Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “stratum”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1996

Photoprotection in vitiligo and normal skin. A quantitative assessment of the role of stratum corneum, viable epidermis and pigmentation.

Pigmentation, stratum corneum and viable epidermis are considered to be the main factors protecting against ultraviolet radiation. We quantitatively investigated the degree of photoprotection provided by these structures in vitiligo and adjacent normally pigmented skin. In 14 patients 61 MED tests were performed in vitiligo and adjacent normally pigmented skin using a solar simulator. The thickness of stratum corneum and viable epidermis was determined from frozen skin sections, and pigmentation was calculated by measuring skin reflectance at 555 nm and 660 nm. To analyse photoprotection, the UV dose necessary to evoke erythema was regressed against the thickness of stratum corneum and viable epidermis, pigmentation and the erythema grade in the MED test. By analysing regression coefficients we found that stratum corneum was the main photoprotective factor not only in vitiligo but also in normally pigmented skin. The effect of pigmentation in normal skin was slightly less prominent. Stratum corneum was thicker in vitiligo than in normally pigmented skin. However, the photoprotection due to stratum corneum was similar in both groups because significantly less photoprotection was achieved per thickness unit of stratum corneum in vitiligo than in normal skin. Neither in vitiligo nor in normally pigmented skin did the photoprotection depend on viable epidermis. Our data quantitatively document the importance of stratum corneum and pigmentation. Hyperkeratosis in vitiligo offers just as efficient photoprotection as does the normal stratum corneum in pigmented skin.

Adolescent↗
PubMed2000

Alzheimer-related tau-pathology in the perforant path target zone and in the hippocampal stratum oriens and radiatum correlates with onset and degree of dementia.

Abnormal phosphorylation of the tau-protein is regarded as a crucial step in the formation of neurofibrillary tangles in the neuronal cell body and neuropil threads in dendrites. We studied the effects of tau-pathology on the clinical expression of dementia in 106 autopsy cases in the entorhinal region, the hippocampal stratum oriens, the stratum radiatum, and the perforant path target zone. The first cytoskeletal lesions were located in the perikarya and dendrites of the pre-alpha cells of the transentorhinal and entorhinal region. Next, abnormally phosphorylated tau-protein (PHF-tau) was found in the neuropil of the CA1-subiculum region. Thereafter, the stratum radiatum and stratum oriens began to be involved in PHF-tau pathology in Braak stage II. In the Braak stages IV and V, the stratum radiatum was completely involved, the stratum oriens increasingly so. Beginning in Braak stage III, we noted cases having PHF-tau pathology in the perforant path target zone of the outer molecular layer of the dentate gyrus. The increase of this pathology with ever greater involvement on the part of the entorhinohippocampal circuit correlated significantly not only with the Braak stages and with the neurochemically determined hippocampal content of PHF-tau but also with the degree of dementia as defined by the clinical dementia rating (CDR) scale. The affection of the stratum oriens in combination with PHF-tau pathology in the stratum radiatum and in the outer molecular layer of the dentate gyrus was encountered almost exclusively in demented individuals (CDR 1-3). These results indicate that axonal PHF-tau pathology in hippocampal pathways presumably is critical for the clinical expression of dementia and may constitute an anatomical substrate of clinically verifiable memory dysfunction in Alzheimer's disease.

Aged↗
PubMed1994

Evidence for a role of corneodesmosin, a protein which may serve to modify desmosomes during cornification, in stratum corneum cell cohesion and desquamation.

Corneodesmosin, defined as the protein recognized by the monoclonal antibody G36-19, is a recently described late differentiation protein of human cornified epithelium. In the stratum corneum it is localized in the extracellular parts of modified desmosomes (corneodesmosomes) and adjacent parts of the cornified cell envelope. The aim of the present study was to investigate whether corneodesmosin undergoes changes in the stratum corneum which can be related to the cohesive state of the tissue and to desquamation. Extracts of plantar stratum corneum from various tissue levels and tape-stripped non-palmoplantar stratum corneum were analysed by immunoblotting with G36-19. In addition, the fate of corneodesmosin during shedding of surface cells in a recently described in vitro model of desquamation in plantar stratum corneum was investigated and compared with the degradation of the desmosomal protein desmoglein I in this system. The apparent molecular weights of the major G36-19-positive components in plantar stratum corneum ranged between 33 and 48 kDa. The components with the highest molecular weights were predominant in the deepest tissue layers. In the intermediate tissue layers G36-19-positive components of molecular weight 33-36, 39 and 44-48 kDa were found. There seemed to be a further degradation of the 33 to 36-kDa components in the most superficial parts of the tissue. In surface cells dissociated in vivo as well as in vitro no G36-19-positive components with molecular weights above 36 kDa were detected. Results from analyses of nonpalmoplantar stratum corneum suggested that corneodesmosin is degraded in this tissue in a way that may be similar to that in plantar stratum corneum.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Differentiation↗
PubMed2001

Water modulation of stratum corneum chymotryptic enzyme activity and desquamation.

Exposure to a dry environment leads to depletion of water from the peripheral stratum corneum layers in a process dependent on the relative humidity (RH) and the intrinsic properties of the tissue. We hypothesized that by modulating the water content of the stratum corneum in the surface layers, RH effects the rate of desquamation by modulating the activity of the desquamatory enzymes, and specifically stratum corneum chymotryptic enzyme (SCCE). Using a novel air interface in vitro desquamatory model, we demonstrated RH-dependent corneocyte release with desquamatory rates decreasing below 80% RH. Application of 10% glycerol or a glycerol-containing moisturizing lotion further increased desquamation, even in humid conditions, demonstrating that water was the rate-limiting factor in the final stages of desquamation. Furthermore, even in humid conditions desquamation was sub-maximal. In situ stratum corneum SCCE activity showed a dependence on RH: activity was significantly higher at 100% than at 44% RH. Further increases in SCCE activity were induced by applying a 10% glycerol solution. Since SCCE, a water-requiring enzyme, must function in the water-depleted outer stratum corneum, we sought to determine whether this enzyme has a tolerance to lowered water activity. Using concentrated sucrose solutions to lower water activity, we analysed the activity of recombinant SCCE and compared it to that of trypsin and chymotrypsin. SCCE activity demonstrated a tolerance to water restriction, and this may be an adaptation to maintain enzyme activity even within the water-depleted stratum corneum intercellular space. Overall these findings support the concept that in the upper stratum corneum, RH modulates desquamation by its effect upon SCCE activity, and possibly other desquamatory hydrolases. In addition, SCCE may be adapted to function in the water-restricted stratum corneum intercellular space.

Animals↗
PubMed2006

Biophysical and morphological changes in the stratum corneum lipids induced by UVB irradiation.

BACKGROUND: UV irradiation induces a variety of responses in the epidermis, including sunburn cell formation, epidermal hyperplasia, and epidermal permeability barrier disruption. OBJECTIVE: The aim of present study was to assess the effects of UVB irradiation in the intercellular lipids in murine stratum corneum. METHODS: Adult hairless mice were exposed to a single UVB dose (0.15 J/cm(2)), the Fourier transform infrared (FT-IR) spectroscopic study was performed to investigate the effect on the biophysical changes in the stratum corneum lipids, barrier function was monitored by transepidermal water loss (TEWL) measurement, and the morphological alterations of stratum corneum was examined by electron microscopy using ruthenium tetroxide postfixation. RESULTS: The FT-IR spectroscopic study revealed that there was the shift to higher wavenumbers of the symmetric and asymmetric stretching peaks near 2850 and 2920 cm(-1) respectively at days 3-4 after a single UVB irradiation, reflecting to the increase in motional freedom of lipids hydrocarbon chains, call as disordering of lipids. Moreover, A single UVB irradiation also caused a significant increase in TEWL, the increase in TEWL began after 2 days and peaked at day 4. Electron microscopic observations revealed that marked morphological abnormalities in the intercellular domains, including abnormal profile of lamellar granules and its contents at the interface between stratum corneum and stratum granulosum and the persistence of the nuclei in the stratum corneum. Moreover, the separated fragmentary lipid lamellae, excessive numbers of lamellae in stacks, both the elongated and enlarged lacuna as well as the extracellular whorls were present within the widen space of the stratum corneum. CONCLUSION: The both of biophysical and morphological changes of the stratum corneum lipids may reflect to the mechanisms of perturbation of the epidermal permeability barrier induced by UVB irradiation.

Animals↗
PubMed2005

Comparative studies on the effects of water, ethanol and water/ethanol mixtures on chemical partitioning into porcine stratum corneum and silastic membrane.

The effects of water and ethanol vehicles on stratum corneum and silastic membrane partitioning of 11 industrial and agricultural compounds were studied to aid in characterizing and assessing risk from skin exposure. Zero percent, 50% and 100% aqueous ethanol solutions were used as solvents for (14)C labeled phenol, 4-nitrophenol, pentachlorophenol, dimethyl parathion, parathion, chloropyrifos, fenthion, triazine, atrazine, simazine and propazine. Compound partitioning between the solvents and porcine stratum corneum/silastic membrane were estimated. Stratum corneum was exposed to aqueous ethanol ranging from 0% to 100% v/v ethanol in 20% increments and Fourier transform infrared spectroscopy (FT-IR) was used to obtain an index of lipid disorder. Gravimetry and FT-IR were used to demonstrate lipid extraction in aqueous ethanol solutions. Partitioning patterns in silastic membranes resembled those in stratum corneum and were correlated with octanol/water partitioning. Partitioning was highest in water and was higher from 50% ethanol than from 100% ethanol, except for parathion, 4-nitrophenol, atrazine and propazine. Correlation existed between molecular weight and partitioning in water, but not in ethanol and ethanol/water mixtures. Lipid order, as reflected in FT-IR spectra, was not altered. These studies suggest that stratum corneum partitioning of the compounds tested is primarily determined by relative compound solubility between the stratum corneum lipids and the donor solvent. Linear relationships existed between octanol/water partitioning and stratum corneum partitioning. Partitioning was also correlated with molecular weight in water solvent systems, but not in ethanol and ethanol/water mixtures. Ethanol and ethanol/water mixtures altered the stratum corneum through lipid extraction, rather than through disruption of lipid order.

Animals↗
PubMed1992

Cohesion and desquamation of epidermal stratum corneum.

This article attempts to provide a comprehensive review on the roles of various classes of molecules in the cohesion and desquamation of the stratum corneum. In the first part of this monograph we review the field of epidermal differentiation in vivo and vitro, describing the expression and functions of a number of key structural molecules that characterize the process. In the second part we emphasize terminal differentiation and the biogenesis of the stratum corneum. The stratum corneum is a cell layer unique to fully differentiated squamous epithelia such as skin. While it is a dead stratum, it nevertheless is in a homeostatic process of continual shedding and renewal in synchrony with basal cell replication. It is also a degradative layer containing many proteinases and glycosidases in which a variety of intracellular and intercellular macromolecules are degraded. We highlight the molecules localized within the intercorneal matrix that are most likely to play a role in cohesion and desquamation, including: glycoproteins, lipids and enzymes. Because it is difficult to study the stratum corneum and desquamation in the native tissue, we discuss a number of model systems that have been used. The stratum corneum can be dispersed into single squames in different ways; these include mechanical dispersion as well as agents such as detergents and enzymes. The solubilized molecules and the structures remaining can then be studied as to their specific roles in desquamation. Using this approach it is possible to reconstitute multilayered structures that resemble a real stratum corneum. We have shown that glycoproteins play a key role in squame reaggregation and that this process can be modulated with amino sugars in a lectin-like fashion. Cohesion and desquamation can also be studied in tissue culture. Depending on the culture system, the extent of terminal differentiation and squame accumulation varies. Yet desquamation does not normally occur. It can be induced however by the inclusion of exogenous agents such as IFN-gamma which are found in the native epidermis but are absent in vitro. Modulation of desquamation by other exogenous agents is likely to yield further knowledge of how shedding occurs in vivo. Insight has also come from studies of scaling skin disorders. The glycoprotein and lipid profiles are altered in the stratum corneum in many diseases of aberrant terminal differentiation. A number of abnormalities in the levels of cytokines and growth factors have also been reported in the lesional tissue of such diseases.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Distribution of salicylic acid in human stratum corneum following topical application in vivo: a comparison of six different formulations.

Distribution of salicylic acid in human stratum corneum from treatment of six different formulations was assessed by quantitation of drug content in sequentially tape-stripped stratum corneum after a single 2-h dose was applied unoccluded to skin on the ventral forearm of four female subjects. The profile and total amounts of stratum corneum removed in 20 tape-strips varied among different types of formulations. With or without normalization by the total stratum corneum weights removed, the extent of drug delivery to the stratum corneum decreased in the following order: SA (5%) > > SAC (10%), Duofilm (16.7%) > TSSS (2%) > SAO (10%), Salic (2.5%), the percentage in parentheses indicating the salicylic acid concentration in each formulation. The greatest topical bioavailability was observed for the alcoholic solution containing glycerol (SA). The 10% collodion formulation (SAC) was found to deliver an amount of salicylic acid into the stratum corneum 2-fold greater than 10% ointment formulation (SAO). Use of absorption ointment (TSSS) also increased the uptake of salicylic acid into the stratum corneum in comparison with formulations based on simple ointment (SAO) and oil in water (o/w) cream (Salic). The partitioning of salicylic acid from collodion formulations (SAC and Duofilm) appeared to be concentration-independent. The results of this study indicate that topical bioavailability of salicylic acid in the stratum corneum varies substantially among different formulations.

Adhesives↗
PubMed1988

Heterogeneity effects on permeability-partition coefficient relationships in human stratum corneum.

The relationship between the permeability of solutes undergoing transport via the lipid pathway of the stratum corneum and the degree to which the same solutes partition into the stratum corneum has been explored by measuring the permeability coefficients and stratum corneum/water partition coefficients of a series of hydrocortisone esters varying in lipophilicity. Isolated human stratum corneum, used in both the permeability and the uptake experiments, was shown to resemble full-thickness skin in its overall resistance and selectivity to solute structure. As with full-thickness skin, delipidization destroys the barrier properties of isolated stratum corneum. Although a linear relationship is frequently assumed to exist between permeability coefficients and membrane/water partition coefficients, a log-log plot of permeability coefficients versus the intrinsic stratum corneum/water partition coefficients for the series of hydrocortisone esters studied is distinctly nonlinear. This nonlinearity arises from the fact that the transport of these solutes is rate limited by a lipid pathway in the stratum corneum, while uptake reflects both lipid and protein domains. From the relative permeability coefficients of 21-esters of hydrocortisone varying in acyl-chain structure, group contributions to the free energy of transfer of solute into the rate-limiting barrier microenvironment of the stratum corneum lipid pathway are calculate for a variety of functional groups including the -CH2-, -CONH2, -CON(CH3)2, -COOCH3, -COOH, and -OH groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport↗
PubMed1999

Electron diffraction provides new information on human stratum corneum lipid organization studied in relation to depth and temperature.

The outermost layer of mammalian skin, the stratum corneum, provides the body with a barrier against transepidermal water loss and penetration of agents from outside. The lipid-rich extracellular matrix surrounding the corneocytes in the stratum corneum is mainly responsible for this barrier function. In this study (cryo-) electron diffraction was applied to obtain information about the local lateral lipid organization in the extracellular matrix in relation to depth in human stratum corneum. For this purpose, stratum corneum grid-strips were prepared from native skin in vivo and ex vivo. It was found that the lipid packing in samples prepared at room temperature is predominantly orthorhombic. In samples prepared at 32 degrees C the presence of a hexagonal packing is more pronounced in the outer layers of the stratum corneum. Gradually increasing the specimen temperature from 30 to 40 degrees C induced a further transition from an orthorhombic to a hexagonal sublattice. At 90 degrees C all lipids were present in a fluid phase. These results are in good agreement with previously reported wide angle X-ray diffraction and Fourier transformed infrared spectroscopy studies. We conclude that the lipids in human stratum corneum are highly ordered throughout the stratum corneum and that electron diffraction allows monitoring of the local lipid organization, which contributes to the understanding of stratum corneum barrier function.

Cryoultramicrotomy↗
PubMed2001

Human stratum corneum adsorption of nickel salts. Investigation of depth profiles by tape stripping in vivo.

Sequential adhesive tape stripping was implemented to characterize the penetration of nickel salts in human stratum corneum. Exposure areas of the salts in methanol applied open on arm and back skin in low volume were stripped 20 times to the level of the glistening layer at intervals of 30 min to 24 h post-dosing, and the strips analyzed for metal content by inductively coupled plasma-atomic emission spectroscopy. In the case of nickel chloride, sulfate, nitrate and acetate, material left on the skin surface, the depth-penetration profiles in the stratum corneum, and the dosage unaccounted for suggest the following conclusions: (a) Up to 24 h, most of the nickel dose applied remains on the skin surface or is adsorbed in the uppermost layers of the stratum corneum. (b) At higher concentrations, incomplete material recovery becomes discernible; within 24 h, nickel salts thus appear to penetrate beyond the stratum corneum to a minor degree, possibly via the skin shunts. (c) While the concentration gradients of nickel adsorbed vary with counter ion, anatomical site, dose and exposure time, for all variables tested the depth profiles converge to non-detectable levels (< 20 ppb) towards the level of the glistening layer. A notable exception is nickel as nitrate, for which levels continue at low but constant levels (1% of dose) beyond the third stratum corneum strip, indicative of intercellular diffusion. (d) Differences in material recovered suggest that the stratum corneum on the arm is more penetrable to nickel than stratum corneum on the back. (e) The counter ion in nickel salts plays a major part in their diffusion into the stratum corneum, suggestive of ion pairing. Overall, the data point to all three avenues of skin penetration by nickel: intracellular, intercellular, and transappendageal.

Adult↗
PubMedDate not supplied

Drug testing with alternative matrices I. Pharmacological effects and disposition of cocaine and codeine in plasma, sebum, and stratum corneum.

This study examined the disposition of cocaine, codeine, and metabolites in stratum corneum, sebum, and plasma collected from five African-American males after administrations of cocaine and codeine during a 10-week inpatient clinical study. The subjects were experienced, healthy drug users with a recent history of cocaine and heroin abuse. The first drug administration was delayed by three weeks to allow for the elimination of previously administered drugs from the body. Subjects received three 75 mg cocaine hydrochloride/70 kg doses by the subcutaneous route and three 60 mg codeine sulfate/70 kg doses by the oral route on alternating days beginning in week 4. The same dosing sequence was repeated in week 8 with doubled (x 2) doses. Pharmacological measures (heart rate, pupil diameter, subject "High" and "Liking") were obtained simultaneously with blood. Stratum corneum was collected by scraping regions of the back once each week. Sebum was collected periodically from the forehead by applying Sebutape patches for 1-2-h intervals. Plasma, stratum corneum, and sebum were analyzed for cocaine, codeine, and metabolites by gas chromatography-mass spectrometry. Peak plasma cocaine concentrations occurred within the 30 min following dosing and followed peak pharmacological effects. Peak plasma codeine concentrations occurred within 1-2 h of dosing and before peak pharmacological effects. Cocaine and codeine were the primary analytes in sebum and stratum corneum. After dosing, these drugs appeared in sebum within 1-2 h and were detected for 1-2 days. Peak-drug concentrations in stratum corneum occurred one day after completion of dosing; elimination of the drugs continued over the next 1-2 weeks after dosing. Overall, no definitive relationship was observed between drug concentrations in sebum and stratum corneum compared with dose. Interpretation of drug distribution and elimination in sebum and stratum corneum was complicated by possible contamination of specimens with drugs from sweat. The mechanism(s) for deposition of cocaine and codeine in sebum and stratum corneum appeared to be complex and could involve the transfer of drugs between different body fluids (i.e., sebum and sweat) and other matrices (i.e., skin and hair).

Administration, Oral↗
PubMed1996

Elevation of interleukin 1 receptor antagonist in the stratum corneum of sun-exposed and ultraviolet B-irradiated human skin.

Keratinocytes produce not only interleukin 1 (IL-1) but also IL-1 receptor antagonist (IL-1ra), a competitive inhibitor of IL-1. Because little is known about the presence of IL-1ra in the stratum corneum, we examined the content of IL-1ra in the stratum corneum, especially the balance between IL-1 and IL-1ra. IL-1 alpha and IL-1ra, but not IL-1 beta, were detected in the tape-stripped stratum corneum of healthy volunteers by enzyme-linked immunosorbent assays. IL-1 alpha and IL-1ra were bioactive as determined by thymocyte co-stimulation assay, and their molecular masses were 17 and 20 kDa, respectively, suggesting that the stratum corneum contains active forms of IL-1 alpha and IL-1ra produced by keratinocytes. The stratum corneum of an unexposed area, the inner side of the upper arm. contained more IL-1 alpha than a sun-exposed area, the face. In contrast, the stratum corneum of the sun-exposed area contained a markedly higher amount of IL-1ra than that of the unexposed area. The ratio of IL-1ra to IL-1 alpha was 8 in the unexposed area, and over 100 in the sun-exposed area. Therefore, IL-1 alpha activity was dominant in the unexposed area, and in contrast, IL-1ra activity was dominant in the sun-exposed area. An elevated level of IL-1ra was detected in the stratum corneum of the sun-exposed area independently of age. In the unexposed area, however, IL-1a increased, but IL-1ra decreased, with age, resulting in a significant decline of the ratio of IL-1ra to IL-1a with increasing age. Irradiation of 2 MED of ultraviolet B to the back skin, an unexposed area, resulted in striking elevation of IL-1ra in the stratum corneum in desquamating scales. These data suggest that IL-1ra in the epidermis may be inducible by chronic UV irradiation, although IL-1ra production in the epidermis may decrease with aging in the absence of any stimulus. IL-1ra in the epidermis may play a role in the regulation of IL-1-induced inflammatory responses, and an appropriate balance between IL-1 and IL-1ra may help to maintain homeostasis of the skin.

Adolescent↗
PubMed1991

Structural investigations of human stratum corneum by small-angle X-ray scattering.

The structure of human stratum corneum was investigated with small-angle X-ray scattering (SAXS). At room temperature the scattering curve was characterized by a strong intensity at low scattering vector (Q less than 0.8 nm-1) and two complicated diffraction peaks originating from a lamellar structure of the lipids. The lamellar lipid structure in the stratum corneum transformed to a disordered structure between 65 degrees C and 75 degrees C, the same temperature region at which a thermal lipid transition occurred. After cooling down to room temperature a recrystallization of at least a part of the lipids took place, after which only one unit cell with a repeat distance of 13.4 nm could be detected. Comparison of the scattering curve of the stratum corneum after crystallization with the scattering curve of the stratum corneum before recrystallization leads to the conclusion that in the original curve the lipids are arranged in two unit cells with repeat distances of 6.4 nm and 13.4 nm. From model calculations it appears that the latter unit cell consists of more than one bilayer. The scattering curves of stratum corneum hydrated to various levels were measured. A change in the water content of stratum corneum between 6% w/w and 60% w/w (fully hydrated) did not result in swelling of the bilayers, but the scattering curve obtained with stratum corneum hydrated to 60% w/w differed from those at lower hydration levels: the scattering curve at 60% w/w showed only the diffraction peaks corresponding to a unit cell with a repeat distance of 6.4 nm. This observation implies that the ordering of a part of the lipids is reduced at very high water contents, which may explain the strong penetration-enhancing effects of water in the stratum corneum.

Crystallization↗
PubMed1995

Interactions between liposomes and human stratum corneum in vitro: freeze fracture electron microscopical visualization and small angle X-ray scattering studies.

The interactions between three liposomal formulations and human stratum corneum were visualized using freeze fracture electron microscopy. A new replica cleaning method was introduced. Human stratum corneum was submerged for 48 h in liposome suspensions prepared from commercially available phospholipid mixtures. The size, lamellarity and lipid moieties of the liposomes were similar. The main difference between the three phospholipid formulations was the hydrophilicity of the headgroups. The composition dependence of the interactions between these vesicles and human stratum corneum was investigated. In essence, two types of interaction were observed: adsorption of the liposomes on to the outer surface of the stratum corneum, and ultrastructural changes in deeper layers of the stratum corneum caused by mixing of the liposomal constituents and the stratum corneum lipids. The electron microscopic observations were verified with small-angle X-ray scattering. It was found that liposomes composed of phospholipids containing relatively small hydrophilic headgroups showed a marked interaction with the skin lipids of human stratum corneum in vitro. The complexity of the phospholipid mixtures, however, made it very difficult to determine the exact effect each of these headgroups has on the interactions between these vesicles and human stratum corneum.

Adsorption↗
PubMed1999

[Experimental studies on the penetration into the human stratum corneum of the dermatophyte].

We present results on the experimental penetration of Trichophyton mentagrophytes and T. rubrum under designated condition of humidity into human stratum corneum obtained from a healthy human heelregion. When mycelia were applied to the surface side of stratum corneum and then incubated at 100 % humidity, T. mentagrophytes and T. rubrum were observed in the stratum corneum on day 1 and day 1.5, respectively. At 95% humidity, T. mentagrophytes and T. rubrum penetrated on day 1.5 and day 4, and at 90% humidity, they penetrated on day 3 and day 7, respectively. At less than 85% humidity, no fungal elements of either strain were observed in stratum corneum for up to 7 days. These datasuggest that at least 90% humidity is necessary for these two fungi to penetrate into stratum corneum within a few days. However, when T. mentagrophytes was applied to the cutting side of the stratum corneum and thenincubated at more than 70% humidity, the mycelia were able to penetrate within a day. The same results were obtained when T. rubrum was applied on the cutting side and incubated at 95 and 100% humidity. T. rubrum was also able to penetrate into the stratum corneum within several days at 70 and 80% humidity. These results may indicate that not only persistent moisture but also minor injuries of stratum corneum are the most important factors in the development of tinea pedis.

Culture Techniques↗
PubMedDate not supplied

Dermatophyte growth and degradation of human stratum corneum in vitro (pathogenesis of dermatophytosis).

BACKGROUND: This study was carried out to determine growth of dermatophytes using human stratum corneum in vitro and the degrading effect of Keratinases (Proteinases) on stratum corneum for a complete understanding of the host parasite relationship. METHOD: Trichophyton rubrum isolates derived from patients with tinea cruris infections were obtained from the Department of Medical Microbiology, University Hospital of Wales, U.K. Human stratum corneum sterilized with ethylene oxide was used as a nitrogen source in agar culture medium plates. RESULT: Fungal growth took place in plates which contained human stratum corneum particles while there was no growth in the plates without stratum corneum at three weeks after initiation. There was a gradual disappearance of the particles of stratum corneum from the plates at the end of the third week CONCLUSION: The growth of organisms in plates with human stratum corneum and their disappearance at third week suggested that stratum corneum was not only source of nutrition for the dermatophytes, but also the growing fungal mycelia and the proteinases induced by them were playing a part in the digestion of granules and thus may have an important role in the pathogenesis of dermatophyte infections.

Agar↗
PubMed1997

Electroperturbation of the human skin barrier in vitro: II. Effects on stratum corneum lipid ordering and ultrastructure.

In transdermal iontophoresis, drugs can be driven across the skin by electrorepulsion, but their transport can also be enhanced by electrical perturbation of the skin barrier. Our objective was to study perturbing effects of electrical current on human stratum corneum lipid fine structure combining techniques including freeze-fracture electron microscopy. Human stratum corneum was subjected to pulsed constant currents, varying from 0.013-13 mA.cm-2. The voltage across the stratum corneum was high-frequency-sampled and s.c. impedence values derived from it. Upon termination of the current, skin samples were rapidly frozen and processed for freeze-fracture electron microscopy or subjected to X-ray diffraction analysis. Initially a rapid decrease of the resistance and, overall, a rapid increase of the capacitances was observed; generally, these effects became more pronounced with increasing current density. Wide- and small-angle X-ray diffractograms of human stratum corneum exposed for 1 h to the highest current indicated a disordering of both the lateral packaging arrangement and long-range lamellar stacking of the intercellular lipids of stratum corneum. Furthermore, an increase in the stratum corneum hydration level as a result of electrical current application was observed. On electron micrographs of freeze-fracture replicas of human stratum corneum, exposed for 1 h to current densities between 0.013 and 13 mA.cm-2, perturbations of the intercellular lipid structure were observed in accordance with the results of X-ray diffraction; these perturbations aggravated with increasing current density. Together, the data suggest that both the lateral and the longitudinal disordering of the intercellular lipids observed with X-ray diffraction may be responsible for the appearance of perturbed structures observed with freeze-fracture electron microscopy. The lipid disordering may be due to polarization of the lipid head groups induced by the electrical field, followed by mutual repulsion.

Adult↗