Artificial Ultraviolet Research Articles

Detection of Differentially Regulated Genes in Keratinocytes by cDNA Array Hybridization: Hsp27 and Other Novel Players in Response to Artificial Ultraviolet Radiation

cDNA array technology was used to identify novel genes participating in the ultraviolet response of cultured human keratinocytes. cDNA arrays representing more than 50,000 different cDNA clones were hybridized with complex probes generated by SMART-polymerase chain reaction amplification of 150 ng of total RNA extracted 24 h after ultraviolet irradiation. Fifty-one clones with differential hybridization signals were detected, representing 19 different sequences; 10 known genes (seven ultraviolet induced, three ultraviolet suppressed) and further nine expressed sequence tags of unknown genes. In seven of 10 genes the data from cDNA arrays probed with SMART-cDNA could be confirmed by northern blot analysis. The 27 kDa heat shock protein mRNA was induced. Keratins 6 and 17, markers for the hyperproliferative status of keratinocytes, were among the ultraviolet suppressed genes. The change of expression profile of keratins indicates a differentiation towards a phenotype of keratinocytes present in the suprabasal layers of the epidermis. These mechanisms may contribute to the ultraviolet protective function of the epidermis and to the anti-proliferative action of ultraviolet in the therapy of psoriasis. We also detected an induction of adenylyl cyclase associated protein and the suppression of G(s)alpha (a stimulating subunit of the trimeric membrane bound GTPase).

Effect of solar ultraviolet radiation on growth in the marine macroalga Dictyota dichotoma (Phaeophyceae) at Helgoland and its ecological consequences

At Helgoland, in the North Sea, growth of the high sublittoral brown macroalga Dictyota dichotoma (Hudson) Lamoroux was examined in October (the time of tetraspore release) in an outdoor tank by exposing 2-day-old germlings to four solar radiation treatments achieved with different filter materials or an additional artificial light source: photosynthetically active radiation (PAR; 395–700 nm), PAR plus ultraviolet (UV)-A (320–700 nm), full solar spectrum, or solar spectrum plus artificial UV radiation (UVR). Based on length measurements over a period of 3 weeks, the growth rate in germlings strongly decreased in conditions with UVR compared to PAR: by 14% under PAR+UV-A, by 31% under the full solar spectrum and by 65% with additional UVR. Although growth rates of germlings under UVR were reduced mainly in the first week, the plants did not regain the size of the untreated plants even after 9 weeks. Regardless of the exposure, no defects in morphology or anatomy including the exposed apical meristem were detected, except for a reduction in cell division rates perhaps due to additional cost for photoprotective or repair mechanisms. Depending on the actual position of D. dichotoma plants in the natural habitat, individuals in high positions receive substantial amounts of the more harmful UV-B while those lower down might only receive UV-A during part of the day, thus the effect of UV-B on the growth of D. dichotoma will depend on its position in the field. The effects of tidal variation of the light climate and the implications of our results for the zonation of D. dichotoma are discussed.

The effect of UV irradiation on uracil thin layer measured by optical waveguide lightmode spectroscopy

The polycrystalline uracil thin-layer dosimeter is a well-established method to monitor the biological effects of the environmental ultraviolet (UV) radiation. It is based on the optical density (OD) decrease of the uracil layer in the UV absorption band due to photodimerization of the crystal caused by UV irradiation. In the present study, we report measurements made with optical waveguide lightmode spectroscopy (OWLS) to characterize the changes in the optogeometrical parameters of the uracil layer caused by an artificial UV source. It is shown that UV irradiation causes a decrease in the refractive index and an increase of the optical anisotropy. The determined kinetic parameters of the UV dose–sensor response curves correlate well with results of OD measurements, but the sensitivity of OWLS is about ten times higher. The results show that OWLS is capable of analyzing the UV response of the uracil layer and opens the way for dosimetrical applications.

Effect of ultraviolet radiation on thallus absorption and photosynthetic pigments in the red alga Porphyra umbilicalis

The effect of ultraviolet (UV) radiation on thallus absorption, package effect, the concentration of photosynthetic pigments, photosynthetic oxygen production and effective quantum yield has been studied in the intertidal red macroalga Porphyra umbilicalis in the laboratory. High doses of UV-A and UV-B radiation result in a rapid decrease of thallus absorption and, after a 6 h exposure, total absorption is reduced to 25% of the initial value. Moreover, significant differences in the absorption peaks of the main pigments are found: while chlorophyll a (Chl a) and phycocyanin absorption peaks decrease by 65–67%, carotenoids and phycoerythrin (PE) peaks decrease by 75–82%. Uncoupling of the transfer of energy between PE and Chl a by UV is revealed by a gradual increase of fluorescence of PE up to 11 h of exposure, followed by a subsequent decrease of fluorescence of the PE, in parallel with the photobleaching of the pigments. Thalli with higher pigment concentration present a greater sensitivity to UV radiation, as revealed by a more pronounced decrease in total thallus absorption, oxygen production and effective quantum yield, and a less effective recovery under low irradiation. Exposure of the thalli to artificial UV radiation in an experimental chamber with spectra and doses more similar to those of the natural environment reveals that PAR + UV-A radiation promotes a gradual increase of the total absorption over 24 h; in contrast, PAR + UV-A + UV-B induces a significant decrease of the thallus absorption. However, the concentration in vitro of Chl a, carotenoids and biliproteins does not change in any of these light treatments. The spectrally averaged in vivo absorption cross section normalized to Chl a ( a *) increases after 24 h in PAR + UV-A, but it does not change in PAR and PAR + UV- A + UV-B, indicating that the degree of packing of the pigments in the membranes of the thylakoids (package effect) is decreased by PAR + UV-A, but that the reverse is induced by PAR + UV-A + UV-B. It is proposed that UV-A radiation induces an enhancement of the efficiency of light capture mediated by a relaxation of pigment packing in the light-harvesting antennae of this intertidal macroalga, while the reverse is promoted by UV-B radiation.

The potential use of annealed high-albite (AlSi3O8Na) as an ultraviolet radiation dosimeter

The potential use of annealed high-albite (AlSi3O8Na) as an ultraviolet radiation dosimeter

Effects of photoinduced toxicity of fluoranthene on amphibian embryos and larvae

AbstractEmbryos and newly hatched larvae of three amphibian species, the spotted salamander (Ambystoma maculatum), the northern leopard frog (Rana pipiens), and the African clawed frog (Xenopus laevis), were exposed to fluoranthene and ultraviolet (UV) light in two scenarios. Embryos were exposed in a laboratory setting from an early developmental stage through hatching under artificial UV light, and newly hatched larvae were exposed outdoors in varying sunlight intensity levels. Outdoor exposures indicated greater sensitivity in the toxic response than did laboratory exposures. In the laboratory, mortality and malformation of X. laevis were the most sensitive indicators of exposure. Xenopus laevis was also the most sensitive species tested to the effects of UV light alone. Hatching success of R. pipiens was monitored outdoors and was not a useful predictive endpoint in the determination of photoinduced toxicity; however, newly hatched larvae were sensitive to the effects of photoinduced toxicity. Amybstoma maculatum and X. laevis larvae were affected by low (μg/L) concentrations of fluoranthene in sunlight. These findings suggest that low levels of polycyclic aromatic hydrocarbons could be acting synergistically with environmental factors such as UV light to place young amphibians at risk.

Effectiveness of Eye Drops Protective against Ultraviolet Radiation

Background: To test the effectiveness of commercially available ultraviolet (UV)-protective eye drops (8-hydroxy-1-methylchinolinium methylsulphate) which are recommended for protection against both solar and artificial UV radiation. Methods: The spectral transmission in the wavelength range from 250 to 500 nm was investigated in 1-nm steps using a high-resolution double monochromator with holographic gratings of 2,400 lines/mm and a 1,000-watt halogen lamp as light source. The transmission spectrum was measured for different values of the layer thickness. Results: The transmission of a liquid layer of about 10 µm, which corresponds to the thickness of the human tear film, shows a cut-off at 290 nm with a transmission of about 25–50% at shorter wavelengths. For wavelengths longer than 290 nm the transmission is higher than 90%. The threshold time ratio for keratitis formation with and without eye drops is above 0.93 considering solar radiation on the earth’s surface and above 0.65 considering radiation from arc-welding, respectively. Discussion: The transmission spectrum of the eye drops under realistic conditions does not show a protective effect against solar UV radiation. However, there exists reduction of UVC radiation in the spectral range typical of artificial UV sources such as arc-welding. We cannot recommend the application of these eye drops as an UV-protective aid against eye damage by solar UV radiation.

EFFECTS OF PHOTOINDUCED TOXICITY OF FLUORANTHENE ON AMPHIBIAN EMBRYOS AND LARVAE

Embryos and newly hatched larvae of three amphibian species, the spotted salamander (Ambystoma maculatum), the northern leopard frog (Rana pipiens), and the African clawed frog (Xenopus laevis), were exposed to fluoranthene and ultraviolet (UV) light in two scenarios. Embryos were exposed in a laboratory setting from an early developmental stage through hatching under artificial UV light, and newly hatched larvae were exposed outdoors in varying sunlight intensity levels. Outdoor exposures indicated greater sensitivity in the toxic response than did laboratory exposures. In the laboratory, mortality and malformation of X. laevis were the most sensitive indicators of exposure. Xenopus laevis was also the most sensitive species tested to the effects of UV light alone. Hatching success of R. pipiens was monitored outdoors and was not a useful predictive endpoint in the determination of photoinduced toxicity; however, newly hatched larvae were sensitive to the effects of photoinduced toxicity. Amybstoma maculatum and X. laevis larvae were affected by low (μg/L) concentrations of fluoranthene in sunlight. These findings suggest that low levels of polycyclic aromatic hydrocarbons could be acting synergistically with environmental factors such as UV light to place young amphibians at risk.

Vitamin D3 in Tilapia mossambica: relevance of photochemical synthesis.

The capability of fish to synthesize vitamin D on exposure to ultraviolet (UV) light was examined. Purposeful exposure of the freshwater fish Tilapia mossambica (Tilapia) to artificial UV light (300 nm) resulted in a significant increase of vitamin D3 with a concomitant decrease in provitamin D3 [7-dehydrocholesterol (7-DHC)], indicating that provitamin D3 was converted to vitamin D3. However, only 0.13% of the intraperitoneally injected 4-14C cholesterol was recovered in the vitamin D3 and 25-hydroxyvitamin D3 (25-OH-D3) fractions after 15 h of irradiation. Thus, although fish is capable of photosynthesizing vitamin D through constant, prolonged exposure to UV light of appropriate wavelength, the contribution of this mode of synthesis is unlikely to be of any significance in its natural habitat.

Dorsal skin reactions to sunlight and artificial ultraviolet light in hairless descendants of Mexican hairless dogs.

Dorsal skin reactions to irradiation with two different types of ultraviolet (UV) light sources (sunlight and artificial UV light) were investigated in hairless descendants of Mexican hairless dogs. The total energy dose of solar UV exposure and artificial UV irradiation was 90 kJ/m2 and 40 kJ/m2, respectively. Histological examinations were done up to 7 days after UV irradiation (7 DAI). At 1 DAI, the solar UV-exposed skin did not show marked changes, while artificial UV irradiated skin exhibited a visible erythematous reaction and prominent histological alterations such as epidermal thickening, appearance of sunburn cells and deformation elastic fibers. At 4 DAI of solar UV-exposure, the skin color became moderately dark and noticeable pigmentation developed in the epidermis. In contrast, at 4 DAI of artificial UV irradiation, there still remained moderate degeneration in the epidermis and dermis, and delayed tanning was weak. At 7 DAI of solar exposure, delayed suntan reactions became more prominent. Histologically, there were heavy pigmentation of melanin granules mainly in the stratum basale. On the other hand, artificial UV irradiated skin showed less pigmentation. Thus, solar exposure provoked remarkable pigmentation while artificial UV irradiation brought about severe sunburn reactions in the dorsal skin of hairless dogs.

Photodegradation of sulfamethoxazole: a chemical system capable of monitoring seasonal changes in UVB intensity.

Sulfamethoxazole (SMX) in its nonionized form in aqueous solution has ultraviolet (UV) absorption that is maximal at 268 nm but extends through the ultraviolet-B (UVB) region. It was found to be extremely susceptible to photodegradation when exposed to artificial UV radiation through a Pyrex filter or to unfiltered natural sunlight. The SMX anion was more stable. The quantum yields of the photodegradation of both forms were determined by use of monochromatic light and ferrioxalate chemical actinometry, the values of 0.47 (pH 3.0) and 0.084 (pH 9.0) at the maximum absorption wavelengths (268 and 257 nm, respectively) being obtained. Using literature data on sunlight intensity, the photochemical shelf-life of SMX solutions exposed to direct sunlight was calculated for Sydney (latitude 33.5 degrees S) as a function of season of the year and verified experimentally. A fixed correlation was established between the rate constant for SMX degradation and UVB intensity measured by a radiometer, suggesting the capacity of this chemical system to monitor changes in the UVB region of sunlight.

Pigmented lesions as a sign of photodamage.

Chronic exposure to ultraviolet (UV) radiation causes skin changes, known as photodamage. Apart from damage to the connective tissue of the dermis and to keratinocytes, pigmented lesions, known as 'age spots', occur. There are several types, but the most common lesions are the senile lentigines. The main differential diagnoses include reticular seborrhoeic keratosis and lentigo maligna, and histopathological examination is required for exact differentiation. Variants of lentigo senilis with acute onset after intense UV radiation are sunburn freckles. Psoralens- and UVA-induced freckles, and lentigines occur after phototherapy with artificial UV sources or use of sunbeds for cosmetic tanning. Ephelids are common genetically determined pigment spots appearing during childhood in a distinct photodistribution. Exposure to UV radiation also seems to play a role in the manifestation of acquired nevi. Since pigmented lesions in sun-damaged skin represent more than one entity, they differ in their response to treatment. This should be taken into account when the efficacy of topical therapy is evaluated.

Weathering characteristics of hardwood surfaces

Four hardwoods, red oak, white oak, yellow-poplar, and sweetgum, were exposed to outdoor weathering and to artificial ultraviolet (UV) light with wavelengths of λ>220 and >254 nm. Discoloration and loss of brightness were observed from all specimens regardless of their exposure conditions. White oak and sweetgum changed color at a slower rate than did red oak and yellow-poplar. SEM micrographs showed that all wood species exhibited surface deterioration after 30 days exposure to sunlight or 500 hrs to UV light. Loss of middle lamella, separation of procumbent cells, and damage of pit structures were observed on transverse sections for all species. ESCA studies revealed a high oxygen content at the wood surfaces indicating severe oxidation of wood exposed either outdoors or to artificial UV light. The generation of new chromophoric groups such as carbonyls, carboxylic acids and quinones, and the loss of lignin at the oxidized surface were demonstrated experimentally by infrared studies.

Reusable ultraviolet monitors: Design, characteristics, and efficacy

Reusable ultraviolet dosimetry badges have been developed that provide a visual indication of daily cumulative ultraviolet (UV) exposure. These two-sided, tapelike devices measure UV radiation emitted by sunlight or an artificial UV light source exposure by means of a photochromic aziridine color change reaction that is UV-integrating but optically reversible. UV radiation falling on the exposure side of the badge generates a color change that can be seen from the opposite or readout side. End points are indicated by a visual match of the photochromic with a surrounding reference. This paper describes the construction, component characteristics, and clinical testing of two versions of a new photochromic dosimeter that selectively responds to either UVB (280–320 nm) radiation or UVA (320–400 nm) radiation of the solar spectrum. One version of this monitor, sensitive only to the mid-range UVB, has a peak sensitivity to 300 nm and has four end point markers revealing color changes corresponding to 0.4, 0.8, 2.2, and 6.5 times the minimal erythema dose of an average Caucasian. A second version, sensitive only to UVA, has a peak sensitivity at 355 nm and can monitor exposures ranging from 0.8 to 10 joules/cm 2. Outdoor efficacy testing has shown that the UVB monitor is an effective predictor of UV dose—related 24-hour erythema response induced by sunlight. Following a measurement, these monitors can be rezeroed by exposing the readout side to sunlight for a few minutes. They can be reused for eight to ten times. The limitation of the sunlight-calibrated UVB monitor tag is its failure to predict erythema response produced by artificial UVB sources such as FS40 sunlamps.

Contribution to the Staining of Neuroglia

The chemistry of Weigert's glia staining method is critically discussed. An investigation of the Heidelberger Victoria blue staining method has shown that Victoria blue may be replaced by other phenylmethane dyes as methyl violet, ethyl violet, and crystal violet. It was found that the exposure of the stained section to sunlight is an oxidation process. Artificial ultra violet rays or chemical oxidation agents give the same effect. Frozen sections fixed in formalin or alcohol may be stained in a concentrated aqueous solution of any of the above mentioned phenylmethane dyes, dried, and exposed to ultra violet rays for 30 minutes, then treated with 1/10 N. iodine solution, differentiated in xylol anilin and cleared in xylol. The glia cell body as well as the fibrils are clearly differentiated from the nervous elements and connective tissue.