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At least 217 records · Page 12Linked to original sources
PubMed1989

The water-holding capacity of the stratum corneum measured by 1H-NMR.

The amount of bound water in the stratum corneum of the hairless rat was measured by using proton nuclear magnetic resonance (1H-NMR) spectrometry in the temperature range of -5 degrees C to -30 degrees C. A decrease in the bound water content was observed when the stratum corneum was extracted using water, a mixed solvent of chloroform:methanol (2:1), or a 1% sodium dodecyl sulfate (SDS) aqueous solution. However, extraction using a mixed solvent of acetone:ether (1:1) did not change the bound water content at temperatures above -20 degrees C. The lipids extracted by acetone:ether-extraction method consisted of sebaceous gland lipids, cholesterol, free fatty acids, and ceramides. In contrast, the lipids extracted by chloroform:methanol-extraction method contained more polar lipids such as sphingomyelin, which had the same amount of bound water in itself as that of the water-extracted stratum corneum. These results suggest that the polar lipids soluble in the chloroform and methanol mixture may contribute to enhance the bound water content. Therefore, it is hypothesized that the water-holding capacity of the stratum corneum is dependent on both the hygroscopic components such as the natural moisturizing factor (NMF) and the polar lipids, such as sphingolipids, existing in the intercellular spaces of the stratum corneum.

Animals↗
PubMed1993

Purification and preliminary characterization of stratum corneum chymotryptic enzyme: a proteinase that may be involved in desquamation.

In recent work we have shown that a serine proteinase, stratum corneum chymotryptic enzyme, with properties compatible with a role in desquamation in vitro as well as in vivo, is generally present in human stratum corneum. The enzymologic properties of the stratum corneum chymotryptic enzyme in a KCl extract of dissociated plantar corneocytes were compared with those of other known chymotryptic serine proteinases. Stratum corneum chymotryptic enzyme was found to differ significantly from bovine chymotrypsin, human cathepsin G, and human mast cell chymases in regard to inhibitor profile and substrate specificity. Stratum corneum chymotryptic enzyme was further purified from KCl extracts of dissociated plantar corneocytes by affinity chromatography on gels with covalently linked soybean trypsin inhibitor. The purified preparation contained one major component with apparent molecular weight 25 kD and one minor component with slightly higher apparent molecular weight as revealed by Coomassie staining after electrophoresis in polyacrylamide gels with sodium dodecyl sulphate of samples that had not been reduced. Both these components were associated with chymotrypsin-like activity as revealed by zymography in polyacrylamide gels with co-polymerized casein. On zymography gels, the purified preparation was also found to contain minor amounts of components with trypsin-like activity. The major purified protein had an apparent molecular weight of around 28 kD after reduction and full denaturation and was shown to contain carbohydrate.

Animals↗
PubMed1986

Selective recovery of deranged water-holding properties by stratum corneum lipids.

Selective removal of stratum corneum lipids following applications of acetone/ether to the human forearm for extremely prolonged periods of 5-20 min induced an enduring (more than 4 days), chapped and scaly appearance of the skin which was accompanied by a significant decrease in the water-holding properties of the stratum corneum. In order to further elucidate the significance of lipids in the water-holding properties, lipids, which were extracted as sebaceous-rich lipids (SL) for the first 10-min acetone/ether treatment and as stratum corneum lipids (SCL) for the additional 30-min treatment, were topically applied daily on lipid-depleted forearm skin which had been pretreated with acetone/ether for 40 min. Two daily applications of the SCL which were solubilized in squalane containing 1% alpha-monomethyl heptadecyl glyceryl ether (GE) caused a significant increase of conductance, accompanied by a marked improvement in the level of scaling as compared with nontreatment or GE/squalane base, whereas the SL in the GE/squalane base did not exhibit any significant recovery in either conductance value or scaling. To clarify which components of the SCL are primarily responsible for the observed recovery of the water-holding properties, chromatographically separated fractions of the SCL were also topically applied in the same manner for 2 successive days. Out of the following separated fractions: cholesterol, cholesterol ester, free fatty acid, glycolipids, and ceramide, 2 daily topical applications of ceramide fraction induced a significant and the highest increase in the conductance value as compared with GE/squalane base. Furthermore, glycolipids and cholesterol fractions also exhibited a significant recovery when compared with no application at all. In contrast, free fatty acid and cholesterol ester fractions did not indicate any significant increase in the conductance value. These findings strengthen the hypothesis that structural lipids present in the intercellular spaces of the stratum corneum, especially ceramide, play a critical role in the water-holding properties of the stratum corneum.

Acetone↗
PubMed1987

The cystine-rich envelope protein from human epidermal stratum corneum cells.

A cystine-rich protein has been extracted from the membrane region of stratum corneum cells with 50 mM Tris-HCl buffer, pH 7.3. The protein has been purified by molecular sieve chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and preparative isoelectric focusing. An antibody, raised to the purified protein, was located in the cell membrane region in the stratum spinosum, stratum granulosum, and the inner part of the stratum corneum. In addition, the antibody also reacted with the protein extracted from the outer part of the stratum corneum by the immunoblotting method. Amino acid analysis of the protein revealed a distribution of 4.3% cystine residues, 9% lysine, 18.5% glycine, and 12.6% glutamic acid residues. The isoelectric point was found to be 4.8 and the molecular weight of the protein was 16,000.

Antibodies↗
PubMed1987

Effect of preheating on the permeability of neonatal rat stratum corneum to alkanols.

We heated flat sheets of neonatal rat stratum corneum for various times at temperatures between 40 and 90 degrees C before determining the permeability coefficient (Kp) of propanol and/or hexanol from water. Below 70 degrees C, Kp remained constant; at 75 degrees C, Kp increased linearly with exposure time; at 80 degrees C and above, there was a large increase in under 2 h, with no further increase on longer heating. There was a 15-fold increase in 6-h Kp between 70 degrees C and 80 degrees C, values being constant above 80 degrees C but at a figure less than for lipid-extracted stratum corneum. Thermal analysis showed that the increase in Kp corresponds to changes in the 80 degrees C lipid endotherm, suggesting that the increased Kp is due to a disordering of the lipid structures. The effect of treating preheated stratum corneum with dimethylsulfoxide (DMSO) vapor for 16 h was also studied. Below 70 degrees C, Kp was increased five-fold, but between 70 and 80 degrees C this difference was eliminated, so that above 80 degrees C the Kp was the same as with heat treatment alone. We concluded that both heat and DMSO affect the lipid structures of stratum corneum. DMSO produced a small, reversible structural change, while the effect of heat is irreversible and produces a greater degree of disorder in the lipid structures, but the lipid still contributed to the barrier effect of stratum corneum.

1-Propanol↗
PubMed1977

Viscoelastic properties of intact human skin: instrumentation, hydration effects, and the contribution of the stratum corneum.

Past attempts to relate mechanical properties of the stratum corneum to its state of hydration or disease condition have been hampered by the lack of adequate in vivo methodology. With the technique described herein, viscoelastic properties of the skin surface can be measured in vivo or on excised skin in vitro. This method is sensitive enough to detect changes in the properties of the stratum corneum induced by topically applied agents or by mechanical disruption of it. The viscoelastic data suggest that the outermost layers of the stratum corneum may become dry in vivo despite their proximity to the underlying wet tissue, and that the instrument is sensitive enough to measure the changes that occur. It also appears that the in vivo behavior of the stratum corneum is similar to that of isolated stratum corneum membranes which become brittle when they are dried and supple when they are hydrated.

Biomechanical Phenomena↗
PubMed1991

Oriented structure in human stratum corneum revealed by X-ray diffraction.

Various types of human stratum corneum (sheets or callus) were exposed, in parallel and perpendicular geometry, to the high flux of X rays produced by a synchrotron radiation source. Under these conditions, very clear and rich diffraction patterns, corresponding to the supramolecular organization of stratum corneum proteins and lipids, were obtained. The comparative study of normal or delipidized stratum corneum sheets and membrane couplets allows one to attribute certain diffraction features to lipids. Our results in the 3-7-nm range show two different distances for lipid bilayers. Concerning the protein nature of normal stratum corneum, the results show that keratin would occur in the beta form, whereas for callus it is in the alpha form. Indeed, normal stratum corneum sheets never display the 0.514-nm characteristic of alpha keratin. This result means that the supramolecular organization of keratin could depend on the keratinization process. Finally, our studies also confirm the presence of a still-unknown protein component existing in the beta form that would be located either inside the corneocytes or in some dilatated zones of the intercellular spaces.

Humans↗
PubMed1990

Evidence that cell shedding from plantar stratum corneum in vitro involves endogenous proteolysis of the desmosomal protein desmoglein I.

We have recently described a process leading to a unipolar cell shedding from pieces of plantar stratum corneum incubated in vitro, which seems to be dependent on the activity of a serine proteinase. This process has been studied further. Electron microscopy studies suggest that cell dissociation is preceded by a degradation of the intercellular parts of desmosomes. An antiserum was raised against the transmembrane protein desmoglein I (DG I) of bovine desmosomes. In extracts of layers of plantar stratum corneum with strong intercellular cohesion, this antiserum reacted with a protein of the same apparent molecular weight as bovine DG I. In dissociated cells this DG I-like protein could not be detected; instead components with molecular weights lower than DG I which reacted with the antiserum were found. During incubation of pieces of plantar stratum corneum, under conditions leading to unipolar cell shedding, there was a progressive decrease in the amounts of the DG I-like protein, and the appearance of the lower molecular weight components with DG I-like immunoreactivity. This apparent degradation of the DG I-like protein was inhibited by aprotinin, chymostatin, and zinc ion, but not by leupeptin. The results suggest that proteolytic degradation of desmosomes may be an important part of the process leading to cell dissociation in plantar stratum corneum in vitro, and that desmosomes may play an important role in plantar stratum corneum cell cohesion.

Animals↗
PubMed2004

Stratum corneum keratin structure, function, and formation: the cubic rod-packing and membrane templating model.

A new model for stratum corneum keratin structure, function, and formation is presented. The structural and functional part of the model, which hereafter is referred to as "the cubic rod-packing model", postulates that stratum corneum keratin intermediate filaments are arranged according to a cubic-like rod-packing symmetry with or without the presence of an intracellular lipid membrane with cubic-like symmetry enveloping each individual filament. The new model could account for (i) the cryo-electron density pattern of the native corneocyte keratin matrix, (ii) the X-ray diffraction patterns, (iii) the swelling behavior, and (iv) the mechanical properties of mammalian stratum corneum. The morphogenetic part of the model, which hereafter is referred to as "the membrane templating model", postulates the presence in cellular space of a highly dynamic small lattice parameter (<30 nm) membrane structure with cubic-like symmetry, to which keratin is associated. It further proposes that membrane templating, rather than spontaneous self-assembly, is responsible for keratin intermediate filament formation and dynamics. The new model could account for (i) the cryo-electron density patterns of the native keratinocyte cytoplasmic space, (ii) the characteristic features of the keratin network formation process, (iii) the dynamic properties of keratin intermediate filaments, (iv) the close lipid association of keratin, (v) the insolubility in non-denaturating buffers and pronounced polymorphism of keratin assembled in vitro, and (vi) the measured reduction in cell volume and hydration level between the stratum granulosum and stratum corneum. Further, using cryo-transmission electron microscopy on native, fully hydrated, vitreous epidermis we show that the subfilametous keratin electron density pattern consists, both in corneocytes and in viable keratinocytes, of one axial subfilament surrounded by an undetermined number of peripheral subfilaments forming filaments with a diameter of approximately 8 nm.

Adult↗
PubMed2004

Near-infrared Fourier transform Raman spectroscopic analysis of proteins, water and lipids in intact normal stratum corneum and psoriasis scales.

Previous biochemical studies demonstrated differences in the structure of lipids in normal skin and psoriatic lesions. Raman spectroscopy provides a unique possibility of studying the molecular structure of proteins, lipids and water in intact skin. Near-infrared Fourier transform Raman spectroscopy was used to study changes in molecular structure and conformation of proteins and lipids of stratum corneum in healthy persons and patients with psoriasis. In vitro Raman spectra were obtained from intact psoriatic scales in 11 patients and from normal stratum corneum of forearm, elbow and heel in a group of age-matched healthy persons. The spectra of stratum corneum differed between psoriasis and normal skin but not between investigated regions. No major changes of lipid band positions in Raman spectra were found, but the crystalline lipid structure was disrupted in psoriatic scales (assessed as the ratio of the symmetric methylene C-H stretching-mode intensities, S(lat)). Major spectral differences were seen in the molecular structure of the proteins. In the spectra of psoriatic scales, the peak position of the amide I band, in comparison with the normal skin, was shifted to higher wavenumbers, suggesting unfolding of proteins. Moreover, alterations in the disulfide stretch bonds of proteins were found in psoriasis scales, resulting in a less energetically favourable gauche-gauche-trans conformation (band around 520 cm(-1)). Psoriatic scales and normal stratum corneum did not statistically differ in their water content. The findings further define the molecular abnormalities in the stratum corneum in psoriasis.

Adult↗
PubMed1989

The substrate of epidermal proteases--effects of in situ activation of epidermal thiol proteases on stratum granulosum cells.

In newborn rat skin, disulfide bonds exist in the cell membrane of the stratum corneum and in the cytoplasm of the stratum granulosum. However, in the latter region, they can be detected after ethanol fixed epidermis remains for 2 weeks at 4 degrees C. Thus, the idea arose that the visualization of the disulfide bonds in the stratum granulosum may be caused by proteases. Therefore, the in situ effects by both activation and inhibition of epidermal proteases were examined in tissue sections. Cryostat sections which were fixed in cold ethanol (-20 degrees C, 98%) were incubated either in PBS, pH 7.4, containing 10mM 2-ME as a control or in an epidermal homogenate (15,000 x g supernatant fraction containing 2-ME) at 37 degrees C for 30 minutes and 4 hours, respectively, in order to activate the epidermal proteases and then reacted with NEM, 2-ME, and DACM in steps. Many minute fluorescent particles were seen in the stratum granulosum under both of the above conditions. However, with incubation in PBS without 2-ME, no fluorescent particles were seen. In addition, when the tissue was treated with NEM and zinc chloride before incubation, no fluorescent particles were seen. O-phenanthrolin remarkably inhibited the appearance of these fluorescent particles. In contrast, leupeptin and antipain only slightly inhibited the appearance of these fluorescent particles, and pepstatin and phenylmethylsulfonyl fluoride didn't inhibit at all. In general, as NEM and zinc chloride strongly inhibit thiol proteases, these findings suggest that presence of the minute fluorescent particles in the stratum granulosum could be due to the effects of proteases, especially thiol proteases.

Animals↗
PubMed1988

Methodology to measure the transient effect of occlusion on skin penetration and stratum corneum hydration in vivo.

The effect of short duration occlusion on skin penetration and stratum corneum water content was studied in vivo in eight human subjects. Percutaneous absorption of hexyl nicotinate was monitored non-invasively by laser Doppler velocimetry (LDV) following each of three randomly assigned pre-treatments: untreated control, 30 min occlusion with a polypropylene chamber and 30 min occlusion followed by exposure to ambient conditions for 1 h. Stratum corneum water content after the same pre-treatments was measured with the dielectric probe technique. The local vasodilatory effect of the nicotinic acid ester was quantified using LDV by the onset of increased blood flow, the time of maximal increase in response, the magnitude of the peak response and the area under the response-time curve. Each of these parameters was significantly different, immediately following occlusion, from the untreated control values. However, if the occluded site was exposed for 1 h prior to hexyl nicotinate application these parameters did not differ significantly from the controls. Stratum corneum water content (expressed as a percentage of a maximal value) showed the same behaviour: the pre-treatment control value was 31.8 +/- 4.8%; after 30 min occlusion, this had risen to 46.9 +/- 6.2%; 1 h later, the reading had returned to 32.1 +/- 6.2%. There was a significant correlation between stratum corneum water content and area under the LDV response-time curve. It appears, therefore, that this method may be useful for quantifying the relationship between increased stratum corneum hydration and enhanced percutaneous absorption in vivo in man.

Adult↗
PubMed1997

Characterization of the influence of some cyclodextrins on the stratum corneum from the hairless mouse.

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.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed1998

Enhancement by terpenes of 5-fluorouracil permeation through the stratum corneum: model solvent approach.

5-Fluorouracil permeates the stratum corneum through the intercellular pathway. 5-Fluorouracil is hydrophilic and, therefore, its partitioning from the aqueous region into the hydrocarbon interior of stratum corneum lipids is expected to be an important stage of its permeation and a target for some permeation enhancers. It has also been reported that complexation plays a role in the enhancement effect of some accelerants. These mechanisms have been investigated. For partitioning-permeation studies, isooctane was chosen as a model of the hydrocarbon interior of stratum corneum lipid bilayers and the effects of 26 different terpene enhancers on the solubility of 5-fluorouracil in isooctane were measured. Results were then compared with the effects of the same enhancers on the permeation of 5-fluorouracil through the epidermis in man. The stoichiometry of interaction of cineole and limonene with 5-fluorouracil were also studied to reveal possible complex formation. Solubility studies revealed good correlation between solubility and enhancement ratios for the majority of terpenes, indicating that one mechanism by which terpenes increase permeation of the stratum corneum by 5-fluorouracil is by improvement of partitioning. Stoichiometry studies showed that cineole can form 1:1 or higher complexes with 5-fluorouracil. With limonene, only a weak 1:1 complex was indicated. Data obtained using epidermis from man show that the enhancement effect of cineole toward 5-fluorouracil is much higher than that of limonene. These data reveal that terpenes might increase the permeation of 5-fluorouracil through the stratum corneum as a result of complex formation and a form of facilitated transport.

Antimetabolites↗
PubMed2004

Intracutaneous distributions of fluconazole, itraconazole, and griseofulvin in Guinea pigs and binding to human stratum corneum.

We have compared the distribution of fluconazole (FLC) with that of itraconazole (ITC) and griseofulvin (GRF) in the abdominal skin tissues after a single oral dose was administered to guinea pigs. The FLC concentrations in the stratum corneum reached a peak at 2 h after administration and were similar to those of ITC and higher than those of GRF in spite of the administration of a lower dose. GRF was eliminated from the stratum corneum faster than FLC and ITC. The FLC concentrations were also remarkably higher than those of ITC and GRF in the epidermis-cutis but lower in the subcutaneous fatty tissue. The distribution characteristics of each drug result from differences in their physicochemical properties. Following the administration of multiple doses, the FLC concentrations in the stratum corneum were highest in the abdominal skin tissues; those at 24 h after each administration increased gradually and were maintained at a level more than 10 times higher than that of the plasma concentrations. The FLC concentrations in the planta pedis stratum corneum and in the nail showed good dose proportionality and obvious accumulation and were 60 and 40 times as high as that in plasma on day 14. The extent of binding of FLC to human corneous keratin in vitro was about 10%, which is lower than those of ITC (94 to 97%) and GRF (36 to 38%). FLC, unlike ITC, therefore, is presumed to exist in the stratum corneum at high concentrations in an active nonbinding form. These excellent intracutaneous pharmacokinetic properties of FLC probably account in large part for the in vivo efficacy of FLC.

Administration, Topical↗
PubMed1977

Stratum corneum of frog skin: inferences for studies of Na entry and transport pool.

Pieces of isolated stratum corneum from frog skins were studied. Preliminary data showed that approximately 56% of the total sodium of split skins was associated with the stratum corneum. In more detailed studies, the sodium space estimated with 22Na and the volume of tissue water were identical, averaging 0.95 mul/cm2. Thus, the stratum corneum contained approximately 0.11 mueq Na+/cm2. Similar determinations of the sucrose, mannitol, and inulin spaces of the stratum corneum gave mean values of 0.84, 2.21, and 1.84 mul/cm2, respectively. Surprisingly, the mannitol and inulin spaces were observed to be at least twice as large as the space occupied by the tissue water, and this can be interpreted to mean that mannitol and inulin bind in appreciable amounts and thus are unsuitable markers of the sodium space. Whereas the kinetics of sodium uptake and washout could be described simply, similar studies for sucrose, mannitol, and inulin were more complex and consistent with appreciable binding of the substances to the stratum corneum.

Animals↗
PubMedDate not supplied

Stratum corneum maturation. A review of neonatal skin function.

The importance of the stratum corneum and its barrier function for infants, especially for newborns, is clinically evident. Research regarding the maturation of the stratum corneum in neonates, i.e. when full barrier function is obtained, has produced varying results. Based on transepidermal water loss and percutaneous absorption studies, term infants seem to possess stratum corneum with adult barrier properties. Additionally, postnatal life is thought to accelerate stratum corneum maturation, so that even preterm infants have barrier function similar to term infants at 2-3 weeks of gestational age. However, a look at other parameters, such as skin thickness, skin pH and stratum corneum hydration, shows that neonatal skin is always adjusting to the extrauterine environment in contrast to the steady state of adult skin. This suggests that barrier stabilization may be dependent on achieving a balance between different parameters. However, it is still in question, which parameters, what balance and what timing. This paper provides an up-to-date overview on the neonatal skin barrier based on the review of current literature.

Epidermal Cells↗
PubMed1997

Effect of organic solvents on normal human stratum corneum: evaluation by the corneoxenometry bioassay.

BACKGROUND: Organic solvents alter the stratum corneum structure and barrier function. OBJECTIVE: To measure the effect of various solvents upon human stratum corneum using the ex vivo corneoxenometry bioassay which is a variant of corneosurfametry. METHODS: Corneoxenometry entails collection of human stratum corneum by cyanoacrylate. The material is immersed in organic solvents for periods ranging from 1 to 120 min. After staining the samples with a toluidine blue-basic fuchsin solution, the color is measured using reflectance colorimetry. Solvent aggressivity to the stratum corneum correlates with the color darkening of the samples. RESULTS: The least aggressive solvent was hexane, followed by ethanol, methanol, hexane-ethanol, chloroform, chloroform-methanol and hexane-methanol. The influence of contact time between solvents and the stratum corneum showed a logarithmic pattern which varied according to the solvent. CONCLUSION: Data are in line with previous experiments conducted in vivo and in vitro, thus indicating the predictive value of corneoxenometry. Such a bioassay may avoid hazards of some in vivo human testings.

Alcohols↗