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Biomedical subjects

W Song

Publications and source records attributed to W Song.

At least 109 records · Page 6Linked to original sources
PubMed1999

[A clinical study on solute removal index as an index to quantitate the adequacy of hemodialysis].

OBJECTIVE: In order to find a proper hemodialysis dosage and improve the life quality of the patients undergoing hemodialysis. METHODS: A clinical study of solute removal index (SRI) was performed in 20 stable maintenance hemodialysis patients. Plasma BUN level was tested before and at the end of hemodialysis as well as 1 hr post-hemodialysis. Urea regeneration rate (G), protein catabolic rate (PCR), solute removal amount (R) and SRI were calculated by double-pool urea kinetic model. RESULTS: It is shown that urea rebound rate was (18.50 +/- 3.35)% 1 hr post-hemodialysis, R was (13.82 +/- 5.48)g, G was (4.85 +/- 1.39)g, PCR was (0.94 +/- 0.29)g x kg(-1) x d(-1), SRI was (71.33 +/- 6.80)% respectively. CONCLUSION: The results indicated that SRI is a better index to quantitate the adequacy of hemodialysis.

Adolescent↗
PubMed1998

Identification of amino acid substitutions that confer a high affinity for sulfaphenazole binding and a high catalytic efficiency for warfarin metabolism to P450 2C19.

Human cytochrome P450s 2C9 and 2C19 metabolize many important drugs including tolbutamide, phenytoin, and (S)-warfarin. Although they differ at only 43 of 490 amino acids, sulfaphenazole (SFZ) is a potent and selective inhibitor of P450 2C9 with an IC50 and a spectrally determined binding constant, KS, of <1 microM. P450 2C19 is not affected by SFZ at concentrations up to 100 microM. A panel of CYP2C9/2C19 chimeric proteins was constructed in order to identify the sequence differences that underlie this difference in SFZ binding. Replacement of amino acids 227-338 in 2C19 with the corresponding region of 2C9 resulted in high-affinity SFZ binding (KS approximately 4 microM) that was not seen when a shorter fragment of 2C9 was substituted (227-282). However, replacement of amino acids 283-338 resulted in extremely low holoenzyme expression levels in Escherichia coli, indicating protein instability. A single mutation, E241K, which homology modeling indicated would restore a favorable charge pair interaction between K241 in helix G and E288 in helix I, led to successful expression of this chimera that exhibited a KS < 10 microM for SFZ. Systematic replacement of the remaining differing amino acids revealed that two amino acid substitutions in 2C19 (N286S, I289N) confer high-affinity SFZ binding (KS < 5 microM). When combined with a third substitution, E241K, the resulting 2C19 triple mutant exhibited a high cataltyic efficiency for warfarin metabolism with the relaxed stereo- and regiospecificity of 2C19 and a lower KM for (S)-warfarin metabolism (<10 microM) typical of 2C9.

Amino Acid Sequence↗
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

Molecular cloning of the promoter of the gene encoding the Rhesus monkey beta-amyloid precursor protein: structural characterization and a comparative study with other species.

Abnormal regulation of transcription of the beta-amyloid precursor protein (betaAPP) gene is implicated in the pathogenesis of Alzheimer's disease (AD). We have examined 17- kb genomic region which contains the 5'-flanking region (promoter), first exon and on of the betaAPP gene of the Rhesus monkey (rhbetaAPP). A predominant scription start site was tified 146 bp upstream of the translation initiation codon. Sequencing 5848 bp of 5'-flanking revealed the presence of multiple near consensus sequences for binding potential transcriptional regulatory factors, such as activator proteins (AP-1, AP-2), an apolipoprotein E-B1 element, estrogen-responsive element, heat shock element and NF-kappaB. The sequence of the rhbetaAPP promoter also contains several sites for the binding of proteins that serve as signal transducers and activators of transcription (STAT1) (GAS). The rhbetaAPP promoter is highly homologous to the human promoter, but less homologous to the rodents. The homology between human and Rhesus monkey of the further upstream region gradually decreased over its length. A region of 270 bp of the human betaAPP promoter is missing from the Rhesus monkey promoter. Structural analysis of the promoter suggests that it contains characteristics of inducible genes and sites for regulated activity by various transcription factors.

Amino Acid Sequence↗
PubMed1998

Functional identification of the promoter of the gene encoding the Rhesus monkey beta-amyloid precursor protein.

Misregulation of the transcription of the beta-amyloid precursor protein (betaAPP) gene is implicated in the pathogenesis of Alzheimer's disease (AD). Here we characterize the 5'-flanking region, the first exon and intron of the betaAPP gene of the Rhesus monkey (rhbetaAPP). For functional analysis, transient transfection in PC12 cells was performed with a series of 5'-deletion constructs (fused with a reporter gene), that extended as far upstream as -7900 down to -1bp. Chloramphenicol acetyltransferase/promoter fusion assays showed that both -7900/+104 and -75/+104-bp regions possessed strong promoter activity. However, -2542/+104bp had the strongest promoter activity, whereas -204/+104bp showed a major reduction in activity and -47/+104bp showed almost a complete loss of activity. A region from -75 to +104bp was essential for minimal basic promoter activity because mutation at the activating site of an upstream stimulator factor (USF) within this region abolished the promoter activity. The very upstream region (-5529/-3416bp) displayed a negative effect on promoter activity. Two blocks of the sequence, 641bp (-1131 /-490) and 105bp (-309/-204), acted as positive regulators for promoter activity. Another 61-bp block (-204/-143) acted as a negative regulator. Gel shift assay indicated that the -249-242-bp region contains a binding domain for the AP-2 transcription factor. No second promoter or bidirectional promoter was observed. A region spanning the first exon and part of the first intron (+99 to +6800bp) acted as a negative regulator. These results suggest that a region of -75 to +104bp, which contains the pyrimidine-rich initiator element, the 5'-untranslated region and the binding site for USF, constitute the minimal promoter element and that interactions between multiple positive and negative elements, the USF and initiator element are crucial for transcription of the TATA-less betaAPP promoter.

Amyloid beta-Protein Precursor↗
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↗
PubMed1998

Adenovirus-mediated expression of melanoma antigen gp75 as immunotherapy for metastatic melanoma.

Melanocyte differentiation antigens, such as the brown locus protein gp75, are potential biological targets for immunotherapy. We investigated whether expression of the murine gp75 cDNA mediated by an adenovirus (Ad) vector could induce melanoma rejection using this model self antigen that usually induces tolerance, and whether Ad vector-directed production of interleukin-2 (IL2) might augment this response. To evaluate this approach, Ad vectors were constructed containing the murine gp75 cDNA (Ad.gp75) and the human IL2 cDNA (Ad.IL2). Efficacy was evaluated in C57BI/6 mice challenged i.v. with 10(5) B16 cells, using the number of lung metastases as the efficacy parameter. Naive control mice developed 175 +/- 12 metastases by day 14. Controls receiving intranasal Ad.IL2 1 day after B16 cell injection, intraperitoneal (i.p.) mitomycin-C-treated B16 cells +/- i.p. Ad.IL2 before B16 cell challenge and Ad.beta gal-treated mice had similar numbers of metastases as controls (P > 0.1). In marked contrast, preimmunization with intradermal Ad.gp75 provided dramatic reduction in the number of lung metastases (52 +/- 7, 29% of control). Addition of regional (intranasal delivery to the lung) Ad.IL2 to intradermal Ad.gp75 preimmunization 1 day following tumor challenge provided further protection (18 +/- 6, 10% of control). Depletion of CD4+ and CD8+ T-cell subsets effectively blocked the protective effect seen following immunization. Adoptive transfer of macrophage-depleted splenocytes from Ad.gp75-immunized mice similarly afforded significant protection against B16 tumor cell challenge. Further, serum obtained 21 days following Ad.gp75 immunization showed no detectable anti-gp75 antibody by immunoprecipitation. These results suggest that immunization with Ad.gp75 induces cellular immune responses that are capable of rejecting B16 melanoma in a host that is usually tolerant to gp75 antigen.

Adenoviridae↗
PubMed1998

Isolation of the genomic clone of the rhesus monkey beta-amyloid precursor protein.

A change in the regulation of the beta-amyloid precursor protein (beta APP) gene may be a factor for Alzheimer's disease (AD). We have screened a rhesus monkey genomic library and pulled out a approximately 17 kb genomic DNA region which contains the 5'-flanking region (promoter), first exon and intron of the beta APP gene of the Rhesus monkey (rh beta APP). We have partially characterized the genomic clone by selective restriction enzyme digestion followed by Southern blotting against the beta APP gene-specific DNA probes. The identity and authenticity of the different bands of the clone were also confirmed by Southern blot analysis of the rhesus monkey genomic DNA. Functional identification of the genomic fragment was determined by a promoter assay using the chloramphenicol acetyltransferase (CAT) enzyme as a reported gene. Our results showed that a 1.2 kb fragment from the 5'-flanking region of the rh beta APP gene possessed strong promoter activity. The isolation of this genomic clone will enable characterization of the structure and function of the promoter of the rh beta APP gene. Our initial results indicate a high degree of homology between the structure of the rhesus monkey and human beta APP promoter.

Amyloid beta-Protein Precursor↗
PubMed1998

Korean Nationwide Surveillance of Antimicrobial Resistance of bacteria in 1997.

Antimicrobial-resistant bacteria are known to be prevalent in tertiary-care hospitals in Korea. Twenty hospitals participated to this surveillance to determine the nationwide prevalence of resistance bacteria in 1997. Seven per cent and 26% of Escherichia coli and Klebsiella pneumoniae were resistant to 3rd-generation cephalosporin. Increased resistance rates, 19% of Acinetobacter baumannii to ampicillin/sulbactam, and 17% of Pseudomonas aeruginoa to imipenem, were noted. The resistance rate to fluoroquinolone rose to 24% in E. coli, 56% in A. baumannii and 42% in P. aeruginosa. Mean resistance rates were similar in all hospital groups: about 17% of P. aeruginosa to imipenem, 50% of Haemophilus influenzae to ampicillin, 70% of Staphylococcus aureus to methicillin, and 70% of pneumococci to penicillin. In conclusion, nosocomial pathogens and problem resistant organisms are prevalent in smaller hospitals too, indicating nosocomial spread is a significant cause of the increasing prevalence of resistant bacteria in Korea.

Bacterial Physiological Phenomena↗