UVC Range Research Articles

Transmittance properties of flurandrenolide tape for psoriasis: helpful adjunct to phototherapy.

Flurandrenolide tape is a valuable agent in the treatment of lichen simplex chronicus and in psoriasis. The corticosteroid is helpful for reducing the symptoms and induration of the lichen simplex chronicus lesion, and occlusion of the lesion with the tape reduces the patient's opportunity to rub and scratch the affected area. The purpose of this study was to determine to what extent flurandrenolide tape may block ultraviolet (UV) light and interfere with phototherapy of psoriasis. Flurandrenolide tape was applied to quartz spectroscopy cuvettes, and the absorption spectrum was determined using a Beckman DU-600 spectrophotometer. The effect of the tape on UV light transmission was also determined using our UVA-UVB office phototherapy unit. Flurandrenolide tape has considerable UV absorption in the UVC range with less absorption in the UVB and UVA range. The transmittance is greater (less absorption) with longer wavelengths. There was greater UV absorption in the UVB range than in the UVA range. Although flurandrenolide tape may be left in place during PUVA therapy, adjustment of UV dose or removal of the tape is probably needed during UVB phototherapy.

Phenolic compounds and antioxidant properties in the snow alga Chlamydomonas nivalis after exposure to UV light

The snow alga Chlamydomonas nivalis was collected from the Sierra Nevada, California, USA, and examined for its ability to produce phenolic compounds, free proline, and provide antioxidant protection factor in response to UV-A and UV-C light. Exposure of C. nivalis cells to UV-A light (365nm) for 5 days resulted in a 5–12% increase in total phenolics, where as exposure to UV-C light (254 nm) resulted in a 12–24% increase in phenolics after 7 days of exposure. Free proline was not affected by UV-A, but increased markedly after UV-C exposure. A three-fold increase in free proline occurred within two days after exposure to UV-C, but then dropped as cells became bleached. Antioxidant protection factor (PF) increased after treatment of cells with UV-A and remained constant throughout UV-C exposure. Spectral analysis of algal extracts revealed a decrease in absorption in the 215–225 nm region, short-term (2day) stimulation of pigment at 280 nm, and an increase in carotenoids (473 nm), after exposure to UV-A. Snow alga exposed to UV-C light had a different spectrum from that of UV-A exposed cells, i.e. an enhancement of three major peaks at 220, 260, and 280 nm, and loss of absorption in the carotenoid region.We report that UV light exposure, especially in the UV-C range, can stimulate phenolic-antioxidant production in aplanospores of C. nivalis effecting biochemical pathways related to proline metabolism.

Ultraviolet radiation and malignant melanoma

Electromagnetic radiation from the sun is divided into three regions: ultraviolet (UV), visible, and infrared. The UV spectrum is further subdivided into UVA (320400 nm), UVB (290-320 nm), and UVC (200-290 nm). Solar energy in the UVC range is completely absorbed by the ozone layer, and thus it does not reach the Earth’s surface.3 Although epidemiologic evidence supports the notion that sunlight is germane to the development of cutaneous melanoma, the precise action spectrum for melanoma formation is still unknown. For nonmelanoma skin cancer, UVB appears to be the most carcinogenic.” What is the evidence for UVB’s involvement in melanoma? First, UVB can be absorbed by DNA, leading to mutations and cellular transformation. Second, UVB can stimulate melanocytic proliferation. Third, UVB is immunosuppressive in mice and can lead to diminished tumor resistance. Fourth, blistering sunburns are caused by UVB and represent a risk factor for melanoma. Lastly, melanoma incidence correlates directly with UVB flux and gradients of UVB by latitude.” Absorption of UVB energy by DNA leads to photoproducts such as pyrimidine dimers.6 If DNA repair is not properly executed, mutations in critical oncogenes, such as the ras oncogene, can lead to uncontrolled melanocyte proliferation and eventual tumor formation.7,8 Likewise, UVB may also interfere with normal functioning of tumor-suppressor genes, thereby inducing melanoma. A group of investigators has shown that UVB-

Effects of vacuum UV and UVC radiation on dry Escherichia coli plasmid pUC19 II. Mutational specificity at the lacZ gene

The mutational spectra at the lacZ gene, induced either by vacuum UV at 160 nm or UVC at 254 nm in vacuum-dried preparations of Escherichia coli plasmid pUC19 DNA, have been characterized from 72 E. coli-propagated mutants by DNA sequencing. In plasmids irradiated in vacuum, vacuum UV is five times more mutagenic than UVC. In the UV-induced mutants, base substitutions largely predominate, with GC → AT (G, guanine; C, cytosine; A, adenine; T, thymine) transitions being the most abundant type of base change for vacuum UV (61%) and UVC (47%). Most of the GC → AT transitions appear to occur at dipyrimidine sites, which are located at the non-transcribed DNA strand. Some, but not all, hot spots for GC → AT transitions are identical for vacuum UV and UVC. Frameshifts, resulting from a loss of the thymine residue, are specific for UVC (22%), and were not detected after treatent with vacuum UV. They occur predominantly at thymine runs of the transcribed DNA strand. Only a few deletions were detected following irradiation with vacuum UV (7.5%) and UVC (2%); however, their frequency is not enhanced compared with the spontaneous mutation spectrum. The data confirm the important role of base substitution mutations in UV-induced mutagenesis, which is not only valid for the UVC range, but extends towards the vacuum UV range.

Effects of vacuum UV and UVC radiation on dry E. coli plasmid pUC19 I. Inactivation, lacZ − mutation induction and strand breaks

Using Escherichia coli plasmid pUC19 as a test system to study the effects of radiation on DNA at the molecular level, the wavelength (160–254 nm) dependence of inactivation (loss of the ability to transform E. coli), mutation induction in the target gene lacZ and induction of single-strand breaks and double-strand breaks was investigated. The same fluences were applied for all endpoints tested. In the UVC range, the cross-sections of inactivation and mutation induction match the DNA absorption curve, whereas the cross-section for single-strand break induction deviates from the DNA curve, especially at 220 nm. In the vacuum UV range, with increasing energy of the photons, the cross-sections of inactivation and single-strand breaks increase sharply (from 190 to 160 nm by more than one order of magnitude), which is not reflected by the DNA curve. In this UV range, the shape of the action spectrum is similar to that of the absorption curve of the sugar phosphate moiety of DNA. Only after irradiation with vacuum UV at 160 nm are double-strand breaks detected. Their induction rate is about one order of magnitude lower than that of single-strand breaks at the same wavelength; however, their induction rate is at least twice that of single-strand breaks at longer wavelengths. Concerning mutation induction, the increment in the vacuum UV range is less well expressed. The data suggest the contribution of different kinds of photochemical injury to inactivation and mutation induction.

Do Human Tears Absorb Ultraviolet Light?

We analyzed human tears by ultraviolet (UV) spectrophotometry for transmittance of UV light. Ultraviolet light was readily transmitted through human tears in the UV-A (320-400 nm) and UV-B (290-320 nm) ranges. Tears partially absorbed UV light in the UV-C (100-290 nm) range. The clinical implications of these findings include prevention of phototoxic ocular damage and effects upon excimer laser corneal photoablative techniques.

Sensitive Detection of the Leaching‐out from Membrane‐surrounded Compartments: a New Approach Explored with Cells and Tissues of Nicotiana tabacum L.

AbstractIn search of a simple method for testing the very early events of ozone damage to susceptible plants as well as complete destruction after threshold‐exceeding treatments an over‐all measurement of cell ingredients by their optical density in the UVB and UVC range was investigated. The cell particles were liberated after membrane permeabilization or after cell bursting. Uncontrolled results could be excluded. Furthermore, the results of the developed spectrophotometrical test could be, in the case of tissue samples (leaf discs), very well reproduced with an osmometrical measurement. The latter was less sensitive and not suitable for cellular samples because the protoplasts must be dissolved in a nearly isotonic medium which caused too large a background for this method but not for the UVS test. Contrary to the osmometric measurement, the photometric one cannot be used for determining the absolute amount of cell ingredients but only for relative measurement between samples in a given range of concentrations. Oxidative changes of the liberated ingredients do not influence their detection, which was demonstrated with ascorbate. The developed leaching test was also useful for determining the membrane damage caused by the detergent Triton X‐100, although this was known to have UV absorbance by itself. It was noted that the far UV maximum is not only caused by absorbance and scattering is discussed as an additional explanation.

UVB and UVC, but Not UVA, Potently Induce the Appearance of T6-DR+ Antigen-Presenting Cells in Human Epidermis

Non-Langerhans cell, antigen-presenting T6- DR+ epidermal cells (EC) appear 3 days following broad band ultraviolet radiation exposure of human skin and are responsible for the increased antigen presentation capacity of EC seen 3 days after UV exposure. To determine the UV wavelengths that induce T6- DR+ EC, volar forearm skin of 10 human volunteers was irradiated in vivo with 4 minimal erythema doses (MED) each of pure UVA (mean 482 J cm-2), UVB (mean 0.390 J cm-2), and UVC (mean 0.397 J cm-2). The purity of the light sources was as follows: UVB, 98% of the emission was in the UVB range; UVC, 97% of the irradiance was in the UVC range; UVA, 100% of the energy had wavelengths longer than 340 nm. Three days after UV irradiation with 4 MED of each wavelength band, suction blister-derived EC suspensions were prepared from the UV-exposed and unirradiated sites. Percentages of T6+ DR+ Langerhans cells (LC) and T6- DR+ EC were quantitated. Relative to control EC, which contained 2.4 +/- 0.3% T6+ DR+ LC, the mean percentage (+/- SEM) of T6+ DR+ LC contained within UV-exposed EC was significantly decreased as follows: UVB, 0.5 +/- 0.2%; UVC, 0.9 +/- 0.1%; UVA, 0.5 +/- 0.2% (n = 10). T6- DR+ EC, absent in control EC, were induced both by UVB, 5.2 +/- 1.7% and UVC; 1.5 +/- 0.4%. Despite the use of more than 1200 times greater doses in J cm-2 of UVA than UVB and UVC, UVA was a poor inducer of T6- DR+ EC (0.5 +/- 0.2%) and in about half of these individuals, T6- DR+ EC were undetectable. The UV wavelengths for induction of T6- DR+ EC lies predominantly within the UVB band, but also to a lesser extent within the UVC band. These wavelengths appear to be analogous to both the wavelengths for generation of increased host susceptibility to UV-induced murine tumors and to the wavelengths for UV-induced systemic suppression of contact hypersensitivity. However, our data indicate that UV wavelengths for decreasing the number of T6+ DR+ LC in humans differs from the wavelengths for induction of systemic suppression of contact hypersensitivity in mice. Taken together, these data suggest that the appearance of T6- DR+ EC, but not the disappearance of T6+ DR+ LC, following UV exposure may be related to the induction of such antigen-specific suppressor T cells.