Confocal laser scanning microscopy is a technique that permits the direct visualization in unfixed material of diffusion pathways and the cellular distribution of fluorescent markers after topical applications. This approach, in which the tissue specimen is optically sectioned, allows the study of changes in distribution pattern of applied compounds depending on the vehicle, time and depth without the interference of chemical alterations induced by most of the current techniques used for such studies. Using this technique the permeability properties of in-vitro-reconstructed epidermis were compared with those of the native counterpart. The epidermis was reconstructed by culturing human adult keratinocytes at the air-liquid interface either on fibroblast-populated collagen or on de-epidermized dermis. A fluorescent probe--Nile red (NR)--was applied in three different vehicles--polyethylene glycol (PEG) with a molecule mass of 400 (Da), propylene glycol (PG) and dimethyl sulphoxide (DMSO)--which perturb the SC barrier function to different extents. When NR was applied in PEG and PG on native epidermis, the amount of NR penetrating into and through the SC was very low, but was markedly increased when NR was applied in DMSO. Unlike native epidermis, the reconstructed epidermis allowed rapid NR penetration after the application in any of the solvents used. Furthermore, NR applied on reconstructed epidermis, was distributed quite homogeneously between the cellular and the intercellular spaces throughout the SC, suggesting that not only intercellular lipid structures but also the properties of the cornified envelopes differed markedly from those found in native epidermis.(ABSTRACT TRUNCATED AT 250 WORDS)
synopsisMany of the properties of surfactants can be related to their ability to concentrate at phase interfaces, leading to a reduction in interfacial tension. In biological systems the effects of surfactants are complex, particularly their effect on cell and other membranes, and this can lead to alterations in permeability characteristics. This is of particular relevance when considering the stratum corneum which has long been recognized as the major barrier to skin permeation. The magnitude of skin barrier function alteration is dependent on surfactant structure, both the hydrophobic alkyl chain and the hydrophilic ethylene oxide chain demonstrating some structure-activity behaviour. In many biological systems, including skin, surfactants with a similar hydrophilic group will show maximum membrane activity if they possess a decyl or dodecyl alkyl chain. It is difficult to rationalise this phenomenon, given that such solution properties as partition coefficients and CMCs do not show maxima or minima at these chain lengths. It may be that the physical parameters and molecular dimensions of the decyV dodecyl chain provide the optimal ability to intercalate with the lipid bilayer structure. There is little doubt that once the surfactant has intercalated with the lipid bilayers in the lamellar liquid crystals of the stratum corneum, fluidity in the hydrophobic regions is increased. Effectively, this leads to a looser, more permeable structure. The significance of data obtained using commercially available surfactants, however, can be questioned on the grounds of purity. The purpose of this review is to describe some of the methods used to evaluate the effects of surfactants on the skin barrier and to discuss recent attempts to predict surfactant action on the skin using various biological and physical techniques. R C u dLa plupart des proprittts des surfactants dtpend de leur facilitt ii se concentrer aux interfaces, menant ainsi ii la rtdiiction de la tension interfaciale. Dans le cas d'un systbme biologique les effets des surfactants sont complexes, particulierement leur action sur les cellules et les membranes et ceci mbne B I'alttration des caracttristiques de la permtabilitk. Ce point est trbs pertinent pour le stratum corneum qui a Ct6 longtemps considtrt comme la principale baniere ii la ptnttration cutanbe. L'importance de I'alttration de cette fonction banibre est en relation avec la structure du surfactant. L'importance de son alteration est like B la fois B la chaine alkyle hydrophobe et B la chaine d'oxyde d'tthylhe hydrophile ayant une activitC due Bsastructure. Dans de nombreux systbmes biologiques, incluant la peau, les surfactants avec une chaine hydrophile identique montreront une activit6 maximum sur les membranes si ils comprennent une chaine alkyle dkcylique ou dodtcylique. II est * Presented at the IFSCC Between-Congress Conference, Helsinki, 12-13th September, 1991.$ To whom correspondence should be addressed. Le but de cet article est de commenter quelques mtthodes appliqutes pour tvaluer le...
Der vorliegende Text stellt eine Analyse eines recht untypischen Kriminalromans von Friedrich Ani dar. Der Titel Süden ist der Name eines im Rahmen der Gattung ebenso untypischen Protagonisten/Detektivs. Wenn im Zentrum einer typischen Kriminalgeschichte das Rätsel eines Verbrechens, meistens eines Mordes, steht und somit im Vordergrund die Frage nach dem „Wer?“, so liegt hier das Hauptanliegen des Erzählers auf der Suche nach einem Verschwundenen, dessen Existenz erst durch sein Verschwinden sichtbar wird. Genauso unkonventionell ist die Arbeitsmethode des Ermittlers, der im Gegensatz zu seinen idealtypischen ‚Kollegen‘ nicht abfragt, sondern durch eigenes Schweigen, lies: Abwarten, seine Gegenspieler zum Sprechen bringt. Der Roman von Ani ist ein Bestandteil des Romanzyklus mit dem Verschwundenen- Sucher Süden in der Hauptrolle.
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