bluuebunny/crossref_metadata_2025_split huggingface dataset:
SPECTRAL QUALITY OF TWO FLUORESCENT UV SOURCES DURING LONG‐TERM USE
Authors: Adamse Paulien , Britz Steven J. 
Published: January 2008

Abstract—The characteristics of a fluorescent ultraviolet (UV) lamp (UVB‐313), UV‐B transmitting cellulose diacetate (CA) and UV‐B absorbing polyester (PE) films were determined during actual use. Although lamp emission was stable between 70 and 386 h of burn time (longer times were not investigated), the absorbance of UV‐B and UV‐A radiation by CA and PE films, respectively, increased with time when wrapped around lamps. As a result, the irradiance of lamp/filter combinations decreased steadily (even when CA films were presolarized for 10 h), making it necessary to compensate by adjusting the height of the lamp bank or by changing filters frequently. Note that corrective action is required for UV‐A controls (PE films) as well as UV‐B experimental treatments (CA films). Changing filters is preferable, since aging of CA filters caused shifts in the ratio of UV‐B to UV‐A. However, in spite of these shifts, the normalized spectrum of weighted biologically effective UV‐B radiation did not change to a large extent.
RAPID STOMATAL RESPONSE TO RED LIGHT IN Zea mays
Authors: Assma Sarah M. , Lee David M. , Malkus Per 
Published: January 2008

Abstract—Gas exchange techniques were employed to study responses of stomatal conductance to pulses of red and blue light in the grass, Zea mays. Zea mays exhibited conductance increases following brief (< 1 min) pulses of either red or blue light, in contrast to other species (e.g. Commelina communis; Assmann, 1988, Plant Physiol. 87, 226–231) that exhibit consistent conductance responses only to pulses of blue light. Red light pulses of 450 μmol m−2s−1 for x min or 225 μmol m−2s−1 for 2x min were used to probe the fluence dependence of the red light response. The red light‐stimulated conductance increase was constant for a given fluence, and increased with increasing total fluence. The conductance response to red light was larger in field grown plants (maximum growth irradiance ˜ 1600 μmol m‐2s−l) than in plants raised in growth chambers (maximum growth irradiance ˜ 150 μmol m−2s−1).
NONPHOTOCHEMICAL HOLE BURNING OF THE B800‐B850 ANTENNA COMPLEX OF Rhodopseudomonas acidophila
Authors: Reddy N. R. S. , Cogdell R. J. , Zhao L. , Small G. J. 
Published: January 2008

AbstractDetailed burn wavelength‐dependent hole‐burning studies of the title complex have been performed. The zero‐phonon hole (ZPH) widths for B800 at 4.2 K are 6.0 ± 0.3 cm and are discussed in terms of B80O‐B850 and B800‐B800 energy transfer. The B800* lifetime is 1.8 ± 0.2 ps. The site inhomogeneous broadening (r,) of B800 is 240 cm−1. The B850 (located at 864 nm at 4.2 K) hole spectra reveal that B850 suffers from significant homogeneous broadening, which is attributed to unit cell exciton level structure and ultrafast interexciton level relaxation. Novel ZPH action spectra lead to the resolution of a minor component at 885 nm, which is the analogue of B870 of Rhodobacter sphaeroides previously assigned as the lowest exciton level of the B850 exciton band. The B870 ZPH width of 2.0 ± 0.2 cm−1for Rhodopseudomonas acidophila leads to a total dephasing time of 5.3 ps, which is attributed to exciton scattering that stems from the energetic inequivalence of neighboring B850 unit cells.
ULTRAVIOLET RADIATION‐INDUCED PHOSPHOLIPASE A2 ACTIVATION OCCURS IN MAMMALIAN CELL MEMBRANE PREPARATIONS
Authors: Cohen Dianne , DeLeo Vincent A. 
Published: January 2008

AbstractUltraviolet erythema in human skin is mediated in part by membrane derivatives of arachidonic acid (AA). UVA (320–400nm) and UVB (290–320nm) have been shown to induce release of AA from intact mammalian cells in culture. In order to investigate the mechanism of this release we examined the effect of UVA and UVB on release of [3H] AA from membrane preparations of murine fibroblasts. C3H 10T1/2 cells were prelabelled for 24 h with [3H] AA. The membrane fractions of the cells were separated after lysis by differential centrifugation. The membranes were irradiated in suspension and the [3H] AA released from the membranes was determined by scintillation spectroscopy of supernatants3–4 h after irradiation. Both UVA and UVB induced release of AA from the membrane preparations. The response to UVB was small but significant, reaching levels approximately 150% of control release at doses of 1,200‐4,000 J/m2. The response to UVA was larger; doses of 2.5‐5.0 J/cm2 induced release equal to twice control (200%) levels, while doses of10–20 J/cm2 induced maximal release at levels approximately 400% of control. Time course studies with UVB and UVA showed maximal release at 4 h after irradiation. When the membrane preparations were incubated with a polyclonal anti‐phospholipase A2 antibody the UV induced release of [3H] AA was completely inhibited in both UVB (1200 J/m2) and UVA (10 J/cm2) treated cells. These data suggest that activation of phospholipase A2 is responsible for the UV induced release of AA in mammalian cells and that the mechanism of this activation is due, in part at least, to direct photon‐membrane interaction.
SPECTROSCOPIC PROPERTIES OF POTENTIAL SENSITIZERS FOR NEW PHOTODYNAMIC THERAPY START MECHANISMS via TWO‐STEP EXCITED ELECTRONIC STATES
Authors: Teuchner K. , Pfarrherr A. , Stiel H. , Freyer W. , Leupold D. 
Published: January 2008

AbstractThree substituted tetraazaporphyrins, octa‐(4‐tert‐butylphenyl)‐tetrapyrazinoporphyrazine, tetra‐(4‐tert‐butyl)phthalocyanine and tetra‐(4‐tert‐butyi)phthalocyanatomagnesium (t4‐PcMg), were spectroscopically checked in solutions and liposomes with respect to suitability as potential sensitizers of a possible new start mechanism for photodynamic therapy (PDT) from a stepwise excited higher singlet state. This PDT start mechanism was recently proposed to overcome the problem of O2 (1δ2)‐caused cutaneous phototoxicity in PDT.By means of absorption and fluorescence measurements as well as nonlinear absorption investigation, transient spectroscopy and lasing experiments, compound t4‐PcMg was found to have the most appropriate properties: Based on a high fluorescence quantum yield (φfi= 0.84) and a very low crossing to the triplet (φisc= 0.05), two higher excited states can be effectively populated both by two stepwise absorption transitions at 674 nm and consecutive absorption transitions at 674 and 710 nm. Moreover, t4‐PcMg incorporates into liposomes very well with spectroscopic properties similar to those in solution.
DETERMINING THE OPTIMAL DOSE OF PHOTOFRIN® IN MINISWINE ATHEROSCLEROTIC PLAQUE
Authors: Hsiang York N. , Fragoso Miguel , Tsang Vincent , Schreiber William E. 
Published: January 2008

AbstractThe purpose of this study was to determine the lowest dose of Photofrin (P) that would produce a 3:1 or greater ratio between atherosclerotic (AS) and control arterial walls. Aortoiliac AS was created in 24 Yucatan miniswine by a combination of balloon endothelial injury and 2% cholesterol and 15% lard diet for 7 weeks. Arteriography was then performed to demonstrate AS lesions. Following this, swine were given intravenously P in one of the following single dosages: 2.5, 1.0 or 0.5 mg/kg. Twenty‐four hours later, swine were sacrificed and aortoiliac and control carotid artery segments removed and photographed with ultraviolet light to differentiate fluorescent from nonfluorescent areas. Arterial specimens were submitted for histologic analysis and chemical extraction for determination of fluorescence using a spectrofluorometer. Tissue concentration (ng/g tissue) of P from AS vessels were: Group I, 130.4 ± 82.7; Group II, 10.0 ± 1.2; and Group HI, 9.1 ± 0.6, respectively (P < 0.05). Ratios of P concentration in AS:control vessels were: Group I, 8.1 ± 13.7; Group II, 1.1 ± 0.2; and Group III, 0.9 ± 0.1, respectively (P < 0.05).These results demonstrated that a P dose of 2.5 mg/kg provided at least a 3:1 ratio between AS:control artery wall.
THE PHOTOOXIDATION OF DIETHYLHYDROXYLAMINE BY ROSE BENGAL IN MICELLAR AND NONMICELLAR AQUEOUS SOLUTIONS
Authors: Bilski P. , Motten A. G. , Bilska M. , Chignell C. F. 
Published: January 2008

AbstractThe photooxidation of N,N‐diethylhydroxylamine (DEHA) by Rose Bengal (RB) has been investigated in micellar and nonmicellar aqueous solutions. We measured the quantum yield of oxygen consumption forming H2O2 and monitored two intermediates, the superoxide and diethylnitroxide radicals. When the pH was vaned, the quantum yield of oxidation remained constant for 6 < pH < 10.5, decreased in acidic pH, and increased considerably in NaOH solution; these changes could be attributed to the protonation and dissociation processes of the >N‐OH moiety of DEHA. The formation of diethylnitroxide radical was enhanced by superoxide dismutase or strong alkaline solution. Around neutral pH, the oxidation proceeded mainly via electron transfer from DEHA to the RB triplet (kq= 107M‐1 s‐1) with little 1O2 participation (kq < 105M‐1 s‐1). However, when RB was incorporated into micelles in alkaline solution, the contribution of the singlet oxygen pathway increased at the expense of electron transfer, which was inhibited by the less polar micellar environment. Dark autoxidation of DEHA was accelerated by heavy metal impurities and increased very strongly in NaOH solution.
FUROCOUMARIN SENSITIZATION INDUCES DNA‐PROTEIN CROSS‐LINKS
Authors: Bordin F. , Carlassare F. , Busulini L. , Baccichetti F. 
Published: January 2008

AbstractThe capacity of some linear and angular furocoumarins to induce DNA‐protein cross‐links by UVA (320–400 nm) irradiation has been evaluated in Chinese hamster ovary cells. Two linear furocoumarins, psoralen and 8‐methoxypsoralen appeared to be capable of inducing DNA‐protein cross‐links to a noticeable extent. 4′‐Methylangelicin and 4,4′‐dimethylangelicin formed only reduced amounts of DNA‐protein cross‐links, while angelicin and 4,6,4′‐trimethylangelicin seemed to be unable to induce significant levels of this lesion. The biological significance of this damage remains to be elucidated, but it might have an important role in furocoumarin sensitization. In the examined compounds, the capacity for inducing DNA‐protein cross‐links appears to be a property of the skin phototoxic furocoumarins. This result suggests the hypothesis of a connection between this damage and the formation of skin erythemas.
PROTECTIVE EFFECT OF SELENIUM AND ZINC ON UV‐A DAMAGE IN HUMAN SKIN FIBROBLASTS
Authors: Leccia M. T. , Richard M. J. , Bean J. C. , Faure H. , Monjo A. M. , Cadet J. , Amblard P. , Favier A. 
Published: January 2008

AbstractUltraviolet A radiation participates in cytotoxicity and carcinogenesis of the skin by a mechanism involving the generation of reactive oxygen species. Endogenous antiradical defense systems utilize metalloenzymes including Se‐dependent glutathione peroxidase and Cu and Zn superoxide dismutase. The aim of the present work was to determine the protective effect of two trace elements, Se and Zn, on cultured human diploid fibroblasts exposed to UV‐A radiation (broad‐spectrum source with a maximum intensity at 375 nm). Selenium in the culture medium (0.1 mg/L) in the form of sodium selenite increased the synthesis and activity of glutathione peroxidase by 60.5% in the absence of exposure to UV‐A radiation and by 35% after irradiation with 5 J/cm2 (P= 0.043). The presence of this element significantly increased the survival of UV‐A‐irradiated fibroblasts (P < 0.0001). This confirms the essential role of Se in the detoxifying activity of the enzyme. In addition, thiobarbituric acid‐reacting substances (TBAR), which are lipid peroxidation markers, decreased in the presence of exogenous Se:—19% and ‐22% without irradiation and after irradiation with 5 J/cm2 (P= 0.056). When Zn was added at the dose of 6.5 mg/L as ZnCl2, fibroblasts subjected to oxidizing stress induced by UV‐A were protected from cytotoxicity (P <0.0001). The TBAR production decreased significantly: ‐33% without irradiation and ‐34% after irradiation with 5 J/cm2 (P = 0.008). Superoxide dismutase activity, however, decreased after supplementing with Zn: ‐ 26% without irradiation and ‐ 20% after UV‐A irradiation (P= 0.017). The antioxidant properties of Zn are thus apparently independent of superoxide dismutase activity.
PHOTOCLEAVAGE OF DNA: IRRADIATION OF QUINONE‐CONTAINING REAGENTS CONVERTS SUPERCOILED TO LINEAR DNA
Authors: Koch Troels , Ropp J. Dezz , Sligar Stephen G. , Schuster Gary B. 
Published: January 2008

AbstractIrradiation (350 nm) of air‐saturated solutions of reagents containing an anthraquinone group linked to quaternary alkyl ammonium groups converts supercoiled DNA to circular and to linear DNA. Generation of linear DNA does not occur by accumulation of numerous single‐strand cuts but by coincident‐site double‐strand cleavage of DNA. Irradiation forms the triplet state of the anthraquinone, which reacts either by hydrogen atom abstraction from a sugar of DNA or by electron transfer from a base of the DNA. Subsequent reactions result in chain scission. The quinone is apparently reformed after this sequence and reirradiation leads to double‐strand cleavage.
ULTRAVIOLET RADIATION IN ANTARCTICA: INHIBITION OF PRIMARY PRODUCTION
Authors: Holm‐Hansen Osmund , Helbling E. Walter , Lubin Dan 
Published: January 2008

AbstractWith the seasonal formation of the ozone hole over Antarctica, there is much concern regarding the effects of increased solar UV‐B radiation (280–320 nm) on the marine ecosystem in the Southern Ocean. In situ incubations of natural phytoplankton assemblages in antarctic waters indicate that under normal ozone conditions UV‐B radiation is responsible for a loss of approximately 4.9% of primary production in the euphotic zone, whereas UV radiation with wavelengths between 320 and 360 nm causes a loss of approximately 6.2%. When combined with data on the action spectrum for photoinhibition by UV radiation, our data suggest that the enhanced fluence of UV‐B radiation under a well‐developed ozone hole (150 Dobson units) would decrease daily primary productivity by an additional amount of 3.8%. Calculations that take into consideration the extent and duration of low stratospheric ozone concentrations during September to November indicate that the decrease in total annual primary production in antarctic waters due to enhanced UV‐B radiation would be 0.20%.
THE 75°C THERMOLUMINESCENCE BAND OF GREEN TISSUES: CHEMILUMINESCENCE FROM MEMBRANE‐CHLOROPHYLL INTERACTION
Authors: Hideg ÉVa , Vass Imre 
Published: January 2008

Abstract— Exposure of thylakoid membranes of green plants to high temperature promotes the appearance of free radicals resulting in a thermoluminesccnce (TL) band peaking around 75°C. The occurrence of this band with the same intensity in prcilluminated and in dark‐adapted samples demonstrates that, contrary to several other TL bands, it is not a result of charge recombination. The high temperature TL band is oxygen dependent. Parallel to TL emission singlet oxygen is formed, as demonstrated by spin trapping EPR measurements and by the decrease of TL intensity in the presencc of sodium‐azide, a singlet oxygen scavenger.We suggest that the 75°C TL band is a result of a temperature‐enhanced interaction between molecular oxygen and the photosynthetic membrane, possibly involving lipid peroxidation. The spectral maximum of the emission (around 720 nm) implics that light emission occurs upon energy transfer from an excited product to chlorophyll molecules destablized from pigment‐protein complexes.
DELAY OF CELL DIFFERENTIATION IN Anabaena aequalis CAUSED BY UV‐B RADIATION AND THE ROLE OF PHOTOREACTIVATION AND EXCISION REPAIR
Authors: Blakefield Mary K. , Harris Denny O. 
Published: January 2008

AbstractThe effect of ultraviolet light on cell differentiation was studied in the cyanobacterium Anabaena aequalis. Exposure of cells to UV‐B wavelengths (280‐320 nm) significantly delayed the differentiation of vegetative cells into heterocysts and akinetes at doses up to 56 kJ m‐2. Heterocyst differentiation was essentially stopped at all exposure levels when photoreactivation was prevented, even when excision repair was available to the cells. Photoreactivated samples produced heterocysts at doses through 28 kJ m‐2, after which differentiation dropped steeply to near zero levels. Some recovery of differentiation was evident at higher doses but at levels much below that of controls. Akinete differentiation was only slightly delayed by the exposures when cells were photoreactivated. Samples then showed rapid differentiation with the numbers of akinetes significantly greater than controls. Cells that did not receive photoreactivating light showed a greater initial delay in differentiation but 2 weeks after the exposures had recovered to control levels. Caffeine had more effect on the differentiation of akinetes than heterocysts. Inhibition of excision repair greatly reduced differentiation in photoreactivated samples and essentially eliminated differentiation in the nonphotoreactivated samples.
PHOTOPHYSICAL STUDIES ON HUMAN RETINAL LIPOFUSCIN
Authors: Gaillard Elizabeth R. , Atherton Stephen J. , Eldred Graig , Dillon James 
Published: January 2008

AbstractFluorescent material generated in the human retina accumulates within lipofuscin granules of the retinal pigment epithelium (RPE) during aging. Its presence has been suggested to contributed to various diseases including age‐related macular degeneration. Because this material absorbs light at wave lengths as long as 550 nm, photophysical studies were performed to determine whether lipofuscin could contribute to light damage and to determine if its composition is similar to a synthetically prepared lipofuscin. Time‐resolved experiments were performed to monitor (1) fluorescence decay, (2) the UV‐visible absorption of longer‐lived excited states and (3) the formation and decay of singlet oxygen at 1270 nm. Steady‐state and time‐resolved fluorescence studies indicate that human and synthetic lipofuscin have fluorophores in common. Time‐resolved absorption experiments on human retinal lipofuscin and synthetic lipofuscin showed the presence of at least two transient species, one absorbing at 430 nm (lifetime caμs) and a second absorbing at 580 nm, which decays via second order kinetics. In addition, there is a third absorbing species stable to several hundred milliseconds. The transient species at 430 nm is quenched by oxygen, suggesting that it is a triplet state. Subsequent studies showed the formation of singlet oxygen, which was monitored by its phosphorescence decay at 1270 nm. These studies demonstrate that lipofuscin can act as a sensitizer for the generation of reactive oxygen species that may contribute to the age‐related decline of RPE function and blue light damage.
REGULATION and INHIBITION OF COLLAGENASE EXPRESSION BY LONG‐WAVELENGTH ULTRAVIOLET RADIATION IN CULTURED HUMAN SKIN FIBROBLASTS*
Authors: Petersen Marta , Hamilton Tiffani , Li Hai‐Li 
Published: January 2008

Abstract—The cellular mechanisms responsible for the connective tissue changes produced by chronic exposure to UV light are poorly understood. Collagenase, a metalloproteinase, initiates degradation of types I and III collagen and thus plays a key role in the remodeling of dermal collagen. Collagenase synthesis by fibroblasts and keratinocytes involves the protein kinase C (PKC) second messenger system, and corticosteroids have been shown to suppress its synthesis at the level of gene transcription. Long‐wavelength UV light (UVA,320–400 nm) stimulates the synthesis of interstitial collagenase, as well as increasing PKC activity, in human skin fibroblasts in vitro. This study explores the regulation of collagenase expression by UVA in cultured human skin fibroblasts. Specifically, the time course, the effect of actinomycin D, an inhibitor of RNA synthesis, as well as the effect of PKC inhibitors and dexa‐methasone on expression of collagenase following UVA irradiation were examined. After UVA irradiation, collagenase mRNA rose rapidly between 4 and 12 h postirradiation, peaking 18 h post‐UVA. Actinomycin D completely suppressed the UVA‐induced increase in collagenase mRNA. Thus, new RNA synthesis is required for the UVA‐induced increase in collagenase mRNA. The PKC inhibitor, H‐7, blocked the increase in collagenase mRNA in response to UVA in a dose‐dependent manner. Similarly, dexamethasone also inhibited collagenase gene expression induced by UVA in a dose‐dependent fashion; the majority of the inhibitory effect was seen within the first 4 h after irradiation. These studies demonstrate that the effect of UVA on collagenase gene expression is regulated at the pretranscriptional level and may involve the PKC pathway.
BIOLUMINESCENCE OF BRAZILIAN FIREFLIES (COLEOPTERA: LAMPYRIDAE): SPECTRAL DISTRIBUTION and pH EFFECT ON LUCIFERASE‐ELICITED COLORS. COMPARISON WITH ELATERID and PHENGODID LUCIFERASES
Authors: Viviani Vadim R. , Bechara Etelvino J. H. 
Published: January 2008

Abstract—Twenty‐five Brazilian species (nine genera: Phorinus, Photinoides, Macrolampis, Aspisoma, Cratomorphus, Amydetes, Photuris, Bicellonychia, Pyrogaster) of adult fireflies were found to emit light in vivo in the green‐yellow range (Λmax=548–573 nm) of the spectrum, more frequently near the green region, in contrast with North‐American species, which predominantly emit yellow light. Distinct ecological contexts where these species evolved, such as the habitat (open field vs forests) and the duration of twilight, are discussed as possible factors responsible for these differences. Except for Photuris and Bicellonychia spp., the in vivo and in vitro bioluminescence spectra for various species of a given genus agree within ±5 nm. Lowering the pH caused the typical red shift in the in vitro bioluminescence spectrum from lampyrid luciferases (six species), which has been interpreted as due to the presence of a basic residue in the enzyme active site catalyzing fast enolization of the initially formed excited keto‐oxyluciferin (red emitter) to the excited enol form (yellow‐green emitter). The in vitro bioluminescence colors obtained from larval or adult elaterid (five species) and phengodid (three species) luciferases studied here, spanning the green‐red region, do not respond to pH changes. This could indicate either the absence of the neighboring basic center (in red‐emitting luciferases) or the presence of a non‐pH affected proximal basic residue in the active site of the luciferase (in yellow‐green‐emitting luciferases).
RESONANCE RAMAN EVIDENCE FOR 15‐cis TO MA,‐trans PHOTOISOMERIZATION OF SPIRILLOXANTHIN BOUND TO A REDUCED FORM OF THE REACTION CENTER OF Rhodospirillum rubrum SI
Authors: Kuki Michitaka , Naruse Mitsuru , Kakuno Tomlsaburo , Koyamai Yasushi 
Published: January 2008

Abstract—The reaction center (RC) of Rhodospirillum rubrum SI, which was prepared by ultrafiltration, showed one peak in molecular‐sieve HPLC, but it showed two peaks in diethylaminoethyl (DEAE) ion‐exchange HPLC; they were named as RC‐α and RC‐β in the order of elution, Nonequilibrated isoelectric electrophoresis, together with DEAE ion‐exchange HPLC, showed that RC‐β is electronically more negative than RC‐α. Oxidation of RC‐β by addition of ferricyanide caused its transformation into RC‐α, while reduction of RC‐α by adding ascorbate and subsequent illumination caused its transformation into RC‐β. Resonance Raman spectroscopy of the RC at liquid nitrogen temperature detected the all‐trans and the 15‐cis isomers in a ratio of 1:1, but HPLC analyses of the carotenoid extracted from the RC before and after the Raman measurements detected the pair of isomers in a ratio of 1:6. Thus, the 15‐cis to all‐trans isomerization takes place during irradiation at liquid nitrogen temperature, while the reverse isomerization takes place in the dark. The isolated RC‐α and RC‐β exhibited the bleaching of the 868 nm band, and contained the H, M and L subunits and 1.2‐1.4 molecules of ubiquinone‐10 per RC. Each RC slowly equilibrated in the dark toward a mixture of RC‐α and RC‐β. Generation of the all‐trans isomer in the light was found not in RC‐α but in RC‐β.