Estimation of Ligament Loading and Anterior Tibial Translation in Healthy and ACL-Deficient Knees During Gait and the Influence of Increasing Tibial Slope Using EMG-Driven Approach

The purpose of this study was to develop a biomechanical model to estimate anterior tibial translation (ATT), anterior shear forces, and ligament loading in the healthy and anterior cruciate ligament (ACL)-deficient knee joint during gait. This model used electromyography (EMG), joint position, and force plate data as inputs to calculate ligament loading during stance phase. First, an EMG-driven model was used to calculate forces for the major muscles crossing the knee joint. The calculated muscle forces were used as inputs to a knee model that incorporated a knee–ligament model in order to solve for ATT and ligament forces. The model took advantage of using EMGs as inputs, and could account for the abnormal muscle activation patterns of ACL-deficient gait. We validated our model by comparing the calculated results with previous in vitro, in vivo, and numerical studies of healthy and ACL-deficient knees, and this gave us confidence on the accuracy of our model calculations. Our model predicted that ATT increased throughout stance phase for the ACL-deficient knee compared with the healthy knee. The medial collateral ligament functioned as the main passive restraint to anterior shear force in the ACL-deficient knee. Although strong co-contraction of knee flexors was found to help restrain ATT in the ACL-deficient knee, it did not counteract the effect of ACL rupture. Posterior inclination angle of the tibial plateau was found to be a crucial parameter in determining knee mechanics, and increasing the tibial slope inclination in our model would increase the resulting ATT and ligament forces in both healthy and ACL-deficient knees

Geminin Is Required for Zygotic Gene Expression at the Xenopus Mid-Blastula Transition

In many organisms early development is under control of the maternal genome and zygotic gene expression is delayed until the mid-blastula transition (MBT). As zygotic transcription initiates, cell cycle checkpoints become activated and the tempo of cell division slows. The mechanisms that activate zygotic transcription at the MBT are incompletely understood, but they are of interest because they may resemble mechanisms that cause stem cells to stop dividing and terminally differentiate. The unstable regulatory protein Geminin is thought to coordinate cell division with cell differentiation. Geminin is a bi-functional protein. It prevents a second round of DNA replication during S and G2 phase by binding and inhibiting the essential replication factor Cdt1. Geminin also binds and inhibits a number of transcription factors and chromatin remodeling proteins and is thought to keep dividing cells in an undifferentiated state. We previously found that the cells of Geminin-deficient Xenopus embryos arrest in G2 phase just after the MBT then disintegrate at the onset of gastrulation. Here we report that they also fail to express most zygotic genes. The gene expression defect is cell-autonomous and is reproduced by over-expressing Cdt1 or by incubating the embryos in hydroxyurea. Geminin deficient and hydroxyurea-treated blastomeres accumulate DNA damage in the form of double stranded breaks. Bypassing the Chk1 pathway overcomes the cell cycle arrest caused by Geminin depletion but does not restore zygotic gene expression. In fact, bypassing the Chk1 pathway by itself induces double stranded breaks and abolishes zygotic transcription. We did not find evidence that Geminin has a replication-independent effect on transcription. We conclude that Geminin is required to maintain genome integrity during the rapid cleavage divisions, and that DNA damage disrupts zygotic gene transcription at the MBT, probably through activation of DNA damage checkpoint pathways

Estudos em modalidades esportivas de combate: estado da arte

O objetivo do presente texto foi apresentar o estado da arte dos estudos sobre as modalidades esportivas de combate (MEC). Inicialmente, é destacada a relevância destas modalidades, tanto do ponto de vista histórico, quanto em relação à sua representatividade em competições internacionais, como os Jogos Olímpicos. Também são apresentadas as áreas mais comuns de atuação do profissional de Esporte nas MEC, bem como as iniciativas de organização de eventos, publicações, grupos de estudos e instituições científicas direcionadas às MEC. Posteriormente, estudos com possibilidade de aplicação em diferentes áreas de intervenção - preparação física, técnica e tática, gestão e organização - por parte do profissional do Esporte foram destacados. Finalmente, perspectivas de novos estudos e aspectos relacionados à preparação profissional são evidenciados.The objective of the present text was to present the state of art of studies related to combat sports (CS). Initially, it is presented the relevancy of these sports, from a historical perspective to its representativeness in international competitions, as the Olympic Games. The common areas of Sport's professional intervention, the initiatives of events, publications, research groups and scientific organizations related to the CS are also presented. Additionally, studies applied to different areas of Sport's professional intervention - physical training, technical and tactical preparation, management and organization - were also illustrated. Finally, perspectives of new studies and aspects related to professional preparation were reported

The Effect of winter sports participation on high school football players: strength, power, agility, and body composition

Contains fulltext : mmubn000001_160085268.pdf (publisher's version ) (Open Access)Promotores : T. Thien en P. Smits126 p