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Articles by J. Yu
Total Records ( 7 ) for J. Yu
  W Qiu , E. B Carson Walter , S. F Kuan , L Zhang and J. Yu

Defective apoptosis contributes to tumorigenesis, although the critical molecular targets remain to be fully characterized. PUMA, a BH3-only protein essential for p53-dependent apoptosis, has been shown to suppress lymphomagenesis. In this study, we investigated the role of PUMA in intestinal tumorigenesis using two animal models. In the azoxymethane (AOM)/dextran sulfate sodium salt model, PUMA deficiency increased the multiplicity and size of colon tumors but reduced the frequency of β-catenin hotspot mutations. The absence of PUMA led to a significantly elevated incidence of precursor lesions induced by AOM. AOM was found to induce p53-dependent PUMA expression and PUMA-dependent apoptosis in the colonic crypts and stem cell compartment. Furthermore, PUMA deficiency significantly enhanced the formation of spontaneous macroadenomas and microadenomas in the distal small intestine and colon of APCMin/+ mice. These results show an essential role of PUMA-mediated apoptosis in suppressing intestinal tumorigenesis in mice. [Cancer Res 2009;69(12):4999–5006]

  C. Zhu , J. Yu , Z. Yang , K. Davis , H. Rios , B. Wang , G. Glenn and E. C. Boedeker
  Enterohemorrhagic Escherichia coli (EHEC) strains are important human food-borne pathogens. EHEC strains elaborate potent Shiga toxins (Stx1, and/or Stx2) implicated in the development of hemorrhagic colitis (HC) or hemolytic-uremic syndrome (HUS). In this report, we evaluated the immunogenicity and protective efficacy of Stx1 subunit B (StxB1) administered by transcutaneous immunization (TCI). Three groups of Dutch Belted rabbits received patches containing StxB1, StxB1 in combination with Escherichia coli heat-labile enterotoxin (LT), or LT alone. An additional group of naïve rabbits served as controls. The protective efficacy following TCI with StxB1 was assessed by challenging rabbits with a virulent Stx1-producing strain, RDEC-H19A, capable of inducing HC and HUS in rabbits. Antibodies specific to StxB1 from serum and bile samples were determined by enzyme-linked immunosorbent assay and toxin neutralization test. Rabbits immunized with StxB1 demonstrated improved weight gain and reduced Stx-induced histopathology. Rabbits receiving StxB or StxB1/LT showed a significant increase in serum immunoglobulin G titers specific to StxB1 as well as toxin neutralization titers. These data demonstrated that the StxB delivered by TCI could induce significant systemic immune responses. Thus, Stx subunit B vaccine delivered by a patch for a high-risk population may be a practical approach to prevent (and/or reduce) Stx-induced pathology.
  I. Lee , J. Yu , Y. Yoon , H.J. Gim , S.M. Lee , J.W. Park , R. Jeon and B.H. Park
  The nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) plays an important role in adipocyte differentiation and is the target for anti-diabetic drugs known as thiazolidinediones. Here, we synthesized and characterized a new PPARγ agonist, SPA0432. COS-7 cells treated with SPA0432 showed significantly increased PPARγ transcriptional activity compared to that of vehicle-treated cells. However, its efficacy was less than that of rosiglitazone. Using a standard differentiation protocol, SPA0432 effectively enhanced differentiation of 3T3-L1 preadipocytes as evidenced by increased lipid droplet formation and triglyceride accumulation. Real-time RT-PCR analysis indicated that SPA0432 significantly increased the expressions of adipogenesis-related genes, CAAT/enhancer binding protein α, PPARγ, fatty acid synthase, aP2 and lipoprotein lipase and significantly decreased the expression of Pref-1, a preadipocyte marker. Moreover, SPA0432 increased insulin-stimulated glucose uptake in differentiated 3T3-L1 adipocytes. These results suggest that SAP0432 may exert beneficial effects against insulin resistance through its ability to promote adipocyte differentiation and insulin-stimulated glucose uptake.
  J. Lu , Z. Dong , L. Chen and J. Yu
  We have theoretically and experimentally investigated polarization insensitive of all optical wavelength conversion for polarization multiplexing signal based on four-wave mixing (FWM) in nonlinear optical fiber. Optical polarization multiplexing technique can be used to double the transmission bit rate by adding data on each of two orthogonal optical states. At the receiver side, the two orthogonal signals can be obtained by direct detection. The eye diagrams of the original signals have been probed and compared with the converted one in this experiment. The characteristics of the converted signal have been fully studied and a little crosstalk which leads a better corresponding eye diagram has been obtained after polarization demultiplexing.
  L. Maness , I. Goktepe , B. Hardy , J. Yu and M. Ahmedna
  Phytolacca americana, native to North and South America and East Asia, has been used by Native Americans as a laxative, and to treat inflammation, rashes and breast problems. Recent investigations include determining anti-viral and anti-cancer properties of purified pokeweed antiviral protein conjugated to monoclonal antibodies. However, there is limited information on the activities of P. americana extracts directly against cancer cells. This study was carried out to evaluate the antiproliferative activities of crude ethanol, methanol and water extracts from P. americana against MCF-7 human breast and HCT-116 colon cancer cells using the 3-(4, 5-Dimethylthiazol-2-yl-)-2, 5-diphenyltetrazolium bromide (MTT) assay. The ethanol extract of P. americana (PRE) had significantly higher antiproliferative activity against HCT-116 cells than the methanol extract (PRM) and the water extract (PRW). None of the extracts showed a significant antiproliferative activity against MCF-7 cells. The ethanol extract was further fractionated and the water fraction showed the greatest antiproliferative activity against HCT-11 Cells compared to the ethyl acetate and butanol fractions. Changes in caspase 2, 3, 6, 8 and 9 activities in HCT-116 cells after exposure to the ethanol extract and its most active fraction were also examined. Caspases 6 and 9 showed increased activities in HCT-116 cells exposed to the ethanol extract. Caspases 3, 8 and 9 were activated in HCT-116 cells exposed to the water fraction. Relatively strong antiproliferative and apoptotic activities were exhibited against HCT-116 cells by the ethanol extract and its water fraction. These findings suggest that further investigation into their potential use in pharmaceutical applications as chemopreventive supplements or in complementary treatment of colon cancer is warranted.
  P. C. B Phillips and J. Yu

A new methodology is proposed to estimate theoretical prices of financial contingent claims whose values are dependent on some other underlying financial assets. In the literature, the preferred choice of estimator is usually maximum likelihood (ML). ML has strong asymptotic justification but is not necessarily the best method in finite samples. This paper proposes a simulation-based method. When it is used in connection with ML, it can improve the finite-sample performance of the ML estimator while maintaining its good asymptotic properties. The method is implemented and evaluated here in the Black-Scholes option pricing model and in the Vasicek bond and bond option pricing model. It is especially favored when the bias in ML is large due to strong persistence in the data or strong nonlinearity in pricing functions. Monte Carlo studies show that the proposed procedures achieve bias reductions over ML estimation in pricing contingent claims when ML is biased. The bias reductions are sometimes accompanied by reductions in variance. Empirical applications to U.S. Treasury bills highlight the differences between the bond prices implied by the simulation-based approach and those delivered by ML. Some consequences for the statistical testing of contingent-claim pricing models are discussed.

  J. Yu , Z.A. Tang , G.Z. Yan , P.C.H. Chan and Z.X. Huang
  Micro-cracks in tin oxide thin film may cause bad stability to the micro-hotplate (MHP) gas sensor, especially at high operation temperature or in moisture ambience. In order to reduce micro-cracks, tin oxide thin films on a 2 x 2 MHP gas sensor array are patterned as narrow strips. It is proved by SEM that micro-cracks induced by thermal stress can be greatly restrained in narrow strip shape films comparing with the traditional rectangle board film. Stability of the MHP sensors with narrow strip films was characterized by testing their resistance in air for 60 h, and their responses respectively to methane and carbon monoxide for 300 h. The results show that the strip shape SnO2 films are really helpful to enhance stability of the MHP gas sensors.
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