UVB Radiation (uvb + radiation)

Distribution by Scientific Domains

Selected Abstracts

"Ultraviolet spring" and the ecological consequences of catastrophic impacts

Charles S. Cockell
Asteroid and comet impacts cause ozone depletion. For the first time, we have quantified the photobiological characteristics of these events and speculate on some of the associated ecological consequences. Following the clearing of stratospheric dust after "impact winter", levels of damaging UVB radiation (280,315 nm) could increase by at least 100%, resulting in an "ultraviolet spring". Many of the taxa stressed by the cold and dark conditions of impact are the same that would be stressed by large increases in UVB radiation. Furthermore, depletion of dissolved organic carbon (DOC) by impact-induced acid rain would increase UVB penetrability into freshwater systems. Although an increase in UVB radiation is an attractive hypothesis for exacerbating the demise of land animals at the Cretaceous-Tertiary (K/T) boundary, e.g. dinosaurs, our calculations suggest the impact into rare sulphate-rich target rock may have prevented an ultraviolet spring in this case. If the K/T impact event had occurred in any other region on Earth, the stress to the biosphere would probably have been considerably greater. [source]

E6* oncoprotein expression of human papillomavirus type-16 determines different ultraviolet sensitivity related to glutathione and glutathione peroxidase antioxidant defence

Stéphane Mouret
Abstract:, Clinical observations of non-melanoma skin cancer in immunocompromised patients, such as organ transplant recipients, suggest co-operative effects of human papillomavirus (HPV) and ultraviolet (UV) radiation. The aim of the present study is to evaluate UV sensitivity and DNA damage formation according to antioxidant status in HPV16-infected keratinocytes. We used SKv cell lines, infected with HPV16 and well characterized for their proliferative and tumorigenic capacities. We showed that SKv cell lines presented various E6* (a truncated form of E6) RNA levels. We demonstrated that the higher oncoprotein RNA expression level was associated with a higher resistance to solar-simulated radiation, more specifically to UVB radiation and to hydrogen peroxide. Moreover, this high resistance was associated with a low oxidative DNA damage formation after UV radiation and was related to high glutathione content and glutathione peroxidase activities. Therefore, the results of our study suggest that E6* levels could modulate the glutathione/glutathione peroxidase pathway providing a mechanism to protect HPV-infected keratinocytes against an environmental oxidative stress, such as UV radiation. [source]

Modulation of the bacterial response to spectral solar radiation by algae and limiting nutrients

J. M. Medina-Sánchez
SUMMARY 1. The response of bacterial production (measured as [3H]TdR incorporation rate) to spectral solar radiation was quantified experimentally in an oligotrophic high-mountain lake over 2 years. Bacterial responses were consistent: ultraviolet-B (UVB) was harmful, whereas ultraviolet-A (UVA) + photosynthetically active radiation (PAR) and PAR enhanced bacterial activity. Full sunlight exerted a net stimulatory effect on bacterial activity in mid-summer but a net inhibitory effect towards the end of the ice-free period. 2. Experiments were undertaken to examine whether the bacterial response pattern depended on the presence of algae and/or was modulated by the availability of a limiting inorganic nutrient (phosphorus, P). In the absence of algae, [3H]TdR incorporation rates were significantly lower than when algae were present under all light treatments, and the consistent bacterial response was lost. This suggests that the bacterial response to spectral solar radiation depends on fresh-C released from algae, which determines the net stimulatory outcome of damage and repair in mid-summer. 3. In the absence of algae, UVB radiation inhibited bacteria when they were strongly P-deficient (mean values of N : P ratio: 46.1), whereas it exerted no direct effect on bacterial activity when they were not P-limited. 4. P-enrichment of lake water markedly altered the response of bacteria to spectral solar radiation at the end of ice-free period, when bacteria were strongly P-deficient. Phosphorus enrichment suppressed the inhibitory effect of full sunlight that was observed in October, both in whole lake water (i.e. including algae) and in the absence of algae. This indicates that the bacterial P-deficiency, measured as the cellular N : P ratio, was partly responsible for the net inhibitory effect of full sunlight, implying a high bacterial vulnerability to UVB. [source]

Effects of ultraviolet radiation on the eggs of landlocked Galaxias maculatus (Galaxiidae, Pisces) in northwestern Patagonia

M. Battini
Summary 1Ultraviolet radiation (UVR) damages early life stages of several fish species. Galaxias maculatus is a small catadromous fish, with landlocked forms occurring in many lakes within the Nahuel Huapi National Park (Patagonia, Argentina). In this work, the vulnerability of G. maculatus eggs exposed to both natural and artificial UVR was investigated in relation to water transparency. 2Field experiments were performed in two lakes differing in UVR attenuation. Galaxias maculatus eggs were exposed to in situ levels of UVR in quartz tubes incubated at various depths. For laboratory experiments, the eggs were exposed to five levels of artificial UVB radiation. 3Exposure to natural UVR causes various degrees of egg mortality depending on water transparency and incubation depth. In the less transparent lake (Kd320 = 3.08 m -1), almost complete mortality was observed near the surface. At a depth of 43 cm the observed mortality was only 22%, but was still significantly different from the dark control. In the most transparent lake (Kd320 = 0.438 m -1), almost total mortality was observed in tubes incubated at 2.56 m or shallower. A gradual decline in mortality was recorded from that depth to 3.78 m where the values approached those in the dark control treatments. 4A monotonic relationship between mortality and UV exposure could be observed both in field and laboratory experiments. Using the results from field incubations, a LD50 of 2.5 J cm -2 nm -1 was estimated. In a few mountain lakes, this value would be exceeded even if the eggs were laid at the maximum depth of the lake. Thus UVR seems a sufficient cause to explain the absence of G. maculatus populations in some mountain lakes. For most lakes, however, UVR is probably one of several important environmental factors, which together determine the habitat suitability. [source]

Responses of plants in polar regions to UVB exposure: a meta-analysis

Abstract We report a meta-analysis of data from 34 field studies into the effects of ultraviolet B (UVB) radiation on Arctic and Antarctic bryophytes and angiosperms. The studies measured plant responses to decreases in UVB radiation under screens, natural fluctuations in UVB irradiance or increases in UVB radiation applied from fluorescent UV lamps. Exposure to UVB radiation was found to increase the concentrations of UVB absorbing compounds in leaves or thalli by 7% and 25% (expressed on a mass or area basis, respectively). UVB exposure also reduced aboveground biomass and plant height by 15% and 10%, respectively, and increased DNA damage by 90%. No effects of UVB exposure were found on carotenoid or chlorophyll concentrations, net photosynthesis, Fv/Fm or ,PSII, belowground or total biomass, leaf mass, leaf area or specific leaf area (SLA). The methodology adopted influenced the concentration of UVB absorbing compounds, with screens and natural fluctuations promoting significant changes in the concentrations of these pigments, but lamps failing to elicit a response. Greater reductions in leaf area and SLA, and greater increases in concentrations of carotenoids, were found in experiments based in Antarctica than in those in the Arctic. Bryophytes typically responded in the same way as angiosperms to UVB exposure. Regression analyses indicated that the percentage difference in UVB dose between treatment and control plots was positively associated with concentrations of UVB absorbing compounds and carotenoids, and negatively so with aboveground biomass and leaf area. We conclude that, despite being dominated by bryophytes, the vegetation of polar regions responds to UVB exposure in a similar way to higher plant-dominated vegetation at lower latitudes. In broad terms, the exposure of plants in these regions to UVB radiation elicits the synthesis of UVB absorbing compounds, reduces aboveground biomass and height, and increases DNA damage. [source]

Solar UVB and warming affect decomposition and earthworms in a fen ecosystem in Tierra del Fuego, Argentina

Abstract Combined effects of co-occurring global climate changes on ecosystem responses are generally poorly understood. Here, we present results from a 2-year field experiment in a Carex fen ecosystem on the southernmost tip of South America, where we examined the effects of solar ultraviolet B (UVB, 280,315 nm) and warming on above- and belowground plant production, C : N ratios, decomposition rates and earthworm population sizes. Solar UVB radiation was manipulated using transparent plastic filter films to create a near-ambient (90% of ambient UVB) or a reduced solar UVB treatment (15% of ambient UVB). The warming treatment was imposed passively by wrapping the same filter material around the plots resulting in a mean air and soil temperature increase of about 1.2 °C. Aboveground plant production was not affected by warming, and marginally reduced at near-ambient UVB only in the second season. Aboveground plant biomass also tended to have a lower C : N ratio under near-ambient UVB and was differently affected at the two temperatures (marginal UVB × temperature interaction). Leaf decomposition of one dominant sedge species (Carex curta) tended to be faster at near-ambient UVB than at reduced UVB. Leaf decomposition of a codominant species (Carex decidua) was significantly faster at near-ambient UVB; root decomposition of this species tended to be lower at increased temperature and interacted with UVB. We found, for the first time in a field experiment that epigeic earthworm density and biomass was 36% decreased by warming but remained unaffected by UVB radiation. Our results show that present-day solar UVB radiation and modest warming can adversely affect ecosystem functioning and engineers of this fen. However, results on plant biomass production also showed that treatment manipulations of co-occurring global change factors can be overridden by the local climatic situation in a given study year. [source]

Cooler temperatures increase sensitivity to ultraviolet B radiation in embryos and larvae of the frog Limnodynastes peronii

Abstract Recent studies suggest that complex interacting processes are driving global amphibian declines. Increased ultraviolet B (UVB) radiation in the solar spectrum associated with ozone depletion has been implicated in declines, and evidence suggests that the effects of UVB radiation on amphibians may be greater at cooler temperatures. We tested the thermal sensitivity of UVB effects on amphibians in a controlled factorial experiment using the striped marsh frog, Limnodynastes peronii as a model species. We compared survival, growth and locomotor performance of embryonic and larval L. peronii reared under low and high UVB exposures at both 20 and 30 °C. Embryonic and larval L. peronii proved extremely sensitive to UVB damage and exhibited greater sensitivity at 20 °C compared with 30 °C. Embryonic survival to Gosner stage 25 was unaffected by UVB exposure at 30 °C, but at 20 °C survival was reduced to 52% under high UVB. Larval survival exhibited a similar trend. At 20 °C, all tadpoles survived under low UVB, whereas under high UVB there was 100% mortality after 15 days of exposure. At 30 °C, 86% survived under low UVB, but only 46% survived under high UVB. Sublethal effects such as, embryonic malformation, retarded larval growth and reduced larval swimming performance were also greater at 20 °C compared with 30 °C. Our results strongly indicate that UVB damage in amphibians is markedly increased at cooler temperatures. Thus, populations of UVB sensitive species occurring at cold climates may be at greater risk of declines due to increased solar UVB radiation. [source]

Photochemical cleavage of a tattoo pigment by UVB radiation or natural sunlight

Eva Engel
Summary Background: Millions of people have at least one tattoo. Complex and light absorbing molecules are implanted in the skin. When tattooed skin receives UV radiation or natural sunlight, photochemical cleavage of the pigments may occur. As a first step, we dissolved pigments in a suitable solvent and analyzed them after light irradiation. Methods: The widespread Pigment Red 22 was dissolved in different solvents. The solutions were irradiated with either UVB radiation (up to 8 h) or with natural sunlight (110 days). After irradiation, the solutions were analyzed by means of liquid chromatography and mass spectrometry. Results: A clear cleavage of the pigment was detected in all solvents and the primary decomposition products were identified. In tetrahydrofuran and dioxane, the pigment concentration decreased significantly during UVB irradiation, whereas the pigment was completely destroyed during sunlight exposure. In chloroform and dichloromethane, the pigment concentration decreased slightly during UVB irradiation, whereas the pigment was almost completely destroyed during sunlight exposure. Conclusion: Since chloroform and dichloromethane do not affect the cleavage process, these solvents are optimal for such in vitro experiments. We have shown the cleavage of the tattoo pigment Red 22 when exposed to UVB radiation or natural sunlight. The decomposition products are hazardous showing a potential risk of being toxic or even carcinogenic. At present, a risk assessment is not feasible since the concentration of pigments and their decomposition products in skin are unknown. [source]

Susceptibility of zoospores to UV radiation determines upper depth distribution limit of Arctic kelps: evidence through field experiments

Summary 1The UV susceptibility of zoospores of the brown seaweeds Saccorhiza dermatodea, Alaria esculenta and Laminaria digitata (Laminariales) was determined in field experiments in June 2004 on Spitsbergen (78°55, N, 11°56, E). 2Freshly released zoospores were exposed for 1 or 2 days at various water depths to ambient solar radiation, ambient solar radiation depleted of UVB radiation (UVBR) and ambient solar radiation depleted of both UVBR and UVAR. Subsequently, germination rates were determined after exposure to favourable light and temperature conditions in the laboratory. 3The radiation regime was monitored at the water surface and in the water column using data loggers attached adjacent to each experimental platform for the duration of the field exposure. 4Under ambient solar radiation, the tolerance of zoospores to UVR was highest in the shallow water species S. dermatodea, intermediate in the upper to mid sublittoral A. esculenta and lowest in the upper to mid sublittoral L. digitata. There was, however, no difference in the susceptibility of the zoospores to ambient solar radiation or to solar radiation depleted of UVBR. 5The water column was relatively UV transparent, especially in the upper water layers. The 1% UVB depth ranged between 5.35 and 6.87 m, although on one stormy day the 1% UVB depth was only 3.57 m, indicating resuspension of sediments. 6Early developmental stages are most susceptible to environmental stress. Tolerance of zoospores to UVR is a major if not one of the most important factors determining the upper distribution limit of different Laminariales on the shore. 7Kelps are very important primary producers in inshore coastal ecosystems, serving as food for herbivores and as habitat for many organisms. Enhanced UVBR due to stratospheric ozone depletion may lead to changes in the depth distribution of kelps and may cause significant ecological domino effects. [source]

The CO2 -concentrating mechanism in the bloom-forming cyanobacterium Microcystis aeruginosa (Cyanophyceae) and effects of UVB radiation on its operation,

Yanfang Song
The bloom-forming cyanobacterium Microcystis aeruginosa (Kütz.) Kütz. 854 was cultured with 1.05 W · m,2 ultraviolet-B radiation (UVBR) for 3 h every day, and the CO2 -concentrating mechanism (CCM) within this species as well as effects of UVBR on its operation were investigated. Microcystis aeruginosa 854 possessed at least three inorganic carbon transport systems and could utilize external HCO3, and CO2 for its photosynthesis. The maximum photosynthetic rate was approximately the same, but the apparent affinity for dissolved inorganic carbon was significantly decreased from 74.7 ,mol · L,1 in the control to 34.7 ,mol · L,1 in UVBR-treated cells. At 150 ,mol · L,1 KHCO3 and pH 8.0, Na+ -dependent HCO3, transport contributed 43.4%,40.2% to the photosynthesis in the control and 34.5%,31.9% in UVBR-treated cells. However, the contribution of Na+ -independent HCO3, transport increased from 8.7% in the control to 18.3% in UVBR-treated cells. The contribution of CO2 -uptake systems showed little difference: 47.9%,51.0% in the control and 49.8%,47.2% in UVBR-treated cells. Thus, the rate of total inorganic carbon uptake was only marginally affected, although UVBR had a differential effect on various inorganic carbon transporters. However, the number of carboxysomes in UVBR-treated cells was significantly decreased compared to that in the control. [source]

The efficacy of excimer laser (308 nm) for vitiligo at different body sites

A Hofer
Abstract Background, The treatment with XeCl-excimer laser generated 308-nm UVB radiation has shown promising results in patients with vitiligo. Objective, In this controlled, prospective trial we studied the primary efficacy (start and grade of repigmentation) and patient's satisfaction of XeCl-excimer laser for treatment of vitiligo patches at different body sites and re-evaluated the achieved repigmentation 12 months after the end of therapy. Methods, Twenty-five patients with generalized or localized vitiligo with a total of 85 lesions at different body sites were enrolled in this study. Vitiligo patches were treated with 308-nm XeCl-excimer laser 3 times a week for 6 to 10 weeks. The overall repigmentation grade of each treated lesion was evaluated once a week on a 5 point scale rating from 0 (no repigmentation), 1 (1,5%), 2 (6,25%), 3 (26,50%), 4 (51,75%), to 5 (76,100%). Results, Twenty-four patients completed the study. Within 6 to 10 weeks of treatment 67% of the patients (16/24) developed follicular repigmentation of at least one of their vitiligo lesions. Lesion repigmentation started after a mean of 13 treatments in lesions located on the face, trunk, arm, and/or leg (high-responder location), and after a mean of 22 treatments in lesions located on the elbow, wrist, dorsum of the hand, knee, and/or dorsum of the foot (low-responder location). Untreated control lesions and lesions located on the fingers did not achieve any repigmentation. After 10 weeks of treatment repigmentation of more than 75% was found in 25% (7/28) of lesions of the high-responder location group versus 2% (1/43) of lesions of the low-responder location group. In most cases, laser-induced repigmentation was persistent, as determined 12 months after the end of treatment. Conclusions, 308-nm excimer laser is an effective modality for the treatment of vitiligo. However, similar to other non-surgical treatment modalities, the therapeutic effect is mainly dependent on the location of vitiligo lesions. [source]

Common and distinct mechanisms of different redox-active carcinogens involved in the transformation of mouse JB6P+ cells

Sun Yang
Abstract We transformed JB6P+ cells with prolonged intermittent low-dose UVB radiation or prolonged exposure to low-dose H2O2 or CdCl2. Stable transformation was confirmed by an anchorage-independence assay. The JB6P+ transformants formed more colonies (,six folds) in soft agar as compared to their JB6P+ parent cells and were associated with increased intracellular reactive oxygen species (ROS) levels. Activating protein-1 (AP-1) is a family of transcription factors that are rapidly activated by elevated intracellular ROS levels, and their composition is important in the process of cellular transformation and/or tumor progression. To investigate if carcinogenesis induced by distinct carcinogens was via similar molecular mechanisms in these transformants, gel mobility shift and immunoblot analyses were utilized to determine the distinct AP-1 compositions. Compared to parent JB6P+ cells, the gain of JunB and Fra-1 in AP-1 DNA binding complexes was markedly increased in all transformed cells, which might contribute to a more proliferative phenotype, while loss of Fra-2 occurred in JB6P+/H2O2 and JB6P+/Cd cells. Differential AP-1 components in the transformants suggested that their transformations might be mediated by distinct transcription signalings with distinct AP-1 dimer compositions. However, all three transformants exhibited increased activation of pathways involved in cell proliferation (ERK/Fra-1/AP-1 and JNK/c- jun/AP-1) and anti-apoptosis (Bcl-xl). The development of the JB6P+ transformants (JB6P+/UVB; JB6P+/H2O2; JB6P+/Cd) provides a unique tool to study the mechanisms that contribute to different redox-active carcinogens in a single model. © 2007 Wiley-Liss, Inc. [source]

Protective effect of vitamin E on ultraviolet B light,induced damage in keratinocytes

Samar Maalouf
Abstract Ultraviolet (UV) B radiation is the most common environmental factor in the pathogenesis of skin cancer. Exposure of human skin to UVB radiation leads to the depletion of cutaneous antioxidants, the activation of nuclear factor kappa B (NF-,B), and programmed cell death (apoptosis). Although antioxidant supplementation has been shown to prevent UVB-induced photooxidative damage, its effect on components of cell signaling pathways leading to gene expression has not been clearly established. In the present study, the effect of the antioxidant vitamin, ,-tocopherol (,-T), and its acetate analog, ,-tocopherol acetate (,-TAc), on UVB-induced damage in primary and neoplastic mouse keratinocytes was investigated. The ability of both vitamins to modulate UVB-induced apoptosis and activation of the transcription factor NF-,B were studied. Treatment of normal and neoplastic mouse epidermal keratinocytes (308 cells) with 30,60 mJ/cm2 UVB markedly decreased viable cell number and was accompanied by DNA fragmentation. When both vitamins were applied to cells at times before and after UVB radiation, a significant increase in the percentage of viable cells and concomitant decrease in the number of apoptotic cells was noted, with vitamin pretreatment providing a better protection than posttreatment. Simultaneous posttreatment of irradiated cells with ,-TAc abolished the cytotoxic effects of UVB and restored cell viability to control levels. In addition, simultaneous posttreatment of irradiated cells with ,-T reduced the number of apoptotic cells by half, indicating a synergistic effect of two such treatments compared with any single one. Flow cytometry analysis indicated that vitamin treatment suppressed both an increase in pre-G0 cells and a decrease in cycling cells by UVB exposure. In addition, NF-,B activation was detected 2 h after UV exposure and was maintained for up to 8 h. Pretreatment with vitamins significantly inhibited NF-,B activation at 4 and 8 h. These results indicate that vitamin E and its acetate analog can modulate the cellular response to UVB partly through their action on NF-,B activation. Thus, these antioxidant vitamins are potential drugs for the protection from or the reduction of UVB-associated epidermal damage. © 2002 Wiley-Liss, Inc. [source]

Time series analysis of ultraviolet B radiation and type 1 diabetes in Newfoundland

Scott Sloka
Background:, Type 1 diabetes mellitus (T1DM) has been previously been associated with decreased levels of vitamin D. This study investigates the temporal association between average daily ultraviolet B (UVB) irradiance and T1DM in Newfoundland. Methods:, A complete list of patients diagnosed with T1DM in the province of Newfoundland and Labrador was constructed using multiple sources. Pooled and unpooled monthly incidence data along with monthly UVB measurements were used to build a time series transfer function model. The model was used to predict the future incidence of T1DM based on previous monthly trends, and these predictions were compared with actual measured incidences. Results:, A seasonal variation in pooled monthly incidence was observed. The transfer function model was able to reasonably predict the future incidence of T1DM based on previous observations and monthly UVB measurements. Tests of seasonality demonstrated a significant seasonal trend (p = 0.0003). Conclusions:, This study suggests that erythemal UVB radiation may be temporally associated with the incidence of T1DM. [source]

Requirement for Metalloproteinase-dependent ERK and AKT Activation in UVB-induced G1-S Cell Cycle Progression of Human Keratinocytes

Weinong Han
UVB (280,315 nm) in natural sunlight represents a major environmental challenge to the skin and is clearly associated with human skin cancer. Here we demonstrate that low doses of UVB induce keratinocyte proliferation and cell cycle progression of human HaCaT keratinocytes. Different from UVA, UVB irradiation induced extracellular signal-regulated kinase (ERK) and AKT activation and their activation are both required for UVB-induced cell cycle progression. Activation of epidermal growth factor receptor (EGFR) was observed after UVB exposure and is upstream of ERK/AKT/cyclin D1 pathway activation and cell cycle progression following UVB radiation. Furthermore, metalloproteinase (MP) inhibitor GM6001 blocked UVB-induced ERK and AKT activation, cell cycle progression, and decreased the EGFR phosphorylation, demonstrating that MPs mediate the EGFR/ERK/AKT/cyclin D1 pathways and cell cycle progression induced by UVB radiation. In addition, ERK or AKT activation is essential for EGFR activation because ERK or AKT inhibitor blocks EGFR activation following UVB radiation, indicating that EGFR/AKT/ERK pathways form a regulatory loop and converge into cell cycle progression following UVB radiation. Identification of these signaling pathways in UVB-induced cell cycle progression of quiescent keratinocytes as a process mimicking tumor promotion in vivo will facilitate the development of efficient and safe chemopreventive and therapeutic strategies for skin cancer. [source]

Study of UV Radiation Dose Received by the Spanish Population

Gonzalo Gurrea
Excess exposure to UV radiation can affect our health by causing sunburn, skin cancer, etc. It is therefore useful to determine the UV dosage received by people as a way of protecting them from the possible negative effects that this kind of radiation can cause. In this work, the personal outdoor percentage, which shows the time spent in outdoor activities, as well as personal UV doses, has been calculated by means of global UV radiation on a horizontal plane. A database of average daily UVB radiation on the horizontal plane given by the National Institute of Meteorology has been used. In this work we evaluate the standard erythema dose of the Spanish population throughout the year. [source]

Evaluation of a High Exposure Solar UV Dosimeter for Underwater Use

Peter W. Schouten
ABSTRACT Solar ultraviolet radiation (UV) is known to have a significant effect upon the marine ecosystem. This has been documented by many previous studies using a variety of measurement methods in aquatic environments such as oceans, streams and lakes. Evidence gathered from these investigations has shown that UVB radiation (280,320 nm) can negatively affect numerous aquatic life forms, while UVA radiation (320,400 nm) can both damage and possibly even repair certain types of underwater life. Chemical dosimeters such as polysulphone have been tested to record underwater UV exposures and in turn quantify the relationship between water column depth and dissolved organic carbon levels to the distribution of biologically damaging UV underwater. However, these studies have only been able to intercept UV exposures over relatively short time intervals. This paper reports on the evaluation of a high exposure UV dosimeter for underwater use. The UV dosimeter was fabricated from poly 2,6-dimethyl-1,4-phenylene oxide (PPO) film. This paper presents the dose response, cosine response, exposure additivity and watermarking effect relating to the PPO dosimeter as measured in a controlled underwater environment and will also detail the overnight dark reaction and UVA and visible radiation response of the PPO dosimeter, which can be used for error correction to improve the reliability of the UV data measured by the PPO dosimeters. These results show that this dosimeter has the potential for long-term underwater UV exposure measurements. [source]

Topically Applied Eicosapentaenoic Acid Protects Against Local Immunosuppression Induced by UVB Irradiation, cis -Urocanic Acid and Thymidine Dinucleotides,

Ralf M. W. Moison
ABSTRACT UVB-induced immunosuppression, a promoter of photocarcinogenesis, involves the formation of pyrimidine dimers and cis -urocanic acid (cis -UCA), but reactive oxygen species (ROS) also plays an important role. Eicosapentaenoic acid (EPA) can inhibit photocarcinogenesis, but due to its polyunsaturated nature it is susceptible to oxidative damage by ROS. The antioxidant defense system may therefore be challenged upon ultraviolet-B (UVB) irradiation in the presence of EPA. We investigated whether topically applied EPA in mice could protect against local immunosuppression (contact hypersensitivity response to dinitrofluorobenzene) induced by UVB radiation (1.5 J/cm2), or topically applied cis -UCA (150 nmol/cm2) or thymidine dinucleotides (pTpT) (5 nmol/cm2). The influence of EPA on epidermal lipid peroxidation and antioxidant status was also measured. UVB irradiation, cis -UCA and pTpT all caused 70% immunosuppression. Topical pretreatment of mice with EPA partially protected against immunosuppression; the EPA dose needed to accomplish this was 10 nmol/cm2 for UVB irradiation, 100 nmol/cm2 for cis -UCA and 1000 nmol/cm2 for pTpT. Higher EPA doses caused higher UVB-induced lipid peroxidation and lower vitamin C levels. Glutathione only decreased with the highest EPA dose whereas vitamin E was not decreased after UVB irradiation. In conclusion, topically applied EPA protects against UVB-, cis -UCA- and pTpT-induced immunosuppression and maintenance of an adequate antioxidant defense seems to be an important prerequisite for the protective action by EPA. [source]

Ultraviolet B radiation suppresses Langerhans cell migration in the dermis by down-regulation of ,4 integrin

Motoko Hamakawa
Background/Purpose: Ultraviolet B (UVB) radiation affects the migration and function of epidermal Langerhans cells (LC) and causes immunosuppression of contact hypersensitivity. It is known that LC leaves the epidermis after exposure to UVB. To know the behavior of LC in the dermis after UVB radiation, we studied the effect of UVB radiation on the expression of integrin families on freshly isolated or cultured murine LC. We also examined whether UVB radiation affects the migration of LC to secondary lymphoid tissue chemokine (SLC/6Ckine). Methods: Integrin expressions of murine LC cultured in epidermal cell suspension were analyzed using flowcytometry. We used murine LC sorted flowcytometrically for binding assay to extracellular matrix and for migration assay to chemokine. Skin explant assay and immnohistochemical staining for ,cords formation' were performed as previously described. Results: Twenty and 40 mJ/cm2 of UVB radiation down-regulated the expression of ,4 integrin on 24 h-cultured LC, but not that of ,6, ,1, or ,4 integrin. The number of cultured LC adhered to fibronectin, a ligand for ,4 integrin, was decreased after UVB irradiation, while that to laminin, a ligand for ,6 integrin, was not influenced. UVB radiation reduced the number of migrating LC to SLC. Furthermore, skin sheet explant experiments showed that UVB radiation inhibited the ,cords' formation in dermal vessels of the 48 h-cultured skin. Conclusions: These data suggest that UVB radiation may suppress the migration of LC from the dermis to lymphatic vessels. UVB radiation may downregulate the adherence of LC to dermal fibronectin and migration to SLC, and consequently suppress the migration of LC from the UVB-irradiated dermis to lymphatics. [source]

Ultraviolet B induces hyperproliferation and modification of epidermal differentiation in normal human skin grafted on to nude mice

S. Del Bino
Summary Background For ethical and technical reasons, the in vivo biological effects of ultraviolet (UV) radiation on skin are difficult to study in human volunteers. The use of human skin grafted on to nude mice may circumvent this difficulty. Objectives To investigate the effects of a single moderate UVB exposure on human skin grafted on to nude mice. Methods Modifications of epidermal differentiation markers and patterns of keratin expression were assessed from 24 h to 14 days after a physiological UVB irradiation characterized by the induction of sunburn cells. Results During the first 48 h postexposure, involucrin, loricrin, transglutaminase type I, filaggrin and keratin K2e expression were altered together with the formation of abnormal horny layers. Constitutive keratin K14 was increased while keratin K10 expression was delayed. Newly synthesized keratins K6, K16, K17 and K19 were induced in parallel with an increase in the epidermal proliferation rate. A progressive normalization of both keratinocyte proliferation and differentiation took place during the following days, reaching completion within 2 weeks. Conclusions Exposure of human skin to a UVB dose corresponding to a mild sunburn reaction induces epidermal hyperproliferation and alterations of several constitutive differentiation markers, as well as a drastic modification in the pattern of epidermal keratins. Although these modifications were shown to be progressively reversed in a single exposure model, the data also suggest that subsequent UV exposures occurring during the recovery period may lead to potentially deleterious long-term consequences, such as photoageing and photocarcinogenesis. Grafted human skin appeared to be an attractive and promising model for investigating the biological consequences of UVB radiation in vivo. [source]

Change in ultraviolet (UV) transmission following the application of vaseline to non-irradiated and UVB-exposed split skin

K. Hoffmann
Background ,Topical preparations such as emollients used in combination with phototherapy can interfere with such treatment. Objectives,This study was performed to investigate the impact of vaseline on the ultraviolet (UV) transmission of non-irradiated split skin and on split skin previously exposed to UVB radiation. Methods,Split-skin specimens were obtained from 20 patients. In each case, one sample was taken from an area of non-irradiated skin, while the second was taken from an area that had been previously exposed to UVB. The transmission was spectrophotometrically measured with split skin placed in specially designed quartz glass cuvettes before and after the application of two different amounts of vaseline (2·5 and 17·5 mg cm,2). Results,Application of vaseline to skin previously exposed to UVB caused significant (P < 0·0001) changes in UV transmission in certain wavelength ranges. In the UVA range, a greater increase in transmission was achieved with 2·5 mg cm,2 vaseline, whereas in the UVB range, a greater increase was achieved with 17·5 mg cm,2 vaseline. The thicker the layer of vaseline applied, the lower was the difference in transmission between non-irradiated split skin and UVB-exposed split skin. Conclusions,Application of the correct amount of vaseline can enhance transmission in either the UVA or UVB range, and would enable dose reduction during a course of phototherapy. [source]

Ultraviolet B radiation improves serum levels of vitamin D in patients with cystic fibrosis

Eva Gronowitz
Abstract Background: Ultraviolet B (UVB) radiation can be used in the prevention and treatment of vitamin D deficiency. Aim: To investigate, in a controlled study of patients with cystic fibrosis (CF), whether regular UVB radiation would improve serum levels of calcidiol during the dark season (October,April). Methods: Thirty patients with mild to moderate disease were included (aged 9,40 y). All patients had cholecalciferol supplementation. One group (15 patients) was given UVB one to three times a week for 6 mo and one group (15 sex- and age-matched patients) served as controls. The radiation source consisted of three TL 12/40W UVB fluorescent lamps. Initial treatment duration was 1 min, subsequently increased by 0.5,1 min/treatment to a maximum of 10 min. Results: The mean initial serum calcidiol levels were 21 ng/ml in the controls and 22 ng/ml in the intervention group. Serum calcidiol levels increased to 44 ng/ml after 8 wk and to 50 ng/ml after 24 wk of UVB radiation; the corresponding serum levels in the controls were 19 and 25 ng/ml, respectively. The mean serum calcitriol levels increased in the treated group and were unaltered in the control group. Conclusions: UVB radiation was effective in increasing vitamin D levels in patients with CF. The study results imply that UVB radiation is valuable in chronic conditions associated with vitamin D deficiency. [source]