Ultraviolet Radiation Sensitivity Research Articles

Reproductive factors, hormone use, and incidence of melanoma in a cohort of US Radiologic Technologists.

Are reproductive factors and exogenous hormone use associated with incidence of cutaneous melanoma while accounting for ultraviolet radiation (UVR) exposure across different life periods and sun sensitivity factors? Earlier age at menarche and late age at first birth, but not other estrogen-related factors were associated with an increased incidence rate of melanoma, with higher risks observed for earlier age at menarche and light hair color at age 15 years. Although estrogens have been recognized as photosensitizing, previous studies have reported inconsistent findings for the association of melanoma with estrogen-related factors. Most have not collected detailed skin cancer risk factors and have not thoroughly investigated effect modification by ambient UVR and sun sensitivity. Participants in the US Radiologic Technologists study, an occupational cohort of 146 022 radiologic technologists (73% women), were included and followed during the four time periods (1983-1989, 1994-1998, 2003-2005 and 2012-2014). Non-Hispanic white female participants who completed both the second (baseline) and third questionnaires, and did not report having cancer (except keratinocyte carcinoma) at baseline, were included and followed from their age at completion of the second (baseline) questionnaire until the earlier of first primary cancer diagnosis, including invasive melanoma of the skin, or completion of either the third or fourth questionnaire. Reproductive and exogenous hormonal factors were ascertained from the second (baseline) questionnaire, which also collected information on demographic, lifestyle factors and sun sensitivity factors. Ambient UVR was assigned by linking geocoded residential locations, based on self-reported residential history information collected from the third questionnaire to satellite-based ambient UVR data from the National Aeronautics and Space Administration's Total Ozone Mapping Spectrometer database. To examine the association of reproductive factors, exogenous hormone use, and first primary invasive melanoma of the skin, we used Poisson regression to calculate rate ratios (RRs) and 95% likelihood-based CIs, adjusting for attained age, birth cohort, lifetime average annual ambient UVR, contraceptives and menopausal hormone therapy use. To address the effect modification of ambient UVR exposure and sun sensitivities on melanoma risk, we conducted likelihood-ratio tests for multiplicative interaction. Over a median follow-up time of 17.1 years, 0.95% of eligible participants had an incident first primary melanoma (n = 444). Higher melanoma incidence rates were observed in participants with older attained age, blue/green/gray eye color, blonde/red/auburn natural hair color at age 15, fair skin complexion, and higher UVR. We found an increased incidence rate of melanoma in women who experienced menarche at an earlier age (13, 12 and <12 years vs ≥14 years: RR = 1.48, 95% CI = 1.11-1.98; 1.19, 0.89-1.61; 1.26, 0.93-1.73), and in women with older age at first birth (25-29 and ≥30 years vs <25 years; 1.09, 0.86-1.39; 1.48, 1.12-1.95; P-value for trend = 0.006). However, no significant association was observed for other reproductive factors, and for all exogenous hormone use. The associations of melanoma incidence for most reproductive factors and exogenous hormone use were not modified by ambient UVR, eye color, natural hair color at age 15 and skin complexion. The exception was that natural hair color at age 15 modified the associations of melanoma for age at menarche (P-value for interaction = 0.004) and age at first birth among parous women (0.005). In participants with blonde/red/auburn natural hair color at age 15, we found increased risk of melanoma among women who experienced menarche at age 13, 12 and <12 years (vs ≥14 years: RR = 3.54, 95% CI = 1.98-6.90; 2.51, 1.37-4.98; 2.66, 1.41-5.36, respectively; P-value for trend = 0.10). However, the association between age at menarche and melanoma was null in participants with brown/black natural hair color at age 15. Information on reproductive history and exogenous hormone use was self-reported. We did not have information on specific doses or formulations of exogenous hormone medications or breastfeeding. Women residing in areas of high ambient UVR and those with blonde/red/auburn natural hair color may constitute an additional high-risk group in need of more frequent skin cancer screening. Identifying susceptible periods of exposure or factors that modify UVR susceptibility may aid in guiding more targeted guidelines for melanoma prevention. This research was supported by the Intramural Research Program, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, US Department of Health and Human Services. Authors declare no conflict of interest. N/A.

Ultraviolet radiation and incidence of cataracts in a nationwide US cohort

ABSTRACTPurpose: We examine the risk of cataract and cataract surgery with measures of ultraviolet radiation (UVR) exposure and UVR sensitivity in a large, nationwide population of indoor workers.Methods: Participants from the US Radiologic Technologists Study were followed from age at baseline survey (2003–2005) to age at earliest of cataract diagnosis, cataract surgery, or completion of last survey (2012–2013). UVR-related factors included satellite-based ambient UVR linked to lifetime residences, time spent outdoors across various age periods, history of blistering sunburns, prior diagnosis of keratinocyte carcinoma, and iris color. We used Cox proportional hazards models with age as timescale to compute hazard ratios (HRs) and 95% confidence intervals (CIs) for cataract and cataract surgery.Results: Participants had a median age of entry of 54.0 years, were 80.0% female, and 95.7% white. Of the 44, 891 eligible participants, 9399 cases of cataract and 3826 cases of cataract surgery were reported. Ambient UVR (quintile 5 vs. 1) was associated with an increased risk of cataract (HR = 1.08; 95% CI: 1.01–1.16) and cataract surgery (HR = 1.16; 95% CI: 1.05–1.29). Lifetime average time spent outdoors was not associated with cataract risk. History of blistering sunburns before and after age 15, but not previous keratinocyte carcinoma diagnosis was associated with both cataract and cataract surgery.Conclusion: Our results suggest a modest role for residence-based ambient UVR and cataract risk among indoor workers in the United States.

Solar UVR sensitivity of phyto- and bacterioplankton communities from Patagonian coastal waters under increased nutrients and acidification

The effects of ultraviolet radiation (UVR) under future expected conditions of acidification and increase in nutrient inputs were studied on a post-bloom phytoplankton and bacterioplankton community of Patagonian coastal waters. We performed an experiment using microcosms where two environmental conditions were mimicked using a cluster approach: present (ambient nutrients and pH) and future (increased nutrients and acidification), and acclimating the samples for five days to two radiation treatments (full solar radiation [+UVR] and exclusion of UVR [–UVR]). We evaluated the short-term (hours) sensitivity of the community to solar UVR through chlorophyll a fluorescence parameters (e.g. the effective photochemical quantum yield of PSII [ΦPSII]) at the beginning, at the mid-point and at the end of the acclimation period. Primary production and heterotrophic bacterial production (HBP) were determined, and biological weighting functions were calculated, at the beginning and at the end of the acclimation period. Mid-term effects (days) were evaluated as changes in taxonomic composition, growth rates and size structure of the community. Although the UVR-induced inhibition on ΦPSII decreased in both clusters, samples remained sensitive to UVR after the 5 days of acclimation. Also, under the future conditions, there was, in general, an increase in the phytoplankton carbon incorporation rates along the experiment as compared to the present conditions. Bacterioplankton sensitivity to UVR changed along the experiment from inhibition to enhancement of HBP, and future environmental conditions stimulated bacterial growth, probably due to indirect effects caused by phytoplankton. Those changes in the microbial loop functioning and structure under future global change conditions might have important consequences for the carbon pump and thus for the carbon sequestration and trophodynamics of Patagonian coastal waters.

An optimal thermal evaporation synthesis of c-axis oriented ZnO nanowires with excellent UV sensing and emission characteristics

Well-aligned (c-axis oriented) ZnO nanowire arrays were successfully synthesized on Si (100) substrates through an optimized self-seeding thermal evaporation method. An open-ended chemical vapor deposition (CVD) setup was used in the experiment, with argon and purified air as reaction gases. Epitaxial growth of c-axis oriented ZnO nanowires was observed for 5sccm flow rate of purified air, whereas Zn/Zn suboxide layers and multiple polycrystalline layers of ZnO were obtained for absence and excess of purified air, respectively. Ultraviolet (UV) sensing and emission properties of the as-grown ZnO nanostructures were investigated through the current–voltage (I–V) characteristics of the nanowires under UV (λ=365nm) illumination of 8mW/cm2 and using photoluminescence spectra. Nanowires grown under optimum flow of air emitted four times higher intensity of 380nm UV light as well as exhibited 34 times higher UV radiation sensitivity compared to that of other nanostructures synthesized in this study.

Increased ultraviolet radiation sensitivity ofEscherichia coligrown at low temperature

The repair of DNA damage caused by ultraviolet radiation (UVR) is well understood in both lower and higher organisms. Genetic studies carried out at optimum temperature for growth, 37 °C in Escherichia coli, have revealed the major pathways of DNA repair. We show that E. coli cells grown at 20 °C are more sensitive to UVR than cells grown at 37 °C. The analysis of knockout mutants demonstrates that cells impaired in recombinational DNA repair pathways show increased UV sensitivity at 20 °C. Cells with mutations in the nucleotide excision repair (NER) pathway genes are highly sensitive to UVR when grown at 37 °C and retain that sensitivity when grown at 20 °C, whereas wild-type cells are not sensitive when grown at 37 °C but become more sensitive to UVR when grown at low temperatures. Our results taken along with reports from the literature suggest that the UVR sensitivity of E. coli cells at low temperature could be due to impaired NER function.

Influence of Merocyanine Molecular Dipole Moments on the Valence Levels in Thin Films and the Interface Energy Level Alignment with Au(111)

We study the effect of increasing permanent dipole moment of four dipolar merocyanine dyes on the energy level alignment with Au(111) and the energy levels in thin films with ultraviolet (UV) photoemission spectroscopy. Preceding X-ray diffraction experiments showed that these dipolar molecules form centrosymmetric dimeric units in their bulk crystal structure. The effect of dimerization was also seen in a splitting of the highest occupied level of bilayers and thin films of all four molecules. This split into two components due to intermolecular electronic coupling between two merocyanines is estimated to be 0.2–0.3 eV. Monolayer films on Au(111) did not exhibit such splitting due to a different adsorption structure. A significant ultraviolet radiation sensitivity of the dyes near the metal surface was noticed. Unlike other radiation-sensitive compounds, the reason for molecule damage is related to the secondary electrons produced in the metal substrate during photoelectron spectroscopy measurements and not to the UV radiation itself.

Non-invasive diffuse reflectance measurements of cutaneous melanin content can predict human sensitivity to ultraviolet radiation.

The diversity of human skin phenotypes and the ubiquitous exposure to ultraviolet radiation (UVR) underscore the need for a non-invasive tool to predict an individual's UVR sensitivity. We analysed correlations between UVR sensitivity, melanin content, diffuse reflectance spectroscopy (DR) and UVR-induced DNA damage in the skin of subjects from three racial/ethnic groups: Asian, black or African American and White. UVR sensitivity was determined by evaluating each subject's response to one minimal erythemal dose (MED) of UVR one day after the exposure. Melanin content was measured using DR and by densitometric analysis of Fontana-Masson staining (FM) in skin biopsies taken from unexposed areas. An individual's UVR sensitivity based on MED was highly correlated with melanin content measured by DR and by FM. Therefore, a predictive model for the non-invasive determination of UVR sensitivity using DR was developed. The MED precision was further improved when we took race/ethnicity into consideration. The use of DR serves as a tool for predicting UVR sensitivity in humans that should be invaluable for determining appropriate UVR doses for therapeutic, diagnostic and/or cosmetic devices.

Molecular effects of UVA1 in human skin in vivo

The carcinogenic potential of UVA1 (340–400nm) is increasingly being recognised as evidence accumulates of its ability to induce cyclobutane pyrimidine dimers (CPD) ex vivo and in vivo in human beings which if unrepaired may lead to skin cancer. Despite widespread use in phototherapy, tanning lamps and its abundance in terrestrial UVR (ultraviolet radiation), we lack data on its effects on gene expression in human skin. 12 volunteers with skin type I/II were tested for UVR sensitivity: five were given 1 minimal erythema dose (MED) of UVA1 and biopsy samples taken at 6 h and 24 h; an unirradiated control sample was also taken. A further four participants were given 1 MED of UVB and UVA1 and biopsy samples taken at 6 h and 24 h, RNA extracted, converted to cRNA, and hybridised to agilent 44K oligomicroarray plates. After rosetta resolver software analysis, the data were analysed using GeneGo metacore v7 and DAVID.UVA1 upregulated 301 genes at 6 h and 264 genes at 24 h (p<0·05, ≥2 fold change). At 6 h, key gene expression pathways upregulated were inflammation (p=3·46×10−17), apoptosis (p=2·148×10−8), and response to oxidative stress (p=6·457×10−7). CD83 was also dramatically upregulated (positively regulates interleukin 10). At 24 h the top pathway enriched was extracellular matrix remodelling (p=5·549×10−7). A pathway analysis demonstrated that UVB induced the same pathways at 6 h and 24 h as did UVA1; however, functional studies shows that UVB induces a greater upregulation of apoptotic proteins and in terms of genes, similar levels of immunomodulatory genes (CD83, IL10) upregulated.Erythemally equivalent doses of UVA1 induce less apoptosis than UVB but there are similar levels of immunosuppression. Our data suggest that UVA1 might be inducing less of a photoprotective response in vivo in human beings than UVB, which might explain the mechanism of some of our other new findings—that UVA1 CPDs are slower to be repaired at the basal epidermis than UVB CPDs. These findings are important for our understanding of skin cancer. FundingUK Medical Research Council, La Roche- Posay, and Biomedical Research Council.

The spectral sensitivity of phytoplankton communities to ultraviolet radiation‐induced photoinhibition differs among clear and humic temperate lakes

We determined the spectral sensitivity of phytoplankton communities to photoinhibition in six temperate lakes spanning a transparency gradient due to variation in dissolved organic carbon (DOC) content. Changes in variable fluorescence (FV : FM) were monitored during experimental irradiance exposures and used to estimate spectral weighting functions for damage by ultraviolet radiation (UVR) and recovery rates. DOC explained a high proportion of the variation in UVR sensitivity, with clear‐water phytoplankton communities showing greater resistance to UVR‐induced photoinhibition than those of browner waters. These differences were greater when assessed in September, after clear‐sky conditions, than in July, after several days of overcast skies, especially in the long‐wavelength UVA spectral region. Surprisingly, the most UVR‐sensitive phytoplankton communities were dominated by filamentous cyanobacteria, a putatively UVR‐resistant taxon, whereas small unicellular eukaryotes were common in the most UVR‐tolerant assemblages. Model estimates of in situ photoinhibition after 2 h exposure to an incident solar spectrum were only slightly higher in the clear lakes than browner ones, despite appreciably higher UVR exposure in the former. Phytoplankton in clear lakes can maintain values of FV : FM comparable to communities protected from UVR by high concentrations of DOC.

Differential sensitivity of coral larvae to natural levels of ultraviolet radiation during the onset of larval competence

Scleractinian corals are the major builders of the complex structural framework of coral reefs. They live in tropical waters around the globe where they are frequently exposed to potentially harmful ultraviolet radiation (UVR). The eggs and early embryonic stages of some coral species are highly buoyant and remain near the sea surface for prolonged periods of time and may therefore be the most sensitive life stages with respect to UVR. Here, we analysed gene expression changes in five developmental stages of the Caribbean coral Montastraea faveolata to natural levels of UVR using high-density cDNA microarrays (10 930 clones). We found that larvae exhibit low sensitivity to natural levels of UVR during early development as reflected by comparatively few transcriptomic changes in response to UVR. However, we identified a time window of high UVR sensitivity that coincides with the motile planula stage and the onset of larval competence. These processes have been shown to be affected by UVR exposure, and the transcriptional changes we identified explain these observations well. Our analysis of differentially expressed genes indicates that UVR alters the expression of genes associated with stress response, the endoplasmic reticulum, Ca(2+) homoeostasis, development and apoptosis during the motile planula stage and affects the expression of neurogenesis-related genes that are linked to swimming and settlement behaviour at later stages. Taken together, our study provides further data on the impact of natural levels of UVR on coral larvae. Furthermore, our results might allow a better prediction of settlement and recruitment rates after coral spawning events if UVR climate data are taken into account.

Impact of iris pigment and pupil size in ultraviolet radiation cataract in rat

To investigate the effect of iris pigment and pupil size in ultraviolet radiation (UVR)-induced cataract. Brown-Norway rats (pigmented) and Fischer-344 rats (non-pigmented) were unilaterally exposed in vivo to 5 kJ/m(2) UVR. Each strain was split into two groups, each receiving either mydriatic (tropicamide) or miotic (pilocarpine) eye-drops. One week after exposure, the degree of ocular inflammation and damage in the anterior segment was determined. The lenses were extracted, photographed and the degree of forward light scattering (cataract) was quantified. The cataract types differed between the two strains. All Fischer rats developed macroscopically identifiable UVR cataract while only 41% of Brown-Norway rats did so. All groups except the miotic Brown-Norway developed significant light scattering. The Fischer rats developed 3-4-fold more lens light scattering than the Brown-Norway rats. The miotic Fischer group exhibited significantly more light scattering than the mydriatic Fischer group. There was no significant difference in light scattering between the two Brown-Norway groups. There was a correlation between ocular inflammation and degree of light scattering, with Brown-Norway rats exhibiting less inflammation and lens light scattering. Pigmented rats develop less UVR cataract and less ocular inflammation than non-pigmented rats. Pupil size plays a smaller role in UVR cataract development in pigmented rats than in non-pigmented. The role of UVR-induced ocular inflammation in cataract development is still ambiguous.

Ultraviolet radiation sensitivity in cave bacteria: evidence of adaptation to the subsurface?

We hypothesize that a reduced capacity to withstand or repair cellular damage from ultraviolet radiation may be present in cave-adapted microorganisms that never experience such conditions. However, a small number of previous studies have shown that some subsurface bacteria do not show greater sensitivity to ultraviolet radiation (UVR) than surface bacteria. To estimate UVR sensitivity in cave bacteria, bacterial isolates were collected from Carlsbad Cavern, New Mexico, U.S.A., and percent survival following exposure to various UVC and UVA radiation doses was determined. Cave bacteria from Left Hand Tunnel in Carlsbad Cavern and surface bacteria from soil and rocks above Carlsbad Cavern were grown on low and high nutrient media then exposed to 0, 10,000 and 20,000 μWs/ cm2 of UVR in a laboratory biological safety cabinet. Incubations were conducted at 15°C or 37ºC, in accordance with the isolates’ natural temperature environments. In addition, DNA repair capacity was estimated by exposing the organisms to various doses of UVC radiation and measuring survivability. Gram status and pigmentation also were determined. Results showed that most of the cave isolates were more sensitive to UVR than the surface isolates, but survivability data suggest that cave microbes retain some of their capacity to repair UV-induced DNA damage. Selection appears to have favored bacteria that can survive in this low nutrient environment, while not maintaining (or paying the cost of maintaining) unneeded traits such as UVR resistance. Cave bacteria appear to have maintained DNA repair capacity, most likely because of the need to repair damage to their DNA from other environmental stressors found in caves.

Structural Basis for the Recognition of Histone H4 by the Histone-Chaperone RbAp46

SummaryRbAp46 and RbAp48 (pRB-associated proteins p46 and p48, also known as RBBP7 and RBBP4, respectively) are highly homologous histone chaperones that play key roles in establishing and maintaining chromatin structure. We report here the crystal structure of human RbAp46 bound to histone H4. RbAp46 folds into a seven-bladed β propeller structure and binds histone H4 in a groove formed between an N-terminal α helix and an extended loop inserted into blade six. Surprisingly, histone H4 adopts a different conformation when interacting with RbAp46 than it does in either the nucleosome or in the complex with ASF1, another histone chaperone. Our structural and biochemical results suggest that when a histone H3/H4 dimer (or tetramer) binds to RbAp46 or RbAp48, helix 1 of histone H4 unfolds to interact with the histone chaperone. We discuss the implications of our findings for the assembly and function of RbAp46 and RbAp48 complexes.

Dose Response for UV-induced Immune Suppression in People of Color: Differences Based on Erythemal Reactivity Rather than Skin Pigmentation¶†

Ultraviolet radiation (UVR) is known to suppress immune responses in human subjects. The purpose of this study was to develop dose responses across a broad range of skin pigmentation in order to facilitate risk assessment. UVR was administered using FS 20 bulbs. Skin pigmentation and UVR sensitivity were evaluated using Fitzpatrick classifications, minimal erythemal dose (MED), slope of the erythemal dose response curve (sED), baseline pigmentation and tanning response. To assess immune responses dinitrochlorobenzene (DNCB) was applied to irradiated buttock skin 72 h after irradiation. Two weeks later DNCB was applied to the inside upper arm. Skin thickness was measured before and after challenge. Dose response was modeled (to obtain a regression line) for the entire group of 185 subjects. With the exception of sED none of the above-mentioned pigmentation indicators contributed significantly to variability around the regression line. Thus, differences in sensitivity for multiple skin types based on Fitzpatrick classification or MED were not observed. However, differences in immune sensitivity to UVR were detected between subjects with steep erythemal dose response curves and those with moderate or flat responses. For subjects with steep erythemal responses the dose calculated to suppress the immune response by 50% was 114 mJ/cm2. This group included individuals with Fitzpatrick skin types I–V, MED for these subjects ranged from 30 to 80 mJ/cm2. The 50% suppression dose for subjects with weak or no erythemal response could not be computed (the dose response was flat). This resistant group included subjects with skin types IV–VI and MED for these subjects ranged from 41 to >105 mJ/cm2. This study provides a human dose response for UVR suppression of contact sensitivity that will be useful in risk assessment. It is the first study to provide this information using the FS sun lamp and is the first study to include people of color. The sED appears to be a new variable for identifying sensitive subjects at risk of UVR-induced immune suppression.

Identification of MMS19 domains with distinct functions in NER and transcription

Nucleotide excision repair (NER) and RNA polymerase II (Pol II) transcription are essential cellular processes which are intimately intertwined. They share an indispensable multiprotein complex, TFIIH, and impairments in either process can impact the efficiency of the other. Like TFIIH, MMS19 is required for NER and Pol II transcription, but its precise role in each process is unknown. We showed previously that the human MMS19 gene originates multiple splice variants, some of which may encode distinct MMS19 protein isoforms. Here we characterize a novel MMS19 transcript and demonstrate for the first time that MMS19 splice variants are conserved across species and are functionally distinct. Expression of human MMS19 splice variants in mms19-deleted yeast cells produced unique patterns of thermosensitivity and ultraviolet radiation-sensitivity that point to three MMS19 structural domains with distinct in vivo functions. MMS19 polypeptides lacking domain A are able to fulfill the role of full-length MMS19 in NER but not in transcription. MMS19 polypeptides lacking part of domain B are efficient in transcription but not in NER. MMS19 polypeptides lacking domain C (HEAT repeats) are unable to fulfill either function. Our data suggest that the MMS19 HEAT repeat domain is essential for MMS19 function in NER and transcription, while domains A and B, within MMS19 N-terminus, modulate the balance between DNA repair and transcription. Our results highlight the functional significance of MMS19 transcripts and the possible contribution of MMS19 isoforms to regulate the switch between NER and transcription. Furthermore, our work associates for the first time specific protein domains with MMS19's role in NER and transcription.

Ultraviolet Radiation Sensitivity in Vitiligo and Adjacent Normal Skin

Ultraviolet Radiation Sensitivity in Vitiligo and Adjacent Normal Skin

Characterization of Lysine 56 of Histone H3 as an Acetylation Site in Saccharomyces cerevisiae

Post-translational histone modifications abound and regulate multiple nuclear processes. Most modifications are targeted to the amino-terminal domains of histones. Here we report the identification and characterization of acetylation of lysine 56 within the core domain of histone H3. In the crystal structure of the nucleosome, lysine 56 contacts DNA. Phenotypic analysis suggests that lysine 56 is critical for histone function and that it modulates formamide resistance, ultraviolet radiation sensitivity, and sensitivity to hydroxyurea. We show that the acetylated form of histone H3 lysine 56 (H3-K56) is present during interphase, metaphase, and S phase. Finally, reverse genetic analysis indicates that none of the known histone acetyltransferases is solely responsible for H3-K56 acetylation in Saccharomyces cerevisiae.

Natural variation of carotenoids in the eggs and gonads of the echinoid genus, Strongylocentrotus: implications for their role in ultraviolet radiation photoprotection

We examined variability in carotenoid concentration in the gonads and eggs of four sea urchin species ( Strongylocentrotus purpuratus, Strongylocentrotus franciscanus, Strongylocentrotus pallidus and Strongylocentrotus droebachiensis) to explore the possible role of carotenes as photoprotectants. Carotene concentrations were measured in gonads and gametes of each species, while in eggs the ultraviolet radiation (UV-R) sensitivity and self-shading capacity by carotenes were calculated. Mean concentrations of carotenes in gonads ranged from 0.13±0.017 mg g −1 dw ( S. purpuratus), 0.14±0.019 mg g −1 dw ( S. franciscanus), 0.29±0.079 mg g −1 dw ( S. pallidus) to 0.36±0.06 mg g −1 dw ( S. droebachiensis). In eggs, concentrations ranged from 0.026±0.003 to 0.09±0.034 mg g −1 dw. UV-R sensitivity in eggs was quantified by measuring UV-R induced first-cleavage delay. Intra-specifically, cleavage delay varied significantly between individuals, and could be correlated with carotene concentration. Interspecific differences in cleavage delay and carotene concentrations were not correlated. Using the observed concentration of β, β-echinenone (which makes up between 82.4% and 94.9% of the total carotene concentration in the eggs) and a molar extinction coefficient of ε=13.7×10 3 mol −1 cm −1 at 334 nm, we calculated self-shading efficiency in the eggs. Self-shading capacity ( J 334) indicated that the eggs could only screen from 4.6% ( J 334=0.046) down to 1.5% ( J 334=0.015) of UV-R at 334 nm. While not sunscreens, we suggest that carotenes can photoprotective in echinoid eggs, probably by mitigating the effects of reactive oxygen species.

Impact of age and sex in ultraviolet radiation cataract in the rat.

The purpose of this study was to determine the influence of age and sex on the development of ultraviolet radiation (UVR) cataract in rats. Current safety limits for lens damage due to UVR do not consider age or sex. Four age groups of Sprague-Dawley rats (3, 6, 17, and 52 weeks) were exposed to 300-nm UVR at either 5 or 8 kJ/m(2), delivered during 15 minutes. The interval between irradiation and cataract assessment was 1 or 8 weeks. Moreover, two groups of 6-week-old male and female rats were exposed to 5 kJ/m(2) UVR, with cataract assessment after 1 week. The severity of cataract was quantified by measurement of forward light-scattering in isolated lenses. The youngest age group showed development of anterior subcapsular, equatorial, and nuclear cataract, whereas the three older groups exhibited the first two types. The two younger age groups had significantly more cataract than the other groups. The degree of cataract increased from 1 to 8 weeks after irradiation. There was no difference in cataract severity between sexes. Young rats are more sensitive to UVR than old rats. Nuclear UVR cataract develops in young rats but not in adult rats. With the chosen waveband and dose, the time for maximum cataract development to occur is longer than 1 week. There is no difference in UVR sensitivity between the sexes.

Ultraviolet radiation sensitivity of photosynthesis in phytoplankton from an estuarine environment

We have studied temporal variation in the sensitivity of phytoplankton photosynthesis to inhibition by ultraviolet radiation (UV; 280–400 nm) using biological weighting functions (BWFs) that quantify the biological effect of different wavelengths of UV. Variations in irradiance‐dependent BWFs were evaluated for natural phytoplankton assemblages from the Rhode River, a shallow subestuary of the Chesapeake Bay, Maryland, from October 1994 to July 1996. Phytoplankton assemblages were sensitive to UV throughout the year. Rhode River assemblages are inhibited more strongly in the UV‐B (280–320 nm), particularly below 300 nm, but there is a significant influence well into the UV‐A (320–400 nm). There was no inhibition of phytoplankton photosynthesis by photosynthetically available radiation (400–700 nm), but there was significant seasonal variation in the saturated rate of photosynthesis (PsB) and in the light saturation parameter (Es). There was little variation in seasonal average BWFs through the year, but there was considerable variation in BWFs during each season. Individual BWFs varied both in absolute values of the weightings (reciprocal [mW m−2]) and in the spectral shape or relative effect of UV‐B versus UV‐A, which may be due to changes in species composition, light, temperature, and nutrient availability. Comparison of the most sensitive assemblage (spring) with the least sensitive assemblage (winter) indicates that these BWFs are close to the upper and lower bounds in sensitivity for irradiance‐dependent BWFs from all natural and cultured phytoplankton populations. The average, absolute spectral weightings for inhibition of photosynthesis in assemblages from the Rhode River are similar to an average BWF for Antarctic assemblages.