UVB Dose (uvb + dose)

Distribution by Scientific Domains

Selected Abstracts

Influence of narrowband UVB phototherapy on vitamin D and folate status

Emanuela Cicarma
Please cite this paper as: Influence of narrowband UVB phototherapy on vitamin D and folate status. Experimental Dermatology 2010; 19: e67,e72. Abstract Background:, A variety of studies have shown beneficial effects of different types of phototherapy in skin disorders. Such therapy leads to enhanced cutaneous vitamin D synthesis, which may be one of the mechanisms of action. Furthermore, another nutrient, folate, can probably also be influenced by UV radiation. Objective:, The aim of our study was to investigate the influence of low-dose narrowband UVB (nUVB) phototherapy of patients with psoriasis, atopic eczema and other skin disorders on serum levels of 25(OH) vitamin D (the serum marker for vitamin D status) and on serum and erythrocyte-folate. Methods:, 25(OH) vitamin D (25(OH)D), serum and erythrocyte-folate levels were measured before and after low-dose nUVB (TL-01 tubes) phototherapy of these patients. The spectrum of the TL-01 tube was compared with the solar spectrum, and the efficiency spectra of vitamin D photosynthesis were calculated. Results:, For patients with a high initial 25(OH)D serum level (> 80 nmol/l), no significant (P = 0.36) increase in 25(OH)D levels was seen, in contrast to patients with a low initial level (< 80 nmol/l) where a significant increase (P < 0.001) was observed. The increase was 30,60%, depending on the UVB dose (2.35,13.4 J/cm2). No significant nUVB-effect was found on the erythrocyte and serum-folate level. Conclusion:, Low-dose nUVB treatment gives a significant increase (P < 0.001) of the vitamin D status in persons with low initial levels of 25(OH)D, but no effect on the folate level. [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]

Radiation Sources Providing Increased UVNUVB Ratios Induce Photoprotection Dependent on the UVA Dose in Hairless Mice

Vivienne E. Reeve
ABSTRACT In studies involving mice in which doses of UVA (320,400 nm) and UVB (290,320 nm) radiation were administered alone or combined sequentially, we observed a protective effect of UVA against UVB-induced erythemdedema and systemic suppression of contact hypersensitivity. The UVA immunoprotection was mediated by the induction of the stress enzyme heme oxygenase-1 (HO-1) in the skin, protection of the cutaneous Th1 cytokines interferon-gM (IFN-,) and IL-12 and inhibition of the UVB-induced expression of the Th2 cytokine IL-10. In this study, we seek evidence for an immunological waveband interaction when UVA and UVB are administered concurrently to hairless mice as occurs during sunlight exposure in humans. A series of spectra providing varying ratios of UVA/UVB were developed, with the UVA ratio increased to approximately 3.5 times the UVA component in solar simulated UV (SSUV). We report that progressively increasing the UVA component of the radiation while maintaining a constant UVB dose resulted in a reduction of both the erythemdedema reaction and the degree of systemic immunosuppression, as measured as contact hypersensitivity. The UVA-enhanced immunoprotection was abrogated in mice treated with a specific HO enzyme inhibitor. UVA-enhanced radiation also upregulated the expression of cutaneous IFN-, and IL-12 and inhibited expression of both IL-6 and IL-10, compared with the activity of SSUV. The results were consistent with the previously characterized mechanisms of photoprotection by the UVA waveband alone and suggest that the UVA component of solar UV may have beneficial properties for humans. [source]

The Vitamin D Status Among Tibetans

Gelsor Norsang
UVB from the sun and intake from food are the only human sources of vitamin D. Tibet is a unique region for comparisons of these sources: (1) it lies at a low latitude and at a high altitude and has very large annual fluences of UVB; (2) the traditional Tibetan food is poor in vitamin D. Blood samples were taken from 63 persons of different age, with different occupations and staying at different places. UVB doses at these places were measured. The samples were analyzed by a standard radioimmune assay for determination of the serum concentration of 25 hydroxyvitamin D (25(OH)D). The main finding was that among nomads, there seems to be severe vitamin D deficiency (serum levels of 25(OH)D < 30 nm). We tentatively propose that the low level of 25(OH)D of nomads is related to their clothing and sun exposure habits. For persons of other occupations (students, teachers and farmers) the levels are higher, although a significant fraction of these persons also have lower levels than 75 nm, by many regarded as a limit for insufficiency related to a number of negative health conditions. The annual dose of vitamin D-generating UVB is about five times larger in Lhasa than in Oslo. Despite this, the average vitamin D status seems to be similar, except in the case of nomads. This phenomenon is certainly related to food habits. In conclusion, the 25(OH)D status among nomads in Tibet appears to be alarmingly low. However, for people of other occupations the status is more normal. [source]

A New Model Using Liposomes That Allow to Distinguish Between Absorption and Oxidative Properties of Sunscreens,

Christian Tran
ABSTRACT We have developed a new model using liposome-encapsulated fluorescent probes, aiming at assessing both the physical and the biological protection provided by filter molecules such as those incorporated in sunscreens. The fluorescent indicator Indo-1 or 2,,7,-dichlorofluorescin (DCFH) was inside the liposomes, in the aqueous inner compartment, whereas the filter molecules octyl methoxycinnamate (OMC), benzophenone-3 (BP3) or avobenzone, widely used in sunscreens, were incorporated into liposome membranes. When liposome suspensions were placed in a fluorometer cuvette exposed to an incident UV beam, the decrease of Indo-1 fluorescence as a function of filter concentration was related to the extinction coefficient of the filters. On the other hand, when liposome suspensions were exposed to moderate UVB doses allowing Indo-1 photobleaching, the remaining intact Indo-1 was linked to the protection provided by filter-containing liposome membranes. Finally, when liposome-encapsulated DCFH was exposed to UVB, the degree of photo-oxidation of the fluorescent probe into 2,,7,-dichlorofluorescein accounted for the photoprotection provided by the filter contained in liposome membranes. BP3 was more potent and slightly less efficient than the other two filters in preventing Indo-1 fluorescence; all three filters provided a similar concentration-dependent protection of Indo-1 photobleaching, whereas only OMC was able to prevent the photooxidation of DCFH. The liposome model presented here has the advantage of combining both physical and biological parameters to assess the photoprotection provided by filter molecules, and the lack of photoprotection by two sunscreen molecules having a good filter capacity highlights the need for such a biological parameter when talking about the safety of sunscreens. [source]

Comparison of the 308-nm excimer laser and a 308-nm excimer lamp with 311-nm narrowband ultraviolet B in the treatment of psoriasis

K. Köllner
Summary Background, Psoriasis is a chronic, genetically determined inflammatory disease, characterized by an immunomediated pathogenesis, which affects approximately 1,3% of the population. Various modalities have been used for psoriasis treatment, including ultraviolet (UV) radiation. Narrowband UVB (311 nm) phototherapy is a well-established, widely used and highly efficient treatment for psoriasis, but a big disadvantage is that large areas of unaffected skin are irradiated along with the psoriatic lesions. Objectives, This investigation evaluates a 308-nm excimer laser and a 308-nm excimer lamp in comparison with 311-nm narrowband UVB in the treatment of patch psoriasis by using two different dose-increase schemes. Materials and methods, Fifteen patients with plaque psoriasis were enrolled in the study (first regime). Three different psoriatic lesions were treated with the 308-nm excimer laser, the 308-nm excimer lamp or 311-nm narrowband UVB three times per week. UVB doses were increased slowly and stepwise (1, 1, 2, 2, 3, 3, ,multiple MEDs). Sixteen patients were enrolled in the second regime. Two plaques were treated with the 308-nm excimer laser or with the 308-nm lamp with an accelerated scheme (2, 2, 4, 4, 6, 6, ,multiple MEDs) three times per week. We increased the UVB doses every second treatment (first and second regime) during the whole treatment. If blistering occurred, the blistered plaque was not treated on the next scheduled treatment. At every third visit and 1, 2 and 4 months after the last treatment a Psoriasis Severity Index (PSI) score was assigned in both regimes. Results, Using Friedman analysis, the PSI scores did not show a statistically significant difference (P > 0ˇ05) comparing 308-nm laser therapy, 308-nm lamp therapy and 311-nm narrowband therapy after 10 weeks in the first regime. The mean number of treatments to achieve clearance was 24. With the accelerated scheme, clearance could be achieved with fewer treatments and with half the cumulative dose of the first regime. Nevertheless, the side-effects such as blistering and crusting were also increased. Conclusions, Both 308-nm light sources can clear patch psoriasis in a similar manner to standard phototherapy, with the advantage of the ability to treat exclusively the affected skin and with a reduced cumulative dose, thus perhaps reducing the long-term risk of carcinogenicity. [source]