• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 305
  • 70
  • 59
  • 43
  • 34
  • 25
  • 13
  • 12
  • 11
  • 9
  • 9
  • 6
  • 4
  • 2
  • 2
  • Tagged with
  • 726
  • 239
  • 121
  • 75
  • 69
  • 61
  • 60
  • 49
  • 46
  • 44
  • 41
  • 36
  • 34
  • 33
  • 32
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Involvement of purinergic P2X and P2Y2 receptors in urinary bladder sensation

Chen, Xiaowei 01 December 2009 (has links)
Interstitial cystitis (IC)/painful bladder syndrome (PBS) is a functional visceral disorder characterized by increased bladder activity and chronic pelvic pain in the absence of a pathobiological condition. Enhanced sensory transduction of peripheral bladder afferents is hypothesized to contribute to the pain and mechanical hypersensitivity of IC/PBS patients. The aim of this thesis is to test the hypothesis that purinergic receptors, including ionotropic P2X and metabotropic P2Y, are important for sensory transmission in bladder afferent neurons and may be involved in bladder hypersensitivity after bladder tissue insults. Electrophysiological, single cell RT-PCR and immunohistochemistry techniques were performed in bladder afferent neurons from naïve and bladder inflamed mice to test the hypothesis. In Chapter 2, I characterized the distribution and function of P2X receptors in thoracolumbar (TL) and lumbosacral (LS) dorsal root ganglia (DRG) neurons innervating the urinary bladder, and found that LS and TL bladder neurons have differential purinergic signaling and distinct membrane electrical properties. In Chapter 3, I examined the sensitization of bladder afferent neurons and the plasticity of P2X receptor function in a mouse model of chemical induced bladder inflammation. P2X-mediated signals in LS and TL bladder neurons after bladder inflammation were enhanced compared with those in saline-treated controls, suggesting the importance of P2X in bladder hypersensitivity associated with cystitis. In Chapter 4, the modulation of P2Y on P2X function and the co-localization of P2Y and P2X were examined in bladder sensory neurons. It has been found that P2Y2 receptor enhances bladder sensory neuron excitability and facilitates the response of homomeric P2X2 receptor to the purinergic agonist (ATP). The present study provides evidence that LS and TL mouse bladder sensory neurons exhibit distinct P2X signaling, and the function of P2X receptors could be facilitated during bladder inflammation and modulated by activation of P2Y2 receptor, indicating an involvement of P2X and P2Y2 receptors as mechano- and chemosensors in bladder sensory transmission under normal conditions and in bladder hypersensitivity associated with inflammation.
92

Evaluation ultrasonore des réparations de structures métalliques par collage de patchs composites.

Le Crom - Levasseur, Bénédicte 10 May 2010 (has links) (PDF)
Cette thèse s'est déroulée dans le contexte de l'évaluation non destructive du collage de patches composites employés pour la réparation de structures aéronautiques. Le besoin a été exprimé par la DGA Techniques Aéronautiques (Toulouse). Le travail effectué a consisté en l'exploitation des ondes guidées, de type SH puis Lamb, pour mesurer des caractéristiques mécaniques d'un joint de colle et tenter d'évaluer, de manière non destructive, la qualité du collage. Dans un premier temps, les propriétés viscoélastiques des matériaux assemblés sont déterminées. Elles servent alors de données d'entrée à des modèles, basés sur la méthode SAFE (Semi Analytical Finite Element method), permettant d'obtenir les courbes de dispersion ainsi que les champs des différents modes guidés se propageant le long de l'assemblage collé. Ces simulations numériques permettent alors d'évaluer le potentiel des ondes guidées à caractériser un adhésif. Des mesures expérimentales sont ensuite menées pour confirmer les prédictions numériques. Finalement la résolution d'un problème inverse, qui consiste à évaluer les modules de rigidité de la couche de colle se situant entre une plaque d'aluminium et un patch, est proposée pour établir des pistes d'évaluation non destructive d'un collage répondant au besoin industriel. Cette étude a été financée par la DGA, France.
93

The expression of thermoTRP channels in the brood patch of jungle fowl (<em>Gallus gallus</em>) during egg incubation

Jafari, Shadi January 2009 (has links)
<p> </p><p>The regulation of egg temperature requires the transfer of heat from the brood patch. Thus, the brood patch needs the presence of thermo receptors as well as an appropriate vasomotor response. During the incubation an exact detection of the egg’s temperature is essential. So, in this study we attempted to detect the presence and regulation of the expressionof  thermoTRP channels (thermo Transient Receptor Potential channels) (TRPV1, TRPV3, TRPV4, TRPM8 and TRPA1) during egg incubation. Six incubating Jungle fowl hens, and five non incubating jungle fowl hens and one jungle fowl cock were used as main samples and controls. Total RNA was extracted from liver, kidney, heart, blood, White Blood Cell, Dorsal Root Ganglion and skin. The samples from the skin were taken from the brood patch and inter scapular region. PCR investigation showed that different thermo TRP channels were expressed in different tissues. TRPV1, V3, V4 and M8 mRNA were detected in the skin of brood patch. However, V1 and V3 expression in the brood patch skin did not differ between broody and non broody hens. In conclusion, although considerable morphological changes in the skin of brood patch could be seen, the expression of TRPV1 and V3 channels did not change significantly, but this cannot exclude the alteration in the expression of TRP channels in different stages of broodiness or specific parts of skin like AVAs (Arteriovenous anastomosis) which will be the subject for more studies.</p>
94

The Impact of CYP2A6 Genotype on Smoking Cessation in an Extended Nicotine Patch Therapy Clinical Trial

Mroziewicz, Margaret 15 February 2010 (has links)
We investigated the efficacy of standard (8-week nicotine, 16-week placebo) vs extended (24-week nicotine) patch therapy for smoking cessation, and the effect of slow nicotine metabolism, indicated by CYP2A6 reduced metabolizer (RM) genotype or low 3-hydroxycotinine/cotinine ratio (3HC/COT), on abstinence. RM versus normal genotype predicted lower 3HC/COT. Extended vs standard treatment produced higher abstinence at 24 weeks (32% vs 20%), but not at 52 weeks (both 14%). Low 3HC/COT and RM genotype predicted higher abstinence on extended versus standard treatment at 24 (47% vs 25%, 38% vs 17%) and 28 weeks (34% vs 19%, 23% vs 11%), while high 3HC/COT or normal genotype did not. Within extended treatment, low versus high 3HC/COT predicted higher abstinence at 8 (48% vs 29%), 24 (47% vs 25%), and 28 weeks (34% vs 16%), with similar trends for the genotype effect. Overall, extending nicotine treatment increased abstinence during therapy, particularly for slow metabolizers.
95

The Impact of CYP2A6 Genotype on Smoking Cessation in an Extended Nicotine Patch Therapy Clinical Trial

Mroziewicz, Margaret 15 February 2010 (has links)
We investigated the efficacy of standard (8-week nicotine, 16-week placebo) vs extended (24-week nicotine) patch therapy for smoking cessation, and the effect of slow nicotine metabolism, indicated by CYP2A6 reduced metabolizer (RM) genotype or low 3-hydroxycotinine/cotinine ratio (3HC/COT), on abstinence. RM versus normal genotype predicted lower 3HC/COT. Extended vs standard treatment produced higher abstinence at 24 weeks (32% vs 20%), but not at 52 weeks (both 14%). Low 3HC/COT and RM genotype predicted higher abstinence on extended versus standard treatment at 24 (47% vs 25%, 38% vs 17%) and 28 weeks (34% vs 19%, 23% vs 11%), while high 3HC/COT or normal genotype did not. Within extended treatment, low versus high 3HC/COT predicted higher abstinence at 8 (48% vs 29%), 24 (47% vs 25%), and 28 weeks (34% vs 16%), with similar trends for the genotype effect. Overall, extending nicotine treatment increased abstinence during therapy, particularly for slow metabolizers.
96

Modulation of Kir6.1 channels heterologously expressed in HEK-293 cells by nicotine and acetylocholine

Hanna, Salma Toma 04 January 2005
ATP-sensitive K+ channels (KATP) channels were first described in the cardiac muscles. KATP channels are a complex of regulatory sulphonylurea receptor subunits and pore-forming inward rectifier subunits such as Kir6.1. Nicotine, an exogenous substance, adversely affects cardiovascular function in humans. Acetylcholine (ACh) is well known as a key neurotransmitter of the parasympathetic nervous system. ACh effects are usually related to binding to muscarinic receptors and stimulating second messengers that relay and direct the extracellular signals to different intracellular destinations, resulting in modulated cellular activity. We hypothesize that nicotine and ACh may modulate Kir6.1 channels via different mechanisms. Using the whole cell patch-clamp technique, the interactions of nicotine and ACh with Kir6.1 subunit permanently expressed in Human Embryonic Kidney (HEK-293) cells as well as the underlying mechanisms were studied.<p> Non-transfected HEK-293 cells possess an endogenous K+ current with current density of 3.2 ± 1.4 pA/pF at 150 mV (n = 9). Stable expression of Kir6.1 subunits cloned from rat mesenteric artery in HEK-293 cells yielded a detectable inward rectifier KATP current (-23.9 ± 1.6 pA/pF at 150 mV, n = 6). In the presence of 0.3 mM ATP in the pipette solution, nicotine at 30 and 100 µM increased the expressed Kir6.1 currents by 42 ± 11.8 and 26.2 ± 14.6%, respectively (n = 4-6, p<0.05). In contrast, nicotine at 1-3 mM inhibited Kir6.1 currents (p<0.05). Nicotine at 100 µM increased the production of superoxide anion (O2.-) by 20.3 ± 5.7% whereas at 1 mM it significantly decreased the production of O2.- by 37.7 ± 4.3%. The hypoxanthine/xanthine oxidase (HX/XO) reaction was used as a source of O2.-. Co-application of HX and XO to the transfected HEK-293 cells resulted in a significant and reproducible increase in Kir6.1 currents. Tempol, a scavenger of O2.-, abolished the stimulatory effect of HX/XO on Kir6.1 currents. Tempol also abolished the stimulatory effect of 30 mM nicotine on Kir6.1 currents (-28.3 ± 6.1 pA/pF vs. -31.2 ± 7.3 pA/pF at -150 mV, n = 6-9 for each group, p>0.05). <p> In the presence of 0.3 mM ATP in the pipette solution, ACh concentration-dependently increased the expressed Kir6.1 currents. At 1 µM, ACh increased Kir6.1 currents from -19 ± 2.5 to 31.7 ± 2.1 pA/pF (n = 8, p < 0.05). Pretreatment of the transfected HEK-293 cells with either 2 or 20 µM atropine, 100 nM a-bungarotoxin, 100 µM mecamylamine, 2 µM prazosin, 1 µM propranolol, or 10 µM dihydro-b-erythroidine hydrobromide did not alter the stimulatory effect of ACh on Kir6.1 currents (n = 4 - 5 for each group, p<0.05). When intracellular ATP was increased to 5 mM, ACh at 10 µM still exhibited its stimulatory effect (-16.4 ± 2.3 to 25.5 ± 3.8 pA/pF, n = 8, p<0.05). For the first time, the present study provides an insight for the interactions of nicotine and ACh with Kir6.1 subunits. Our data demonstrate that micromolar concentration of nicotine and ACh stimulated Kir6.1 channels. Nicotine at millimolar concentrations inhibited Kir6.1 channels. The dual effect of nicotine, not mediated by nAChR, are mediated partially by O2.- levels in the cells. The ACh excitatory effect is mediated neither by an AChR-dependent mechanism, nor by alteration in ATP metabolism. This study challenges the traditional explanations for the receptor-mediated effects of nicotine and ACh on ion channels and opens a new door to understand the effects of nicotine and ACh on KATP channels in many cellular systems.
97

The expression of thermoTRP channels in the brood patch of jungle fowl (Gallus gallus) during egg incubation

Jafari, Shadi January 2009 (has links)
The regulation of egg temperature requires the transfer of heat from the brood patch. Thus, the brood patch needs the presence of thermo receptors as well as an appropriate vasomotor response. During the incubation an exact detection of the egg’s temperature is essential. So, in this study we attempted to detect the presence and regulation of the expressionof  thermoTRP channels (thermo Transient Receptor Potential channels) (TRPV1, TRPV3, TRPV4, TRPM8 and TRPA1) during egg incubation. Six incubating Jungle fowl hens, and five non incubating jungle fowl hens and one jungle fowl cock were used as main samples and controls. Total RNA was extracted from liver, kidney, heart, blood, White Blood Cell, Dorsal Root Ganglion and skin. The samples from the skin were taken from the brood patch and inter scapular region. PCR investigation showed that different thermo TRP channels were expressed in different tissues. TRPV1, V3, V4 and M8 mRNA were detected in the skin of brood patch. However, V1 and V3 expression in the brood patch skin did not differ between broody and non broody hens. In conclusion, although considerable morphological changes in the skin of brood patch could be seen, the expression of TRPV1 and V3 channels did not change significantly, but this cannot exclude the alteration in the expression of TRP channels in different stages of broodiness or specific parts of skin like AVAs (Arteriovenous anastomosis) which will be the subject for more studies.
98

Design of an Antenna for a Wireless Sensor Network for Trains

Hinnemo, Malkolm January 2011 (has links)
An antenna for a wireless sensor network for trains is designed and built. The network will monitor temperature and vibrations of the wheel bearings on the train wagons. Doing this will allow for an earlier detection of damaged wheels, which will ease planning of maintenance and reduce wear on the rails considerably. The requirement of the system is that it is to be installed without any cables attached to the sensor nodes. This calls for wireless communication, and that for that antennas are needed.A train is a difficult environment to transmit electromagnetic (EM) waves in. It is full of metal and EM-waves cannot pass through a conducting material. Having much metal in its vicinity also affects the function of the antenna. This needs to be taken into consideration when making the design.The constructed antenna is a small dual-layer patch antenna. Dual layer means that it is constructed out of two sheets known as substrates of isolating material with different characteristics. The lower one of these substrates is made in such a way that integration with a circuit board is possible. Such integration would reduce the production cost considerably. The antenna is designed for direct placement on a conducting surface. This surface could be part of the train. It uses the surrounding metal as a ground plane in order to reduce its size. The result is a small patch antenna with good radiation qualities in metallic surroundings. The longest side is 18.35 mm, equaling 14.9 % of the wavelength that the antenna is designed for. / WISENET
99

Modulation of Kir6.1 channels heterologously expressed in HEK-293 cells by nicotine and acetylocholine

Hanna, Salma Toma 04 January 2005 (has links)
ATP-sensitive K+ channels (KATP) channels were first described in the cardiac muscles. KATP channels are a complex of regulatory sulphonylurea receptor subunits and pore-forming inward rectifier subunits such as Kir6.1. Nicotine, an exogenous substance, adversely affects cardiovascular function in humans. Acetylcholine (ACh) is well known as a key neurotransmitter of the parasympathetic nervous system. ACh effects are usually related to binding to muscarinic receptors and stimulating second messengers that relay and direct the extracellular signals to different intracellular destinations, resulting in modulated cellular activity. We hypothesize that nicotine and ACh may modulate Kir6.1 channels via different mechanisms. Using the whole cell patch-clamp technique, the interactions of nicotine and ACh with Kir6.1 subunit permanently expressed in Human Embryonic Kidney (HEK-293) cells as well as the underlying mechanisms were studied.<p> Non-transfected HEK-293 cells possess an endogenous K+ current with current density of 3.2 ± 1.4 pA/pF at 150 mV (n = 9). Stable expression of Kir6.1 subunits cloned from rat mesenteric artery in HEK-293 cells yielded a detectable inward rectifier KATP current (-23.9 ± 1.6 pA/pF at 150 mV, n = 6). In the presence of 0.3 mM ATP in the pipette solution, nicotine at 30 and 100 µM increased the expressed Kir6.1 currents by 42 ± 11.8 and 26.2 ± 14.6%, respectively (n = 4-6, p<0.05). In contrast, nicotine at 1-3 mM inhibited Kir6.1 currents (p<0.05). Nicotine at 100 µM increased the production of superoxide anion (O2.-) by 20.3 ± 5.7% whereas at 1 mM it significantly decreased the production of O2.- by 37.7 ± 4.3%. The hypoxanthine/xanthine oxidase (HX/XO) reaction was used as a source of O2.-. Co-application of HX and XO to the transfected HEK-293 cells resulted in a significant and reproducible increase in Kir6.1 currents. Tempol, a scavenger of O2.-, abolished the stimulatory effect of HX/XO on Kir6.1 currents. Tempol also abolished the stimulatory effect of 30 mM nicotine on Kir6.1 currents (-28.3 ± 6.1 pA/pF vs. -31.2 ± 7.3 pA/pF at -150 mV, n = 6-9 for each group, p>0.05). <p> In the presence of 0.3 mM ATP in the pipette solution, ACh concentration-dependently increased the expressed Kir6.1 currents. At 1 µM, ACh increased Kir6.1 currents from -19 ± 2.5 to 31.7 ± 2.1 pA/pF (n = 8, p < 0.05). Pretreatment of the transfected HEK-293 cells with either 2 or 20 µM atropine, 100 nM a-bungarotoxin, 100 µM mecamylamine, 2 µM prazosin, 1 µM propranolol, or 10 µM dihydro-b-erythroidine hydrobromide did not alter the stimulatory effect of ACh on Kir6.1 currents (n = 4 - 5 for each group, p<0.05). When intracellular ATP was increased to 5 mM, ACh at 10 µM still exhibited its stimulatory effect (-16.4 ± 2.3 to 25.5 ± 3.8 pA/pF, n = 8, p<0.05). For the first time, the present study provides an insight for the interactions of nicotine and ACh with Kir6.1 subunits. Our data demonstrate that micromolar concentration of nicotine and ACh stimulated Kir6.1 channels. Nicotine at millimolar concentrations inhibited Kir6.1 channels. The dual effect of nicotine, not mediated by nAChR, are mediated partially by O2.- levels in the cells. The ACh excitatory effect is mediated neither by an AChR-dependent mechanism, nor by alteration in ATP metabolism. This study challenges the traditional explanations for the receptor-mediated effects of nicotine and ACh on ion channels and opens a new door to understand the effects of nicotine and ACh on KATP channels in many cellular systems.
100

Studies on the spatial distribution of coral communities in Dongsha Lagoon

Huang, Teng-yi 05 February 2010 (has links)
The purpose of this study is to investigate the factors that are responsible for the distribution of coral communities in the lagoon of the Dongsha Atoll. Previous surveys proposed that there was significant difference of coral cover between the east and west sides of the lagoon. Two hypotheses, seawater temperature and water depth, were proposed to explain the spatial variation of coral distribution. In addition, the growth rate of poritid corals, coral recruits, sexual reproduction, and the occurrence of coral predators and diseases were also studied. Ten patch reefs 5 on the west and 5 on the east sides in the lagoon were selected and the corals on reef tops (1-3 m) and deep reef bases (10-15 m) were investigated. The growth rates of poritid corals on reef tops were higher on reef bases than those on reef tops, and higher in eastern lagoon than those in western lagoon. On average, the growth rate is 0.9 cm/year. A total of 10 families of small corals were recorded in which Faviidae (61.6%), Fungiidae (16.6%) and Poritidae (9.7%) constituted the majority. Diversity index comparisons indicated that reef bases have higher diversities than reef tops. The densities of small corals, ranging between 0.1-3.0 ind./m2, are higher on reef bases than on reef tops. In fungiids, individuals in the eastern lagoon were larger than those in the western lagoon. Tissues of corals were sampled in June 2009 for examination of gonads. However, no reproductive tissues were found after decalcification and histology. The morphological classes, live-coral coverage, dead-coral coverage and dead-coral ratio among the comparisons of reef bases vs reef tops and western vs eastern lagoons, only dead-coral coverage was found to be higher in eastern than in western lagoon. The live-coral coverage was 0.3-46%, dead-coral coverage was 8%-76% and dead-coral ratio was 10%-100%. Among the 10 patch reefs, patch reefs 6, 7, 9 and 10 are represented by mostly K type competitors and belongs to Conservation Class 2, patch reefs 1, 2 and 3 are presented by mostly S type stress-tolerated corals and belongs to Conservation Class 1. The remaining 3 patch reefs 4, 5 and 8 belong to the highest Conservation Class 4 and are represented by diverse types of corals. The water temperature exceeded 30¢XC in 36% of the time at reef tops, and 13% of the time at reef bases, during the summer period, i.e., between June and September, 2009. And the water temperatures were found in 95% of the time to be ~ 1¢XC higher at reef tops than at reef bases. The water temperatures were also higher in the west than in the east of the lagoon that 29% of the time exceeded 30¢XC in the west and 9% in the east only. No coral diseases or pests were found that may pose a large-scale threat in the near future. The variations of coral fauna found among habitats in the lagoon are consistent with the temperature patterns, i.e., the higher the temperature the poorer the coral condition. To the two hypothesis, in the eastern or western lagoon and the different depth are the factors of coral distribution in the lagoon.

Page generated in 0.0332 seconds