Objective measurement of minimal erythema and melanogenic doses using natural and solar-simulated light

Very little information exists on the amount of natural and artificial UV light required to cause sunburn and tanning in individuals with very pale skin who are at the greatest risk of developing skin cancer. We have investigated minimal erythema dose (MED) and minimal melanogenic dose (MMD) in a group of 31 volunteers with Fitzpatrick skin types I and II using an Oriel 1000 W xenon arc solar simulator and natural sunlight in Sydney, Australia. We measured the erythemal and melanogenic responses using conventional visual scoring, a chromameter and an erythema meter. We found that the average MED measured visually using the artificial UV source was 68.7 +/- 3.3 mJ/cm2 (3.4 +/- 0.2 standard erythema doses [SED]), which was significantly different from the MED of sunlight, which was 93.6 +/- 5.6 mJ/cm2 (P < 0.001) (11.7 +/- 0.7 SED). We also found significant correlations between the solar-simulated MED values, the melanin index (erythema meter) and the L* function (chromameter). The average MMD (obtained in 16 volunteers only) using solar-simulated light was 85.6 +/- 4.9 mJ/cm2, which was significantly less than that measured with natural sunlight (118.3 +/- 8.6 mJ/cm2; P < 0.05). We mathematically modeled the data for both the chromameter and the erythema meter to see if we were able to obtain a more objective measure of MED and differentiation between skin types. Using this model, we were able to detect erythemal responses using the erythema index function of the erythema meter and the a* function of the chromameter at lower UV doses than either the standard visual or COLIPA methods.     

Dose response for UV-induced immune suppression in people of color: differences based on erythemal reactivity rather than skin pigmentation.

Ultraviolet radiation (UVR) is known to suppress immune responses in human subjects. The purpose of this study was to develop dose responses across a broad range of skin pigmentation in order to facilitate risk assessment. UVR was administered using FS 20 bulbs. Skin pigmentation and UVR sensitivity were evaluated using Fitzpatrick classifications, minimal erythemal dose (MED), slope of the erythemal dose response curve (sED), baseline pigmentation and tanning response. To assess immune responses dinitrochlorobenzene (DNCB) was applied to irradiated buttock skin 72 h after irradiation. Two weeks later DNCB was applied to the inside upper arm. Skin thickness was measured before and after challenge. Dose response was modeled (to obtain a regression line) for the entire group of 185 subjects. With the exception of sED none of the above-mentioned pigmentation indicators contributed significantly to variability around the regression line. Thus, differences in sensitivity for multiple skin types based on Fitzpatrick classification or MED were not observed. However, differences in immune sensitivity to UVR were detected between subjects with steep erythemal dose response curves and those with moderate or flat responses. For subjects with steep erythemal responses the dose calculated to suppress the immune response by 50% was 114 mJ/cm2. This group included individuals with Fitzpatrick skin types I-V, MED for these subjects ranged from 30 to 80 mJ/cm2. The 50% suppression dose for subjects with weak or no erythemal response could not be computed (the dose response was flat). This resistant group included subjects with skin types IV-VI and MED for these subjects ranged from 41 to > 105 mJ/cm2. This study provides a human dose response for UVR suppression of contact sensitivity that will be useful in risk assessment. It is the first study to provide this information using the FS sun lamp and is the first study to include people of color. The sED appears to be a new variable for identifying sensitive subjects at risk of UVR-induced immune suppression.     

Reference limits for erythema-effective UV doses

Diagnostic phototesting, including the determination of the minimal erythema dose (MED), is a useful procedure to detect abnormal sensitivity to UV radiation. We aimed to estimate the reference limits (RLs) of the MED in a reasonably large reference sample of white individuals. Skin phototypes and MED values for broadband UVB and for UVA were determined in 461 white subjects. When appropriate, the 95% reference intervals, including the 0.025 fractile and 0.975 fractile, were computed for the MED-UVB reference values (by means of parametric methods) and the MED-UVA reference values (by means of nonparametric methods). MED data were also converted to standard erythema doses (SEDs). As described elsewhere we observed a considerable overlap of MED values for all skin phototypes and confirmed that age and sex do not substantially influence the MED. The lower RLs observed for MED-UVB were 33 mJ cm(-2) (0.5 SEDs) and for MED-UVA 12.6 mJ cm(-2) (1.2 SEDs). The MED and SED findings from this investigation may serve as reference data for white individuals and give support to the clinician in differentiating between normal and pathologically abnormal photosensitivity. Although the MED data given here are limited to the phototest device used in the present study, the SED results establish comparability between our data and phototest results obtained from laboratories using different UV sources.     

Hyperpigmentation induced by topical 5-aminolaevulinic acid plus visible light

Photodynamic therapy (PDT) with 5-aminolaevulinic acid (ALA) is an alternative tool for the treatment of superficial non-melanoma skin cancers. Recently ALA-PDT has been employed with encouraging results also for warts, condylomata and psoriasis. In this study the effects of topical ALA plus irradiation with visible light on intact human skin have been evaluated. Five skin areas (A, B, C, D, and E) on the inner upper part of the arms of five healthy volunteers (skin types III and IV) were treated with (A) ALA 20% in base cream without irradiation, (B) only the vehicle (base cream) without ALA, (C, D and E) ALA cream at the concentrations of 5, 10 and 20%, respectively; all treatments were applied with an occlusive dressing. Four hours after ALA or vehicle application areas B, C, D and E were irradiated with a fixed dose of 40 J/cm(2). ALA penetration through the intact skin was evaluated by in vivo fluorescence determination. The effects on healthy skin were evaluated by clinical and chromometric examinations, light microscopy, immunohistochemistry and electron microscopy. RESULTS: (1) in vivo fluorescence demonstrated that ALA is able to penetrate through the intact skin, when applied with occlusive dressing and induces a classical fluorescence peak due to Protoporphyrin IX (PpIX) formation, which is the active photosensitiser. (2) Skin areas receiving ALA plus irradiation showed erythema and swelling just after the irradiative session and hyperpigmentation 48-72 h later. (3) Colourimetric data confirmed significant skin colour changes: values a* (representing the erythematous changes) increased only on the skin areas where ALA+irradiation were applied and during the 48 h after irradiation, thereafter a* began to decrease; values L* (pigmentation) increased during the 2 weeks following treatment. (4) Histopathological, immunohistochemical (S100, HMB-45) and electron microscopic findings showed an absolute increment of the number of melanocytes, which appeared clearly activated. In conclusion the application of ALA cream followed by irradiation is able to induce a pigmentation response in healthy human skin, at least in skin types III and IV. This melanocytic activation could have a potential for the treatment of skin disorders characterised by hypopigmentation.     

A comparative pilot study on ultraviolet-induced skin changes assessed by noninvasive imaging techniques in vivo

The effects of acute and chronic ultraviolet (UV) on the morphology of human skin have been extensively studied ex vivo by means of histological investigations. However, innovative skin imaging techniques enable visualization of micromorphological structures in vivo. We aimed to perform a correlation study evaluating in vivo dose and time dependent skin changes following solar-simulated irradiation using noninvasive techniques such as optical coherence tomography (OCT) and confocal laser scanning microscopy (CLSM). The forearms of 10 healthy subjects were exposed to 1 minimal erythema dose (MED) and 3 MED of solar-simulated radiation. Noninvasive measurements were performed before and 24 h and 72 h after UV exposures. We demonstrate definite OCT and CLSM findings obtained from UV-exposed skin, including an increase in epidermal thickness (hyperproliferation, acanthosis), a reduction in dermal reflectivity (dermal edema), an increase in brightness of the basal layer (pigmentation), and an increase in vessel diameter within the dermal papillae (vasodilatation). A moderate to strong linear association between the methods employed was observed. In conclusion, noninvasive high-resolution imaging techniques such as OCT and CLSM may be promising tools for photobiological studies aimed at assessing photoadaptive and/or phototoxic processes in vivo. However, larger studies are needed to demonstrate the applicability of the findings presented in this pilot study.     

Ultrasound measurements of skin thickness after UV exposure: a feasibility study

High-frequency ultrasound images were used to measure the thickness of the dermis and epidermis of four human subjects. These measurements were performed before and after a single exposure to ultraviolet radiation (UV). Doses ranging from 0.5 to 3 minimal erythema doses (MED) were delivered to the skin of the back of four human subjects, and thickness measurements were made over a period of 16 days. We found: (1) exposures > or = 2 MED caused a 10-30% increase in the thickness of the dermis-epidermis layer; (2) the thickening response was not always in direct proportion to the UV dose; (3) maximum thickening response time was 48 h for the 2.8-3.0 MED exposure levels; (4) "diffusion" or spreading of the thickening response to neighboring areas occurred in some cases, as far as 4 cm from the exposed region (center-to-center), with changes ranging from 12% to 17%; (5) decreased thickness of the dermis-epidermis layer of up to 12% was observed for 3 out of 4 of the subjects.     

Salt water bathing prior to UVB irradiation leads to a decrease of the minimal erythema dose and an increased erythema index without affecting skin pigmentation

The combination of salt water baths and solar radiation is known as an effective treatment for patients with psoriasis and atopic dermatitis. To determine whether increased susceptibility to UVB radiation may contribute to this therapeutic effect we have studied the effect of bathing the skin in salt water prior to UVB irradiation. Twelve subjects were phototested on the volar aspects of their forearms with increasing doses of UVB radiation. One forearm was exposed to 5% salt water prior to irradiation. The minimal erythema dose (MED) was determined and the erythema index and skin pigmentation were assessed by photometric measurement. The combination of salt water bath and irradiation yielded a significant decrease of the MED when compared to UVB alone (median 90 mJ/cm2 vs 130 mJ/cm2, P < 0.01). Analysis of variance showed a significant influence of salt water bath on erythema (P < 0.05) but not on skin pigmentation. Within the MED test area the erythema index of the salt water exposed forearms was elevated significantly (P < 0.05) while skin pigmentation was not affected. Thus, bathing the skin in salt water leads to a decreased threshold level for the elicitation of UVB-induced erythema and a selective increase of the erythemal response. This sensitization to the effects of shortwave UVB radiation may increase immunosuppressive effects of UVB radiation and may lead to an increased efficacy of UVB phototherapy. However, there is also an increased sunburn risk when salt water baths are followed by exposure to UV radiation.     

Relationship between Skin Color and Sun Exposure History: A Statistical Classification Approach

In this study our aim was to determine the biophysical values of constitutive skin color in Caucasians and to define the correlation between skin color and phototype assessed according to the Fitzpatrick method. Constitutive skin color was measured on the buttock, with a Minolta CR-200 colorimeter, in a population of 557 consecutive subjects belonging to phototype categories I, II, III and IV. The colorimeter expresses the results in five different color systems. We used the “Yxy” and L*a*b* systems, which are the most widespread in dermatology. Statistical analysis of the data showed that the “Yxy” system is even more discriminant than the L*a*b* system when the Fitzpatrick classification scheme is adopted as the reference and shows a poor ability to correctly classify the intermediate phototypes (II and III). On the contrary the “Yxy” system performs well in distinguishing phototypes I and IV. To establish whether this low discriminating capacity for phototypes II and III is related to a low discriminating capacity of the method suggested by Fitzpatrick or by our procedure, an objective technique (minimal erythemal dose) should be used to evaluate the percentage errors of classification of both the Fitzpatrick method and instrumental measurement of skin color. The results of such a study are extremely important because the evaluation of skin color is objective, simple and has potential applications in dermatology and cosmetology.     

UV-induced unscheduled DNA synthesis in human skin: dose response, correlation with erythema, time course and split dose exposure in vivo

Unscheduled DNA synthesis (UDS) has been shown to be saturated above a threshold dose of UV-C in human fibroblasts in vitro. We have investigated by autoradiography whether a similar saturation occurs in human skin in vivo with UV-B and whether this phenomenon correlates with the erythemal response. In addition, we determined the time course of UDS at 24 h after exposure and the effect of dual exposures separated by 24 h. The dose-response curve was established by exposure to 1/16, 1/8, 1/4, 1/2, 1, 2, 3, 4 and 6 MEDs UV-B. For the time-course study, areas exposed to 1/2 and 2 MEDs were biopsied after 1, 3, 6, 12 and 24 h. Autoradiography was performed in vitro. The dose-response curve showed a significant increase in UDS from 1/16 to 1 minimal erythema dose (MED), whereas no significant difference was observed between 1 MED and the higher UV-B doses tested. The 24 h time sequence revealed a gradual decrease in UDS activity. The 1/2 MED curve declined more rapidly and reached the zero-level between 12 h and 24 h, whereas about 50% of the initial UDS value was still retained 24 h after 2 MEDs. The dual-dose study revealed that a second hit of fractions of the MED resulted in lower levels of UDS than induced by these fractions alone in previously untreated areas. UDS increases with the erythemal dose between 1/16 and 1 MED. It reaches a plateau after 1 MED and cannot be increased by doses up to 6 MEDs, suggesting a saturation of excision repair in vivo. Time course studies support such a saturation phenomenon. The failure to increase significantly UDS by a second irradiation 24 h after the first exposure needs further clarification. Since persistence of DNA lesions may lead to an accumulation after repeated exposures, additional mechanisms other than excision repair may protect human skin by error-free removal of possibly mutagenic sites. Photoreactivation may be important in this respect.     

Standardization of In Vitro Macrophotography for Assessment of Cutaneous Responses

The increased popularity of commercially available three-dimensional human skin equivalents in recent years has allowed for assessment of melanogenesis modulated by compounds topically applied to the skin or directly incorporated from the medium. These skin equivalents provide a suitable model for elucidating the mechanisms of action of various factors that modulate skin pigmentation or other properties of the skin. As such, researchers need to objectively quantify cutaneous responses at the macroscopic level. A simple method to standardize macrophotography images is reported that can quantify cutaneous responses in human skin equivalents of Asian, Black or African American, and Caucasian or White racial/ethnic origin. Macrophotographs are analyzed using the Commission Internationale de l'Eclairage L * a * b * color space system in combination with a personal computer and image editing software. Pigmentation changes monitored over a 9 day period showed a high correlation with melanin content evaluated in Fontana–Masson-stained sections. These results indicate the feasibility of using a macrophotography setup in a sterile tissue culture environment to objectively assess in vitro cutaneous responses in human skin equivalents. This serves as an adjunct tool to biochemical and morphological methods to effectively quantify changes in pigmentation over time.     

Lower body anatomical distribution of solar ultraviolet radiation on the human form in standing and sitting postures

Humans undertake their daily activities in a number of different postures. This paper aims to compare the anatomical distribution of the solar erythemal UV to human legs for standing and sitting postures. The exposure ratios to the legs (ratio of the UV exposure to a particular anatomical site compared to the ambient) have been measured with UV dosimeters for standing and sitting postures of a manikin. The exposure ratios for the legs ranged from 0 to 0.75 for the different anatomical sites for the sitting posture in summer (December through February) compared to 0.14 to 0.39 for the standing posture. In winter (June through August) the exposure ratios ranged from 0.01 to 0.91 for sitting to 0.17 to 0.81 for standing. For the anterior thigh and shin, the erythemal UV exposures increased by a factor of approximately 3 for sitting compared to standing postures. The exposure ratios to specific anatomical sites have been multiplied by the ambient erythemal UV exposures for each day to calculate the annual exposures. The annual erythemal exposures to the anterior thigh and ankle were predicted to be higher than 800 MED for humans sitting outdoors each day between noon and 13:00 h Australian Eastern Standard Time (EST). For humans standing outdoors during this time, the annual erythemal UV exposure averaged over each leg site was 436 MED, whereas, the averaged annual erythemal UV exposure was 512 MED for the sitting posture. Similarly, the annual erythemal UV exposure averaged over each of the sites was 173 MED for humans standing outdoors between 09:00 h EST and noon each Saturday morning and 205 MED for humans sitting outdoors during this time. These results show that there is increased risk of non-melanoma skin cancer and malignant melanoma to the lower body if no UV preventative strategies are employed while in a sitting posture compared to a standing posture.     

Adaptation of the human skin by chronic solar-simulating UV irradiation prevents ultraviolet-B irradiation-induced rise in serum C-reactive protein levels

Exposure of the skin to UV radiation induces local inflammation. We hypothesized that inflammation induced by erythemal UV-B irradiation could elevate levels of serum C-reactive protein (CRP) and that suberythemal repeating doses of solar-simulating UV radiation (SSR) would produce photoadaptation to such inflammation. Separation-free high-sensitivity assays of CRP show an increase by 42% (P = 0.046) in CRP concentrations in healthy human subjects 24 h after a 3 minimal erythemal dose (MED) dose of UV-B delivered onto a 100 cm2 skin area. Preceding daily suberythemal doses of whole-body SSR for 10 or 30 consecutive days completely prevented the CRP increase. UV-B-induced skin erythema was partially attenuated by 30 preceding days of SSR only (P = 0.00066). After 10 daily SSR doses, the mean baseline CRP concentrations (0.24 +/- 0.21 mg/L) declined by 35% (P = 0.018). Using high-sensitivity analysis of serum CRP as the endpoint marker for cutaneous inflammation, we show that acute exposure of even a relatively small skin area to erythemal UV-B induces skin inflammation detectable also at the systemic level and that photoadaptation by preceding repeating suberythemal doses of SSR reduces signs of inflammation. Our data complement the view given by previous studies in that local photoadaptation also has systemic manifestations.     

Tanning in Human Skin Types II and III Offers Modest Photoprotection Against Erythema

We have investigated the photoprotective properties of tanning using erythema as an endpoint. Previously unexposed buttock skin sites of 16 young, healthy adults (8 skin type II, and 8 skin type III) were exposed daily (Mon-Fri) for 2 weeks to 0.5 and 0.75 minimal erythema doses (MED) of solar-simulated radiation (SSR). Erythema and melanin levels were assessed daily both visually and quantitatively using a reflectance device. One week after the last tanning treatment, MED reassessments were made on pretreated sites and on adjacent nontreat-ed sites, including sites from which stratum corneum was removed by tape stripping. Compared to skin type II, similar daily SSR treatments produced less erythema and more evident tanning in skin types III. Independent of skin type, all volunteers showed an increased MED value when assessed on the 0.75 MED- and 0.5 MED-treated sites compared to the MED value assessed on adjacent untreated sites. We express any increase in MED as an induced protection factor (IPF), i.e. (MED post-tan/MED pre-tan). Our data show mean IPF of 1.4 and of 2.1 in the 0.5 and 0.75 MED-treated sites respectively, in skin types II. Similar values were obtained in skin types III with IPF of 1.5 and 2.3 for the 0.5 and 0.75 MED-treated sites, respectively. In all cases, removal of the stratum corneum lowered the IPF by about 20%. Our results show that SSR-induced melanogenesis, whether in skin type II or III, offers only moderate protection against erythema and suggest that SSR-induced stratum corneum thickening affords less photoprotection than tanning.     

ULTRAVIOLET ERYTHEMA SENSITIVITY IN ANAMNESTIC (I-IV) and PHOTOTESTED (1–4) CAUCASIAN SKIN PHOTOTYPES: THE NEED FOR A NEW CLASSIFICATION SYSTEM

Abstract— The anamnestic skin phototypes (ASP) I-IV^1,2 of 21 Caucasian volunteers were compared with their phototested skin phototypes (PSP) using solar simulating, broadband UV radiation. The Commission Internationale de' éclairage (CIE)-weighted (i.e. erythemally effective) minimal erythema doses (MED) for solar simulating radiation varied from 20 mJ/cm² (PSP type 1) to 57 mJ/cm² (PSP type 4). In only 11 of 21 volunteers did the ASP (I-IV) and PSP (1–4) classifications coincide, and the MED values of the volunteers within the different ASP groups (I-IV) overlapped considerably. To compare the reactivity to erythematogenic radiation of different wavelengths, narrowband monochromator irradiations were performed at 298 nm, 310 nm and 330 nm. The CIE-weighted MED values at these wavelengths (20–80 mJ/cm²) corresponded well with those obtained in the broadband testing. Our results indicate that, with classification by interrogation, Caucasian skin can reliably be classified into only two subtypes, corresponding to Fitzpatrick phototypes I–III and phototype IV, respectively. A classification into four sensitivity types can be achieved by phototesting, only. We propose that the concept of ASP should be used with caution. The concept of PSP 1–4 should be favored.     

Transmission of UV-radiation through human epidermal layers as a factor influencing the minimal erythema dose

Abstract— The extent to which transmission of human Caucasian epidermis and stratum corneum influences the Minimal Erythema Dose (MED) was examined for UV-B and UV-C.
Transmission correlated well with variations in MED for UV-B and UV-C that exist between individuals, as measured on the skin of the lower back and anterior upper leg.
Regional differences of the MED that occur within the same individual between different parts of the body, were related less well to differences in transmission. For UV-B, the difference in transmission of stratum corneum and epidermis between upper leg and lower back was on the average too small to completely account for the difference in MED UV-B. Other parameters, therefore, have to be involved in determining such regional variations in MED UV-B. For UV-C, on average, the difference in transmission of stratum corneum was smaller and of epidermis larger than the difference in MED UV-C between upper leg and lower back, though the deviations were not significant.
A series of UV-B irradiations of the lower back resulted in an increase in MED UV-B and MED UV-C, which was paralleled by a decrease in transmission of stratum corneum and epidermis. The average decrease in UV-B transmission of stratum corneum was too small and that of epidermis somewhat too large to account for the average increase in MED UV-B. The average decrease in UV-C transmission of stratum corneum was about as large as the average increase in MED UV-C. Consequences of these observations for the location of the primary reactions leading to erythema are discussed.
The relationship between log MED UV-C and log MED UV-B was confirmed to be approximately linear.     

Skin Responses to Micro Scale Field Size of Solar‐Simulated Radiation – Preliminary Evaluation by Reflectance Confocal Microscopy in vivo

Erythema and pigment responses of human skin following an acute exposure to ultraviolet radiation (UVR) are frequently used to determine the photosensitivity of the skin. In this study we investigated the responses of the skin to a micro‐scale area of UVR exposure (MiR) and compared the responses to a macro‐scale area of exposure (MaR). Ten human volunteers were tested with solar‐simulated radiation on their upper arm or back using a beam size of 8 mm and 0.2 mm in diameter. The fluence required to produce a minimally perceptible erythema (MED) using the MiR was found to be higher than that for the MaR. The erythema response extended beyond the exposed area and this became pronounced when the beam size was microscopic. Reflectance confocal microscopy in vivo revealed that MiR induced cellular alterations within a confined area of smaller dimensions than the area of exposure. Pigment responses were confined within the areas of cellular damage. The erythema expression of exposed skin recovered faster for the sites receiving MiR even when the applied fluence was higher than the MED for the MaR. Through the use of MiR we were able to visualize spatially dissimilar skin responses of erythema and pigmentation suggesting different cellular mechanisms.     

In vitro model of vitamin D3 (cholecalciferol) synthesis by UV radiation: dose-response relationships

Vitamin D deficiency is a major health concern worldwide. Very little is understood regarding its production in the human body by exposure to UV radiation. In particular, we have no means of predicting how much vitamin D (cholecalciferol) will be produced in the skin after exposure to sunlight. Using a refined in vitro model, we found that there is a nonlinear relationship between UV dose and cholecalciferol synthesis. Two minimal erythemal doses (MED) of UV radiation produced 1.84 microg/mL of cholecalciferol whereas 4 MED produced 2.81 microg/mL. We also found that the production of cholecalciferol is restricted by the initial concentration of its precursor (7-dehydrocholesterol, 7-DHC). For example, using an initial concentration of 7-DHC of 102 microg/mL, the resultant cholecalciferol production was 1.05 microg/mL after receiving 4 MED exposure. Under the same exposure conditions, an initial concentration of 305 microg/mL yielded 2.81 g/mL of cholecalciferol. The data presented in this paper has important implications for humans, including: (1) increasing UV exposure does not result in a proportionate increase in the amount of cholecalciferol that is produced; and (2) the initial concentration of 7-DHC in the skin may impact the amount of cholecalciferol that can be synthesized. When translating these results to population groups, we will discuss how the sun exposure message needs to be carefully formulated to account for such considerations.     

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.     

The effects of grape seeds polyphenols on SKH-1 mice skin irradiated with multiple doses of UV-B

The study investigated the protective activity of red grape seeds (Vitis vinifera L, Burgund Mare variety) (BM) extracts in vivo on multiple doses of ultraviolet radiation (UV)-B-induced deleterious effects in SKH-1 mice skin. Eighty 8-weeks-old female SKH-1 mice were divided into 8 groups: control, vehicle, UV-B irradiated, vehicle+UV-B irradiated, BM 2.5mg polyphenols (PF)/cm(2)+UV-B irradiated, BM 4 mg PF/cm(2)+UV-B irradiated, UV-B+BM 2.5mg PF/cm(2), UV-B+BM 4 mg PF/cm(2). The extract was applied topically before or after each UV-B exposure (240 mJ/cm(2)), for 10 days consecutively. The antioxidant activity of BM extract is higher than gallic acid (k(BM)=0.017, k(gallic acid)=0.013). Multiple doses of UV-B generated the formation of cyclobutane pyrimidine dimers (CPDs) and sunburn cells, increased glutathione peroxidase (GPx) and catalase (CAT) activities respectively glutathione (GSH) and IL-1β levels in skin. In group treated with 2.5mg PF/cm(2) before UV-B irradiation BM extract inhibited UV-B-induced sunburn cells, restored the superoxide dismutase (MnSOD) activity, increased insignificantly CAT and GPx activities and reduced IL-1β level. The BM 4.0 mg PF/cm(2) treatment decreased GSH level and reduced the percentage of CPDs positive cells in skin. Both doses of BM extract administered after UV-B irradiation increased the MnSOD and GPx activities and reduced the formation of sunburn cells in skin. Our results suggest that BM extract might be a potential chemo-preventive candidate in reducing the oxidative stress and apoptosis induced by multiple doses of UV-B in skin.     

Correlation between hue angle and lightness of light irradiated wood

The objective of this study was to investigate irradiation characteristics of Beech (Fagus crenata Blume), black locust (Robinia pseudoacacia L.), Japanese cedar (Cryptomeria japonica D. Don) and spruce (Picea abies Karst.) wood samples by sunlight, xenon light and mercury vapour light. The colour change of the samples was evaluated by CIE L*a*b* and L*h*c* colour co-ordinate systems. It was found that the samples showed a rapid colour change at the initial period of treatment but the rate of change decreased with treatment time. It was determined that neither xenon nor mercury lamp light can accurately simulate sunlight. A wide range of colour changes were caused by the applied light sources. In spite of this wide colour range a good linear correlation was found between the lightness and the colour hue. The coefficients of determination (R²) are between 0.7 and 0.96. Accordingly, this linear correlation gives the possibility of following the colour change during photodegradation by measuring only the lightness.