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At least 145 records · Page 8Linked to original sources
PubMed2000

Intradermal microdialysis: kinetics of iontophoretically delivered propranolol in forearm dermis.

Intradermal microdialysis permits us to measure the concentration in dermis of drugs applied to the skin. Microdialysis is especially efficient in sampling water-soluble molecules. Consequently, it appears particularly suitable to study current based delivery systems like iontophoresis that deliver ions or highly polar molecules. The purpose of this work was to evaluate the adequacy of a skin microdialysis technique to characterize and quantify the dermatopharmacokinetics of iontophoretically delivered propranolol in the dermis of healthy human volunteers. Linear microdialysis probes were inserted in the subject's forearm skin and an iontophoresis device was installed above them. Constant current was applied for two periods of 1 h each separated by a 1-h interval. Dialysate samples were collected every 6 min for 4.4 h and analyzed by HPLC. Probes were always placed in the dermis as measured by ultrasonography. Propranolol was detectable in the dialysate. It was possible to build detailed concentration vs. midtime profiles that mirrored the current applied. Elimination rate from the dermis had first-order kinetics and was similar in all subjects. Quantification of the absorption process, indexed by lag-time and area under the concentration curve showed a high inter- and intrasubject variability that did not correlate with probe depth.

Adult↗
PubMed1995

Use of drug kinetics in dermis to predict in vivo blood concentration after topical application.

PURPOSE: To use the drug kinetics in dermis to predict the in vivo blood concentration after topical administration. METHODS: A two-step pharmacokinetic model was established. The first step was to calculate the drug input rate or flux from the skin to the systemic circulation using the drug kinetic parameters in dermis. These parameters include (a) distance over which the drug concentration declines by 50%, (b) drug concentration at the epidermal-dermal junction, and (c) minimal plateauing drug concentration in the muscle layer. These parameters were experimentally determined from the drug concentration-tissue depth profiles in the dermis, after the application of a topical dose of ddI (200 mg/kg) to rats. The second step was to use the drug input rate together with the systemic disposition pharmacokinetics of ddI in rats to predict the plasma concentration-time profiles. The model-predicted plasma concentration-time profiles were compared with the observed profiles, to determine the validity of the proposed pharmacokinetic model. RESULTS: The observed steady state concentration (CSS) in individual animals (n = 6) deviated from the predicted values by 3 to 55% with 3 of 6 rats showing a < 15% deviation. The mean observed CSS of all animals deviated from the mean predicted values by less than 15%. CONCLUSIONS: The close agreement between the observed and the model-predicted drug concentrations indicates that the systemic drug input can be calculated from the drug kinetics in the dermis.

Administration, Topical↗
PubMed1995

Penetration kinetics of 2',3'-dideoxyinosine in dermis is described by the distributed model.

The present study evaluated the kinetics of drug penetration in the dermis. A rat was given a dermal dose of 2',3'-dideoxyinosine (ddI). At 6 hr, the skin tissue was excised, immediately frozen and sectioned, and the decline of drug concentration as a function of tissue depth was determined. The tissue concentration-depth profile showed a semilogarithmic decline, as would be expected in a distributed tissue kinetic model which incorporates diffusion and capillary membrane transport. The goodness of fit of the profiles by the simple diffusion and the distributed models were compared using four statistical criteria, i.e., coefficient of determination. Akaike Information criterion, Schwartz criterion and Imbimbo criterion. These analyses showed that the decline of tissue concentration versus tissue depth in the dermis was better described by the distributed model than by the diffusion model in all 7 animals. To examine the effect of blood perfusion on the tissue concentration-depth profiles, some of the tissues were frozen after 1 and 2 hr storage at room temperature. In contrast to the adjacent tissues frozen immediately, the concentration-depth profiles in tissues frozen after a 1-2 hr delay were described equally well by distributed and diffusion models. A comparison of the concentration-depth profiles in the tissues processed immediately or after a delay showed a 7 fold more shallow slope and a 60% lower concentration at the epidermis-dermis interface after storage. However, storage did not alter the total amount of drug in the entire dermis. Drug degradation during storage was further ruled out by the insignificant ddI degradation in 10% skin homogenate (a half-life of approximately 70 hr).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Immunophenotypic analysis of normal human dendritic cells isolated from epidermis and dermis.

BACKGROUND: The skin immune system comprises two types of dendritic cells, i.e. CD1a-positive Langerhans cells in the epidermis and CD36-positive dendritic macrophages in the dermis. Dendritic cells can migrate from skin explants into a culture medium. METHODS: We have examined the morphology and immunophenotype of the dendritic cells migrating from epidermal and dermal sheets in vitro. The epidermis and dermis of keratomes of normal human skin were separated with dispase and cultured for 72 h. At this time, the non-adherent cells in the medium were removed, enriched on a metrizamide or Lymphoprep gradient, counted, prepared by cytospin, and labeled for CD1a, CD36, and HLADr. RESULTS: Cells migrating from the epidermis and dermis show many thin projections or a few veils from the cell surface. Approximately four times more cells migrate from epidermal than dermal sheets from the same keratome. CONCLUSIONS: Using methods to separate the epidermis from the dermis, both CD1a-positive Langerhans cells and CD36-positive dendritic macrophages can be obtained from both tissues, although in different numbers.

Antibodies, Monoclonal↗
PubMed1997

Treatment of giant pigmented nevus using artificial dermis and a secondary skin graft from the scalp.

From January 1994 to October 1995, 5 patients with congenital giant pigmented nevi were treated using artificial dermis with a secondary skin graft from the scalp. The nevus was excised in full thickness and the open wound was grafted with artificial dermis. About 3 weeks later, thin split-thickness skin grafting on the newly synthesized, dermis-like tissue was required. We chose the scalp as the donor of the secondary skin graft. Epithelialization of each donor site was completed within 1 week. In addition, the donor site was not complicated with alopecia or hypertrophic scars. Morbidity at the donor site was minimized and favorable tissue quality of the grafted skin was obtained. The clinical results revealed that the scalp was a favorable donor of a secondary skin graft for the treatment of giant pigmented nevus with artificial dermis.

Adolescent↗
PubMedDate not supplied

Acellular allogenic dermis does not hinder initial engraftment in burn wound resurfacing and reconstruction.

Donor site morbidity, including pain and potential hypertrophic scarring, increases directly as donor site thickness increases. Autograft hypertrophy increases inversely to the thickness of autograft harvest. Both of these liabilities might be lessened by the ready availability of a functioning, "off-the-shelf" dermal substitute. The most immunogenic components of transplanted allograft skin are the cellular elements of the epidermis and dermis. If these components are removed, the remaining noncellular dermal tissue is relatively immunologically inert. We grafted 10 sites with matched control areas in six patients, with limited (< 25%) areas of the body surface appropriate for donor harvest, who required either acute resurfacing or a reconstructive procedure requiring split-thickness autografting. The six children (three girls and three boys) had an average age of 5.2 +/- 0.9 years (range, 2.8 to 10), and an average burn size of 68.7% +/- 6.7% (range, 47% to 85%). The 10 study and control sites were all parts of 10 separate procedures in these massively burned children, nine sites being reconstructive releases, and one excised acute burn. Successful epithelialization was noted at 7 days over 83% +/- 3.4% (range, 60% to 95%) at the cryopreserved acellular human dermis sites and 83.3% +/- 4.3% (range, 60% to 98%) at the control sites (NS, p = 0.96). Duration of follow-up has been 11.9 +/- 3.5 weeks (range, 2 to 29), with no difference in results by Vancouver Scar Scores. We conclude that cryopreserved acellular human dermis will engraft successfully and support engraftment of overlying thin autograft. Initial results relating to the effectiveness of cryopreserved acellular human dermis in optimizing appearance and function are encouraging, but longer follow-up is required before definitive conclusions can be made.

Burns↗
PubMed1985

Pharmacokinetics of topically applied radiolabeled retinoids in hairless mouse epidermis and dermis after single applications.

The retention of tritium-labeled all-trans-retinoic acid (RA), 13-cis-retinoic acid (13-cis-RA), aromatic retinoid, and arotinoid ethyl ester in the epidermis and dermis of hairless mice was measured up to 24 h following a single topical application in an acetone vehicle. The radioactivity in the tissues was extractable with chloroform:methanol, and the identities of the radioactive species extracted were confirmed as retinoids using thin-layer chromatography. All the retinoids were absorbed into the skin rapidly. After an initial period of distribution and penetration (lasting for about 1 h) the amount of the applied retinoid remaining in the epidermis and dermis decreased more slowly, obeying first order (exponential) decay kinetics. Both the arotinoid and the aromatic retinoid persisted for longer in the epidermis than equivalent doses of RA or 13-cis-RA. The half-lives of the retinoids in the dermis tended to be longer than in the epidermis, except for the arotinoid. Aromatic retinoid persisted for longest in the dermis with a half-life of 11 h.

Administration, Topical↗
PubMed1996

Macrophages, but not Langerhans cell-like cells of dendritic lineage, express the CD36 molecule in normal human dermis: relevance to downregulatory cutaneous immune responses?

The CD36 molecule has been shown to be associated with subsets of peripheral blood monocyte/macrophages and, in cells isolated from either ultraviolet (UV)-irradiated or diseased skin, to induce downregulatory immune responses. Although macrophages are certainly present within normal human dermis, whether they normally express CD36 is still a matter of debate. In this study, we investigated dermal CD36-expressing macrophages in situ using the gold immunoelectron microscopic technique on tissue ultracryosections. This is a very sensitive and specific method, and its results clearly reflect the in vivo immunophenotypic constitutive situation. Macrophages in normal human dermis were variously shaped from round to dendritic and were localized either immediately beneath the epidermis, in perivascular areas, or in intervascular zones. Macrophages showed consistent gold-positive staining on their cell surface. In contrast, other dermal cells, including fibroblasts, lymphocytes, and mast cells, as well as dermal fibers, were not decorated with gold; dermal Langerhans cell-like dendritic cells (LC/DC), though they did show gold labeling in some intracytoplasmic organelles, did not show any gold particles along their plasma membranes. Therefore, although macrophages in normal human dermis exhibit variability with regard to their localization and shape, they regularly and constitutively expressed CD36. CD36 molecules may be considered a useful marker for macrophages in normal human dermis and may furthermore confer on macrophages, or a subpopulation thereof, intriguing functional properties (e.g., downregulatory capacity versus upregulatory capacity subserved by LC/DC) within the cutaneous immune system.

Antibodies, Monoclonal↗
PubMed1993

Regulation of hair follicle development: an in vitro model for hair follicle invasion of dermis and associated connective tissue remodeling.

During embryonic development presumptive hair follicle cells of epithelial and mesenchymal origin are determined in defined body locations. This is followed by rapid proliferation of epithelial cells and associated penetration into the dermis in response to as yet undetermined signals. A collagen matrix culture system, which maintains the three-dimensional relationships of hair follicle cells to each other, was developed to study the regulation of the enlargement of immature hair follicles and the accompanying remodeling of the dermis. In studies with a heterogeneous dermis-derived preparation of murine hair follicles, ranging in size from the earliest down-growing budding cell mass to hair-forming follicles, we had previously shown that cell proliferation was stimulated by cholera toxin and epidermal growth factor, but only the epidermal growth factor-stimulated proliferation was accompanied by digestion of the collagen matrix due to release of collagenolytic enzymes. Further studies revealed that transforming growth factor-alpha also stimulated hair follicle cell proliferation and collagenase release. However, although transforming growth factor-beta inhibited the transforming growth factor-alpha-stimulated proliferation, it enhanced the release and activation of collagenases and other gelatin-degrading enzymes detectable by gelatin zymography. Stimulation of collagenolytic activity depended on the three-dimensional hair follicle structure and did not occur in monolayer cultures of hair follicle cells. Comparison of hair follicle buds with more developed dermis-derived hair follicles, plated at the same cell density (based on DNA content), suggested that a greater fraction of cells in the bud-stage follicle responded to the growth factors by release of collagenases. Possibly only the cells in the advancing portion of growing hair follicles that are closest to the dermal papilla cell cluster produce the collagenases in response to growth factors. To examine the participation of dermal papilla cells in collagenase release and activation, several immortalized rat whisker dermal papilla cell lines were co-cultured with mouse hair follicle buds. Co-culture resulted in a marked enlargement of follicles as well as activation of the 92-kDa type IV collagenase, produced by hair follicle buds, that correlated with ability of the dermal papilla cells to stimulate hair formation in grafts of hair follicle buds on nude mice. Dermal papilla cells cultured alone produced the 72-kDa type IV collagenase, which was also activated during co-culture with hair follicle buds. Thus, two activities, both relevant for hair follicle development, namely, cell proliferation and release and activation of collagenases, have been stimulated in immature hair follicle buds by either growth-factor supplementation or interaction with dermal papilla cells.(ABSTRACT TRUNCATED AT 400 WORDS)

3T3 Cells↗
PubMed1994

Dose-response effects of acute ultraviolet irradiation on antioxidants and molecular markers of oxidation in murine epidermis and dermis.

There has not as yet been an integrated, comprehensive study of the responses of dermis and epidermis in vivo to a wide range of ultraviolet (UV) doses, encompassing all major antioxidants and a sensitive marker of oxidative damage. We have irradiated hairless mice with simulated solar light at doses of 2, 5, 12.5, and 25 J/cm2 combined UVA and UVB (0.8 to 10 MED) and measured enzymic and non-enzymic antioxidants as well as lipid hydroperoxides in both epidermis and dermis to elucidate the response of cutaneous antioxidant defense mechanisms to UV stress. Among the nonenzymic antioxidants two different dose-response patterns were seen. Ascorbate was rapidly depleted at doses between 0 and 5 J/cm2 but was less affected between 5 and 25 J/cm2. In contrast, glutathione, ubiquinol/one, and alpha-tocopherol levels remained approximately equal to control levels between 0 and 5 J/cm2, then decreased to varying degrees from 5 to 25 J/cm2; ubiquinol was almost completely depleted, whereas alpha-tocopherol dropped only 30%. The concentration of lipid hydroperoxides increased throughout the dose range. These results may be explained partly by direct destruction of some antioxidants by UV light, partly by the separate antioxidant functions of the compounds, and partly by recycling of some antioxidants (e.g., alpha-tocopherol) at the expense of others (e.g., ubiquinol). Even at the lowest dose (0.8 MED) lipid hydroperoxide formation was observed. Among the enzymic antioxidants, superoxide dismutase activity decreased significantly (to 63.6% of initial activity for epidermis and 51.5% for dermis at 25 J), whereas activities of glutathione peroxidase and glutathione reductase decreased slightly. Catalase activity decreased dramatically at doses above 5 J (to 11.8% of initial activity in epidermis and 27.7% in dermis at 25 J). The dramatic loss of catalase is almost entirely accounted for by direct destruction by the simulated solar light, but superoxide dismutase was unaffected by direct exposure; hence its destruction must be due to indirect effects, either mediated by free radicals or other harmful species formed upon irradiation. At low doses of UV light many components of the cutaneous antioxidant system were damaged, whereas at high doses all components were damaged and some were almost completely destroyed.

Animals↗
PubMed1991

Proliferating cells in psoriatic dermis are comprised primarily of T cells, endothelial cells, and factor XIIIa+ perivascular dendritic cells.

Determination of the cell types proliferating in the dermis of patients with psoriasis should identify those cells experiencing activation or responding to growth factors in the psoriatic dermal milieu. Toward that end, sections of formalin-fixed biopsies obtained from 3H-deoxyuridine (3H-dU)-injected skin of eight psoriatic patients were immunostained, followed by autoradiography. Proliferating dermal cells exhibit silver grains from tritium emissions. The identity of the proliferating cells could then be determined by simultaneous visualization with antibodies specific for various cell types. UCHL1+ (CD45RO+) T cells (recall antigen-reactive helper T-cell subset) constituted 36.6 +/- 3.1% (mean +/- SEM, n = 6) of the proliferating dermal cells in involved skin, whereas Leu 18+ (CD45RA+) T cells (recall antigen naive T-cell subsets) comprised only 8.7 +/- 1.5% (n = 6). The Factor XIIIa+ dermal perivascular dendritic cell subset (24.9 +/- 1.5% of proliferating dermal cells, n = 6) and Factor VIII+ endothelial cells (23.0 +/- 2.3%, n = 6) represented the two other major proliferating populations in lesional psoriatic dermis. Differentiated tissue macrophages, identified by phase microscopy as melanophages or by immunostaining with antibodies to Leu M1 (CD15) or myeloid histiocyte antigen, comprised less than 5% of the proliferating population in either skin type. In addition to calculating the relative proportions of these cells to each other as percent, we also determined the density of cells, in cells/mm2 of tissue. The density of proliferating cells within these populations was increased in involved versus uninvolved skin: UCHL1+, 9.0 +/- 1.7 cells/mm2 versus 1.8 +/- 0.6 cells/mm2, p less than 0.01; Factor XIIIa+, 6.0 +/- 0.7 cells/mm2 versus 1.5 +/- 0.5 cells/mm2, p less than 0.01; Factor VIII+, 5.5 +/- 1.4 cells/mm2 versus 0.0 cells/mm2, p less than 0.05. The presence of preferential active proliferation of a T-cell subset in lesional dermis suggests that activating signals specific for this subset are contained within the psoriatic dermis in vivo. The activation of recall antigen-reactive T cells may be a driving force behind the dendritic cell and endothelial cell proliferation. Alternatively, the selective proliferation and expansion of these two constitutive cell types (Factor XIIIa+ and Factor VIII+) may result in signals that promote activation of UCHL1+ (CD45RO+) T cells.

Cell Division↗
PubMed1977

A comparison of the glycosaminoglycans of weight-bearing and non-weight-bearing human dermis.

Twenty-six samples of human skin from three non-weight-bearing and 27 samples from three weight-bearing sites were obtained at autopsy from 11 subjects varying in age from 4 to 91 years. The dermis was idssected free of other tissues and after proteolytic digestion, the glycosaminoglycans were isolated quantitatively by ion-exchange chromatography. Analysis of the preparations showed that there was significantly more glycosaminoglycan in the dermis from weight-bearing sites (p less than 0.001). The major glycosaminoglycans were hyaluronic acid and dermatan sulfate with chondroitin sulfate as a minor component, but the relative proportions of these components were not significantly different in the two sets of samples (p greater than 0.1). It is suggested that the quantity of glycosaminoglycan in the dermis is influenced by the functional requirements of the dermis at that site.

Adolescent↗
PubMed1979

Aging model for unexposed human dermis.

Young human dermis is charterized by the presence of many fibroblasts with distended endoplasmic reticulum, extensive Golgi bodies, and orderly and "clean"-appearing groundwork. Older dermis contains inactive fibrocytes with lipofuscin-like granules, macrophages with dense granules, and extracellular spaces with evidence of degeneration. We have found the sex skin of cycling pigtail macaques (Macaca nemestrina) a predictable model for studies on aging changes in human dermis. Swollen sex skin has many biochemical and ultrastructural properties that are similar to those of young dermis, and deflated sex skin resembles older human skin. Sex skin, however, is unique in that it becomes "rejuvenated" with each succeeding ovarian cycle. This animal model may prove useful to researchers attempting to increase their understanding of aging in connective tissue.

Aged↗
PubMed1982

Biomechanical properties of dermis.

Data obtained from a wide variety of test methods both in vitro and in vivo and histological studies of stressed skin have led to an understanding of the mechanical properties of the dermis and the relation of these properties to the structure of the collagen and elastin fiber networks of the dermis. The mechanical properties are found to be well adapted to the mechanical function of the dermis. The viscoelastic nature of the skin shows that a simple structural model based only on collagen and elastin is not adequate for a full understanding of this tissue. The role of proteoglycans in bonding collagen fibrils into large fibers and in connecting these fibers into the fibrous net of the dermis is not well understood. Mechanical testing can yield information on the nature of bonds at this level of structure.

Biomechanical Phenomena↗
PubMed1990

Characterization of "neo-dermis" formation beneath cultured human epidermal autografts transplanted on muscle fascia.

Cultured human keratinocyte autografts were transplanted to burn wounds that had been completely excised down to muscle fascia such that all cutaneous elements were removed from the wounds. Healing autografts were biopsied from days 6-153 in five patients, and the "neo-dermis" beneath the autografts was examined by immunofluorescent staining using antibody probes to connective tissue molecules, by histochemical staining for elastin fibers, and by electron microscopy. We found that the neo-dermis contained most of the major connective tissue elements early in the post-transplantation period. However, regardless of the time examined, there was a paucity of elastin fibers and poor organization of linkin (microthread-like fibers) in the neo-dermis beneath autografts. The perturbations of these connective tissue components in the neo-dermis may play a role in the poor recoil and elastic properties of burn wounds treated with autografts.

Collagen↗
PubMed1992

Increased expression of tenascin in the dermis in scleroderma.

The expression of tenascin, a recently discovered extracellular matrix protein, was studied by immunohistochemical techniques in scleroderma skin and compared with its distribution in normal skin. In progressive systemic sclerosis, a marked increase in tenascin content was observed in the superficial reticular dermis. In localized scleroderma, the deposition of tenascin was increased both in the superficial and deep dermis of involved skin, whereas in clinically uninvolved skin the distribution of tenascin was the same as in normal control skin, i.e. the papillary dermis and peri-appendiceal zone. The distribution of tenascin did not strictly parallel that of fibronectin. These findings and the current knowledge of tenascin biology suggest that the overproduction of tenascin in scleroderma dermis could be secondary to stimulation of fibroblasts by immune cell-derived cytokines, or could be due to abnormal fibroblasts, or a subpopulation of fibroblasts, producing high levels of this extracellular matrix protein.

Adult↗
PubMed1993

Human papillomavirus DNA in the dermis of condyloma acuminatum.

Condyloma acuminatum (CA) has high recurrence rates after local treatments. Why this lesion is difficult to eradicate is unclear. One possible explanation for recurrence after superficial destructive therapy is the presence of residual human papillomavirus (HPV) in the superficial dermis beneath the treated epidermis. Thirteen samples of CA were excised from 13 patients. Thirteen samples of basal cell carcinoma (BCC) were studied for purposes of control. Epidermis was separated from dermis by treatment with sodium bromide. DNA was extracted from both tissues and used sodium bromide solution and amplified for the presence of HPV DNA using the polymerase chain reaction. HPV DNA was detected in the epidermis of 11 samples of CA. HPV type 6 was seen in 7 specimens; HPV type 11, in 4. HPV DNA was found in the dermis of 3 specimens of CA; type 6 in 2 and type 11 in 1. Two samples were excluded because of contamination of the sodium bromide solution by HPV. HPV DNA was not detected in tissue samples from BCC. The presence of HPV DNA in the dermis of some condylomata may explain recurrence in sporadic cases.

Base Sequence↗
PubMed1987

Pinch skin grafting or porcine dermis in venous ulcers: a randomised clinical trial.

Chronic venous ulcers are common, and even with effective compression or elevation large ulcers may take months to heal. Pinch skin grafting may allow healing from epithelial islands throughout the surface area of the ulcer, and a prospective randomised trial was therefore conducted comparing this treatment with porcine dermis dressings. Most patients were treated as outpatients, 25 ulcers being randomised to treatment with pinch skin grafts and 28 to treatment with porcine dermis. Though the groups were well matched, the mean healing rate in the first week was 15 cm2 for pinch skin grafts compared with 3.5 cm2 with porcine dermis (p less than 0.02). By life table analysis 64% of ulcers treated by pinch grafts were healed at six weeks and 74% by 12 weeks compared with 29% and 46% of ulcers, respectively, treated with porcine dermis dressings (chi2 = 4.1; p less than 0.05). All ulcers that failed to heal within 12 weeks included an area posterior to the medial malleolus, where local compression may have been inadequate. Pinch skin grafting improves the rate of healing in large venous ulcers and is a simple technique that may be performed as an outpatient procedure under local anaesthesia.

Bandages↗