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Abstract: Fibroscan® is a new medical device that measures liver stiffness noninvasively. The method is based on one-dimensional transient elastography. Ultrasound signals (3,5 MHz) are used to follow the propagation of a low-frequency shear elastic wave (50 Hz) that propagates at a velocity that depends on liver stiffness. Measurement is performed on the right lobe of the liver using a probe that is placed on the skin surface. Result is obtained at the end of examination that takes about 5 minutes. Pilot and multicentre studies have shown that liver stiffness is strongly correlated to fibrosis stage obtained from liver biopsy on patients with chronic hepatitis C. Fibroscan® could be used to improve the evaluation of patients with liver chronic diseases by reducing the number of liver biopsies and by allowing the following of treatments. [Copyright &y& Elsevier]

Abstract: The preferred assessment of bone biomechanical competence in vitro is by direct mechanical testing and in vivo by X-ray absorptiometry techniques. For more than 30 years investigators have been developing alternative techniques, by ultrasonic methods, aimed at providing (i) the elastic properties in vitro without the complications related the destructive character of mechanical testing and (ii) the evaluation of the fracture risk in vivo, taking benefit of the propagation of elastic wave which are inherently affected by both material and structural bone properties. The in vitro strategy includes the use of multiscale ultrasonic assessment for the combined evaluation of both the material (or intrinsic) and the structural elastic properties in various axes of symmetry. The in vivo approach involves the use of the different propagation modes (bulk wave, guided wave, surface wave) permitted by the ultrasonic approach. We will review the in vitro and clinical data on each ultrasonic approach and discuss potential areas of development in the field of quantitative bone assessment bone. [Copyright &y& Elsevier]

Abstract: After a historical introduction the authors describe their most recent results on the structure, assembly and elasticity of elastin. Recent results obtained by analyzing the conformation of polypeptide sequences encoded by the single exons of human tropoelastin demonstrated the presence of labile conformations such as poly-proline II helix (PPII) and β-turns whose stability is strongly dependent on the microenvironment. Stable, periodic structures, such as α-helices, are only present in the poly-alanine cross-linking domains. These findings give a strong experimental basis to the understanding of the molecular mechanism of elasticity of elastin. In particular, they strongly support the description of the native relaxed state of the protein in terms of trans-conformational equilibria between extended and folded structures as previously proposed [Int. J. Biochem. Cell. Biol. 31 (1999) 261]. The same polypeptide sequences have been analyzed for their ability to coacervate and to self-assembly. Although the great majority of them were shown to be able to adopt more or less organized structures, only a few were indeed able to coacervate. Studies carried out by transmission electron microscopy showed the polypeptides to adopt a variety of supramolecular structures going from a filamentous organization (typical of elastin) to amyloid-like fibers. On the whole, the results obtained gave significant insight to the roles played by specific polypeptide sequences in self-assembly and possibly in elasticity. [Copyright &y& Elsevier]

Abstract: The mobility of our body structures is so intrinsic and natural to us that we tend to take it for granted. The very fact of being able to pinch your skin and lift it, then let it go and see it return to its initial shape and texture in just a few seconds may seem banal enough until you begin to think of all the elements involved. The same is true when you bend your fingers and think of the movement of the flexor tendon across the palm without external translation. For decades, scientists thought that the skin was simply an elastic structure with loose connective tissue and a more or less virtual space. However, in biomechanical terms, this explanation is very vague. These old concepts developed more than 50 years ago have evolved thanks to the impact of research at the microscopic level, and the global, mesospheric concept has been abandoned. And yet, surgical dissection in vivo demonstrates that there are only tissue connections, simply a histological continuum without any clear separation between skin and hypodermis, the vessels, the aponeurosis and the muscles. In fact, visible everywhere are structures, which ensure a gliding movement between the aponeurosis, the fat structures and the dermis. As they studied this system of gliding between the various organs, in particular at the level of the tendons, the authors noted the existence of a type of system composed of cables and veil-like structures that they term the Multimicrovacuolar Collagen Dynamic Absorption System (MCDAS). This system looks totally chaotic in organization and seems to function in a manner far removed from traditional mechanical structures. The functional unity of this sliding system is dependent upon a polyhedral three-dimensional crisscrossing in space of the microvacuoles, whose collagen envelope is type 1 or type 4 and whose content is made up of proteoglycoaminoglycans. The dynamic of this multimicrovacuolar system allows all of the subtle movements that occur within the body, thanks to its pre-stressed nature and the molecular fusion-scission-dilacerations that it is capable of. In this way, the system is mobile, can move quickly and interdependently, and is able to adapt is plasticity. This notion of microvacuoles is a fascinating one because it provides an explanation for the system’s space-filling ability.The matter is composed of elements. However, although they seem to be arranged in a haphazard manner, this is not the case. In fact, they occupy space in an optimal manner. If we accept this notion of microvacuoles, then it becomes possible to explain certain pathologies occurring with age, such as edema, obesity, aging and inflammation. This sliding system is to be found everywhere in the body and would seem to be the basic network of tissue organization.For this reason, it should be thought of in global terms. Since it constitutes the inseparable link and occurs in all living structures and at many levels, could it be that it the basic architectural design of Life? [Copyright &y& Elsevier]

Summary Background Muscle parameters like muscle tone and elasticity are important for development of the training program in relationship with speed reaction and to maintain the body position. Objectives We propose to make a comparative study between two types of muscle training using myotonometry to estimate the muscle tone. Equipment and methods We make a comparison between two types of muscle training for two athletes (age –18 years) that participate at two different muscle training programs. The assessment of muscle parameters included: muscle tone (frequency F), elasticity (decrement), stiffness and index force, by myotonometry for rectus femoris (RF) and tibialis anterior (TA). The training program: develop the execution speed by increasing explosive strength-training program T1 of the lower limbs versus the training program which aims to develop the maxim force by isometric exercises T2. Results We observe that for RF, F has a symmetry right/left for T1 and very close to norms, but at the same time for T2 we observe a high difference between right/left side, and high value for RF left side, that means an overuse of muscle group and an important decrease of the RF right side, that means muscle fatigue. Conclusions The results of muscle tone assessment by myotonometry can be an indicator for fatigue. The training program based on plyometry, stretching and development of speed, improve the muscle parameters and reduce the risk of muscle fatigue and muscle injury. At the same time the T2 training program, based on isometric contraction and static strength training, increase the asymmetry between right and left side and also decrease the elasticity. [ABSTRACT FROM AUTHOR]