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PubMed1998

Purification and characterization of interleukin 1 beta from human plantar stratum corneum. Evidence of interleukin 1 beta processing in vivo not involving interleukin 1 beta convertase.

The major interleukin 1 beta (IL-1 beta) species from human plantar stratum corneum was purified and found to have an N-terminal amino acid sequence homologous to a stretch of the human IL-1 beta precursor, starting with His115. Whereas SDS-polyacrylamide gel electrophoresis followed by immunoblotting revealed only one component in plantar stratum corneum with IL-1 beta-like immunoreactivity, and with an apparent molecular mass around 18 kDa, isoelectric focusing under non-denaturing conditions showed one major component with isoelectric point around 6.1 and two minor components isoelectric at pH 6.3 and 6.9, respectively. Digestion of recombinant human IL-1 beta precursor with chymotrypsin, producing a C-terminal fragment with N-terminal Yal114, yielded a component with IL-1 beta-like immunoreactivity isoelectric at pH 6.3. Recombinant bacterial variants of human IL-1 beta with N-terminal amino acids corresponding to Val114, His115 and Ala117 were isoelectric at pH 6.3, 6.1 and 6.9, respectively. Cloning and subsequent nucleotide sequencing of IL-1 beta precursor cDNA from a human keratinocyte line showed total identify with the sequence previously published for the human monocyte IL-1 beta precursor. The authors conclude that the IL-1 beta species present in plantar stratum corneum have isoelectric points determined by their respective amino acid sequences, and that there is a mechanism for IL-1 beta activation in human epidermis not involving interleukin 1 beta convertase.

Amino Acid Sequence↗

PubMed1980

Ultrastructure of the human enamel organ. I. External enamel epithelium, stellate reticulum, and stratum intermedium.

The fine structure of external enamel epithelium, stellate reticulum and stratum intermedium in primary tooth germs (bell stage) from four human foetuses was investigated. Characteristically, the cells of the differentiated external enamel epithelium, stellate reticulum and stratum intermedium exhibit many free ribosomes, few rough endoplasmic reticulum cisterns, well-developed Golgi complexes, many coated and smooth vesicles, often in relation to the cell membranes, and many bundles of tonofilaments. The cells are connected by numerous desmosomes and gap junctions. A parallel differentiation of stratum intermedium - external enamel epithelium, and the ameloblast layer is demonstrated. The morphology of the cells of the three layers indicates that these have secretory, transport and supporting functions.

Cell Membrane↗

PubMed1992

Stratum corneum sphingolipids and free amino acids in experimentally-induced scaly skin.

Stratum corneum sphingolipids are of particular importance in maintaining the water permeability barrier of mammalian epidermis. Free amino acids also play an important role in water retention in the stratum corneum. To clarify the way in which these substances affect scaly skin, stratum corneum sphingolipids and free amino acids collected from artificially-induced scaly skin were analysed. Scaly skin was induced by tape stripping. The total amount of sphingolipids was quantified by gas chromatography and five of sphingolipid fractions were isolated and quantified by thin-layer chromatography. Free amino acids were analysed using a high-speed amino analyser. The total amount of sphingolipid in scaly skin did not differ statistically from that in control skin. However, a significant change in the distribution of the five sphingolipid species was observed in scaly skin and the total amount of amino acids was decreased in scaly skin. These results suggest that the distribution of these five types of sphingolipid and the total amount of amino acids are responsible for scaly skin.

Adult↗

PubMed1993

Age- and sex-dependent change in stratum corneum sphingolipids.

We measured six stratum corneum sphingolipid species (ceramides 1-6) in 26 males and 27 females, and found a significant change in their percentage composition only among female subjects of different age groups. There was a significant increase in ceramide 1 and 2 with a corresponding decrease in ceramide 3 and 6 from prepubertal age to adulthood. Thereafter the ratio of ceramide 2 to total sphingolipids decreased with age in contrast to ceramide 3 which showed an increase. Such a pattern of change in the aging population is different from that observed in scaly skin experimentally induced by tape stripping. The present results suggest a significant influence of female hormones on the composition of stratum corneum sphingolipids. Moreover, the different patterns of change in sphingolipid composition of stratum corneum lipids between scales from inflammatory skin and those from aged skin also suggest that epidermal biosynthesis of sphingolipids is influenced by epidermal proliferative activity.

Adolescent↗

PubMed1985

Human stratum corneum polar lipids and desquamation.

The ceramides and steryl-sulfate components from desquamated and cohesive human stratum corneum were examined using a combination of chemical and chromatographic means. Six structurally distinct series of ceramides were identified, and the relative amounts of these species, as measured by quantitative thin-layer chromatography, did not differ in cohesive and desquamated stratum corneum. In contrast, the level of cholesteryl sulfate was significantly reduced in the desquamated material. The results are in accord with the hypothesis that cholesteryl sulfate serves in cell-to-cell cohesion within the stratum corneum, and its hydrolysis may be necessary to permit shedding of cells from the surface.

Ceramides↗

PubMed1988

Preparation and characterization of a reconstituted stratum corneum film as a model membrane for skin transport.

A zwitterionic surfactant, 6-eicosyldimethyl ammoniohexanoate (C20AH), completely disaggregates stratum corneum into individual cells. The cells can be cast into a film of reconstituted stratum corneum (RSC). Such films prepared from pig and human skin mimic intact human stratum corneum in microscopic, mechanical, and barrier evaluations. The films are useful as model membranes for skin transport experiments.

Animals↗

PubMed1979

Abnormal fibrous protein isolated from the stratum corneum of a patient with bullous congenital ichthyosiform erythroderma (BCIE).

The fibrous protein of stratum corneum was isolated from a patient with bullous congenital ichthyosiform erythroderma (BCIE), and its properties characterized using electron microscopy, amino acid analysis and SDS gel electrophoresis. Results were compared with the characteristics of the fibrous protein isolated from stratum corneum of normal controls. From 900 mg (dry weight) of stratum corneum, 68 mg of fibrous protein was obtained from the patient, while 178 mg was obtained from the normal control. Structural differences were observed with electron microscopy and chemical differences, were shown in the ratio of several amino acids. On SDS electrophoresis, the 55,000 dalton constituent of normal fibrous protein could not be identified in the fibrous protein from this patient. These results suggest that an alteration of the polypeptide composition of fibrous protein from this patient with BCIE occurred, and this alteration induced the morphological and clinical features of this dominant genetic keratinization disorder.

Amino Acids↗

PubMed1976

Permeability parameters of the toad isolated stratum corneum.

A technique for isolating the stratum corneum from the subjacent layers of the epithelium was developed which permits studying the stratum corneum as an isolated membrane mounted between half-chambers. The method basically consists of an osmotic shock induced by immersing a piece of skin in distilled water at 50 degrees C for 2 min. When the membrane is bathed on each surface by NaCl-Ringer's solution, its electrical resistance is 14.1 +/- 1.3 omega cm2 (n=10). This value is about 1/100 of the whole skin resistance in the presence of the same solution. The hydraulic filtration coefficient (Lp) measured by a hydrostatic pressure method, with identical solutions on each side of the membrane, is 8.8 X 10(-5) +/- 1.5 X 10(-5) cm sec-1 atm-1 (n=10) in distilled water and 9.2 X 10(-5) +/- 1.4 X 10(-5) cm sec-1 atm-1 (n=10) in NaCl-Ringer's solution. These values are not statistically different and are within the range of 1/80 to 1/120 of the whole skin Lp. The stratum corneum shows an amphoteric character when studied by KCl diffusion potentials at different pH'S. The membrane presents an isoelectric pH of 4.6 +/- 0.3 (n=10). Above the isoelectric pH the potassium transport number is higher than the chloride transport number; below it, the reverse situation is valid. Divalent cations (Ca++ or Cu++) reduce membrane ionic discrimination when the membrane is negatively charged and are ineffective when the membrane fixed charges are protonated at low pH.

Animals↗

PubMed1997

Dielectric properties of some keratinised tissues. Part 1: Stratum corneum and nail in situ.

Blister-skin and warts have been studied as possible sources of 'pure' stratum corneum without sweat ducts. The purpose of the study was to assess whether the DC electrical conductance measured on human skin is totally dominated by the sweat ducts, or is also significantly contributed to by the stratum corneum itself. By means of galvanic skin response (GSR) measurements, these tissues were found to be unrealiable as sources of 'pure' stratum corneum. This is because they displayed significant GSR waves, and hence should have some form of active pores. However, measurements on blister-skin and nail in situ revealed a substantial frequency independent electrical conductance at frequencies typically below 10 Hz.

Blister↗

PubMed2004

[Topically applied arginine hydrochloride. Effect on urea content of stratum corneum and skin hydration in atopic eczema and skin aging].

BACKGROUND AND OBJECTIVE: Currently, there are no data on how the topical application of amino acids influences the complex moisture retaining system of the skin in vivo. PATIENTS/METHODS: An open study was performed to investigate the effects of topical application of arginine hydrochloride on epidermal stratum corneum urea content, transepidermal water loss, skin hydration, and clinical status of patients with atopic dermatitis and dry elderly skin. RESULTS: Treatment of patients with atopic dermatitis with 2.5% arginine hydrochloride ointment over 4 weeks showed a significant increase in urea in the stratum corneum as well as a continuous increase in skin moisture. CONCLUSIONS: The urea deficit in the stratum corneum in atopic dermatitis and elderly skin was corrected not by applying the moisturizer urea itself but instead by using arginine - its precursor in the Krebs-Henseleit urea cycle. This topical treatment also improved the clinical symptoms of dry skin.

Administration, Topical↗

PubMed2001

Neurons with complex receptive fields in the stratum griseum centrale of the zebra finch (Taeniopygia guffata castanotis Gould) optic tectum.

The electrophysiological and morphological features of visually driven neurons of the stratum griseum centrale of the zebra finch optic tectum were studied by extracellular recording and staining techniques. Stratum griseum centrale neuron responses are sustained in most cases. Receptive fields are big, up to 150 degrees of the visual field. The excitatory center (hot spot) varies in size from 1 degrees to 15 degrees. It can be mapped by small static stimuli, adapts slower than the surround, and has a shape comparable to the excitatory fields of upper-layer neurons. In contrast, the big surround shows responses only to small moving objects which elicit a typical pattern of alternating bursts and silent periods. Alternatively, the same stimuli elicit long-lasting bursts followed by strong adaption. Anatomically, stratum griseum centrale neurons are characterized by far reaching dendrites which terminate with "bottlebrush"-like endings in the upper retinorecipient layers. In addition, they are connected with retinorecipient structures by an interneuron located between layers 10 and 11. The role of the structure of inputs for the organization of the receptive fields is discussed.

Action Potentials↗

PubMed2002

Dandruff: a condition characterized by decreased levels of intercellular lipids in scalp stratum corneum and impaired barrier function.

Dandruff is a major problem, yet little is known about the underlying mechanism and subsequent biochemical changes occurring in the scalp skin that lead to its manifestation. The characteristic flaking and scaling of the scalp experienced by dandruff sufferers suggests, similar to the changes classically seen in xerosis, that the desquamation process is impaired. We initiated studies to quantify the biochemical nature of the stratum corneum in the scalp of healthy individuals and dandruff sufferers. Total amounts and relative ratios of stratum corneum lipids species were analysed in scalp stratum corneum samples collected during studies conducted in the UK and Thailand in order to examine ethnic differences. In both populations, dandruff was associated with a dramatic decrease in free lipid levels, with significant decreases in ceramides, fatty acids, and cholesterol. Detailed sub-analysis of the major ceramide species within the total ceramide fraction revealed a decrease in ceramide 1 and increased proportions of ceramide 6i and 6ii. In a separate study, we demonstrated that dandruff sufferers show both an elevated blood flow and an increased reported incidence of itch in response to histamine topically applied to the scalp compared with no-dandruff controls. Taken together these two studies indicate that the quality and resilience of the epidermal water barrier is impaired in the scalp of dandruff sufferers. We propose that the perturbed barrier leaves dandruff sufferers more prone to the adverse effects of microbial and fungal toxins, and environmental pollutants, thus perpetuating their impaired barrier.

Administration, Cutaneous↗

PubMed1997

Existence of a lipid gradient in the upper stratum corneum and its possible biological significance.

The internal stratum corneum lipid composition was investigated in relation to depth in vivo in healthy human volunteers by extraction following one, three or five strippings. Automated multiple development high-performance thin-layer chromatography (AMD-HPTLC) and gas chromatography (GC) followed by normalized principal component analysis showed a decrease in the amount of lipids extracted after one, three and five strippings. Between levels 0, 1, 3 and 5 the stratum corneum lipid composition showed an increase in phospholipids and cholesterol-3-sulphate at level 3, a decrease in ceramide, cholesterol and free fatty acids after level 1, and a slight decrease in sterol esters at level 3. Lipids extracted after three strippings displayed a characteristic composition with an increase in the proportion of phospholipids and cholesterol-3-sulphate. Free fatty acid analysis in relation to depth revealed a decrease in the amounts of C14:0, C16:0, C16:1, C18:0 and C18:1 between levels 1 and 5 and an increase in the C24:0. A decrease in the unsaturated/saturated chain ratio with depth was also observed, reflecting a greater decrease in unsaturated than saturated free fatty acids. A decrease in the ratios of free fatty acids to cholesterol and free fatty acids to ceramides after three and five strippings, respectively, and previously reported results, confirm the importance of this level of stratum corneum lipids in skin barrier properties.

Adult↗

PubMed2004

Partial ablation of porcine stratum corneum by argon-fluoride excimer laser to enhance transdermal drug permeability.

To enhance skin permeability to medicine, the argon-fluoride excimer laser (ArF laser) was used to partially ablate the stratum corneum. Skin permeability to dextran (20 kDa) was studied in the Yucatan micro-pig skin in vitro. The cumulative amount of dextran permeating across the full-thickness skin was not detected for 30 h in the unirradiated skin; we obtained up to 90.5 microg/cm2 in laser-irradiated skin. In the case where the total laser energy was kept constant at 7.1 J/cm2, permeability was mainly influenced by laser fluence rather than laser pulses. Many granular structures of about 2 microm were found on the stratum corneum surface of ablated skin. Size and density of these structures were changed according to irradiation conditions. Skin permeability may be estimated by these structural changes. Our partial stratum corneum ablation by ArF laser could be suitable for transdermal drug delivery.

Administration, Cutaneous↗

PubMed2005

Modeling of diffusion with partitioning in stratum corneum using a finite element model.

Partitioning and diffusion of chemicals in skin is of interest to researchers in areas such as transdermal penetration and drug disposition, either for risk assessment or transdermal delivery. In this study a finite element method is used to model diffusion in the skin's outermost layer, the stratum corneum (SC). The SC is considered to be a finite two-dimensional composite having different diffusivity values in each medium as well as a partition coefficient at the interfaces between media. A commercial finite element package with thermal analysis capabilities is selected due to the flexibility of this software to handle irregular geometries. Partitioning is accommodated through a change of variables technique. This technique is validated by comparison of model results with analytical solutions of steady-state flux, transient concentration profiles, and time lag for diffusion in laminates. Two applications are presented. Diffusion is solved in a two-dimensional "brick and mortar" geometry that is a simplification of human stratum corneum, with a partition coefficient between corneocyte and lipid. Results are compared to the diffusion in multiple laminates to examine effects of the partition coefficient. The second application is the modeling of diffusion with partitioning through an irregular geometry which is obtained from a micrograph of hairless mouse stratum corneum.

Administration, Cutaneous↗

PubMed1988

Effect of epidermal acylglucosylceramides and acylceramides on the morphology of liposomes prepared from stratum corneum lipids.

Epidermal acylglucosylceramides (AGC) and acylceramides (AC) cause aggregation and stacking of stratum corneum lipid liposomes formed from a lipid mixture containing epidermal ceramides (40%), cholesterol (25%), palmitic acid (25%), and cholesteryl sulfate (10%). This demonstrates the ability of these sphingolipids to hold adjacent bilayers in close apposition and their roles in the assembly of lamellar structures in the epidermis. However, AGC and AC in their hydrogenated form also caused aggregation and stacking of the stratum corneum lipid liposomes. This throws into doubt the proposed structural specificity of linoleate in the function of AGC and AC as molecular rivets in the assembly of the epidermal lamellar granules and the stratum corneum intercellular lamellae, respectively.

Animals↗

PubMed1992

The stratum corneum lipid thermotropic phase behavior.

The stratum corneum, the outermost layer of mammalian skin, is considered the least permeable skin layer to the diffusion of water and other solutes. It is generally accepted that the intercellular lipid multilayer domain is the diffusional pathway for most lipophilic solutes. Fluidization of the lipid multilayers is believed to result in the loss of barrier properties of the stratum corneum. Current investigations address the lipid thermotropic phase behavior in terms of lipid alkyl chain packing, mobility and conformational order as measured by Fourier transform infrared (FTIR) spectroscopy. A solid-solid phase transition is observed with increased alkyl chain mobility followed by a gel to liquid-crystalline phase transition near 65 degrees C. These results further elucidate the role of lipid fluidity that may contribute to the transport properties of the stratum corneum.

Animals↗

PubMed1994

Polymorphism in stratum corneum lipids.

Fourier transform infrared spectroscopy (FTIR) was employed to investigate the thermotropic phase behavior of stratum corneum lipid multilamellae. Stratum corneum (SC), the uppermost layer of mammalian skin, is unusual in many respects. It has been demonstrated that the lipids of the stratum corneum provide the primary electrical and transport resistance in the skin. These lipids are unusual in their composition, structure and localization; they contain only cholesterol, fatty acids and ceramides and they form broad, multi-lamellar sheets which are located extracellularly. The FTIR results from both the symmetric CH2 stretching and the CH2 scissoring vibrations suggest that the SC lipids exhibit polymorphic phase behavior below the main phase transition temperature. The multiple phases are most likely crystalline mixtures of different alkyl chain packings, along with solid-liquid phases. Similarities between the FTIR results reported here for SC lipids and those obtained for cholesterol-containing gel phase phospholipids suggest that the non-uniform distribution of cholesterol occurs in each system.

Animals↗