Master of Science in Medicine / Saccadic and vestibular-evoked eye movements are similar in that their three-dimensional kinematic properties show eye position-dependence. When the line of sight is directed towards an eccentric target, the eye velocity axis tilts in a manner that depends on the instantaneous position of the eye in the head, with the magnitude of tilt also depending on whether the eye movement is saccadic or vestibular-evoked. The mechanism responsible for producing eye velocity axis tilting phenomena is not well understood. Some authorities have suggested that muscle pulleys in the orbit are critical for implementing eye velocity axis tilting, while others have suggested that the cerebellum plays an important role. In the current study, three-dimensional eye and head rotation data were acquired, using the magnetic search coil technique, to confirm the presence of eye position-dependent eye velocity axis tilting during saccadic eye movements. Both normal humans and humans with cerebellar atrophy were studied. While the humans with cerebellar atrophy were noted to have abnormalities in the two-dimensional metrics and consistency of their saccadic eye movements, the eye position-dependent eye velocity axis tilts were similar to those observed in the normal subjects. A mathematical model of the human saccadic and vestibular systems was utilized to investigate the means by which these eye position-dependent properties may arise for both types of eye movement. The predictions of the saccadic model were compared with the saccadic data obtained in the current study, while the predictions of the vestibular model were compared with vestibular-evoked eye movement data obtained in a previous study. The results from the model simulations suggest that the muscle pulleys are responsible for bringing about eye position-dependent eye velocity axis tilting for both saccadic and vestibular-evoked eye movements, and that these phenomena are not centrally programmed.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 7 uppsatser.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [268]-281).

Thesis (Ph. D.)--Memorial University of Newfoundland, Faculty of Medicne, 2001. / Typescript. Includes bibliographical references (leaves 156-172).

Thesis (M.Sc.)--York University, 2004. Graduate Programme in Biology. / Typescript. Includes bibliographical references. Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11866

Stair locomotion is one of the most difficult and challenging type of locomotion for older adults, with a high risk of fall and injuries. A major reason is that the neuromuscular system undergoes various changes through the aging process. The aim of this doctoral thesis is to study the age-related neuro-mechanical adjustments associated with stair locomotion and more specifically to investigate the interaction between neural and muscular changes in the plantarflexor muscles. To that aim, three main projects have been performed. The first two projects investigated the influence of age on spinal and supraspinal excitability when individuals stood at the bottom and the top of a 3-steps staircase and spinal excitability during stair locomotion. The third one focused on the age-related influence on the muscle-tendon behavior during stair locomotion. The result of the first project indicate a lower dependence on spinal pathway to control soleus motoneurons with a similar change observed in both age groups suggesting that healthy older adults preserved their ability to adjust postural control to environmental demands. The second project is the first to report the modulation of H-reflex amplitude in the plantarflexor muscles during stair ascent and descent in healthy young and older adults. This modulation likely reflects an increased role of descending inputs in controlling plantarflexor muscle activation during the stair gait cycle. However, similarly to the first project the modulation of the net excitatory inputs from group I afferents during the stair gait cycle does not seem to be influenced by healthy aging. The third project suggest that length changes of the Achilles tendon and lateral gastrocnemius (LG) fascicles favour the storage and recovery the tendon elastic strain energy over the muscle work, improving thereby the mechanical efficiency of stair ascent in young adults. In older adults, it seems that a different behavior is used to maintain a mechanical efficiency during stair ascent. In contrast, during stair descent, no difference was observed between age groups regarding the LG muscle-complex behavior despite some kinematics changes. In conclusion, this doctoral thesis indicates that despite some age-related structural and functional changes of the neuromuscular system, similar neural modulations occur during stair locomotion in young and healthy older adults. During stair ascent, a similar global pattern of change in length for the fascicle’s length and the modulation of the H reflex can be observed. However, during stair descent, H reflex modulation cannot be simply explained by the pattern of muscle length change. / Doctorat en Sciences de la motricité / info:eu-repo/semantics/nonPublished

Master of Science / Department of Kinesiology / Steven W. Copp / Mechanical signals within contracting skeletal muscles contribute to the generation of the exercise pressor reflex; an important autonomic and cardiovascular control mechanism. In decerebrate rats, GsMTx4, a mechanically–activated channel inhibitor that is partially selective for piezo channels, was found recently to reduce the pressor response during static hindlimb muscle stretch; a maneuver used to investigate the mechanical component of the exercise pressor reflex (i.e., the mechanoreflex). However, the effect was found only during the very initial phase of the stretch when muscle length was changing which may have reflected the inhibition of rapidly-deactivating piezo 2 channels and the fact that different mechanically-activated channels with slower deactivation kinetics evoked the pressor response during the static phase of the maneuver. We tested the hypothesis that in decerebrate, unanesthetized rats, GsMTx4 would reduce the pressor response throughout the duration of a 30 second, 1 Hz dynamic hindlimb muscle stretch protocol. We found that the injection of 10 µg of GsMTx4 into the arterial supply of a hindlimb reduced the peak pressor response (control: 15±4, GsMTx4: 5±2 mmHg, p<0.05, n=8) and the pressor response at multiple time points throughout the duration of the stretch. GsMTx4, however, had no effect on the pressor response to the hindlimb arterial injection of lactic acid. Moreover, the injection of GsMTx4 into the jugular vein (a systemic control, n=5) or the injection of saline into the hindlimb arterial supply (a vehicle control, n=4) had no effect on the pressor response during dynamic stretch. We conclude that GsMTx4 reduced the pressor response throughout the duration of a 1 Hz dynamic stretch protocol which may have reflected the inhibition of piezo 2 channels throughout the dynamic stretch maneuver.

Made available in DSpace on 2018-07-27T18:26:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-03-25. Added 1 bitstream(s) on 2018-07-27T18:29:50Z : No. of bitstreams: 1 000865781.pdf: 17935151 bytes, checksum: 7ceb972aa90983bb4105def9cb38d793 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O reflexo auditivo de sobressalto (RAS) é uma reação motora rápida e evidente frente a um estímulo acústico intenso e inesperado. Trata-se de um reflexo acústico-motor do tronco encefálico que está presente em muitas espécies de mamíferos, incluindo o homem. Possui caráter tanto defensivo frente a uma possível agressão quanto de alerta frente a aconteci-mentos não esperados. Além do RAS resultar em uma resposta sobre a musculatura esque-lética, possui ação sobre o sistema nervoso autônomo promovendo aumento da pressão arterial e da freqüência cardíaca. No rato o circuito neural elementar do RAS é constituído por: neurônios do gânglio espiral, neurônios da raiz coclear (CRN), neurônios reticuloespi-nais do núcleo reticular caudal da ponte (PnC) e motoneurônios da medula espinal. O RAS pode ser modulado pela habituação, sensibilização, inibição por estímulo prévio (PPI) e pela potenciação por um estímulo adverso. Estas modulações podem ocorrer mediante a influên-cia de diversas substâncias neuroativas sobre os componentes deste circuito. Neste traba-lho avaliamos a origem de aferências monoaminérgicas (serotonina e noradrenalina) e CART-érgicas para os CRN e PnC. Para isso foram utilizados 54 ratos Wistar, adultos fê-meas, que foram submetidos a injeções de traçadores neuronais anterógrados e retrógrados para mapeamento de vias nervosas e a identificação imuno-histoquímica de substâncias neuroativas. Todos os protocolos experimentais foram aprovados pela Comissão de Ética no Uso de Animais do Instituto de Biociências de Botucatu - UNESP (protocolo no 17/08). Nos-sos resultados demonstram que o grupamento noradrenérgico A5 é uma fonte de aferências noradrenérgicas e CART-érgicas para os CRN e PnC, enquanto que o núcleo dorsal da rafe (DR) é a origem de aferências serotoninérgicas para estas regiões. Existem conexões recí-procas entre o DR, o A5 e o PnC. Além disso,... / The acoustic startle reflex (ASR) is a rapid motor reaction elicited by a sudden intense acoustic stimulus. This is an acoustic-motor reflex of brainstem conserved across mammal's species including man. Moreover the ASR is defensive behavior against both possible ag-gressive and alert to unexpected events. The ASR evokes responses of skeletal muscles as well as of autonomic nervous system with elevation of blood pressure and acceleration of the heart rate. In the rat, the elementary neural circuitry of ASR is mediated by ganglion cells of the organ of Corti, the cochlear root neurons (CRN), the pontine caudal reticular nucleus (PnC) and motoneurons of the spinal cord. The ASR could be modulated by habituation, sensitization, prepulse inhibition (PPI), and fear potentiation. These modulations were medi-ated by the influence of neuroactive substances on components of neuronal circuitry of ASR. In this work we evaluate the origin of monoaminergic (serotonin and noradrenaline) and CART-ergic afferents to CRN and PnC. Adult Female Wistar rats (n=54) were submitted to injections of retrograde and anterograde neuronal tracers in track-tracing experiments and identification of neuroactive substances in brain by immunohistochemistry technique. All ex-perimental protocols are according with Ethics Committee on Animal Use (protocol: 17/08). Our results demonstrate that noradrenergic area A5 (A5) is a source of noradrenergic and CART-ergic afferents to CRN and PnC, and dorsal raphe nucleus (DR) is origin of seroto-ninergic afferents to these regions. There are reciprocal connections between DR, A5 and PnC. Furthermore, after 14 and 21 days of lesion in A5, the percentage of PPI increased during intervals of 100 and 150 milliseconds without modification of ASR. This data suggest that A5 have direct action on elementary circuit of ASR evidenced his connections and modulation of PPI. Moreover, A5 and DR connections bring new insights about modulation ... / FAPESP: 08/02771-6

Analisamos o efeito do sistema serotoninérgico no desenvolvimento somático e na ontogênese de reflexos dos filhotes, cujas mães foram submetidas a tratamento farmacológico durante a prenhez. Ratas wistar prenhas foram divididas em dois grupos (N=11): Grupo AD, tratadas com água destilada, Grupo Sert, tratadas com sertralina 30mg/kg, 0,5mL/100g, s.c. Um dia após o parto 8 neonatos (4 machos e 4 fêmeas) foram mantidos com suas mães do 1º ao 21º dia pós-natal. O investigador cego avaliou o crescimento somático, características físicas e maturação de reflexos. Aos 22 e 60 dias de idade os encéfalos foram processados com técnicas de imunoistoquímica contra 5-HT. O grupo Sert, macho ou fêmea, apresentou atraso no crescimento somático e na maturação de alguns reflexos. A quantidade de neurônios 5-HT-IR foi alterada nos núcleos da rafe nos ratos aos 22 dias de idade, mas não aos 60 dias. A análise da morfometria dos neurônios 5-HT-IR, em ambas as idades estudadas, revelou alterações em sua forma. Os resultados deste estudo demonstram a ação inibitória da serotonina sobre o crescimento somático e desenvolvimento sensório-motor bem como alterações na quantidade e na forma dos neurônios 5-HT em ratos. / The aim of the present study was to investigate the effects of prenatal sertraline exposure on offspring in growth and somatic development and even in the maturation of reflex in rats. Female wistar rats were treated with sertraline (Sert, 30 mg/kg, 0,5 mL/100 g, s.c., N=11) or distilled water (Control, N=11) during the whole pregnancy. After the birth, 8 pups (4 males and 4 females) were kept in each litter during lactation. The blind investigator evaluated indicators of general body growth parameters, somatic maturation and ontogeny of reflex during the period of lactation. The central nervous system alterations were approached by 5-HT-IR using the ABC-DAB-Peroxidase techniques in animals at the 22st and 60st postnatal day. The Sert group, showed reduction on the somatic growth and on the maturation of reflexes. There was reduction in the amount of the 5-HT-IR neurons in the raphe nuclei at the 22st postnatal day, but did not change at the 60st. The morphometric analysis revealed alterations in the shape of these cells at the 22st and 60st postnatal day. An inhibitory action of the 5-HT on the somatic and sensory-motor growth in these rats was also observed. After the lactation period, the amount and shape of the 5-HT neurons were altered.