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1.
Long-term records of solar UV radiation reaching the Earth’s surface are scarce. Radiative transfer calculations and statistical
models are two options used to reconstruct decadal changes in solar UV radiation from long-term records of measured atmospheric
parameters that contain information on the effect of clouds, atmospheric aerosols and ground albedo on UV radiation. Based
on earlier studies, where the long-term variation of daily solar UV irradiation was derived from measured global and diffuse
irradiation as well as atmospheric ozone by a non-linear regression method [Feister et al. (2002) Photochem Photobiol 76:281–293], we present another approach for the reconstruction of time series of solar UV radiation.
An artificial neural network (ANN) was trained with measurements of solar UV irradiation taken at the Meteorological Observatory
in Potsdam, Germany, as well as measured parameters with long-term records such as global and diffuse radiation, sunshine
duration, horizontal visibility and column ozone. This study is focussed on the reconstruction of daily broad-band UV-B (280–315 nm),
UV-A (315–400 nm) and erythemal UV irradiation (ER). Due to the rapid changes in cloudiness at mid-latitude sites, solar UV
irradiance exhibits appreciable short-term variability. One of the main advantages of the statistical method is that it uses
doses of highly variable input parameters calculated from individual spot measurements taken at short time intervals, which
thus do represent the short-term variability of solar irradiance. 相似文献
2.
Surface ultraviolet (UV) radiation plays an important role in human health. Increased exposure to UV radiation increases the risk of skin cancer. In Australia, public campaigns to prevent skin cancer include the promotion of daily UV forecasts. If all other atmospheric factors are equal, stratospheric ozone decreases result in UV increases. Given that Australia still has the highest skin cancer rates in the world, it is important to monitor Australia’s stratospheric ozone and UV radiation levels over time because of the effects cumulative exposure can have on humans. In this paper, two long-term ozone datasets derived from surface and satellite measurements, a radiation code and atmospheric meteorological fields are used to calculate clear-sky UV radiation over a 50-year period (1959–2009) for Australia. The deviations from 1970–1980 levels show that clear-sky UV is on the rise. After the 1990s, an overall annual increase from 2 to 6% above the 1970–1980 levels was observed at all latitudes. Examining the summer and winter deviations from 1970–1980 showed that the winter signal dominated the annual changes, with winter increases almost twice those in summer. With ozone levels not expected to recover to pre-depletion levels until the middle of this century, UV levels are expected to continue to rise. Combined with Australians favoring an outdoor life-style, when temperatures are warmer, under high levels of UV, the associated risk of skin cancer will increase. 相似文献
3.
Thornberg C Vesanen R Wallström E Zvonova I Jesko T Albinsson J Börjesson J Mattsson S 《Radiation and environmental biophysics》2001,40(4):287-294
The western Bryansk region in south-western Russia was highly contaminated with 137Cs and 134Cs due to the Chernobyl accident in 1986. In 1990, a joint Nordic-Russian project was initiated in order to make measurements
and estimates of the absorbed doses to selected groups of inhabitants in this area. The participating individuals were living
in small villages with contamination levels between 0.9 and 2.7 MBq m–2. Only some villages had been decontaminated. Both schoolchildren and adults participated in the study and the number of persons
was between 100 and 130 each year, residing in 5 villages. Every year in September–October, from 1990 to 1998, we performed
individual measurements of external absorbed doses, assessed with thermoluminescent (TL) dosemeters (LiF). The mean effective
dose per year from external irradiation due to the Chernobyl accident of the inhabitants in the villages ranged between 0.8
and 2.9 mSv during the study period and decreased with an apparent half-time of 3.7–8.2 years, depending on village and group.
The highest individual doses within one village were, on average higher by a factor of 3 than the mean value for that village.
Under the conservative assumption of a decrease rate in the external effective dose of 2% per year after 1998, individuals
in the most highly exposed village are assumed to receive a life-time effective dose of about 75 mSv (between 1986 and 2056)
from external exposure to caesium radionuclides. The mean value for the villages under study was estimated to be around 65
mSv using the assumed rate of decrease.
Received: 20 December 2000 / Accepted: 1 October 2001 相似文献
4.
To establish a relation between biologically effective erythemal radiation (EER) and global solar radiation, the hourly and
daily clear-sky broadband (310–2,800 nm) global solar radiation (G) and spectral ultraviolet radiation incident on a horizontal
surface at Esfahan, Iran (32°37′N, 51°40′E) were measured during the period 2001–2005. Good correlations at statistically
significant levels between the daily values of EER and the daily G were found. The seasonal variability of EER/G is also discussed
and the correction factors are determined for inclusion of vertical column ozone and solar zenith angle (SZA) cycles. The
comparison of the estimated daily EER against the independent observed EER revealed that under clear sky conditions the estimations
are accurate to 10% or better over SZA of 10–60° and column ozone of 250–350 Dobson. The comparison of the results with the
similar works that have used shorter period of experimental data showed more accurate estimates. The deduced relations could
be used to a rough estimate of the daily EER from G in arid climate regions, where there is no measured UV radiation or there
are instrumental and other difficulties encountered in measuring UV radiation. 相似文献
5.
Host-cell reactivation (HCR) of UV-irradiated herpes simplex virus type 2 (HSV-2), capacity of UV-irradiated cells to support HSV-2 plaque formation and UV-enhanced reactivation (UVER) of UV-irradiated HSV-2 were examined in fibroblasts from 4 patients with Cockayne syndrome (CS), 5 with xeroderma pigmentosum and 5 normals. All UV-survival curves for HSV-2 plaque formation showed 2 components. HCR was similar to normal for the XP variant strain and the 2 CS strains tested, but substantially reduced in the 4 excision-deficient XP strains. The capacity of UV-irradiated fibroblasts to support HSV-2 plaque formation was determined by UV-irradiating fibroblast monolayers with various doses of UV and 48 h later, infecting the monolayers with unirradiated HSV-2. The D37 values for the delayed-capacity curves so obtained were in the range 8.6-12.4 J/m2 for the normal strains, 2.8-3.2 J/m2 for the CS strains, 6.7 J/m2 for an XP variant strain and between 0.3 and 1.5 for the XP excision-deficient strains tested. These results indicate that delayed capacity for HSV-2 plaque formation is a more sensitive assay than HCR in the detection of cellular DNA-repair deficiency for XP and CS. For the examination of UVER, fibroblasts were irradiated with various UV doses and subsequently infected with either unirradiated or UV-irradiated HSV and scored for plaque formation 2 days later. UVER expression was maximum when the delay between UV-irradiation of the cells and HSV infection was 48 h. The magnitude of UVER expression was also found to be dependent on the UV dose to the cells and increased with increasing UV dose to the virus. Using a UV dose to the virus resulting in a plaque survival of about 10(-2) on unirradiated cells, the the maximum UVER factor had a mean value of 1.3 for the normal strains following a dose of 15 J/m2 to the cells. Somewhat higher UVER values were found for all the patient strains tested and resulted from lower UV doses to the cells than for normal strains. Maximum UVER factors for the CS strains ranged from 2.2 to 3.3 at a dose of 5 J/m2 to the cells, for the XP excision-deficient strains; 2.1 to 2.6 at doses of 0.5 to 2.5 J/m2 to the cells and for the XP variant strain tested; 2.5 at UV dose of 10 J/m2 to the cells. 相似文献
6.
Claire Marionnet Cécile Pierrard Fran?ois Lejeune Juliette Sok Marie Thomas Fran?oise Bernerd 《PloS one》2010,5(8)
Experiments characterizing the biological effects of sun exposure have usually involved solar simulators. However, they addressed the worst case scenario i.e. zenithal sun, rarely found in common outdoor activities. A non-extreme ultraviolet radiation (UV) spectrum referred as “daily UV radiation” (DUVR) with a higher UVA (320–400 nm) to UVB (280–320 nm) irradiance ratio has therefore been defined. In this study, the biological impact of an acute exposure to low physiological doses of DUVR (corresponding to 10 and 20% of the dose received per day in Paris mid-April) on a 3 dimensional reconstructed skin model, was analysed. In such conditions, epidermal and dermal morphological alterations could only be detected after the highest dose of DUVR. We then focused on oxidative stress response induced by DUVR, by analyzing the modulation of mRNA level of 24 markers in parallel in fibroblasts and keratinocytes. DUVR significantly modulated mRNA levels of these markers in both cell types. A cell type differential response was noticed: it was faster in fibroblasts, with a majority of inductions and high levels of modulation in contrast to keratinocyte response. Our results thus revealed a higher sensitivity in response to oxidative stress of dermal fibroblasts although located deeper in the skin, giving new insights into the skin biological events occurring in everyday UV exposure. 相似文献
7.
Y. Furusawa L. E. Quintern H. Holtschmidt P. Koepke M. Saito 《Applied microbiology and biotechnology》1998,50(5):597-603
The available physical and biological broadband radiometers designed to determine erythema-effective radiation do not show
any response or over/underestimate the biologically effective radiation to a high extent in the ultraviolet (UV)A spectral
region. The data presented in this paper demonstrate that the biological system used in this study is the first one to make
possible measurements of erythema-effective radiation in the sun in the UVA and UVB spectral region. These measurements were
performed with a spore-film filter system as well as with spectroradiometers. It was demonstrated that this biotechnological
method could be used to determine exact values expressed as minimal erythemal dose (MED). The spore-film system was tested
in various field campaigns performed in Germany and in Japan. The seasonal daily variation of UV radiation in Germany determined
in the period November 1995 to December 1996 using the spore-film filter system in sunny conditions tallied well with model
calculations. The daily dose in Germany measured with the spore-film system close to the summer solstice, in sunny conditions
(20.45 MED), was approximately 20 times higher than the lowest value measured close to the winter solstice (0.82 MED), a result
which was in accordance with model calculations. The data determined with the spore-film filter system in Sapporo and Naha,
Japan, fitted to the erythema-weighted data calculated from spectroradiometric measurements (Brewer), even at low solar radiation
angles in a solar spectrum with less UVB but significant UVA. The spore-film dosimeter values were about 103 ± 8% of the integrated
dose of the Brewer instrument. The standard deviation of the spore-film measurements obtained in Japan was 12.8%. The responsivity
of the spore-film system towards longer wavelengths within the UVA spectrum was tested with the Okasaki Large Spectrograph
with monochromatic radiation. At a wavelength of 365 nm – in a spectral region which is dominant in many tanning lamps and
with minor importance for solar radiation in summer conditions – the tested spore-film system gave results that were close
(112% compared to the calibration dose) to the calibration dose which was used for irradiation.
Received: 27 January 1998 / Received last revision: 21 July 1998 / Accepted: 29 July 1998 相似文献
8.
Mäkinen TM Raatikka VP Rytkönen M Jokelainen J Rintamäki H Ruuhela R Näyhä S Hassi J 《International journal of biometeorology》2006,51(1):27-36
The extent of outdoor exposure during winter and factors affecting it were examined in a cross-sectional population study in Finland. Men and women aged 25–74 years from the National FINRISK 2002 sub-study (n=6,591) were queried about their average weekly occupational, leisure-time and total cold exposure during the past winter. The effects of gender, age, area of residence, occupation, ambient temperature, self-rated health, physical activity and education on cold exposure were analysed. The self-reported median total cold exposure time was 7 h/week (8 h men, 6 h women),<1 h/week (2 h men, 0 h women) at work, 4 h/week (5 h men, 4 h women) during leisure time and 1 h/week (1 h men, 1.5 h women) while commuting to work. Factors associated with increased occupational cold exposure among men were: being employed in agriculture, forestry and industry/mining/construction or related occupations, being less educated and being aged 55–64 years. Factors associated with increased leisure-time cold exposure among men were: employment in industry/mining/construction or related occupations, being a pensioner or unemployed, reporting at least average health, being physically active and having college or vocational education. Among women, being a housewife, pensioner or unemployed and engaged in physical activity increased leisure-time cold exposure, and young women were more exposed than older ones. Self-rated health was positively associated with leisure time cold exposure in men and only to a minor extent in women. In conclusion, the subjects reported spending 4% of their total time under cold exposure, most of it (71%) during leisure time. Both occupational and leisure-time cold exposure is greater among men than women. 相似文献
9.
The UV-absorbing mycosporine-like amino acids (MAAs) are hypothesized to protect organisms against harmful UV radiation (UVR).
Since the physiology and metabolism of these compounds are unknown, the induction and kinetics of MAA biosynthesis by various
natural radiation conditions were investigated in the marine red alga Chondrus crispus collected from Helgoland, Germany. Three photosynthetically active radiation (PAR, 400–700 nm) treatments without UVR and
three UV-A/B (290–400 nm) treatments without PAR were given. Chondrus crispus collected from 4–6 m depth contained only traces of the MAA palythine. After 24 h exposure to 100% ambient PAR, traces of
three additional MAAs, shinorine, palythinol and palythene, were detected, and their concentrations increased strongly during
a one-week exposure to all PAR treatments. The concentration of all MAAs varied directly with PAR dose, with palythine and
shinorine being four- to sevenfold higher than palythinol and palythene. Likewise, naturally high doses of both UV-A and UV-B
resulted in a strong accumulation of all MAAs, in particular shinorine. While shinorine accumulation was much more stimulated
by UVR, the content of all other MAAs was more affected by high PAR, indicating an MAA-specific induction triggered by UVR
or PAR.
Received: 24 September 1997 / Accepted: 17 December 1997 相似文献
10.
The short wavelength cut-off (λc), the wavelength of the maximum spectral UV (λMax) of spectral pre-vitamin D3 effective solar UV irradiance (UVD3), and the spectral erythemal UV (UVEry) were compared at 5-min intervals over a 6-month period at solar zenith angles (SZA) ranging from 4.7° to 80°. Averaged over
the entire period, λc for UVD3 is higher by 1.05 nm than that for UVEry. The λMax is higher for UVD3 compared to UVEry for SZA < ~50°. For higher SZA (>55°), the ratio of λMax for UVD3 to that for UVEry is less than 1. As the erythemal action spectrum extends into the UVA, the ratio of UVD3 to UVEry irradiances decreases with increasing SZA, along with a decrease in the ratio of λMax for UVD3 compared to UVEry. The changes in λc and λMax influence both personal UVD3 and UVEry exposure and, to take this into account, a dual calibration technique for polysulphone dosimeters has been developed to simultaneously
provide measurements of both types of exposure. 相似文献
11.
A. Reischauer C. Ellenberger S. Döll S. Dänicke S. Dhein U. Schnurrbusch H. -A. Schoon 《Mycotoxin Research》2005,21(2):143-146
The objective of this study was to investigate the effects of four different concentrations (groups II–V) of orally administered
zearalenone (ZON) over a feeding period of 35 days on parts of the genital tract of 75 day-old female piglets in comparison
to a control group (I). In order to determine possible dose related characteristics for a ZON intoxication in ovaries and
uteri, histomorphological (HE and Azan stained slides) and immunohistochemical methods [expression patterns of estrogen (ER)
and progesterone (PR) receptor, proliferating cell nuclear antigen (PCNA)] were carried out. Using these methods, there were
no obvious (immuno-) histomorphological differences within the treatment groups or in comparison to the control group. Nevertheless,
compared to the group I, statistical analyses of all parameters investigated revealed significance only in the increased mitotic
activity of muscle cells in the uterinelamina muscularis in treatment group V.
Presented at the 26th Mykotoxin-Workshop in Herrsching, Germany, May 17–19, 2004 相似文献
12.
As the outermost layer of the skin, the stratum corneum is exposed to environmental oxidants. To investigate putative synergisms of environmental oxidative stressors in stratum corneum, hairless mice were exposed to ultraviolet radiation (UV) and ozone (O(3)) alone and in combination. Whereas a significant depletion of alpha-tocopherol was observed after individual exposure to either a 0.5 minimal erythemal dose of UV or 1 ppm O(3) for 2 h, the combination did not increase the effect of UV alone. However, a dose of 0.5 ppm O(3) x 2 h, which had no effect when used alone, significantly enhanced the UV-induced depletion of vitamin E. We conclude that concomitant exposure to low doses of UV and O(3) at levels near those that humans can be exposed to causes additive oxidative stress in the stratum corneum. 相似文献
13.
Increased Lipid Peroxidation and Ascorbic Acid Utilization in Testis and Epididymis of Rats Chronically Exposed to Lead 总被引:4,自引:0,他引:4
Mariola Marchlewicz Barbara Wiszniewska Bolesław Gonet Irena Baranowska-Bosiacka Krzysztof Safranow Agnieszka Kolasa Wojciech Głąbowski Rafał Kurzawa Katarzyna Jakubowska Monika E. Rać 《Biometals》2007,20(1):13-19
The hypothesis has been recently presented that lead may exert its negative effect at least partially through the increase
of reactive oxygen species (ROS) level in tissues. However, little is known about the influence of lead intoxication on equilibrium
between generation and elimination of ROS in the male reproductive system. Sexually mature male Wistar rats were given ad libitum 1% of aqueous solution of lead acetate (PbAc) for 9 months. Significantly higher lead concentrations were found in blood
[median 7.03 (Q25–Q75: 2.99–7.65) versus 0.18 (0.12–0.99) μg dl−1, P < 0.01], caput epididymis [median 5.51 (Q25–Q75: 4.31–7.83) versus 0.51 (0.11–0.80) μg g−1 d.m., P < 0.001], cauda epididymis [median 5.88 (Q25–Q75: 4.06–8.37) versus 0.61 (0.2 – 1.08) μg g−1 d.m., P < 0.001] and testis [median 1.81 (Q25–Q75: 0.94–2.31) versus 0.17 (0.03–0.3) μg g−1 d.m., P < 0.01] of lead-intoxicated rats when compared to the control. The concentration of ascorbyl radical, generated in vitro from l-ascorbic acid (present in tissues in vivo) was measured by means of Electron Paramagnetic Resonance (EPR) spectroscopy. The EPR signal of ascorbyl radical in caput
epididymis, cauda epididymis, testis and liver of lead acetate-treated animals revealed a significant decrease by 53%, 45%,
40% and 69% versus control tissues, respectively. Plasma l-ascorbic acid content measured by high performance liquid chromatography (HPLC) method and total antioxidant status (TAS)
measured by means of spectrophotometry were also significantly lower in the intoxicated versus control animals (28% and 21%, respectively). In the group exposed to lead the concentration of lipid peroxide in homogenates
of the reproductive system organs was significantly elevated versus control group. It can be assumed that the lower EPR signal was caused by decreased tissue concentrations of l-ascorbic acid. The latter may have resulted from consumption of ascorbic acid for scavenging of ROS excess in tissues of
animals chronically exposed to lead. 相似文献
14.
15.
Summary. 3-Hydroxynorvaline (HNV; 2-amino-3-hydroxypentanoic acid), a microbial L-threonine analogue, is toxic to mammalian cells and
displays antiviral properties. In view of this, we investigated the toxicity and/or potential teratogenicity of HNV in developing
chicken and mouse embryos. HNV was administered to chicken embryos (in ovo; dose 75–300 μmole/egg; 48 h post-incubation) and pregnant Hanover NMRI mice (per os; total dose 900–1800 mg/kg body mass; gestation days 7–9). Control animals received sterile saline solutions. Harvested embryos
(chicken embryos, 10 days post-incubation; mouse embryos; gestation day 18) were fixed in glutaraldehyde and stereomicroscopically
inspected for signs of dysmorphogenesis. Body mass, body and toe length and mortality of chicken embryos, and the body mass
and mortality of mouse embryos were recorded. HNV exposure significantly increased the incidence of embryotoxic (growth retardation,
toxic mortality) and congenital defects in both chicken and mouse embryos. All the observed effects were dose-dependent. In
conclusion, HNV is an embryotoxic and teratogenic compound, which caused significant developmental delay and congenital defects
in developing chicken and mouse embryos. 相似文献
16.
Solar ultraviolet-B (UVB) radiation has deleterious effects on plant-dwelling mites. We assessed the biological effects of
UVB radiation on the eggs of the twospotted spider mite, Tetranychus urticae Koch, under both near ambient (UV+) and UV-attenuated (UV−) conditions from spring to autumn and compared them to the effects
of temperature and humidity. The ambient daily UVB irradiance increased from January to August and then decreased rapidly
until December, whereas egg hatchability under UV+ was lowest in April (10.7%) and increased almost linearly until October
(74.9–92.3%). In contrast, hatchability under UV− was consistently high (96.2–99.8%) through all seasons. For UV+, the stepwise
multiple linear regression analysis supported the negative correlation of hatchability with cumulative UVB irradiance during
egg periods (cumulative dose), but did not support that with the mean daily UVB irradiance (dose rate), suggesting that UVB-induced
mortality in T. urticae eggs is cumulative dose dependent rather than dose rate dependent. The high mortality in April may have reflected the slower
development caused by the relatively lower temperature and higher UVB radiation, increasing the cumulative dose, while the
low mortality in October may have reflected the faster development caused by the relatively higher temperature and lower UVB
radiation, decreasing the cumulative dose. 相似文献
17.
Thyroid cancer risk in Belarus after the Chernobyl accident: Comparison with external exposures 总被引:1,自引:0,他引:1
Jacob P Kenigsberg Y Goulko G Buglova E Gering F Golovneva A Kruk J Demidchik EP 《Radiation and environmental biophysics》2000,39(1):25-31
Within the time period 1990–1993, childhood thyroid cancer incidence due to the Chernobyl accident increased dramatically
in Belarus, especially with regard to the birth cohort January 1, 1971, to May 31, 1986. This rise subsequently slowed down,
i.e. during the period 1994–1996. The respective data were analysed and compared with the results of an analysis on the time
dependence of thyroid cancer incidence in a pooled cohort of persons who had been exposed during childhood to external radiation
with high dose rates. Concerning the period of 5–10 years following exposure, the excess absolute cancer risk per unit thyroid
dose in the latter (external) exposure group was found to exceed the one in the Belarus group by a factor of two. This difference,
however, is not statistically significant. The age-adjusted average excess absolute risk per unit thyroid dose for the period
of 5–50 years following external childhood exposure was found to be 8 female and 14 male cases per 104 person-year · Gy, which is a factor about 2.5 times higher than for the non-adjusted risk in the pooled cohort, as reported
by Ron et al. in 1995. Assessments of future excess thyroid cancer cases due to the Chernobyl accident were done on the basis
of the time dependence of thyroid cancer risk following external exposure. The thyroid cancer incidence among the birth cohort
considered in Belarus and for a period starting from the cessation of the available observation data (1 January 1997) and
extending to 50 years after the Chernobyl accident has been estimated to be about 15,000 cases, with an uncertainty range
of 5000–45,000 cases. According to our calculations, 80% of these cases exceed the baseline risk under enhanced thyroid surveillance.
Received: 8 June 1999 / Accepted in revised form: 20 November 1999 相似文献
18.
Freddy Guihéneuf Manuela Fouqueray Virginie Mimouni Lionel Ulmann Boris Jacquette Gérard Tremblin 《Journal of applied phycology》2010,22(5):629-638
Polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic and docosahexaenoic acids (EPA and DHA), are abundantly synthesized
by some phytoplankton species and play a key role in the marine food chain. However, they are generally considered to be sensitive
to oxidation by UV radiation (UV-R). In order to investigate the effect of UV-R on the lipid composition of two marine microalgae,
Pavlova lutheri and Odontella aurita, they were exposed to a combination of UVA-R and UVB-R with a total UV-R daily dose of 110 kJ m−2. Chlorophyll a, photochemical efficiency, and lipid composition were then determined on days 3, 5, and 8 of UV-R exposure. In P. lutheri, exposure to UV-R treatment led to a decrease in the proportions of PUFAs, such as EPA and DHA, especially into structural
lipids (glycolipids and phospholipids). Our findings reveal a reduction of 20% in EPA levels and 16% in DHA levels, after
8 days of UV-R treatment. In O. aurita, exposure to UV-R did not change the fatty acid composition of the total lipids and lipid fractions of the cells. EPA levels
remained high (27–28% of total lipids) during the 8 days of treatment. Consequently, the n-3 fatty acid content of P. lutheri was altered which highlights the sensitivity of this species to UV-R, whereas the results obtained for O. aurita suggest a more UV-R resistance. As a result, in latitude countries with medium UV-R level, outdoor “race-way” culture of
O. aurita could yield a high-EPA algal biomass, whatever the seasonal variations in UV-R. 相似文献
19.
The fission yeast, Schizosaccharomyces pombe, possesses a UV-damaged DNA endonuclease-dependent excision repair (UVER) pathway in addition to nucleotide excision repair pathway for UV-induced DNA damage. We examined cyclobutane pyrimidine dimer removal from the myo2 locus on the nuclear genome and the coI locus on the mitochondrial genome by the two repair pathways. While nucleotide excision repair repairs damage only on the nuclear genome, UVER efficiently removes cyclobutane pyrimidine dimers on both nuclear and mitochondrial genomes. The ectopically expressed wild type UV-damaged DNA endonuclease was localized to both nucleus and mitochondria, while modifications of N-terminal methionine codons restricted its localization to either of two organelles, suggesting an alternative usage of multiple translation initiation sites for targeting the protein to different organelles. By introducing the same mutations into the chromosomal copy of the uvde(+) gene, we selectively inactivated UVER in either the nucleus or the mitochondria. The results of UV survival experiments indicate that although UVER efficiently removes damage on the mitochondrial genome, UVER in the mitochondria hardly contributes to UV resistance of S. pombe cells. We suggest a possible UVER function in mitochondria as a backup system for other UV damage tolerance mechanisms. 相似文献
20.
Weihs P 《International journal of biometeorology》2002,46(2):95-104
Erythemal UV irradiance incident on a horizontal surface is not always the best way of estimating the real dose received by humans or animals. For this purpose knowledge of the irradiance incident on inclined planes is required. This study presents a physically accurate model for the calculation of erythemal UV on inclined planes. The influence of ground reflectivity and topography on erythemal UV on inclined planes is investigated as a function of solar zenith and azimuth angle. It is shown that including directional reflectivity does not substantially change the incident dose on inclined planes, the maximum deviation being 10%. The incident erythemal UV may, however, be much more influenced by the surrounding topography and by the direct/diffuse partitioning of the irradiance (which is a function of altitude). Maximum increases in erythemal UV of +57%, compared with the incident erythemal UV on a horizontal plane, were found when the sensor faced the sun with a mountain slope to the left and right of it and for very high altitudes. 相似文献