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Skin ageing is a complex process which strongly impacts the three skin layers (epidermis, dermis, hypodermis) both functionally and structurally. Of particular interest are the effects of ageing on the dermis biomechanics and how this evolution can impact the reorganization of the cutaneous lines which compose the skin relief. It has been argued that the skin relief could reflect the underlying mechanical condition of the skin. Nevertheless, there is not yet conclusive evidence of the existence of such a link. This work aims at experimentally studying, in vivo, the correlation between the anisotropy of human skin biomechanics and skin topography as a function of ageing. The study was conducted on a panel of 20 men divided into 4 groups according to age (from 23 to 64 years old). The measurements were performed on the right volar forearm of each volunteer. For the biomechanical measurements, an innovative contactless bio-rheometer was developed. It allows access to the mechanical behaviour of the skin in several directions. This device generates an air blast without any contact with the skin area and measures its dynamic response (evaluation of speed of wave propagation) with a linear laser. Moreover, a turntable enables measurements to be made in different angular directions. To analyse the topography of skin relief, we proposed a new method, based on watershed and linear radon transformations. First, an optical analysis of a replica of the skin relief is performed. Then, from the skin image obtained, the density of the cutaneous lines is calculated in different directions using watersheld transformation. The orientation of the detected lines is then estimated with an algorithm based on linear radon transformation. The results observed show a good correlation between the skin relief and the mechanical properties of the skin all along the ageing process. For both topography and mechanical properties, there is a transition from an almost isotropic mechanical behaviour to an anisotropic one as a function of ageing process. Thus, we might conclude that the skin relief reflects the underlying mechanical conditions of the skin.

The wave phenomenon in free surface media stems from the propagation of mode grouping. Due to the nature of propagation in a given medium, this phenomenon expresses different types of dependence on the medium's properties and represents its mechanical admittance. In contrast with body wave propagation, dependencies related to surface propagation in a medium can be described by spatial-temporal characteristics. These characteristics can be obtained by performing appropriate experiments and do not require prior knowledge of the physical properties of the medium. In this study, we propose an original surface wave investigation and a phenomenological analysis approach adapted to the mechano-bio-structural states evaluation of in vivo human skin. Two objectives are sought with the method proposed: the first concerns the development of a non-invasive device for generating and tracking surface waves in human skin called Free-Skin-Surface-Wave (FSSW); the second concerns the adaptation of the Multi-Chanel Analysis of Surface Waves (MASW) method to evaluate the mechano-bio-structural states of human cutaneous tissue in vivo on the basis of the propagating phenomena observed. As an illustration of the proposed method application, we have done an in vivo evaluation, on intern-forearm of female volunteers population. In addition, we proposed a study of the aging effect and a comparison with ultrasound B-Mode technique, to validate the method sensitivity to follow the mechano-morphological properties of the in vivo human skin. In this study, our medium of application was human skin in vivo, but it is conceivable to extend this application to other soft biological media.

Human hair has a complex multi-scale structure that is extremely sensitive to several external factors. Hair fiber has three compartments: cuticle (scales), cortex and medulla. In the everyday life, hair experience important mechanical and chemical solicitations, such as smoothing, combing, drying and even washing, which can induce cracks in the cuticle. These damages diminish the mechanical properties of the cortex and contribute to a decrease in the brightness and softness of the hair. In the present article, the effects of different cosmetic treatments: bleaching, coloring and smoothing (with different temperatures) have been explored. Firstly, the morphology of hair was measured by interferometry. A multi-scale roughness characterization was performed by applying continuous wavelet transform. This method quantified the arithmetic mean of the surface topography at each wave length and permitted observing the evolution of the cuticle morphology before and after treatment. Secondly, a patented haptic tribometer system was used to measure the friction coefficient and acoustic vibrations generated during the tribological test. Previous results have shown that vibrations are related to the softness of the hair surface. The results show that all the treatments change the morphology and biotribology of hair by damaging the hair cuticle. These changes impact the sensorial properties of hair. In particular, the morphology of colored and bleached hair, compared to virgin one, is strongly modified: the scales are less defined, and the roughness is increased. These morphological modifications are correlated with an increase of the friction coefficient of around 50%, and acoustic vibratory level of around 2%, indicated a decrease of the sensorial properties. The hair fiber becomes rougher, dull and less soft. On the contrary, thermomechanical treatments of previously damaged hair, impact the morphology and biotribology of hair differently. The cuticle scales are flattened and the values of the friction coefficient and acoustic vibratory level decrease to reach the virgin hair values. Thus, the hair fiber seems to be smoother, brighter and softer. In conclusion, these results are essential for understanding the impact of different solicitations on the physical and sensorial properties of hair.

Chronological skin ageing is a phenomenon which imposes structural and functional changes on the cutaneous tissue. Mechanically, these changes can be related to structural rearrangements of the cutaneous tissue on surface and in volume (layers thickness). At the micro-structural level, the constitutional elements of the skin, collagen and elastin fibres, undergo also this rearrangement. The evolution of skin's mechanical properties at this level is the origin of a primordial in-vivo mechanical characteristic known as the natural pretension. In the context of understanding the in-vivo skin mechanical behaviour, related to the natural pretension, a lot of instrumentations have been demonstrated in the literature. They are mainly based on the interaction between dynamic adapted solicitation and the observed reaction on the skin. In this study, we evaluate the mechanical behaviour of human skin, following an impact which induces wave propagation. The use of impact solicitation allows the direct correlation between the dynamic induced reaction (vibration, and wave propagation) of the cutaneous tissue and its mechanical property. In our development, impact solicitation is contactless, with an air blast as generator of local deformation. The estimation of the speed of wave propagation enables the characterization of the mechanical behaviour of the skin. In order to validate the developed approaches, to understand the chronological ageing, gender and anisotropy effects on the skin properties, measurements have been realized on 77 healthy volunteers separated in five age groups. The obtained results are consistent with earlier works and confirm the efficiency of the developed instrumentation to estimate the changes of mechanical behaviour of the skin under age and gender effects.

To assess overall and malformation-specific trends in the prevalence and prenatal diagnosis of congenital anomalies in the Parisian population.The Paris Registry of Congenital Malformations is population-based and since 1981 has registered all cases with structural birth defects or chromosomal anomalies in the Parisian population. The total and livebirth prevalence and the proportion of cases with prenatal diagnosis were calculated for all anomalies and 20 malformations selected based on their higher frequency and their impact on health outcomes.The overall prevalence was 3.30% (95% CI 3.27-3.33), and the livebirth prevalence 2.42% (95% CI 2.39-2.45). The proportion of cases diagnosed prenatally increased from 16.5% (95% CI 14.1-19.1) in 1983 to 70.7% (95% CI 68.3-73.1) in 2007. Terminations of pregnancy for fetal anomaly (TOPFA) increased from 8.8% (95% CI 7.0-10.8) in 1983 to 35.6% (95% CI 33.1-38.1) in 2007. These results varied substantially for the 20 congenital anomalies studied.We found an increase in the overall prevalence of all anomalies, especially for chromosomal abnormalities. The observed increase is at least to a large extent due to trends in delayed childbearing and an increase in both pre- and postnatal diagnosis of congenital anomalies in our population.

Les donnees concernant les modifications quantitatives et qualitatives des principaux composants lipidiques cellulaires liees aux processus de differenciation et de maturation de la muqueuse intestinale sont passees en revue

Alterations in lipids linked to intestinal maturation and enterocyte differentiation were reviewed. The 3 main lipid components of cell membranes, ie cholesterol, phospholipids and glycolipids, were examined. Cell phospholipid content increases from the crypts to the mid-villus, which accounts for membrane development and organelle growth in differentiating cells. Changes in the proportion of phospholipid polar head groups occur in brush border membrane during postnatal maturation of the small intestine. The possibility that phospholipid fatty acid composition in differentiating cells might be altered by dietary lipids is discussed. Cholesterol biosynthesis mainly occurs in crypt and lower villus cells whereas its absorption from luminal content and esterification into lipoproteins occur in upper villus mature cells. Cholesterol cell content increases in mature cells in comparison to immature cells on the one hand, and in the distal by comparison with proximal parts of the intestine on the other. Increasing cholesterol content is generally correlated with decreasing membrane fluidity, which in turn could modulate functional properties of the mucosa. Glycosphingolipids are mainly found in the brush border membrane, which contains 20-30% glycolipids by weight of total lipids. These components tend to reinforce the membrane stability and significantly contribute to the surface properties of epithelial cells. The latter undergo noticeable changes during cell differentiation and postnatal maturation. Significant changes in both the glycosidic and lipophilic parts of glycosphingolipid molecules occur in differentiating cells and are of possible importance in the process of mucosal maturation. It is possible that the addition of a terminal sialic acid (sialyltransferase activity) instead of a terminal galactose (galactosyltransferase) to an endogenous acceptor (lactosylceramide) could constitute an important event in the differentiation process, and may account for the increasing content of hematosides along the intestinal villus of rat. Alterations in lipid counterpart mainly consist of hydroxylation of fatty acids in hematosides during postnatal maturation or in glucosylceramides during cell differentiation. Collectively these intestinal lipid changes may contribute in part to the development of mucosal barrier, selective permeability and functional properties of the mature intestinal mucosa.