PubMed Health⌕ Search

Biomedical subjects

W Song

Publications and source records attributed to W Song.

At least 19 recordsLinked to original sources
PubMed1998

A carboxyl-terminal extension of the zinc finger domain contributes to the specificity and polarity of peroxisome proliferator-activated receptor DNA binding.

Heterodimers of the peroxisome proliferator-activated receptors (PPAR) and the retinoid X receptors (RXR) recognize response elements (PPREs) that exhibit the consensus sequence 5'-A(A/T)CT(A/G)GGNCAAAG(G/T)TCA-3'. The consensus PPRE includes both a 5'-extension and a direct repeat (DR1) comprised of two canonical core recognition sequences (underlined) for nuclear receptor zinc fingers separated by a single nucleotide spacer. The extended binding site recognized by PPARs is very similar to sites that bind monomers of the nuclear receptors Rev-ErbA and ROR suggesting that the latter could bind to PPREs and affect gene transcription. However, Rev-ErbA and ROR bind weakly to naturally occurring PPREs relative to the consensus binding site, and significant effects on PPARalpha transactivation of a CYP4A6-Z reporter were not observed. In contrast, PPAR/RXR heterodimers bind to a DR2 element containing the conserved 5'-extended sequence that is recognized by dimers of RORalpha or Rev-ErbA. PPARalpha/RXRalpha positively regulate transcription from this element, and co-expression of Rev-ErbA blocks this effect. The nuclear receptors NGFI-B and ROR utilize a carboxyl-terminal extension (CTE) of the zinc finger DNA binding domain in their interactions with the 5'-extension of a single zinc finger-binding site. DNA binding domains (DBD) of PPARs alpha, delta, and gamma that contain the zinc finger motif and a CTE display binding to core recognition sequences that is dependent on the 5'-extended sequence found in PPREs. Unlike DBDs of other nuclear receptors that form heterodimers with RXR, the PPAR-DBDs did not exhibit cooperative binding with the DBD of RXR and exhibit the opposite polarity for binding to the direct repeat motif. In contrast to the corresponding DBD of RXR, the PPAR-DBDs bind as monomers to a single extended binding site as well as to the consensus PPRE. A chimera linking the zinc finger domain of RXRalpha to the CTE from PPARalpha bound to a single extended binding site indicating a functional role for the CTE of PPARs in extended binding site recognition.

Amino Acid Sequence↗
PubMed1998

Srb/mediator proteins interact functionally and physically with transcriptional repressor Sfl1.

Srb/mediator proteins that are associated with RNA polymerase II holoenzyme have been implicated in transcriptional repression in Saccharomyces cerevisiae. We show here that the defect in repression of SUC2 caused by mutation of SRB8, SRB9, SRB11, SIN4 or ROX3 is suppressed by increased dosage of the SFL1 gene, and the genetic behavior of the sfl1Delta mutation provides further evidence for a functional relationship. Sfl1 acts on SUC2 through a repression site located immediately 5' to the TATA box, and Sfl1 binds this DNA sequence in vitro. Moreover, LexA-Sfl1 represses transcription of a reporter, and repression is reduced in an srb9 mutant. Finally, we show that Sfl1 co-immunoprecipitates from cell extracts with Srb9, Srb11, Sin4 and Rox3. We propose that Sfl1, when bound to its site, interacts with Srb/mediator proteins to inhibit transcription by RNA polymerase II holoenzyme.

Bacterial Proteins↗
PubMed1998

A study of sexual behavior among rural residents of China.

OBJECTIVE: Although the recent spread of HIV/AIDS and other sexually transmitted diseases (STDs) in China has been associated with sexual activities, little information has been available about sexual behavior in rural areas with high HIV prevalence. Studies identifying high-risk sexual behaviors are needed to formulate effective prevention programs. METHODS: A cross-sectional study design was used to measure sexual activities using a two-stage cluster sampling method. A two-part anonymous questionnaire was used. Sensitive questions related to sexual behavior were administered using a tape recorder, earphones, and an answer sheet which did not include the text. RESULTS: In total, 1057 subjects were interviewed. Among 886 sexually active individuals, 7.8% had >1 sexual partner, 22.8% had premarital sex, 2.4% had anal intercourse, 4.1% had oral intercourse, and 2.3% had both anal and oral intercourse. Less than 2% reported past or current sexually transmitted diseases. Overall, 10.4% used condoms; only 11.2% for every sexual act. History of premarital and extramarital sex was higher in younger people. CONCLUSIONS: Sexual norms in rural China are changing rapidly and high-risk sexual behavior among young rural residents is increasing. Strategies to prevent HIV/AIDS should include education to promote delayed onset of sexual activity, safer sexual behavior, and condom use.

Adolescent↗
PubMed1998

DARPP-32: regulator of the efficacy of dopaminergic neurotransmission.

Dopaminergic neurons exert a major modulatory effect on the forebrain. Dopamine and adenosine 3',5'-monophosphate-regulated phosphoprotein (32 kilodaltons) (DARPP-32), which is enriched in all neurons that receive a dopaminergic input, is converted in response to dopamine into a potent protein phosphatase inhibitor. Mice generated to contain a targeted disruption of the DARPP-32 gene showed profound deficits in their molecular, electrophysiological, and behavioral responses to dopamine, drugs of abuse, and antipsychotic medication. The results show that DARPP-32 plays a central role in regulating the efficacy of dopaminergic neurotransmission.

Amphetamines↗
PubMed1998

Intermittent, repetitive corticosteroid-induced upregulation of platelet levels after adenovirus-mediated transfer to the liver of a chimeric glucocorticoid-responsive promoter controlling the thrombopoietin cDNA.

For many in vivo gene therapy clinical applications, it is desirable to control the expression of the transferred transgene using pharmacologic agents. To evaluate the feasibility of accomplishing this using corticosteroids, pharmacologic agents widely used in clinical medicine, we constructed replication deficient adenoviral (Ad) vectors containing an expression cassette with a chimeric promoter comprised of five glucocorticoid response elements (GRE) and the chloramphenicol acetyltransferase reporter gene (AdGRE.CAT) or the murine thrombopoietin cDNA (AdGRE.mTPO). In vitro studies showed the vectors functioned as expected, with marked glucocorticoid-induced upregulation of the CAT or mTPO transgenes. To evaluate the inducibility of the GRE promoter in vivo, the AdGRE. CAT vector was administered intravenously to C57B1/6 mice, and CAT activity was quantified in liver before and after intraperitoneal administration of dexamethasone. The GRE promoter activity was dependent on the dexamethasone dose, with a 100-fold increase in CAT expression with 50 microg dexamethasone, similar to the levels observed in vivo with the Rous sarcoma virus long terminal repeat constitutive promoter. After dexamethasone administration, maximum CAT activity was observed at day 2, with a slow decline to baseline levels by 2 weeks. Based on these observations, we hypothesized that a single administration of an Ad vector-mediated transfer of the chimeric GRE inducible promoter driving the mTPO cDNA would enable repetitive administration of corticosteroids to repetitively upregulate platelet levels for 1 to 2 weeks. The data show that this occurs, with dexamethasone administration every 3 weeks associated with 1-week elevations (at each 3-week interval) of serum mTPO levels, megakaryocyte numbers in bone marrow, and platelet levels fourfold to sixfold over baseline. Thus, with the appropriate promoter, it is possible to use a commonly used pharmacologic agent to upregulate the expression of a newly transferred gene on demand.

Adenoviruses, Human↗
PubMed1998

Purification and characterization of hamster liver microsomal 7alpha-hydroxycholesterol dehydrogenase. Similarity to type I 11beta-hydroxysteroid dehydrogenase.

While studying the bile acid synthetic pathway of hamsters, we discovered an NADP+-dependent liver microsomal 7alpha-hydroxycholesterol dehydrogenase (7alpha-HCD) activity that was not observed in rat liver microsomal fractions. The hamster liver microsomal 7alpha-HCD was purified to homogeneity using 2', 5'-ADP and cholic acid-agarose affinity chromatography. 7alpha-HCD displayed a molecular weight of approximately 34,000 on SDS-polyacrylamide gel electrophoresis; it is an intrinsic membrane protein of the hamster liver endoplasmic reticulum and exists as a multimeric aggregate in pure form. Partial N-terminal amino acid sequence analysis showed that 7alpha-HCD had high sequence similarity to human 11beta-hydroxysteroid dehydrogenase (11beta-HSD; 24/30 amino acid identity). The Km values for corticosterone and 7alpha-hydroxycholesterol were 1.2 and 1.9 microM, respectively, for purified 7alpha-HCD; both reactions displayed identical Vmax values (approximately 170 nmol/min/mg of protein). The IC50 of carbenoxolone, a competitive inhibitor of 11beta-HSD, was 75 nM for 7alpha-hydroxycholesterol dehydrogenation and 210 nM for corticosterone dehydrogenation. The tissue-specific expression in hamster was as follows: adrenal >/= liver > kidney > testis >> brain > lung. Microsomal 7alpha-HCD is uniquely expressed in hamster liver and to some extent in human liver but not in rat liver. Western blot analysis with two antibodies elicited against an N-terminal peptide of the human 11beta-HSD and purified hamster liver 7alpha-HCD, respectively, suggested the presence of multiple forms of 7alpha-HCD in hamster liver, most likely due to the existence of a family of 11beta-HSD proteins. Since 7-oxocholesterol is a potent inhibitor of cholesterol 7alpha-hydroxylase, alternative mechanisms for regulation of bile acid synthesis may exist in human and hamster liver due to production of this metabolite and its potential as an oxysterol.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1998

Regional suppression of tumor growth by in vivo transfer of a cDNA encoding a secreted form of the extracellular domain of the flt-1 vascular endothelial growth factor receptor.

Vascular endothelial growth factor (VEGF), a potent angiogenic mediator, is overexpressed in most solid tumors. On the basis of the knowledge that solid tumor growth beyond a small volume is critically dependent on angiogenesis, and that adenovirus (Ad) vectors can mediate efficient in vivo gene transfer and expression, we hypothesized that Ad-mediated transfer of a secreted form of the extracellular domain of the flt-1 VEGF receptor (Adsflt) would suppress tumor growth on a regional basis. To evaluate this concept, three tumor models were examined using a murine colon carcinoma cell line and syngeneic BALB/c mice. First, mice with preestablished splenic CT26.CL25 tumors and liver metastases were given Adsflt on AdNull intravenously and, after 15 days, spleens and livers were harvested to quantify tumor burden. Adslft-treated animals had minimal residual splenic tumors and liver metastases; in contrast, control animals had bulky splenic tumors and extensive liver metastases (p < 0.003). Second, mice with preestablished lung metastases showed a significant reduction in pulmonary metastases with regionally administered Adslft (intratracheal, p < 0.02) but not when the vector was systemically administered (intravenous, p > 0.9). Finally, mice with primary subcutaneous tumors treated with intratumoral administration of Adslft showed significant tumor suppression (p < 0.05) not observed in AdNull-treated mice or mice given Adslft intravenously (p > 0.3). We conclude that Ad-mediated in vivo regional delivery of a secreted form of the extracellular domain of the flt-1 VEGF receptor can effectively inhibit regional tumor growth, a strategy that may provide a means to control tumor growth within the treated organ without the risk of systemic antiangiogenesis.

Adenoviridae↗
PubMed1998

Monophosphoryl lipid A reduces both arrhythmia severity and infarct size in a rat model of ischaemia.

A non-toxic derivative of the active lipid A component of the endotoxin molecule (monophosphoryl lipid A) when given to rats in a dose of 5 mg kg(-1) by intraperitoneal injection 24 h prior to anaesthesia and coronary artery occlusion, markedly decreased the severity of ischaemia-reduced ventricular arrhythmias (ventricular fibrillation reduced from 60 to 21%; P < 0.05) and reduced myocardial infarct size (from 35.8 +/- 1.6% of the area at risk to 22.7 +/- 2.0%; P < 0.05). It did not modify blood pressure or heart rate either before or during the period of ischaemia.

Adjuvants, Immunologic↗
PubMed1997

Dendritic cells genetically modified with an adenovirus vector encoding the cDNA for a model antigen induce protective and therapeutic antitumor immunity.

Dendritic cells (DCs) are potent antigen-presenting cells that play a critical role in the initiation of antitumor immune responses. In this study, we show that genetic modifications of a murine epidermis-derived DC line and primary bone marrow-derived DCs to express a model antigen beta-galactosidase (betagal) can be achieved through the use of a replication-deficient, recombinant adenovirus vector, and that the modified DCs are capable of eliciting antigen-specific, MHC-restricted CTL responses. Importantly, using a murine metastatic lung tumor model with syngeneic colon carcinoma cells expressing betagal, we show that immunization of mice with the genetically modified DC line or bone marrow DCs confers potent protection against a lethal tumor challenge, as well as suppression of preestablished tumors, resulting in a significant survival advantage. We conclude that genetic modification of DCs to express antigens that are also expressed in tumors can lead to antigen-specific, antitumor killer cells, with a concomitant resistance to tumor challenge and a decrease in the size of existing tumors.

Adenocarcinoma↗
PubMed1997

Gp60 activation mediates albumin transcytosis in endothelial cells by tyrosine kinase-dependent pathway.

We investigated the function of gp60, an endothelial cell membrane 60-kDa albumin-binding protein localized in caveolae, and the mechanism of its activation in regulating endothelial permeability of albumin. Gp60 organization on the bovine pulmonary microvessel endothelial cell (BPMVEC) surface was punctate as shown by immunofluorescence using an anti-gp60 antibody (Ab) conjugated with bisfunctional, N-hydroxysuccinimidyl fluorophore (Cy3). Addition of a secondary Ab to anti-gp60 Ab-treated BPMVEC induced cross-linking of gp60 as evident by increased size of fluorescent particles and cell surface gp60 clustering. Gp60 cross-linking also produced 2-3-fold increases in the endothelial cell uptake and the luminal to abluminal permeability of 125I-albumin as well as the fluid-phase tracer, horseradish peroxidase. The increased transendothelial permeability of macromolecules was the result of transcytosis as it was not associated with an increase in the paracellular pathway. Incubation of anti-gp60 Ab with BPMVEC at 37 degrees C caused internalization of gp60, and thereby reduced the uptake of the macromolecules. Activation of gp60 by either albumin (the gp60 ligand) or gp60 cross-linking induced the phosphorylation of both gp60 and caveolin-1 (the major structural caveolar protein) on tyrosine residues. Gp60 activation also phosphorylated the Src family tyrosine kinases pp60(c-Src) and Fyn. The activated pp60(c-Src) and Fyn co-immunoprecipitated with caveolin-1 in BPMVEC membrane. Protein tyrosine kinase (PTK) inhibitors, herbimycin A and genistein, prevented gp60-activated macromolecule uptake and transcytosis in a concentration-dependent manner, indicating the functional significance of the PTK pathway in activating albumin transcytosis. These findings indicate that activation of gp60 stimulates the Src PTK signaling pathway, and thus regulates the transcytosis of albumin across the endothelial cell monolayer.

Animals↗
PubMed1997

Cytotoxic T lymphocyte responses to proteins encoded by heterologous transgenes transferred in vivo by adenoviral vectors.

Although replication-deficient adenovirus (Ad) vectors are efficient vehicles for in vivo gene transfer, persistence of expression of the Ad genome is limited in immunocompetent hosts by cellular immunity directed against the gene product of the vector. While most attention has been focused on cytotoxic T lymphocytes (CTL) directed against the low-level early and late Ad gene expression in the Ad vector-infected target cells, significant cellular immunity is likely also directed against the product of heterologous transgenes. To evaluate this concept, in vivo generation of CTL was evaluated in C57B1/6 and BALB/c mice with Ad vectors expressing a variety of heterologous transgenes, including Escherichia coli chloramphenicol acetyl transferase (CAT), beta-galactosidase (beta-Gal), cytosine deaminase, and human thrombopoietin (hTPO), with an Ad vector expressing no transgene ("null") as a control. Following intravenous administration of Ad vectors, spleen cells were harvested 2 weeks later, stimulated for 5 days with syngeneic cells infected with various Ad vectors, and then evaluated for CTL activity using 51Cr-release from syngeneic Ad vector-infected targets. In all cases, CTL directed against the heterologous transgene products was observed, although there were differences in the amounts of transgene-specific CTL. CTL directed against the transgene were also observed with other routes of administration, including intratracheal, subcutaneous, and intraperitoneal administration. These observations suggest that inclusion of a heterologous transgene in Ad vectors enhances the elimination of vector-infected cells, a circumstance that will be partially circumvented using autologous genes. For some applications, specific immune responses to products of transgenes delivered by Ad vectors might be exploited for therapeutic purposes.

Adenoviridae↗
PubMed1997

Melatonin alters the metabolism of the beta-amyloid precursor protein in the neuroendocrine cell line PC12.

The deposition of amyloid plaques in brain parenchyma is one of the major pathological hallmarks of Alzheimer's disease (AD). The amyloid in senile plaques is composed of the amyloid beta-peptide (A beta) of 39-43 amino acid residues derived from a larger beta-amyloid precursor protein (beta APP). Soluble derivatives of beta APP (sAPP) lacking the cytoplasmic tail, transmembrane domain, and a small portion of the extracellular domain are generated proteolytically by "secretases." Using cell cultures, the authors analyzed the level of sAPP in neuroblastoma and pheochromocytoma (PC12) cells by immunoblotting samples from conditioned media and cell lysates. Normal levels of secretion of sAPP into conditioned media were severely inhibited by treating cells with melatonin (3-4 mM). The inhibitory effect of melatonin on the secretion of sAPP can be reversed. When the cells that were pretreated with melatonin for 10 h were washed, the normal level of secretion of sAPP was restored. Northern blot analyses indicated that the treatment of PC12 cells with melatonin resulted in a significant decrease in the level of mRNA encoding beta APP, beta-actin, and glyceraldehyde-3-phosphate dehydrogenase, and that the treatment of a human neuroblastoma cell line with melatonin resulted in no change in levels of these messages. The secretion of sAPP into the conditioned medium was substantially reduced in the differentiated cells similar to reductions observed in melatonin-treated undifferentiated PC12 cells. Melatonin was found to potentiate the nerve growth factor-mediated differentiation in PC12 cells at 24 h. Taken together, these data suggest that melatonin regulates the metabolism of beta APP and other housekeeping genes in a cell-type specific manner, and that melatonin accelerates the early process of neuronal differentiation.

Amyloid beta-Protein Precursor↗
PubMed1997

Wortmannin, a phosphatidylinositol 3-kinase inhibitor, blocks the assembly of peptide-MHC class II complexes.

Peptide-class II complexes are assembled in endocytic, lysosome-like compartments where newly synthesized class II molecules are targeted from the trans-Golgi network (TGN). Recent studies have implicated phosphatidylinositol 3-kinase (PI3-kinase) as an essential component in membrane trafficking from the TGN to lysosomes. Here, using subcellular fractionation, we show PI3-kinase activity associated with subcellular fractions which contain the class II peptide-loading compartment (IIPLC) in B cells. At concentrations required for inhibition of PI3-kinase activity in vivo, wortmannin blocked the processing and presentation of antigen by B cells to T cells. Treatment of B cells with wortmannin significantly limited the proteolytic degradation of invariant chain and the formation of peptide-class II complexes. Subcellular fractionation coupled with pulse-chase analyses showed that invariant chain and class II molecules trafficked to the IIPLC in wortmannin-treated cells. However, wortmannin prevented the maturation and correct targeting to the IIPLC of cathepsin D, a protease necessary for the degradation of invariant chain and assembly of processed antigen-class II complexes. These results suggest that li-class II complexes traffic to the IIPLC via a pathway that is relatively insensitive to wortmannin, but suggest a role for PI3-kinases in the trafficking of other components necessary for the assembly of processed antigen class II complexes to the IIPLC.

Androstadienes↗
PubMed1997

Antisense expression of the peptide transport gene AtPTR2-B delays flowering and arrests seed development in transgenic Arabidopsis plants.

Previously, we identified a peptide transport gene, AtPTR2-B, from Arabidopsis thaliana that was constitutively expressed in all plant organs, suggesting an important physiological role in plant growth and development. To evaluate the function of this transporter, transgenic Arabidopsis plants were constructed expressing antisense or sense AtPTR2-B. Genomic Southern analysis indicated that four independent antisense and three independent sense AtPTR2-B transgenic lines were obtained, which was confirmed by analysis of the segregation of the kanamycin resistance gene carried on the T-DNA. RNA blot data showed that the endogenous AtPTR2-B mRNA levels were significantly reduced in transgenic leaves and flowers, but not in transgenic roots. Consistent with this reduction in endogenous AtPTR2-B mRNA levels, all four antisense lines and one sense line exhibited significant phenotypic changes, including late flowering and arrested seed development. These phenotypic changes could be explained by a defect in nitrogen nutrition due to the reduced peptide transport activity conferred by AtPTR2-B. These results suggest that AtPTR2-B may play a general role in plant nutrition. The AtPTR2-B gene was mapped to chromosome 2, which is closely linked to the restriction fragment length polymorphism marker m246.

Agrobacterium tumefaciens↗
PubMed1996

Nucleotide homologies in genes encoding members of the S100 protein family.

Members of the S100 protein family exhibit a unique pattern of cell/tissue-specific expression and approx. 50% similarity at the amino-acid level. The cDNAs encoding many of these proteins from a variety of species are now available making a comparison of these family members at the nucleotide level possible. With few exceptions, family members exhibited less nucleotide identity than amino-acid similarity. Furthermore, the pattern of divergence calculated on the basis of nucleotide identity did not always agree with that calculated on the basis of amino-acid similarity. The majority of sequence diversity occurred in the nontranslated regions suggesting that these regions may be involved in directing the expression of particular members of the family to specific cell types. When comparisons of individual family members were made across species, the following order of species diversity was observed: rat/mouse < human/bovine < porcine < rabbit/avian < Xenopus laevis. The structure of the gene loci encoding these proteins was remarkably conserved both within family members of a given species as well as in individual family members from different species. Although there appears to be great diversity in the 5' flanking regions of these genes, members of the family share at least one common potential regulatory element-the S100 protein element. Thus, membership in the S100 family could be ascertained on the basis of gene organization and the presence of an SPE. Although functional data are limited, the available data indicate that the regulation of the expression of S100 family members is complex and involves both positive and negative regulatory elements. Additional nucleic acid sequences and complimentary functional studies will be required to dissect the mechanisms which target the expression of the members of this family to specific cell types during development.

Animals↗
PubMed1996

Expression of the rat S100A1 gene in neurons, glia, and skeletal muscle.

Using a rat S100A1 cDNA probe, S100A1 expression has been documented in rat C6 glioma cells, a cell line previously thought to express only the S100B protein. To identify the molecular mechanisms which target S100A1 gene expression to specific cell types, the rat S100A1 gene was cloned, and functional analysis of the 5' flanking region of the gene was performed. The rat S100A1 gene was located in an 8.5 kb BamHI genomic fragment which contained 3 exons plus 1.6 kb of 5'-upstream and 0.37 kb of 3'-downstream flanking sequence. A single transcription initiation start site and a single polyadenylation signal were identified in this gene. A number of potential regulatory consensus sequences were identified in the rat S100A1 gene including general transcription factor binding sequences (TATA box, GC box and CCAAT box), cAMP regulated sequences (CRE), skeletal muscle specific sequences (E-box and M-CAT), an S100 protein element, and a (GCT) trinucleotide repeat. Analysis of an S100A1 promoter-CAT construct by ribonuclease protection assay demonstrated that this gene is functional in three S100A1 expressing cell lines, C6 cells, PC12 cells and L6 cells. CAT constructs containing progressive deletions of the S100A1 promoter region revealed a positive regulatory element in skeletal muscle (L6) cells between -1600/-1081. The fact that these same sequences were negative in glial (C6) cells and neutral in neuronal (PC12) cells suggests that this region plays a major role in targeting S100A1 expression to specific cell types. The -1081/+10 region contained both positive and negative elements, some of which were cell-type specific. Thus, S100A1 expression is under complex transcriptional control which involves positive and negative elements as well as cell type specific elements.

Animals↗