Search PubMed⌕ Search

Biomedical subjects

F Chen

Publications and source records attributed to F Chen.

At least 91 records · Page 5Linked to original sources
PubMed2001

Identification of TNF-alpha-sensitive sites in HCMVie1 promoter.

Viral vectors using the human cytomegalovirus immediate-early promoter (HCMVie1 promoter) are potentially efficient tools for gene delivery in vivo to diverse cell types. We previously demonstrated that two cytokines, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (INF-gamma), inhibited transgene expression from this promoter in skeletal and cardiac myocytes. In this study, electrophoretic mobility shift assays (EMSAs) were performed to identify the TNF-alpha response elements from the HCMVie1 promoter. The results show that TNF-alpha enhances the interaction of nuclear proteins from the C2C12 myocyte line with a single restricted segment of the HCMVie1 promoter. In vitro DNase I footprinting defined precisely the sites of interaction to two elements: nucleotides -1 to 0 and +24 to +36 relative to a transcription initiation cap homologous in the HCMVie1 promoter. These sites contain homologous sequences for cap initiation site (82%) and NFkappaB (62%) sites, respectively. Specificity was further ascertained by competitive EMSAs with wild-type and mutant oligonucleotide probes. Southwestern blotting showed that three proteins (45, 30, and 20 kDa) bound to this TNF-alpha-sensitive element, separately. However, EMSAs failed to prove a role for Yin Yang-1 (YY-1), NFkappaB (p65), or NFkappaB (p50) in binding to these sites. Our results provide evidence for two novel sites in the HCMVie1 promoter that are targets for TNF-alpha enhanced binding of transcription factors.

Antigens, Viral↗
PubMed2001

Metastatic thyroid cancer manifesting as a mediastinal mass in a man with an aberrant right subclavian artery.

We treated a case of thyroid cancer manifesting as a mediastinal mass, completely resecting it without difficulty despite a vascular anomaly. An asymptomatic 42-year-old woman was admitted with a mediastinal mass. Ten years earlier, she had undergone surgery for a thyroid tumor diagnosed as follicular adenoma. She also had an aberrent subclavian artery anomaly with a non-recurrent laryngeal nerve, radiographically recognized preoperatively. The mediastinal mass was completely resected through median sternotomy. Pathological examination showed the previous thyroid tumor had been follicular carcinoma, and that the mass was a mediastinal-node metastasis from the thyroid cancer. Preoperative recognition of the vascular anomaly was helpful in completing resection, in addition to safe, quick surgical procedures.

Adenoma↗
PubMed2001

A perfusion-cell bleeding culture strategy for enhancing the productivity of eicosapentaenoic acid by Nitzschia laevis.

A perfusion-cell bleeding culture strategy was developed for enhancing the productivity of eicosapentaenoic acid (EPA) by the diatom Nitzschia laevis. As the strategy combined the concepts of continuous culture and perfusion culture, it allowed continuously and simultaneously harvesting the algal cells and removing inhibitory compounds during the cultivation. Compared with a single operation of continuous culture, the perfusion-cell bleeding culture greatly enhanced the steady-state biomass concentration, biomass productivity, EPA yield, EPA productivity and glucose utilization efficiency. The perfusion-cell bleeding culture also allowed higher biomass productivity and EPA productivity than the single perfusion culture did. At a bleeding rate of 0.67 day(-1) and a perfusion rate of 0.6 day(-1), the EPA productivity achieved 175 mg l(-1) day(-1), which is the highest ever reported in microalgal cultures.

Biomass↗
PubMed2001

DQX1, an RNA-dependent ATPase homolog with a novel DEAQ box: expression pattern and genomic sequence comparison of the human and mouse genes.

DQX1 is a novel gene related to the RNA-dependent ATPases. The gene was classified as a member of the DEAD/H family on the basis of the conserved order and spacing of ten short protein motifs. The unique features of DQX1 include replacement of the signature DEAH motif with DEAQ and the absence of the helicase motif. We determined the coding sequences of human and mouse DQX1, which encode proteins of 717 and 718 amino acids with 84% amino acid sequence identity. The 3.2-kb Dqx1 transcript has highest expression in muscle and liver. DQX1 is located between AUP1 and HOX11L1 in a gene-dense region of human Chromosome (Chr) 2p13 and mouse Chr 6. Although DQX1 is within the nonrecombinant region for the mouse neuromuscular mutant mnd2, no difference in coding sequence, transcript length, or transcript abundance was observed between normal mice and mnd2 mutant mice. The ubiquitous expression of DQX1 and its close phylogenetic relationship to the yeast pre-mRNA processing (Prp) proteins suggest a role in cellular RNA metabolism.

Adenosine Triphosphatases↗
PubMed2001

New insights into the role of nuclear factor-kappaB in cell growth regulation.

The nuclear factor (NF)-kappaB family of eukaryotic transcription factors plays an important role in the regulation of immune response, embryo and cell lineage development, cell apoptosis, cell-cycle progression, inflammation, and oncogenesis. A wide range of stimuli, including cytokines, mitogens, environmental particles, toxic metals, and viral or bacterial products, activate NF-kappaB, mostly through IkappaB kinase (IKK)-dependent phosphorylation and subsequent degradation of its inhibitor, the IkappaB family of proteins. Activated NF-kappaB translocates into the nucleus where it modulates the expression of a variety of genes, including those encoding cytokines, growth factors, acute phase response proteins, cell adhesion molecules, other transcription factors, and several cell apoptosis regulators. During the past few years, tremendous progress has been achieved in our understanding on how intracellular signaling pathways are transmitted in either a linear or a network manner leading to the activation of NF-kappaB and subsequent cell growth control. However, a detailed molecular mechanism of NF-kappaB regulating cell growth has yet to be determined. Elucidation of the relationships between NF-kappaB activation and cell growth will be important in developing new strategies for the treatment of various human diseases, such as chronic autoimmune disorder and cancer.

Animals↗
PubMed2001

Successful treatment of mucoepidermoid carcinoma of the carina.

We successfully treated a 33-year-old man with mucoepidermoid carcinoma at the carina. Through preoperative spiral computed tomography with multiplanar and three-dimensional reconstructions, the lesion extended along the right main bronchus across the orifice of the right upper lobe. He underwent a carinal resection plus right upper lobectomy and reconstruction of the carina. He shows neither anastomotic complication nor recurrence of disease 1 year after surgery. Spiral computed tomography was used to evaluate the preoperative and postoperative state of the central airway.

Adult↗
PubMed2001

The biosynthesis of monolignols: a "metabolic grid", or independent pathways to guaiacyl and syringyl units?

Lignin is a complex polymer formed by the oxidative polymerization of hydroxycinnamyl alcohol derivatives termed monolignols. The major monolignols in dicotyledonous angiosperm lignin are monomethylated guaiacyl (G) units derived from coniferyl alcohol, and dimethylated syringyl (S) units derived from sinapyl alcohol. The biochemical pathways leading to the formation of monolignols feature successive hydroxylation and O-methylation of the aromatic ring and conversion of the side chain carboxyl to an alcohol function. The current view of the monolignol biosynthetic pathway envisages a metabolic grid leading to G and S units, through which the successive hydroxylation and O-methylation reactions may occur at different levels of side chain oxidation. The present article assesses biochemical and genetic evidence for and against such a model, including recent data on the methylation reactions of monolignol biosynthesis in alfalfa. We draw attention to portions of the currently accepted monolignol pathway that may require revision, and suggest an alternative model in which metabolic channeling allows for independent pathways to G and S lignin.

Fabaceae↗
PubMed2001

Chemical syntheses of caffeoyl and 5-OH coniferyl aldehydes and alcohols and determination of lignin O-methyltransferase activities in dicot and monocot species.

To investigate the substrate preferences of O-methyltransferases in the monolignol biosynthetic pathways, caffeoyl and 5-hydroxy coniferyl aldehydes were synthesized by a new procedure involving a Wittig reaction with the corresponding hydroxybenzaldehydes. The same procedure can also be used to synthesize caffeoyl and 5-hydroxyconiferyl alcohols. Relative O-methyltransferase activities against these substrates were determined using crude extracts and recombinant caffeic acid O-methyltransferase from alfalfa (Medicago sativa), and crude extracts from the model legume Medicago truncatula, tobacco, wheat and tall fescue. Extracts from all these species catalyzed methylation of the various monolignol aldehydes and alcohols more effectively than the corresponding hydroxycinnamic acids.

Alcohols↗
PubMed2001

Photocatalytic degradation of dyes on a magnetically separated photocatalyst under visible and UV irradiation.

A novel kind of magnetically separable photocatalyst of TiO2/SiO2/gamma-Fe2O3 (TSF) is prepared. Scanning tunnel microscope (STM) and X-ray diffractometer (XRD) were used to characterize the structure of the photocatalyst. In the TSF photocatalyst, a TiO2 shell is for photocatalysis, a gamma-Fe2O3 core as a carrier is for separation by the magnetic field and a SiO2 membrane between the TiO2 shell and the gamma-Fe2O3 core is used to weaken the adverse influence of gamma-Fe2O3 on the photocatalysis of TiO2. Three kinds of dyes, Fluoresein, Orange II and Red acid G, were used to examine the photocatalytic activity of TSF. Due to strong UV adsorption of the gamma-Fe2O3, the photocatalytic activity of TSF was lower than that of the pure TiO2. Deducting the light absorption of the gamma-Fe2O3 particles, the photocatalytic activity of TSF was found to be higher than that of the P25 under UV irradiation. On the other hand, the photocatalytic activity of TSF under visible irradiation was much lower than that of the P25 TiO2 even deducting the visible light absorption of the gamma-Fe2O3 particles. Differences in the photocatalytic mechanisms under UV and visible irradiation lead to the differences in the photodegradation characteristics of dyes on TSF. The recycled TSF exhibited a good repeatability of photocatalytic activity.

Catalysis↗
PubMed2001

MRI based diffusion and perfusion predictive model to estimate stroke evolution.

In this study we present a novel automated strategy for predicting infarct evolution, based on MR diffusion and perfusion images acquired in the acute stage of stroke. The validity of this methodology was tested on novel patient data including data acquired from an independent stroke clinic. Regions-of-interest (ROIs) defining the initial diffusion lesion and tissue with abnormal hemodynamic function as defined by the mean transit time (MTT) abnormality were automatically extracted from DWI/PI maps. Quantitative measures of cerebral blood flow (CBF) and volume (CBV) along with ratio measures defined relative to the contralateral hemisphere (r(a)CBF and r(a)CBV) were calculated for the MTT ROIs. A parametric normal classifier algorithm incorporating these measures was used to predict infarct growth. The mean r(a)CBF and r(a)CBV values for eventually infarcted MTT tissue were 0.70 +/- 0.19 and 1.20 +/- 0.36. For recovered tissue the mean values were 0.99 +/- 0.25 and 1.87 +/- 0.71, respectively. There was a significant difference between these two regions for both measures (p < 0.003 and p < 0.001, respectively). Mean absolute measures of CBF (ml/100g/min) and CBV (ml/100g) for the total infarcted territory were 33.9 +/- 9.7 and 4.2 +/- 1.9. For recovered MTT tissue, the mean values were 41.5 +/- 7.2 and 5.3 +/- 1.2, respectively. A significant difference was also found for these regions (p < 0.009 and p < 0.036, respectively). The mean measures of sensitivity, specificity, positive and negative predictive values for modeling infarct evolution for the validation patient data were 0.72 +/- 0.05, 0.97 +/- 0.02, 0.68 +/- 0.07 and 0.97 +/- 0.02. We propose that this automated strategy may allow possible guided therapeutic intervention to stroke patients and evaluation of efficacy of novel stroke compounds in clinical drug trials.

Aged↗
PubMed2001

NFAT signaling in vertebrate development.

NFATc proteins transduce Ca(2+) signals to the nucleus and then pair with other proteins on DNA to generate NFAT complexes that activate transcription in response to both electrical and tyrosine kinase signaling. The four NFATc genes arose at the origin of vertebrates, implying that they have evolved for the development of vertebrate-specific functions, such as a complex nervous system, a recombinational immune system, and a vascular system with a complex heart. These speculations are borne out by studies of mice with null mutations in the different family members.

Animals↗
PubMed2001

Dosimetry of blood irradiation using an alanine/ESR dosimeter.

A batch of 80 DL-alanine dosimeters was supplied to Hemocentro of the Hospital and Clinics of Faculdade de Medicina de Ribeirão Preto (HC-FM RP) SP, Brazil for the purpose of quality control of the radiation dose delivered to blood bags. The irradiation was made using two (40 x 40) cm2 parallel opposed radiation fields each with 80 cm of source to surface distance in the Radiotherapy Section of HC-FMRP with the 60Co teletherapy unit. The calculated radiation absorbed dose at the center of the box was 20 Gy. The dosimeter readings were performed using a Varian E-4 ESR Spectrometer operating in X-band. For the 80 dosimeters and over the irradiation volume throughout a blood bag, the minimum and maximum doses were 14 and 23 Gy, respectively. The mean dose was (18 +/- 2) Gy (1sigma), and the coefficient of variability was 11.1%. Alanine dosimeters demonstrated easy handling, good precision and adequate sensitivity for this application.

Alanine↗
PubMed2001

Effect of two conserved amino acid residues on DREB1A function.

Transcription factors of the DREBP subgroup and the EREBP subgroup contain conserved DNA-binding domains called AP2/EREBP domains, which specifically bind to DRE cis-element and GCC-box, respectively. The 14th and 19th amino acid residues of AP2/EREBP domains are absolutely conserved in the transcription factors of the DREBP subgroup as well as in the EREBP subgroup. However, these two residues of transcription factors of the DREBP subgroup are different from those of the EREBP subgroup. To assess the functional significance of these two residues in binding to the target sequence, the Val (14th residue) and Glu (19th residue) of the AP2/EREBP domain of DREB1A (a transcription factor of the DREBP subgroup) were mutated individually or doubly to Ala and Asp, respectively. This made the 14th and 19th amino acid residues of mutant DREB1A identical to the corresponding residues of transcription factors of the EREBP subgroup. Yeast in vivo analysis showed that: 1) on a selective medium plate of SD/His- Ura- Trp- + 30 mM approximately 60 mM 3-AT, the growth of yeast cells containing HIS and lacZ double reporter genes was normal in the transformation of the 19th singly mutated DREB1A, obviously inhibited in the transformation of the 14th singly mutated DREB1A, and seriously inhibited in the transformation of the 14th/19th doubly mutated DREB1A; 2) quantitative assay of beta-galactosidase activity showed that the intensities of lacZ expression decreased in the transformations of the 14th singly mutated and 14th/19th doubly mutated types. The experimental results revealed that the 19th site mutation did not affect the binding of the DREB1A transcription factor to the DRE cis-element; the 14th site mutation obviously inhibited their binding; and the double mutation of the 14th/19th sites seriously inhibited their binding. This suggests that the conserved Val (14th) and Glu (19th) residues are crucial in the regulation of the binding activity of DREB1A to the DRE cis-element.

Amino Acid Sequence↗
PubMed2001

Nootkatone is a repellent for Formosan subterranean termite (Coptotermes formosanus).

We examined the behavior of Formosan subterranean termites toward one of the components of vetiver grass oil, the roots of which manufacture insect repellents. We found nootkatone, a sesquiterpene ketone, isolated from vetiver oil is a strong repellent and toxicant to Formosan subterranean termites. The lowest effective concentration tested was 10 micrograms/g substrate. This is the first report of nootkatone being a repellent to insects.

Animals↗
PubMed2001

Evaluation of vetiver oil and seven insect-active essential oils against the Formosan subterranean termite.

Repellency and toxicity of 8 essential oils (vetiver grass, cassia leaf, clove bud, cedarwood, Eucalyptus globules, Eucalyptus citrodora, lemongrass and geranium) were evaluated against the Formosan subterranean termite, Coptotermes formosanus Shiraki. Vetiver oil proved the most effective repellent because of its long-lasting activity. Clove bud was the most toxic, killing 100% of termites in 2 days at 50 micrograms/cm2. The tunneling response of termites to vetiver oil also was examined. Vetiver oil decreased termite tunneling activity at concentrations as low as 5 micrograms/g sand. Tunneling and paper consumption were not observed when vetiver oil concentrations were higher than 25 micrograms/g sand. Bioactivity of the 8 oils against termites and chemical volatility were inversely associated. Listed in decreasing order of volatility, the major constituents of the 8 oils were: eucalyptol, citronellal, citral, citronellol, cinnamaldehyde, eugenol, thujopsene, and both alpha- and beta-vetivone. Vetivor oil is a promising novel termiticide with reduced environmental impact for use against subterranean termites.

Animals↗
PubMed2001

Improvement of in-rumen digestibility of alfalfa forage by genetic manipulation of lignin O-methyltransferases.

Lignin inhibits forage digestibility by ruminant animals, and lignin levels and the proportion of dimethylated syringyl (S) lignin monomers increase with progressive maturity in stems of forage crops. We generated transgenic alfalfa (Medicago sativa L.) with reduced lignin content and altered lignin composition. Down-regulation of caffeic acid 3-O-methyltransferase (COMT) reduces lignin content, accompanied by near total loss of S lignin, whereas down-regulation of caffeoyl coenzyme A 3-O-methyltransferase (CCoAOMT) reduces lignin content without reduction in S lignin. These changes are not accompanied by altered ratios of cell wall polysaccharides. Analysis of rumen digestibility of alfalfa forage in fistulated steers revealed improved digestibility of forage from COMT down-regulated plants, but a greater improvement in digestibility following down-regulation of CCoAOMT. The results indicate that both lignin content and composition affect digestibility of alfalfa forage, and reveal a new strategy for forage quality improvement by genetic manipulation of CCoAOMT expression.

Animals↗
PubMed2001

Nicastrin binds to membrane-tethered Notch.

The presenilins and nicastrin, a type 1 transmembrane glycoprotein, form high molecular weight complexes that are involved in cleaving the beta-amyloid precursor protein (betaAPP) and Notch in their transmembrane domains. The former process (termed gamma-secretase cleavage) generates amyloid beta-peptide (Abeta), which is involved in the pathogenesis of Alzheimer's disease. The latter process (termed S3-site cleavage) generates Notch intracellular domain (NICD), which is involved in intercellular signalling. Nicastrin binds both full-length betaAPP and the substrates of gamma-secretase (C99- and C83-betaAPP fragments), and modulates the activity of gamma-secretase. Although absence of the Caenorhabditis elegans nicastrin homologue (aph-2) is known to cause an embryonic-lethal glp-1 phenotype, the role of nicastrin in this process has not been explored. Here we report that nicastrin binds to membrane-tethered forms of Notch (substrates for S3-site cleavage of Notch), and that, although mutations in the conserved 312-369 domain of nicastrin strongly modulate gamma-secretase, they only weakly modulate the S3-site cleavage of Notch. Thus, nicastrin has a similar role in processing Notch and betaAPP, but the 312-369 domain may have differential effects on these activities. In addition, we report that the Notch and betaAPP pathways do not significantly compete with each other.

Alzheimer Disease↗