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Extension Movements (extension + movement)
Selected AbstractsConvergence and extension movements affect dynamic notochord-somite interactions essential for zebrafish slow muscle morphogenesisDEVELOPMENTAL DYNAMICS, Issue 10 2007Chunyue Yin Abstract During vertebrate gastrulation, convergence and extension (C&E) movements shape and position the somites that form the fast and slow muscles. In zebrafish knypek;trilobite non-canonical Wnt mutants, defective C&E movements cause misshapen somites and reduction of slow muscle precursors, the adaxial cells. Here, we demonstrate essential roles of C&E in slow muscle morphogenesis. During segmentation, the adaxial cells change shapes and migrate laterally to form slow muscles at the myotome surface. Using confocal imaging techniques, we show that the adaxial cells undergo three-step shape changes, including dorsoventral elongation, anterior-ward rotation, and anteroposterior elongation. The adaxial cells in knypek;trilobite double mutants maintain prolonged contact with the notochord and fail to rotate anteriorly. Such a defect was suppressed by physical removal of their notochord or by introducing wild-type notochord cells into the mutant. We propose that in the double mutants, impaired C&E movements disrupt notochord development, which impedes the adaxial cell shape changes. Developmental Dynamics 236:2742,2756, 2007. © 2007 Wiley-Liss, Inc. [source] Local activation of protein kinase A inhibits morphogenetic movements during Xenopus gastrulationDEVELOPMENTAL DYNAMICS, Issue 1 2003Byung-Ho Song Abstract cAMP-dependent protein kinase (PKA) has various biological roles in many organisms. However, little is known about its role in the developmental processes of vertebrates. In this study, we describe the functional analysis of PKA during gastrulation movements in Xenopus laevis. Overexpression of constitutively active PKA (cPKA) in the dorsal equatorial region of the embryo affects morphogenetic movement during gastrulation. We also show that intrinsic differences of PKA activities along the dorsoventral axis are set up and the level of PKA activity on the dorsal region is lower than that on the ventral region from late blastula to gastrula stages. In addition, PKA activation in animal explants inhibits activin-induced elongation. In cPKA-injected embryos, there were no changes in the expressions of markers involved in mesoderm specification, although the correct expression domains of these genes were altered. The effects of PKA activation can be restored by coexpression of PKI, a pseudosubstrate of PKA. We further analyzed the effects of PKA activation on the behavior of migratory gastrulating cells in vitro. Expression of cPKA in head mesoderm cells causes less polarized and/or randomized migration as demonstrated by a directional cell migration assay. Finally, we show that RhoA GTPase lies downstream of PKA, affecting activin-induced convergent extension movements. Taken together, these results suggest that overexpressed PKA can modulate a pathway responsible for morphogenetic movements during Xenopus gastrulation. Developmental Dynamics 227:91,103, 2003. © 2003 Wiley-Liss, Inc. [source] Nucleoredoxin regulates the Wnt/planar cell polarity pathway in XenopusGENES TO CELLS, Issue 9 2008Yosuke Funato The Wnt signaling pathway is conserved across species, and is essential for early development. We previously identified nucleoredoxin (NRX) as a protein that interacts with dishevelled (Dvl) in vivo to negatively regulate the Wnt/,-catenin pathway. However, whether NRX affects another branch of the Wnt pathway, the Wnt/planar cell polarity (PCP) pathway, remains unclear. Here we show that NRX regulates the Wnt/PCP pathway. In Xenopus laevis, over-expression or depletion of NRX by injection of NRX mRNA or antisense morpholino oligonucleotide, respectively, yields the bent-axis phenotype that is typically observed in embryos with abnormal PCP pathway activity. In co-injection experiments of Dvl and NRX mRNA, NRX suppresses the Dvl-induced bent-axis phenotype. Over-expression or depletion of NRX also suppresses the convergent extension movements that are believed to underlie normal gastrulation. We also found that NRX can inhibit Dvl-induced up-regulation of c-Jun phosphorylation. These results indicate that NRX plays crucial roles in the Wnt/PCP pathway through Dvl and regulates Xenopus gastrulation movements. [source] fMRI analysis for motor paradigms using EMG-based designs: A validation studyHUMAN BRAIN MAPPING, Issue 11 2007Anne-Fleur van Rootselaar Abstract The goal of the present validation study is to show that continuous surface EMG recorded simultaneously with 3T fMRI can be used to identify local brain activity related to (1) motor tasks, and to (2) muscle activity independently of a specific motor task, i.e. spontaneous (abnormal) movements. Five healthy participants performed a motor task, consisting of posture (low EMG power), and slow (medium EMG power) and fast (high EMG power) wrist flexion,extension movements. Brain activation maps derived from a conventional block design analysis (block-only design) were compared with brain activation maps derived using EMG-based regressors: (1) using the continuous EMG power as a single regressor of interest (EMG-only design) to relate motor performance and brain activity, and (2) using EMG power variability as an additional regressor in the fMRI block design analysis to relate movement variability and brain activity (mathematically) independent of the motor task. The agreement between the identified brain areas for the block-only design and the EMG-only design was excellent for all participants. Additionally, we showed that EMG power variability correlated well with activity in brain areas known to be involved in movement modulation. These innovative EMG-fMRI analysis techniques will allow the application of novel motor paradigms. This is an important step forward in the study of both the normally functioning motor system and the pathophysiological mechanisms in movement disorders. Hum Brain Mapp, 2007. © 2007 Wiley-Liss, Inc. [source] Hypertonia in childhood secondary dystonia due to cerebral palsy is associated with reflex muscle activation,MOVEMENT DISORDERS, Issue 7 2009Johan van Doornik PhD Abstract It is often assumed that co-contraction of antagonist muscles is responsible for increased resistance to passive movement in hypertonic dystonia. Although co-contraction may certainly contribute to hypertonia in some patients, the role of reflex activation has never been investigated. We measured joint torque and surface electromyographic activity during passive flexion and extension movements of the elbow in 8 children with hypertonic arm dystonia due to dyskinetic cerebral palsy. In all cases, we found significant phasic electromyographic activity in the lengthening muscle, consistent with reflex activity. By correlating activation with position or velocity of the limb, we determined that some children exhibit position-dependent activation, some exhibit velocity-dependent activation, and some exhibit a mixed pattern of activation. We conclude that involuntary or reflex muscle activation in response to stretch may be a significant contributor to increased tone in hypertonic dystonia, and we conjecture that this activation may be more important than co-contraction for determining the resistance to passive movement. © 2009 Movement Disorder Society [source] Impact of gravity loading on post-stroke reaching and its relationship to weaknessMUSCLE AND NERVE, Issue 2 2007Randall F. Beer PhD Abstract The ability to extend the elbow following stroke depends on the magnitude and direction of torques acting at the shoulder. The mechanisms underlying this link remain unclear. The purpose of this study was to evaluate whether the effects of shoulder loading on elbow function were related to weakness or its distribution in the paretic limb. Ten subjects with longstanding hemiparesis performed movements with the arm either passively supported against gravity by an air bearing, or by activation of shoulder muscles. Isometric maximum voluntary torques at the elbow and shoulder were measured using a load cell. The speed and range of elbow extension movements were negatively impacted by actively supporting the paretic limb against gravity. However, the effects of gravity loading were not related to proximal weakness or abnormalities in the elbow flexor,extensor strength balance. The findings support the existence of abnormal descending motor commands that constrain the ability of stroke survivors to generate elbow extension torque in combination with abduction torque at the shoulder. Muscle Nerve, 2007 [source] Isoresistive dynamometer measurement of trunk muscle velocity at different angular phases of flexion and extensionCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 4 2001J. Surakka Isoresistive trunk muscle dynamometer is a potentially useful piece of equipment in evaluation of trunk muscle velocity, but to date, studies analysing the possibilities and limitations of such measurements are scarce. The aim of this study was to analyse the trunk muscle velocity in repetitive flexion and extension movements at three different angular phases, using an isoresistive trunk muscle dynamometer, and to assess the reliability of the measurements. The study population consisted of 120 healthy, sedentary men and women who volunteered for the study. The measurements were carried out before and after a 22-week training intervention programme. The results show that the peak velocities of the phases between 15 and 35° in flexion and 20,0° in extension (i.e. the second phases) correlated highly (r=0·99 in flexion and in extension) with the peak velocity of the whole movement ranging from ,5 to 55° in flexion and 40 to ,20° in extension. Correlations were high, both before and after the intervention. The LISREL model analysis showed high reliability of measurement for the second angular phases (in flexion and extension). According to the model, the correlation between the first and second measurement (with a 22-week training intervention in between) was 0·78 in flexion and 0·81 in extension. In conclusion, the angular phases from 15 to 35° in flexion and from 20 to 0° in extension represent the peak velocity of the whole movement. Negative residual correlations between the first and last angular phases in the LISREL model reflect the way of performing the movement: the faster the start the slower the end, and vice versa. [source] Precues enable multiple response preprogramming: Evidence from startlePSYCHOPHYSIOLOGY, Issue 2 2009Anthony N. Carlsen Abstract When one or more response dimensions in a choice reaction time (RT) task are provided beforehand (or precued), RT decreases, indicating that the precued part of a response was prepared in advance. In this study, a startling acoustic stimulus was used to investigate the amount of preprogramming that occurs when part of the response is precued because a startling stimulus has been shown to directly trigger preprogrammed responses. Participants performed wrist flexion/extension movements in a precued one to four choice RT paradigm. A control auditory stimulus (82 dB) or a startling acoustic stimulus (124 dB) accompanied the visual "go" signal on each trial. Although RT latencies were significantly reduced by the startle, many more errors were observed in the startled conditions. Importantly, the errors seen at short RT latencies largely reflected multiple movements to the cued response alternatives, suggesting that multiple responses were preprogrammed. [source] | |||||||||||||