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D Wu

Publications and source records attributed to D Wu.

At least 19 recordsLinked to original sources
PubMed1998

Specific involvement of G proteins in regulation of serum response factor-mediated gene transcription by different receptors.

Regulation of serum response factor (SRF)-mediated gene transcription by G protein subunits and G protein-coupled receptors was investigated in transfected NIH3T3 cells and in a cell line that was derived from mice lacking Galphaq and Galpha11. We found that the constitutively active forms of the alpha subunits of the Gq and G12 class of G proteins, including Galphaq, Galpha11, Galpha14, Galpha16, Galpha12, and Galpha13, can activate SRF in NIH3T3 cells. We also found that the type 1 muscarinic receptor (m1R) and alpha1-adrenergic receptor (AR)-mediated SRF activation is exclusively dependent on Galphaq/11, while the receptors for thrombin, lysophosphatidic acid (LPA), thromboxane A2, and endothelin can activate SRF in the absence of Galphaq/11. Moreover, RGS12 but not RGS2, RGS4, or Axin was able to inhibit Galpha12 and Galpha13-mediated SRF activation. And RGS12, but not other RGS proteins, blocked thrombin- and LPA-mediated SRF activation in the Galphaq/11-deficient cells. Therefore, the thrombin, LPA, thromboxane A2, and endothelin receptors may be able to couple to Galpha12/13. On the contrary, receptors including beta2- and alpha2-ARs, m2R, the dopamine receptors type 1 and 2, angiotensin receptors types 1 and 2, and interleukin-8 receptor could not activate SRF in the presence or absence of Galphaq/11, suggesting that these receptors cannot couple to endogenous G proteins of the G12 or Gq classes.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1998

Tec/Bmx non-receptor tyrosine kinases are involved in regulation of Rho and serum response factor by Galpha12/13.

A transient transfection system was used to identify regulators and effectors for Tec and Bmx, members of the Tec non-receptor tyrosine kinase family. We found that Tec and Bmx activate serum response factor (SRF), in synergy with constitutively active alpha subunits of the G12 family of GTP-binding proteins, in transiently transfected NIH 3T3 cells. The SRF activation is sensitive to C3, suggesting the involvement of Rho. The kinase and Tec homology (TH) domains of the kinases are required for SRF activation. In addition, kinase-deficient mutants of Bmx are able to inhibit Galpha13- and Galpha12-induced SRF activation, and to suppress thrombin-induced SRF activation in cells lacking Galphaq/11, where thrombin's effect is mediated by G12/13 proteins. Moreover, expression of Galpha12 and Galpha13 stimulates autophosphorylation and transphosphorylation activities of Tec. Thus, the evidence indicates that Tec kinases are involved in Galpha12/13-induced, Rho-mediated activation of SRF. Furthermore, Src, which was previously shown to activate kinase activities of Tec kinases, activates SRF predominantly in Rho-independent pathways in 3T3 cells, as shown by the fact that C3 did not block Src-mediated SRF activation. However, the Rho-dependent pathway becomes significant when Tec is overexpressed.

3T3 Cells↗
PubMed1998

Tissue and T cell distribution of precursor and mature IL-16.

IL-16 is a novel cytokine, which is chemoattractant for CD4+ T cells, macrophages, and eosinophils. Recently, it was reported that IL-16 is synthesized as an approximately 80-kDa precursor molecule, pro-IL-16. Since little is known about the processing and tissue distribution of IL-16 and pro-IL-16, we investigated the distribution of IL-16 mRNA and protein in human lymphoid tissue. Northern blotting identified IL-16 mRNA predominantly in normal lymphoid organs, including PBMC, spleen, and thymus. Immunohistochemistry of human lymph node localized IL-16 protein to lymphocyte cytoplasm within T cell zones and occasionally in lymphocytes in B cell zones. Flow cytometric detection of intracellular IL-16 showed that >70% of CD4+ and CD8+ T cells constitutively expressed IL-16 protein. Western blot analysis of PBMC revealed nearly all of this protein to be approximately 80-kDa pro-IL-16 in unstimulated PBMC, and upon cell activation, the amino terminus of pro-IL-16 is processed into multiple fragments. These results show that pro-IL-16 is widely and constitutively expressed and suggest that the amino terminus of the protein can be processed upon cell activation.

Adolescent↗
PubMed1998

Disease incidence and longevity are unaltered by dietary antioxidant supplementation initiated during middle age in C57BL/6 mice.

The ability of augmented antioxidant consumption to alter disease incidence, lesion burden and/or longevity was studied in adult male C57BL/6 mice. Mice were fed modified AIN76 diet or modified AIN76 supplemented with vitamin E, glutathione (GSH), vitamin E and GSH, melatonin or strawberry extract starting at 18 months of age. All the mice in this study were heavier than reference populations of male C57BL/6 mice fed NIH-07 or NIH-31, which were maintained without a mid-life change in diet. Fatty liver, focal kidney atrophy and proteinacious casts in the renal tubules were observed more frequently in this study population than in the reference populations. Lesion burden and incidence of specific lesions observed amongst the various groups in this study did not differ. There were no differences observed for longevity of any of the study groups. The longevity observed in this study was similar to that previously reported for male C57BL/6 mice. Thus, diet supplementation with antioxidants initiated during middle age did not appear to affect age-associated lesions patterns, lesion burden or longevity for ad libitum fed male C57BL/6 mice.

Aging↗
PubMed1998

GLUT1 glucose transporter: differential gene transcription and mRNA binding to cytosolic and polysome proteins in brain and peripheral tissues.

The ratio of GLUT1 mRNA to actin mRNA in brain was 6- to 13- fold greater than the corresponding ratio in spleen, lung, testis, heart, and skeletal muscle in the rat. However, the ratio of GLUT1 transcription rate to actin transcription rate is comparable in brain and the five other organs. Organ extracts were fractionated into cytosol and polysomes, and ultraviolet light cross-linking studies were performed with these proteins and 32P-labeled GLUT1 mRNA containing the 3'-untranslated region (UTR) generated from transcription plasmids. The cytosol of brain, lung, spleen, C6 glioma cells in tissue culture, and freshly isolated bovine brain capillaries express a pair of 95 kDa and 74 kDa proteins, designated collectively as p88, and the polysome fraction of brain, testis, or C6 glioma cells express a 44-kDa protein, designated p44. In a middle cerebral artery occlusion model, brain cytosol p88 was up-regulated and p44 was down-regulated. These findings are consistent with the hypothesis that GLUT1 gene expression is subject to regulation at the post-transcriptional level.

Animals↗
PubMed1998

Low blood-brain barrier permeability to azidothymidine (AZT), 3TC, and thymidine in the rat.

The blood-brain barrier (BBB) permeability to [3H]-azidodeoxythymidine (AZT), deoxythiacytidine (3TC), and thymidine was studied using both an intravenous injection/external organ (IV/EO) method and an internal carotid artery perfusion (ICAP) technique in parallel with [14C]-sucrose as a plasma volume marker. The brain volumes of distribution (VD) of the three compounds approximated that of sucrose with either method. Although the lipid solubility of AZT, as determined by the 1-octanol/buffer partition coefficient (P), was 16-fold higher than that of thymidine, the BBB permeability-surface area (PS) products were almost identical, consistent with preferential efflux of AZT from brain to blood.

Animals↗
PubMed1998

Bcl-XL interacts with Apaf-1 and inhibits Apaf-1-dependent caspase-9 activation.

Recent studies indicate that Caenorhabditis elegans CED-4 interacts with and promotes the activation of the death protease CED-3, and that this activation is inhibited by CED-9. Here we show that a mammalian homolog of CED-4, Apaf-1, can associate with several death proteases, including caspase-4, caspase-8, caspase-9, and nematode CED-3 in mammalian cells. The interaction with caspase-9 was mediated by the N-terminal CED-4-like domain of Apaf-1. Expression of Apaf-1 enhanced the killing activity of caspase-9 that required the CED-4-like domain of Apaf-1. Furthermore, Apaf-1 promoted the processing and activation of caspase-9 in vivo. Bcl-XL, an antiapoptotic member of the Bcl-2 family, was shown to physically interact with Apaf-1 and caspase-9 in mammalian cells. The association of Apaf-1 with Bcl-XL was mediated through both its CED-4-like domain and the C-terminal domain containing WD-40 repeats. Expression of Bcl-XL inhibited the association of Apaf-1 with caspase-9 in mammalian cells. Significantly, recombinant Bcl-XL purified from Escherichia coli or insect cells inhibited Apaf-1-dependent processing of caspase-9. Furthermore, Bcl-XL failed to inhibit caspase-9 processing mediated by a constitutively active Apaf-1 mutant, suggesting that Bcl-XL regulates caspase-9 through Apaf-1. These experiments demonstrate that Bcl-XL associates with caspase-9 and Apaf-1, and show that Bcl-XL inhibits the maturation of caspase-9 mediated by Apaf-1, a process that is evolutionarily conserved from nematodes to humans.

Animals↗
PubMed1998

Identification of a structural element in phospholipase C beta2 that interacts with G protein betagamma subunits.

To delineate the specific regions of phospholipase C beta2 (PLC beta2) involved in binding and activation by G protein betagamma subunits, we synthesized peptides corresponding to segments of PLC beta2. Two overlapping peptides corresponding to Asn-564-Lys-583 (N20K) and Glu-574-Lys-593 (E20K) inhibited the activation of PLC beta2 by betagamma subunits (IC50 50 and 150 microM, respectively), whereas two control peptides did not. N20K and E20K, but not the control peptides, inhibited betagamma-dependent ADP-ribosylation of Galphai1 by pertussis toxin and betagamma-dependent activation of phosphoinositide 3-kinase. To demonstrate direct binding of the peptides to betagamma subunits, the peptides were chemically cross-linked to purified beta1gamma2. N20K and E20K cross-linked to both beta1 and gamma2 subunits, whereas the control peptides did not. Cross-linking to beta and gamma was inhibited by incubation with excess PLC beta2 or PLC beta3, whereas cross-linking to gamma but not beta was inhibited by r-myr-alphai1. These data together demonstrate specificity of N20K and E20K for G betagamma binding and inhibition of effector activation by betagamma subunits. The results suggest that an overlapping region of the two active peptides, Glu-574-Lys-583, mimics a region of PLC beta2 that is involved in binding to betagamma subunits. Changing a tyrosine to a glutamine in this overlapping region of the peptides inhibited binding of the peptide to betagamma subunits. Alignment of these peptides with the three-dimensional structure from PLC delta1 identifies a putative alpha helical region on the surface of the catalytic domain of PLC beta2 that could interact with betagamma subunits.

Adenosine Diphosphate Ribose↗
PubMed1998

Determinants of tachycardia recurrences after radiofrequency ablation of idiopathic ventricular tachycardia.

Clinical and electrophysiologic parameters were analyzed to define the factors potentially related to tachycardia recurrences in 79 patients undergoing successful radiofrequency ablation of idiopathic right or left ventricular tachycardia. It was found that the endocardial activation time at the successful ablation site was the only independent predictor of tachycardia recurrences.

Adolescent↗
PubMed1998

Interaction of 1-hydroxyethyl radical with glutathione, ascorbic acid and alpha-tocopherol.

Ethanol has been shown to be oxidized to a free radical metabolite, the 1-hydroxyethyl radical (HER). Interaction of HER with cellular antioxidants may contribute to the known ability of ethanol administration to lower levels of GSH and alpha-tocopherol. Experiments were carried out to establish a model system for the generation of HER and to study its interaction with GSH, ascorbic acid and alpha-tocopherol. A standard reaction for formation of azo-compounds using acetaldehyde and hydroxylamine-O-sulfonic acid was applied for the synthesis of 1,1'-dihydroxyazoethane (CH3CH(OH)-N=N-CH(OH)CH3). Although stable at -70 degrees C, thermal decomposition of this compound at room temperature was shown to produce HER, detected by EPR spectrometry as the PBN/HER or DMPO/HER spin adducts, and validated by computer simulation. GSH, present at the beginning of the experiment, inhibited formation of the PBN/HER signal. However, GSH did not cause any decay of pre-formed PBN/HER spin adduct. GSH was consumed in the presence of the HER-generating system in a reaction largely reversed by addition of NADPH plus glutathione reductase. Ascorbate also inhibited formation of the PBN/HER spin adduct and rapidly reduced the pre-formed adduct. HER amplified the oxidation of ascorbate, which was associated with the formation of the semidehydroascorbyl radical. Alpha-tocopherol was also consumed in the presence of HER. Production of HER in intact HepG2 cells by the redox cycling of 2,3-dimethoxy-1,4-naphthoquinone was associated with consumption of GSH. These data demonstrate the use of a simple chemical system for the controlled, continuous formation of HER and indicate that cellular antioxidants such as GSH, ascorbate, and alpha-tocopherol, interact with HER. The ability of agents such as ascorbate to reduce the PBN/HER spin adduct to EPR-silent product(s) may mask the quantitative detection of HER in biological systems.

Ascorbic Acid↗
PubMed1998

High throughput liquid chromatography/mass spectrometry bioanalysis using 96-well disk solid phase extraction plate for the sample preparation.

The 96 well solid phase extraction (SPE) operated by robot in the LC/MS/MS bioanalysis offered rapid sample preparation for drugs and metabolites in biological matrices, based on simultaneous extraction of 96 samples. The use of a disk as sorbent in the 96 well plate further improved the performance of SPE and allowed for small elution volumes, making it possible to 'dilute and shoot" after SPE elution. In this study, a 96 well plate (Empore) was developed, characterized and optimized for several pharmaceutical compounds. In addition, a robot (MultiProbe) was modified to automate the 96 well plate operation. Examples were given to illustrate the major differences of using 96 well disk plate SPE in the method development as compared to the traditional SPE. This technology has been successfully used to support many clinical studies. Typically, a batch of 96 samples were prepared in 1-1.5 hours unattended (except for the replacement of a collection plate). Considerable savings in disposable supplies were also noted.

Anti-Asthmatic Agents↗
PubMed1998

Brain activation during silent word generation evaluated with functional MRI.

This is a study of word generation during functional MRI (fMRI). Eleven normal healthy subjects were instructed to generate words covertly, (i.e., silently) that began with particular letters. Images were acquired on a conventional 1.5T scanner at three contiguous axial planes encompassing language-related areas of the temporal and frontal lobe. The data were analyzed at the level of a Talairach box, after individually fitting the proportional Talairach grid system to each slice. The main variable of interest was the number of activated pixels within a Talairach box. Boxes with a significant increase in the proportion of activated pixels were located in three regions of the left neocortex: (1) Brodmann areas 44 and 45 in the dorsolateral frontal cortex (Broca's area), (2) areas 21 and 37 in the temporal cortex, (3) and the striate/extrastriate cortex (areas 17 & 18). The results are discussed in terms of a cognitive model of word generation and are compared, in detail, with the results of prior relevant imaging studies.

Adolescent↗
PubMed1998

Evidence for the presence of a Na+-H+ exchanger in the endolymphatic sac epithelium of guinea-pigs.

The intracellular pH (pHi) of epithelial cells from the endolymphatic sac (ES) of the guinea-pig was measured microfluorometrically with the pH-sensitive fluorescent dye, 2', 7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) to examine the presence of a Na+-H+ exchanger (NHE) in the ES epithelial cells. pHi recovery from acid loading with an NH4+-prepulse in a nominally HCO3-free solution was dependent on extracellular Na+ ([Na+]o) and was inhibited by amiloride and its analogue ethylisopropylamiloride (EIPA), suggesting that a decreased pHi induced by an acute acid load may be equilibrated by a NHE. In the steady-state, amiloride had no effect on pHi, indicating that the NHE activity is low at the resting pHi. However, the intracellular acidification induced by the removal of [Na+]o was inhibited by the simultaneous application of amiloride. H+-efflux rate (JH, mean activity of NHE), which was calculated as the product of the recovery rate (dpHi/dt) from the acid loading and the intrinsic buffering capacity (betai) at the corresponding pHi, was decreased as pHi was increased. The concentration/response curve for the inhibition of initial JH by EIPA revealed an apparent 50% inhibitory constant (Ki ) of 0.85 microM. Kinetic analysis of initial JH as a function of [Na+]o revealed a Michaelis-Menten constant (Km) of 24.14 mM for Na+-dependent H+ efflux. The results indicate that NHE in the ES epithelium belongs to an amiloride-sensitive subtype.

Amiloride↗
PubMed1998

Late coronary artery stenting in patients with acute myocardial infarction.

BACKGROUND: The safety and efficacy of late coronary artery stenting of the infarct-related artery after acute infarction has not been evaluated previously. METHODS AND RESULTS: Coronary artery stenting was performed in 117 consecutive patients with acute infarction who were receiving ticlopidine/aspirin regimen without coumarin. There were 97 men and 18 women, aged 58+/-11 (mean +/- SD) years. A total of 136 Palmaz-Schatz stents were successfully implanted in 130 lesions 15+/-8 days after acute myocardial infarction (median 9 days) in 115 of 117 (98%) patients. The minimal luminal diameter (MLD) increased from 0.66+/-0.46 to 3.14+/-0.53 mm (P< .001), with an acute gain of 2.49+/-0.61 mm. One patient had acute thrombosis requiring further stenting and another patient received emergency bypass surgery. There was no subacute thrombosis or other complications. During a follow-up duration of 14+/-3 months, 2 patients had angina pectoris develop and 1 died suddenly. Sixty-two patients underwent a follow-up coronary angiography 195+/-36 days after stenting. Restenosis was noted in 8 patients (13%); the MLD was 2.19+/-0.73 mm, the late loss was 0.96+/-0.65 mm (P< .001), the loss index was 0.39+/-0.28, and the net gain was 1.56+/-0.79 mm (P< .001). The angiographic left ventricular ejection fraction increased from 47%+/-12% to 55%+/-12% (P< .001). CONCLUSIONS: Late coronary stenting of the infarct-related artery in patients with acute myocardial infarction is a safe and effective late reperfusion therapy and may be beneficial to the patients.

Adult↗
PubMed1998

Baroreflex-mediated bradycardia but not tachycardia is blunted peripherally by intravenous mu-opioid agonists.

OBJECTIVE: We sought to test the hypothesis that an intravenous dose of H-Tyr-D-Arg-Phe-Lys-NH2, a highly mu-receptor selective opioid peptide, suppresses baroreflex sensitivity through a peripheral mechanism. STUDY DESIGN: A transient change in mean arterial pressure was produced in chronically instrumented pregnant ewes by norepinephrine or sodium nitroprusside in the absence or in the presence of H-Tyr-D-Arg-Phe-Lys-NH2, a highly mu-selective opioid peptide. In some studies naloxone methiodide, a peripheral opioid antagonist, was infused starting 60 minutes before the administration of H-Tyr-D-Arg-Phe-Lys-NH2 and maintained for a total of 90 minutes. Linear plots were obtained when the changes in mean arterial pressure during the pressure rise were plotted against the changes in heart rate and the sensitivity of the baroreflex was derived as the slope of the linear regression line. RESULTS: We observed (1) lower baroreflex sensitivity after H-Tyr-D-Arg-Phe-Lys-NH2 administration with a hypertensive stimulus; (2) unchanged baroreflex sensitivity after H-Tyr-D-Arg-Phe-Lys-NH2 administration with a hypotensive stimulus; and (3) unchanged baroreflex sensitivity after H-Tyr-D-Arg-Phe-Lys-NH2 administration with a hypertensive stimulus in the presence of naloxone methiodide. CONCLUSION: H-Tyr-D-Arg-Phe-Lys-NH2 suppresses the hypertensive but not the hypotensive arm of the baroreflex through peripheral opioid receptors. These results suggest that mu-opioid receptors are present in the vagus nerves and that the activation of these opioid receptors inhibits reflex bradycardia in pregnant sheep.

Animals↗
PubMed1998

Cardiovascular and metabolic responses to two receptor-selective opioid agonists in pregnant sheep.

OBJECTIVE: Our purpose was to assess the effects of an intravenous dose of a highly selective mu-(DALDA) and delta-(DPDPE) opioid peptide to determine which class of peptide has the best clinical potential. STUDY DESIGN: Chronically instrumented pregnant ewes received a 0.3 mg/kg intravenous bolus of each peptide with and without opioid receptor blockade by means of a randomized prospective design. RESULTS: Intravenous DALDA produced only mild hypertension and a loss of heart rate variability, whereas DPDPE produced respiratory depression, maternal hypertension, and a fall in heart rate in both mother and fetus. Uterine blood flow, oxygen uptake, and glucose uptake were unchanged with both drugs. The effects of DALDA but not DPDPE were reversed by opioid receptor blockade. CONCLUSION: The delta-selective agonist had multiple nonopioid adverse effects, whereas the mu-selective agonist was well tolerated by the pregnant ewe, suggesting that mu-selective agonists have better potential for clinical use as an analgesic in pregnancy.

Animals↗
PubMed1998

Multiplane transesophageal echocardiography in diagnosis of anomalous origin of the left coronary artery from the pulmonary artery: a case report.

Anomalous origin of the left coronary artery from the pulmonary artery in adults is difficult to identify reliably by transthoracic echocardiography (TTE). We describe a 32-year-old woman with this coronary anomaly mimicking a coronary artery fistula on conventional TTE study. This anomaly was suggested by multiplane transesophageal echocardiography (TEE) and subsequently confirmed by coronary angiography. Multiplane TEE thus may serve as a first-line diagnostic tool for detecting anomalous origin of coronary arteries.

Adult↗