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1.
  • af Klinteberg, C, et al. (author)
  • Kinetic fluorescence studies of 5-aminolaevulinic acid-induced protoporphyrin IX accumulation in basal cell carcinomas
  • 1999
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 49:2-3, s. 120-128
  • Journal article (peer-reviewed)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.
  • Andersson-Engels, Stefan, et al. (author)
  • Effects of Optical-constants On Time-gated Transillumination of Tissue and Tissue-like Media
  • 1992
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 16:2, s. 155-167
  • Journal article (peer-reviewed)abstract
    • Light transillumination was used to study structures inside turbid media. Time-gated viewing was performed to suppress multiply-scattered light and thus improve spatial resolution. We demonstrate that, for the case of scattering-dominated attenuation (scattering coefficient much greater than the absorption coefficient), the detection of early transmitted light will be practically insensitive to variations in the absorption coefficient. This is an important observation for the development of time-gated optical mammography, since optical mammography using continuous-wave light is based on increased light absorption in the tumour region caused by the neovascularization surrounding a tumour. In order to detect tumours in time-gated viewing it is the scattering coefficient of the tumour that must be characteristic. The scattering coefficient is measured to be lower in the tumour region than in the surrounding breast tissue for one resected breast specimen.
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5.
  • Buffoni Hall, Roberta, et al. (author)
  • UV-induced changes in pigment content and light penetration in the fruticose lichen Cladonia arbuscula ssp. mitis
  • 2002
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 66:1, s. 13-20
  • Journal article (peer-reviewed)abstract
    • The response of the lichen, Cladonia arbuscula (Wallr.) Flot. ssp. mitis (Sandst.) Ruoss to enhanced UV-B (280-315 nm) radiation was investigated with respect to: (a) changes in phenolic content; (b) differential pigment accumulation under visible and UV radiation with increasing distance from thallus apices; and (c) the internal distribution of UV-B radiation within the thallus measured with quartz optical fibres. In a short-term experiment, lichens were exposed for 7 days in a growth chamber to visible light with or without additional UV-B radiation. For a longer term experiment, lichens were grown outdoors under both natural UV radiation, and supplemental UV-A (315–400 nm)+UV-B provided by lamps. Controls were placed under filters that removed the radiation below 290 nm from the natural sunlight. The concentration of total phenolic compounds was measured spectrophotometrically at the termination of the experiments, in different parts of the lichen podetia. UV-exposed lichens showed increased accumulation of phenolics compared to those not grown under UV. At the termination of the long-term experiment, fibre optic measurements of the penetration of radiation into lichen thallus reflected the influence of growth under UV radiation, whereby UV was more strongly attenuated as compared to that in lichens not exposed to enhanced levels of UV-B radiation. Results indicated that in Cladonia, UV-B radiation induces the accumulation of phenolic compounds that may have a protective role. In addition, the morphological distribution of phenolic compounds was different under visible and supplemental UV-B radiation. Internal radiation measurements served to visualise the attenuation of radiation with thallus depth for different wavelengths in the UV-B waveband.
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6.
  • Caldwell, M M, et al. (author)
  • Effects of increased solar ultraviolet radiation on terrestrial ecosystems
  • 1998
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 46:1-3, s. 40-52
  • Journal article (peer-reviewed)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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7.
  • Cen, Yan-Ping, et al. (author)
  • Action spectra for enhancement of ultraweak luminescence by UV radiation (270–340 nm) in leaves of Brassica napus
  • 1994
  • In: Journal of Photochemistry and Photobiology, B: Biology. - : Elsevier BV. - 1011-1344. ; 22:2, s. 125-129
  • Journal article (peer-reviewed)abstract
    • Fluence-response relationships for the enhancement of ultraweak luminescence by UV radiation were determined in leaves of Brassica napus L. (cv. Ceres) when either the adaxial or abaxial leaf surface was exposed to monochromatic radiation (270–340 nm). Action spectra for both leaf surfaces were constructed from the fluence-response curves at the fluence required to obtain a doubling of the ultraweak luminescence level over the unirradiated controls. The action spectrum for the abaxial leaf surface showed a steeper slope than that for the adaxial leaf surface at wavelengths below 280 nm. Both action spectra were flatter than the generalized plant action spectrum of Caldwell (M.M. Caldwell, in A.C. Giese (ed.), Photophysiology, Vol. 6, Academic Press, New York, 1971, pp. 131–177) at wavelengths above 280 nm. Under a depleted ozone layer, the action spectra yielded a radiation amplification factor approximately 50% of that obtained with Caldwell's generalized plant action spectrum. The shape of the action spectrum for the induction of ultraweak luminescence was approximately the same for both surfaces above 290 nm.
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8.
  • Gaberscik, Alenka, et al. (author)
  • Growth and production of buckwheat (Fagopyrum esculentum) treated with reduced, ambient, and enhanced UV-B radiation
  • 2002
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 66:1, s. 30-36
  • Journal article (peer-reviewed)abstract
    • The effect of enhanced UV-B radiation on buckwheat (Fagopyrum esculentum Moench. variety ‘Darja’), an important high elevation crop, was studied in order to estimate its vulnerability in changing UV-B environment. Plants were grown in outdoor experiments from July to October under reduced and ambient UV-B levels, and an UV-B level simulating 17% ozone depletion in Ljubljana. During the development the following parameters were monitored: light saturated photosynthetic activity, transpiration, potential and effective photochemical efficiencies of photosystem II, the contents of photosynthetic pigments and methanol soluble UV-B absorbing compounds. At the end of the experiment, growth rate and production of seeds were estimated. In the following growth season the seeds collected from plants exposed to different UV-B treatments were tested for germination capacity. Total UV-B absorbing compounds during plant development were increased by UV-B radiation, photosynthetic pigments (chlorophyll a and b and carotenoids) decreased. Photosynthetic rate was lowered in an early stage of development. UV-B treatment resulted in the increase in the transpiration rate and consequently the decrease in water use efficiency (WUE). The disturbances in water economy and in photosynthesis affected the reproduction potential negatively; the production of seeds in plants cultivated under ambient and enhanced UV-B was 57 and 39% of the production of specimens treated with reduced UV-B, respectively. The germination of seeds collected from treated plants revealed on average about 95% success, independently of the treatment, but the time needed for germination was the shortest for seeds developed under enhanced UV-B level treatment. Enhanced UV-B radiation affected water relations and production of buckwheat, but not the potential of seeds for germination. This is the final, accepted and revised manuscript of this article. Use alternative location to go to the published article. Requires subscription.
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9.
  • Li, Shaoshan, et al. (author)
  • Temperature-dependent formation and photorepair of DNA damage induced by UV-B radiation in suspension-cultured tobacco cells
  • 2002
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 66:1, s. 67-72
  • Journal article (peer-reviewed)abstract
    • Two photoproducts of DNA damage, i.e. cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs), induced by UV-B radiation in suspension-cultured tobacco cells were quantified by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. CPDs and 6-4PPs were induced in tobacco cells by UV-B radiation. Photorepair of CPDs was faster than that of 6-4PPs. UV-B radiation induces formation of CPDs and 6-4PPs even at 0 °C, but low temperature significantly decreases the UV-B-induced (in contrast to UV-C-induced) formation of CPDs and 6-4PPs. Low temperature also retarded the removal of CPDs and 6-4PPs under white light, and almost no photorepair of CPDs and 6-4PPs was detected at 0 °C. When purified DNA from tobacco cells grown in darkness was irradiated with UV-B, formation of CPDs and 6-4PPs took place at the same speed at different temperatures. It indicated that formation of CPDs and 6-4PPs induced by UV-B was temperature-independent in a non-cellular system. Based on our results for suspension-cultured tobacco cells, not only the photorepair but also UV-B-induced formation of CPDs and 6-4PPs are temperature-dependent. This is the final, accepted and revised manuscript of this article. Use alternative location to go to the published article. Requires subscription.
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10.
  • Madronich, S, et al. (author)
  • Changes in biologically active ultraviolet radiation reaching the Earth's surface
  • 1998
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 46:1-3, s. 5-19
  • Journal article (peer-reviewed)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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11.
  • Nielsen, Tom, et al. (author)
  • Impact of natural and artificial UVB radiation on motility and growth rate of marine dinoflagellates
  • 1995
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 27:1, s. 73-79
  • Journal article (peer-reviewed)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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12.
  • Panagopoulos, Ioannis, et al. (author)
  • Effects of ultraviolet radiation and visible light on growth, fluorescence induction, ultraweak luminescence and peroxidase activity in sugar beet plants
  • 1990
  • In: Journal of Photochemistry and Photobiology, B: Biology. - : Elsevier BV. - 1011-1344. ; 8:1, s. 73-87
  • Journal article (peer-reviewed)abstract
    • Experiments were conducted under growth chamber conditions in order to investigate the importance of the background light quality for the effect of UVB (280–320 nm) radiation on plants. Three week-old sugar beet (Beta vulgaris L.) plants were irradiated for three weeks with enhanced levels of UVB radiation with the following background light conditions: white light (WL) (350–700 nm), WL+UVA (supplementary UVA, 320–400 nm) and "yellow" light (YL) (450–700 nm). The effects of the enhanced UVB radiation were estimated on leaf area, fresh and dry weights of storage roots, chlorophyll and carotenoids, peroxidase activity, fluorescence induction and ultraweak luminescence (UL). Plants grown under YL+UVB died after 10 days. The lowest values for leaf area and fresh and dry weights of storage roots were observed under WL+UVA+UVB conditions. Under WL+UVA and WL+UVA+UVB the decrease in total chlorophyll was mainly a result of the reduction in chlorophyll a. Photosystem II appeared to be inhibited by UVB radiation, while the addition of UVA suggested an ameliorating effect with respect to the rise time kinetics of the chlorophyll fluorescence induction curves. UL of leaves was highest in plants grown under WL+UVB conditions. It is suggested that part of the UL derives from lipid peroxidation. Protective measures may have been afforded by the increase in carotenoids under YL and WL+UVB radiation. Also the leaf peroxidase activity was highest under WL+UVB conditions.
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  • Rozema, J, et al. (author)
  • The role of UV-B radiation in aquatic and terrestrial ecosystems—an experimental and functional analysis of the evolution of UV-absorbing compounds
  • 2002
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 66:1, s. 2-12
  • Journal article (peer-reviewed)abstract
    • We analysed and compared the functioning of UV-B screening pigments in plants from marine, fresh water and terrestrial ecosystems, along the evolutionary line of cyanobacteria, unicellular algae, primitive multicellular algae, charophycean algae, lichens, mosses and higher plants, including amphibious macrophytes. Lichens were also included in the study. We were interested in the following key aspects: (a) does the water column function effectively as an ‘external UV-B filter’?; (b) do aquatic plants need less ‘internal UV-B screening’ than terrestrial plants?; (c) what role does UV screening play in protecting the various plant groups from UV-B damage, such as the formation of thymine dimers?; and (d) since early land ‘plants’ (such as the predecessors of present-day cyanobacteria, lichens and mosses) experienced higher UV-B fluxes than higher plants, which evolved later, are primitive aquatic and land organisms (cyanobacteria, algae, lichens, mosses) better adapted to present-day levels of UV-B than higher plants? Furthermore, polychromatic action spectra for the induction of UV screening pigments of aquatic organisms have been determined. This is relevant for translating ‘physical’ radiation measurements of solar UV-B into ‘biological’ and ‘ecological’ effects. From the action spectra, radiation amplification factors (RAFs) have been calculated. These action spectra allow us to determine any mitigating or antagonistic effects in the ecosystems and therefore qualify the damage prediction for the ecosystems under study. We summarize and discuss the main results based on three years of research of four European research groups. The central theme of the work was the investigation of the effectiveness of the various screening compounds from the different species studied in order to gain some perspective of the evolutionary adaptations from lower to higher plant forms. The induction of mycosporine-like amino acids (MAAs) was studied in the marine dinoflagellate Gyrodinium dorsum, the green algal species Prasiola stipitata and in the cyanobacterium Anabaena sp. While visible (400–700 nm) and long wavelength UV-A (315–400 nm) showed only a slight effect, MAAs were effectively induced by UV-B (280–315 nm). The growth of the lower land organisms studied, i.e. the lichens Cladina portentosa, Cladina foliacaea and Cladonia arbuscula, and the club moss Lycopodiumannotinum, was not significantly reduced when grown under elevated UV-B radiation (simulating 15% ozone depletion). The growth in length of the moss Tortula ruralis was reduced under elevated UV-B. Of the aquatic plants investigated the charophytes Chara aspera showed decreased longitudinal growth under elevated UV-B. In the ‘aquatic higher plants’ studied, Ceratophyllum demersum, Batrachium trichophyllum and Potamogeton alpinus, there was no such depressed growth with enhanced UV-B. In Chara aspera, neither MAAs nor flavonoids could be detected. Of the terrestrial higher plants studied, Fagopyrum esculentum, Deschampsia antarctica, Vicia faba, Calamagrostis epigejos and Carex arenaria, the growth of the first species was depressed with enhanced UV-B, in the second species length growth was decreased, but the shoot number was increased, and in the latter two species of a dune grassland there was no reduced growth with enhanced UV-B. In the dune grassland species studied outdoors, at least five different flavonoids appeared in shoot tissue. Some of the flavonoids in the monocot species, which were identified and quantified with HPLC, included orientin, luteolin, tricin and apigenin. A greenhouse study with Vicia faba showed that two flavonoids (aglycones) respond particularly to enhanced UV-B. Of these, quercetin is UV-B inducible and mainly located in epidermal cells, while kaempferol occurs constitutively. In addition to its UV-screening function, quercetin may also act as an antioxidant. Polychromatic action spectra were determined for induction of the UV-absorbing pigments in three photosynthetic organisms, representing very different taxonomic groups and different habitats. In ultraviolet photobiology, action spectra mainly serve two purposes: (1) identification of the molecular species involved in light absorption; and (2) calculation of radiation amplification factors for assessing the effect of ozone depletion. Radiation amplification factors (RAFs) were calculated from the action spectra. In a somewhat simplified way, RAF can be defined as the percent increase of radiation damage for a 1% depletion of the ozone layer. Central European summer conditions were used in the calculations, but it has been shown that RAF values are not critically dependent on latitude or season. If only the ultraviolet spectral region is considered, the RAF values obtained are 0.7 for the green alga Prasiola stipitata, 0.4 for the dinoflagellate Gyrodinium dorsum, and 1.0 for the cyanobacterium Anabaena sp. In the case of P. stipitata, however, the effect of visible light (PAR, photosynthetically active radiation, 400–700 nm) is sufficient to lower the RAF to about 0.4, while the PAR effect for G. dorsum is negligible. RAFs for some damage processes, such as for DNA damage (RAF=2.1 if protective effects or photorepair are not considered [1]), are higher than those above. Our interpretation of this is that if the ozone layer is depleted, increased damaging radiation could overrule increased synthesis of protective pigments. In addition to investigating the functional effectiveness of the different screening compounds, direct UV effects on a number of key processes were also studied in order to gain further insight into the ability of the organisms to withstand enhanced UV-B radiation. To this end, the temperature-dependent repair of cyclobutane dimers (CPD) and (6–4) photoproducts induced by enhanced UV-B was studied in Nicotiana tabacum, and the UV-B induction of CPD was studied in the lichen Cladonia arbuscula [2]. Also, photosynthesis and motility were monitored and the response related to the potential function of the screening compounds of the specific organism.
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  • Wang, T, et al. (author)
  • Provitamins and vitamins D2 and D3 in Cladina spp. over a latitudinal gradient: possible correlation with UV levels
  • 2001
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 62:1-2, s. 118-122
  • Journal article (peer-reviewed)abstract
    • Provitamin D2, vitamin D2 and vitamin D3 were identified in the thallus of a lichen species, Cladina arbuscula (Wallr.) Hale and W.L. Culb. The identification of vitamin D3 was supported by: (1) co-chromatography in both reverse and straight phase HPLC (high performance liquid chromatography), (2) ultraviolet absorption spectrum, and (3) molecular ion peaks demonstrated by ESI (electrospray ionisation) mass spectrometry. The contents of vitamin D3 range from 0.67 to 2.04 g g−1 dry matter in the thalli of C. arbuscula specimens grown under different natural conditions, while provitamin D3 could not be detected. The ranges for provitamin D2 and vitamin D2 were 89–146 and 0.22–0.55 g g−1 dry matter, respectively, while the contents of provitamin D3 were below the detection limit (0.01 g g−1 dry matter). When C. arbuscula thalli collected at different latitudes from northern Finland to Greece were compared, a positive correlation of vitamin D2 and D3 contents with modelled UV-B radiation at the collection sites was found. A single sample of C. rangiferina from northern Finland gave much higher values for the vitamins. A possible reason could be the lower content of UV-B absorbing pigment in the latter species. This is the final, accepted and revised manuscript of this article. Use alternative location to go to the published article. Requires subscription.
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16.
  • Yu, Shi-Gui, et al. (author)
  • Differences in UV-B sensitivity between PSII from grana lamellae and stroma lamellae
  • 1996
  • In: Journal of Photochemistry and Photobiology, B: Biology. - : Elsevier BV. - 1011-1344. ; 34:1, s. 35-38
  • Journal article (peer-reviewed)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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17.
  • Yu, Shi-Gui, et al. (author)
  • Ultraviolet-B stimulates grana formation in chloroplasts in the African desert plant Dimorphotheca pluvialis
  • 1999
  • In: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 49:1, s. 65-70
  • Journal article (peer-reviewed)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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19.
  • Ekelund, N. G. A. (author)
  • Interactions between photosynthesis and 'light-enhanced dark respiration' (LEDR) in the flagellate Euglena gracilis after irradiation with ultraviolet radiation
  • 2000
  • In: Journal of Photochemistry and Photobiology. B. - 1011-1344 .- 1873-2682. ; 55:1, s. 63-69
  • Journal article (peer-reviewed)abstract
    • The effects of ultraviolet radiation (UV-A, 315-400 nm plus UV-B, 280-315 nm) on photosynthesis and 'light-enhanced dark respiration' (LEDR) in Euglena gracilis have been investigated by using light pulses (80 s) with increasing photon fluence rates of 59, 163, 600, 1180, 2080 and 3340 mu mol m(-2) s(-1) and dark periods between the light pulses. LEDR is estimated as the maximum rate of oxygen consumption after a period of Light minus the rate of oxygen consumption 30 s after the maximum rate. Without any exposure to UV radiation, the photosynthetic rate and LEDR increase with increasing photon fluence rate. After 20 and 40 min exposures to UV radiation, the photosynthetic rate and LEDR as functions of photon fluence rate are reduced. After a 20 min UV treatment respiration is greater than photosynthesis after the first light pulse of 59 mu mol m(-2) s(-1) radiation, and especially at higher photon fluence rates photosynthesis is lower than the control values. The inhibitory effects of UV radiation on photosynthetic rate and LEDR are greater after a 40 min UV exposure than after a 20 min exposure. Only at 600 mu mol m(-2) s(-1) is the rate of oxygen evolution greater than that of oxygen consumption after a 40 min UV treatment. Both photosynthetic rate and LEDR are inhibited by the photosynthetic inhibitor DCMU (10(-5) M) in a similar way, which indicates close regulatory interactions between photosynthesis and LEDR. Potassium cyanide (KCN) inhibits dark respiration more than it inhibits LEDR. Dark respiration is not affected to the same degree by UV radiation as are photosynthesis and LEDR.
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21.
  • Nielsen, Tom, 1956-, et al. (author)
  • Impact of natural and artificial ultraviolet-B radiation on motility and growth rate of marine dinoflagellates
  • 1995
  • In: Journal of Photochemistry and Photobiology. B. - 1011-1344 .- 1873-2682. ; 27, s. 73-79
  • Journal article (peer-reviewed)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.
  •  
22.
  • Andreasson, Kristin I. M., 1963, et al. (author)
  • Biological weighting functions as a tool for evaluating two ways to measure UVB radiation inhibition on photosynthesis
  • 2006
  • In: Journal of Photochemistry and Photobiology B-Biology. - : Elsevier BV. - 1011-1344. ; 84:2, s. 111-118
  • Journal article (peer-reviewed)abstract
    • To estimate the inhibitory effect of the changing UVB radiation (UVBR, 280-315 nm) on earth's ecosystems, an understanding of its wavelength dependency is needed. The tool used for these estimations is the biological weighting function (BWF), whereby the inhibition of different wavelengths is calculated. B\WFs were determined for three algae species from different classes, Phaeodactylum tricornutum (Bacillariophyceae), Dunaliella tertiolecta (Chlorophyceae) and Rhodomonas sp. (Cryptophyceae), using polychromatic irradiation, where the UVBR spectra were varied with cut-off filters. For each alga, BWFs were determined for two photosynthetic parameters; the quantum yield measured as fluorescence from Photo System II in a pulse-amplitude-modulation (PAM) fluorometer, and the fixation of C-14-labelled carbon dioxide. The BWFs were calculated with the Rundel method, using the radiation data between 270 and 360 nm with 1 nm resolution. The results show that the UVBR damages were generally higher when using the carbon fixation measurements than when measuring with the PAM technique. When using PAM, P. tricornutum in particular had a sensitivity intermediate between the sensitive Rhodomonas sp. and the more tolerant D. tertiolecta, but was as sensitive as, or even more sensitive, than Rhodomonas sp. when using carbon fixation. D. tertiolecta was shown to be less sensitive when using both techniques and the inhibition of its photosynthesis was almost as high when using PAM as when using carbon fixation. We concluded that, although the PAM technique has advantages such as being cleaner and easier to use, it is unable to Substitute the carbon fixation measurements. Not only are the algae less sensitive when measured with PAM than they are when measured as carbon fixation, the relationship between the effects on the algae measured with the two techniques also differs. As fixation of carbon dioxide integrates a larger part of the photosynthetic machinery, it should be favoured as a measure of photosynthesis. (c) 2006 Elsevier B.V. All rights reserved.
  •  
23.
  • Andreasson, Kristin I. M., 1963, et al. (author)
  • Reduction in growth rate in Phaeodactylum tricornutum (Bacillarlophyceae) and Dunaliella tertiolecta (Chlorophyceae) induced by UV-B radiation
  • 2007
  • In: Journal of Photochemistry and Photobiology B-Biology. - : Elsevier BV. - 1011-1344. ; 86:3, s. 227-233
  • Journal article (peer-reviewed)abstract
    • The effect of UV-B radiation (UVBR, 280-315 nm) on growth rate during 72 h of incubation, was measured for two marine microalgae - Dunaliella tertiolecta (Chlorophyceae) and Phaeodactyhan tricornutum (Bacillariophyceae). The resulting inhibition of growth rate was analysed by calculating biological weighting functions (BWFs). The growth rate of D. tertiolecta was slightly more inhibited by UVBR (over the whole range of the spectrum) than was the growth rate of P. tricornutum, but the wavelength dependencies were the same. Our results were compared with results from photosynthesis experiments of Andreasson and Wangberg [1], where two methods, pulse amplitude modulation (PAM) fluorescence and carbon fixation, were measured for these same algae. The BWF for the growth rate, here, showed more wavelength dependency than the BWF for the previous two photosynthesis measurements - except for the carbon fixation BWF in P. tricornutum, which was closer to the BWF for growth rate. The wavelength dependency of the growth rate inhibition showed less variation between the species than the inhibition of the photosynthesis. (c) 2006 Elsevier B.V. All rights reserved.
  •  
24.
  •  
25.
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26.
  • Carr, Herman, et al. (author)
  • Parallel changes in non-photochemical quenching properties, photosynthesis and D1 levels at sudden, prolonged irradiance exposures in Ulva fasciata Delile
  • 2007
  • In: Journal of Photochemistry and Photobiology. B. - : Elsevier. - 1011-1344 .- 1873-2682. ; 87, s. 18-26
  • Journal article (peer-reviewed)abstract
    • The photosynthetic response to a sudden and prolonged high irradiance exposure and following recovery at low irradiance were studiedwith the aim of investigating the ability to withstand and adapt to high irradiance without prior high light adaptation. When thalli ofUlva fasciata, accustomed to a low irradiance (80 lmol photons m2 s1), were exposed to a high irradiance (1500 lmol photonsm2 s1), the D1 protein was rapidly degraded, reaching a steady-state level after 110 min. This was followed by a fast recovery whenthalli were transferred to dim light. The overall ability of non-photochemical quenching of chlorophyll fluorescence decreased and levelledoff at a sudden and prolonged exposure to high irradiance and followed the same trend as the D1 level with a fast recovery in dimlight. Ulva had intrinsic means to acclimate rapidly to high irradiance, when non-photochemical quenching did not operate properly, bymaintaining a smaller fraction of high light tolerant PSII assemblages and by maintaining a high non-photochemical quenching capacityof chlorophyll fluorescence in relation to the variable fluorescence. The overall absorption of light (400–700 nm) remained high duringthe period of high irradiance exposure. When Ulva were deprived of nutrients in the form of PES media the ability of non-photochemicalquenching decreased at photoinhibitory conditions. The possible causes for the responses at prolonged irradiance and the mechanismsfor the decrease of non-photochemical quenching are discussed, with implications for field measurements. 2006 Elsevier B.V. All rights reserved.
  •  
27.
  • Cheregi, Otilia, et al. (author)
  • Inactivation of the Deg protease family in the cyanobacterium Synechocystis sp. PCC 6803 has impact on the outer cell layers
  • 2015
  • In: Journal of Photochemistry and Photobiology. B. - : Elsevier. - 1011-1344 .- 1873-2682. ; , s. 383-394
  • Journal article (peer-reviewed)abstract
    • The serine type Deg/HtrA proteases are distributed in a wide range of organisms from Escherichia coli to humans. The cyanobacterium Synechocystis sp. PCC 6803 possesses three Deg protease orthologues: HtrA, HhoA and HhoB. Previously we compared Synechocystis 6803 wild type cells exposed to mild or severe stress conditions with a mutant lacking all three Deg proteases and demonstrated that stress had strong impact on the proteomes and metabolomes [1]. To identify the biochemical processes, which this protease family is involved in, here we compared Synechocystis sp. PCC 6803 wild type cells with a mutant lacking all three Deg proteases grown under normal growth conditions (30 °C and 40 μmol photons m−2 s−1). Deletion of the Deg proteases lead to the down-regulation of proteins related to the biosynthesis of outer cell layers (e.g. the GDP mannose 4,6-dehydratase) and affected protein secretion. During the late growth phase of the culture Deg proteases were found to be secreted to the extracellular medium of the Synechocystis sp. PCC 6803 wild type strain. While cyanobacterial Deg proteases seem to act mainly in the periplasmic space, deletion of the three proteases influences the proteome and metabolome of the whole cell. Impairments in the outer cell layers of the triple mutant might explain the higher sensitivity toward light and oxidative stress, which was observed earlier by Barker and coworkers [2].
  •  
28.
  • Ericson, Marica B, 1974, et al. (author)
  • Fluorescence contrast and threshold limit: implications for photodynamic diagnosis of basal cell carcinoma
  • 2003
  • In: Journal of Photochemistry and Photobiology. B: Biology. - 1011-1344. ; 69:2, s. 121-7
  • Journal article (peer-reviewed)abstract
    • This study was designed to evaluate what application time of delta-5-aminolaevulinic acid (ALA) results in highest contrast between tumour and normal skin, in the interval 1-4 h, when using photodynamic diagnosis (PDD) of basal cell carcinomas (BCC) located on the face. Moreover, a value of the demarcation limit has been derived based on the fluorescence variation in normal skin adjacent to the tumour. Forty patients were included in the study, randomly allocated to four different groups with varying ALA application time in the range 1-4 h. The contrast, defined as the ratio between the fluorescence intensity in ALA-treated tumour tissue and normal skin, was calculated for each patient, and the mean values in each group were evaluated as a function of ALA application time. In addition, the fluorescence intensity variation in ALA-treated normal skin adjacent to the tumour was assessed. The results from this study show a peak of the mean contrast values after 3 h ALA application, but due to large interpatient variation, the mean contrast did not differ significantly in the interval 2-4 h. After 2 h ALA application, the fluorescence intensity variation in the normal ALA-treated skin was found to be at a maximum, which suggests that 2 h ALA application is not preferable when using PDD. Based on data of the fluorescence variation in ALA-treated normal skin after 3 and 4 h ALA application, a tolerance interval was calculated implying that values above 1.4 times the mean normal fluorescence indicate an abnormal condition. This tolerance limit agrees well with results obtained in a former study.
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29.
  • Fernandes, Sara R.G., et al. (author)
  • Photoactive immunoconjugates for targeted photodynamic therapy of cancer
  • 2023
  • In: Journal of Photochemistry and Photobiology. B. - : Elsevier. - 1011-1344 .- 1873-2682. ; 243
  • Journal article (peer-reviewed)abstract
    • Photodynamic therapy (PDT) has been used as an alternative or as a complement of conventional approaches for cancer treatment. In PDT, the reactive oxygen species (ROS) produced from the interaction between the photosensitizer (PS), visible light and molecular oxygen, kill malignant cells by triggering a cascade of cytotoxic reactions. In this process, the PS plays an extremely important role in the effectiveness of the therapy. In the present work, a new photoimmunoconjugate (PIC), based on cetuximab and the known third generation PS-glycophthalocyanine ZnPcGal4, was synthesized via reductive amination. The rationale behind this was the simultaneous cancer-associated specific targeting of PIC and photosensitization of targeted receptor positive cells. Varied reaction parameters and photodynamic conditions, such as PS concentrations and both type and intensities of light, were optimized. ZnPcGal4 showed significant photoactivity against EGFR expressing A431, EGFR-transfected HCT116 and HT29 cells when irradiated with white light of stronger intensity (38 mW/cm2). Similarly, the synthesized PICs-T1 and T2 also demonstrated photoactivity with high intensity white light. The best optimized PIC: sample 28 showed no precipitation and aggregation when inspected visually and analyzed through SE-HPLC. Fluorescence excitation of sample 28 and 125I-sample 28 radioconjugate (125I-PIC, 125I-radiolabeling yield ≥95%, determined with ITLC) at 660 nm showed presence of appended ZnPcGal4. In addition, simultaneous fluorescence and radioactivity detection of the 125I-PIC in serum and PBS (pH 7.4) for the longest incubated time point of 72 h, respectively, and superimposed signals thereof demonstrated ≥99% of loading and/or labeling yield, assuring overall stability of the PIC and corresponding PIC-radioconjugate w.r.t. both the appended ZnPcGal4 and bound-125I. Moreover, real-time binding analyses on EGFR-transfected HCT116 cells showed specific binding of 125I-PIC, suggesting no alternation in the binding kinetics of the mAb after appending it with ZnPcGal4. These results suggest dual potential applications of synthesized PICs both for PDT and radio-immunotherapy of cancer.
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30.
  • Figueroa, Felix, et al. (author)
  • Photobiological characteristics and photosynthetic UV responses in two Ulva species (Chlorophyta) from southern Spain.
  • 2003
  • In: Journal of Photochemistry and Photobiology. B. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 72:1-3, s. 35-44
  • Journal article (peer-reviewed)abstract
    • The effect of different wavebands of artificial UV (UVB and UVA) and photosynthetically active radiation (PAR) was assessed in two species of the genus Ova, U. olivascens and U rotundata, from southern Spain in order to test for possible differences in acclimation of photosynthesis. Both species share similar morphology but are subject to different light environments: U. rotundata is an estuarine alga, inhabiting subtidal locations, while U. olivascens is an intertidal, sun-adapted organism. Algae were exposed to three different UV conditions, PAR + UVA + UVB, PAR + UVA and PAR for 7 d. Short-term exposure (6 h) was also carried out, using two PAR levels, 150 and 700 mumol m(-2) s(-1). Pigment contents and photosynthesis vs. irradiance curves from oxygen evolution were used to contrast sun- and shade adaptation between these species. O-2-based net photosynthesis (P-max) and PAM-chlorophyll fluorescence (optimal quantum yield, F-v/F-m) were used as parameters to evaluate photoinhibition of photosynthesis in the experiments. The results underline different photobiological characteristics among species: the subtidal U rotundata had higher contents of pigments (Chl a, Chl b and carotenoids) than the sun-adapted U olivascens, which resulted in higher thallus absorptance and P-I parameters characterized by higher photosynthetic efficiency at limiting irradiances (alpha) and lower saturating points for photosynthesis (E-k). After 7 d exposure, photoinhibition of F-v/F-m was close to 40-45% in both species. Differences between UV treatments were seen in U. rotundata after 5 0 and after 7 d in U olivascens, in which PAR + UVA impaired strongly photosynthesis (80%). Such patterns were correlated with a progressive decrease in pigment contents, specially chlorophylls. In short-term (6 h) exposures, combinations of UVA + UVB and high PAR level resulted in high rates of photoinhibition of chlorophyll fluorescence (68-92%) in U rotundata, whereas in U. olivascens photoinhibition ranged between 42% and 53%. Photoinhibition under low PAR combined to UV radiation was lower than observed under high PAR. Net O-2-P-max revealed similar response among the species, with maximal photoinhibition rates close to 60% in algae incubated under high PAR + UVA + UVB. In the case of UV exposure in combination with low PAR, the highest photoinhibition rates were measured in U. rotundata. 
  •  
31.
  • Gasanov, Ralphreed, et al. (author)
  • Comparative study of the water oxidizing reactions and the millisecond delayed chlorophyll fluorescence in photosystem II at different pH
  • 2007
  • In: Journal of Photochemistry and Photobiology. B. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 86:2, s. 160-164
  • Journal article (peer-reviewed)abstract
    • Water splitting activity, the multiline EPR signal associated with S2-state of the CaMn4-cluster and the fast and slow phases of the induction curve of the millisecond delayed chlorophyll fluorescence from photosystem II (PSII) in the pH range of 4.5–8.5 were studied in the thylakoid membranes and purified PSII particles. It has been found that O2 evolution and the multiline EPR signal were inhibited at acidic (pK 5.3) and alkaline (pK 8.1) pH values, and were maximal at pH 6.0–7.0. Our results indicate that the loss of O2 evolution and the S2-state multiline EPR signal associated with the decrease of the millisecond delayed chlorophyll fluorescence only in alkaline region (pH 7.0–8.5). Possible correlations of the millisecond delayed chlorophyll fluorescence components with the donor side reactions in PSII are discussed.
  •  
32.
  • Humble, Mats B. (author)
  • Vitamin D, light and mental health
  • 2010
  • In: Journal of Photochemistry and Photobiology. B. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 101:2, s. 142-149
  • Journal article (peer-reviewed)abstract
    • Vitamin D receptors and vitamin D metabolizing enzymes are present in the central nervous system. Calcitriol (the active vitamin D hormone) affects numerous neurotransmitters and neurotrophic factors, relevant for mental disorders. In the case of depressive disorders, considerable evidence supports a role of suboptimal vitamin D levels. However, the data are not conclusive and further studies are necessary. Especially, the relative importance o/f the pineal-melatonin system versus the vitamin D-endocrine system for the pathogenesis of seasonal affective disorders is presently unresolved. Two diagnoses, schizophrenia and autism, have been hypothetically linked to developmental (prenatal) vitamin D deficiency, however, also in adult patients, low levels have been reported, supporting the notion that vitamin D deficiency may not only be a predisposing developmental factor but also relate to the adult patients' psychiatric state. Two cases are described, whose psychiatric improvement coincided with effective treatment of vitamin D deficiency.
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33.
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34.
  • Kayani, Waqas Khan (author)
  • Production of biomass and medicinal metabolites through adventitious roots in Ajuga bracteosa under different spectral lights
  • 2019
  • In: Journal of Photochemistry and Photobiology B: Biology. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 193, s. 109-117
  • Journal article (peer-reviewed)abstract
    • Ajuga bracteosa an important medicinal herb, is getting endangered worldwide due to destructive harvesting by pharmaceutical industries in its different habitats. It is in dire need for protection and demands conservation and sustainable utilization. In the present study, effects of a-naphthalene acetic acid (NAA) under different spectral lights were estimated on the growth, secondary metabolism and biosynthesis of phenolic acids in adventitious roots (AR) cultures of A. bracteosa. Among the different spectral lights, highest AR induction frequency (88%) and formation of biomass (72 g/L FW and 22 g/L DW) were recorded in explants incubated in the presence of 1.5 mg/L NAA under yellow light. Maximum production of poly phenols (TPC;44.2 mg) and flavonoids (TFC;2.51 mg) were recorded in the AR cultures grown in the presence of blue light. Further, highest total protein content of (401.6 mu g) was detected in the AR in response to normal white light. Blue spectral light induced maximum superoxide dismutase (SOD; 2.5 nM) and peroxidase activity (POD;0.85 nM) respectively, in AR cultures. Compared with other monochromatic lights, red light significantly enhanced the antioxidant potential of the AR cultures. Analysis through High performance liquid chromatography (HPLC-DAD) revealed significant variations in the levels of important phenolic acids such as gallic acid, catechin, rutin, caffeic acid, myricetin and apigenin in the AR samples treated with the lights of different spectra.
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35.
  • Liao, Rong-Zhen, et al. (author)
  • Mechanism for O-O bond formation in a biomimetic tetranuclear manganese cluster - A density functional theory study
  • 2015
  • In: Journal of Photochemistry and Photobiology. B. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 152:Part A, s. 162-172
  • Journal article (peer-reviewed)abstract
    • Density functional theory calculations have been used to study the reaction mechanism of water oxidation catalyzed by a tetranuclear Mn-oxo cluster Mn4O4L6 (L = (C6H4)(2)PO4-). It is proposed that the O-O bond formation mechanism is different in the gas phase and in a water solution. In the gas phase, upon phosphate ligand dissociation triggered by light absorption, the O-O bond formation starting with both the Mn-4(III,III,IV,IV) and Mn-4(III,IV,IV,IV) oxidation states has to take place via direct coupling of two bridging oxo groups. The calculated barriers are 42.3 and 37.1 kcal/mol, respectively, and there is an endergonicity of more than 10 kcal/mol. Additional photons are needed to overcome these large barriers. In water solution, water binding to the two vacant sites of the Mn ions, again after phosphate dissociation triggered by light absorption, is thermodynamically and kinetically very favorable. The catalytic cycle is suggested to start from the Mn-4(III,III,III,IV) oxidation state. The removal of three electrons and three protons leads to the formation of a Mn-4(III,IV,IV,IV)-oxyl radical complex. The O-O bond formation then proceeds via a nucleophilic attack of water on the Mn-IV-oxyl radical assisted by a Mn-bound hydroxide that abstracts a proton during the attack. This step was calculated to be rate-limiting with a total barrier of 29.2 kcal/mol. This is followed by proton-coupled electron transfer, O-2 release, and water binding to start the next catalytic cycle.
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36.
  • Malmberg, Per, 1974, et al. (author)
  • A new approach to measuring vitamin D in human adipose tissue using time-of-flight secondary ion mass spectrometry: A pilot study
  • 2014
  • In: Journal of Photochemistry and Photobiology. B: Biology. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 138, s. 295-301
  • Journal article (peer-reviewed)abstract
    • Circulating concentrations of vitamin D, 25(OH)D, and 1,25(OH)2D are lower in obese than lean individuals, but little is known about the adipose tissue content of these molecules. The aim of this study was to explore the possibility to use time-of-flight secondary ion mass spectrometry (TOF-SIMS) to measure vitamin D and its metabolites in fat tissue in obese and lean subjects. Abdominal subcutaneous adipose tissue (SAT) biopsies were obtained from three lean and three obese women, and paired biopsies SAT and visceral adipose tissue (VAT) were obtained from three obese subjects during gastric bypass surgery. TOF-SIMS was used to measure vitamin D3, 25(OH)D3, and 1,25(OH)2D3 in adipose tissue. We found that vitamin D3, 25(OH)D3, and 1,25(OH)2D3 in adipose tissue can be measured with TOF-SIMS. In adipose tissue, vitamin D3 and its metabolites were located in adipocyte lipid droplets. The content of vitamin D3 (P = 0.006) and 25(OH)D3 (P = 0.018) were lower in SAT in obese compared with lean women. TOF-SIMS has the potential to semi-quantitatively measure vitamin D metabolites in adipose tissue, and offers a possibility to compare vitamin D levels in different depots and groups of individuals. It also gives the opportunity to explore the localization of vitamin D metabolites at a cellular level.
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37.
  • Manoil, Daniel, et al. (author)
  • Photo-oxidative stress response and virulence traits are co-regulated in E. faecalis after antimicrobial photodynamic therapy
  • 2022
  • In: Journal of Photochemistry and Photobiology. B. - : Elsevier. - 1011-1344 .- 1873-2682. ; 234
  • Journal article (peer-reviewed)abstract
    • Knowledge of photo-oxidative stress responses in bacteria that survive antimicrobial photodynamic therapy (aPDT) is scarce. Whereas aPDT is attracting growing clinical interest, subsequent stress responses are crucial to evaluate as they may lead to the up-regulation of pathogenic traits. Here, we aimed to assess transcriptional responses to sublethal aPDT-stress and identify potential connections with virulence-related genes. Six Enterococcus faecalis strains were investigated; ATCC 29212, three dental root-canal isolates labelled UmID1, UmID2 and UmID3 and two vancomycin-resistant isolates labelled A1 and A2. TMPyP was employed as a photosensitiser. A viability dose-response curve to increasing concentrations of TMPyP was determined by culture plating. Differential expression of genes involved in oxidative stress responses (dps and hypR), general stress responses (dnaK, sigma-factorV and relA), virulence-related genes (ace, fsrC and gelE) and vancomycin-resistance (vanA) was assessed by reverse-transcription qPCR. TMPyP-mediated aPDT inactivated all strains with comparable efficiencies. TMPyP at 0.015 μM was selected to induce sublethal photo-oxidative stress. Despite heterogeneities in gene expression between strains, transcriptional profiles revealed up-regulations of transcripts dps, hypR as well as dnaK and sigma factorV after exposure to TMPyP alone and to light-irradiated TMPyP. Specifically, the alternative sigma factorV reached up to 39 ± 113-fold (median ± IQR) (p = 0.0369) in strain A2. Up-regulation of the quorum sensing operon, fsr, and its downstream virulence-related gelatinase gelE were also observed in strains ATCC-29212, A1, A2 and UmID3. Finally, photo-oxidative stress induced vanA-type vancomycin-resistance gene in both carrier isolates, reaching up to 3.3 ± 17-fold in strain A2 (p = 0.015). These findings indicate that, while aPDT successfully inactivates vancomycin-resistant and naïve strains of E. faecalis, subpopulations of surviving cells respond by co-ordinately up-regulating a network of genes involved in stress survival and virulence. This includes the induction of vancomycin-resistance genes in carrier isolates. These data may provide the mechanistic basis to circumvent bacterial responses and improve future clinical protocols.
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38.
  • Nakamura, K., et al. (author)
  • Reactions of dental pulp to hydrogen peroxide photolysis-based antimicrobial chemotherapy under ultraviolet-A irradiation in rats
  • 2020
  • In: Journal of Photochemistry and Photobiology B-Biology. - : Elsevier BV. - 1011-1344. ; 212
  • Journal article (peer-reviewed)abstract
    • Hydrogen peroxide photolysis-based antimicrobial chemotherapy that utilizes ultraviolet-A irradiation (UVA-H2O2 photolysis) has been previously proposed as a method of treatment of cariogenic biofilm. Therefore, in the present study, we aimed to assess time-dependent reactions in the dental pulp of rats after UVA-H2O2 photolysis. Maxillary first molars were treated. UVA irradiation (wavelength: 365 nm) with 3 wt% H2O2 was performed for 90 s at a radiant emittance of 500-2000 mW/cm(2) on the rats for 3 consecutive days or only 1 day. The animals were sacrificed at Days 1, 3, 7, and 21 after the treatment for the histological evaluation of inflammatory cells and immunohistochemistry of heat shock protein (HSP)-25, a marker of odontoblasts. Tertiary dentin formation was evaluated at Day 21 by histomorphometry and micro-CT analysis. UVA-H2O2 photolysis elicited little infiltration of inflammatory cells, but disturbances in the odontoblast layer and/or presence of localized degenerative tissue were observed on Day 3. This condition was followed by a healing process that was characterized by the reappearance of HSP-25 positive odontoblast-like cells at Day 7 and tertiary dentin formation at Day 21. The amount of tertiary dentin formed was dependent on the intensity of treatment; repeated UVA irradiations of H(2)O(2 )at 2000 mW/cm(2) resulted in the largest amount of tertiary dentin formation at the pulp horn regions. Our findings suggest that UVA-H2O2 photolysis treatment can be used to treat dental caries clinically because the post-treatment inflammatory reaction was minimal and tertiary dentin formation was substantial, which may prove effective in protecting dental pulp from external irritants. As a cautionary consideration, the radiant emittance of the UVA irradiation should be carefully optimized before clinical application.
  •  
39.
  • Osmancevic, Amra, 1968, et al. (author)
  • Size of the exposed body surface area, skin erythema and body mass index predict skin production of vitamin D
  • 2015
  • In: Journal of Photochemistry and Photobiology B-Biology. - : Elsevier BV. - 1011-1344. ; 149, s. 224-229
  • Journal article (peer-reviewed)abstract
    • Background: Cholecalciferol (vitamin D-3), produced in the skin by UVB irradiation (290-315 nm) of 7-dehydrocholesterol, is metabolized in the liver into 25-hydroxyvitamin D [25(OH)D] which is a major circulating metabolite. Aim: To examine changes in serum concentrations of cholecalciferol and its metabolites after UVB exposure of different skin areas. Methods: 21 healthy Caucasians (skin type II and III, aged 23-47 years) were exposed to broadband UVB (290-320 nm) and randomized to either exposure to one minimal erythema dose given as a single dose, or a suberythemic dose given for 3 subsequent days. The following areas were exposed: face and back of hands, upper half of the body and the whole body, respectively. Serum cholecalciferol and 25(OH)D were measured immediately before start and 24 h after the 1st and last exposure, respectively. Results: Subjects with whole body exposure had an average S-cholecalciferol increase per dose unit of 0.18 ng m1(-1) mJ(-1) cm(2), 0.95 CI: (0.16, 0.20), upper body treatment 0.13 ng ml(-1) mJ(-1) cm(2), 0.95 CI: (0.10, 0.15) and face and hands exposure 0.013 ng ml(-1) mJ(-1) cm(2), 0.95 CI: (-0.012, 0.037). The increase in cholecalciferol correlated positively to the UVB dose and skin erythema and negatively to body mass index (BMI) when controlling for other factors. Exposure of face and hands induces smaller cholecalciferol production in comparison with exposure of larger skin areas. Conclusion: Size of the exposed skin area, UVB dose, skin erythema and BMI were the major determinants for serum levels of skin synthesized cholecalciferol. Exposure of hands and face induces smaller cholecalciferol production in comparison with exposure of larger skin areas.
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40.
  • Osmancevic, Amra, 1968, et al. (author)
  • Vitamin D production after UVB exposure - A comparison of exposed skin regions.
  • 2015
  • In: Journal of photochemistry and photobiology. B, Biology. - : Elsevier BV. - 1873-2682 .- 1011-1344. ; 143, s. 38-43
  • Journal article (peer-reviewed)abstract
    • Cholecalciferol is an essential steroid produced in the skin by solar ultraviolet B radiation (UVB 290-315nm). Skin production of cholecalciferol depends on factors affecting UVB flux, age and exposed skin area.
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41.
  • Osmancevic, Amra, 1968, et al. (author)
  • Vitamin D status in psoriasis patients during different treatments with phototherapy
  • 2010
  • In: Journal of Photochemistry and Photobiology B: Biology. - 1011-1344. ; 101:2, s. 117-123
  • Journal article (peer-reviewed)abstract
    • BACKGROUND: Phototherapy (broadband UVB (BUVB), narrowband UVB (NBUVB) and heliotherapy) is commonly used treatment modalities for widespread psoriasis. Vitamin D3, cholecalciferol, is produced in the epidermis by ultraviolet radiation (290-315 nm) of 7-dehydrocholesterol. 25-hydroxyvitamin D [25(OH)D], and 1,25-dihydroxyvitamin D [1,25(OH)(2)D] are the major circulating metabolites. Sun exposure is the strongest factor influencing 25(OH)D. The similar wavelength spectrum of UVB responsible for D vitamin synthesis (BUVB, 280-315 nm) has been successfully used for years to treat psoriasis. PURPOSE: The aim was: (1) To increase the knowledge about the effects of phototherapy on vitamin D production during treatment of psoriasis. (2) To examine if there were differences between the effect of BUVB, NBUVB and heliotherapy on vitamin D synthesis in psoriasis patients. METHODS: Serum concentrations of 25(OH)D, 1,25(OH)(2)D, PTH, calcium and creatinine, measured before and after phototherapy in white Caucasian patients with moderate to severe active plaque psoriasis, were aggregated from three studies. RESULTS: Psoriasis improved in all patients, with a reduction in PASI ((Psoriasis Area and Severity Index) score of about 75% on all regimes. Serum 25(OH)D increased and PTH decreased after the phototherapy. The increase in 25(OH)D was higher in the BUVB treated patients compared with NBUVB. There was no correlation between the dose of UVB and the increase of 25(OH)D. CONCLUSION: UVB and heliotherapy improved the psoriasis score, increased the serum 25(OH)D levels and reduced the serum PTH concentrations. Vitamin D production in psoriasis patients increased less with NBUVB than with BUVB phototherapy.
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42.
  • Rigolio, Roberta, et al. (author)
  • A new device to study ex-vivo the effects of extracorporeal photochemotherapy on the immune system
  • 2007
  • In: Journal of Photochemistry and Photobiology, B: Biology. - : Elsevier BV. - 1011-1344. ; 88:1, s. 68-75
  • Journal article (peer-reviewed)abstract
    • Extracorporeal photochemotherapy (ECP) is a medical procedure effective in the treatment of several different T-cell mediated diseases such as cutaneous T-cell lymphoma and Graft-versus-Host Disease. During ECP treatment the patient's blood is processed by means of a cell separator to collect leukocytes (leukapheresis), mostly lymphocytes and monocytes, which are then incubated with the photoactive drug 8-methoxypsoralen (8-MOP), exposed to ultraviolet-A light (UV-A) and reinfused to the patient. It has been suggested that during ECP not only UV-A irradiation but also changes in the environmental condition may be relevant. Although ECP has been shown to have an in-vivo immunomodulatory effect, the mechanisms through which ECP exerts its effect remain elusive. One of the reasons for this incomplete knowledge is the absence of a reliable model for ECP. In order to investigate the effect of ECP on the peripheral immune system, we developed a new device which mimics the complete ECP cycle including blood transit through the cell separator. Peripheral blood samples (50 ml) were obtained from volunteers and processed using a peristaltic pump. Peripheral blood mononuclear cells (PBMC) were then collected and treated with 8-MOP and UV-A under the same conditions used for the patients' therapy. Using this strategy we investigated 8-MOP, UV-A and their combined effect on the production of the pro-inflammatory cytokines interferon-gamma (IFN-gamma), interleukine-2 (IL-2) and tumor necrosis factor-a (TNF-alpha) in PBMC with and without polyclonal stimulation. We firstly demonstrated that our device does not affect total red and white blood cell counts. After 8-MOP and UV-A irradiation a significant decrease was observed in both activated CD4(+) and CD8(+) T lymphocytes producing IFN-gamma, IL-2 and TNF-alpha. Our findings are in line with those previously obtained in humans after complete ECP treatment, thus suggesting that our newly developed device is suitable for investigating the mechanism of action of ECP ex-vivo. (c) 2007 Elsevier B.V. All rights reserved.
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43.
  • Sengupta, Bidisa, 1971, et al. (author)
  • Interactions of the plant flavonoid fisetin with macromolecular targets: Insights from fluorescence spectroscopic studies
  • 2005
  • In: Journal of Photochemistry and Photobiology B: Biology. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 80:2, s. 79-86
  • Journal article (peer-reviewed)abstract
    • Fisetin (3,7,3′,4′-tetrahydroxyflavone) is a bioactive plant flavonoid of immense importance as a potentially useful therapeutic drug, for various free radical mediated as well as other diseases. In a recent paper, we demonstrated the novel uses of the exquisitely sensitive intrinsic fluorescence of this compound to explore its binding characteristics in liposomal membranes [B. Sengupta, A. Banerjee, P.K. Sengupta, Investigations on the binding and antioxidant properties of the plant flavonoid fisetin in model biomembranes, FEBS Lett. 570 (2004) 77-81]. Here, we have exploited this technique to examine its interactions with relevant macromolecular targets, namely double stranded DNA (from calf thymus), and the physiologically important circulatory protein, Human Serum Albumin (HSA). In the presence of DNA dramatic changes are observed in the intrinsic fluorescence behaviour of fisetin. These, along with other relevant supporting spectroscopic data, suggest that fisetin binds intercalatively between the base pairs of DNA. From the studies on fisetin-HSA interaction, the existence of two distinct binding sites are inferred. Furthermore we present evidence for the occurrence of efficient Förster type fluorescence resonance energy transfer from tryptophan to fisetin, indicating that both binding sites of fisetin in HSA are proximal to the unique tryptophan - 214 residue present in the interdomain (between IIA and IIIA domains) loop region of the protein.
  •  
44.
  • Shirato, M., et al. (author)
  • Time-kill kinetic analysis of antimicrobial chemotherapy based on hydrogen peroxide photolysis against Streptococcus mutans biofilm
  • 2017
  • In: Journal of Photochemistry and Photobiology B-Biology. - : Elsevier BV. - 1011-1344. ; 173, s. 434-440
  • Journal article (peer-reviewed)abstract
    • A recently developed antimicrobial technique utilizing hydroxyl radicals generated by hydrogen peroxide (H2O2) photolysis represents a promising new therapy for preventing and treating dental caries. The present study compared the antimicrobial time-kill kinetics of H2O2 photolysis, conventional antiseptics, and antimicrobial photodynamic therapy (aPDT) against biofilm-forming Streptococcus mutans (cariogenic bacteria) grown on hydroxyapatite disks. H2O2 photolysis was performed by irradiating the biofilm immersed in 3% H2O2 with 365-nm light-emitting diode (LED) light at an irradiance of 1000 mW/cm(2) for up to 1.5 min. Antiseptic treatments consisted of 0.2% chlorhexidine gluconate, 0.5% povidone-iodine, and 3% H2O2. The biofilm was immersed in each antiseptic for up to 4 min. aPDT was performed by irradiating the biofilm immersed in 100 Oil methylene blue or toluidine blue O with 655-nm laser light at 1000 mW/cm(2) for up to 4 min. Based on the time kill assay, the decimal reduction value (D-value) of each treatment was determined. With a D-value of 0.06 min, H2O2 photolysis exhibited the highest bactericidal effect against biofilm-forming S. mutans. In contrast, antiseptics and aPDT exerted a slower bactericidal effect, with D-values of 0.9-2.7 min. In conclusion, the antimicrobial technique based on H2O2 photolysis using 365-nm LED represents a strong adjunctive chemotherapy for dental caries treatment.
  •  
45.
  • Shitov, A V, et al. (author)
  • A carbonic anhydrase inhibitor induces bicarbonate-reversible suppression of electron transfer in pea photosystem 2 membrane fragments
  • 2011
  • In: Journal of Photochemistry and Photobiology. B. - : Elsevier. - 1011-1344 .- 1873-2682. ; 104:1-2, s. 366-371
  • Journal article (peer-reviewed)abstract
    • The effects of suppression of the carbonic anhydrase (CA) activity by a CA-inhibitor, acetazolamide (AA), on the photosynthetic activities of photosystem II (PS II) particles from higher plants were investigated. AA along with CA-activity inhibits the PS II photosynthetic electron transfer and the AA-induced suppression is totally reversed by the addition of bicarbonate (3-5 mM). Similar effect of recovery in the PS II photosynthetic activity was also revealed upon the addition of known artificial electron donors (potassium ferrocyanide and TMPD). Significance and possible functions of CA for the PS II donor side are discussed.
  •  
46.
  • Siegbahn, Per E. M. (author)
  • Recent theoretical studies of water oxidation in photosystem II
  • 2011
  • In: Journal of Photochemistry and Photobiology. B. - : Elsevier BV. - 1011-1344 .- 1873-2682. ; 104:1-2, s. 94-99
  • Research review (peer-reviewed)abstract
    • In the present mini-review, computational work over the past decade on water oxidation in photosystem II (PSII) is summarized. The size of the chemical model used for the oxygen evolving complex (OEC) has during this time increased from the initial 20 atoms to the present day 220 atoms. The electronic structure methods used have during the same period only undergone minor improvements. It is concluded that the results have now reached a high level of convergence and the predictions for both the structure of the OEC and the O-O bond formation mechanism are most probably of higher accuracy than presently available from experiments.
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47.
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48.
  • Wojewoda, Karolina, et al. (author)
  • Optimizing treatment of acne with photodynamic therapy (PDT) to achieve long-term remission and reduce side effects. A prospective randomized controlled trial.
  • 2021
  • In: Journal of photochemistry and photobiology. B, Biology. - : Elsevier BV. - 1873-2682 .- 1011-1344. ; 223
  • Journal article (peer-reviewed)abstract
    • Photodynamic therapy with methyl aminolevulinate (MAL-PDT) is an effective treatment of acne vulgaris, but is associated with side effects. We performed a prospective randomized split-face study aimed at optimizing MAL-PDT treatment. Patients (n=33) were randomized to two or four treatments of PDT with MAL on one cheek and placebo vehicle on the other cheek, 1-2weeks apart. A 1.5-h pre-treatment with the MAL cream was followed by illumination with red light (20J/cm2). Assessments were performed before treatment and 4, 10, and 20weeks after the last treatment. In comparison to baseline, the number of inflammatory lesions at 20weeks on cheeks treated with MAL-PDT showed a relative decrease of 74% in the group with two treatments and 85% in the group with four treatments. This new treatment regimen for both MAL-PDT and red-light-only PDT, with shortened pre-treatment and reduced light dose, could be an effective modality.
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49.
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