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Biomedical subjects

N Fang

Publications and source records attributed to N Fang.

At least 19 recordsLinked to original sources
PubMed2006

Increased glycophorin A somatic cell variant frequency in arsenic-exposed patients of Guizhou, China.

Exposure to arsenic through domestic burning arsenic-containing coal causes various tumors in a population of Guizhou, China. The glycophorin A (GPA) assay is a human mutation assay detecting somatic variation in erythrocytes expressing the MN blood type, and was used to assess genotoxicity of arsenic-exposed patients. Peripheral blood was collected from 18 adult healthy subjects and 40 arsenic-exposed patients in heparin-treated tubes. Erythrocytes were isolated, fixed in formalin and immuno-labeled with fluorescent antibodies against GPA, followed by flow cytometry analysis. Arsenic exposure increased the variant frequency (expressed as the number of variant red cells per 10(6) erythrocytes): NN, 3.7 in healthy subjects versus 21.2 in arsenic-exposed patients; N phi, 12.6 versus 33.1; MM, 13.1 versus 110; and M phi, 5.2 versus 20.3. The total GPA variant frequency was increased about five-fold (34.7 in healthy subjects versus 185 in arsenosis patients). Furthermore, the variant frequency was significantly higher in skin tumor-bearing patients: NN, 19.4 in arsenic-exposed non-tumor patients versus 31.5 in tumor-bearing patients; N phi, 29.5 versus 54.5; MM, 102 versus 159; M phi, 15.9 versus 45.1. Total GPA variant frequency in arsenic-exposed patients bearing skin tumors was significantly increased compared to patients without skin tumors (167 versus 290). The relationship between arsenic exposure history and GPA variant frequency was less evident. These data demonstrate that arsenic exposure is associated with mutations at the GPA locus, an effect exaggerated in patients bearing arsenic-induced skin tumors. The variant frequency of GPA could be a useful biomarker for arsenic exposure and arsenic carcinogenesis.

Adult↗
PubMed2004

Terahertz magnetic response from artificial materials.

We show that magnetic response at terahertz frequencies can be achieved in a planar structure composed of nonmagnetic conductive resonant elements. The effect is realized over a large bandwidth and can be tuned throughout the terahertz frequency regime by scaling the dimensions of the structure. We suggest that artificial magnetic structures, or hybrid structures that combine natural and artificial magnetic materials, can play a key role in terahertz devices.

Journal Article↗
PubMed2004

Optimization of submerged culture requirements for the production of mycelial growth and exopolysaccharide by Cordyceps jiangxiensis JXPJ 0109.

AIMS: The objective of the present study was to investigate the optimal culture requirements for mycelial growth and exopolysaccharide production by Cordyceps jiangxiensis JXPJ 0109 in submerged culture. METHODS AND RESULTS: The effects of medium ingredients (i.e. carbon and nitrogen sources, and growth factor) and other culture requirements (i.e. initial pH, temperature, etc.) on the production of mycelia and exopolysaccharide were observed using a one-factor-at-a-time method. More suitable culture requirements for mycelial growth and exopolysaccharide production were proved to be maltose, glycerol, tryptone, soya bean steep powder, yeast extract, medium capacity 200 ml in a 500-ml flask, agitation rate 180 rev min(-1), seed age 4-8 days, inoculum size 2.5-7.5% (v/v), etc. The optimal temperatures and initial pHs for mycelial growth and exopolysaccharide production were at 26 degrees C and pH 5 and at 28 degrees C and pH 7, respectively, and corresponding optimal culture age were observed to be 8 and 10 days respectively. According to the primary results of the one-factor-at-a-time experiments, the optimal medium for the mycelial growth and exopolysaccharide production were obtained using an orthogonal layout method to optimize further. Herein the effects of medium ingredients on the mycelial growth of C. jiangxiensis JXPJ 0109 were in the order of yeast extract > tryptone > maltose > CaCl2 > glycerol > MgSO4 > KH2PO4 and the optimal concentration of each composition was 15 g maltose (food-grade), 10 g glycerol, 10 g tryptone, 10 g yeast extract, 1 g KH2PO4, 0.2 g MgSO4, and 0.5 g CaCl2 in 1 l of distilled water, while the order of effects of those components on exopolysaccharide production was yeast extract > maltose > tryptone > glycerol > KH2PO4 > CaCl2 > MgSO4, corresponding to the optimal concentration of medium was as follows: 20 g maltose (food-grade), 8 g glycerol, 5 g tryptone, 10 g yeast extract, 1 g KH2PO4, and 0.5 g CaCl2 in 1 l of distilled water. CONCLUSIONS: Under the optimal culture requirements, the maximum exopolysaccharide production reached 3.5 g l(-1) after 10 days of fermentation, while the maximum production of mycelial growth achieved 14.5 g l(-1) after 8 days of fermentation. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the submerged culture requirements for mycelial growth and exopolysaccharide in C. jiangxiensis, and this two-step optimization strategy in this study can be widely applied to other microbial fermentation processes.

Carbon↗
PubMed2001

Interactions of phospholipid bilayer with chitosan: effect of molecular weight and pH.

Chitosan has demonstrated its potentials as a gene carrier and a membrane perturbant for subsequent drug delivery to cells. However, there is currently a lack of experimental correlation between the physiochemical properties of chitosan and the resulting degree of lipid bilayer destabilization. In this study, the effect of pH and chitosan molecular weight on the interaction between chitosan and dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayer was examined with cross-polarization microscopy, differential scanning calorimetry (DSC), and Fourier transform- (FT-) Raman spectroscopy. Cross-polarized images showed that the direct hydration of the DPPC/chitosan mixture led to the formation of larger DPPC multilamellar vesicles (MLV), and pure chitosan also induced fusions of individual MLV. Under the influence of chitosan, the calorimetric enthalpy of DPPC was reduced in a concentration-dependent manner, and a new phase appeared at 28 degrees C during sample cooling. Even the lowest chitosan mole fraction of 0.04% reduced the cooperative unit of the DPPC bilayer by more than 70%. In addition, the electrostatic effect between chitosan and DPPC tuned the degree of membrane bilayer perturbation. Reduction of pH increased the number of protonated amines on the chitosan backbone and caused further disruption on the membrane organization. Mixing DPPC with chitosan in an organic medium before hydration enhanced the hydrophobic interactions between the two molecules and greatly reduced the cooperative unit among individual lipids during the main phase transition. The increase of chitosan molecular weight also affected the cooperativity in the thermotropic transition of DPPC bilayer. FT-Raman spectroscopy provided additional evidence that chitosan directly perturbed the organizations of the hydrophobic inner core of the DPPC bilayer.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2000

Cbl-b, a RING-type E3 ubiquitin ligase, targets phosphatidylinositol 3-kinase for ubiquitination in T cells.

Cbl-b is implicated in setting the threshold of T lymphocyte activation. In Cbl-b-deficient T cells, the activation of Vav, a guanine nucleotide exchange factor, is significantly enhanced. The molecular mechanism underlying Cbl-b-regulated Vav activation was unclear. Here it is shown that Cbl-b interacts with and induces ubiquitin conjugation to the p85 regulatory subunit of phosphatidylinositol 3-kinase, an upstream regulator of Vav. A functional RING finger of Cbl-b was essential for p85 ubiquitination. However, a loss of function mutation at the well-conserved amino-terminal variant src homology (SH) 2 domain of Cbl-b did not affect its ligase activity. A distal carboxyl-terminal proline-rich region in Cbl-b was mapped to contain the primary binding sequences for the SH3 domain of p85. Deletion of either the distal proline-rich region in Cbl-b or the SH3 domain of p85 severely reduced ubiquitin conjugation to p85. The data suggest a molecular link for Cbl-b-mediated negative regulation of Vav, with phosphatidylinositol 3-kinase as a direct target for Cbl-b E3 ubiquitin ligase.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Recognition and ubiquitination of Notch by Itch, a hect-type E3 ubiquitin ligase.

Genetic studies identified Itch, which is a homologous to the E6-associated protein carboxyl terminus (Hect) domain-containing E3 ubiquitin-protein ligase that is disrupted in non-agouti lethal mice or Itchy mice. Itch-deficiency results in abnormal immune responses and constant itching in the skin. Here, Itch was shown to associate with Notch, a protein involved in cell fate decision in many mammalian cell types, including cells in the immune system. Itch binds to the N-terminal portion of the Notch intracellular domain via its WW domains and promotes ubiquitination of Notch through its Hect ubiquitin ligase domain. Thus, Itch may participate in the regulation of immune responses by modifying Notch-mediated signaling.

Animals↗
PubMed2000

Oligonucleotide microarray based detection of repetitive sequence changes.

Prior studies of oligonucleotide microarray-based mutational analysis have demonstrated excellent sensitivity and specificity except in circumstances where a frameshift mutation occurs in the context of a short repeated sequence. To further evaluate this circumstance, a series of nucleic acid samples having heterozygous mutations within repetitive BRCA1 sequence tracts was prepared and evaluated. These mutations included single nucleotide insertions and deletions in homopolymer runs, insertions and deletions of trinucleotide repeats, and duplications. Two-color comparative hybridization experiments were used wherein wild type reference and test targets are co-hybridized to microarrays designed to screen the entire BRCA1 coding sequence for all possible sequence changes. Mutations in simulated heterozygote samples were detected by observing relative losses of test target hybridization signal to select perfect match oligonucleotide probes. While heterozygous mutations could be readily distinguished above background noise in 9/19 cases, it was not possible to detect alterations in a poly dA/dT tract, small triplet repeat expansions, and a 10 bp direct repeat. Unexpectedly, samples containing (GAT)(3) triplet repeat expansions showed significantly higher affinity toward specific perfect match probes relative to their wild type counterparts. Therefore, markedly increased as well as decreased test sample hybridization to perfect match probes should be used to raise a suspicion of repetitive sequence changes.

Algorithms↗
PubMed2000

Potent and stage-specific action of glutathione on the development of goat early embryos in vitro.

The effect of glutathione (GSH) addition on the development of 1- or 2-cell goat early embryos in vitro was examined. Embryos were collected from superovulated Korean black goat (Capra hircus aegagrus) and cultured for 6 days in synthetic oviduct fluid medium supplemented with either bovine serum albumin (BSA) or serum. Without GSH addition, almost all embryos could not develop beyond 8- to 16-cell block. However, GSH addition greatly improved in vitro development of early embryos to blastocyst stage, and its action was highly dependent on the presence and source of proteins supplemented into the culture medium. Among the protein-supplemented cultures, GSH effect was most prominent in 10% FBS-supplemented culture, in which the proportion (91%) of blastocysts developed from early embryos was much higher than that of BSA- (42-64% depending on its content) or goat serum (GS)-supplemented cultures (21%), or even than that of somatic cell-supported co-culture (60%). As well as in terms of the morphological development, mean cell number of blastocysts (185 +/- 12) developed from FBS condition was significantly higher than that of blastocysts developed from any other culture conditions and moreover comparable to that of blastocysts developed in vivo (190 +/- 9). The viability of these blastocysts was finally confirmed by their term development (6/12) from embryo transfer. To delineate action time of GSH during embryo development, GSH was treated at 1-day intervals through 6-days culture periods excepting the last day. In the GSH-treated embryos at day 3 of culture, which corresponds to the time of in vitro 8- to 16-cell block stage, the proportion of blastocyst was markedly increased up to 77% of cultured embryos and conversely that of the arrested embryos was decreased to 7%. In the embryos treated later, however, their developmental potency decreased abruptly. Therefore, these results clearly demonstrated that GSH could greatly improve the in vitro development of goat early embryos by specifically acting on the 8- to 16-cell block stage during in vitro development, suggesting that GSH may be one of the important regulators on the development of goat embryos in vivo.

Animals↗
PubMed2000

Production of biologically active human granulocyte colony stimulating factor in the milk of transgenic goat.

We have developed a transgenic female goat harboring goat beta-casein promoter/human granulocyte colony stimulating factor (G-CSF) fusion gene by microinjection into fertilized one-cell goat zygotes. Human G-CSF was produced at levels of up to 50 microg/ml in transgenic goat milk. Its biological activity was equivalent to recombinant human G-CSF expressed from Chinese hamster ovary (CHO) cell when assayed using in vitro HL-60 cell proliferation. Human G-CSF from transgenic goat milk increased the total number of white blood cells in C57BL/6N mice with leucopenia induced by cyclophosphamide (CPA). The secreted human G-CSF was glycosylated although the degree of O-glycosylation was lower compared to CHO cell-derived human G-CSF.

Animals↗
PubMed1999

SLP-76 and Vav function in separate, but overlapping pathways to augment interleukin-2 promoter activity.

SLP-76 and Vav, two hematopoietic cell specific molecules, are critical for T cell development and activation. Following T cell antigen receptor stimulation, SLP-76 and Vav both undergo tyrosine phosphorylation and associate with each other via the SH2 domain of Vav and phosphorylated tyrosines of SLP-76. Furthermore, SLP-76 and Vav have a synergistic effect on interleukin (IL)-2 promoter activity in T cells. In this report, we show that two tyrosines, Tyr-113 and Tyr-128, of SLP-76 are required for its binding to Vav, both in vitro and in intact cells. Surprisingly, we find also that the interaction between SLP-76 and Vav is not required for their cooperation in augmenting IL-2 promoter activity, as the two molecules appear to function in different signaling pathways upstream of IL-2 gene expression. Overexpression of SLP-76 in the Jurkat T cell line potentiates the activities of both nuclear factor of activated T cells and AP-1 transcription factors. In contrast, overexpression of Vav leads to enhanced nuclear factor of activated T cells activity without affecting AP-1. Additionally, overexpression of Vav, but not SLP-76, augments CD28-induced IL-2 promoter activity. These findings suggest that the synergy between SLP-76 and Vav in regulating IL-2 gene expression reflects the cooperation between different signaling pathways.

Adaptor Proteins, Signal Transducing↗
PubMed1999

The hematopoietic-specific adaptor protein gads functions in T-cell signaling via interactions with the SLP-76 and LAT adaptors.

BACKGROUND: The adaptor protein Gads is a Grb2-related protein originally identified on the basis of its interaction with the tyrosine-phosphorylated form of the docking protein Shc. Gads protein expression is restricted to hematopoietic tissues and cell lines. Gads contains a Src homology 2 (SH2) domain, which has previously been shown to have a similar binding specificity to that of Grb2. Gads also possesses two SH3 domains, but these have a distinct binding specificity to those of Grb2, as Gads does not bind to known Grb2 SH3 domain targets. Here, we investigated whether Gads is involved in T-cell signaling. RESULTS: We found that Gads is highly expressed in T cells and that the SLP-76 adaptor protein is a major Gads-associated protein in vivo. The constitutive interaction between Gads and SLP-76 was mediated by the carboxy-terminal SH3 domain of Gads and a 20 amino-acid proline-rich region in SLP-76. Gads also coimmunoprecipitated the tyrosine-phosphorylated form of the linker for activated T cells (LAT) adaptor protein following cross-linking of the T-cell receptor; this interaction was mediated by the Gads SH2 domain. Overexpression of Gads and SLP-76 resulted in a synergistic augmentation of T-cell signaling, as measured by activation of nuclear factor of activated T cells (NFAT), and this cooperation required a functional Gads SH2 domain. CONCLUSIONS: These results demonstrate that Gads plays an important role in T-cell signaling via its association with SLP-76 and LAT. Gads may promote cross-talk between the LAT and SLP-76 signaling complexes, thereby coupling membrane-proximal events to downstream signaling pathways.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Cubé resin insecticide: identification and biological activity of 29 rotenoid constituents.

Cubé resin, the root extract from Lonchocarpus utilis and urucu, is an important insecticide, acaricide, and piscicide. The four major active ingredients are rotenone, deguelin, rotenolone, and tephrosin, totaling 77 wt %. As a commercial pesticide, the minor constituents are also of chemical interest and toxicological relevance. This study identifies 25 minor rotenoids in cubé resin "brittle" of which 12 are new compounds, the most unusual being 7'-chloro-5'-hydroxy-4',5'-dihydrodeguelin (the first chlororotenoid from a plant extract) and four isomers of 4',5'-dihydro-4', 5'-dihydroxytephrosin. Several of the minor rotenoids may be decomposition products from free radical processes during sample preparation, extraction with trichloroethylene, and processing the resin. Assays of the 29 rotenoids as inhibitors of NADH:ubiquinone oxidoreductase activity (primary target for toxicity) and phorbol ester-induced ornithine decarboxylase activity (indicator of cancer chemopreventive action) and for cytotoxicity establish similar structure-activity relationships in each system and the importance of the overall molecular conformation and the E-ring substituents.

Animals↗
PubMed1999

New bioactive flavonoids and stilbenes in cubé resin insecticide.

Fractionation of cubé resin from Lonchocarpus utilus and L. urucu roots led to the isolation and identification of 11 minor flavonoids and stilbenes containing the gem-dimethylpyran moiety or a dihydrodiol derivative thereof. The eight new compounds were as follows: the isoflavonoid cis-4'',5''-dihydro-4'',5' '-dihydroxylonchocarpusone (2); four (2S)-6-(gamma, gamma-dimethylallyl)-6'',6''-dimethylpyran[2'',3'':7, 8]flavanones with substituents of 5-hydroxy-3',4'-dimethoxy (3), 5, 3'-dihydroxy-4'-methoxy (4), 5,4'-dihydroxy-3'-methoxy (5), and 3', 4'-dimethoxy (6); and three 6'',6''-dimethylpyran[2'',3'':3', 4']stilbenes with 4-hydroxy-5'-methoxy (9), 3,5'-dimethoxy-4-hydroxy (10) and 3,4,5-trimethoxy (11) substitution patterns. Structure-activity relationships for inhibition of NADH:ubiquinone oxidoreductase activity (bovine heart electron transport particles) and phorbol ester-induced ornithine decarboxylase activity (cultured MCF-7 cells) generally parallel those for cytotoxicity (MCF-7 and Hepa 1clc7 cells).

Animals↗
PubMed1998

SLP-76 is a direct substrate of SHP-1 recruited to killer cell inhibitory receptors.

Activation of immune system cells via antigen-, Fc-, or natural killer cell-triggering-receptor stimulation is aborted by co-engagement of inhibitory receptors. Negative signaling by killer cell inhibitory receptors and related receptors depends on the Src homology 2 (SH2)-containing protein tyrosine phosphatase SHP-1. Using a combination of direct binding and functional assays, we demonstrated that the SH2 domain-containing leukocyte protein 76 (SLP-76) is a specific target for dephosphorylation by SHP-1 in T cells and natural killer cells. Furthermore, we showed that tyrosine-phosphorylated SLP-76 is required for optimal activation of cytotoxic lymphocytes, suggesting that the targeted dephosphorylation of SLP-76 by SHP-1 is an important mechanism for the negative regulation of immune cell activation by inhibitory receptors.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Anticancer action of cubé insecticide: correlation for rotenoid constituents between inhibition of NADH:ubiquinone oxidoreductase and induced ornithine decarboxylase activities.

Rotenone and rotenoid-containing botanicals, important insecticides and fish poisons, are reported to have anticancer activity in rats and mice. The toxic action of rotenone is attributed to inhibition of NADH:ubiquinone oxidoreductase activity and the purported cancer chemopreventive effect of deguelin analogs has been associated with inhibition of phorbol ester-induced ornithine decarboxylase (ODC) activity. This study defines a possible relationship between these two types of activity important in evaluating the toxicology of rotenoid pesticides and the suitability of the anticancer model. Fractionation of cubé resin (the commercial rotenoid pesticide) establishes that the activity in both assays is due primarily to rotenone (IC50 = 0.8-4 nM), secondarily to deguelin, and in small part to rotenolone and tephrosin. In addition, the potency of 29 rotenoids from cubé insecticide for inhibiting NADH:ubiquinone oxidoreductase in vitro assayed with bovine heart electron transport particles satisfactorily predicts their potency in vivo in the induced ODC assay using noncytotoxic rotenoid concentrations with cultured MCF-7 human breast cancer cells (r = 0.86). Clearly the molecular features of rotenoids essential for inhibiting NADH:ubiquinone oxidoreductase are similar to those for blocking ODC induction. This apparent correlation extends to 11 flavonoids and stilbenoids from cubé resin (r = 0.98) and genistein and resveratrol except for lower potency and less selectivity than the rotenoids relative to cytotoxicity. These findings on cubé insecticide constituents and our earlier study comparing rotenone and pyridaben miticide indicate that inhibition of NADH:ubiquinone oxidoreductase activity lowers the level of induced ODC activity leading to the antiproliferative effect and anticancer action.

Animals↗
PubMed1998

Adaptor proteins in lymphocyte antigen-receptor signaling.

Adaptor molecules, proteins that possess no intrinsic enzymatic function, but which mediate protein-protein interactions, have a critical role in integrating signal transduction pathways following engagement of cell-surface receptors. Several newly described adaptor molecules have been shown to serve important functions in the regulation of signaling events initiated by lymphocyte antigen receptors. Understanding how these adaptor proteins function to modulate signaling cascades will provide important insights into the complex biology of lymphocyte activation.

Adaptor Proteins, Signal Transducing↗
PubMed1998

[Separation and determination of eight plant hormones by reversed-phase high performance liquid chromatography].

In this paper, reversed-phase high performance liquid chromatographic technique was used for the separation and determination of eight plant hormones. Methanol-water-acetic acid system was chosen as the mobile phase. The effects of different separation conditions, such as the methanol and acetic acid concentrations in mobile phase, on the retention behaviours of eight plant hormones in this system were studied. The general trends in retention behaviours could be correlated to the methanol concentration in mobile phase. The experimental results showed that the optimum separation was achieved with following gradient elution condition: 0-3 minutes, 70% (water percentage in mobile phase), 3-13 minutes, 70%-20%, 13-48 minutes, 20%. Benzene was added to be as the internal standard. Under this experimental condition, the eight plant hormones could be separated completely and detected quantitatively at 260 nm within 16 minutes. The calibration curves for the eight compounds gave linearity over a wide range. The correlation coefficients of each components were r(ZT) = 0.9971, r(GAs) = 0.9999, r(K) = 0.9997, r(BA) = 0.9995, r(IAA) = 0.9998, r(IPA) = 0.9982, r(IBA) = 0.9995 and r(NAA) = 0.9995. The method is rapid, simple and efficient. It is a suitable method for the accurate determination of gibberellic acid (GA) and alpha-naphthaleneacetic acid (alpha-NAA) in products for agricultural use.

Chromatography, High Pressure Liquid↗