[Not Available]. / Peau sèche-rêche et "Hydratation". Concept de la capture de l'eau organisée comme de la glace.

About sixty years ago Frank and Evans showed, by entropy measurements, that when a "non-polar molecule dissolves in water it modifies the water structure in the direction of greater 'cristallinity', the water builds a microscopic iceberg around it" Now, we propose the "concept of ice-like-water capture": a lowering of organized ice-like water promotes aggregation (loss of solubility) of the filaggrin/keratin1/keratin10 associations through their hydrophobic patches. The capture of ice-like water may be performed by the glucoceramides-rich bilayers in stratum granulosum. Probably, the same process aggregates the proteins of corneocytes envelope as well as corneodesmosomes proteins. According to the "concept of ice-like-water capture", to regulate the keratinization, it is not total water that must be added to the stratum corneum, but ice-like water that must be removed from stratum granulosum. Both petrolatum (lipophilic ingredient) and glycerol (hydrophilic ingredient) would capture the ice-like water, most probably after combination with the lipid bilayers of stratum corneum. Moisturizing cream, when organized in secondary droplets is likely to perform the same action. Measurements by near-infrared reflectance spectroscopy of the skin show that petrolatum; glycerol and/or moisturizing cream enhance the quantity of bulk water (1890-1897 nm band). As the ice-like water is the complement of bulk water, the enhanced bulk water let presume an ice-like water lessening. Some desynchronization (late or forward) of the keratinization/differentiation which confer the somatosensory problems associated with "dry and flaky skin" may be linked to an excess or lack of ice-like. For instance, the winter xerosis, very common by chilling weather, could be explained by an increase of ice-like water driven by the fall of the temperature.

Les enzymes de l'espace extra-cellulaire du stratum corneum.

Synopsis Bien que le stratum corneum soit composé de cellules 'mortes', il est le siège d'une activité métabolique très importante. Mais, contrairement à la plupart d'autres tissus, cette activité a la particularité d'étre extra-cellulaire. Elle est due à des enzymes excrétées par les Corps d'Odland avec les bicouches céramidiques. Ces enzymes sont des hydrolases, elles sont identiques ou très proches de celles des lysosomes. Les principales activités observées correspondent à une (ou des) glycosidase(s), une phospholipase, une sphingomyélinase, une phosphatase, une (ou des) estérase(s), des sulfatases, des protéases. Comme les hydrolases des lysosomes, elles semblent peu spécifiques. Ce pool enzymatique pourrait jouer plusieurs rôles fondamentaux, notamment: 1. La transformation des bicouches gluco-céramidiques en bicouches ceramidiques plus lipophiles; 2. L'élimination de la membrane plasmique, dont certains produits du catabolisme, comme les acides gras et les céramides, peuvent être intégrés aux bicouches céramidiques; 3. La diminution de la cohésion entre les cornéocytes; 4. La protection contre l'intrusion de corps étrangers. Comme tout système enzymatique, les hydrolases extra-cellulaires, sont certainement soumises à des régulations. Plusieurs de ces régulations sont envisagées. A partir de considérations d'enzymologie, le pH de la base du stratum corneum peut être estiméà environ 5. En cosmétologie, les enzymes du stratum corneum sont mises à contribution pour rendre actifs des précurseurs. L'étude des conséquences des modifications de l'activité enzymatique sur l'état de la peau pourrait constituer une future voie de recherche extrêmement prometteuse.

Approche osmotique de l'hydratation du stratum corneum.

Summary An osmotic approach to a study of hydration of the stratum corneum At first Middleton, in his classic studies, explains the water sorption of stratum corneum by osmotic processes. To follow Middleton, and in order to study water osmosis diffusion, we made an osmotic model of stratum corneum (OMSC). The OMSC was constituted by 0.8 g of sheep wool, which was closed in a dialysis bag. When the OMSC was placed in the water, its weight increased, due to water diffusing through the membrane to bind with the protein. The rate of sorption was slow, but the value was about the same as that which Scheuplein has observed for the stratum corneum. At saturation, the weight of 'bound water'was 13 times greater than the weight of keratine. The components of Natural Moisturizing Factor and glycerol enhance the sorption rate and the weight fraction 'bound water'at saturation. The best component is urea. This observation suggests that humectants increase the number of water-binding sites of keratin. The OMSC could allow preliminary tests of water-soluble skin moisturizers.

Study of a ternary diagram gel according to a methodology of experimental research.

Synopsis The purpose of this work was to compare two methods to determine the formulation of a gel: a 'classical'method previously used and a rational method using matrixes based on the Scheffe algorithm which is particularly useful in the study of these type of mixtures. This gel was composed of three products: C12-C15 Alcohols Benzoate, Cyclomethicone and Ethylene Vinyl Acetate Copolymer in water. The ratios of these compounds were studied according to five criteria: compatibility between phases, consistency, whiteness, cost and 'skin spreading'. To determine the incompatibility zone inside the ternary diagram, we carried out our study by a systematic sequential walk strategy (seven experiments). Three parameters (consistency, whiteness, cost) were optimized using the Scheffe algorithm. This method only needs a limited number of experiments on which to base an empirical mathematical model of the studied phenomena as a function of the different experimental factors. The formulation is therefore discussed as a function of the first degree linear, the second degree and a third degree 'reduced cubical'model. The validity of the possible models are also discussed and the 'reduced cubical'best fits our phenomena.

A cosmetic senna, Cassia obovata: 'neutral henna'.

Summary The powder made with leaflets of a senna, Cassia obovata Coll., is a cosmetic mis-called 'neutral henna' The traditional use of C. obovata is as a laxative. The principal active components of this laxative drug are sennosides A and B. In the Middle Ages the blend of henna (Lawsonia inermis) and senna was called 'the two hennas'. The traditional dermatological uses of C. obovata concern the henna component. The antibacterial activity of C. obovata (Table III) may explain these uses. Thin layer chromatographs showed that several C. obovata components are fixed to keratin (Table IV). The fixation hypothesis is given in Fig. 8. Bleached hair and, to a lesser extent, light (and white) hairs, turned golden light-brown or brown differing with the time of treatment. The hair absorbs the C. obovata components. In the initial stages uptake was linear with the square root of time, indicative of a diffusion process. In bleached hair diffusion is fast (7.5% uptake in 9 h), but there was no diffusion in dark hair. The sorption by hair pre-treated by hydrogen peroxide was greater than virgin hair, suggesting that the C. obovata components were chemically bound to the cysteic function of keratin. The initial 'uptake jump' suggests that the diffusion process was biphasic and/or several components diffused. The henna (Lawsonia inermis) seemed to enhance the penetration of C. obovata components. The hair treated by C. obovara became less hydrophilic: the water sorption of bleached hair decreased by 25%. The stress-strain curves and torsion-breaking of individual hairs, after drastic C. obovata treatment, showcd the mechanical properties of the treated hair were not very changed, but the hair was more heterogeneous. Microphotography showed that, after the drastic treatment, the hair seemed unaltered, but the cuticle scales were little opened. The C. obovata treatment crimps the hair. As a sunscreen, which is bound to keratin, C. obovata components provide ultraviolet protection.