Results 1 - 10 of 10843
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[en] For myogenesis, new myotubes are formed by the fusion of differentiated myoblasts. In the sequence of events for myotube formation, intercellular communication through gap junctions composed of connexin 43 (Cx43) plays critical roles in regulating the alignment and fusion of myoblasts in advances of myotube formation in vitro. On the other hand, the relationship between the expression patterns of Cx43 and the process of myotube formation in satellite cells during muscle regeneration in vivo remains poorly understood. The present study investigated the relationship between Cx43 and satellite cells in muscle regeneration in vivo. The expression of Cx43 was detected in skeletal muscles on day 1 post-muscle injury, but not in control muscles. Interestingly, the expression of Cx43 was not localized on the inside of the basement membrane of myofibers in the regenerating muscles. Moreover, although the clusters of differentiated satellite cells, which represent a more advanced stage of myotube formation, were observed on the inside of the basement membrane of myofibers in regenerating muscles, the expression of Cx43 was not localized in the clusters of these satellite cells. Therefore, in the present study, it was suggested that Cx43 may not directly contribute to muscle regeneration via satellite cells
[en] Myogenesis is a highly regulated multi-step process involving myoblast proliferation and differentiation. Although studies over the last decades have identified several factors governing these distinct major phases, many of them are not yet known. In order to identify novel genes, we took advantage of the C2C12 myoblastic line to establish a functional siRNA screen combined with quantitative-imaging analysis of a large amount of differentiated myoblasts. We knocked down 100 preselected mouse genes without a previously characterized role in muscle. Using image analysis, we tracked gene-silencing phenotypes by quantitative assessment of cellular density, myotube quantity, myotube morphology and fusion index. Our results have revealed six genes involved in both stages of C2C12 myogenesis and 13 genes specific to the differentiation stage. These findings prove that our RNAi-based screen could be an efficient tool to detect clear and subtle phenotypes allowing the identification of new myogenic regulators in mammals. - Highlights: • A new optimized protocol to perform a functional siRNA based screen. • 100 preselected genes knocked-down in C2C12 myoblastic cell line. • 19 candidates genes identified as novel myogenic actors.
[en] We present a normally closed, remotely actuated, secure coded, electrostatically driven active microvalve using passive components. This is carried out by utilizing the complex signal processing capabilities of two identical 5 × 2-bit Barker sequence encoded acoustic wave correlators. An electrostatically driven microchannel, comprising two conducting diaphragms as the top and bottom walls, is placed in between the compressor interdigital transducers of the two correlators. Secure interrogability of the microvalve is demonstrated by finite element modelling of the complete structure and the quantitative deduction of the code dependent microchannel actuation. Furthermore, the influence of the excited acoustic modes of the correlator on the microchannel deflection is investigated to optimize the microvalve design
[en] In this study, a new piezoactuator-based prototype microactuator is proposed with a hydraulic displacement amplification system. A piezoactuator is used to deflect a diaphragm which displaces a certain volume of hydraulic fluid into a smaller-diameter piston chamber, thereby amplifying the displacement at the other end of the piston. An electro-mechanical model is implemented to estimate the displacement of a multilayer piezoelectric actuator for the applied input voltage considering the hysteresis behavior. The displacement characteristics of the proposed microactuator are studied for triangular actuation voltage signal. Results of the experiments and simulation of the displacement behavior of the stacked piezoactuator and the amplified displacement of the prototype actuator were compared. Experimental results suggest that the mathematical model developed for the new piezoactuator-based prototype actuator is capable of estimating its displacement behavior accurately, within an error of 1.2%.
[en] Muscular dystrophy and peripheral neuropathy have been linked to mutations in genes encoding nuclear envelope proteins; however, the molecular mechanisms underlying these disorders remain unresolved. Nuclear envelope protein p19A is a protein of unknown function encoded by a gene at chromosome 4q35. p19A levels are significantly reduced in human muscle as cells differentiate from myoblasts to myotubes; however, its levels are not similarly reduced in all differentiation systems tested. Because 4q35 has been linked to facioscapulohumeral muscular dystrophy (FSHD) and some adjacent genes are reportedly misregulated in the disorder, levels of p19A were analyzed in muscle samples from patients with FSHD. Although p19A was increased in most cases, an absolute correlation was not observed. Nonetheless, p19A downregulation in normal muscle differentiation suggests that in the cases where its gene is inappropriately re-activated it could affect muscle differentiation and contribute to disease pathology.
[en] This paper reports on a differential pressure sensor using a piezoresistive cantilever with the dimensions of 125 µm×100 µm×0.3 µm. The sensor has a higher sensitivity than a traditional diaphragm sensor because of the three free edges of the cantilever. The measured results indicated that the fabricated cantilever bent according to theory when differential pressure was applied. The sensitivity and resolution of the differential pressure were 3.2×10"−"4 Pa"−"1 and 0.02 Pa from −20 Pa to 20 Pa, respectively. (paper)
[en] To determine the variations in morphology of the diaphragm with aging, 120 CT studies of patients in their third to eighth decade of life were systematically evaluated for the appearance and thickness of the muscular diaphragm. The thickness of the muscular diaphragm decreased with advancing age from 8 +- 1.8 mm to 6.5 +- 0.7 mm. The number of irregularities and defects of the diaphragm increased with age from 0% to 60% between the fourth and eighth decades. A strong correlation with emphysema was demonstrated. The majority of these defects appeared in the posterior medial aspect of the diaphragm corresponding to the foramen of Bochdalek. However, these defects were most probably acquired and not congenital as they were not demonstrable in the younger population. The suggest that there exists a structurally weak area in this region of the diaphragm that becomes apparent with increased laxity of connective tissue and decreased muscle tone with advancing age