Search PubMed⌕ Search

Biomedical subjects

X Fang

Publications and source records attributed to X Fang.

At least 127 records · Page 7Linked to original sources
PubMed1998

Recent developments in capillary isoelectric focusing with whole-column imaging detection.

Capillary isoelectric focusing (CIEF) is a high resolution technique for protein separation. The on-column single point detector requires a mobilization step which lengthens the analysis time and causes an uneven resolution along the separation column. The real time and whole column imaging detection has been developed for performing CIEF without mobilization. Three types of imaging detection systems have been developed: optical absorption, refractive index gradient, and laser induced fluorescence. This technique provides a fast analysis speed (about 6 min) and a good resolution of 0.03 pH unit level. Using the absorption imaging detector, ampholyte-free IEF in tapered capillary is being demonstrated, which eliminates the interference of the expensive carrier ampholytes for protein detection in UV region. Recent advancements in this imaged CIEF technique as well as its applications are reviewed.

Electrophoresis, Capillary↗
PubMed1998

Role of carboxy-extended forms of oxytocin in the rat uterus in the process of parturition.

The hypothalamic synthetic pathway of oxytocin (OT) involves the synthesis of carboxy-extended forms that serve as intermediate prohormones. We hypothesized that extended forms of OT are synthesized in the late-gestational rat uterus and that they compete for OT receptor binding. Parturition occurs only when the ratio of OT to its extended forms reaches a critical level. We have measured OT and its extended forms using two antisera, one recognizing OT and its extended forms, the other recognizing only mature amidated OT. Uterine tissue concentrations of extended forms of OT were 5- to 30-fold greater than those of OT, and both increased progressively and significantly through late gestation. The ratio of OT to its extended forms did not change significantly. Antagonists of estrogen or progesterone receptors reduced concentrations of extended forms by > 90% and of OT by 50%, though the estrogen antagonist significantly prolonged gestation and the progesterone antagonist induced preterm delivery. Using a muscle bath preparation, extended forms of OT were weak uterine stimulants and did not alter the OT concentration-response curves. Extended forms of OT were two to three orders of magnitude less able than OT to displace radiolabeled OT from late-gestational uterine binding sites. We conclude that uterine carboxy-extended OT prohormones are regulated in part by estrogen and progesterone. However, these extended forms of OT have little direct biological activity and do not compete with OT for receptor binding. Their role in the process of parturition may be confined to acting as substrates for OT synthesis.

Animals↗
PubMed1998

14,15-Epoxyeicosatrienoic acid inhibits prostaglandin E2 production in vascular smooth muscle cells.

14,15-Epoxyeicosatrienoic acid (EET), a cytochrome P-450 epoxygenase product of arachidonic acid (AA), reduced PGE2 formation by 40-75% in porcine aortic and murine brain microvascular smooth muscle cells. The inhibition was reversed 6-10 h after removal of 14,15-EET from the medium and was regioisomeric specific; 8,9-EET produced a smaller effect, whereas 11,12- and 5,6-EET were ineffective. Although the cells converted 14,15-EET to 14, 15-dihydroxyeicosatrienoic acid (14,15-DHET), 14,15-DHET did not inhibit PGE2 formation, and the 14,15-EET-induced inhibition was potentiated by 4-phenylchalcone oxide, an epoxide hydrolase inhibitor. The inhibition occurred when substrate amounts of AA were used and was not accompanied by enhanced production of other PGs, suggesting an effect on PGH synthase; however, in murine cells, 14, 15-EET did not reduce PGH synthase mRNA or protein. Moreover, the 14, 15-EET-induced decrease in PGE2 production was overcome by increasing the concentration of AA, but not oleic acid (which is not a substrate for PGH synthase). These findings suggest that 14,15-EET competitively inhibits PGH synthase activity in vascular smooth muscle cells. The 14,15-EET-induced inhibition of PGE2 production resulted in potentiation of platelet-derived growth factor-induced smooth muscle cell proliferation, suggesting that the competitive inhibition of PGH synthase by 14,15-EET can affect growth responses in smooth muscle cells.

8,11,14-Eicosatrienoic Acid↗
PubMed1998

Oxytocin: a paracrine hormone in the regulation of parturition?

The role of oxytocin in parturition is controversial. When considered as an endocrine hormone, the balance of evidence suggests that oxytocin has little involvement in the initiation of labour. However, recent research has demonstrated synthesis of mRNA encoding oxytocin within the pregnant human uterus. This article reviews the hypothesis that oxytocin is an important paracrine (or autocrine) hormone with respect to the control of myometrial contractility in late gestation. Experimental data are provided from humans when possible and from studies using the rat as an experimental model. The processing of oxytocin prohormones in uterine tissues is reviewed and the presence and possible role of carboxy-extended forms of oxytocin in late gestational tissues of rats are discussed. The regulation of oxytocin and its receptor, particularly by oestrogen and progesterone, is reviewed. The inter-relationship between oxytocin and prostaglandins is discussed. Finally, the metabolism of oxytocin within intrauterine tissues and the recent development of specific antagonistic analogues to oxytocin are considered. It is concluded that further clarification of this paracrine system within intrauterine tissues during late gestation could lead to more successful strategies for preventing or arresting preterm labour in women.

Animals↗
PubMed1998

[Inhibitory activity of azithromycin on biofilm synthesis and synergism between azithromycin and fleroxacin on Pseudomonas aeruginosa in biofilms].

OBJECTIVE: The influence of azithromycin (AZT) on the production of glycocalyx (GLX) from P. aeruginosa biofilms and synergism of antibacterial activities between AZT and fleroxacin (FLX) on P. aeruginosa were investigated. METHOD: GLX production was measured by using a L-tryptophan method and viable counts in biofilms was determined by using a methylthiazolyldiphenyltetrazolium(MTT) method. RESULT: GLX production was reduced significantly from 28.0 +/- 8.1 micrograms/ml at 0MIC to 21.8 +/- 8.2 micrograms/ml at 1/16MIC and 16.7 +/- 7.9 micrograms/ml at 1/4MIC respectively (P = 0.0002). 1/16MIC and 1/4MIC AZT showed no bactericidal activities to P. Aeruginosa in biofilms. Viable counts in biofilms were 6.2 +/- 0.61 Lg/cm2 at 0MIC, 6.1 +/- 0.4 Lg/cm2 at 1/16MIC and 6.2 +/- 0.4 Lg CFU/cm2 at 1/4 MIC respectively (P = 0.63). However, AZT could enhance bactericidal activity of FLX on P. aeruginosa in biofilms. When 1/4MIC FLX was combined with 1/16MIC and 1/4 MIC AZT, viable counts were reduced significantly from 6.1 +/- 0.5 Lg CFU/cm2 to 5.9 +/- 0.3 Lg CFU/cm2 and 5.8 +/- 0.4 Lg CFU/cm2 respectively (P = 0.02). When 1/2MIC FLX was combined with 1/16MIC and 1/4MICAZT, viable counts were reduced significantly from 6.3 +/- 0.7 Lg CFU/cm2 to 5.8 +/- 0.5 LgCFU/cm2 and 5.7 +/- 0.6 Lg CFU/cm2 respectively (P = 0.03). CONCLUSION: Because AZT did not have direct bactericidal activities on P. aeruginosa in biofilms but could inhibit GLX production, We considered that AZT could enhance antibacterial activities of FLX by enhancing permeability of FLX into biofilms.

Anti-Bacterial Agents↗
PubMed1998

[A survey of the social and psychological factors of the heroin dependence].

The survey studied 100 dependence about their age, marriage, occupation, the way of heroin taking, history of heroin taking, and the reason of the first heroin taking. The data showed that most dependence were young or middle aged men, or people unable to graduate from junior middle school, self-employed laborers and unemployed. Dependence of cadres and people with better education were increasing. The heroin injection is becoming popular.

Adult↗
PubMed1998

[Synthesis and application of novel acrylic resin as enteric coating].

The pH sensitive two- and three-component acrylic resins were synthesized by radical solution copolymerization of methyl methacrylate (MMA), methacrylic acid (MAA) and/or butyl acrylate (BA) and their acid values were measured by acid-base titration. The dissolution of naproxen pellets coated with the synthesized resins in dissolution medium of different pH value was studied. The results show that the acrylic resin with different acid value can be prepared by adjusting the monomer ratios (MMA:MAA or MMA:MAA:BA). The smaller the acid value of the resin is, the higher pH sensitive value it has. The release of naproxen from pellets coated with these resins is greatly influenced by the pH value of the dissolution medium and the pH sensitive value of the coating resin. The three-component resins are plastic and can be used as coating material without adding plastisizers.

Acrylic Resins↗
PubMed1998

Oltipraz chemoprevention trial in Qidong, People's Republic of China: modulation of serum aflatoxin albumin adduct biomarkers.

In 1995, 234 adults from Qidong, People's Republic of China, were enrolled and followed in a Phase IIa 4-methyl-5-(N-2-pyrazinyl)-1,2-dithiole-3-thione (oltipraz) chemoprevention trial. Residents of this area are at high risk for development of hepatocellular carcinoma, in part due to consumption of aflatoxin-contaminated foods. The intervention was a randomized, placebo-controlled, double-blind study. Elements of the study design and clinical outcomes have been recently published (Jacobson et al, Cancer Epidemiol. Biomark. Prev., 6: 257-265, 1997). The primary objective was to conduct a preliminary assessment of the ability of oltipraz to modulate levels of a validated biomarker of aflatoxin exposure and of the risk of hepatocellular carcinoma by determining levels of aflatoxin-albumin adducts in sera. Healthy eligible individuals were randomized into three arms to receive p.o. 125 mg of oltipraz daily, 500 mg of oltipraz weekly, or placebo for 8 weeks. There were no consistent changes in biomarker levels in the placebo arm over the 16-week observation period, nor was any apparent effect observed in the arm receiving 125 mg of oltipraz each day. However, individuals receiving 500 mg of oltipraz once a week for 8 weeks showed a triphasic response to oltipraz. No effect was observed during the 1st month of the intervention, whereas a significant (P = 0.001) diminution in adduct levels was observed during the 2nd month of active intervention and during the lst month of follow-up. A partial rebound in adduct levels toward baseline values was observed during the 2nd month postintervention. Linear regression models up to week 13 confirmed a significant (P = 0.008) weekly decline of biomarker levels in the group receiving 500 mg of oltipraz once a week. However, despite these effects relative to baseline values within the 500-mg weekly arm, there were no statistically significant differences in biomarker trajectories between treatment arms. The genotype for glutathione S-transferase M1, an oltipraz-inducible isoform involved in the detoxification of aflatoxin B1, did not appear to affect either baseline levels or rates of decline in the biomarker. A follow-up Phase IIb trial with a longer intervention period will be necessary to determine the full extent to which aflatoxin biomarker burden can be reduced and whether diminution of biomarkers can be sustained over the long term.

Adult↗
PubMed1997

Stoichiometry of 7-ethoxycoumarin metabolism by cytochrome P450 2B1 wild-type and five active-site mutants.

Recombinant P450 2B1 wild-type and the active-site mutants I114V, F206L, V363A, V363L, and G478S were purified and studied. The efficiency of coupling of reducing equivalents to 7-hydroxycoumarin formation was decreased for all the mutants except I114V. Uncoupling to H2O was increased for F206L, V363A, and G478S, decreased for V363L, and unchanged for I114V. Uncoupling to H2O2 was increased for V363L and decreased for I114V, F206L, and V363A. The findings from this study provide firm biochemical evidence that residues 206, 363, and 478 comprise part of the substrate binding site of P450 2B1.

Binding Sites↗
PubMed1997

7-spirobenzocyclohexyl derivatives of naltrexone, oxymorphone, and hydromorphone as selective opioid receptor ligands.

On the basis of previous structure-activity studies of the highly potent and selective delta-opioid receptor antagonist naltrindole (1) and the spiroindanyl analogues 2 and 3, we have synthesized epimeric pairs of spirobenzocyclohexyl derivatives of naltrexone, oxymorphone, and hydromorphone (4-9). Pharmacologic evaluation in smooth muscle assays has revealed that the oxymorphone derivatives (6, 7) are delta-selective agonists and possess receptor binding profiles that are consistent with their agonist activity. It is proposed that the spirobenzocyclohexyl group of 6 and 7 orients its benzene moiety orthogonally with respect to the C ring of the opiate in a manner similar to that of the spiroindanyl analogue 3. It is suggested that this orthogonal orientation serves as an "address" to facilitate activation of delta receptors. The finding that the hydromorphone analogues (8, 9) were full mu agonists and exhibited only partial delta agonist activity suggests that the 14-hydroxyl group also contributes to the delta agonist activity. The naltrexone derivatives (4, 5) were mu-selective antagonists and exhibited relatively weak delta antagonist activity. However, the binding data indicated a very high-affinity delta-selective binding profile that was not consistent with the pharmacology. This study illustrates the differential contributions of the delta "address" to agonist and antagonist activity and supports the idea of different recognition sites for interaction of agonist and antagonist ligands with delta-opioid receptors.

Animals↗
PubMed1997

Lysophosphatidylcholine stimulates activator protein 1 and the c-Jun N-terminal kinase activity.

Lysophosphatidylcholine (lyso-PC), a natural lipid generated through the action of phospholipase A2 on membrane phosphatidylcholine, has been implicated in atherogenesis and the inflammatory process. In vitro studies have established a role for lyso-PC in modulation of gene expression and other cellular responses including differentiation and proliferation. There is also evidence that lyso-PC may act as an intracellular second messenger transducing signals elicited from membrane-associated receptors. The mechanisms behind the diverse activities of lyso-PC are poorly understood. We report, in this study, that treatment of cultured cells with exogenous lyso-PC, at nontoxic concentrations, potently induced activator protein-1 (AP-1) DNA binding and transcriptional activity independent of well known AP-1 activators, protein kinase C or mitogen-activated protein kinases ERK1 and ERK2. Lyso-PC also activated the c-Jun N-terminal kinase (JNK/SAPK), a recently characterized member of the mitogen-activated protein kinase family, known to activate AP-1. The stimulated JNK and AP-1 activities probably mediate or contribute to some bioactive effects of lyso-PC.

Animals↗
PubMed1997

Evolution of risk behaviors over 2 years among a cohort of urban African American adolescents.

OBJECTIVE: To examine the evolution of risk behaviors over 2 years among a community-based cohort of low-income African American preadolescents and young adolescents enrolled in a randomized trial of an acquired immunodeficiency syndrome risk reduction intervention. DESIGN: Longitudinal, community-based cohort. SETTING: Nine recreation centers serving 3 public housing developments. SUBJECTS: Three hundred eighty-three African American youths aged 9 through 15 years at baseline. INTERVENTIONS: Frequency distributions, chi 2 analyses, and regression analyses regarding 10 risk behaviors were conducted. To assess whether a specific risk behavior or its protective (nonrisk) behavioral analogue, composing a risk-nonrisk behavioral complex (eg, was sexually active and was sexually abstinent or used drugs and refrained from drugs), was stable over time, kappa values were determined for the 10 risk-nonrisk behavioral complexes. MAIN OUTCOME MEASURES: Instrument assessing risk/ behaviors administered at baseline and every 6 months aurally and visually via talking computer. RESULTS: The prevalence of sexual intercourse, cigarette smoking, alcohol consumption, and drug use increased notably over time. Drug use increased from a 6-month cumulative prevalence of 7% at baseline to 27% at the 24-month follow-up (P < .001). Cumulatively over the 2-year study interval, 81% of youths had engaged in fighting, 58% had engaged in sexual intercourse, and from 33% to 40% had engaged in truancy, knife or bat carrying or both, alcohol consumption, drug use, and cigarette smoking. All of the risk-nonrisk behavioral complexes except weapon carrying were stable during the semiannual assessment intervals. Fighting (kappa = 0.22, P < .01), sexual intercourse (kappa = 0.33, P < .001), alcohol consumption (kappa = 0.21, P < .001), and unprotected sexual intercourse (kappa = 0.34, P < .05) were stable for 2 years. Six risk-nonrisk behavioral complexes were stable for the 2-year interval among youths aged 13 through 15 years at baseline, while only 2 risk-nonrisk behavioral complexes were stable among younger youths. The intervention seemed to affect the stability of 4 risk behaviors: truancy, drug use, unprotected sexual intercourse, and, possibly, fighting. For unprotected sexual intercourse, this intervention effect seemed to be due to stabilization of nonparticipation in risky behavior. Intervention youths were less likely to adopt a risk behavior (ie, engage in it for > or = 2 risk assessment periods) than control youths, but they were not less likely to experiment with a risk behavior. CONCLUSIONS: There is evidence that although the prevalence of risk behaviors does change with age, most risk-nonrisk behavioral complexes seem to be relatively stable over time and stability may increase with time. Risk reduction interventions seem to decrease risk adoption, stabilize nonrisk behaviors, and possibly destabilize risk behavior.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Cytochrome P450 metabolites of arachidonic acid: rapid incorporation and hydration of 14,15-epoxyeicosatrienoic acid in arterial smooth muscle cells.

Arachidonic acid is converted to epoxyeicosatrienoic acids (EETs) by cytochrome P450 monooxygenases. EETs produce arterial vasodilatation, and recent evidence suggests that they are endothelium-derived hyperpolarizing factors. In porcine coronary arteries contracted with a thromboxane mimetic agent, we find that relaxation is rapidly initiated by exposure to 14,15-EET. The relaxation slowly increases in magnitude, resulting in a response which is sustained for more than 10 min. Cultured porcine aortic smooth muscle cells rapidly take up [3H]14,15-EET. After 3 min, radioactivity is present in neutral lipids, phosphatidylcholine, and phosphatidylinositol. The cells also convert 14,15-EET to 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), and some DHET is detected in the medium after only 1 min of incubation. Like 14,15-EET, 14,15-DHET produces relaxation of the contracted coronary artery rings. These findings suggest that the incorporation into phospholipids and conversion to 14,15-DHET can occur at a rate that is fast enough to modulate the vasorelaxation produced by 14,15-EET.

8,11,14-Eicosatrienoic Acid↗
PubMed1997

Cross-cultural consensus in personality judgments.

Building on recent research demonstrating consensus and accuracy in interpersonal perception based on minimal information, the present studies examined American and Chinese participants' within- and cross-cultural judgments. In Study 1, the authors used the zero-acquaintance paradigm in the People's Republic of China and found consensus on all personality dimensions. In Study 2, Chinese and American participants judged each other on the basis of photographs, and consensus was found among Americans' judgments of Chinese and Chinese participants' judgments of Americans. Further, by correlating target effects based on within-culture zero-acquaintance judgments and cross-cultural photographic judgments, the authors found agreement in the judgments of individuals by members of their own culture and the other culture for both Chinese and Americans.

China↗
PubMed1997

Metabolism of oxytocin in rat uterus and placenta in late gestation.

Concentrations of oxytocin (OT) peptide increase in rat uterine tissues at the time of parturition. We have measured the rate of OT metabolism in these tissues in late gestation to determine whether a decrease in OT catabolism is responsible for the increase in OT concentrations. Uterine and placental tissues were obtained from groups of rats at Days 16, 19, 21, 21.5, 22, and after delivery of the first pup. Delivery usually occurs in the early afternoon of Day 22. Some animals were treated with the estrogen receptor blocker tamoxifen, which will delay parturition by approximately 24 h. Cytosolic and microsomal preparations obtained using ultracentrifugation were incubated with radiolabeled OT. Metabolites were separated using HPLC, and enzyme kinetic parameters were calculated. OT was actively metabolized in both uterine and placental tissues. Total oxytocinase activity was similar in the two tissues. In uterine tissues, activity was greater in the cytosolic fractions. In placenta, activity was evenly distributed between the cytosolic and microsomal fractions. The cytosolic fractions of each tissue contained predominantly post-proline endopeptidase activity, whereas the microsomes contained predominantly aminopeptidase activity. There was a slight trend to decreasing oxytocinase activity with advancing gestation in both subcellular fractions, but this was statistically significant only in the microsomal fraction. The maximal decline in activity was only 25-50%. Tamoxifen treatment had no effect on oxytocinase activity. We conclude that rat uterine and placental tissues contain post-proline endopeptidase and aminopeptidase activities that metabolize OT. It is doubtful that changes in these activities are major factors in regulating the increase in OT concentrations measured in rat intrauterine tissues at the time of parturition.

Aminopeptidases↗
PubMed1997

Synthetic-peptide-based enzyme-linked immunosorbent assay for screening human serum or plasma for antibodies to human immunodeficiency virus type 1 and type 2.

A synthetic-peptide-based enzyme-linked immunosorbent assay (EIA) capable of screening for antibodies to both human immunodeficiency virus type 1 (HIV-1) and HIV-2 has been developed for use in blood banks and diagnostic laboratories. Microtiter wells are coated with two synthetic peptides, one corresponding to the highly conserved envelope region of HIV-1 and another corresponding to the conserved envelope region of HIV-2. Overall, sensitivity was 100% in 303 individuals diagnosed with AIDS and 96 individuals diagnosed with AIDS-related complex, 14.8% in a study of 500 high-risk group members, 99.9% in 600 EIA repeatedly reactive (RR)-HIV-1 Western blot (WB)-positive repository specimens, and 100% for 222 geographically diverse HIV-1 specimens and 216 confirmed HIV-2-positive specimens evaluated. The specificity was determined to be 99.72% for a total of 13,004 serum and plasma samples from random volunteer donors evaluated across five blood banks. Forty donors who were found to be EIA RR-WB indeterminate but nonreactive on the United Biomedical, Inc., test (UBI HIV 1/2 EIA) were prospectively followed as an additional measure of specificity. None of the 40 low-risk cases evolved into a positive WB pattern at follow-up. The sensitivity and specificity of this new assay are comparable to those of other Food and Drug Administration-licensed HIV-1 and HIV-1-HIV-2 assays that are currently available in the United States. The UBI HIV 1/2 EIA affords laboratories another choice in the detection of antibodies for HIV-1 and HIV-2 with a test based on an alternative antigen format.

AIDS Serodiagnosis↗