Skin of the udder in Merino sheep

The skin of the mammary gland of the merino sheep was investigated on 5 different areas by light microscopical and morphometrical means. The epidermis is continuously developed in the same manner, in which a stratum lucidum is lacking. It contains relatively large melanocytes in pigmented regions. In the sinus inguinalis, in the sulcus intermammarius and in the skin of the middle part of the teat skin it is constantly thick, whereas the epidermis of the mammary complexes and of the teat basis varies strongly and is underlayed by a distinct papillary layer. In general, the arrector pili muscle is poorly present. The skin of the mammary complexes as well as the skin of the sinus inguinalis possess numerous sweat glands, which form associated structures. Due to its strong morphokinesis, frequently occur dom-like cells, enveloped by a net of myoepithelial cells at the periphery. The sebaceous coating of the sinus inguinales does not influence the morphology of the stratified squamous keratinized epithelium.     

Ultrastructural study of the skin after facial chemical peels and the effect of moisturization on wound healing

Ultrastructural changes occurring in the skin at early times after chemical peels as well as effects on the wound healing with moisturization after these peels have been examined. This study evaluated the changes seen in the skin 3 days and 5 days after 35% trichloroacetic acid peels, and the effect of moisturization on this healing was evaluated. Biopsies at 3 days showed an outermost layer of necrotic stratum corneum and stratum granulosum and an underlying layer of new stratum corneum. There were increased cytoplasmic vacuoles in the keratinocytes of the stratum spinosum, stratum granulosum, and stratum basale layers. There was extensive intercellular spacing between the basal keratinocytes. At 5 days the necrotic layer of stratum corneum and stratum granulosum was gone. The lower epidermis at 5 days showed less intercellular spacing, and there was less vacuolization within keratinocytes. In seven of eight patients treated with moisturization after the peel (p = 0.0325), the ultrastructural changes at 5 days were consistent with a more advanced state of healing compared with those that were treated dry. Ultrastructural morphology at this time showed less intercellular spacing and fewer cytoplasmic vacuoles, indicative of an advanced state of wound repair. These moisturized skin specimens had returned to an almost normal state of structure compared with the skin that had been treated dry.     

Imaging regions of transport across human stratum corneum during high-voltage and low-voltage exposures

Scanning confocal fluorescence microscopy was used to image localized regions of calcein transport across human stratum corneum during constant low-voltage (iontophoresis) and pulsed high-voltage exposures. Following an electrical protocol, imaging revealed regions of fluorescence which were interpreted as sites where transport of a fluorescent probe (calcein) into the stratum corneum had taken place. Electrically-assisted transport of calcein, whether enhanced by iontophoresis or high-voltage pulsing, appears to occur through intercellular and, to some extent, transcellular pathways into localized regions of stratum corneum that are not associated with appendages. Uniquely associated with the highest voltage pulses used (300 V across the skin) was the appearance of small, brightly fluorescent areas containing nonfluorescent interiors, i.e., fluorescent "rings". We present evidence which suggests that the dark interiors represent sites through which transport occurred during pulsing, but where calcein was no longer present at the time of imaging. Transport of charged microspheres into the stratum corneum was also observed.     

Phase transitions of rat stratum corneum lipids by an electron paramagnetic resonance study and relationship of phase states to drug penetration

In order to relate barrier function to stratum corneum structure and the thermal transitions of corneum lipids, samples from hairless rat skin were investigated by using ESR and drug penetration techniques. The phase transition of stratum corneum lipids was estimated using a deeper probe (16-doxyl-stearic acid) inserted in the lipid bilayers and measuring the rotational correlation time, tau(c). Results of ESR study showed that stratum corneum lipids underwent thermal transitions at 39.3 +/- 1.6 degrees C and 63.6 +/- 2.6 degrees C roughly similar to the data obtained by differential scanning calorimetry measurements. Cholesterol oxidase treatment decreased the fluidity of the lipids at lower temperatures. The treatment of stratum corneum with laurocapram (1%) and isopropyl myristate (IPM, 2%) little changed both phase transition temperatures, although the treatment highly increased the molecular motion of the lipids. The flux (J(s)) of lipophilic drugs (beta-estradiol, indomethacin and betahistine) through the skin was enhanced with increasing temperatures, with an increase in the diffusion constant within skin and a decrease in the lag time. There was a good relationship between log J(s) or log permeability coefficient (K(p)) and 1/tau(c) in the temperature range of 45 to 64 degrees C. The calculated activation energy (delta E) for diffusion of these drugs across skin was 17-40 kcal/mol. Judging from our data, stratum corneum lipids of rat probably exist as the gel, crystalline state below 39 degrees C, the mesomorphic state between 39 and 64 degrees C and the fluid, liquid-crystalline state at temperatures of 64 degrees C or above. These results are in line with the permeability of these lipophilic drugs through the intercellular lipids disordered is highly increased.     

Relationship between the amount of propranolol permeating through the stratum corneum of guinea pig skin after application of propranolol adhesive patches and skin irritation

In the present study we evaluated the relationship between the cumulative amount of propranolol permeating through the stratum corneum and the formation of erythema, a skin irritation reaction, after transdermal application of adhesive patches containing propranolol to the skin of guinea pigs. The intensity of erythema was expressed in terms of a* values measured with a chromameter. The a* values increased in guinea pigs after application of the adhesive patches containing 0.4 mg/cm2 of propranolol to the skin. Since the adhesive patches showed good adhesion to the skin (propranolol content is less than the saturated concentration in the adhesive base) and the cumulative amount of propranolol permeating through the stratum corneum is small, the development of erythema was considered to be mainly due to physical factors such as peeling. Even in adhesive patches containing 0.8 mg/cm2 or 1.2 mg/cm2 of propranolol, a* values increased, although adhesion to the skin is low because of crystallization of propranolol in the adhesive base. On the other hand, in these two adhesive patches, the cumulative amount of propranolol permeating through the stratum corneum increased up to 24 h after application. These findings suggest that the skin irritation reaction is due to propranolol mainly absorbed transdermally, because there is a high correlation between the cumulative amount of propranolol permeating through the stratum corneum and the a* values (r = 0.928).     

A new HPLC-based method for the quantitative analysis of inner stratum corneum lipids with special reference to the free fatty acid fraction

The inner stratum corneum is likely to represent the location of the intact skin barrier, unperturbed by degradation processes. In our studies of the physical skin barrier a new high-performance liquid chromatography (HPLC)-based method was developed for the quantitative analysis of lipids of the inner stratum corneum. All main lipid classes were separated and quantitated by HPLC/light scattering detection (LSD) and the free fatty acid fraction was further analysed by gas-liquid chromatography (GLC). Mass spectrometry (MS) was used for peak identification and flame ionization detection (FID) for quantitation. Special attention was paid to the free fatty acid fraction since unsaturated free fatty acids may exert a key function in the regulation of the skin barrier properties by shifting the physical equilibrium of the multilamellar lipid bilayer system towards a noncrystalline state. Our results indicated that the endogenous free fatty acid fraction of the stratum corneum barrier lipids in essence exclusively consisted of saturated long-chain free fatty acids. This fraction was characterized as a very stable population (low interindividual peak variation) dominated by saturated lignoceric acid (C24:0, 39 molar%) and hexacosanoic acid (C26:0, 23 molar%). In addition, trace amounts of very long-chain (C32-C36) saturated and monounsaturated free fatty acids were detected in human forearm inner stratum corneum. Our analysis method gives highly accurate and precise quantitative information on the relative composition of all major lipid species present in the skin barrier. Such data will eventually permit skin barrier model systems to be created which will allow a more detailed analysis of the physical nature of the human skin barrier.     

Measuring memory for source: some theoretical assumptions and technical limitations

In a search for pathogenetic mechanisms underlying retention hyperkeratosis, we examined the pH gradient over the stratum corneum in 13 male patients suffering from either x-linked recessive (XRI) or autosomal dominant ichthyosis vulgaris. For recording pH values, a flat glass electrode was repeatedly applied to the skin during tape stripping of mildly involved forearm skin. Before stripping, surface pH was higher in ichthyosis vulgaris (5.3 +/- 0.7; n = 7) than in XRI (4.6 +/- 0.4; n = 6; p < 0.05) and healthy control men (4.5 +/- 0.2; n = 7; p < 0.01). Removal of stratum corneum, which required 100-240 strippings in ichthyotic skin and 80-120 strippings in healthy control skin, disclosed markedly different pH variations in the two types of ichthyosis. The major abnormality in ichthyosis vulgaris skin was that a neutral pH was attained already halfway through the horny layer, possibly reflecting a congenital lack of acidic breakdown products from keratohyaline. By contrast, stripping of XRI skin revealed a shallow pH gradient that plateaued at 6.2-6.6, instead of about 7 as in normal and ichthyosis vulgaris skin. A likely explanation is the XRI-associated accumulation of cholesterol sulfate in lower stratum corneum. Our results suggest that the "acid mantle" of normal skin, which penetrates deep into the stratum corneum, is the combined result of cornification-associated organic acids and back-diffusion of acid material from the surface. Because corneocyte desquamation involves many pH-dependent enzymes, abnormalities in the transcorneal pH gradient might play a role in the pathogenesis of ichthyosis.     

Dust from carpeted and smooth floors. VI. Allergens in homes compared with those in schools in Norway

This study examined 20 cases of tinea versicolor to assess the dermato-physiological, immunological and pathological status of lesion sites as compared to 20 normal control subjects. Lesion sites showed a significant decrease in sebaceous gland secretions and water content and an increase in pH value compared to normal skin. There was no significant change in involucrin, filaggrin, or number of stratum corneum cell layers. However, lesions showed weak positive staining of IL-1 alpha. A possible mechanism for these changes is that profuse sweat gland secretions predispose to fungal growth and acid mantle destruction, with the pathogens consuming amino acids and sebum as nutrients. Slight increases in IL-1 alpha levels seen in infected areas could be due to a fungus-stimulated immune reaction in the stratum corneum.     

Light and electron microscopy of excoriated psoriatic lesions in patients during topical treatment

This is a light- and electron-microscopic study of excoriated, recalcitrant psoriatic lesions in ambulatory patients undergoing topical treatment. During regeneration of a stratum corneum without scales, in areas showing excoriations bounded by a non-cornified epidermis, horny cell layers, designated I and II, are formed. In areas in which excoriations are delimited by an epidermis with a retained stratum corneum, the latter is composed of a horny cell layer I and/or II or III. The horny cell layers differ, as shown by light- and electron-microscopy. In the less fresh excoriations, a homogeneous substance, which includes fibrin deposits, is observed. This substance is also seen frequently in the stratum corneum. In the less fresh excoriations and in the stratum corneum there are numerous polymorphonuclear leukocytes. In these locations, however, they are only found simultaneously with the homogeneous substance containing fibrin deposits. Polymorphonuclear leukocytes are also seen in the dermal papillae and in the non-cornified epidermis, particularly in the macroscopically "old" excoriations. The changes observed in these recalcitrant lesions have been interpreted as secondary and are believed to be expressions of a non-specific reaction to the mechanical damage to which the ambulatory patients have constantly exposed the lesions. They are not interpreted as changes in the psoriatic condition per se.     

X-ray diffraction analysis of isolated skin lipids: reconstitution of intercellular lipid domains

Low- and wide-angle X-ray diffraction were used to determine the structural organization of lipids isolated from the stratum corneum extracellular matrix that forms the major water permeability barrier in mammalian epidermis. Hydrated pig skin ceramides gave a single low-angle reflection of about 62 angstroms and a wide-angle-reflection at 4.15 angstroms. The addition of either cholesterol or fatty acid, the other major lipid components of the skin stratum corneum extracellular matrix, modified this diffraction pattern, depending on the lipid mole ratios. In the absence of water, lipid mixtures exhibited lipid phase separation, as shown by low- and wide-angle reflections typical of a separate cholesterol phase. However, a hydrated 2:1:1 mole ratio of ceramide:cholesterol:palmitic acid (similar to that found in stratum corneum) produced a diffraction pattern with a single sharp wide-angle reflection at 4.10 angstroms and low-angle reflections which indexed as the first eight orders of a single repeat period of 130 angstroms. The repeat period and intensity distribution of the low-angle data were similar to those found in intact stratum corneum [White et al. (1988) Biochemistry 27, 3725-3732; Bouwstra et al. (1994) Biochim. Biophys. Acta 1212, 183-192]. Higher concentrations of cholesterol or palmitic acid resulted in lipid phase separations. The 130 angstrom repeat period decreased only about 3 angstroms as water was removed by incubation in low-relative humidity atmospheres. The 130 angstrom repeat period depended on the presence of a particular ceramide, N-(omega-acyloxy)-acylsphingosine, which is found only in the epidermis. In contrast, 2:1:1 mixtures of brain ceramide:cholesterol:palmitic acid gave reflections of 56 and 34 angstroms. These results indicate that a structure with dimensions similar to those of the lamellar repeating unit found in skin stratum corneum does not depend on the presence of protein but does depend on the presence of specific skin ceramides and appropriate concentrations of cholesterol and fatty acid.     

The effect of preoperative intra-aortic balloon pump support in high risk patients requiring myocardial revascularization

Differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) have been used to determine the influence of beta-cyclodextrin (beta-CyD), hydroxypropyl-beta-CyD (HP-beta-CyD) and gamma-CyD on the structural properties of the stratum corneum from the hairless mouse. Some modest changes in the stratum corneum lipid transition temperature were induced by HP-beta-CyD and blue shifts were observed in the FTIR spectra of the C-H asymmetric and symmetric stretching of the lipids from the stratum corneum. Results from TEM studies indicated that HP-beta-CyD caused removal and possible disorganization of the lipid matrix that envelopes the corneocytes of the stratum corneum, whereas no effect was seen after treatment of the samples with beta-CyD and gamma-CyD. These results suggest that HP-beta-CyD can increase the permeability of the stratum corneum possibly as a result of extraction of lipids, and might thus enhance drug permeation through the skin.     

Localization of sphingomyelinase in lesional skin of atopic dermatitis patients

Because it has been suggested that the majority of the activity hydrolysing [N-methyl-14C] sphingomyelin is due to sphingomyelin acylase in the lesional skins of atopic dermatitis (AD), in this study we used immunologic techniques to localize and quantitate sphingomyelinase in AD lesional and normal skin. A polyclonal antibody raised against a synthetic polypeptide corresponding to a portion of the amino acid sequence deduced from the cDNA of human acid sphingomyelinase, cross-reacted with a 58 kDa, pI 5.8 human epidermal protein in an immunoblot analysis. The 58 kDa protein-rich fraction, partially purified by immunoprecipitation, converted [N-methyl-14C]-sphingomyelin to 14C-phosphorylcholine and ceramides. The reaction products were immunohistochemically observed in the intercellular domain from the upper spinous cell layer to the upper stratum corneum cell layers in the lesional skin of AD patients. Immunoelectron-microscopically, gold particles appeared to be concentrated in the intercellular domains of the granular-upper stratum corneum cells in the lesional skin of AD patients. The total amount of the 58 kDa protein in a 7 mm2 area of the skin was measured by quantitative immunoblot analysis; and was slightly increased in the lesional skin samples [3.5 +/- 0.3 microg per 7 mm2 (n = 7)], as compared with the nonlesional skin samples of AD patients [2.8 +/- 0.19 microg per 7 mm2 (n = 10)] and with the normal skin samples [2.7 +/- 0.22 microg per 7 mm2 (n = 10)]. This difference (between the lesional skin of AD and the nonlesional skin of AD or the normal control) was significant (nonpaired student's t test, p < 0.05).     

Diversity of lactic acid bacteria associated with ducks

We have investigated the photoprotective properties of tanning using erythema as an endpoint. Previously unexposed buttock skin sites of 16 young, healthy adults (8 skin type II, and 8 skin type III) were exposed daily (Mon-Fri) for 2 weeks to 0.5 and 0.75 minimal erythema doses (MED) of solar-simulated radiation (SSR). Erythema and melanin levels were assessed daily both visually and quantitatively using a reflectance device. One week after the last tanning treatment, MED reassessments were made on pretreated sites and on adjacent nontreated sites, including sites from which stratum corneum was removed by tape stripping. Compared to skin type II, similar daily SSR treatments produced less erythema and more evident tanning in skin types III. Independent of skin type, all volunteers showed an increased MED value when assessed on the 0.75 MED- and 0.5 MED-treated sites compared to the MED value assessed on adjacent untreated sites. We express any increase in MED as an induced protection factor (IPF), i.e. (MED post-tan/MED pre-tan). Our data show mean IPF of 1.4 and of 2.1 in the 0.5 and 0.75 MED-treated sites respectively, in skin types II. Similar values were obtained in skin types III with IPF of 1.5 and 2.3 for the 0.5 and 0.75 MED-treated sites, respectively. In all cases, removal of the stratum corneum lowered the IPF by about 20%. Our results show that SSR-induced melanogenesis, whether in skin type II or III, offers only moderate protection against erythema and suggest that SSR-induced stratum corneum thickening affords less photoprotection than tanning.     

Stratum corneum lipids: the effect of ageing and the seasons

Stratum corneum lipids play a predominant role in maintaining the water barrier of the skin. In order to understand the biological variation in the levels and composition of ceramides, ceramide 1 subtypes, cholesterol and fatty acids, stratum corneum lipids collected from tape strippings from three body sites (face, hand, leg) of female Caucasians of different age groups were analysed. In addition, we studied the influence of seasonal variation on the lipid composition of stratum corneum from the same body sites. The main lipid species were quantified using high-performance thin-layer chromatography and individual fatty acids using gas chromatography. Our findings demonstrated significantly decreased levels of all major lipid species, in particular ceramides, with increasing age. Similarly, the stratum corneum lipid levels of all the body sites examined were dramatically depleted in winter compared with spring and summer. The relative levels of ceramide 1 linoleate were also depleted in winter and in aged skin whereas ceramide 1 oleate levels increased. The other fatty acid levels remained fairly constant with both season and age, apart from lignoceric and heptadecanoic acid which showed a decrease in winter compared with summer. The decrease in the mass levels of intercellular lipids and the altered ratios of fatty acids esterified to ceramide 1, are likely to contribute to the increased susceptibility of aged skin to perturbation of barrier function and xerosis, particularly during the winter months.     

Extraskeletal osteosarcoma of the hand. A case report

T cell mediated autoimmunity may be important in inflammatory skin disease, but target autoantigens have not previously been described. In studies aimed at defining T cell epitopes, aqueous extracts of normal facial and plantar stratum corneum have consistently been found to induce potent proliferation of peripheral blood mononuclear cells from normal donors and patients with inflammatory skin disease, giving stimulation indices up to 80. Potent stimulation was seen with both autologous and allogeneic stratum corneum extracts. Because of the presence of inhibitory material, demonstration of the stimulatory activity was critically dependent on extract concentration, and was facilitated by short-term pulsing of cultures with extract. The proliferation of cells purified from peripheral blood mononuclear cells by immunomagnetic beads and immunophenotyping of cell lines generated from peripheral blood mononuclear cells, confirmed the T cell nature of the response to stratum corneum extracts. The activity was inhibited by HLA-DR monoclonal antibody, indicating the presence of antigen or superantigen. Tetanus toxoid reactive clones and a purified protein derivative reactive line failed to respond to the stratum corneum extracts, indicating that the active material is not a nonspecific T cell stimulant such as a cytokine or mitogen. This and the failure of recombinant interleukin-1alpha to stimulate peripheral blood mononuclear cells in concentrations up to 1000 U per ml, indicate that the activity is not due to interleukin-1. We propose the hypothesis that antigenic or superantigenic material is normally sequestered from the immune system in the epidermis, but induces T cell activation when released following wounding and in disease, and that this represents an important and previously unrecognized pathogenic mechanism.     

Differences in stratum corneum pH gradient when comparing white Caucasian and black African-American skin

This study assessed pH gradient changes in relation to stratum corneum (SC) depth and possible differences between white caucasian and black African-American skin. Ten white and eight black people entered the study. SC was progressively removed by cellophane tape stripping on the volar forearm and weighed with a microbalance. Transepidermal water loss (TEWL) and SC pH were measured every three tape strippings. Significantly increased TEWL and decreased pH values were found with increasing SC depth in both races. Significantly increased TEWL in black people was found after three and six tape strippings (P < 0.05 and 0.03, respectively); pH was significantly decreased in black people after three tape strippings (P < 0.005). No differences were found between the races after nine, 12 and 15 strippings, i.e. in the deeper SC layers. The data confirm that pH in the superficial SC layers decreases with SC depth; only total SC removal results in increased pH values. In the superficial layers, there are significant differences in both water evaporation and skin pH, possibly explaining the contradictory literature.     

Extracellular stimulation of epidermal DNA synthesis

The removal of the topmost cell layers of the epidermal stratum corneum by stripping initiates a series of biochemical events which alters the normal homeostatic control of and results in the acceleration of the cell cycle in basal cells which are ten to twenty cell layers removed from the site of stripping. One measure of accelerated events is a stimulation of thymidine incorporation into epidermal DNA at time intervals following stripping. Two peaks of maximal stimulation occur between 12 and 24 hr and 48 and 54 hr after stripping. Stimulation of thymidine incorporation into epidermal DNA by limited stripping is a useful technique for studying the stripping-initiated signal at the stratum corneum and its subsequent translation at the proliferative cell receptor site.     

Non-uniform cellular packing of the stratum corneum and permeability barrier function of intact skin: a high-resolution confocal laser scanning microscopy study using highly deformable vesicles (Transfersomes)

Novel, functional skin staining with fluorescent, ultradeformable lipid vesicles (Transfersomes, IDEA, Munich, Germany) was developed and combined with confocal laser scanning microscopy. This revealed the structural and barrier characteristics of intact skin to a resolution of > or = 0.2 micron, that is, to the limit of light microscopy. Different routes of penetration into the stratum corneum were visualized and new details in the skin anatomy and barrier were unveiled. Most prominent was the lateral inhomogeneity of the stratum corneum, where three to 10 neighbouring corneocyte 'columns' were found to form a cluster. Corneocyte edges inside each cluster intercalated extensively, but adjacent clusters were separated by 'gorges' a few micrometers deep; lipid packing was also less regular and tight in the intercluster region. Two quantitatively different hydrophilic pathways were found in the horny layer: an intercluster route with low penetration resistance comprising < or = 1% of the total or < or = 20% of the pathway area in the skin, and an intercorneocyte pathway that resists penetration better and is more abundant (> or = 3% of the skin or > or = 80% of the pathway area). This latter route is strongly tortuous, as it goes between all the corneocytes in a cluster. It traces the irregularities between the intercellular lipid lamellae and/or the adjacent corneocyte envelopes which may act as virtual channels in the skin. It was inferred that such channels coincide with the route of water evaporation through the skin and exhibit the permeability barrier maximum in the stratum corneum conjunctum.     

Solitary splenic metastasis of an adenocarcinoma of the ovaries

BACKGROUND: Topical application of inhibitors of HMGCoA reductase, the rate-limiting enzyme of cholesterol synthesis, has been shown to induce impairment of barrier function. OBJECTIVE: Assessing whether oral administration of statins used for reducing blood levels of cholesterol induces functional changes in stratum corneum barrier. MATERIALS AND METHODS: 69 subjects of both sexes under-going treatment for hypercholesterolemia (mean age 48 +/- 11 years) entered the study; 43 had been treated with simvastatin and 11 with pravastatin for 6 months; 15 only on dietary regimen served as controls. Efficiency of stratum corneum water barrier was evaluated by transepidermal water loss (TEWL) measurement using an evaporimeter; water-holding capacity of the stratum corneum was assessed by the sorption-desorption test measured by capacitance. Statistical analysis was performed using ANOVA. RESULTS: No differences were found between the groups (simvastatin, pravastatin, diet) concerning both basal TEWL and the dynamic of water binding in the stratum corneum. CONCLUSIONS: Prolonged treatment with cholesterol-lowering drugs based on inhibition of HMGCoA reductase does not alter the permeability barrier of the skin.     

Paired pulse analysis of ATP and noradrenaline release from sympathetic nerves of rat tail artery and mouse vas deferens: effects of K+ channel blockers

The barrier function of the skin resides in the stratum corneum (SC). This outermost layer consists of protein-rich corneocytes and lipid-rich intercellular domains. These domains form the rate-limiting step for transepidermal water loss and the penetration of substances from the environment. To study the nature of the barrier function, stratum corneum lipid models have been examined with wide-angle X-ray diffraction. A disadvantage of this technique is that it requires bulk quantities of lipid and thus information on variations in the lateral packing cannot be obtained in the microm-range. To the best of our knowledge, this is the first study in which electron diffraction is applied on SC lipid model systems. Using this technique, local structural information was obtained about mixtures prepared from isolated pig ceramides, cholesterol, and long-chain free fatty acids. It appeared that addition of free fatty acids caused a transition from a hexagonal to an orthorhombic packing and that electron diffraction can be applied to distinguish between these two lattices. The results are in good agreement with wide-angle X-ray diffraction data and suggest that application of electron diffraction in skin studies can provide new information on the lipid organization in well-defined areas of the stratum corneum.