Analysis of cardiac motion using MRI and nonrigid image registration

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Imaging displacement and strain in the medial gastrocnemius muscle during ankle-joint motion using 2D-ciné DENSE MRI

Skeletal muscle structure has been defined on both macro and microscopic levels by gross dissection, light- and electron-microscopy. The basic physiological building blocks involve the electromechanical coupling between interlinking actin and myosin fibres. Detailed intramuscular behaviour during contraction can be clearly defined when examining a single isolated muscle. However, there are few areas in the human body where single muscles act independently to affect motion. This thesis attempts to address the compounded effect that muscles have on each other, while working synergistically in a group, such as the calf muscle

Influence of an insole intervention on biomechanical parameters during running with and without fatigue

El uso de soportes plantares está aumentando dentro de la población de corredores por sus demostrados beneficios sobre la redistribución de presiones plantares, la reducción del dolor, y la mejora de la función mecánica de las extremidades inferiores. Sin embargo, en contraposición a los soportes personalizados diseñados por un podólogo, la aparición de soportes prefabricados comercializados sin indicación médica ha provocado una gran controversia. El objetivo de este estudio fue analizar el efecto de soportes plantares (prefabricados, personalizados, control) y el estado de fatiga sobre parámetros espacio-temporales, presiones plantares, impactos de aceleración, y percepción de confort y esfuerzo durante la carrera. Para ello, en tres ocasiones diferentes (para cada uno de los soportes plantares de estudio), 40 participantes (20 hombres y 20 mujeres) fueron analizados antes y después de una carrera fatigante con un sistema de plantillas instrumentadas (Biofoot®) y acelerómetros colocados en tibia y cabeza (Sportmetrics). Además, también se midió la percepción de confort de cada soporte plantar, así como la fatiga percibida durante la carrera. Los soportes personalizados redujeron la presión plantar en el primer dedo (45%), arco interno (36%) y externo (40%) respecto a los soportes control; y en el talón interno (31%) y externo (53%) respecto a los soportes prefabricados. Además, los soportes prefabricados redujeron la presión en los dedos menores (35%), el arco interno (31%) y externo (31%) en comparación a los soportes control. De igual manera, se observó que los soportes personalizados redujeron la ratio de aceleración en cabeza respecto a los soportes prefabricados (11%) y de control (2%), mientras que los soportes prefabricados condujeron a una mayor ratio de aceleración en tibia (20%). Además, tanto los soportes personalizados como los prefabricados fueron percibidos como más confortables que la condición control. En conclusión, el uso de soportes plantares personalizados reduce significativamente la carga plantar en zonas de gran importancia para corredores respecto a no llevar soporte y respecto a soportes prefabricados, lo que respalda su uso como estrategia efectiva en la reducción de presiones. Por otro lado, el uso de soportes no alteró de forma significativa los impactos de aceleración, por lo no se debería prescribir su uso con el objetivo de reducir estos impactos. Sin embargo, en los casos donde se prescribe su uso por otras razones (presión plantar, dolor, corrección de la función mecánica, etc.), los soportes personalizados podrían mejorar la transmisión de impactos de aceleración respecto a los soportes prefabricados. Además, el uso de soportes plantares es percibido como algo confortable, lo que favorece la adherencia del corredor a este tipo de soportes.The use of insoles is increasing within the running population due to their associated benefits such as reduction of plantar pressures and pain, as well as improvement of the mechanical function of the lower limb. However, in contrast to custom-made insoles designed by a podiatrist in order to face a specific need, the use of prefabricated insoles commercialised without medical prescription is arising a great controversy. The aim of this study was therefore to analyse the effect of insoles (prefabricated, custom-made, control) and the fatigue state on spatio-temporal, plantar pressure, impact acceleration, comfort and fatigue parameters during running. Forty participants (20 men and 20 women) came to the lab on three occasions (each of them corresponding to an insole condition) where spatio-temporal parameters and plantar pressure (Biofoot®), tibial and head impact acceleration (Sportmetrics) were measured before and after a fatiguing run. Moreover, the perception of comfort of each insole and the fatigue perceived during the fatiguing procotol was also analysed. The custom-made insoles reduced the plantar pressure under the hallux (45%), the medial (36%) and lateral arch (40%) compared to the control condition; as well as under the medial (31%) and lateral heel (53%) compared to the prefabricated insoles. Furthermore, the prefabricated insoles reduced the plantar pressure under the toes (35%), the medial (31%) and the lateral arch (31%) compared to the control condition. Also, the custom-made insoles decreased the head impact rate compared to the prefabricated insoles (11%) and the control condition (2%), while the prefabricated insoles increased the tibial acceleration rate (20%). Finally, both types of insoles (custom-made and prefabricated) were perceived more comfortable than the control condition. In conclusion, the use of custom-made insoles reduces the plantar loading under areas that are of great interest to runners, what supports their use as an effective strategy to reduce plantar pressures and their potentially role as a strategy to reduce overuse running-related injuries. On the other hand, the use of insoles did not modify impact acceleration and therefore they should not be prescribed with the aim of reducing these impacts. However, in those situations where an insole intervention is needed (to reduce plantar pressure, pain, or correct the mechanical function of the lower limb), the custom-made insoles may provide a greater reduction of the impact accelerations compared to the prefabricated insoles. Moreover, the use of insoles is perceived as comfortable, what favours the adherence to their use

Removal of antagonistic spindle forces can rescue metaphase spindle length and reduce chromosome segregation defects

Regular Abstracts - Tuesday Poster Presentations: no. 1925Metaphase describes a phase of mitosis where chromosomes are attached and oriented on the bipolar spindle for subsequent segregation at anaphase. In diverse cell types, the metaphase spindle is maintained at a relatively constant length. Metaphase spindle length is proposed to be regulated by a balance of pushing and pulling forces generated by distinct sets of spindle microtubules and their interactions with motors and microtubule-associated proteins (MAPs). Spindle length appears important for chromosome segregation fidelity, as cells with shorter or longer than normal metaphase spindles, generated through deletion or inhibition of individual mitotic motors or MAPs, showed chromosome segregation defects. To test the force balance model of spindle length control and its effect on chromosome segregation, we applied fast microfluidic temperature-control with live-cell imaging to monitor the effect of switching off different combinations of antagonistic forces in the fission yeast metaphase spindle. We show that spindle midzone proteins kinesin-5 cut7p and microtubule bundler ase1p contribute to outward pushing forces, and spindle kinetochore proteins kinesin-8 klp5/6p and dam1p contribute to inward pulling forces. Removing these proteins individually led to aberrant metaphase spindle length and chromosome segregation defects. Removing these proteins in antagonistic combination rescued the defective spindle length and, in some combinations, also partially rescued chromosome segregation defects. Our results stress the importance of proper chromosome-to-microtubule attachment over spindle length regulation for proper chromosome segregation.postprin

Psr1p interacts with SUN/sad1p and EB1/mal3p to establish the bipolar spindle

Regular Abstracts - Sunday Poster Presentations: no. 382During mitosis, interpolar microtubules from two spindle pole bodies (SPBs) interdigitate to create an antiparallel microtubule array for accommodating numerous regulatory proteins. Among these proteins, the kinesin-5 cut7p/Eg5 is the key player responsible for sliding apart antiparallel microtubules and thus helps in establishing the bipolar spindle. At the onset of mitosis, two SPBs are adjacent to one another with most microtubules running nearly parallel toward the nuclear envelope, creating an unfavorable microtubule configuration for the kinesin-5 kinesins. Therefore, how the cell organizes the antiparallel microtubule array in the first place at mitotic onset remains enigmatic. Here, we show that a novel protein psrp1p localizes to the SPB and plays a key role in organizing the antiparallel microtubule array. The absence of psr1+ leads to a transient monopolar spindle and massive chromosome loss. Further functional characterization demonstrates that psr1p is recruited to the SPB through interaction with the conserved SUN protein sad1p and that psr1p physically interacts with the conserved microtubule plus tip protein mal3p/EB1. These results suggest a model that psr1p serves as a linking protein between sad1p/SUN and mal3p/EB1 to allow microtubule plus ends to be coupled to the SPBs for organization of an antiparallel microtubule array. Thus, we conclude that psr1p is involved in organizing the antiparallel microtubule array in the first place at mitosis onset by interaction with SUN/sad1p and EB1/mal3p, thereby establishing the bipolar spindle.postprin