bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification of Global Erythemally Effective Irradiance by Clouds
Authors: Thiel Stephan , Steiner Karl , Seidlitz Harald K. 
Published: January 2008

ABSTRACTThe role clouds play in the modification of global radiation is still a major uncertainty in the risk assessment of UV effects on ecological systems and human health. This study presents cloud transmission data obtained from measurements with Robertson‐Berger meters and simultaneous cloud observations. The global transmission of erythemally weighted irradiance depends strongly on cloud amount and can be described by a cubic function. The comparison with results derived from long‐term records of total global irradiance indicates no statistically significant difference between the attenuation of ery‐themal and total global radiation. The large variance of data results from lumping together data from different cloud types. Classification of data according to cloud forms yields a more statisfactory fit. The coefficient of the cubic term characterizes the ability of various cloud forms to attenuate UV radiation. It varies between 0.4 for high clouds and approximately 1.0 for cumulonimbus. This attenuation parameter allows a quantitative description of the cloud influence on irradiance and therefore a more accurate risk assessment.
Comparative Action Spectrum for Ultraviolet Light Killing of Mouse Melanocytes from Different Genetic Coat Color Backgrounds
Authors: Hill Helene Z. , Hill George J. , Cieszka Krystyna , Plonka Przemyslaw M. , Mitchell David L. , Meyenhofer Markus F. , Xin Patrick , Boissy Raymond E. 
Published: January 2008

ABSTRACTThe photobiology of mouse melanocyte lines with different pigment genotypes was studied by measuring colony‐forming ability after irradiation. The cell lines were wild‐type black (melan‐a) and the mutants brown (melan‐b) and albino (melan‐c). Four lamps emitting various UV wavelengths were used. These were germicidal (UVC, 200–280 Dm), 82.3% output at 254 nm, TL01 (UVB, 280–320 nm), 64.2% at 310–311 nm, FS20, broadband with peak output at 312 nm and Alisun‐S (UVA, 320–400 nm), broadband with peak output at 350–354 nm. Appropriate filtration reduced the contaminating UVC to nonlethal levels for the longer waverange lamps. Wild‐type melan‐a was resistant to UVC and UVA compared to the other two cell lines, but the differences were small. The melan‐c cell line was more resistant to UVB and markedly more resistant to FS20 than the pigmented lines. With the exception of FS20 responses, melan‐b was more sensitive than melan‐a to killing by the various UV lamps. There were more pyrimidine dimers (cyclobutane dimers and 6–4 photoproducts) produced in melan‐a than in melan‐c cells by UVC, UVB and FS20 lamps. Unlike melan‐c, melan‐a and melan‐b showed a strong free radical signal of melanin character with a detectable contribution of pheomelanin‐like centers. The contribution of pheome‐lanin was higher in melan‐b than in melan‐a, while the total melanin content in these two cell lines was comparable. The abundant melanin granules of wild‐type melan‐a melanocytes were well melanized and ellipsoidal, whereas those of melan‐b melanocytes tended to be spherical. In the albino line (melan‐c) the melanocytes contained only early‐stage melanosomes, all of which were devoid of melanin. The results indicate that pigment does not protect against direct effect DNA damage in the form of pyrimidine dimers nor does it necessarily protect against cell death. High pigment content is not very protective against killing by UVC and UVA, and it may photosensitize in UVB the very wavelength range that is of greatest concern with respect to the rising incidence in skin cancer, especially melanoma. It is clear from these studies that, in pigment cells, monochromatic results cannot predict polychromatic responses and that cell death from solar irradiations is a complex phenomenon that depends on more than DNA damage.
Benzophenone Photoprobes for Phosphoinositides, Peptides and Drugs
Authors: Prestwich Glenn D. , Dormán György , Elliott John T. , Marecak Dale M. , Chaudhary Anu 
Published: January 2008

AbstractBenzophenones (BP) and related aryl ketone photophores have become established as the photoactivatable group of choice for high‐efficiency covalent modification of hydrophobic regions of binding proteins, including enzymes and receptors that recognize peptide hormones, (oligonucleotides and nucleosides, phosphoinositides, inositol polyphosphates and a wide variety of therapeutic molecules. This review presents the advantages of BP as pho‐toafnnity labels and provides specific examples from the last 3 years of applications of BP‐containing ligands used in biochemistry.
Peroxidase Activity May Play a Role in the Cytotoxic Effect of Indole Acetic Acid*
Authors: de Melo Mariza Pires , Curi Tania Cristina Pithon , Curl Rui , Mascio Paolo Di , Cilento Giuseppe 
Published: January 2008

AbstractPeroxidase activity in neutrophils is higher than in thioglycollate macrophages, while in lymphocytes this enzyme activity is very low. Indole‐3‐acetic acid is oxidized by peroxidase and the role of this enzyme in the cytotoxic effect of the compound was evaluated by measuring oxygen consumption, light emission and cell death in neutrophils, macrophages and lymphocytes. The increase in light emission, oxygen consumption and rate of cell death in cells cultured in the presence of indole‐3‐acetic acid presented a direct correlation with the peroxidase activity of the cells as follows: neutrophils > thioglycollate macrophages > resident macrophages > lymphocytes. Indeed, in lymphocytes that possess very low peroxidase activity, indole‐3‐acetic acid did not result in an increase in light emission or oxygen consumption and it was not cytotoxic.
Antiviral Activities of Photoactive Perylenequinones
Authors: Hudson J. B. , Imperial V. , Haugland R. P. , Diwu Z. 
Published: January 2008

AbstractNine perylenequinones (PQ), including some familiar naturally occurring pigments, were compared for their light‐mediated antiviral efficacies. Calphostin C was the most active compound against the two target viruses, herpes simplex virus type 1 and Sindbis virus. Hypo‐crellins A and B were also very active. However, three cercosporin‐like PQ were substantially less active in spite of their high quantum yields of singlet oxygen, whereas phleichrome, another efficient singlet oxygen producer, showed no detectable antiviral activity. One other PQ, which was a very weak singlet oxygen producer, also showed no antiviral activity. None of the active compounds showed significant antiviral activity in the dark. Thus, for some groups of PQ there was correlation between quantum yield of singlet oxygen C02) and antiviral efficacy, but there are evidently other structural features of PQ that influence activity.
Changes in Optical Properties of Human Whole Blood in vitro Due to Slow Heating
Authors: Nilsson Annika M. K. , Lucassen Gerald W. , Verkruysse Wim , Andersson‐Engels Stefan , van Gemert Martin J. C. 
Published: January 2008

AbstractOptical properties of human whole blood were investigated in vitro at 633 nm using a double integrating sphere set‐up. The blood flow was maintained at a constant rate through a flow cell while continuously heating the blood at 0.2–1.lC/min from approximately 25 to 55°C in a heat exchanger. A small, but rather abrupt decrease in the scattering asymmetry factor (g‐factor) of 1.7 ± 0.6% and a similar increase in the scattering coefficient of 2.9 ± 0.6% were observed at approximately 45–46°C yielding an increase in the reduced scattering coefficient of 40 ± 10%. Furthermore, a continuous, manifest increase in the absorption coefficient was seen with increasing temperature, on average 80 ± 70% from 25 to 50°C. The effect of the heating on the blood cells was also studied under a white‐light transmission microscope. A sudden change in the shape of the red blood cells, from discshaped to spherical, was observed at approximately the same temperature at which the distinct changes in g‐factor and scattering coefficient were observed, i.e. at 45–46°C. The results indicate that this shape transformation could explain the sudden change in scattering properties.
The Synthesis, Photophysical and Photobiological Properties and in vitro Structure‐Activity Relationships of a Set of Silicon Phthalocyanine PDT Photosensitizers
Authors: Li Ying‐Syi , Zaidi S. I. A. , Rodgers Michael A. J. , Mukhtar Hasan , Kenney Malcolm E. , Oleinick Nancy L. , He Jin , Larkin Hedy E. , Rihter Boris D. 
Published: January 2008

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Fluorescence Lifetime Imaging of Experimental Tumors in Hematoporphyrin Derivative‐Sensitized Mice
Authors: Cubeddu Rinaldo , Canti Gianfranco , Pifferi Antonio , Taroni Paola , Valentini Gianluca 
Published: January 2008

AbstractTumor detection has been carried out in mice sensitized with hematoporphyrin derivative (HpD) by measuring the spatial distribution of the fluorescence lifetime of the exogenous compound. This result has been achieved using a time‐gated video camera and a suitable mathematical processing that led to the so‐called “lifetime images.” Extensive experimental tests have been performed on mice bearing the MS‐2 fibrosarcoma or the L1210 leukemia. Lifetime images of mice show that the fluorescence decay of HpD is appreciably slower in the tumor than in healthy tissues nearby, allowing a reliable detection of the neoplasia. The lengthening of the lifetime in tumors depends little on the drug dose, which in our experiments could be lowered down to 0.1 mg/kg body weight, still allowing a definite tumor detection. In order to ascertain the results achieved with the imaging apparatus, high‐resolution spectroscopy, based on a time‐correlated single photon counting system, has also been performed to measure the fluorescence lifetime of the drug inside the tumor and outside. The outcomes obtained with two techniques are in good agreement.
A Role for Neuropeptides in UVB‐Induced Systemic Immunosuppression
Authors: Garssen Johan , Buckley Theresa L. , Loveren Henk Van 
Published: January 2008

AbstractThe aim of this study was to investigate the possible role of sensory nerves in UV light‐induced systemic immunomodulation. Contact hypersensitivity to the low molecular weight compound picrylchloride was used as a model for cellular immunity that can be suppressed by low (i.e. suberythemal) doses of UV light even after exposure at a distant locus (i.e. systemic immunosuppression). In sensory nerve‐depleted mice, achieved by two subcutaneous injections with the neurotoxin capsaicin before the age of 4 weeks, UV light exposure failed to inhibit contact hypersensitivity responses to picrylchloride. This indicates that sensory nerves are at least partially involved in the induction of systemic immunosuppression by UV light. In order to analyze whether sensory neuropeptides, such as calcitonin gene‐related peptide (CGRP) and tachykinins, are involved in UV light‐induced systemic immunosuppression, mice were pretreated with selective antagonists prior to each UV light exposure. These experiments indicated that CGRP but not the tachykinins plays a crucial role in the UV light‐induced systemic immunosuppression.
Characterization and Purification of the Mammalian COP9 Complex, a Conserved Nuclear Regulator Initially Identified as a Repressor of Photomorphogenesis in Higher Plants
Authors: Wei Ning , Deng Xing‐Wang 
Published: January 2008

AbstractThe COP9 complex has been identified as a repressor of photomorphogenesis in Arabidopsis. Here we demonstrate that the COP9 complex is also present in mammals. Specific antibodies were generated against human counterparts of the Arabidopsis COP9 and COP11, the two known subunits of plant COP9 complex. Using these antibodies, we showed that indeed mammalian COP9 and COP11, also known as GPS1, could be coimmuno‐precipitated using either of the two specific antibodies, definitively confirming that they are physically part of the same complex. Further, the mammalian COP9 and COP11/GPS1 were cofractionated in the same large molecular weight fractions of about 500 kDa and were absent from the monomeric fractions. The mammalian COP9 complex was present in all organs examined but abundances vary. Indirect immunofluorescence studies suggested that the mammalian COP9 complex is largely nuclear localized. Both conventional biochemical and affinity purifications of the COP9 complex from pig spleen indicated that the mammalian COP9 complex consists of eight distinct subunits. These findings indicate that mammals also have a COP9 complex with conserved molecular composition and biochemical and cellular properties similar to the higher plant counterpart.
Kinetics and Mechanism of the Photosensitized Oxidation of Furosemide*
Authors: Zanocco A. L. , S. G. Günther , M. E. Lemp , Fuente J. R. de la , U. N. Pizarro 
Published: January 2008

AbstractDetection of O2(1δg) phosphorescence emission, γmax = 1270 nm, following laser excitation and steady‐state competitive methods was employed to measure total rate constants, kT, for the reactions of the diuretic furosemide, 2‐methylfurane and furfurylamine with singlet oxygen in several solvents. Correlation of kT values with solvent parameters and product identification shows that the reaction mechanism is strongly solvent dependent. In aliphatic alcohols, the dependence of kT on solvent parameters is similar to the one observed for triethylamine, suggesting a reaction mechanism involving partial charge transfer from the amino group to the singlet oxygen. In nonprotic solvents, the dependence of kT on solvent parameters resembles the behavior found for 2‐methylfur‐ane and furfurylamine, implying that mostly a 2 + 4 cy‐cloaddition mechanism of singlet oxygen to furane ring of furosemide occurs in these solvents. These mechanistic differences are explained in terms of hydrogen‐bonding interactions between the carboxylic group in the aromatic ring and the amino group of furosemide. Furthermore, direct generation of C2(1δg) by furosemide was detected. Quantum yields of 0.047 ± 0.003 and 0.078 ± 0.004 were determined in acetonitrile and benzene, respectively. This last result may be related, at least partially, to the photodynamic effects of this diuretic drug.
Tanning in Human Skin Types II and III Offers Modest Photoprotection Against Erythema
Authors: Sheehan John M. , Potten Christopher S. , Young Antony R. 
Published: January 2008

AbstractWe have investigated the photoprotective properties of tanning using erythema as an endpoint. Previously unexposed buttock skin sites of 16 young, healthy adults (8 skin type II, and 8 skin type III) were exposed daily (Mon‐Fri) for 2 weeks to 0.5 and 0.75 minimal erythema doses (MED) of solar‐simulated radiation (SSR). Erythema and melanin levels were assessed daily both visually and quantitatively using a reflectance device. One week after the last tanning treatment, MED reassessments were made on pretreated sites and on adjacent nontreat‐ed sites, including sites from which stratum corneum was removed by tape stripping. Compared to skin type II, similar daily SSR treatments produced less erythema and more evident tanning in skin types III. Independent of skin type, all volunteers showed an increased MED value when assessed on the 0.75 MED‐ and 0.5 MED‐treated sites compared to the MED value assessed on adjacent untreated sites. We express any increase in MED as an induced protection factor (IPF), i.e. (MED post‐tan/MED pre‐tan). Our data show mean IPF of 1.4 and of 2.1 in the 0.5 and 0.75 MED‐treated sites respectively, in skin types II. Similar values were obtained in skin types III with IPF of 1.5 and 2.3 for the 0.5 and 0.75 MED‐treated sites, respectively. In all cases, removal of the stratum corneum lowered the IPF by about 20%. Our results show that SSR‐induced melanogenesis, whether in skin type II or III, offers only moderate protection against erythema and suggest that SSR‐induced stratum corneum thickening affords less photoprotection than tanning.
Photoproduction and Direct Spectral Detection of Singlet Molecular Oxygen (102) in Keratinocytes Stained with Rose Bengal
Authors: Bilski Piotr , Kukielczak Barbara M. , Chignell Colin F. 
Published: January 2008

AbstractIn vivo, keratinocyte skin cells are exposed to photoox‐idative processes, some of which can be mediated by singlet molecular oxygen (1O2), a species that is very difficult to detect spectrally in cells. We photosensitized 1O2 in cultured HaCaT keratinocytes stained with rose bengal (RB) that localizes exclusively inside the keratinocyte hydrophobic regions, as evidenced by strongly red‐shifted absorbance and intense fluorescence. We used keratinocytes grown in a monolayer on a plastic coverslip and in suspension. The phosphorescence spectrum (1200–1350nm) from 1O2 was strongest when the coverslip containing RB‐stained keratinocytes was irradiated in air. The spectral intensity decreased when the coverslip was immersed in D2O during irradiation and was almost completely quenched when it was irradiated while immersed in water. Water not only shortens the 1O2 lifetime but also reabsorbs part of the 1O2 phosphorescence, processes that do not occur when 1O2 is produced in a keratinocyte layer exposed to air. Because the RB was inside keratinocytes, singlet oxygen must also be produced inside the keratinocytes. However, the sensitivity to the extracellular environment suggests that most of the detectable 1O2 phosphorescence originates from those 1O2molecules that escaped from the cell through its membrane into D2O or into the air, where 1O2 has longer lifetimes. Our results confirm directly that 1O2 is indeed photosensitized in living cells by RB. They also suggest that keratinocyte monolayers may be a good cell model to examine in vitro the production of 1O2 by other photo‐sensitizers of environmental and photomedical interest.
Study of Photochemical Reactions of Coniferyl Alcohol. II. Comparative Structural Study of a Photochemical and Enzymatic Polymer of Coniferyl Alcohol
Authors: Radotic Ksenija , Todorovic Smilja , Zakrzewska Joanna , Jeremic Milorad 
Published: January 2008

AbstractThe structure of the polymer synthesized by UV irradiation of coniferyl alcohol was studied, using UV‐visible, Raman, IR, H‐NMR and 13C‐NMR spectroscopy. The photochemical polymer was compared with the structure of the polymer obtained by peroxidase‐catalyzed polymerization of coniferyl alcohol. General similarity of the spectra of the two polymers was shown. However, differences in the fine structure of particular regions of the NMR spectra, as well as in certain bands in the Raman and IR spectra, could be explained through the various bond types and organization within the polymers. These results are consistent with molecular mass distribution of the polymers. Two fractions of enzymatic polymer correspond to the main two fractions of photochemical polymer. The later polymer has additional fractions that are probably the main reason for the observed spectral differences.
Human BCL‐2 Expression Delays Ultraviolet‐Induced Apoptosis in Marsupial Cells
Authors: Miyaji Eliane N. , Menck Carlos F. M. 
Published: January 2008

AbstractWe have introduced the human bcl‐2 gene under the control of the human metallothionein MTIIA promoter into the rat kangaroo PtK2 cell line. Two independent clones were obtained in which the levels of Bcl‐2 protein expression can be controlled by the addition of metals in the culture medium. These cell lines were employed to investigate the effects of this protein in UV‐induced apoptosis. Overexpression of Bcl‐2 in PtK2 cells resulted in a delay in the appearance of apoptosis markers, such as chromatin condensation and internucleosomal DNA fragmentation. However, colony survival after UV was not affected, suggesting that Bcl‐2 did not impose a definitive block for cell death. The elimination of cyclobutane py‐rimidine dimers through photoreactivation 24 h after irradiation in cells overexpressing Bcl‐2 did not affect apoptosis. This indicates that irreversible events in the signaling pathway of apoptosis occur in the period between irradiation and photoreactivation even in the presence of high levels of Bcl‐2 in the cell. Therefore, although the human Bcl‐2 protein can delay the onset of UV‐induced apoptosis in these marsupial cells, early events triggered by the pyrimidine dimers, upstream from the Bcl‐2 action, lead the cell to a state committed to die.
The Configuration of β‐Carotene in the Photosystem II Reaction Center
Authors: Yruela Inmaculada , Tomás Raquel , Sanjuán María L. , Torrado Elena , Aured Maria , Picorel Rafael 
Published: January 2008

AbstractDifferent pigment extraction procedures and HPLC methods were tested to investigate the geometric configuration of the β‐carotene in two forms of the photosystem II reaction center (Dl‐D2‐cytochrome (Cyt) b559) complex containing one and two β‐carotene molecules per two pheophytin a. All the handling steps and HPLC analyses were done in darkness at room temperature and at 4°C. Two different pigment extracts were analyzed, a mixture of chlorophyll a, pheophytin a and 3‐carotene, and the isolated p‐carotene from that mixture. In both cases only the all‐frans‐β‐carotene was detected. The chromatographic profiles were similar at both temperatures only differing in the retention times that were longer at 4°C. This result was independent of the concentration of photosynthetic starting material. Furthermore, no differences were observed between Dl‐D2‐Cyt b559 complexes with one and two p‐carotene molecules per reaction center. The analysis of the β‐carotene chromatographic peak indicated no 15‐cis to all‐fraws isom‐erization occurred during the HPLC chromatography in our experimental conditions. Resonance Raman spectra were also recorded in the isolated Dl‐D2‐Cyt b559 complex at room and liquid nitrogen temperature with excitation at 514.5 nm from an Ar+ laser. Spectra of control preparations showed main bands at 1532, 1264, 1213, 1185, 1154 and 1003 cm−1 corresponding to the M‐trans isomer and confirm previous results. The presence in the reaction center suspension of artificial electron acceptors such as silicomolybdate or 2,5‐dibromo‐3‐methyl‐6‐iso‐propyl‐p‐benzoquinone that are able to quench 3P680 did not modify the resonance Raman spectra of the native Dl‐D2‐Cyt b559 complex. The results suggest that no isomerization takes place during the laser irradiation.
The N‐Terminal Amino Acid Sequences of the Firefly Luciferase Are Important for the Stability of the Enzyme
Authors: Sung Deukyong , Kang Hunseung 
Published: January 2008

AbstractThe structural and catalytic role of the N‐terminal amino acid sequence of Photinus pyralis luciferase was investigated by site‐directed mutagenesis. The firefly luciferase activity of a series of deletion and site‐directed mutants in the amino‐terminal region was investigated in vitro and in vivo. The mutant luciferases were produced either by in vitro transcription and translation or by expressing the cDNA encoding firefly luciferase in the yeast Saccha‐romyces cerevisiae as a fusion protein to the galactose DNA binding domain protein. Deleting the N‐terminal amino acid residues from 3 to 10 dramatically reduced the luciferase activity to less than 1% of the wild‐type activity. A marked decrease in the activity (to 5%) was also observed with the Lys8Glu mutant. The Glyl 0Arg and ProllAla mutants showed20–30% activity compared to the wild type. On the other hand, mutant Asn6Lys retained the wild‐type activity level. Randomizing3–11 N‐terminal amino acids also showed a marked decrease in activity (1%). The mutant luciferases with extremely low levels of enzymatic activity were thermally unstable. These mutational and stability data correlate with the crystal structure of firefly luciferase in which specific amino acids in the N‐terminal region form hydrogen bonds to the amino acids in the neighboring p‐stranded sheet. Because the N‐terminal region is not part of the active site, the present results suggest that the highly conserved N‐terminal amino acid sequences of the firefly luciferase are important for stabilizing the protein in its proper conformation for optimal enzyme activity.