WorldWideScience

Sample records for endothelium dependent relaxation

  1. Preservation of endothelium-dependent relaxation in atherosclerotic mice with endothelium-restricted endothelin-1 overexpression.

    Science.gov (United States)

    Mian, Muhammad Oneeb Rehman; Idris-Khodja, Noureddine; Li, Melissa W; Leibowitz, Avshalom; Paradis, Pierre; Rautureau, Yohann; Schiffrin, Ernesto L

    2013-10-01

    In human atherosclerosis, which is associated with elevated plasma and coronary endothelin (ET)-1 levels, ETA receptor antagonists improve coronary endothelial function. Mice overexpressing ET-1 specifically in the endothelium (eET-1) crossed with atherosclerosis-prone apolipoprotein E knockout mice (Apoe(-/-)) exhibit exaggerated high-fat diet (HFD)-induced atherosclerosis. Since endothelial dysfunction often precedes atherosclerosis development, we hypothesized that mice overexpressing endothelial ET-1 on a genetic background deficient in apolipoprotein E (eET-1/Apoe(-/-)) would have severe endothelial dysfunction. To test this hypothesis, we investigated endothelium-dependent relaxation (EDR) to acetylcholine in eET-1/Apoe(-/-) mice. EDR in mesenteric resistance arteries from 8- and 16-week-old mice fed a normal diet or HFD was improved in eET-1/Apoe(-/-) compared with Apoe(-/-) mice. Nitric oxide synthase (NOS) inhibition abolished EDR in Apoe(-/-). EDR in eET-1/Apoe(-/-) mice was resistant to NOS inhibition irrespective of age or diet. Inhibition of cyclooxygenase, the cytochrome P450 pathway, and endothelium-dependent hyperpolarization (EDH) resulted in little or no inhibition of EDR in eET-1/Apoe(-/-) compared with wild-type (WT) mice. In eET-1/Apoe(-/-) mice, blocking of EDH or soluble guanylate cyclase (sGC), in addition to NOS inhibition, decreased EDR by 36 and 30%, respectively. The activation of 4-aminopyridine-sensitive voltage-dependent potassium channels (Kv) during EDR was increased in eET-1/Apoe(-/-) compared with WT mice. We conclude that increasing eET-1 in mice that develop atherosclerosis results in decreased mutual dependence of endothelial signaling pathways responsible for EDR, and that NOS-independent activation of sGC and increased activation of Kv are responsible for enhanced EDR in this model of atherosclerosis associated with elevated endothelial and circulating ET-1.

  2. Arbutus unedo induces endothelium-dependent relaxation of the isolated rat aorta.

    Science.gov (United States)

    Ziyyat, Abderrahim; Mekhfi, Hassane; Bnouham, Mohamed; Tahri, Abdelhafid; Legssyer, Abdelkhaleq; Hoerter, Jacqueline; Fischmeister, Rodolphe

    2002-09-01

    Arbutus unedo L. (Ericaceae) is used in oriental Morocco to treat arterial hypertension. We studied its vasodilator effect and mechanisms of action in vitro. The root aqueous extract of Arbutus (0.25 mg/mL) produced a relaxation of noradrenaline-precontracted ring preparations of rat aorta with intact endothelium. Relaxation by Arbutus did not occur in specimens without endothelium and was inhibited by pretreatment with 100 microM N(G)-methyl-L-arginine (L-NMA), 10 microM methylene blue or 50 microM 1H-[1,2,4] oxadiazolo [4,3-a] quinoxaline-1-one (ODQ) but not by 10 microM atropine. These results suggest that Arbutus produces an endothelium-dependent relaxation of the isolated rat aorta which may be mediated mainly by a stimulation of the endothelial nitric oxide synthase by mechanisms other than activation of muscarinic receptors. Copyright 2002 John Wiley & Sons, Ltd.

  3. Maternal smoking and impaired endothelium-dependent nitric oxide-mediated relaxation of uterine small arteries in vitro

    DEFF Research Database (Denmark)

    Andersen, Malene R; Uldbjerg, Niels; Stender, Steen

    2011-01-01

    This study aimed to investigate the endothelium-dependent relaxation of uterine small arteries from pregnant nonsmokers, smokers, and ex-smokers who stopped smoking early in pregnancy.......This study aimed to investigate the endothelium-dependent relaxation of uterine small arteries from pregnant nonsmokers, smokers, and ex-smokers who stopped smoking early in pregnancy....

  4. Endothelium-dependent relaxation induced by cathepsin G in porcine pulmonary arteries

    Science.gov (United States)

    Glusa, Erika; Adam, Christine

    2001-01-01

    Serine proteinases elicit profound cellular effects in various tissues mediated by activation of proteinase-activated receptors (PAR). In the present study, we investigated the vascular effects of cathepsin G, a serine proteinase that is present in the azurophil granules of leukocytes and is known to activate several cells that express PARs. In prostaglandin F2α (3 μM)-precontracted rings from porcine pulmonary arteries with intact endothelium, cathepsin G caused concentration-dependent relaxant responses (pEC50=9.64±0.12). The endothelium-dependent relaxant effect of cathepsin G could also be demonstrated in porcine coronary arteries (pEC50=9.23±0.07). In pulmonary arteries the cathepsin G-induced relaxation was inhibited after blockade of nitric oxide synthesis by L-NAME (200 μM) and was absent in endothelium-denuded vessels. Bradykinin- and cathepsin G-induced relaxant effects were associated with a 5.7 fold and 2.4 fold increase in the concentration of cyclic GMP, respectively. Compared with thrombin and trypsin, which also produced an endothelium-dependent relaxation in pulmonary arteries, cathepsin G was 2.5 and four times more potent, respectively. Cathepsin G caused only small homologous desensitization. In cathepsin G-challenged vessels, thrombin was still able to elicit a relaxant effect. The effects of cathepsin G were blocked by soybean trypsin inhibitor (IC50=0.043 μg ml−1), suggesting that proteolytic activity is essential for induction of relaxation. Recombinant acetyl-eglin C proved to be a potent inhibitor (IC50=0.14 μg ml−1) of the cathepsin G effect, whereas neither indomethacin (3 μM) nor the thrombin inhibitor hirudin (5 ATU ml−1) elicited any inhibitory activity. Due to their polyanionic structure defibrotide (IC50=0.11 μg ml−1), heparin (IC50=0.48 μg ml−1) and suramin (IC50=1.85 μg ml−1) diminished significantly the relaxation in response to the basic protein cathepsin G. In conclusion, like

  5. Resveratrol Protects and Restores Endothelium-Dependent Relaxation in Hypercholesterolemic Rabbit Corpus Cavernosum.

    Science.gov (United States)

    Murat, Nergiz; Korhan, Peyda; Kizer, Onur; Evcim, Sinem; Kefi, Aykut; Demir, Ömer; Gidener, Sedef; Atabey, Neşe; Esen, Ahmet Adil

    2016-01-01

    Oxidative stress dependent-decrease in nitric oxide (NO) bioavailability plays an integral role in hypercholesterolemia-induced erectile dysfunction (ED). Resveratrol has been demonstrated to exert beneficial effects against oxidative stress and improve NO bioavailability. The protective and restorative potentials of resveratrol on endothelium-dependent relaxations were evaluated in hypercholesterolemic rabbit corpus cavernosum (CC). Hypercholesterolemia was induced by administering 2% cholesterol diet (CD) (w/w) to the rabbits for 6 weeks. Two different protocols were applied to test the effects of resveratrol on hypercholesterolemia-induced ED. In Protocol-1 (P1), resveratrol was administrated to the rabbits simultaneously with CD in order to evaluate the protective effect, and for Protocol-2 (P2), resveratrol was administrated for 6 weeks after termination of CD in order to evaluate the restorative effect. Endothelium-dependent relaxations of CC were evaluated by using organ bath studies. In order to elucidate the possible molecular mechanisms, we measured endothelial NO synthase (eNOS) and phosphovasodilator-stimulated phosphoprotein (VASP) expressions and activations, NADPH oxidase, superoxide dismutase (SOD), and catalase (CAT) and glutathione peroxidase (GPx) activity in cavernosal tissues obtained at the end of the study. Resveratrol showed an improvement in the endothelium-dependent relaxation responses in vitro. We demonstrated significantly increased activatory-phosphorylation (p[S1177]-eNOS) and activated phosphovasodilator-stimulated phosphoprotein (phospho-VASP) levels, but reduced phosphorylation (p[T495]-eNOS) of eNOS and NADPH oxidase activity in the resveratrol-administered HC animals compared with hypercholesterolemic control rabbits in the P1. In the P2, resveratrol exhibited an improvement in endothelium-dependent relaxation responses and more pronounced effects on eNOS activation. Resveratrol administration, either simultaneously with HC diet

  6. Gou-teng (from Uncaria rhynchophylla Miquel)-induced endothelium-dependent and -independent relaxations in the isolated rat aorta.

    Science.gov (United States)

    Kuramochi, T; Chu, J; Suga, T

    1994-01-01

    Gou-teng is a drug used for treatment of hypertension in Chinese medicine. Its antihypertensive action has been previously confirmed in the spontaneously hypertensive rat (SHR). Here, its vasorelaxing effect and the mechanisms of actions were studied in vitro. Gou-teng extract (GTE) relaxed the norepinephrine (NE)-precontracted aortic ring preparations isolated from Wistar Kyoto rats (WKY) with and without intact endothelium; the latter was significantly less sensitive than the former. The GTE-induced endothelium-dependent relaxation was significantly inhibited by NG-monomethyl-L-arginine (NMMA) in a dose-dependent manner while indomethacin did not affect the relaxation. Atropine inhibited the acetylcholine (ACh)-induced endothelium-dependent relaxation but did not the GTE-induced one. Furthermore, once GTE was applied, the following NE-induced contraction was significantly reduced even after repeated washout. NMMA effectively reduced and rather reversed this residual effect of GTE. From these results, it is concluded that GTE relaxes the NE-precontracted rat aorta through endothelium-dependent and, to lesser extent, -independent mechanisms. The endothelium-dependent component would be mediated by EDRF/NO pathway in which the muscarinic cholinoceptors were not involved. Thus, GTE appears to be a potent and long-lasting vasodilator mainly through EDRF/NO release.

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

    International Nuclear Information System (INIS)

    Cheng Wei; Oike, Masahiro; Hirakawa, Masakazu; Ohnaka, Keizo; Koyama, Tetsuya; Ito, Yushi

    2005-01-01

    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 2+ transients and cellular uptake of L-[ 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-[ 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

  8. Effect of lithium on endothelium-dependent and neurogenic relaxation of rat corpus cavernosum: role of nitric oxide pathway.

    Science.gov (United States)

    Sadeghipour, Hamed; Ghasemi, Mehdi; Ebrahimi, Farzad; Dehpour, Ahmad Reza

    2007-02-01

    Some studies have reported erectile dysfunction in patients receiving lithium through a mechanism that has not yet been defined. The aim of the present study was to verify the effect of acute lithium administration on the nonadrenergic noncholinergic (NANC)- and endothelium-mediated relaxation of rat isolated corpus cavernosum. The isolated rat corporeal strips were precontracted with phenylephrine hydrochloride (7.5 microM) and electrical field stimulation (EFS) was applied at different frequencies (2, 5, 10, and 15 Hz) to obtain NANC-mediated relaxation or relaxed by adding cumulative doses of acetylcholine (10nM-1mM) to obtain endothelium-dependent relaxation in the presence or absence of lithium (0.3, 0.5, 1, and 5mM). Also, effects of combining lithium (0.3mM) with 30 nM and 0.1 nM L-NAME (an NO synthase inhibitor) on NANC- and acetylcholine-mediated relaxation was investigated, respectively. Moreover, effects of combining lithium (1mM) with 0.1mM and 10 microM L-arginine (a precursor of NO) on NANC- and endothelium-mediated relaxation was assessed, respectively. Also, the effect of lithium (1mM) on relaxation to sodium nitroprusside (SNP; 1nM-1mM), an NO donor, was investigated. The NANC-mediated relaxation was significantly (Pacetylcholine in a concentration-dependent manner. Combination of lithium (0.3mM) with 30 and 0.1 nM L-NAME, which separately had a minimum effect on NANC- and endothelium-mediated relaxation, significantly (Pacetylcholine and EFS, it improved the inhibition by lithium (1mM) of relaxant responses to acetylcholine and EFS, respectively. Also, SNP produced similar concentration-dependent relaxations from both groups. Our experiments indicated that lithium likely by interfering with NO pathway in both endothelium and nitrergic nerve can result in impairment of both the endothelium- and NANC-mediated relaxation of rat corpus cavernosum.

  9. Effect of prolonged incubation with copper on endothelium-dependent relaxation in rat isolated aorta

    Science.gov (United States)

    Chiarugi, Alberto; Pitari, Giovanni Mario; Costa, Rosa; Ferrante, Margherita; Villari, Loredana; Amico-Roxas, Matilde; Godfraind, Théophile; Bianchi, Alfredo; Salomone, Salvatore

    2002-01-01

    We investigated the effects of prolonged exposure to copper (Cu2+) on vascular functioning of isolated rat aorta. Aortic rings were exposed to CuSO4 (3–24 h) in Dulbecco's modified Eagle medium with or without 10% foetal bovine serum (FBS) and then challenged with vasoconstrictors or vasodilators in the absence of Cu2+. Exposure to 2 μM Cu2+ in the absence of FBS did not modify the response to phenylephrine (PE) or acetylcholine (ACh) in aortic rings incubated for 24 h. Identical exposure in the presence of FBS increased the contractile response to 1 μM PE by 30% (P<0.05) and impaired the relaxant response to 3 μM ACh or 1 μM A23187 (ACh, from 65.7±7.1 to 6.2±1.1%, n=8; A23187, from 74.6±8.2 to 12.0±0.8%, n=6; P<0.01 for both). Cu2+ exposure did not affect the relaxant response to NO-donors. Impairment of vasorelaxation appeared 3 h after incubation with 2 μM Cu2+ and required 12 h to attain a steady state. Vasorelaxation to ACh was partially restored by 1 mM tiron (intracellular scavenger of superoxide ions; maximum relaxation 34.2±6.4%, n=10, P<0.01 vs Cu2+ alone), whereas catalase, superoxide dismutase or cycloheximide were ineffective. Twenty-four hour-exposure to 2 μM Cu2+ did not affect endothelium integrity or eNOS expression, and increased the Cu content in arterial rings from 6.8±1.1 to 18.9±2.9 ng mg−1 wet weight, n=8; P<0.01. Our results show that, in the presence of FBS, prolonged exposure to submicromolar concentrations of Cu2+ impaired endothelium-dependent vasorelaxation in aortic rings, probably through an intracellular generation of superoxide ions. PMID:12163352

  10. Endothelium-dependent relaxation and angiotensin II sensitivity in experimental preeclampsia.

    Directory of Open Access Journals (Sweden)

    Anne Marijn van der Graaf

    Full Text Available OBJECTIVE: We investigated endothelial dysfunction and the role of angiotensin (Ang-II type I (AT1-R and type II (AT2-R receptor in the changes in the Ang-II sensitivity in experimental preeclampsia in the rat. METHODS: Aortic rings were isolated from low dose lipopolysaccharide (LPS infused pregnant rats (experimental preeclampsia; n=9, saline-infused pregnant rats (n=8, and saline (n=8 and LPS (n=8 infused non-pregnant rats. Endothelium-dependent acetylcholine-mediated relaxation was studied in phenylephrine-preconstricted aortic rings in the presence of vehicle, N(G-nitro-L-arginine methyl ester and/or indomethacin. To evaluate the role for AT1-R and AT2-R in Ang-II sensitivity, full concentration response curves were obtained for Ang-II in the presence of losartan or PD123319. mRNA expression of the AT1-R and AT2-R, eNOS and iNOS, COX1 and COX2 in aorta were evaluated using real-time RT-PCR. RESULTS: The role of vasodilator prostaglandins in the aorta was increased and the role of endothelium-derived hyperpolarizing factor and response of the AT1-R and AT2-R to Ang-II was decreased in pregnant saline infused rats as compared with non-pregnant rats. These changes were not observed during preeclampsia. CONCLUSION: Pregnancy induced adaptations in endothelial function, which were not observed in the rat model for preeclampsia. This role of lack of pregnancy induced endothelial adaptation in the pathophysiology of experimental preeclampsia needs further investigation.

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

    Directory of Open Access Journals (Sweden)

    Êurica Adélia Nogueira Ribeiro

    2012-01-01

    Full Text Available 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.

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

    Directory of Open Access Journals (Sweden)

    Yeh Siang Lau

    2015-06-01

    Full Text Available 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, NG-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.

  13. Endothelium-independent and endothelium-dependent ...

    African Journals Online (AJOL)

    This endothelium-independent relaxant effect was also sensitive to combination of 1H-[1,2,4]-oxadiazole-[4,3-á]-quinoxalin- 1-one (ODQ, 10 ìM, soluble guanylyl cyclase inhibitor) and N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinoline sulfonamide dihydrochloride (H89, 100 nM, Protein Kinase A inhibitor). Taken together ...

  14. Pharmacology of Endothelium-Dependent and Independent Relaxation of Rabbit Aorta

    DEFF Research Database (Denmark)

    Larsen, Kirsten Vendelbo

    2001-01-01

    The purpose of this study was to investigate several aspects of the acetylcholine-evoked relaxation of blood vessels: methodologic aspects; gender; storage; elevated glucose incubation; the signal transduction pathway; and effects of prolonged exposure. Furthermore, the relaxing effect of some ad...

  15. Endothelium-dependent hyperpolarization-related relaxations diminish with age in murine saphenous arteries of both sexes

    DEFF Research Database (Denmark)

    Chennupati, R.; Lamers, W. H.; Koehler, S. E.

    2013-01-01

    nitroprusside and to ACh in the absence of pharmacological inhibitors (indomethacin and L-NAME), were similar in all age groups and sexes, but those mediated by endothelium-derived NO were slightly but significantly increased in 64-week-old male mice. In the presence of inhibitors, 12-week-old animals showed...... pronounced ACh-induced relaxation, which was significantly reduced in 34- and 64-week-old mice of both sexes. The EDH-related component of ACh-induced relaxations was abolished by TRAM-34 (K(Ca)3.1 blocker) or UCL 1684 (K(Ca)2.3 blocker). Although the maximal relaxation induced by NS309 (K-Ca activator......) was not affected by aging, the sensitivity for NS309 significantly decreased with aging. The presence of SKA-31 (K-Ca modulator) potentiated relaxations induced by ACh in arteries of 12-week-old but not older mice. CONCLUSION AND IMPLICATIONS In a small muscular artery of mice of either sex, total endothelium...

  16. Great heterogeneity of commercial fruit juices to induce endothelium-dependent relaxations in isolated porcine coronary arteries: role of the phenolic content and composition.

    Science.gov (United States)

    Auger, Cyril; Pollet, Brigitte; Arnold, Cécile; Marx, Céline; Schini-Kerth, Valérie B

    2015-01-01

    Since polyphenol-rich products such as red wine, grape juice, and grape extracts have been shown to induce potent endothelium-dependent relaxations, we have evaluated whether commercial fruit juices such as those from berries are also able to induce endothelium-dependent relaxations of isolated coronary arteries and, if so, to determine whether this effect is related to their phenolic content. Among the 51 fruit juices tested, 2/12 grape juices, 3/7 blackcurrant juices, 4/5 cranberry juices, 1/6 apple juices, 0/5 orange juices, 2/6 red fruit and berry juices, 3/6 blends of red fruit juices, and 0/4 non-red fruit juices were able to induce relaxations achieving more than 50% at a volume of 1%. The active fruit juices had phenolic contents ranging from 0.31 to 1.86 g GAE/L, which were similar to those of most of the less active juices with the exception of one active grape juice (2.14 g GAE/L) and one active blend of red fruit juices (3.48 g GAE/L). Altogether, these findings indicate that very few commercial fruit juices have the ability to induce potent endothelium-dependent relaxations, and that this effect is not related to their quantitative phenolic content, but rather to their qualitative phenolic composition.

  17. Extracellular Calcium-Dependent Modulation of Endothelium Relaxation in Rat Mesenteric Small Artery

    DEFF Research Database (Denmark)

    Hangaard, Lise; Jessen, Peter B; Kamaev, Dmitrii

    2015-01-01

    The nature of NO- and COX-independent endothelial hyperpolarization (EDH) is not fully understood but activation of small- and intermittent-conductance Ca(2+)-activated K(+) channels (SKCa and IKCa) is important. Previous studies have suggested that the significance of IKCa depends on [Ca(2+)]out...

  18. Pomegranate Extract Enhances Endothelium-Dependent Coronary Relaxation in Isolated Perfused Hearts from Spontaneously Hypertensive Ovariectomized Rats

    Science.gov (United States)

    Delgado, Nathalie T. B.; Rouver, Wender do N.; Freitas-Lima, Leandro C.; de Paula, Tiago D.-C.; Duarte, Andressa; Silva, Josiane F.; Lemos, Virgínia S.; Santos, Alexandre M. C.; Mauad, Helder; Santos, Roger L.; Moysés, Margareth R.

    2017-01-01

    prevented the decreasing in plasmatic nitrite. We observed a reduction in total cholesterol and LDL in the Sham-PHE group. The treatment with PHE enhances the endothelium-dependent coronary relaxation and improves cardiovascular parameters, which suggests a therapeutic role of PHE. PMID:28101057

  19. Kaempferol enhances endothelium-dependent relaxation in the porcine coronary artery through activation of large-conductance a2+-activated K+ channels

    Science.gov (United States)

    Xu, Y C; Leung, S W S; Leung, G P H; Man, R Y K

    2015-01-01

    Background and Purpose Kaempferol, a plant flavonoid present in normal human diet, can modulate vasomotor tone. The present study aimed to elucidate the signalling pathway through which this flavonoid enhanced relaxation of vascular smooth muscle. Experimental Approach The effect of kaempferol on the relaxation of porcine coronary arteries to endothelium-dependent (bradykinin) and -independent (sodium nitroprusside) relaxing agents was studied in an in vitro organ chamber setup. The whole-cell patch-clamp technique was used to determine the effect of kaempferol on potassium channels in porcine coronary artery smooth muscle cells (PCASMCs). Key Results At a concentration without direct effect on vascular tone, kaempferol (3 × 10−6 M) enhanced relaxations produced by bradykinin and sodium nitroprusside. The potentiation by kaempferol of the bradykinin-induced relaxation was not affected by Nω-nitro-L-arginine methyl ester, an inhibitor of NO synthase (10−4 M) or TRAM-34 plus UCL 1684, inhibitors of intermediate- and small-conductance calcium-activated potassium channels, respectively (10−6 M each), but was abolished by tetraethylammonium chloride, a non-selective inhibitor of calcium-activated potassium channels (10−3 M), and iberiotoxin, a selective inhibitor of large-conductance calcium-activated potassium channel (KCa1.1; 10−7 M). Iberiotoxin also inhibited the potentiation by kaempferol of sodium nitroprusside-induced relaxations. Kaempferol stimulated an outward-rectifying current in PCASMCs, which was abolished by iberiotoxin. Conclusions and Implications The present results suggest that, in smooth muscle cells of the porcine coronary artery, kaempferol enhanced relaxations caused by endothelium-derived and exogenous NO as well as those due to endothelium-dependent hyperpolarization. This vascular effect of kaempferol involved the activation of KCa1.1 channels. PMID:25652142

  20. Kaempferol enhances endothelium-dependent relaxation in the porcine coronary artery through activation of large-conductance Ca(2+) -activated K(+) channels.

    Science.gov (United States)

    Xu, Y C; Leung, S W S; Leung, G P H; Man, R Y K

    2015-06-01

    Kaempferol, a plant flavonoid present in normal human diet, can modulate vasomotor tone. The present study aimed to elucidate the signalling pathway through which this flavonoid enhanced relaxation of vascular smooth muscle. The effect of kaempferol on the relaxation of porcine coronary arteries to endothelium-dependent (bradykinin) and -independent (sodium nitroprusside) relaxing agents was studied in an in vitro organ chamber setup. The whole-cell patch-clamp technique was used to determine the effect of kaempferol on potassium channels in porcine coronary artery smooth muscle cells (PCASMCs). At a concentration without direct effect on vascular tone, kaempferol (3 × 10(-6) M) enhanced relaxations produced by bradykinin and sodium nitroprusside. The potentiation by kaempferol of the bradykinin-induced relaxation was not affected by N(ω)-nitro-L-arginine methyl ester, an inhibitor of NO synthase (10(-4) M) or TRAM-34 plus UCL 1684, inhibitors of intermediate- and small-conductance calcium-activated potassium channels, respectively (10(-6) M each), but was abolished by tetraethylammonium chloride, a non-selective inhibitor of calcium-activated potassium channels (10(-3) M), and iberiotoxin, a selective inhibitor of large-conductance calcium-activated potassium channel (KCa 1.1; 10(-7) M). Iberiotoxin also inhibited the potentiation by kaempferol of sodium nitroprusside-induced relaxations. Kaempferol stimulated an outward-rectifying current in PCASMCs, which was abolished by iberiotoxin. The present results suggest that, in smooth muscle cells of the porcine coronary artery, kaempferol enhanced relaxations caused by endothelium-derived and exogenous NO as well as those due to endothelium-dependent hyperpolarization. This vascular effect of kaempferol involved the activation of KCa 1.1 channels. © 2015 The British Pharmacological Society.

  1. Tocotrienol rich tocomin attenuates oxidative stress and improves endothelium-dependent relaxation in aortae from rats fed a high-fat western diet

    Directory of Open Access Journals (Sweden)

    Saher F Ali

    2016-10-01

    Full Text Available We have previously reported that tocomin, a mixture high in tocotrienol content and also containing tocopherol, acutely preserves endothelial function in the presence of oxidative stress. In this study we investigated whether tocomin treatment would preserve endothelial function in aortae isolated from rats fed a high fat diet known to cause oxidative stress. Wistar hooded rats were fed a western diet (WD, 21% fat or control rat chow (SD, 6% fat for 12 weeks. Tocomin (40 mg/kg/day sc or its vehicle (peanut oil was administered for the last 4 weeks of the feeding regime. Aortae from WD rats showed an impairment of endothelium-dependent relaxation that was associated with an increased expression of the NADPH oxidase Nox2 subunit and an increase in the vascular generation of superoxide measured using L-012 chemiluminescence. The increase in vascular oxidative stress was accompanied by a decrease in basal NO release and impairment of the contribution of NO to ACh-induced relaxation. The impaired relaxation is likely contributed to by a decreased expression of eNOS, calmodulin and phosphorylated Akt and an increase in caveolin-Tocotrienol rich tocomin, which prevented the diet-induced changes in vascular function, reduced vascular superoxide production and abolished the diet-induced changes in eNOS and other protein expression. Using selective inhibitors of nitric oxide synthase (NOS, soluble guanylate cyclase (sGC and calcium activated potassium (KCa channels we demonstrated that tocomin increased NO mediated relaxation, without affecting the contribution of endothelium-dependent hyperpolarization type relaxation to the endothelium-dependent relaxation. The beneficial actions of tocomin in this diet-induced model of obesity suggests that it may have potential to be used as a therapeutic agent to prevent vascular disease in obesity.

  2. Endothelium-dependent relaxation of rat aorta to a histamine H3 agonist is reduced by inhibitors of nitric oxide synthase, guanylate cyclase and Na+,K+-ATPase

    Directory of Open Access Journals (Sweden)

    D. M. Djuric

    1996-01-01

    Full Text Available The possible involvement of different effector systems (nitric oxide synthase, guanylate cyclase, β-adrenergic and muscarinic cholinergic receptors, cyclooxygenase and lipoxygenase, and Na+,K+-ATPase was evaluated in a histamine H3 receptor agonist-induced ((Rα-methylhistamine, (Rα-MeHA endothelium-dependent rat aorta relaxation assay. (Rα-MeHA (0.1 nM – 0.01 mM relaxed endothelium-dependent rat aorta, with a pD2 value of 8.22 ± 0.06, compared with a pD2 value of 7.98 ± 0.02 caused by histamine (50% and 70% relaxation, respectively. The effect of (Rα-MeHA (0.1 nM – 0.01 mM was competitively antagonized by thioperamide (1, 10 and 30 nM (pA2 = 9.21 ± 0.40; slope = 1.03 ± 0.35 but it was unaffected by pyrilamine (100 nM, cimetidine (1 μM, atropine (10 μM, propranolol (1 μM, indomethacin (10 μM or nordthydroguaiaretic acid (0.1 mM. Inhibitors of nitric oxide synthase, L-NG-monomethylarginine (L-NMMA, 10 μM and NG-nitro-L-arginine methylester (L-NOARG, 10 μM inhibited the relaxation effect of (Rα-MeHA, by approximately 52% and 70%, respectively. This inhibitory effect of L-NMMA was partially reversed by L-arginine (10 μM. Methylene blue (10 μM and ouabain (10 μM inhibited relaxation (Rα-MeHA-induced by approximately 50% and 90%, respectively. The products of cyclooxygenase and lipoxygenase are not involved in (Rα-MeHA-induced endothelium-dependent rat aorta relaxation nor are the muscarinic cholinergic and β-adrenergic receptors. The results also suggest the involvement of NO synthase, guanylate cyclase and Na+,K+-ATPase in (Rα-MeHA-induced endothelium-dependent rat aorta relaxation.

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

    Directory of Open Access Journals (Sweden)

    Yang Wu

    Full Text Available 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.

  4. Angiotensin-(1-7) augments endothelium-dependent relaxations of porcine coronary arteries to bradykinin by inhibiting angiotensin-converting enzyme 1.

    Science.gov (United States)

    Raffai, Gábor; Khang, Gilson; Vanhoutte, Paul M

    2014-05-01

    Angiotensin-converting enzyme 2 (ACE2) converts angiotensin II to angiotensin-(1-7) that activates Mas receptors, inhibits ACE1, and modulates bradykinin receptor sensitivity. This in vitro study compared the direct and indirect effects of angiotensin-(1-7), the ACE1 inhibitor captopril, and diminazene aceturate (DIZE) an alleged ACE2 activator in rings of porcine coronary arteries, by measuring changes of isometric tension. Angiotensin-(1-7), captopril, and DIZE did not cause significant changes in tension before or after desensitization of bradykinin receptors in preparations contracted with U46619. Bradykinin caused concentration-dependent and endothelium-dependent relaxations that were not affected by DIZE but were potentiated to a similar extent by angiotensin-(1-7) and captopril, given alone or in combination. Bradykinin responses potentiated by angiotensin-(1-7) and captopril were not affected by the BK1 antagonist SSR240612 and remained augmented in the presence of either N-nitro-L-arginine methyl ester hydrochloride plus indomethacin or TRAM-34 plus UCL-1684. ACE2 was identified in the coronary endothelium by immunofluorescence, but its basal activity was not influenced by DIZE. These results suggest that in coronary arteries, angiotensin-(1-7) and captopril both improves NO bioavailability and enhances endothelium-dependent hyperpolarization to bradykinin solely by ACE1 inhibition. Endothelial ACE2 activity cannot be increased by DIZE to produce local adequate amounts of angiotensin-(1-7) to influence vascular tone.

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

    Directory of Open Access Journals (Sweden)

    Saher F. Ali

    2015-01-01

    Full Text Available 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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

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

    Directory of Open Access Journals (Sweden)

    Chu-Lin Chou

    Full Text Available 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

  9. Efeito dos ácidos graxos ômega-3 sobre o relaxamento-dependente do endotélio em coelhos hipercolesterolêmicos Effects of omega-3 fatty acids on endothelium-dependent relaxation in hypercholesterolemic rabbits

    Directory of Open Access Journals (Sweden)

    Paulo Afonso Ribeiro Jorge

    1997-07-01

    Full Text Available OBJETIVO: Estudar o efeito dos ácidos graxos ômega-3 sobre o relaxamento-dependente do endotélio, o colesterol plasmático, as LDL, VLDL, HDL, triglicérides e a peroxidação lipídica das partículas de LDL-nativas, oxidadas e da parede arterial. MÉTODOS: Coelhos da raça Nova Zelândia foram submetidos a dieta enriquecida com colesterol (0,5% e gordura de coco (2%, por 30 dias e separados em grupo hipercolesterolemia (H e ômega-3 (O-3, sendo administrado ao O-3 ácidos graxos ômega-3 na dose de 300mg/kg/dia, durante 15 dias, através de gavagem. O colesterol plasmático, triglicérides, LDL-colesterol, VLDL e HDL-colesterol foram medidos através de kits enzimáticos e os resultados expressos em mg/dl. As LDL foram obtidas por ultracentrifugação e oxidadas através da exposição ao Cu++. A peroxidação lipídica das LDL e da parede da aorta foi mensurada pela dosagem do malondialdeido (MDA. A função endotelial foi avaliada por curvas de concentração-efeito obtidas pela acetilcolina e nitroprussiato, após contração com norepinefrina. RESULTADOS: Houve aumento do colesterol plasmático e das VLDL, sem interferência nos níveis de LDL e HDL, no O-3. Observou-se redução significante dos triglicérides. Verificou-se aumento significante do teor de MDA nas LDL-nativas e oxidadas, assim como na parede arterial. O relaxamento-dependente do endotélio foi significativamente menor no O-3. CONCLUSÃO: A administração de ácidos graxos ômega-3 na dosagem de 300/mg/kg/dia, a coelhos hipercolesterolêmicos aumentou o colesterol e as VLDL plasmáticas, enquanto reduziu os triglicérides. O relaxamento-dependente do endotélio foi menor que no grupo H.PURPOSE: To study the effect of omega-3 fatty acid on endothelium-dependent relaxation, total plasma cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides levels as well as, the malondialdehyde (MDA content of the LDL particles and arterial wall. METHODS: Fourteen male rabbits

  10. Endothelium-dependent relaxant responses to selective 5-HT(1B/1D) receptor agonists in the isolated middle cerebral artery of the rat

    DEFF Research Database (Denmark)

    Hansen-Schwartz, Jacob; Løvland Hoel, Natalie; Nilsson, Elisabeth

    2003-01-01

    perfused. Luminally added 5- hydroxytryptamine (5-HT), sumatriptan and rizatriptan induced maximal dilatations of 22 +/- 4, 10 +/- 2 and 13 +/- 5%, respectively, compared to the resting diameter. The relaxant effect of sumatriptan was blocked by the 5- HT(1B/1D) receptor selective antagonist GR 55562 (10......The vasomotor effects of triptans in the middle cerebral artery (MCA) of rats were studied using the pressurised arteriography method and in vitro vessel baths. Using the arteriograph, MCAs from Sprague-Dawley rats were mounted on two glass micropipettes, pressurised to 85 mm Hg and luminally...... response to 5-HT and triptans. Using the vessel bath technique, MCA segments were mounted on two metal wires. The relaxant responses to sumatriptan could not be reproduced using this model; instead, weak contractile responses (6 +/- 3% of submaximal contractile capacity) were observed. The difference...

  11. Human urotensin-II is an endothelium-dependent vasodilator in rat small arteries

    Science.gov (United States)

    Bottrill, Fiona E; Douglas, Stephen A; Hiley, C Robin; White, Richard

    2000-01-01

    The possible role of the endothelium in modulating responses to human urotensin-II (U-II) was investigated using isolated segments of rat thoracic aorta, small mesenteric artery, left anterior descending coronary artery and basilar artery.Human U-II was a potent vasoconstrictor of endothelium-intact isolated rat thoracic aorta (EC50=3.5±1.1 nM, Rmax=103±10% of control contraction induced by 60 mM KCl and 1 μM noradrenaline). However the contractile response was not significantly altered by removal of the endothelium or inhibition of nitric oxide synthesis with L-NAME (100 μM). Human U-II did not cause relaxation of noradrenaline-precontracted, endothelium-intact rat aortae.Human U-II contracted endothelium-intact rat isolated left anterior descending coronary arteries (EC50=1.3±0.8 nM, Rmax=20.1±4.9% of control contraction induced by 10 μM 5-HT). The contractile response was significantly enhanced by removal of the endothelium (Rmax=55.4±16.1%). Moreover, human U-II caused concentration-dependent relaxation of 5-HT-precontracted arteries, which was abolished by L-NAME or removal of the endothelium.No contractile effects of human U-II were found in rat small mesenteric arteries. However the peptide caused potent, concentration- and endothelium-dependent relaxations of methoxamine-precontracted vessels. The relaxant responses were potentiated by L-NAME (300 μM) but abolished in the additional presence of 25 mM KCl (which inhibits the actions of endothelium-derived hyperpolarizing factor).The present study is the first to show that human U-II is a potent endothelium-dependent vasodilator in some rat resistance vessels, and acts through release of EDHF as well as nitric oxide. Our findings have also highlighted clear anatomical differences in the responses of different vascular beds to human U-II which are likely to be important in determining the overall cardiovascular activity of this peptide. PMID:10952676

  12. Vildagliptin improves endothelium-dependent vasodilatation in type 2 diabetes

    NARCIS (Netherlands)

    van Poppel, P.C.; Netea, M.G.; Smits, P.; Tack, C.J.J.

    2011-01-01

    OBJECTIVE: To investigate whether the dipeptidyl peptidase-4 inhibitor vildagliptin improves endothelium-dependent vasodilatation in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: Sixteen subjects with type 2 diabetes (age 59.8 +/- 6.8 years, BMI 29.1 +/- 4.8 kg/m(2), HbA(1c) 6.97 +/-

  13. Gamma irradiation induces acetylcholine-evoked, endothelium-independent relaxation and activatesk-channels of isolated pulmonary artery of rats

    International Nuclear Information System (INIS)

    Eder, Veronique; Gautier, Mathieu; Boissiere, Julien; Girardin, Catherine; Rebocho, Manuel; Bonnet, Pierre

    2004-01-01

    Purpose: To test the effects of irradiation (R*) on the pulmonary artery (PA). Methods and materials: Isolated PA rings were submitted to gamma irradiation (cesium, 8 Gy/min -1 ) at doses of 20 Gy-140 Gy. Rings were placed in an organ chamber, contracted with serotonin (10 -4 M 5-hydroxytryptamine [5-HT]), then exposed to acetylcholine (ACh) in incremental concentrations. Smooth muscle cell (SMC) membrane potential was measured with microelectrodes. Results: A high dose of irradiation (60 Gy) increased 5HT contraction by 20%, whereas lower (20 Gy) doses slightly decreased it compared with control. In the absence of the endothelium, 5-HT precontracted rings exposed to 20 Gy irradiation developed a dose-dependent relaxation induced by acetylcholine (EI-ACh) with maximal relaxation of 60 ± 17% (n = 13). This was totally blocked by L-NAME (10 -4 M), partly by 7-nitro indazole; it was abolished by hypoxia and iberiotoxin, decreased by tetra-ethyl-ammonium, and not affected by free radical scavengers. In irradiated rings, hypoxia induced a slight contraction which was never observed in control rings. No differences in SMC membrane potential were observed between irradiated and nonirradiated PA rings. Conclusion: Irradiation mediates endothelium independent relaxation by a mechanism involving the nitric oxide pathway and K-channels

  14. Vildagliptin Improves Endothelium-Dependent Vasodilatation in Type 2 Diabetes

    Science.gov (United States)

    van Poppel, Pleun C.M.; Netea, Mihai G.; Smits, Paul; Tack, Cees J.

    2011-01-01

    OBJECTIVE To investigate whether the dipeptidyl peptidase-4 inhibitor vildagliptin improves endothelium-dependent vasodilatation in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS Sixteen subjects with type 2 diabetes (age 59.8 ± 6.8 years, BMI 29.1 ± 4.8 kg/m2, HbA1c 6.97 ± 0.61) on oral blood glucose–lowering treatment were included. Participants received vildagliptin 50 mg b.i.d. or acarbose 100 mg t.i.d. for four consecutive weeks in a randomized, double-blind, cross-over design. At the end of each treatment period, we measured forearm vasodilator responses to intra-arterially administered acetylcholine (endothelium-dependent vasodilator) and sodium nitroprusside (endothelium-independent vasodilator). RESULTS Infusion of acetylcholine induced a dose-dependent increase in forearm blood flow in the experimental arm, which was higher during vildagliptin (3.1 ± 0.7, 7.9 ± 1.1, and 12.6 ± 1.4 mL ⋅ dL−1 ⋅ min−1 in response to three increasing dosages of acetylcholine) than during acarbose (2.0 ± 0.7, 5.0 ± 1.2, and 11.7 ± 1.6 mL ⋅ dL−1 ⋅ min−1, respectively; P = 0.01 by two-way ANOVA). Treatment with vildagliptin did not significantly change the vascular responses to sodium nitroprusside. CONCLUSIONS Four weeks’ treatment with vildagliptin improves endothelium-dependent vasodilatation in subjects with type 2 diabetes. This observation might have favorable cardiovascular implications. PMID:21788633

  15. Effect of subchronic exposure to mainstream cigarette smoke on endothelium-dependent vasodilation in rat arteries

    Directory of Open Access Journals (Sweden)

    Helena Lenasi

    2005-07-01

    Full Text Available Background: Cigarette smoking is reported to impair endothelium-dependent vasodilation. The aim of the present study was to assess the effect of 30-day exposure to mainstream cigarette smoke on vascular reactivity of rat abdominal aorta, carotid, renal and mesenteric artery. Separately, the NO-mediated and the EDHF-mediated, endothelium-dependent vascular relaxations were determined.Methods: Two groups of »Whistar Kyoto« rats were exposed to mainstream cigarette smoke (2 hours/day, 5 days/week for 30 days and to fresh conditioned air, respectively. Rats were sacrificed on the second day after the last exposition to cigarette smoke. Vascular reactivity studies were performed on isolated, endothelium-intact, phenylephrine-preconstricted rat artery rings. Cumulative concentration-relaxation curves to acetylcholine (ACh were obtained in the absence and presence of the endothelial NO synthase (eNOS inhibitor N ω nitro L-arginine (L-NA and the cyclo-oxygenase (COX inhibitor diclofenac, respectively. After washing period of 1 hour, vessels were exposed either to the intracellular superoxide scavenger tiron, to the cytochrome P450 (CYP inhibitor miconazole or the Na-K-ATPase inhibitor ouabain before being preconstricted with phenylephrine and determining the concentration-response curve to ACh.Results: ACh induced concentration-dependent relaxations. In none of the vessels investigated did we observe a significant difference in the relaxations obtained in arteries from control rats and rats exposed to cigarettee smoke. Although smoking is known to cause an increase in oxidative stress, treatment of the vessels with tiron did not affect the NOmediated relaxations. To evaluate the contribution of EDHF to endothelium-dependent vasodilation rings were preincubated with L-NA. The EDHF-mediated relaxations were significantly attenuated compared to the NO-mediated relaxations in renal and mesenteric artery and almost completely abolished in aorta and

  16. Mechanisms underlying epithelium-dependent relaxation in rat bronchioles

    DEFF Research Database (Denmark)

    Kroigaard, Christel; Dalsgaard, Thomas; Simonsen, Ulf

    2010-01-01

    This study investigated the mechanisms underlying epithelium-derived hyperpolarizing factor (EpDHF)-type relaxation in rat bronchioles. Immunohistochemistry was performed, and rat bronchioles and pulmonary arteries were mounted in microvascular myographs for functional studies. An opener of small...... (SK(Ca)) and intermediate (IK(Ca))-conductance calcium-activated potassium channels, NS309 (6,7-dichloro-1H-indole-2,3-dione 3-oxime) was used to induce EpDHF-type relaxation. IK(Ca) and SK(Ca)3 positive immunoreactions were observed mainly in the epithelium and endothelium of bronchioles and arteries......, respectively. In 5-hydroxytryptamine (1 microM)-contracted bronchioles (828 +/- 20 microm, n = 84) and U46619 (0.03 microM)-contracted arteries (720 +/- 24 microm, n = 68), NS309 (0.001-10 microM) induced concentration-dependent relaxations that were reduced by epithelium/endothelium removal and by blocking IK...

  17. CYP epoxygenase-derived H2O2 is involved in the endothelium-derived hyperpolarization (EDH) and relaxation of intrarenal arteries.

    Science.gov (United States)

    Muñoz, Mercedes; López-Oliva, Maria Elvira; Pinilla, Estéfano; Martínez, María Pilar; Sánchez, Ana; Rodríguez, Claudia; García-Sacristán, Albino; Hernández, Medardo; Rivera, Luis; Prieto, Dolores

    2017-05-01

    Reactive oxygen species (ROS) like hydrogen peroxide (H 2 O 2 ) are involved in the in endothelium-derived hyperpolarization (EDH)-type relaxant responses of coronary and mesenteric arterioles. The role of ROS in kidney vascular function has mainly been investigated in the context of harmful ROS generation associated to kidney disease. The present study was sought to investigate whether H 2 O 2 is involved in the endothelium-dependent relaxations of intrarenal arteries as well the possible endothelial sources of ROS generation involved in these responses. Under conditions of cyclooxygenase (COX) and nitric oxide (NO) synthase inhibition, acetylcholine (ACh) induced relaxations and stimulated H 2 O 2 release that were reduced by catalase and by the glutathione peroxidase (GPx) mimetic ebselen in rat renal interlobar arteries, suggesting the involvement of H 2 O 2 in the endothelium-dependent responses. ACh relaxations were also blunted by the CYP2C inhibitor sulfaphenazole and by the NADPH oxidase inhibitor apocynin. Acetylcholine stimulated both superoxide (O 2 •- ) and H 2 O 2 production that were reduced by sulfaphenazole and apocynin. Expression of the antioxidant enzyme CuZnSOD and of the H 2 O 2 reducing enzymes catalase and GPx-1 was found in both intrarenal arteries and renal cortex. On the other hand, exogenous H 2 O 2 relaxed renal arteries by decreasing vascular smooth muscle (VSM) intracellular calcium concentration [Ca 2+ ] i and markedly enhanced endothelial K Ca currents in freshly isolated renal endothelial cells. CYP2C11 and CYP2C23 epoxygenases were highly expressed in interlobar renal arteries and renal cortex, respectively, and were co-localized with eNOS in renal endothelial cells. These results demonstrate that H 2 O 2 is involved in the EDH-type relaxant responses of renal arteries and that CYP 2C epoxygenases are physiologically relevant endothelial sources of vasodilator H 2 O 2 in the kidney. Copyright © 2017 Elsevier Inc. All rights

  18. Endothelium-dependent vasorelaxant effect of procyanidin B2 on human internal mammary artery.

    Science.gov (United States)

    Novakovic, Aleksandra; Marinko, Marija; Jankovic, Goran; Stojanovic, Ivan; Milojevic, Predrag; Nenezic, Dragoslav; Kanjuh, Vladimir; Yang, Qin; He, Guo-Wei

    2017-07-15

    The aim of the present study was to investigate and characterize vasorelaxant effect of procyanidin B2 on human internal mammary artery (HIMA) as one of the mechanisms of its protective effect against vascular risk. Procyanidin B2 induced strong concentration-dependent relaxation of HIMA rings pre-contracted by phenylephrine. Pretreatment with L-NAME, a NO synthase inhibitor, hydroxocobalamin, a NO scavenger, and ODQ, an inhibitor of soluble guanylate cyclase, significantly inhibited procyanidin B2-induced relaxation of HIMA, while indomethacin, a cyclooxygenase inhibitor, considerably reduced effects of low concentrations. Among K + channel blockers, iberiotoxin, a selective blocker of large conductance Ca 2+ -activated K + channels (BK Ca ), abolished procyanidin B2-induced relaxation, glibenclamide, a selective ATP-sensitive K + (K ATP ) channels blocker, induced partial inhibition, while 4-aminopyridine, a blocker of voltage-gated K + (K V ) channels, and TRAM-34, an inhibitor of intermediate-conductance Ca 2+ -activated K + (IK Ca ) channels, slightly reduced maximal relaxation of HIMA. Further, procyanidin B2 relaxed contraction induced by phenylephrine in Ca 2+ -free Krebs solution, but had no effect on contraction induced by caffeine. Finally, thapsigargin, a sarcoplasmic reticulum Ca 2+ -ATPase inhibitor, significantly reduced relaxation of HIMA produced by procyanidin B2. These results demonstrate that procyanidin B2 produces endothelium-dependent relaxation of HIMA pre-contracted by phenylephrine. This effect is primarily the result of an increased NO synthesis and secretion by endothelial cells and partially of prostacyclin, although it involves activation of BK Ca and K ATP , as well as K V and IK Ca channels in high concentrations of procyanidin B2. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. EDRF [endothelium-derived relaxing factor]-release and Ca++-channel blockage by Magnolol, an antiplatelet agent isolated from Chinese herb Magnolia officinalis, in rat thoracic aorta

    International Nuclear Information System (INIS)

    Teng, Cheming; Yu, Sheumeei; Chen, Chienchih; Huang, Yulin; Huang, Turfu

    1990-01-01

    Magnolol is an antiplatelet agent isolated from Chinese herb Magnolia officinalis. It inhibited norepinephrine-induced phasic and tonic contractions in rat thoracic aorta. At the plateau of the NE-induced tonic contraction, addition of magnolol caused two phases (fast and slow) of relaxation. These two relaxations were concentration-dependent, and were not inhibited by indomethacin. The fast relaxation was completely antagonized by hemoglobin and methylene blue, and disappeared in de-endothelialized aorta while the slow relaxation was not affected by the above treatments. Magnolol also inhibited high potassium-induced, calcium-dependent contraction of rat aorta in a concentration-dependent manner. 45 Ca ++ influx induced by high potassium or NE was markedly inhibited by magnolol. Cyclic GMP, but not PGI 2 , was increased by magnolol in intact, but not in de-endothelialized aorta. It is concluded that magnolol relaxed vascular smooth muscle by releasing endothelium-derived relaxing factor (EDRF) and by inhibiting calcium influx through voltage-gated calcium channels

  20. Endothelium-Dependent Vasorelaxant Effect of Butanolic Fraction from Caryocar brasiliense Camb. Leaves in Rat Thoracic Aorta

    Directory of Open Access Journals (Sweden)

    Lais Moraes de Oliveira

    2012-01-01

    Full Text Available Caryocar brasiliense Camb. “pequi” is a native plant from the Cerrado region of Brazil that contains bioactive components reported to be antioxidant agents. Previous work has demonstrated that dietary supplementation with pequi decreased the arterial pressure of volunteer athletes. We found that the crude hydroalcoholic extract (CHE of C. brasiliense leaves relaxed, in a concentration-dependent manner, rat aortic rings precontracted with phenylephrine, and that the butanolic fraction (BF produced an effect similar to that of the CHE. Aortic relaxation induced by BF was abolished by endothelium removal, by incubation of the nitric oxide synthase inhibitor L-NAME, or the soluble guanylatecyclase inhibitor ODQ. However, incubation with atropine and pyrilamine had no effect on the BF-induced vasorelaxation. Moreover, this effect was not inhibited by indomethacin and tetraethylammonium. The concentration-response curve to calcium in denuded-endothelium rings was not modified after incubation with BF, and the vasorelaxation by BF in endothelium-intact rings precontracted with KCl was abolished after incubation with L-NAME. In addition, administration of BF in anesthetized rats resulted in a reversible hypotension. The results reveal that C. brasiliense possesses both in vivo and in vitro activities and that the vascular effect of BF involves stimulation of the nitric oxide/cyclic GMP pathway.

  1. Effect of the Menstrual Cycle on Maximum Oxygen Consumption and Endothelium-Dependent Vasodilation

    National Research Council Canada - National Science Library

    Andrews, Thomas

    1997-01-01

    .... We studied endothelium-dependent vasodilation of the brachial artery during three phases of the menstrual cycle in 20 eumenorrheic subjects to determine the effect of endogenous estradiol and progesterone...

  2. Decreased endothelium-dependent coronary vasomotion in healthy young smokers

    International Nuclear Information System (INIS)

    Iwado, Yasuyoshi; Yoshinaga, Keiichiro; Furuyama, Hideto; Tsukamoto, Eriko; Tamaki, Nagara; Ito, Yoshinori; Noriyasu, Kazuyuki; Katoh, Chietsugu; Kuge, Yuji

    2002-01-01

    Chronic cigarette smoking alters coronary vascular endothelial response. To determine whether altered response also occurs in young individuals without manifest coronary disease we quantified coronary blood flow at rest, following adenosine vasodilator stress and during the cold pressor test in healthy young smokers. Myocardial blood flow (MBF) was quantified by oxygen-15 labelled water positron emission tomography in 30 healthy men aged from 20 to 35 years (18 smokers and 12 non-smokers, aged 27.4±4.4 vs 26.3±3.3). The smokers had been smoking cigarettes for 9.4±4.9 pack-years. MBF was measured at rest, during intravenous adenosine triphosphate (ATP: 0.16 mg kg -1 min -1 ) infusion (hyperaemic response), and during cold pressor test (CPT) (endothelial vasodilator response). Rest MBF and hyperaemic MBF did not differ significantly between the smokers and the non-smokers (rest: 0.86±0.11 vs 0.92±0.14 and ATP: 3.20±1.12 vs 3.69±0.76 ml g -1 min -1 ; P=NS). Coronary flow reserve was similar between the two groups (smokers: 3.78±1.83; non-smokers: 4.03±0.68; P=NS). Although CPT induced a similar increase in rate-pressure product (RPP) in the smokers and the non-smokers (10,430±1,820 vs 9,236±1,356 beats min -1 mmHg -1 ), CPT MBF corrected by RPP was significantly decreased in the smokers (0.65±0.12 ml g -1 min -1 ) compared with the non-smokers (0.87±0.12 ml g -1 min -1 ) (P<0.05). In addition, the ratio of CPT MBF to resting MBF was inversely correlated with pack-years (r=-0.57, P=0.014). Endothelium-dependent coronary artery vasodilator function is impaired in apparently healthy young smokers. (orig.)

  3. Decreased endothelium-dependent coronary vasomotion in healthy young smokers

    Energy Technology Data Exchange (ETDEWEB)

    Iwado, Yasuyoshi; Yoshinaga, Keiichiro; Furuyama, Hideto; Tsukamoto, Eriko; Tamaki, Nagara [Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, Kita-Ku, Kita 15 Nishi 7, Sapporo, 060-8638 (Japan); Ito, Yoshinori; Noriyasu, Kazuyuki [Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo (Japan); Katoh, Chietsugu; Kuge, Yuji [Department of Tracer Kinetics, Hokkaido University Graduate School of Medicine, Sapporo (Japan)

    2002-08-01

    Chronic cigarette smoking alters coronary vascular endothelial response. To determine whether altered response also occurs in young individuals without manifest coronary disease we quantified coronary blood flow at rest, following adenosine vasodilator stress and during the cold pressor test in healthy young smokers. Myocardial blood flow (MBF) was quantified by oxygen-15 labelled water positron emission tomography in 30 healthy men aged from 20 to 35 years (18 smokers and 12 non-smokers, aged 27.4{+-}4.4 vs 26.3{+-}3.3). The smokers had been smoking cigarettes for 9.4{+-}4.9 pack-years. MBF was measured at rest, during intravenous adenosine triphosphate (ATP: 0.16 mg kg{sup -1} min{sup -1}) infusion (hyperaemic response), and during cold pressor test (CPT) (endothelial vasodilator response). Rest MBF and hyperaemic MBF did not differ significantly between the smokers and the non-smokers (rest: 0.86{+-}0.11 vs 0.92{+-}0.14 and ATP: 3.20{+-}1.12 vs 3.69{+-}0.76 ml g{sup -1} min{sup -1}; P=NS). Coronary flow reserve was similar between the two groups (smokers: 3.78{+-}1.83; non-smokers: 4.03{+-}0.68; P=NS). Although CPT induced a similar increase in rate-pressure product (RPP) in the smokers and the non-smokers (10,430{+-}1,820 vs 9,236{+-}1,356 beats min{sup -1} mmHg{sup -1}), CPT MBF corrected by RPP was significantly decreased in the smokers (0.65{+-}0.12 ml g{sup -1} min{sup -1}) compared with the non-smokers (0.87{+-}0.12 ml g{sup -1} min{sup -1}) (P<0.05). In addition, the ratio of CPT MBF to resting MBF was inversely correlated with pack-years (r=-0.57, P=0.014). Endothelium-dependent coronary artery vasodilator function is impaired in apparently healthy young smokers. (orig.)

  4. Endothelium-dependent vasodilatation, plasma markers of endothelial function, and adrenergic vasoconstrictor responses in type 1 diabetes under near-normoglycemic conditions

    NARCIS (Netherlands)

    Huvers, F C; De Leeuw, P W; Houben, A J; De Haan, C H; Hamulyak, K; Schouten, H; Wolffenbuttel, B H; Schaper, N C

    It is unknown whether and to what extent changes in various endothelial functions and adrenergic responsiveness are related to the development of microvascular complications in type 1 diabetes. Therefore, endothelium-dependent and endothelium-independent vasodilatation, endothelium-dependent

  5. The relationship of vascular endothelial marker and endothelium-dependent vasodilatation in patients with essential hypertension

    International Nuclear Information System (INIS)

    Chen Yongjian; Zhou Yonglie; Hu Qingfeng; Qiu Liannv

    2009-01-01

    Objective: To explore the relationship of vascular endothelial marker and endothelium-dependent vasodilatation in patients with essential hypertension (EH). Methods: Plasma endothlium (ET-1) (with RIA) and von Willber factor (vWF)(with ELISA) levels were measured both before and after 12 wks' treatment in 56 patients with essential hypertension and 32 controls. The brachial artery endothelium-dependent vasodilatation function was examined with high resolving color doppler ultra-sonography. The 56 patients with EH were of two groups A. high and very high risk, n=26 B. low and moderate risk, n=30. Results: Plasma levels of ET-1, vWF in patients with EH as a whole were significantly higher than those in controls group [(53.3±16.2)pg/ml vs(42.5±8.5)pg/ml, (158.2±28.6)% vs(130.6±35.2)%], endothelium-dependent vasodilatation function wasmuch reduced in patients with EH(7.5±4.2)% vs controls(12.3±4.3)%. Among the patients, values in Group A were significantly different from those in Group B. After treatment for 12 weeks, plasma ET-1 and vWF and endothelium-dependent vasodilatation function were significantly improved. There was negative correlation between vascular endothelial marker levels and endothelium-dependent vasodilatation function. Conclusion: The endothelium-dependent vasodilatation function was impaired and plasma ET-1 and vWF levels were increased in patients with EH, the endothelial dysfunction was closely associated with the risk level of EH. Vascular endothelial markers were useful indicators for evaluation of the endothelium-dependent vasodilatation function. (authors)

  6. Novel approaches to improving endothelium-dependent nitric oxide-mediated vasodilatation

    DEFF Research Database (Denmark)

    Simonsen, Ulf; Rodriguez-Rodriguez, Rosalia; Dalsgaard, Thomas

    2009-01-01

    Endothelial dysfunction, which is defined by decreased endothelium-dependent vasodilatation, is associated with an increased number of cardiovascular events. Nitric oxide (NO) bioavailability is reduced by altered endothelial signal transduction or increased formation of radical oxygen species...... reacting with NO. Endothelial dysfunction is therapeutically reversible and physical exercise, calcium channel blockers, angiotensin converting enzyme inhibitors, and angiotensin receptor antagonists improve flow-evoked endothelium-dependent vasodilation in patients with hypertension and diabetes. We have...... the endothelial signal transduction pathways involved in vasorelaxation and NO release induced by an olive oil component, oleanolic acid, and (3) investigated the role of calcium-activated K channels in the release of NO induced by receptor activation. Tempol increases endothelium-dependent vasodilatation...

  7. Opening of small and intermediate calcium-activated potassium channels induces relaxation mainly mediated by nitric-oxide release in large arteries and endothelium-derived hyperpolarizing factor in small arteries from rat

    DEFF Research Database (Denmark)

    Stankevicius, Edgaras; Dalsgaard, Thomas; Kroigaard, Christel

    2011-01-01

    This study was designed to investigate whether calcium-activated potassium channels of small (SK(Ca) or K(Ca)2) and intermediate (IK(Ca) or K(Ca)3.1) conductance activated by 6,7-dichloro-1H-indole-2,3-dione 3-oxime (NS309) are involved in both nitric oxide (NO) and endothelium-derived hyperpolar......This study was designed to investigate whether calcium-activated potassium channels of small (SK(Ca) or K(Ca)2) and intermediate (IK(Ca) or K(Ca)3.1) conductance activated by 6,7-dichloro-1H-indole-2,3-dione 3-oxime (NS309) are involved in both nitric oxide (NO) and endothelium...... in human umbilical vein endothelial cells (HUVECs), and calcium concentrations were investigated in both HUVECs and mesenteric arterial endothelial cells. In both superior (∼1093 μm) and small mesenteric (∼300 μm) arteries, NS309 evoked endothelium- and concentration-dependent relaxations. In superior....... In small mesenteric arteries, NS309 relaxations were reduced slightly by ADMA, whereas apamin plus an IK(Ca) channel blocker almost abolished relaxation. Iberiotoxin did not change NS309 relaxation. HUVECs expressed mRNA for SK(Ca) and IK(Ca) channels, and NS309 induced increases in calcium, outward...

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

    Science.gov (United States)

    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

  9. Arginase up-regulation and eNOS uncoupling contribute to impaired endothelium-dependent vasodilation in a rat model of intrauterine growth restriction.

    Science.gov (United States)

    Grandvuillemin, Isabelle; Buffat, Christophe; Boubred, Farid; Lamy, Edouard; Fromonot, Julien; Charpiot, Philippe; Simoncini, Stephanie; Sabatier, Florence; Dignat-George, Françoise; Peyter, Anne-Christine; Simeoni, Umberto; Yzydorczyk, Catherine

    2018-05-09

    Individuals born after intrauterine growth restriction (IUGR) are at increased risk of developing cardiovascular diseases in adulthood, notably hypertension (HTN). Alterations in the vascular system, particularly impaired endothelium-dependent vasodilation, may play an important role in long-term effects of IUGR. Whether such vascular dysfunction precedes HTN has not been fully established in individuals born after IUGR. Moreover, the intimate mechanisms of altered endothelium-dependent vasodilation remain incompletely elucidated. We therefore investigated, using a rat model of IUGR, whether impaired endothelium-dependent relaxation precedes the development of HTN and whether key components of the L-Arginine-nitric oxide (NO) pathway are involved in its pathogenesis. Pregnant rats were fed with a control (CTRL, 23% casein) or low-protein diet (LP, 9% casein) to induce IUGR. Systolic blood pressure (SBP) was measured by tail-cuff plethysmography in 5- and 8-week-old male offspring. Aortic rings were isolated to investigate relaxation to acetylcholine, NO production, eNOS protein content, arginase activity, and superoxide anion production. SBP was not different at 5 weeks, but significantly increased in 8-week-old LP vs. CRTL offspring. In 5-week-old LP vs. CRTL males, endothelium-dependent vasorelaxation was significantly impaired, but restored by pre-incubation with L-Arginine or the arginase inhibitor BEC; NO production was significantly reduced, but restored by L-Arginine pretreatment; total eNOS protein, dimer/monomer ratio, and arginase activity were significantly increased; superoxide anion production was significantly enhanced, but normalized by pretreatment with the NOS inhibitor L-NNA. In this model, IUGR leads to early-impaired endothelium-dependent vasorelaxation, resulting from arginase up-regulation and eNOS uncoupling, which precedes the development of HTN.

  10. Preserved endothelium-dependent vasodilation in coronary segments previously treated with balloon angioplasty and intracoronary irradiation

    NARCIS (Netherlands)

    M. Sabaté (Manel); A.J. Wardeh (Alexander); I.P. Kay (Ian Patrick); A. Cequier (Angel); J.M.R. Ligthart (Jürgen); J.A. Gómez-Hospital (Joan Antoni); S.G. Carlier (Stephan); V.L.M.A. Coen (Veronique); J.P. Marijnissen (Johannes); P.W.J.C. Serruys (Patrick); P.C. Levendag (Peter); W.J. van der Giessen (Wim)

    1999-01-01

    textabstractBACKGROUND: Abnormal endothelium-dependent coronary vasomotion has been reported after balloon angioplasty (BA), as well as after intracoronary radiation. However, the long-term effect on coronary vasomotion is not known. The aim of this study was to evaluate the

  11. Pravastatin and endothelium dependent vasomotion after coronary angioplasty: the PREFACE trial.

    Science.gov (United States)

    Mulder, H J; Schalij, M J; Kauer, B; Visser, R F; van Dijkman, P R; Jukema, J W; Zwinderman, A H; Bruschke, A V

    2001-11-01

    To test the hypothesis that the 3-hydroxy-3-methylglutaryl coenzyme-A reductase inhibitor pravastatin ameliorates endothelium mediated responses of dilated coronary segments: the PREFACE (pravastatin related effects following angioplasty on coronary endothelium) trial. A double blind, randomised, placebo controlled, multicentre study. Four hospitals in the Netherlands. 63 non-smoking, non-hypercholesterolaemic patients scheduled for elective balloon angioplasty (pravastatin 34, placebo 29). The effects of three months of pravastatin treatment (40 mg daily) on endothelium dependent vasomotor function were studied. Balloon angioplasty was undertaken one month after randomisation, and coronary vasomotor function tests using acetylcholine were performed two months after balloon angioplasty. The angiograms were analysed quantitatively. The efficacy measure was the acetylcholine induced change in mean arterial diameter, determined in the dilated segment and in an angiographically normal segment of an adjacent non-manipulated coronary artery. Increasing acetylcholine doses produced vasoconstriction in the dilated segments (p = 0.004) but not in the normal segments. Pravastatin did not affect the vascular response to acetylcholine in either the dilated segments (p = 0.09) or the non-dilated sites. Endothelium dependent vasomotion in normal segments was correlated with that in dilated segments (r = 0.47, p < 0.001). There were fewer procedure related events in the pravastatin group than in the placebo group (p < 0.05). Endothelium dependent vasomotion in normal segments is correlated with that in dilated segments. A significant beneficial effect of pravastatin on endothelial function could not be shown, but in the dilated segments there was a trend towards a beneficial treatment effect in the pravastatin group.

  12. Ethanol extract of seeds of Oenothera odorata induces vasorelaxation via endothelium-dependent NO-cGMP signaling through activation of Akt-eNOS-sGC pathway.

    Science.gov (United States)

    Kim, Hye Yoom; Oh, Hyuncheol; Li, Xiang; Cho, Kyung Woo; Kang, Dae Gill; Lee, Ho Sub

    2011-01-27

    The vasorelaxant effect of ethanol extract of seeds of Oenothera odorata (Onagraceae) (one species of evening primroses) (ESOO) and its mechanisms involved were defined. Changes in vascular tension, guanosine 3',5'-cyclic monophosphate (cGMP) levels, and Akt expression were measured in carotid arterial rings from rats. Seeds of Oenothera odorata were extracted with ethanol (94%) and the extract was filtered, concentrated and stored at -70°C. ESOO relaxed endothelium-intact, but not endothelium-denuded, carotid arterial rings in a concentration-dependent manner. Similarly, ESOO increased cGMP levels of the carotid arterial rings. Pretreatment of endothelium-intact arterial rings with L-NAME, an inhibitor of nitric oxide synthase (NOS), or ODQ, an inhibitor of soluble guanylyl cyclase (sGC), blocked the ESOO-induced vasorelaxation and increase in cGMP levels. Nominally Ca(2+)-free but not L-typed Ca(2+) channel inhibition attenuated the ESOO-induced vasorelaxation. Thapsigargin, Gd(3+), and 2-aminoethyl diphenylborinate, modulators of store-operated Ca(2+) entry (SOCE), significantly attenuated the ESOO-induced vasorelaxation and increase in cGMP levels. Further, wortmannin, an inhibitor of Akt, attenuated the ESOO-induced vasorelaxation and increases in cGMP levels and phosphorylated Akt2 expression. K(+) channel blockade with TEA, 4-aminopyridine, and glibenclamide attenuated the ESOO-induced vascular relaxation. Taken together, the present study demonstrates that ESOO relaxes vascular smooth muscle via endothelium-dependent NO-cGMP signaling through activation of the Akt-eNOS-sGC pathway. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  13. Effects of sapropterin on endothelium-dependent vasodilation in patients with CADASIL: a randomized controlled trial.

    Science.gov (United States)

    De Maria, Renata; Campolo, Jonica; Frontali, Marina; Taroni, Franco; Federico, Antonio; Inzitari, Domenico; Tavani, Alessandra; Romano, Silvia; Puca, Emanuele; Orzi, Francesco; Francia, Ada; Mariotti, Caterina; Tomasello, Chiara; Dotti, Maria Teresa; Stromillo, Maria Laura; Pantoni, Leonardo; Pescini, Francesca; Valenti, Raffaella; Pelucchi, Claudio; Parolini, Marina; Parodi, Oberdan

    2014-10-01

    Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a rare autosomal dominant disorder caused by NOTCH3 mutations, is characterized by vascular smooth muscle and endothelial cells abnormalities, altered vasoreactivity, and recurrent lacunar infarcts. Vasomotor function may represent a key factor for disease progression. Tetrahydrobiopterin, essential cofactor for nitric oxide synthesis in endothelial cells, ameliorates endothelial function. We assessed whether supplementation with sapropterin, a synthetic tetrahydrobiopterin analog, improves endothelium-dependent vasodilation in CADASIL patients. In a 24-month, multicenter randomized, double-blind, placebo-controlled trial, CADASIL patients aged 30 to 65 years were randomly assigned to receive placebo or sapropterin 200 to 400 mg BID. The primary end point was change in the reactive hyperemia index by peripheral arterial tonometry at 24 months. We also assessed the safety and tolerability of sapropterin. Analysis was done by intention-to-treat. The intention-to-treat population included 61 patients. We found no significant difference between sapropterin (n=32) and placebo (n=29) in the primary end point (mean difference in reactive hyperemia index by peripheral arterial tonometry changes 0.19 [95% confidence interval, -0.18, 0.56]). Reactive hyperemia index by peripheral arterial tonometry increased after 24 months in 37% of patients on sapropterin and in 28% on placebo; however, after adjustment for age, sex, and clinical characteristics, improvement was not associated with treatment arm. The proportion of patients with adverse events was similar on sapropterin and on placebo (50% versus 48.3%); serious adverse events occurred in 6.3% versus 13.8%, respectively. Sapropterin was safe and well-tolerated at the average dose of 5 mg/kg/day, but did not affect endothelium-dependent vasodilation in CADASIL patients. https://www.clinicaltrialsregister.eu. Unique

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

    Science.gov (United States)

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

    2012-02-01

    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. 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. © 2011 The Authors. British Journal of Pharmacology © 2011 The British Pharmacological Society.

  15. Leptin-induced endothelium-dependent vasorelaxation of peripheral arteries in lean and obese rats: role of nitric oxide and hydrogen sulfide.

    Directory of Open Access Journals (Sweden)

    Anna Jamroz-Wiśniewska

    Full Text Available Adipose tissue hormone leptin induces endothelium-dependent vasorelaxation mediated by nitric oxide (NO and endothelium-derived hyperpolarizing factors (EDHF. Previously it has been demonstrated that in short-term obesity the NO-dependent and the EDHF-dependent components of vascular effect of leptin are impaired and up-regulated, respectively. Herein we examined the mechanism of the EDHF-dependent vasodilatory effect of leptin and tested the hypothesis that alterations of acute vascular effects of leptin in obesity are accounted for by chronic hyperleptinemia. The study was performed in 5 groups of rats: (1 control, (2 treated with exogenous leptin for 1 week to induce hyperleptinemia, (3 obese, fed highly-palatable diet for 4 weeks, (4 obese treated with pegylated superactive rat leptin receptor antagonist (PEG-SRLA for 1 week, (5 fed standard chow and treated with PEG-SRLA. Acute effect of leptin on isometric tension of mesenteric artery segments was measured ex vivo. Leptin relaxed phenylephrine-preconstricted vascular segments in NO- and EDHF-dependent manner. The NO-dependent component was impaired and the EDHF-dependent component was increased in the leptin-treated and obese groups and in the latter group both these effects were abolished by PEG-SRLA. The EDHF-dependent vasodilatory effect of leptin was blocked by either the inhibitor of cystathionine γ-lyase, propargylglycine, or a hydrogen sulfide (H2S scavenger, bismuth (III subsalicylate. The results indicate that NO deficiency is compensated by the up-regulation of EDHF in obese rats and both effects are accounted for by chronic hyperleptinemia. The EDHF-dependent component of leptin-induced vasorelaxation is mediated, at least partially, by H2S.

  16. Nitric oxide, cholesterol oxides and endothelium-dependent vasodilation in plasma of patients with essential hypertension

    Directory of Open Access Journals (Sweden)

    P. Moriel

    2002-11-01

    Full Text Available The objective of the present study was to identify disturbances of nitric oxide radical (·NO metabolism and the formation of cholesterol oxidation products in human essential hypertension. The concentrations of·NO derivatives (nitrite, nitrate, S-nitrosothiols and nitrotyrosine, water and lipid-soluble antioxidants and cholesterol oxides were measured in plasma of 11 patients with mild essential hypertension (H: 57.8 ± 9.7 years; blood pressure, 148.3 ± 24.8/90.8 ± 10.2 mmHg and in 11 healthy subjects (N: 48.4 ± 7.0 years; blood pressure, 119.4 ± 9.4/75.0 ± 8.0 mmHg.Nitrite, nitrate and S-nitrosothiols were measured by chemiluminescence and nitrotyrosine was determined by ELISA. Antioxidants were determined by reverse-phase HPLC and cholesterol oxides by gas chromatography. Hypertensive patients had reduced endothelium-dependent vasodilation in response to reactive hyperemia (H: 9.3 and N: 15.1% increase of diameter 90 s after hyperemia, and lower levels of ascorbate (H: 29.2 ± 26.0, N: 54.2 ± 24.9 µM, urate (H: 108.5 ± 18.9, N: 156.4 ± 26.3 µM, ß-carotene (H: 1.1 ± 0.8, N: 2.5 ± 1.2 nmol/mg cholesterol, and lycopene (H: 0.4 ± 0.2, N: 0.7 ± 0.2 nmol/mg cholesterol, in plasma, compared to normotensive subjects. The content of 7-ketocholesterol, 5alpha-cholestane-3ß,5,6ß-triol and 5,6alpha-epoxy-5alpha-cholestan-3alpha-ol in LDL, and the concentration of endothelin-1 (H: 0.9 ± 0.2, N: 0.7 ± 0.1 ng/ml in plasma were increased in hypertensive patients. No differences were found for ·NO derivatives between groups. These data suggest that an increase in cholesterol oxidation is associated with endothelium dysfunction in essential hypertension and oxidative stress, although ·NO metabolite levels in plasma are not modified in the presence of elevated cholesterol oxides.

  17. Hypotensive effect and endothelium-dependent vascular action of leaves of Alpinia purpurata (Vieill K. Schum

    Directory of Open Access Journals (Sweden)

    Alessandra Tesch da Silva

    2014-04-01

    Full Text Available The aims of this study were to evaluate the chemical profile, vascular reactivity, and acute hypotensive effect (AHE of the ethanolic extract of leaves of Alpinia purpurata (Vieill K. Schum (EEAP. Its chemical profile was evaluated using HPLC-UV, ICP-OES, and colorimetric quantification of total flavonoids and polyphenols. The vascular reactivity of the extract was determined using the mesenteric bed isolated from WKY. AHE dose-response curves were obtained for both EEAP and inorganic material isolated from AP (IAP in WKY and SHR animals. Cytotoxic and mutagenic safety levels were determined by the micronucleus test. Rutin-like flavonoids were quantified in the EEAP (1.8 ± 0.03%, and the total flavonoid and polyphenol ratios were 4.1 ± 1.8% and 5.1 ± 0.3%, respectively. We observed that the vasodilation action of EEAP was partially mediated by nitric oxide (·NO. The IAP showed the presence of calcium (137.76 ± 4.08 μg mg-1. The EEAP and IAP showed an AHE in WKY and SHR animals. EEAP did not have cytotoxic effects or cause chromosomic alterations. The AHE shown by EEAP could result from its endothelium-dependent vascular action. Rutin-like flavonoids, among other polyphenols, could contribute to these biological activities, and the calcium present in EEAP could act in a synergistic way.

  18. Density dependence of relaxation dynamics in glass formers, and ...

    Indian Academy of Sciences (India)

    Anshul D S Parmar

    formers, we study the variation of relaxation dynamics with density, rather than temperature, as a control ... stronger behaviour, the use of scaled variables involving temperature and ... of the temperature dependence of B as written defines.

  19. Inward rectifier potassium (Kir2.1) channels as end-stage boosters of endothelium-dependent vasodilators.

    Science.gov (United States)

    Sonkusare, Swapnil K; Dalsgaard, Thomas; Bonev, Adrian D; Nelson, Mark T

    2016-06-15

    Increase in endothelial cell (EC) calcium activates calcium-sensitive intermediate and small conductance potassium (IK and SK) channels, thereby causing hyperpolarization and endothelium-dependent vasodilatation. Endothelial cells express inward rectifier potassium (Kir) channels, but their role in endothelium-dependent vasodilatation is not clear. In the mesenteric arteries, only ECs, but not smooth muscle cells, displayed Kir currents that were predominantly mediated by the Kir2.1 isoform. Endothelium-dependent vasodilatations in response to muscarinic receptor, TRPV4 (transient receptor potential vanilloid 4) channel and IK/SK channel agonists were highly attenuated by Kir channel inhibitors and by Kir2.1 channel knockdown. These results point to EC Kir channels as amplifiers of vasodilatation in response to increases in EC calcium and IK/SK channel activation and suggest that EC Kir channels could be targeted to treat endothelial dysfunction, which is a hallmark of vascular disorders. Endothelium-dependent vasodilators, such as acetylcholine, increase intracellular Ca(2+) through activation of transient receptor potential vanilloid 4 (TRPV4) channels in the plasma membrane and inositol trisphosphate receptors in the endoplasmic reticulum, leading to stimulation of Ca(2+) -sensitive intermediate and small conductance K(+) (IK and SK, respectively) channels. Although strong inward rectifier K(+) (Kir) channels have been reported in the native endothelial cells (ECs) their role in EC-dependent vasodilatation is not clear. Here, we test the idea that Kir channels boost the EC-dependent vasodilatation of resistance-sized arteries. We show that ECs, but not smooth muscle cells, of small mesenteric arteries have Kir currents, which are substantially reduced in EC-specific Kir2.1 knockdown (EC-Kir2.1(-/-) ) mice. Elevation of extracellular K(+) to 14 mm caused vasodilatation of pressurized arteries, which was prevented by endothelial denudation and Kir channel

  20. Circulating microparticles from patients with valvular heart disease and cardiac surgery inhibit endothelium-dependent vasodilation.

    Science.gov (United States)

    Fu, Li; Hu, Xiao-Xia; Lin, Ze-Bang; Chang, Feng-Jun; Ou, Zhi-Jun; Wang, Zhi-Ping; Ou, Jing-Song

    2015-09-01

    Vascular function is very important for maintaining circulation after cardiac surgery. Circulating microparticles (MPs) generated in various diseases play important roles in causing inflammation, coagulation, and vascular injury. However, the impact of MPs generated from patients who have valvular heart disease (VHD), before and after cardiac surgery, on vascular function remains unknown. This study is designed to investigate the impact of such MPs on vasodilation. Microparticles were isolated from age-matched healthy subjects and patients who had VHD, before cardiac surgery, and at 12 hours and 72 hours afterward. The number of MPs was measured and compared. Effects evaluated were of the impact of MPs on: vasodilation of mice aorta; the phosphorylation and expression of Akt, endothelial nitric oxide synthase (eNOS), protein kinase C-βII (PKC-βII), and p70 ribosomal protein S6 kinase (p70S6K); expression of caveolin-1; the association of eNOS with heat shock protein 90 (HSP90); and generation of nitric oxide and superoxide anion of human umbilical vein endothelial cells. Compared with the healthy subjects, VHD patients had significantly higher levels of circulating MPs and those MPs before cardiac surgery can: impair endothelium-dependent vasodilation; inhibit phosphorylation of Akt and eNOS; increase activation of PKC-βII and p70S6K; enhance expression of caveolin-1; reduce the association of HSP90 with eNOS; decrease nitric oxide production, and increase superoxide anion generation. These deleterious effects were even stronger in postoperative MPs. Our data demonstrate that MPs generated from VHD patients before and after cardiac surgery contributed to endothelial dysfunction, by uncoupling and inhibiting eNOS. Circulating MPs are potential therapeutic targets for the maintenance of vascular function postoperatively. Copyright © 2015 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

  1. Stress susceptibility as a determinant of endothelium-dependent vascular reactivity in rat mesenteric arteries.

    NARCIS (Netherlands)

    Riksen, N.P.; Ellenbroek, B.A.; Cools, A.R.; Siero, H.L.M.; Rongen, G.A.P.J.M.; Smits, B.W.; Russel, F.G.M.; Smits, P.

    2003-01-01

    In order to investigate the consequences of stress susceptibility on vascular function, the authors assessed the respective contributions of nitric oxide (NO), prostanoids, and endothelium-derived hyperpolarizing factor to the vascular tone in rats with a constitutionally determined high and low

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

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    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. [Departamento de Ciências Fisiológicas, Centro de Ciências da Saúde, Universidade Federal de Espírito Santo, Vitória, ES (Brazil); Podratz, P.L.; Graceli, J.B. [Departamento de Morfologia, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES (Brazil); Abreu, G.R. [Departamento de Ciências Fisiológicas, Centro de Ciências da Saúde, Universidade Federal de Espírito Santo, Vitória, ES (Brazil)

    2015-11-17

    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.

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

    Directory of Open Access Journals (Sweden)

    M.V. Borgo

    2016-01-01

    Full Text Available 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.

  5. Field dependence of the electron spin relaxation in quantum dots.

    Science.gov (United States)

    Calero, Carlos; Chudnovsky, E M; Garanin, D A

    2005-10-14

    The interaction of the electron spin with local elastic twists due to transverse phonons is studied. The universal dependence of the spin-relaxation rate on the strength and direction of the magnetic field is obtained in terms of the electron gyromagnetic tensor and macroscopic elastic constants of the solid. The theory contains no unknown parameters and it can be easily tested in experiment. At high magnetic field it provides a parameter-free lower bound on the electron spin relaxation in quantum dots.

  6. Temperature dependence of the kinetics of isometric myocardium relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Izakov, V.Ya.; Bykov, B.L.; Kimmelman, I.Ya.

    1981-11-01

    The dependence of the exponential decay constant expressing the isometric relaxation of the myocardium on temperature is investigated in animals with various specific contents of myocardial sarcoplasmic reticulum. Experiments were performed on cardiac ventricles and atria isolated from rabbits, frogs and turtles and electrically stimulated to produce maximal contraction at temperatures from 10 to 35 C. Arrhenius plots derived from the data are found to be linear in the myocardia of the rabbit and frog, with a greater activation energy for the relaxation found in the rabbit. The Arrhenius plot for the turtle, which has a sarcoplasmic reticulum content intermediate between those of the frog and rabbit, corresponds to two straight lines with different activation energies. Results thus support the hypothesis of two separate mechanisms of calcium removal, involving the sarcoplasmic reticulum and cellular membrane, in muscle relaxation.

  7. Activation of eNOS by D-pinitol Induces an Endothelium-Dependent Vasodilatation in Mouse Mesenteric Artery

    Directory of Open Access Journals (Sweden)

    Luciana N. Moreira

    2018-05-01

    Full Text Available D-pinitol is a cyclitol present in several edible plant species and extensively investigated for the treatment of metabolic diseases in humans, as food supplement, and demonstrated protective effects in the cardiovascular system. For these reasons, the present work aimed at investigating the mechanisms involved in the vascular effects of D-pinitol in mouse mesenteric artery. Mesenteric arteries from male C57BL/6 mice were mounted in a wire myograph. Nitrite was measured by the 2,3-diaminonaphthalene (DAN method. Protein expression and phosphorylation were measured by Western blot. The systolic blood pressure (SBP was measured by tail-cuff plethysmography. D-pinitol induced a concentration-dependent vasodilatation in endothelium-intact, but not in endothelium-denuded arteries. Nω-Nitro-L-arginine methyl ester (300 μM abolished the effect of D-pinitol, while 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 10 μM shifted the concentration-response curve to the right. KN-93 (1 μM blunted the vasodilator effect of D-pinitol, but H-89 (0.1 μM did not change it. 1-[2-(Trifluoromethyl phenyl]imidazole (300 μM, indomethacin (10 μM, celecoxib (5 μM, wortmannin (1 μM, ruthenium red (10 μM, tiron (10 μM, MnTMPyP (30 μM, MPP (0.1 μM, PHTPP (0.1 μM, and atropine (1 μM did not change the effect of D-pinitol. D-pinitol increased the concentration of nitrite, which was inhibited by L-NAME and calmidazolium (10 μM. D-pinitol increased the phosphorylation level of eNOS activation site at Ser1177 and reduced the phosphorylation level of its inactivation site at Thr495. In normotensive mice, the intraperitoneal administration of D-pinitol (10 mg/kg induced a significant reduction of the SBP after 30 min. The present results led us to conclude that D-pinitol has an endothelium- and NO-dependent vasodilator effect in mouse mesenteric artery through a mechanism dependent on the activation of eNOS by the calcium-calmodulin complex, which can explain its

  8. Hyperglycaemia-induced impairment of endothelium-dependent vasorelaxation in rat mesenteric arteries is mediated by intracellular methylglyoxal levels in a pathway dependent on oxidative stress

    DEFF Research Database (Denmark)

    Brouwers, O; Niessen, P M; Haenen, G

    2010-01-01

    -hydro-5-methylimidazolone (MG-H1) was detected with an antibody against MG-H1 and quantified with ultra-performance liquid chromatography (tandem) mass spectrometry. Reactive oxygen species formation was measured with a 5-(and-6)-chloromethyl-2'7'-dichlorodihydrofluorescein diacetate acetyl ester probe...... for AGE ligand S100b did (p cells and adventitia by fivefold accompanied by an eightfold increase in the oxidative stress marker nitrotyrosine. Antioxidant pre-incubation prevented methylglyoxal......-induced impairment of vasoreactivity. CONCLUSIONS/INTERPRETATION: These data show that hyperglycaemia-induced impairment of endothelium-dependent vasorelaxation is mediated by increased intracellular methylglyoxal levels in a pathway dependent on oxidative stress....

  9. Time-Dependent Behaviors of Granite: Loading-Rate Dependence, Creep, and Relaxation

    Science.gov (United States)

    Hashiba, K.; Fukui, K.

    2016-07-01

    To assess the long-term stability of underground structures, it is important to understand the time-dependent behaviors of rocks, such as their loading-rate dependence, creep, and relaxation. However, there have been fewer studies on crystalline rocks than on tuff, mudstone, and rock salt, because the high strength of crystalline rocks makes the detection of their time-dependent behaviors much more difficult. Moreover, studies on the relaxation, temporal change of stress and strain (TCSS) conditions, and relations between various time-dependent behaviors are scarce for not only granites, but also other rocks. In this study, previous reports on the time-dependent behaviors of granites were reviewed and various laboratory tests were conducted using Toki granite. These tests included an alternating-loading-rate test, creep test, relaxation test, and TCSS test. The results showed that the degree of time dependence of Toki granite is similar to other granites, and that the TCSS resembles the stress-relaxation curve and creep-strain curve. A viscoelastic constitutive model, proposed in a previous study, was modified to investigate the relations between the time-dependent behaviors in the pre- and post-peak regions. The modified model reproduced the stress-strain curve, creep, relaxation, and the results of the TCSS test. Based on a comparison of the results of the laboratory tests and numerical simulations, close relations between the time-dependent behaviors were revealed quantitatively.

  10. The metabolism of L-arginine and its significance for the biosynthesis of endothelium-derived relaxing factor: L-glutamine inhibits the generation of L-arginine by cultured endothelial cells

    International Nuclear Information System (INIS)

    Sessa, W.C.; Hecker, M.; Mitchell, J.A.; Vane, J.R.

    1990-01-01

    The mechanism by which L-glutamine (L-Gln) inhibits the release of endothelium-derived factor from bovine aortic cultured endothelial cells was investigated. The intracellular concentration of L-arginine (L-Arg) in Arg-depleted endothelial cells was inversely related to the level of L-Gln. Removal of L-Gln from the culture medium (usually containing L-Gln at 2 mM) abolished the inhibitory effect of the culture medium on L-Arg generation. L-Gln (0.2 and 2 mM) but not D-Gln inhibited the generation of L-Arg by both Arg-depleted and nondepleted endothelial cells. L-Gln did not interfere with the uptake of L-Arg or the metabolism of L-Arg-L-Phe to L-Arg but inhibited the formation of L-Arg from L-citrulline (L-Cit), L-Cit-L-Phe, and N G -monomethyl-L-arginine. L-Gln also inhibited the conversion of L-[ 14 C]Cit to L-[ 14 C]Arg by Arg-depleted endothelial cells. However, L-Gln did not inhibit the conversion of L-argininosuccinic acid to L-Arg by endothelial cell homogenates. Thus, L-Gln interferes with the conversion of L-Cit to L-Arg probably by acting on argininosuccinate synthetase rather than argininosuccinate lyase. L-Gln also inhibited the generation of L-Arg by the monocyte-macrophage cell line J774 but had no effect on the conversion of L-Cit to L-Arg by these cells. As the release of endothelium-derived relaxing factor from cultured and non-cultured endothelial cells is limited by the availability of L-Arg, endogenous L-Gln may play a regulatory role in the biosynthesis of endothelium-derived relaxing factor

  11. Effects of Buddhism walking meditation on depression, functional fitness, and endothelium-dependent vasodilation in depressed elderly.

    Science.gov (United States)

    Prakhinkit, Susaree; Suppapitiporn, Siriluck; Tanaka, Hirofumi; Suksom, Daroonwan

    2014-05-01

    The objectives of this study were to determine the effects of the novel Buddhism-based walking meditation (BWM) and the traditional walking exercise (TWE) on depression, functional fitness, and vascular reactivity. This was a randomized exercise intervention study. The study was conducted in a university hospital setting. Forty-five elderly participants aged 60-90 years with mild-to-moderate depressive symptoms were randomly allocated to the sedentary control, TWE, and BWM groups. The BWM program was based on aerobic walking exercise incorporating the Buddhist meditations performed 3 times/week for 12 weeks. Depression score, functional fitness, and endothelium-dependent vasodilation as measured by the flow-mediated dilation (FMD) were the outcome measures used. Muscle strength, flexibility, agility, dynamic balance, and cardiorespiratory endurance increased in both exercise groups (p<0.05). Depression score decreased (p<0.05) only in the BWM group. FMD improved (p<0.05) in both exercise groups. Significant reduction in plasma cholesterol, triglyceride, high-density lipoprotein cholesterol, and C-reactive protein were found in both exercise groups, whereas low-density lipoprotein cholesterol, cortisol, and interleukin-6 concentrations decreased only in the BWM group. Buddhist walking meditation was effective in reducing depression, improving functional fitness and vascular reactivity, and appears to confer greater overall improvements than the traditional walking program.

  12. Magneto-dependent stress relaxation of magnetorheological gels

    KAUST Repository

    Xu, Yangguang; Liu, Taixiang; Liao, G J; Lubineau, Gilles

    2017-01-01

    The stress relaxation behaviors of magnetorheological (MR) gels under stepwise shear loading are systematically investigated. The particle-enhanced effect, the magneto-induced effect, and the temperature-enhanced effect on the stress relaxation of MR gels are discussed. For further analysis of the magneto-induced stress relaxation mechanism in MR gels, a phenomenological model is established to describe the stress relaxation behavior of the matrix and the magnetic particle chains. All characteristic parameters introduced in the model, i.e. relaxation time, instantaneous modulus, and stable modulus, have well-defined physical meanings and are fitted based on the experimental results. The influence of each parameter on the macroscopic response is discussed and it is found that the relaxation stress induced by the magneto-mechanical coupling effect plays an important role in the stress relaxation process of MR gels.

  13. Magneto-dependent stress relaxation of magnetorheological gels

    KAUST Repository

    Xu, Yangguang

    2017-09-01

    The stress relaxation behaviors of magnetorheological (MR) gels under stepwise shear loading are systematically investigated. The particle-enhanced effect, the magneto-induced effect, and the temperature-enhanced effect on the stress relaxation of MR gels are discussed. For further analysis of the magneto-induced stress relaxation mechanism in MR gels, a phenomenological model is established to describe the stress relaxation behavior of the matrix and the magnetic particle chains. All characteristic parameters introduced in the model, i.e. relaxation time, instantaneous modulus, and stable modulus, have well-defined physical meanings and are fitted based on the experimental results. The influence of each parameter on the macroscopic response is discussed and it is found that the relaxation stress induced by the magneto-mechanical coupling effect plays an important role in the stress relaxation process of MR gels.

  14. Inhibition of PKC-dependent extracellular Ca2+ entry contributes to the depression of contractile activity in long-term pressure-overloaded endothelium-denuded rat aortas

    International Nuclear Information System (INIS)

    Padilla, J.; López, R.M.; López, P.; Castillo, M.C.; Querejeta, E.; Ruiz, A.; Castillo, E.F.

    2014-01-01

    We examined the contractile responsiveness of rat thoracic aortas under pressure overload after long-term suprarenal abdominal aortic coarctation (lt-Srac). Endothelium-dependent angiotensin II (ANG II) type 2 receptor (AT 2 R)-mediated depression of contractions to ANG II has been reported in short-term (1 week) pressure-overloaded rat aortas. Contractility was evaluated in the aortic rings of rats subjected to lt-Srac or sham surgery (Sham) for 8 weeks. ANG I and II levels and AT 2 R protein expression in the aortas of lt-Srac and Sham rats were also evaluated. lt-Srac attenuated the contractions of ANG II and phenylephrine in the aortas in an endothelium-independent manner. However, lt-Srac did not influence the transient contractions induced in endothelium-denuded aortic rings by ANG II, phenylephrine, or caffeine in Ca 2+ -free medium or the subsequent tonic constrictions induced by the addition of Ca 2+ in the absence of agonists. Thus, the contractions induced by Ca 2+ release from intracellular stores and Ca 2+ influx through stored-operated channels were not inhibited in the aortas of lt-Srac rats. Potassium-elicited contractions in endothelium-denuded aortic rings of lt-Srac rats remained unaltered compared with control tissues. Consequently, the contractile depression observed in aortic tissues of lt-Srac rats cannot be explained by direct inhibition of voltage-operated Ca 2+ channels. Interestingly, 12-O-tetradecanoylphorbol-13-acetate-induced contractions in endothelium-denuded aortic rings of lt-Srac rats were depressed in the presence but not in the absence of extracellular Ca 2+ . Neither levels of angiotensins nor of AT 2 R were modified in the aortas after lt-Srac. The results suggest that, in rat thoracic aortas, lt-Srac selectively inhibited protein kinase C-mediated activation of contraction that is dependent on extracellular Ca 2+ entry

  15. Vogel-Fulcher dependence of relaxation rates in a nematic monomer and elastomer

    Science.gov (United States)

    Shenoy, D.; Filippov, S.; Aliev, F.; Keller, P.; Thomsen, D.; Ratna, B.

    2000-12-01

    Dielectric relaxation spectroscopy is used to study the relaxation processes in a nematic monomer and the corresponding cross-linked polymer nematic liquid crystal (elastomer). In the frequency window 10 mHz to 2 GHz the monomer liquid crystal shows a single relaxation whereas the polymer exhibits three relaxation processes, two of which are quantitatively analyzed. The temperature dependence of relaxation times in both the monomer and polymer follows a Vogel-Fulcher behavior. The relaxation processes are identified with specific molecular motions and activation energies are calculated in a linear approximation for comparison with literature data.

  16. Amiodarona causa vasodilatação dependente do endotélio em artérias coronárias caninas Amiodarone causes endothelium-dependent vasodilation in canine coronary arteries

    Directory of Open Access Journals (Sweden)

    Alfredo José Rodrigues

    2005-03-01

    polysorbate 80, amiodarone dissolved in water, amiodarone dissolved in polysorbate 80, and a commercial presentation of amiodarone (Cordarone. The experiments were conducted in the presence of the following enzymatic blockers: only indomethacin, Nw-nitro-L-arginine associated with indomethacin, and only Nw-nitro-L-arginine. RESULTS: Polysorbate 80 caused a small degree of nonendothelium-dependent relaxation. Cordarone, amiodarone dissolved in water, and amiodarone dissolved in polysorbate 80 caused endothelium-dependent relaxation, which was greater for amiodarone dissolved in polysorbate and for Cordarone. Only the association of indomethacin and Nw-nitro-L-arginine could eliminate the endothelium-dependent relaxation caused by amiodarone dissolved in polysorbate 80. CONCLUSION: The results obtained indicate that vasodilation promoted by amiodarone in canine coronary arteries is mainly caused by stimulation of the release of nitric oxide and cyclooxygenase-dependent relaxing endothelial factors.

  17. Dependence of Brownian and Néel relaxation times on magnetic field strength

    International Nuclear Information System (INIS)

    Deissler, Robert J.; Wu, Yong; Martens, Michael A.

    2014-01-01

    Purpose: In magnetic particle imaging (MPI) and magnetic particle spectroscopy (MPS) the relaxation time of the magnetization in response to externally applied magnetic fields is determined by the Brownian and Néel relaxation mechanisms. Here the authors investigate the dependence of the relaxation times on the magnetic field strength and the implications for MPI and MPS. Methods: The Fokker–Planck equation with Brownian relaxation and the Fokker–Planck equation with Néel relaxation are solved numerically for a time-varying externally applied magnetic field, including a step-function, a sinusoidally varying, and a linearly ramped magnetic field. For magnetic fields that are applied as a step function, an eigenvalue approach is used to directly calculate both the Brownian and Néel relaxation times for a range of magnetic field strengths. For Néel relaxation, the eigenvalue calculations are compared to Brown's high-barrier approximation formula. Results: The relaxation times due to the Brownian or Néel mechanisms depend on the magnitude of the applied magnetic field. In particular, the Néel relaxation time is sensitive to the magnetic field strength, and varies by many orders of magnitude for nanoparticle properties and magnetic field strengths relevant for MPI and MPS. Therefore, the well-known zero-field relaxation times underestimate the actual relaxation times and, in particular, can underestimate the Néel relaxation time by many orders of magnitude. When only Néel relaxation is present—if the particles are embedded in a solid for instance—the authors found that there can be a strong magnetization response to a sinusoidal driving field, even if the period is much less than the zero-field relaxation time. For a ferrofluid in which both Brownian and Néel relaxation are present, only one relaxation mechanism may dominate depending on the magnetic field strength, the driving frequency (or ramp time), and the phase of the magnetization relative to the

  18. Assessment of endothelium: Dependent vasodilation with a non-invasive method in patients with preeclampsia compared to normotensive pregnant women

    Directory of Open Access Journals (Sweden)

    Seyedeh Zahra Allameh

    2014-01-01

    Full Text Available Background: To assess the endothelial function via noninvasive method, in pregnant women with preeclampsia compared to to normotensive pregnant women. Materials and Methods: Brachial artery diameter was measured via ultrasound, in 28 women with preeclampcia in case group and normotensive pregnant women in control group, at rest, after inflation of sphygmomanometer cuff up to 250-300 mmHg, immediately after deflation of the cuff, 60-90 minutes later and 5 min after administration of sublingual trinitroglycerin (TNG. Results of these measurements as well as demographic characteristics of participants in both groups were recorded in special forms. Data were analyzed via Statistical Package for Social Sciences (SPSS version 16, using t-test and repeated measures analysis of variance (ANOVA. P-value < 0.05 was considered statistically significant. The results were presented as mean ± standard deviation (SD. Results: The mean of brachial artery diameter at rest in the case and control groups was 4.49 ± 0.39 and 4.08 ± 0.38 mm, respectively (P = 0.1. Also the results showed that the brachial artery diameter, immediately after deflation of the cuff, was 4.84 ± 0.4 and 4.37 ± 0.30 mm in the case and control groups (P < 0.001, respectively. The mean brachial artery diameter, 60-90 s after deflation of the cuff, was 4.82 ± 0.41 and 4.42 ± 0.38 mm in the case and control groups (P < 0.00, respectively. The brachial artery diameter, 5 min after sublingual NO administration, was 4.95 ± 0.6 and 4.40 ± 0.45 mm in case and control groups (P < 0.001, respectively. Applying of repeated measures ANOVA showed that the mean difference between case and control groups was statistically significant (P < 0.001. Conclusion: Current study concluded that there is no difference in endothelium-dependent vasodilation between women with preeclampsia and pregnant women with normal blood pressure.

  19. K(Ca)3.1 channel downregulation and impaired endothelium-derived hyperpolarization-type relaxation in pulmonary arteries from chronically hypoxic rats

    DEFF Research Database (Denmark)

    Kroigaard, Christel; Kudryavtseva, Olga; Dalsgaard, Thomas

    2013-01-01

    hypoxia-induced pulmonary hypertension in rats. For functional studies, pulmonary arteries were mounted in microvascular myographs for isometric tension recordings. The K(Ca) channel expression was evaluated by immunoblotting and quantitative PCR. Although ACh induced similar relaxations, the ACh...

  20. Rho-kinase inhibitor and nicotinamide adenine dinucleotide phosphate oxidase inhibitor prevent impairment of endothelium-dependent cerebral vasodilation by acute cigarette smoking in rats.

    Science.gov (United States)

    Iida, Hiroki; Iida, Mami; Takenaka, Motoyasu; Fukuoka, Naokazu; Dohi, Shuji

    2008-06-01

    We previously reported that acute cigarette smoking can cause a dysfunction of endothelium-dependent vasodilation in cerebral vessels, and that blocking the angiotensin II (Ang II) type 1 (AT1) receptor with valsartan prevented this impairment. Our aim was to investigate the effects of a Rho-kinase inhibitor (fasudil) and a Nicotinamide Adenine Dinucleotide PHosphate (NADPH) oxidase inhibitor (apocynin) on smoking-induced endothelial dysfunction in cerebral arterioles. In Sprague-Dawley rats, we used a closed cranial window preparation to measure changes in pial vessel diameters following topical acetylcholine (ACh) before smoking. After one-minute smoking, we again examined the arteriolar responses to ACh. Finally, after intravenous fasudil or apocynin pre-treatment we re-examined the vasodilator responses to topical ACh (before and after cigarette smoking). Under control conditions, cerebral arterioles were dose-dependently dilated by topical ACh (10(-6) M and 10(-5) M). One hour after a one-minute smoking (1 mg-nicotine cigarette), 10(-5) M ACh constricted cerebral arterioles. However, one hour after a one-minute smoking, 10(-5) M ACh dilated cerebral pial arteries both in the fasudil pre-treatment and the apocynin pre-treatment groups, responses that were significantly different from those obtained without fasudil or apocynin pre-treatment. Thus, inhibition of Rho-kinase and NADPH oxidase activities may prevent the above smoking-induced impairment of endothelium-dependent vasodilation.

  1. Relaxation of Isolated Ventricular Cardiomyocytes by a Voltage-Dependent Process

    Science.gov (United States)

    Bridge, John H. B.; Spitzer, Kenneth W.; Ershler, Philip R.

    1988-08-01

    Cell contraction and relaxation were measured in single voltage-clamped guinea pig cardiomyocytes to investigate the contribution of sarcolemmal Na+-Ca2+ exchange to mechanical relaxation. Cells clamped from -80 to 0 millivolts displayed initial phasic and subsequent tonic contractions; caffeine reduced or abolished the phasic and enlarged the tonic contraction. The rate of relaxation from tonic contractions was steeply voltage-dependent and was significantly slowed in the absence of a sarcolemmal Na+ gradient. Tonic contractions elicited in the absence of a Na+ gradient promptly relaxed when external Na+ was applied, reflecting activation of Na+-Ca2+ exchange. It appears that a voltage-dependent Na+-Ca2+ exchange can rapidly mechanically relax mammalian heart muscle.

  2. Targeted Delivery of Neutralizing Anti-C5 Antibody to Renal Endothelium Prevents Complement-Dependent Tissue Damage

    Directory of Open Access Journals (Sweden)

    Paolo Durigutto

    2017-09-01

    Full Text Available Complement activation is largely implicated in the pathogenesis of several clinical conditions and its therapeutic neutralization has proven effective in preventing tissue and organ damage. A problem that still needs to be solved in the therapeutic control of complement-mediated diseases is how to avoid side effects associated with chronic neutralization of the complement system, in particular, the increased risk of infections. We addressed this issue developing a strategy based on the preferential delivery of a C5 complement inhibitor to the organ involved in the pathologic process. To this end, we generated Ergidina, a neutralizing recombinant anti-C5 human antibody coupled with a cyclic-RGD peptide, with a distinctive homing property for ischemic endothelial cells and effective in controlling tissue damage in a rat model of renal ischemia/reperfusion injury (IRI. As a result of its preferential localization on renal endothelium, the molecule induced complete inhibition of complement activation at tissue level, and local protection from complement-mediated tissue damage without affecting circulating C5. The ex vivo binding of Ergidina to surgically removed kidney exposed to cold ischemia supports its therapeutic use to prevent posttransplant IRI leading to delay of graft function. Moreover, the finding that the ex vivo binding of Ergidina was not restricted to the kidney, but was also seen on ischemic heart, suggests that this RGD-targeted anti-C5 antibody may represent a useful tool to treat organs prior to transplantation. Based on this evidence, we propose preliminary data showing that Ergidina is a novel targeted drug to prevent complement activation on the endothelium of ischemic kidney.

  3. Influence of endothelium on the membrane-stabilizing effect of calcium

    African Journals Online (AJOL)

    Dr Olaleye

    increase in [Ca2+]o (low bicarbonate PSS) from 5.0 to 25.0mM in rings with intact endothelium resulted in relaxation responses. These relaxation responses were attenuated in endothelium- denuded rings as well as following exposure to methylene blue. Conclusion: The results show that relaxation responses induced by ...

  4. Temperature-dependent structural relaxation in As{sub 40}Se{sub 60} glass

    Energy Technology Data Exchange (ETDEWEB)

    Golovchak, R., E-mail: roman_ya@yahoo.com [Lviv Sci. and Res. Institute of Materials of SRC ' Carat' , 202 Stryjska str., 79031 Lviv (Ukraine); Kozdras, A. [Opole University of Technology, 75, Ozimska str., Opole, PL-45370 (Poland); Academy of Management and Administration, 18 Niedzialkowski str., Opole, PL-45085 (Poland); Shpotyuk, O. [Jan Dlugosz University, 13/15, al. Armii Krajowej, 42201, Czestochowa (Poland); Gorecki, Cz. [Opole University of Technology, 75, Ozimska str., Opole, PL-45370 (Poland); Kovalskiy, A.; Jain, H. [Department of Materials Science and Engineering, Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States)

    2011-08-01

    The origin of structural relaxation in As{sub 40}Se{sub 60} glass at different annealing temperatures is studied by differential scanning calorimetry (DSC) and in situ extended X-ray absorption fine structure (EXAFS) methods. Strong physical aging effect, expressed through the increase of endothermic peak area in the vicinity of T{sub g}, is recorded by DSC technique at the annealing temperatures T{sub a}>90{sup o}C. EXAFS data show that the observed structural relaxation is not associated with significant changes in the short-range order of this glass. An explanation is proposed for this relaxation behavior assuming temperature-dependent constraints. -- Highlights: → In this study we report experimental evidence for temperature-dependent constraints theory. → Structural relaxation of As{sub 2}Se{sub 3} glass at higher annealing temperatures is studied by DSC technique. → Accompanied changes in the structure are monitored by in situ EXAFS measurements.

  5. Hemodynamics, functional state of endothelium and renal function, platelets depending on the body mass index in patients with chronic heart failure and preserved systolic function

    Directory of Open Access Journals (Sweden)

    Kushnir Yu.

    2014-03-01

    Full Text Available The aim of the study was to evaluate hemodynamics, endothelium function of kidneys and platelets depending on the body mass index (BMI in patients with chronic heart failure (CHF and preserved systolic function. 42 patients (mean age - 76,690,83 years with CHF II-III FC NYHA with preserved systolic function (LVEF>45% were enrolled. Echocardiography was performed, endothelial function, serum creatinine levels and microalbuminuria were determined in patients. BMI and glomerulation filtration rate were calculated by formulas. The morphological and functional status of platelets was estimated by electronic microscopy. It was defined that increased BMI in patients with CHF and preserved systolic function determines the structural and functional changes of the myocardium and leads to the endothelial and renal functional changes. An increased risk of thrombogenesis was established in patients with overweight and obesity.

  6. The Deletion of Endothelial Sodium Channel α (αENaC Impairs Endothelium-Dependent Vasodilation and Endothelial Barrier Integrity in Endotoxemia in Vivo

    Directory of Open Access Journals (Sweden)

    Magdalena Sternak

    2018-04-01

    Full Text Available The role of epithelial sodium channel (ENaC activity in the regulation of endothelial function is not clear. Here, we analyze the role of ENaC in the regulation of endothelium-dependent vasodilation and endothelial permeability in vivo in mice with conditional αENaC subunit gene inactivation in the endothelium (endo-αENaCKO mice using unique MRI-based analysis of acetylcholine-, flow-mediated dilation and vascular permeability. Mice were challenged or not with lipopolysaccharide (LPS, from Salmonella typhosa, 10 mg/kg, i.p.. In addition, changes in vascular permeability in ex vivo organs were analyzed by Evans Blue assay, while changes in vascular permeability in perfused mesenteric artery were determined by a FITC-dextran-based assay. In basal conditions, Ach-induced response was completely lost, flow-induced vasodilation was inhibited approximately by half but endothelial permeability was not changed in endo-αENaCKO vs. control mice. In LPS-treated mice, both Ach- and flow-induced vasodilation was more severely impaired in endo-αENaCKO vs. control mice. There was also a dramatic increase in permeability in lungs, brain and isolated vessels as evidenced by in vivo and ex vivo analysis in endotoxemic endo-αENaCKO vs. control mice. The impaired endothelial function in endotoxemia in endo-αENaCKO was associated with a decrease of lectin and CD31 endothelial staining in the lung as compared with control mice. In conclusion, the activity of endothelial ENaC in vivo contributes to endothelial-dependent vasodilation in the physiological conditions and the preservation of endothelial barrier integrity in endotoxemia.

  7. The partitioning of nanoparticles to endothelium or interstitium during ultrasound-microbubble-targeted delivery depends on peak-negative pressure

    International Nuclear Information System (INIS)

    Hsiang, Y.-H.; Song, J.; Price, R. J.

    2015-01-01

    Patients diagnosed with advanced peripheral arterial disease often face poor prognoses and have limited treatment options. For some patient populations, the therapeutic growth of collateral arteries (i.e. arteriogenesis) that bypass regions affected by vascular disease may become a viable treatment option. Our group and others are developing therapeutic approaches centered on the ability of ultrasound-activated microbubbles to permeabilize skeletal muscle capillaries and facilitate the targeted delivery of pro-arteriogenic growth factor-bearing nanoparticles. The development of such approaches would benefit significantly from a better understanding of how nanoparticle diameter and ultrasound peak-negative pressure affect both total nanoparticle delivery and the partitioning of nanoparticles to endothelial or interstitial compartments. Toward this goal, using Balb/C mice that had undergone unilateral femoral artery ligation, we intra-arterially co-injected nanoparticles (50 and 100 nm) with microbubbles, applied 1 MHz ultrasound to the gracilis adductor muscle at peak-negative pressures of 0.7, 0.55, 0.4, and 0.2 MPa, and analyzed nanoparticle delivery and distribution. As expected, total nanoparticle (50 and 100 nm) delivery increased with increasing peak-negative pressure, with 50 nm nanoparticles exhibiting greater tissue coverage than 100 nm nanoparticles. Of particular interest, increasing peak-negative pressure resulted in increased delivery to the interstitium for both nanoparticle sizes, but had little influence on nanoparticle delivery to the endothelium. Thus, we conclude that alterations to peak-negative pressure may be used to adjust the fraction of nanoparticles delivered to the interstitial compartment. This information will be useful when designing ultrasound protocols for delivering pro-arteriogenic nanoparticles to skeletal muscle

  8. The partitioning of nanoparticles to endothelium or interstitium during ultrasound-microbubble-targeted delivery depends on peak-negative pressure

    Energy Technology Data Exchange (ETDEWEB)

    Hsiang, Y.-H.; Song, J.; Price, R. J., E-mail: rprice@virginia.edu [University of Virginia, Department of Biomedical Engineering (United States)

    2015-08-15

    Patients diagnosed with advanced peripheral arterial disease often face poor prognoses and have limited treatment options. For some patient populations, the therapeutic growth of collateral arteries (i.e. arteriogenesis) that bypass regions affected by vascular disease may become a viable treatment option. Our group and others are developing therapeutic approaches centered on the ability of ultrasound-activated microbubbles to permeabilize skeletal muscle capillaries and facilitate the targeted delivery of pro-arteriogenic growth factor-bearing nanoparticles. The development of such approaches would benefit significantly from a better understanding of how nanoparticle diameter and ultrasound peak-negative pressure affect both total nanoparticle delivery and the partitioning of nanoparticles to endothelial or interstitial compartments. Toward this goal, using Balb/C mice that had undergone unilateral femoral artery ligation, we intra-arterially co-injected nanoparticles (50 and 100 nm) with microbubbles, applied 1 MHz ultrasound to the gracilis adductor muscle at peak-negative pressures of 0.7, 0.55, 0.4, and 0.2 MPa, and analyzed nanoparticle delivery and distribution. As expected, total nanoparticle (50 and 100 nm) delivery increased with increasing peak-negative pressure, with 50 nm nanoparticles exhibiting greater tissue coverage than 100 nm nanoparticles. Of particular interest, increasing peak-negative pressure resulted in increased delivery to the interstitium for both nanoparticle sizes, but had little influence on nanoparticle delivery to the endothelium. Thus, we conclude that alterations to peak-negative pressure may be used to adjust the fraction of nanoparticles delivered to the interstitial compartment. This information will be useful when designing ultrasound protocols for delivering pro-arteriogenic nanoparticles to skeletal muscle.

  9. Size dependence of 13C nuclear spin-lattice relaxation in micro- and nanodiamonds

    Science.gov (United States)

    Panich, A. M.; Sergeev, N. A.; Shames, A. I.; Osipov, V. Yu; Boudou, J.-P.; Goren, S. D.

    2015-02-01

    Size dependence of physical properties of nanodiamond particles is of crucial importance for various applications in which defect density and location as well as relaxation processes play a significant role. In this work, the impact of defects induced by milling of micron-sized synthetic diamonds was studied by magnetic resonance techniques as a function of the particle size. EPR and 13C NMR studies of highly purified commercial synthetic micro- and nanodiamonds were done for various fractions separated by sizes. Noticeable acceleration of 13C nuclear spin-lattice relaxation with decreasing particle size was found. We showed that this effect is caused by the contribution to relaxation coming from the surface paramagnetic centers induced by sample milling. The developed theory of the spin-lattice relaxation for such a case shows good compliance with the experiment.

  10. Time, stress, and temperature-dependent deformation in nanostructured copper: Stress relaxation tests and simulations

    International Nuclear Information System (INIS)

    Yang, Xu-Sheng; Wang, Yun-Jiang; Wang, Guo-Yong; Zhai, Hui-Ru; Dai, L.H.; Zhang, Tong-Yi

    2016-01-01

    In the present work, stress relaxation tests, high-resolution transmission electron microscopy (HRTEM), and molecular dynamics (MD) simulations were conducted on coarse-grained (cg), nanograined (ng), and nanotwinned (nt) copper at temperatures of 22 °C (RT), 30 °C, 40 °C, 50 °C, and 75 °C. The comprehensive investigations provide sufficient information for the building-up of a formula to describe the time, stress, and temperature-dependent deformation and clarify the relationship among the strain rate sensitivity parameter, stress exponent, and activation volume. The typically experimental curves of logarithmic plastic strain rate versus stress exhibited a three staged relaxation process from a linear high stress relaxation region to a subsequent nonlinear stress relaxation region and finally to a linear low stress relaxation region, which only showed-up at the test temperatures higher than 22 °C, 22 °C, and 30 °C, respectively, in the tested cg-, ng-, and nt-Cu specimens. The values of stress exponent, stress-independent activation energy, and activation volume were determined from the experimental data in the two linear regions. The determined activation parameters, HRTEM images, and MD simulations consistently suggest that dislocation-mediated plastic deformation is predominant in all tested cg-, ng-, and nt-Cu specimens in the initial linear high stress relaxation region at the five relaxation temperatures, whereas in the linear low stress relaxation region, the grain boundary (GB) diffusion-associated deformation is dominant in the ng- and cg-Cu specimens, while twin boundary (TB) migration, i.e., twinning and detwinning with parallel partial dislocations, governs the time, stress, and temperature-dependent deformation in the nt-Cu specimens.

  11. Nicotine impairs cyclooxygenase-2-dependent kinin-receptor-mediated murine airway relaxations

    International Nuclear Information System (INIS)

    Xu, Yuan; Cardell, Lars-Olaf

    2014-01-01

    Introduction: Cigarette smoke induces local inflammation and airway hyperreactivity. In asthmatics, it worsens the symptoms and increases the risk for exacerbation. The present study investigates the effects of nicotine on airway relaxations in isolated murine tracheal segments. Methods: Segments were cultured for 24 h in the presence of vehicle, nicotine (10 μM) and/or dexamethasone (1 μM). Airway relaxations were assessed in myographs after pre-contraction with carbachol (1 μM). Kinin receptors, cyclooxygenase (COX) and inflammatory mediator expressions were assessed by real-time PCR and confocal-microscopy-based immunohistochemistry. Results: The organ culture procedure markedly increased bradykinin- (selective B 2 receptor agonist) and des-Arg 9 -bradykinin- (selective B 1 receptor agonist) induced relaxations, and slightly increased relaxation induced by isoprenaline, but not that induced by PGE 2 . The kinin receptor mediated relaxations were epithelium-, COX-2- and EP2-receptor-dependent and accompanied by drastically enhanced mRNA levels of kinin receptors, as well as inflammatory mediators MCP-1 and iNOS. Increase in COX-2 and mPGES-1 was verified both at mRNA and protein levels. Nicotine selectively suppressed the organ-culture-enhanced relaxations induced by des-Arg 9 -bradykinin and bradykinin, at the same time reducing mPGES-1 mRNA and protein expressions. α7-nicotinic acetylcholine receptor inhibitors α-bungarotoxin and MG624 both blocked the nicotine effects on kinin B 2 receptors, but not those on B 1 . Dexamethasone completely abolished kinin-induced relaxations. Conclusion: It is tempting to conclude that a local inflammatory process per se could have a bronchoprotective component by increasing COX-2 mediated airway relaxations and that nicotine could impede this safety mechanism. Dexamethasone further reduced airway inflammation together with relaxations. This might contribute to the steroid resistance seen in some patients with asthma

  12. Nicotine impairs cyclooxygenase-2-dependent kinin-receptor-mediated murine airway relaxations

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yuan, E-mail: yuan.xu@ki.se; Cardell, Lars-Olaf

    2014-02-15

    Introduction: Cigarette smoke induces local inflammation and airway hyperreactivity. In asthmatics, it worsens the symptoms and increases the risk for exacerbation. The present study investigates the effects of nicotine on airway relaxations in isolated murine tracheal segments. Methods: Segments were cultured for 24 h in the presence of vehicle, nicotine (10 μM) and/or dexamethasone (1 μM). Airway relaxations were assessed in myographs after pre-contraction with carbachol (1 μM). Kinin receptors, cyclooxygenase (COX) and inflammatory mediator expressions were assessed by real-time PCR and confocal-microscopy-based immunohistochemistry. Results: The organ culture procedure markedly increased bradykinin- (selective B{sub 2} receptor agonist) and des-Arg{sup 9}-bradykinin- (selective B{sub 1} receptor agonist) induced relaxations, and slightly increased relaxation induced by isoprenaline, but not that induced by PGE{sub 2}. The kinin receptor mediated relaxations were epithelium-, COX-2- and EP2-receptor-dependent and accompanied by drastically enhanced mRNA levels of kinin receptors, as well as inflammatory mediators MCP-1 and iNOS. Increase in COX-2 and mPGES-1 was verified both at mRNA and protein levels. Nicotine selectively suppressed the organ-culture-enhanced relaxations induced by des-Arg{sup 9}-bradykinin and bradykinin, at the same time reducing mPGES-1 mRNA and protein expressions. α7-nicotinic acetylcholine receptor inhibitors α-bungarotoxin and MG624 both blocked the nicotine effects on kinin B{sub 2} receptors, but not those on B{sub 1}. Dexamethasone completely abolished kinin-induced relaxations. Conclusion: It is tempting to conclude that a local inflammatory process per se could have a bronchoprotective component by increasing COX-2 mediated airway relaxations and that nicotine could impede this safety mechanism. Dexamethasone further reduced airway inflammation together with relaxations. This might contribute to the steroid resistance seen in

  13. Melanopsin mediates light-dependent relaxation in blood vessels.

    Science.gov (United States)

    Sikka, Gautam; Hussmann, G Patrick; Pandey, Deepesh; Cao, Suyi; Hori, Daijiro; Park, Jong Taek; Steppan, Jochen; Kim, Jae Hyung; Barodka, Viachaslau; Myers, Allen C; Santhanam, Lakshmi; Nyhan, Daniel; Halushka, Marc K; Koehler, Raymond C; Snyder, Solomon H; Shimoda, Larissa A; Berkowitz, Dan E

    2014-12-16

    Melanopsin (opsin4; Opn4), a non-image-forming opsin, has been linked to a number of behavioral responses to light, including circadian photo-entrainment, light suppression of activity in nocturnal animals, and alertness in diurnal animals. We report a physiological role for Opn4 in regulating blood vessel function, particularly in the context of photorelaxation. Using PCR, we demonstrate that Opn4 (a classic G protein-coupled receptor) is expressed in blood vessels. Force-tension myography demonstrates that vessels from Opn4(-/-) mice fail to display photorelaxation, which is also inhibited by an Opn4-specific small-molecule inhibitor. The vasorelaxation is wavelength-specific, with a maximal response at ∼430-460 nm. Photorelaxation does not involve endothelial-, nitric oxide-, carbon monoxide-, or cytochrome p450-derived vasoactive prostanoid signaling but is associated with vascular hyperpolarization, as shown by intracellular membrane potential measurements. Signaling is both soluble guanylyl cyclase- and phosphodiesterase 6-dependent but protein kinase G-independent. β-Adrenergic receptor kinase 1 (βARK 1 or GRK2) mediates desensitization of photorelaxation, which is greatly reduced by GRK2 inhibitors. Blue light (455 nM) regulates tail artery vasoreactivity ex vivo and tail blood blood flow in vivo, supporting a potential physiological role for this signaling system. This endogenous opsin-mediated, light-activated molecular switch for vasorelaxation might be harnessed for therapy in diseases in which altered vasoreactivity is a significant pathophysiologic contributor.

  14. Load dependence of left ventricular contraction and relaxation. Effects of caffeine.

    Science.gov (United States)

    Leite-Moreira, A F; Correia-Pinto, J; Gillebert, T C

    1999-08-01

    Load dependence of left ventricular (LV) contraction and relaxation was investigated at baseline and after alteration of intracellular calcium handling by caffeine. Afterload was increased by aortic clamp occlusions (n = 281) in anesthetized open-chest dogs (n = 7). Control and first heartbeat after the intervention were considered for analysis. Caffeine (50 mg/kg, iv) had no inotropic effect. The systolic LV pressure (LVP), developed in response to aortic occlusion, decreased as ejection proceeded and this pressure generating capacity was not affected by caffeine. Late-systolic aortic occlusions induced premature onset and accelerated rate of initial LVP fall at baseline and similarly after caffeine. Graded diastolic aortic occlusions induced systolic LVP elevations of various magnitudes. Smaller LVP elevations prolonged ejection and accelerated LVP fall, while larger elevations had opposite effects. The transition from acceleration to deceleration was observed at 83.1 +/- 1.1% of peak isovolumetric LVP at baseline and at lower loads, at 77.6 +/- 1.2%, after caffeine (p caffeine (p dependence of relaxation, was also modified by caffeine. Caffeine affected LV relaxation without altering contractility. As a consequence contraction-relaxation coupling was modified by caffeine. These results might help to understand load dependence of relaxation in conditions where intracellular calcium handling is altered.

  15. Viscoelastic characterization of compacted pharmaceutical excipient materials by analysis of frequency-dependent mechanical relaxation processes

    Science.gov (United States)

    Welch, K.; Mousavi, S.; Lundberg, B.; Strømme, M.

    2005-09-01

    A newly developed method for determining the frequency-dependent complex Young's modulus was employed to analyze the mechanical response of compacted microcrystalline cellulose, sorbitol, ethyl cellulose and starch for frequencies up to 20 kHz. A Debye-like relaxation was observed in all the studied pharmaceutical excipient materials and a comparison with corresponding dielectric spectroscopy data was made. The location in frequency of the relaxation peak was shown to correlate to the measured tensile strength of the tablets, and the relaxation was interpreted as the vibrational response of the interparticle hydrogen and van der Waals bindings in the tablets. Further, the measured relaxation strength, holding information about the energy loss involved in the relaxation processes, showed that the weakest material in terms of tensile strength, starch, is the material among the four tested ones that is able to absorb the most energy within its structure when exposed to external perturbations inducing vibrations in the studied frequency range. The results indicate that mechanical relaxation analysis performed over relatively broad frequency ranges should be useful for predicting material properties of importance for the functionality of a material in applications such as, e.g., drug delivery, drug storage and handling, and also for clarifying the origin of hitherto unexplained molecular processes.

  16. The time-dependence of exchange-induced relaxation during modulated radio frequency pulses.

    Science.gov (United States)

    Sorce, Dennis J; Michaeli, Shalom; Garwood, Michael

    2006-03-01

    The problem of the relaxation of identical spins 1/2 induced by chemical exchange between spins with different chemical shifts in the presence of time-dependent RF irradiation (in the first rotating frame) is considered for the fast exchange regime. The solution for the time evolution under the chemical exchange Hamiltonian in the tilted doubly rotating frame (TDRF) is presented. Detailed derivation is specified to the case of a two-site chemical exchange system with complete randomization between jumps of the exchanging spins. The derived theory can be applied to describe the modulation of the chemical exchange relaxation rate constants when using a train of adiabatic pulses, such as the hyperbolic secant pulse. Theory presented is valid for quantification of the exchange-induced time-dependent rotating frame longitudinal T1rho,ex and transverse T2rho,ex relaxations in the fast chemical exchange regime.

  17. Tibolone and its metabolites acutely relax rabbit coronary arteries in vitro

    DEFF Research Database (Denmark)

    Lund, Claus Otto; Nilas, Lisbeth; Pedersen, Susan Helene

    2004-01-01

    under curve (AUC). RESULTS: Tibolone and its metabolites induced a concentration-dependent vasodilatation comparable to that of 17 beta-estradiol with the rank of potency: 3 beta-OH-tibolone approximately = to tibolone>3 alpha-OH-tibolone>Delta 4-isomer (ANOVA). l-NAME partly inhibited the relaxation.......05, ANOVA). CONCLUSIONS: Our data indicate that the acute relaxation induced by tibolone and its metabolites in coronary arteries in vitro are probably mediated by endothelium independent inhibition of calcium channels but may also involve an endothelium-dependent mechanism via nitric oxide. The effect...

  18. Enhanced K+-channel-mediated endothelium-dependent local and conducted dilation of small mesenteric arteries from ApoE−/− mice

    Science.gov (United States)

    Beleznai, Timea; Takano, Hiromichi; Hamill, Claire; Yarova, Polina; Douglas, Gillian; Channon, Keith; Dora, Kim

    2011-01-01

    Aims Agonists that evoke smooth muscle cell hyperpolarization have the potential to stimulate both local and conducted dilation. We investigated whether the endothelium-dependent vasodilators acetylcholine (ACh) and SLIGRL stimulated conducted dilation and whether this was altered by deficiency in apolipoprotein E (ApoE−/−). Methods and results Isolated mesenteric arteries were cannulated, pressurized, and precontracted with phenylephrine. Agonists were either added to the bath to study local dilation or were restricted to one end of arteries to study conducted dilation. An enhanced sensitivity to both ACh and SLIGRL was observed in mesenteric arteries from ApoE−/− mice compared with wild-type controls. Inhibition of nitric oxide (NO) synthase blocked ACh responses, but had no effect on maximum dilation to SLIGRL. SLIGRL increased endothelial cell Ca2+, hyperpolarized smooth muscle cells, and fully dilated arteries. The NO-independent dilation to SLIGRL was blocked with high [KCl] or Ca2+-activated K+-channel blockers. The hyperpolarization and dilation to SLIGRL passed through the artery to at least 2.5 mm upstream. The conducted dilation was not affected by a deficit in ApoE and could also be stimulated by ACh, suggesting NO itself could stimulate conducted dilation. Conclusion In small mesenteric arteries of ApoE−/− mice, NO-independent dilation is enhanced. Since both NO-dependent and -independent pathways can stimulate local and conducted dilation, the potential for reducing vascular resistance is improved in these vessels. PMID:21690174

  19. Acrolein relaxes mouse isolated tracheal smooth muscle via a TRPA1-dependent mechanism.

    Science.gov (United States)

    Cheah, Esther Y; Burcham, Philip C; Mann, Tracy S; Henry, Peter J

    2014-05-01

    Airway sensory C-fibres express TRPA1 channels which have recently been identified as a key chemosensory receptor for acrolein, a toxic and highly prevalent component of smoke. TRPA1 likely plays an intermediary role in eliciting a range of effects induced by acrolein including cough and neurogenic inflammation. Currently, it is not known whether acrolein-induced activation of TRPA1 produces other airway effects including relaxation of mouse airway smooth muscle. The aims of this study were to examine the effects of acrolein on airway smooth muscle tone in mouse isolated trachea, and to characterise the cellular and molecular mechanisms underpinning the effects of acrolein. Isometric tension recording studies were conducted on mouse isolated tracheal segments to characterise acrolein-induced relaxation responses. Release of the relaxant PGE₂ was measured by EIA to examine its role in the response. Use of selective antagonists/inhibitors permitted pharmacological characterisation of the molecular and cellular mechanisms underlying this relaxation response. Acrolein induced dose-dependent relaxation responses in mouse isolated tracheal segments. Importantly, these relaxation responses were significantly inhibited by the TRPA1 antagonists AP-18 and HC-030031, an NK₁ receptor antagonist RP-67580, and the EP₂ receptor antagonist PF-04418948, whilst completely abolished by the non-selective COX inhibitor indomethacin. Acrolein also caused rapid PGE₂ release which was suppressed by HC-030031. In summary, acrolein induced a novel bronchodilator response in mouse airways. Pharmacologic studies indicate that acrolein-induced relaxation likely involves interplay between TRPA1-expressing airway sensory C-fibres, NK₁ receptor-expressing epithelial cells, and EP₂-receptor expressing airway smooth muscle cells. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Temperature dependence of 1H NMR relaxation time, T2, for intact and neoplastic plant tissues

    Science.gov (United States)

    Lewa, Czesław J.; Lewa, Maria

    Temperature dependences of the spin-spin proton relaxation time, T2, have been shown for normal and tumorous tissues collected from kalus culture Nicotiana tabacum and from the plant Kalanchoe daigremontiana. For neoplastic plant tissues, time T2 was increased compared to that for intact plants, a finding similar to that for animal and human tissues. The temperature dependences obtained were compared to analogous relations observed with animal tissues.

  1. Low-field one-dimensional and direction-dependent relaxation imaging of bovine articular cartilage

    Science.gov (United States)

    Rössler, Erik; Mattea, Carlos; Mollova, Ayret; Stapf, Siegfried

    2011-12-01

    The structure of articular cartilage is separated into three layers of differently oriented collagen fibers, which is accompanied by a gradient of increasing glycosaminoglycan (GAG) and decreasing water concentration from the top layer towards the bone interface. The combined effect of these structural variations results in a change of the longitudinal and transverse relaxation times as a function of the distance from the cartilage surface. In this paper, this dependence is investigated at a magnetic field strength of 0.27 T with a one-dimensional depth resolution of 50 μm on bovine hip and stifle joint articular cartilage. By employing this method, advantage is taken of the increasing contrast of the longitudinal relaxation rate found at lower magnetic field strengths. Furthermore, evidence for an orientational dependence of relaxation times with respect to an axis normal to the surface plane is given, an observation that has recently been reported using high-field MRI and that was explained by preferential orientations of collagen bundles in each of the three cartilage zones. In order to quantify the extent of a further contrast mechanism and to estimate spatially dependent glycosaminoglycan concentrations, the data are supplemented by proton relaxation times that were acquired in bovine articular cartilage that was soaked in a 0.8 mM aqueous Gd ++ solution.

  2. Concentration dependence of fluorine impurity spin-lattice relaxation rate in bone mineral

    International Nuclear Information System (INIS)

    Code, R.F.; Armstrong, R.L.; Cheng, P.-T.

    1992-01-01

    The concentration dependence of the fluoride ion spin-lattice relaxation rate has been observed by nuclear magnetic resonance experiments on samples of defatted and dried bone. The 19 F spin-lattice relaxation rates increased linearly with bone fluoride concentration. Different results were obtained from trabecular than from cortical bone. For the same macroscopic fluoride content per gram of bone calcium, relaxation rate is significantly faster in cortical bone. Relaxation rates in cortical bone samples prepared from rats and dogs were apparently controlled by the same species-independent processes. For samples from beagle dogs, bulk fluoride concentrations measured by neutron activation analysis were 3.1±0.3 times greater in trabecular bone than in corresponding cortical bone. The beagle spin-lattice relaxation data suggest that microscopic fluoride concentrations in bone mineral were 1.8±0.4 times greater in trabecular bone than in cortical bone. It is concluded that accumulation of fluoride impurities in bone mineral is non-uniform. (author)

  3. Single-Molecule Imaging Reveals Topology Dependent Mutual Relaxation of Polymer Chains

    KAUST Repository

    Abadi, Maram

    2015-08-24

    The motion and relaxation of linear and cyclic polymers under entangled conditions are investigated by means of a newly developed single-molecule tracking technique, cumulative-area (CA) tracking. CA tracking enables simultaneous quantitative characterization of the diffusion mode, diffusion rate, and relaxation time that have been impossible with a widely used conventional single-molecule localization and tracking method, by analyzing cumulative areas occupied by the moving molecule. Using the novel approach, we investigate the motion and relaxation of entangled cyclic polymers, which have been an important but poorly understood question. Fluorescently labeled 42 kbp linear or cyclic tracer dsDNAs in concentrated solutions of unlabeled linear or cyclic DNAs are used as model systems. We show that CA tracking can explicitly distinguish topology-dependent diffusion mode, rate, and relaxation time, demonstrating that the method provides an invaluable tool for characterizing topological interaction between the entangled chains. We further demonstrate that the current models proposed for the entanglement between cyclic polymers which are based on cyclic chains moving through an array of fixed obstacles cannot correctly describe the motion of the cyclic chain under the entangled conditions. Our results rather suggest the mutual relaxation of the cyclic chains, which underscore the necessity of developing a new model to describe the motion of cyclic polymer under the entangled conditions based on the mutual interaction of the chains.

  4. Single-Molecule Imaging Reveals Topology Dependent Mutual Relaxation of Polymer Chains

    KAUST Repository

    Abadi, Maram; Serag, Maged F.; Habuchi, Satoshi

    2015-01-01

    The motion and relaxation of linear and cyclic polymers under entangled conditions are investigated by means of a newly developed single-molecule tracking technique, cumulative-area (CA) tracking. CA tracking enables simultaneous quantitative characterization of the diffusion mode, diffusion rate, and relaxation time that have been impossible with a widely used conventional single-molecule localization and tracking method, by analyzing cumulative areas occupied by the moving molecule. Using the novel approach, we investigate the motion and relaxation of entangled cyclic polymers, which have been an important but poorly understood question. Fluorescently labeled 42 kbp linear or cyclic tracer dsDNAs in concentrated solutions of unlabeled linear or cyclic DNAs are used as model systems. We show that CA tracking can explicitly distinguish topology-dependent diffusion mode, rate, and relaxation time, demonstrating that the method provides an invaluable tool for characterizing topological interaction between the entangled chains. We further demonstrate that the current models proposed for the entanglement between cyclic polymers which are based on cyclic chains moving through an array of fixed obstacles cannot correctly describe the motion of the cyclic chain under the entangled conditions. Our results rather suggest the mutual relaxation of the cyclic chains, which underscore the necessity of developing a new model to describe the motion of cyclic polymer under the entangled conditions based on the mutual interaction of the chains.

  5. Endothelium derived nitric oxide synthase negatively regulates the PDGF-survivin pathway during flow-dependent vascular remodeling.

    Directory of Open Access Journals (Sweden)

    Jun Yu

    Full Text Available Chronic alterations in blood flow initiate structural changes in vessel lumen caliber to normalize shear stress. The loss of endothelial derived nitric oxide synthase (eNOS in mice promotes abnormal flow dependent vascular remodeling, thus uncoupling mechanotransduction from adaptive vascular remodeling. However, the mechanisms of how the loss of eNOS promotes abnormal remodeling are not known. Here we show that abnormal flow-dependent remodeling in eNOS knockout mice (eNOS (-/- is associated with activation of the platelet derived growth factor (PDGF signaling pathway leading to the induction of the inhibitor of apoptosis, survivin. Interfering with PDGF signaling or survivin function corrects the abnormal remodeling seen in eNOS (-/- mice. Moreover, nitric oxide (NO negatively regulates PDGF driven survivin expression and cellular proliferation in cultured vascular smooth muscle cells. Collectively, our data suggests that eNOS negatively regulates the PDGF-survivin axis to maintain proportional flow-dependent luminal remodeling and vascular quiescence.

  6. Rat Liver Enzyme Release Depends on Blood Flow-Bearing Physical Forces Acting in Endothelium Glycocalyx rather than on Liver Damage

    Directory of Open Access Journals (Sweden)

    Julieta A. Díaz-Juárez

    2017-01-01

    Full Text Available We have found selective elevation of serum enzyme activities in rats subjected to partial hepatectomy (PH, apparently controlled by hemodynamic flow-bearing physical forces. Here, we assess the involvement of stretch-sensitive calcium channels and calcium mobilization in isolated livers, after chemical modifications of the endothelial glycocalyx and changing perfusion directionality. Inhibiting in vivo protein synthesis, we found that liver enzyme release is influenced by de novo synthesis of endothelial glycocalyx components, and released enzymes are confined into a liver “pool.” Moreover, liver enzyme release depended on extracellular calcium entry possibly mediated by stretch-sensitive calcium channels, and this endothelial-mediated mechanotransduction in liver enzyme release was also evidenced by modifying the glycocalyx carbohydrate components, directionality of perfusing flow rate, and the participation of nitric oxide (NO and malondialdehyde (MDA, leading to modifications in the intracellular distribution of these enzymes mainly as nuclear enrichment of “mitochondrial” enzymes. In conclusion, the flow-induced shear stress may provide fine-tuned control of released hepatic enzymes through mediation by the endothelium glycocalyx, which provides evidence of a biological role of the enzyme release rather to be merely a biomarker for evaluating hepatotoxicity and liver damage, actually positively influencing progression of liver regeneration in mammals.

  7. 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.

    Science.gov (United States)

    Ramírez-Vélez, Robinson; Romero, Miryam; Echeverri, Isabella; Ortega, José Guillermo; Mosquera, Mildrey; Salazar, Blanca; Girón, Sandra Lorena; Saldarriaga, Wilmar; Aguilar de Plata, Ana Cecilia; Mateus, Julio Cesar

    2011-02-28

    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. 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. 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. 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. NCT00872365.

  8. Effect of environmental particulates on cultured human and bovine endothelium. Cellular injury via an oxidant-dependent pathway

    International Nuclear Information System (INIS)

    Garcia, J.G.; Dodson, R.F.; Callahan, K.S.

    1989-01-01

    The effects of respirable environmental fibers on cultures of human umbilical vein and bovine pulmonary artery endothelial cell monolayers were studied. Interaction among endothelial cell monolayers and amosite and chrysotile asbestos, attapulgite, fiberglass, or latex beads resulted in rapid phagocytosis of the particulates. A gradient of time-dependent and concentration-dependent endothelial cell injury (measured by specific 51Cr release) was observed with amosite and attapulgite being markedly toxic. Chrysotile and fiberglass were much less toxic, and latex beads were not significantly injurious at any time or dose examined. Responses of bovine pulmonary artery and human endothelial vein endothelial cells to fiber phagocytosis and fiber-induced injury were similar. In human umbilical cell monolayers, fiber-mediated stimulation of the arachidonate metabolite prostacyclin paralleled endothelial cell injury; i.e. amosite and attapulgite were stimulatory, whereas fiberglass (0-500 micrograms/ml) and latex beads (10(9) beads/ml) did not significantly increase prostacyclin generation. Although chrysotile was only weakly cytotoxic, significant stimulation of prostacyclin was observed at the highest dose tested (500 micrograms/ml). To investigate whether toxic oxygen species may be involved in fiber-induced cytotoxicity, oxidant scavengers or inhibitors were used in injury studies. Both superoxide dismutase (a scavenger of O2-) and catalase (an inhibitor of H2O2) produced significant protection against fiber-mediated endothelial cell injury. In addition, chelation by deferoxamine of elemental Fe present in the fiber preparations was also protective, suggesting Fe, via the modified Haber-Weiss reaction, may promote hydroxyl radical formation and contribute to endothelial cell injury induced by these particulates

  9. Jabuticaba-Induced Endothelium-Independent Vasodilating Effect on Isolated Arteries

    Directory of Open Access Journals (Sweden)

    Daniela Medeiros Lobo de Andrade

    2016-01-01

    Full Text Available Abstract Background: Despite the important biological effects of jabuticaba, its actions on the cardiovascular system have not been clarified. Objectives: To determine the effects of jabuticaba hydroalcoholic extract (JHE on vascular smooth muscle (VSM of isolated arteries. Methods: Endothelium-denuded aortic rings of rats were mounted in isolated organ bath to record isometric tension. The relaxant effect of JHE and the influence of K+ channels and Ca2+ intra- and extracellular sources on JHE-stimulated response were assessed. Results: Arteries pre-contracted with phenylephrine showed concentration-dependent relaxation (0.380 to 1.92 mg/mL. Treatment with K+ channel blockers (tetraethyl-ammonium, glibenclamide, 4-aminopyridine hindered relaxation due to JHE. In addition, phenylephrine-stimulated contraction was hindered by previous treatment with JHE. Inhibition of sarcoplasmic reticulum Ca2+ ATPase did not change relaxation due to JHE. In addition, JHE inhibited the contraction caused by Ca2+ influx stimulated by phenylephrine and KCl (75 mM. Conclusion: JHE induces endothelium-independent vasodilation. Activation of K+ channels and inhibition of Ca2+ influx through the membrane are involved in the JHE relaxant effect.

  10. Characterization of relaxation processes in interacting vortex matter through a time-dependent correlation length

    International Nuclear Information System (INIS)

    Pleimling, Michel; Täuber, Uwe C

    2015-01-01

    Vortex lines in type-II superconductors display complicated relaxation processes due to the intricate competition between their mutual repulsive interactions and pinning to attractive point or extended defects. We perform extensive Monte Carlo simulations for an interacting elastic line model with either point-like or columnar pinning centers. From measurements of the space- and time-dependent height-height correlation function for lateral flux line fluctuations, we extract a characteristic correlation length that we use to investigate different non-equilibrium relaxation regimes. The specific time dependence of this correlation length for different disorder configurations displays characteristic features that provide a novel diagnostic tool to distinguish between point-like pinning centers and extended columnar defects. (paper)

  11. Ca²⁺-dependent nitric oxide release in the injured endothelium of excised rat aorta: a promising mechanism applying in vascular prosthetic devices in aging patients.

    Science.gov (United States)

    Berra-Romani, Roberto; Avelino-Cruz, José Everardo; Raqeeb, Abdul; Della Corte, Alessandro; Cinelli, Mariapia; Montagnani, Stefania; Guerra, Germano; Moccia, Francesco; Tanzi, Franco

    2013-01-01

    Nitric oxide is key to endothelial regeneration, but it is still unknown whether endothelial cell (EC) loss results in an increase in NO levels at the wound edge. We have already shown that endothelial damage induces a long-lasting Ca²⁺ entry into surviving cells though connexin hemichannels (CxHcs) uncoupled from their counterparts on ruptured cells. The physiological outcome of injury-induced Ca²⁺ inflow is, however, unknown. In this study, we sought to determine whether and how endothelial scraping induces NO production (NOP) in the endothelium of excised rat aorta by exploiting the NO-sensitive fluorochrome, DAF-FM diacetate and the Ca²⁺-sensitive fluorescent dye, Fura-2/AM. We demonstrated that injury-induced NOP at the lesion site is prevented in presence of the endothelial NO synthase inhibitor, L-NAME, and in absence of extracellular Ca²⁺. Unlike ATP-dependent NO liberation, the NO response to injury is insensitive to BTP-2, which selectively blocks store-operated Ca²⁺ inflow. However, injury-induced NOP is significantly reduced by classic gap junction blockers, and by connexin mimetic peptides specifically targeting Cx37Hcs, Cx40HCs, and Cx43Hcs. Moreover, disruption of caveolar integrity prevents injury-elicited NO signaling, but not the accompanying Ca²⁺ response. The data presented provide the first evidence that endothelial scraping stimulates NO synthesis at the wound edge, which might both exert an immediate anti-thrombotic and anti-inflammatory action and promote the subsequent re-endothelialization.

  12. 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

    Directory of Open Access Journals (Sweden)

    Girón Sandra

    2011-02-01

    Full Text Available Abstract 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.

  13. Temperature dependence of relaxation times in proton components of fatty acids

    International Nuclear Information System (INIS)

    Kuroda, Kagayaki; Iwabuchi, Taku; Saito, Kensuke; Obara, Makoto; Honda, Masatoshi; Imai, Yutaka

    2011-01-01

    We examined the temperature dependence of relaxation times in proton components of fatty acids in various samples in vitro at 11 tesla as a standard calibration data for quantitative temperature imaging of fat. The spin-lattice relaxation time, T 1 , of both the methylene (CH 2 ) chain and terminal methyl (CH 3 ) was linearly related to temperature (r>0.98, P 2 signal for calibration and observed the signal with 18% of CH 3 to estimate temperature. These findings suggested that separating the fatty acid components would significantly improve accuracy in quantitative thermometry for fat. Use of the T 1 of CH 2 seems promising in terms of reliability and reproducibility in measuring temperature of fat. (author)

  14. Relaxivity of blood pool contrast agent depends on the host tissue as suggested by semianalytical simulations

    DEFF Research Database (Denmark)

    Jensen, Birgitte Fuglsang; Østergaard, Leif; Kiselev, Valerij G

    Concentration of MRI contrast agents (CA) is commonly determined indirectly using their relaxation effect. In quantitative perfusion studies, the change in the relaxation following a bolus passage is converted into concentrations assuming identical relaxivities for tissue and blood. Simulations...

  15. Deducting the temperature dependence of the structural relaxation time in equilibrium far below the nominal Tg by aging the decoupled conductivity relaxation to equilibrium.

    Science.gov (United States)

    Wojnarowska, Z; Ngai, K L; Paluch, M

    2014-05-07

    Using broadband dielectric spectroscopy we investigate the changes in the conductivity relaxation times τσ observed during the physical aging of the protic ionic conductor carvedilol dihydrogen phosphate (CP). Due to the large decoupling of ion diffusion from host molecule reorientation, the ion conductivity relaxation time τσ(Tage,tage) can be directly measured at temperatures Tage below Tg for exceedingly long aging times tage till τσ(Tage,tage) has reached the equilibrium value τσ(eq)(Tage). The dependence of τσ(Tage,tage) on tage is well described by the stretched exponential function, τσ(Tage, tage) = Aexp[-((tage)/(τage(Tage)))(β)] + τσ(eq)(Tage), where β is a constant and τage(Tage) can be taken as the structural α-relaxation time of the equilibrium liquid at T = Tage. The value of τσ(eq)(Tage) obtained after 63 days long annealing of CP, deviates from the Vogel-Fulcher-Tammann-Hesse (VFTHσ) dependence of τσ(T) determined from data taken above Tg and extrapolated down to Tage. Concurrently, τage(Tage) also deviates from the Vogel-Fulcher-Tammann-Hesse (VFTHα) dependence. The results help to answer the longstanding question of whether the VFTH dependence of τσ(T) as well as the structural α-relaxation time τα(T) holds or not in the equilibrium liquid state far below Tg.

  16. The laser second threshold: Its exact analytical dependence on detuning and relaxation rates

    International Nuclear Information System (INIS)

    Bakasov, A.A.; Abraham, N.B.

    1992-11-01

    An exact analysis has been carried out for general analytical expressions for the second threshold of a single-mode homogeneously broadened laser and for the initial pulsation frequency at the second threshold for arbitrary physical values of the relaxation rates, and at arbitrary detuning between the cavity frequency and the atomic resonance frequency. These expressions also give correspondingly exact forms for asymptotic cases that have previously studied with some approximations. Earlier approximate results are partly confirmed and partly improved by these more general expressions. The physical status of various expressions and approximations is re-considered and specified more clearly, including an analysis of which reasonably can be attained in lasers or masers. A general analytical proof is given that for larger detuning of the laser cavity from resonance a higher value of the laser excitation is required to destabilize the steady state solution (the second threshold). We also present results for the minimum value of the second threshold at fixed detuning as a function of the other parameters of the system and on the dependence of the ratio of the second threshold to the first threshold as a function of detuning. Minima of the second threshold and of the threshold ratio occur only if the population relaxation rate is equal to zero. The minima of the threshold ratio are shown to be bounded from above as well as from below (as functions of the relaxation rates, so long as the second threshold exists). The upper bound on the threshold ratio is equal to 17. The variation of the second threshold in the semi-infinite parameter space of the decay rates is shown at various detunings in plots with a finite domain by normalizing the material relaxation rates to the cavity decay rate. (author). 53 refs, 22 figs, 3 tabs

  17. Adaptação de um sistema de ensaio biológico para detecção de fatores relaxantes endoteliais derivados do endocárdio atrial canino Adaptation of bioassay to detect endothelium-derived relaxing factors from the canine atrial endocardium

    Directory of Open Access Journals (Sweden)

    Yeow Leng Chua

    2009-06-01

    Full Text Available OBJETIVO: Estudar a liberação de fatores relaxantes derivados do endotélio (EDRF pelo endocárdio de aurículas de corações caninos. MÉTODOS: Aurículas atriais caninas foram suturadas em forma de tubos e o efluente desses tubos foram submetidos a ensaios biológicos (sistema de perfusão isolada em câmaras de órgãos utilizando artéria coronária canina, para a detecção de EDRFs. RESULTADOS: O efluente da aurícula direita promoveu relaxamento de 58,4 + 10,1% e da aurícula esquerda 74,9 + 8,5% da contração inicial obtida pela ação da prostagladina F2α em artéria coronária. Não houve diferença estatística no relaxamento da artéria coronária induzido pelos efluentes das aurículas direita e esquerda. O relaxamento induzido pelos efluentes das aurículas direita e esquerda foi abolido pelo tratamento das mesmas com Triton X-100. O tratamento das aurículas com L-NMMA, um inibidor competitivo da síntese de óxido nítrico, e com indometacina, um inibidor da via da ciclooxigenase, promoveu redução no relaxamento da artéria coronária induzido pelo efluente auricular, indicando que o endotélio endocárdico libera óxido nítrico e prostanóides. CONCLUSÕES: Esse estudo demonstra, pela primeira vez, a liberação luminal in vitro de EDRF e prostaciclina pelo átrio de coração canino. A habilidade do endotélio endocárdico em produzir esses fatores pode ter um papel importante na prevenção da formação de trombos nas câmaras cardíacas.OBJECTIVE: The aim of this study was to assess the release of endothelium-derived relaxing factors from the endocardium of canine atrial appendage. METHODS: To study the release of endothelium-derived relaxing factor (EDRF from intact atrial endocardial endothelium, tube-shaped sutures of canine atrial appendages were performed and effluents from these tubes were bioassayed (isolated perfused organ chamber system for detection of EDRF in canine coronary artery. RESULTS: Effluent from

  18. Cajaninstilbene acid relaxes rat renal arteries: roles of Ca2+ antagonism and protein kinase C-dependent mechanism.

    Directory of Open Access Journals (Sweden)

    Dong-Mei Zhang

    Full Text Available Cajaninstilbene acid (CSA is a major active component present in the leaves of Cajanus cajan (L. Millsp. The present study explores the underlying cellular mechanisms for CSA-induced relaxation in rat renal arteries. Vascular reactivity was examined in arterial rings that were suspended in a Multi Myograph System and the expression of signaling proteins was assessed by Western blotting method. CSA (0.1-10 µM produced relaxations in rings pre-contracted by phenylephrine, serotonin, 9, 11-dideoxy-9α, 11α-epoxymethanoprostaglandin F(2α (U46619, and 60 mM KCl. CSA-induced relaxations did not show difference between genders and were unaffected by endothelium denudation, nor by treatment with N(G-nitro-L-arginine methyl ester, indomethacin, ICI-182780, tetraethylammonium ion, BaCl(2, glibenclamide, 4-aminopyridine or propranolol. CSA reduced contraction induced by CaCl(2 (0.01-5 mM in Ca(2+-free 60 mM KCl solution and by 30 nM (--Bay K8644 in 15 mM KCl solution. CSA inhibited 60 mM KCl-induced Ca(2+ influx in smooth muscle of renal arteries. In addition, CSA inhibited contraction evoked by phorbol 12-myristate 13-acetate (PMA, protein kinase C agonist in Ca(2+-free Krebs solution. Moreover, CSA reduced the U46619- and PMA-induced phosphorylation of myosin light chain (MLC at Ser19 and myosin phosphatase target subunit 1 (MYPT1 at Thr853 which was associated with vasoconstriction. CSA also lowered the phosphorylation of protein kinase C (PKCδ at Thr505. In summary, the present results suggest that CSA relaxes renal arteries in vitro via multiple cellular mechanisms involving partial inhibition of calcium entry via nifedipine-sensitive calcium channels, protein kinase C and Rho kinase.

  19. Temperature dependence of the NMR spin-lattice relaxation rate for spin-1/2 chains

    Science.gov (United States)

    Coira, E.; Barmettler, P.; Giamarchi, T.; Kollath, C.

    2016-10-01

    We use recent developments in the framework of a time-dependent matrix product state method to compute the nuclear magnetic resonance relaxation rate 1 /T1 for spin-1/2 chains under magnetic field and for different Hamiltonians (XXX, XXZ, isotropically dimerized). We compute numerically the temperature dependence of the 1 /T1 . We consider both gapped and gapless phases, and also the proximity of quantum critical points. At temperatures much lower than the typical exchange energy scale, our results are in excellent agreement with analytical results, such as the ones derived from the Tomonaga-Luttinger liquid (TLL) theory and bosonization, which are valid in this regime. We also cover the regime for which the temperature T is comparable to the exchange coupling. In this case analytical theories are not appropriate, but this regime is relevant for various new compounds with exchange couplings in the range of tens of Kelvin. For the gapped phases, either the fully polarized phase for spin chains or the low-magnetic-field phase for the dimerized systems, we find an exponential decrease in Δ /(kBT ) of the relaxation time and can compute the gap Δ . Close to the quantum critical point our results are in good agreement with the scaling behavior based on the existence of free excitations.

  20. Inhibition of PKC-dependent extracellular Ca{sup 2+} entry contributes to the depression of contractile activity in long-term pressure-overloaded endothelium-denuded rat aortas

    Energy Technology Data Exchange (ETDEWEB)

    Padilla, J.; López, R.M.; López, P.; Castillo, M.C.; Querejeta, E.; Ruiz, A.; Castillo, E.F. [Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, México, DF (Mexico)

    2014-08-01

    We examined the contractile responsiveness of rat thoracic aortas under pressure overload after long-term suprarenal abdominal aortic coarctation (lt-Srac). Endothelium-dependent angiotensin II (ANG II) type 2 receptor (AT{sub 2}R)-mediated depression of contractions to ANG II has been reported in short-term (1 week) pressure-overloaded rat aortas. Contractility was evaluated in the aortic rings of rats subjected to lt-Srac or sham surgery (Sham) for 8 weeks. ANG I and II levels and AT{sub 2}R protein expression in the aortas of lt-Srac and Sham rats were also evaluated. lt-Srac attenuated the contractions of ANG II and phenylephrine in the aortas in an endothelium-independent manner. However, lt-Srac did not influence the transient contractions induced in endothelium-denuded aortic rings by ANG II, phenylephrine, or caffeine in Ca{sup 2+}-free medium or the subsequent tonic constrictions induced by the addition of Ca{sup 2+} in the absence of agonists. Thus, the contractions induced by Ca{sup 2+} release from intracellular stores and Ca{sup 2+} influx through stored-operated channels were not inhibited in the aortas of lt-Srac rats. Potassium-elicited contractions in endothelium-denuded aortic rings of lt-Srac rats remained unaltered compared with control tissues. Consequently, the contractile depression observed in aortic tissues of lt-Srac rats cannot be explained by direct inhibition of voltage-operated Ca{sup 2+} channels. Interestingly, 12-O-tetradecanoylphorbol-13-acetate-induced contractions in endothelium-denuded aortic rings of lt-Srac rats were depressed in the presence but not in the absence of extracellular Ca{sup 2+}. Neither levels of angiotensins nor of AT{sub 2}R were modified in the aortas after lt-Srac. The results suggest that, in rat thoracic aortas, lt-Srac selectively inhibited protein kinase C-mediated activation of contraction that is dependent on extracellular Ca{sup 2+} entry.

  1. Relaxation behavior and dose dependence of radiation induced radicals in irradiated mango

    International Nuclear Information System (INIS)

    Kameya, Hiromi; Kakita, Daisuke; Kaimori, Yoshihiko; Ukai, Mitsuko; Kikuchi, Masahiro; Kobayashi, Yasuhiko; Shimoyama, Yuhei

    2010-01-01

    Mangoes are imported to Japan after treated with hot water. Recently, irradiated mangoes imported to U. S. are widely used. This paper reports on the ESR method for analyzing the radiation induced radicals of irradiated mangoes. Upon the γ ray irradiation, a strong single peak in the flesh and skin of mangoes was observed at g=2.004. This singlet peak may be attributed to organic free radicals. The ESR spectra of the flesh and skin of mangoes showed the radiation induced radicals due to cellulose by irradiation over 12 kGy. The relaxation times (T 1 and T 2 ) of the singlet signal were calculated. T 2 showed dose response according to increasing the irradiation dose levels, while T 1 was almost constant. The value of (T 1 T 2 ) 1/2 showed the dependence of irradiation dose level. (author)

  2. Role of endothelium-derived hyperpolarization in the vasodilatation of rat intrarenal arteries

    DEFF Research Database (Denmark)

    Pinilla, Estéfano; Sánchez-Pina, Ana; Muñoz Picos, Mercedes

    2016-01-01

    Background and purpose: Endothelium-dependent vasodilation plays an important role in the regulation of vascular tone in different vascular beds. Besides the release of prostacyclin (PGI2) and nitric oxide (NO), the endothelium mediates vasodilation through endothelium-derived hyperpolarization (...

  3. Electric field dependence of the spin relaxation anisotropy in (111) GaAs/AlGaAs quantum wells

    International Nuclear Information System (INIS)

    Balocchi, A; Amand, T; Renucci, P; Duong, Q H; Marie, X; Wang, G; Liu, B L

    2013-01-01

    Time-resolved optical spectroscopy experiments in (111)-oriented GaAs/AlGaAs quantum wells (QWs) show a strong electric field dependence of the conduction electron spin relaxation anisotropy. This results from the interplay between the Dresselhaus and Rashba spin splitting in this system with C 3v symmetry. By varying the electric field applied perpendicular to the QW plane from 20 to 50 kV cm −1 the anisotropy of the spin relaxation time parallel (τ s ∥ ) and perpendicular (τ s ⊥ ) to the growth axis can be first canceled and eventually inversed with respect to the one usually observed in III–V zinc-blende QW (τ s ⊥ = 2τ s ∥ ). This dependence stems from the nonlinear contributions of the k-dependent conduction band spin splitting terms which begin to play the dominant spin relaxing role while the linear Dresselhaus terms are compensated by the Rashba ones through the applied bias. A spin density matrix model for the conduction band spin splitting including both linear and cubic terms of the Dresselhaus Hamiltonian is used which allows a quantitative description of the measured electric field dependence of the spin relaxation anisotropy. The existence of an isotropic point where the spin relaxation tensor reduces to a scalar is predicted and confirmed experimentally. The spin splitting compensation electric field and collision processes type in the QW can be likewise directly extracted from the model without complementary measurements. (paper)

  4. Endothelium-Independent Vasorelaxant Effect of Ligusticum jeholense Root and Rhizoma on Rat Thoracic Aorta

    Directory of Open Access Journals (Sweden)

    Bumjung Kim

    2015-06-01

    Full Text Available Ligusticum jeholense has been used as the traditional medicine ‘Go-Bon’ (Chinese name, Gao-ben in China and Korea. Considering the increased use of medicinal herbs to treat hypertension, in this study, we aimed to investigate the mechanisms of the vasorelaxation effect caused by L. jeholense. We tested the methanol (MeOH extract of L. jeholense root and rhizoma for vasorelaxant effects; while using an isolated organ-chamber technique, L. jeholense extract (LJE induced relaxation in the rat aortic rings by stimulating vascular endothelial and smooth muscle cells. LJE showed concentration-dependent relaxant effects on endothelium-intact and endothelium-denuded aortic rings pre-contracted with both phenylephrine (PE and potassium chloride (KCl in Krebs-Henseleit (KH buffer. The vasorelaxant effect of LJE was partly attenuated by pre-treatment with glibenclamide or 4-aminopyridine (4-AP as K+ channel blockers. Moreover, LJE showed concentration-dependent inhibition of vasoconstriction by Ca2+ supplementation in the aortic rings that were pre-contracted with PE or KCl in Ca2+-free KH buffer. In addition, a combination of LJE and nifedipine, pre-incubated further, decreased PE-induced contractions. The results suggested that LJE-induced vasorelaxation were related to blocking K+ channels and inhibiting entry of extracellular Ca2+ via receptor-operative Ca2+ channels (ROCCs or voltage-dependent Ca2+ channels (VDCCs.

  5. Relaxation oscillations induced by amplitude-dependent frequency in dissipative trapped electron mode turbulence

    International Nuclear Information System (INIS)

    Terry, P.W.; Ware, A.S.; Newman, D.E.

    1994-01-01

    A nonlinear frequency shift in dissipative trapped electron mode turbulence is shown to give rise to a relaxation oscillation in the saturated power density spectrum. A simple non-Markovian closure for the coupled evolution of ion momentum and electron density response is developed to describe the oscillations. From solutions of a nonlinear oscillator model based on the closure, it is found that the oscillation is driven by the growth rate, as modified by the amplitude-dependent frequency shift, with inertia provided by the memory of the growth rate of prior amplitudes. This memory arises from time-history integrals common to statistical closures. The memory associated with a finite time of energy transfer between coupled spectrum components does not sustain the oscillation in the simple model. Solutions of the model agree qualitatively with the time-dependent numerical solutions of the original dissipative trapped electron model, yielding oscillations with the proper phase relationship between the fluctuation energy and the frequency shift, the proper evolution of the wave number spectrum shape and particle flux, and a realistic period

  6. Effects of BM-573 on Endothelial Dependent Relaxation and Increased Blood Pressure at Early Stages of Atherosclerosis.

    Directory of Open Access Journals (Sweden)

    Miguel Romero

    Full Text Available Endothelial dysfunction is considered to be an early event in atherosclerosis and plays a pivotal role in the development, progression and clinical complications of atherosclerosis. Previous studies have shown the beneficial effects of combined inhibition of thromboxane synthase and antagonism of thromboxane receptors by BM-573 on atherosclerosis; however our knowledge about the beneficial effects of BM-573 on endothelial function and increased blood pressure related to early stage of atherosclerosis is limited. In the present study, we investigated the effects of short-term (3 μM, 1 hour and chronic (10 mg/L, 8 weeks treatments with BM-573 on vasodilatory function, nitric oxide (NO bioavailability, oxidative stress and systolic blood pressure in 15 weeks old apolipoprotein E-deficient (ApoE-KO mice. ApoE-KO mice showed a reduced endothelium-derived relaxation. In addition, NO bioavailability was reduced and oxidative stress and blood pressure were increased in ApoE-KO mice versus wild-type mice. BM-573 treatments were able to improve the relaxation profile in ApoE-KO mice. Short-term effects of BM-573 were mainly mediated by an increased phosphorylation of both eNOS and Akt, whereas BM-573 in vivo treatment also reduced oxidative stress and restored NO bioavailability. In addition, chronic administration of BM-573 reduced systolic blood pressure in ApoE-KO mice. In conclusion, pharmacological modulation of TxA2 biosynthesis and biological activities by dual TP antagonism/TxAS inhibition with BM-573, already known to prevent plaque formation, has the potential to correct vasodilatory dysfunction at the early stages of atherosclerosis.

  7. Relaxation effect of abacavir on rat basilar arteries.

    Directory of Open Access Journals (Sweden)

    Rachel Wai Sum Li

    Full Text Available The use of abacavir has been linked with increased cardiovascular risk in patients with human immunodeficiency virus infection; however, the mechanism involved remains unclear. We hypothesize that abacavir may impair endothelial function. In addition, based on the structural similarity between abacavir and adenosine, we propose that abacavir may affect vascular contractility through endogenous adenosine release or adenosine receptors in blood vessels.The relaxation effect of abacavir on rat basilar arteries was studied using the myograph technique. Cyclic GMP and AMP levels were measured by immunoassay. The effects of abacavir on nucleoside transporters were studied using radiolabeled nucleoside uptake experiments. Ecto-5' nucleotidase activity was determined by measuring the generation of inorganic phosphate using adenosine monophosphate as the substrate.Abacavir induced the relaxation of rat basilar arteries in a concentration-dependent manner. This relaxation was abolished when endothelium was removed. In addition, the relaxation was diminished by the nitric oxide synthase inhibitor, L-NAME, the guanylyl cyclase inhibitor, ODQ, and the protein kinase G inhibitor, KT5820. Abacavir also increased the cGMP level in rat basilar arteries. Abacavir-induced relaxation was also abolished by adenosine A2 receptor blockers. However, abacavir had no effect on ecto-5' nucleotidase and nucleoside transporters. Short-term and long-term treatment of abacavir did not affect acetylcholine-induced relaxation in rat basilar arteries.Abacavir induces acute endothelium-dependent relaxation of rat basilar arteries, probably through the activation of adenosine A2 receptors in endothelial cells, which subsequently leads to the release of nitric oxide, resulting in activation of the cyclic guanosine monophosphate/protein kinase G-dependent pathway in vascular smooth muscle cells. It is speculated that abacavir-induced cardiovascular risk may not be related to

  8. Safety factor profile dependence of turbulent structure formation in relevant to internal transport barrier relaxation

    International Nuclear Information System (INIS)

    Tokunaga, S.; Yagi, M.; Itoh, S.-I.; Itoh, K.

    2009-01-01

    Full text: It is widely understood that the improved confinement mode with transport barrier is necessary to achieve the self-ignition condition in ITER. The negative magnetic shear, mean ExB flow shear, and zonal flow are considered to play important roles for ITB formation. In our previous study, it is found that the non-linear interaction between the meso-scale modes produces non-local energy transfer to the off-resonant mode in the vicinity of q min surface and brings global relaxation of the temperature profile involving ITB collapse. Experimental studies indicate that a relationship exists between the ITB formation and safety factor q-profile, with a reversed magnetic shear (RS) configuration. Transitional ITB events occur on the low-order rational resonant surface. The ITB shape and location depend on the q-profile and q min position. These observations indicate that the q-profile might play an essential role in determining the turbulent structure. In this study, the effect of safety factor profile on the ion temperature gradient driven drift wave (ITG) turbulence is investigated using a global non-linear simulation code based on the gyro-fluid model. A heat source and toroidal momentum source are introduced. Dependence of safety factor profiles on ITB formation and its stability is examined to clarify the influence of the radial distribution of the rational surfaces and the q min value. It is found that the nonlinearly excited meso-scale mode in the vicinity of q min depends on the value of q min . A detailed analysis of the structure selection rule is in progress. (author)

  9. Ionic relaxation in PEO/PVDF-HFP-LiClO4 blend polymer electrolytes: dependence on salt concentration

    Science.gov (United States)

    Das, S.; Ghosh, A.

    2016-06-01

    In this paper, we have studied the effect of LiClO4 salt concentration on the ionic conduction and relaxation in poly ethylene oxide (PEO) and poly (vinylidene fluoride hexafluoropropylene) (PVDF-HFP) blend polymer electrolytes, in which the molar ratio of ethylene oxide segments to lithium ions (R  =  EO: Li) has been varied between 3 and 35. We have observed two phases in the samples containing low salt concentrations (R  >  9) and single phase in the samples containing high salt concentrations (R  ⩽  9). The scanning electron microscopic images indicate that there exists no phase separation in the blend polymer electrolytes. The temperature dependence of the ionic conductivity shows two slopes corresponding to high and low temperatures and follows Arrhenius relation for the samples containing low salt concentrations (R  >  9). The conductivity relaxation as well as the structural relaxation has been clearly observed at around 104 Hz and 106 Hz for these concentrations of the blended electrolytes. However, a single conductivity relaxation peak has been observed for the compositions with R  ⩽  9. The scaling of the conductivity spectra shows that the relaxation mechanism is independent of temperature, but depends on salt concentration.

  10. Temperature dependent dielectric relaxation and ac-conductivity of alkali niobate ceramics studied by impedance spectroscopy

    Science.gov (United States)

    Yadav, Abhinav; Mantry, Snigdha Paramita; Fahad, Mohd.; Sarun, P. M.

    2018-05-01

    Sodium niobate (NaNbO3) ceramics is prepared by conventional solid state reaction method at sintering temperature 1150 °C for 4 h. The structural information of the material has been investigated by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FE-SEM). The XRD analysis of NaNbO3 ceramics shows an orthorhombic structure. The FE-SEM micrograph of NaNbO3 ceramics exhibit grains with grain sizes ranging between 1 μm to 5 μm. The surface coverage and average grain size of NaNbO3 ceramics are found to be 97.6 % and 2.5 μm, respectively. Frequency dependent electrical properties of NaNbO3 is investigated from room temperature to 500 °C in wide frequency range (100 Hz-5 MHz). Dielectric constant, ac-conductivity, impedance, modulus and Nyquist analysis are performed. The observed dielectric constant (1 kHz) at transition temperature (400 °C) are 975. From conductivity analysis, the estimated activation energy of NaNbO3 ceramics is 0.58 eV at 10 kHz. The result of Nyquist plot shows that the electrical behavior of NaNbO3 ceramics is contributed by grain and grain boundary responses. The impedance and modulus spectrum asserts that the negative temperature coefficient of resistance (NTCR) behavior and non-Debye type relaxation in NaNbO3.

  11. Relaxivity of blood pool contrast agent depends on the host tissue as suggested by semianalytical simulations

    DEFF Research Database (Denmark)

    Kjølby, Birgitte Fuglsang; Østergaard, Leif; Kiselev, Valerij

    Concentration of magnetic resonance imaging (MRI) contrast agents (CA) cannot be measured directly and is commonly determined indirectly using their relaxation effect. This requires knowledge of the relaxivity of the used CA. Quantitative perfusion studies involve measurement of CA concentration...... studies (3,4) as demonstrated in (5). It was previously found (6) that the perfusion measurements using dynamic susceptibility contrast inherently overestimate cerebral blood flow and volume. In view of the present result, this is attributed to the significant difference in the relaxivity of the CA...

  12. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA); Scientific Opinion on the substantiation of a health claim related to cocoa flavanols and maintenance of normal endothelium-dependent vasodilation pursuant to Article 13(5) of Regulation (EC) No 1924/2006

    DEFF Research Database (Denmark)

    Tetens, Inge

    Following an application from Barry Callebaut Belgium nv, submitted pursuant to Article 13(5) of Regulation (EC) No 1924/2006 via the Competent Authority of Belgium, the Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on the scientific substantiation...... of a health claim related to cocoa flavanols and maintenance of normal endothelium-dependent vasodilation. Cocoa flavanols are sufficiently characterised. The claimed effect is “help maintain endothelium-dependent vasodilation which contributes to healthy blood flow”. The target population proposed...... by the applicant is the general healthy adult population. The Panel considers that maintenance of normal endothelium-dependent vasodilation is a beneficial physiological effect. In weighing the evidence, the Panel took into account that cocoa flavanols consumed for 12 weeks have been shown to increase fasting ED...

  13. Activation of endothelial and epithelial K(Ca) 2.3 calcium-activated potassium channels by NS309 relaxes human small pulmonary arteries and bronchioles

    DEFF Research Database (Denmark)

    Kroigaard, Christel; Dalsgaard, Thomas; Nielsen, Gorm

    2012-01-01

    BACKGROUND AND PURPOSE: Small (K(Ca) 2) and intermediate (K(Ca) 3.1) conductance calcium-activated potassium channels (K(Ca) ) may contribute to both epithelium- and endothelium-dependent relaxations, but this has not been established in human pulmonary arteries and bronchioles. Therefore, we inv...... targets for treatment of pulmonary hypertension and chronic obstructive pulmonary disease....

  14. Impairment of the vascular relaxation and differential expression of caveolin-1 of the aorta of diabetic +db/+db mice.

    Science.gov (United States)

    Lam, Tze Yan; Seto, Sai Wang; Lau, Yee Man; Au, Lai Shan; Kwan, Yiu Wa; Ngai, Sai Ming; Tsui, Kwong Wing

    2006-09-28

    In this study, we compared the endothelium-dependent and -independent relaxation of the isolated thoracic aorta of control (+db/+m) and diabetic (+db/+db) (C57BL/KsJ) mice. The gene expression (mRNA and protein) level of the muscarinic M(3) receptors, endothelial nitric oxide synthase (eNOS) and caveolin-1 of the aorta was also evaluated. Acetylcholine caused a concentration-dependent, N(G)-nitro-L-arginine methyl-ester (20 microM)-sensitive relaxation, with approximately 100% relaxation at 10 microM, in +db/+m mice. In +db/+db mice, the acetylcholine-induced relaxation was significantly smaller (maximum relaxation: approximately 80%). The sodium nitroprusside-mediated relaxation was slightly diminished in +db/+db mice, compared to +db/+m mice. However, there was no significant difference in the isoprenaline- and cromakalim-induced relaxation observed in both species. The mRNA and protein expression levels of caveolin-1 were significantly higher in the aorta of +db/+db mice. In contrast, there was no difference in the mRNA and protein expression levels of eNOS and muscarinic M(3) receptors between these mice. Our results demonstrate that the impairment of the acetylcholine-induced, endothelium-dependent aortic relaxation observed in +db/+db mice was probably associated with an enhanced expression of caveolin-1 mRNA and protein.

  15. Peptidoglycan crosslinking relaxation plays an important role in Staphylococcus aureus WalKR-dependent cell viability.

    Directory of Open Access Journals (Sweden)

    Aurelia Delaune

    Full Text Available The WalKR two-component system is essential for viability of Staphylococcus aureus, a major pathogen. We have shown that WalKR acts as the master controller of peptidoglycan metabolism, yet none of the identified regulon genes explain its requirement for cell viability. Transmission electron micrographs revealed cell wall thickening and aberrant division septa in the absence of WalKR, suggesting its requirement may be linked to its role in coordinating cell wall metabolism and cell division. We therefore tested whether uncoupling autolysin gene expression from WalKR-dependent regulation could compensate for its essential nature. Uncoupled expression of genes encoding lytic transglycosylases or amidases did not restore growth to a WalKR-depleted strain. We identified only two WalKR-regulon genes whose expression restored cell viability in the absence of WalKR: lytM and ssaA. Neither of these two genes are essential under our conditions and a ΔlytM ΔssaA mutant does not present any growth defect. LytM is a glycyl-glycyl endopeptidase, hydrolyzing the pentaglycine interpeptide crossbridge, and SsaA belongs to the CHAP amidase family, members of which such as LysK and LytA have been shown to have D-alanyl-glycyl endopeptidase activity, cleaving between the crossbridge and the stem peptide. Taken together, our results strongly suggest that peptidoglycan crosslinking relaxation through crossbridge hydrolysis plays a crucial role in the essential requirement of the WalKR system for cell viability.

  16. Agmatine induced NO dependent rat mesenteric artery relaxation and its impairment in salt-sensitive hypertension.

    Science.gov (United States)

    Gadkari, Tushar V; Cortes, Natalie; Madrasi, Kumpal; Tsoukias, Nikolaos M; Joshi, Mahesh S

    2013-11-30

    l-Arginine and its decarboxylated product, agmatine are important mediators of NO production and vascular relaxation. However, the underlying mechanisms of their action are not understood. We have investigated the role of arginine and agmatine in resistance vessel relaxation of Sprague-Dawley (SD) and Dahl salt-sensitive hypertensive rats. Second or 3rd-order mesenteric arterioles were cannulated in an organ chamber, pressurized and equilibrated before perfusing intraluminally with agonists. The vessel diameters were measured after mounting on the stage of a microscope fitted with a video camera. The gene expression in Dahl rat vessel homogenates was ascertained by real-time PCR. l-Arginine initiated relaxations (EC50, 5.8±0.7mM; n=9) were inhibited by arginine decarboxylase (ADC) inhibitor, difluoromethylarginine (DFMA) (EC50, 18.3±1.3mM; n=5) suggesting that arginine-induced vessel relaxation was mediated by agmatine formation. Agmatine relaxed the SD rat vessels at significantly lower concentrations (EC50, 138.7±12.1μM; n=22), which was compromised by l-NAME (l-N(G)-nitroarginine methyl ester, an eNOS inhibitor), RX821002 (α-2 AR antagonist) and pertussis toxin (G-protein inhibitor). The agmatine-mediated vessel relaxation from high salt Dahl rats was abolished as compared to that from normal salt rats (EC50, 143.9±23.4μM; n=5). The α-2A AR, α-2B AR and eNOS mRNA expression was downregulated in mesenteric arterioles of high-salt treated Dahl hypertensive rats. These findings demonstrate that agmatine facilitated the relaxation via activation of α-2 adrenergic G-protein coupled receptor and NO synthesis, and this pathway is compromised in salt-sensitive hypertension. Copyright © 2013 Elsevier Inc. All rights reserved.

  17. Frequency and Temperature Dependence of Anharmonic Phonon Relaxation Rate in Carbon Nanotubes

    International Nuclear Information System (INIS)

    Hepplestone, S P; Srivastava, G P

    2007-01-01

    The relaxation rate of phonon modes in the (10, 10) single wall carbon nanotube undergoing three-phonon interactions at various temperatures has been studied using both qualitative and quantitative approaches based upon Fermi's Golden Rule and a quasi-elastic continuum model for the anharmonic potential. For the quantitative calculations, dispersion relations for the phonon modes were obtained from analytic expressions developed by Zhang et al. The qualitative expressions were derived using simple linear phonon dispersions relations. We show that in the high temperature regime the relaxation rate varies linearly with temperature and with the square of the frequency. In the low temperature regime we show that the relaxation rate varies exponentially with the inverse of temperature. These results have some very interesting implifications for effects for mean free path and thermal conductivity calculations

  18. Temperature dependence of levitation force and its relaxation in a HTS levitation system

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Jun; Zhang Xingyi [Key Laboratory of Mechanics on Western Disaster and Environment, Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China); Zhou Youhe, E-mail: zhouyh@lzu.edu.c [Key Laboratory of Mechanics on Western Disaster and Environment, Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

    2010-03-01

    Using a modified Gifford-McMahon refrigerator to cool the cylindrical bulk YBaCuO superconductor within the region of 100-10 K, and using an updated high-temperature superconductor (HTS) maglev measurement system, the levitation force and its time relaxation at different temperatures between a YBaCuO bulk superconductor and a permanent magnet (PM) have been measured under zero-field cooling. It is found that decrease the cooling temperature of HTS can decrease the hysteresis of magnetization and increase the maximum levitation force of each hysteresis loop. For the relaxation of levitation force, if the temperature is continually lowered to 10 K after the relaxation measurement at given cooling temperature is performed for 600 s, the levitation force will continue to decrease sharply with the lowering of temperature even though it will get stable if the temperature is not lowered. Our results shown in this work are a benefit to the understanding of levitation systems.

  19. Rotational dynamics account for pH-dependent relaxivities of PAMAM dendrimeric, Gd-based potential MRI contrast agents.

    Science.gov (United States)

    Laus, Sabrina; Sour, Angélique; Ruloff, Robert; Tóth, Eva; Merbach, André E

    2005-05-06

    The EPTPA5) chelate, which ensures fast water exchange in GdIII complexes, has been coupled to three different generations (5, 7, and 9) of polyamidoamine (PAMAM) dendrimers through benzylthiourea linkages (H5EPTPA = ethylenepropylenetriamine-N,N,N',N'',N''-pentaacetic acid). The proton relaxivities measured at pH 7.4 for the dendrimer complexes G5-(GdEPTPA)111, G7-(GdEPTPA)253 and G9-(GdEPTPA)1157 decrease with increasing temperature, indicating that, for the first time for dendrimers, slow water exchange does not limit relaxivity. At a given field and temperature, the relaxivity increases from G5 to G7, and then slightly decreases for G9 (r1 = 20.5, 28.3 and 27.9 mM(-1) s(-1), respectively, at 37 degrees C, 30 MHz). The relaxivities show a strong and reversible pH dependency for all three dendrimer complexes. This originates from the pH-dependent rotational dynamics of the dendrimer skeleton, which was evidenced by a combined variable-temperature and multiple-field 17O NMR and 1H relaxivity study performed at pH 6.0 and 9.9 on G5-(GdEPTPA)111. The longitudinal 17O and 1H relaxation rates of the dendrimeric complex are strongly pH-dependent, whereas they are not for the [Gd(EPTPA)(H2O)]2- monomer chelate. The longitudinal 17O and 1H relaxation rates have been analysed by the Lipari-Szabo spectral density functions and correlation times have been calculated for the global motion of the entire macromolecule (tau(gO)) and the local motion of the GdIII chelates on the surface (tau(lO)), correlated by means of an order parameter S2. The dendrimer complex G5-(GdEPTPA)111 has a considerably higher tau(gO) under acidic than under basic conditions (tau(298)gO = 4040 ps and 2950 ps, respectively), while local motions are less influenced by pH (tau(298)lO = 150 and 125 ps). The order parameter, characterizing the rigidity of the macromolecule, is also higher at pH 6.0 than at pH 9.9 (S2 = 0.43 vs 0.36, respectively). The pH dependence of the global correlation time can be

  20. PDE1A inhibition elicits cGMP-dependent relaxation of rat mesenteric arteries

    DEFF Research Database (Denmark)

    Khammy, Makhala Michell; Dalsgaard, Thomas; Larsen, Peter Hjorringgaard

    2017-01-01

    (EC50 = 32 nM). Inhibition of NOS with L-NAME, soluble GC with ODQ, or PKG with Rp-8-Br-PET-cGMP all attenuated PDE1 inhibition-induced relaxation, whereas PKA inhibition with H89 had no effect. CONCLUSION AND IMPLICATIONS: Pde1a was the dominant PDE1 isoform present in VSMC and relaxation mediated...... by PDE1A-inhibition was predominantly driven by enhanced cGMP signalling. These results imply that isoform-selective PDE1 inhibitors are powerful investigative tools allowing examination of physiological and pathological roles of PDE1 isoforms....

  1. Temperature Dependence of Logarithmic-like Relaxational Dynamics of Hydrated tRNA.

    Science.gov (United States)

    Chu, Xiang-Qiang; Mamontov, Eugene; O'Neill, Hugh; Zhang, Qiu

    2013-03-21

    The dynamics of RNA within the β-relaxation region of 10 ps to 1 ns is crucial to its biological function. Because of its simpler chemical building blocks and the lack of the side methyl groups, faster relaxational dynamics of RNA compared to proteins can be expected. However, the situation is actually opposite. In this work, the relaxational dynamics of tRNA is measured by quasielastic neutron scattering and analyzed using the mode coupling theory, originally developed for glass-forming liquids. Our results reveal that the dynamics of tRNA follows a log-decay within the β-relaxation region, which is an important trait demonstrated by the dynamics of proteins. The dynamics of hydrated tRNA and lysozyme compared in the time domain further demonstrate that the slower dynamics of tRNA relative to proteins originates from the difference in the folded states of tRNA and proteins, as well as the influence of their hydration water.

  2. Upregulation of SK3 and IK1 channels contributes to the enhanced endothelial calcium signaling and the preserved coronary relaxation in obese Zucker rats.

    Directory of Open Access Journals (Sweden)

    Belén Climent

    Full Text Available Endothelial small- and intermediate-conductance KCa channels, SK3 and IK1, are key mediators in the endothelium-derived hyperpolarization and relaxation of vascular smooth muscle and also in the modulation of endothelial Ca2+ signaling and nitric oxide (NO release. Obesity is associated with endothelial dysfunction and impaired relaxation, although how obesity influences endothelial SK3/IK1 function is unclear. Therefore we assessed whether the role of these channels in the coronary circulation is altered in obese animals.In coronary arteries mounted in microvascular myographs, selective blockade of SK3/IK1 channels unmasked an increased contribution of these channels to the ACh- and to the exogenous NO- induced relaxations in arteries of Obese Zucker Rats (OZR compared to Lean Zucker Rats (LZR. Relaxant responses induced by the SK3/IK1 channel activator NS309 were enhanced in OZR and NO- endothelium-dependent in LZR, whereas an additional endothelium-independent relaxant component was found in OZR. Fura2-AM fluorescence revealed a larger ACh-induced intracellular Ca2+ mobilization in the endothelium of coronary arteries from OZR, which was inhibited by blockade of SK3/IK1 channels in both LZR and OZR. Western blot analysis showed an increased expression of SK3/IK1 channels in coronary arteries of OZR and immunohistochemistry suggested that it takes place predominantly in the endothelial layer.Obesity may induce activation of adaptive vascular mechanisms to preserve the dilator function in coronary arteries. Increased function and expression of SK3/IK1 channels by influencing endothelial Ca2+ dynamics might contribute to the unaltered endothelium-dependent coronary relaxation in the early stages of obesity.

  3. Electron Tunneling in Lithium Ammonia Solutions Probed by Frequency-Dependent Electron-Spin Relaxation Studies

    Science.gov (United States)

    Maeda, Kiminori; Lodge, Matthew T.J.; Harmer, Jeffrey; Freed, Jack H.; Edwards, Peter P.

    2012-01-01

    Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T1) and spin-spin (T2) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multi-exponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1–10)×10−12 s over a temperature range 230–290K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a timescale of ca. 10−13 s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great potential

  4. Electron tunneling in lithium-ammonia solutions probed by frequency-dependent electron spin relaxation studies.

    Science.gov (United States)

    Maeda, Kiminori; Lodge, Matthew T J; Harmer, Jeffrey; Freed, Jack H; Edwards, Peter P

    2012-06-06

    Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T(1)) and spin-spin (T(2)) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multiexponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1-10) × 10(-12) s over a temperature range 230-290 K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a time scale of ∼10(-13) s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great

  5. Mechanisms behind the relaxing effect of furosemide on the isolated rabbit ear artery

    Energy Technology Data Exchange (ETDEWEB)

    Tian, R.; Aalkjaer, C.; Andreasen, F. (Institute of Pharmacology, University of Aarhus, Aarhus (Denmark))

    1991-01-01

    The effect of furosemide on isometric contration and {sup 86}Rb uptake were studied in the isolated rabbit central ear artery (CEA). A concentration-dependent relaxing effect of furosemide (0.06 mM-1.0 mM) was found in vessel segments with intact endothelium. The maximal relaxation was 28.6+-3.9% (10). The effect was not diminished in segments deprived of endothelium, and removal of endothelium itself caused no change of the force development to electrical field stimualtion. The relaxing effect was time-dependent and stimulation-dependent and was not significantly affected by membrane depolarization induced by increasing external (K{sup +}) from 10 to 120 mM. The {sup 86}Rb uptake was inhibited by both furosemide and ouabain (8.0+-0.5(8) and 5.3+-0.5(8) versus 12.8+-0.9(16) nmol (K{sup +})x mm{sup -1}x(10 min.){sup -1} in the furosemide (1.0 mM), ouabain (1.0 mM) and control groups, respectively) without interaction between the two drugs. The {sup 86}Rb uptake was not further inhibited by increasing the furosemide concentration from 0.12 mM to 1.0 mM. Our results suggest: firstly, the direct relaxing effect of furosemide on isolated vessel segments in endothelium-independent and secondly, the inhibition of the Na{sup +}-K{sup +}-Cl{sup -} cotransport and a possible consequent hyperpolarization of the membrane is unlikely to be the sole mechanism responsible for the vasorelaxant effect of furosemide. The demonstrated direct effect on vascular tone may be of clinical importance in situations with very high plasma concentrations of the drug or very low concentrations of serum albumin. (aluthor).

  6. Temperature dependence of electron spin-lattice relaxation of radiation-produced silver atoms in polycrystalline aqueous and glassy organic matrices. Importance of relaxation by tunneling modes in disordered matrices

    International Nuclear Information System (INIS)

    Michalik, J.; Kevan, L.

    1978-01-01

    The electron spin-lattice relaxation of trapped silver atoms in polycrystalline ice matrices and in methanol, ethanol, propylene carbonate, and 2-methyltetrahydrofuran organic glasses has been directly studied as a function of temperature by the saturation-recovery method. Below 40 K the dominant electron spin-lattice relaxation mechanism involves modulation of the electron nuclear dipolar interaction with nuclei in the radical's environment by tunneling of those nuclei between two nearly equal energy configurations. This relaxation mechanism occurs with high efficiency, has a characteristic linear temperature dependence, and is typically found in highly disordered matrices. The efficiency of this relaxation mechanism seems to decrease with decreasing polarity of the matrix. Deuteration experiments show that the tunneling nuclei are protons and in methanol it is shown that the methyl protons have more tunneling modes available than the hydroxyl protons. In polycrystalline ice matrices silver atoms can be stabilized with two different orientations of surrounding water molecules; the efficiency of the tunneling relaxation reflects this difference. From these and previous results on tunneling relaxation of trapped electrons in glassy matrices it appears that tunneling relaxation may be used to distinguish models with different geometrical configurations and to determine the relative rigidity of such configurations around trapped radicals in disordered solids. (author)

  7. Strain Rate Dependence of Compressive Yield and Relaxation in DGEBA Epoxies

    Science.gov (United States)

    Arechederra, Gabriel K.; Reprogle, Riley C.; Clarkson, Caitlyn M.; McCoy, John D.; Kropka, Jamie M.; Long, Kevin N.; Chambers, Robert S.

    2015-03-01

    The mechanical response in uniaxial compression of two diglycidyl ether of bisphenol-A epoxies were studied. These were 828DEA (Epon 828 cured with diethanolamine (DEA)) and 828T403 (Epon 828 cured with Jeffamine T-403). Two types of uniaxial compression tests were performed: A) constant strain rate compression and B) constant strain rate compression followed by a constant strain relaxation. The peak (yield) stress was analyzed as a function of strain rate from Eyring theory for activation volume. Runs at different temperatures permitted the construction of a mastercurve, and the resulting shift factors resulted in an activation energy. Strain and hold tests were performed for a low strain rate where a peak stress was lacking and for a higher strain rate where the peak stress was apparent. Relaxation from strains at different places along the stress-strain curve was tracked and compared. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  8. Sarpogrelate hydrochloride, a selective 5-hydroxytryptamine(2A) antagonist, augments autologous bone marrow mononuclear cell implantation-induced improvement in endothelium-dependent vasodilation in patients with critical limb ischemia.

    Science.gov (United States)

    Higashi, Yukihito; Miyazaki, Masanori; Goto, Chikara; Sanada, Hiroaki; Sueda, Taijiro; Chayama, Kazuaki

    2010-01-01

    The purpose of this study was to determine the effect of a combination of bone marrow mononuclear cell (BM-MNC) implantation and sarpogrelate, a selective 5-HT(2A) antagonist, on endothelial function in patients with critical limb ischemia (CLI). We evaluated the leg blood flow (LBF) responses to acetylcholine (ACh) and sodium nitroprusside before and after BM-MNC implantation in 16 patients with CLI. We divided patients with CLI into 2 groups: those cotreated with sarpogrelate orally for 12 weeks (sarpogrelate group, n = 8) and those who remained on conventional therapy (control group, n = 8). LBF was measured by strain gauge plethysmography. BM-MNC implantation improved ankle brachial pressure index, transcutaneous oxygen pressure, and pain-free walking time. There was no significant difference in these parameters between the 2 groups. Before BM-MNC implantation, LBF responses to ACh were similar in the sarpogrelate group and control group. Twelve weeks of BM-MNC implantation enhanced LBF responses to ACh in the sarpogrelate and control groups. After 12 weeks of BM-MNC implantation, LBF response to ACh was significantly greater in the sarpogrelate group than in the control group. BM-MNC implantation did not alter the LBF responses to sodium nitroprusside in either group. These findings suggest that BM-MNC implantation improved not only limb ischemic symptoms but also endothelium-dependent vasodilation in patients with CLI. A combination of BM-MNC implantation and sarpogrelate had a more beneficial effect on vascular function in these patients.

  9. Bias Dependent Spin Relaxation in a [110]-InAs/AlSb Two Dimensional Electron System

    Science.gov (United States)

    Hicks, J.; Holabird, K.

    2005-03-01

    Manipulation of electron spin is a critical component of many proposed semiconductor spintronic devices. One promising approach utilizes the Rashba effect by which an applied electric field can be used to reduce the spin lifetime or rotate spin orientation through spin-orbit interaction. The large spin-orbit interaction needed for this technique to be effective typically leads to fast spin relaxation through precessional decay, which may severely limit device architectures and functionalities. An exception arises in [110]-oriented heterostructures where the crystal magnetic field associated with bulk inversion asymmetry lies along the growth direction and in which case spins oriented along the growth direction do not precess. These considerations have led to a recent proposal of a spin-FET that incorporates a [110]-oriented, gate-controlled InAs quantum well channel [1]. We report measurements of the electron spin lifetime as a function of applied electric field in a [110]-InAs 2DES. Measurements made using an ultrafast, mid-IR pump-probe technique indicate that the spin lifetime can be reduced from its maximum to minimum value over a range of less than 0.2V per quantum well at room temperature. This work is supported by DARPA, NSERC and the NSF grant ECS - 0322021. [1] K. C. Hall, W. H. Lau, K. Gundogdu, M. E. Flatte, and T. F. Boggess, Appl. Phys. Lett. 83, 2937 (2003).

  10. (-)-Epicatechin-induced relaxation of isolated human saphenous vein: Roles of K+ and Ca2+ channels.

    Science.gov (United States)

    Marinko, Marija; Jankovic, Goran; Nenezic, Dragoslav; Milojevic, Predrag; Stojanovic, Ivan; Kanjuh, Vladimir; Novakovic, Aleksandra

    2018-02-01

    In this study, we aimed to investigate relaxant effect of flavanol (-)-epicatechin on the isolated human saphenous vein (HSV), as a part of its cardioprotective action, and to define the mechanisms underlying this vasorelaxation. (-)-Epicatechin induced a concentration-dependent relaxation of HSV pre-contracted by phenylephrine. Among K + channel blockers, 4-aminopyridine, margatoxin, and iberiotoxin significantly inhibited relaxation of HSV, while glibenclamide considerably reduced effects of the high concentrations of (-)-epicatechin. Additionally, (-)-epicatechin relaxed contraction induced by 80 mM K + , whereas in the presence of nifedipine produced partial relaxation of HSV rings pre-contracted by phenylephrine. In Ca 2+ -free solution, (-)-epicatechin relaxed contraction induced by phenylephrine, but had no effect on contraction induced by caffeine. A sarcoplasmic reticulum Ca 2+ -ATPase inhibitor, thapsigargin, significantly reduced relaxation of HSV produced by (-)-epicatechin. These results demonstrate that (-)-epicatechin produces endothelium-independent relaxation of isolated HSV rings. Vasorelaxation to (-)-epicatechin probably involves activation of 4-aminopyridine- and margatoxin-sensitive K V channels, BK Ca channels, and at least partly, K ATP channels. In addition, not only the inhibition of extracellular Ca 2+ influx, but regulation of the intracellular Ca 2+ release, via inositol-trisphosphate receptors and reuptake into sarcoplasmic reticulum, via stimulation of Ca 2+ -ATPase, as well, most likely participate in (-)-epicatechin-induced relaxation of HSV. Copyright © 2017 John Wiley & Sons, Ltd.

  11. Dynamic regulation of GDP binding to G proteins revealed by magnetic field-dependent NMR relaxation analyses.

    Science.gov (United States)

    Toyama, Yuki; Kano, Hanaho; Mase, Yoko; Yokogawa, Mariko; Osawa, Masanori; Shimada, Ichio

    2017-02-22

    Heterotrimeric guanine-nucleotide-binding proteins (G proteins) serve as molecular switches in signalling pathways, by coupling the activation of cell surface receptors to intracellular responses. Mutations in the G protein α-subunit (Gα) that accelerate guanosine diphosphate (GDP) dissociation cause hyperactivation of the downstream effector proteins, leading to oncogenesis. However, the structural mechanism of the accelerated GDP dissociation has remained unclear. Here, we use magnetic field-dependent nuclear magnetic resonance relaxation analyses to investigate the structural and dynamic properties of GDP bound Gα on a microsecond timescale. We show that Gα rapidly exchanges between a ground-state conformation, which tightly binds to GDP and an excited conformation with reduced GDP affinity. The oncogenic D150N mutation accelerates GDP dissociation by shifting the equilibrium towards the excited conformation.

  12. Orientation dependence in collision induced electronic relaxation studied through van der Waals complexes with isomeric structures. Invited feature article

    International Nuclear Information System (INIS)

    Cheng, P.Y.; Lapierre, L.; Ju, S.S.; DeRose, P.; Dai, H.L.

    1994-01-01

    Weakly bound molecular complexes with more than one well-defined structures provide us with an unique opportunity to investigate dynamic processes induced by intermolecular interactions with specific orientations. The relative orientation of the two interacting molecules or atoms is defined by the complex structure. The effect of the orientation in the spin changing collisions glyoxal (S 1 ) + Ar → glyoxal (T 1 ) + Ar and acetylene (S 1 ) + Ar → acetylene (T) + Ar have been studied by measuring the intersystem crossing (ISC) rates of the glyoxal(S 1 ).Ar and acetylene(S 1 ).Ar complexes with different isomeric structures. Results show that there is a strong orientation dependence in the ISC of glyoxal(S 1 ) induced by interaction with the Ar atom: the Ar atom positioned in the molecular plane is much more effective than in the out-of-plane position in inducing the S 1 → T 1 transition of glyoxal. On the other hand, studies of acetylene(S 1 ).Ar complexes indicate that the Ar-induced ISC rates are nearly identical for the in-plane and out-of-plane positions. Orientation dependence in the collision induced vibrational relaxation process C 2 H 2 (S 1 , v i ) + Ar → C 2 H 2 (S 1 , v f i ) + Ar is also studied by measuring the vibrational predissociation rates of the acetylene(S 1 ).Ar complex isomers. The results indicate that collisions of C 2 H 2 (S 1 , v 3 = 3, 4) with Ar at two orthogonal orientations are equally effective in causing vibrational relaxation of C 2 H 2 . (orig.)

  13. Increased CEST specificity for amide and fast-exchanging amine protons using exchange-dependent relaxation rate.

    Science.gov (United States)

    Zhang, Xiao-Yong; Wang, Feng; Xu, Junzhong; Gochberg, Daniel F; Gore, John C; Zu, Zhongliang

    2018-02-01

    Chemical exchange saturation transfer (CEST) imaging of amides at 3.5 ppm and fast-exchanging amines at 3 ppm provides a unique means to enhance the sensitivity of detection of, for example, proteins/peptides and neurotransmitters, respectively, and hence can provide important information on molecular composition. However, despite the high sensitivity relative to conventional magnetic resonance spectroscopy (MRS), in practice, CEST often has relatively poor specificity. For example, CEST signals are typically influenced by several confounding effects, including direct water saturation (DS), semi-solid non-specific magnetization transfer (MT), the influence of water relaxation times (T 1w ) and nearby overlapping CEST signals. Although several editing techniques have been developed to increase the specificity by removing DS, semi-solid MT and T 1w influences, it is still challenging to remove overlapping CEST signals from different exchanging sites. For instance, the amide proton transfer (APT) signal could be contaminated by CEST effects from fast-exchanging amines at 3 ppm and intermediate-exchanging amines at 2 ppm. The current work applies an exchange-dependent relaxation rate (R ex ) to address this problem. Simulations demonstrate that: (1) slowly exchanging amides and fast-exchanging amines have distinct dependences on irradiation powers; and (2) R ex serves as a resonance frequency high-pass filter to selectively reduce CEST signals with resonance frequencies closer to water. These characteristics of R ex provide a means to isolate the APT signal from amines. In addition, previous studies have shown that CEST signals from fast-exchanging amines have no distinct features around their resonance frequencies. However, R ex gives Lorentzian lineshapes centered at their resonance frequencies for fast-exchanging amines and thus can significantly increase the specificity of CEST imaging for amides and fast-exchanging amines. Copyright © 2017 John Wiley & Sons

  14. Nitric oxide and catalase-sensitive relaxation by scutellarin in the mouse thoracic aorta.

    Science.gov (United States)

    Yang, Weimin; Lust, Robert M; Bofferding, April; Wingard, Christopher J

    2009-01-01

    The vascular activity of scutellarin (SCU), a flavonoid isolated from a Chinese traditional medicinal plant, was investigated in isolated thoracic aortic rings of mice. SCU-induced dose-dependent relaxation of phenylephrine (1 microM) stimulated contractions. This relaxation was reduced by endothelium removal, significantly reduced by both the nitric oxide synthase inhibitor (Nomega-nitro-L-arginine methylester, 300 microM) and slightly limited by the soluble guanylyl cyclase inhibitor (1 H-[1,2,4] oxidazolol [4,3-a] quinoxalin-1-one, 100 microM). The catalase inhibitor (3-amino-1,2,4-triazole, 50 mM) augmented the constriction and blocked the lowest SCU concentration relaxation, whereas catalase addition was without effect. Preincubation with 300 and 1000 microM SCU significantly suppressed the contractile dose-response to phenylephrine, causing both a significant rise in half maximal effective concentration and a decrease in the maximal developed force. Western blot analysis showed that SCU inhibition of contraction was independent of reductions in myosin light chain phosphorylation. These results suggested that SCU relaxation was predominantly endothelium dependent and likely involved the catalase-sensitive nitric oxide synthase signaling pathway, without loss of myosin phosphorylation. The potential clinical use of SCU may prove to be effective in increasing vasoreactivity, independently of smooth muscle contractile activity that is mediated by the 20-kDa myosin light chain phosphorylation.

  15. Effects of a Single Bout of Resistance Exercise in Different Volumes on Endothelium Adaptations in Healthy Animals

    Directory of Open Access Journals (Sweden)

    Marcelo Mendonça Mota

    Full Text Available Abstract Background: Resistance exercise (RE has been recommended for patients with cardiovascular diseases. Recently, a few studies have demonstrated that the intensity of a single bout of RE has an effect on endothelial adaptations to exercise. However, there is no data about the effects of different volumes of RE on endothelium function. Objective: The aim of the study was to evaluate the effects of different volumes of RE in a single bout on endothelium-dependent vasodilatation and nitric oxide (NO synthesis in the mesenteric artery of healthy animals. Methods: Male Wistar rats were divided into three groups: Control (Ct; low-volume RE (LV, 5 sets x 10 repetitions and high-volume RE (HV, 15 sets x 10 repetitions. The established intensity was 70% of the maximal repetition test. After the exercise protocol, rings of mesenteric artery were used for assessment of vascular reactivity, and other mesenteric arteries were prepared for detection of measure NO production by DAF-FM fluorescence. Insulin responsiveness on NO synthesis was evaluated by stimulating the vascular rings with insulin (10 nM. Results: The maximal relaxation response to insulin increased in the HV group only as compared with the Ct group. Moreover, the inhibition of nitric oxide synthesis (L-NAME completely abolished the insulin-induced vasorelaxation in exercised rats. NO production showed a volume-dependent increase in the endothelial and smooth muscle layer. In endothelial layer, only Ct and LV groups showed a significant increase in NO synthesis when compared to their respective group under basal condition. On the other hand, in smooth muscle layer, NO fluorescence increased in all groups when compared to their respective group under basal condition. Conclusions: Our results suggest that a single bout of RE promotes vascular endothelium changes in a volume-dependent manner. The 15 sets x 10 repetitions exercise plan induced the greatest levels of NO synthesis.

  16. Time dependence of volcano inflation: mass influx or viscoelastic relaxation? Insights from Grímsvötn volcano, Iceland

    Science.gov (United States)

    Segall, P.

    2017-12-01

    Distinguishing magma chamber pressurization from relaxation of a viscoelastic aureole surrounding the chamber based on geodetic measurements has remained challenging. Elastic models with mass inflow proportional to the pressure difference between the chamber and a deep reservoir predict exponentially decaying flux. For a spherical chamber surrounded by a Maxwell viscoelastic shell with pressure dependent recharge, the surface deformation is the sum of two exponentials (Segall, 2016). GPS displacements following eruptions of Grímsvötn, Iceland in 2004 and 2011 exhibit rapid post-eruptive inflation (time scale of 0.1 yr), followed by inflation with a much longer time constant. Markov Chain Monte Carlo inversion with the viscoelastic model shows the GPS time series can be fit with viscosity of 2e16 Pa-s, and a relatively incompressible magma, B = beta_c/ (beta_m + beta_c) > 0.6, where beta_m and beta_c are chamber and magma compressibility. The latter appears to conflict with the ratio of erupted volume to geodetically inferred source volume change, rv 10, obtained for the best fitting spherical (Mogi ) source (Hreinsdóttir, 2014). Since rv = 1/B, this implies a relatively compressible melt, B 0.1. Reexamination of the co-eruptive GPS and tilt data with the more general ellipsoidal model of Cervelli (2013), reveals that the best fitting sources are oblate (b/a 3), deeper, and with larger volume changes, rv 3, relative to spherical models. Oblate magma chambers are consistent with seismic tomography. FEM calculations including free surface effects lead to even larger co-eruptive volume changes, smaller rv and hence larger B. I conclude that the data are consistent with rapid post-eruptive inflation driven by viscoelastic relaxation with a relatively incompressible magma, although other interpretations will be discussed.

  17. Grid dependency and relaxation of an iteration procedure for flow calculations in stationary hydraulic turbine parts

    Energy Technology Data Exchange (ETDEWEB)

    Iliev, Igor; Markov, Zoran [Faculty of Mechanical Engineering, ' Ss. Cyril and Methodius' University, Skopje (Macedonia, The Former Yugoslav Republic of)

    2014-07-01

    The numerical methods for iterative solving of discretized governing equations often require special treatment for the purpose of achieving not only sufficiently accurate and reliable results, but stable and gradual convergence of the solution too. The general remedy for such challenge, for a certain case, is to use a fine mesh to a certain level and/or to slow down the numerical procedure, a two useful strategies by which numerical instabilities will be avoided on the account of a greater CPU load. This paper presents the employment of these two strategies by conducting a grid dependency analysis for a 2D model of the stay and guide vanes of a hydraulic Francis turbine and furthering the solution to iteration procedure adjustment for a 3D representation of the same model. The ultimate accent is placed on how to deal with a particular numerical instability problem in a pure mathematical fashion without getting into the experimental validation of the results and calibration of the method. (Author)

  18. Time-dependent entropy evolution in microscopic and macroscopic electromagnetic relaxation

    International Nuclear Information System (INIS)

    Baker-Jarvis, James

    2005-01-01

    This paper is a study of entropy and its evolution in the time and frequency domains upon application of electromagnetic fields to materials. An understanding of entropy and its evolution in electromagnetic interactions bridges the boundaries between electromagnetism and thermodynamics. The approach used here is a Liouville-based statistical-mechanical theory. I show that the microscopic entropy is reversible and the macroscopic entropy satisfies an H theorem. The spectral entropy development can be very useful for studying the frequency response of materials. Using a projection-operator based nonequilibrium entropy, different equations are derived for the entropy and entropy production and are applied to the polarization, magnetization, and macroscopic fields. I begin by proving an exact H theorem for the entropy, progress to application of time-dependent entropy in electromagnetics, and then apply the theory to relevant applications in electromagnetics. The paper concludes with a discussion of the relationship of the frequency-domain form of the entropy to the permittivity, permeability, and impedance

  19. Investigation of the Temperature Dependence of the Acceptor Center Relaxation Rate in Silicon by the mu^-SR-Method

    CERN Document Server

    Mamedov, T N; Stojkov, A V; Andrianov, D G; Gerlach, D; Zimmermann, U; Gorelkin, V N; Kormann, O; Major, J V; Shevchik, M

    2000-01-01

    Results on the temperature dependence of the residual polarization of negative muons in silicon with phosphorus (3.2 cdot 10^12, 2.3 cdot 10^15 and 4.5 cdot 10^18 cm^-3) and aluminium (2 cdot 10^14 and 2.4 cdot 10^18 cm^-3) impurities are presented. The measurements were carried out in a transverse to the direction of the muon spin magnetic field of 2000 Oe in the temperature range 4.2-300 K. The temperature dependence of the relaxation rate of the magnetic moment of the Al shallow acceptor centre in undeformed silicon is determined for the first time. The constant of the hyperfine interaction between the magnetic moment of the muon and that of the electron shell of the muonic atom A_hf/2pi approx 3 cdot 10^7 s^-1) and the coefficient for capture of free electrons by a neutral aluminium atom in silicon (beta (Al^0) approx 7 cdot 10^-14 cm^3 s^-1 at 30 K) are estimated.

  20. Ab initio relaxation times and time-dependent Hamiltonians within the steepest-entropy-ascent quantum thermodynamic framework

    Science.gov (United States)

    Kim, Ilki; von Spakovsky, Michael R.

    2017-08-01

    Quantum systems driven by time-dependent Hamiltonians are considered here within the framework of steepest-entropy-ascent quantum thermodynamics (SEAQT) and used to study the thermodynamic characteristics of such systems. In doing so, a generalization of the SEAQT framework valid for all such systems is provided, leading to the development of an ab initio physically relevant expression for the intrarelaxation time, an important element of this framework and one that had as of yet not been uniquely determined as an integral part of the theory. The resulting expression for the relaxation time is valid as well for time-independent Hamiltonians as a special case and makes the description provided by the SEAQT framework more robust at the fundamental level. In addition, the SEAQT framework is used to help resolve a fundamental issue of thermodynamics in the quantum domain, namely, that concerning the unique definition of process-dependent work and heat functions. The developments presented lead to the conclusion that this framework is not just an alternative approach to thermodynamics in the quantum domain but instead one that uniquely sheds new light on various fundamental but as of yet not completely resolved questions of thermodynamics.

  1. Factor VIII-associated antigen in human lymphatic endothelium.

    Science.gov (United States)

    Nagle, R B; Witte, M H; Martinez, A P; Witte, C L; Hendrix, M J; Way, D; Reed, K

    1987-03-01

    Lymphatic vascular endothelium both on tissue section and in culture exhibits positivity for Factor VIII-associated antigen although staining is generally less intense and more spotty than in comparable blood vascular endothelium. Lymphatic endothelium also exhibits Weibel-Palade bodies. Neither marker, therefore, reliably distinguishes blood vascular endothelium from lymphatic endothelium.

  2. Distinct mechanisms of relaxation to bioactive components from chamomile species in porcine isolated blood vessels

    International Nuclear Information System (INIS)

    Roberts, R.E.; Allen, S.; Chang, A.P.Y.; Henderson, H.; Hobson, G.C.; Karania, B.; Morgan, K.N.; Pek, A.S.Y.; Raghvani, K.; Shee, C.Y.; Shikotra, J.; Street, E.; Abbas, Z.; Ellis, K.; Heer, J.K.; Alexander, S.P.H.

    2013-01-01

    German chamomile (Matricaria recutita L.), a widely-used herbal medicine, has been reported to have a wide range of biological effects, including smooth muscle relaxation. The aim of this study was to compare the effects of representative compounds from chamomile (apigenin, luteolin, (−)-α-bisabolol, farnesene, umbelliferone; 3–30 μM) on vascular tone using porcine coronary and splenic arteries mounted for isometric tension recording in isolated tissue baths and precontracted with the thromboxane-mimetic U46619. Apigenin, luteolin, and (−)-α-bisabolol produced slow, concentration-dependent relaxations in both the coronary and splenic arteries that were not blocked by inhibition of nitric oxide synthase or potassium channels. Removal of extracellular calcium inhibited the relaxations to all three compounds, and these compounds also inhibited calcium re-addition-evoked contractions, indicating that the relaxation response may be mediated through inhibition of calcium influx. Apigenin and luteolin, but not (−)-α-bisabolol, enhanced the relaxation to the nitric oxide donor sodium nitroprusside, indicating that apigenin and luteolin may act to regulate cyclic GMP levels. Umbelliferone produced a rapid, transient relaxation in the splenic artery, but not the coronary artery, that was inhibited by L-NAME and removal of the endothelium, suggesting an influence on nitric oxide production. Farnesene, at concentrations up to 30 μM, was without effect in either blood vessel. In conclusion, hydroxylated compounds (apigenin, luteolin and (−)-α-bisabolol) found in chamomile all caused a slow relaxation of isolated blood vessels through an effect on calcium influx. Umbelliferone, on the other hand, produced a rapid, transient relaxation dependent upon release of nitric oxide from the endothelium. - Highlights: • Apigenin, luteolin, and (-)-α-bisabolol are present in chamomile. • They produced slow, concentration-dependent relaxations in arteries. • These

  3. Distinct mechanisms of relaxation to bioactive components from chamomile species in porcine isolated blood vessels

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, R.E., E-mail: Richard.roberts@nottingham.ac.uk; Allen, S.; Chang, A.P.Y.; Henderson, H.; Hobson, G.C.; Karania, B.; Morgan, K.N.; Pek, A.S.Y.; Raghvani, K.; Shee, C.Y.; Shikotra, J.; Street, E.; Abbas, Z.; Ellis, K.; Heer, J.K.; Alexander, S.P.H., E-mail: steve.alexander@nottingham.ac.uk

    2013-11-01

    German chamomile (Matricaria recutita L.), a widely-used herbal medicine, has been reported to have a wide range of biological effects, including smooth muscle relaxation. The aim of this study was to compare the effects of representative compounds from chamomile (apigenin, luteolin, (−)-α-bisabolol, farnesene, umbelliferone; 3–30 μM) on vascular tone using porcine coronary and splenic arteries mounted for isometric tension recording in isolated tissue baths and precontracted with the thromboxane-mimetic U46619. Apigenin, luteolin, and (−)-α-bisabolol produced slow, concentration-dependent relaxations in both the coronary and splenic arteries that were not blocked by inhibition of nitric oxide synthase or potassium channels. Removal of extracellular calcium inhibited the relaxations to all three compounds, and these compounds also inhibited calcium re-addition-evoked contractions, indicating that the relaxation response may be mediated through inhibition of calcium influx. Apigenin and luteolin, but not (−)-α-bisabolol, enhanced the relaxation to the nitric oxide donor sodium nitroprusside, indicating that apigenin and luteolin may act to regulate cyclic GMP levels. Umbelliferone produced a rapid, transient relaxation in the splenic artery, but not the coronary artery, that was inhibited by L-NAME and removal of the endothelium, suggesting an influence on nitric oxide production. Farnesene, at concentrations up to 30 μM, was without effect in either blood vessel. In conclusion, hydroxylated compounds (apigenin, luteolin and (−)-α-bisabolol) found in chamomile all caused a slow relaxation of isolated blood vessels through an effect on calcium influx. Umbelliferone, on the other hand, produced a rapid, transient relaxation dependent upon release of nitric oxide from the endothelium. - Highlights: • Apigenin, luteolin, and (-)-α-bisabolol are present in chamomile. • They produced slow, concentration-dependent relaxations in arteries. • These

  4. Differential effect of amylin on endothelial-dependent vasodilation in mesenteric arteries from control and insulin resistant rats.

    Directory of Open Access Journals (Sweden)

    Mariam El Assar

    Full Text Available Insulin resistance (IR is frequently associated with endothelial dysfunction and has been proposed to play a major role in cardiovascular disease (CVD. On the other hand, amylin has long been related to IR. However the role of amylin in the vascular dysfunction associated to IR is not well addressed. Therefore, the aim of the study was to assess the effect of acute treatment with amylin on endothelium-dependent vasodilation of isolated mesenteric arteries from control (CR and insulin resistant (IRR rats and to evaluate the possible mechanisms involved. Five week-old male Wistar rats received 20% D-fructose dissolved in drinking water for 8 weeks and were compared with age-matched CR. Plasmatic levels of glucose, insulin and amylin were measured. Mesenteric microvessels were dissected and mounted in wire myographs to evaluate endothelium-dependent vasodilation to acetylcholine. IRR displayed a significant increase in plasmatic levels of glucose, insulin and amylin and reduced endothelium-dependent relaxation when compared to CR. Acute treatment of mesenteric arteries with r-amylin (40 pM deteriorated endothelium-dependent responses in CR. Amylin-induced reduction of endothelial responses was unaffected by the H2O2 scavenger, catalase, but was prevented by the extracellular superoxide scavenger, superoxide dismutase (SOD or the NADPH oxidase inhibitor (VAS2870. By opposite, amylin failed to further inhibit the impaired relaxation in mesenteric arteries of IRR. SOD, or VAS2870, but not catalase, ameliorated the impairment of endothelium-dependent relaxation in IRR. At concentrations present in insulin resistance conditions, amylin impairs endothelium-dependent vasodilation in mircrovessels from rats with preserved vascular function and low levels of endogenous amylin. In IRR with established endothelial dysfunction and elevated levels of amylin, additional exposure to this peptide has no effect on endothelial vasodilation. Increased superoxide

  5. Temperature and momentum transfer dependence of the dynamics of the α-relaxation in polymer melts. A quasielastic neutron scattering study

    Science.gov (United States)

    Colmenero, J.; Alegría, A.; Arbe, A.; Frick, B.

    1992-12-01

    The dynamics of the α-relaxation in three glass-forming polymeric systems, poly(vinyl methyl ether) (PVME), poly(vinyl chloride) (PVC), and poly(bisphenol A, 2-hydroxypropylether) (PH) has been studied by means of quasielastic neutron scattering and compared with the results obtained from relaxation techniques. The results indicate that the dynamics of the α-relaxation in a wide timescale shows a clear non-Debye behaviour and can be well described by means of the same spectral shape, which is found to be independent of temperature and momentum transfer ( Q). Moreover, the Havriliak-Negami characteristic times deduced from the fitting of the experimental data can also be described using only one Vogel-Fulcher functional form. This implies a self-consistent description of the dynamics of the α-relaxation obtained by very different probes. Besides, we found that the Q-dependence of the characteristic times obtained by QENS is given by a power law, τ(Q) ∝ Q - n ( n > 2), n being dependent on the system, and that the Q-behaviour and the non-Debye behaviour are directly correlated. These results have main implications about the physical mechanisms behind the dynamics of the α-relaxation.

  6. The age dependence of T2 relaxation times of N-acetyl aspartate, creatine and choline in the human brain at 3 and 4T

    Czech Academy of Sciences Publication Activity Database

    Jirů, F.; Škoch, A.; Wágnerová, D.; Dezortová, M.; Visková, J.; Profant, Oliver; Syka, Josef; Hájek, M.

    2016-01-01

    Roč. 29, č. 3 (2016), s. 284-292 ISSN 0952-3480 Institutional support: RVO:68378041 Keywords : MRS * T2 relaxation times of metabolites * age dependence of T2 Subject RIV: FH - Neurology Impact factor: 2.872, year: 2016

  7. Perinatal development influences mechanisms of bradykinin-induced relaxations in pulmonary resistance and conduit arteries differently.

    Science.gov (United States)

    Boels, P J; Deutsch, J; Gao, B; Haworth, S G

    2001-07-01

    As bradykinin (BYK) relaxes conduit (EPA) and resistance (RPA) pulmonary arteries from both perinatal and adult lungs, we investigated whether this vasodilator's relaxation-mechanisms were altered during perinatal development, differed between EPA and RPA and differed with other endothelium-dependent vasodilators, acetyicholine (ACH) and substance P (SP). Arteries from mature foetal (5 days), neonatal (approximately 5 min), newborn (60-84 h) and adult pigs (> or =6 months) were isolated, mounted for in vitro isometric force recording, activated with PGF(2alpha) (30 micromol/l) and relaxed with BYK (10 pmol/l-1 micromol/l), SP (10 pmol/l-0.1 micromol/l) or ACH (1 nmol/l-1 mmol/l). (i) BYK: L-NAME (100 micromol/l) attenuated relaxations in foetal EPA ( approximately 55%) but nearly abolished them in the adult ( approximately 80%). In RPA, L-NAME nearly abolished ( approximately 90%) relaxations in the foetus and this effect diminished progressively with age to approximately 20% in the adult. Indomethacin (IND, micromol/l) attenuated relaxations in neonatal (approximately 25%), new-born and adult EPA (both approximately 45%). Together, L-NAME and IND abolished relaxations in all EPA and in neonatal RPA but not in older RPA. SKF525a (100 micromol/l) attenuated relaxations in foetal RPA ( approximately 4%), diminishing in the adult RPA to approximately 10%. Together, SKF52Sa and L-NAME largely abolished relaxations in postnatal RPA (approximately 80%). Activation with K(+)=125 mmol/l attenuated relaxations in adult EPA (approximately 80%), foetal RPA ( approximately 45%) and neonatal RPA (approximately 75%) and abolished relaxations in RPA from older ages. (ii) ACH: L-NAME abolished relaxations in new-born EPA and RPA. In adult EPA, combined L-NAME and IND moderately attenuated relaxations. (iii) SP: Combined application of L-NAME and IND attenuated relaxations to a similar degree in new-born and adult EPA and RPA. In postnatal EPA, BYK-relaxations depend completely on

  8. Energy relaxation and separation of a hot electron-hole pair in organic aggregates from a time-dependent wavepacket diffusion method

    International Nuclear Information System (INIS)

    Han, Lu; Liang, WanZhen; Zhao, Yi; Zhong, Xinxin

    2014-01-01

    The time-dependent wavepacket diffusive method [X. Zhong and Y. Zhao, J. Chem. Phys. 138, 014111 (2013)] is extended to investigate the energy relaxation and separation of a hot electron-hole pair in organic aggregates with incorporation of Coulomb interaction and electron-phonon coupling. The pair initial condition generated by laser pulse is represented by a Gaussian wavepacket with a central momentum. The results reveal that the hot electron energy relaxation is very well described by two rate processes with the fast rate much larger than the slow one, consistent with experimental observations, and an efficient electron-hole separation is accomplished accompanying the fast energy relaxation. Furthermore, although the extra energy indeed helps the separation by overcoming the Coulomb interaction, the width of initial wavepacket is much sensitive to the separation efficiency and the narrower wavepacket generates the more separated charges. This behavior may be useful to understand the experimental controversy of the hot carrier effect on charge separation

  9. Pulmonary allergic reactions impair systemic vascular relaxation in ragweed sensitive mice.

    Science.gov (United States)

    Hazarika, Surovi; Van Scott, Michael R; Lust, Robert M; Wingard, Christopher J

    2010-01-01

    Asthma is often associated with cardiovascular complications, and recent observations in animal models indicate that induction of pulmonary allergic inflammation increases susceptibility of the myocardium to ischemia and reperfusion injury. In this study, we used a murine model of allergen sensitization in which aspiration of allergen induces pulmonary and systemic inflammation, to test the hypothesis that pulmonary exposure to allergen alters vascular relaxation responses. BALB/C mice were sensitized by intraperitoneal injection of ragweed and challenged by intratracheal instillation of allergen. Airway hyperreactivity and pulmonary inflammation were confirmed, and endothelium-dependent and -independent reactivity of thoracic aorta rings were evaluated. Ragweed sensitization and challenge induced airway hyperreactivity to methacholine and pulmonary inflammation, but did not affect constrictor responses of the aortic rings to phenylephrine and K+ depolarization. In contrast, maximal relaxation of aortic rings to acetylcholine and sodium nitroprusside decreased from 87.6±3.9% and 97.7±1.2% to 32±4% and 51±6%, respectively (p<0.05). The sensitivity to acetylcholine was likewise reduced (EC₅₀=0.26±0.05 μM vs. 1.09±0.16 μM, p<0.001). The results demonstrate that induction of allergic pulmonary inflammation in mice depresses endothelium-dependent and -independent vascular relaxation, which can contribute to cardiovascular complications associated with allergic inflammation. Copyright © 2010 Elsevier Inc. All rights reserved.

  10. Effect of an Ethanol Extract of Scutellaria baicalensis on Relaxation in Corpus Cavernosum Smooth Muscle

    Directory of Open Access Journals (Sweden)

    Xiang Li

    2012-01-01

    Full Text Available Aims of study. The aim of the present study was to investigate whether an ethanol extract of Scutellaria baicalensis (ESB relaxes penile corpus cavernosum muscle in organ bath experiments. Materials and methods. Changes in tension of cavernous smooth muscle strips were determined by penile strip chamber model and in penile perfusion model. Isolated endothelium-intact rabbit corpus cavernosum was precontracted with phenylephrine (PE and then treated with ESB. Results. ESB relaxed penile smooth muscle in a dose-dependent manner, and this was inhibited by pre-treatment with NG-nitro-l-arginine methyl ester (l-NAME, a nitric oxide (NO synthase inhibitor, and 1H-[1, 2, 4]-oxadiazolo-[4,3-α]-quinoxalin-1-one (ODQ, a soluble guanylyl cyclase (sGC inhibitor. ESB-induced relaxation was significantly attenuated by pretreatment with tetraethylammonium (TEA, a nonselective K+ channel blocker, and charybdotoxin, a selective Ca2+-dependent K+ channel inhibitor. ESB increased the cGMP levels of rabbit corpus cavernosum in a concentration-dependent manner without changes in cAMP levels. In a perfusion model of penile tissue, ESB also relaxed penile corpus cavernosum smooth muscle in a dose-dependent manner. Conclusion. Taken together, these results suggest that ESB relaxed rabbit cavernous smooth muscle via the NO/cGMP system and Ca2+-sensitive K+ channels in the corpus cavernosum.

  11. The contrasting roles of creep and stress relaxation in the time-dependent deformation during in-situ cooling of a nickel-base single crystal superalloy.

    Science.gov (United States)

    Panwisawas, Chinnapat; D'Souza, Neil; Collins, David M; Bhowmik, Ayan

    2017-09-11

    Time dependent plastic deformation in a single crystal nickel-base superalloy during cooling from casting relevant temperatures has been studied using a combination of in-situ neutron diffraction, transmission electron microscopy and modelling. Visco-plastic deformation during cooling was found to be dependent on the stress and constraints imposed to component contraction during cooling, which mechanistically comprises creep and stress relaxation. Creep results in progressive work hardening with dislocations shearing the γ' precipitates, a high dislocation density in the γ channels and near the γ/γ' interface and precipitate shearing. When macroscopic contraction is restricted, relaxation dominates. This leads to work softening from a decreased dislocation density and the presence of long segment stacking faults in γ phase. Changes in lattice strains occur to a similar magnitude in both the γ and γ' phases during stress relaxation, while in creep there is no clear monotonic trend in lattice strain in the γ phase, but only a marginal increase in the γ' precipitates. Using a visco-plastic law derived from in-situ experiments, the experimentally measured and calculated stresses during cooling show a good agreement when creep predominates. However, when stress relaxation dominates accounting for the decrease in dislocation density during cooling is essential.

  12. Diet-induced obesity impairs endothelium-derived hyperpolarization via altered potassium channel signaling mechanisms.

    Directory of Open Access Journals (Sweden)

    Rebecca E Haddock

    Full Text Available BACKGROUND: The vascular endothelium plays a critical role in the control of blood flow. Altered endothelium-mediated vasodilator and vasoconstrictor mechanisms underlie key aspects of cardiovascular disease, including those in obesity. Whilst the mechanism of nitric oxide (NO-mediated vasodilation has been extensively studied in obesity, little is known about the impact of obesity on vasodilation to the endothelium-derived hyperpolarization (EDH mechanism; which predominates in smaller resistance vessels and is characterized in this study. METHODOLOGY/PRINCIPAL FINDINGS: Membrane potential, vessel diameter and luminal pressure were recorded in 4(th order mesenteric arteries with pressure-induced myogenic tone, in control and diet-induced obese rats. Obesity, reflecting that of human dietary etiology, was induced with a cafeteria-style diet (∼30 kJ, fat over 16-20 weeks. Age and sexed matched controls received standard chow (∼12 kJ, fat. Channel protein distribution, expression and vessel morphology were determined using immunohistochemistry, Western blotting and ultrastructural techniques. In control and obese rat vessels, acetylcholine-mediated EDH was abolished by small and intermediate conductance calcium-activated potassium channel (SK(Ca/IK(Ca inhibition; with such activity being impaired in obesity. SK(Ca-IK(Ca activation with cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl-6-methyl-pyrimidin-4-yl]-amine (CyPPA and 1-ethyl-2-benzimidazolinone (1-EBIO, respectively, hyperpolarized and relaxed vessels from control and obese rats. IK(Ca-mediated EDH contribution was increased in obesity, and associated with altered IK(Ca distribution and elevated expression. In contrast, the SK(Ca-dependent-EDH component was reduced in obesity. Inward-rectifying potassium channel (K(ir and Na(+/K(+-ATPase inhibition by barium/ouabain, respectively, attenuated and abolished EDH in arteries from control and obese rats, respectively; reflecting differential K

  13. Heteronuclear relaxation in time-dependent spin systems: 15N-T1ρ dispersion during adiabatic fast passage

    International Nuclear Information System (INIS)

    Konrat, Robert; Tollinger, Martin

    1999-01-01

    A novel NMR experiment comprising adiabatic fast passage techniques for the measurement of heteronuclear self-relaxation rates in fully 15N-enriched proteins is described. Heteronuclear self-relaxation is monitored by performing adiabatic fast passage (AFP) experiments at variable adiabaticity (e.g., variation of RF spin-lock field intensity). The experiment encompasses gradient- selection and sensitivity-enhancement. It is shown that transverse relaxation rates derived with this method are in good agreement with the ones measured by the classical Carr-Purcell-Meiboom-Gill (CPMG) sequences. An application of this method to the study of the carboxyl-terminal LIM domain of quail cysteine and glycine-rich protein qCRP2(LIM2) is presented

  14. The relaxation time approximation

    International Nuclear Information System (INIS)

    Gairola, R.P.; Indu, B.D.

    1991-01-01

    A plausible approximation has been made to estimate the relaxation time from a knowledge of the transition probability of phonons from one state (r vector, q vector) to other state (r' vector, q' vector), as a result of collision. The relaxation time, thus obtained, shows a strong dependence on temperature and weak dependence on the wave vector. In view of this dependence, relaxation time has been expressed in terms of a temperature Taylor's series in the first Brillouin zone. Consequently, a simple model for estimating the thermal conductivity is suggested. the calculations become much easier than the Callaway model. (author). 14 refs

  15. P2X1 receptors and the endothelium

    Directory of Open Access Journals (Sweden)

    LS Harrington

    2005-03-01

    Full Text Available Adenosine triphosphate (ATP is now established as a principle vaso-active mediator in the vasculature. Its actions on arteries are complex, and are mediated by the P2X and P2Y receptor families. It is generally accepted that ATP induces a bi-phasic response in arteries, inducing contraction via the P2X and P2Y receptors on the smooth muscle cells, and vasodilation via the actions of P2Y receptors located on the endothelium. However, a number of recent studies have placed P2X1 receptors on the endothelium of some arteries. The use of a specific P2X1 receptor ligand, a, b methylene ATP has demonstrated that P2X1 receptors also have a bi-functional role. The actions of ATP on P2X1 receptors is therefore dependant on its location, inducing contraction when located on the smooth muscle cells, and dilation when expressed on the endothelium, comparable to that of P2Y receptors.

  16. Hypertrophy of cultured bovine aortic endothelium following irradiation

    International Nuclear Information System (INIS)

    Rosen, E.M.; Vinter, D.W.; Goldberg, I.D.

    1989-01-01

    The vascular endothelium is a vital multifunctional tissue which covers the entire luminal surface of the circulatory system. Loss of continuity of the endothelial lining normally results in cell migration and proliferation to make up for cell loss and to ensure that exposure of the thrombogenic subendothelium to platelets and clotting factors is minimized. We showed that ionizing radiation (400-3000 cGy) causes dose-dependent cell loss from confluent monolayer cultures of bovine aortic endothelium, which cannot immediately be compensated by cell proliferation. Within 24 h, the remaining attached cells undergo substantial somatic hypertrophy (evidenced by increased protein content, cell volume, and attachment area) but remain diploid. If cell loss is not excessive, monolayer continuity is restored within several days. Although reduced protein degradation may contribute, most of the protein accumulation is due to synthesis of new protein. Unlike endothelium, irradiation of smooth muscle cultures causes neither cell loss nor increased protein synthesis. Hypertrophy of irradiated endothelial cells appears to be a consequence of a proliferative stimulus (cell loss) in a population of cells which is unable to divide. It can be modulated by replating irradiated cells at different densities. We suggest that endothelial hypertrophy is an early vascular homeostatic response before clonal proliferation of surviving cells or repopulation by cells from outside of the irradiated field can compensate for cell loss

  17. Jabuticaba-Induced Endothelium-Independent Vasodilating Effect on Isolated Arteries.

    Science.gov (United States)

    Andrade, Daniela Medeiros Lobo de; Borges, Leonardo Luis; Torres, Ieda Maria Sapateiro; Conceição, Edemilson Cardoso da; Rocha, Matheus Lavorenti

    2016-09-01

    Despite the important biological effects of jabuticaba, its actions on the cardiovascular system have not been clarified. To determine the effects of jabuticaba hydroalcoholic extract (JHE) on vascular smooth muscle (VSM) of isolated arteries. Endothelium-denuded aortic rings of rats were mounted in isolated organ bath to record isometric tension. The relaxant effect of JHE and the influence of K+ channels and Ca2+ intra- and extracellular sources on JHE-stimulated response were assessed. Arteries pre-contracted with phenylephrine showed concentration-dependent relaxation (0.380 to 1.92 mg/mL). Treatment with K+ channel blockers (tetraethyl-ammonium, glibenclamide, 4-aminopyridine) hindered relaxation due to JHE. In addition, phenylephrine-stimulated contraction was hindered by previous treatment with JHE. Inhibition of sarcoplasmic reticulum Ca2+ ATPase did not change relaxation due to JHE. In addition, JHE inhibited the contraction caused by Ca2+ influx stimulated by phenylephrine and KCl (75 mM). JHE induces endothelium-independent vasodilation. Activation of K+ channels and inhibition of Ca2+ influx through the membrane are involved in the JHE relaxant effect. Embora a jabuticaba apresente importantes efeitos biológicos, suas ações sobre o sistema cardiovascular ainda não foram esclarecidas. Determinar os efeitos do extrato de jabuticaba (EHJ) sobre o músculo liso vascular (MLV) em artérias isoladas. Aortas (sem endotélio) de ratos foram montadas em banho de órgãos isolados para registro de tensão isométrica. Foram verificados o efeito relaxante, a influência dos canais de K+ e das fontes de Ca2+ intra- e extracelular sob a resposta estimulada pelo EHJ. Artérias pré-contraídas com fenilefrina apresentaram relaxamento concentração-dependente (0,380 a 1,92 mg/mL). O tratamento com bloqueadores de canais de K+ (tetraetilamônio, glibenclamida, 4-aminopiridina) prejudicaram o relaxamento pelo EHJ. A contração estimulada com fenilefrina tamb

  18. Maternal nutrient restriction during pregnancy impairs an endothelium-derived hyperpolarizing factor-like pathway in sheep fetal coronary arteries.

    Science.gov (United States)

    Shukla, Praveen; Ghatta, Srinivas; Dubey, Nidhi; Lemley, Caleb O; Johnson, Mary Lynn; Modgil, Amit; Vonnahme, Kimberly; Caton, Joel S; Reynolds, Lawrence P; Sun, Chengwen; O'Rourke, Stephen T

    2014-07-15

    The mechanisms underlying developmental programming are poorly understood but may be associated with adaptations by the fetus in response to changes in the maternal environment during pregnancy. We hypothesized that maternal nutrient restriction during pregnancy alters vasodilator responses in fetal coronary arteries. Pregnant ewes were fed a control [100% U.S. National Research Council (NRC)] or nutrient-restricted (60% NRC) diet from days 50 to 130 of gestation (term = 145 days); fetal tissues were collected at day 130. In coronary arteries isolated from control fetal lambs, relaxation to bradykinin was unaffected by nitro-l-arginine (NLA). Iberiotoxin or contraction with KCl abolished the NLA-resistant response to bradykinin. In fetal coronary arteries from nutrient-restricted ewes, relaxation to bradykinin was fully suppressed by NLA. Large-conductance, calcium-activated potassium channel (BKCa) currents did not differ in coronary smooth muscle cells from control and nutrient-restricted animals. The BKCa openers, BMS 191011 and NS1619, and 14,15-epoxyeicosatrienoic acid [a putative endothelium-derived hyperpolarizing factor (EDHF)] each caused fetal coronary artery relaxation and BKCa current activation that was unaffected by maternal nutrient restriction. Expression of BKCa-channel subunits did not differ in fetal coronary arteries from control or undernourished ewes. The results indicate that maternal undernutrition during pregnancy results in loss of the EDHF-like pathway in fetal coronary arteries in response to bradykinin, an effect that cannot be explained by a decreased number or activity of BKCa channels or by decreased sensitivity to mediators that activate BKCa channels in vascular smooth muscle cells. Under these conditions, bradykinin-induced relaxation is completely dependent on nitric oxide, which may represent an adaptive response to compensate for the absence of the EDHF-like pathway. Copyright © 2014 the American Physiological Society.

  19. Spin-polarization dependent carrier recombination dynamics and spin relaxation mechanism in asymmetrically doped (110) n-GaAs quantum wells

    Science.gov (United States)

    Teng, Lihua; Jiang, Tianran; Wang, Xia; Lai, Tianshu

    2018-05-01

    Carrier recombination and electron spin relaxation dynamics in asymmetric n-doped (110) GaAs/AlGaAs quantum wells are investigated with time-resolved pump-probe spectroscopy. The experiment results reveal that the measured carrier recombination time depends strongly on the polarization of pump pulse. With the same pump photon flux densities, the recombination time of spin-polarized carriers is always longer than that of the spin-balanced carriers except at low pump photon flux densities, this anomaly originates from the polarization-sensitive nonlinear absorption effect. Differing from the traditional views, in the low carrier density regime, the D'yakonov-Perel' (DP) mechanism can be more important than the Bir-Aronov-Pikus (BAP) mechanism, since the DP mechanism takes effect, the spin relaxation time in (110) GaAs QWs is shortened obviously via asymmetric doping.

  20. Magnetic relaxation in anisotropic magnets

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1971-01-01

    The line shape and the kinematic and thermodynamic slowing down of the critical and paramagnetic relaxation in axially anisotropic materials are discussed. Kinematic slowing down occurs only in the longitudinal relaxation function. The thermodynamic slowing down occurs in either the transverse...... or longitudinal relaxation function depending on the sign of the axial anisotropy....

  1. Semi-quantitative assessments of dextran toxicity on corneal endothelium: conceptual design of a predictive algorithm.

    Science.gov (United States)

    Filev, Filip; Oezcan, Ceprail; Feuerstacke, Jana; Linke, Stephan J; Wulff, Birgit; Hellwinkel, Olaf J C

    2017-03-01

    Dextran is added to corneal culture medium for at least 8 h prior to transplantation to ensure that the cornea is osmotically dehydrated. It is presumed that dextran has a certain toxic effect on corneal endothelium but the degree and the kinetics of this effect have not been quantified so far. We consider that such data regarding the toxicity of dextran on the corneal endothelium could have an impact on scheduling and logistics of corneal preparation in eye banking. In retrospective statistic analyses, we compared the progress of corneal endothelium (endothelium cell loss per day) of 1334 organ-cultured corneal explants in media with and without dextran. Also, the influence of donor-age, sex and cause of death on the observed dextran-mediated effect on endothelial cell counts was studied. Corneas cultured in dextran-free medium showed a mean endothelium cell count decrease of 0.7% per day. Dextran supplementation led to a mean endothelium cell loss of 2.01% per day; this reflects an increase by the factor of 2.9. The toxic impact of dextran was found to be time dependent; while the prevailing part of the effect was observed within the first 24 h after dextran-addition. Donor age, sex and cause of death did not seem to have an influence on the dextran-mediated toxicity. Based on these findings, we could design an algorithm which approximately describes the kinetics of dextran-toxicity. We reproduced the previously reported toxic effect of dextran on the corneal endothelium in vitro. Additionally, this is the first work that provides an algorithmic instrument for the semi-quantitative calculation of the putative endothelium cell count decrease in dextran containing medium for a given incubation time and could thus influence the time management and planning of corneal transplantations.

  2. Effect of hypothyroidism on the nitrergic relaxant responses of corpus cavernosal smooth muscle in rabbits.

    Science.gov (United States)

    Sarac, Bulent; Yildirim, Mustafa K; Bagcivan, Ihsan; Kaya, Kemal; Kilicarslan, Hakan; Yildirim, Sahin

    2006-01-01

    The incidence of hormonal dysfunction as a cause of impotence remains controversial. However, several recent studies have reported evidence of hormonal abnormalities in 25-35% of impotent men. Hypothyroidism has been reported to occur in 6% of impotent men. In the present study, we examined nitrergic responses in hypothyroidism in rabbit corpus cavernosum and compared them with controls. Carbachol-induced relaxation responses and electrical field stimulation (EFS)-induced frequency-dependent relaxations decreased significantly in hypothyroid rabbits. Papaverine and sodium nitroprusside (SNP)-induced relaxation responses did not change significantly in hypothyroid rabbits. The contraction responses of phenylephrine and EFS-induced frequency-dependent contractions were significantly decreased in the hypothyroid group. We can speculate that the reduction of relaxant responses to EFS and carbachol in hypothyroid rabbits can depend on a decreased release of nitric oxide (NO) from nitrergic nerves and endothelium or a reduction of muscarinic receptor density. Also, decreases in contraction responses may depend on diminished adrenoceptor density.

  3. Peroxynitrite-induced relaxation in isolated canine cerebral arteries and mechanisms of action

    International Nuclear Information System (INIS)

    Li Jianfeng; Li Wenyan; Altura, Bella T.; Altura, Burton M.

    2004-01-01

    The present study was undertaken to determine the vascular actions of peroxynitrite (ONOO - ), the product of superoxide and nitric oxide (NO), in isolated canine cerebral arteries and to gain insight into its potential mechanisms of action. In the absence of any vasoactive agent, ONOO - (from 10 -7 to 10 -6 M) was able to reduce the basal tension. In prostaglandin F2α-precontracted canine basilar arterial rings, ONOO - elicited concentration-dependent relaxation at concentrations from 10 -8 to 10 -5 M. The effective concentrations producing approximately 50% maximal relaxation (EC 50 ) to ONOO - were 4.06 x 10 -6 and 4.12 x 10 -6 M in intact and denuded rings, respectively (P > 0.05). No significant differences in relaxation responses were found in ring preparations with or without endothelium (P > 0.05). The presence of either 5 μM methylene blue (MB) or 5 μM 1H-[1,2,4]oxadiazolo-[4,3-α]quinoxalin-1-one (ODQ) significantly inhibited the relaxations induced by ONOO - . Tetraethylammonium chloride (T-2265) significantly decreased the ONOO - -induced relaxations in a concentration-dependent manner. However, ONOO - had no effect on rings precontracted by high KCL (P > 0.05). Addition of low concentrations of calyculin A (50 nM) was able to abolish the ONOO - -induced relaxation. Furthermore, ONOO - significantly inhibited calcium-induced contractions of K + -depolarized canine cerebral rings in a concentration-related manner. Lastly, a variety of pharmacological agents and antagonists including L-NMMA, L-arginine, indomethacin, atropine, naloxone, diphenhydramine, cimetine, glibenclamide, haloperidol, etc., did not influence the relaxant effects of ONOO - on the rings. Our new results suggest that ONOO - -triggered relaxation, on canine cerebral arteries, is mediated by elevation of cyclic guanosine monophosphate (cGMP) levels, membrane hyperpolarization via K+ channel activation, activation of myosin light chain phosphatase activity, and interference with

  4. The dependence of shear modulus on dynamic relaxation and evolution of local structural heterogeneity in a metallic glass

    International Nuclear Information System (INIS)

    Huo, L.S.; Zeng, J.F.; Wang, W.H.; Liu, C.T.; Yang, Y.

    2013-01-01

    Starting from the nanoscale structural heterogeneities intrinsic to metallic glasses (MGs), here we show that there are two concurrent contributions to their microscale quasi-static shear modulus G I : one (μ) is related to the atomic bonding strength of solid-like regions and the other (G II ) to the change in the possible configurations of liquid-like regions (dynamic relaxation). Through carefully designed high-rate nanoscale indentation tests, a simple constitutive relation (μ = G I + G II ) is experimentally verified. On a fundamental level, our current work provides a structure–property correlation that may be applicable to a wide range of glassy materials

  5. Composition-dependent hot carrier relaxation dynamics in cesium lead halide (CsPbX{sub 3}, X=Br and I) perovskite nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Heejae; Jung, Seok Il; Kim, Hyo Jin; Cha, Wonhee; Sim, Eunji; Kim, Dongho [Department of Chemistry, Yonsei University, Seoul (Korea, Republic of); Koh, Weon-Kyu [Device Laboratory, Samsung Advanced Institute of Technology, Suwon (Korea, Republic of); Kim, Jiwon [School of Integrated Technology and Underwood International College, Yonsei University, Incheon (Korea, Republic of)

    2017-04-03

    Cesium-based perovskite nanocrystals (NCs) have outstanding photophysical properties improving the performances of lighting devices. Fundamental studies on excitonic properties and hot-carrier dynamics in perovskite NCs further suggest that these materials show higher efficiencies compared to the bulk form of perovskites. However, the relaxation rates and pathways of hot-carriers are still being elucidated. By using ultrafast transient spectroscopy and calculating electronic band structures, we investigated the dependence of halide in Cs-based perovskite (CsPbX{sub 3} with X=Br, I, or their mixtures) NCs on the hot-carrier relaxation processes. All samples exhibit ultrafast (<0.6 ps) hot-carrier relaxation dynamics with following order: CsPbBr{sub 3} (310 fs)>CsPbBr{sub 1.5}I{sub 1.5} (380 fs)>CsPbI{sub 3} NC (580 fs). These result accounts for a reduced light emission efficiency of CsPbI{sub 3} NC compared to CsPbBr{sub 3} NC. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Thickness Dependence of Magnetic Relaxation and E-J Characteristics in Superconducting (Gd-Y)-Ba-Cu-O Films with Strong Vortex Pinning

    Energy Technology Data Exchange (ETDEWEB)

    Polat, Ozgur [ORNL; Sinclair IV, John W [ORNL; Zuev, Yuri L [ORNL; Thompson, James R [ORNL; Christen, David K [ORNL; Cook, Sylvester W [ORNL; Kumar, Dhananjay [ORNL; Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York

    2011-01-01

    The dependence of the critical current density Jc on temperature, magnetic field, and film thickness has been investigated in (Gd-Y)BaCu-oxide materials of 0.7, 1.4, and 2.8 m thickness. Generally, the Jc decreases with film thickness at investigated temperatures and magnetic fields. The nature and strength of the pinning centers for vortices have been identified through angular and temperature measurements, respectively. These films do not exhibit c-axis correlated vortex pinning, but do have correlated defects oriented near the ab-planes. For all film thicknesses studied, strong pinning dominates at most temperatures. The vortex dynamics were investigated through magnetic relaxation studies in the temperature range of 5 77 K in 1 T and 3 T applied magnetic fields, H || surface-normal. The creep rate S is thickness dependent at high temperatures, implying that the pinning energy is also thickness dependent. Maley analyses of the relaxation data show an inverse power law variation for the effective pinning energy Ueff ~ (J0/J) . Finally, the electric field-current density (E-J) characteristics were determined over a wide range of dissipation by combining experimental results from transport, swept field magnetometry (VSM), and Superconducting Quantum Interference Device (SQUID) magnetometry. We develop a self-consistent model of the combined experimental results, leading to an estimation of the critical current density Jc0(T) in the absence of flux creep.

  7. In vivo field dependence of proton relaxation times in human brain, liver and skeletal muscle: a multicenter study

    DEFF Research Database (Denmark)

    Henriksen, O; de Certaines, J D; Spisni, A

    1993-01-01

    and MRS, the in vivo field dispersion of T1 and T2 has been measured in order to evaluate whether ex vivo data are representative for the in vivo situation. Brain, skeletal muscle, and liver of healthy human volunteers were studied. Fifteen MR units with a field strength ranging from 0.08 T to 1.5 T took......T1 and T2 relaxation times are fundamental parameters for signal contrast behaviour in MRI. A number of ex vivo relaxometry studies have dealt with the magnetic field dispersion of T1. By means of multicenter study within the frame of the COMAC BME Concerted Action on Tissue Characterization by MRI......, whereas no significant variations were seen for T2. Our in vivo data were generally in reasonable agreement with proposed models based on ex vivo measurements....

  8. 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.

    Science.gov (United States)

    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.

  9. Nitric oxide-dependent vasorelaxation induced by extractive solutions and fractions of Maytenus ilicifolia Mart ex Reissek (Celastraceae) leaves.

    Science.gov (United States)

    Rattmann, Yanna D; Cipriani, Thales R; Sassaki, Guilherme L; Iacomini, Marcello; Rieck, Lia; Marques, Maria C A; da Silva-Santos, José E

    2006-04-06

    This study reveals that an ethanolic supernatant obtained from an aqueous extractive solution prepared from residues of methanolic extracts of ground leaves of Maytenus ilicifolia is able to cause a concentration- and endothelium-dependent relaxation in pre-contract rat aorta rings, with EC(50) of 199.7 (190-210) microg/ml. The non-selective nitric oxide synthase inhibitors l-NAME and l-NMMA abolished this effect, while superoxide dismutase and MnTBAP (a non-enzymatic superoxide dismutase mimetic) enhanced it. Further, relaxation induced by this ethanolic supernatant have been strongly inhibited by the guanylate cyclase inhibitors methylene blue and ODQ, as well as by the potassium channel blockers 4-aminopyridine and tetraethylammonium, but was unchanged by the cyclooxygenase inhibitor indomethacin and the membrane receptor antagonists atropine, HOE-140 and pirilamine. Partition of the ethanolic supernatant between H(2)O and EtOAc generated a fraction several times more potent, able to fully relax endothelium-intact aorta rings with an EC(50) of 4.3 (3.9-4.8) microg/ml. (13)C NMR spectrum of this fraction showed signals typical of catechin. This study reveals that the leaves of M. ilicifolia possess one or more potent substances able to relax endothelium-intact rat aorta rings, an event that appears to involve nitric oxide production, guanylate cyclase activation and potassium channel opening.

  10. Density-dependent lines of one- and two-electron ions in diagnostics of laboratory plasma. I. The rates of collision relaxation of excited levels

    Energy Technology Data Exchange (ETDEWEB)

    Shevelko, V P; Skobelev, I Yu; Vinogradov, A V [Lebedev Physical Institute, Academy of Sciences of the USSR, Moscow, USSR

    1977-01-01

    Plasma devices with inertial plasma confinement such as laser produced plasmas, exploding wires, plasma focus, etc., which have been rapidly developed during recent years., appear to be very intensive sources of spectral line radiation in far UV and X-ray regions. Analysis of this radiation provides a good tool for plasma diagnostics with very high electron densities up to 10/sup 22/cm/sup -3/. In this work, consisting of two parts, the authors consider the mechanism of the formation of spectral lines in hot and dense plasma. The key point for density diagnostics is the fact that for some ion levels the rate of collisional relaxation has the same order of magnitude as the radiative decay. Thus the intensities of spectral lines arising from these levels show a strong dependence on electron density which makes diagnostics possible. In this paper, emphasis is laid on the calculation of rates of transition between close ion levels induced by electron or ion impact, which usually gives the main contribution to the collisional relaxation constants. The influence of plasma polarization effects on the collision frequency in a dense plasma is also considered.

  11. Proton nuclear magnetic resonance study on the barrier function of pig corneal epithelium and endothelium

    International Nuclear Information System (INIS)

    Yokoi, Norihiko; Kinoshita, Shigeru; Morimoto, Taketoshi; Yoshizaki, Kazuo.

    1995-01-01

    Using gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) as a tracer, the barrier function of the corneal epithelium and endothelium was evaluated by proton nuclear magnetic resonance. Whole pig eyes and cornea excised with scleral rim, which had been incubated in dextran-added Gd-DTPA solution, were subjected to T 1 relaxation measurement and magnetic resonance imaging (MRI). After incubation, the T 1 relaxation rate (1/T 1 ) of the excised cornea increased to a steady value, whereas that of the cornea from the whole eye increased only slightly. These results indicated that the increase in the T 1 relaxation rate of the excised cornea was attributable to Gd-DTPA penetration from the corneal endothelium and that the corneal epithelium exhibited a strong barrier function against Gd-DTPA entry. The MRI study also confirmed the strong barrier, enhanced signals being detected within the aqueous fluid in the T 1 -weighted image only when the corneal epithelium was abraded. Since Gd-DTPA scarcely penetrates the intact corneal epithelium, Gd-DTPA-enhanced MRI shows potential as a quantitative tracer in evaluating epithelial barrier disruption. (author)

  12. Local NMR relaxation rates T1-1 and T2-1 depending on the d -vector symmetry in the vortex state of chiral and helical p -wave superconductors

    Science.gov (United States)

    Tanaka, Kenta K.; Ichioka, Masanori; Onari, Seiichiro

    2018-04-01

    Local NMR relaxation rates in the vortex state of chiral and helical p -wave superconductors are investigated by the quasiclassical Eilenberger theory. We calculate the spatial and resonance frequency dependences of the local NMR spin-lattice relaxation rate T1-1 and spin-spin relaxation rate T2-1. Depending on the relation between the NMR relaxation direction and the d -vector symmetry, the local T1-1 and T2-1 in the vortex core region show different behaviors. When the NMR relaxation direction is parallel to the d -vector component, the local NMR relaxation rate is anomalously suppressed by the negative coherence effect due to the spin dependence of the odd-frequency s -wave spin-triplet Cooper pairs. The difference between the local T1-1 and T2-1 in the site-selective NMR measurement is expected to be a method to examine the d -vector symmetry of candidate materials for spin-triplet superconductors.

  13. Relaxation System

    Science.gov (United States)

    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.

  14. The study of the functional state of the endothelium via a complex of markers with reactive hyperemia

    Directory of Open Access Journals (Sweden)

    Berezhniy V.

    2016-03-01

    Full Text Available Diagnosis of endothelial dysfunction is a key point in the prevention and treatment of cardiovascular diseases. In scientific research the study of the state of the endothelium used test with reactive hyperemia of brachial artery wich present as the value of endothelium dependent and independent artery dilatation. However, the disadvantage of this marker is ignoring the size of arteries, well know that small arteries has a greater degree of dilation more than big arterias, this fact making difficult to compare results between different patients. The aim of our study was to examine the state of endothelium using a complex of markers, compare them informative in children with JRA who are at risk for the development of endothelial dysfunction. Materials and Methods. The study was included 40 children with juvenile rheumatoid arthritis who were treated at the department of children's cardiorheumatology Kyiv City Children's Hospital #1 and Kiev Regional Hospital m. Boyarka. Results. The study found a development of endothelial dysfunction changes in endothelium dependent vasodilation, reactive hyperemia and coefficient of vasodilation. Simultaneous marked change of endothelium vasodilation of the brachial artery and coefficient of vasodilatation. There were no pathological changes in endothelial shear stress in patients compared with healthy children. Conclusions. Evaluate the state of the endothelium is necessary with the help of a set of indicators (RH, EDVD, VC that will help to avoid diagnostic mistakes during the test with the reactive hyperemia.

  15. Hyperhomocysteinemia potentiates diabetes-impaired EDHF-induced vascular relaxation: Role of insufficient hydrogen sulfide

    Directory of Open Access Journals (Sweden)

    Zhongjian Cheng

    2018-06-01

    Full Text Available Insufficient hydrogen sulfide (H2S has been implicated in Type 2 diabetic mellitus (T2DM and hyperhomocysteinemia (HHcy-related cardiovascular complications. We investigated the role of H2S in T2DM and HHcy-induced endothelial dysfunction in small mesenteric artery (SMA of db/db mice fed a high methionine (HM diet. HM diet (8 weeks induced HHcy in both T2DM db/db mice and non-diabetic db/+ mice (total plasma Hcy: 48.4 and 31.3 µM, respectively, and aggravated the impaired endothelium-derived hyperpolarization factor (EDHF-induced endothelium-dependent relaxation to acetylcholine (ACh, determined by the presence of eNOS inhibitor N(ω-nitro-L-arginine methyl ester (L-NAME and prostacyclin (PGI2 inhibitor indomethacin (INDO, in SMA from db/db mice but not that from db/+ mice. A non-selective Ca2+-active potassium channel (KCa opener NS309 rescued T2DM/HHcy-impaired EDHF-mediated vascular relaxation to ACh. EDHF-induced relaxation to ACh was inhibited by a non-selective KCa blocker TEA and intermediate-conductance KCa blocker (IKCa Tram-34, but not by small-conductance KCa (SKCa blocker Apamin. HHcy potentiated the reduction of free sulfide, H2S and cystathionine γ-lyase protein, which converts L-cysteine to H2S, in SMA of db/db mice. Importantly, a stable H2S donor DATS diminished the enhanced O2- production in SMAs and lung endothelial cells of T2DM/HHcy mice. Antioxidant PEG-SOD and DATS improved T2DM/HHcy impaired relaxation to ACh. Moreover, HHcy increased hyperglycemia-induced IKCa tyrosine nitration in human micro-vascular endothelial cells. EDHF-induced vascular relaxation to L-cysteine was not altered, whereas such relaxation to NaHS was potentiated by HHcy in SMA of db/db mice which was abolished by ATP-sensitive potassium channel blocker Glycolamide but not by KCa blockers. Conclusions: Intermediate HHcy potentiated H2S reduction via CSE-downregulation in microvasculature of T2DM mice. H2S is justified as an EDHF. Insufficient H2S

  16. The dependence of the ultrafast relaxation kinetics of the S2 and S1 states in β-carotene homologs and lycopene on conjugation length studied by femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies

    Science.gov (United States)

    Kosumi, Daisuke; Fujiwara, Masazumi; Fujii, Ritsuko; Cogdell, Richard J.; Hashimoto, Hideki; Yoshizawa, Masayuki

    2009-06-01

    The ultrafast relaxation kinetics of all-trans-β-carotene homologs with varying numbers of conjugated double bonds n(n =7-15) and lycopene (n =11) has been investigated using femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies, both carried out under identical excitation conditions. The nonradiative relaxation rates of the optically allowed S2(1Bu+1) state were precisely determined by the time-resolved fluorescence. The kinetics of the optically forbidden S1(2Ag-1) state were observed by the time-resolved absorption measurements. The dependence of the S1 relaxation rates upon the conjugation length is adequately described by application of the energy gap law. In contrast to this, the nonradiative relaxation rates of S2 have a minimum at n =9 and show a reverse energy gap law dependence for values of n above 11. This anomalous behavior of the S2 relaxation rates can be explained by the presence of an intermediate state (here called the Sx state) located between the S2 and S1 states at large values of n (such as n =11). The presence of such an intermediate state would then result in the following sequential relaxation pathway S2→Sx→S1→S0. A model based on conical intersections between the potential energy curves of these excited singlet states can readily explain the measured relationships between the decay rates and the energy gaps.

  17. Nitric oxide-dependent vasodilation and Ca2+ signalling induced by erythrodiol in rat aorta

    Directory of Open Access Journals (Sweden)

    Fidèle Ntchapda

    2015-06-01

    Full Text Available Objective: To evaluate the pharmacological property of erythrodiol, a natural triterpenoid contained in propolis, as vasodilatory agent, and to determine its mechanism of action. Methods: Rats aortic rings were isolated and suspended in organ baths, and the effects of erythrodiol were studied by means of isometric tension recording experiments. Nitric oxide (NO was detected by ozone-induced chemiluminescence. The technique used to evaluate changes in intracellular Ca2+ concentration in intact endothelium was opened aortic ring and loaded with 16 µmol Fura-2/AM for 60 min at room temperature, washed and fixed by small pins with the luminal face up. In situ, ECs were visualized by an upright epifluorescence Axiolab microscope (Carl Zeiss, Oberkochen, Germany equipped with a Zeiss×63 Achroplan objective (water immersion, 2.0 mm working distance, 0.9 numerical apertures. ECs were excited alternately at 340 and 380 nm, and the emitted light was detected at 510 nm. Results: In aortic rings with intact endothelium pre-contracted with norepinephrine (10-4 mol/L, the addition of erythrodiol (10-8-10-4 mol/L induced vasorelaxation in a concentration-dependent manner; in endothelium-denuded rings, the relaxant response induced by erythrodiol was almost completely abolished suggesting that vasorelaxation was endothelium-dependent. They had almost no relaxant effect on depolarised or endothelium-denuded aortic segments. The relaxation was significantly attenuated by pre-treatment with the NO synthase inhibitor Nvnitro-L-arginine-methylester. Erythrodiol (10-4 mol/L was able to significantly increase NOx levels. This effect was completely abolished after removal of the vascular endothelium. Erythrodiol (100 µmol/L caused a slow, long-lasting increase in intracellular Ca2+ concentration. These results further supported the hypothesis that erythrodiol can induce activation of the NO/soluble guanylate cyclase/cyclic guanosine monophosphate pathway, as

  18. Social defeat promotes a reactive endothelium in a brain region-dependent manner with increased expression of key adhesion molecules, selectins and chemokines associated with the recruitment of myeloid cells to the brain.

    Science.gov (United States)

    Sawicki, C M; McKim, D B; Wohleb, E S; Jarrett, B L; Reader, B F; Norden, D M; Godbout, J P; Sheridan, J F

    2015-08-27

    Repeated social defeat (RSD) in mice causes myeloid cell trafficking to the brain that contributes to the development of prolonged anxiety-like behavior. Myeloid cell recruitment following RSD occurs in regions where neuronal and microglia activation is observed. Thus, we hypothesized that crosstalk between neurons, microglia, and endothelial cells contributes to brain myeloid cell trafficking via chemokine signaling and vascular adhesion molecules. Here we show that social defeat caused an exposure- and brain region-dependent increase in several key adhesion molecules and chemokines involved in the recruitment of myeloid cells. For example, RSD induced distinct patterns of adhesion molecule expression that may explain brain region-dependent myeloid cell trafficking. VCAM-1 and ICAM-1 mRNA expression were increased in an exposure-dependent manner. Furthermore, RSD-induced VCAM-1 and ICAM-1 protein expression were localized to the vasculature of brain regions implicated in fear and anxiety responses, which spatially corresponded to previously reported patterns of myeloid cell trafficking. Next, mRNA expression of additional adhesion molecules (E- and P-selectin, PECAM-1) and chemokines (CXCL1, CXCL2, CXCL12, CCL2) were determined in the brain. Social defeat induced an exposure-dependent increase in mRNA levels of E-selectin, CXCL1, and CXCL2 that increased with additional days of social defeat. While CXCL12 was unaffected by RSD, CCL2 expression was increased by six days of social defeat. Last, comparison between enriched CD11b(+) cells (microglia/macrophages) and enriched GLAST-1(+)/CD11b(-) cells (astrocytes) revealed RSD increased mRNA expression of IL-1β, CCL2, and CXCL2 in microglia/macrophages but not in astrocytes. Collectively, these data indicate that key mediators of leukocyte recruitment were increased in the brain vasculature following RSD in an exposure- and brain region-dependent manner. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights

  19. Evidence for Reduced Hydrogen-Bond Cooperativity in Ionic Solvation Shells from Isotope-Dependent Dielectric Relaxation

    Science.gov (United States)

    Cota, Roberto; Ottosson, Niklas; Bakker, Huib J.; Woutersen, Sander

    2018-05-01

    We find that the reduction in dielectric response (depolarization) of water caused by solvated ions is different for H2O and D2O . This isotope dependence allows us to reliably determine the kinetic contribution to the depolarization, which is found to be significantly smaller than predicted by existing theory. The discrepancy can be explained from a reduced hydrogen-bond cooperativity in the solvation shell: we obtain quantitative agreement between theory and experiment by reducing the Kirkwood correlation factor of the solvating water from 2.7 (the bulk value) to ˜1.6 for NaCl and ˜1 (corresponding to completely uncorrelated motion of water molecules) for CsCl.

  20. trans-Caryophyllene, a Natural Sesquiterpene, Causes Tracheal Smooth Muscle Relaxation through Blockade of Voltage-Dependent Ca2+ Channels

    Directory of Open Access Journals (Sweden)

    Jader Santos Cruz

    2012-10-01

    Full Text Available trans-Caryophyllene is a major component in the essential oils of various species of medicinal plants used in popular medicine in Brazil. It belongs to the chemical class of the sesquiterpenes and has been the subject of a number of studies. Here, we evaluated the effects of this compound in airway smooth muscle. The biological activities of trans-caryophyllene were examined in isolated bath organs to investigate the effect in basal tonus. Electromechanical and pharmacomechanical couplings were evaluated through the responses to K+ depolarization and exposure to acetylcholine (ACh, respectively. Isolated cells of rat tracheal smooth muscle were used to investigate trans-caryophyllene effects on voltage-dependent Ca2+ channels by using the whole-cell voltage-clamp configuration of the patch-clamp technique. trans-Caryophyllene showed more efficiency in the blockade of electromechanical excitation-contraction coupling while it has only minor inhibitory effect on pharmacomechanical coupling. Epithelium removal does not modify tracheal smooth muscle response elicited by trans-caryophyllene in the pharmacomechanical coupling. Under Ca2+-free conditions, pre-exposure to trans-caryophyllene did not reduce the contraction induced by ACh in isolated rat tracheal smooth muscle, regardless of the presence of intact epithelium. In the whole-cell configuration, trans-caryophyllene (3 mM, inhibited the inward Ba2+ current (IBa to approximately 50% of control levels. Altogether, our results demonstrate that trans-caryophyllene has anti-spasmodic activity on rat tracheal smooth muscle which could be explained, at least in part, by the voltage-dependent Ca2+ channels blockade.

  1. Uridine Adenosine Tetraphosphate-Induced Coronary Relaxation Is Blunted in Swine With Pressure Overload: A Role for Vasoconstrictor Prostanoids.

    Science.gov (United States)

    Zhou, Zhichao; Lankhuizen, Inge M; van Beusekom, Heleen M; Cheng, Caroline; Duncker, Dirk J; Merkus, Daphne

    2018-01-01

    Plasma levels of the vasoactive substance uridine adenosine tetraphosphate (Up 4 A) are elevated in hypertensive patients and Up 4 A-induced vascular contraction is exacerbated in various arteries isolated from hypertensive animals, suggesting a potential role of Up 4 A in development of hypertension. We previously demonstrated that Up 4 A produced potent and partially endothelium-dependent relaxation in the porcine coronary microvasculature. Since pressure-overload is accompanied by structural abnormalities in the coronary microvasculature as well as by endothelial dysfunction, we hypothesized that pressure-overload blunts the coronary vasodilator response to Up 4 A, and that the involvement of purinergic receptors and endothelium-derived factors is altered. The effects of Up 4 A were investigated using wire-myography in isolated coronary small arteries from Sham-operated swine and swine with prolonged (8 weeks) pressure overload of the left ventricle induced by aortic banding (AoB). Expression of purinergic receptors and endothelium-derived factors was assessed in isolated coronary small arteries using real-time PCR. Up 4 A (10 -9 to 10 -5 M) failed to produce contraction in isolated coronary small arteries from either Sham or AoB swine, but produced relaxation in preconstricted arteries, which was significantly blunted in AoB compared to Sham. Blockade of purinergic P1, and P2 receptors attenuated Up 4 A-induced coronary relaxation more, while the effect of P2X 1 -blockade was similar and the effects of A 2A - and P2Y 1 -blockade were reduced in AoB as compared to Sham. mRNA expression of neither A1, A2, A3, nor P2X 1 , P2X 7 , P2Y 1 , P2Y 2 , nor P2Y 6 -receptors was altered in AoB as compared to Sham, while P2Y 12 expression was higher in AoB. eNOS inhibition attenuated Up 4 A-induced coronary relaxation in both Sham and AoB. Additional blockade of cyclooxygenase enhanced Up 4 A-induced coronary relaxation in AoB but not Sham swine, suggesting the involvement

  2. Transition from Arrhenius to non-Arrhenius temperature dependence of structural relaxation time in glass-forming liquids: continuous versus discontinuous scenario.

    Science.gov (United States)

    Popova, V A; Surovtsev, N V

    2014-09-01

    The temperature dependences of α relaxation time τ(α)(T) of three glass-forming liquids (salol, o-terphenyl, and α-picoline) were investigated by a depolarized light scattering technique. A detailed description of τ(α)(T) near T(A), the temperature of the transition from the Arrhenius law at high temperatures to a non-Arrhenius behavior of τ(α)(T) at lower temperatures, was done. It was found that this transition is quite sharp. If the transition is described as switching from the Arrhenius law to the Vogel-Fulcher-Tammann law, it occurs within the temperature range of about 15 K or less. Most of the known expressions for τ(α)(T) cannot describe this sharp transition. Our analysis revealed that this transition can be described either as a discontinuous transition in the spirit of the frustration-limited domain theory [D. Kivelson, G. Tarjus, X. Zhao, and S. A. Kivelson, Phys. Rev. E 53, 751 (1996)], implying a phase transition, or by a phenomenological expression recently suggested [B. Schmidtke, N. Petzold, R. Kahlau, M. Hofmann, and E. A. Rössler, Phys. Rev. E 86, 041507 (2012)], where the activation energy includes the term depending exponentially on temperature.

  3. Peroxynitrite-induced relaxation in isolated rat aortic rings and mechanisms of action

    International Nuclear Information System (INIS)

    Li Jianfeng; Li Wenyan; Altura, Bella T.; Altura, Burton M.

    2005-01-01

    The present study was designed to evaluate the effects of peroxynitrite (ONOO - ), the product of superoxide and nitric oxide, on isolated segments of rat aorta. In the absence of any vasoactive agent, ONOO - (from 10 -8 to 10 -4 M) failed to alter the basal tension. In phenylephrine (PE; 5 x 10 -7 M)-precontracted rat aortic rings (RAR), ONOO - elicited concentration-dependent relaxation at concentrations of from 10 -8 to 10 -4 M. The effective concentrations producing approximately 50% of maximal relaxation (ED 5 ) to ONOO - were 1.84 x 10 -5 M and 1.96 x 10 -5 M in intact and denuded RAR, respectively (P > 0.05). No significant differences in the relaxation responses were found between RAR with or without endothelium (P > 0.05). The presence of either 5 μM methylene blue (MB) or 5 μM 1H-[1,2,4]oxadiazolo-[4,3-α]quinoxalin-1-one (ODQ) significantly inhibited the relaxations induced by ONOO - . Sildenafil (10 -7 M), on the other hand, significantly potentiated the ONOO - -induced relaxations. Tetraethylammonium chloride (T-2265) significantly decreased the ONOO - -induced relaxations in a concentration-dependent manner. However, ONOO - had no effect on RAR precontracted by high KCL (40 mM, n = 6, P > 0.05). Addition of calyculin A also significantly decreased the ONOO - -induced relaxation in a dose-dependent manner. Furthermore, ONOO - significantly inhibited calcium-induced contractions of K + -depolarized aortic rings in a concentration-related manner. Lastly, a variety of other pharmacological agents and antagonists including L-NMMA, L-arginine, indomethacin, atropine, naloxone, diphenhydramine, cimetine, glibenclamide, haloperidol, superoxide dismutase (SOD), and catalase did not influence the relaxant effects of ONOO - on RAR. Our new results suggest that ONOO - -triggered relaxation on rat aortic rings is mediated by elevation of cGMP levels, membrane hyperpolarization via K + -channel activation, activation of myosin phosphatase activity, and

  4. Thrombin-induced increase in albumin permeability across the endothelium

    International Nuclear Information System (INIS)

    Garcia, J.G.; Siflinger-Birnboim, A.; Bizios, R.; Del Vecchio, P.J.; Fenton, J.W. II; Malik, A.B.

    1986-01-01

    We studied the effect of thrombin on albumin permeability across the endothelial monolayer in vitro. Bovine pulmonary artery endothelial cells were grown on micropore membranes. Morphologic analysis confirmed the presence of a confluent monolayer with interendothelial junctions. Albumin permeability was measured by the clearance of 125I-albumin across the endothelial monolayer. The control 125I-albumin clearance was 0.273 +/- 0.02 microliter/min. The native enzyme, alpha-thrombin (10(-6) to 10(-10) M), added to the luminal side of the endothelium produced concentration-dependent increases in albumin clearance (maximum clearance of 0.586 +/- 0.08 microliter/min at 10(-6) M). Gamma (gamma) thrombin (10(-6) M and 10(-8) M), which lacks the fibrinogen recognition site, also produced a concentration-dependent increase in albumin clearance similar to that observed with alpha-thrombin. Moreover, the two proteolytically inactive forms of the native enzyme, i-Pr2 P-alpha-thrombin and D-Phe-Pro-Arg-CH2-alpha-thrombin, increased the 125I-albumin clearance (0.610 +/- 0.09 microliter/min and 0.609 +/- 0.02 microliter/min for i-Pr2 P-alpha-thrombin and D-Phe-Pro-Arg-CH2-alpha-thrombin at 10(-6) M, respectively). Since the modified forms of thrombin lack the fibrinogen recognition and active serine protease sites, the results indicate that neither site is required for increased albumin permeability. The increase in albumin clearance with alpha-thrombin was not secondary to endothelial cell lysis because lactate dehydrogenase concentration in the medium following thrombin was not significantly different from baseline values. There was also no morphological evidence of cell lysis. Moreover, the increase in 125I-albumin clearance induced by alpha-thrombin was reversible by washing thrombin from the endothelium

  5. Capturing molecular multimode relaxation processes in excitable gases based on decomposition of acoustic relaxation spectra

    Science.gov (United States)

    Zhu, Ming; Liu, Tingting; Wang, Shu; Zhang, Kesheng

    2017-08-01

    Existing two-frequency reconstructive methods can only capture primary (single) molecular relaxation processes in excitable gases. In this paper, we present a reconstructive method based on the novel decomposition of frequency-dependent acoustic relaxation spectra to capture the entire molecular multimode relaxation process. This decomposition of acoustic relaxation spectra is developed from the frequency-dependent effective specific heat, indicating that a multi-relaxation process is the sum of the interior single-relaxation processes. Based on this decomposition, we can reconstruct the entire multi-relaxation process by capturing the relaxation times and relaxation strengths of N interior single-relaxation processes, using the measurements of acoustic absorption and sound speed at 2N frequencies. Experimental data for the gas mixtures CO2-N2 and CO2-O2 validate our decomposition and reconstruction approach.

  6. Detailing magnetic field strength dependence and segmental artifact distribution of myocardial effective transverse relaxation rate at 1.5, 3.0, and 7.0 T.

    Science.gov (United States)

    Meloni, Antonella; Hezel, Fabian; Positano, Vincenzo; Keilberg, Petra; Pepe, Alessia; Lombardi, Massimo; Niendorf, Thoralf

    2014-06-01

    Realizing the challenges and opportunities of effective transverse relaxation rate (R2 *) mapping at high and ultrahigh fields, this work examines magnetic field strength (B0 ) dependence and segmental artifact distribution of myocardial R2 * at 1.5, 3.0, and 7.0 T. Healthy subjects were considered. Three short-axis views of the left ventricle were examined. R2 * was calculated for 16 standard myocardial segments. Global and mid-septum R2 * were determined. For each segment, an artifactual factor was estimated as the deviation of segmental from global R2 * value. The global artifactual factor was significantly enlarged at 7.0 T versus 1.5 T (P = 0.010) but not versus 3.0 T. At 7.0 T, the most severe susceptibility artifacts were detected in the inferior lateral wall. The mid-septum showed minor artifactual factors at 7.0 T, similar to those at 1.5 and 3.0 T. Mean R2 * increased linearly with the field strength, with larger changes for global heart R2 * values. At 7.0 T, segmental heart R2 * analysis is challenging due to macroscopic susceptibility artifacts induced by the heart-lung interface and the posterior vein. Myocardial R2 * depends linearly on the magnetic field strength. The increased R2 * sensitivity at 7.0 T might offer means for susceptibility-weighted and oxygenation level-dependent MR imaging of the myocardium. Copyright © 2013 Wiley Periodicals, Inc.

  7. [The endothelium injuries caused by homocysteine and treatmental effects of Tongxinluo powder].

    Science.gov (United States)

    Liang, Jun-Qing; Wu, Yi-Ling; Xu, Hai-Bo; Zhao, Shao-Hua; Jia, Zhen-Hua; Zhang, Qiu-Yan; Wei, Cong; Dong, Xiao-Wei

    2008-02-01

    To observe the effect of homocysteine (HCY) on the function of endothelium cell, and to discuss the possible mechanisms that Tongxinluo super powder affected. Healthy male Wistar rats were divided into randomly the control group, the model group, the Tongxinluo group. The effect of Ach on isolated rat thoracic aorta in vitro was examined, the microcirculation was observed by microcirculation meter, the activity of SOD and GSH-PX and content of NO, MDA, ET, Ang II, TXA2, PGI2 was detected. Compared with control group, the effect of Ach on isolated rat thoracic aorta in vitro weakened markablely (P homocystein might cause the contracted and dilated function decreased, it might get involved in endothelium disfunction as a result of the massive free radicals production and diastolic-contract factors balance disorder induced by high homocystein. (2) Tongxinluo powder could improve the function of endothelium-dependment dilation induced by high homocystein, that associated with inhibitting the excessive production of free radicals, and improved function of endothelium.

  8. Glucose-coated gold nanoparticles transfer across human brain endothelium and enter astrocytes in vitro.

    Directory of Open Access Journals (Sweden)

    Radka Gromnicova

    Full Text Available The blood-brain barrier prevents the entry of many therapeutic agents into the brain. Various nanocarriers have been developed to help agents to cross this barrier, but they all have limitations, with regard to tissue-selectivity and their ability to cross the endothelium. This study investigated the potential for 4 nm coated gold nanoparticles to act as selective carriers across human brain endothelium and subsequently to enter astrocytes. The transfer rate of glucose-coated gold nanoparticles across primary human brain endothelium was at least three times faster than across non-brain endothelia. Movement of these nanoparticles occurred across the apical and basal plasma membranes via the cytosol with relatively little vesicular or paracellular migration; antibiotics that interfere with vesicular transport did not block migration. The transfer rate was also dependent on the surface coating of the nanoparticle and incubation temperature. Using a novel 3-dimensional co-culture system, which includes primary human astrocytes and a brain endothelial cell line hCMEC/D3, we demonstrated that the glucose-coated nanoparticles traverse the endothelium, move through the extracellular matrix and localize in astrocytes. The movement of the nanoparticles through the matrix was >10 µm/hour and they appeared in the nuclei of the astrocytes in considerable numbers. These nanoparticles have the correct properties for efficient and selective carriers of therapeutic agents across the blood-brain barrier.

  9. Thermal- and pH-Dependent Size Variable Radical Nanoparticles and Its Water Proton Relaxivity for Metal-Free MRI Functional Contrast Agents.

    Science.gov (United States)

    Morishita, Kosuke; Murayama, Shuhei; Araki, Takeru; Aoki, Ichio; Karasawa, Satoru

    2016-09-16

    For development of the metal-free MRI contrast agents, we prepared the supra-molecular organic radical, TEMPO-UBD, carrying TEMPO radical, as well as the urea, alkyl group, and phenyl ring, which demonstrate self-assembly behaviors using noncovalent bonds in an aqueous solution. In addition, TEMPO-UBD has the tertiary amine and the oligoethylene glycol chains (OEGs) for the function of pH and thermal responsiveness. By dynamic light scattering and transmission electron microscopy imaging, the resulting self-assembly was seen to form the spherical nanoparticles 10-150 nm in size. On heating, interestingly, the nanoparticles showed a lower critical solution temperature (LCST) behavior having two-step variation. This double-LCST behavior is the first such example among the supra-molecules. To evaluate of the ability as MRI contrast agents, the values of proton ((1)H) longitudinal relaxivity (r1) were determined using MRI apparatus. In conditions below and above CAC at pH 7.0, the distinguishable r1 values were estimated to be 0.17 and 0.21 mM(-1) s(1), indicating the suppression of fast tumbling motion of TEMPO moiety in a nanoparticle. Furthermore, r1 values became larger in the order of pH 7.0 > 9.0 > 5.0. Those thermal and pH dependencies indicated the possibility of metal-fee MRI functional contrast agents in the future.

  10. Vascular endothelium receptors and transduction mechanisms

    CERN Document Server

    Gillis, C; Ryan, Una; Proceedings of the Advanced Studies Institute on "Vascular Endothelium: Receptors and Transduction Mechanisms"

    1989-01-01

    Beyond their obvious role of a barrier between blood and tissue, vascular endothelial cells are now firmly established as active and essential participants in a host of crucial physiological and pathophysiological functions. Probably the two most important factors responsible for promoting the current knowledge of endothelial functions are 1) observations in the late sixties-early seventies that many non-ventilatory properties of the lung could be attributed to the pulmonary endothelium and 2) the establishment, in the early and mid-seventies of procedures for routine culture of vascular endothelial cells. Many of these endothelial functions require the presence of receptors on the surface of the plasma membrane. There is now evidence for the existence among others of muscarinic, a-and /3-adrenergic, purine, insulin, histamine, bradykinin, lipoprotein, thrombin, paf, fibronectin, vitronectin, interleukin and albumin receptors. For some of these ligands, there is evidence only for the existence of endothelial ...

  11. Plasmon-mediated energy relaxation in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Ferry, D. K. [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287-5706 (United States); Somphonsane, R. [Department of Physics, King Mongkut' s Institute of Technology, Ladkrabang, Bangkok 10520 (Thailand); Ramamoorthy, H.; Bird, J. P. [Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260-1500 (United States)

    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.

  12. The influence of DOCA-salt hypertension and chronic administration of the FAAH inhibitor URB597 on KCa2.3/KCa3.1-EDH-type relaxation in rat small mesenteric arteries.

    Science.gov (United States)

    Kloza, Monika; Baranowska-Kuczko, Marta; Malinowska, Barbara; Karpińska, Olga; Harasim-Symbor, Ewa; Kasacka, Irena; Kozłowska, Hanna

    2017-12-01

    The aim of this study was to examine the influence of deoxycorticosterone acetate-salt (DOCA-salt) hypertension and chronic treatment with the fatty acid amide hydrolase inhibitor, URB597, on small and intermediate conductance calcium-activated potassium channels and endothelium-dependent hyperpolarization (K Ca 2.3/K Ca 3.1-EDH) in rat small mesenteric arteries (sMAs). The EDH-type response was investigated, in endothelium-intact sMAs using a wire myograph, by examining acetylcholine-evoked vasorelaxation in the presence of N ω -nitro-L-arginine methyl ester and indomethacin (inhibitors of nitric oxide synthase and cyclooxygenase, respectively). In normo- and hypertension the efficacy of EDH-type relaxation was similar and inhibition of K Ca 2.3 and K Ca 3.1 by UCL1684 and TRAM-34, respectively, given alone or in combination, attenuated EDH-mediated vasorelaxation. K Ca 3.1 expression and NS309 (K Ca 2.3/K Ca 3.1 activator)-induced relaxation was reduced in sMAs of DOCA-salt rats. Endothelium denudation and incubation with UCL1684 and TRAM-34 attenuated the maximal NS309-evoked vasorelaxation in both groups. URB597 had no effect in functional studies, but increased the expression of K Ca 3.1 in the sMAs. K Ca 2.3/K Ca 3.1-EDH-mediated relaxation was maintained in the sMAs of DOCA-salt rats despite endothelial dysfunction and down-regulation of K Ca 3.1. Furthermore, K Ca 3.1 played a key role in the EDH-type dilator response of sMAs in normo- and hypertension. The hypotensive effect of URB597 is independent of K Ca 2.3/K Ca 3.1-EDH-type relaxation. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Visualization of three pathways for macromolecule transport across cultured endothelium and their modification by flow.

    Science.gov (United States)

    Ghim, Mean; Alpresa, Paola; Yang, Sung-Wook; Braakman, Sietse T; Gray, Stephen G; Sherwin, Spencer J; van Reeuwijk, Maarten; Weinberg, Peter D

    2017-11-01

    Transport of macromolecules across vascular endothelium and its modification by fluid mechanical forces are important for normal tissue function and in the development of atherosclerosis. However, the routes by which macromolecules cross endothelium, the hemodynamic stresses that maintain endothelial physiology or trigger disease, and the dependence of transendothelial transport on hemodynamic stresses are controversial. We visualized pathways for macromolecule transport and determined the effect on these pathways of different types of flow. Endothelial monolayers were cultured under static conditions or on an orbital shaker producing different flow profiles in different parts of the wells. Fluorescent tracers that bound to the substrate after crossing the endothelium were used to identify transport pathways. Maps of tracer distribution were compared with numerical simulations of flow to determine effects of different shear stress metrics on permeability. Albumin-sized tracers dominantly crossed the cultured endothelium via junctions between neighboring cells, high-density lipoprotein-sized tracers crossed at tricellular junctions, and low-density lipoprotein-sized tracers crossed through cells. Cells aligned close to the angle that minimized shear stresses across their long axis. The rate of paracellular transport under flow correlated with the magnitude of these minimized transverse stresses, whereas transport across cells was uniformly reduced by all types of flow. These results contradict the long-standing two-pore theory of solute transport across microvessel walls and the consensus view that endothelial cells align with the mean shear vector. They suggest that endothelial cells minimize transverse shear, supporting its postulated proatherogenic role. Preliminary data show that similar tracer techniques are practicable in vivo. NEW & NOTEWORTHY Solutes of increasing size crossed cultured endothelium through intercellular junctions, through tricellular

  14. Cigarette smoke extract increases albumin flux across pulmonary endothelium in vitro

    International Nuclear Information System (INIS)

    Holden, W.E.; Maier, J.M.; Malinow, M.R.

    1989-01-01

    Cigarette smoking causes lung inflammation, and a characteristic of inflammation is an increase in vascular permeability. To determine if cigarette smoke could alter endothelial permeability, we studied flux of radiolabeled albumin across monolayers of porcine pulmonary artery endothelium grown in culture on microporous membranes. Extracts (in either dimethylsulfoxide or phosphate-buffered saline) of cigarette smoke in a range estimate of concentrations simulating cigarette smoke exposure to the lungs in vivo caused a dose-dependent increase in albumin flux that was dependent on extracellular divalent cations and associated with polymerization of cellular actin. The effect was reversible, independent of the surface of endothelial cells exposed (either luminal or abluminal), and due primarily to components of the vapor phase of smoke. The effects occurred without evidence of cell damage, but subtle morphological changes were produced by exposure to the smoke extracts. These findings suggest that cigarette smoke can alter permeability of the lung endothelium through effects on cytoskeletal elements

  15. Relaxed states with plasma flow

    International Nuclear Information System (INIS)

    Avinash, K.; Taylor, J.B.

    1991-01-01

    In the theory of relaxation, a turbulent plasma reaches a state of minimum energy subject to constant magnetic helicity. In this state the plasma velocity is zero. Attempts have been made by introducing a number of different constraints, to obtain relaxed states with plasma flow. It is shown that these alternative constraints depend on two self-helicities, one for ions, and one for electrons. However, whereas there are strong arguments for the effective invariance of the original magnetic-helicity, these arguments do not apply to the self-helicities. Consequently the existence of relaxed states with flow remains in doubt. (author)

  16. Toxicity of methods of implant material sterilization on corneal endothelium

    Energy Technology Data Exchange (ETDEWEB)

    Singh, G.; Boehnke, Mv.; von Domarus, D.; Draeger, J.

    1985-11-01

    The toxicity of different procedures utilized for the sterilization of intraocular implant material was assessed on the endothelium of organ-cultured porcine corneas. Polymethylmethacrylate lenses sterilized by treatment with sodium hydroxide (NaOH), ethylene oxide, formaldehyde, and gamma radiation were added to a culture medium containing normal porcine corneas. Considering the viability of endothelial cells, appearance of intracellular degenerative vacuoles, and denudation of corneal Descemet's membrane as criterion for the evaluation of toxicity of different methods of sterilization, the NaOH-treated lenses were found to be the least toxic to porcine corneal endothelium. Phase-contrast microscopy and vital staining of the endothelium permitted direct viewing of the endothelium aiding in the assessment of toxicity.

  17. P2Y purinoceptor and nucleotide receptor-induced relaxation of precontracted bovine aortic collateral artery rings: differential sensitivity to suramin and indomethacin.

    Science.gov (United States)

    Wilkinson, G F; McKechnie, K; Dainty, I A; Boarder, M R

    1994-02-01

    We have examined a series of adenine nucleotides and UTP for their ability to cause relaxation of precontracted bovine aortic collateral artery rings. The overall rank order of agonist potency for relaxation was 2-methylthioadenosine 5'-triphosphate (2MeSATP) > adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S) > UTP > ADP > ATP. These responses were endothelium-dependent. Interaction studies showed that responses to the selective P2Y purinoceptor agonist 2MeSATP, and to ADP, were mediated by different receptors from those mediating responses to UTP. Suramin, a P2 purinoceptor antagonist that binds to diverse sites for ATP, produced a concentration-dependent shift in the agonist concentration-effect curve to 2MeSATP, with a pKB of 5.45 +/- 0.15 and a slope of 0.94 +/- 0.09. Suramin produced a small, nonsignificant shift in the UTP response curve and had little effect on responses to ATP. Indomethacin (2.8 x 10(-6) M) had no effect on concentration-effect curves to UTP but almost abolished the relaxations produced by 2MeSATP and ADP. The concentration-effect curves to ATP and ATP gamma S showed a significant (P effects of indomethacin show that these receptors differentially modulate the release of cyclooxygenase-derived mediators of relaxation.

  18. El ejercicio físico aeróbico incrementa la vasodilatación dependiente del endotelio y el consumo de oxígeno de mujeres primigestantes saludables. Ensayo clínico controlado, aleatorizado. NCT00741312 Aerobic physical exercise increases endothelium-dependent vasodilation and oxygen consumption in healthy primigravida. Controlled randomized clinical trial. NCT00741312

    Directory of Open Access Journals (Sweden)

    Róbinson Ramírez-Vélez

    2010-12-01

    Full Text Available OBJETIVO: evaluar el efecto del ejercicio aeróbico en la función dependiente del endotelio (VDE y en el consumo de oxígeno en mujeres primigestantes. MÉTODOS: ensayo clínico controlado, enmascarado y aleatorizado, llevado a cabo en 67 mujeres saludables, primigestantes, entre 16 a 20 semanas de gestación. Grupo de intervención: ejercicio aeróbico entre 50% y 65% de la frecuencia cardiaca máxima, durante 45 minutos, tres veces por semana, durante dieciséis semanas. Grupo control: actividad física habitual. Mediciones: VDE: vasodilatación mediada por flujo (VMF, consumo de oxígeno VO2max: prueba de caminata de seis minutos; antropometría: peso y talla. RESULTADOS: en las mediciones iniciales no se encontraron diferencias entre grupos en ninguna de las variables. Al finalizar la intervención, las participantes que realizaron ejercicio tenían mayor capacidad física, medida por la distancia recorrida en el test de caminata (p=0,043 y por el VO2max (p=0,023. Además, el grupo de ejercicio tuvo menor frecuencia cardiaca en reposo y mayor VMF que el grupo control (pOBJECTIVE: evaluate the effect of aerobic exercise on endothelium-dependent function (EDF and oxygen consumption in primigravida. METHODS: double-blind, randomized controlled clinical trial carried out in primigravida between 16 to 20 weeks of gestation. The intervention group had aerobic exercise between 50% to 65% of the maximum heart rate during 45 minutes, three times a week for sixteen weeks. The control group had habitual physical activity. MEASUREMENTS REALIZED: EDF: flow-mediated dilation (FMD, oxygen consumption VO2max: 6 minute walking test, anthropometry: weight and size. RESULTS: no differences were found between the two groups in any variables in the initial measurements. At the end of the intervention, participants who exercised had greater physical capacity, measured by the distance covered in walking test (p = 0.043 and VO2max (p = 0.023. In addition, the

  19. Adiponectin improves coronary no-reflow injury by protecting the endothelium in rats with type 2 diabetes mellitus.

    Science.gov (United States)

    Han, Xue; Wu, Ye; Liu, Xin; Ma, Lu; Lv, Tingting; Sun, Qi; Xu, Wenli; Zhang, Suli; Wang, Ke; Wang, Wen; Ma, Xinliang; Liu, Huirong

    2017-08-31

    To determine the effect of adiponectin (APN) on the coronary no-reflow (NR) injury in rats with Type 2 diabetes mellitus (T2DM), 80 male Sprague-Dawley rats were fed with a high-sugar-high-fat diet to build a T2DM model. Rats received vehicle or APN in the last week and then were subjected to myocardial ischemia reperfusion (MI/R) injury. Endothelium-dependent vasorelaxation of the thoracic aorta was significantly decreased and serum levels of endothelin-1 (ET-1), intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were noticably increased in T2DM rats compared with rats without T2DM. Serum APN was positively correlated with the endothelium-dependent vasorelaxation, but negatively correlated with the serum level of ET-1. Treatment with APN improved T2DM-induced endothelium-dependent vasorelaxation, recovered cardiac function, and decreased both NR size and the levels of ET-1, ICAM-1 and VCAM-1. Hypoadiponectinemia was associated with the aggravation of coronary NR in T2DM rats. APN could alleviate coronary NR injury in T2DM rats by protecting the endothelium and improving microcirculation. © 2017 The Author(s).

  20. HOXB4 Promotes Hemogenic Endothelium Formation without Perturbing Endothelial Cell Development

    Directory of Open Access Journals (Sweden)

    Nadine Teichweyde

    2018-03-01

    Full Text Available Summary: Generation of hematopoietic stem cells (HSCs from pluripotent stem cells, in vitro, holds great promise for regenerative therapies. Primarily, this has been achieved in mouse cells by overexpression of the homeotic selector protein HOXB4. The exact cellular stage at which HOXB4 promotes hematopoietic development, in vitro, is not yet known. However, its identification is a prerequisite to unambiguously identify the molecular circuits controlling hematopoiesis, since the activity of HOX proteins is highly cell and context dependent. To identify that stage, we retrovirally expressed HOXB4 in differentiating mouse embryonic stem cells (ESCs. Through the use of Runx1(−/− ESCs containing a doxycycline-inducible Runx1 coding sequence, we uncovered that HOXB4 promoted the formation of hemogenic endothelium cells without altering endothelial cell development. Whole-transcriptome analysis revealed that its expression mediated the upregulation of transcription of core transcription factors necessary for hematopoiesis, culminating in the formation of blood progenitors upon initiation of Runx1 expression. : In this article, Klump and colleagues demonstrate that the human homeotic selector protein HOXB4 promotes ESC-derived hematopoiesis by inducing hemogenic endothelium formation, in vitro. It propels hematopoietic specification by upregulating the transcription of genes essential for hematopoietic development, such as those encoding members of the so-called heptad transcription factors. Keywords: HOXB4, hematopoietic stem cells, hemangioblast, hemogenic endothelium, hematopoietic specification, EHT, RUNX1, pluripotent stem cells

  1. Low-dose ultraviolet-B irradiation of donor corneal endothelium and graft survival

    International Nuclear Information System (INIS)

    Dana, M.R.; Olkowski, S.T.; Ahmadian, H.; Stark, W.J.; Young, E.M.

    1990-01-01

    Donor rabbit corneal endothelium was pretreated with different doses of ultraviolet (UV-B) irradiation (302 nm) before grafting to test whether allograft survival could be favorably affected in comparison with untreated corneas grafted into the same recipients. Endothelial rejection was observed in 19 of 32 (59%) eyes that received no treatment compared with five of 32 (16%) eyes that received UV-B (P less than 0.001), and increasing doses of UV-B were associated with lower rejection rates (P less than 0.05). Although exposure of donor endothelium significantly reduced endothelial rejection at all doses tested, it resulted in primary graft failure in a substantial proportion of corneas treated at high doses. Class II (Ia) antigen staining of corneal tissue was present in conjunction with clinical evidence of rejection, and the magnitude of staining correlated with the histologic extent of inflammation. Scanning electron microscopy revealed various endothelial cell surface irregularities and membrane defects in high-dose UV-treated corneas. Endothelial cell cultures exposed in vitro to UV-B light showed a dose-dependent loss in cell viability. These data suggest that UV-B pretreatment of donor corneal endothelium prolongs graft survival but that toxic side effects must be carefully controlled

  2. Dielectric relaxation dependent memory elements in pentacene/[6,6]-phenyl-C61-butyric acid methyl ester bi-layer field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Park, Byoungnam

    2015-03-02

    We fabricate a pentacene/[6,6]-phenyl-C{sub 61}-butyric acid methyl ester (PCBM) bi-layer field effect transistor (FET) featuring large hysteresis that can be used as memory elements. Intentional introduction of excess electron traps in a PCBM layer by exposure to air caused large hysteresis in the FET. The memory window, characterized by the threshold voltage difference, increased upon exposure to air and this is attributed to an increase in the number of electron trapping centers and (or) an increase in the dielectric relaxation time in the underlying PCBM layer. Decrease in the electron conduction in the PCBM close to the SiO{sub 2} gate dielectric upon exposure to air is consistent with the increase in the dielectric relaxation time, ensuring that the presence of large hysteresis in the FET originates from electron trapping at the PCBM not at the pentacene. - Highlights: • Charge trapping-induced memory effect was clarified using transistors. • The memory window can be enhanced by controlling charge trapping mechanism. • Memory transistors can be optimized by controlling dielectric relaxation time.

  3. Cross relaxation in nitroxide spin labels

    DEFF Research Database (Denmark)

    Marsh, Derek

    2016-01-01

    Cross relaxation, and mI-dependence of the intrinsic electron spin-lattice relaxation rate We, are incorporated explicitly into the rate equations for the electron-spin population differences that govern the saturation behaviour of 14N- and 15N-nitroxide spin labels. Both prove important in spin......-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We, the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from...... the hyperfine line pumped or observed follows directly from solution of the rate equations including cross relaxation, even when the intrinsic spin-lattice relaxation rate We is mI-dependent....

  4. Relative permeability of the endothelium and epithelium of rabbit lungs

    International Nuclear Information System (INIS)

    Effros, R.M.; Mason, G.R.; Silverman, P.; Hukkanen, J.

    1986-01-01

    Electron micrographic studies of lungs suggest that the epithelial cells are more tightly joined than the underlying endothelium, and macromolecules penetrate the endothelium more readily than the epithelium. Comparisons of epithelial and endothelial permeability to small molecules have been based upon the relative rates at which solutes traverse the alveolar-capillary barrier in fluid filled lungs and those at which they equilibrate across the capillaries in air-filled lungs. Because the former process is much slower than the latter, it has been concluded that the epithelium is less permeable to small solutes than the endothelium. However this difference may be related to inadequate access of solutes to airway surfaces. In this study, solute losses from the vascular space were compared to those from the airspace in perfused, fluid-filled rabbit lungs. 36 Cl - and 125 I - were lost from air-spaces almost twice as rapidly as 22 Na + . In contrast, the endothelium is equally permeable to 22 Na + and these anions. Loss of 3 H-mannitol from the perfusate resembled that of 22 Na + for about 30 minutes, after which diffusion of 3 H-mannitol into the tissue nearly ceased. These observations suggest that the epithelium is more permselective than the endothelium. By resisting solute and water transport, the epithelium tends to prevent alveolar flooding and confines edema to the interstitium, where it is less likely to interfere with gas exchange

  5. Phosphodiesterase-9 (PDE9) inhibition with BAY 73-6691 increases corpus cavernosum relaxations mediated by nitric oxide-cyclic GMP pathway in mice.

    Science.gov (United States)

    da Silva, F H; Pereira, M N; Franco-Penteado, C F; De Nucci, G; Antunes, E; Claudino, M A

    2013-01-01

    Phosphodiesterase-9 (PDE9) specifically hydrolyzes cyclic GMP, and was detected in human corpus cavernosum. However, no previous studies explored the selective PDE9 inhibition with BAY 73-6691 in corpus cavernosum relaxations. Therefore, this study aimed to characterize the PDE9 mRNA expression in mice corpus cavernosum, and investigate the effects of BAY 73-6691 in endothelium-dependent and -independent relaxations, along with the nitrergic corpus cavernosum relaxations. Male mice received daily gavage of BAY 73-6691 (or dimethylsulfoxide) at 3 mg kg(-1) per day for 21 days. Relaxant responses to acetylcholine (ACh), nitric oxide (NO) (as acidified sodium nitrite; NaNO2 solution), sildenafil and electrical-field stimulation (EFS) were obtained in corpus cavernosum in control and BAY 73-6691-treated mice. BAY 73-6691 was also added in vitro 30 min before construction of concentration-responses and frequency curves. PDE9A and PDE5 mRNA expression was detected in the mice corpus cavernosum in a similar manner. In vitro addition of BAY 73-6691 neither itself relaxed mice corpus cavernosum nor changed the NaNO2, sildenafil and EFS-induced relaxations. However, in mice treated chronically with BAY 73-6691, the potency (pEC50) values for ACh, NaNO2 and sildenafil were significantly greater compared with control group. The maximal responses (Emax) to NaNO2 and sildenafil were also significantly greater in BAY 73-6691-treated mice. BAY 73-6691 treatment also significantly increased the magnitude and duration of the nitrergic corpus cavernosum relaxations (8-32 Hz). In conclusion, murine corpus cavernosum expresses PDE9 mRNA. Prolonged PDE9 inhibition with BAY 73-6691 amplifies the NO-cGMP-mediated cavernosal responses, and may be of therapeutic value for erectile dysfunction.

  6. Dependence of cross-relaxation on temperature and concentration from the 1D2 level of Pr3+ in YPO4

    International Nuclear Information System (INIS)

    Collins, John; Geen, Megan; Bettinelli, M.; Di Bartolo, B.

    2012-01-01

    We report on the role of cross-relaxation in the decay of the 1 D 2 level of trivalent Pr in YPO 4 in crystals with Pr concentrations of 0.1%, 1%, 2%, and 5%. We have found that the 1 D 2 level decay is purely radiative in the low-doped system. As the Pr concentration is increased, the 1 D 2 luminescence is quenched due to a cross-relaxation energy transfer between two Pr ions. The temporal behavior of the 1 D 2 luminescence following pulsed excitation has been monitored in each sample at temperatures between 30 K and 300 K, and all decay curves were fit to the Yokota–Tanimoto model. The decay times decrease as temperature increases, due to an increase in both the radiative rate and the energy transfer rate with temperature. There is little evidence of diffusion at any temperature, even in the more concentrated samples. We have also fit the decay curves using the LumiTrans computer simulation. A comparison of the fits to the decay curves of the two methods is presented. - Highlights: ► We present data on the decay of the 1 D 2 level of Pr in YPO 4 from 30–300 K. ► We determine the 1 D 2 cross-relaxation rate throughout that temperature range. ► Fits to the data indicate diffusion among the Pr ions is negligible. ► Radiative efficiencies of the 1 D 2 level are determined.

  7. The change of longitudinal relaxation rate in oxygen enhanced pulmonary MRI depends on age and BMI but not diffusing capacity of carbon monoxide in healthy never-smokers.

    Directory of Open Access Journals (Sweden)

    Simon Sven Ivan Kindvall

    Full Text Available Oxygen enhanced pulmonary MRI is a promising modality for functional lung studies and has been applied to a wide range of pulmonary conditions. The purpose of this study was to characterize the oxygen enhancement effect in the lungs of healthy, never-smokers, in light of a previously established relationship between oxygen enhancement and diffusing capacity of carbon monoxide in the lung (DL,CO in patients with lung disease.In 30 healthy never-smoking volunteers, an inversion recovery with gradient echo read-out (Snapshot-FLASH was used to quantify the difference in longitudinal relaxation rate, while breathing air and 100% oxygen, ΔR1, at 1.5 Tesla. Measurements were performed under multiple tidal inspiration breath-holds.In single parameter linear models, ΔR1 exhibit a significant correlation with age (p = 0.003 and BMI (p = 0.0004, but not DL,CO (p = 0.33. Stepwise linear regression of ΔR1 yields an optimized model including an age-BMI interaction term.In this healthy, never-smoking cohort, age and BMI are both predictors of the change in MRI longitudinal relaxation rate when breathing oxygen. However, DL,CO does not show a significant correlation with the oxygen enhancement. This is possibly because oxygen transfer in the lung is not diffusion limited at rest in healthy individuals. This work stresses the importance of using a physiological model to understand results from oxygen enhanced MRI.

  8. Breathing and Relaxation

    Science.gov (United States)

    ... Find a Doctor Relaxation is the absence of tension in muscle groups and a minimum or absence ... Drill Meditation Progressive Muscle Relaxation Minimizing Shortness of Breath Visualization This information has been approved by Shelby ...

  9. Monoclonal antibody PAL-E specific for endothelium

    NARCIS (Netherlands)

    Schlingemann, R. O.; Dingjan, G. M.; Emeis, J. J.; Blok, J.; Warnaar, S. O.; Ruiter, D. J.

    1985-01-01

    A monoclonal antibody, PAL-E, is described that is specific for endothelial cells. The monoclonal antibody, an IgG2a, markedly stains endothelium of capillaries, medium-sized and small veins, and venules in frozen sections of human and some animal tissues tested. It reacts not at all or only weakly

  10. Helium induces preconditioning in human endothelium in vivo

    NARCIS (Netherlands)

    Smit, Kirsten F.; Oei, Gezina T. M. L.; Brevoord, Daniel; Stroes, Erik S.; Nieuwland, Rienk; Schlack, Wolfgang S.; Hollmann, Markus W.; Weber, Nina C.; Preckel, Benedikt

    2013-01-01

    Helium protects myocardium by inducing preconditioning in animals. We investigated whether human endothelium is preconditioned by helium inhalation in vivo. Forearm ischemia-reperfusion (I/R) in healthy volunteers (each group n = 10) was performed by inflating a blood pressure cuff for 20 min.

  11. Pressure dependence of thermal conductivity and specific heat in CeRh2Si2 measured by an extended thermal relaxation method

    Science.gov (United States)

    Nishigori, Shijo; Seida, Osamu

    2018-05-01

    We have developed a new technique for measuring thermal conductivity and specific heat under pressure by improving a thermal relaxation method. In this technique, a cylindrical sample with a small disc heater is embedded in the pressure-transmitting medium, then temperature variations of the sample and heater were directly measured by thermocouples during a heating and cooling process. Thermal conductivity and specific heat are estimated by comparing the experimental data with temperature variations simulated by a finite element method. The obtained thermal conductivity and specific heat of the test sample CeRh2Si2 exhibit a small enhancement and a clear peak arising from antiferromagnetic transition, respectively. The observation of these typical behaviors for magnetic compounds indicate that the technique is valid for the study on thermal properties under pressure.

  12. pH-Dependent Regulation of the Relaxation Rate of the Radical Anion of the Secondary Quinone Electron Acceptor QB in Photosystem II As Revealed by Fourier Transform Infrared Spectroscopy.

    Science.gov (United States)

    Nozawa, Yosuke; Noguchi, Takumi

    2018-05-15

    Photosystem II (PSII) is a protein complex that performs water oxidation using light energy during photosynthesis. In PSII, electrons abstracted from water are eventually transferred to the secondary quinone electron acceptor, Q B , and upon double reduction, Q B is converted to quinol by binding two protons. Thus, excess electron transfer in PSII increases the pH of the stroma. In this study, to investigate the pH-dependent regulation of the electron flow in PSII, we have estimated the relaxation rate of the Q B - radical anion in the pH region between 5 and 8 by direct monitoring of its population using light-induced Fourier transform infrared difference spectroscopy. The decay of Q B - by charge recombination with the S 2 state of the water oxidation center in PSII membranes was shown to be accelerated at higher pH, whereas that of Q A - examined in the presence of a herbicide was virtually unaffected at pH ≤7.5 and slightly slowed at pH 8. These observations were consistent with the previous studies that included rather indirect monitoring of the Q B - and Q A - decays using fluorescence detection. The accelerated relaxation of Q B - was explained by the shift of a redox equilibrium between Q A - and Q B - to the Q A - side due to the decrease in the redox potential of Q B at higher pH, which is induced by deprotonation of a single amino acid residue near Q B . It is proposed that this pH-dependent Q B - relaxation is one of the mechanisms of electron flow regulation in PSII for its photoprotection.

  13. HIF-1α Deletion in the Endothelium, but Not in the Epithelium, Protects From Radiation-Induced Enteritis

    Directory of Open Access Journals (Sweden)

    Aurore Toullec

    2018-01-01

    Conclusions: We demonstrate in vivo that HIF-1α impacts radiation-induced enteritis and that this role differs according to the targeted cell type. Our work provides a new role for HIF-1α and endothelium-dependent mechanisms driving inflammatory processes in gut mucosae. Results presented show that effects on normal tissues have to be taken into account in approaches aiming to modulate hypoxia or hypoxia-related molecular mechanisms.

  14. Conformational exchange in pseudoazurin: different kinds of microsecond to millisecond dynamics characterized by their pH and buffer dependence using 15N NMR relaxation.

    Science.gov (United States)

    Hass, Mathias A S; Vlasie, Monica D; Ubbink, Marcellus; Led, Jens J

    2009-01-13

    The dynamics of the reduced form of the blue copper protein pseudoazurin from Alcaligenes faecalis S-6 was investigated using (15)N relaxation measurements with a focus on the dynamics of the micro- to millisecond time scale. Different types of conformational exchange processes are observed in the protein on this time scale. At low pH, the protonation of the C-terminal copper-ligated histidine, His81, is observed. A comparison of the exchange rates in the presence and absence of added buffers shows that the protonation is the rate-limiting step at low buffer concentrations. This finding agrees with previous observations for other blue copper proteins, e.g., amicyanin and plastocyanin. However, in contrast to plastocyanin but similar to amicyanin, a second conformational exchange between different conformations of the protonated copper site is observed at low pH, most likely triggered by the protonation of His81. This process has been further characterized using CPMG dispersion methods and is found to occur with a rate of a few thousands per second. Finally, micro- to millisecond motions are observed in one of the loop regions and in the alpha-helical regions. These motions are unaffected by pH and are unrelated to the conformational changes in the active site of pseudoazurin.

  15. Consequences of PAI-1 specific deletion in endothelium on radiation-induced intestinal damage

    International Nuclear Information System (INIS)

    Rannou, Emilie

    2015-01-01

    Radiation-induced injury to healthy tissues is a real public health problem, since they are one of the most limiting factors that restrict efficiency of radiation therapy. This problematic is also part of the French Cancer Plan 2014-2017, and involves clinical research. Concepts surrounding the development of radiation-induced damage have gradually evolved into a contemporary and integrated view of the pathogenesis, involving all compartments of target tissue. Among them, endothelium seems to be central in the sequence of interrelated events that lead to the development of radiation-induced damage, although there are rare concrete elements that support this concept. By using new transgenic mouse models, this PhD project provides a direct demonstration of an endothelium-dependent continuum in evolution of radiation-induced intestinal damage. Indeed, changes in the endothelial phenotype through targeted deletion of the gene SERPINE1, chosen because of its key role in the development of radiation enteritis, influences various parameters of the development of the disease. Thus, lack of PAI-1 secretion by endothelial cells significantly improves survival of the animals, and limits severity of early and late tissue damage after a localized small bowel irradiation. Furthermore, these mice partially KO for PAI-1 showed a decrease in the number of apoptotic intestinal stem cells in the hours following irradiation, a decrease in the macrophages infiltrate density one week after irradiation, and a change in the polarization of macrophages throughout the pathophysiological process. In an effort to protect healthy tissues from radiation therapy side effects, without hindering the cancer treatment, PAI-1 seems to be an obvious therapeutic target. Conceptually, this work represents the direct demonstration of the link between endothelium phenotype and radiation enteritis pathogenesis. (author)

  16. Hypoxia and hydrogen sulfide differentially affect normal and tumor-derived vascular endothelium

    Directory of Open Access Journals (Sweden)

    Serena Bianco

    2017-08-01

    Full Text Available Background: endothelial cells play a key role in vessels formation both under physiological and pathological conditions. Their behavior is influenced by blood components including gasotransmitters (H2S, NO and CO. Tumor cells are subjected to a cyclic shift between pro-oxidative and hypoxic state and, in this scenario, H2S can be both cytoprotective and detrimental depending on its concentration. H2S effects on tumors onset and development is scarcely studied, particularly concerning tumor angiogenesis. We previously demonstrated that H2S is proangiogenic for tumoral but not for normal endothelium and this may represent a target for antiangiogenic therapeutical strategies. Methods: in this work, we investigate cell viability, migration and tubulogenesis on human EC derived from two different tumors, breast and renal carcinoma (BTEC and RTEC, compared to normal microvascular endothelium (HMEC under oxidative stress, hypoxia and treatment with exogenous H2S. Results: all EC types are similarly sensitive to oxidative stress induced by hydrogen peroxide; chemical hypoxia differentially affects endothelial viability, that results unaltered by real hypoxia. H2S neither affects cell viability nor prevents hypoxia and H2O2-induced damage. Endothelial migration is enhanced by hypoxia, while tubulogenesis is inhibited for all EC types. H2S acts differentially on EC migration and tubulogenesis. Conclusions: these data provide evidence for a great variability of normal and altered endothelium in response to the environmental conditions. Keywords: Hydrogen sulfide, Human microvascular endothelial cells, Human breast carcinoma-derived EC, Human renal carcinoma-derived EC, Tumor angiogenesis

  17. Confocal microscopy and electrophysiological study of single patient corneal endothelium cell cultures

    Science.gov (United States)

    Tatini, Francesca; Rossi, Francesca; Coppi, Elisabetta; Magni, Giada; Fusco, Irene; Menabuoni, Luca; Pedata, Felicita; Pugliese, Anna Maria; Pini, Roberto

    2016-04-01

    The characterization of the ion channels in corneal endothelial cells and the elucidation of their involvement in corneal pathologies would lead to the identification of new molecular target for pharmacological treatments and to the clarification of corneal physiology. The corneal endothelium is an amitotic cell monolayer with a major role in preserving corneal transparency and in regulating the water and solute flux across the posterior surface of the cornea. Although endothelial cells are non-excitable, they express a range of ion channels, such as voltage-dependent Na+ channels and K+ channels, L-type Ca2 channels and many others. Interestingly, purinergic receptors have been linked to a variety of conditions within the eye but their presence in the endothelium and their role in its pathophysiology is still uncertain. In this study, we were able to extract endothelial cells from single human corneas, thus obtaining primary cultures that represent the peculiarity of each donor. Corneas were from tissues not suitable for transplant in patients. We characterized the endothelial cells by confocal microscopy, both within the intact cornea and in the primary endothelial cells cultures. We also studied the functional role of the purinergic system (adenosine, ATP and their receptors) by means of electrophysiological recordings. The experiments were performed by patch clamp recordings and confocal time-lapse microscopy and our results indicate that the application of purinergic compounds modulates the amplitude of outward currents in the isolated endothelial cells. These findings may lead to the proposal of new therapies for endothelium-related corneal diseases.

  18. Mechanical relaxation in glasses

    International Nuclear Information System (INIS)

    Hiki, Y.

    2004-01-01

    The basic properties of glasses and the characteristics of mechanical relaxation in glasses were briefly reviewed, and then our studies concerned were presented. Experimental methods adopted were viscosity, internal friction, ultrasonic attenuation, and Brillouin scattering measurements. The specimens used were several kinds of inorganic, organic, and metallic glasses. The measurements were mainly carried out from the room temperature up to the glass transition temperature, and the relaxation time was determined as a function of temperature. The 'double relaxation' composed of two Arrhenius-type relaxations was observed in many materials. In both relaxations, the 'compensation effect' showing a correlation of the pre-exponential factor and the activation energy was observed. These results were explained by considering the 'complex relaxation' due to cooperative motions of atoms or group of atoms. Values of activation energy near the glass transition determined by the various experimental methods were compared with each other

  19. Targeted modulation of reactive oxygen species in the vascular endothelium

    OpenAIRE

    Shuvaev, Vladimir V.; Muzykantov, Vladimir R.

    2011-01-01

    Endothelial cells lining vascular luminal surface represent an important site of signaling and injurious effects of reactive oxygen species (ROS) produced by other cells and endothelium itself in ischemia, inflammation and other pathological conditions. Targeted delivery of ROS modulating enzymes conjugated with antibodies to endothelial surface molecules (vascular immunotargeting) provides site-specific interventions in the endothelial ROS, unattainable by other formulations including PEG-mo...

  20. Stress relaxation under cyclic electron irradiation

    International Nuclear Information System (INIS)

    Bystrov, L.N.; Reznitskij, M.E.

    1990-01-01

    The kinetics of deformation process in a relaxating sample under 2 MeV electron cyclic irradiation was studied experimentally. The Al-Mg alloys with controllable and different (in dislocation density precipitate presence and their character) structure were used in experiments. It was established that after the beam was switched on the deformation rate increased sharply and then, during prolonged irradiation, in a gradual manner. After the switching-off the relaxation rate decreases by jumps up to values close to extrapolated rates of pre-radiation relaxation. The exhibition of these effects with radiation switching-off and switchin-on is dependent on the initial rate of thermal relaxation, the test temperature, the preliminary cold deformation and the dominating deformation dislocation mechanism. The preliminary cold deformation and test temperature elevation slightly decrease the effect of instantaneous relaxation acceleration with the irradiation switch-on. 17 refs., 5 figs

  1. Vibrational and Rotational Energy Relaxation in Liquids

    DEFF Research Database (Denmark)

    Petersen, Jakob

    Vibrational and rotational energy relaxation in liquids are studied by means of computer simulations. As a precursor for studying vibrational energy relaxation of a solute molecule subsequent to the formation of a chemical bond, the validity of the classical Bersohn-Zewail model for describing......, the vibrational energy relaxation of I2 subsequent to photodissociation and recombination in CCl4 is studied using classical Molecular Dynamics simulations. The vibrational relaxation times and the time-dependent I-I pair distribution function are compared to new experimental results, and a qualitative agreement...... is found in both cases. Furthermore, the rotational energy relaxation of H2O in liquid water is studied via simulations and a power-and-work analysis. The mechanism of the energy transfer from the rotationally excited H2O molecule to its water neighbors is elucidated, i.e. the energy-accepting degrees...

  2. Relaxation properties in classical diamagnetism

    Science.gov (United States)

    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.

  3. In vitro study of histamine and histamine receptor ligands influence on the adhesion of purified human eosinophils to endothelium.

    Science.gov (United States)

    Grosicki, Marek; Wójcik, Tomasz; Chlopicki, Stefan; Kieć-Kononowicz, Katarzyna

    2016-04-15

    It is a well-known fact that histamine is involved in eosinophil-dependent inflammatory responses including cellular chemotaxis and migration. Nevertheless, the relative role of histamine receptors in the mechanisms of eosinophils adhesion to endothelial cells is not known. Therefore the aim of presented study was to examine the effect of selective histamine receptors ligands on eosinophils adhesion to endothelium. For that purpose the highly purified human eosinophils have been isolated from the peripheral blood. The viability and functional integrity of isolated eosinophils have been validated in several tests. Histamine as well as 4-methylhistamine (selective H4 agonist) in concentration-dependent manner significantly increased number of eosinophils that adhere to endothelium. Among the selective histamine receptors antagonist or H1 inverse agonist only JNJ7777120 (histamine H4 antagonist) and thioperamide (dual histamine H3/H4 antagonist) had direct effect on eosinophils adhesion to endothelial cells. Antagonists of H1 (diphenhydramine, mepyramine) H2 (ranitidine and famotidine) and H3 (pitolisant) histamine receptors were ineffective. To the best of our knowledge, this is the first study to demonstrate that histamine receptor H4 plays a dominant role in histamine-induced eosinophils adhesion to endothelium. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Relaxation characteristics of hastelloy X

    International Nuclear Information System (INIS)

    Suzuki, Kazuhiko

    1980-02-01

    Relaxation diagrams of Hastelloy X (relaxation curves, relaxation design diagrams, etc.) were generated from the creep constitutive equation of Hastelloy X, using inelastic stress analysis code TEPICC-J. These data are in good agreement with experimental relaxation data of ORNL-5479. Three typical inelastic stress analyses were performed for various relaxation behaviors of the high-temperature structures. An attempt was also made to predict these relaxation behaviors by the relaxation curves. (author)

  5. Role of coronary endothelium in cyclic AMP formation by the heart

    International Nuclear Information System (INIS)

    Kroll, K.; Schrader, J.

    1986-01-01

    In order to quantify the activation of adenylate cyclase of the coronary endothelium in vivo, endothelial adenine nucleotides of isolated guinea pig hearts were selectively pre-labeled by intracoronary infusion of tritiated (H3)-adenosine, and the coronary efflux of H3-cAMP was measured. The adenosine receptor agonist, NECA (12 μM), increased total cAMP release 4 fold, and raised H3-cAMP release 22 fold. Several classes of coronary vasodilators (adenosine, L-PIA, D-PIA, the beta 2-adrenergic agonist procaterol, and PGE1) caused dose-dependent increases in endothelial-derived H3-cAMP release. These increases were accompanied by decreases in vascular resistance, at agonist doses without positive intropic effects. Hypoxic perfusion also raised H3-cAMP release, and this was antagonized by theophylline. It is concluded: (1) cyclic AMP formation by coronary endothelium can dominate total cAMP production by the heart; (2) coronary endothelial adenylate cyclase-coupled receptors for adenosine (A2), catecholamines (beta2) and prostaglandins are activated in parallel with coronary vasodilation; (3) endothelial adenylate cyclase can be activated by endogenous adenosine

  6. Properties of the manganese(II) binding site in ternary complexes of Mnter dot ADP and Mnter dot ATP with chloroplast coupling factor 1: Magnetic field dependence of solvent sup 1 H and sup 2 H NMR relaxation rates

    Energy Technology Data Exchange (ETDEWEB)

    Haddy, A.E.; Frasch, W.D.; Sharp, R.R. (Univ. of Michigan, Ann Arbor (USA))

    1989-05-02

    The influence of the binding of ADP and ATP on the high-affinity Mn(II) binding site of chloroplast coupling factor 1 (CF{sub 1}) was studied by analysis of field-dependent solvent proton and deuteron spin-lattice relaxation data. In order to characterize metal-nucleotide complexes of CF{sub 1} under conditions similar to those of the NMR experiments, the enzyme was analyzed for bound nucleotides and Mn(II) after incubation with AdN and MnCl{sub 2} and removal of labile ligands by extensive gel filtration chromatography. In the field-dependent NMR experiments, the Mn(II) binding site of CF{sub 1} was studied for three mole ratios of added Mn(II) to CF{sub 1}, 0.5, 1.0, and 1.5, in the presence of an excess of either ADP or ATP. The results were extrapolated to zero Mn(II) concentration to characterize the environment of the first Mn(II) binding site of Cf{sub 1}. In the presence of both adenine nucleotides, pronounced changes in the Mn(II) environment relative to that in Mn(II)-CF{sub 1} were evident; the local relaxation rate maxima were more pronounced and shifted to higher field strengths, and the relaxation rate per bound Mn(II) increased at all field strengths. Analysis of the data revealed that the number of exchangeable water molecules liganded to bound Mn(II) increased from one in the binary Mn(II)-CF{sub 1} complex to three and two in the ternary Mn(II)-ADP-CF{sub 1} and Mn(II)-ATP-CF{sub 1} complexes, respectively; these results suggest that a water ligand to bound Mn(II) in the Mn(II)-ADP-CF{sub 1} complex is replaced by the {gamma}-phosphate of ATP in the Mn(II)-ATP-CF{sub 1} complex. A binding model is presented to account for these observations.

  7. TEACHING NEUROMUSCULAR RELAXATION.

    Science.gov (United States)

    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…

  8. Relaxation of Anisotropic Glasses

    DEFF Research Database (Denmark)

    Deubener, Joachim; Martin, Birgit; Wondraczek, Lothar

    2004-01-01

    . When the load was removed at room temperature a permanent optical anisotropy (birefringence) was observed only perpendicular to cylinder axis and the pressure direction indicating complete elimination of thermal stresses. Relaxation of structural anisotropy was studied from reheating experiments using...... the energy release, thermo-mechanical and optical relaxation behaviour are drawn....

  9. Relaxation techniques for stress

    Science.gov (United States)

    ... raise your heart rate. This is called the stress response. Relaxation techniques can help your body relax and lower your blood pressure ... also many other types of breathing techniques you can learn. In many cases, you do not need much ... including those that cause stress. Meditation has been practiced for thousands of years, ...

  10. Effects of a Single Bout of Resistance Exercise in Different Volumes on Endothelium Adaptations in Healthy Animals.

    Science.gov (United States)

    Mota, Marcelo Mendonça; Silva, Tharciano Luiz Teixeira Braga da; Macedo, Fabricio Nunes; Mesquita, Thássio Ricardo Ribeiro; Quintans, Lucindo José; Santana-Filho, Valter Joviniano de; Lauton-Santos, Sandra; Santos, Márcio Roberto Viana

    2017-05-01

    Resistance exercise (RE) has been recommended for patients with cardiovascular diseases. Recently, a few studies have demonstrated that the intensity of a single bout of RE has an effect on endothelial adaptations to exercise. However, there is no data about the effects of different volumes of RE on endothelium function. The aim of the study was to evaluate the effects of different volumes of RE in a single bout on endothelium-dependent vasodilatation and nitric oxide (NO) synthesis in the mesenteric artery of healthy animals. Male Wistar rats were divided into three groups: Control (Ct); low-volume RE (LV, 5 sets x 10 repetitions) and high-volume RE (HV, 15 sets x 10 repetitions). The established intensity was 70% of the maximal repetition test. After the exercise protocol, rings of mesenteric artery were used for assessment of vascular reactivity, and other mesenteric arteries were prepared for detection of measure NO production by DAF-FM fluorescence. Insulin responsiveness on NO synthesis was evaluated by stimulating the vascular rings with insulin (10 nM). The maximal relaxation response to insulin increased in the HV group only as compared with the Ct group. Moreover, the inhibition of nitric oxide synthesis (L-NAME) completely abolished the insulin-induced vasorelaxation in exercised rats. NO production showed a volume-dependent increase in the endothelial and smooth muscle layer. In endothelial layer, only Ct and LV groups showed a significant increase in NO synthesis when compared to their respective group under basal condition. On the other hand, in smooth muscle layer, NO fluorescence increased in all groups when compared to their respective group under basal condition. Our results suggest that a single bout of RE promotes vascular endothelium changes in a volume-dependent manner. The 15 sets x 10 repetitions exercise plan induced the greatest levels of NO synthesis. O exercício resistido (ER) tem sido recomendado para pacientes com doen

  11. Activation of muscarinic receptors by a hydroalcoholic extract of Dicksonia sellowiana Presl. HooK (Dicksoniaceae) induces vascular relaxation and hypotension in rats.

    Science.gov (United States)

    Rattmann, Yanna D; Crestani, Sandra; Lapa, Fernanda R; Miguel, Obdúlio G; Marques, Maria C A; da Silva-Santos, J Eduardo; Santos, Adair R S

    2009-01-01

    Dicksonia sellowiana (Presl.) Hook is a native plant from the Central and South Americas that contain high levels of polyphenols, antioxidant compounds involved in protection against inflammation, cancer and cardiovascular risk. A phytomedicinal preparation obtained from aerial parts of D. sellowiana is currently under clinical evaluation in Brazil against asthma, and has been associated with several other beneficial effects. This study demonstrates that a hydroalcoholic extract obtained from D. sellowiana leaves (HEDS) fully relax, in a concentration-dependent manner, rat aortic rings precontracted with phenylephrine. Moreover, administration of HEDS (10, 20 and 40 mg/kg, i.v.) in anaesthetized rats resulted in a strong but reversible hypotension. Aortic relaxation induced by HEDS was abolished by endothelium removal, by incubation of the nitric oxide synthase inhibitor L-NAME, or the soluble guanylate cyclase inhibitor ODQ. In addition, this effect was partially inhibited by indomethacin (a cyclooxygenase inhibitor) and KT 5730 (a PKA inhibitor). The potassium channels blockade by either tetraethylammonium or charybdotoxin also resulted in a potent inhibition of HEDS-induced aortic relaxation, whereas apamine only slightly reduced it. In addition HEDS-induced relaxation was unchanged by 4-amynopiridine and glibenclamide. The selective muscarinic receptor antagonist atropine counteracted both aortic relaxation and blood pressure reduction generated by HEDS. Experiments using HPLC revealed the presence of high amounts of phenolic compounds in this extract. Taken together, our results reveal that the D. sellowiana possess substances with both in vivo and in vitro activities and that the vascular effect of HEDS involves activation of muscarinic receptors, stimulation of the nitric oxide pathway and opening of calcium-activated potassium channels.

  12. Collisional relaxation of electron tail distribution

    International Nuclear Information System (INIS)

    Yamagiwa, Mitsuru; Okamoto, Masao.

    1985-05-01

    Relaxation due to the Coulomb collisions of the electron velocity distribution function with a high energy tail is investigated in detail. In the course of the relaxation, a 'saddle' point can be created in velocity space owing to upsilon -3 dependence of the deflection rate and a positive slope or a 'dip' appears in the tail direction. The time evolution of the electron tail is studied analytically. A comparison is made with numerical results by using a Fokker-Planck code. Also discussed is the kinetic instability concerned with the positive slope during the relaxation. (author)

  13. Strain relaxation during solid-phase epitaxial crystallisation of Ge{sub x}Si{sub 1-x} alloy layers with depth dependent G{sub e} compositions

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Wahchung; Elliman, R G; Kringhoj, P [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences

    1994-12-31

    The solid-phase epitaxial crystallisation of depth dependent Ge{sub x}Si{sub lx} alloy layers produced by implanting Ge into Si substrates was studied. In-situ monitoring was done using time-resolved reflectivity (TRR) whilst post-anneal defect structures were characterised by Rutherford backscattering and channeling spectrometry (RBS-C) and transmission electron microscopy (TEM). Particular attention was directed at Ge concentrations above the critical concentration for the growth of fully strained layers. Strain relief is shown to be correlated with a sudden reduction in crystallisation velocity caused by roughening of the crystalline/amorphous interface. 11 refs., 1 tab., 2 figs.

  14. Strain relaxation during solid-phase epitaxial crystallisation of Ge{sub x}Si{sub 1-x} alloy layers with depth dependent G{sub e} compositions

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Wahchung; Elliman, R.G.; Kringhoj, P. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences

    1993-12-31

    The solid-phase epitaxial crystallisation of depth dependent Ge{sub x}Si{sub lx} alloy layers produced by implanting Ge into Si substrates was studied. In-situ monitoring was done using time-resolved reflectivity (TRR) whilst post-anneal defect structures were characterised by Rutherford backscattering and channeling spectrometry (RBS-C) and transmission electron microscopy (TEM). Particular attention was directed at Ge concentrations above the critical concentration for the growth of fully strained layers. Strain relief is shown to be correlated with a sudden reduction in crystallisation velocity caused by roughening of the crystalline/amorphous interface. 11 refs., 1 tab., 2 figs.

  15. Relaxing Responses to Hydrogen Peroxide and Nitric Oxide in Human Pericardial Resistance Arteries Stimulated with Endothelin-1

    DEFF Research Database (Denmark)

    Leurgans, Thomas M; Bloksgaard, Maria; Irmukhamedov, Akhmadjon

    2018-01-01

    In human pericardial resistance arteries, effects of the endothelium-dependent vasodilator bradykinin are mediated by NO during contraction induced by K(+) or the TxA2 analogue U46619 and by H2 O2 during contraction by endothelin-1 (ET-1), respectively. We tested the hypotheses that ET-1 reduces...... also acts as an endothelium-dependent vasodilator. This article is protected by copyright. All rights reserved....

  16. From field to health: a simple way to increase the nutraceutical content of grape as shown by NO-dependent vascular relaxation.

    Science.gov (United States)

    Fumagalli, Francesca; Rossoni, Mara; Iriti, Marcello; di Gennaro, Antonio; Faoro, Franco; Borroni, Emanuele; Borgo, Michele; Scienza, Attilio; Sala, Angelo; Folco, Giancarlo

    2006-07-26

    Polyphenolic grapevine components involved in plant resistance against pathogens possess various pharmacological properties that include nitric oxide (NO)-dependent vasodilation and anti-inflammatory and free radical scavenging activities, which may explain the protective effect of moderate red wine consumption against cardiovascular disease. The aim of this work was (a) to verify the possibility that preharvest treatments of grapevine with a plant activator, benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), could lead to an enriched nutraceutical potential of wine and (b) to characterize the profile of metabolites responsible for pharmacological activity. Plant spraying at the end of veraison, with a water suspension of BTH (0.3 mM), led to increased whole anthocyanin content as confirmed by HPLC comparative analysis. Extracts from berry skins of BTH-treated grapevines caused NO-dependent vasorelaxation, with a concentration-response curve that was significantly shifted to the left of the control non-BTH-treated curve. Moreover, 1:1000 dilutions of berry extracts from BTH-treated plants significantly increased basal production of guanosine 3',5'-cyclic monophosphate (cGMP) in human vascular endothelial cells when compared to the corresponding extracts of untreated plants. These results show that BTH treatment increases anthocyanin content of grape extracts, as well as their ability to induce NO-mediated vasoprotection. No increase of anthocyanin content was observed in the wine extracts from BTH-treated vines. It is concluded that BTH treatment could be exploited to increase the nutraceutical potential of grapes.

  17. Crucial roles of Nox2-derived oxidative stress in deteriorating the function of insulin receptors and endothelium in dietary obesity of middle-aged mice.

    Science.gov (United States)

    Du, Junjie; Fan, Lampson M; Mai, Anna; Li, Jian-Mei

    2013-11-01

    Systemic oxidative stress associated with dietary calorie overload plays an important role in the deterioration of vascular function in middle-aged patients suffering from obesity and insulin resistance. However, effective therapy is still lacking. In this study, we used a mouse model of middle-aged obesity to investigate the therapeutic potential of pharmaceutical inhibition (apocynin, 5 mM supplied in the drinking water) or knockout of Nox2, an enzyme generating reactive oxygen species (ROS), in high-fat diet (HFD)-induced obesity, oxidative stress, insulin resistance and endothelial dysfunction. Littermates of C57BL/6J wild-type (WT) and Nox2 knockout (KO) mice (7 months old) were fed with a HFD (45% kcal fat) or normal chow diet (NCD, 12% kcal fat) for 16 weeks and used at 11 months of age. Compared to NCD WT mice, HFD WT mice developed obesity, insulin resistance, dyslipidaemia and hypertension. Aortic vessels from these mice showed significantly increased Nox2 expression and ROS production, accompanied by significantly increased ERK1/2 activation, reduced insulin receptor expression, decreased Akt and eNOS phosphorylation and impaired endothelium-dependent vessel relaxation to acetylcholine. All these HFD-induced abnormalities (except the hyperinsulinaemia) were absent in apocynin-treated WT or Nox2 KO mice given the same HFD. In conclusion, Nox2-derived ROS played a key role in damaging insulin receptor and endothelial function in dietary obesity after middle-age. Targeting Nox2 could represent a valuable therapeutic strategy in the metabolic syndrome. © 2013 The British Pharmacological Society.

  18. Dynamic, nondestructive imaging of a bioengineered vascular graft endothelium.

    Directory of Open Access Journals (Sweden)

    Bryce M Whited

    Full Text Available Bioengineering of vascular grafts holds great potential to address the shortcomings associated with autologous and conventional synthetic vascular grafts used for small diameter grafting procedures. Lumen endothelialization of bioengineered vascular grafts is essential to provide an antithrombogenic graft surface to ensure long-term patency after implantation. Conventional methods used to assess endothelialization in vitro typically involve periodic harvesting of the graft for histological sectioning and staining of the lumen. Endpoint testing methods such as these are effective but do not provide real-time information of endothelial cells in their intact microenvironment, rather only a single time point measurement of endothelium development. Therefore, nondestructive methods are needed to provide dynamic information of graft endothelialization and endothelium maturation in vitro. To address this need, we have developed a nondestructive fiber optic based (FOB imaging method that is capable of dynamic assessment of graft endothelialization without disturbing the graft housed in a bioreactor. In this study we demonstrate the capability of the FOB imaging method to quantify electrospun vascular graft endothelialization, EC detachment, and apoptosis in a nondestructive manner. The electrospun scaffold fiber diameter of the graft lumen was systematically varied and the FOB imaging system was used to noninvasively quantify the affect of topography on graft endothelialization over a 7-day period. Additionally, results demonstrated that the FOB imaging method had a greater imaging penetration depth than that of two-photon microscopy. This imaging method is a powerful tool to optimize vascular grafts and bioreactor conditions in vitro, and can be further adapted to monitor endothelium maturation and response to fluid flow bioreactor preconditioning.

  19. Corneal endothelium in xeroderma pigmentosum: clinical specular microscopy study.

    Science.gov (United States)

    Mohamed, Ashik; Peguda, Rajini; Ramappa, Muralidhar; Ali, Mohammad Javed; Chaurasia, Sunita

    2016-06-01

    Xeroderma pigmentosum is a condition caused due to a defective DNA repair mechanism when exposed to ultraviolet radiation. Many of the patients with this disorder develop severely oedematous cornea with varying degrees of anterior corneal haze, which necessitates a full-thickness keratoplasty or selective endothelial keratoplasty. Presence of corneal oedema suggests that these patients have a dysfunctional endothelium. The purpose of this study is to evaluate the corneal endothelium in the patients with xeroderma pigmentosum when clinical specular microscopy was feasible. Thirteen patients with classic skin changes of xeroderma pigmentosum were included in the study conducted during January 2010-December 2012. An age-matched group of 13 volunteers were included as controls who were emmetropes without any history of ocular or systemic illness. Corneal endothelium was assessed using specular microscopy from the central clear area of cornea. The mean age of the patients with xeroderma pigmentosum was 16.6±7.2 years and that of the controls was 17.4±6.9 years (p=0.78). The number of analysed cells and endothelial cell density were significantly higher in controls (pxeroderma pigmentosum (p≤0.007). The specular microscopic findings in patients with xeroderma pigmentosum are suggestive of an accelerated endothelial cell loss. It is pertinent that the treating physicians must be involved in emphasising proper ocular protection from ultraviolet radiation to prevent avoidable blindness from xeroderma pigmentosum. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  20. Abrupt relaxation in high-spin molecules

    International Nuclear Information System (INIS)

    Chang, C.-R.; Cheng, T.C.

    2000-01-01

    Mean-field model suggests that the rate of resonant quantum tunneling in high-spin molecules is not only field-dependent but also time-dependent. The relaxation-assisted resonant tunneling in high-spin molecules produces an abrupt magnetization change during relaxation. When the applied field is very close to the resonant field, a time-dependent interaction field gradually shifts the energies of different collective spin states, and magnetization tunneling is observed as two energies of the spin states coincide

  1. Interstitial relaxations due to hydrostatic stress in niobium--oxygen alloys

    International Nuclear Information System (INIS)

    Tewari, S.N.

    1974-01-01

    Experimental investigations of the anelastic relaxation induced by hydrostatic stress in the range from ambient to 81 ksi were made for niobium--oxygen alloys. The anelastic responses, both for the pressurization and the pressure release experiments, were followed by measuring the relative length change between the oxygenated niobium sample and a pure niobium frame with a precision of about 2 A. The relaxation spectrum observed was shown to be made up of three distinct relaxations with unique relaxation times and strengths. The pressure dependence of the relaxation times gave the apparent activation volume for these relaxations of the order of 4 cm 3 /mole. The relaxations were observed to have relaxation strengths of the order of 10 -4 which were found to be independent of pressure up to 81 ksi. The relaxation times for these relaxations were found to occur in the same general temperature range as those for the Snoek relaxations of oxygen clusters in niobium. The temperature dependence of the relaxation times, however, gave activation energies of about 11 to 15 kcal/mole, as compared with roughly 27 to 29 kcal/mole for the Snoek relaxation of oxygen clusters in niobium. Several possible models for these relaxations were developed, however, none could predict the observed temperature dependence. The best interpretation of the data is that due to some anomalous competing relaxation the actual temperature dependence of these relaxations could not be observed. A completely self-consistent analysis is found which is based upon this assumption. (U.S.)

  2. Targeted modulation of reactive oxygen species in the vascular endothelium.

    Science.gov (United States)

    Shuvaev, Vladimir V; Muzykantov, Vladimir R

    2011-07-15

    'Endothelial cells lining vascular luminal surface represent an important site of signaling and injurious effects of reactive oxygen species (ROS) produced by other cells and endothelium itself in ischemia, inflammation and other pathological conditions. Targeted delivery of ROS modulating enzymes conjugated with antibodies to endothelial surface molecules (vascular immunotargeting) provides site-specific interventions in the endothelial ROS, unattainable by other formulations including PEG-modified enzymes. Targeting of ROS generating enzymes (e.g., glucose oxidase) provides ROS- and site-specific models of endothelial oxidative stress, whereas targeting of antioxidant enzymes SOD and catalase offers site-specific quenching of superoxide anion and H(2)O(2). These targeted antioxidant interventions help to clarify specific role of endothelial ROS in vascular and pulmonary pathologies and provide basis for design of targeted therapeutics for treatment of these pathologies. In particular, antibody/catalase conjugates alleviate acute lung ischemia/reperfusion injury, whereas antibody/SOD conjugates inhibit ROS-mediated vasoconstriction and inflammatory endothelial signaling. Encapsulation in protease-resistant, ROS-permeable carriers targeted to endothelium prolongs protective effects of antioxidant enzymes, further diversifying the means for targeted modulation of endothelial ROS. Copyright © 2011 Elsevier B.V. All rights reserved.

  3. Injuries to the vascular endothelium: vascular wall and endothelial dysfunction.

    Science.gov (United States)

    Fisher, Mark

    2008-01-01

    Vascular endothelial injury has multiple elements, and this article focuses on ischemia-related processes that have particular relevance to ischemic stroke. Distinctions between necrotic and apoptotic cell death provide a basic science context in which to better understand the significance of classical core and penumbra concepts of acute stroke, with apoptotic processes particularly prominent in the penumbra. The mitochondria are understood to serve as a reservoir of proteins that mediate apoptosis. Oxidative stress pathways generating reactive oxygen species (ROS) are prominent in endothelial injury, both ischemic and nonischemic, with prominent roles of enzyme- and nonenzymemediated pathways; mitochondria once again have a critical role, particularly in the nonenzymatic pathways generating ROS. Inflammation also contributes to vascular endothelial injury, and endothelial cells have the capacity to rapidly increase expression of inflammatory mediators following ischemic challenge; this leads to enhanced leukocyte-endothelial interactions mediated by selectins and adhesion molecules. Preconditioning consists of a minor version of an injurious event, which in turn may protect vascular endothelium from injury following a more substantial event. Presence of the blood-brain barrier creates unique responses to endothelial injury, with permeability changes due to impairment of endothelial-matrix interactions compounding altered vasomotor tone and tissue perfusion mediated by nitric oxide. Pharmacological protection against vascular endothelial injury can be provided by several of the phosphodiesterases (cilostazol and dipyridamole), along with statins. Optimal clinical responses for protection of brain vascular endothelium may use preconditioning as a model, and will likely require combined protection against apoptosis, ROS, and inflammation.

  4. Relaxed plasma-vacuum systems

    International Nuclear Information System (INIS)

    Spies, G.O.; Lortz, D.; Kaiser, R.

    2001-01-01

    Taylor's theory of relaxed toroidal plasmas (states of lowest energy with fixed total magnetic helicity) is extended to include a vacuum between the plasma and the wall. In the extended variational problem, one prescribes, in addition to the helicity and the magnetic fluxes whose conservation follows from the perfect conductivity of the wall, the fluxes whose conservation follows from the assumption that the plasma-vacuum interface is also perfectly conducting (if the wall is a magnetic surface, then one has the toroidal and the poloidal flux in the vacuum). Vanishing of the first energy variation implies a pressureless free-boundary magnetohydrostatic equilibrium with a Beltrami magnetic field in the plasma, and in general with a surface current in the interface. Positivity of the second variation implies that the equilibrium is stable according to ideal magnetohydrodynamics, that it is a relaxed state according to Taylor's theory if the interface is replaced by a wall, and that the surface current is nonzero (at least if there are no closed magnetic field lines in the interface). The plane slab, with suitable boundary conditions to simulate a genuine torus, is investigated in detail. The relaxed state has the same double symmetry as the vessel if, and only if, the prescribed helicity is in an interval that depends on the prescribed fluxes. This interval is determined in the limit of a thin slab

  5. Relaxation strain measurements in cellular dislocation structures

    International Nuclear Information System (INIS)

    Tsai, C.Y.; Quesnel, D.J.

    1984-01-01

    The conventional picture of what happens during a stress relaxation usually involves imagining the response of a single dislocation to a steadily decreasing stress. The velocity of this dislocation decreases with decreasing stress in such a way that we can measure the stress dependence of the dislocation velocity. Analysis of the data from a different viewpoint enables us to calculate the apparent activation volume for the motion of the dislocation under the assumption of thermally activated glie. Conventional thinking about stress relaxation, however, does not consider the eventual fate of this dislocation. If the stress relaxes to a low enough level, it is clear that the dislocation must stop. This is consistent with the idea that we can determine the stress dependence of the dislocation velocity from relaxation data only for those cases where the dislocation's velocity is allowed to approach zero asymptotically, in short, for those cases where the dislocation never stops. This conflict poses a dilemma for the experimentalist. In real crystals, however, obstacles impede the dislocation's progress so that those dislocations which are stopped at a given stress will probably never resume motion under the influence of the steadily declining stress present during relaxation. Thus one could envision stress relaxation as a process of exhaustion of mobile dislocations, rather than a process of decreasing dislocation velocity. Clearly both points of view have merit and in reality both mechanisms contribute to the phenomena

  6. The relaxation of plasmas with dust particles

    International Nuclear Information System (INIS)

    Chutov, Yu.I.; Kravchenko, A.Yu.; Schram, P.P.J.M.

    1997-01-01

    Various parameters of relaxing plasmas with dust particles including the electron and ion energy distributions function are numerically simulated at various parameters of the dust particles using the PIC method and taking into account the dynamics of the dust particle charge without the assumption about the equilibrium of electrons and ions. Coulomb collisions are taken into account in the framework of the method of stochastic differential equations. The relaxation of bounded plasma clouds expanding into a vacuum as well as the relaxation of a uniform plasma, in which dust particles appear at some initial time, are investigated. The obtained results show that the relaxation of plasmas can be accompanied by a deviation of the ion distribution function from equilibrium as well as a change of the mean energy of electrons and ions because of the dependence of the collection of electrons and ions by dust particles on their energy. (author)

  7. Binding of human endothelium to Ulex europaeus I-coated Dynabeads: application to the isolation of microvascular endothelium.

    Science.gov (United States)

    Jackson, C J; Garbett, P K; Nissen, B; Schrieber, L

    1990-06-01

    A major problem encountered when isolating human microvascular endothelium is the presence of contaminating cells such as fibroblasts that rapidly over-grow the endothelial cells. We describe here a simple, rapid technique for purifying endothelial cells derived from the microvasculature of neonatal foreskin and osteoarthritic and rheumatoid arthritic synovium. This technique is based on the selective binding of the lectin Ulex europaeus I (UEA I) to the endothelial cell surface via fucose residues. Initially UEA I was covalently bound to tosyl-activated super-paramagnetic polystyrene beads (Dynabeads) by incubation for 24 h at room temperature. Cells were isolated by extracting microvascular segments from enzyme-treated (trypsin and Pronase) cubes of tissue. The mixed population of cells obtained were purified by incubating them at 4 degrees C for 10 min with the UEA I-coated Dynabeads. Endothelium bound to the beads whilst contaminating cells were removed by five washes with HBSS using a magnetic particle concentrator. The endothelial cells thus obtained grew to confluence as a cobblestone-like monolayer and expressed von Willebrand factor antigen. The cells were released from the Dynabeads by the competitive binding of fucose (10 min at 4 degrees C). This new method is simple and reproducible and allows pure human microvascular endothelial cells to be cultured within 2 h of obtaining a specimen.

  8. An in vitro model of hemogenic endothelium commitment and hematopoietic production

    NARCIS (Netherlands)

    Yvernogeau, Laurent; Gautier, Rodolphe; Khoury, Hanane; Menegatti, Sara; Schmidt, Melanie; Gilles, Jean Francois; Jaffredo, Thierry

    2016-01-01

    Adult-type hematopoietic stem and progenitor cells are formed during ontogeny from a specialized subset of endothelium, termed the hemogenic endothelium, via an endothelial-to-hematopoietic transition (EHT) that occurs in the embryonic aorta and the associated arteries. Despite efforts to generate

  9. Phototoxic effects of 8-methoxypsoralen on rabbit corneal endothelium

    Energy Technology Data Exchange (ETDEWEB)

    Menon, I.A.; Basu, P.K.; Hasany, S.M.; Persad, S.D. (Univ. of Toronto, Ontario (Canada))

    1989-01-01

    The phototoxic effects of 8-methoxypsoralen (8-MOP) were investigated using the rabbit corneal endothelium in organ culture. The corneas were divided into four groups: (a) irradiated with a mercury vapor lamp (emitting UVA and visible radiation) in the presence of 8-MOP (experimental), (b) irradiated without 8-MOP (control A), (c) incubated with 8-MOP (control B) and (d) incubated without 8-MOP (control C). Specular and light microscopic examination showed that the experimental corneas had greater cellular damage compared to the control corneas. The effects of 8-MOP were restricted to certain localized areas of the cornea. However there was no significant difference in the amounts of 51Cr released from the labelled experimental and control corneas. These results show phototoxic damage of the corneal endothelial cells.

  10. Relaxation of synchronization on complex networks.

    Science.gov (United States)

    Son, Seung-Woo; Jeong, Hawoong; Hong, Hyunsuk

    2008-07-01

    We study collective synchronization in a large number of coupled oscillators on various complex networks. In particular, we focus on the relaxation dynamics of the synchronization, which is important from the viewpoint of information transfer or the dynamics of system recovery from a perturbation. We measure the relaxation time tau that is required to establish global synchronization by varying the structural properties of the networks. It is found that the relaxation time in a strong-coupling regime (K>Kc) logarithmically increases with network size N , which is attributed to the initial random phase fluctuation given by O(N-1/2) . After elimination of the initial-phase fluctuation, the relaxation time is found to be independent of the system size; this implies that the local interaction that depends on the structural connectivity is irrelevant in the relaxation dynamics of the synchronization in the strong-coupling regime. The relaxation dynamics is analytically derived in a form independent of the system size, and it exhibits good consistency with numerical simulations. As an application, we also explore the recovery dynamics of the oscillators when perturbations enter the system.

  11. Stress relaxation in viscous soft spheres.

    Science.gov (United States)

    Boschan, Julia; Vasudevan, Siddarth A; Boukany, Pouyan E; Somfai, Ellák; Tighe, Brian P

    2017-10-04

    We report the results of molecular dynamics simulations of stress relaxation tests in athermal viscous soft sphere packings close to their unjamming transition. By systematically and simultaneously varying both the amplitude of the applied strain step and the pressure of the initial condition, we access both linear and nonlinear response regimes and control the distance to jamming. Stress relaxation in viscoelastic solids is characterized by a relaxation time τ* that separates short time scales, where viscous loss is substantial, from long time scales, where elastic storage dominates and the response is essentially quasistatic. We identify two distinct plateaus in the strain dependence of the relaxation time, one each in the linear and nonlinear regimes. The height of both plateaus scales as an inverse power law with the distance to jamming. By probing the time evolution of particle velocities during relaxation, we further identify a correlation between mechanical relaxation in the bulk and the degree of non-affinity in the particle velocities on the micro scale.

  12. COMPARATIVE ASSESSMENT OF NUCLEAR MAGNETIC RELAXATION CHARACTERISTICS OF SUNFLOWER AND RAPESEED LECITHIN

    OpenAIRE

    Lisovaya E. V.; Victorova E. P.; Agafonov O. S.; Kornen N. N.; Shahray T. A.

    2015-01-01

    The article presents a comparative assessment and peculiarities of nuclear magnetic relaxation characteristics of rapeseed and sunflower lecithin. It was established, that lecithin’s nuclear magnetic relaxation characteristics, namely, protons’ spin-spin relaxation time and amplitudes of nuclear magnetic relaxation signals of lecithin components, depend on content of oil’s fat acids and phospholipids, contained in the lecithin. Comparative assessment of protons’ spin-spin relaxation time of r...

  13. Potentiation of phorbol ester-induced coronary vasoconstriction in dogs following endothelium disruption

    International Nuclear Information System (INIS)

    Roberts, R.B.; Ku, D.D.

    1986-01-01

    In the present study, the effect of phorbol ester, 12-0-tetradecanoylphorbol 13-acetate (TPA), activation of protein kinase C on coronary vascular reactivity was studied in isolated dog coronary arteries. Addition of TPA (10-100 nM) produced a slow, time- and dose-dependent contraction reaching a maximum at approx 2-3 hrs and was essentially irreversible upon washing. Disruption of the endothelium(EC) greatly accelerated the development as well as increase the magnitude of TPA contraction (50-100%). Prior treatment of vessels with phentolamine (1μM), cyproheptadine (1μH) and ibuprofen (1μg/ml) did not alter the TPA contraction. Furthermore, in contrast to previously reported calcium-dependence of TPA contraction in other vessels, complete removal of extracellular calcium (Ca 0 ) or addition of 1μM nimodipine after TPA(30nM) resulted in only 32 +/- 4% and 25 +/- 3% reversal of TPA contraction, respectively. Addition of amiloride (10μM to 1mM), however, resulted in a dose-dependent reversal of TPA contraction. The results of the present study indicate that a similar activation of protein kinase C by TPA leads to potent coronary vasoconstriction, which is not completely dependent on Ca 0 . More importantly, these results further support their hypothesis that EC also functions as an inhibitory barrier to prevent circulating vasoconstrictors from exerting their deleterious constrictory effects

  14. Muon spin relaxation in ferromagnets. Pt. 1

    International Nuclear Information System (INIS)

    Lovesey, S.W.; Karlsson, E.B.

    1991-04-01

    Expressions for the dipolar and hyperfine contributions to the relaxation rate of muons implanted in a ferromagnet are presented and analysed using the Heisenberg model of spin-waves including dipolar and Zeeman energies. Calculations for EuO indicate that relaxation is likely to be dominated by the hyperfine mechanism, even if the ratio of the hyperfine and dipolar coupling constants is small. The hyperfine mechanism is sensitive to the dipolar energy of the atomic spins, whereas the dipolar mechanisms depend essentially on the exchange energy. For both mechanisms there is an almost quadratic dependence on temperature, throughout much of the ordered magnetic phase, which reflects two-spin-wave difference events from the Raman-type relaxation processes. (author)

  15. Temperature dependence of the hydrated electron's excited-state relaxation. I. Simulation predictions of resonance Raman and pump-probe transient absorption spectra of cavity and non-cavity models

    Science.gov (United States)

    Zho, Chen-Chen; Farr, Erik P.; Glover, William J.; Schwartz, Benjamin J.

    2017-08-01

    We use one-electron non-adiabatic mixed quantum/classical simulations to explore the temperature dependence of both the ground-state structure and the excited-state relaxation dynamics of the hydrated electron. We compare the results for both the traditional cavity picture and a more recent non-cavity model of the hydrated electron and make definite predictions for distinguishing between the different possible structural models in future experiments. We find that the traditional cavity model shows no temperature-dependent change in structure at constant density, leading to a predicted resonance Raman spectrum that is essentially temperature-independent. In contrast, the non-cavity model predicts a blue-shift in the hydrated electron's resonance Raman O-H stretch with increasing temperature. The lack of a temperature-dependent ground-state structural change of the cavity model also leads to a prediction of little change with temperature of both the excited-state lifetime and hot ground-state cooling time of the hydrated electron following photoexcitation. This is in sharp contrast to the predictions of the non-cavity model, where both the excited-state lifetime and hot ground-state cooling time are expected to decrease significantly with increasing temperature. These simulation-based predictions should be directly testable by the results of future time-resolved photoelectron spectroscopy experiments. Finally, the temperature-dependent differences in predicted excited-state lifetime and hot ground-state cooling time of the two models also lead to different predicted pump-probe transient absorption spectroscopy of the hydrated electron as a function of temperature. We perform such experiments and describe them in Paper II [E. P. Farr et al., J. Chem. Phys. 147, 074504 (2017)], and find changes in the excited-state lifetime and hot ground-state cooling time with temperature that match well with the predictions of the non-cavity model. In particular, the experiments

  16. Relaxed Binaural LCMV Beamforming

    NARCIS (Netherlands)

    Koutrouvelis, A.; Hendriks, R.C.; Heusdens, R.; Jensen, Jesper Rindom

    2017-01-01

    In this paper, we propose a new binaural beamforming technique, which can be seen as a relaxation of the linearly constrained minimum variance (LCMV) framework. The proposed method can achieve simultaneous noise reduction and exact binaural cue preservation of the target source, similar to the

  17. Structural relaxation monitored by instantaneous shear modulus

    DEFF Research Database (Denmark)

    Olsen, Niels Boye; Dyre, Jeppe; Christensen, Tage Emil

    1998-01-01

    time definition based on a recently proposed expression for the relaxation time, where G [infinity] reflects the fictive temperature. All parameters entering the reduced time were determined from independent measurements of the frequency-dependent shear modulus of the equilibrium liquid....

  18. Endothelin-1 shifts the mediator of bradykinin-induced relaxation from NO to H2 O2 in resistance arteries from patients with cardiovascular disease

    DEFF Research Database (Denmark)

    Leurgans, Thomas M; Bloksgaard, Maria; Brewer, Jonathan R

    2016-01-01

    -activated K(+) -channels, but markedly blunted by catalase during ET-1-induced contraction. This catalase-sensitive relaxation was not modified by inhibitors of NADPH oxidases or allopurinol. Exogenous H2 O2 caused significantly larger relaxation of ET-1- than K(+) - or U46619-induced contraction...... in the presence of inhibitors of other endothelium-derived relaxing factors. Catalase-sensitive staining of cellular reactive oxygen species with CellROX Deep Red was significantly increased in presence of both 1 μM BK and 2 nM ET-1 but not either peptide alone. CONCLUSIONS AND IMPLICATIONS: In patient resistance...

  19. The Role of the Endothelium in HPS Pathogenesis and Potential Therapeutic Approaches

    Directory of Open Access Journals (Sweden)

    Irina Gavrilovskaya

    2012-01-01

    Full Text Available American hantaviruses cause a highly lethal acute pulmonary edema termed hantavirus pulmonary syndrome (HPS. Hantaviruses nonlytically infect endothelial cells and cause dramatic changes in barrier functions of the endothelium without disrupting the endothelium. Instead hantaviruses cause changes in the function of infected endothelial cells that normally regulate fluid barrier functions of capillaries. The endothelium of arteries, veins, and lymphatic vessels is unique and central to the function of vast pulmonary capillary beds, which regulate pulmonary fluid accumulation. The endothelium maintains vascular barrier functions through a complex series of redundant receptors and signaling pathways that serve to both permit fluid and immune cell efflux into tissues and restrict tissue edema. Infection of the endothelium provides several mechanisms for hantaviruses to alter capillary permeability but also defines potential therapeutic targets for regulating acute pulmonary edema and HPS disease. Here we discuss interactions of HPS causing hantaviruses with the endothelium, potential endothelial cell-directed permeability mechanisms, and therapeutic targeting of the endothelium as a means of reducing the severity of HPS disease.

  20. Spin relaxation of iron in mixed state hemoproteins

    International Nuclear Information System (INIS)

    Wajnberg, E.; Kalinowski, H.J.; Bemski, G.; Helman, J.S.

    1984-01-01

    In pure states hemoproteins the relaxation of iron depends on its spin state. It is found that in both mixed state met-hemoglobin and met-myoglobin, the low and high spin states relax through an Orbach-like process. Also, very short (approx. 1 ns) and temperature independent transverse relaxation times T 2 were estimated. This peculiar behaviour of the relaxation may result from the unusual electronic structure of mixed state hemoproteins that allows thermal equilibrium and interconversion of the spin states. (Author) [pt

  1. Hyperfine relaxation of an optically pumped cesium vapor

    International Nuclear Information System (INIS)

    Tornos, J.; Amare, J.C.

    1986-01-01

    The relaxation of hyperfine orientation indirectly induced by optical pumping with a σ-polarized D 1 -light in a cesium vapor in the presence of Ar is experimentally studied. The detection technique ensures the absence of quadrupole relaxation contributions in the relaxation signals. The results from the dependences of the hyperfine relaxation rate on the temperature and argon pressure are: diffusion coefficient of Cs in Ar, D 0 = 0.101 +- 0.010 cm 2 s -1 at 0 0 C and 760 Torr; relaxation cross section by Cs-Ar collisions, σ/sub c/ = (104 +- 5) x 10 -23 cm 2 ; relaxation cross section by Cs-Cs (spin exchange) collisions, σ/sub e//sub x/ = (1.63 +- 0.13) x 10 -14 cm 2

  2. Cross-relaxation in multiple pulse NQR spin-locking

    Energy Technology Data Exchange (ETDEWEB)

    Beltjukov, P. A.; Kibrik, G. E. [Perm State University, Physics Department (Russian Federation); Furman, G. B., E-mail: gregoryf@bgu.ac.il; Goren, S. D. [Ben Gurion University, Physics Department (Israel)

    2008-01-15

    The experimental and theoretical NQR multiple-pulse spin locking study of cross-relaxation process in solids containing nuclei of two different sorts I > 1/2 and S = 1/2 coupled by the dipole-dipole interactions and influenced by an external magnetic field. Two coupled equations for the inverse spin temperatures of the both spin systems describing the mutual spin lattice relaxation and the cross-relaxation were obtained using the method of the nonequilibrium state operator. It is shown that the relaxation process is realized with non-exponential time dependence describing by a sum of two exponents. The cross relaxation time is calculated as a function of the multiple-pulse field parameters which agree with the experimental data. The calculated magnetization cross relaxation time vs the strength of the applied magnetic field agrees well with the obtained experimental data.

  3. Hair Dye and Hair Relaxers

    Science.gov (United States)

    ... 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 ...

  4. Statistical mechanics of violent relaxation

    International Nuclear Information System (INIS)

    Shu, F.H.

    1978-01-01

    We reexamine the foundations of Lynden-Bell's statistical mechanical discussion of violent relaxation in collisionless stellar systems. We argue that Lynden-Bell's formulation in terms of a continuum description introduces unnecessary complications, and we consider a more conventional formulation in terms of particles. We then find the exclusion principle discovered by Lynden-Bell to be quantitatively important only at phase densities where two-body encounters are no longer negligible. Since the edynamical basis for the exclusion principle vanishes in such cases anyway, Lynden-Bell statistics always reduces in practice to Maxwell-Boltzmann statistics when applied to stellar systems. Lynden-Bell also found the equilibrium distribution function generally to be a sum of Maxwellians with velocity dispersions dependent on the phase density at star formation. We show that this difficulty vanishes in the particulate description for an encounterless stellar system as long as stars of different masses are initially well mixed in phase space. Our methods also demonstrate the equivalence between Gibbs's formalism which uses the microcanonical ensemble and Boltzmann's formalism which uses a coarse-grained continuum description. In addition, we clarify the concept of irreversible behavior on a macroscopic scale for an encounterless stellar system. Finally, we comment on the use of unusual macroscopic constraints to simulate the effects of incomplete relaxation

  5. Experiments in paramagnetic relaxation

    International Nuclear Information System (INIS)

    Lijphart, E.E.

    1976-01-01

    This thesis presents two attempts to improve the resolving power of the relaxation measurement technique. The first attempt reconsiders the old technique of steady state saturation. When used in conjunction with the pulse technique, it offers the possibility of obtaining additional information about the system in which all-time derivatives are zero; in addition, non-linear effects may be distinguished from each other. The second attempt involved a systematic study of only one system: Cu in the Tutton salts (K and Rb). The systematic approach, the high accuracy of the measurement and the sheer amount of experimental data for varying temperature, magnetic field and concentration made it possible in this case to separate the prevailing relaxation mechanisms reliably

  6. Relaxation from particle production

    Energy Technology Data Exchange (ETDEWEB)

    Hook, Anson; Marques-Tavares, Gustavo [Stanford Institute for Theoretical Physics, Stanford University, Stanford, CA 94305 (United States)

    2016-12-20

    We consider using particle production as a friction force by which to implement a “Relaxion” solution to the electroweak hierarchy problem. Using this approach, we are able to avoid superplanckian field excursions and avoid any conflict with the strong CP problem. The relaxation mechanism can work before, during or after inflation allowing for inflationary dynamics to play an important role or to be completely decoupled.

  7. Excited-state relaxation of some aminoquinolines

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available The absorption and fluorescence spectra, fluorescence quantum yields and lifetimes, and fluorescence rate constants ( k f of 2-amino-3-( 2 ′ -benzoxazolylquinoline (I, 2-amino-3-( 2 ′ -benzothiazolylquinoline (II, 2-amino-3-( 2 ′ -methoxybenzothiazolyl-quinoline (III, 2-amino-3-( 2 ′ -benzothiazolylbenzoquinoline (IV at different temperatures have been measured. The shortwavelength shift of fluorescence spectra of compounds studied (23–49 nm in ethanol as the temperature decreases (the solvent viscosity increases points out that the excited-state relaxation process takes place. The rate of this process depends essentially on the solvent viscosity, but not the solvent polarity. The essential increasing of fluorescence rate constant k f (up to about 7 times as the solvent viscosity increases proves the existence of excited-state structural relaxation consisting in the mutual internal rotation of molecular fragments of aminoquinolines studied, followed by the solvent orientational relaxation.

  8. Momentum constraint relaxation

    International Nuclear Information System (INIS)

    Marronetti, Pedro

    2006-01-01

    Full relativistic simulations in three dimensions invariably develop runaway modes that grow exponentially and are accompanied by violations of the Hamiltonian and momentum constraints. Recently, we introduced a numerical method (Hamiltonian relaxation) that greatly reduces the Hamiltonian constraint violation and helps improve the quality of the numerical model. We present here a method that controls the violation of the momentum constraint. The method is based on the addition of a longitudinal component to the traceless extrinsic curvature A ij -tilde, generated by a vector potential w i , as outlined by York. The components of w i are relaxed to solve approximately the momentum constraint equations, slowly pushing the evolution towards the space of solutions of the constraint equations. We test this method with simulations of binary neutron stars in circular orbits and show that it effectively controls the growth of the aforementioned violations. We also show that a full numerical enforcement of the constraints, as opposed to the gentle correction of the momentum relaxation scheme, results in the development of instabilities that stop the runs shortly

  9. Encapsulated Bacillus anthracis interacts closely with liver endothelium.

    Science.gov (United States)

    Piris-Gimenez, Alejandro; Corre, Jean-Philippe; Jouvion, Gregory; Candela, Thomas; Khun, Huot; Goossens, Pierre L

    2009-11-01

    The Bacillus anthracis poly-gamma-D-glutamate capsule is essential for virulence. It impedes phagocytosis and protects bacilli from the immune system, thus promoting systemic dissemination. To further define the virulence mechanisms brought into play by the capsule, we characterized the interactions between encapsulated nontoxinogenic B. anthracis and its host in vivo through histological analysis, perfusion, and competition experiments with purified capsule. Clearance of encapsulated bacilli from the blood was rapid (>90% clearance within 5 min), with 75% of the bacteria being trapped in the liver. Competition experiments with purified capsule polyglutamate inhibited this interaction. At the septicemic phase of cutaneous infection with spores, the encapsulated bacilli were trapped in the vascular spaces of the liver and interacted closely with the liver endothelium in the sinusoids and terminal and portal veins. They often grow as microcolonies containing capsular material shed by the bacteria. We show that, in addition to its inhibitory effect on the interaction with the immune system, the capsule surrounding B. anthracis plays an active role in mediating the trapping of the bacteria within the liver and may thus contribute to anthrax pathogenesis. Because other microorganisms produce polyglutamate, it may also represent a general mechanism of virulence or in vivo survival.

  10. Identification of a potent endothelium-derived angiogenic factor.

    Directory of Open Access Journals (Sweden)

    Vera Jankowski

    Full Text Available The secretion of angiogenic factors by vascular endothelial cells is one of the key mechanisms of angiogenesis. Here we report on the isolation of a new potent angiogenic factor, diuridine tetraphosphate (Up4U from the secretome of human endothelial cells. The angiogenic effect of the endothelial secretome was partially reduced after incubation with alkaline phosphatase and abolished in the presence of suramin. In one fraction, purified to homogeneity by reversed phase and affinity chromatography, Up4U was identified by MALDI-LIFT-fragment-mass-spectrometry, enzymatic cleavage analysis and retention-time comparison. Beside a strong angiogenic effect on the yolk sac membrane and the developing rat embryo itself, Up4U increased the proliferation rate of endothelial cells and, in the presence of PDGF, of vascular smooth muscle cells. Up4U stimulated the migration rate of endothelial cells via P2Y2-receptors, increased the ability of endothelial cells to form capillary-like tubes and acts as a potent inducer of sprouting angiogenesis originating from gel-embedded EC spheroids. Endothelial cells released Up4U after stimulation with shear stress. Mean total plasma Up4U concentrations of healthy subjects (N=6 were sufficient to induce angiogenic and proliferative effects (1.34 ± 0.26 nmol L(-1. In conclusion, Up4U is a novel strong human endothelium-derived angiogenic factor.

  11. Role of endothelium in radiation-induced normal tissue damages

    International Nuclear Information System (INIS)

    Milliat, F.

    2007-05-01

    More than half of cancers are treated with radiation therapy alone or in combination with surgery and/or chemotherapy. The goal of radiation therapy is to deliver enough ionising radiation to destroy cancer cells without exceeding the level that the surrounding healthy cells can tolerate. Unfortunately, radiation-induced normal tissue injury is still a dose limiting factor in the treatment of cancer with radiotherapy. The knowledge of normal tissue radiobiology is needed to determine molecular mechanisms involved in normal tissue pathogenic pathways in order to identify therapeutic targets and develop strategies to prevent and /or reduce side effects of radiation therapy. The endothelium is known to play a critical role in radiation-induced injury. Our work shows that endothelial cells promote vascular smooth muscle cell proliferation, migration and fibro-genic phenotype after irradiation. Moreover, we demonstrate for the first time the importance of PAI-1 in radiation-induced normal tissue damage suggesting that PAI-1 may represent a molecular target to limit injury following radiotherapy. We describe a new role for the TGF-b/Smad pathway in the pathogenesis of radiation-induced damages. TGF-b/Smad pathway is involved in the fibro-genic phenotype of VSMC induced by irradiated EC as well as in the radiation-induced PAI-1 expression in endothelial cells. (author)

  12. Effects of iodinated contrast media on blood and endothelium

    International Nuclear Information System (INIS)

    Aspelin, Peter; Stacul, Fulvio; Thomsen, Henrik S.; Morcos, Sameh K.; Molen, Aart J. van der

    2006-01-01

    The aim of the study was to assess the effects of iodinated contrast media on blood components and endothelium based on experimental and clinical studies and to produce clinically relevant guidelines for reducing thrombotic and hematologic complications following the intravascular use of contrast media. A report was drafted after review of the literature and discussions among the members of the Contrast Media Safety Committee of the European Society of Urogenital Radiology. The final report was produced following discussion at the 12th European Symposium on Urogenital Radiology in Ljubljana, Slovenia (2005). Experimental data indicate that all iodinated contrast media produce an anticoagulant effect and that this effect is greater with ionic contrast media. Several of the in vitro and experimental in vivo studies on haematological effects of contrast media have not been confirmed by clinical studies. Low- or iso-osmolar contrast media should be used for diagnostic and interventional angiographic procedures, including phlebography. Meticulous angiographic technique is the most important factor for reducing the thrombotic complications associated with angiographic procedures. Drugs and interventional devices that decrease the risk of thromboembolic complications during interventional procedures minimize the importance of the effects of contrast media. (orig.)

  13. Effects of iodinated contrast media on blood and endothelium

    Energy Technology Data Exchange (ETDEWEB)

    Aspelin, Peter [Karolinska Institute/Huddinge University Hospital, Division of Radiology, Centre for Surgical Sciences, Stockholm (Sweden); Stacul, Fulvio [Institute of Radiology, Trieste (Italy); Thomsen, Henrik S. [Copenhagen University Hospital at Herlev, Department of Diagnostic Radiology 54E2, Herlev (Denmark); Morcos, Sameh K. [Sheffield Teaching Hospitals NHS Trust, Department of Diagnostic Imaging, Northern General Hospital, Sheffield (United Kingdom); Molen, Aart J. van der [Leiden University Medical Centre, Department of Radiology, Leiden (Netherlands)

    2006-05-15

    The aim of the study was to assess the effects of iodinated contrast media on blood components and endothelium based on experimental and clinical studies and to produce clinically relevant guidelines for reducing thrombotic and hematologic complications following the intravascular use of contrast media. A report was drafted after review of the literature and discussions among the members of the Contrast Media Safety Committee of the European Society of Urogenital Radiology. The final report was produced following discussion at the 12th European Symposium on Urogenital Radiology in Ljubljana, Slovenia (2005). Experimental data indicate that all iodinated contrast media produce an anticoagulant effect and that this effect is greater with ionic contrast media. Several of the in vitro and experimental in vivo studies on haematological effects of contrast media have not been confirmed by clinical studies. Low- or iso-osmolar contrast media should be used for diagnostic and interventional angiographic procedures, including phlebography. Meticulous angiographic technique is the most important factor for reducing the thrombotic complications associated with angiographic procedures. Drugs and interventional devices that decrease the risk of thromboembolic complications during interventional procedures minimize the importance of the effects of contrast media. (orig.)

  14. Changes in corneal endothelium cell characteristics after cataract surgery with and without use of viscoelastic substances during intraocular lens implantation

    Directory of Open Access Journals (Sweden)

    Schulze SD

    2015-11-01

    Full Text Available Stephan D Schulze,1 Thomas Bertelmann,1 Irena Manojlovic,2 Stefan Bodanowitz,2 Sebastian Irle,3 Walter Sekundo11Department of Ophthalmology, Philipps University of Marburg, Marburg, 2Private Practice and Ambulatory Surgical Center, Bremen, 3Freelance Statistician, Friedberg, GermanyPurpose: To evaluate whether the use of balanced salt solution (BSS or an ophthalmic viscoelastic device (OVD during hydrophilic acrylic intraocular lens (IOL implantation variously impacts corneal endothelial cell characteristics in eyes undergoing uneventful phacoemulsifications.Methods: Prospective nonrandomized observational clinical trial. Patients were assigned either to the BSS plus® or to the OVD Z-Celcoat™ group depending on the substance used during IOL implantation. Corneal endothelium cell characteristics were obtained before, 1 week, and 6 weeks after surgery. Intraoperative parameters (eg, surgery time, phacoemulsification energy were recorded.Results: Ninety-seven eyes were assigned to the BSS plus and 86 eyes to the Z-Celcoat group. Preoperative corneal endothelium cell density (ECD and endothelium cell size were 2,506±310 cells/mm2/2,433±261 cells/mm2 and 406±47 µm2/416±50 µm2 (P=0.107/P=0.09. After 1 and 6 weeks, ECD decreased and endothelium cell size increased significantly in both groups (each P<0.001 without significant differences between both groups (each P>0.05. Irrigation–aspiration suction time (30.3±16.6 versus 36.3±14.5 seconds and overall surgical time (7.2±1.2 versus 8.0±1.4 minutes were significantly longer in the OVD Z-Celcoat group (each P<0.001. No complications or serious side effects occurred.Conclusion: Implantation of a hydrophilic acrylic IOL under BSS infusion seems to be a useful and faster alternative in experienced hands without generating higher ECD loss rates.Keywords: phacoemulsification, ophthalmic viscoelastic device, endothelial cell density, IOL

  15. Junctional transfer in cultured vascular endothelium: II. Dye and nucleotide transfer

    International Nuclear Information System (INIS)

    Larson, D.M.; Sheridan, J.D.

    1985-01-01

    Vascular endothelial cultures, derived from large vessels, retain many of the characteristics of their in vivo counterparts. However, the observed reduction in size and complexity of intercellular gap and tight junctions in these cultured cells suggests that important functions, thought to be mediated by these structures, may be altered in vitro. In continuing studies on intercellular communication in vessel wall cells, the authors have quantitated the extent of junctional transfer of small molecular tracers (the fluorescent dye Lucifer Yellow CH and tritiated uridine nucleotides) in confluent cultures of calf aortic (BAEC) and umbilical vein (BVEC) endothelium. Both BAEC and BVEC show extensive (and quantitatively equivalent) dye and nucleotide transfer. As an analogue of intimal endothelium, the authors have also tested dye transfer in freshly isolated sheets of endothelium. Transfer in BAEC and BVEC sheets was more rapid, extensive and homogeneous than in the cultured cells, implying a reduction in molecular coupling as endothelium adapts to culture conditions. In addition, they have documented heterocellular nucleotide transfer between cultured endothelium and vascular smooth muscle cells, of particular interest considering the prevalence of ''myo-endothelial'' junctions in vivo. These data yield further information on junctional transfer in cultured vascular endothelium and have broad implications for the functional integration of the vessel wall in the physiology and pathophysiology of the vasculature

  16. Oxidative stress upregulates the NMDA receptor on cerebrovascular endothelium.

    Science.gov (United States)

    Betzen, Christian; White, Robin; Zehendner, Christoph M; Pietrowski, Eweline; Bender, Bianca; Luhmann, Heiko J; Kuhlmann, Christoph R W

    2009-10-15

    N-methyl-d-aspartate receptor (NMDA-R)-mediated oxidative stress has been implicated in blood-brain barrier (BBB) disruption in a variety of neuropathological diseases. Although some interactions between both phenomena have been elucidated, possible influences of reactive oxygen species (ROS) on the NMDA-R itself have so far been neglected. The objective of this study was to examine how the cerebroendothelial NMDA-R is affected by exposure to oxidative stress and to assess possible influences on BBB integrity. RT-PCR confirmed several NMDA-R subunits (NR1, NR2B-D) expressed in the bEnd3 cell line (murine cerebrovascular endothelial cells). NR1 protein expression after exposure to ROS was observed via in-cell Western. The functionality of the expressed NMDA-R was determined by measuring DiBAC fluorescence in ROS-preexposed cells upon stimulation with the specific agonist NMDA. Finally, the effects on barrier integrity were evaluated using the ECIS system to detect changes in monolayer impedance upon NMDA-R stimulation after exposure to ROS. The expression of NR1 significantly (p<0.001) increased 72 h after 30 min exposure to superoxide (+33.8+/-7.5%), peroxynitrite (+84.9+/-10.7%), or hydrogen peroxide (+92.8+/-7.6%), resulting in increased cellular response to NMDA-R stimulation and diminished monolayer impedance. We conclude that oxidative stress upregulates NMDA-R on cerebrovascular endothelium and thus heightens susceptibility to glutamate-induced BBB disruption.

  17. Traction force dynamics predict gap formation in activated endothelium

    Energy Technology Data Exchange (ETDEWEB)

    Valent, Erik T.; Nieuw Amerongen, Geerten P. van; Hinsbergh, Victor W.M. van; Hordijk, Peter L., E-mail: p.hordijk@vumc.nl

    2016-09-10

    In many pathological conditions the endothelium becomes activated and dysfunctional, resulting in hyperpermeability and plasma leakage. No specific therapies are available yet to control endothelial barrier function, which is regulated by inter-endothelial junctions and the generation of acto-myosin-based contractile forces in the context of cell-cell and cell-matrix interactions. However, the spatiotemporal distribution and stimulus-induced reorganization of these integral forces remain largely unknown. Traction force microscopy of human endothelial monolayers was used to visualize contractile forces in resting cells and during thrombin-induced hyperpermeability. Simultaneously, information about endothelial monolayer integrity, adherens junctions and cytoskeletal proteins (F-actin) were captured. This revealed a heterogeneous distribution of traction forces, with nuclear areas showing lower and cell-cell junctions higher traction forces than the whole-monolayer average. Moreover, junctional forces were asymmetrically distributed among neighboring cells. Force vector orientation analysis showed a good correlation with the alignment of F-actin and revealed contractile forces in newly formed filopodia and lamellipodia-like protrusions within the monolayer. Finally, unstable areas, showing high force fluctuations within the monolayer were prone to form inter-endothelial gaps upon stimulation with thrombin. To conclude, contractile traction forces are heterogeneously distributed within endothelial monolayers and force instability, rather than force magnitude, predicts the stimulus-induced formation of intercellular gaps. - Highlights: • Endothelial monolayers exert dynamic- and heterogeneous traction forces. • High traction forces correlate with junctional areas and the F-actin cytoskeleton. • Newly formed inter-endothelial gaps are characterized by opposing traction forces. • Force stability is a key feature controlling endothelial permeability.

  18. Traction force dynamics predict gap formation in activated endothelium

    International Nuclear Information System (INIS)

    Valent, Erik T.; Nieuw Amerongen, Geerten P. van; Hinsbergh, Victor W.M. van; Hordijk, Peter L.

    2016-01-01

    In many pathological conditions the endothelium becomes activated and dysfunctional, resulting in hyperpermeability and plasma leakage. No specific therapies are available yet to control endothelial barrier function, which is regulated by inter-endothelial junctions and the generation of acto-myosin-based contractile forces in the context of cell-cell and cell-matrix interactions. However, the spatiotemporal distribution and stimulus-induced reorganization of these integral forces remain largely unknown. Traction force microscopy of human endothelial monolayers was used to visualize contractile forces in resting cells and during thrombin-induced hyperpermeability. Simultaneously, information about endothelial monolayer integrity, adherens junctions and cytoskeletal proteins (F-actin) were captured. This revealed a heterogeneous distribution of traction forces, with nuclear areas showing lower and cell-cell junctions higher traction forces than the whole-monolayer average. Moreover, junctional forces were asymmetrically distributed among neighboring cells. Force vector orientation analysis showed a good correlation with the alignment of F-actin and revealed contractile forces in newly formed filopodia and lamellipodia-like protrusions within the monolayer. Finally, unstable areas, showing high force fluctuations within the monolayer were prone to form inter-endothelial gaps upon stimulation with thrombin. To conclude, contractile traction forces are heterogeneously distributed within endothelial monolayers and force instability, rather than force magnitude, predicts the stimulus-induced formation of intercellular gaps. - Highlights: • Endothelial monolayers exert dynamic- and heterogeneous traction forces. • High traction forces correlate with junctional areas and the F-actin cytoskeleton. • Newly formed inter-endothelial gaps are characterized by opposing traction forces. • Force stability is a key feature controlling endothelial permeability.

  19. Hyperglycemia and Diabetes Downregulate the Functional Expression of TRPV4 Channels in Retinal Microvascular Endothelium

    Science.gov (United States)

    Monaghan, Kevin; McNaughten, Jennifer; McGahon, Mary K.; Kelly, Catriona; Kyle, Daniel; Yong, Phaik Har

    2015-01-01

    Retinal endothelial cell dysfunction is believed to play a key role in the etiology and pathogenesis of diabetic retinopathy. Numerous studies have shown that TRPV4 channels are critically involved in maintaining normal endothelial cell function. In the current paper, we demonstrate that TRPV4 is functionally expressed in the endothelium of the retinal microcirculation and that both channel expression and activity is downregulated by hyperglycaemia. Quantitative PCR and immunostaining demonstrated molecular expression of TRPV4 in cultured bovine retinal microvascular endothelial cells (RMECs). Functional TRPV4 activity was assessed in cultured RMECs from endothelial Ca2+-responses recorded using fura-2 microfluorimetry and electrophysiological recordings of membrane currents. The TRPV4 agonist 4α-phorbol 12,13-didecanoate (4-αPDD) increased [Ca2+]i in RMECs and this response was largely abolished using siRNA targeted against TRPV4. These Ca2+-signals were completely inhibited by removal of extracellular Ca2+, confirming their dependence on influx of extracellular Ca2+. The 4-αPDD Ca2+-response recorded in the presence of cyclopiazonic acid (CPA), which depletes the intracellular stores preventing any signal amplification through store release, was used as a measure of Ca2+-influx across the cell membrane. This response was blocked by HC067047, a TRPV4 antagonist. Under voltage clamp conditions, the TRPV4 agonist GSK1016790A stimulated a membrane current, which was again inhibited by HC067047. Following incubation with 25mM D-glucose TRPV4 expression was reduced in comparison with RMECs cultured under control conditions, as were 4αPDD-induced Ca2+-responses in the presence of CPA and ion currents evoked by GSK1016790A. Molecular expression of TRPV4 in the retinal vascular endothelium of 3 months’ streptozotocin-induced diabetic rats was also reduced in comparison with that in age-matched controls. We conclude that hyperglycaemia and diabetes reduce the

  20. Variational formulation of relaxed and multi-region relaxed magnetohydrodynamics

    Science.gov (United States)

    Dewar, R. L.; Yoshida, Z.; Bhattacharjee, A.; Hudson, S. R.

    2015-12-01

    > Ideal magnetohydrodynamics (IMHD) is strongly constrained by an infinite number of microscopic constraints expressing mass, entropy and magnetic flux conservation in each infinitesimal fluid element, the latter preventing magnetic reconnection. By contrast, in the Taylor relaxation model for formation of macroscopically self-organized plasma equilibrium states, all these constraints are relaxed save for the global magnetic fluxes and helicity. A Lagrangian variational principle is presented that leads to a new, fully dynamical, relaxed magnetohydrodynamics (RxMHD), such that all static solutions are Taylor states but also allows state with flow. By postulating that some long-lived macroscopic current sheets can act as barriers to relaxation, separating the plasma into multiple relaxation regions, a further generalization, multi-region relaxed magnetohydrodynamics (MRxMHD) is developed.

  1. Uptake of low density lipoproteins by the hamster lung. Interactions with capillary endothelium

    International Nuclear Information System (INIS)

    Nistor, A.; Simionescu, M.

    1986-01-01

    The mechanism by which the circulating low density lipoproteins (LDL) contribute to the lung surfactant cholesterol was investigated by perfusing the hamster lung in situ with LDL either radiolabeled or coupled to gold, or both. Part of [ 125 I]-LDL and [ 3 H]-cholesterol LDL were taken up by a specific process which was time- and concentration-dependent and reached saturation within 20 to 30 min of perfusion. Competition experiments and removal of receptor-bound LDL by heparin suggested that about 50% of LDL uptake is receptor-independent. Experiments using double labeled LDL showed a preferential uptake of 3 H-cholesterol versus 125 I by the lung both in situ and in vivo. LDL-gold particles (LDL-Au), recirculated through the isolated lung, bound to the endothelial luminal plasma membrane and to features potentially involved in receptor-mediated endocytosis (coated pits, coated vesicles, lysosomelike structures) and in transcytosis (plasmalemmal vesicles). The results suggest that LDL uptake by the lung takes place by both receptor-mediated and receptor-independent mechanisms. Cholesterol may be in part transferred to the lung without the apoprotein moiety; the alveolar capillary endothelium appears to be the first monitor of this complex process

  2. The dielectric α relaxation at a temperature close to T sub(g)

    International Nuclear Information System (INIS)

    Gomez Ribelles, J.L.; Diaz Calleja, R.

    1985-01-01

    It is shown in this work how the dependence of the mean relaxation times of the dielectric α relaxation on temperature deviates from the Williams, Landel and Ferry model at a temperature close to T sub(g). In some cases, an Arrhenius-like relationship for this relaxation can be observed for temperatures below T sub(g)

  3. Dynamics of relaxed inflation

    Science.gov (United States)

    Tangarife, Walter; Tobioka, Kohsaku; Ubaldi, Lorenzo; Volansky, Tomer

    2018-02-01

    The cosmological relaxation of the electroweak scale has been proposed as a mechanism to address the hierarchy problem of the Standard Model. A field, the relaxion, rolls down its potential and, in doing so, scans the squared mass parameter of the Higgs, relaxing it to a parametrically small value. In this work, we promote the relaxion to an inflaton. We couple it to Abelian gauge bosons, thereby introducing the necessary dissipation mechanism which slows down the field in the last stages. We describe a novel reheating mechanism, which relies on the gauge-boson production leading to strong electro-magnetic fields, and proceeds via the vacuum production of electron-positron pairs through the Schwinger effect. We refer to this mechanism as Schwinger reheating. We discuss the cosmological dynamics of the model and the phenomenological constraints from CMB and other experiments. We find that a cutoff close to the Planck scale may be achieved. In its minimal form, the model does not generate sufficient curvature perturbations and additional ingredients, such as a curvaton field, are needed.

  4. Electron spin-lattice relaxation in fractals

    International Nuclear Information System (INIS)

    Shrivastava, K.N.

    1986-08-01

    We have developed the theory of the spin-fracton interaction for paramagnetic ions in fractal structures. The interaction is exponentially damped by the self-similarity length of the fractal and by the range dimensionality d Φ . The relaxation time of the spin due to the absorption and emission of the fracton has been calculated for a general dimensionality called the Raman dimensionality d R , which for the fractons differs from the Hausdorff (fractal) dimensionality, D, as well as from the Euclidean dimensionality, d. The exponent of the energy level separation in the relaxation rate varies with d R d Φ /D. We have calculated the spin relaxation rate due to a new type of Raman process in which one fracton is absorbed to affect a spin transition from one electronic level to another and later another fracton is emitted along with a spin transition such that the difference in the energies of the two fractons is equal to the electronic energy level separation. The temperature and the dimensionality dependence of such a process has been found in several approximations. In one of the approximations where the van Vleck relaxation rate for a spin in a crystal is known to vary with temperature as T 9 , our calculated variation for fractals turns out to be T 6.6 , whereas the experimental value for Fe 3+ in frozen solutions of myoglobin azide is T 6.3 . Since we used d R =4/3 and the fracton range dimensionality d Φ =D/1.8, we expect to measure the dimensionalities of the problem by measuring the temperature dependence of the relaxation times. We have also calculated the shift of the paramagnetic resonance transition for a spin in a fractal for general dimensionalities. (author)

  5. Relaxation in the XX quantum chain

    International Nuclear Information System (INIS)

    Platini, Thierry; Karevski, Dragi

    2007-01-01

    We present the results obtained on the magnetization relaxation properties of an XX quantum chain in a transverse magnetic field. We first consider an initial thermal kink-like state where half of the chain is initially thermalized at a very high temperature T b while the remaining half, called the system, is put at a lower temperature T s . From this initial state, we derive analytically the Green function associated with the dynamical behaviour of the transverse magnetization. Depending on the strength of the magnetic field and on the temperature of the system, different regimes are obtained for the magnetic relaxation. In particular, with an initial droplet-like state, that is a cold subsystem of the finite size in contact at both ends with an infinite temperature environment, we derive analytically the behaviour of the time-dependent system magnetization

  6. Mechanism of nuclear cross-relaxation in magnetically ordered media

    Energy Technology Data Exchange (ETDEWEB)

    Buishvili, L L; Volzhan, E B; Giorgadze, N P [AN Gruzinskoj SSR, Tbilisi. Inst. Fiziki

    1975-09-01

    A mechanism of two-step nuclear relaxation in magnetic ordered dielectrics is proposed. The case is considered where the energy conservation in the cross relaxation (CR) process is ensured by the lattice itself without spin-spin interactions. Expressions have been obtained describing the temperature dependence of the CR rate. For a nonuniform broadened NMR line it has been shown that the spin-lattice relaxation time for a spin packet taken out from the equilibrium may be determined by the CR time owing to the mechanism suggested. When the quantization axes for electron and nuclear spins coincide, the spin-lattice relaxation is due to the three-magnon mechanism. The cross-relaxation stage has been shown to play a significant role in the range of low temperatures (T<10 deg K) and to become negligible with a temperature increase.

  7. Muon spin relaxation in random spin systems

    International Nuclear Information System (INIS)

    Toshimitsu Yamazaki

    1981-01-01

    The longitudinal relaxation function Gsub(z)(t) of the positive muon can reflect dynamical characters of local field in a unique way even when the correlation time is longer than the Larmor period of local field. This method has been applied to studies of spin dynamics in spin glass systems, revealing sharp but continuous temperature dependence of the correlation time. Its principle and applications are reviewed. (author)

  8. Charge Relaxation Dynamics of an Electrolytic Nanocapacitor

    Science.gov (United States)

    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

  9. Communication: Relaxation-limited electronic currents in extended reservoir simulations

    Science.gov (United States)

    Gruss, Daniel; Smolyanitsky, Alex; Zwolak, Michael

    2017-10-01

    Open-system approaches are gaining traction in the simulation of charge transport in nanoscale and molecular electronic devices. In particular, "extended reservoir" simulations, where explicit reservoir degrees of freedom are present, allow for the computation of both real-time and steady-state properties but require relaxation of the extended reservoirs. The strength of this relaxation, γ, influences the conductance, giving rise to a "turnover" behavior analogous to Kramers turnover in chemical reaction rates. We derive explicit, general expressions for the weak and strong relaxation limits. For weak relaxation, the conductance increases linearly with γ and every electronic state of the total explicit system contributes to the electronic current according to its "reduced" weight in the two extended reservoir regions. Essentially, this represents two conductors in series—one at each interface with the implicit reservoirs that provide the relaxation. For strong relaxation, a "dual" expression-one with the same functional form-results, except now proportional to 1/γ and dependent on the system of interest's electronic states, reflecting that the strong relaxation is localizing electrons in the extended reservoirs. Higher order behavior (e.g., γ2 or 1/γ2) can occur when there is a gap in the frequency spectrum. Moreover, inhomogeneity in the frequency spacing can give rise to a pseudo-plateau regime. These findings yield a physically motivated approach to diagnosing numerical simulations and understanding the influence of relaxation, and we examine their occurrence in both simple models and a realistic, fluctuating graphene nanoribbon.

  10. Effectiveness of relaxation techniques before diagnostic screening of cancer patients

    Directory of Open Access Journals (Sweden)

    Montserrat Aiger

    2016-07-01

    Full Text Available Psychophysiological arousal was observed in cancer patients during the application of relaxation techniques prior to a diagnostic scan (PET-CT. The aim of the study is twofold: firstly, it is sought to establish whether such techniques can minimize patient arousal before diagnostic screening begins, and secondly to measure which of them are most effective. The dependent variable is electrodermal activity, recording the attentional level and emotional response, and the independent variable comprises the relaxation techniques used, namely Jacobson, breathing and visualization. The 39 patients were split into experimental groups to whom the relaxation techniques (Jacobson, breathing exercises, and visualization were applied before they went for the PET-CT. An activity-module procedure was applied to track electrodermal activity during the relaxation sessions, consisting of instructions, timeout; wait, task; relaxation and end of the recording session. The control group received no relaxation techniques before the PET-CT. Session-end results show that patients who perform relaxation techniques achieve greater attentional focus using Jacobson's technique (M = .212 and enhanced emotional containment using visualization (M = .206. It is concluded that relaxation techniques minimize the state of activation during the waiting period before a diagnostic scan.

  11. Vascular Cognitive Impairment Linked to Brain Endothelium Inflammation in Early Stages of Heart Failure in Mice.

    Science.gov (United States)

    Adamski, Mateusz G; Sternak, Magdalena; Mohaissen, Tasnim; Kaczor, Dawid; Wierońska, Joanna M; Malinowska, Monika; Czaban, Iwona; Byk, Katarzyna; Lyngsø, Kristina S; Przyborowski, Kamil; Hansen, Pernille B L; Wilczyński, Grzegorz; Chlopicki, Stefan

    2018-03-26

    Although advanced heart failure (HF) is a clinically documented risk factor for vascular cognitive impairment, the occurrence and pathomechanisms of vascular cognitive impairment in early stages of HF are equivocal. Here, we characterize vascular cognitive impairment in the early stages of HF development and assess whether cerebral hypoperfusion or prothrombotic conditions are involved. Tgαq*44 mice with slowly developing isolated HF triggered by cardiomyocyte-specific overexpression of G-αq*44 protein were studied before the end-stage HF, at the ages of 3, 6, and 10 months: before left ventricle dysfunction; at the stage of early left ventricle diastolic dysfunction (with preserved ejection fraction); and left ventricle diastolic/systolic dysfunction, respectively. In 6- to 10-month-old but not in 3-month-old Tgαq*44 mice, behavioral and cognitive impairment was identified with compromised blood-brain barrier permeability, most significantly in brain cortex, that was associated with myelin sheet loss and changes in astrocytes and microglia. Brain endothelial cells displayed increased E-selectin immunoreactivity, which was accompanied by increased amyloid-β 1-42 accumulation in piriform cortex and increased cortical oxidative stress (8-OHdG immunoreactivity). Resting cerebral blood flow measured by magnetic resonance imaging in vivo was preserved, but ex vivo NO-dependent cortical arteriole flow regulation was impaired. Platelet hyperreactivity was present in 3- to 10-month-old Tgαq*44 mice, but it was not associated with increased platelet-dependent thrombogenicity. We report for the first time that vascular cognitive impairment is already present in the early stage of HF development, even before left ventricle systolic dysfunction. The underlying pathomechanism, independent of brain hypoperfusion, involves preceding platelet hyperreactivity and brain endothelium inflammatory activation. © 2018 The Authors. Published on behalf of the American Heart

  12. PPARα-Independent Arterial Smooth Muscle Relaxant Effects of PPARα Agonists

    Directory of Open Access Journals (Sweden)

    Neerupma Silswal

    2012-01-01

    Full Text Available We sought to determine direct vascular effects of peroxisome proliferator-activated receptor alpha (PPARα agonists using isolated mouse aortas and middle cerebral arteries (MCAs. The PPARα agonists GW7647, WY14643, and gemfibrozil acutely relaxed aortas held under isometric tension and dilated pressurized MCAs with the following order of potency: GW7647≫WY14643>gemfibrozil. Responses were endothelium-independent, and the use of PPARα deficient mice demonstrated that responses were also PPARα-independent. Pretreating arteries with high extracellular K+ attenuated PPARα agonist-mediated relaxations in the aorta, but not in the MCA. In the aorta, the ATP sensitive potassium (KATP channel blocker glibenclamide also impaired relaxations whereas the other K+ channel inhibitors, 4-aminopyridine and Iberiotoxin, had no effect. In aortas, GW7647 and WY14643 elevated cGMP levels by stimulating soluble guanylyl cyclase (sGC, and inhibition of sGC with ODQ blunted relaxations to PPARα agonists. In the MCA, dilations were inhibited by the protein kinase C (PKC activator, phorbol 12,13-dibutyrate, and also by ODQ. Our results demonstrated acute, nonreceptor-mediated relaxant effects of PPARα agonists on smooth muscle of mouse arteries. Responses to PPARα agonists in the aorta involved KATP channels and sGC, whereas in the MCA the PKC and sGC pathways also appeared to contribute to the response.

  13. On the Volterra integral equation relating creep and relaxation

    International Nuclear Information System (INIS)

    Anderssen, R S; De Hoog, F R; Davies, A R

    2008-01-01

    The evolving stress–strain response of a material to an applied deformation is causal. If the current response depends on the earlier history of the stress–strain dynamics of the material (i.e. the material has memory), then Volterra integral equations become the natural framework within which to model the response. For viscoelastic materials, when the response is linear, the dual linear Boltzmann causal integral equations are the appropriate model. The choice of one rather than the other depends on whether the applied deformation is a stress or a strain, and the associated response is, respectively, a creep or a relaxation. The duality between creep and relaxation is known explicitly and is referred to as the 'interconversion equation'. Rheologically, its importance relates to the fact that it allows the creep to be determined from knowledge of the relaxation and vice versa. Computationally, it has been known for some time that the recovery of the relaxation from the creep is more problematic than the creep from the relaxation. Recent research, using discrete models for the creep and relaxation, has confirmed that this is an essential feature of interconversion. In this paper, the corresponding result is generalized for continuous models of the creep and relaxation

  14. Relaxation towards phase-locked dynamics in long Josephson junctions

    DEFF Research Database (Denmark)

    Salerno, M.; Grønbech-Jensen, Niels; Samuelsen, Mogens Rugholm

    1995-01-01

    We study the relaxation phenomenon towards phase-locked dynamics in long Josephson junctions. In particular the dependence of the relaxation frequency for the equal time of flight solution on the junction parameters is derived. The analysis is based on a phase-locked map and is compared with direct...... numerical experiments performed both on the map and on the perturbed sine-Gordon equation. As an interesting result we find that very close to a bifurcation the relaxation frequency is exactly equal to the half of the step frequency, i.e., the frequency characterizing the period-one solution....

  15. Ultrastructure of endothelium in ovules of Penstemon gentianoides Poir. (Scrophulariaceae) at mature embryo sac phase.

    Science.gov (United States)

    Dane, Feruzan; Olgun, Göksel; Ekici, Nuran

    2007-06-01

    In this study ultrastructural differences between endothelial cells of different location in Penstemon gentianoides have been examined with electron microscope at mature embryo sac phase. Embryo sac is of the Polygonum type and surrounded by endothelium except the micropylar region. The cuticle is located primarily around the chalazal three-fourths of the embryo sac. Endothelium cells around the chalaza and toward the micropylar region are rich in cytoplasmic organelles. The cytoplasm of endothelial cells near the central cell has large vacuoles and few organelles. There are also plasmodesmas on the anticlinal walls of endothelial cells. The endothelium and the micropylar integumentary cells play a role in transport of metabolites into the embryo sac.

  16. A moving mesh method with variable relaxation time

    OpenAIRE

    Soheili, Ali Reza; Stockie, John M.

    2006-01-01

    We propose a moving mesh adaptive approach for solving time-dependent partial differential equations. The motion of spatial grid points is governed by a moving mesh PDE (MMPDE) in which a mesh relaxation time \\tau is employed as a regularization parameter. Previously reported results on MMPDEs have invariably employed a constant value of the parameter \\tau. We extend this standard approach by incorporating a variable relaxation time that is calculated adaptively alongside the solution in orde...

  17. Nuclear relaxation in semiconductors doped with magnetic impurities

    International Nuclear Information System (INIS)

    Mel'nichuk, S.V.; Tovstyuk, N.K.

    1984-01-01

    The temperature and concentration dependences are investigated of the nuclear spin-lattice relaxation time with account of spin diffusion for degenerated and non-degenerated semicon- ductors doped with magnetic impurities. In case of the non-degenerated semiconductor the time is shown to grow with temperature, while in case of degenerated semiconductor it is practically independent of temperature. The impurity concentration growth results in decreasing the spin-lattice relaxation time

  18. Cocoa reduces blood pressure and insulin resistance and improves endothelium-dependent vasodilation in hypertensives.

    Science.gov (United States)

    Grassi, Davide; Necozione, Stefano; Lippi, Cristina; Croce, Giuseppe; Valeri, Letizia; Pasqualetti, Paolo; Desideri, Giovambattista; Blumberg, Jeffrey B; Ferri, Claudio

    2005-08-01

    Consumption of flavanol-rich dark chocolate (DC) has been shown to decrease blood pressure (BP) and insulin resistance in healthy subjects, suggesting similar benefits in patients with essential hypertension (EH). Therefore, we tested the effect of DC on 24-hour ambulatory BP, flow-mediated dilation (FMD), and oral glucose tolerance tests (OGTTs) in patients with EH. After a 7-day chocolate-free run-in phase, 20 never-treated, grade I patients with EH (10 males; 43.7+/-7.8 years) were randomized to receive either 100 g per day DC (containing 88 mg flavanols) or 90 g per day flavanol-free white chocolate (WC) in an isocaloric manner for 15 days. After a second 7-day chocolate-free period, patients were crossed over to the other treatment. Noninvasive 24-hour ambulatory BP, FMD, OGTT, serum cholesterol, and markers of vascular inflammation were evaluated at the end of each treatment. The homeostasis model assessment of insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), and insulin sensitivity index (ISI) were calculated from OGTT values. Ambulatory BP decreased after DC (24-hour systolic BP -11.9+/-7.7 mm Hg, Pbenefit if included as part of a healthy diet for patients with EH.

  19. Abnormal endothelium-dependent microvascular dilator reactivity in pregnancies complicated by normotensive intrauterine growth restriction

    NARCIS (Netherlands)

    Koopmans, C.M.; Blaauw, Judith; van Pampus, Maria; Rakhorst, G.; Aarnoudse, J.G.

    OBJECTIVE: Normotensive intrauterine growth restriction and preeclampsia share a similar placenta pathophysiology, whereas maternal clinical manifestations differ. Clinical symptoms of preeclampsia are partly attributed to vascular endothelial dysfunction, but it is unclear whether this phenomenon

  20. Activation of TRPV1 by dietary capsaicin improves endothelium-dependent vasorelaxation and prevents hypertension

    DEFF Research Database (Denmark)

    Yang, Dachun; Luo, Zhidan; Ma, Shuangtao

    2010-01-01

    Some plant-based diets lower the cardiometabolic risks and prevalence of hypertension. New evidence implies a role for the transient receptor potential vanilloid 1 (TRPV1) cation channel in the pathogenesis of cardiometabolic diseases. Little is known about impact of chronic TRPV1 activation...

  1. Milrinone relaxes pulmonary veins in guinea pigs and humans.

    Directory of Open Access Journals (Sweden)

    Annette D Rieg

    Full Text Available INTRODUCTION: The phosphodiesterase-III inhibitor milrinone improves ventricular contractility, relaxes pulmonary arteries and reduces right ventricular afterload. Thus, it is used to treat heart failure and pulmonary hypertension (PH. However, its action on pulmonary veins (PVs is not defined, although particularly PH due to left heart disease primarily affects the pulmonary venous bed. We examined milrinone-induced relaxation in PVs from guinea pigs (GPs and humans. MATERIAL AND METHODS: Precision-cut lung slices (PCLS were prepared from GPs or from patients undergoing lobectomy. Milrinone-induced relaxation was studied by videomicroscopy in naïve PVs and in PVs pre-constricted with the ETA-receptor agonist BP0104. Baseline luminal area was defined as 100%. Intracellular cAMP was measured by ELISA and milrinone-induced changes of segmental vascular resistances were studied in the GP isolated perfused lung (IPL. RESULTS: In the IPL (GP, milrinone (10 µM lowered the postcapillary resistance of pre-constricted vessels. In PCLS (GP, milrinone relaxed naïve and pre-constricted PVs (120% and this relaxation was attenuated by inhibition of protein kinase G (KT 5823, adenyl cyclase (SQ 22536 and protein kinase A (KT 5720, but not by inhibition of NO-synthesis (L-NAME. In addition, milrinone-induced relaxation was dependent on the activation of K ATP-, BK Ca (2+- and Kv-channels. Human PVs also relaxed to milrinone (121%, however only if pre-constricted. DISCUSSION: Milrinone relaxes PVs from GPs and humans. In GPs, milrinone-induced relaxation is based on K ATP-, BK Ca (2+- and Kv-channel-activation and on cAMP/PKA/PKG. The relaxant properties of milrinone on PVs lead to reduced postcapillary resistance and hydrostatic pressures. Hence they alleviate pulmonary edema and suggest beneficial effects of milrinone in PH due to left heart disease.

  2. Milrinone relaxes pulmonary veins in guinea pigs and humans.

    Science.gov (United States)

    Rieg, Annette D; Suleiman, Said; Perez-Bouza, Alberto; Braunschweig, Till; Spillner, Jan W; Schröder, Thomas; Verjans, Eva; Schälte, Gereon; Rossaint, Rolf; Uhlig, Stefan; Martin, Christian

    2014-01-01

    The phosphodiesterase-III inhibitor milrinone improves ventricular contractility, relaxes pulmonary arteries and reduces right ventricular afterload. Thus, it is used to treat heart failure and pulmonary hypertension (PH). However, its action on pulmonary veins (PVs) is not defined, although particularly PH due to left heart disease primarily affects the pulmonary venous bed. We examined milrinone-induced relaxation in PVs from guinea pigs (GPs) and humans. Precision-cut lung slices (PCLS) were prepared from GPs or from patients undergoing lobectomy. Milrinone-induced relaxation was studied by videomicroscopy in naïve PVs and in PVs pre-constricted with the ETA-receptor agonist BP0104. Baseline luminal area was defined as 100%. Intracellular cAMP was measured by ELISA and milrinone-induced changes of segmental vascular resistances were studied in the GP isolated perfused lung (IPL). In the IPL (GP), milrinone (10 µM) lowered the postcapillary resistance of pre-constricted vessels. In PCLS (GP), milrinone relaxed naïve and pre-constricted PVs (120%) and this relaxation was attenuated by inhibition of protein kinase G (KT 5823), adenyl cyclase (SQ 22536) and protein kinase A (KT 5720), but not by inhibition of NO-synthesis (L-NAME). In addition, milrinone-induced relaxation was dependent on the activation of K ATP-, BK Ca (2+)- and Kv-channels. Human PVs also relaxed to milrinone (121%), however only if pre-constricted. Milrinone relaxes PVs from GPs and humans. In GPs, milrinone-induced relaxation is based on K ATP-, BK Ca (2+)- and Kv-channel-activation and on cAMP/PKA/PKG. The relaxant properties of milrinone on PVs lead to reduced postcapillary resistance and hydrostatic pressures. Hence they alleviate pulmonary edema and suggest beneficial effects of milrinone in PH due to left heart disease.

  3. Stress relaxation of thermally bowed fuel pins

    International Nuclear Information System (INIS)

    Crossland, I.G.; Speight, M.V.

    1983-01-01

    The presence of cross-pin temperature gradients in nuclear reactor fuel pins produces differential thermal expansion which, in turn, causes the fuel pin to bow elastically. If the pin is restrained in any way, such thermal bowing causes the pin to be stressed. At high temperatures these stresses can relax by creep and it is shown here that this causes the pin to suffer an additional permanent deflection, so that when the cross-pin temperature difference is removed the pin remains bowed. By representing the cylindrical pin by an equivalent I-beam, the present work examines this effect when it takes place by secondary creep. Two restraint systems are considered, and it is demonstrated that the rate of relaxation depends mainly upon the creep equation, and hence the temperature, and also the magnitude of the initial stresses. (author)

  4. Creep and relaxation behavior of Inconel-617

    International Nuclear Information System (INIS)

    Osthoff, W.; Ennis, P.J.; Nickel, H.; Schuster, H.

    1984-01-01

    The static and dynamic creep behavior of Inconel alloy 617 has been determined in constant load creep tests, relaxation tests, and stress reduction tests in the temperature range 1023 to 1273 K. The results have been interpreted using the internal stress concept: The dependence of the internal stress on the applied stress and test temperature was determined. In a few experiments, the influence of cold deformation prior to the creep test on the magnitude of the internal stress was also investigated. It was found that the experimentally observed relaxation behavior could be more satisfactorily described using the Norton creep equation modified by incorporation of the internal stress than by the conventional Norton creep equation

  5. Activation of the sweet taste receptor, T1R3, by the artificial sweetener sucralose regulates the pulmonary endothelium.

    Science.gov (United States)

    Harrington, Elizabeth O; Vang, Alexander; Braza, Julie; Shil, Aparna; Chichger, Havovi

    2018-01-01

    A hallmark of acute respiratory distress syndrome (ARDS) is pulmonary vascular permeability. In these settings, loss of barrier integrity is mediated by cell-contact disassembly and actin remodeling. Studies into molecular mechanisms responsible for improving microvascular barrier function are therefore vital in the development of therapeutic targets for reducing vascular permeability in ARDS. The sweet taste receptor T1R3 is a G protein-coupled receptor, activated following exposure to sweet molecules, to trigger a gustducin-dependent signal cascade. In recent years, extraoral locations for T1R3 have been identified; however, no studies have focused on T1R3 within the vasculature. We hypothesize that activation of T1R3, in the pulmonary vasculature, plays a role in regulating endothelial barrier function in settings of ARDS. Our study demonstrated expression of T1R3 within the pulmonary vasculature, with a drop in expression levels following exposure to barrier-disruptive agents. Exposure of lung microvascular endothelial cells to the intensely sweet molecule sucralose attenuated LPS- and thrombin-induced endothelial barrier dysfunction. Likewise, sucralose exposure attenuated bacteria-induced lung edema formation in vivo. Inhibition of sweet taste signaling, through zinc sulfate, T1R3, or G-protein siRNA, blunted the protective effects of sucralose on the endothelium. Sucralose significantly reduced LPS-induced increased expression or phosphorylation of the key signaling molecules Src, p21-activated kinase (PAK), myosin light chain-2 (MLC2), heat shock protein 27 (HSP27), and p110α phosphatidylinositol 3-kinase (p110αPI3K). Activation of T1R3 by sucralose protects the pulmonary endothelium from edemagenic agent-induced barrier disruption, potentially through abrogation of Src/PAK/p110αPI3K-mediated cell-contact disassembly and Src/MLC2/HSP27-mediated actin remodeling. Identification of sweet taste sensing in the pulmonary vasculature may represent a novel

  6. Biexciton relaxation associated with dissociation into a surface polariton pair in semiconductor films

    Science.gov (United States)

    Mitsumori, Yasuyoshi; Matsuura, Shimpei; Uchiyama, Shoichi; Saito, Kentarao; Edamatsu, Keiichi; Nakayama, Masaaki; Ajiki, Hiroshi

    2018-04-01

    We study the biexciton relaxation process in CuCl films ranging from 6 to 200 nm. The relaxation time is measured as the dephasing time and the lifetime. We observe a unique thickness dependence of the biexciton relaxation time and also obtain an ultrafast relaxation time with a timescale as short as 100 fs, while the exciton lifetime monotonically decreases with increasing thickness. By analyzing the exciton-photon coupling energy for a surface polariton, we theoretically calculate the biexciton relaxation time as a function of the thickness. The calculated dependence qualitatively reproduces the observed relaxation time, indicating that the biexciton dissociation into a surface polariton pair is one of the major biexciton relaxation processes.

  7. Exercise-mediated wall shear stress increases mitochondrial biogenesis in vascular endothelium.

    Directory of Open Access Journals (Sweden)

    Boa Kim

    Full Text Available Enhancing structural and functional integrity of mitochondria is an emerging therapeutic option against endothelial dysfunction. In this study, we sought to investigate the effect of fluid shear stress on mitochondrial biogenesis and mitochondrial respiratory function in endothelial cells (ECs using in vitro and in vivo complementary studies.Human aortic- or umbilical vein-derived ECs were exposed to laminar shear stress (20 dyne/cm2 for various durations using a cone-and-plate shear apparatus. We observed significant increases in the expression of key genes related to mitochondrial biogenesis and mitochondrial quality control as well as mtDNA content and mitochondrial mass under the shear stress conditions. Mitochondrial respiratory function was enhanced when cells were intermittently exposed to laminar shear stress for 72 hrs. Also, shear-exposed cells showed diminished glycolysis and decreased mitochondrial membrane potential (ΔΨm. Likewise, in in vivo experiments, mice that were subjected to a voluntary wheel running exercise for 5 weeks showed significantly higher mitochondrial content determined by en face staining in the conduit (greater and lesser curvature of the aortic arch and thoracic aorta and muscle feed (femoral artery arteries compared to the sedentary control mice. Interestingly, however, the mitochondrial biogenesis was not observed in the mesenteric artery. This region-specific adaptation is likely due to the differential blood flow redistribution during exercise in the different vessel beds.Taken together, our findings suggest that exercise enhances mitochondrial biogenesis in vascular endothelium through a shear stress-dependent mechanism. Our findings may suggest a novel mitochondrial pathway by which a chronic exercise may be beneficial for vascular function.

  8. Effect of inorganic lead on some functions of the cerebral microvessel endothelium

    International Nuclear Information System (INIS)

    Maxwell, K.; Vinters, H.V.; Berliner, J.A.; Bready, J.V.; Cancilla, P.A.

    1986-01-01

    The effect of inorganic lead on two functions of cerebral microvessel endothelium, cell division and glucose analog uptake, was investigated. Lead concentrations considered to be toxic in humans inhibited both functions in cultured endothelial cells. Both effects were dependent on the length of lead exposure and dose over the range of 10(-4) to 10(-6) M lead acetate. After 4 days of exposure there were 76% fewer cells in 10(-4) M lead-exposed cultures relative to control cultures. After 4 days of exposure to 10(-5) M lead there were 55% fewer cells, and after 10(-6) M lead exposure there were 15% fewer cells. Two days after 10(-4) M lead exposure [methyl-3H]thymidine incorporation into endothelial cells was inhibited by 71%. Incorporation was inhibited 47% by 10(-5) M lead but 10(-6) M lead did not inhibit incorporation after 2 days of exposure. Glucose analog uptake was inhibited in both contact-inhibited and log-phase cells; however, the latter were more sensitive to lead and this increased sensitivity correlated with a higher lead content in this cell population. Both the specific carrier-mediated and the nonspecific components of glucose analog uptake were inhibited by exposure of the endothelial cells to lead. A lead exposure of 40 min produced a significant effect on the uptake mechanism. In order to manifest its effects the lead had to be present in serum-containing medium, suggesting that some serum component was necessary to present the lead to the endothelial cells. These findings imply that the initial target of inorganic lead in the CNS may be the plasma membrane of the capillary endothelial cells, and that lead may act by altering the physiological function of these membranes

  9. Dynamics of the α-relaxation in glass-forming polymers. Study by neutron scattering and relaxation techniques

    Science.gov (United States)

    Colmenero, J.

    1993-12-01

    The dynamics of the α-relaxation in three different polymeric systems, poly(vinyl methyl ether) (PVME), poly(vinyl chloride) (PVC) and poly(bisphenol A, 2-hydroxypropylether) (PH) has been studied by means of relaxation techniques and quasielastic neutron scattering (backscattering spectrometers IN10 and IN13 at the ILL-Grenoble). By using these techniques we have covered a wide time scale ranging from mesoscopic to macroscopic times (10 -10 -10 1 s). For analyzing the experimental data we have developed a phenomenological procedure in the frequency domain based on the Havriliak-Negami relaxation function, which in fact implies a Kohlrausch-Williams-Watts relaxation function in the time domain. The results obtained indicate that the dynamics of the α-relaxation in a wide time scale shows a clear non-Debye behaviour. The shape of the relaxation functions is found to be similar for the different techniques used and independent of temperature and momentum transfer ( Q). Moreover, the characteristic relaxation times deduced from the fitting of the experimental data can also be described using only one Vogel-Fulcher functional form. Besides we found that the Q-dependence of the relaxation times obtained by QENS is given by a power law, τ( Q) ∞ Q- n ( n>2), n being dependent on the system, and that the Q-behaviour and the non-Debye behaviour are directly correlated. In the case of PVC, time of flight (TOF) neutron scattering experiments confirm these results in a shorter time scale (2×10 -11 -2× 10 -12 s). Moreover, TOF results also suggest the possibility of interpreting the “fast process” usually detected in glass-forming systems as a Debye-like short regime of the α-relaxation.

  10. Relaxed Bell inequalities and Kochen-Specker theorems

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Michael J. W. [Theoretical Physics, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

    2011-08-15

    The combination of various physically plausible properties, such as no signaling, determinism, and experimental free will, is known to be incompatible with quantum correlations. Hence, these properties must be individually or jointly relaxed in any model of such correlations. The necessary degrees of relaxation are quantified here via natural distance and information-theoretic measures. This allows quantitative comparisons between different models in terms of the resources, such as the number of bits of randomness, communication, and/or correlation, that they require. For example, measurement dependence is a relatively strong resource for modeling singlet-state correlations, with only 1/15 of one bit of correlation required between measurement settings and the underlying variable. It is shown how various ''relaxed'' Bell inequalities may be obtained, which precisely specify the complementary degrees of relaxation required to model any given violation of a standard Bell inequality. The robustness of a class of Kochen-Specker theorems, to relaxation of measurement independence, is also investigated. It is shown that a theorem of Mermin remains valid unless measurement independence is relaxed by 1/3. The Conway-Kochen ''free will'' theorem and a result of Hardy are less robust, failing if measurement independence is relaxed by only 6.5% and 4.5%, respectively. An appendix shows that existence of an outcome-independent model is equivalent to existence of a deterministic model.

  11. Nuclear spin-lattice relaxation in carbon nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Panich, A.M., E-mail: pan@bgu.ac.i [Department of Physics, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105 (Israel); Sergeev, N.A. [Institute of Physics, University of Szczecin, 70-451 Szczecin (Poland)

    2010-04-15

    Interpretation of nuclear spin-lattice relaxation data in the carbon nanostructures is usually based on the analysis of fluctuations of dipole-dipole interactions of nuclear spins and anisotropic electron-nuclear interactions responsible for chemical shielding, which are caused by molecular dynamics. However, many nanocarbon systems such as fullerene and nanotube derivatives, nanodiamonds and carbon onions reveal noticeable amount of paramagnetic defects with unpaired electrons originating from dangling bonds. The interaction between nuclear and electron spins strongly influences the nuclear spin-lattice relaxation, but usually is not taken into account, thus the relaxation data are not correctly interpreted. Here we report on the temperature dependent NMR spectra and spin-lattice relaxation measurements of intercalated fullerenes C{sub 60}(MF{sub 6}){sub 2} (M=As and Sb), where nuclear relaxation is caused by both molecular rotation and interaction between nuclei and unpaired electron spins. We present a detailed theoretical analysis of the spin-lattice relaxation data taking into account both these contributions. Good agreement between the experimental data and calculations is obtained. The developed approach would be useful in interpreting the NMR relaxation data in different nanostructures and their intercalation compounds.

  12. Calorimetric and relaxation properties of xylitol-water mixtures

    Science.gov (United States)

    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. Relaxed states of tokamak plasmas

    International Nuclear Information System (INIS)

    Kucinski, M.Y.; Okano, V.

    1993-01-01

    The relaxed states of tokamak plasmas are studied. It is assumed that the plasma relaxes to a quasi-steady state which is characterized by a minimum entropy production rate, compatible with a number of prescribed conditions and pressure balance. A poloidal current arises naturally due to the anisotropic resistivity. The minimum entropy production theory is applied, assuming the pressure equilibrium as fundamental constraint on the final state. (L.C.J.A.)

  14. Negative magnetic relaxation in superconductors

    Directory of Open Access Journals (Sweden)

    Krasnoperov E.P.

    2013-01-01

    Full Text Available It was observed that the trapped magnetic moment of HTS tablets or annuli increases in time (negative relaxation if they are not completely magnetized by a pulsed magnetic field. It is shown, in the framework of the Bean critical-state model, that the radial temperature gradient appearing in tablets or annuli during a pulsed field magnetization can explain the negative magnetic relaxation in the superconductor.

  15. Relaxation effects in ferrous complexes

    International Nuclear Information System (INIS)

    Nicolini, C.; Mathieu, J.P.; Chappert, J.

    1976-01-01

    The slow relaxation mechanism of the Fe 2+ ion in the tri-fluorinated TF(acac) and hexafluorinated HF(acac) complexes of Fe(II) acetylacetonate was investigated. The 300K and 77K Moessbauer spectra for TF(acac) consist in a slightly asymmetric quadrupole doublet. On the contrary, at 4.2K the higher energy line is strongly widened; that is typical of a slowing down in the electron relaxation frequency [fr

  16. THE ROLE OF ENDOTHELIUM FUNCTIONAL STATUS IN PULMONARY HYPERTENSION DEVELOPMENT AMONG CHILDREN

    Directory of Open Access Journals (Sweden)

    S.N. Ivanov

    2008-01-01

    Full Text Available The background paper approaches the problems of functional status of endothelium, significance of vasоactive substances as markers of endothelial dysfunction and reason of its development, role of endothelial dysfunction in the pathogenesis of primary and secondary pulmonary hypertension.Key words: pulmonary hypertension, endothelial dysfunction, vasoactive substances.

  17. Cultivation of Human Microvascular Endothelial Cells on Topographical Substrates to Mimic the Human Corneal Endothelium

    Directory of Open Access Journals (Sweden)

    Jie Shi Chua

    2013-03-01

    Full Text Available Human corneal endothelial cells have a limited ability to replicate in vivo and in vitro. Allograft transplantation becomes necessary when an accident or trauma results in excessive cell loss. The reconstruction of the cornea endothelium using autologous cell sources is a promising alternative option for therapeutic or in vitro drug testing applications. The native corneal endothelium rests on the Descemet’s membrane, which has nanotopographies of fibers and pores. The use of synthetic topographies mimics the native environment, and it is hypothesized that this can direct the behavior and growth of human microvascular endothelial cells (HMVECs to resemble the corneal endothelium. In this study, HMVECs are cultivated on substrates with micron and nano-scaled pillar and well topographies. Closely packed HMVEC monolayers with polygonal cells and well-developed tight junctions were formed on the topographical substrates. Sodium/potassium (Na+/K+ adenine triphosphatase (ATPase expression was enhanced on the microwells substrate, which also promotes microvilli formation, while more hexagonal-like cells are found on the micropillars samples. The data obtained suggests that the use of optimized surface patterning, in particular, the microtopographies, can induce HMVECs to adopt a more corneal endothelium-like morphology with similar barrier and pump functions. The mechanism involved in cell contact guidance by the specific topographical features will be of interest for future studies.

  18. Function of endothelium at adolescents with constitutional exogenous obesity before and after rehabilitation

    OpenAIRE

    Miroshnichenko, O.

    2011-01-01

    Function of endothelium at 43 adolescents with constitutional exogenous obesity before rehabilitation and at 33 healthy adolescents has been studied. Disorder of endothelial function has been established in 32 (74.4%) adolescents with constitutional exogenous obesity and in 7 (21.2%) healthy adolescents. We showed the efficiency of the rehabilitation program on restoration of endothelial function at adolescents with constitutional exogenous obesity.

  19. Gastrin-releasing peptide induces monocyte adhesion to vascular endothelium by upregulating endothelial adhesion molecules

    International Nuclear Information System (INIS)

    Kim, Mi-Kyoung; Park, Hyun-Joo; Kim, Yeon; Kim, Hyung Joon; Bae, Soo-Kyung; Bae, Moon-Kyoung

    2017-01-01

    Gastrin-releasing peptide (GRP) is a neuropeptide that plays roles in various pathophysiological conditions including inflammatory diseases in peripheral tissues; however, little is known about whether GRP can directly regulate endothelial inflammatory processes. In this study, we showed that GRP promotes the adhesion of leukocytes to human umbilical vein endothelial cells (HUVECs) and the aortic endothelium. GRP increased the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) by activating nuclear factor-κB (NF-κB) in endothelial cells. In addition, GRP activated extracellular signal-regulated kinase 1/2 (ERK1/2), p38MAPK, and AKT, and the inhibition of these signaling pathways significantly reduced GRP-induced monocyte adhesion to the endothelium. Overall, our results suggested that GRP may cause endothelial dysfunction, which could be of particular relevance in the development of vascular inflammatory disorders. - Highlights: • GRP induces adhesion of monocytes to vascular endothelium. • GRP increases the expression of endothelial adhesion molecules through the activation of NF-κB. • ERK1/2, p38MAPK, and Akt pathways are involved in the GRP-induced leukocyte adhesiveness to endothelium.

  20. Intracavitary ultrasound impairs left ventricular performance: presumed role of endocardial endothelium

    NARCIS (Netherlands)

    Gillebert, T. C.; de Hert, S. G.; Andries, L. J.; Jageneau, A. H.; Brutsaert, D. L.

    1992-01-01

    Irradiation of isolated cardiac muscle by high-power, high-frequency, continuous wave ultrasound selectively damages endocardial endothelium (EE). We evaluated this ultrasound effect in vivo on the performance of the intact ejecting canine left ventricle (LV). A cylindrical ultrasound probe (0.9

  1. Human haemato-endothelial precursors: cord blood CD34+ cells produce haemogenic endothelium.

    Directory of Open Access Journals (Sweden)

    Elvira Pelosi

    Full Text Available Embryologic and genetic evidence suggest a common origin of haematopoietic and endothelial lineages. In the murine embryo, recent studies indicate the presence of haemogenic endothelium and of a common haemato-endothelial precursor, the haemangioblast. Conversely, so far, little evidence supports the presence of haemogenic endothelium and haemangioblasts in later stages of development. Our studies indicate that human cord blood haematopoietic progenitors (CD34+45+144-, triggered by murine hepatocyte conditioned medium, differentiate into adherent proliferating endothelial precursors (CD144+CD105+CD146+CD31+CD45- capable of functioning as haemogenic endothelium. These cells, proven to give rise to functional vasculature in vivo, if further instructed by haematopoietic growth factors, first switch to transitional CD144+45+ cells and then to haematopoietic cells. These results highlight the plasticity of haemato-endhothelial precursors in human post-natal life. Furthermore, these studies may provide highly enriched populations of human post-fetal haemogenic endothelium, paving the way for innovative projects at a basic and possibly clinical level.

  2. Proton NMR relaxation in hydrous melts

    International Nuclear Information System (INIS)

    Braunstein, J.; Bacarella, A.L.; Benjamin, B.M.; Brown, L.L.; Girard, C.

    1976-01-01

    Pulse and continuous wave NMR measurements are reported for protons in hydrous melts of calcium nitrate at temperatures between -4 and 120 0 C. Although measured in different temperature ranges, spin-lattice (T 1 ) and spin-spin (T 2 ) relaxation times appear to be nearly equal to each other and proportional to the self-diffusion coefficients of solute metal cations such as Cd 2+ . At temperatures near 50 0 C, mean Arrhenius coefficients Δ H/sub T 1 / (kcal/mol) are 7.9, 7.3, and 4.8, respectively, for melts containing 2.8, 4.0, and 8.0 moles of water per mole of calcium nitrate, compared to 4.6 kcal/mol for pure water. Temperature dependence of T 1 and T 2 in Ca(NO 3 ) 2 -2.8 H 2 O between -4 and 120 0 C are non-Arrhenius and can be represented by a Fulcher-type equation with a ''zero mobility temperature'' (T 0 ) of 225 0 K, close to the value of T 0 for solute diffusion, electrical conductance and viscosity. Resolution of the relaxation rates into correlation times for intramolecular (rotational) and intermolecular (translational) diffusional motion is discussed in terms of the Bloembergen-Purcell-Pound and more recent models for dipolar relaxation

  3. Gap junctions and hydrogen peroxide are involved in endothelium-derived hyperpolarising responses to bradykinin in omental arteries and veins isolated from pregnant women.

    Science.gov (United States)

    Hammond, Stephanie; Mathewson, Alastair M; Baker, Philip N; Mayhew, Terry M; Dunn, William R

    2011-10-01

    Altered endothelial function may underlie human cardiovascular diseases, including hypertension, diabetes and pre-eclampsia. While much is known about endothelial function in small arteries, very little is known about endothelial responses in small veins isolated from humans. Therefore, we assessed endothelium-dependent responses in omental arteries and veins isolated from healthy pregnant women, focussing on endothelium-dependent hyperpolarising (EDH) mechanisms. Human omental arteries and veins were obtained from women undergoing elective caesarean sections and examined using pressure myography. In pressurised vessels, the effects of proposed inhibitors of EDH production/function were examined on responses to bradykinin. The expression of connexins Cx37, 40 and 43 was assessed using immunohistochemistry. Bradykinin caused vasodilatation in human pressurised omental arteries and veins. In both vessels, responses to bradykinin were partially blocked in the presence of the gap junction uncoupler, carbenoxolone, and reduced further with the addition of catalase, which acts to degrade H(2)O(2). The effect of catalase alone was more pronounced in venous preparations. All three connexins were expressed in both arteries and veins, with a similar distribution pattern, where Cx37 and Cx40 were located mainly in the endothelium and Cx43 located mostly in the media. These data show that, in human omental vessels, an EDH mechanism is produced in response to bradykinin that involves gap junction communication and the production of H(2)O(2). These mechanisms may be involved in the haemodynamic alterations that take place during pregnancy, and any aberration in their function could contribute to raised blood pressure in hypertensive disorders of pregnancy, such as pre-eclampsia. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Modelling Creep (Relaxation of the Urinary Bladder

    Directory of Open Access Journals (Sweden)

    Zdravkovic Nebojsa

    2017-12-01

    Full Text Available We first present the results of an experiment in which the passive properties of the urinary bladder were investigated using strips of rabbit bladder. Under the assumption that the urinary bladder had orthopaedic characteristics, the strips were taken in the longitudinal and in the circumferential directions. The material was subjected to uniaxial tension, and stress-stretch curves were generated for various rates of deformation. We found that the rates did not have a significantly effect on the passive response of the material. Additionally, the stress-stretch dependence during relaxation of the material when exposed to isometric conditions was determined experimentally.

  5. Relaxation oscillations in stimulated Raman scattering

    International Nuclear Information System (INIS)

    Kachen, G.I.; Lowdermilk, W.H.

    1977-01-01

    Light pulses created by stimulated Raman scattering having been found to exhibit a complex time dependence which resembles relaxation oscillations. A focused laser pulse generated both forward and backward Raman emissions which appeared as a series of pulses with durations much shorter than the incident laser pulse. Time dependence of the Raman emission was observed directly by use of a streak camera. The number of observed pulses increased with the intensity of the incident pulse, while separation of the pulses in time depended on the length of the focal region. Beam focusing was incorporated in the coupled wave equations for stimulated Raman scattering. These rate equations were then solved numerically, and the results are in good qualitative agreement with the experimental observations. The short Raman pulses are created by a process associated with depletion of the incident laser pulse. This process occurs under a broad range of conditions

  6. Dangerous Liaisons: Deviant Endothelium NOTCHes toward Tumor Metastasis.

    Science.gov (United States)

    Guo, Peipei; Rafii, Shahin

    2017-03-13

    In this issue of Cancer Cell, Wieland et al. uncover a feedback loop in which tumor cells, by augmenting Notch signaling, provoke a senescent and pro-inflammatory state in endothelial cells, promoting neutrophil infiltration, tumor cell adhesion, and metastasis. Interfering with this Notch-dependent crosstalk may be a therapeutic approach to block metastasis. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Parameterization of NMR relaxation curves in terms of logarithmic moments of the relaxation time distribution.

    Science.gov (United States)

    Petrov, Oleg V; Stapf, Siegfried

    2017-06-01

    This work addresses the problem of a compact and easily comparable representation of multi-exponential relaxation data. It is often convenient to describe such data in a few parameters, all being of physical significance and easy to interpret, and in such a way that enables a model-free comparison between different groups of samples. Logarithmic moments (LMs) of the relaxation time constitute a set of parameters which are related to the characteristic relaxation time on the log-scale, the width and the asymmetry of an underlying distribution of exponentials. On the other hand, the calculation of LMs does not require knowing the actual distribution function and is reduced to a numerical integration of original data. The performance of this method has been tested on both synthetic and experimental NMR relaxation data which differ in a signal-to-noise ratio, the sampling range and the sampling rate. The calculation of two lower-order LMs, the log-mean time and the log-variance, has proved robust against deficiencies of the experiment such as scattered data point and incomplete sampling. One may consider using them as such to monitor formation of a heterogeneous structure, e.g., in phase separation, vitrification, polymerization, hydration, aging, contrast agent propagation processes. It may also assist in interpreting frequency and temperature dependences of relaxation, revealing a crossover from slow to fast exchange between populations. The third LM was found to be a less reliable quantity due to its susceptibility to the noise and must be used with caution. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. Parameterization of NMR relaxation curves in terms of logarithmic moments of the relaxation time distribution

    Science.gov (United States)

    Petrov, Oleg V.; Stapf, Siegfried

    2017-06-01

    This work addresses the problem of a compact and easily comparable representation of multi-exponential relaxation data. It is often convenient to describe such data in a few parameters, all being of physical significance and easy to interpret, and in such a way that enables a model-free comparison between different groups of samples. Logarithmic moments (LMs) of the relaxation time constitute a set of parameters which are related to the characteristic relaxation time on the log-scale, the width and the asymmetry of an underlying distribution of exponentials. On the other hand, the calculation of LMs does not require knowing the actual distribution function and is reduced to a numerical integration of original data. The performance of this method has been tested on both synthetic and experimental NMR relaxation data which differ in a signal-to-noise ratio, the sampling range and the sampling rate. The calculation of two lower-order LMs, the log-mean time and the log-variance, has proved robust against deficiencies of the experiment such as scattered data point and incomplete sampling. One may consider using them as such to monitor formation of a heterogeneous structure, e.g., in phase separation, vitrification, polymerization, hydration, aging, contrast agent propagation processes. It may also assist in interpreting frequency and temperature dependences of relaxation, revealing a crossover from slow to fast exchange between populations. The third LM was found to be a less reliable quantity due to its susceptibility to the noise and must be used with caution.

  9. Peeling mode relaxation ELM model

    International Nuclear Information System (INIS)

    Gimblett, C. G.

    2006-01-01

    This paper discusses an approach to modelling Edge Localised Modes (ELMs) in which toroidal peeling modes are envisaged to initiate a constrained relaxation of the tokamak outer region plasma. Relaxation produces both a flattened edge current profile (which tends to further destabilise a peeling mode), and a plasma-vacuum negative current sheet which has a counteracting stabilising influence; the balance that is struck between these two effects determines the radial extent (rE) of the ELM relaxed region. The model is sensitive to the precise position of the mode rational surfaces to the plasma surface and hence there is a 'deterministic scatter' in the results that has an accord with experimental data. The toroidal peeling stability criterion involves the edge pressure, and using this in conjunction with predictions of rE allows us to evaluate the ELM energy losses and compare with experiment. Predictions of trends with the edge safety factor and collisionality are also made

  10. Topology Synthesis of Structures Using Parameter Relaxation and Geometric Refinement

    Science.gov (United States)

    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. Mechanical relaxation in chalcogenide glasses of the Ge-As-S system

    International Nuclear Information System (INIS)

    Bilanych, V.S.; Melnychenko, T.D.; Rizak, V.M.; Makauz, I.I.

    2006-01-01

    The temperature and frequency-related dependences of the internal friction and the shear modulus in Ge x As 40-x S 60 glasses have been studied. The maxima of internal friction of both the relaxation and non relaxation types have been found in the low-temperature range. A relaxation maximum has been revealed in the vitrification region, and its parameters have been determined. Possible mechanisms of these processes have been discussed

  12. Comparison and Supervised Learning of Segmentation Methods Dedicated to Specular Microscope Images of Corneal Endothelium

    Directory of Open Access Journals (Sweden)

    Yann Gavet

    2014-01-01

    Full Text Available The cornea is the front of the eye. Its inner cell layer, called the endothelium, is important because it is closely related to the light transparency of the cornea. An in vivo observation of this layer is performed by using specular microscopy to evaluate the health of the cells: a high spatial density will result in a good transparency. Thus, the main criterion required by ophthalmologists is the cell density of the cornea endothelium, mainly obtained by an image segmentation process. Different methods can perform the image segmentation of these cells, and the three most performing methods are studied here. The question for the ophthalmologists is how to choose the best algorithm and to obtain the best possible results with it. This paper presents a methodology to compare these algorithms together. Moreover, by the way of geometric dissimilarity criteria, the algorithms are tuned up, and the best parameter values are thus proposed to the expert ophthalmologists.

  13. Ulex europaeus I lectin as a marker for vascular endothelium in human tissues.

    Science.gov (United States)

    Holthöfer, H; Virtanen, I; Kariniemi, A L; Hormia, M; Linder, E; Miettinen, A

    1982-07-01

    Ulex europaeus I agglutinin, a lectin specific for some alpha-L-fucose-containing glycocompounds, was used in fluorescence microscopy to stain cryostat sections of human tissues. The endothelium of vessels of all sizes was stained ubiquitously in all tissues studied as judged by double staining with a known endothelial marker, antibodies against human clotting factor VIII. Cultured human umbilical vein endothelial cells, but not fibroblasts, also bound Ulex lectin. The staining was not affected by the blood group type of the tissue donor. In some tissues Ulex lectin presented additional binding to epithelial structures. Also, this was independent on the blood group or the ability of the tissue donor to secrete soluble blood group substances. Lotus tetragonolobus agglutinin, another lectin specific for some alpha-L-fucose-containing moieties failed to react with endothelial cells. Our results suggest that Ulex europaeus I agglutinin is a good histologic marker for endothelium in human tissues.

  14. Early dynamic fate changes in haemogenic endothelium characterized at the single-cell level

    Science.gov (United States)

    Swiers, Gemma; Baumann, Claudia; O'Rourke, John; Giannoulatou, Eleni; Taylor, Stephen; Joshi, Anagha; Moignard, Victoria; Pina, Cristina; Bee, Thomas; Kokkaliaris, Konstantinos D.; Yoshimoto, Momoko; Yoder, Mervin C.; Frampton, Jon; Schroeder, Timm; Enver, Tariq; Göttgens, Berthold; de Bruijn, Marella F. T. R.

    2013-12-01

    Haematopoietic stem cells (HSCs) are the founding cells of the adult haematopoietic system, born during ontogeny from a specialized subset of endothelium, the haemogenic endothelium (HE) via an endothelial-to-haematopoietic transition (EHT). Although recently imaged in real time, the underlying mechanism of EHT is still poorly understood. We have generated a Runx1 +23 enhancer-reporter transgenic mouse (23GFP) for the prospective isolation of HE throughout embryonic development. Here we perform functional analysis of over 1,800 and transcriptional analysis of 268 single 23GFP+ HE cells to explore the onset of EHT at the single-cell level. We show that initiation of the haematopoietic programme occurs in cells still embedded in the endothelial layer, and is accompanied by a previously unrecognized early loss of endothelial potential before HSCs emerge. Our data therefore provide important insights on the timeline of early haematopoietic commitment.

  15. Permeability of the arterial endothelium of spontaneously hypertensive rats to plasma macromolecules

    International Nuclear Information System (INIS)

    Yurukova, Z.B.; Georgiev, P.G.

    1979-01-01

    By means of vascular labelling technique at cellular level, the permeability of the arterial endothelium of spontaneously hypertensive rats has been studied. For this purpose colloidal carbon and plasma lipoproteins were introduced into the jugular vein of the animals. Material for light- and electron-microscopic and radioautographic examinations was taken from the thoracic and abdominal parts of the aorta. The results show that in long-term hypertension substances from plasma enter the aortic wall in increased amounts through two main pathways. First, through the selective physiological pathways of transendothelial transport (through cell junctions and vesicular transport) and secondly, through discontinuities of the endothelial lining (separation of the intercellular junctions, areas of loss of one to several endothelial cells). The alteration of the arterial endothelium barrier function in chronic hypertension seems to be an important mechanism for the progression of hypertensive arterial lesions. (A.B.)

  16. [The effects of intraocular irrigating solutions on the human corneal endothelium (author's transl)].

    Science.gov (United States)

    Weekers, J F; Dethinne, M

    1978-11-01

    Human corneas from enucleated eyes get thicker during perfusion with B.S.S. On the contrary, their thickness decreases when perfused with T.C. Earle solution. Addition of reduced glutathion and adenosine does not change the results obtained with T.C. Earle. Histological study of the endothelium after a 24 hours perfusion demonstrates a better conservation of the cells with T.C. Earle and T.C. Earle glutathion--adenosine than with B.S.S.

  17. Effect of diatrizoate (Angiografin) on the aortic endothelium in rats during the course of endotoxin shock

    Energy Technology Data Exchange (ETDEWEB)

    Gospos, C; Freudenberg, N; Hauenstein, K H; Kauffmann, G W; Koch, H K

    1982-08-01

    Investigations have been carried out on the endothelial changes produced by diatrizoate (Angiografin) during the course of endotoxin shock. A single injection was given directly into the aorta of 1 ml of the contrast medium, with an iodine content of 300 mg/ml. The increased proliferation of the aortic endothelium could be shown to be due to the endotoxin shock, but was not further increased by administration of the contrast medium.

  18. Relationship between vascular endothelium and periodontal disease in atherosclerotic lesions: Review article

    Science.gov (United States)

    Saffi, Marco Aurélio Lumertz; Furtado, Mariana Vargas; Polanczyk, Carisi Anne; Montenegro, Márlon Munhoz; Ribeiro, Ingrid Webb Josephson; Kampits, Cassio; Haas, Alex Nogueira; Rösing, Cassiano Kuchenbecker; Rabelo-Silva, Eneida Rejane

    2015-01-01

    Inflammation and endothelial dysfunction are linked to the pathogenesis of atherosclerotic disease. Recent studies suggest that periodontal infection and the ensuing increase in the levels of inflammatory markers may be associated with myocardial infarction, peripheral vascular disease and cerebrovascular disease. The present article aimed at reviewing contemporary data on the pathophysiology of vascular endothelium and its association with periodontitis in the scenario of cardiovascular disease. PMID:25632316

  19. Conversion of adult endothelium to immunocompetent haematopoietic stem cells.

    Science.gov (United States)

    Lis, Raphael; Karrasch, Charles C; Poulos, Michael G; Kunar, Balvir; Redmond, David; Duran, Jose G Barcia; Badwe, Chaitanya R; Schachterle, William; Ginsberg, Michael; Xiang, Jenny; Tabrizi, Arash Rafii; Shido, Koji; Rosenwaks, Zev; Elemento, Olivier; Speck, Nancy A; Butler, Jason M; Scandura, Joseph M; Rafii, Shahin

    2017-05-25

    Developmental pathways that orchestrate the fleeting transition of endothelial cells into haematopoietic stem cells remain undefined. Here we demonstrate a tractable approach for fully reprogramming adult mouse endothelial cells to haematopoietic stem cells (rEC-HSCs) through transient expression of the transcription-factor-encoding genes Fosb, Gfi1, Runx1, and Spi1 (collectively denoted hereafter as FGRS) and vascular-niche-derived angiocrine factors. The induction phase (days 0-8) of conversion is initiated by expression of FGRS in mature endothelial cells, which results in endogenous Runx1 expression. During the specification phase (days 8-20), RUNX1 + FGRS-transduced endothelial cells commit to a haematopoietic fate, yielding rEC-HSCs that no longer require FGRS expression. The vascular niche drives a robust self-renewal and expansion phase of rEC-HSCs (days 20-28). rEC-HSCs have a transcriptome and long-term self-renewal capacity similar to those of adult haematopoietic stem cells, and can be used for clonal engraftment and serial primary and secondary multi-lineage reconstitution, including antigen-dependent adaptive immune function. Inhibition of TGFβ and CXCR7 or activation of BMP and CXCR4 signalling enhanced generation of rEC-HSCs. Pluripotency-independent conversion of endothelial cells into autologous authentic engraftable haematopoietic stem cells could aid treatment of haematological disorders.

  20. Holographic grating relaxation technique for soft matter science

    Energy Technology Data Exchange (ETDEWEB)

    Lesnichii, Vasilii, E-mail: vasilii.lesnichii@physchem.uni-freiburg.de [Institute of Physical Chemistry, Albertstraße 21, Institute of Macromolecular Chemistry, Stefan-Meier-Str. 31, Albert-Ludwigs Universität, Freiburg im Breisgau 79104 (Germany); ITMO University, Kronverksky prospekt 49, Saint-Petersburg 197101 (Russian Federation); Kiessling, Andy [Institute of Physical Chemistry, Albertstraße 21, Institute of Macromolecular Chemistry, Stefan-Meier-Str. 31, Albert-Ludwigs Universität, Freiburg im Breisgau 79104 (Germany); Current address: Illinois Institute of Technology, 10 West 33rd Street, Chicago,IL60616 (United States); Bartsch, Eckhard [Institute of Physical Chemistry, Albertstraße 21, Institute of Macromolecular Chemistry, Stefan-Meier-Str. 31, Albert-Ludwigs Universität, Freiburg im Breisgau 79104 (Germany); Veniaminov, Andrey, E-mail: veniaminov@phoi.ifmo.ru [ITMO University, Kronverksky prospekt 49, Saint-Petersburg 197101 (Russian Federation)

    2016-06-17

    The holographic grating relaxation technique also known as forced Rayleigh scattering consists basically in writing a holographic grating in the specimen of interest and monitoring its diffraction efficiency as a function of time, from which valuable information on mass or heat transfer and photoinduced transformations can be extracted. In a more detailed view, the shape of the relaxation curve and the relaxation rate as a function of the grating period were found to be affected by the architecture of diffusing species (molecular probes) that constitute the grating, as well as that of the environment they diffuse in, thus making it possible to access and study spatial heterogeneity of materials and different modes of e.g., polymer motion. Minimum displacements and spatial domains approachable by the technique are in nanometer range, well below spatial periods of holographic gratings. In the present paper, several cases of holographic relaxation in heterogeneous media and complex motions are exemplified. Nano- to micro-structures or inhomogeneities comparable in spatial scale with holographic gratings manifest themselves in relaxation experiments via non-exponential decay (stepwise or stretched), spatial-period-dependent apparent diffusion coefficient, or unusual dependence of diffusion coefficient on molecular volume of diffusing probes.

  1. F19 relaxation in non-magnetic hexafluorides

    International Nuclear Information System (INIS)

    Rigny, P.

    1969-01-01

    The interesting properties of the fluorine magnetic resonance in the hexafluorides of molybdenum, tungsten and uranium, are very much due to large anisotropies of the chemical shift tensors. In the solid phases these anisotropies, the values of which are deduced from line shape studies, allow one to show that the molecules undergo hindered rotations about the metal atom. The temperature and frequency dependence of the fluorine longitudinal relaxation times shows that the relaxation is due to the molecular motion. The dynamical parameters of this motion are then deduced from the complete study of the fluorine relaxation in the rotating frame. In the liquid phases, the existence of anisotropies allows an estimation of the different contributions to the relaxation. In particular, the frequency and temperature dependence of the relaxation shows it to be dominated by the spin-rotation interaction. We have shown that the strength of this interaction can be deduced from the chemical shifts, and the angle through which the molecule rotates quasi-freely can be determined. In the hexafluorides, this angle is roughly one radian at 70 C, and with the help of this value, the friction coefficients which describe the intermolecular interactions are discussed. (author) [fr

  2. Evolutionary Pseudo-Relaxation Learning Algorithm for Bidirectional Associative Memory

    Institute of Scientific and Technical Information of China (English)

    Sheng-Zhi Du; Zeng-Qiang Chen; Zhu-Zhi Yuan

    2005-01-01

    This paper analyzes the sensitivity to noise in BAM (Bidirectional Associative Memory), and then proves the noise immunity of BAM relates not only to the minimum absolute value of net inputs (MAV) but also to the variance of weights associated with synapse connections. In fact, it is a positive monotonically increasing function of the quotient of MAV divided by the variance of weights. Besides, the performance of pseudo-relaxation method depends on learning parameters (λ and ζ), but the relation of them is not linear. So it is hard to find a best combination of λ and ζ which leads to the best BAM performance. And it is obvious that pseudo-relaxation is a kind of local optimization method, so it cannot guarantee to get the global optimal solution. In this paper, a novel learning algorithm EPRBAM (evolutionary psendo-relaxation learning algorithm for bidirectional association memory) employing genetic algorithm and pseudo-relaxation method is proposed to get feasible solution of BAM weight matrix. This algorithm uses the quotient as the fitness of each individual and employs pseudo-relaxation method to adjust individual solution when it does not satisfy constraining condition any more after genetic operation. Experimental results show this algorithm improves noise immunity of BAM greatly. At the same time, EPRBAM does not depend on learning parameters and can get global optimal solution.

  3. Onsager relaxation of toroidal plasmas

    International Nuclear Information System (INIS)

    Samain, A.; Nguyen, F.

    1997-01-01

    The slow relaxation of isolated toroidal plasmas towards their thermodynamical equilibrium is studied in an Onsager framework based on the entropy metric. The basic tool is a variational principle, equivalent to the kinetic equation, involving the profiles of density, temperature, electric potential, electric current. New minimization procedures are proposed to obtain entropy and entropy production rate functionals. (author)

  4. Anisotropic spin relaxation in graphene

    NARCIS (Netherlands)

    Tombros, N.; Tanabe, S.; Veligura, A.; Jozsa, C.; Popinciuc, M.; Jonkman, H. T.; van Wees, B. J.

    2008-01-01

    Spin relaxation in graphene is investigated in electrical graphene spin valve devices in the nonlocal geometry. Ferromagnetic electrodes with in-plane magnetizations inject spins parallel to the graphene layer. They are subject to Hanle spin precession under a magnetic field B applied perpendicular

  5. Stochastic and Chaotic Relaxation Oscillations

    NARCIS (Netherlands)

    Grasman, J.; Roerdink, J.B.T.M.

    1988-01-01

    For relaxation oscillators stochastic and chaotic dynamics are investigated. The effect of random perturbations upon the period is computed. For an extended system with additional state variables chaotic behavior can be expected. As an example, the Van der Pol oscillator is changed into a

  6. Tensions relaxation in Zircaloy-4

    International Nuclear Information System (INIS)

    Cuniberti, A.M.; Picasso, A.C.

    1990-01-01

    Traction and stress relaxation studies were performed on polycrystalline Zry-4 at room temperature. The effect of loading velocity on the plastic behaviour of the material is discussed, analysing log σ vs. log dε/dt at different deformation levels. The contribution introduced by the testing machine was taken into account in data evaluation. (Author). 7 refs., 3 figs., 3 tabs

  7. gamma. -relaxation process in crystallizable polymers

    Energy Technology Data Exchange (ETDEWEB)

    Mindiyarov, Kh G; Zelenev, Yu V; Bartenev, G M [Birskij Gosudarstvennyj Pedagogicheskij Inst. (USSR)

    1975-07-01

    In the present paper, with the aid of radiothermoluminescence technique ..gamma..-relaxation processes are investigated, which are conditioned by molecular mobility and are associated with defects in the crystalline structure of polymers PEh, PP, and elastomers PIB, NK, SKD, SKI exposed to ..gamma..-rays of Co/sup 60/ at a dose rate of 1 Mrad. The shape of the thermoluminescence curve, i.e. the luminescence intensity in the ..cap alpha.. - ..gamma..-maxima, their relationship, position with respect to temperature are strongly dependent on the degree of crystallinity, on the thermal and mechanical prehistory. In highly crystalline samples of PEh and PP ..cap alpha..-maximum may be absent. Dependence has been studied of the luminescence intensity in the ..cap alpha..- and ..gamma..-maxima (Isub(..cap alpha..)/Isub(..gamma..)) on the crystallization temperature; the curve passes through the minimum when the crystallization rate is maximum. The relationship Isub(..gamma..)re of crystallinity degree.

  8. ENDOTHELIUM LESION MARKERS AND THROMBOCYTE AGGREGATION IN CHRONIC HEPATITIS AND HEPATIC CIRRHOSIS

    Directory of Open Access Journals (Sweden)

    A. P. Shchekotova

    2012-01-01

    Full Text Available Aim — to estimate endothelium lesion, quantity and thrombocyte aggregation function correlation in viral chronic hepatitis C (CHC and hepatic cirrhosis (HC.Materials and methods. 50 CHC patients and 28 HC patients were examined. Using IFA method the total nitric oxide, endothelin‑1, vasculoendothelial growth factor levels, Willebrand factor (vWF activity were investigated, blood plasma desquamated endotheliocyte (DEC number was calculated with Hladovec method, 1978, thrombocyte aggregation (TA with ADP, collagen, ristocetine was determined.Results. DEC and vWF demonstrated correlation in CHC (p = 0.014 and HC (p = 0.000004. In HC patients reliable correlation of all the investigated indices of endothelium lesion with the thrombocyte number and TA was detected, but in CHC patients no correlations were revealed. Thus, significant elevation of TA with ristocetine was noted only in CHC. Decrease in thrombocyte amount among CHC patients and,especially in HC, and heightened vWF activity could change true TA indices. The corrected TA, whose indices in hepatic diseases significantlyincreased, was calculated taking into account the correction factor vWF / thrombocytes that in CHC did not differ from that of healthy patients and in HC was essentially higher.Conclusion. Endothelium dysfunction markers in CH and HC demonstrate correlation with thrombocyte reduction and TA elevation. Determinationof corrected TA permits to reveal disturbances of thrombocyte hemostasis in the form of elevated aggregation in all CHC and HC patients.

  9. Metabolic syndrome enhances endoplasmic reticulum, oxidative stress and leukocyte-endothelium interactions in PCOS.

    Science.gov (United States)

    Bañuls, Celia; Rovira-Llopis, Susana; Martinez de Marañon, Aranzazu; Veses, Silvia; Jover, Ana; Gomez, Marcelino; Rocha, Milagros; Hernandez-Mijares, Antonio; Victor, Victor M

    2017-06-01

    Polycystic ovary syndrome (PCOS) is associated with insulin resistance, which can lead to metabolic syndrome (MetS). Oxidative stress and leukocyte-endothelium interactions are related to PCOS. Our aim was to evaluate whether the presence of MetS in PCOS patients can influence endoplasmic reticulum (ER) and oxidative stress and leukocyte-endothelium interactions. This was a prospective controlled study conducted in an academic medical center. The study population consisted of 148 PCOS women (116 without/32 with MetS) and 112 control subjects (87 without / 25 with MetS). Metabolic parameters, reactive oxygen species (ROS) production, ER stress markers (GRP78, sXBP1, ATF6), leukocyte-endothelium interactions, adhesion molecules (VCAM-1, ICAM-1, E-Selectin), TNF-α and IL-6 were determined. Total ROS, inflammatory parameters and adhesion molecules were enhanced in the presence of MetS (pPCOS+MetS group showed higher levels of IL-6 and ICAM-1 than controls (pPCOS and PCOS+MetS groups vs their respective controls (pPCOS groups (pPCOS+MetS patients exhibited higher GRP78 and ATF6 levels than controls and PCOS patients without MetS (pPCOS women, HOMA-IR was positively correlated with ICAM-1 (r=0.501; pPCOS, all of which are related to vascular complications. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Simulated hypogravity impairs the angiogenic response of endothelium by up-regulating apoptotic signals

    International Nuclear Information System (INIS)

    Morbidelli, Lucia; Monici, Monica; Marziliano, Nicola; Cogoli, Augusto; Fusi, Franco; Waltenberger, Johannes; Ziche, Marina

    2005-01-01

    Health hazards in astronauts are represented by cardiovascular problems and impaired bone healing. These disturbances are characterized by a common event, the loss of function by vascular endothelium, leading to impaired angiogenesis. We investigated whether the exposure of cultured endothelial cells to hypogravity condition could affect their behaviour in terms of functional activity, biochemical responses, morphology, and gene expression. Simulated hypogravity conditions for 72 h produced a reduction of cell number. Genomic analysis of endothelial cells exposed to hypogravity revealed that proapoptotic signals increased, while antiapoptotic and proliferation/survival genes were down-regulated by modelled low gravity. Activation of apoptosis was accompanied by morphological changes with mitochondrial disassembly and organelles/cytoplasmic NAD(P)H redistribution, as evidenced by autofluorescence analysis. In this condition cells were not able to respond to angiogenic stimuli in terms of migration and proliferation. Our study documents functional, morphological, and transcription alterations in vascular endothelium exposed to simulated low gravity conditions, thus providing insights on the occurrence of vascular tissue dysregulation in crewmen during prolonged space flights. Moreover, the alteration of vascular endothelium can intervene as a concause in other systemic effects, like bone remodelling, observed in weightlessness

  11. Activation of the Arterial Program Drives Development of Definitive Hemogenic Endothelium with Lymphoid Potential

    Directory of Open Access Journals (Sweden)

    Mi Ae Park

    2018-05-01

    Full Text Available Summary: Understanding the pathways guiding the development of definitive hematopoiesis with lymphoid potential is essential for advancing human pluripotent stem cell (hPSC technologies for the treatment of blood diseases and immunotherapies. In the embryo, lymphoid progenitors and hematopoietic stem cells (HSCs arise from hemogenic endothelium (HE lining arteries but not veins. Here, we show that activation of the arterial program through ETS1 overexpression or by modulating MAPK/ERK signaling pathways at the mesodermal stage of development dramatically enhanced the formation of arterial-type HE expressing DLL4 and CXCR4. Blood cells generated from arterial HE were more than 100-fold enriched in T cell precursor frequency and possessed the capacity to produce B lymphocytes and red blood cells expressing high levels of BCL11a and β-globin. Together, these findings provide an innovative strategy to aid in the generation of definitive lymphomyeloid progenitors and lymphoid cells from hPSCs for immunotherapy through enhancing arterial programming of HE. : Park et al. find that activation of the arterial program through ETS1 overexpression or by modulating MAPK/ERK signaling pathways at the mesodermal stage of development dramatically enhances formation of arterial-type hemogenic endothelium (HE from hPSCs. Blood cells generated from arterial HE are highly enriched in definitive lymphomyeloid progenitors. Keywords: human pluripotent stem cells, hemogenic endothelium, T cells, hematopoietic stem cells, hematopoiesis, ETS1, MAPK/ERK signaling

  12. EFFECTS OF ENALAPRIL ON ENDOTHELIUM FUNCTION IN PATIENTS WITH ISCHEMIC HEART DISEASE

    Directory of Open Access Journals (Sweden)

    L. I. Katelnizkaya

    2006-01-01

    Full Text Available Aim. To study endothelium vasomotor function (EF in patients with ischemic heart disease (IHD and the influence of angiotensin converting enzyme inhibitor enalapril (Enam, Dr .Reddy’s, India on it. Material and methods. 87 patients were examined totally. 49 patients were suffering from IHD: 18 patients were younger than 60 years old and 31 patients were older . The combination of arterial hypertension (HT and IHD were registered in 38 patients: 18 patients were below and 20 patients were above 60 years old. All patients additionally to basic IHD therapy took enalapril in dose 2,5-30 mg/daily during 12 weeks. Before the beginning and in the end of treatment cuff test, test with nitroglycerine, bicycle exercise test and Holter monitoring were made, the thickness of intima-media complex of carotid artery and the level of endothelin-1 in blood plasma were defined. Results. EF disorders were shown in IHD, maximal disorders were determined in patients with combination of IHD and HT. EF disorders were also more expressive in patients of elder group. Enalapril restored of cuff tests results, nitroglycerine tests results, reduced a number of myocardial ischemia episodes and provided target blood pressure in 60, 5% patients with HT. Conclusion. Enalapril improves endothelium vasomotor function, endothelium reaction on nitroglycerine and clinical course of IHD and HT.

  13. Sleep, Stress & Relaxation: Rejuvenate Body & Mind

    Science.gov (United States)

    Sleep, Stress & Relaxation: Rejuvenate Body & Mind; Relieve Stress; best ways to relieve stress; best way to relieve stress; different ways to relieve stress; does smoking relieve stress; does tobacco relieve stress; how can I relieve stress; how can you relieve stress; how do I relieve stress; reduce stress; does smoking reduce stress; how can I reduce stress; how to reduce stress; reduce stress; reduce stress levels; reducing stress; smoking reduce stress; smoking reduces stress; stress reducing techniques; techniques to reduce stress; stress relief; best stress relief; natural stress relief; need stress relief; relief for stress; relief from stress; relief of stress; smoking and stress relief; smoking for stress relief; smoking stress relief; deal with stress; dealing with stress; dealing with anger; dealing with stress; different ways of dealing with stress; help dealing with stress; how to deal with anger; how to deal with stress; how to deal with stress when quitting smoking; stress management; free stress management; how can you manage stress; how do you manage stress; how to manage stress; manage stress; management of stress; management stress; managing stress; strategies for managing stress; coping with stress; cope with stress; copeing with stress; coping and stress; coping skills for stress; coping strategies for stress; coping strategies with stress; coping strategy for stress; coping with stress; coping with stress and anxiety; emotional health; emotional health; emotional health article; emotional health articles; deep relaxation; deep breathing relaxation techniques; deep muscle relaxation; deep relaxation; deep relaxation meditation; deep relaxation technique; deep relaxation techniques; meditation exercises; mindful exercises; mindful meditation exercises; online relaxation exercises; relaxation breathing exercises; relaxation exercise; relaxation exercises; stress relaxation; methods of relaxation for stress; relax stress; relax techniques stress

  14. Magnetic relaxation behaviour in Pr_2NiSi_3

    International Nuclear Information System (INIS)

    Pakhira, Santanu; Mazumdar, Chandan; Ranganathan, R.

    2016-01-01

    Time dependent isothemal remanent magnetizatin (IRM) behaviour for polycrystalline compound Pr_2NiSi_3 have been studied below its characteristic temperature. The compound undergoes slow magnetic relaxation with time. Along with competing interaction, non-magnetic atom disorder plays an important role in formation of non-equilibrium glassy like ground state for this compound.

  15. Energy equation for the analysis of magnetization relaxation to equilibrium

    Energy Technology Data Exchange (ETDEWEB)

    Bertotti, G. [IEN Galileo Ferraris, Materials Department, Strada delle Cacce, 91, I-10135 Torino (Italy)]. E-mail: bertotti@ien.it; Bonin, R. [Dipartimento di Fisica, Politecnico di Torino, I-10129 Torino (Italy); Magni, A. [IEN Galileo Ferraris, Materials Department, Strada delle Cacce, 91, I-10135 Torino (Italy); Mayergoyz, I.D. [Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland, 20742 (United States); Serpico, C. [Dipartimento di Ingegneria Elettrica, Universita di Napoli ' Federico II' , I-80125 Naples (Italy)

    2005-02-01

    Magnetization relaxation starting from a generic non-equilibrium state is analytically described. An equation for the energy decay is obtained. On this basis, an approximate expression for the magnetization motion during the ringing process is obtained in terms of Jacobi elliptic functions with time-dependent parameters.

  16. Energy equation for the analysis of magnetization relaxation to equilibrium

    International Nuclear Information System (INIS)

    Bertotti, G.; Bonin, R.; Magni, A.; Mayergoyz, I.D.; Serpico, C.

    2005-01-01

    Magnetization relaxation starting from a generic non-equilibrium state is analytically described. An equation for the energy decay is obtained. On this basis, an approximate expression for the magnetization motion during the ringing process is obtained in terms of Jacobi elliptic functions with time-dependent parameters

  17. Hotspot relaxation dynamics in a current-carrying superconductor

    Science.gov (United States)

    Marsili, F.; Stevens, M. J.; Kozorezov, A.; Verma, V. B.; Lambert, Colin; Stern, J. A.; Horansky, R. D.; Dyer, S.; Duff, S.; Pappas, D. P.; Lita, A. E.; Shaw, M. D.; Mirin, R. P.; Nam, S. W.

    2016-03-01

    We experimentally studied the dynamics of optically excited hotspots in current-carrying WSi superconducting nanowires as a function of bias current, bath temperature, and excitation wavelength. We observed that the hotspot relaxation time depends on bias current, temperature, and wavelength. We explained this effect with a model based on quasiparticle recombination, which provides insight into the quasiparticle dynamics of superconductors.

  18. Hierarchical nitrogen-doped porous carbon with high surface area derived from endothelium corneum gigeriae galli for high-performance supercapacitor

    International Nuclear Information System (INIS)

    Hong, Xiaoting; Hui, K.S.; Zeng, Zhi; Hui, K.N.; Zhang, Luojiang; Mo, Mingyue; Li, Min

    2014-01-01

    Highlights: • Porous carbons were prepared using endothelium corneum gigeriae galli as precursor. • Surface and structural properties strongly depend on carbonization temperatures. • Resultant carbons possess nitrogen heteroatom and high surface areas. • ECGG-900 sample exhibits excellent electrochemical capacitive performances. - Abstract: Endothelium corneum gigeriae galli derived 3D hierarchical nitrogen-doped porous carbon was for the first time prepared by preliminary carbonization at 450 °C and final KOH activation at high temperatures. The surface and structural properties of the as-synthesized samples are analyzed with Brunauer–Emmett–Teller surface analyzer apparatus, X-Ray Diffractometer, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectrometer. The electrochemical performances are analyzed by cyclic voltammetry, galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy. The obtained results show that the sample carbonized at 900 °C possesses the SSA of 2149.9 m 2 g −1 , average micropore diameter of 1.78 nm, and exhibits the highest initial specific capacitance of 198.0 F g −1 at current density of 1 A g −1 in 6 M KOH solution. It retains good specific capacitance retention of 91.6% after 3000 charge/discharge cycles at current density of 2 A g −1

  19. Relaxation processes and structural transformations in amorphous Co-Fe-Si-B alloys

    International Nuclear Information System (INIS)

    Dus-Sitek, M.; Olszowski, Z.

    1994-01-01

    The thermostimulated electron emission (TSEE) method was applied for determination of relaxation and crystallization processes in amorphous alloys. By using the analogy of DTA-method, the activation energy of relaxation and crystallization processes has been determined from the measurements of changes of TSEE temperature maxima depending on the heating rate

  20. Effect of magnetic field on charge imbalance relaxation of non-equilibrium superconductivity

    International Nuclear Information System (INIS)

    Tsuboi, Kazuki; Yagi, Ryuta

    2010-01-01

    We have studied relaxation of charge imbalance of non-equilibrium superconductivity in magnetic field. We found that excess current due to charge imbalance showed striking dependence on magnitude of magnetic field and its orientation. We discussed origin of the relaxation.

  1. Investigation of the proteins relaxation time in human blood serum; Badania relaksacyjne bialek surowicy krwi II

    Energy Technology Data Exchange (ETDEWEB)

    Blicharska, B.; Klauza, M. [Inst. Fizyki, Uniwersytet Jagiellonski, Cracow (Poland); Kuliszkiewicz-Janus, M. [Akademia Medyczna, Wroclaw (Poland)

    1994-12-31

    In this paper the results of human blood serum proteins relaxation time measurements by means of NMR method are presented. The measurements have been done for three samples of human blood: i/laudably ii/leukemia iii/granulomas. The dependences of the relaxation time on the temperature are also presented. 3 refs, 4 figs.

  2. Picosecond buildup and relaxation of intense stimulated emission in GaAs

    International Nuclear Information System (INIS)

    Ageeva, N. N.; Bronevoi, I. L.; Zabegaev, D. N.; Krivonosov, A. N.

    2013-01-01

    In support of the idea developed previously based on circumstantial evidence, we have found that stimulated emission emerges in GaAs and its intensity increases with a picosecond delay relative to the front of powerful picosecond optical pumping that produced a dense electron-hole plasma. The emission intensity relaxes with decreasing pumping with a characteristic time of ∼10 ps. We have derived the dependences of the delay time, the relaxation time, and the duration of the picosecond emission pulse on its photon energy. The estimates based on the fact that the relaxation of emission is determined by electron-hole plasma cooling correspond to the measured relaxation time.

  3. Composition effect of potassium-borate glasses on their relaxation properties

    International Nuclear Information System (INIS)

    Lomovskoj, V.A.; Bartenev, G.M.

    1995-01-01

    Relaxation processes in potassium-borate glasses have been investigated in detail for the first time. It is shown that low-temperature β-process of relaxation relating to rotational mobility of the B-O bond is the same for all potassium-borate glasses and B 2 O 3 . The process of β k -relaxation related to diffusion mobility of potassium ions depends on the composition of the glasses in the same way as α-relaxation (glass formation).12 refs., 10 figs., 2 tabs

  4. Suppression of Dyakonov-Perel Spin Relaxation in High-Mobility n-GaAs

    Science.gov (United States)

    Dzhioev, R. I.; Kavokin, K. V.; Korenev, V. L.; Lazarev, M. V.; Poletaev, N. K.; Zakharchenya, B. P.; Stinaff, E. A.; Gammon, D.; Bracker, A. S.; Ware, M. E.

    2004-11-01

    We report a large and unexpected suppression of the free electron spin-relaxation in lightly doped n-GaAs bulk crystals. The spin-relaxation rate shows a weak mobility dependence and saturates at a level 30 times less than that predicted by the Dyakonov-Perel theory. The dynamics of the spin-orbit field differs substantially from the usual scheme: although all the experimental data can be self-consistently interpreted as a precessional spin-relaxation induced by a random spin-orbit field, the correlation time of this random field, surprisingly, is much shorter than, and is independent of, the momentum relaxation time determined from transport measurements.

  5. Vascular relaxation induced by C-type natriuretic peptide involves the ca2+/NO-synthase/NO pathway.

    Directory of Open Access Journals (Sweden)

    Fernanda A Andrade

    Full Text Available AIMS: C-type natriuretic peptide (CNP and nitric oxide (NO are endothelium-derived factors that play important roles in the regulation of vascular tone and arterial blood pressure. We hypothesized that NO produced by the endothelial NO-synthase (NOS-3 contributes to the relaxation induced by CNP in isolated rat aorta via activation of endothelial NPR-C receptor. Therefore, the aim of this study was to investigate the putative contribution of NO through NPR-C activation in the CNP induced relaxation in isolated conductance artery. MAIN METHODS: Concentration-effect curves for CNP were constructed in aortic rings isolated from rats. Confocal microscopy was used to analyze the cytosolic calcium mobilization induced by CNP. The phosphorylation of the residue Ser1177 of NOS was analyzed by Western blot and the expression and localization of NPR-C receptors was analyzed by immunohistochemistry. KEY FINDINGS: CNP was less potent in inducing relaxation in denuded endothelium aortic rings than in intact ones. L-NAME attenuated the potency of CNP and similar results were obtained in the presence of hydroxocobalamin, an intracellular NO0 scavenger. CNP did not change the phosphorylation of Ser1177, the activation site of NOS-3, when compared with control. The addition of CNP produced an increase in [Ca2+]c in endothelial cells and a decrease in [Ca2+]c in vascular smooth muscle cells. The NPR-C-receptors are expressed in endothelial and adventitial rat aortas. SIGNIFICANCE: These results suggest that CNP-induced relaxation in intact aorta isolated from rats involves NO production due to [Ca2+]c increase in endothelial cells possibly through NPR-C activation expressed in these cells. The present study provides a breakthrough in the understanding of the close relationship between the vascular actions of nitric oxide and CNP.

  6. A simple measurement method of molecular relaxation in a gas by reconstructing acoustic velocity dispersion

    Science.gov (United States)

    Zhu, Ming; Liu, Tingting; Zhang, Xiangqun; Li, Caiyun

    2018-01-01

    Recently, a decomposition method of acoustic relaxation absorption spectra was used to capture the entire molecular multimode relaxation process of gas. In this method, the acoustic attenuation and phase velocity were measured jointly based on the relaxation absorption spectra. However, fast and accurate measurements of the acoustic attenuation remain challenging. In this paper, we present a method of capturing the molecular relaxation process by only measuring acoustic velocity, without the necessity of obtaining acoustic absorption. The method is based on the fact that the frequency-dependent velocity dispersion of a multi-relaxation process in a gas is the serial connection of the dispersions of interior single-relaxation processes. Thus, one can capture the relaxation times and relaxation strengths of N decomposed single-relaxation dispersions to reconstruct the entire multi-relaxation dispersion using the measurements of acoustic velocity at 2N  +  1 frequencies. The reconstructed dispersion spectra are in good agreement with experimental data for various gases and mixtures. The simulations also demonstrate the robustness of our reconstructive method.

  7. Nuclear quadrupole relaxation and viscosity in liquid metals

    International Nuclear Information System (INIS)

    Schirmacher, W.

    1976-01-01

    It is shown that the nuclear quadrupole relaxation rate due to the molecular motions in liquid metals is related to the shear and bulk viscosity and hence to the absorption coefficient of ultrasound. Application of the 'extended liquid phonon' model of Ortoleva and Nelkin - which is the third of a series of continued-fraction-approximations for the van Hove neutron scattering function - gives a relation to the self diffusion constant. The predictions of the theory concerning the temperature dependence are compared with quadrupole relaxation measurements of Riegel et al. and Kerlin et al. in liquid gallium. Agreement is found only with the data of Riegel et al. (orig.) [de

  8. Anomalous behavior of secondary dielectric relaxation in polypropylene glycols

    Energy Technology Data Exchange (ETDEWEB)

    Grzybowska, K; Grzybowski, A; Ziolo, J; Rzoska, S J; Paluch, M [Institute of Physics, Silesian University, Uniwersytecka 4, 40-007 Katowice (Poland)

    2007-09-19

    A surprising slow down in the dielectric secondary {gamma}-relaxation with temperature increasing near the glass transition is confirmed for several polypropylene glycols. The peculiar behavior diminishes as the molecular weight grows. The minimal model (Dyre and Olsen 2003 Phys. Rev. Lett. 91 155703) is applied successfully to describe the temperature dependences of the {gamma}-relaxation times. The minimal model parameters are analyzed for different molecular weights. A molecular explanation of the {gamma}-process anomaly for polypropylene glycols is proposed on the basis of the minimal model prediction.

  9. Low temperature dielectric relaxation and charged defects in ferroelectric thin films

    Directory of Open Access Journals (Sweden)

    A. Artemenko

    2013-04-01

    Full Text Available We report a dielectric relaxation in BaTiO3-based ferroelectric thin films of different composition and with several growth modes: sputtering (with and without magnetron and sol-gel. The relaxation was observed at cryogenic temperatures (T < 100 K for frequencies from 100 Hz up to 10 MHz. This relaxation activation energy is always lower than 200 meV and is very similar to the relaxation that we reported in the parent bulk perovskites. Based on our Electron Paramagnetic Resonance (EPR investigation, we ascribe this dielectric relaxation to the hopping of electrons among Ti3+-V(O charged defects. Being dependent on the growth process and on the amount of oxygen vacancies, this relaxation can be a useful probe of defects in actual integrated capacitors with no need for specific shaping.

  10. Relaxation Techniques to Manage IBS Symptoms

    Science.gov (United States)

    ... for 15–20 seconds and then begin again. Progressive Muscle Relaxation This method of relaxation focuses on ... helpful, please consider supporting IFFGD with a small tax- deductible donation. Make Donation Adapted from IFFGD Publication # ...

  11. Relaxation and Distraction in Experimental Desensitization.

    Science.gov (United States)

    Weir, R. O.; Marshall, W. L.

    1980-01-01

    Compared experimental desensitization with a procedure that replaced relaxation with a distraction task and with an approach that combined both relaxation and distraction. Desensitization generally was more effective than the other two procedures. (Author)

  12. Relaxation as a Factor in Semantic Desensitization

    Science.gov (United States)

    Bechtel, James E.; McNamara, J. Regis

    1975-01-01

    Relaxation and semantic desensitization were used to alleviate the fear of phobic females. Results showed that semantic desensitization, alone or in combination with relaxation, failed to modify the evaluative meanings evoked by the feared object. (SE)

  13. Hydrodynamic relaxations in dissipative particle dynamics

    Science.gov (United States)

    Hansen, J. S.; Greenfield, Michael L.; Dyre, Jeppe C.

    2018-01-01

    This paper studies the dynamics of relaxation phenomena in the standard dissipative particle dynamics (DPD) model [R. D. Groot and P. B. Warren, J. Chem. Phys. 107, 4423 (1997)]. Using fluctuating hydrodynamics as the framework of the investigation, we focus on the collective transverse and longitudinal dynamics. It is shown that classical hydrodynamic theory predicts the transverse dynamics at relatively low temperatures very well when compared to simulation data; however, the theory predictions are, on the same length scale, less accurate for higher temperatures. The agreement with hydrodynamics depends on the definition of the viscosity, and here we find that the transverse dynamics are independent of the dissipative and random shear force contributions to the stress. For high temperatures, the spectrum for the longitudinal dynamics is dominated by the Brillouin peak for large length scales and the relaxation is therefore governed by sound wave propagation and is athermal. This contrasts the results at lower temperatures and small length scale, where the thermal process is clearly present in the spectra. The DPD model, at least qualitatively, re-captures the underlying hydrodynamical mechanisms, and quantitative agreement is excellent at intermediate temperatures for the transverse dynamics.

  14. A study of vibrational relaxation of electronically-excited molecules

    International Nuclear Information System (INIS)

    Datsyuk, V.V.; Izmailov, I.A.; Kochelap, V.A.

    1992-09-01

    The time kinetics of the vibrational relaxation of excimers is studied in the diffusional approximation. Simple formulae for functions of nonstationary vibrational distribution are found for the electronically excited molecules. Some spectral-kinetic dependencies of the excimer luminescence are explained in a new way. The possibilities of the determination of excimer parameters are discussed. The dependence of energetical characteristics of excimer lasers on these parameters is particularly emphasized. (author). 22 refs, 5 figs

  15. Relaxation model of radiation-induced conductivity in polymers

    Science.gov (United States)

    Zhutayeva, Yu. R.; Khatipov, S. A.

    1999-05-01

    The paper suggests a relaxation model of radiation-induced conductivity (RIC) in polymers. According to the model, the transfer of charges generated in the polymer volume by ionizing radiation takes place with the participation of molecular relaxation processes. The mechanism of electron transport consists in the transfer of the charge directly between traps when they draw close to one another due to the rotation of macromolecule segments. The numerical solutions of the corresponding kinetic equations for different distribution functions Q( τ) of the times of molecular relaxation and for different functions of the probability P( τ, τ') of charge transfer in the `overlapping' regions of the diffusion spheres of the segments are analyzed. The relaxation model provides an explanation of the non-Arrhenius behavior of the RIC temperature dependence, the power dependence of RIC on the dose rate with a power index in the interval 0.5-1.0, the appearance of maxima in the curves of the RIC temporal dependence and their irreversible character in the region of large dose rates (more than 1 Gy/s). The model can be used for interpreting polymer RIC in conditions of kinetic mobility of macromolecules.

  16. Nonlinear Relaxation in Population Dynamics

    Science.gov (United States)

    Cirone, Markus A.; de Pasquale, Ferdinando; Spagnolo, Bernardo

    We analyze the nonlinear relaxation of a complex ecosystem composed of many interacting species. The ecological system is described by generalized Lotka-Volterra equations with a multiplicative noise. The transient dynamics is studied in the framework of the mean field theory and with random interaction between the species. We focus on the statistical properties of the asymptotic behaviour of the time integral of the ith population and on the distribution of the population and of the local field.

  17. Structural relaxation: low temperature properties

    International Nuclear Information System (INIS)

    Cruz, F. de la

    1984-01-01

    We discuss the changes in transport and superconducting properties of amorphous Zr 70 Cu 30 , induced by thermal relaxation. The experimental results are used to investigate the relation between the microscopic parameters and the observed physical properties. It is shown that the density of eletronic states determines the shift Tc as well as the variation of the electrical resistivity. It is necessary to assume strong hybridization between s and d bands to understand the eletrodynamic response of the superconductor. (Author) [pt

  18. Nuclear magnetic relaxation in picolines solutions in carbon tetrachloride

    International Nuclear Information System (INIS)

    Jurga, J.; Pajak, Z.; Jurga, K.; Jurga, S.

    1973-01-01

    Spin-lattice relaxation times of the ring and CH 3 group have been measured in order to establish the temperature dependence of the longitudinal relaxation times for picolins in carbon tetrachloride solutions. The information concerning the intramolecular contribution to the relaxation times have been obtained. The high resolution NPR spectrometer operating at 25 MHz has been used. The measurements have been performed in the temperature range from -60degC to 80degC. The experimental results are compared to the predictions given by the Nora Hill and Debye models and it has been found that the Nora Hill model fits the experimental data better than the Debye model. (S.B.)

  19. The Effects of Suggestibility on Relaxation.

    Science.gov (United States)

    Rickard, Henry C.; And Others

    1985-01-01

    Selected undergraduates (N=32) on the basis of Creative Imagination Scale scores and randomly assigned high and low suggestibility subjects to progressive relaxation (PR) and suggestions of relaxation (SR) training modes. Results revealed a significant pre-post relaxation effect, and main efffects for both suggestibility and training mode. (NRB)

  20. Relaxed Poisson cure rate models.

    Science.gov (United States)

    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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Arresting relaxation in Pickering Emulsions

    Science.gov (United States)

    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.

  2. Vibrational relaxation in OCS mixtures

    International Nuclear Information System (INIS)

    Simpson, C.J.S.M.; Gait, P.D.; Simmie, J.M.

    1976-01-01

    Experimental measurements are reported of vibrational relaxation times which may be used to show whether there is near resonant vibration-rotation energy transfer between OCS and H 2 , D 2 or HD. Vibrational relaxation times have been measured in OCS and OCS mixtures over the temperature range 360 to 1000 K using a shock tube and a laser schlieren system. The effectiveness of the additives in reducing the relaxation time of OCS is in the order 4 He 3 He 2 2 and HD. Along this series the effect of an increase in temperature changes from the case of speeding up the rate with 4 He to retarding it with D 2 , HD and H 2 . There is no measurable difference in the effectiveness of n-D 2 and o-D 2 and little, or no, difference between n-H 2 and p-H 2 . Thus the experimental results do not give clear evidence for rotational-vibration energy transfer between hydrogen and OCS. This contrasts with the situation for CO 2 + H 2 mixtures. (author)

  3. Regularized Label Relaxation Linear Regression.

    Science.gov (United States)

    Fang, Xiaozhao; Xu, Yong; Li, Xuelong; Lai, Zhihui; Wong, Wai Keung; Fang, Bingwu

    2018-04-01

    Linear regression (LR) and some of its variants have been widely used for classification problems. Most of these methods assume that during the learning phase, the training samples can be exactly transformed into a strict binary label matrix, which has too little freedom to fit the labels adequately. To address this problem, in this paper, we propose a novel regularized label relaxation LR method, which has the following notable characteristics. First, the proposed method relaxes the strict binary label matrix into a slack variable matrix by introducing a nonnegative label relaxation matrix into LR, which provides more freedom to fit the labels and simultaneously enlarges the margins between different classes as much as possible. Second, the proposed method constructs the class compactness graph based on manifold learning and uses it as the regularization item to avoid the problem of overfitting. The class compactness graph is used to ensure that the samples sharing the same labels can be kept close after they are transformed. Two different algorithms, which are, respectively, based on -norm and -norm loss functions are devised. These two algorithms have compact closed-form solutions in each iteration so that they are easily implemented. Extensive experiments show that these two algorithms outperform the state-of-the-art algorithms in terms of the classification accuracy and running time.

  4. Effect of iodine impurity on relaxation of photoexcited silver chloride

    International Nuclear Information System (INIS)

    Vostrikova, Yu. V.; Klyuev, V. G.

    2008-01-01

    The time and temperature dependences of relaxation of excited AgCl and AgCl:I crystals is studied by the method of photostimulated flash of luminescence. The presence of iodine impurity in silver chloride gives rise to hole recombination (luminescence) centers and hole traps in the band gap. It is shown that the main contribution to the decrease in the concentration of electrons localized at deep traps is made by the recombination of electrons with holes released thermally from shallow localization levels (iodine-related centers). Estimation of activation energy for the relaxation process showed that these energies for the AgCl and AgCl:I samples under study are the same within the experimental error and are equal to E rel1 = 0.01 ± 0.0005 eV for the initial stage of relaxation and E rel2 = 0.09 ± 0.005 eV for the final state. This fact indicates that the majority of hole traps involved in the relaxation process in AgCl are related to iodine impurity. In the course of thermal relaxation in AgCl, relocalization of nonequilibrium charge carriers from shallow levels to deep levels is observed. The depth of the corresponding trap is E arl = 0.174 ± 0.03 eV.

  5. Thermally induced magnetic relaxation in square artificial spin ice

    Science.gov (United States)

    Andersson, M. S.; Pappas, S. D.; Stopfel, H.; Östman, E.; Stein, A.; Nordblad, P.; Mathieu, R.; Hjörvarsson, B.; Kapaklis, V.

    2016-11-01

    The properties of natural and artificial assemblies of interacting elements, ranging from Quarks to Galaxies, are at the heart of Physics. The collective response and dynamics of such assemblies are dictated by the intrinsic dynamical properties of the building blocks, the nature of their interactions and topological constraints. Here we report on the relaxation dynamics of the magnetization of artificial assemblies of mesoscopic spins. In our model nano-magnetic system - square artificial spin ice - we are able to control the geometrical arrangement and interaction strength between the magnetically interacting building blocks by means of nano-lithography. Using time resolved magnetometry we show that the relaxation process can be described using the Kohlrausch law and that the extracted temperature dependent relaxation times of the assemblies follow the Vogel-Fulcher law. The results provide insight into the relaxation dynamics of mesoscopic nano-magnetic model systems, with adjustable energy and time scales, and demonstrates that these can serve as an ideal playground for the studies of collective dynamics and relaxations.

  6. Nuclear magnetic relaxation of methyl group in liquids

    International Nuclear Information System (INIS)

    Blicharska, B.

    1986-01-01

    The theoretical description of the relaxation process of methyl group in liquids and some results of the measurements of relaxation function and relaxation times for cryoprotective solutions are presented. Starting from the application of the operator formalism the general equation for spin operators e.g. components of the nuclear spin and magnetization is founded. Next, the spin Hamiltonian is presented as contraction of the symmetry adapted spherical tensors as well as the correlation functions and spectral densities. On the basis of extended and modified Woessner model of motion the correlation functions and spectral densities are calculated for methyl group in liquids. Using these functions the relaxation matrix elements, the spin-spin and spin-lattice relaxation times can be expressed. The prediction of the theory agrees with author's previous experiments on cryoprotective solutions. The observed dependence on temperature, frequency and isotopic dilution in methanol-water, methanol-dimethyl sulfoxide (DMSO) and DMSO-water solutions is in a satisfactory agreement with theoretical equations. 34 refs. (author)

  7. Magnetic-relaxation method of analysis of inorganic substances

    International Nuclear Information System (INIS)

    Popel', A.A.

    1978-01-01

    The magnetic-relaxation method is considered of the quantitative analysis of inorganic substances based on time dependence of magnetic nuclei relaxation on the quantity of paramagnetic centres in a solution. The characteristic is given of some methods of measuring nuclear magnetic relaxation times: method of weak oscillation generator and pulse methods. The effect of temperature, general solution viscosity, diamagnetic salt concentration, medium acidity on nuclear relaxation velocity is described. The determination sensitivity is estimated and the means of its increase definable concentration intervals and method selectivity are considered. The method application when studying complexing in the solution is described. A particular attention is given to the investigation of heteroligand homocentre, heterocentre and protonated complexes as well as to the problems of particle exchange of the first coordination sphere with particles from the mass of solution. The equations for equilibrium constant calculation in different systems are given. Possibilities of determining diamagnetic ions by the magnetic-relaxation method using paramagnetic indicators are confirmed by the quantitative analysis of indium, gallium, thorium and scandium in their salt solutions

  8. Adaptive under relaxation factor of MATRA code for the efficient whole core analysis

    International Nuclear Information System (INIS)

    Kwon, Hyuk; Kim, S. J.; Seo, K. W.; Hwang, D. H.

    2013-01-01

    Such nonlinearities are handled in MATRA code using outer iteration with Picard scheme. The Picard scheme involves successive updating of the coefficient matrix based on the previously calculated values. The scheme is a simple and effective method for the nonlinear problem but the effectiveness greatly depends on the under-relaxing capability. Accuracy and speed of calculation are very sensitively dependent on the under-relaxation factor in outer-iteration updating the axial mass flow using the continuity equation. The under-relaxation factor in MATRA is generally utilized with a fixed value that is empirically determined. Adapting the under-relaxation factor to the outer iteration is expected to improve the calculation effectiveness of MATRA code rather than calculation with the fixed under-relaxation factor. The present study describes the implementation of adaptive under-relaxation within the subchannel code MATRA. Picard iterations with adaptive under-relaxation can accelerate the convergence for mass conservation in subchannel code MATRA. The most efficient approach for adaptive under relaxation appears to be very problem dependent

  9. Motional spin relaxation in photoexcited triplet states

    International Nuclear Information System (INIS)

    Harryvan, D.; Faassen, E. van

    1997-01-01

    Transient EPR experiments were performed on photoexcited spin triplet states of the luminescent dye EOSIN-Y in diluted (order of 1 nMol) frozen propane-1-ol solutions at various temperatures. Photoexcitation was achieved by irradiation with intense, short laser pulses. The details of the spin relaxation, in particular the dependence on time, magnetic field and microwave field strength are all reproduced by a model which computes the total magnetization in a population of photoexcited triplet states undergoing random reorientational motion. Using this model, we estimated the motional correlation times to be around a microsecond. This timescale is two orders of magnitude slower than the phase memory time of the triplets. (author)

  10. Sandpile model for relaxation in complex systems

    International Nuclear Information System (INIS)

    Vazquez, A.; Sotolongo-Costa, O.; Brouers, F.

    1997-10-01

    The relaxation in complex systems is, in general, nonexponential. After an initial rapid decay the system relaxes slowly following a long time tail. In the present paper a sandpile moderation of the relaxation in complex systems is analysed. Complexity is introduced by a process of avalanches in the Bethe lattice and a feedback mechanism which leads to slower decay with increasing time. In this way, some features of relaxation in complex systems: long time tails relaxation, aging, and fractal distribution of characteristic times, are obtained by simple computer simulations. (author)

  11. The Anti-Apoptotic Properties of APEX1 in the Endothelium Require the First 20 Amino Acids and Converge on Thioredoxin-1.

    Science.gov (United States)

    Dyballa-Rukes, Nadine; Jakobs, Philipp; Eckers, Anna; Ale-Agha, Niloofar; Serbulea, Vlad; Aufenvenne, Karin; Zschauer, Tim-Christian; Rabanter, Lothar L; Jakob, Sascha; von Ameln, Florian; Eckermann, Olaf; Leitinger, Norbert; Goy, Christine; Altschmied, Joachim; Haendeler, Judith

    2017-04-20

    The APEX nuclease (multifunctional DNA repair enzyme) 1 (APEX1) has a disordered N-terminus, a redox, and a DNA repair domain. APEX1 has anti-apoptotic properties, which have been linked to both domains depending on cell type and experimental conditions. As protection against apoptosis is a hallmark of vessel integrity, we wanted to elucidate whether APEX1 acts anti-apoptotic in primary human endothelial cells and, if so, what the underlying mechanisms are. APEX1 inhibits apoptosis in endothelial cells by reducing Cathepsin D (CatD) cleavage, potentially by binding to the unprocessed form. Diminished CatD activation results in increased Thioredoxin-1 protein levels leading to reduced Caspase 3 activation. Consequently, apoptosis rates are decreased. This depends on the first twenty amino acids in APEX1, because APEX1 (21-318) induces CatD activity, decreases Thioredoxin-1 protein levels, and, thus, increases Caspase 3 activity and apoptosis. Along the same lines, APEX1 (1-20) inhibits Caspase 3 cleavage and apoptosis. Furthermore, re-expression of Thioredoxin-1 via lentiviral transduction rescues endothelial cells from APEX1 (21-318)-induced apoptosis. In an in vivo model of restenosis, which is characterized by oxidative stress, endothelial activation, and smooth muscle cell proliferation, Thioredoxin-1 protein levels are reduced in the endothelium of the carotids. APEX1 acts anti-apoptotic in endothelial cells. This anti-apoptotic effect depends on the first 20 amino acids of APEX1. As proper function of the endothelium during life span is a hallmark for individual health span, a detailed characterization of the functions of the APEX1N-terminus is required to understand all its cellular properties. Antioxid. Redox Signal. 26, 616-629.

  12. Vascular endothelium as a target of immune response in renal transplant rejection

    Directory of Open Access Journals (Sweden)

    Giovanni ePiotti

    2014-10-01

    Full Text Available This review of clinical and experimental studies aims at analysing the interplay between graft endothelium and host immune system in renal transplantation, and how it affects the survival of the graft. Graft endothelium is indeed the first barrier between self and non-self that is encountered by host lymphocytes upon reperfusion of vascularised solid transplants. Endothelial cells express all the major sets of antigens that elicit host immune response, and therefore represent a preferential target in organ rejection.Some of the antigens expressed by endothelial cells are target of the antibody-mediated response, such as the AB0 blood group system, the HLA and MICA systems, and the endothelial cell-restricted antigens; for each of these systems, the mechanisms of interaction and damage of both preformed and de novo donor-specific antibodies are reviewed along with their impact on renal graft survival. Moreover the rejection process can force injured endothelial cells to expose cryptic self-antigens, toward which an auto-immune response mounts, overlapping to the allo-immune response in the damaging of the graft. Not only are endothelial cells a passive target of the host immune response, but also an active player in lymphocyte activation; therefore their interaction with allogenic T-cells is analysed on the basis of experimental in vitro and in vivo studies, according to the patterns of expression of the HLA class I and II and the co-stimulatory molecules specific for cytotoxic and helper T-cells.Finally, as the response that follows transplantation has proven to be not necessarily destructive, the factors that foster graft endothelium functioning in spite of rejection, and how they could be therapeutically harnessed to promote long-term graft acceptance, are described: accommodation that is resistance of endothelial cells to donor-specific antibodies, and endothelial cell ability to induce Foxp3+ Regulatory T-cells, that are crucial mediators of

  13. The relationships between suggestibility, influenceability, and relaxability.

    Science.gov (United States)

    Polczyk, Romuald; Frey, Olga; Szpitalak, Malwina

    2013-01-01

    This research explores the relationships between relaxability and various aspects of suggestibility and influenceability. The Jacobson Progressive Muscle Relaxation procedure was used to induce relaxation. Tests of direct suggestibility, relating to the susceptibility of overt suggestions, and indirect suggestibility, referring to indirect hidden influence, as well as self-description questionnaires on suggestibility and the tendency to comply were used. Thayer's Activation-Deactivation Adjective Check List, measuring various kinds of activation and used as a pre- and posttest, determined the efficacy of the relaxation procedure. Indirect, direct, and self-measured suggestibility proved to be positively related to the ability to relax, measured by Thayer's subscales relating to emotions. Compliance was not related to relaxability. The results are discussed in terms of the aspects of relaxation training connected with suggestibility.

  14. Interphase death and repair of radiation injuries to thoracic aorta endothelium of mammals

    International Nuclear Information System (INIS)

    Shcherbova, E.N.; Ivanov, Yu.V.

    1978-01-01

    Using the method of plane preparations injury to the thoracic aorta endothelium of guinea-pigs, rats and rabbits exposed to various doses of γ-rays ( 60 Co) has been studied. The value of the threshold dose, tested by diminution of the endothelial cell quantity, has been found to be 250 R for guinea-pigs, 830 R, for rats and 880 R, for rabbits. It has been shown by means of the fractionated irradiation model that the interphase endothelial cells of guinea-pigs and rats can recover from sublethal radiation injuries

  15. The role of the endothelium in asthma and chronic obstructive pulmonary disease (COPD).

    Science.gov (United States)

    Green, Clara E; Turner, Alice M

    2017-01-18

    COPD and asthma are important chronic inflammatory disorders with a high associated morbidity. Much research has concentrated on the role of inflammatory cells, such as the neutrophil, in these diseases, but relatively little focus has been given to the endothelial tissue, through which inflammatory cells must transmigrate to reach the lung parenchyma and cause damage. There is evidence that there is an abnormal amount of endothelial tissue in COPD and asthma and that this tissue and its' progenitor cells behave in a dysfunctional manner. This article reviews the evidence of the involvement of pulmonary endothelium in COPD and asthma and potential treatment options for this.

  16. A New Vogel-Like Law: Ionic Conductivity, Dielectric Relaxation and Viscosity Near the Glass Transition

    National Research Council Canada - National Science Library

    Bendler, John

    2001-01-01

    A model, based on defect diffusion, is developed that describes temperature and pressure dependence of dielectric relaxation, ionic conductivity and viscosity of glass-forming liquids near the glass...

  17. Dielectric and mechanical relaxation in isooctylcyanobiphenyl (8*OCB)

    Energy Technology Data Exchange (ETDEWEB)

    Pawlus, S; Mierzwa, M; Paluch, M; Rzoska, S J [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Roland, C M, E-mail: michal.mierzwa@us.edu.p [Chemistry Division, Naval Research Laboratory, Code 6120, Washington, DC 20375-5342 (United States)

    2010-06-16

    The dynamics of isooctylcyanobiphenyl (8*OCB) was characterized using dielectric and mechanical spectroscopies. This isomer of the liquid crystalline octylcyanobiphenyl (8OCB) vitrifies during cooling or on application of pressure, exhibiting the typical features of glass-forming liquids: non-Debye relaxation function, non-Arrhenius temperature dependence of the relaxation times, {tau}{sub {alpha}}, a dynamic crossover at T {approx} 1.6T{sub g}. This crossover is evidenced by changes in the behavior of both the peak shape and the temperature dependence of {tau}{sub {alpha}}. The primary relaxation time at the crossover, 2 ns at ambient pressure, is the smallest value reported to date for any molecular liquid or polymer. Interestingly, at all temperatures below this crossover, {tau}{sub {alpha}}and the dc conductivity remain coupled (i.e., conform to the Debye-Stokes-Einstein relation). Two secondary relaxations are observed in the glassy state, one of which is identified as the Johari-Goldstein process. Unlike the case for 8OCB, no liquid crystalline phase could be attained for 8*OCB, demonstrating that relatively small differences in chemical structure can effect substantial changes in the intermolecular potential.

  18. Compaction and relaxation of biofilms

    KAUST Repository

    Valladares Linares, R.

    2015-06-18

    Operation of membrane systems for water treatment can be seriously hampered by biofouling. A better characterization of biofilms in membrane systems and their impact on membrane performance may help to develop effective biofouling control strategies. The objective of this study was to determine the occurrence, extent and timescale of biofilm compaction and relaxation (decompaction), caused by permeate flux variations. The impact of permeate flux changes on biofilm thickness, structure and stiffness was investigated in situ and non-destructively with optical coherence tomography using membrane fouling monitors operated at a constant crossflow velocity of 0.1 m s−1 with permeate production. The permeate flux was varied sequentially from 20 to 60 and back to 20 L m−2 h−1. The study showed that the average biofilm thickness on the membrane decreased after elevating the permeate flux from 20 to 60 L m−2 h−1 while the biofilm thickness increased again after restoring the original flux of 20 L m−2 h−1, indicating the occurrence of biofilm compaction and relaxation. Within a few seconds after the flux change, the biofilm thickness was changed and stabilized, biofilm compaction occurred faster than the relaxation after restoring the original permeate flux. The initial biofilm parameters were not fully reinstated: the biofilm thickness was reduced by 21%, biofilm stiffness had increased and the hydraulic biofilm resistance was elevated by 16%. Biofilm thickness was related to the hydraulic biofilm resistance. Membrane performance losses are related to the biofilm thickness, density and morphology, which are influenced by (variations in) hydraulic conditions. A (temporarily) permeate flux increase caused biofilm compaction, together with membrane performance losses. The impact of biofilms on membrane performance can be influenced (increased and reduced) by operational parameters. The article shows that a (temporary) pressure increase leads to more

  19. Aging of the Johari-Goldstein relaxation in the glass-forming liquids sorbitol and xylitol

    Science.gov (United States)

    Yardimci, Hasan; Leheny, Robert L.

    2006-06-01

    Employing frequency-dependent dielectric susceptibility we characterize the aging in two supercooled liquids, sorbitol and xylitol, below their calorimetric glass transition temperatures. In addition to the alpha relaxation that tracks the structural dynamics, the susceptibility of both liquids possesses a secondary Johari-Goldstein relaxation at higher frequencies. Following a quench through the glass transition, the susceptibility slowly approaches the equilibrium behavior. For both liquids, the magnitude of the Johari-Goldstein relaxation displays a dependence on the time since the quench, or aging time, that is quantitatively very similar to the age dependence of the alpha peak frequency. The Johari-Goldstein relaxation time remains constant during aging for sorbitol while it decreases slightly with age for xylitol. Hence, one cannot sensibly assign a fictive temperature to the Johari-Goldstein relaxation. This behavior contrasts with that of liquids lacking distinct Johari-Goldstein peaks for which the excess wing of the alpha peak tracks the main part of the peak during aging, enabling the assignment of a single fictive temperature to the entire spectrum. The aging behavior of the Johari-Goldstein relaxation time further calls into question the possibility that the relaxation time possesses stronger temperature dependence in equilibrium than is observed in the out-of-equilibrium state below the glass transition.

  20. Relaxation response of A533B steel from 25 to 600/degree/C

    International Nuclear Information System (INIS)

    Swindeman, R.W.; Bolling, E.

    1989-01-01

    Relaxation tests were performed on A533B steel over the range 25 to 600/degree/C in order to examine the general features of time- dependent deformation. It was found that the relaxation strength increased with the flow stress at low temperatures and was relatively independent of history at high temperatures. In the temperature range 400 to 600/degree/C the inelastic strain rates calculated from the relaxation rates followed stress dependencies that were consistent with expectations based on a model proposed by Hart and coworkers for matrix deformation. 21 refs., 10 figs

  1. Correlation of carrier localization with relaxation time distribution and electrical conductivity relaxation in silver-nanoparticle-embedded moderately doped polypyrrole nanostructures

    Science.gov (United States)

    Biswas, Swarup; Dutta, Bula; Bhattacharya, Subhratanu

    2014-02-01

    The electrical conductivity relaxation in moderately doped polypyrrole and its nanocomposites reinforced with different proportion of silver nanoparticles was investigated in both frequency and time domain. An analytical distribution function of relaxation times is constructed from the results obtained in the frequency domain formalism and is used to evaluate the Kohlrausch-Williams-Watts (KWW) type decay function in the time domain. The thermal evolution of different relaxation parameters was analyzed. The temperature-dependent dc electrical conductivity, estimated from the average conductivity relaxation time is observed to depend strongly on the nanoparticle loading and follows Mott three-dimensional variable range hopping (VRH) conduction mechanism. The extent of charge carrier localization calculated from the VRH mechanism is well correlated to the evidences obtained from the structural characterizations of different nanostructured samples.

  2. Thermodynamic scaling of α-relaxation time and viscosity stems from the Johari-Goldstein β-relaxation or the primitive relaxation of the coupling model.

    Science.gov (United States)

    Ngai, K L; Habasaki, J; Prevosto, D; Capaccioli, S; Paluch, Marian

    2012-07-21

    By now it is well established that the structural α-relaxation time, τ(α), of non-associated small molecular and polymeric glass-formers obey thermodynamic scaling. In other words, τ(α) is a function Φ of the product variable, ρ(γ)/T, where ρ is the density and T the temperature. The constant γ as well as the function, τ(α) = Φ(ρ(γ)/T), is material dependent. Actually this dependence of τ(α) on ρ(γ)/T originates from the dependence on the same product variable of the Johari-Goldstein β-relaxation time, τ(β), or the primitive relaxation time, τ(0), of the coupling model. To support this assertion, we give evidences from various sources itemized as follows. (1) The invariance of the relation between τ(α) and τ(β) or τ(0) to widely different combinations of pressure and temperature. (2) Experimental dielectric and viscosity data of glass-forming van der Waals liquids and polymer. (3) Molecular dynamics simulations of binary Lennard-Jones (LJ) models, the Lewis-Wahnström model of ortho-terphenyl, 1,4 polybutadiene, a room temperature ionic liquid, 1-ethyl-3-methylimidazolium nitrate, and a molten salt 2Ca(NO(3))(2)·3KNO(3) (CKN). (4) Both diffusivity and structural relaxation time, as well as the breakdown of Stokes-Einstein relation in CKN obey thermodynamic scaling by ρ(γ)/T with the same γ. (5) In polymers, the chain normal mode relaxation time, τ(N), is another function of ρ(γ)/T with the same γ as segmental relaxation time τ(α). (6) While the data of τ(α) from simulations for the full LJ binary mixture obey very well the thermodynamic scaling, it is strongly violated when the LJ interaction potential is truncated beyond typical inter-particle distance, although in both cases the repulsive pair potentials coincide for some distances.

  3. Analysis of biological characteristics of corneal endothelium in old patients with high myopia

    Directory of Open Access Journals (Sweden)

    Ya-Qiong Chen

    2014-11-01

    Full Text Available AIM: To analyze quantitatively the biological characteristics of corneal endothelium in old patients of high myopia with non-contact automatic corneal endothelial microscope.METHODS:A total of 189 old patients(197 eyeswere divided into the high myopia group and the normal control group according to refractive diopter, in which the former 98 cases(103 eyes, the latter 91 cases(94 eyes. The hexagonal cell(6A, the coefficient of variation(CV, the average cell area(AVE, the average cell density(CDand the central corneal thickness(CCTwere measured by non-contact automatic corneal endothelium. SPSS 14.0 software was used to analyze their percentage. Z-test was used to compare the mean and Chi-square test was used to compare the rate in between. RESULTS: The average cell density in high myopia patients decreased, but there were 14 eyes >3 000/mm2, 11 eyes 2 and 78 eyes in the 2 000~3 000/mm2, there were each 0 eye, 3 eyes and 91 eyes respectively in the normal control group. There was statistically significant difference between high myopia group and control(χ2=19.11, PPP>0.05. CONCLUSION: There will provide a reference valuable for clinical surgeon. Because according to the changes of parameters and morphology of the corneal endothelial cells, we can understand the repair ability, to predict the consequence of the treatment, in order to determine the design and the choice of a surgical.

  4. Accumulation of the Vitamin D Precursor Cholecalciferol Antagonizes Hedgehog Signaling to Impair Hemogenic Endothelium Formation

    Directory of Open Access Journals (Sweden)

    Mauricio Cortes

    2015-10-01

    Full Text Available Hematopoietic stem and progenitor cells (HSPCs are born from hemogenic endothelium in the dorsal aorta. Specification of this hematopoietic niche is regulated by a signaling axis using Hedgehog (Hh and Notch, which culminates in expression of Runx1 in the ventral wall of the artery. Here, we demonstrate that the vitamin D precursor cholecalciferol (D3 modulates HSPC production by impairing hemogenic vascular niche formation. Accumulation of D3 through exogenous treatment or inhibition of Cyp2r1, the enzyme required for D3 25-hydroxylation, results in Hh pathway antagonism marked by loss of Gli-reporter activation, defects in vascular niche identity, and reduced HSPCs. Mechanistic studies indicated the effect was specific to D3, and not active 1,25-dihydroxy vitamin D3, acting on the extracellular sterol-binding domain of Smoothened. These findings highlight a direct impact of inefficient vitamin D synthesis on cell fate commitment and maturation in Hh-regulated tissues, which may have implications beyond hemogenic endothelium specification.

  5. Comparison of the effects of intraocular irrigating solutions on the corneal endothelium in intraocular lens implantation.

    Science.gov (United States)

    Matsuda, M; Kinoshita, S; Ohashi, Y; Shimomura, Y; Ohguro, N; Okamoto, H; Omoto, T; Hosotani, H; Yoshida, H

    1991-01-01

    We conducted a randomised prospective controlled study to determine the effects of a glucose glutathione bicarbonate solution (BSS Plus) and a citrate acetate bicarbonate solution (S-MA2) on the corneal endothelium in patients undergoing extracapsular cataract extraction with posterior chamber lens implantation. One eye of each patient was randomly assigned to receive BSS Plus, and the other eye to receive S-MA2. BSS Plus caused significantly less corneal swelling on the first postoperative day than did S-MA2. There was no difference between the two solutions in their effect on corneal thickness one week and one month postoperatively. Computer assisted morphometric analysis of wide-field specular microscopic photographs demonstrated minimal changes in endothelial morphological characteristics in the eyes irrigated with BSS Plus. By comparison S-MA2, caused a significant loss of endothelial cells and a marked reduction in the figure coefficient. These results indicated that BSS Plus has a clinical advantage over S-MA2 with respect to the corneal endothelium. PMID:1873266

  6. Vitamin D and the endothelium: basic, translational and clinical research updates

    Directory of Open Access Journals (Sweden)

    Rinkoo Dalan

    2014-09-01

    Results and conclusion: Vitamin D deficiency is associated with endothelial dysfunction and cardiovascular diseases. Vitamin D stabilizes the quiescent endothelium, modulates certain stages of endothelial activation, and is involved in the repair of the damaged endothelium in vitro and in vivo. Twelve recent cross sectional studies, including 2086 subjects of varying ethnic groups, show an association between endothelial dysfunction and vitamin D deficiency. Yet 10 recent RCTs of vitamin D supplementation involving 824 subjects have failed to show significant improvements in endothelial function in the short term. So far, RCTs have not been able to confirm or refute the benefit of vitamin D supplementation on vascular mortality. Longer term randomized controlled trials using doses of vitamin D to optimize serum 25(OHD concentrations to 20.0–40.0 ng/mL (50.0–100.0 nmol/L or using vitamin D analogues with no calciotropic effects are needed to assess endothelial function and cardiovascular outcomes.

  7. Endogenous ovarian hormones affect mitochondrial efficiency in cerebral endothelium via distinct regulation of PGC-1 isoforms.

    Science.gov (United States)

    Kemper, Martin F; Zhao, Yuanzi; Duckles, Sue P; Krause, Diana N

    2013-01-01

    Mitochondria support the energy-intensive functions of brain endothelium but also produce damaging-free radicals that lead to disease. Previously, we found that estrogen treatment protects cerebrovascular mitochondria, increasing capacity for ATP production while decreasing reactive oxygen species (ROS). To determine whether these effects occur specifically in endothelium in vivo and also explore underlying transcriptional mechanisms, we studied freshly isolated brain endothelial preparations from intact and ovariectomized female mice. This preparation reflects physiologic influences of circulating hormones, hemodynamic forces, and cell-cell interactions of the neurovascular unit. Loss of ovarian hormones affected endothelial expression of the key mitochondrial regulator family, peroxisome proliferator-activated receptor γ coactivator 1 (PGC-1), but in a unique way. Ovariectomy increased endothelial PGC-1α mRNA but decreased PGC-1β mRNA. The change in PGC-1β correlated with decreased mRNA for crucial downstream mitochondrial regulators, nuclear respiratory factor 1 and mitochondrial transcription factor A, as well as for ATP synthase and ROS protection enzymes, glutamate-cysteine ligase and manganese superoxide dismutase. Ovariectomy also decreased mitochondrial biogenesis (mitochondrial/nuclear DNA ratio). These results indicate ovarian hormones normally act through a distinctive regulatory pathway involving PGC-1β to support cerebral endothelial mitochondrial content and guide mitochondrial function to favor ATP coupling and ROS protection.

  8. An in situ study of the enhancement of atomic mobility under neutron irradiation in a Ag-30at%Zn alloy, using the Zener relaxation

    International Nuclear Information System (INIS)

    Halbwachs, M.; Hillairet, J.; Gonzalez, H.; Cost, J.

    1975-01-01

    An application of the Zener relaxation to the study of fast neutron effects on a Ag-Zn alloy is presented. The temperature dependence of the relaxation time is shown. It can be seen that the measured relaxation time at a given temperature increases with the irradiation doses [fr

  9. Ultrasonic relaxations in borate glasses

    International Nuclear Information System (INIS)

    D'Angelo, G.; Tripodo, G.; Carini, G.; Cosio, E.; Bartolotta, A.; Di Marco, G.

    2004-01-01

    The attenuation and velocity of ultrasonic waves of frequencies in the range from 10 to 70 MHz have been measured in M 2 O-B 2 O 3 borate glasses (M: Li or Ag) as a function of temperature between 15 and 350 K. The velocity of sound waves decreases with increasing temperature in all the glasses, the decrease as the temperature is increased is larger in glasses containing silver than in those with lithium. A broad relaxation peak characterises the attenuation behaviour of the lithium and silver borate glasses at temperatures below 100 K and is paralleled by a corresponding dispersive behaviour of the sound velocity. Above 100 K, the ultrasonic velocity shows a nearly linear behaviour regulated by the vibrational anharmonicity, which decreases with increasing content of modifier oxide and is smaller in lithium than in silver borates. These results suggest that the relaxation of structural defects and the anharmonicity of borate glasses are strongly affected by two parameters: the number of bridging bonds per network forming ion and the polarising power of network modifier ions which occupy sites in the existing interstices

  10. Endothelium-derived vasoactive factors and hypertension: possible roles in pathogenesis and as treatment targets

    DEFF Research Database (Denmark)

    Félétou, Michel; Köhler, Ralf; Vanhoutte, Paul M

    2010-01-01

    Endothelial cells regulate vascular tone by releasing various contracting and relaxing factors including nitric oxide (NO), arachidonic acid metabolites (derived from cyclooxygenases, lipoxygenases, and cytochrome P450 monooxygenases), reactive oxygen species, and vasoactive peptides. Additionally...

  11. Molecular order and T1-relaxation, cross-relaxation in nitroxide spin labels

    Science.gov (United States)

    Marsh, Derek

    2018-05-01

    Interpretation of saturation-recovery EPR experiments on nitroxide spin labels whose angular rotation is restricted by the orienting potential of the environment (e.g., membranes) currently concentrates on the influence of rotational rates and not of molecular order. Here, I consider the dependence on molecular ordering of contributions to the rates of electron spin-lattice relaxation and cross relaxation from modulation of N-hyperfine and Zeeman anisotropies. These are determined by the averages and , where θ is the angle between the nitroxide z-axis and the static magnetic field, which in turn depends on the angles that these two directions make with the director of uniaxial ordering. For saturation-recovery EPR at 9 GHz, the recovery rate constant is predicted to decrease with increasing order for the magnetic field oriented parallel to the director, and to increase slightly for the perpendicular field orientation. The latter situation corresponds to the usual experimental protocol and is consistent with the dependence on chain-labelling position in lipid bilayer membranes. An altered dependence on order parameter is predicted for saturation-recovery EPR at high field (94 GHz) that is not entirely consistent with observation. Comparisons with experiment are complicated by contributions from slow-motional components, and an unexplained background recovery rate that most probably is independent of order parameter. In general, this analysis supports the interpretation that recovery rates are determined principally by rotational diffusion rates, but experiments at other spectral positions/field orientations could increase the sensitivity to order parameter.

  12. Characterization of structural relaxation in inorganic glasses using length dilatometry

    Science.gov (United States)

    Koontz, Erick

    characterization technique is comprised of three main components: experimental measurements, fitting of configurational length change, and description of glass behavior by analysis of fitting parameters. N-BK7 optical glass from Schott was used as the proof of concept glass but the main scientific interest was in three chalcogenide glasses: As40Se 60, As20Se80, and Ge17.9As19.7 Se62.4. The dilatometric experiments were carried out using a thermomechanical analyzer (TMA) on glass sample that were synthesized by the author, in all cases except N-BK7. Isothermal structural relaxation measurements were done on (12 mm tall x 3 mm x 3 mm) beams placed vertically in the TMA. The samples were equilibrated at a starting temperature (T 0) until structural equilibrium was reached then a temperature down step was initiated to the final temperature (T 1) and held isothermally until relaxation concluded. The configurational aspect of length relaxation, and therefore volume relaxation was extracted and fit with a Prony series. The Prony series parameters indicated a number of relaxation events occurring within the glass on timescales typically an order of magnitude apart in time. The data analysis showed as many as 4 discrete relaxation times at lower temperatures. The number of discrete relaxation decreased as the temperature increased until just one single relaxation was left in the temperature range just at or above Tg. In the case of N-BK7 these trends were utilized to construct a simple model that could be applied to glass manufacturing in the areas of annealing or PGM. A future development of a rather simple finite element model (FEM) would easily be able to use this model to predict the exponential-like, temperature and time dependent relaxation behaviors of the glass. The predictive model was not extended to the chalcogenide glass studied here, but could easily be applied to them in the future. The relaxation time trends versus temperature showed a definite region of transition between a

  13. Paramagnetic relaxation effects in perturbed angular correlations for arbitrary electronic relaxation time

    International Nuclear Information System (INIS)

    Chopin, C.; Spanjaard, D.; Hartmann-Boutron, F.

    1975-01-01

    Previous perturbation treatments of paramagnetic relaxation effects in γγ PAC were limited to the case of very short electronic relaxation times. This limitation is circumvented by invoking a new perturbation theory recently elaborated by Hirst and others for handling relaxation effects in Moessbauer spectra. Under the assumption of spherical electronic relaxation the perturbation factors are computed as functions of certain relaxation parameters which are directly related to the microscopic relaxation Hamiltonian. The results are compared to those of the stochastic theory of Scherer and Blume [fr

  14. Temperature relaxation in collisional non equilibrium plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Potapenko, I.F.; Bobylev, A.V.; Azevedo, C.A.; Assis, A.S. [Universidade do Estado, Rio de Janeiro, RJ (Brazil). Inst. de Fisica

    1997-12-31

    Full text. We study the relaxation of a space uniform plasma composed of electrons and one species of ions. To simplified the consideration, standard approach is usually accepted: the distribution functions are considered to be a Maxwellian with time dependent electron T{sub e}(t) and ion T{sub i}(t) temperatures. This approach imposes a severe restriction on the electron/ion distributions that could be very far from the equilibrium. In the present work the problem is investigated on the basis of the nonlinear kinetic Fokker - Planck equation, which is widely used for the description of collisional plasmas. This equation has many applications in plasma physics as an intrinsic part of physical models, both analytical and numerical. A new detailed description of this classical problem of the collisional plasma kinetic theory is given. A deeper examination of the problem shows that the unusual perturbation theory can not be used. The part of the perturbation of the electron distribution has the character of a boundary layer in the neighborhood of small velocities. In this work the boundary layer is thoroughly studied. The correct distribution electron function is given. Nonmonotonic character of the distribution relaxation in the tail region is observed. The corrected formula for temperature equalization is obtained. The comparison of the calculation results with the asymptotic approach is made. We should stress the important role of the completely conservative different scheme used here, which keeps the symmetric properties of the nonlinear exact equation. This allows us to make calculations without numerical error accumulations, except for machine errors. (author)

  15. Role of endothelium in radiation-induced normal tissue damages; Role de l'endothelium dans les dommages radio-induits aux tissus sains

    Energy Technology Data Exchange (ETDEWEB)

    Milliat, F

    2007-05-15

    More than half of cancers are treated with radiation therapy alone or in combination with surgery and/or chemotherapy. The goal of radiation therapy is to deliver enough ionising radiation to destroy cancer cells without exceeding the level that the surrounding healthy cells can tolerate. Unfortunately, radiation-induced normal tissue injury is still a dose limiting factor in the treatment of cancer with radiotherapy. The knowledge of normal tissue radiobiology is needed to determine molecular mechanisms involved in normal tissue pathogenic pathways in order to identify therapeutic targets and develop strategies to prevent and /or reduce side effects of radiation therapy. The endothelium is known to play a critical role in radiation-induced injury. Our work shows that endothelial cells promote vascular smooth muscle cell proliferation, migration and fibro-genic phenotype after irradiation. Moreover, we demonstrate for the first time the importance of PAI-1 in radiation-induced normal tissue damage suggesting that PAI-1 may represent a molecular target to limit injury following radiotherapy. We describe a new role for the TGF-b/Smad pathway in the pathogenesis of radiation-induced damages. TGF-b/Smad pathway is involved in the fibro-genic phenotype of VSMC induced by irradiated EC as well as in the radiation-induced PAI-1 expression in endothelial cells. (author)

  16. Role of endothelium in radiation-induced normal tissue damages; Role de l'endothelium dans les dommages radio-induits aux tissus sains

    Energy Technology Data Exchange (ETDEWEB)

    Milliat, F

    2007-05-15

    More than half of cancers are treated with radiation therapy alone or in combination with surgery and/or chemotherapy. The goal of radiation therapy is to deliver enough ionising radiation to destroy cancer cells without exceeding the level that the surrounding healthy cells can tolerate. Unfortunately, radiation-induced normal tissue injury is still a dose limiting factor in the treatment of cancer with radiotherapy. The knowledge of normal tissue radiobiology is needed to determine molecular mechanisms involved in normal tissue pathogenic pathways in order to identify therapeutic targets and develop strategies to prevent and /or reduce side effects of radiation therapy. The endothelium is known to play a critical role in radiation-induced injury. Our work shows that endothelial cells promote vascular smooth muscle cell proliferation, migration and fibro-genic phenotype after irradiation. Moreover, we demonstrate for the first time the importance of PAI-1 in radiation-induced normal tissue damage suggesting that PAI-1 may represent a molecular target to limit injury following radiotherapy. We describe a new role for the TGF-b/Smad pathway in the pathogenesis of radiation-induced damages. TGF-b/Smad pathway is involved in the fibro-genic phenotype of VSMC induced by irradiated EC as well as in the radiation-induced PAI-1 expression in endothelial cells. (author)

  17. Vibrational energy transfer in selectively excited diatomic molecules. [Relaxation rates, self-relaxation, upper limits

    Energy Technology Data Exchange (ETDEWEB)

    Dasch, C.J.

    1978-09-01

    Single rovibrational states of HCl(v=2), HBr(v=2), DCl(v=2), and CO(v=2) were excited with a pulsed optical parametric oscillator (OPO). Total vibrational relaxation rates near - resonance quenchers were measured at 295/sup 0/K using time resolved infrared fluorescence. These rates are attributed primarily to V - V energy transfer, and they generally conform to a simple energy gap law. A small deviation was found for the CO(v) + DCl(v') relaxation rates. Upper limits for the self relaxation by V - R,T of HCl(v=2) and HBr(v=2) and for the two quantum exchange between HCl and HBr were determined. The HF dimer was detected at 295/sup 0/K and 30 torr HF pressure with an optoacoustic spectrometer using the OPO. Pulsed and chopped, resonant and non-resonant spectrophones are analyzed in detail. From experiments and first order perturbation theory, these V - V exchange rates appear to behave as a first order perturbation in the vibrational coordinates. The rotational dynamics are known to be complicated however, and the coupled rotational - vibrational dynamics were investigated theoreticaly in infinite order by the Dillon and Stephenson and the first Magnus approximations. Large ..delta..J transitions appear to be important, but these calculations differ by orders of magnitude on specific rovibrational transition rates. Integration of the time dependent semiclassical equations by a modified Gordon method and a rotationally distorted wave approximation are discussed as methods which would treat the rotational motion more accurately. 225 references.

  18. Longitudinal relaxation of initially straight flexible and stiff polymers

    Science.gov (United States)

    Dimitrakopoulos, Panagiotis; Dissanayake, Inuka

    2004-11-01

    The present talk considers the relaxation of a single flexible or stiff polymer chain from an initial straight configuration in a viscous solvent. This problem commonly arises when strong flows are turned off in both industrial and biological applications. The problem is also motivated by recent experiments with single biopolymer molecules relaxing after being fully extended by applied forces as well as by the recent development of micro-devices involving stretched tethered biopolymers. Our results are applicable to a wide array of synthetic polymers such as polyacrylamides, Kevlar and polyesters as well as biopolymers such as DNA, actin filaments, microtubules and MTV. In this talk we discuss the mechanism of the polymer relaxation as was revealed through Brownian Dynamics simulations covering a broad range of time scales and chain stiffness. After the short-time free diffusion, the chain's longitudinal reduction at early intermediate times is shown to constitute a universal behavior for any chain stiffness caused by a quasi-steady relaxation of tensions associated with the deforming action of the Brownian forces. Stiff chains are shown to exhibit a late intermediate-time longitudinal reduction associated with a relaxation of tensions affected by the deforming Brownian and the restoring bending forces. The longitudinal and transverse relaxations are shown to obey different laws, i.e. the chain relaxation is anisotropic at all times. In the talk, we show how from the knowledge of the relaxation mechanism, we can predict and explain the polymer properties including the polymer stress and the solution birefringence. In addition, a generalized stress-optic law is derived valid for any time and chain stiffness. All polymer properties which depend on the polymer length are shown to exhibit two intermediate-time behaviors with the early one to constitute a universal behavior for any chain stiffness. This work was supported in part by the Minta Martin Research Fund. The

  19. Resonant tunneling measurements of size-induced strain relaxation

    Science.gov (United States)

    Akyuz, Can Deniz

    Lattice mismatch strain available in such semiconductor heterostructures as Si/SiGe or GaAs/AlGaAs can be employed to alter the electronic and optoelectronic properties of semiconductor structures and devices. When deep submicron structures are fabricated from strained material, strained layers relax by sidewall expansion giving rise to size- and geometry-dependent strain gradients throughout the structure. This thesis describes a novel experimental technique to probe the size-induced strain relaxation by studying the tunneling current characteristics of strained p-type Si/SiGe resonant tunneling diodes. Our current-voltage measurements on submicron strained p-Si/SiGe double- and triple-barrier resonant tunneling structures as a function of device diameter, D, provide experimental access to both the average strain relaxation (which leads to relative shifts in the tunneling current peak positions) and strain gradients (which give rise to a fine structure in the current peaks due to inhomogeneous strain-induced lateral quantization). We find that strain relaxation is significant, with a large fraction of the strain energy relaxed on average in D ≤ 0.25 m m devices. Further, the in-plane potentials that arise from inhomogeneous strain gradients are large. In the D ˜ 0.2 m m devices, the corresponding lateral potentials are approximately parabolic exceeding ˜ 25 meV near the perimeter. These potentials create discrete hole states in double-barrier structures (single well), and coupled hole states in triple-barrier structures (two wells). Our results are in excellent agreement with finite-element strain calculations in which the strained layers are permitted to relax to a state of minimum energy by sidewall expansion. Size-induced strain relaxation will undoubtedly become a serious technological issue once strained devices are scaled down to the deep submicron regime. Interestingly, our calculations predict and our measurements are consistent with the appearance of

  20. Effect of radiation and non-Maxwellian electron distribution on relaxation processes in an atmospheric cesium seeded argon plasma

    International Nuclear Information System (INIS)

    Borghi, C.A.; Veefkind, A.; Wetzer, J.M.

    1982-03-01

    A model, describing the time dependent behaviour of a noble gas MHD generator plasma, has been set up. With this model it is possible to calculate the relaxation for ionization or recombination as a response to a stepwise temperature development, once the initial and final conditions are given. In model radiative transitions and a deviation from Maxwellian electron distribution are included. Radiation causes an enhancement of both the ionization relaxation time and the recombination relaxation time. A non-Maxwellian electron distribution results in an increase of the relaxation time for an ionizing plasma because of an underpopulation of the high energy electrons. A decrease of the relaxation time for a recombining plasma is caused by an overpopulation of high energy electrons. The relaxation time is strongly dependent on the seed ratio and the temperature step. (Auth.)

  1. Structural relaxation in annealed hyperquenched basaltic glasses

    DEFF Research Database (Denmark)

    Guo, Xiaoju; Mauro, John C.; Potuzak, M.

    2012-01-01

    The enthalpy relaxation behavior of hyperquenched (HQ) and annealed hyperquenched (AHQ) basaltic glass is investigated through calorimetric measurements. The results reveal a common onset temperature of the glass transition for all the HQ and AHQ glasses under study, indicating that the primary...... relaxation is activated at the same temperature regardless of the initial departure from equilibrium. The analysis of secondary relaxation at different annealing temperatures provides insights into the enthalpy recovery of HQ glasses....

  2. Dielectric relaxation in Yb-doped SrZrO3

    International Nuclear Information System (INIS)

    Kamishima, O; Abe, Y; Ishii, T; Kawamura, J; Hattori, T

    2004-01-01

    The dielectric constant of the proton conductor SrZr 1-x Yb x O 3 (x 0-0.1) was measured as a function of temperature and frequency. Two well-defined relaxation peaks were observed in SrZrO 3 doped with more than 1 mol% of Yb. The assignment of the two dielectric relaxations is discussed in terms of IR spectra and by free energy calculation for a miscibility of dopant Yb ions. The Yb concentration dependence of the relaxation strength of the two dielectric relaxations is in agreement with the results calculated from the free energy. The two relaxations can be assigned to a reorientation of a single Yb-OH dipole and of Yb-OH dipoles associated with Yb-clusters. The attractive energy for Yb-clustering in SrZrO 3 is evaluated at about -85 meV

  3. Dielectric Relaxation of Water: Theory and Experiment

    International Nuclear Information System (INIS)

    Adhikari, Narayan Prasad; Paudyal, Harihar; Johri, Manoj

    2010-06-01

    We have studied the hydrogen bond dynamics and methods for evaluation of probability and relaxation time for hydrogen bond network. Further, dielectric relaxation time has been calculated by using a diagonalization procedure by obtaining eigen values (inverse of relaxation time) of a master equation framed on the basis of Fokker-Planck equations. Microwave cavity spectrometer has been described to make measurements of relaxation time. Slater's perturbation equations are given for the analysis of the data. A comparison of theoretical and experimental data shows that there is a need for improvements in the theoretical model and experimental techniques to provide exact information about structural properties of water. (author)

  4. Relaxation periodic solutions of one singular perturbed system with delay

    Science.gov (United States)

    Kashchenko, A. A.

    2017-12-01

    In this paper, we consider a singularly perturbed system of two differential equations with delay, simulating two coupled oscillators with a nonlinear compactly supported feedback. We reduce studying nonlocal dynamics of initial system to studying dynamics of special finite-dimensional mappings: rough stable (unstable) cycles of these mappings correspond to exponentially orbitally stable (unstable) relaxation solutions of initial problem. We show that dynamics of initial model depends on coupling coefficient crucially. Multistability is proved.

  5. Pair plasma relaxation time scales.

    Science.gov (United States)

    Aksenov, A G; Ruffini, R; Vereshchagin, G V

    2010-04-01

    By numerically solving the relativistic Boltzmann equations, we compute the time scale for relaxation to thermal equilibrium for an optically thick electron-positron plasma with baryon loading. We focus on the time scales of electromagnetic interactions. The collisional integrals are obtained directly from the corresponding QED matrix elements. Thermalization time scales are computed for a wide range of values of both the total-energy density (over 10 orders of magnitude) and of the baryonic loading parameter (over 6 orders of magnitude). This also allows us to study such interesting limiting cases as the almost purely electron-positron plasma or electron-proton plasma as well as intermediate cases. These results appear to be important both for laboratory experiments aimed at generating optically thick pair plasmas as well as for astrophysical models in which electron-positron pair plasmas play a relevant role.

  6. Relaxing Chosen-Ciphertext Security

    DEFF Research Database (Denmark)

    Canetti, Ran; Krawczyk, Hugo; Nielsen, Jesper Buus

    2003-01-01

    Security against adaptive chosen ciphertext attacks (or, CCA security) has been accepted as the standard requirement from encryption schemes that need to withstand active attacks. In particular, it is regarded as the appropriate security notion for encryption schemes used as components within...... general protocols and applications. Indeed, CCA security was shown to suffice in a large variety of contexts. However, CCA security often appears to be somewhat too strong: there exist encryption schemes (some of which come up naturally in practice) that are not CCA secure, but seem sufficiently secure...... “for most practical purposes.” We propose a relaxed variant of CCA security, called Replayable CCA (RCCA) security. RCCA security accepts as secure the non-CCA (yet arguably secure) schemes mentioned above; furthermore, it suffices for most existing applications of CCA security. We provide three...

  7. Nuclear relaxation and critical fluctuations in membranes containing cholesterol

    Science.gov (United States)

    McConnell, Harden

    2009-04-01

    Nuclear resonance frequencies in bilayer membranes depend on lipid composition. Our calculations describe the combined effects of composition fluctuations and diffusion on nuclear relaxation near a miscibility critical point. Both tracer and gradient diffusion are included. The calculations involve correlation functions and a correlation length ξ =ξ0T/(T -Tc), where T -Tc is temperature above the critical temperature and ξ0 is a parameter of molecular length. Several correlation functions are examined, each of which is related in some degree to the Ising model correlation function. These correlation functions are used in the calculation of transverse deuterium relaxation rates in magic angle spinning and quadrupole echo experiments. The calculations are compared with experiments that report maxima in deuterium and proton nuclear relaxation rates at the critical temperature [Veatch et al., Proc. Nat. Acad. Sci. U.S.A. 104, 17650 (2007)]. One Ising-model-related correlation function yields a maximum 1/T2 relaxation rate at the critical temperature for both magic angle spinning and quadrupole echo experiments. The calculated rates at the critical temperature are close to the experimental rates. The rate maxima involve relatively rapid tracer diffusion in a static composition gradient over distances of up to 10-100 nm.

  8. Spin-lattice relaxation of individual solid-state spins

    Science.gov (United States)

    Norambuena, A.; Muñoz, E.; Dinani, H. T.; Jarmola, A.; Maletinsky, P.; Budker, D.; Maze, J. R.

    2018-03-01

    Understanding the effect of vibrations on the relaxation process of individual spins is crucial for implementing nanosystems for quantum information and quantum metrology applications. In this work, we present a theoretical microscopic model to describe the spin-lattice relaxation of individual electronic spins associated to negatively charged nitrogen-vacancy centers in diamond, although our results can be extended to other spin-boson systems. Starting from a general spin-lattice interaction Hamiltonian, we provide a detailed description and solution of the quantum master equation of an electronic spin-one system coupled to a phononic bath in thermal equilibrium. Special attention is given to the dynamics of one-phonon processes below 1 K where our results agree with recent experimental findings and analytically describe the temperature and magnetic-field scaling. At higher temperatures, linear and second-order terms in the interaction Hamiltonian are considered and the temperature scaling is discussed for acoustic and quasilocalized phonons when appropriate. Our results, in addition to confirming a T5 temperature dependence of the longitudinal relaxation rate at higher temperatures, in agreement with experimental observations, provide a theoretical background for modeling the spin-lattice relaxation at a wide range of temperatures where different temperature scalings might be expected.

  9. BREATHING EXERCISE RELAXATION INCREASE PHSYCOLOGICAL RESPONSE PRESCHOOL CHILDREN

    Directory of Open Access Journals (Sweden)

    Yuni Sufyanti Arief

    2017-07-01

    Full Text Available Introduction: Being hospitalize will be made the children become stress. Hospitalization response of the child particularly is afraid sense regard to painfull procedure and increase to attack the invasive procedure. The aimed of this study was to describe the influence of breathing exercise relaxation technique regarded to phsycological receiving responses in the preeliminary school chidren while they were receiving invasive procedure. Method: A quasy experimental purposive sampling design was used in this study. There were 20 respondents who met to the inclusion criteria. The independent variable was the breathing exercise relaxation technique and the dependent variable was phsycological receiving responses. Data for phsylogical response were collected by using observation form then analyzed by using Wilcoxon Signed Rank Test and Mann Whitney U Test with significance level α≤0.05. Result :  The result showed that breathing exercise relaxation technique had significance influence to phsycological response (p=0.000. Discussion: It,s can be concluded that breathing exercise relaxation technique has an effect to increase pshycological response in preeliminary school children who received invasive procedure.

  10. Magnon interaction and relaxation in yttrium iron garnet

    International Nuclear Information System (INIS)

    Mukimov, K.M.; Jumaev, M.R.; Kenjaev, Z.M.

    2007-01-01

    Full text: Magnon interaction and relaxation are the fundamental characteristics describing the response of any system to an external AC field. Almost all experiments aimed at magnon excitation have been carried out in the microwave frequency range where only magnons with energies 0.1 - 5 K can be excited. Nevertheless, all magnons with energy lower or order of the temperature are involved in the processes of low energy magnon relaxation. The present study deals with the interactions of magnons in YIG in thermodynamic equilibrium at temperatures up to 300 K. We consider the exchange and magnetic - dipole terms in the YIG Hamiltonian and a term due to the local uniaxial crystallographic anisotropy, find the corresponding amplitudes of three - and four - magnon process, and calculate the relaxation rate and the correction to the ferromagnon frequency to the first order in the interaction. This correction is positive, in contrast to the case of ferromagnets, and it is proportional to at temperatures up to, in agreement with experiment. The exchange - relaxation rate of the magnons is found as a function of the wave vector and temperature. In the region this rate agrees with the familiar expression for ferromagnets. At higher temperatures, at which the main contribution to the exchange damping is from the magnons of the linear part of the spectrum, the temperature dependence of the damping becomes stronger. (authors)

  11. Relaxation path of metastable nanoclusters in oxide dispersion strengthened materials

    Energy Technology Data Exchange (ETDEWEB)

    Ribis, J., E-mail: joel.ribis@cea.fr [DEN-Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette (France); Thual, M.A. [LLB, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191, Gif-sur-Yvette (France); Guilbert, T.; Carlan, Y. de [DEN-Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette (France); Legris, A. [UMET, CNRS/UMR 8207, Bât. C6, Univ. Lille 1, 59655 Villeneuve d’Ascq (France)

    2017-02-15

    ODS steels are a promising class of structural materials for sodium cooled fast reactor application. The ultra-high density of the strengthening nanoclusters dispersed within the ferritic matrix is responsible of the excellent creep properties of the alloy. Fine characterization of the nanoclusters has been conducted on a Fe-14Cr-0.3Ti-0.3Y{sub 2}O{sub 3} ODS material using High Resolution and Energy Filtered Transmission Electron Microscopy. The nanoclusters exhibit a cubic symmetry possibly identified as f.c.c and display a non-equilibrium YTiCrO chemical composition thought to be stabilized by a vacancy supersaturation. These nanoclusters undergo relaxation towards the Y{sub 2}Ti{sub 2}O{sub 7}-like state as they grow. A Cr shell is observed around the relaxed nano-oxides, this size-dependent shell may form after the release of Cr by the particles. The relaxation energy barrier appears to be higher for the smaller particles probably owing to a volume/surface ratio effect in reason to the full coherency of the nanoclusters. - Highlights: • The nanoclusters display a f.c.c. cubic symmetry and a non-equilibrium YTiCrO chemical composition. • During thermal annealing the coherent nanocluster transform into semi-coherent pyrochlore particles. • A Cr ring is observed around the relaxed pyrochlore type particles.

  12. Transverse magnetic field effects on the relaxation time of the magnetization in Mn12 measured by 55Mn-NMR

    International Nuclear Information System (INIS)

    Furukawa, Y.; Watanabe, K.; Kumagai, K.; Borsa, F.; Gatteschi, D.

    2003-01-01

    The longitudinal (H Z ) and transverse (H T ) magnetic field dependence of the relaxation time of the magnetization in Mn12 in its S=10 ground state was measured by NMR. The minima in the relaxation time at the fields for level crossing are due to the quantum tunneling of the magnetization. The shortening of the relaxation time under the application of H T is shown to be due mainly to the reduction of the energy barrier

  13. The pleiotropic effects of simvastatin on retinal microvascular endothelium has important implications for ischaemic retinopathies.

    Directory of Open Access Journals (Sweden)

    Reinhold J Medina

    Full Text Available BACKGROUND: Current guidelines encourage the use of statins to reduce the risk of cardiovascular disease in diabetic patients; however the impact of these drugs on diabetic retinopathy is not well defined. Moreover, pleiotropic effects of statins on the highly specialised retinal microvascular endothelium remain largely unknown. The objective of this study was to investigate the effects of clinically relevant concentrations of simvastatin on retinal endothelium in vitro and in vivo. METHODS AND FINDINGS: Retinal microvascular endothelial cells (RMECs were treated with 0.01-10 microM simvastatin and a biphasic dose-related response was observed. Low concentrations enhanced microvascular repair with 0.1 microM simvastatin significantly increasing proliferation (p<0.05, and 0.01 microM simvastatin significantly promoting migration (p<0.05, sprouting (p<0.001, and tubulogenesis (p<0.001. High concentration of simvastatin (10 microM had the opposite effect, significantly inhibiting proliferation (p<0.01, migration (p<0.01, sprouting (p<0.001, and tubulogenesis (p<0.05. Furthermore, simvastatin concentrations higher than 1 microM induced cell death. The mouse model of oxygen-induced retinopathy was used to investigate the possible effects of simvastatin treatment on ischaemic retinopathy. Low dose simvastatin (0.2 mg/Kg promoted retinal microvascular repair in response to ischaemia by promoting intra-retinal re-vascularisation (p<0.01. By contrast, high dose simvastatin(20 mg/Kg significantly prevented re-vascularisation (p<0.01 and concomitantly increased pathological neovascularisation (p<0.01. We also demonstrated that the pro-vascular repair mechanism of simvastatin involves VEGF stimulation, Akt phosphorylation, and nitric oxide production; and the anti-vascular repair mechanism is driven by marked intracellular cholesterol depletion and related disorganisation of key intracellular structures. CONCLUSIONS: A beneficial effect of low

  14. Differential expression of the Slc4 bicarbonate transporter family in murine corneal endothelium and cell culture.

    Science.gov (United States)

    Shei, William; Liu, Jun; Htoon, Hla M; Aung, Tin; Vithana, Eranga N

    2013-01-01

    To characterize the relative expression levels of all the solute carrier 4 (Slc4) transporter family members (Slc4a1-Slc4a11) in murine corneal endothelium using real-time quantitative (qPCR), to identify further important members besides Slc4a11 and Slc4a4, and to explore how close to the baseline levels the gene expressions remain after cells have been subjected to expansion and culture. Descemet's membrane-endothelial layers of 8-10-week-old C57BL6 mice were stripped from corneas and used for both primary cell culture and direct RNA extraction. Total RNA (from uncultured cells as well as cultured cells at passages 2 and 7) was reverse transcribed, and the cDNA was used for real time qPCR using specific primers for all the Slc4 family members. The geNorm method was applied to determine the most stable housekeeping genes and normalization factor, which was calculated from multiple housekeeping genes for more accurate and robust quantification. qPCR analyses revealed that all Slc4 bicarbonate transporter family members were expressed in mouse corneal endothelium. Slc4a11 showed the highest expression, which was approximately three times higher than that of Slc4a4 (3.4±0.3; p=0.004). All Slc4 genes were also expressed in cultured cells, and interestingly, the expression of Slc4a11 in cultured cells was significantly reduced by approximately 20-fold (0.05±0.001; p=0.000001) in early passage and by approximately sevenfold (0.14±0.002; p=0.000002) in late passage cells. Given the known involvement of SLC4A4 and SLC4A11 in corneal dystrophies, we speculate that the other two highly expressed genes in the uncultured corneal endothelium, SLC4A2 and SLC4A7, are worthy of being considered as potential candidate genes for corneal endothelial diseases. Moreover, as cell culture can affect expression levels of Slc4 genes, caution and careful design of experiments are necessary when undertaking studies of Slc4-mediated ion transport in cultured cells.

  15. Influence of metabolism modifiers of cyclic nucleotides on contractility of right ventricle of rat heart with intact and removed endocardial endothelium

    Directory of Open Access Journals (Sweden)

    Savić Slađana

    2010-01-01

    Full Text Available Introduction. Endocardial endothelium, a natural biological barrier between circulating blood in heart ventricle and cells, creates a complex yet finely tuned balance of interactions with the immediate environment. Objective. We investigated the roles of theophylline, nonspecific phosphodiesterase inhibitor, and imidazole, an activator of phosphodiesterase on contractility of the right ventricle of rat heart, with intact and removed endocardial endothelium. Methods. Adult rats, of both sexes, type Wistar albino, were used in this experiment. All experiments were conducted on the preparations of the right ventricle using two experimental models. In the first experimental model, an endocardial endothelium (EE was preserved, and in the second model, an endocardial endothelium (-EE was removed using 1% solution Triton X-100. Results. Theophylline (1x10-2 mol/l expressed the positive inotropic effect on the heart, regardless of the presence of the endocardial endothelium. Inotropic response as multiple process can be induced by inhibition of phosphodiesterase, accumulation of cyclic nucleotides and activation of Ca2+ channels. Imidazole (2x10-3 mol/l increased the contractility of the right ventricle of the heart with EE. The modulator effect of endocardial endothelium on contractility of imidazole proved to be significant. As imidazole influenced the contractility of the right ventricle only in the presence of the endocardial endothelium, it is assumed that its effect is mediated via deliverance of endothelial mediators with positive inotropic effect. Conclusion. An intact endocardial endothelium is necessary for completion of contractile performance of the heart.

  16. Stress relaxation behavior and mechanism of AEREX350 and Waspaloy superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuzhou; Dong, Jianxin; Zhang, Maicang; Yao, Zhihao

    2016-12-15

    The relaxation properties of AEREX350 and Waspaloy were studied contrastively at temperatures ranging from 600 °C to 800 °C with the same initial stress 510 MPa. The relationship between the microstructure and relaxation properties was elucidated using scanning and transmission electron microscopy techniques. It was found that the relaxation limit and relaxation stability of the two alloys decreased obviously with the increase of temperature, but the relaxation stability of AEREX350 decreased more slowly compared with Waspaloy. Further investigations show that the relaxation behavior is mainly depended on both precipitate characteristics and its interaction with dislocations. The complex precipitates evolution of AEREX350 alloy leads to a higher relaxation limit at high temperature 800 °C, but more quantity of γ′ in Waspaloy results in a higher relaxation limit at the low temperature of 600 °C. Thus it is suggested that as fastener alloys, Waspaloy is more suitable for low temperature service while AEREX350 is the preferred choice for high temperature service.

  17. Glass transition and relaxation dynamics of propylene glycol-water solutions confined in clay

    Science.gov (United States)

    Elamin, Khalid; Björklund, Jimmy; Nyhlén, Fredrik; Yttergren, Madeleine; Mârtensson, Lena; Swenson, Jan

    2014-07-01

    The molecular dynamics of aqueous solutions of propylene glycol (PG) and propylene glycol methylether (PGME) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy and differential scanning calorimetry. As typical for liquids in confined geometries the intensity of the cooperative α-relaxation becomes considerably more suppressed than the more local β-like relaxation processes. In fact, at high water contents the calorimetric glass transition and related structural α-relaxation cannot even be observed, due to the confinement. Thus, the intensity of the viscosity related α-relaxation is dramatically reduced, but its time scale as well as the related glass transition temperature Tg are for both systems only weakly influenced by the confinement. In the case of the PGME-water solutions it is an important finding since in the corresponding bulk system a pronounced non-monotonic concentration dependence of the glass transition related dynamics has been observed due to the growth of hydrogen bonded relaxing entities of water bridging between PGME molecules [J. Sjöström, J. Mattsson, R. Bergman, and J. Swenson, Phys. Chem. B 115, 10013 (2011)]. The present results suggest that the same type of structural entities are formed in the quasi-two-dimensional space between the clay platelets. It is also observed that the main water relaxation cannot be distinguished from the β-relaxation of PG or PGME in the concentration range up to intermediate water contents. This suggests that these two processes are coupled and that the water molecules affect the time scale of the β-relaxation. However, this is most likely true also for the corresponding bulk solutions, which exhibit similar time scales of this combined relaxation process below Tg. Finally, it is found that at higher water contents the water relaxation does not merge with, or follow, the α-relaxation above Tg, but instead crosses the α-relaxation

  18. The Effects of Progressive Relaxation and Music on Attention, Relaxation, and Stress Responses: An Investigation of the Cognitive-Behavioral Model of Relaxation

    National Research Council Canada - National Science Library

    Scheufele, Peter

    1999-01-01

    ...) suggested that stress management techniques have specific effects A compromise position suggests that the specific effects of relaxation techniques are superimposed upon a general relaxation response...

  19. Endothelium-derived fibronectin regulates neonatal vascular morphogenesis in an autocrine fashion.

    Science.gov (United States)

    Turner, Christopher J; Badu-Nkansah, Kwabena; Hynes, Richard O

    2017-11-01

    Fibronectin containing alternatively spliced EIIIA and EIIIB domains is largely absent from mature quiescent vessels in adults, but is highly expressed around blood vessels during developmental and pathological angiogenesis. The precise functions of fibronectin and its splice variants during developmental angiogenesis however remain unclear due to the presence of cardiac, somitic, mesodermal and neural defects in existing global fibronectin KO mouse models. Using a rare family of surviving EIIIA EIIIB double KO mice, as well as inducible endothelial-specific fibronectin-deficient mutant mice, we show that vascular development in the neonatal retina is regulated in an autocrine manner by endothelium-derived fibronectin, and requires both EIIIA and EIIIB domains and the RGD-binding α5 and αv integrins for its function. Exogenous sources of fibronectin do not fully substitute for the autocrine function of endothelial fibronectin, demonstrating that fibronectins from different sources contribute differentially to specific aspects of angiogenesis.

  20. Circulating endothelial progenitor cells do not contribute to regeneration of endothelium after murine arterial injury

    DEFF Research Database (Denmark)

    Hagensen, Mette; Raarup, Merete Krog; Mortensen, Martin Bødtker

    2012-01-01

    into endothelial cells (ECs). We tested this theory in a murine arterial injury model using carotid artery transplants and fluorescent reporter mice. METHODS AND RESULTS: Wire-injured carotid artery segments from wild-type mice were transplanted into TIE2-GFP transgenic mice expressing green fluorescent protein...... (GFP) in ECs. We found that the endothelium regenerated with GFP(+) ECs as a function of time, evolving from the anastomosis sites towards the centre of the transplant. A migration front of ECs at Day 7 was verified by scanning electron microscopy and by bright-field microscopy using recipient TIE2-lac......Z mice with endothelial β-galactosidase expression. These experiments indicated migration of flanking ECs rather than homing of circulating cells as the underlying mechanism. To confirm this, we interposed non-injured wild-type carotid artery segments between the denuded transplant and the TIE2-GFP...

  1. Mechanism of resveratrol-induced relaxation of the guinea pig fundus.

    Science.gov (United States)

    Tsai, Ching-Chung; Tey, Shu-Leei; Lee, Ming-Che; Liu, Ching-Wen; Su, Yu-Tsun; Huang, Shih-Che

    2018-04-01

    Resveratrol is a polyphenolic compound that can be isolated from plants and also is a constituent of red wine. Resveratrol induces relaxation of vascular smooth muscle and may prevent cardiovascular diseases. Impaired gastric accommodation plays an important role in functional dyspepsia and fundic relaxation and is a therapeutic target of functional dyspepsia. Although drugs for fundic relaxation have been developed, these types of drugs are still rare. The purpose of this study was to investigate the relaxant effects of resveratrol in the guinea pig fundus. We studied the relaxant effects of resveratrol in the guinea pig fundus. In addition, we investigated the mechanism of resveratrol-induced relaxation on the guinea pig fundus by using tetraethylammonium (a non-selective potassium channel blocker), apamine (a selective inhibitor of the small conductance calcium-activated potassium channel), iberiotoxin (an inhibitor of large conductance calcium-activated potassium channels), glibenclamide (an ATP-sensitive potassium channel blocker), KT 5720 (a cAMP-dependent protein kinase A inhibitor), KT 5823 (a cGMP-dependent protein kinase G inhibitor), NG-nitro-L-arginine (a competitive inhibitor of nitric oxide synthase), tetrodotoxin (a selective neuronal Na + channel blocker), ω-conotoxin GVIA (a selective neuronal Ca 2+ channel blocker) and G-15 (a G-protein coupled estrogen receptor antagonist). The results of this study showed that resveratrol has potent and dose-dependent relaxant effects on the guinea pig fundic muscle. In addition, the results showed that resveratrol-induced relaxation of the guinea pig fundus occurs through nitric oxide and ATP-sensitive potassium channels. This study provides the first evidence concerning the relaxant effects of resveratrol in the guinea pig fundic muscle strips. Furthermore, resveratrol may be a potential drug to relieve gastrointestinal dyspepsia. Copyright © 2018 Elsevier GmbH. All rights reserved.

  2. Time Window Is Important for Adenosine Preventing Cold-induced Injury to the Endothelium.

    Science.gov (United States)

    Li, Yan; Hu, Xiao-Xia; Fu, Li; Chen, Jing; Lu, Li-He; Liu, Xiang; Xu, Zhe; Zhou, Li; Wang, Zhi-Ping; Zhang, Xi; Ou, Zhi-Jun; Ou, Jing-Song

    2017-06-01

    Cold cardioplegia is used to induce heart arrest during cardiac surgery. However, endothelial function may be compromised after this procedure. Accordingly, interventions such as adenosine, that mimic the effects of preconditioning, may minimize endothelial injury. Herein, we investigated whether adenosine prevents cold-induced injury to the endothelium. Cultured human cardiac microvascular endothelial cells were treated with adenosine for different durations. Phosphorylation and expression of endothelial nitric oxide synthase (eNOS), p38MAPK, ERK1/2, and p70S6K6 were measured along with nitric oxide (NO) production using diaminofluorescein-2 diacetate (DAF-2DA) probe. Cold-induced injury by hypothermia to 4°C for 45 minutes to mimic conditions of cold cardioplegia during open heart surgery was induced in human cardiac microvascular endothelial cells. Under basal conditions, adenosine stimulated NO production, eNOS phosphorylation at serine 1177 from 5 minutes to 4 hours and inhibited eNOS phosphorylation at threonine 495 from 5 minutes to 6 hours, but increased phosphorylation of ERK1/2, p38MAPK, and p70S6K only after exposure for 5 minutes. Cold-induced injury inhibited NO production and the phosphorylation of the different enzymes. Importantly, adenosine prevented these effects of hypothermic injury. Our data demonstrated that adenosine prevents hypothermic injury to the endothelium by activating ERK1/2, eNOS, p70S6K, and p38MAPK signaling pathways at early time points. These findings also indicated that 5 minutes after administration of adenosine or release of adenosine is an important time window for cardioprotection during cardiac surgery.

  3. Net Fluorescein Flux Across Corneal Endothelium Strongly Suggests Fluid Transport is due to Electro-osmosis.

    Science.gov (United States)

    Sanchez, J M; Cacace, V; Kusnier, C F; Nelson, R; Rubashkin, A A; Iserovich, P; Fischbarg, J

    2016-08-01

    We have presented prior evidence suggesting that fluid transport results from electro-osmosis at the intercellular junctions of the corneal endothelium. Such phenomenon ought to drag other extracellular solutes. We have investigated this using fluorescein-Na2 as an extracellular marker. We measured unidirectional fluxes across layers of cultured human corneal endothelial (HCE) cells. SV-40-transformed HCE layers were grown to confluence on permeable membrane inserts. The medium was DMEM with high glucose and no phenol red. Fluorescein-labeled medium was placed either on the basolateral or the apical side of the inserts; the other side carried unlabeled medium. The inserts were held in a CO2 incubator for 1 h (at 37 °C), after which the entire volume of the unlabeled side was collected. After that, label was placed on the opposite side, and the corresponding paired sample was collected after another hour. Fluorescein counts were determined with a (Photon Technology) DeltaScan fluorometer (excitation 380 nm; emission 550 nm; 2 nm bwth). Samples were read for 60 s. The cells utilized are known to transport fluid from the basolateral to the apical side, just as they do in vivo in several species. We used 4 inserts for influx and efflux (total: 20 1-h periods). We found a net flux of fluorescein from the basolateral to the apical side. The flux ratio was 1.104 ± 0.056. That difference was statistically significant (p = 0.00006, t test, paired samples). The endothelium has a definite restriction at the junctions. Hence, an asymmetry in unidirectional fluxes cannot arise from osmosis, and can only point instead to paracellular solvent drag. We suggest, once more, that such drag is due to electro-osmotic coupling at the paracellular junctions.

  4. Expression of follicle-stimulating hormone receptor by the vascular endothelium in tumor metastases

    International Nuclear Information System (INIS)

    Siraj, Ahsan; Gonin, Julie; Radu, Aurelian; Ghinea, Nicolae; Desestret, Virginie; Antoine, Martine; Fromont, Gaëlle; Huerre, Michel; Sanson, Marc; Camparo, Philippe; Pichon, Christophe; Planeix, François

    2013-01-01

    The Follicle Stimulating Hormone receptor (FSHR) is expressed by the vascular endothelium in a wide range of human tumors. It was not determined however if FSHR is present in metastases which are responsible for the terminal illness. We used immunohistochemistry based on a highly FSHR-specific monoclonal antibody to detect FSHR in cancer metastases from 6 major tumor types (lung, breast, prostate, colon, kidney, and leiomyosarcoma) to 6 frequent locations (bone, liver, lymph node, brain, lung, and pleura) of 209 patients. In 166 patients examined (79%), FSHR was expressed by blood vessels associated with metastatic tissue. FSHR-positive vessels were present in the interior of the tumors and some few millimeters outside, in the normally appearing tissue. In the interior of the metastases, the density of the FSHR-positive vessels was constant up to 7 mm, the maximum depth available in the analyzed sections. No significant differences were noticed between the density of FSHR-positive vessels inside vs. outside tumors for metastases from lung, breast, colon, and kidney cancers. In contrast, for prostate cancer metastases, the density of FSHR-positive vessels was about 3-fold higher at the exterior of the tumor compared to the interior. Among brain metastases, the density of FSHR-positive vessels was highest in lung and kidney cancer, and lowest in prostate and colon cancer. In metastases of breast cancer to the lung pleura, the percentage of blood vessels expressing FSHR was positively correlated with the progesterone receptor level, but not with either HER-2 or estrogen receptors. In normal tissues corresponding to the host organs for the analyzed metastases, obtained from patients not known to have cancer, FSHR staining was absent, with the exception of approx. 1% of the vessels in non tumoral temporal lobe epilepsy samples. FSHR is expressed by the endothelium of blood vessels in the majority of metastatic tumors

  5. Characterization of VCAM-1-binding peptide-functionalized quantum dots for molecular imaging of inflamed endothelium.

    Directory of Open Access Journals (Sweden)

    Yun Chen

    Full Text Available Inflammation-induced activation of endothelium constitutes one of the earliest changes during atherogenesis. New imaging techniques that allow detecting activated endothelial cells can improve the identification of persons at high cardiovascular risk in early stages. Quantum dots (QDs have attractive optical properties such as bright fluorescence and high photostability, and have been increasingly studied and developed for bio-imaging and bio-targeting applications. We report here the development of vascular cell adhesion molecule-1 binding peptide (VCAM-1 binding peptide functionalized QDs (VQDs from amino QDs. It was found that the QD fluorescence signal in tumor necrosis factor [Formula: see text] (TNF-[Formula: see text] treated endothelial cells in vitro was significantly higher when these cells were labeled with VQDs than amino QDs. The VQD labeling of TNF-[Formula: see text]-treated endothelial cells was VCAM-1 specific since pre-incubation with recombinant VCAM-1 blocked cells' uptake of VQDs. Our ex vivo and in vivo experiments showed that in the inflamed endothelium, QD fluorescence signal from VQDs was also much stronger than that of amino QDs. Moreover, we observed that the QD fluorescence peak was significantly blue-shifted after VQDs interacted with aortic endothelial cells in vivo and in vitro. A similar blue-shift was observed after VQDs were incubated with recombinant VCAM-1 in tube. We anticipate that the specific interaction between VQDs and VCAM-1 and the blue-shift of the QD fluorescence peak can be very useful for VCAM-1 detection in vivo.

  6. Relaxation property of the fractional Brownian particle

    International Nuclear Information System (INIS)

    Wang Litan; Lung, C.W.

    1988-08-01

    Dynamic susceptibility of a diffusion system associated with the fractional Brownian motion (fBm) was examined for the fractal property of the Non-Debye relaxation process. The comparisons between fBm and other approaches were made. Anomalous diffusion and the Non-Debye relaxation processes were discussed with this approach. (author). 8 refs, 1 fig

  7. Lifshitz quasinormal modes and relaxation from holography

    NARCIS (Netherlands)

    Sybesma, Watse|info:eu-repo/dai/nl/369283074; Vandoren, Stefan|info:eu-repo/dai/nl/304830739

    2015-01-01

    We obtain relaxation times for field theories with Lifshitz scaling and with holographic duals Einstein-Maxwell-Dilaton gravity theories. This is done by computing quasinormal modes of a bulk scalar field in the presence of Lifshitz black branes. We determine the relation between relaxation time and

  8. Superparamagnetic relaxation of weakly interacting particles

    DEFF Research Database (Denmark)

    Mørup, Steen; Tronc, Elisabeth

    1994-01-01

    The influence of particle interactions on the superparamagnetic relaxation time has been studied by Mossbauer spectroscopy in samples of maghemite (gamma-Fe2O3) particles with different particle sizes and particle separations. It is found that the relaxation time decreases with decreasing particl...

  9. Models of Flux Tubes from Constrained Relaxation

    Indian Academy of Sciences (India)

    tribpo

    J. Astrophys. Astr. (2000) 21, 299 302. Models of Flux Tubes from Constrained Relaxation. Α. Mangalam* & V. Krishan†, Indian Institute of Astrophysics, Koramangala,. Bangalore 560 034, India. *e mail: mangalam @ iiap. ernet. in. † e mail: vinod@iiap.ernet.in. Abstract. We study the relaxation of a compressible plasma to ...

  10. Superparamagnetic relaxation in alpha-Fe particles

    DEFF Research Database (Denmark)

    Bødker, Franz; Mørup, Steen; Pedersen, Michael Stanley

    1998-01-01

    The superparamagnetic relaxation time of carbon-supported alpha-Fe particles with an average size of 3.0 Mm has been studied over a large temperature range by the use of Mossbauer spectroscopy combined with AC and DC magnetization measurements. It is found that the relaxation time varies...

  11. Baryogenesis via Elementary Goldstone Higgs Relaxation

    DEFF Research Database (Denmark)

    Gertov, Helene; Pearce, Lauren; Sannino, Francesco

    2016-01-01

    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 ...... but radiatively generated, it is possible to generate the observed matter-antimatter asymmetry via the relaxation mechanism....

  12. Vibrational relaxation in liquids: Comparisons between gas phase and liquid phase theories

    International Nuclear Information System (INIS)

    Russell, D.J.

    1990-12-01

    The vibrational relaxation of iodine in liquid xenon was studied to understand what processes are important in determining the density dependence of the vibrational relaxation. This examination will be accomplished by taking simple models and comparing the results to both experimental outcomes and the predictions of molecular dynamics simulations. The vibration relaxation of iodine is extremely sensitive to the iodine potential. The anharmonicity of iodine causes vibrational relaxation to be much faster at the top of the iodine well compared to the vibrational relaxation at the bottom. A number of models are used in order to test the ability of the Isolated Binary Collision theory's ability to predict the density dependence of the vibrational relaxation of iodine in liquid xenon. The models tested vary from the simplest incorporating only the fact that the solvent occupies volume to models that incorporate the short range structure of the liquid in the radial distribution function. None of the models tested do a good job of predicting the actual relaxation rate for a given density. This may be due to a possible error in the choice of potentials to model the system

  13. [Binding studies with Ulex europaeus agglutinin I (UEA-I) of the vascular endothelium of the synovial membrane].

    Science.gov (United States)

    Zschäbitz, A; Stofft, E

    1988-01-01

    The lectin binding sites of the synovium of patients with rheumatoid arthritis and osteoarthritis were investigated. It was shown that Ulex europaeus agglutinin is a constant marker of the vascular endothelium and is not induced during the course of inflammatory process in rheumatoid arthritis.

  14. The original Pathologische Anatomie Leiden-Endothelium monoclonal antibody recognizes a vascular endothelial growth factor binding site within neuropilin-1

    NARCIS (Netherlands)

    Jaalouk, Diana E.; Ozawa, Nfichael G.; Sun, Jessica; Lahdenranta, Johanna; Schlingemann, Reinier O.; Pasqualini, Renata; Arap, Wadih

    2007-01-01

    For two decades, the antigen recognized by the Pathologische Anatomie Leiden-Endothelium (PAL-E) monoclonal antibody, a standard vascular endothelial cell marker, has remained elusive. Here, we used a combinatorial phage display-based approach ("epitope mapping") to select peptides binding to the

  15. Relaxation dynamics following transition of solvated electrons

    International Nuclear Information System (INIS)

    Barnett, R.B.; Landman, U.; Nitzan, A.

    1989-01-01

    Relaxation dynamics following an electronic transition of an excess solvated electron in clusters and in bulk water is studied using an adiabatic simulation method. In this method the solvent evolves classically and the electron is constrained to a specified state. The coupling between the solvent and the excess electron is evaluated via the quantum expectation value of the electron--water molecule interaction potential. The relaxation following excitation (or deexcitation) is characterized by two time scales: (i) a very fast (/similar to/20--30 fs) one associated with molecular rotations in the first solvation shell about the electron, and (ii) a slower stage (/similar to/200 fs), which is of the order of the longitudinal dielectric relaxation time. The fast relaxation stage exhibits an isotope effect. The spectroscopical consequences of the relaxation dynamics are discussed

  16. Anomalous enthalpy relaxation in vitreous silica

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    2015-01-01

    scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here, we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy...... relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hyperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas...... the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica....

  17. Cross-relaxation solid state lasers

    International Nuclear Information System (INIS)

    Antipenko, B.M.

    1989-01-01

    Cross-relaxation functional diagrams provide a high quantum efficiency for pumping bands of solid state laser media and a low waste heat. A large number of the cross-relaxation mechanisms for decay rare earth excited states in crystals have been investigated. These investigations have been a starting-point for development of the cross-relaxation solid state lasers. For example, the cross-relaxation interactions, have been used for the laser action development of LiYF 4 :Gd-Tb. These interactions are important elements of the functional diagrams of the 2 μm Ho-doped media sensitized with Er and Tm and the 3 μm Er-doped media. Recently, new efficient 2 μm laser media with cross-relaxation pumping diagrams have been developed. Physical aspects of these media are the subject of this paper. A new concept of the Er-doped medium, sensitized with Yb, is illustrated

  18. Strengthening and stress relaxation of Opalinus Clay

    International Nuclear Information System (INIS)

    Schulze, Otto

    2010-01-01

    undisturbed far-field for the long lasting periods of geological times. Consequently, demands on concepts for backfilling and closure of a repository in a clay-stone formation as well as model calculations for safety analyses generally do not take into account convergence by viscous deformation, which would result from stress re-distribution at underground openings. Although there is some doubt, whether Opalinus Clay is creeping at all, some very long lasting laboratory tests were performed on this item in the author's laboratory. A nearly linear dependence of the long-term creep rate on the deviatoric stress was found. In recent work, the technique of stress-relaxation was used. For this, strengthening by strain rate controlled deformation was stopped, i.e. the strain was kept constant for a long time, and the relaxation of the stress was measured. In course of this technique, the deformability which may result from artefacts is ruled out as far as possible by compaction and strengthening. Then, the stress relaxation - if any - will be maintained by true long-term deformation processes which should be active and responsible for any convergence in an at least only partly backfilled mine. In this contribution, the results of the laboratory work and their discussion will be presented. (authors)

  19. NMR relaxation dispersion of Miglyol molecules confined inside polymeric micro-capsules.

    Science.gov (United States)

    Nechifor, Ruben; Ardelean, Ioan; Mattea, Carlos; Stapf, Siegfried; Bogdan, Mircea

    2011-11-01

    Frequency dependent NMR relaxation studies have been carried out on Miglyol molecules confined inside core shell polymeric capsules to obtain a correlation between capsule dimension and the measurable parameters. The polymeric capsules were prepared using an interfacial polymerization technique for three different concentrations of Miglyol. It was shown that the variation of Miglyol concentration influences the capsule dimension. Their average size was estimated using the pulsed field gradient diffusometry technique. The relaxation dispersion curves were obtained at room temperature by a combined use of a fast field cycling instrument and a high-field instrument. The frequency dependence of relaxation rate shows a transition from a diffusion-limited to a surface-limited relaxation regime. Copyright © 2011 John Wiley & Sons, Ltd.

  20. Relaxed and partially relaxed magnetic equilibria in tight-aspect-ratio tori

    International Nuclear Information System (INIS)

    Browning, P.K.; Clegg, J.R.; Duck, R.C.; Rusbridge, M.G.

    1993-01-01

    Force-free equilibrium magnetic fields in tight-aspect-ratio toroidal configurations are investigated. The study is mainly directed to modelling field configurations in the 'rodomak', a modification to the SPHEX gun-injected spheromak in which a current-carrying rod is inserted along the geometric axis. A family of analytical relaxed states (∇ x B = μB, μ constant) is presented for a torus of rectangular cross section, with boundary conditions allowing for flux embedded in the walls, representing the gun. Numerically calculated fields in SPHEX geometry, with μ profiles relevant to the driven phase of operation, are also given. The dependence of the field configurations and global quantities such as energy, helicity and toroidal current on the controlling parameters (gun flux, gun current and rod current) and geometry is discussed. (author)

  1. Magnetic Resonance Fingerprinting with short relaxation intervals.

    Science.gov (United States)

    Amthor, Thomas; Doneva, Mariya; Koken, Peter; Sommer, Karsten; Meineke, Jakob; Börnert, Peter

    2017-09-01

    The aim of this study was to investigate a technique for improving the performance of Magnetic Resonance Fingerprinting (MRF) in repetitive sampling schemes, in particular for 3D MRF acquisition, by shortening relaxation intervals between MRF pulse train repetitions. A calculation method for MRF dictionaries adapted to short relaxation intervals and non-relaxed initial spin states is presented, based on the concept of stationary fingerprints. The method is applicable to many different k-space sampling schemes in 2D and 3D. For accuracy analysis, T 1 and T 2 values of a phantom are determined by single-slice Cartesian MRF for different relaxation intervals and are compared with quantitative reference measurements. The relevance of slice profile effects is also investigated in this case. To further illustrate the capabilities of the method, an application to in-vivo spiral 3D MRF measurements is demonstrated. The proposed computation method enables accurate parameter estimation even for the shortest relaxation intervals, as investigated for different sampling patterns in 2D and 3D. In 2D Cartesian measurements, we achieved a scan acceleration of more than a factor of two, while maintaining acceptable accuracy: The largest T 1 values of a sample set deviated from their reference values by 0.3% (longest relaxation interval) and 2.4% (shortest relaxation interval). The largest T 2 values showed systematic deviations of up to 10% for all relaxation intervals, which is discussed. The influence of slice profile effects for multislice acquisition is shown to become increasingly relevant for short relaxation intervals. In 3D spiral measurements, a scan time reduction of 36% was achieved, maintaining the quality of in-vivo T1 and T2 maps. Reducing the relaxation interval between MRF sequence repetitions using stationary fingerprint dictionaries is a feasible method to improve the scan efficiency of MRF sequences. The method enables fast implementations of 3D spatially

  2. Corroborative evidences of TV γ -scaling of the α-relaxation originating from the primitive relaxation/JG β relaxation

    Science.gov (United States)

    Ngai, K. L.; Paluch, M.

    2017-12-01

    Successful thermodynamic scaling of the structural alpha-relaxation time or transport coefficients of glass-forming liquids determined at various temperatures T and pressures P means the data conform to a single function of the product variable TVgamma, where V is the specific volume and gamma is a material specific constant. In the past two decades we have witnessed successful TVgamma-scaling in many molecular, polymeric, and even metallic glass-formers, and gamma is related to the slope of the repulsive part of the intermolecular potential. The advances made indicate TVgamma-scaling is an important aspect of the dynamic and thermodynamic properties of glass-formers. In this paper we show the origin of TVgamma-scaling is not from the structural alpha-relaxation time. Instead it comes from its precursor, the Johari-Goldstein beta-relaxation or the primitive relaxation of the Coupling Model and their relaxation times or tau_0 respectively. It is remarkable that all relaxation times are functions of TVgamma with the same gama, as well as the fractional exponent of the Kohlrausch correlation function of the structural alpha-relaxation. We arrive at this conclusion convincingly based on corroborative evidences from a number of experiments and molecular dynamics simulations performed on a wide variety of glass-formers and in conjunction with consistency with the predictions of the Coupling Model.

  3. The atypical structure and function of newborn arterial endothelium is mediated by Rho/Rho kinase signaling.

    Science.gov (United States)

    Flavahan, Sheila; Flavahan, Nicholas A

    2014-08-15

    Endothelium of fetal or newborn arteries is atypical, displaying actin stress fibers and reduced nitric oxide (NO)-mediated dilatation. This study tested the hypothesis that Rho/Rho kinase signaling, which promotes endothelial stress fibers and inhibits endothelial dilatation, contributed to this phenotype. Carotid arteries were isolated from newborn [postnatal day 1 (P1)], P7, and P21 mice. Endothelial dilatation to acetylcholine (pressure myograph) was minimal at P1, increased at P7, and further increased at P21. Inhibition of Rho (C3 transferase) or Rho kinase (Y27632, fasudil) significantly increased dilatation to acetylcholine in P1 arteries but had no effect in P7 or P21 arteries. After inhibition of NO synthase (N(G)-nitro-l-arginine methyl ester), Rho kinase inhibition no longer increased acetylcholine responses in P1 arteries. Rho kinase inhibition did not affect dilatation to the NO donor DEA-NONOate. The endothelial actin cytoskeleton was labeled with phalloidin and visualized by laser-scanning microscopy. In P1 arteries, the endothelium had prominent transcytoplasmic stress fibers, whereas in P7 and P21 arteries, the actin fibers had a significantly reduced intensity and were restricted to cell borders. Phosphorylation of myosin light chains, a Rho kinase substrate, was highest in P1 endothelium and significantly reduced in P7 and P21 endothelium (laser-scanning microscopy). In P1 arteries, inhibition of Rho (C3 transferase) or Rho kinase (Y27632) significantly reduced the intensity of actin fibers, which were restricted to cell borders. Similarly, in P1 arteries, Rho inhibition significantly reduced endothelial levels of phosphorylated myosin light chains. These results indicate that the atypical function and morphology of newborn endothelium is mediated by Rho/Rho kinase signaling. Copyright © 2014 the American Physiological Society.

  4. SH2 domain-containing protein tyrosine phosphatase 2 and focal adhesion kinase protein interactions regulate pulmonary endothelium barrier function.

    Science.gov (United States)

    Chichger, Havovi; Braza, Julie; Duong, Huetran; Harrington, Elizabeth O

    2015-06-01

    Enhanced protein tyrosine phosphorylation is associated with changes in vascular permeability through formation and dissolution of adherens junctions and regulation of stress fiber formation. Inhibition of the protein tyrosine phosphorylase SH2 domain-containing protein tyrosine phosphatase 2 (SHP2) increases tyrosine phosphorylation of vascular endothelial cadherin and β-catenin, resulting in disruption of the endothelial monolayer and edema formation in the pulmonary endothelium. Vascular permeability is a hallmark of acute lung injury (ALI); thus, enhanced SHP2 activity offers potential therapeutic value for the pulmonary vasculature in diseases such as ALI, but this has not been characterized. To assess whether SHP2 activity mediates protection against edema in the endothelium, we assessed the effect of molecular activation of SHP2 on lung endothelial barrier function in response to the edemagenic agents LPS and thrombin. Both LPS and thrombin reduced SHP2 activity, correlated with decreased focal adhesion kinase (FAK) phosphorylation (Y(397) and Y(925)) and diminished SHP2 protein-protein associations with FAK. Overexpression of constitutively active SHP2 (SHP2(D61A)) enhanced baseline endothelial monolayer resistance and completely blocked LPS- and thrombin-induced permeability in vitro and significantly blunted pulmonary edema formation induced by either endotoxin (LPS) or Pseudomonas aeruginosa exposure in vivo. Chemical inhibition of FAK decreased SHP2 protein-protein interactions with FAK concomitant with increased permeability; however, overexpression of SHP2(D61A) rescued the endothelium and maintained FAK activity and FAK-SHP2 protein interactions. Our data suggest that SHP2 activation offers the pulmonary endothelium protection against barrier permeability mediators downstream of the FAK signaling pathway. We postulate that further studies into the promotion of SHP2 activation in the pulmonary endothelium may offer a therapeutic approach for patients

  5. Relaxing a large cosmological constant

    International Nuclear Information System (INIS)

    Bauer, Florian; Sola, Joan; Stefancic, Hrvoje

    2009-01-01

    The cosmological constant (CC) problem is the biggest enigma of theoretical physics ever. In recent times, it has been rephrased as the dark energy (DE) problem in order to encompass a wider spectrum of possibilities. It is, in any case, a polyhedric puzzle with many faces, including the cosmic coincidence problem, i.e. why the density of matter ρ m is presently so close to the CC density ρ Λ . However, the oldest, toughest and most intriguing face of this polyhedron is the big CC problem, namely why the measured value of ρ Λ at present is so small as compared to any typical density scale existing in high energy physics, especially taking into account the many phase transitions that our Universe has undergone since the early times, including inflation. In this Letter, we propose to extend the field equations of General Relativity by including a class of invariant terms that automatically relax the value of the CC irrespective of the initial size of the vacuum energy in the early epochs. We show that, at late times, the Universe enters an eternal de Sitter stage mimicking a tiny positive cosmological constant. Thus, these models could be able to solve the big CC problem without fine-tuning and have also a bearing on the cosmic coincidence problem. Remarkably, they mimic the ΛCDM model to a large extent, but they still leave some characteristic imprints that should be testable in the next generation of experiments.

  6. Stress relaxation in SSC 50mm dipole coils

    International Nuclear Information System (INIS)

    Rogers, D.; Markley, F.

    1992-04-01

    We are measuring the stress relaxation of SSC 50mm outer coils with the goal of predicting how much of the coil prestress will be lost while the coils are warehoused between manufacture and cooldown. We manufacture 3 inch (76.2mm) long segments of coil with the same materials and techniques that have been used for prototype coils. We are running four simultaneous tests in an attempt to separate the contributions of the different coil materials. Test one is a completely insulated coil section where the insulation is the all polyamide system being tested at Brookhaven; test two is a wire stack insulated only with the normal Kapton overwrap; test three is a stack of bare cable; and test four is a completely insulated normal coil section. All, except for the bare cable, include the ground insulation. The insulated coil sections are carefully dried before loading and testing in order to eliminate stress changes due to varying moisture content. The temperature dependence of the stress relaxation is being studied separately. Three companion papers presented at this conference will be: (1) ''Temperature dependence of the viscoelastic properties of SSC coil insulation'' (2) ''Measurement of the elastic modulus of Kapton perpendicular to the plane of the film at room and cryogenic temperatures'' (3) ''Theoretical methods for creep and stress relaxation studies of SSC coil.''

  7. Multiplied effect of heat and radiation in chemical stress relaxation

    International Nuclear Information System (INIS)

    Ito, Masayuki

    1981-01-01

    About the deterioration of rubber due to radiation, useful knowledge can be obtained by the measurement of chemical stress relaxation. As an example, the rubber coating of cables in a reactor containment vessel is estimated to be irradiated by weak radiation at the temperature between 60 and 90 deg C for about 40 years. In such case, it is desirable to establish the method of accelerated test of the deterioration. The author showed previously that the law of time-dose rate conversion holds in the case of radiation. In this study, the chemical stress relaxation to rubber was measured by the simultaneous application of heat and radiation, and it was found that there was the multiplied effect of heat and radiation in the stress relaxation speed. Therefore the factor of multiplication of heat and radiation was proposed to describe quantitatively the degree of the multiplied effect. The chloroprene rubber used was offered by Hitachi Cable Co., Ltd. The experimental method and the results are reported. The multiplication of heat and radiation is not caused by the direct cut of molecular chains by radiation, instead, it is based on the temperature dependence of various reaction rates at which the activated species reached the cut of molecular chains through complex reaction mechanism and the temperature dependence of the diffusion rate of oxygen in rubber. (Kako, I.)

  8. The effects of progressive muscle relaxation and autogenic relaxation on young soccer players' mood states.

    Science.gov (United States)

    Hashim, Hairul Anuar; Hanafi Ahmad Yusof, Hazwani

    2011-06-01

    This study was designed to compare the effects of two different relaxation techniques, namely progressive muscle relaxation (PMR) and autogenic relaxation (AGR) on moods of young soccer players. sixteen adolescent athletes (mean age: 14.1 ± 1.3) received either PMR or AGR training. Using Profile of Mood States- Adolescents, their mood states were measured one week before relaxation training, before the first relaxation session, and after the twelfth relaxation session. Mixed ANOVA revealed no significant interaction effects and no significant main effects in any of the subscales. However, significant main effects for testing sessions were found for confusion, depression, fatigue, and tension subscales. Post hoc tests revealed post-intervention reductions in the confusion, depression, fatigue, and tension subscale scores. These two relaxation techniques induce equivalent mood responses and may be used to regulate young soccer players' mood states.

  9. The Effects of Progressive Muscle Relaxation and Autogenic Relaxation on Young Soccer Players’ Mood States

    Science.gov (United States)

    Hashim, Hairul Anuar; Hanafi@Ahmad Yusof, Hazwani

    2011-01-01

    Purpose This study was designed to compare the effects of two different relaxation techniques, namely progressive muscle relaxation (PMR) and autogenic relaxation (AGR) on moods of young soccer players. Methods Sixteen adolescent athletes (mean age: 14.1 ± 1.3) received either PMR or AGR training. Using Profile of Mood States- Adolescents, their mood states were measured one week before relaxation training, before the first relaxation session, and after the twelfth relaxation session. Results Mixed ANOVA revealed no significant interaction effects and no significant main effects in any of the subscales. However, significant main effects for testing sessions were found for confusion, depression, fatigue, and tension subscales. Post hoc tests revealed post-intervention reductions in the confusion, depression, fatigue, and tension subscale scores. Conclusion These two relaxation techniques induce equivalent mood responses and may be used to regulate young soccer players’ mood states. PMID:22375225

  10. Vibrational relaxation of matrix-isolated CH3F and HCl

    International Nuclear Information System (INIS)

    Young, L.

    1981-08-01

    Kinetic and spectroscopic studies have been performed on CH 3 F and HCl as a function of host matrix and temperature. Temporally and spectrally resolved infrared fluorescence was used to monitor the populations of both the initially excited state and the lower lying levels which participate in the relaxation process. For CH 3 F, relaxation from any of the levels near 3.5 μ, i.e. the CH stretching fundamentals or bend overtones, occurs via rapid ( 3 with subsequent relaxation of the ν 3 (CF stretch) manifold. Lifetimes of 2ν 3 and ν 3 were determined through overtone, ΔV = 2, and fundamental fluorescence. These lifetimes show a dramatic dependence on host lattice, an increase of two orders of magnitude in going from Xe and Ar matrices. Lifetimes depend only weakly on temperature. The relaxation of 2ν 3 and ν 3 is consistent with a model in which production of a highly rotationally excited guest via collisions with the repulsive wall of the host is the rate limiting step. For HCl, lifetimes of v = 1,2,3 have been determined. In all hosts, the relaxation is non-radiative. For a given vibrational state, v, the relaxation rate increases in the series k(Ar) < k(Kr) < k(Xe). The dependence of the relaxation rate; on v is superlinear in all matrices, the deviation from linearity increasng in the order Ar < Kr < Xe. The relaxation rates become more strongly temperature dependent with increasing vibrational excitation. The results are consistent with a mechanism in which complex formation introduces the anisotropy necessary to induce a near resonant V → R transition in the rate limiting step

  11. Photoconductivity relaxation and electron transport in macroporous silicon structures