Xenon chloride ultraviolet B laser is more effective in treating psoriasis and in inducing T cell apoptosis than narrow-band ultraviolet B

Earlier we reported that a 308-nm xenon chloride (XeCl) UVB laser is highly effective for treating psoriasis. As ultraviolet B light seems to cause T cell apoptosis, in the present study we studied the ability of the XeCl laser to induce T-cell apoptosis in vitro, and then compared the apoptosis-inducing capacities of narrow-band UVB (NB-UVB) light and the XeCl laser. The role of laser impulse frequency and intensity in the therapeutical and apoptosis-inducing efficacy of XeCl laser was also investigated. Both XeCl laser and NB-UVB induced T cell apoptosis, but quantitative induction was greater with XeCl laser. Changes in the frequency and intensity of impulses of XeCl laser did not influence its therapeutic and T cell apoptosis-inducing efficacy. These results suggest that the more effective induction of T cell apoptosis can be responsible for the greater clinical efficacy of XeCl laser compared to NB-UVB. Additionally, the optical properties of the XeCl laser (a monochromatic, coherent, pulse-mode laser; easier precise dosimetry, there are no 'contaminating' wavelengths) can make this laser light an ideal tool for studies of the mode of action of UVB light.     

DYES AND DYE MIXTURES USEFUL FOR GENERATION OF UV IN A FLASHLAMP DRIVEN TUNABLE DYE LASER

Abstract— We have used a flashlamp driven tunable dye laser combined with angle tuned frequency doubling crystals for producing UV-B radiation for action spectra studies of various organisms. Optimum UV-B power generation is needed to provide biologically effective doses at wavelengths greater than 300 nm. Optimizing power will also serve to lengthen the lifetime of dyes and other laser components at shorter wavelengths where UV-B output is more than adequate. While much information is available on dyes and dye performance from manufacturers, little information is available on the use of dyes and dye mixtures for providing the continuous high power spectrum of wavelengths necessary for biological UV action spectroscopy. We have examined a number of dyes and dye mixtures for optimal laser performance at wavelengths from 260 to 330 nm. The dyes and dye mixtures discussed here provide adequate power output in the UV-B wavelength range and have allowed us to perform numerous UV-B action spectra studies using the tunable dye laser.     

A NOVEL EFFECT OF UV-B IN A HIGHER PLANT (SORGHUM VULGARE)

Abstract— Two non-photosynthetic photoreceptors (phytochrome and the usual blue/UV light photoreceptor) were previously found to be involved in light-mediated anthocyanin synthesis in the mesocotyl of Sorghum seedlings (Drumm and Mohr, 1978). The decisive point is that phytochrome can act only after a blue/UV light effect has occurred. On the other hand, the expression of the blue/UV light effect is controlled by phytochrome ('obligatory sequential action'). A strong positive interaction between the blue/UV-A and the UV-B part of the spectrum was found, in addition to the above sequential action: an inductive effect of blue or UV-A light can only express itself fully if short wavelength UV (approximately 300–320nm. UV-B range) is also given, either after the blue/UV-A light or simultaneously. Since even small amounts of the UV-B are strongly effective it is probable that this effect plays a role under natural conditions and may not be considered as a mere laboratory artifact.     

Analysis of glass by UV laser ablation inductively coupled plasma atomic emission spectrometry. Part 1. Effects of the laser parameters on the amount of ablated material and the temporal behaviour of the signal for different types of laser

Two lasers working in the UV part of the spectrum have been used for the analysis of glass samples. An XeCl excimer laser (308 nm) and a Nd:YAG laser operating at the third harmonic (355 nm) and the fourth harmonic (266 nm) have been selected. The energy was 100 mJ and 5 mJ for the excimer laser and the Nd:YAG laser, respectively. Because of different spot sizes, the fluence was of the same magnitude for both lasers. Crater characterization indicated that the laser ablation efficiency was similar for the two lasers when normalized to the same energy. However, the XeCl was found to be more efficient when the results were normalized to irradiance unit. The amount of probed material and ablated material was measured, leading to an efficiency higher than 80%. The influence of the glass colour and the laser wavelength was evaluated. The XeCl laser provided the largest amount of material but was sensitive to the glass colour. This laser was mainly suitable for bulk analysis. In contrast, the Nd:YAG, particularly at 266 nm, was insensitive to the glass colour and was appropriate for localized analysis. Inductively coupled plasma atomic emission spectrometry was used for atomization and excitation of the ablated material. A good agreement was found between the temporal behaviour of the amount of ablated material and the analyte signal.     

OBSERVED AND PREDICTED MINIMAL ERYTHEMA DOSES: A COMPARATIVE STUDY

Abstract This study compared how well minimal erythema doses predicted using the reference action spectrum for UV erythema proposed by the International Commission on Illumination (CIE) in 1987 agreed with those observed in phototesting a large number of subjects with normal responses to sunlight to six different wavelengths of UV radiation (UVR) between 300 and 400 nm. It was found that, within the limits of experimental error, the hypothesis that the CIE reference action spectrum is a valid predictor of the erythemal effectiveness of different wavelengths of UVR could not be dismissed. There is no strong reason, therefore, why the CIE action spectrum should not continue to be used as a reference to compare the erythemal effectivenesses of different broadband sources. However, close examination of the residuals from the regression analysis suggested that the erythemal sensitivity of skin at longer UV wavelengths (>350 nm) in the population studied here is greater than predicted from the CIE reference action spectrum.     

ULTRAVIOLET RADIATION IN ANTARCTICA: INHIBITION OF PRIMARY PRODUCTION

With the seasonal formation of the ozone hole over Antarctica, there is much concern regarding the effects of increased solar UV-B radiation (280–320 nm) on the marine ecosystem in the Southern Ocean. In situ incubations of natural phytoplankton assemblages in antarctic waters indicate that under normal ozone conditions UV-B radiation is responsible for a loss of approximately 4.9% of primary production in the euphotic zone, whereas UV radiation with wavelengths between 320 and 360 nm causes a loss of approximately 6.2%. When combined with data on the action spectrum for photoinhibition by UV radiation, our data suggest that the enhanced fluence of UV-B radiation under a well-developed ozone hole (150 Dobson units) would decrease daily primary productivity by an additional amount of 3.8%. Calculations that take into consideration the extent and duration of low stratospheric ozone concentrations during September to November indicate that the decrease in total annual primary production in antarctic waters due to enhanced UV-B radiation would be 0.20%.     

Wavelength dependence of histological, physical, and visible changes in chronically UV-irradiated hairless mouse skin

Albino hairless mice (Skh: HR-1) exposed chronically to sub-erythemal doses of UV radiation display physical, visible and histological alterations. Using narrow bandwidth radiation covering the UV radiation spectrum from 280-380 nm, the wavelength dependence of these alterations was determined. The wavelength dependence spectra indicate that for all but one parameter measured (skin sagging), UV-B radiation is considerably more efficient than UV-A radiation in producing changes in the skin. However, in natural sunlight there is considerably more UV-A than UV-B radiation, providing the potential for UV-A to have a larger contribution to skin damage than UV-B. This argues in favor of using broad spectrum photoprotective agents to shield the skin adequately from UV-induced aging. The spectra were also used to develop potential associations among events by determining which events occur at similar wavelengths. There seems to be a correspondence between mouse visible skin wrinking (UV-B event) and two histological events: increase in glycosaminoglycans and alteration in collagen. There was no obvious correspondence among UV-A-induced events.     

GENETIC EFFECTS OF UV-B: MUTAGENICITY OF 308 nm LIGHT IN CHINESE HAMSTER V79 CELLS

Abstract —Chinese hamster V79 cells were irradiated with 254 nm (UV-C) and 308 nm (UV-B) light, emitted by a germicidal lamp and an excimer laser, respectively. Induction of mutations at two distinct genetic loci was measured by selecting colonies resistant to 6-thioguanine or to ouabain. Unlike 6-thioguanine resistance which can be presumed to be due to many different types of genetic damage, mutation to ouabain resistance seems to result from base-pair substitution events only. Much higher doses of 308 than of 254 nm radiation are required to induce equivalent numbers of mutants. However, induction of cell inactivation and 6-thioguanine resistant mutations with the two UV sources appears to be correlated, suggesting that a common mechanism, perhaps involving the induction of pyrimidine-containing dimers, is involved. The frequency of ouabain resistant mutants per lethal event is on the other hand much higher after irradiation with the 308 nm light. This latter finding further defines a part of the UV-B spectral region which seems to induce a unique kind of DNA damage which specifically results in base-pair substitution events. Action spectra studies therefore appear necessary in the definition of the mutagenic effects of UV-B radiations in mammalian cells.     

Intranasal irradiation with the xenon chloride ultraviolet B laser improves allergic rhinitis

We earlier reported that the 308 nm xenon chloride (XeCl) ultraviolet B (UVB) laser is highly effective for the treatment of inflammatory skin diseases. Since UVB irradiation has been shown to exert both local and systemic immunosuppression, we investigated the clinical efficacy of UVB irradiation in allergic rhinitis. In an open study, groups of patients with severe allergic rhinitis received intranasal irradiation with a 308 nm XeCl UVB excimer laser for two weeks. In the low-dose group (n=10), treatment was given twice weekly, starting with 0.25x the individual minimal erythema dose (MED), whereas patients in the medium-dose group (n=8) were treated four times weekly, starting with 0.4x MED. In each group, the dosage was gradually increased. Evaluation was based on the symptom scores. The effect of the XeCl laser on the skin prick test reaction was also studied. In the low-dose group, seven patients completed the study, and there was no improvement in the nasal symptoms. In the medium-dose group, the XeCl UVB irradiation significantly inhibited the rhinorrhoea, the sneezing, the nasal obstruction and the total nasal score (p<0.05). The XeCl UVB excimer laser also inhibited the allergen-induced skin prick test in a dose-dependent manner. These results suggest that the XeCl UVB excimer laser might serve as a new therapeutic tool in the treatment of allergic rhinitis.     

Two types of kinetics of membrane potential of water plant leaves illuminated by ultraviolet light

The effects of ultraviolet-B (UV-B) radiation on plasma membrane of water plant (Elodea canadensis, Vallisneria spiralis) cells were investigated by using microelectrode methods. A fast and reversible depolarization of membrane potential occurs initially during exposure of leaf cells to UV on a white light background, after which a slow phase of depolarization sets in. On action series, UV is pulsed for 15 s, with dark interval of 3 min, no monotonous response of systems on the UV excitation is observed. The action spectrum of the fast UV response lies in the interval of 300-330 nm and that of the slow phase-in the interval of 280-300 nm. The input impedance of membranes remains unchanged during the period of exposure. It is concluded that the H(+)-extruding complex of plant cell plasma membranes really consists of two types of interrelated electronic H(+)-pumps: an H(+)-pump of redox-active nature and the H(+)-pump of the H(+)-ATPase enzyme complex. Clearly, during the exposure of leaf cells to UV light, initially, the H(+)-pump of redox-active nature and then H(+)-ATPase are inhibited. It is proposed that the initial chromophore of UV-B light on plasma membrane can be one of the components of H(+)-pump of redox-active nature. It is probably the molecular of quinone.     

ANALYSIS OF LIGHT-CONTROLLED ANTHOCYANIN FORMATION IN COLEOPTILES OF Zea mays L.: THE ROLE OF UV-B, BLUE, RED AND FAR-RED LIGHT

Abstract— Light-induced anthocyanin formation in Zea mays L. coleoptiles was investigated in seven different varieties of this species. Under the test conditions, four varieties showed practically no response to any waveband used (UV, continuous red and continuous far-red), two responded strongly to both UV and far-red, and one showed a strong response only to far-red. The radiation-sensitive varieties showed, however, only a very weak response to continuous red light. In those varieties sensitive to far-red light, a pretreatment with continuous red light led to a greatly enhanced response to UV or in one case the manifestation of a response to UV that was previously lacking. Further investigations in one radiation-sensitive variety (INRA) showed that the UV response was to UV-B radiation below 350 nm. The UV response, as well as the far-red and blue responses in this variety, showed fluence-rate dependency. Red light was almost ineffective and showed only a very weak fluence-rate dependency.     

PHOTOAGING EFFECTS ON SPECTRAL TRANSMITTANCE OF PLASTIC FILTERS

We examined the effects of ultraviolet (UV) radiation in combination with high levels of infrared (IR) radiation on the spectral transmittance of plastic filters. The biological action spectrum for damage to the human eye and skin changes dramatically in the 300-400 nm wavelength range. Cut-off filters used in this region to shape the spectrum of exposure sources are thus critical to the design of experiments which use broadband light sources. The changes in transmittance of three types of plastic filters were observed over an exposure period of 1000 h. One set of three filters was exposed mainly to UV radiation, while the other set was exposed to UV radiation plus IR radiation. Filters exposed to both UV and IR radiation showed spectral changes in their transmittance, while the filters exposed to UV only showed no measurable changes.     

Analysis of glass by UV laser ablation inductively coupled plasma atomic emission spectrometry. Part 2. Analytical figures of merit

Two lasers working in the UV part of the spectrum have been used for the direct analysis of glass samples by laser ablation ICP-AES. An XeCl excimer laser (308 nm) and a Nd:YAG laser operating at the third harmonic (355 nm) and the fourth harmonic (266 nm) have been selected. The energy was 70 mJ and 5 mJ for the excimer laser and the Nd:YAG laser, respectively, with a 10 Hz repetition rate. Figures of merit such as repeatability, reproducibility, accuracy and limits of detection have been studied. Si was used as an internal standard to improve the repeatability, the reproducibility and the accuracy. Use of internal standardardization led to an RSD of less than 1% for most elements and to a linear calibration graph irrespective of the colour of the glass samples. Limits of detection in the solid were of the same magnitude as those obtained using sample dissolution and pneumatic nebulization. Results confirmed that the XeCl laser provided the best results of detection whereas the Nd:YAG laser, particularly at 266 nm, was less sensitive to glass colour.     

PUVA treatment of the nasal cavity improves the clinical symptoms of allergic rhinitis and inhibits the immediate-type hypersensitivity reaction in the skin

We earlier reported that intranasal irradiation with the 308 nm xenon chloride (XeCl) ultraviolet-B laser and irradiation with a combination of ultraviolet-B (UVB), ultraviolet-A (UVA) and visible light (VIS) is highly effective in the treatment of allergic rhinitis and inhibit the immediate-type hypersensitivity reaction in the skin. Since photochemotherapy with 8-methoxypsoralen (8-MOP) plus UVA light (PUVA) is widely used in the treatment of different inflammatory skin disorders due to its immunosuppressive effect, in the present study we investigated the efficacy of intranasal PUVA treatment in allergic rhinitis and the effect of PUVA treatment on the skin prick test (SPT) reaction. An open study was performed in 17 patients with hay fever. Intranasal PUVA therapy was given four times weekly for 3 weeks. The treatment was started with a fluence of 0.5x of the individual minimal phototoxic dose (MPD) and the dosages were gradually increased. Evaluation was based on the symptom scores. The effect of PUVA treatment on the allergen-induced wheal formation was also studied in the SPT. PUVA treatment of the nasal cavity significantly decreased the nasal symptoms of the patients with allergic rhinitis. Treatment of the skin with PUVA also significantly suppressed the allergen-induced wheal formation in the SPT reaction. These data suggest that intranasal PUVA phototherapy is also an effective modality in the treatment of allergic rhinitis.     

Reduction of UV-B radiation causes an enhancement of photoinhibition in high light stressed aquatic plants from New Zealand lakes

Anthropogenic stratospheric ozone depletion causes an increase of UV-B radiation impinging on the earth surface, which is a threat to plants not adapted to higher UV-B irradiances. Investigations were undertaken with aquatic plants from New Zealand, where UV-irradiances are naturally higher due to the southern latitude, to compare with former results of polar species. The experiments reported in this study were undertaken with plants collected from different lakes of the South Island, with different UV transparencies. Photoinhibition was induced under controlled conditions using a sun simulator, which mimicked the natural underwater radiation spectrum. Photosynthetic activity during high light stress, and during recovery in dim light, was determined in vivo by measuring fluorescence changes, using a PAM fluorometer device. A comparison of different species showed that the extent to which UV causes an additional decrease of photosynthetic performance during high light stress varies according to the depth of growth and UV transparency of the water body. This observation fits with previous studies. However, a new finding was that some species were even more strongly inhibited when UV-B was filtered out of the simulated sun spectrum, indicating a supporting effect of the short UVR wavelength range against photoinhibition. These results were also confirmed by field experiments under natural radiation conditions. Thus, UV-B does not solely cause negative effects on photosynthesis, but it may even support recovery processes in aquatic plants adapted to a high UV-radiation environment. The latter is in contrast to earlier studies, in which UV-B radiation was considered causing only harmful effects on photosynthesis of aquatic plants.     

INHIBITION OF PHOTOTAXIS IN Volvox aureus BY NATURAL AND SIMULATED SOLAR ULTRAVIOLET LIGHT

Exposure to artificial UV wavelengths and the UV component of sunlight delays positive phototaxis in the green alga Volvox aureus. Broad band wavelength filters were used to modify the output from UV-B sources (280-320 nm) and natural sunlight. The delay in phototaxis by artificial UV is increased with exposure to shorter UV-B wavelengths. Natural sunlight experiments were performed with exposure to full sunlight and to its UV component only. The UV component present in summer sunlight produced long periods of inhibition in phototaxis and even lethality, while exposure to the total spectrum of sunlight had no significant effects on movement or survival. The data indicate that although this species of alga is well equipped to deal with present levels of UV exposure, increases in the short UV-B wavelengths in sunlight may force an alteration in patterns of photomovement.     

The European Light Dosimeter Network: four years of measurements

The European Light Dosimeter Network (ELDONET) has now been functional for more than four years. The network is based on dosimeters which measure radiation in three biologically relevant wavelength bands (UV-B, 280-315 nm; UV-A, 315-400 nm; and Photosynthetic Active Radiation, PAR, 400-700 nm). The ELDONET network is currently based on 33 stations with 40 instruments. The distribution of the instruments all over Europe allows measurement of the latitudinal and longitudinal light climate distribution. In addition, several instruments are active in South America, New Zealand, India, Africa and Japan. With some exceptions, the measured yearly doses depend on the latitude. While the maximal daily doses are almost comparable from station to station, seasonal changes and the different maximal solar zenith angles account for the differences in total yearly doses. Ratioing between UV-B and PAR allows the detection of subtle changes in the local light climate, due, for example, to mini-ozone holes encountered in northern Europe during spring. Comparison of satellite ozone data with terrestrial ELDONET measurements revealed an overall weak correlation between these data sets. However, local weather conditions, solar zenith angle and latitude as well as reflectivity (i.e. clouds and aerosol; satellite data) show a much stronger correlation to the doses received. The close relationship between the spectral sensitivity of the UV-B sensor used in the ELDONET dosimeter and the CIE erythemal action spectrum allows determination of the erythemal dose on the basis of the dosimeter readings.     

An estimation of biological hazards due to solar radiation

A spectrum evaluator based on four different dosimeter materials has been employed to estimate the spectral irradiances of solar radiation for exposed humans. The result is used to calculate the biologically effective irradiance using the erythemal action spectrum and a fish melanoma action spectrum. Measurements are made in winter at a sub-tropical site on the chest and shoulder of subjects during normal daily activities. Up to 95% of the total UV exposure received is in the UV-A waveband (320-400 nm). The UV-A waveband is found to contribute approximately 14% of the erythemal UV and 93% of the biologically effective UV for fish melanoma. Extrapolation to humans suggests that exposure to the UV-A band will contribute to photodamage in human skin during exposure to solar radiation.