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Sample records for acetylcholine-induced endothelium-dependent relaxation

  1. Endothelium-dependent relaxation of blood vessels

    SciTech Connect

    Hynes, M.R.

    1987-01-01

    Dilation of blood vessels in response to a large number of agents has been shown to be dependent on an intact vascular endothelium. The present studies examine some aspects of endothelium-dependent vasodilation in blood vessels of the rabbit and rat. Using the rabbit ear artery and the subtype-selective muscarinic antagonist pirenzepine, muscarinic receptors of the endothelium and smooth muscle cells were shown to be of the low affinity M/sub 2/ subtype. Inhibition of (/sup 3/H)(-)quinuclidinyl benzilate was used to determine affinity for the smooth muscle receptors while antagonism of methacholine induced vasodilation yielded the endothelial cell receptor affinity. The effect of increasing age (1-27 months) on endothelium-dependent relaxation was studied in aortic rings, perfused tail artery and perfused mesenteric bed of the Fisher 344 rat. The influence of endothelium on contractile responses was examined using the perfused caudal artery.

  2. Effects of reactive oxygen species and neutrophils on endothelium-dependent relaxation of rat thoracic aorta

    PubMed Central

    Bauer, Viktor; Sotníková, Ružena; Drábiková, Katarína

    2011-01-01

    Reactive oxygen species (ROS) are produced in different metabolic processes including the respiratory burst of neutrophils accompanying local inflammation. The aim of this study was to analyze the effects of N-formyl-methionyl-leucyl-phenylalanine (FMLP)-activated neutrophils, isolated from the guinea pig peritoneal cavity, on isolated rings of a large (conduit) artery, the rat thoracic aorta. FMLP-activated neutrophils enhanced the basal tension increased by α1-adrenergic stimulation. In phenylephrine-precontracted aortae, they elicited marked contraction, while in noradrenaline-precontracted rat aortal rings they caused a biphasic response (contraction-relaxation). To eliminate interaction of activated neutrophils with catecholamines, in the subsequent experiments the basal tension was increased by KCl-induced depolarization. Activated neutrophils evoked a low-amplitude biphasic response (relaxation-contraction) on the KCl-induced contraction. Not only the acetylcholine- and A23187-induced relaxations but also the catalase sensitive hydrogen peroxide (H2O2) elicited contractions were endothelium-dependent. Even though the acetylcholine-induced relaxation was changed by activated neutrophils and by the ROS studied, their effects differed significantly, yet none of them did eliminate fully the endothelium-dependent acetylcholine relaxation. The effect of activated neutrophils resembled the effect of superoxide anion radical (O2 •–) produced by xanthine/xanthine oxidase (X/XO) and differed from the inhibitory effects of Fe2SO4/H2O2-produced hydroxyl radical (•OH) and H2O2. Thus O2 •– produced either by activated neutrophils or X/XO affected much less the endothelium-dependent acetylcholine-activated relaxation mechanisms than did •OH and H2O2. In the large (conduit) artery, the effects of activated neutrophils and various ROS (O2 •–, •OH and H2O2) seem to be more dependent on muscle tension than on endothelial mechanisms. PMID:22319253

  3. Endothelium dependent hyperpolarization-type relaxation compensates for attenuated nitric oxide-mediated responses in subcutaneous arteries of diabetic patients.

    PubMed

    Mokhtar, Siti Safiah; Vanhoutte, Paul M; Leung, Susan Wai Sum; Yusof, Mohd Imran; Wan Sulaiman, Wan Azman; Mat Saad, Arman Zaharil; Suppian, Rapeah; Rasool, Aida Hanum Ghulam

    2016-02-29

    Diabetes impairs endothelium-dependent relaxations. The present study evaluated the contribution of different endothelium-dependent relaxing mechanisms to the regulation of vascular tone in subcutaneous blood vessels of humans with Type 2 diabetes mellitus. Subcutaneous arteries were isolated from tissues of healthy controls and diabetics. Vascular function was determined using wire myography. Expressions of proteins were measured by Western blotting and immunostaining. Endothelium-dependent relaxations to acetylcholine were impaired in arteries from diabetics compared to controls (P = 0.009). Acetylcholine-induced nitric oxide (NO)-mediated relaxations [in the presence of an inhibitor of cyclooxygenases (COX; indomethacin) and small and intermediate conductance calcium-activated potassium channel blockers (UCL1684 and TRAM 34, respectively)] were attenuated in arteries from diabetics compared to controls (P < 0.001). However, endothelium-dependent hyperpolarization (EDH)-type relaxations [in the presence of indomethacin and the NO synthase blocker, l-NAME] were augmented in arteries from diabetics compared to controls (P = 0.003). Endothelium-independent relaxations to sodium nitroprusside (NO donor) and salbutamol (β-adrenoceptor agonist) were preserved, but those to prostacyclin were attenuated in diabetics compared to controls (P = 0.017). In arteries of diabetics, protein expressions of endothelial NO synthase, prostacyclin synthase and prostacyclin receptors were decreased, but those of COX-2 were increased. These findings suggest that in human diabetes, the impairment of endothelium-dependent relaxations is caused by a diminished NO bioavailability; however, EDH appears to compensate, at least in part, for this dysfunction. PMID:26768833

  4. A differential impact of lithium on endothelium-dependent but not on endothelium-independent vessel relaxation.

    PubMed

    Bosche, Bert; Molcanyi, Marek; Noll, Thomas; Rej, Soham; Zatschler, Birgit; Doeppner, Thorsten R; Hescheler, Jürgen; Müller, Daniel J; Macdonald, R Loch; Härtel, Frauke V

    2016-06-01

    Lithium is drug for bipolar disorders with a narrow therapeutic window. Lithium was recently reported to prevent stroke and protect vascular endothelium but tends to accumulate particularly in the brain and kidney. Here, adverse effects are common; however mechanisms are still vaguely understood. If lithium could also negatively influence the endothelium is unclear. We hypothesize that at higher lithium levels, the effects on endothelium reverses--that lithium also impairs endothelial-dependent relaxation of blood vessels. Vessel grafts from de-nerved murine aortas and porcine middle cerebral arteries were preconditioned using media supplemented with lithium chloride or acetate (0.4-100 mmol/L). Native or following phenylephrine-induced vasoconstriction, the relaxation capacity of preconditioned vessels was assessed by isometric myography, using acetylcholine to test the endothelium-dependent or sodium nitroprusside to test the endothelium-independent vasorelaxation, respectively. At the 0.4 mmol/L lithium concentration, acetylcholine-induced endothelium-dependent vessel relaxation was slightly increased, however, diminished in a concentration-dependent manner in vessel grafts preconditioned with lithium at higher therapeutic and supratherapeutic concentrations (0.8-100 mmol/L). In contrast, endothelium-independent vasorelaxation remained unaltered in preconditioned vessel grafts at any lithium concentration tested. Lithium elicits opposing effects on endothelial functions representing a differential impact on the endothelium within the narrow therapeutic window. Lithium accumulation or overdose reduces endothelium-dependent but not endothelium-independent vasorelaxation. The differentially modified endothelium-dependent vascular response represents an additional mechanism contributing to therapeutic or adverse effects of lithium. PMID:26875501

  5. Polydatin Restores Endothelium-Dependent Relaxation in Rat Aorta Rings Impaired by High Glucose: A Novel Insight into the PPARβ-NO Signaling Pathway.

    PubMed

    Wu, Yang; Xue, Lai; Du, Weimin; Huang, Bo; Tang, Cuiping; Liu, Changqing; Qiu, Hongmei; Jiang, Qingsong

    2015-01-01

    Polydatin, a natural component from Polygonum Cuspidatum, has important therapeutic effects on metabolic syndrome. A novel therapeutic strategy using polydatin to improve vascular function has recently been proposed to treat diabetes-related cardiovascular complications. However, the biological role and molecular basis of polydatin's action on vascular endothelial cells (VECs)-mediated vasodilatation under diabetes-related hyperglycemia condition remain elusive. The present study aimed to assess the contribution of polydatin in restoring endothelium-dependent relaxation and to determine the details of its underlying mechanism. By measuring endothelium-dependent relaxation, we found that acetylcholine-induced vasodilation was impaired by elevated glucose (55 mmol/L); however, polydatin (1, 3, 10 μmol/L) could restore the relaxation in a dose-dependent manner. Polydatin could also improve the histological damage to endothelial cells in the thoracic aorta. Polydatin's effects were mediated via promoting the expression of endothelial NO synthase (eNOS), enhancing eNOS activity and decreasing the inducible NOS (iNOS) level, finally resulting in a beneficial increase in NO release, which probably, at least in part, through activation of the PPARβ signaling pathway. The results provided a novel insight into polydatin action, via PPARβ-NO signaling pathways, in restoring endothelial function in high glucose conditions. The results also indicated the potential utility of polydatin to treat diabetes related cardiovascular diseases. PMID:25941823

  6. Inhibition by quinine of endothelium-dependent relaxation of rabbit aortic strips.

    PubMed

    Gebremedhin, D; Hadházy, P; Magyar, K

    1987-12-01

    1 The effects of quinine sulphate, tetramethylammonium chloride (TMA) and tetraethylammonium chloride (TEA) (all blockers of the Ca2+-activated K+ channels) on the relaxations induced by acetylcholine (ACh), calcium ionophore A23187 and sodium nitrite were studied in helical strips of rabbit aorta. 2 The strips were contracted to a moderate stable tone with phenylephrine (10(-7) M). ACh (4 X 10(-9) to 10(-6) M) as well as A23187 (10(-8) to 3 X 10(-7) M) reduced this tone in a concentration- and endothelium-dependent manner. 3 Pretreatment of the tissues with quinine (2.5 X 10(-5) to 10(-4) M) for 60 min produced a concentration-dependent inhibition of the relaxation induced by ACh. Also 90 min incubation of the strips with TMA (3 X 10(-3) to 6.5 X 10(-2) M) or TEA (10(-3) to 3 X 10(-2) M) inhibited the ACh-evoked relaxation in a manner similar to quinine. 4 Quinine (10(-4) M, 60 min), TMA (6.5 X 10(-2) M, 90 min) or TEA (3 X 10(-2) M, 90 min) produced 5 to 10 fold reductions in the relaxant EC50 values of A23187 and ACh and depressed (by 40 to 95%) the maximal relaxations to the ionophore and ACh. 5. On a molar basis, quinine was more effective than the two tetraalkylammonium ions in reducing the endothelium-dependent relaxations of the aortic strips induced by ACh or A23187. The inhibitory actions were reversible after 60 to 90 min washout. 6. Exposure of the strips to either quinine (10-4M, 60 min), TMA (6.5 x 10-2 M, 90 min) or TEA (3 X 10-2 M, 90 min), however, did not influence significantly the relaxations evoked by sodium nitrite, a direct smooth muscle relaxant. 7. These results suggest that stimulation of the Ca2+-activated K' channels could be, at least partially, responsible for the endothelium-dependent relaxations induced by ACh or A23 187. Their activation might not be required for the endothelium-independent relaxant effects of sodium nitrite. PMID:2827827

  7. Lipid Emulsion Attenuates Acetylcholine-Induced Relaxation in Isolated Rat Aorta

    PubMed Central

    Ok, Seong-Ho; Lee, Soo Hee; Yu, Jongsun; Park, Jungchul; Shin, Il-Woo; Lee, Youngju; Cho, Hyunhoo; Choi, Mun-Jeoung; Baik, Jiseok; Hong, Jeong-Min; Han, Jeong Yeol; Lee, Heon Keun; Chung, Young-Kyun; Sohn, Ju-Tae

    2015-01-01

    We investigated the effect of Lipofundin MCT/LCT and Intralipid on acetylcholine-induced nitric oxide- (NO-) mediated relaxation in rat aorta to determine which lipid emulsion (LE) is more potent in terms of inhibition of NO-induced relaxation. Dose-response curves of responses induced by acetylcholine, the calcium ionophore A23187, and sodium nitroprusside were generated using isolated rat aorta with or without LE. The effect of Lipofundin MCT/LCT on acetylcholine-induced endothelial nitric oxide synthase (eNOS) phosphorylation in human umbilical vein endothelial cells (HUVECs) was investigated using western blotting. Lipofundin MCT/LCT (0.1 and 0.2%) attenuated acetylcholine-induced relaxation in endothelium-intact aorta with or without tiron, whereas 0.2% Intralipid only inhibited relaxation. Lipofundin MCT/LCT inhibited relaxation induced by the calcium ionophore A23187 and sodium nitroprusside in endothelium-intact aorta, but Lipofundin MCT/LCT had no effect on sodium nitroprusside-induced relaxation in the endothelium-denuded aorta. Combined pretreatment with l-arginine plus Lipofundin MCT/LCT increased acetylcholine-induced maximal relaxation in endothelium-intact aorta compared with Lipofundin MCT/LCT alone. l-Arginine attenuated Lipofundin MCT/LCT-mediated inhibition of acetylcholine-induced eNOS phosphorylation in HUVECs. Taken together, Lipofundin MCT/LCT attenuated acetylcholine-induced NO-mediated relaxation via an inhibitory effect on the endothelium including eNOS, which is proximal to activation of guanylyl cyclase. PMID:26273653

  8. Laser-induced endothelial damage inhibits endothelium-dependent relaxation in the cerebral microcirculation of the mouse

    SciTech Connect

    Rosenblum, W.I.; Nelson, G.H.; Povlishock, J.T.

    1987-02-01

    This study demonstrates endothelium-dependent relaxation in the surface arterioles of the brain. A helium-neon laser was used to injure endothelium in situ following i.v. injection of Evans blue dye, which sensitizes the bed to the laser. Areas 18 or 36 micron in diameter were injured and no longer relaxed to either 1 ml of acetylcholine chloride or bradykinin triacetate, 80 micrograms/ml delivered for 60 seconds. Dilations to sodium nitroprusside (30 micrograms/ml) were unaffected. Normal responses to nitroprusside, plus electron microscopy, established that vascular smooth muscle was uninjured. Endothelium-dependent relaxation was impaired when only minor ultrastructural damage was present. Dilation was inhibited downstream and upstream as far as 80 micron from the center of the laser beam. This suggests a spread of endothelium injury around the site of laser impact. However, inhibition was somewhat more marked downstream than upstream, implying that a portion of the downstream response was dependent on a substance released from an upstream site. To date, very few studies have reported endothelium-dependent relaxation in vivo, especially in the microcirculation. The present study accomplishes this. Moreover, in contrast to in vitro observations of endothelium-dependent relaxation in large vessels, the in vivo elimination of endothelium-dependent relaxation in the microcirculation required neither removal of endothelium nor injury to large numbers of endothelium cells. Since endothelium-dependent relaxation in the microcirculation has now been demonstrated using three different techniques to injure endothelium, it is reasonable to conclude that the phenomenon is real.

  9. Multiple pathways underlying endothelium-dependent relaxation in the rabbit isolated femoral artery.

    PubMed Central

    Plane, F.; Pearson, T.; Garland, C. J.

    1995-01-01

    1. In isolated segments of the rabbit femoral artery stimulated with noradrenaline, both acetylcholine (1 nM-10 microM) and the calcium ionophore A23187 (1 nM-100 microM) evoked endothelium-dependent smooth muscle relaxation and hyperpolarization while bradykinin (0.01-100 nM) had no effect. 2. The nitric oxide synthase inhibitors, NG-nitro-L-arginine (L-NOARG; 100 microM; 20 min) or NG-nitro-L-arginine methyl ester (L-NAME; 100 microM; 20 min) each abolished the hyperpolarization and the majority of the relaxation to acetylcholine (maximal response reduced from 96.8 +/- 2.3% to 2.0 +/- 1.4%). 3. The potassium channel blocker, glibenclamide (10 microM; 10 min) also abolished the change in membrane potential to acetylcholine but did not modify the smooth muscle relaxation. 4. In contrast, neither L-NAME nor glibenclamide modified the comparable responses of the femoral artery to A23187, which were also unaffected by the cyclo-oxygenase inhibitor, indomethacin (10 microM). 5. In artery segments stimulated with potassium chloride (25 mM), the maximal change in tension and membrane potential evoked by A23187 (100 microM) was significantly reduced from 95.0 +/- 4.5% and 23.0 +/- 2.0 mV to 69.0 +/- 10.1% and 12.0 +/- 1.5 mV, respectively. Under these conditions L-NAME further reduced the relaxation but not the accompanying hyperpolarization to A23187. 6. Endothelium-denuded arterial segments sandwiched with endothelium-intact 'donor' segments gave qualitatively similar relaxant responses to those described above for acetylcholine and A23187.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7647981

  10. Excess L-arginine restores endothelium-dependent relaxation impaired by monocrotaline pyrrole

    SciTech Connect

    Cheng Wei; Oike, Masahiro . E-mail: moike@pharmaco.med.kyushu-u.ac.jp; Hirakawa, Masakazu; Ohnaka, Keizo; Koyama, Tetsuya; Ito, Yushi

    2005-09-15

    The pyrrolizidine alkaloid plant toxin monocrotaline pyrrole (MCTP) causes pulmonary hypertension in experimental animals. The present study aimed to examine the effects of MCTP on the endothelium-dependent relaxation. We constructed an in vitro disease model of pulmonary hypertension by overlaying MCTP-treated bovine pulmonary artery endothelial cells (CPAEs) onto pulmonary artery smooth muscle cell-embedded collagen gel lattice. Acetylcholine (Ach) induced a relaxation of the control CPAEs-overlaid gels that were pre-contracted with noradrenaline, and the relaxation was inhibited by L-NAME, an inhibitor of NO synthase (NOS). In contrast, when MCTP-treated CPAEs were overlaid, the pre-contracted gels did not show a relaxation in response to Ach in the presence of 0.5 mM L-arginine. Expression of endothelial NOS protein, Ach-induced Ca{sup 2+} transients and cellular uptake of L-[{sup 3}H]arginine were significantly smaller in MCTP-treated CPAEs than in control cells, indicating that these changes were responsible for the impaired NO production in MCTP-treated CPAEs. Since cellular uptake of L-[{sup 3}H]arginine linearly increased according to its extracellular concentration, we hypothesized that the excess concentration of extracellular L-arginine might restore NO production in MCTP-treated CPAEs. As expected, in the presence of 10 mM L-arginine, Ach showed a relaxation of the MCTP-treated CPAEs-overlaid gels. These results indicate that the impaired NO production in damaged endothelial cells can be reversed by supplying excess L-arginine.

  11. Endothelium-Dependent Relaxation Effect of Apocynum venetum Leaf Extract via Src/PI3K/Akt Signalling Pathway.

    PubMed

    Lau, Yeh Siang; Ling, Wei Chih; Murugan, Dharmani; Kwan, Chiu Yin; Mustafa, Mohd Rais

    2015-07-01

    Botanical herbs are consumed globally not only as an essential diet but also as medicines or as functional/recreational food supplements. The extract of the Apocynum venetum leaves (AVLE), also known as Luobuma, exerts its antihypertensive effect via dilating the blood vessels in an endothelium- and concentration-dependent manner with optimal effect seen at as low as 10 µg/mL. A commercial Luoboma "antihypertensive tea" is available commercially in the western province of China. The present study seeks to investigate the underlying cellular mechanisms of the nitric oxide (NO)-releasing property of AVLE in rat aortas and human umbilical vein endothelial cells (HUVECs). Endothelium-dependent relaxation induced by AVLE was assessed in organ chambers in the presence or absence of polyethyleneglycol catalase (PP2, 20 µM; inhibitor of Src kinase), wortmannin (30 nM) and LY294002 (20 µM; PI3 (phosphatidylinositol3)-Kinase inhibitor), N(G)-nitro-L-arginine (L-NAME, 100 µM; endothelial NO synthase inhibitor (eNOS)) and ODQ (1 µM; soluble guanylyl cyclase inhibitor). Total nitrite and nitrate (NOx) level and protein expression of p-Akt and p-eNOS were measured. AVLE-induced endothelium-dependent relaxation was reduced by PP2, wortmannin and LY294002 and abolished by L-NAME and ODQ. AVLE significantly increased total NOx level in rat aortas and in HUVECs compared to control. It also instigated phosphorylation of Akt and eNOS in cultured HUVECs in a concentration-dependent manner and this was markedly suppressed by PP2, wortmannin and LY294002. AVLE also inhibited superoxide generated from both NADPH oxidase and xanthine/xanthine oxidase system. Taken together, AVLE causes endothelium-dependent NO mediated relaxations of rat aortas through Src/PI3K/Akt dependent NO signalling pathway and possesses superoxide scavenging activity. PMID:26133970

  12. Polyphenol-enriched extract of oil palm fronds (Elaeis guineensis) promotes vascular relaxation via endothelium-dependent mechanisms.

    PubMed

    Abeywardena, Mahinda; Runnie, Irine; Nizar, Mohd; Suhaila, Momamed; Head, Richard

    2002-01-01

    Plant-based polyphenolic compounds have been reported to possess cardiovascular health benefits. Several dietary sources, including herbs and spices, fruits and vegetables, and tea and wine, contain an array of biologically active compounds that have been shown to be effective in retarding oxidation of low-density lipoproteins (LDL) and promoting vascular relaxation. In the present study four different plant sources, both edible and non-edible, were evaluated for potential activity. Organic extracts enriched in polyphenols were prepared from palm fronds (Elaesis guineensis); lemongrass (Cymbopogon citrates); papaya shoots (Carica papaya) and green chilli (Capsicum frutescenes) and tested for their ability to prevent in vitro oxidation of LDL, and for potential vascular relaxation actions. Rings of rat thoracic aorta and isolated perfused mesenteric vascular beds were mounted in organ baths, contracted using a half-maximal dose of noradrenaline and exposed to cumulative additions of test extracts. Palm frond extract resulted in considerable relaxation (>75%) in both preparations and was found to be endothelium-dependent as removal of endothelium or inhibition of endogenous nitric oxide (NO) led to a total loss in relaxant activity. Lemongrass extract caused a greater relaxation action in the mesenteric preparation compared to aortic rings, and appears to be mediated via NO-independent and non-prostanoid mechanisms. Of the extracts tested, palm fronds also demonstrated the highest antioxidant capacity, as determined by the ferric reducing activity/potential assay, and resulted in a significant delay (P < 0.05) in the oxidation of LDL. Collectively, these preliminary findings lend further support to the potential cardiovascular actions of plant polyphenols and also identify oil palm fronds as containing constituents that promote vascular relaxation via endothelium-dependent mechanisms. PMID:12492636

  13. The DPP-4 inhibitor linagliptin and the GLP-1 receptor agonist exendin-4 improve endothelium-dependent relaxation of rat mesenteric arteries in the presence of high glucose.

    PubMed

    Salheen, S M; Panchapakesan, U; Pollock, C A; Woodman, O L

    2015-04-01

    The aim of the study was to investigate the effects of the DPP-4 inhibitors and GLP-1R agonist, exendin-4 on the mechanism(s) of endothelium-dependent relaxation in rat mesenteric arteries exposed to high glucose concentration (40 mM). Organ bath techniques were employed to investigate vascular endothelial function in rat mesenteric arteries in the presence of normal (11 mM) or high (40 mM) glucose concentrations. Pharmacological tools (1μM TRAM-34, 1μM apamin, 100 nM Ibtx, 100 μM l-NNA, 10 μM ODQ) were used to distinguish between NO and EDHF-mediated relaxation. Superoxide anion levels were assessed by L-012 and lucigenin enhanced-chemiluminescence techniques. Incubation of mesenteric rings with high glucose for 2 h caused a significant increase in superoxide anion generation and a significant impairment of endothelium-dependent relaxation. Exendin-4 and DPP-4 inhibitor linagliptin, but not sitagliptin or vildagliptin, significantly reduced vascular superoxide and improved endothelium-dependent relaxation in the presence of high glucose. The beneficial actions of exendin-4, but not linagliptin, were attenuated by the GLP-1R antagonist exendin fragment (9-39). Further experiments demonstrated that the presence of high glucose impaired the contribution of both nitric oxide and endothelium-dependent hyperpolarisation to relaxation and that linagliptin improved both mechanisms involved in endothelium-dependent relaxation. These findings demonstrate that high glucose impaired endothelium-dependent relaxation can be improved by exendin-4 and linagliptin, likely due to their antioxidant activity and independently of any glucose lowering effect. PMID:25697548

  14. Long-lasting endothelium-dependent relaxation of isolated arteries caused by an extract from the bark of Combretum leprosum

    PubMed Central

    Alves, Francisco das Chagas; Cavalcanti, Paulo Marques da Silva; Passaglia, Rita de Cassia Aleixo Tostes; Ballejo, Gustavo

    2015-01-01

    Objective To describe and to characterize the relaxing effect of an extract of the bark of Combretum leprosum on isolated arterial rings from different animals. Methods Rings (3 to 4mm) from rabbit, rat, or porcine arteries rings were suspended in an organ bath (Krebs, 37°C, 95%O2/5%CO2) to record isometric contractions. After the stabilization period (2 to 3 hours) contractions were induced by the addition of phenylephrine (0.1 to 0.3µM) or U46619 (10 to 100nM), and Combretum leprosum extract was added on the plateau of the contractions. Experiments were performed to determine the potency, duration, reversibility, and to get insights on the potential mechanism involved in extract-induced relaxations. Results In all rings tested, Combretumleprosum extract (1.5μg/mL) was able to cause relaxations, which were strictly endothelium-dependent. In rabbit or rat thoracic aorta rings, the relaxations were reversed by vitamin B12a or L-NG-nitroarginine. In porcine right coronary arteries and rabbit abdominal aorta, extract caused both L-NG-nitroarginine-sensitive and L-NG-nitroarginine-resistant relaxations. In rabbit thoracic aorta, the extract was relatively potent (EC50=0.20µg/mL) and caused relaxations; intriguingly the endothelium continued to produce relaxing factors for a long period after removing the extract. The magnitude of extract-induced relaxations was significantly reduced in the absence of extracellular Ca2+; in addition, the TRPs channels blocker ruthenium red (10µM) was able to revert extract-induced relaxations. Phytochemical analyses indicated that the extract was rich in polyphenol-like reacting substances. Conclusions Combretum leprosum extract contains bioactive compounds capable of promoting Ca2+-dependent stimulation of endothelial cells which results in a prolonged production of relaxing factors. PMID:26466063

  15. Fruit juice-induced endothelium-dependent relaxations in isolated porcine coronary arteries: evaluation of different fruit juices and purees and optimization of a red fruit juice blend.

    PubMed

    Auger, Cyril; Kim, Jong-Hun; Trinh, Sandrine; Chataigneau, Thierry; Popken, Anne M; Schini-Kerth, Valérie B

    2011-05-01

    Numerous studies have indicated that several polyphenol-rich sources such as red wine and green tea are potent inducers of endothelium-dependent relaxations in isolated arteries. As various fruits and berries are known to contain high levels of polyphenols, the aim of the present study was to assess the ability of selected pure fruit juices and purees as well as blends to cause endothelium-dependent relaxations in isolated arteries. Vascular reactivity was assessed using porcine coronary artery rings, and fruit juices, purees and blends were characterized for their content in vitamin C, total phenolic, sugar and antioxidant activity. Fruit juices and purees caused variable concentration-dependent relaxations, with blackcurrant, aronia, cranberry, blueberry, lingonberry, and grape being the most effective fruits. Several blends of red fruits caused endothelium-dependent relaxations. Relaxations to blend D involved both a NO- and an EDHF-mediated components. The present findings indicate that some berries and blends of red fruit juices are potent inducers of endothelium-dependent relaxations in the porcine coronary artery. This effect involves both endothelium-derived NO and EDHF, and appears to be dependent on their polyphenolic composition rather than on the polyphenolic content. PMID:21779562

  16. Impaired endothelium-dependent and -independent relaxation of aorta from diabetic rats.

    PubMed

    Yakubu, M A; Sofola, O A; Igbo, I; Oyekan, A O

    2012-01-01

    Vascular complication in diabetes has been reported to be due to the effects of chronic high blood glucose on the vascular system. Different relaxation mechanisms exist in the vasculature and effect of chronic high glucose on vascular relaxation mechanisms is not clearly understood. We assessed the effect of streptozotocin (STZ, 70 mg/kg, for 12 wks)-induced diabetes on vascular reactivity to isoproterenol (Isop, 10-9-10-5 M), a cAMP-dependent agent, acetylcholine (ACh, 10-9-10-5 M), a stimulant of NO (nitric oxide) synthase, sodium nitroprusside (SNP, 10-10-10-5 M), NO donor, or bradykinin (BK, 10-9-10-5 M) in the rat isolated aortic ring. Isop, ACh, SNP, or BK dose-dependently relaxed phenylephrine (PE, 10-7 M) pre-constricted ring producing a maximum relaxation of 82 % for Isop (10-5 M), 85 % for ACh (10-5 M), 100 % for SNP (10-6 M), and 30 % for BK (10-5 M) respectively. STZ attenuated Isop, ACh, and BK-induced relaxation by 45 % (n=7, pn (Fig. 5, Ref. 24). PMID:22394031

  17. Marginal copper deficiency impairs endothelium-dependent relaxation responses across two generations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The generational effects of marginal copper (Cu) deficiency on vascular function have not been characterized.In this study, the vascular consequences of marginal Cu deficiency were determined by relaxation responses in mesenteric arteries of dams and two generations of offspring. Pups from dams (fir...

  18. Paullinia pinnata extracts rich in polyphenols promote vascular relaxation via endothelium-dependent mechanisms.

    PubMed

    Zamble, Alexis; Carpentier, Marie; Kandoussi, Abdelmejid; Sahpaz, Sevser; Petrault, Olivier; Ouk, Tawarak; Hennuyer, Nathalie; Fruchart, Jean-Charles; Staels, Bart; Bordet, Régis; Duriez, Patrick; Bailleul, François; Martin-Nizard, Françoise

    2006-04-01

    Paullinia pinnata L. (Sapindaceae) is an African tropical plant whose roots and leaves are used in traditional medicine for many purposes, especially for erectile dysfunction, but its action mechanism is unknown. P. pinnata root and leaf methanolic extracts are rich in phenolic compounds. This study shows that both extracts are highly antioxidative and induce a slight transcriptional activity of peroxisome proliferator activated receptor-alpha. They also increased and decreased endothelial nitric oxide synthase and endothelin-1 mRNA levels in bovine aortic endothelial cells, respectively. In this study P. pinnata methanolic extracts in cumulative doses elicited in a dose-dependent manner the relaxation of phenylephrine precontracted isolated rat aortic rings. N-nitro-L-arginine methyl ester significantly attenuated the capacity of both extracts to induce arterial relaxation, indicating that this arterial relaxation was mediated by endothelial nitric oxide release. It could be suggested that the arterial relaxation induced by both extracts could be mainly linked to their capacities to inhibit nitric oxide oxidation through their antioxidant properties. PMID:16680075

  19. Role of arachidonic acid lipoxygenase metabolites in acetylcholine-induced relaxations of mouse arteries.

    PubMed

    Gauthier, Kathryn M; Goldman, Daniel H; Aggarwal, Nitin T; Chawengsub, Yuttana; Falck, J R; Campbell, William B

    2011-03-01

    immunoblot analysis and RT-PCR of the aorta and mesenteric arteries demonstrated protein and mRNA expression of leukocyte-type 12/15-LO. Thus, in mouse resistance arteries, 12/15-LO AA metabolites mediate endothelium-dependent relaxations to ACh and AA. PMID:21193584

  20. Involvement of histamine in endothelium-dependent relaxation of mesenteric lymphatic vessels

    PubMed Central

    Nizamutdinova, Irina Tsoy; Maejima, Daisuke; Nagai, Takashi; Bridenbaugh, Eric; Thangaswamy, Sangeetha; Chatterjee, Victor; Meininger, Cynthia J.; Gashev, Anatoliy A.

    2014-01-01

    Objectives The knowledge of the basic principles of lymphatic function, still remains, to a large degree, rudimentary and will require significant research efforts. Recent studies of the physiology of the mesenteric lymphatic vessels (MLVs) suggested the presence of an endothelium-derived relaxing factor (EDRF) other than nitric oxide. In this study we tested the hypothesis that lymphatic endothelium-derived histamine relaxes MLVs. Methods We measured and analyzed parameters of lymphatic contractility in isolated and pressurized rat mesenteric lymphatic vessels under control conditions and after pharmacological blockade of nitric oxide by Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME, 100 μM) or/and histamine production by α-methyl-DL-histidine dihydrochloride (α-MHD, 10 μM). Effectiveness of α-MHD was confirmed immunohistochemically. We also used immunohistochemical labeling and western blot analysis of the histamine-producing enzyme, histidine decarboxylase (HDC). Additionally we blocked HDC protein expression in MLVs by transient transfection with vivo-morpholino oligos. Results We found that only combined pharmacological blockade of nitric oxide and histamine production completely eliminates flow-dependent relaxation of lymphatic vessels, thus confirming a role for histamine as an EDRF in MLVs. We also confirmed the presence of histidine decarboxylase and histamine inside lymphatic endothelial cells. Conclusions Our study supports a role for histamine as an EDRF in MLVs. PMID:24750494

  1. Brazilin isolated from the heartwood of Caesalpinia sappan L induces endothelium-dependent and -independent relaxation of rat aortic rings

    PubMed Central

    Yan, Yu; Chen, Yu-cai; Lin, Yi-huang; Guo, Jing; Niu, Zi-ran; Li, Li; Wang, Shou-bao; Fang, Lian-hua; Du, Guan-hua

    2015-01-01

    Aim: Brazilin is one of the major constituents of Caesalpinia sappan L with various biological activities. This study sought to investigate the vasorelaxant effect of brazilin on isolated rat thoracic aorta and explore the underlying mechanisms. Methods: Endothelium-intact and -denuded aortic rings were prepared from rats. The tension of the preparations was recorded isometrically with a force displacement transducer connected to a polygraph. The phosphorylation levels of ERK1/2 and myosin light chain (MLC) were analyzed using Western blotting assay. Results: Application of brazilin (10–100 μmol/L) dose-dependently relaxed the NE- or high K+-induced sustained contraction of endothelium-intact aortic rings (the EC50 was 83.51±5.6 and 79.79±4.57 μmol/L, respectively). The vasorelaxant effect of brazilin was significantly attenuated by endothelium removal or by pre-incubation with L-NAME, methylene blue or indomethacin. In addition, pre-incubation with brazilin dose-dependently attenuated the vasoconstriction induced by KCl, NE or Ang II. Pre-incubation with brazilin also markedly suppressed the high K+-induced extracellular Ca2+ influx and NE-induced intracellular Ca2+ release in endothelium-denuded aortic rings. Pre-incubation with brazilin dose-dependently inhibited the NE-stimulated phosphorylation of ERK1/2 and MLC in both endothelium-intact and -denuded aortic rings. Conclusion: Brazilin induces relaxation in rat aortic rings via both endothelium-dependent and -independent ways as well as inhibiting NE-stimulated phosphorylation of ERK1/2 and MLC. Brazilin also attenuates vasoconstriction via blocking voltage- and receptor-operated Ca2+ channels. PMID:26564314

  2. The impairment of endothelium-dependent arterial relaxation by7-ketocholesterol is associated with an early activation of protein kinase C

    PubMed Central

    Deckert, Valérie; Duverneuil, Linda; Poupon, Sandrine; Monier, Serge; Le Guern, Naig; Lizard, Gérard; Masson, David; Lagrost, Laurent

    2002-01-01

    Among components of oxidized low density lipoproteins, cholesterol derivatives oxidized in position 7 inhibit endothelium-dependent arterial relaxation by decreasing the release of the main endothelium-derived relaxing factor, nitric oxide (NO). The aim of the present study was to bring new insights into the molecular mechanism by which 7-ketocholesterol can block the endothelium-dependent arterial relaxation. Superoxide dismutase did not prevent the inhibitory effect of 7-ketocholesterol on endothelium-dependent relaxation, and consistent observations were made whether superoxide dismutase was conjugated or not to polyethylene glycol. In addition, neither glutathione supplementation, nor oxypurinol, i.e. a xanthine oxidase inhibitor could reverse the effect of 7-ketocholesterol, indicating that NO was not inactivated by superoxide anion. A direct alteration of the activity of the calcium-dependent NO synthase could also be ruled out, since identical relaxing effects of the calcium ionophore A23187 were observed whether arterial rings were treated or not with 7-ketocholesterol. Whereas the above observations come in support of an early, inhibitory action of 7-ketocholesterol, the specific blockade of one given subtype of membrane receptors could be discarded, and similar inhibitions were observed when either muscarinic or purinergic receptors were stimulated. Finally, the blockade of protein kinase C activity by chelerythrine arose as the sole relevant tool in preventing the effect of 7-ketocholesterol on the endothelium-dependent relaxation of rabbit aortic rings. In addition, complementary studies on cultured bovine aortic endothelial cells came in direct support of the ability of 7-ketocholesterol to activate PKC. In conclusion, 7-ketocholesterol that is present in human hypercholesterolaemic plasma, in atherosclerotic arteries, and in many processed foods can block the release of NO by vascular endothelial cells through its ability to activate PKC. PMID

  3. Endothelium-dependent relaxation and hyperpolarization evoked by bradykinin in canine coronary arteries: enhancement by exercise-training.

    PubMed Central

    Mombouli, J. V.; Nakashima, M.; Hamra, M.; Vanhoutte, P. M.

    1996-01-01

    bradykinin were also shifted to the left by perindoprilat. The shift induced by the ACE-inhibitor in either type of preparation was not significantly different. 8. These findings demonstrate that exercise-training augments the sensitivity of the coronary artery of the dog to the endothelium-dependent effects of bradykinin. This sensitization to bradykinin may reflect an increased role of both NO and EDHF, and is not the consequence of differences in ACE activity in the receptor compartment. PMID:8821528

  4. Aronia melanocarpa juice, a rich source of polyphenols, induces endothelium-dependent relaxations in porcine coronary arteries via the redox-sensitive activation of endothelial nitric oxide synthase.

    PubMed

    Kim, Jong Hun; Auger, Cyril; Kurita, Ikuko; Anselm, Eric; Rivoarilala, Lalainasoa Odile; Lee, Hyong Joo; Lee, Ki Won; Schini-Kerth, Valérie B

    2013-11-30

    This study examined the ability of Aronia melanocarpa (chokeberry) juice, a rich source of polyphenols, to cause NO-mediated endothelium-dependent relaxations of isolated coronary arteries and, if so, to determine the underlying mechanism and the active polyphenols. A. melanocarpa juice caused potent endothelium-dependent relaxations in porcine coronary artery rings. Relaxations to A. melanocarpa juice were minimally affected by inhibition of the formation of vasoactive prostanoids and endothelium-derived hyperpolarizing factor-mediated responses, and markedly reduced by N(ω)-nitro-l-arginine (endothelial NO synthase (eNOS) inhibitor), membrane permeant analogs of superoxide dismutase and catalase, PP2 (Src kinase inhibitor), and wortmannin (PI3-kinase inhibitor). In cultured endothelial cells, A. melanocarpa juice increased the formation of NO as assessed by electron paramagnetic resonance spectroscopy using the spin trap iron(II)diethyldithiocarbamate, and reactive oxygen species using dihydroethidium. These responses were associated with the redox-sensitive phosphorylation of Src, Akt and eNOS. A. melanocarpa juice-derived fractions containing conjugated cyanidins and chlorogenic acids induced the phosphorylation of Akt and eNOS. The present findings indicate that A. melanocarpa juice is a potent stimulator of the endothelial formation of NO in coronary arteries; this effect involves the phosphorylation of eNOS via the redox-sensitive activation of the Src/PI3-kinase/Akt pathway mostly by conjugated cyanidins and chlorogenic acids. PMID:23973200

  5. Is the presence of hyperlipidemia associated with impairment of endothelium-dependent neointimal relaxation after percutaneous transluminal coronary angioplasty?

    PubMed

    Sakai, A; Hirayama, A; Adachi, T; Nanto, S; Hori, M; Inoue, M; Kamada, T; Kodama, K

    1996-01-01

    To determine whether hyperlipidemia affects the endothelium-dependent vasomotor response along the dilated vessel after percutaneous transluminal coronary angioplasty (PTCA), we evaluated 32 patients with one-vessel disease, 3-6 months after successful PTCA without restenosis. Fourteen patients had mild stenotic lesions not subjected to PTCA (non-PTCA sites) in addition to the PTCA sites. Vessel diameter changes at 32 PTCA and 36 non-PTCA sites were assessed by quantitative angiography, before and after intracoronary injection of acetylcholine (20 micrograms to the right and 50 micrograms to the left coronary artery) and of nitroglycerin (0.1-0.3 mg). The acetylcholine response ranged from 46% (dilation) to -100% (constriction). All coronary arteries were dilated in response to nitroglycerin, which suggested preservation of the function of vascular smooth muscle, and the presence of an abnormality in endothelial function in those patients with a constrictor response to acetylcholine. There was a negative correlation between the acetylcholine response and the serum total cholesterol level at PTCA sites (r = -0.37; P = 0.038) and at non-PTCA sites (r = -0.46; P = 0.005). These findings indicate that hyperlipidemia is associated with a loss of endothelium-dependent vasodilation, not only at non-PTCA but also at PTCA sites, at which restoration of endothelial function might have occurred. They also suggest that hyperlipidemia may be related to the functional state of the regenerated endothelium at sites where PTCA had been previously performed. PMID:9129246

  6. Vascular Protective Effect of an Ethanol Extract of Camellia japonica Fruit: Endothelium-Dependent Relaxation of Coronary Artery and Reduction of Smooth Muscle Cell Migration

    PubMed Central

    Park, Sin-Hee; Shim, Bong-Sup; Yoon, Jun-Seong; Lee, Hyun-Ho; Lee, Hye-Won; Yoo, Seok-Bong; Wi, An-Jin; Park, Whoa-Shig; Kim, Hyun-Jung; Kim, Dong-Wok; Oak, Min-Ho

    2016-01-01

    Camellia japonica is a popular garden plant in Asia and widely used as cosmetic sources and traditional medicine. However, the possibility that C. japonica affects cardiovascular system remains unclear. The aim of the present study was to evaluate vascular effects of an extract of C. japonica. Vascular reactivity was assessed in organ baths using porcine coronary arteries and inhibition of proliferation and migration were assessed using human vascular smooth muscle cells (VSMCs). All four different parts, leaf, stem, flower, and fruits, caused concentration-dependent relaxations and C. japonica fruit (CJF) extract showed the strongest vasorelaxation and its effect was endothelium dependent. Relaxations to CJF were markedly reduced by inhibitor of endothelial nitric oxide synthase (eNOS) and inhibitor of PI3-kinase, but not affected by inhibitor of cyclooxygenase and endothelium-derived hyperpolarizing factor-mediated response. CJF induced activated a time- and concentration-dependent phosphorylation of eNOS in endothelial cells. Altogether, these studies have demonstrated that CJF is a potent endothelium-dependent vasodilator and this effect was involved in, at least in part, PI3K-eNOS-NO pathway. Moreover, CJF attenuated TNF-α induced proliferation and PDGF-BB induced migration of VSMCs. The present findings indicate that CJF could be a valuable candidate of herbal medicine for cardiovascular diseases associated with endothelial dysfunction and atherosclerosis. PMID:26697138

  7. Vascular Protective Effect of an Ethanol Extract of Camellia japonica Fruit: Endothelium-Dependent Relaxation of Coronary Artery and Reduction of Smooth Muscle Cell Migration.

    PubMed

    Park, Sin-Hee; Shim, Bong-Sup; Yoon, Jun-Seong; Lee, Hyun-Ho; Lee, Hye-Won; Yoo, Seok-Bong; Wi, An-Jin; Park, Whoa-Shig; Kim, Hyun-Jung; Kim, Dong-Wok; Oak, Min-Ho

    2015-01-01

    Camellia japonica is a popular garden plant in Asia and widely used as cosmetic sources and traditional medicine. However, the possibility that C. japonica affects cardiovascular system remains unclear. The aim of the present study was to evaluate vascular effects of an extract of C. japonica. Vascular reactivity was assessed in organ baths using porcine coronary arteries and inhibition of proliferation and migration were assessed using human vascular smooth muscle cells (VSMCs). All four different parts, leaf, stem, flower, and fruits, caused concentration-dependent relaxations and C. japonica fruit (CJF) extract showed the strongest vasorelaxation and its effect was endothelium dependent. Relaxations to CJF were markedly reduced by inhibitor of endothelial nitric oxide synthase (eNOS) and inhibitor of PI3-kinase, but not affected by inhibitor of cyclooxygenase and endothelium-derived hyperpolarizing factor-mediated response. CJF induced activated a time- and concentration-dependent phosphorylation of eNOS in endothelial cells. Altogether, these studies have demonstrated that CJF is a potent endothelium-dependent vasodilator and this effect was involved in, at least in part, PI3K-eNOS-NO pathway. Moreover, CJF attenuated TNF-α induced proliferation and PDGF-BB induced migration of VSMCs. The present findings indicate that CJF could be a valuable candidate of herbal medicine for cardiovascular diseases associated with endothelial dysfunction and atherosclerosis. PMID:26697138

  8. Chicago sky blue and a helium neon laser abolish endothelium dependent relaxation in vivo in the microcirculation

    SciTech Connect

    Nishimura, H.; Nelson, G.H.; Rosenblum, W.I. )

    1989-12-01

    Chicago sky blue, also known as Niagara sky blue, is a vital dye that can successfully be used as an intravascular energy absorbing target for the light from a helium-neon (HeNe) laser. The result of this light/dye interaction is endothelium damage which can be controlled by adjusting the duration of the laser exposure and the amount of dye injected intravenously. The endothelial damage probably is the result of the heat generated by the dyes absorption of energy at the interface between plasma and endothelium. The most minimal damage resulted in selective loss of the dilation normally produced by acetylcholine and bradykinin, two endothelium dependent dilators. The dilation produced by sodium nitroprusside, a dilator acting directly on vascular smooth muscle, was preserved. More severe injury (i.e. more prolonged exposure to light and/or more dye), resulted in local platelet aggregation at the site of laser impact.

  9. The ent-15α-Acetoxykaur-16-en-19-oic Acid Relaxes Rat Artery Mesenteric Superior via Endothelium-Dependent and Endothelium-Independent Mechanisms

    PubMed Central

    Ribeiro, Êurica Adélia Nogueira; Herculano, Edla de Azevedo; da Costa, Cintia Danieli Ferreira; Furtado, Fabiola Fialho; da-Cunha, Emídio Vasconcelos Leitão; Barbosa-Filho, José Maria; da Silva, Marcelo Sobral; de Medeiros, Isac Almeida

    2012-01-01

    The objective of the study was to investigate the mechanism of the relaxant activity of the ent-15α-acetoxykaur-16-en-19-oic acid (KA-acetoxy). In rat mesenteric artery rings, KA-acetoxy induced a concentration-dependent relaxation in vessels precontracted with phenylephrine. In the absence of endothelium, the vasorelaxation was significantly shifted to the right without reduction of the maximum effect. Endothelium-dependent relaxation was significantly attenuated by pretreatment with L-NAME, an inhibitor of the NO-synthase (NOS), indomethacin, an inhibitor of the cyclooxygenase, L-NAME + indomethacin, atropine, a nonselective antagonist of the muscarinic receptors, ODQ, selective inhibitor of the guanylyl cyclase enzyme, or hydroxocobalamin, a nitric oxide scavenger. The relaxation was completely reversed in the presence of L-NAME + 1 mM L-arginine or L-arginine, an NO precursor. Diterpene-induced relaxation was not affected by TEA, a nonselective inhibitor of K+ channels. The KA-acetoxy antagonized CaCl2-induced contractions in a concentration-dependent manner and also inhibited an 80 mM KCl-induced contraction. The KA-acetoxy did not interfere with Ca2+ release from intracellular stores. The vasorelaxant induced by KA-acetoxy seems to involve the inhibition of the Ca2+ influx and also, at least in part, by endothelial muscarinic receptors activation, NO and PGI2 release. PMID:23346202

  10. Increased Superoxide Anions Level may be Related with Impaired Endothelium-Dependent Relaxation of Cerebral and Carotid Arteries in Simulated Microgravity Rats

    NASA Astrophysics Data System (ADS)

    Ma, Jin; Zhang, Ran; Ren, Xin-Ling

    2008-06-01

    Our previous works showed that there is a significant increase in nitrite and nitrate content of cerebral and carotid arteries of hindlimb unweighting rats, and this result suggests that NOS activity or NO production may be increased by HU in the cerebral and carotid arteries ,and this may result in a enhanced endothelium-dependent dilatory responses in these artery of hindlimb unweighting rats. The aim of this work is to investigate the effects of hindlimb unweighting on endothelium mediated relaxation and find the possible mechanisms which may result in the alteration. Twenty male healthy SD rats, which body weight ranged from 250g to 280g, were divided into control and hindlimb unweighting simulated microgravity groups randomly. After three weeks, the basilar artery and carotid artery were isolated and arterial dilatory responsiveness were examined in vitro using isolated arterial rings from rats. And the Superoxide Anions Levels were detected by oxidation-sensitive dye dihydroethidium and laser scanning confocal microscope. The data showed: Dilatory responses of both basilar and carotid arterial rings to Acetylcholine(10-10~10-4 mol/L ) was decreased in simulated microgravity rats as compared with that of controls, but dilatory responses of isolated arterial rings to Sodium Nitroprussid (10-10~10-4 mol/L ) was similar in both simulated Microgravity rats and control rats, and stronger superoxide anions signals were detected in basilar and carotid arteries from HU rats, while compared with that of control rats. These results indicate that endothelium-dependent relaxation of both basilar artery and carotid artery have been diminished by 3-week hindlimb unweighting, and increased superoxide anions levels may contribute to this alteration.

  11. 17β-estradiol potentiates endothelium-dependent nitric oxide- and hyperpolarization-mediated relaxations in blood vessels of male but not female apolipoprotein-E deficient mice.

    PubMed

    Kong, Billy W C; Vanhoutte, Paul M; Man, Ricky Y K; Leung, Susan W S

    2015-08-01

    The present study investigated the influence of gender on the changes underlying endothelial dysfunction in hyperlipidemia during aging. Isometric tension in rings (with endothelium) of the aortae and superior mesenteric arteries from apolipoprotein-E deficient mice was determined in wire myographs. Nitric oxide (NO)- and endothelium-dependent hyperpolarization (EDH)-mediated relaxations were smaller in the aortae and mesenteric arteries of 32weeks old males than eight weeks old males. In females, NO- and EDH-mediated relaxations were impaired only at 84weeks of age. The levels of reactive oxygen species were elevated in the blood vessels of 32weeks old males, but not females. Acute in vitro treatment with 17β-estradiol and apocynin improved NO- and EDH-mediated relaxations in 32weeks old males but not in 84weeks old males. Relaxations to SKA-31, activator of intermediate (IKCa) and small (SKCa) conductance calcium-activated potassium channels, were attenuated in the mesenteric arteries of 32weeks old males. Such impairment was restored by acute treatment with apocynin. These findings suggest that male hyperlipidemic mice develop endothelial dysfunction at an earlier age than females. This endothelial dysfunction is associated with impaired NO bioavailability and reduced IKCa and SKCa activity. Apocynin and 17β-estradiol restore the endothelial function only in younger male animals but not in older male or female animals. PMID:25869512

  12. Role of membrane potential in endothelium-dependent relaxation of guinea-pig coronary arterial smooth muscle.

    PubMed

    Parkington, H C; Tonta, M A; Coleman, H A; Tare, M

    1995-04-15

    1. Membrane potential and tension were measured simultaneously in ring segments of main coronary artery of guinea-pigs. The synthetic thromboxane A2 analogue U46619 depolarized the tissues from -58 +/- 2 to -40 +/- 1 mV and increased tension by 12 +/- 1 mN mm-1. Nitric oxide (NO) and Iloprost, the stable analogue of prostacyclin, evoked hyperpolarization and relaxation. 2. The concentration of NO required to evoke half-maximal hyperpolarization (EC50 of 2 x 10(-5) M) was 40-fold higher than that which was required to induce relaxation (EC50 of 5 x 10(-7) M). The EC50 for Iloprost-induced hyperpolarization (3 x 10(-8) M) was similar to that for relaxation (4 x 10(-8) M). 3. Glibenclamide (10(-6) M) abolished the hyperpolarization in response to both NO and Iloprost but was without effect on the amplitudes of the relaxations over the complete concentration-response curves. 4. Acetylcholine evoked concentration-dependent hyperpolarization and relaxation in the presence of N omega-nitro-L-arginine methyl ester (NAME; 10(-5) M) and indomethacin (10(-6) M), and these responses were attributed to endothelium-derived hyperpolarizing factor (EDHF). The hyperpolarization produced by EDHF always preceded relaxation, and relaxation never occurred at concentrations of acetylcholine that were insufficient to evoke hyperpolarization. 5. The concentration-hyperpolarization and concentration-relaxation curves in response to acetylcholine were not affected by glibenclamide or barium (1-3 mM) but were shifted to the right 4- and 5-fold, respectively, by 1 mM tetraethylammonium. The hyperpolarization and relaxation evoked by acetylcholine were also reduced in a parallel manner when the potassium concentration in the superfusate was increased. 6. Hyperpolarizing current steps, applied to spiral strips of coronary artery denuded of endothelium and depolarized and constricted with U46619, caused relaxation. The relationship between hyperpolarization and relaxation evoked electronically

  13. Endothelium-dependent relaxation to acetylcholine in bovine oviductal arteries: mediation by nitric oxide and changes in apamin-sensitive K+ conductance.

    PubMed Central

    García-Pascual, A.; Labadía, A.; Jimenez, E.; Costa, G.

    1995-01-01

    1. Mechanisms underlying the relaxant response to acetylcholine (ACh) were examined in bovine oviductal arteries (o.d. 300-500 microns and i.d. 150-300 microns) in vitro. Vascular rings were treated with indomethacin (10 microM) to prevent the effects of prostaglandins. 2. ACh elicited a concentration-related relaxation in ring segments precontracted with noradrenaline (NA), which was abolished by endothelium denudation. 3. The ACh-induced relaxation was attenuated but not abolished by NG-nitro-L-arginine (L-NOARG, 1 microM-1 mM), an inhibitor of nitric oxide (NO) formation. The inhibition caused by L-NOARG (10 microM) was reversed by addition of excess of L-arginine but not D-arginine (1 mM). 4. In high K+ (40-60 mM)-contracted rings, ACh was a much less effective vasodilator and its relaxant response was completely abolished by L-NOARG (100 microM). 5. In NA (10 microM)-contracted rings, ACh induced sustained and concentration-dependent increases in cyclic GMP, which were reduced below basal values by L-NOARG (100 microM), while potent relaxation persisted. Similar increases in cyclic GMP were evoked by ACh in high K+ (50 mM)-treated arteries and under these conditions, both cyclic GMP accumulation and relaxation were L-NOARG-sensitive. 6. S-nitroso-L-cysteine (NC), a proposed endogenous precursor of endothelial NO, also induced cyclic GMP accumulation in NA-contracted oviductal arteries. 7. Methylene blue (MB, 10 microM), a proposed inhibitor of soluble guanylate cyclase, inhibited both endothelium-dependent relaxation to ACh and endothelium-independent response to exogenous NO, whereas relaxation to NC remained unaffected. 8. The L-NOARG-resistant response to ACh was not affected by either ouabain (0.5 mM), glibenclamide (3 microM), tetraethylammonium (TEA, 1 mM) or charybdotoxin (50 nM), but was selectively blocked by apamin (0.1-1 microM). However, apamin did not inhibit either relaxation to ACh in high K(+)-contracted rings or endothelium

  14. Ultrasonic Measurement of Change in Elasticity due to Endothelium Dependent Relaxation Response by Accurate Detection of Artery-Wall Boundary

    NASA Astrophysics Data System (ADS)

    Kaneko, Takuya; Hasegawa, Hideyuki; Kanai, Hiroshi

    2007-07-01

    Ross hypothesized that an endothelial dysfunction is considered to be an initial step in atherosclerosis. Endothelial cells, which release nitric oxide (NO) in response to shear stress from blood flow, have a function of relaxing smooth muscle in the media of the arterial wall. For the assessment of the endothelial function, there is a conventional method in which the change in the diameter of the brachial artery caused by flow-mediated dilation (FMD) is measured with ultrasound. However, despite the fact that the collagen-rich hard adventitia does not respond to NO, the conventional method measures the change in diameter depending on the mechanical property of the entire wall including the adventitia. Therefore, we developed a method of measuring the change in the thickness and the elasticity of the brachial artery during a cardiac cycle using the phased tracking method for the evaluation of the mechanical property of only the intima-media region. In this study, the initial positions of echoes from the lumen-intima and media-adventitia boundaries are determined using complex template matching to accurately estimate the minute change in the thickness and the elasticity of the brachial and radial arteries. The ambiguity in the determination of such boundaries was eliminated using complex template matching, and the change in elasticity measured by the proposed method was larger than the change in inner diameter obtained by the conventional method.

  15. Tocotrienol Rich Palm Oil Extract Is More Effective Than Pure Tocotrienols at Improving Endothelium-Dependent Relaxation in the Presence of Oxidative Stress

    PubMed Central

    Ali, Saher F.; Woodman, Owen L.

    2015-01-01

    Oxidative endothelial dysfunction is a critical initiator of vascular disease. Vitamin E is an effective antioxidant but attempts to use it to treat vascular disorders have been disappointing. This study investigated whether tocotrienols, the less abundant components of vitamin E compared to tocopherols, might be more effective at preserving endothelial function. Superoxide generated by hypoxanthine/xanthine oxidase or rat aorta was measured using lucigenin-enhanced chemiluminescence. The effect of α-tocopherol, α-, δ-, and γ-tocotrienols and a tocotrienol rich palm oil extract (tocomin) on levels of superoxide was assessed. Endothelial function in rat aorta was assessed in the presence of the auto-oxidant pyrogallol. Whilst all of the compounds displayed antioxidant activity, the tocotrienols were more effective when superoxide was produced by hypoxanthine/xanthine oxidase whereas tocomin and α-tocopherol were more effective in the isolated aorta. Tocomin and α-tocopherol restored endothelial function in the presence of oxidant stress but α-, δ-, and γ-tocotrienols were ineffective. The protective effect of tocomin was replicated when the tocotrienols were present with, but not without, α-tocopherol. Tocotrienol rich tocomin is more effective than α-tocopherol at reducing oxidative stress and restoring endothelium-dependent relaxation in rat aortae and although α-, δ-, and γ-tocotrienols effectively scavenged superoxide, they did not improve endothelial function. PMID:26075031

  16. Beneficial effects of calcitriol on hypertension, glucose intolerance, impairment of endothelium-dependent vascular relaxation, and visceral adiposity in fructose-fed hypertensive rats.

    PubMed

    Chou, Chu-Lin; Pang, Cheng-Yoong; Lee, Tony J F; Fang, Te-Chao

    2015-01-01

    Besides regulating calcium homeostasis, the effects of vitamin D on vascular tone and metabolic disturbances remain scarce in the literature despite an increase intake with high-fructose corn syrup worldwide. We investigated the effects of calcitriol, an active form of vitamin D, on vascular relaxation, glucose tolerance, and visceral fat pads in fructose-fed rats. Male Wistar-Kyoto rats were divided into 4 groups (n = 6 per group). Group Con: standard chow diet for 8 weeks; Group Fru: high-fructose diet (60% fructose) for 8 weeks; Group Fru-HVD: high-fructose diet as Group Fru, high-dose calcitriol treatment (20 ng / 100 g body weight per day) 4 weeks after the beginning of fructose feeding; and Group Fru-LVD: high-fructose diet as Group Fru, low-dose calcitriol treatment (10 ng / 100 g body weight per day) 4 weeks after the beginning of fructose feeding. Systolic blood pressure was measured twice a week by the tail-cuff method. Blood was examined for serum ionized calcium, phosphate, creatinine, glucose, triglycerides, and total cholesterol. Intra-peritoneal glucose intolerance test, aortic vascular reactivity, the weight of visceral fat pads, adipose size, and adipose angiotensin II levels were analyzed at the end of the study. The results showed that the fructose-fed rats significantly developed hypertension, impaired glucose tolerance, heavier weight and larger adipose size of visceral fat pads, and raised adipose angiotensin II expressions compared with the control rats. High- and low-dose calcitriol reduced modestly systolic blood pressure, increased endothelium-dependent aortic relaxation, ameliorated glucose intolerance, reduced the weight and adipose size of visceral fat pads, and lowered adipose angiotensin II expressions in the fructose-fed rats. However, high-dose calcitriol treatment mildly increased serum ionized calcium levels (1.44 ± 0.05 mmol/L). These results suggest a protective role of calcitriol treatment on endothelial function, glucose

  17. Transient Receptor Potential Channel Opening Releases Endogenous Acetylcholine, which Contributes to Endothelium-Dependent Relaxation Induced by Mild Hypothermia in Spontaneously Hypertensive Rat but Not Wistar-Kyoto Rat Arteries.

    PubMed

    Zou, Q; Leung, S W S; Vanhoutte, P M

    2015-08-01

    Mild hypothermia causes endothelium-dependent relaxations, which are reduced by the muscarinic receptor antagonist atropine. The present study investigated whether endothelial endogenous acetylcholine contributes to these relaxations. Aortic rings of spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats were contracted with prostaglandin F2 α and exposed to progressive mild hypothermia (from 37 to 31°C). Hypothermia induced endothelium-dependent, Nω-nitro-l-arginine methyl ester-sensitive relaxations, which were reduced by atropine, but not by mecamylamine, in SHR but not in WKY rat aortae. The responses in SHR aortae were also reduced by acetylcholinesterase (the enzyme responsible for acetylcholine degradation), bromoacetylcholine (inhibitor of acetylcholine synthesis), hemicholinium-3 (inhibitor of choline uptake), and vesamicol (inhibitor of acetylcholine release). The mild hypothermia-induced relaxations in both SHR and WKY rat aortae were inhibited by AMTB [N-(3-aminopropyl)-2-[(3-methylphenyl)methoxy]-N-(2-thienylmethyl)-benzamide; the transient receptor potential (TRP) M8 inhibitor]; only those in SHR aortae were inhibited by HC-067047 [2-methyl-1-[3-(4-morpholinyl)propyl]-5-phenyl-N-[3-(trifluoromethyl)phenyl]-1H-pyrrole-3-carboxamide; TRPV4 antagonist] while those in WKY rat aortae were reduced by HC-030031 [2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)-N-(4-isopropylphenyl)acetamide; TRPA1 antagonist]. The endothelial uptake of extracellular choline and release of cyclic guanosine monophosphate was enhanced by mild hypothermia and inhibited by HC-067047 in SHR but not in WKY rat aortae. Compared with WKY rats, the SHR preparations expressed similar levels of acetylcholinesterase and choline acetyltransferase, but a lesser amount of vesicular acetylcholine transporter, located mainly in the endothelium. Thus, mild hypothermia causes nitric oxide-dependent relaxations by opening TRPA1 channels in WKY rat aortae

  18. Endothelium-dependent vasorelaxation in the aorta of transgenic mice expressing human apolipoprotein(a) or lipoprotein(a).

    PubMed

    Rubanyi, G M; Freay, A D; Lawn, R M

    2000-01-01

    of acetylcholine-induced endothelium-dependent vasorelaxation. These results show for the first time that elevated plasma levels of apo(a) and Lp(a) do not cause endothelial dysfunction in transgenic mice. PMID:11201523

  19. Low-intensity voluntary running lowers blood pressure with simultaneous improvement in endothelium-dependent vasodilatation and insulin sensitivity in aged spontaneously hypertensive rats.

    PubMed

    Sun, Meng-Wei; Qian, Feng-Lei; Wang, Jian; Tao, Tao; Guo, Jing; Wang, Lie; Lu, Ai-Yun; Chen, Hong

    2008-03-01

    Our objective is to examine the effects of voluntary running at different intensity levels on blood pressure, endothelium-dependent vessel dysfunction and insulin resistance in aged spontaneously hypertensive rats (SHR) with severe hypertension. Ten-month-old male and female SHR with severe hypertension were assigned to voluntary running at either low intensity (30% of maximal aerobic velocity) or moderate intensity (60% of maximal aerobic velocity) on a motor-driven treadmill for 6 weeks, 20 min per day and 7 days per week. Age-matched Wistar-Kyoto rats and SHR were kept under sedentary conditions as controls. Blood pressure and heart rate were measured by the tail-cuff method. At the end of the exercise training, blood samples were collected for glucose, insulin and lipids assay, and aortae were isolated to examine their function in vitro. Low-intensity but not moderate-intensity running significantly lowered blood pressure in both male and female SHR (p<0.01). There was significant impairment in acetylcholine-induced vasorelaxation in SHR (p<0.01), which was improved by low-intensity training (p<0.05). Nitric oxide synthase blockade abrogated the improvement in endothelium-dependent relaxation. Hypertensive rats had elevated blood glucose and insulin levels with lowered insulin sensitivity that was ameliorated by low-intensity running. A significant increase in blood high-density lipoprotein (HDL)-cholesterol and a significant decrease in triglycerides were found in exercised SHR. In conclusion, low-intensity voluntary exercise lowers hypertension in aged SHR with severe hypertension. Exercise-induced simultaneous improvement in endothelium-dependent vessel relaxation and insulin sensitivity may act concomitantly in attenuating cardiovascular risk factors in aged hypertensive rats with significantly high blood pressure. PMID:18497475

  20. Role of Endothelium-Dependent Hyperpolarisation and Prostacyclin in Diabetes

    PubMed Central

    MOKHTAR, Siti Safiah; RASOOL, Aida Hanum Ghulam

    2015-01-01

    The endothelium plays a crucial role in maintaining vascular homeostasis by producing several vasodilating factors, including nitric oxide (NO), prostacyclin (PGI2), and endothelium-dependent hyperpolarisation (EDH); however, the balance between endothelial relaxing and contracting factors is disrupted in disease states such as diabetes mellitus and hypertension. Most reported studies of endothelial dysfunction in diabetes focused on the actions of NO; however, there is accumulating evidence demonstrating that in addition to NO, PGI2 and EDH are likely to contribute to the vasodilatation of blood vessels. EDH plays an important role as a regulator of vascular tone and reactivity in resistance and conduit arteries of animal models and humans. PGI2 only plays a minimal role in endothelium-dependent vasodilatation but may serve as an important compensatory mechanism in conditions in which NO and EDH activities are decreased. Further studies are needed to determine the exact roles of EDH and PGI2 in the development of endothelial dysfunction and clinical vasculopathy in humans with type 1 and type 2 diabetes. PMID:26023290

  1. Endothelium-Dependent Hyperpolarization and Endothelial Dysfunction.

    PubMed

    Félétou, Michel

    2016-05-01

    The endothelium controls vascular tone not only by releasing various vasoactive substances but also by another pathway associated with the hyperpolarization of both endothelial and vascular smooth muscle cells and is termed endothelium-dependent hyperpolarization (EDH). These responses involve an increase in the endothelial intracellular Ca concentration by the activation of transient receptor potential channels (predominantly TRPV4) followed by the opening of Ca-activated K channels of small and intermediate conductance (SKCa and IKCa). These channels show a distinct subcellular distribution. SKCa are widely distributed over the plasma membrane but segregates at sites of homocellular endothelial junctions, whereas IKCa are preferentially expressed in the myoendothelial projections. Following KCa activation, smooth muscle hyperpolarization is evoked by electrical coupling through myoendothelial gap junctions and/or by the potassium efflux that subsequently activates smooth muscle Kir2.1 and/or Na/K-ATPase. Alteration of the EDH contributes to the endothelial dysfunctions observed in various pathologies or conversely compensates for the loss in NO bioavailability. A better characterization of EDH should allow determining whether new druggable targets can be identified for the treatment of cardiovascular diseases. PMID:26657714

  2. Acute but not chronic metabolic acidosis potentiates the acetylcholine-induced reduction in blood pressure: an endothelium-dependent effect.

    PubMed

    Celotto, A C; Ferreira, L G; Capellini, V K; Albuquerque, A A S; Rodrigues, A J; Evora, P R B

    2016-02-01

    Metabolic acidosis has profound effects on vascular tone. This study investigated the in vivo effects of acute metabolic acidosis (AMA) and chronic metabolic acidosis (CMA) on hemodynamic parameters and endothelial function. CMA was induced by ad libitum intake of 1% NH4Cl for 7 days, and AMA was induced by a 3-h infusion of 6 M NH4Cl (1 mL/kg, diluted 1:10). Phenylephrine (Phe) and acetylcholine (Ach) dose-response curves were performed by venous infusion with simultaneous venous and arterial blood pressure monitoring. Plasma nitrite/nitrate (NOx) was measured by chemiluminescence. The CMA group had a blood pH of 7.15±0.03, which was associated with reduced bicarbonate (13.8±0.98 mmol/L) and no change in the partial pressure of arterial carbon dioxide (PaCO2). The AMA group had a pH of 7.20±0.01, which was associated with decreases in bicarbonate (10.8±0.54 mmol/L) and PaCO2 (47.8±2.54 to 23.2±0.74 mmHg) and accompanied by hyperventilation. Phe or ACh infusion did not affect arterial or venous blood pressure in the CMA group. However, the ACh infusion decreased the arterial blood pressure (ΔBP: -28.0±2.35 mm Hg [AMA] to -4.5±2.89 mmHg [control]) in the AMA group. Plasma NOx was normal after CMA but increased after AMA (25.3±0.88 to 31.3±0.54 μM). These results indicate that AMA, but not CMA, potentiated the Ach-induced decrease in blood pressure and led to an increase in plasma NOx, reinforcing the effect of pH imbalance on vascular tone and blood pressure control. PMID:26648089

  3. Acute but not chronic metabolic acidosis potentiates the acetylcholine-induced reduction in blood pressure: an endothelium-dependent effect

    PubMed Central

    Celotto, A.C.; Ferreira, L.G.; Capellini, V.K.; Albuquerque, A.A.S.; Rodrigues, A.J.; Evora, P.R.B.

    2015-01-01

    Metabolic acidosis has profound effects on vascular tone. This study investigated the in vivo effects of acute metabolic acidosis (AMA) and chronic metabolic acidosis (CMA) on hemodynamic parameters and endothelial function. CMA was induced by ad libitum intake of 1% NH4Cl for 7 days, and AMA was induced by a 3-h infusion of 6 M NH4Cl (1 mL/kg, diluted 1:10). Phenylephrine (Phe) and acetylcholine (Ach) dose-response curves were performed by venous infusion with simultaneous venous and arterial blood pressure monitoring. Plasma nitrite/nitrate (NOx) was measured by chemiluminescence. The CMA group had a blood pH of 7.15±0.03, which was associated with reduced bicarbonate (13.8±0.98 mmol/L) and no change in the partial pressure of arterial carbon dioxide (PaCO2). The AMA group had a pH of 7.20±0.01, which was associated with decreases in bicarbonate (10.8±0.54 mmol/L) and PaCO2 (47.8±2.54 to 23.2±0.74 mmHg) and accompanied by hyperventilation. Phe or ACh infusion did not affect arterial or venous blood pressure in the CMA group. However, the ACh infusion decreased the arterial blood pressure (ΔBP: -28.0±2.35 mm Hg [AMA] to -4.5±2.89 mmHg [control]) in the AMA group. Plasma NOx was normal after CMA but increased after AMA (25.3±0.88 to 31.3±0.54 μM). These results indicate that AMA, but not CMA, potentiated the Ach-induced decrease in blood pressure and led to an increase in plasma NOx, reinforcing the effect of pH imbalance on vascular tone and blood pressure control. PMID:26648089

  4. Developmental changes in endothelium-dependent pulmonary vasodilatation in pigs.

    PubMed Central

    Liu, S. F.; Hislop, A. A.; Haworth, S. G.; Barnes, P. J.

    1992-01-01

    1. We compared in vitro endothelium-dependent vasorelaxant responses to acetylcholine (ACh) and the endothelium-independent vasodilator response to sodium nitroprusside (SNP) in prostaglandin F2 alpha (PGF2 alpha)-precontracted muscular pulmonary arteries (PA) from pigs aged 5 min to 2 h (neonatal), 3-10 days, 3-8 weeks and adults. 2. In the pulmonary artery (PA) rings from neonatal animals, the vasodilator response to ACh was negligible. However, responses to ACh were present in all PA rings from older animals, being greatest at 3-10 days and then decreasing with age (P less than 0.001, ANOVA). ACh (30 microM) induced a 1 +/- 1%, 92 +/- 9%, 62 +/- 5% and 51 +/- 6% reduction of the PGF2 alpha-generated tension in neonatal, 3-10 days, 3-8 weeks and adult groups, respectively. 3. The relaxant response to SNP was present in the PA rings from all age groups and increased with age (P less than 0.001, ANOVA). SNP (1 microM)-induced relaxation was 55 +/- 9%, 73 +/- 7%, 97 +/- 5% and 93 +/- 6% in neonatal, 3-10 days, 3-8 week and adult groups, respectively. 4. Removal of the vascular endothelium abolished the relaxant response to ACh but had no effect on the response to SNP in any groups. 5. NG-monomethyl-L-arginine (30 microM), a nitric oxide synthesis inhibitor, inhibited the response to ACh but not to SNP. The lipoxygenase inhibitor, nordihydroguaiaretic acid, had no significant effect on responses to ACh or SNP in any group.(ABSTRACT TRUNCATED AT 250 WORDS) Images Figure 1 PMID:1393265

  5. Nafamostat mesilate promotes endothelium-dependent vasorelaxation via the Akt-eNOS dependent pathway.

    PubMed

    Choi, Sujeong; Kwon, Hyon-Jo; Song, Hee-Jung; Choi, Si Wan; Nagar, Harsha; Piao, Shuyu; Jung, Saet-Byel; Jeon, Byeong Hwa; Kim, Dong Woon; Kim, Cuk-Seong

    2016-09-01

    Nafamostat mesilate (NM), a synthetic serine protease inhibitor, has anticoagulant and anti-inflammatory properties. The intracellular mediator and external anti-inflammatory external signal in the vascular wall have been reported to protect endothelial cells, in part due to nitric oxide (NO) production. This study was designed to examine whether NM exhibit endothelium dependent vascular relaxation through Akt/endothelial nitric oxide synthase (eNOS) activation and generation of NO. NM enhanced Akt/eNOS phosphorylation and NO production in a dose- and time-dependent manner in human umbilical vein endothelial cells (HUVECs) and aorta tissues obtained from rats treated with various concentrations of NM. NM concomitantly decreased arginase activity, which could increase the available arginine substrate for NO production. Moreover, we investigated whether NM increased NO bioavailability and decreased aortic relaxation response to an eNOS inhibitor in the aorta. These results suggest that NM increases NO generation via the Akt/eNOS signaling pathway, leading to endothelium-dependent vascular relaxation. Therefore, the vasorelaxing action of NM may contribute to the regulation of cardiovascular function. PMID:27610041

  6. Nafamostat mesilate promotes endothelium-dependent vasorelaxation via the Akt-eNOS dependent pathway

    PubMed Central

    Choi, Sujeong; Kwon, Hyon-Jo; Song, Hee-Jung; Choi, Si Wan; Nagar, Harsha; Piao, Shuyu; Jung, Saet-byel; Jeon, Byeong Hwa

    2016-01-01

    Nafamostat mesilate (NM), a synthetic serine protease inhibitor, has anticoagulant and anti-inflammatory properties. The intracellular mediator and external anti-inflammatory external signal in the vascular wall have been reported to protect endothelial cells, in part due to nitric oxide (NO) production. This study was designed to examine whether NM exhibit endothelium dependent vascular relaxation through Akt/endothelial nitric oxide synthase (eNOS) activation and generation of NO. NM enhanced Akt/eNOS phosphorylation and NO production in a dose- and time-dependent manner in human umbilical vein endothelial cells (HUVECs) and aorta tissues obtained from rats treated with various concentrations of NM. NM concomitantly decreased arginase activity, which could increase the available arginine substrate for NO production. Moreover, we investigated whether NM increased NO bioavailability and decreased aortic relaxation response to an eNOS inhibitor in the aorta. These results suggest that NM increases NO generation via the Akt/eNOS signaling pathway, leading to endothelium-dependent vascular relaxation. Therefore, the vasorelaxing action of NM may contribute to the regulation of cardiovascular function. PMID:27610041

  7. Reduced nitric oxide-mediated relaxation and endothelial nitric oxide synthase expression in the tail arteries of streptozotocin-induced diabetic rats.

    PubMed

    Mokhtar, Siti Safiah; Vanhoutte, Paul M; Leung, Susan Wai Sum; Suppian, Rapeah; Yusof, Mohd Imran; Rasool, Aida Hanum Ghulam

    2016-02-15

    Diabetes is associated with endothelial dysfunction, which is characterized by impaired endothelium-dependent relaxations. The present study aimed to examine the role of nitric oxide (NO), prostacyclin and endothelium-dependent hyperpolarization (EDH), in the relaxation of ventral tail arteries of rats under diabetic conditions. Relaxations of tail arteries of control and diabetic rats were studied in wire myograph. Western blotting and immunostaining were used to determine the presence of proteins. Acetylcholine-induced relaxations were significantly smaller in arteries of diabetic compared to control rats (Rmax; 70.81 ± 2.48% versus 85.05 ± 3.15%). Incubation with the combination of non-selective cyclooxygenase (COX) inhibitor, indomethacin and potassium channel blockers, TRAM 34 and UCL 1684, demonstrated that NO-mediated relaxation was attenuated significantly in diabetic compared to control rats (Rmax; 48.47 ± 5.84% versus 68.39 ± 6.34%). EDH-type (in the presence of indomethacin and NO synthase inhibitor, LNAME) and prostacyclin-mediated (in the presence of LNAME plus TRAM 34 and UCL 1684) relaxations were not significantly reduced in arteries of diabetic compared to control rats [Rmax: (EDH; 17.81 ± 6.74% versus 34.16 ± 4.59%) (prostacyclin; 15.85 ± 3.27% versus 17.23 ± 3.75%)]. Endothelium-independent relaxations to sodium nitroprusside, salbutamol and prostacyclin were comparable in the two types of preparations. Western blotting and immunostaining indicated that diabetes diminished the expression of endothelial NO synthase (eNOS), while increasing those of COX-1 and COX-2. Thus, since acetylcholine-induced NO-mediated relaxation was impaired in diabetes because of reduced eNOS protein expression, pharmacological intervention improving NO bioavailability could be useful in the management of diabetic endothelial dysfunction. PMID:26825543

  8. Chronic in vivo or acute in vitro resveratrol attenuates endothelium-dependent cyclooxygenase-mediated contractile signaling in hypertensive rat carotid artery.

    PubMed

    Denniss, Steven G; Ford, Rebecca J; Smith, Christopher S; Jeffery, Andrew J; Rush, James W E

    2016-05-15

    Exaggerated cyclooxygenase (COX) and thromboxane-prostanoid (TP) receptor-mediated endothelium-dependent contraction can contribute to endothelial dysfunction. This study examined the effect of resveratrol (RSV) on endothelium-dependent contraction and cell signaling in the common carotid artery (CCA) from spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). Acetylcholine (Ach)-stimulated endothelium-dependent nitric oxide synthase (NOS)-mediated relaxation in precontracted SHR CCA was impaired (maximum 73 ± 6% vs. 87 ± 5% in WKY) (P < 0.05) by competitive COX-mediated contraction. Chronic (28-day) treatment in vivo (drinking water) with a ∼0.075 mg·kg(-1)·day(-1) RSV dose affected neither endothelium-dependent relaxation nor endothelium-dependent contraction and associated prostaglandin (PG) production evaluated in non-precontracted NOS-blocked CCA. In contrast, a chronic ∼7.5 mg·kg(-1)·day(-1) RSV dose improved endothelium-dependent relaxation (94 ± 6%) and attenuated endothelium-dependent contraction (58 ± 4% vs. 73 ± 5% in No-RSV) and PG production (183 ± 43 vs. 519 ± 93 pg/ml) in SHR CCA, while U46619-stimulated TP receptor-mediated contraction was unaffected. In separate acute in vitro experiments, 20-μM RSV preincubation attenuated endothelium-dependent contraction (6 ± 4% vs. 62 ± 2% in No Drug) and PG production (121 ± 15 vs. 491 ± 93 pg/ml) and attenuated U46619-stimulated contraction (134 ± 5% vs. 171 ± 4%) in non-precontracted NOS-blocked SHR CCA. Compound C, a known AMP-activated protein kinase (AMPK) inhibitor, did not prevent the RSV attenuating effect on Ach- and U46619-stimulated contraction but did prevent the RSV attenuating effect on PG production (414 ± 58 pg/ml). These data demonstrate that RSV can attenuate endothelium-dependent contraction both by suppressing arterial wall PG production, which may be partially mediated by AMPK, and by TP receptor hyporesponsiveness, which does not appear to be mediated by

  9. Nanoparticle inhalation impairs endothelium-dependent vasodilation in subepicardial arterioles

    PubMed Central

    LeBlanc, AJ; Cumpston, JL; Chen, BT; Frazer, D; Castranova, V; Nurkiewicz, TR

    2009-01-01

    Exposure to fine particulate matter (PM, mean aerodynamic diameter ≤ 2.5 μm) has been shown to be a risk factor for cardiovascular disease mortality and may contribute to acute coronary events such as myocardial infarction (MI). There is sufficient reason to believe that smaller particles, such as nanoparticles, might be even more detrimental than larger-sized particles due to their increased surface area and higher pulmonary deposition. Our lab showed that nanoparticle inhalation impairs endothelium-dependent arteriolar vasodilation in skeletal muscle. However, it is not known if coronary microvascular endothelial function is affected in a similar manner. Rats were exposed to filtered air (control) or TiO2 nanoparticles (primary particle diameter, ~21 nm) via inhalation at concentrations that produced measured depositions (10 μg) relevant to ambient air pollution. Subepicardial arterioles (~150 μm in diameter) were isolated and responses to transmural pressure, flow-induced dilation (FID), acetylcholine, the Ca2+ ionophore A23187, and sodium nitroprusside (SNP) assessed. Myogenic responsiveness was preserved between groups. In addition, there was no difference in the vasodilation to SNP, signifying that smooth muscle sensitivity to nitric oxide (NO) is unaffected by nano-TiO2 exposure. However, inhalation of nano-TiO2 produced an increase in spontaneous tone in coronary arterioles and also impaired endothelium-dependent FID. In addition, ACh- and A23187-induced vasodilation was also blunted in arterioles after inhalation of nano-TiO2. Data showed that nanoparticle exposure significantly impairs endothelium-dependent vasodilation in subepicardial arterioles. Such disturbances in coronary microvascular function are consistent with the cardiac events associated with particle pollution exposure. PMID:20077232

  10. Mechanisms of endothelial dysfunction after ionized radiation: selective impairment of the nitric oxide component of endothelium-dependent vasodilation

    PubMed Central

    Soloviev, Anatoly I; Tishkin, Sergey M; Parshikov, Alexander V; Ivanova, Irina V; Goncharov, Eugene V; Gurney, Alison M

    2003-01-01

    Gamma radiation impairs vascular function, leading to the depression of endothelium-dependent vasodilatation. Loss of the nitric oxide (NO) pathway has been implicated, but little is known about radiation effects on other endothelial mediators. This study investigated the mechanisms of endothelial dysfunction in rabbits subjected to whole-body irradiation from a cobalt60 source. The endothelium-dependent relaxation of rabbit aorta evoked by acetylcholine (ACh) or A23187 was impaired in a dose-dependent manner by irradiation at 2 Gy or above. Inhibition was evident 9 days post-irradiation and persisted over the 30 day experimental period. Endothelium-independent responses to glyceryl trinitrate (GTN), sodium nitroprusside (SNP) and 3-morpholino-sydnonimine (SIN-1) were suppressed over a similar dose range at 7–9 days post-irradiation, but recovered fully by 30 days post-irradiation. In healthy vessels, ACh-induced relaxation was inhibited by L-Nω-nitroarginine (L-NA; 3×10−4 M) and charybdotoxin (10−8 M) plus apamin (10−6 M) but resistant to indomethacin, indicating the involvement of NO and endothelium-derived hyperpolarizing factor (EDHF). Supporting this, ACh caused smooth muscle hyperpolarization that was reduced by L-NA and charybdotoxin plus apamin. In irradiated vessels, responses to ACh were insensitive to L-NA but abolished by charybdotoxin plus apamin, indicating selective loss of NO-mediated relaxation. In animals treated shortly after irradiation with the antioxidant, α-tocopherol acetate, the NO-dependent relaxation was restored without effect on the EDHF-dependent component. The results imply that radiation selectively impairs the NO pathway as a consequence of oxidative stress, while EDHF is able to maintain endothelium-dependent relaxation at a reduced level. PMID:12642385

  11. The vasorelaxant effect of gallic acid involves endothelium-dependent and -independent mechanisms.

    PubMed

    de Oliveira, Lais Moraes; de Oliveira, Thiago Sardinha; da Costa, Rafael Menezes; de Souza Gil, Eric; Costa, Elson Alves; Passaglia, Rita de Cassia Aleixo Tostes; Filgueira, Fernando Paranaíba; Ghedini, Paulo César

    2016-06-01

    The mechanisms of action involved in the vasorelaxant effect of gallic acid (GA) were examined in the isolated rat thoracic aorta. GA exerted a relaxant effect in the highest concentrations (0.4-10mM) in both endothelium-intact and endothelium-denuded aortic rings. Pre-incubation with L-NAME, ODQ, calmidazolium, TEA, 4-aminopyridine, and barium chloride significantly reduced the pEC50 values. Moreover, this effect was not modified by indomethacin, wortmannin, PP2, glibenclamide, or paxillin. Pre-incubation of GA (1, 3, and 10mM) in a Ca(2+)-free Krebs solution attenuated CaCl2-induced contractions and blocked BAY K8644-induced vascular contractions, but it did not inhibit a contraction induced by the release of Ca(2+) from the sarcoplasmatic reticulum stores. In addition, a Western blot analysis showed that GA induces phosphorylation of eNOS in rat thoracic aorta. These results suggest that GA induces relaxation in rat aortic rings through an endothelium-dependent pathway, resulting in eNOS phosphorylation and opening potassium channels. Additionally, the relaxant effect by an endothelium-independent pathway involves the blockade of the Ca(2+) influx via L-type Ca(2+) channels. PMID:26643780

  12. Age Impaired endothelium-dependent vasodilation is improved by resveratrol in rat mesenteric arteries

    PubMed Central

    Gocmez, Semil S; Scarpace, Philip J; Whidden, Melissa A; Erdos, Benedek; Kirichenko, Nataliya; Sakarya, Yasemin; Utkan, Tijen; Tumer, Nihal

    2016-01-01

    [Purpose] To determine whether resveratrol improves the adverse effects age on vascular function in mesenteric arteries (MAs), and diminishes the hyperactivity in adrenal gland with age. [Methods] Male F344 x Brown Norway rats were assigned to 6-month control (YC), 6-month resveratrol (YR), 24-month control (OC) and 24-month resveratrol (OR). Resveratrol (15 mg/kg) was provided to resveratrol groups in drinking water for 14 days. [Results] Concentration response curves to phenylephrine (PE, 10-9-10-5M), acetylcholine (Ach, 10-9-10-5M) and resveratrol (10-8-10-4M) were evaluated in pressurized isolated MAs. The Ach concentration-response curve was right shifted with maximal response diminished in OC compared with YC rats. These effects were reversed by resveratrol treatment. The resveratrol-mediated relaxant responses were unchanged with age or resveratrol suggesting an endothelium-independent mechanism. Resveratrol tended to increase endothelial nitric oxide synthase; caused no effect on copper-zinc superoxide dismutase; and normalized the age-related elevatation in DβH and NPY levels in adrenal medulla, two indicators of sympathetic activity [Conclusion] These data indicate that resveratrol reverses age-related dysfunction in endothelium-dependent vasodilation in MAs and partially reverses hyperactivity of adrenomedullary function with age. This treatment may have a therapeuticpotential in the treatment of cardiovascular diseases or hypertension in the elderly. PMID:27298812

  13. An ordinary mixed meal transiently impairs endothelium-dependent vasodilation in healthy subjects.

    PubMed

    Sarabi, M; Fugmann, A; Karlström, B; Berne, C; Lithell, H; Lind, L

    2001-06-01

    This study was designed to evaluate the effects of an ordinary mixed meal on endothelium-dependent vasodilation. Ten young healthy volunteers were given a mixed meal (minced meat sauce with rice, 900 kcal, 34% of the energy content was fat). In the fasting state, at 60 and 120 min after the start of the meal, endothelium-dependent vasodilation and endothelium-independent vasodilation were evaluated by local infusion of metacholine (4 microg min (-1)) and sodium nitroprusside (10 microg min (-1)) in the brachial artery. Blood flow in the forearm was measured using venous occlusion plethysmography. Endothelium-dependent vasodilation decreased from 15.4 +/- 3.3 (mean +/- SD) at fasting to 13.7 +/- 3.5 mL min (-1) (100 mL tissue)-1 (P < 0.01) 60 min after feeding, but had returned to the fasting level at 120 min. At 60 min, but not in the fasting state, the serum level of free fatty acids was inversely related to endothelium-dependent vasodilation (r=-0.74, P < 0.05), although no significant net changes in FFA levels were seen. Endothelium-independent vasodilation was not affected by the mixed meal. No similar attenuations in endothelium-dependent vasodilation were seen during control meals. In conclusion, an ordinary mixed meal transiently attenuated endothelium-dependent vasodilation. Free fatty acids may be involved in this effect on endothelial function. PMID:11442450

  14. Vasorelaxant and antihypertensive effects of formononetin through endothelium-dependent and -independent mechanisms

    PubMed Central

    SUN, Tao; LIU, Rui; CAO, Yong-xiao

    2011-01-01

    Aim: To investigate the mechanisms underlying the vasorelaxant effect of formononetin, an O-methylated isoflavone, in isolated arteries, and its antihypertensive activity in vivo. Methods: Arterial rings of superior mesenteric arteries, renal arteries, cerebral basilar arteries, coronary arteries and abdominal aortas were prepared from SD rats. Isometric tension of the arterial rings was recorded using a myograph system. Arterial pressure was measured using tail-cuff method in spontaneously hypertensive rats. Results: Formononetin (1–300 μmol/L) elicited relaxation in arteries of the five regions that were pre-contracted by KCl (60 mmol/L), U46619 (1 μmol/L) or phenylephrine (10 μmol/L). The formononetin-induced relaxation was reduced by removal of endothelium or by pretreatment with L-NAME (100 μmol/L). Under conditions of endothelium denudation, formononetin (10, 30, and 100 μmol/L) inhibited the contraction induced by KCl and that induced by CaCl2 in Ca2+-free depolarized medium. In the absence of extracellular Ca2+, formononetin (10, 30, and 100 μmol/L) depressed the constriction caused by phenylephrine (10 μmol/L), but did not inhibit the tonic contraction in response to the addition of CaCl2 (2 mmol/L). The contraction caused by caffeine (30 mmol/L) was not inhibited by formononetin (100 μmol/L). Formononetin (10 and 100 μmol/L) reduced the change rate of Ca2+-fluorescence intensity in response to KCl (50 mmol/L). In spontaneously hypertensive rats, formononetin (5, 10, and 20 mg/kg) slowly lowered the systolic, diastolic and mean arterial pressure. Conclusion: Formononetin causes vasodilatation via two pathways: (1) endothelium-independent pathway, probably due to inhibition of voltage-dependent Ca2+ channels and intracellular Ca2+ release; and (2) endothelium-dependent pathway by releasing NO. Both the pathways may contribute to its antihypertensive effect. PMID:21818108

  15. Impairment of endothelium-dependent responses of cerebral arterioles in chronic hypertension.

    PubMed

    Mayhan, W G; Faraci, F M; Heistad, D D

    1987-12-01

    The goal of this study was to determine whether endothelium-dependent responses are impaired in the cerebral microcirculation of stroke-prone spontaneously hypertensive rats (SHRSP). We measured diameters of cerebral arterioles using intravital microscopy in normotensive rats (WKY) and SHRSP (6-8 mo old). Cerebral vasodilator responses to superfusion with adenosine, which is an endothelium-independent agonist, were similar in WKY and SHRSP. In contrast, cerebral vasodilator responses to superfusion with endothelium-dependent agonists were profoundly impaired in SHRSP. Acetylcholine (10(-4) M) increased pial arteriolar diameter 23 +/- 2% (means +/- SE) in WKY and did not change arteriolar diameter in SHRSP (-2 +/- 3%, P less than 0.05 vs. WKY). Serotonin (10(-5) M) increased pial arteriolar diameter 23 +/- 1% in WKY and, in contrast, reduced diameter 11 +/- 1% in SHRSP (P less than 0.05 vs. WKY). Nitroglycerin and acetylcholine produce vasodilatation by activation of guanosine 3',5'-cyclic monophosphate (cGMP). Nitroglycerin was used to determine whether impaired responses of cerebral arterioles in SHRSP were related to altered cGMP activity. We found similar dilatation of cerebral arterioles in WKY and SHRSP in response to nitroglycerin. Thus impaired endothelium-dependent dilatation in SHRSP is not related to alteration of cGMP activity. We speculate that impairment of cerebral vasodilator responses to endothelium-dependent agonists, including vasoactive substances released by platelets, may predispose SHRSP to cerebral ischemia. PMID:3122590

  16. Vitamin C improves endothelium-dependent vasodilation in patients with non-insulin-dependent diabetes mellitus.

    PubMed

    Ting, H H; Timimi, F K; Boles, K S; Creager, S J; Ganz, P; Creager, M A

    1996-01-01

    Endothelium-dependent vasodilation is impaired in humans with diabetes mellitus. Inactivation of endothelium-derived nitric oxide by oxygen-derived free radicals contributes to abnormal vascular reactivity in experimental models of diabetes. To determine whether this observation is relevant to humans, we tested the hypothesis that the antioxidant, vitamin C, could improve endothelium-dependent vasodilation in forearm resistance vessels of patients with non-insulin-dependent diabetes mellitus. We studied 10 diabetic subjects and 10 age-matched, nondiabetic control subjects. Forearm blood flow was determined by venous occlusion plethysmography. Endothelium-dependent vasodilation was assessed by intraarterial infusion of methacholine (0.3-10 micrograms/min). Endothelium-independent vasodilation was measured by intraarterial infusion of nitroprusside (0.3-10 micrograms/min) and verapamil (10-300 micrograms/min). Forearm blood flow dose-response curves were determined for each drug before and during concomitant intraarterial administration of vitamin C (24 mg/min). In diabetic subjects, endothelium-dependent vasodilation to methacholine was augmented by simultaneous infusion of vitamin C (P = 0.002); in contrast, endothelium-independent vasodilation to nitroprusside and to verapamil were not affected by concomitant infusion of vitamin C (P = 0.9 and P = 0.4, respectively). In nondiabetic subjects, vitamin C administration did not alter endothelium-dependent vasodilation (P = 0.8). We conclude that endothelial dysfunction in forearm resistance vessels of patients with non-insulin-dependent diabetes mellitus can be improved by administration of the antioxidant, vitamin C. These findings support the hypothesis that nitric oxide inactivation by oxygen-derived free radicals contributes to abnormal vascular reactivity in diabetes. PMID:8550838

  17. Muscarinic Receptor Activation Affects Pulmonary Artery Contractility in Sheep: The Impact of Maturation and Chronic Hypoxia on Endothelium-Dependent and Endothelium-Independent Function.

    PubMed

    Giang, Michael; Papamatheakis, Demosthenes G; Nguyen, Dan; Paez, Ricardo; Blum Johnston, Carla; Kim, Joon; Brunnell, Alexander; Blood, Quintin; Goyal, Ravi; Longo, Lawrence D; Wilson, Sean M

    2016-06-01

    Giang, Michael, Demosthenes G. Papamatheakis, Dan Nguyen, Ricardo Paez, Carla Blum Johnston, Joon Kim, Alexander Brunnell, Quintin Blood, Ravi Goyal, Lawrence D. Longo, and Sean M. Wilson. Muscarinic receptor activation affects pulmonary artery contractility in sheep: the impact of maturation and chronic hypoxia on endothelium-dependent and endothelium-independent function. High Alt Med Biol. 17:122-132, 2015.-Muscarinic receptor activation in the pulmonary vasculature can cause endothelium-dependent vasodilation and smooth muscle-dependent vasoconstriction. Chronic hypoxia (CH) can modify both of these responses. This study aimed to assess the combined influence of CH and maturation on endothelium-dependent and endothelium-independent muscarinic-induced vasoreactivity. This was accomplished by performing wire myography on endothelium-intact or endothelium-disrupted pulmonary arterial rings isolated from normoxic or CH fetal and adult sheep. In endothelium-intact arteries, vasodilation was evaluated using cumulative bradykinin doses in phenylephrine and carbachol precontracted pulmonary arterial segments; and vasoconstriction was examined using cumulative doses of carbachol following bradykinin predilation. Effects of nonselective (atropine) and selective M1 (pirenzepine), M2 (AFDX116), and M3 (4-DAMP and Dau5884) muscarinic receptor antagonists were assessed in disrupted arteries. In normoxic arteries, bradykinin relaxation was twofold greater in the adult compared to fetus, while carbachol contraction was fourfold greater. In adult arteries, CH increased bradykinin relaxation and carbachol contraction. In vessels with intact endothelium, maturation and CH augmented maximal response and efficacy for carbachol constriction and bradykinin relaxation. Approximately 50%-80% of adult normoxic and CH endothelium-disrupted arteries contracted to acetylcholine, while ∼50% of fetal normoxic and ∼10% of CH arteries responded. Atropine reduced carbachol

  18. Stimulation of calcium-sensing receptors induces endothelium-dependent vasorelaxations via nitric oxide production and activation of IKCa channels.

    PubMed

    Greenberg, Harry Z E; Shi, Jian; Jahan, Kazi S; Martinucci, Matthew C; Gilbert, Steven J; Vanessa Ho, W-S; Albert, Anthony P

    2016-05-01

    Stimulation of vascular calcium-sensing receptors (CaSRs) is reported to induce both constrictions and relaxations. However, cellular mechanisms involved in these responses remain unclear. The present study investigates the effect of stimulating CaSRs on vascular contractility and focuses on the role of the endothelium, nitric oxide (NO) and K(+) channels in these responses. In wire myography studies, increasing [Ca(2+)]o from 1mM to 6mM induced concentration-dependent relaxations of methoxamine pre-contracted rabbit mesenteric arteries. [Ca(2+)]o-induced relaxations were dependent on a functional endothelium, and were inhibited by the negative allosteric CaSR modulator Calhex-231. [Ca(2+)]o-induced relaxations were reduced by inhibitors of endothelial NO synthase, guanylate cyclase, and protein kinase G. CaSR activation also induced NO production in freshly isolated endothelial cells (ECs) in experiments using the fluorescent NO indicator DAF-FM. Pre-treatment with inhibitors of large (BKCa) and intermediate (IKCa) Ca(2+)-activated K(+) channels (iberiotoxin and charybdotoxin), and Kv7 channels (linopirdine) also reduced [Ca(2+)]o-induced vasorelaxations. Increasing [Ca(2+)]o also activated IKCa currents in perforated-patch recordings of isolated mesenteric artery ECs. These findings indicate that stimulation of CaSRs induces endothelium-dependent vasorelaxations which are mediated by two separate pathways involving production of NO and activation of IKCa channels. NO stimulates PKG leading to BKCa activation in vascular smooth muscle cells, whereas IKCa activity contributes to endothelium-derived hyperpolarisations. PMID:26772767

  19. Stimulation of calcium-sensing receptors induces endothelium-dependent vasorelaxations via nitric oxide production and activation of IKCa channels

    PubMed Central

    Greenberg, Harry Z.E.; Shi, Jian; Jahan, Kazi S.; Martinucci, Matthew C.; Gilbert, Steven J.; Vanessa Ho, W.-S.; Albert, Anthony P.

    2016-01-01

    Stimulation of vascular calcium-sensing receptors (CaSRs) is reported to induce both constrictions and relaxations. However, cellular mechanisms involved in these responses remain unclear. The present study investigates the effect of stimulating CaSRs on vascular contractility and focuses on the role of the endothelium, nitric oxide (NO) and K+ channels in these responses. In wire myography studies, increasing [Ca2 +]o from 1 mM to 6 mM induced concentration-dependent relaxations of methoxamine pre-contracted rabbit mesenteric arteries. [Ca2 +]o-induced relaxations were dependent on a functional endothelium, and were inhibited by the negative allosteric CaSR modulator Calhex-231. [Ca2 +]o-induced relaxations were reduced by inhibitors of endothelial NO synthase, guanylate cyclase, and protein kinase G. CaSR activation also induced NO production in freshly isolated endothelial cells (ECs) in experiments using the fluorescent NO indicator DAF-FM. Pre-treatment with inhibitors of large (BKCa) and intermediate (IKCa) Ca2 +-activated K+ channels (iberiotoxin and charybdotoxin), and Kv7 channels (linopirdine) also reduced [Ca2 +]o-induced vasorelaxations. Increasing [Ca2 +]o also activated IKCa currents in perforated-patch recordings of isolated mesenteric artery ECs. These findings indicate that stimulation of CaSRs induces endothelium-dependent vasorelaxations which are mediated by two separate pathways involving production of NO and activation of IKCa channels. NO stimulates PKG leading to BKCa activation in vascular smooth muscle cells, whereas IKCa activity contributes to endothelium-derived hyperpolarisations. PMID:26772767

  20. Endothelium-dependent mechanisms of the vasodilatory effect of the endocannabinoid, anandamide, in the rat pulmonary artery.

    PubMed

    Baranowska-Kuczko, Marta; MacLean, Margaret R; Kozłowska, Hanna; Malinowska, Barbara

    2012-09-01

    Endocannabinoids exhibit vasodilatory properties and reduce blood pressure in vivo. However, the influence and mechanism of action of the prominent endocannabinoid, anandamide (AEA), in pulmonary arteries are not known. The present study determined the vascular response to AEA in isolated rat pulmonary arteries. AEA relaxed rat pulmonary arteries that were pre-constricted with U-46619. This relaxation was reduced by the following conditions:removal of the endothelium; in KCl pre-constricted preparations; in the presence of the potassium channel (K(Ca)) blockers, tetraethylammonium and the combination of charybdotoxin and apamin, and the prostacyclin receptor antagonist, RO1138452. Inhibitors of cyclooxygenase (indomethacin), nitric oxide (NO) synthase (N(G)-nitro-l-arginine methyl ester) and fatty acid amide hydrolase (URB597) alone or in combination diminished AEA-induced relaxation in endothelium-intact vessels. The remaining experiments were performed in the presence of URB597 to eliminate the influence of AEA metabolites. Antagonists of the endothelial cannabinoid receptor (CB(x)), O-1918 and cannabidiol, attenuated the AEA-induced response. Antagonists of CB(1), CB(2) and TRPV1 receptors, AM251, AM630 and capsazepine, respectively, did not modify the AEA-induced response. A reference activator of CB(x) receptors, abnormal cannabidiol, mimicked the receptor-mediated AEA effects. The present study demonstrated that AEA relaxed rat pulmonary arteries in an endothelium-dependent fashion via the activation of the O-1918-sensitive CB(x) receptor and/or prostacyclin-like vasoactive products of AEA. One or both of these mechanisms may involve K(Ca) or the NO pathway. PMID:22627170

  1. Pycnogenol, French maritime pine bark extract, augments endothelium-dependent vasodilation in humans.

    PubMed

    Nishioka, Kenji; Hidaka, Takayuki; Nakamura, Shuji; Umemura, Takashi; Jitsuiki, Daisuke; Soga, Junko; Goto, Chikara; Chayama, Kazuaki; Yoshizumi, Masao; Higashi, Yukihito

    2007-09-01

    Pycnogenol, an extract of bark from the French maritime pine, Pinus pinaster Ait., consists of a concentrate of water-soluble polyphenols. Pycnogenol contains the bioflavonoids catechin and taxifolin as well as phenolcarbonic acids. Antioxidants, such as bioflavonoids, enhance endothelial nitric oxide (NO) synthase expression and subsequent NO release from endothelial cells. The purpose of this study was to determine Pycnogenol's effects on endothelium-dependent vasodilation in humans. This was a double-blind, randomized, placebo and active drug study. We evaluated forearm blood flow (FBF) responses to acetylcholine (ACh), an endothelium-dependent vasodilator, and to sodium nitroprusside (SNP), an endothelium-independent vasodilator, in healthy young men before and after 2 weeks of daily oral administration of Pycnogenol (180 mg/day) (n=8) or placebo (n=8). FBF was measured by using strain-gauge plethysmography. Neither the placebo nor Pycnogenol altered forearm or systemic hemodynamics. Pycnogenol, but not placebo, augmented FBF response to ACh, from 13.1 +/- 7.0 to 18.5 +/- 4.0 mL/min per 100 mL tissue (p<0.05). SNP-stimulated vasodilation was similar before and after 2 weeks of treatment in the control and Pycnogenol groups. The administration of N(G)-monomethyl-L-arginine, an NO synthase inhibitor, completely abolished Pycnogenol-induced augmentation of the FBF response to ACh. These findings suggest that Pycnogenol augments endothelium-dependent vasodilation by increasing in NO production. Pycnogenol would be useful for treating various diseases whose pathogeneses involve endothelial dysfunction. PMID:18037769

  2. Cyclo-oxygenase-2 inhibition and endothelium-dependent vasodilation in younger vs. older healthy adults

    PubMed Central

    Eisenach, John H; Gullixson, Leah R; Allen, Alexander R; Kost, Susan L; Nicholson, Wayne T

    2014-01-01

    Aim A major feature of endothelial dysfunction is reduced endothelium-dependent vasodilation, which in ageing may be due to decreased production of endothelial prostacyclin, or nitric oxide (NO), or both. Method We tested this hypothesis in 12 younger (age 18–38 years, six women) and 12 older healthy adults (age 55–73 years, six post-menopausal women). Endothelium-dependent vasodilation was assessed by the forearm vascular conductance (FVC) response to intra-arterial acetylcholine (ACh) (0.5, 1.0, 2.0, 4.0 μg dl−1 forearm tissue min−1) before and 90 min after inhibition of the enzyme cyclo-oxygenase-2 (COX-2) with oral celecoxib (400 mg), followed by the addition of endothelial NO synthase inhibition with intra-arterial NG-monomethyl-l arginine acetate (L-NMMA). Results Ageing was associated with a significantly reduced FVC response to ACh (P = 0.009, age-by-dose interaction; highest dose FVC ± SEM in ageing: 11.2 ± 1.4 vs. younger: 17.7 ± 2.4 units, P = 0.02). Celecoxib did not reduce resting FVC or the responses to ACh in any group. L-NMMA significantly reduced resting FVC and the responses to ACh in all groups, and absolute FVC values following L-NMMA were similar between groups. Conclusion In healthy normotensive younger and older adults, there is minimal contribution of prostacyclin to ACh-mediated vasodilation, yet the NO component of vasodilation is reduced with ageing. In the clinical context, these findings suggest that acute administration of medications that inhibit prostacyclin (i.e. COX-2 inhibitors) evoke modest vascular consequences in healthy persons. Additional studies are necessary to test whether chronic use of COX-2 medications reduces endothelium dependent vasodilation in older persons with or without cardiovascular risk factors. PMID:24698105

  3. Vascular Endothelium-Dependent and Independent Actions of Oleanolic Acid and Its Synthetic Oleanane Derivatives as Possible Mechanisms for Hypotensive Effects

    PubMed Central

    Madlala, Hlengiwe P.; Metzinger, Thomas; van Heerden, Fanie R.; Mubagwa, Kanigula; Dessy, Chantal

    2016-01-01

    Purpose Plant-derived oleanolic acid (OA) and its related synthetic derivatives (Br-OA and Me-OA) possess antihypertensive effects in experimental animals. The present study investigated possible underlying mechanisms in rat isolated single ventricular myocytes and in vascular smooth muscles superfused at 37°C. Methods Cell shortening was assessed at 1 Hz using a video-based edge-detection system and the L-type Ca2+ current (ICaL) was measured using the whole-cell patch-clamp technique in single ventricular myocytes. Isometric tension was measured using force transducer in isolated aortic rings and in mesenteric arteries. Vascular effects were measured in endothelium-intact and denuded vessels in the presence of various enzyme or channel inhibitors. Results OA and its derivatives increased cell shortening in cardiomyocytes isolated from normotensive rats but had no effect in those isolated from hypertensive animals. These triterpenes also caused relaxation in aortic rings and in mesenteric arteries pre-contracted with either phenylephrine or KCl-enriched solution. The relaxation was only partially inhibited by endothelium denudation, and also partly inhibited by the cyclooxygenase (COX) inhibitor indomethacin, with no additional inhibitory effect of the NO synthase inhibitor, N-ω-Nitro-L-arginine. A combination of both ATP-dependent channel inhibition by glibenclaminde and voltage-dependent K+ channel inhibition by 4-aminopyridine was necessary to fully inhibit the relaxation. Conclusion These data indicate that the effects of OA and its derivatives are mediated via both endothelium-dependent and independent mechanisms suggesting the involvement of COX in the endothelium-dependent effects and of vascular muscle K+ channels in the endothelium-independent effects. Finally, our results support the view that the antihypertensive action of OA and its derivatives is due to a decrease of vascular resistance with no negative inotropic effect on the heart. PMID:26799746

  4. In vivo evidence for an endothelium-dependent mechanism in radiation-induced normal tissue injury

    PubMed Central

    Rannou, Emilie; François, Agnès; Toullec, Aurore; Guipaud, Olivier; Buard, Valérie; Tarlet, Georges; Mintet, Elodie; Jaillet, Cyprien; Iruela-Arispe, Maria Luisa; Benderitter, Marc; Sabourin, Jean-Christophe; Milliat, Fabien

    2015-01-01

    The pathophysiological mechanism involved in side effects of radiation therapy, and especially the role of the endothelium remains unclear. Previous results showed that plasminogen activator inhibitor-type 1 (PAI-1) contributes to radiation-induced intestinal injury and suggested that this role could be driven by an endothelium-dependent mechanism. We investigated whether endothelial-specific PAI-1 deletion could affect radiation-induced intestinal injury. We created a mouse model with a specific deletion of PAI-1 in the endothelium (PAI-1KOendo) by a Cre-LoxP system. In a model of radiation enteropathy, survival and intestinal radiation injury were followed as well as intestinal gene transcriptional profile and inflammatory cells intestinal infiltration. Irradiated PAI-1KOendo mice exhibited increased survival, reduced acute enteritis severity and attenuated late fibrosis compared with irradiated PAI-1flx/flx mice. Double E-cadherin/TUNEL labeling confirmed a reduced epithelial cell apoptosis in irradiated PAI-1KOendo. High-throughput gene expression combined with bioinformatic analyses revealed a putative involvement of macrophages. We observed a decrease in CD68+cells in irradiated intestinal tissues from PAI-1KOendo mice as well as modifications associated with M1/M2 polarization. This work shows that PAI-1 plays a role in radiation-induced intestinal injury by an endothelium-dependent mechanism and demonstrates in vivo that the endothelium is directly involved in the progression of radiation-induced enteritis. PMID:26510580

  5. Bilateral common carotid artery stenosis in normotensive rats impairs endothelium-dependent dilation of parenchymal arterioles.

    PubMed

    Matin, Nusrat; Fisher, Courtney; Jackson, William F; Dorrance, Anne M

    2016-05-15

    Chronic cerebral hypoperfusion is a risk factor for cognitive impairment. Reduced blood flow through the common carotid arteries induced by bilateral carotid artery stenosis (BCAS) is a physiologically relevant model of chronic cerebral hypoperfusion. We hypothesized that BCAS in 20-wk-old Wistar-Kyoto (WKY) rats would impair cognitive function and lead to reduced endothelium-dependent dilation and outward remodeling in the parenchymal arterioles (PAs). After 8 wk of BCAS, both short-term memory and spatial discrimination abilities were impaired. In vivo assessment of cerebrovascular reserve capacity showed a severe impairment after BCAS. PA endothelial function and structure were assessed by pressure myography. BCAS impaired endothelial function in PAs, as evidenced by reduced dilation to carbachol. Addition of nitric oxide synthase and cyclooxygenase inhibitors did not change carbachol-mediated dilation in either group. Inhibiting CYP epoxygenase, the enzyme that produces epoxyeicosatrienoic acid (EETs), a key determinant of endothelium-derived hyperpolarizing factor (EDHF)-mediated dilation, abolished dilation in PAs from Sham rats, but had no effect in PAs from BCAS rats. Expression of TRPV4 channels, a target for EETs, was decreased and maximal dilation to a TRPV4 agonist was attenuated after BCAS. Together these data suggest that EET-mediated dilation is impaired in PAs after BCAS. Thus impaired endothelium-dependent dilation in the PAs may be one of the contributing factors to the cognitive impairment observed after BCAS. PMID:26968546

  6. Whole blood viscosity and erythrocyte deformability are related to endothelium-dependent vasodilation and coronary risk in the elderly. The prospective investigation of the vasculature in Uppsala seniors (PIVUS) study.

    PubMed

    Sandhagen, Bo; Lind, Lars

    2012-01-01

    It has previously been shown that a high hemoglobin value, a major determinant of whole blood viscosity (WBV), predicts cardiovascular events. One putative mechanism might be an impaired endothelial function. Erythrocyte deformability is another rheologic feature of the erythrocyte being of importance for the flow properties of the blood, especially in the capillaries. The present study evaluates the relationships between blood viscosity, erythrocyte deformability assessed as erythrocyte fluidity (EF), coronary risk and endothelial vasodilatory function. In the population-based PIVUS study (1016 subjects aged 70); endothelium-dependent vasodilation (EDV) was evaluated by the invasive forearm technique with acetylcholine given in the brachial artery and the brachial artery ultrasound technique with measurement of flow-mediated dilatation (FMD). WBV, plasma viscosity (PV) and EF were measured in a random sample of 573 subjects. WBV and PV were positively and EF negatively related to Framingham risk score. EDV was inversely related to both whole blood and plasma viscosity. FMD was not related to any rheologic variable. In multiple regression analyses WBV and EF were significantly related to EDV independently of gender, hypertension, smoking, hypercholesterolemia, obesity and diabetes. Acetylcholine-induced vasodilation in the forearm, but not FMD, was negatively related to whole blood viscosity and positively related to EF independently of traditional risk factors in elderly subjects, indicating a pathophysiological link between impaired hemorheology and coronary risk. PMID:22240364

  7. Endothelium-dependent vasodilator effects of the extract from Salviae Miltiorrhizae radix. A study on the identification of lithospermic acid B in the extracts.

    PubMed

    Kamata, K; Iizuka, T; Nagai, M; Kasuya, Y

    1993-07-01

    1. The aqueous extract of Salviae Miltiorrhizae radix (Chinese crude drug named "dan-shen") relaxed the noradrenaline-precontracted aorta with endothelium. 2. Vasodilation by the extract disappeared in aorta without endothelium, and was inhibited by pretreatment with 10(-4) M NG-monomethyl-L-arginine (L-NMMA) or 10(-5) M methylene blue. 3. The inhibition of the extract-induced vasodilation by L-NMMA was reversed by L-arginine (3 x 10(-4) M). 4. The component of the extract was analyzed by chromatography, fast atom bombardment mass spectroscopy (FAB-MS) and 1H-NMR. 5. An active component of the extract, which showed endothelium-dependent vasodilation, was found to be identical with lithospermic acid B. PMID:8224751

  8. Singlet oxygen scavengers affect laser-dye impairment of endothelium-dependent responses of brain arterioles.

    PubMed

    Rosenblum, W I; Nelson, G H

    1996-04-01

    This study investigates the possible role of singlet oxygen in accounting for the inhibitory effect of laser-dye injury on endothelium-dependent dilations. The combination of helium-neon (HeNe) laser (20-s exposure) and intravascular Evans blue impairs endothelium-dependent dilation of mouse pial arterioles by acetylcholine (ACh), bradykinin (BK), and calcium ionophore A23187. Each has a different endothelium-derived mediator (EDRFACh, EDRFBK, EDRFionophore, respectively). In this study, diameters at a craniotomy site were monitored in vivo with an image splitter-television microscope. The laser-dye injury, as usual, abolished the responses 10 and 30 min after injury, with recovery, complete or partial, at 60 min. Dilations by sodium nitroprusside, an endothelium-independent dilator, were not affected by laser-dye. When the singlet oxygen scavengers L-histidine (10(-3) M) and L-tryptophan (10(-2) M) were added to the suffusate over the site, the responses to ACh at 10 and 30 min were relatively intact, the response to BK was partly protected at 10 min only, and the response to ionophore was still totally impaired at 10 and 30 min. Lysine, a nonscavenging amino acid, had no protective effects with any dilator. We postulate that a heat-induced injury initiates a chain of events resulting in prolonged singlet oxygen generation by the endothelial cell (not by the dye). We postulate further that destruction of EDRFACh by singlet oxygen is responsible for laser-dye inhibition of ACh and that generation of the radical must continue for > or = 30 min. On the other hand, the heat injury itself is probably responsible for the elimination of the response to ionophore. Heat plus singlet oxygen generated by heat-damaged tissue may initially impair the response to BK, but by 30 min only the effects of some other factor, presumably heat injury, account for the impaired response to BK. PMID:8967364

  9. Hindlimb unweighting decreases endothelium-dependent dilation and eNOS expression in soleus not gastrocnemius

    NASA Technical Reports Server (NTRS)

    Woodman, C. R.; Schrage, W. G.; Rush, J. W.; Ray, C. A.; Price, E. M.; Hasser, E. M.; Laughlin, M. H.

    2001-01-01

    We tested the hypothesis that hindlimb unweighting (HLU) decreases endothelium-dependent vasodilation and expression of endothelial nitric oxide synthase (eNOS) and superoxide dismutase-1 (SOD-1) in arteries of skeletal muscle with reduced blood flow during HLU. Sprague-Dawley rats (300-350 g) were exposed to HLU (n = 15) or control (n = 15) conditions for 14 days. ACh-induced dilation was assessed in muscle with reduced [soleus (Sol)] or unchanged [gastrocnemius (Gast)] blood flow during HLU. eNOS and SOD-1 expression were measured in feed arteries (FA) and in first-order (1A), second-order (2A), and third-order (3A) arterioles. Dilation to infusion of ACh in vivo was blunted in Sol but not Gast. In arteries of Sol muscle, HLU decreased eNOS mRNA and protein content. eNOS mRNA content was significantly less in Sol FA (35%), 1A arterioles (25%) and 2A arterioles (18%). eNOS protein content was less in Sol FA (64%) and 1A arterioles (65%) from HLU rats. In arteries of Gast, HLU did not decrease eNOS mRNA or protein. SOD-1 mRNA expression was less in Sol 2A arterioles (31%) and 3A arterioles (29%) of HLU rats. SOD-1 protein content was less in Sol FA (67%) but not arterioles. SOD-1 mRNA and protein content were not decreased in arteries from Gast. These data indicate that HLU decreases endothelium-dependent vasodilation, eNOS expression, and SOD-1 expression primarily in arteries of Sol muscle where blood flow is reduced during HLU.

  10. MACC-1 Promotes Endothelium-Dependent Angiogenesis in Gastric Cancer by Activating TWIST1/VEGF-A Signal Pathway

    PubMed Central

    Zhao, Yang; Dong, Shaoting; Zhang, Jingwen; Luo, Yuhao; Huang, Na; Shi, Min; Bin, Jianping; Liao, Yulin; Liao, Wangjun

    2016-01-01

    Endothelium-dependent angiogenesis is thought to be a crucial step in cancer progression. We previously reported that metastasis-associated in colon cancer-1 (MACC1) contributed to the vasculogenic mimicry in gastric cancer (GC), but it remains unknown whether MACC1 promotes endothelium-dependent angiogenesis of GC and whether TWIST1 is involved in this process. In the present study, we detected MACC1 expression and microvessel density (MVD) by immunohistochemistry in 159 patients with stage I-III GC, and investigated the role of TWIST1 and vascular endothelial growth factor A (VEGF-A) in MACC1-induced endothelium-dependent angiogenesis using nude mice with GC xenografts, and human umbilical vein endothelial cells (HUVECs) that were co-cultured with conditioned media from overexpression and interference MACC1 GC cells. We found that MACC1 expression was positively correlated with an increased MVD and tumor recurrence in GC patients. In GC xenograft models, MACC1 elevated MVD and upregulated the expression of VEGF-A as well as accelerated tumor growth. In addition, MACC1 obviously increased the expression of TWIST1 and induced tube-like formation of HUVECs, whereas attenuation of TWIST1 suppressed the protein expression of VEGF-A and repealed the effect of MACC1 on tube formation. Our findings shed light on the function of MACC1 in endothelium-dependent angiogenesis of GC and suggest potential prognostic and therapeutic value. PMID:27280289

  11. Local 24-h hyperglycemia does not affect endothelium-dependent or -independent vasoreactivity in humans.

    PubMed

    Houben, A J; Schaper, N C; de Haan, C H; Huvers, F C; Slaaf, D W; de Leeuw, P W; Nieuwenhuijzen Kruseman, C

    1996-06-01

    Hyperglycemia induces regional hemodynamic changes, as suggested by animal studies. These hemodynamic changes may play an initiating role in the pathogenesis of diabetic microangiopathy. The aim of the present study was to evaluate the effects of acute local hyperglycemia for 24 h on basal human forearm muscle and skin blood flow and endothelium-dependent and -independent vasoreactivity. Local hyperglycemia (approximately 15 mM) was induced by infusion of 5% glucose into the brachial artery of the nondominant arm. In control experiments, the same individual amount of glucose was infused intravenously in the dominant arm to correct for possible systemic effects of the infused glucose. Vasoreactivity of the forearm vasculature was evaluated by local infusion of acetylcholine (ACh), sodium nitroprusside (SNP), NG-monomethyl-L-arginine (L-NMMA), and norepinephrine (NE) into the brachial artery. Regional hemodynamic measurements were performed at baseline and after 6, 12, and 24 h of local hyperglycemia. Median (with interquartile range) basal forearm (muscle) blood flow (FBF) was not influenced by the 24-h local hyperglycemia [infused-to-contralateral arm FBF ratio for glucose 1.32 (1.16-1.64) vs. control 1.54 (1.34-1.69)]. Skin microcirculatory blood flow (laser Doppler flowmetry, LDF) was not influenced by the 24-h local hyperglycemia [LDF ratio for glucose 1.00 (0.62-1.56) vs control 0.80 (0.58-1.14)]. In addition, the vasoreactivity of both muscle and skin (not shown) vasculature to ACh [percent change in FBF ratio for glucose 167% (81-263) vs. control 148% (94-211)], SNP [for glucose 486% (178-586) vs. control 293% (196-454)], L-NMMA [for glucose -36% (-56 to -22) vs. control -41% (-51 to -24)], and NE [for glucose -48% (-72 to -41) vs. control -66% (-79 to -33)] was also not affected by the local hyperglycemia. Thus, in contrast to animal studies, our results suggest that a moderate-to-severe hyperglycemia does not affect the regulation of basal blood flow or

  12. IDH2 deficiency impairs mitochondrial function in endothelial cells and endothelium-dependent vasomotor function.

    PubMed

    Park, Jung-Bum; Nagar, Harsha; Choi, Sujeong; Jung, Saet-Byel; Kim, Hyun-Woo; Kang, Shin Kwang; Lee, Jun Wan; Lee, Jin Hyup; Park, Jeen-Woo; Irani, Kaikobad; Jeon, Byeong Hwa; Song, Hee-Jung; Kim, Cuk-Seong

    2016-05-01

    Mitochondrial NADP(+)-dependent isocitrate dehydrogenase (IDH2) plays an essential role protecting cells against oxidative stress-induced damage. A deficiency in IDH2 leads to mitochondrial dysfunction and the production of reactive oxygen species (ROS) in cardiomyocytes and cancer cells. However, the function of IDH2 in vascular endothelial cells is mostly unknown. In this study the effects of IDH2 deficiency on mitochondrial and vascular function were investigated in endothelial cells. IDH2 knockdown decreased the expression of mitochondrial oxidative phosphorylation (OXPHOS) complexes I, II and III, which lead to increased mitochondrial superoxide. In addition, the levels of fission and fusion proteins (Mfn-1, OPA-1, and Drp-1) were significantly altered and MnSOD expression also was decreased by IDH2 knockdown. Furthermore, knockdown of IDH2 decreased eNOS phosphorylation and nitric oxide (NO) concentration in endothelial cells. Interestingly, treatment with Mito-TEMPO, a mitochondrial-specific superoxide scavenger, recovered mitochondrial fission-fusion imbalance and blunted mitochondrial superoxide production, and reduced the IDH2 knockdown-induced decrease in MnSOD expression, eNOS phosphorylation and NO production in endothelial cells. Endothelium-dependent vasorelaxation was impaired, and the concentration of bioavailable NO decreased in the aortic ring in IDH2 knockout mice. These findings suggest that IDH2 deficiency induces endothelial dysfunction through the induction of dynamic mitochondrial changes and impairment in vascular function. PMID:26898144

  13. Effects of raloxifene on carotid blood flow resistance and endothelium-dependent vasodilation in postmenopausal women.

    PubMed

    Ceresini, Graziano; Marchini, Lorenzo; Rebecchi, Isabella; Morganti, Simonetta; Bertone, Luca; Montanari, Ilaria; Bacchi-Modena, Alberto; Sgarabotto, Maria; Baldini, Monica; Denti, Licia; Ablondi, Fabrizio; Ceda, Gian Paolo; Valenti, Giorgio

    2003-03-01

    Raloxifene is one of the most important selective estrogen receptor modulators currently employed for the treatment of postmenopausal osteoporosis. However, it has also been suggested that this compound affects the vascular system. We evaluated both carotid blood flow resistance and endothelium-dependent vasodilation in 50 healthy postmenopausal women randomly assigned to receive, in a double blind design, either raloxifene (60 mg per day; N=25 subjects) or placebo (N=25 subjects) for 4 months. Indices of carotid blood flow resistance, such as the pulsatility index (PI) and resistance index (RI), as well as the flow-mediated brachial artery dilation were measured both at baseline and at the end of treatment. Changes in PI were -1.86+/-2.24 and -2.15+/-2.22% after placebo and raloxifene treatment, respectively, with no significant differences between groups. Changes in RI were -0.77+/-1.72 and -1.81+/-1.54% after placebo and raloxifene treatment, respectively, with no significant differences between groups. At the end of the treatment period, the increments in artery diameter measured after the flow stimulus were 10.79+/-2.39 and 6.70+/-1.23% for placebo and raloxifene, respectively, with no significant differences between groups. These results demonstrate no significant effects of raloxifene on either carotid blood flow resistance or brachial artery flow-mediated dilation in postmenopausal women. PMID:12618276

  14. Obesity and risk of vascular disease: importance of endothelium-dependent vasoconstriction

    PubMed Central

    Barton, Matthias; Baretella, Oliver; Meyer, Matthias R

    2012-01-01

    Obesity has become a serious global health issue affecting both adults and children. Recent devolopments in world demographics and declining health status of the world's population indicate that the prevalence of obesity will continue to increase in the next decades. As a disease, obesity has deleterious effects on metabolic homeostasis, and affects numerous organ systems including heart, kidney and the vascular system. Thus, obesity is now regarded as an independent risk factor for atherosclerosis-related diseases such as coronary artery disease, myocardial infarction and stroke. In the arterial system, endothelial cells are both the source and target of factors contributing to atherosclerosis. Endothelial vasoactive factors regulate vascular homeostasis under physiological conditions and maintain basal vascular tone. Obesity results in an imbalance between endothelium-derived vasoactive factors favouring vasoconstriction, cell growth and inflammatory activation. Abnormal regulation of these factors due to endothelial cell dysfunction is both a consequence and a cause of vascular disease processes. Finally, because of the similarities of the vascular pathomechanisms activated, obesity can be considered to cause accelerated, ‘premature’ vascular aging. Here, we will review some of the pathomechanisms involved in obesity-related activation of endothelium-dependent vasoconstriction, the clinical relevance of obesity-associated vascular risk, and therapeutic interventions using ‘endothelial therapy’ aiming at maintaining or restoring vascular endothelial health. LINKED ARTICLES This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3 PMID:21557734

  15. Contribution of non-endothelium-dependent substances to exercise hyperaemia: are they O2 dependent?

    PubMed Central

    Marshall, Janice M; Ray, Clare J

    2012-01-01

    This review considers the contributions to exercise hyperaemia of substances released into the interstitial fluid, with emphasis on whether they are endothelium dependent or O2 dependent. The early phase of exercise hyperaemia is attributable to K+ released from contracting muscle fibres and acting extraluminally on arterioles. Hyperpolarization of vascular smooth muscle and endothelial cells induced by K+ may also facilitate the maintained phase, for example by facilitating conduction of dilator signals upstream. ATP is released into the interstitium from muscle fibres, at least in part through cystic fibrosis transmembrane conductance regulator-associated channels, following the fall in intracellular H+. ATP is metabolized by ectonucleotidases to adenosine, which dilates arterioles via A2A receptors, in a nitric oxide-independent manner. Evidence is presented that the rise in arterial achieved by breathing 40% O2 attenuates efflux of H+ and lactate, thereby decreasing the contribution that adenosine makes to exercise hyperaemia; efflux of inorganic phosphate and its contribution may likewise be attenuated. Prostaglandins (PGs), PGE2 and PGI2, also accumulate in the interstitium during exercise, and breathing 40% O2 abolished the contribution of PGs to exercise hyperaemia. This suggests that PGE2 released from muscle fibres and PGI2 released from capillaries and venular endothelium by a fall in their local act extraluminally to dilate arterioles. Although modest hyperoxia attenuates exercise hyperaemia by improving O2 supply, limiting the release of O2-dependent adenosine and PGs, higher O2 concentrations may have adverse effects. Evidence is presented that breathing 100% O2 limits exercise hyperaemia by generating O2−, which inactivates nitric oxide and decreases PG synthesis. PMID:23045341

  16. Serum alkaline phosphatase negatively affects endothelium-dependent vasodilation in naïve hypertensive patients.

    PubMed

    Perticone, Francesco; Perticone, Maria; Maio, Raffaele; Sciacqua, Angela; Andreucci, Michele; Tripepi, Giovanni; Corrao, Salvatore; Mallamaci, Francesca; Sesti, Giorgio; Zoccali, Carmine

    2015-10-01

    Tissue nonspecific alkaline phosphatase, promoting arterial calcification in experimental models, is a powerful predictor of total and cardiovascular mortality in general population and in patients with renal or cardiovascular diseases. For this study, to evaluate a possible correlation between serum alkaline phosphatase levels and endothelial function, assessed by strain gauge plethysmography, we enrolled 500 naïve hypertensives divided into increasing tertiles of alkaline phosphatase. The maximal response to acetylcholine was inversely related to alkaline phosphatase (r=−0.55; P<0.001), and this association was independent (r=−0.61; P<0.001) of demographic and classical risk factors, body mass index, estimated glomerular filtration rate, serum phosphorus and calcium, C-reactive protein, and albuminuria. At multiple logistic regression analysis, the risk of endothelial dysfunction was ≈3-fold higher in patients in the third tertile than that of patients in the first tertile. We also tested the combined role of alkaline phosphatase and serum phosphorus on endothelial function. The steepness of the alkaline phosphatase/vasodilating response to acetylcholine relationship was substantially attenuated (P<0.001) in patients with serum phosphorus above the median value when compared with patients with serum phosphorus below the median (−5.0% versus −10.2% per alkaline phosphatase unit, respectively), and this interaction remained highly significant (P<0.001) after adjustment of all the previously mentioned risk factors. Our data support a strong and significant inverse relationship between alkaline phosphatase and endothelium-dependent vasodilation, which was attenuated by relatively higher serum phosphorus levels. PMID:26324506

  17. Impairment of Coronary Arteriolar Endothelium-Dependent Dilation after Multi-Walled Carbon Nanotube Inhalation: A Time-Course Study

    PubMed Central

    Stapleton, Phoebe A.; Minarchick, Valerie C.; Cumpston, Amy M.; McKinney, Walter; Chen, Bean T.; Sager, Tina M.; Frazer, David G.; Mercer, Robert R.; Scabilloni, James; Andrew, Michael E.; Castranova, Vincent; Nurkiewicz, Timothy R.

    2012-01-01

    Engineered nanomaterials have been developed for widespread applications due to many highly unique and desirable characteristics. The purpose of this study was to assess pulmonary inflammation and subepicardial arteriolar reactivity in response to multi-walled carbon nanotube (MWCNT) inhalation and evaluate the time course of vascular alterations. Rats were exposed to MWCNT aerosols producing pulmonary deposition. Pulmonary inflammation via bronchoalveolar lavage and MWCNT translocation from the lungs to systemic organs was evident 24 h post-inhalation. Coronary arterioles were evaluated 24–168 h post-exposure to determine microvascular response to changes in transmural pressure, endothelium-dependent and -independent reactivity. Myogenic responsiveness, vascular smooth muscle reactivity to nitric oxide, and α-adrenergic responses all remained intact. However, a severe impact on endothelium-dependent dilation was observed within 24 h after MWCNT inhalation, a condition which improved, but did not fully return to control after 168 h. In conclusion, results indicate that MWCNT inhalation not only leads to pulmonary inflammation and cytotoxicity at low lung burdens, but also a low level of particle translocation to systemic organs. MWCNT inhalation also leads to impairments of endothelium-dependent dilation in the coronary microcirculation within 24 h, a condition which does not fully dissipate within 168 h. The innovations within the field of nanotechnology, while exciting and novel, can only reach their full potential if toxicity is first properly assessed. PMID:23203034

  18. Characteristics of arterial wall shear stress which cause endothelium-dependent vasodilatation in the anaesthetized dog

    PubMed Central

    Snow, H M; Markos, F; O'Regan, D; Pollock, K

    2001-01-01

    The effects of changes in the mean and amplitude of arterial wall shear stress on endothelium-dependent arterial dilatation of the iliac artery of the anaesthetized dog were examined. Changes in the mean and amplitude of blood flow and wall shear stress were brought about by varying local peripheral resistance and stroke volume using a distal infusion of acetylcholine and the stimulation of the left ansa subclavia. Changes in the diameter of a segment of the iliac artery with the endothelium intact, relative to a segment with no endothelium, were used as an index of the release of nitric oxide. The increase in mean blood flow was from 84 ± 12 to 527 ± 53 ml min−1 and in amplitude was from 365 ± 18 to 695 ± 38 ml min−1 (means ±s.e.m.). The increase in mean wall shear stress was from 1.78 ± 0.30 to 7.66 ± 1.01 N m−2 and in amplitude was from 7.37 ± 0.46 to 13.9 ± 2.00 N m−2 (means ±s.e.m.). Increases in mean shear stress caused an increase in the diameter only of the section of artery with endothelium; the slope of the relationship was 0.064 ± 0.006 mm N−1 m2 (mean ±s.e.m., P < 0.001); changes in the amplitude of shear stress did not cause an increase in diameter. Changes in both the mean and amplitude of shear stress had no significant effect on the diameter of the section of artery with no endothelium. These findings coupled with the known anti-atheroma effects of nitric oxide and the effect of shear stress on cell adhesion and platelet aggregation offer a possible explanation for the disposition of atheroma in those parts of the arterial system which have low mean and high amplitude of wall shear stress. PMID:11251063

  19. Acyl chain-dependent effect of lysophosphatidylcholine on endothelium-dependent vasorelaxation.

    PubMed

    Rao, Shailaja P; Riederer, Monika; Lechleitner, Margarete; Hermansson, Martin; Desoye, Gernot; Hallström, Seth; Graier, Wolfgang F; Frank, Saša

    2013-01-01

    Previously we identified palmitoyl-, oleoyl-, linoleoyl-, and arachidonoyl-lysophosphatidylcholine (LPC 16:0, 18:1, 18:2 and 20:4) as the most prominent LPC species generated by endothelial lipase (EL). In the present study, we examined the impact of those LPC on acetylcholine (ACh)- induced vascular relaxation. All tested LPC attenuated ACh-induced relaxation, measured ex vivo, using mouse aortic rings and wire myography. The rank order of potency was as follows: 18:2>20:4>16:0>18:1. The attenuating effect of LPC 16:0 on relaxation was augmented by indomethacin-mediated cyclooxygenase (COX)-inhibition and CAY10441, a prostacyclin (PGI2)- receptor (IP) antagonist. Relaxation attenuated by LPC 20:4 and 18:2 was improved by indomethacin and SQ29548, a thromboxane A2 (TXA2)- receptor antagonist. The effect of LPC 20:4 could also be improved by TXA2- and PGI2-synthase inhibitors. As determined by EIA assays, the tested LPC promoted secretion of PGI2, TXA2, PGF2α, and PGE2, however, with markedly different potencies. LPC 16:0 was the most potent inducer of superoxide anion production by mouse aortic rings, followed by LPC 18:2, 20:4 and 18:1, respectively. The strong antioxidant tempol recovered relaxation impairment caused by LPC 18:2, 18:1 and 20:4, but not by LPC 16:0. The tested LPC attenuate ACh-induced relaxation through induction of proconstricting prostanoids and superoxide anions. The potency of attenuating relaxation and the relative contribution of underlying mechanisms are strongly related to LPC acyl-chain length and degree of saturation. PMID:23741477

  20. Hormonal therapy with estradiol and drospirenone improves endothelium-dependent vasodilation in the coronary bed of ovariectomized spontaneously hypertensive rats.

    PubMed

    Borgo, M V; Claudio, E R G; Silva, F B; Romero, W G; Gouvea, S A; Moysés, M R; Santos, R L; Almeida, S A; Podratz, P L; Graceli, J B; Abreu, G R

    2016-01-01

    Drospirenone (DRSP) is a progestin with anti-aldosterone properties and it reduces blood pressure in hypertensive women. However, the effects of DRSP on endothelium-dependent coronary vasodilation have not been evaluated. This study investigated the effects of combined therapy with estrogen (E2) and DRSP on endothelium-dependent vasodilation of the coronary bed of ovariectomized (OVX) spontaneously hypertensive rats. Female spontaneously hypertensive rats (n=87) at 12 weeks of age were randomly divided into sham operated (Sham), OVX, OVX treated with E2 (E2), and OVX treated with E2 and DRSP (E2+DRSP) groups. Hemodynamic parameters were directly evaluated by catheter insertion into the femoral artery. Endothelium-dependent vasodilation in response to bradykinin in the coronary arterial bed was assessed using isolated hearts according to a modified Langendorff method. Coronary protein expression of endothelial nitric oxide synthase and estrogen receptor alpha (ER-α) was assessed by Western blotting. Histological slices of coronary arteries were stained with hematoxylin and eosin, and morphometric parameters were analyzed. Oxidative stress was assessed in situ by dihydroethidium fluorescence. Ovariectomy increased systolic blood pressure, which was only prevented by E2+DRSP treatment. Estrogen deficiency caused endothelial dysfunction, which was prevented by both treatments. However, the vasodilator response in the E2+DRSP group was significantly higher at the three highest concentrations compared with the OVX group. Reduced ER-α expression in OVX rats was restored by both treatments. Morphometric parameters and oxidative stress were augmented by OVX and reduced by E2 and E2+DRSP treatments. Hormonal therapy with E2 and DRSP may be an important therapeutic option in the prevention of coronary heart disease in hypertensive post-menopausal women. PMID:26577845

  1. Hormonal therapy with estradiol and drospirenone improves endothelium-dependent vasodilation in the coronary bed of ovariectomized spontaneously hypertensive rats

    PubMed Central

    Borgo, M.V.; Claudio, E.R.G.; Silva, F.B.; Romero, W.G.; Gouvea, S.A.; Moysés, M.R.; Santos, R.L.; Almeida, S.A.; Podratz, P.L.; Graceli, J.B.; Abreu, G.R.

    2015-01-01

    Drospirenone (DRSP) is a progestin with anti-aldosterone properties and it reduces blood pressure in hypertensive women. However, the effects of DRSP on endothelium-dependent coronary vasodilation have not been evaluated. This study investigated the effects of combined therapy with estrogen (E2) and DRSP on endothelium-dependent vasodilation of the coronary bed of ovariectomized (OVX) spontaneously hypertensive rats. Female spontaneously hypertensive rats (n=87) at 12 weeks of age were randomly divided into sham operated (Sham), OVX, OVX treated with E2 (E2), and OVX treated with E2 and DRSP (E2+DRSP) groups. Hemodynamic parameters were directly evaluated by catheter insertion into the femoral artery. Endothelium-dependent vasodilation in response to bradykinin in the coronary arterial bed was assessed using isolated hearts according to a modified Langendorff method. Coronary protein expression of endothelial nitric oxide synthase and estrogen receptor alpha (ER-α) was assessed by Western blotting. Histological slices of coronary arteries were stained with hematoxylin and eosin, and morphometric parameters were analyzed. Oxidative stress was assessed in situ by dihydroethidium fluorescence. Ovariectomy increased systolic blood pressure, which was only prevented by E2+DRSP treatment. Estrogen deficiency caused endothelial dysfunction, which was prevented by both treatments. However, the vasodilator response in the E2+DRSP group was significantly higher at the three highest concentrations compared with the OVX group. Reduced ER-α expression in OVX rats was restored by both treatments. Morphometric parameters and oxidative stress were augmented by OVX and reduced by E2 and E2+DRSP treatments. Hormonal therapy with E2 and DRSP may be an important therapeutic option in the prevention of coronary heart disease in hypertensive post-menopausal women. PMID:26577845

  2. Reduced agonist-induced endothelium-dependent vasodilation in uremia is attributable to an impairment of vascular nitric oxide.

    PubMed

    Passauer, Jens; Pistrosch, Frank; Büssemaker, Eckhart; Lässig, Grit; Herbrig, Kay; Gross, Peter

    2005-04-01

    Current concepts for the explanation of endothelial dysfunction and accelerated atherosclerosis in uremia propose a reduced vascular bioavailability of nitric oxide (NO). The aim of the present study was to test the contributions of NO and NO/prostacyclin (PGI(2))-independent mechanisms to both baseline vascular tone and agonist-induced endothelium-dependent vasodilation in patients on hemodialysis (HD). In 10 HD patients and eight matched healthy control subjects, forearm blood flow (FBF) was measured at rest and during intrabrachial infusions of norepinephrine (NE; endothelium-independent vasoconstrictor, 60, 120, and 240 pmol/min) and N-monomethyl-L-arginine (blocker of NO synthases, 16 micromol/min). After inhibition of cyclo-oxygenase by ibuprofen (1200 mg orally), endothelium-dependent and -independent vasodilation was assessed by infusion of acetylcholine (ACh; 1, 5, 10, 50, 100, and 300 nmol/min) and sodium-nitroprusside (2.5, 5, and 10 microg/min). NO/PGI(2)-independent vasodilation was tested by equal infusions of ACh during NO clamp. N-monomethyl-L-arginine reduced resting FBF to a comparable degree in both groups. Vascular responses to ACh were reduced in HD (P = 0.003 versus control by ANOVA), whereas those to sodium nitroprusside were mainly at control level. Infusion of ACh during NO clamp caused a similar increment of FBF in both groups. NO-mediated vasodilation as calculated by the difference between ACh-induced responses without and with NO clamp was substantially impaired in HD (P < 0.001) compared with control. In HD patients, baseline NO-mediated arteriolar tone is at control level. This study provides first evidence that endothelial dysfunction of uremic patients as shown by reduced agonist-induced endothelium-dependent vasodilation is attributable to reduced stimulation of NO, whereas the NO/PGI(2)-resistant portion of ACh-mediated vasodilation is unaffected. PMID:15728785

  3. Endothelium-Dependent and -Independent Vasodilator Effects of Dimethyl Sulfoxide in Rat Aorta.

    PubMed

    Kaneda, Takeharu; Sasaki, Noriyasu; Urakawa, Norimoto; Shimizu, Kazumasa

    2016-01-01

    This study examined the mechanism of vasorelaxation induced by dimethyl sulfoxide (DMSO) in endothelium-intact and -denuded rat aorta. DMSO (0.1-3%) inhibited phenylephrine (PE, 1 μmol/l)-induced contraction in a dose-dependent manner. However, this relaxation was lower in the absence of the endothelium. Increase in DMSO-induced relaxation in the presence of the endothelium was attenuated by preincubation in L-NG-nitroarginine methyl ester (L-NAME, 100 μmol/l) and by the removal of the endothelium. In the aorta with endothelium, DMSO (3%) and CCh (3 μmol/l) increased cGMP contents, significantly and L-NAME (100 μmol/l) inhibited the DMSO-induced increases of cGMP. In fura 2-loaded endothelium-denuded aorta, cumulative application of DMSO (1-3%) inhibited PE-induced muscle tension; however, this application did not affect the [Ca2+]i level. In PE-precontracted endothelium-denuded aorta, relaxation responses to fasudil were significantly less in the presence of DMSO compared to the control. These results suggest that DMSO causes relaxation by increasing the cGMP content in correlation with the release of NO from endothelial cells and by decreasing the Ca2+ sensitivity of contractile elements partly via inhibiting Rho-kinase in rat aorta. PMID:26836124

  4. Vascular microRNA-204 is remotely governed by the microbiome and impairs endothelium-dependent vasorelaxation by downregulating Sirtuin1.

    PubMed

    Vikram, Ajit; Kim, Young-Rae; Kumar, Santosh; Li, Qiuxia; Kassan, Modar; Jacobs, Julia S; Irani, Kaikobad

    2016-01-01

    Gut microbiota promotes atherosclerosis, and vascular endothelial dysfunction, signalled by impaired endothelium-dependent vasorelaxation, is an early marker of atherosclerosis. Here we show that vascular microRNA-204 (miR-204) expression is remotely regulated by the microbiome, and impairs endothelial function by targeting the Sirtuin1 lysine deacetylase (Sirt1). MiR-204 is downregulated, while Sirt1 is upregulated, in aortas of germ-free mice. Suppression of gut microbiome with broad-spectrum antibiotics decreases miR-204, increases Sirt1 and bioavailable vascular nitric oxide, and improves endothelium-dependent vasorelaxation in mouse aortas. Antibiotics curtail aortic miR-204 upregulation, and rescue decline of aortic Sirt1 and endothelium-dependent vasorelaxation, triggered by high-fat diet feeding. Improvement of endothelium-dependent vasorelaxation by antibiotics is lost in mice lacking endothelial Sirt1. Systemic antagonism of miR-204 rescues impaired endothelium-dependent vasorelaxation and vascular Sirt1, and decreases vascular inflammation induced by high-fat diet. These findings reveal a gut microbe-vascular microRNA-Sirtuin1 nexus that leads to endothelial dysfunction. PMID:27586459

  5. Inhibition of the release of endothelium-derived relaxing factor in vitro and in vivo by dipeptides containing NG-nitro-L-arginine.

    PubMed Central

    Thiemermann, C.; Mustafa, M.; Mester, P. A.; Mitchell, J. A.; Hecker, M.; Vane, J. R.

    1991-01-01

    1. We have shown that dipeptides containing NG-nitro-L-arginine (NO2Arg) inhibit the biosynthesis of endothelium-derived relaxing factor (EDRF) in vitro and in vivo. 2. In anaesthetized rats, intravenous administration at 1-30 mg kg-1 of the methyl ester of NO2Arg, NO2-Arg-L-phenylalanine (NO2Arg-Phe), L-alanyl-NO2Arg (Ala-NO2Arg) or NO2Arg-L-arginine (NO2Arg-Arg) produced dose-related increases in mean arterial blood pressure (MABP) which were unaffected by D-arginine (D-Arg; 20 mg kg-1 min-1 for 15 min), but prevented by co-infusions of L-arginine (L-Arg; 20 mg kg-1 min-1 for 15 min) or by their parent dipeptides. 3. NO2Arg methyl ester, NO2Arg-Phe methyl ester or Ala-NO2Arg methyl ester (10 mg kg-1, i.v.) also inhibited the reduction in MABP caused by the endothelium-dependent vasodilator, acetylcholine (30 micrograms kg-1 min-1 for 3 min), but not those induced by glycerly trinitrate (20 micrograms kg-1 min-1 for 3 min) or iloprost (6 micrograms kg-1 min-1 for 3 min) which act directly on the vascular smooth muscle. 4. Moreover, NO2Arg methyl ester, NO2Arg-Phe methyl ester or NO2Arg-Arg methyl ester (100 microM) inhibited the acetylcholine-induced relaxation of rabbit aortic strips, and NO2Arg-Phe methyl ester (30 microM) blocked the stimulated (bradykinin, 30 pmol) release of EDRF from bovine aortic endothelial cells grown on microcarrier beads.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1786515

  6. Sex differences in the role of transient receptor potential (TRP) channels in endothelium-dependent vasorelaxation in porcine isolated coronary arteries.

    PubMed

    Wong, Pui San; Roberts, Richard E; Randall, Michael D

    2015-03-01

    Endothelial and smooth muscle Transient Receptor Potential (TRP) channels contribute to regulation of vascular tone. We have previously reported sex differences in the endothelial function in porcine isolated coronary arteries (PCAs). The present study examined the role of TRP channels in endothelium-dependent and H2O2-induced vasorelaxations in male and female PCAs. Distal PCAs were mounted in a wire myograph and precontracted with U46619. Concentration-response curves to bradykinin, H2O2 and A23187 were constructed in the presence of TRP channel antagonists with or without L-NAME and indomethacin to inhibit NO synthase and cyclooxygenase respectively. 2-APB (TRPC & TRPM antagonist) inhibited the maximum relaxation (Rmax) of the bradykinin-induced vasorelaxation and abolished the EDH-type response in PCAs from both sexes. SKF96365 (TRPC antagonist) inhibited the Rmax of bradykinin-induced vasorelaxation in males, and inhibited Rmax of the EDH-type response in both sexes. Pyr3 (TRPC3 antagonist) inhibited both the NO and EDH components of the bradykinin-induced vasorelaxation in males, but not females. RN1734 (TRPV4 antagonist) reduced the potency of the NO component of the bradykinin-induced vasorelaxation in females only, but inhibited the Rmax of the EDH-type component in both sexes. 2-APB, SKF96365 and RN1734 all reduced the H2O2-induced vasorelaxation, whereas Pyr3 had no effect. No differences in expression level of TRPC3 and TRPV4 between sexes were detected using Western blot. Present study demonstrated a clear sex differences in the role TRP channels where TRPC3 play a role in the NO- and EDH-type response in males and TRPV4 play a role in the NO-mediated response in females. PMID:25620134

  7. Endothelium-dependent vasodilator effects of platelet activating factor on rat resistance vessels.

    PubMed Central

    Kamata, K.; Mori, T.; Shigenobu, K.; Kasuya, Y.

    1989-01-01

    1. To elucidate the mechanisms of the powerful and long-lasting hypotension produced by platelet activating factor (PAF), its effects on perfusion pressure in the perfused mesenteric arterial bed of the rat were examined. 2. Infusion of PAF (10(-11) to 3 x 10(-10) M; EC50 = 4.0 x 10(-11) M; 95%CL = 1.6 x 10(-11) - 9.4 x 10(-11) M) and acetylcholine (ACh) (10(-10) to 10(-6) M; EC50 = 3.0 +/- 0.1 x 10(-9) M) produced marked concentration-dependent vasodilatations which were significantly inhibited by treatment with detergents (0.1% Triton X-100 for 30 s or 0.3% CHAPS for 90 s). 3. Pretreatment with CV-6209, a PAF antagonist, inhibited PAF- but not ACh-induced vasodilation. 4. Treatment with indomethacin (10(-6) M) had no effect on PAF- or ACh-induced vasodilatation. 5. These results demonstrate that extremely low concentrations of PAF produce vasodilatation of resistance vessels through the release of endothelium-derived relaxing factor (EDRF). This may account for the strong hypotension produced by PAF in vivo. PMID:2611496

  8. Apamin-sensitive K+ channels mediate an endothelium-dependent hyperpolarization in rabbit mesenteric arteries.

    PubMed Central

    Murphy, M E; Brayden, J E

    1995-01-01

    1. Vascular endothelial cells release a variety of substances which affect the membrane potential and tone of underlying vascular smooth muscle. In the presence of N omega-nitro-L-arginine to inhibit nitric oxide synthase and indomethacin to inhibit cyclo-oxygenase, acetylcholine (ACh; EC50 approximately 1 microM) elicited the release of an endothelium-derived hyperpolarizing factor (EDHF) in rabbit mesenteric arteries. 2. The hyperpolarization due to EDHF was blocked by apamin (IC50 approximately 0.3 nM), and by other inhibitors of the apamin-sensitive K+ channel (10 nM scyllatoxin, 100 microM d-tubocurarine, 300 microM gallamine) in the presence of indomethacin and N omega-nitro-L-arginine. The hyperpolarization was not blocked by glibenclamide (5 microM), iberiotoxin (10 nM), tetraethylammonium (1 mM), barium (500 microM), 4-aminopyridine (500 microM), ouabain (10 microM), bumetanide (10 microM), or nimodipine (100 nM). 3. In the presence of apamin and N omega-nitro-L-arginine, but the absence of indomethacin, ACh triggered a hyperpolarization that was blocked by glibenclamide, an inhibitor of ATP-sensitive K+ (KATP) channels. A similar glibenclamide-sensitive hyperpolarization was caused by Iloprost, a stable analogue of prostacyclin. 4. In experiments which distinguished the effects of EDHF, prostanoids and nitric oxide, hyperpolarizations and/or relaxations triggered by ACh were antagonized by muscarinic antagonists, the relative potencies (atropine approximately 4-DAMP > pirenzepine) of which indicated that the release of all three endothelium-derived factors was mediated by M3 receptors. 5. Our results suggest that ACh stimulates M3 receptors on endothelial cells, triggering the release of nitric oxide and prostanoids, which hyperpolarize underlying smooth muscle by activation of KATP channels, and the release of an EDHF, which hyperpolarizes smooth muscle through the activation of apamin-sensitive K+ (KAS) channels. Images Figure 4 PMID:8788937

  9. Unitary TRPV3 channel Ca2+ influx events elicit endothelium-dependent dilation of cerebral parenchymal arterioles.

    PubMed

    Pires, Paulo W; Sullivan, Michelle N; Pritchard, Harry A T; Robinson, Jennifer J; Earley, Scott

    2015-12-15

    Cerebral parenchymal arterioles (PA) regulate blood flow between pial arteries on the surface of the brain and the deeper microcirculation. Regulation of PA contractility differs from that of pial arteries and is not completely understood. Here, we investigated the hypothesis that the Ca(2+) permeable vanilloid transient receptor potential (TRPV) channel TRPV3 can mediate endothelium-dependent dilation of cerebral PA. Using total internal reflection fluorescence microscopy (TIRFM), we found that carvacrol, a monoterpenoid compound derived from oregano, increased the frequency of unitary Ca(2+) influx events through TRPV3 channels (TRPV3 sparklets) in endothelial cells from pial arteries and PAs. Carvacrol-induced TRPV3 sparklets were inhibited by the selective TRPV3 blocker isopentenyl pyrophosphate (IPP). TRPV3 sparklets have a greater unitary amplitude (ΔF/F0 = 0.20) than previously characterized TRPV4 (ΔF/F0 = 0.06) or TRPA1 (ΔF/F0 = 0.13) sparklets, suggesting that TRPV3-mediated Ca(2+) influx could have a robust influence on cerebrovascular tone. In pressure myography experiments, carvacrol caused dilation of cerebral PA that was blocked by IPP. Carvacrol-induced dilation was nearly abolished by removal of the endothelium and block of intermediate (IK) and small-conductance Ca(2+)-activated K(+) (SK) channels. Together, these data suggest that TRPV3 sparklets cause dilation of cerebral parenchymal arterioles by activating IK and SK channels in the endothelium. PMID:26453324

  10. Endothelial Small- and Intermediate-Conductance K Channels and Endothelium-Dependent Hyperpolarization as Drug Targets in Cardiovascular Disease.

    PubMed

    Köhler, R; Oliván-Viguera, A; Wulff, H

    2016-01-01

    Endothelial calcium/calmodulin-gated K channels of small (KCa2.3) and intermediate conductance (KCa3.1) produce membrane hyperpolarization and endothelium-dependent hyperpolarization (EDH)-mediated vasodilation. Dysfunctions of the two channels and ensuing EDH impairments are found in several cardiovascular pathologies such as diabetes, atherosclerosis, postangioplastic neointima formation, but also inflammatory disease, cancer, and organ fibrosis. Moreover, KCa3.1 plays an important role in endothelial barrier dysfunction, edema formation in cardiac and pulmonary disease, and in ischemic stroke. Concerning KCa2.3, genome-wide association studies revealed an association of KCa2.3 channels with atrial fibrillation in humans. Accordingly, both channels are considered potential drug targets for cardio- and cerebrovascular disease states. In this chapter, we briefly review the function of the two channels in EDH-type vasodilation and systemic circulatory regulation and then highlight their pathophysiological roles in ischemic stroke as well as in pulmonary and brain edema. Finally, the authors summarize recent advances in the pharmacology of the channels and explore potential therapeutic utilities of novel channel modulators. PMID:27451095

  11. Effects of red and white wine on endothelium-dependent vasorelaxation of rat aorta and human coronary arteries.

    PubMed

    Flesch, M; Schwarz, A; Böhm, M

    1998-10-01

    Beneficial effects of wine on myocardial infarction mortality may be because of its vasodilatory properties. This study investigated whether the vasodilatory activity involves the endothelium and is specific for certain wines. Effects of different red and white wines and phenolic grape ingredients on vascular tension and cGMP content were studied in human coronary arteries and rat aortic rings in vitro. Only French and Italian red wines produced "en barrique" (Bordeaux, Châteauneuf du Pape, Barolo) (1:1,000, vol/vol), quercetin (1-100 microM), and tannic acid (1-100 microgram/ml) decreased tension of precontracted vascular rings and increased vascular cGMP content (both P < 0.001). The effects were abolished after endothelial denudation and reversible by nitric oxide synthase inhibition. Red wines not produced en barrique (Valpolicella, Ahr Spätburgunder), white wines (en barrique-produced Rioja, Chardonnay, Mosel-Riesling), and ethanol did not affect vascular tension or cGMP content. Thus endothelium-dependent vasodilatory effects appear to be specific for red barrique wines, possibly because of their high content of phenolic substances. Divergent effects of wines indicate that a general view on the effects of wine and alcoholic beverages is not warranted. PMID:9746465

  12. Retrospectively gated MRI for in vivo assessment of endothelium-dependent vasodilatation and endothelial permeability in murine models of endothelial dysfunction.

    PubMed

    Bar, Anna; Skórka, Tomasz; Jasiński, Krzysztof; Sternak, Magdalena; Bartel, Żaneta; Tyrankiewicz, Urszula; Chlopicki, Stefan

    2016-08-01

    Endothelial dysfunction is linked to impaired endothelial-dependent vasodilatation and permeability changes. Here, we quantify both of these phenomena associated with endothelial dysfunction by MRI in vivo in mice. Endothelial function was evaluated in the brachiocephalic artery (BCA) and left carotid artery (LCA) in ApoE/LDLR(-/-) and high-fat diet (HFD)-fed mice as compared with control mice (C57BL/6J). The 3D IntraGate® FLASH sequence was used for evaluation of changes in vessels' cross-sectional area (CSA) and volume following acetylcholine (Ach) administration. Evaluation of endothelial permeability after administration of contrast agent (Galbumin, BioPAL) was based on the variable flip angle method for the assessment of parameters based on the relaxation time (T1 ) value. In order to confirm the involvement of nitric oxide (NO) in response to Ach, L-NAME-treated mice were also analyzed. To confirm that endothelial permeability changes accompany the impairment of Ach-dependent vasodilatation, permeability changes were analyzed in isolated, perfused carotid artery. In C57BL/6J mice, Ach-induced vasodilatation led to an approximately 25% increase in CSA in both vessels, which was temporarily dissociated from the effect of Ach on heart rate. In ApoE/LDLR(-/-) or HFD-fed mice Ach induced a paradoxical vasoconstriction that amounted to approximately 30% and 50% decreases in CSA of BCA and LCA respectively. In ApoE/LDLR(-/-) and HFD-fed mice endothelial permeability in BCA was also increased (fall in T1 by about 25%). In L-NAME-treated mice Ach-induced vasodilatation in BCA was lost. In isolated, perfused artery from ApoE/LDLR(-/-) mice endothelial permeability was increased. MRI-based assessment of endothelium-dependent vasodilatation induced by Ach and endothelial permeability using a retrospectively self-gated 3D gradient-echo sequence (IntraGate® FLASH) enables the reliable detection of systemic endothelial dysfunction in mice and provides an important tool

  13. Diabetes and the Mediterranean diet: a beneficial effect of oleic acid on insulin sensitivity, adipocyte glucose transport and endothelium-dependent vasoreactivity.

    PubMed

    Ryan, M; McInerney, D; Owens, D; Collins, P; Johnson, A; Tomkin, G H

    2000-02-01

    Abnormalities in endothelial function may be associated with increased cardiovascular risk in diabetic patients. We examined the effect of an oleic-acid-rich diet on insulin resistance and endothelium-dependent vasoreactivity in type 2 diabetes. Eleven type 2 diabetic patients were changed from their usual linoleic-acid-rich diet and treated for 2 months with an oleic-acid-rich diet. Insulin-mediated glucose transport was measured in isolated adipocytes. Fatty acid composition of the adipocyte membranes was determined by gas-liquid chromatography and flow-mediated endothelium-dependent and -independent vasodilatation were measured in the superficial femoral artery at the end of each dietary period. There was a significant increase in oleic acid and a decrease in linoleic acid on the oleic-acid-rich diet (p<0.0001). Diabetic control was not different between the diets, but there was a small but significant decrease in fasting glucose/insulin on the oleic-acid-rich diet. Insulin-stimulated (1 ng/ml) glucose transport was significantly greater on the oleic- acid-rich diet (0.56+/-0.17 vs. 0.29+/-0.14 nmol/10(5) cells/3 min, p<0.0001). Endothelium-dependent flow-mediated vasodilatation (FMD) was significantly greater on the oleic-acid-rich diet (3.90+/-0.97% vs. 6.12+/-1.36% p<0.0001). There was a significant correlation between adipocyte membrane oleic/linoleic acid and insulin-mediated glucose transport (p<0.001) but no relationship between insulin-stimulated glucose transport and change in endothelium-dependent FMD. There was a significant positive correlation between adipocyte membrane oleic/linoleic acid and endothelium-dependent FMD (r=0.61, p<0.001). Change from polyunsaturated to monounsaturated diet in type 2 diabetes reduced insulin resistance and restored endothelium-dependent vasodilatation, suggesting an explanation for the anti-atherogenic benefits of a Mediterranean-type diet. PMID:10700478

  14. Mechanism underlying H2O2-induced inhibition of acetylcholine-induced contraction in rabbit tracheal smooth muscle.

    PubMed

    Saito, Michihiro; Watanabe, Yoshimasa; Itoh, Takeo

    2007-02-28

    The mechanism underlying the inhibition by H2O2 of acetylcholine-induced contraction was investigated in epithelium-denuded strips of rabbit trachea. Acetylcholine (10 microM) generated a phasic, followed by a tonic increase in both the intracellular Ca2+ concentration ([Ca2+]i) and force. Although the acetylcholine-induced tonic contraction was around 9 times the high K+ (80 mM)-induced one, the two stimulants induced similar [Ca2+]i increases (around 0.2 microM), indicating that acetylcholine generates tonic contraction via increases in both [Ca2+]i and myofilament Ca2+-sensitivity. H2O2 (30 microM) (a) enhanced the acetylcholine-induced tonic (not phasic) increase in [Ca2+]i but attenuated both phases of the acetylcholine-induced contraction and (b) enhanced the high K+-induced increase in [Ca2+]i but did not modify the high K+-induced contraction. In beta-escin-skinned strips, application of acetylcholine in the presence of GTP enhanced the contraction induced by 0.3 microM Ca2+ so that its amplitude became similar to that induced by 1 microM Ca2+. H2O2 (30 microM) attenuated the contraction induced by 0.3 microM Ca2+ (alone or in the presence of acetylcholine) but not those induced by higher concentrations of Ca2+ alone (0.5 microM and 1 microM). These results indicate that H2O2 acts directly on contractile proteins in rabbit tracheal smooth muscle to inhibit the contraction induced by low concentrations of Ca2+ (<0.5 microM). An action of H2O2 that increases [Ca2+]i (and thereby masks this reactive-oxygen-induced inhibition of myofilament Ca2+-sensitivity) is apparent in the presence of high K+ but not of acetylcholine. Thus, in rabbit tracheal smooth muscle H2O2 downregulates myofilament Ca2+-sensitivity more potently during acetylcholine-induced contraction than during high-K+-induced contraction, leading to an effective inhibition of the former contraction. PMID:17188263

  15. Hyperoxic gassing with Tiron enhances bradykinin-induced endothelium-dependent and EDH-type relaxation through generation of hydrogen peroxide.

    PubMed

    Wong, Pui San; Roberts, Richard E; Randall, Michael D

    2015-01-01

    Oxygenation with 95%O2 is routinely used in organ bath studies. However, hyperoxia may affect tissue responses, particularly in studies which involve reactive oxygen species (ROS). Here, the effects of the antioxidant, Tiron, were investigated under different gassing conditions in the porcine isolated coronary artery (PCA). Distal PCAs from male and female pigs were mounted in a wire myograph gassed with either 95%O2/5%CO2 or 95% air/5%CO2 and pre-contracted with U46619. Concentration-response curves to bradykinin were constructed in the presence of Tiron (1mM), a cell permeable superoxide scavenger and catalase (1000Uml(-1)) to breakdown H2O2. The H2O2 level in Krebs'-Henseleit solution was detected using Amplex Red. Bradykinin produced concentration-dependent vasorelaxations in male and female PCAs when gassed with either 95%O2 or air, with no differences in the Rmax or EC50. Tiron increased the potency of bradykinin only when gassed with 95%O2 in PCAs from both sexes. At 95%O2, catalase prevented the leftward shift caused by Tiron in both sexes indicating that catalase prevented the formation of H2O2 by Tiron. In female PCAs, addition of catalase to Tiron significantly reduced the Rmax. In the EDH-type response (using L-NAME and indomethacin), Tiron enhanced the potency of the bradykinin-induced vasorelaxation when gassed with 95%O2 in PCAs from both sexes. Biochemical analysis using Amplex Red demonstrated that H2O2 was generated in Krebs'-Henseleit solution when gassed with 95%O2, but not with air. Therefore, hyperoxic gassing conditions could alter the environment generating superoxide within the Krebs'-Henseleit buffer, which may, in turn, influence the in vitro pharmacological responses. PMID:25450247

  16. Comparison of endothelium-derived relaxing factor activity between nonpregnant and pregnant rats.

    PubMed

    Honda, H; Kaneko, H; Kondo, M; Kogo, H

    1996-07-01

    The tension of isolated ring preparation of aorta from nonpregnant and pregnant rats was measured isometrically to study the effect of pregnancy on endothelium-derived relaxing factor activity. Contraction in response to norepinephrine and potassium chloride was greater in aortae from nonpregnant rats than in those from pregnant rats. The endothelium-dependent relaxation that was caused by acetylcholine (10(-10)-3 x 10(-9) M) in aortae precontracted with norepinephrine was significantly enhanced in aortae from pregnant rats compared with the relaxation in those from nonpregnant rats. NG-nitro-L-arginine methyl ester (L-NAME) inhibited the endothelium-dependent relaxation in both aorta from pregnant and nonpregnant rats. L-Arginine reversed the inhibition of L-NAME. Those results suggest that the enhanced endothelium-derived relaxing factor activity in rats aortae is associated with pregnancy. PMID:8856958

  17. Endothelium-derived Relaxing Factors of Small Resistance Arteries in Hypertension

    PubMed Central

    2014-01-01

    Endothelium-derived relaxing factors (EDRFs), including nitric oxide (NO), prostacyclin (PGI2), and endothelium-derived hyperpolarizing factor (EDHF), play pivotal roles in regulating vascular tone. Reduced EDRFs cause impaired endothelium-dependent vasorelaxation, or endothelial dysfunction. Impaired endothelium-dependent vasorelaxation in response to acetylcholine (ACh) is consistently observed in conduit vessels in human patients and experimental animal models of hypertension. Because small resistance arteries are known to produce more than one type of EDRF, the mechanism(s) mediating endothelium-dependent vasorelaxation in small resistance arteries may be different from that observed in conduit vessels under hypertensive conditions, where vasorelaxation is mainly dependent on NO. EDHF has been described as one of the principal mediators of endothelium-dependent vasorelaxation in small resistance arteries in normotensive animals. Furthermore, EDHF appears to become the predominant endothelium-dependent vasorelaxation pathway when the endothelial NO synthase (NOS3)/NO pathway is absent, as in NOS3-knockout mice, whereas some studies have shown that the EDHF pathway is dysfunctional in experimental models of hypertension. This article reviews our current knowledge regarding EDRFs in small arteries under normotensive and hypertensive conditions. PMID:25343007

  18. Renal hypoperfusion and impaired endothelium-dependent vasodilation in an animal model of VILI: the role of the peroxynitrite-PARP pathway

    PubMed Central

    2010-01-01

    Introduction Mechanical ventilation (MV) can injure the lungs and contribute to an overwhelming inflammatory response, leading to acute renal failure (ARF). We previously showed that poly(adenosine diphosphate-ribose) polymerase (PARP) is involved in the development of ventilator-induced lung injury (VILI) and the related ARF, but the mechanisms underneath remain unclear. In the current study we therefore tested the hypothesis that renal blood flow and endothelial, functional and tissue changes in the kidney of rats with lipopolysaccharide (LPS)-induced lung injury aggravated by MV, is caused, in part, by activation of PARP by peroxynitrite. Methods Anesthetized Sprague Dawley rats (n = 31), were subjected to intratracheal instillation of lipopolysaccharide at 10 mg/kg followed by 210 min of mechanical ventilation at either low tidal volume (6 mL/kg) with 5 cm H2O positive end-expiratory pressure or high tidal volume (19 mL/kg) with zero positive end-expiratory pressure in the presence or absence of a peroxynitrite decomposition catalyst, WW85 or a PARP inhibitor, PJ-34. During the experiment, hemodynamics and blood gas variables were monitored. At time (t) t = 0 and t = 180 min, renal blood flow was measured. Blood and urine were collected for creatinine clearance measurement. Arcuate renal arteries were isolated for vasoreactivity experiment and kidneys snap frozen for staining. Results High tidal volume ventilation resulted in lung injury, hypotension, renal hypoperfusion and impaired renal endothelium-dependent vasodilation, associated with renal dysfunction and tissue changes (leukocyte accumulation and increased expression of neutrophil gelatinase-associated lipocalin). Both WW85 and PJ-34 treatments attenuated lung injury, preserved blood pressure, attenuated renal endothelial dysfunction and maintained renal blood flow. In multivariable analysis, renal blood flow improvement was, independently from each other, associated with both maintained blood pressure

  19. Characterization of agonist-induced endothelium-dependent vasodilatory responses in the vascular bed of the equine digit.

    PubMed

    Berhane, Y; Bailey, S R; Putignano, C; Elliott, J

    2008-02-01

    The role of endothelium-derived relaxing factors was studied in the regulation of vascular responses in the Krebs perfused equine isolated digit. Perfusion pressure was recorded in response to bolus doses of 5-hydroxytryptamine (6 nmol) alone or co-administered with carbachol (CCh; 0.2 micromol), bradykinin (BK; 0.2 nmol), substance P (SP; 0.2 nmol) or sodium nitroprusside (SNP; 0.2 micromol). N(omega)-Nitro-L-Arginine methyl ester hydrochloride (L-NAME; 300 microm) caused partial but significant inhibition of CCh-induced vasodilatory response, whereas BK and SP-induced responses were resistant to L-NAME. High potassium (K(+), 30 mm) and the cytochrome P-450 (CYP) epoxygenase inhibitor, clotrimazole (10 microm) plus L-NAME (100 microm), completely abolished the CCh, BK and SP-induced vasodilatory responses, whereas the response to SNP was unaffected. In contrast, the L-NAME-resistant proportion of CCh, BK and SP-induced vasodilatory response was not inhibited by the highly selective CYP2C9 inhibitor, sulphaphenazole (10 microm). The cyclo-oxygenase inhibitor, ibuprofen (10 microm) did not affect the CCh, BK and SP-induced responses. These data demonstrate that CCh, BK and SP-induced relaxation in the equine digit involve a combination of the NO and endothelium-derived hyperpolarizing factor (EDHF) pathways. These results do not support the evidence for the involvement of CYP-derived epoxyeicosatrienoic acids and the exact nature of EDHF in the equine digit remains to be established. PMID:18177312

  20. Blood pressure lowering effect of the extract of aerial parts of Capparis aphylla is mediated through endothelium-dependent and independent mechanisms.

    PubMed

    Shah, Abdul Jabbar; Gilani, Anwarul Hassan

    2011-01-01

    This investigation was aimed to provide pharmacological evidences for the medicinal use of Capparis aphylla in hypertension. In normotensive anesthetized rats, intravenous administration of the crude extract of Capparis aphylla (Ca.Cr; 3-100 mg/kg) caused a fall in mean arterial pressure (MAP), which was partially blocked in the presence of atropine (2 mg/kg). In isolated rabbit aortic rings, Ca.Cr inhibited phenylephrine (1 μM) and high K(+) (80 mM) precontractions with respective EC(50) values of 0.10 (0.07-0.15) and 1.22 mg/mL (1.00-1.50), suggesting calcium channel blocking (CCB) activity with a predominant inhibitory effect on receptor operated Ca(2+) channels. Pretreatment of the arotic rings with Ca.Cr (0.1-1 mg/mL) caused a rightward shift in the Ca(2+) concentration response curves, similar to verapamil. In isolated rat aorta preparations, Ca.Cr caused a partial endothelium-dependent L-NAME/atropine-sensitive vasodilator effect. In guinea-pig atria, Ca.Cr suppressed both rate and force of spontaneous atrial contractions with respective EC(50) values of 1.35 (1.01-1.79) and 1.60 mg/mL (1.18-2.17), which remained unchanged in the presence of atropine (1 μM). These data indicate that the blood pressure (BP) lowering effect of the crude extract of Capparis aphylla is mediated through a vasodilator and cardiac depressant effect. The vasodilator effect is partly mediated by an endothelium-dependent, atropine-sensitive NO pathway, while the CCB effect is partly responsible for endothelium-independent vasodilatation and also for the cardiac depressant effect; thus, this study provides pharmacologic evidence with respect to the medicinal use of the plant in hypertension. PMID:21978026

  1. Tirofiban induces vasorelaxation of the coronary artery via an endothelium-dependent NO-cGMP signaling by activating the PI3K/Akt/eNOS pathway.

    PubMed

    Xia, Tianyang; Guan, Weiwei; Fu, Jinjuan; Zou, Xue; Han, Yu; Chen, Caiyu; Zhou, Lin; Zeng, Chunyu; Wang, Wei Eric

    2016-06-01

    Tirofiban, a glycoprotein IIb/IIIa inhibitor, is an antiplatelet drug extensively used in patients with acute coronary syndrome (ACS) and exerts an therapeutic effect on no-reflow phenomenon during percutaneous coronary intervention (PCI). Previous studies elucidated the vasodilation caused by tirofiban in the peripheral artery. However, whether tirofiban exerts a vasodilator effect on the coronary artery is unclear. Our present study found that tirofiban induced endothelium-dependent vasodilation in a concentration- and time-dependent manner in the isolated rat coronary artery pre-constricted by 5-hydroxytryptamine (5-HT). Further study showed that incubation of human umbilical venous endothelial cells (HUVECs) with tirofiban increased NO production, which was ascribed to the increased eNOS phosphorylation. This was confirmed by the loss of the vasorelaxant effect of tirofiban in the presence of l-NAME (eNOS inhibitor) and L-NMMA (NOS inhibitor) but not SMT (iNOS inhibitor) on isolated rat coronary arteries. The vasorelaxation was also blocked by the PI3K inhibitors, wortmannin and LY294002, as well as the Akt inhibitor SH-5, indicating the role of PI3K and Akt in tirofiban-mediated vasodilation. Moreover, further study showed that soluble guanylyl cyclase (sGC) inhibitor ODQ, or blockers of potassium channel (big-conductance calcium-activated potassium channel) blocked tirofiban-induced vasodilation of the coronary artery. These findings suggest that tirofiban induces vasorelaxation via an endothelium-dependent NO-cGMP signaling through the activation of the Akt/eNOS/sGC pathway. PMID:27018249

  2. Dietary obesity increases NO and inhibits BKCa-mediated, endothelium-dependent dilation in rat cremaster muscle artery: association with caveolins and caveolae.

    PubMed

    Howitt, Lauren; Grayson, T Hilton; Morris, Margaret J; Sandow, Shaun L; Murphy, Timothy V

    2012-06-15

    Obesity is a risk factor for hypertension and other vascular disease. The aim of this study was to examine the effect of diet-induced obesity on endothelium-dependent dilation of rat cremaster muscle arterioles. Male Sprague-Dawley rats (213 ± 1 g) were fed a cafeteria-style high-fat or control diet for 16-20 wk. Control rats weighed 558 ± 7 g compared with obese rats 762 ± 12 g (n = 52-56; P < 0.05). Diet-induced obesity had no effect on acetylcholine (ACh)-induced dilation of isolated, pressurized (70 mmHg) arterioles, but sodium nitroprusside (SNP)-induced vasodilation was enhanced. ACh-induced dilation of arterioles from control rats was abolished by a combination of the K(Ca) blockers apamin, 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34), and iberiotoxin (IBTX; all 0.1 μmol/l), with no apparent role for nitric oxide (NO). In arterioles from obese rats, however, IBTX had no effect on responses to ACh while the NO synthase (NOS)/guanylate cyclase inhibitors N(ω)-nitro-L-arginine methyl ester (L-NAME; 100 μmol/l)/1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 10 μmol/l) partially inhibited ACh-induced dilation. Furthermore, NOS activity (but not endothelial NOS expression) was increased in arteries from obese rats. L-NAME/ODQ alone or removal of the endothelium constricted arterioles from obese but not control rats. Expression of caveolin-1 and -2 oligomers (but not monomers or caveolin-3) was increased in arterioles from obese rats. The number of caveolae was reduced in the endothelium of arteries, and caveolae density was increased at the ends of smooth muscle cells from obese rats. Diet-induced obesity abolished the contribution of large-conductance Ca(2+)-activated K(+) channel to ACh-mediated endothelium-dependent dilation of rat cremaster muscle arterioles, while increasing NOS activity and inducing an NO-dependent component. PMID:22492718

  3. The expression of p66shc in peripheral blood monocytes is increased in patients with coronary heart disease and correlated with endothelium-dependent vasodilatation.

    PubMed

    Miao, Qin; Wang, Qiong; Dong, Lini; Wang, Yanjiao; Tan, Yi; Zhang, Xiangyu

    2015-07-01

    The objective of this study is to detect the p66shc mRNA and protein expression of the peripheral blood monocytes (PBMs) in coronary heart disease patients (CHD) and controls, to evaluate the correlation between the expression of p66shc mRNA in the PBMs and endothelium-dependent vasodilatation. This study included 78 coronary angiography-documented CHD patients (CHD group) and 38 non-CHD controls (control group). The p66shc mRNA and protein levels were determined by quantitative real-time PCR and western blotting. The flow-mediated dilatation (FMD, endothelium-dependent), nitroglycerine-induced dilatation (NID, endothelium-independent) and carotid intimal medial thickness (CIMT) were detected using high-resolution ultrasound. The p66shc mRNA and the protein expression levels in the PBMs were significantly higher in the CHD group compared with the control group (p = 0.007 and 0.001). The FMD (p < 0.001) and NID (p = 0.013) were significantly lower and the CIMT (p = 0.007) was significantly thicker in the CHD patients than in the controls. In the univariate analysis, the expression of the p66shc mRNA in the PBMs was significantly positively correlated with the serum LDL-C and homocysteine levels and the CIMT and was inversely correlated with the FMD and the NID (all p < 0.001). In the multiple linear regression analysis, the FMD (p < 0.001), LDL-C (p = 0.002) and homocysteine levels (p = 0.002) remained independently correlated with the p66shc mRNA expression. These findings highlight a pivotal role for the expression of p66shc in CHD and endothelial dysfunction, which might represent a molecular target to prevent endothelial dysfunction-related disease. PMID:24676406

  4. Cilostazol Enhances Mobilization of Circulating Endothelial Progenitor Cells and Improves Endothelium-Dependent Function in Patients at High Risk of Cardiovascular Disease.

    PubMed

    Chao, Ting-Hsing; Chen, I-Chih; Lee, Cheng-Han; Chen, Ju-Yi; Tsai, Wei-Chuan; Li, Yi-Heng; Tseng, Shih-Ya; Tsai, Liang-Miin; Tseng, Wei-Kung

    2016-08-01

    This is the first study to investigate the vasculoangiogenic effects of cilostazol on endothelial progenitor cells (EPCs) and flow-mediated dilatation (FMD) in patients at high risk of cardiovascular disease (CVD). This double-blind, placebo-controlled study included 71 patients (37 received 200 mg/d cilostazol and 34 received placebo for 12 weeks). Use of cilostazol, but not placebo, significantly increased circulating EPC (kinase insert domain receptor(+)CD34(+)) counts (percentage changes: 149.0% [67.9%-497.8%] vs 71.9% [-31.8% to 236.5%], P = .024) and improved triglyceride and high-density lipoprotein cholesterol levels (P = .002 and P = .003, respectively). Plasma levels of vascular endothelial growth factor (VEGF)-A165 and FMD significantly increased (72.5% [32.9%-120.4%] vs -5.8% [-46.0% to 57.6%], P = .001; 232.8% ± 83.1% vs -46.9% ± 21.5%, P = .003, respectively) in cilostazol-treated patients. Changes in the plasma triglyceride levels significantly inversely correlated with the changes in the VEGF-A165 levels and FMD. Cilostazol significantly enhanced the mobilization of EPCs and improved endothelium-dependent function by modifying some metabolic and angiogenic markers in patients at high risk of CVD. PMID:27401788

  5. Effect of membrane potential on acetylcholine-induced inward current in guinea-pig ileum.

    PubMed Central

    Inoue, R; Isenberg, G

    1990-01-01

    1. The whole-cell patch clamp technique with caesium aspartate internal solution was used with single isolated cells from the longitudinal muscle layer of guinea-pig ileum, to investigate the voltage-dependent gating of ACh-induced inward current. 2. In voltage clamp experiments, at holding potentials ranging from -80 to -30 mV, ACh (300 microM) produced a slow sustained inward current in physiological salt bath solution (PSS). The measurements of the reversal potentials on substituting Na+ by other monovalent and divalent cations showed that this current is through non-selective cation channels (Ins, ACh). 3. During hyperpolarizations, Ins, ACh instantaneously increased in amplitude and then relaxed to a new steady-state level. The I-V relationship of the instantaneous peak was linear with a reversal potential of 0 mV, while that of the steady state was bell-shaped. The time course of relaxation appeared to be monoexponential and its time constants were reduced by stronger hyperpolarizations. 4. These results were not affected by the organic Ca2+ antagonists D600 or nitrendipine (10 microM). Under this condition, maximal chord conductance of Ins, Ach which was observed at 0 mV was about 1.5 nS. The steady-state activation relationship was well fitted by Boltzmann's equation with a half-maximal activation (Vh) of -50 mV and a slope factor (k) of -15 mV at membrane potentials negative to 0 mV, but over 0 mV the degree of activation was again decreased. The time constants for relaxation also appeared to follow a sigmoid curve. 5. In current clamp experiments, superfusion of ACh (300 microM) depolarized the membrane up to -10 to 0 mV. Inward current injection resulting in the moderate hyperpolarization of the membrane (-70 to -80 mV) attenuated ACh-induced depolarization and stronger hyperpolarization (less than -80 mV) abolished it. 6. These results show that ACh-induced depolarization is controlled by the membrane potential, which is explained by the voltage

  6. Acute effect of rosiglitazone on relaxation responses in hypercholesterolemic corpus cavernosum.

    PubMed

    Akdag, H; Murat, N; Evcim, S; Esen, A; Gidener, S

    2016-05-01

    Thiazolidinediones (TZDs) improve vascular endothelial dysfunction through non-genomic effects of peroxisomal proliferator-activated receptor γ. This study investigated the acute effect of one of the TZD, rosiglitazone, on endothelium-dependent relaxation response of corpus cavernosum (CC) in hypercholesterolemic rabbits. New Zealand rabbits were divided into two groups randomly as control and cholesterol groups. Hypercholesterolemia was induced by feeding rabbits with 2% cholesterol diet (w/w) for 6 weeks. Endothelium-dependent and -independent relaxation response of CC were evaluated in the presence of rosiglitazone by organ bath studies with cumulative doses of acetylcholine (Ach) and sodium nitroprusside (SNP). Maximal relaxation (Emax) response to Ach significantly decreased owing to hypercholesterolemia in CC tissues. However, in vitro incubation of rosiglitazone with different concentrations (0.1, 1 and 10 μm) did not improve the Ach-dependent Emax responses in hypercholesterolemic rabbit CC. Surprisingly, rosiglitazone caused a significant decrease in Ach-dependent relaxation in healthy CC. Emax responses to SNP did not differ in the presence of rosiglitazone in both the control and hypercholesterolemic groups. Rosiglitazone does not improve hypercholesterolemia-induced endothelial dysfunction in CC tissues while it dose-dependently impairs endothelium-dependent relaxation in healthy CC tissue. PMID:27030054

  7. Perturbation of chemical coupling by an endothelial Cx40 mutant attenuates endothelium-dependent vasodilation by KCa channels and elevates blood pressure in mice.

    PubMed

    Chaston, Daniel J; Haddock, Rebecca E; Howitt, Lauren; Morton, Susan K; Brown, Russell D; Matthaei, Klaus I; Hill, Caryl E

    2015-09-01

    Mutant forms of connexin40 (Cx40) exist in the human population and predispose carriers to atrial fibrillation. Since endothelial expression of Cx40 is important for electrical and chemical communication within the arterial wall, carriers of mutant Cx40 proteins may be predisposed to peripheral arterial dysfunction and dysregulation of blood pressure. We have therefore studied mice expressing either a chemically dysfunctional mutant, Cx40T202S, or wild-type Cx40, with native Cx40, specifically in the endothelium. Blood pressure was measured by telemetry under normal conditions and during cardiovascular stress induced by locomotor activity, phenylephrine or nitric oxide blockade (N(ɷ)-nitro-L-arginine methyl ester hydroxide, L-NAME). Blood pressure of Cx40T202STg mice was significantly elevated at night when compared with wild-type or Cx40Tg mice, without change in mean heart rate, pulse pressure or locomotor activity. Analysis over 24 h showed that blood pressure of Cx40T202STg mice was significantly elevated at rest and additionally during locomotor activity. In contrast, neither plasma renin concentration nor pressor responses to phenylephrine or L-NAME were altered, the latter indicating that nitric oxide bioavailability was normal. In isolated, pressurised mesenteric arteries, hyperpolarisation and vasodilation evoked by SKA-31, the selective modulator of SKCa and IKCa channels, was significantly reduced in Cx40T202STg mice, due to attenuation of the SKCa component. Acetylcholine-induced ascending vasodilation in vivo was also significantly attenuated in cremaster muscle arterioles of Cx40T202STg mice, compared to wild-type and Cx40Tg mice. We conclude that endothelial expression of the chemically dysfunctional Cx40T202S reduces peripheral vasodilator capacity mediated by SKCa-dependent hyperpolarisation and also increases blood pressure. PMID:25369777

  8. A factorial randomized controlled trial to evaluate the effect of micronutrients supplementation and regular aerobic exercise on maternal endothelium-dependent vasodilatation and oxidative stress of the newborn

    PubMed Central

    2011-01-01

    Background Many studies have suggested a relationship between metabolic abnormalities and impaired fetal growth with the development of non-transmissible chronic diseases in the adulthood. Moreover, it has been proposed that maternal factors such as endothelial function and oxidative stress are key mechanisms of both fetal metabolic alterations and subsequent development of non-transmissible chronic diseases. The objective of this project is to evaluate the effect of micronutrient supplementation and regular aerobic exercise on endothelium-dependent vasodilation maternal and stress oxidative of the newborn. Methods and design 320 pregnant women attending to usual prenatal care in Cali, Colombia will be included in a factorial randomized controlled trial. Women will be assigned to the following intervention groups: 1. Control group: usual prenatal care (PC) and placebo (maltodextrine). 2. Exercise group: PC, placebo and aerobic physical exercise. 3. Micronutrients group: PC and a micronutrients capsule consisting of zinc (30 mg), selenium (70 μg), vitamin A (400 μg), alphatocopherol (30 mg), vitamin C (200 mg), and niacin (100 mg). 4. Combined interventions Group: PC, supplementation of micronutrients, and aerobic physical exercise. Anthropometric measures will be taken at the start and at the end of the interventions. Discussion Since in previous studies has been showed that the maternal endothelial function and oxidative stress are related to oxidative stress of the newborn, this study proposes that complementation with micronutrients during pregnancy and/or regular physical exercise can be an early and innovative alternative to strengthen the prevention of chronic diseases in the population. Trial registration NCT00872365. PMID:21356082

  9. NAD(P)H oxidase-derived reactive oxygen species contribute to age-related impairments of endothelium-dependent dilation in rat soleus feed arteries

    PubMed Central

    Trott, Daniel W.; Seawright, John W.; Luttrell, Meredith J.

    2011-01-01

    We tested the hypothesis that age-related endothelial dysfunction in rat soleus muscle feed arteries (SFA) is mediated in part by NAD(P)H oxidase-derived reactive oxygen species (ROS). SFA from young (4 mo) and old (24 mo) Fischer 344 rats were isolated and cannulated for examination of vasodilator responses to flow and acetylcholine (ACh) in the absence or presence of a superoxide anion (O2−) scavenger (Tempol; 100 μM) or an NAD(P)H oxidase inhibitor (apocynin; 100 μM). In the absence of inhibitors, flow- and ACh-induced dilations were attenuated in SFA from old rats compared with young rats. Tempol and apocynin improved flow- and ACh-induced dilation in SFA from old rats. In SFA from young rats, Tempol and apocynin had no effect on flow-induced dilation, and apocynin attenuated ACh-induced dilation. To determine the role of hydrogen peroxide (H2O2), dilator responses were assessed in the absence and presence of catalase (100 U/ml) or PEG-catalase (200 U/ml). Neither H2O2 scavenger altered flow-induced dilation, whereas both H2O2 scavengers blunted ACh-induced dilation in SFA from young rats. In old SFA, catalase improved flow-induced dilation whereas PEG-catalase improved ACh-induced dilation. Compared with young SFA, in response to exogenous H2O2 and NADPH, old rats exhibited blunted dilation and constriction, respectively. Immunoblot analysis revealed that the NAD(P)H oxidase subunit gp91phox protein content was greater in old SFA compared with young. These results suggest that NAD(P)H oxidase-derived reactive oxygen species contribute to impaired endothelium-dependent dilation in old SFA. PMID:21233343

  10. NAD(P)H oxidase-derived reactive oxygen species contribute to age-related impairments of endothelium-dependent dilation in rat soleus feed arteries.

    PubMed

    Trott, Daniel W; Seawright, John W; Luttrell, Meredith J; Woodman, Christopher R

    2011-05-01

    We tested the hypothesis that age-related endothelial dysfunction in rat soleus muscle feed arteries (SFA) is mediated in part by NAD(P)H oxidase-derived reactive oxygen species (ROS). SFA from young (4 mo) and old (24 mo) Fischer 344 rats were isolated and cannulated for examination of vasodilator responses to flow and acetylcholine (ACh) in the absence or presence of a superoxide anion (O(2)(-)) scavenger (Tempol; 100 μM) or an NAD(P)H oxidase inhibitor (apocynin; 100 μM). In the absence of inhibitors, flow- and ACh-induced dilations were attenuated in SFA from old rats compared with young rats. Tempol and apocynin improved flow- and ACh-induced dilation in SFA from old rats. In SFA from young rats, Tempol and apocynin had no effect on flow-induced dilation, and apocynin attenuated ACh-induced dilation. To determine the role of hydrogen peroxide (H(2)O(2)), dilator responses were assessed in the absence and presence of catalase (100 U/ml) or PEG-catalase (200 U/ml). Neither H(2)O(2) scavenger altered flow-induced dilation, whereas both H(2)O(2) scavengers blunted ACh-induced dilation in SFA from young rats. In old SFA, catalase improved flow-induced dilation whereas PEG-catalase improved ACh-induced dilation. Compared with young SFA, in response to exogenous H(2)O(2) and NADPH, old rats exhibited blunted dilation and constriction, respectively. Immunoblot analysis revealed that the NAD(P)H oxidase subunit gp91phox protein content was greater in old SFA compared with young. These results suggest that NAD(P)H oxidase-derived reactive oxygen species contribute to impaired endothelium-dependent dilation in old SFA. PMID:21233343

  11. Increment of body mass index is positively correlated with worsening of endothelium-dependent and independent changes in forearm blood flow.

    PubMed

    Kraemer-Aguiar, Luiz G; de Miranda, Marcos L; Bottino, Daniel A; Lima, Ronald de A; de Souza, Maria das Graças C; Balarini, Michelle de Moura; Villela, Nivaldo R; Bouskela, Eliete

    2015-01-01

    Obesity is associated with the impairment of endothelial function leading to the initiation of the atherosclerotic process. As obesity is a multiple grade disease, we have hypothesized that an increasing impairment of endothelial and vascular smooth muscle cell functions occurs from lean subjects to severe obese ones, creating a window of opportunities for preventive measures. Thus, the present study was carried out to investigate the grade of obesity in which endothelial dysfunction can be detected and if there is an increasing impairment of endothelial and vascular smooth muscle cell functions as body mass index increases. According to body mass index, subjects were allocated into five groups: Lean controls (n = 9); Overweight (n = 11); Obese class I (n = 26); Obese class II (n = 15); Obese class III (n = 19). Endothelial and vascular smooth muscle cell functions were evaluated measuring forearm blood flow responses to increasing intra-arterial infusions of acetylcholine and sodium nitroprusside using venous occlusion plethysmography. We observed that forearm blood flow was progressively impaired from lean controls to severe obese and found no significant differences between Lean controls and Overweight groups. Known determinants of endothelial dysfunction, such as inflammatory response, insulin resistance, and diagnosis of metabolic syndrome, did not correlate with forearm blood flow response to vasodilators. Moreover, several risk factors for atherosclerosis were excluded as independent predictors after confounder-adjusted analysis. Our data suggests that obesity per se could be sufficient to promote impairment of vascular reactivity, that obesity class I is the first grade of obesity in which endothelial dysfunction can be detected, and that body mass index positively correlates with the worsening of endothelium-dependent and independent changes in forearm blood flow. PMID:26913005

  12. Isoprenaline can activate the acetylcholine-induced K+ current in canine atrial myocytes via Gs-derived betagamma subunits.

    PubMed

    Sorota, S; Rybina, I; Yamamoto, A; Du, X Y

    1999-01-15

    1. G protein betagamma subunits activate the acetylcholine-induced potassium current IK,ACh. There is no evidence of specificity at the level of the betagamma subunits. Therefore all G protein-coupled receptors in atrial myocytes should be able to activate IK,ACh. Paradoxically, it is often stated that isoprenaline does not activate IK,ACh. Rationales to explain this negative result include insufficient concentrations of Gs in the atrium or restricted access of Gs-derived betagamma subunits to the IK,ACh channel. We took advantage of a non-specific increase in Gs that results after infection with adenovirus. 2. Adenoviral infection unmasked a 1 microM isoprenaline-induced IK,ACh which was prevented by propranolol. Isoprenaline occasionally activated IK,ACh in uninfected and freshly dissociated atrial myocytes but the effect was larger and more consistent in infected myocytes. 3. Pertussis toxin pretreatment (100 ng ml-1 overnight) did not block the effect of isoprenaline. The effect of isoprenaline became persistent if cells were pretreated with cholera toxin (200 ng nl-1). 4. Signal transduction events distal to adenylyl cyclase were not involved in isoprenaline-induced IK,ACh. Forskolin (10 microM) did not activate IK,ACh. Inhibition of adenylyl cyclase with cytoplasmic application of 300 microM 2'-deoxyadenosine 3'-monophosphate did not prevent the activation of IK,ACh by isoprenaline. 5. Cytoplasmic application of a betagamma binding peptide derived from the C terminus of beta-adrenergic receptor kinase 1 (50 microM) prevented the effect of isoprenaline on IK,ACh. The peptide did not prevent the stimulation of the L-type calcium current by isoprenaline. 6. The results indicate that beta-adrenoceptors can activate IK,ACh in atrial myocytes through the release of betagamma subunits from Gs. PMID:9852323

  13. Role of different types of potassium channels in the relaxation of corpus cavernosum induced by resveratrol

    PubMed Central

    Dalaklioglu, Selvinaz; Ozbey, G.

    2014-01-01

    Background: Resveratrol (RVT), one of the most commonly employed dietary polyphenol, is used in traditional Japanese and Chinese medicine for treatment of cardiovascular diseases. Recently, we have shown that RVT has a potent relaxant effect on rat corpus cavernosum via endothelium-dependent and -independent mechanisms. Objective: The present study addressed the question whether different types of potassium channels are involved in the endothelium-dependent and -independent mechanism of corpus cavernosum relaxation induced by RVT. Materials and Methods: Strips of corpus cavernosum from rats were mounted in an organ-bath system for isometric tension studies. Results: RVT (1-100 μmol/L) produced concentration-dependent relaxation responses in rat corpus cavernosum pre-contracted by phenylephrine. The non-selective potassium channels blocker tetraethylammonium chloride (TEA, 10 mmol/L), ATP-sensitive potassium (KATP) channels blocker glibenclamide (10 μmol/L), and inward rectifier potassium (Kir) channels inhibitor barium chloride (BaCl2, 30 μmol/L) caused a significant inhibition on the relaxation response to RVT, whereas voltage-dependent potassium channels inhibitor 4-aminopyridine (4-AP, 1 mmol/L), and large conductance calcium-activated potassium (BKCa) channels inhibitor iberiotoxin (IbTX, 0.1 μmol/L) did not significantly alter relaxant responses of corpus cavernosum strips to RVT. In addition, relaxant responses to RVT did not significantly inhibited by the combination of selective inhibitors of small and intermediate conductance BKCa channels (0.1 μmol/L charybdotoxin and 1 μmol/L apamin, respectively). Conclusion: These results demonstrated that endothelial small and intermediate conductance BKCa channels are not thought to be an important role in RVT-induced endothelium-dependent relaxation of corpus cavernosum. The endothelium-independent corpus cavernosum relaxation induced by RVT is seems to largely depend on Kir channels and KATP channels in

  14. Substance P-induced relaxation and hyperpolarization in human cerebral arteries.

    PubMed Central

    Petersson, J.; Zygmunt, P. M.; Brandt, L.; Högestätt, E. D.

    1995-01-01

    1. Vascular effects of substance P were studied in human isolated pial arteries removed from 14 patients undergoing cerebral cortical resection. 2. Substance P induced a concentration-dependent relaxation in the presence of indomethacin. No relaxation was seen in arteries where the endothelium had been removed. 3. N omega-nitro-L-arginine (L-NOARG, 0.3 mM) abolished the relaxation in arteries from six patients. The relaxation was only partially inhibited in the remaining eight patients, the reduction of the maximum relaxation being less than 50% in each patient. 4. The L-NOARG-resistant relaxation was abolished when the external K+ concentration was raised above 30 mM. 5. Substance P caused a smooth muscle hyperpolarization (in the presence of L-NOARG and indomethacin), but only when the artery showed an L-NOARG-resistant relaxation. 6. The results indicate that nitric oxide is an important mediator of endothelium-dependent relaxation in human cerebral arteries. Furthermore, another endothelium-dependent pathway, causing hyperpolarization and vasodilatation, was identified in arteries from more than half the population of patients. PMID:7582516

  15. Alterations in EDHF-mediated hyperpolarization and relaxation in mesenteric arteries of female rats in long-term deficiency of oestrogen and during oestrus cycle

    PubMed Central

    Liu, Ming-Yue; Hattori, Yuichi; Fukao, Mistuhiro; Sato, Atsushi; Sakuma, Ichiro; Kanno, Morio

    2001-01-01

    This study was undertaken to determine whether endothelium-dependent relaxations are altered in mesenteric arteries from young female rats during oestrus cycle and after castration. The contractile response to phenylephrine (Phe) was significantly enhanced in arteries from rats subjected to ovariectomy than in those from sham-operated (control) rats. Treatment of ovariectomized rats with 17β-oestradiol returned the Phe response to the control level. Arteries from rats at the diestrus stage also exhibited greater contraction in response to Phe. In the presence of 100 μM NG-nitro-L-arginine (L-NOARG), the enhancement of the Phe contractile response associated with oestrogen deficiency was not observed. Endothelium-dependent relaxations elicited by acetylcholine (ACh) in arteries precontracted with Phe were significantly reduced in ovariectomized and diestrus rats regardless of whether endothelium-derived nitric oxide (NO) was blocked with L-NOARG. Treatment with 17β-oestradiol prevented the reduced vascular relaxant response to ACh in ovariectomized rats. The reduction in the ACh responses observed in ovariectomized and diestrus rats was eliminated when 500 nM apamin and 100 nM charybdotoxin were present. ACh-induced endothelium-dependent hyperpolarizations were depressed in arteries from ovariectomized and diestrus rats. The hyperpolarizing response to ACh was significantly improved when ovariectomized rats were treated with 17β-oestradiol. The resting membrane potentials and pinacidil-induced hyperpolarizations were unaffected by ovariectomy or the diestrus stage. These results suggest that oestrogen-deficient states of both short and long duration reduce the basal release of NO from the endothelium and specifically attenuate endothelium-dependent hyperpolarization and relaxation transduced by endothelium-derived hyperpolarizing factor. PMID:11226134

  16. Acetylcholine-induced cation translocation across cell membranes and inactivation of the acetylcholine receptor: chemical kinetic measurements in the millisecond time region.

    PubMed Central

    Cash, D J; Aoshima, H; Hess, G P

    1981-01-01

    Acetylcholine-induced flux of inorganic ions across membranes and inactivation of the acetylcholine receptor were measured at pH 7.0, 1 degrees C, over a 5000-fold concentration range of acetylcholine. Receptor-containing electroplax membrane vesicles prepared from Electrophorus electricus and a quench-flow technique were used, allowing flux to be measured in the 2-msec to 1-min time region. Five different measurements were made: (i) rate of ion translocation with the active state of the receptor, (ii) rate of the slower ion translocation after equilibration of active and inactive receptor states, (iii) rate of inactivation, (iv) equilibrium between active and inactive forms of the receptor, and (v) reactivation of inactivated receptor. The kinetics of the steps in the receptor-controlled ion flux follow single-exponential rate laws, and simple analytical expressions for their ligand concentration dependence can be used. Thus, the rate and equilibrium constants in a scheme that relates the ligand binding steps to ion translocation could be evaluated. It was found that the dependence of the receptor-controlled ion translocation over the concentration range investigated obeys the integrated rate equation based on the proposed mechanism. The flux rate before inactivation was approximately 10(7) ions sec-1 per receptor, which is comparable with that measured electrophysiologically in muscle cells. The half-time of inactivation is approximately 100 msec when the receptor is saturated with acetylcholine. The specific reaction rate of the ion translocation (J) is 3 X 10(7) M-1 sec-1. The results support a minimum reaction mechanism previously proposed on the basis of experiments in which carbamylcholine was used. PMID:6267581

  17. Effect of cyanide on nitrovasodilator-induced relaxation, cyclic GMP accumulation and guanylate cyclase activation in rat aorta.

    PubMed

    Rapoport, R M; Murad, F

    1984-09-01

    The effects of sodium cyanide on relaxation, increases in cyclic GMP accumulation and guanylate cyclase activation induced by sodium nitroprusside and other nitrovasodilators were examined in rat thoracic aorta. Cyanide abolished nitroprusside-induced relaxation and the associated increase in cyclic GMP levels. Basal levels of cyclic GMP and cyclic AMP were also depressed. Reversal of nitroprusside-induced relaxation by cyanide was independent of the tissue level of cyclic GMP prior to addition of cyanide. Incubation of nitroprusside with cyanide prior to addition to aortic strips did not alter the relaxant effect of nitroprusside. Sodium azide-, hydroxylamine-, N-methyl-N'-nitro-N-nitrosoguanide-, nitroglycerin- and acetylcholine-induced relaxations and increased levels of cyclic GMP were also inhibited by cyanide. Relaxations induced by nitric oxide were also inhibited by cyanide, although the relaxation with the low concentration of nitric oxide employed was not accompanied by detectable increases in cyclic GMP. Relaxation to 8-bromo-cyclic GMP was essentially unaltered by cyanide; however, isoproterenol-induced relaxation was inhibited. Guanylate cyclase in soluble and particulate fractions of aorta homogenates was activated by nitroprusside and the activation was prevented by cyanide. The present results suggest that cyanide inhibits nitrovasodilator-induced relaxation through inhibition of guanylate cyclase activation; however, cyanide may also have nonspecific effects which inhibit relaxation. PMID:6149944

  18. Relaxed Intensity

    ERIC Educational Resources Information Center

    Ramey, Kyle

    2004-01-01

    Relaxed intensity refers to a professional philosophy, demeanor, and way of life. It is the key to being an effective educational leader. To be successful one must be relaxed, which means managing stress efficiently, having fun, and enjoying work. Intensity allows one to get the job done and accomplish certain tasks or goals. Educational leaders…

  19. Differences in responsiveness of intrapulmonary artery and vein to arachidonic acid: mechanism of arterial relaxation involves cyclic guanosine 3':5'-monophosphate and cyclic adenosine 3':5'-monophosphate

    SciTech Connect

    Ignarro, L.J.; Harbison, R.G.; Wood, K.S.; Wolin, M.S.; McNamara, D.B.; Hyman, A.L.; Kadowitz, P.J.

    1985-06-01

    The objective of this study was to examine the relationship between responses of bovine intrapulmonary artery and vein to arachidonic acid and cyclic nucleotide levels in order to better understand the mechanism of relaxation elicited by arachidonic acid and acetylcholine. Arachidonic acid relaxed phenylephrine-precontracted arterial rings and elevated both cyclic GMP and cyclic AMP levels in arteries with intact endothelium. In contrast, endothelium-damaged arterial rings contracted to arachidonic acid without demonstrating significant changes in cyclic nucleotide levels. Indomethacin partially inhibited endothelium-dependent relaxation and abolished cyclic AMP accumulation whereas methylene blue, a guanylate cyclase inhibitor, partially inhibited relaxation and abolished cyclic GMP accumulation in response to arachidonic acid. All vessel responses were blocked by a combination of the two inhibitors. Prostaglandin (PG) I2 relaxed arterial rings and elevated cyclic AMP levels whereas PGE2 and PGF2 alpha caused contraction, suggesting that the indomethacin-sensitive component of arachidonic acid-elicited relaxation is due to PGI2 formation and cyclic AMP accumulation. The methylene blue-sensitive component is attributed to an endothelium-dependent but cyclooxygenase-independent generation of a substance causing cyclic GMP accumulation. Intrapulmonary veins contracted to arachidonic acid with no changes in cyclic nucleotide levels and PGI2 was without effect. Homogenates of intrapulmonary artery and vein formed 6-keto-PGF1 alpha, PGF2 alpha and PGE2 from (/sup 14/C)arachidonic acid, which was inhibited by indomethacin. Thus, bovine intrapulmonary vein may not possess receptors for PGI2.

  20. EDHF, NO and a prostanoid: hyperpolarization-dependent and -independent relaxation in guinea-pig arteries

    PubMed Central

    Tare, Marianne; Parkington, Helena C; Coleman, H A

    2000-01-01

    The contribution of endothelium-derived hyperpolarizing factor (EDHF), nitric oxide (NO) and a prostanoid (PG) to endothelium-dependent hyperpolarization and relaxation were assessed in coronary and mammary arteries of guinea-pigs by integration of the responses evoked during discrete applications of acetylcholine (ACh). The results of this integration approach were compared with those using traditional peak analysis methods.Nω-nitro-L-arginine methyl ester (L-NAME, 100 μM) and indomethacin (1 μM), alone or in combination, were without effect on peak hyperpolarizations or relaxations while they markedly reduced the integrated responses in both arteries.Integrated responses attributed to NO and PG were larger than those attributed to EDHF in the coronary artery (at 2 μM ACh, hyperpolarization (mV s): NO, 4200±91; PG, 5046±157; EDHF, 1532±94; relaxation (mN s mm−1): NO, 2488±122; PG, 2234±96; EDHF, 802±54). Integrated responses attributed to NO, PG and EDHF were similar in the mammary artery (at 2 μM ACh, hyperpolarization: NO, 347±69; PG, 217±49; EDHF, 310±63; relaxation: NO, 462±94; PG, 456±144; EDHF, 458±40).Gilbenclamide (1 μM) all but abolished the hyperpolarization attributable to NO and PG but not EDHF in both arteries allowing assessment of the role of the hyperpolarization in relaxation. Gilbenclamide was without effect on the integrated relaxation due to NO but significantly reduced the relaxation associated with PG in the two arteries.In conclusion, integration of the responses enabled a more complete assessment of the contribution of EDHF, NO and PG to endothelium-dependent responses, which were strikingly different in the two arteries. There is commonality in the role of hyperpolarization in relaxation in both arteries: EDHF-dependent relaxation is strongly dependent on hyperpolarization; hyperpolarization plays an important role in PG relaxation, whereas it has a small facilitatory role in NO-dependent relaxation. PMID

  1. Different mechanism of relaxation induced by aporphine alkaloids in rat uterus.

    PubMed

    Ivorra, M D; Martinez, F; Serrano, A; D'Ocon, P

    1993-05-01

    We have examined the uterine relaxant action of three aporphine molecules (S-glaucine, S-boldine and R-apomorphine) in two experimental conditions, with and without calcium in the bathing solution, and compared these effects with those obtained with the calcium antagonists verapamil and diltiazem. The present study shows that the alkaloids relax the uterine muscle but with different mechanisms of action. In Ca(2+)-containing solution all three alkaloids relaxed the uterus previously contracted by KCl or acetylcholine, but in Ca(2+)-free medium only R-apomorphine was able to relax oxytocin-induced contraction. The calcium antagonists, verapamil and diltiazem, relaxed KCl- or acetylcholine-induced contraction in Ca(2+)-containing solution, whereas they only relaxed oxytocin-induced contraction in Ca(2+)-free medium at much higher doses. These results suggest that glaucine and boldine behave as specific calcium entry blockers without affecting the contractile machinery or intracellular Ca2+ levels as apomorphine does. The absolute configuration (S-glaucine and S-boldine vs R-apomorphine) may account for this different action. PMID:8099963

  2. Relaxation System

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Environ Corporation's relaxation system is built around a body lounge, a kind of super easy chair that incorporates sensory devices. Computer controlled enclosure provides filtered ionized air to create a feeling of invigoration, enhanced by mood changing aromas. Occupant is also surrounded by multidimensional audio and the lighting is programmed to change colors, patterns, and intensity periodically. These and other sensory stimulators are designed to provide an environment in which the learning process is stimulated, because research has proven that while an individual is in a deep state of relaxation, the mind is more receptive to new information.

  3. Involvement of nitric oxide pathway in the PAF-induced relaxation of rat thoracic aorta.

    PubMed Central

    Moritoki, H.; Hisayama, T.; Takeuchi, S.; Miyano, H.; Kondoh, W.

    1992-01-01

    1. The mechanism of the vasorelaxant effect of platelet activating factor (PAF) on rat thoracic aorta and the effect of aging on the PAF-induced relaxation were investigated. 2. PAF at concentrations causing relaxation induced marked increases in guanosine 3':5'-cyclic monophosphate (cyclic GMP) production, but did not induce an increase in adenosine 3':5'-cyclic monophosphate (cyclic AMP). 3. Removal of the endothelium by mechanical rubbing, and treatment with the PAF antagonists CV-3988, CV-6209 and FR-900452, the nitric oxide biosynthesis inhibitor, NG-nitro L-arginine, the radical scavenger, haemoglobin, and the soluble guanylate cyclase inhibitor, methylene blue, inhibited PAF-induced relaxation and abolished or attenuated PAF-stimulated cyclic GMP production. 4. The relaxation was greatest in arteries from rats aged 4 weeks. With an increase in age, the response of the arteries to PAF was attenuated. 5. Endothelium-dependent cyclic GMP production also decreased with increase in age of the rats. 6. These results suggest that PAF stimulates production of nitric oxide from L-arginine by acting on the PAF receptors in the endothelium, which in turn stimulates soluble guanylate cyclase in the smooth muscle cells, and so increases production of cyclic GMP, thus relaxing the arteries. Age-associated decrease in PAF-induced relaxation may result from a reduction of cyclic GMP formation. PMID:1358382

  4. Cinnamaldehyde and cinnamaldehyde-containing micelles induce relaxation of isolated porcine coronary arteries: role of nitric oxide and calcium

    PubMed Central

    Raffai, Gábor; Kim, Byungkuk; Park, Sanga; Khang, Gilson; Lee, Dongwon; Vanhoutte, Paul M

    2014-01-01

    Background and purpose Cinnamaldehyde, a major component of cinnamon, induces the generation of reactive oxygen species and exerts vasodilator and anticancer effects, but its short half-life limits its clinical use. The present experiments were designed to compare the acute relaxing properties of cinnamaldehyde with those of self-assembling polymer micelles either loaded with cinnamaldehyde or consisting of a polymeric prodrug [poly(cinnamaldehyde)] that incorporates the compound in its backbone. Methods Rings of porcine coronary arteries were contracted with the thromboxane A2 receptor agonist U46619 or 40 mM KCl, and changes in isometric tension were recorded. Results Cinnamaldehyde induced concentration-dependent but endothelium-independent, nitric oxide synthase (NOS)-independent, cyclooxygenase-independent, soluble guanylyl cyclase (sGC)-independent, calcium-activated potassium-independent, and TRPA1 channel-independent relaxations. Cinnamaldehyde also inhibited the contractions induced by 40 mM KCl Ca2+ reintroduction in 40 mM KCl Ca2+-free solution or by the Ca2+ channel opener Bay K8644. Cinnamaldehyde-loaded control micelles induced complete, partly endothelium-dependent relaxations sensitive to catalase and inhibitors of NOS or sGC, but not cyclooxygenase or TRPA1, channels. Cinnamaldehyde-loaded micelles also inhibited contractions induced by 40 mM KCl Ca2+ reintroduction or Bay K8644. Poly(cinnamaldehyde) micelles induced only partial, endothelium-dependent relaxations that were reduced by inhibitors of NOS or sGC and by catalase and the antioxidant tiron, but not by indomethacin or TRPA1 channel blockers. Conclusion The present findings demonstrate that cinnamaldehyde-loaded and poly(cinnamaldehyde) micelles possess vasodilator properties, but that the mechanism underlying the relaxation that they cause differs from that of cinnamaldehyde, and thus could be used both to relieve coronary vasospasm and for therapeutic drug delivery. PMID:24904214

  5. Mechanisms of the vasorelaxing effects of CORM-3, a water-soluble carbon monoxide-releasing molecule: interactions with eNOS.

    PubMed

    Alshehri, Ali; Bourguignon, Marie-Pierre; Clavreul, Nicolas; Badier-Commander, Cécile; Gosgnach, Willy; Simonet, Serge; Vayssettes-Courchay, Christine; Cordi, Alex; Fabiani, Jean-Noël; Verbeuren, Tony J; Félétou, Michel

    2013-03-01

    The purpose of the present work was to elucidate the mechanisms underlying the endothelium-dependent and endothelium-independent components of the vascular relaxation induced by a water-soluble and ruthenium-based carbon monoxide (CO)-releasing agent, tricarbonylchloro(glycinato)ruthenium(II) (CORM-3). Changes in isometric tension and cyclic guanosine monophosphate (cGMP) production were measured in isolated aortic rings from normotensive Wistar-Kyoto rats. Nitric oxide (NO) generation was assessed in cultured human umbilical vein endothelial cells (HUVEC) by electron spin resonance. In rat aortic rings, CORM-3, but not the inactivated compound, iCORM, induced relaxations. In rings with but not in those without endothelium relaxations were partially inhibited by L-nitro-arginine (L-NA), 1H-(1,2,4)-oxadiazolo(4,2-a)quinoxalin-1-one (ODQ), or hydroxocobalamin, inhibitors of NO-synthase, soluble guanylyl cyclase, and scavenger of NO, respectively. In rings with and without endothelium, deoxyhemoglobin abolished the relaxations. A combination of potassium channel blockers (barium, glibenclamide, and iberiotoxin) blunted the relaxation in rings without endothelium. CORM-3 produced an endothelium-dependent generation of cGMP that was inhibited by L-NA. CORM-3, but not iCORM, inhibited the endothelium-dependent relaxation to acetylcholine without affecting the response to sodium nitroprusside. In HUVEC, CORM-3 produced a concentration-dependent release of NO. Therefore, CORM-3-induced relaxations involve the soluble guanylyl cyclase-independent activation of smooth muscle potassium channels. Additionally, CO can produce concomitantly activation and inhibition of NO synthase, the former being responsible for the endothelium- and cGMP-dependent effect of CORM-3, the latter for the inhibition of acetylcholine-induced endothelium-dependent relaxations. PMID:23296254

  6. Mechanism of attenuation of diabetes mellitus and hypercholesterolemia induced vascular endothelial dysfunction by protein tyrosine phosphatase inhibition.

    PubMed

    Sharma, Saurabh; Singh, Manjeet; Sharma, Pyare Lal

    2011-01-01

    The study has been designed to investigate downstream mechanisms in the PTPase inhibition mediated attenuation of diabetes mellitus and hypercholesterolemia-induced vascular endothelial dysfunction. Diabetes mellitus was induced in rats using streptozotocin (55 mg/kg, i.v. once), while hypercholesterolemia was produced by feeding high cholesterol diet. After 4 weeks of streptozotocin and Cholesterol rich diet administration, vascular endothelium dysfunction was assessed, in terms of attenuation of acetylcholine-induced, endothelium-dependent relaxation (Isolated Aortic Ring Preparation), a decrease in serum nitrate/nitrite level, as well as mRNA expression of eNOS (rtPCR) and disruption of integrity of vascular endothelium (Electron microscopy). After 14 days of daily administration, sodium orthovanadate (8 mg/kg, p.o., 16 mg/kg, p.o and 24 mg/kg, p.o) and atorvastatin (30 mg/kg, p.o) (positive control) significantly improved acetylcholine-induced endothelium-dependent relaxation, serum nitrate/nitrite level, mRNA expression of eNOS and maintained integrity of vascular endothelium. However, this ameliorative effect of SOV was significantly blocked by UCN-01, (PDK inhibitor) and L-NAME (Inhibitor of eNOS). Therefore, it may be concluded that sodium orthovanadate, a specific inhibitor of PTPase, may stimulate PDK and eNOS and consequently improve vascular endothelium dysfunction. Thus, inhibition of PTPase might be a useful approach in the therapeutics of vascular endothelium dysfunction. PMID:21237289

  7. Possible involvement of PPARγ-associated eNOS signaling activation in rosuvastatin-mediated prevention of nicotine-induced experimental vascular endothelial abnormalities.

    PubMed

    Kathuria, Sonam; Mahadevan, Nanjaian; Balakumar, Pitchai

    2013-02-01

    Nicotine exposure via cigarette smoking and tobacco chewing is associated with vascular complications. The present study investigated the effect of rosuvastatin in nicotine (2 mg/kg/day, i.p., 4 weeks)-induced vascular endothelial dysfunction (VED) in rats. The development of VED was assessed by employing isolated aortic ring preparation and estimating aortic and serum nitrite/nitrate concentration. Further, scanning electron microscopy and hematoxylin-eosin staining of thoracic aorta were performed to assess the vascular endothelial integrity. Moreover, oxidative stress was assessed by estimating aortic superoxide anion generation and serum thiobarbituric acid-reactive substances. The nicotine administration produced VED by markedly reducing acetylcholine-induced endothelium-dependent relaxation, impairing the integrity of vascular endothelium, decreasing aortic and serum nitrite/nitrate concentration, increasing oxidative stress, and inducing lipid alteration. However, treatment with rosuvastatin (10 mg/kg/day, i.p., 4 weeks) markedly attenuated nicotine-induced vascular endothelial abnormalities, oxidative stress, and lipid alteration. Interestingly, the co-administration of peroxisome proliferator-activated receptor γ (PPARγ) antagonist, GW9662 (1 mg/kg/day, i.p., 2 weeks) submaximally, significantly prevented rosuvastatin-induced improvement in vascular endothelial integrity, endothelium-dependent relaxation, and nitrite/nitrate concentration in rats administered nicotine. However, GW9662 co-administration did not affect rosuvastatin-associated vascular anti-oxidant and lipid-lowering effects. The incubation of aortic ring, isolated from rosuvastatin-treated nicotine-administered rats, with L-NAME (100 μM), an inhibitor of nitric oxide synthase (NOS), significantly attenuated rosuvastatin-induced improvement in acetylcholine-induced endothelium-dependent relaxation. Rosuvastatin prevents nicotine-induced vascular endothelial abnormalities by activating

  8. Breathing and Relaxation

    MedlinePlus

    ... Top Doctors in the Nation Departments & Divisions Home Health Insights Stress & Relaxation Breathing and Relaxation Breathing and Relaxation Make ... Management Assess Your Stress Coping Strategies Identifying ... & Programs Health Insights Doctors & Departments Research & Science Education & Training Make ...

  9. Relaxation Assessment with Varied Structured Milieu (RELAX).

    ERIC Educational Resources Information Center

    Cassel, Russell N.; Cassel, Susie L.

    1983-01-01

    Describes Relaxation Assessment with Varied Structured Milieu (RELAX), a clinical program designed to assess the degree to which an individual is able to demonstrate self-control for overall general relaxation. The program is designed for use with the Cassel Biosensors biofeedback equipment. (JAC)

  10. Hydrogen peroxide induced relaxation in porcine pulmonary arteries in vitro is mediated by EDRF and cyclic GMP

    SciTech Connect

    Zellers, T.; McCormick, J. )

    1991-03-15

    Xanthine and xanthine oxidase induced relaxations in porcine pulmonary arteries in vitro are augmented in the presence of the endothelium and abolished by catalase, implicating hydrogen peroxide as an endothelium-dependent effector. To determine the mechanism whereby H{sub 2}O{sub 2} causes relaxations, isolated rings of fifth order porcine pulmonary artery, with (E{sup +}) and without (E{sup {minus}}) endothelium, were suspended in organ baths filled with buffer, and isometric tension was recorded. Hydrogen peroxide caused concentration-dependent, endothelium-augmented relaxations which were abolished by catalase and hydroquinone and reversed by L-nitroarginine and methylene blue. Prostacyclin (PGI{sub 2}) levels, measured after a two minute exposure to H{sub 2}O{sub 2} in rings with endothelium were comparable to controls. This concentration of PGI{sub 2} does not cause relaxations in these rings. These data suggest that H{sub 2}O{sub 2} stimulates the release of an EDRF, causing relaxations mediated by cyclic GMP, which is independent of prostacyclin.

  11. Characterization of relaxant mechanism of H2 S in mouse corpus cavernosum.

    PubMed

    Aydinoglu, Fatma; Ogulener, Nuran

    2016-04-01

    The aim of this study was to investigate the mechanism of H2 S-induced relaxation in mouse corpus cavernosal tissue. l-cysteine (10(-6) × 10(-3) mol/L) and exogenous H2 S (NaHS; 10(-6) to 10(-3) mol/L) induced concentration-dependent relaxation. l-cysteine-induced relaxations was reduced by d,l-propargylglycine, a cystathionine gamma lyase (CSE) inhibitor but not influenced by aminooxyacetic acid, a cystathionine beta synthase (CBS) inhibitor. l-cysteine induced relaxations, but not of those of H2 S diminished in endothelium-denuded tissues. N(ω) -nitro-l-arginine (l-NA; 10(-4) mol/L), a nitric oxide synthase inhibitor, and ODQ (10(-4) mol/L), a guanylyl cyclase inhibitor, increased the H2 S-induced relaxation. Zaprinast (5 × 10(-6) mol/L) and sildenafil (10(-6) mol/L), phosphodiesterase inhibitors, inhibited H2 S-induced relaxation. Adenylyl cyclase inhibitors N-ethylmaleimide (2.5 × 10(-5) mol/L) and SQ22536 (10(-4) mol/L) reduced relaxation to H2 S. Also, H2 S-induced relaxation was reduced by KCl (50 mmol/L), 4-aminopyridine (10(-3) mol/L), a Kv inhibitor, glibenclamide (10(-5) mol/L), a KATP inhibitor or barium chloride (10(-5) mol/L), a KIR inhibitor. However, H2 S-induced relaxation was not influenced by apamin (10(-6) mol/L), a SKC a (2+) inhibitor, charybdotoxin (10(-7) mol/L), an IKC a (2+) and BKC a (2+) inhibitor or combination of apamin and charybdotoxin. Nifedipine (10(-6) mol/L), an L-type calcium channel blocker and atropine (10(-6) mol/L), a muscarinic receptor blocker, inhibited H2 S-induced relaxation. However, H2 S-induced relaxation was not influenced by ouabain (10(-4) mol/L), a Na(+) /K(+) -ATPase inhibitor. This study suggests that H2 S endogenously synthesizes from l-cysteine by CSE endothelium-dependent in mouse corpus cavernosum tissue, and exogenous H2 S may cause endothelium-independent relaxations via activation of K channels (KATP channel, KV channels, KIR channels), L-type voltage-gated Ca(2+) channels, adenylyl cyclase

  12. The Endothelium-Dependent Nitric Oxide-cGMP Pathway.

    PubMed

    Mónica, F Z; Bian, K; Murad, F

    2016-01-01

    Nitric oxide (NO)-cyclic 3'-5' guanosine monophosphate (cGMP) signaling plays a critical role on smooth muscle tone, platelet activity, cardiac contractility, renal function and fluid balance, and cell growth. Studies of the 1990s established endothelium dysfunction as one of the major causes of cardiovascular diseases. Therapeutic strategies that benefit NO bioavailability have been applied in clinical medicine extensively. Basic and clinical studies of cGMP regulation through activation of soluble guanylyl cyclase (sGC) or inhibition of cyclic nucleotide phosphodiesterase type 5 (PDE5) have resulted in effective therapies for pulmonary hypertension, erectile dysfunction, and more recently benign prostatic hyperplasia. This section reviews (1) how endothelial dysfunction and NO deficiency lead to cardiovascular diseases, (2) how soluble cGMP regulation leads to beneficial effects on disorders of the circulation system, and (3) the epigenetic regulation of NO-sGC pathway components in the cardiovascular system. In conclusion, the discovery of the NO-cGMP pathway revolutionized the comprehension of pathophysiological mechanisms involved in cardiovascular and other diseases. However, considering the expression "from bench to bedside" the therapeutic alternatives targeting NO-cGMP did not immediately follow the marked biochemical and pathophysiological revolution. Some therapeutic options have been effective and released on the market for pulmonary hypertension and erectile dysfunction such as inhaled NO, PDE5 inhibitors, and recently sGC stimulators. The therapeutic armamentarium for many other disorders is expected in the near future. There are currently numerous active basic and clinical research programs in universities and industries attempting to develop novel therapies for many diseases and medical applications. PMID:27451093

  13. Endothelium-derived relaxing factor produced and released from artery and vein is nitric oxide

    SciTech Connect

    Ignarro, L.J.; Buga, G.M.; Wood, K.S.; Byrns, R.E.; Chaudhuri, G.

    1987-12-01

    The objective of this study was to determine whether nitric oxide (NO) is responsible for the vascular smooth muscle relaxation elicited by endothelium-derived relaxing factor (EDRF). EDRF is an unstable humoral substance released from artery and vein that mediates the action of endothelium-dependent vasodilators. NO is and unstable endothelium-independent vasodilator that is released from vasodilator drugs such as nitroprusside and glyceryl trinitrate. The authors have repeatedly observed that the actions of NO on vascular smooth muscle closely resemble those of EDRF. In the present study the vascular effects of EDRF released from perfused bovine intrapulmonary artery and vein were compared with the effects of NO delivered by superfusion over endothelium-denuded arterial and venous strips arranged in a cascade. EDRF was indistinguishable from NO in that both were labile inactivated by pyrogallol or superoxide anion, stabilized by superoxide dismutase, and inhibited by oxyhemoglobin or potassium. Both EDRF and NO produced comparable increases in cyclic GMP accumulation in artery and vein, and this cyclic GMP accumulation was inhibited by pyrogallol, oxyhemoglobin, potassium, and methylene blue. EDRF was identified chemically as NO, or a labile nitroso species, by two procedures. Thus, EDRF released from artery and vein possesses identical and biological and chemical properties as NO.

  14. Influence of decompression sickness on vasomotion of isolated rat vessels.

    PubMed

    Mazur, A; Lambrechts, K; Buzzacott, P; Wang, Q; Belhomme, M; Theron, M; Mansourati, J; Guerrero, F

    2014-06-01

    Several studies have demonstrated that endothelial function is impaired following a dive even without decompression sickness. During this study we determined the effect of decompression sickness on endothelium-dependent and independent vasoreactivity. For this purpose twenty-seven male Sprague-Dawley rats were submitted to a simulated dive up to 1,000 kPa absolute pressure and divided into 3 groups: safe diving without decompression sickness or dives provoking mild or severe sickness. A fourth control group remained at atmospheric pressure. Endothelium-dependent and independent vasomotion was assessed ex vivo by measuring isometric tension in rings of abdominal aorta and mesenteric arteries. Dose-response curves were obtained with phenylephrine, acetylcholine and sodium nitroprusside. Acetylcholine-induced relaxation was measured in the presence of L-NAME, indometacin or both of them at once.Contraction was significantly decreased after each protocol compared with the control rats. Additionally, the response in animals from the severe group was significantly different from that of the safe and mild groups. Dose response curves for acetylcholine alone and in the presence of inhibitors remained unchanged. We did not observe differences in endothelium-dependent vasodilation after diving or in the presence of decompression sickness. Contractile response to phenylephrine was progressively impaired with increased decompression stress. These results may indicate smooth muscle injury. PMID:24258471

  15. Reduced activity of SKC a and Na-K ATPase underlies the accelerated impairment of EDH-type relaxations in mesenteric arteries of aging spontaneously hypertensive rats.

    PubMed

    Kong, Billy W C; Man, Ricky Y K; Gao, Yuansheng; Vanhoutte, Paul M; Leung, Susan W S

    2015-06-01

    Aging is accompanied by endothelial dysfunction due to reduced bioavailability of nitric oxide (NO) and/or reduced endothelium-dependent hyperpolarizations (EDH). This study examines the hypothesis that hypertension aggravates the impairment of EDH-type relaxation due to aging. EDH-type relaxations were studied in superior mesenteric arteries isolated from Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats of 12, 36, 60, and 72 weeks of age. EDH-type relaxations in WKY were reduced with aging, and this was associated with an impairment of the function of small-conductance calcium-activated potassium channels (SKC a) and sodium-potassium ATPase (Na-K ATPase). EDH-type relaxation in SHR was smaller than that in WKY arteries, and further reduction occurred with aging. Pharmacological experiments suggested a reduced involvement of SKC a and Na-K ATPase and activation of adenosine monophosphate-activated protein kinase and silent information regulator T1 (sirtuin-1; SIRT1) in mesenteric arteries of 12-week-old SHR. These pharmacological findings suggest that in superior mesenteric arteries of the rat, the reduction in EDH-type relaxation occurs with aging and that such a reduction is exacerbated in hypertension. The latter exacerbation appears to involve proteins associated with the process of cellular senescence and is related to impaired function of SKC a and Na-K ATPase, a phenomenon that is also observed in mesenteric arteries of older normotensive rats. PMID:26171229

  16. The involvement of the endothelium in the relaxation of the leopard frog (Rana pipiens) aorta in response to acetylcholine.

    PubMed Central

    Knight, G. E.; Burnstock, G.

    1996-01-01

    1. The vasodilator response to acetylcholine (ACh) was investigated in the aortic arches of the leopard frog (Rana pipiens). 2. With adrenaline pre-constricted preparations, both ACh and sodium nitroprusside (SNP) caused concentration-dependent relaxations. Damage to the endothelial layer abolished relaxations to ACh, or reduced them greatly, but had no effect on vasodilatation to SNP. 3. NG-Nitro-L-arginine methyl ester (L-NAME; 1-100 microM) concentration-dependently inhibited relaxations in response to ACh, but had no effect on the ability of SNP to induce vasodilatation. 4. L-Arginine (L-Arg; 100-200 times the concentration of L-NAME) failed to reverse the inhibitory effect of L-NAME (1-100 microM) apart from one isolated instance. 5. In summary, this study has shown endothelium-dependent vasodilatation to ACh in an amphibian blood vessel that appears to be mediated via nitric oxide (NO). The response to ACh differs from many mammalian preparations in that the inhibitory effect of L-NAME could not be overcome by L-Arg, in addition to L-NAME itself having no direct effect upon the tone of the vessel. PMID:8832080

  17. Extracellular Calcium-Dependent Modulation of Endothelium Relaxation in Rat Mesenteric Small Artery: The Role of Potassium Signaling

    PubMed Central

    Hangaard, Lise; Jessen, Peter B.; Kamaev, Dmitrii; Aalkjaer, Christian; Matchkov, Vladimir V.

    2015-01-01

    The nature of NO- and COX-independent endothelial hyperpolarization (EDH) is not fully understood but activation of small- and intermittent-conductance Ca2+-activated K+ channels (SKCa and IKCa) is important. Previous studies have suggested that the significance of IKCa depends on [Ca2+]out. Also it has been suggested that K+ is important through localized [K+]out signaling causing activation of the Na+,K+-ATPase and inward-rectifying K+ channels (Kir). Here we tested the hypothesis that the modulating effect of [Ca2+]out on the EDH-like response depends on [K+]out. We addressed this possibility using isometric myography of rat mesenteric small arteries. When [K+]out was 4.2 mM, relaxation to acetylcholine (ACh) was stronger at 2.5 mM [Ca2+]out than at 1 mM [Ca2+]out. Inhibition of IKCa with TRAM34 suppressed the relaxations but did not change the relation between the relaxations at the low and high [Ca2+]out. This [Ca2+]out-dependence disappeared at 5.9 mM [K+]out and in the presence of ouabain or BaCl2. Our results suggest that IKCa are involved in the localized [K+]out signaling which acts through the Na+,K+-ATPase and Kir channels and that the significance of this endothelium-dependent pathway is modulated by [Ca2+]out. PMID:26504829

  18. Altered potassium ATP channel signaling in mesenteric arteries of old high salt-fed rats

    PubMed Central

    Whidden, Melissa A.; Basgut, Bilgen; Kirichenko, Nataliya; Erdos, Benedek; Tümer, Nihal

    2016-01-01

    [Purpose] Both aging and the consumption of a high salt diet are associated with clear changes in the vascular system that can lead to the development of cardiovascular disease; however the mechanisms are not clearly understood. Therefore, we examined whether aging and the consumption of excess salt alters the function of potassium ATP-dependent channel signaling in mesenteric arteries [Methods] Young (7 months) and old (29 months) Fischer 344 x Brown Norway rats were fed a control or a high salt diet (8% NaCl) for 12 days and mesenteric arteries were utilized for vascular reactivity measurements. [Results] Acetylcholine-induced endothelium relaxation was significantly reduced in old arteries (81 ± 4%) when compared with young arteries (92 ± 2%). Pretreatment with the potassium-ATP channel blocker glibenclamide reduced relaxation to acetylcholine in young arteries but did not alter dilation in old arteries. On a high salt diet, endothelium dilation to acetylcholine was significantly reduced in old salt arteries (60 ± 3%) when compared with old control arteries (81 ± 4%). Glibenclamide reduced acetylcholine-induced dilation in young salt arteries but had no effect on old salt arteries. Dilation to cromakalim, a potassium-ATP channel opener, was reduced in old salt arteries when compared with old control arteries. [Conclusion] These findings demonstrate that aging impairs endothelium-dependent relaxation in mesenteric arteries. Furthermore, a high salt diet alters the function of potassium-ATP-dependent channel signaling in old isolated mesenteric arteries and affects the mediation of relaxation stimuli. PMID:27508155

  19. Urinary Bladder-Relaxant Effect of Kurarinone Depending on Potentiation of Large-Conductance Ca2+-Activated K+ Channels.

    PubMed

    Lee, Sojung; Chae, Mee Ree; Lee, Byoung-Cheol; Kim, Yong-Chul; Choi, Jae Sue; Lee, Sung Won; Cheong, Jae Hoon; Park, Chul-Seung

    2016-08-01

    The large-conductance calcium-activated potassium channel (BKCa channel) plays critical roles in smooth muscle relaxation. In urinary bladder smooth muscle, BKCa channel activity underlies the maintenance of the resting membrane potential and repolarization of the spontaneous action potential triggering the phasic contraction. To identify novel BKCa channel activators, we screened a library of natural compounds using a cell-based fluorescence assay and a hyperactive mutant BKCa channel (Lee et al., 2013). From 794 natural compounds, kurarinone, a flavanone from Sophora flavescens, strongly potentiated BKCa channels. When treated from the extracellular side, this compound progressively shifted the conductance-voltage relationship of BKCa channels to more negative voltages and increased the maximum conductance in a dose-dependent manner. Whereas kurarinone strongly potentiated the homomeric BKCa channel composed of only the α subunit, its effects were much smaller on heteromeric channels coassembled with auxiliary β subunits. Although the activation kinetics was not altered significantly, the deactivation of BKCa channels was dramatically slowed by kurarinone treatment. At the single-channel level, kurarinone increased the open probability of the BKCa channel without affecting its single-channel conductance. Kurarinone potently relaxed acetylcholine-induced contraction of rat bladder smooth muscle and thus decreased the micturition frequency of rats with overactive bladder symptoms. These results indicate that kurarinone can directly potentiate BKCa channels and demonstrate the therapeutic potentials of kurarinone and its derivatives for developing antioveractive bladder medications and supplements. PMID:27251362

  20. L-arginine and arginine analogues: effects on isolated blood vessels and cultured endothelial cells.

    PubMed Central

    Schmidt, H. H.; Baeblich, S. E.; Zernikow, B. C.; Klein, M. M.; Böhme, E.

    1990-01-01

    1. The present study examined effects of arginine (Arg) and various Arg analogues on the vascular tone of rabbit and rat aortic rings, the release of nitrite from cultured bovine aortic endothelial cells and the metabolism of L-Arg in bovine and porcine endothelial cell homogenates. The respective D-enantiomers or N-alpha-benzoyl-L-arginine ethyl ester did not substitute for L-Arg. 2. In bovine aortic endothelial cells, the release of nitrite was only observed in the presence of L-Arg or L-Arg methyl ester in the cell culture medium. 3. In dialyzed homogenates of porcine and bovine aortic endothelial cells, L-Arg was metabolized independently of NADPH and Ca2+ to yield L-ornithine (L-Orn) and L-citrulline (L-Cit). No concomitant nitrite formation was detected. 4. Pretreatment of rabbit and rat aortic rings with L-canavanine (L-Can) or NG-monomethyl-L-Arg (L-NMMA) inhibited ATP- and acetylcholine-induced relaxations (endothelium-dependent) but not glyceryltrinitrate-induced relaxations (endothelium-independent). 5. In rabbit aortic rings, Arg and monomeric Arg analogues induced endothelium-independent relaxations. L-Arg methyl ester induced an endothelium-independent contraction, and L-NMMA induced a relaxation in the absence of endothelium and a contraction in the presence of endothelium. Polymeric basic amino acids such as poly L-Arg induced endothelium-dependent relaxations (inhibited by L-Can), a subsequent refractoriness to endothelium-dependent vasodilators (not prevented by L-Can) and endothelial cell death.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2282457

  1. TEACHING NEUROMUSCULAR RELAXATION.

    ERIC Educational Resources Information Center

    NORRIS, JEANNE E.; STEINHAUS, ARTHUR H.

    THIS STUDY ATTEMPTED TO FIND OUT WHETHER (1) THE METHODS FOR ATTAINING NEUROMUSCULAR RELAXATION THAT HAVE PROVED FRUITFUL IN THE ONE-TO-ONE RELATIONSHIP OF THE CLINIC CAN BE SUCCESSFULLY ADAPTED TO THE TEACHER-CLASS RELATIONSHIP OF THE CLASSROOM AND GYMNASIUM, AND (2) NEUROMUSCULAR RELAXATION CAN BE TAUGHT SUCCESSFULLY BY AN APPROPRIATELY TRAINED…

  2. Mechanism of rotational relaxation.

    NASA Technical Reports Server (NTRS)

    Polanyi, J. C.; Woodall, K. B.

    1972-01-01

    A model is presented which describes the characteristic pattern of relaxation of a nonthermal rotational distribution of hydrogen halide, peaked initially at high rotational quantum number J, to a thermal distribution without generating a peak at intermediate J. A method for correcting infrared chemiluminiscence data for modest rotational relaxation is also suggested.

  3. Nitrovasodilator-induced relaxation and tolerance development in porcine vena cordis magna: dependence on intact endothelium.

    PubMed Central

    Kojda, G.; Beck, J. K.; Meyer, W.; Noack, E.

    1994-01-01

    1. Isolated segments of porcine vena cordis magna exhibited a reproducible contractile activity upon application of prostaglandin F2 alpha (PGF2 alpha) or KCl, that was independent of the presence of intact endothelium. Substance P (3 nM) elicited strictly endothelium-dependent relaxations amounting to 46.1 +/- 1.4% (n = 206) of contractions induced by 10 microM PGF2 alpha. 2. S-nitroso-N-acetyl-D,L-penicillamine (SNAP), a compound that spontaneously liberates nitric oxide, concentration-dependently relaxed PGF2 alpha-precontracted (50 microM) venous segments. Tolerance induction (incubation with 100 microM SNAP for 30 min) within the same segments resulted in a 3 fold attenuation of this effect, which was not further reduced after additional preincubation with glyceryl trinitrate (GTN). Removal of endothelium or the presence of N omega-nitro-L-arginine methylester (L-NAME) significantly improved the potency of SNAP before and after tolerance induction. 3. Concentration-dependent relaxations induced by GTN in non-tolerant veins were similar in the presence and absence of endothelium but much more reduced in tolerant endothelium-denuded (75 fold) compared to intact (20 fold) segments. In contrast, the presence of L-NAME significantly improved GTN-activity solely in non-tolerant veins, which, therefore, also resulted in a more pronounced attenuation of activity due to tolerance induction (100 fold). Preincubation of intact veins with SNAP also reduced GTN-activity but to a lesser extent (10 fold). 4. The more delayed but much longer, and compared to GTN somewhat weaker, acting new nitrovasodilator N-(3-nitrato-pivaloyl)-1-cysteineethylester (SPM 3672) was more potent in denuded than intact non-tolerant venous segments.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7521258

  4. Functional inhibition of urea transporter UT-B enhances endothelial-dependent vasodilatation and lowers blood pressure via L-arginine-endothelial nitric oxide synthase-nitric oxide pathway

    PubMed Central

    Sun, Yi; Lau, Chi-Wai; Jia, Yingli; Li, Yingjie; Wang, Weiling; Ran, Jianhua; Li, Fei; Huang, Yu; Zhou, Hong; Yang, Baoxue

    2016-01-01

    Mammalian urea transporters (UTs), UT-A and UT-B, are best known for their role in urine concentration. UT-B is especially distributed in multiple extrarenal tissues with abundant expression in vascular endothelium, but little is known about its role in vascular function. The present study investigated the physiological significance of UT-B in regulating vasorelaxations and blood pressure. UT-B deletion in mice or treatment with UT-B inhibitor PU-14 in Wistar-Kyoto rats (WKYs) and spontaneous hypertensive rats (SHRs) reduced blood pressure. Acetylcholine-induced vasorelaxation was significantly augmented in aortas from UT-B null mice. PU-14 concentration-dependently produced endothelium-dependent relaxations in thoracic aortas and mesenteric arteries from both mice and rats and the relaxations were abolished by Nω-nitro-L-arginine methyl ester. Both expression and phosphorylation of endothelial nitric oxide synthase (eNOS) were up-regulated and expression of arginase I was down-regulated when UT-B was inhibited both in vivo and in vitro. PU-14 induced endothelium-dependent relaxations to a similar degree in aortas from 12 weeks old SHRs or WKYs. In summary, here we report for the first time that inhibition of UT-B plays an important role in regulating vasorelaxations and blood pressure via up-regulation of L-arginine-eNOS-NO pathway, and it may become another potential therapeutic target for the treatment of hypertension. PMID:26739766

  5. Activation of endothelial and epithelial KCa2.3 calcium-activated potassium channels by NS309 relaxes human small pulmonary arteries and bronchioles

    PubMed Central

    Kroigaard, Christel; Dalsgaard, Thomas; Nielsen, Gorm; Laursen, Britt E; Pilegaard, Hans; Köhler, Ralf; Simonsen, Ulf

    2012-01-01

    BACKGROUND AND PURPOSE Small (KCa2) and intermediate (KCa3.1) conductance calcium-activated potassium channels (KCa) may contribute to both epithelium- and endothelium-dependent relaxations, but this has not been established in human pulmonary arteries and bronchioles. Therefore, we investigated the expression of KCa2.3 and KCa3.1 channels, and hypothesized that activation of these channels would produce relaxation of human bronchioles and pulmonary arteries. EXPERIMENTAL APPROACH Channel expression and functional studies were conducted in human isolated small pulmonary arteries and bronchioles. KCa2 and KCa3.1 currents were examined in human small airways epithelial (HSAEpi) cells by whole-cell patch clamp techniques. RESULTS While KCa2.3 expression was similar, KCa3.1 protein was more highly expressed in pulmonary arteries than bronchioles. Immunoreactive KCa2.3 and KCa3.1 proteins were found in both endothelium and epithelium. KCa currents were present in HSAEpi cells and sensitive to the KCa2.3 blocker UCL1684 and the KCa3.1 blocker TRAM-34. In pulmonary arteries contracted by U46619 and in bronchioles contracted by histamine, the KCa2.3/ KCa3.1 activator, NS309, induced concentration-dependent relaxations. NS309 was equally potent in relaxing pulmonary arteries, but less potent in bronchioles, than salbutamol. NS309 relaxations were blocked by the KCa2 channel blocker apamin, while the KCa3.1 channel blocker, charybdotoxin failed to reduce relaxation to NS309 (0.01–1 µM). CONCLUSIONS AND IMPLICATIONS KCa2.3 and KCa3.1 channels are expressed in the endothelium of human pulmonary arteries and epithelium of bronchioles. KCa2.3 channels contributed to endo- and epithelium-dependent relaxations suggesting that these channels are potential targets for treatment of pulmonary hypertension and chronic obstructive pulmonary disease. PMID:22506557

  6. Fenofibrate attenuates nicotine-induced vascular endothelial dysfunction in the rat.

    PubMed

    Chakkarwar, Vishal Arvind

    2011-01-01

    The study has been designed to investigate the effect of fenofibrate on nicotine-induced vascular endothelial dysfunction (VED) in rats. Nicotine (2 mg/kg/day, i.p., 4 weeks) was administered to produce VED in rats. The development of VED was assessed by employing isolated aortic ring preparation and estimating serum and aortic concentration of nitrite/nitrate. Further, the integrity of vascular endothelium was assessed using the scanning electron microscopy of thoracic aorta. The expression of mRNA for p22phox and eNOS was assessed by using reverse transcriptase-polymerase chain reaction. Serum thiobarbituric acid reactive substances concentration (TBARS) and aortic superoxide anion concentration were estimated to assess oxidative stress. Moreover, the serum lipid profile was assessed by estimating serum cholesterol, triglycerides and high density lipoprotein. The administration of nicotine induces VED by increased oxidative stress, altered lipid profile and impaired the integrity of vascular endothelium as assessed in terms of decrease in expression of mRNA for endothelial nitric oxide synthase (eNOS), impairing the integrity of vascular endothelium and subsequently decreasing serum and aortic nitrite/nitrate and attenuating acetylcholine-induced endothelium dependent relaxation. Further, nicotine produced oxidative stress, assessed in terms of increase in serum TBARS and aortic superoxide anion generation and increase in expression of mRNA for p22phox. Nicotine altered the lipid profile by increasing the serum cholesterol, triglycerides and decreasing the high density lipoprotein. However, treatment with fenofibrate (32 mg/kg, p.o.) markedly prevented nicotine-induced VED by decreasing oxidative stress and improving integrity of vascular endothelium, normalising the altered lipid profile, increasing the concentration of serum and aortic nitrite/nitrate, enhancing the acetylcholine-induced endothelium dependent relaxation and decreasing serum TBARS and aortic

  7. The novel role of fenofibrate in preventing nicotine- and sodium arsenite-induced vascular endothelial dysfunction in the rat.

    PubMed

    Kaur, Jagdeep; Reddy, Krishna; Balakumar, Pitchai

    2010-09-01

    The present study investigated the effect of fenofibrate, an agonist of PPAR-alpha, in nicotine- and sodium arsenite-induced vascular endothelial dysfunction (VED) in rats. Nicotine (2 mg/kg/day, i.p., 4 weeks) and sodium arsenite (1.5 mg/kg/day, i.p., 2 weeks) were administered to produce VED in rats. The scanning electron microscopy study in thoracic aorta revealed that administration of nicotine or sodium arsenite impaired the integrity of vascular endothelium. Further, administration of nicotine or sodium arsenite significantly decreased serum and aortic concentrations of nitrite/nitrate and subsequently reduced acetylcholine-induced endothelium-dependent relaxation. Moreover, nicotine or sodium arsenite produced oxidative stress by increasing serum thiobarbituric acid reactive substances (TBARS) and aortic superoxide generation. However, treatment with fenofibrate (30 mg/kg/day, p.o.) or atorvastatin (30 mg/kg/day p.o., a standard agent) significantly prevented nicotine- and sodium arsenite-induced VED and oxidative stress by improving the integrity of vascular endothelium, increasing the concentrations of serum and aortic nitrite/nitrate, enhancing the acetylcholine-induced endothelium-dependent relaxation and decreasing serum TBARS and aortic superoxide anion generation. Conversely, co-administration of L-NAME (25 mg/kg/day, i.p.), an inhibitor of nitric oxide synthase, markedly attenuated these vascular protective effects of fenofibrate. The administration of nicotine or sodium arsenite altered the lipid profile by increasing serum cholesterol and triglycerides and consequently decreasing high-density lipoprotein levels, which were significantly prevented by treatment with fenofibrate or atorvastatin. It may be concluded that fenofibrate improves the integrity and function of vascular endothelium, and the vascular protecting potential of fenofibrate in preventing the development of nicotine- and sodium arsenite-induced VED may be attributed to its

  8. Effect of rosiglitazone in sodium arsenite-induced experimental vascular endothelial dysfunction.

    PubMed

    Kaur, Tajpreet; Goel, Rajesh Kumar; Balakumar, Pitchai

    2010-04-01

    The present study has been designed to investigate the effect of rosiglitazone, a peroxisome proliferator activated receptor gamma agonist in sodium arsenite-induced vascular endothelial dysfunction (VED) in rats. The rats were administered sodium arsenite (1.5 mg/kg/day, i.p., 2 weeks) to induce VED. The development of VED was assessed by employing isolated aortic ring preparation and estimating serum nitrite/nitrate concentration. Further, the integrity of the aortic endothelium was assessed histologically using haematoxylin-eosin staining. Moreover, the oxidative stress was assessed by estimating serum thiobarbituric acid reactive substances, aortic reactive oxygen species and reduced form of glutathione. The administration of sodium arsenite produced VED by impairing acetylcholine-induced endothelium dependent relaxation, diminishing the integrity of vascular endothelium and decreasing the serum nitrite/nitrate concentration. In addition, sodium arsenite was noted to produce oxidative stress as it increased serum thiobarbituric acid reactive substances and aortic reactive oxygen species and consequently decreased glutathione. Treatment with rosiglitazone (3 mg/kg/day, p.o., 2 weeks and 5 mg/kg/day, p.o., 2 weeks) significantly prevented sodium arsenite-induced VED by enhancing acetylcholine-induced endothelium dependent relaxation, improving the integrity of vascular endothelium, increasing the nitrite/nitrate concentration and decreasing the oxidative stress. However, the vascular protective effect of rosiglitazone was markedly abolished by co-administration of nitric oxide synthase inhibitor, N-Omega-Nitro-L-Arginine Methyl Ester (L-NAME) (25 mg/kg/day, i.p., 2 weeks). Thus, it may be concluded that rosiglitazone reduces oxidative stress, activates eNOS and enhances the generation of nitric oxide to prevent sodium arsenite-induced VED in rats. PMID:20422371

  9. Benfotiamine attenuates nicotine and uric acid-induced vascular endothelial dysfunction in the rat.

    PubMed

    Balakumar, Pitchai; Sharma, Ramica; Singh, Manjeet

    2008-01-01

    The study has been designed to investigate the effect of benfotiamine, a thiamine derivative, in nicotine and uric acid-induced vascular endothelial dysfunction (VED) in rats. Nicotine (2 mg kg(-1)day(-1), i.p., 4 weeks) and uric acid (150 mg kg(-1)day(-1), i.p., 3 weeks) were administered to produce VED in rats. The development of VED was assessed by employing isolated aortic ring preparation and estimating serum and aortic concentration of nitrite/nitrate. Further, the integrity of vascular endothelium was assessed using the scanning electron microscopy (SEM) of thoracic aorta. Moreover, the oxidative stress was assessed by estimating serum thiobarbituric acid reactive substances (TBARS) and aortic superoxide anion generation. The administration of nicotine and uric acid produced VED by impairing the integrity of vascular endothelium and subsequently decreasing serum and aortic concentration of nitrite/nitrate and attenuating acetylcholine-induced endothelium dependent relaxation. Further, nicotine and uric acid produced oxidative stress, which was assessed in terms of increase in serum TBARS and aortic superoxide generation. However, treatment with benfotiamine (70 mg kg(-1)day(-1), p.o.) or atorvastatin (30 mg kg(-1)day(-1) p.o., a standard agent) markedly prevented nicotine and uric acid-induced VED and oxidative stress by improving the integrity of vascular endothelium, increasing the concentration of serum and aortic nitrite/nitrate, enhancing the acetylcholine-induced endothelium dependent relaxation and decreasing serum TBARS and aortic superoxide anion generation. Thus, it may be concluded that benfotiamine reduces the oxidative stress and consequently improves the integrity of vascular endothelium and enhances the generation of nitric oxide to prevent nicotine and uric acid-induced experimental VED. PMID:18951979

  10. Suxiao Jiuxin Pill Induces Potent Relaxation and Inhibition on Contraction in Human Artery and the Mechanism

    PubMed Central

    Bai, Xiao-Yan; Zhang, Ping; Yang, Qin; Liu, Xiao-Cheng; Wang, Jun; Tong, Yong-Ling; Xiong, Song-Jin; Liu, Li-Hua; Wang, Lei; He, Guo-Wei

    2014-01-01

    Suxiao Jiuxin Pill, a compound Chinese traditional medicine with main components of tetramethylpyrazine and borneol, is widely used for antiangina treatment in China but its pharmacological effect on human blood vessels is unknown. We investigated the effect and possible mechanism of SJP in the human internal mammary artery (IMA, n = 78) taken from patients undergoing coronary surgery. SJP caused full relaxation in KCl- (99.4 ± 10.5%, n = 6) and U46619- (99.9 ± 5.6%, n = 6) contracted IMA. Pretreatment of IMA with plasma concentrations of SJP (1 mg/mL), calculated from the plasma concentration of its major component borneol, significantly depressed the maximal contraction to KCl (from 35.8 ± 6.0 mN to 12.6 ± 5.6 mN, P = 0.03) and U46619 (from 19.4 ± 2.9 mN to 5.7 ± 2.4 mN, P = 0.007) while SJP at 10 mg/mL abolished the subsequent contraction. Endothelium denudation and inhibition of eNOS significantly altered the SJP-induced relaxation without changes of eNOS expression. We conclude that SJP has a potent inhibitory effect on the vasoconstriction mediated by a variety of vasoconstrictors in human arteries. The vasorelaxation involves both endothelium-dependent and -independent mechanisms. Thus, the effect of SJP on human arteries demonstrated in this study may prove to be particularly important in vasorelaxing therapy in cardiovascular disease. PMID:24808920

  11. Angiotensin II type 2 receptor- and acetylcholine-mediated relaxation: essential contribution of female sex hormones and chromosomes.

    PubMed

    Pessôa, Bruno Sevá; Slump, Denise E; Ibrahimi, Khatera; Grefhorst, Aldo; van Veghel, Richard; Garrelds, Ingrid M; Roks, Anton J M; Kushner, Steven A; Danser, A H Jan; van Esch, Joep H M

    2015-08-01

    Angiotensin-induced vasodilation, involving type 2 receptor (AT2R)-induced generation of nitric oxide (NO; by endothelial NO synthase) and endothelium-derived hyperpolarizing factors, may be limited to women. To distinguish the contribution of female sex hormones and chromosomes to AT2R function and endothelium-derived hyperpolarizing factor-mediated vasodilation, we made use of the four-core genotype model, where the testis-determining Sry gene has been deleted (Y(-)) from the Y chromosome, allowing XY(-) mice to develop a female gonadal phenotype. Simultaneously, by incorporating the Sry gene onto an autosome, XY(-)Sry and XXSry transgenic mice develop into gonadal male mice. Four-core genotype mice underwent a sham or gonadectomy (GDX) operation, and after 8 weeks, iliac arteries were collected to assess vascular function. XY(-)Sry male mice responded more strongly to angiotensin than XX female mice, and the AT2R antagonist PD123319 revealed that this was because of a dilator AT2R-mediated effect occurring exclusively in XX female mice. The latter could not be demonstrated in XXSry male and XY(-) female mice nor in XX female mice after GDX, suggesting that it depends on both sex hormones and chromosomes. Indeed, treating C57bl/6 GDX male mice with estrogen could not restore angiotensin-mediated, AT2R-dependent relaxation. To block acetylcholine-induced relaxation of iliac arteries obtained from four-core genotype XX mice, both endothelial NO synthase and endothelium-derived hyperpolarizing factor inhibition were required, whereas in four-core genotype XY animals, endothelial NO synthase inhibition alone was sufficient. These findings were independent of gonadal sex and unaltered after GDX. In conclusion, AT2R-induced relaxation requires both estrogen and the XX chromosome sex complement, whereas only the latter is required for endothelium-derived hyperpolarizing factors. PMID:26056343

  12. Ferulic acid, a natural polyphenol, alleviates insulin resistance and hypertension in fructose fed rats: Effect on endothelial-dependent relaxation.

    PubMed

    El-Bassossy, Hany; Badawy, Dina; Neamatallah, Thikryat; Fahmy, Ahmed

    2016-07-25

    Ferulic acid (FER) is a polyphenolic compound contained in various types of fruits. It has a substantial therapeutic effect inhibitory activity against aldose reductase (AR) inhibition. In this study, we examined the effect of FER on fructose-fed rats in comparison to a standard AR inhibitor, zopolrestat (ZOP). We determined the protective role of FER against metabolic syndrome by examining serum insulin/Glucose levels, triglycerides (TGs), cholesterol and advanced glycation end product (AGE) in rats supplied with 10% fructose drinking water. In addition, blood pressure, vascular reactivity of isolated thoracic aortas and acetylcholine-induced NO were all evaluated to estimate the cardiovascular complications of metabolic syndrome (MetS) associated with fructose feeding. Animals were randomly divided into four groups: control, (+10% fructose, Fru), zopolrestat-treated fructose fed (Fru-zop) and ferulic acid-treated fructose fed rats (Fru-Fer). After 12 weeks of FER treatment, we found significant reduction in both hyperinsulinemia and elevated diastolic blood pressure associated with fructose-fed to levels comparable to those achieved with ZOP. Both FER and ZOP significantly augmented the impaired relaxation associated with fructose-fed, whereas neither showed any significant effect on the developed vasoconstriction. Isolated aortas from fructose-fed rats incubated with either FER or ZOP, reinstated normal relaxation response to acetylcholine (ACh). Furthermore, isolated aortas showed attenuated nitric oxide (NO) production following the addition of (ACh), while both FER and ZOP restored normal induction of NO. Taken together, the current study shows that, FER alleviated insulin resistance and hypertension associated with metabolic syndrome compared to the standard AR inhibitor (ZOP). This potential protective effect is at least mediated by restoring endothelial relaxation. PMID:27287418

  13. Dielectric relaxation time spectroscopy.

    PubMed

    Paulson, K S; Jouravleva, S; McLeod, C N

    2000-11-01

    A new mathematical method is developed to recover the permittivity relaxation spectrum of living tissue from measurements of the real and imaginary parts of the impedance. Aiming to derive information about electrical properties of living tissue without the prior selection of any impedance model, the procedure calculates the relaxation time distribution. It provides new characteristic independent parameters: time constants, their distribution, and the amplitudes of the associated dispersion. As the beta-dispersion is the most important in the area of electrical impedance spectroscopy of tissue, the paper gives an estimate of the essential frequency range to cover the whole relaxation spectrum in that area. Results are presented from both simulation and known lumped--constant element circuit. PMID:11077745

  14. RELAX: detecting relaxed selection in a phylogenetic framework.

    PubMed

    Wertheim, Joel O; Murrell, Ben; Smith, Martin D; Kosakovsky Pond, Sergei L; Scheffler, Konrad

    2015-03-01

    Relaxation of selective strength, manifested as a reduction in the efficiency or intensity of natural selection, can drive evolutionary innovation and presage lineage extinction or loss of function. Mechanisms through which selection can be relaxed range from the removal of an existing selective constraint to a reduction in effective population size. Standard methods for estimating the strength and extent of purifying or positive selection from molecular sequence data are not suitable for detecting relaxed selection, because they lack power and can mistake an increase in the intensity of positive selection for relaxation of both purifying and positive selection. Here, we present a general hypothesis testing framework (RELAX) for detecting relaxed selection in a codon-based phylogenetic framework. Given two subsets of branches in a phylogeny, RELAX can determine whether selective strength was relaxed or intensified in one of these subsets relative to the other. We establish the validity of our test via simulations and show that it can distinguish between increased positive selection and a relaxation of selective strength. We also demonstrate the power of RELAX in a variety of biological scenarios where relaxation of selection has been hypothesized or demonstrated previously. We find that obligate and facultative γ-proteobacteria endosymbionts of insects are under relaxed selection compared with their free-living relatives and obligate endosymbionts are under relaxed selection compared with facultative endosymbionts. Selective strength is also relaxed in asexual Daphnia pulex lineages, compared with sexual lineages. Endogenous, nonfunctional, bornavirus-like elements are found to be under relaxed selection compared with exogenous Borna viruses. Finally, selection on the short-wavelength sensitive, SWS1, opsin genes in echolocating and nonecholocating bats is relaxed only in lineages in which this gene underwent pseudogenization; however, selection on the functional

  15. Relaxation techniques for stress

    MedlinePlus

    ... Know. February 2013. Available at: nccih.nih.gov/health/stress/relaxation.htm . Accessed September 21, 2015. National Center ... A.D.A.M. Editorial team. Related MedlinePlus Health Topics Stress Browse the Encyclopedia A.D.A.M., Inc. ...

  16. Hair Dye and Hair Relaxers

    MedlinePlus

    ... For Consumers Consumer Information by Audience For Women Hair Dye and Hair Relaxers Share Tweet Linkedin Pin it More sharing ... products. If you have a bad reaction to hair dyes and relaxers, you should: Stop using the ...

  17. Dielectric Relaxation of Hexadeutero Dimethylsulfoxide

    NASA Astrophysics Data System (ADS)

    Betting, H.; Stockhausen, M.

    1999-11-01

    The dielectric relaxation parameters of the title substance (DMSO-d6) in its pure liquid state are determined from meas-urements up to 72 GHz at 20°C in comparison to protonated DMSO. While the relaxation strengths do not differ, the relax-ation time of DMSO-d 6 is significantly longer (21.3 ps) than that of DMSO (19.5 ps).

  18. Relaxation in Physical Education Curricula.

    ERIC Educational Resources Information Center

    Coville, Claudia A.

    1979-01-01

    A theoretical framework for incorporating relaxation instruction in the physical education curriculum is presented based on the assumption that relaxation is a muscular-skeletal skill benefitting general motor skill acquisition. Theoretical principles, a definition of relaxation, and an analysis of stages of skill development are also used in the…

  19. Relaxation phenomena in disordered systems

    NASA Astrophysics Data System (ADS)

    Sciortino, F.; Tartaglia, P.

    1997-02-01

    In this article we discuss how the assumptions of self-similarity imposed on the distribution of independently relaxing modes, as well as on their amplitude and characteristic times, manifest in the global relaxation phenomena. We also review recent applications of such approach to the description of relaxation phenomena in microemulsions and molecular glasses.

  20. A Comparison of Relaxation Strategies.

    ERIC Educational Resources Information Center

    Matthews, Doris B.

    Some researchers argue that all relaxation techniques produce a single relaxation response while others support a specific-effects hypothesis which suggests that progressive relaxation affects the musculoskeletal system and that guided imagery affects cognitive changes. Autogenics is considered a technique which is both somatic and cognitive. This…

  1. Prostaglandin E2 induces vascular relaxation by E-prostanoid 4 receptor-mediated activation of endothelial nitric oxide synthase.

    PubMed

    Hristovska, Ana-Marija; Rasmussen, Lasse E; Hansen, Pernille B L; Nielsen, Susan S; Nüsing, Rolf M; Narumiya, Shuh; Vanhoutte, Paul; Skøtt, Ole; Jensen, Boye L

    2007-09-01

    The present experiments were designed to test the hypothesis that prostaglandin (PG) E(2) causes vasodilatation through activation of endothelial NO synthase (eNOS). Aortic rings from mice with targeted deletion of eNOS and E-prostanoid (EP) receptors were used for contraction studies. Blood pressure changes in response to PGE(2) were measured in conscious mice. Single doses of PGE(2) caused concentration-dependent relaxations during contractions to phenylephrine (EC(50)=5*10(-8) mol/L). Relaxation after PGE(2) was absent in rings without endothelium and in rings from eNOS(-/-) mice and was abolished by N(G)-nitro-l-arginine methyl ester and the soluble guanylate cyclase inhibitor 1H(1,2,4)-oxadiazolo-[4,3-a]quinoxalin-1-one. In PGE(2)-relaxed aortic rings, the cGMP content increased significantly. PGE(2)-induced relaxations were abolished by the EP4 receptor antagonist AE3-208 (10(-8) mol/L) and mimicked by an EP4 agonist (AE1-329, 10(-7) mol/L) in the presence of endothelium and eNOS only. Relaxations were attenuated significantly in rings from EP4(-/-) mice but normal in EP2(-/-). Inhibitors of the cAMP-protein kinase A pathway attenuated, whereas the inhibitor of protein phosphatase 1C, calyculin (10(-8) mol/L), abolished the PGE(2)-mediated relaxation. In aortic rings, PGE(2) dephosphorylated eNOS at Thr(495). Chronically catheterized eNOS(-/-) mice were hypertensive (137+/-3.6 mm Hg, n=13, versus 101+/-3.9 mm Hg, n=9) and exhibited a lower sensitivity of blood pressure reduction in response to PGE(2) compared with wild-type mice. There was no difference in the blood pressure response to nifedipine. These findings show that PGE(2) elicits EP4 receptor-mediated, endothelium-dependent stimulation of eNOS activity by dephosphorylation at Thr(495) resulting in guanylyl cyclase-dependent vasorelaxation and accumulation of cGMP in aortic rings. PMID:17635857

  2. Analysis of the role of nitric oxide in the relaxant effect of the crude extract and fractions from Eugenia uniflora in the rat thoracic aorta.

    PubMed

    Wazlawik, E; Da Silva, M A; Peters, R R; Correia, J F; Farias, M R; Calixto, J B; Ribeiro-Do-Valle, R M

    1997-04-01

    This study has evaluated the possible role played by the L-arginine-nitric oxide pathway in the vasorelaxant action of the hydroalcoholic extract from Eugenia uniflora, and fractions from the extract, in rings of rat thoracic aorta. The addition of an increasing cumulative concentration of hydroalcoholic extract from E. uniflora (1-300 micrograms mL-1) caused a concentration-dependent relaxation response in intact endothelium-thoracic aorta rings pre-contracted with noradrenaline (30-100 nM). The IC50 value, with its respective confidence limit, and the maximum relaxation (Rmax) were 7.02 (4.77-10.00) micrograms mL-1 and 83.94 +/- 3.04%, respectively. The removal of the endothelium completely abolished these responses. The nitric oxide synthase inhibitors N omega-nitro-L-arginine (L-NOARG, 30 microM) and N omega-nitro-L-arginine methyl ester (L-NAME, 30 microM), inhibited the relaxation (Rmax) to -10.43 +/- 7.81% and -3.69 +/- 2.62%, respectively. In addition, L-arginine (1 mM), but not D-arginine (1 mM), completely reversed inhibition by L-NOARG. Methylene blue (30 microM), a soluble guanylate cyclase inhibitor, reduced the relaxation induced by the extract to 14.60 +/- 7.40%. These data indicate that in the rat thoracic aorta the hydroalcoholic extract, and its fractions, from the leaves of E. uniflora have graded and endothelium-dependent vasorelaxant effects. PMID:9232544

  3. Relaxing music for anxiety control.

    PubMed

    Elliott, Dave; Polman, Remco; McGregor, Richard

    2011-01-01

    The purpose of this investigation was to determine the characteristics of relaxing music for anxiety control. Undergraduate students (N=84) were instructed to imagine themselves in an anxiety producing situation while listening to a selection of 30 music compositions. For each composition, level of relaxation, the factors that either enhanced or detracted from its relaxing potential and the emotional labels attached were assessed. Participants were also asked to state which music components (e.g., tempo, melody) were most conducive to relaxation. Additional information was obtained through the use of a focus group of 6 undergraduate music students. This paper presents details on the characteristics of relaxing-music for anxiety control and emotional labels attached to the relaxing compositions. Furthermore, an importance value has been attached to each of the music components under scrutiny, thus providing an indication of which music components should receive greatest attention when selecting music for anxiety control. PMID:22097099

  4. Vascular relaxation induced by Eucommiae Ulmoides Oliv. and its compounds Oroxylin A and wogonin: implications on their cytoprotection action

    PubMed Central

    Akinyi, Mary; Gao, Xiu Mei; Li, Yu Hong; Wang, Bing Yao; Liu, Er Wei; Chai, Li Juan; JawoBah, Abdulai; Fan, Guan Wei

    2014-01-01

    The vascular relaxation action of Eucommiae Ulmoides Oliv. also known as Duzhong has been seen on arteries of the heart such as the aorta and the coronary artery which are elastic in nature. Duzhong is historically an active ingredient commonly used in hypertensive herbal prescriptions in China. This work investigated the vasodilating effect of Duzhong and its compounds (wogonin 10 μM and oroxylin-A) in the isolated intact rat heart, perfused retrograde according the method of Langendorff and the cytoprotective effect in EA.hy926 cell lines Coronary perfusion pressure was monitored with a pressure transducer connected to a side-arm of the aortic perfusion cannula. Duzhong induced vasorelaxation in a dose dependent manner, on precontracting the vessels with endothelin-1, Duzhong 10 mg/ml, wogonin 10 μM and oroxylin-A 10 μM could significantly lower the perfusion pressure in reference to positive control SNP, Duzhong induced vasodilation was not inhibited by L-NAME (nitric oxide inhibitor), but was significantly inhibited by Tetraethyl ammonium (TEA, a K+ channel blocker and almost abolished by potassium chloride. The underlying mechanism was carried out in EA.hy926 cell lines. When these cells were treated with H2O2, there was higher expression of NOX-4, TNF-α and COX-2 mRNA. However, wogonin treatment attenuated the mRNA of NOX-4, TNF-α and COX-2. Wogonin also upregulated the mRNA expression of CAT, SOD-1 and GSR in oxidative stress induced by H2O2 EA.hy926 cells. Duzhong and compounds can exert an in vitro relaxation effect of the coronary artery and improve the heart function in Langendorff apparatus. This action appears to be endothelium dependent but not NO mediated. Cell culture findings indicated that wogonin can exert vascular and cellular protection by scavenging Reactive Oxygen Species. PMID:25419347

  5. Renormalized reaction and relaxation rates

    NASA Astrophysics Data System (ADS)

    Gorbachev, Yuriy E.

    2016-06-01

    Impact of the non-equilibrium on the reaction and relaxation rates (called as generalized relaxation rates - GRR), for the spatially inhomogeneous gas mixture is considered. Discarding the assumption that the 'chemical' part of the collisional integral is a small correction to non-reactive part, the expression for the zero-order GRR is derived. They are represented as a renormalization of the traditional reaction and relaxation rates, which means mixing of all corresponding processes. Thus all reactions and relaxation processes are entangled.

  6. Comet Bursting Through Relaxation

    NASA Astrophysics Data System (ADS)

    Jacobson, Seth A.; Scheeres, D. J.

    2012-10-01

    Comets may be excited and occupy non-principal axis (complex) rotation states for a large fraction of their lifetimes. Many comet nuclei have been identified or are suspected to occupy non-principal axis (complex) rotation [Belton 2005, etc.] as well as have evolving rotation rates [Belton 2011, etc.]. Comet orbits drive these rotation states through cycles of excitation due to surface jets and relaxation due to time variable internal stresses that dissipate energy in the anelastic comet interior. Furthermore, relaxation from complex rotation can increase the loads along the symmetry axis of prolate comets. These loads stretch the body along the symmetry axis and may be the cause of the characteristic ``bowling pin’’ shape and eventually may lead to failure. This is an alternative model for comet bursting. Each cycle deposits only a small amount of energy and stress along the axis, but this process is repeated every orbit during which jets are activated. Our model for the evolution of comet nuclei includes torques due to a number of discrete jets located on the surface based on Neishtadt et al. [2002]. The model also includes internal dissipation using an approach developed by Sharma et al. [2005] and Vokrouhlicky et al. [2009]. These equations are averaged over the instantaneous spin state and the heliocentric orbit so the long-term evolution of the comet can be determined. We determine that even after the inclusion of internal dissipation there still exist non-principal axis equilibrium states for certain jet geometries. For ranges of dissipation factors and jet geometries, prolate comets are found to occupy states that have time variable internal loads over long time periods. These periodic loadings along the symmetry axis may lead to ``necking’’ as the body extends along the axis to release the stress and eventually disruption.

  7. Measuring the Longitudinal NMR Relaxation Rates of Fast Relaxing Nuclei Using a Signal Eliminating Relaxation Filter

    NASA Astrophysics Data System (ADS)

    Hansen, D. Flemming; Led, Jens J.

    2001-08-01

    A new experiment for selective determination of the relaxation rates of fast relaxing NMR signals is presented. The experiment is derived from the conventional inversion recovery experiment by substituting the 180° inversion pulse of this experiment with a signal eliminating relaxation filter (SERF) consisting of three 180° pulses separated by two variable delays, Δ1 and Δ2. The SERF experiment allows a selective suppression of signals with relaxation rates below a given limit while monitoring the relaxation of faster relaxing signals. The experiment was tested on a sample of 20% oxidized plastocyanin from Anabaena variabilis, where the fast exchange of an electron between the reduced (diamagnetic) and the oxidized (paramagnetic) form results in a series of average signals with widely different relaxation rates. To ensure an optimum extraction of information from the experimental data, the relaxation rates were obtained from the SERF experiment by a simultaneous analysis of all the FIDs of the experiment using a fast linear prediction model method developed previously. The reliability of the relaxation rates obtained from the SERF experiment was confirmed by a comparison of the rates with the corresponding rates obtained from a conventional inversion recovery experiment.

  8. Role of NO-cGMP pathway in ovine cervical relaxation induced by Erythroxylum caatingae Plowman.

    PubMed

    Santos, K C; Monte, A P O; Lima, J T; Ribeiro, L A A; Palheta Junior, R C

    2016-01-01

    Erythroxylum caatingae Plowman has a myorelaxing effect on smooth muscle tissue. We investigated the effect of the crude ethanolic extract of E. caatingae Plowman (Ec-EtOH) on the contractility of the ovine cervix. In an isometric system, circular strips were subjected to 90mM potassium (K(+)) or 30μM carbamylcholine (CCh)-induced contraction. We then exposed the tissue to cumulative concentrations of Ec-EtOH (1-729 μg/ml). In other bath solutions, the tissues were exposed to l-NG-nitroarginine methyl ester (l-NAME; 100μM), l-NAME (100μM)+l-arginine (300μM), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, ODQ; 5μM), 4-aminopyridine (4-AP; 3mM), tetraethylammonium (TEA; 0.3mM), glybenclamide (1μM), atosiban (10μM) or verapamil (3μM), followed by the addition of Ec-EtOH (1-729 μg/ml). We also evaluated the effect of cervical Ec-EtOH infusion (2mg) on cervical contractility in vivo. Ec-EtOH decreased cervical contractility induced by K(+) or CCh, and 729 μg/ml Ec-EtOH decreased 85.4±5.1% the amplitude of basal contractility in vitro, with an EC50 of 17.9±3.7 μg/ml. This effect of Ec-EtOH was prevented by l-NAME or ODQ. l-arginine impaired the blunting effect of l-NAME on cervical relaxation caused by Ec-EtOH. However, the potassium channel blockers 4-AP, TEA, and glybenclamide did not modify this myorelaxation triggered by Ec-EtOH. Ec-EtOH also decreased acetylcholine-induced contractions in tissue preincubated with verapamil. In addition, Ec-EtOH decreased ovine cervical contractions in vivo. Thus, Ec-EtOH had a relaxant effect on ovine cervical contractions. This may involve the nitric oxide signal, mediated by cGMP cellular transduction, and be related to intracellular calcium sequestration. PMID:26619941

  9. Insensitivity of calcium-dependent endothelial stimulation in rat isolated aorta to the calcium entry blocker, flunarizine.

    PubMed Central

    Miller, R. C.; Schoeffter, P.; Stoclet, J. C.

    1985-01-01

    In rat aortic segments complete with endothelium, acetylcholine (1 microM) relaxed noradrenaline, phenylephrine and prostaglandin F2 alpha (PGF2 alpha)-induced contractions of various magnitudes. Maximal 1 microM phenylephrine-induced contractions were relaxed to a greater extent than were maximal contractions induced by the other two agonists. Contractions elicited by various concentrations of phenylephrine and PGF2 alpha in the presence of a maximal effective concentration of the calcium entry blocker flunarizine (3 microM) were relaxed by acetylcholine to about the same residual tension as were contractions elicited in the absence of flunarizine. Acetylcholine (1 microM) and phenylephrine (1 microM) increased tissue levels of guanosine cyclic 3'5'-monophosphate (cyclic GMP) by about 37 fold and 2 fold respectively. Preincubation of tissues in the absence of calcium abolished these agonist-induced increases in cyclic GMP levels, but preincubation with flunarizine had no significant effect on the increase in cyclic GMP level induced by the agonists. Pretreatment with flunarizine had no significant effect on the basal tissue level of cyclic GMP, but pretreatment in calcium-free solution reduced the basal tissue level of the cyclic nucleotide by about half. It is concluded that in rat aorta, endothelium-dependent acetylcholine-induced relaxation and endothelium-dependent acetylcholine and phenylephrine-induced increases in tissue levels of cyclic GMP, are dependent on extracellular calcium, but are not antagonized by flunarizine. This may indicate that if calcium channels of endothelial cells are activated by these agonists, their characteristics are not identical with those of the calcium channels of the smooth muscle cells. PMID:2992665

  10. Stress Relaxation of Magnetorheological Fluids

    NASA Astrophysics Data System (ADS)

    Li, W. H.; Chen, G.; Yeo, S. H.; Du, H.

    In this paper, the experimental and modeling study and analysis of the stress relaxation characteristics of magnetorheological (MR) fluids under step shear are presented. The experiments are carried out using a rheometer with parallel-plate geometry. The applied strain varies from 0.01% to 100%, covering both the pre-yield and post-yield regimes. The effects of step strain, field strength, and temperature on the stress modulus are addressed. For small step strain ranges, the stress relaxation modulus G(t,γ) is independent of step strain, where MR fluids behave as linear viscoelastic solids. For large step strain ranges, the stress relaxation modulus decreases gradually with increasing step strain. Morever, the stress relaxation modulus G(t,γ) was found to obey time-strain factorability. That is, G(t,γ) can be represented as the product of a linear stress relaxation G(t) and a strain-dependent damping function h(γ). The linear stress relaxation modulus is represented as a three-parameter solid viscoelastic model, and the damping function h(γ) has a sigmoidal form with two parameters. The comparison between the experimental results and the model-predicted values indicates that this model can accurately describe the relaxation behavior of MR fluids under step strains.

  11. Simulation of DNA Supercoil Relaxation.

    PubMed

    Ivenso, Ikenna D; Lillian, Todd D

    2016-05-24

    Several recent single-molecule experiments observe the response of supercoiled DNA to nicking endonucleases and topoisomerases. Typically in these experiments, indirect measurements of supercoil relaxation are obtained by observing the motion of a large micron-sized bead. The bead, which also serves to manipulate DNA, experiences significant drag and thereby obscures supercoil dynamics. Here we employ our discrete wormlike chain model to bypass experimental limitations and simulate the dynamic response of supercoiled DNA to a single strand nick. From our simulations, we make three major observations. First, extension is a poor dynamic measure of supercoil relaxation; in fact, the linking number relaxes so fast that it cannot have much impact on extension. Second, the rate of linking number relaxation depends upon its initial partitioning into twist and writhe as determined by tension. Third, the extensional response strongly depends upon the initial position of plectonemes. PMID:27224483

  12. Des-aspartate angiotensin I (DAA-I) reduces endothelial dysfunction in the aorta of the spontaneously hypertensive rat through inhibition of angiotensin II-induced oxidative stress.

    PubMed

    Loh, Wei Mee; Ling, Wei Chih; Murugan, Dharmani D; Lau, Yeh Siang; Achike, Francis I; Vanhoutte, Paul M; Mustafa, Mohd Rais

    2015-08-01

    Des-aspartate angiotensin I (DAA-I), an endogenous nonapeptide, counteracts several effects of angiotensin II on vascular tone. The aim of this study was to investigate the acute protective effect of DAA-I on endothelial function in the spontaneously hypertensive rat (SHR) as well as its effect on angiotensin II-induced contractions and oxidative stress. Aortic rings were incubated with DAA-I (0.1μM) for 30min prior to the assessment of angiotensin II-induced contractions (0.1nM-10μM) in WKY and SHR aortas. Total nitrate and nitrite levels were assessed using a colorimetric method and reactive oxygen species (ROS) were measured by dihydroethidium (DHE) fluorescence and lucigenin-enhanced chemiluminescence. The effect of DAA-I was also assessed against endothelium-dependent and -independent relaxations to acetylcholine and sodium nitroprusside, respectively. Angiotensin II-induced contractions were significantly reduced by DAA-I, losartan and tempol. Incubation with ODQ (soluble guanylyl cyclase inhibitor) and removal of the endothelium prevented the reduction of angiotensin II-induced contractions by DAA-I. Total nitrate and nitrite levels were increased in DAA-I, losartan and tempol treated-SHR tissues while ROS level was reduced by DAA-I and the latter inhibitors. In addition, DAA-I significantly improved the impaired acetylcholine-induced relaxation in SHR aortas whilst sodium nitroprusside-induced endothelium-independent relaxation remained unaffected. The present findings indicate that improvement of endothelial function by DAA-I in the SHR aorta is mediated through endothelium-dependent release of nitric oxide and inhibition of angiotensin II-induced oxidative stress. PMID:25869508

  13. Relaxation schemes for Chebyshev spectral multigrid methods

    NASA Technical Reports Server (NTRS)

    Kang, Yimin; Fulton, Scott R.

    1993-01-01

    Two relaxation schemes for Chebyshev spectral multigrid methods are presented for elliptic equations with Dirichlet boundary conditions. The first scheme is a pointwise-preconditioned Richardson relaxation scheme and the second is a line relaxation scheme. The line relaxation scheme provides an efficient and relatively simple approach for solving two-dimensional spectral equations. Numerical examples and comparisons with other methods are given.

  14. Phase transitions in semidefinite relaxations

    PubMed Central

    Javanmard, Adel; Montanari, Andrea; Ricci-Tersenghi, Federico

    2016-01-01

    Statistical inference problems arising within signal processing, data mining, and machine learning naturally give rise to hard combinatorial optimization problems. These problems become intractable when the dimensionality of the data is large, as is often the case for modern datasets. A popular idea is to construct convex relaxations of these combinatorial problems, which can be solved efficiently for large-scale datasets. Semidefinite programming (SDP) relaxations are among the most powerful methods in this family and are surprisingly well suited for a broad range of problems where data take the form of matrices or graphs. It has been observed several times that when the statistical noise is small enough, SDP relaxations correctly detect the underlying combinatorial structures. In this paper we develop asymptotic predictions for several detection thresholds, as well as for the estimation error above these thresholds. We study some classical SDP relaxations for statistical problems motivated by graph synchronization and community detection in networks. We map these optimization problems to statistical mechanics models with vector spins and use nonrigorous techniques from statistical mechanics to characterize the corresponding phase transitions. Our results clarify the effectiveness of SDP relaxations in solving high-dimensional statistical problems. PMID:27001856

  15. Phase transitions in semidefinite relaxations.

    PubMed

    Javanmard, Adel; Montanari, Andrea; Ricci-Tersenghi, Federico

    2016-04-19

    Statistical inference problems arising within signal processing, data mining, and machine learning naturally give rise to hard combinatorial optimization problems. These problems become intractable when the dimensionality of the data is large, as is often the case for modern datasets. A popular idea is to construct convex relaxations of these combinatorial problems, which can be solved efficiently for large-scale datasets. Semidefinite programming (SDP) relaxations are among the most powerful methods in this family and are surprisingly well suited for a broad range of problems where data take the form of matrices or graphs. It has been observed several times that when the statistical noise is small enough, SDP relaxations correctly detect the underlying combinatorial structures. In this paper we develop asymptotic predictions for several detection thresholds, as well as for the estimation error above these thresholds. We study some classical SDP relaxations for statistical problems motivated by graph synchronization and community detection in networks. We map these optimization problems to statistical mechanics models with vector spins and use nonrigorous techniques from statistical mechanics to characterize the corresponding phase transitions. Our results clarify the effectiveness of SDP relaxations in solving high-dimensional statistical problems. PMID:27001856

  16. Global relaxation of superconducting qubits

    SciTech Connect

    Ojanen, T.; Niskanen, A. O.; Nakamura, Y.; Abdumalikov, A. A. Jr.

    2007-09-01

    We consider coupled quantum two-state systems (qubits) exposed to a global relaxation process. The global relaxation refers to the assumption that qubits are coupled to the same quantum bath with approximately equal strengths, appropriate for long-wavelength environmental fluctuations. We show that interactions do not spoil the picture of Dicke's subradiant and super-radiant states where quantum interference effects lead to striking deviations from the independent relaxation picture. Remarkably, the system possess a stable entangled state and a state decaying faster than single qubit excitations. We propose a scheme for how these effects can be experimentally accessed in superconducting flux qubits and, possibly, used in constructing long-lived entangled states.

  17. Shoreline relaxation at pocket beaches

    NASA Astrophysics Data System (ADS)

    Turki, Imen; Medina, Raul; Kakeh, Nabil; González, Mauricio

    2015-09-01

    A new physical concept of relaxation time is introduced in this research as the time required for the beach to dissipate its initial perturbation. This concept is investigated using a simple beach-evolution model of shoreline rotation at pocket beaches, based on the assumption that the instantaneous change of the shoreline plan-view shape depends on the long-term equilibrium plan-view shape. The expression of relaxation time is developed function of the energy conditions and the physical characteristics of the beach; it increases at longer beaches having coarse sediments and experiencing low-energy conditions. The relaxation time, calculated by the developed model, is validated by the shoreline observations extracted from video images at two artificially embayed beaches of Barcelona (NW Mediterranean) suffering from perturbations of sand movement and a nourishment project. This finding is promising to estimate the shoreline response and useful to improve our understanding of the dynamic of pocket beaches and their stability.

  18. Multigrid Methods for Mesh Relaxation

    SciTech Connect

    O'Brien, M J

    2006-06-12

    When generating a mesh for the initial conditions for a computer simulation, you want the mesh to be as smooth as possible. A common practice is to use equipotential mesh relaxation to smooth out a distorted computational mesh. Typically a Laplace-like equation is set up for the mesh coordinates and then one or more Jacobi iterations are performed to relax the mesh. As the zone count gets really large, the Jacobi iteration becomes less and less effective and we are stuck with our original unrelaxed mesh. This type of iteration can only damp high frequency errors and the smooth errors remain. When the zone count is large, almost everything looks smooth so relaxation cannot solve the problem. In this paper we examine a multigrid technique which effectively smooths out the mesh, independent of the number of zones.

  19. Ellipsoidal Relaxation of Deformed Vesicles

    NASA Astrophysics Data System (ADS)

    Yu, Miao; Lira, Rafael B.; Riske, Karin A.; Dimova, Rumiana; Lin, Hao

    2015-09-01

    Theoretical analysis and experimental quantification on the ellipsoidal relaxation of vesicles are presented. The current work reveals the simplicity and universal aspects of this process. The Helfrich formula is shown to apply to the dynamic relaxation of moderate-to-high tension membranes, and a closed-form solution is derived which predicts the vesicle aspect ratio as a function of time. Scattered data are unified by a time scale, which leads to a similarity behavior, governed by a distinctive solution for each vesicle type. Two separate regimes in the relaxation are identified, namely, the "entropic" and the "constant-tension" regimes. The bending rigidity and the initial membrane tension can be simultaneously extracted from the data analysis, posing the current approach as an effective means for the mechanical analysis of biomembranes.

  20. Relaxed Poisson cure rate models.

    PubMed

    Rodrigues, Josemar; Cordeiro, Gauss M; Cancho, Vicente G; Balakrishnan, N

    2016-03-01

    The purpose of this article is to make the standard promotion cure rate model (Yakovlev and Tsodikov, ) more flexible by assuming that the number of lesions or altered cells after a treatment follows a fractional Poisson distribution (Laskin, ). It is proved that the well-known Mittag-Leffler relaxation function (Berberan-Santos, ) is a simple way to obtain a new cure rate model that is a compromise between the promotion and geometric cure rate models allowing for superdispersion. So, the relaxed cure rate model developed here can be considered as a natural and less restrictive extension of the popular Poisson cure rate model at the cost of an additional parameter, but a competitor to negative-binomial cure rate models (Rodrigues et al., ). Some mathematical properties of a proper relaxed Poisson density are explored. A simulation study and an illustration of the proposed cure rate model from the Bayesian point of view are finally presented. PMID:26686485

  1. A mixed relaxed clock model

    PubMed Central

    2016-01-01

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325829

  2. A mixed relaxed clock model.

    PubMed

    Lartillot, Nicolas; Phillips, Matthew J; Ronquist, Fredrik

    2016-07-19

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees.This article is part of the themed issue 'Dating species divergences using rocks and clocks'. PMID:27325829

  3. Statistical mechanics of violent relaxation

    NASA Technical Reports Server (NTRS)

    Spergel, David N.; Hernquist, Lars

    1992-01-01

    We propose a functional that is extremized through violent relaxation. It is based on the Ansatz that the wave-particle scattering during violent dynamical processes can be approximated as a sequence of discrete scattering events that occur near a particle's perigalacticon. This functional has an extremum whose structure closely resembles that of spheroidal stellar systems such as elliptical galaxies. The results described here, therefore, provide a simple framework for understanding the physical nature of violent relaxation and support the view that galaxies are structured in accord with fundamental statistical principles.

  4. Relaxation dynamics of branched polymers

    NASA Astrophysics Data System (ADS)

    Ghosh, Arnav

    The Rouse model for star polymers was successfully derived by solving the differential equations governing the net force acting on each bead in a star polymer chain. As opposed to a linear polymer, where we have N unique roots for N beads, in the case of star polymers, there are only 2 Na+1 unique roots and all odd unique roots (except the last root corresponding to the branch point) starting with the first root have a multiplicity of f-1. The relaxation time of the pth unique Rouse mode of a star polymer varies as (2Na + 1)2/p2. Since alternate Rouse modes in a star polymer have a multiplicity of f-1, they add to the terminal modulus of the star polymers and the terminal modulus, G(tau) ends up being proportional to f-1 (besides being inversely proportional to N, which is also the case with linear polymers). A self-consistent theory for the relaxation of entangled star polymers was developed based on the work done by Colby and Rubinstein on linear blends. This theory considers the duality of relaxation dynamics (direct stress relaxation and indirect relaxation by release of constraints) and models the relaxation due to constraint release R(t) based on Dean's approach in solving the vibration frequencies of glassy chains with random spring constants. In our case, the mobilities of beads were considered to be random and based on the relative weight of the prefactor of a Maxwell function, a group of which was fitted to the stress relaxation function mu(t) of a star polymer (proposed and derived by Doi). The tube dilation model for star and comb polymers was investigated in detail and predictions compared to rheological data from polypropylene, polybutadiene and polystyrene comb polymers along with PEP star polymers. The relaxation time from the Tube Dilation Model was compared with the classical Tube Model and was shown to have an extra power dependence on the fraction of the comb backbone.

  5. Spin relaxation in disordered media

    NASA Astrophysics Data System (ADS)

    Dzheparov, F. S.

    2011-10-01

    A review is given on theoretical grounds and typical experimental appearances of spin dynamics and relaxation in solids containing randomly distributed nuclear and/or electronic spins. Brief content is as follows. Disordered and magnetically diluted systems. General outlines of the spin transport theory. Random walks in disordered systems (RWDS). Observable values in phase spin relaxation, free induction decay (FID). Interrelation of longitudinal and transversal relaxation related to dynamics of occupancies and phases. Occupation number representation for equations of motion. Continuum media approximation and inapplicability of moment expansions. Long-range transitions vs percolation theory. Concentration expansion as a general constructive basis for analytical methods. Scaling properties of propagators. Singular point. Dynamical and kinematical memory in RWDS. Ways of regrouping of concentration expansions. CTRW and semi-phenomenology. Coherent medium approximation for nuclear relaxation via paramagnetic impurities. Combining of memory functions and cumulant expansions for calculation of FID. Path integral representations for RWDS. Numerical simulations of RWDS. Spin dynamics in magnetically diluted systems with low Zeeman and medium low dipole temperatures. Cluster expansions, regularization of dipole interactions and spectral dynamics.

  6. Theory of nuclear magnetic relaxation

    NASA Technical Reports Server (NTRS)

    Mcconnell, J.

    1983-01-01

    A theory of nuclear magnetic interaction is based on the study of the stochastic rotation operator. The theory is applied explicitly to relaxation by anisotropic chemical shift and to spin-rotational interactions. It is applicable also to dipole-dipole and quadrupole interactions.

  7. NMR Relaxation and Petrophysical Properties

    NASA Astrophysics Data System (ADS)

    Fleury, Marc

    2011-03-01

    NMR relaxation is routinely used in the field of geosciences to give basic petrophysical properties such as porosity, pore size distribution, saturation etc. In this tutorial, we focus on the pore size distribution deduced from NMR. We recall the basic principle used in the interpretation of the NMR signal and compare the results with other standard petrophysical techniques such as mercury pore size distribution, BET specific surface measurements, thin section visualizations. The NMR pore size distribution is a unique information available on water saturated porous media and can give similar results as MICP in certain situations. The scaling of NMR relaxation time distribution (s) into pore sizes (μm) requires the knowledge of the surface relaxivity (μm/s) and we recommend using specific surface measurements as an independent determination of solid surface areas. With usual surface relaxivities, the NMR technique can explore length-scales starting from nano-meters and ending around 100 μm. Finally, we will introduce briefly recent techniques sensitive to the pore to pore diffusional exchange, providing new information on the connectivity of the pore network, but showing another possibility of discrepancy in the determination of pore size distribution with standard techniques.

  8. Distributed Relaxation for Conservative Discretizations

    NASA Technical Reports Server (NTRS)

    Diskin, Boris; Thomas, James L.

    2001-01-01

    A multigrid method is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work that is a small (less than 10) multiple of the operation count in one target-grid residual evaluation. The way to achieve this efficiency is the distributed relaxation approach. TME solvers employing distributed relaxation have already been demonstrated for nonconservative formulations of high-Reynolds-number viscous incompressible and subsonic compressible flow regimes. The purpose of this paper is to provide foundations for applications of distributed relaxation to conservative discretizations. A direct correspondence between the primitive variable interpolations for calculating fluxes in conservative finite-volume discretizations and stencils of the discretized derivatives in the nonconservative formulation has been established. Based on this correspondence, one can arrive at a conservative discretization which is very efficiently solved with a nonconservative relaxation scheme and this is demonstrated for conservative discretization of the quasi one-dimensional Euler equations. Formulations for both staggered and collocated grid arrangements are considered and extensions of the general procedure to multiple dimensions are discussed.

  9. Ellipsoidal relaxation of electrodeformed vesicles

    NASA Astrophysics Data System (ADS)

    Yu, Miao; Lin, Hao; Lira, Rafael; Dimova, Rumiana; Riske, Karin

    2015-11-01

    Electrodeformation has been extensively applied to investigate the mechanical behavior of vesicles and cells. While the deformation process often exhibits complex behavior and reveals interesting physics, the relaxation process post-pulsation is equally intriguing yet less frequently studied. In this work theoretical analysis and experimental quantification on the ellipsoidal relaxation of vesicles are presented, which reveal the simplicity and universal aspects of this process. The Helfrich formula, which is derived only for equilibrated shapes, is shown to be applicable to dynamic situations such as in relaxation. A closed-form solution is derived which predicts the vesicle aspect ratio as a function of time. Scattered data are unified by a timescale, which leads to a similarity behavior, governed by a distinctive solution for each vesicle type. Two separate regimes in the relaxation are identified, namely, the ``entropic'' and the ``constant-tension'' regime. The bending rigidity and the initial membrane tension can be simultaneously extracted from the data/model analysis, posing the current approach as an effective means for the mechanical analysis of biomembranes.

  10. Choosing a skeletal muscle relaxant.

    PubMed

    See, Sharon; Ginzburg, Regina

    2008-08-01

    Skeletal muscle relaxants are widely used in treating musculoskeletal conditions. However, evidence of their effectiveness consists mainly of studies with poor methodologic design. In addition, these drugs have not been proven to be superior to acetaminophen or nonsteroidal anti-inflammatory drugs for low back pain. Systematic reviews and meta-analyses support using skeletal muscle relaxants for short-term relief of acute low back pain when nonsteroidal anti-inflammatory drugs or acetaminophen are not effective or tolerated. Comparison studies have not shown one skeletal muscle relaxant to be superior to another. Cyclobenzaprine is the most heavily studied and has been shown to be effective for various musculoskeletal conditions. The sedative properties of tizanidine and cyclobenzaprine may benefit patients with insomnia caused by severe muscle spasms. Methocarbamol and metaxalone are less sedating, although effectiveness evidence is limited. Adverse effects, particularly dizziness and drowsiness, are consistently reported with all skeletal muscle relaxants. The potential adverse effects should be communicated clearly to the patient. Because of limited comparable effectiveness data, choice of agent should be based on side-effect profile, patient preference, abuse potential, and possible drug interactions. PMID:18711953

  11. Relaxation properties in classical diamagnetism

    NASA Astrophysics Data System (ADS)

    Carati, A.; Benfenati, F.; Galgani, L.

    2011-06-01

    It is an old result of Bohr that, according to classical statistical mechanics, at equilibrium a system of electrons in a static magnetic field presents no magnetization. Thus a magnetization can occur only in an out of equilibrium state, such as that produced through the Foucault currents when a magnetic field is switched on. It was suggested by Bohr that, after the establishment of such a nonequilibrium state, the system of electrons would quickly relax back to equilibrium. In the present paper, we study numerically the relaxation to equilibrium in a modified Bohr model, which is mathematically equivalent to a billiard with obstacles, immersed in a magnetic field that is adiabatically switched on. We show that it is not guaranteed that equilibrium is attained within the typical time scales of microscopic dynamics. Depending on the values of the parameters, one has a relaxation either to equilibrium or to a diamagnetic (presumably metastable) state. The analogy with the relaxation properties in the Fermi Pasta Ulam problem is also pointed out.

  12. "Stressing" Relaxation in the Classroom.

    ERIC Educational Resources Information Center

    Prager-Decker, Iris

    A rationale is offered for incorporating relaxation training in elementary school classroom activities. Cited are research studies which focus on the reaction of children to stressful life changes and resulting behavioral and physical disorders. A list is given of significant life events which may be factors in causing diseases or misbehavior in…

  13. Relaxation times estimation in MRI

    NASA Astrophysics Data System (ADS)

    Baselice, Fabio; Caivano, Rocchina; Cammarota, Aldo; Ferraioli, Giampaolo; Pascazio, Vito

    2014-03-01

    Magnetic Resonance Imaging is a very powerful techniques for soft tissue diagnosis. At the present, the clinical evaluation is mainly conducted exploiting the amplitude of the recorded MR image which, in some specific cases, is modified by using contrast enhancements. Nevertheless, spin-lattice (T1) and spin-spin (T2) relaxation times can play an important role in many pathology diagnosis, such as cancer, Alzheimer or Parkinson diseases. Different algorithms for relaxation time estimation have been proposed in literature. In particular, the two most adopted approaches are based on Least Squares (LS) and on Maximum Likelihood (ML) techniques. As the amplitude noise is not zero mean, the first one produces a biased estimator, while the ML is unbiased but at the cost of high computational effort. Recently the attention has been focused on the estimation in the complex, instead of the amplitude, domain. The advantage of working with real and imaginary decomposition of the available data is mainly the possibility of achieving higher quality estimations. Moreover, the zero mean complex noise makes the Least Square estimation unbiased, achieving low computational times. First results of complex domain relaxation times estimation on real datasets are presented. In particular, a patient with an occipital lesion has been imaged on a 3.0T scanner. Globally, the evaluation of relaxation times allow us to establish a more precise topography of biologically active foci, also with respect to contrast enhanced images.

  14. Catechin averts experimental diabetes mellitus-induced vascular endothelial structural and functional abnormalities.

    PubMed

    Bhardwaj, Pooja; Khanna, Deepa; Balakumar, Pitchai

    2014-03-01

    Diabetes mellitus is associated with an induction of vascular endothelial dysfunction (VED), an initial event that could lead to the pathogenesis of atherosclerosis and hypertension. Previous studies showed that catechin, a key component of green tea, possesses vascular beneficial effects. We investigated the effect of catechin hydrate in diabetes mellitus-induced experimental vascular endothelial abnormalities (VEA). Streptozotocin (50 mg/kg, i.p., once) administration to rats produced diabetes mellitus, which subsequently induced VEA in 8 weeks by markedly attenuating acetylcholine-induced endothelium-dependent relaxation in the isolated aortic ring preparation, decreasing aortic and serum nitrite/nitrate concentrations and impairing aortic endothelial integrity. These abnormalities in diabetic rats were accompanied with elevated aortic superoxide anion generation and serum lipid peroxidation in addition to hyperglycemia. Catechin hydrate treatment (50 mg/kg/day p.o., 3 weeks) markedly prevented diabetes mellitus-induced VEA and vascular oxidative stress. Intriguingly, in vitro incubation of L-NAME (100 μM), an inhibitor of nitric oxide synthase, or Wortmannin (100 nM), a selective inhibitor of phosphatidylinositol 3-kinase (PI3K), markedly prevented catechin hydrate-induced improvement in acetylcholine-provoked endothelium-dependent relaxation in the diabetic rat aorta. Moreover, catechin hydrate treatment considerably reduced the elevated level of serum glucose in diabetic rats. In conclusion, catechin hydrate treatment prevents diabetes mellitus-induced VED through the activation of endothelial PI3K signal and subsequent activation of eNOS and generation of nitric oxide. In addition, reduction in high glucose, vascular oxidative stress, and lipid peroxidation might additionally contribute to catechin hydrate-associated prevention of diabetic VEA. PMID:24048981

  15. Boldine protects endothelial function in hyperglycemia-induced oxidative stress through an antioxidant mechanism.

    PubMed

    Lau, Yeh Siang; Tian, Xiao Yu; Huang, Yu; Murugan, Dharmani; Achike, Francis I; Mustafa, Mohd Rais

    2013-02-01

    Increased oxidative stress is involved in the pathogenesis and progression of diabetes. Antioxidants are therapeutically beneficial for oxidative stress-associated diseases. Boldine ([s]-2,9-dihydroxy-1,10-dimethoxyaporphine) is a major alkaloid present in the leaves and bark of the boldo tree (Peumus boldus Molina), with known an antioxidant activity. This study examined the protective effects of boldine against high glucose-induced oxidative stress in rat aortic endothelial cells (RAEC) and its mechanisms of vasoprotection related to diabetic endothelial dysfunction. In RAEC exposed to high glucose (30 mM) for 48 h, pre-treatment with boldine reduced the elevated ROS and nitrotyrosine formation, and preserved nitric oxide (NO) production. Pre-incubation with β-NAPDH reduced the acetylcholine-induced endothelium-dependent relaxation; this attenuation was reversed by boldine. Compared with control, endothelium-dependent relaxation in the aortas of streptozotocin (STZ)-treated diabetic rats was significantly improved by both acute (1 μM, 30 min) and chronic (20mg/kg/daily, i.p., 7 days) treatment with boldine. Intracellular superoxide and peroxynitrite formation measured by DHE fluorescence or chemiluminescence assay were higher in sections of aortic rings from diabetic rats compared with control. Chronic boldine treatment normalized ROS over-production in the diabetic group and this correlated with reduction of NAD(P)H oxidase subunits, NOX2 and p47(phox). The present study shows that boldine reversed the increased ROS formation in high glucose-treated endothelial cells and restored endothelial function in STZ-induced diabetes by inhibiting oxidative stress and thus increasing NO bioavailability. PMID:23178655

  16. Dielectric relaxations in aliphatic polyesters

    NASA Astrophysics Data System (ADS)

    Sen, Sudeepto

    2001-07-01

    The dielectric technique was used to study the relaxation processes of five linear aliphatic polyesters. The polyesters studied were poly (ethylene succinate/adipate) or PESA, poly (trimethylene succinate/adipate) or PTSA, poly (butylene succinate/adipate) or PBSA, poly (ethylene succinate) or PES, and poly (ethylene adipate) or PEA. Three of the polyesters were copolymers (PESA, PTSA, and PBSA), and the remaining two (PES and PEA) were homopolymers. Two of the five were amorphous (PESA and PTSA), and the remaining three (PBSA, PES, and PEA) were semicrystalline. All the five polyesters were synthesized in the laboratory using a poly-condensation reaction between a series of aliphatic diols and diesters. The succinic and adipic groups in the copolymers are in equimolar amounts. The polymers were characterized by differential scanning calorimetry and density measurements. Elemental analysis done on the polymers confirmed that their compositions matched theoretical estimates. The relaxation processes were studied dielectrically using an IMASS time domain dielectric spectrometer (TDS) and an HP 4284A LCR meter. Together they allowed a frequency range from 0.001 Hz to 1 MHz. Typically in the subglass region, good data were obtained between 0.01 Hz and 100 kHz. In the glass transition region, good data were occasionally available over the entire range. Two relaxation processes were detected in the subglass temperature region for all the polymers, and in the case of the copolymers PTSA and PBSA, they were also well resolved. Both the processes showed Arrhenius behavior with modest activation energies characteristic of subglass processes in general. They also progressively merged with increasing temperature, which implies a lower activation energy for the faster process which is consistent with the current understanding of relaxation phenomena. The glass transition region of all the polymers also showed a merging of the dominant alpha relaxation with the subglass

  17. Equivalent Relaxations of Optimal Power Flow

    SciTech Connect

    Bose, S; Low, SH; Teeraratkul, T; Hassibi, B

    2015-03-01

    Several convex relaxations of the optimal power flow (OPF) problem have recently been developed using both bus injection models and branch flow models. In this paper, we prove relations among three convex relaxations: a semidefinite relaxation that computes a full matrix, a chordal relaxation based on a chordal extension of the network graph, and a second-order cone relaxation that computes the smallest partial matrix. We prove a bijection between the feasible sets of the OPF in the bus injection model and the branch flow model, establishing the equivalence of these two models and their second-order cone relaxations. Our results imply that, for radial networks, all these relaxations are equivalent and one should always solve the second-order cone relaxation. For mesh networks, the semidefinite relaxation and the chordal relaxation are equally tight and both are strictly tighter than the second-order cone relaxation. Therefore, for mesh networks, one should either solve the chordal relaxation or the SOCP relaxation, trading off tightness and the required computational effort. Simulations are used to illustrate these results.

  18. Plasmon-mediated energy relaxation in graphene

    NASA Astrophysics Data System (ADS)

    Ferry, D. K.; Somphonsane, R.; Ramamoorthy, H.; Bird, J. P.

    2015-12-01

    Energy relaxation of hot carriers in graphene is studied at low temperatures, where the loss rate may differ significantly from that predicted for electron-phonon interactions. We show here that plasmons, important in the relaxation of energetic carriers in bulk semiconductors, can also provide a pathway for energy relaxation in transport experiments in graphene. We obtain a total loss rate to plasmons that results in energy relaxation times whose dependence on temperature and density closely matches that found experimentally.

  19. Plasmon-mediated energy relaxation in graphene

    SciTech Connect

    Ferry, D. K.; Somphonsane, R.; Ramamoorthy, H.; Bird, J. P.

    2015-12-28

    Energy relaxation of hot carriers in graphene is studied at low temperatures, where the loss rate may differ significantly from that predicted for electron-phonon interactions. We show here that plasmons, important in the relaxation of energetic carriers in bulk semiconductors, can also provide a pathway for energy relaxation in transport experiments in graphene. We obtain a total loss rate to plasmons that results in energy relaxation times whose dependence on temperature and density closely matches that found experimentally.

  20. Homocysteine-induced attenuation of vascular endothelium-dependent hyperalgesia in the rat.

    PubMed

    Joseph, E K; Green, P G; Ferrari, L F; Levine, J D

    2015-01-22

    We have recently demonstrated a role of the vascular endothelium in peripheral pain mechanism by disrupting endothelial cell function using intravascular administration of octoxynol-9, a non-selective membrane active agent. As an independent test of the role of endothelial cells in pain mechanisms, we evaluated the effect of homocysteine, an agent that damages endothelial cell function. Mechanical stimulus-induced enhancement of endothelin-1 hyperalgesia in the gastrocnemius muscle of the rat was first prevented then enhanced by intravenous administration of homocysteine, but was only inhibited by its precursor, methionine. Both homocysteine and methionine significantly attenuated mechanical hyperalgesia in two models of ergonomic muscle pain, induced by exposure to vibration, and by eccentric exercise, and cutaneous mechanical hyperalgesia in an ischemia-reperfusion injury model of Complex Regional Pain Syndrome type I, all previously shown responsive to octoxynol-9. This study provides independent support for a role of the endothelial cell in pain syndromes thought to have a vascular basis, and suggests that substances that are endothelial cell toxins can enhance vascular pain. PMID:25451284

  1. The Gatekeepers in the Mouse Ophthalmic Artery: Endothelium-Dependent Mechanisms of Cholinergic Vasodilation

    PubMed Central

    Manicam, Caroline; Staubitz, Julia; Brochhausen, Christoph; Grus, Franz H.; Pfeiffer, Norbert; Gericke, Adrian

    2016-01-01

    Cholinergic regulation of arterial luminal diameter involves intricate network of intercellular communication between the endothelial and smooth muscle cells that is highly dependent on the molecular mediators released by the endothelium. Albeit the well-recognized contribution of nitric oxide (NO) towards vasodilation, the identity of compensatory mechanisms that maintain vasomotor tone when NO synthesis is deranged remain largely unknown in the ophthalmic artery. This is the first study to identify the vasodilatory signalling mechanisms of the ophthalmic artery employing wild type mice. Acetylcholine (ACh)-induced vasodilation was only partially attenuated when NO synthesis was inhibited. Intriguingly, the combined blocking of cytochrome P450 oxygenase (CYP450) and lipoxygenase (LOX), as well as CYP450 and gap junctions, abolished vasodilation; demonstrating that the key compensatory mechanisms comprise arachidonic acid metabolites which, work in concert with gap junctions for downstream signal transmission. Furthermore, the voltage-gated potassium ion channel, Kv1.6, was functionally relevant in mediating vasodilation. Its localization was found exclusively in the smooth muscle. In conclusion, ACh-induced vasodilation of mouse ophthalmic artery is mediated in part by NO and predominantly via arachidonic acid metabolites, with active involvement of gap junctions. Particularly, the Kv1.6 channel represents an attractive therapeutic target in ophthalmopathologies when NO synthesis is compromised. PMID:26831940

  2. Cannabidiol causes endothelium-dependent vasorelaxation of human mesenteric arteries via CB1 activation

    PubMed Central

    Stanley, Christopher P.; Hind, William H.; Tufarelli, Cristina; O'Sullivan, Saoirse E.

    2015-01-01

    Aims The protective effects of cannabidiol (CBD) have been widely shown in preclinical models and have translated into medicines for the treatment of multiple sclerosis and epilepsy. However, the direct vascular effects of CBD in humans are unknown. Methods and results Using wire myography, the vascular effects of CBD were assessed in human mesenteric arteries, and the mechanisms of action probed pharmacologically. CBD-induced intracellular signalling was characterized using human aortic endothelial cells (HAECs). CBD caused acute, non-recoverable vasorelaxation of human mesenteric arteries with an Rmax of ∼40%. This was inhibited by cannabinoid receptor 1 (CB1) receptor antagonists, desensitization of transient receptor potential channels using capsaicin, removal of the endothelium, and inhibition of potassium efflux. There was no role for cannabinoid receptor-2 (CB2) receptor, peroxisome proliferator activated receptor (PPAR)γ, the novel endothelial cannabinoid receptor (CBe), or cyclooxygenase. CBD-induced vasorelaxation was blunted in males, and in patients with type 2 diabetes or hypercholesterolemia. In HAECs, CBD significantly reduced phosphorylated JNK, NFκB, p70s6 K and STAT5, and significantly increased phosphorylated CREB, ERK1/2, and Akt levels. CBD also increased phosphorylated eNOS (ser1177), which was correlated with increased levels of ERK1/2 and Akt levels. CB1 receptor antagonism prevented the increase in eNOS phosphorylation. Conclusion This study shows, for the first time, that CBD causes vasorelaxation of human mesenteric arteries via activation of CB1 and TRP channels, and is endothelium- and nitric oxide-dependent. PMID:26092099

  3. Viscoelastic Relaxation of Lunar Basins

    NASA Astrophysics Data System (ADS)

    Mohit, P. S.; Phillips, R. J.

    2004-12-01

    The large lunar impact basins provide a unique glimpse into early lunar history. Here we investigate the possibility that the relief of the oldest lunar basins (with the exception of South-Pole Aitken) has decayed through viscous relaxation. We identify nine ancient multi-ring basins with very low relief and low-amplitude Bouguer and free-air gravity anomalies. The characteristics of these basins are consistent with either 1) relaxation of topographic relief by ductile flow (e.g. Solomon et al., 1982) or 2) obliteration of basin topography during crater collapse immediately following impact. Both scenarios require that the basins formed early in lunar history, when the Moon was hot. The latter possibility appears to be unlikely due to the great topographic relief of South Pole-Aitken basin (SPA), the largest and oldest impact basin on the Moon (with the possible exception of the putative Procellarum basin; Wilhelms, 1987). On the other hand, the thin crust beneath SPA may not have allowed ductile flow in its lower portions, even for a hot Moon, implying that a thicker crust is required beneath other ancient basins for the hypothesis of viscous relaxation to be tenable. Using a semi-analytic, self-gravitating viscoelastic model, we investigate the conditions necessary to produce viscous relaxation of lunar basins. We model topographic relaxation for a crustal thickness of 30 km, using a dry diabase flow law for the crust and dry olivine for the mantle. We find that the minimum temperature at the base of the crust (Tb) permitting nearly complete relaxation of topography by ductile flow on a timescale < 108 yrs is 1400 K, corresponding to a heat flow of 55mW/m2, into the crust. Ductile flow in the lower crust becomes increasingly difficult as the crustal thickness decreases. The crust beneath SPA, thinned by the impact, is only 15-20 km thick and would require Tb ≥ 1550 K for relaxation to occur. The fact that SPA has maintained high-amplitude relief suggests that

  4. Kinetic activation-relaxation technique.

    PubMed

    Béland, Laurent Karim; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand

    2011-10-01

    We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon). PMID:22181304

  5. Models of violently relaxed galaxies

    NASA Astrophysics Data System (ADS)

    Merritt, David; Tremaine, Scott; Johnstone, Doug

    1989-02-01

    The properties of spherical self-gravitating models derived from two distribution functions that incorporate, in a crude way, the physics of violent relaxation are investigated. The first distribution function is identical to the one discussed by Stiavelli and Bertin (1985) except for a change in the sign of the 'temperature', i.e., e exp(-aE) to e exp(+aE). It is shown that these 'negative temperature' models provide a much better description of the end-state of violent relaxation than 'positive temperature' models. The second distribution function is similar to the first except for a different dependence on angular momentum. Both distribution functions yield single-parameter families of models with surface density profiles very similar to the R exp 1/4 law. Furthermore, the central concentration of models in both families increases monotonically with the velocity anisotropy, as expected in systems that formed through cold collapse.

  6. Shear Relaxations of Confined Liquids.

    NASA Astrophysics Data System (ADS)

    Carson, George Amos, Jr.

    Ultrathin (<40 A) films of octamethylcyclotetrasiloxane (OMCTS), hexadecane, and dodecane were subjected to linear and non-linear oscillatory shear between flat plates. Shearing frequencies of 0.1 to 800 s^{-1} were applied at pressures from zero to 0.8 MPa using a surface rheometer only recently developed. In most cases the plates were atomically smooth mica surfaces; the role of surface interactions was examined by replacing these with alkyl chain monolayers. OMCTS and hexadecane were examined at a temperature about 5 Celsius degrees above their melting points and tended to solidify. Newtonian plateaus having enormous viscosities were observed at low shear rates. The onset of shear thinning implied relaxation times of about 0.1 s in the linear structure of the confined liquids. Large activation volumes (~80 nm ^3) suggested that shear involved large-scale collective motion. Dodecane was studied at a much higher temperature relative to its melting point and showed no signs of impending solidification though it exhibited well-defined regions of Newtonian response and power law shear thinning. When treated with molecular sieves before use, dodecane had relaxation times which were short (0.02 s) compared to hexadecane, but still exhibited large-scale collective motion. When treated with silica gel, an unexplained long -time relaxation (10 s) was seen in the Newtonian viscosity of dodecane. The relaxation time of the linear structure, 0.005 s was very small, and the storage modulus was unresolvable. The small activation volume (7nm^3) indicated a much lower level of collective motion. The activation volume remained small when dodecane was confined between tightly bound, low energy, alkyl monolayers. At low strains the storage and loss moduli became very large (>10^4 Pa), probably due to interactions with flaws in the monolayers. Dramatic signs of wall slip were observed at large strains even at low pressures.

  7. Dynamic Relaxation of Financial Indices

    NASA Astrophysics Data System (ADS)

    Shen, J.; Zheng, B.; Lin, H.; Qiu, T.

    The dynamic relaxation of the German DAX both before and after a large price-change is investigated. The dynamic behavior is characterized by a power law. At the minutely time scale, the exponent p governing the power-law behavior takes a same value before and after the large price change, while at the daily time scale, it is different. Numerical simulations of an interacting EZ herding model are performed for comparison.

  8. Shear relaxations of confined liquids

    SciTech Connect

    Carson, G.A. Jr.

    1992-01-01

    Ultrathin (<40 [angstrom]) films of octamethylcyclotetrasiloxane (OMCTS), hexadecane, and dodecane were subjected to linear and non-linear oscillatory shear between flat plates. Shearing frequencies of 0.1 to 800 s[sup [minus]1] were applied at pressures from zero to 0.8 MPa using a surface rheometer only recently developed. In most cases the plates were atomically smooth mica surfaces; the role of surface interactions was examined by replacing these with alkyl chain monolayers. OMCTS and hexadecane were examined at a temperature about 5 Celcius degrees above their melting points and tended to solidify. Newtonian plateaus having enormous viscosities were observed at low shear rates. The onset of shear thinning implied relaxation times of about 0.1 s in the linear structure of the confined liquids. Large activation volumes ([approximately]80 nm[sup 3]) suggested that shear involved large-scale collective motion. Dodecane was studied at a much higher temperature relative to its melting point and showed no signs of impending solidification though it exhibited well-defined regions of Newtonian response and power law shear thinning. When treated with molecular sieves before use, dodecane had relaxation times which were short (0.02 s) compared to hexadecane, but still exhibited large-scale collective motion. When treated with silica gel, an unexplained long-time relaxation (10 s) was seen in the Newtonian viscosity of dodecane. The relaxation time of the linear structure, 0.005 s was very small, and the storage modulus was unresolvable. The small activation volume (7 nm[sup 3]) indicated a much lower level of collective motion. The activation volume remained small when dodecane was confined between tightly bound, low energy, alkyl monolayers. At low strains the storage and loss moduli became very large (>10[sup 4] Pa), probably due to interactions with flaws in the monolayers. Dramatic signs of wall slip were observed at large strains even at low pressures.

  9. Relaxation: A Fourth "R" for Education.

    ERIC Educational Resources Information Center

    Frederick, A. B.

    Relaxation training helps the individual handle tension through concentrating upon efficient use of muscles. A program of progressive relaxation can be easily incorporated into elementary and secondary schools. Objectives of such a program include the following: (a) to learn to relax technically for purposes of complete rest (deep muscle…

  10. Arresting relaxation in Pickering Emulsions

    NASA Astrophysics Data System (ADS)

    Atherton, Tim; Burke, Chris

    2015-03-01

    Pickering emulsions consist of droplets of one fluid dispersed in a host fluid and stabilized by colloidal particles absorbed at the fluid-fluid interface. Everyday materials such as crude oil and food products like salad dressing are examples of these materials. Particles can stabilize non spherical droplet shapes in these emulsions through the following sequence: first, an isolated droplet is deformed, e.g. by an electric field, increasing the surface area above the equilibrium value; additional particles are then adsorbed to the interface reducing the surface tension. The droplet is then allowed to relax toward a sphere. If more particles were adsorbed than can be accommodated by the surface area of the spherical ground state, relaxation of the droplet is arrested at some non-spherical shape. Because the energetic cost of removing adsorbed colloids exceeds the interfacial driving force, these configurations can remain stable over long timescales. In this presentation, we present a computational study of the ordering present in anisotropic droplets produced through the mechanism of arrested relaxation and discuss the interplay between the geometry of the droplet, the dynamical process that produced it, and the structure of the defects observed.

  11. Spin relaxation in metallic ferromagnets

    NASA Astrophysics Data System (ADS)

    Berger, L.

    2011-02-01

    The Elliott theory of spin relaxation in metals and semiconductors is extended to metallic ferromagnets. Our treatment is based on the two-current model of Fert, Campbell, and Jaoul. The d→s electron-scattering process involved in spin relaxation is the inverse of the s→d process responsible for the anisotropic magnetoresistance (AMR). As a result, spin-relaxation rate 1/τsr and AMR Δρ are given by similar formulas, and are in a constant ratio if scattering is by solute atoms. Our treatment applies to nickel- and cobalt-based alloys which do not have spin-up 3d states at the Fermi level. This category includes many of the technologically important magnetic materials. And we show how to modify the theory to apply it to bcc iron-based alloys. We also treat the case of Permalloy Ni80Fe20 at finite temperature or in thin-film form, where several kinds of scatterers exist. Predicted values of 1/τsr and Δρ are plotted versus resistivity of the sample. These predictions are compared to values of 1/τsr and Δρ derived from ferromagnetic-resonance and AMR experiments in Permalloy.

  12. Relation between Direct Observation of Relaxation and Self-Reported Mindfulness and Relaxation States

    ERIC Educational Resources Information Center

    Hites, Lacey S.; Lundervold, Duane A.

    2013-01-01

    Forty-four individuals, 18-47 (MN 21.8, SD 5.63) years of age, took part in a study examining the magnitude and direction of the relationship between self-report and direct observation measures of relaxation and mindfulness. The Behavioral Relaxation Scale (BRS), a valid direct observation measure of relaxation, was used to assess relaxed behavior…

  13. Effects of Progressive Relaxation versus Biofeedback-Assisted Relaxation with College Students.

    ERIC Educational Resources Information Center

    See, John D.; Czerlinsky, Thomas

    1990-01-01

    Examined use of biofeedback, relaxation training, or both in a college relaxation class with an enrollment of 33 students. Results indicated students receiving relaxation training plus biofeedback improved significantly more on psychological variables than did students receiving only relaxation training. (Author/ABL)

  14. Dynamics of Glass Relaxation at Room Temperature

    NASA Astrophysics Data System (ADS)

    Welch, Roger C.; Smith, John R.; Potuzak, Marcel; Guo, Xiaoju; Bowden, Bradley F.; Kiczenski, T. J.; Allan, Douglas C.; King, Ellyn A.; Ellison, Adam J.; Mauro, John C.

    2013-06-01

    The problem of glass relaxation under ambient conditions has intrigued scientists and the general public for centuries, most notably in the legend of flowing cathedral glass windows. Here we report quantitative measurement of glass relaxation at room temperature. We find that Corning® Gorilla® Glass shows measurable and reproducible relaxation at room temperature. Remarkably, this relaxation follows a stretched exponential decay rather than simple exponential relaxation, and the value of the stretching exponent (β=3/7) follows a theoretical prediction made by Phillips for homogeneous glasses.

  15. Time of relaxation in dusty plasma model

    NASA Astrophysics Data System (ADS)

    Timofeev, A. V.

    2015-11-01

    Dust particles in plasma may have different values of average kinetic energy for vertical and horizontal motion. The partial equilibrium of the subsystems and the relaxation processes leading to this asymmetry are under consideration. A method for the relaxation time estimation in nonideal dusty plasma is suggested. The characteristic relaxation times of vertical and horizontal motion of dust particles in gas discharge are estimated by analytical approach and by analysis of simulation results. These relaxation times for vertical and horizontal subsystems appear to be different. A single hierarchy of relaxation times is proposed.

  16. Unusual fast secondary relaxation in metallic glass

    PubMed Central

    Wang, Q.; Zhang, S.T.; Yang, Y.; Dong, Y.D.; Liu, C.T.; Lu, J.

    2015-01-01

    The relaxation spectrum of glassy solids has long been used to probe their dynamic structural features and the fundamental deformation mechanisms. Structurally complicated glasses, such as molecular glasses, often exhibit multiple relaxation processes. By comparison, metallic glasses have a simple atomic structure with dense atomic packing, and their relaxation spectra were commonly found to be simpler than those of molecular glasses. Here we show the compelling evidence obtained across a wide range of temperatures and frequencies from a La-based metallic glass, which clearly shows two peaks of secondary relaxations (fast versus slow) in addition to the primary relaxation peak. The discovery of the unusual fast secondary relaxation unveils the complicated relaxation dynamics in metallic glasses and, more importantly, provides us the clues which help decode the structural features serving as the ‘trigger' of inelasticity on mechanical agitations. PMID:26204999

  17. Diesel exhaust particles induce endothelial dysfunction in apoE{sup -/-} mice

    SciTech Connect

    Hansen, Christian S.; Sheykhzade, Majid; Moller, Peter; Folkmann, Janne Kjaergaard; Amtorp, Ole; Jonassen, Thomas; Loft, Steffen . E-mail: s.loft@pubhealth.ku.dk

    2007-02-15

    Background: Particulate air pollution can aggravate cardiovascular disease by mechanisms suggested to involve translocation of particles to the bloodstream and impairment of endothelial function, possibly dependent on present atherosclerosis. Aim: We investigated the effects of exposure to diesel exhaust particles (DEP) in vivo and ex vivo on vasomotor functions in aorta from apoE{sup -/-} mice with slight atherosclerosis and from normal apoE{sup +/+} mice. Methods: DEP 0, 0.5 or 5 mg/kg bodyweight in saline was administered i.p. The mice were sacrificed 1 h later and aorta ring segments were mounted on wire myographs. Segments from unexposed mice were also incubated ex vivo with 0, 10 and 100 {mu}g DEP/ml before measurement of vasomotor functions. Results: Exposure to 0.5 mg/kg DEP in vivo caused a decrease in the endothelium-dependent acetylcholine elicited vasorelaxation in apoE{sup -/-} mice, whereas the response was enhanced in apoE{sup +/+} mice. No significant change was observed after administration of 5 mg/kg DEP. In vivo DEP exposure did not affect constriction induced by K{sup +} or phenylephrine. In vitro exposure to 100 {mu}g DEP/ml enhanced acetylcholine-induced relaxation and attenuated phenylephrine-induced constriction. Vasodilation induced by sodium nitroprusside was not affected by any DEP exposure. Conclusion: Exposure to DEP has acute effect on vascular functions. Endothelial dysfunction possibly due to decreased NO production as suggested by decreased acetylcholine-induced vasorelaxation and unchanged sodium nitroprusside response can be induced by DEP in vivo only in vessels of mice with some atherosclerosis.

  18. Relaxation phenomenon in composite materials

    NASA Astrophysics Data System (ADS)

    Moznine, R. El.; Blanc, F.; Lieutier, M.; Lefort, A.

    1998-08-01

    Dielectric measurement characteristics such as the dissipation factor, relative permittivity and conductivity as a function of temperature and frequency have been achieved on composite materials based on different epoxy resins filled with alumina inclusions. The analysis of the results show the presence of porosity and inhomogeneity in these materials. The study of the dissipation factor, as a function of temperature at high frequencies, has shown an unexpected absorption phenomenon in materials designed to be utilized as electrical insulators. The identification of the entities responsible for this relaxation shows that the entities result from one of the components of the material. These results can also confirm the inhomogeneity of the materials.

  19. Image compression using constrained relaxation

    NASA Astrophysics Data System (ADS)

    He, Zhihai

    2007-01-01

    In this work, we develop a new data representation framework, called constrained relaxation for image compression. Our basic observation is that an image is not a random 2-D array of pixels. They have to satisfy a set of imaging constraints so as to form a natural image. Therefore, one of the major tasks in image representation and coding is to efficiently encode these imaging constraints. The proposed data representation and image compression method not only achieves more efficient data compression than the state-of-the-art H.264 Intra frame coding, but also provides much more resilience to wireless transmission errors with an internal error-correction capability.

  20. Endothelium-derived relaxing factor released by 5-HT: distinct from nitric oxide in basilar arteries of normotensive and hypertensive rats.

    PubMed Central

    Yokota, Y; Imaizumi, Y; Asano, M; Matsuda, T; Watanabe, M

    1994-01-01

    1. The role of the endothelium in cerebrovascular responses to 5-hydroxytryptamine (5-HT) was investigated in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) in vitro. 2. Cumulative addition of 5-HT caused concentration-dependent contractions in ring preparations of SHR basilar arteries; the contractile response was smaller in WKY basilar arteries. 3. Removal of the endothelium enhanced markedly the contractile responses to 5-HT in WKY arteries but had only a slight effect in SHR arteries. The responsiveness to 5-HT in WKY arteries after removal of endothelium was comparable to that in SHR arteries. 4. The endothelium-dependent relaxation induced by acetylcholine in WKY basilar arteries was almost abolished by treatment with 10 microM methylene blue or 10 microM NG-nitro-L-arginine (L-NOARG). However, the response to 5-HT was not affected by treatment with methylene blue, L-NOARG or indomethacin. 5. Application of 10-20 mM K+ or 3.2 mM tetraethylammonium (TEA) did not change significantly, or only increased slightly, the resting tension, but markedly enhanced the contractile response to 5-HT in WKY arteries with endothelium. In contrast, the submaximal response to 5-HT in SHR arteries with endothelium was significantly enhanced by 0.3 mM TEA. 6. In the presence of 1 mM TEA, the application of 10 microM L-NOARG further enhanced the responses of 5-HT in WKY arteries with endothelium. In SHR arteries with endothelium, 10 microM L-NOARG per se enhanced slightly but significantly the responses to 5-HT.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7812628

  1. Relaxation damping in oscillating contacts

    PubMed Central

    Popov, M.; Popov, V.L.; Pohrt, R.

    2015-01-01

    If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect “relaxation damping”. The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential oscillations with superimposed high frequency normal oscillations, the dissipation is proportional to the ratio of the frequencies. Generalization of the results for macroscopically planar, randomly rough surfaces as well as for the case of finite friction is discussed. PMID:26549011

  2. Relaxation damping in oscillating contacts

    NASA Astrophysics Data System (ADS)

    Popov, M.; Popov, V. L.; Pohrt, R.

    2015-11-01

    If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect “relaxation damping”. The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential oscillations with superimposed high frequency normal oscillations, the dissipation is proportional to the ratio of the frequencies. Generalization of the results for macroscopically planar, randomly rough surfaces as well as for the case of finite friction is discussed.

  3. Conservation of magnetic helicity during plasma relaxation

    SciTech Connect

    Ji, H.; Prager, S.C.; Sarff, J.S.

    1994-07-01

    Decay of the total magnetic helicity during the sawtooth relaxation in the MST Reversed-Field Pinch is much larger than the MHD prediction. However, the helicity decay (3--4%) is smaller than the magnetic energy decay (7--9%), modestly supportive of the helicity conservation hypothesis in Taylor`s relaxation theory. Enhanced fluctuation-induced helicity transport during the relaxation is observed.

  4. Dielectric polarization evolution equations and relaxation times

    SciTech Connect

    Baker-Jarvis, James; Riddle, Bill; Janezic, Michael D.

    2007-05-15

    In this paper we develop dielectric polarization evolution equations, and the resulting frequency-domain expressions, and relationships for the resulting frequency dependent relaxation times. The model is based on a previously developed equation that was derived using statistical-mechanical theory. We extract relaxation times from dielectric data and give illustrative examples for the harmonic oscillator and derive expressions for the frequency-dependent relaxation times and a time-domain integrodifferential equation for the Cole-Davidson model.

  5. Dielectric relaxation in a protein matrix

    SciTech Connect

    Pierce, D.W.; Boxer, S.G.

    1992-06-25

    The dielectric relaxation of a sperm whale ApoMb-DANCA complex is measured by the fluorescence dynamic Stokes shift method. Emission energy increases with decreasing temperature, suggesting that the relaxation activation energies of the rate-limiting motions either depend on the conformational substrate or different types of protein motions with different frequencies participate in the reaction. Experimental data suggest that there may be relaxations on a scale of <100 ps. 61 refs., 7 figs., 2 tabs.

  6. Delayed Over-Relaxation for iterative methods

    NASA Astrophysics Data System (ADS)

    Antuono, M.; Colicchio, G.

    2016-09-01

    We propose a variant of the relaxation step used in the most widespread iterative methods (e.g. Jacobi Over-Relaxation, Successive Over-Relaxation) which combines the iteration at the predicted step, namely (n + 1), with the iteration at step (n - 1). We provide a theoretical analysis of the proposed algorithm by applying such a delayed relaxation step to a generic (convergent) iterative scheme. We prove that, under proper assumptions, this significantly improves the convergence rate of the initial iterative method. As a relevant example, we apply the proposed algorithm to the solution of the Poisson equation, highlighting the advantages in comparison with classical iterative models.

  7. Baryogenesis via elementary Goldstone Higgs relaxation

    NASA Astrophysics Data System (ADS)

    Gertov, Helene; Pearce, Lauren; Sannino, Francesco; Yang, Louis

    2016-06-01

    We extend the relaxation mechanism to the elementary Goldstone Higgs framework. Besides studying the allowed parameter space of the theory, we add the minimal ingredients needed for the framework to be phenomenologically viable. The very nature of the extended Higgs sector allows to consider very flat scalar potential directions along which the relaxation mechanism can be implemented. This fact translates into wider regions of applicability of the relaxation mechanism when compared to the Standard Model Higgs case. Our results show that if the electroweak scale is not fundamental but radiatively generated it is possible to generate the observed matter-antimatter asymmetry via the relaxation mechanism.

  8. The multigrid method: Fast relaxation

    NASA Technical Reports Server (NTRS)

    South, J. C., Jr.; Brandt, A.

    1976-01-01

    A multi-level grid method was studied as a possible means of accelerating convergence in relaxation calculations for transonic flows. The method employs a hierarchy of grids, ranging from very coarse (e.g. 4 x 2 mesh cells) to fine (e.g. 64 x 32); the coarser grids are used to diminish the magnitude of the smooth part of the residuals, hopefully with far less total work than would be required with optimal iterations on the finest grid. To date the method was applied quite successfully to the solution of the transonic small-disturbance equation for the velocity potential in conservation form. Nonlifting transonic flow past a parabolic arc airfoil is the example studied, with meshes of both constant and variable step size.

  9. Dielectric secondary relaxations in polypropylene glycols.

    PubMed

    Grzybowska, K; Grzybowski, A; Zioło, J; Paluch, M; Capaccioli, S

    2006-07-28

    Broadband dielectric measurements of polypropylene glycol of molecular weight M(w)=400 g / mol (PPG 400) were carried out at ambient pressure over the wide temperature range from 123 to 353 K. Three relaxation processes were observed. Besides the structural alpha relaxation, two secondary relaxations, beta and gamma, were found. The beta process was identified as the true Johari-Goldstein relaxation by using a criterion based on the coupling model prediction. The faster gamma relaxation, well separated from the primary process, undoubtedly exhibits the anomalous behavior near the glass transition temperature (T(g)) which is reflected in the presence of a minimum of the temperature dependence of the gamma-relaxation time. We successfully applied the minimal model [Dyre and Olsen, Phys. Rev. Lett. 91, 155703 (2003)] to describe the entire temperature dependence of the gamma-relaxation time. The asymmetric double-well potential parameters obtained by Dyre and Olsen for the secondary relaxation of tripropylene glycol at ambient pressure were modified by fitting to the minimal model at lower temperatures. Moreover, we showed that the effect of the molecular weight of polypropylene glycol on the minimal model parameters is significantly larger than that of the high pressure. Such results can be explained by the smaller degree of hydrogen bonds formed by longer chain molecules of PPG at ambient pressure than that created by shorter chains of PPG at high pressure. PMID:16942189

  10. Analysis of sawtooth relaxation oscillations in tokamaks

    SciTech Connect

    Yamazaki, K.; McGuire, K.; Okabayashi, M.

    1982-07-01

    Sawtooth relaxation oscillations are analyzed using the Kadomtsev's disruption model and a thermal relaxation model. The sawtooth period is found to be very sensitive to the thermal conduction loss. Qualitative agreement between these calculations and the sawtooth period observed in several tokamaks is demonstrated.

  11. Magnetization Transfer Induced Biexponential Longitudinal Relaxation

    PubMed Central

    Prantner, Andrew M.; Bretthorst, G. Larry; Neil, Jeffrey J.; Garbow, Joel R.; Ackerman, Joseph J.H.

    2009-01-01

    Longitudinal relaxation of brain water 1H magnetization in mammalian brain in vivo is typically analyzed on a per voxel basis using a monoexponential model, thereby assigning a single relaxation time constant to all 1H magnetization within a given voxel. This approach was tested by obtaining inversion recovery data from grey matter of rats at 64 exponentially-spaced recovery times. Using Bayesian probability for model selection, brain water data were best represented by a biexponential function characterized by fast and slow relaxation components. At 4.7 T, the amplitude fraction of the rapidly relaxing component is 3.4 ± 0.7 % with a rate constant of 44 ± 12 s-1 (mean ± SD; 174 voxels from 4 rats). The rate constant of the slow relaxing component is 0.66 ± 0.04 s-1. At 11.7 T, the corresponding values are 6.9 ± 0.9 %, 19 ± 5 s-1, and 0.48 ± 0.02 s-1 (151 voxels from 4 rats). Several putative mechanisms for biexponential relaxation behavior were evaluated, and magnetization transfer between bulk water protons and non-aqueous protons was determined to be the source of biexponential longitudinal relaxation. MR methods requiring accurate quantification of longitudinal relaxation may need to take this effect explicitly into account. PMID:18759367

  12. AQUEOUS RELAXATION REAGENTS IN NITROGEN-15 NMR

    EPA Science Inventory

    Electron-nuclear relaxation times T(1)supe's for 15N and 13C in natural abundance are measured for a series of amines in aqueous solution using Gd(III) complexes of a series of polyaminocarboxylate ligands as paramagnetic relaxation reagents (PARRs). The PARRs are classified by t...

  13. Relaxed States in Magnetized Pair Plasmas

    NASA Astrophysics Data System (ADS)

    Shukla, P. K.; Mahajan, S. M.

    2004-01-01

    We discuss possibility of possible relaxed states in magnetized pair plasmas. It is shown that stationary relaxed states are described by the double curl Beltrami/Mahajan-Yoshida equation. We can thus have steady state tructures on the scale sizes of the order of the electron (ion) skin depth in an electron-positron (electron-positron-ion) plasma.

  14. On relaxations and aging of various glasses

    PubMed Central

    Amir, Ariel; Oreg, Yuval; Imry, Yoseph

    2012-01-01

    Slow relaxation occurs in many physical and biological systems. “Creep” is an example from everyday life. When stretching a rubber band, for example, the recovery to its equilibrium length is not, as one might think, exponential: The relaxation is slow, in many cases logarithmic, and can still be observed after many hours. The form of the relaxation also depends on the duration of the stretching, the “waiting time.” This ubiquitous phenomenon is called aging, and is abundant both in natural and technological applications. Here, we suggest a general mechanism for slow relaxations and aging, which predicts logarithmic relaxations, and a particular aging dependence on the waiting time. We demonstrate the generality of the approach by comparing our predictions to experimental data on a diverse range of physical phenomena, from conductance in granular metals to disordered insulators and dirty semiconductors, to the low temperature dielectric properties of glasses. PMID:22315418

  15. On relaxations and aging of various glasses.

    PubMed

    Amir, Ariel; Oreg, Yuval; Imry, Yoseph

    2012-02-01

    Slow relaxation occurs in many physical and biological systems. "Creep" is an example from everyday life. When stretching a rubber band, for example, the recovery to its equilibrium length is not, as one might think, exponential: The relaxation is slow, in many cases logarithmic, and can still be observed after many hours. The form of the relaxation also depends on the duration of the stretching, the "waiting time." This ubiquitous phenomenon is called aging, and is abundant both in natural and technological applications. Here, we suggest a general mechanism for slow relaxations and aging, which predicts logarithmic relaxations, and a particular aging dependence on the waiting time. We demonstrate the generality of the approach by comparing our predictions to experimental data on a diverse range of physical phenomena, from conductance in granular metals to disordered insulators and dirty semiconductors, to the low temperature dielectric properties of glasses. PMID:22315418

  16. Nuclear spin relaxation of polycrystalline 129 xenon

    NASA Astrophysics Data System (ADS)

    Samuelson, Gary Lee, Jr.

    Through spin exchange optical pumping, it is possible to achieve upwards of 30% nuclear spin polarization in 129Xe with an NMR signal enhancement of some 5 orders of magnitude over typical thermal signals. Hyperpolarized 129Xe has thus found application in several leading-edge technologies. At 1 T and 4.2 K, the characteristic relaxation time of enriched polycrystalline 129Xe (86% 129Xe, 0.1% 131Xe) is well over 200 hrs, sufficient for long-term storage and transport. Longitudinal nuclear spin relaxation of 129Xe at more convenient fields from 1 to 200 G is studied in detail. Significant structure in relaxation times vs. magnetic field is seen; the most prominent new finding being a sharp local long-time T 1 maximum of 1000 mins at ≈3 G. Such structure has not been observed in previous measurements of natural Xe. Below temperatures of 10 K, relaxation can be attributed to cross relaxation with 131Xe, mediated by spin diffusion. Measurements of 129Xe relaxation as a function of magnetic field, temperature and Xe isotopic content are reported and compared with expected theoretical behaviors. It is seen that the characteristic nuclear spin relaxation of enriched 129Xe at 4.2 K is nonexponential at these low fields. For fields between 10 G and 200 G, these nonexponential relaxation curves can be fit well with a specific spin diffusion model. Below 10 G no such fit is possible and thus quantum mechanical details of the coupling between 129Xe, 131Xe and the bulk lattice are considered. These findings support the hypothesis that cross relaxation with 131Xe is indeed a dominant actor in the nuclear spin relaxation of polycrystalline 129 Xe at such low fields and low temperatures.

  17. Amine metabolism: a novel path to coronary artery vasospasm.

    PubMed

    Conklin, D J; Boyce, C L; Trent, M B; Boor, P J

    2001-09-01

    We hypothesized that allylamine (AA) induces subendocardial necrosis in mammals via coronary artery (CA) vasospasm. Additionally, AA toxicity is likely dependent on the enzyme semicarbazide-sensitive amine oxidase (SSAO), which is highly expressed in the aorta of rats and humans. We tested whether AA or acrolein (1, 10, 100, and 1000 microM), a highly reactive product of AA metabolism by SSAO, could contract CA or thoracic aorta (TA) in vitro and if the AA effects involved SSAO. AA or acrolein produced a similar pattern of responses in both CA and TA rings at 100 and 1000 microM, including (1) increased basal tension, (2) enhanced agonist-induced contraction (hypercontractility or vasospasm), (3) remarkable, agonist-induced slow wave vasomotion (vasospasm), and (4) irreversible reduction in vessel contractility after 1 mM exposure. Endothelium-dependent acetylcholine-induced relaxation was not altered during vasospasm in either vessel. Pretreatment with the SSAO inhibitor semicarbazide (1 mM; 10 min) prevented or significantly reduced the majority of AA's effects in both CA and TA rings and inhibited 100% of the SSAO activity present in rat TA and human CA and TA. We propose a two-step model for AA induction of CA vasospasm and resultant myocardial necrosis: (1) metabolism of AA to acrolein by coronary arterial SSAO activity and (2) acrolein induction of CA vasospasm independent of endothelial injury-a novel path. PMID:11543647

  18. Vasoactive and antioxidant activities of plants used in Mexican traditional medicine for the treatment of cardiovascular diseases.

    PubMed

    Ibarra-Alvarado, C; Rojas, A; Mendoza, S; Bah, M; Gutiérrez, D M; Hernández-Sandoval, L; Martínez, M

    2010-07-01

    This study demonstrated that the aqueous extracts of plants employed in Mexican traditional medicine for the treatment of cardiovascular diseases are able to modify the tone of arterial smooth muscle. Agastache mexicana (Kunth) Lint & Epling (Labiatae), Chenopodium murale L. (Chenopodiaceae), Chirantodendron pentadactylon Larreat (Sterculiaceae), Dracocephalum moldavica L. (Labiatae), Psittacanthus calyculatus G. Don (Loranthaceae), Prunus serotina ssp. capuli (Cav. ex Spreng) McVaugh (Rosaceae), and Sechium edule Sw. (Cucurbitaceae) contain secondary metabolites that promote vascular relaxation and display antioxidant activities. As expected, their antioxidant effects showed a significant correlation with the polyphenolics content. However, a lower correlation was found between the antioxidant activity and the maximum vasodilatory effect, suggesting that the vasodilatation elicited by the plant extracts could be only partly attributed to their antioxidant properties. The extract of P. calyculatus, which displayed a maximum vasorelaxant effect that was higher than that of acetylcholine, induced endothelium-dependent vasodilatation. Futhermore, the vasorelaxant response to the P. calyculatus extract was reduced after adding an inhibitor of soluble guanylate cyclase activity, providing evidence that the NO/cGMP pathway is involved. On the other hand, the extracts of Bocconia frutescens L. (Papaveraceae), Magnolia grandiflora L. (Magnoliaceae), and Solanum rostratum Dunal (Solanaceae) induced concentration-dependent contraction of rat aortic rings, suggesting that these plants have potential health benefits for the treatment of ailments such as venous insufficiency. The pharmacological activities of the extracts studied provide scientific support for their ethnomedical use. PMID:20645769

  19. Renal endothelial function is associated with the anti-proteinuric effect of ACE inhibition in 5/6 nephrectomized rats.

    PubMed

    Vettoretti, Simone; Vavrinec, Peter; Ochodnicky, Peter; Deelman, Leo E; De Zeeuw, Dick; Henning, Rob H; Buikema, Hendrik

    2016-05-01

    In healthy rats, the physiological variation of baseline endothelial function of intrarenal arteries correlates with the severity of renal damage in response to a subsequent specific renal injury. However, whether such a variation in endothelial function may also condition or predict the variable response to angiotensin-converting enzyme-inhibiting treatment in these individuals has not been addressed before. To study this, 5/6 nephrectomy was performed to induce renal injury and chronic kidney disease in a group of healthy Wistar rats. At the time of nephrectomy, interlobar arteries were obtained from the extirpated right kidney and studied in vitro for endothelium-dependent relaxation to acetylcholine. Six weeks thereafter, treatment with lisinopril was started (n = 11) and continued for 9 wk. Proteinuria (metabolic cages) and systolic blood pressure (SBP; tail cuff) were evaluated weekly, and these were analyzed in relation to renal endothelial function at baseline. 5/6 Nephrectomy induced an increase in SBP and progressive proteinuria. Treatment with lisinopril reduced SBP and slowed proteinuria, albeit to a variable degree among individuals. The acetylcholine-induced renal artery dilation at baseline negatively correlated with lisinopril-induced reduction of proteinuria (r(2) = 0.648, P = 0.003) and with the decrease in SBP (r(2) = 0.592, P = 0.006). Our data suggest that angiotensin-converting enzyme-inhibitor attenuates the progression of renal damage the most in those individuals with decreased basal renal endothelial-mediated vasodilation. PMID:26911850

  20. Postseismic relaxation and transient creep

    USGS Publications Warehouse

    Savage, J.C.; Svarc, J.L.; Yu, S.-B.

    2005-01-01

    Postseismic deformation has been observed in the epicentral area following the 1992 Landers (M = 7.3), 1999 Chi-Chi (M = 7.6), 1999 Hector Mine (M = 7.1), 2002 Denali (M = 7.9), 2003 San Simeon (M = 6.5), and 2004 Parkfield (M = 6.0) earthquakes. The observations consist of repeated GPS measurements of the position of one monument relative to another (separation ???100 km). The early observations (t < 0.1 year) are well fit by the function a' + c'log(t), where t is the time after the earthquake and a' and c' are constants chosen to fit the data. Because a log(t) time dependence is characteristic of transient (primary) creep, the early postseismic response may be governed by transient creep as Benioff proposed in 1951. That inference is provisional as the stress conditions prevailing in postseismic relaxation are not identical to the constant stress condition in creep experiments. The observed logarithmic time dependence includes no characteristic time that might aid in identifying the micromechanical cause.

  1. Relaxation time of 3He

    NASA Astrophysics Data System (ADS)

    Gao, Hayian

    2004-10-01

    The next generation of searches for the neutron electric dipole moment using ultra cold neutrons will use polarized ^3He as a co-magnetometer. The first such experiment has been proposed, with a goal of improving the current limit on the neutron EDM by two orders of magnitude. This experiment requires a systematic study of the properties of polarized ^3He at cryogenic temperatures under actual experimental conditions. These experimental conditions include polarized ^3He mixed in a bath of superfluid ^4He in low magnetic field and held in an acrylic cell which is coated with deuterated TetraphenylButadiene . Parts of these systematic studies will be done at Duke University using a newly built, novel refillable double cell ^3 He polarizer based on spin exchange optical pumping with Rubidium vapor. The polarimetry for this apparatus is done with a NMR polarimeter using the adiabatic fast passage method. An alternate polarimeter using free induction decay method is also being built. This apparatus is being used to study the relaxation time and other critical properties of polarized ^3He at temperatures ranging from 2.3 - 4.2 K, under simulated experimental conditions. We will present details about this novel polarizer and show preliminary results of our measurements.

  2. A quantum-mechanical relaxation model

    NASA Astrophysics Data System (ADS)

    Skomski, R.; Kashyap, A.; Sellmyer, D. J.

    2012-04-01

    The atomic origin of micromagnetic damping is investigated by developing and solving a quantum-mechanical relaxation model. A projection-operator technique is used to derive an analytical expression for the relaxation time as a function of the heat-bath and interaction parameters. The present findings are consistent with earlier research beyond the Landau-Lifshitz-Gilbert (LLG) equation and show that the underlying relaxation mechanism is very general. Zermelo's recurrence paradox means that there is no true irreversibility in non-interacting nanoparticles, but the corresponding recurrence times are very long and can be ignored in many cases.

  3. Violation of detailed balance accelerates relaxation

    NASA Astrophysics Data System (ADS)

    Ichiki, Akihisa; Ohzeki, Masayuki

    2013-08-01

    Recent studies have experienced the acceleration of convergence in Markov chain Monte Carlo methods implemented by the systems without detailed balance condition (DBC). However, such advantage of the violation of DBC has not been confirmed in general. We investigate the effect of the absence of DBC on the convergence toward equilibrium. Surprisingly, it is shown that the DBC violation always makes the relaxation faster. Our result implies the existence of a kind of thermodynamic inequality that connects the nonequilibrium process relaxing toward steady state with the relaxation process which has the same probability distribution as its equilibrium state.

  4. Relaxation time in disordered molecular systems

    SciTech Connect

    Rocha, Rodrigo P.; Freire, José A.

    2015-05-28

    Relaxation time is the typical time it takes for a closed physical system to attain thermal equilibrium. The equilibrium is brought about by the action of a thermal reservoir inducing changes in the system micro-states. The relaxation time is intuitively expected to increase with system disorder. We derive a simple analytical expression for this dependence in the context of electronic equilibration in an amorphous molecular system model. We find that the disorder dramatically enhances the relaxation time but does not affect its independence of the nature of the initial state.

  5. Relaxation of vibrational degrees of freedom

    NASA Astrophysics Data System (ADS)

    Frohn, A.

    Shock tubes were used to measure relaxation times of the degrees of freedom in inelastic collisions of gas molecules. Design and construction of the experimental setup are described. For relaxation time measurements of vibrational degrees of freedom an initial pressure between 0.1 and 1 mbar is found to be optimal, and for dissociation between 1 and 10 mbar. The density gradients in the shock tube flow are measured with four differential laser interferometers and plotted with a transient recorder. A FORTRAN program was developed to determine the relaxation times. This measurement technique does not in general allow the degrees of freedom to be investigated separately.

  6. Momentum relaxation of a relativistic Brownian particle.

    PubMed

    Felderhof, B U

    2012-12-01

    The momentum relaxation of a relativistic Brownian particle immersed in a fluid is studied on the basis of the Fokker-Planck equation for the relativistic Ornstein-Uhlenbeck process. An analytical expression is derived for the short-time relaxation rate. The relaxation spectrum has both discrete and continuum components. It is shown that the Fokker-Planck equation under consideration is closely related to the Schrödinger equation for the hydrogen atom. Hence it follows that there is an infinite number of discrete states. The momentum autocorrelation function is calculated numerically for a strongly relativistic particle. PMID:23367889

  7. Collisionless Relaxation in Non-Neutral Plasmas

    SciTech Connect

    Levin, Yan; Pakter, Renato; Teles, Tarcisio N.

    2008-02-01

    A theoretical framework is presented which allows us to quantitatively predict the final stationary state achieved by a non-neutral plasma during a process of collisionless relaxation. As a specific application, the theory is used to study relaxation of charged-particle beams. It is shown that a fully matched beam relaxes to the Lynden-Bell distribution. However, when a mismatch is present and the beam oscillates, parametric resonances lead to a core-halo phase separation. The approach developed accounts for both the density and the velocity distributions in the final stationary state.

  8. Fiber Creep Evaluation by Stress Relaxation Measurements

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Dicarlo, James A.; Wagner, Timothy

    1991-01-01

    A simple bend stress relaxation (BSR) test has been used to measure the creep related properties of a chemically vapor-deposited SiC fiber. Time, temperature, and strain dependent BSR data were analyzed to ascertain the ability of the stress relaxation results to predict tensile creep as a function of the same parameters. The predictions compared very well to actual creep data obtained by axial measurements, indicating that the BSR test could be used for determining both creep and stress relaxation of polycrystalline ceramic fibers under tensile loading.

  9. 129Xe spin relaxation in frozen xenon

    NASA Astrophysics Data System (ADS)

    Fitzgerald, R. J.; Gatzke, M.; Fox, David C.; Cates, G. D.; Happer, W.

    1999-04-01

    We discuss the longitudinal spin relaxation of 129Xe nuclei in frozen xenon. Over a large range of temperatures and magnetic fields, the dominant spin-lattice relaxation mechanism is shown to be nuclear spin-flip Raman scattering of lattice phonons. Two closely related interactions couple the lattice phonons to the spins of 129Xe nuclei: (1) the nuclear spin-rotation interaction between nearest-neighbor atoms, and (2) the paramagnetic antishielding of the externally applied field at the site of 129Xe nuclei by the electrons of neighboring Xe atoms. We show that relaxation rates can be predicted by using measured chemical shifts of gaseous and condensed xenon. The predicted relaxation rates are in good agreement with measurements. We outline a simple way to estimate the spin-rotation coupling and paramagnetic antishielding in terms of the small perturbations of the outermost electron orbitals of one xenon atom due to a neighboring atom.

  10. Low-temperature relaxations in amorphous polyolefins

    NASA Technical Reports Server (NTRS)

    Hiltner, A.; Baer, E.; Martin, J. R.; Gillham, J. K.

    1974-01-01

    The dynamic mechanical relaxation behavior of two series of amorphous polyolefins, was investigated from 4.2 K to the glass transition. Most of the polymers show a damping maximum or plateau in the 40 to 50 K region. Various mechanisms which have been suggested for cryogenic relaxations in amorphous polymers are considered as they might relate to the polyolefins. Two secondary relaxation processes above 80 K are distinguished. A relaxation at about 160 K (beta) in the second and third member of each series is associated with restricted blackbone motion. This process requires a certain degree of chain flexibility since it is not observed in the first member of each series. A lower temperature process (gamma) is observed in each member of the second series and is attributed to motion of the ethyl side group.

  11. Nonexponential relaxation in a simple liquid metal.

    PubMed

    Demmel, F; Morkel, C

    2012-05-01

    A hallmark of the changes in dynamics towards the glass transition is the stretched exponential structural relaxation. Quasielastic neutron scattering results on liquid rubidium demonstrate such a nonexponential relaxation process in a simple liquid metal above the melting point. The nonexponential decay is an indication of non-Markovian dynamics and points to the collective character of the relaxation process. Describing the relaxation dynamics by a two-step process, the long lasting part of the decay process is in remarkable quantitative agreement with predictions from mode coupling theory. The feedback mechanism of the slowing down process in the theoretical description suggests that this contribution is at the origin of the structural arrest. With rising temperature the intermediate scattering function transforms into a simple exponential decay at a temperature range which indicates the end of the highly viscous solidlike behavior in the liquid. PMID:23004742

  12. Relaxation oscillations in optically pumped molecular lasers

    NASA Technical Reports Server (NTRS)

    Lawandy, N. M.; Koepf, G. A.

    1980-01-01

    The observation of relaxation oscillations in both the (C-13)H3F and (C-12)H3F optically pumped lasers is reported. Expressions are derived for the oscillation frequency and its temperature and pressure dependences using a four-level rate equation model. Excellent agreement between measured frequencies and the theory presented is observed. Models are considered for using this phenomenon to determine the rotational and vibrational relaxation mechanisms of the laser gases.

  13. Relaxation techniques for children and young people.

    PubMed

    Hobbie, C

    1989-01-01

    The relaxation response, relaxation with mental imagery/self-hypnosis, and centering are techniques that can be used by the nurse practitioner in a variety of clinical situations to help children and young people manage stress. These approaches also can be used to treat certain common pediatric problems, such as headaches, enuresis, acute and chronic pain, and habit disorders. The techniques and their appropriate use are described. PMID:2647960

  14. Difference between nuclear spin relaxation and ionic conductivity relaxation in superionic glasses

    NASA Astrophysics Data System (ADS)

    Ngai, K. L.

    1993-04-01

    Tatsumisago, Angell, and Martin [J. Chem. Phys. 97, 6968 (1992)] have compared conductivity relaxation data and 7Li nuclear spin lattice relaxation (SLR) data measured on a lithium chloroborate glass and found pronounced differences in the most probable relaxation times. The electrical conductivity relaxation (ECR) time, τ*σ, at some temperature occurs on a time scale shorter by some two orders of magnitude than the 7Li spin lattice relaxation correlation time, τ*s, and has a significantly lower activation energy. SLR and ECR monitor the motions of ions through different dynamic variables and correlation functions. Using this fact and the coupling model, I am able to explain quantitatively all aspects of the difference between SLR and ECR, and to establish relations between their different relaxation characteristics. The large difference between the observed activation energies of SLR and ECR alone should have implications on the validity of any proposed theory of the dynamics of ionic transport.

  15. Dielectric relaxation of gamma irradiated muscovite mica

    SciTech Connect

    Kaur, Navjeet; Singh, Mohan; Singh, Lakhwant; Awasthi, A.M.; Lochab, S.P.

    2015-03-15

    Highlights: • The present article reports the effect of gamma irradiation on the dielectric relaxation characteristics of muscovite mica. • Dielectric and electrical relaxations have been analyzed in the framework of dielectric permittivity, electric modulus and Cole–Cole formalisms. • The frequency dependent electrical conductivity has been rationalized using Johnsher’s universal power law. • The experimentally measured electric modulus and conductivity data have been fitted using Havriliak–Negami dielectric relaxation function. - Abstract: In the present research, the dielectric relaxation of gamma irradiated muscovite mica was studied in the frequency range of 0.1 Hz–10 MHz and temperature range of 653–853 K, using the dielectric permittivity, electric modulus and conductivity formalisms. The dielectric constants (ϵ′ and ϵ′′) are found to be high for gamma irradiated muscovite mica as compared to the pristine sample. The frequency dependence of the imaginary part of complex electric modulus (M′′) and dc conductivity data conforms Arrhenius law with single value of activation energy for pristine sample and two values of activation energy for gamma irradiated mica sample. The experimentally assessed electric modulus and conductivity information have been interpreted by the Havriliak–Negami dielectric relaxation explanation. Using the Cole–Cole framework, an analysis of real and imaginary characters of the electric modulus for pristine and gamma irradiated sample was executed which reflects the non-Debye relaxation mechanism.

  16. Vibrational Relaxation in Several Derivatives of Benzene

    NASA Astrophysics Data System (ADS)

    Linde, Bogumił B. J.; Skrodzka, Ewa B.; Lezhnev, Nikołaj B.

    2012-04-01

    Acoustical spectroscopy at frequencies up to 10 GHz gives the possibility of the investigation of liquid substances, where the relaxation process observed is caused by energy transfer between translational and vibrational degrees of freedom. The compounds presented in this article belong to this group of liquids. The acoustic investigations in the group of benzene derivatives, particularly research of the dependencies of acoustic parameters and the structure of organic liquids, demonstrated some interesting regularities in the group of these compounds in gas and liquid states. In this article, the results of research on five cyclic liquids: bromo-, chloro-, fluoro-, iodo-, and nitrobenzene as well as toluene and aniline are discussed and compared to benzene. The acoustic relaxation observed in all these compounds was found to result from Kneser's processes (vibrational relaxation). Based on investigations reported in this article, as well as by other authors, and taking into account experimental and literature data concerning a great number of compounds, one can draw a conclusion that almost all acoustic relaxation (Kneser-type) processes in liquids can be described using a single relaxation time. It also seems that all vibrational degrees of freedom of the molecule take part in this process. It is known that the appearance of differences in transition probabilities could be caused by additional attraction in interactions of molecules having dipole moments. Halogen derivatives have higher values of dipole moments than benzene. This difference could be responsible for the difference of transition probabilities and changes in the relaxation times. However, benzene derivatives with amino, nitro, and methyl groups and halides show the other type of relaxation.

  17. The Global Scale Relaxation State of Ceres

    NASA Astrophysics Data System (ADS)

    Fu, R. R.; Ermakov, A.; Zuber, M. T.; Hager, B. H.

    2015-12-01

    Planetary surfaces relax over time to a hydrostatic configuration at a rate governed by a body's rheological properties. Because rheology is a strong function of composition and temperature, observations of a body's relaxation state offers a means to probe its interior structure and thermal evolution. In the case of Ceres, such analysis potentially constrains the hydration state of the rocky core, the rock content of the ice-rich shell, and the abundance of heat-producing radionuclides. Ground-based observations of Ceres suggested that the long-wavelength topography of Ceres has undergone significant relaxation, closely approaching hydrostatic equilibrium. Recent preliminary data from the Dawn spacecraft show that the topography of Ceres exhibits anomalously low power at the longest wavelengths (exceeding ~150 km; spherical harmonic degree n = 20; Fig. 1). Using the deal.II finite element library, we model global scale (n < 40) viscoelastoplastic relaxation on Ceres to constrain the range of compositional and thermal structures consistent with the observed topography. Simulations assuming a 60 km thick pure ice layer overlying a rocky interior suggests that medium wavelength topography (10 ≤ n ≤ 40) relaxes efficiently over timescales of << 1 My, while relaxation at n ≤ 8 occurs only over much longer timescales as determined by the rheology of the deep interior (Fig. 1). The comparable degrees of relaxation observed on Ceres at all spherical harmonic degrees less than 20 therefore suggest that the rheological contrast between the shell and core is less extreme than that of pure ice and dry rock. Potential explanations include: (1) the presence of silicates and dissolved contaminants in the ice-rich shell and (2) high temperatures (e.g., >400˚C given a wet olivine rheology) in the deep interior during Ceres's early evolution. Ongoing simulations will test the viability of these scenarios in reproducing the observed topography.

  18. Convex relaxations for gas expansion planning

    SciTech Connect

    Borraz-Sanchez, Conrado; Bent, Russell Whitford; Backhaus, Scott N.; Hijazi, Hassan; Van Hentenryck, Pascal

    2016-01-01

    Expansion of natural gas networks is a critical process involving substantial capital expenditures with complex decision-support requirements. Here, given the non-convex nature of gas transmission constraints, global optimality and infeasibility guarantees can only be offered by global optimisation approaches. Unfortunately, state-of-the-art global optimisation solvers are unable to scale up to real-world size instances. In this study, we present a convex mixed-integer second-order cone relaxation for the gas expansion planning problem under steady-state conditions. The underlying model offers tight lower bounds with high computational efficiency. In addition, the optimal solution of the relaxation can often be used to derive high-quality solutions to the original problem, leading to provably tight optimality gaps and, in some cases, global optimal solutions. The convex relaxation is based on a few key ideas, including the introduction of flux direction variables, exact McCormick relaxations, on/off constraints, and integer cuts. Numerical experiments are conducted on the traditional Belgian gas network, as well as other real larger networks. The results demonstrate both the accuracy and computational speed of the relaxation and its ability to produce high-quality solution

  19. Convex relaxations for gas expansion planning

    DOE PAGESBeta

    Borraz-Sanchez, Conrado; Bent, Russell Whitford; Backhaus, Scott N.; Hijazi, Hassan; Van Hentenryck, Pascal

    2016-01-01

    Expansion of natural gas networks is a critical process involving substantial capital expenditures with complex decision-support requirements. Here, given the non-convex nature of gas transmission constraints, global optimality and infeasibility guarantees can only be offered by global optimisation approaches. Unfortunately, state-of-the-art global optimisation solvers are unable to scale up to real-world size instances. In this study, we present a convex mixed-integer second-order cone relaxation for the gas expansion planning problem under steady-state conditions. The underlying model offers tight lower bounds with high computational efficiency. In addition, the optimal solution of the relaxation can often be used to derive high-quality solutionsmore » to the original problem, leading to provably tight optimality gaps and, in some cases, global optimal solutions. The convex relaxation is based on a few key ideas, including the introduction of flux direction variables, exact McCormick relaxations, on/off constraints, and integer cuts. Numerical experiments are conducted on the traditional Belgian gas network, as well as other real larger networks. The results demonstrate both the accuracy and computational speed of the relaxation and its ability to produce high-quality solution« less

  20. Doppler effect induced spin relaxation boom.

    PubMed

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-01-01

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures. PMID:26996253

  1. Doppler effect induced spin relaxation boom

    PubMed Central

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-01-01

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures. PMID:26996253

  2. Doppler effect induced spin relaxation boom

    NASA Astrophysics Data System (ADS)

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-03-01

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures.

  3. Temperature relaxation in a magnetized plasma

    SciTech Connect

    Dong, Chao; Ren, Haijun; Cai, Huishan; Li, Ding

    2013-10-15

    A magnetic field greatly affects the relaxation phenomena in a plasma when the particles’ thermal gyro-radii are smaller than the Debye length. Its influence on the temperature relaxation (TR) is investigated through consideration of binary collisions between charged particles in the presence of a uniform magnetic field within a perturbation theory. The relaxation times are calculated. It is shown that the electron-electron (e-e) and ion-ion (i-i) TR rates first increase and then decrease as the magnetic field grows, and the doubly logarithmic term contained in the electron-ion (e-i) TR rate results from the exchange between the electron parallel and the ion perpendicular kinetic energies.

  4. Structural relaxation of vacancies in amorphous silicon

    SciTech Connect

    Kim, E.; Lee, Y.H.; Chen, C.; Pang, T.

    1997-07-01

    The authors have studied the structural relaxation of vacancies in amorphous silicon (a-Si) using a tight-binding molecular-dynamics method. The most significant difference between vacancies in a-Si and those in crystalline silicon (c-Si) is that the deep gap states do not show up in a-Si. This difference is explained through the unusual behavior of the structural relaxation near the vacancies in a-Si, which enhances the sp{sup 2} + p bonding near the band edges. They have also observed that the vacancies do not migrate below 450 K although some of them can still be annihilated, particularly at high defect density due to large structural relaxation.

  5. A general relaxation theory of simple liquids

    NASA Technical Reports Server (NTRS)

    Merilo, M.; Morgan, E. J.

    1973-01-01

    A relatively simple relaxation theory to account for the behavior of liquids under dynamic conditions was proposed. The general dynamical equations are similar in form to the phenomenological relaxation equations used in theories of viscoelasticity, however, they differ in that all the coefficients of the present equations are expressed in terms of thermodynamic and molecular quantities. The theory is based on the concept that flow in a liquid distorts both the radial and the velocity distribution functions, and that relaxation equations describing the return of these functions to their isotropic distributions, characterizing a stationary liquid, can be written. The theory was applied to the problems of steady and oscillatory shear flows and to the propagation of longitudinal waves. In all cases classical results are predicted for strain rates, and an expression for the viscosity of a liquid, simular to the Macedo-Litovitz equation, is obtained.

  6. RELAXATION PROCESSES IN SOLAR WIND TURBULENCE

    SciTech Connect

    Servidio, S.; Carbone, V.; Gurgiolo, C.; Goldstein, M. L.

    2014-07-10

    Based on global conservation principles, magnetohydrodynamic (MHD) relaxation theory predicts the existence of several equilibria, such as the Taylor state or global dynamic alignment. These states are generally viewed as very long-time and large-scale equilibria, which emerge only after the termination of the turbulent cascade. As suggested by hydrodynamics and by recent MHD numerical simulations, relaxation processes can occur during the turbulent cascade that will manifest themselves as local patches of equilibrium-like configurations. Using multi-spacecraft analysis techniques in conjunction with Cluster data, we compute the current density and flow vorticity and for the first time demonstrate that these localized relaxation events are observed in the solar wind. Such events have important consequences for the statistics of plasma turbulence.

  7. Ubiquitous ``glassy'' relaxation in catalytic reaction networks

    NASA Astrophysics Data System (ADS)

    Awazu, Akinori; Kaneko, Kunihiko

    2009-10-01

    Study of reversible catalytic reaction networks is important not only as an issue for chemical thermodynamics but also for protocells. From extensive numerical simulations and theoretical analysis, slow relaxation dynamics to sustain nonequlibrium states are commonly observed. These dynamics show two types of salient behaviors that are reminiscent of glassy behavior: slow relaxation along with the logarithmic time dependence of the correlation function and the emergence of plateaus in the relaxation-time course. The former behavior is explained by the eigenvalue distribution of a Jacobian matrix around the equilibrium state that depends on the distribution of kinetic coefficients of reactions. The latter behavior is associated with kinetic constraints rather than metastable states and is due to the absence of catalysts for chemicals in excess and the negative correlation between two chemical species. Examples are given and generality is discussed with relevance to bottleneck-type dynamics in biochemical reactions as well.

  8. Substrate stress relaxation regulates cell spreading

    PubMed Central

    Chaudhuri, Ovijit; Gu, Luo; Darnell, Max; Klumpers, Darinka; Bencherif, Sidi A.; Weaver, James C.; Huebsch, Nathaniel; Mooney, David J

    2015-01-01

    Studies of cellular mechanotransduction have converged upon the idea that cells sense extracellular matrix (ECM) elasticity by gauging resistance to the traction forces they exert on the ECM. However, these studies typically utilize purely elastic materials as substrates, whereas physiological ECM are viscoelastic, and exhibit stress relaxation, so that cellular traction forces exerted by cells remodel the ECM. Here we investigate the influence of ECM stress relaxation on cell behavior through computational modeling and cellular experiments. Surprisingly, both our computational model and experiments find that spreading for cells cultured on soft substrates that exhibit stress relaxation is greater than cells spreading on elastic substrates of the same modulus, but similar to that of cells spreading on stiffer elastic substrates. These findings challenge the current view of how cells sense and respond to the ECM. PMID:25695512

  9. Stratospheric Relaxation in IMPACT's Radiation Code

    SciTech Connect

    Edis, T; Grant, K; Cameron-Smith, P

    2006-11-13

    While Impact incorporates diagnostic radiation routines from our work in previous years, it has not previously included the stratospheric relaxation required for forcing calculations. We have now implemented the necessary changes for stratospheric relaxation, tested its stability, and compared the results with stratosphere temperatures obtained from CAM3 met data. The relaxation results in stable temperature profiles in the stratosphere, which is encouraging for use in forcing calculations. It does, however, produce a cooling bias when compared to CAM3, which appears to be due to differences in radiation calculations rather than the interactive treatment of ozone. The cause of this bias is unclear as yet, but seems to be systematic and hence cancels out when differences are taken relative to a control simulation.

  10. Dielectric relaxation of high-k oxides

    PubMed Central

    2013-01-01

    Frequency dispersion of high-k dielectrics was observed and classified into two parts: extrinsic cause and intrinsic cause. Frequency dependence of dielectric constant (dielectric relaxation), that is the intrinsic frequency dispersion, could not be characterized before considering the effects of extrinsic frequency dispersion. Several mathematical models were discussed to describe the dielectric relaxation of high-k dielectrics. For the physical mechanism, dielectric relaxation was found to be related to the degree of polarization, which depended on the structure of the high-k material. It was attributed to the enhancement of the correlations among polar nanodomain. The effect of grain size for the high-k materials' structure mainly originated from higher surface stress in smaller grain due to its higher concentration of grain boundary. PMID:24180696

  11. Hair relaxer ingestion: a new trend.

    PubMed

    Forsen, J W; Muntz, H R

    1993-10-01

    Although the health care system has done much to reduce the incidence of ingestion of such alkalis as drain and oven cleaners, in recent years we have seen an overwhelming increase in the incidence of hair relaxer ingestion. In a 5-year review (1987 to 1992) of 48 cases of caustic ingestion, 15 cases involved alkaline hair-relaxing agents. This retrospective study was undertaken to evaluate the agents ingested, the presenting signs and symptoms, the diagnostic procedures, and the outcomes in those 15 cases. Oral cavity and lip burns were common in these children, but none of the 15 had significant esophageal burns. Education of the medical and lay community about the risk of hair relaxer ingestion should be undertaken to reverse this worrisome trend. PMID:8215098

  12. Substrate stress relaxation regulates cell spreading.

    PubMed

    Chaudhuri, Ovijit; Gu, Luo; Darnell, Max; Klumpers, Darinka; Bencherif, Sidi A; Weaver, James C; Huebsch, Nathaniel; Mooney, David J

    2015-01-01

    Studies of cellular mechanotransduction have converged upon the idea that cells sense extracellular matrix (ECM) elasticity by gauging resistance to the traction forces they exert on the ECM. However, these studies typically utilize purely elastic materials as substrates, whereas physiological ECMs are viscoelastic, and exhibit stress relaxation, so that cellular traction forces exerted by cells remodel the ECM. Here we investigate the influence of ECM stress relaxation on cell behaviour through computational modelling and cellular experiments. Surprisingly, both our computational model and experiments find that spreading for cells cultured on soft substrates that exhibit stress relaxation is greater than cells spreading on elastic substrates of the same modulus, but similar to that of cells spreading on stiffer elastic substrates. These findings challenge the current view of how cells sense and respond to the ECM. PMID:25695512

  13. Swelling and Stress Relaxation in Portland Brownstone

    NASA Astrophysics Data System (ADS)

    Jimenez, I.; Scherer, G.

    2003-04-01

    Portland Brownstone (PB) is an arkose sandstone extensively used in the northeast-ern USA during the nineteenth century. This reddish-brown stone contains a fraction of swelling clays that are thought to contribute to its degradation upon cycles of wet-ting and drying. During drying events, contraction of the drying surface leads to stresses approaching the tensile strength of the stone. However, we have found that the magnitude of these stresses is limited by the ability of the stone to undergo stress relaxation. In this paper we describe novel methods to determine the magnitude of the stresses and the rate at which they develop and relax. We also discuss the influ-ence of surfactants on the magnitude of swelling and the rate of the stress relaxation of PB. The implications of our findings for the understanding of damage due to swelling of clays are discussed.

  14. Magnetic Relaxation Detector for Microbead Labels

    PubMed Central

    Liu, Paul Peng; Skucha, Karl; Duan, Yida; Megens, Mischa; Kim, Jungkyu; Izyumin, Igor I.; Gambini, Simone; Boser, Bernhard

    2014-01-01

    A compact and robust magnetic label detector for biomedical assays is implemented in 0.18-μm CMOS. Detection relies on the magnetic relaxation signature of a microbead label for improved tolerance to environmental variations and relaxed dynamic range requirement, eliminating the need for baseline calibration and reference sensors. The device includes embedded electromagnets to eliminate external magnets and reduce power dissipation. Correlated double sampling combined with offset servo loops and magnetic field modulation, suppresses the detector offset to sub-μT. Single 4.5-μm magnetic beads are detected in 16 ms with a probability of error <0.1%. PMID:25308988

  15. Soft Sphere Suspensions: Flow and Relaxation

    NASA Astrophysics Data System (ADS)

    Workamp, Marcel; Dijksman, Joshua A.

    We experimentally study the role of particle elasticity on the rheology of soft sphere suspensions. Experiments consist of custom designed particles with tuneable stiffness. These particles allow us to probe the role of elastic timescales, relaxation and anisotropy in a custom 3D printed shear cell. We find robust rheological features, such as a flow instability, that are not well captured by existing models for suspension flows. In addition, we find relaxation effects after shear even in the absence of shear or thermal fluctuations. We aim to integrate these findings in the emerging unified framework for structured fluids.

  16. Signal prediction by anticipatory relaxation dynamics

    NASA Astrophysics Data System (ADS)

    Voss, Henning U.

    2016-03-01

    Real-time prediction of signals is a task often encountered in control problems as well as by living systems. Here, a parsimonious prediction approach based on the coupling of a linear relaxation-delay system to a smooth, stationary signal is described. The resulting anticipatory relaxation dynamics (ARD) is a frequency-dependent predictor of future signal values. ARD not only approximately predicts signals on average but can anticipate the occurrence of signal peaks, too. This can be explained by recognizing ARD as an input-output system with negative group delay. It is characterized, including its prediction horizon, by its analytically given frequency response function.

  17. Magnetic relaxation of high spin magnetic molecules

    NASA Astrophysics Data System (ADS)

    Luo, Nie

    The magnetic relaxation phenomena in Mn12 and the physics underlining these experiment results are investigated in this dissertation. We give a review on currently available theories to account for the spin or paramagnetic relaxation occurring in this system. Density matrix formalism is used to investigate the general problem of a system interacting with a bath of thermal equilibrium phonons, which gives a set of rate equations. Numerical solutions to the rate equations are also carried out. Finally comparisons between the theory and the experimentals are made to show the merits and deficiencies of the theoretical approach that we have adopted.

  18. 1H NMR relaxation in urea

    NASA Astrophysics Data System (ADS)

    Taylor, R. E.; Bacher, Alfred D.; Dybowski, C.

    2007-11-01

    Proton NMR spin-lattice relaxation times T1 were measured for urea as a function of temperature. An activation energy of 46.3 ± 4.7 kJ/mol was extracted and compared with the range of 38-65 kJ/mol previously reported in the literature as measured by different magnetic resonance techniques. In addition, proton NMR spin-lattice relaxation times in the rotating frame T1 ρ were measured as a function of temperature. These measurements provide acquisition conditions for the 13C and 15N CP/MAS spectra of pure urea in the crystalline phase.

  19. Dielectric relaxation characteristics of muscovite mica

    NASA Astrophysics Data System (ADS)

    Kaur, Navjeet; Singh, Lakhwant; Singh, Mohan; Awasthi, A. M.; Kumar, Jitender

    2014-04-01

    In the present work, the dielectric relaxation phenomenon in muscovite mica has been studied over the frequency range 0.1 Hz-10 MHz and in the temperature range of 653-853K, using the dielectric permittivity, electric modulus and conductivity formalisms. The values of the activation energy obtained from electric modulus and conductivity data are found to be nearly similar, suggesting that same types of charge carriers are involved in the relaxation mechanism. This type of study will explore the potential of this material for various applications in electrical engineering.

  20. Vibrational relaxation in hypersonic flow fields

    NASA Technical Reports Server (NTRS)

    Meador, Willard E.; Miner, Gilda A.; Heinbockel, John H.

    1993-01-01

    Mathematical formulations of vibrational relaxation are derived from first principles for application to fluid dynamic computations of hypersonic flow fields. Relaxation within and immediately behind shock waves is shown to be substantially faster than that described in current numerical codes. The result should be a significant reduction in nonequilibrium radiation overshoot in shock layers and in radiative heating of hypersonic vehicles; these results are precisely the trends needed to bring theoretical predictions more in line with flight data. Errors in existing formulations are identified and qualitative comparisons are made.

  1. Carnitine palmitoyltransferase-1 up-regulation by PPAR-β/δ prevents lipid-induced endothelial dysfunction.

    PubMed

    Toral, Marta; Romero, Miguel; Jiménez, Rosario; Mahmoud, Ayman Moawad; Barroso, Emma; Gómez-Guzmán, Manuel; Sánchez, Manuel; Cogolludo, Ángel; García-Redondo, Ana B; Briones, Ana M; Vázquez-Carrera, Manuel; Pérez-Vizcaíno, Francisco; Duarte, Juan

    2015-11-01

    Fatty acids cause endothelial dysfunction involving increased ROS (reactive oxygen species) and reduced NO (nitric oxide) bioavailability. We show that in MAECs (mouse aortic endothelial cells), the PPARβ/δ (peroxisome- proliferator-activated receptor β/δ) agonist GW0742 prevented the decreased A23187-stimulated NO production, phosphorylation of eNOS (endothelial nitric oxide synthase) at Ser1177 and increased intracellular ROS levels caused by exposure to palmitate in vitro. The impaired endothelium-dependent relaxation to acetylcholine in mouse aorta induced by palmitate was restored by GW0742. In vivo, GW0742 treatment prevented the reduced aortic relaxation, phosphorylation of eNOS at Ser1177, and increased ROS production and NADPH oxidase in mice fed on a high-fat diet. The PPARβ/δ antagonist GSK0660 abolished all of these protective effects induced by GW0742. This agonist enhanced the expression of CPT (carnitine palmitoyltransferase)-1. The effects of GW0742 on acetylcholine- induced relaxation in aorta and on NO and ROS production in MAECs exposed to palmitate were abolished by the CPT-1 inhibitor etomoxir or by siRNA targeting CPT-1. GW0742 also inhibited the increase in DAG (diacylglycerol), PKCα/βII (protein kinase Cα/βII) activation, and phosphorylation of eNOS at Thr495 induced by palmitate in MAECs, which were abolished by etomoxir. In conclusion, PPARβ/δ activation restored the lipid-induced endothelial dysfunction by up-regulation of CPT-1, thus reducing DAG accumulation and the subsequent PKC-mediated ROS production and eNOS inhibition. PMID:26253087

  2. High relaxivity MRI contrast agents part 2: Optimization of inner- and second-sphere relaxivity

    PubMed Central

    Jacques, Vincent; Dumas, Stephane; Sun, Wei-Chuan; Troughton, Jeffrey S.; Greenfield, Matthew T.; Caravan, Peter

    2011-01-01

    Rationale and objectives The observed relaxivity of gadolinium based contrast agents has contributions from the water molecule(s) that bind directly to the gadolinium ion (inner-sphere water), long lived water molecules and exchangeable protons that make up the second-sphere of coordination, and water molecules that diffuse near the contrast agent (outer-sphere). Inner- and second-sphere relaxivity can both be increased by optimization of the lifetimes of the water molecules and protons in these coordination spheres, the rotational motion of the complex, and the electronic relaxation of the gadolinium ion. We sought to identify new high relaxivity contrast agents by systematically varying the donor atoms that bind directly to gadolinium to increase inner-sphere relaxivity and concurrently including substituents that influence the second-sphere relaxivity. Methods Twenty GdDOTA derivatives were prepared and their relaxivity determined in presence and absence of human serum albumin as a function of temperature and magnetic field. Data was analyzed to extract the underlying molecular parameters influencing relaxivity. Each compound had a common albumin-binding group and an inner-sphere donor set comprising the 4 tertiary amine N atoms from cyclen, an α-substituted acetate oxygen atom, two amide oxygen atoms, an inner-sphere water oxygen atom, and a variable donor group. Each amide nitrogen was substituted with different groups to promote hydrogen bonding with second-sphere water molecules. Results Relaxivites at 0.47T and 1.4T, 37 °C, in serum albumin ranged from 16.0 to 58.1 mM−1s−1 and from 12.3 to 34.8 mM−1s−1 respectively. The reduction of inner-sphere water exchange typical of amide donor groups could be offset by incorporating a phosphonate or phenolate oxygen atom donor in the first coordination sphere resulting in higher relaxivity. Amide nitrogen substitution with pendant phosphonate or carboxylate groups increased relaxivity by as much as 88

  3. Dipole Relaxation in an Electric Field.

    ERIC Educational Resources Information Center

    Neumann, Richard M.

    1980-01-01

    Derives an expression for the orientational entropy of a rigid rod (electric dipole) from Boltzmann's equation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium. (Author/GS)

  4. Controlling spin relaxation with a cavity

    NASA Astrophysics Data System (ADS)

    Bienfait, Audrey; Pla, Jarryd; Kubo, Yuimaru; Zhou, Xin; Stern, Michael; Lo, Cheuk; Weis, Christopher; Schenkel, Thomas; Vion, Denis; Esteve, Daniel; Morton, John; Bertet, Patrice

    Spontaneous emission of radiation is one of the fundamental relaxation mechanisms for a quantum system. For spins, however, it is negligible compared to non-radiative relaxation processes due to their weak coupling to the electromagnetic field. In 1946, Purcell realized that spontaneous emission is strongly enhanced when the quantum system is placed in a resonant cavity - an effect now used to control the lifetime of systems with an electrical dipole. Here, by coupling donor spins in silicon to a high quality factor superconducting microwave cavity of small mode volume, we reach the regime where spontaneous emission constitutes the dominant spin relaxation channel. The relaxation rate is increased by three orders of magnitude when the spins are tuned to the cavity resonance, showing it can be engineered and controlled on-demand. Our results provide a novel way to initialize any spin into its ground state, with applications in magnetic resonance and quantum information processing. They also show for the first time an alteration of spin dynamics by quantum fluctuations, a step towards the coherent magnetic coupling of a spin to microwave photons.

  5. BOOK REVIEW: Magnetohydrodynamics of Plasma Relaxation

    NASA Astrophysics Data System (ADS)

    Connor, J. W.

    1998-06-01

    This monograph on magnetohydrodynamic (MHD) relaxation in plasmas by Ortolani and Schnack occupies a fascinating niche in the plasma physics literature. It is rare in the complex and often technically sophisticated subject of plasma physics to be able to isolate a topic and deal with it comprehensively in a mere 180 pages. Furthermore, it brings a refreshingly original and personal approach to the treatment of plasma relaxation, synthesizing the experiences of the two authors to produce a very readable account of phenomena appearing in such diverse situations as laboratory reversed field pinches (RFPs) and the solar corona. Its novelty lies in that, while it does acknowledge the seminal Taylor theory of relaxation as a general guide, it emphasizes the role of large scale numerical MHD simulations in developing a picture for the relaxation phenomena observed in experiment and nature. Nevertheless, the volume has some minor shortcomings: a tendency to repetitiveness and some omissions that prevent it being entirely self-contained. The monograph is divided into nine chapters, with the first a readable, `chatty', introduction to the physics and phenomena of relaxation discussed in the later chapters. Chapter 2 develops the tools for describing relaxation processes, namely the resistive MHD model, leading to a discussion of resistive instabilities and the stability properties of RFPs. This chapter demonstrates the authors' confessed desire to avoid mathematical detail with a rather simplified discussion of Δ' and magnetic islands; it also sets the stage for their own belief, or thesis, that numerical simulation of the non-linear consequences of the MHD model is the best approach to explaining the physics of relaxation. Nevertheless, in Chapter 3 they provide a reasonably good account and critique of one analytic approach that is available, and which is the commonly accepted picture for relaxation in pinches - the Taylor relaxation theory based on the conservation of

  6. Stretched Exponential relaxation in pure Se glass

    NASA Astrophysics Data System (ADS)

    Dash, S.; Ravindren, S.; Boolchand, P.

    A universal feature of glasses is the stretched exponential relaxation, f (t) = exp[ - t / τ ] β . The model of diffusion of excitations to randomly distributed traps in a glass by Phillips1 yields the stretched exponent β = d[d +2] where d, the effective dimensionality. We have measured the enthalpy of relaxation ΔHnr (tw) at Tg of Se glass in modulated DSC experiments as glasses age at 300K and find β = 0.43(2) for tw in the 0 relaxation is a narrowing of the glass transition width from 7.1°C to 1.4°C, and the ΔHnr term increasing from 0.21 cal/gm to 0.92 cal/gm. In bulk GexSe100-x glasses as x increases to 20%, the length of the polymeric Sen chains between the Ge-crosslinks decreases to n = 2. and the striking relaxation effects nearly vanish. J.C. Phillips, Rep.Prog.Phys. 59 , 1133 (1996). Supported by NSF Grant DMR 08-53957.

  7. Charge Relaxation Dynamics of an Electrolytic Nanocapacitor

    PubMed Central

    2015-01-01

    Understanding ion relaxation dynamics in overlapping electric double layers (EDLs) is critical for the development of efficient nanotechnology-based electrochemical energy storage, electrochemomechanical energy conversion, and bioelectrochemical sensing devices as well as the controlled synthesis of nanostructured materials. Here, a lattice Boltzmann (LB) method is employed to simulate an electrolytic nanocapacitor subjected to a step potential at t = 0 for various degrees of EDL overlap, solvent viscosities, ratios of cation-to-anion diffusivity, and electrode separations. The use of a novel continuously varying and Galilean-invariant molecular-speed-dependent relaxation time (MSDRT) with the LB equation recovers a correct microscopic description of the molecular-collision phenomena and enhances the stability of the LB algorithm. Results for large EDL overlaps indicated oscillatory behavior for the ionic current density, in contrast to monotonic relaxation to equilibrium for low EDL overlaps. Further, at low solvent viscosities and large EDL overlaps, anomalous plasmalike spatial oscillations of the electric field were observed that appeared to be purely an effect of nanoscale confinement. Employing MSDRT in our simulations enabled modeling of the fundamental physics of the transient charge relaxation dynamics in electrochemical systems operating away from equilibrium wherein Nernst–Einstein relation is known to be violated. PMID:25678941

  8. Relaxation/Covert Rehearsal for Problematic Children.

    ERIC Educational Resources Information Center

    Fling, Sheila; McKenzie, Patricia

    A study was conducted to determine whether group relaxation training combined with guided fantasy as a method of covert cognitive rehearsal would be more effective than story-listening or no special treatment in enabling "problematic" children to decrease muscle tension, activity level, and behavior problems and to increase academic performance…

  9. Towards a Calm Baby and Relaxed Parents.

    ERIC Educational Resources Information Center

    Schaper, Karen Kennedy

    1982-01-01

    Reviews research findings concerning benefits of particular forms of infant stimulation. Suggests stimulation has a soothing effect on infants. Proposes that, because many parents react with anxiety to infant stress, the use of these stimulation techniques may not only soothe the infant, but also relax the parents. (Author/RC)

  10. Ionic transport and electrical relaxation in glass

    NASA Astrophysics Data System (ADS)

    Moynihan, C. T.; Barkatt, A.

    1987-09-01

    The basic purpose of the work described was to achieve extensive and quantitative understanding of ionic transport processes in melts and glasses by means of a combination of experimental measurements and theoretical modeling. Two major subjects of the study were the mechanism of dielectric relaxation in ionically conducting glasses and the large retardation of ionic transport in mixed alkali systems.

  11. Nonconical Relaxation for Supersonic Potential Flow

    NASA Technical Reports Server (NTRS)

    Siclari, M. J.

    1986-01-01

    Nonlinear, three-dimensional effects computed from full potentialflow equation. Nonconical Relaxation program, NCOREL, employs new computational technique for prediction of inviscid, nonlinear supersonic aerodynamics. Unlike conventional linear potential equations, NCOREL utilizes full potential flow equation to predict formation of supercritical crossflow regions, embedded shocks, and bow shocks. NCOREL written in FORTRAN IV for batch execution.

  12. Relaxation Treatment for Insomnia: A Component Analysis.

    ERIC Educational Resources Information Center

    Woolfolk, Robert L.; McNulty, Terrence F.

    1983-01-01

    Compared four relaxation treatments for sleep onset insomnia with a waiting-list control. Treatments varied in presence or absence of muscular tension-release instructions and in foci of attention. Results showed all treatment conditions reduced latency of sleep onset and fatigue; visual focusing best reduced the number of nocturnal awakenings.…

  13. Relaxation for Children. (Revised and Expanded Edition.)

    ERIC Educational Resources Information Center

    Rickard, Jenny

    Intended as a guide to reduce negative stress in children, this book suggests relaxation and meditation techniques to help children cope with stressful events. Part 1 provides an introduction to the format of the book. Part 2 contains summaries of the 10 sessions that make up the program. Each session has six sequential stages in which students…

  14. Collection Development: Relaxation & Meditation, September 1, 2010

    ERIC Educational Resources Information Center

    Lettus, Dodi

    2010-01-01

    One of the first books to document the relationship between stress and physical and emotional health was "The Relaxation Response" by Herbert Benson, M.D., with Miriam Z. Klipper. Originally published in 1975, the book grew out of Benson's observations as a cardiologist and his research as a fellow at Harvard Medical School. Benson's study of…

  15. Relaxation processes in administered-rate pricing

    NASA Astrophysics Data System (ADS)

    Hawkins, Raymond J.; Arnold, Michael R.

    2000-10-01

    We show how the theory of anelasticity unifies the observed dynamics and proposed models of administered-rate products. This theory yields a straightforward approach to rate model construction that we illustrate by simulating the observed relaxation dynamics of two administered rate products. We also demonstrate how the use of this formalism leads to a natural definition of market friction.

  16. Novel Roles for Kv7 Channels in Shaping Histamine-Induced Contractions and Bradykinin-Dependent Relaxations in Pig Coronary Arteries

    PubMed Central

    Chen, Xingjuan; Li, Wennan; Hiett, S. Christopher; Obukhov, Alexander G.

    2016-01-01

    -contracted CAs. We propose that in CAs, a decreased expression or a loss of function of Kv7 channels may lead to sustained histamine-induced contractions and reduced endothelium-dependent relaxation, both risk factors for coronary spasm. PMID:26844882

  17. Collisionless relaxation in beam-plasma systems

    SciTech Connect

    Backhaus, Ekaterina Yu.

    2001-05-01

    This thesis reports the results from the theoretical investigations, both numerical and analytical, of collisionless relaxation phenomena in beam-plasma systems. Many results of this work can also be applied to other lossless systems of plasma physics, beam physics and astrophysics. Different aspects of the physics of collisionless relaxation and its modeling are addressed. A new theoretical framework, named Coupled Moment Equations (CME), is derived and used in numerical and analytical studies of the relaxation of second order moments such as beam size and emittance oscillations. This technique extends the well-known envelope equation formalism, and it can be applied to general systems with nonlinear forces. It is based on a systematic moment expansion of the Vlasov equation. In contrast to the envelope equation, which is derived assuming constant rms beam emittance, the CME model allows the emittance to vary through coupling to higher order moments. The CME model is implemented in slab geometry in the absence of return currents. The CME simulation yields rms beam sizes, velocity spreads and emittances that are in good agreement with particle-in-cell (PIC) simulations for a wide range of system parameters. The mechanism of relaxation is also considered within the framework of the CME system. It is discovered that the rapid relaxation or beam size oscillations can be attributed to a resonant coupling between different modes of the system. A simple analytical estimate of the relaxation time is developed. The final state of the system reached after the relaxation is complete is investigated. New and accurate analytical results for the second order moments in the phase-mixed state are obtained. Unlike previous results, these connect the final values of the second order moments with the initial beam mismatch. These analytical estimates are in good agreement with the CME model and PIC simulations. Predictions for the final density and temperature are developed that show

  18. Prominent β-relaxations in yttrium based metallic glasses

    SciTech Connect

    Luo, P.; Lu, Z.; Zhu, Z. G.; Li, Y. Z.; Bai, H. Y.; Wang, W. H.

    2015-01-19

    Most metallic glasses (MGs) exhibit weak slow β-relaxation. We report the prominent β-relaxation in YNiAl metallic glass with a wide composition range. Compared with other MGs, the MGs show a pronounced β-relaxation peak and high β-relaxation peak temperature, and the β-relaxation behavior varies significantly with the changes of the constituent elements, which is attributed to the fluctuations of chemical interactions between the components. We demonstrate the correlation between the β-relaxation and the activation of flow units for mechanical behaviors of the MG and show that the MG is model system for studying some controversial issues in glasses.

  19. The effect of music relaxation versus progressive muscular relaxation on insomnia in older people and their relationship to personality traits.

    PubMed

    Ziv, Naomi; Rotem, Tomer; Arnon, Zahi; Haimov, Iris

    2008-01-01

    A large percentage of older people suffer from chronic insomnia, affecting many aspects of life quality and well-being. Although insomnia is most often treated with medication, a growing number of studies demonstrate the efficiency of various relaxation techniques. The present study had three aims: first, to compare two relaxation techniques--music relaxation and progressive muscular relaxation--on various objective and subjective measures of sleep quality; second, to examine the effect of these techniques on anxiety and depression; and finally, to explore possible relationships between the efficiency of both techniques and personality variables. Fifteen older adults took part in the study. Following one week of base-line measurements of sleep quality, participants followed one week of music relaxation and one week of progressive muscular relaxation before going to sleep. Order of relaxation techniques was controlled. Results show music relaxation was more efficient in improving sleep. Sleep efficiency was higher after music relaxation than after progressive muscular relaxation. Moreover, anxiety was lower after music relaxation. Progressive muscular relaxation was related to deterioration of sleep quality on subjective measures. Beyond differences between the relaxation techniques, extraverts seemed to benefit more from both music and progressive muscular relaxation. The advantage of non-pharmacological means to treat insomnia, and the importance of taking individual differences into account are discussed. PMID:18959456

  20. Audio-visual relaxation training for anxiety, sleep, and relaxation among Chinese adults with cardiac disease.

    PubMed

    Tsai, Sing-Ling

    2004-12-01

    The long-term effect of an audio-visual relaxation training (RT) treatment involving deep breathing, exercise, muscle relaxation, guided imagery, and meditation was compared with routine nursing care for reducing anxiety, improving sleep, and promoting relaxation in Chinese adults with cardiac disease. This research was a quasi-experimental, two-group, pretest-posttest study. A convenience sample of 100 cardiology patients (41 treatment, 59 control) admitted to one large medical center hospital in the Republic of China (ROC) was studied for 1 year. The hypothesized relationships were supported. RT significantly (p <.05) improved anxiety, sleep, and relaxation in the treatment group as compared to the control group. It appears audio-visual RT might be a beneficial adjunctive therapy for adult cardiac patients. However, considerable further work using stronger research designs is needed to determine the most appropriate instructional methods and the factors that contribute to long-term consistent practice of RT with Chinese populations. PMID:15514963

  1. High relaxivity Gd(III)-DNA gold nanostars: investigation of shape effects on proton relaxation.

    PubMed

    Rotz, Matthew W; Culver, Kayla S B; Parigi, Giacomo; MacRenaris, Keith W; Luchinat, Claudio; Odom, Teri W; Meade, Thomas J

    2015-03-24

    Gadolinium(III) nanoconjugate contrast agents (CAs) have distinct advantages over their small-molecule counterparts in magnetic resonance imaging. In addition to increased Gd(III) payload, a significant improvement in proton relaxation efficiency, or relaxivity (r1), is often observed. In this work, we describe the synthesis and characterization of a nanoconjugate CA created by covalent attachment of Gd(III) to thiolated DNA (Gd(III)-DNA), followed by surface conjugation onto gold nanostars (DNA-Gd@stars). These conjugates exhibit remarkable r1 with values up to 98 mM(-1) s(-1). Additionally, DNA-Gd@stars show efficient Gd(III) delivery and biocompatibility in vitro and generate significant contrast enhancement when imaged at 7 T. Using nuclear magnetic relaxation dispersion analysis, we attribute the high performance of the DNA-Gd@stars to an increased contribution of second-sphere relaxivity compared to that of spherical CA equivalents (DNA-Gd@spheres). Importantly, the surface of the gold nanostar contains Gd(III)-DNA in regions of positive, negative, and neutral curvature. We hypothesize that the proton relaxation enhancement observed results from the presence of a unique hydrophilic environment produced by Gd(III)-DNA in these regions, which allows second-sphere water molecules to remain adjacent to Gd(III) ions for up to 10 times longer than diffusion. These results establish that particle shape and second-sphere relaxivity are important considerations in the design of Gd(III) nanoconjugate CAs. PMID:25723190

  2. Phenomenological theory of structural relaxation based on a thermorheologically complex relaxation time distribution

    NASA Astrophysics Data System (ADS)

    Andreozzi, L.; Faetti, M.; Salmerã³n Sanchez, M.; Gã³mez Ribelles, J. L.

    2008-09-01

    The aim of this work is to explore the consequences on the kinetics of structural relaxation of considering a glass-forming system to consist of a series of small but macroscopic relaxing regions that evolve independently from each other towards equilibrium in the glassy state. The result of this assumption is a thermorheologically complex model. In this approach each relaxing zone has been assumed to follow the Scherer-Hodge model for structural relaxation (with the small modification of taking a linear dependence of configurational heat capacity with temperature). The model thus developed contains four fitting parameters. A least-squares search routine has been used to find the set of model parameters that fit simultaneously four DSC thermograms in PVAc after different thermal histories. The computer-simulated curves are compared with those obtained with Scherer-Hodge model and the model proposed by Gómez and Monleón. The evolution of the relaxation times during cooling or heating scans and also during isothermal annealing below the glass transition has been analysed. It has been shown that the relaxation times distribution narrows in the glassy state with respect to equilibrium. Isothermal annealing causes this distribution to broaden during the process to finally attain in equilibrium the shape defined at temperatures above Tg.

  3. Muscle Relaxation Therapy in Hyperkinesis: Is It Effective?

    ERIC Educational Resources Information Center

    Bhatara, Vinod; And Others

    1979-01-01

    The literature on two forms of muscle relaxation training (electro-myographic (EMG) biofeedback and progressive muscle relaxation) with learning disabled and hyperkinetic children is reviewed and the authors' own study is discussed. (Author/PHR)

  4. NMR relaxation in multipolar AX systems under spin locking conditions.

    PubMed

    Kaikkonen, A; Kowalewski, J

    1999-12-01

    A relaxation matrix has been calculated for a multipolar AX spin system under the on-resonance spin-locking condition. Auto- and cross-correlation terms between dipolar, quadrupolar, and CSA interactions are considered. It is shown that the spin-lock leads to many relaxation pathways being blocked, resulting in a considerably simplified relaxation network. The presence of spectral densities at zero frequency, associated with locked nuclei, allows efficient relaxation also in the absence of fast molecular motions. PMID:10579956

  5. Effect of Bosentan on Claudication Distance and Endothelium-Dependent Vasodilation in Hispanic Patients With Peripheral Arterial Disease.

    PubMed

    De Haro, Joaquin; Bleda, Silvia; Varela, Cesar; Esparza, Leticia; Acin, Francisco

    2016-01-15

    Endothelin (ET) is involved in the etiopathogenesis of peripheral arterial disease (PAD). We hypothesized that ET antagonism might improve the endothelial function, inflammatory status, and symptoms in PAD. This pilot randomized clinical trial was designed to determine the clinical efficacy, pleiotropic effects, and safety of dual ET-receptor antagonist bosentan in Hispanic patients with PAD presenting intermittent claudication. The Bosentan Population-Based Randomized Trial for Clinical and Endothelial Function Assessment on Endothelin Antagonism Therapy was a 12-month, randomized, controlled, parallel-group, double-blind, proof-of-concept pilot study evaluating the effect of bosentan on absolute claudication distance (primary efficacy end point), flow-mediated arterial dilation, and C-reactive protein levels (primary pleiotropic end points) in patients with PAD with Rutherford category 1 to 2 of recent diagnosis. Secondary end points included ankle-brachial index, subjective claudication distance, and safety. Of the 629 screened subjects, 56 patients were randomized 1:1 to receive bosentan for 12 weeks (n = 27) or placebo (n = 29). Six months after the initiation, a significant treatment effect in flow-mediated arterial dilation of 2.43 ± 0.3% (95% CI 1.75 to 3.12; p = 0.001), absolute claudication distance of 283 ± 23 m (95% CI 202 to 366; p = 0.01), ankle-brachial index of 0.16 ± 0.03 (95% CI 0.09 to 0.23; p = 0.001), and a decrease in C-reactive protein levels of -2.0 ± 0.5 mg/L (95% CI -2.8 to -1.1; p = 0.02) were observed in the bosentan-treated group compared to the control group. No severe adverse effects were found in the bosentan group. In conclusion, in Hispanic patients with intermittent claudication, bosentan was well tolerated and improved endothelial function and claudication distance as well as inflammatory and hemodynamic states. PMID:26651453

  6. Ultrasonic Measurement of Transient Change in Stress-Strain Property of Radial Arterial Wall Caused by Endothelium-Dependent Vasodilation

    NASA Astrophysics Data System (ADS)

    Ikeshita, Kazuki; Hasegawa, Hideyuki; Kanai, Hiroshi

    2008-05-01

    The endothelial dysfunction is considered to be an initial step of atherosclerosis. Additionally, it was reported that the smooth muscle, which constructs the media of the artery, changes its characteristics owing to atherosclerosis. Therefore, it is essential to develop a method for assessing the regional endothelial function and mechanical property of the arterial wall. There is a conventional technique of measuring the transient change in the diameter of the brachial artery caused by flow-mediated dilation (FMD) after the release of avascularization. For more sensitive and regional evaluation, we developed a method of measuring the change in the elasticity of the radial artery due to FMD. In this study, the transient change in the mechanical property of the arterial wall was further revealed by measuring the stress-strain relationship during each heartbeat. The minute change in the thickness (strain) of the radial arterial wall during a cardiac cycle was measured by the phased tracking method, together with the waveform of blood pressure which was continuously measured with a sphygmometer at the radial artery. The transient change in stress-strain relationship during a cardiac cycle was obtained from the measured changes in wall thickness and blood pressure to show the transient change in instantaneous viscoelasticity. From the in vivo experimental results, the stress-strain relationship shows the hysteresis loop. The slope of the loop decreased owing to FMD, which shows that the elastic modulus decreased, and the increasing area of the loop depends on the ratio of the loss modulus (depends on viscosity) to the elastic modulus when the Voigt model is assumed. These results show a potential of the proposed method for the thorough analysis of the transient change in viscoelasticity due to FMD.

  7. AKAP150-dependent cooperative TRPV4 channel gating is central to endothelium-dependent vasodilation and is disrupted in hypertension

    PubMed Central

    Sonkusare, Swapnil K.; Dalsgaard, Thomas; Bonev, Adrian D.; Hill-Eubanks, David C.; Kotlikoff, Michael I.; Scott, John D.; Santana, Luis F.; Nelson, Mark T.

    2015-01-01

    Endothelial cell dysfunction, characterized by a diminished response to endothelial cell–dependent vasodilators, is a hallmark of hypertension. TRPV4 channels play a major role in endothelial-dependent vaso-dilation, a function mediated by local Ca2+ influx through clusters of functionally coupled TRPV4 channels rather than by a global increase in endothelial cell Ca2+. We showed that stimulation of muscarinic acetylcholine receptors on endothelial cells of mouse arteries exclusively activated TRPV4 channels that were localized at myoendothelial projections (MEPs), specialized regions of endothelial cells that contact smooth muscle cells. Muscarinic receptor–mediated activation of TRPV4 depended on protein kinase C (PKC) and the PKC-anchoring protein AKAP150, which was concentrated at MEPs. Cooperative opening of clustered TRPV4 channels specifically amplified Ca2+ influx at MEPs. Cooperativity of TRPV4 channels at non-MEP sites was much lower, and cooperativity at MEPs was greatly reduced by chelation of intracellular Ca2+ or AKAP150 knockout, suggesting that Ca2+ entering through adjacent channels underlies the AKAP150-dependent potentiation of TRPV4 activity. In a mouse model of angiotensin II–induced hypertension, MEP localization of AKAP150 was disrupted, muscarinic receptor stimulation did not activate TRPV4 channels, cooperativity among TRPV4 channels at MEPs was weaker, and vasodilation in response to muscarinic receptor stimulation was reduced. Thus, endothelial-dependent dilation of resistance arteries is enabled by MEP-localized AKAP150, which ensures the proximity of PKC to TRPV4 channels and the coupled channel gating necessary for efficient communication from endothelial to smooth muscle cells in arteries. Disruption of this molecular assembly may contribute to altered blood flow in hypertension. PMID:25005230

  8. Electron-vibration relaxation in oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Heritier, K. L.; Panesi, M.

    2016-06-01

    An ideal chemical reactor model is used to study the vibrational relaxation of oxygen molecules in their ground electronic state, X3 Σg-, in presence of free electrons. The model accounts for vibrational non-equilibrium between the translational energy mode of the gas and the vibrational energy mode of individual molecules. The vibrational levels of the molecules are treated as separate species, allowing for non-Boltzmann distributions of their population. The electron and vibrational temperatures are varied in the range [0-20,000] K. Numerical results show a fast energy transfer between oxygen molecules and free electron, which causes strong deviation of the vibrational distribution function from Boltzmann distribution, both in heating and cooling conditions. Comparison with Landau-Teller model is considered showing a good agreement for electron temperature range [2000-12,000] K. Finally analytical fit of the vibrational relaxation time is given.

  9. Multi-region relaxed magnetohydrodynamics with flow

    SciTech Connect

    Dennis, G. R. Dewar, R. L.; Hole, M. J.; Hudson, S. R.

    2014-04-15

    We present an extension of the multi-region relaxed magnetohydrodynamics (MRxMHD) equilibrium model that includes plasma flow. This new model is a generalization of Woltjer's model of relaxed magnetohydrodynamics equilibria with flow. We prove that as the number of plasma regions becomes infinite, our extension of MRxMHD reduces to ideal MHD with flow. We also prove that some solutions to MRxMHD with flow are not time-independent in the laboratory frame, and instead have 3D structure which rotates in the toroidal direction with fixed angular velocity. This capability gives MRxMHD potential application to describing rotating 3D MHD structures such as 'snakes' and long-lived modes.

  10. Relaxation mechanism of the hydrated electron.

    PubMed

    Elkins, Madeline H; Williams, Holly L; Shreve, Alexander T; Neumark, Daniel M

    2013-12-20

    The relaxation dynamics of the photoexcited hydrated electron have been subject to conflicting interpretations. Here, we report time-resolved photoelectron spectra of hydrated electrons in a liquid microjet with the aim of clarifying ambiguities from previous experiments. A sequence of three ultrashort laser pulses (~100 femtosecond duration) successively created hydrated electrons by charge-transfer-to-solvent excitation of dissolved anions, electronically excited these electrons via the s→p transition, and then ejected them into vacuum. Two distinct transient signals were observed. One was assigned to the initially excited p-state with a lifetime of ~75 femtoseconds, and the other, with a lifetime of ~400 femtoseconds, was attributed to s-state electrons just after internal conversion in a nonequilibrated solvent environment. These assignments support the nonadiabatic relaxation model. PMID:24357314

  11. Post-glitch relaxation in pulsars

    NASA Astrophysics Data System (ADS)

    Jones, P. B.

    2002-09-01

    The glitch model of Ruderman, Zhu & Chen is applied to the problem of post-glitch relaxation. The energy dissipated in a glitch is such that motion of both solid and liquid phases during and after spin-up is strictly constrained to surfaces of constant chemical composition. The amorphous and heterogeneous nature of the solid phase of neutron star matter is used to deduce the qualitative form of the dissipative force acting on unit length of a neutron vortex as a function of its velocity. The analysis of post-glitch relaxation given here is necessarily qualitative owing to the stochastic nature of the model, but is consistent with both the normal and anomalous cases observed.

  12. Relaxation times and charge conductivity of silicene

    NASA Astrophysics Data System (ADS)

    Mazloom, Azadeh; Parhizgar, Fariborz; Abedinpour, Saeed H.; Asgari, Reza

    2016-07-01

    We investigate the transport and single particle relaxation times of silicene in the presence of neutral and charged impurities. The static charge conductivity is studied using the semiclassical Boltzmann formalism when the spin-orbit interaction is taken into account. The screening is modeled within Thomas-Fermi and random-phase approximations. We show that the transport relaxation time is always longer than the single particle one. Easy electrical controllability of both carrier density and band gap in this buckled two-dimensional structure makes it a suitable candidate for several electronic and optoelectronic applications. In particular, we observe that the dc charge conductivity could be easily controlled through an external electric field, a very promising feature for applications as electrical switches and transistors. Our findings would be qualitatively valid for other buckled honeycomb lattices of the same family, such as germanine and stanine.

  13. Modeling aftershocks as a stretched exponential relaxation

    NASA Astrophysics Data System (ADS)

    Mignan, A.

    2015-11-01

    The decay rate of aftershocks has been modeled as a power law since the pioneering work of Omori in the late nineteenth century. Although other expressions have been proposed in recent decades to describe the temporal behavior of aftershocks, the number of model comparisons remains limited. After reviewing the aftershock models published from the late nineteenth century until today, I solely compare the power law, pure exponential and stretched exponential expressions defined in their simplest forms. By applying statistical methods recommended recently in applied mathematics, I show that all aftershock sequences tested in three regional earthquake catalogs (Southern and Northern California, Taiwan) and with three declustering techniques (nearest-neighbor, second-order moment, window methods) follow a stretched exponential instead of a power law. These results infer that aftershocks are due to a simple relaxation process, in accordance with most other relaxation processes observed in Nature.

  14. Braided magnetic fields: equilibria, relaxation and heating

    NASA Astrophysics Data System (ADS)

    Pontin, D. I.; Candelaresi, S.; Russell, A. J. B.; Hornig, G.

    2016-05-01

    We examine the dynamics of magnetic flux tubes containing non-trivial field line braiding (or linkage), using mathematical and computational modelling, in the context of testable predictions for the laboratory and their significance for solar coronal heating. We investigate the existence of braided force-free equilibria, and demonstrate that for a field anchored at perfectly-conducting plates, these equilibria exist and contain current sheets whose thickness scales inversely with the braid complexity—as measured for example by the topological entropy. By contrast, for a periodic domain braided exact equilibria typically do not exist, while approximate equilibria contain thin current sheets. In the presence of resistivity, reconnection is triggered at the current sheets and a turbulent relaxation ensues. We finish by discussing the properties of the turbulent relaxation and the existence of constraints that may mean that the final state is not the linear force-free field predicted by Taylor’s hypothesis.

  15. Stress relaxation in discontinuously reinforced composites

    SciTech Connect

    Shi, N.; Arsenault, R.J.

    1995-05-01

    It has been observed that in discontinuously-reinforced Al{sub 2}0{sub 3}/NiAl composites that as the reinforcement size increases the average density of dislocations generated from the relaxation of the thermal stresses increases, and the corresponding thermal residual stresses slightly decrease. Similar changes result when the reinforcement morphology changes from spheres to short fibers to continuous filaments. The changes of dislocation density and thermal residual stresses with respect to particle size are in contrast to those observed in the SiC/Al counterpart A previously developed simple model used to explain the SiC/Al data, which was based on prismatic dislocation punching, suggested that the density of the misfit dislocations decreases when the reinforcement size increases. In this investigation, a simple model is proposed to explain the anomaly in the development of thermal residual stresses and the generation of misfit dislocations as a function of the particle size and shape in Al{sub 2}0{sub 3}/NiAl composites. As a result of a lack of sufficient independent-slip-systems in low symmetry materials such as NiAl, plastic relaxation of the thermal stresses is severely constrained as compared to fcc Al. As such, plastic relaxation requires collaborative slips in an aggregate of grains. This only occurs when the length scale of the varying misfit thermal stress field is much larger than the average grain size. That is, the mechanism of plastic relaxation becomes operative when the reinforcement size increases.

  16. Controlling spin relaxation with a cavity

    NASA Astrophysics Data System (ADS)

    Bienfait, A.; Pla, J. J.; Kubo, Y.; Zhou, X.; Stern, M.; Lo, C. C.; Weis, C. D.; Schenkel, T.; Vion, D.; Esteve, D.; Morton, J. J. L.; Bertet, P.

    2016-03-01

    Spontaneous emission of radiation is one of the fundamental mechanisms by which an excited quantum system returns to equilibrium. For spins, however, spontaneous emission is generally negligible compared to other non-radiative relaxation processes because of the weak coupling between the magnetic dipole and the electromagnetic field. In 1946, Purcell realized that the rate of spontaneous emission can be greatly enhanced by placing the quantum system in a resonant cavity. This effect has since been used extensively to control the lifetime of atoms and semiconducting heterostructures coupled to microwave or optical cavities, and is essential for the realization of high-efficiency single-photon sources. Here we report the application of this idea to spins in solids. By coupling donor spins in silicon to a superconducting microwave cavity with a high quality factor and a small mode volume, we reach the regime in which spontaneous emission constitutes the dominant mechanism of spin relaxation. The relaxation rate is increased by three orders of magnitude as the spins are tuned to the cavity resonance, demonstrating that energy relaxation can be controlled on demand. Our results provide a general way to initialize spin systems into their ground state and therefore have applications in magnetic resonance and quantum information processing. They also demonstrate that the coupling between the magnetic dipole of a spin and the electromagnetic field can be enhanced up to the point at which quantum fluctuations have a marked effect on the spin dynamics; as such, they represent an important step towards the coherent magnetic coupling of individual spins to microwave photons.

  17. On real statistics of relaxation in gases

    NASA Astrophysics Data System (ADS)

    Kuzovlev, Yu. E.

    2016-02-01

    By example of a particle interacting with ideal gas, it is shown that the statistics of collisions in statistical mechanics at any value of the gas rarefaction parameter qualitatively differ from that conjugated with Boltzmann's hypothetical molecular chaos and kinetic equation. In reality, the probability of collisions of the particle in itself is random. Because of that, the relaxation of particle velocity acquires a power-law asymptotic behavior. An estimate of its exponent is suggested on the basis of simple kinematic reasons.

  18. Magnetic relaxation in uranium ferromagnetic superconductors

    NASA Astrophysics Data System (ADS)

    Mineev, V. P.

    2013-12-01

    There is proposed a phenomenological description of quasielastic neutron scattering in the ferromagnetic metals UGe2 and UCoGe based on their property that magnetization supported by the moments located at uranium atoms is not a conserved quantity relaxing to equilibrium by the interaction with an itinerant electron subsystem. As a result the linewidth of quasielastic neutron scattering at q→0 acquires nonvanishing value at all temperatures but the Curie temperature.

  19. Controlling spin relaxation with a cavity.

    PubMed

    Bienfait, A; Pla, J J; Kubo, Y; Zhou, X; Stern, M; Lo, C C; Weis, C D; Schenkel, T; Vion, D; Esteve, D; Morton, J J L; Bertet, P

    2016-03-01

    Spontaneous emission of radiation is one of the fundamental mechanisms by which an excited quantum system returns to equilibrium. For spins, however, spontaneous emission is generally negligible compared to other non-radiative relaxation processes because of the weak coupling between the magnetic dipole and the electromagnetic field. In 1946, Purcell realized that the rate of spontaneous emission can be greatly enhanced by placing the quantum system in a resonant cavity. This effect has since been used extensively to control the lifetime of atoms and semiconducting heterostructures coupled to microwave or optical cavities, and is essential for the realization of high-efficiency single-photon sources. Here we report the application of this idea to spins in solids. By coupling donor spins in silicon to a superconducting microwave cavity with a high quality factor and a small mode volume, we reach the regime in which spontaneous emission constitutes the dominant mechanism of spin relaxation. The relaxation rate is increased by three orders of magnitude as the spins are tuned to the cavity resonance, demonstrating that energy relaxation can be controlled on demand. Our results provide a general way to initialize spin systems into their ground state and therefore have applications in magnetic resonance and quantum information processing. They also demonstrate that the coupling between the magnetic dipole of a spin and the electromagnetic field can be enhanced up to the point at which quantum fluctuations have a marked effect on the spin dynamics; as such, they represent an important step towards the coherent magnetic coupling of individual spins to microwave photons. PMID:26878235

  20. Relaxation, Structure, and Properties of Semicoherent Interfaces

    NASA Astrophysics Data System (ADS)

    Shao, S.; Wang, J.

    2016-01-01

    Materials containing a high density of interfaces are promising candidates for future energy technologies because interfaces acting as sources, sinks, and barriers for defects can improve mechanical and irradiation properties of materials. A semicoherent interface widely occurring in various materials is composed of a network of misfit dislocations and coherent regions separated by misfit dislocations. In this article, we review the relaxation mechanisms, structure, and properties of (111) semicoherent interfaces in face-centered cubic structures.

  1. Relaxation time measurements by an electronic method.

    NASA Technical Reports Server (NTRS)

    Brousseau, R.; Vanier, J.

    1973-01-01

    Description of a simple electronic system that permits the direct measurement of time constants of decaying signals. The system was used in connection with relaxation experiments on hydrogen and rubidium masers and was found to operate well. The use of a computing counter in the systems gives the possibility of making averages on several experiments and obtaining the standard deviation of the results from the mean. The program for the computing counter is given.

  2. The Efficacy of Relaxation Training in Treating Anxiety

    ERIC Educational Resources Information Center

    Francesco, Pagnini; Mauro, Manzoni Gian; Gianluca, Castelnuovo; Enrico, Molinari

    2009-01-01

    This paper provides a review of scientific literature about relaxation training and its effects on anxiety. Research investigating progressive relaxation, meditation, applied relaxation and autogenic training were considered. All these methods proved to be effective in reducing anxiety in all kind of samples, affected or not by physical or…

  3. Is Relaxation Training Effective in the Treatment of Clinical Depression?

    ERIC Educational Resources Information Center

    Beaty, Lee A.

    The process of relaxation is a complex triarchic phenomenon that incorporates behavioral, cognitive, and physiological components. Existing literature is surveyed in order to determine the efficacy of treating various forms of depression with cognitive-behavioral relaxation strategies. Relaxation training has been shown to be effective in treating…

  4. Alternate Forms Reliability of the Behavioral Relaxation Scale: Preliminary Results

    ERIC Educational Resources Information Center

    Lundervold, Duane A.; Dunlap, Angel L.

    2006-01-01

    Alternate forms reliability of the Behavioral Relaxation Scale (BRS; Poppen,1998), a direct observation measure of relaxed behavior, was examined. A single BRS score, based on long duration observation (5-minute), has been found to be a valid measure of relaxation and is correlated with self-report and some physiological measures. Recently,…

  5. Graph Matching: Relax at Your Own Risk.

    PubMed

    Lyzinski, Vince; Fishkind, Donniell E; Fiori, Marcelo; Vogelstein, Joshua T; Priebe, Carey E; Sapiro, Guillermo

    2016-01-01

    Graph matching-aligning a pair of graphs to minimize their edge disagreements-has received wide-spread attention from both theoretical and applied communities over the past several decades, including combinatorics, computer vision, and connectomics. Its attention can be partially attributed to its computational difficulty. Although many heuristics have previously been proposed in the literature to approximately solve graph matching, very few have any theoretical support for their performance. A common technique is to relax the discrete problem to a continuous problem, therefore enabling practitioners to bring gradient-descent-type algorithms to bear. We prove that an indefinite relaxation (when solved exactly) almost always discovers the optimal permutation, while a common convex relaxation almost always fails to discover the optimal permutation. These theoretical results suggest that initializing the indefinite algorithm with the convex optimum might yield improved practical performance. Indeed, experimental results illuminate and corroborate these theoretical findings, demonstrating that excellent results are achieved in both benchmark and real data problems by amalgamating the two approaches. PMID:26656578

  6. Relaxed Phylogenetics and Dating with Confidence

    PubMed Central

    Ho, Simon Y. W; Phillips, Matthew J

    2006-01-01

    In phylogenetics, the unrooted model of phylogeny and the strict molecular clock model are two extremes of a continuum. Despite their dominance in phylogenetic inference, it is evident that both are biologically unrealistic and that the real evolutionary process lies between these two extremes. Fortunately, intermediate models employing relaxed molecular clocks have been described. These models open the gate to a new field of “relaxed phylogenetics.” Here we introduce a new approach to performing relaxed phylogenetic analysis. We describe how it can be used to estimate phylogenies and divergence times in the face of uncertainty in evolutionary rates and calibration times. Our approach also provides a means for measuring the clocklikeness of datasets and comparing this measure between different genes and phylogenies. We find no significant rate autocorrelation among branches in three large datasets, suggesting that autocorrelated models are not necessarily suitable for these data. In addition, we place these datasets on the continuum of clocklikeness between a strict molecular clock and the alternative unrooted extreme. Finally, we present analyses of 102 bacterial, 106 yeast, 61 plant, 99 metazoan, and 500 primate alignments. From these we conclude that our method is phylogenetically more accurate and precise than the traditional unrooted model while adding the ability to infer a timescale to evolution. PMID:16683862

  7. Cortex phellodendri Extract Relaxes Airway Smooth Muscle

    PubMed Central

    Jiang, Qiu-Ju; Chen, Weiwei; Dan, Hong; Tan, Li; Zhu, He; Yang, Guangzhong; Shen, Jinhua; Peng, Yong-Bo; Zhao, Ping; Xue, Lu; Yu, Meng-Fei; Ma, Liqun; Si, Xiao-Tang; Wang, Zhuo; Dai, Jiapei; Qin, Gangjian; Zou, Chunbin; Liu, Qing-Hua

    2016-01-01

    Cortex phellodendri is used to reduce fever and remove dampness and toxin. Berberine is an active ingredient of C. phellodendri. Berberine from Argemone ochroleuca can relax airway smooth muscle (ASM); however, whether the nonberberine component of C. phellodendri has similar relaxant action was unclear. An n-butyl alcohol extract of C. phellodendri (NBAECP, nonberberine component) was prepared, which completely inhibits high K+- and acetylcholine- (ACH-) induced precontraction of airway smooth muscle in tracheal rings and lung slices from control and asthmatic mice, respectively. The contraction induced by high K+ was also blocked by nifedipine, a selective blocker of L-type Ca2+ channels. The ACH-induced contraction was partially inhibited by nifedipine and pyrazole 3, an inhibitor of TRPC3 and STIM/Orai channels. Taken together, our data demonstrate that NBAECP can relax ASM by inhibiting L-type Ca2+ channels and TRPC3 and/or STIM/Orai channels, suggesting that NBAECP could be developed to a new drug for relieving bronchospasm. PMID:27239213

  8. Multicomponent T2 relaxation analysis in cartilage

    PubMed Central

    Reiter, David A.; Lin, Ping-Chang; Fishbein, Kenneth W.; Spencer, Richard G.

    2009-01-01

    MR techniques are sensitive to the initial phases of osteoarthritis, characterized by disruption of collagen and loss of proteoglycan (PG), but are of limited specificity. Here, water compartments in normal and trypsin-degraded bovine nasal cartilage were identified using a non-negative least squares multiexponential analysis of T2 relaxation. Three components were detected: T2,1 = 2.3 ms, T2,2 = 25.2 ms, and T2,3 = 96.3 ms, with fractions w1 = 6.2%, w2 = 14.5%, and w3 = 79.3%, respectively. Trypsinization resulted in increased (p<0.01) values of T2,2 = 64.2 ms and T2,3 = 149.4 ms, supporting their assignment to water compartments that are bound and loosely associated with PG, respectively. The T2 of the rapidly-relaxing component was not altered by digestion, supporting assignment to relatively immobile collagen-bound water. Relaxation data were simulated for a range of TE, number of echoes, and SNR to guide selection of acquisition parameters and assess the accuracy and precision of experimental results. Based on this, the expected experimental accuracy of measured T2’s and associated weights was within 2% and 4% respectively, with precision within 1% and 3%. These results demonstrate the potential of multiexponential T2 analysis to increase the specificity of MR characterization of cartilage. PMID:19189393

  9. Experimental characterization of stress relaxation in glass

    NASA Astrophysics Data System (ADS)

    Kadali, Hemanth C.

    Glass viscoelasticity has gained importance in recent years as glass lens molding appeared as a valuable alternative to the traditional grinding and polishing process for manufacturing glass lenses. In the precision lens molding process, knowledge of viscoelastic properties of glass in the transition region, which affect the stress relaxation behavior, is required to precisely predict the final size and shape of molded lenses. The purpose of this study is to establish a step-by-step procedure for characterizing the viscoelastic behavior of glass in the glass transition region using a finite term Prony series of a Generalized Maxwell model. This study focuses on viscoelastic characterization of stabilized glass samples at lower stress levels between 3 and 12 MPa where it demonstrates linearity. Analysis and post-processing of creep data, performed in MATLAB and MAPLE, include displacement-to-strain conversion, determination of viscoelastic moments and constants, normalization, curve fitting and retardation-to-relaxation conversion. The process of curve fitting is carried out using a constrained optimization scheme to satisfy the constraint equations involving viscoelastic constants and functions. A set of relaxation parameters needed in numerical modeling, i.e., weights and times of the Prony series are presented in this thesis for borosilicate glass at different temperatures. Additionally, the issues related to the characterization of optical glasses were identified and discussed.

  10. Relaxation strategies for patients during dermatologic surgery.

    PubMed

    Shenefelt, Philip D

    2010-07-01

    Patient stress and anxiety are common preoperatively and during dermatologic procedures and surgeries. Stress and anxiety can occasionally interfere with performance of procedures or surgery and can induce hemodynamic instability, such as elevated blood pressure or syncope, as well as producing considerable discomfort for some patients. Detection of excess stress and anxiety in patients can allow the opportunity for corrective or palliative measures. Slower breathing, biofeedback, progressive muscular relaxation, guided imagery, hypnosis, meditation and music can help calm and rebalance the patient's autonomic nervous system and immune functioning. Handheld miniaturized heart rate variability biofeedback devices are now available. The relaxation response can easily be taught. Guided imagery can be recorded or live. Live rapid induction hypnosis followed by deepening and then self-guided imagery requires no experience on the part of the patient but does require training and experience on the part of a provider. Recorded hypnosis inductions may also be used. Meditation generally requires more prior experience and training, but is useful when the patient already is skilled in it. Live, guided meditation or meditation recordings may be used. Relaxing recorded music from speakers or headphones or live performance music may also be employed to ease discomfort and improve the patient's attitude for dermatologic procedures and surgeries. PMID:20677535

  11. Vibrational-translational relaxation in liquid chloroform

    NASA Astrophysics Data System (ADS)

    Takagi, K.; Choi, P.-K.; Negishi, K.

    1981-01-01

    Ultrasonic measurements were made in liquid chloroform over the frequency range from 3 MHz to 5 GHz by means of three experimental techniques, pulse-echo overlap, high-resolution Bragg reflection, and Brillouin scattering. The observed velocity dispersion revealed two relaxation processes, one at 650 MHz and the other at 5.1 GHz at 20 °C. They are interpreted in terms of vibrational-translational relaxation. Quantitative analysis of specific heat shows the lowest (261 cm-1) and the second lowest (366 cm-1) fundamental vibrational modes should have a common relaxation time at 50 ps and the group of all above the third mode (667 cm-1) at 290 ps. The present results are combined with recent data obtained by Laubereau et al. with the picosecond spectroscopy technique; a diagram illustrating V-T and V-V energy transfer is presented. A brief comment is given also on V-T and V-V processes in dichloromethane.

  12. OCT-based approach to local relaxations discrimination from translational relaxation motions

    NASA Astrophysics Data System (ADS)

    Matveev, Lev A.; Matveyev, Alexandr L.; Gubarkova, Ekaterina V.; Gelikonov, Grigory V.; Sirotkina, Marina A.; Kiseleva, Elena B.; Gelikonov, Valentin M.; Gladkova, Natalia D.; Vitkin, Alex; Zaitsev, Vladimir Y.

    2016-04-01

    Multimodal optical coherence tomography (OCT) is an emerging tool for tissue state characterization. Optical coherence elastography (OCE) is an approach to mapping mechanical properties of tissue based on OCT. One of challenging problems in OCE is elimination of the influence of residual local tissue relaxation that complicates obtaining information on elastic properties of the tissue. Alternatively, parameters of local relaxation itself can be used as an additional informative characteristic for distinguishing the tissue in normal and pathological states over the OCT image area. Here we briefly present an OCT-based approach to evaluation of local relaxation processes in the tissue bulk after sudden unloading of its initial pre-compression. For extracting the local relaxation rate we evaluate temporal dependence of local strains that are mapped using our recently developed hybrid phase resolved/displacement-tracking (HPRDT) approach. This approach allows one to subtract the contribution of global displacements of scatterers in OCT scans and separate the temporal evolution of local strains. Using a sample excised from of a coronary arteria, we demonstrate that the observed relaxation of local strains can be reasonably fitted by an exponential law, which opens the possibility to characterize the tissue by a single relaxation time. The estimated local relaxation times are assumed to be related to local biologically-relevant processes inside the tissue, such as diffusion, leaking/draining of the fluids, local folding/unfolding of the fibers, etc. In general, studies of evolution of such features can provide new metrics for biologically-relevant changes in tissue, e.g., in the problems of treatment monitoring.

  13. TRANSIENT LOWER ESOPHAGEAL SPHINCTER RELAXATION IN ACHALASIA: EVERYTHING BUT LES RELAXATION

    PubMed Central

    KWIATEK, Monika A.; POST, Jennifer; PANDOLFINO, John E.; KAHRILAS, Peter J.

    2009-01-01

    Background: In conducting clinical high resolution esophageal pressure topography (HREPT) studies we observed that after subjects sat upright between series of supine and upright test swallows, they frequently had a transient lower esophageal sphincter relaxation (tLESR). When achalasia patients were studied in the same protocol, they exhibited a similar HREPT event leading to the hypothesis that achalasics had incomplete tLESRs. Methods: We reviewed clinical HREPT studies of 94 consecutive non-achalasics and 25 achalasics. Studies were analyzed for a tLESR-like event during the study and, when observed, that tLESR-like event was characterized for the degree and duration of distal esophageal shortening, the degree of LES relaxation, associated crural diaphragm (CD) inhibition, esophageal pressurization, and upper esophageal sphincter (UES) relaxation. Results: 64/94 (68%) non-achalasics and 15/24 (63%) of achalasics had a pressure topography event after the posture change characterized by a prolonged period of distal esophageal shortening and/or LES relaxation. Events among the non-achalasics and achalasics were similar in terms of magnitude and duration of shortening and all were associated with CD inhibition. Similar proportions had associated non-deglutitive UES relaxations. The only consistent differences were the absence of associated LES relaxation and the absence of HREPT evidence of reflux among the achalasics leading us to conclude that their events were incomplete tLESRs. Conclusions: Achalasic patients exhibit a selective defect in the tLESR response suggesting preservation of all sensory, central, and efferent aspects of the requisite neural substrate with the notable exception of LES relaxation, a function of inhibitory (nitrergic) myenteric plexus neurons. PMID:19552630

  14. Relaxation-relaxation exchange experiments in porous media with portable Halbach-Magnets.

    NASA Astrophysics Data System (ADS)

    Haber, A.; Haber-Pohlmeier, S.; Casanova, F.; Blümich, B.

    2009-04-01

    Mobile NMR became a powerful tool following the development of portable NMR sensors for well logging. By now there are numerous applications of mobile NMR in materials analysis and chemical engineering where, for example, unique information about the structure, morphology and dynamics of polymers is obtained, and new opportunities are provided for geo-physical investigations [1]. In particular, dynamic information can be retrieved by two-dimensional Laplace exchange NMR, where the initial NMR relaxation environment is correlated with the final relaxation environment of molecules migrating from one environment to the other within a so-called NMR mixing time tm [2]. Relaxation-relaxation exchange experiments of water in inorganic porous media were performed at low and moderately inhomogeneous magnetic field with a simple, portable Halbach-Magnet. By conducting NMR transverse relaxation exchange experiments for several mixing times and converting the results to 2D T2 distributions (joint probability densities of transverse relaxation times T2) with the help of the inverse 2D Laplace Transformation (ILT), we obtained characteristic exchange times for different pore sizes. The results of first experiments on soil samples are reported, which reveal information about the complex pore structure of soil and the moisture content. References: 1. B. Blümich, J. Mauler, A. Haber, J. Perlo, E. Danieli, F. Casanova, Mobile NMR for Geo-Physical Analysis and Material Testing, Petroleum Science, xx (2009) xxx - xxx. 2. K. E. Washburn, P.T. Callaghan, Tracking pore to pore exchange using relaxation exchange spectroscopy, Phys. Rev. Lett. 97 (2006) 175502.

  15. Contribution of intracortical inhibition in voluntary muscle relaxation.

    PubMed

    Motawar, Binal; Hur, Pilwon; Stinear, James; Seo, Na Jin

    2012-09-01

    Terminating a voluntary muscle contraction is an important aspect of motor control, and yet, its neurophysiology is unclear. The objective of this study was to determine the role of short-interval intracortical inhibition (SICI) by comparing SICIs during relaxation from a power grip versus during a sustained power grip at the matching muscle activity level. Right-handed healthy young adults gripped and relaxed from power grip following auditory cues. The relaxation period was determined as the time for the flexor digitorum superficialis (FDS) muscle to reach its pre-contraction baseline level after the cue to relax. SICI during relaxation was obtained at different times into the relaxation period in two separate studies (70, 80, 90 % into relaxation in Study 1; 25, 50, 75 % into relaxation in Study 2). In addition, SICI during sustained contraction was assessed while subjects maintained a power grip at the matching FDS EMG levels (obtained during relaxation, for both Studies). Results showed that the mean SICI was greater during relaxation than during sustained contraction at the matching muscle activity level in both Studies (p < 0.05), indicating increased activation of intracortical inhibitory circuits for muscle relaxation. SICI gradually increased from 25 to 50 and 75 % into relaxation (Study 2, p < 0.05), but did not change from 70 to 80 and 90 % into relaxation (Study 1). MEP decreased with progression of relaxation (p < 0.05) in both Studies, reflecting gradual decreases in corticomotor excitability. This work supports the hypothesis that relaxation from a voluntary muscle contraction involves inhibitory activity in the primary motor cortex. PMID:22791231

  16. Psychophysiological Effects of Progressive Relaxation in Anxiety Neurotic Patients and of Progressive Relaxation and Alpha Feedback in Nonpatients.

    ERIC Educational Resources Information Center

    Lehrer, Paul M.

    1978-01-01

    Compared physiological effects of progressive relaxation, alpha feedback, and a no-treatment condition. Nonpatients showed more psychophysiological habituation than patients in response to hearing very loud tones and to reaction time tasks. Patients showed greater physiological response to relaxation than nonpatients. After relaxation, autonomic…

  17. Fluctuation model for structural relaxation and the glass transition

    SciTech Connect

    Moynihan, C.T.; Whang, J.H.

    1997-12-31

    The fluctuation or independently relaxing nanoregion model attributes the distribution of structural relaxation times in a glassforming melt to a physical distribution of nanoregions which vary in their properties. A quantitative test of this model is described, in which parameters derived from relaxational data on B{sub 2}O{sub 3} glass are shown to be capable of predicting the anomalous light scattering in the glass transition region. It is also shown that the local inhomogeneities which lead to the distribution of structural relaxation times make only a very minor contribution to the distribution of electrical relaxation times in ionically conducting glasses and melts.

  18. Stretched Exponential Relaxation of Glasses at Low Temperature

    NASA Astrophysics Data System (ADS)

    Yu, Yingtian; Wang, Mengyi; Zhang, Dawei; Wang, Bu; Sant, Gaurav; Bauchy, Mathieu

    2015-10-01

    The question of whether glass continues to relax at low temperature is of fundamental and practical interest. Here, we report a novel atomistic simulation method allowing us to directly access the long-term dynamics of glass relaxation at room temperature. We find that the potential energy relaxation follows a stretched exponential decay, with a stretching exponent β =3 /5 , as predicted by Phillips's diffusion-trap model. Interestingly, volume relaxation is also found. However, it is not correlated to the energy relaxation, but it is rather a manifestation of the mixed alkali effect.

  19. Dynamics of nanoscale ripple relaxation on alloy surfaces.

    PubMed

    Ramasubramaniam, Ashwin; Shenoy, Vivek B

    2008-02-01

    As an alloy surface evolves under capillary forces, differing mobilities of the individual components can lead to kinetic alloy decomposition at the surface. In this paper, we address the relaxation of nanoscale sinusoidal ripples on alloy surfaces by considering the effects of both surface and bulk diffusion. In the absence of bulk diffusion, we derive exact analytical expressions for relaxation rates and identify two natural time scales that govern the relaxation dynamics. Bulk diffusion is shown to reduce kinetic surface segregation and enhance relaxation rates, owing to intermixing near the surface. Our results provide a quantitative framework for the interpretation of relaxation experiments on alloy surfaces. PMID:18352033

  20. Febuxostat, a novel xanthine oxidoreductase inhibitor, improves hypertension and endothelial dysfunction in spontaneously hypertensive rats.

    PubMed

    Shirakura, Takashi; Nomura, Johji; Matsui, Chieko; Kobayashi, Tsunefumi; Tamura, Mizuho; Masuzaki, Hiroaki

    2016-08-01

    Xanthine oxidase (XO) is an enzyme responsible for the production of uric acid. XO produces considerable amount of oxidative stress throughout the body. To date, however, its pathophysiologic role in hypertension and endothelial dysfunction still remains controversial. To explore the possible involvement of XO-derived oxidative stress in the pathophysiology of vascular dysfunction, by use of a selective XO inhibitor, febuxostat, we investigated the impact of pharmacological inhibition of XO on hypertension and vascular endothelial dysfunction in spontaneously hypertensive rats (SHRs). Sixteen-week-old SHR and normotensive Wistar-Kyoto (WKY) rats were treated with tap water (control) or water containing febuxostat (3 mg/kg/day) for 6 weeks. Systolic blood pressure (SBP) in febuxostat-treated SHR (220 ± 3 mmHg) was significantly (P < 0.05) decreased compared with the control SHR (236 ± 4 mmHg) while SBP in febuxostat-treated WKY was constant. Acetylcholine-induced endothelium-dependent relaxation in aortas from febuxostat-treated SHR was significantly (P < 0.05) improved compared with the control SHR, whereas relaxation in response to sodium nitroprusside was not changed. Vascular XO activity and tissue nitrotyrosine level, a representative indicator of local oxidative stress, were considerably elevated in the control SHR compared with the control WKY, and this increment was abolished by febuxostat. Our results suggest that exaggerated XO activity and resultant increase in oxidative stress in this experimental model contribute to the hypertension and endothelial dysfunction, thereby supporting a notion that pharmacological inhibition of XO is valuable not only for hyperuricemia but also for treating hypertension and related endothelial dysfunction in human clinics. PMID:27198514

  1. Melatonin and L-carnitin improves endothelial disfunction and oxidative stress in Type 2 diabetic rats.

    PubMed

    Salmanoglu, Derya Selcen; Gurpinar, Tugba; Vural, Kamil; Ekerbicer, Nuran; Darıverenli, Ertan; Var, Ahmet

    2016-08-01

    Vascular dysfunction is thought to play a major role in the development of diabetic cardiovascular disease. The roles of endothelial dysfunction, oxidative stress, and dyslipidemia will be considered. Melatonin as well as L-carnitine were shown to possess strong antioxidant properties. Diabetes induced with high fat diet (for 8 weeks) and multipl low doses intraperitoneal injection of STZ (twice, 30mg/kg/d i.p). The diabetic animals were randomly assigned to one of the experimental groups as follows: Control group (C), high fat diet (HFD), STZ-induced diabetic group (HFD+STZ) , HFD+STZ diabetic group received melatonin (10mg/kg/d i.p), HFD+STZ diabetic group received L-carnitine (0.6g/kg/d i.p), and HFD+STZ diabetic group received glibenclamide (5mg/kg/d, oral). The serum fasting blood glucose, insulin, total cholesterol, HDL- cholesterol, LDL-cholesterol, triglyceride and malondialdehyde (MDA) levels were tested. Acetylcholine induced endothelium-dependent relaxation and sodium nitroprusside induced endothelium-independent relaxation were measured in aortas for estimating endothelial function. Also, glutathione peroxidase (GPx), superoxide dismutase (SOD) and nitric oxide (NO) levels activities were determined in rat liver. According to our results melatonin and L-carnitine treatment decreased fasting blood glucose, total cholesterol, and LDL levels. MDA levels significantly decreased with the melatonin treatment whereas SOD levels were not significantly changed between the groups. The results suggest that especially melatonin restores the vascular responses and endothelial dysfunction in diabetes. PMID:26803481

  2. Abolition of flow-dependent EDRF release before that evoked by agonists in hypercholesterolaemic rabbits.

    PubMed Central

    Hutcheson, I R; Smith, J A; Griffith, T M

    1994-01-01

    1. We have used a pulsatile cascade bioassay system to investigate the effects of dietary-induced hypercholesterolaemia on EDRF release evoked by acetylcholine and by the oscillatory and time-averaged components of flow, in isolated segments of rabbit abdominal aorta. 2. Flow pulsatility (frequency range 0.1-10 Hz) was studied with constant flow (9 ml min-1) at a pulse pressure amplitude of 2 mmHg. Frequency-related EDRF release, maximal at 6 Hz, was slightly attenuated after 4 weeks and abolished after 8 weeks of cholesterol feeding. 3. Time-averaged shear stress was manipulated with dextran (1-4% w/v, 80000 mol. wt.), to increase perfusate viscosity. EDRF release induced by increased perfusate viscosity was unaffected after 4 weeks but abolished after 8 weeks of cholesterol feeding. 4. Endothelium-dependent relaxations to acetylcholine (0.1-10 microM) were not influenced after 4 weeks and only partially attenuated (by 60% of the maximal response, EC50 unchanged at 6.45 +/- 0.04 vs. 6.4 +/- 0.1 microM) after 8 weeks of cholesterol feeding. 5. Blood cholesterol levels were significantly (P < 0.001) increased after 4 weeks (26 +/- 3.6 vs 2.6 +/- 0.6 mmol l-1) and 8 weeks (56.2 +/- 3.8 vs 1.3 +/- 0.1 mmol l-1) of cholesterol feeding but after 8 weeks plasma L-arginine levels were not significantly different from the age-matched controls (0.2 +/- 0.05 vs. 0.19 +/- 0.04 mmol l-1). 6. We conclude that hypercholesterolaemia impairs flow-related (pulsatile- and time-averaged shear-induced) EDRF release earlier than acetylcholine-induced relaxation in rabbit aorta.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7529109

  3. Melatonin and L-carnitin improves endothelial disfunction and oxidative stress in Type 2 diabetic rats

    PubMed Central

    Salmanoglu, Derya Selcen; Gurpinar, Tugba; Vural, Kamil; Ekerbicer, Nuran; Darıverenli, Ertan; Var, Ahmet

    2016-01-01

    Vascular dysfunction is thought to play a major role in the development of diabetic cardiovascular disease. The roles of endothelial dysfunction, oxidative stress, and dyslipidemia will be considered. Melatonin as well as L-carnitine were shown to possess strong antioxidant properties. Diabetes induced with high fat diet (for 8 weeks) and multipl low doses intraperitoneal injection of STZ (twice, 30 mg/kg/d i.p). The diabetic animals were randomly assigned to one of the experimental groups as follows: Control group (C), high fat diet (HFD), STZ-induced diabetic group (HFD+STZ) , HFD+STZ diabetic group received melatonin (10 mg/kg/d i.p), HFD+STZ diabetic group received L-carnitine (0.6 g/kg/d i.p), and HFD+STZ diabetic group received glibenclamide (5 mg/kg/d, oral). The serum fasting blood glucose, insulin, total cholesterol, HDL- cholesterol, LDL-cholesterol, triglyceride and malondialdehyde (MDA) levels were tested. Acetylcholine induced endothelium-dependent relaxation and sodium nitroprusside induced endothelium-independent relaxation were measured in aortas for estimating endothelial function. Also, glutathione peroxidase (GPx), superoxide dismutase (SOD) and nitric oxide (NO) levels activities were determined in rat liver. According to our results melatonin and L-carnitine treatment decreased fasting blood glucose, total cholesterol, and LDL levels. MDA levels significantly decreased with the melatonin treatment whereas SOD levels were not significantly changed between the groups. The results suggest that especially melatonin restores the vascular responses and endothelial dysfunction in diabetes. PMID:26803481

  4. Pharmacological characterization of guanidinoethyldisulphide (GED), a novel inhibitor of nitric oxide synthase with selectivity towards the inducible isoform.

    PubMed Central

    Szabó, C.; Bryk, R.; Zingarelli, B.; Southan, G. J.; Gahman, T. C.; Bhat, V.; Salzman, A. L.; Wolff, D. J.

    1996-01-01

    1. Guanidines, amidines, S-alkylisothioureas, and recently, mercaptoalkylguanidines have been described as inhibitors of the generation of nitric oxide (NO) from L-arginine by NO synthases (NOS). We have recently demonstrated that guanidinoethyldisulphide (GED), formed from the dimerisation of mercaptoethylguanidine (MEG), is a novel inhibitor of nitric oxide synthases. Here we describe the pharmacological properties of GED on purified NOS isoforms, various cultured cell types, vascular ring preparations, and in endotoxin shock. 2. GED potently inhibited NOS activity of purified inducible NOS (iNOS), endothelial NOS (ecNOS), and brain NOS (bNOS) enzymes with Ki values of 4.3, 18 and 25 microM, respectively. Thus, GED has a 4 fold selectivity for iNOS over ecNOS at the enzyme level. The inhibitory effect of GED on ecNOS and iNOS was competitive vs. L-arginine and non-competitive vs. tetrahydrobiopterin. 3. Murine J774 macrophages, rat aortic smooth muscle cells, murine lung epithelial cells, and human intestinal DLD-1 cells were stimulated with appropriate mixtures of pro-inflammatory cytokines or bacterial lipopolysaccharide to express iNOS. In these cells, GED potently inhibited nitrite formation (EC50 values: 11, 9, 1 and 30 microM, respectively). This suggests that uptake of GED may be cell type and species-dependent. The inhibitory effect of GED on nitrite production was independent of whether GED was given together with immunostimulation or 6 h afterwards, indicating that GED does not interfere with the process of iNOS induction. 4. GED caused relaxations in the precontracted vascular ring preparations (EC50: 20 microM). Part of this relaxation was endothelium-dependent, but was not blocked by methylene blue (100 microM), an inhibitor of soluble guanylyl cyclase. In precontracted rings, GED enhanced the acetylcholine-induced, endothelium-dependent relaxations at 10 microM and caused a slight inhibition of the relaxations at 100 microM. The vascular studies

  5. Evidence of Incomplete Left Ventricular Relaxation in the Dog

    PubMed Central

    Weisfeldt, Myron L.; Frederiksen, James W.; Yin, Frank C. P.; Weiss, James L.

    1978-01-01

    Although it has been proposed that incomplete relaxation explains certain increases in left ventricular end diastolic pressure relative to volume, there has been no clear demonstration that incomplete relaxation occurs in the intact working ventricle. To identify incomplete relaxation, left ventricular pressure-dimension relationships were studied in 10 canine right heart bypass preparations during ventricular pacing. The fully relaxed, exponential diastolic pressure-dimension line for each ventricle was first determined from pressure and dimension values at the end of prolonged diastoles after interruption of pacing. For 167 beats during pacing under widely varying hemodynamic conditions, diastolic pressure-dimension values encountered this line defining the fully relaxed state during the filling period indicating that relaxation was complete before end diastole. The time constant for isovolumic exponential pressure fall (T) was determined for all beats. For this exponential function, if no diastolic filling occurred, 97% of pressure fall would be complete by 3.5 T after maximal negative dP/dt. For the 167 beats the fully relaxed pressure-dimension line was always encountered before 3.5 T. With very rapid pacing rates (170-200 beats/min) and(or) with pharmacologic prolongation of relaxation, incomplete relaxation occurred as evidenced by the fact that the line defining the fully relaxed state was never reached during diastole (n = 15). This evidence of incomplete relaxation occurred only when the subsequent beat began before 3.5 T but did not always occur under these conditions. Thus, an increase in end diastolic pressure relative to diastolic volume may result from incomplete relaxation under conditions of sufficiently rapid heart rate or sufficiently prolonged ventricular relaxation. Incomplete relaxation does not occur when the next beat begins more than 3.5 T after maximum negative dP/dt. PMID:748380

  6. High Relaxivity Gd(III)–DNA Gold Nanostars: Investigation of Shape Effects on Proton Relaxation

    PubMed Central

    Rotz, Matthew W.; Culver, Kayla S. B.; Parigi, Giacomo; MacRenaris, Keith W.; Luchinat, Claudio; Odom, Teri W.; Meade, Thomas J.

    2015-01-01

    Gadolinium(III) nanoconjugate contrast agents (CAs) have distinct advantages over their small-molecule counterparts in magnetic resonance imaging. In addition to increased Gd(III) payload, a significant improvement in proton relaxation efficiency, or relaxivity (r1), is often observed. In this work, we describe the synthesis and characterization of a nanoconjugate CA created by covalent attachment of Gd(III) to thiolated DNA (Gd(III)–DNA), followed by surface conjugation onto gold nanostars (DNA–Gd@stars). These conjugates exhibit remarkable r1 with values up to 98 mM−1 s−1. Additionally, DNA–Gd@stars show efficient Gd(III) delivery and biocompatibility in vitro and generate significant contrast enhancement when imaged at 7 T. Using nuclear magnetic relaxation dispersion analysis, we attribute the high performance of the DNA–Gd@stars to an increased contribution of second-sphere relaxivity compared to that of spherical CA equivalents (DNA–Gd@spheres). Importantly, the surface of the gold nanostar contains Gd(III)–DNA in regions of positive, negative, and neutral curvature. We hypothesize that the proton relaxation enhancement observed results from the presence of a unique hydrophilic environment produced by Gd(III)–DNA in these regions, which allows second-sphere water molecules to remain adjacent to Gd(III) ions for up to 10 times longer than diffusion. These results establish that particle shape and second-sphere relaxivity are important considerations in the design of Gd(III) nanoconjugate CAs. PMID:25723190

  7. The influence of the secondary relaxation processes on the structural relaxation in glass-forming materials

    NASA Astrophysics Data System (ADS)

    Khamzin, A. A.; Popov, I. I.; Nigmatullin, R. R.

    2013-06-01

    In the frame of fractional-kinetic approach, the model of the structural α-relaxation in the presence of the secondary β-relaxation processes is suggested. The model is based on the rigorous bond between β-processes with α-process and leads to the generalized and justified expression for the complex dielectric permittivity (CDP). It allows to form a new sight on the problem of the fitting of multi-peak structure of the dielectric loss spectra in glass-forming materials. The consistency of the CDP expressions obtained is based on a good fit of experimental data for binary methanol-water mixtures.

  8. The influence of the secondary relaxation processes on the structural relaxation in glass-forming materials.

    PubMed

    Khamzin, A A; Popov, I I; Nigmatullin, R R

    2013-06-28

    In the frame of fractional-kinetic approach, the model of the structural α-relaxation in the presence of the secondary β-relaxation processes is suggested. The model is based on the rigorous bond between β-processes with α-process and leads to the generalized and justified expression for the complex dielectric permittivity (CDP). It allows to form a new sight on the problem of the fitting of multi-peak structure of the dielectric loss spectra in glass-forming materials. The consistency of the CDP expressions obtained is based on a good fit of experimental data for binary methanol-water mixtures. PMID:23822251

  9. Abnormal right ventricular relaxation in pulmonary hypertension

    PubMed Central

    La Gerche, Andre; Roberts, Timothy J.; Prior, David L.; MacIsaac, Andrew I.; Burns, Andrew T.

    2015-01-01

    Abstract Left ventricular diastolic dysfunction is a well-described complication of systemic hypertension. However, less is known regarding the effect of chronic pressure overload on right ventricular (RV) diastolic function. We hypothesized that pulmonary hypertension (PHT) is associated with abnormal RV early relaxation and that this would be best shown by invasive pressure measurement. Twenty-five patients undergoing right heart catheterization for investigation of breathlessness and/or suspected PHT were studied. In addition to standard measurements, RV pressure was sampled with a high-fidelity micromanometer, and RV pressure/time curves were analyzed. Patients were divided into a PHT group and a non-PHT group on the basis of a derived mean pulmonary artery systolic pressure of 25 mmHg. Eleven patients were classified to the PHT group. This group had significantly higher RV minimum diastolic pressure ( vs. mmHg, ) and RV end-diastolic pressure (RVEDP; vs. mmHg, ), and RV τ was significantly prolonged ( vs. ms, ). There were strong correlations between RV τ and RV minimum diastolic pressure (, ) and between RV τ and RVEDP (, ). There was a trend toward increased RV contractility (end-systolic elastance) in the PHT group ( vs. mmHg/mL, ) and a correlation between RV systolic pressure and first derivative of maximum pressure change (, ). Stroke volumes were similar. Invasive measures of RV early relaxation are abnormal in patients with PHT, whereas measured contractility is static or increasing, which suggests that diastolic dysfunction may precede systolic dysfunction. Furthermore, there is a strong association between measures of RV relaxation and RV filling pressures. PMID:26064464

  10. Collisional relaxation in a nonintegrable potential

    NASA Astrophysics Data System (ADS)

    Kandrup, H. E.; Willmes, D. E.

    1994-03-01

    In galactic dynamics, a test star is assumed typically to follow a smooth trajectory in some slowly varying mean field potential and, in addition, to be subjected to 'random' close encounters with neighboring field stars which are modeled essentially as a Brownian process. With the noteable exception of Pfenniger (1986), most analyses of the collisonal relaxation induced by these close encounters have assumed that the effects of the mean field may be ignored completely, and that it suffices to consider Brownian particles moving in the absence of any systematic potential. The idealization of zero potential is problematic, as is any integrable potential in which all the mean field orbits are stable. For this reason, the paradigm of Brownian motion is reexamined here, allowing for a time-dependent, non-integrable potential, in which some subset of the mean field trajectories correspond to exponentially unstable orbits with positive Liapounov exponent. A nontrivial deterministic equation of motion is convereted into a stochastic differential equation incorporating dynamical friction and delta-correlated white noise, related via a fluctuation-dissipation theorem, and the effects of the friction and noise are analyzed perturbatively. The principal conclusion is that a coupling to a nonintegrable background potential can decrease by orders of magnitude the time scale on which noise and friction modify positions and velocities along an unperturbed, deterministic trajectory. Specifically, one finds that, even in the weak noise limit, perturbations in position and velocity grow exponentially on a time scale tlambda determined by the Liapounov exponent, although, for a strictly time-dependent potential, perturbations in energy and other collisionless invariants will only grow on a much longer relaxation time tr. Some potential implications of this accelerated collisional relaxation are discussed.

  11. Spin-lattice and spin-spin relaxation in porous media: A generalized two site relaxation model

    SciTech Connect

    Su, M.Y.; Nalcioglu, O. . Dept. of Radiological Sciences)

    1993-10-15

    The T[sub 1] and T[sub 2] relaxation times in porous media have been greatly used in the field of petrophysics and biology. The relaxation behavior can be used as a fingerprint of a system, or can provide information on some other parameters which cannot be easily measured. In this paper, the authors investigate the behavior of the T[sub 1] and T[sub 2] relaxation in two types of media, (1) an object consisting of closely packed glass beads and (2) a column of gel beads. They assume a generalized two site relaxation process for both of the objects. This model assumes that the spins in the medium are under two different relaxation modes and the two modes are in fast exchange with each other. The results confirm that the generalized two site relaxation model is applicable for both types of porous media. A possible explanation for the relaxation mechanism is also discussed.

  12. Idiosyncratic reality claims, relaxation dispositions, and ABC relaxation theory: happiness, literal christianity, miraculous powers, metaphysics, and the paranormal.

    PubMed

    Smith, Jonathan C; Karmin, Aaron D

    2002-12-01

    This study examined idiosyncratic reality claims, that is, irrational or paranormal beliefs often claimed to enhance relaxation and happiness and reduce stress. The Smith Idiosyncratic Reality Claims Inventory and the Smith Relaxation Dispositions Inventory (which measures relaxation and stress dispositions, or enduring states of mind frequently associated with relaxation or stress) were given to 310 junior college student volunteers. Principal components factor analysis with varimax rotation identified five idiosyncratic reality claim factors: belief in Literal Christianity; Magic; Space Aliens: After Death experiences; and Miraculous Powers of Meditation, Prayer, and Belief. No factor correlated with increased relaxation dispositions Peace, Energy, or Joy, or reduced dispositional somatic stress, worry, or negative emotion on the Smith Relaxation Dispositions Inventory. It was concluded that idiosyncratic reality claims may not be associated with reported relaxation, happiness, or stress. In contrast, previous research strongly supported self-affirming beliefs with few paranormal assumptions display such an association. PMID:12578252

  13. Relaxation dynamics in correlated quantum dots

    SciTech Connect

    Andergassen, S.; Schuricht, D.; Pletyukhov, M.; Schoeller, H.

    2014-12-04

    We study quantum many-body effects on the real-time evolution of the current through quantum dots. By using a non-equilibrium renormalization group approach, we provide analytic results for the relaxation dynamics into the stationary state and identify the microscopic cutoff scales that determine the transport rates. We find rich non-equilibrium physics induced by the interplay of the different energy scales. While the short-time limit is governed by universal dynamics, the long-time behavior features characteristic oscillations as well as an interplay of exponential and power-law decay.

  14. Oxygen-induced relaxation of Ni(111)

    NASA Astrophysics Data System (ADS)

    Caputi, L. S.; Jiang, S. L.; Tucci, R.; Amoddeo, A.; Papagno, L.

    1989-04-01

    The electron energy loss fine structures technique has been used to study the local coordination around surface nickel atoms on the Ni(111) face. clean and in the presence of a p(2×2) oxygen overlayer. The surface sensitivity of the technique has been enhanced by using a glancing primary electron beam. Comparison of the radial distribution functions obtained on the clean and oxygen-covered surface shows evidence of an oxygen-induced relaxation, in agreement with the results obtained by Narusawa et al. using high energy He + ion scattering.

  15. Dipole relaxation in an electric field

    NASA Astrophysics Data System (ADS)

    Neumann, Richard M.

    1980-07-01

    From Boltzmann's equation, S=k lnΩ, an expression for the orientational entropy, S of a rigid rod (electric dipole) is derived. The free energy of the dipole in an electric field is then calculated as a function of both the dipole's average orientation and the field strength. Application of the equilibrium criterion to the free energy yields the field dependence of the entropy of the dipole. Irreversible thermodynamics is used to derive the general form of the equation of motion of the dipole's average orientation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium.

  16. Relaxation properties of weakly coupled classical systems

    SciTech Connect

    Romero-Rochin, V.; Oppenheim, I.

    1988-10-01

    The relaxation properties of a small classical system weakly coupled to a large classical system which acts as a heat bath are described using a generalized Fokker-Planck equation. The Fokker-Planck equation is derived in general using a modification of the elimination of fast variables techniques previously described. The specific example in which the small system is a harmonic oscillator linearly coupled to the heat bath is treated in detail and it is demonstrated that there is a dynamic frequency shift as well as a statistical shift of the oscillator frequency.

  17. Compatible Relaxation and Coarsening in Algebraic Multigrid

    SciTech Connect

    Brannick, J J; Falgout, R D

    2009-09-22

    We introduce a coarsening algorithm for algebraic multigrid (AMG) based on the concept of compatible relaxation (CR). The algorithm is significantly different from standard methods, most notably because it does not rely on any notion of strength of connection. We study its behavior on a number of model problems, and evaluate the performance of an AMG algorithm that incorporates the coarsening approach. Lastly, we introduce a variant of CR that provides a sharper metric of coarse-grid quality and demonstrate its potential with two simple examples.

  18. Slow relaxation in structure-forming ferrofluids

    NASA Astrophysics Data System (ADS)

    Sreekumari, Aparna; Ilg, Patrick

    2013-10-01

    We study the behavior of colloidal magnetic fluids at low density for various dipolar interaction strengths by performing extensive Langevin dynamics simulations with model parameters that mimic cobalt-based ferrofluids used in experiments. Our study mainly focuses on the structural and dynamical properties of dipolar fluids and the influence of structural changes on their dynamics. Drastic changes from chainlike to networklike structures in the absence of an external magnetic field are observed. This crossover plays an important role in the slowing down of dynamics that is reflected in various dynamical properties including the tracer diffusion and the viscosity and also in the structural relaxation.

  19. Structural relaxation of amorphous silicon carbide.

    PubMed

    Ishimaru, Manabu; Bae, In-Tae; Hirotsu, Yoshihiko; Matsumura, Syo; Sickafus, Kurt E

    2002-07-29

    We have examined amorphous structures of silicon carbide (SiC) using both transmission electron microscopy and a molecular-dynamics approach. Radial distribution functions revealed that amorphous SiC contains not only heteronuclear (Si-C) bonds but also homonuclear (Si-Si and C-C) bonds. The ratio of heteronuclear to homonuclear bonds was found to change upon annealing, suggesting that structural relaxation of the amorphous SiC occurred. Good agreement was obtained between the simulated and experimentally measured radial distribution functions. PMID:12144449

  20. Slow relaxation in structure-forming ferrofluids.

    PubMed

    Sreekumari, Aparna; Ilg, Patrick

    2013-10-01

    We study the behavior of colloidal magnetic fluids at low density for various dipolar interaction strengths by performing extensive Langevin dynamics simulations with model parameters that mimic cobalt-based ferrofluids used in experiments. Our study mainly focuses on the structural and dynamical properties of dipolar fluids and the influence of structural changes on their dynamics. Drastic changes from chainlike to networklike structures in the absence of an external magnetic field are observed. This crossover plays an important role in the slowing down of dynamics that is reflected in various dynamical properties including the tracer diffusion and the viscosity and also in the structural relaxation. PMID:24229180

  1. Dielectric relaxations investigation of a synthesized epoxy resin polymer

    NASA Astrophysics Data System (ADS)

    Jilani, Wissal; Mzabi, Nissaf; Gallot-Lavallée, Olivier; Fourati, Najla; Zerrouki, Chouki; Zerrouki, Rachida; Guermazi, Hajer

    2015-04-01

    A diglycidylether of bisphenol A (DGEBA) epoxy resin was synthesized, and cured with 3,3'-diaminodiphenyl sulfone (DDS) at a curing temperature of 120 °C. The relaxation properties of the realized polymers were studied by two complementary techniques: dielectric relaxation spectroscopy (DRS), in the temperature range 173-393K and in the frequency interval 10-1-106 Hz, and thermally stimulated depolarization current (TSDC) with a windowing polarization process. Current-voltage (I-V) measurements were also carried out to study interfacial relaxations. Dielectric data were analyzed in terms of permittivity and electric modulus variations. Three relaxation processes ( γ, β and α) have been identified. They were found to be frequency and temperature dependent and were interpreted in terms of the Havriliak-Negami approach. Relaxation parameters were determined by fitting the experimental data. The temperature dependence of the relaxation time was well fitted by the Arrhenius law for secondary relaxations, while the Vogel-Fulcher-Tamann model was found to better fit the τ( T) variations for α relaxation. We found τ 0 = 4.9 10-12 s, 9.6 10-13 s and 1.98 10-7 s for γ, β and α relaxations, respectively. The obtained results were found to be consistent with those reported in the literature. Due to the calculation of the low-frequency data of dielectric loss by the Hamon approximation, the Maxwell-Wagner-Sillars (MWS) relaxation was highlighted.

  2. Paramagnetic relaxation of long-lived coherences in solution NMR.

    PubMed

    Singh, Maninder; Srinivas, Chinthalapalli; Deb, Mayukh; Kurur, Narayanan D

    2013-12-01

    Long-lived coherences (LLCs) are known to have lifetimes much longer than transverse magnetization or single quantum coherences (SQCs). The effect of paramagnetic ions on the relaxation of LLCs is not known. This is particularly important, as LLCs have potential applications in various fields like analytical NMR, in vivo NMR and MR imaging methods. We study here the behaviour of LLCs in the presence of paramagnetic relaxation agents. The stepwise increase in the concentration of the metal ion is followed by measuring various relaxation rates. The effect of paramagnetic ions is analysed in terms of the external random field's contribution to the relaxation of two coupled protons in 2,3,6-trichlorobenzaldehyde. The LLCs relax faster than ordinary SQCs in the presence of paramagnetic ions of varying character. This is explained on the basis of an increase in the contribution of the external random field to relaxation due to a paramagnetic relaxation mechanism. Comparison is also made with ordinary Zeeman relaxation rates like R1, R2, R1ρ and also with rate of relaxation of long-lived states RLLS which are known to be less sensitive to paramagnetically induced relaxation. Also, the extent of correlation of random fields at two proton sites is studied and is found to be strongly correlated with each other. The obtained correlation constant is found to be independent of the nature of added paramagnetic impurities. PMID:24151221

  3. Relaxing effect of rose oil on humans.

    PubMed

    Hongratanaworakit, Tapanee

    2009-02-01

    One increasingly popular type of alternative therapy is aromatherapy, but scientific validation in this field is still rare. The aim of this study was to investigate the effect of rose oil (Rosa damascena Mill, Rosaceae) on human autonomic parameters and emotional responses in healthy subjects after transdermal absorption. In order to exclude any olfactory stimulation the inhalation of the fragrances was prevented by breathing masks. Forty healthy volunteers participated in the experiments. Five autonomic parameters, i.e. blood pressure, breathing rate, blood oxygen saturation, pulse rate, and skin temperature, were recorded. Emotional responses were assessed by means of rating scales. Compared to placebo, rose oil caused significant decreases of breathing rate, blood oxygen saturation and systolic blood pressure, which indicate a decrease of autonomic arousal. At the emotional level, subjects in the rose oil group rated themselves as more calm, more relaxed and less alert than subjects in the control group. These findings are likely to represent a relaxing effect of the rose oil and provide some evidence for the use of rose oil in aromatherapy, such as causing relief of depression and stress in humans. PMID:19370942

  4. Relaxation measurements on the acetylcholine receptor.

    PubMed Central

    Sheridan, R E; Lester, H A

    1975-01-01

    In Electrophorus electroplaques, the agonist-induced postsynaptic conductance depends on membrane potential. During steady exposure to agonists, after a voltage step the conductance relaxes on a millisecond time scale, exponentially approaching a new equilibrium value. The relaxation rate constant k is an instantaneous function of voltage, insensitive to the past or present conductance. Two components sum to form k. A concentration-sensitive component increases linearly with agonist concentration and decreases during desensitization or exposure to curare. Thus this component reflects the average frequency at which acetylcholine receptors are opening. The voltage-sensitive component, obtained by extrapolating k to zero agonist concentration, increases at more positive potentials. For acetylcholine, the voltage-sensitive component equals the rate constant for the exponential decay of postsynaptic currents; it thus seems to be the closing rate for active receptors. The voltage-sensitive component has the relative amplitudes acetylcholine less than carbamoylcholine less than decamethonium, and for each agonist equals the closing rate determined from "noise" measurements at neuromuscular junctions. The kinetic data explain several aspects of the steady-state conductance induced by agonists, but shed no light on apparent cooperative effects. PMID:1059136

  5. Dynamic Relaxational Behaviour of Hyperbranched Polyether Polyols

    NASA Astrophysics Data System (ADS)

    Navarro-Gorris, A.; Garcia-Bernabé, A.; Stiriba, S.-E.

    2008-08-01

    Hyperbranched polymers are highly cascade branched polymers easily accessible via one-pot procedure from ABm type monomers. A key property of hyperbranched polymers is their molecular architecture, which allows core-shell morphology to be manipulated for further specific applications in material and medical sciences. Since the discovery of hyperbranched polymer materials, an increasing number of reports have been published describing synthetic procedures and technological applications of such materials, but their physical properties have remained less studied until the last decade. In the present work, different esterified hyperbranched polyglycerols have been prepared starting from polyglycerol precursors in presence of acetic acid, thus generating functionalization degree with range from 0 to 94%. Thermal analysis of the obtained samples has been studied by Differential Scanning Calorimetry (DSC). Dielectric Spectroscopy measurements have been analyzed by combining loss spectra deconvolution with the modulus formalism. In this regard, all acetylated polyglycerols exhibited a main relaxation related to the glass transition (α process) and two sub-glassy relaxations (β and γ processes) which vanish at high functionalization degrees.

  6. Relaxation behavior of oxygen deficient strontium manganite

    SciTech Connect

    Pandey, Namita Thakur, Awalendra Kumar

    2014-04-24

    Conduction behavior of nanocrystalline oxygen deficient ceramic-SrMnO{sub 3–δ}(δ∼0.14) has been studied. The structural analysis of nano-SrMnO{sub 2.86} follows hexagonal unit cell structure with P6{sub 3}/mmc (194) space group belonging to 6/mmm point group with 4H – layered type hexagonal-cubic layers. The system have lattice parameters; a = 5.437(92) Å, c = 9.072(92) Å, c/a∼1.66 (85) with α =90° γ= 120° and cell volume, V= 232.35(18). The relaxation times estimated from complex impedance and modulus relaxation spectrum, show the thermally activated system with corresponding activation energies as 0.66 eV and 0.51 eV The stretching factor ‘β’ from the scaled modulus spectrum shows the poly-dispersive non-Debye nature of the system. The hopping number ‘n’ shows the influence of ionic charge carriers which controls the conduction mechanism of nano-SrMnO{sub 2.86}.

  7. Dielectric relaxation of CdO nanoparticles

    NASA Astrophysics Data System (ADS)

    Tripathi, Ramna; Dutta, Alo; Das, Sayantani; Kumar, Akhilesh; Sinha, T. P.

    2016-02-01

    Nanoparticles of cadmium oxide have been synthesized by soft chemical route using thioglycerol as the capping agent. The crystallite size is determined by X-ray diffraction technique and the particle size is obtained by transmission electron microscope. The band gap of the material is obtained using Tauc relation to UV-visible absorption spectrum. The photoluminescence emission spectra of the sample are measured at various excitation wavelengths. The molecular components in the material have been analyzed by FT-IR spectroscopy. The dielectric dispersion of the material is investigated in the temperature range from 313 to 393 K and in the frequency range from 100 Hz to 1 MHz by impedance spectroscopy. The Cole-Cole model is used to describe the dielectric relaxation of the system. The scaling behavior of imaginary part of impedance shows that the relaxation describes the same mechanism at various temperatures. The frequency-dependent electrical data are also analyzed in the framework of conductivity and electrical modulus formalisms. The frequency-dependent conductivity spectra are found to obey the power law.

  8. Relaxation in glassforming liquids and amorphous solids

    SciTech Connect

    Angell, C. A.; Ngai, K. L.; McKenna, G. B.; McMillan, P. F.; Martin, S. W.

    2000-09-15

    The field of viscous liquid and glassy solid dynamics is reviewed by a process of posing the key questions that need to be answered, and then providing the best answers available to the authors and their advisors at this time. The subject is divided into four parts, three of them dealing with behavior in different domains of temperature with respect to the glass transition temperature, T{sub g}, and a fourth dealing with ''short time processes.'' The first part tackles the high temperature regime T>T{sub g}, in which the system is ergodic and the evolution of the viscous liquid toward the condition at T{sub g} is in focus. The second part deals with the regime T{approx}T{sub g}, where the system is nonergodic except for very long annealing times, hence has time-dependent properties (aging and annealing). The third part discusses behavior when the system is completely frozen with respect to the primary relaxation process but in which secondary processes, particularly those responsible for ''superionic'' conductivity, and dopart mobility in amorphous silicon, remain active. In the fourth part we focus on the behavior of the system at the crossover between the low frequency vibrational components of the molecular motion and its high frequency relaxational components, paying particular attention to very recent developments in the short time dielectric response and the high Q mechanical response. (c) 2000 American Institute of Physics.

  9. A simple holographic superconductor with momentum relaxation

    NASA Astrophysics Data System (ADS)

    Kim, Keun-Young; Kim, Kyung Kiu; Park, Miok

    2015-04-01

    We study a holographic superconductor model with momentum relaxation due to massless scalar fields linear to spatial coordinates( ψ I = βδ Ii x i ), where β is the strength of momentum relaxation. In addition to the original superconductor induced by the chemical potential( μ) at β = 0, there exists a new type of superconductor induced by β even at μ = 0. It may imply a new `pairing' mechanism of particles and antiparticles interacting with β, which may be interpreted as `impurity'. Two parameters μ and β compete in forming superconducting phase. As a result, the critical temperature behaves differently depending on β/μ. It decreases when β/μ is small and increases when β/μ is large, which is a novel feature compared to other models. After analysing ground states and phase diagrams for various β/μ, we study optical electric( σ), thermoelectric( α), and thermal() conductivities. When the system undergoes a phase transition from normal to a superconducting phase, 1 /ω pole appears in the imaginary part of the electric conductivity, implying infinite DC conductivity. If β/μ < 1, at small ω, a two-fluid model with an imaginary 1 /ω pole and the Drude peak works for σ, α, and , but If β/μ > 1 a non-Drude peak replaces the Drude peak. It is consistent with the coherent/incoherent metal transition in its metal phase. The Ferrell-Glover-Tinkham (FGT) sum rule is satisfied for all cases even when μ = 0.

  10. Random template banks and relaxed lattice coverings

    SciTech Connect

    Messenger, C.; Prix, R.; Papa, M. A.

    2009-05-15

    Template-based searches for gravitational waves are often limited by the computational cost associated with searching large parameter spaces. The study of efficient template banks, in the sense of using the smallest number of templates, is therefore of great practical interest. The traditional approach to template-bank construction requires every point in parameter space to be covered by at least one template, which rapidly becomes inefficient at higher dimensions. Here we study an alternative approach, where any point in parameter space is covered only with a given probability {eta}<1. We find that by giving up complete coverage in this way, large reductions in the number of templates are possible, especially at higher dimensions. The prime examples studied here are random template banks in which templates are placed randomly with uniform probability over the parameter space. In addition to its obvious simplicity, this method turns out to be surprisingly efficient. We analyze the statistical properties of such random template banks, and compare their efficiency to traditional lattice coverings. We further study relaxed lattice coverings (using Z{sub n} and A{sub n}* lattices), which similarly cover any signal location only with probability {eta}. The relaxed A{sub n}* lattice is found to yield the most efficient template banks at low dimensions (n < or approx. 10), while random template banks increasingly outperform any other method at higher dimensions.

  11. Facioscapulohumeral muscular dystrophy: consequences of chromatin relaxation

    PubMed Central

    van der Maarel, Silvère M.; Miller, Daniel G.; Tawil, Rabi; Filippova, Galina N.; Tapscott, Stephen J.

    2013-01-01

    Purpose of review In recent years we have seen remarkable progress in our understanding of the disease mechanism underlying facioscapulohumeral muscular dystrophy (FSHD). The purpose of this review is to provide a comprehensive overview of our current understanding of the disease mechanism and to discuss the observations supporting the possibility of a developmental defect in this disorder. Recent findings In the majority of cases FSHD is caused by contraction of the D4Z4 repeat array (FSHD1). This results in local chromatin relaxation and stable expression of the DUX4 retrogene in skeletal muscle, but only when a polymorphic DUX4 polyadenylation signal is present. In some cases (FSHD2), D4Z4 chromatin relaxation and stable DUX4 expression occurs in the absence of D4Z4 array contraction. DUX4 is a germline transcription factor and its expression in skeletal muscle leads to activation of early stem cell and germline programs and transcriptional activation of retroelements. Summary Recent studies have provided a plausible disease mechanism for FSHD where FSHD results from inappropriate expression of the germline transcription factor DUX4. The genes regulated by DUX4 suggest several mechanisms of muscle damage, and provide potential biomarkers and therapeutic targets that should be investigated in future studies. PMID:22892954

  12. The in vivo relaxivity of MRI contrast agents

    NASA Astrophysics Data System (ADS)

    Shuter, Borys

    1999-11-01

    Post-contrast clinical 1H Magnetic Resonance Images have to date been interpreted with little regard for possible variations in the in-vivo properties of injected magnetic pharmaceuticals (contrast agents), particularly in their relaxivity or ability to alter tissue relaxation rates, T2-1 and T 2-1, per unit concentration. The relaxivities of contrast agents have only rarely been measured in-vivo, measurements usually being performed on excised tissues and at magnetic field strengths lower than used in clinical practice. Some researchers have simply assumed that relaxivities determined in homogeneous tissue phantoms were applicable in-vivo. In this thesis, the relaxivities of two contrast agents, Gd-DTPA and Gd-EOB-DTPA, were measured in simple tissue phantoms and in the kidney and liver of intact, but sacrificed, Wistar rats using a clinical MR scanner with a magnetic field of 1.5 Tesla. T1 and T2 were determined from sets of images acquired using a standard clinical spin-echo pulse sequence. The contrast agent concentration in tissue was assessed by radioassay of 153Gd-DTPA or 153Gd-EOB-DTPA, mixed with the normal compound prior to injection. Relaxivity was taken as the slope of a linear regression fit of relaxation rate against Gd concentration. The relaxivities of Gd-EOB-DTPA were similarly determined in normal and biliary- obstructed guinea pigs. Relaxivities in tissue differed significantly from values obtained in simple phantoms. Kidney T1 relaxivity was reduced for both compounds in normal animals. Three days or more of biliary obstruction produced further reductions in kidney T1 relaxivity of Gd-EOB-DTPA, providing strong evidence that disease affects contrast agent relaxivity. Kidney T2 relaxivity was much greater than T1 relaxivity and was also depressed by biliary obstruction. Liver T1 and T 2 relaxivites were increased above phantom values, but were not affected by the biliary obstruction. Water compartmentalisation, macromolecular binding, proton

  13. Rotational stretched exponential relaxation in random trap-barrier model

    NASA Astrophysics Data System (ADS)

    Aydiner, Ekrem

    2015-07-01

    The relaxation behavior of complex-disordered systems, such as spin glasses, polymers, colloidal suspensions, structural glasses,and granular media, has not been clarified. Theoretical studies show that relaxation in these systems has a topological origin. In this paper, we focus on the rotational stretched exponential relaxation behavior in complex-disordered systems and introduce a simple phase space model to understand the mechanism of the non-exponential relaxation of these systems. By employing the Monte Carlo simulation method to the model, we obtain the rotational relaxation function as a function of temperature. We show that the relaxation function has a stretched exponential form under the critical temperature while it obeys the Debye law above the critical temperature. Project supported by Istanbul University (Grant Nos. 28432 and 45662).

  14. Dielectric Relaxation and Rheological Behavior of Supramolecular Polymeric Liquid

    SciTech Connect

    Lou, Nan; Wang, Yangyang; Li, Xiaopeng; Li, Haixia; Wang, Ping

    2013-01-01

    A model self-complementary supramolecular polymer based on thymine and diamidopyridine triple hydrogen-bonding motifs has been synthesized, and its dielectric and rheological behavior has been investigated. The formation of supramolecular polymers has been unequivocally demonstrated by nuclear magnetic resonance, electrospray ionization mass spectrometry with traveling wave ion mobility separation, dielectric spectroscopy, and rheology. The dynamical behaviors of this associating polymer generally conform to those of type-A polymers, with a low-frequency chain relaxation and a high-frequency relaxation visible in both rheological and dielectric measurements. The dielectric chain relaxation shows the ideal symmetric Debye-like shape, resembling the peculiar features of hydrogen-bonding monoalcohols. Detailed analysis shows that there exists a weak decoupling between the mechanical terminal relaxation and dielectric Debye-like relaxation. The origin of the Debye-like dielectric relaxation is further discussed in the light of monoalcohols.

  15. Multilayer Relaxation and Surface Energies of Metallic Surfaces

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Rodriguez, Agustin M.; Ferrante, John

    1994-01-01

    The perpendicular and parallel multilayer relaxations of fcc (210) surfaces are studied using equivalent crystal theory (ECT). A comparison with experimental and theoretical results is made for AI(210). The effect of uncertainties in the input parameters on the magnitudes and ordering of surface relaxations for this semiempirical method is estimated. A new measure of surface roughness is proposed. Predictions for the multilayer relaxations and surface energies of the (210) face of Cu and Ni are also included.

  16. Anomalous rotational relaxation: a fractional Fokker-Planck equation approach.

    PubMed

    Aydiner, Ekrem

    2005-04-01

    In this study we have analytically obtained the relaxation function in terms of rotational correlation functions based on Brownian motion for complex disordered systems in a stochastic framework. We found out that the rotational relaxation function has a fractional form for complex disordered systems, which indicates that relaxation has nonexponential character and obeys the Kohlrausch-William-Watts law, following the Mittag-Leffler decay. PMID:15903722

  17. Methodologic aspects of acetylcholine-evoked relaxation of rabbit aorta.

    PubMed

    Hansen, K; Nedergaard, O A

    1999-08-01

    The acetylcholine-evoked relaxation of rabbit isolated thoracic aorta precontracted by phenylephrine was studied. Phenylephrine caused a steady contraction that was maintained for 6 h. In the presence of calcium disodium ethylenediaminetetraacetate (EDTA) and ascorbic acid the contraction decreased with time. N(G)-Nitro-L-arginine abolished the inhibitory effect of EDTA and ascorbic acid. Acetylcholine evoked a rapid concentration-dependent relaxation that recovered spontaneously and slowly, but fully, with time. Relaxation evoked by equieffective concentrations of carbachol and acetylcholine had the same time course. Cumulative addition of acetylcholine (10(-7)-3 x 10(-5) M) caused a marked relaxation that was reverted slightly at high concentrations. The relaxation was the same with rings derived from the upper, middle, and lower part of the thoracic aorta. Two consecutive concentration-response curves for acetylcholine obtained at a 2-h interval demonstrated a slight development of tachyphylaxis. The relaxation was inversely related to precontractile tension evoked by phenylephrine when expressed as a percentage, but independent when expressed as g tension. Storage of aorta in cold salt solution for 24 h did not alter the relaxation. EDTA and ascorbic acid did not alter the relaxation. It is concluded that (1) EDTA and ascorbic acid can not be used with impunity to stabilize catecholamines used as preconstriction agents; (2) the reversal of the acetylcholine-evoked relaxation is not due to hydrolysis of acetylcholine; (3) the relaxation is uniform in all segments of thoracic aorta; (4) cold storage of aorta does not alter the relaxation; and (5) acetylcholine releases the same amount of relaxing factor, irrespective of the precontractile tension. PMID:10691020

  18. Sub-Tg relaxations in heavy metal fluoride glasses

    NASA Astrophysics Data System (ADS)

    Moynihan, C. T.; Opalka, S. M.; Mossadegh, R.; Crichton, S. N.; Bruce, A. J.

    Structural relaxation studies during annealing of a series of ZrF4-based glasses below the glass transition temperature have been carried out. Indications are that no property changes due to structural relaxation are likely to occur at ambient temperature over periods of tens of years. Some of the lower Tg glasses, however, did exhibit detectable structural relaxation on annealing at temperatures as low as 100°C over roughly a one year time period.

  19. Electrical Relaxation in ULTEM® and ULTEM® Containing Mesoporous Silica

    NASA Astrophysics Data System (ADS)

    Turo, Andrew; Edmondson, Charles E.; Lomax, Joseph F.; Bendler, John T.; Fontanella, John J.; Wintersgill, Mary C.

    2008-08-01

    Mesoporous silica has been added to Ultem® 1000 polyetherimide using solution casting. The mesoporous silica that was added was either uncoated or coated with polystyrene. Audio frequency dielectric relaxation studies were then carried out over the temperature range 5.5 to 550 K. Several interesting results were obtained. First, the uncoated mesoporous silica caused essentially no change in the relaxation spectrum of pure Ultem®. The polystyrene coated mesoporous silica caused rather large changes. The most striking example is the introduction of a new relaxation. This relaxation occurs at about 150 K and 1000 Hz as showing in fig. 1 via the open circles.

  20. Torsional mode relaxation of DABCO in a seeded supersonic beam

    NASA Astrophysics Data System (ADS)

    Wang, Z. W.; Quesada, M. A.; Parker, D. H.

    1987-10-01

    DABCO's ν 13 torsional mode relaxation is monitored in a helium-DABCO and argon-DABCO supersonic jet under low expansion conditions. Both cw and pulsed nozzles are employed. Modeling of the relaxation using the linear Landau-Teller relaxation equation is undertaken with various attempts to incorporate the effects of velocity slip. The relaxation rate is found to be independent of slip and the cross section dependent on the inverse of translational temperature. A V → R process is suggested as the rate determining mechanism.

  1. Ultra-Slow Dielectric Relaxation Process in Polyols

    NASA Astrophysics Data System (ADS)

    Yomogida, Yoshiki; Minoguchi, Ayumi; Nozaki, Ryusuke

    2004-04-01

    Dielectric relaxation processes with relaxation times larger than that for the structural α process are reported for glycerol, xylitol, sorbitol and their mixtures for the first time. Appearance of this ultra-slow process depends on cooling rate. More rapid cooling gives larger dielectric relaxation strength. However, relaxation time is not affected by cooling rate and shows non-Arrhenius temperature dependence with correlation to the α process. It can be considered that non-equilibrium dynamic structure causes the ultra-slow process. Scale of such structure would be much larger than that of the region for the cooperative molecular orientations for the α process.

  2. Temperature relaxation in supernova remnants, revisited

    NASA Technical Reports Server (NTRS)

    Itoh, H.

    1984-01-01

    Some supernova remnants are expanding into a partially neutral medium. The neutral atoms which are engulfed by the fast blast shock are collisionally ionized to eject low-energy secondary electrons. Calculations are conducted of the temperature relaxation through Coulomb collisions among the secondary electrons, the shocked electrons, and the ions, assuming that the three species have Maxwellian velocity distributions. The results are applied to a self-similar blast wave. If the efficiency of collisionless electron heating at the shock front is high in young remnants such as Tycho, the secondary electrons may be much cooler than both the shocked electrons and the ions. In this case, the emergent X-ray continuum spectrum will have a two-temperature, or a power-law, appearance. This effect may have been observed in the bright rim of the remnant of SN 1006.

  3. Dielectric Relaxation of Molecular Dipolar Rotors

    NASA Astrophysics Data System (ADS)

    Clarke, L.; Horansky, R.; Hinderer, T.; Price, J.; Nunez, J.; Khuong, T.; Garcia-Garibay, M.; Horinek, D.; Kottas, G.; Varaska, N.; Magnera, T.; Michl, J.

    2003-03-01

    Molecular rotors, molecules with a rotational degree of freedom about a single bond, are a fundamental element of nanoscale machinery. We study dipolar rotors arranged into either three-dimensional crystalline arrays or surface mounted to form two-dimensional films. Through dielectric relaxation experiments, we probe fundamental rotor attributes such as torsional barriers, polarization, and dipole-dipole interactions. We have measured the dielectric response of chloromethylsilyl rotors, surface mounted on fused silica, at frequencies in the kHz range and temperatures from 4 to 300 K, and find an inhomogeneous system, where the intrinsic barrier to rotation in the vapor phase has been modified by surface interactions. Using computer simulations, we have studied both thermally activated and driven rotors. We discuss work towards experimental realization of more homogeneous systems.

  4. Universal stretched exponential relaxation in nanoconfined water

    NASA Astrophysics Data System (ADS)

    Shekhar, Adarsh; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Alm, Camilla K.; Malthe-Sørenssen, Anders

    2014-10-01

    Understanding the behavior of water confined at the nanometer scale is a fundamental problem not only in physics but also in life sciences, geosciences, and atmospheric sciences. Here, we examine spatial and dynamic heterogeneities in water confined in nanoporous silica using molecular dynamics (MD) simulations. The simulations reveal intermixed low-density water and high-density water with distinct local structures in nanopores of silica. The MD simulations also show dynamic heterogeneities in nanoconfined water. The temporal decay of cage correlation functions for room temperature and supercooled, nanoconfined water is very well described by stretched exponential relaxation, exp(-(t/τ)β). The exponent β has a unique value, d/(d + 2), which agrees with an exact result for diffusion in systems with static, random traps in d = 3 dimensions.

  5. Dielectric relaxation in proteins: the computational perspective.

    PubMed

    Simonson, Thomas

    2008-07-01

    In photoexcitation and electron transfer, a new dipole or charge is introduced, and the structure is adjusted. This adjustment represents dielectric relaxation, which is the focus of this review. We concentrate on a few selected topics. We discuss linear response theory, as a unifying framework and a tool to describe non-equilibrium states. We review recent, molecular dynamics simulation studies that illustrate the calculation of dynamic and thermodynamic properties, such as Stokes shifts or reorganization free energies. We then turn to the macroscopic, continuum electrostatic view. We recall the physical definition of a dielectric constant and revisit the decomposition of the free energy into a reorganization and a static term. We review some illustrative continuum studies and discuss some difficulties that can arise with the continuum approach. In conclusion, we consider recent developments that will increase the accuracy and broaden the scope of all these methods. PMID:18443919

  6. Theory of spin relaxation at metallic interfaces

    NASA Astrophysics Data System (ADS)

    Belashchenko, K. D.; Kovalev, Alexey A.; van Schilfgaarde, Mark

    Spin-flip scattering at metallic interfaces affects transport phenomena in nanostructures, such as magnetoresistance, spin injection, spin pumping, and spin torques. It has been characterized for many material combinations by an empirical parameter δ, which is obtained by matching magnetoresistance data for multilayers to the Valet-Fert model [J. Bass and W. P. Pratt, J. Phys.: Condens. Matter 19, 183201 (2007)]. However, the relation of the parameter δ to the scattering properties of the interface remains unclear. Here we establish this relation using the scattering theory approach and confirm it using a generalization of the magnetoelectronic circuit theory, which includes interfacial spin relaxation. The results of first-principles calculations of spin-flip scattering at the Cu/Pd and Cu/Pt interfaces are found to be in reasonable agreement with experimental data. Supported by NSF Grant DMR-1308751.

  7. Grueneisen relaxation photoacoustic microscopy in vivo

    NASA Astrophysics Data System (ADS)

    Ma, Jun; Shi, Junhui; Hai, Pengfei; Zhou, Yong; Wang, Lihong V.

    2016-06-01

    Grueneisen relaxation photoacoustic microscopy (GR-PAM) can achieve optically defined axial resolution, but it has been limited to ex vivo demonstrations so far. Here, we present the first in vivo image of a mouse brain acquired with GR-PAM. To induce the GR effect, an intensity-modulated continuous-wave laser was employed to heat absorbing objects. In phantom experiments, an axial resolution of 12.5 μm was achieved, which is sixfold better than the value achieved by conventional optical-resolution PAM. This axial-resolution improvement was further demonstrated by imaging a mouse brain in vivo, where significantly narrower axial profiles of blood vessels were observed. The in vivo demonstration of GR-PAM shows the potential of this modality for label-free and high-resolution anatomical and functional imaging of biological tissues.

  8. Multichannel applications of double relaxation oscillation SQUIDs

    NASA Astrophysics Data System (ADS)

    Lee, Yong-Ho; Kwon, Hyukchan; Kim, Jin-Mok; Park, Yong-Ki

    2001-12-01

    Double relaxation oscillation SQUIDs (DROSs) provided high flux-to-voltage transfers of larger than 1 mV Φ0-1 and simple flux-locked loop circuits were used for SQUID operation. We constructed two multichannel systems based on DROSs. The first system is a 40-channel planar gradiometer system consisting of integrated first-order pickup coils. average noise level of the 40 channels is 1 fT cm-1 Hz-1/2 at 100 Hz, corresponding to a field noise of 4 fT Hz-1/2, operating inside a magnetically shielded room. The second one is a 37-channel magnetometer system with 37 integrated magnetometers distributed on a spherical surface and measures field component normal to the head surface. The average noise of the magnetometers is 3 fT Hz-1/2 at 100 Hz. The two systems were applied to measure neuromagnetic fields.

  9. Stress relaxation of vitreous silica on irradiation

    SciTech Connect

    Primak, W.

    1982-11-01

    The radiation-induced stress relaxation which is observed on ion bombardment of vitreous silica is described as a viscoelastic behavior in which the apparent viscosity is reduced to approx.10/sup 14/ Poise during irradiation and then increases rapidly by 4 or 5 orders of magnitude on cessation or interruption of irradiation. The bombarded layer appears to possess a viscosity approx.10/sup 19/ Poise, lower than would be expected for normal vitreous silica. On electron bombardment the viscosity is also reduced, but not as greatly as an ion bombardment, yet sufficiently to result in the whole radiation-induced volume contraction being realized perpendicularly to the surface, as has been found for ion bombardment. The maximum elastic stored energy which can be realized is but a fraction of a calorie per gram, hence the reported values of 200 cal/g would seem to be associated with the fragmentation of the network responsible for the reduced viscosity.

  10. MACC1 mediates acetylcholine-induced invasion and migration by human gastric cancer cells

    PubMed Central

    Xia, Jianling; Zhou, Rui; Wu, Zhenzhen; Zhao, Yang; Shi, Min

    2016-01-01

    The neurotransmitter acetylcholine (ACh) promotes the growth and metastasis of several cancers via its M3 muscarinic receptor (M3R). Metastasis-associated in colon cancer-1 (MACC1) is an oncogene that is overexpressed in gastric cancer (GC) and plays an important role in GC progression, though it is unclear how MACC1 activity is regulated in GC. In this study, we demonstrated that ACh acts via M3Rs to promote GC cell invasion and migration as well as expression of several markers of epithelial-mesenchymal transition (EMT). The M3R antagonist darifenacin inhibited GC cell activity in both the presence and absence of exogenous ACh, suggesting GC cells secrete endogenous ACh, which then acts in an autocrine fashion to promote GC cell migration/invasion. ACh up-regulated MACC1 in GC cells, and MACC1 knockdown using siRNA attenuated the effects of ACh on GC cells. AMP-activated protein kinase (AMPK) served as an intermediate signal between ACh and MACC1. These findings suggest that ACh acts via a M3R/AMPK/MACC1 signaling pathway to promote GC cell invasion/migration, which provides insight into the mechanisms underlying GC growth and metastasis and may shed light on new targets for GC treatment. PMID:26919111

  11. Captopril augments acetylcholine-induced bronchial smooth muscle contractions in vitro via kinin-dependent mechanisms.

    PubMed

    Agrawal, Naman; Akella, Aparna; Deshpande, Shripad B

    2016-06-01

    Angiotensin converting enzyme (ACE) inhibitors therapy is aassociated with bothersome dry cough as an adverse effect. The mechanisms underlying this adverse effect are not clear. Therefore, influence of captopril (an ACE inhibitor) on acetylcholine (ACh)-induced bronchial smooth muscle contractions was investigated. Further, the mechanisms underlying the captopril-induced changes were also explored. In vitro contractions of rat bronchial smooth muscle to cumulative concentrations of ACh were recorded before and after exposure to captopril. Further, the involvement of kinin and inositol triphosphate (IP₃) pathways for captopril-induced alterations were explored. ACh produced concentration-dependent (5-500 µM) increase in bronchial smooth muscle contractions. Pre-treatment with captopril augmented the ACh-induced contractions at each concentration significantly. Pre-treatment with aprotinin (kinin synthesis inhibitor) or heparin (inositol triphosphate, IP₃-inhibitor), blocked the captopril-induced augmentation of bronchial smooth muscle contractions evoked by ACh. Further, captopril-induced augmentation was absent in calcium-free medium. These results suggest that captopril sensitizes bronchial smooth muscles to ACh-induced contractions. This sensitization may be responsible for dry cough associated with captopril therapy. PMID:27468462

  12. Receptor-mediated presynaptic facilitation of quantal release of acetylcholine induced by pralidoxime in Aplysia.

    PubMed

    Fossier, P; Baux, G; Poulain, B; Tauc, L

    1990-09-01

    1. Possible interactions of contrathion (pralidoxime sulfomethylate), a reactivator of phosphorylated acetylcholinesterase (AChE), with the regulation of cholinergic transmission were investigated on an identified synapse in the buccal ganglion of Aplysia californica. 2. Transmitter release was evoked either by a presynaptic action potential or, under voltage clamp, by a long depolarization of the presynaptic cell. At concentrations higher than 10(-5) M, bath-applied contrathion decreased the amplitude of miniature postsynaptic currents and increased their decay time. At the same time, the quantal release of ACh was transiently facilitated. The facilitatory effect of contrathion was prevented by tubocurarine but not by atropine. Because in this preparation, these drugs block, respectively, the presynaptic nicotinic-like and muscarinic-like receptors involved in positive and negative feedback of ACh release, we proposed that contrathion activates presynaptic nicotinic-like receptors. 3. Differential desensitization of the presynaptic receptors is proposed to explain the transience of the facilitatory action of contrathion on ACh release. 4. The complexity of the synaptic action of contrathion raises the possibility that its therapeutic effects in AChE poisonings are not limited to AChE reactivation. PMID:2253262

  13. The effect of cooling on the acetylcholine-induced current of identified Helix pomatia Br neuron.

    PubMed

    Nedeljkovic, Miodrag; Kartelija, Gordana; Radenovic, Lidija; Todorovic, Natasa

    2005-05-01

    The Br neuron of the snail Helix pomatia, involved in neuronal regulation of various homeostatic and adaptive mechanisms, represents an interesting model for studying effects of temperature changes on neuronal activity of poikilotherms. The acetylcholine (ACh) induces a transient, inward dose-dependent current in the identified Br neuron. In the work presented, we analyses the effects of cooling on the ACh-induced inward current. The amplitude of ACh-induced inward current was markedly decreased after cooling and the speed of the decay of ACh response was decreased. Sensitivity to cooling of Ach-activated current on the Br neuron is mediated by a mechanism that does not involve change in the apparent receptor affinity or the cooperativity of binding. PMID:15759140

  14. Relaxation mechanisms in architecturally complex macromolecules

    NASA Astrophysics Data System (ADS)

    Vlassopoulos, Dimitris

    2004-03-01

    With the important recent advances in polymer chemistry as well as in tube model theories and simulations, the elucidation of the relaxation mechanisms of branched and hyperbranched macromolecules has emerged as a field of great significance, both from the scientific and the technological viewpoints. Here we present a systematic approach to analyze the response of model polymers with progressive complexation in architecture, both in the melt and in solution. In particular, we present dynamic data on series of well-defined nearly monodisperse branched polymer melts (polystyrenes, polybutadienes and polyisoprenes) of the Cayley-tree, comb and star-comb types. We discuss quantitatively the complex relaxation of these systems in terms of hierarchical motions. Special mention is made to analogies with commercial polymers such as polyethylenes exhibiting long-chain branching. We address the phenomenology of gel-like regimes in the melt state, whereas by comparing with their linear counterparts we demonstrate the possibilities of altering the rheology of polymeric systems in a controlled way by introducing branches. Based on these results we also show that it is possible to analyze the viscoelastic response of telechelic polymers forming dendritic supramolecular structures in the melt. In solution, dendritic structures can be viewed as colloidal particles exhibiting ultrasoft interactions, which can be tailored on the molecular level, and their dynamic response spans the range from polymeric to colloidal behavior. Simple rheometric data confirm this trend. In the dense state such soft suspensions exhibit complex dynamics which is interpreted in terms of colloidal vitrification. This suggests possibilities for obtaining a unified description of the response of suspensions of varying interactions and thus controlling their flow behavior. This work is in collaboration with M. Kapnistos, E. Stiakakis, J. Roovers, N. Hadjichristidis and R. Blackwell.

  15. A fast determination method for transverse relaxation of spin-exchange-relaxation-free magnetometer

    SciTech Connect

    Lu, Jixi Qian, Zheng; Fang, Jiancheng

    2015-04-15

    We propose a fast and accurate determination method for transverse relaxation of the spin-exchange-relaxation-free (SERF) magnetometer. This method is based on the measurement of magnetic resonance linewidth via a chirped magnetic field excitation and the amplitude spectrum analysis. Compared with the frequency sweeping via separate sinusoidal excitation, our method can realize linewidth determination within only few seconds and meanwhile obtain good frequency resolution. Therefore, it can avoid the drift error in long term measurement and improve the accuracy of the determination. As the magnetic resonance frequency of the SERF magnetometer is very low, we include the effect of the negative resonance frequency caused by the chirp and achieve the coefficient of determination of the fitting results better than 0.998 with 95% confidence bounds to the theoretical equation. The experimental results are in good agreement with our theoretical analysis.

  16. Definition, evaluation, and management of brain relaxation during craniotomy.

    PubMed

    Li, J; Gelb, A W; Flexman, A M; Ji, F; Meng, L

    2016-06-01

    The term 'brain relaxation' is routinely used to describe the size and firmness of the brain tissue during craniotomy. The status of brain relaxation is an important aspect of neuroanaesthesia practice and is relevant to the operating conditions, retraction injury, and likely patient outcomes. Brain relaxation is determined by the relationship between the volume of the intracranial contents and the capacity of the intracranial space (i.e. a content-space relationship). It is a concept related to, but distinct from, intracranial pressure. The evaluation of brain relaxation should be standardized to facilitate clinical communication and research collaboration. Both advantageous and disadvantageous effects of the various interventions for brain relaxation should be taken into account in patient care. The outcomes that matter the most to patients should be emphasized in defining, evaluating, and managing brain relaxation. To date, brain relaxation has not been reviewed specifically, and the aim of this manuscript is to discuss the current approaches to the definition, evaluation, and management of brain relaxation, knowledge gaps, and targets for future research. PMID:27121854

  17. Dynamic Analyses of Polymer Surface using Dielectric Relaxation

    NASA Astrophysics Data System (ADS)

    Ishii, Masashi

    A new dielectric relaxation measurement technique for analyses of polymer surface was developed. In this technique, in order to maintain the original surface, probing electrodes were placed away from the sample, and a liquid to stabilize the surface was filled in the space between the sample and the electrodes. From difference of dielectric relaxation between a bare polyimide and gold-coated polyimide, the surface of polyimide was characterized. The surface dielectric relaxation spectrum at room temperature depended on the liquid species: The Debye relaxation was obtained for ethanol, while multiple-relaxation was observed for ultrapure water. A thermal activation process of the polyimide surface was investigated using temperature-controlled ultrapure water, and it was found that the surface transited from the multiple-relaxation to the Debye relaxation at ∼95°C. In the Debye relaxation condition, the surface can be characterized with a capacitance independent of the liquid species. The capacitance estimated at 110 pF provided a characteristic curve of the polyimide surface. A surface model was proposed to explain the thermal activation process.

  18. The infinite interface limit of multiple-region relaxed magnetohydrodynamics

    SciTech Connect

    Dennis, G. R.; Dewar, R. L.; Hole, M. J.; Hudson, S. R.

    2013-03-15

    We show the stepped-pressure equilibria that are obtained from a generalization of Taylor relaxation known as multi-region, relaxed magnetohydrodynamics (MRXMHD) are also generalizations of ideal magnetohydrodynamics (ideal MHD). We show this by proving that as the number of plasma regions becomes infinite, MRXMHD reduces to ideal MHD. Numerical convergence studies illustrating this limit are presented.

  19. Long-Term Psychosomatic Effects of Biofeedback vs. Relaxation Training.

    ERIC Educational Resources Information Center

    Nowlis, David P.; Borzone, Ximena C.

    Differences were compared in the short-term and long-term responses of subjects with headache, insomnia, or hypertension to biofeedback training, relaxation, or a combination of both. Headache sufferers, insomniacs, and hypertensives were randomly assigned in equal numbers to biofeedback, relaxation training or a record-keeping control. Over 2…

  20. Novel gigahertz frequency dielectric relaxations in chitosan films.

    PubMed

    Kumar-Krishnan, Siva; Prokhorov, Evgen; Ramírez, Marius; Hernandez-Landaverde, Martín A; Zarate-Triviño, Diana G; Kovalenko, Yu; Sanchez, Isaac C; Méndez-Nonell, Juan; Luna-Bárcenas, Gabriel

    2014-11-21

    Molecular relaxations of chitosan films have been investigated in the wide frequency range of 0.1 to 3 × 10(9) Hz from -10 °C to 110 °C using dielectric spectroscopy. For the first time, two high-frequency relaxation processes (in the range 10(8) to 3 × 10(9) Hz) are reported in addition to the low frequency relaxations α and β. These two relaxation processes are related to the vibrations of OH and NH2/NH3(+), respectively. The high-frequency relaxations exhibit Arrhenius-type dependencies in the temperature range 10 °C to 54 °C with negative activation energy; this observation is traceable to hydrogen bonding reorientation. At temperatures above the glass transition temperature (54 °C), the activation energy changes from negative to positive values due to breaking of hydrogen bonding and water loss. Upon cooling in a sealed environment, the activation energies of two relaxation processes are nearly zero. FTIR and XRD analyses reveal associated structural changes upon heating and cooling. These two new high-frequency relaxation processes can be attributed to the interaction of bound water with OH and NH2/NH3(+), respectively. A plausible scenario for these high-frequency relaxations is discussed in light of impedance spectroscopy, TGA, FTIR and XRD measurements. PMID:25254949

  1. Relaxation Theory for Rural Youth. Research Bulletin No. 46.

    ERIC Educational Resources Information Center

    Matthews, Doris B.

    This document synthesizes research findings to formulate a theory to guide relaxation training in educational settings, particularly rural schools. Young people experience many intense life events that require coping skills or relaxation. Family-related stress factors include instability in the home, lack of a support system, conflicting values,…

  2. Evaluation of Multiple Component Relaxation Training with Developmentally Disabled Persons.

    ERIC Educational Resources Information Center

    Calamari, John E.; And Others

    1987-01-01

    A specific progressive muscle relaxation training procedure was combined with auditory electromyographic (EMG) biofeedback, modeling, and reinforcement procedures to teach relaxation skills to 32 mentally retarded adults. The procedure was effective in reducing subjects' EMG levels and activity levels. Intellectual and adaptive behavior levels…

  3. MRI Contrast from Relaxation Along a Fictitious Field (RAFF)

    PubMed Central

    Liimatainen, Timo; Sorce, Dennis J.; O’Connell, Robert; Garwood, Michael; Michaeli, Shalom

    2016-01-01

    A new method to measure rotating frame relaxation and to create contrast for MRI is introduced. The technique exploits relaxation along a fictitious field (RAFF) generated by amplitude- and frequency-modulated irradiation in a sub-adiabatic condition. Here, RAFF is demonstrated using a radiofrequency pulse based on sine and cosine amplitude and frequency modulations of equal amplitudes, which gives rise to a stationary fictitious magnetic field in a doubly rotating frame. According to dipolar relaxation theory, the RAFF relaxation time constant (TRAFF) was found to differ from laboratory frame relaxation times (T1 and T2) and rotating frame relaxation times (T1ρ and T2ρ). This prediction was supported by experimental results obtained from human brain in vivo and three different solutions. Results from relaxation mapping in human brain demonstrated the ability to create MRI contrast based on RAFF. The value of TRAFF was found to be insensitive to the initial orientation of the magnetization vector. Finally, as compared with adiabatic pulse trains of equal durations, RAFF required less radiofrequency power and therefore can be more readily used for rotating frame relaxation studies in humans. PMID:20740665

  4. MRI contrast from relaxation along a fictitious field (RAFF).

    PubMed

    Liimatainen, Timo; Sorce, Dennis J; O'Connell, Robert; Garwood, Michael; Michaeli, Shalom

    2010-10-01

    A new method to measure rotating frame relaxation and to create contrast for MRI is introduced. The technique exploits relaxation along a fictitious field (RAFF) generated by amplitude- and frequency-modulated irradiation in a subadiabatic condition. Here, RAFF is demonstrated using a radiofrequency pulse based on sine and cosine amplitude and frequency modulations of equal amplitudes, which gives rise to a stationary fictitious magnetic field in a doubly rotating frame. According to dipolar relaxation theory, the RAFF relaxation time constant (T(RAFF)) was found to differ from laboratory frame relaxation times (T(1) and T(2)) and rotating frame relaxation times (T(1ρ) and T(2ρ)). This prediction was supported by experimental results obtained from human brain in vivo and three different solutions. Results from relaxation mapping in human brain demonstrated the ability to create MRI contrast based on RAFF. The value of T(RAFF) was found to be insensitive to the initial orientation of the magnetization vector. In the RAFF method, the useful bandwidth did not decrease as the train length increased. Finally, as compared with an adiabatic pulse train of equal duration, RAFF required less radiofrequency power and therefore can be more readily used for rotating frame relaxation studies in humans. PMID:20740665

  5. Use of Biofeedback/Relaxation Procedures with Learning Disabled Children.

    ERIC Educational Resources Information Center

    Carter, John L.; Russell, Harold L.

    The report covers a series of investigations on the effects of biofeedback/muscle relaxation training on the academic achievement of learning disabled (LD) students. In the first study, 32 LD elementary school students made gains in all measures except arithmetic following electromyograph biofeedback/relaxation treatment. Implementation of the…

  6. Involvement of Rho-kinase in experimental vascular endothelial dysfunction.

    PubMed

    Shah, Dhvanit I; Singh, Manjeet

    2006-02-01

    The present study has been designed to investigate the effect of fasudil (Rho-kinase inhibitor) in diabetes mellitus (DM) and hyperhomocyteinemia (HHcy) induced vascular endothelial dysfunction (VED). Streptozotocin (55 mg kg(-1), i.v., once only) and methionine (1.7% w/w, p.o., daily for 4 weeks) were administered to rats to produce DM (serum glucose >140 mg dl(-1)) and HHcy (serum homocysteine >10 microM) respectively. VED was assessed using isolated aortic ring, electron microscopy of thoracic aorta, and serum concentration of nitrite/nitrate. Serum thiobarbituric acid reactive substances (TBARS) concentration was estimated to assess oxidative stress. Atorvastatin has been employed in the present study as standard agent to improve vascular endothelial dysfunction. Fasudil (15 mg kg(-1) and 30 mg kg(-1), p.o., daily) and atorvastatin (30 mg kg(-1), p.o., daily) treatments significantly attenuated increase in serum glucose and homocysteine but their concentrations remained markedly higher than sham control value. Fasudil and atorvastatin treatments markedly prevented DM and HHcy-induced (i) attenuation of acetylcholine induced endothelium-dependent relaxation, (ii) impairment of vascular endothelial lining, (iii) decrease in serum nitrite/nitrate concentration, and (iv) increase in serum TBARS. It may be concluded that fasudil prevented DM and HHcy-induced VED partially by decreasing serum glucose and homocysteine concentration due to inhibition of Rho-kinase. Moreover, inhibition of Rho-kinase by fasudil and consequent prevention of oxidative stress may have directly improved VED in diabetic and hyperhomocysteinemic rats. The Rho-kinase appears to be a pivotal target site involved in DM and HHcy-induced VED. PMID:16444602

  7. Tert-butylhydroquinone lowers blood pressure in AngII-induced hypertension in mice via proteasome-PTEN-Akt-eNOS pathway.

    PubMed

    Xu, Bing-Can; Long, Hui-Bao; Luo, Ke-Qin

    2016-01-01

    Tert-butylhydroquinone (tBHQ), as an antioxidant, has been widely used for many years to prevent oxidization of food products. The aim of this study was to investigate whether tBHQ activates endothelial nitric oxide synthase (eNOS) to prevent endothelial dysfunction and lower blood pressure. The role of Akt in tBHQ-induced eNOS phosphorylation was examined in human umbilical vein endothelial cells (HUVEC) or in mice. tBHQ treatment of HUVEC increased both Akt-Ser473 phosphorylation, accompanied with increased eNOS-Ser1177 phosphorylation and NO release. Mechanically, pharmacologic or genetic inhibition of Akt abolished tBHQ-enhanced NO release and eNOS phosphorylation in HUVEC. Gain-function of PTEN or inhibition of 26S proteasome abolished tBHQ-enhanced Akt phosphorylation in HUVEC. Ex vivo analysis indicated that tBHQ improved Ach-induced endothelium-dependent relaxation in LPC-treated mice aortic arteries, which were abolished by inhibition of Akt or eNOS. In animal study, administration of tBHQ significantly increased eNOS-Ser1177 phosphorylation and acetylcholine-induced vasorelaxation, and lowered AngII-induced hypertension in wildtype mice, but not in mice deficient of Akt or eNOS. In conclusion, tBHQ via proteasome-dependent degradation of PTEN increases Akt phosphorylation, resulting in upregulation of eNOS-derived NO production and consequent improvement of endothelial function in vivo. In this way, tBHQ lowers blood pressure in hypertensive mice. PMID:27435826

  8. Boldine Ameliorates Vascular Oxidative Stress and Endothelial Dysfunction: Therapeutic Implication for Hypertension and Diabetes

    PubMed Central

    Lau, Yeh Siiang; Ling, Wei Chih; Murugan, Dharmani

    2015-01-01

    Abstract: Epidemiological and clinical studies have demonstrated that a growing list of natural products, as components of the daily diet or phytomedical preparations, are a rich source of antioxidants. Boldine [(S)-2,9-dihydroxy-1,10-dimethoxy-aporphine], an aporphine alkaloid, is a potent antioxidant found in the leaves and bark of the Chilean boldo tree. Boldine has been extensively reported as a potent “natural” antioxidant and possesses several health-promoting properties like anti-inflammatory, antitumor promoting, antidiabetic, and cytoprotective. Boldine exhibited significant endothelial protective effect in animal models of hypertension and diabetes mellitus. In isolated thoracic aorta of spontaneously hypertensive rats, streptozotocin-induced diabetic rats, and db/db mice, repeated treatment of boldine significantly improved the attenuated acetylcholine-induced endothelium-dependent relaxations. The endothelial protective role of boldine correlated with increased nitric oxide levels and reduction of vascular reactive oxygen species via inhibition of the nicotinamide adenine dinucleotide phosphate oxidase subunits, p47phox and nicotinamide adenine dinucleotide phosphate oxidase 2, and angiotensin II–induced bone morphogenetic protein-4 oxidative stress cascade with downregulation of angiotensin II type 1 receptor and bone morphogenetic protein-4 expression. Taken together, it seems that boldine may exert protective effects on the endothelium via several mechanisms, including protecting nitric oxide from degradation by reactive oxygen species as in oxidative stress–related diseases. The present review supports a complimentary therapeutic role of the phytochemical, boldine, against endothelial dysfunctions associated with hypertension and diabetes mellitus by interfering with the oxidative stress–mediated signaling pathway. PMID:25469805

  9. Boldine Ameliorates Vascular Oxidative Stress and Endothelial Dysfunction: Therapeutic Implication for Hypertension and Diabetes.

    PubMed

    Lau, Yeh Siiang; Ling, Wei Chih; Murugan, Dharmani; Mustafa, Mohd Rais

    2015-06-01

    Epidemiological and clinical studies have demonstrated that a growing list of natural products, as components of the daily diet or phytomedical preparations, are a rich source of antioxidants. Boldine [(S)-2,9-dihydroxy-1,10-dimethoxy-aporphine], an aporphine alkaloid, is a potent antioxidant found in the leaves and bark of the Chilean boldo tree. Boldine has been extensively reported as a potent "natural" antioxidant and possesses several health-promoting properties like anti-inflammatory, antitumor promoting, antidiabetic, and cytoprotective. Boldine exhibited significant endothelial protective effect in animal models of hypertension and diabetes mellitus. In isolated thoracic aorta of spontaneously hypertensive rats, streptozotocin-induced diabetic rats, and db/db mice, repeated treatment of boldine significantly improved the attenuated acetylcholine-induced endothelium-dependent relaxations. The endothelial protective role of boldine correlated with increased nitric oxide levels and reduction of vascular reactive oxygen species via inhibition of the nicotinamide adenine dinucleotide phosphate oxidase subunits, p47 and nicotinamide adenine dinucleotide phosphate oxidase 2, and angiotensin II-induced bone morphogenetic protein-4 oxidative stress cascade with downregulation of angiotensin II type 1 receptor and bone morphogenetic protein-4 expression. Taken together, it seems that boldine may exert protective effects on the endothelium via several mechanisms, including protecting nitric oxide from degradation by reactive oxygen species as in oxidative stress-related diseases. The present review supports a complimentary therapeutic role of the phytochemical, boldine, against endothelial dysfunctions associated with hypertension and diabetes mellitus by interfering with the oxidative stress-mediated signaling pathway. PMID:25469805

  10. Tert-butylhydroquinone lowers blood pressure in AngII-induced hypertension in mice via proteasome-PTEN-Akt-eNOS pathway

    PubMed Central

    Xu, Bing-Can; Long, Hui-Bao; Luo, Ke-Qin

    2016-01-01

    Tert-butylhydroquinone (tBHQ), as an antioxidant, has been widely used for many years to prevent oxidization of food products. The aim of this study was to investigate whether tBHQ activates endothelial nitric oxide synthase (eNOS) to prevent endothelial dysfunction and lower blood pressure. The role of Akt in tBHQ-induced eNOS phosphorylation was examined in human umbilical vein endothelial cells (HUVEC) or in mice. tBHQ treatment of HUVEC increased both Akt-Ser473 phosphorylation, accompanied with increased eNOS-Ser1177 phosphorylation and NO release. Mechanically, pharmacologic or genetic inhibition of Akt abolished tBHQ-enhanced NO release and eNOS phosphorylation in HUVEC. Gain-function of PTEN or inhibition of 26S proteasome abolished tBHQ-enhanced Akt phosphorylation in HUVEC. Ex vivo analysis indicated that tBHQ improved Ach-induced endothelium-dependent relaxation in LPC-treated mice aortic arteries, which were abolished by inhibition of Akt or eNOS. In animal study, administration of tBHQ significantly increased eNOS-Ser1177 phosphorylation and acetylcholine-induced vasorelaxation, and lowered AngII-induced hypertension in wildtype mice, but not in mice deficient of Akt or eNOS. In conclusion, tBHQ via proteasome-dependent degradation of PTEN increases Akt phosphorylation, resulting in upregulation of eNOS-derived NO production and consequent improvement of endothelial function in vivo. In this way, tBHQ lowers blood pressure in hypertensive mice. PMID:27435826

  11. Proton-nuclear magnetic resonance relaxation times in brain edema

    SciTech Connect

    Kamman, R.L.; Go, K.G.; Berendsen, H.J. )

    1990-01-01

    Proton relaxation times of protein solutions, bovine brain, and edematous feline brain tissue were studied as a function of water concentration, protein concentration, and temperature. In accordance with the fast proton exchange model for relaxation, a linear relation could be established between R1 and the inverse of the weight fraction of tissue water. This relation also applied to R2 of gray matter and of protein solutions. No straightforward relation with water content was found for R2 of white matter. Temperature-dependent studies indicated that in this case, the slow exchange model for relaxation had to be applied. The effect of macromolecules in physiological relevant concentrations on the total relaxation behavior of edematous tissue was weak. Total water content changes predominantly affected the relaxation rates. The linear relation may have high clinical potential for assessment of the status of cerebral edema on the basis of T1 and T2 readings from MR images.

  12. Dielectric relaxation in monoclinic hydroxyapatite: Observation of hydroxide ion dipoles

    NASA Astrophysics Data System (ADS)

    Horiuchi, N.; Wada, N.; Nozaki, K.; Nakamura, M.; Nagai, A.; Yamashita, K.

    2016-02-01

    We prepared monoclinic hydroxyapatite (HAp) ceramics and measured their dielectric properties. The dielectric dispersion that was observed in the monoclinic HAp consisted of two different relaxations and could be expressed by a summation of two Debye-like relaxations. One relaxation was ascribed to the reorientational motions of OH- ions. The temperature dependence of the relaxation time obeyed the Arrhenius equation. The relaxation time decreased with temperature but decreased discontinuously at 483 K, the monoclinic-hexagonal phase transition temperature of HAp. Correspondingly, the activation energy changed from 0.74 eV for the monoclinic phase to 0.43 eV for the hexagonal phase. The results suggest that the mobility of the OH- ions increases discontinuously with the phase transition to hexagonal HAp. However, critical phenomena, such as critical slowing down, were not observed.

  13. Stress Relaxation in Entangled Melts of Unlinked Ring Polymers

    NASA Astrophysics Data System (ADS)

    Milner, Scott T.; Newhall, Jillian D.

    2010-11-01

    Stress relaxation in unlinked ring polymer melts poses an important challenge to our theoretical understanding of entangled polymer dynamics. Recent experiments on entangled unlinked ring melts show power-law stress relaxation with no hint of a rubbery plateau, usually the hallmark of entangled polymers. Here we present a theory for stress relaxation in rings analogous to the successful approach for star polymers. We augment our theory with mesoscale Monte Carlo dynamics simulations of equivalent “lattice animal” configurations. We find a stress relaxation function G(t)˜t-α with α≈1/2 consistent with experiment, emerging ultimately from the disparate relaxation times of more- and less-central portions of ring conformations.

  14. Defect-related relaxation processes in irradiated rare gas solids

    NASA Astrophysics Data System (ADS)

    Savchenko, E. V.; Grigorashchenko, O. N.; Gumenchuk, G. B.; Ogurtsov, A. N.; Frankowski, M.; Smith-Gicklhorn, A. M.; Bondybey, V. E.

    Electronic and atomic relaxation processes in preirradiated solid Ar doped with N-2 were studied with a focus on the role of radiative electronic transitions in relaxation cascades. Combining methods of activation spectroscopy - thermally stimulated and photon-stimulated exoelectron emission, a new channel of relaxation induced by photon emission from metastable N atoms was detected. It was shown that in insulating materials with a wide conduction band photons of visible range can release electrons from both kinds of traps - shallow (lattice defects) and deep thermally disconnected ones. Correlation in the charge recombination reaction yield and the yield of low temperature desorption - important relaxation channel in a preirradiated solid - clearly demonstrates interconnection between atomic and electronic processes of relaxation.

  15. Correlation of transverse relaxation time with structure of biological tissue

    NASA Astrophysics Data System (ADS)

    Furman, Gregory B.; Meerovich, Victor M.; Sokolovsky, Vladimir L.

    2016-09-01

    Transverse spin-spin relaxation of liquids entrapped in nanocavities with different orientational order is theoretically investigated. Based on the bivariate normal distribution of nanocavities directions, we have calculated the anisotropy of the transverse relaxation time for biological systems, such as collagenous tissues, articular cartilage, and tendon. In the framework of the considered model, the dipole-dipole interaction is determined by a single coupling constant. The calculation results for the transverse relaxation time explain the angular dependence observed in MRI experiments with biological objects. The good agreement with the experimental data is obtained by adjustment of only one parameter which characterizes the disorder in fiber orientations. The relaxation time is correlated with the degree of ordering in biological tissues. Thus, microstructure of the tissues can be revealed from the measurement of relaxation time anisotropy. The clinical significance of the correlation, especially in the detection of damage must be evaluated in a large prospective clinical trials.

  16. Ingestion of caustic hair relaxer: is endoscopy necessary?

    PubMed

    Cox, A J; Eisenbeis, J F

    1997-07-01

    Hair relaxer, a commercially available alkaline product, is commonly the offending agent in caustic ingestion. These patients often experience oral cavity and facial burns; however, no clinically significant esophageal injuries have been reported. Therefore, we questioned the therapeutic and economic efficacy of the "standard treatment protocol" that includes hospitalization and endoscopic evaluation. Twenty-six patients over a 7-year period presented to our institution having ingested hair relaxer. Presenting signs and symptoms, esophageal findings, and cost of the standard treatment protocol were reviewed. Also, we analyzed the caustic potential and current packaging of hair relaxer. Our findings support modifications in the standard treatment protocol for hair relaxer ingestion including elimination of hospitalization and endoscopy in most patients. We also question compliance with childproof packaging laws and suggest avenues for prevention of hair relaxer ingestion. PMID:9217127

  17. Viscoelastic Relaxation of Topographic Highs on Venus to Produce Coronae

    NASA Technical Reports Server (NTRS)

    Janes, Daniel M.; Squyres, Steven W.

    1995-01-01

    Coronae on Venus are believed to result from the gravitationally driven relaxation of topography that was originally raised by mantle diapirs. We examine this relaxation using a viscoelastic finite element code, and show that an initially plateau shaped load will evolve to the characteristic corona topography of central raised bowl, annular rim, and surrounding moat. Stresses induced by the relaxation are consistent with the development of concentric extensional fracturing common on the outer margins of corona moats. However, relaxation is not expected to produce the concentric faulting often observed on the annular rim. The relaxation timescale is shorter than the diapir cooling timescale, so loss of thermal support controls the rate at which topography is reduced. The final corona shape is supported by buoyancy and flexural stresses and will persist through geologic time. Development of lower, flatter central bowls and narrower and more pronounced annular rims and moats enhanced by thicker crusts, higher thermal gradients, and crustal thinning over the diapir.

  18. Ultraslow dielectric relaxation process in supercooled polyhydric alcohols

    NASA Astrophysics Data System (ADS)

    Yomogida, Yoshiki; Minoguchi, Ayumi; Nozaki, Ryusuke

    2006-04-01

    Complex permittivity was obtained on glycerol, xylitol, sorbitol and sorbitol-xylitol mixtures in the supercooled liquid state in the frequency range between 10μHz and 500MHz at temperatures near and above the glass transition temperature. For all the materials, a dielectric relaxation process was observed in addition to the well-known structural α and Johari-Goldstein β relaxation process [G. P. Johari and M. Goldstein, J. Chem. Phys. 53, 2372 (1970)]. The relaxation time for the new process is always larger than that for the α process. The relaxation time shows non-Arrhenius temperature dependence with correlation to the behavior of the α process and it depends on the molecular size systematically. The dielectric relaxation strength for the new process shows the effect of thermal history and decreases exponentially with time at a constant temperature. It can be considered that a nonequilibrium dynamics causes the new process.

  19. Enceladus' extreme heat flux as revealed by its relaxed craters

    NASA Astrophysics Data System (ADS)

    Bland, Michael T.; Singer, Kelsi N.; McKinnon, William B.; Schenk, Paul M.

    2012-09-01

    Enceladus' cratered terrains contain large numbers of unusually shallow craters consistent with deformation by viscous relaxation of water ice under conditions of elevated heat flow. Here we use high-resolution topography to measure the relaxation fraction of craters on Enceladus far from the active South Pole. We find that many craters are shallower than expected, with craters as small as 2 km in diameter having relaxation fractions in excess of 90%. These measurements are compared with numerical simulations of crater relaxation to constrain the minimum heat flux required to reproduce these observations. We find that Enceladus' nominal cold surface temperature (70 K) and low surface gravity strongly inhibit viscous relaxation. Under such conditions less than 3% relaxation occurs over 2 Ga even for relatively large craters (diameter 24 km) and high, constant heat fluxes (150 mW m-2). Greater viscous relaxation occurs if the effective temperature at the top of the lithosphere is greater than the surface temperature due to insulating regolith and/or plume material. Even for an effective temperature of 120 K, however, heat fluxes in excess of 150 mW m-2 are required to produce the degree of relaxation observed. Simulations of viscous relaxation of Enceladus' largest craters suggest that relaxation is best explained by a relatively short-lived period of intense heating that decayed quickly. We show that infilling of craters by plume material cannot explain the extremely shallow craters at equatorial and higher northern latitudes. Thus, like Enceladus' tectonic terrains, the cratered regions of Enceladus have experienced periods of extreme heat flux.

  20. A Psychophysiological Comparison of the Effects of Three Relaxation Techniques: Respiratory Manipulation Training, Progressive Muscle Relaxation, and Pleasant Imagery.

    ERIC Educational Resources Information Center

    Longo, David J.

    A within-subjects, three condition design was employed to examine the effects of three relaxation techniques on blood pressures, pulse rates, and self-report measures of relaxation for 12 college students. Respiratory Manipulation Training incorporated instructions to exhale and not to inhale for as long as possible. When breathing could no longer…

  1. During Training and Posttraining Effects of Live and Taped Extended Progressive Relaxation, Self-Relaxation, and Electromyogram Biofeedback.

    ERIC Educational Resources Information Center

    Beiman, Irving; And Others

    1978-01-01

    Compared live and taped progressive relaxation (LR, TR), self-relaxation (SR), and electromyogram biofeedback (BF) on measures of autonomic and somatic arousal and subjective tension. LR was superior to RE on reductions in physiological arousal; SR and BR were equivalent except for the superiority of SR on reductions in autonomic arousal.…

  2. Relaxed core projector-augmented-wave method.

    PubMed

    Marsman, M; Kresse, G

    2006-09-14

    We extend the full-potential projector-augmented-wave method beyond the frozen core approximation, i.e., include the self-consistent optimization of the core charge density, in such a manner that the valence wave functions remain orthogonal to the core. The method consists of an on-the-fly repseudization of the all-electron problem, solving for the self-consistent core charge density within a spherical approximation. The key ideas in our procedure are to keep the projector functions fixed throughout the electronic minimization and to derive the new pseudopartial waves from these original projector functions, at each step of the electronic minimization procedure. Results of relaxed core calculations for atomic interconfigurational energies, structural energy differences between bulk phases of Fe, atomization energies of a subset of Pople's G2-1 set, and the Rh 3d surface core level shifts for the (log3 x log3)-Rh(111) surface at 1/3 CO coverage are presented. PMID:16999509

  3. Relaxed core projector-augmented-wave method

    NASA Astrophysics Data System (ADS)

    Marsman, M.; Kresse, G.

    2006-09-01

    We extend the full-potential projector-augmented-wave method beyond the frozen core approximation, i.e., include the self-consistent optimization of the core charge density, in such a manner that the valence wave functions remain orthogonal to the core. The method consists of an on-the-fly repseudization of the all-electron problem, solving for the self-consistent core charge density within a spherical approximation. The key ideas in our procedure are to keep the projector functions fixed throughout the electronic minimization and to derive the new pseudopartial waves from these original projector functions, at each step of the electronic minimization procedure. Results of relaxed core calculations for atomic interconfigurational energies, structural energy differences between bulk phases of Fe, atomization energies of a subset of Pople's G2-1 set, and the Rh 3d surface core level shifts for the (√3 ×√3 )-Rh(111) surface at 1/3 CO coverage are presented.

  4. Post-shock relaxation in crystalline nitromethane

    NASA Astrophysics Data System (ADS)

    Rivera-Rivera, Luis A.; Sewell, Thomas D.; Thompson, Donald L.

    2013-02-01

    Molecular dynamics simulations of shocked (100)-oriented crystalline nitromethane were carried out to determine the rates of relaxation behind the shock wave. The forces were described by the fully flexible non-reactive Sorescu-Rice-Thompson force field [D. C. Sorescu, B. M. Rice, and D. L. Thompson, J. Phys. Chem. B 104, 8406 (2000)], 10.1021/jp000942q. The time scales for local and overall thermal equilibration in the shocked crystal were determined. The molecular center-of-mass and atomic kinetic energy distributions rapidly reach substantially different local temperatures. Several picoseconds are required for the two distributions to converge, corresponding to establishment of thermal equilibrium in the shocked crystal. The decrease of the molecular center-of-mass temperature and the increase of the atomic temperature behind the shock front exhibit essentially exponential dependence on time. Analysis of covalent bond distance distributions ahead of, immediately behind, and well behind the shock front showed that the effective bond stretching potentials are essentially harmonic. Effective force constants for the C-N, C-H, and N-O bonds immediately behind the shock front are larger by factors of 1.6, 2.5, and 2.0, respectively, than in the unshocked crystal; and by factors of 1.2, 2.2, and 1.7, respectively, compared to material sufficiently far behind the shock front to be essentially at thermal equilibrium.

  5. Relaxation oscillations in chalcogenide phase change memory

    NASA Astrophysics Data System (ADS)

    Nardone, M.; Karpov, V. G.; Karpov, I. V.

    2010-03-01

    The results of a comprehensive experimental study of relaxation oscillations in chalcogenide phase change memory are presented. Extending the previous work, voltage and current oscillations were measured over much longer periods of time and with a broad range of applied voltages, load resistances, and device thicknesses. The effects of various reset voltage levels and material types were also considered. Several types of oscillation patterns were observed; most were continuous through the measurement period while others exhibited few or no oscillations. Also observed were two distinct regimes of oscillations; one of stable amplitudes followed by one of decaying amplitudes. The duration of the stable regime and the total time for oscillation decay were found to be directly proportional to the device thickness. In addition, temporal drift of the threshold voltage was observed which provided a method for measuring the variation in the drift coefficient between different materials. A numerical model was developed to simulate oscillations and extrapolate our results to lower circuit time constants. The physical mechanism of oscillations and their stochastic nature are effectively described in the framework of field-induced nucleation, while the transition from stable to decaying amplitudes is attributed to concomitant thermally induced nucleation.

  6. Spectral relaxation in pump-probe transients

    NASA Astrophysics Data System (ADS)

    Farrow, Darcie A.; Yu, Anchi; Jonas, David M.

    2003-05-01

    The relationship between pump-probe transients and the transition frequency correlation function, M(t), is examined. Calculations of pump-probe transients are carried out with a full-quantum expression for a displaced harmonic oscillator coupled to a heat bath. Pump-probe transients for a slowly decaying, overdamped, Brownian oscillator are shown to resemble a power series in M(t), where the slowest time scale is always equal to the slowest decay in M(t). This equality is consistent with a semiclassical model of pump-probe and valid over the full range of temperature, pulse duration, and detuning explored. The contribution of time scales faster than M(t) to the pump-probe transient increases with increasing temperature, pulse duration, and detuning of the pulse center frequency below resonance. Pump-probe transients for a critically damped oscillator that decays on a femtosecond time scale also have faster early time decay at higher temperatures. Based on these calculations a bootstrap method is suggested for extracting M(t) from pump-probe data starting with the slowest decay. Comparisons are made between simulations of pump-probe and three pulse echo peak shift (3PEPS) transients for a single oscillator and for multiple oscillator systems. Additional fast relaxations similar to those in pump-probe are also present in the 3PEPS transients. For the models investigated, pump-probe is comparable to 3PEPS for the extraction of M(t).

  7. Gene teams with relaxed proximity constraint.

    PubMed

    Kim, Sun; Choi, Jeong-Hyeon; Yang, Jiong

    2005-01-01

    Functionally related genes co-evolve, probably due to the strong selection pressure in evolution. Thus we expect that they are present in multiple genomes. Physical proximity among genes, known as gene team, is a very useful concept to discover functionally related genes in multiple genomes. However, there are also many gene sets that do not preserve physical proximity. In this paper, we generalized the gene team model, that looks for gene clusters in a physically clustered form, to multiple genome cases with relaxed constraint. We propose a novel hybrid pattern model that combines the set and the sequential pattern models. Our model searches for gene clusters with and/or without physical proximity constraint. This model is implemented and tested with 97 genomes (120 replicons). The result was analyzed to show the usefulness of our model. Especially, analysis of gene clusters that belong to B. subtilis and E. coli demonstrated that our model predicted many experimentally verified operons and functionally related clusters. Our program is fast enough to provide a sevice on the web at http://platcom. informatics.indiana.edu/platcom/. Users can select any combination of 97 genomes to predict gene teams. PMID:16447961

  8. Formation of magnetic discontinuities through viscous relaxation

    SciTech Connect

    Kumar, Sanjay; Bhattacharyya, R.; Smolarkiewicz, P. K.

    2014-05-15

    According to Parker's magnetostatic theorem, tangential discontinuities in magnetic field, or current sheets (CSs), are generally unavoidable in an equilibrium magnetofluid with infinite electrical conductivity and complex magnetic topology. These CSs are due to a failure of a magnetic field in achieving force-balance everywhere and preserving its topology while remaining in a spatially continuous state. A recent work [Kumar, Bhattacharyya, and Smolarkiewicz, Phys. Plasmas 20, 112903 (2013)] demonstrated this CS formation utilizing numerical simulations in terms of the vector magnetic field. The magnetohydrodynamic simulations presented here complement the above work by demonstrating CS formation by employing a novel approach of describing the magnetofluid evolution in terms of magnetic flux surfaces instead of the vector magnetic field. The magnetic flux surfaces being the possible sites on which CSs develop, this approach provides a direct visualization of the CS formation, helpful in understanding the governing dynamics. The simulations confirm development of tangential discontinuities through a favorable contortion of magnetic flux surfaces, as the magnetofluid undergoes a topology-preserving viscous relaxation from an initial non-equilibrium state with twisted magnetic field. A crucial finding of this work is in its demonstration of CS formation at spatial locations away from the magnetic nulls.

  9. Magnetic relaxation in dysprosium-dysprosium collisions

    SciTech Connect

    Newman, Bonna K.; Johnson, Cort; Kleppner, Daniel; Greytak, Thomas J.; Brahms, Nathan; Au, Yat Shan; Connolly, Colin B.; Doyle, John M.

    2011-01-15

    The collisional magnetic reorientation rate constant g{sub R} is measured for magnetically trapped atomic dysprosium (Dy), an atom with large magnetic dipole moments. Using buffer gas cooling with cold helium, large numbers (>10{sup 11}) of Dy are loaded into a magnetic trap and the buffer gas is subsequently removed. The decay of the trapped sample is governed by collisional reorientation of the atomic magnetic moments. We find g{sub R}=1.9{+-}0.5x10{sup -11} cm{sup 3} s{sup -1} at 390 mK. We also measure the magnetic reorientation rate constant of holmium (Ho), another highly magnetic atom, and find g{sub R}=5{+-}2x10{sup -12} cm{sup 3} s{sup -1} at 690 mK. The Zeeman relaxation rates of these atoms are greater than expected for the magnetic dipole-dipole interaction, suggesting that another mechanism, such as an anisotropic electrostatic interaction, is responsible. Comparison with estimated elastic collision rates suggests that Dy is a poor candidate for evaporative cooling in a magnetic trap.

  10. "Basic MR Relaxation Mechanisms & Contrast Agent Design"

    PubMed Central

    De León-Rodríguez, Luis M.; Martins, André F.; Pinho, Marco; Rofsky, Neil; Sherry, A. Dean

    2015-01-01

    The diagnostic capabilities of magnetic resonance imaging (MRI) have undergone continuous and substantial evolution by virtue of hardware and software innovations and the development and implementation of exogenous contrast media. Thirty years since the first MRI contrast agent was approved for clinical use, a reliance on MR contrast media persists largely to improve image quality with higher contrast resolution and to provide additional functional characterization of normal and abnormal tissues. Further development of MR contrast media is an important component in the quest for continued augmentation of diagnostic capabilities. In this review we will detail the many important considerations when pursuing the design and use of MR contrast media. We will offer a perspective on the importance of chemical stability, particularly kinetic stability, and how this influences one's thinking about the safety of metal-ligand based contrast agents. We will discuss the mechanisms involved in magnetic resonance relaxation in the context of probe design strategies. A brief description of currently available contrast agents will be accompanied by an in-depth discussion that highlights promising MRI contrast agents in development for future clinical and research applications. Our intention is to give a diverse audience an improved understanding of the factors involved in developing new types of safe and highly efficient MR contrast agents and, at the same time, provide an appreciation of the insights into physiology and disease that newer types of responsive agents can provide. PMID:25975847

  11. Nonlinear wave scattering and electron beam relaxation

    NASA Technical Reports Server (NTRS)

    Muschietti, L.; Dum, C. T.

    1991-01-01

    The role played by nonlinear scattering during the relaxation of a warm electron beam is investigated through a numerical code based on kinetic equations. The code encompasses the quasi-linear wave-electron interaction and wave-wave scattering off ion clouds. Ions with velocities 2 nu sub i (nu sub i being the ion thermal velocity) are found to be the most efficient for scattering the Langmuir waves off their polarization clouds. The transfer rate of the spectrum out of resonance with the beam is larger by a factor 3 compared to usual estimates. The changes produced in the dispersion relation by the presence of the beam electrons dramatically alter the characteristics of the secondary spectrum. In a late phase the classic condensate K of about 0 is depleted, with the formation of a new condensate in resonance with the flat-topped beam distribution, which follows from the fact that the mere presence of the beam electrons creates a minimum in the frequency-wave-number relation. For strong and slow beams, the predictions of the code are found to be in excellent agreement with the results of the particle simulation if a dispersion relation that includes the beam is used.

  12. Relaxation mode analysis and Markov state relaxation mode analysis for chignolin in aqueous solution near a transition temperature.

    PubMed

    Mitsutake, Ayori; Takano, Hiroshi

    2015-09-28

    It is important to extract reaction coordinates or order parameters from protein simulations in order to investigate the local minimum-energy states and the transitions between them. The most popular method to obtain such data is principal component analysis, which extracts modes of large conformational fluctuations around an average structure. We recently applied relaxation mode analysis for protein systems, which approximately estimates the slow relaxation modes and times from a simulation and enables investigations of the dynamic properties underlying the structural fluctuations of proteins. In this study, we apply this relaxation mode analysis to extract reaction coordinates for a system in which there are large conformational changes such as those commonly observed in protein folding/unfolding. We performed a 750-ns simulation of chignolin protein near its folding transition temperature and observed many transitions between the most stable, misfolded, intermediate, and unfolded states. We then applied principal component analysis and relaxation mode analysis to the system. In the relaxation mode analysis, we could automatically extract good reaction coordinates. The free-energy surfaces provide a clearer understanding of the transitions not only between local minimum-energy states but also between the folded and unfolded states, even though the simulation involved large conformational changes. Moreover, we propose a new analysis method called Markov state relaxation mode analysis. We applied the new method to states with slow relaxation, which are defined by the free-energy surface obtained in the relaxation mode analysis. Finally, the relaxation times of the states obtained with a simple Markov state model and the proposed Markov state relaxation mode analysis are compared and discussed. PMID:26429000

  13. Relaxing music counters heightened consolidation of emotional memory.

    PubMed

    Rickard, Nikki S; Wong, Wendy Wing; Velik, Lauren

    2012-02-01

    Emotional events tend to be retained more strongly than other everyday occurrences, a phenomenon partially regulated by the neuromodulatory effects of arousal. Two experiments demonstrated the use of relaxing music as a means of reducing arousal levels, thereby challenging heightened long-term recall of an emotional story. In Experiment 1, participants (N=84) viewed a slideshow, during which they listened to either an emotional or neutral narration, and were exposed to relaxing or no music. Retention was tested 1 week later via a forced choice recognition test. Retention for both the emotional content (Phase 2 of the story) and material presented immediately after the emotional content (Phase 3) was enhanced, when compared with retention for the neutral story. Relaxing music prevented the enhancement for material presented after the emotional content (Phase 3). Experiment 2 (N=159) provided further support to the neuromodulatory effect of music by post-event presentation of both relaxing music and non-relaxing auditory stimuli (arousing music/background sound). Free recall of the story was assessed immediately afterwards and 1 week later. Relaxing music significantly reduced recall of the emotional story (Phase 2). The findings provide further insight into the capacity of relaxing music to attenuate the strength of emotional memory, offering support for the therapeutic use of music for such purposes. PMID:22207009

  14. Shape relaxation of liquid drops in a microgravity environment.

    PubMed

    Sadhal, S S; Rednikov, A; Ohsaka, K

    2004-11-01

    We investigated shape relaxation of liquid drops in a microgravity environment that was created by letting the drops fall freely. The drops were initially levitated in air by an acoustic/electrostatic hybrid levitator. The levitated drops were deformed due to the force balance among the levitating force, surface tension, and gravity. During the free fall, the deformed drops underwent shape relaxation driven by the surface tension to restore a spherical shape. The progress of the shape relaxation was characterized by measuring the aspect ratio as a function of time, and was compared to a simple linear relaxation model (in which only the fundamental mode was considered) for perfectly conductive drops. The results show that the model quite adequately describes the shape relaxation of uncharged/charged drops released from an acoustically levitated state. However, the model is less successful in describing the relaxation of drops that were levitated electrostatically before the free fall. This may be due to finite electrical conductivities of liquids, which somehow affects the initial stage of the shape relaxation process. PMID:15644374

  15. Ultrafast energy relaxation in single light-harvesting complexes

    PubMed Central

    Malý, Pavel; Gruber, J. Michael; Cogdell, Richard J.; Mančal, Tomáš; van Grondelle, Rienk

    2016-01-01

    Energy relaxation in light-harvesting complexes has been extensively studied by various ultrafast spectroscopic techniques, the fastest processes being in the sub–100-fs range. At the same time, much slower dynamics have been observed in individual complexes by single-molecule fluorescence spectroscopy (SMS). In this work, we use a pump–probe-type SMS technique to observe the ultrafast energy relaxation in single light-harvesting complexes LH2 of purple bacteria. After excitation at 800 nm, the measured relaxation time distribution of multiple complexes has a peak at 95 fs and is asymmetric, with a tail at slower relaxation times. When tuning the excitation wavelength, the distribution changes in both its shape and position. The observed behavior agrees with what is to be expected from the LH2 excited states structure. As we show by a Redfield theory calculation of the relaxation times, the distribution shape corresponds to the expected effect of Gaussian disorder of the pigment transition energies. By repeatedly measuring few individual complexes for minutes, we find that complexes sample the relaxation time distribution on a timescale of seconds. Furthermore, by comparing the distribution from a single long-lived complex with the whole ensemble, we demonstrate that, regarding the relaxation times, the ensemble can be considered ergodic. Our findings thus agree with the commonly used notion of an ensemble of identical LH2 complexes experiencing slow random fluctuations. PMID:26903650

  16. Nanosecond Relaxation Dynamics of Hydrated Proteins: Water versus protein contributions

    SciTech Connect

    Khodadadi, S; Curtis, J. E.; Sokolov, Alexei P

    2011-01-01

    We have studied picosecond to nanosecond dynamics of hydrated protein powders using dielectric spectroscopy and molecular dynamics (MD) simulations. Our analysis of hydrogen-atom single particle dynamics from MD simulations focused on main ( main tens of picoseconds) and slow ( slow nanosecond) relaxation processes that were observed in dielectric spectra of similar hydrated protein samples. Traditionally, the interpretation of these processes observed in dielectric spectra has been ascribed to the relaxation behavior of hydration water tightly bounded to a protein and not to protein atoms. Detailed analysis of the MD simulations and comparison to dielectric data indicate that the observed relaxation process in the nanosecond time range of hydrated protein spectra is mainly due to protein atoms. The relaxation processes involve the entire structure of protein including atoms in the protein backbone, side chains, and turns. Both surface and buried protein atoms contribute to the slow processes; however, surface atoms demonstrate slightly faster relaxation dynamics. Analysis of the water molecule residence and dipolar relaxation correlation behavior indicates that the hydration water relaxes at much shorter time scales.

  17. Branch Flow Model: Relaxations and Convexification-Part II

    SciTech Connect

    Farivar, M; Low, SH

    2013-08-01

    We propose a branch flow model for the analysis and optimization of mesh as well as radial networks. The model leads to a new approach to solving optimal power flow (OPF) that consists of two relaxation steps. The first step eliminates the voltage and current angles and the second step approximates the resulting problem by a conic program that can be solved efficiently. For radial networks, we prove that both relaxation steps are always exact, provided there are no upper bounds on loads. For mesh networks, the conic relaxation is always exact but the angle relaxation may not be exact, and we provide a simple way to determine if a relaxed solution is globally optimal. We propose convexification of mesh networks using phase shifters so that OPF for the convexified network can always be solved efficiently for an optimal solution. We prove that convexification requires phase shifters only outside a spanning tree of the network and their placement depends only on network topology, not on power flows, generation, loads, or operating constraints. Part I introduces our branch flow model, explains the two relaxation steps, and proves the conditions for exact relaxation. Part II describes convexification of mesh networks, and presents simulation results.

  18. Branch Flow Model: Relaxations and Convexification-Part I

    SciTech Connect

    Farivar, M; Low, SH

    2013-08-01

    We propose a branch flow model for the analysis and optimization of mesh as well as radial networks. The model leads to a new approach to solving optimal power flow (OPF) that consists of two relaxation steps. The first step eliminates the voltage and current angles and the second step approximates the resulting problem by a conic program that can be solved efficiently. For radial networks, we prove that both relaxation steps are always exact, provided there are no upper bounds on loads. For mesh networks, the conic relaxation is always exact but the angle relaxation may not be exact, and we provide a simple way to determine if a relaxed solution is globally optimal. We propose convexification of mesh networks using phase shifters so that OPF for the convexified network can always be solved efficiently for an optimal solution. We prove that convexification requires phase shifters only outside a spanning tree of the network and their placement depends only on network topology, not on power flows, generation, loads, or operating constraints. Part I introduces our branch flow model, explains the two relaxation steps, and proves the conditions for exact relaxation. Part II describes convexification of mesh networks, and presents simulation results.

  19. A quantum relaxation-time approximation for finite fermion systems

    SciTech Connect

    Reinhard, P.-G.; Suraud, E.

    2015-03-15

    We propose a relaxation time approximation for the description of the dynamics of strongly excited fermion systems. Our approach is based on time-dependent density functional theory at the level of the local density approximation. This mean-field picture is augmented by collisional correlations handled in relaxation time approximation which is inspired from the corresponding semi-classical picture. The method involves the estimate of microscopic relaxation rates/times which is presently taken from the well established semi-classical experience. The relaxation time approximation implies evaluation of the instantaneous equilibrium state towards which the dynamical state is progressively driven at the pace of the microscopic relaxation time. As test case, we consider Na clusters of various sizes excited either by a swift ion projectile or by a short and intense laser pulse, driven in various dynamical regimes ranging from linear to strongly non-linear reactions. We observe a strong effect of dissipation on sensitive observables such as net ionization and angular distributions of emitted electrons. The effect is especially large for moderate excitations where typical relaxation/dissipation time scales efficiently compete with ionization for dissipating the available excitation energy. Technical details on the actual procedure to implement a working recipe of such a quantum relaxation approximation are given in appendices for completeness.

  20. Relaxation rate in the assessment of masseter muscle fatigue.

    PubMed

    Lyons, M F; Aggarwal, A

    2001-02-01

    The aim of this study was to assess a simple method of measuring relaxation rate in the jaw-closing system for the purpose of quantifying jaw muscle fatigue. A summary of the various different methods of measuring relaxation rate is also provided. The rates of twitch contraction and relaxation were measured in 30 symptom-free subjects following bilateral direct electrical stimulation of the masseter muscles. The resulting twitch force was recorded via a force transducer placed between the anterior teeth. The transducer was held between the teeth with as little force as possible while four single stimuli were delivered at 5-s intervals. The stimulating electrodes were then removed and replaced and the experiment was repeated. The force records of the resulting twitches were averaged and the half-contraction time, twitch amplitude and half-relaxation time were measured. There was a significant difference in half-relaxation time between males and females, being faster in females (P=0.0045, independent t-test). No significant difference was found in twitch amplitude and half-contraction time between males and females. Half-relaxation time and half-contraction time were independent of twitch amplitude. This method of measuring the relaxation rate of the masseter muscles was found to be practical and the results were reproducible between sessions. PMID:11298267

  1. Ultrafast energy relaxation in single light-harvesting complexes.

    PubMed

    Malý, Pavel; Gruber, J Michael; Cogdell, Richard J; Mančal, Tomáš; van Grondelle, Rienk

    2016-03-15

    Energy relaxation in light-harvesting complexes has been extensively studied by various ultrafast spectroscopic techniques, the fastest processes being in the sub-100-fs range. At the same time, much slower dynamics have been observed in individual complexes by single-molecule fluorescence spectroscopy (SMS). In this work, we use a pump-probe-type SMS technique to observe the ultrafast energy relaxation in single light-harvesting complexes LH2 of purple bacteria. After excitation at 800 nm, the measured relaxation time distribution of multiple complexes has a peak at 95 fs and is asymmetric, with a tail at slower relaxation times. When tuning the excitation wavelength, the distribution changes in both its shape and position. The observed behavior agrees with what is to be expected from the LH2 excited states structure. As we show by a Redfield theory calculation of the relaxation times, the distribution shape corresponds to the expected effect of Gaussian disorder of the pigment transition energies. By repeatedly measuring few individual complexes for minutes, we find that complexes sample the relaxation time distribution on a timescale of seconds. Furthermore, by comparing the distribution from a single long-lived complex with the whole ensemble, we demonstrate that, regarding the relaxation times, the ensemble can be considered ergodic. Our findings thus agree with the commonly used notion of an ensemble of identical LH2 complexes experiencing slow random fluctuations. PMID:26903650

  2. Spectroscopic Studies of the Super Relaxed State of Skeletal Muscle

    PubMed Central

    Naber, Nariman; Pate, Edward; Canton, Marcella; Reggiani, Carlo; Cooke, Roger

    2016-01-01

    In the super-relaxed state of myosin, ATPase activity is strongly inhibited by binding of the myosin heads to the core of the thick filament in a structure known as the interacting-heads motif. In the disordered relaxed state myosin heads are not bound to the core of the thick filament and have an ATPase rate that is 10 fold greater. In the interacting-heads motif the two regulatory light chains appear to bind to each other. We have made single cysteine mutants of the regulatory light chain, placed both paramagnetic and fluorescent probes on them, and exchanged them into skinned skeletal muscle fibers. Many of the labeled light chains tended to disrupt the stability of the super-relaxed state, and showed spectral changes in the transition from the disordered relaxed state to the super-relaxed state. These data support the putative interface between the two regulatory light chains identified by cryo electron microscopy and show that both the divalent cation bound to the regulatory light chain and the N-terminus of the regulatory light chain play a role in the stability of the super-relaxed state. One probe showed a shift to shorter wavelengths in the super-relaxed state such that a ratio of intensities at 440nm to that at 520nm provided a measure of the population of the super-relaxed state amenable for high throughput screens for finding potential pharmaceuticals. The results provide a proof of concept that small molecules that bind to this region can destabilize the super-relaxed state and provide a method to search for small molecules that do so leading to a potentially effective treatment for Type 2 diabetes and obesity. PMID:27479128

  3. Spectroscopic Studies of the Super Relaxed State of Skeletal Muscle.

    PubMed

    Nogara, Leonardo; Naber, Nariman; Pate, Edward; Canton, Marcella; Reggiani, Carlo; Cooke, Roger

    2016-01-01

    In the super-relaxed state of myosin, ATPase activity is strongly inhibited by binding of the myosin heads to the core of the thick filament in a structure known as the interacting-heads motif. In the disordered relaxed state myosin heads are not bound to the core of the thick filament and have an ATPase rate that is 10 fold greater. In the interacting-heads motif the two regulatory light chains appear to bind to each other. We have made single cysteine mutants of the regulatory light chain, placed both paramagnetic and fluorescent probes on them, and exchanged them into skinned skeletal muscle fibers. Many of the labeled light chains tended to disrupt the stability of the super-relaxed state, and showed spectral changes in the transition from the disordered relaxed state to the super-relaxed state. These data support the putative interface between the two regulatory light chains identified by cryo electron microscopy and show that both the divalent cation bound to the regulatory light chain and the N-terminus of the regulatory light chain play a role in the stability of the super-relaxed state. One probe showed a shift to shorter wavelengths in the super-relaxed state such that a ratio of intensities at 440nm to that at 520nm provided a measure of the population of the super-relaxed state amenable for high throughput screens for finding potential pharmaceuticals. The results provide a proof of concept that small molecules that bind to this region can destabilize the super-relaxed state and provide a method to search for small molecules that do so leading to a potentially effective treatment for Type 2 diabetes and obesity. PMID:27479128

  4. Simultaneous measurement of heat capacity and internal relaxation time.

    PubMed

    Nagasawa, Mitsuharu

    2016-05-01

    A new steady-state method is proposed to simultaneously measure the heat capacity and internal relaxation time using superimposed constant and square-wave power. This method is appropriate for small sample systems with low thermal conductance. The accuracies of the heat capacity and internal relaxation time are almost the same as those determined using other similar methods, but correction for the effect of internal relaxation on the heat capacity is more flexible. The thermal diffusivity and thermal conductivity are also simultaneously determined for rod- and slab-shaped samples. We demonstrate the method for small slabs of synthetic silica in the 80-320 K temperature range. PMID:27250459

  5. Is spin lattice relaxation time independent of species?

    PubMed

    Akber, S F

    1996-08-01

    It has been suggested that the spin lattice relaxation time is independent of species. It was further stated that, from a nuclear magnetic resonance standpoint, the human muscle is similar to rat muscle and to pig muscle, etc. However, it is observed that, in normal liver and kidney of human, rat, dog, rabbit and hamster, spin lattice relaxation time varies in different species as a function of percentage of body-weight of the organ. The result shows that spin lattice relaxation time is different in different species because of the organ weight which in turn dictates the metabolism in an individual species. PMID:8869924

  6. α and β relaxation dynamics of a fragile plastic crystal

    NASA Astrophysics Data System (ADS)

    Pardo, L. C.; Lunkenheimer, P.; Loidl, A.

    2006-03-01

    We present a thorough dielectric investigation of the relaxation dynamics of plastic crystalline Freon112, which exhibits freezing of the orientational degrees of freedom into a glassy crystal below 90K. Among other plastic crystals, Freon112 stands out by being relatively fragile within Angell's [Relaxations in Complex Systems, edited by K. L. Ngai and G. B. Wright (NRL, Washington, DC, 1985), p. 3] classification scheme and by showing an unusually strong β relaxation. Comparing the results to those on Freon112a, having only a single molecular conformation, points to the importance of the presence of two molecular conformations in Freon112 for the explanation of its unusual properties.

  7. Femtosecond time-resolved electronic relaxation dynamics in tetrathiafulvalene

    SciTech Connect

    Staedter, D.; Polizzi, L.; Thiré, N.; Mairesse, Y.; Mayer, P.; Blanchet, V.

    2015-05-21

    In the present paper, the ultrafast electronic relaxation of tetrathiafulvalene (TTF) initiated around 4 eV is studied by femtosecond time-resolved velocity-map imaging. The goal is to investigate the broad double structure observed in the absorption spectrum at this energy. By monitoring the transients of the parent cation and its fragments and by varying the pump and the probe wavelengths, two internal conversions and intramolecular vibrational relaxation are detected both on the order of a few hundred of femtoseconds. Photoelectron images permit the assignment of a dark electronic state involved in the relaxation. In addition, the formation of the dimer of TTF has been observed.

  8. Relaxation dynamics of amorphous dibucaine using dielectric studies

    NASA Astrophysics Data System (ADS)

    Sahra, M.; Jumailath, K.; Thayyil, M. Shahin; Capaccioli, S.

    2015-06-01

    Using broadband dielectric spectroscopy the molecular mobility of dibucaine is investigated in the supercooled liquid and gassy states, over a wide temperature range for some test frequencies. Above the glass transition temperature Tg, the presence of structural α- relaxation peak was observed due to the cooperative motions of the molecule and upon cooling frozen kinetically to form the glass. The secondary relaxation process was perceivable below Tg due to localized motions. The peak loss frequency of α-relaxation process shows non-Arrhenius behavior and obeys Vogel-Fulcher-Tammann equation over the measured temperature range whereas the β- process shows Arrhenius behavior.

  9. Diffusive mesh relaxation in ALE finite element numerical simulations

    SciTech Connect

    Dube, E.I.

    1996-06-01

    The theory for a diffusive mesh relaxation algorithm is developed for use in three-dimensional Arbitary Lagrange/Eulerian (ALE) finite element simulation techniques. This mesh relaxer is derived by a variational principle for an unstructured 3D grid using finite elements, and incorporates hourglass controls in the numerical implementation. The diffusive coefficients are based on the geometric properties of the existing mesh, and are chosen so as to allow for a smooth grid that retains the general shape of the original mesh. The diffusive mesh relaxation algorithm is then applied to an ALE code system, and results from several test cases are discussed.

  10. Stress Relaxation for Granular Materials near Jamming under Cyclic Compression

    NASA Astrophysics Data System (ADS)

    Farhadi, Somayeh; Zhu, Alex Z.; Behringer, Robert P.

    2015-10-01

    We have explored isotropically jammed states of semi-2D granular materials through cyclic compression. In each compression cycle, systems of either identical ellipses or bidisperse disks transition between jammed and unjammed states. We determine the evolution of the average pressure P and structure through consecutive jammed states. We observe a transition point ϕm above which P persists over many cycles; below ϕm, P relaxes slowly. The relaxation time scale associated with P increases with packing fraction, while the relaxation time scale for collective particle motion remains constant. The collective motion of the ellipses is hindered compared to disks because of the rotational constraints on elliptical particles.

  11. Spin relaxation of iron in mixed state hemoproteins.

    PubMed Central

    Wajnberg, E; Kalinowski, H J; Bemski, G; Helman, J S

    1986-01-01

    In hemoproteins the relaxation mechanism of iron is Orbach for high spin (HS) and Raman for low spin (LS). We found that in met-hemoglobin and met-myoglobin, under conditions in which the two spin states coexist, both the HS and the LS states relax to the lattice through Orbach-like processes. Alos, very short (approximately 1 ns) and temperature independent transverse relaxation times T2 were estimated. This may result from the unusual electronic structure of mixed states hemoproteins that allows thermal equilibrium and interconversion of the spin states. PMID:3013333

  12. Calorimetric and relaxation properties of xylitol-water mixtures

    NASA Astrophysics Data System (ADS)

    Elamin, Khalid; Sjöström, Johan; Jansson, Helén; Swenson, Jan

    2012-03-01

    We present the first broadband dielectric spectroscopy (BDS) and differential scanning calorimetry study of supercooled xylitol-water mixtures in the whole concentration range and in wide frequency (10-2-106 Hz) and temperature (120-365 K) ranges. The calorimetric glass transition, Tg, decreases from 247 K for pure xylitol to about 181 K at a water concentration of approximately 37 wt. %. At water concentrations in the range 29-35 wt. % a plentiful calorimetric behaviour is observed. In addition to the glass transition, almost simultaneous crystallization and melting events occurring around 230-240 K. At higher water concentrations ice is formed during cooling and the glass transition temperature increases to a steady value of about 200 K for all higher water concentrations. This Tg corresponds to an unfrozen xylitol-water solution containing 20 wt. % water. In addition to the true glass transition we also observed a glass transition-like feature at 220 K for all the ice containing samples. However, this feature is more likely due to ice dissolution [A. Inaba and O. Andersson, Thermochim. Acta, 461, 44 (2007)]. In the case of the BDS measurements the presence of water clearly has an effect on both the cooperative α-relaxation and the secondary β-relaxation. The α-relaxation shows a non-Arrhenius temperature dependence and becomes faster with increasing concentration of water. The fragility of the solutions, determined by the temperature dependence of the α-relaxation close to the dynamic glass transition, decreases with increasing water content up to about 26 wt. % water, where ice starts to form. This decrease in fragility with increasing water content is most likely caused by the increasing density of hydrogen bonds, forming a network-like structure in the deeply supercooled regime. The intensity of the secondary β-relaxation of xylitol decreases noticeably already at a water content of 2 wt. %, and at a water content above 5 wt. % it has been replaced by a

  13. Dielectric relaxation of electrolyte solutions using terahertz transmission spectroscopy

    NASA Astrophysics Data System (ADS)

    Asaki, M. L. T.; Redondo, A.; Zawodzinski, T. A.; Taylor, A. J.

    2002-05-01

    We use terahertz (THz) transmission spectroscopy to obtain the frequency dependent complex dielectric constants of water, methanol, and propylene carbonate, and solutions of lithium salts in these solvents. The behavior of the pure solvents is modeled with either two (water) or three (methanol and propylene carbonate) Debye relaxations. We discuss the effects of ionic solvation on the relaxation behavior of the solvents in terms of modifications to the values of the Debye parameters of the pure solvents. In this way we obtain estimates for numbers of irrotationally bound solvent molecules, the numbers of bonds broken or formed, and the effects of ions on the higher-frequency relaxations.

  14. Caffeine relaxes smooth muscle through actin depolymerization.

    PubMed

    Tazzeo, Tracy; Bates, Genevieve; Roman, Horia Nicolae; Lauzon, Anne-Marie; Khasnis, Mukta D; Eto, Masumi; Janssen, Luke J

    2012-08-15

    Caffeine is sometimes used in cell physiological studies to release internally stored Ca(2+). We obtained evidence that caffeine may also act through a different mechanism that has not been previously described and sought to examine this in greater detail. We ruled out a role for phosphodiesterase (PDE) inhibition, since the effect was 1) not reversed by inhibiting PKA or adenylate cyclase; 2) not exacerbated by inhibiting PDE4; and 3) not mimicked by submillimolar caffeine nor theophylline, both of which are sufficient to inhibit PDE. Although caffeine is an agonist of bitter taste receptors, which in turn mediate bronchodilation, its relaxant effect was not mimicked by quinine. After permeabilizing the membrane using β-escin and depleting the internal Ca(2+) store using A23187, we found that 10 mM caffeine reversed tone evoked by direct application of Ca(2+), suggesting it functionally antagonizes the contractile apparatus. Using a variety of molecular techniques, we found that caffeine did not affect phosphorylation of myosin light chain (MLC) by MLC kinase, actin-filament motility catalyzed by MLC kinase, phosphorylation of CPI-17 by either protein kinase C or RhoA kinase, nor the activity of MLC-phosphatase. However, we did obtain evidence that caffeine decreased actin filament binding to phosphorylated myosin heads and increased the ratio of globular to filamentous actin in precontracted tissues. We conclude that, in addition to its other non-RyR targets, caffeine also interferes with actin function (decreased binding by myosin, possibly with depolymerization), an effect that should be borne in mind in studies using caffeine to probe excitation-contraction coupling in smooth muscle. PMID:22683573

  15. Scheduled Relaxation Jacobi method: Improvements and applications

    NASA Astrophysics Data System (ADS)

    Adsuara, J. E.; Cordero-Carrión, I.; Cerdá-Durán, P.; Aloy, M. A.

    2016-09-01

    Elliptic partial differential equations (ePDEs) appear in a wide variety of areas of mathematics, physics and engineering. Typically, ePDEs must be solved numerically, which sets an ever growing demand for efficient and highly parallel algorithms to tackle their computational solution. The Scheduled Relaxation Jacobi (SRJ) is a promising class of methods, atypical for combining simplicity and efficiency, that has been recently introduced for solving linear Poisson-like ePDEs. The SRJ methodology relies on computing the appropriate parameters of a multilevel approach with the goal of minimizing the number of iterations needed to cut down the residuals below specified tolerances. The efficiency in the reduction of the residual increases with the number of levels employed in the algorithm. Applying the original methodology to compute the algorithm parameters with more than 5 levels notably hinders obtaining optimal SRJ schemes, as the mixed (non-linear) algebraic-differential system of equations from which they result becomes notably stiff. Here we present a new methodology for obtaining the parameters of SRJ schemes that overcomes the limitations of the original algorithm and provide parameters for SRJ schemes with up to 15 levels and resolutions of up to 215 points per dimension, allowing for acceleration factors larger than several hundreds with respect to the Jacobi method for typical resolutions and, in some high resolution cases, close to 1000. Most of the success in finding SRJ optimal schemes with more than 10 levels is based on an analytic reduction of the complexity of the previously mentioned system of equations. Furthermore, we extend the original algorithm to apply it to certain systems of non-linear ePDEs.

  16. Effects of Institut Georges Lopez-1 and Celsior preservation solutions on liver graft injury

    PubMed Central

    Tabka, Donia; Bejaoui, Mohamed; Javellaud, James; Roselló-Catafau, Joan; Achard, Jean-Michel; Abdennebi, Hassen Ben

    2015-01-01

    AIM: To compare Institut Georges Lopez (IGL-1) and Celsior preservation solutions for hepatic endothelium relaxation and liver cold ischemia reperfusion injury (IRI). METHODS: Two experimental models were used. In the first one, acetylcholine-induced endothelium-dependent relaxation (EDR) was measured in isolated ring preparations of rat hepatic arteries preserved or not in IGL-1 or Celsior solutions (24 h at 4 °C). To determine nitric oxide (NO) and cyclooxygenase EDR, hepatic arteries were incubated with L-NG-nitroarginine methyl ester (L-NAME), an inhibitor of endothelium nitric oxide synthase (eNOS), or with L-NAME plus indomethacin, an inhibitor of cyclooxygenase. In the second experiment, rat livers were cold-stored in IGL-1 or Celsior solutions for 24 h at 4 °C and then perfused “ex vivo” for 2 h at 37 °C. Liver injury was assessed by transaminase measurements, liver function by bile production and bromosulfophthalein clearance, oxidative stress by malondialdehyde levels and catalase activity and alterations in cell signaling pathways by pAkt, pAMPK, eNOS and MAPKs proteins level. RESULTS: After cold storage for 24 h with either Celsior or IGL-1, EDR was only slightly altered. In freshly isolated arteries, EDR was exclusively mediated by NO. However, cold-stored arteries showed NO- and COX-dependent relaxation. The decrease in NO-dependent relaxation after cold storage was significantly more marked with Celsior. The second study indicated that IGL-1 solution obtained better liver preservation and protection against IRI than Celsior. Liver injury was reduced, function was improved and there was less oxidative stress. IGL-1 solution activated Akt and AMPK, which was concomitant with increased eNOS expression and nitrite/nitrate levels. Furthermore, MAPKs kinases were regulated in livers preserved with IGL-1 solution since reductions in p-p38, p-ERK and p-JNK protein levels were observed. CONCLUSION: IGL-1 solution preserved NO-dependent relaxation

  17. Magnetic decoupling studies of Rb relaxation in Xe

    NASA Astrophysics Data System (ADS)

    Griffith, W. M.; Walter, D. K.; Happer, W.

    2001-05-01

    We present the results of extensive experiments on the relaxation of ^85Rb and ^87Rb due to gas-phase interactions with Xe in the presence of third-body gases in the pressure range from tens of torr to more than an atmosphere. By studying the relaxation as a function of applied magnetic field from 0 to 6000 G, we are able to separate the Rb relaxation into contributions from Rb--Xe binary collisions and from Rb--Xe van der Waals molecules. We have determined to high accuracy the strength of the Rb--Xe spin-rotation coupling constant, and we report the temperature dependences of the Rb--Xe binary relaxation cross section, the molecular formation rate, and the molecular break-up rate.

  18. Effects of magnetic field on anisotropic temperature relaxation

    SciTech Connect

    Dong Chao; Ren Haijun; Cai Huishan; Li Ding

    2013-03-15

    In a strongly magnetized plasma, where the particles' thermal gyro-radii are smaller than the Debye length, the magnetic field greatly affects the plasma's relaxation processes. The expressions for the time rates of change of the electron and ion parallel and perpendicular temperatures are obtained and calculated analytically for small anisotropies through considering binary collisions between charged particles in the presence of a uniform magnetic field by using perturbation theory. Based on these expressions, the effects of the magnetic field on the relaxation of anisotropic electron and ion temperatures due to electron-electron collisions, ion-ion collisions, and electron-ion collisions are investigated. Consequently, the relaxation times of anisotropic electron and ion temperatures to isotropy are calculated. It is shown that electron-ion collisions can affect the relaxation of an anisotropic ion distribution in the strong magnetic field.

  19. Nonexistence results for relaxation spectra with compact support

    NASA Astrophysics Data System (ADS)

    Douglas, R. J.; Whittle Gruffudd, H. R.

    2016-03-01

    In this paper we consider the problem of recovering the (transformed) relaxation spectrum h from the (transformed) loss modulus g by inverting the integral equation g={{sech}}\\ast h, where \\ast denotes convolution, using Fourier transforms. We are particularly interested in establishing properties of h, having assumed that the Fourier transform of g has entire extension to the complex plane. In the setting of square integrable functions, we demonstrate that the Paley-Wiener theorem cannot be used to show the existence of non-trivial relaxation spectra with compact support. We prove a stronger result for tempered distributions: there are no non-trivial relaxation spectra with compact support. Finally we establish necessary and sufficient conditions for the relaxation spectrum h to be strictly positive definite.

  20. Analysis of the Palierne model by relaxation time spectrum

    NASA Astrophysics Data System (ADS)

    Kwon, Mi Kyung; Cho, Kwang Soo

    2016-02-01

    Viscoelasticity of immiscible polymer blends is affected by relaxation of the interface. Several attempts have been made for linear viscoelasticity of immiscible polymer blends. The Palierne model (1990) and the Gramespacher-Meissner model (1992) are representative. The Gramespacher-Meissner model consists of two parts: ingredients and interface. Moreover, it provides us the formula of the peak of interface in weighted relaxation time spectrum, which enables us to analyze the characteristics relating to interface more obviously. However, the Gramespacher-Meissner model is a kind of empirical model. Contrary to the Gramespacher-Meissner model, the Palierne model was derived in a rigorous manner. In this study, we investigated the Palierne model through the picture of the Gramespacher-Meissner model. We calculated moduli of immiscible blend using two models and obtained the weighted relaxation time spectra of them. The fixed-point iteration of Cho and Park (2013) was used in order to determine the weighted relaxation spectra.

  1. Internal friction and mode relaxation in a simple chain model.

    PubMed

    Fugmann, S; Sokolov, I M

    2009-12-21

    We consider the equilibrium relaxation properties of the end-to-end distance and of the principal components in a one-dimensional polymer chain model with nonlinear interaction between the beads. While for the single-well potentials these properties are similar to the ones of a Rouse chain, for the double-well interaction potentials, modeling internal friction, they differ vastly from the ones of the harmonic chain at intermediate times and intermediate temperatures. This minimal description within a one-dimensional model mimics the relaxation properties found in much more complex polymer systems. Thus, the relaxation time of the end-to-end distance may grow by orders of magnitude at intermediate temperatures. The principal components (whose directions are shown to coincide with the normal modes of the harmonic chain, whatever interaction potential is assumed) not only display larger relaxation times but also subdiffusive scaling. PMID:20025352

  2. Low temperature dielectric relaxation study of aqueous solutions of diethylsulfoxide

    NASA Astrophysics Data System (ADS)

    Gabrielyan, Liana; Markarian, Shiraz; Lunkenheimer, Peter; Loidl, Alois

    2014-11-01

    In the present work, dielectric spectra of mixtures of diethylsulfoxide (DESO) and water are presented, covering a concentration range of 0.2-0.3 molar fraction of DESO. The measurements were performed at frequencies between 1Hz and 10MHz and for temperatures between 150 and 300K. It is shown that DESO/water mixtures have strong glass-forming abilities. The permittivity spectra in these mixtures reveal a single relaxation process. It can be described by the Havriliak-Negami relaxation function and its relaxation times follow the Vogel-Fulcher-Tammann law, thus showing the typical signatures of glassy dynamics. The concentration dependence of the relaxation parameters, like fragility, broadening, and glass temperature, are discussed in detail.

  3. Suppression of β Relaxation in Vapor-Deposited Ultrastable Glasses.

    PubMed

    Yu, H B; Tylinski, M; Guiseppi-Elie, A; Ediger, M D; Richert, R

    2015-10-30

    Glassy materials display numerous important properties which relate to the presence and intensity of the secondary (β) relaxations that dominate the dynamics below the glass transition temperature. However, experimental protocols such as annealing allow little control over the β relaxation for most glasses. Here we report on the β relaxation of toluene in highly stable glasses prepared by physical vapor deposition. At conditions that generate the highest kinetic stability, about 70% of the β relaxation intensity is suppressed, indicating the proximity of this state to the long-sought "ideal glass." While preparing such a state via deposition takes less than an hour, it would require ~3500 years of annealing an ordinary glass to obtain similarly suppressed dynamics. PMID:26565473

  4. (129)Xe NMR Relaxation-Based Macromolecular Sensing.

    PubMed

    Gomes, Muller D; Dao, Phuong; Jeong, Keunhong; Slack, Clancy C; Vassiliou, Christophoros C; Finbloom, Joel A; Francis, Matthew B; Wemmer, David E; Pines, Alexander

    2016-08-10

    We report a (129)Xe NMR relaxation-based sensing approach that exploits changes in the bulk xenon relaxation rate induced by slowed tumbling of a cryptophane-based sensor upon target binding. The amplification afforded by detection of the bulk dissolved xenon allows sensitive detection of targets. The sensor comprises a xenon-binding cryptophane cage, a target interaction element, and a metal chelating agent. Xenon associated with the target-bound cryptophane cage is rapidly relaxed and then detected after exchange with the bulk. Here we show that large macromolecular targets increase the rotational correlation time of xenon, increasing its relaxation rate. Upon binding of a biotin-containing sensor to avidin at 1.5 μM concentration, the free xenon T2 is reduced by a factor of 4. PMID:27472048

  5. Two relaxation time lattice Boltzmann model for rarefied gas flows

    NASA Astrophysics Data System (ADS)

    Esfahani, Javad Abolfazli; Norouzi, Ali

    2014-01-01

    In this paper, the lattice Boltzmann equation (LBE) with two relaxation times (TRT) is implemented in order to study gaseous flow through a long micro/nano-channel. A new relation is introduced for the reflection factor in the bounce-back/specular reflection (BSR) boundary condition based on the analytical solution of the Navier-Stokes equations. The focus of the present study is on comparing TRT with the other LBE models called multiple relaxation times (MRT) and single relaxation time (SRT) in simulation of rarefied gas flows. After a stability analysis for the TRT and SRT models, the numerical results are presented and validated by the analytical solution of the Navier-Stokes equations with slip boundary condition, direct simulation of Monte Carlo (DSMC) and information preservation (IP) method. The effect of various gases on flow behavior is also investigated by using the variable hard sphere (VHS) model through the symmetrical relaxation time.

  6. Plasmid-protein relaxation complexes in Staphylococcus aureus.

    PubMed

    Novick, R

    1976-09-01

    Protein-deoxyribonucleic acid relaxation complexes have been demonstrated for six Staphylococcus aureus plasmids out of sixteen examined. Four of these encode stretomycin resistence, have molecular weights of about 2.7 x 10(6), and are isolated as supercoiled molecules that are virtally 100% relaxable by treatment with sodium dodecyl sulfate. It is probable that these four isolates represent a single widely disseminated plasmid species. The other two plasmids showing relaxation complexes have molecular weights of about 3 x 10(6) and encode chloramphenicol resistance. The complexes in these cases are unstable, and it has not been possible to induce more than 50% relaxation by any of the standard treatments. Ten other plasmids do not show detectable complexes. These include three penicillinase plasmids, four tetracycline-resistance plasmids, one plasmid carrying kanamycin-neomycin resistance, and finally, two chloramphenicol-resistance plasmids. PMID:956124

  7. Lateral stress relaxation and collapse in lipid monolayers†

    PubMed Central

    Pocivavsek, Luka; Frey, Shelli L.; Krishan, Kapilanjan; Gavrilov, Kseniya; Ruchala, Piotr; Waring, Alan J.; Walther, Frans J.; Dennin, Michael; Witten, Thomas A.; Lee, Ka Yee C.

    2009-01-01

    Surfactants at air/water interfaces are often subjected to mechanical stresses as the interfaces they occupy are reduced in area. The most well characterized forms of stress relaxation in these systems are first order phase transitions from lower density to higher density phases. Here we study stress relaxation in lipid monolayers that occurs once chemical phase transitions have been exhausted. At these highly compressed states, the monolayer undergoes global mechanical relaxations termed collapse. By studying four different types of monolayers, we determine that collapse modes are most closely linked to in-plane rigidity. We characterize the rigidity of the monolayer by analyzing in-plane morphology on numerous length scales. More rigid monolayers collapse out-of-plane via a hard elastic mode similar to an elastic membrane, while softer monolayers relax in-plane by shearing. PMID:19657472

  8. Some puzzles about logarithmic relaxations and a few possible resolutions

    SciTech Connect

    Pollak, M.

    2014-08-20

    Three subjects are examined in connection with the relaxation of an electron glass. 1. In most cases the experimental decay time τ is found to relate to a history of the system rather than to the time it takes to reach equilibrium. The reason is that in a non-ergodic system equilibrium cannot be reached in any experiment but the knowledge of an equilibrium property is essential in evaluating the time to reach it. 2. An alternative theory is proposed for the interpretation of aging experiments. The proposed theory is deemed to better represent the physics and is more in keeping with the relaxation theory. 3. A current relaxation theory for the electron glass fails to take into account a certain renewal process during the evolution of the relaxation, namely the possibility of fast transitions following a slow transition. Ramifications of such a neglect are explored.

  9. Multi-region relaxed Hall magnetohydrodynamics with flow

    NASA Astrophysics Data System (ADS)

    Lingam, Manasvi; Abdelhamid, Hamdi M.; Hudson, Stuart R.

    2016-08-01

    The recent formulations of multi-region relaxed magnetohydrodynamics (MRxMHD) have generalized the famous Woltjer-Taylor states by incorporating a collection of "ideal barriers" that prevent global relaxation and flow. In this paper, we generalize MRxMHD with flow to include Hall effects, and thereby obtain the partially relaxed counterparts of the famous double Beltrami states as a special subset. The physical and mathematical consequences arising from the introduction of the Hall term are also presented. We demonstrate that our results (in the ideal MHD limit) constitute an important subset of ideal MHD equilibria, and we compare our approach against other variational principles proposed for deriving the partially relaxed states.

  10. Influence of coherent optical phonon on ultrafast energy relaxation

    NASA Astrophysics Data System (ADS)

    Wang, J. L.; Guo, L.; Liu, C. H.; Xu, X.; Chen, Y. F.

    2015-08-01

    Ultrafast energy relaxation process in Bi2Te3 thin films is studied using a collinear two color pump-probe technique. The coherent optical phonon is enhanced and destroyed by changing the separation times of double pump pulses. The non-oscillatory component of the reflectivity trace after the second pump pulse shows a distinct difference with and without the presence of coherent optical phonons, thus providing a direct evidence of the effect of optical phonon on the hot carrier relaxation process. The deduced characteristic times are systematically smaller when coherent optical phonons are involved in the energy transfer process. Comparatively, the conventional relaxation process is relatively slow, which is explained by the screening effect of the incoherent optical phonon. This work suggests that the energy relaxation can be manipulated through the excitation of coherent optical phonons.

  11. A unifying perspective: the relaxed linear micromorphic continuum

    NASA Astrophysics Data System (ADS)

    Neff, Patrizio; Ghiba, Ionel-Dumitrel; Madeo, Angela; Placidi, Luca; Rosi, Giuseppe

    2014-09-01

    We formulate a relaxed linear elastic micromorphic continuum model with symmetric Cauchy force stresses and curvature contribution depending only on the micro-dislocation tensor. Our relaxed model is still able to fully describe rotation of the microstructure and to predict nonpolar size effects. It is intended for the homogenized description of highly heterogeneous, but nonpolar materials with microstructure liable to slip and fracture. In contrast to classical linear micromorphic models, our free energy is not uniformly pointwise positive definite in the control of the independent constitutive variables. The new relaxed micromorphic model supports well-posedness results for the dynamic and static case. There, decisive use is made of new coercive inequalities recently proved by Neff, Pauly and Witsch and by Bauer, Neff, Pauly and Starke. The new relaxed micromorphic formulation can be related to dislocation dynamics, gradient plasticity and seismic processes of earthquakes. It unifies and simplifies the understanding of the linear micromorphic models.

  12. Ferrohydrodynamic evaluation of rotational viscosity and relaxation in certain ferrofluids.

    PubMed

    Patel, Rajesh

    2012-07-01

    A significant effect of aggregation dynamics for aqueous ferrofluid (AF) and kerosene based ferrofluid (KF) using magnetic field dependent capillary viscosity and magneto-optical relaxation measurements is studied. For better comparison parameters of AF and KF are kept similar. Ferrohydrodynamic equations of chain forming ferrofluids, dilute ferrofluids, and Brownian dynamic simulations are compared. It is observed that the rotational viscosity of AF is larger than that of KF due to field induced aggregates in it and strong dipolar interactions. It is also observed that at Ωτ ~ 0.04 both AF and KF viscosity becomes almost similar, suggesting similar behavior at that shear rate. The magneto-optical relaxation in AF exhibits nonexponential behavior when relaxed from higher magnetic field and follows irreversible thermodynamics, whereas for KF the relaxation is exponential and follows the effective field method. This discrepancy is explained based on aggregation dynamics of magnetic particles. Results are well described by the corresponding theoretical models. PMID:23005542

  13. Ab Initio Electronic Relaxation Times and Transport in Noble Metals

    NASA Astrophysics Data System (ADS)

    Mustafa, Jamal I.; Bernardi, Marco; Neaton, Jeffrey B.; Louie, Steven G.

    Relaxation times employed to study electron transport in metals are typically assumed to be constants and obtained empirically using the Drude model. Here, we employ ab initio calculations to compute the electron-phonon relaxation times of Cu, Ag, and Au, and find that they vary significantly on the Fermi surface, spanning ~15 -45 fs. We compute room temperature resistivities in excellent agreement with experiment by combining GW bandstructures, Wannier-interpolated band velocities, and ab initio relaxation times. Our calculations are compared to other approximations used for the relaxation times. Additionally, an importance sampling scheme is introduced to speed up the convergence of resistivity and transport calculations by sampling directly points on the Fermi surface. This work was supported by NSF Grant No. DMR15-1508412 and U.S. DOE under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at LBNL's NERSC facility.

  14. Nuclear-spin-lattice relaxation in rhenium metal

    SciTech Connect

    Dimitropoulos, C.; Bucher, J.P.; Borsa, F.; Corti, M.

    1989-04-01

    Nuclear-spin-lattice relaxation measurements are presented for /sup 187/Re in Re metal as a function of temperature. The relaxation transition probabilities were extracted from the nuclear magnetization recovery curves both in high magnetic field (H/sub 0/ = 8 T) nuclear-magnetic-resonance experiments and in nuclear-quadrupole-resonance (H/sub 0/ = 0) experiments. It is found that the dominant relaxation mechanisms is due to magnetic rather then quadrupolar hyperfine interaction with W/sub M/ = 1.32 T. The data are analyzed in terms of the electronic structure of Re metal. The analysis confirms that Re is a ''weakly enhanced'' transition metal with a nuclear relaxation rate dominated by the s-contact hyperfine interaction.

  15. Spin relaxation characteristics in Ag nanowire covered with various oxides

    NASA Astrophysics Data System (ADS)

    Karube, S.; Idzuchi, H.; Kondou, K.; Fukuma, Y.; Otani, Y.

    2015-09-01

    We have studied spin relaxation characteristics in a Ag nanowire covered with various oxide layers of Bi2O3, Al2O3, HfO2, MgO, or AgOx by using non-local spin valve structures. The spin-flip probability, a ratio of momentum relaxation time to spin relaxation time at 10 K, exhibits a gradual increase with an atomic number of the oxide constituent elements, Mg, Al, Ag, and Hf. Surprisingly, the Bi2O3 capping was found to increase the probability by an order of magnitude compared with other oxide layers. This finding suggests the presence of an additional spin relaxation mechanism such as Rashba effect at the Ag/Bi2O3 interface, which cannot be explained by the simple Elliott-Yafet mechanism via phonon, impurity, and surface scatterings. The Ag/Bi2O3 interface may provide functionality as a spin to charge interconversion layer.

  16. Dynamics in supercooled polyalcohols: Primary and secondary relaxation

    NASA Astrophysics Data System (ADS)

    Döß, A.; Paluch, M.; Sillescu, H.; Hinze, G.

    2002-10-01

    We have studied details of the molecular dynamics in a series of pure polyalcohols by means of dielectric spectroscopy and 2H nuclear magnetic resonance (NMR). From glycerol to threitol, xylitol and sorbitol a systematic change in the dynamics of the primary and secondary relaxation is found. With increasing molecular weight and fragility an increase in the width of the α-peak is observed. Details of the molecular reorientation process responsible for the α-relaxation were exploited by two-dimensional NMR experiments. It is found that in the same sequence of polyalcohols the appearance of the secondary relaxation changes gradually from a wing type scenario to a pronounced β-peak. From NMR experiments using selectively deuterated samples the molecular origin of the secondary relaxation could be elucidated in more detail.

  17. Multilayer relaxation and surface structure of ordered alloys

    NASA Technical Reports Server (NTRS)

    Kobistek, Robert J.; Bozzolo, Guillermo; Ferrante, John; Schlosser, Herbert

    1993-01-01

    Using BFS, a new semiempirical method for alloys, we study the surface structure of fcc ordered binary alloys in the Ll(sub 2) structure (Ni3Al and Cu3Au). We show that the surface energy is lowest for the mixed composition truncation of the low-index faces of such systems. Also, we present results for the interlayer relaxations for planes close to the surface, revealing different relaxations for atoms of different species producing a rippled surface layer.

  18. Exchange and relaxation effects in low-energy radiationless transitions

    NASA Technical Reports Server (NTRS)

    Chen, M. H.; Crasemann, B.; Aoyagi, M.; Mark, H.

    1978-01-01

    The effect on low-energy atomic inner-shell Coster-Kronig and super Coster-Kronig transitions that is produced by relaxation and by exchange between the continuum electron and bound electrons was examined and illustrated by specific calculations for transitions that deexcite the 3p vacancy state of Zn. Taking exchange and relaxation into account is found to reduce, but not to eliminate, the discrepancies between theoretical rates and measurements.

  19. Relaxant effects of selected sildenafil analogues in the rat aorta.

    PubMed

    Mojzych, Mariusz; Kubacka, Monika; Mogilski, Szczepan; Filipek, Barbara; Fornal, Emilia

    2016-06-01

    A new series of sulfonamide derivatives of pyrazolo[4,3-e][1,2,4]triazine with chiral amino group has been synthesized and characterized. The compounds were tested for their relaxant effects in the rat aorta. Evaluation of prepared derivatives demonstrated that compound (8a) is probably a non-selective phosphodiesterase (PDE) inhibitor, as it induced aortic relaxation through endothelium-independent mechanism. PMID:25798686

  20. Asymptotic stability of relaxation shock profiles for hyperbolic conservation laws

    NASA Astrophysics Data System (ADS)

    Liu, Hailiang

    This paper studies the asymptotic stability of traveling relaxation shock profiles for hyperbolic systems of conservation laws. Under a stability condition of subcharacteristic type the large time relaxation dynamics on the level of shocks is shown to be determined by the equilibrium conservation laws. The proof is due to the energy principle, using the weighted norms, the interaction of waves from various modes is treated by imposing suitable weight matrix.

  1. Relaxation in Plasmas with Several Types of Free Energy

    SciTech Connect

    Weiland, Jan

    2008-10-15

    The problem of relaxation in plasmas with several types of free energy is discussed. In particular the competition between the relaxation of different free energies as expressed through e.g. the ratio of length scales such as {eta} = L{sub n}/L{sub T} etc. Parameters giving instability thresholds in linear theory tend to determine the ratio of outgoing, diagonal, fluxes and ingoing pinch fluxes nonlinearly. In general pinch fluxes require the coupling between different instability feedback loops.

  2. Control of Transport-Barrier Relaxations by Resonant Magnetic Perturbations

    SciTech Connect

    Leconte, M.; Beyer, P.; Benkadda, S.

    2009-01-30

    Transport-barrier relaxation oscillations in the presence of resonant magnetic perturbations are investigated using three-dimensional global fluid turbulence simulations from first principles at the edge of a tokamak. It is shown that resonant magnetic perturbations have a stabilizing effect on these relaxation oscillations and that this effect is due mainly to a modification of the pressure profile linked to the presence of both residual magnetic island chains and a stochastic layer.

  3. Multiple-Relaxation-Time Lattice Boltzmann Models in 3D

    NASA Technical Reports Server (NTRS)

    dHumieres, Dominique; Ginzburg, Irina; Krafczyk, Manfred; Lallemand, Pierre; Luo, Li-Shi; Bushnell, Dennis M. (Technical Monitor)

    2002-01-01

    This article provides a concise exposition of the multiple-relaxation-time lattice Boltzmann equation, with examples of fifteen-velocity and nineteen-velocity models in three dimensions. Simulation of a diagonally lid-driven cavity flow in three dimensions at Re=500 and 2000 is performed. The results clearly demonstrate the superior numerical stability of the multiple-relaxation-time lattice Boltzmann equation over the popular lattice Bhatnagar-Gross-Krook equation.

  4. Method to measure the relaxation rates of molecular levels

    NASA Astrophysics Data System (ADS)

    Bakos, J. S.; Mandula, K.; Sorlei, Zsuzsa

    The influence of buffer gases (He and SF6) on vibrational and relaxational rates has been studied. The line shapes (width and amplitude) of the small signal gain of the 119-micron methanol laser line are measured at different methanol vapor and buffer gas pressures using an infrared far-infrared double resonance method. The relaxation rates are calculated using the modified rate equations of the Henningsen-Jensen model.

  5. Relaxation dispersion in MRI induced by fictitious magnetic fields.

    PubMed

    Liimatainen, Timo; Mangia, Silvia; Ling, Wen; Ellermann, Jutta; Sorce, Dennis J; Garwood, Michael; Michaeli, Shalom

    2011-04-01

    A new method entitled Relaxation Along a Fictitious Field (RAFF) was recently introduced for investigating relaxations in rotating frames of rank ≥ 2. RAFF generates a fictitious field (E) by applying frequency-swept pulses with sine and cosine amplitude and frequency modulation operating in a sub-adiabatic regime. In the present work, MRI contrast is created by varying the orientation of E, i.e. the angle ε between E and the z″ axis of the second rotating frame. When ε > 45°, the amplitude of the fictitious field E generated during RAFF is significantly larger than the RF field amplitude used for transmitting the sine/cosine pulses. Relaxation during RAFF was investigated using an invariant-trajectory approach and the Bloch-McConnell formalism. Dipole-dipole interactions between identical (like) spins and anisochronous exchange (e.g., exchange between spins with different chemical shifts) in the fast exchange regime were considered. Experimental verifications were performed in vivo in human and mouse brain. Theoretical and experimental results demonstrated that changes in ε induced a dispersion of the relaxation rate constants. The fastest relaxation was achieved at ε ≈ 56°, where the averaged contributions from transverse components during the pulse are maximal and the contribution from longitudinal components are minimal. RAFF relaxation dispersion was compared with the relaxation dispersion achieved with off-resonance spin lock T(₁ρ) experiments. As compared with the off-resonance spin lock T(₁ρ) method, a slower rotating frame relaxation rate was observed with RAFF, which under certain experimental conditions is desirable. PMID:21334231

  6. Relaxation Dispersion in MRI Induced by Fictitious Magnetic Fields

    PubMed Central

    Liimatainen, Timo; Mangia, Silvia; Ling, Wen; Ellermann, Jutta; Sorce, Dennis J.; Garwood, Michael; Michaeli, Shalom

    2011-01-01

    A new method entitled Relaxation Along a Fictitious Field (RAFF) was recently introduced for investigating relaxations in rotating frames of rank ≥ 3. RAFF generates a fictitious field (E) by applying frequency-swept pulses with sine and cosine amplitude and frequency modulation operating in a sub-adiabatic regime. In the present work, MRI contrast is created by varying the orientation of E, i.e. the angle ε between E and the z″ axis of the second rotating frame. When ε > 45°, the amplitude of the fictitious field E generated during RAFF is significantly larger than the RF field amplitude used for transmitting the sine/cosine pulses. Relaxation during RAFF was investigated using an invariant-trajectory approach and the Bloch-McConnell formalism. Dipole-dipole interactions between identical (like) spins and anisochronous exchange (e.g., exchange between spins with different chemical shifts) in the fast exchange regime were considered. Experimental verifications were performed in vivo in human and mouse brain. Theoretical and experimental results demonstrated that changes in ε induced a dispersion of the relaxation rate constants. The fastest relaxation was achieved at ε ≈ 56°, where the averaged contributions from transverse components during the pulse are maximal and the contribution from longitudinal components are minimal. RAFF relaxation dispersion was compared with the relaxation dispersion achieved with off-resonance spin lock T1ρ experiments. As compared with the off-resonance spin lock T1ρ method, a slower rotating frame relaxation rate was observed with RAFF, which under certain experimental conditions is desirable. PMID:21334231

  7. Relaxation dispersion in MRI induced by fictitious magnetic fields

    NASA Astrophysics Data System (ADS)

    Liimatainen, Timo; Mangia, Silvia; Ling, Wen; Ellermann, Jutta; Sorce, Dennis J.; Garwood, Michael; Michaeli, Shalom

    2011-04-01

    A new method entitled Relaxation Along a Fictitious Field (RAFF) was recently introduced for investigating relaxations in rotating frames of rank ⩾2. RAFF generates a fictitious field ( E) by applying frequency-swept pulses with sine and cosine amplitude and frequency modulation operating in a sub-adiabatic regime. In the present work, MRI contrast is created by varying the orientation of E, i. e. the angle ɛ between E and the z″ axis of the second rotating frame. When ɛ > 45°, the amplitude of the fictitious field E generated during RAFF is significantly larger than the RF field amplitude used for transmitting the sine/ cosine pulses. Relaxation during RAFF was investigated using an invariant-trajectory approach and the Bloch-McConnell formalism. Dipole-dipole interactions between identical (like) spins and anisochronous exchange ( e. g., exchange between spins with different chemical shifts) in the fast exchange regime were considered. Experimental verifications were performed in vivo in human and mouse brain. Theoretical and experimental results demonstrated that changes in ɛ induced a dispersion of the relaxation rate constants. The fastest relaxation was achieved at ɛ ≈ 56°, where the averaged contributions from transverse components during the pulse are maximal and the contribution from longitudinal components are minimal. RAFF relaxation dispersion was compared with the relaxation dispersion achieved with off-resonance spin lock T1ρ experiments. As compared with the off-resonance spin lock T1ρ method, a slower rotating frame relaxation rate was observed with RAFF, which under certain experimental conditions is desirable.

  8. Anisotropic nuclear spin relaxation in single-crystal xenon

    NASA Astrophysics Data System (ADS)

    Kuzma, N. N.; Babich, D.; Happer, W.

    2002-04-01

    We extend the theory of longitudinal spin relaxation of 129Xe nuclei in frozen xenon to the case of single-crystal samples, where the relaxation rate depends on the direction of the applied magnetic field with respect to the crystalline axes. For sufficiently large magnetic fields, the relaxation is dominated by spin-flip Raman scattering of lattice phonons. Two closely related interactions couple the lattice phonons to the spins of 129Xe nuclei: the nuclear spin-rotation interaction between nearest-neighbor atoms, which leads to an isotropic, field-independent relaxation rate, and the paramagnetic antishielding of the externally applied field at the site of 129Xe nuclei by the electrons of neighboring Xe atoms. The latter interaction, also known as the chemical shift anisotropy (CSA) interaction, leads to an anisotropic relaxation rate proportional to the square of the applied field. This mechanism dominates spin relaxation at fields of the order of the Debye field BD=kBTD/μB=82 T.

  9. Thermomechanical Modeling of Stress Relaxation in Shape Memory Alloy Wires

    NASA Astrophysics Data System (ADS)

    Zare, Fateme; Kadkhodaei, Mahmoud; Salafian, Iman

    2015-04-01

    When a shape memory alloy (SMA) is subjected to a mechanical load, especially at high strain rates, its temperature varies due to thermomechanical coupling in the response of these materials. Thus, if strain is kept constant during the transformation, temperature change will cause stress to decrease during loading and to increase during unloading. A decrease in stress under constant strain indicates stress relaxation, and an increase in stress indicates stress recovery, i.e., reverse stress relaxation. In this paper, a fully coupled thermomechanical model is developed in a continuum framework to study stress relaxation and stress recovery in SMA wires. Numerical simulations at different ambient temperatures, applied strain rates, wire radii, and relaxation intervals are done to show the abilities of the proposed model in predicting relaxation phenomena in various conditions where strain remains constant during loading or unloading. Relaxation experiments were also performed on NiTi wires, and the numerical and empirical results are shown to be in a good agreement.

  10. Topology Synthesis of Structures Using Parameter Relaxation and Geometric Refinement

    NASA Technical Reports Server (NTRS)

    Hull, P. V.; Tinker, M. L.

    2007-01-01

    Typically, structural topology optimization problems undergo relaxation of certain design parameters to allow the existence of intermediate variable optimum topologies. Relaxation permits the use of a variety of gradient-based search techniques and has been shown to guarantee the existence of optimal solutions and eliminate mesh dependencies. This Technical Publication (TP) will demonstrate the application of relaxation to a control point discretization of the design workspace for the structural topology optimization process. The control point parameterization with subdivision has been offered as an alternative to the traditional method of discretized finite element design domain. The principle of relaxation demonstrates the increased utility of the control point parameterization. One of the significant results of the relaxation process offered in this TP is that direct manufacturability of the optimized design will be maintained without the need for designer intervention or translation. In addition, it will be shown that relaxation of certain parameters may extend the range of problems that can be addressed; e.g., in permitting limited out-of-plane motion to be included in a path generation problem.

  11. Thermal relaxation of molecular oxygen in collisions with nitrogen atoms.

    PubMed

    Andrienko, Daniil A; Boyd, Iain D

    2016-07-01

    Investigation of O2-N collisions is performed by means of the quasi-classical trajectory method on the two lowest ab initio potential energy surfaces at temperatures relevant to hypersonic flows. A complete set of bound-bound and bound-free transition rates is obtained for each precollisional rovibrational state. Special attention is paid to the vibrational and rotational relaxations of oxygen as a result of chemically non-reactive interaction with nitrogen atoms. The vibrational relaxation of oxygen partially occurs via the formation of an intermediate NO2 complex. The efficient energy randomization results in rapid vibrational relaxation at low temperatures, compared to other molecular systems with a purely repulsive potential. The vibrational relaxation time, computed by means of master equation studies, is nearly an order of magnitude lower than the relaxation time in N2-O collisions. The rotational nonequilibrium starts to play a significant effect at translational temperatures above 8000 K. The present work provides convenient relations for the vibrational and rotational relaxation times as well as for the quasi-steady dissociation rate coefficient and thus fills a gap in data due to a lack of experimental measurements for this system. PMID:27394110

  12. Thermal relaxation of molecular oxygen in collisions with nitrogen atoms

    NASA Astrophysics Data System (ADS)

    Andrienko, Daniil A.; Boyd, Iain D.

    2016-07-01

    Investigation of O2-N collisions is performed by means of the quasi-classical trajectory method on the two lowest ab initio potential energy surfaces at temperatures relevant to hypersonic flows. A complete set of bound-bound and bound-free transition rates is obtained for each precollisional rovibrational state. Special attention is paid to the vibrational and rotational relaxations of oxygen as a result of chemically non-reactive interaction with nitrogen atoms. The vibrational relaxation of oxygen partially occurs via the formation of an intermediate NO2 complex. The efficient energy randomization results in rapid vibrational relaxation at low temperatures, compared to other molecular systems with a purely repulsive potential. The vibrational relaxation time, computed by means of master equation studies, is nearly an order of magnitude lower than the relaxation time in N2-O collisions. The rotational nonequilibrium starts to play a significant effect at translational temperatures above 8000 K. The present work provides convenient relations for the vibrational and rotational relaxation times as well as for the quasi-steady dissociation rate coefficient and thus fills a gap in data due to a lack of experimental measurements for this system.

  13. Dielectric relaxations on erythrocyte membrane as revealed by spectrin denaturation.

    PubMed

    Ivanov, I T; Paarvanova, B

    2016-08-01

    We studied the effect of spectrin denaturation at 49.5°C (TA) on the dielectric relaxations and related changes in the complex impedance, Z*, complex capacitance, C*, and dielectric loss curve of suspensions containing human erythrocytes, erythrocyte ghost membranes (EMs) and Triton-X-100 residues of EMs. The loss curve prior to, minus the loss curve after TA, resulted in a bell-shaped peak at 1.5MHz. The changes in the real and imaginary components of Z* and C* at TA, i.e., ΔZre, ΔZim, ΔCre and ΔCim, calculated in the same way, strongly varied with frequency. Between 1.0 and 12MHz the -ΔZim vs ΔZre, and ΔCim vs ΔCre plots depicted semicircles with critical frequencies, fcr, at 2.5MHz expressing recently reported relaxation of spectrin dipoles. Between 0.02 and 1.0MHz the -ΔZim vs ΔZre plot exhibited another relaxation whose fcr mirrored that of beta relaxation. This relaxation was absent on Triton-X-shells, while on erythrocytes and EMs it was inhibited by selective dissociation of either attachment sites between spectrin and bilayer. Considering above findings and inaccessibility of cytosole to outside field at such frequencies, the latter relaxation was assumed originating from a piezoelectric effect on the highly deformable spectrin filaments. PMID:27071054

  14. Relaxation dynamics of internal segments of DNA chains in nanochannels

    NASA Astrophysics Data System (ADS)

    Jain, Aashish; Muralidhar, Abhiram; Dorfman, Kevin; Dorfman Group Team

    We will present relaxation dynamics of internal segments of a DNA chain confined in nanochannel. The results have direct application in genome mapping technology, where long DNA molecules containing sequence-specific fluorescent probes are passed through an array of nanochannels to linearize them, and then the distances between these probes (the so-called ``DNA barcode'') are measured. The relaxation dynamics of internal segments set the experimental error due to dynamic fluctuations. We developed a multi-scale simulation algorithm, combining a Pruned-Enriched Rosenbluth Method (PERM) simulation of a discrete wormlike chain model with hard spheres with Brownian dynamics (BD) simulations of a bead-spring chain. Realistic parameters such as the bead friction coefficient and spring force law parameters are obtained from PERM simulations and then mapped onto the bead-spring model. The BD simulations are carried out to obtain the extension autocorrelation functions of various segments, which furnish their relaxation times. Interestingly, we find that (i) corner segments relax faster than the center segments and (ii) relaxation times of corner segments do not depend on the contour length of DNA chain, whereas the relaxation times of center segments increase linearly with DNA chain size.

  15. In situ determination of surface relaxivities for unconsolidated sediments

    NASA Astrophysics Data System (ADS)

    Duschl, Markus; Galvosas, Petrik; Brox, Timothy I.; Pohlmeier, Andreas; Vereecken, Harry

    2015-08-01

    NMR relaxometry has developed into a method for rapid pore-size determination of natural porous media. Nevertheless, it is prone to uncertainties because of unknown surface relaxivities which depend mainly on the chemical composition of the pore walls as well as on the interfacial dynamics of the pore fluid. The classical approach for the determination of surface relaxivities is the scaling of NMR relaxation times by surface to volume ratios measured by gas adsorption or mercury intrusion. However, it is preferable that a method for the determination of average pore sizes uses the same substance, water, as probe molecule for both relaxometry and surface to volume measurements. One should also ensure that in both experiments the dynamics of the probe molecule takes place on similar length scales, which are in the order of some microns. Therefore, we employed NMR diffusion measurements with different observation times using bipolar pulsed field gradients and applied them to unconsolidated sediments (two purified sands, two natural sands, and one soil). The evaluation by Mitra's short-time model for diffusion in restricted environments yielded information about the surface to volume ratios which is independent of relaxation mechanisms. We point out that methods based on NMR diffusometry yield pore dimensions and surface relaxivities consistent with a pore space as sampled by native pore fluids via the diffusion process. This opens a way to calibrate NMR relaxation measurements with other NMR techniques, providing information about the pore-size distribution of natural porous media directly from relaxometry.

  16. Dielectric relaxation of α -tocopherol acetate (vitamin E)

    NASA Astrophysics Data System (ADS)

    Kaminski, K.; Maslanka, S.; Ziolo, J.; Paluch, M.; McGrath, K. J.; Roland, C. M.

    2007-01-01

    Dielectric loss spectra are reported for α -tocopherol acetate (an isomer of vitamin E) in the supercooled and glassy states. The α -relaxation times, τα , measured over a 190° range of temperatures, T , at pressures, P , up to 400MPa can be expressed as a single function of TV3.9 ( V is specific volume, measured herein as a function of T and P ). At ambient pressure, there is no dynamic crossover over eight decades of measured τα . The relaxation spectra above the glass transition temperature Tg show ionic conductivity and an excess wing on the high-frequency flank of the α -relaxation loss peak. Temperature-pressure superpositioning is valid for the α process; moreover, the peak shape is constant (stretch exponent equal to 0.65). However, application of pressure changes the shape of the dielectric spectrum at higher frequencies due to the shift of the excess wing to form a resolved peak. Additionally, another relaxation process, absent at atmospheric pressure, emerges on the high-frequency side of the α -process. We propose that this new peak reflects a more compact conformation of the α -tocopherol acetate molecule. Drawing on the coupling model, the experimentally determined relaxation times, activation energy, and activation volume for the Johari-Goldstein process are compared to values calculated from the properties of the α relaxation. The agreement is generally satisfactory, at least for T

  17. Difference and similarity of dielectric relaxation processes among polyols

    NASA Astrophysics Data System (ADS)

    Minoguchi, Ayumi; Kitai, Kei; Nozaki, Ryusuke

    2003-09-01

    Complex permittivity measurements were performed on sorbitol, xylitol, and sorbitol-xylitol mixture in the supercooled liquid state in an extremely wide frequency range from 10 μHz to 500 MHz at temperatures near and above the glass transition temperature. We determined detailed behavior of the relaxation parameters such as relaxation frequency and broadening against temperature not only for the α process but also for the β process above the glass transition temperature, to the best of our knowledge, for the first time. Since supercooled liquids are in the quasi-equilibrium state, the behavior of all the relaxation parameters for the β process can be compared among the polyols as well as those for the α process. The relaxation frequencies of the α processes follow the Vogel-Fulcher-Tammann manner and the loci in the Arrhenius diagram are different corresponding to the difference of the glass transition temperatures. On the other hand, the relaxation frequencies of the β processes, which are often called as the Johari-Goldstein processes, follow the Arrhenius-type temperature dependence. The relaxation parameters for the β process are quite similar among the polyols at temperatures below the αβ merging temperature, TM. However, they show anomalous behavior near TM, which depends on the molecular size of materials. These results suggest that the origin of the β process is essentially the same among the polyols.

  18. PREFACE: Muon spin rotation, relaxation or resonance

    NASA Astrophysics Data System (ADS)

    Heffner, Robert H.; Nagamine, Kanetada

    2004-10-01

    To a particle physicist a muon is a member of the lepton family, a heavy electron possessing a mass of about 1/9 that of a proton and a spin of 1/2, which interacts with surrounding atoms and molecules electromagnetically. Since its discovery in 1937, the muon has been put to many uses, from tests of special relativity to deep inelastic scattering, from studies of nuclei to tests of weak interactions and quantum electrodynamics, and most recently, as a radiographic tool to see inside heavy objects and volcanoes. In 1957 Richard Garwin and collaborators, while conducting experiments at the Columbia University cyclotron to search for parity violation, discovered that spin-polarized muons injected into materials might be useful to probe internal magnetic fields. This eventually gave birth to the modern field of muSR, which stands for muon spin rotation, relaxation or resonance, and is the subject of this special issue of Journal of Physics: Condensed Matter. Muons are produced in accelerators when high energy protons (generally >500 MeV) strike a target like graphite, producing pions which subsequently decay into muons. Most experiments carried out today use relatively low-energy (~4 MeV), positively-charged muons coming from pions decaying at rest in the skin of the production target. These muons have 100% spin polarization, a range in typical materials of about 180 mg cm-2, and are ideal for experiments in condensed matter physics and chemistry. Negatively-charged muons are also occasionally used to study such things as muonic atoms and muon-catalysed fusion. The muSR technique provides a local probe of internal magnetic fields and is highly complementary to inelastic neutron scattering and nuclear magnetic resonance, for example. There are four primary muSR facilities in the world today: ISIS (Didcot, UK), KEK (Tsukuba, Japan), PSI (Villigen, Switzerland) and TRIUMF (Vancouver, Canada), serving about 500 researchers world-wide. A new facility, JPARC (Tokai, Japan

  19. PREFACE: Muon spin rotation, relaxation or resonance

    NASA Astrophysics Data System (ADS)

    Heffner, Robert H.; Nagamine, Kanetada

    2004-10-01

    To a particle physicist a muon is a member of the lepton family, a heavy electron possessing a mass of about 1/9 that of a proton and a spin of 1/2, which interacts with surrounding atoms and molecules electromagnetically. Since its discovery in 1937, the muon has been put to many uses, from tests of special relativity to deep inelastic scattering, from studies of nuclei to tests of weak interactions and quantum electrodynamics, and most recently, as a radiographic tool to see inside heavy objects and volcanoes. In 1957 Richard Garwin and collaborators, while conducting experiments at the Columbia University cyclotron to search for parity violation, discovered that spin-polarized muons injected into materials might be useful to probe internal magnetic fields. This eventually gave birth to the modern field of muSR, which stands for muon spin rotation, relaxation or resonance, and is the subject of this special issue of Journal of Physics: Condensed Matter. Muons are produced in accelerators when high energy protons (generally >500 MeV) strike a target like graphite, producing pions which subsequently decay into muons. Most experiments carried out today use relatively low-energy (~4 MeV), positively-charged muons coming from pions decaying at rest in the skin of the production target. These muons have 100% spin polarization, a range in typical materials of about 180 mg cm-2, and are ideal for experiments in condensed matter physics and chemistry. Negatively-charged muons are also occasionally used to study such things as muonic atoms and muon-catalysed fusion. The muSR technique provides a local probe of internal magnetic fields and is highly complementary to inelastic neutron scattering and nuclear magnetic resonance, for example. There are four primary muSR facilities in the world today: ISIS (Didcot, UK), KEK (Tsukuba, Japan), PSI (Villigen, Switzerland) and TRIUMF (Vancouver, Canada), serving about 500 researchers world-wide. A new facility, JPARC (Tokai, Japan

  20. Characterization of structural relaxation in inorganic glasses using length dilatometry

    NASA Astrophysics Data System (ADS)

    Koontz, Erick

    The processes that govern how a glass relaxes towards its thermodynamic quasi-equilibrium state are major factors in understanding glass behavior near the glass transition region, as characterized by the glass transition temperature (Tg). Intrinsic glass properties such as specific volume, enthalpy, entropy, density, etc. are used to map the behavior of the glass network below in and near the transition region. The question of whether a true thermodynamic second order phase transition takes place in the glass transition region is another pending question. Linking viscosity behavior to entropy, or viewing the glass configuration as an energy landscape are just a couple of the most prevalent methods used for attempting to understand the glass transition. The structural relaxation behavior of inorganic glasses is important for more than scientific reasons, many commercial glass processing operations including glass melting and certain forms of optical fabrication include significant time spent in the glass transition region. For this reason knowledge of structural relaxation processes can, at a minimum, provide information for annealing duration of melt-quenched glasses. The development of a predictive model for annealing time prescription has the potential to save glass manufacturers significant time and money as well as increasing volume throughput. In optical hot forming processes such as precision glass molding, molded optical components can significantly change in shape upon cooling through the glass transition. This change in shape is not scientifically predictable as of yet though manufacturers typically use empirical rules developed in house. The classification of glass behavior in the glass transition region would allow molds to be accurately designed and save money for the producers. The work discussed in this dissertation is comprised of the development of a dilatometric measurement and characterization method of structural relaxation. The measurement and