Dissertations / Theses on the topic 'Length Contraction'
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Almasri, Atheer. "MECHANICAL BEHAVIOR AND LENGTH ADAPTATION OF RABBIT BLADDER SMOOTH MUSCLE." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1967.
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Overactive bladder (OAB), involuntary contractions during bladder filling, is a common condition affecting 17% of the adult population worldwide, and in the U.S. ranks ahead of diabetes in a list of the 10 most common chronic disorders (Mullins 2009). Mechanical mechanisms contributing to OAB are not completely understood and because of the unique function and broad volume range of the bladder, there may be mechanical characteristics that distinguish detrusor smooth muscle (DSM) in bladder from other smooth muscles. Recent studies have shown that the length-passive tension curve in DSM exhibits adjustable passive stiffness (APS) characterized by a passive curve that can be shifted along the length axis as a function of strain history and activation history; however, the mechanical mechanisms responsible for APS remain to be determined. Also, whether DSM exhibits a dynamic length-active tension relationship, as has been identified in airway and vascular smooth muscles, has not been investigated. This dissertation focused on both the passive and active length-tension relationships in DSM and the mechanical mechanisms responsible for these relationships. The first objective was to study the impact of APS on the length-total tension relationship and identify the mechanical mechanisms responsible for generating APS. The second objective was to determine whether the length-active tension relationship is adaptive and identify specific mechanical mechanisms contributing to any adaptive behavior. The results showed that a shift in the length-passive tension curve due to APS corresponded with a shift in the length-total tension curve in DSM, and that APS was 27.0±8.4% of active tension at the optimum length for active tension generation. Most importantly, low-grade rhythmic contraction (RC), which can occur spontaneously in rabbit and human bladders, regenerated APS. Results also showed that the length-active tension curve shifted due to stretch to and then activation at long lengths, as well as either multiple KCl-induced maximal contractions or RC. Thus, DSM exhibits length adaptation, and RC may contribute to both APS and length adaptation. Because increased RC has been correlated with OAB, understanding RC, APS and length-adaptation in bladder may enable the identification of specific targets for new treatments for OAB.
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Pulcastro, Hannah C., Peter O. Awinda, Mei Methawasin, Henk Granzier, Wenji Dong, and Bertrand C. W. Tanner. "Increased Titin Compliance Reduced Length-Dependent Contraction and Slowed Cross-Bridge Kinetics in Skinned Myocardial Strips from Rbm20ΔRRM Mice." FRONTIERS MEDIA SA, 2016. http://hdl.handle.net/10150/621415.
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Titin is a giant protein spanning from the Z-disk to the M-band of the cardiac sarcomere. In the I-band titin acts as a molecular spring, contributing to passive mechanical characteristics of the myocardium throughout a heartbeat. RNA Binding Motif Protein 20 (RBM20) is required for normal titin splicing, and its absence or altered function leads to greater expression of a very large, more compliant N2BA titin isoform in Rbm20 homozygous mice (Rbm20(Delta RRm)) compared to wild-type mice (WT) that almost exclusively express the stiffer N2B titin isoform. Prior studies using Rbm20(Delta RRm) animals have shown that increased titin compliance compromises muscle ultrastructure and attenuates the Frank-Starling relationship. Although previous computational simulations of muscle contraction suggested that increasing compliance of the sarcomere slows the rate of tension development and prolongs cross-bridge attachment, none of the reported effects of Rbm20(Delta RRm) on myocardial function have been attributed to changes in cross-bridge cycling kinetics. To test the relationship between increased sarcomere compliance and cross-bridge kinetics, we used stochastic length-perturbation analysis in Ca2+-activated, skinned papillary muscle strips from Rbrn20<^>R'Rm and WT mice. We found increasing titin compliance depressed maximal tension, decreased Ca2+-sensitivity of the tension-pCa relationship, and slowed myosin detachment rate in myocardium from Rbm20(Delta RRm) vs. WT mice. As sarcomere length increased from 1.9 to 2.2 mu m, length-dependent activation of contraction was eliminated in the Rbrn20<^>R'Rm myocardium, even though myosin MgADP release rate decreased similar to 20% to prolong strong cross-bridge binding at longer sarcomere length. These data suggest that increasing N2BA expression may alter cardiac performance in a length-dependent manner, showing greater deficits in tension production and slower cross-bridge kinetics at longer sarcomere length. This study also supports the idea that passive mechanical characteristics of the myocardium influence ensemble cross-bridge behavior and maintenance of tension generation throughout the sarcomere.
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Sagit, Rauan. "Variation in length of proteins by repeats and disorder regions." Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-88553.
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Protein-coding genes evolve together with their genome and acquire changes, some of which affect the length of their protein products. This explains why equivalent proteins from different species can exhibit length differences. Variation in length of proteins during evolution arguably presents a large number of possibilities for improvement and innovation of protein structure and function. In order to contribute to an increased understanding of this process, we have studied variation caused by tandem domain duplications and insertions or deletions of intrinsically disordered residues. The study of two proteins, Nebulin and Filamin, together with a broader study of long repeat proteins (>10 domain repeats), began by confirming that tandem domains evolve by internal duplications. Next, we show that vertebrate Nebulins evolved by duplications of a seven-domain unit, yet the most recent duplications utilized different gene parts as duplication units. However, Filamin exhibits a checkered duplication pattern, indicating that duplications were followed by similarity erosions that were hindered at particular domains due to the presence of equivalent binding motifs. For long repeat proteins, we found that human segmental duplications are over-represented in long repeat genes. Additionally, domains that have formed long repeats achieved this primarily by duplications of two or more domains at a time. The study of homologous protein pairs from the well-characterized eukaryotes nematode, fruit fly and several fungi, demonstrated a link between variation in length and variation in the number of intrinsically disordered residues. Next, insertions and deletions (indels) estimated from HMM-HMM pairwise alignments showed that disordered residues are clearly more frequent among indel than non-indel residues. Additionally, a study of raw length differences showed that more than half of the variation in fungi proteins is composed of disordered residues. Finally, a model of indels and their immediate surroundings suggested that disordered indels occur in already disordered regions rather than in ordered regions.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In press. Paper 4: Manuscript.
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Nordlund, Maria M. "On spinal mechanisms for reflex control in man : modulation of Ia-afferent excitation with changes in muscle length, activation level and fatigue /." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7349-821-1/.
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Tillin, Neale A. "The influence of training and athletic performance on the neural and mechanical determinants of muscular rate of force development." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8524.
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Neuromuscular explosive strength (defined as rate of force development; RFD) is considered important during explosive functional human movements; however this association has been poorly documented. It is also unclear how different variants of strength training may influence RFD and its neuromuscular determinants. Furthermore, RFD has typically been measured in isometric situations, but how it is influenced by the types of contraction (isometric, concentric, eccentric) is unknown. This thesis compared neuromuscular function in explosive power athletes (athletes) and untrained controls, and assessed the relationship between RFD in isometric squats with sprint and jump performance. The athletes achieved a greater RFD normalised to maximum strength (+74%) during the initial phase of explosive contractions, due to greater agonist activation (+71%) in this time. Furthermore, there were strong correlations (r2 = 0.39) between normalised RFD in the initial phase of explosive squats and sprint performance, and between later phase absolute explosive force and jump height (r2 = 0.37), confirming an association between explosive athletic performance and RFD. This thesis also assessed the differential effects of short-term (4 weeks) training for maximum vs. explosive strength, and whilst the former increased maximum strength (+20%) it had no effect on RFD. In contrast explosive strength training improved explosive force production over short (first 50 ms; +70%) and long (>50 ms; +15%) time periods, due to improved agonist activation (+65%) and maximum strength (+11%), respectively. Explosive strength training therefore appears to have greater functional benefits than maximum strength training. Finally, the influence of contraction type on RFD was assessed, and the results provided unique evidence that explosive concentric contractions are 60% more effective at utilising the available force capacity of the muscle, that was explained by superior agonist activation. This work provides a comprehensive analysis of the association between athletic performance and RFD, the differential effects of maximum vs. explosive strength training, and the influence of contraction type on the capacity for RFD.
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Kluka, Virginie. "Etude des propriétés neuromusculaires chez l'enfant : approche par la stimulation magnétique périphérique." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22649/document.
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L’objectif de ce travail était de comparer l’importance de la composante nerveuse dans les différences de production de force entre les enfants et les adultes en tenant compte des conditions mécaniques qui sont susceptibles de l’influencer (longueur musculaire, mode et vitesse de contraction) et des effets de la fatigue. Trente et un garçons pré-pubères de 8-12 ans et 37 hommes de 18-30 ans ont été recrutés et répartis dans les 3 études composant ce projet. La première étude portait sur les effets de la longueur musculaire et de la fatigue sur la production de force et le niveau d’activation maximal volontaire (VA) des extenseurs du genou.La seconde traitait des effets de la longueur musculaire sur la production de force et le VA des fléchisseurs plantaires. Enfin, la troisième portait sur les effets du mode et de la vitesse de contraction sur le VA des extenseurs du genou. Les propriétés neuromusculaires ont été évaluées à l’aide de stimulations magnétiques périphériques et de contractions maximales volontaires. Les résultats montrent un VA des extenseurs du genou supérieur chez l’adulte lors de grande longueur musculaire (90°-100° de flexion) (étude 1), mais aucune différence avec l’enfant à courte longueur musculaire (20° de flexion). En revanche, sur des groupes musculaires tels que les fléchisseurs plantaires, aucun effet de la longueur sur le VA n’a été observé chez les enfants et les adultes (étude 2). En ce qui concerne les effets du mode de contraction, nos résultats montrent que le VA est inférieur en conditions excentrique et concentrique par rapport à la condition isométrique, mais aucune différence n’était observée entre les groupes (étude 3). Toutefois, l’effet de cette baisse de VA sur la production de force variait entre les groupes ; une diminution de force accompagnant la diminution de VA n’était retrouvée que chez l’adulte. Enfin,nous avons montré que la baisse du VA au cours d’un protocole de fatigue est plus conséquente chez les enfants par rapport aux adultes (étude 1), ce qui témoigne de l’existence d’une fatigue centrale majorée chez l’enfant. Une maturation inaboutie et les propriétés musculo-tendineuses particulières de l’enfant (compliance supérieure) pourraient expliquer les résultats obtenus au cours de ce travailThe purpose of this PhD thesis was to compare the contribution of the maximal voluntary activation level (VA) of the motor units to force production differences between children and adults in various mechanical conditions that affect force production (muscle length, contraction mode and velocity), and in fatigue condition. Thirty one pre-pubertal 8 to 12-year old boys and 37 men (18-30 years) were recruited and allocated into the 3 studies ofthis project. The first study was devoted to compare the effects of muscle length and fatigue on the VA and force generating capacity of the knee extensors between children and adults. In the second study, we compared the effects of muscle length on the VA and force generating capacity of the plantar flexors between children and adults. The third study analysed the effect of contraction mode and velocity on the VA and force generating capacity of the knee extensors between children and adults. Neuromuscular properties were assessed with peripheral magnetic stimulation and maximal voluntary contractions. Results showed a higher VA of the knee extensors in adults at long muscle length (90° and 100° knee flexion) but no difference between children and adults at short length (20° knee flexion; study 1). However, the VA of the plantar flexors was not affected by muscle length changes whatever the age group considered (study 2). Results also showed a higher VA in isometric mode compared to eccentric and concentric conditions whatever the age group (study 3). However, the effect of this VA reduction on force generating capacity differed between groups, a concomitant force reduction being observed in adults, but not in children. Finally, we observed a greater VA reduction and therefore greater central fatigue in children during the fatiguing protocol (study 1). A relative immaturity and the particular musculo-tendinous properties of children (higher compliance) may account for the reported results
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WANG, YUJEN. "SOFT POLYELECTROLYTE HYDROGEL AS VERSATILE MATERIAL IN DIFFERENT APPLICATION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1469459792.
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Kosterina, Natalia. "Muscular force production during non-isometric contractions : towards numerical muscle modeling /." Licentiate thesis, Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10672.
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Pun, Clara. "History-dependent properties of skeletal muscle myofibrils contracting along the ascending limb of the force-length relationship." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92265.
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Liu, Jeffrey Chao-Yu. "Length distribution of myosin filaments in smooth muscle and implications in the structure and function of contractile units." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52272.
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Smooth muscle is an essential component of the walls of numerous hollow or tubular organs throughout the body, including blood vessels, airways, and the bladder. Proper physiological functioning of these organs relies heavily on the appropriate activation and contraction of the smooth muscle tissue. Pathophysiological conditions may arise from both excessive and insufficient smooth muscle contraction.
Muscle function is closely associated with muscle structure. More specifically, during a contraction, cyclic interactions between myosin cross-bridges and actin filaments allow for muscle shortening and force generation. Myosin molecules from smooth muscle and non-muscle cells are known to self-assemble into side-polar filaments in vitro. However the in situ mechanism of filament assembly is not clear and the question of whether there is a unique length for myosin filaments in smooth muscle is still under debate. In this study we measured the lengths of 16,587 myosin filaments in three types of smooth muscle cells using serial electron microscopy (EM). Sheep airway and pulmonary arterial smooth muscle as well as rabbit carotid arterial smooth muscle were fixed for EM and serial ultra-thin (50-60 nm) sections were obtained. Myosin filaments were traced in consecutive sections to determine their lengths. The results indicate that there is not a single length for the myosin filaments; instead there is a wide variation in lengths. The plots of observation frequency versus myosin filament length follow an exponential decay pattern.
The most significant finding of this study is that myosin filaments in smooth muscle do not have a uniform length and analysis suggests that the distribution of filament length is a result of a dynamic equilibrium between polymerization and de-polymerization of myosin molecules driven by predictable probabilities of the myosin dimers to bind with and dissociate from each other.Medicine, Faculty of
Medicine, Department of
Experimental Medicine, Division of
Graduate
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Sharifnezhad, Ali. "Longitudinal adaptation of vastus lateralis muscle in response to eccentric exercise." Doctoral thesis, Humboldt-Universität zu Berlin, Philosophische Fakultät IV, 2014. http://dx.doi.org/10.18452/16918.
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In der vorliegenden Studie wurde daher den Einfluss exzentrischen Trainings, mit unterschiedlicher Reizmagnitude, Bewegungsgeschwindigkeit und Muskellänge bei Reizapplikation, auf die Adaptation des M. vastus lateralis (VL) untersucht. Die 31 Studienteilnehmer wurden randomisiert in zwei Trainings- und eine Kontrollgruppe aufgeteilt. Die Trainingsgruppen führten 30 Trainingseinheiten mit exzentrischem Training der Knieextensoren an einem Isokineten durch. Gruppe 1 (n=10) trainierte ein Bein mit 65% der maximalen willkürlichen isometrischen Kontraktion (MVC) und das andere Bein mit 100% MVC, bei einer Winkelgeschwindigkeit von 90°/s und einem Kniewinkel von 25°-100°. Gruppe 2 (n=10) trainierte beide Beine mit 100% MVC, ein Bein aber mit einer Winkelgeschwindigkeit von 90°/s in einem Kniewinkel von 25°-65° und das andere Bein mit 240°/s und 25°-100°. In der Pre- und Postmessung wurde die VL Muskelfaserlänge mittels Ultraschall bestimmt und die Moment-Winkel- und Leistungs-Winkelgeschwindigkeitsrelation mit einem Dynamometer erfasst. Die Ergebnisse zeigen nur für Bein mit 240°/s eine signifikante (pThe present study investigated the effects of magnitude, velocity and muscle length at which the eccentric stimulus is applied on the longitudinal adaptation of the vastus lateralis muscle (VL). The 31 participants were randomly assigned into two experimental groups to perform 30 sessions of eccentric training for the knee extensors (3 times/week) and one control group. The first experimental group (n=10) exercised one leg at 65% of maximum voluntary isometric contraction (MVC) and the second leg at 100% MVC at 90°/s from 25° to 100° knee angle on an isokinetic device (Biodex 3). The second experimental group (n=10) exercised one leg at 100% MVC at 90°/s from 25° to 65° knee angle and the other leg at 100% MVC at an angular velocity of 240°/s from 25° to 100° knee angle. In pre and post measurements the fascicle length of the VL was examined by ultrasonography and the moment-angle and power-angular velocity relationship of the knee extensors with a dynamometer. The results showed an increase (p
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Ekstrand, Mathias. "The effects of muscle damaging electrically stimulated contractions and ibuprofen on muscle regeneration and telomere lengths in healthy sedentary males." Thesis, Örebro universitet, Institutionen för hälsovetenskap och medicin, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-27906.
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Introduction: The effect of electrical stimulation on muscle degeneration and regeneration is largely unknown and it has not been studied in conjunction with telomeres. The consumption of non-steroidal anti-inflammatory drugs (NSAIDs) is widespread in athletes and the general population when faced with muscle soreness or injury. Furthermore, the effect of NSAIDs on muscle regeneration is controversial and its effect on telomere lengths is also unknown. Methods: Young adult males performed 200 electrically stimulated maximal isokinetic contractions with one leg (ES) and the other worked as a control (CON). They received either 1200mg ibuprofen (IBU) per day or placebo (PLA) from 21 days pre- to 30 days post-exercise. Muscle biopsies were obtained from the vastus lateralis of the CON leg at baseline (H0) and ES leg at 2.5h (H2.5) and both legs at 2, 7 and 30 days post-exercise. Blood samples were obtained at the same time points and at day 4 post-exercise. Afterwards the muscle and blood specimen were analysed for skeletal muscle and peripheral blood telomere lengths by Southern blot and signs of muscle degeneration and regeneration were quantified histologically. Results: Histological changes occurred in the ES leg, including; increased proportion of damaged myofibres (2.1±2.8%) and infiltrated myofibres (5.0±6.0%) at day 7, small myofibres (3.0±4.4%) and internally located myonuclei (2.9±3.1%) at day 30. The IBU group had significantly less internally located myonuclei at day 30 compared to PLA (1.7±2.4% vs. 4.1±3.8%). No significant differences were observed in skeletal muscle mean and minimum telomere lengths between ES and CON leg, between IBU and PLA group or between time points. Peripheral blood mean telomere lengths were not significantly different between IBU and PLA group, but between time points; H0 (9.6±1.2kb) and H2.5 (9.1±1.1kb) were significantly shorter than day 4 (10.3±1.6kb) and day 7 (10.1±1.5kb) (P<0.05). Conclusion: Electrically stimulated contractions caused significant muscle degeneration and regeneration in the 30 days post-exercise. Electrical stimulation also appeared to cause fluctuations in peripheral blood telomere lengths, but not skeletal muscle telomeres. The intake of ibuprofen appeared to interfere with muscle regeneration, but did not seem to affect the peripheral blood or skeletal muscle telomeres. However, due to marked individual variations and the small participant group it is difficult to conclude on the effects of electrical stimulation and ibuprofen on proliferative potential. Further studies are warranted to elucidate the effects of electrical stimulation and ibuprofen on blood and skeletal muscle telomeres.
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Borrani, Fabio. "Mécanismes de la cinétique de la composante lente de VO2 chez l'homme : hypothèse d'un recrutement de fibres rapides." Montpellier 1, 2002. http://www.theses.fr/2002MON14001.
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L'objectif de ce travail etait d'investiguer la nature des mecanismes responsables de la composante lente (cl) de la consommation d'oxygene (vo2) lors d'exercices a intensite superieure au seuil d'accumulation du lactate sanguin. Conformement a l'hypothese la plus souvent evoquee, notre attention s'est essentiellement orientee sur le recrutement progressif de fibres rapides au fur et a mesure que les fibres lentes actives des le debut de l'exercice atteignent un etat d'epuisement. Pour cela trois etudes ont ete realisees. La premiere concerne l'effet d'un exercice sur tapis roulant a 95% de la consommation maximale d'oxygene mene jusqu'a epuisement. [. . . ] finalement, la derniere etude a permis de preciser les mecanismes en testant si le recrutement progressif de nouvelles fibres musculaires etait du au moins en partie a une augmentation du travail mecanique lors de cl. D'une maniere surprenante, l'epuisement survenait sans qu'il y ait une deterioration du cout mecanique (p<0. 05). Nos resultats suggerent que l'exces de consommation d'oxygene est davantage lie a la force verticale developpee pendant le temps de contact et/ou a une alteration de la quantite d'energie stockee et restituee par les complexes muscle-tendon.
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GARCIA, LUIS. "Implication du canal ca#2#+ lent dans le couplage excitation-contraction du muscle squelettique : etude d'une mutation murine spontannee affectant ce couplage." Paris 7, 1989. http://www.theses.fr/1989PA077057.
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Etude des relations spatio-temporelles entre l'expression des canaux ca#2#+ (ontogenese et localisation) et la morphogenese des triades au cours de la myogenese in vitro. Analyse comparative des proprietes d'inactivation du canal ca#2#+ et du couplage excitation-contraction au cours de la phase de declenchement du couplage
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Gauthier-Erfanian, Chantal. "Modulation bêta-adrénergique du courant entrant lent calcique et de la contraction phasique de la fibre atriale de grenouille : intervention d'un mécanisme indépendant de l'AMPc." Poitiers, 1991. http://www.theses.fr/1991POIT2259.
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Afin de preciser le mecanisme d'action des beta-agonistes sur l'oreillette de grenouille, la technique de potentiel impose par double separation de mannitol a permis de comparer les effets de l'isoprenaline a ceux de la forskoline, en presence d'un inhibiteur de l'adenylate cyclase et d'inhibiteurs de phosphodiesterases. Les phosphodiesterases (pdes) des fibres atriales hydrolysant les nucleotides cycliques ont ete isolees par chromatographie et caracterisees pharmacologiquement. Seules trois formes de pdes sont presentes. La cam-pde hydrolyse l'ampc et le gmpc et est stimulable par la calmoduline; elle est inhibee par le m & b 22, 948. La cgs-pde hydrolyse les deux nucleotides mais l'hydrolyse de l'ampc est stimulee par le gmpc; elle est inhibee par le dipyridamole. La camp-pde hydrolyse specifiquement l'ampc et est inhibee par le rolipram. La forskoline augmente de maniere dose-dependante le courant entrant lent calcique (i#s#i) et la contraction phasique par activation de l'adenylate cyclase. Ainsi sur l'oreillette de grenouille, la phosphorylation des canaux calciques peut etre regulee par l'ampc. Les effets de la forskoline inhibes par l'adenosine sont diversement potentialises en presence d'inhibiteurs de pdes, suggerant une compartimentation de l'ampc. L'isoprenaline augmente de maniere dose-dependante i#s#i et la contraction phasique; cependant l'isoprenaline ne modifie pas le taux d'ampc tissulaire et ses effets sont inchanges en presence d'adenosine et des inhibiteurs specifiques de pdes. Donc le schema classique du controle beta-adrenergique de i#s#i par stimulation de l'adenylate cyclase, admis pour le cur de mammifere, ne s'applique pas a l'oreillette de batracien. Il serait possible d'envisager une voie directe d'activation de i#s#i par les proteines g
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Sol-Rolland, José. "Les sulfone indolizines : caractérisation et purification de leur site de liaison associé au canal calcique lent voltage-dépendant du muscle squelettique de babouin." Montpellier 2, 1991. http://www.theses.fr/1991MON20097.
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Les sulfone indolizines constituent une nouvelle famille d'antagonistes du calcium destines au traitement des pathologies cardiovasculaires. Le sr trente trois mille cinq cent cinquante sept appartient a cette famille. L'utilisation de ce produit tritie nous a permis de caracteriser son site de liaison sur les membranes de muscle squelettique de babouin. Le choix de cet animal a ete motive par le fait, qu'apparemment, aucun travail concernant les recepteurs chez le babouin n'a ete publie, alors que cette espece est largement utilisee dans les etudes de securite des medicaments. Nous avons montre que le sr trente trois mille cinq cent cinquante sept tritie se lie specifiquement avec une tres haute affinite a un site associe au canal calcique lent voltage-dependant. Ce site est distinct de ceux des trois principales familles d'antagonistes du calcium connues et est couple allosteriquement a leurs recepteurs. Il existe dans un rapport stchiometrique un sur un avec chacun d'eux. Nous avons egalement montre que le canal calcique de type l du muscle squelettique de babouin purifie sur wga-sepharose et heparine-sepharose possede quatre sous-unites dont les poids moleculaires sont proches de ceux des monomeres alpha un, alpha deux, beta et gamma du canal calcique lent des especes animales etudiees par d'autres auteurs. Sa purification devrait permettre d'elucider sa structure primaire
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Martin, Christine. "Etude in situ de l'action des hormones thyroi͏̈diennes sur la réponse contractile et le métabolisme énergétique de muscles lents et rapides chez le rat : investigation par spectroscopie de RMN du proton et du phosphore 31." Aix-Marseille 1, 1990. http://www.theses.fr/1990AIX11310.
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L'action des hormones thyroidiennes sur la reponse contractile et le metabolisme energetique musculaire de muscles lents et rapides de rat a ete etudiee a l'aide de la spectroscopie de rmn du proton et du phosphore 31. Un protocole de stimulation in situ a une frequence de 5 hz des muscles gastrocnemius et soleus a ete utilise. La resistance a la fatigue du muscle gastrocnemius est notablement amelioree par le traitement hormonal (t3) alors que celle du muscle soleus n'est pas affectee. Par spectroscopie de rmn du #1h et du #3#1p, les concentrations intracellulaires des metabolites impliques dans le metabolisme energetique glycolytique, ainsi que celles de certains intermediaires du metabolisme des phospholipides, ont ete mesurees au repos et au cours d'une epreuve de fatigue. La comparaison entre rats eu- et hyperthyroidiens a mis en evidence une reduction de la participation de la glycolyse au metabolisme energetique du gastrocnemius, sous l'effet de t3. La tendance inverse a ete observee avec le soleus. Sous l'effet de t3, les muscles evoluent vers un type metabolique et contractile intermediaire (fog)
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Ferrás, Luís Jorge Lima. "Theoretical and numerical studies of slip flows." Doctoral thesis, 2012. http://hdl.handle.net/1822/22933.
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Tese de doutoramento em Ciência e Engenharia de Polímeros e CompósitosThis thesis presents an intensive study on slip flows of Newtonian and Non-Newtonian fluids carried out both analytically and numerically. Industrial applications of these flows are found in classical industries such as in polymer processing (for instance in extrusion) and in more modern applications as in lab-on-chip devices. Analytical solutions for flows under slip, are presented for both Newtonian, inelastic Newtonian and Non-Newtonian flows. These analytical solutions were missing in the literature and are helpful for both theoretical analysis and computer code validation. Slip boundary conditions were implemented in a computational fluid dynamics code, based on the finite volume method framework. New techniques for their implementation were devised, allowing to obtain convergence for reasonable Weissenberg numbers, using an appropriate iterative procedure to couple velocity, pressure and stress. The numerical code was then used to simulate benchmark problems, such as the 4:1 contraction, 1:4 expansion and slip-stick flows under slip, usually found in polymer processing.. The theoretical study of development length for Newtonian and viscoelastic fluids was performed for a channel flow under slip. New correlations for predicting the development length in micro and macro channels were devised. Other part of these thesis was dedicated to the theoretical study of electro-osmotic flows of complex fluids, for which analytical solutions for simple flows under the influence of the linear and nonlinear Navier slip boundary conditions were devised.
Nesta tese é apresentado um estudo intensivo de escoamentos com escorregamento, envolvendo fluidos newtonianos e não-newtonianos. Este tipo de escoamentos pode ser encontrado na indústria, por exemplo no processo de extrusão e ainda em aplicações mais modernas, tais como aparelhos baseados no conceito “lab-on-chip”. São apresentadas soluções analíticas com escorregamento para fluidos newtonianos, e diversos fluidos não-newtonianos, tanto inelásticos como viscoelásticos. Estas soluções analíticas não existiam na literatura e são úteis tanto em termos teóricos assim como para a validação de códigos numéricos. As condições de fronteira de escorregamento foram implementadas num código numérico de mecânica dos fluidos computacional baseado no métodos dos volumes finitos. Foram desenvolvidas novas técnicas para a implementação destas condições de fronteira, permitindo obter convergência para valores razoáveis do número de Weissenberg, usando um processo iterativo para acoplar os campos de velocidades, pressões e tensões. Este código numérico foi depois usado para simular problemas de referência, tais como os escoamentos numa contracção súbita 4:1, numa expansão 1:4 e o escoamento “slip-stick”, sob a influência do escorregamento na parede. Estas geometrias são frequentemente utilizadas em processamento de polímeros, o que substancia a utilidade prática destas simulações. Foi feito um estudo numérico e teórico para descobrir o comprimento de desenvolvimento do escoamento num canal simples com escorregamento na parede, de fluidos newtonianos e viscoelásticos. Foram ainda propostas novas correlações para prever esse comprimento. Outra parte do trabalho foi dedicada ao estudo de electro-osmose, onde novas soluções analíticas para escoamentos simples sob a influência do modelo de escorregamento linear de Navier, são apresentadas.
Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/37586/2007
Fundo Social Europeu Europeu (FSE) - Human Potential Operational Programme
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Patino, Descovich Carlos. "Characterizing cortical myosin mini-filament regulation, length and its macroscopic implications in cytokinetic dynamics." Thèse, 2013. http://hdl.handle.net/1866/11328.
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