L’opossum nait dans un état très immature, mais rampe avec ses membres antérieurs (MA) de l’orifice urogénital de la mère à une tétine, où il s’attache pour poursuivre son développement. Des informations sensorielles sont nécessaires pour guider le nouveau-né vers une tétine et déclencher son attachement. Des expériences précédentes ont montré que le système du trijumeau, dont dépend l’innervation somesthésique du museau, influence les mouvements précoces des MA. Le présent projet vise à déterminer si les mécanorécepteurs faciaux sont fonctionnels et exercent une influence sur les MA. On s’intéresse particulièrement aux cellules de Merkel, un mécanorécepteur épidermique innervé par des fibres à adaptation lente de type I (SA I). Ces cellules ont été localisées sur le pourtour du museau de l’opossum nouveau-né en utilisant un traceur cellulaire, l’AM1-43. Nous avons analysé les réponses musculaires des MA consécutives à l’application de forces calibrées au museau sur des préparations in vitro. Ces réponses sont bilatérales et simultanées, très variables, et leur intensité augmente avec la force de la stimulation. Lors de stimulations répétitives pendant 60 min, les réponses diminuent avec le temps. Le retrait de la peau faciale abolit presque ces réponses. De plus, l’application d’un antagoniste des récepteurs métabotropiques du glutamate, qui affecte l’activité des fibres SA I, ou d’un antagoniste des récepteurs purinergiques les diminue fortement, suggérant une participation des cellules de Merkel. Ces résultats soutiennent que le sens du toucher facial relayé par le système du trijumeau est fonctionnel chez l’opossum nouveau-né et qu’il pourrait influencer les mouvements des MA. / The opossum, Monodelphis domestica, is born very immature but crawls, unaided, with its forelimbs (FL) from the mother's birth canal to a nipple where it attaches to pursue its development. Sensory clues are needed to guide the newborn to the nipple and trigger its attachment to it. We postulated that the trigeminal system, responsible for sensory innervation of the face, is involved. Indeed, light pressure applied on the snout evokes FL movements in vivo, low intensity electrical stimulation of the trigeminal ganglion induces motor responses of the FL in vitro, and trigeminal fibers is distributed in the facial dermis and basal epidermis of the newborn. Also, slowly adapting mechanosensory receptors Merkel cells (AM1-43 positive) are present in the face epidermis. To determine if Merkel cells exert an influence on locomotion of newborn opossums, we analyzed the FL muscles responses following application of calibrated forces on the snout in in vitro preparations. Pressure applied to the face induced bilateral and simultaneous FL motor responses, which intensity is proportional to stimulation force. Following consecutive stimulations during 60 min, the responses tended to decrease. Removing the facial skin nearly abolished the responses. Bath applications of the glutamate metabotropic receptor antagonist YM298198, and of the purinergic receptors (P2) antagonist PPADS, decreased the muscles responses. These results support that touch sensitivity of the snout relayed by the trigeminal system is functional in newborn opossums and may influence FL movement, possibly contributing to guiding the animal to the nipple.

Desenvolvemos um protocolo experimental para estudar a codificação do movimento horizontal pelo neurônio H1 de moscas varejeiras Chrysomya megacephala durante o voo. Tradicionalmente, o neurônio H1 é considerado puramente sensorial, e a maioria dos trabalhos tem utilizado o trem de potenciais de ação deste neurônio para explorar o código neural visual da mosca enquanto esta se encontra imobilizada (cabeça, asas, patas) e observa passivamente uma imagem que se move de maneira controlada. Nosso laboratório já dispunha de um aparato para registrar de maneira adequada a atividade do H1, enquanto a mosca imobilizada observava um padrão de barras verticais se movendo de acordo com uma sequência de velocidades previamente escolhidas pelo experimentador. Por meio de um novo suporte, especialmente desenvolvido neste trabalho, pudemos obter as medidas eletrofisiológicas quando apenas parte do corpo do inseto se encontra fixo. Além disso, conseguimos encontrar uma maneira de estimular a mosca para que esta apresentasse períodos de atividade, com batimentos de asa, similares ao voo. Utilizamos estes períodos de atividade de voo para registrar a atividade dos músculos que controlam a direção do voo. Também utilizamos microfones que captam pequenas diferenças de pressão do batimento das asas para inferir quando a mosca quer mudar a direção do voo e validamos estas medidas com o auxílio de um pequeno acelerômetro adaptado à haste de fixação da mosca. Mostramos que a taxa média de disparo do H1 é mais alta quando a mosca está voando do que quando está com as asas paradas. Além disso, a resposta ao estímulo visual é mais rápida e mais intensa quando a mosca está voando. Estes resultados são evidências de que a codificação da informação visual é diferente nos dois casos. Nossos experimentos com registro da atividade de controle motor do voo através de microfones permitiram encontrar padrões que podem ser usados para inferir a tentativa do inseto de mudar a direção do voo, em um intervalo de poucas batidas de asas e de maneira não invasiva. Esta informação poderá ser utilizada no futuro para produzir um equipamento em que a própria mosca controle o movimento da imagem em tempo real. / We developed a protocol do address the movement information coding in flying Chrysomya Megacephala by the horizontal sensitive H1neuron. H1 is traditionally considered a purely sensory neuron and his sequence of action potentials is used to explore the visual neural code while an immobilized fly passively watch a movie generated by the experimenter. We improved an apparatus to perform such experiments, that was already working in our laboratory, by developing a new holder for the fly and electrode that allowed to record from H1 while only part of the fly was fixed, keeping wings and legs free to move. Moreover we found a protocol to stimulate the fly to present long periods of wing beating activity, very similar to the insect flying. During these flying periods of activity, we also recorded from the steering muscles that control fly direction as well as from small microphones sensitive to subtle pressure variations of the beating wings when the fly try to change direction. These recordings were validated by using an accelerometer adapted to the fly fixation rod. According to our results, the firing rate of H1 increases during the flying periods. Moreover, the response to visual stimuli is faster and more intense during the flying than the response when the wings are not beating. These are evidences that the information coding is different in both cases. We could also find some patterns in the time series of the microphones recordings that allowed us to infer, in a small number of wing beatings, when the insect tries to turn and what is the turning direction. This information can be useful to perform new experiments in the future, were the fly controls in real-time the image movement.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / A Hipóxia-Isquêmica (HI) pré-natal é caracterizada por uma redução no aporte de oxigênio e nutrientes para o feto durante o período gestacional, que pode acarretar, a longo prazo, em dificuldade de concentração e aprendizagem, hiperatividade e déficit de memória. Esses prejuízos podem persistir ou se agravar até a idade adulta, levando ainda ao aparecimento de doenças como epilepsia e paralisia cerebral (PC). A privação de oxigênio e nutrientes, assim como o estresse materno, anemia, eclâmpsia e uso de drogas durante a gestação, podem causar estresse oxidativo durante os períodos críticos do desenvolvimento, e pode ser a principal razão para as mudanças que levam a programação fetal. O objetivo deste estudo foi relacionar a geração de espécies reativas e a consequente formação de estresse oxidativo nos animais adultos, com as alterações da biodisponibilidade do óxido nítrico de forma sistêmica, além de mudanças nos comportamentos motor e de ansiedade, manutenção da memória e aprendizado. Para a hipóxia, foi utilizado o modelo de clampeamento das artérias uterinas das ratas no 18 dia gestacional por 45 min, analisando os filhotes após 90 dias de nascidos. Foram utilizados os testes Open Field e labirinto em cruz elevada para a análise comportamental, e análises das enzimas glutationa peroxidase (GPx), superóxido desmutase (SOD) e catalase, além de quantificação de nitritos, TBARs e carbonilação de proteínas para avaliação de mecanismos oxidantes e antioxidantes. Os resultados demonstraram que o insulto durante a gestação pode acarretar em redução na formação da enzima GPx, além de maior concentração de nitritos analisados nos soros dos animais hipoxiados quando comparados aos controles, contribuindo para o dano oxidativo. Também foi observada redução na memória de habituação e comportamento motor, além de elevado comportamento ansioso em animais hipoxiados, diferentemente de controles. Concluímos assim que a hipóxia isquêmica pré-natal pode alterar permanentemente o estado oxidativo dos animais, além de atuar na formação do comportamento motor, memória de habituação e ansiedade. As descobertas aqui apresentadas contribuem para ampliar o entendimento acerca do evento de hipóxia isquêmica pré-natal, além de prover ferramentas para o desenvolvimento de mecanismos protetores e preventivos aos possíveis danos por ela causados. / The prenatal hypoxia ischemic (HI) is characterized by a decreased supply of oxygen and nutrients to the fetus during the gestational period that could be followed in a long term by poor concentration and learning, hyperactivity and memory deficits. These damages can persist or become more severe, leading to diseases like epilepsy or cerebral palsy. The oxygen and nutrients privation, as well as maternal stress, anemia, eclampsia and drugs abuse in gestation, may cause oxidative stress during the critical periods of development, and could be the main reason to changes leading to a fetal programming. The aim of the present study was to investigate the association of reactive species generation and consequent formation of oxidative stress in HI adult animals, with systemic alterations in nitric oxide bioavailability, in addition to changes on motor behavior and anxiety, memory maintenance and learning. To hypoxia, we used the model of rats uterine arteries clamping in 18 day of gestation for 45 min, analyzing the pups after 90 days of life. The open field test and elevated plus maze test were used to behavioral analysis, and GPx, SOD and catalase enzymes analysis, besides nitrite quantification, TBARs and protein carbonyl to verify oxidative stress. The results have shown that a hypoxic insult during gestation can cause reduction in GPx enzyme formation associated with elevated nitrite concentration in serum of hypoxic animals when compared to controls, contributing to oxidative damage. Also it was observed an impairment of habituation memory and motor behavior, besides the increased anxiety in hypoxic animals, in contrast to controls. Thus, it can be conclude that prenatal hypoxia ischemia can permanently alter the oxidative status in animals, and also act in formation of motor, habituation memory and anxiety behavior. The findings contribute to increase the knowledge about the prenatal hypoxia ischemia, and provide tools for the development of protective mechanisms and preventions to possible damages caused by this critical event.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / A Hipóxia-Isquêmica (HI) pré-natal é caracterizada por uma redução no aporte de oxigênio e nutrientes para o feto durante o período gestacional, que pode acarretar, a longo prazo, em dificuldade de concentração e aprendizagem, hiperatividade e déficit de memória. Esses prejuízos podem persistir ou se agravar até a idade adulta, levando ainda ao aparecimento de doenças como epilepsia e paralisia cerebral (PC). A privação de oxigênio e nutrientes, assim como o estresse materno, anemia, eclâmpsia e uso de drogas durante a gestação, podem causar estresse oxidativo durante os períodos críticos do desenvolvimento, e pode ser a principal razão para as mudanças que levam a programação fetal. O objetivo deste estudo foi relacionar a geração de espécies reativas e a consequente formação de estresse oxidativo nos animais adultos, com as alterações da biodisponibilidade do óxido nítrico de forma sistêmica, além de mudanças nos comportamentos motor e de ansiedade, manutenção da memória e aprendizado. Para a hipóxia, foi utilizado o modelo de clampeamento das artérias uterinas das ratas no 18 dia gestacional por 45 min, analisando os filhotes após 90 dias de nascidos. Foram utilizados os testes Open Field e labirinto em cruz elevada para a análise comportamental, e análises das enzimas glutationa peroxidase (GPx), superóxido desmutase (SOD) e catalase, além de quantificação de nitritos, TBARs e carbonilação de proteínas para avaliação de mecanismos oxidantes e antioxidantes. Os resultados demonstraram que o insulto durante a gestação pode acarretar em redução na formação da enzima GPx, além de maior concentração de nitritos analisados nos soros dos animais hipoxiados quando comparados aos controles, contribuindo para o dano oxidativo. Também foi observada redução na memória de habituação e comportamento motor, além de elevado comportamento ansioso em animais hipoxiados, diferentemente de controles. Concluímos assim que a hipóxia isquêmica pré-natal pode alterar permanentemente o estado oxidativo dos animais, além de atuar na formação do comportamento motor, memória de habituação e ansiedade. As descobertas aqui apresentadas contribuem para ampliar o entendimento acerca do evento de hipóxia isquêmica pré-natal, além de prover ferramentas para o desenvolvimento de mecanismos protetores e preventivos aos possíveis danos por ela causados. / The prenatal hypoxia ischemic (HI) is characterized by a decreased supply of oxygen and nutrients to the fetus during the gestational period that could be followed in a long term by poor concentration and learning, hyperactivity and memory deficits. These damages can persist or become more severe, leading to diseases like epilepsy or cerebral palsy. The oxygen and nutrients privation, as well as maternal stress, anemia, eclampsia and drugs abuse in gestation, may cause oxidative stress during the critical periods of development, and could be the main reason to changes leading to a fetal programming. The aim of the present study was to investigate the association of reactive species generation and consequent formation of oxidative stress in HI adult animals, with systemic alterations in nitric oxide bioavailability, in addition to changes on motor behavior and anxiety, memory maintenance and learning. To hypoxia, we used the model of rats uterine arteries clamping in 18 day of gestation for 45 min, analyzing the pups after 90 days of life. The open field test and elevated plus maze test were used to behavioral analysis, and GPx, SOD and catalase enzymes analysis, besides nitrite quantification, TBARs and protein carbonyl to verify oxidative stress. The results have shown that a hypoxic insult during gestation can cause reduction in GPx enzyme formation associated with elevated nitrite concentration in serum of hypoxic animals when compared to controls, contributing to oxidative damage. Also it was observed an impairment of habituation memory and motor behavior, besides the increased anxiety in hypoxic animals, in contrast to controls. Thus, it can be conclude that prenatal hypoxia ischemia can permanently alter the oxidative status in animals, and also act in formation of motor, habituation memory and anxiety behavior. The findings contribute to increase the knowledge about the prenatal hypoxia ischemia, and provide tools for the development of protective mechanisms and preventions to possible damages caused by this critical event.

Made available in DSpace on 2016-06-02T20:18:13Z (GMT). No. of bitstreams: 1 3542.pdf: 2125981 bytes, checksum: dc4d268edf82cba3471e3345587f4cb9 (MD5) Previous issue date: 2011-02-22 / Universidade Federal de Sao Carlos / This study aimed to describe the method used for the kinematic analysis of kicking movements in infants and to determine the effect of additional weighting in the pattern of the kicking movements of infants in the first four months of life. For this, two studies are presented. The first study describes the method used for the kinematic analysis of kicking movements in infants. In the study, four infants were longitudinally videotaped at ages from one to six months and analysis was performed on the Dvideow system. It was verified that the use four video cameras was required. Moreover, six plumb lines were used to calibrate the system and ensure an accuracy of 2 mm. It was concluded, based in the first estudy that the use of the Dvideow system to perform kinematic analysis of the kicking movement in infants proved to be appropriate and feasible. The second study aimed to verify the influence of weights of 1/10 e 1/3 the mass of lower limb in the pattern of the kicking movements of infants in the first four months of life. Fourteen healthy infants participated in the study, longitudinally videotaped. Kicking frequency, foot/panel contact frequency, intralimb coordination pattern, movement time, average speed and straightness index were analyzed. Comparing the ages, we found differences in the kicking frequency, foot/panel contact frequency, movement time, and average speed. Comparing the weighting conditions, we found changes in the kicking frequency and foot/panel contact frequency; the kinematic variables remained unchanged. Therefore, we suggest that during the first four months of life, infants change the kicking frequency according to their ages, the intra-session training and additional weighting. These features are probably the result of intrinsic factors such as increased mass and muscle strength, behavior status of infants, maturation of the Central Nervous System and extrinsic factors such as the weight and the interest in the environment and in performing the proposed task. / Este trabalho teve por objetivos descrever o método utilizado para análise cinemática dos chutes e verificar os efeitos do peso adicional no padrão dos chutes nas idades de um a quatro meses de vida. Para tanto, são apresentados dois estudos. O primeiro estudo descreve o método empregado para análise da cinemática dos movimentos de chutes de lactentes. Neste estudo, quatro lactentes foram filmados longitudinalmente nas idades de um a seis meses e a análise foi realizada no sistema Dvideow 6.3. Foi verificado que o uso de quatro câmeras de vídeo é necessário. Além disso, utilizamos seis fios de prumo para calibrar o sistema e garantir uma precisão de 2mm. Portanto, concluímos, com base no primeiro estudo, que a utilização do sistema Dvideow para realizar a análise cinemática dos chutes de lactentes mostrou-se adequada e viável. O segundo estudo teve por objetivo verificar a influência de pesos de 1/10 e 1/3 da massa do membro inferior no padrão dos chutes de lactentes de um a quatro meses de vida. Participaram deste estudo 14 lactentes, filmados longitudinalmente. Foram analisadas as variáveis frequência de chutes, freqüência de contato do pé com o painel, padrão de coordenação intramembro, tempo de movimento, velocidade média e índice de retidão. Quando consideramos as idades, verificamos diferença na freqüência de chutes, na freqüência de contatos do pé com o painel, no tempo do movimento e na velocidade média. Quando comparamos as condições de peso, verificamos alteração da freqüência de chutes e da freqüência de contatos do pé com o painel; as variáveis cinemáticas mantiveram-se inalteradas. Portanto, podemos sugerir que no decorrer dos quatro primeiros meses de vida, os lactentes alteram a freqüência dos chutes em função das suas idades, do treinamento intra-sessão e do peso adicional. Essas características são, provavelmente, resultado de fatores intrínsecos, como aumento da massa e força musculares, estado comportamental dos lactentes, maturação do Sistema Nervoso Central e fatores extrínsecos como o peso e o interesse pelo ambiente e em realizar a tarefa.

Desenvolvemos um protocolo experimental para estudar a codificação do movimento horizontal pelo neurônio H1 de moscas varejeiras Chrysomya megacephala durante o voo. Tradicionalmente, o neurônio H1 é considerado puramente sensorial, e a maioria dos trabalhos tem utilizado o trem de potenciais de ação deste neurônio para explorar o código neural visual da mosca enquanto esta se encontra imobilizada (cabeça, asas, patas) e observa passivamente uma imagem que se move de maneira controlada. Nosso laboratório já dispunha de um aparato para registrar de maneira adequada a atividade do H1, enquanto a mosca imobilizada observava um padrão de barras verticais se movendo de acordo com uma sequência de velocidades previamente escolhidas pelo experimentador. Por meio de um novo suporte, especialmente desenvolvido neste trabalho, pudemos obter as medidas eletrofisiológicas quando apenas parte do corpo do inseto se encontra fixo. Além disso, conseguimos encontrar uma maneira de estimular a mosca para que esta apresentasse períodos de atividade, com batimentos de asa, similares ao voo. Utilizamos estes períodos de atividade de voo para registrar a atividade dos músculos que controlam a direção do voo. Também utilizamos microfones que captam pequenas diferenças de pressão do batimento das asas para inferir quando a mosca quer mudar a direção do voo e validamos estas medidas com o auxílio de um pequeno acelerômetro adaptado à haste de fixação da mosca. Mostramos que a taxa média de disparo do H1 é mais alta quando a mosca está voando do que quando está com as asas paradas. Além disso, a resposta ao estímulo visual é mais rápida e mais intensa quando a mosca está voando. Estes resultados são evidências de que a codificação da informação visual é diferente nos dois casos. Nossos experimentos com registro da atividade de controle motor do voo através de microfones permitiram encontrar padrões que podem ser usados para inferir a tentativa do inseto de mudar a direção do voo, em um intervalo de poucas batidas de asas e de maneira não invasiva. Esta informação poderá ser utilizada no futuro para produzir um equipamento em que a própria mosca controle o movimento da imagem em tempo real. / We developed a protocol do address the movement information coding in flying Chrysomya Megacephala by the horizontal sensitive H1neuron. H1 is traditionally considered a purely sensory neuron and his sequence of action potentials is used to explore the visual neural code while an immobilized fly passively watch a movie generated by the experimenter. We improved an apparatus to perform such experiments, that was already working in our laboratory, by developing a new holder for the fly and electrode that allowed to record from H1 while only part of the fly was fixed, keeping wings and legs free to move. Moreover we found a protocol to stimulate the fly to present long periods of wing beating activity, very similar to the insect flying. During these flying periods of activity, we also recorded from the steering muscles that control fly direction as well as from small microphones sensitive to subtle pressure variations of the beating wings when the fly try to change direction. These recordings were validated by using an accelerometer adapted to the fly fixation rod. According to our results, the firing rate of H1 increases during the flying periods. Moreover, the response to visual stimuli is faster and more intense during the flying than the response when the wings are not beating. These are evidences that the information coding is different in both cases. We could also find some patterns in the time series of the microphones recordings that allowed us to infer, in a small number of wing beatings, when the insect tries to turn and what is the turning direction. This information can be useful to perform new experiments in the future, were the fly controls in real-time the image movement.

Made available in DSpace on 2014-08-20T13:49:14Z (GMT). No. of bitstreams: 1 angelicakaefer.pdf: 395526 bytes, checksum: fa5c5d2a2a4fa53dfa537189b4bacc07 (MD5) Previous issue date: 2009-03-26 / The relationship between extroversion-introversion personality trait and the selfcontrolled frequency of extrinsic feedback, in the learning of a sequential timing motor skill in adults was investigated in the current study. The subjects answered to the Eysenck Personality Questionnaire (EPQ) for the personality evaluation of. 56 citizens. University students of both genders had been selected through the EPQ and had then been submitted to a motor task that consisted of pressing computer keyboard keys, with specific space and timing sequence established by the experimenter. The experiment counted on phases of acquisition, retention and transfer. The retention and transfer phases were carried out 24 hours after the acquisition phase. The subjects were distributed in 4 groups, formed by the combination of the trace (extroversão/introversion) and frequency of KR (selfcontrolled and externally controlled). The dependent variable used in the study was the partial errors in absolute and relative timing in each block. The results indicated superior learning for the groups that had practiced in a self controlled schedule. Complementary analyses were carried out, evidencing inferior learning for the group of introverts that requested more KR at the beginning of the practice and less at the end, in relation to all the other groups. Hence, these complementary analyses demonstrated a significant interaction between personality trait and KR frequency in relation to a high or low request of KR in relative timing, that is; introverts who requested high frequency of KR learned more than introverts who requested low frequency of KR and extroverts who requested low KR frequency learned more than extroverts who requested high KR. / No presente trabalho investigou-se a relação entre o traço de personalidade extroversão-introversão e a freqüência de feedback extrínseco auto-controlado na aprendizagem de uma habilidade motora de timing seqüencial em adultos. Os sujeitos responderam ao Eysenck Personality Questionnaire (EPQ) para a avaliação da personalidade. 56 sujeitos, estudantes universitários de ambos os sexos foram selecionados através do EPQ e posteriormente, foram submetidos a uma tarefa motora que consistiu em pressionar teclas do teclado numérico acoplado de um computador portátil, com uma seqüência espacial e temporal específica estabelecida pelo experimentador. O experimento contou com fases de aquisição (60 tentativas), retenção (10 tentativas) e transferência (10 tentativas). As fases de retenção e transferência foram realizadas 24 horas após a fase de aquisição. Os sujeitos foram distribuídos em 4 grupos, formados com a combinação do traço (extroversão/introversão) e a freqüência de fornecimento de CR (auto-controlado e externamente controlado). As variáveis dependentes utilizadas no estudo foram os erros parciais em timing absoluto e timing relativo obtidos em cada bloco. Os resultados apontaram aprendizagem superior para os grupos que praticaram com freqüência auto-controlada de CR em relação aos grupos que praticaram com freqüência externamente controlada. Análises complementares foram realizadas, evidenciando aprendizagem inferior para o grupo de introvertidos que solicitou mais CR no início da prática e menos no final, em relação a todos os outros grupos. Ainda, estas análises complementares evidenciaram, em timing relativo, uma significativa interação entre traço de personalidade e freqüência em relação à alta e baixa solicitação de CR, ou seja, introvertidos que solicitaram alta freqüência de CR aprenderam mais que introvertidos que solicitaram baixa freqüência de CR e, extrovertidos que solicitaram baixa freqüência de CR aprenderam mais que extrovertidos que solicitaram alta freqüência de CR

La présente recherche traite des mécanismes de communication de type praxique qui sont au cœur des interactions ludomotrices qui se nouent au sein de la pratique du volleyball. Cette perspective de recherche offre la possibilité de mieux appréhender et comprendre les conduites motrices des joueurs qui se façonnent dans un réseau sociomoteur s’articulant autour de rapports de coopération et d’opposition. De là, il nous a semblé intéressant d’étudier le contenu du volleyball qui se pratique aussi bien dans le milieu professionnel qu’à l’école. Le réseau de communication mixte de ce sport est bâti sur la trame de comportements moteurs observables des pratiquants dont l’aisance et l’efficacité motrices espérées s’acquièrent au fil des séances d’entraînements conduits par les entraîneurs/enseignants. Dans ce contexte, l’approche techniciste et classique du Volleyball est-elle privilégiée à l’approche « sémiotrice » fondée sur la lecture des conduites motrices des pratiquants et sur la communication praxique ? La recherche de l’efficacité en situation de match accentue-t-elle cette tendance auprès des éducateurs et des joueurs sur le plan de leurs représentations ? Pour répondre à ces interrogations et mettre en évidence ce réseau subtil d’interactions motrices, nous avons analysé des matchs chez trois populations issues du sport de haut niveau, d’association sportive scolaire et en éducation physique à l’école. Ces observations ont été croisées avec des entretiens semi-directifs réalisés auprès des joueurs et des éducateurs et avec un questionnaire reposant sur la procédure de Condorcet. Les résultats ont révélé d’une part qu’au sein du sport de haut niveau les rapports d’interactions motrices des joueurs se fondent sur des réseaux de communications praxiques plus riches qu’au sein du volleyball scolaire et associatif, mettant en valeur des rapports d’opposition et de coopération autour de sous-rôles sociomoteurs variés et privilégiés. D’autre part, le niveau de pratique à l’échelle scolaire, observé dans le contenu des séances menées par les enseignants, privilégie l’aspect technique et physique du volleyball. Par ailleurs, on relève des distinctions quant aux représentations des pratiquants et de la part de leurs entraîneurs et ce, dans les trois populations comparées : pour les pratiquants, l’intérêt porte principalement sur les aspects techniques, tactiques et physiques. Quant aux entraîneurs, outre les aspects techniques et tactiques, l’organisation et la planification de l’entraînement sont valorisés pour atteindre les objectifs visés. La sportivisation des pratiques telles que le préconisent depuis longtemps les finalités éducatives des instructions officielles (1990) en Tunisie, et observées ici, ne facilite pas la mise en œuvre pédagogique et didactique du volleyball dans une perspective sémiotrice. La référence sportive fondée sur des habiletés motrices (techniques corporelles) du volleyball ne fait qu’entraver la réussite des échanges praxiques entre les élèves. Nous nous proposons ainsi de construire une approche originale de l’enseignement du volleyball scolaire sous l’angle d’un apprentissage fondé principalement sur la sémiotricité. / This study deals with praxis communication mechanisms that are at the heart of motor playfulness interactions that are formed in the practice of volleyball. This research perspective offers the opportunity to better grasp and understand the motor behavior of players that are shaping a social motor skills network revolving around cooperative and adversarial. From there, it seemed interesting to study the content of practicing volleyball both high level and at school. The joint communication network of sport is built on the frame of observable motor behavior of practitioners whose ease and hoped drive efficiency gain over the trainings sessions led by trainers / teachers. In this context, is the technocratic and traditional approach of Volleyball is preferred over the approach motor semiotic based on the studyof motor behavior of practitioners and the praxis communication? The search for efficiency in game situations accentuates this trend with educators and players in terms of their representations? To answer these questions and highlight the subtle network of motor interactions, we analyzed the matches of three populations from high-level sport, school sports association and physical education at school. These observations were crossed with semi-structured interviews with players and educators with a questionnaire based on Condorcet Method. Results revealed that within high level sports, motor interactions of players are based on praxis communication networks are richer within school and club volleyball, thus highlighting links of opposition and cooperation around diverse and under-privileged social motor skills roles. On the other hand, the level of practice at the school level, observed in the content of the sessions conducted by teachers, emphasizes the technical and physical aspects of volleyball. Furthermore, we note distinctions as to the representations and practitioners from their coaches and within three populations: for the first, mainly the focus is on the technical, tactical and physical aspect. As for the second category, in addition to technical and tactical aspects, organization and training of planning are emphasized to achieve objectives. The sportization practices such as have long advocated the educational purposes of official instructions (1990) in Tunisia, observed here, do not make easy the educational and teaching work in a volleyball motor semiotic perspective. Sports reference based on motor skills (body techniques) volleyball only hinder the success of praxis exchanges between students. We thus propose to build an original approach to teach school volleyball in terms of learning based primarily on motor skills semiotic.

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The National Occupational Research Agenda stresses the importance of identifying work-related musculoskeletal disorder (WMSD) risk factors, understanding their exposure dependent nature, and identifying strategies to reduce their incidence and severity. We first examined behavioral changes after exposure to a low repetition low force (LRLF) reaching task for 12 weeks in young rats. We observed increased movement reversals in LRLF - week 8, indicative of a decline in fine motor control, and a small decrease in voluntary task participation in LRLF - week 12, compared to controls. This decline was associated temporally with a low-grade increase of macrophages in peripheral nerve and distal forelimb bones that correlated with nociceptive neurochemical increases in the spinal cord. We next examined motor behavior changes in young rats exposed to either a food retrieval high repetition negligible force (HRNF) task or a lever pulling high repetition low force (HRLF) reaching task. We found that both tasks led to motor declines, with more marked declines in fine motor control in the HRNF group. Thus, repetition, rather than the difference in force magnitude between the 2 tasks, appears to be the key factor in the induction of motor declines associated with repetitive motion injuries (RMIs). Also, these findings indicate that activities involving negligible force do not necessarily pose a lower risk than activities involving low force. Factors such as fine motor coordination requirements may even pose greater risks. Also, compared to the LRLF task, the high repetition tasks resulted in more motor performance declines, thus confirming exposure-dependency in the context of RMI. We also explored the effects of HRNF and HRLF tasks on supraspinatus tendon of young adult rats in 6 and 12 weeks. We found a small but non-significant elevation of ED1+ macrophages in 6 weeks. The supraspinatus tendon does not appear to develop as many pathological changes as forelimb flexor tendons (Barbe, et al., 2003) with task performance. Lastly, we examined the effects of performing HRLF tasks in aged rats. We found that aged rats demonstrate both declines in motor performance and pathological tissue changes over the course of 12 weeks of exposure to the HRLF lever pulling task. The observed declines in grip strength in aged trained control and HRLF rats over time suggest that both age and cumulative exposure to the repetitive task are factors in the development of WMSDs. Our findings suggest that additional study of exposure-dependency and risk factors is warranted. Deeper understanding of the relative contributions of various risk factors can help inform prophylactic programs and/or interventions for individuals who are at risk for, or suffer from, WMSDs. / Physical Therapy