Penetration, permeation, and resorption of 8-methoxypsoralen. Comperative in vitro and in vivo studies after topical application of four standard preparations

The penetration, permeation, and resorption of radioactively labelled 8-Methoxypsoralen was investigated in human skin. Siultaneously, the effects to time and ointment carrier on the penetration kinetics were ascertained. The carriers tested were: vaseline, aqueous wool-wax alcohol ointment, aqueous hydrophilic ointment and polyethylene glycol ointment. The absolute concentrations of 8-Methoxypsoralen were estimated in the horny layer, epidermis and dermis. With the most advantageous carrier, aqueous wool-wax alcohol ointment, 4-6X10(-5) M and 10(-5) M were attained in the epidermis and dermis, respectively. Moreover, it was shown that the substance penetrates rapidly (10 min) into the epidermis and dermis and the high concentrations reached constant over a period of 16 h. Only with a formulation of aqueous wool-wax alcohols is any accumulation at all achieved in the deeper areas of the horny layer. A uniform decrease in drug concentration with increasing depth of the horny layer is found with the other 3 vehicles, whereby slight variations in concentrations pertain from carrier to carrier. 4 h after local application, 8-Methoxypsoralen can be detected in the urine. Regardless of the ointment base employed, 8-Methoxypsoralen is no longer detectable in the urine 40 h after application. In comparison to the oral therapy, the same magnitude of percutaneous resorption into the central compartment is to be derived from the data, if half the body surface is treated locally.     

Hair cycle-dependent plasticity of skin and hair follicle innervation in normal murine skin

The innervation of normal, mature mammalian skin is widely thought to be constant. However, the extensive skin remodeling accompanying the transformation of hair follicles from resting stage through growth and regression back to resting (telogen-anagen-catagen-telogen) may also be associated with alteration of skin innervation. We, therefore, have investigated the innervation of the back skin of adolescent C57BL/6 mice at various stages of the depilation-induced hair cycle. By using antisera against neuronal (protein gene product 9.5 [PGP 9.5], neurofilament 150) and Schwann cell (S-100, myelin basic protein) markers, as well as against neural cell adhesion molecule (NCAM) and growth-associated protein-43 (GAP-43), we found a dramatic increase of single fibers within the dermis and subcutis during early anagen. This was paralleled by an increase in the number of anastomoses between the cutaneous nerve plexuses and by distinct changes in the nerve fiber supply of anagen vs. telogen hair follicles. The follicular isthmus, including the bulge, the seat of epithelial follicle stem cells, was found to be the most densely innervated skin area. Here, a defined subpopulation of nerve fibers increased in number during anagen and declined during catagen, accompanied by dynamic alterations in the expression of NCAM and GAP-43. Thus, our study provides evidence for a surprising degree of plasticity of murine skin innervation. Because hair cycle-associated tissue remodeling evidently is associated with tightly regulated sprouting and regression of nerve fibers, hair cycle-dependent alterations in murine skin and hair follicle innervation offer an intriguing model for studying the controlled rearrangement of neuronal networks in peripheral tissues under physiological conditions.     

In vitro screening of biochemical activity of folic acid antagonists in skin

Dihydrofolate reductase (DHFR) inhibitors, which differ from the classical folate antagonists in physicochemical and pharmacologic parameters such as lipid solubility and mechanisms of cellular transport, were screened for DHFR inhibitory activity and biologic activity in newborn rat skin. The most effective drugs from this screen were tested for their effects on de novo DNA synthesis in psoriatic epidermis in vitro. Of the 24 compounds studied, methotrexate (MTX) was the most potent inhibitor of rat skin DHFR (I50=8.6 X 10(-9) M). Methotrexate-dimethylester, methasquin-diethylester, DDEP (2,4-diamino-5-(3',4'-dichlorophenyl)-6-ethylprimidine), and Baker's triazine antifolate (NSC 139105), while less effective than MTX as DHFR inhibitors, were more effective than MTX as inhibitors of de novo DNA synthesis in rat skin in vitro. Baker's antifolate was the only compound tested which was considerably more effective than MTX as an inhibitor of de novo DNA synthesis in psoriatic epidermis in vitro.     

Antioxidant defense mechanisms in murine epidermis and dermis and their responses to ultraviolet light

A comprehensive comparison of antioxidant defenses in the dermis and epidermis and their response to exposure to ultraviolet (UV) irradiation has not previously been attempted. In this study, enzymic and non-enzymic antioxidants in epidermis and dermis of hairless mice were compared. Enzyme activities are presented both as units/gram of skin and units/milligram of protein; arguments are presented for the superiority of skin wet weight as a reference base. Catalase, glutathione peroxidase, and glutathione reductase (units/gram of skin) were higher in epidermis than dermis by 49%, 86%, and 74%, respectively. Superoxide dismutase did not follow this pattern. Lipophilic antioxidants (alpha-tocopherol, ubiquinol 9, and ubiquinone 9) and hydrophilic antioxidants (ascorbic acid, dehydroascorbic acid, and glutathione) were 24-95% higher in epidermis than in dermis. In contrast, oxidized glutathione was 60% lower in epidermis than in dermis. Mice were irradiated with solar light to examine the response of these cutaneous layers to UV irradiation. After irradiation with 25 J/cm2 (UVA + UVB, from a solar simulator), 10 times the minimum erythemal dose, epidermal and dermal catalase and superoxide dismutase activities were greatly decreased. alpha-Tocopherol, ubiquinol 9, ubiquinone 9, ascorbic acid, dehydroascorbic acid, and reduced glutathione decreased in both epidermis and dermis by 26-93%. Oxidized glutathione showed a slight, non-significant increase. Because the reduction in total ascorbate and catalase was much more severe in epidermis than dermis, it can be concluded that UV light is more damaging to the antioxidant defenses in the epidermis than in the dermis.     

Centralized echocardiogram quality control in a multicenter study of regression of left ventricular hypertrophy in hypertension

Deep skin wounds in the adult mammal close spontaneously by epithelialization, wound contraction, and scar synthesis. In previous wound healing studies, it has been unsuccessfully attempted to separate from each other the natural processes that close wounds. In this study, we attempted to isolate skin regeneration from spontaneous processes of wound closure using "island" grafts. A porous analog of the extracellular matrix, composed of a graft copolymer of type I collagen and chondroitin 6-sulfate, was seeded with uncultured autologous keratinocytes and served to induce regeneration of the dermis and the epidermis. Grafts of the copolymer, measuring 1 x 2 cm, were placed in the center of 5 x 6-cm wounds in guinea pigs. By day 14, the edges of the island grafts were clearly separated from the host epidermis and dermis by a distinct bed of granulation tissue. Histologic study of island grafts on day 14 showed that the copolymer grafts had largely degraded and that a new epidermis and dermis had been synthesized in its place. The thickness of the new epidermis increased as the density of cells seeded into the graft increased. No synthesis of epidermis or dermis was observed in the granulation tissue outside the perimeter of the island grafts. We conclude that island grafting allows the study of early events in skin regeneration in isolation from epithelialization, contraction, and scar synthesis.     

Intact hair follicle innervation is not essential for anagen induction and development

Neuropeptides produced, stored and secreted by the unusually dense sensory and autonomic innervation of hair follicles (HFs) can induce hair growth (anagen) and may be involved in hair growth control. To test the role of follicle innervation of HF cycling in vivo, we generated innervation-deficient HFs by unilateral surgical denervation of a defined region of back skin in C57BL/6 mice and assessed its effect on spontaneous and induced anagen development. Successful denervation was demonstrated by the absence of PGP 9.5+ or tyrosine hydroxylase+ nerves and nerve-associated neuropeptides (substance P, CGRP). By quantitative histomorphometry, no significant difference in spontaneous or cyclosporin A-induced anagen development could be detected between sham-operated control skin and denervated skin. Only after hair growth induction by depilation, a discrete, marginally significant retardation of anagen development was apparent in denervated HFs. Thus, even though cutaneous nerves may exert a minor modulatory role in depilation-induced hair growth, they are not essential for normal murine anagen development.     

Harlequin ichthyosis (ichq): a juvenile lethal mouse mutation with ichthyosiform dermatitis

The harlequin ichthyosis (ichq) mouse mutation arose spontaneously in 1989 in a colony of BALB/cJ mice at The Jackson Laboratory. Affected mice developed thick skin due to formation of compact, orthokeratotic scales that fractured over articular surfaces, secondary to bending. Harlequin ichthyosis mice on the inbred BALB/cJ background died between 9 and 12 days of age. Onset of the clinical phenotype corresponded with emergence of hair fibers from follicles at 5 days of age. There was marked proliferation of the root sheaths of anagen hair follicles, limited to the region within the dermis. Sebaceous glands were present but small compared with those of littermate controls. Emerging hair fibers were surrounded by a thick, compact sheath of cornified cells. Mutant skin contained large mitochondria with lamellar-shaped, electron-dense structures at the ultrastructural level. Keratohyalin granules were smaller and less pleomorphic than those in control mice. Lamellar bodies were not evident in either mutant or littermate control mice. Using a panel of antibodies to evaluate changes in keratinocyte differentiation, mouse-specific keratin 6 was overexpressed in the suprabasilar, hyperplastic epidermis. Loricrin expression, within the cytoplasm of cells in the stratum granulosum, decreased rapidly postmortem, unlike that in normal mice where it was stable for over 24 hours postmortem. Filaggrin expression, within granules of cells in the stratum granulosum, was prominent, corresponding to hypergranulosis evident by light microscopy in mutant mouse skin. Skin grafts from harlequin ichthyosis mice grafted onto immunodeficient nude mice maintained the phenotype for the 10-week observation period. The mutant gene locus mapped to the proximal end of mouse chromosome 19 and is inherited as a fully penetrant autosomal recessive gene. The harlequin ichthyosis mouse mutation is very similar to human type 2 harlequin ichthyosis for which it may be a good model.     

Effects of monoclonal anti-c-kit antibody (ACK2) on melanocytes in newborn mice

Previous studies indicate that c-Kit is required for postnatal melanocyte development. To understand the precise mechanisms of c-Kit dependence, we studied melanocyte development in newborn C57BL/6 mice by means of peritoneal injection of a monoclonal anti-c-Kit antibody (ACK2), which blocks c-Kit functions. The mice were injected once or more with ACK2 at various intervals after birth. In experiment 1, skin samples were examined on day 10 post-partum and in experiment 2 they were examined daily until day 10 post-partum. We studied melanocytes in the hair follicles, epidermis, and dermis by light and electron microscopy with dopa reactions and immunohistochemistry. Epidermal melanocytes in untreated mice were dopa negative and c-Kit positive on day 0 post-partum but became dopa positive soon thereafter. In ACK2-treated mice, the earlier the mice received ACK2 injections after birth, the fewer melanocytes they had, not only in the epidermis, but also in follicles. In these mice, melanocytes that had undergone apoptosis in the dermis and the follicles were detected ultrastructurally. Some appeared to have produced tyrosinase, because they had dopa-positive melanosomes. These results suggest that melanocytes in newborn mice are c-Kit dependent and undergo apoptosis when c-Kit receptors are blocked by ACK2 in the early days after birth. During this c-Kit-dependent period, melanocytes differentiate from dopa negative to positive and migrate from the epidermis to hair follicles.     

Different populations of melanocytes are present in hair follicles and epidermis

Melanocytes in human skin reside both in the epidermis and in the matrix and outer root sheath of anagen hair follicles. Comparative study of melanocytes in these different locations has been difficult as hair follicle melanocytes could not be cultured . In this study we used a recently described method of growing hair follicle melanocytes to characterize and compare hair follicle and epidermal melanocytes in the scalp of the same individual. Three morphologically and antigenically distinct types of melanocytes were observed in primary culture. These included (1) moderately pigmented and polydendritic melanocytes derived from epidermis; (2) small, bipolar, amelanotic melanocytes; and (3) large, intensely pigmented melanocytes; the latter two were derived from hair follicles. The three sub-populations of cells all reacted with melanocyte-specific monoclonal antibody. Epidermal and amelanotic hair follicle melanocytes proliferated well in culture, whereas the intensely pigmented hair follicle melanocytes did not. Amelanotic hair follicle melanocytes differed from epidermal melanocytes in being less differentiated, and they expressed less mature melanosome antigens. In addition, hair follicle melanocytes expressed some antigens associated with alopecia areata, but not antigens associated with vitiligo, whereas the reverse was true for epidermal melanocytes. Thus antigenically different populations of melanocytes are present in epidermis and hair follicle. This could account for the preferential destruction of hair follicle melanocytes in alopecia areata and of epidermal melanocytes in vitiligo.     

Epidermal and dermal phospholipids of the human eyelid: a 31P nuclear magnetic resonance spectroscopy study

The phospholipids of the skin are difficult to quantify because they represent only a small fraction of the skin tissue. In this study, 31P nuclear magnetic resonance, which permits precise profiling of these phospholipids, was used to compare the phospholipids of upper eyelid epidermal and dermal lipid extracts (n = 13 profiles). Phospholipid profiles included alkylacylphosphatidylcholine (AAPC), dihydrosphingomyelin (DHSM), diphosphatidylglycerol (cardiolipin), ethanolamine plasmalogen (EPLAS), lysophosphatidylcholine, phosphatidic acid, phosphatidylcholine (PC), phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, sphingomyelin, and uncharacterized phospholipids (U1 and U2, particularly enriched in the epidermis). The computed phospholipid metabolic index (n = 86 indexes) findings can be summarized as follows: a lower content of the en-ol and ether phospholipids in the epidermis relative to the dermis, internal compensation among the component phospholipids so as to maintain the choline functional group ratio, and a greater concentration of hydroxyl-containing functional groups in the epidermis. A membrane index (fmem) value of -0.37 for the epidermis deviated considerably from the value of -0.06 characteristic of living membranes and the dermis. The production of the reduced phosphatides, EPLAS and AAPC, indicates the use of alternative pathways between the two tissues. Relative to the dermis, increased PC in the epidermis coupled with decreased DHSM, EPLAS, and AAPC are factors enabling the epidermis of eyelid tissue to be an effective water barrier.     

Apoptosis, necrosis, and proliferation: possible implications in the etiology of keloids

Keloids are collagenous lesions acquired as a result of abnormal wound heating. In this study we have assessed the potential role of proliferation, apoptosis, and necrosis in keloids. Samples were immunolabeled for proliferating cell nuclear antigen or DNA strand breaks or stained with acridine orange. Proliferating cells were observed in the basal layer of the epidermis and fibroblasts in the dermis, the numbers of the latter being increased in comparison with normal skin. No proliferating cells were observed in the central region of the keloid. In normal skin, apoptotic cells were restricted to the basal layer of the epidermis. In keloid samples, numerous apoptotic cells were observed in the epidermis and dermis; the number and distribution of positive cells decreased more distal to the keloid lesion. Apoptotic endothelial cells of a small proportion of blood vessels in the dermis were also observed. Evidence of necrosis was also seen in the dermis. These results suggest that, with maturity, progressive cell degeneration primarily by apoptosis results in clearance of certain cellular populations resulting in the typical keloid lesion. However, the persistence of fibroblast proliferation at the dermal/keloid interface propagates the fibrosis.     

Interleukin-1 alpha gene expression and localization of interleukin-1 alpha protein during tumor promotion

Treatment of the dorsal epidermis of SENCAR mice with 12-O-tetradecanoylphorbol-13-acetate (TPA) induced a time- and dose-dependent stimulation of interleukin-1 alpha (IL-1 alpha) gene expression. Levels of IL-1 alpha mRNA were elevated as early as 15 min and peaked at 3-4 h after a single application of TPA (2 micrograms or 10 micrograms). IL-1 alpha gene expression increased in epidermal tissue isolated from SENCAR mice at 1, 3, 6, 10, 16, and 22 wk after a single treatment with 10 nmol 7,12-dimethylbenz[a]anthracene (DMBA) and subsequent twice-weekly application of 2 micrograms TPA. IL-1 alpha-immunoreactive protein was specifically localized within suprabasal keratinocytes in cutaneous tissue isolated from mice treated with DMBA-TPA for 1-22 wk and in nonproliferating cells located within papilloma tissue isolated from SENCAR mice at 22 wk after initiation and promotion. Basal cells within hyperplastic epidermis did not produce IL-1 alpha-immunoreactive protein. DMBA treatment alone did not induce IL-1 alpha gene expression. Injection of IL-1 alpha-specific antibodies (50 micrograms) into SENCAR mice via the tail vein 2 h before treatment with TPA (2 micrograms or 10 micrograms) significantly (P < 0.05) inhibited the skin thickening usually observed 24 h after treatment with TPA. Autoradiography studies showed that injection of anti-IL-1 alpha antibodies inhibited incorporation of [methyl-3H]thymidine by keratinocytes within the epidermis and by cells within hair follicles. It also inhibited neutrophil infiltration into the dermis, which usually results from topical application of TPA. These data suggest that IL-1 alpha is a pivotal cytokine produced by specific subpopulations of epidermal keratinocytes and that IL-1 alpha primarily regulates the epidermal proliferative response of a distinctly separate population of keratinocytes after topical exposure of murine epidermis to TPA and secondarily modulates neutrophil migration into the dermis. Consequently, manipulation of IL-1 alpha may be a way to attenuate or abrogate the cutaneous response to TPA by altering keratinocyte proliferation, the resultant hyperplasia, and a portion of the inflammatory response characterized by dermal infiltration of neutrophils.     

Expression of a functional endothelin (ETA) receptor in human meningiomas

Endothelin (ET) receptor subtypes (ETA and ETB) in human meningiomas were characterized using quantitative receptor autoradiography. A single class of high-affinity 125I-ET-1 binding sites was localized in all meningioma tissue studied (dissociation constant: 2.4 +/- 0.3 nM, maximum binding capacity: 319 +/- 66 fmol/mg (mean +/- standard error of the mean for 13 tumors)). Unlabeled ET-1 showed a strong affinity for 125I-ET-1 binding to tissue sections of the tumors with a 50% inhibiting concentration (IC50) of 2.9 +/- 0.7 x 10(-9) M, whereas ET-3 showed a much lower affinity (IC50: 8.4 +/- 2.5 x 10(-6) M). Sarafotoxin S6c, a selective agonist for the ETB receptor, could not compete for 125I-ET-1 binding to meningiomas. Endothelin-1 significantly stimulated deoxyribonucleic acid (DNA) synthesis in a dose-dependent manner in cultured human meningioma cells. In contrast, no significant stimulation of DNA synthesis occurred with an S6c concentration up to 10(-7) M. Pretreatment of the meningioma cells with pertussis toxin, a bacterial toxin that adds adenosine 5'-diphosphate-ribose to the alpha subunit of guanine nucleotide binding (G) proteins such as Gi or G(o), induced a concentration-dependent reduction in ET-stimulated DNA synthesis in meningioma cells, but did not affect the epidermal growth factor-induced DNA synthesis. These observations suggest that the ETA receptor is predominantly expressed in human meningioma tissue and that ET may act as a growth factor on the meningioma cells by interacting with the ETA receptor and by pertussis toxin-sensitive mechanisms.     

Characterisation of ACTH peptides in human skin and their activation of the melanocortin-1 receptor

Alpha-Melanocyte-stimulating hormone (alpha-MSH) is a proopiomelanocortin (POMC)-derived peptide, which is produced in the pituitary and at other sites including the skin. It has numerous effects and in the skin has a pigmentary action through the activation of the melanocortin-1 (MC-1) receptor, which is expressed by melanocytes. Recent evidence suggests that the related POMC peptides such as adrenocorticotrophin (ACTH), which is the precursor of alpha-MSH, is also an agonist at the MC-1 receptor. By using immunocytochemistry, we confirmed the presence of alpha-MSH in human skin where staining was evident in keratinocytes and especially strong in melanocytes and possibly Langerhans cells. ACTH was also present and tended to show the strongest reaction in differentiated keratinocytes. Immunostaining was also observed for the prohormone convertases, PC1 and PC2, which are involved in the formation of ACTH and its cleavage to alpha-MSH, respectively. The amounts of immunoreactive ACTH exceeded those of alpha-MSH. Using HPLC we identified for the first time the presence of ACTH1-39, ACTH1-17, ACTH1-10, acetylated ACTH1-10, alpha-MSH, and desacetyl alpha-MSH in epidermis and in cultured keratinocytes. The ability of these peptides to activate the human MC-1 receptor was examined in HEK 293 cells that had been transfected with the receptor. All peptides increased adenylate cyclase in these cells with the following order of potency: ACTH1-17 > alpha-MSH > ACTH1-39 > desacetyl alpha-MSH > acetylated ACTH1-10 > ACTH1-10. ACTH1-17 also increased the dendricity and melanin content of cultured human melanocytes indicating that the peptide was able to activate MC-1 receptors when present in their normal location. However, as found with alpha-MSH, not all cultures were responsive and, as we have previously suggested, we suspect that this was the result of changes at the MC-1 receptor. Nevertheless, it would appear that ACTH peptides can serve as natural ligands of the MC-1 receptor on human melanocytes and their presence in the skin suggests that, together with alpha-MSH, they may have a role in the regulation of human melanocytes.     

Suppression of the tumorigenicity of prostatic cancer cells by gene(s) located on human chromosome 19p13.1-13.2

PURPOSE: The lateral iontophoretic transport of three solutes (sodium, ethanolamine, lidocaine) from an active electrode through skin and other tissues to an indifferent electrodes was investigated. METHODS: Anodal epidermal iontophoresis was carried out on an in vivo rat model using constant direct current of 0.38 mA/cm2. Cells were fixed on the epidermis of anesthetized rats at distances of adjacent, 3 cm and 7 cm apart. After iontophoresis, tissues were dissected at I cm intervals between the electrodes. Concentrations of the radiolabelled solutes in tissues were determined by liquid scintillation counting or gamma counting. RESULTS: The concentration of each solutes in the epidermis, dermis and other tissues was found to decrease in an exponential manner with lateral distance from the active electrode to the indifferent electrode. The detectable lateral distance for ethanolamine and lidocaine was less than 2 cm from the donor sites, at which distance the concentrations were not significantly different to those found in the corresponding contralateral site. The lateral drift velocities for all solutes in the epidermis and dermis were consistent with diffusivities of the order of 10(-6) cm2/s. The drift velocity of sodium was greater than either lidocaine or ethanolamine. CONCLUSIONS: The decline in solute concentration with lateral distance is mainly due to clearance from the site of application by the skin's microcirculation and decreases with distance from the active electrode until a baseline concentration, similar to the contralateral tissue concentration is reached.     

Analysis of the ability of 12-O-tetradecanoylphorbol-13-acetate to induce epidermal hyperplasia, transforming growth factor-alpha, and skin tumor promotion in wa-1 mice

Wa-1 mutant mice possess a defect in the production of transforming growth factor-alpha (TGF-alpha) that leads to a phenotype characterized by wavy hair and curly whiskers. In light of recent evidence indicating the importance of TGF-alpha in epithelial tumorigenesis, this study characterizes the responsiveness of wa-1 mice to skin tumor promotion by the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA). The responsiveness of wa-1 mice to TPA was compared with that of SENCAR and C57BL/6 mice, representing mouse lines highly sensitive and resistant to skin tumor promotion, respectively. Wa-1 mice were found to be very resistant to skin tumor promotion by TPA after initiation with 10 nmol DMBA, similar to C57BL/6 mice. TPA failed to induce a dramatic increase in TGF-alpha mRNA and protein in the skin of wa-1 mice, whereas TGF-alpha mRNA and protein were dramatically induced in the skin (both epidermis and dermis) of SENCAR and C57BL/6 mice. TPA treatment dramatically increased mRNA levels of two other EGF receptor ligands, amphiregulin and heparin binding-EGF, however, in the skin of all three mouse lines. Comparison of histologic changes in skin revealed that wa-1 mice exhibited only modest sustained epidermal hyperplasia after multiple treatments with TPA, similar in magnitude to that of C57BL/6 mice and significantly lower than that of SENCAR mice. The current data indicate that wa-1 mice are relatively resistant to TPA promotion. Possible mechanisms for this resistance are discussed.     

Lipoxygenase activity in rat dermis and epidermis: partial purification and characterization

Lipoxygenase (LOX) activity in epidermis and dermis was distributed among microsomal and cytosolic fractions. The main products of polyunsaturated fatty acid metabolism were 12-hydroperoxy-cis-5,8,14, trans-10-eicosatetraenoic acid (12-HPETE), 15-hydroperoxy-cis-5,8,11, trans-13-eicosatetraenoic acid (15-HPETE) and 13-hydroxy-cis-9, trans-11-octadecadienoic acid (13-HOD). Enzyme activities were isolated from rat dermis and epidermis by ammonium sulphate precipitation, hydrophobic chromatography and gel filtration. In the dermis, activity was found at a molecular mass of 68 kDa, a pI of 4.6 and a Km of 50 microM. This activity was inhibited by known LOX inhibitors. The main reaction products indicated that this was 15-LOX. In the epidermis, activity was found in a fraction with a molecular mass of 68 kDa, a pI of 4.6 and a Km of 80 microM. Activity was inhibited by known LOX inhibitors whereas the reaction products indicated that this was 12-LOX. LOX activity in rat skin may involve one enzyme with dual regional specificities or may comprise two different enzymes.     

CO2 laser debridement of sulphur mustard (bis-2-chloroethyl sulphide) induced cutaneous lesions accelerates production of a normal epidermis with elimination of cytological atypia

Sulphur mustard (bis-2-chloroethyl sulphide; HD) exposure acutely produces lesions that vary from mild erythema, to blister formation, to necrosis. When blisters occur, with or without necrosis, healing of the lesions is delayed. Weanling pigs exposed to a mild erythema-producing dose of HD and to a moderate erythema-producing dose that consistently gave microblister formation were treated with CO2 laser (Tru-Pulse) debridement at 6, 24 or 48 h after exposure. The histopathological features observed at 14 days after exposure in control skin and skin exposed to both HD doses were compared with the features observed in CO2 laser-debrided skin in non-exposed and HD-exposed skin sites. The overlying epidermis in the non-laser treated lesions was thin, with cytological atypia and squamoid changes within the basal cell layer, as well as scattered apoptotic/necrotic keratinocytes. An increased inflammatory infiltrate and necrobiotic changes in the dermis were seen at the higher HD dose. All laser-treated lesions appeared identical, with a thick, differentiated epidermis and a well-formed basal cell layer. There was minimal inflammatory infiltrate. In the papillary dermis there were increased stromal cells. Laser debridement of mild clinical lesions induced by HD produced a more functional epidermis by 14 days as well as clearing the epidermis of damaged keratinocytes.