Skeletal

Hundreds of genes, including muscle creatine kinase (MCK), are differentially expressed in fast- and slow-twitch muscle fibers, but the fiber type-specific regulatory mechanisms are not well understood. Modulatory region 1 (MR1) is a 1-kb regulatory region within MCK intron 1 that is highly active in terminally differentiating skeletal myocytes in vitro. A MCK small intronic enhancer (MCK-SIE) containing a paired E-box/myocyte enhancer factor 2 (MEF2) regulatory motif resides within MR1. The SIE's transcriptional activity equals that of the extensively characterized 206-bp MCK 5'-enhancer, but the MCK-SIE is flanked by regions that can repress its activity via the individual and combined effects of about 15 different but highly conserved 9- to 24-bp sequences. ChIP and ChIP-Seq analyses indicate that the SIE and the MCK 5'-enhancer are occupied by MyoD, myogenin and MEF2. Many other E-boxes located within or immediately adjacent to intron 1 are not occupied by MyoD or my...

Bone is a dynamic tissue, responding locally to differential mechanical loading and systemically to hormonal stimuli. Although the tendency is to consider compact bone a homogenous tissue, regional variations in microarchitecture are known to have quite different properties relating to processes of growth and mechanical loading. Specifically, we investigated an example of microstructural variation of the human, adult femoral endocortex, referred to here as the endosteal lamellar pocket (ELP). The femoral ELP is characterised as a histomorphological meta-feature, made distinct from general circumferential lamellae by its hemicircumferential lamellar orientation, medial positioning, radially oriented Volkmann's canals and decreased presence of Haversian systems. Our preliminary observations of mid-diaphyseal transverse thin-ground sections demonstrate the ELP as a regular meta-feature of adult human femora unearthed from the Maya archaeological site of Xcambó, Mexico. ELPs were easily identified in 38 of 45 examined individuals. Their size, shape and degree of secondary remodelling were variable. In comparison, ELP lamellae and those originating from the periosteum are divergent, or non-concentric in orientation. This divergence, along with the ELP's medial position, suggest it forms during growth through endosteal modelling drift. Possible considerations for ELP formation and persistence with age are discussed as well as its implications for the study of bone dynamics during growth and activity. Further research is necessary to quantitatively measure the morphology of ELPs and to identify any co-variance between ELP characteristics and age, sex or indicators of mechanical loading. Copyright © 2010 John Wiley & Sons, Ltd.

"Estimates of muscle and other soft tissue properties derived from hominin skeletal and fossil remains would greatly enhance descriptions of body size and shape, and prior physical and metabolic capabilities. Presently, the utility of this approach is uncertain given the complex nature of the relationship between
muscle and bone. To address various principal issues, peripheral quantitative computed tomography (pQCT) imaging was used to quantify these relationships at the midshaft of the arm, forearm, and lower leg of modern human athletes (runners, field hockey players, swimmers, and cricketers) and control
subjects. Given the presumed behavior patterns of prehistoric hominins, the inclusion of highly active human participants was required. Soft tissue and muscle area was compared with bone area, diaphyseal shape, and torsional rigidity. Relationships were found between muscle area and bone area in the arm,
and muscle area and torsional rigidity in the forearm. However, the high standard error and prediction error that define these relationships indicate that muscle or other soft tissue predictions derived from hominin fossil or skeletal remains would be untenable. In the tibia, the relationship between soft tissue
properties and bone properties were primarily explained by covariation with body size. While the strength of the muscle-bone relationships in the arm and forearm vary among athletes and control subgroups, it appears that habitual upper limb loading performed throughout adolescence neither
strengthens nor weakens this relationship. Future attempts to estimate soft tissue properties from osseous tissue may be improved through the use of medical CT or MRI to image complete limb segments and isolate individual muscles."

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset progressive muscle disorder caused by a poly-alanine expansion mutation in the Poly(A) Binding Protein Nuclear 1 (PABPN1). The molecular mechanisms that regulate disease onset and progression are largely unknown. In order to identify molecular pathways that are consistently associated with OPMD, we performed an integrated high-throughput transcriptome study in affected muscles of OPMD animal models and patients. The ubiquitin-proteasome system (UPS) was found to be the most consistently and significantly OPMD-deregulated pathway across species. We could correlate the association of the UPS OPMD-deregulated genes with stages of disease progression. The expression trend of a subset of these genes is age-associated and therefore, marks the late onset of the disease, and a second group with expression trends relating to disease-progression. We demonstrate a correlation between expression trends and entrapment into PABPN1 insolubl...

Crustaceans have been successfully employed to study legged locomotion for decades. Most studies have focused on either forwards-walking macrurans, or sideways-walking brachyurans. Libinia emarginata is a Majoid crab (Brachyura) and as such belongs to the earliest group to have evolved the crab form from homoloid ancestors. Unlike most brachyurans, Libinia walks forwards 80% of the time. We employed standard anatomical techniques and motion analysis to compare the skeleton, stance, and the range of motion of the legs of Libinia to the sideways-walking green shore crab (Carcinus maenas), and to the forwards-walking crayfish (Procambarus clarkii). We found animals tended to have greater ranges of motion for joints articulating in the preferred direction of locomotion. Leg segments proximal to such joints were comparatively longer. Thorax elongation, leg length and placement at rest also reflected walking preference. Comparative studies of walking in Libinia and other brachyurans may shed light on the neuroethology of legged locomotion, and on the anatomical and physiological changes necessary for sideways-walking in crustaceans.