Biomedical subjects

X Wang

Publications and source records attributed to X Wang.

At least 559 records · Page 31Linked to original sources

PubMed2001

Three-drug combinations of emivirine and nucleoside reverse transcriptase inhibitors in vitro: long-term culture of HIV-1-infected cells and breakthrough viruses.

Emivirine (EMV) is a non-nucleoside reverse transcriptase inhibitor currently undergoing Phase III clinical trials in HIV-1-infected patients. In this study, the anti-HIV-1 activity of EMV in combination with two nucleoside reverse transcriptase inhibitors was examined in cell cultures. The combinations EMV plus stavudine (d4T) plus lamivudine (3TC) and EMV plus d4T plus didanosine (ddI) synergistically inhibited HIV-1 replication in MT-4 cells. Although not statistically significant, EMV plus d4T plus 3TC appeared to be more synergistic than EMV plus d4T plus ddI. Synergism was also observed with any two-drug combinations, such as EMV plus d4T, EMV plus 3TC, EMV plus ddI, d4T plus 3TC, or d4T plus ddI. The three-drug combinations completely suppressed HIV-1 replication for at least 40 days after virus infection. Except for d4T, virus emerged in the presence of every compound alone or some combinations at lower concentrations. Susceptibility tests of the breakthrough viruses to each compound showed that the viruses obtained in the presence of EMV alone and 3TC alone were significantly less susceptible to EMV and 3TC, respectively. These viruses had specific amino acid mutations in their reverse transcriptase.

Anti-HIV Agents↗

PubMed2001

Glucagon-like peptide-1 causes pancreatic duodenal homeobox-1 protein translocation from the cytoplasm to the nucleus of pancreatic beta-cells by a cyclic adenosine monophosphate/protein kinase A-dependent mechanism.

Glucagon-like peptide-1 (GLP-1) enhances insulin secretion and synthesis. It also regulates the insulin, glucokinase, and GLUT2 genes. It mediates increases in glucose-stimulated insulin secretion by activating adenylyl cyclase and elevating free cytosolic calcium levels in the beta-cell. In addition, GLP-1 has been shown, both in vitro and in vivo, to be involved in regulation of the transcription factor, pancreatic duodenal homeobox-1 protein (PDX-1), by increasing its total protein levels, its translocation to the nucleus and its binding and resultant increase in activity of the insulin gene promoter in beta-cells of the pancreas. Here we have investigated the role of protein kinase A (PKA) in these processes in RIN 1046-38 cells. Three separate inhibitors of PKA, and a cAMP antagonist, inhibited the effects of GLP-1 on PDX-1. Furthermore, forskolin, (which stimulates adenylyl cyclase and insulin secretion), and 8-Bromo-cAMP, (an analog of cAMP which also stimulates insulin secretion), mimicked the effects of GLP-1 on PDX-1. These effects were also prevented by PKA inhibitors. Glucose-mediated increases in nuclear translocation of PDX-1 were not prevented by PKA inhibitors. Our results suggest that regulation of PDX-1 by GLP-1 occurs through activation of adenylyl cyclase and the resultant increase in intracellular cAMP, in turn, activates PKA, which ultimately leads to increases in PDX-1 protein levels and translocation of the protein to the nuclei of beta-cells.

Animals↗

PubMed2001

Characterization of signal transduction pathway in neurotropic action of angiotensin II in brain neurons.

Interaction of angiotensin II with the neuronal angiotensin type 1 receptor stimulates the PI3K signaling pathway. Our objective in this study was to investigate the hypothesis that the PI3K cascade regulates the neurotropic actions of angiotensin II in rat brain neurons. We followed growth associated protein-43 expression and neurite extension as markers of neurotropic activity. Angiotensin II, through its interaction with the angiotensin type 1 receptor, increased growth associated protein-43 expression and neurite extension. These effects were abolished by pretreatment of neurons with wortmannin and rapamycin, but not by PD 98059. Antisense oligonucleotides specific for p70(S6) kinase also inhibited angiotensin II-stimulated neurotropic activity. These data confirm the involvement of PI3K and p70(S6) kinase in angiotensin II-mediated neurotropic action. Further support for this was provided by the observation that angiotensin II caused a time-dependent stimulation of p70(S6) kinase by an angiotensin type 1 receptor-mediated process. We also found that the neurotropic actions of angiotensin II are mediated by plasminogen activator inhibitor-1. Evidence for this includes 1) angiotensin II-stimulated neuronal plasminogen activator inhibitor-1 gene expression, 2) potent neurotropic action of exogenous plasminogen activator inhibitor-1, and 3) inhibitory neurotropic effect of angiotensin II by antisense oligonucleotide-mediated depletion of plasminogen activator inhibitor-1. Finally, we found that the neurotropic action of plasminogen activator inhibitor-1 is not blocked by either angiotensin type 1 receptor antagonist or inhibitors of PI3K or p70(S6) kinase, indicating that the plasminogen activator inhibitor-1 step is downstream from the p70(S6) kinase. These observations demonstrate that angiotensin II is a neurotropic hormone that engages a distinct PI3K-p70(S6) kinase-plasminogen activator inhibitor-1 signaling pathway for this action.

Angiotensin II↗

PubMed2001

CCAAT/enhancer binding protein alpha assembles essential cooperating factors in common subnuclear domains.

The transcription factor CCAAT/enhancer binding protein alpha (C/EBP alpha) is the DNA binding subunit of a multiprotein complex that regulates the pituitary-specific GH promoter. C/EBP alpha is absent from the GHFT1-5 pituitary progenitor cell line in which ectopic C/EBP alpha expression leads to activation of the otherwise dormant GH promoter. Transcriptional regulatory complexes are commonly envisaged as assembling from components that evenly diffuse throughout the nucleoplasm. We show that C/EBP alpha, expressed in GHFT1-5 cells as a fusion with color variants of the green fluorescent protein (GFP), concentrated specifically at peri-centromeric chromosomal domains. Although we found the CREB-binding protein (CBP) to activate C/EBP alpha-dependent transcription, CBP was absent from the pericentromeric chromatin. C/EBP alpha expression was accompanied by the translocation of endogenous and ectopically expressed CBP to pericentromeric chromatin. The intranuclear recruitment of CBP required the transcriptional activation domains of C/EBP alpha. C/EBP alpha also caused GFP-tagged TATA binding protein (TBP) to relocate to the Hoechst-stained domains. The altered intranuclear distribution of critical coregulatory factors defines complexes formed upon C/EBP alpha expression. It also identifies an organizational activity, which we label "intranuclear marshalling," that may regulate gene expression by determining the cooperative and antagonistic interactions available at specific nuclear sites.

3T3 Cells↗

PubMed2001

Mesodermal patterning defect in mice lacking the Ste20 NCK interacting kinase (NIK).

We have previously shown that the Drosophila Ste20 kinase encoded by misshapen (msn) is an essential gene in Drosophila development. msn function is required to activate the Drosophila c-Jun N-terminal kinase (JNK), basket (Bsk), to promote dorsal closure of the Drosophila embryo. Later in development, msn expression is required in photoreceptors in order for their axons to project normally. A mammalian homolog of msn, the NCK-interacting kinase (NIK) (recently renamed to mitogen-activated protein kinase kinase kinase kinase 4; Map4k4), has been shown to activate JNK and to bind the SH3 domains of the SH2/SH3 adapter NCK. To determine whether NIK also plays an essential role in mammalian development, we created mice deficient in NIK by homologous recombination at the Nik gene. Nik(-/-) mice die postgastrulation between embryonic day (E) 9.5 and E10.5. The most striking phenotype in Nik(-/-) embryos is the failure of mesodermal and endodermal cells that arise from the anterior end of the primitive streak (PS) to migrate to their correct location. As a result Nik(-/- )embryos fail to develop somites or a hindgut and are truncated posteriorly. Interestingly, chimeric analysis demonstrated that NIK has a cell nonautonomous function in stimulating migration of presomitic mesodermal cells away from the PS and a second cell autonomous function in stimulating the differentiation of presomitic mesoderm into dermomyotome. These findings indicate that despite the large number of Ste20 kinases in mammalian cells, members of this family play essential nonredundant function in regulating specific signaling pathways. In addition, these studies provide evidence that the signaling pathways regulated by these kinases are diverse and not limited to the activation of JNK because mesodermal and somite development are not perturbed in JNK1-, and JNK2-deficient mice.

Animals↗

PubMed2001

Latifolosides I and J, two new triterpenoid saponins from the bark of Ilex latifolia.

Two new triterpenoid saponins, latifoloside I (1), 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl 3beta,21alpha,28-trihydroxy-urs-12-ene 21-O-beta-D-glucopyranoside; latifoloside J (2), 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl-3beta,21alpha-dihydroxy-ursolic acid 21-O-beta-D-glucopyranoside, along with two known compounds, latifoloside C (3) and latifoloside E (4), were isolated from the bark of Ilex latifolia THUNB. Structure assignments were established on the basis of spectroscopic data and chemical evidence.

Carbohydrate Conformation↗

PubMed2001

Latifolosides K and L, two new triterpenoid saponins from the bark of Llex latifolia.

Two new triterpenoid saponins, latifoloside K (1), 3-O-beta-D-glucopyranosyl-(1-->3)-[alpha-L-rhamnopyranosyl-(1-->2)-]-alpha-L-arabinopyranosyl 3beta-hydroxy-urs-12,18-dien-28-oic acid 28-O-beta-D-glucopyranosyl ester and latifoloside L (2), 3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->3)-[alpha-L-rhamnopyranosyl-(1-->2)-]-alpha-L-arabinopyranosyl 3beta,19alpha-dihydroxyursolic acid, were isolated from the bark of Ilex latifolia Thunb. Also isolated were two known compounds, ilekudinoside A (3) and kudinoside G (4). Structural assignments were established on the basis of spectroscopic data and chemical evidence.

Carbohydrate Conformation↗

PubMed2001

Oxidized low-density lipoprotein and autoimmune antibodies in patients with antiphospholipid syndrome with a history of thrombosis.

The prevalence and clinical significance of plasma oxidized low-density lipoprotein (oxLDL) and antibodies against oxLDL (anti-oxLDL) were evaluated in patients with antiphospholipid syndrome (APS). OxLDL and IgG anti-oxLDL were determined by enzyme-linked immunosorbent assay in plasma samples from 80 patients with APS. Positive values (mean + 3 SD) for oxLDL and anti-oxLDL were found in 21 (26%) and 19 (24%) of 80 patients with APS, respectively These values were significantly higher than those in healthy subjects. Levels of oxLDL and anti-oxLDL antibodies in subgroupings of patients with APS who had experienced thrombotic events were compared. There were significant differences among the groups for the levels of both oxLDL and anti-oxLDL antibodies. Pairwise comparisons between the groups yielded similar but not identical results. There was a significant, positive correlation between levels of plasma oxLDL and anti-oxLDL. These results suggest that elevated levels of plasma oxLDL and anti-oxLDL may be risk factors and potential markers for thrombosis, especially for arterial thrombotic events, in patients with APS.

Adult↗

PubMed2001

The release and activation of transforming growth factor beta2 associated with apoptosis of chick hypertrophic chondrocytes.

The apoptosis of hypertrophic chondrocytes at the interface between growth cartilage and invading vessels is at the center of a series of critical events in endochondral formation. We have shown that the hypertrophy and apoptosis of chick chondrocytes in culture is associated with the release and activation of transforming growth factor beta2 (TGF-beta2). Supplementation of the culture medium with agents that influenced the maintenance of hypertrophic differentiation also influenced the release of TGF-beta2. A large proportion of the TGF-beta2 released from the cells was shown to be in an active form-particularly TGF-beta2 associated with the support matrix. Inhibition of apoptosis with a broad-spectrum caspase inhibitor inhibited activation of the matrix-associated TGF-beta2. However, inhibition of apoptosis did not diminish the release of TGF-beta2. Release of TGF-beta2 by chondrocytes at a late stage of their terminal differentiation and its activation in association with apoptosis may provide a mechanism controlling the processes of vascular invasion of growth cartilage and the deposition of bone matrix on nearby cartilage remnants.

Animals↗

PubMed2001

Propofol vs midazolam for ICU sedation : a Canadian multicenter randomized trial.

STUDY OBJECTIVES: To determine whether sedation with propofol would lead to shorter times to tracheal extubation and ICU length of stay than sedation with midazolam. DESIGN: Multicenter, randomized, open label. SETTING: Four academic tertiary-care ICUs in Canada. PATIENTS: Critically ill patients requiring continuous sedation while receiving mechanical ventilation. INTERVENTIONS: Random allocation by predicted requirement for mechanical ventilation (short sedation stratum, < 24 h; medium sedation stratum, > or = 24 and < 72 h; and long sedation stratum, > or = 72 h) to sedation regimens utilizing propofol or midazolam. MEASUREMENTS AND RESULTS: Using an intention-to-treat analysis, patients randomized to receive propofol in the short sedation stratum (propofol, 21 patients; midazolam, 26 patients) and the long sedation stratum (propofol, 4 patients; midazolam, 10 patients) were extubated earlier (short sedation stratum: propofol, 5.6 h; midazolam, 11.9 h; long sedation stratum: propofol, 8.4 h; midazolam, 46.8 h; p < 0.05). Pooled results showed that patients treated with propofol (n = 46) were extubated earlier than those treated with midazolam (n = 53) (6.7 vs 24.7 h, respectively; p < 0.05) following discontinuation of the sedation but were not discharged from ICU earlier (94.0 vs 63.7 h, respectively; p = 0.26). Propofol-treated patients spent a larger percentage of time at the target Ramsay sedation level than midazolam-treated patients (60.2% vs 44.0%, respectively; p < 0.05). Using a treatment-received analysis, propofol sedation either did not differ from midazolam sedation in time to tracheal extubation or ICU discharge (sedation duration, < 24 h) or was associated with earlier tracheal extubation but longer time to ICU discharge (sedation duration, > or = 24 h, < 72 h, or > or = 72 h). CONCLUSIONS: The use of propofol sedation allowed for more rapid tracheal extubation than when midazolam sedation was employed. This did not result in earlier ICU discharge.

Aged↗

PubMed2001

Distribution of trace elements in normal and tumor-bearing mice using the multitracer technique.

A multitracer solution obtained from the nuclear reaction of selenium with 25-MeV/nucleon 40Ar ions was orally administered to normal and tumor-bearing Balb/c male mice. After 96 h, the mice were sacrificed and the elemental distribution was determined in various tissues, organs, and blood. The uptake of Na, Rb, Ga, Sc, V, Cr, Mn, Co, Fe, Zn, Y, Zr, Tc, Ru, Ag, and In in normal and, except for zinc, in tumor-bearing mice was simultaneously detected. Most elements were distributed in about the same manner in the skin and liver of animals in both groups. The distribution of Rb, Ga, V, Cr, Tc, and In showed little or no significant differences between the two study groups. The distribution of Na, Mn, Fe, Ag, Sc, and Co showed significant differences between normal and tumor-bearing mice. In the blood, spleen, and kidney of the normal mice, there was good absorption of Na, Mn, Fe, Ag, Co, and Zn. In the heart, these elements were well absorbed, except for Na and Mn.

Animals↗

PubMed2001

In vitro maturation, fertilization and embryo development after ultrarapid freezing of immature human oocytes.

The purpose of this study was to determine the rates of maturation, fertilization and embryo development of ultrarapidly frozen immature oocytes (immature cumulus-oocyte complexes; COCs) obtained from antral follicles in ovaries of patients with chocolate ovarian cysts. The COCs were cryopreserved by a vitrification method using 5.5 mol ethylene glycol l (-1) plus 1.0 mol sucrose l (-1) in Dulbecco's PBS (DPBS). The survival, maturation and fertilization rates, and the percentage of embryos developing to the two-cell stage were 59, 64, 70 and 71%, respectively. No significant differences were noted in the rates of maturation, fertilization and embryo development between control and cryopreserved oocytes. Two embryos that developed from cryopreserved oocytes of the oocyte donor programme were selected for transfer into the uterus of a recipient with premature ovarian failure, after the recipient had received steroid replacement. A biochemical pregnancy occurred in the recipient after embryo transfer. These results indicate that immature oocytes can survive after cryopreservation and subsequently can be cultured to mature oocytes that are capable of undergoing fertilization in vitro and developing into embryos.

Adult↗

PubMed2001

Quantitative structure-activity relationships: comparative inhibition of nitrogen-containing aromatics on germination of Cucumis sativus.

Comparative inhibition effect of selected nitrogen-containing aromatics on germination rate of Cucumis sativus was investigated, and quantitative structure-activity relationships were developed and mechanistically interpreted. Energy of lowest unoccupied orbital was found to successfully model the toxicity of the test chemicals. It was discovered that inhibition of nitrogen-containing aromatics to germination of Cucumis sativus was caused mainly by their in vivo redox reaction.

Aminopyridines↗

PubMed2001

An electrochemical quartz crystal impedance study on the rising of an aqueous solution meniscus for a partially immersed gold electrode during the electrochemical reduction of oxygen.

An electrochemical quartz crystal impedance system (EQCIS) was used to study the resonance behavior of an AT-cut 9-MHz piezoelectric quartz crystal (PQC) with its Au electrode partially immersed in KCl, Na2SO4 and NaClO4 aqueous solutions, respectively. An in situ determination of the immersed area and the height of the electrode was achieved by simultaneous measurements of the PQC electroacoustic admittance and the electrochemical impedance. The rising of the solution meniscus for a gold electrode partially immersed in aqueous solutions was found at oxygen reduction potentials and evaluated versus the electrolyte, electrolyte concentration, solution pH and oxygen concentration. The solution meniscus rising was explained based on a lowering of the contact-angle hysteresis and a continued collection of the water product at the solid-gas-solution interface during oxygen reduction.

Journal Article↗

PubMed2001

General strategy for constructing large HSV-1 plasmid vectors that co-express multiple genes.

Herpes simplex virus type 1 (HSV-1) plasmid vectors have a number of attractive features for gene transfer into neurons. In particular, the large size of the HSV-1 genome suggests that HSV-1 vectors might be designed to co-express multiple genes. Here, we report a general strategy for constructing large HSV-1 plasmid vectors that co-express multiple genes. Each transcription unit is linked to an antibiotic resistance gene, and genetic selections are used to assemble large vectors. Using this strategy, we constructed large (26 or 31 kb) HSV-1 vectors that contain two transcription units and two or three genes. These vectors were efficiently packaged into HSV-1 particles using a helper virus-free packaging system. The resulting vector stocks supported the expression of two or three genes in both cultured cells and the rat brain. Potential applications of HSV-1 vectors that co-express multiple genes are discussed.

Gene Expression Regulation, Viral↗

PubMed2001

High throughput log D determination using liquid chromatography-mass spectrometry.

A method has been developed which allows direct measurement of partition coefficients (log D, log P) using liquid chromatography-mass spectrometry (LC-MS). The high throughput, microtiter plate based protocol uses small quantities of 10 mM analyte in DMSO solution (5 microL) and is therefore amenable to standard archive and screening formats. Single Ion Monitoring (SIM) mass spectrometry is used to achieve optimal sensitivity. Experimental log D values for 34 known drugs have been determined, with partition coefficients ranging from -2 to 5, giving data very similar to literature values. In these analyses, deviations from known values average less than 0.3 log units. The sample handling and data processing have been significantly automated, and the protocol has been applied to over 800 in-house lead molecules to date. In its format, sensitivity, throughput, and amenability to automation, it represents significant progress in the direct measurement of partitioning behavior [1].

Cell Line↗

PubMed2001

[A study of phenylketonuria heterozygotes screening in married population of Tianjin area].

OBJECTIVE: To find out a method that is simple and reliable for screening phenylketonuria(PKU) heterozygotes. METHODS: Detecting and analyzing plasma phenylalanine(Phe) and tyrosine(Tyr) from 101 known-PKU heterozygotes and 2023 married people by means of a high performance liquid chromatograph. RESULTS: Significant differences were observed between known- PKU heterozygotes and screening population in plasma Phe, Phe/Tyr and Phe(2)/Tyr. The values of plasma Phe, Phe/Tyr and Phe(2)/ Tyr from 94.1% known-PKU heterozygotes were higher than mean+2s of those values from screening population. According to the limits of mean+2s, 81 cases were screened out from the 2023 married people. It was the first time to get the actual heterozygote frequency of 4% from population. CONCLUSION: The biochemical method mentioned above is available for use in screening PKU heterozygotes.

Adult↗

PubMed2001

Development of cataractous macrophthalmia in mice expressing an active MEK1 in the lens.

PURPOSE: To characterize the extracellular signal-regulated kinase (ERK) pathway in the lens and to try to understand how this pathway contributes to lens function and cataractogenesis. METHODS: The members of the ERK pathway in the lens were examined by Western blotting, immunohistochemical staining, and kinase assay. A gain-of-function approach was used to perturb the ERK pathway in the lenses of transgenic mice via expression of a constitutively active mutant of the mitogen-activated protein kinase kinase 1 (MEK1(E)), the direct upstream kinase of the ERK1 and ERK2 kinases, under the alphaA-crystallin promoter. RESULTS: The presence of an active ERK pathway was found in lens epithelial cells and in differentiating fibers. Transgenic mice that expressed MEK1(E) developed postnatal cataracts as well as macrophthalmia. Distinct morphologic alterations, such as lens enlargement, swelling fiber cells, enlarged extracellular space, and vacuole formation, were observed in the lenses of these transgenic mice. A significant increase in the glucose transporter 1 (GLUT1) level, as well as in the glucose level, was detected in the lens. CONCLUSIONS: The MAP kinase pathway is involved in the regulation of glucose metabolism and balance in the mouse lens. Moreover, the alteration of MAP kinase activity in the lens is sufficient to cause cataract formation with enlarged extracellular space and vacuoles in the differentiating fibers. This transgenic mouse may provide a useful model for understanding the mechanism(s) for some aspects of human cataracts.

Animals↗