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Notes: Transepidermal water loss (TEWL), skin surface water loss (SSWL) and water content of the stratum corneum are utilized to assess the hydration effects of moisturizers and soaps. The relationship among these parameters may help differentiating hydration obtained via occlusion or by water-holding in the stratum corneum. Furthermore, skin function (hydration, dehydration, barrier damage) can be studied comparing the data obtained with these techniques. In this study, the effects of glycerol, petrolatum, soaps and commercial moisturizers on the skin are investigated and discussed.

Notes: Skin acts a major target as well as a principle barrier for topical/transdermal drug delivery. Despite the many advantages of this system, the major obstacle is the low diffusion rate of drugs across the stratum corneum. Several methods have been assessed to increase the permeation rate of drugs temporarily. One simple and convenient approach is application of drugs in formulation with elastic vesicles or skin enhancers. Elastic vesicles are classified with phospholipid (Transfersomes® and ethosomes) and detergent-based types. Elastic vesicles were more efficient at delivering a low and high molecular weight drug to the skin in terms of quantity and depth. Their effectiveness strongly depends on their physicochemical properties: composition, duration and application volume, and entrapment efficiency and application methods. This review focuses on the effect of elastic liposomes for enhancing the drug penetration and defines the action mechanism of penetration into deeper skin.

Notes: Glutathione is an ubiquitous compound found in our bodies. Aside from its many ascribed biologic functions, it has also been implicated in skin lightening. We review in vitro and in vivo studies that show evidence of its involvement in the melanogenic pathway and shed light on the its anti-melanogenic effect. Proposed mechanisms of action include: (a) direct inactivation of the enzyme tyrosinase by binding with the copper-containing active site of the enzyme; (b) mediating the switch mechanism from eumelanin to phaeomelanin production; (c) quenching of free radicals and peroxides that contribute to tyrosinase activation and melanin formation; and d) modulation of depigmenting abilities of melanocytotoxic agents. These concepts supported by the various experimental evidence presented form basis for future research in the use of glutathione in the treatment of pigmentary disorders.

Notes: Stratum corneum moisturization was measured by two instruments simultaneously on the same subjects at different body sites. One instrument is based on the 1 GHz focused mirowave dielectric measurement; the other instrument measures impedance at 16 Hz.A linear relationship r = 0.86 was observed between the measurements by the two above-mentioned instruments. The 1 GHz focused microwave measurement is more accurate in measuring water concentration in the stratum corneum, especially in the upper layers relevant to “moisturization”; it is, however, an expensive research instrument. The low frequency impedance measurement involves a much simpler, cheaper and portable instrument which can be used routinely to evaluate ‘moisturization’ for the purpose of skin classification under field conditions.Comparaison de divers appareils de mesure de I'hydratation de la couche cornee〈section xml:id="abs1-2"〉〈title type="main"〉ésuméL'hydratation de la couche cornée a été mesurée simultanément par deux appareils sur plusieurs sites de mêmes sujets: le front, la face et les membres. Un appareil est basé sur la mesure par micro ondes, I'autre mesure I'impédance à 16 Hz.On observe une relation linéaire, r= 0.86, entre les mesures effectuées par les deux appareils ci-dessus. L'appareil à micro ondes est plus précis pour la mesure de la concentration en eau de la couche cornée et plus spécialement dans les couches supérieures qui sont importantes pour I'hydratation, mais cet appareil est onéreux. La mesure des impédances à basse fréquence utilisé un appareil portable, simple et bon marché qui peut être utilisé en routine pour évaluer I'hydratation dans le but de classer des types de peaux sur le terrain.II n'est pas toujours possible de comparer des appareils diffeérents sur les mêmes personnes et dans le même temps et il est encore plus difficile d'obtenir des donneées sur un nombre de personnes de type diffeérent. Nous suggeérons d'utiliser à I'avenir une meéthode de comparaison diffeérente basée sur I'application d'un traitement standard bien défini, qui pourrait par example consister en I'application pendant une heure d'une solution à 2% de glycérine sur I'avant bras, avant la mesure.Ces données, avec la connaissance de la distribution des valeur du prétraitement pour les divers appareils, permettraient également la comparaison et la validation des différentes méthodes.

Notes: The effect of short duration occlusion on skin penetration and stratum corneum water content was studied in vivo in eight human subjects. Percutaneous absorption of hexyl nicotinate was monitored non-invasively by laser Doppler velocimetry (LDV) following each of three randomly assigned pre-treatments: untreated control, 30 min occlusion with a polypropylene chamber and 30 min ocdusion followed by exposure to ambient conditions for i h. Stratum corneum water content after the same pre-treatments was measured with the dielectric probe technique. The local vasodilatory effect of the nicotinic acid ester was quantified using LDV by the onset of increased blood flow, the time of maximal increase in response, the magnitude of the peak response and the area under the response-time curve. Each of these parameters was significantly different, immediately following occlusion, from the untreated control values. However, if the occluded site was exposed for i h prior to hexyl nicotinate application these parameters did not differ significantly from the controls. Stratum corneum water content (expressed as a percentage of a maximal value) showed the same behaviour: the pre-treatment control value was 31.8 ± 4.8%; after 30 min occlusion, this had risen to 46.9 ± 6.2% 1h later, the reading had returned to 32.1 ± 6.2%. There was a significant correlation between stratum corneum water content and area under the LDV response-time curve. It appears, therefore, that this method may be useful for quantifying the relationship between increased stratum corncum hydration and enhanced percutaneous absorption in vivo in man.

Notes: Laser Doppler velocimetry (LDV) was used to assess the effect of treatment upon cutaneous blood flow in psoriatic skin lesions. The resolution of two separate plaques in each of seven subjects was followed. Six of the subjects received the Goeckerman regimen, the seventh was reated with psoralen-ultraviolet A (PUVA) therapy. Control LDV readings were taken from uninvolved skin sites during the treatment period. Cutaneous blood flow in the psoriatic lesions of the Goeckerman-treated patients decreased to levels comparable to those in uninvolved skin early in the course of treatment and significantly preceeded the observed clinical resolution from 4 to 8 days after initiation of therapy (P 〈 0.05). Visible flare-ups sometimes appeared when patients were untreated (over a weekend, for example) and these eruptions were accompanied by a transient elevation of LDV readings. Perfusion of the lesions of the PUVA-treated patient remained consistently higher than perfusion of uninvolved skin despite clinical healing. In a separate series of experiments, blood flow at the extensor surface of the forearm was measured in the skin of normal subjects, the uninvolved skin of psoriatic patients and the untreated lesional skin of psoriatic patients. While the lesional skin had significantly higher perfusion levels than uninvolved psoriatic or normal control skin (P 〈 0.01), there was no significant difference between blood flow to the uninvolved psoriatic skin of psoriatics and that to the skin of healthy controls.

Notes: The postocclusive hyperaemic reaction before and after a single 1 h application of a potent corticoid (clobetasol 0.05% in ointment) was recorded by means of laser Doppler velocimetry in order to elucidate different racial responses in skin vasoconstriction. Fourteen young male subjects entered the study (eight Caucasians, six Blacks). Reactive hyperaemia was recorded after 4 min of occlusion of the forearm blood flow. The following parameters of the hyperaemic reaction were investigated: area under the curve response, peak response, rise of blood flow slope to peak and decay of blood flow slope after peak. Different responses were recorded in the Black subjects after the vasoconstrictive stimulus compared to the Caucasians, namely: decreased area under the curve response (P 〈 0.04); decreased peak response (P 〈 0.01); decreased decay slope after peak blood flow (P 〈 0.04). These data are consistent with a different reactivity of blood vessels in black skin and possibly not related to the transcutaneous penetration of the chemical compound.