Lipid lamellae

The membrane-coating granules in keratinized epithelia contain electron-dense lipid lamellae [68, 77], and therefore, the intercellular spaces of the stratum corneum are filled with short stacks of lipid lamellae [67, 132], Most of the membrane-coating granules in nonkeratinized epithelia consist of amorphous material [120] however, some studies have shown that a small number of these granules in nonkeratinized epithelia contain lamellae [151]. Therefore,... 

Maksymiw, R., Sui, S. F., Gaub, H., and Sackmann, E. (1987). Electrostatic coupling of spectrin dimers to phosphatidylserine containing lipid lamellae. Biochemistry 26, 2983-2990. 

The lipid composition changes dramatically during terminal differentiation. After extrusion from the lamellar bodies, the polar lipid precursors are enzymatically converted into more hydrophobic lipids. As a result, phospholipids are almost absent in the stratum corneum. The lipid lamellae surrounding the corneocytes are predominantly composed of ceramides, cholesterol, and free fatty acids. It is generally assumed that these lipids are present in nearly equimolar ratios. However, inspection of literature data shows that there is a high interindividual variability in the lipid composition [37],... 

The composition of the free fatty acids is also unique. In both human and pig stratum cornea, the free fatty acid fraction consists mainly of long and saturated hydrocarbon chains [44,45], Oleic and linoleic acid are the only unsaturated free fatty acids detected in the stratum corneum. There are various sterols present in human stratum corneum, of which cholesterol predominates. Cholesterol is the only major lipid class that is present in both plasma membranes and the intercellular lipid lamellae. Cholesterol is synthesized in the epidermis and this synthesis is independent of the hepatic one. A minor fraction is sulfated to... 

Madison, K.C., et al. Presence of intact intercellular lipid lamellae in the upper layers of the stratum corneum. J Invest Dermatol 88 714. 

Generally, lipids forming lamellar phase by themselves, form lamellar lipoplexes in most of these cases, lipids forming Hn phase by themselves tend to form Hn phase lipoplexes. Notable exceptions to this rule are the lipids forming cubic phase. Their lipoplexes do not retain the cubic symmetry and form either lamellar or inverted hexagonal phase [20, 24], The lamellar repeat period of the lipoplexes is typically 1.5 nm higher than that of the pure lipid phases, as a result of DNA intercalation between the lipid bilayers. In addition to the sharp lamellar reflections, a low-intensity diffuse peak is also present in the diffraction patterns (Fig. 23a) [81]. This peak has been ascribed to the in-plane positional correlation of the DNA strands arranged between the lipid lamellae [19, 63, 64, 82], Its position is dependent on the lipid-DNA ratio. The presence of DNA between the bilayers has been verified by the electron density profiles of the lipoplexes [16, 62-64] (Fig. 23b). 

Figure 4 Nat 106 liposomes have a strong effect on the microstructure of the stratum corneum. The corneocytes (C) were swollen considerably, and the smooth ultrastructure of the intercellular lipid lamellae showed flattened spherical structures (see arrows). The linear arranged keratin filaments along the cell boundary of the corneocytes are absent. The scale bar indicates 0.1 pm. 

Figure 7 The possible mechanisms involved in the effect of penetration enhancers on the lipid organization of the intercellular domains in the stratum corneum. (A) Intercalation of the enhancer in the lipid lamellae. (B) Phase separation between enhancer and skin lipids in the lamellae. (C) Phase separation between lipid lamellae and an enhancer-rich phase. (D) Intercalation of the enhancer in the lipid lamellae and simultaneous phase separation between lipid lamellae and enhancer. (E) Phase separation within the lamellae and separation between an enahncer-rich phase and the lamellar phase. (F) Disappearance of the lamellar phases.

Figure 9 Freeze-fracture electron microscopy of control (a) or after treatment of alkyl-azones (b-f). (b) Hexyl-azone (c) octyl-azone (d) dodecyl-azone (e) myristyl-azone and (f) oleyl-azone. Bar represents 100 nm. represents rough structures indicating either separate domains of enhancer or more perturbation of lipid lamellae. Arrows indicate a clear presentation of the intact smooth regions of intact lamellae with steps (fracture across the lamellae). C, Corneocyte scl, stratum corneum lipid lamellae. 

Fartasch, M., Bassuskas, I.D., and Diepgen, T.L., Structural relationship between epidermal lipid lamellae, lamellar bodies and desmosomes in humans epidermis an unltrastructural study, Br. J. Dermatol.,... 

FIGURE 3.3 Intercellular lipid lamellae in the stratum corneum. Bar equals 30 nm. 

Interactions between water and the polar head groups of lipid molecules are necessary for the formation of lamellar phases however, it appears that there is no free water associated with the 13 nm trilaminar units. This is supported by the observation that this periodicity does not increase with increasing stratum corneum water content.22 There is likely water hydrogen bonded to the polar regions of the lamellae. In contrast, the minor short periodicity swells from 5.8 to 6.6 nm as the water content of stratum corneum increases from 12 to 50%.23 This suggests that the lipid lamellae are simple individual bilayers and free water molecules can exist between adjacent bilayers, thus causing the increase in the lamellar spacing. 

Kuempel, D., Swartzendruber, D.C., Squier, C.A., and Wertz, P.W, In vitro reconstitution of stratum corneum lipid lamellae, Biochim. Biophys. Acta, 1372, 135, 1998. 

Swartzendruber, D.C., Wertz, P.W., Kitko, D.J., Madison, K.C., and Downing, D.T. (1989) Molecular models of the intercellular lipid lamellae in mammalian stratum comeum. J. Invest. Dermatol. 92 251-257. 

Many of these enzymes have been immunolocalized to the intercorneocyte lipid lamellae. Sondell et al.17 used antibodies that immuno-react precisely with pro-SCCE to confirm that this enzyme is transported to the SC extracellular space via lamellar bodies. Watkinson et al.18 demonstrated that... 

FIGURE 28.1 Normal structure ofthe lipid lamellae in the intercellular space. Shown are three Landmann units... 

The Landmann-unit structure of intercellular lipid lamellae is illustrated in Figure 28.1. This structure is found throughout nearly all of the normal SC. Swartzendruber et al. proposed a plausible molecular model that accounts for the electron-lucent and electron-dense lamellar structure of the Landmann unit.10 These Landmann units are dynamic in nature. At least in the inner and middle SC they are altered by age,19 disease,8 11 20-22 and hormonal status23,24 by experimental solvent treatment25-27 and topical inhibitor treatment.28,29 They are known to reform spontaneously following solvent extraction,5,26 and topical application of certain lipids is also reported to effect lamellar repair and barrier improvement.29-33... 

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