THE OCULAR DOSE OF ULTRAVIOLET RADIATION FROM SUNLIGHT EXPOSURE

Abstract— The ocular toxicity of ultraviolet radiation has been demonstrated in acute photokeratitis and is suspected of contributing to cataractogenesis and senile macular degeneration. While previous studies have emphasized photochemical and epidemiologic aspects of ocular UV-B irradiation, little is known about the extent of such exposure in human subjects. To determine levels of ocular UV-B exposure from sunlight, four mannikin headforms were fitted with UV-B sensitive film (polysulphone) and exposed on an unobstructed rooftop (Baltimore, Md.: latitude = 39.5 degrees) to four hours of sunlight (11 am-3 pm local time) over a three month period (June-August). Simultaneous measurements of ocular and ambient exposure revealed a ratio of 19.5 ± 2.9% that was independent of ambient level (P < 0.05). Measurements performed during earlier hours (8 am-11 am) revealed a similar ratio. Mannikin headforms fitted with brimmed baseball caps showed a22–95% reduction in ocular exposure, depending on the angle of the hat brim to the forehead. Three sets of spectacles substantially reduced ocular UV-B exposure,62–94% dependent on the absorption properties of the spectacle lenses. These anthropomorphic measurements indicate that a substantial percentage of ambient UV-B light is incident upon the cornea and that personal factors, such as wearing a hat or spectacles, can markedly affect UV-B exposure.     

Ambient solar UV radiation causes mortality in larvae of three species of Rana under controlled exposure conditions

Recent reports concerning the lethal effects of solar ultraviolet-B (UV-B) (290-320 nm) radiation on amphibians suggest that this stressor has the potential to impact some amphibian populations. In this study embryos and larvae of three anuran species, Rana pipiens, Rana clamitans and Rana septentrionalis, were exposed to full-spectrum solar radiation and solar radiation filtered to attenuate UV-B radiation or UV-B and ultraviolet-A (UV-A) (290-380 nm) radiation to determine the effects of each wavelength range on embryo and larval survival. Ambient levels of solar radiation were found to be lethal to all three species under exposure conditions that eliminated shade and refuge. Lethality was ameliorated by filtration of UV-B radiation alone, demonstrating that ambient UV-B radiation is sufficient to cause mortality. Although several studies have qualitatively demonstrated the lethality of UV-B to early life stage amphibians this study demonstrates that the larval life stages of the three species tested are more sensitive than the embryonic stages. This suggests that previous reports that have not included the larval life stage may underestimate the risk posed to some anuran populations by increasing UV-B exposure. Furthermore, this study reports quantitative UV-B dosimetry data, collected in conjunction with the exposures, which can be used to begin the assessment of the impact of environmental changes which increase UV-B exposure of these anurans.     

Influence of PAR and UV-A in determining plant sensitivity and photomorphogenic responses to UV-B radiation

The role of photosynthetically active radiation (400-700 nm) (PAR) in modifying plant sensitivity and photomorphogenic responses to ultraviolet-B (280-320 nm) (UV-B) radiation has been examined by a number of investigators, but few studies have been conducted on ultraviolet-A (320-400 nm) (UV-A), UV-B and PAR interactions. High ratios of PAR-UV-B and UV-A-UV-B have been found to be important in ameliorating UV-B damage in both terrestrial and aquatic plants. Growth chamber and greenhouse studies conducted at low PAR, low UV-A and high UV-B often show exaggerated UV-B damage. Spectral balance of PAR, UV-A and UV-B has also been shown to be important in determining plant sensitivity in field studies. In general, one observes a reduction in total biomass and plant height with decreasing PAR and increasing UV-B. The protective effects of high PAR against elevated UV-B may also be indirect, by increasing leaf thickness and the concentration of flavonoids and other phenolic compounds known to be important in UV screening. The quality of PAR is also important, with blue light, together with UV-A radiation, playing a key role in photorepair of DNA lesions. Further studies are needed to determine the interactions of UV-A, UV-B and PAR.     

THE DEVELOPMENT OF PERSONAL DOSIMETERS FOR USE IN THE VISIBLE AND ULTRAVIOLET WAVELENGTH REGIONS

Abstract—
We have designed, developed, and field evaluated a two-part personal dosimeter for estimating ocular exposure to visible and ultraviolet radiation. The detector head is compact enough to be mounted on the bow of eyeglass frames, and the recorder is small enough to be carried in a shirt pocket. The detector head consists of a silicon photodiode with filter (Schott glass GG400) and diffuser for visible light measurements and a polysulphone film badge for ultraviolet-B (UVB, 290–320 nm) measurements. The measurements correspond well to those obtained using ambient monitors and should be useful for studies of ocular UVB exposure.     

Ultraviolet-B radiation causes an upregulation of survivin in human keratinocytes and mouse skin

Understanding of the mechanism of ultraviolet (UV)-mediated cutaneous damages is far from complete. The cancer-specific expression of Survivin, a member of the inhibitor of apoptosis family of proteins, coupled with its importance in inhibiting cell death and in regulating cell division, makes it a target for cancer treatment. This study was designed to investigate the modulation of Survivin during UV response, both in vitro and in vivo. We used UV-B-mediated damages in normal human epidermal keratinocytes (NHEK) cells as an in vitro model and SKH-1 hairless mouse model for the in vivo studies. For in vitro studies, NHEK were treated with UV-B and samples were processed at 5, 15, 30 min, 1, 3, 6, 12 and 24 h after treatment. Our data demonstrated that UV-B exposure (50 mJ/cm2) to NHEK resulted in a significant upregulation in Survivin messenger RNA (mRNA) and protein levels. We also observed that UV-B exposure to NHEK resulted in significant (1) decrease in Smac/DIABLO and (2) increase in p53. For in vivo studies, the SKH-1 hairless mice were subjected to a single exposure of UV-B (180 mJ/cm2), and samples were processed at 3, 6, 12 and 24 h after UV-B exposure. UV-B treatment resulted in a significant increase in protein or mRNA levels (or both) of Survivin, phospho-Survivin and p53 and a concomitant decrease in Smac/DIABLO in mouse skin. This study demonstrated, for the first time, the involvement of Survivin (and the associated events) in UV-B response in vitro and in vivo in experimental models regarded to have relevance to human situations.     

UV-B-induced secondary conformational changes in lens alpha-crystallin.

The changes in turbidity and protein secondary structure of alpha-crystallin after a 72 h UV-B (302 nm) irradiation in aqueous solution have been determined by UV spectrophotometry and Fourier transform infrared (FT-IR) microspectroscopy with reflection mode. The relative transmission of alpha-crystallin aqueous solution gradually decreases with the exposure time, indicating that the transparent alpha-crystallin aqueous solution becomes opaque with prolonged UV-B irradiation. The turbidity induced by UV-B shows first-order kinetics due to the photo-induced aggregation. The modification of the secondary structure of the alpha-crystallin molecule in aqueous solution caused by this aggregation might enhance the alpha-helix and beta-turn structures from 8.14 to 14.92% and from 24.46 to 35.54%, respectively; reduce the beta-sheet structure from 60.20% to 43.77%; and leave the random coil structure almost unaltered. The secondary conformation of alpha-crystallin changes gradually but evidently with its increase of turbidity during UV-B exposure.     

DETERMINATION OF CYTOSINE-CYTOSINE PHOTODIMERS IN THE DNA OF CLOUDMAN S91 MELANOMA CELLS USING HIGH PRESSURE LIQUID CHROMATOGRAPHY

I measured the induction of cytosine-cytosine dimer (C-C) densities after UV-C (less than 290 nm) and UV-B irradiation (290-320 nm) in the 2'-deoxy-[3H]cytidine labeled DNA of Cloudman S91 mouse melanoma cells using a new, sensitive high pressure liquid chromatography procedure. UV-B exposure resulted in 0.000034% C-C/J m-2 of the total cytosine radioactivity which is 10 times less than the rate during UV-C irradiation. Previous work with these melanoma cells showed a 4-fold lower rate of induction of thymine-containing pyrimidine dimers by UV-B than UV-C light (Niggli Photochem. Photobiol. 52, 519-524, 1990). Based on these results, the calculated ratios for the pyrimidine dimer subspecies showed no significant difference following UV-C and UV-B exposure. However, UV-C and UV-B light induce 10-20 times more thymine-containing pyrimidine dimers than C-C in the DNA of S91 cells.     

EFFECTS OF ULTRAVIOLET RADIATION ON THE IMMUNE SYSTEM IN HUMANS

In experimental animals, exposure to UV-B radiation produces selective alterations of immune function which are mainly in the form of suppression of normal immune responses. This immune suppression is important in the development of nonmelanoma skin cancer, may influence the development and course of infectious disease and possibly protects against autoimmune reactions. The evidence that this form of immune suppression occurs in humans is less compelling and very incomplete. The wavelengths of radiation most affected by a depletion of the stratospheric ozone layer are those known to be most immunosuppressive in animals and it is likely that such depletion will increase any suppressive effect of sunlight on immunity in humans. In addition to establishing whether or not UV-B radiation can cause suppression of immune function in humans, studies are required to determine if melanin can provide protection against such suppression, the role of this suppression in the pathogenesis of skin cancer, the development of infectious disease and vaccine effectiveness, and the capacity for humans to develop adaptive, protective mechanisms which may limit damage from continued exposure to UV-B radiation.     

THE EFFECT OF SYSTEMIC CYCLOSPORIN A ON A HAIRLESS MOUSE MODEL OF PHOTOAGING

The mechanisms that cause skin wrinkling in response to chronic exposure to sunlight are unknown. We investigated the possibility that wrinkling of Skh-1 hairless mice is associated with an ultraviolet (UV) radiation-induced immunologic alteration. Exposing Skh-1 hairless mice to a regimen of nonerythemal UV-B (290-320 nm) radiation induced skin wrinkles after 6-7 weeks. Concomitant treatment with cyclosporin A decreased the time to the onset of wrinkles to approximately 4 weeks. Exposing HRS/J hairless mice or athymic nude mice to a similar nonerythemal UV-B radiation regimen for 10 weeks failed to induce skin wrinkles. Concomitant administration of cyclosporin A and UV-B radiation for 7 weeks to HRS/J hairless mice induced no skin wrinkles. Ultraviolet-B or UV-B plus cyclosporin A exposure caused increased immunohistochemical staining for Ia and F4/80 antigens in the upper dermis of tissue from Skh-1 mice, as compared to controls. Treating Skh-1 mice with UV-B radiation plus cyclosporin A was also associated with a large increase in the number of CD3+ cells in the dermis. These staining patterns were absent in similarly treated HRS/J hairless mice. Dermal mast cell numbers in Skh-1 mice were 2-3-fold higher than in HRS/J, athymic nude or NSA mice. Treatment with cyclosporin A increased Skh-1 dermal mast cell numbers approximately 2-fold but had no effect on the dermal mast cell numbers in HRS/J or NSA mice. Based on these findings we postulate that UV-B light and cyclosporin A exacerbate an immunological condition in Skh-1 mice, one consequence of which is manifested as skin wrinkles. Thus, the induction of skin wrinkles in this mouse strain may have no relevance to the wrinkles observed in human skin after chronic exposure to sunlight.     

DETERMINATION OF CYTOSINE-CYTOSINE PHOTODIMERS IN THE DNA OF CLOUDMAN S91 MELANOMA CELLS USING HIGH PRESSURE LIQUID CHROMATOGRAPHY

Abstract
I measured the induction of cytosine-cytosine dimer (C-C) densities after UV-C (< 290 nm) and UV-B irradiation (290–320 nm) in the 2'-deoxy-[³H]cytidine labeled DNA of Cloudman S91 mouse melanoma cells using a new, sensitive high pressure liquid chromatography procedure. UV-B exposure resulted in 0.000034% C-C/J m^-2 of the total cytosine radioactivity which is 10 times less than the rate during UV-C irradiation. Previous work with these melanoma cells showed a 4-fold lower rate of induction of thymine-containing pyrimidine dimers by UV-B than UV-C light (Niggli Photochem. Photobiol . 52 , 519–524, 1990). Based on these results, the calculated ratios for the pyrimidine dimer subspecies showed no significant difference following UV-C and UV-B exposure. However, UV-C and UV-B light induce 10–20 times more thymine-containing pyrimidine dimers than C-C in the DNA of S91 cells.     

Effect of ultraviolet-B radiation on intact cells of the cyanobacterium Spirulina platensis: characterization of the alterations in the thylakoid membranes

Intact trichomes of Spirulina platensis are exposed to ultraviolet- B (UV-B) radiation (270-320 nm; 1.9 mW m(-2)) for 9 h. This UV-B exposure results in alterations in the pigment-protein complexes and in the fluorescence emission profile of the chlorophyll-protein complexes of the thylakoids as compared with thylakoids isolated from control dark-adapted Spirulina cells. The UV-B exposure causes a significant decrease in photosystem II activity, but no loss in photosystem I activity. Although there is no change in the photosystem I activity in thylakoids from UV-B-exposed cells, the chlorophyll a emission at room temperature and at 77 K indicates alterations associated with photosystem I. Additionally, the results clearly demonstrate that the photosystem II core antennae of chlorophyll proteins CP47 and CP43 are affected by UV-B exposure, as revealed by Western blot analysis. Furthermore, a prominent 94 kDa protein band appears in the sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) profile of UV-B-exposed cell thylakoids, which is absent from the control thylakoids. This 94 kDa protein appears not to be newly induced by UV-B exposure, but could possibly have originated from the UV-B-induced cross-linking of the thylakoid proteins. The exposure of isolated Spirulina thylakoids to the same intensity of UV-B radiation for 1-3 h induces losses in the CP47 and CP43 levels, but does not induce the appearance of the 94 kDa protein band in SDS-PAGE. These results clearly demonstrate that prolonged exposure of Spirulina cells to moderate levels of UV-B affects the chlorophyll a-protein complexes and alters the fluorescence emission spectral profile of the pigment-protein complexes of the thylakoid membranes. Thus, it is clear that chlorophyll a antennae of Spirulina platensis are significantly altered by UV-B radiation.     

DNA as a solar dosimeter in the ocean.

Stratospheric ozone depletion may result in increased solar UV-B radiation to the ocean's upper layers and may cause deleterious effects on marine organisms. The primary UV-B damage induced in biological systems is to DNA. While physical measurements of solar UV-B penetration into the sea have been made, the effective depth and magnitude of actual DNA damage have not been determined. In the experiments reported here, UV-B-induced photoproducts (cyclobutane pyrimidine dimers) have been quantified in DNA molecules exposed to solar UV at the surface and at various depths in clear, tropical marine waters off Lee Stocking Island (23 degrees 45' N, 76 degrees 0.7' W), Exuma Cays, Bahamas. (14C)thymidine-labeled DNA or unlabeled bacteriophage phi X174 DNA was placed in specially designed quartz tubes at various depths for up to five days. Following exposure, DNA samples were removed to the laboratory where UV-B-induced pyrimidine dimers were quantified using a radiochromatographic assay, and bacteriophage DNA inactivation by solar UV-B was assayed by plaque formation in spheroplasts of Escherichia coli. Pyrimidine dimer induction was linear with time but the accumulation of dimers in DNA with time varied greatly with depth. Attenuation of dimer formation with depth of water was exponential. DNA at 3 m depth had only 17% of the pyrimidine dimers found at the surface. Bacteriophage phi X174 DNA, while reduced 96% in plaque-forming ability by a one day exposure to solar UV at the surface of the water, showed no effect on plaque formation after a similar exposure at 3 m. The data collected at the water's surface showed a "surface-enhanced dose" in that DNA damages at the real surface were greater than at the imaginary surface, which was obtained by extrapolating the data at depth to the surface. These results show the sensitivity of both the biochemical (dimers) and biological (phage plaques) DNA dosimeters. DNA dosimeters offer a sensitive, convenient and relatively inexpensive monitoring system, having both biochemical and biological endpoints for monitoring the biologically effective UV-B flux in the marine environment. Unlike physical dosimeters, DNA dosimeters do not have to be adjusted for biological effectiveness since they are sensitive only to DNA-mediated biologically effective UV-B radiation. Results of pyrimidine dimer induction in DNA by solar UV accurately predicted UV doses to the phage DNA.     

Changes in blood platelets exposed to UV-B radiation.

The effects of UV-B radiation (312 nm) on the pig-blood platelet secretory process (platelet activation) and platelet lipid peroxidation have been studied. The responses of platelets to UV-B radiation are compared with the response of these cells to thrombin, which is a strong platelet agonist. The obtained results show that exposure of blood platelets to UV-B radiation (1.2 mW/cm2, 0.072-8.64 J/cm2) causes dose-dependent platelet lipid peroxidation (measured as thiobarbituric acid reactive substances, TBARS) and release of adenine nucleotides and proteins from irradiated platelets. The dose-dependent release of platelet compounds from irradiated platelet does not correlate with the activity of platelet lactic dehydrogenase (marker of cell lysis) in the extracellular medium. It seems that UV-B radiation can partly activate platelets by stimulating the platelet secretory process and metabolism of arachidonate.     

Vibrational spectroscopic studies on the disulfide formation and secondary conformational changes of captopril-HSA mixture after UV-B irradiation

The effects of pH and ultraviolet-B (UV-B) irradiation on the secondary structure of human serum albumin (HSA) in the absence or presence of captopril were investigated by an attenuated total reflection (ATR)/Fourier transform infrared (FTIR) spectroscopy. The UV-B exposure affecting the stability of captopril before and after captopril-HSA interaction was also examined by using confocal Raman microspectroscopy. The results indicate that the transparent pale-yellow solution for captopril-HSA mixture in all pH buffer solutions, except pH 5.0 approximately 7.0, changed into a viscous form then a gel form with UV-B exposure time. The secondary structural transformation of HSA in the captopril-HSA mixture with or without UV-B irradiation was found to shift the maxima amide I peak in IR spectra from 1652 cm(-1) assigned to alpha-helix structure to 1622 cm(-1) because of a beta-sheet structure, which was more evident in pH 3.0, 8.0 or 9.0 buffer solutions. The Raman shift from 1653 cm(-1) (alpha-helix) to 1670 cm(-1) (beta-sheet) also confirmed this result. Captopril dissolved in distilled water with or without UV-B irradiation was determined to form a captopril disulfide observed from the Raman spectra of 512 cm(-1), which was exacerbated by UV-B irradiation. There was little disulfide formation in the captopril-HSA mixture even with long-term UV-B exposure, but captopril might interact with HSA to change the protein secondary structure of HSA whether there was UV-B irradiation or not. The pH of the buffer solution and captopril-HSA interaction may play more important roles in transforming the secondary structure of HSA from alpha-helix to beta-sheet in the corresponding captopril-HSA mixture than UV-B exposure. The present study also implies that HSA has the capability to protect the instability of captopril in the course of UV-B irradiation. In addition, a partial unfolding of HSA induced by pH or captopril-HSA interaction under UV-B exposure is proposed.     

D1 protein turnover is involved in protection of Photosystem II against UV-B induced damage in the cyanobacterium Arthrospira (Spirulina) platensis

By using two strains of Arthrospira (Spirulina)platensis, an economically important filamentous cyanobacterium, we compared the impairment of PSII activity and loss of D1 protein content under UV-B radiation. Our study showed that UV-B radiation induced a gradual loss of the oxygen-evolving activity to about 56% after 180 min UV-B irradiation both in strains 439 and D-0083, which have been kept under indoor and an outdoor culturing conditions, respectively for a prolonged period of time. The loss of oxygen evolution was accelerated in both strains in the presence of lincomycin, an inhibitor of protein synthesis, and the amount of D1 protein showed a decrease comparable to that of oxygen evolution during the UV-B exposure. However, the UV-B induced loss of oxygen-evolving activity and D1 protein amount was largely prevented when A. platensis cells were exposed to UV-B irradiance supplemented with visible light. Comparison of the two strains also showed a smaller extent of D1 protein synthesis dependent PSII repair in the indoor strain. Our results show that turnover of the D1 protein is an important defense mechanism to counteract the UV-B induced damage of PSII in A. platensis, and also that visible light plays an important role in maintaining the function of PSII under simultaneous exposure to UV-B and visible light.     

Influence of solar ultraviolet-B radiation on Antarctic terrestrial plants: results from a 4-year field study.

We examined the influence of solar ultraviolet-B radiation (UV-B; 280-315 nm) on the performance of Antarctic vascular plants (Colobanthus quitensis and Deschampsia antarctica) by placing filters that either absorbed or transmitted most solar UV-B over tundra along the Antarctic Peninsula for four consecutive growing seasons. The difference in biologically effective UV-B levels between our treatments was 65%, which was similar to the enhancement in ambient UV-B levels that appeared attributable to ozone depletion during the first 2 months of the growing season (November and December) at our site (62%). In both species, exposure to UV-B reduced vegetative growth, primarily through slower leaf elongation rates that led to shorter fully expanded leaves. In C. quitensis, exposure to UV-B also led to reductions in leaf longevity, branch production, cushion diameter growth, aboveground biomass, and thickness of the non-green cushion base and litter layer. Exposure to UV-B accelerated the development of reproductive structures and increased the number of panicles (D. antarctica) and capsules (C. quitensis) that reached maturity per unit of ground surface area covered by mother plants. However, this effect was offset by a tendency for these panicles and capsules to produce fewer spikelets and seeds. Ultimately, UV-B exposure did not effect the numbers of spikelets or seeds produced per unit of ground surface area. While seeds from plants exposed to UV-B tended to be lighter, germination rates were similar between UV-B treatments. The relative reductions in leaf elongation rates in D. antarctica attributable to UV-B exposure increased from the first (23%) through the fourth (43%) growing season, and relative reductions in leaf longevity in C. quitensis tended to increase from the first (9%) through the fourth (19%) growing season, suggesting that UV-B growth responses tended to be cumulative over successive years.     

UV-B-induced generation of free radicals in blood platelets

UV-B irradiation of blood-platelet concentrates is used in transfusion practice to prevent the development of post-transfusion alloimmunization and inactivate viruses and bacteria in the concentrates. UV-B radiation may affect the blood-platelet metabolism and function; therefore we have investigated the effect of UV-B irradiation on free radical production in blood platelets. Our results show that exposure of pig blood platelets to UV-B radiation (0.36 and 1.08 J/cm2) induces the generation of free radicals measured by the chemiluminescence method (respectively 28 and 148.6% above the control). The superoxide radical level after UV-B irradiation measured by the cytochrome c reduction method shows only a slight increase (p > 0.05). Free radical generation induced by UV-B radiation is dependent partly on blood-platelet activation and enzymatic pathways, since we have shown that wortmannin, an inhibitor of phosphatidylinositide 3-kinase, reduces the level of radicals formed in blood platelets after UV-B irradiation. This indicates that free radicals generated in blood platelets after stimulation by UV-B radiation are involved in platelet activation and metabolism of platelet polyphosphoinositides.     

Ultraviolet-B radiation effects on antioxidant status and survival in the zebrafish, Brachydanio rerio

Direct impact of ambient (1.95 W/m2) and subambient doses of UV-B radiation on muscle/skin tissue antioxidant status was assessed in mature zebrafish (Brachydanio rerio). The influence of these doses on hatching success and survival in earlier life stages was also examined. Subambient doses of UV-B radiation in the presence (1.28 W/m2) and absence (1.72 W/m2) of a cellulose acetate filter significantly depressed muscle/skin total glutathione (TGSH) levels compared with controls (0.15 W/m2) and low (0.19 W/m2) UV-B-treated fish after 6 and 12 h cumulative exposure. Ambient UV-B exposure significantly decreased muscle/skin glutathione peroxidase (GPx) activity after a 6 h exposure; activities of glutathione reductase (GR) were unchanged over this exposure period. Superoxide dismutase (SOD) and catalase activities peaked after 6 and 12 h cumulative exposure, respectively, but fell back to control levels by the end of the exposure period. The changes in tissue antioxidant status suggested UV-B-mediated increases in cytosolic superoxide anion radicals (O2-) and hydrogen peroxide (H2O2). This apparent UV-B-mediated increase in oxidative stress is further supported by a significant increase in muscle/skin thiobarbituric acid reactive substances (TBARS). Hatching success of newly fertilized eggs continuously exposed to ambient UV-B was only 2% of the control value. Even at 30 and 50% of ambient UV-B, hatching success was only 80 and 20%, respectively, of the control. Newly hatched larvae exposed to an ambient dose of UV-B, experienced 100% mortality after a 12 h cumulative exposure period. This study supports a major impact of UV-B on both the mature and embryonic zebrafish.     

Removing UV-A and UV-C radiation from UV-B fluorescent lamp emissions. Differences in the inhibition of photosynthesis in the marine alga Dunaliella tertiolecta using chromate versus cellulose acetate-polyester filters

Ultraviolet-B (UV-B; 280-320 nm)-emitting lamps unavoidably emit ultraviolet-A (UV-A; 320-400 nm) and ultraviolet-C (UV-C; <280 nm) radiation. Short-wavelength-blocking filters are generally used to limit the wave bands of UV under investigation. The widespread use of such filters means that all exposures to UV-B radiation will have a significant UV-A component. Therefore, the physiological effects unique to UV-B exposure are difficult to clearly isolate. This study presents a method to remove the UV-A and UV-C "contamination" using a liquid potassium chromate (K(2)CrO(4)) filter, thus allowing more direct assessment of the effects of UV-B exposure. Cultures of the green marine alga Dunaliella tertiolecta were grown in the absence of UV radiation. Sunlamps supplied the UV radiation for a 24 h exposure (solar radiation was not used in this study). The UV radiation was filtered either by the standard method (i.e. cellulose acetate (CA) with polyester = Mylar controls) or by a liquid filter of potassium chromate. Photosynthetic responses were compared. Major decreases in the ratio of variable to maximal fluorescence in dark-adapted cells and photosynthetic capacity were observed in CA-filtered cultures, whereas no change was observed in cells exposed to the same UV-B flux with the UV-A removed by K(2)CrO(4). The use of a CA filter with a Mylar control does not link results unequivocally to UV-B radiation. Such results should be interpreted with caution.     

Resistance of a Lizard (the Green Anole, Anolis carolinensis; Polychridae) to Ultraviolet Radiation–induced Immunosuppression¶

The green anole (Anolis carolinensis) is the most northerly distributed of its Neotropical genus. This lizard avoids a winter hibernation phase by the use of sun basking behaviors. Inevitably, this species is exposed to high doses of ambient solar ultraviolet radiation (UVR). Increases in terrestrial ultraviolet-B (UV-B) radiation secondary to stratospheric ozone depletion and habitat perturbation potentially place this species at risk of UVR-induced immunosuppression. Daily exposure to subinflammatory UVR (8 kJ/m2/day UV-B, 85 kJ/m2/day ultraviolet A [UV-A]), 6 days per week for 4 weeks (total cumulative doses of 192 kJ/m2 UV-B, 2.04 x 10(3) kJ/m2 UV-A) did not suppress the anole's acute or delayed type hypersensitivity (DTH) response to horseshoe crab hemocyanin. In comparison with the available literature UV-B doses as low as 0.1 and 15.9 kJ/m2 induced suppression of DTH responses in mice and humans, respectively. Exposure of anoles to UVR did not result in the inhibition of ex vivo splenocyte phagocytosis of fluorescein labeled Escherichia coli or ex vivo splenocyte nitric oxide production. Doses of UV-B ranging from 0.35 to 45 kJ/m2 have been reported to suppress murine splenic/peritoneal macrophage phagocytosis and nitric oxide production. These preliminary studies demonstrate the resistance of green anoles to UVR-induced immunosuppression. Methanol extracts of anole skin contained two peaks in the ultraviolet wavelength range that could be indicative of photoprotective substances. However, the resistance of green anoles to UVR is probably not completely attributable to absorption by UVR photoprotective substances in the skin but more likely results from a combination of other factors including absorption by the cutis and absorption and reflectance by various components of the dermis.