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S Yang

Publications and source records attributed to S Yang.

At least 235 records · Page 13Linked to original sources
PubMed2000

[PCR amplification and cloning of virulence expression regulatory gene toxR of Vibrio cholerae].

In order to construct a genomic bivalent oral vaccine of Leishmania donovani and Vibrio cholerae, we amplified a 1.3 kb DNA fragment from 7 strains of Vibrio cholerae with primers P1 and P2. Restriction endonuclease analysis of PCR amplified products from 9 strains of Vibrio cholerae was performed by digestion with EcoR I. The results revealed an EcoR I site in the central part of toxR gene. The entire toxR gene of Vibrio cholerae Non-CT strain 7743 was amplified by PCR with primers P1 and P2, digested with endonucleases BamH I and Hind III, then was orientationally cloned into plasmid pAT153. The restriction endonuclease analysis demonstrates that the recombinant plasmid ptR4 contains a 1.3 kb toxR gene fragment.

Bacterial Proteins↗
PubMed2000

[Effects of Nilestriol on reproductive system in ovariectomized rats].

The purpose of this study was to determine the effects of Nilestriol on reproductive system. Female SD rats, aged 4 months, were randomly divided into three groups. The OVX group's rats were subjected to bilateral ovariectomy, the SHAM group's rats received sham surgery; the Nilestriol(CEE3) group's rats were subjected to bilateral ovariectomy and treated with CEE3(0.15 mg/100 g BW, once a week). A computerized image analyzer was used to evaluate the endometrial pathological changes 10 weeks later. The weight of uterus was measured. The results showed that in OVX group, atrophic uteri; and atrophied endometria were noted. The weight of uterus was increased in CEE3 group, compared with that in OVX group (642.20 +/- 283.60 mg vs. 297.00 +/- 106.90 mg, P < 0.05). The volume fraction of endometrial glands was also significantly elevated in CEE3 group, compared with that in OVX group (1.84% vs 0.58%). The endometria in CEE3 group were at an early proliferative stage. These suggest that Nilestriol has a slight stimulating effect on the uteri of ovariectomized rats, including their endometria and uterine smooth muscles. Nilestriol is suited to be used in combination with progestogen.

Animals↗
PubMed2000

[Studies on detection methods of two DNA probes in Mycobacterium tuberculosis].

Two different biotinylated DNA probes which are highly specific to M. tuberculosis(MT) were made and studied. One probe is a 20 bp oligonucleotide labeled with biotin at 5' end, the other is a long DNA probe produced by PCR amplification procedure allowed for the incorporation of biotin labeled UTP. The two probes were hybridized with MT genome DNA and a 317 bp PCR product amplified from IS6110 sequence of MT, and then detected by alkaline phosphatase conjugates through colorimetric reaction. The detection sensitivity and specificity of the two probes were comparatively studied. The hybridization condition including concentration of probe, temperature of hybridization and washing filter thereafter were also investigated preliminary. The detection limit of the oligonucleotide probe and the 188 bp PCR probe were 100 ng and 6 ng of DNA respectively in detection of M. T genome, and 400 pg and 50 pg of DNA respectively in detection of PCR products of MT. The two probes can be only hybridized to MT and BCG, but not with other 24 mycobacterium or non-mycobacterium tested. The optimal hybridization temperature and washing filter temperature of oligonucleotide were 42 degrees C and 60 degrees C respectively; and that of 188 bp probe, 68 degrees C and 60 degrees C-68 degrees C. Generally the specificity of two probes were all high, but the sensitivity of 188 bp DNA probe was 7-16 times that of the oligonucleotide probe. The higher sensitivity, lower hybridization background and faster revelation of the 188 bp DNA probe made it a better choice in detection of MT.

Biotin↗
PubMed2000

[Study on production of poly-beta-hydroxybutyrate by recombinant strain VG1(pTU14)].

Cloning and expression of Vitreoscilla hemoglobin gene (vgb) and lambda phage lytic genes (S-RRz) in production of Poly-beta-hydroxybutyrate(PHB) was studied in different Escherichia coli hosts such as E. coliJM105, E. coliJM109 and VG1. In the recombinant strains, VG1(pTU14) was a superior one which simultaneously contained three exogenes including vgb, S-RRz and PHB biosynthesis genes(phbCAB). The experimental results showed that after 82 hours fed-batch cult ure in LBG medium in shaking flask, cell concentration of VG1(pTU14) could reach 25.9 g/L, which was the highest PHB production ever reported, and till 52 h PHB content could be higher than 95%. Additionally, inducible cell lysis was also attained successfully in recombinant VG1(pTU14) accompanying with its high cell density culture. Therefore, VG1(pTU14) is a novel potential strain with promising prospect in industrial production of PHB.

Bacterial Proteins↗
PubMed2000

[Audiological findings and mitochondrial DNA mutation in a large family with matrilineal sensorineural hearing loss].

OBJECTIVE: To explore audiological features of matrilineal non-syndromic deafness and its molecular mechanism. METHODS: A large family with 41 members having inherited deafness was studied. Complete history and the data of general and otolaryngological examinations were collected. All subjects were screened for mitochondrial DNA A1555G mutation by molecular analysis. Audiological evaluation included puretone audiometry, auditory brainstem responses and transiently evoked otoacoustic emissions. RESULTS: All subjects were in good health generally. Molecular analysis showed that all maternal relatives with or without hearing loss harbored the A1555G mitochondrial mutation. No mutation was found among spouses and paternal relatives. Audiological results showed notable symmetric bilateral sensorineural hearing loss in 17 of 20 maternal relatives, in which 5 cases had a progressive hearing loss in the recent 11 years. The age of appearance of hearing loss ranged from 1 to 50 years. CONCLUSION: All hearing-impaired subjects of this family had late-onset sensorineural hearing loss. Most of which were progressive. The A1555G mitochondrial mutation in the 12S rRNA gene is responsible for the disorder. Other factors, such as nuclear genes or environmental determinants, may influence the clinical expression of mutant mtDNA.

Acoustic Impedance Tests↗
PubMed2000

[Chemical constituents of annonaceae plants and their antitumor activities].

This report is the summary of our research on the chemical constitutents and their antitumor activities of Annonaceae plants. Annonaceous acetogenins, polyoxy-cyclohexenoids, and styryl-lactones from Annonaceae are the main constituents of antitumor activities. They are expected to develop a kind of new antitumor medicines.

Annonaceae↗
PubMed2000

[Comparison of FTIR microspectroscopy and diffuse reflectance spectroscopy for monitor of solid phase reaction].

17 FTIR micro transmission spectra of single resin beads of each sample, from polystyrene sulfonyl chloride resin changing to polystyrene sulfonyl amide resin in solid-phase reaction in water at 0 degree C, 20 degrees C, 40 degrees C, 60 degrees C, were recorded. The reaction was monitored by the means of FTIR microspectroscopy and diffuse reflectance spectroscopy upon the products. It was showed that the pressed single bead as a piece of biscuit was able to give higher quality spectrum. In comparison, 8 diffuse reflectance spectra of each sample were also collected. It seems that the diffuse reflectance spectroscopy is a more easy dealing with and effective method to control the whole reaction. However, the microspectroscopy is the first choice to check the difference between resin beads.

Ion Exchange Resins↗
PubMed2000

[The molecular spectra and existence state of sulfonated phthalimidomethyl phthalocyanine hydroxyl aluminum as amphiphilic photosensitizer in aqueous alcoholic solutions and water].

The sulfonated phthalimidomethyl phthalocyanine hydroxyl aluminum (Al(OH)PcSP) is an amphiphilic photosensitizer which was proved to have the photodynamic activities against cancer. The electronic absorption spectra and aggregation state of the Al(OH)PcSP in aqueous alcoholic solutions and water were investigated. The results showed that the Al(OH)PcSP existed in the form of monomer in aqueous alcoholic solutions. The increase in the carbon chain and hydroxy of alcohol in solutions had no significant effects on the absorption spectra behaviors of Al(OH)PcSP. But in water, the Al(OH)PcSP existed in the equilibrium between monomer and dimer. The dimerization constant was 5.7307 x 10(4) mol-1.L. The characteristic absorption peak of the Q band of the Al(OH)PcSP dimer was red shifted to 740.5 nm from that of the monomer (676.5 nm), which contrast with those of other metal phthalocyanines dimer. The study on the fluorescence spectra of Al(OH)PcSP in aqueous alcoholic solutions suggested that the fluorescence of the dimer was weak.

Electron Probe Microanalysis↗
PubMed2000

[The monomer electronic spectra and fluorescence spectra of some metal phthalocyanines].

The monomer electronic absorption spectra of the ZnPcS2P2 (disulfonated diphthalimidomethyl phthalocyanine zinc) in 11 kinds of solvents and 5 kinds of unsubstituted metal phthalocyanines in DMF were investigated. The monomer electronic absorption spectra of some substituted phthalocyanine zinc including ZnPcS4 (tetrasulfonated phthalocyanine zinc), ZnPcS4 (tetraphthalimidomethyl phthalocyanine zinc), ZnPc(NO2)4 (tetranitro phthalocyanine zinc) and ZnPcS2P2 in the same solvent were also studied. The result showed that (1) with the strengthening of coordination ability of the solvent, the maximum absorption wavelength of ZnPcS2P2 increased slightly. (2) with the increasing of electronegativity of central ion, the maximum absorption wavelength of MPcs had a little blue shift. (3) the electron-donating substituting group caused slightly blue shift. The monomer fluorescence spectra of ZnPcS4, ZnPcP4, and ZnPcS2P2 in different solvents were determined. The result showed that (1) the electron-withdrawing substituting group caused slightly red shift of the fluorescence spectra. (2) with the strenghtening of coordination ability of the solvent, the maximum emission wavelength increased slightly. (3) the fluorescence intensity of ZnPcS2P2 in the solution which contains Cremophor EL was remarkable stronger than that in other solvents. This is an important suggest to the development of photodynamic diagnose agent. The effect of solvents, central ions and substituents on spectra were partly explained by means of the quantrum chemistry.

Electrochemistry↗
PubMed1999

Murine dendritic cells transfected with human GP100 elicit both antigen-specific CD8(+) and CD4(+) T-cell responses and are more effective than DNA vaccines at generating anti-tumor immunity.

Dendritic cells (DCs) are potent inducers of cytotoxic T lymphocytes (CTLs) when pulsed with an antigenic peptide or tumor lysate. In this report, we have used liposome-mediated gene transfer to examine the ability of plasmid DNA encoding the human melanoma-associated antigen gp100 to elicit CD8(+) and CD4(+) T-cell responses. We also compared the efficacy between gp100 gene-modified DCs and naked DNA (pCDNA3/gp100)-based vaccines at inducing anti-tumor immunity. DCs were generated from murine bone marrow and transfected in vitro with plasmid DNA containing the gp100 gene. These gp100-modified DCs (DC/gps) were used to stimulate syngeneic naive spleen T cells in vitro or to immunize mice in vivo. Antigen-specific, MHC-restricted CTLs were generated when DC/gps were used to prime T cells both in vitro and in vivo. Thus, these CTLs were cytolytic for gp100-transfected syngeneic (H-2(b)) tumor MCA106 (MCA/gp) and vaccinia-pMel17/gp100-infected syngeneic B16 and MCA106, but not parental tumor MCA106 and B16, or gp100-transfected allogeneic tumor P815 (H-2(d)). Immunization with DC/gp protected mice from subsequent challenge with MCA/gp but not parental MCA106. Antibody-mediated T-cell subset depletion experiments demonstrate that induction of CTLs in vivo is dependent on both CD4(+) and CD8(+) T cells. Furthermore, DC/gp immunization elicits an antigen-specific CD4(+) T-cell response, suggesting that DC/gps present MHC class II epitopes to CD4(+) T cells. In addition, our data show that gene-modified, DC-based vaccines are more effective than the naked DNA-based vaccines at eliciting anti-tumor immunity in both prophylactic and therapeutic models. These results suggest that the use of DCs transfected with plasmid DNA containing a gene for TAA may be superior to peptide-pulsed DCs and naked DNA-based vaccines for immunotherapy and could provide an alternative strategy for tumor vaccine design.

Animals↗
PubMed1999

Stage-specific expression of alpha1,2-fucosyltransferase and alpha1, 3-fucosyltransferase (FT) during mouse embryogenesis.

Lex [Galbeta1-4(Fucalpha1-3)GlcNAc] and Ley [Fucalpha1-2Galbeta1-4(Fucalpha1-3)GlcNAc] are both stage-specific embryonic antigens. Lex is first detected on the blastomeres of the 8-cell stage embryo, which correlates with the onset of blastomere compaction. Ley is highly expressed on the surface of the blastocyst, which has been shown to be involved in blastocyst attachment in the mouse. In the present study, mouse alpha1,2-FT (also known as FUT1) and alpha1,3-FT (also known as Fuc-TIV), which were responsible for Lex and Ley formation, were examined in preimplantation stage embryos by reverse transcription-PCR and in situ hybridization. alpha1,3-FT mRNA was detected in all embryos of preimplantation stage, while alpha1,2-FT mRNA emerged in the later stage embryos from 8-cell to 16-cell to the blastocyst. These results indicated the expression of Ley was regulated by alpha1,2-FT. In situ hybridization showed that these two enzyme mRNAs were detected only in morula and blastocyst stage embryos. The alpha1,2-FT and alpha1, 3-FT mRNAs were located in both the inner cell mass and the trophoblast cells. 2-Cell and 4-cell embryos were isolated from the oviduct and cultured in vitro to the 8-cell, morula and blastocyst stage. The expression of alpha1,2-FT and alpha1,3-FT were observed in these embryos developed in vitro; immunohistochemical analysis also showed that Ley expression was positive. These results suggested the stage-specific expression of Ley on the embryos was synthesized by endogenous alpha1,2-FT and alpha1,3-FT rather than transfer from other sources. In addition, the expression of alpha1, 2-FT was differentially regulated and the uterine factor was not prerequisite of the expression of Ley.

Animals↗
PubMed1999

Nitric oxide suppresses apoptosis via interrupting caspase activation and mitochondrial dysfunction in cultured hepatocytes.

Nitric oxide (NO) is a potent inhibitor of apoptosis in many cell types, including hepatocytes. We and others have described NO-dependent decreases in caspase activity in cells undergoing apoptosis. However, previous work has not determined whether NO disrupts the proteolytic processing and thus the activation of pro-caspases. Here we report that NO suppresses proteolytic processing and activation of multiple pro-caspases in intact cells, including caspase-3 and caspase-8. We found that both exogenous NO as well as endogenously produced NO via adenoviral inducible NO synthase gene transfer protected hepatocytes from tumor necrosid factor (TNF) alpha plus actinomycin D (TNFalpha/ActD)-induced apoptosis. Affinity labeling with biotin-VAD-fmk of all active caspase species in TNFalpha-mediated apoptosis identified four newly labeled spots (activated caspases) present exclusively in TNFalpha/ActD-treated cells. Both NO and the caspase inhibitor, Ac-DEVD-CHO, prevented the appearance of the four newly labeled spots or active caspases. Immunoanalysis of affinity labeled caspases demonstrated that caspase-3 was the major effector caspase. Western blot analysis also identified the activation of caspase-8 in the TNFalpha/ActD-treated cells, and the activation was suppressed by NO. Furthermore, NO inhibited several other events associated with caspase activation in cells, including release of cytochrome c from mitochondria, decrease in mitochondrial transmembrane potential, and cleavage of poly(ADP-ribose) polymerase in TNFalpha/ActD-treated cells. These findings indicate the involvement of multiple caspases in TNFalpha-mediated apoptosis in hepatocytes and establish the capacity of NO to inhibit not only active caspases but also caspase activation.

Animals↗
PubMed1999

Decreased imino proton exchange and base-pair opening in the IHF-DNA complex measured by NMR.

Integration Host Factor, IHF, is an E. coli DNA binding protein that imposes a substantial bend on DNA. Previous footprinting studies and bending assays have characterized several recognition sequences in the bacterial and lambda phage genome as unique in the way they are bound by IHF. We have chosen one of the lambda phage sites, H1, for study because it presents a small yet sequence-specific substrate for NMR analysis of the complex. A 19 base-pair duplex, H19, corresponding to the recognition sequence at the H1 site was constructed by isotopically labeling one of the strands with 15N. (1H, 15N) heteronuclear NMR experiments aided in assigning the imino proton resonances of the DNA alone and in complex with IHF. The NMR results are consistent with a mode of binding observed in the recent crystal structure of IHF bound to another of its sites from the lambda phage genome. Additionally, the dramatic change that IHF imposes on the imino proton chemical shifts is indicative of a severe deviation from canonical B-DNA structure. In order to understand the dynamic properties of the DNA in the complex with IHF, the exchange rates of the imino protons with the solvent have been measured for H19 with and without IHF bound. A drastic reduction in exchange is observed for the imino protons in the IHF bound DNA. In the DNA-protein complex, groups of adjacent base-pair exchange at the same rate, and appear to close more slowly than the rate of imino proton exchange with bulk water, since their exchange rate is independent of catalyst concentration. We infer that segments of the double helix as large as 6 bp open in a cooperative process, and remain open much longer than is typical for opening fluctuations in naked duplex DNA. We discuss these results in terms of the specific protein-DNA contacts observed in the crystal structure.

Bacterial Proteins↗
PubMed1999

Peroxisome proliferator-activated receptor gamma ligands are potent inhibitors of angiogenesis in vitro and in vivo.

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor that functions as a transcription factor to mediate ligand-dependent transcriptional regulation. Activation of PPARgamma by the naturally occurring ligand, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), or members of a new class of oral antidiabetic agents, e.g. BRL49653 and ciglitizone, has been linked to adipocyte differentiation, regulation of glucose homeostasis, inhibition of macrophage and monocyte activation, and inhibition of tumor cell proliferation. Here we report that human umbilical vein endothelial cells (HUVEC) express PPARgamma mRNA and protein. Activation of PPARgamma by the specific ligands 15d-PGJ2, BRL49653, or ciglitizone, dose dependently suppresses HUVEC differentiation into tube-like structures in three-dimensional collagen gels. In contrast, specific PPARalpha and -beta ligands do not affect tube formation although mRNA for these receptors are expressed in HUVEC. PPARgamma ligands also inhibit the proliferative response of HUVEC to exogenous growth factors. Treatment of HUVEC with 15d-PGJ2 also reduced mRNA levels of vascular endothelial cell growth factor receptors 1 (Flt-1) and 2 (Flk/KDR) and urokinase plasminogen activator and increased plasminogen activator inhibitor-1 (PAI-1) mRNA. Finally, administration of 15d-PGJ2 inhibited vascular endothelial cell growth factor-induced angiogenesis in the rat cornea. These observations demonstrate that PPARgamma ligands are potent inhibitors of angiogenesis in vitro and in vivo, and suggest that PPARgamma may be an important molecular target for the development of small-molecule inhibitors of angiogenesis.

Animals↗
PubMed1999

Novel protein kinases Ark1p and Prk1p associate with and regulate the cortical actin cytoskeleton in budding yeast.

Ark1p (actin regulating kinase 1) was identified as a yeast protein that binds to Sla2p, an evolutionarily conserved cortical actin cytoskeleton protein. Ark1p and a second yeast protein, Prk1p, contain NH2-terminal kinase domains that are 70% identical. Together with six other putative kinases from a number of organisms, these proteins define a new protein kinase family that we have named the Ark family. Lack of both Ark1p and Prk1p resulted in the formation of large cytoplasmic actin clumps and severe defects in cell growth. These defects were rescued by wild-type, but not by kinase-dead versions of the proteins. Elevated levels of either Ark1p or Prk1p caused a number of actin and cell morphological defects that were not observed when the kinase-dead versions were overexpressed instead. Ark1p and Prk1p were shown to localize to actin cortical patches, making these two kinases the first signaling proteins demonstrated to be patch components. These results suggest that Ark1p and Prk1p may be downstream effectors of signaling pathways that control actin patch organization and function. Furthermore, results of double-mutant analyses suggest that Ark1p and Prk1p function in overlapping but distinct pathways that regulate the cortical actin cytoskeleton.

Actins↗
PubMed1999

Obesity induces expression of uncoupling protein-2 in hepatocytes and promotes liver ATP depletion.

Uncoupling protein 2 (UCP2) uncouples respiration from oxidative phosphorylation and may contribute to obesity through effects on energy metabolism. Because basal metabolic rate is decreased in obesity, UCP2 expression is predicted to be reduced. Paradoxically, hepatic expression of UCP2 mRNA is increased in genetically obese (ob/ob) mice. In situ hybridization and immunohistochemical analysis of ob/ob livers demonstrate that UCP2 mRNA and protein expression are increased in hepatocytes, which do not express UCP2 in lean mice. Mitochondria isolated from ob/ob livers exhibit an increased rate of H+ leak which partially dissipates the mitochondrial membrane potential when the rate of electron transport is suppressed. In addition, hepatic ATP stores are reduced and these livers are more vulnerable to necrosis after transient hepatic ischemia. Hence, hepatocytes adapt to obesity by up-regulating UCP2. However, because this decreases the efficiency of energy trapping, the cells become vulnerable to ATP depletion when energy needs increase acutely.

Adenosine Triphosphate↗
PubMed1999

Generation of retroviral vector for clinical studies using transient transfection.

Transient transfection of 293T cells was utilized to produce high-titer murine recombinant retroviral vectors for clinical studies. This system was initially optimized by gene transfer using different retroviral envelope proteins into activated human CD4+ T lymphocytes in vitro. Higher titer and infectivity were obtained than with stable murine producer lines; titers of 0.3-1 x 10(7) infectious units per milliliter for vectors encoding the green fluorescent protein (GFP) were achieved. Virions pseudotyped with envelope proteins from gibbon ape leukemia virus or amphotropic murine leukemia virus resulted in gene transfer of > or = 50% in CD4+ human T lymphocytes with this marker. Gene transfer of Rev M10 with this vector conferred resistance to HIV infection compared with negative controls in the absence of drug selection. Thus, the efficiency of transduction achieved under these conditions obviated the need to include selection to detect biologic effects in T cells. Finally, a protocol for the production of large-scale supernatants using transient transfection was optimized up to titers of 1.9 x 10(7) IU/ml. These packaging cells can be used to generate high-titer virus in sufficient quantities for clinical studies and will facilitate the rapid, cost-effective generation of improved retroviral, lentiviral, or other viral vectors for human gene therapy.

Animals↗