speed counter-current chromatography (HSCCC) method was developed for the separation and purification of canthaxanthin from the microalga Chlorella zofingiensis. The crude canthaxanthin was obtained by extraction with organic solvents after the microalgal sample had been saponified. Preparative HSCCC, with a two-phase solvent system composed of n-hexane-ethanol-water (10:9:1 v/v), was successfully performed yielding canthaxanthin at 98.7% purity from 150 mg of the crude extract (2.1% canthaxanthin) in a one-step separation. The recovery of canthaxanthin was 92.3%. This was the first report that canthaxanthin was successfully separated and purified from microalgae.

Animals↗
PubMed2006

Kinetic modeling of lutein production by heterotrophic Chlorella at various pH and temperatures.

Kinetics of lutein production by heterotrophic Chlorella protothecoides was investigated with respect to pH and temperature. Flask cultures with initial pH 5.0-8.0 were carried out, and it was found that pH 6.0 was optimal for the algal growth. Further tests in fermentors showed that the highest biomass concentration, maximum cellular lutein content and lutein yield were achieved at pH 6. 6. In addition, it was shown that optimal biomass concentration and lutein yield were obtained at 28 degrees C, while application of 35 degrees C resulted in the highest cellular lutein content. A mathematical model was developed for the description of the processes under these cultivation conditions and the kinetic model fitted well to the experimental data. The obtained results may contribute to the commercial production of lutein by C. protothecoides.

Chlorella↗
PubMed2006

Heterocyclic amines: chemistry and health.

Heterocyclic amines (HAs) occur at the ppb range in foods. Most of them demonstrate potent mutagenicity in bacteria mutagenicity test, and some of them have been classified by the International Agency for Research on Cancer as probable/possible human carcinogens. Their capability of formation even during ordinary cooking practices implies frequent exposure by the general public. Over the past 30 years, numerous studies have been stimulated aiming to alleviate human health risk associated with HAs. These studies contribute to the understanding of their formation, characterization, and quantification in foods; their mutagenesis/carcinogenesis, mechanisms of antimutagenesis by chemical or phytogenic modulators; and strategies to inhibit their formation. The chemistry of HAs, their implications in human health, factors influencing their formation, and feasible ways of suppression will be briefly reviewed. Their occurrence in trace amounts in foods necessitates continuous development and amelioration of analytical techniques. Various inhibitory strategies, ranging from modifying cooking conditions to incorporation of different modulators, have been developed. This will remain one of the foremost areas of research in the field of food chemistry and safety.

Amines↗
PubMed2006

Growing phototrophic cells without light.

Many phototrophic microorganisms contain large quantities of high-value products such as n-3 polyunsaturated fatty acids and carotenoids but phototrophic growth is often slow due to light limitation. Some phototrophic microorganisms can also grow on cheap organic substrate heterotrophically. Heterotrophic cultivation can be well controlled and provides the possibility to achieve fast growth and high yield of valuable products on a large scale. Several strategies have been investigated for cultivation of phototrophic microorganisms without light. These include trophic conversion of obligate photoautotrophic microorganisms by genetic engineering, development of efficient cultivation systems and optimization of culture conditions. This paper reviews recent advances in heterotrophic cultivation of phototrophic cells with an emphasis on microalgae.

Biotechnology↗
PubMed2006

Ponicidin, an ent-kaurane diterpenoid derived from a constituent of the herbal supplement PC-SPES, Rabdosia rubescens, induces apoptosis by activation of caspase-3 and mitochondrial events in lung cancer cells in vitro.

Ponicidin, an ent-kaurane diterpenoid derived from a constituent of the herbal supplement PC-SPES, Rabdosia rubescens, is recently reported to have anti-tumor effects on a large variety of cancers. In this study, we demonstrate that ponicidin exhibits cytotoxicity, induces apoptosis, disrupts the mitochondrial membrane potential, and triggers the activation of caspase-3, -8 and -9 in lung cancer A549 and GLC-82 cells. Ponicidin treatment of lung cancer cells caused downregulation of anti-apoptotic protein Bcl-2 and survivin as well as upregulaton of pro-apoptotic protein Bax in a time dependent manner when apoptosis ocurred. Ponicidin induced activation of caspase-3 can be blocked by a caspase-3-specific inhibitor z-DEVD-FMK Furthermore, the caspase-8-specific inhibitor z-IETD-FMK could block the ponicidin-induced activation of caspase-3, PARP cleavage, and prevented the release of cytochrome c from mitochondria into the cytoplasm. This indicate that activated caspase-8 initiates the release of cytochrome c during ponicidin-induced apoptosis. We therefore conclude that ponicidin has significant apoptosis-inducing effects by activation of caspase-3 -8, and -9 as well as downregulation of anti-apoptotic protein Bcl-2, survivin and upregulation of pro-apoptotic protein Bax, with caspase-8 acting as an upstream activator. The data offer a potential mechanism for ponicidin-induced apoptosis in lung cancer cells, suggesting that ponicidin may severve as an effective reagent for the treatment of lung cancer, and that in vivo anti-cancer effects as well as its potential clinical effectiveness need further investigation.

Animals↗
PubMed2006

Antiproliferative activities of parthenolide and golden feverfew extract against three human cancer cell lines.

The medicinal herb feverfew [Tanacetum parthenium (L.) Schultz-Bip.] has long been used as a folk remedy for the treatment of migraine and arthritis. Parthenolide, a sesquiterpene lactone, is considered to be the primary bioactive compound in feverfew having anti-migraine, anti-tumor, and anti-inflammatory properties. In this study we determined, through in vitro bioassays, the inhibitory activity of parthenolide and golden feverfew extract against two human breast cancer cell lines (Hs605T and MCF-7) and one human cervical cancer cell line (SiHa). Feverfew ethanolic extract inhibited the growth of all three types of cancer cells with a half-effective concentration (EC50) of 1.5 mg/mL against Hs605T, 2.1 mg/mL against MCF-7, and 0.6 mg/mL against SiHa. Among the tested constituents of feverfew (i.e., parthenolide, camphor, luteolin, and apigenin), parthenolide showed the highest inhibitory effect with an EC50 against Hs605T, MCF-7, and SiHa of 2.6 microg/mL, 2.8 microg/mL, and 2.7 microg/mL, respectively. Interactions between parthenolide and flavonoids (apigenin and luteolin) in feverfew extract also were investigated to elucidate possible synergistic or antagonistic effects. The results revealed that apigenin and luteolin might have moderate to weak synergistic effects with parthenolide on the inhibition of cancer cell growth of Hs605T, MCF-7, and SiHa.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

Genotyping of human papillomavirus in cervical lesions by L1 consensus PCR and the Luminex xMAP system.

Infection with human papillomavirus (HPV) is the main cause of cervical cancer, the principal cancer in women in most developing countries. Molecular epidemiologic evidence clearly indicates that certain types of HPV are the principal cause of invasive cervical cancer and cervical intraepithelial neoplasia. Comprehensive, high-throughput typing assays for HPV, however, are not currently available. By combining L1 consensus PCR and multiplex hybridization using a Luminex xMAP system-based suspension array, the authors developed a rapid high-throughput assay, the HPV DNA suspension array (HPV-SA), capable of simultaneously typing 26 HPVs, including 18 high-risk HPV genotypes and eight low-risk HPV genotypes. The performance of the HPV-SA applied to 26 synthetic oligonucleotide targets was evaluated. The HPV-SA system perfectly discriminated 18 high-risk HPV targets from eight low-risk HPV targets. To assess the clinical applicability of the assay, the HPV-SA was performed with 133 MY09/MY11 primer set-mediated PCR (MY-PCR)-positive clinical specimens; of the 133 samples, 121 were positive by HPV-SA. Both single and multiple types were easily identified. The authors believe that improvement of the assay may be useful for epidemiological studies, cancer-screening programmes, the monitoring of therapeutic interventions, and the evaluation of the efficacy of HPV vaccine trials.

Bacterial Typing Techniques↗