Showing papers by "Yu Huang published in 1998"
TL;DR: The present results suggest that epicatechin derivatives from green tea leaves relaxed rat mesenteric arteries probably by inhibiting Ca2+ influx and the protein kinase C-dependent contractile pathway and intracellular Ca2+, and may not be involved.
72 citations
TL;DR: The results suggest that hawthorn contains active components which cause vasorelaxation in rat isolated mesenteric arteries and Nitric oxide but not other endothelium-derived vasoactive factors was probably involved in the relaxation induced by hawthorns extract.
68 citations
TL;DR: The results indicate that hydroxylamine relaxes the rat aorta partially through activation of tetrapentylammonium-, tetraethylammonia- and charybdotoxin-sensitive K+ channels and its action is comparable with that of sodium nitroprusside, an exogenous nitric oxide donor.
24 citations
TL;DR: The inhibitory effect of glibenclamide on the high-K+-induced contraction suggests that glibanclamide may interfere with Ca2+ influx, which in turn affects intracellularCa2+ levels in arterial smooth muscle, leading to reduction of muscle contractility.
11 citations
TL;DR: The effects of inhibitors of nitric oxide activity, blockers of K+ channels and high extracellular K+ were studied by measuring isometric tension in both endothelium‐intact and ‐denuded arteries.
Abstract: 1. In order to examine the possible involvement of the endothelium and K+ channel activation in the relaxation induced by dobutamine, a beta 1-adrenoceptor agonist, in rat isolated mesenteric arteries, the effects of inhibitors of nitric oxide (NO) activity, blockers of K+ channels and high extracellular K+ were studied by measuring isometric tension in both endothelium-intact and -denuded arteries. 2. Dobutamine inhibited the phenylephrine (PE)-induced sustained tension with a pEC50 of 7.40 +/- 0.08 in endothelium-intact arteries. Removal of functional endothelium attenuated the effect of dobutamine. The relaxation induced by dobutamine was inhibited by the beta 1-adrenoceptor antagonist CGP 20712A (3 mumol/L) but not by the beta 2-adrenoceptor antagonist ICI 118,551 (3 mumol/L) in endothelium-denuded arteries. 3. Pretreatment with NG-nitro-L-arginine (L-NNA; 100 mumol/L) or methylene blue (3 mumol/L) induced a similar degree of inhibition of the dobutamine-induced relaxation in endothelium-intact arteries, while NG-nitro-D-arginine (100 mumol/L) and indomethacin (10 mumol/L) had no effect. In contrast, pretreatment with L-NNA (100 mumol/L) did not affect the relaxation induced by sodium nitroprusside (SNP) or forskolin. Methylene blue (3 mumol/L) inhibited the relaxant response to SNP. 4. Charybdotoxin (CTX; 100 nmol/L), iberiotoxin (IBX; 100 nmol/L) and tetraethylammonium ions (TEA+; 3 mmol/L) significantly reduced the dobutamine-induced relaxation. Tetrapentylammonium ions (TPA+; 5 mumol/L) markedly inhibited the relaxant effect of dobutamine. The pEC50 values for control and in the presence of TPA+ in endothelium-intact arteries were 7.35 +/- 0.11 and 6.14 +/- 0.17, respectively, and 6.35 +/- 0.09 and 5.87 +/- 0.17 for control and in the presence of TPA+ in endothelium-denuded arteries, respectively. In contrast, glibenclamide (3 mumol/L) was ineffective. At 5 mumol/L, TPA+ also inhibited the relaxation induced by forskolin. 5. The maximal relaxation of PE-contracted arteries induced by 3 mumol/L dobutamine was completely abolished in the 60 mmol/L K(+)-contracted arteries with and without endothelium, while dobutamine at a concentration greater than 3 mumol/L induced inhibition of the high-K+ response. 6. The present results indicate that endothelium, probably NO but not prostacyclin, was involved in the dobutamine-induced relaxation in rat mesenteric arteries. Activation of CTX-, IBX- and TPA(+)-sensitive K+ channels contributed towards the observed relaxation. Loss of the ability to relax the 60 mmol/L K(+)-contracted arteries suggests that endothelium-derived vasoactive factors affected by concentrations of dobutamine less than 3 mumol/L may also act through K+ channels in our preparations. Higher concentrations of dobutamine may have a direct, endothelium-independent relaxant effect.
11 citations
TL;DR: It is revealed that the N-terminal signal sequence may not act through the endocytotic pathway, and removal of two charged residues through amino acid substitution effectively raises the amplitude of expressed current, further indicating the importance of charged residues.
7 citations
25 Sep 1998
TL;DR: A motion-based segmentation scheme that can directly estimate image motion of an object in two unsegmented images and obtain fine segmentation of that object from background at the same time and construct various motion features, shape features, or their combinations for the purpose of hand gesture interpretation.
Abstract: The key motivation for visual interpretation of hand gestures is to introduce this natural and intuitive communication mode to human computer interaction. Visual interpretation of hand gesture had typically made use of high-level parametric models representing the body parts such as arms, figures, palms etc. and their connections to each other. Such 3D model-based interpretation has been successful in some case; however, heavy computation makes this approach a very difficult task. By use of variable- order parameterized models of image motion and robust dominant motion regression, in this paper, we propose a motion-based segmentation scheme to feature extraction of hand gestures. The proposed scheme can directly estimate image motion of an object in two unsegmented images and obtain fine segmentation of that object from background at the same time. Based on inter-frame image motion parameters and the fine segmentation, we can construct various motion features, shape features, or their combinations for the purpose of hand gesture interpretation. With these features 12 kind of hand gestures used in our experiment can be reliably interpreted.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
5 citations
Journal Article•
TL;DR: The proposed motion-based segmcntation scheme can estimate image molion of an object in two unsegmcnled imagcs and obtain fine segmentation of that ob,iect rronr background a( Ihe same lime.
Abstract: Vision-based interptelation of hand gesture had lypically made use of high-level parametric models representing the bodv parts such as arms, figures. palms etc :rnd t l~cir connections no each other. Such 3-D modelbascd inrcrprctation has been successful In some case: howcvcr. heavy computation makes this approach a veiy djficull task. Recent ty appearance-based methods are more widely used Tor their computational cfliciency. By l ac of variable-order pararnetcrized models of image rnotion and robust dominant motion regression. in this paper. we propose n motion-based segmcntation scheme to fealurc estnction of hand gestures. The proposed scheme can dircctlv estimate image molion of an object in two unsegmcnled imagcs and obtain fine segmentation of that ob,iect rronr background a( Ihe same lime. Based on intcr-framc lmagc morlon parameters and ihc fine scgmenratlon. we can constnrcl various motion features. sbapc fcat~ires, or he i r combinations for thc purpose of hand gesture interpretation. With t hcsc features 12 kind of hand gcslurcs used i n our esperimcnt can be reIiablp
4 citations
TL;DR: Results indicate that isoprenaline-induced inhibition of the electrically evoked (both purinergic and adrenergic) contraction was mediated primarily through activation of prejunctional beta-adrenoceptors, which probably inhibited release of contractile transmitters from sympathetic nerves supplying vas deferens.
3 citations
11 Oct 1998
TL;DR: An approach to isolated gesture recognition, which uses as input the monocular sequence of dynamic gesturing with the single hand based on robust A P-estimator and the dominant motion model to realize gesture segmentation by image registration and warping.
Abstract: In this paper, we present an approach to isolated gesture recognition, which uses as input the monocular sequence of dynamic gesturing with the single hand. We use the direct method of motion estimation, and realize gesture segmentation by image registration and warping based on robust A P-estimator and the dominant motion model. After extracting the spatial-temporal features of gestures, we perform dynamic time warping (DTW) to recognize 12 types of control gestures (6 for translation, 6 for rotation) replacing the 3-D mouse tool. A small demonstration system has been set to verify, our method, i.e. controlling a panorama image (set by mosaicing a sequence of standard "Garden" images) viewer with gesturing.
3 citations
TL;DR: It is indicated that TPA at low concentrations could contract the arterial smooth muscle probably through promoting Ca2+ influx and relaxes arterial smoother muscle at higher concentrations through inhibition of both nifedipine-sensitive Ca-sensitive channels and internal Ca-2+-sup release.
Abstract: Both contractile and relaxant responses to tetrapentylammonium ions (TPA+) were studied in rat isolated mesenteric artery. TPA+ (5–10 µmol/l) caused a sustained increase of muscle tension. The contractile effect of TPA+ (10 µmol/l) was dependent upon the presence of extracellular Ca2+ but independent of the presence of endothelium. TPA+ (10–50 µmol/l) induced biphasic contraction, and the amplitude of peak and sustained tension decreased with increasing TPA+ concentration. TPA+ (100–300 µmol/l) only produced monophasic contraction. TPA+ (50 µmol/l) abolished the transient contraction induced by caffeine (10 mmol/l) or phenylephrine (1 µmol/l) in the absence of extracellular Ca2+. Nifedipine and verapamil concentration-dependently reduced the TPA+-induced contraction with respective IC50 values of 1.34 ± 0.24 and 9.46 ± 1.36 nmol/l, these values were similar to 1.35 ± 0.21 and 16.07 ± 1.71 nmol/l, respectively, for the inhibitory effects of nifedipine and verapamil on the high K+ (60 mmol/l)-induced contraction. TPA+ (>10 µmol/l) concentration-dependently reduced the phenylephrine (1 µmol/l)-, U46619 (30 nmol/l)-, endothelin I (10 nmol/l)- and high K+ (60 mmol/l)-induced sustained tension with respective IC50 values of 53.7 ± 9.5, 31.9 ± 5.3, 30.9 ± 3.4 and 20.9 ± 2.8 µmol/l. The present results indicate that TPA+ at low concentrations could contract the arterial smooth muscle probably through promoting Ca2+ influx. At higher concentrations (>20 µmol/l), TPA+ relaxes arterial smooth muscle probably through inhibition of both nifedipine-sensitive Ca+ channels and internal Ca2+ release. TPA+, unlike other quaternary ammonium ions, could therefore act at multiple sites in arterial smooth muscle.
TL;DR: In this article, the authors reported the emittance and brightness measurement of an electron beam produced in a pseudospark discharge device driven by a pulse line accelerator, which was operated at 200 kV, in a nitrogen gas fill pressure of 15 Pa and the typical value of emittance was measured to be 47 mn mrad about 5 cm downstream of the anode plane.
Abstract: This is a report of the emittance and brightness measurement of an electron beam produced in a pseudospark discharge device driven by a pulse line accelerator A ten-gap pseudospark device was operated at 200 kV, in a nitrogen gas fill pressure of 15 Pa The typical value of emittance was measured to be 47 mn mrad about 5 cm downstream of the anode plane The dependence of the beam current, HWHM emittance, the normalized emittance, and the normalized brightness on the axial distance from the anode were obtained The highest brightness is about 27 × 1012A/(mrad)2 near the anode, and is still higher than 1010A/(mrad)2, 160 mm downstream of the anode Such a high quality electron beam can be used for Raman free electron laser, X ray laser producing, and high power microwave
TL;DR: The present results show that TPA+ at low concentrations may act at prejunctional nerve membranes to enhance release of contractile transmitters and act as a putative K+ channel blocker at postJunctional membranes to increase muscle contractility in rat vas deferens; whilst at high concentrations TPA+.
Abstract: 1. Effects of tetrapentylammonium ions (TPA+) on contractile responses induced by electric field stimulation and by exogenous agonist such as noradrenaline, ATP and high K+ were examined in the isolated epididymal half of the rat vas deferens. 2. The electrically evoked monophasic contractions (0.5 Hz, 1 ms pulse duration, 40 V) were potentiated by TPA+ at low concentrations (1-3 microM) and inhibited by TPA+ at a concentration greater than 10 microM. 3. TPA+ (0.3-3 microM) potentiated the contractile responses induced by noradrenaline and ATP, whilst, TPA+ (10 microM) concentration-dependently reduced the agonist-induced contractions. TEA+ enhanced both electrically evoked and agonist-induced contractions. 4. TPA+ (0.3 microM) potentiated 30 mM K+-induced phasic contraction which was inhibited by pretreatment with alpha,beta-methylene ATP (3 microM) and prazosin (3 microM). 5. TPA+ (10-300 microM) reduced the contractions induced by 100 mM extracellular K+ while TBA+ and TEA+ had no effect. 6. The present results show that TPA+ at low concentrations may act at prejunctional nerve membranes to enhance release of contractile transmitters and act as a putative K+ channel blocker at postjunctional membranes to increase muscle contractility in rat vas deferens; whilst at high concentrations TPA+ mainly acts on smooth muscle probably as a non-selective relaxant against the agonist-induced contraction probably through inhibition of Ca2+ influx; this inhibitory effect appears unique for TPA+ since TEA+ and TBA+ did not induce muscle relaxation.