Showing papers by "Joke A. Bouwstra published in 1998"
TL;DR: The role of CER 1 for the SC lipid lamellar organization was studied and it was showed that in the absence of C ER 1 almost no long periodicity phase was formed over a wide CHOL/CER molar ratio.
274 citations
TL;DR: The thermodynamic state of the bilayer and, to a smaller extent, the flexibility of thebilayer influence, strongly the penetration depth of the label into the skin.
102 citations
01 Aug 1998
TL;DR: In contrast to lamellar ordering, changes in pH did not affect the lateral packing in any of the lipid mixtures studied, and a major phase change from an hexagonal to an orthorhombic lateral packing has been observed in the presence of free fatty acids.
Abstract: Lipid mixtures prepared from cholesterol (CHOL), isolated ceramides (CER), and free fatty acids can serve as attractive tools to study the role various stratum corneum (SC) lipids or microenvironmental conditions play in the SC lipid organization, as the phase behavior in these mixtures and in SC are similar: two lamellar phases with periodicities of ≈6 and 13 nm are present. Because pH and cholesterol sulfate (CSO4) gradients exist in SC and may affect the local SC lipid organization, the effects of pH and CSO4 on lipid phase behavior was examined. X-ray diffraction studies with CHOL:CER mixtures revealed that the lamellar ordering at pH 5 and 7.4 were similar: both the short and the long periodicity phases were present. Upon addition of free fatty acids the phase behavior became pH dependent; the long periodicity phase being more dominant at pH 7.4 than at pH 5. Similar observations have been made upon addition of CSO4. Furthermore, only in the presence of CSO4 did phase-separated CHOL disappear, indicating that CHOL completely dissolves in the lamellar phases. A major phase change from an hexagonal to an orthorhombic lateral packing has been observed in the presence of free fatty acids. Furthermore, in the presence of CSO4 next to orthorhombic also liquid lateral packing could be detected. In contrast to lamellar ordering, changes in pH did not affect the lateral packing in any of the lipid mixtures studied. Journal of Investigative Dermatology Symposium Proceedings 3:69–74, 1998
98 citations
TL;DR: The vesicular form and the thermodynamic state of the bilayer and to a smaller extent the flexibility of thebilayer influence the penetration depth of the label into the skin at longer application periods, in good agreement with CLSM results obtained from in vitro experiments with human skin.
66 citations
43 citations
TL;DR: Application of electron diffraction in skin studies can provide new information on the lipid organization in well-defined areas of the stratum corneum, according to the results of the first study in which this technique is applied on SC lipid model systems.
35 citations
TL;DR: It was observed that both gel-state liposome suspensions were able to form large stacks and networks of lipid bilayers at the surface of the stratum corneum in contrast to the liquid-state DLPC liposomes, which showed no adsorption.
34 citations
TL;DR: Surface-bound protein was observed as particles by freeze-fracture electron microscopy and was confirmed by immunogold cryo microscopy, and SAXS was shown to be a suitable means to further characterize liposomes with, or without bound protein.
32 citations
TL;DR: Improved the microscope settings and developed a new preparation method to study ex vivo human SC by cryo‐electron diffraction based on the conventional tape‐stripping method and offers the possibility to study depth‐related changes in the lipid organization of human SC.
Abstract: The human skin provides the body with a barrier against transepidermal water loss and the penetration of harmful agents (e.g. microbes) from outside. This barrier function is produced mainly by the outermost, nonviable layer of the epidermis, the stratum corneum (SC). The SC consists of terminally differentiated corneocytes surrounded by a continuous intercellular lipid domain, which contains mostly ceramides, cholesterol and free fatty acids. Small- and wide-angle X-ray diffraction studies have elucidated the lamellar and lateral lipid organizations in these domains. However, these techniques require bulk quantities of SC, as a result of which local structure information on the lipids cannot be obtained. Insights to these local lipid arrangements are important when new transdermal drug delivery systems have to be developed. Therefore, the technique of electron diffraction arose as a tool to study the lateral packing of the lipids in the intercellular domains of SC, locally. In a previous study, the suitability of electron diffraction was demonstrated using a lipid model system that resembled the lipid composition of the SC. The spacings calculated from the electron diffraction patterns were in good agreement with the spacings revealed by wide-angle X-ray diffraction. The results presented here succeed this previous study. We improved the microscope settings and developed a new preparation method to study ex vivo human SC by cryo-electron diffraction. The method is based on the conventional tape-stripping method and offers the possibility to study depth-related changes in the lipid organization of human SC. Diffraction patterns of both hexagonal and orthorhombic lipid lattices have been recorded with spacings that resembled those found in human SC by wide-angle X-ray diffraction. After lipid extraction, such diffraction patterns could no longer be detected in the samples.
30 citations
01 Aug 1998
TL;DR: The freeze-fracture electron microscopy and differential thermal analysis studies suggest that HVP application induces a general perturbation of the stratum corneum lipid ultrastructure.
Abstract: Application of high voltage pulses (HVP) to the skin has been shown to promote the transdermal drug delivery by a mechanism involving skin electroporation. The aim of this study was to detect potential changes in lipid phase and ultrastructure induced in human stratum corneum by various HVP protocols, using differential thermal analysis and freeze-fracture electron microscopy. Due to the time involved between the moment the electric field is switched off and the analysis, only "secondary" phenomena rather than primary events could be observed. A decrease in enthalpies for the phase transitions observed at 70 degrees C and 85 degrees C was detected by differential thermal analysis after HVP treatment. No changes in transition temperature could be seen. The freeze-fracture electron microscopy study revealed a dramatic perturbation of the lamellar ordering of the intercellular lipid after application of HVP. Most of the planes displayed rough surfaces. The lipid lamellae exhibited rounded off steps or a vanished stepwise order. There was no evidence for perturbation of the corneocytes content. In conclusion, the freeze-fracture electron microscopy and differential thermal analysis studies suggest that HVP application induces a general perturbation of the stratum corneum lipid ultrastructure.
25 citations
01 Aug 1998
TL;DR: The X-ray diffraction showed differences in the diffraction pattern at 2 y after grafting, suggesting that the organization of stratum corneum lipids in all epidermal grafts differs from that of the native skin.
Abstract: Restoration of an epidermal barrier is a definitive requirement for wound closure. Cultured skin substitutes grafted onto athymic nude mice were used as a model for a long-term study of stratum corneum barrier lipid metabolism and organization. Samples of stratum corneum collected after 12 and 21 d in vitro and 6, 11, and 24 mo postgrafting were examined for their lipid and fatty acid composition, and their lipid organization and structure using electron microscopy and small angle X-ray diffraction, respectively. All of these methods confirm the impaired barrier function of cultured skin substitutes in vitro, as judged from the deviations in lipid composition and from poor organization of the stratum corneum lipids that show no lamellar structure. At 6 mo postgrafting, the total stratum corneum lipid profiles of the epidermal grafts is close to that of the human stratum corneum with the exception of the presence of mouse specific lipids. The increase of ceramides 4–7 in cultured skin substitutes after grafting indicates restored activity of processes involved in the hydroxylation of fatty acids and sphingoid bases. Conversely, the ceramide profile still reveals some abnormalities (elevated content of ceramide 2 and slightly lower content of ceramide 3) and the content of long-chain fatty acids remains below its physiologic level at 6 mo postgrafting, but normalizes by 2 y postgrafting. The ultramicroscopic observations revealed the formation of lamellar extracellular lipid domains by 4 mo postgrafting. Despite these findings, the X-ray diffraction showed differences in the diffraction pattern at 2 y after grafting, suggesting that the organization of stratum corneum lipids in all epidermal grafts differs from that of the native skin. Journal of Investigative Dermatology Symposium Proceedings 3:114–120, 1998