Unexposed Skin Research Articles

Basal cell carcinoma of the vulva

Basal cell carcinoma (BCC), the most common human malignancy, accounting for 75% of all non-melanoma skin cancer, is uncommon on unexposed skin such as the perianal and genital regions. We describe a woman with BCC of the vulva treated with local resection. All margins of excision were free of disease. The patient recovered without complication and there have been no recurrences after 2 years of follow-up. Approximately 200 cases of BCC on perianal and genital skin have been reported in the literature. Although the aetiology of vulvar BCC is not known, early diagnosis is important. Because BCC in these sites sometimes seems innocuous, biopsy of all suspect lesions is advisable.

Effect of In Vivo Jet Fuel Exposure on Subsequent In Vitro Dermal Absorption of Individual Aromatic and Aliphatic Hydrocarbon Fuel Constituents

The percutaneous absorption of topically applied jet fuel hydrocarbons (HC) through skin previously exposed to jet fuel has not been investigated, although this exposure scenario is the occupational norm. Pigs were exposed to JP-8 jet fuel-soaked cotton fabrics for 1 and 4 d with repeated daily exposures. Preexposed and unexposed skin was then dermatomed and placed in flow-through in vitro diffusion cells. Five cells with exposed skin and four cells with unexposed skin were dosed with a mixture of 14 different HC consisting of nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, ethyl benzene, o-xylene, trimethyl benzene (TMB), cyclohexyl benzene (CHB), naphthalene, and dimethyl naphthalene (DMN) in water + ethanol (50:50) as diluent. Another five cells containing only JP-8-exposed skin were dosed solely with diluent in order to determine the skin retention of jet fuel HC. The absorption parameters of flux, diffusivity, and permeability were calculated for the studied HC. The data indicated that there was a two-fold and four-fold increase in absorption of specific aromatic HC like ethyl benzene, o-xylene, and TMB through 1- and 4-dJP-8 preexposed skin, respectively. Similarly, dodecane and tridecane were absorbed more in 4-d than 1-dJP-8 preexposed skin experiments. The absorption of naphthalene and DMN was 1.5 times greater than the controls in both 1- and 4-d preexposures. CHB, naphthalene, and DMN had significant persistent skin retention in 4-d preexposures as compared to 1-d exposures that might leave skin capable of further absorption several days postexposure. The possible mechanism of an increase in HC absorption in fuel preexposed skin may be via lipid extraction from the stratum corneum as indicated by Fourier transform infrared (FTIR) spectroscopy. This study suggests that the preexposure of skin to jet fuel enhances the subsequent in vitro percutaneous absorption of HC, so single-dose absorption data for jet fuel HC from naive skin may not be optimal to predict the toxic potential for repeated exposures. For certain compounds, persistent absorption may occur days after the initial exposure. This work was supported by U.S. Air Force Office of Scientific Research, grant F49620-01-1-0080.

Transcutaneous Bilirubinometry in Preterm Infants Receiving Phototherapy

The accuracy of transcutaneous bilirubin (TcB) measurements obtained with a Bilicheck device in 70 preterm neonates before phototherapy and during phototherapy from the exposed and unexposed skin of the forehead (under the eye patch) was evaluated by comparing the TcB with the total serum bilirubin (TSB) that was performed within +/- 30 minutes of the TcB measurements. The correlation and proportion of similar, overestimated, and underestimated paired TcB/TSB measurements was calculated. A TSB point estimate of +/- 1.5 mg/dL was used for comparison of differences between the TcB and TSB. There was weaker correlation between TcB and TSB when the TcB was obtained from the exposed skin (r = 0.70; p > 0.05) as compared with an unexposed area (r = 0.77; p < 0.04) or before initiation of phototherapy (r = 0.86; p < 0.01). The TcB measurements from the area unexposed to phototherapy were predominantly (97.2%) in the similar (57%) or overestimation categories (40.2%). A significantly lower proportion of the paired TcB/TSB measurements obtained from exposed area were similar (42%) or overestimated (27%; p < 0.001). More importantly, in 31% of the measurements, the TSB levels were underestimated by the TcB. We conclude that the Bilicheck can be used for the evaluation of bilirubin levels in preterm neonates receiving phototherapy by using the unexposed skin of the forehead (under the eye patch) for TcB measurements; this may significantly reduce the number of blood draws.

Osteoporosis, a unitary hypothesis of collagen loss in skin and bone

Progress in osteoporosis has been stultified by repetitive, statistic-driven studies and catechistic reviews; in the absence of concept and hypothesis research is aimless, and the trivial associations it continually reveals, has led to the cul-de-sac of multifactorialism. A return to hypothesis-led research which seeks major causal defects and the conclusive therapies that arise from them is essential. The hypothesis proposed evolved from research into the mechanism of senile purpura. This predicted a causal loss of skin collagen that was contrary to contemporary opinion, but was confirmed when collagen was expressed absolutely, instead as a percentage or ratio: women have less collagen than men and it decreases by 1% a year in exposed and unexposed skin. Corticosteroids (which also produce shear purpura) reduce skin collagen and androgen and virilism increase it; growth hormone produces the greatest increase, and there is a decrease in hypopituitarism. All these changes in skin collagen correspond to changes in bone density, and the circumstances are too various for coincidence. This led to the hypothesis that the changes found in skin collagen also occur in bone collagen, leading to the associated changes in bone density; thus a loss of collagen in skin and bones with aging is the causal counterpart to loss of bone density in senile osteoporosis. If this is correct then, as with aging, androgen and virilisation, corticosteroids, growth hormone and hypopituitarism, changes in bone density should correspond to systemic changes in skin collagen. This correspondence is found to occur in osteogenesis imperfecta and Ehlers-Danlos syndrome, two genetically discrete families of disordered collagen production, and other situations, e.g., scurvy and homocystinuria. A primary loss of collagen in osteoporotic bones is an essential prediction of the hypothesis; in fact this loss is well established but, inexplicably, it has been assumed to be secondary to the bone loss. Because of the comparable changes in skin and bones, the hypothesis implies that skin collagen could be used to predict the state of the bones and their response to treatment. It also implies androgen should be an effective treatment of osteoporosis, and growth hormone even more effective (likewise, of course, skin aging). More importantly, skin collagen and the production of collagen by skin fibroblasts could be used for the assay and industrial development of more potent, if not less toxic treatments and prevention of loss of bone (and skin) substance.

Systemic lupus erythematosus and pemphigus vulgaris: association or coincidence

Few cases have been published relating systemic lupus erythematosus (SLE) and pemphigus vulgaris (PV). We describe a patient with this association. A 35-year old woman who started to develop persistent pain and morning stiffness of proximal inter and metacarpo-phalangeal joints. During the following year, the patient recalled the onset of blisters on both legs, face, arms and thorax, as well as erosions appearing on oral mucous membranes. We observed generalized multiple erosions on her trunk and legs, flaccid bullae located on her right thigh and multiple erosions on oral mucous membranes. A skin biopsy reported PV Direct immunofluorescence on the perilesional skin specimen, showed beehive intercellular IgG deposits in the epidermis (+++), suggesting PV; granular discontinuous IgM and C3 deposits in the dermal-epidermal union (+++), suggesting SLE. Direct immunofluorescence of the healthy unexposed skin specimen, reported granular discontinuous IgG deposits in the dermal-epidermal union and beehive intercellular IgG deposits in the lower levels of the epidermis (+++); granular continuous IgM deposits in the dermal-epidermal union (+++). The results of rheumatic studies were obtained as follows: ANA :3 +, Anti-DNA, Anti-Sm, Anti-Ro and Anti-La :4 + . The definite diagnosis was PVand SLE. Treatment with 50 mg of prednisone daily with good evolution.

Effects of oral vitamin E and β-carotene supplementation on ultraviolet radiation–induced oxidative stress in human skin

Ultraviolet radiation (UVR) generates reactive oxygen species in skin that can play a role in skin damage, but reports about the photoprotective properties of oral antioxidant supplements are conflicting. We examined the ability of 2 lipid-soluble antioxidants, vitamin E and beta-carotene, to reduce markers of oxidative stress and erythema in human skin exposed to UVR. Sixteen healthy subjects took either alpha-tocopherol (n = 8; 400 IU/d) or beta-carotene (n = 8; 15 mg/d) for 8 wk. Biopsy samples before and after supplementation were taken from unexposed skin and skin 6 h after 120 mJ/cm(2) UVR. The effects of supplements on markers of oxidative stress in skin and the minimal erythema dose to UVR were assessed. Supplementary vitamin E was bioavailable, the plasma concentration increased from 14.0 +/- 0.66 (x +/- SEM) to 18.2 +/- 0.64 mug/mL (P < 0.01), and the skin concentration increased from 0.55 +/- 0.09 to 1.6 +/- 0.19 ng/mg protein (P < 0.01). Supplementary beta-carotene increased plasma concentrations from 1 +/- 0.3 to 2.25 +/- 0.3 mug/mL (P < 0.05), but skin concentrations were undetectable. Before vitamin E supplementation, UVR increased the skin malondialdehyde concentration from 0.42 +/- 0.07 to 1.24 +/- 0.16 nmol/mg protein (P < 0.01), whereas oxidized or total glutathione increased from 9.98 +/- 0.4% to 12.0 +/- 1.0% (P < 0.05). Vitamin E supplementation significantly decreased the skin malondialdehyde concentration, but neither vitamin E nor beta-carotene significantly influenced other measures of oxidation in basal or UVR-exposed skin. Vitamin E or beta-carotene supplementation had no effect on skin sensitivity to UVR. Although vitamin E supplements significantly reduced the skin malondialdehyde concentration, neither supplement affected other measures of UVR-induced oxidative stress in human skin, which suggested no photoprotection of supplementation.

Gene expression profiling of in vivo UVB-irradiated human epidermis.

Several recent studies have employed microarray profiling to study UVB-regulated gene expression in human skin. These studies are all based on UV-irradiated cultured cells that differ substantially from the intact tissues they are supposed to imitate. The purpose of the present study was to analyze the differential expression of UVB-regulated genes in intact human epidermis following in vivo UV irradiation. The forearms of human volunteers were exposed to 4 MED of UVB in vivo, followed by removal of epidermal samples from exposed and non-exposed areas after 24 h. RNA samples were analyzed using oligonucleotide microarray (Affymetrix) technology analyzing 12 500 genes simultaneously. Verification of selected genes was performed by semi-quantitative reverse transcriptase polymerase chain reaction. Gene expression patterns clearly distinguished UV-exposed epidermis from unexposed skin. Classification of these genes into functional categories revealed that several biological processes are globally affected by UVB. Significant changes were seen in more than 800 genes. Human intact epidermis responds to a single low dose of in vivo UVB irradiation by differential regulation of numerous genes. Our results illustrate the power of global gene expression analysis of human epidermis to identify molecular pathways involved in UV-induced photodamage.

Changes in matrix gene and protein expressions after single or repeated exposure to one minimal erythemal dose of solar‐simulated radiation in human skin in vivo

ASTRACTDamage to the skin extracellular matrix (ECM) is the hallmark of long‐term exposure to solar UV radiation. The aim of our study was to investigate the changes induced in unexposed human skin in vivo after single or repeated (five times a week for 6 weeks) exposure to 1 minimal erythemal dose (MED) of UV solar‐simulated rediation. Morphological and iochemical analyses were used to evaluate the stuctural ECM components and the balance between teh degrading enzymes the their physiologic inhibitors. a three‐fold increse in matrix metalloproteinase 2 messenger RNA (mRNA) (P &lt; 0.02, unexposed versus exposed) was observed after both single and repeated exposures. Fibrillin 1 mRNA level was incresed by chronic exposure (P &lt;0.02) and unaltered y a single MED. On the cotrary, a single MED singnificantly enhanced mRNA levels of interleukin‐1α (1L‐1α), IL‐1β (P &lt; 0.02) and plasminogen activator inhibitor‐1 (P &lt; 0.05). Immkunohistochemistry demonstrated a singnificant decrese in Type‐I procollagen localized just below the dermal‐epidermal junction in both types of expozed sites. at the same location, teh immunodetected tenascin was singnificantly enhanced, whereas a slight increase in Type‐III procollagen deposits was also unale to observe any change in elastic iers in chronically exposed uttock skin, a significant increase in lysozyme and alpha‐1 antitrypsin deposits on these fibers was oserved. These results demonstrate the existence of diffenentaia regulation, after chronic exposure compared with an acute one, of some ECM components and inflammatory mediators.

Ultraviolet Radiation-Induced Inflammation as a Model for Cutaneous Hyperalgesia

The effects of UVA-I and solar simulated radiation on skin sensitivity to thermal and mechanical stimuli were compared in normal volunteers. Individual minimal erythema doses (MED) for each source were determined and previously unexposed buttock skin was exposed to 1, 2 and 3 MED of each spectrum. Erythema, and mechanical and thermal pain thresholds were quantified from 3 to 72 hours post-irradiation. Irradiated skin did not exhibit pain but hyperalgesia and allodynia were provoked by the applied stimuli after exposure to 2 or 3 MED. There were highly significant decreases in thresholds for both stimuli in exposed skin compared with non-exposed skin. These changes began within a few hours of irradiation, peaked about 24 hours later and persisted throughout the test period. The sensitivity changes broadly followed the erythema response and did not extend beyond the irradiated area. There were only minor differences between the two spectra at comparable erythemal doses. These data demonstrate the usefulness of UVR-induced inflammation as a model of cutaneous hypersensitivity. This model has clinical relevance for the study of hyperalgesia in general and the abnormal sensitivity of sunburnt skin in particular. It is likely to be useful in the assessment of peripherally acting analgesic drugs.

Changes in matrix gene and protein expressions after single or repeated exposure to one minimal erythemal dose of solar-simulated radiation in human skin in vivo.

Damage to the skin extracellular matrix (ECM) is the hallmark of long-term exposure to solar UV radiation. The aim of our study was to investigate the changes induced in unexposed human skin in vivo after single or repeated (five times a week for 6 weeks) exposure to 1 minimal erythemal dose (MED) of UV solar-simulated radiation. Morphological and biochemical analyses were used to evaluate the structural ECM components and the balance between the degrading enzymes and their physiologic inhibitors. A three-fold increase in matrix metalloproteinase 2 messenger RNA (mRNA) (P < 0.02, unexposed versus exposed) was observed after both single and repeated exposures. Fibrillin 1 mRNA level was increased by chronic exposure (P < 0.02) and unaltered by a single MED. On the contrary, a single MED significantly enhanced mRNA levels of interleukin-1alpha (IL-1alpha), IL-1beta (P < 0.02) and plasminogen activator inhibitor-1 (P < 0.05). Immunohistochemistry demonstrated a significant decrease in Type-I procollagen localized just below the dermal-epidermal junction in both types of exposed sites. At the same location, the immunodetected tenascin was significantly enhanced, whereas a slight increase in Type-III procollagen deposits was also observed in chronically exposed areas. Although we were unable to observe any change in elastic fibers in chronically exposed buttock skin, a significant increase in lysozyme and alpha-1 antitrypsin deposits on these fibers was observed. These results demonstrate the existence of a differential regulation, after chronic exposure compared with an acute one, of some ECM components and inflammatory mediators.

A study of differences in surface roughness between sun-exposed and unexposed skin with age.

To understand and separate the roles of age and solar ultraviolet exposure (sun damage) on the surface roughness of skin. To determine the effects of age and site (sun exposed vs. unexposed) on skin roughness in normal healthy subjects. Using a stylus profilometer and silicone skin surface replicas, we have measured skin surface roughness parameters on habitually exposed (back of hand) and habitually unexposed (upper buttock) skin sites from the same individual in a sample of 73 subjects from the normal population. We compared the two sites in order to determine any differences in roughness caused, we postulate, by the effect of solar ultraviolet exposure on the exposed site. We found that the two sites are indistinguishable in roughness until after 30 years of age. For the over 30 years group, the difference between exposed and unexposed skin roughness correlated strongly with age. For all ages, skin roughness showed a positive correlation with age on the unexposed, but not the exposed, site. On the hand site subjects aged 40 years and older had significantly smoother skin than those aged less than 40 years, as measured by one roughness parameter. On the back, the older group had significantly rougher skin than the younger group measured by two roughness parameters. We propose that on the back of the hands, solar damage reverses or reduces the increase in roughness which would otherwise be caused by intrinsic ageing.

Repair of UV light-induced DNA damage and risk of cutaneous malignant melanoma.

The mechanism underlying the role of UV light exposure from sunlight in the etiology of cutaneous malignant melanoma (CMM) is unclear. Patients with xeroderma pigmentosum, a disease characterized by severe sensitivity to UV radiation and a defect in nucleotide excision repair, have a high incidence of CMM, which suggests that DNA repair capacity (DRC) plays a role in sunlight-induced CMM in the general population as well. We conducted a hospital-based case-control study of DRC and CMM among 312 non-Hispanic white CMM patients who had no prior chemotherapy or radiation therapy, and 324 cancer-free control subjects who were frequency-matched to case patients on age, sex, and ethnicity. Information on demographic variables, risk factors, and tumor characteristics was obtained from questionnaires and medical records. We used the host-cell reactivation assay to measure the DRC in study subjects' lymphocytes. All statistical tests were two sided. Case patients had a 19% lower mean (+/- standard deviation [SD]) DRC (8.5 +/- 3.4%) than control subjects (10.5 +/- 5.1%), a statistically significant difference (P<.001). DRC that was at or below the median value (i.e., 9.4%) in control subjects was associated with increased risk for CMM after adjustment for age, sex, and other covariates (odds ratio [OR] = 2.02, 95% confidence interval [CI] = 1.45 to 2.82). We observed a dose-response relationship between decreased DRC and increased risk of CMM (P(trend)<.001). Patients with tumors on sun-exposed skin had statistically significantly lower DRC than patients with tumors on unexposed skin (8.2 +/- 3.3% versus 9.5 +/- 3.5%; P =.004). Reduced DRC is an independent risk factor for CMM and may contribute to susceptibility to sunlight-induced CMM among the general population.

IL-4 Expression by Neutrophils in Psoriasis Lesional Skin upon High-Dose UVB Exposure

Background: Upon a single high dose of UVB irradiation of psoriatic lesional skin, IFN-γ expression is decreased, whereas IL-4 expression is enhanced. A similar type 1 to type 2 shift was found in dermal T cells derived from irradiated lesional skin as compared to unexposed lesional psoriatic skin. We have found recently that the IL-4 protein detected in situ upon UVB exposure of normal skin was not associated with T cells but with infiltrating neutrophils. Objective: To determine which cell types express IL-4 in psoriatic skin after UVB irradiation. Methods: Skin biopsies were obtained from healthy controls and psoriasis patients before and after local UVB exposure. Double immunohistochemical stainings were performed to determine the identity of IL-4-expressing cells. Results: In the irradiated skin of both healthy controls and patients, IL-4-positive cells coexpressed elastase and CD15, but not CD3. Conclusion: IL-4-expressing cells found in psoriatic skin after a single high-dose UVB exposure appeared to be neutrophils.

A commercial sunscreen's protection against ultraviolet radiation-induced immunosuppression is more than 50% lower than protection against sunburn in humans.

Ultraviolet radiation (280-400 nm)-induced suppression of cutaneous cell-mediated immunity plays an important part in the development of skin cancer. Sunscreens are widely advocated to protect against skin cancer but if they offer insufficient protection against immunosuppression they may inadvertently increase skin cancer risk. This human study evaluated immunoprotection afforded by a commercial sunscreen preparation (labeled sun protection factor 15) offering primarily ultraviolet B (280-320 nm) protection. Indirectly, it also investigated whether ultraviolet A (320-400 nm) plays a part in ultraviolet radiation-induced immunosuppression. Healthy white-skinned volunteers were used (n=119). Ultraviolet radiation exposures were on previously unexposed buttock skin with an ultraviolet radiation source that complied with European recommendations for sunscreen testing. Ultraviolet radiation dose-response curves for sunburn/erythema and suppression of the contact hypersensitivity response were generated either with or without sunscreen in vivo and protection factors were derived for both end-points. The ultraviolet radiation wavelengths transmitted by the sunscreen were determined in vitro and showed that the sunscreen was primarily an ultraviolet B absorber, with relatively poor absorption in the ultraviolet A region. The sun-screen protected against both erythema and immunosuppression but protection against immunosuppression (IPF=4.9, 95% confidence interval: 2.3-10.6) was less than half that for erythema (Ery-PFg=14.2, 95% confidence interval: 10.2-19.8). Failure of the sunscreen to afford comparable protection against both end-points was probably due to immunosuppression by ultraviolet A, a part of the solar spectrum that does not readily cause sunburn. The sunscreen protected against both end-points, which supports the use of sunscreens to reduce immunosuppression but protection against immunosuppression may be improved if sunscreens are formulated to offer equivalent protection against ultraviolet B and ultraviolet A.

Clinical Snippets

Hair regrowth after chemotherapy or alopecia areata commonly results in white hair. In mice treated with cyclophosphamide, Sharvov et al (p. 27) showed Fas ligand mediated melanocyte apoptosis. Melanocyte migration accompanied the recovery phase, suggesting new paradigms for treating disorders with hypopigmentation. These studies also suggest a mechanism for the hyperpigmentation of the nail bed seen with antimetabolite therapy. Endemic pemphigus foliaceus in Brazil, Fogo Selvagem, is associated with IgG antibodies against desmoglein-1 in all affected individuals and, surprisingly, half of the normal subjects living in endemic regions (Warren et al, p. 104). The clinically affected individuals and those only with antibodies differed from those with the disease by having an increased anti-desmoglein1 IgG4 level. This two-stage model for disease suggests that preventing the IgG1 to IgG4 conversion might prevent clinical disease. From Star Wars to skin tumor treatment, lasers are usually destructive devices. Yu and co-workers (p. 56) emphasize the “biostimulation” of the low energy Helium–Neon (632.8nm) laser. Basic fibroblast growth factor was induced from fibroblasts and keratinocytes and media from these irradiated cells stimulated melanocyte proliferation and migration. Thirty patients with segmental vitiligo were treated with the laser and 60% of those treated had greater than 50% repigmentation. Further studies of this treatment, especially in those recalcitrant to other forms of treatment, will be of interest. In Doctor's Dilemma, one of Shaw's characters spouts, “Stimulate the phagocytes”; some day we may shout “stimulate the melanocytes”. Prudent sunbathers – possibly an oxymoron – can avoid acute sunburn but have immunosuppression. Kelly and colleagues (p. 65) studied unexposed buttock skin of 119 white-skinned volunteers from 18–35 years for both sun-protective factor responses and the ability to be immunized with dinitrochlorobenzene. Sun Protection Factors (SPF) and Immune Protective Factors (IPF) were calculated. Although the acute sunburn response from simulated sunlight could be suppressed with commercial sunscreen, there was still immunosuppression – possibly due to unfiltered UVA. This study has important implications for the health of the public and those concerned with optimum sunscreen composition and usage and understanding the epidemiology of skin malignancies. Beta-endorphin, a peptide, is the endogenous ligand for the alpha-opiate receptor that stimulates the production of cytokeratin 16, a cytokeratin associated with wound healing and epidermal proliferation in organ culture (Bigliardi et al, p. 145). Beta-endorphins induced fibroblast and capillary proliferation in animal models. These peptides, opiates themselves and modulators of the receptors, may lead to new treatments for chronic wounds. Opiate antagonists might have roles in treating keloids or preventing hypertrophic scars. Watch Fido jump.

The mutagenic effect of ultraviolet-A1 on human skin demonstrated by sequencing the p53 gene in single keratinocytes.

Sun exposure is accepted as the major risk factor for developing skin cancer, the most common cancer in the western world. Ultraviolet-B (UV-B) radiation is considered the causative agent, but recently several findings suggest a role also for ultraviolet-A (UV-A) radiation. Repeated suberythemal doses of ultraviolet-A1 (UV-A1) on healthy human skin induce an increase of p53 immunoreactive cells in epidermis, which may indicate cell cycle arrest and/or occurrence of p53 mutations. We have investigated the possible mutagenic effect of UV-A1 on skin by sequencing exons 4-11 and adjacent intron sequence of the p53 gene in immunoreactive single cells from three healthy individuals. Previously unexposed buttock skin was irradiated three times a week for 2 weeks with physiological fluences (40 J/cm2) of UV-A1. Punch biopsies were taken before and at different time-points after the exposure, and from these single p53 immunoreactive cells were isolated by using laser-assisted microdissection. Three mutations--all being indicative of oxidative damage and most likely related to UV-A exposure--were found among the 37 single cells from exposed skin, whereas no mutations were found in the 22 single cells taken before exposure. The findings indicate a mutagenic effect of low-dose UV-A1 on healthy human skin, which further demonstrates the importance of considering UV-A when taking protective measures against skin cancer.

Evaluation of respiratory and cutaneous doses of chlorothalonil during re-entry in greenhouses

Five female workers were monitored for 5 consecutive days during re-entry into a greenhouse containing ornamental plants. Skin contamination (excluding hands) was evaluated with nine pads of filter paper placed on the skin. Hand contamination was assessed by washing with 95% ethanol. Respiratory exposure was evaluated by personal air sampling. The respiratory dose was based on a lung ventilation of 15 l/min. The doses absorbed were estimated assuming 10% skin absorption and 100% lung retention. Dislodgeable foliar residue was determined on days of re-entry to evaluate the decay of chlorothalonil. Chlorothalonil was analysed in the different matrices by GC–MS. Respiratory exposure was less than skin contamination, being 11.4±5.1% (mean±SD) of total exposure. The estimated total absorbed dose did not exceed the acceptable daily intake of 0.03 mg/kg body mass. The hands and unexposed skin of all workers were always found to be contaminated. Greater precautions are therefore needed to reduce skin exposure (clean gloves and suitable clean clothing every day).

Ultraviolet radiation-induced erythema in human skin

We have evaluated UVR-induced erythema in previously unexposed buttock skin of volunteers of skin types I, II, III, and IV. Studies were done with solar-simulated radiation (SSR), UVB, and UVAI and we determined the just perceptible minimal erythema dose (MED) and, in some cases, quantified erythema with a reflectance device. The results show that there is a trend for increased SSR MED with skin type, with the MED of skin type IV being approximately twice that of skin type I, a smaller difference than one might have expected. However, there is a very considerable overlap of MED between skin types which shows that MED is a very poor indictor of skin type. Quantitative dose–response and time course studies with SSR and UVAI showed broadly similar responses when comparable MED-based exposures were given. We used our data to test the new concept of the standard erythema dose (SED) with two different erythema action spectra, and confirmed that the SED approach works with the different UVR sources that we studied.

Repeated Ultraviolet Exposure Affords the Same Protection Against DNA Photodamage and Erythema in Human Skin Types II and IV but is Associated with Faster DNA Repair in Skin Type IV

We have investigated the photoprotective properties of induced pigmentation using erythema and epidermal DNA photodamage as endpoints. Previously unexposed buttock skin of 12 young, healthy adults (six skin type II and six skin type IV) was exposed daily (Monday to Friday) for 2 wk (days 1-12) with 0.65 minimal erythema dose of solar simulated radiation. Mean skin type IV minimal erythema dose was 1.8-fold greater than for skin type II. Compared to skin type II, solar simulated radiation treatments produced less erythema and more tanning in skin type IV. To assess DNA photodamage, biopsies were taken and prepared for paraffin sections that were stained with a monoclonal antibody for thymine dimers. Thymine dimers were quantified by image analysis. The single exposure data (0.65 and 2 minimal erythema dose) showed that DNA damage was related to physical dose (J per cm2) independent of skin type. Our data also showed that DNA photodamage accumulates in both skin types with repeated, suberythemal doses of solar simulated radiation. On day 12, there were more thymine dimers in skin type IV than skin type II, again indicating that physical rather than biologic dose determines the level of DNA damage. Comparisons on days 12 and 19, however, showed a much greater loss of thymine dimers in skin type IV, suggesting better thymine dimer repair. Protection factors for erythema and thymine dimers were calculated and shown to be about 2 in both skin types. This provides further indirect evidence that DNA is a chromophore for erythema, but also suggests that a tan may not be the major factor in natural photoprotection.

Epidermal Langerhans Cell Depletion After Artificial Ultraviolet B Irradiation of Human Skin In Vivo: Apoptosis Versus Migration

Ultraviolet B radiation can suppress cellular immunity. One of the mechanisms related to this immunosuppression is the disappearance of Langerhans cells from the epidermis. The aim of this study was to establish the mechanism of ultraviolet B-induced Langerhans cell disappearance in healthy individuals. The two most likely mechanisms for Langerhans cell disappearance are apoptosis and migration. Apoptosis was assessed in vivo by exposing buttock skin of 10 healthy volunteers to six minimal erythema doses of ultraviolet B. Only very few apoptotic Langerhans cells could be observed in sections from the ultraviolet B-exposed skin. Migration of Langerhans cells cannot be established in skin sections and suction blisters were therefore raised in an attempt to trap migrating Langerhans cells in the sub-basal membrane blister fluid. Blisters were raised on the flexor side of the lower arm of 30 healthy volunteers at several time points after exposure of the skin to six minimal erythema doses of ultraviolet B. Blister fluid was collected and blister roofs were removed to check for Langerhans cell disappearance. Langerhans cells were detected in the blister fluid of the ultraviolet B-exposed skin and not of the unexposed skin. The number of Langerhans cells in the blister fluid peaked at about 18 h after ultraviolet exposure, which coincided with the largest depletion of Langerhans cells in the blister roof. A fraction (20-30%) of the Langerhans cells in the blister fluid stained positive for DNA damage (cyclobutyl pyrimidine dimers), showing that they originated from the epidermis. Ultraviolet B-induced Langerhans cell disappearance appears to be mainly attributable to migration.