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Notes: Summary The morphology of the hippocampus of Mongolian gerbils was investigated by light and electron microscopy after 5-min forebrain ischemia and survival times of up to 10 months. After 3 weeks recirculation only 5.8% of pyramidal neurons of the CA1 (cornu ammonis 1) sector had survived but the thickness of the inner and outer hippocampal layers did not change. After recirculation times of 6 and 10 months the number of surviving neurons declined no further but all layers of the CA1 subfield shrank markedly. Ultrastructurally, many but not all surviving CA1 neurons were altered. After 3 weeks both “dark” and “pale” type neurons were present, while after 6 and 10 months only the “pale” type of injury persisted. Axonal enlargements and myelin breakdown were observed at all survival times up to 10 months of recirculation. The astrocytes of CA1 sector contained numerous glial fibrils which were most pronounced after the longer recirculation times. The stratum radiatum presented intact presynaptic terminals densely packed with an abundance of clear vesicles even after survival of 10 months. Initially, morphologically damaged postsynaptic structures were still attached to these terminals but they disappeared after longer recirculation times. However, even after 10 months some intact synapses were observed involving dendrites which probably originated from surviving CA1 neurons. In CA3 sector and dentate gyrus no ultrastructural changes occurred at any survival time. The close association of surviving CA1 neurons with intact presynaptic terminals and reactive glial cells may be of importance for the development of epileptogenic foci which are characteristic of this particular brain region.

Notes: L'analyse des résultats obtenus pour certains antiseborrheiques, avec differentes methodes d'étude expérimentale, a conduit à se poser le problème du caractère prévisionnel à l'homme de ces méthodes.L'utilisation des estrogènes dans la séborrhée se trouve largement justifiée par des essais chez l'animal dans lesquels des dérivés estrogéniques puissants (ethynyl estradiol,…) ont un reel effet par voie générale tant sur la cible sébacée que sur les organes sexuels. Une spécificité plus particulière pour la glande sébacée a été reconnue par contre à d'autres dérivés moins puissants (promestriène, CM 4727). Par voie topique, cette justification est discutable.Parmi les anti-androgènes, l'activité par voie générale des produits de type acetate de cyprotérone est bien mise en évidence, tant au niveau de la sécrétion sébacée qu'au niveau des mitoses, chez l'animal comme chez l'homme. Cet effet n'est guère retrouvé par voie topique chez l'homme, même à très forte concentration. En ce qui concerne la progestérone, une etroite correlation existerait entre l'animal et l'homme au niveau de la dissociation de l'effet anti-séborrhéique local suivant le sexe.Enfin, les produits non hormonaux décrits comme anti-séborrhéiques chez l'homme (clofibrate, dérivés de la cystéine, acide eicosa tétraynoïque) posent sur le plan expérimental de nombreux problèmes pour mettre en évidence leur activité.Cette étude de corrélation confirme ainsi que la prédiction de l'activité des antiséborrhéiques de l'animal à l'homme est loin d'être aisée et que le choix du modèle animal prend une valeur toute particulière en fonction de la molécule àétudier. Predictable nature of the laboratory investigation methods of anti-seborrhoeic drugs 〈section xml:id="abs1-2"〉〈title type="main"〉SummaryThe aim of this work is to evaluate the predictable nature in human therapeutics of results obtained with some anti-seborrhoeic drugs in various experimental tests performed in vitro or in vivo on animal models. This correlative study applies to anti-seborrhoiec drugs (mainly of the hormonal type) for which the results of tests based on objective measurement criteria (secretion of sebum, synthesis of sebaceous lipids, height and mitoses number of sebaceous gland) are available in the animal as well as in man (literature references or assays performed in our laboratory).Natural or more often synthetic oestrogens are currently used in women with seborrhoea or acne, as an oral contraceptive drug and, more recently, as a local therapy in both sexes. Benefits of such utilisation have been well assessed by assays on animal models in which powerful oestrogen derivatives (ethinyl estradiol, diethylstilboestrol) are actually active by systemic administration on the sebaceous target as well as on the sexual organs. Nevertheless a more specific action on the sebaceous gland has been found for other less powerful estrogen derivatives (promestriene or CM 4727). The topic use may yet be criticised because the inhibition observed in the animal is usually a systemic one and, on the other hand, depending on the animal chosen and its sex, the results may not be in agreement with those described for human tests.

Notes: La glande sébacée est une structure androgéno-dépendante et un site majeur pour le métabolisme des androgènes. Par ailleurs, on sait que les androgènes sont largement impliqués dans la stimulation de la sécrétion sébacée chez l'homme. L'objet de ce travail est ainsi de contribuer à l'étude du rôle de ces hormones et de leurs métabolites dans la séborrhée et de commenter l'activité locale de certains inhibiteurs.Les méthodes utilisées mesurent les paramètres suivants: la sécrétion sébacée et la synthèse des lipides sébacés marqués au carbone-14 chez l'animal, le métabolisme d'androgènes marqués dans la peau de l'animal et de l'homme.Nos résultats montrent:– en administration sous cutanée chez le rat, il existe une spécificité relative des androgènes faibles (type DHA) pour la glande sébacée contrairement aux androgènes puissants (type testostérone);– par voie locale chez le hamster, la 5α-DHT est plus active pour stimuler la lipogénèse sébacée que la testostérone et les dérivés 17β-OH sont plus actifs que les dérivés 17-cétones;–in vitro, la synthèse des lipides sébacés n'est pas associée à des changements profonds des voies métaboliques habituelles des androgènes dans l'organe cible;– sur la base de cette expérimentation certains antiséborrhéiques potentiels ont étéétudiés.L'ensemble de ces résultats sera discuté en fonction de leurs implications éventuelles en cosmétologie, particulièrement au niveau du problème des peaux grasses.

Notes: Après avoir rappelé brièvement le spectre d'action biologique du rayonnement ultraviolet du soleil sur la peau normale et les données theoriques de protection qui en découlent, le caractère prévisionnel de différentes méthodes d'étude in vitro et in vivo des antisolaires est commentéà partir de résultats obtenus en laboratoire sur différents principes actifs (PABA, Eusolex 4360, Giv Tan F), et préparations cosmétiques du commerce.Les méthodes in vitro, basées sur l'absorption dans l'UV des produits, aboutissent à une protection surévaluée et dans ces conditions à une extrapolation trés aléatoire du pouvoir de protection.La méthode utilisée in vivo (détermination classique d'un indice de protection) souligne, dans le cadre de la prédiction, le choix de la qualité d'absorption du filtre, de la source UV utilisée, mais aussi de nombreux autres facteurs agissant sur la protection. Dans ces conditions, les résultats obtenus chez le cobaye et l'homme avec des irradiations simulant le spectre solaire, montrent alors une concordance satisfaisante pour les principes actifs étudies. Ces observations sont ensuite commentees par comparaison à d'autres travaux publiés faisant mention d'autre source d'irradiation (spectre de raies) et de méthode de détection (thermométrique en particulier). Predictive nature of laboratory methods in sunscreen studies

Notes: Human skin sections were studied using synchrotron-powered infrared microscopy. The superior lateral resolution achieved with this technique (diffraction-limited spot sizes) allows the detailed analysis of the biocomposition of the skin layers. It is shown that highly organized lipids are present in the stratum corneum, as evidenced by a slight frequency difference in the symmetric stretch mode of the methylene groups. Biochemical images were generated showing the precise location of the lipids, proteins and collagen across the skin section. More enhanced images were generated using a statistical approach (fuzzy C-means clustering). Penetration of two external agents (cyanophenol and a cosmetic compound, ethylhexyl methoxycinnamate) was studied. The penetration pathway across the stratum corneum is favored at locations of lower lipid concentration. Both compounds penetrated into the epidermis, but neither of them induced a change in the protein secondary structure. It was shown that hair follicle is a favored penetration pathway for these agents.

Notes: We report an in situ grazing incidence x-ray scattering study of the Ni/MgO (001) interface during its formation at room temperature. In-plane measurements reveal that the interface is sharp and that the epitaxial relationship is complex. In the early stages of growth, up to one monolayer of "on site" Ni, in-plane strained to the lattice parameter of MgO, is observed. An oxygen epitaxial site is found. For the on-site fraction the interfacial and Ni interlayer distances were determined. For coverages larger than one monolayer two distinct lattices exist: expanded Ni (001) and Ni (110). The latter exhibits several orientations with respect to the substrate depending on the thickness. The Ni (110) orientations disappear by annealing at high temperature, leaving only the Ni cube/cube orientation. The layer was also almost fully transformed into NiO (001) by high temperature oxidation. © 1998 American Institute of Physics.

Notes: The growth of hexagonal aluminum nitride directly on (111) silicon has been studied by grazing incidence x-ray diffraction and high resolution electron microscopy as a function of film thickness. Two epitaxial relationships were observed: (1) AlN (0001) [2110]//Si(111) [022¯], which prevails at deposition temperatures larger than 650 °C, and (2) AlN (0001) [101¯0]//Si(111) [022¯]. For a 40 Å thick layer, the average in-plane crystallite size is 162 Å, the in-plane rotation is ∼2° and the dislocations induce an average strain distribution of 0.8%. The Si/AlN interface is very sharp and complete relaxation (down to ∼0.2%) occurs within one bilayer. No long range order was observed at the interface. This implies a low mobility of the AlN species on Si, inhibiting any structural rearrangement. In particular the in-plane rotations originate from the early stage of the layer growth and decrease with the layer thickness, especially for thicknesses larger than 250 Å. © 1998 American Institute of Physics.

Notes: Allergic contact dermatitis is a T-cell-mediated inflammation, induced by contact with sensitizers and occurring through the release of epidermal cytokines and the activation of epidermal Langerhans cells (LCs). The aim of this study was to analyse early events of LC activation induced either by contact allergens or by irritants devoid of any contact allergenic properties, in order to obtain an in vitro method to discriminate between these two groups of molecules. Various contact sensitizers and irritants were studied for their effects on the endocytosis of major histocompatibility complex class II (MHC-II) molecules by freshly-isolated human epidermal LCs. As observed by flow cytometry, a spontaneous decrease in the surface expression of MHC-II (HLA-DR) molecules, linked to spontaneous internalization of the MHC-II molecules by LCs, was obtained by moving freshly-isolated LCs from 4 °C to 37 °C. Pre-incubation of LCs with either sensitizers or irritants increased the spontaneous internalization of HLA-DR molecules with a similar magnitude, but no clear discrimination between sensitizer and irritant effects was obtained by flow cytometry analysis. In contrast, confocal microscopy enabled discrimination between the effects of sensitizers and irritants: sensitizer-treated samples showed internalized HLA-DR molecules aggregated in large vesicles with very bright fluorescence; irritant-treated samples were not different from untreated controls and showed compact HLA-DR molecules in small vesicles with diffuse fluorescence, and mostly localized in the submembranous zone. Electron microscopy demonstrated that sensitizer-treated LCs internalized HLA-DR molecules preferentially in lysosomes collected near the nucleus, whereas the irritant-treated and non-treated LCs internalized these molecules in the prelysosomes only near the cell membrane. We conclude that contact allergens and irritants induce distinct patterns of HLA-DR endocytosis, which may be useful for the development of in vitro screening tests.