Le syndrome de Down (SD), ou Trisomie 21, est l'aneuploïdie la plus fréquente chez l'humain. Le désordre génomique est tel qu'aucun traitement unique ne peut pallier à tous les symptômes (retard mental, troubles moteurs...). C'est pourquoi l'utilisation de modèles murins permet d'étudier l'impact de régions partielles du Hsa21 dans l'apparition des déficits. Mon projet de thèse s'est orienté sur un locus télomérique encadré par les gènes Abcg1 et U2af1. Mes recherches se sont focalisées sur deux modèles, Ts1Yah et Ms2Yah, dédiés à cette région. L'étude de ces lignées, combinées à d'autres modèles transgéniques, a montré la contribution de l'intervalle génique dans l'optimisation de l'apprentissage locomoteur. Dans un deuxième temps, le gène Cbs, candidat à la perte de fonction de mémoire, a permis de mettre en évidence un sauvetage fonctionnel dans une expérience à effets de doses. Cette découverte ouvre la voie à de nouvelles perspectives thérapeutiques.

The current understanding of lactate metabolism in fish is based almost entirely on interpretation of concentration measurements that cannot be used to infer changes in flux. Moreover, the transporters regulating these fluxes have never been characterized in rainbow trout. My goals were: (1) to quantify lactate fluxes in rainbow trout under normoxic resting conditions, during acute hypoxia, and exercise by continuous infusion of [U-14C] lactate; (2) to determine lactate uptake capacity of trout tissues by infusing exogenous lactate in fish rest and during graded exercise, and (3) to clone monocarboxylate transporters (MCTs) and determine the effects of exhausting exercise on their expression. Such information could prove important to understand the mechanisms underlying the classic “lactate retention” seen in trout white muscle after intense exercise. In normoxic resting fish, the rates of appearance (Ra) and disappearance (Rd) of lactate were always matched (~18 to 13 µmol kg-1 min-1), thereby maintaining a low baseline blood lactate concentration (~0.8 mM). In hypoxic fish, Ra lactate increased from baseline to 36.5 µmol kg-1 min-1, and was accompanied by an unexpected 52% increase in Rd reaching 30.3 µmol kg-1 min-1, accounting for a rise in blood lactate to 8.9 mM. In exercising fish, lactate flux was stimulated > 2.4 body lengths per second (BL s-1). As the fish reached critical swimming speed (Ucrit), Ra lactate was more stimulated (+67% to 40.4 μmol kg-1 min-1) than Rd (+41% to 34.7 μmol kg-1 min-1), causing an increase in blood lactate to 5.1mM. Fish infused with exogenous lactate stimulated Rd lactate by 300% (14 to 56 μmol kg-1 min-1) during graded exercise, whereas the Rd in resting fish increased by only 90% (21 to 40 µmol kg-1 min-1). Four MCT isoforms were partially cloned and characterized in rainbow trout: MCT1b was the most abundant in heart, and red muscle, but poorly expressed in gill and brain where MCT1a and MCT2 were prevalent. MCT4 was more expressed in the heart. Transcript levels of MCT2 (+260%; brain), MCT1a (+90%; heart) and MCT1b (+50%; heart) were stimulated by exhausting exercise. This study shows that: (i) the increase in Rd lactate plays a strategic role in reducing the lactate load imposed on the circulation. Without this response, blood lactate accumulation would double; (ii) a high capacity for lactate disposal in rainbow trout tissues is elicited by the increased blood-to-tissue lactate gradient when extra lactate is administered; and (iii) rainbow trout may be unable to release large lactate loads rapidly from white muscle after exhausting exercise (lactate retention) because they poorly express MCT4 in white muscle and fail to upregulate its expression during exercise.

No description available.

No description available.

Mechanical forces have been observed to affect various aspects of life, for example, cell differentiation, cell migration, locomotion and behavior of multicellular organisms etc. Such forces are generated either by external entities such as mechanical touch, fluid flow, electric and magnetic fields or by the living organisms themselves. Study of forces sensed and applied by living organisms is important to understand the interactions between organisms and their environment. Such studies may reveal molecular mechanisms involved in mechanosensation and locomotion. Several techniques have been successfully applied to measure forces exerted by single cells and cell monolayers. The earliest technique made use of functionalized soft surfaces and membranes as substrates on which cell monolayers were grown. The forces exerted by the cells could be measured by observing deformation of the substrates. Atomic Force Microscope (AFM) is another sensitive instrument that allows one to exert and measure forces in pico-Newton range. Advances in micromachining technology have enabled development of miniature force sensors and actuators. Latest techniques for mechanical force application and measurement use micromachined Silicon cantilevers in single as well as array form and micropillar arrays. Micropillar arrays fabricated using soft lithography enabled the use of biocompatible materials for force sensors. Together, these techniques provide access to a wide range of forces, from sub micro-Newton to milli-Newton. In the present work, types of forces experienced in biological systems and various force measurement and actuation techniques will be introduced. This will be followed by in depth description of the two major contributions of this thesis, 1) ―Colored polydimethylsiloxane micropillar arrays for high throughput measurements of forces applied by genetic model organisms‖. Biomicrofluidics, January 29, 2015. doi: 10.1063/1.4906905 2) ―Air microjet system for non-contact force application and the actuation of micro-structures‖. Journal of micromechanics and microengineering, December 15, 2015. doi: 10.1088/0960-1317/26/1/017001 Device developed for force measurement consists of an array of micropillars made of a biocompatible polymer Poly Dimethyl Siloxane (PDMS). Such devices have been used by researchers to measure traction forces exerted by single cells and also by nematode worm Caenorhabditis elegans (C. elegans). C. elegans is allowed to move in between the micropillars and the locomotion is video recorded. Deflection of the micropillar tips as the worm moves is converted into force exerted. Transparent appearance of C. elegans and PDMS poses difficulties in distinguishing micropillars from the worm, thus making it challenging to automate the analysis process. We address this problem by developing a technique to color the micropillars selectively. This enabled us to develop a semi-automated graphical user interface (GUI) for high throughput data extraction and analysis, reducing the analysis time for each worm to minutes. Moreover, increased contrast because of the color also delivered better images. Addition of color changed the Young‘s modulus of PDMS. Thus the dye-PDMS composite was characterized using hyper-elastic model. The micropillars were also calibrated using commercial force sensor. Analysis of forces exerted by wild type and mutant C. elegans moving on an agarose surface was performed. Wild type C. elegans exerted a total average force of 7.68 µN and an average force of ~1 µN on an individual pillar. We show that the middle of C. elegans exerts more force than its extremities. We find that C. elegans mutants with defective body wall muscles apply significantly lower force on individual pillars, while mutants defective in sensing externally applied mechanical forces still apply the same average force per pillar compared to wild type animals. Average forces applied per pillar are independent of the length, diameter, or cuticle stiffness of the animal. It was also observed that the motility of the worms with mechanosensation defects, lower cuticle stiffness, and body wall muscle defects was reduced with worms that have defective body wall muscle having the largest degree. Thus, we conclude that while reduced ability to apply forces affects the locomotion of the worm in the micropillar array, the reduced motility/locomotion may not indicate that the worm has reduced ability to apply forces on the micropillars. We also used the colored micropillar array for the first time to measure forces exerted by Drosophila larvae. Our device successfully captured the peristaltic rhythm of the body wall muscles of the larva and allowed us to measure the forces applied on each deflected pillar during this motion. Average force exerted by 1st instar wild type Drosophila larvae was measured to be ~ 1.5 µN per pillar. We demonstrated that a microjet of air can be used to apply forces in micro-Newton range. We developed a standalone system to generate a controlled air microjet. Microjet was generated using a controlled electromagnetic actuation of a diaphragm. With a nozzle diameter of 150 µm, the microjet diameter was maintained to a maximum of 1 mm at a distance of 5 mm from the nozzle. The force generated by the microjet was measured using a commercial force sensor to determine the velocity profile of the jet. Axial flow velocities of up to 25 m/s were obtained at distances as long as 6 mm. The microjet exerted a force up to 1 µN on a poly dimethyl siloxane (PDMS) micropillar (50 µm in diameter, 157 µm in height) and 415 µN on a PDMS membrane (3 mm in diameter, 28 µm thick). We also demonstrate that from a distance of 6 mm our microjet can exert a peak pressure of 187 Pa with a total force of about 84 µN on a flat surface with 8 V operating voltage. Next, we demonstrated that the response of C. elegans worms to the impinging air microjet is similar to the response evoked using a manual gentle touch. This contactless actuation tool avoids contamination and mechanical damage to the samples. Out of the cleanroom fabrication and robust design make this system cost effective and durable. Magnetic micropillars have been used as actuators. We fabricated magnetic micropillar arrays and designed actuation mechanisms using permanent magnet and a pulsed electromagnet. Force of about 19 µN was achievable using a permanent magnet actuation. In a pulsed electromagnetic field micropillar exerted a force of about 10 µN on a commercial force sensor. These techniques have promising applications when actuation needs to be controlled from long distances.

Made available in DSpace on 2014-07-29T15:08:17Z (GMT). No. of bitstreams: 1 Dissertacao Marco A de F Borges.pdf: 5922161 bytes, checksum: 25a7f4da4201499fe0a986400e8ae5b8 (MD5) Previous issue date: 2011-06-02 / The concept of Central Pattern Generator-CPG can be described as neural network capable of producing coordinated rhythmic locomotor activity apart from any external rhythm or sensorial stimuli. As this group of neurons are autonomic and are located in the spinal medulla, is experimentally observed that brainless animal‟s exhibit robotized locomotor activity, for its march has no defined direction nor respond to any obstacles. Studies has shown that is possible to activate this specialized networks using specific drugs or electric stimuli depending only of the access area as brainstem, medulla or some brain areas. For this paper many models proposed in current literature were evaluated, in its majority conceptual models. Within this models the Rybak (2006) computational model was chosen to be reproduced and evaluated regarding its robustness. The model in question consist in a CPG based in experimental data collected in cats and it posses two level of neurons based in the half-center models in its structure, the Rhythmic Generator-RG and the Pattern Formation-PF. This groups control the activity of the motoneurons flexors and extensors in an articulation. For its implementation were necessary a simplification in the original model and new parameterization of the variables. The implemented model allows a locomotor activity simulation produced by the CPG when stimulating a Mesencephalic Locomotion Region. Two protocols of variation of conductance inn GR were applied intending to evaluate its strength. The results show that the CPG computer model created operates within physiological values in variations up to . This model presents an adaptation in the first and the current is the current that plays a major role in the occurrence of outbreaks. The conductance has a direct relationship with the period as a result of its increase, a decrease in frequency of the bursts occurs. The conductance of has an inverse relationship with the period and as a result of its increase, a decrease in the period and increased in the frequency of the bursts occurs. The conductance has a direct relation with the period of the bursts before the 100% and a reverse relation after 100% of the reference value. The default behavior extensor/ flexor dominant not only depend on the synaptic weight of RLM, but rather the result of all the conductance values that make up the neuron GR. / O conceito de Gerador Central de Padrões (do inglês Central Pattern Generator-CPG) pode ser descrito como redes neuronais capazes de produzir atividade locomotora rítmica coordenada, independente de qualquer ritmo externo ou estímulos sensoriais. Como esses conjuntos de neurônios são autônomos e estão situados na medula espinhal, observa-se experimentalmente que animais descerebrados exibem uma atividade locomotora robotizada, assim chamada por que não tem direção definida e, também, não reagem a obstáculos. Estudos demonstram que é possível ativar essas redes especializadas por fármacos ou estímulos elétricos, dependendo da área de acesso, como: tronco encefálico, medula ou algumas áreas do cérebro. Para esse trabalho foram levantados vários modelos propostos na literatura, na maioria, modelos conceituais. Dentre os quais, foi identificado o modelo computacional de Rybak (2006) e então escolhido para ser reproduzido e avaliado com relação à sua robustez. O modelo em questão consiste em um CPG baseado em dados experimentais obtidos em gatos e possui dois níveis de neurônios baseados no modelo half-center em sua estrutura, o Gerador Rítmico-GR e Formador de Padrão-FP. Esses grupos controlam a atividade dos Motoneurônios flexores e extensores de uma articulação. Para implementação foram necessários uma simplificação no modelo original e nova parametrização das variáveis. O modelo implementado permite simular atividade locomotora produzida pelo CPG ao estimular a Região Locomotora Mesencefálica. Foram aplicados dois protocolos de variação das condutâncias no GR no intuito de avaliar sua robustez. Os resultados indicam que o modelo computacional de CPG criado opera dentro de valores fisiológicos sob variações de até . Esse modelo apresenta uma adaptação nos primeiros e a corrente é a corrente que desempenha o papel principal na ocorrência dos surtos.A condutância tem uma relação direta com o período dos surtos e em consequência ao seu aumento ocorre uma diminuição na frequência dos surtos. A condutância de tem uma relação inversa com o período dos surtos e em consequência ao seu aumento, ocorre uma diminuição no período e aumento na frequência dos surtos. A condutância tem uma relação direta com o período dos surtos antes de e inversa após do valor de referência. O comportamento padrão extensor/ flexor dominante não depende apenas do peso sináptico da RLM, mas sim, do resultado de todos os valores de condutância que compõem o neurônio GR.

The current understanding of lactate metabolism in fish is based almost entirely on interpretation of concentration measurements that cannot be used to infer changes in flux. Moreover, the transporters regulating these fluxes have never been characterized in rainbow trout. My goals were: (1) to quantify lactate fluxes in rainbow trout under normoxic resting conditions, during acute hypoxia, and exercise by continuous infusion of [U-14C] lactate; (2) to determine lactate uptake capacity of trout tissues by infusing exogenous lactate in fish rest and during graded exercise, and (3) to clone monocarboxylate transporters (MCTs) and determine the effects of exhausting exercise on their expression. Such information could prove important to understand the mechanisms underlying the classic “lactate retention” seen in trout white muscle after intense exercise. In normoxic resting fish, the rates of appearance (Ra) and disappearance (Rd) of lactate were always matched (~18 to 13 µmol kg-1 min-1), thereby maintaining a low baseline blood lactate concentration (~0.8 mM). In hypoxic fish, Ra lactate increased from baseline to 36.5 µmol kg-1 min-1, and was accompanied by an unexpected 52% increase in Rd reaching 30.3 µmol kg-1 min-1, accounting for a rise in blood lactate to 8.9 mM. In exercising fish, lactate flux was stimulated > 2.4 body lengths per second (BL s-1). As the fish reached critical swimming speed (Ucrit), Ra lactate was more stimulated (+67% to 40.4 μmol kg-1 min-1) than Rd (+41% to 34.7 μmol kg-1 min-1), causing an increase in blood lactate to 5.1mM. Fish infused with exogenous lactate stimulated Rd lactate by 300% (14 to 56 μmol kg-1 min-1) during graded exercise, whereas the Rd in resting fish increased by only 90% (21 to 40 µmol kg-1 min-1). Four MCT isoforms were partially cloned and characterized in rainbow trout: MCT1b was the most abundant in heart, and red muscle, but poorly expressed in gill and brain where MCT1a and MCT2 were prevalent. MCT4 was more expressed in the heart. Transcript levels of MCT2 (+260%; brain), MCT1a (+90%; heart) and MCT1b (+50%; heart) were stimulated by exhausting exercise. This study shows that: (i) the increase in Rd lactate plays a strategic role in reducing the lactate load imposed on the circulation. Without this response, blood lactate accumulation would double; (ii) a high capacity for lactate disposal in rainbow trout tissues is elicited by the increased blood-to-tissue lactate gradient when extra lactate is administered; and (iii) rainbow trout may be unable to release large lactate loads rapidly from white muscle after exhausting exercise (lactate retention) because they poorly express MCT4 in white muscle and fail to upregulate its expression during exercise.

No description available.

This paper deals with study of human movement and using that in identification. In the first part of my work are explained characteristics of human movement and factors which take effect on these characteristics. Practical part is dealing with design of program which is solving mentioned problems. The input of program is created by video sequence with lateral movement of human. The program is finding coordinates of lower limbs joints. From this coordinates are created locomotion characteristics used for human identification. Matching of time behaviors is based on correlation.

This research deals with impacts of pesticide substances on spider populations. In this case pesticides of the neonicotinoids classes were tested. Specific neonicotinoids were applied to different of spiders which were collected in various localities and at some stage of development - nymph, adult or subadult individuals. The diploma thesis analyzes and the documents the effects of neonicotinoids to spiders. The results show that some pesticides can have a significant negative effect to locomotion, predation, ballooning, drop or to spiders mortality. Keywords: spider, arthropod, pesticides, insecticides, neonicotinoids, sublethal effects, mortality, EthoVision XT, locomotion, drop, ballooning, predation, Philodromus, Oedothorax, Pardosa, Xerolycosa, Phylloneta