| 1. |
- af Klinteberg, C, et al.
(författare)
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Kinetic fluorescence studies of 5-aminolaevulinic acid-induced protoporphyrin IX accumulation in basal cell carcinomas
- 1999
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Ingår i: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 49:2-3, s. 120-128
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Tidskriftsartikel (refereegranskat)abstract
- Laser-induced fluorescence (LIF) investigations have been performed in connection with photodynamic therapy (PDT) of basal cell carcinomas and adjacent normal skin following topical application of 5-aminolaevulinic acid (ALA) in order to study the kinetics of the protoporphyrin TX (PpIX) build-up. Five superficial and 10 nodular lesions in 15 patients are included in the study. Fluorescence measurements are performed prior to the application of ALA, 2, 4 and 6 h port ALA application, immediately post PDT (60 J cm(-2) at 635 nm), and 2 h after the treatment. Hence, the build-up, photobleaching and re-accumulation of PpIX can be followed. Superficial lesions show a maximum PpIX fluorescence 6 h post ALA application, whereas the intensity is already the highest 2-4 h after the application in nodular lesions. Immediately post PDT, the fluorescence contribution at 670 Mm from the photoproducts is about 2% of the pre-PDT PpIX fluorescence at 635 nm. Two hours after the treatment, a uniform distribution of PpIX is found in the lesion and surrounding normal tissue. During the whole procedure, the autofluorescence of the lesions and the normal skin does not vary significantly from the values recorded before the application of ALA. (C) 1999 Elsevier Science S.A. All rights reserved.
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| 2. |
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| 3. |
- Caldwell, M M, et al.
(författare)
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Effects of increased solar ultraviolet radiation on terrestrial ecosystems
- 1998
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Ingår i: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 46:1-3, s. 40-52
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Tidskriftsartikel (refereegranskat)abstract
- Elevated solar UV-B radiation associated with stratospheric ozone reduction may exert effects on terrestrial ecosystems through actions on plants, microbes, and perhaps on some animals. At the ecosystem level, the effects are less well understood than at the molecular and organismal levels. Many of the most important, yet less predictable, consequences will be indirect effects of elevated UV-B acting through changes in the chemical composition and form of plants and through changes in the abiotic environment. These indirect effects include changes in the susceptibility of plants to attack by insects and pathogens in both agricultural and natural ecosystems; the direction of these changes can result in either a decrease or an increase in susceptibility. Other indirect effects of elevated UV-B include changes in competitive balance of plants and nutrient cycling. The direct UV-B action on plants that results in changes in form or function of plants appears to occur more often through altered gene activity rather than damage. The yield of some crop varieties can be decreased by elevated UV-B, but other varieties are not affected. Plant breeding and genetic engineering efforts should be able to cope with the potential threats to crop productivity due to elevated UV-B. For forest trees, this may be more difficult if effects of elevated UV-B accumulate over several years. All effects of elevated UV-B radiation must be considered in the context of other climate changes such as increased temperature and levels of carbon dioxide, which may alter the UV-B responses, especially for plants. The actions of elevated carbon dioxide and UV-B appear to be largely independent, but interactions occur between changes in UV-B and other factors. Other ecosystem-level consequences of elevated UV-B radiation are emerging and their magnitude and direction will not be easily predicted.
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| 4. |
- Madronich, S, et al.
(författare)
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Changes in biologically active ultraviolet radiation reaching the Earth's surface
- 1998
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Ingår i: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 46:1-3, s. 5-19
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Tidskriftsartikel (refereegranskat)abstract
- Stratospheric ozone levels are near their lowest point since measurements began, so current ultraviolet-B (UV-B) radiation levels are thought to be close to their maximum. Total stratospheric content of ozone-depleting substances is expected to reach a maximum before the year 2000. All other things being equal, the current ozone losses and related UV-B increases should be close to their maximum. Increases in surface erythemal (sunburning) UV radiation relative to the values in the 1970s are estimated to be: about 7% at Northern Hemisphere mid-latitudes in winter/spring; about 4% at Northern Hemisphere mid-latitudes in summer/fall; about 6% at Southern Hemisphere mid-latitudes on a year-round basis; about 130% in the Antarctic in spring; and about 22% in the Arctic in spring. Reductions in atmospheric ozone are expected to result in higher amounts of UV-B radiation reaching the Earth's surface. The expected correlation between increases in surface UV-B radiation and decreases in overhead ozone has been further demonstrated and quantified by ground-based instruments under a wide range of conditions. Improved measurements of UV-B radiation are now providing better geographical and temporal coverage. Surface UV-B radiation levels are highly variable because of cloud cover, and also because of local effects including pollutants and surface reflections. These factors usually decrease atmospheric transmission and therefore the surface irradiances at UV-B as well as other wavelengths. Occasional cloud-induced increases have also been reported. With a few exceptions, the direct detection of UV-B trends at low- and mid-latitudes remains problematic due to this high natural variability, the relatively small ozone changes, and the practical difficulties of maintaining long-term stability in networks of UV-measuring instruments. Few reliable UV-B radiation measurements are available from pre-ozone-depletion days. Satellite-based observations of atmospheric ozone and clouds are being used, together with models of atmospheric transmission, to provide global coverage and long-term estimates of surface UV-B radiation. Estimates of long-term (1979-1992) trends in zonally averaged UV irradiances that include cloud effects are nearly identical to those for clear-sky estimates, providing evidence that clouds have not influenced the UV-B trends. However, the limitations of satellite-derived UV estimates should be recognized. To assess uncertainties inherent in this approach, additional validations involving comparisons with ground-based observations are required. Direct comparisons of ground-based UV-B radiation measurements between a few mid-latitude sites in the Northern and Southern Hemispheres have shown larger differences than those estimated using satellite data. Ground-based measurements show that summertime erythemal UV irradiances in the Southern Hemisphere exceed those at comparable latitudes of the Northern Hemisphere by up to 40%, whereas corresponding satellite-based estimates yield only 10-15% differences. Atmospheric pollution may be a factor in this discrepancy between ground-based measurements and satellite-derived estimates. UV-B measurements at more sites are required to determine whether the larger observed differences are globally representative. High levels of UV-B radiation continue to be observed in Antarctica during the recurrent spring-time ozone hole. For example, during ozone-hole episodes, measured biologically damaging radiation at Palmer Station, Antarctica (64°S) has been found to approach and occasionally even exceed maximum summer values at San Diego, CA, USA (32°N). Long-term predictions of future UV-B levels are difficult and uncertain. Nevertheless, current best estimates suggest that a slow recovery to pre-ozone depletion levels may be expected during the next half-century. Although the maximum ozone depletion, and hence maximum UV-B increase, is likely to occur in the current decade, the ozone layer will continue to be in its most vulnerable state into the next century. The peak depletion and the recovery phase could be delayed by decades because of interactions with other long-term atmospheric changes, e.g., increasing concentrations of greenhouse gases. Other factors that could influence the recovery include non-ratification and/or non-compliance with the Montreal Protocol and its Amendments and Adjustments, and future volcanic eruptions. The recovery phase for surface UV-B irradiances will probably not be detectable until many years after the ozone minimum.
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| 5. |
- Nielsen, Tom, et al.
(författare)
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Impact of natural and artificial UVB radiation on motility and growth rate of marine dinoflagellates
- 1995
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Ingår i: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 27:1, s. 73-79
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Tidskriftsartikel (refereegranskat)abstract
- The growth rates and motility of dinoflagellates were studied in the field in the presence or absence of UVB radiation, as well as in the laboratory under artificial radiation conditions. Photosynthetically active radiation (PAR, 400–700 nm) and UVB radiation showed large variations due to cloud cover and seasonal changes in natural daylight. In Swedish coastal water, UVB radiation was attenuated to about 10% of surface irradiance at a depth of 120 cm. There was no significant difference in the motility of two strains of Prorocentrum minimum (Atlantic, LAC4LI; Kattegat, LAC6KA83) kept in the water at different depths (35 and 120 cm) for 4 h, with or without natural solar UV radiation, except for a day with high UVB irradiance (1.2 W m−2), which decreased the motility at a depth of 35 cm for the two species). Simulated in situ experiments with 2 h natural daylight, with and without natural UV radiation (UVB, 1.6 W m−2), had a dramatic effect on the motility of Gyrodinium aureolum. Artificial UVB radiation from UV lamps (4 h, 2.72 kJ m−2 day−1, biologically effective UVB radiation, UVBBE) in the laboratory decreased the motility of Heterocapsa triquetra (LAC20) by 56% and the two strains of P. minimum (Atlantic, LAC4LI; Kattegat, LAC6KA83) by 43% and 36% respectively; the growth was inhibited for all species, as well as for Amphidinium carterae (LAC1KA83), when organisms were exposed to more than 0.7 kJ m−2 day−1 of UVBBE radiation.
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| 6. |
- Yu, Shi-Gui, et al.
(författare)
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Differences in UV-B sensitivity between PSII from grana lamellae and stroma lamellae
- 1996
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Ingår i: Journal of Photochemistry and Photobiology, B: Biology. - : Elsevier BV. - 1011-1344. ; 34:1, s. 35-38
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Tidskriftsartikel (refereegranskat)abstract
- UV-B treatment of thylakoid membranes or fractions derived from them accelerates the first rise (Fo---Fi phase) of variable fluorescence and slows down the second (Fi---Fm) rise. This can be observed for all membrane fractions but to different extents. The grana fraction is affected more by the UV-B treatment than are the intact thylakoids and the stroma lamella fraction. An exogenous electron acceptor, 2,6-dichloro-p-benzoquinone, inhibits both the initial and second rises of the fluorescence induction kinetics including the changes induced by UV-B. However, other electron acceptors, such as 2,5-dimethyl-p-benzoquinone and methyl viologen quench only the second rise of the curve. Oxygen evolution from grana-derived membranes is more sensitive to UV-B treatment than oxygen evolution from stroma lamella-derived membranes.
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| 7. |
- Yu, Shi-Gui, et al.
(författare)
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Ultraviolet-B stimulates grana formation in chloroplasts in the African desert plant Dimorphotheca pluvialis
- 1999
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Ingår i: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 49:1, s. 65-70
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Tidskriftsartikel (refereegranskat)abstract
- Chloroplasts isolated from a plant species, Dimorphotheca pluvialis Moench (Asteraceae), grown under visible light without supplementary UV-B radiation, have poor grana development. The dominant components in the membrane organizations are doublets and triplets of stroma lamellae. However, such chloroplasts possess the capacity for electron transfer through the whole photosynthetic chain, based on the measurement of the reduction of ferredoxin. The chloroplasts isolated from D. pluvialis plants grown under visible light in combination with supplementary UV-B radiation have much greater membrane stacking in the thylakoid organization when compared with those grown without supplementary UV-B. The changes in the membrane organization induced by UV-B are also reflected in photochemical activity: oxygen-evolving phoptosystem II (PSII) activity is increased in UV-B chloroplasts compared with chloroplasts grown without UV-B. On this basis, it is concluded that the dynamic relation between the granal stacks and the stroma lamellae in the chloroplasts is closely related to the strategy by which plants are able to cope with a variety of environments and to optimize the photosynthetic machinery for the environmental conditions. The increase in membrane stacking in D. pluvialis, induced by supplementary UV-B radiation during plant growth, suggests that UV-B may be an essential factor for the development of membrane stacking in chloroplasts of higher plants. The mechanism of action of UV-B in this process is discussed.
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| 8. |
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| 9. |
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| 10. |
- Nielsen, Tom, 1956-, et al.
(författare)
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Impact of natural and artificial ultraviolet-B radiation on motility and growth rate of marine dinoflagellates
- 1995
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Ingår i: Journal of Photochemistry and Photobiology. B. - 1011-1344 .- 1873-2682. ; 27, s. 73-79
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Tidskriftsartikel (refereegranskat)abstract
- The growth rates and motility of dinoflagellates were studied in the field in the presence or absence of UVB radiation, as well as in the laboratory under artificial radiation conditions. Photosynthetically active radiation (PAR, 400–700 nm) and UVB radiation showed large variations due to cloud cover and seasonal changes in natural daylight. In Swedish coastal water, UVB radiation was attenuated to about 10% of surface irradiance at a depth of 120 cm. There was no significant difference in the motility of two strains of Prorocentrum minimum (Atlantic, LAC4LI; Kattegat, LAC6KA83) kept in the water at different depths (35 and 120 cm) for 4 h, with or without natural solar UV radiation, except for a day with high UVB irradiance (1.2 W m−2), which decreased the motility at a depth of 35 cm for the two species). Simulated in situ experiments with 2 h natural daylight, with and without natural UV radiation (UVB, 1.6 W m−2), had a dramatic effect on the motility of Gyrodinium aureolum. Artificial UVB radiation from UV lamps (4 h, 2.72 kJ m−2 day−1, biologically effective UVB radiation, UVBBE) in the laboratory decreased the motility of Heterocapsa triquetra (LAC20) by 56% and the two strains of P. minimum (Atlantic, LAC4LI; Kattegat, LAC6KA83) by 43% and 36% respectively; the growth was inhibited for all species, as well as for Amphidinium carterae (LAC1KA83), when organisms were exposed to more than 0.7 kJ m−2 day−1 of UVBBE radiation.
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