Biomedical subjects

Fang Chen

Publications and source records attributed to Fang Chen.

At least 55 records · Page 3Linked to original sources

PubMed2005

Isolation and characterization of thermo-acidophilic endospore-forming bacteria from the concentrated apple juice-processing environment.

Forty-five thermo-acidophilic, spore-forming bacteria were isolated from a concentrated apple juice-processing environment. All of them were Gram-positive, rod shaped, and strictly aerobic that most likely belong to the genus of Alicyclobacillus. A fast identification method-16S rDNA PCR-RFLP was used to identify them. The results indicated that at the similarity level of 87%, apple juice isolates strains of 1-4 and 1-2-4 clustered with the reference strain of A. acidoterrstris DSM 3922T, and 4-2-1, S-22 and 5-1 with A. cycloheptanicus DSM 4006T, respectively. The other tested strains were different from all the reference strains in this study and may be new species of Alicyclobacillus genus or the other. In order to confirm this conclusion, we selected 7 16S rDNA PCR-RFLP identified strains and 5 type strains of Alicyclobacillus genus, carried on 51 kinds of phenotypic characteristics and analysis the data by unweighted pair group method with arithmetic mean (UPGMA). The results showed that the similarity degree between every two strains was lower than 80%. It also suggested that they may be different from each other and the unidentified strains may be new species. In addition, spoilage effects of them on 12 Brix apple juice were also studied. The result suggested that all 19 tested bacterial strains caused apple juice to become turbid, form a precipitate and off odor at varying rates when incubated at 37 degrees C up to 12 days. It suggested that these bacteria are associated with the spoilage of apple juice during storage.

Bacillus↗

PubMed2005

Glutathione S-transferase pi1 promotes tumorigenicity in HCT116 human colon cancer cells.

GSTP1 is a member of the glutathione S-transferase enzyme superfamily, which catalyzes the conjugation of electrophiles with glutathione in the process of detoxification. GSTP1 is widely overexpressed in colorectal cancer, from aberrant crypt foci to advanced carcinomas. Increased expression of GSTP1 is associated with multidrug resistance and a worse clinical prognosis. However, GSTP1-null mice have an increased risk of tumor formation. Thus, the biological function of GSTP1 in colorectal cancer biology remains speculative. In an effort to gain further insights into the role of GSTP1 in tumorigenesis, we disrupted the GSTP1 gene in HCT116 human colorectal cancer cells using targeted homologous recombination. We find that loss of GSTP1 resulted in impaired clonogenic survival and proliferation. Specifically, under growth-limiting conditions, (a) GSTP1 protected HCT116 cells from oxidative stress and associated apoptosis and (b) promoted mitogen-activated protein kinase-extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase-mediated G1-S cell cycle progression. In vivo, GSTP1 was critical for engraftment and growth of HCT116 tumor xenografts. These studies directly show that GSTP1 promotes clonogenic survival and proliferation in HCT116 human colon cancer cells.

Animals↗

PubMed2005

Antagonist-induced, activation function-2-independent estrogen receptor alpha phosphorylation.

Estrogen receptor alpha (ERalpha) serine 118 (Ser118) phosphorylation modulates activation function-1 (AF1) function. Correct positioning of helix 12 promotes agonist-dependent recruitment of cyclin-dependent kinase-7 to catalyze this event. In this study we show robust cyclin-dependent kinase-7-independent, AF2 antagonist-induced Ser118 phosphorylation. Estradiol (E2) and ICI-182,780 (ICI-780) induce Ser118 phosphorylation of wild-type ERalpha and either of two helix 12 mutants, suggesting AF2-independent action, probably via shedding of 90-kDa heat shock protein. With E2 treatment, the predominantly nuclear, phosphorylated ERalpha in COS-1 cells is detergent soluble. Although levels of ICI-780-induced phosphorylation are profound, Ser118-phosphorylated ERalpha is aggregated over the nucleus or in the cytoplasm, fractionating with the cell debris and making detection in cleared lysates improbable. Selective ER modulators (SERMs) elicit a mixed response with phosphorylated ERalpha in both detergent-soluble and -insoluble compartments. Apparent ligand-induced loss of ERalpha protein from cleared lysates is thus due to ligand-induced redistribution into the pellet, not degradation. The COS-1 response to ICI-780 can be mimicked in MCF-7 cells treated with a proteasome inhibitor to block authentic ligand-induced degradation. With SERMs and antagonists, the magnitude of Ser118-phosphorylated receptor redistribution into the insoluble fraction of COS-1 cells correlates with the magnitude of authentic ERalpha degradation in MCF-7 cells. A strong inverse correlation with ligand-induced uterotropism in vivo (P < 0.0001) and direct correlation with AF2-independent transrepression of the matrix metalloprotease-1 promoter in endometrial cells in vitro are seen. These data suggest that ligand-induced Ser118 phosphorylation of ERalpha can be AF2 independent. Furthermore, they identify translocation of Ser118-phosphorylated ERalpha out of the nucleus, leading to cytoplasmic aggregation, as an antagonist pathway that may precede receptor degradation.

Animals↗

PubMed2005

Mechanism of the greening color formation of "laba" garlic, a traditional homemade chinese food product.

While green discoloration during garlic processing is of a major concern, this greening is desirable and required for the traditional homemade Chinese "Laba" garlic. To obtain insights into the mechanism of color formation, simulation of the greening of "Laba" garlic was carried out in the laboratory by soaking aged garlic in 5% (v/v, pH 2.33) acetic acid solution. After 2 days, the garlic cloves turned green. Up to 4 days, pigment(s) diffused from garlic cloves to the pickling solution. The solution exhibits two maximal absorbances at approximately 440 and approximately 590 nm, corresponding to yellow and blue species, respectively, the combination of which creates the green coloration. With increasing time from 4 to 25 days, the concentration of both yellow and blue species increases at nearly the same rate, while after 25 days, the concentration of the yellow species increases faster than that of the blue species. Interestingly, most thiosulfinates ( approximately 85%) in garlic cloves were converted within 4 days, suggesting that thiosulfinate conversion is proportional to the formation of the pigments. Consistent with this conclusion, alliinase and acetic acid were required for the color formation. UV-vis spectral measurements and pH results suggest that the color formation occurs by two kinds of processes: one enzymatic and the other nonenzymatic. Low pH (2.0-3.0) favors nonenzymatic reactions, while high pH (6.0 or above) is conducive to enzymatic reactions. Thus, the ideal pH for the entire process of garlic greening is between 4.0 and 5.0, which is a compromise of the optimal pH of both the enzymatic and nonenzymatic reactions.

Acetic Acid↗

PubMed2005

Electrochemistry and voltammetry of procaine using a carbon nanotube film coated electrode.

A new rapid, convenient and sensitive electrochemical method is described for the determination of procaine in pharmaceutical preparations, based on the unique properties of a multi-wall carbon nanotube (MWNT) thin film. The electrochemical behavior of procaine at the MWNT film-coated glassy carbon electrode (GCE) was investigated in detail, showing that the MWNT-coated GCE exhibits electrocatalytic activity to the oxidation of procaine because of the significant peak current enhancement and the lowering of oxidation overpotential. Furthermore, the mechanism for the oxidation of procaine at the MWNT-coated GCE was also studied. Finally, various experimental parameters such as solution pH value, the amount of MWNT, accumulation conditions and scan rate were optimized for the determination of procaine, and a new method with detection limit of 2 x 10(-7) mol/L was developed for procaine determination. This newly proposed method was successfully demonstrated with procaine hydrochloride injection.

Biosensing Techniques↗

PubMed2005

Direct agonist/antagonist functions of dehydroepiandrosterone.

Dehydroepiandrosterone (DHEA) exhibits peak adrenal secretion in the fetus at term and around age 30 yr in the adult. Levels then progressively decline, which is associated with decreased levels of testosterone, dihydrotestosterone, and estrogen in peripheral tissues. DHEA supplementation in postmenopausal women increases bone formation and density, an effect mainly attributed to peripheral conversion to sex hormones. In this study, we tested DHEA for direct effects on the androgen (AR) and estrogen (ER) receptors. DHEA bound to AR with a Ki of 1 microM, which was associated with AR transcriptional antagonism on both the mouse mammary tumor virus and prostate-specific antigen promoters, much like the effects of bicalutamide. Unlike bicalutamide, DHEA stimulated, rather than inhibited, LNCaP cell growth, suggesting possible interaction with other hormone receptors. Indeed DHEA bound to ERalpha and ERbeta, with Ki values of 1.1 and 0.5 microM, respectively. Despite the similar binding affinities, DHEA showed preferential agonism of ERbeta with an EC50 of approximately 200 nm and maximal activation at 1 microM. With ERalpha we found 30-70% agonism at 5 microM, depending on the assay. Physiological levels of DHEA are approximately 30 nM and up to 90 nM in the prostate. DHEA at 30 nM is actually sufficient to activate ERbeta transcription to the same degree as estrogen at its circulating concentration, and additive effects are seen when the two were combined. Taken together, DHEA has the potential for physiologically relevant direct activation of ERbeta. With peak levels at term and age 30 yr, there is also a potential for antagonist effects on AR and partial agonism of ERalpha.

Androgen Receptor Antagonists↗

PubMed2005

Unexpected behavior of coniferin in lignin biosynthesis of Ginkgo biloba L.

To gain insight into the behavior of monolignol glucoside in Ginkgo biloba L., we examined glucosides potentially involved in lignin biosynthetic pathway. Coniferin (coniferyl alcohol 4O-beta-D-glucoside) is a strong candidate for the storage form of monolignol. Coniferaldehyde glucoside may also have a role in lignin biosynthesis; this was examined with tracer experiments using labeled glucosides fed to stem segments. A series of tracer experiments showed that coniferin and coniferaldehyde glucoside were modified into coniferyl alcohol and then efficiently incorporated into lignin under the experimental conditions used. Interestingly, more than half of the administered coniferin underwent an oxidation to the aldehyde form before its aglycone; coniferyl alcohol was polymerized into lignin. This suggests that there is an alternative pathway for coniferin to enter the monolignol biosynthetic pathway, in addition to the direct pathway beginning with the deglucosylation of coniferin catalyzed by beta-glucosidase. Enzymatic assays revealed that coniferaldehyde glucoside was produced enzymatically from coniferin, and that coniferaldehyde glucoside can be deglucosylated to yield coniferaldehyde, which could be fated to become coniferyl alcohol . Albeit the findings cannot be taken as proof for the in-planta functioning, these results present a possibility for the existence of alternative pathway in which some of the stored coniferin is oxidized to coniferaldehyde glucoside, which is deglucosylated to generate coniferaldehyde that joins the monolignol biosynthesis pathway.

Cinnamates↗

PubMed2005

Controllable interconnection of single-walled carbon nanotubes under ac electric field.

We demonstrated the controllable interconnection of single-walled carbon nanotubes (SWNTs) under alternating current (ac) electric field. The interconnected carbon nanotubes were found to be parallel with the electric flux and increased abruptly with deposition time following a self-accelerating process. Theoretical simulation indicates that the alignment and the interconnection of carbon nanotubes were induced by the dielectrophoresis force and the electric field redistribution at the nanotube apexes.

Letter↗

PubMed2005

[Amniotic fluid: a novel source for tissue engineering].

OBJECTIVE: To investigate the possibility of using amniotic fluid cells as seed cells for tissue engineering. METHODS: Amniotic fluid was obtained by ultrasound-guided amniocentesis performed on pregnant women with a gestational age ranging from 16(th) approximately 23(rd) weeks. The cells isolated from the amniotic fluid were cultured in F10 culture fluid with 10% FBS. Immunocytochemistry was used to examine the standard intermediate filaments. After 3 passages of subculture, the cells were harvested and seeded onto PGA polymer scaffold. The cellular morphology, structure and adhesion with scaffold were evaluated by contrast microscope and scanning electronic microscope. RESULTS: The amniocytes expanded rapidly in culture media. Immunocytochemistry revealed positive signals for vimentin, smooth muscle action (SMA), and pan cytokeratin, and negative signals for desmin. Amniocytes-polymer complex analysis showed confluent cells firmly attached to the scaffold, with no evidence of cell death. CONCLUSION: The expansion potential of amniotic fluid cells is active. They express the characteristics of mesenchymal cells. The cells on PGA polymer scaffold can grow rapidly and maintain its morphological property. So the amniotic fluid may be a practical cell source for tissue engineering.

Actins↗

PubMed2005

Cross-host evolution of severe acute respiratory syndrome coronavirus in palm civet and human.

The genomic sequences of severe acute respiratory syndrome coronaviruses from human and palm civet of the 2003/2004 outbreak in the city of Guangzhou, China, were nearly identical. Phylogenetic analysis suggested an independent viral invasion from animal to human in this new episode. Combining all existing data but excluding singletons, we identified 202 single-nucleotide variations. Among them, 17 are polymorphic in palm civets only. The ratio of nonsynonymous/synonymous nucleotide substitution in palm civets collected 1 yr apart from different geographic locations is very high, suggesting a rapid evolving process of viral proteins in civet as well, much like their adaptation in the human host in the early 2002-2003 epidemic. Major genetic variations in some critical genes, particularly the Spike gene, seemed essential for the transition from animal-to-human transmission to human-to-human transmission, which eventually caused the first severe acute respiratory syndrome outbreak of 2002/2003.

Amino Acid Substitution↗

PubMed2005

Genetic diversity and genetic structure of an endangered species, Trillium tschonoskii.

The genetic diversity and genetic structure of Trillium tschonoskii (Maxim) were investigated using amplified fragment length polymorphism markers. Eight primer combinations were carried out on 105 different individuals sampled from seven populations. Of the 619 discernible DNA fragments generated, 169 (27.3%) were polymorphic. The percentage of polymorphic bands within populations ranged from 4.52 to 10.50. Genetic diversity (H(E)) within populations ranged from 0.0130 to 0.0379, averaging 0.0536 at the species level. Genetic differentiation among populations was detected based on Nei's genetic diversity analysis (53.03%) and analysis of molecular variance (AMOVA) (52.43%). AMOVA indicated significant genetic differentiation among populations (52.43% of the variance) and within populations (47.57% of the variance) (p < 0.0002). Gene flow was low (0.4429) among populations. Species breeding system and limited gene flow among populations are plausible reasons for the high genetic differentiation observed for this species. We propose an appropriate strategy for conserving the genetic resources of T. tschonoskii in China.

China↗

PubMed2005

Antisense bcl-2 transfection up-regulates anti-apoptotic and anti-oxidant thioredoxin in neuroblastoma cells.

Antisense bcl-2 therapy combined with chemotherapy has been proved to be effective in various tumors. However, the role played by antisense bcl-2 therapy alone is not clear. In this study, we compared the apoptosis and the protein profiles of antisense bcl-2 transfected human neuroblastoma SK-N-MC cells to the control cells. Flow cytometric data indicated that antisense bcl-2 transfection did not lead to more extensive apoptosis in SK-N-MC cells (14.9 +/- 3.8%) than the control cells (10.3 +/- 2.3%). The above observation was confirmed by fluorescence microscopy using Hoechst 33258 staining. However, antisense bcl-2 induced changes in the expression of various proteins as shown by proteomic comparison, which included the up-regulation of the anti-apoptotic and anti-oxidant protein thioredoxin. By western blot validation, thioredoxin was found to be up-regulated by 2.9-folds with the corresponding down-regulation of Bcl-2 by 2.1-folds. The up-regulation of thioredoxin may be a compensating mechanism for cell survival in neuroblastoma when Bcl-2 expression is suppressed, and it may to some extent attenuate the effectiveness of antisense bcl-2 therapy.

Apoptosis↗

PubMed2005

Effect of amino acid residue and oligosaccharide chain chemical modifications on spectral and hemagglutinating activity of Millettia dielsiana Harms. ex Diels. lectin.

The effects of modifying the carbohydrate chain and amino acids on the conformation and activity of Millettia dielsiana Harms. ex Diels. lectin (MDL) were studied by hemagglutination, fluorescence and circular dichroism analysis. The modification of tryptophan residues led to a compete loss of hemagglutinating activity; however, the addition of mannose was able to prevent this loss of activity. The results indicate that two tryptophan residues are involved in the carbohydrate-binding site. Modifications of the carboxyl group residues produced an 80% loss of activity, but the presence of mannose protected against the modification. The results suggest that the carboxyl groups of aspartic and glutamic acids are involved in the carbohydrate-binding site of the lectin. However, oxidation of the carbohydrate chain and modification of the histidine and arginine residues did not affect the hemagglutinating activity of MDL. Fluorescence studies of MDL indicate that tryptophan residues are present in a relatively hydrophobic region, and the binding of mannose to MDL could quench tryptophan fluorescence without any change in lambda(max). The circular dichroism spectrum showed that all of these modifications affected the conformation of the MDL molecule to different extents, except the modification of arginine residues. Fluorescence quenching showed that acrylamide and iodoacetic acids are able to quench 77% and 98% of the fluorescence of tryptophan in MDL, respectively. However, KI produced a barely perceptible effect on the fluorescence of MDL, even when the concentration of I(-) was 0.15 M. This demonstrates that most of tryptophan residues are located in relatively hydrophobic or negatively charged areas near the surface of the MDL molecule.

Acrylamide↗

PubMed2005

[The effects of 4 laboratory test kits in early detecting of severe acute respiratory syndrome coronavirus].

OBJECTIVE: To compare the 4 test kits on severe acute respiratory syndrome coronavirus (SARS-CoV) gene, antigen and antibody for early diagnose of SARS patients. METHODS: Three enzyme linked immunosorbent assay (ELISA) kits were used to detect SARS-CoV IgG, IgM and N protein and fluorescent polymerase chain reaction (F-PCR) kit was used to detect SARS-CoV RNA. RESULTS: In 162 serum samples, 90.2% (55/61) became N protein positive in 1 - 5 days and 92.8% (13/14) became positive IgM and IgG in 15 - 18 days after the onset of disease, respectively. On 82 gorgling samples, the positive rates of F-PCR were 56.3% (14/24) in 1 - 5 days and 71.4% (10/14) in 6 - 9 days after the onset. CONCLUSION: Other than F-PCR, N protein had good effect in the early detection on dubious patients which could lead to effective prevention and control of the epidemic.

Antibodies, Viral↗

PubMed2005

[The studies of risk factors and early intervention in patients with acute coronary syndromes without ST-segment elevation].

OBJECTIVE: To investigate the risk factors and the values of early invasive intervention in patients with acute coronary syndromes (ACS) without ST-segment elevation. METHODS: Five hundred and forty-five patients of ACS without ST-segment elevation were randomly assigned to an early conservative strategy or early invasive strategy who had been admitted to hospitals consecutively from Oct. 2001 to Oct. 2003. The combined cardiovascular events (a combination of cardiac death, nonfatal myocardial infarction, nonfatal heart failure and re-hospital admission due to recurrent ischemia angina) within 30 days and 6 months were analyzed and the primary high risk factors for combined cardiovascular events were evaluated by means of multivariate logistic regression analysis among baseline clinical characteristics and laboratory data, meanwhile, the effects of an early conservative strategy or early invasive strategy on outcomes were also investigated. RESULTS: The incidences of combined cardiovascular events within 30 days and 6 months among 513 cases were 14.0% and 25.7% respectively. Multivariate logistic regression analysis implied ST-segment depression, elevation of troponin I level, increased C-reactive protein, lower ejection fraction of left ventricular and higher TIMI risk scores were all associated with an increases in cardiovascular events within 6 months, and they were respectively independent predictive factor for the increases of cardiovascular events. Early invasive strategy was associated with a lower rate of re-hospital admission due to recurrent ischemia angina within 30 days and a decreased incidences of combined cardiovascular events within 30 days and 6 months compared with early conservative strategy (all P < 0.05). CONCLUSIONS: ST-segment depression, elevation of troponin I level, increased C-reactive protein, lower ejection fraction of left ventricular and higher TIMI risk scores are high risk factors for patients with ACS without ST-segment elevation, and early invasive strategy can have a substantial impact in reducing combined cardiovascular events.

Acute Coronary Syndrome↗

PubMed2005

[A case-control study on road-related traffic injury in Shanghai].

OBJECTIVE: To explore the risk factors that influencing the occurrence of road-related traffic injuries, so as to provide related bases for controlling injuries. METHODS: A case-control study was conducted on 256 drivers with histories of accidents and their controls. EPQ questionnaire and a self-designed questionnaire were used to collect data. Risk factors would include behaviors as driving time per day, types of vehicles, time and status of sleep, degree of education, diet habits, feeling of tiredness, alcohol intake, time of watching television before driving and marriage status. Physiological index as blood type, blood pressure, cordial, using tranquillizers, disease history, reaction time, eyesight, overweight, etc. were also tested. Conditional logistic regression model was used to analyze risk factors. RESULTS: From all these tests, risk factors which including dietetic rhythm (OR = 1.815), tiredness (OR = 3.263), history of digestive disease (OR = 3.504), weak eye sight (OR = 3.825), being divorced (OR = 3.226), wake up early (OR = 4.931), mixed insomnia (OR = 5.719), simple reaction time (OR = 3.498), complex reaction time (OR = 2.292), P score (OR = 1.352), E score (OR = 1.439) were noticed to be significantly important. CONCLUSION: The occurrence of road-related injuries were related to a series of physiological, psychological and behavioral risk factors among drivers.

Accidents, Traffic↗

PubMed2005

[Effects of glyphosate on life histroy characteristics of freshwater rotifer Brachionus calyciflorus].

The life table study on the life history characteristics of freshwater rotifer Brachionus calyciflorus under effects of different concentrations glyphosate showed that glyphosate had significant effects on the embryonic developmental time, duration of juvenile and reproductive periods, average lifespan, net reproductive rate, and intrinsic population increasing rate of the rotifer. The embryonic developmental time was significantly lengthened when exposed to 3 and 8 mg x L(-1) glyphosate, the juvenile period began to be lengthened significantly when exposed to 3 mg x L(-1) glyphosate, while the net reproductive rate and intrinsic population increasing rate decreased significantly when the rotifer was exposed to 8.00 and 10.50 mg x L(-1) glyphosate, respectively. Among all the parameters, intrinsic population increasing rate was the most sensitive parameter which could be used in monitoring the effects of glyphosate on the life history characteristics of B. calyciflorus.

Animals↗

PubMed2005

[Enhancement of wound healing by taspine and its effect on fibroblast].

OBJECTIVE: To study the effect of taspine on enhancement of skin wound healing and its effect on fibroblast proliferation and autocrine. METHODS: The plerosis effect of taspine on experimental skin wound was observed in vivo. Different concentrations of taspine were added in vitro and MTT technique was applied to observe its effect on fibroblast proliferation, the levels of transforming growth factor-beta1 (TGF-13P) and epidermal growth factor (EGF) were determined by ELISA. RESULTS: In vivo, exo-applied taspine 300 microg and 150 microg accelerated the recovery of skin wound. In vitro, 0.50-0.4 microg/ml taspine could increase autocrine of TGF-beta1and EGF by fibroblast, but it showed no effect on L929 fibroblast proliferation. CONCLUSIONS: Taspine enhances wound healing by increasing the autocrine of TGF-beta1 and EGF by fibroblast.

Alkaloids↗