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Fluence Rate (fluence + rate)
Selected AbstractsFluence Rate or Cumulative Dose?PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2007Vulnerability of Larval Northern Pike (Esox lucius) to Ultraviolet Radiation Newly hatched larvae of northern pike were exposed in the laboratory to four fluence rates of ultraviolet radiation (UVR; 290,400 nm) over three different time periods, resulting in total doses ranging from 3.0 ± 0.2 to 63.0 ± 4.4 kJ·m,2. Mortality and behavior of the larvae were followed for 8,12 days, and growth measured at the end of the experiment. Also, the principle of reciprocity,that the UVR-induced mortality depends on the cumulative dose, independent of fluence rate,was tested. Fluence rates higher than 1480 ± 150 mW·m,2 caused mortality and growth retardation. The highest fluence rate (3040 ± 210 mW·m,2) caused 100% mortality in 5 days. All fluence rates caused behavioral disorders, which led to death at fluence rates higher than 1480 mW·m,2. Reciprocity failure occurred with the lowest and highest dose (550 ± 45 and 3040 ± 210 mW·m,2, respectively). The results show that fluence rate is of primary importance when assessing the UVR-related risk. [source] Monitoring ALA-induced PpIX Photodynamic Therapy in the Rat Esophagus Using Fluorescence and Reflectance SpectroscopyPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2008Bastiaan Kruijt The presence of phased protoporphyrin IX (PpIX) bleach kinetics has been shown to correlate with esophageal response to 5-aminolevulinic acid-based photodynamic therapy (ALA-PDT) in animal models. Here we confirm the existence of phased PpIX photobleaching by increasing the temporal resolution of the fluorescence measurements using the therapeutic illumination and long wavelength fluorescence detection. Furthermore fluorescence differential pathlength spectroscopy (FDPS) was incorporated to provide information on the effects of PpIX and tissue oxygenation distribution on the PpIX bleach kinetics during illumination. ALA at a dose of 200 mg kg,1 was orally administered to 15 rats, five rats served as control animals. PDT was performed at an in situ measured fluence rate of 75 mW cm,2 using a total fluence of 54 J cm,2. Forty-eight hours after PDT the esophagus was excised and histologically examined for PDT-induced damage. Fluence rate and PpIX photobleaching at 705 nm were monitored during therapeutic illumination with the same isotropic probe. A new method, FDPS, was used for superficial measurement on saturation, blood volume, scattering characteristics and PpIX fluorescence. Results showed two-phased PpIX photobleaching that was not related to a (systematic) change in esophageal oxygenation but was associated with an increase in average blood volume. PpIX fluorescence photobleaching measured using FDPS, in which fluorescence signals are only acquired from the superficial layers of the esophagus, showed lower rates of photobleaching and no distinct phases. No clear correlation between two-phased photobleaching and histologic tissue response was found. This study demonstrates the feasibility of measuring fluence rate, PpIX fluorescence and FDPS during PDT in the esophagus. We conclude that the spatial distribution of PpIX significantly influences the kinetics of photobleaching and that there is a complex interrelationship between the distribution of PpIX and the supply of oxygen to the illuminated tissue volume. [source] Photodynamic therapy with topical 5-aminolevulinic acid as a post-operative adjuvant therapy for an incompletely resected primary nasopharyngeal papillary adenocarcinoma: A case reportLASERS IN SURGERY AND MEDICINE, Issue 5 2006Cheng-Ping Wang MD Abstract Background and Objectives Surgical excision of primary nasopharyngeal papillary adenocarcinoma is sometimes incomplete with remaining microscopic disease. Post-operative radiotherapy only has limited efficacy but may cause many complications. Study Design/Materials and Methods Photodynamic therapy (PDT) was used as a post-operative adjuvant therapy for an incompletely resected primary nasopharyngeal papillary adenocarcinoma. A special form of 20% topical 5-aminolevulinic acid (5-ALA), which was originally a liquid form and became a gel form after applied on the nasopharynx, was used as the photosensitizer. A 2-mm optic fiber delivered the light (633 nm wavelength) to the lesion with a fluence rate of 100 mW/cm2 generated by a diode laser under 5 mm 0° endoscope assistance. The total energy delivered was 150 joules/cm2. Results No significant acute side effect was noted and the nasopharyngeal wound healed rapidly. The patient is alive without locoregional recurrence or distant metastasis for 5 years. Articulation, salivation, and swallowing functions are all well preserved. Conclusion Post-operative adjuvant PDT can successfully cure an otherwise difficult to treat disease with preservation of good life quality of the patient. Potential complications of PDT (e.g., photosensitivity) can be prevented by a special formulation of topical 5-ALA preparation. Lasers Surg. Med. © 2006 Wiley-Liss, Inc. [source] NH3 and NO2 fluxes between beech trees and the atmosphere , correlation with climatic and physiological parametersNEW PHYTOLOGIST, Issue 3 2000ARTHUR GESSLER The dynamic-chamber technique was used to investigate the correlation between NH3 and NO2 fluxes and different climatic and physiological parameters: air temperature; relative air humidity; photosynthetic photon fluence rate; NH3 and NO2 concentrations; transpiration rate; leaf conductance for water vapour; and photosynthetic activity. The experiments were performed with twigs from the sun crown of mature beech trees (Fagus sylvatica) at a field site (Höglwald, Germany), and with 12-wk-old beech seedlings under controlled conditions. Both sets of experiments showed that NO2 and NH3 fluxes depended linearly on NO2 and NH3 concentration, respectively, in the concentration ranges representative for the field site studied, and on water-vapour conductance as a measure for stomatal aperture. The NO2 compensation point determined in the field studies (the atmospheric NO2 concentration with no net NO2 flux) was 1.8,1.9 nmol mol,1. The NH3 compensation point varied between 3.3 and 3.5 nmol mol,1 in the field experiments, and was 3.0 nmol mol,1 in the experiments under controlled conditions. The climatic factors T and PPFR were found to influence both NO2 and NH3 fluxes indirectly, by changing stomatal conductance. Whilst NO2 flux showed a response to changing relative humidity that could be explained by altered stomatal conductance, increased NH3 flux with increasing relative humidity (>50%) depended on other factors. The exchange of NO2 between above-ground parts of beech trees and the atmosphere could be explained exclusively by uptake or emission of NO2 through the stomata, as indicated by the quotient between measured and predicted NO2 conductance of approx. 1 under all environmental conditions examined. Neither internal mesophyll resistances nor additional sinks could be observed for adult trees or for beech seedlings. By contrast, the patterns of NH3 flux could not be explained by an exclusive exchange of NH3 through the stomata. Deposition into additional sinks on the leaf surface, as indicated by an increase in the quotient between measured and predicted NH3 conductance, gained importance in high air humidity, when the stomata were closed or nearly closed and/or when atmospheric NH3 concentrations were high. Although patterns of NH3 gas exchange did not differ between different months or years at high NH3 concentrations (c. 140 nmol mol,1), it must be assumed that emission or deposition fluxes at low ambient NH3 concentration (0.8 and 4.5 nmol mol,1) might vary significantly with time because of variation in the NH3 compensation point. [source] The Neovessel Occlusion Efficacy of 151 -Hydroxypurpurin-7-Lactone Dimethyl Ester Induced with Photodynamic TherapyPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2010Siang Hui Lim In this study, the photodynamic therapy (PDT) induced efficacy of a semi-synthesized analogue 151 -hydroxypurpurin-7-lactone dimethyl ester or G2, in terms of chick chorioallantoic membrane blood vessel occlusion was evaluated in reference to verteporfin. Early formulation studies showed that G2 prepared in a system of cremophor EL 2.5% and ethanol 2.5% in saline was biocompatible up to 20 ,L volume of injection. Following injection, G2 accumulation peaked within the first minute and its extravasation from intra- to extra-vascular occurred somewhat slower as compared with verteporfin. In the PDT study, closure of capillaries and small neovessels was observed with 4 ,g per embryo of G2 and a light dose of 20 J cm,2 at a fluence rate of 40 mW cm,2 filtered at 400,440 nm,a result that may be considered optimum for the treatment of age-related macular degeneration (AMD). Also, partial occlusion of the large vessels was observed using the same dose of G2 and light,an effect which is desirable for cancer treatment. From this study, we conclude that G2 has the potential to be developed as a therapeutic agent for photodynamic treatment for AMD and cancer. [source] Monitoring ALA-induced PpIX Photodynamic Therapy in the Rat Esophagus Using Fluorescence and Reflectance SpectroscopyPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2008Bastiaan Kruijt The presence of phased protoporphyrin IX (PpIX) bleach kinetics has been shown to correlate with esophageal response to 5-aminolevulinic acid-based photodynamic therapy (ALA-PDT) in animal models. Here we confirm the existence of phased PpIX photobleaching by increasing the temporal resolution of the fluorescence measurements using the therapeutic illumination and long wavelength fluorescence detection. Furthermore fluorescence differential pathlength spectroscopy (FDPS) was incorporated to provide information on the effects of PpIX and tissue oxygenation distribution on the PpIX bleach kinetics during illumination. ALA at a dose of 200 mg kg,1 was orally administered to 15 rats, five rats served as control animals. PDT was performed at an in situ measured fluence rate of 75 mW cm,2 using a total fluence of 54 J cm,2. Forty-eight hours after PDT the esophagus was excised and histologically examined for PDT-induced damage. Fluence rate and PpIX photobleaching at 705 nm were monitored during therapeutic illumination with the same isotropic probe. A new method, FDPS, was used for superficial measurement on saturation, blood volume, scattering characteristics and PpIX fluorescence. Results showed two-phased PpIX photobleaching that was not related to a (systematic) change in esophageal oxygenation but was associated with an increase in average blood volume. PpIX fluorescence photobleaching measured using FDPS, in which fluorescence signals are only acquired from the superficial layers of the esophagus, showed lower rates of photobleaching and no distinct phases. No clear correlation between two-phased photobleaching and histologic tissue response was found. This study demonstrates the feasibility of measuring fluence rate, PpIX fluorescence and FDPS during PDT in the esophagus. We conclude that the spatial distribution of PpIX significantly influences the kinetics of photobleaching and that there is a complex interrelationship between the distribution of PpIX and the supply of oxygen to the illuminated tissue volume. [source] Fluence Rate or Cumulative Dose?PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2007Vulnerability of Larval Northern Pike (Esox lucius) to Ultraviolet Radiation Newly hatched larvae of northern pike were exposed in the laboratory to four fluence rates of ultraviolet radiation (UVR; 290,400 nm) over three different time periods, resulting in total doses ranging from 3.0 ± 0.2 to 63.0 ± 4.4 kJ·m,2. Mortality and behavior of the larvae were followed for 8,12 days, and growth measured at the end of the experiment. Also, the principle of reciprocity,that the UVR-induced mortality depends on the cumulative dose, independent of fluence rate,was tested. Fluence rates higher than 1480 ± 150 mW·m,2 caused mortality and growth retardation. The highest fluence rate (3040 ± 210 mW·m,2) caused 100% mortality in 5 days. All fluence rates caused behavioral disorders, which led to death at fluence rates higher than 1480 mW·m,2. Reciprocity failure occurred with the lowest and highest dose (550 ± 45 and 3040 ± 210 mW·m,2, respectively). The results show that fluence rate is of primary importance when assessing the UVR-related risk. [source] Calculation of Singlet Oxygen Dose from Photosensitizer Fluorescence and Photobleaching During mTHPC Photodynamic Therapy of MLL Cells,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2005Jonathan S. Dysart ABSTRACT Predicting the therapeutic outcome of photodynamic therapy (PDT) requires knowledge of the amount of cytoxic species generated. An implicit approach to assessing PDT efficacy has been proposed where changes in photosensitizer (PS) fluorescence during treatment are used to predict treatment outcome. To investigate this, in vitro experiments were performed in which Mat-LyLu cells were incubated in meta -tetra(hydroxyphenyl)chlorin (mTHPC) and then irradiated with 652 nm light. PS concentration, fluence rate and oxygenation were independently controlled and monitored during the treatment. Fluorescence of mTHPC was monitored during treatment and, at selected fluence levels, cell viability was determined using a colony-formation assay. Singlet oxygen dose was calculated using four different models and was compared with cell survival. For the dose metric based on singlet oxygen,mediated PS photobleaching, a universal relationship between cell survival and singlet oxygen dose was found for all treatment parameters. Analysis of the concentration dependence of bleaching suggests that the lifetime of singlet oxygen within the cell is 0.05,0.25 ,s. Generation of about 9 × 108 molecules of singlet oxygen per cell reduces the surviving fraction by 1/e. [source] Effects of Combined Photodynamic Therapy and Ionizing Radiationon Human Glioma Spheroids,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2002Steen J. Madsen ABSTRACT The effects of combined photodynamic therapy (PDT) and ionizing radiation are studied in a human glioma spheroid model. The degree of interaction between the two modalities depends in a complex manner on factors such as PDT irradiation fluence, fluence rate and dose of ionizing radiation. It is shown that gamma radiation and PDT interact in a synergistic manner only if both light fluence and gamma radiation dose exceed approximately 25 J cm,2 and 8 Gy, respectively. Synergistic interactions are observed only for the lower fluence rate (25 mW cm,2) investigated. The degree of interaction appears to be independent of both sequence and the PDT or ionizing radiation time intervals investigated (1 and 24 h). Terminal deoxynucleotidyl transferase,mediated deoxyuridine triphosphate nick-end labeling assays show that low-fluence rate PDT is very efficient at inducing apoptotic cell death, whereas neither high-fluence rate PDT nor ionizing radiation produces significant apoptosis. Although the mechanisms remain to be elucidated, the data imply that the observed synergism is likely not due to gamma-induced cell cycle arrest or to PDT-induced inhibition of DNA repair. [source] Photodynamic therapy for the treatment of a giant superficial basal cell carcinomaPHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 1 2009Donato Calista Summary A 74-year-old man was referred to our department for the treatment of a 15 × 15 cm superficial basal cell carcinoma (BCC) on his lumbar region. As surgical excision was considered too destructive, photodynamic therapy (PDT) was proposed. Methyl 5-aminolevulinate (MAL) cream was applied under occlusion for 3 h before illumination with a light-emitting diode lamp with an emission peak of 632 nm, a fluence rate of 83.3 mW/cm, and a light dose of 37 J/cm. A second MAL-PDT session was repeated 1 week later. The neoplastic area healed in 30 days. No recurrence has occurred after a 40-month follow-up period, but clinical observation continues. Although surgery still remains the treatment of choice for giant BCC, for which the local invasiveness and metastatic potential are well known, we offered our patient the option of PDT because we believed that classical surgery could hardly provide the same satisfactory outcome. As far as we know, this is the first case of giant BCC treated with PDT. [source] 013 Effect of UV on the susceptibility of acid-soluble Skh-1 hairless mouse collagen to collagenasePHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 2 2002J.M. Menter To test the hypothesis that UV could alter collagen susceptibility to interstitial collagenase, acid-extracted Skh-1 hairless mouse collagen samples were (un)irradiated with 0,140 J/cm2 of radiation from bank of filtered FS lamp (UVB/UVA = 0.33, fluence rate = 0.81 mW/cm2). Subsequent to UV irradiation, collagen samples were coupled with fluorescein isothiocyanate (FITC) and assayed for its susceptibility to bacterial collagenase by monitoring the appearance of supernatant FITC fluorescence (a measure of lysed collagen) over time of incubation. As a reference. unirradiated commercial FITC , labeled collagen (Elastin Products) was similarly analyzed. Mouse collagen had a lower rate of cleavage than did the calf skin sample. Mouse collagen initial cleavage followed a quasi-linear time course over the first 5 h. Calf-skin collagen displayed a ,sigmoidal' time course, reminiscent of a cooperative mechanism. UV irradiation afforded no significant effect on the ability of collagenase to cleave mouse collagen, although a small effect could be discerned after 48 h (140 J/cm2). On the other hand, these samples exhibited significant chain degradation. cross-linking and loss of intrinsic collagen fluorescence on UV photolysis. It appears that the rate of cleavage depends on the superstructure of the collagen, and that the collagen fluorophores are not in proximity to the specific site of collagenase cleavage. Supported in part by NIH/MBRS Grant #GM 08248 and RCMI Grant #RR 03034. [source] Light-to-dark transitions trigger a transient increase in intracellular Ca2+ modulated by the redox state of the photosynthetic electron transport chain in the cyanobacterium Anabaena sp.PLANT CELL & ENVIRONMENT, Issue 7 2004PCC7120 ABSTRACT Light-to-dark transitions represent one of the most crucial environmental stresses that photosynthetic organisms must cope with, since substantial metabolism adaptations are required in order to utilize alternative energy and carbon sources. Although signal transduction systems for changing light regimes are not sufficiently understood, calcium has been implicated in plants as a second messenger in light-on and light-off events. Much less is known about light signalling in cyanobacteria, but it has been shown that calcium probably performs similar signalling roles in these organisms and other prokaryotes. Herein it is reported that light-to-dark transitions trigger a calcium transient in aequorin expressing Anabaena sp. PCC7120. The magnitude of this transient depends on the fluence rate previously irradiated and can reach a peak height over 2 µm free calcium when the fluence rate of light is around 400 µmol photons s,1 m,2. The use of increasing calcium concentration, ethylene glycol-bis (, -aminoethylether) N,N,N,,N,-tetraacetic acid (EGTA), verapamil and trifluoperazine indicated that these transients are originated by a calcium influx probably through verapamil-sensitive Ca2+ channels and are probably modulated by calcium-binding proteins. Experiments with different light spectral qualities and the photosynthetic inhibitors 3-(3,4 dichlorophenyl)1,1,dimelthylurea (DCMU) and 3,5-dibromo-3-methyl-b-isopropyl-p-benzoquinone (DBMIB) indicate that the calcium transient triggered by the light-to-dark transition is not coupled to a specific photoreceptor but rather to changes in the redox state of photosynthetic electron transport chain components other than the plastoquinone pool. [source] Photodynamic therapy of actinic keratosis at varying fluence rates: assessment of photobleaching, pain and primary clinical outcomeBRITISH JOURNAL OF DERMATOLOGY, Issue 6 2004M.B. Ericson Summary Background, Although photodynamic therapy (PDT) is becoming an important treatment method for skin lesions such as actinic keratosis (AK) and superficial basal cell carcinoma, there are still discussions about which fluence rate and light dose are preferable. Recent studies in rodents have shown that a low fluence rate is preferable due to depletion of oxygen at high fluence rates. However, these results have not yet been verified in humans. Objectives, The objective was to investigate the impact of fluence rate and spectral range on primary treatment outcome and bleaching rate in AK using aminolaevulinic acid PDT. In addition, the pain experienced by the patients has been monitored during treatment. Patients/methods, Thirty-seven patients (mean age 71 years) with AK located on the head, neck and upper chest were treated with PDT, randomly allocated to four groups: two groups with narrow filter (580,650 nm) and fluence rates of 30 or 45 mW cm,2, and two groups with broad filter (580,690 nm) and fluence rates of 50 or 75 mW cm,2. The total cumulative light dose was 100 J cm,2 in all treatments. Photobleaching was monitored by fluorescence imaging, and pain experienced by the patients was registered by using a visual analogue scale graded from 0 (no pain) to 10 (unbearable pain). The primary treatment outcome was evaluated at a follow-up visit after 7 weeks. Results, Our data showed a significant correlation between fluence rate and initial treatment outcome, where lower fluence rate resulted in favourable treatment response. Moreover, the photobleaching dose (1/e) was found to be related to fluence rate, ranging from 4·5 ± 1·0 J cm,2 at 30 mW cm,2, to 7·3 ± 0·7 J cm,2 at 75 mW cm,2, indicating higher oxygen levels in tissue at lower fluence rates. After a cumulative light dose of 40 J cm,2 no further photobleaching took place, implying that higher doses are excessive. No significant difference in pain experienced by the patients during PDT was observed in varying the fluence rate from 30 to 75 mW cm,2. However, the pain was found to be most intense up to a cumulative light dose of 20 J cm,2. Conclusions, Our results imply that the photobleaching rate and primary treatment outcome are dependent on fluence rate, and that a low fluence rate (30 mW cm,2) seems preferable when performing PDT of AK using noncoherent light sources. [source] Phototropism of Thalli and Rhizoids Developed from the Thallus Segments of Bryopsis hypnoides LamourouxJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2006Nai-Hao Ye Abstract Newly regenerated thalli were used to study the phototropism of Bryopsis hypnoides Lamouroux under different qualities of light. Positive phototropism in the thalli and negative phototropism in the rhizoids of B. hypnoides were investigated and analyzed in terms of bending. Both thalli and rhizoids developed from thallus segments exhibited typical tip growth, and their photoreceptive sites for phototropism were also restricted to the apical hemisphere. The bending curvature of rhizoids and thalli were determined with unilateral lights at various wavelengths and different fluence rates after a fixed duration of illumination. The trends of bending from the rhizoid and thallus were coincident, which showed that the action spectrum had a large range, from ultraviolet radiation (366.5 nm) to green light (524 nm). Based on the bending curvatures, blue light had the highest efficiency, while the efficiency of longer wavelengths (>500 nm) was significantly lower. External Ca2+ had no effect on the bending curvature of thalli and rhizoids. Blue light (440 nm) induced thallus branching from rhizoids, while red light (650 nm) had no such effect. Fast-occurring chloroplast accumulation in the outermost cytoplasmic layer of the blue light (440 nm)-irradiated region in the rhizoid was observed, from which protrusions (new thalli) arose after 4 h of the onset of illumination, and this action was thought to be driven by the dynamics of actin microfilaments. (Managing editor: Wei Wang) [source] Fluence Rate or Cumulative Dose?PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2007Vulnerability of Larval Northern Pike (Esox lucius) to Ultraviolet Radiation Newly hatched larvae of northern pike were exposed in the laboratory to four fluence rates of ultraviolet radiation (UVR; 290,400 nm) over three different time periods, resulting in total doses ranging from 3.0 ± 0.2 to 63.0 ± 4.4 kJ·m,2. Mortality and behavior of the larvae were followed for 8,12 days, and growth measured at the end of the experiment. Also, the principle of reciprocity,that the UVR-induced mortality depends on the cumulative dose, independent of fluence rate,was tested. Fluence rates higher than 1480 ± 150 mW·m,2 caused mortality and growth retardation. The highest fluence rate (3040 ± 210 mW·m,2) caused 100% mortality in 5 days. All fluence rates caused behavioral disorders, which led to death at fluence rates higher than 1480 mW·m,2. Reciprocity failure occurred with the lowest and highest dose (550 ± 45 and 3040 ± 210 mW·m,2, respectively). The results show that fluence rate is of primary importance when assessing the UVR-related risk. [source] Spatial separation of light perception and growth response in maize root phototropismPLANT CELL & ENVIRONMENT, Issue 9 2002J. L. Mullen Abstract Although the effects of gravity on root growth are well known and interactions between light and gravity have been reported, details of root phototropic responses are less documented. We used high-resolution image analysis to study phototropism in primary roots of Zea mays L. Similar to the location of perception in gravitropism, the perception of light was localized in the root cap. Phototropic curvature away from the light, on the other hand, developed in the central elongation zone, more basal than the site of initiation of gravitropic curvature. The phototropic curvature saturated at approximately 10 µmol m,2 s,1 blue light with a peak curvature of 29 ± 4°, in part due to induction of positive gravitropism following displacement of the root tip from vertical during negative phototropism. However, at higher fluence rates, development of phototropic curvature is arrested even if gravitropism is avoided by maintaining the root cap vertically using a rotating feedback system. Thus continuous illumination can cause adaptation in the signalling pathway of the phototropic response in roots. [source] Strategies providing success in a variable habitat: III.PLANT CELL & ENVIRONMENT, Issue 8 2001Dynamic control of photosynthesis in Cladophora glomerata Abstract Diurnal patterns of photosynthesis were studied in July and April populations of Cladophora glomerata (L.) Kütz. from open and from shaded sites. Summer samples exposed to full sunlight showed decreased efficiency of open photosystem II at noon, and only slight differences were found between samples that had grown at open or at shaded sites. Electron transport rate was limited at highest fluence rates in shade plants, and non-photochemical quenching (NPQ) revealed faster regulation in samples from open sites. Daily course of de-epoxidation was not linearly correlated with the course of NPQ. The comparison of samples from open and from shaded sites revealed a higher capacity of thermal energy dissipation and an increase in the total amount of xanthophyll-cycle pigments (21%) in samples from open sites. In April, down-regulation of the efficiency of open photosystem II was related to lower water temperature, and hence, increased excitation pressure. In April the pool size of xanthophyll-cycle pigments was increased by 21% in comparison with summer and suggested higher levels of thermal energy dissipation via de-epoxidized xanthophylls. In both, summer and spring the amount of xanthophyll-cycle pigments was 20% higher in samples from open sites. Acclimation of C. glomerata to growth light conditions was further shown by experimental induction of NPQ, indicating NPQ increases of 23%, and increases of 77% in the reversible component of NPQ in open site samples. The effect of temperature on photosynthetic rate was non-linear, and different optimum temperatures of electron transport rate and oxygen evolution were exhibited. [source] The AT-hook-containing proteins SOB3/AHL29 and ESC/AHL27 are negative modulators of hypocotyl growth in ArabidopsisTHE PLANT JOURNAL, Issue 1 2008Ian H. Street Summary SOB3, which encodes a plant-specific AT-hook motif containing protein, was identified from an activation-tagging screen for suppressors of the long-hypocotyl phenotype of a weak phyB allele, phyB-4. sob3-D (suppressor of phyB-4#3 dominant) overexpressing seedlings have shorter hypocotyls, and as adults develop larger flowers and leaves, and are delayed in senescence compared with wild-type plants. At the nucleotide level, SOB3 is closely related to ESCAROLA (ESC), which was identified in an independent activation-tagging screen. ESC overexpression also suppresses the phyB-4 long-hypocotyl phenotype, and confers an adult morphology similar to sob3-D, suggesting similar functions. Analysis of transgenic plants harboring SOB3:SOB3-GUS or ESC:ESC-GUS translational fusions, driven by their endogenous promoter regions, showed GUS activity in the hypocotyl and vasculature tissue in light- and dark-grown seedlings. A loss-of-function SOB3 allele (sob3-4) was generated through an ethyl methanesulfonate intragenic suppressor screen of sob3-D phyB-4 plants, and this allele was combined with a predicted null allele, disrupting ESC (esc-8), to examine potential genetic interactions. The sob3-4 esc-8 double mutant had a long hypocotyl in multiple fluence rates of continuous white, far-red, red and blue light. sob3-4 esc-8 phyB-9 and sob3-4 esc-8 cry-103 triple mutants also had longer hypocotyls than photoreceptor single mutants. In contrast, the sob3-4 esc-8 phyA-211 triple mutant was the same length as phyA-211 single mutants. Taken together, these data indicate that SOB3 and ESC act redundantly to modulate hypocotyl growth inhibition in response to light. [source] Photodynamic therapy of actinic keratosis at varying fluence rates: assessment of photobleaching, pain and primary clinical outcomeBRITISH JOURNAL OF DERMATOLOGY, Issue 6 2004M.B. Ericson Summary Background, Although photodynamic therapy (PDT) is becoming an important treatment method for skin lesions such as actinic keratosis (AK) and superficial basal cell carcinoma, there are still discussions about which fluence rate and light dose are preferable. Recent studies in rodents have shown that a low fluence rate is preferable due to depletion of oxygen at high fluence rates. However, these results have not yet been verified in humans. Objectives, The objective was to investigate the impact of fluence rate and spectral range on primary treatment outcome and bleaching rate in AK using aminolaevulinic acid PDT. In addition, the pain experienced by the patients has been monitored during treatment. Patients/methods, Thirty-seven patients (mean age 71 years) with AK located on the head, neck and upper chest were treated with PDT, randomly allocated to four groups: two groups with narrow filter (580,650 nm) and fluence rates of 30 or 45 mW cm,2, and two groups with broad filter (580,690 nm) and fluence rates of 50 or 75 mW cm,2. The total cumulative light dose was 100 J cm,2 in all treatments. Photobleaching was monitored by fluorescence imaging, and pain experienced by the patients was registered by using a visual analogue scale graded from 0 (no pain) to 10 (unbearable pain). The primary treatment outcome was evaluated at a follow-up visit after 7 weeks. Results, Our data showed a significant correlation between fluence rate and initial treatment outcome, where lower fluence rate resulted in favourable treatment response. Moreover, the photobleaching dose (1/e) was found to be related to fluence rate, ranging from 4·5 ± 1·0 J cm,2 at 30 mW cm,2, to 7·3 ± 0·7 J cm,2 at 75 mW cm,2, indicating higher oxygen levels in tissue at lower fluence rates. After a cumulative light dose of 40 J cm,2 no further photobleaching took place, implying that higher doses are excessive. No significant difference in pain experienced by the patients during PDT was observed in varying the fluence rate from 30 to 75 mW cm,2. However, the pain was found to be most intense up to a cumulative light dose of 20 J cm,2. Conclusions, Our results imply that the photobleaching rate and primary treatment outcome are dependent on fluence rate, and that a low fluence rate (30 mW cm,2) seems preferable when performing PDT of AK using noncoherent light sources. [source] | |||||||||||||