UV-A Lamp Research Articles

UVA, pheomelanin and the carcinogenesis of melanoma.

Cloudman S91 mouse melanoma cells vary in constitutive and inducible melanin levels. Survival, mutation induction and DNA damage were quantitated after exposure to UVB, UVA and FS20 lamps. Assuming that the observed differences are related to melanin, induced pigment is photo-protective for survival and mutation after UVB and FS20 exposure, and is photosensitizing for survival after UVA exposure. No changes in pyrimidine dimers could be measured. DNA damage in pigmented mouse melanocytes (melan-a and melan-b) was greater than that in albino melanocytes (melan-c) after UVB and FS20, and the pigmented cells were more sensitive to killing. Pigment appears to be protective for killing by UVA in these melanocytes. Human melanocytes from different skin types vary in both melanin amount and composition (eu- and pheomelanin). Effects of pigmentation on UVB responses are unclear. In UVA, heavily pigmented cells have more DNA damage than lightly pigmented cells, but are resistant to killing. Increased pheomelanin photosensitizes DNA damage in lightly pigmented cells. Since eumelanin predominates in the mouse melanoma cells and melanocytes, they are less likely than human cells to provide a satisfactory model for human solar melanomagenesis. In order to understand the mechanism of photocarcinogenesis of melanoma, melanins in human melanocytes from different pigment types should be carefully quantitated and characterized. Mutations induced in them by solar wavelength-emitting lamps with well-characterized spectra should be measured, and mutant DNA should be sequenced to determine the nature of the solar-induced lesions. Research should focus on UVA and pheomelanin.

Sunlamp use and the risk of cutaneous malignant melanoma: a population-based case-control study in Connecticut, USA.

The relationship between cutaneous malignant melanoma and sunlamp use is examined in a Caucasian population in Connecticut, United States. Cases were diagnosed between 15 January 1987 and 15 May 1987 with a first primary cutaneous melanoma. Controls were obtained from the general population, frequency matched to cases by sex and age, through random digit dialling of Connecticut telephone numbers. Of all study subjects, 141 (23%) cases and 95 (19%) controls reported ever having used sunlamps. The crude odds ratio (OR) for developing malignant melanoma after ever having used sunlamps was 1.30 (95% confidence interval [CI]: 0.97-1.74). This was reduced to 1.13 (95% CI: 0.82-1.54) after further adjusting for cutaneous phenotype and recreational sun exposure. Those who used more than one type of sunlamp had a threefold higher risk for melanoma compared to never users. Subgroup analyses showed that sunlamp use was associated with a greater increase in risk for melanoma among those who used sunlamps at home and those who were first exposed to sunlamps prior to 1971. The first use of sunlamps before the age of 25 showed somewhat higher risk for melanoma compared to first use later in life. The current study provides limited evidence that use of sunlamps increases the risk of melanoma. For future studies, it is crucial that type of sunlamp, year of first use and amount of exposure are all taken into account. The association between melanoma and tanning with both UV-A and UV-B lamps and tanning under sunlamps early in life merits further investigation.

人工光下でのＵＶ‐Ａ付加照射がレタスとハツカダイコンの成長と葉の苦味に与える影響

In order to know the effect of supplemental UV-A irradiation on the growth of lettuce (Lactuca sativa L. cv. Okayama) and radish (Raphanus sativus L, cv. Comet), these plants were grown under artificial irradiation with 3-band fluorescent lamps and additional UV-A lamps. The UV-A irradiation promoted shoot growth of both plants, and reduced the bitter taste intensity of mature lettuce leaves. However, the UV-A effects varied with stage of vegetative development. Moreover, there was no significant effect of the UV-A on the hypocotyl growth of radish plants.

The effects of UVA-I (340-400 nm), UVA-II (320-340 nm) and UVA-I+II on the photoisomerization of urocanic acid in vivo.

Ultraviolet B radiation (280-320 nm) can systemically suppress contact hypersensitivity (CHS), delayed type hypersensitivity (DTH) and tumor rejection responses in mice. Several models have been postulated for the initiation of this UVB-induced immune suppression and, although the complete mechanism is unclear, our early studies suggested that initiation is via the activation of a photoreceptor in the skin, identified as urocanic acid (UCA). Recent preliminary data from our laboratory and others indicated that UVA (320-400 nm)-emitting broad-band sunlamps can also isomerize UCA but may not lead to immune suppression, in contrast to UVB-emitting sunlamps, which cause both effects. Although the reason for this inconsistency is unknown, the emission spectra of UVA lamps contain differing amounts of UVB, UVA-I (340-400 nm) and UVA-II (320-340 nm) from those of UVB sources. In this study we determined a detailed dose-response for the isomerization of UCA in mouse skin using the UVA-I, UVA-II and UVA-I+II wavelength ranges. The dose-response curves obtained were put on an equal energy basis by quantum correction and the possibility of wavelength interaction for this effect investigated. A simple additive wavelength interaction between UVA-I, UVA-II, and UVA-I+II was observed for trans-UCA photoisomerization. This result indicates that the failure of UVA-I, UVA-II or UVA-I+II radiation to induce immune suppression of the CHS response in an animal model is not due to complex wavelength interactions and/or the presence of an in vivo endogenous photosensitizer of UCA isomerization. Other factors, such as downstream blocking by UVA of the cis-UCA generated signal, may be involved.

Prediction of minimal erythema dose with a reflectance melanin meter

The relationship between skin pigmentation and sensitivity to ultraviolet (UV) radiation-induced erythema was investigated in 60 healthy subjects of sun-reactive skin types I-V. Using a portable reflectance spectrometer, skin pigmentation was measured as the 'melanin index' (MI) in all subjects. A solar-simulated array of filtered UVA and UVB-emitting fluorescent lamps was then used to determine the UVB minimal erythema dose (MED) of each subject. MI readings and MED testing were both performed on the subjects' mid to upper backs. Using this technique, we found a close correlation between MI and MED. Comparison of the mean MI or MED of subjects with different skin types revealed progressive differences in MI and MED between all five skin types. Erythema dose-response curves, which provide further information about UV sensitivity, were also calculated for 43 subjects. A significant negative correlation was found between the gradients of these curves and both MI and MED, indicating that paler subjects respond more strongly to increments of UV above the MED than subjects with greater pigmentation. Our results indicate that although traditional, subjective means of predicting UV sensitivity to erythema are not without some value, MED correlates particularly strongly with objective measures of skin pigmentation. We therefore conclude that the reflectance spectrometer can rapidly and accurately predict UVB sensitivity, and should prove clinically useful for planning and optimizing UVB phototherapy.

Identification of Chlorothiazide and Hydrochlorothiazide UV-A Photolytic Decomposition Products

Methanol solutions of hydrochlorothiazide and chlorothiazide were irradiated with fluorescent UV-A lamps in order to simulate degradation under normal conditions. The degradation products were identified by comparison to synthetic standards featuring electrospray ionization mass spectroscopy, ultraviolet spectroscopy, and high performance liquid chromatography. The standards were characterized by high resolution fast atom bombardment MS and 1H NMR. The photolysis of chlorothiazide resulted in photodehalogenation products exclusively, while the irradiation of hydrochlorothiazide primarily yielded photodehalogenation products with significant yields of photodehydrogenation products and minor amounts of thermal hydrolysis products.

Comparison of psoralen-UVB and psoralen-UVA photochemotherapy in the treatment of psoriasis

Background: PUVA treatment of psoriasis is usually given with broad-band fluorescent UVA lamps. Narrow-band UVB exposure after oral methoxsalen has been shown to achieve a greater therapeutic response in psoriasis than identical UVB exposure given without psoralen. Objective: The purpose of this study was to compare conventional PUVA with psoralen-UVB therapy in psoriasis. Methods: We studied 100 patients with plaque-type psoriasis who were randomly selected to receive either conventional psoralen-UVA or psoralen-UVB treatment. Results: No significant difference was found between the two treatments in the proportion of patients whose skin cleared during treatment or in the number of exposures required for clearance of psoriasis. As expected, the cumulative UV dose for clearance was smaller in the group treated with UVB compared with those receiving UVA. Side effects and disease status at 3 months after the end of treatment were similar for the two groups. Conclusion: Psoralen-UVB treatment of psoriasis is as effective as conventional PUVA. The mechanism of psoralen–311 nm UVB action on psoriasis requires study to predict the long-term safety of this treatment. (J Am Acad Dermatol 1997;36:577-81.)

Effects of solar and artificial UV irradiation on pigments and assimilation of 15N ammonium and 15N nitrate by macroalgae

Three macroalgal species, Fucus vesiculosus, Laminaria saccharina and Ulva lactuca were exposed to natural daylight in UV-transparent and UV-non-transparent Plexiglas vessels at different water depths. Uptake of 15NH 4 + and 15NO 3 − was measured at different light intensities. In general, uptake rates in August surpassed those in May 1987 and Ulva assimilated significantly more nitrogen than Fucus and Laminaria. A negative influence of ambient solar UV radiation on nitrogen uptake was dound in Fucus and Ulva. Additionally, the impact of UV of different wave bands, using cut-off filters (WG 295, WG 305 and WG 320) and special UV-A and UV-B lamps, on pigments and 15N ammonium assimilation by several macroalgae was studied under controlled laboratory conditions. UV-B irradiation of shorter wave bands led to a reduction in the main pigments of Fucus except antheraxanthin and those of Ulva except lutein and violaxanthin. Uptake of 15N-ammonium by Fucus and Ulva was reduced after UV-B radiation whereas an increase was observed after UV-A irradiance in Ulva. Ammonia utilization by Halidrys was more damaged by UV-A than UV-B. The impact of UV radiation on the labelling of free amino acids and the pattern of pool sizes varied with the species and the UV wave bands. A marked reduction in 15N incorporation into the amino acids of Plocamium was found after UV-B exposure. The 15N labelling of the amino acids of Halidrys and Rhodomela was less affected. Results are discussed with reference to photoinhibitory effects on the enzymes of the nitrogen metabolism.

Kinetics of acrylamide photopolymerization as investigated by capillary zone electrophoresis

Riboflavin-mediated photopolymerization of acrylamide had been investigated earlier and found to give a poor conversion of the monomer into the polymeric phase (barely 60% with standard 1-h light exposure at room temperature with a 12-W neon source). The kinetics of such process were re-examined by using capillary zone electrophoresis and it was found that the efficiency could be augmented to > 95% (even higher than in peroxodisulphate polymerization) under the following conditions: by conducting the photopolymerization process at 70°C 1 h, instead of at room temperature, alterantively, by using a 105-W UV-A lamp, having a radiation spectrum extending also in the UV region, instead of the standard 12-W neon bulbs, and by increasing the amount of catalyst (riboflavin 5′-phosphate) from 6 to 12 ppm. In all instances, it was found that atmospheric oxygen would act as a retarder, the lag time being ca. 17 min at an oxygen partial pressure of 35 mmHg and increasing progressively to > 70min at > 200 mmHg. However, even at a partial pressure as high as 900 mmHg (as obtained by oxygen insufflation from a tank), once the retarder had been consumed a conversion of monomers into the polymer chains of > 92% was still obtained. In contrast, oxygen acts as an inhibitor in peroxidisulphate polymerization: from an incorporation efficiency of ca. 92% at 25 mmHg oxygen partial O 2 pressure, the conversion is lowered to only 40% at 900 mmHg.

UVA-induced tumours in pigmented hairless mice and the carcinogenic risks of tanning with UVA

An animal experiment is presented in which two groups of pigmented hairless mice were exposed daily to suberythemal doses of UVA to study tumourigenesis. The aim of the study was to estimate the carcinogenic risks of tanning by UVA. The pigmented hairless mice, Skh-hr2, were separated by selective breeding into two groups, the "browns" and the "blacks". Both groups were exposed daily to UVA from fluorescent UVA lamps (Philips TL40W/09) purified by rigorously filtering out the shorter wavelengths. No acute actinic damage was observed after any exposure. However, in most UVA exposed animals, especially in the blacks, a marked scratching preceded the development of tumours. Hyperkeratosis was also observed. All animals developed tumours. Histopathologically at least 60% of the tumours were squamous cell carcinomas. Depositions of melanophages were observed, but no melanomas. It is beyond any doubt that UVA is carcinogenic in laboratory animals. The present state of knowledge justifies no preference for tanning with UVA over tanning with UVB.

Quantitative studies on UVA-induced erythema in human skin.

The erythemal response of normal human skin to UVA and UVB radiation was measured objectively using a reflectance instrument in seven subjects, and a laser Doppler velocimeter in two subjects. UVA radiation was produced using a newly-developed high-intensity UVA lamp. The slope of the log dose-erythemal response curve for UVA at 24 h after irradiation was found not to differ significantly from that for UVB. The time course of UVA erythema was biphasic; erythema was present immediately after irradiation, fell to a minimum at about 4 h and then rose to a broad plateau between 6 and 24 h. The intensity of the early phase was dose-rate dependent, whereas that in the later phase depended on dose only.

Use of UV-A sunbeds for cosmetic tanning.

A survey has been carried out of people using UV-A sunbeds at commercial premises in the U.K. The degree of tan achieved was found to be closely related to the subject's ability to tan in sunlight, and subjects who burnt easily in sunlight were most at risk of developing erythema after using a sunbed. Side-effects, particularly itching, were common. The prevalence of itching, nausea and skin rashes were higher in women taking oral contraceptives than in women on no medication. Although long-term quantitative estimates of the risks of UV-A sunbed use (such as skin ageing and skin cancer) are unknown, it is recommended that individuals who do not tan or tan poorly should be discouraged from using sunbeds.

Artificial suntanning: spectral irradiance and hazard evaluation of ultraviolet sources.

High incidences of skin damage and skin cancer amongst Australians have resulted in numerous campaigns to encourage people to protect themselves against solar ultraviolet radiation (UVR). The detrimental effects of UV-B radiation have been known for some time but recently there has been concern over the effects of UV-A radiation which had been thought of as relatively harmless. The proliferation of solaria, which incorporate UV-A sources, prompted the issuing of an Australian standard dealing with technical and non-technical aspects of the artificial suntanning industry. The purpose of this study was to measure the irradiance and spectral distribution of the emission from sunbeds and other UVR sources used for tanning, to evaluate the hazard potential and also the compliance with the standard. It was found that the majority of the UV-A lamps evaluated met the requirements of the standard. The UV-B lamps and portable sunlamps are potentially hazardous and their use should be discouraged. In general, the survey of solaria highlighted the need for further education of the public and especially the users and operators of solaria, on the hazards of UVR and of protective measures required for its safe use.

Phototoxic reactions from some common drugs provoked by a high-intensity UVA lamp

No abstract available.