Biomedical subjects

Y Sun

Publications and source records attributed to Y Sun.

At least 73 records · Page 4Linked to original sources

PubMed2003

The promoter of an antifungal protein gene from Gastrodia elata confers tissue -specific and fungus-inducible expression patterns and responds to both salicylic acid and jasmonic acid.

Gastrodia antifungal proteins (GAFPs) are a group of mannose-binding lectins purified from Gastrodia elata that show strong resistance against a wide spectrum of fungi. The GAFP-2 promoter was analyzed for its ability to control the expression of the reporter gene, beta-glucuronidase (GUS) in transgenic tobacco plants. The GUS assays revealed that the GAFP-2 promoter is expressed in a tissue-specific manner, which mainly expressed in the vascular cells. The highest GUS activity was observed in roots, followed by stems. GAFP-2-GUS expression was strongly induced by the fungus Trichoderma viride and by the plant stress regulators, salicylic acid and jasmonic acid in the stably transformed tobacco plants. The -537 region of the GAFP-2 promoter was sufficient for its tissue-specific and inducible expression of the promoter.

Cyclopentanes↗

PubMed2003

Beta-platelet-derived growth factor receptor mediates motility and growth of Ewing's sarcoma cells.

The Ewing's sarcoma family of tumors (ESFT) contain a translocation, t(11;22), which results in the novel oncogenic fusion protein EWS/FLI1. Platelet-derived growth factors (PDGF) and their receptors (PDGFR) are involved in the induction and proliferation of numerous solid tumors and are the potential candidates for novel targeted antitumor therapy. Since a relation was reported between PDGF-C and EWS/FLI1, we sought to characterize the PDGF signaling pathway in ESFT. Eight out of nine ESFT cell lines were found to express significant levels of beta-PDGFR. Interestingly, none of the tested cell lines expressed alpha-PDGFR, which is the receptor isotype required for PDGF-C binding. By immunohistochemical staining 47 of 52 (90.4%) archival tumor samples from patients with ESFT were positive for beta-PDGFR. ESFT cell lines were treated with PDGF-AA or PDGF-BB ligands to evaluate downstream signaling. Autophosphorylation of beta-PDGFR and tyrosine phosphorylation of PLC-gamma, PI3Kp85 and Shc were detected only in PDGF-BB-stimulated cells that express beta-PDGFR. Receptor function was further evaluated using chemotaxis assays that showed TC-32 cell migration towards PDGF-BB. A specific PDGFR kinase inhibitor AG1295 blocked beta-PDGFR activation, downstream signaling, growth in cell culture and chemotaxis of TC-32 cells. AG1295 also delayed tumor formation and prolonged survival in an ESFT animal model. We conclude that ESFT express beta-PDGFR and that this is a functional and potentially crucial signaling pathway. Therefore, beta-PDGFRs may provide a novel therapeutic target in ESFT that can be utilized to design better treatment modalities.

Animals↗

PubMed2003

A systematic comparison of methods to measure HIV-1 specific CD8 T cells.

Several methods are now available to evaluate the frequencies of virus-specific CD8 T cells but require a systematic comparison to help at choosing the best strategy for evaluation. First, we compared the ELISpot-IFNgamma assay, intracellular IFNgamma staining and HLA class I tetramer-binding assay to quantify the HIV-specific CD8 T cells. Second, we determined the frequency of recognition of HIV antigens and evaluated whether the mode of antigen presentation might influence the results: We compared HIV antigen presentation in the same ELISpot-IFNgamma assays by using recombinant vaccinia viruses (rVVs) encoding for HIV-LAI Gag, Pol, Env, Nef, Tat and Vif proteins, or a panel of 49 synthetic 8-11 amino acid length peptides tested either individually or pooled. Third, we compared the antigens recognized by memory CTL analysis using chromium release assay (CRA) on CTL lines and by effector CD8 cell analysis using ELISpot assay. Our results show that: (1) Flow cytometry and ELISpot assay measuring IFNgamma production give the same frequency of HIV-specific CD8 T cells; (2) tetramer-binding assay detects more HIV-specific CD8 T cells than other methods; (3) pools of optimal peptides and sum frequencies of individual optimal peptides give similar results in ELISpot assay; (4) ELISpot assays using peptides are more sensitive than those using rVV; and (5) CRA and ELISpot assay when using rVV provide a comparable profile of HIV antigen recognition by memory CTLs (CRA) and effector CTLs (ELISpot) in two thirds cases. These results have important implications for the choice of immunological methods to evaluate CD8 T cells responses to vaccines.

AIDS Vaccines↗

PubMed2003

The shape parameter of liposomes and DNA-lipid complexes determined by viscometry utilizing small sample volumes.

A minicapillary viscometer utilizing <0.5 ml of sample at a volume fraction of <0.1% is described. The calculated a/b of DPPC/DPPG multilamellar liposome was 1.14 as prolate ellipsoids and a/b of dioleoylpropyltrimethyl ammonium methylsulfate-DNA complex at a charge ratio of 4:1 (+/-) was 3.7 as prolate ellipsoids or 4.9 as oblate ellipsoids. The deviation of shape from perfect sphere is thus expressed quantitatively in more than two significant figures. In these measurement, the necessary amount of DNA is <0.5 mg.

Capillary Action↗

PubMed2003

SAG attenuates apoptotic cell death caused by simulated ischaemia/reoxygenation in rat cardiomyocytes.

Sensitive to apoptosis gene (SAG) is a novel RING finger protein that has been shown to be involved in protection against apoptotic cell death induced by oxidative stress in various cell types. As SAG has been previously shown to be expressed in the heart, we assessed its role in cardiac myocytes exposed to ischaemic stress. SAG expression was enhanced by hypoxia in neonatal cardiomyocytes as well as in the intact heart exposed to ischaemia/reperfusion. SAG levels remain elevated during the first 4 h of reoxygenation and return to control levels after 16 h of reoxygenation. We also show that overexpression of SAG in cardiac myocytes is able to protect against simulated ischaemia/reperfusion-induced apoptotic cell death. However, abrogation of the RING finger of the protein eliminates the anti-apoptotic properties of SAG. Furthermore, an antisense SAG construct enhances cell death, both in normoxic and hypoxic conditions. Hence, we conclude that SAG is a cardioprotective agent in cardiac cells exposed to ischaemic stress and an important protein involved in cardiomyocyte survival.

Amino Acid Motifs↗

PubMed2003

A multicenter phase II study of the efficacy and safety of docetaxel plus cisplatin in Asian chemonaïve patients with metastatic or locally advanced non-small cell lung cancer.

AIMS: To evaluate the efficacy and safety of docetaxel-cisplatin in patients with metastatic or locally advanced non-small cell lung cancer (NSCLC). METHODS: Chemotherapy-naïve patients with histologically confirmed TNM stage III or IV NSCLC were recruited from 12 Asian trial centers. Patients received docetaxel (75 mg/m2) and cisplatin (75 mg/m2) every 3 weeks for 6 cycles. RESULTS: 130 of 146 patients were evaluable for efficacy (60% stage IV). Three complete and 58 partial responses were observed (overall response rate: 46.9%; 95% CI: 38.3-55.5%). Median time to progression was 6.9 months and median survival was 14.0 months; 1-year survival was 59.5%. Grade 3/4 neutropenia, thrombocytopenia and anemia occurred in 69.2%, 6.2% and 18.5% of patients, respectively. Grade 3/4 vomiting was observed in 13.7% and grade 3/4 neurosensory effects were observed in 2.7% of patients. There was one case of treatment-related death due to sepsis. CONCLUSION: Docetaxel-cisplatin is an effective and well-tolerated treatment in Asian patients with NSCLC.

Adult↗

PubMed2003

Adeno-associated virus-mediated delivery of BCL-w gene improves outcome after transient focal cerebral ischemia.

A recombinant adeno-associated virus (rAAV) vector was used to overexpress the anti-apoptotic Bcl-2-family protein, BCL-w, in rat brain. Three weeks after injecting the vector into cerebral cortex and striatum on one side, temporary focal ischemia was induced by occlusion of the ipsilateral middle cerebral artery for 90 min, followed by reperfusion for 24 h. BCL-w expression was increased in cerebral cortex and striatum--and in neurons, astroglia and endothelial cells--in the brains of rats that received the rAAV-BCL-w vector, compared to rats given phosphate-buffered saline or a control vector containing the gene for green fluorescent protein. Recipients of the rAAV-BCL-w vector also showed a 30% reduction in infarct size and a 33-40% improvement in neurological function, compared to the control groups. These results provide evidence for a role of BCL-w in regulating histological and functional outcome after focal cerebral ischemia.

Animals↗

PubMed2003

In vivo release of oxytetracycline from a biodegradable controlled-release gel injected subcutaneously in Japanese quail (Coturnix coturnix japonica).

A long-acting, biodegradable, controlled-release formulation of oxytetracycline (CR-OTC) was evaluated in 18 adult Japanese quail (Coturnix coturnix japonica) following a single subcutaneous (s.c.) injection. Prior to characterizing the release of oxytetracycline (OTC) from the CR-OTC, the pharmacokinetic parameters of intravenously (i.v.) administered OTC were determined. Concentrations of free OTC were measured using a bioassay. The plasma concentration-time profile of OTC after a single i.v. injection at 20 mg/kg was best fit to an open two-compartmental model, with the following pharmacokinetic parameters: area under the curve (AUC) = 36.72 mg. h/L, terminal elimination half-life = 2.34 h, clearance (Cl) = 0.545 L/kg/h. Plasma [OTC] was >1.0 micro g/mL for at least 4 h following i.v. injection. The CR-OTC gel was well tolerated at a dosage of 1500 mg/kg s.c. Plasma [OTC] rose to >1.0 micro g/mL within 24 h; it remained >1.0 micro g/mL for at least 10 days in all birds sampled at that time point (n = 9) and for at least 18 days in two of nine birds. Using a deconvolution technique, it was determined that approximately 54.8% of the administered OTC was released from the CR-OTC over the 45-day observation period. This long-acting, biodegradable controlled-release OTC formulation may have potential for the treatment of chlamydophila infections and other OTC-sensitive bacteria in Japanese quail, however further studies are necessary to determine its safety and clinical application.

Animals↗

PubMed2003

The interaction defect of accessory molecules is responsible for the poor ex vivo response to human antigens of mouse T helper cells.

Mouse T cells fail to respond to xenogeneic pig and human antigens using the direct antigen-presenting pathway. The poor response by mouse CD8 cells is because of multiple defects in the molecular interactions between mouse CD8 cells and xenogeneic antigen-presenting cells (APCs). Using human CD4/DR3+, mouse CD4-/major histocompatibility complex (MHC) class II - mice, we investigated the defects in molecular interaction responsible for the poor response to xenogeneic antigens by naïve mouse CD4+ cells. Mouse CD4 cells failed to respond to human leucocyte antigen (HLA)-DR3 expressed on mouse APCs but developed a strong response to alloantigens, indicating a defect in the interaction between mouse CD4 and HLA-DR3 molecules. Human CD4+/mouse CD4- mouse T cells respond poorly to human and pig APCs but not allogeneic APCs, indicating that accessory molecular interactions are deficient across highly separated species. Adding mouse interleukin-2 (IL-2) to the mixed lymphocyte reaction system did not improve the poor response to human or pig antigens by mouse or human CD4+/mouse CD4- mouse T cells. Therefore, multiple molecular interactions deficient between mouse CD4 cells and human or pig APCs may lead to the poor response to xenogeneic antigens by naïve mouse CD4 cells.

Animals↗

PubMed2003

99mTc-MIBI myocardial perfusion imaging in myocarditis.

Myocardial perfusion imaging with technetium-99m-labelled methoxyisobutyl isonitrile single photon emission computed tomography (99mTc-MIBI SPECT) has proven to be an important clinical procedure in assessing the severity of myocardial ischaemia. The uptake and clearance of 99mTc-MIBI by the myocardium is affected by cell viability and membrane integrity. Consequently, infectious diseases, such as myocarditis, may also affect myocardial perfusion by inducing local inflammation and necrosis. We compared 99mTc-MIBI myocardial perfusion imaging with other heart monitoring methods in order to assess its value in the diagnosis of children with Coxsackie viral myocarditis. We examined 46 patients (age, 3-12 years) with Coxsackie viral myocarditis using 99mTc-MIBI myocardial perfusion imaging and compared the perfusion data with myocardial enzymes, electrocardiographic findings and echocardiography. Regions of hypoperfusion were found in all 46 patients. Seventeen patients (37%) showed two or more areas of diminished perfusion. Myocardial hypoperfusion was mild-to-moderate (<30%) in 33 (72%) patients and severe (>30%) in 13 (28%) patients. Characteristic creatine-kinase isoenzyme (CK-MB) increases, ST-T segment changes and diminished heart function were significantly correlated with reduced myocardial perfusion (all comparisons P<0.05). The results of this study suggest that the presence of myocardial uptake of 99mTc-MIBI may be a marker of myocardial inflammation and necrosis. All 46 patients with Coxsackie viral myocarditis showed a certain degree of reduced perfusion. When the perfusion findings were compared with other parameters, it was shown that myocardial enzyme levels, ST-T segment changes and left ventricular function correlated well with the 99mTc-MIBI-established perfusion defect severity. 99mTc-MIBI SPECT imaging is therefore helpful in providing additional diagnostic information in patients with Coxsackie viral myocarditis.

Child↗

PubMed2003

Thyrotropin-releasing hormone receptors -- similarities and differences.

Thyrotropin-releasing hormone (TRH) initiates its effects by interacting with cell-surface membrane receptors. Two G protein-coupled receptors for TRH, TRH receptor type 1 (TRH-R1) and TRH receptor type 2 (TRH-R2), have been cloned from mammals. In this review, we compare TRH-R1 and TRH-R2 with regard to their tIssue distribution, binding affinities for TRH and TRH analogs, basal and activated signaling activities and characteristics of internalization. TRH-R1 and TRH-R2 are distributed differently in the brain and peripheral tIssues, but exhibit indistinguishable binding affinities for TRH and TRH analogs. Although they both can be stimulated by TRH to similar maximal signaling levels, TRH-R2 exhibits higher basal signaling activity and is more rapidly internalized than TRH-R1. These differences in signaling and internalization properties are probably important in the distinct parts that TRH-R1 and TRH-R2 may play in mammalian physiology.

Animals↗

PubMed2003

Gender-specific genetic determinants of blood pressure and organ weight: pharmacogenetic approach.

A total genome scan and pharmacogenetic study were designed to search for genetic determinants of blood pressure (BP) as well as heart and kidney weights. Genome scanning was carried out in 266 F(2) intercrosses from Prague hypertensive hypertriglyceridemic rats for phenotypes of organ weights, baseline BP, BP after blockade of the renin-angiotensin system (RAS) by losartan, of the sympathetic nervous system (SNS) by pentolinium, and of the nitric oxide (NO) synthase by N(G)-nitro-L-arginine methyl ester. Pharmacogenetic analysis showed that, in males, BP was controlled by two loci on chromosomes 1 and 5 (Chr1, Chr5) through the SNS, and these loci showed a positive contribution for relative kidney weight (KW/BW). On the other hand, baseline BP in females was controlled by two loci on Chr3 and Chr7. The effect of these loci was not mediated by the RAS, SNS or NO system. These loci did not show any effect for KW/BW. Negatively-linked loci for KW/BW and relative heart weight (HW/BW) were identified on Chr2 in both genders. Another negatively-linked locus for KW/BW, located on Chr8 in males, affected BP through the SNS. This locus on Chr8 overlapped with a previously-reported modifier locus for polycystic kidney disease (PKD). In conclusion, this pharmacogenetic study determined two loci for BP and relative organ mass implicating sympathetic overactivity. Concordance of the identified locus for KW/BW and BP through the SNS on Chr8 with the PKD locus revealed the importance of this region for renal complications in various diseases.

Animals↗

PubMed2002

Purification of lysozyme by multistage affinity filtration.

A multistage affinity filtration process was developed for the purification of proteins. An affinity adsorbent was prepared by immobilizing Cibacron Blue 3GA to TSK gel HW-65F. Adsorption equilibrium experiments showed that the blue TSK gel had a high affinity for lysozyme, while its binding to bovine serum albumin (BSA) was weaker. Using a three-stage affinity filtration system, lysozyme was purified from a model system (a mixture of lysozyme and BSA) and a natural source (chicken egg white). From the chicken egg white, the three-stage affinity filtration increased the recovery yield of lysozyme from 61 to 96%, compared with the one-stage process. A mathematical model taking into account the film and interior diffusions of protein and eluant was developed for the modeling and analysis of the experimental data. Both the experimental and modeling results indicate that the multistage affinity filtration technique can be employed for the selective recovery of proteins.

Journal Article↗

PubMed2002

The casein mRNA decay changes in parallel with the poly(A) tail length in the mouse mammary gland.

Using beta- and gamma-casein mRNAs, the relationship between poly(A) tail length and half-life of mRNA is determined in the mouse mammary gland during pregnancy and lactation. beta- and gamma-Casein mRNAs increase before and after parturition, respectively. The poly(A) tail as well as the half-life of casein mRNA becomes longer upon the active casein mRNA synthesis. The poly(A) tail is shortened gradually as lactation progresses. The half-life of mRNA decreases approximately from 20 h at early to 4 h at late lactation. Northern blot analysis reveals that nuclear RNA has the same poly(A) tail length as casein mRNA in the cytoplasm does. Thus, the mammary gland changes the poly(A) tail length of casein mRNA. The poly(A) tail length changes in parallel with the level of poly(A) polymerase (PAP) mRNA during pregnancy and lactation, suggesting that the mammary gland determines the poly(A) tail length of casein mRNA through the change in the PAP gene expression. As the half-life of casein mRNA is related with the degree of polyadenylation, we conclude that the poly(A) tail elongation and shortening is a mechanism in regulating the mRNA decay.

Amanitins↗

PubMed2002

Cesium cholate: determination of X-ray crystal structure indicates participation of the ring hydroxyl groups in metal binding.

The crystal structure of cesium cholate, C(24)H(36)(OH)(3) COOCs has been determined with three-dimensional X-ray diffractometer data. It crystallized in the monoclinic space group P2(1) with unit-cell dimensions a = 11.543(5) A, b = 8.614(3) A, and c = 12.662(5) A, beta(deg) = 107.95(2), V = 1197.7 A(3) and Z = 2. The atomic parameters were refined to a final r = 0.0269 and R(omega) = 0.0280 for 2342 observed reflections. Each Cs(+) is coordinated to 7 oxygen atoms from 5 different cholate anions with Cs-O distances ranging from 2.957(4) A to 3.678(5) A. In this crystal, 5 cholates are coordinated with 1 Cs(+), and 5 Cs(+) are coordinated with 1 cholate anion. Carboxyl and all the 3 ring hydroxyl groups of cholate anion participate in binding to Cs(+) simultaneously, and there is no water molecule coordinated with the Cs(+). The pattern of successive rows arranged with polar (p) and non-polar (n) faces in apposition leads to the formation of a sandwich sheet structure with polar and non-polar channels. The Cs ions lie within the polar interior of the sandwich. The H-bond network is reorganized in forming cesium cholate from cholic acid. All the oxygen atoms in cholate anion are involved in H-bonding reciprocally or with water molecules to form an extensive 3-dimensional network of H-bonds. Compared with cholic acid and other similar type of steroids, the coordination structure and H-bonding of Cs cholate crystal are distinct.

Binding Sites↗

PubMed2002

Expression of poly(C)-binding proteins is differentially regulated by hypoxia and ischemia in cortical neurons.

Hypoxia and ischemia regulate the expression of several important genes at the level of transcription and of mRNA stability. Two isoforms of a 40-kDa poly(C)-binding protein, previously identified as RNA-binding proteins, bind to a hypoxia-inducible protein-binding site in the 3'-untranslated region of erythropoietin and tyrosine hydroxylase mRNAs and regulate mRNA stability. To determine if poly(C)-binding proteins show changes in expression -- which might regulate mRNA stability -- in hypoxic or ischemic neuronal cells, we examined poly(C)-binding protein 1 and poly(C)-binding protein 2 expression in hypoxic cortical neuron cultures and in rat cerebral cortex after focal ischemia. Reverse transcription-polymerase chain reaction and western blotting showed hypoxic up-regulation of poly(C)-binding protein 1, and down-regulation of poly(C)-binding protein 2, mRNA and protein expression. Hypoxia-inducible expression of poly(C)-binding protein 1 was mediated by p38 mitogen-activated protein kinase, while hypoxia-reducible expression of poly(C)-binding protein 2 was mediated by protein kinase C. Immunostaining showed that poly(C)-binding protein 1, but not poly(C)-binding protein 2, expression was increased in the ischemic boundary zone (penumbra) of the frontal cortex after 90 min of ischemia, and persisted for at least 72 h after reperfusion. These results demonstrate that poly(C)-binding protein 1 and poly(C)-binding protein 2 in cortical neurons are differentially affected by hypoxic/ischemic insults, suggesting that there are functional differences between poly(C)-binding protein isoforms. Since we observed no poly(C)-binding protein expression in astroglia, alternative mRNA stability mechanisms may exist in these cells.

Animals↗

PubMed2002

The interaction of Cu2 + ions and NaDC micelles.

By mixing an aqueous solution of CuCl2 with an NaDC aqueous solution of various concentration and initial molar ratio, seven coordinated samples with distinct appearances and characters were obtained. Their structures and components were investigated by FT-IR spectroscopy, EXAFS (the extended X-ray absorption fine structure), thermal analysis, X-ray diffraction, laser light scattering, TEM (transmission electron micrograph), element analysis and ICP (inductively coupled plasma) analysis. The following conclusions were given: (1) The complexes of Cu2+-NaDC with distinct appearances and properties were synthesized. (2) After Cu(DC)2 dissolved in NaDC aqueous solution, larger micelles (30-90 nm diameter) formed in the supernate, it is a mixed micelle with Cu(DC)2 and NaDC. So these micelles are a new kind of micelle containing two kinds of metal ions. This is a new result using metal ions as bridges to form micelle. (3) According to the different concentration of Cu2+ to NaDC, the complexes formed as gel or poly-crystals. Both the composition of gel complexes and the coordination structure of carboxyl groups with metal ions varied with the initial molar ratio of Cu2+ to Na+. The gel complexes exhibits the non-stoichiometric character. (4) These results are in agreement with physiological condition. All the different states such as gel, precipitate, micelles of various structures are present in bile of gallbladder. We can suggest an ideal model of the interaction between Cu2+ and bile salts in vivo.

Biophysical Phenomena↗

PubMed2002

Dietary pectin, but not cellulose, influences Heligmosomoides polygyrus (Nematoda) reproduction and intestinal morphology in the mouse.

Dietary texture has been reported to influence parasite establishment and survival, but to what degree this relationship is modified by either the type or quantity of dietary fibre is unknown. Using a 2 x 4 factorial design, we explored the relationship between fibre type (soluble pectin vs insoluble = cellulose) and fibre quantity (0, 5, 10 and 20% by dry weight) on parasitic outcomes in BALB/c mice infected with 100 Heligmosomoides polygyrus (Nematoda) larvae. Pectin, but not cellulose, exerted a significant effect on parasite egg production. Following in vitro culture of female worms, increasing levels of dietary pectin were associated with increasing release of eggs. Yet this pattern was not observed in vivo, where per capita egg production peaked at the 10% pectin concentration, but was very low in mice fed 20% pectin. Parasite establishment was elevated in mice fed 20% pectin, but was unaffected by cellulose concentration. Neither type nor quantity of fibre affected H. polygyrus survival or spatial distribution along the gastrointestinal tract. To what degree differences in parasite establishment and reproduction could be attributed to the marked effects of pectin on gut morphology (increased intestinal length, villus length, mucosa thickness and villus/crypt ratio) requires further exploration. Our data indicate that cellulose is preferable to pectin as the source of fibre for experimental diets as cellulose did not affect H. polygyrus establishment, reproduction or survival during a 4-week primary infection.

Animals↗